Method for manufacturing welded metal blank

Abstract

A method for manufacturing a welded metal blank according to the present invention comprises: a step of providing a first blank by cutting a first plating layer constituting a first plated steel sheet and providing a second blank by cutting a second plating layer constituting a second plated steel sheet; a step of arranging the first blank and the second blank in a die for welding; and a step of manufacturing the welded metal blank by welding the first blank and the second blank, wherein the die can be relatively moved in position to match the center lines of the first blank and the second blank in the width direction.

Description

Method for manufacturing welded metal blanks

[0001] The present invention relates to a method for manufacturing a welded metal blank, and more particularly, to a method for manufacturing a welded metal blank in which the soundness of welding is secured and strength reduction is prevented.

[0002] Recently, automobile parts are manufactured using the Tailor Welded Blank (TWB) method to reduce weight and improve safety, and then are formed using the hot stamping method.

[0003] The TWB method is a method for manufacturing TWB steel plates in a pre-forming state by butt-welding plated steel plates of different or similar thicknesses.

[0004] The plated steel sheet for manufacturing TWB steel sheet has a plated layer formed on both sides of the base material, boron steel, and the plated layer is usually formed of aluminum alloy (Al-Si).

[0005] Here, aluminum (Al) acts as a factor that reduces the soundness of the weld, so if aluminum (Al) is not removed during welding, partial strength reduction occurs.

[0006] For the above reasons, as disclosed in Korean Patent No. 10-2337605, welding is performed after cutting the plating layer during welding. However, this method does not effectively remove aluminum (Al) contained in the plating steel sheet, so the required strength is not satisfied. At the same time, it is possible that components of the plating layer may enter through the cut surface during welding, resulting in the production of defective TWB steel sheets.

[0007] In addition, as mentioned above, the plated steel sheets to be welded may have different thicknesses, and in this case, the welding process must be carried out with the center lines in the horizontal direction aligned to ensure the soundness and reliability of the weld.

[0008] However, the conventional welding process is carried out by placing two plated steel plates to be welded on a flat die, and thus there is a problem in terms of welding reliability because a compensation process for the difference in thickness of the two plated steel plates is not applied.

[0009] Therefore, there is an urgent need to develop a technology that effectively removes aluminum components contained in the plated steel sheet during welding, blocks the inflow of components into the plated layer, and simultaneously provides a compensation process for thickness differences, thereby ensuring the soundness of the weld and preventing a decrease in strength in advance.

[0010] The purpose of the present invention is to provide a method for manufacturing a welded metal blank in which the aluminum component contained in a plated steel sheet is removed under optimal conditions, a blank is manufactured in which the inflow of the plated material is prevented during welding, and then the welding is performed while compensating for the difference in the thickness of the blank, thereby ensuring the reliability and soundness of the welding.

[0011] A method for manufacturing a welded metal blank according to the present invention comprises: a first step in which a first plated steel sheet and a second plated steel sheet are provided; a second step in which a first plated layer constituting the first plated steel sheet is cut based on a thickness of the first plated steel sheet to provide a first blank, and a second step in which a second plated layer constituting the second plated steel sheet is cut based on a thickness of the second plated steel sheet to provide a second blank; a third step in which the first blank and the second blank are placed in a die for welding; and a fourth step in which the first blank and the second blank are welded to manufacture the welded metal blank; wherein the die comprises a first die and a second die in which the first blank and the second blank are placed, respectively, and the first die and the second die are capable of relative positional movement to match center lines in the width direction of the first blank and the second blank.

[0012] The first die and the second die of the method for manufacturing a welded metal blank according to the present invention may be characterized in that they are capable of positional movement in the vertical direction and positional movement in the width direction to match the center lines of the first blank and the second blank in the width direction.

[0013] The first die and the second die of the method for manufacturing a welded metal blank according to the present invention may be characterized in that, when the first blank and the second blank are respectively placed, the positional movement in the up-and-down direction and the positional movement in the width direction are controlled based on the results detected by a sensor that detects the thickness of the first blank and the second blank.

