JP5353105B2 - Surface treatment liquid for heat treatment steel and method for producing heat treatment steel - Google Patents

Description

  The present invention relates to, for example, the field of heat treatment of steel for obtaining high-strength parts. Specifically, the present invention relates to a surface treatment solution for steel for heat treatment and a method for producing a surface-treated steel suitable for heat treatment. .

  In efforts to reduce the weight of automobile bodies, research and development are underway to obtain high-strength parts and components that are equal to or better than conventional steel parts. The direction of increasing strength is to 1) form high-strength steel materials such as ultra-high tension originally, and 2) increase strength by heat-treating relatively soft steel materials during or after the forming process. Broadly divided.

  When a high-strength steel material is used, there are cases where the range in which the forming process can be performed is restricted, and it is difficult to obtain the accuracy of the molded product such as the occurrence of springback. On the other hand, an example of 2) is a hot press molding technique. This is, for example, a process in which a steel material (steel plate) is heated to a high temperature and then pressed with a cooled mold, and the molding process and quenching are performed in one process, and are also restrained by the mold. Since it is quenched, there is a feature that the accuracy of the molded product is good.

  However, in the method of heat-treating a steel material at the time of forming represented by the hot press technique, when normal steel is used, a steel scale is formed on the surface by the heat treatment. Since the steel scale is easily peeled off from the base material, there is a risk that the mold may be damaged or the coating film may be peeled off or the corrosion resistance may be deteriorated in the molded product to be coated.

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 1 discloses a method using an Al-plated steel sheet, and Patent Document 2 discloses a method using a Zn-based or Zn-Al-based plated steel sheet. Further, Patent Document 3 discloses a coating layer containing an organic silane as a binder, and Patent Documents 4 and 5 include an electrically 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 scale, but the technique using the surface-treated steel sheet provided with a lubricating coating as in Patent Document 6 There is also.
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

  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 techniques disclosed in Patent Documents 3 to 5, improvement in weldability and the like is achieved by providing a coating layer containing a conductive metal pigment (Al, Fe, etc.) or a nonmetal 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.

  The present invention provides a surface treatment liquid for obtaining a heat treated steel material having excellent weldability and paint adhesion by suppressing the generation of steel scale due to the heat treatment by forming a film on the surface of the steel material before the heat treatment. In particular, it is an object to provide a surface treatment liquid that is easy to handle, in which metal pigments and the like in the treatment liquid are not easily settled, and to provide a method for producing a heat-treated steel material using the surface treatment liquid.

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 solvent, wherein the inorganic binder is silica, titania, zirconia, an organosilicon compound, an organotitanium compound, and an organozirconium It is 1 type, or 2 or more types chosen from the group which consists of a compound, and is 5-20 mass% of (a) zinc oxide powder with respect to the total amount of the said metal pigment and the said inorganic type binder as said metal pigment, (b ) 15-60 mass% of one or more kinds of metal powders selected from Cr, Ni, W, V, Mo, Zr, Ti, Co and Cu and their alloy powders as high temperature oxidation resistant metal powders, and ( c) The metal foil contains 10 to 25% by mass, and the total content of the metal pigment is 50 to 75% by mass with respect to the total amount of the metal pigment and the inorganic binder. Surface treatment solution, characterized in that.

  (2) The surface treatment liquid according to (1) above, wherein the metal foil is a brass foil.

  (3) The metal pigment is further (d) one or more selected from the group consisting of Zn, Zn alloy, Al, and Al alloy powder, with respect to the total amount of the metal pigment and the inorganic binder. The surface treatment liquid according to (1) or (2) above, containing 10 to 30% by mass.

  (4) Among the metal pigments, the average particle diameter of components other than the metal foil is less than 70 μm, and the metal foil has a thickness of 2 μm or less and a foil diameter of 3 to 10 μm. The surface treatment liquid according to any one of the above.

