JOINT COMPONENT AND METHOD OF MANUFACTURING THE SAME

Abstract

This joining component is a joining component that includes a first steel member, a second steel member, and a spot-welded portion joining the first steel member and the second steel member, wherein the first steel member includes a steel sheet substrate having a predetermined chemical composition and a coating that forms on a surface of the steel sheet substrate, containing Al and Fe, and having a thickness of 25 µm or more, in a cross-section in the thickness direction of the first steel member and the second steel member including the spot-welded portion, a filler metal containing Al and Fe is present in a space between the first steel member and the second steel member on a periphery of the spot-welded portion, in the cross-section, the filler metal has a cross-sectional area of ​​3.0 × 104 µm2 or more, and has a space fill ratio of 80% or more within a 100 µm interval from an extreme portion of a corona bond formed at the periphery of the spot-welded portion, and includes a first region and a second region.

Description

JOINT COMPONENT AND METHOD OF MANUFACTURING THE SAME zofrRnn / zznz / E / YiAi Technical field of the invention [1] The present invention relates to a joining component and a method of manufacturing the same. Priority is claimed in Japanese Patent Application No. 2020-022754, filed on February 13, 2020, the contents of which are incorporated herein by reference. Related technique [2] In the automotive field, in order to improve both fuel consumption and collision safety in the context of stringent environmental regulations and recent collision safety standards, the application of high-tensile-strength steel sheet (high-strength steel sheet) has been expanded. However, the formability of steel sheet by pressing decreases with high hardening, making it difficult to manufacture steel sheet into products with complex shapes. [3] Specifically, the ductility of steel sheet decreases with high reinforcement, and the sheet fractures in a highly processed portion when it is machined into a complex shape, which is problematic. Furthermore, with the high strength of steel sheet, residual stress after processing causes elastic recovery and wall deformation, and dimensional accuracy deteriorates, which is also problematic. Therefore, it is not easy to process a high-strength steel sheet, particularly one with a tensile strength of 780 MPa or more, into a complex-shaped product using press forming. Roll forming makes it easier to process high-strength steel sheet than press forming, but it is limited to components with a uniform cross-section in the longitudinal direction. [4] Therefore, in recent years, for example, as described in Patent Documents 1 to 3, hot stamping has been adopted as a press forming technique for materials that are difficult to form, such as high-strength steel sheets. Hot stamping is a hot forming technique that involves heating a material intended for shaping and then forming the material. [5] In this technique, the material is heated and then formed. Therefore, during forming, the steel is soft and has good formability. Consequently, even a high-strength steel sheet can be precisely shaped into a complex form. Furthermore, in the hot stamping technique, since tempering is performed simultaneously with forming using a press die, a steel part obtained after forming has sufficient strength. [6] For example, Patent Document 1 describes that a steel member having a tensile strength of 1400 MPa or more can be obtained after forming by the hot stamping technique. [7] In recent years, countries around the world have set higher CO2 reduction targets, and every vehicle manufacturer has made progress in reducing fuel consumption while considering collision safety. Not only gasoline vehicles, but also the rapidly developing electric vehicles, require high-strength materials that protect not only passengers but also batteries in collisions and offset any increase in weight. For example, a hot-formed steel member used in vehicles and similar applications requires a higher strength than that commonly used in hot-formed steel members today, namely more than 1.5 GPa (1500 MPa). [8] However, most metallic materials experience deterioration in several properties with high hardening, and in particular, increased susceptibility to hydrogen embrittlement. It is known that susceptibility to hydrogen embrittlement increases when the tensile strength of a steel member is 1.2 GPa or higher, and there is a case of hydrogen embrittlement cracking in bolt steel for which high reinforcement has progressed earlier than in the automotive field. Therefore, in hot-stamped components with a tensile strength greater than 1.5 GPa, there is a further increase in susceptibility to hydrogen embrittlement. [9] In steel components used for vehicles, there is a risk of hydrogen embrittlement cracking due to hydrogen generated from steel corrosion while the vehicles are in operation. As described above, since the susceptibility of steel to hydrogen embrittlement increases significantly, particularly in strength ranges above 1.5 GPa, steel is considered susceptible to hydrogen embrittlement from even a small amount of hydrogen generated by slight corrosion. However, designing a vehicle that completely prevents steel corrosion is difficult. Therefore, to incorporate hot-stamped components with strengths above 1.5 GPa into the vehicle body for further weight reduction, it is necessary to sufficiently reduce the risk of hydrogen embrittlement cracking.

[10] One area where hydrogen embrittlement is particularly relevant while vehicles are in operation is a spot-welded portion. There are three main reasons why the spot-welded portion is particularly prone to hydrogen embrittlement. Specifically, the spot-welded portion is likely to become hydrogen brittle because (i) corrosion is likely to progress in the spot-welded portion, (ii) stress is generated in the spot-welded portion when a dimensionally accurate component is welded or similarly, and (iii) the structure of a cast and solidified portion, such as the spot-welded portion, is coarse and likely to become brittle.In other words, in the spot-welded portion, all hydrogen generation, stress application, and material limits, which are the causes of hydrogen embrittlement, are under stricter conditions than in the stationary portions of the base metal. As a complement to reason (i), since the effect of a chemical conversion treatment and painting is unlikely to reach a portion where the steel sheets (or members) overlap and weld, and the presence of a gap caused by dimensional defects causes corrosion to progress locally, a large amount of hydrogen is generated (gap corrosion reaction).

[11] With respect to a high-strength steel having a tensile strength of more than 1.5 GPa, for example, Patent Document 2 describes a press-formed article having excellent toughness and a tensile strength of 1.8 GPa or more, formed by hot pressing. Patent Document 3 describes a steel having an extremely high tensile strength of 2.0 GPa or more and, furthermore, good toughness and ductility. Patent Document 4 describes a steel having a high tensile strength of 1.8 GPa or more and, furthermore, good toughness. Patent Document 5 describes a steel having an extremely high tensile strength of 2.0 GPa or more and, furthermore, good toughness. However, in Patent Documents 2 to 5, regarding resistance to hydrogen embrittlement, the measures against hydrogen embrittlement in a spot-welded portion, particularly in a corrosive environment, are insufficient. Therefore, the steels in Patent Documents 2 to 5 have a tensile strength of more than 1.5 GPa, but do not adequately meet the strictest safety requirements in some cases when used as vehicle components.

[12] With respect to high-strength steels that have a spot-welded portion, for example, Patent Documents 6 to 8 describe spot-welding methods in which electrode contamination or welding dust generation is suppressed on an aluminum-clad steel sheet. However, in all patent documents, the measures against hydrogen embrittlement in the spot-welded portion of the high-strength steel are insufficient, and a requirement for greater safety in the application of high-strength steel having a tensile strength of more than 1.5 GPa to vehicle members may not be sufficiently satisfied. zofrAnn / zznz / E / YiAi Previous technique document Patent document

[13] Patent Document 1: Unexamined Japanese Patent Application, First Publication No. 2002-102980 Patent Document 2: Unexamined Japanese Patent Application, First Publication No. 2012-180594 Patent Document 3: Unexamined Japanese Patent Application, First Publication No. 2012-1802 Patent Document 4: International Publication PCT No. WO2015 / 182596 Patent Document 5: International Publication PCT No. WO2015 / 182591 Patent Document 6: Unexamined Japanese Patent Application, First Publication No. 2006-212649 Patent Document 7: Unexamined Japanese Patent Application, First Publication No. 2011-167742 Patent Document 8: Unexamined Japanese Patent Application, First Publication No. 2004-2932 Description of the invention Problems to be solved by the invention

[14] The present invention has been made to solve the above problems, and an object of the present invention is to provide a joining component having a spot-welded portion having excellent resistance to hydrogen embrittlement in a corrosive environment and a method of manufacturing the same. Means to solve the problem

[15] The essence of the present invention is the following joining component and the method of manufacturing the same. (1) A joining component according to an aspect of the present invention is a joining component comprising a first steel member, a second steel member, and a spot-welded portion joining the first steel member and the second steel member, wherein the first steel member comprises a steel sheet substrate containing, as a chemical composition, in % by mass, C: 0.25% to 0.65%, Si: 0.10% to 1.00%, Mn: 0.30% to 1.50%, P: 0.050% or less, S: 0.0100% or less, N: 0.010% or less, Ti: 0.010% to 0.100%, B: 0.0005% to 0.0100%, Mo: 0% to 1.00%, Cu: 0% to 1.00%, Ni: 0% to 1.00%, Cr: 0% to 1.00%, Nb: 0% to 0.10%, V: 0% to 1.00%, Ca: 0% to 0.010%, Al: 0% to 1.00%, Sn: 0% to 1.00%, W: 0% to 1.00%, Sb: 0% to 1.00%, Zr: 0% to 1.00%, REM: 0% to 0.30%, and a remainder of Fe and an impurity and a coating that forms on a surface of the steel sheet substrate, containing Al and Fe, and having a thickness of 25 pm or more, in a cross section in the thickness direction of the first steel member and the second steel member including the spot-welded portion, a filler metal containing Al and Fe is present in a space between the first steel member and the second steel member on a periphery of the spot-welded portion, in the cross section, the filler metal has a cross-sectional area of ​​3.0 × 104 pm2 or more and has a fill ratio of 80% or more in the space within a 100 pm interval from an extreme portion of a crown bond formed at the periphery of the spot-welded portion, and the filler metal includes a first region containing, by mass %, Al: 15% or more and less than 35%, Fe: 55% or more and 75% or less, and Si: 4% or more and 9% or less and a second region containing, by mass %, Al: 35% or more and 55% or less, Fe: 40% or more and less than 55%, and Si: 1% or more and less than 4%. (2) In the joining component in accordance with (1) above, the steel sheet substrate of the first steel member may contain, as chemical composition, in % by mass, one or more of Mo: 0.10% to 1.00%, Cu: 0.10% to 1.00% and Ni: 0.10% to 1.00%, the first region may further contain one or more of Mo, Cu and Ni in a total content of 0.25% or more, and the second region may further contain one or more of Mo, Cu and Ni in a total content of 0.15% or more. (3) In the joining component in accordance with (2) above, an average of the Feret diameters of the second region may be adjusted to 30 pm or less. (4) A method of manufacturing a joining component according to another aspect of the present invention includes a heat treatment step of heating a coated steel sheet comprising a steel sheet containing, as a chemical composition, in % by mass, C: 0.25% to 0.65%, Si: 0.10% to 1.00%, Mn: 0.30% to 1.50%, P: 0.050% or less, S: 0.0100% or less, N: 0.010% or less, Ti: 0.010% to 0.100%, B: 0.0005% to 0.0100%, Mo: 0% to 1.00%, Cu: 0% to 1.00%, Ni: 0% to 1.00%, Cr: 0% to 1.00%, Nb: 0% to 0.10%, V: 0% to 1.00%, Ca: 0% to 0.010%, Al: 0% to 1.00%, Sn: 0% to 1.00%, W: 0% to 1.00%, Sb: 0% to 1.00%, Zr: 0% to 1.00%, REM: 0% to 0.30%, and a residue of Fe and an impurity and a coating that forms on a surface of the steel sheet, contains Al and has an amount of adhesion of 50 g / m2 or more to an Ac3 up to (point Ac3 + 300)°C at a temperature increase rate of 1.0 to 1000°C / s and cooling the coated steel sheet to a point Ms or less at a higher or faster critical cooling rate to obtain a steel member and a spot welding pass to join the steel member after the heat treatment pass and a second steel member serving as opposing material by spot welding, wherein, in the spot welding pass, at least in one position where there is a pressed energizing electrode, the steel member and the second steel member are arranged to overlap each other with a spacing of 50 pm to 500 pm between them, the energizing electrode is pressed against the steel member and the second steel member such that a contact angle is 15 degrees or less and the electrode force is 300 kgf or more,Five or more upslope cycles are imparted in which an amount of energization is gradually increased with an alternating source of 50 Hz or 60 Hz, and then a weld nugget is formed to join the steel member and the second steel member. (5) In the method of manufacturing joining components in accordance with (4) above, the chemical composition of the steel sheet may contain, in % by mass, one or more of No: 0.10% to 1.00%, Cu: 0.10% to 1.00% and Ni: 0.10% to 1.00%. (6) In the method of manufacturing a joining component in accordance with (5) above, in the spot welding step, an average cooling rate of 800°C to 500°C can be adjusted to 500°C / so faster. zofrAnn / zznz / E / YiAi Effects of the invention

[16] According to the aspect of the present invention, it is possible to provide a joining component having a spot-welded portion that has excellent resistance to hydrogen embrittlement in a corrosive environment and a method of manufacturing the same. The bonding component according to the aspect of the present invention has high strength and excellent resistance to hydrogen embrittlement and thus contributes to improved fuel consumption and collision safety when applied to a vehicle component. Brief description of the drawings

[17] Figure 1 is a schematic view showing an example of a joining component in accordance with this modality. Modalities of the invention

[18] In order to obtain a joining component with a spot-welded portion that has high tensile strength and excellent resistance to hydrogen embrittlement in a corrosive environment, the inventors hereof investigated the influence of the weld structure or the steel used as the material on these properties. The following findings were obtained as a result.

