JP6515356B2 - Steel plate for hot stamping, method of manufacturing the same, and hot stamped steel - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a steel plate for hot stamping excellent in scale adhesion at the time of hot stamping, a method for producing the same, and a hot stamped steel which is a molded article thereof.

  The weight reduction of members such as door guard bars and side members of automobiles is being considered in response to the recent trend of fuel efficiency, and in terms of materials, from the viewpoint that strength and collision safety can be ensured even if thinning. From this point of view, steel sheets are being strengthened. Hereinafter, strength means both tensile strength and yield strength. However, since the formability of the material deteriorates as the strength increases, it is necessary to produce a steel plate that satisfies both formability and high strength in order to realize the weight reduction of the above-mentioned members. As a method to obtain high strength and high formability simultaneously, there is TRIP (TRansformation Induced Plasticity) steel using martensitic transformation of retained austenite described in Patent Document 1 and Patent Document 2, and the application is expanding in recent years . However, although this steel improves deep drawability and elongation at the time of molding, it has a problem that the shape freezeability of the member after press forming is poor because the steel plate strength is high.

  On the other hand, as a method for forming a high strength steel plate inferior in formability with good shape freezeability, there is a method called warm press described in Patent Document 3 and Patent Document 4. This method is a method of forming at a temperature of about 200 ° C. to 500 ° C. where the steel plate strength decreases. However, in the case of forming a high strength steel plate of 780 MPa or more, even if the forming temperature is raised, the steel plate strength may still be high and it may be difficult to form, or the steel plate strength after forming may be reduced by heating. There is a problem that a predetermined strength may not be obtained.

  As a method of solving these problems, after cutting a soft steel plate into a predetermined size, the steel plate is heated to an austenite single phase region of 800 ° C. or more, and then pressed in an austenite single phase region as disclosed in Patent Document 5 There is a method called hot stamping which performs shaping and then hardening. As a result, it became possible to manufacture a member having high strength of 980 MPa or more and excellent shape freezeability.

  However, in hot stamping, the steel sheet is inserted into a heating furnace or heated to a high temperature exceeding 800 ° C. in the atmosphere by electric heating or far infrared heating, so that the scale is generated on the steel sheet surface. have. Since the generated scale is worn out at the time of hot stamping and the mold is worn away, it is required that the scale adhesion at the time of hot stamping be excellent. As a technique for solving these problems, for example, Patent Document 6 discloses a technique for suppressing the generation of scale by setting the atmosphere in the heating furnace to a non-oxidizing atmosphere. However, strict control of the atmosphere in the heating furnace is required, which increases the cost of equipment and lowers productivity. In addition, since the steel sheet taken out is exposed to the atmosphere, there is a problem that the formation of scale can not be avoided. In addition, in recent years, a method of electrically heating a steel sheet in the atmosphere has been developed for the purpose of improving the productivity of hot stamping. At the time of heating in the atmosphere, it is difficult to avoid the oxidation of the steel sheet, and the problem of mold wear and tear due to scale detachment at the time of hot stamping tends to be apparent. As a result, regular mold repair is essential.

  As a steel plate which solves these subjects, the art which controls wear of a metallic mold by exfoliation of scale is known by using a steel plate which gave galvanization or Al plating to a steel plate surface for a hot stamp. However, since galvanization or plating of Al is molten to form a liquid phase at the time of heating, zinc or Al adheres to the inside of the furnace and to the mold at the time of transportation or pressing of the steel plate. Deposits of deposited zinc or Al cause the pressing wrinkles of the hot stamped molded product, and have a problem of adhering to the molded product and deteriorating the appearance. From this, it was necessary to repair the mold regularly.

  From this, development of the steel plate for hot stampings which does not carry out scale exfoliation at the time of hot stamping, and adhesion of fusion metal to a metallic mold does not arise is called for.

Unexamined-Japanese-Patent No. 1-230715 JP-A-2-217425 JP 2002-143935 A JP, 2003-154413, A Japanese Patent Laid-Open No. 2002-18531 JP 2004-106034 Japanese Patent Laid-Open No. 2002-18531 JP 2008-240046 A JP, 2010-174302, A JP 2008-214650 A

  In view of the above-mentioned problems, the present invention provides a steel plate for hot stamping which is excellent in scale adhesion at the time of hot stamping and in which adhesion of molten metal to a mold does not occur, a method for producing the same and its hot stamped steel. With the goal.

The present inventors diligently studied methods for solving the above problems. As a result, 0.50 mass% to 3.00 mass% of Si is contained in the steel sheet for the purpose of improving the scale adhesion of the steel sheet, and the amount of rustproof oil applied to the steel sheet is 50 mg / m. The surface roughness of the steel plate is Rz> 2.5 μm, in the range of ^{2 to} 1500 mg / m ² . Further, preferably, the S content contained in the antirust oil is 5% by mass or less. It has been found that this improves the scale adhesion at the time of heating and at the time of hot stamping. In general, the content in the oil is degraded to the interface between the ground iron and the scale to deteriorate the scale adhesion. However, it has been found that it is possible to secure scale adhesion by combining the amount of inclusion and the anchor effect utilizing the unevenness of the steel sheet surface.

The present invention has been made based on the above findings, and the summary thereof is as follows.
(1) mass%,
C: 0. 100% to 0.600%,
Si: 0.50% to 3.00%,
Mn: 1.20% to 4.00%,
Ti: 0.005% to 0.100%,
B: 0.0005% to 0.0100%,
P: 0. 100% or less,
S: 0.0001% to 0.0100%,
Al: 0.005% to 1.000%,
N: 0.0100% or less,
Ni: 0% to 2.00%,
Cu: 0% to 2.00%,
Cr: 0% to 2.00%,
Mo: 0% to 2.00%,
Nb: 0% to 0.100%,
V: 0% to 0.100%,
W: 0% to 0.100%, and one or more selected from the group consisting of REM, Ca, Ce and Mg in total: 0% to 0.0300%
Containing a composition the balance being Fe and impurities, the surface roughness of the steel sheet is the Rz> 2.5 [mu] m, the coating oil oiled amount 50mg / m ² ~1500mg / m ² on the surface is coated Yes,
The steel sheet for hot stamping, wherein the amount of S contained in the oil applied to the surface is 5% or less by mass .

( 2 ) The composition of the steel plate is, in mass%,
Ni: 0.01% to 2.00%,
Cu: 0.01% to 2.00%,
Cr: 0.01% to 2.00%,
Mo: 0.01% to 2.00%,
Nb: 0.005% to 0.100%,
V: 0.005% to 0.100%, and W: 0.005% to 0.100%,
The steel sheet for hot stamping according to the above (1) , which contains one or more selected from the group consisting of

( 3 ) The composition of the steel plate is in mass%,
The hot according to the above (1) or (2) characterized in that it contains 0.0003% to 0.0300% in total of one or more selected from the group consisting of REM, Ca, Ce and Mg. Stamp steel plate.

