WO2021066192A1 - 溶接継手、及び自動車部品 - Google Patents

溶接継手、及び自動車部品 Download PDF

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Publication number
WO2021066192A1
WO2021066192A1 PCT/JP2020/037775 JP2020037775W WO2021066192A1 WO 2021066192 A1 WO2021066192 A1 WO 2021066192A1 JP 2020037775 W JP2020037775 W JP 2020037775W WO 2021066192 A1 WO2021066192 A1 WO 2021066192A1
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WIPO (PCT)
Prior art keywords
weld metal
steel base
welding
base material
valley
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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.)
Ceased
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PCT/JP2020/037775
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English (en)
French (fr)
Japanese (ja)
Inventor
和貴 松田
真二 児玉
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Nippon Steel Corp
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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 US17/761,196 priority Critical patent/US12202075B2/en
Priority to CN202080065718.2A priority patent/CN114423558B/zh
Priority to JP2021551652A priority patent/JP7368760B2/ja
Priority to EP20872949.1A priority patent/EP4039396A4/en
Publication of WO2021066192A1 publication Critical patent/WO2021066192A1/ja
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • 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
    • B23K31/00—Processes relevant to this subclass, specially adapted for particular articles or purposes, but not covered by any single one of main groups B23K1/00 - B23K28/00
    • 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
    • B23K9/02—Seam welding; Backing means; Inserts
    • B23K9/0216—Seam profiling, e.g. weaving, multilayer
    • 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
    • B23K31/00—Processes relevant to this subclass, specially adapted for particular articles or purposes, but not covered by any single one of main groups B23K1/00 - B23K28/00
    • B23K31/02—Processes relevant to this subclass, specially adapted for particular articles or purposes, but not covered by any single one of main groups B23K1/00 - B23K28/00 relating to soldering or welding
    • 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
    • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/062—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam
    • B23K26/0622—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam by shaping pulses
    • 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
    • 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
    • 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
    • B23K2101/00—Articles made by soldering, welding or cutting
    • B23K2101/006—Vehicles
    • 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
    • B23K2103/00—Materials to be soldered, welded or cut
    • B23K2103/02—Iron or ferrous alloys
    • B23K2103/04—Steel or steel alloys
    • 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
    • B23K2103/00—Materials to be soldered, welded or cut
    • B23K2103/08—Non-ferrous metals or alloys
    • B23K2103/10—Aluminium or alloys thereof

Definitions

  • This disclosure relates to welded joints and automobile parts.
  • the automobile parts include welded joints having a plurality of high-strength steel plates as a base material.
  • Non-Patent Document 1 "By making the weld metal (welding bead) meander, the toe portion of the toe portion of the weld metal is raised from the weld metal side to the toe portion of the toe portion of the meandering weld metal. A crack is generated from the melting boundary of the region protruding toward the material side, the crack grows along the toe of the meandering weld metal, and the toe is the weld metal at the valley (the toe of the meandering weld metal). By coalescing cracks near (the region closer to the side), the time required for crack coalescing increases and the fatigue life is improved. "
  • Non-Patent Document 1 M.D. Chapetti, J. L. Otegui. International Journal of Fatigue, Vol.19, No.10, pp.667-675, 1997
  • the technique of Non-Patent Document 1 is to combine cracks generated at the melting boundary of the peak portion of the weld toe in the vicinity of the valley portion when a steel base material with a thick plate thickness is welded. It is a technology that increases the time required and improves the fatigue life. That is, the technique of Non-Patent Document 1 is a technique of improving the fatigue life when a steel base material having a large plate thickness, which has a large fatigue crack propagation life in the fatigue life, is welded.
  • structures in which thin steel plates are welded are smaller in size and thinner, such as automobile members. , The generated fatigue cracks are likely to become through cracks.
  • the fatigue crack propagation life occupies the fatigue life is small, and the fatigue crack generation life is dominant. Therefore, when a steel base material having a thin plate thickness is welded, the fatigue life is not improved by the same mechanism as when a steel base material having a thick plate thickness is welded.
  • an object of the present disclosure is to provide a welded joint having excellent fatigue strength and an automobile part having the same, even if a pair of steel base materials having a thin plate thickness and at least one having a tensile strength of 780 MPa or more are welded. To provide.
  • Means for solving the problem include the following aspects.
  • a pair of steel base materials having a plate thickness of 0.4 to 4.0 mm and at least one having a tensile strength of 780 MPa or more. It is a weld metal for welding the pair of steel base materials, and when the weld metal is viewed in a plan view, the toe of the weld metal has a peak and a valley, and the apex and the valley of the adjacent peaks are adjacent to each other.
  • the average distance between the bottom point of the portion and the welding line direction and the direction orthogonal to the welding line direction is 3.0 mm or less, and the distance between the apex of the adjacent mountain portion and the bottom point of the valley portion is the distance perpendicular to the welding line direction.
  • Welded metal with an average number of 2 to 30 pieces / 15 mm including the peaks and valleys of 0.1 mm to 3.0 mm, and Welded fittings with.
  • the total number of the peaks and valleys where the distance between the apex of the adjacent peak and the bottom of the valley in the direction orthogonal to the welding line direction is 0.1 mm to 3.0 mm is The welded joint according to [2], which is 4 to 9 pieces / 15 mm.
  • FIG. 6A shows a cross-sectional view of the mountain portion. It is an example of the weld metal of the welded joint of the present disclosure, and is an optical micrograph after chemical etching the cross section of the weld metal at the time of weaving welding.
  • FIG. 6B shows a cross-sectional view of a valley portion of the weld metal. It is a schematic diagram for demonstrating the calculation method of "the number of waviness and the distance between a peak part and a valley part" in the weld metal of the welded joint of this disclosure. It is a schematic diagram for demonstrating "weaving amplitude" in an example of the manufacturing method of the welded joint of this disclosure.
  • the numerical range represented by using “-" means a range including the numerical values before and after "-" as the lower limit value and the upper limit value.
  • the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of another numerical range described stepwise.
  • the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples.
  • the term "process” is included in this term as long as the intended purpose of the process is achieved, not only in an independent process but also in cases where it cannot be clearly distinguished from other processes.
  • the "combination of preferred embodiments" is a more preferred embodiment.
  • the “mountain portion” indicates a region where the toe end portion (specifically, the molten boundary) protrudes from the weld metal side to the base metal side when the weld metal is viewed in a plan view.
  • the “top of the mountain” indicates the pole that protrudes to the most base material side of the region. That is, the “vertex of the mountain portion” indicates the point where the shortest length from the toe portion (specifically, the melting boundary) protruding from the weld metal side to the base metal side to the weld line is the longest.
  • the “valley” indicates a region where the toe (specifically, the molten boundary) is closer to the weld metal when the weld metal is viewed in a plan view.
  • the “bottom point of the valley” indicates the pole closest to the weld metal side in the region. That is, the “bottom point of the valley portion” indicates the point where the shortest length from the toe portion (specifically, the melting boundary) closer to the weld metal side to the weld line is the shortest.
  • “Looking at the weld metal in a plan view” means observing the weld metal from the plate thickness direction of the steel base material on the side where the peak portion at the toe of the weld metal to be observed protrudes.
  • the welded joint of the present disclosure is A pair of steel base materials having a plate thickness of 0.4 to 4.0 mm and at least one having a tensile strength of 780 MPa or more. It is a weld metal that welds the pair of steel base materials, and when the weld metal is viewed in a plan view, the toe of the weld metal has peaks and valleys, and the peaks and valleys of adjacent peaks.
  • the average distance to the bottom point in the direction perpendicular to the welding line direction is 3.0 mm or less, and the distance between the apex of the adjacent mountain part and the bottom point of the valley part in the direction orthogonal to the welding line direction is 0.1 mm or more.
  • the welded joint of the present disclosure is excellent in fatigue strength even when a pair of steel base materials having a thin plate thickness and at least one having a tensile strength of 780 MPa or more are welded.
  • the welded joint of the present disclosure has been found based on the following findings.
  • the weld metal may be undermatched (a state in which the weld metal strength is lower than the steel base material strength).
  • a weld metal (weld bead) welded without welding such as weaving welding or wave pulse welding causes fatigue cracks from any position on the toe of the weld metal, that is, structural stress concentration. Fatigue cracks occur from the position where the fatigue strength is the lowest, which is a combination of local stress concentration or strength. Therefore, the fatigue strength of the weld metal tends to decrease.
  • the number and distance between the peaks and valleys at the toes of the meandering weld metal when welding a thin steel base material, which has a large ratio of fatigue cracking life to the fatigue life, should be adjusted appropriately. Then, the starting point of the fatigue crack can be limited to the mountain portion, and the stress concentration at the starting point can be further reduced. As a result, the fatigue crack generation life of the weld metal is extended, and the fatigue strength is improved.
  • the welded joint of the present disclosure is excellent in fatigue strength even when a pair of steel base materials having a thin plate thickness and at least one having a tensile strength of 780 MPa or more are welded.
  • the weld metal when a steel base material having a thin plate thickness is welded by, for example, weaving welding or wave pulse welding, the weld metal may be closed and the throat thickness may be reduced.
  • the "throat thickness" of the weld metal decreases, the stress generated in the weld metal tends to increase when stress is applied from the outside.
  • the weld metal In a steel base material with a tensile strength of less than 780 MPa, the weld metal often has a higher strength (overmatch) than the steel base material, so it is unlikely to affect the fatigue strength.
  • the weld metal Is often lower in strength (undermatch) than the steel base material, which may lead to a decrease in fatigue strength.
  • At least one of the pair of steel base materials may contain 0.100 to 1.000% by mass of Al.
  • the welded joint 10 of the present disclosure includes, for example, a pair of steel base materials overlapped with each other (in FIG. 1, 1 is a lower first steel base material, and 2 is an upper first steel base material. 2 shows the steel base material), and the weld metal (weld bead) 3 extending along the corner 4 formed by the surface 1a of the first steel base material 1 and the end surface 2a of the second steel base material 2.
  • An example is a lap fillet welded joint provided with.
  • the surface 1a of the first steel base material 1 (the surface facing the plate thickness direction) and the end surface 2a of the second steel base material 2 (for example, the steel base material is a flat plate).
  • the aspect of the lap fillet welded joint in which the weld metal 3 extends along the corner 4 formed by the surface facing the plate thickness direction and the direction orthogonal to the plate thickness direction is shown, but is limited to this aspect. It is not something that can be done. Specifically, the following aspects can be mentioned.
  • the first steel base material 1 and the second steel base material 2 are arranged in an L-shape or a T-shape, and the surfaces of the first steel base material 1 and the second steel base material 2 face each other (opposing in the plate thickness direction).
  • the end faces of the first steel base material 1 and the second steel base material 2 (for example, when the steel base material is a flat plate, the surfaces facing each other in the plate thickness direction) are abutted and arranged along the abutting portion.
  • Other modes of well-known welded welded joints such as groove joints and edge welded joints.
  • FIG. 1 is a view of the welded joint 10 in a cross section orthogonal to the welding line W (see FIG. 2) of the weld metal 3.
  • the direction parallel to the welding line W is the Z-axis direction
  • the direction orthogonal to the Z-axis direction and parallel to the surface 1a of the first steel base material 1 is the X-axis direction.
  • the direction orthogonal to the X-axis direction and the Z-axis direction and parallel to the plate thickness direction of the first steel base material 1 is defined as the Y-axis direction.
  • the toe portion of the weld metal 3 has peaks and valleys in the welding line direction (weld metal, that is, the longitudinal direction of the weld bead) (see FIG. 3).
  • B indicates the “bottom point of the valley”
  • T indicates the “top of the mountain”.
  • the weld metal of the present disclosure has an average distance (hereinafter, also referred to as "distance between the peak and valley”) in the direction orthogonal to the welding line direction between the apex of the adjacent peak and the bottom of the valley. It is 0 mm or less.
  • the average distance between the peaks and valleys in the direction orthogonal to the welding line direction exceeds 3.0 mm, the shape of the weld metal 3 is likely to be locally disturbed, resulting in a decrease in fatigue strength. Local disturbance in the shape of the weld metal 3 is particularly likely to occur when welding is performed by weaving welding. Therefore, the average distance between the peaks and valleys in the direction orthogonal to the welding line is 3.0 mm or less. From the viewpoint of improving fatigue strength, the average distance between the peaks and valleys is preferably 2.8 mm or less, more preferably 2.5 mm or less, and even more preferably 2.0 mm or less.
  • the total number of peaks and valleys where the distance between the apex of the adjacent peak and the bottom of the valley in the direction orthogonal to the welding line direction is 0.1 mm to 3.0 mm (hereinafter, "the number of swells"”. (Also referred to as), but 2 to 30 pieces / 15 mm (see FIG. 4).
  • the number of swells is the total number of peaks and valleys that exist within a range of 15 mm in the direction of the weld line.
  • B indicates the “bottom point of the valley” and T indicates the “top of the mountain”.
  • W1 indicates "welding line direction”
  • 31 indicates “welded metal”
  • 11 indicates "steel base material”. A1 to A4 will be described later.
  • the apex (or the bottom point of the valley) of any mountain is the bottom point (or the bottom of the valley) of one of the two valleys (or two peaks) existing on both sides.
  • the apex (or the bottom point of the valley) of the arbitrary mountain portion is not counted as the number of undulations.
  • the number of swells and the distance between the peaks and valleys are measured by skipping adjacent peaks and valleys with a distance of less than 0.1 mm (see FIG. 5).
  • the meaning of the reference numerals in FIG. 5 is the same as that in FIG.
  • the apex of any mountain is the same as the apex of both valleys (or the apex of the mountain) of the two valleys (or two peaks) existing on both sides. If the distance in the direction orthogonal to the welding line direction is less than 0.1 mm or more than 3.0 mm, the apex (or the bottom point of the valley) of any mountain portion is not counted as the number of undulations.
  • the apex (or the apex of the valley) of any mountain is the apex (or the apex of the mountain) of at least one of the two valleys (or two peaks) existing on both sides.
  • the apex (or the bottom point of the valley) of the arbitrary peak portion is counted as the number of the undulations.
  • the distances "A1 to A4" and "A” between the apex of the adjacent mountain and the bottom of the valley in the direction orthogonal to the welding line direction are the distance between the mountain and the valley.
  • the distance in the X-axis direction that is, the distance along the direction orthogonal to the welding line direction corresponding to the X direction in FIG. 1) is shown.
  • the number of undulations and the distance between the peak and the valley are based on the above criteria and are in an arbitrary range of the weld metal 3 excluding 5 mm each at the start and end (minimum, a range of 15 mm or more in length in the welding line direction). ) Is measured and used as the average value. If the number of undulations is less than 2/15 mm, the function of localizing the origin of fatigue cracks in the mountainous area is lost. If the number of undulations exceeds 30/15 mm, the number of peaks that are the starting points of fatigue cracks is too large, and the advantage of localizing the starting points of fatigue cracks in the peaks is lost. Therefore, the number of swells is within the above range. From the viewpoint of improving fatigue strength, the number of waviness is preferably 2 to 28/15 mm, more preferably 3 to 15/15 mm.
  • the number of swells is more preferably 4 to 9/15 mm, and the fatigue strength is further improved by setting the number of swells within the range.
  • the reason is presumed to be as follows.
  • the region where the occurrence of fatigue cracks is suppressed due to the structure of the valley portion of the weld metal can easily extend to a range close to the apex of the mountain portion. Therefore, the starting point of the fatigue crack approaches the apex of the mountain part where the toe shape is gentle. As a result, it is presumed that the fatigue crack generation life of the weld metal is further extended and the fatigue strength is further improved.
  • a method of calculating "the number of swells and the distance between the peak and the valley" when the welding line of the weld metal 3 is curved will be described with reference to FIG. 7.
  • a welding line W is drawn on the welding metal 3, and the toe of the welding metal 3 to be measured is directed upward.
  • the number of waviness and the distance between the peak and the valley are measured in an arbitrary range of the weld metal 3 (at least, a range of 15 mm or more in the direction of the welding line) excluding 5 mm at the beginning and the end. Measure the length Wr of the weld line.
  • the length Wr of the weld line may be measured by a device that measures the length directly on the weld line, or an arbitrary curve f (x) may be measured from an image of the weld metal 3 in a plan view.
  • f (x) may be measured from an image of the weld metal 3 in a plan view.
  • the shortest length of the mountain part Is simply referred to as “the shortest length of the mountain part", and the shortest lengths T1, T3, T5, and T7 from the bottom point of the valley to the welding line (hereinafter, simply “from the bottom of the valley to the welding line”).
  • the shortest length of the valley is also called “the shortest length of the valley”).
  • a straight line having the same length as the welding line length Wr is drawn on an arbitrary recording medium (for example, paper) (hereinafter, the straight line is also referred to as a "simulated welding line").
  • a point “P1” is drawn at the same position as the shortest valley length T1 from the simulated welding line at the upper part of the simulated welding line and in the direction orthogonal to the simulated welding line. Then, the point "P1” is set as the bottom point of the valley.
  • a point "P2" is written on the right side of the "P1", above the simulated welding line, and at the same position as the shortest length T2 of the mountain portion from the simulated welding line in the direction orthogonal to the simulated welding line.
  • the point "P2" is set as the apex of the mountain part.
  • the distance between the points "P1" and “P2” along the simulated welding line is set to be the same as the distance Wr1.
  • the procedure after "P3" will be described in the same manner as in “P2". This work will be carried out in all of the numbered peaks and valleys.
  • the distance between the apex of the adjacent mountain part and the bottom point of the valley part in the direction orthogonal to the simulated welding line direction is set in the direction orthogonal to the welding line direction of the apex of the adjacent mountain part and the bottom point of the valley part.
  • Distance A ".
  • At least one toe has a distance of 3.0 mm or less between the peak and the valley when the weld metal is viewed in a plan view, and the number of undulations is 2. It suffices to fill up to 30 pieces / 15 mm.
  • At least the toes on the steel base material on the side where fatigue cracks are more likely to occur at the toes have a distance between the peaks and valleys. It is preferably 3.0 mm or less, and the number of waviness is preferably 2 to 30/15 mm.
  • fatigue cracks are likely to occur from the toe on that side.
  • fatigue cracks at the toe are, for example, when the shape of the toe is steep, when there is a welding defect (for example, undercut, etc.) near the toe, the toe It tends to occur when spatter adheres in the vicinity.
  • the features of the toe on the side where fatigue cracks are likely to occur for each type of welded joint are as follows.
  • the "waviness of the toe of the weld metal 3" on the lower steel base material 1 often affects the fatigue strength. Therefore, in the present disclosure, the number of undulations of the "toe portion of the weld metal 3" on the lower steel base material 1 and the distance between the peak portion and the valley portion may be within the above ranges.
  • the number of swells of the "toe of weld metal 3" on the steel base material on the side where fatigue cracks are a concern and the distance between the peaks and valleys are within the above range. Anything is fine.
  • the "toe of the weld metal 3" on the steel base material on the main plate side (stress transmission side) and the "welded metal 3" on the steel base material on the side with a short welding leg length are different, on the steel base material on the side with a thin plate thickness Since fatigue cracks are likely to occur from a certain "toe portion of the weld metal 3", the number of undulations on these sides and the distance between the peak and the valley may be within the above range.
  • the chemical composition of the weld metal 3 is not particularly limited, but in terms of mass%, C: 0.01 to 0.50%. Si: 0.005 to 2.000% Mn: 0.01 to 3.00% P: 0.100% or less S: A chemical composition composed of steel containing 0.0500% or less can be exemplified. Specifically, for example, the weld metal 3 has C: 0.01 to 0.50%, Si: 0.005 to 2.000%, Mn: 0.01 to 3.00%, P: 0.100. % Or less, and S: 0.0500% or less, and optionally an optional element, and the balance is Fe and impurities.
  • the chemical composition of the weld metal 3 is the chemical composition inside the weld metal 3 which is separated from the surface of the weld metal 3 and the fusion boundary by 500 ⁇ m or more, respectively.
  • the amount of C is preferably 0.01% or more.
  • the amount of C is preferably 0.50% or less.
  • Si 0.005 to 2.000%- Si is an element that functions as a strength adjusting and deoxidizing material for the weld metal 3. In addition, therefore, when the amount of Si is extremely reduced, the cost of refining is increased.
  • the amount of Si is preferably 0.005% or more.
  • the amount of Si is preferably 2.000% or less.
  • Mn 0.01 to 3.00%- Mn is an element that increases the hardenability of the weld metal 3. Therefore, the amount of Mn is preferably 0.01% or more. If the amount of Mn is large, the toughness decreases. Therefore, the amount of Mn is preferably 3.00% or less.
  • the amount of P is preferably 0.100% or less.
  • the amount of P may be 0%, but it is economically disadvantageous to completely remove P mixed from the raw material of the steel base material or the like. Therefore, the amount of P is preferably 0.001% or more.
  • the amount of S is preferably 0.0500% or less, while it is economically disadvantageous to completely remove S mixed from the raw material of the steel base material or the like. Therefore, the amount of S is preferably 0.0001% or more.
  • the chemical composition of the weld metal 3 is, as an arbitrary element, in mass% within a range that does not affect the fatigue strength of the weld metal 3.
  • Ti: 0-0.5%, Cr: 0-2.0%, Mo: 0-1.0%, Ni: 0-5.0%, B: 0 to 0.01%, N: 0 to 0.01%, Al: 0 to 1.0% May include one or more.
  • Al contained in the weld metal 3 may be oxidized and the weld slag may float. Therefore, even if Al in the steel base material enters the weld metal 3 before solidification, the amount of Al remaining in the weld metal 3 after solidification is small.
  • At least one of the pair of steel base materials is a steel base material having a tensile strength of 780 MPa or more.
  • a steel base material having high tensile strength is particularly suitable as a steel base material for a welded joint 10 for automobiles, which is strongly required to reduce weight and improve collision safety.
  • both of the pair of steel base materials are preferably steel base materials having a tensile strength of 780 MPa or more. The tensile strength is measured according to JIS Z2241 (2011).
  • At least one of the pair of steel base materials preferably contains 0.100 to 1.000% by mass of Al from the viewpoint of improving the fatigue strength of the weld metal 3.
  • the viscosity of the molten metal increases, and welding such as weaving welding and wave pulse welding is performed.
  • the stress concentration in the mountainous area is greatly reduced without a decrease in the throat thickness when the welding is performed.
  • the fatigue strength of the weld metal 3 is significantly improved.
  • a pair of steel base materials containing 1.000% or less of Al is preferable from the viewpoint of ensuring the toughness of the weld metal 3.
  • the amount of Al is preferably 0.100 to 0.500% by mass, and more preferably 0.200 to 0.500% by mass. From the viewpoint of improving fatigue strength, it is preferable that both of the pair of steel base materials contain 0.100 to 1.000% by mass of Al.
  • the welding wire contains Al in the above range, it is easily oxidatively consumed during welding, and the amount of Al contained in the weld metal is smaller than when it is added to the steel base metal. Therefore, it is desirable that the steel base material contains the above amount of Al.
  • the chemical composition of the pair of steel base materials is preferably a chemical composition that suppresses a decrease in the "throat thickness" of the weld metal 3 and obtains mechanical properties having a tensile strength of 780 MPa or more.
  • C 0.002 to 0.400% by mass% Si: 0.002 to 2.000% Mn: 0.1-3.0%
  • P 0.1% or less
  • S 0.05% or less
  • Al 0.100 to 0.500%
  • N 0-0.01%
  • Cr 0-2.0%
  • Mo 0-1.0%
  • Ni 0-5.0%
  • Residue Chemical composition consisting of Fe and impurities.
  • the plate thickness of the pair of steel base materials is 0.4 to 4.0 mm. If the plate thickness of the pair of steel base materials is less than 0.4 mm, stable welding cannot be performed and the fatigue strength decreases. When the plate thickness of the pair of steel base materials exceeds 4.0 mm, the welding residual stress becomes dominant over the fatigue strength, and the influence of the fatigue strength improving effect by the peak portion of the weld metal 3 becomes small.
  • the plate thickness of the preferred pair of steel base materials is 0.8 to 3.2 mm.
  • the plate thickness of the pair of steel base materials is 3 mm away from the apex of the toe of the welded joint in the direction orthogonal to the welding line direction toward the base material side when the weld metal is viewed in a plan view. It is a value measured at the position.
  • the plate thickness is measured using a contact type displacement meter that sandwiches the plate thickness in the thickness direction.
  • the ratio of the Vickers hardness of the weld metal to the Vickers hardness of the steel base material is preferably 0.75 or more and 0.95 or less.
  • the fact that the Vickers hardness ratio is within the above range indicates that the hardness of the weld metal is lower than that of the steel base material. That is, when welding is performed in the production of a welded joint in which the Vickers hardness ratio is within the above range, the weld metal is formed by a welding wire having a hardness lower than that of the steel base material. Since the cost of a welded wire having a low hardness is low, it becomes easy to obtain a welded joint while suppressing the manufacturing cost. Therefore, by setting the ratio of the Vickers hardness within the above range, the number of undulations of the weld metal, and the distance between the peak and the valley within the above range, the fatigue strength can be reduced while suppressing the manufacturing cost.
  • the ratio of the Vickers hardness of the weld metal to the Vickers hardness of one of the pair of steel base materials is within the above range. It is preferable that the ratio of the Vickers hardness of the weld metal to the Vickers hardness of both steel base materials in the pair of steel base materials is within the above range.
  • the measurement of the ratio of the Vickers hardness of the weld metal to the Vickers hardness of the steel base material is calculated by the following procedure.
  • the Vickers hardness of the weld metal is measured on the surface of the welded joint formed by the X-axis and the Y-axis as shown in FIG. At a position 0.2 mm or more away from the weld metal surface (solid line portion of the weld metal 3 shown in FIG. 1) and from the melting boundary (dotted portion of the weld metal 3 shown in FIG. 1).
  • the Vickers hardness of 5 points or more is measured at a position separated by 2 mm or more, and the arithmetic average value of the obtained measured values is defined as the Vickers hardness of the weld metal.
  • the steel base material is placed in the thickness direction of the steel base material at a position 5 mm or more in the direction orthogonal to the welding line direction toward the base material side from the apex of an arbitrary mountain portion of the toe of the welded joint.
  • a cross-section sample is collected by cutting.
  • the Vickers hardness of the steel base material is measured at the cut surface of the cross-sectional sample.
  • the Vickers hardness is measured at 5 points or more within a range of 0.1 mm or more from the surface of the steel plate of the steel base material and 40% or less of the plate thickness.
  • the arithmetic mean value of the obtained measured values is taken as the Vickers hardness of the steel base material.
  • the Vickers hardness of the steel base material is increased. , Calculate the Vickers hardness ratio of the weld metal.
  • An example of the method for manufacturing a welded joint of the present disclosure is a method for manufacturing a welded joint by weaving arc welding that satisfies the following conditions.
  • Welding speed 40 to 110 cm / min
  • Weaving frequency 0.2 to 20 Hz
  • Weaving amplitude 0.6 to 20 mm
  • Shield gas composition (volume%): CO 2 concentration 20% or less or O 2 concentration 8% or less
  • Ar Welding current: 150-250A
  • the welding wire is not particularly limited as long as it is a wire that satisfies the shape of the toe of the weld metal 3.
  • C 0.002 to 0.400% by mass% Si: 0.002 to 2.000% Mn: 0.1-3.0%
  • P 0.1% or less
  • S 0.05% or less
  • Al 0.1 to 1.0%
  • Ti 0-0.5%
  • N 0 to 0.01%
  • Cr 0-2.0%
  • Mo 0-1.0%
  • Cu 0-1.0%
  • Residue Chemical composition consisting of Fe and impurities.
  • the welding speed is preferably 40 to 110 cm / min.
  • the weaving frequency By setting the weaving frequency to 0.2 to 20 Hz, the "number of swells" tends to be in the range of 2 to 30 pieces / 15 mm. In order to keep the "number of swells" within the range of 2 to 30 pieces / 15 mm, it is preferable to increase the weaving frequency when increasing the welding speed. On the other hand, when the welding speed is slowed down, it is preferable to lower the weaving frequency. Therefore, the weaving frequency is preferably 0.2 to 20 Hz.
  • the weaving amplitude is preferably 0.6 to 20 mm.
  • the "weaving amplitude” will be described with reference to FIG. It is a value twice the amplitude Wa of the movement M of the welding torch when the welding torch is weaved. That is, the weaving amplitude is indicated by Wb in FIG. In FIG. 8, D indicates the welding direction.
  • the composition (volume%) of the shield gas is preferably a CO 2 concentration of 20% or less or an O 2 concentration of 8% or less, and the balance: Ar.
  • the welding current By setting the welding current to 150 A or more, the disorder of welding is suppressed and the shape of the weld metal 3 becomes stable (weld bead shape).
  • the welding current By setting the welding current to 250 A or less, it becomes easy to suppress the occurrence of problems such as melting off. Therefore, it is preferably 150 to 250 A.
  • the automotive parts of the present disclosure include the welded joints of the present disclosure.
  • the automobile parts of the present disclosure include the welded joints shown in FIGS. 1 and 2.
  • the automobile parts of the present disclosure are exemplified by skeleton parts, panel parts, suspension parts of a vehicle body, and specifically, suspension arms, suspension frames, chassis frames and the like that require high strength are preferable. Can be mentioned.
  • Example 2 As a pair of steel base materials, steel plates having the chemical composition, plate thickness and tensile strength shown in Table 1 were used, and lap fillet welding was performed under the welding conditions shown in Tables 3 and 4. However, the composition of the shield gas was Ar + 20% CO 2 . As the welding wire, a wire equivalent to YGW16 of JIS Z 3312 (2009) (see Table 2) was used.
  • the toes of the weld metal of the welded test piece are 1) the number of waviness (the total number of peaks and valleys), and 2) peaks.
  • the distance between the part and the valley was investigated by the method described above. Except for 5 mm each at the beginning and end, 15 mm near the center of the total length of the weld metal (welded bead) was examined.
  • the Vickers hardness of the steel base material and the Vickers hardness of the weld metal in the welded test piece were measured according to the method described above, and the ratio of the Vickers hardness of the weld metal to the Vickers hardness of the steel base material was calculated.
  • the fatigue limit was set to the maximum stress amplitude that was unbroken 10 million times.
  • the bending stress was based on the maximum bending stress on the surface without considering the stress concentration in the minimum cross section (width 20 mm, plate thickness 2.9 mm) of the test piece.
  • the results obtained are shown in Tables 3 and 4.
  • the "fatigue limit improvement rate" in Tables 3 and 4 was calculated as follows.
  • the fatigue limit improvement rate was defined as the value obtained by dividing the fatigue limit of the test piece welded under the condition with weaving by the fatigue limit of the test piece welded under the same welding condition except that without weaving.
  • Test Examples 2 to 3, 5, 7, 10 to 12, 16 can obtain a fatigue strength of 200 MPa or more, which is a fatigue limit, as compared with Test Examples 1, 4, 6, 8, 9, 13 to 15. I understand. In particular, it can be seen that excellent fatigue strength can be obtained in Test Examples 2 to 3, 7, 10 to 12 to which a steel base material containing an Al amount in an appropriate range is applied.

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PCT/JP2020/037775 2019-10-04 2020-10-05 溶接継手、及び自動車部品 Ceased WO2021066192A1 (ja)

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US17/761,196 US12202075B2 (en) 2019-10-04 2020-10-05 Welded joint and automobile component
CN202080065718.2A CN114423558B (zh) 2019-10-04 2020-10-05 焊接接头及汽车部件
JP2021551652A JP7368760B2 (ja) 2019-10-04 2020-10-05 溶接継手、及び自動車部品
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JP2023166120A (ja) * 2022-05-09 2023-11-21 日本製鉄株式会社 アーク溶接継手、自動車部品、及びアーク溶接継手の製造方法
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