JP2011074409A - Plated steel sheet for hot press forming, and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plated steel sheet for hot press forming having excellent oxidation resistance. <P>SOLUTION: A galvanized steel sheet is brought into contact with acid solution containing oxide colloidal particles and kept for 1-90 seconds after completing the contact treatment, and then, the steel sheet is subjected to water rinsing and drying to deposit an oxide layer having the mean thickness of ≥10 nm on the surface of the galvanized steel sheet. When the oxide colloidal particles are contained, the oxide colloidal particle containing one or more of Ti, Al, Si, Zr, Fe, Zn, Mn, Mo, Ni, Cr, Mg, and Cu are preferably contained in a range of 0.1-20% in terms of the mass concentration. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a plated steel sheet for hot press forming excellent in oxidation resistance and a method for producing the same.

In recent years, efforts have been made to increase the strength of steel sheets (for example, 780 MPa class) and reduce the thickness of the steel sheets used in order to reduce the weight of automobile bodies. However, when press-working a steel plate, for example, when drawing is performed, if the strength of the steel plate is increased, the contact pressure with the mold is increased during drawing, and the steel plate is galvanized or broken. In addition, in order to alleviate such problems as much as possible, when the blank pressing pressure for increasing the inflow of the material into the mold during drawing of the steel sheet is lowered, the shape after forming varies. There is.
In addition, the problem of shape stability, so-called spring back, also occurs. There is a method to solve this by using a lubricant, but the effect is small with a high strength steel plate of 780 MPa class.

  In view of such a current situation, as a technique for press-forming a difficult press-molding material such as a high-strength steel plate of 780 MPa or more, a method in which the material to be formed is pre-heated and formed can be considered. These are so-called hot press forming and warm press forming (hereinafter, hot press forming and warm press forming are collectively referred to as hot press forming).

  However, since hot press forming is a forming method for processing a heated steel plate, surface oxidation is unavoidable. Even if the steel plate is heated in a non-oxidizing atmosphere, for example, for press forming from a heating furnace. When exposed to the atmosphere, iron oxide is formed on the surface. This iron-based oxide falls off at the time of pressing and adheres to the mold, reducing productivity. Or it remains in the product after pressing and causes the appearance defect. Furthermore, when it coats at the next process, the adhesiveness of a steel plate and a coating film will be inferior.

  Therefore, after hot press molding, it is necessary to perform shot blasting to remove scales made of such iron-based oxides. However, this is subject to an increase in cost.

  In order to solve such a problem, Patent Document 1 proposes a steel sheet having a predetermined composition and structure, which is coated with aluminum in order to provide the oxidation resistance of the base steel sheet during hot forming. However, such a steel sheet has a significant cost increase when compared with ordinary steel.

  As described above, in hot press molding, a substantial increase in cost cannot be avoided. That is, a steel plate coated with aluminum having a predetermined steel composition and steel structure increases costs. In addition, when hot press forming is performed on a high-strength steel sheet that does not have a surface treatment layer such as a plating layer, a step for removing the generated iron-based oxide is necessary, and the oxide is not significantly increased. There is a problem in that the step of removing can not be omitted. Further, even if the oxide is removed due to an increase in cost, a problem remains in that the steel sheet having no surface treatment layer such as a plating layer has poor rust prevention. In hot press forming, iron-based oxides generated during heating are peeled off and removed from the press mold during press forming, necessitating maintenance of the mold, leading to loss of production time and concern about productivity reduction. Is done.

JP 2000-38640 A

  In view of such circumstances, an object of the present invention is to provide a hot press-formed plated steel sheet having excellent oxidation resistance and a method for producing the same without significantly increasing costs.

  The inventors of the present invention have made extensive studies to solve the above problems. As a result, the following knowledge was obtained.

  An oxide layer containing Zn and an oxide derived from the oxide colloid particles as an essential component on the surface of the plating layer by contacting a steel plate (zinc-based plating layer) with an acidic solution containing oxide colloid particles before hot press forming It has been found that the oxidation resistance can be remarkably improved without deteriorating the appearance after hot pressing and without significantly increasing the cost.