(5) A method for producing a heat-treated steel material, comprising: a film forming step for forming a film layer on a steel surface; and a heat treatment step including a process for heating the steel material on which the film layer is formed to 700 ° C. or more. The process is a surface treatment liquid for a heat-treating steel material containing an inorganic binder and a metal pigment in a solvent, wherein the inorganic binder is silica, titania, zirconia, organosilicon compound, organotitanium compound, and organozirconium. It is 1 type, or 2 or more types chosen from the group which consists of a compound, and is 5-20 mass% of (a) zinc oxide powder with respect to the total amount of the said metal pigment and the said inorganic type binder as said metal pigment, (b ) one or more kinds of gold selected Cr as high temperature oxidation resistant metal powder, Ni, W, V, Mo , Zr, Ti, from powders of Co and Cu and their alloys Flour 15-60% by weight, and (c) a metal foil containing 10 to 25 wt%, the total content of the metallic pigment, 50 to the total amount of the inorganic binder and the metal pigment A method for producing a heat-treated steel material, comprising applying a surface treatment liquid of 75% by mass to a steel material and baking and drying to form a coating film.

  (6) The method for producing a heat-treated steel material according to (5), wherein the metal foil is a brass foil.

  (7) The metal pigment further includes (d) one or more selected from the group consisting of Zn, Zn alloy, Al, and Al alloy powder with respect to the total amount of the metal pigment and the inorganic binder. The manufacturing method of the heat-treated steel materials according to (5) or (6) above, containing 10 to 30% by mass.

(8) Of the metal pigment, the average particle size of components other than the metal foil is less than 70 μm, and the metal foil has a thickness of 2 μm or less and a foil diameter of 3 to 10 μm.
The method for producing a heat-treated steel material according to any one of (5) to (7).

  By applying the surface treatment liquid of the present invention to the surface of the steel material before heat treatment to form a coating, it is possible to suppress the generation of steel scale due to heat treatment, and the heat treated steel material is excellent in weldability and paint adhesion. Can be obtained. In addition, the surface treatment liquid of the present invention is easy to handle because metal pigments and the like in the liquid are unlikely to settle.

1. Surface treatment liquid (1) Inorganic binder The surface treatment liquid of this invention has an inorganic binder as a binder component which disperse | distributes a metal pigment. Known inorganic binders can be used, and inorganic compounds and / or organic inorganic compounds having an X—O bond (X: Si, Ti, Zr, etc.) are preferable. Specific examples include one or more selected from the group consisting of silica, titania, zirconia, organosilicon compounds, organotitanium compounds, and organozirconium compounds. Since these binders are excellent in heat resistance, it is considered that they are effective in suppressing steel scale.

  The inorganic compound may contain components other than silica, such as lithium silicate. Moreover, it is preferable to use colloidal silica because of its high dispersibility. Specific examples of the organic inorganic compound include alkoxysilane.

(2) Component of metal pigment The treatment liquid contains at least the following metal pigment, (a) zinc oxide powder, (b) high-temperature oxidation-resistant metal powder, and (c) metal foil. ) Further containing Zn, Zn alloy, Al and / or Al alloy powder. 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. In the following description, the content of the metal pigment is expressed as a ratio (% by mass) with the sum of the inorganic binder and the metal pigment as the denominator unless otherwise specified.

(A) Zinc oxide powder If the heat-treated steel material is, for example, an automobile part, it is assembled on the vehicle body, subjected to chemical conversion treatment, and then coated by electrodeposition coating or the like. By containing zinc oxide powder in the treatment liquid, a chemical conversion treatment layer is easily formed on the coating film made of the treatment liquid. For this reason, the adhesiveness of the film which consists of a process liquid, and coating (coating film) improves. The preferable content of zinc oxide is 5 to 20%. When the content is less than 5%, it is difficult to obtain the effect of improving the adhesion between the coating film and the coating film. When the content is more than 20%, 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%.

(B) High-temperature oxidation-resistant metal powder 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. Spot weldability is improved by containing the high-temperature oxidation-resistant metal powder in the treatment liquid. Examples of the high temperature oxidation-resistant metal powder include Cr, Ni, W, V, Mo, Zr, Ti, Co and Cu and powders of these alloys. Since these metal powders have a high melting point and high oxidation resistance, they do not easily deteriorate during heat treatment heated to about 800 ° C. or more, so they remain on the surface of the steel after the heat treatment and serve as current-carrying sites during spot welding. Presumed to be. A preferred high-temperature oxidation-resistant metal powder is Cr or Ni or an alloy thereof, and has an excellent balance between performance and cost. Moreover, the high temperature oxidation resistant metal powder may be composed of one kind of metal powder or may be composed of a plurality of kinds of metal powder.

