JP4656804B2 - Cutting method using wire saw and method for producing rare earth magnet - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cutting method using a wire saw, a wire saw device, and a method for manufacturing a rare earth magnet.
[0002]
[Prior art]
Rare earth alloys are used as, for example, powerful magnet materials. A rare earth magnet obtained by magnetizing a rare earth alloy is suitably used, for example, as a magnet for a voice coil motor used for positioning a magnetic head of a magnetic recording apparatus.
[0003]
As a method of cutting a rare earth alloy ingot (including a sintered body), conventionally, for example, a technique of slicing an ingot using a rotating slicing blade has been employed. However, according to the method of cutting with a slicing blade, since the thickness of the cutting blade is relatively large, the machining allowance increases, the yield of rare earth alloy materials is low, and the cost of rare earth alloy products (for example, rare earth magnets) increases. It is a factor.
[0004]
As a cutting method with less cutting margin than a slicing blade, there is a method using a wire. For example, Patent Document 1 uses a wire in which superabrasive grains are fixed on a peripheral surface of a high-strength core wire by a bond layer (sometimes referred to as a “fixed abrasive wire”), silicon, sapphire, quartz, It discloses that hard and brittle materials such as glass, neodymium and ferrite can be cut.
[0005]
If a large number of plates having a predetermined thickness can be simultaneously produced from a rare earth alloy lump (ingot) using a fixed abrasive wire as described above, the manufacturing cost of the rare earth magnet can be greatly reduced. . However, there is still no report that a rare earth alloy was cut at a mass production level using a fixed abrasive wire.
[0006]
Based on the results of various studies by the inventor, the main cause of this is that the mechanical properties of rare earth alloys, particularly rare earth alloys manufactured by a sintering method (hereinafter referred to as “rare earth sintered alloys”) are silicon. And so on. Specifically, rare earth sintered alloys have a hard main phase (R ₂ Fe ₁₄ B phase) and a grain boundary phase (R rich phase) causing ductile fracture, unlike hard and brittle materials represented by silicon, it is difficult to cut. That is, the cutting resistance is higher than that in the case of cutting a hard and brittle material such as silicon, and as a result, the amount of generated heat is large. In addition, the specific gravity of the rare earth alloy is about 7.5, which is larger than that of materials such as silicon, and it is difficult for the cutting waste (sludge) generated by cutting to be discharged from the cutting portion.
[0007]
Therefore, in order to efficiently cut the rare earth alloy with high machining accuracy, it is necessary to sufficiently reduce the cutting resistance and to efficiently dissipate the heat generated during cutting, that is, to efficiently cool the cutting portion. . Moreover, it is necessary to discharge | emit the cutting waste produced | generated by cutting efficiently.
[0008]
By sufficiently supplying a coolant with excellent lubricity (also referred to as “cutting fluid”) to the cutting portion of the rare earth alloy, cutting resistance can be reduced and heat generated during cutting can be efficiently dissipated. . As a result of experiments by the inventors, if the wire is wetted with a sufficient amount of coolant using an oil-based coolant, the coolant can be sufficiently supplied to a narrow cutting portion by the traveling wire.
[0009]
However, oil-based coolants are expensive to treat the waste liquid so as not to cause environmental damage, and it is difficult to separate the cutting waste in the waste liquid. There is a problem that is difficult. In addition, when recycling rare earth alloy cutting scraps, there is also a problem that the carbon content in the raw material is increased and the magnetic properties are deteriorated, which is not preferable. Considering these things, water (or a water-soluble cooling liquid) is preferable as the cooling liquid. However, when water is used as the cooling liquid, the water has a viscosity (kinematic viscosity: 1.0 mm). ² Since / s) is low, it is not possible to attach a sufficient amount to the traveling wire, so that even when the wire is wetted with water, a sufficient amount of water cannot be supplied to the cutting portion.
[0010]
In Patent Document 1, even when a fixed abrasive wire is run at a high speed (for example, 2000 m / min) by running the wire into the coolant overflowing from the tank of the coolant, the coolant is reliably attached to the wire. It is disclosed that it can be made. However, according to experiments by the present inventor, even if a rare earth alloy is cut while running a wire (disclosed in, for example, Patent Document 1) in overflowing water, the abrasive grains fall off or are severely damaged. In some cases, wire breakage occurs. This problem occurred even when the wire traveling speed was about 800 m / min, for example. This is presumably because even when the above method is adopted, cutting resistance is high and water is not sufficiently supplied to the cutting portion.
[0011]
As a result of various studies by the present inventor, as a result of cooling with water as a main component, the surface tension at 25 ° C. is in the range of 25 mN / m to 60 mN / m (or the dynamic friction coefficient is in the range of 0.1 to 0.3) It has been found that the wire can be efficiently cooled by supplying the liquid to the cutting part (Japanese Patent Application Nos. 2000-358462 and 2001-318867). A coolant having a surface tension or a dynamic friction coefficient within the above range is superior in wettability (or familiarity) to rare earth alloys and / or wires compared to water, so that cutting parts (rare earth alloys and wires come into contact with each other). This is probably because the coolant efficiently penetrates into the portion where the rare earth alloy is cut (also referred to as a cutting groove). Of course, the cooling liquid mainly composed of water has high specific heat as compared with the oil-based cooling liquid (for example, mineral oil), and therefore has high cooling efficiency. In this specification, “coolant mainly composed of water” refers to a coolant whose water is 70% by weight or more.
[0012]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-198020
[0013]
[Problems to be solved by the invention]
However, as a result of further investigation by the present inventors, when a coolant containing water as a main component is used, the abrasive grains are peeled off from the wire by contact friction between the wires in the reel bobbin around which the wire is wound (sometimes referred to as degranulation). It has been found that there is a problem that this phenomenon occurs.
[0014]
This is because the water-based cooling liquid has a lower adhesion to the wire than the oil-based cooling liquid and evaporates easily, so that the cooling liquid adhering to the wire is slightly or almost not wound when wound on the reel bobbin. It was also found that heat generation due to friction between wires and mechanical frictional force cannot be reduced. That is, it is presumed that this is because the coolant is supplied to the wire at the cutting portion, but the coolant is repelled during traveling before being wound around the reel bobbin.
[0015]
Further, the friction between the wires causes mechanical damage to the abrasive grains even if the abrasive grains do not fall off, so that the cutting accuracy is lowered and the cutting efficiency is lowered. In a more severe case, the abrasive grains may be peeled off together with the resin layer (bond layer). That is, when a coolant containing water as a main component is used, the life of the wire is shortened by friction between the wires in the reel bobbin. Since fixed abrasive wires are relatively expensive, it is desirable to extend the life of the wires in order to reduce the cost of cutting.
[0016]
In addition, when a wire in which abrasive grains are fixed by a resin layer formed on the outer peripheral surface of the core wire is used, “resin peeling” in which the resin layer peels (detaches) from the core wire may occur. As a result of various investigations, the cause of this resin peeling is not only the damage caused by the contact friction between the wires described above, but also the resin layer contains a coolant mainly containing water (especially amines such as alkaline rust preventives). It has been found that there is a cause for the damage caused by the coolant.
[0017]
As described above, in particular, rare earth alloys are difficult to cut using a wire saw, but the problem of shortening the life of the wire when using a coolant mainly composed of water is that silicon, sapphire, quartz, glass, It also occurs when cutting hard and brittle materials such as neodymium and ferrite.
[0018]
The present invention has been made in view of the above-mentioned various points, and its main object is to extend the life of a wire when it is cut with a wire saw device using a coolant mainly composed of water.