[19] Most of the materials used for hot stamping commonly manufactured members are coated steel sheets, one surface of which is subjected to an aluminum plating that has excellent corrosion resistance. When hot stamping is performed on this coated steel sheet, an alloying reaction between the Al in the plating layer on the surface and the Fe in the steel sheet progresses during heating, resulting in a steel member that includes a coating containing Al and Fe (coated steel member) (hereafter referred to in some cases as an Al-Fe-based coating). Most commonly used steel sheets that exhibit a tensile strength of approximately 1.5 GPa after hot stamping contain approximately 0.20% C by mass, and the strength after hot stamping is ensured due to the C content.This steel member is joined to another member by spot welding, so a joining component can be obtained.

[20] (a) In order to achieve a further reduction in the weight of the vehicle body, the inventors hereof carried out a detailed study to obtain a high-strength member having a tensile strength of more than 1.5 GPa (1500 MPa) after hot stamping by means of an increase in the C content. As a result, it was found that, in terms of tensile strength, an ultra-high strength of more than 1.5 GPa could be obtained after a heat treatment including quenching, such as hot stamping, by adjusting the C content to 0.25% by mass or more. On the other hand, there was concern about the risk of increased susceptibility to hydrogen embrittlement with ultra-high hardening to a tensile strength of more than 1.5 GPa.5 GPa and hydrogen embrittlement cracking was caused by hydrogen generated in a corrosive environment while the vehicles were in operation. In particular, when a joint component was produced using this coated steel member, since a spot-welded portion melted once, corrosion resistance from the aluminum plating could not be guaranteed and there was a risk of hydrogen embrittlement.

[21] (b) The inventors hereof studied a method for suppressing hydrogen embrittlement by preventing corrosion of a spot-welded portion, which acts as the starting point of embrittlement, in a joint component zofrRnn / zznz / E / YiAi made of a coated steel member having a high strength of more than 1.5 GPa and an AlFe-based coating. As a result, it was found that corrosion can be sufficiently prevented by covering the periphery of a weld with an alloy containing Al and Fe.

[22] (c) The inventors hereof further investigated the resistance to hydrogen embrittlement of a coated steel member having a tensile strength of more than 1.5 GPa and found a component design or structure design that was excellent in terms of resistance to hydrogen embrittlement.

[23] Based on the above findings, the inventors hereof developed a joining component made of a high-strength coated steel member having a tensile strength of more than 1.5 GPa, in which resistance to hydrogen embrittlement in a corrosive environment is significantly improved by preventing corrosion of a spot-welded portion, reducing the amount of hydrogen intrusion, and enhancing the hydrogen embrittlement resistance of the steel. Such a joining component has high strength and a low risk of hydrogen embrittlement and can therefore be applied more safely to vehicle bodies.

[24] Each requirement of a joining component according to an embodiment of the present invention (the joining component according to the present embodiment) and a method of manufacturing the same will now be described in detail.

[25] (A) Bonding component As shown in Figure 1, a joining component 1 according to the present embodiment includes a first steel member 11, a second steel member 12, and a spot-welded portion 21 joining the first steel member 11 and the second steel member 12. This first steel member 11 is a coated steel member having a steel sheet substrate 111 having a predetermined chemical composition and a coating (Ai-Fe based coating) 112 forming on the surface of the steel sheet substrate 111 and containing Al and Fe. Furthermore, in the joining component 1 according to the present embodiment, in a cross-section in the thickness direction of the first steel member 11 and the second steel member 12 that includes the spot-welded portion 21, a filler metal 31 containing Al and Fe is present in a space g between the first steel member 11 and the second steel member 12 at the periphery of the spot-welded portion 21. The filler metal 31 includes a first region containing, by mass %, Al: 15% or more and less than 35%, Fe: 55% or more and 75% or less, and Si: 4% or more and zofrRnn / zznz / E / YiAi 9% or less and a second region containing, in % by mass, Al: 35% or more and 55% or less, Fe: 40% or more and less than 55%, and Si: 1% or more and less than 4%. Furthermore, in cross section, the filler metal 31 has a cross section area of ​​3.0 × 104 pm2 or more and has a fill ratio of 80% or more in the g space within a 100 pm interval from the extreme portion of a crown bond formed at the periphery of the spot-welded portion 21. From now on, each one will be described below.

[26] (Al) First steel member As described above, the first steel member 11 included in the joining component 1 in accordance with the present embodiment has the steel sheet substrate 111 and the coating (Al-Fe based coating) 112 that is formed on the surface of the steel sheet substrate 111 and contains Al and Fe. As described below, the first steel member 11 is obtained by performing a heat treatment that accompanies tempering, such as hot stamping on a coated steel sheet having a steel sheet substrate and an Al-based coating.

[27] (Al-1) Steel sheet substrate The steel sheet substrate 111 of the first steel member 11 included in the joining component 1 in accordance with this modality has a predetermined chemical composition. Specifically, the 111 steel sheet substrate has a chemical composition containing, in % by mass, C: 0.25% to 0.65%, Si: 0.10% to 1.00%, Mn: 0.30% to 1.50%, P: 0.050% or less, S: 0.0100% or less, N: 0.010% or less, Ti: 0.010% to 0.100%, B: 0.0005% to 0.0100%, Mo: 0% to 1.00%, Cu: 0% to 1.00%, Ni: 0% to 1.00%, Cr: 0% to 1.00%, Nb: 0% to 0.10%, V: 0% to 1.00%, Ca: 0% to 0.010%, Al: 0% to 1.00%, Sn: 0% to 1.00%, W: 0% to 1.00%, Sb: 0% to 1.00%, Zr: 0% to 1.00%, REM: 0% to 0.30% and a remainder of Fe and an impurity. The reasons for limiting each element are as follows. Here, the chemical composition of the steel sheet substrate 111 refers to the chemical composition of a portion of the first steel member 11 excluding the Al-Fe based coating 112 on the surface (e.g., a position 1 / 4 of the thickness from the surface of the steel sheet substrate). Hereafter, % with respect to content is % by mass unless otherwise specified.

[28] C: 0.25% to 0.65% Carbon (C) is an element that improves the hardenability of steel and increases the strength of the steel component obtained after quenching, such as after hot stamping. When the carbon content is less than 0.25%, it becomes difficult to ensure sufficient strength (more than 1.5 GPa) in the steel component after quenching. Therefore, the carbon content is adjusted to 0.25% or higher. The preferred carbon content is 0.28% or higher. On the other hand, when the carbon content exceeds 0.65%, the strength of the steel member after tempering becomes too high, and the deterioration of its resistance to hydrogen embrittlement becomes significant. Therefore, the carbon content is adjusted to 0.65% or less. Preferably, the carbon content is 0.60% or less.

[29] Yes: 0.10% to 1.00% Silicon (Si) is an element that effectively improves the hardenability of steel and ensures the stable strength of the steel member after quenching. To achieve this effect, the Si content should be adjusted to 0.10% or more. Preferably, the Si content is 0.35% or more. On the other hand, when the silicon content in steel exceeds 1.00%, the heating temperature required for austenitic transformation becomes significantly higher during heat treatment (quenching). Consequently, the cost of heat treatment may increase, or ferrite may remain during heating, reducing the strength of the steel member. Therefore, the silicon content is adjusted to 1.00% or less. Preferably, the silicon content is 0.60% or less.

[30] Mn: 0.30% to 1.50% Manganese (Mn) is a highly effective element for improving the hardenability of steel and ensuring stable strength after quenching. Furthermore, Mn lowers the Ac3 point and facilitates a reduction in the quenching temperature. However, when the Mn content is below 0.30%, the effect is insufficient. Therefore, the Mn content is adjusted to 0.30% or higher. Ideally, the Mn content should be 0.40% or higher. On the other hand, when the Mn content exceeds 1.50%, the resistance to hydrogen embrittlement of the steel member after rapid cooling deteriorates. Therefore, the Mn content is adjusted to 1.50% or less. The Mn content is preferably 1.30% or less, and very preferably 1.10% or less.

[31] P: 0.050% or less Phosphorus (P) is an element that degrades the hydrogen embrittlement resistance of steel members after cooling. In particular, when the P content exceeds 0.050%, the deterioration of hydrogen embrittlement resistance becomes significant. Therefore, the P content is limited to 0.050% or less. Preferably, the P content is limited to 0.005% or less. Since a low P content is preferable, the P content can be 0%. However, the P content can be adjusted to 0.001% or more from a cost perspective.

[32] S: 0.0100% or less Sulfur (S) is an element that degrades the hydrogen embrittlement resistance of steel members after rapid cooling. In particular, when the S content exceeds 0.0100%, the deterioration of hydrogen embrittlement resistance becomes significant. Therefore, the S content is limited to 0.0100% or less. Preferably, the S content is limited to 0.0050% or less. Since a low S content is preferable, it can be 0%. However, the S content can be adjusted to 0.0001% or more for cost reasons.

[33] N: 0.010% or less Nitrogen (N) is an element that degrades the hydrogen embrittlement resistance of steel components after cooling. In particular, when the N content exceeds 0.010%, coarse nitrides form in the steel, and the hydrogen embrittlement resistance deteriorates significantly. Therefore, the N content is adjusted to 0.010% or less. A lower limit for the N content does not have to be particularly strict and can be 0%. However, adjusting the N content to less than 0.0002% leads to an increase in the steelmaking cost and is economically undesirable. Therefore, the N content can be adjusted to 0.0002% or more, or 0.0008% or more.

[34] Ti: 0.010% to 0.100% Titanium (Ti) is an element that refines austenite grains by suppressing recrystallization and grain growth through the formation of fine carbides when steel sheet is heat-treated above its Ac30 temperature. Therefore, Ti content can increase the hydrogen embrittlement resistance of steel components. Furthermore, Ti preferentially bonds with nitrogen (N) in steel to suppress boron consumption caused by BN precipitation and to promote boron-induced hardenability enhancement, as described below. When the Ti content is less than 0.010%, the aforementioned effects are insufficient. Therefore, the Ti content is adjusted to 0.010% or higher. Preferably, the Ti content is 0.015% or higher. On the other hand, when the Ti content exceeds 0.100%, the amount of TiC precipitation increases and C is consumed, thus decreasing the strength of the steel member after tempering. Therefore, the content of Ti is adjusted to 0.100% or less. The Ti content is preferably 0.080% or less.

[35] B: 0.0005% to 0.0100% Boron (B) is an important element that dramatically improves the hardenability of steel, even in small amounts. Furthermore, B segregates at grain boundaries, strengthening them and improving resistance to hydrogen embrittlement. It also suppresses the growth of austenite grains when the steel sheet is heated. When the B content is less than 0.0005%, these effects may not be sufficiently achievable. Therefore, the B content is adjusted to 0.0005% or higher. Preferably, the B content is 0.0010% or higher. Furthermore, when the B content exceeds 0.0100%, a large amount of coarse compounds precipitates, and the resistance to hydrogen embrittlement of the steel member deteriorates. Therefore, the B content is adjusted to 0.0100% or less. The B content is preferably 0.0080% or less.

[36] In the chemical composition of the steel sheet substrate 111 included in the first steel member 11 included in the joining component of this embodiment, elements other than those listed above, i.e., the remainder may be Fe and an impurity, but one or more elements selected from the group consisting of Mo, Cu, Ni, Cr, Nb, V, Ca, Al, Sn, W, Sb, Zr, and REM may be contained within the ranges described below to improve various properties (hardenability, strength, resistance to hydrogen embrittlement, deoxidation properties, corrosion resistance, and the like) of the steel member and the joining component including this steel member. These elements are optional and do not necessarily have to be contained. Therefore, the lower limit thereof is 0%.

[37] Mo: 0% to 1.00% Molybdenum (Mo) is a highly effective element for improving the hardenability of steel and ensuring the stable strength of the steel member after quenching. In particular, a synergistic effect of improved hardenability can be achieved by containing both Mo and boron (B). Furthermore, Mo can further enhance corrosion resistance when contained in a filler metal (Al-Fe based filler metal) that forms at the periphery of the spot welded portion. Therefore, Mo is preferably included. When the Mo content is less than 0.10%, since these effects are insufficient, the Mo content is preferably adjusted to 0.10% or more, and very preferably to 0.20% or more. On the other hand, Mo has a stabilizing effect on iron carbides. When the Mo content exceeds 1.00%, coarse iron carbides may remain undissolved when the steel sheet is heated, and the resistance to hydrogen embrittlement of the steel member after rapid cooling may be compromised. Furthermore, the cost increase is significant. Therefore, when Mo is present, the Mo content is adjusted to 1.00% or less. The Mo content is preferably 0.80% or less.