[0014] The first die and the second die of the method for manufacturing a welded metal blank according to the present invention may be characterized in that their heights are different when the overall thickness of the first blank and the overall thickness of the second blank are different.

[0015] The first blank of the method for manufacturing a welded metal blank according to the present invention may include a first base layer provided as a steel plate, the first plating layer formed on one side and the other side of the first base layer using a plating material, and a first intermediate layer formed between the first base layer and the first plating layer by a reaction between the steel plate and the plating material during the process of forming the first plating layer, wherein the first base layer includes a first basic base layer positioned inside the first plating layer and the first intermediate layer, and a first exposed base layer in which the first plating layer and the first intermediate layer are exposed to the outside by a cutting process along a thickness direction, and may further include a blocking layer formed on a cut surface of the first plating layer and the first intermediate layer by the cutting process to block the inflow of the plating material due to melting of the first plating layer during welding with the second blank.

[0016] According to the method for manufacturing a welded metal blank according to the present invention, the aluminum component contained in the plated steel sheet is removed under optimal conditions, a blank is manufactured in which the inflow of the plated material is prevented during welding, and then the welding is performed while the thickness difference of the blank is compensated for, thereby ensuring the reliability and soundness of the welding.

[0017] Figure 1 is a schematic perspective view illustrating a plated steel sheet provided for manufacturing a welded metal blank and a blank provided by processing the plated steel sheet.

[0018] Fig. 2 is a schematic cross-sectional view illustrating a welded metal blank manufactured by welding the blank of Fig. 1.

[0019] Figure 3 is a schematic cross-sectional view illustrating a welded metal blank manufactured by welding blanks of different thicknesses.

[0020] Figure 4 is a flowchart illustrating a method for manufacturing a welded metal blank according to the present invention.

[0021] A method for manufacturing a welded metal blank according to the present invention comprises: a first step in which a first plated steel sheet and a second plated steel sheet are provided; a second step in which a first plated layer constituting the first plated steel sheet is cut based on a thickness of the first plated steel sheet to provide a first blank, and a second step in which a second plated layer constituting the second plated steel sheet is cut based on a thickness of the second plated steel sheet to provide a second blank; a third step in which the first blank and the second blank are placed in a die for welding; and a fourth step in which the first blank and the second blank are welded to manufacture the welded metal blank; wherein the die comprises a first die and a second die in which the first blank and the second blank are placed, respectively, and the first die and the second die are capable of relative positional movement to match center lines in the width direction of the first blank and the second blank.

[0022] Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. However, the spirit of the present invention is not limited to the presented embodiments, and those skilled in the art who understand the spirit of the present invention will be able to easily propose other inventions that are retrograde or other embodiments included within the scope of the spirit of the present invention by adding, modifying, or deleting other components within the scope of the same spirit. However, this will also be considered to be included within the scope of the spirit of the present invention.

[0023]

[0024] In addition, components having the same function within the same scope of the same idea shown in the drawings of each embodiment are described using the same reference numerals.

[0025]

[0026] FIG. 1 is a schematic perspective view illustrating a plated steel sheet provided for manufacturing a welded metal blank and a blank provided by processing the plated steel sheet, and FIG. 2 is a schematic cross-sectional view illustrating a welded metal blank manufactured by welding the blank of FIG. 1.

[0027]

[0028] Referring to FIGS. 1 and 2, a plated steel plate (10) provided for manufacturing a welded metal blank (200) may include a base layer (110), a plated layer (120), and an intermediate layer (130).

[0029] The above base layer (110) may be a base material provided as a steel plate, and may be, for example, boron steel.

[0030] Here, the boron steel may include Fe, C, Mn, Al, Si, P, S, Cr, Ti, B, Cu, or Mo, and the component ratio may be slightly different depending on the type.