[0019]
[Means for Solving the Problems]
The cutting method of the present invention is a cutting method using a wire in which abrasive grains are fixed by a resin layer formed on the outer peripheral surface of a core wire, and a wire whose surface is coated with a lubricating liquid containing glycol is wound around a reel bobbin. A preparatory step, a step of causing a wire wound around the reel bobbin to travel between a plurality of rollers, and a first coolant containing water as a main component at a portion where a workpiece (workpiece) is cut by the wire Cutting the workpiece with the traveling wire while supplying the above, thereby achieving the above object. In particular, the occurrence of the problem of resin peeling can be suppressed.
[0020]
It is preferable that the method further includes a step of supplying a second coolant mainly composed of water to the wire wound around the reel bobbin or the wire traveling in the vicinity of the reel bobbin.
[0021]
The second coolant preferably has a dynamic friction coefficient at 25 ° C. of 0.3 or less with respect to the rare earth alloy.
[0022]
The second coolant may include glycol.
[0023]
The second cooling liquid may be supplied to the wire by a spraying method.
[0024]
In the preparation step, it is preferable that a tension when the wire is wound around the reel bobbin is in a range of 7N to 15N.
[0025]
The pitch when the wire is wound around the reel bobbin is preferably less than twice the outer diameter of the wire, and more preferably more than 100% and 190% or less of the outer diameter.
[0026]
The first coolant preferably has a dynamic friction coefficient at 25 ° C. with respect to the rare earth alloy in the range of 0.1 to 0.3.
[0027]
The resin is preferably a phenol resin, an epoxy resin, or a polyimide resin.
[0028]
The average distance between the abrasive grains adjacent to each other in the traveling direction of the wire is in the range of 100% to 600% of the average grain diameter of the abrasive grains, and the abrasive grains are separated from the surface of the resin layer. The average height of the protruding portion is preferably in the range of 10 μm to 40 μm.
[0029]
The second coolant preferably has a higher viscosity than the first coolant.
[0030]
The temperatures of the first coolant and the second coolant are preferably in the range of 15 ° C to 35 ° C.
[0031]
Each of the plurality of rollers has a polymer layer in which a guide groove is formed, and the guide groove has a pair in which at least one inclined surface forms an angle of 25 ° or more and less than 45 ° with the radial direction of the roller. Preferably, the wire is allowed to travel between the pair of slopes.
[0032]
The workpiece may be an R—Fe—B rare earth sintered alloy. For example, the workpiece may be an Nd—Fe—B rare earth sintered alloy.
[0033]
The method for producing a rare earth magnet of the present invention includes a step of producing a sintered body of a rare earth magnet from a rare earth alloy powder, and a step of separating a plurality of rare earth magnets from the sintered body using any one of the cutting methods described above. It is characterized by including.
[0034]
The wire saw device of the present invention includes a wire in which abrasive grains are fixed by a resin layer formed on an outer peripheral surface of a core wire, a reel bobbin around which the wire is wound, and the wire wound around the reel bobbin A plurality of rollers for drawing and running, a device for supplying a first coolant to a portion where the wire cuts a workpiece, and the wire running around the reel bobbin or the vicinity of the reel bobbin And a device for supplying a second coolant containing glycol to the wire, thereby achieving the above object.
[0035]
The device for supplying the second coolant may be configured to include a spray device.
[0036]
The rare earth magnet produced by the method for producing a rare earth magnet of the present invention is suitably used for a voice coil motor.
[0037]
DETAILED DESCRIPTION OF THE INVENTION
Below, the cutting method of embodiment by this invention is demonstrated.
[0038]
The cutting method according to the present invention uses a wire (fixed abrasive wire) in which abrasive grains (typically diamond abrasive grains) are fixed to a core wire (typically piano wire). A wire wound around a pair of reel bobbins is run between a plurality of rollers, and cut while pressing a rare earth alloy (workpiece) against the running wire. At this time, cutting is performed while supplying a cooling liquid (first cooling liquid) containing water as a main component to a portion where the rare earth alloy is cut by the wire. Here, in the preparation step of winding the wire around the reel bobbin, the surface of the wire is covered with a lubricating liquid containing glycol, so that the resin peeling of the wire in which the abrasive grains are fixed by the resin layer formed on the outer peripheral surface of the core wire is performed. Occurrence can be suppressed.
[0039]
As the lubricating liquid containing glycol, a glycol stock solution or an aqueous solution containing 50% by mass or more of glycol can be preferably used. As glycol, for example, polyoxyalkylene can be suitably used. Since glycol has higher hydrophilicity (water retention) than the resin layer, it is considered that the glycol acts to prevent the resin layer from absorbing water. Moreover, it is preferable that the lubricating liquid containing the glycol provided to a wire in the preparatory process which winds a wire to a reel bobbin is supplied to the part to be cut, and has higher lubricity than a cooling liquid.
[0040]
The step of covering the surface of the wire with the lubricant containing glycol is preferably performed when the wire is wound around the reel bobbin of the wire saw device. As a method for applying glycol (or an aqueous glycol solution) to the wire surface, a spraying method, a dropping method, a coating method, a dipping method, or the like can be appropriately used. The tension when winding the wire on the reel bobbin is preferably in the range of 7N to 15N. If the tension is lower than 7N, the winding of the wire may occur, and if it exceeds 15N, damage due to friction between the wires tends to occur. Moreover, it is preferable to set the tension within this range because good cutting accuracy can be obtained.
[0041]
Further, the pitch (the distance between the centers of the wires) when winding the wire around the reel bobbin is preferably less than twice the outer diameter of the wire, and more preferably more than 100% and not more than 190% of the outer diameter. By adjusting the pitch at the time of winding in this way, it is possible to prevent the next wire from entering between the wires previously wound on the reel bobbin, and to suppress the bending of the wire and the generation of friction between the wires. be able to.
[0042]
Thus, in the preparation process of the wire saw device, when the wire is covered with the lubricating liquid containing glycol when winding the wire on the reel bobbin, the deterioration of the resin layer of the wire due to moisture absorption in the state of storing the wire is suppressed. I can do it. Application of the lubricating liquid containing glycol to the wire is not limited to the preparation step, and for example, glycol may be added and mixed in the second cooling liquid.
[0043]
In order to extend the life of the wires, a coolant (second coolant) mainly containing water is also supplied to the wires wound around the pair of reel bobbins or the wires traveling in the vicinity of the pair of reel bobbins. It is preferable. By supplying the coolant also to the wire wound around the reel bobbin, heat generation due to friction between the wires in the reel bobbin and mechanical frictional force are reduced. As a result, mechanical damage to the wire is reduced, so that a reduction in cutting accuracy and cutting efficiency is suppressed, and the life of the wire is extended.
[0044]
The first coolant preferably has a dynamic friction coefficient at 25 ° C. with respect to the rare earth alloy in the range of 0.1 to 0.3. The second cooling liquid preferably has a dynamic friction coefficient at 25 ° C. of 0.3 or less, more preferably 0.15 or less, relative to the rare earth alloy. In addition, the dynamic friction coefficient shown by the following embodiment is the value calculated | required with the four-ball friction tester using the sintered compact of the R-Fe-B type rare earth alloy. Compositions and production methods of rare earth alloys suitably used as R-Fe-B rare earth magnets are described, for example, in US Pat. No. 4,770,723 and US Pat. No. 4,792,368.