[38] Cu: 0% to 1.00% Copper (Cu) is an element that effectively improves the hardenability of steel and ensures the stable strength of the steel member after quenching. Furthermore, copper further enhances corrosion resistance when contained within an aluminum-iron (Al-Fe) filler metal that forms around the periphery of the spot-welded portion, as described below. Therefore, copper is preferably included. When the copper content is less than 0.10%, these effects are insufficient; if copper is present, the copper content should preferably be adjusted to 0.10% or higher. A copper content of 0.20% or higher is highly preferable. On the other hand, when the copper content exceeds 1.00%, the aforementioned effects become saturated and the cost increases. Therefore, if copper is involved, the copper content should be adjusted to 1.00% or less. The copper content is preferably 0.80% or less.

[39] Ni: 0% to 1.00% Nickel (Ni) is an element that effectively improves the hardenability of steel and ensures the stable strength of the steel member after quenching. Furthermore, Ni further enhances corrosion resistance when contained within an aluminum-Fe (Al-Fe) filler metal that forms at the periphery of the spot-welded portion. Therefore, Ni is preferably included. When the Ni content is less than 0.10%, these effects are insufficient; if Ni is present, the Ni content should preferably be adjusted to 0.10% or higher. A Ni content of 0.20% or higher is highly preferred. On the other hand, when the Ni content exceeds 1.00%, the critical hydrogen content of the steel member decreases. Furthermore, the cost increase is significant. Therefore, if Ni is present, the Ni content should be adjusted to 1.00% or less. The Ni content is preferably 0.25% or less, and very preferably 0.20% or less.

[40] Cr: 0% to 1.00% Chromium (Cr) is an element that effectively improves the hardenability of steel and ensures the stable strength of the steel member after quenching. Therefore, Cr may be included. To achieve the aforementioned effects, the Cr content is preferably 0.01% or more, very preferably 0.05% or more, and even more preferably 0.08% or more. On the other hand, when the Cr content exceeds 1.00%, the aforementioned effects become saturated and the cost increases. Furthermore, since Cr has the action of stabilizing iron carbides, when the Cr content exceeds 1.00%, coarse iron carbides may remain undissolved when the steel sheet is heated, and the resistance to hydrogen embrittlement of the steel member after quenching may deteriorate. Therefore, in the case of Cr content, it is adjusted to 1.00% or less. The Cr content is preferably 0.80% or less.

[41] Nb: 0% to 0.10% Nitrogen (Nb) is an element that forms fine carbides and increases the resistance of steel to hydrogen embrittlement through a refining effect. When the Nb content is less than 0.02%, these effects may not be sufficiently achievable. Therefore, to obtain these effects, the Nb content is preferably adjusted to 0.02% or higher. A Nb content of 0.03% or higher is highly preferable. On the other hand, when the Nb content exceeds 0.10%, the carbides become coarse and the hydrogen embrittlement resistance of the steel member deteriorates. Therefore, in the case of Nb content, it is adjusted to 0.10% or less. The Nb content is preferably 0.08% or less.

[42] V: 0% to 1.00% Zinc (V) is an element that forms fine carbides and improves the resistance to hydrogen embrittlement of the steel member through the refining or hydrogen trapping effect. Therefore, zinc may be included. To obtain the above effects, the zinc content is preferably adjusted to 0.01% or more, and very preferably to 0.10% or more. On the other hand, when the V content exceeds 1.00%, the aforementioned effects become saturated and economic efficiency decreases. Therefore, if V is present, the V content should be adjusted to 1.00% or less.

[43] Ca: 0% to 0.010% Calcium (Ca) is an element that refines inclusions in steel and improves the resistance to hydrogen embrittlement of the steel member after rapid cooling. Therefore, Ca may be present. To achieve this effect, the Ca content is preferably adjusted to 0.001% or more, and very preferably to 0.002% or more. Conversely, when the Ca content exceeds 0.010%, the effect becomes saturated and the cost increases. Therefore, if Ca is present, the Ca content is adjusted to 0.010% or less. The Ca content is preferably 0.005% or less, and very preferably 0.004% or less.

[44] Al: 0% to 1.00% Aluminum (Al) is a commonly used element as a deoxidizing agent for steel. Therefore, Al may be present. To achieve the desired effect, the Al content is preferably adjusted to 0.01% or more. On the other hand, when the aluminum content exceeds 1.00%, the aforementioned effect saturates and economic efficiency decreases. Therefore, if aluminum is present, the aluminum content should be adjusted to 1.00% or less.

[45] Sn: 0% to 1.00% Tin (Sn) is an element that improves corrosion resistance in corrosive environments. Therefore, tin may be present in the product. To achieve this effect, the tin content is preferably adjusted to 0.01% or higher. On the other hand, when the Sn content exceeds 1.00%, the grain boundary strength decreases and the resistance to hydrogen embrittlement of the steel member after rapid cooling deteriorates. Therefore, in the case of Sn-containing steel, the Sn content is adjusted to 1.00% or less.

[46] W: 0% to 1.00% Water (W) is an element that effectively improves the hardenability of steel and ensures the stable strength of the steel member after quenching. Therefore, W can be included in steel. Furthermore, W improves corrosion resistance in corrosive environments. To achieve these effects, the W content is preferably adjusted to 0.01% or more. On the other hand, when the W content exceeds 1.00%, the aforementioned effects saturate and economic efficiency decreases. Therefore, if the product contains W, the W content should be adjusted to 1.00% or less.

[47] Sb: 0% to 1.00% Antimony (Sb) is an element that improves corrosion resistance in corrosive environments. Therefore, Sb may be present in the product. To achieve this effect, the Sb content is preferably adjusted to 0.01% or higher. On the other hand, when the Sb content exceeds 1.00%, the grain boundary strength decreases, and the resistance to hydrogen embrittlement of the steel member after rapid cooling deteriorates. Therefore, in cases where Sb is present, the Sb content is adjusted to 1.00% or less.

[48] ​​Zr: 0% to 1.00% Zinc (Zr) is an element that improves corrosion resistance in corrosive environments. Therefore, Zr may be present in the product. To achieve this effect, the Zr content is preferably set at 0.01% or higher. Furthermore, when the Zr content exceeds 1.00%, the grain boundary strength decreases, and the resistance to hydrogen embrittlement of the steel member after rapid cooling deteriorates. Therefore, when Zr is present, the Zr content is adjusted to 1.00% or less.

[49] REM: 0% to 0.30% Similar to calcium, REM is an element that refines inclusions in steel and improves the resistance to hydrogen embrittlement of the steel member after rapid cooling. Therefore, REM may be included. To achieve the aforementioned effects, the REM content is preferably adjusted to 0.01% or more, and very preferably to 0.02% or more. Conversely, when the REM content exceeds 0.30%, the effect becomes saturated and the cost increases. Therefore, if the product contains REM, the REM content should be adjusted to 0.30% or less. Ideally, the REM content should be 0.20% or less.

[50] Here, REM refers to a total of 17 elements, including Se, Y, and lanthanides such as La and Nd, and the REM content means the total content of these elements. REM is added to molten steel using, for example, an Fe-Si-REM alloy, and this alloy contains, for example, La, Nd, Ce, and Pr.

[51] In the chemical composition of the steel sheet substrate 111 included in the first steel member 11 included in the joining component of the present embodiment, elements other than the above elements, i.e., the remainder may be Fe and an impurity. Here, impurity is a component that is mixed in due to various factors, including raw materials such as ore and scrap, and a manufacturing step when the steel sheet is manufactured industrially, and is acceptable within a range without adversely affecting the properties of the bonding component in accordance with the present modality.

[52] The chemical composition of the steel sheet substrate 111 can be obtained by the following method. The chemical composition can be obtained by averaging the contents obtained by performing an elemental analysis using a general method such as TCP from a position 1 / 4 of the sheet thickness from the surface of the steel sheet substrate 111 in the direction of the sheet thickness. zofrAnn / zznz / E / YiAi

[53] Internal structure of steel sheet substrate 111 The internal structure (metallographic structure) of the steel sheet substrate 111 included in the first steel member 11 included in the joining component 1, according to the present embodiment, is a structure containing primarily high-strength martensite. Preferably, the martensite occupies 70% or more in terms of area fraction. Very preferably, the martensite occupies 80% or more. The martensite may occupy 100%.

[54] The internal structure of the 111 steel sheet substrate may contain one or more of the residual austenite, bainite, ferrite, and pearlite as remnants other than martensite. Martensite includes not only fresh martensite but also quenched martensite and self-hardening martensite. Self-hardening martensite is quenched martensite formed during quenching at the time of tempering without a heat treatment for tempering, and is formed by in-situ tempering of the martensite formed due to self-heating associated with the martensitic transformation.

[55] The internal structure of the steel sheet substrate 111 can be determined by the following method. The area fraction of martensite (including quenched and self-quenched martensite) is measured using a transmission electron microscope (TEM) and an electron beam diffractometer connected to the TEM. Measurement samples are cut from a 1 / 4-width portion of the steel member sheet (a 1 / 4-width section of the sheet in the width direction from an extreme section in the width direction) and a 1 / 4-thick portion of the steel sheet substrate 111 (a section of zofrRnn / zznz / E / YiAi) One-quarter of the sheet thickness (in the sheet thickness direction from the surface) is used as a thin-film sample for TEM observation. The thin-film sample is a cut from a cross-section orthogonal to the rolling direction. The TEM observation range is set to 400 pm². The electron beam diffraction pattern of the thin-film sample allows differentiation between martensite or bainite, which have body-centered cubic lattices, and residual austenite, which has face-centered cubic lattices. Iron carbides (Fe₃C) in martensite and bainite are then identified by the diffraction pattern, and their precipitation morphology is observed to determine the microstructural fractions of martensite and bainite.Specifically, regarding the morphology of the precipitation, precipitation in three directions is determined to be martensite, and precipitation limited to one direction is determined to be bainite. The microstructural fractions of martensite and bainite measured by TEM are expressed as percentages of area; however, since the metallographic structure of the steel member in this modality is isotropic, the area fraction values ​​can be directly replaced with volume fractions. Carbides are observed to distinguish between martensite and bainite, but in this modality, carbides are not included in the volume fraction of the structure. Ferrite or pearlite that may be present as residual microstructure can be easily confirmed using an optical or scanning electron microscope. Specifically, measurement samples are cut from a 1 / 4-width portion of the steel member sheet and a 1 / 4-thick portion of the steel sheet substrate and used as observation samples. A cross-sectional sample cut in the direction orthogonal to the rolling direction is used as the sample. The microscope's observation interval is set to 40,000 pm². The cut samples are mechanically polished and then mirror-finished. Etching is then performed with a nital etching solution to reveal ferrite and pearlite, and the cut sample is observed under the microscope to confirm the presence of ferrite or pearlite.A structure in which ferrite and cementite are arranged alternately in layers is distinguished as pearlite, and a structure in which cementite precipitates into particles is distinguished as bainite. zofrRnn / zznz / E / YiAi

[56] (Al-2) Coating The first steel member 11 included in the joining component according to this embodiment has the coating 112 containing Al and Fe (Al-Fe based coating) on ​​the surface of the steel sheet substrate 111 described above. In this embodiment, the Al-Fe based coating is a coating containing primarily Al and Fe, and preferably containing Al and Fe in a total amount of 70% or more by mass. The Al-Fe based coating is also referred to as the coating, alloy coating layer, or intermetallic compound layer. In addition to Al and Fe, the Al-Fe based coating may contain Si, Mg, Ca, Sr, Ni, Cu, Mo, Mn, Cr, C, Nb, Ti, B, V, Sn, W, Sb, Zr, REM, and Zn, and the remainder may be impurities. The thickness of the Al-Fe-based coating is preferably 25 µm or more. The upper limit of the Al-Fe-based coating thickness is not particularly restricted and can be adjusted to 100 µm or less.

[57] The chemical composition and thickness of the Al-Fe-based coating can be obtained by observing the cross-section using a scanning electron microscope and an electron probe microanalyzer (ERMA). Ten fields of view are observed, and the chemical composition and coating thickness are obtained using the average values.

[58] (A2) Second steel member In the joining component 1 according to the present embodiment, the second steel member 12 joined to the first steel member 11 through the spot-welded portion 21 is not particularly limited from the point of view of the hydrogen embrittlement resistance of the spot-welded portion 21. However, when considering the corrosion resistance of the joining component 1, the second steel member 12 is preferably, similarly to the first steel member 11, a coated steel member having an Al-Fe based coating.

[59] (A3) Welding The joining component 1 according to this embodiment has a spot-welded portion (spot-welded portion 21), and the first steel member 11 and the second steel member 12 are joined via the spot-welded portion 21. The spot-welded portion 21 is made of a nugget formed by spot welding. A crown bond (a solid-phase bonded part in the form of a ring) may be formed at the periphery of the nugget. The size of the nugget of the spot-welded portion 21 of the joining component 1 according to this embodiment is not particularly limited; however, when the sheet thickness is defined as t (mm), the size is preferably 3χVt (mm) or more in the direction parallel to the sheet surface.

