JP3764807B2 - COMPOSITE DIE MATERIAL FOR PRESS MOLDING, ITS MANUFACTURING METHOD, AND PRESS MOLDING DIE CONTAINING THE COMPOSITE DIE MATERIAL - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a composite mold material for press molding, in particular, a mold material to be a block for constituting a mold used in a pressing process in producing a fired tile from an ore powder raw material, a method for producing the same, and The present invention relates to a mold for press molding formed from a mold material.
[0002]
[Prior art]
Many stamping molds are made of steel typified by hardened and tempered die steel (JIS SKD11, etc.), but when the object of press molding is hard like ore powder. Has a problem in terms of wear resistance, and in order to improve this problem, WC-Co based, WC-Ni based, etc. composed of tungsten carbide (WC) containing Co and Ni as binder phase components. A steel plate made by brazing a steel material to a cemented carbide plate is proposed.
[0003]
However, when brazing a large area like a mold, there is a problem of brazing, and the thermal expansion coefficients of cemented carbide and steel are greatly different. There is also a problem that stress is generated on the hard alloy side, and deformation or cracking occurs in the cemented carbide due to a temperature change or a slight impact during cooling from the brazing temperature or during use. Also, brazing has low bonding strength and lacks reliability.
[0004]
In order to withstand the press molding of hard materials, the surface layer of the mold steel material may be coated with a hard material using a surface coating method such as thermal spraying, CVD, PVD, plating, etc. to make it hard. Although it has been proposed, pores are likely to occur in thermal spraying, the coating thickness is limited in CVD and PVD, and there is no suitable hard material in plating, and in these surface coating methods, adhesion to the base material is not possible. The properties are not sufficient, and cracking and peeling are likely to occur when subjected to a pressing pressure, and none of them can achieve a satisfactory effect.
[0005]
In order to solve these problems, the surface layer portion is formed from a WC-based cemented carbide having a low content of binder phase components such as Co, and the WC After laminating the hard alloy in layers, it is sintered by energization to produce an integrated composite cemented carbide sintered body. The surface layer portion is improved in wear resistance and the inner layer portion with a high binder phase component content is made of stainless steel. Cemented carbide materials that can be directly welded to steel and carbon steel have been proposed. (Japanese Patent Laid-Open No. 7-300375)
[0006]
When the above cemented carbide material is applied as a mold material, satisfactory results can be obtained in terms of performance. However, after joining the cemented carbide material by brazing or welding, In addition, since the mold back plate made of steel or the like must be fixed by means such as welding and bolt fastening, the process for producing the mold becomes longer, and the mold requires strict dimensional tolerances. However, since the bonding process is performed twice, there is a problem in terms of dimensions.
[0007]
[Problems to be solved by the invention]
The present invention has been made in order to solve the above-mentioned problems, and its purpose is to improve the wear resistance of the press-molded surface and to fix it directly to the back plate of the mold by welding, bolt fastening or the like. Provided is a composite mold material that is a block for forming a press mold that can shorten the mold manufacturing process, a manufacturing method thereof, and a press mold formed from the composite mold block There is.
[0008]
[Means for Solving the Problems]
A composite mold material for press molding, which is a block for constituting a mold according to the present invention for achieving the above object, is a mold material obtained by integrally joining a tungsten carbide-based cemented carbide and a steel material, and has a surface layer. The portion is composed of a sintered body of at least three layers of tungsten carbide-based cemented carbide in which the content of the binder phase component is gradually increased from the surface layer portion to the inner layer portion, and the inner layer portion is formed in the inner layer portion. The first feature of the construction is that the steel materials are joined by a diffusion reaction.
[0009]
In the sintered body of the tungsten carbide-based cemented carbide, the surface layer portion includes a tungsten carbide-based cemented carbide having a binder phase component of 5 to 12%, and the intermediate layer includes a binder phase component of 10 to 20%. The second feature is that the tungsten carbide-based cemented carbide has three layers of tungsten carbide-based cemented carbide containing an inner layer portion of 20 to 40% of the binder phase component.