[0045]
In addition, although the 1st and 2nd coolant used by the cutting method of this invention was specified using the dynamic friction coefficient of 25 degreeC, the temperature of the coolant at the time of actually using is not restricted to 25 degreeC. However, in order to obtain the effect of the present invention, it is preferable to use a coolant whose temperature is controlled within a range of 15 ° C to 35 ° C, and more preferably within a range of 20 ° C to 30 ° C. As is well known, the dynamic friction coefficient of the coolant depends on the temperature, so if the actual coolant temperature deviates too much from the above temperature range, the dynamic friction coefficient of the coolant deviates from the above numerical range. It becomes a state that is very similar to the above state, and cooling efficiency decreases.
[0046]
By using the coolant having the above dynamic friction coefficient, it is possible to effectively suppress an abnormal increase in the temperature of the wire, so that it is possible to effectively suppress / prevent abnormal grain shedding and wire breakage. . As a result, the processing accuracy is prevented from being lowered and the wire can be used over a longer period than before, so that the manufacturing cost can be reduced.
[0047]
This effect is common to the first coolant supplied to the cutting unit and the second coolant supplied to the wire wound around the reel bobbin or the wire traveling in the vicinity of the pair of reel bobbins. The same coolant may be used as the second coolant. However, a coolant having a viscosity higher than that of the first coolant may be used so that the second coolant can easily adhere to a wire wound around the reel bobbin or a wire traveling in the vicinity of the reel bobbin. The second coolant and the first coolant have a viscosity of 1 mPa · s to 50 mPa · s (kinematic viscosity: 1 mm ² / S to 50mm ² / S) can be preferably used. In order to enhance the adhesion of the second coolant to the wire, a viscosity of 5 mPa · s or more (5 mm ² It is preferable to use a coolant having a kinematic viscosity of at least / s. The viscosity of the coolant can be adjusted by controlling the concentration of the lubricant mixed with water, which will be described later.
[0048]
The second cooling liquid does not necessarily have to be supplied over the entire period of the cutting process, and the second cooling liquid can be used as long as a sufficient amount of the cooling liquid is applied to the wire wound around the reel bobbin. The liquid may be supplied intermittently. In addition, since a coolant mainly containing water (especially containing alkanolamine) has a more adverse effect on the resin than an oil-based coolant, when using a wire in which abrasive grains are fixed using a resin layer The amount of the cooling liquid is preferably small. Therefore, it is preferable to supply the cooling liquid to the wire wound around the reel bobbin or the wire traveling in the vicinity of the reel bobbin using a spraying method or a dropping method. In particular, the spray method is preferable because a small amount of cooling liquid can be uniformly supplied to the wire wound around the reel bobbin. The supply amount of the cooling liquid may be set as appropriate depending on the type, length, scanning speed, and the like of the wire, and is set in the range of 50 ml / min to 500 ml / min, for example. However, when using a wire excellent in resistance to an aqueous coolant such as an electrodeposition wire (for example, a wire in which abrasive grains are fixed using a Ni plating layer), the entire reel bobbin may be immersed in the coolant.
[0049]
The coolant is prepared by adding a surfactant or a synthetic lubricant called “Synthetic” to water. A predetermined dynamic friction coefficient can be obtained by adjusting the type and the amount of addition. In addition, when a coolant mainly composed of water is used, the viscosity is relatively low, so it is possible to easily separate rare earth alloy cutting waste from the sludge generated by cutting using a magnet. Can be used. Further, it is possible to prevent the natural environment from being adversely affected by the disposal of the coolant. In addition, the amount of carbon contained in the sludge can be reduced, and the magnetic properties of the magnet using the cutting waste recovered from the sludge as a raw material can be improved.
[0050]
If cutting is performed while the wire is traveling at a high speed, the cooling liquid may foam and cooling efficiency may be reduced. By using a cooling liquid containing an antifoaming agent, it is possible to suppress a decrease in cooling efficiency due to foaming of the cooling liquid. Furthermore, corrosion of the rare earth alloy can be suppressed by using a coolant having a PH in the range of 8 to 11. Moreover, oxidation of a rare earth alloy can be suppressed by using a coolant containing a rust inhibitor. These may be appropriately adjusted in consideration of the type of rare earth alloy, cutting conditions, and the like.
[0051]
As the wire, a diamond-type abrasive grain fixed with a resin is preferably used. That is, a wire in which diamond abrasive grains are fixed to the outer peripheral surface of a core wire (typically a piano wire) using a resin can be suitably used. Among these, it is preferable to use a phenol resin, an epoxy resin, and a polyimide resin as the resin. These resins have high adhesive strength to the outer peripheral surface of the piano wire (hard steel wire), and are excellent in wettability (penetration) with respect to a coolant described later. Moreover, it is cheaper than the wire manufactured using the electrodeposition method, and the cost required for cutting the rare earth alloy can be reduced. In addition, the core wire of the wire is not limited to the piano wire, but is formed of an alloy such as Ni—Cr or Fe—Ni, a high melting point metal such as W or Mo, or a bundle of high strength fibers such as nylon fibers. It may be formed from. The material of the abrasive grains is not limited to diamond, and may be SiC, B, C, CBN (Cubic Boron Nitride) or the like.
[0052]
In order to obtain the advantage that the cutting margin is small, the outer diameter of the wire is preferably 0.3 mm or less, and more preferably 0.25 mm or less. The lower limit value of the outer diameter of the wire is set so that sufficient strength can be obtained, and in order to fix the abrasive grains of a predetermined size with sufficient strength, the diameter is about 0.12 mm to 0.20 mm. A core wire is used. The average particle diameter D of the abrasive grains preferably satisfies the relationship of 20 μm ≦ D ≦ 60 μm, and particularly preferably satisfies the relationship of 40 μm ≦ D ≦ 60 μm, from the viewpoint of cutting efficiency. From the viewpoint of cutting efficiency and cutting waste (sludge) discharge efficiency, the average distance between adjacent abrasive grains in the wire traveling direction is within the range of 100% to 600% of the average grain diameter D of the abrasive grains. The average height of the portion where the abrasive grains protrude from the surface of the phenol resin layer is preferably in the range of 10 μm to 40 μm. This wire can be supplied from a general wire manufacturer (for example, Allied Material Co., Ltd.) if the above specifications are specified.
[0053]
When such a wire is used, good cutting efficiency can be realized and cutting waste can be discharged well, so that cutting can be performed even at a relatively high traveling speed (for example, 1000 m / min). Moreover, since it cools efficiently with said cooling fluid, a rare earth alloy can be cut stably over a long period of time with good machining accuracy. When a coolant mainly composed of water is used, the cutting efficiency is set by setting the traveling speed about 20 to 30% faster (for example, 1100 m / min to 1200 m / min) than when using an oil-based coolant. Can be optimized.
[0054]
The coolant mainly composed of water used in the cutting method of the present invention has a low viscosity (kinematic viscosity is about 1 mm). ² / S), so that the coolant that discharges cutting waste is oily (generally kinematic viscosity is 5 mm) ² / S or higher). Therefore, in order to enhance the dischargeability of cutting waste, in the cutting process, the cutting part is maintained in a state immersed in the cooling liquid accommodated in the tank, and the cooling liquid is supplied into the tank from the bottom of the tank. In addition, it is preferable to maintain a state overflowing from the opening of the tank by being supplied from the opening of the tank.
[0055]
The cutting waste discharged into the low-viscosity coolant easily settles, and only a small amount of cutting waste floats near the opening of the tank. In order to perform cutting with the cutting part immersed in the cooling liquid, the wire is arranged so as to run in the cooling liquid near the opening of the tank, so the wire runs in the cooling liquid with less cutting waste. The coolant is supplied with a small amount of cutting waste to the cutting part. In particular, the amount of cutting waste in the coolant supplied to the cutting portion can be reduced by supplying the coolant also from the opening of the tank and maintaining the state overflowing from the opening. Furthermore, the effect of mechanically washing away the cutting waste adhering to the wire by the flow of the coolant supplied from the opening of the tank is also obtained. The amount of the coolant that overflows in one minute is preferably 50% or more of the tank volume. Moreover, it is preferable that the quantity of the cooling fluid supplied from an opening part is larger than the quantity of the cooling fluid supplied from the bottom part of a tank.
