JP2011157577A - Surface treatment liquid for steel for heat treatment and method of producing heat-treated steel using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface treatment liquid for obtaining heat-treated steel suppressing the occurrence of scale of steel due to heat treatment and having excellent weldability and coating adhesion and to provide a method of producing the heat-treated steel using the surface treatment liquid. <P>SOLUTION: The surface treatment liquid for steel for heat treatment contains an inorganic binder and metal pigment in a medium. The metal pigment contains 5-20 mass% zinc oxide powder, 10-25 mass% in total of copper foil and/or bronze foil and no high temperature oxidation resistant metal powder per total of metal pigment and the solid portion of the inorganic binder. The method of producing the heat-treated steel comprises a contact step of forming a liquid layer comprising the surface treatment liquid on the surface of a base material by bringing the surface treatment liquid into contact with the base material and a drying step of drying the based material on the surface of which the liquid layer comprising the surface treatment liquid is formed through the contact step to form a protective film on the surface of the base material. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a surface treatment liquid for a heat-treating steel material for forming a heat-treated steel material such as a hardened steel pipe, and a method for producing a heat-treated steel material using the same.
In the present invention, “heat-treated steel material” means a steel material that has been subjected to heat treatment, and “steel material for heat treatment” refers to a steel material that has undergone heat treatment and has not yet undergone heat treatment.

  As is well known, a metal strength member, reinforcement member, or structural member used in automobiles, various machines, and the like is required to have high strength, light weight, and small size. Conventionally, this type of member has been manufactured by welding a pressed product, punching a thick plate, and forging. However, there is a limit to reducing the weight and size of the members manufactured by these manufacturing methods, and the realization thereof is not easy.

  In recent years, in order to enable these problems, a processing method called hydroform disclosed in Non-Patent Document 1, for example, has been developed and applied to automobile parts. Hydroform has a complicated shape by setting the material pipe in the mold, introducing a high-pressure machining fluid into the pipe to bulge the pipe, and aligning the outer diameter of the pipe with the mold. The automobile parts are molded.

  In other words, a surplus part called a flange part is unavoidably necessary at the welded part of a welded product by press working, which causes an increase in weight, whereas hydroform uses a pipe as a raw material. Since it is possible to integrally mold parts having complicated shapes while omitting the flange portion, the weight of the automobile parts can be reduced.

  However, because hydroforming is (a) cold work, high strength members such as 780 MPa or more have inherently low ductility of the material, so there is a limit to molding complex-shaped automobile parts. (B) Generally, three steps of bending, preforming and hydroforming are required, and the process becomes relatively complicated. (C) The hydroforming machine is large and relatively expensive. There is.

In response to these problems, the present applicant has previously disclosed an invention relating to a bending apparatus according to Patent Document 1. FIG. 2 is an explanatory view showing an outline of the bending apparatus 0. As shown in FIG.
As shown in FIG. 2, the present invention bends downstream of the support means 2 while feeding the steel pipe 1 supported by the support means 2 so as to be movable in the axial direction from the upstream side to the downstream side by the feeding device 3. When a bending member is manufactured using a bending method for performing processing, the steel pipe 1 is rapidly heated to a temperature range in which the steel pipe 1 can be partially hardened by the high-frequency heating coil 5 downstream of the support means 2, and the high-frequency heating coil 5. The steel pipe 1 is rapidly cooled by a water-cooling device 6 arranged downstream of the pipe, and the position of the movable roller die 4 having at least one pair of roll pairs 4a that can be supported while feeding the steel pipe 1 is changed in two dimensions or three dimensions. Since bending is performed by applying a bending moment to the heated portion of the steel pipe 1, it is possible to manufacture a bending member with high work efficiency while ensuring sufficient bending accuracy.

  According to the present invention, the bent portion and the quenched portion that are bent two-dimensionally or three-dimensionally are surely intermittently or continuously directed in the longitudinal direction and / or in the circumferential direction in the plane intersecting the longitudinal direction. It is possible to manufacture the bending member having high working efficiency while ensuring sufficient bending accuracy.

  According to the invention disclosed in Patent Document 1, a high-strength automobile part such as 780 MPa or more can be integrally formed by a simple process using a relatively inexpensive molding machine, which is extremely beneficial.

  However, the present inventors have made extensive studies to further improve the present invention, and in this invention, the steel pipe 1 is rapidly heated to a temperature range that can be partially quenched by the high-frequency heating coil 5. It has been clarified that oxide scale is inevitably generated on the surface of the steel pipe 1 and oxide scale remains on the outer surface of the bending member to be manufactured. For this reason, there exists a problem that the surface property of a bending member deteriorates and corrosion resistance after coating also falls. In addition, since oxide scale is generated not only on the outer surface of the steel pipe 1 but also on the inner surface, a decrease in the corrosion resistance of the manufactured bending member is inevitable.