[0010]
The press-molding die according to the present invention has the above-described composite material for press-molding arranged in a predetermined shape with the surface layer portion as the upper surface and the steel material joined to the inner layer portion as the lower surface, and the steel material on the lower surface is fixed to the back plate. And forming a mold surface.
[0011]
Further, a method for producing a composite material for press molding, which is a block for constituting a mold according to the present invention, is a method in which a powder material is charged into a molding die and compressed by an upper punch and a lower punch. In addition, in the method of applying a voltage to the green compact through a punch and performing current sintering to form a sintered body, a steel material molded into a predetermined shape is placed on a lower punch set on a molding die, Three or more layers of tungsten carbide based cemented carbide powder adjusted so that the content of the binder phase component is reduced stepwise on the steel material are stacked and filled in order, then an upper punch is set, and the powder is compressed and energized. A sintered body is obtained by sintering, and the sintered body and the steel material are joined by a diffusion reaction.
[0012]
As shown in FIG. 1, the composite mold material for press molding of the present invention is obtained by integrally joining a tungsten carbide-based cemented carbide 2 and a steel material 3, and the tungsten carbide-based cemented carbide 2 is a sintered body. The surface layer portion 4 has a low content of binder phase components such as Co, Ni, Fe, etc., and at least the surface layer portion 4 in which the binder phase component content is gradually increased from the surface layer portion 4 to the inner layer portion 6; The intermediate layer portion 5 and the inner layer portion 6 are composed of three layers, and the steel material 3 is joined to the inner layer portion 6 by a diffusion reaction.
[0013]
In the present invention, WC—Co, WC—Ni, WC—Co—Ni, WC—Fe, and the like can be used as the tungsten carbide base cemented carbide. The sintered body 2 of the tungsten carbide base cemented carbide has at least three layers. The purpose of this is to reduce the difference in thermal expansion coefficient between the surface layer part 4 and the inner layer part 6 and to relieve the stress caused by the thermal expansion difference. The number of layers is determined based on the type, content, gold content of the binder phase component. It is determined according to the dimensions of the mold material.
[0014]
In the case of three layers, the tungsten carbide base cemented carbide in which the surface layer portion 4 contains 5 to 12% of the binder phase component, and the tungsten carbide base cemented carbide in which the intermediate layer 5 contains 10 to 20% of the binder phase component. The inner layer portion 6 is preferably a tungsten carbide base cemented carbide containing 20-40% of a binder phase component. With this configuration, the difference in thermal expansion between the surface layer portion 4 and the inner layer portion 6 is reduced to reduce stress. And the occurrence of deformation and cracking can be suppressed.
[0015]
The composite metal mold material 1 for press molding of the present invention is a small block serving as an element constituting the mold surface. As shown in FIG. 2, the composite metal mold material 1 for press molding has a surface layer portion 4 as an upper surface and an inner layer portion. The steel material 3 joined to 6 is arranged in a predetermined shape with the lower surface as a lower surface, and the lower surface steel material 3 is fixed to a back plate 8 such as a steel plate to form a mold surface 7.
[0016]
If the size of the composite mold material constituting the mold surface 7 is increased, the cemented carbide portion is likely to bend and may crack, and the cemented carbide portion may be non-uniformly sintered. However, in the present invention, the composite mold material is made into a small block, and this block is combined according to the shape of the mold, and the mold surface is configured to be fixed to the back plate. Therefore, as shown in 1A of FIG. The block can be repaired and replaced independently. In addition, when using the mold, the mold surface is composed of small blocks that are independent of each other, so the stress during the pressing process is dispersed and the mold surface is damaged by the stress during the pressing process. It can be avoided.
[0017]
The mold material block 1 and the steel plate of the back plate 8 are fixed by means such as welding and bolt fastening. However, since the fixed side of the composite mold material 1 with the back plate 8 is the steel material 3, the steel is welded together. Thus, it can be joined very easily by a conventional method. The bolt hole for the steel material 3 can be processed very easily, and the bolt fastening with the back plate steel plate is easily performed. In addition, in the case of bolt fastening, there is an advantage that a damaged mold material block can be removed from the mold surface, and its repair and replacement can be performed more easily. Moreover, it can be set as a more accurate structure by using in parallel the bolt fastening and the positioning method by a keyway.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Manufacture of the composite mold material of the present invention is performed by electric current sintering. The electric current sintering is inserted into the forming die 9 and the forming die 9 in a sintering furnace (not shown) provided in a vacuum vessel (not shown) as shown in FIG. A molding die composed of an upper punch 10 and a lower punch 11 is disposed, and a powder material M is inserted into the molding die 9, and a load P of, for example, 100 to 1000 kg / cm ² is applied to the punches 10 and 11. The powder material M is compressed from above and below, and a voltage is applied to the powder material M through the punches 10 and 11 to energize. The forming die is made of carbon material, cemented carbide or the like, and the punch is also made of carbon material, cemented carbide or the like.
[0019]
In order to manufacture the composite mold material according to the present invention, the lower punch 11 is set on the forming die 9, and the steel material 12 such as carbon steel previously formed and processed into a predetermined shape is placed on the lower punch 11. First, tungsten carbide (WC) filled with tungsten carbide (WC) -based cemented carbide powder 13 having a high content of binder phase components such as Co, Ni, Fe, etc., and further the content of the binder phase component is gradually reduced. After the base cemented carbide powders 14 and 15 are stacked and filled, the upper punch 10 is set and lightly pressed and attached to the electric sintering machine, the punch is operated and pressurized to a predetermined pressure, and then passed through the punches 10 and 11. Energize and heat-sinter the cemented carbide powder.
[0020]
A composite mold material in which a steel material is integrally bonded to a sintered body of cemented carbide made of tungsten carbide (WC) -based cemented carbide of three or more layers having different binder phase component contents by heating and sintering by energization. Is obtained. The cemented carbide part (inner layer part) to be joined to steel contains a large amount of binder phase components, and has high toughness and weldability (wetting) to steel. Bond firmly. On the other hand, since the surface layer portion has a small content of the binder phase component, it is possible to form a press-worked surface of a mold having excellent wear resistance.
[0021]
The thickness of each layer such as a surface layer portion and an inner layer portion in the cemented carbide after sintering is adjusted to be several mm to several tens mm depending on the use conditions. The thickness of the steel material is in the range of several mm to several hundred mm depending on the pressing pressure, the fixing method with the back plate, and the like. In addition, when using low carbon steel as a steel material, carbon steel containing 0.6% or more of carbon is used to reduce the amount of C (carbon) on the cemented carbide side and form the η phase during joining. Or alloy steel is preferable.
[0022]
The mold for press molding is required to have hardness that can withstand sliding wear, and is required to have abrasive wear resistance against movement of material powder, rigidity to withstand high loads, and bending resistance. According to this, it is possible to obtain a mold material that has a wear resistance several times to several tens of times that of heat-treated steel and can constitute a mold that can sufficiently withstand a high-pressure load during press working.
[0023]
【Example】
Examples of the present invention will be described below.
Example 1
Using the apparatus configuration shown in FIG. 3, a graphite cylindrical forming die having an outer diameter of 55 mm and an inner diameter of 30 mm is combined with an upper punch and a lower punch made of graphite, and first, the upper punch is set in the forming die. A WC-Co containing 10% thick carbon steel plate and 6%, 12% and 24% Co powder having an average particle size of 1 μm mixed with WC powder having an average particle size of 1.5 μm on the WC-Co. The cemented carbide powder was stacked and filled in three stages in the order of increasing Co content.
[0024]
After setting the upper punch and pressurizing with a pressure of 100 kg / cm ² so that the thickness of each of the packed layers is 5 mm, it is mounted on an electric current sintering machine, and further, 500 kg / cm ² is applied. It is compression-molded with pressure and energized (current: 2000 A), heated to a temperature of 1200 ° C. and held for 120 seconds to conduct current sintering, diameter 30 mm, height 17.5 mm (steel plate part: 10 mm thickness) ) Was obtained.
[0025]
The obtained composite sintered body was cut in half parallel to the pressing direction, the cut surface was polished on one side, and when the cut surface was observed with a microscope, no cracks or pores were observed, and the boundary portion of each layer was A complete diffusion bonding was observed. The hardness of the surface layer portion containing 6% Co of the composite sintered body was Hv 1750 kg / mm ² .