The present invention has been made based on the above findings, and the gist thereof is as follows.
[1] A zinc-based plated steel sheet is brought into contact with an acidic solution, held for 1 to 90 seconds after completion of the contact treatment, and then washed with water and dried to form an oxide layer having an average thickness of 10 nm or more on the surface of the plated steel sheet. In the manufacturing method of a plated steel plate, the said acidic solution contains an oxide colloid particle, The manufacturing method of the plated steel plate for hot press forming characterized by the above-mentioned.
[2] In the above [1], the oxide colloidal particle is an oxide containing one or more of Ti, Al, Si, Zr, Fe, Zn, Mn, Mo, Ni, Cr, Mg, and Cu. A method for producing a hot-press-formed plated steel sheet, characterized by being colloidal particles.
[3] In the above [1] or [2], the acidic colloidal particles contain the oxide colloidal particles in a mass concentration in the range of 0.1% to 20%. Manufacturing method.
[4] In any one of [1] to [3], the acidic solution has a pH buffering action, and 1.0 mol necessary to increase the pH of 1 liter of the acidic solution from 2.0 to 5.0. A method for producing a plated steel sheet for hot press forming, characterized in that the pH increase defined by the amount (l) of / l sodium hydroxide solution is in the range of 0.05 to 0.5.
[5] In any one of the above [1] to [4], the acidic solution includes acetate, phthalate, citrate, succinate, lactate, tartrate, borate, phosphate. For hot press molding, characterized in that at least one of them is contained in a range of 5 to 50 g / l of the component content, pH is 0.5 to 2.0, and liquid temperature is in the range of 20 to 70 ° C. Manufacturing method of plated steel sheet.
[6] In any one of [1] to [5], the acidic solution film formed on the surface of the plated steel sheet after contact with the acidic solution is 20 g / m ² or less, and the acidic solution film is A method for producing a hot-press-formed plated steel sheet, wherein the holding time in a state of being formed on the surface of the plated steel sheet is in the range of 1 to 90 seconds.
[7] An oxide having a mean thickness of 10 nm or more, comprising Zn and an oxide derived from the oxide colloidal particles, produced by the method for producing a hot-pressed plated steel sheet according to any one of [1] to [5] A plated steel sheet for hot press forming, comprising a physical layer.

  In the present invention, steel plates having a plated layer containing Zn are collectively referred to as zinc-based plated steel plates. Therefore, it is the zinc-based plated steel sheet of the present invention as long as it has a plating layer containing Zn regardless of whether or not the alloying treatment is performed after the plating treatment. That is, the galvanized steel sheet in the present invention is a hot dip galvanized steel sheet not subjected to alloying treatment, an alloyed hot dip galvanized steel sheet subjected to alloying treatment, an electrogalvanized steel sheet, a hot dip galvanized steel sheet, etc. Both are included.

  According to the present invention, a hot press-formed plated steel sheet having excellent oxidation resistance can be obtained. And, by performing hot press forming using the hot-press-formed plated steel sheet of the present invention, processing can be performed without causing galling or breakage of the steel sheet, and there is no need to remove scale such as shot blasting. Therefore, the cost can be reduced.

  During hot press forming, the steel plate is heated above the A3 transformation point (about 900 ° C or higher). In this case, since the melting point of Zn is 418 ° C and the boiling point is 907 ° C, in the case of zinc-based plated steel sheet, it is expected that the Zn plating on the steel sheet will evaporate, and as a result, the steel sheet substrate will be oxidized become. For this reason, it is considered that the presence of a hard and high melting point substance on the surface of the plated steel sheet is very effective from the viewpoint of preventing oxidation of the steel sheet substrate.

  Therefore, studies were made to form a hard and high melting point material on the plating surface layer. As a result, it has been found that forming an oxide layer having a high melting point and a predetermined thickness on the surface of a galvanized steel sheet is very effective as a technique for imparting excellent oxidation resistance. Furthermore, by containing an oxide derived from high melting point oxide colloidal particles in this oxide layer, a higher melting point oxide layer can be obtained, and the oxidation resistance can be drastically improved. I also found out.

  From the above, in the present invention, the surface of the zinc-based plated steel sheet has an oxide layer containing Zn and an oxide derived from oxide colloidal particles.

  The average thickness of the oxide layer formed on the surface of the galvanized steel sheet is 10 nm or more. By setting the thickness to 10 nm or more, this oxide layer becomes a barrier layer even at the heating temperature (temperature above the Ac3 transformation point) during hot press molding, and scale generation can be suppressed. On the other hand, if the thickness is 200 nm or less, the effect of hot press formability can be obtained, and there is no need to consider the line length for forming an oxide layer having this thickness on the surface of the plating layer. There will be no problems with the equipment. Therefore, the upper limit is preferably 200 nm or less.