[0056]
Furthermore, by forming a curtain-like coolant flow (or airflow) at the opening of the tank and suppressing the overflow of the cooling liquid from the opening of the tank, the liquid level of the overflowing coolant is controlled from the wall of the tank. If it is higher, more cooling liquid is supplied to the periphery of the cutting portion, so that the amount of cutting waste in the cooling liquid can be further reduced. Here, a coolant flow was formed in a curtain shape on the side of the opening of the tank that intersects the traveling direction of the wire. The discharge pressure for forming the coolant flow is 0.2 MPa (2 kg / cm ² ) To 1.0 MPa (10 kg / cm ² ) Is preferably within the range of 0.4 MPa (4 kg / cm ² ) To 0.6 MPa (6 kg / cm ² More preferably, it is within the range of If the discharge pressure is lower than this range, sufficient effects may not be obtained. If the discharge pressure is higher than this range, the wire may bend and the processing accuracy may be reduced.
[0057]
Moreover, it is preferable to discharge the cooling liquid to a pair of main rollers that are arranged on both sides of the tank among the main rollers provided to run the wire and regulate the running position of the wire. By discharging cooling liquid to these main rollers, while suppressing the temperature rise of the organic polymer layer (for example, urethane rubber layer) provided on the surface of the main roller and having a groove for guiding the wire, By washing away the cutting waste (or sludge) adhering to or staying in the wire or the guide groove, it is possible to prevent the running position of the wire from shifting or the wire from coming out of the groove.
[0058]
In addition, by collecting the dirty liquid made of sludge containing rare earth alloy cutting waste and coolant generated in the cutting process, and separating the rare earth alloy cutting waste from the sludge using a magnet, Can be reused (eg, used cyclically). As described above, the coolant containing water as a main component has a low viscosity, so that cutting waste can be easily separated. Further, by separating the rare earth alloy cutting waste, the waste liquid treatment of the cooling liquid can be easily carried out without damaging the environment. Further, the cutting waste can be used as a recycled raw material for the rare earth alloy. Since the coolant used in the cutting method of the present invention contains water as a main component, it is easy to reduce the amount of carbon contained in the rare earth alloy regenerated from the cutting waste. Obtainable. For example, the method disclosed by the applicant of the present application in Japanese Patent Application No. 2000-244481 can be used as a method for separating cutting waste from sludge.
[0059]
As described above, the cutting method according to the present invention is suitably applied to cutting of rare earth sintered alloys that are difficult to cut, particularly R-Fe-B rare earth sintered alloys. A rare earth magnet can be obtained by magnetizing a rare earth alloy cut by the cutting method according to the present invention. The magnetizing step may be performed before or after the cutting step. A rare earth sintered magnet manufactured using an R—Fe—B rare earth sintered alloy is suitably used as a material for a voice coil motor used for positioning a magnetic head. The cutting method according to the present invention is particularly suitable for the R—Fe—B based rare earth firing disclosed in US Pat. No. 4,770,723 and US Pat. No. 4,792,368 by the applicants. It is suitably used for cutting magnetized magnets (alloys). Further, among them, neodymium (Nd), iron (Fe), and boron (B) as main components, and Nd having a tetragonal structure. ₂ Fe ₁₄ A rare earth sintered magnet (alloy) (hereinafter referred to as “neodymium magnet (alloy)”) having a hard main phase (iron rich phase) composed of B intermetallic compound and a grain boundary phase with Nd rich viscosity. It is suitably applied to cutting and manufacturing. As a representative example of a neodymium magnet, there is a trade name NEOMAX manufactured by Sumitomo Special Metals.
[0060]
When the cutting method according to the present invention is adopted, the rare earth alloy can be cut with high accuracy and efficiency. For example, a small rare earth magnet for a voice coil motor used for positioning a magnetic head (for example, a thickness of 0.5 mm to 3 mm). 0.0 mm) can be manufactured with high accuracy and efficiency.
[0061]
In the above-described embodiment of the present invention, the guide groove formed in the polymer layer of the roller that runs the wire has an angle of 25 ° or more and less than 45 ° with respect to the radial direction of the roller. By adopting a configuration having a pair of slopes and allowing the wire to travel between the pair of slopes, it is possible to suppress the cutting of the wire that occurs when a coolant containing water as a main component is used. Of course, it is preferable that the pair of inclined surfaces form an angle of 25 ° or more and less than 45 ° with respect to the radial direction of the roller. In particular, the tension of the wire that can run between the rollers is preferably 25N or more and 35N or less. The surface of the roller is a plane parallel to the axial direction of the roller.
[0062]
(Embodiment)
Hereinafter, embodiments of the cutting method according to the present invention will be described more specifically with reference to the drawings. This embodiment demonstrates the cutting method of the neodymium magnet sintered compact used for manufacture of the above-mentioned neodymium magnet.
[0063]
A method for producing a neodymium (Nd—Fe—B) sintered magnet will be briefly described. A method for producing a rare earth alloy as a magnet material is disclosed in detail in, for example, the above-mentioned US Pat. No. 4,770,723 and US Pat. No. 4,792,368.
[0064]
First, the raw metal is accurately weighed to a predetermined component ratio, and then the raw metal is melted in a high-frequency melting furnace in a vacuum or an argon gas atmosphere. The melted raw material metal is cast into a water-cooled mold to form a raw material alloy having a predetermined composition. This raw material alloy is pulverized to produce fine powder having an average particle size of about 3 to 4 μm. This fine powder is put into a mold and press-molded in a magnetic field. At this time, if necessary, the fine powder is mixed with a lubricant before press molding. Next, a neodymium magnet sintered body can be produced by performing a sintering step of about 1000 ° C. to about 1200 ° C. Thereafter, in order to improve the coercive force of the magnet, an aging treatment is performed at about 600 ° C. to complete the production of the rare earth magnet sintered body. The size of the sintered body is, for example, 30 mm × 50 mm × 50 mm.
[0065]
The obtained sintered body is cut to form a plurality of thin plates (sometimes referred to as substrates or wafers) cut from the sintered body. Each thin plate of the obtained sintered body is subjected to a finishing process by polishing, and after adjusting the size and shape, a surface treatment is applied in order to improve long-term reliability. Then, after performing a magnetization process, a neodymium permanent magnet is completed through an inspection process. In addition, you may perform a magnetization process before a cutting process.
[0066]
Next, the cutting method according to the present invention will be described with reference to FIGS.
[0067]
FIG. 1 is a schematic configuration diagram showing a wire saw device 100 that is suitably used for executing the cutting method according to the embodiment of the present invention.
[0068]
The wire saw device 100 includes three main rollers 10a, 10b and 10c, and a pair of reel bobbins 40a and 40b. The main roller 10a provided in the lower part of the tank 30 for storing the cooling liquid is a driving roller, and the main rollers 10b and 10c provided on both sides of the tank 30 are driven rollers. The wire 20 is wound, for example, from one reel bobbin 40a to the other reel bobbin 40b while reciprocating. At this time, by making the winding time of the reel bobbin 40a longer than the winding time of the other reel bobbin 40b, the new wire 20 can be supplied to the reel bobbin 40a side while reciprocating the wire 20. . The traveling speed of the wire 20 is, for example, in the range of 200 m / min to 1500 m / min, and the speed of supplying the new line is, for example, in the range of 0 m / min to 5 m / min.