  The preferred content of these high temperature oxidation resistant metal powders is 15-60%. When the content is less than 15%, it becomes difficult to obtain the effect of improving spot weldability. When the content is more than 60%, the content of other metal pigments is relatively lowered, so there is a problem. It tends to occur. A particularly preferable content is 40 to 60%.

  Various processes for producing a molded product for forming a coating film with the surface treatment liquid according to the present invention are conceivable. A typical example is a case where the present invention is applied in a hot press forming process of a steel sheet as shown in FIG. Will be described.

(C) Metal foil The metal pigments of the above (a) and (b) have a specific gravity that is considerably larger than that of the binder-forming component and the solvent (water, solvent), and thus are easily precipitated in the treatment liquid. Therefore, the treatment liquid according to the present invention suppresses the precipitation of the metal pigment by containing a metal foil. By including this foil-like metal powder, the viscosity increases regardless of the concentration of the inorganic binder in the treatment liquid, and it is assumed that it is difficult to settle. As the metal foil, Al foil, brass (Cu—Zn) foil or the like can be used. Moreover, preferable content is 10 to 25%. When the content is less than 10%, it is difficult to obtain the effect of suppressing sedimentation. When the content is more than 25%, the content of other metal pigments is relatively lowered, resulting in problems. It becomes easy. A particularly preferable content is 15 to 25%.

(D) Zn, Zn alloy, Al and / or Al alloy powder When the treatment liquid contains one or more selected from the group consisting of Zn, Zn alloy, Al and Al alloy powder, the corrosion resistance of the steel material after heat treatment Will improve. A preferable content is 10 to 30%. When the content is less than 10%, it is difficult to obtain the effect of improving the corrosion resistance, and when the content is more than 30%, the content of other metal pigments is relatively lowered, which causes a problem. There is concern that the possibility will increase. A particularly preferable content is 20 to 30%. In addition, if these metal powders, such as Zn, are foil shape, it will have the function of the metal foil of said (c), and it is preferable. In this case, the upper limit may be about 50%.

(3) Metal Pigment Shape As described above, (c) the metal foil has a foil shape for preventing sedimentation, and has an average thickness of 2 μm or less and an average foil diameter (foil long diameter) of 3 to 10 μm. Is preferred. 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.

  On the other hand, the shape of the metal pigments (a), (b) and (d) is not limited. However, when the particle size (sphere equivalent diameter) is excessively large, it may be difficult to suppress sedimentation even with the metal foil of (c). In addition, the tendency of the metal pigment to protrude from the coating is particularly strong, and the possibility of the pigment falling off may increase, or the design may be significantly reduced. Therefore, the average particle diameter of these metal pigments is preferably less than 70 μm, and particularly preferably 30 μm or less.

(4) Content of metal pigment The content of the entire metal pigment in the surface treatment liquid is preferably 50 to 75%. When it is less than 50%, there is a concern that the conductivity of the coating is lowered. On the other hand, if it exceeds 75%, the content of the inorganic binder is relatively low, so that it may be difficult to fix the metal pigment as a film, and problems such as peeling may occur. Will increase.

(5) Medium The medium is not limited as long as it is stable as a treatment liquid, in particular, an inorganic binder that can be stably dissolved or dispersed. In view of 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.

(6) 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 the lubricant include an organic lubricant such as wax and an inorganic lubricant such as molybdenum disulfide. In addition, about a thickener, since it is supposed that a process liquid viscosity is raised by using said (c) metal foil in this invention, it is not necessary to use it darely.

2. Coating A case where the above-described treatment liquid is applied to a steel material will be described as an example.
The coating preferably has siliceous, titanate, zirconate or a mixture thereof as a binder, and the above (a) to (c) or the above (a) to (d) in which the metal pigment is dispersed Become.

  Since these metal pigments can have a particle size of about 30 μm as described above even in a preferred embodiment, the 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 layer. In some cases. In the present invention, the thickness of the binder layer when the coating is observed from the cross section of the coating is defined as the thickness of the coating.

  The thickness of the 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, while considering the weldability, it is preferably 15 μm or less, and around 5 μm (4 to 10 μm). Particularly preferred.

3. Manufacturing method of heat-treated steel (1) Hot forming of surface-treated steel sheet In the following, a process as shown in FIG. 1, that is, a surface-treated steel sheet is obtained by applying a surface treatment liquid to a steel sheet to form a film. The process of hot forming the steel sheet will be mainly described.