( 4 ) mass%,
C: 0. 100% to 0.600%,
Si: 0.50% to 3.00%,
Mn: 1.20% to 4.00%,
Ti: 0.005% to 0.100%,
B: 0.0005% to 0.0100%,
P: 0. 100% or less,
S: 0.0001% to 0.0100%,
Al: 0.005% to 1.000%,
N: 0.0100% or less,
Ni: 0% to 2.00%,
Cu: 0% to 2.00%,
Cr: 0% to 2.00%,
Mo: 0% to 2.00%,
Nb: 0% to 0.100%,
V: 0% to 0.100%,
W: 0% to 0.100%, and one or more selected from the group consisting of REM, Ca, Ce and Mg in total: 0% to 0.0300%
Casting a slab containing Fe and the remainder comprising Fe and impurities, directly or temporarily cooling, and then heating and hot rolling to obtain a hot rolled steel sheet;
Carrying out pickling for 30 seconds or more in an aqueous solution having a temperature of 80 ° C. or more and less than 100 ° C. and an inhibitor-containing acid concentration of 3% by mass to 20% by mass;
Applying an anticorrosion oil having an S content of 5% or less by mass on a steel plate after the pickling;
Have
Method for producing a hot stamping steel plate, characterized in that to limit the anti-rust oil residual amount of the steel sheet surface to ^{50mg / m 2 ~1500mg / m 2} .

( 5 ) The method for producing a steel plate for hot stamping as described in ( 4 ) above, characterized in that the anticorrosion oil is applied to the pickled hot rolled steel sheet.

( 6 ) The method further includes the step of cold rolling the pickled hot rolled steel sheet to obtain a cold rolled steel sheet,
The method for producing a steel plate for hot stamping according to ( 4 ), characterized in that the anticorrosion oil is applied to the cold rolled steel plate.

( 7 ) The method further includes the step of cold-rolling the pickled hot-rolled steel plate, and further performing heat treatment in a continuous annealing facility or a box-type annealing furnace to obtain a cold-rolled steel plate,
The method for producing a steel plate for hot stamping according to ( 4 ), characterized in that the anticorrosion oil is applied to the cold rolled steel plate.

( 8 ) The composition of the slab is, by mass%,
Ni: 0.01% to 2.00%,
Cu: 0.01% to 2.00%,
Cr: 0.01% to 2.00%,
Mo: 0.01% to 2.00%,
Nb: 0.005% to 0.100%,
V: 0.005% to 0.100%, and W: 0.005% to 0.100%,
The manufacturing method of the steel plate for hot stampings in any one of said (4)-(7) characterized by including 1 type (s) or 2 or more types selected from the group which consists of.

( 9 ) The composition of the slab is, by mass%,
One or more selected from the group consisting of REM, Ca, Ce and Mg in total of 0.0003% to 0.0300% are contained in any one of the above (4) to (8) The manufacturing method of the steel plate for hot stamping as described.

(10) in mass%,
C: 0. 100% to 0.600%,
Si: 0.50% to 3.00%,
Mn: 1.20% to 4.00%,
Ti: 0.005% to 0.100%,
B: 0.0005% to 0.0100%,
P: 0. 100% or less,
S: 0.0001% to 0.0100%,
Al: 0.005% to 1.000%,
N: 0.0100% or less,
Ni: 0% to 2.00%,
Cu: 0% to 2.00%,
Cr: 0% to 2.00%,
Mo: 0% to 2.00%,
Nb: 0% to 0.100%,
V: 0% to 0.100%,
W: 0% to 0.100%, and one or more selected from the group consisting of REM, Ca, Ce and Mg in total: 0% to 0.0300%
Contain, comprises the balance consisting of Fe and impurities, the interface between the scale and the base steel, Ri per unevenness 100μm to be a range of depth 0.2Myuemu～8.0Myuemu, there three or more And a thickness of the scale is 10 μm or less, and a tensile strength is 1180 MPa or more.

(11) the the surface of the hot stamping material, Si oxide, FeO, Fe ₃ O _4, and hot stamping molded article according to (10), characterized in that to have a Fe ₂ O _3.

( 12 ) The composition of the hot stamped molded body is, by mass%,
Ni: 0.01% to 2.00%,
Cu: 0.01% to 2.00%,
Cr: 0.01% to 2.00%,
Mo: 0.01% to 2.00%,
Nb: 0.005% to 0.100%,
V: 0.005% to 0.100%, and W: 0.005% to 0.100%,
The hot stamped molded article according to the above (10) or (11) , which contains one or more selected from the group consisting of

( 13 ) The composition of the hot stamped molded body is, by mass%,
One or more selected from the group consisting of REM, Ca, Ce, and Mg in total of 0.0003% to 0.0300% are contained in any one of the above (10) to (12). The hot stamped molded object as described in a term.

  According to the present invention, it is possible to provide a steel plate for hot stamping which is excellent in scale adhesion at the time of hot stamping and in which adhesion of molten metal to a mold does not occur, a method for producing the same and a hot stamped steel body.

FIG. 1 is a view showing the relationship between the amount of oil applied to a steel plate and the surface roughness Rz of the steel plate. FIG. 2 is a view for explaining that the scale is easily peeled off when the concentration of S in the oil increases. FIG. 3 is a view showing the relationship between the pickling time and the surface roughness Rz of the steel plate. FIG. 4A is a photograph showing the microstructure of the surface layer of the hot-rolled steel plate before pickling. FIG. 4B is a photograph showing the surface layer microstructure after pickling. FIG. 5 is a view showing the relationship between the amount of oil applied and the thickness of the scale. FIG. 6A is a photograph showing a cross section of the surface of the hot stamped molded article of the example of the present invention. FIG. 6B is a photograph showing a cross section of the surface of the hot stamped molded article of the comparative example. FIG. 7 is a view for explaining that when the surface roughness Rz before the hot stamp heat treatment is less than 2.5, the number density of the asperities after the hot stamp heat treatment is less than 3.

The steel plate for hot stamping according to the present invention contains 0.5% by mass to 3.0% by mass of Si in the steel plate, and the amount of rustproof oil applied to the steel plate is 50 mg / m ^{2 to} 1500 mg / m ² the ^second range, the surface roughness of the steel sheet, characterized in that the Rz> 2.5 [mu] m. And Preferably, S content contained in rustproof oil shall be 5 mass% or less.
First, the reason why the present inventors focused on oiling will be described.

  The inventors of the present invention have investigated the effects of the surface properties of the steel sheet and various treatments in order to improve the scale adhesion of the steel sheet (cold-rolled steel sheet or hot-rolled steel sheet) which is not plated. As a result, it has been found that although the steel sheet after degreasing exhibits excellent scale adhesion, application of a rust preventive oil significantly deteriorates the scale adhesion. More specifically, when the relationship between the scale adhesion and the antirust oil was investigated, it became clear that when the amount of S contained as an impurity in the antirust oil increases, the scale tends to be peeled off. It is considered that S in rust preventive oil has an influence on scale adhesion although the detailed reason is unknown.