  In order to suppress the generation of such steel scales, a technique for utilizing a steel material whose surface is coated with plating or the like has been developed. In an example of hot press forming, for example, Patent Document 2 discloses a method using an Al-plated steel sheet, and Patent Document 3 discloses a method using a Zn-based or Zn-Al-based plated steel sheet. Patent Document 4 discloses a coating layer containing an organic silane as a binder, and Patent Documents 5 and 6 include a conductive metal pigment (Al, Fe) in an organic binder (polyurethane, acrylic, etc.) or an organic-inorganic binder. Etc.) or a method using a steel sheet provided with a coating layer containing a non-metallic pigment, a lubricant or the like. Moreover, in the process in which the steel sheet is formed by cold pressing and then heated and cooled by the mold, it is not intended to suppress the scale, but the technique using the surface-treated steel sheet provided with a lubricating coating as in Patent Document 7 There is also.

International Publication WO2006 / 093006 Pamphlet JP 2000-38640 A JP 2001-353548 A International Publication WO2006 / 040030 Pamphlet International Publication WO2007 / 76766 Pamphlet International Publication WO2007 / 76769 Pamphlet JP 2005-305539 A

Automotive Technology Nov. 57, no. 6 (2003) 23-28

  As described above, the technology for forming a film for suppressing the generation of steel scale can be divided into plating and technology for forming a coating agent. However, it is possible to form a film with simpler equipment than plating.

  On the other hand, in the case of drug application, the conductivity of the formed film is usually low, so weldability can be a problem. In addition, chemical conversion processability as a coating base and resultant coating adhesion can also be a problem. In this regard, in the technologies disclosed in Patent Documents 4 to 6, improvement in weldability and the like is achieved by providing a coating layer containing a conductive metal pigment (Al, Fe, etc.) or a non-metal pigment. ing. This coating layer is formed from a treatment liquid (paint) containing the metal pigment. However, the above-described weldability and paint adhesion are not practically sufficient simply by dispersing a metal pigment or the like. Further, the treatment liquid (paint) containing a metal pigment has a large difference in specific gravity between the binder or solvent and the metal pigment, and the pigment is likely to settle. Therefore, strong agitation and circulation are required even during painting, workability during painting is deteriorated, and the performance of the obtained surface-treated steel sheet may not be stable.

  In the present invention, by forming a film on the surface of a steel material before heat treatment such as the processing method according to the invention disclosed in Patent Document 1, it is possible to suppress the generation of steel scale due to the heat treatment, A surface treatment liquid for obtaining a heat-treated steel material having excellent coating adhesion, and in particular, providing a surface treatment liquid that is easy to handle, in which metal pigments in the treatment liquid are difficult to settle, and heat treatment using the surface treatment liquid It aims at providing the manufacturing method of steel materials.

The present invention provided to solve the above problems is as follows.
(1) A surface treatment liquid for a heat-treating steel material containing an inorganic binder and a metal pigment in a medium, wherein the metal pigment is based on the total amount of the metal pigment and the solid content of the inorganic binder. Zinc oxide powder is contained in an amount of 5% by mass to 20% by mass, and one or two metal foils selected from copper foil and brass foil are contained in an amount of 10% by mass to 25% by mass, and no high-temperature oxidation resistant metal powder is contained. A surface treatment liquid characterized by that.

  (2) Furthermore, the inorganic solid lubricant is contained so that the content of the inorganic solid lubricant in the coating obtained from the surface treatment liquid with respect to the total coating solid content is 5% by mass or more and 20% by mass or less. The surface treatment liquid according to (1) above.

  (3) A contact step of bringing the surface treatment liquid described in (1) or (2) above into contact with a base material to form a liquid layer made of the surface treatment liquid on the surface of the base material, and the contact step. A method for producing a steel material for heat treatment, comprising: a drying step of drying a substrate on which a liquid layer made of a surface treatment liquid is formed and forming a protective film on the surface of the substrate.

(4) A heat treatment characterized by comprising a heat treatment step of heating and quenching the steel for heat treatment produced by the production method described in (3) above to a temperature of Ac ₃ or higher. Steel manufacturing method.

(5) Heating the steel for heat treatment to a temperature of Ac ₃ points or higher is performed at a rate of temperature increase of 100 ° C./second, and the time for which the heated steel for heat treatment is maintained at a temperature of Ac ₃ points or higher The production method according to (4), wherein the production method is within 1 second.

(6) The manufacturing method according to the above (5), wherein the heat treatment steel material is shaped before the heat treatment steel material heated to a temperature of _three or more points of Ac is cooled for quenching.

(7) While feeding the steel for heat treatment in the longitudinal direction, the steel for heat treatment is heated to a temperature of Ac ₃ or higher by a heating device arranged at a first position apart from the steel for heat treatment to be sent. The heat treatment steel material is quenched by spraying a cooling medium onto the heat treatment steel material by a cooling device disposed at a second position downstream of the first position in the feed direction of the heat treatment steel material. The manufacturing method according to (5) above.

(8) The heat treatment steel material according to the above (7), wherein the heat treatment steel material that has undergone shape processing is obtained by deforming the steel material for heat treatment whose deformation resistance is reduced by being heated to a temperature of Ac ₃ or higher at the first position. Production method.

  According to the present invention, even if the heat treatment represented by the processing method disclosed in Patent Document 1 is performed, the heat treatment steel material that can suppress the generation of steel scale due to the heat treatment and has excellent weldability and paint adhesion. Can be provided.