  In applying the treatment liquid, the metal pigment is uniformly dispersed in the treatment liquid in advance by stirring or the like. Thereby, if it is the processing liquid of this invention, separation and sedimentation of a processing liquid can be suppressed for a comparatively long period of time, and it is not necessary to continue strong circulation during processing liquid application | coating operation | work. The application method may be a known method such as spraying, roll coating, bar coating, or dipping.

  Before applying the treatment liquid, the surface may be washed with alkali or the like, or subjected to chemical treatment such as physical treatment such as shot blasting or chemical conversion treatment for the purpose of improving the adhesion of the coating. Also good.

  After the treatment liquid is applied, it is dried. Thereby, a coating film is formed on the steel material surface. Since the solvent component of the treatment liquid only needs to be volatilized and dried sufficiently, strict temperature control as in the production of a so-called coated steel sheet is not necessary. For example, what is necessary is just to heat and dry to about 80-150 degreeC with oven.

  The surface-treated steel sheet thus obtained is blanked for processing and then heated. In the case of quenching, the heating temperature is about 700 to 1200 ° C. (although depending on the steel components and the like). At this time, in the case of the zinc-based plated steel sheet or the Al-based plated steel sheet of Patent Document 1 or 2, since the heating temperature is higher than the melting point of the plating film, a liquid phase appears on the surface when the heating rate is very fast, etc. Although there is a concern that it may adversely affect the subsequent hot forming, such a phenomenon does not occur in the present invention, and rapid heating may be performed.

  The heated blank is hot-formed while being in the heated temperature range. At this time, rapid cooling (for example, molding with a water-cooled mold) may be performed simultaneously with or immediately after molding. For example, if press molding is performed with a water-cooled mold, it is quenched at the same time as press molding, so that a molded product having high strength and good shape accuracy can be obtained.

(2) Other Manufacturing Methods In addition to the above-described hot forming of the surface-treated steel material, the steel material manufacturing process to which the surface treatment liquid according to the present invention is applied is illustrated in FIG. 2 or 3.

  That is, FIG. 2 shows a method of heat treatment (quenching) after forming a surface-treated steel sheet. FIG. 3 shows a method of applying heat treatment (quenching) after applying a treatment liquid to a molded product. Compared with the processes according to FIGS. 1 and 2, the method of FIG. 3 has an advantage that the processing liquid is applied to the molded product, so that it can be applied to the cut end face and does not have to be applied to the remaining material portion by blanking. Have. However, there are cases where the application equipment is restricted or the management of the amount of adhesion becomes difficult.

  Although the above description has been made with a steel plate as an example, the surface treatment liquid according to the present invention is applied not only to a steel plate and its molded product, but also to heat treatment of other steel materials such as steel pipes and steel bars and these molded products. Thus, a film can be formed.

(3) Other conditions The chemical composition of the steel material 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.

EXAMPLES Hereinafter, although this invention is further demonstrated using an Example, this invention is not limited to a following example.
1. Preparation of surface treatment solution (1) As a binder binder for coating, a ceramic coating agent (Ceramica; G90, G-301, G-401) manufactured by Niita Laboratory Co., Ltd. was used.

(2) Pigment Zinc oxide (1 type of zinc oxide manufactured by Honjo Chemical Co., Ltd.) was used to improve chemical conversion properties.
Moreover, in order to improve weldability, any of the following metal powders (made by Fukuda Metal Foil Powder Industry Co., Ltd.) whose main components are Ni and Cr was used.
FP-4H: Average particle size of about 30 μm
FP453G-100: average particle size 63 μm

Furthermore, in order to improve the dispersion stability of the conductive metal for improving weldability, one of the following brass foils (manufactured by 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

Further, in some cases, the following metals such as zinc powder (hereinafter referred to as “second metal”) were also added.
Zinc powder: F500 and F-1000 manufactured by Honjo Chemical (average particle sizes of 11 and 5 μm, respectively)
Iron zinc powder: ZWA-B made by DOWAIP Creation (average particle size 7 μm, Fe concentration 16%)
Al powder: made by Nippon Moistureproof Industry, average particle size 11μm, 5μm

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

  First, C: 0.21% by mass, Si: 0.2% by mass, Mn: 1.3% by mass, P: 0.005% by mass, S: 0.001% by mass, balance Fe and chemical composition consisting of impurities Then, a steel sheet (100 × 200 mm, thickness 1.6 mm) having an alkali was degreased with alkali, and a paint sample blended and dispersed with the composition shown in Table 1 was applied on both sides with a bar coater aiming at a thickness of 5 μm. The coated steel sheet was dried in an oven at 150 ° C. to form a film. The coating thickness of the test piece thus obtained was 4 to 6 μm for any test piece when the test piece was resin-embedded and polished, and measured by cross-sectional SEM observation.