On the other hand, pickled hot-stamped hot-rolled steel sheets, cold-rolled or annealed cold-rolled steel sheets for hot stamping use mineral oil etc. in order to suppress the occurrence of rusting from production to use. It is necessary to apply an antirust oil. In particular, after pickling, assuming that the period from delivery to use to a customer becomes long, it was common to apply oil exceeding 1500 mg / m ² . The present inventors investigated the influence of the amount of applied oil for the purpose of achieving both the scale adhesion and the antirust property. As shown in FIG. 1, the range of the amount of applied oil and the surface roughness of the steel sheet is strict. It was found that the adhesion to the scale was improved by controlling the Unction amount effect is exhibited by a ^{50mg / m 2 ~1500mg / m 2} . The lower limit of 50 mg / m ² is defined as 50 mg / m ² as the lower limit of coating oil amount, since it is difficult to ensure excellent rust prevention if the amount is less than the coating oil amount. Preferably, it is 100 mg / m ² or more, more preferably 200 mg / m ² or more. The upper limit of the amount of oil applied is set to 1500 mg / m ² in order to obtain the effect of excellent scale adhesion. Is 1500 mg / ^{m 2} and the upper limit since the oiling weight scale adhesion is deteriorated more than 1500 mg / ^{m 2.} Preferably, the upper limit is 1000 mg / m ² , more preferably, the upper limit is 900 mg / m ² , and still more preferably, the upper limit is 800 mg / m ² . In addition, since the oil on the surface of the steel sheet burns during heating, it causes soot. Also from this point, it is preferable that the amount of oil applied is small.

  The scale adhesion shown in FIG. 1 was evaluated by a hot shallow drawing test using a cylindrical mold of 70 mm in diameter and 20 mm in depth. The steel plate is heated to a temperature range of 800 ° C. to 1100 ° C. at 50 ° C./s with an electric heating device and held for 0 seconds to 120 seconds, and then the current flow is stopped to allow 650 ° C. It was cooled down and hot shallow drawing was performed with the above mold. The test specimen after molding was visually observed, and the scale peeling was good when the area of scale peeling was 5% or less (○), the one with a scale peeling area of 5 to 15% was bad (Δ), scale When the area of peeling was more than 15%, it was regarded as poor (x). An area having a scale exfoliation of 5% or less was considered to be within the scope of the present invention.

  The evaluation of scale adhesion is possible without particular limitation on the heating method. For example, any conditions of a heating furnace, far infrared rays, near infrared rays, and electric current heating may be used. Moreover, when heating a steel plate with a heating furnace, the further outstanding scale adhesiveness can be obtained by controlling the atmosphere in a heating furnace, suppressing the oxidation of a steel plate, and thinning a scale.

  The shallow drawing test temperature may be any temperature range as long as the steel plate can be processed, but generally, the steel plate for hot stamping has high strength and excellent due to processing in the austenite region and subsequent die hardening. It has shape freezing property. From this, the characteristic evaluation was carried out by hot shallow drawing at 650 ° C., which is higher than Ar 3.

  Although an electrostatic oil, a spray, a roll coater etc. are generally used as an oil method, if an amount of oil can be secured, the oil method is not limited.

  Although the oil type is not specified, for example, if it is a mineral oil type, NOX-RUST 530F (manufactured by Parker Kosan Co., Ltd.) etc. is generally used, but if the oil amount satisfies the scope of the present invention, oil The species is not limited.

  The amount of oil applied may be measured by any method as long as it can be measured, but the present inventors measured it by the following method. First, a steel plate coated with an antirust oil was cut into 150 mm squares, and then a tape was attached so that an area of 100 mm × 100 mm was exposed. Then, the weight of the oil and the steel plate (including the weight of the tape) subjected to the sealing is measured in advance. Next, degreasing is performed by wiping off the rustproof oil on the surface of the steel plate with a cloth containing acetone, the weight of this degreased steel plate is measured, and the amount of oil applied per unit area by comparing the weight before and after degreasing Was calculated. It implemented by three places of each steel plate, and made the average value of the adhesion amount the amount of oil adhesion of each steel plate.

It is preferable to limit the S content contained in the antirust oil to 5% by mass or less. The inventors investigated the relationship between the S content in the coating oil and the scale peeling area ratio as shown in FIG. 2. As the S content in the coating oil decreases, the scale adhesion improves. In particular, when the S content in the oil was 5% by mass or less, the scale exfoliation area was found to be approximately 0%. Although the detailed mechanism is unknown, the oil contained in the rustproof oil does not burn during heating, but S contained as an impurity remains on the surface of the steel sheet and concentrates in scale, thereby deteriorating the scale adhesion. It is considered to be something that From this, it is preferable to reduce the S content contained in the antirust oil. Preferably, it is 4% by mass or less, more preferably 3% by mass or less. Although any method can be used for analysis of S in the antirust oil, the present inventors collected 5 mL of antirust oil to be applied to a steel plate, and fluorescent X-ray (fluorescent X- ray sulfur analyzer SLFA The analysis was performed at -2800 / HORIBA). The measurement was performed at n = 3, and the average value was defined as the S content.

  Next, the surface roughness of the steel plate will be described. In order to ensure scale adhesion, the surface roughness of the steel sheet needs to be Rz> 2.5 μm. The result obtained by investigating the relationship between the surface roughness Rz of the steel plate and the scale adhesion is as shown in FIG. 1 described above. By providing asperities at the interface between the scale formed at the time of the hot stamp heat treatment and the base steel, asperities are formed at the interface between the base iron and the scale, leading to a further improvement in adhesion. This effect is generally called an anchor effect. In particular, the scale produced on heating with this steel sheet is thin. As a result, in the case of the present steel sheet having a small scale thickness, a scale having irregularities is formed under the influence of the surface condition of the base iron. From this, it is necessary to set the surface roughness of the steel plate before hot stamping to Rz> 2.5 μm. When Rz ≦ 2.5 μm, the surface roughness of the steel sheet is small and the anchor effect is insufficient, so that excellent scale adhesion at the time of hot stamping can not be ensured. Although the upper limit is not particularly set, the excellent scale adhesion effect of the present invention can be obtained, but if the scale adhesion is excessively improved excessively, for example, it is difficult to remove the scale in the subsequent steps such as shot blasting. It becomes. Therefore, it is preferable to set Rz <8.0 μm. More preferably, Rz <7.0 μm. However, even when Rz ≧ 8.0 μm, the excellent scale adhesion which is the effect of the present invention can be secured. In the case of steel plates with a Si content of less than 0.50 mass%, even if the surface roughness is Rz> 2.5 μm, thick Fe-based scales are formed during heating, even if the steel plate surface has irregularities. Excessive oxidation causes the interface between the ground iron and the scale to be flat. As a result, the unevenness at the interface between the scale and the base iron is eliminated, and the excellent effect of scale adhesion, which is the effect of the present invention, is not exhibited.

  The surface roughness Rz may be measured by any method, but the present inventors measured the surface angle of a stylus with a tip angle of 60 ° and a tip R of 2 μm (SURFCOM 2000 DX / SD3 Tokyo Seimitsu Co., Ltd.) In the above, the area of 10 mm in length was measured at n = 3, and the average value was taken as the surface roughness Rz of each steel plate.

