Welding components

Abstract

A welded component with excellent corrosion resistance and made of a steel plate that is cheaper than a pure Ni plate is obtained. The welded component of the present invention is a component formed by connecting a Ni-plated steel plate having a Ni plating layer and a Fe-Ni diffusion alloy layer to another steel plate by means of a welding portion, wherein the Ni concentration in the surface layer of the weld toe, the area near the weld toe, and the weld portion is 70% by mass or more, and the Fe concentration is 30% by mass or less, and in the non-welded portion, the thickness of the Fe-Ni diffusion alloy layer is 0.5 to 1.5 μm, and the total thickness of the Ni plating layer and the Fe-Ni diffusion alloy layer is 2.7 to 14.0 μm, and in the Ni plating layer of the non-welded portion, the total concentration of S and C is less than 20 ppm.

Description

Technical Field

[0001] The invention relates to a welding component. Background Art

[0002] Conventionally, a Ni-plated steel sheet which is annealed after Ni electroplating and has a Fe-Ni diffusion alloy layer formed between the Ni plating layer and the steel sheet is press-formed and used as a battery can (for example, refer to Patent Document 1 below).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2012 / 153728 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] In devices such as hydrogen manufacturing devices, which are used in high temperature and alkaline environments, it is required to ensure the corrosion resistance of the metal plate used as the blank, so pure Ni plates are generally used as the metal plates. In such devices, the metal plates used as the blank are generally welded to achieve the desired shape.

[0008] On the other hand, pure Ni plates are relatively expensive, and in order to reduce costs, welded members formed of steel plates having higher corrosion resistance are desired as an alternative to pure Ni plates.

[0009] Therefore, the present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a welded member having excellent corrosion resistance and made of a steel plate which is cheaper than a pure Ni plate.

[0010] Solutions for solving problems

[0011] Among them, the inventors of the present invention conceived the use of Ni-plated steel sheets, which are cheaper than pure Ni sheets, in order to achieve the cost reduction of the above-mentioned device. However, as mentioned above, Ni-plated steel sheets are generally subjected to stamping processes in the past, and are not conceived to be subjected to processes that generate a large amount of heat, such as welding. The inventors of the present invention have obtained the following findings: when welding Ni-plated steel sheets to produce welded components, there is a case where pinholes are formed in the Ni plating layer near the weld toe, which causes the corrosion resistance to deteriorate.

[0012] Furthermore, the inventors have found that when welding Ni-plated steel sheets, Fe from the steel sheets may diffuse thermally during welding and reach the surface of the Ni plating layer, thereby reducing the Ni concentration of the Ni plating layer and causing deterioration in corrosion resistance.

[0013] Based on the new findings found by the present inventors as described above, it has been conceived that there is room for improvement in ensuring corrosion resistance when welding Ni-plated steel sheets to produce welded parts.

[0014] In order to solve the above-mentioned problems, the present inventors have conducted intensive research and have obtained the following insights: by using a pure Ni-based welding wire to weld Ni-plated steel sheets having a Fe-Ni diffusion alloy layer in which the Ni plating layer is set to a specific state, it is possible to manufacture welded components with excellent corrosion resistance even when the Ni-plated steel sheets are used as the blanks.

[0015] The gist of the present invention completed based on this finding is as follows.

[0016] (1) A welded member, wherein a Ni-plated steel plate is connected to another steel plate by a weld, wherein the Ni-plated steel plate comprises: a steel plate as a base material; a Ni-plated layer located on the steel plate; and a Fe-Ni diffusion alloy layer located between the steel plate and the Ni-plated layer, wherein the Ni-plated steel plate comprises: a steel plate as a base material; a Ni-plated layer located on the steel plate; and a Fe-Ni diffusion alloy layer located between the steel plate and the Ni-plated layer. In the surface layers of the weld toe, the area near the weld toe and the weld portion specified in Z3001 (2018), the Ni concentration is 70 mass% or more, and the Fe concentration is 30 mass% or less. The area near the weld toe is an area in the Ni-plated steel sheet that is 10 μm or more and 1 mm or less from the weld toe in a direction away from the weld portion. In the Ni-plated steel sheet, when a portion where welding is not performed is set as a non-weld portion, in the non-weld portion, the thickness of the Fe-Ni diffusion alloy layer is 0.5 to 1.5 μm, and the total thickness of the Ni plating layer and the Fe-Ni diffusion alloy layer is 2.7 to 14.0 μm. In the Ni plating layer of the non-weld portion, the total concentration of S and C is less than 20 ppm.

[0017] (2) The welded component according to (1), wherein the Ni concentration and the Fe concentration in the surface layer of each of the weld toe, the area near the weld toe, and the weld portion are concentrations obtained when element concentrations are measured using Auger electron spectroscopy on the following surface, wherein the surface is obtained by removing the surfaces of the weld toe, the Ni-plated steel sheet, and the weld portion by Ar ion etching until the oxygen concentration becomes less than 25% by mass.

[0018] (3) The welded member according to (1) or (2), wherein the Ni concentration in the surface layer of each of the weld toe, the region near the weld toe, and the weld portion is 90 mass % or more, and the Fe concentration is 10 mass % or less.

[0019] (4) The welded member according to any one of (1) to (3), wherein the amount of Ni deposited on the Ni-plated steel sheet is 20 to 100 g / m in terms of metal.2 .

[0020] (5) A welding component according to any one of (1) to (4), wherein, on the surface of the Ni plating layer, the number of pinholes having a circle equivalent diameter of 10 μm or more in a rectangular area having a length of 10 cm along the extension direction of the weld toe in an area 1 mm away from the weld toe in a direction away from the weld portion is 3 or less.

[0021] Effects of the Invention

[0022] According to the present invention as described above, a welded member having excellent corrosion resistance can be obtained using a steel plate which is cheaper than a pure Ni plate as a base material. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is an explanatory diagram schematically showing an example of a welded member according to an embodiment of the present invention by enlarging a part thereof.