[0031] The above plating layer (120) is a layer formed on one side and the other side of the base layer (110) using a plating material, and the plating material may include Al and Si as an aluminum alloy.

[0032] The process for forming the plating layer (120) may be carried out through a process such as immersing the steel plate, which is the boron steel, in a molten bath made of the aluminum alloy, and in this process, a chemical reaction is induced at the interface between the boron steel and the aluminum alloy, and the reaction product by the chemical reaction may be the intermediate layer (130).

[0033] The above intermediate layer (130) is a layer formed between the base layer (110) and the plating layer (120) by a reaction between the steel plate and the plating material during the process of forming the plating layer (120), and is made of Fe x Al y (x, y represent 1 or more) or Fex Al y Si z It may be an intermetallic compound layer represented by (x, y, z represent 1 or more).

[0034] As shown in Fig. 1(a), the plated steel plate (10) composed of a base layer (110), an intermediate layer (130), and a plating layer (120) contains aluminum in all layers as described above, and aluminum acts as a factor that reduces the soundness of the weld during the welding process, causing a partial decrease in strength.

[0035] Therefore, in the past, in order to secure the soundness of welding, the plating layer and / or intermediate layer corresponding to the welded portion was removed through laser cutting or mechanical cutting, but this cutting alone did not remove the negative aspects caused by aluminum contained in the base layer, and thus did not effectively address the problem of reduced strength.

[0036] Ultimately, in order to secure the soundness of the weld, the aluminum included in the base layer (110) also needs to be removed, and for this purpose, the base layer (110) also needs to be cut to some extent under predetermined conditions as shown in Fig. 1(b).

[0037] However, as the base layer (110) is cut, the aluminum component is removed, which has a positive effect on welding, but the reduction in thickness may result in the tensile stress or tensile strength, which are indicators of the performance of the welded metal blank (200) manufactured through the welding process, not being met.

[0038] Accordingly, the base layer (110) of the blank (100) provided by processing the plated steel plate (10) can include a basic base layer (102) located inside the plated layer (120) and the intermediate layer (130), and an exposed base layer (104) exposed to the outside.

[0039] The above-mentioned exposed base layer (104) can be exposed to the outside by a cutting process along the thickness direction (D) of the plating layer (120) and the intermediate layer (130), and the cutting process is performed based on the predetermined conditions, thereby optimally removing aluminum that interferes with welding, thereby ensuring the soundness of welding and satisfying the performance indicators of the welded metal blank (200).

[0040] Meanwhile, the blank (100) may further include a blocking layer (140) formed on the cut surface of the plating layer (120) and the intermediate layer (130) by the cutting process to block the inflow of the plating material due to melting of the plating layer (120) when welding with another plating steel sheet.

[0041] The above blocking layer (140) can be formed by a cutting process for forming the exposed base layer (104), and the cutting process can be performed through laser cutting or chemical cutting for forming the above blocking layer (140).

[0042] The above blocking layer (140) can be formed by melting and then hardening the materials constituting each of the plating layer (120), the intermediate layer (130), and the base layer (110) during the cutting process.

[0043] The above blocking layer (140) may include a first blocking layer (142) and a second blocking layer (144) formed on the cut surfaces of the plating layer (120) and the intermediate layer (130), respectively, and may further include a third blocking layer (146) formed on one surface of the exposed base layer (104).

[0044] The first blocking layer (142), the second blocking layer (144), and the third blocking layer (146) may have different component compositions, and the boundaries between them and the plating layer (120), the intermediate layer (130), and the base layer (110) may be ambiguous. However, for the convenience of explanation, it is noted that the boundaries are indicated by lines in FIG. 1.

[0045] As shown in FIG. 2, the above-mentioned blocking layer (140) blocks the inflow of the plating material, i.e., aluminum, due to melting of the plating layer (120) even when the plating layer (120) and the intermediate layer (130) are included in the penetration when welding is performed, thereby increasing the soundness of the welding.