Next, the scale structure of the hot stamped molded body will be described. The steel plate for hot stamping of the present invention secures the scale adhesion by controlling the unevenness of the interface between the scale and the base steel. From this, the scale may be a scale mainly composed of Si oxide, Fe ₃ O ₄ , Fe ₂ O ₃ , and FeO. The Si oxide controls the thickness of the iron-based scale by being present at the interface between the ground iron and the iron-based scale (FeO, Fe ₂ O ₃ , Fe ₃ O ₄ ). From this, it is necessary to include Si oxide in the scale. Since the main purpose is to control the thickness of the iron-based oxide, the Si oxide may be present even if it is very thin. For example, even if it is 1 nm, the effect is exhibited.

  Composition analysis of the scale of the molded body was performed by cutting the plate from the bottom of the cylindrical portion of the shallow drawn test piece and performing X-ray diffraction. The volume fraction of each Fe-based oxide was measured from the peak intensity ratio of each oxide. Since the Si oxide was present very thin and the volume fraction was less than 1%, quantitative evaluation by X-ray diffraction was difficult. However, it is possible to confirm the presence of Si oxide at the interface between the scale and the base iron by line analysis of EPMA (Electron Probe Micro Analyzer).

  The thickness of the scale is preferably 10 μm or less. When the thickness of the scale is 10 μm or less, the scale adhesion is further improved. When the thickness of the scale exceeds 10 μm, the scale tends to be easily exfoliated due to the thermal stress that works during cooling at the time of hot stamping. On the other hand, thereafter, in a scale removing process such as shot blasting or wet blasting, cracking occurs between Fe-based scales, and the scale present outside is exfoliated. As a result, it had the subject that it was inferior also to scale removability. From this, the thickness of the scale is preferably 10 μm or less. More preferably, it is 7 micrometers or less, More preferably, it is 5 micrometers or less. The thickness of the scale is achieved by controlling the amount of oil applied to a predetermined range at the same time as controlling the Si content of the steel sheet within a predetermined range. FIG. 5 shows the relationship between the amount of oil applied and the scale thickness.

  In the interface between the ground iron and the scale in the hot stamped molded article of the present invention, three or more irregularities having a diameter of 0.2 μm to 8.0 μm are present per 100 μm. FIG. 6A shows a photograph of the interface between the ground iron and the scale of the molded product excellent in scale adhesion, and FIG. 6B shows a photograph of the interface between the ground iron and the scale which is inferior in scale adhesion. This unevenness contributes to the improvement of the scale adhesion at the time of hot stamping, so that the excellent scale adhesion can be secured by controlling the above range. If the unevenness is less than 0.2 μm, the anchor effect is not sufficient and the scale adhesion is poor. If the unevenness is more than 8.0 μm, the scale adhesion is too strong, and it is difficult to remove the scale by, for example, shot blasting or wet blasting in the subsequent scale removing process, so the unevenness at the interface between the scale and the base iron is 8 It is preferable that the thickness be less than or equal to 0 μm. More preferably, it is 6.0 micrometers or less, More preferably, it is 4.0 micrometers or less. However, even if the unevenness exceeds 8.0 μm, the excellent scale adhesion which is the effect of the present invention can be ensured.

  If the number per 100 μm of irregularities of 0.2 μm to 8.0 μm is less than 3, the improvement effect of the scale adhesion is not sufficient, and therefore, it is 3 or more. On the other hand, the upper limit of the number is not particularly limited, and the excellent scale adhesion which is the effect of the present invention can be secured. In addition, as shown in FIG. 7, the unevenness | corrugation of a molded object has correlation with surface roughness Rz of a steel plate, and it can control by setting it as the surface roughness Rz> 2.5 micrometers of a steel plate.

Next, the chemical compositions of the steel plate and the hot stamped steel of the present invention will be described. Hereinafter,% means mass%.
C: 0. 100% to 0.600%
C is an element contained to increase the strength of the steel plate. If the C content is less than 0.100%, a tensile strength of 1180 MPa or more can not be secured, and a high-strength molded body, which is the purpose of a hot stamp, can not be secured. On the other hand, if the C content exceeds 0.600%, the weldability and the processability become insufficient, so the C content is made 0.100% to 0.600%. It is preferably 0.100% to 0.550%, more preferably 0.150% to 0.500%. However, excellent scale adhesion can be ensured even if the C content is less than 0.150% as long as the strength of the molded body is not required.

Si: 0.50% to 3.00%
Si is an essential element because it improves scale adhesion by controlling the scale composition at the time of hot stamping. If the Si content is less than 0.50%, the thickness of the Fe-based scale can not be controlled, and excellent scale adhesion can not be secured. From this, the Si content needs to be 0.50% or more. In addition, in view of application to a member having severe molding at the time of hot stamping, it is preferable to increase the Si content. Therefore, the Si content is preferably 0.70% or more, more preferably 0.90% or more. On the other hand, Si increases the Ae3 point and increases the heating temperature required to make martensite the main phase, so if it is included excessively, the productivity and the economy decline. From this, the Si content has an upper limit of 3.00%. Preferably, the upper limit of the Si content is 2.5%, and more preferably the upper limit is 2.0%. However, it is possible to ensure excellent scale adhesion except for productivity and economy.

Mn: 1.20% to 4.00%
Mn is required to be contained by 1.20% or more in order to delay the ferrite transformation in the cooling process at the time of hot stamping and to make the hot stamped molded body into a structure having a martensitic main phase. When the Mn content is less than 1.20%, martensite can not be used as the main phase, and it is difficult to secure high strength, which is the purpose of the hot stamped steel, so the lower limit of the Mn content is 1.20%. Do. However, if the strength of the molded body is not required, excellent scale adhesion can be ensured even if the Mn content is less than 1.20%. On the other hand, if the Mn content exceeds 4.00%, the effect is saturated and embrittlement is caused to cause cracking during casting, cold rolling or hot rolling, so the upper limit of the Mn content is 4 And .00%. Preferably, the Mn content is in the range of 1.50% to 3.50%, and more preferably in the range of 2.00% to 3.00%.

Ti: 0.005% to 0.100%
Ti is an element that combines with N to form TiN, thereby suppressing B from becoming a nitride and improving the hardenability. Since this effect becomes remarkable when the Ti content is 0.005% or more, the Ti content is made 0.005% or more. However, if the Ti content exceeds 0.100%, Ti carbide is formed, the amount of C contributing to the strengthening of martensite is reduced, and a reduction in strength is caused, so the upper limit of the Ti content is 0.100. And%. Preferably, the Ti content is in the range of 0.005% to 0.080%, and more preferably in the range of 0.005% to 0.060%.

B: 0.0005% to 0.0100%
B improves the hardenability at the time of hot stamping and contributes to making the main phase martensite. This effect is remarkable when the B content is 0.0005% or more, so the B content needs to be 0.0005% or more. On the other hand, when the B content exceeds 0.0100%, the effect saturates and iron boride precipitates, and the hardenability effect of B is lost, so the upper limit of the B content is 0.0100. And%. Preferably, the B content is in the range of 0.0005% to 0.0080%, and more preferably in the range of 0.0005% to 0.0050%.

P: 0. 100% or less P is an element that segregates in the central portion of the thickness of the steel sheet, and is also an element that embrittles the weld. Therefore, the upper limit of the P content is 0.100%. A more preferred upper limit is 0.050%. The lower P content is preferable, and the lower limit is not particularly defined. The effects of the present invention can be exhibited. However, reducing P to less than 0.001% is an economy from the viewpoint of de-P productivity and cost. And the lower limit is preferably 0.001%.