[0024] Figure 2 This is an explanatory diagram schematically showing an example of a welded member according to the embodiment by enlarging a part thereof.

[0025] Figure 3 It is a schematic diagram for explaining an example of a welded member according to this embodiment.

[0026] Figure 4 This is an explanatory diagram for explaining a welded member produced in a test example. DETAILED DESCRIPTION

[0027] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In addition, in this specification and the drawings, components having substantially the same functional configuration are given the same reference numerals to omit repeated descriptions.

[0028] (For welded components)

[0029] Below, while referring to Figure 1 to Figure 3 Next, a welding member according to an embodiment of the present invention will be described in detail. Figure 1 and Figure 2 This is an explanatory diagram schematically showing an example of a welded member according to the present embodiment by enlarging a part thereof. Figure 3 It is a schematic diagram for explaining an example of a welded member according to the present embodiment.

[0030] The welded component of the present embodiment is a welded component formed by connecting a Ni-plated steel plate to another steel plate via a welded portion. More specifically, the welded component is manufactured by welding such a Ni-plated steel plate described in detail below using a Ni welding wire containing 90% by mass or more of Ni and a total content of S and C of 0.1% by mass or less.

[0031] like Figure 1 As schematically shown, the welding member 1 of the present embodiment includes a Ni-plated steel plate 10A, a Ni-plated steel plate 10B, and a welded portion 20. Hereinafter, when the Ni-plated steel plate 10A and the Ni-plated steel plate 10B are described without distinguishing between them, they are also referred to as the Ni-plated steel plate 10. Here, a method of welding Ni-plated steel plates to each other is described, but the method is not limited to this method, and at least one steel plate constituting the welding member may be the Ni-plated steel plate 10 described below.

[0032] Reference Figure 2 The structure of the welded member 1 according to the present embodiment will be described in detail. The welded member 1 includes a Ni-plated steel sheet 10 , a weld portion 20 , and an alloy portion 30 .

[0033] like Figure 2 As schematically shown, the Ni-plated steel sheet 10 is a plated steel sheet in which a Ni plating layer 103 and a Fe-Ni diffusion alloy layer 105 are formed on the surface of a steel sheet 101 serving as a substrate. The Ni-plated steel sheet 10 will be described again in detail below.

[0034] The welded portion 20 is also called a weld bead portion, and is a portion formed by welding the Ni-plated steel sheet 10 using a Ni alloy or pure Ni welding wire. By this welding, mutual diffusion of constituent elements occurs between the Ni plating layer 103 and the Fe-Ni diffusion alloy layer 105 of the Ni-plated steel sheet 10 and the Ni alloy or pure Ni welding wire, thereby forming the welded portion 20. In addition, as the welded portion 20 is formed, the Ni plating layer 103, the Fe-Ni diffusion alloy layer 105, and a portion of the base material steel sheet 101 change to an alloy portion 30 at a portion of the Ni-plated steel sheet 10 that reacts with the welding wire. In addition, the welded portion 20 and the alloy portion 30 can be distinguished by cross-sectional observation.

[0035] Hereinafter, in the welded member 1 of the present embodiment, a portion where welding is not performed (for example, a portion of the Ni-plated steel sheet 10 that is 5 mm or more away from a weld toe described later) is referred to as a “non-welded portion”.

[0036] <For Ni-plated steel sheet 10>

[0037] like Figure 2As schematically shown, the Ni-plated steel plate 10 of the present embodiment (more specifically, the portion of the Ni-plated steel plate 10 corresponding to the non-welding portion) has: a steel plate 101 as a substrate; a Ni plating layer 103 located on the steel plate 101; and a Fe-Ni diffusion alloy layer 105 located between the steel plate 101 and the Ni plating layer 103.

[0038] The steel plate 101 used as the base material of the Ni-plated steel plate 10 of the present embodiment is not particularly limited, and various steel plates can be used depending on the mechanical strength required of the Ni-plated steel plate 10. As such a steel plate 101, for example, various steel plates such as various Al-killed steels, ultra-low carbon steels containing Ti, Nb, etc., and high-strength steels containing strengthening elements such as P, Si, and Mn in ultra-low carbon steels can be cited.

[0039] The thickness of the steel sheet 101 is not particularly limited, and may be appropriately set according to the mechanical strength required of the Ni-plated steel sheet 10 .

[0040] In addition, in the Ni-plated steel sheet 10 of the present embodiment, the Fe-Ni diffusion alloy layer 105 refers to a portion where the Ni concentration obtained by analyzing only the metal elements is within the range of 30 mass % or more and less than 70 mass % when a cross-sectional analysis based on a scanning electron microscope (SEM) equipped with an energy dispersive X-ray analyzer (EDS) (hereinafter, abbreviated as SEM-EDS) is performed under the conditions shown below. In addition, the Ni plating layer 103 of the present embodiment refers to a portion where the Ni concentration obtained by analyzing only the metal elements is 70 mass % or more when a cross-sectional analysis based on SEM-EDS is performed under the conditions shown below.

[0041] The measurement conditions of SEM-EDS in the above analysis may be, for example, an acceleration voltage of 15.0 kV, an irradiation current of 0.00564 nA, and an energy range of 0 to 20 keV.

[0042] The Ni coating amount in the Ni-plated steel sheet 10 (more specifically, the total Ni coating amount of the Ni plating layer 103 and the Fe-Ni diffusion alloy layer 105) is preferably 20 to 100 g / m per single surface in terms of metal. 2 . When the Ni coating is less than 20g / m 2 In the case of 20 g / m, the corrosion resistance required of the welded member 1 may not be fully exhibited. 2 As described above, the corrosion resistance required of the welded member 1 can be fully exhibited. The Ni deposition amount in the Ni-plated steel sheet 10 is more preferably 30 g / m 2 More than 40g / m 2On the other hand, the Ni coating amount in the Ni-plated steel sheet 10 exceeds 100 g / m 2 In the case of , the corrosion resistance of the Ni-plated steel sheet 10 is saturated, and there is a tendency for the cost of Ni plating to increase. 2 The amount of Ni deposited on the Ni-plated steel sheet 10 is more preferably 90 g / m 2 Below, more preferably 60g / m 2 the following.