  In addition, the average thickness of the oxide layer in this invention is the film thickness of the silica conversion calculated | required using the analytical curve created with the K (alpha) fluorescence X-ray intensity of O (oxygen) of a silica membrane | film | coat with a known film thickness.

  From the above, in the present invention, an oxide layer having an average thickness of 10 nm or more is formed on the surface of a zinc-plated steel sheet for hot press forming, containing an oxide derived from Zn and colloidal oxide particles. These are the features of the present invention, and the presence of such an oxide layer on the surface of the steel sheet prevents oxidation of the steel sheet substrate and has excellent oxidation resistance.

  As a method of forming the oxide layer on the surface of the zinc-based plated steel sheet, a method using a reaction of the plating layer with an aqueous solution is the most effective. That is, the method for producing a hot-pressed plated steel sheet according to the present invention, in which the zinc-based plated steel sheet is brought into contact with an acidic solution containing colloidal oxide particles, held for 1 to 90 seconds after completion of the contact treatment, and then washed and dried. Thus, the oxide layer can be formed.

Although the oxide layer formation mechanism is not clear, it can be considered as follows. When the galvanized steel sheet is brought into contact with an acidic solution, Zn is dissolved from the steel sheet side. This dissolution of Zn causes hydrogen generation at the same time. As the dissolution of Zn proceeds, the hydrogen ion concentration in the acidic solution decreases, and as a result, the pH of the acidic solution rises and oxides (hydroxides) are formed. When reaching a stable pH region, it is considered that an oxide layer containing Zn is formed on the surface of the zinc-based plated steel sheet. At this time, when an acidic solution containing oxide colloidal particles is used, the oxide colloidal particles are dispersed or adhered in the oxide layer or on the surface of the oxide layer. Since the oxide colloidal particles dispersed or attached in the oxide layer or on the surface of the oxide layer have a high melting point, it is considered that the effect of improving the oxidation resistance can be obtained.
The acidic solution preferably contains colloidal oxide particles containing one or more of Ti, Al, Si, Zr, Fe, Zn, Mn, Mo, Ni, Cr, Mg, and Cu. Since the oxide derived from these oxide colloidal particles has a high melting point, the effect of improving the oxidation resistance can be obtained if it is dispersed or adhered to the oxide layer to be formed. Furthermore, the mass concentration of the oxide colloidal particles is preferably 0.1% to 20% with respect to the acidic solution. If the oxide colloid particle concentration is 0.1% or more, the amount of oxide colloid particles dispersed or adhered to the formed oxide layer becomes an appropriate amount, and the amount of dispersion or adhesion necessary to ensure oxidation resistance can be obtained. . On the other hand, if it is 20% or less, the amount of oxide derived from the oxide colloidal particles in the formed oxide layer will not increase too much, so it is compatible with adhesives designed for galvanized steel sheets. It does not deteriorate the sex.
The acidic solution used preferably has a pH buffering action in the region of pH = 0.5 to 5.0. This is because, when an acidic solution having a pH buffering action in the above pH range is used, the dissolution of Zn and the formation of an oxide layer are caused by the reaction between the acidic solution and the plating layer by holding the acidic solution for a predetermined time after contact. This is because it occurs sufficiently and the oxide layer targeted by the present invention can be stably obtained on the steel sheet surface.

  In addition, as an index of such pH buffering action, evaluated by the degree of pH increase defined by the amount (l) of 1.0 mol / l sodium hydroxide aqueous solution required to raise the pH of a 1 liter acidic solution from 2.0 to 5.0 This value is preferably in the range of 0.05 to 0.5. If the degree of pH increase is 0.05 or more, the pH will rise rapidly and Zn dissolution sufficient for formation of the oxide layer will not be obtained, so that sufficient oxide layer formation will occur. On the other hand, if it is 0.5 or less, the dissolution of Zn is not promoted too much, not only does it have a long time to form the oxide layer, but also the plating layer is not severely damaged, compared to the original Zn steel It is because it is thought that the role of sacrificial protection will not be lost. Here, the pH increase degree of an acidic solution having a pH exceeding 2.0 is obtained by adding an inorganic acid having almost no buffering property in the pH range of 2.0 to 5.0 such as sulfuric acid to the acidic solution, and once reducing the pH to 2.0. We will evaluate it.