[0069]
Between the main rollers 10a, 10b, and 10c, the wires 20 are stretched, for example, in 150 rows. In order to determine the traveling position of the wire 20, an organic polymer layer (for example, a depth of about 0.6 mm, not shown) for guiding the wire 20 is formed on the surface of the main rollers 10a, 10b, and 10c (for example, (Urethane rubber layer) is provided. The spacing between the rows of wires 20 is determined by the pitch of the guide grooves. The pitch of the guide groove is set according to the thickness of the plate to be cut out from the workpiece.
[0070]
In the vicinity of the reel bobbins 40a and 40b, traversers 42a and 42b for adjusting the winding position are provided, respectively. In the path from the reel bobbins 40a and 40b to the main roller 10a, five guide rollers 44 and one tension roller 46 are provided on each side for guiding the wire 20 and its tension. Is adjusted. Although the tension | tensile_strength of the wire 20 can be suitably changed according to various conditions (cutting length, cutting speed, traveling speed, etc.), it sets to the range of 20N-40N, for example.
[0071]
Note that the damage received when the wires 20 wound around the reel bobbins 40a and 40b rub against each other also depend on the tension of the wire 20. Therefore, it is preferable to provide a mechanism for reducing the tension for winding the reel ribbons 40a and 40b. As a mechanism for reducing the winding tension, for example, as described in JP-A-9-29607, JP-A-9-314548, JP-A-10-166353, and JP-A-10-277914. A mechanism can be used. The winding tension in the reel bobbins 40a and 40b is preferably in the range of 7N to 15N.
[0072]
The wire saw device 100 further includes spray devices 80a and 80b for supplying a coolant to the wire 20 wound around the reel bobbins 40a and 40b. In this embodiment, since the wire 20 in which abrasive grains are fixed with resin is used, a spraying method is employed in order to efficiently apply a small amount of cooling liquid to the wire 20.
[0073]
For example, as shown in FIG. 2, the spraying devices 80 a and 80 b supply coolant (for example, 200 ml / min), air (for example, 0.4 MPa), and a spray nozzle to a coolant 60 cutting portion described later. The same coolant as described later is used. The coolant can be sprayed over the entire wire 20 wound around the reel bobbins 40a and 40b (for example, core outer diameter 170 mm, height 340 mm). Here, a cooling liquid stored in a cooling liquid tank 60, which will be described later, is commonly used as the cooling liquid, and is pumped to the spraying devices 80a and 80b through a pipe by a discharge pump. Of course, a coolant tank may be separately provided to supply the coolant to the spraying devices 80a and 80b, and a coolant different from the coolant supplied to the cutting unit may be used.
[0074]
Furthermore, in order to reduce the damage to the wire 20 by the coolant and / or reduce the amount of coolant used, the region where the coolant is sprayed may be limited. A mechanism may be employed in which the winding liquid (and feeding) operation is performed in synchronization with the movement of the traversers 42a and 42b shown in FIG. 1, and the cooling liquid is selectively supplied to the region where the friction between the wires 20 is generated. . In particular, when the wire 20 is reciprocated as illustrated, a strong frictional force is generated between the wires 20 wound around the reel bobbins 40a and 40b when the traveling direction is reversed, so that at least the coolant is supplied to this region. Is preferred.
[0075]
The means for supplying the cooling liquid is not limited to the illustrated spraying apparatuses 80a and 80b, and a dropping apparatus or the like may be used. When supplying a relatively large amount of cooling liquid, it is preferable to provide a recovery pan for recovering and reusing excess cooling liquid below the reel bobbins 40a and 40b as necessary. It is preferable to provide a filter and / or a magnetic separator in the coolant recovery path to separate and remove chips contained in the recovered coolant.
[0076]
In the present embodiment, the configuration in which the coolant is sprayed on the wire 20 wound around the reel bobbins 40a and 40b is exemplified. However, the wire immediately before being wound (or just after being sent out) on the reel bobbins 40a and 40b. A coolant may be supplied to 20. If at least one of the wires in contact with each other is wet, damage to the abrasive grains can be reduced. Further, by supplying the coolant to the wire 20 immediately after being sent out from the reel bobbins 40a and 40b, the wire 20 comes into contact with the guide rollers 44, the tension roller 46, and the guide grooves of the main rollers 10a, 10b and 10c. The damage caused by can also be reduced.
[0077]
The sintered workpiece 50 produced as described above is set in the wire saw device 100 as follows.
[0078]
The plurality of workpieces 50 are fixed to each other by, for example, an epoxy-based or hot-melt adhesive (not shown), and are assembled as a plurality of blocks, with a carbon base plate 52 interposed therebetween, and an iron workpiece plate 54. Fixed to.
The work plate 54, each block of the work 50, and the carbon base plate 52 are also fixed to each other by an adhesive (not shown). The carbon base plate 52 functions as a dummy that protects the work plate 54 by being cut by the wire 20 until the lowering operation of the work plate 54 stops after the work 50 has been cut.
[0079]
In this embodiment, the size of each block is designed so that the size of each block measured along the traveling direction of the wire 20 is about 100 mm. Therefore, here, the cutting length by the wire 20 is about 200 mm. In the present embodiment, the workpiece 50 is divided into a plurality of blocks as described above. However, the size of the wire 20 in the traveling direction should be set depending on the dynamic friction coefficient of the coolant and traveling. It also changes depending on the speed. Further, the number and arrangement of the workpieces 50 constituting one block also vary depending on the size of each workpiece 50. In consideration of these, the work 50 may be arranged by appropriately dividing the block into optimally sized blocks.
[0080]
The workpiece 50 set as described above is lowered by an elevating device including a motor 58, pressed against the traveling wire 20, and cut. The descending speed of the workpiece 50 can be changed according to various conditions, but is set within a range of 20 mm / hr to 50 mm / hr, for example.
[0081]
The cooling liquid stored in the cooling liquid tank 60 is pumped through the pipe 63 by the discharge pump 62. The pipe 63 is branched into a lower pipe 64 and an upper pipe 66 on the way. The lower pipe 64 and the upper pipe 66 are provided with valves 63b and 63a for adjusting the flow rate of the coolant to each. The lower pipe 64 is connected to a lower nozzle 64a provided at the bottom of the tank 30 for immersing the cutting part. The upper pipe 66 is connected to upper nozzles 66a, 66b and 66c for supplying the coolant from the opening of the tank 30, and upper nozzles 66d and 66e provided for cooling the main rollers 10b and 10c, respectively. ing.
[0082]
Cooling liquid is supplied to the tank 30 from the upper nozzles 66a, 66b and 66c and the lower nozzle 64a, and at least during the cutting process, as shown by the arrow F in FIG. It is maintained in a state overflowing from the department. The cooling liquid overflowing from the tank 30 is guided to the collection tank 72 by the collection pan 70 provided below the tank 30 and accumulated. For example, as shown in FIG. 1, the recovered cooling liquid is sent to the cooling liquid tank 60 through the circulation pipe 76 by the discharge pump 74. A filter 78 is provided in the middle of the circulation pipe 76, and the cutting waste contained in the recovered coolant is separated and removed. The collection method is not limited to this, and a mechanism for separating cutting waste using magnetic force may be provided (see, for example, Japanese Patent Application No. 2000-224481).
[0083]
Next, the cutting process according to the present invention will be described in more detail with reference to FIG.