[0046] Meanwhile, the predetermined condition for the cutting process may be the following <Conditional Expression 1>, and the technical characteristics and derivation process of the above <Conditional Expression 1> are specifically described below.

[0047] <Condition 1>

[0048]

[0049] Referring to Figure 1(c), H is the thickness cut along the thickness direction from each side of the plating layer exposed to the outside, t is the total thickness before the cutting is performed, and σ min is the minimum tensile stress reference value of the TWB steel plate, and σ1 is the tensile stress measurement value before the above cutting is performed.

[0050]

[0051] Typically, a customer who receives a molded product, such as an automobile part, using a welded metal blank manufactured by welding a plated steel plate, will be asked to provide a performance indicator, and the performance indicator may be tensile stress or tensile strength.

[0052] Tensile stress (σ), which is one of the above performance indicators, is measured by taking a specimen of a molded product, and the tensile stress (σ) of the specimen defined by <Formula 1> below is the minimum tensile stress standard value (σ) presented by the customer. min ) should be ideal.

[0053] <Formula 1>

[0054]

[0055] P is the tensile load that can be applied to the specimen, and A is the cross-sectional area of ​​the specimen.

[0056] In the case of Fig. 1(a) where the cross-sectional area is uniform before cutting is performed, <Formula 2> is derived from <Formula 1> above, and in the case of Fig. 1(b), <Formula 3> is derived from <Formula 1> above.

[0057] <Formula 2>

[0058]

[0059] <Formula 3>

[0060]

[0061] σ1 is a tensile stress measurement value before the above cutting is performed, H is the thickness cut along the thickness direction from each side of the plating layer exposed to the outside, and t is the total thickness before the above cutting is performed.

[0062] Here, since it is normal for the above <Formula 3> to be destroyed in a part with a narrow cross-sectional area during tension due to a change in cross-sectional area caused by a reduction in thickness due to cutting, the denominator becomes A2.

[0063] In the case of Fig. 1(b), since the cross-sectional area is generally reduced compared to Fig. 1(a) and the tensile load is also reduced, it is safe to assume that the following <Equation 4> is established.

[0064] <Formula 4>

[0065] σ1= σ2

[0066] Meanwhile, in the case of Fig. 1(b) showing the blank (100), P2, which is a value smaller than P1, will be measured by a tensile load test, etc., and the tensile stress derived by dividing the measured P2 by A1 in the state before cutting is the minimum tensile stress reference value (σ) presented by the customer. min ) If this is the case, the amount of cutting that can be judged as normal can be derived.

[0067] That is, the following development is possible.

[0068] ··············①

[0069] ···········②

[0070] Substitute the above equation 3 into the above equation ②.

[0071] ············③

[0072] ············④

[0073] ············ ⑤

[0074] ············· ⑥

[0075] ··········· ⑦

[0076] By substituting the above <Formula 4> into the above formula ⑦, the following <Conditional Formula 1> can be finally derived.

[0077] <Condition 1>

[0078]

[0079] Here, σ1> σ min , and H > (h c + h m ) / 2 may be.

[0080] h c is h c1 +h c2 is the total thickness of the plating layer, h m Silver h m1 +h m2 is the total thickness of the middle layer.

[0081]

[0082] Meanwhile, if <Formula 4> is substituted into the above formula ⑥, the following <Conditional Formula 2> can be derived.

[0083] <Condition 2>

[0084]

[0085] H total is the total thickness cut along the thickness direction from each side of the plating layer exposed to the outside, t is the total thickness before the cutting is performed, and σ min is the minimum tensile stress reference value of the TWB steel plate, and σ1 is the tensile stress measurement value before the above cutting is performed.

[0086] Here, σ1> σ min and H total > (h c + h m ) may be.

[0087] h c is h c1 +h c2 is the total thickness of the plating layer, h m Silver h m1 +h m2 is the total thickness of the middle layer.

[0088]

[0089] Meanwhile, the above <Conditional Expression 2> can be developed as follows to derive <Conditional Expression 3>.