Acidic solutions with such pH buffering properties include acetates such as sodium acetate (CH ₃ COONa), phthalates such as potassium hydrogen phthalate ((KOOC) ₂ C ₆ H ₄ ), sodium citrate (Na Citrates such as ₃ C ₆ H ₅ O ₇ ) and potassium dihydrogen citrate (KH ₂ C ₆ H ₅ O ₇ ), succinates such as sodium succinate (Na ₂ C ₄ H ₄ O ₄ ), and lactic acid lactates such as sodium (NaCH ₃ CHOHCO _2), tartrates such as sodium tartrate _{(Na 2 C 4 H 4 O} 6), borate, at least one or more of phosphate, the respective ingredient content An aqueous solution containing 5 to 50 g / l can be used. When the concentration is 5 g / l or more, the pH of the solution does not increase relatively quickly with the dissolution of Zn, so that an oxide layer sufficient for improving the oxidation resistance can be formed. Further, if it is 50 g / l or less, the dissolution of Zn is not promoted too much, and not only does it take a long time to form the oxide layer, but also the plating layer is not severely damaged. It is because it is thought that the role of sacrificial protection against losing will not be lost.

  Furthermore, the pH of the acidic solution is desirably in the range of 0.5 to 2.0. When the pH is 2.0 or less, Zn is sufficiently dissolved in the solution, and the oxide layer is sufficiently formed. On the other hand, when the pH is 0.5 or more, dissolution of Zn is not promoted too much, and not only the amount of plating is not decreased, but also the plating layer is not cracked and is not easily peeled off during processing. . When the pH of the acidic solution is higher than the range of 0.5 to 2.0, the pH can be adjusted with an inorganic acid having no pH buffering property such as sulfuric acid.

  Moreover, it is preferable that it is the range of 20-70 degreeC about the temperature of an acidic solution. If it is 20 ° C. or higher, the production reaction of the oxide layer does not take a long time, and the productivity is not lowered. On the other hand, when the temperature is 70 ° C. or lower, there is no processing unevenness on the surface of the steel sheet, and the reaction can proceed relatively quickly.

  There is no particular limitation on the method of bringing the galvanized steel sheet into contact with the acidic solution. The method of immersing the galvanized steel sheet in the acidic solution, the method of spraying the acidic solution onto the galvanized steel sheet, and the acidic solution through the coating roll. There is a method of applying to a galvanized steel sheet.

After the galvanized steel sheet is brought into contact with the acidic solution composed of the above, it is desirable that the solution exists in the form of a thin liquid film on the steel sheet surface. This is because if the amount of the solution present on the steel plate surface is too large, the pH of the solution will hardly rise even if zinc dissolution occurs, and only zinc dissolution will occur one after another, forming the desired oxide layer. This is because it takes a long time to complete. In addition, the plating layer is severely damaged, and it may be possible to lose its original role as a rust-proof steel plate. From this viewpoint, the amount of the solution film formed on the steel plate surface is preferably adjusted to 20 g / m ² or less. More preferably, a liquid film amount of 3 g / m ² or more is suitable for the purpose of preventing the liquid film from drying. The amount of the solution film can be adjusted by a squeeze roll, air wiping or the like.
Moreover, after contacting an acidic solution, the time to water washing (holding time to water washing) needs to be 1 to 90 seconds. When the time until washing with water is less than 1 second, the acidic solution is washed away before the pH of the solution rises and the oxide layer is formed, so that the effect of improving oxidation resistance cannot be obtained. On the other hand, even if it exceeds 90 seconds, there is no change in the amount of layer formation.
In addition, you may give a surface activation process before making it contact with an acidic solution. The chemical solution used for the surface activation treatment is preferably an alkaline solution having a pH of 11 or more. The purpose of this treatment is, for example, in the case of a hot-dip galvanized steel sheet, removing the Zn-based oxide formed on the surface, exposing the new surface to the surface, and activating the reaction at the exposed part of the new surface, This is to facilitate the formation of a new oxide layer.

  Moreover, you may perform temper rolling before this surface activation process. Furthermore, after the plating treatment, surface activation treatment may be performed, temper rolling may be performed, and then contacted with an acidic solution. Part of the Zn-based oxide layer present on the surface of the galvanized steel sheet can be destroyed by a pressure-control roll used during temper rolling, and the Zn-based oxide layer can be combined with a surface activation treatment. Can be effectively removed.