Subsequently, the test piece on which this film was formed was held in a natural gas combustion atmosphere furnace at 900 ° C. for 4 minutes and heated, and sandwiched between flat plate molds having a water-cooled jacket within 3 seconds after removal (surface pressure: 100 kgf / cm ² ), and cooled at a cooling rate of 50 ° C./second or higher, and held and cooled for 20 seconds so that the temperature of the test piece became 100 ° C. or lower.

3. Evaluation test method (1) Evaluation of dispersion stability of pigment in paint
After the pigment-dispersed paint was left for 1 hour, the pigment was once stirred with a stir bar for 1 minute and left for 3 minutes. Then, in order to measure the amount of pigment settled on the bottom of the paint container, the paint supernatant is transferred to another container by the gradient method, the mass of the precipitated pigment remaining on the container bottom is measured, and the mass ratio with respect to the initial blended pigment (Precipitated pigment ratio) was determined and evaluated according to the following criteria.
○: 10% by mass or less (10% by mass or less is judged to be good)
Δ: more than 10% by mass and less than 30% by mass ×: more than 30% by mass

(2) Evaluation of scale generation status, etc. (A) Visual observation The surface of the test piece was visually observed to evaluate the presence or absence of scale generation.

(B) Film adhesion A Nichiban Co., Ltd. cello tape (registered trademark) is applied to the surface of the test piece, peeled off almost vertically, and the area of the peeled portion attached to the tape is measured. The ratio (peeling area ratio) was determined and evaluated according to the following criteria.
○: 5% or less (5% or less is judged good)
Δ: More than 5% and 30% or less ×: More than 30%

(3) Paint adhesion Using a known chemical conversion treatment liquid (surface adjustment treatment PL-ZN, manufactured by Nihon Parkerizing Co., Ltd., zinc phosphate treatment liquid PBL3080, manufactured by Nihon Parkerizing Co., Ltd.) on the test piece after molding, depending on the chemical conversion treatment conditions. After the zinc phosphate treatment, an electrodeposition paint (New Peyton Black E FU-NPB) manufactured by Uemura Kogyo Co., Ltd. was electrodeposited by slope energization at a voltage of 200 V and baked at a baking temperature of 170 ° C. for 20 minutes.

On the surface of the test piece, 11 cuts that reach the substrate with a cutter knife were placed at 1 mm intervals vertically and horizontally to form 100 squares in a 10 mm × 10 mm square region. 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 pieces (5 pieces or less are judged to be good)
Δ: 6-30 pieces ×: 31-100 pieces

(4) Weldability (electric resistance)
As an indicator of weldability, the electrical resistance of the test piece after molding was measured. In the electrical resistance measurement method, two molded specimens were sandwiched by a dome-shaped electrode tip (tip diameter: 6 mm) (pressing force: 2450 N), and the resistance value was calculated from the voltage value when the current 2 A was passed for 4 seconds. . Judgment criteria based on the resistance value are as follows.
A: 25 mΩ or less ○: Over 25 mΩ and 50 mΩ or less (50 mΩ or less is judged as good)
×: Over 50mΩ

(5) Corrosion resistance test For some of the test pieces after molding (test numbers No. 26 to 36), a known chemical conversion liquid (surface conditioning treatment PL-ZN manufactured by Nippon Parkerizing Co., Ltd., zinc phosphate manufactured by the same company) Treatment solution PBL3080), and after the zinc phosphate treatment according to the chemical conversion treatment conditions, electrodeposition coating of Uemura Kogyo Co., Ltd. (New Peyton Black E FU-NPB) was applied by slope energization with a voltage of 200V, Baking was applied at a baking temperature of 170 ° C. for 20 minutes. The coating layer obtained in this way is cut into two bases with a cutter knife, 90 cycles of tests based on JIS standards (standard number: H8502) are performed, and the maximum swelling width of the scratched part after the test is measured. Evaluation was made according to the following criteria.
A: Less than 3 mm B: 3 mm or more and less than 6 mm (less than 6 mm is judged as good)
×: 6 mm or more

4). Evaluation Results Table 1 shows the results other than visual observation among the results of the above evaluations for each test piece. In addition, when the molded test piece obtained after cooling was visually observed, no scale was observed in any of the test pieces.

The test piece to which zinc oxide was added obtained better coating adhesion than the test piece to which zinc oxide was not added.
When metal powder composed of Ni and Cr was added, the electrical resistance was reduced.
There was a tendency that the dispersion stability of the paint was improved by adding brass foil.
Corrosion resistance was improved in the system in which the second metal was additionally dispersed, compared to the system containing only the binder and the system in which zinc oxide was added to the binder.

It is a flow figure showing one form of a manufacturing process of a surface treatment steel plate provided with a coat which consists of a surface treatment liquid concerning the present invention. It is a flowchart which shows another form of the manufacturing process of a surface treatment steel plate provided with the film which consists of a surface treatment liquid concerning this invention. It is a flowchart which shows another one form of the manufacturing process of a surface treatment steel plate provided with the film which consists of a surface treatment liquid concerning this invention.

Claims (8)

A surface treatment liquid for a heat treatment steel material containing an inorganic binder and a metal pigment in a medium,
The inorganic binder is one or more selected from the group consisting of silica, titania, zirconia, organosilicon compounds, organotitanium compounds, and organozirconium compounds,
As the metal pigment, with respect to the total amount of the metal pigment and the inorganic binder,
(A) 5 to 20% by mass of zinc oxide powder,
(B) 15 to 60% by mass of one or more kinds of metal powders selected from Cr, Ni, W, V, Mo, Zr, Ti, Co and Cu and their alloy powders as high temperature oxidation resistant metal powders, And (c) containing 10-25% by mass of metal foil,
The total amount of the metal pigment is 50 to 75% by mass with respect to the total amount of the metal pigment and the inorganic binder.   The surface treatment liquid according to claim 1, wherein the metal foil is a brass foil. The metal pigment further includes
(D) containing one or more selected from the group consisting of Zn, Zn alloy, Al and Al alloy powder in an amount of 10 to 30% by mass based on the total amount of the metal pigment and the inorganic binder,
The surface treatment liquid according to claim 1 or 2. Among the metal pigments,
The average particle size of the components other than the metal foil is less than 70 μm,
The metal foil has a thickness of 2 μm or less and a foil diameter of 3 to 10 μm.
The surface treatment liquid according to claim 1. A method for producing a heat treated steel material comprising a film forming step of forming a film layer on the surface of the steel material, and a heat treatment step including a step of heating the steel material on which the film layer is formed to 700 ° C or higher,
The film forming step includes
A surface treatment liquid for a heat treating steel material containing an inorganic binder and a metal pigment in a medium, wherein the inorganic binder comprises silica, titania, zirconia, an organic silicon compound, an organic titanium compound, and an organic zirconium compound. One or more selected from the group, and as the metal pigment, 5 to 20% by mass of (a) zinc oxide powder and (b) high temperature resistance with respect to the total amount of the metal pigment and the inorganic binder 15 to 60% by mass of one or more kinds of metal powders selected from Cr, Ni, W, V, Mo, Zr, Ti, Co and Cu and their alloy powders as oxidizing metal powders, and (c) metals The foil contains 10 to 25% by mass, and the total content of the metal pigment is 50 to 75% by mass with respect to the total amount of the metal pigment and the inorganic binder. The surface treatment solution was applied to steel, and characterized in that to form a coating film by baking and drying, the manufacturing method of the heat treatment steel.   The manufacturing method of the heat-treated steel materials of Claim 5 whose said metal foil is a brass foil. The metal pigment further includes
(D) containing one or more selected from the group consisting of Zn, Zn alloy, Al and Al alloy powder in an amount of 10 to 30% by mass based on the total amount of the metal pigment and the inorganic binder,
The manufacturing method of the heat-treated steel materials of Claim 5 or 6. Among the metal pigments,
The average particle size of the components other than the metal foil is less than 70 μm,
The metal foil has a thickness of 2 μm or less and a foil diameter of 3 to 10 μm.
The manufacturing method of the heat-treated steel materials in any one of Claim 5 to 7.

Images