[0026]
Using the other of the cut composite sintered bodies, when the steel plate portion of the composite sintered body was arc welded to a stainless steel plate having a thickness of 30 mm using a Ni welding rod, welding was easy because the steel plates were welded together. Yes, joints with sufficiently high welding strength and impact strength were formed.
[0027]
Next, using a composite sintered body welded to a stainless steel plate, a wear resistance test was performed on the surface layer portion containing Co: 6%. For the abrasion resistance test, an # 80 alumina abrasive grain was placed on the polishing table using an Olsen-type abrasion tester, the polishing table was rotated at 50 rpm, and the surface layer portion of the composite sintered body was pressed with a load of 400 kg / cm ² by a dry method. When the amount of wear after 600 rotations was measured, the wear volume was about 3 × 10 ⁻⁴ cm ² (weight loss: about 5.1 mg), and the wear resistance was extremely excellent.
[0028]
【The invention's effect】
As described above, according to the present invention, since a die constituting block in which a cemented carbide sintered body and a steel material are metallurgically joined together is obtained, welding to the back plate of the mold, bolt fastening means Can be easily fixed via a steel material, and by arranging the blocks, it is possible to produce press-molding dies having various shapes. Since the surface layer portion of the cemented carbide sintered body that becomes the press-worked surface of the mold has a characteristic excellent in wear resistance, a mold surface having durability is formed. Even when the mold is damaged, it can be easily repaired by removing and repairing each block or replacing it.
[Brief description of the drawings]
FIG. 1 is a partially sectional perspective view showing a composite mold material (block) for press molding according to the present invention.
FIG. 2 is a perspective view showing a mold surface of a mold formed by arranging composite mold materials according to the present invention on a back plate.
FIG. 3 is a cross-sectional view of an essential part showing the arrangement of a mold in electric sintering.
[Explanation of symbols]
1 Composite mold material
1A Composite mold material for repair and replacement 2 Composite sintered body 3 Steel material 4 Surface layer portion 5 Intermediate layer portion 6 Inner layer portion 7 Mold 8 Back plate 9 Molding die
10 top punch
11 Bottom punch
12 Steel
13 Cemented carbide powder
14 Cemented carbide powder
15 Cemented carbide powder M Powder material

Claims (4)

A mold material in which tungsten carbide base cemented carbide and steel material are joined together. The surface layer portion has a low content of binder phase component, and the binder phase component content is gradually increased from the surface layer portion to the inner layer portion. Further, a composite metal for press molding, which is a block for forming a metal mold, comprising a sintered body of at least three layers of tungsten carbide base cemented carbide, wherein a steel material is joined to the inner layer portion by a diffusion reaction Mold material. The sintered body of the tungsten carbide-based cemented carbide has a tungsten carbide-based cemented carbide whose surface layer contains 5-12% (mass%, hereinafter the same) binder phase component, and the intermediate layer has a binder phase component of 10-20. 2. The composite mold material for press molding according to claim 1, wherein the tungsten carbide-based cemented carbide contains 3%, and the inner layer portion comprises three layers of tungsten carbide-based cemented carbide containing 20 to 40% of a binder component. . The composite mold material for press molding according to claim 1 or 2 is arranged in a predetermined shape with the steel layer bonded to the upper layer as the upper surface and the lower surface as the steel material bonded to the inner layer, and the steel material on the lower surface is fixed to the back plate to form the mold surface. A press-molding die characterized by comprising. A method in which a powder material is charged into a forming die and compressed with an upper punch and a lower punch to form a green compact, and a voltage is applied to the green compact through a punch to sinter current to form a sintered body. The tungsten carbide-based cemented carbide is prepared by placing a steel material formed in a predetermined shape on a lower punch set on a forming die, and adjusting the content of the binder phase component stepwise on the steel material. After three or more layers of powder are stacked and filled in order, the upper punch is set, and the powder is compressed and energized and sintered to form a sintered body, and the sintered body and the steel material are joined by a diffusion reaction. A method for producing a composite mold material for press molding, which becomes a block for constituting a characteristic mold.

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