The aqueous solution used for the surface activation treatment preferably has a pH of 11 or more, a temperature of 30 ° C. or more, and a contact time with the solution of 1 to 30 seconds. In the case of less than 1 second, the Zn-based oxide cannot be sufficiently dissolved, so that the reactivity with the subsequent acidic solution cannot be increased, and the oxide layer is not sufficiently formed. On the other hand, it may be longer than 30 seconds, but it is not preferable to perform the treatment for a long time because the productivity is lowered. More preferably, the pH is 11 or more and the temperature is 50 ° C. or more. If it is pH within the said range, there will be no restriction | limiting in the kind of solution, Sodium hydroxide, a sodium hydroxide type | system | group degreasing agent, etc. can be used.
The surface activation treatment is preferably performed before contact with the acidic solution, and may be performed before or after temper rolling performed after the plating treatment, if necessary. However, if the surface activation treatment is performed after temper rolling, the Zn-based oxide is mechanically destroyed at the portion that has been crushed by the rolling roll to become a convex portion. There is a tendency that the amount of removal of objects differs. For this reason, the amount of the Zn-based oxide after the surface activation treatment becomes non-uniform in the surface, and the subsequent reaction with the acidic solution becomes non-uniform so that sufficient characteristics may not be obtained. For this reason, more preferably, after the plating treatment, the surface activation treatment is performed, and after removing an appropriate amount of the Zn-based oxide uniformly in the surface, the temper rolling is performed, and then the process of contacting with the acidic solution is performed. preferable.
The method for the surface activation treatment is not particularly limited. Examples of the method include a dipping method, a spray method, and a roll coating method.
As described above, an oxide layer having an average thickness of 10 nm or more is formed on the surface of the galvanized steel sheet.

  In addition, the oxide layer in this invention is a layer which consists of an oxide and / or a hydroxide containing the oxide derived from Zn and an oxide colloid particle. The average thickness of the oxide layer containing such an oxide derived from Zn and oxide colloidal particles needs to be 10 nm or more. If the average thickness of the oxide layer is reduced to less than 10 nm in the pressure-regulating part and the non-pressure-regulating part, the effect on the oxidation resistance becomes insufficient. On the other hand, if the average thickness of the oxide layer containing the oxide derived from Zn and colloidal oxide particles is 200 nm or less, the coating does not break during hot press molding, so the sliding resistance does not increase. Moreover, since weldability does not fall, it is preferable. Furthermore, since the formed oxide does not become coarse and does not have a large amount, it does not adhere to a press die or the like and productivity is not lowered, which is preferable.

  In the present invention, if oxide colloid particles are contained in the acidic solution to be used, an oxide layer having excellent oxidation resistance, that is, excellent hot press formability can be stably formed. The acidic solution may contain other metal ions or inorganic compounds as impurities or intentionally. For example, S, N, Pb, Cl, Na, Mn, Ca, Mg, Ba, Sr, etc. are contained in the acidic solution, and even if these are incorporated in the oxide layer, the effect of the present invention is impaired. is not. In particular, Zn ions elute when the zinc-plated steel sheet and the acidic solution come into contact with each other, so an increase in the Zn concentration in the acidic solution is observed during the operation. The effect of the invention is not particularly affected.

  Moreover, although the base steel material concerning this invention is not specifically limited, It is preferable to set it as the steel composition from which the plating wettability at the time of a plating process and the plating adhesiveness after plating become favorable. In consideration of the case where hot press forming is performed, a hardened steel, such as a high-tensile steel plate, which is rapidly cooled after hot press forming to become high strength and high hardness, such as a high-strength steel plate, is particularly preferable.

In the present invention, the plating method is not particularly limited, but the hot dipping method is preferable in terms of cost. Of course, if an oxide layer containing a predetermined Zn and oxide derived from oxide colloidal particles can be obtained on the surface of the plated steel sheet, for example, the plating layer can be formed by any other method such as electroplating, thermal spray plating, vapor deposition plating, etc. It may be provided.
In addition to pure Zn, the plating composition includes Zn-Fe, Zn-Al, Zn-Ni, Zn-Mg, and the like. However, in the practice of the present invention, any zinc-based plated steel sheet containing Zn as a main component can dissolve Zn and form an oxide layer, so the type of plating is not limited.

Moreover, it does not specifically limit about the method of hot press molding. For example, with respect to the zinc-based plated steel sheet for hot press forming of the present invention, it is heated to the Ac3 transformation point or more at a heating rate of 1 to 100 ° C./second, and after holding for 5 to 6000 seconds, 400 to 800 ° C. By performing hot press molding in the temperature range, the effect of oxidation resistance of the present invention can be maximized.
Furthermore, during hot press molding, the member is cooled at a cooling rate of 10 to 200 ° C / s using a die and punch, or after hot press molding, the hot press molded member is taken out from the mold. It is also possible to cool with liquid or gas.

