Component and manufacturing method thereof

Abstract

The present invention relates to a member and a manufacturing method thereof, and more particularly to a hot press-formed member having excellent chemical conversion treatability and a manufacturing method thereof.

Description

[Technical Field]

[0001] The present invention relates to a member and a manufacturing method thereof, and more particularly to a hot press-formed member having excellent chemical conversion treatability and a manufacturing method thereof. [Background technology]

[0002] In recent years, automobile manufacturers have been conducting research into reducing the weight of vehicles in order to improve fuel efficiency and comply with CO2 emission regulations. In response to this, there are steel materials that contain various alloying elements to improve the strength of the steel material while maintaining the same weight, but this increases the hardenability, which causes problems such as poor workability, such as springback.

[0003] To solve these problems, hot press forming has been proposed. Hot press forming is a technology that involves processing a steel material with a certain strength in the austenite single-phase region and then rapidly cooling it to a low temperature to form a low-temperature structure such as martensite within the steel material, thereby dramatically improving the strength of the product. This minimizes workability issues when forming high-strength components.

[0004] On the other hand, aluminum plating is widely used to improve the corrosion resistance of steel materials used in the hot press forming method. However, from the viewpoint of chemical conversion treatment, the growth of phosphate crystals is difficult because the main component of the plating bath is aluminum, and various methods have been attempted to improve this. Summary of the Invention [Problem to be solved by the invention]

[0005] According to one embodiment of the present invention, a component and a method for manufacturing the same are provided.

[0006] According to one embodiment of the present invention, it is intended to provide a hot press-formed part having excellent chemical conversion treatability and a method for producing the same.

[0007] The object of the present invention is not limited to the above-mentioned content, and a person skilled in the art will have no problem in understanding further object of the present invention from the overall content of this specification. [Means for solving the problem]

[0008] According to one embodiment of the present invention, a base steel sheet; and a plating layer formed on the base steel sheet; The plating layer includes a first alloy layer, a second alloy layer, a third alloy layer, and a fourth alloy layer formed in this order on the base steel sheet, The fourth alloy layer can provide a member having an R value defined by the following relational expression 1 of 1200 to 4500.

[0009] R=[Rpc]*[Zn] (In the formula, [Rpc] is the surface roughness expressed as the number of peaks per 10 mm, and [Zn] is the weight percent of the element.)

[0010] The above-mentioned base steel sheet may contain, by weight, C: 0.02 to 0.6%, Si: 0.001 to 2%, Al: 0.001 to 1%, Mn: 0.1 to 4%, P: 0.05% or less, S: 0.02% or less, N: 0.02% or less, B: 0.0001 to 0.01%, and the balance being Fe and unavoidable impurities.

[0011] The base steel sheet may further contain, by weight percent, one or more selected from Ti: 0.1% or less, Cu: 1.00% or less, Mo: 1.00% or less, Cr: 1.00% or less, Ni: 1.00% or less, V: 1.00% or less, Ca: 0.01% or less, Nb: 0.1% or less, Sn: 1% or less, W: 1% or less, Sb: 1% or less, Mg: 0.1% or less, Co: 1% or less, As: 1% or less, Zr: 1% or less, Bi: 1% or less, and REM: 0.3% or less.

[0012] The Zn content of the fourth alloy layer may be 12.0 to 40.0% by weight.

[0013] The fourth alloy layer may have an Rpc of 80.0 to 130.0.

[0014] The first alloy layer contains, by weight %, Al: 5.0 to 18.0%, Si: 1.0 to 10.0%, Fe: 75.0 to 90.0%, and Zn: 2.0% or less, The second alloy layer contains, by weight percent, 25.0 to 48.0% Al, 1.0 to 7.0% Si, 36.0 to 53.0% Fe, and 6.0 to 20.0% Zn, The third alloy layer contains, by weight percent, 18.0 to 43.0% Al, 8.0 to 15.0% Si, 47.0 to 68.0% Fe, and 2.0% or less Zn, The fourth alloy layer may contain, by weight, O: 6.0% or less, Al: 36.0 to 73.0%, Si: 10.0% or less, Fe: 42.0% or less, and Zn: 12.0 to 40.0%.

[0015] The member may have a coverage of 50% or more after chemical conversion treatment.