FIG. 1 is an explanatory view schematically showing a configuration of a hardened steel material manufacturing apparatus according to a processing method disclosed by Patent Document 1 which is an example of heat treatment according to the present invention. FIG. 2 is an explanatory diagram showing an outline of the bending apparatus disclosed in Patent Document 1. As shown in FIG.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings.
1. Base Material A base material that is a target member that is subjected to surface treatment using the surface treatment liquid according to the present invention may be a steel material that is not subjected to surface coating such as plating (hereinafter also referred to as “bare steel material”). In order to improve the corrosion resistance based on the sacrificial anticorrosive action, a steel material plated with zinc, aluminum or an alloy thereof (hereinafter also simply referred to as “plated steel material”) may be used. In the present invention, bare steel and plated steel are collectively referred to as “steel”.

  Note that zinc, aluminum, and the like, which are the main components of the plating material formed on the surface of the plated steel material and play a central role in sacrificial corrosion protection, evaporate at a relatively low temperature. For this reason, a surface treatment using the surface treatment liquid according to the present invention is performed on the plated steel material, and a film (hereinafter referred to as a protective film formed by the surface treatment according to the present invention) is formed on the plated steel material by the surface treatment. ") Is formed, the protective film suppresses evaporation of zinc, aluminum, and the like from the plated steel material during heat treatment. Moreover, although these elements are also elements that are easily oxidized, the protective coating suppresses excessive oxidation of the plating components in the heat treatment. The protective film which concerns on this invention contributes to the improvement of the corrosion resistance of heat-treated steel materials by these inhibitory actions.

  The chemical composition of the bare steel material is not particularly limited, but is preferably a composition that can achieve high strength by heat treatment (quenching). Although it depends on the required strength, for example, C is preferably 0.10 to 0.40% by mass, and Mn is 0.1 to 3.0% by mass and / or Cr is 0.1 to 1%. 0.0% by mass or B: 0.0001 to 0.01% by mass may be contained. Further, elements such as Ni, Mo, V, Ti, Nb, etc., that enhance the hardenability and the strength after quenching may be contained.

2. Surface treatment liquid The surface treatment liquid according to the present invention contains an inorganic binder and a metal pigment in a medium, and the inorganic binder has a characteristic A to be described later. (A) component and (b) component are included, and (c) is not included.

(A) 5 to 20% by mass of zinc oxide powder as a mass ratio with respect to the total amount of the metal pigment and the solid content of the inorganic binder (hereinafter also referred to as “solid content concentration”),
(B) One to two metal foils selected from copper foil and brass foil (hereinafter also referred to as “brass foil”) as a solid content concentration of 10 to 30% by mass,
(C) High temperature oxidation resistant metal powder Each component will be described in detail below.

(1) Inorganic binder The surface treatment liquid of the present invention contains an inorganic binder provided as a binder component for dispersing a metal pigment. As a suitable example of the surface treatment liquid composed of such a binder component, G-90 (silica-based binder) manufactured by Nippon Sheet Laboratory Co., Ltd. may be mentioned.

  As the binder component, it is preferable that film formation at a low temperature is possible and stability is not impaired even when heated to a high temperature. That is, if decomposition or dehydration of the film occurs during high temperature heating, the base steel or plating may be oxidized to form an oxide with poor adhesion.

  Table 1 shows the weight loss (mostly dehydration or deoxygenation) after applying various binder components on a Cu plate and baking at 150 ° C for 10 minutes, followed by heating at 850 ° C and 950 ° C for 10 minutes. Is estimated). G-90 mentioned above as a preferred example had a weight loss of about 3% by mass even when heated to 950 ° C. An acceptable weight loss standard is 10% by weight. Accordingly, it is considered that G-90 is almost completely formed by baking at 150 ° C. and is relatively stable even when heated to a high temperature.

(2) Metal pigment (a) Zinc oxide powder The surface treatment liquid contains at least the following metal pigment, (a) zinc oxide powder and (b) brass foil, and (c) high temperature oxidation resistant metal powder. Does not contain. These components are described below.

  Zinc oxide is not strictly a metal, but in the present invention, zinc oxide powder is classified as a metal pigment for convenience. Moreover, in the following description, the content of the metal pigment is indicated by the solid content concentration (% by mass) unless otherwise specified.

  If the heat-treated steel material is, for example, an automobile part, it is assembled into a vehicle body, subjected to chemical conversion treatment, and then painted by electrodeposition coating or the like. By containing zinc oxide powder in the surface treatment liquid, a chemical conversion treatment layer is easily formed on the surface of the heat treated steel material even after the heat treatment. For this reason, the adhesiveness of heat-treated steel materials and coating (coating film) improves. The preferable content of zinc oxide is 5 to 20% by mass. When the content is less than 5% by mass, it is difficult to obtain the effect of improving the adhesion to the coating film, and when the content exceeds 20% by mass, the content of other metal pigments is relatively lowered. As a result, problems are likely to occur. A particularly preferable content is 6 to 14% by mass.

  There is no limitation on the shape of the zinc oxide powder. However, when the particle size (sphere equivalent diameter) is excessively large, it may be difficult to suppress sedimentation even if (b) a brass foil or the like is contained. In addition, the tendency of the metal pigment to protrude from the protective coating is particularly strong, and the possibility of the pigment dropping off may be increased, or the design may be significantly reduced. Accordingly, the average value of the sphere converted diameters of these metal pigments is preferably less than 70 μm, and particularly preferably 30 μm or less.

(B) Brass foil, etc. Since the specific gravity of the above (a) zinc oxide powder is considerably larger than that of the binder component and the solvent (water, solvent), it is easy to settle in the surface treatment liquid. Therefore, the surface treatment liquid according to the present invention suppresses sedimentation by containing a metal foil, specifically, a brass foil. By including this foil-like metal powder, the viscosity increases regardless of the concentration of the inorganic binder in the surface treatment liquid, and it is thus presumed that it is difficult to settle. Further, the inclusion of brass foil or the like functions as an energization path at the time of spot welding, but further, the appropriate welding current range (details will be described later) that these foils are made of the same or close material as the material Cu of the welding tip. It is speculated that it works favorably in ensuring.

  A preferable content of brass foil or the like is 10 to 25% by mass. When the content is less than 10% by mass, it is difficult to obtain the effect of sedimentation suppression. When the content is more than 25% by mass, the content of other metal pigments is relatively lowered, which causes a problem. It tends to occur. A particularly preferable content is 15 to 25% by mass. Moreover, it is preferable that a foil-like shape shall be 3-10 micrometers in average thickness of 2 micrometers or less and an average foil diameter (foil long diameter). The aspect ratio (foil diameter / thickness) is preferably about 3 to 10. If the thickness is too large or the aspect ratio is too small, the function of preventing sedimentation is deteriorated. Moreover, when the foil diameter is too large or the aspect ratio is too large, the foil is easily broken, and as a result, there are many metal foils that do not have an appropriate shape.

(C) High-temperature oxidation-resistant metal powder The surface treatment liquid according to the present invention does not contain a high-temperature oxidation-resistant metal powder. Here, the “high temperature oxidation resistant metal powder” refers to a powder made of a metal that hardly changes in quality even in a heat treatment heated to about 800 ° C. or more, specifically, has a high melting point and is difficult to oxidize, Cr, Ni, Examples include W, V, Mo, Zr, Ti and Co, and powders of these alloys, and examples in which Cu is further included as an alloy component.

  If the heat-treated steel material is, for example, an automobile part, it is assembled to the vehicle body mainly by spot welding or the like. It was initially thought that spot weldability would be improved by including high temperature oxidation resistant metal powder in the surface treatment solution. This is because these metal powders remain as they are on the surface of the steel material after the heat treatment, and it is assumed that welding can be performed by acting as a current-carrying site during spot welding.

  However, if the surface treatment liquid containing the above (a) and (b) further contains a high-temperature oxidation resistant metal powder, a welding current range (hereinafter referred to as “appropriate”) that can form an appropriate nugget diameter without generating dust or welding. It became clear that the welding current range ") does not exist or is extremely narrow.

  An example when the appropriate welding current range exists and an example when it does not exist are shown in FIG. FIG. 1 shows the relationship between the welding current during spot welding of the heat-treated steel and the nugget diameter formed in No. 10 (FIG. 1 (a)) and No. 17 (FIG. 1 (b)) of Examples to be described later. Or it shows the occurrence of welding. In any case, since the thickness of the welded portion of the base material is 0.7 mm, the appropriate nugget diameter d is 3.8 mm or more.

  In No. 10 which does not contain Ni powder, spot welding having an appropriate nugget diameter is achieved in the range of 6 kA or more and less than 8 kA without generating dust or welding. On the other hand, in No. 17 containing Ni powder, strength welding occurs before reaching the welding current for forming an appropriate nugget diameter, and there is no appropriate welding current range.

(3) Medium The medium is not limited as long as it is stable as a surface treatment liquid, in particular, an inorganic binder can be stably dissolved or dispersed. From the recent environmental demands, water or a medium containing water as a main component is preferable, and alcohol or other additives may be added as necessary.

(4) Other components The surface treatment liquid according to the present invention may have other components such as a lubricant and a surfactant in addition to the above inorganic binder and metal pigment to the extent that the performance is not impaired. Good. These can be appropriately selected from known ones.

  Examples of solid lubricants include inorganic lubricants such as graphite and molybdenum disulfide. The content of the inorganic solid lubricant in the protective coating obtained from the surface treatment liquid is preferably 5% by mass or more and 20% by mass or less with respect to the total solid content of the coating.

  Further, for adjusting the viscosity of the paint, silicate (aluminum, magnesium, sodium alone or two or more complex salts) clays (smectite, hectorite, etc.), titanium oxide and silica may also be included.

3. Steel Material for Heat Treatment The steel material for heat treatment according to the present invention has the above protective coating on the surface thereof.
In the protective coating, the above-described inorganic binder component is formed and crosslinked, and the above-described solid lubricant blended as necessary is dispersed in the above-described metal pigments (a) and (b). It becomes.