  Next, the present invention will be described in detail with reference to examples.

As a steel component, C: 0.23 mass%, Si: 0.12 mass%, Mn: 1.5 mass%, Cr: 0.50 mass%, B: 0.0020 mass%, with respect to the steel sheet consisting of the balance Fe and inevitable impurities, Alloying hot dip galvanizing treatment, hot dip galvanizing treatment, electro galvanizing treatment and hot dip galvanized aluminum plating treatment are performed, respectively, and alloyed hot dip galvanized steel sheet, hot dip galvanized steel sheet, electro galvanized steel sheet having a thickness of 1.2 mm, and A hot dip galvanized steel sheet was prepared. In addition, the coating adhesion amount of the hot dip galvanized steel sheet, the alloyed hot dip galvanized steel sheet, the electrogalvanized steel sheet, and the hot dip galvanized steel sheet is 45 g / m ² per side.

  Next, an acid solution contact treatment was performed on the galvannealed steel sheet (GA), the hot dip galvanized steel sheet (GI), the electrogalvanized steel sheet (EG), and the hot dip galvanized steel sheet (GL). In the acidic solution treatment, an acidic aqueous solution of sodium acetate 30 g / l having buffering properties was prepared, and then immersed in an acidic solution whose pH was adjusted with sulfuric acid for 3 seconds. Then, after squeezing the roll and adjusting the amount of liquid, left in the atmosphere at room temperature for 1 to 60 seconds, washed thoroughly with water, dried, and the surface of the plated steel sheet derived from Zn and oxide colloidal particles An oxide layer containing an oxide was formed. Detailed conditions are shown in Tables 1 to 4. Moreover, what did not perform the said acidic solution process as a comparative example was also produced.

The steel sheet produced as described above is judged to have sufficient hot press formability (appearance after forming) as an automobile outer sheet, and the average thickness of the oxide layer on the plating surface layer and the oxide colloid in the oxide layer The particle size of the oxide derived from the particles was measured. Details of the hot press moldability evaluation method, the oxide layer thickness, and the measurement method of the oxide particle size derived from the oxide colloid particles in the oxide layer are as follows.
・ Hot press formability (appearance evaluation)
In a heating furnace, it was heated to 900 ° C. at a heating rate of 15 ° C./s in an air atmosphere, held at 900 ° C. for 60 seconds, taken out from the heating furnace, and subjected to hot press molding of a cylindrical drawing. Hot press molding was performed under the conditions of drawing height: 25 mm, shoulder R: 5 mm, blank diameter: 90 mm, punch diameter: 50 mm, and die diameter: 53 mm. As the plating layer adhesion state of the test piece after molding, the peeling state of the plating layer was observed, and the hot press formability was evaluated in three stages.
○: Peeling area ratio 0% (no peeling), △: Peeling area ratio more than 0% to less than 3% (no peeling), X: Peeling area ratio 3% or more ・ Oxide layer thickness measurement Heat with a film thickness of 96 nm The average thickness of the oxide layer in terms of SiO ₂ was determined by measuring the O · Kα X-ray with a fluorescent X-ray analyzer using the Si wafer on which the oxidized SiO ₂ film was formed as a reference substance. The analysis area is 30 mmφ.
・ Measurement of the particle size of oxide derived from oxide colloidal particles in the oxide layer Take a cross-sectional photograph of the oxide layer with a scanning electron microscope (observation conditions: acceleration voltage 25 kV, magnification x 10000) and select at random The average value of 10 oxide particles (each maximum diameter) derived from colloidal oxide particles was obtained.

  The results obtained as described above are shown in Tables 1 to 4 together with the conditions.

  Nos. 1 to 38 shown in Table 1 are examples in which an alloyed hot-dip galvanized steel sheet was processed.

  No. 1 is a comparative example in which treatment with an acidic solution is not performed. Plating peeling was observed in the appearance after hot press forming, and the hot press formability was poor.

  Nos. 2 to 6 are comparative examples using an acidic solution which is treated with an acidic solution but does not contain oxide colloid particles. In this case, it is an oxide layer mainly composed of Zn, and the appearance after hot press forming tends to slightly suppress plating peeling, but the hot press formability is not sufficient.