S: 0.0001% to 0.0100%
Since S has a large effect on scale adhesion, it is necessary to limit the content in the steel sheet. Therefore, the upper limit of the S content is made 0.0100%. On the other hand, since it is economically disadvantageous from the viewpoint of productivity and cost of de-P, the lower limit of the S content is made 0.0001%. Preferably, the S content is in the range of 0.0001% to 0.0070%, and more preferably in the range of 0.0003% to 0.0050%.

Al: 0.005% to 1.000%
Since Al acts as a deoxidizer, the Al content is made 0.005% or more. If the Al content is less than 0.005%, a sufficient deoxidizing effect can not be obtained, and a large amount of inclusions (oxides) will be present in the steel sheet. These inclusions are not preferable because they become a starting point of breakage at the time of hot stamping and cause breakage. This effect is remarkable when the Al content is 0.005% or more, so the Al content needs to be 0.005% or more. On the other hand, if the Al content exceeds 1.000%, the Ac3 point is increased to increase the heating temperature at the time of hot stamping. That is, the hot stamp heats the steel plate to the austenite single-phase region, and performs a hot-pressing of the steel plate with excellent formability, and quenching by using a die to obtain a complex shape. It is a technology to obtain a strong molded body. As a result, when a large amount of Al is contained, the Ac3 point is significantly improved, the heating temperature required for heating the austenite single phase region is increased, and the productivity is lowered. From this, the upper limit of the Al content needs to be 1.000%. Preferably, the Al content is in the range of 0.005% to 0.500%, and more preferably in the range of 0.005% to 0.300%.

N: 0.0100% or less N is an element that forms coarse nitrides and degrades bendability and hole expandability. If the N content exceeds 0.0100%, the bendability and the hole expansibility deteriorate significantly, so the upper limit of the N content is made 0.0100%. In addition, since it becomes a cause of generation | occurrence | production of the blowhole at the time of welding, it is preferable that there is little N. Therefore, preferably the N content is 0.0070 or less, more preferably 0.0050% or less. On the other hand, the lower limit of the N content does not have to be particularly defined, but when the N content is reduced to less than 0.0001%, the manufacturing cost is significantly increased, so 0.0001% is a substantial lower limit. From the viewpoint of the manufacturing cost, the N content is more preferably 0.0005% or more.

In addition, it may contain a trace amount of other unavoidable elements. For example, O forms an oxide and exists as an inclusion.
The steel sheet of the present invention further contains the following elements, as necessary.

Ni: 0.01% to 2.00%
Cu: 0.01% to 2.00%
Cr: 0.01% to 2.00%
Mo: 0.01% to 2.00%
Ni, Cu, Cr, and Mo are elements contributing to high strength by enhancing the hardenability at the time of hot stamping and making the main phase martensite. Since this effect becomes remarkable when each of one or more selected from the group consisting of Ni, Cu, Cr and Mo is contained by 0.01% or more, the content of these elements is It is preferable that each is 0.01%. If the content of each element exceeds a predetermined amount, the weldability, hot workability, etc. may deteriorate, or the strength of the steel plate for hot stamping may be too high, which may cause manufacturing problems. It is preferable to set the upper limit of the content of the element of 2.00%.

Nb: 0.005 to 0.100%
V: 0.005 to 0.100%
W: 0.005 to 0.100%
Nb, V, and W are elements that strengthen fine grains by suppressing the growth of austenite at the time of hot stamping, and contribute to increase in strength and improvement in toughness. From this, you may contain 1 type, or 2 or more types selected from the group which consists of these elements. Since this effect becomes remarkable when each element is contained by 0.005% or more, it is preferable to contain these elements by 0.005% or more. If each of these elements is contained in excess of 0.100%, Nb, V, and W carbides are formed, the amount of C contributing to the strengthening of martensite is reduced, and a reduction in strength is caused. Not desirable. Preferably, they are each in the range of 0.005% to 0.090%.

A total of one or more selected from the group consisting of REM, Ca, Ce, and Mg: 0.0003% to 0.0300%
In the present invention, one or more selected from the group consisting of REM, Ca, Ce, and Mg may be further contained in total of 0.0003% to 0.0300%.
REM, Ca, Ce, and Mg are elements contributing to the improvement of the material while improving the strength. If the sum of one or more selected from the group consisting of REM, Ca, Ce, and Mg is less than 0.0003%, a sufficient effect can not be obtained, so the lower limit of the sum is made 0.0003%. It is preferable to do. On the other hand, if the sum of one or more selected from the group consisting of REM, Ca, Ce, and Mg exceeds 0.0300%, castability and hot workability may be degraded. It is preferable to set the upper limit of the total as 0.0300%. REM is an abbreviation of Rare Earth Metal, and refers to an element belonging to the lanthanoid series. In the present invention, REM is often added as a misch metal, and in addition to Ce, it may contain a compound of a lanthanoid series element in a composite.

  In the present invention, even if elements of lanthanoid series other than La and Ce are contained as unavoidable impurities, the effect of the present invention is exhibited, and even if elements such as other metals are contained as impurities, the present invention Effects are manifested.

Next, the features of the microstructures of the steel plate for hot stamping and the hot stamped steel according to the present invention will be described.
If the chemical composition, the surface roughness of the steel sheet, and the amount of coating oil satisfy the range of the present invention, then the pickled hot rolled steel sheet, cold rolled steel sheet obtained by cold rolling the hot rolled steel sheet, or after cold rolling The effect of the present invention can be exhibited with any of the cold-rolled steel sheets subjected to annealing.

  Since these steel plates are heated to an austenite region of over 800 ° C. during hot stamping, their performance as a steel plate for hot stamping having excellent scale adhesion, which is an effect of the present invention, is not particularly limited in microstructure. It is exhibited. However, when performing mechanical cutting and cold stamping of the steel plate prior to hot stamping, the strength of the steel plate should be as low as possible to reduce wear of the die, cutter blade, or punching die. Is preferred. From this, it is preferable that the microstructure of the steel plate for hot stamping be a ferrite and pearlite structure, or a bainite structure and a tempered structure of martensite. However, if the wear of punches and dies during machine cutting and cold punching is not an issue, even if it contains one or more of retained austenite, as-quenched martensite, and bainite. The excellent scale adhesion which is the effect of the present invention can be secured. Moreover, in order to reduce the strength of the steel plate, heat treatment in a box annealing furnace or continuous annealing equipment may be performed. Alternatively, after the softening treatment, cold rolling is performed to control the plate thickness to a predetermined thickness, and the excellent scale adhesion which is the effect of the present invention is secured.

  In order to increase the strength of the formed body after hot stamping and obtain high strength of the member, it is preferable that the microstructure of the formed body has martensite as a main phase. In particular, in order to secure a tensile strength of 1180 MPa or more, it is preferable to set the volume fraction of martensite which is the main phase to 60% or more. Martensite may be tempered after hot stamping, and may be tempered martensite. The structure other than martensite may include bainite, ferrite, pearlite, cementite, and retained austenite. In addition, even when the volume fraction of martensite is less than 60%, the excellent scale adhesion of the present invention can be secured.