  Since these metal pigments can have a particle size of about 30 μm as described above even in the preferred embodiment, the protective coating has not only a structure in which the pigment is embedded in the binder layer but also a structure in which the pigment protrudes from the binder phase. Sometimes it becomes. In the present invention, the thickness of the binder portion when the protective coating is observed from the cross section of the protective coating is defined as the thickness of the protective coating.

  The thickness of the protective coating based on this rule is preferably 3 μm or more from the viewpoint of fulfilling the basic function of suppressing the generation of scale, and is preferably 15 μm or less in consideration of weldability. Therefore, the thickness of the protective coating is particularly preferably 4 to 10 μm.

  Since the steel for heat treatment according to the present invention has an appropriate protective coating, the heat-treated steel obtained by heat-treating the steel can ensure a sufficient appropriate welding current range in spot welding. For this reason, it is excellent in workability | operativity of a welding process, and a welding defect does not generate | occur | produce easily.

4). A heat treatment steel material and a method for producing a heat treatment steel material The method for producing a heat treatment steel material according to the present invention comprises a protective film forming step for forming a protective film on a surface of a steel material, that is, a base material made of a bare steel material or a plated steel material. Prepare.

  Moreover, the manufacturing method of the heat-treated steel material which concerns on this invention is equipped with the heat processing process which heat-processes with respect to the steel material for heat processing which has the protective film obtained by the manufacturing method of said heat-processing steel material, and makes it heat-treated steel material.

(1) Protective film forming step In order to obtain a heat-treating steel material having a protective film formed thereon, the surface treatment liquid according to the present invention is brought into contact with the substrate and the surface of the substrate is made of the surface treatment liquid according to the present invention. What is necessary is just to implement the contact process which forms a liquid layer, and the drying process which forms a protective film, drying the base material in which this liquid layer was formed, and volatilizing the medium contained in a liquid layer.

  Prior to carrying out the contacting step, the metal pigment is uniformly dispersed in the treatment liquid by stirring or the like in advance. Thereby, if it is the surface treatment liquid of this invention, isolation | separation and sedimentation of a surface treatment liquid can be suppressed over a comparatively long period, and it is not necessary to continue strong circulation during the operation | work of a contact process. In addition, the surface of the substrate to be subjected to the contact process may be washed with alkali or the like, and physical treatment such as shot blasting or chemical conversion treatment is performed on the substrate for the purpose of improving the adhesion of the film. A chemical treatment such as

  The specific means of the contact process is arbitrary. Known methods such as spraying, roll coating, bar coating, and dipping may be used. The contact conditions (temperature of the surface treatment liquid, contact time, etc.) are not particularly limited. The liquid temperature may be room temperature. Since the surface treatment liquid according to the present invention is not a reaction type treatment liquid, the contact time hardly affects the protective film to be formed.

  In the drying process, the substrate on which the liquid layer made of the surface treatment liquid is formed on the surface through the contact process is dried. Thereby, a protective film is formed on the surface of the substrate. Since the medium contained in the surface treatment liquid only needs to be volatilized and dried sufficiently, strict temperature control as in the case of manufacturing a so-called coated steel sheet is not necessary. For example, it may be dried by heating to about 150 to 200 ° C. in an oven.

  When the steel material for heat treatment is a steel pipe, for example, it is simple to use a surface-treated steel sheet in which a surface treatment liquid is applied to the steel sheet to form a protective coating, thereby forming a welded steel pipe. As described above, when the surface-treated steel sheet is used as a welded pipe, the protective film is incomplete in the welded portion, so that a protective film may be formed on the welded portion as necessary. Further, a method may be considered in which a steel plate before film formation is formed into a welded pipe and then coated by immersing it in a surface treatment solution.

(2) Heat treatment step The heat treatment steel material having a protective film formed on the surface thereof by the above-described protective film formation step is heat treated to obtain a heat treated steel material.

The heating temperature in the heat treatment step is set to Ac ₃ points or more of the steel material to be the base material, maintained for a predetermined time in a state of Ac ₃ points or more, and then cooled and quenched. The heating temperature is preferably 50 ° C./s or higher. Rapidly raising the temperature is not only advantageous for productivity but also shortens the time in the high temperature range, so if the substrate is a plated steel material, the alloying of the plating layer and the steel will progress much. A layer derived from the plating layer tends to remain, which is advantageous for corrosion resistance. As shown in the specific examples described later, when heat treatment is performed while feeding a steel pipe in the longitudinal direction, for example, high frequency induction heating is suitable. Also, it is preferable that the period of time in which Ac is _three or more points be as short as possible within the range where the desired mechanical characteristics can be obtained. 1 second or less is particularly preferable. When hot working is performed, it is performed while the steel material is at Ac ₃ point or higher. Cooling is performed rapidly so that a predetermined quenched structure and performance can be obtained.

(3) An example of a specific method for manufacturing a heat-treated steel material Hereinafter, a case where the manufacturing method according to the present invention is applied to the processing method disclosed in Patent Document 1 will be described. In the following description, the case where the steel material for heat treatment is a steel pipe that is a representative example of a hollow member having a closed cross-sectional shape will be described as an example.