[60] (A4) Filler metal The joining component 1 according to the present embodiment has the filler metal 31 containing Al and Fe on the periphery of the spot-welded portion 21 described above. That is, in a cross-section in the thickness direction of the first steel member 11 and the second steel member 12, including the spot-welded portion 21, the filler metal 31 containing Al and Fe is present between the first steel member 11 and the second steel member 12 on the periphery of the spot-welded portion 21 (for example, an end portion of the nugget or a position within an interval of 100 pm or less from an end portion of a crown joint when the crown joint is formed). In the joining component 1 according to the present modality, as described below, the first steel member 11 and the second steel member 12 are arranged to overlap each other with a spacing of 50 pm to 500 pm between them, an activation electrode is pressed against the first steel member 11 and the second steel member 12 so that the contact angle is 15 degrees or less and the electrode force is 300 kgf or more to perform spot welding, and the first steel member and the second steel member are joined together.Therefore, in the joining component 1 according to the present embodiment, as shown in Figure 1, while the first steel member 11 and the second steel member 12 are in contact with each other at the spot-welded portion 21, at the periphery thereof, the space g is present between the first steel member 11 and the second steel member 12. The space is filled with filler metal 31, thereby suppressing corrosion of the spot-welded portion 21 and improving resistance to hydrogen embrittlement. Filler metal 31 must be present to fill the space g between the first steel member 11 and the second steel member 12 to suppress corrosion of the spot-welded portion 21. The filler metal 31 must have a cross-sectional area of ​​3.0 * 104pm2 or more and have a fill ratio of 80% or more in a space within a 100pm interval from the extreme portion of the crown joint formed at the periphery of the spot-welded portion. The fill ratio is preferably 90% or more and may be 100%. When the cross-sectional area is small or the fill ratio is small, corrosion of the spot-welded portion cannot be sufficiently suppressed. Provided the filler metal 31 fills the space p between the first steel member 11 and the second steel member 12 as described above in at least one cross-section in the thickness direction of the first steel member 11 and the second steel member 12, including the spot-welded portion 21, the effect can be achieved, but it is preferable that the space g be filled as described above in all cross-sections because the effect becomes stronger.

[61] Filler metal 31 includes a region that has two types of chemical compositions. A first region contains, in its chemical composition, in % by mass, Al: 15% or more and less than 35%, Fe: 55% or more and 75% or less, and Si: 4% or more and 9% or less. The first region may also contain Mo, Cu, and Ni as required, and in that case, the total content of Mo, Cu, and Ni is preferably adjusted to 0.25% by mass or more. A second region contains, in its chemical composition, in % by mass, Al: 35% or more and 55% or less, Fe: 40% or more and less than 55%, and Si: 1% or more and less than 4%. The second region may also contain Mo, Cu, and Ni as required, and in that case, the total content of Mo, Cu, and Ni is preferably adjusted to 0.15% by mass or more. This filler metal can be obtained by welding, which will be described below, to the steel members above (the first steel member 11 and the second steel member 12). Other chemical compositions that are contained in the steel sheet substrate and the coating may also be contained as the rest of the chemical compositions of the first region and the second region.

[62] Furthermore, in filler metal 31, the second region is preferably finely dispersed. In this case, corrosion resistance is further improved. The reason for this is considered as follows. The second region has a higher aluminum content than the first region and therefore exhibits a stronger sacrificial protective effect. Consequently, when the filler metal corrodes, the second region corrodes preferentially over the first. Since the second region is dispersed within the filler metal as a fine, network-like structure, the area that corrodes preferentially becomes larger. Therefore, as the second region becomes more finely dispersed within the filler metal, the anti-corrosive effect of the filler metal intensifies. Specifically, the second region is preferentially dispersed in a fine particle size with an average Feret diameter of 30 pm or less. Since the second region is dispersed in a network-like pattern, its shape is variable. Therefore, the size of the second region is regulated by the Feret diameter. A method for measuring the size of the second region will be described below for ease of description.

[63] The cross-sectional area and filling ratio of the loaded metal 31 are obtained by the following method. A vertical cross-section is cut through the center of a spot weld, revealing the spot weld portion (the nugget and crown joint) and a cross-section of the filler metal in the joint component 1. The area of ​​the filler metal is then obtained from this cross-section. One cutting method is based, for example, on JIS Z 3139: 2009. Under welding conditions, five or more samples are cut, their cross-sectional areas are measured, and the average value is taken as the cross-sectional area of ​​the filler metal. Furthermore, the proportion occupied by the filler metal in the region excluding the steel members is obtained over an interval from the end of a press-welded portion (crown joint) in the cross-section up to 100 pm towards the separation portion. Under welding conditions, 5 or more samples are cut and the proportions obtained, and the minimum value is considered the filler metal fill ratio.

[64] The amount of Al, Fe, Si, Mo, Cu and Ni contained in the filler metal 31 is obtained by the following method. A vertical cross-section is cut through the central position of the spot weld so that a cross-section of the spot-welded portion (the nugget and the crown joint) and the filler metal in the joint component 1 can be observed. A reflected electron image of this sample is acquired using a scanning electron microscope and a point elemental analysis (beam diameter: 1 pm or less) is performed using an electron probe microanalyzer (ERMA) on two types of structures with different contrasts that make up the filler metal, so that the amount of Al, Fe, Si, Mo, Cu and Ni contained in the filler metal can be obtained.At the time of measurement, the analysis is performed at 10 points in each of the two types of structures in the first region that appears bright because it contains a relatively large amount of Fe, which is a heavy element, and the other second region, and the average values ​​are considered as the amount of Al, Fe, Si, Mo, Cu and Ni contained in the filler metal.

[65] The size of the second region included in the filler metal 31 is obtained by the following method. A vertical cross-section is cut through the center of the spot weld, exposing the spot weld portion (the nugget and crown) and a cross-section of the filler metal in the joint component 1. A reflected electron image of this sample is acquired using a scanning electron microscope (ZofrAnn / zznz / E / YiAi). As described above, the second region can be determined by contrast. Furthermore, the size of the second region is defined as the average distance between parallel lines parallel to the horizontal direction and intersecting the second region (horizontal Feret diameter) and the distance between parallel lines parallel to the horizontal and vertical directions intersecting the second region (vertical Feret diameter).The horizontal direction refers to the longitudinal direction of the joint components, and the vertical direction refers to the direction of the sheet thickness perpendicular to the longitudinal direction. In the bonding component according to this modality, the second region often has an island-like shape surrounded by the first regions. At the time of measurement, the size of the second island-like region surrounded by 15 first regions is measured, and the average value thereof is taken as the size of the second region included in the filler metal. zofrRnn / zznz / E / YiAi

[66] (A5) Bonding component properties In the joining component 1 according to this embodiment, the filler metal 31 is controlled as described above, thereby reducing the intrusion of a corrosion factor into the spot-welded portion 21 and preventing corrosion. Furthermore, the joining component 1 according to this embodiment has high strength, namely a tensile strength of more than 1.5 GPa, and is excellent in terms of resistance to hydrogen embrittlement in a corrosive environment.

[67] In the present modality, resistance to hydrogen embrittlement in a corrosive environment is evaluated by an exposure test in an environment where the joining component is actually used or by a corrosion promotion test (CCT). For example, CCT is performed in accordance with the provisions of JASO M609 and M610, and resistance to hydrogen embrittlement is evaluated by the number of cycles during which the spot-welded portion does not fracture.

[68] The shape of the joining component 1 is not particularly restricted. That is, the first steel member 11 and / or the second steel member 12 can be a flat sheet or a formed body. The hot-formed coated steel member is, in many cases, a formed body, and in the present embodiment, the formed body and flat sheet cases are collectively referred to as the coated steel member. Furthermore, the coated steel member can be a custom-made material having varying strengths at different points.

[69] (B) Coated steel sheet that serves as material The coated steel sheet used as the material for the first steel member (coated steel member) included in the joining component according to this modality (hereinafter referred to in some cases as the coated steel sheet according to this modality) will now be described. The first steel member can be obtained by heat-treating the coated steel sheet described below as the material for the first steel member 11. This coated steel sheet can also be used as the material for the second steel member 12. The coated steel sheet in accordance with the present modality has a steel sheet having a predetermined chemical composition and a coating that is formed on the surface of the steel sheet and contains Al (Al-based coating). zofrAnn / zznz / E / YiAi

[70] (Bl) Chemical composition of the steel sheet The chemical composition range of the steel sheet included in the coated steel sheet according to this embodiment is the same as the chemical composition of the steel sheet substrate 111 in the first steel member 11 described above, and the reason for its limitation is also the same. Here, the chemical composition of the steel sheet refers to the chemical composition of a portion of the coated steel sheet, excluding the Al-based coating on the surface and the boundary region between the Al-based coating and the steel sheet. For example, the chemical composition is obtained by taking a position 1 / 4 of the sheet thickness in the thickness direction from the surface of the steel sheet as a representative position and performing elemental analysis at that position using a general method such as PIC. zofrAnn / zznz / E / YiAi

[71] (B2) Coating The steel sheet coated according to this specification has a coating (hereinafter referred to as the Al-based coating) containing Al on its surface. The Al-based coating is a coating that contains primarily Al and preferably contains 40% or more Al. The Al-based coating is also called the coating or plating layer. In addition to Al, the Al-based coating may also contain Si, Mg, Ca, Sr, Ti, Zn, Sb, Sn, Ni, Cu, Co, In, Bi, and REM, with the remainder being impurities. Generally, the Al-based coating contains approximately 10% Si by mass in many cases. The type of aluminum-based coating is not limited. For example, the coating can be formed by hot-dip plating, electroplating, thermal spraying, or similar processes. The adhesion quantity of the Al-based coating is preferably 50 g / m² or higher. The upper limit of the adhesion quantity of the Al-based coating is not particularly restricted, but the adhesion quantity can be adjusted to 150 g / m² or lower.

[72] The chemical composition and coating thickness can be obtained, similarly to the coating of the first steel member, by observing the cross-section using a scanning electron microscope and an electron probe microanalyzer (ERMA).

[73] (B3) Internal structure of the steel sheet The internal structure (metallographic structure) of the steel sheet contained within the coated steel sheet manufactured in accordance with this modality is not limited, but is ferrite or pearlite in many cases. Under the conditions of a manufacturing method described below, bainite, martensite, and residual austenite may be present. Martensite also includes quenched or self-hardening martensite. Self-hardening martensite is quenched martensite formed during quenching at the time of tempering without heat treatment for tempering, and is formed by in-situ tempering of the martensite formed due to the heat generated in association with the martensitic transformation. The internal structure of the steel sheet is a structure of the steel sheet that excludes the limiting portion described above. The internal structure of the steel sheet can be determined by the same method as that of the internal structure of the steel sheet substrate described above. zofrRnn / zznz / E / YiAi

[74] (C) Method of manufacturing the joining component The following will describe a method for manufacturing the joining component 1 in accordance with this modality.

[75] The joining component 1 according to this embodiment is obtained by performing a heat treatment, which will be described below, on the coated steel sheet according to this embodiment as described above to produce a steel member and then joining a plurality of steel members including this steel member by spot welding. Each step will be described below.

[76] Heat treatment step The heat treatment is carried out, for example, under conditions in which the coated steel sheet obtained by the above method is heated to point Ac3 (Ac3+ 300)°C at a temperature increase rate of 1.0 to 1,000°C / s and cooled to point Ms or lower at a higher or faster critical cooling rate. When the temperature rise rate is less than 1.0°C / s, the heat treatment productivity decreases, which is undesirable. On the other hand, when the temperature rise rate exceeds 1000°C / s, a duplex grain structure forms and the critical hydrogen content decreases, which is also undesirable. Furthermore, when the heat treatment temperature is below the Ac3 point, ferrite remains after cooling, resulting in insufficient strength, which is undesirable. Conversely, when the heat treatment temperature exceeds the Ac3 point (300°C), the structure becomes coarse, and the critical hydrogen content decreases, which is also undesirable. The upper critical cooling rate is the minimum cooling rate at which austenite is supercooled to form martensite without causing ferrite or pearlite to precipitate in the structure, and when cooling is done at a rate slower than the upper critical cooling rate, ferrite or pearlite forms, and the strength is insufficient. During heating, retention can be performed within a heating temperature range of ± 10°C for 1 to 300 seconds. Furthermore, after cooling, a tempering treatment can be performed in a temperature range of approximately 100°C to 600°C to adjust the strength of the steel member.

[77] The AC3 point, the Ms point and the upper critical cooling rate are measured using the following method. Test pieces in the form of strips, each 30 mm wide and 200 mm long, are cut from a steel sheet having the same chemical composition as that of the steel sheet included in the coated steel sheet according to this modality. The test pieces are heated to 1000°C at a rate of temperature increase of 10°C / s in a nitrogen atmosphere, held at that temperature for five minutes, and then cooled to room temperature at various cooling rates. The cooling rates are adjusted in 10°C / s increments from 1°C / s to 100°C / s. By measuring the change in thermal expansion of each of the test pieces during heating at that time, the AC3 point is measured. Furthermore, among the test pieces cooled at the above cooling rates, the minimum cooling rate at which ferrite does not precipitate is defined as the upper critical cooling rate. A change in thermal expansion is measured during cooling at a rate equal to or greater than the upper critical cooling rate, and the transformation onset temperature at that time is considered the Ms point.

[78] Herein, in the series of heat treatments, hot forming, such as hot stamping, can be performed simultaneously with cooling to point Ms after heating within a temperature range of point Ac3a (Ac3 + 300)°C, i.e., a cooling step is performed at the upper or faster critical cooling rate. Illustrative examples of hot forming include bending, stretching, elongation, hole expansion, flange forming, and the like. Furthermore, the present invention can be applied to a forming method such as roll forming, other than press forming, provided that a device is provided for cooling the steel sheet simultaneously with or immediately after forming. If the thermal history described above is followed, the hot forming can be performed repeatedly.

[79] As described above, in the present embodiment, the first steel member 11 and the second steel member 12 of the joining component 1 include both a formed body obtained by hot forming and a flat sheet obtained by performing only a heat treatment.

[80] In addition, as the first steel member 11, a hot forming or heat treatment can be performed on a portion of the coated steel sheet that serves as material to obtain a coated steel member having regions that have different strengths.

[81] The series of heat treatments can be carried out by any method and can be performed, for example, by high-frequency heating, activation heating, infrared heating, or furnace heating. Cooling can also be performed by water cooling, die cooling, or similar methods. zofrAnn / zznz / E / YiAi

[82] Spot welding pass In a spot welding step, at least in one position where an energizing electrode is pressed, the coated steel member that has undergone heat treatment (first steel member) and a steel member that serves as the weld-opposite material (second steel member) are arranged with a space of 50 µm to 500 µm provided between them, the energizing electrode is pressed against the coated steel member and the steel member that serves as the weld-opposite material in such a way that the contact angle is 15 degrees or less and the electrode force is 300 kgf or more, 5 or more upslope cycles are imparted in which an amount of energization is gradually increased with an alternating source of 50 Hz or 60 Hz, and then a weld nugget is formed to join the coated steel member and the weld-opposite material.A spot welding method, device, and electrode for the same are not limited; however, for example, those described in JIS Z 30016: 2013, JIS C 9305: 2011, and JIS C 9304: 1999 may be used. When the alternating source is of the single-phase AC type, the frequency is 50 Hz or 60 Hz, an electrode having a tip diameter of 6 mm or more is used, and the welding time is preferably 10 or more cycles. Furthermore, when the distribution state of the second region in the filler metal is controlled, the cooling conditions of the spot weld are preferably controlled. Each condition will be described below. zofrAnn / zznz / E / YiAi

[83] Spacing between the coated steel member and the steel member serving as the opposing material: 50 pm to 500 pm In spot welding of the joining component, the Al-Fe coating of the surface layer melts and is discharged to the weld periphery, forming a filler metal. At least in the position where the energizing electrode is pressed in, when a gap of 50 µm or more is not provided between the coated steel member and the material opposite the weld, the discharge of the molten Al-Fe alloy to the weld periphery is disrupted, and the cross-sectional area of ​​the filler metal can fall below 3.0 × 10⁴ µm², which is undesirable. On the other hand, when the space is greater than 500 pm, the filler metal filling ratio can be less than 80%, which is not preferable.

[84] Contact angle of 15 degrees or less The contact angle of the energizing electrode is the angle of contact between the energizing electrode and the coated steel sheet. It indicates a deviation from 0 degrees, where the axial direction of the energizing electrode and the direction parallel to the surface of the coated steel sheet are perpendicular to each other. When the contact angle exceeds 15 degrees, the discharge of molten Al-Fe alloy to the weld periphery becomes uneven, the filler metal does not form uniformly at the weld periphery, and the filler ratio may fall below 80%, which is undesirable. In this case, corrosion prevention is insufficient, and resistance to hydrogen embrittlement in a corrosive environment is compromised, which is also undesirable. The contact angle should preferably be 10 degrees or less.

[85] Electrode force of 300 kgf or more When pressure is applied between the welding electrodes, the Al-Fe coating comes into contact with the material opposite the weld, and only as much of the Al-Fe alloy in the coating as the contact area is discharged to the weld periphery. When the electrode force is less than 300 kgf, because the contact area between the Al-Fe coating on the coated steel sheet and the material opposite the weld is insufficient, not enough of the Al-Fe alloy is discharged to the weld periphery, and the cross-sectional area of ​​the filler metal at the periphery of the spot weld can be less than 3.0 × 10⁴ pm², which is undesirable. The electrode force should preferably be 400 kgf or more.

[86] Upward slope: 5 or more cycles The upslope is one cycle to reach a current at which the steel sheet substrate melts and a nugget forms. During the upslope, the Al-Fe-based coating in the surface layer of the coated steel sheet melts and is discharged to the weld periphery. When the upslope is less than 5 cycles, because the AlFe alloy in the surface layer melts abruptly and is incorporated into the nugget, the amount of Al, Si, Mo, Cu, and Ni contained in the first or second region of the filler metal may be insufficient, which is undesirable. zofrAnn / zznz / E / YiAi

[87] Cooling rate in spot welding: average cooling rate from 800°C to 500°C of 500°C / s faster When the cooling rate is increased during spot welding (during cooling after nugget formation), the second region becomes finely dispersed in the filler metal, which is preferable. This is thought to be because, when the molten filler metal discharged at the weld periphery cools, if the cooling rate is 500°C / s faster, preferential solidification occurs in the first region, which contains a relatively large amount of Fe and has a high solidification point, while the second region becomes more dispersed, thus suppressing aggregation and thickening. For example, when the electrode retention time is set to 5 or more cycles, and a cooling medium (compressed air or cooling water) is poured directly into the space between the steel sheets, thus promoting cooling, the aforementioned cooling rate can be achieved. A retention time of 5 or more cycles is particularly preferable to obtain the aforementioned cooling rate. The higher the retention time, the better; however, when manufacturing efficiency is a factor, 10 cycles or fewer are preferable. The cooling rate is preferably 5,000°C / s slower because, when the cooling rate is too fast, a defect (shrinkage cavity) is generated in the weld nugget or filler metal. The cooling rate in spot welding can be obtained using the following method. A type R thermocouple is welded within 10 mm of the weld center between the coated steel member and the material opposite the weld, and the temperature change is measured during welding. In this manner, an average cooling rate of 800°C to 500°C, at which solidification of the filler metal progresses and the temperature is relatively stable, is considered the cooling rate for spot welding.

[88] (D) Method of manufacturing coated steel sheets A suitable coated steel sheet as material for the first steel member included in the joining component in accordance with this modality can be manufactured, for example, by a manufacturing method that includes the following steps. zofrRnn / zznz / E / YiAi

[89] Manufacturing method (i) A step of preparing the plate by melting and pouring a steel having the above chemical composition, to manufacture a plate (ii) A hot rolling step of hot rolling the plate obtained into a hot rolled steel sheet (iii) A step of coiling the hot rolled steel sheet (iv) A step of annealing the hot rolled sheet after the coiling step as required (v) As required, a cold rolling step of descaling the hot rolled steel sheet after the coiling step or after the annealing step of the hot rolled sheet,and cold rolling of hot-rolled steel sheet into a cold-rolled steel sheet (vi) An annealing step of annealing the hot-rolled steel sheet or the cold-rolled steel sheet to obtain an annealed steel sheet as required. (vii) A coating step of applying an Al-based coating to hot-rolled steel sheet, cold-rolled steel sheet, or annealed steel sheet to obtain a coated steel sheet

[90] Each step will be described below. zofrRnn / zznz / E / YiAi

[91] Plate preparation step In the plate preparation step, steel with the aforementioned chemical composition is melted and shaped to produce a plate that will undergo hot rolling. For example, a plate manufactured by a continuous casting method can be used after melting molten steel with the aforementioned chemical composition using a converter, electric furnace, or similar equipment. Instead of the continuous casting method, an ingot manufacturing method, a thin-plate casting method, or a similar method can be used.

[92] Hot rolled In the hot rolling process, the plate is heated, rough rolled, then descaled as needed, and finally finished rolled. There are no limitations to the hot rolling conditions. zofrAnn / zznz / E / YiAi

[93] Winding pitch In the coiling step, for example, hot-rolled steel sheet is coiled at a temperature of 800°C or lower. When the coiling temperature exceeds 800°C, because the hot-rolled steel sheet is coiled before the transformation has progressed sufficiently, the coil's shape may become defective.

[94] Hot rolled sheet annealing step In the annealing step of hot-rolled sheet, for example, the hot-rolled steel sheet is annealed at 450°C to 800°C for five hours or more in an atmosphere containing 80% by volume or more nitrogen, or in the atmosphere. Annealing the hot-rolled sheet is not always necessary, but it softens the hot-rolled steel sheet and makes it possible to reduce the load in the subsequent cold-rolling step, which is preferable.

[95] Cold rolling pass In the cold rolling stage, the hot-rolled steel sheet, after the annealing stage (or, if the annealing stage is not performed, the hot-rolled steel sheet after the coiling stage), is pickled and then cold-rolled into a cold-rolled steel sheet. Pickling and cold rolling are not always required. However, if cold rolling is carried out, the cumulative reduction in cold rolling is preferably set to 30% or more to ensure good flatness. On the other hand, to prevent excessive rolling force, the cumulative reduction in cold rolling is preferably set to 80% or less. The pickling method is not particularly limited, but pickling is preferable. Furthermore, if pickling is used, it is preferable that iron flakes be removed only by pickling with hydrochloric or sulfuric acid. zofrRnn / zznz / E / YiAi

[96] Annealing step In the annealing step prior to coating, the hot-rolled steel sheet or the cold-rolled steel sheet is annealed in a temperature range of 700°C to 950°C. Annealing is not always necessary before coating, but the annealing step softens the cold-rolled steel sheet and facilitates threading in the subsequent plating step, which is preferable.

[97] Coating step In the coating step, an aluminum-based coating is applied to the surface of a steel sheet (hot-rolled steel sheet after the coiling step, hot-rolled steel sheet after the annealing step, cold-rolled steel sheet after the cold rolling step, or annealed steel sheet after the annealing step) to obtain a coated steel sheet. The method for forming the aluminum-based coating is not particularly limited, and methods such as hot-dip plating, electroplating, vacuum vapor deposition, coating, thermal spraying, and others can be used. The hot-dip coating method is the most widely used in industry.

[98] When hot-dip plating is performed, in addition to Al, Fe is often mixed into the plating bath as an impurity. Furthermore, besides the elements mentioned above, the plating bath may contain Si, Ni, Mg, Ti, Zn, Sb, Sn, Cu, Co, In, Bi, Ca, metal misch, and similar materials, provided that it contains 70% or more Al. In the case of hot-dip plating, after the annealed steel sheet cools to room temperature following the annealing step, the temperature can be raised again and then the plating can be carried out, or the annealed steel sheet after the annealing step can be cooled to 650°C to 750°C, which is close to the plating bath temperature, after annealing and then the hot-dip plating can be carried out without cooling the annealed steel sheet to room temperature once.

[99] The pre- and post-treatments of the Al-based coating are not particularly limited, and pre-coating, solvent coating, alloying, quench rolling, or similar treatments are possible. As an alloying treatment, for example, the Al-based coating can be annealed between 450°C and 800°C. Furthermore, as a post-heat treatment, quench rolling is useful for shape adjustment and similar applications, and, for example, a reduction in roll thickness of 0.1% to 0.5% is possible. Example

[100] The present invention will now be described more specifically with examples, but the present invention is not limited to these examples.

[101] First, in the manufacture of coated steel sheets, coated steel members, and joining components, steels with the chemical compositions shown in Table 1 were melted to obtain hot-rolled plates.

[102] Table 1 Steel No. Chemical composition (% by mass), remainder Fe and impurity Transformation point (“O) Upper critical cooling rate (°C / s) C Si Mn PSN Ti B Mo Cu Ni Nb Cr V Ca Al Sn W Sb Zr REM Ac3 Ms | Example of the invention A1 0.27 0.61 1.35 0.009 0.0018 0.005 0.030 0.0021 826 392 30 A2 0.55 0.28 0.35 0.003 0.0003 0.003 0.027 0.0023 0.03 776 316 10 A3 0.37 0.19 1.12 0.009 0.0008 0.005 0.032 0.0022 0.21 783 360 30 A4 0.33 0.81 0.77 0.007 0.0012 0.003 0.040 0.0028 0.17 850 386 20 A5 0.40 0.30 0.35 0.009 0.0007 0.004 0.033 0.0030 0.20 803 371 40 A6 0.28 0.27 1.30 0.010 0.0009 0.006 0.026 0.0026 0.04 0.002 797 389 30 A7 0.28 0.30 0.55 0.040 0.0004 0.004 0.030 0.0023 0.27 0.12 834 413 30 A8 0.28 0.32 0.60 0.009 0.0080 0.003 0.028 0.0023 0.03 0.22 826 412 30 A9 0.29 0.45 0.60 0.013 0.0011 0.008 0.050 0.0027 0.12 839 408 30 A10 0.30 0.29 0.78 0.010 0.0013 0.003 0.015 0.0028 0.04 805 404 20 A11 0.36 0.43 0.70 0.009 0.0012 0.004 0.075 0.0026 0.25 826 375 30 A12 0.30 0.40 0.76 0.008 0.0014 0.005 0.035 0.0008 0.34 829 402 40 A13 0.30 0.38 0.63 0.010 0.0008 0.006 0.040 0.0070 0.25 838 405 10 A14 0.34 0.40 1.12 0.010 0.0016 0.005 0.041 0.0024 0.22 0.10 820 373 20 A15 0.33 0.36 0.55 0.006 0.0020 0.004 0.038 0.0020 0.62 840 392 10 A16 0.43 0.40 1.05 0.011 0.0021 0.005 0.036 0.0023 0.30 0.08 790 330 20 A17 0.29 0.30 0.45 0.009 0.0017 0.006 0.043 0.0023 0.80 816 401 10 A18 0.30 0.47 0.90 0.010 0.0017 0.004 0.040 0.0022 0.26 0.15 840 393 20 A19 0.42 0.37 0.51 0.012 0.0014 0.004 0.038 0.0021 0.75 0.20 798 349 10 A20 0.28 0.20 1.30 0.007 0.0005 0.003 0.029 0.0020 0.01 0.02 0.01 0.06 0.40 0.04 794 382 20 A21 0.31 0.40 0.80 0.008 0.0006 0.004 0.035 0.0022 0.21 0.25 0.18 0.05 0.15 0.04 816 382 20. A22 0.35 0.43 0.62 0.008 0.0005 0.004 0.035 0.0025 0.21 0.25 0.16 0.04 0.10 0.04 0.20 823 372 20 A23 0.48 0.44 0.45 0.008 0.0005 0.003 0.028 0.0025 0.21 0.25 0.16 0.03 0.12 0.03 0.06 0.26 806 325 20 A24 0.45 0.50 0.45 0.010 0.0006 0.004 0.034 0.0023 0.20 0.02 0.02 0.30 0.02 812 348 20 A25 0.34 0.55 0.60 0.010 0.0006 0.004 0.034 0.0023 0.20 0.02 0.40 0.04 0.40 0.003 0.04 824 376 10 A26 0.35 0.41 0.65 0.008 0.0004 0.004 0.032 0.0024 0.19 0.24 0.08 0.04 0.09 0.04 826 378 20 | Ejemplo comparison a1 0.20 0.30 1.15 0.011 0.0012 0.005 0.034 0.0024 0.20 0.06 827 422 30 a2 0.80 0.40 1.10 0.010 0.0013 0.004 0.035 0.0023 0.15 0.15 742 207 10 a3 0.42 0.65 2.40 0.016 0.0018 0.005 0.037 0.0022 0.20 0.25 780 286 10 a4 0.36 0.25 1.02 0.120 0.0014 0.004 0.033 0.0023 0.29 0.27 896 361 30 a5 0.38 0.63 1.10 0.018 0.0800 0.005 0.032 0.0025 0.32 821 357 30 a6 0.42 0.55 1.24 0.013 0.0018 0.100 0.036 0.0024 0.38 0.12 817 330 20 a7 0.41 0.57 1.30 0.015 0.0012 0.005 0.002 0.0022 0.25 0.20 0.18 791 326 30 a8 0.30 0.21 1.25 0.008 0.0018 0.005 0.300 0.0027 0.13 0.35 901 375 20 a9 0.39 0.66 1.20 0.011 0.0013 0.006 0.034 0.0320 0.28 0.34 842 342 20 a10 0.38 0.50 1.22 0.017 0.0016 0.005 0.031 0.0027 2.00 0.001 0.33 873 342 10 a11 0.40 0.60 1.25 0.015 0.0022 0.005 0.029 0.0026 1.90 0.08 0.38 780 302 10. zofrRnn / zznz / E / YiAi

[103] Example 1 The resulting plates were hot-rolled and coiled at a temperature of 800°C or lower to obtain five hot-rolled steel sheets, each 2.7 mm thick. These hot-rolled steel sheets were then cold-rolled to obtain cold-rolled steel sheets, each 1.6 mm thick. Aluminum cladding was applied to the cold-rolled steel sheets to obtain coated steel sheets, each with an aluminum-based coating. The chemical compositions of the coated steel sheets at a position 1 / 4 of the sheet thickness 15 from the surface of each of the steel sheets in the direction of the sheet thickness were the same as the chemical compositions of the plates.

[104] Heat treatments wherein the coated steel sheet was heated at a rate of temperature increase and heating temperature shown in Table 2A, Table 2D and Table 2G, held within a heating temperature range + 10°C for 60 seconds and cooled to point Ms or below at an average cooling rate shown in Table 2A, Table 2D and Table 2G to obtain coated steel members. The chemical compositions of the coated steel members at a position 1 / 4 of the sheet thickness from the surface of each of the steel sheet substrates in the sheet thickness direction were the same as the chemical compositions of the plates.

[105] The resulting coated steel members were cut and examined using SEM, tensile tests were performed using the following method, and the thicknesses and tensile strengths of the Al-Fe-based coatings were evaluated. The results of the evaluation are shown in Table 2A, Table 2D, and Table 2G. zofrAnn / zznz / E / YiAi

[106] Thickness of the Al-Fe based coating A measurement sample was cut from the steel member, except for the end portion, a cross-section was observed in 10 visual fields with a scanning electron microscope, the thicknesses of the Al-Fe based coating were measured and the average value was considered as the thickness of the Al-Fe based coating. zofrAnn / zznz / E / YiAi

[107] Tensile strength The tensile test was performed according to ASTM E8. After grinding a soaked portion (a portion separated from the end portion by 50 mm or more) of each coated steel member to a thickness of 1.2 mm, a half-size, sheet-shaped test piece (parallel portion length: 32 mm, parallel portion sheet width: 6.25 mm) was collected such that one test direction was parallel to one rolling direction. A tensile test was then performed at room temperature at a strain rate of 3 mm / min to measure the tensile strength (maximum strength). In this example, a tensile strength greater than 1,500 MPa was considered excellent.

[108] The steel members were spot welded under the conditions shown in Table 2A, Table 2D, and Table 2G: gaps, contact angles, electrode forces, upslope, and cooling rates to obtain the joint components. In this example, the opposing materials were also the same steel member. The nugget diameters were 5.1 to 6.3 mm. A single-phase AC welding machine (60 Hz power supply) was used, and a current was applied at which the above nugget diameter was formed in a welding time of 20 cycles. An alumina-dispersed copper electrode with a tip diameter of 8 mmip and a dome radius shape was used as the electrode.

[109] In the resulting bonding components, the cross-sectional areas of the filled metals, the filling ratios, the amounts of Al, Fe, Si, Mo, Cu, and Ni, and the CCT fracture strength were evaluated using the following methods. The evaluation results are shown in Table 2B, Table 2C, Table 2E, Table 2F, Table 2H, and Table 21.

[110] Cross-sectional area of ​​the filler metal A vertical cross-section was cut through the center of a spot weld, revealing both the spot weld portion (the nugget and crown joint) and the filler metal within the joint component. The area of ​​the filler metal was then measured in the cross-section. Under welding conditions, five or more samples were cut, and their cross-sectional areas were measured. The average cross-sectional area was then considered the cross-sectional area of ​​the filler metal.

[111] Fill ratio A vertical cross-section was cut through the center of a spot weld, revealing a cross-section of the spot-welded portion (the nugget and crown joint) and the filler metal in the joint component. The proportion of the area occupied by the filler metal in the region excluding the steel members was determined over a range from the end of the press-welded portion (crown joint) in the cross-section to 100 pm toward the separation portion. Under welding conditions, five or more samples were cut, and the proportions were measured. The minimum value was considered the filler metal fill ratio. zofrAnn / zznz / E / YiAi

[112] The amount of Fe, Al, Si, Mo, Cu and Ni in the filler metal A vertical cross-section was cut through the central position of a spot weld so that a cross-section of the spot-welded portion (the nugget and crown bond) and the filler metal in the joint component could be observed. A reflected electron image of this sample was acquired using a scanning electron microscope. A point elemental analysis (beam diameter: 1 pm or less) was performed at 10 points using an electron probe microanalyzer (ERMA) on two types of structures with different contrasts, and the average value was considered as the amount of Al, Fe, Si, Mo, Cu, and Ni contained in the filler metal. zofrRnn / zznz / E / YiAi

[113] Size of the second region in filler metal A vertical cross-section was cut through the center of a spot weld, allowing observation of the cross-section of the spot-welded portion (the nugget and crown bond) and the filler metal in the joint component, as well as a reflected electron. An image of this sample was acquired using a scanning electron microscope, and the size of a second, island-like region surrounded by first regions was measured in two types of structures with varying contrast. The size of the second region was defined as the average distance between parallel lines parallel to the horizontal direction and intersecting the second region (horizontal Feret diameter) and the distance between parallel lines parallel to the vertical direction and intersecting the second region (vertical Feret diameter).The horizontal direction was the longitudinal direction of the joint components, and the vertical direction was the direction of the sheet thickness perpendicular to the longitudinal direction. At the time of measurement, the size of the second island-shaped region surrounded by the first regions was measured, and the average value of this measurement was considered the size of the second region enclosed within the filler metal.

[114] CCT fracture cycle Resistance to hydrogen embrittlement in a corrosive environment was evaluated using a corrosion promotion test (CCT) by mixed cycle testing. Specifically, a sample with the spot welded portion centered, 100 mm long and 50 mm wide, was taken from the joint component. CCT was performed according to the provisions of JASO M609 and M610, and resistance to hydrogen embrittlement was assessed by the number of cycles during which the spot welded portion did not fracture. CCT was performed for up to 360 cycles. A vertical cross-section was cut through the center of a spot weld from a sample that remained unfractured for all 360 cycles. When the decrease in the cross-sectional area of ​​the filler metal was 10% or less before and after the test, the resistance to hydrogen embrittlement was considered excellent, particularly in a corrosive environment.

[115] Tabla 2A Reference symbol Steel No. Coated steel sheet Heat treatment Steel member Spot welding pitch Amount of Al-based coating Temperature rise rate Heating temperature Cooling rate Al-Fe-based coating thickness Tensile strength Spacing Contact angle Electrode force Upward slope Cooling (g / m2) (°C / s) (°C) (°C / s) (pm) (MPa) (pm) (degrees) (kgf) (cic) (°C / s) Example of the invention B1 A1 72 7 920 60 34 1856 60 0 400 10 800 B2 A2 80 7 920 60 42 2741 60 0 400 10 800 B3 A3 83 7 920 60 43 2256 60 0 400 10 800 B4 A4 72 7 920 60 32 2063 60 0 400 10 800 B5 A5 73 7 920 60 33 2298 60 0 400 10 800 B6 A6 75 7 920 60 35 1882 60 0 400 10 800 B7 A7 73 7 920 60 33 1802 60 0 400 10 800 B8 A8 73 7 920 60 33 1809 60 0 400 10 800 B9 A9 74 7 920 60 34 1855 60 0 400 10 800 B10 A10 74 7 920 60 33 1912 60 0 400 10 800 B11 A11 72 7 920 60 31 2162 60 0 400 10 800 B12 A12 73 7 920 60 32 1907B15 A15 74 7 920 60 0 400 10 800 B13 A13 76 7 920 60 36 1894 60 0 400 10 800 B18 A18 60 33 2018 60 0 400 10 800 B16 A16 78 7 920 60 37 2497 77 7 920 60 36 1924 60 0 400 10 800 B19 A19 81 7 920 60 39 2396 60 0 400 10 800 B20 A20 75 7 920 60 37 1880 60 0 400 10 800 B21 A21 74 7 920 60 38 1956 60 0 400 10 800 B22 A22 76 7 920 60 37 2114 60 0 400 10 800 B23 A23 78 7 920 60 38 2603 60 0 400 10 800 B24 A24 77 7 920 60 38 2528 60 0 400 10 800 B25 A25 79 7 920 60 39 2074 60 0 400 10 800 B26 A20 75 50 920 60 36 1878 60 0 400 10 800 B27 A20 75 7 980 40 38 1875 60 0 400 10 800 B28 A20 75 7 920 60 37 1880 200 0 400 10 800 B29 A20 75 7 920 60 37 1880 60 5 400 10 800 B30 A20 75 7 920 60 37 1880 60 0 500 20 800 B31 A20 75 7 920 60 37 1880 60 0 400 10 1200 B32 A21 74 500 920 60 37 1956 60 0 400 10 800 B33 A21 74 7 980 40 38 1952 60 0 400 10 800 B34 A21 74 7 920 60 38 1956 350 0 400 10 800

[116] Table 2B Reference Symbol Steel No. Bonding Component Filler Metal Cross-Sectional Area Filler Ratio Al Concentration in First Region Fe Concentration in First Region Si Concentration in First Region Al Concentration in Second Region Fe Concentration in Second Region Si Concentration in Second Region (x 104 pm2) (%) (% by mass) (% by mass) (% by mass) (% by mass) (% by mass) (% by mass) B1 A1 7.3 98 25 66 6 42 52 3 B2 A2 7.4 97 24 65 8 43 51 3 B3 A3 7.3 97 25 66 6 43 51 3 B4 A4 8.3 96 28 64 5 43 52 2 B5 A5 7.4 97 27 64 6 47 47 3 B6 A6 6.8 97 26 66 5 48 46 3 B7 A7 6.3 96 28 63 6 46 48 3 B8 A8 7.3 97 30 60 7 45 49 3 B9 A9 7.4 97 23 68 6 48 46 3 B10 A10 9.0 96 28 64 5 49 46 2 B11 A11 8.1 96 27 64 6 44 50 3 B12 A12 8.2 97 24 68 5 43 52 2 B13 A13 8.1 95 23 67 7 43 51 3 B14 A14 7.8 96 31 60 6 42 52 3 B15 A15 7.8 97 27 64 6 43 51 3 B16 A16 6.5 96 24 68 5 45 49 3 Example of B17 A17 6.5 96 27 64 6 44 51 2 the invention B18 A18 7.8 96 28 64 5 44 51 2 B19 A19 7.9 97 29 62 6 46 49 2 B20 A20 6.8 97 26 64 8 42 53 3 B21 A21 8.6 96 28 63 5 44 50 3 B22 A22 8.5 97 25 64 9 41 53 2 B23 A23 8.8 97 29 62 5 43 51 3 B24 A24 9.2 96 27 63 5 43 50 3 B25 A25 10.1 96 28 63 5 43 50 3 B26 A20 6.9 97 26 64 7 41 52 3 B27 A20 6.8 96 26 63 8 41 52 2 B28 A20 7.2 88 26 63 8 41 52 3 B29 A20 6.4 87 26 63 7 42 52 2 B30 A20 7.5 96 28 62 8 43 51 3 B31 A20 6.9 97 25 64 8 42 53 2 B32 A21 8.5 96 27 63 4 44 50 2 B33 A21 8.6 96 28 63 5 44 49 3 B34 A21 8.9 85 28 62 5 43 49 3.

[117] Tabla 2C Reference symbol Steel no. Bonding component Mo concentration in the first region Cu concentration in the first region Ni concentration in the first region Mo + Cu + Ni in the first region Mo concentration in the second region Cu concentration in the second region Ni concentration in the second region Mo + Cu + Ni in the second region Size of the second region CCT cycle limit Cross-sectional area of ​​the filler metal after CCT Rate of decrease of cross-sectional area after 360 CCT cycles (% by mass) (% by mass) (% by mass) (% by mass) (% by mass) (% by mass) (% by mass) (% by mass) (% by mass) (pm) (cíe) (X 104pm2) (%) Example of the invention | B1 A1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 17 360 5.9 19 B2 A2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 14 360 5.9 20 B3 A3 0.00 0.11 0.00 0.11 0.00 0.10 0.00 0.10 16 360 6.0 18 B4 A4 0.08 0.00 0.00 0.08 0.06 0.00 0.00 0.06 19 360 6.7 19 B5 A5 0.00 0.00 0.19 0.19 0.00 0.00 0.07 0Ό7 15 360 5.7 23 B6 A6 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 14 360 5.0 26 B7 A7 0.00 0.16 0.00 0.16 0.00 0.13 0.00 0.13 13 360 4.6 27 B8 A8 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 17 360 6.0 18 B9 A9 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 12 360 6.0 19 B10 A10 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 12 360 7.4 18 B11 A11 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 12 360 6.6 19 B12 A12 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 14 360 6.4 22 B13 A13 0.10 0.00 0.00 0.10 0.07 0.00 0.00 0.07 16 360 6.1 25 B14 A14 0.08 0.00 0.00 0.08 0.05 0.00 0.00 0.05 17 360 5.9 24 B15 A15 0.26 0.00 0.00 0.26 0.17 0.00 0.00 0.17 16 360 7.1 9 B16 A16 0.00 0.17 0.00 0.17 0.00 0.13 0.00 0.13 18 360 4.8 26 B17 A17 0.00 0.41 0.00 0.41 0.00 0.39 0.00 0.39 18 360 6.2 5 B18 A18 0.00 0.00 0.21 0.21 0.00 0.00 0.10 0.10 19 360 6.5 17 B19 A19 0.00 0.00 0.65 0.65 0.00 0.00 0.25 0.25 15 360 7.4 6 B20 A20 0.00 0.01 0.02 0.03 0.00 0.02 0.00 0.03 13 360 5.5 19 B21 A21 0.10 0.16 0.17 0.43 0.07 0.11 0.07 0.25 14 360 8.1 6 B22 A22 0.08 0.14 0.15 0.37 0.06 0.14 0.05 0.25 14 360 8.1 5 B23 A23 0.09 0.13 0.14 0.36 0.05 0.11 0.06 0.22 15 360 8.2 7 B24 A24 0.09 0.00 0.02 0.11 0.07 0.00 0.02 0.09 14 360 8.0 13 B25 A25 0.09 0.02 0.32 0.43 0.07 0.02 0.13 0.22 14 360 9.6 5 B26 A20 0.01 0.01 0.01 0.03 0.00 0.02 0.00 0.02 13 360 5.6 19 B27 A20 0.00 0.02 0.01 0.03 0.00 0.02 0.00 0.02 12 360 5.5 19 B28 A20 0.00 0.01 0.02 0.03 0.00 0.02 0.00 0.02 13 360 6.0 17 B29 A20 0.00 0.01 0.02 0.03 0.01 0.01 0.00 0.02 12 360 5.2 19 B30 A20 0.00 0.01 0.02 0.03 0.00 0.02 0.00 0.02 14 360 6.2 17 B31 A20 0.00 0.01 0.02 0.03 0.01 0.02 0.00 0.03 7 360 6.0 13 B32 A21 0.10 0.16 0.17 0.43 0.07 0.11 0.07 0.25 14 360 8.0 6 B33 A21 0.10 0.15 0.17 0.42 0.07 0.11 0.06 0.24 13 360 8.2 5 B34 A21 0.10 0.16 0.17 0.43 0.06 0.11 0.07 0.24 13 360 8.4 6.

[118] Tabla 2D Reference symbol Steel No. Coated steel sheet Heat treatment Steel member Spot welding pitch Amount of Al-based coating Temperature rise rate Heating temperature Speed Cooling rate AlFe-based coating thickness Tensile strength Space Contact angle Electrode strength Upward slope Cooling rate (g / m2) (°C / s) (°C) (°C / s) (pm) (MPa) (pm) (degrees) (kgf) (cic) (°C / s) Example of the invention B35 A21 74 7 920 60 38 1956 60 10 400 10 800 B36 A21 74 7 920 60 38 1956 60 0 500 25 800 B37 A21 74 7 920 60 38 1956 60 0 400 10 1200 B38 A22 76 200 920 60 37 2114 60 0 400 10 800 B39 A22 76 7 880 40 36 2117 60 0 400 10 800 B40 A22 76 7 920 60 37 2114 300 0 400 10 800 B41 A22 76 7 920 60 37 2114 60 8 400 10 800 B42 A22 76 7 920 60 37 2114 60 0 600 20 800 B43 A22 76 7 920 60 37 2114 60 0 400 10 1200 B44 A23 78 100 920 60 38 2604 60 0 400 10 800 B45 A23 78 7 980 40 37 2600 60 0 400 10 800 B46A23 78 7 920 60 38 2603 250 0 400 10 800 B47 A23 78 7 920 60 38 2603 60 7 400 10 800 B48 A23 78 7 920 60 38 2603 60 0 600 25 800 B49 A23 78 7 920 60 38 2603 60 0 400 10 1200 B50 A24 77 30 920 60 38 2530 60 0 400 10 800 B51 A24 77 7 950 40 39 2526 60 0 400 10 800 B52 A24 77 7 920 60 38 2528 100 0 400 10 800 B53 A24 77 7 920 60 38 2528 60 3 400 10 800 B54 A24 77 7 920 60 38 2528 60 0 500 20 800 B55 A24 77 7 920 60 38 2528 60 0 400 10 1200 B56 A25 79 400 920 60 38 2076 60 0 400 10 800 B57 A25 79 7 1000 40 39 2060 60 0 400 10 800 B58 A25 79 7 920 60 39 2074 400 0 400 10 800 B59 A25 79 7 920 60 39 2074 60 8 400 10 800 B60 A25 79 7 920 60 39 2074 60 0 600 25 800 B61 A25 79 7 920 60 39 2074 60 0 400 10 1200 B62 A26 77 100 920 60 38 2092 60 0 400 10 800 B63 A26 77 7 880 40 38 2092 60 0 400 10 800 B64 A26 77 7 920 60 38 2095 300 0 400 10 800 B65 A26 77 7 920 60 37 2095 60 9 400 10 800 B66 A26 77 7 920 60 37 2092 60 0 600 20 800 B67 A26 77 7 920 60 38 2092 60 0 400 10 1200

[120] Tabla 2F zofrRnn / zznz / E / YiAi Reference symbol Steel No. Bonding component Mo concentration in the first region Cu concentration in the first region Ni concentration in the third region Mo + Cu + Ni in the first region Mo concentration in the second region Cu concentration in the second region Ni concentration in the second region Mo + Cu + Ni in the second region Size of the second region CCT cycle limit Cross-sectional area of ​​the filler metal after CCT Rate of decrease of cross-sectional area after 360 CCT cycles (% by mass) (% by mass) (% by mass) (% by mass) (% by mass) (% by mass) (% by mass) (% by mass) (% by mass) (pm) (cycle) (x 1Q4 pm2) (%) Example of the invention B35 A21 0.10 0.16 0.17 0.43 0.07 0.11 0.07 0.25 14 360 7.7 7 B36 A21 0.11 0.17 0.17 0.45 0.07 0.13 0.08 0.28 12 360 8.7 5 B37 A21 0.11 0.16 0.16 0.43 0.07 0.11 0.07 0.25 6 360 8.2 4 B38 A22 0.09 0.13 0.15 0.37 0.06 0.14 0.05 0.25 13 360 8.1 5 B39 A22 0.08 0.14 0.15 0.37 0.06 0.13 0.04 0.23 13 360 7.9 6 B40 A22 0.09 0.15 0.14 0.38 0.06 0.14 0.05 0.25 13 360 8.3 5 B41 A22 0.08 0.14 0.15 0.37 0.07 0.14 0.04 0.25 14 360 7.6 6 B42 A22 0.10 0.15 0.15 0.40 0.07 0.15 0.06 0.28 13 360 8.7 4 B43 A22 0.08 0.14 0.14 0.36 0.06 0.14 0.05 0.25 7 360 8.2 4 B44 A23 0.09 0.13 0.14 0.36 0.07 0.11 0.04 0.22 14 360 8.0 8 B45 A23 0.09 0.14 0.13 0.36 0.05 0.11 0.06 0.22 14 360 8.2 7 B46 A23 0.09 0.13 0.14 0.36 0.05 0.11 0.06 0.22 12 360 8.5 6 B47 A23 0.08 0.14 0.14 0.36 0.05 0.13 0.04 0.22 13 360 8.0 7 B48 A23 0.10 0.14 0.15 0.39 0.06 0.12 0.07 0.25 12 360 8.9 6 B49 A23 0.08 0.14 0.14 0.36 0.05 0.11 0.06 0.22 5 360 8.4 5 B50 A24 0.09 0.00 0.02 0.11 0.07 0.00 0.02 0.09 12 360 8.0 13 B51 A24 0.08 0.00 0.02 0.10 0.07 0.00 0.02 0.09 13 360 8.1 12 B52 A24 0.09 0.00 0.02 0.11 0.06 0.00 0.02 0.08 13 360 8.1 14 B53 A24 0.09 0.00 0.02 0.11 0.07 0.00 0.02 0.09 13 360 7.9 13 B54 A24 0.11 0.00 0.02 0.13 0.09 0.00 0.02 0.11 13 360 8.6 12 B55 A24 0.09 0.00 0.02 0.11 0.06 0.00 0.02 0.08 6 360 8.1 11 B56 A25 0.09 0.01 0.32 0.42 0.06 0.01 0.14 0.21 13 360 9.7 4 B57 A25 0.08 0.01 0.33 0.42 0.07 0.01 0.13 0.21 13 360 9.5 5 B58 A25 0.08 0.01 0.33 0.42 0.06 0.01 0.15 0.22 14 360 10.0 5 B59 A25 0.08 0.01 0.32 0.41 0.07 0.01 0.13 0.21 13 360 9.3 6 B60 A25 0.09 0.02 0.34 0.45 0.07 0.02 0.15 0.24 12 360 10.1 5 B61 A25 0.09 0.02 0.31 0.42 0.07 0.02 0.13 0.22 8 360 9.8 4 B62 A26 0.10 0.13 0.06 0.29 0.05 0.15 0.02 0.22 13 360 8.0 4 B63 A26 0.09 0.14 0.06 0.29 0.05 0.14 0.02 0.21 12 360 8.0 5 B64 A26 0.08 0.15 0.07 0.30 0.06 0.15 0.03 0.24 13 360 8.2 5 B65 A26 0.09 0.15 0.06 0.30 0.06 0.14 0.03 0.23 13 360 7.7 6 B66 A26 0.10 0.15 0.06 0.31 0.07 0.15 0.02 0.24 13 360 8.8 5 B67 A26 0.09 0.15 0.06 0.30 0.06 0.14 0.02 0.22 7 360 8.3 4.

[121] Tabla 2G Reference symbol Steel No. Coated steel sheet Heat treatment Steel member Spot welding pitch Amount of Al-based coating Temperature rise rate Heating temperature Cooling rate Al-Fe-based coating thickness Tensile strength Spacing Contact angle Electrode force Upward slope cooling rate (g / m') (°C / s) (°C) (°C / s) (pm) (MPa) (pm) (degrees) (kgf) (cic) ('C / s) b1 a1 71 7 920 60 35 1465 60 0 400 10 750 b2 a2 72 7 920 60 34 2852 60 0 400 10 750 b3 a3 73 7 920 60 34 2604 60 0 400 10 750 b4 a4 72 7 920 60 35 2190 60 0 400 10 750 b5 a5 72 7 920 60 33 2292 60 0 400 10 750 b6 a6 71 7 920 60 32 2480 60 0 400 10 750 b7 a7 73 7 920 60 32 2448 60 0 400 10 750 b8 a8 74 7 920 60 33 1374 60 0 400 10 750 b9 a9 71 7 920 60 31 2356 60 0 400 10 750 b10 a10 72 7 920 60 32 2308 60 0 400 10 750 b11 a11 72 7 920 60 33 2399 60 0 400 10 750 b12 A20 20 7 920 60 8 1880 60 0 400 10 750 b13 A21 747 920 60 37 1956 5 0 400 10 750 b14 A22 76 7 920 60 32 2114 1100 0 400 10 750 b15 A23 78 7 920 60 37 2603 60 45 400 10 750 b16 A24 77 7 920 60 38 2528 60 0 100 10 750 b17 A25 79 7 920 60 38 2074 60 0 400 1 750 b18 a2 72 13Q0 920 60 34 2882 60 0 400 10 750 b19 a3 73 7 780 60 34 1392 60 0 400 10 750 b20 a4 72 7 1200 60 35 2082 60 0 400 10 750 b21 a5 72 7 920 1 33 1197 60 0 400 10 750 b22 a6 71 1300 1200 60 32 2400 60 0 400 10 750 b23 a7 ​​73 7 780 1 32 1088 60 0 400 10 750 b24 a9 71 7 920 60 31 2356 60 0 400 10 300 b25 a10 72 7 920 60 32 2308 60 0 400 10 150 b26 a11 72 7 920 60 33 2399 60 0 400 10 150

[122] Tabla 2H Reference Symbol Steel No. Bonding Component Filler Metal Cross-Sectional Area Filler Ratio Al Concentration in First Region Fe Concentration in First Region Si Concentration in First Region Al Concentration in Second Region Fe Concentration in Second Region Si Concentration in Second Region (χ 104 pm2) (%) (% by mass) (% by mass) (% by mass) (% by mass) (% by mass) (% by mass) Comparative Example b1 a1 7.3 96 22 70 5 41 53 3 b2 a2 7.3 96 26 65 6 40 54 2 b3 a3 7.3 96 25 66 6 43 52 2 b4 a4 8.1 95 28 63 6 42 52 3 b5 a5 7.3 95 23 67 7 41 53 3 b6 a6 8.4 95 24 65 8 42 53 2 b7 a7 8.9 96 21 69 7 40 54 3 b8 a8 8.5 95 21 70 6 40 54 3 b9 a9 9.0 95 22 68 7 39 54 3 b10 a10 8.2 96 21 70 6 40 54 2 b11 a11 7.8 96 20 70 7 39 54 3 b12 A20 0.9 85 28 63 6 41 53 3 b13 A21 1.1 83 28 64 5 44 50 3 b14 A22 12.1 45 27 64 6 43 51 3 b15 A23 4.2 40 26 65 6 42 53 2 b16 A24 1.8 84 27 63 7 42 52 3 b17 A25 3.9 85 9 87 1 20 77 0 b18 a2 7.3 96 26 65 6 40 54 2 b19 a3 7.3 96 25 66 6 43 52 2 b20 a4 8.1 95 28 63 6 42 52 3 b21 a5 7.3 95 23 67 7 41 53 3 b22 a6 8.4 95 24 65 8 42 53 2 b23 a7 ​​8.9 96 21 69 7 40 54 3 b24 a9 9.0 95 22 68 7 39 54 3 b25 a10 8.2 96 21 70 6 40 54 2 b26 a11 7.8 96 20 70 7 39 54 3.

[123] Tabla 21 zofrAnn / zznz / E / YiAi Reference Symbol Steel No. Bonding Component Mo Concentration in First Region Cu Concentration in Second Region Ni Concentration in Third Region Mo + Cu + Ni in First Region Mo Concentration in Second Region Cu Concentration in Second Region Ni Concentration in Second Region Mo + Cu + Ni in Second Region Second Region Size CCT Cycle Limit Filler Metal Cross-Sectional Area after CCT Cross-Sectional Area Decrease Rate after 360 CCT Cycles (% by mass) (% by mass) (% by mass) (% by mass) (% by mass) (% by mass) (% by mass) (% by mass) (% by mass) (pm) (cycle) (x 1Q4 pm2) (%) Comparative Example b1 a1 0.00 0.12 0.00 0.12 0.00 0.10 0.00 0.10 20 360 6.2 15 b2 a2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 18 159 b3 a3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 17 180 b4 a4 0.00 0.00 0.24 0.24 0.00 0.00 0.11 0.11 18 180 b5 a5 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 18 183 b6 a6 0.16 0.00 0.00 0.16 0.11 0.00 0.00 0.11 17 192 b7 a7 0.00 0.00 0.22 0.22 0.00 0.00 0.09 0.09 18 2Z0 b8 a8 0.06 0.00 0.00 0.06 0.05 0.00 0.00 0.05 21 360 6.9 19 b9 a9 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 24 276 b10 a10 0.81 0.00 0.00 0.81 0.55 0.00 0.00 0.55 21 261 b11 a11 0.00 0.00 1.65 1.65 0.00 0.00 0.64 0.64 20 252 b12 A20 0.00 0.01 0.02 0.03 0.01 0.02 0.00 0.03 19 243 b13 A21 0.10 0.13 0.1Z 0.40 o.oz 0.12 o.oz 0.26 22 303 b14 A22 0.08 0.14 0.13 0.35 o.oz 0.11 0.05 0.23 23 282 b15 A23 0.10 0.14 0.14 0.38 o.oz 0.11 0.05 0.23 23 225 b16 A24 0.09 0.00 0.03 0.12 o.oz 0.00 0.02 0.09 22 219 b17 A25 0.04 0.01 0.09 0.14 0.01 0.01 0.04 0.06 21 267 b18 a2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 18 129 b19 a3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 17 360 6.0 18 b20 a4 0.00 0.00 0.24 0.24 0.00 0.00 0.11 0.11 18 156 b21 a5 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 18 360 6.1 16 b22 a6 0.16 0.00 0.00 0.16 0.11 0.00 0.00 0.11 17 171 b23 aZ 0.00 0.00 0.22 0.22 0.00 0.00 0.09 0.09 18 360 7.2 19 b24 a9 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 38 210 b25 a10 0.81 0.00 0.00 0.81 0.55 0.00 0.00 0.55 48 207 b26 a11 0.00 0.00 1.65 1.65 0.00 0.00 0.64 0.64 52 201.

[124] As shown in Table 2Ά to Table 21, the Examples of inventions B1 to B67 that satisfied the scope of the present invention showed good results in terms of both structure and properties; however, in the Comparative examples bl to b26 did not meet the scope of the present invention; the chemical compositions or the shaping of the filler metal were insufficient, and at least one of the strength (the strength of the steel member that served as the filler material) and the resistance to hydrogen embrittlement were poor. Furthermore, when the filler metal contained Mo, Cu, and Ni, the resistance to hydrogen embrittlement was excellent, particularly in a corrosive environment. zofrRnn / zznz / E / YiAi Industrial applicability

[125] According to the present invention, it is possible to obtain a high-strength joining component having a spot-welded portion that exhibits excellent resistance to hydrogen embrittlement in a corrosive environment. The joining component according to the present invention is particularly suitable for use as a vehicle frame component. Since the steel member of the present invention has high strength and excellent resistance to hydrogen embrittlement, the steel member contributes to improved fuel economy and collision safety when applied to a vehicle component. Brief description of the reference symbols

[126] 1: Joining component 11: First steel member 12: Second steel member 21: Spot welded portion 31: Filler metal 111: Steel sheet substrate 112: Al-Fe based coating g: Space

Claims

1. A joining component comprising: a first steel member; a second steel member; and a spot-welded portion joining the first steel member and the second steel member, wherein the first steel member includes a steel sheet substrate containing, as chemical composition, in % by mass, C: 0.25% to 0.65%, Si:

0. 10% to 1.00%, Mn: 0.30% to 1.50%, P: 0.0 50% or less, S: 0.0 100% or less, N: 0.0 10% or less, Ti: 0.010% to 0.100%, B: 0.0 005% to 0.0100% Mo: 0% to 1.00%, Cu: 0% to 1.00%, Ni: 0% to 1.00%, Cr: 0% to 1.00%, Nb: 0% to 0.10%, V: 0% to 1.00%, Ca: 0% to 0.010%, Al: 0% to 1.00%, Sn: 0% to 1.00%, W: 0% to 1.00%, Sb: 0% to 1.00%, Zr: 0% to 1.00%, REM: 0% to 0.30%, and a remainder of Fe and an impurity; and a coating that forms on a surface of the steel sheet substrate, containing Al and Fe, and having a thickness of 25 pm or more, in a cross section in the thickness direction of the first steel member and the second steel member that includes the spot-welded portion, a filler metal containing Al and Fe is present in a space between the first steel member and the second steel member on a periphery of the spot-welded portion, in the cross section, the filler metal has a cross-sectional area of ​​3.0 χ 104 pm2 or more, and a fill ratio of 80% or more in the space within a 100 pm interval from an extreme portion of a crown bond formed at the periphery of the spot-welded portion, and the filler metal includes a first region containing, by mass %, Al: 15% or more and less than 35%, Fe: 55% or more and 75% or less, and Si: 4% or more and 9% or less and a second region containing, by mass %, Al: 35% or more and 55% or less, Fe: 40% or more and less than 55%, and Si: 1% or more and less than 4%.

2. The joining component according to claim 1, wherein the steel sheet substrate of the first steel member contains, as a chemical composition, in % by mass, one or more of Mo: 0.10% to 1.00%, Cu: 0.10% to 1.00% and Ni: 0.10% to 1.00%, the first region further contains one or more of Mo, Cu and Ni in a total content of 0.25% or more, and the second region further contains one or more of Mo, Cu and Ni in a total content of 0.15% or more.

3. The joining component according to claim 2, wherein an average of the Feret diameters of the second region is 30 pm or less.

4. A method for manufacturing a joining component, comprising: a heat treatment step of heating a coated steel sheet, including a steel sheet containing, as a chemical composition, in % by mass, C: 0.25% to 0.65%, Si: 0.10% to 1.00%, Mn: 0.30% to 1.50%, P: 0.050% or less, S: 0.0100% or less, N: 0.010% or less, Ti: 0.010% to 0.100%, B: 0.0005% to 0.0100%, Mo: 0% to 1.00%, Cu: 0% to 1.00%, Ni: 0% to 1.00%, Cr: 0% to 1.00%, Nb: 0% to 0.10%, V: 0% to 1.00%, Ca: 0% to 0.010%, Al: 0% to 1.00%, Sn: 0% to 1.00%, W: 0% to 1.00%, Sb: 0% to 1.00%, Zr: 0% to 1.00%, REM: 0% to 0.30%, and a residue of Fe and an impurity and a coating that forms on a surface of the steel sheet,containing Al and having an adhesion quantity of 50 g / m2 or more at an AC3 spot at (AC3 spot + 300) °C at a temperature rise rate of 1.0 to 1000°C / s and cooling the coated steel sheet to an Ms spot or lower at a higher or faster critical cooling rate to obtain a steel member; and a spot welding pass for joining the steel member after the heat treatment pass and a second steel member serving as opposing material by spot welding, wherein, in the spot welding pass, at least in one position where an energizing electrode is pressed, the steel member and the second steel member are arranged so as to overlap each other with a spacing of 50 pm to 500 pm between them,and the energizing electrode is pressed against the steel member and the second steel member in such a way that the contact angle is 15 degrees or less and the electrode force is 300 kgf or more, 5 or more upslope cycles are imparted in which an amount of energization is gradually increased with an alternating source of 50 Hz or 60 Hz, and then a weld nugget is formed to join the steel member and the second steel member.

5. The method of manufacturing a joining component according to claim 4, wherein the steel sheet contains, as a chemical composition, in % by mass, one or more of Mo: 0.10% to 1.00%, Cu: 0.10% to 1.00% and Ni: 0.10% to 1.00%.

6. The method of manufacturing a joining component according to claim 5, wherein, in the spot welding step, an average cooling rate of 800°C to 500°C is adjusted to 500°C / s faster.