  The following methods are used for identification of the microstructure (tempered martensite, martensite, bainite, ferrite, pearlite, retained austenite and residual structure) that constitutes the steel sheet structure, confirmation of the location, and measurement of the area ratio. For example, with the Nital reagent and the reagent disclosed in JP-A-59-219473, the cross section in the steel plate rolling direction or the cross direction perpendicular to the rolling direction is corroded, and a scanning electron microscope (SEM: 1000 to 100000 times) It is possible by observing the tissue with a transmission electron microscope (TEM: Transmission Electron Microscope). The present inventors take a sample with a plate thickness section parallel to the rolling direction of the steel plate as an observation surface, polish the observation surface, and perform nital etching to make 1⁄4 to 1⁄4 of the plate thickness as a center The area fraction was measured by observing the range of 3/8 thickness with a field emission scanning electron microscope (FE-SEM: Field Emission Scanning Electron Microscope), and it was taken as a volume fraction. The volume fraction of retained austenite was measured by performing X-ray diffraction using a plane having a thickness of 1⁄4 parallel to the plate surface of the base steel plate as an observation surface, and the volume fraction was measured.

Next, the method for producing a steel plate for hot stamping according to the present invention will be described.
As other operation conditions, although it is based on a usual method, the following conditions are preferable on productivity.

In order to manufacture the steel plate in the present invention, first, a slab having the same composition as that of the steel plate described above is cast. As a slab to be subjected to hot rolling, one manufactured by a continuous casting slab, a thin slab caster or the like can be used. The method for producing a steel sheet of the present invention is compatible with a process such as continuous casting-direct rolling (CC-DR) in which hot rolling is immediately performed after casting.
Slab heating temperature: 1100 ° C. or more Hot rolling completion temperature: Ar 3 transformation point or more Winding temperature: 700 ° C. or less Cold rolling ratio: 30 to 70%

  The slab heating temperature is preferably 1100 ° C. or more. Since the slab heating temperature in the temperature range below 1100 ° C. causes a decrease in the finish rolling temperature, the strength during finish rolling tends to be high. As a result, there is a possibility that the rolling will be difficult or the shape defect of the steel sheet after rolling may be caused, so the slab heating temperature is preferably set to 1100 ° C. or more.

  The finish rolling temperature is preferably set to the Ar3 transformation point or higher. If the finish rolling temperature is lower than the Ar3 transformation point, the rolling load becomes high, which may make rolling difficult or may cause shape defects of the steel sheet after rolling, so the lower limit of the finish rolling temperature is Ar3 transformation. It is preferable to make it a point. The upper limit of the finish rolling temperature is not particularly limited, but if the finish rolling temperature is excessively high, the slab heating temperature must be excessively high to secure the temperature, so the upper limit of the finish rolling temperature is 1100 ° C is preferred.

  The winding temperature is preferably 700 ° C. or less. When the coiling temperature exceeds 700 ° C., the thickness of the oxide formed on the surface of the steel sheet is excessively increased to deteriorate the pickling property, which is not preferable. After that, when cold rolling is performed, it is preferable to set the lower limit of the winding temperature to 400 ° C. If the coiling temperature is less than 400 ° C., the strength of the hot-rolled steel sheet is extremely increased and it is easy to induce sheet breakage and shape defect during cold rolling, so the lower limit of the coiling temperature is 400 ° C. Is preferred. However, if softening is achieved by heating the wound hot rolled steel sheet in a box annealing furnace or continuous annealing equipment, it may be wound at a low temperature of less than 400 ° C. In addition, rough rolling plates may be joined at the time of hot rolling, and finish rolling may be performed continuously. Also, the rough rolled plate may be wound up once.

  Next, the hot-rolled steel plate manufactured in this manner is pickled in an aqueous solution with a temperature of 80 ° C. or more and less than 100 ° C., an inhibitor-containing acid concentration of 3% by mass to 20% by mass for 30 seconds or more. In the present invention, the pickling under these conditions is extremely important, and the pickling under the above conditions is necessary to control the surface roughness Rz of the steel sheet to more than 2.5 μm. The acid is generally an aqueous solution of hydrochloric acid, sulfuric acid or the like, and may be aqua regia or the like.

  The temperature of the aqueous solution is set to 80 ° C. or more and less than 100 ° C. because the reaction rate is low at less than 80 ° C., and it takes a long time to bring the surface roughness of the heat-rolled steel sheet into an appropriate range. On the other hand, heating at a temperature of 100 ° C. or higher is not preferable because the solution boils and spatters although there is no problem in the reaction of pickling.

  The acid concentration is set to 3% by mass to 20% by mass in order to control the surface roughness Rz of the hot-rolled steel sheet within an appropriate range. When the concentration of the acid is less than 3% by mass, it takes a long time to control the surface asperity by pickling. On the other hand, when the concentration of the acid exceeds 20% by mass, the pickling tank is significantly damaged, and the facility management becomes difficult, which is not preferable. The preferred range of the concentration of the acid is in the range of 5% by mass to 15% by mass.

  In addition, the reason why the pickling time is set to 30 seconds or more is to stably impart predetermined unevenness (roughness of Rz> 2.5 μm or more) on the surface of the steel plate by acid washing. In the case where the pickling tank is divided into a plurality, even if the concentration or temperature of each pickling tank is different, if the partial or total pickling time satisfies the above condition, hot rolling The surface roughness Rz of the steel plate can be made within the scope of the present invention. In addition, the pickling may be performed in plural times. In the experiments of the present inventors, hydrochloric acid containing an inhibitor was used. However, if the surface roughness Rz can be controlled by pickling, other acids such as hydrochloric acid, sulfuric acid, nitric acid, etc. which do not use an inhibitor may be used. The effects of the present invention can be obtained even with these compounds.

  Moreover, since the unevenness | corrugation formed by pickling of a heat-rolled steel plate remains after implementing temper rolling, cold rolling, or annealing, pickling conditions are controlled and it is on the plate surface after pickling. It is extremely important to impart asperities. From this, temper rolling may be performed on the hot-rolled steel sheet after pickling.

  Furthermore, even cold-rolled steel sheets that have only been cold-rolled or cold-rolled steel sheets that have been heat-treated in a continuous annealing facility or a box-type annealing furnace after cold rolling can also be surface pickled by cold pickling. The unevenness can be formed to obtain a predetermined effect. In addition, it is preferable to cold-press the roll roughness Rz for cold rolling in the range of 1.0 micrometer-20.0 micrometers, and the roll for temper rolling is also included in the roll for cold rolling.

  The hot-rolled steel sheet pickled under the conditions as described above may be cold-rolled at a rolling reduction of 30% to 80% and passed through a continuous annealing facility. If the rolling reduction is less than 30%, it will be difficult to keep the shape of the steel sheet flat and the ductility of the final product will deteriorate, so the lower limit of the rolling reduction is preferably 30%. On the other hand, if the rolling reduction exceeds 80%, the rolling load becomes too large and cold rolling becomes difficult, so it is preferable to set the upper limit of the rolling reduction to 80%. More preferably, the rolling reduction is 40% to 70%. Since the effect of the present invention is exhibited even if the number of rolling passes and the rolling reduction per pass are not particularly defined, the number of rolling passes and the rolling reduction per pass need not be defined.