  First, a manufacturing apparatus used in this manufacturing method will be described. FIG. 1 is an explanatory view schematically showing a configuration of a manufacturing apparatus 11 for a steel pipe 10 that is a heat-treated steel material according to the processing method disclosed in Patent Document 1. As shown in FIG. However, the configuration related to (bending) processing is omitted.

The manufacturing apparatus 11 includes a feeding device 12, a heating device 13, and a cooling device 14. These components will be described.
[Feeding device 12]
The feeding device 12 may be any device that can feed the steel pipe 10 in its longitudinal direction, and is not limited to a specific device.

  In the manufacturing apparatus 11 shown in FIG. 1, the feeding device 12 includes a chuck 18 that is installed by being inserted into the rear end portion of the feeding direction of the steel pipe 10 (in the direction of the white arrow in FIG. 1), and the chuck 18 that is installed in the steel pipe 10. A first industrial robot (not shown) that is movably supported in the feed direction, and a chuck 19 that is inserted and installed in the rear end of the feed direction of the steel pipe 10 (the direction of the white arrow in FIG. 1); The chuck 18 is constituted by a second industrial robot (not shown) that supports the steel pipe 10 so as to be movable in the feed direction.

Instead of the first industrial robot and the second industrial robot, a so-called double-arm type industrial robot having two manipulators may be used.
Further, instead of the first industrial robot, a known feeding device such as a ball screw may be used. In this case, in order to manufacture the bending member, a support device composed of a pair of rollers or the like may be disposed in order to position the steel pipe 10 between the feeding device and the heating device 13 at a predetermined position while feeding it. desirable.
The feeding device 12 is configured as described above.

[Heating device 13]
The heating device 13 is a device for heating the steel pipe 10 to a quenchable temperature range by being spaced apart from the steel pipe 10 to be sent by a predetermined distance and disposed at a first position A in the feed direction of the steel pipe 10.

The heating device 13 has the ability to rapidly heat the steel pipe 10 to a temperature of Ac ₃ or higher of the steel pipe 10. As an example of such a heating device 10, the manufacturing apparatus 11 includes a high-frequency heating device.

The heating device 13 is movably supported by a third industrial robot (not shown) as a unit with a cooling device 14 described later.
The heating device 13 is configured as described above.

[Cooling device 14]
The cooling device 14 is heated to a temperature of, for example, Ac ₃ points or more by spraying a cooling medium 20 (for example, cooling water) onto the steel pipe at a second position B downstream of the first position A in the feed direction of the steel pipe 10. It is an apparatus for quenching the steel pipe 10 by rapidly cooling the formed steel pipe 10.

As described above, the cooling device 14 is integrally supported with the heating device 13 and is movably supported by a third industrial robot (not shown).
The cooling device 14 is configured as described above.

  In order to manufacture the bending member using the manufacturing apparatus 11 having the above configuration, the position of the chuck 18 supported by the first industrial robot and the position of the chuck 19 supported by the second industrial robot The positions of the heating device 13 and the cooling device 14 that are integrally supported by the third industrial robot may be controlled in a three-dimensional manner. That is, a bending member having a desired shape can be manufactured by appropriately controlling the positions of the portions on both sides of the portion 21 where the deformation resistance is greatly reduced by being heated by the heating device 13.

  In addition, when using well-known feeders, such as a ball screw, for example instead of the 1st industrial robot, as mentioned above, while sending the steel pipe 10 between this feeder and the heating apparatus 13, it is predetermined. Since a support device composed of a pair of rollers or the like for positioning is arranged, the position of the chuck 19 supported by the second industrial robot is integrated with the third industrial robot as necessary. What is necessary is just to control the position of the heating apparatus 13 and the cooling device 14 to be supported in three dimensions.

Thus, according to the present invention, a heat-treated steel material that has been quenched and a bent member that is a heat-treated steel material having a predetermined bent shape can be manufactured.
In the present invention, the steel pipe provided for the manufacturing apparatus 11 is a heat-treating steel material that has undergone the protective film formation step, and the heating / cooling treatment performed by the heating device 13 and the cooling device 14 is the heat treatment step. It corresponds to.

In addition, the bending member manufactured by said manufacturing apparatus is applicable with respect to the uses (i)-(vii) illustrated below, for example.
(I) Automotive strength members such as lower arms and brake pedals of automobile suspensions;
(Ii) Reinforcing members such as various types of automobile reinforcements and braces,
(Iii) Automotive structural members such as bumpers, door impact beams, side members, suspension mount members, pillars, side sills,
(Iv) Frames for bicycles and motorcycles, cranks (v) Reinforcing members for vehicles such as trains, cart parts (cart frames, various beams, etc.)
(Vi) Frame parts such as hulls, reinforcing members,
(Vii) Home appliance strength member, reinforcing member or structural member

  Hereinafter, the present invention will be further described using experimental examples. In addition, although the following experiment example is an experiment using a steel plate instead of a steel pipe, since the heat history of quenching is the same when using a steel plate, the same result is obtained.

1. Preparation of surface treatment liquid (1) Binder As a binder, a ceramic coating agent (Ceramica; G90) manufactured by Nippon Sheet Laboratory Co., Ltd. was used.

(2) Each component The following components (a) to (d) were prepared in the binder to prepare a surface treatment liquid.
(A) Zinc oxide powder: 1 type of zinc oxide manufactured by Honjo Chemical Co., Ltd.
(B) Brass foil or the like: One of the following brass foils (Fukuda Metal Foil Powder Co., Ltd.) was used. In all cases, the alloy composition was an alloy of 75 mass% copper and 25 mass% zinc.
No. 7000: Average particle size 5 μm
No. 700: Average particle size 7 μm
(C) High temperature oxidation resistant metal powder: The following Ni powder was used.
SNP-122E manufactured by Sumitomo Metal Mining Co., Ltd .; average particle size of about 1μm
(D) Graphite: The following materials were used.
Model number manufactured by Nippon Graphite Industries Co., Ltd .; AP (average particle size 7μm)

2. Production of test piece A test piece was produced by the following method.

First, C: 0.21 mass%, Si: 0.2 mass%, Mn: 1.3 mass%, P: 0.005 mass%, S: 0.001 mass%, Cr: 0.2 mass%, B: An alloyed hot-dip galvanized steel sheet having a chemical composition containing 0.0005% by mass (100 × 200 mm, thickness 1.6 mm, plating adhesion amount: about 45 g / m ² per side) was subjected to alkaline degreasing, and then Table 2 A paint sample blended and dispersed with the composition of 1 was applied on both sides with a bar coater aiming at a thickness of 3 to 12 μm. A coating sample mixed and dispersed in the composition of Table 3 was also applied to both sides of a non-plated steel material of 50 × 150 mm and thickness 1.6 mm having the same base material component with a bar coater with a thickness of 3 to 12 μm.

  The coated steel sheet was dried in an oven at 150 ° C. to form a protective film. The thickness of the protective coating of the test piece obtained in this way was measured by embedding the test piece with a resin, polished, and observed by cross-sectional SEM observation. The thickness of the protective coating of the test piece obtained in this way was measured by embedding the test piece with a resin, polished, and observed by cross-sectional SEM observation.

Then, it prepared to the test piece 40 * 200 mm in which this protective film was formed, and water-cooled immediately after the steel plate temperature reached | attained 950 degreeC by the electric heating method which carries out resistance heating by sending an electric current from the both ends of a steel plate. At this time, the heating rate up to 900 ° C. was an average of 100 ° C./s, and the time during which the steel material was in the temperature range of Ac ₃ points or higher was about 1 second. The heating atmosphere at this time was an air atmosphere. Hereinafter, this process is referred to as “simulated heat treatment”.

3. Evaluation test method (1) Surface peel resistance A cello tape (registered trademark, manufactured by Nichiban Co., Ltd.) is applied to the surface of the test piece after the simulated heat treatment on which the protective film was formed. Measure the area of the attached peeled part (the peeled material derived from the protective coating and the oxide and peeled material derived from the plated steel are not distinguished), and determine the ratio (peeled area ratio) to the peeled area. Evaluation based on the criteria.

○ (Pass): 0% (No peeling)
X (failed): over 0% (with peeling)

(2) Paint adhesion A known chemical conversion solution (surface conditioning treatment PL-Z, manufactured by Nihon Parkerizing Co., Ltd., zinc phosphate treatment solution, manufactured by Nihon Parkerizing Co., Ltd.) on the surface of the test piece after the simulated heat treatment on which the protective film was formed. PBL3080), zinc phosphate treatment according to the chemical conversion treatment conditions, and then electrodeposition coating of Uemura Kogyo Co., Ltd. (New Peyton Black E FU-NPB) is applied by slope energization with a voltage of 200V, baking temperature The coating was baked at 170 ° C. for 25 minutes.

  11 cuts that reach the base with a cutter knife were placed on the painted surface at intervals of 1 mm to form 100 squares in a square area of 10 mm × 10 mm. Subsequently, a peel test was performed using a polyester tape (manufactured by Nichiban Co., Ltd.), and the number of peeled masses was evaluated.

○: 0 to 5 Δ: 6 to 30 ×: 31 to 100 ○ is acceptable, and Δ and × are unacceptable.

(3) Spot weldability The performance when spot-welding a test piece after simulated heat treatment to a 0.7 mm cold-rolled steel sheet was evaluated. At this time, the surface of the test piece on which the protective coating was formed was overlaid on the cold-rolled steel sheet. In the welding machine (single-layer AC stationary spot welding machine), DR type Φ6R40 was used as an electrode. The applied pressure is 200 kgf, and the energization condition is
Squeeze; 60 cycle-wave front 0 cy-welding current 12 cy-holding 10 cy
It was. The welding current is increased at a pitch of 5 kA to 0.2 kA to determine whether or not dust has occurred in welding at each welding current, and whether or not welding has occurred after welding, and By measuring the nugget diameter in the test piece, it was determined whether or not the welding current was in the proper welding current range. Note that “welding” in this case refers to welding in which the welding member adheres to the welding electrode and lifts when only the upper welding electrode is lifted. The nugget diameter d (mm) is
d ≧ 4.5 × t ^1/2
When satisfying, it was decided that an appropriate nugget diameter was formed. Here, t (mm) is the thickness at the welded portion of the substrate, and in this example, a thickness of 0.7 mm of the cold-rolled steel sheet was adopted. Therefore, the appropriate nugget diameter d is 3.8 mm or more.
Based on this determination result, the appropriate welding current range was obtained, and the weldability was evaluated according to the following criteria.

A: The welding proper current range is 0.5 kA or more. B: The welding proper current range is 0.5 kA or less. X: The welding proper current range did not exist. A and B were acceptable, and x was rejected.

4). Evaluation results Table 2 and Table 3 show the results of the above evaluations for each test piece.

As shown in Table 2, when Ni powder, which is a high-temperature oxidation-resistant metal powder, is contained, it becomes difficult to ensure an appropriate welding current range of 0.5 kA or more.
In addition, although the test piece of the test number 1 in which the protective film which concerns on a reference example is not formed gave the favorable result in this evaluation, there exists a possibility that it is inferior to corrosion resistance as mentioned above. The following experiment was conducted to confirm this point.

  No. 1 (reference example) and No. 1 Chemical conversion treatment and electrodeposition coating were performed on the test specimens prepared in the same manner as 10 and 11 (both examples of the present invention) by the method used in the above-described evaluation of coating adhesion. These test pieces were subjected to a cross cut having a length of 30 mm, and a composite corrosion test (JASO test) defined by JIS was performed for 180 cycles on the test piece having the cross cut. Specifically, in this combined corrosion test (JASO M609-91 method), the following (1) to (3) were repeated 180 times as one cycle.

(1) Salt spray: 2 hours (5% NaCl, 35 ° C.),
(2) Drying: 4 hours (60 ° C.), and (3) Wetting: 2 hours (50 ° C., relative humidity 95% or more).

The maximum corrosion depth of the cross cut portion in the test piece after the corrosion test was measured. The results are shown in Table 4.
No. in which the surface treatment according to the present invention was performed. The No. 10 and 11 materials were untreated No. The corrosion depth was small compared to one material. No. It is presumed that materials 10 and 11 have improved corrosion resistance due to the anti-oxidation effect of galvanization by the protective coating.

DESCRIPTION OF SYMBOLS 10 Hardening member 11 Manufacturing apparatus 12 Feed apparatus 13 Heating apparatus 14 Cooling apparatus 15 Scale production | generation prevention gas supply system 15a Supply pump 15b Supply nozzle 16 Leakage suppression member 17 Internal scale production | generation prevention gas supply system 18 Chuck 18a Flow path 19 Chuck 19a Flow path 20 Cooling medium 21 Part 22 Surrounding space A First position B Second position

Claims (8)

A surface treatment liquid for a heat treatment steel material containing an inorganic binder and a metal pigment in a medium,
The metal pigment is
The total amount of the metal pigment and the solid content of the inorganic binder is 5% by mass to 20% by mass of zinc oxide powder, and 10% by mass of one or two metal foils selected from copper foil and brass foil. A surface treatment liquid characterized by containing no less than 25% by mass and no high temperature oxidation-resistant metal powder.   Furthermore, the inorganic solid lubricant is contained so that the content of the inorganic solid lubricant in the coating obtained from the surface treatment liquid with respect to the total coating solid content is 5% by mass or more and 20% by mass or less. 1 surface treatment solution. A contact step of bringing the surface treatment liquid according to claim 1 or 2 into contact with a substrate to form a liquid layer made of the surface treatment liquid on the surface of the substrate;
And a drying step of drying a substrate on which a liquid layer made of a surface treatment liquid is formed on the surface thereof to form a protective film on the surface of the substrate. Manufacturing method. A method for producing a heat-treated steel material, comprising a heat treatment step of heating and quenching the steel material for heat treatment produced by the production method according to claim 3 to a temperature of Ac ₃ or higher. . Heating the steel for heat treatment to a temperature of Ac ₃ points or higher is performed at a temperature increase rate of 100 ° C./second, and the time for which the heated steel for heat treatment is held at a temperature of Ac ₃ points or higher is within 1 second. The manufacturing method of Claim 4 which is. The manufacturing method according to claim 5, wherein the heat treatment steel material is shaped before the heat treatment steel material heated to a temperature of _three or more points of Ac is cooled for quenching. While the steel for heat treatment is being sent in the longitudinal direction, the steel for heat treatment is heated to a temperature of Ac ₃ or higher by a heating device arranged at a first position apart from the steel for heat treatment to be sent, and the first A heat treatment steel material is hardened by spraying a cooling medium onto the heat treatment steel material by a cooling device disposed at a second position downstream of the position 1 in the feed direction of the heat treatment steel material. 5. The production method according to 5. The method of claim 7, wherein obtaining a heat treatment steel which shaping is made by deforming the heat treatment steel material deformation resistance is lowered by being heated to a temperature of at least Ac ₃ point in the first position.

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