[0016] According to one embodiment of the present invention, the method comprises the steps of: preparing a base steel sheet; a step of immersing the base steel sheet in a coating bath containing, by weight %, 26.0 to 30.0% Zn, 6.0 to 9.0% Si, and the remainder being Al and unavoidable impurities; temper rolling the plated steel sheet; heating the temper-rolled steel sheet to a temperature range of Ac3 to 950°C and holding the temperature for 1 to 1000 seconds; and a step of hot press-forming the heated and held steel plate.

[0017] Before the plating step, an annealing step may be further included in which the base steel sheet is heated to a temperature range of 600 to 950°C in a gas atmosphere containing 70% or more of H2 and the remainder of N2 at a dew point temperature of 5 to 20°C and maintained for 100 to 500 seconds.

[0018] The temperature of the plating bath may be 580 to 680°C.

[0019] The temper rolling step can be carried out at a reduction of 200 to 900 tons. [Effects of the Invention]

[0020] According to one embodiment of the present invention, a component and a method for manufacturing the same can be provided.

[0021] According to one embodiment of the present invention, it is possible to provide a hot press-formed part having excellent chemical conversion treatability and a method for producing the same. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a schematic cross-sectional view of a plating layer of a member according to one embodiment of the present invention. [Figure 2] 1 is a photograph of Example 1 according to an embodiment of the present invention, measured by a glow discharge optical emission spectrometer (GDS) analysis method. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, preferred embodiments of the present invention will be described. The embodiments of the present invention can be modified in various forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The present embodiments are provided to explain the present invention in more detail to those skilled in the art to which the invention pertains.

[0024] The present invention will be described in detail below.

[0025] A member according to one embodiment of the present invention may include a base steel sheet; and a plating layer formed on the base steel sheet.

[0026] Base steel sheet The alloy composition of a base steel sheet according to one embodiment of the present invention is not particularly limited, but may contain, by weight percent, 0.02 to 0.6% C, 0.001 to 2% Si, 0.001 to 1% Al, 0.1 to 4% Mn, 0.05% or less P, 0.02% or less S, 0.02% or less N, 0.0001 to 0.01% B, and the balance being Fe and impurities.

[0027] In addition to the above-described composition, the base steel sheet of the present invention may contain the remaining iron (Fe) and inevitable impurities. Since inevitable impurities may be unintentionally mixed in during normal manufacturing processes, they cannot be excluded. Since such impurities are known to any engineer in the field of normal steel manufacturing, the present specification does not specifically mention all of the contents thereof.

[0028] Furthermore, the base steel sheet according to one embodiment of the present invention may optionally contain, by weight, one or more of the following: Ti: 0.1% or less, Cu: 1.00% or less, Mo: 1.00% or less, Cr: 1.00% or less, Ni: 1.00% or less, V: 1.00% or less, Ca: 0.01% or less, Nb: 0.1% or less, Sn: 1% or less, W: 1% or less, Sb: 1% or less, Mg: 0.1% or less, Co: 1% or less, As: 1% or less, Zr: 1% or less, Bi: 1% or less, and REM: 0.3% or less.

[0029] plating layer A member according to one embodiment of the present invention may include a plating layer formed on the base steel sheet, and the plating layer may include a first alloy layer, a second alloy layer, a third alloy layer, and a fourth alloy layer formed in sequence on the base steel sheet.

[0030] FIG. 1 is a schematic cross-sectional view of a coating layer of a member according to one embodiment of the present invention. As shown in FIG. 1, the coating layer of the present invention can be distinguished into four distinct layers based on the diffusion gradient between the components of the coating layer and the Fe, Al, Si, and Zn components of the base steel sheet. In particular, when observing the cross-section of the coating layer in BSE (backscattered electron) mode, the alloy layer can be distinguished by the weight of each alloying element. In particular, since the third alloy layer has a high Si content, it is easy to color-code the second and fourth alloy layers according to the content of their alloying elements.

[0031] According to one embodiment of the present invention, the coating layer may be divided into four alloy layers formed sequentially on the base steel sheet, and may include an α-Fe layer formed on the base steel sheet; a first Fe—Al layer formed on the α-Fe layer; an Al—Fe—Si layer formed on the first Fe—Al layer; and a second Fe—Al layer formed on the Fe—Al—Si layer.