[0043] The Ni deposition amount can be measured as follows.

[0044] In the welded member 1, a high-speed precision cutting machine is used to Figure 2 The position shown as 5 mm away from the weld toe toward the non-weld portion side (i.e., in the direction away from the weld portion 20) is used as the starting point, and a 10 mm square area is cut in the thickness direction on the non-weld portion side to serve as a sample for measuring the amount of Ni adhesion. After sealing one side of the sample cut out in this way with Teflon tape, it is ground from the back side in such a way that the Ni plating and Fe-Ni diffusion alloy layer on the sealed side remain. The ground sample is immersed in 35% hydrochloric acid until the substrate can be removed to obtain a sample. The obtained sample is measured using ICP (Inductively Coupled Plasma: Inductively Coupled Plasma) emission spectrometry (for example, ICPS-8100 manufactured by Shimadzu Corporation) to quantify the amount of Ni, which is converted into a unit of g / m 2 The Ni adhesion amount is obtained.

[0045] In addition, in the Ni-plated steel sheet 10 of the present embodiment, if the Ni plating layer 103 (the portion of the Ni plating layer 103 corresponding to the non-welding portion) is a Ni plating layer having a Ni concentration of 70% by mass or more, there is no particular limitation, and various Ni plating layers can be applied, including various electroplating Ni and chemical Ni plating. The Ni concentration in the Ni plating layer 103 is more preferably 80% by mass or more, and further preferably 90% by mass or more.

[0046] However, in the present embodiment, the total concentration of S (sulfur) and C (carbon) in the Ni plating layer 103 is set to less than 20 ppm.

[0047] The inventors of the present invention conducted intensive research when conceiving the welded member of the present invention, and found the following findings: when welding a plated Ni-plated steel sheet, H as a plating eutectoid vaporizes near the weld toe to form pinholes, which causes corrosion resistance to deteriorate. It was also found that, in particular, when glossy Ni plating containing S and C is used as Ni plating, S and C eutectoids due to welding also vaporize, further facilitating the formation of pinholes. Based on these findings, the inventors of the present invention conducted further research, and found the following findings: when the total concentration of S and C in the Ni plating layer exceeds 20 ppm, pinholes are formed due to the eutectoid S and C as described above.

[0048] The above-mentioned "weld toe" refers to the position specified in JIS Z3001 (2018), which corresponds to the intersection of the surface of the base material (i.e., the steel plate as the base material) and the surface of the weld (i.e., the weld 20). In this embodiment, it corresponds to the intersection of the surface of the Ni plating layer 103 of the Ni-plated steel plate 10 and the surface of the weld 20. Figure 1 and Figure 2 The position of the "weld toe" is schematically shown in FIG. Figure 1 and Figure 2 In the welded member 1 shown, the weld toe can be regarded as a line segment extending in the Y-axis direction.

[0049] From the above viewpoints, in the Ni plating layer 103 (more specifically, the non-welded portion of the Ni plating layer 103) of the present embodiment, the total concentration of S and C is set to less than 20 ppm. The total concentration of S and C in the Ni plating layer 103 is preferably as low as possible, and is more preferably 0 ppm.

[0050] The Ni-plated steel plate 10, which is a non-welded portion, was subjected to S and C concentration analysis using EMIA-920V2, a carbon and sulfur analyzer manufactured by HORIBA. More specifically, after sealing one side of the Ni-plated steel plate with Teflon tape, it was ground from the back side in such a way that the Ni plating on the sealed side remained. The ground sample was immersed in 35% hydrochloric acid until the substrate and the Fe-Ni diffusion alloy layer could be removed to obtain a Ni foil. The sealing material was peeled off, and the obtained Ni foil was set to a diameter of 2 to 3 mm, placed in a ceramic crucible and fired in an oxygen flow. The generated CO was detected using an infrared detector. 2 Gas, CO gas, SO 2 The gas was converted into carbon and sulfur based on the detection result and used as the concentration of S and C in the Ni-plated steel sheet.

[0051] Furthermore, in order to achieve the above-mentioned state, when Ni plating is performed on the steel sheet 101, it is important to appropriately limit the total concentration of S and C in the plating bath used for Ni plating, and it is particularly important not to perform glossy Ni plating (not to use a glossy additive containing S and C).

[0052] The present inventors have also found that H as a plating eutectoid in the Ni plating layer in the plated state can be substantially eliminated by annealing treatment before welding. The annealing treatment will be described again below.

[0053] As the Ni plating layer described above, for example, a pure Ni plating layer can be cited.

[0054] In addition, in the non-welded portion of the present embodiment, the average thickness of the Fe-Ni diffusion alloy layer 105 (hereinafter referred to as thickness) is 0.5 to 1.5 μm, and the average total thickness of the Ni plating layer 103 and the Fe-Ni diffusion alloy layer 105 (hereinafter referred to as thickness) is 2.7 to 14.0 μm. The average thickness of the Fe-Ni diffusion alloy layer 105 is preferably 0.7 μm or more or 1.0 μm or more, preferably 1.3 μm or less. The average total thickness of the Ni plating layer 103 and the Fe-Ni diffusion alloy layer 105 is preferably 3.0 μm or more or 4.0 μm or more, preferably 12.5 μm or less or 10.0 μm or less. In the non-welded portion, the thickness of the Fe-Ni diffusion alloy layer 105 and the total thickness of the Ni plating layer 103 and the Fe-Ni diffusion alloy layer 105 are within the above range, so that the Ni-plated steel sheet 10 of the present embodiment can achieve corrosion resistance to the extent that sufficient corrosion resistance can be maintained even under high temperature and alkaline conditions. In addition, the average thickness of the Ni plating layer 103 is 1.7 μm or more, so that the excessive diffusion of Fe in the weld and its surroundings to the surface layer during welding can be prevented. The thickness of the Fe-Ni diffusion alloy layer 105 is within the above range, so that the eutectoid of C and S during welding can be prevented. On the other hand, when the thickness of the Fe-Ni diffusion alloy layer 105 is 1.5 μm or more, the plating adhesion is reduced and the corrosion resistance is deteriorated.