[0090] ··········· ⑧

[0091] <Condition 3>

[0092]

[0093] H r is the ratio of the total thickness cut along the thickness direction from each side of the plating layer exposed to the outside to the total thickness before the cutting is performed, t is the total thickness before the cutting is performed, and σ min is the minimum tensile stress reference value of the blank, and σ1 is the tensile stress measurement value before the cutting is performed.

[0094]

[0095] Below, an example of deriving the cutting amount by applying <Conditional Expression 1> is described.

[0096]

[0097] Minimum tensile stress standard value (σ) suggested by the customer min ) is 1425 (unit omitted), the total thickness (t) before cutting is 2 (unit omitted), the total thickness of the plating layer (120) and the intermediate layer (130) is 0.03 (unit omitted), and the measured value of the tensile stress (σ1) before cutting is 1450 (unit omitted).

[0098] When <Condition 1> is applied, H is derived as 0.017 as follows.

[0099]

[0100] Here, since the above H is smaller than the total thickness of the plating layer (120) and the intermediate layer (130), cutting cannot be performed in the above example.

[0101]

[0102] As another example, the minimum tensile stress criterion (σ) presented by the customer min ) is 1425 (unit omitted), the total thickness (t) before cutting is 4 (unit omitted), the total thickness of the plating layer (120) and the intermediate layer (130) is 0.03 (unit omitted), and the measured value of the tensile stress (σ1) before cutting is 1450 (unit omitted).

[0103] When <Condition 1> is applied, H is derived as 0.017 as follows.

[0104]

[0105] Here, since the above H is greater than the total thickness of the plating layer (120) and the intermediate layer (130), cutting can be performed by the thickness of 0.004, which is the difference between the total thickness of the plating layer (120) and the intermediate layer (130) and the base layer (110).

[0106]

[0107] FIG. 3 is a schematic cross-sectional view illustrating a welded metal blank manufactured by welding blanks having different thicknesses, and FIG. 4 is a flowchart illustrating a method for manufacturing a welded metal blank according to the present invention.

[0108]

[0109] Welded metal blanks can be manufactured by welding blanks of the same thickness, but can also be manufactured by welding blanks of different thickness, as shown in Fig. 3.

[0110] The first blank (400) illustrated on the left side of FIG. 3 may include a first base layer (410) including a first basic base layer (402) and a first exposed base layer (404), a first plating layer (420), and a first intermediate layer (430).

[0111] The second blank (500) illustrated on the right side of FIG. 3 may include a second base layer (510) including a second basic base layer (502) and a second exposed base layer (504), a second plating layer (520), and a second intermediate layer (530).

[0112] Here, the overall thickness of the first blank (400) may be thinner than the overall thickness of the second blank (500).

[0113] The first blank (400) and the second blank (500) may undergo a cutting process based on predetermined conditions described with reference to FIGS. 1 and 2, and the width (W1) of the exposed side of the first exposed base layer (404) may be formed to be wider than the width of the exposed side of the second exposed base layer (504).

[0114] This is due to the characteristics of welding. When manufacturing a metal blank (300) by welding blanks (400, 500) of different thicknesses, the molten portion flows toward the thin-walled plated steel plate (400) on the left.

[0115] In this case, the molten portion must not be in contact with the first intermediate layer (430) and the first plating layer (420) to prevent the deterioration of the welding soundness due to aluminum included in the first plating layer (420), etc., and for the same reason as above, the width (W1) of the first exposed base layer (404) provided to the first blank (400) is formed to be wider than the width (W2) of the second exposed base layer (504) provided to the second blank (500).

[0116] Hereinafter, with reference to FIG. 4, a method for manufacturing a welded metal blank (300) by welding a first blank (400) and a second blank (500) will be described.