[0032] According to one embodiment of the present invention, the α-Fe layer, which is the first alloy layer, can contain, by weight percent, 5.0-18.0% Al, 1.0-10.0% Si, 75.0-90.0% Fe, and 2.0% or less Zn. The first Fe—Al layer, which is the second alloy layer, can contain, by weight percent, 25.0-48.0% Al, 1.0-7.0% Si, 36.0-53.0% Fe, and 6.0-20.0% Zn. The Al—Fe—Si layer, which is the third alloy layer, can contain, by weight percent, 18.0-43.0% Al, 8.0-15.0% Si, 47.0-68.0% Fe, and 2.0% or less Zn. According to one embodiment of the present invention, the second Fe-Al layer, which is the fourth alloy layer, can contain, by weight, O: 6.0% or less, Al: 36.0 to 73.0%, Si: 10.0% or less, Fe: 42.0% or less, and Zn: 12.0 to 40.0%.

[0033] 4th alloy layer The fourth alloy layer may have an R value defined by the following relational expression 1 of 1200 to 4500.

[0034] [Equation 1] R=[Rpc]*[Zn] (In the formula, [Rpc] is the surface roughness expressed as the number of peaks per 10 mm, and [Zn] is the weight percent of the element.)

[0035] Since the influence of the fourth alloy layer (second Fe-Al layer), which is the outermost layer, on the chemical conversion treatment of the component is determined, the present invention can control the composition and surface roughness of this layer. In the present invention, the composition of this layer was confirmed by cross-sectional SEM analysis, and the surface roughness (Rpc, number of peaks per 10 mm) was measured according to ISO 4287:1997.

[0036] The product of surface roughness and Zn content is primarily determined by the components of the coating layer, and this product is limited in the present invention. If the R value defined by the above Relational Formula 1 is less than 1200, the Zn content will be low, resulting in poor phosphate treatment properties and a low number of peaks, which may lead to problems such as poor paint adhesion. According to one embodiment of the present invention, the R value may be 1500 or greater. On the other hand, if the R value exceeds 4500, the Zn content of the entire coating layer will be high, which may lead to problems such as LME (liquid phase brittle fracture) during welding and a high number of roughness peaks, which may cause deterioration of equipment such as molds and annealing furnaces due to friction and wear. Furthermore, there is a risk of cracks occurring during the production of parts by hot press forming. According to one embodiment of the present invention, the R value may be 4100 or less.

[0037] Meanwhile, the surface roughness (Rpc) of a part manufactured by hot forming can be significantly affected by the composition of the coating layer, regardless of the surface roughness before hot forming. A high roughness increases the friction coefficient at high temperatures, which can cause deterioration of equipment such as molds and annealing furnaces due to friction and wear. Therefore, according to one embodiment of the present invention, the surface roughness may be 130.0 or less. According to one embodiment of the present invention, the surface roughness may be 120.0 or less. Furthermore, unlike cold forming, forming and processing are performed by metal-to-metal or oxide-to-oxide contact without lubrication, so a certain level of friction is necessary. Therefore, in the present invention, the surface roughness may be 80.0 or more.

[0038] In addition, in the present invention, in order to ensure the desired chemical conversion treatability, the Zn content of the fourth alloy layer may be 12.0% or more. In one embodiment of the present invention, it may be 14.0% or more. According to one embodiment of the present invention, the Zn content may be 40.0% or less. According to one embodiment of the present invention, it may be 38% or less.

[0039] The member according to one embodiment of the present invention has a coverage rate of 50% or more after chemical conversion treatment, and can have excellent chemical conversion treatability.

[0040] The method for manufacturing a member of the present invention will be described in detail below.

[0041] A member according to one embodiment of the present invention can be manufactured by preparing a base steel sheet that satisfies the alloy composition of the present invention, and then plating, temper rolling, heating, and hot press forming.

[0042] Prepare the base steel sheet A base steel sheet satisfying the alloy composition according to one embodiment of the present invention can be prepared. The alloy composition of the base steel sheet according to one embodiment of the present invention is not particularly limited, but it is more preferable that the composition satisfies the composition proposed in the present invention. The composition of the base steel sheet can be applied in the same manner as described above.

[0043] plating The base steel sheet can be plated by immersing it in a plating bath containing, by weight, 26.0 to 30.0% Zn, 6.0 to 9.0% Si, and the balance being Al and unavoidable impurities.