  Thereafter, the cold rolled steel sheet may be passed through a continuous annealing line. Since the purpose of this treatment is to soften the steel plate which has been strengthened by cold rolling, any conditions may be used as long as the steel plate is softened. For example, if the annealing temperature is in the range of 550 ° C. to 750 ° C., the dislocation introduced during cold rolling is released by recovery, recrystallization or phase transformation, so annealing may be performed in this temperature range. preferable.

  For the same purpose, even if annealing is performed in a box furnace, the steel plate for hot stamping excellent in the scale adhesion of the present invention can be obtained.

After that, apply oil. Oiling method as electrostatic coating oil, spray, although a roll coater or the like are generally used, the method is not limited as long ensured coating oil amount in the range of ^{50mg / m 2 ~1500mg / m 2} . In the present invention, a predetermined amount of oiling was carried out with an electrostatic oiling machine. ^Further, if the coating amount of oil in the range of 50mg / ^{m 2} ~1500mg / m 2 can be ensured, it may be degreased by oiled the more the amount of rust inhibitor.

  The hot stamping conditions are not particularly limited, and it is possible to achieve both of the excellent scale adhesion and the rust resistance which are the effects of the present invention. For example, by manufacturing with the manufacturing method shown below, coexistence with the outstanding performance and productivity of the tensile strength of 1180 Mpa or more can be achieved. When hot stamping is performed, it is preferable to heat in a temperature range of 800 ° C. to 1100 ° C. at a heating rate of 2 ° C./sec or more. By heating at a rate of 2 ° C./sec or more, scale formation during heating can be suppressed, which is effective in improving scale adhesion. More preferably, the heating rate is 5 ° C./second or more, and more preferably 10 ° C./second or more. In addition, an increase in heating rate is also effective for enhancing productivity.

  It is preferable to make the annealing temperature at the time of hot stamping into the range of 800 degreeC-1100 degreeC. By annealing in this temperature range, it is possible to obtain an austenite single-phase structure, and by performing subsequent cooling, it is possible to make the structure a structure having martensite as a main phase. At this time, if the annealing temperature is below 800 ° C., the structure at the time of annealing becomes a ferrite and an austenite structure, and this ferrite grows in the cooling process, and the volume fraction of ferrite becomes more than 10%, and the tensile strength of the hot stamped molded product Falls below 1180 MPa. From this, it is preferable to set the lower limit of the annealing temperature to 800 ° C. On the other hand, when the annealing temperature exceeds 1100 ° C., not only the effect is saturated but also the scale thickness is significantly increased, which may lower the scale adhesion. From this, it is preferable to perform annealing at 1100 ° C. or less. More preferably, the annealing temperature is in the range of 830 ° C to 1050 ° C.

  Holding may be performed in a temperature range of 800 ° C. to 1100 ° C. after heating. When holding at a high temperature, it is possible to dissolve carbides contained in the steel sheet, which contributes to the increase in strength and hardenability of the steel sheet. Holding includes retention, deheating, and decooling in this temperature range. Since the purpose is to dissolve carbides, the purpose can be achieved as long as the residence time in this temperature range is secured. There is no particular limitation on the holding time, but if the holding time is 1000 s or more, the scale thickness becomes excessive and the scale adhesion deteriorates, so it is preferable to set the upper limit to 1000 s.

  Then, it is preferable to cool 800 degreeC-700 degreeC with the average cooling rate of 5 degree-C / sec or more. Here, 700 ° C. is a mold cooling start temperature, and setting 800 ° C. to 700 ° C. to 5 ° C./sec or more avoids ferrite transformation, bainite transformation, and pearlite transformation, and makes the structure a martensitic main phase It is for. When the cooling rate is less than 5 ° C./sec, these soft tissues are formed, and it is difficult to secure a tensile strength of 1180 MPa or more. On the other hand, the effect of the present invention is exhibited without particularly setting the upper limit of the cooling rate. The temperature range for cooling at 5 ° C./sec or more is set to 800 ° C. to 700 ° C. because a structure that causes a decrease in strength such as ferrite may be formed in this temperature range. The cooling at this time is not limited to continuous cooling, and the effect of the present invention is exhibited as long as the average cooling rate is 5 ° C./sec or more, even when holding and heating in this temperature range. The effect of the present invention can be exhibited without particularly limiting the cooling method. That is, the effect of the present invention can be exhibited regardless of cooling using a mold and mold cooling using water cooling in combination.

  Next, although the Example of this invention is described, the conditions in an Example are one condition example employ | adopted in order to confirm the practicability and effect of this invention, and this invention is the one condition example. It is not limited. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the scope of the present invention.

  First, slabs having the component compositions A to S and a to n shown in Table 1 are cast and temporarily cooled to room temperature, and then heated for 220 minutes in a heating furnace with a furnace temperature of 1230 ° C. Hot rolling was performed at T = 920 ° C. to 960 ° C., and winding was performed under the temperature conditions shown in Table 2.

The finished plate thickness of the heat-rolled steel plate to be subjected to hot stamping as a heat-rolled steel plate was 1.6 mm. On the other hand, the thickness of the hot rolled steel sheet to be subjected to cold rolling was 3.2 mm. Thereafter, pickling was carried out under the conditions of Table 2, and in the case of cold rolling, the plate thickness was 50% (3.2 mm → 1.6 mm). Then, about a part of steel plates, annealing was performed by continuous annealing equipment, and it was set as the cold rolled steel plate. After that, using NOX-RUST 503F (Parker Kosan), the coating oil was applied to the hot-rolled steel plate and the cold-rolled steel plate in an electrostatic oiling machine at NOX 503F (Parker Kosan) in the range of no oil -6090 mg / m ² .

  Thereafter, the steel plate is cut into a predetermined size, and then conduction heating is performed at 50 ° C./second to 900 ° C., holding is performed at 900 ° C. for 10 seconds, and then 10 seconds of free cooling is performed, 650 ° C. or more Quenching was carried out using the above hot shallow drawing die at a temperature of Visual observation of the obtained hot stamped steel compact was performed, and a steel plate without scale peeling was used as a steel plate excellent in scale adhesion.

  The rust resistance was maintained at room temperature for 30 days, and a steel plate in which rust was not generated on the surface of the steel plate was defined as a steel plate excellent in rust resistance. In addition, using a flat plate test piece, hot stamping was performed under the conditions described above, and tensile properties were evaluated. The evaluation results are shown in Table 3.

  For tensile properties, tensile test pieces in accordance with JIS Z 2201 were collected, and tensile tests were performed in accordance with JIS Z 2241 to measure the maximum tensile strength. The maximum tensile strength of 1180 MPa or more was used as the molded article of the present invention.