[0055] In addition, the thickness of the Ni plating layer 103 and the thickness of the Fe-Ni diffusion alloy layer 105 were measured in a cross-sectional view cut in the thickness direction at a position 5 mm away from the weld toe to the non-weld part side during surface observation. Specifically, when observing the surface, a 10 mm square area was cut in the thickness direction on the non-weld part side starting from a position 5 mm away from the weld toe to the non-weld part side, and a sample for cross-sectional observation was prepared. The sample was embedded in resin and polished, and then the cross section as the observation object was obtained. The cross section was observed by SEM-EDS to perform measurement. That is, in the cross section, only the metal element was focused on and elemental analysis was performed, and the thickness of the obtained region where the Ni concentration was within the range of 30 mass % or more and less than 70 mass % (i.e., the Fe-Ni diffusion alloy layer 105) and the thickness of the obtained region where the Ni concentration was 70 mass % or more (i.e., the Ni plating layer 103) were measured. Such measurement was performed at any 10 locations in the cross section. The average values ​​of the remaining eight measured values ​​excluding the maximum value and the minimum value among the obtained measured values ​​are respectively set as the thickness of the Fe—Ni diffusion alloy layer 105 and the thickness of the Ni plating layer 103 .

[0056] <For welded portion 20>

[0057] The weld 20 of the present embodiment is preferably a Ni alloy having a Ni concentration (more specifically, an average Ni concentration) of 70% by mass or more. The weld 20 is formed by welding using a Ni alloy or pure Ni welding wire by a welding method described in detail below. The weld 20 is a Ni alloy having a Ni concentration of 70% by mass or more, thereby increasing the possibility of ensuring corrosion resistance of the welded portion where the Ni plating layer 103 disappears. The Ni concentration of the weld 20 is adjusted as follows. First, for example, Figure 1 The cross section obtained by cutting the welded portion 20 on the XZ plane shown in the figure was embedded and polished, and the cross section was observed. Concentration measurement was performed for any 10 locations in the cross section. The average value of the remaining 8 measurement values ​​excluding the maximum value and the minimum value among the obtained measurement values ​​was set as the average concentration of Ni.

[0058] The Ni concentration of the weld 20 is preferably 90 mass % or more. When the weld 20 has this Ni concentration, the corrosion resistance of the welded portion can be more reliably ensured.

[0059] <Ni concentration and Fe concentration in the surface layer of the weld toe, Ni-plated steel sheet (near the weld toe), and weld>

[0060] The welded component 1 of the present embodiment has a Ni concentration of 70 mass % or more and a Fe concentration of 30 mass % or less in the surface layer of each of the weld toe, the Ni-plated steel sheet 10 and the weld 20 as specified in JIS Z3001 (2018). The position of the Ni-plated steel sheet where the Ni concentration is measured is a region of the Ni-plated steel sheet 10 that is 10 μm or more and 1 mm or less from the weld toe to the non-weld portion side (i.e., in the direction away from the weld 20) (hereinafter, this region is also referred to as the weld toe vicinity region). Generally, thermal diffusion of elemental Fe from the Ni-plated steel sheet occurs due to welding. In the welded component 1 of the present embodiment, the proportion of Fe diffused to the weld toe, the weld toe vicinity region and the surface layer of the weld 20 can be suppressed to 30 mass % or less. The weld toe, the weld toe vicinity region and the weld 20 each have the above-mentioned Ni concentration and Fe concentration, so that corrosion resistance can be achieved to the extent that sufficient corrosion resistance can be maintained even in a high temperature and alkaline environment. Such a configuration is particularly effective in maintaining the corrosion resistance of the Ni-plated steel sheet at the weld portion, weld toe portion, or the vicinity of the weld toe.

[0061] The Ni concentration in the surface layer of each of the weld toe, the region near the weld toe, and the weld 20 is preferably 90 mass % or more. The Fe concentration in the surface layer of each of the weld toe, the region near the weld toe, and the weld 20 is preferably 10 mass % or less.

[0062] Among them, there is a possibility that dirt such as oxide film, grease, etc. generated by reaction with oxygen in the atmosphere adheres to the surface of the weld toe, the area near the weld toe, and the weld 20. Therefore, it is desirable to measure the above-mentioned Ni concentration and Fe concentration in a state where such oxide film, dirt, etc. do not exist. From this point of view, the above-mentioned Ni concentration and Fe concentration are set to the concentration when the element concentration is measured by Auger electron spectroscopy on the following surface in the field of view where the surface of the weld toe, the area near the weld toe, and the weld 20 can be observed, and the surface is obtained by removing from the surface in the thickness direction by Ar ion etching until the oxygen concentration becomes 25% by mass or less. In addition, the removal by Ar ion etching can be carried out until the surface layer of each of the weld toe, the area near the weld toe, and the weld 20 can be observed, and the range that can be removed by Ar ion etching is preferably within a range of 1 μm from the depth of each of the weld toe, the area near the weld toe, and the weld 20.