[0084]
The tank 30 has an auxiliary wall 32 in the vicinity of the opening of the side wall that intersects the traveling direction of the wire 20. The auxiliary wall 32 is formed of a plastic plate (for example, an acrylic plate) and is provided so as to be close to the traveling position of the wire at the time of no load indicated by a broken line in FIG. When the workpiece 50 is lowered and brought into contact with the wire 20 for cutting, the wire 20 bends, and the cutting portion is immersed in the coolant in the tank 30 as shown by the solid line in FIG. At this time, as the wire 20 bends, the wire 20 cuts the auxiliary wall 32 to form a slit. When the cutting by the wire 20 is in a steady state, the amount of deflection is constant, and the wire 20 cuts the workpiece 50 while passing through the slit formed in the auxiliary wall 32. Therefore, the slit formed in the auxiliary wall 32 functions to regulate the traveling position of the wire 20 and contributes to the stability of processing accuracy.
[0085]
The tank 30 has a capacity of, for example, about 35 l (liter). During the cutting process, the coolant is supplied at a flow rate of about 30 l / min from the lower nozzle 64a, and about 90 l from the upper nozzles 66a, 66b and 66c. The coolant is supplied at a flow rate of / min, and the coolant is always maintained in a state of overflowing from the opening. Considering only supplying the coolant to the wire 20, as shown in FIG. 3, since the wire 20 is bent during cutting, the coolant is not necessarily overflowed. When cutting, it is preferable to employ the above-described configuration in order to improve the dischargeability of cutting waste.
[0086]
In order to improve the dischargeability of cutting waste, it is effective to reduce the amount of cutting waste contained in the coolant near the cutting portion. In order to obtain sufficient dischargeability, it is preferable that the amount of the coolant overflowing for one minute is 50% or more of the tank volume. Furthermore, it is preferable to supply more fresh coolant from the opening than from the bottom of the tank 30. Since a low-viscosity coolant having water as a main component is used, the cutting waste discharged into the coolant easily settles. Therefore, when a large amount of coolant is supplied from the bottom of the tank 30, the settled waste Is not preferable because it causes floating near the cutting portion.
[0087]
Further, in order to increase the ratio of the fresh coolant supplied from the opening to the wire 20 (that is, the cutting groove), it is preferable to increase the coolant supplied from above the traveling wire 20. That is, by supplying the coolant from the opening of the tank 30 and maintaining the state overflowing from the opening, the amount of cutting waste contained in the coolant supplied to the cutting unit can be reduced. Furthermore, the effect of mechanically washing away the cutting waste adhering to the wire 20 by the flow of the coolant supplied from the opening of the tank 30 is also obtained.
[0088]
Moreover, since the part other than the slit formed by the wire 20 functions as the side wall of the tank 30, the auxiliary wall 32 described above functions to keep the liquid level S of the coolant high. Furthermore, a curtain-like cooling liquid flow is formed on the side of the opening of the tank 30 intersecting the traveling direction of the wire 20 by using the nozzles 66b and 66c, and the cooling liquid overflows from the opening of the tank 30. Suppress. Thereby, when the liquid level S of the overflowing coolant is made higher than the auxiliary wall 32 of the tank 30, more coolant is supplied to the periphery of the cutting portion, so the amount of cutting waste in the coolant Can be further reduced. The discharge pressure for forming the coolant flow is 0.2 MPa (2 kg / cm ² ) To 1.0 MPa (10 kg / cm ² ) Is preferably within the range of 0.4 MPa (4 kg / cm ² ) To 0.6 MPa (6 kg / cm ² More preferably, it is within the range of If the discharge pressure is lower than this range, a sufficient effect may not be obtained. If the discharge pressure is higher than this range, the wire 20 may be shaken, and as a result, the processing accuracy may be reduced.
[0089]
Further, it is preferable that the coolant is discharged also to the pair of main rollers 10b and 10c that are arranged on both sides of the tank 30 and regulate the traveling position of the wire 20. By discharging a cooling liquid to these main rollers 10b and 10c, an organic polymer layer (for example, a urethane rubber layer) having a groove for guiding the wire 20 provided on the surface of the main rollers 10b and 10c. While suppressing the temperature rise, the cutting waste (or sludge) adhering to or staying in the wire 20 or the guide groove can be washed away, so that the traveling position of the wire 20 is prevented from being displaced and the wire 20 from being detached from the groove. In addition, it is possible to obtain the effect of improving the discharge performance.
[0090]
As the surfactant added to the coolant mainly composed of water, anionic surfactants such as fatty acid derivatives such as fatty acid soaps and naphthenic acid soaps, or sulfate esters such as long-chain alcohol sulfates and sulfated oils of animal and vegetable oils. Type, or sulfonic acid type such as petroleum sulfonate, non-ionic type, polyoxyethylene type such as polyoxyethylene alkylphenyl ether and polyoxyethylene mono fatty acid ester, polyhydric alcohol type such as sorbitan mono fatty acid ester, or An alkylolamide system such as fatty acid diethanolamide can be used. Specifically, the dynamic friction coefficient can be adjusted within a predetermined range by adding about 2 wt% of chemical solution type JP-0497N (manufactured by Castrol Co.) to water.
[0091]
As synthetic type synthetic lubricants, synthetic solution type, synthetic emulsion type and synthetic soluble type can be used, among which synthetic solution type is preferable, specifically glycol and alkanolamine, etc. And lubricants (# 830 and # 870 manufactured by Yushiro Chemical Industry Co., Ltd.) and Cintilo 9954 (manufactured by Castrol Co.). In any case, the dynamic friction coefficient can be adjusted within a suitable range by adding about 2 to 10% by weight to water.
[0092]
Moreover, the corrosion of rare earth alloys can be prevented by containing a rust inhibitor. In particular, when cutting an R—Fe—B rare earth alloy, the pH is preferably 8 to 11. As an antirust agent, organic type, carboxylate such as oleate and benzoate, or amines such as triethanolamine, inorganic type, phosphate, borate, molybdate, tungstate Or carbonates can be used.
[0093]
Moreover, as a nonferrous metal anticorrosive agent, for example, a nitrogen compound such as benztriazole can be used, and as a preservative, a formaldehyde donor such as hexahydrotriazine can be used.
[0094]
Moreover, a silicone emulsion can be used as an antifoamer. By containing an antifoaming agent, the foaming of the cooling liquid is reduced, the permeability of the cooling liquid is improved, the cooling effect is enhanced, the temperature rise in the wire 20 is prevented, the temperature rise of the wire 20 is abnormal, and the wear is abnormal. Is less likely to occur.
[0095]
The structure of the wire 20 that is preferably used in the present embodiment will be described with reference to FIG. In the drawing, the lower half of the wire 20 is simplified from the center line indicated by the one-dot chain line.
[0096]
As the wire 20, a wire in which diamond abrasive grains 24 are fixed to the outer peripheral surface of a core wire (piano wire) 22 with a resin layer 26 is preferably used. Among these, it is preferable to use a phenol resin, an epoxy resin, or a polyimide resin as the resin. These resins have high adhesive strength to the outer peripheral surface of the piano wire (hard steel wire) 22 and are excellent in wettability (penetration) with respect to the above-described cooling liquid. Further, as the abrasive grains, SiC or the like may be used in addition to the diamond abrasive grains.
[0097]
As a specific example of a suitable wire 20, diamond abrasive grains having an average particle diameter of about 45 μm are fixed to the outer periphery of a piano wire 22 having a diameter of about 0.18 mm with a phenol resin layer 26, and the outer diameter is about 0.1 mm. A 24 mm wire 20 can be mentioned. Further, from the viewpoint of cutting efficiency and cutting waste (sludge) discharge efficiency, the average distance between the abrasive grains 24 adjacent to each other in the traveling direction of the wire 20 (axial direction: direction parallel to the dashed line in the figure) is: What is in the range of 100%-600% of the average particle diameter D of an abrasive grain is preferable. Furthermore, it is preferable that the average height of the portion where the abrasive grains 22 protrude from the surface of the phenol resin layer 26 is in the range of 10 μm to 40 μm. Since such a wire 20 has a space 28 (sometimes referred to as a “chip pocket”) 28 having an appropriate size between the abrasive grains 22, it has a good cutting efficiency and a good discharge property. Have.