Composition analysis of the scale of the molded body was performed by cutting the plate from the bottom of the cylindrical portion of the shallow drawn test piece and performing X-ray diffraction. The volume fraction of each Fe-based oxide was measured from the peak intensity ratio of each oxide. Since the Si oxide was present very thin and the volume fraction was less than 1%, quantitative evaluation by X-ray diffraction was difficult. However, it was confirmed by EPMA line analysis that it exists at the interface between the scale and the ground iron.
The unevenness of the interface between the scale formed on the formed body and the base iron was evaluated by SEM observation at a magnification of 3000 from a cross section perpendicular to the rolling direction after the embedded steel plate cut out from the above position was embedded and polished. Each test piece was observed in 5 fields of view, and the number density of the unevenness which became the range of 0.2 μm to 1.0 μm per 100 μm length was measured.

  Those satisfying the conditions of the present invention have both excellent rust resistance and excellent scale adhesion. Those that did not satisfy the conditions of the invention were inferior in scale adhesion or corrosion resistance.

  According to the present invention, it is possible to provide a steel plate excellent in scale adhesion at the time of hot stamping, and to solve the problem of wear of the mold at the time of hot stamping, plating adhesion to the mold, and indentation defects associated therewith. Therefore, it can bring about a significant improvement in productivity, and has great industrial value.

Claims (13)

In mass%,
C: 0. 100% to 0.600%,
Si: 0.50% to 3.00%,
Mn: 1.20% to 4.00%,
Ti: 0.005% to 0.100%,
B: 0.0005% to 0.0100%,
P: 0. 100% or less,
S: 0.0001% to 0.0100%,
Al: 0.005% to 1.000%,
N: 0.0100% or less,
Ni: 0% to 2.00%,
Cu: 0% to 2.00%,
Cr: 0% to 2.00%,
Mo: 0% to 2.00%,
Nb: 0% to 0.100%,
V: 0% to 0.100%,
W: 0% to 0.100%, and one or more selected from the group consisting of REM, Ca, Ce and Mg in total: 0% to 0.0300%
Containing a composition the balance being Fe and impurities, the surface roughness of the steel sheet is the Rz> 2.5 [mu] m, the coating oil oiled amount 50mg / m ² ~1500mg / m ² on the surface is coated Yes,
The steel sheet for hot stamping, wherein the amount of S contained in the oil applied to the surface is 5% or less by mass. The composition of the steel plate is in mass%,
Ni: 0.01% to 2.00%,
Cu: 0.01% to 2.00%,
Cr: 0.01% to 2.00%,
Mo: 0.01% to 2.00%,
Nb: 0.005% to 0.100%,
V: 0.005% to 0.100%, and W: 0.005% to 0.100%,
The steel plate for hot stamping according to claim 1, containing one or more selected from the group consisting of The composition of the steel plate is in mass%,
The steel plate for hot stamping according to claim 1 or 2, characterized in that it contains 0.0003% to 0.0300% in total of one or more selected from the group consisting of REM, Ca, Ce and Mg. . In mass%,
C: 0. 100% to 0.600%,
Si: 0.50% to 3.00%,
Mn: 1.20% to 4.00%,
Ti: 0.005% to 0.100%,
B: 0.0005% to 0.0100%,
P: 0. 100% or less,
S: 0.0001% to 0.0100%,
Al: 0.005% to 1.000%,
N: 0.0100% or less,
Ni: 0% to 2.00%,
Cu: 0% to 2.00%,
Cr: 0% to 2.00%,
Mo: 0% to 2.00%,
Nb: 0% to 0.100%,
V: 0% to 0.100%,
W: 0% to 0.100%, and one or more selected from the group consisting of REM, Ca, Ce and Mg in total: 0% to 0.0300%
Casting a slab containing Fe and the remainder comprising Fe and impurities, directly or temporarily cooling, and then heating and hot rolling to obtain a hot rolled steel sheet;
Carrying out pickling for 30 seconds or more in an aqueous solution having a temperature of 80 ° C. or more and less than 100 ° C. and an inhibitor-containing acid concentration of 3% by mass to 20% by mass;
Applying an anticorrosion oil having an S content of 5% or less by mass on a steel plate after the pickling;
Have
Method for producing a hot stamping steel plate, characterized in that to limit the anti-rust oil residual amount of the steel sheet surface to ^{50mg / m 2 ~1500mg / m 2} .   The method for producing a steel plate for hot stamping according to claim 4, wherein the rustproof oil is applied to the pickled hot-rolled steel plate. The method further includes the step of performing cold rolling on the pickled hot rolled steel plate to obtain a cold rolled steel plate,
The method for producing a steel plate for hot stamping according to claim 4, wherein the rustproof oil is applied to the cold rolled steel plate. The method further includes the step of performing cold rolling on the pickled hot-rolled steel plate, and further performing heat treatment in a continuous annealing facility or a box-type annealing furnace to obtain a cold-rolled steel plate,
The method for producing a steel plate for hot stamping according to claim 4, wherein the rustproof oil is applied to the cold rolled steel plate. The composition of the slab is, in mass%,
Ni: 0.01% to 2.00%,
Cu: 0.01% to 2.00%,
Cr: 0.01% to 2.00%,
Mo: 0.01% to 2.00%,
Nb: 0.005% to 0.100%,
V: 0.005% to 0.100%, and W: 0.005% to 0.100%,
The manufacturing method of the steel plate for hot stamps of any one of the Claims 4-7 characterized by containing 1 type (s) or 2 or more types selected from the group which consists of. The composition of the slab is, in mass%,
The total content of one or more selected from the group consisting of REM, Ca, Ce, and Mg is 0.0003% to 0.0300%, any one of claims 4 to 8 is contained. Manufacturing method of steel plate for hot stamping. In mass%,
C: 0. 100% to 0.600%,
Si: 0.50% to 3.00%,
Mn: 1.20% to 4.00%,
Ti: 0.005% to 0.100%,
B: 0.0005% to 0.0100%,
P: 0. 100% or less,
S: 0.0001% to 0.0100%,
Al: 0.005% to 1.000%,
N: 0.0100% or less,
Ni: 0% to 2.00%,
Cu: 0% to 2.00%,
Cr: 0% to 2.00%,
Mo: 0% to 2.00%,
Nb: 0% to 0.100%,
V: 0% to 0.100%,
W: 0% to 0.100%, and one or more selected from the group consisting of REM, Ca, Ce and Mg in total: 0% to 0.0300%
Contain, comprises the balance consisting of Fe and impurities, the interface between the scale and the base steel, Ri per unevenness 100μm to be a range of depth 0.2Myuemu～8.0Myuemu, there three or more And a thickness of the scale is 10 μm or less, and a tensile strength is 1180 MPa or more. The hot to the surface of the stamping member, Si oxide, FeO, Fe ₃ O _4, and hot stamping molded article according to claim 10, characterized in that to have a Fe ₂ O _3. The composition of the hot stamped molded body is, by mass%,
Ni: 0.01% to 2.00%,
Cu: 0.01% to 2.00%,
Cr: 0.01% to 2.00%,
Mo: 0.01% to 2.00%,
Nb: 0.005% to 0.100%,
V: 0.005% to 0.100%, and W: 0.005% to 0.100%,
The hot stamped molded article according to claim 10 or 11, wherein it contains one or more selected from the group consisting of The composition of the hot stamped molded body is, by mass%,
The total content of one or more selected from the group consisting of REM, Ca, Ce, and Mg is 0.0003% to 0.0300%, as described in any one of claims 10 to 12. Hot stamped molded body.