[0063] In addition, the measurement conditions of the element concentration measurement by Auger electron spectroscopy are set to, for example, an acceleration voltage of 15 kV and an irradiation current of 10 nA. More specifically, under the measurement conditions, in the case of the weld toe vicinity area and the weld 20, the element concentration measurement by Auger electron spectroscopy (measurement of only metal elements) is performed at any five points in the observation plane, and in the case of the weld toe, the element concentration measurement by Auger electron spectroscopy (measurement of only metal elements) is performed at any five points on the intersection line of the weld 20 and the Ni-plated steel sheet 10 in the observation plane. The average values ​​of three measurement values ​​excluding the maximum value and the minimum value of the obtained five Ni concentration and Fe concentration are respectively set as the Ni concentration and the Fe concentration.

[0064] Furthermore, the above-mentioned surface concentration is achieved for the first time by welding using a welding method described in detail below. The detailed welding method is described again below.

[0065] <Average number of pinholes with a circle equivalent diameter of 10 μm or more>

[0066] As mentioned above, when welding the Ni-plated steel sheet in the plated state, it was found that H, which is a plating eutectoid, gasifies near the weld toe to form pinholes, which causes the corrosion resistance to deteriorate. In addition, when a Ni-plated layer containing S and C in the plating layer is used as the Ni-plated layer, it was found that S and C, which are eutectoids due to welding, also gasify, and pinholes are further easily formed. In particular, pinholes with a circle equivalent diameter of 10 μm or more become the starting point of red rust generation, so the number of pinholes with a circle equivalent diameter of 10 μm or more is preferably small.

[0067] In order to suppress the generation of the above-mentioned pinholes, the inventors of the present invention have come up with the idea of ​​limiting the total concentration of S and C in the Ni plating layer 103 to less than 20 ppm, and subjecting the Ni-plated steel sheet 10 to annealing treatment before welding. In this way, the presence of gasifiable S and C can be eliminated, and H, which is a plating eutectoid, can also be gasified during the annealing treatment. In addition, the pinholes formed by the gasification of H during the annealing treatment can be repaired under the heating environment used for the annealing treatment. According to such a treatment, in the welding component 1 of the present embodiment, the average number of pinholes with a circle equivalent diameter of more than 10 μm that can be generated as a result of welding is extremely small. From this point of view, the welding component 1 of the present embodiment also has excellent corrosion resistance.

[0068] Specifically, if Figure 3As schematically shown, in the surface of the Ni plating layer 103, a region with a length of 10 cm in the extension direction in the region from the weld toe to the non-welded portion side by a distance of 1 mm is set as a rectangular region R. Such rectangular regions R can be conceived to be multiple in the welded member 1 of the present embodiment. In the welded member 1 of the present embodiment, the average number of pinholes with a circle equivalent diameter of 10 μm or more existing in the rectangular regions R of any five adjacent locations is 3 or less. Therefore, it can be seen that the welded member 1 of the present embodiment has excellent corrosion resistance even in the vicinity of the weld 20.

[0069] In addition, by performing observation based on SEM, the average number of pinholes with a circle equivalent diameter of 10 μm or more can be measured. Observation is performed at the above-mentioned five locations, and the number of pinholes with a circle equivalent diameter of 10 μm or more is measured in each rectangular area R. The average value of each of the three measured values ​​excluding the maximum value and the minimum value among the five measured values ​​obtained is set as the average number of pinholes.

[0070] Above, while referring to Figure 1 to Figure 3 The welded member 1 of this embodiment is described in detail.

[0071] (An example of a method for manufacturing a welded member)

[0072] Next, the method for manufacturing the welded member according to the present embodiment will be described by giving an example.

[0073] After manufacturing a Ni-plated steel plate having a Fe-Ni diffusion alloy layer, the Ni-plated steel plate is welded using a Ni welding wire to manufacture the welded component of the present embodiment. In the past, the Ni-plated steel plate having a Fe-Ni diffusion alloy layer was not melt-joined using a Ni welding wire. In addition, the welded component of the present embodiment cannot be obtained by welding the Ni-plated steel plate having a Fe-Ni diffusion alloy layer only using a Ni welding wire. It is important to control the heat input during welding on the basis of setting the thickness of the Fe-Ni diffusion alloy layer to a desired state.

[0074] <An example of a method for producing a Ni-plated steel sheet>

[0075] A predetermined Ni plating bath is used to plate Ni on the surface of a steel sheet serving as a substrate so as to obtain a predetermined deposition amount, and then annealing is performed to produce a Ni-plated steel sheet.

[0076] Among them, various Ni plating baths adjusted in such a way that the total concentration of S and C is less than 20 ppm can be used as Ni plating baths. As such Ni plating baths, for example, Watts baths, nickel sulfate baths, nickel chloride baths, etc. can be cited. The amount of plating adhesion is 15 to 100 g / m in terms of metal conversion. 2 The amount of Ni electroplating can be adjusted by controlling the current density, power-on time, etc. during electroplating.

[0077] Thereafter, the obtained Ni-plated steel sheet is subjected to annealing treatment. As a result, Fe from the steel sheet and Ni from the Ni plating layer are mutually thermally diffused to form an Fe-Ni diffusion alloy layer, and H as a plating eutectoid is gasified. As a result, a Ni-plated steel sheet having an Fe-Ni diffusion alloy layer and a Ni plating layer and suppressing the generation of pinholes having a circle equivalent diameter of 10 μm or more during welding can be obtained.

[0078] In the annealing treatment, for example, it is preferred to maintain the holding temperature of 600 to 850° C. for 5 to 60 seconds. This allows the desired Fe-Ni diffusion alloy layer to be formed more reliably, and H, which is a plating eutectoid, to be gasified more reliably. The holding temperature is more preferably 700 to 850° C., and the holding time is more preferably 20 to 60 seconds.

[0079] The heating rate from room temperature to the holding temperature is preferably 5 to 100°C / sec. In addition, after the desired holding time has elapsed, the temperature is preferably increased by, for example, N 2 The Ni-plated steel sheet was cooled to 200° C. by gas cooling and then taken out into the air.

[0080] In addition, the annealing treatment is preferably carried out at 2% H 2 -N 2 The test was carried out in an environment with an atmosphere and a dew point of -60°C.

[0081] <An example of welding method>

[0082] For example, the Ni-plated steel plate having the Fe-Ni diffusion alloy layer manufactured as described above is welded using a Ni alloy containing 90% by mass or more Ni or a pure Ni welding wire containing 99% by mass or more Ni having a desired Ni concentration. Among them, laser welding or arc welding can be used as a welding method. In the welding member 1 of the present embodiment, it can also be applied in a manner where the Ni-plated steel plate and the Ni plate are welded. From the perspective of cost reduction, it is preferred that the Ni-plated steel plates are welded to each other. In addition, one of the welding methods is spot welding, but in the case where spot welding is used as a method for welding at least Ni-plated steel plates to each other, it is impossible to achieve a welded portion with a Ni concentration of 70% or more as focused on in the present embodiment. In the case of laser welding, a fiber laser, a disk laser, and a semiconductor laser are preferred. In addition, in the case of arc welding, in order to set the diffusion of Fe caused by the heat input during welding to a desired state, it is more preferred to use a low heat input welding process such as a cold metal transfer (Cold Metal Transfer: CMT (registered trademark)) method. In addition, SYNCHRO FEED (registered trademark) GMA welding and S-AWP (Super Active Wire Feed Process) welding are also preferable. These are welding methods with different names depending on the welding machine manufacturer, and are welding methods equivalent to CMT.

[0083] In more detail, in the case of laser welding, a welding wire with a diameter of 0.6 mm to 1.6 mm is used, and the beam is preferably adjusted in such a way that the laser beam diameter becomes 0.8 to 3.5 times the diameter of the welding wire. At this time, it is preferred to supply the welding wire to the laser irradiation portion at a speed of 0.6 to 4.0 times the welding speed to perform welding. In addition, in order to prevent oxidation of the laser welded portion, argon, helium, nitrogen, carbon dioxide, or a mixed gas of these gases is preferably used as a shielding gas, and argon is more preferably used. In addition, it is preferred to adjust the flow rate of the shielding gas at 10 to 70 L / min. In order to set the diffusion of Fe caused by the heat input during welding to the desired state, the output and speed of the laser can be appropriately adjusted. For example, it is preferred that the output of the laser is 0.8 to 12 kW and the welding speed is adjusted in the range of 0.5 to 15 m / min.

[0084] In addition, in the case of arc welding, it is preferred to use a welding wire with a diameter of 0.6 to 1.6 mm. In order to prevent oxidation of the weld and stabilize the arc, it is preferred to use argon gas or a shielding gas obtained by adding 3% or less of carbon dioxide or oxygen to argon gas. Among them, it is preferred to adjust the flow rate of the shielding gas at 10 to 50 L / min. Regarding the conditions for arc welding, in order to set the diffusion of Fe caused by the heat input during welding to the desired state, it is preferred to adjust the current and welding speed. For example, it is preferred to adjust the current within the range of 60 to 250 A and the welding speed within the range of 0.2 to 1.8 m / min. In addition, TIG welding or plasma welding using Ni wire is also possible.

[0085] In the manufacturing method of the welded component of the present embodiment, the thickness of the Ni plating layer and the Fe-Ni alloy diffusion layer is appropriately controlled, and the heat input is controlled to an appropriate value while using a Ni wire to perform fusion welding. As a result, the Ni concentration in the surface layer of each of the weld toe, the area near the weld toe, and the weld portion of the welded component can be set to an appropriate value (70 mass % or more).

[0086] The welded member of the present embodiment is manufactured as described above.

[0087] Example

[0088] Hereinafter, the welding member of the present invention will be specifically described while showing examples and comparative examples. In addition, the example shown below is just an example of the welding member of the present invention, and the welding member of the present invention is not limited to the following example.

[0089] <Manufacturing of Ni-plated steel sheets>

[0090] In this test example, aluminum-killed steel (plate thickness 1 mm) to which B was added was prepared as a steel plate serving as a substrate. A Watts bath having a bath composition shown in Table 1 below was prepared as a Ni plating bath for Ni plating. In addition, for comparison, a glossy plating bath was prepared in which 0.2 / L of butynediol as a carbon source and 2 g / L of saccharin Na as a sulfur source were added to the Watts bath shown in Table 1 below. In addition, the current density during electroplating was set to 20 A / dm 2 The desired plating adhesion amount was achieved by changing the power-on time.

[0091] [Table 1]

[0092] Table 1 Watts bath composition and bath temperature

[0093] Nickel sulfate hexahydrate 250g / L Nickel chloride hexahydrate 50g / L Boric acid 30g / L Bath temperature 50℃

[0094] After the above plating, 2% H 2 -N 2The annealing treatment was carried out under the conditions of atmosphere and dew point -60°C. In the annealing treatment, the temperature was raised from room temperature to a predetermined holding temperature at a heating rate of 25°C / sec, and after the holding temperature was held for a predetermined time, the N 2 The mixture was cooled to 200° C. by gas cooling and then taken out to the air atmosphere. The holding temperature and holding time were as shown in Table 6 below.

[0095] <Welding Process>

[0096] The obtained Ni-plated steel sheet was cut into pieces of 150 mm × 50 mm and used for welding. The atmosphere at the welding site was set at 10°C and 20% RH. Figure 4 The schematically shown Cu jig of 100 mm×200 mm, 20 mm thick and the Cu jig of 30 mm×200 mm, 20 mm thick and having a 5 mm notch were cooled to -20°C, and then Ni-plated steel plates were fixed to the jigs and fillet welded using Ni wires of 1.2 mm diameter.

[0097] The details of the metal wire used for welding are shown in Table 2 below. In addition, as the welding method, either laser welding or two types of arc welding was performed. The welding conditions of each welding are shown in Tables 3 to 5 below. In addition, the welding conditions of arc welding shown in Table 5 below are as follows: By setting the voltage to a high level, the heat input to the Ni-plated steel sheet becomes excessive.

[0098] [Table 2]

[0099] Table 2 Welding wire

[0100]

[0101] [Table 3]

[0102] Table 3 Laser welding conditions

[0103]

[0104] [Table 4]

[0105] Table 4 Arc welding conditions

[0106]

[0107] [Table 5]

[0108] Table 5 Arc welding conditions (comparative example)

[0109]

[0110] As described above, the Ni concentration and Fe concentration in the surface layer of each of the weld toe, the weld toe vicinity area in the Ni-plated steel sheet (the area 10 μm or more and 1 mm or less from the weld toe to the non-weld part side), and the weld were measured by Auger electron spectroscopy. The Auger electron spectrometer used was JAMP-9500F manufactured by JEOL. In addition, in this concentration measurement, the surface obtained by removing the surface of the weld toe, the Ni-plated steel sheet, and the weld until the oxygen concentration became 25% by mass or less by Ar ion etching was set as the measurement surface. The amount removed by Ar ion etching was within 1 μm in the thickness direction in any sample. Under the measurement conditions of an acceleration voltage of 15 kV and an irradiation current of 10 nA, element concentration measurement (only measurement of metal elements) by Auger electron spectroscopy was implemented at any 5 points in the observation surface (in the case of the weld toe, any 5 points on the intersection line of the weld and the Ni-plated steel sheet in the observation surface). The average values ​​of three measured values ​​excluding the maximum value and the minimum value among the five measured values ​​of the Ni concentration and the Fe concentration were respectively set as the Ni concentration and the Fe concentration.

[0111] Use high-speed precision cutting machine to Figure 2 The welded component obtained is cut into a 10 mm square area in the thickness direction toward the welded part side, starting from a position where the weld toe is 5 mm away from the non-welded part side, and thus a sample for measuring the amount of Ni adhesion is prepared. After sealing one side of the sample cut out in this way with Teflon tape, it is ground from the back side in such a way that the Ni plating and Fe-Ni diffusion alloy layer on the sealed side remain. The ground sample is immersed in 35% hydrochloric acid until the substrate can be removed to obtain a sample. The obtained sample is measured by using ICP (Inductively Coupled Plasma) emission spectrometry (for example, ICPS-8100 manufactured by Shimadzu Corporation) to quantify the amount of Ni and convert it into g / m 2 The Ni adhesion amount was obtained by measuring the adhesion amount.

[0112] Analysis

[0113] Use high-speed precision cutting machine to cut from Figure 2The welded components obtained were cut at a position where the weld toe was 5 mm away from the non-welded part. Specifically, when observing the surface, a 10 mm square area was cut on the non-welded part side in the thickness direction, starting from a position 5 mm away from the weld toe to the non-welded part. Thus, a sample for cross-sectional observation and a sample for surface observation were cut out for analysis. In terms of analysis, SEM (JSM-7000F manufactured by JEOL) was used, and the cross section and surface were observed using reflected electrons. In addition, when SEM-EDS cross-sectional analysis was performed under the conditions of an acceleration voltage of 15.0 kV, an irradiation current of 0.00564 nA, and an energy range of 0 to 20 keV, only the metal elements were analyzed, and the obtained Ni concentration was 70% or more as the Ni plating layer, and the obtained Ni concentration was within the range of 30% or more and less than 70% as the Fe-Ni diffusion alloy layer. The thickness of the Fe-Ni diffusion alloy layer and the thickness of the Ni plating layer were measured at any 10 locations in the cross section. The average values ​​of the remaining eight measured values ​​excluding the maximum value and the minimum value among the obtained measured values ​​were respectively set as the thicknesses of the Fe—Ni diffusion alloy layer and the Ni plating layer, and the total of the average values ​​of the remaining eight measured values ​​was set as the total thickness.

[0114] [Analysis 1 Confirmation of C and S concentrations in Ni plating]

[0115] The detection limit of element concentration in the SEM-EDS analysis used in the confirmation of the Ni plating is 1500 to 2000 ppm. Therefore, the S and C concentrations of the Ni-plated steel plate were analyzed for the sample before embedment using EMIA-920V2, a carbon and sulfur analyzer manufactured by HORIBA. More specifically, after sealing one side of the Ni-plated steel plate with Teflon tape, it was polished from the back side in such a way that the Ni plating on the sealed side remained. The polished sample was immersed in 35% hydrochloric acid until the substrate and the Fe-Ni diffusion alloy layer were removed, and a Ni foil was obtained. The sealing material was peeled off, and the obtained Ni foil was set to a diameter of 2 to 3 mm, placed in a ceramic crucible and fired in an oxygen flow. The generated CO was detected using an infrared detector. 2 Gas, CO gas, SO 2 The gas is converted into carbon and sulfur. The detection limits of each element measured by this measurement method are 3 ppm for C and 1 ppm for S. If it is below the detection limit, it is considered OK, and if it is above 20 ppm, it is considered NG.

[0116] [Analysis 2: Confirmation of the number of pinholes in the weld toe by surface observation]

[0117] As the sample for surface observation, the shortest distance portion of the sample for cross-sectional observation was cut out at a length of 50 cm. The cut portion was cut into 10 cm units and five samples were prepared. Figure 3 The sample with the rectangular region R shown schematically. Each sample was ultrasonically cleaned in acetone for 60 seconds and then observed. The weld toe 1mm width × 10cm area ( Figure 3 For each sample, observe whether there are pinholes with a circle equivalent diameter of 10 μm or more, and calculate the average number according to the method described above. If the average number obtained is 3 or less, it is OK, and if the average number obtained is more than 4, it is NG.

[0118] <Evaluation of welded components>

[0119] [Evaluation 1 Corrosion resistance]

[0120] The samples used for corrosion resistance evaluation used surface observation samples after surface observation. For each of the five samples, after acetone degreasing, the end faces and the back faces were sealed with paint, and the welds were evaluated by a 35°C, 5%-salt spray test for 3 hours. For each sample, the weld toe was observed, and the number of red rusts produced in the range of 1mm width × 10cm was measured. The average value of the three measured values ​​excluding the maximum and minimum values ​​among the five measured values ​​obtained was calculated and set as the frequency of red rust production. The case where the frequency of red rust production is 3 or less is qualified, the case where the frequency of red rust production is two or less is good, the case where the frequency of red rust production is 1 or less is excellent, and the case where the frequency of red rust production exceeds 4 is unqualified.

[0121] [Evaluation 2 Evaluation of plating adhesion under stress]

[0122] In order to evaluate the peeling of the plating caused by corrosion, the evaluation of the plating adhesion under stress was carried out. The sample for the evaluation of the plating adhesion under stress used the part adjacent to the sample for the corrosion resistance evaluation. In order to apply stress, the sample welded at 90° was expanded to 95°, acetone degreasing was performed, and the end face and the back face were sealed with paint to make the sample for the evaluation of the plating adhesion under stress. The weld was evaluated by a 35°C, 5%-salt spray test for 3 hours. Observe the range of 1mm from the weld toe, and the sample with no plating peeling is set as OK, and the sample with plating peeling is set as NG.

[0123] The obtained results are summarized in Table 6 below.

[0124] As is apparent from the following Table 6, it is known that the welded members corresponding to the examples of the present invention exhibit excellent corrosion resistance. On the other hand, it is clear that the welded members corresponding to the comparative examples of the present invention have poor corrosion resistance.

[0125] [Table 6]

[0126]

[0127] The preferred embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the examples. It is obvious that anyone with common knowledge in the technical field to which the present invention belongs can think of various variations or modifications within the scope of the technical ideas described in the claims, and these are of course understood to belong to the protection scope of the present invention.

[0128] Description of Reference Numerals

[0129] 1. Welding component; 10. Ni-plated steel plate; 20. Welding portion; 101. Steel plate; 103. Ni plating layer; 105. Fe-Ni diffusion alloy layer.

Claims

1. A welded component, which is formed by connecting a Ni-plated steel plate and another steel plate via a welded portion, The Ni-plated steel sheet comprises: a steel sheet as a substrate; a Ni-plated layer located on the steel sheet; and a Fe-Ni diffusion alloy layer located between the steel sheet and the Ni-plated layer. In the surface layer of each of the weld toe, the region near the weld toe and the weld portion specified in JIS Z3001 (2018), the Ni concentration is 70 mass % or more, and the Fe concentration is 30 mass % or less, the region near the weld toe is a region of the Ni-plated steel sheet at a distance of 10 μm or more and 1 mm or less from the weld toe in a direction away from the weld portion, In the Ni-plated steel sheet, when a portion where welding is not performed is defined as a non-welded portion, In the non-welding portion, the thickness of the Fe-Ni diffusion alloy layer is 0.5 to 1.5 μm, and the total thickness of the Ni plating layer and the Fe-Ni diffusion alloy layer is 2.7 to 14.0 μm. In the Ni plating layer of the non-welding portion, the total concentration of S and C is less than 20 ppm.

2. The welding component according to claim 1, wherein: The Ni concentration and the Fe concentration in the surface layer of the weld toe, the area near the weld toe, and the weld portion are concentrations obtained when the element concentration is measured using Auger electron spectroscopy on the following surface, where the surface is obtained by removing the surface of the weld toe, the Ni-plated steel plate, and the weld portion using Ar ion etching until the oxygen concentration becomes less than 25% by mass.

3. The welding member according to claim 1 or 2, wherein: The Ni concentration in the surface layer of each of the weld toe, the region near the weld toe, and the weld portion is 90 mass % or more, and the Fe concentration is 10 mass % or less.

4. The welding member according to claim 1 or 2, wherein: The Ni coating amount of the Ni-plated steel sheet is 20 to 100 g / m in terms of metal conversion. 2 .

5. The welding member according to claim 3, wherein: The Ni coating amount of the Ni-plated steel sheet is 20 to 100 g / m in terms of metal conversion. 2 .

6. The welding member according to claim 1 or 2, wherein: On the surface of the Ni plating layer, the number of pinholes with a circular equivalent diameter of 10 μm or more is 3 or less in the following rectangular area, wherein the rectangular area is an area with a length of 10 cm along the extension direction of the weld toe in an area 1 mm away from the weld toe in a direction away from the weld portion.

7. The welding member according to claim 3, wherein: On the surface of the Ni plating layer, the number of pinholes with a circular equivalent diameter of 10 μm or more is 3 or less in the following rectangular area, wherein the rectangular area is an area with a length of 10 cm along the extension direction of the weld toe in an area 1 mm away from the weld toe in a direction away from the weld portion.

8. The welding member according to claim 4, wherein: On the surface of the Ni plating layer, the number of pinholes with a circular equivalent diameter of 10 μm or more is 3 or less in the following rectangular area, wherein the rectangular area is an area with a length of 10 cm along the extension direction of the weld toe in an area 1 mm away from the weld toe in a direction away from the weld portion.

9. The welding member according to claim 5, wherein: On the surface of the Ni plating layer, the number of pinholes with a circular equivalent diameter of 10 μm or more is 3 or less in the following rectangular area, wherein the rectangular area is an area with a length of 10 cm along the extension direction of the weld toe in an area 1 mm away from the weld toe in a direction away from the weld portion.

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