[0098]
In the wire saw apparatus 100 described above, the effect of cutting the above-described neodymium magnet alloy using a wire made of Allied material that satisfies the above-described specifications as a wire was verified. While spraying about 10% aqueous solution (liquid temperature 23 ° C) of Yushiro Chemical # 830 as a cooling liquid onto a reel bobbin at a supply rate of 200 ml / min, a maximum traveling speed of 1100 m / min, tension of 30 N, cutting depth of 40 mm / hour, new The wire was cut while traveling in both directions under the condition of a wire supply rate of 2 m / min. As a result, the amount of detachment of the abrasive grains and the resin layer was reduced to about one third compared to the case where the coolant was not sprayed on the reel bobbins 40a and 40b (wire length: 38 km). Dynamic friction coefficient 0.11 to 0.13, surface tension 33 to 36 mN / m, viscosity 1 to 4 mPa · s (kinematic viscosity 1 to 4 mm) obtained by adjusting the concentration of # 830 manufactured by Yushiro Chemical ² / S), a similar result was obtained.
[0099]
Further, it was confirmed that the resin peeling was suppressed by coating the surface of the wire with glycol before spraying the cooling liquid. The coating of the wire surface with glycol was performed as follows.
[0100]
When winding the wire (wire outer diameter 0.24 mm) around a reel bobbin, the winding tension is about 10 N, the winding pitch is about 0.46 mm, and using a cloth soaked with glycol while winding, The surface of the wire was coated with glycol (eg, a polyoxyalkylene stock solution).
[0101]
By using a wire coated with glycol, when using a wire not coated with glycol, the rate of occurrence of resin peeling was reduced to about 2% (3/237) from about 20% (382/1900). did it. The conditions other than the new line supply rate being 3 m / min are the same as described above. Further, by coating the surface with a lubricant containing glycol, the effect of reducing the variation in the rate of occurrence of resin peeling depending on the storage environment during the storage period of the wire was also observed. Here, evaluation of resin peeling was performed as follows. After the neodymium magnet alloy was cut for 5 hours under the above-mentioned conditions, a resin peeling of 5 mm or more occurred on the wire (about 900 m) used for cutting was defined as a resin peeling failure.
[0102]
Since glycol is very hydrophilic (water retention), it is considered to act to prevent the resin layer from absorbing water contained in the air. In order to efficiently exhibit this effect of glycol, it is preferable to apply glycol directly to the surface of the wire, but it may be diluted with water. In this case, although depending on the application method, it is preferably used as an aqueous solution having a glycol concentration of 50% by mass or more.
Here, the aqueous solution is used because an aqueous cooling liquid is used as the cooling liquid, and thus does not adversely affect the action of the cooling liquid when mixed with the cooling liquid. Since glycol is excellent in water solubility and lubricity, even if mixed with an aqueous coolant, there is no adverse effect.
[0103]
Here, the embodiment in which the wire is coated with a lubricant containing glycol and the cutting process is performed while spraying the coolant onto the reel bobbin is illustrated, but the coolant is sprayed onto the reel bobbin. Even if the process is omitted, the effect of suppressing resin peeling can be obtained by applying glycol in advance. Of course, as illustrated, it is most preferable to use them together.
[0104]
Next, a preferable structure of the main rollers 10a, 10b, and 10c of the wire saw device 100 according to the first embodiment will be described.
[0105]
When using a coolant containing water as a main component, the wire breakage rate increases (that is, the wire breaks in a shorter time) and the processing accuracy is lower than when an oil-based coolant is used. . As a result of various studies by the present inventor, as schematically shown in FIG. 5, a pair of inclined surfaces that the guide groove 10 </ b> G has as a cross-sectional shape of the guide groove 10 </ b> G formed in the polymer layer 10 </ b> P of the rollers 10 a, 10 b, and 10 c. By adopting a configuration in which 10S forms an angle of 25 ° or more and less than 45 ° with respect to the radial direction 10R of the roller 10a (hereinafter referred to as “inclination angle (α)”), occurrence of disconnection of the wire 20 is suppressed. In addition, it was found that sufficient processing accuracy can be obtained. The inclination angle is more preferably 30 ° or more and 35 ° or less.
[0106]
In addition, as illustrated, it is preferable that both of the pair of slopes 10S included in the guide groove 10G have an inclination angle in the above range with respect to the radial direction 10R of the roller 10a. However, at least one of the pair of slopes 10S is preferred. If it has the inclination angle of said range, the effect which suppresses generation | occurrence | production of a disconnection and sufficient processing precision can be acquired.
[0107]
Conventionally, for example, as shown in FIG. 6, a structure in which the inclined surface 10S of the guide groove 10G forms an inclination angle of 45 ° or more with respect to the radial direction 10R of the roller has been adopted. This is because the sludge is efficiently discharged sufficiently from the guide groove 10G. In particular, the rare earth alloy has a main phase causing brittle fracture and a ductile fracture and a grain boundary phase, and thus has a high cutting resistance. In addition, since the specific gravity is large, the sludge discharge performance is poor. Therefore, in order to increase the sludge discharge performance, the inclination angle is set to exceed 45 °.
[0108]
However, as a result of the study by the present inventors, it has been found that when the inclination angle of the inclined surface 10S is made larger than 45 °, the disconnection occurrence rate does not decrease so much, but rather the problem that the machining accuracy decreases occurs. Hereinafter, this phenomenon will be described with reference to FIG.
[0109]
FIG. 7 is a graph showing the relationship between the inclination angle of the inclined surface 10S of the guide groove of the roller and the twist angle of the wire. The twist angle Ω is proportional to the twisting force that the wire 20 receives from the roll, and indicates that the wire is twisted once when the twist angle Ω = 360 °. In addition, the result shown in FIG. 7 was calculated | required from the dynamic model calculation about the structure demonstrated below. In addition, the inclination angle of the slope 10S is assumed to be equal on the slopes on both sides. Results are shown.
[0110]
Between the pair of rollers (rollers 10b and 10d in FIG. 1 having a diameter of 170 mm) arranged at an interval (span) of 450 mm, 200 wires 20 are arranged with a tension of 30 N (3 kgf). The new line is supplied at a rate of 2 m / min and is reciprocated in a 120-second cycle. At this time, the wire 20 reciprocates about 190 times and then escapes from the roller.
[0111]
Here, as a result of various experiments, when the wire is subjected to a twisting force of 5 times (Ω = 1800 °) in one span (450 mm), the wire 20 is twisted approximately 500 times while traveling for 200 lines. did. That is, when receiving the force of twisting 200 lines × 5 times = 1000 times, about 50% of the amount was accumulated as actual twisting. Therefore, the torsion angle Ω on the vertical axis in FIG. 7 indicates a value obtained by multiplying the torsion angle corresponding to the torsional force obtained from the dynamic model calculation by 0.5. In addition, from a static torsion breaking strength test, it was estimated that the wire breaks with a probability of 10% when the twist angle actually accumulated in the wire 20 reached 1800 ° (five turns).
[0112]
As can be seen from FIG. 7, the twisting force (twist angle) decreases monotonously as the inclination angle α of the groove 10G increases. Considering the breakage of the wire 20 simply by the twisting force, when the wire 20 is thin (diameter d = 0.19 mm), the inclination angle is 10 ° or more, and when the wire 20 is thick (diameter is 0.25 mm), the inclination angle is 25. If it is more than 0 °, breakage of the wire 20 can be suppressed.