Nos. 7-9, 10-12, 13-15, 24-26 are books using acidic solutions containing 1.0% by mass of oxide colloidal particles of Al ₂ O ₃ , TiO ₂ , ZrO ₂ , and SiO ₂ , respectively. It is an example of an invention. In any treatment, the film thickness of the oxide layer is increased compared with No. 4 to 6 of the holding time until the same water washing, and the formation of the oxide layer is promoted. Moreover, in the external appearance after hot press molding, plating peeling was suppressed and hot press formability was excellent.

Nos. 16 to 18, 24 to 26, and 36 to 38 are examples of the present invention in which treatment with an acidic solution was performed by changing only the concentration of the contained SiO ₂ colloidal particles. The formation of the oxide layer is promoted as compared with Comparative Examples Nos. 4 to 6 using an acidic treatment liquid that does not contain oxide colloid particles. In addition, since the oxide layer contains an oxide derived from colloidal oxide particles, oxidation resistance is improved, plating peeling is suppressed in the appearance after hot press forming, and hot press formability is excellent. It was. The higher the concentration of the added oxide colloidal particles, the thicker the oxide layer thickness, and the greater the effect on hot press formability.

  Nos. 19-21, 24-26, 33-35 are examples in which only the temperature of the acidic solution was changed. At any temperature, in the present invention example, the formation of the oxide layer was promoted by the effect of the addition of the oxide colloidal particles, and the plating peeling was suppressed in the appearance after the hot press forming. Was excellent.

  Nos. 24-32 are examples in which the amount of liquid film on the surface of the steel sheet was changed by roll drawing after the steel sheet and the acidic solution contacted each other. In any case, a sufficient oxide layer was formed, plating peeling was suppressed in the appearance after hot press forming, and hot press formability was excellent.

  As described above, in the present invention example, the appearance defect is suppressed by suppressing the evaporation of plating and the generation of scale during hot press forming, and the peeling of the plating layer is not observed, and the oxidation resistance is excellent. The property was good.

  Nos. 39 to 43 shown in Table 2 are examples in which the hot dip galvanized steel sheet was processed.

  No. 39 is a comparative example in which treatment with an acidic solution is not performed. Plating peeling was observed in the appearance after hot press forming, and the hot press formability was poor.

  No. 40 is a comparative example using an acidic solution that is treated with an acidic solution but does not contain colloidal oxide particles. In this case, it is an oxide layer mainly composed of Zn, and the appearance after hot press molding tends to slightly suppress plating peeling, but the hot press formability is not sufficient.

Nos. 41 to 43 are examples of the present invention using an acidic solution containing 1.0% by mass of SiO ₂ oxide colloidal particles, and are examples in which the holding time until water washing was changed. In any case, a sufficient oxide layer was formed, plating peeling was suppressed in the appearance after hot press forming, and hot press formability was excellent.

  Nos. 44 to 48 shown in Table 3 are examples in which the electrogalvanized steel sheet was processed.

  No. 44 is a comparative example in which treatment with an acidic solution is not performed. Plating peeling was observed in the appearance after hot press forming, and the hot press formability was poor.

  No. 45 is a comparative example using an acidic solution that is treated with an acidic solution but does not contain colloidal oxide particles. In this case, it is an oxide layer mainly composed of Zn, and the appearance after hot press forming tends to slightly suppress plating peeling, but the hot press formability is not sufficient.

Nos. 46 to 48 are examples of the present invention using an acidic solution containing 1.0% by mass of SiO ₂ oxide colloidal particles, and are examples in which the holding time until water washing was changed. In any case, a sufficient oxide layer was formed, plating peeling was suppressed in the appearance after hot press forming, and hot press formability was excellent.

  Nos. 49 to 86 shown in Table 4 are examples in which the hot dip zinc-aluminum plated steel sheet was processed.

  No. 49 is a comparative example in which treatment with an acidic solution is not performed. Plating peeling was observed in the appearance after hot press forming, and the hot press formability was poor.

  Nos. 50 to 54 are comparative examples using an acidic solution which is treated with an acidic solution but does not contain oxide colloidal particles. In this case, it is an oxide layer mainly composed of Zn, and the appearance after hot press forming tends to slightly suppress plating peeling, but the hot press formability is not sufficient.