[0044] In the present invention, the composition of the plating bath can be controlled during plating to control the surface roughness and Zn content of the plating layer.

[0045] In the coating layer, Zn can form an Al-Zn phase to ensure sacrificial corrosion protection. In addition, the surface roughness after hot forming can be significantly affected by the components of the coating layer, regardless of the surface roughness before hot forming. As the Zn content increases and the heat treatment time increases, the roughness tends to increase. This is due to the thermal expansion coefficient (x10 -6 The Zn content (m / (m·°C)) (30-35) is higher than that of Al (21-24). When the same amount of heat is applied to the coating layer, the greater the Zn content, the greater the displacement, which is presumably responsible for the increased roughness. To ensure this effect, the present invention allows the Zn content of the coating bath to be 26.0-30.0%. If the Zn content of the coating bath is less than 26.0%, the Zn content in the fourth alloy layer will not reach the desired level, potentially resulting in a decrease in sacrificial corrosion protection. According to one embodiment of the present invention, the Zn content can be limited to 26.5% or more. On the other hand, if the Zn content of the coating bath exceeds 30.0%, the Zn content of the coating layer may exceed the Zn content range, potentially resulting in the occurrence of microcracks due to LME. Furthermore, cracks may occur during hot press forming. According to one embodiment of the present invention, the Zn content can be 29.5% or less.

[0046] Furthermore, to suppress the diffusion of Al into the base steel sheet during manufacturing, the Si content of the coating bath can be limited to 6.0 to 9.0%. The Si content of the coating bath affects the Si solid solution phase, so the weight percent value can be smaller than the Si content of the target coating layer. If the Si content is less than 6.0%, the temperature of the molten metal becomes high, causing the thickness of the FeAl3 and Fe2Al5 intermetallic compounds to become excessively thick, which can lead to problems such as the material being prone to cracking. According to one embodiment of the present invention, the content can be limited to 6.5% or more. On the other hand, if the Si content exceeds 9.0%, the effect of reducing the thickness of the intermetallic compounds due to the addition is reduced, which can lead to problems such as Si precipitation. In one embodiment of the present invention, the Si content can be 8.5% or less.

[0047] According to one embodiment of the present invention, the temperature of the plating bath may be 580 to 680°C.

[0048] Meanwhile, according to one embodiment of the present invention, the method may further include a step of annealing the base steel sheet before the coating step. In one embodiment of the present invention, the base steel sheet may be further annealed by heating it to a temperature range of 600 to 950°C in a gas atmosphere containing 70% or more of H2 and the remainder of N2 at a dew point temperature of 5 to 20°C and maintaining the temperature for 100 to 500 seconds.

[0049] temper rolling The plated steel sheet can be subjected to skin pass milling (SPM).

[0050] In this step, rolling is performed with a constant elongation load or reduction, and roughness can be imparted to the steel sheet to improve its press formability, and surface defects can be removed.

[0051] In the present invention, a rolling reduction of 200 to 900 tons can be applied during rolling. If the rolling reduction is less than 200 tons, defects such as flow patterns and scratches may be observed on the surface. In contrast, if the rolling reduction is 900 tons or more, roll wear becomes severe, which affects the productivity of the steel sheet and increases the elongation of the steel sheet by 1% or more, which may affect the quality of the final product.

[0052] Typically, the transfer rate of a plated steel sheet (Ra sheet / Ra roll) can be calculated as A*HRB (roll hardness)+B*rolling reduction, and is on the order of 30 to 70%. Here, A and B are constants that can be determined based on the roll material, diameter, and scale of the equipment. In this case, the roughness (Ra) of the rolling roll may be 1.5 to 3.0 μm. If the roughness of the rolling roll is less than 1.5 μm, the surface may be smooth, which may result in reduced workability. On the other hand, if the roughness exceeds 3.0 μm, stress may be concentrated on the high peaks of the fine irregularities of the roll, resulting in rapid wear and a shortened service life.

[0053] Heating and Holding The temper-rolled steel sheet can be heated to a temperature range of Ac3 to 950°C and held for 1 to 1000 seconds.

[0054] The heating step may be preceded by a step of processing the steel plate into an appropriate size and shape.