[0117] A method for manufacturing a welded metal blank according to the present invention may include a first step (S10) in which a first plated steel sheet and a second plated steel sheet are provided, a second step (S20) in which a first plated layer constituting the first plated steel sheet is cut based on a thickness of the first plated steel sheet to provide a first blank, and a second plated layer constituting the second plated steel sheet is cut based on a thickness of the second plated steel sheet to provide a second blank, a third step (S30) in which the first blank and the second blank are placed in a die for welding, and a fourth step (S40) in which the first blank and the second blank are welded to manufacture the welded metal blank.

[0118] Here, the die for welding may include a first die and a second die in which the first blank and the second blank are respectively placed.

[0119] In other words, the die can be sectioned based on the number of blanks to be welded.

[0120] The first die and the second die may be capable of relative positional movement to match the center lines (L, see FIG. 3) in the width direction of the first blank and the second blank.

[0121] Specifically, the first die and the second die are capable of vertical positional movement and widthwise positional movement to align the center lines of the first blank and the second blank in the widthwise direction.

[0122] The positional movement of the first die and the second die can be controlled based on the results detected by the sensor.

[0123] When the first blank and the second blank are placed on the first die and the second die, respectively, the sensor detects the thickness of the first blank and the second blank, and the control means can control the positional movement in the vertical direction and the positional movement in the width direction of the first die and the second die based on the result detected by the sensor.

[0124] As a result, the first die and the second die have different heights when the total thickness of the first blank and the total thickness of the second blank are different, and the first blank and the second blank can be placed in an optimal arrangement for welding as shown in FIG. 3.

[0125]

[0126] Although the configuration and features of the present invention have been described above based on embodiments according to the present invention, the present invention is not limited thereto, and it is obvious to those skilled in the art that various changes or modifications can be made within the spirit and scope of the present invention, and therefore, it is made clear that such changes or modifications fall within the scope of the appended patent claims.

Claims

1. A method for manufacturing a welded metal blank, A first step in which first galvanized steel sheets and second galvanized steel sheets are provided; A second step in which a first plating layer constituting the first plating steel sheet is cut based on the thickness of the first plating steel sheet to provide a first blank, and a second plating layer constituting the second plating steel sheet is cut based on the thickness of the second plating steel sheet to provide a second blank; A third step of placing the first blank and the second blank in a die for welding; and A fourth step of manufacturing the welded metal blank by welding the first blank and the second blank; The above die, It has a first die and a second die in which the first blank and the second blank are respectively placed, The above first die and the above second die, A method for manufacturing a welded metal blank, characterized in that the relative positional movement is possible to match the center lines of the first blank and the second blank in the width direction.

2. In paragraph 1, The above first die and the above second die, A method for manufacturing a welded metal blank, characterized in that the first blank and the second blank can be moved up and down and moved in the width direction to match the center lines in the width direction.

3. In paragraph 2, The above first die and the above second die, A method for manufacturing a welded metal blank, characterized in that when the first blank and the second blank are respectively placed, the positional movement in the up-and-down direction and the positional movement in the width direction are controlled based on the results detected by a sensor that detects the thickness of the first blank and the second blank.

4. In paragraph 3, The above first die and the above second die, A method for manufacturing a welded metal blank, characterized in that the height is different when the overall thickness of the first blank and the overall thickness of the second blank are different.

5. In paragraph 1, The above first blank is, The first base layer is provided in the form of a steel plate, The first plating layer formed on one side and the other side of the first base layer using a plating material, and In the process of forming the first plating layer, the steel plate and the plating material react to form a first intermediate layer between the first base layer and the first plating layer, The above first base layer is, A first basic base layer positioned inside the first plating layer and the first intermediate layer, and a first exposed base layer in which the first plating layer and the first intermediate layer are exposed to the outside by a cutting process along the thickness direction, A method for manufacturing a welded metal blank, characterized in that it further includes a blocking layer formed on the cut surface of the first plating layer and the first intermediate layer by the cutting process to block the inflow of the plating material due to melting of the first plating layer when welding with the second blank.

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