This No.55~57,58~60,61~63,72~74 is using _{Al 2 O 3, TiO 2,} ZrO 2, acidic solution of the oxide colloidal particles of SiO ₂ contained 1.0 wt%, respectively It is an example of an invention. In any treatment, the film thickness of the oxide layer is increased compared with No. 52 to 54 having the same holding time until water washing, and the formation of the oxide layer is promoted. Moreover, in the external appearance after hot press molding, plating peeling was suppressed and hot press formability was excellent.

Nos. 64 to 66, 72 to 74, and 84 to 86 are examples of the present invention in which treatment with an acidic solution was performed by changing only the concentration of the contained SiO ₂ colloidal particles. The formation of the oxide layer is promoted as compared with Comparative Examples Nos. 52 to 54 using an acidic treatment liquid that does not contain oxide colloid particles. In addition, since the oxide layer contains an oxide derived from colloidal oxide particles, oxidation resistance is improved, plating peeling is suppressed in the appearance after hot press forming, and hot press formability is excellent. It was. The higher the concentration of the added oxide colloidal particles, the thicker the oxide layer thickness, and the greater the effect on hot press formability.

  Nos. 67 to 69, 72 to 74, and 81 to 83 are examples in which only the temperature of the acidic solution was changed. At any temperature, in the present invention example, the formation of the oxide layer was promoted by the effect of the addition of the oxide colloidal particles, and the plating peeling was suppressed in the appearance after the hot press forming. Was excellent.

  Nos. 72 to 80 are examples in which the amount of liquid film on the surface of the steel sheet was changed by roll drawing after the steel sheet and the acidic solution contacted each other. In any case, a sufficient oxide layer was formed, plating peeling was suppressed in the appearance after hot press forming, and hot press formability was excellent.

  As described above, in the present invention example, the appearance defect is suppressed by suppressing the evaporation of plating and the generation of scale during hot press forming, and the peeling of the plating layer is not observed, and the oxidation resistance is excellent. The property was good.

  On the other hand, in the comparative example, the oxide layer of the present invention was not formed, and plating layer peeling due to scale generation was observed after hot press molding.

  The plated steel sheet for hot press forming according to the present invention is excellent in oxidation resistance, and therefore can be applied in a wide range of fields mainly for automobile body applications such as automobile undercarriages, chassis and reinforcing parts.

Claims (7)

  Plating that forms an oxide layer having an average thickness of 10 nm or more on the surface of the zinc-based plated steel sheet by bringing the zinc-based plated steel sheet into contact with an acidic solution and holding the solution for 1 to 90 seconds after completion of the contact treatment, followed by washing with water and drying. In the manufacturing method of a steel plate, the said acidic solution contains an oxide colloid particle, The manufacturing method of the plated steel plate for hot press forming characterized by the above-mentioned.   The oxide colloidal particles are oxide colloidal particles containing one or more of Ti, Al, Si, Zr, Fe, Zn, Mn, Mo, Ni, Cr, Mg, and Cu. 2. A method for producing a hot-press formed plated steel sheet according to claim 1.   The method for producing a plated steel sheet for hot press forming according to claim 1 or 2, wherein the oxide colloidal particles are contained in the acidic solution in a mass concentration range of 0.1% to 20%.   The acidic solution has a pH buffering action and a pH increase defined by the amount (l) of 1.0 mol / l sodium hydroxide solution required to increase the pH of 1 liter of the acidic solution from 2.0 to 5.0 The method for producing a plated steel sheet for hot press forming according to any one of claims 1 to 3, wherein the degree is in a range of 0.05 to 0.5.   The acidic solution is at least one of acetate, phthalate, citrate, succinate, lactate, tartrate, borate, phosphate, and the content of the components is 5 to 50 g / The hot-press-formed plated steel sheet according to any one of claims 1 to 4, wherein the hot-press formed steel sheet is contained in the range of l, the pH is in the range of 0.5 to 2.0, and the liquid temperature is in the range of 20 to 70 ° C. Production method. The acidic solution film formed on the surface of the plated steel sheet after being contacted with the acidic solution is 20 g / m ² or less, and the holding time in a state where the acidic solution film is formed on the surface of the plated steel sheet is 1 to 90. It is the range of second, The manufacturing method of the plated steel plate for hot press forming as described in any one of Claims 1-5 characterized by the above-mentioned.   An oxide layer produced by the method for producing a hot-pressed plated steel sheet according to any one of claims 1 to 6, comprising Zn and an oxide derived from the oxide colloidal particles and having an average thickness of 10 nm or more A plated steel sheet for hot press forming, characterized by comprising: