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WO2025234086A1 - Joint soudé - Google Patents

Joint soudé

Info

Publication number
WO2025234086A1
WO2025234086A1 PCT/JP2024/017420 JP2024017420W WO2025234086A1 WO 2025234086 A1 WO2025234086 A1 WO 2025234086A1 JP 2024017420 W JP2024017420 W JP 2024017420W WO 2025234086 A1 WO2025234086 A1 WO 2025234086A1
Authority
WO
WIPO (PCT)
Prior art keywords
plating layer
heat
affected zone
welded joint
mass
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/JP2024/017420
Other languages
English (en)
Japanese (ja)
Inventor
卓哉 光延
完 齊藤
浩史 竹林
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nippon Steel Corp
Original Assignee
Nippon Steel Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nippon Steel Corp filed Critical Nippon Steel Corp
Priority to PCT/JP2024/017420 priority Critical patent/WO2025234086A1/fr
Publication of WO2025234086A1 publication Critical patent/WO2025234086A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/20—Bonding
    • B23K26/32—Bonding taking account of the properties of the material involved
    • B23K26/322—Bonding taking account of the properties of the material involved involving coated metal parts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K9/00—Arc welding or cutting
    • B23K9/23—Arc welding or cutting taking account of the properties of the materials to be welded
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C18/00—Alloys based on zinc
    • C22C18/04—Alloys based on zinc with aluminium as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/10—Alloys based on aluminium with zinc as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C23C2/06—Zinc or cadmium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C23C2/12—Aluminium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/26—After-treatment

Definitions

  • This disclosure relates to welded joints.
  • Zn-Al-Mg hot-dip plated steel sheets which have a hot-dip Zn coating containing Al and Mg, have excellent rust resistance and paint adhesion. For this reason, they are widely used as a material for structural components that require corrosion resistance, such as building materials.
  • fusion welding such as arc welding is sometimes used to join materials together.
  • the heat-affected zone on the backside of the bead is divided into areas where the plating layer remains and areas where the plating layer does not.
  • the composition of the plating layer differs from the composition of the plating layer in the non-heat-affected zone, so the expected red rust resistance and paint adhesion may not be achieved.
  • Patent Document 1 discloses an automobile chassis component having a joint formed by arc welding two hot-dip Zn-Al-Mg alloy-plated steel sheet members with a thickness of 1.0 to 3.0 mm, in which the steel sheet surface, which had a plating layer before welding, is continuously covered with a Zn-Al-Mg alloy layer up to the toe of the weld bead, with an Fe-Al alloy layer present between the Zn-Al-Mg alloy layer and the steel base material, and in the steel sheet surface portion within 2 mm from the toe of the weld bead, the Zn-Al-Mg alloy layer has an average Al concentration of 0.2 to 22.0 mass% and an average Mg concentration of 1.0 to 10.0 mass%, and the Fe-Al alloy layer has an average Fe concentration of 70.0 mass% or less.
  • Patent Document 1 discloses that this configuration prevents a decrease in corrosion resistance in the vicinity of the toe of the bead of the arc weld, enabling the construction of an automobile chassis with
  • Patent Document 1 does not take into consideration paint adhesion and rust resistance on the backside of the bead.
  • This disclosure has been made in light of the above-mentioned circumstances. Its purpose is to provide a welded joint that exhibits excellent paint adhesion and red rust resistance on the backside of the bead.
  • the gist of the present disclosure is as follows. [1] A welded joint in which a first steel plate and a second steel plate are welded, The first steel plate and the second steel plate; a weld bead portion formed by the welding, The first steel plate and the second steel plate each have a heat-affected zone located around the weld bead portion and a non-heat-affected zone that is not affected by heat due to the welding, The first steel plate has a plating layer on a surface in the heat-affected zone and the non-heat-affected zone, The chemical composition of the plating layer in the non-heat-affected zone is, in mass%, Al: 5.0-40.0%, Mg: 3.0 to 15.0%, Fe: 0.01-15.00%, Si: 0 to 10.00%, Ca: 0-1.5000%, Sb: 0 to 0.5000%, Pb: 0 to 0.5000%, Sr: 0 to 0.5000%, Cu: 0 to 1.0000%, Ti: 0 to 1.000
  • the chemical composition of the plating layer in the non-heat-affected zone is, in mass%, Si: 0.01-10.00%, Ca: 0.0001-1.5000%, Sb: 0.0001 to 0.5000%, Pb: 0.0001 to 0.5000%, Sr: 0.0001 to 0.5000%, Cu: 0.0001 to 1.0000%, Ti: 0.0001 to 1.0000%, V: 0.0001 to 1.0000%, Cr: 0.0001-1.0000%, Nb: 0.0001 to 1.0000%, Ni: 0.0001 to 1.0000%, Mn: 0.0001 to 1.0000%, Mo: 0.0001 to 1.0000%, Sn: 0.0001 to 1.0000%, Zr: 0.0001 to 1.0000%, Co: 0.0001 to 1.0000%, W: 0.0001-1.0000%, Ag: 0.0001 to 1.0000%, Li: 0.0001 to 1.0000%, La: 0.0001 to 0.5000%, Ce: 0.0001 to 0.500
  • the chemical composition of the plating layer in the non-heat-affected zone is, in mass%, Mg: 4.5 to 15.0%;
  • the chemical composition of the plating layer in the non-heat-affected zone is, in mass%, Mg: contains 5.5 to 15.0%;
  • the chemical composition of the plating layer in the non-heat-affected zone is, in mass%, Al: 10.0 to 40.0%; The welded joint according to any one of [1] to [4], characterized in that the left side of the formula (1) is 6 or more.
  • the chemical composition of the plating layer in the non-heat-affected zone is, in mass%, Al: 15.0 to 40.0%; The welded joint according to any one of [1] to [4], characterized in that the left side of the formula (1) is 8 or more.
  • the chemical composition of the plating layer in the non-heat-affected zone is, in mass%, Sn: 0.0200 to 1.0000%;
  • FIG. 2 is a view showing a cross section of a welded joint near a weld bead portion.
  • FIG. 2 is an enlarged view of the heat-affected zone on the back surface of the bead of the welded joint.
  • FIG. 1 is an enlarged view of a portion of the region from the starting point S to 1000 ⁇ m.
  • FIG. 2 is a view showing a cross section near a weld bead portion of a lap joint.
  • FIG. 1 is a diagram showing a cross section near a weld bead portion of a T-joint.
  • a welded joint according to one embodiment of the present disclosure (hereinafter sometimes referred to as the welded joint according to this embodiment) will be described.
  • this disclosure is not limited to the configuration disclosed in this embodiment, and various modifications are possible within the scope of the spirit of this disclosure.
  • the welded joint is a welded joint 10 in which a first steel plate 1 and a second steel plate 2 are welded together, and includes the first steel plate 1, the second steel plate 2, and a weld bead portion 3 formed by the welding.
  • the first steel plate 1 and the second steel plate 2 each have a heat-affected zone a located around the weld bead portion 3 and a non-heat-affected zone b that is not thermally affected by the welding.
  • At least one of the first steel plate 1 or the second steel plate 2 has a plating layer 4 (not shown in FIG. 1 ) located on at least a portion of the surface of the heat-affected zone a and the non-heat-affected zone b.
  • first steel plate 1 and the second steel plate 2 There are no particular limitations on the materials of the first steel plate 1 and the second steel plate 2.
  • various steel plates such as general steel, Al-killed steel, extra-low carbon steel, high carbon steel, various high-tensile steels, and some high alloy steels (steels containing strengthening elements such as Ni and Cr) can be used.
  • the manufacturing methods (hot rolling method, pickling method, cold rolling method, etc.) of the first steel plate 1 and the second steel plate 2 are not particularly limited.
  • the weld bead portion 3 consists of a weld bead formed by welding. There are no particular restrictions on the shape or composition of the weld bead portion 3.
  • the composition of the plating layer 4 in the heat-affected zone a may differ from the composition of the plating layer 4 in the non-heat-affected zone b. Furthermore, in the heat-affected zone a, the plating layer 4 melts and penetrates into the surface regions of the first steel sheet 1 and the second steel sheet 2, or melts off, leaving areas where the plating layer 4 is not present.
  • the chemical composition of the plating layer 4 in the non-heat-affected zone b will be described below.
  • the chemical composition of the plating layer 4 remaining in the heat-affected zone a can also be favorably controlled, thereby improving paint adhesion and red rust resistance on the back surface A of the bead.
  • the chemical composition of the plating layer 4 in the non-heat-affected zone b is the same on both the surface having the weld bead and the back surface of the bead.
  • the chemical composition of the plating layer 4 of the non-heat-affected zone b contains, in mass %, Al: 5.0 to 40.0%, Mg: 3.0 to 15.0%, and Fe: 0.01 to 15.00%, with the balance being 20.000% or more of Zn and impurities. Each element will be explained below.
  • Al contributes to improving paint adhesion and red rust resistance. If the Al content is less than 5.0%, the paint adhesion and red rust resistance on the bead back surface A will deteriorate. Therefore, the Al content is set to 5.0% or more.
  • the Al content is preferably 10.0% or more, and more preferably 15.0% or more.
  • the Al content is set to 40.0% or less.
  • the Al content is preferably 35.0% or less, 30.0% or less, and more preferably 25.0% or less.
  • Mg 3.0-15.0% Mg is an element necessary for forming the Mg—Zn phase. If the Mg content is less than 3.0%, a sufficient amount of the Mg—Zn phase cannot be formed on the bead back surface A, and the paint adhesion and red rust resistance on the bead back surface A deteriorate. Therefore, the Mg content is set to 3.0% or more.
  • the Mg content is preferably 4.0% or more or 4.5% or more, and more preferably 5.0% or more or 5.5% or more.
  • the Mg content is set to 15.0% or less.
  • the Mg content is preferably 12.0% or less or 10.0% or less, and more preferably 7.0% or less.
  • Fe may be mixed into the plating layer 4 from the first steel sheet 1 during the formation of the plating layer 4, it is difficult to set the Fe content in the plating layer 4 to 0%. Therefore, the Fe content is set to 0.01% or more.
  • the Fe content may be 0.05% or more or 0.10% or more.
  • the Fe content is set to 15.00% or less.
  • the Fe content may also be 10.00% or less, 5.00% or less, or 3.00% or less.
  • the plating layer 4 in the non-heat-affected zone b may have the above chemical composition, with the balance consisting of 20.000% or more Zn and impurities. If the Zn content is less than 20.000%, the desired rust resistance and paint adhesion cannot be achieved on the bead back surface A.
  • the Zn content is preferably 40.000% or more or 50.000% or more, and more preferably 55.000% or more, 60.000% or more, 65.000% or more, or 70.000% or more.
  • impurities refer to substances that are mixed in from the manufacturing environment, etc., and/or substances that are tolerated to the extent that they do not adversely affect the characteristics of the welded joint 10 according to this embodiment.
  • the plating layer 4 may contain the following optional elements. However, since the inclusion of these elements is not required, the lower limit of the content of these elements is 0%.
  • Si 0.01-10.00% Si contributes to improving red rust resistance.
  • the Si content is preferably 0.01% or more, more preferably 0.05% or more, and even more preferably 0.10% or more.
  • the Si content is set to 10.00% or less, and more preferably, 5.00% or less, 3.00% or less, or 1.00% or less.
  • Ca 0.0001-1.5000%
  • Ca is an element that can adjust the optimal amount of Mg elution to impart red rust resistance.
  • the Ca content is preferably 0.0001% or more.
  • the Ca content is more preferably 0.1000% or more, or 0.3000% or more.
  • the Ca content is set to 1.5000% or less, and more preferably, 1.0000% or less, or 0.8000% or less.
  • Sb 0.0001-0.5000%
  • Pb 0.0001-0.5000%
  • Sr 0.0001-0.5000%
  • Sb, Pb, and Sr contribute to improving red rust resistance.
  • the content of any one of Sb, Pb, and Sr is preferably 0.0001% or more.
  • the contents of Sb, Pb, and Sr are more preferably 0.0005% or more and 0.0050% or more, respectively.
  • the contents of Sb, Pb, and Sr are each set to 0.5000% or less.
  • the contents of Sb, Pb, and Sr are more preferably set to 0.3000% or less and 0.2000% or less, respectively.
  • the content of any one of these elements be 0.0001% or more.
  • the contents of the above elements are more preferably 0.0005% or more and 0.0050% or more, respectively.
  • the content of each of the above elements is set to 1.0000% or less.
  • the content of each of the above elements is more preferably 0.3000% or less and 0.2000% or less, respectively.
  • Sn is an element that forms a Mg 2 Sn phase with Mg and improves red rust resistance.
  • the Sn content is preferably 0.0001% or more.
  • the Sn content is more preferably 0.0200% or more.
  • the Sn content is set to 1.0000% or less, preferably 0.5000% or less, and more preferably 0.3000% or less.
  • Zr, Co, W, Ag, and Li are elements that improve red rust resistance. To reliably obtain this effect, it is preferable that the content of at least one of Zr, Co, W, Ag, and Li is 0.0001% or more.
  • the contents of Zr, Co, W, Ag, and Li are more preferably 0.0005% or more and 0.0020% or more, respectively.
  • excessive contents of Zr, Co, W, Ag, and Li deteriorate red rust resistance. If the content of any one of Zr, Co, W, Ag, and Li exceeds 1.0000%, red rust resistance deteriorates significantly. Therefore, the contents of Zr, Co, W, Ag, and Li are each set to 1.0000% or less.
  • the contents of Zr, Co, W, Ag, and Li are preferably set to 0.5000% or less and 0.1000% or less, respectively.
  • La, Ce, and Y contribute to improving red rust resistance.
  • the content of at least one of La, Ce, and Y is preferably 0.0001% or more.
  • the contents of La, Ce, and Y are more preferably 0.0005% or more and 0.0050% or more, respectively.
  • the contents of La, Ce, and Y are each set to 0.5000% or less.
  • the contents of La, Ce, and Y are more preferably set to 0.2000% or less and 0.1000% or less, respectively.
  • Bi 0.0001 ⁇ 0.5000% In: 0.0001-0.5000%
  • B 0.0001-0.5000%
  • Bi, In, and B contribute to improving red rust resistance.
  • the content of at least one of Bi, In, and B is preferably 0.0001% or more.
  • the contents of Bi, In, and B are more preferably 0.0005% or more and 0.0050% or more, respectively.
  • the contents of Bi, In, and B are each set to 0.5000% or less.
  • the contents of Bi, In, and B are more preferably set to 0.2000% or less and 0.1000% or less, respectively.
  • the chemical composition of the plating layer 4 is measured by the following method.
  • a test piece measuring 20 mm ⁇ 20 mm ⁇ plate thickness was taken from the non-heat-affected zone b of the first steel sheet 1 (at a position at least 100 mm away from the weld bead 3).
  • the plating layer 4 was stripped and dissolved using 10% by volume of HCl containing an inhibitor that suppresses corrosion of the first steel sheet 1, to obtain an acid solution.
  • the obtained acid solution was then subjected to ICP analysis, thereby determining the chemical composition of the plating layer 4. If the welded joint 10 has a painted surface, the paint is removed using Descoat 110B manufactured by Neos Corporation before the above measurement is carried out.
  • the bead back surface (surface A in FIG. 1) of the welded joint 10 according to this embodiment will be described with reference to FIGS.
  • the coating start position of the plating layer 4 is defined as a start point S in a region perpendicular to the extension direction of the weld bead 3 and in a direction away from the toe of the weld bead 3
  • the horizontal length of the observation field is defined as L0
  • the length of the surface irregularities of the plating layer 4 within the observation field is defined as L, so that the following formula (1) is satisfied, and the area ratio of the Mg—Zn phase in the plating layer 4 in the region from the start point S to the 1000 ⁇ m position is 5% or more.
  • Figure 1 is a diagram showing a cross section of a welded joint 10 perpendicular to the extension direction of the weld bead portion 3.
  • Figure 2 is an enlarged view of the heat-affected zone a on the bead back side A in Figure 1. As shown in Figure 2, in the heat-affected zone a on the bead back side A, there is no plating layer 4, and there are areas where the first steel sheet 1 is exposed and areas covered with the plating layer 4.
  • the above formula (1) is satisfied in an area extending from the coating start position of the plating layer 4 as a starting point to a position 1000 ⁇ m from the starting point, which is perpendicular to the extension direction of the weld bead 3 and away from the toe of the weld bead 3, when the horizontal length of the observation field is L0 and the length of the surface irregularities of the plating layer 4 within the observation field is L.
  • the toe of the weld bead 3 refers to the boundary between the weld bead 3 and the first steel plate 1, and is point E shown in Figure 1.
  • the direction away from the toe of the weld bead 3 refers to the direction opposite the weld bead 3 when viewed from the toe E, and is direction D shown in Figure 2.
  • the coating start position (starting point) of the plating layer 4 refers to the boundary between the exposed portion of the first steel plate 1 and the portion covered by the plating layer 4 on the surface of the first steel plate 1 at the back surface A of the bead, and is point S shown in Figures 1 and 2.
  • a heat-affected zone a which has been thermally affected by welding, is present in the region of the bead back surface A from the start point S to a position 1000 ⁇ m away.
  • the size of the heat-affected zone a varies depending on the amount of heat input during welding and the plate thicknesses of the first steel sheet 1 and the second steel sheet 2, but the heat-affected zone a is present in at least a portion (particularly on the side of the start point S) in the region from the start point S to a position 1000 ⁇ m away.
  • the surface unevenness of the plating layer 4 in the heat-affected zone a on the bead back surface A is preferably controlled, thereby improving paint adhesion on the bead back surface A.
  • the chemical composition of the plating layer 4 in the heat-affected zone a may be, for example, in mass %, Zn+Mg: 50% or more, Fe: 5% or less, and the balance being Al and impurities.
  • Figure 3 is an enlarged view of a portion of the region from the starting point S to 1000 ⁇ m in Figure 2. Note that Figure 3 is upside down compared to Figure 2.
  • Zn in the plating layer 4 evaporates due to the heat during welding.
  • plating layer 4 contains Mg and Al in addition to Zn and undergoes the manufacturing conditions described below, Zn bonds with Mg. This forms an Mg-Zn phase with a higher melting point.
  • Zn evaporates due to the heat during welding, but the Mg-Zn phase remains in the plating layer 4 without evaporating, creating unevenness on the surface of plating layer 4.
  • the uneven surface of plating layer 4 provides an anchor effect, improving paint adhesion.
  • the value of the left side of the above formula (1) is set to be 3 or more.
  • the value of the left side of the above formula (1) may be, for example, 30 or less, or 25 or less.
  • the length L of the surface irregularities of the plating layer 4 is measured by the following method.
  • a scanning electron microscope is used to observe the cross section of the first steel sheet along the sheet thickness direction as shown in Figure 3, and the length of the surface irregularities of the plating layer 4 is measured in ⁇ m.
  • the length of the surface irregularities of the plating layer 4 is measured in ⁇ m for an arbitrarily selected observation field of 200 ⁇ m in the horizontal direction ⁇ 120 ⁇ m in the sheet thickness direction. Note that L0 is 200 ⁇ m.
  • the above operation is performed for five arbitrarily selected fields of view from the region where the plating layer remains in the region from the start point S to a position 1000 ⁇ m, and the average value is calculated to obtain L.
  • the obtained L is used to calculate the left side of equation (1). If there are multiple start points S on the bead back surface A, the above-mentioned measurements are carried out for a region extending from the start point S closest to the center of the weld bead 3 to a position 1000 ⁇ m away when viewing the cross section of the first steel plate 1 through the plate thickness as shown in Figure 1. In the case of the T-joint of Figure 5, the above-mentioned measurements are carried out for a region extending from the start point S closest to the center of any of the weld bead 3 to a position 1000 ⁇ m away.
  • a 20 mm x 15 mm x thickness sample is taken from the welded joint 10. After embedding in resin, the cross section is mirror-polished to a finished finish before measurement. A backscattered electron image is then taken of the cross section, and based on differences in brightness, the region located closest to the center of the plate thickness is identified as the first steel plate 1, and the remaining layers are identified as the plating layer 4. If the welded joint 10 has a painted surface, the SEM-EPMA analysis described below is performed on the intermediate layer in the backscattered electron image.
  • the resulting chemical composition satisfies the chemical composition of the plating layer 4 in the heat-affected zone a described above (by mass %, Zn + Mg: 50% or more, Fe: 5% or less, balance Al and impurities), that layer is identified as the plating layer 4 in the heat-affected zone a.
  • the Mg—Zn phase has the effect of enhancing red rust resistance. If the area ratio of the Mg—Zn phase in the coating layer 4 in the region from the starting point S to 1000 ⁇ m is less than 5%, the red rust resistance at the bead back surface A will deteriorate. Therefore, the area ratio of the Mg—Zn phase is set to 5% or more. To further improve the red rust resistance at the bead back surface A, the Mg content in the coating layer 4 is increased and the area ratio of the Mg—Zn phase is preferably set to 20% or more, and more preferably 30% or more. The area ratio of the Mg—Zn phase may be 95% or less.
  • the area ratio of the Mg—Zn phase in the plating layer 4 is measured by the following method.
  • a sample is taken using the same method as used to measure the length L of the surface irregularities of the plating layer 4 described above, and the cross section is mirror-polished to a finished surface.
  • a quantitative analysis of elements (Mg, Zn, Fe) is performed on the cross section by point analysis using a SEM-EPMA (JXA-8500F, manufactured by JEOL).
  • a phase with a Mg content of 20 to 60%, a Zn content of 40 to 80%, and the remainder of 5% or less is identified as the Mg—Zn phase.
  • the above analysis is performed on the plating layer 4 in the region from the starting point S to a position 1000 ⁇ m away, thereby obtaining the area ratio of the Mg—Zn phase.
  • the distribution image is measured over a range of 1000 ⁇ m ⁇ the plating layer thickness at an acceleration voltage of 15 kV, a magnification of 5000, and a measurement interval of 1.0 ⁇ m.
  • the area ratio is calculated using the "Analyze" function of the image analysis software "ImageJ.”
  • the plating layer 4 of the non-heat-affected zone b has an Mg 2 Sn phase.
  • Mg 2 Sn phase By having an Mg 2 Sn phase in the plating layer 4 of the non-heat-affected zone b, it is possible to improve the red rust resistance of the non-heat-affected zone.
  • Whether or not the plating layer 4 in the non-heat-affected zone b has an Mg 2 Sn phase is determined by the following method. Because the Mg 2 Sn phase is present in small amounts, its presence is detected and confirmed by X-ray diffraction measurement using the ⁇ -2 ⁇ method. X-ray diffraction measurement for detecting the Mg 2 Sn phase is performed using the ⁇ -2 ⁇ measurement method. In addition, X-ray diffraction measurement is performed on the plating layer 4 of a 20 mm square sample taken from the non-heat-affected zone b (a position 100 mm or more away from the weld bead portion 3) using K ⁇ rays from a Cu tube. If a peak is detected at 23.4 ⁇ 0.3°, it is determined that the Mg 2 Sn phase is present.
  • the coating weight of the plating layer 4 per side may be, for example, within the range of 20 to 250 g/ m2 .
  • the coating weight per side may be, for example, within the range of 20 to 250 g/ m2 .
  • red rust resistance can be further improved.
  • the coating weight per side to 250 g/ m2 or less, workability can be further improved.
  • the welded joint 10 described above is a lap joint
  • the welded joint 10 according to this embodiment is not limited to this.
  • the welded joint 10 according to this embodiment may be, for example, a butt joint having a cross section as shown in FIG. 4, a T-joint having a cross section as shown in FIG. 5, or some other type of joint.
  • surface B shown in FIG. 4 is considered to be the back surface of the bead.
  • surface C shown in FIG. 5 (the surface of the first steel plate 1 opposite the surface welded to the second steel plate 2) is considered to be the back surface of the bead.
  • the weld bead 3 does not reach the bead back surface B, but the weld bead 3 may reach the bead back surface B. Also, the weld bead 3 may be formed on both sides. When the weld bead 3 reaches the bead back surface B, the surface with the smaller weld bead 3 is considered to be the bead back surface B. When the weld bead 3 is formed on both sides, the surface with the smaller weld bead 3 is considered to be the bead back surface B, and if the sizes of the weld bead 3 on both surfaces are the same, either one of the surfaces is considered to be the bead back surface B.
  • the first steel plate has been described, but the same applies even if the first steel plate and the second steel plate are interchanged.
  • a preferred method for manufacturing the welded joint 10 according to this embodiment is as follows: a step of shot blasting the first steel plate; annealing; a step of applying plating; cooling; and a step of welding the first steel plate 1 and the second steel plate 2 together.
  • the manufacturing method for the second steel plate is not particularly limited, but it may be manufactured by the same method as that for the first steel plate. Each step will be explained below.
  • the first steel sheet 1 is subjected to shot blasting to impart strain before plating.
  • preferred strain is imparted to the first steel sheet 1, which, combined with cooling after plating (described later), can promote alloying in the plating layer 4.
  • the morphology of the plating layer 4 can be controlled in a preferred manner.
  • steel balls with a median particle size of 40 to 450 ⁇ m can be used.
  • An example of the equipment is the TSH30 manufactured by IKK Shot Co., Ltd.
  • the shot blasting rate is preferably 10 to 500 kg/ m2 . If the shot blasting rate is less than 10 kg/ m2 , it may be difficult to impart strain to the first steel sheet 1, and as a result, it may be difficult to control the surface unevenness of the plating layer 4 in a desirable manner.
  • strain can also be imparted by surface grinding, the amount of strain imparted by surface grinding is smaller than that imparted by shot blasting, and therefore the desired amount of strain cannot be imparted.
  • the first steel sheet 1 is annealed.
  • the annealing temperature during annealing is in the temperature range of 400 to 600°C, and the holding time in this temperature range (annealing time) is more than 0 seconds and not more than 100 seconds. If the annealing temperature exceeds 600°C or the annealing time exceeds 100 seconds, strain in the first steel sheet 1 and the second steel sheet 2 is released, and as a result, the surface unevenness in the plating layer 4 may not be controlled in a desirable manner. If the annealing temperature is less than 400°C, or if annealing is not performed, the plating may not be applied in a desirable manner.
  • the temperature referred to here is the surface temperature at the center of the plate surface of the first steel plate 1, and can be measured using a thermocouple joined by spot welding, for example.
  • the first steel sheet 1 After annealing, the first steel sheet 1 is immersed in a coating bath.
  • the composition of the coating bath is controlled so that the coating layer 4 has the chemical composition of the coating layer 4 described above.
  • the temperature of the coating bath is preferably 600°C or lower. If the temperature of the coating bath exceeds 600°C, strain in the first steel sheet 1 is released, and as a result, the surface unevenness in the coating layer 4 may not be controlled in a desirable manner.
  • the coating weight may be adjusted by gas wiping or the like.
  • the material After plating, it is preferable to cool the material using a cooling gas with a dew point of -20°C or lower at an average cooling rate of 15°C/s or higher in the temperature range from the bath temperature to 250°C. Then, it is preferable to cool the material using a cooling gas with a dew point of 0°C or higher at an average cooling rate of 5°C/s or lower in the temperature range from 250 to 50°C. If the dew point of the cooling gas exceeds ⁇ 20° C. during cooling in a temperature range of from the bath temperature to 250° C., coarse oxides are formed on the surface of the plating layer, and as a result, it may be impossible to suitably control the morphology of the plating layer 4.
  • the average cooling rate is less than 15° C./s during cooling in a temperature range of from the bath temperature to 250° C., coarse surface oxides are formed during cooling, and as a result, it may be impossible to suitably control the surface unevenness of the plating layer 4.
  • the dew point of the cooling gas is less than 0°C during cooling in the temperature range of 250 to 50°C, it may be impossible to form sufficient oxides of Al and Mg in the plating layer 4, resulting in excessive evaporation of Zn in the plating layer 4 and making it impossible to suitably control the morphology of the plating layer 4.
  • the average cooling rate in the temperature range of 250 to 50°C exceeds 5°C/s, it may be impossible to suitably control the surface unevenness of the plating layer 4.
  • the welding method is not particularly limited as long as it can form a weld bead 3.
  • arc welding or laser welding the following conditions can be used, respectively.
  • Welding current 250A Welding voltage: 26.4V Welding speed: 100 cm/min Welding gas: 20% CO 2 + Ar Gas flow rate: 20 L/min Welding wire: YGW16 manufactured by Nippon Steel Welding Co., Ltd., ⁇ 1.2 mm (C: 0.1 mass%, Si: 0.80 mass%, Mn: 1.5 mass%, P: 0.015 mass%, S: 0.008 mass%, Cu: 0.36 mass%) Welding torch tilt angle: 45°
  • Laser welding output 7kW Welding speed: 400 cm/min. Forward/reverse angle: 0°
  • the method described above allows for the stable production of the welded joint 10 according to this embodiment. Because the welded joint 10 according to this embodiment has excellent paint adhesion, the surface may be painted to improve the corrosion resistance of the welded joint 10, for example.
  • the first steel plate and the second steel plate having the mechanical properties of SS400 of JIS G 3101:2020 were subjected to shot blasting, annealing, plating and cooling under the conditions described in Tables 2A and 2B, and then welded by the welding methods shown in Tables 3A and 3B to obtain lap joints (welded joints).
  • the first and second steel sheets were 200 mm x 100 mm x 3.2 mm in size.
  • the lifting speed from the plating bath was 20 to 200 mm/sec. During lifting, the coating weight was adjusted by gas wiping using N2 gas. Conditions not listed in the table were the same as those described above.
  • the steel plate size was 150 x 50 mm for the upper plate (first steel plate) and 150 x 30 mm for the lower plate (second steel plate), with an overlap of 10 mm and a plate gap of 0 mm.
  • the steel plate size was 150 x 50 mm for the upper plate side (first steel plate) and 150 x 30 mm for the lower plate side (second steel plate), with an overlap of 50 mm and a plate gap of 0 mm.
  • the chemical composition of the coating layer in the non-heat-affected zone, the length of the surface irregularities of the coating layer in the region from the starting point to the position 1000 ⁇ m on the back surface of the bead, and the area ratio of the Mg—Zn phase in the region were measured using the methods described above, and the presence or absence of an Mg 2 Sn phase was also determined.
  • the measurement results of the chemical composition of the coating layer are shown in Tables 1A and 1B, and the other measurement results are shown in Tables 3A and 3B.
  • Paint Adhesion Evaluation The painted welded joints were subjected to a combined cyclic corrosion test in accordance with JASO (M609-91). After the test, paint adhesion was evaluated in a region from the starting point to a position 1000 ⁇ m from the backside of the bead of the welded joint, depending on the timing of blister occurrence. The region was observed with an optical microscope, and if a bulge in the paint film was confirmed, it was determined that a blister had occurred.
  • the evaluation criteria were as follows. A rating of A or higher was determined to be excellent paint adhesion on the backside of the bead and was judged to be pass.
  • a rating of B was determined to be poor paint adhesion on the backside of the bead and was judged to be fail.
  • AAA No blistering after 180 cycles AA: Blisters occurred after 120 cycles or more and less than 180 cycles A: Blisters occurred after 60 cycles or more and less than 120 cycles B: Blisters occurred after less than 60 cycles
  • red rust resistance was evaluated in a region from the starting point to a position of 1000 ⁇ m on the back surface of the bead of the welded joint according to the timing of red rust occurrence. The region was observed with an optical microscope, and if red rust was confirmed, it was determined that red rust had occurred.
  • the evaluation criteria were as follows. A rating of A or higher was determined to be excellent in red rust resistance on the back surface of the bead and was judged to be pass. On the other hand, a rating of B was determined to be poor in red rust resistance on the back surface of the bead and was judged to be fail.
  • AAA No red rust occurs after 360 cycles. AA: Red rust occurs after 150 or more cycles but less than 360 cycles. A: Red rust occurs after 90 or more cycles but less than 150 cycles. B: Red rust occurs after less than 90 cycles.
  • the red rust resistance of the non-heat-affected zone of the welded joint was also evaluated using the same method.
  • the evaluation area was a 50 mm x 50 mm area on the surface having the weld bead, located at a position 100 mm or more away from the weld bead.
  • the evaluation criteria were as follows, and a rating of AA or higher was considered to be excellent in red rust resistance in the non-heat-affected zone.
  • AAA No red rust occurs after 360 cycles.
  • AA Red rust occurs after 150 or more cycles but less than 360 cycles.
  • B Red rust occurs after less than 90 cycles.
  • the examples according to the present disclosure provided welded joints with excellent paint adhesion and red rust resistance on the backside of the bead.
  • the comparative examples showed deterioration in one or more properties.
  • the desired amount of strain could not be imparted, and the length L of the surface irregularities of the plating layer on the back surface of the bead could not be controlled in a preferable manner.

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  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Plasma & Fusion (AREA)
  • Coating With Molten Metal (AREA)

Abstract

Un joint soudé 10 a une première plaque d'acier 1 et une seconde plaque d'acier 2 ayant une couche de placage 4 au moins partiellement soudée à celle-ci. Lorsqu'une section transversale orthogonale à la direction d'extension du cordon de soudure 3 est observée, il est découvert que : lorsque, sur une surface arrière A de la surface ayant un cordon de soudure 3, dans une direction orthogonale à la direction d'extension du cordon de soudure 3 et s'éloignant d'une extrémité E du cordon de soudure 3, la position de début de recouvrement de la couche de placage 4 est désignée comme point de départ S, la longueur horizontale d'un champ de vision d'observation pour une région s'étendant du point de départ S à une position éloignée de 1000 µm est désignée par L0, et la longueur concavo-convexe de surface de la couche de placage 4 dans le champ de vision d'observation est désignée par L, la formule (1) est satisfaite. Le rapport de surface de la phase Mg-Zn dans la couche de placage 4 dans la région s'étendant du point de départ S à la position éloignée de 1000 µm est d'au moins 5 %.　Formule (1) : (L-L0)/L0×100≥3
PCT/JP2024/017420 2024-05-10 2024-05-10 Joint soudé Pending WO2025234086A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/JP2024/017420 WO2025234086A1 (fr) 2024-05-10 2024-05-10 Joint soudé

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018139620A1 (fr) * 2017-01-27 2018-08-02 新日鐵住金株式会社 Matériau d'acier plaqué
WO2023145824A1 (fr) * 2022-01-31 2023-08-03 日本製鉄株式会社 Joint soudé
JP2024502759A (ja) * 2020-12-21 2024-01-23 ポスコ カンパニー リミテッド 耐割れ性に優れた溶接構造部材及びその製造方法

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018139620A1 (fr) * 2017-01-27 2018-08-02 新日鐵住金株式会社 Matériau d'acier plaqué
JP2024502759A (ja) * 2020-12-21 2024-01-23 ポスコ カンパニー リミテッド 耐割れ性に優れた溶接構造部材及びその製造方法
WO2023145824A1 (fr) * 2022-01-31 2023-08-03 日本製鉄株式会社 Joint soudé

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