[0055] If the temperature is lower than the Ac3 temperature during heating, problems may occur in that the material is difficult to completely transform into austenite single phase, and if the temperature exceeds 950°C, problems may occur such as surface oxidation and an increase in the hydrogen content in the steel.

[0056] During the holding period after heating, it is preferable to reduce the holding time as much as possible to reduce carbon emissions and ensure mechanical properties. If the holding time is excessive, the upper limit can be limited to 1000 seconds to reduce carbon emissions and suppress excessive Fe diffusion in the coating layer.

[0057] [formula] Ac3=-230.5[C]+31.6[Si]-20.4[Mn]-39.8[Cu]-18.1[Ni]-14.8[Cr]+16.8[Mo]+912 (In the formula, [C], [Si], [Mn], [Cu], [Ni], [Cr], and [Mo] are the weight percentages of each element.)

[0058] Hot Press Forming The heated and held steel sheet can be hot press formed.

[0059] In the present invention, a heated steel sheet can be hot-formed to produce a desired shape. In the present invention, hot press forming can be performed using a mold, and the conditions for this process are not particularly limited. Hot press forming conditions commonly used in the same technical field can be applied. [Example]

[0060] The present invention will be described in more detail below with reference to examples. However, it should be noted that the following examples are intended to illustrate and explain the present invention in more detail, and are not intended to limit the scope of the present invention.

[0061] (Example) A base steel sheet containing, by weight, 0.22% C, 0.28% Si, 0.036% Al, 1.2% Mn, 0.009% P, 0.0006% S, 0.0039% N, 0.0031% B, 0.03% Ti, 0.21% Cr, and the balance Fe was prepared, and then plated and temper rolled under the conditions shown in Table 1 below to produce plated steel sheets. Thereafter, the produced plated steel sheets were cut into 380 × 400 mm pieces. 2 After shearing to a size of 100 mm, the components were manufactured by heating and hot press forming. The plating was performed using the plating bath composition shown in Table 1, which further contained inevitable impurities in addition to the disclosed Zn, Si, and Al.

[0062] [Table 1]

[0063] Table 2 below shows the characteristics and physical properties of the plating layer observed for the manufactured members.

[0064] First, the plating layer was observed using a scanning electron microscope (SEM). Specifically, the cross section of the hot-formed sample was mounted, and each layer was observed in BSE (backscattered electron) mode at a magnification of x2000. Using energy dispersive X-ray spectroscopy (EDS), the center point of each phase was measured three times at different positions, and the composition of the plating layer was expressed as the average value of the three points.

[0065] Furthermore, since the influence on the chemical conversion treatment is determined by the outermost fourth alloy layer (second Fe-Al layer), the composition of this layer was confirmed by cross-sectional SEM analysis, and the surface roughness (Rpc, number of peaks per 10 mm) was measured according to ISO 4287:1997.

[0066] The prepared test pieces were then subjected to chemical conversion treatment in the following order: degreasing, water washing 1, surface conditioning, phosphate treatment, and water washing 2. The chemically treated test pieces were observed under a scanning electron microscope at 150x magnification, and the phosphate coverage area was calculated using Image Analyzer software, and the results are shown in Table 3 below. The specific chemical conversion treatment conditions were as follows, with a phosphate coverage of 50% or more being rated O and less than 50% being rated X.

[0067] Chemical conversion coating Degreasing: FC-4460A 20g / L, FC-4460B 12g / L (Daihan Parkerizing Co., Ltd.), processing time 90 seconds, temperature 60℃ Washing 1: 10 seconds, room temperature Surface preparation: PL-Z 5g / L (Daihan Parkerizing Co., Ltd.), pH concentration 7.5-11, treatment time 21 seconds, room temperature Phosphate treatment: PB-3111 28.2g / L, NT-4055 5.8g / L (Daihan Parkerizing Co., Ltd.), FA (free acidity) / TA (total acidity) 1.1-1.5 / 11.1-11.8 respectively, treatment time 120 seconds, phosphate treatment solution temperature 40-45℃ Wash 2: 10 seconds, room temperature

[0068] [Table 2]

[0069] [Table 3]

[0070] As shown in Tables 2 and 3, in the case of the examples of the invention that met the conditions of the present invention, the characteristics proposed in the present invention were satisfied and the physical properties aimed at in the present invention were also secured.

[0071] Figure 2 is a photograph of Example 1 according to one embodiment of the present invention, measured using a glow discharge optical emission spectrometry (GDS). As shown in Figure 1, the content of alloying elements can be confirmed depending on the depth in the thickness direction from the surface of the coating layer to the base steel sheet side.

[0072] In contrast, Comparative Examples 1 to 10 and 12 were cases where the coating bath composition or manufacturing conditions proposed in the present invention were deviated from those proposed in the present invention, and it was confirmed that the coating layer intended by the present invention could not be produced and the physical properties were deteriorated. On the other hand, in Comparative Examples 9 to 11, cracks occurred during hot forming, and the product properties were deteriorated.

[0073] Although the present invention has been described in detail with reference to the examples above, other embodiments are possible, and the spirit and scope of the following claims are not limited to the examples.

Claims

1. Base steel sheet; and a plating layer formed on the base steel sheet; the plating layer includes a first alloy layer, a second alloy layer, a third alloy layer, and a fourth alloy layer formed in this order on the base steel sheet, The fourth alloy layer has an R value defined by the following relational expression 1 of 1200 to 4500. R=[Rpc]*[Zn] (In the formula, [Rpc] is the surface roughness indicating the number of peaks per 10 mm, and [Zn] is the weight percent of the element.)

2. The member according to claim 1, wherein the base steel sheet contains, in weight percent, C: 0.02 to 0.6%, Si: 0.001 to 2%, Al: 0.001 to 1%, Mn: 0.1 to 4%, P: 0.05% or less, S: 0.02% or less, N: 0.02% or less, B: 0.0001 to 0.01%, the balance being Fe and unavoidable impurities.

3. 3. The member according to claim 2, wherein the base steel sheet further contains, by weight percent, one or more selected from Ti: 0.1% or less, Cu: 1.00% or less, Mo: 1.00% or less, Cr: 1.00% or less, Ni: 1.00% or less, V: 1.00% or less, Ca: 0.01% or less, Nb: 0.1% or less, Sn: 1% or less, Sn: 1% or less, W: 1% or less, Sb: 1% or less, Mg: 0.1% or less, Co: 1% or less, As: 1% or less, Zr: 1% or less, Bi: 1% or less, and REM: 0.3% or less.

4. 2. The member of claim 1, wherein the Zn content of the fourth alloy layer is, in weight percent, 12.0 to 40.0%.

5. 2. The member of claim 1, wherein the fourth alloy layer has an Rpc of 80.0 to 130.

0.

6. The first alloy layer contains, by weight percent, 5.0 to 18.0% Al, 1.0 to 10.0% Si, 75.0 to 90.0% Fe, and 2.0% or less Zn, The second alloy layer contains, by weight percent, 25.0 to 48.0% Al, 1.0 to 7.0% Si, 36.0 to 53.0% Fe, and 6.0 to 20.0% Zn, the third alloy layer contains, by weight percent, 18.0 to 43.0% Al, 8.0 to 15.0% Si, 47.0 to 68.0% Fe, and 2.0% or less Zn; The member of claim 1, wherein the fourth alloy layer contains, in weight percent, O: 6.0% or less, Al: 36.0 to 73.0%, Si: 10.0% or less, Fe: 42.0% or less, and Zn: 12.0 to 40.0%.

7. The member according to claim 1 , wherein the member has a coverage of 50% or more after chemical conversion treatment.

8. preparing a base steel sheet; dipping the base steel sheet in a plating bath containing, by weight %, 26.0 to 30.0% Zn, 6.0 to 9.0% Si, the balance being Al and unavoidable impurities, to perform plating; temper rolling the plated steel sheet; heating the temper-rolled steel sheet to a temperature range of Ac3 to 950°C and holding the temperature for 1 to 1000 seconds; and hot press forming the heated and held steel plate.

9. Before the plating step, the base steel sheet is heated to a temperature of 5 to 20°C under a dew point of 70% or more H ２ and the rest is N ２ The method for manufacturing a member according to claim 8, further comprising an annealing step of heating to a temperature range of 600 to 950°C in a gas atmosphere and holding the temperature for 100 to 500 seconds.

10. The method for manufacturing a member according to claim 8, wherein the temperature of the plating bath is 580 to 680°C.

11. The method for manufacturing a component according to claim 8, wherein the temper rolling step is carried out at a reduction of 200 to 900 tons.

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