[0113]
However, according to experiments, when any of the wires 20 was used, the disconnection occurrence rate did not decrease so much when the inclination angle was 45 ° or more. Further, when the inclination angle is 45 ° or more, there is a problem that the processing accuracy is lowered.
[0114]
This is because as the inclination angle increases, the width 10W (see FIG. 5) of the guide groove 10G increases, the wire 20 swings in the guide groove 10G, and further jumps to the adjacent guide groove 10G. It is considered that the wire 20 is broken as a result of uneven tension and force applied to the wire 20 and generation of large stress locally. Further, it is considered that the machining accuracy is lowered as a result of the wire 20 not traveling stably in the guide groove 10G. In the experiment, a urethane rubber layer was used as the polymer layer 10P, and an approximately 10% aqueous solution of # 830 manufactured by Yushiro Chemical Industry Co., Ltd. was used as the cooling liquid. Further, the same rare earth sintered magnet workpiece as in the first embodiment was cut.
[0115]
From the above results, the inclination angle of the inclined surface 10S of the guide groove 10G is preferably 25 ° or more and less than 45 °. In order to suppress the disconnection of the wire 20 as much as possible, the inclination angle is preferably set to 30 ° or more so as to reduce the intentional force, and the inclination angle is set to 35 ° or less in order to obtain high processing accuracy. It is preferable. In addition, it is preferable that the bottom 10B of the guide groove 10G is processed to have a slightly smaller radius of curvature than the radius of the wire 20.
[0116]
Here, the result when the tension of the wire 20 is 20 N has been described, but almost the same result can be obtained when the tension of the wire is 20 N or more and 35 N or less.
[0117]
Although the embodiments of the present invention have been described with reference to the wire saw devices 100 and 200, the present invention is not limited to this, and an endless type wire saw device using a single reel bobbin (see, for example, JP-A-11-98018) Can be applied to.
[0118]
As described above, according to the embodiment of the present invention, it is possible to extend the life of a wire when cutting a rare earth alloy using a coolant mainly composed of water in a wire saw device. Since the rare earth alloy has a hard main phase causing brittle fracture and a grain boundary phase causing ductile fracture, it is particularly difficult to cut using a wire saw, and thus the effect of the present invention is particularly remarkable. When the cutting method according to the embodiment of the present invention is adopted, the present invention is not limited to the case of cutting rare earth alloys, and a hard and brittle material such as silicon, sapphire, crystal, glass, neodymium, and ferrite is used as a main component of water. In the case of cutting, the life of the wire can be extended.
[0119]
【The invention's effect】
As described above, according to the present invention, it is possible to extend the life of a wire when it is cut by a wire saw device using a coolant mainly composed of water.
[0120]
When the cutting method of the present invention is used, a rare earth alloy and other hard and brittle materials can be cut with a high processing accuracy and with a small cutting margin using a coolant mainly composed of water. Therefore, the yield of the material is improved, and a cooling liquid mainly composed of water is used as the cooling liquid. Therefore, it is environmentally friendly and the cleaning process after cutting can be simplified. The cost can be reduced.
[0121]
The cutting method of the present invention has a remarkable effect when cutting rare earth alloys that are harder to cut than hard and brittle materials such as silicon. Since the rare earth alloy material is expensive, there is a great cost merit by improving the material yield. Moreover, since cutting waste can be separated from the waste liquid and the circulating use of the cooling liquid can be easily realized, it is environmentally friendly and the cost of the waste liquid treatment can be reduced. Therefore, the processing cost of the rare earth alloy is reduced, and a cut product, for example, a voice coil motor for a magnetic head can be manufactured at a low cost.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a wire saw device 100 suitably used for executing a cutting method according to an embodiment of the present invention.
2 is a view schematically showing a structure for supplying a cooling liquid to the wire 20 wound around the reel bobbins 40a and 40b in the wire saw device 100. FIG.
3 is a schematic diagram showing a configuration in the vicinity of a cutting portion of the wire saw device 100 shown in FIG. 1. FIG.
FIG. 4 is a diagram schematically showing a cross-sectional structure of a wire 20 that is suitably used for executing the cutting method according to the embodiment of the present invention.
FIG. 5 is a diagram schematically showing a cross-sectional structure of a roller suitably used in the wire saw devices 100 and 200. FIG.
FIG. 6 is a diagram schematically showing a cross-sectional structure of a conventional roller.
FIG. 7 is a graph showing a relationship between an inclination angle of a slope 10S of a guide groove of a roller and a wire twist angle.
[Explanation of symbols]
10a, 10b, 10c main roller
20 wires
30 tanks
40a, 40b reel bobbin
42a, 42b traverser
50 workpieces
60 Coolant tank
70 Bread for collection
80a, 80b spraying device

Claims (14)

A cutting method using a wire in which abrasive grains are fixed by a resin layer formed on the outer peripheral surface of a core wire,
A preparation step of winding a wire coated with a lubricating liquid containing glycol on a reel bobbin;
Running the wire wound around the reel bobbin between a plurality of rollers;
Cutting the workpiece with the traveling wire while supplying a first coolant mainly composed of water to a portion where the workpiece is cut by the wire;
Includes the step of supplying the second coolant containing water as a main component in the wire Ya wound on the reel bobbin,
The cutting method, wherein the second coolant includes glycol.   2. The cutting method according to claim 1, wherein the second cooling liquid has a coefficient of dynamic friction at 25 ° C. of 0.3 or less with respect to the rare earth alloy.   The cutting method according to claim 1 or 2, wherein the second coolant is supplied to the wire by a spraying method.   The cutting method according to any one of claims 1 to 3, wherein in the preparation step, a tension when the wire is wound around the reel bobbin is in a range of 7N to 15N.   The cutting method according to any one of claims 1 to 4, wherein a pitch when the wire is wound around the reel bobbin is less than twice the outer diameter of the wire.   The cutting method according to any one of claims 1 to 5, wherein the first coolant has a dynamic friction coefficient at 25 ° C with respect to the rare earth alloy in a range of 0.1 to 0.3.   The cutting method according to claim 1, wherein the resin is a phenol resin, an epoxy resin, or a polyimide resin.   The average distance between the abrasive grains adjacent to each other in the traveling direction of the wire is in the range of 100% to 600% of the average grain diameter of the abrasive grains, and the abrasive grains are separated from the surface of the resin layer. The cutting method according to any one of claims 1 to 7, wherein an average height of the protruding portion is in a range of 10 µm to 40 µm.   The cutting method according to claim 1, wherein the second coolant has a viscosity higher than that of the first coolant.   The cutting method according to any one of claims 1 to 9, wherein temperatures of the second coolant and the first coolant are in a range of 15 ° C to 35 ° C.   Each of the plurality of rollers has a polymer layer in which a guide groove is formed, and the guide groove has a pair in which at least one inclined surface forms an angle of 25 ° or more and less than 45 ° with respect to the radial direction of the roller. The cutting method according to claim 1, wherein the wire is caused to travel between the pair of slopes.   The cutting method according to claim 1, wherein the workpiece is formed of an R—Fe—B rare earth sintered alloy.   The cutting method according to claim 12, wherein the workpiece is formed of an Nd-Fe-B rare earth sintered alloy. Producing a sintered body of a rare earth magnet from rare earth alloy powder;
A step of separating a plurality of rare earth magnets from the sintered body using the cutting method according to claim 1;
A method for producing a rare earth magnet, comprising:

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