Method of forming fillet arc welded joint and fillet arc welded joint

{
  "publication_number": "US2015196967A1",
  "country": "US",
  "kind": "A1",
  "title": "Method of forming fillet arc welded joint and fillet arc welded joint",
  "abstract": "Stiffening beads (55 A, 55 B) are formed in turned portions in a region of a fillet bead (53) formed in a single stroke manner. At this time, it is set in such a manner that welding start positions of the stiffening beads (55 A, 55 B) are in a region near the fillet bead and do not exist independently without mixing with other weld beads.",
  "claims": [
    "1. A method of forming a fillet arc welded joint by fillet arc welding at least a partial region of corner portions that are edge regions of an abutted portion of at least one of a sheet surface portion and a sheet thickness portion of one metal member and a sheet surface portion of the other metal member and have at least one turned portion at at least one portion thereof, the method comprising: forming a fillet bead with respect to a region containing the turned portion of the corner portion by the fillet arc welding; and forming a stiffening bead on one place or plural places of at least the one turned portion by arc welding different from the fillet arc welding so that a welding start point or a welding end point of the stiffening bead overlaps with the fillet bead, wherein the stiffening bead is formed in a direction of, of the one metal member and the other metal member, the metal member in which a larger tensile stress occurs when, to a fillet arc welded joint formed under the same condition as that of the fillet arc welded joint except for the point that the stiffening bead is not formed, a cyclic load expected to be applied to the fillet arc welded joint is applied, the fillet bead is formed with respect to the corner portion of one side of the corner portions formed on both sides of the abutted portion, and at least one metal member of the one metal member and the other metal member is formed of a metal sheet having a sheet thickness of 3.2 mm or less. 2. The method of forming the fillet arc welded joint according to claim 1, wherein the stiffening bead is formed so that the welding start point of the stiffening bead overlaps with another weld bead. 3. The method of forming the fillet arc welded joint according to claim 2, wherein the stiffening bead is formed so that the welding start point of the stiffening bead overlaps with the fillet bead. 4. The method of forming the fillet arc welded joint according to claim 1, wherein the turned portion contains at least one of a bent portion and a curved portion. 5. The method of forming the fillet arc welded joint according to claim 1, wherein the stiffening bead is formed in a region that constitutes the turned portion and where magnitude of a maximum principal stress becomes larger than at a welding start position of the fillet bead when the cyclic load is applied to a fillet arc welded joint formed under the same condition as that of the fillet arc welded joint except for the point that the stiffening bead is not formed. 6. The method of forming the fillet arc welded joint according to claim 1, wherein the stiffening bead is formed in a region that constitutes the turned portion and where the magnitude of the maximum principal stress becomes maximum when the cyclic load is applied to a fillet arc welded joint formed under the same condition as that of the fillet arc welded joint except for the point that the stiffening bead is not formed. 7. The method of forming the fillet arc welded joint according to claim 1, wherein a hardness Hw of the stiffening bead exceeds a metal member maximum hardness Hb of, of the one metal member and the other metal member, the metal member on which the stiffening bead is formed. 8. The method of forming the fillet arc welded joint according to claim 1, wherein a length La of the stiffening bead is two times or more of a width W of the fillet bead, a height Ha of the stiffening bead is 0.5 times or more of a thickness t of, of the one metal member and the other metal member, the metal member on which the stiffening bead is formed, a width Wa of the stiffening bead is 0.5 times or more of the width W of the fillet bead, and an angle γ of the stiffening bead with respect to the fillet bead is not less than 45° nor more than 135°. 9. A fillet arc welded joint formed by fillet arc welding at least a partial region of corner portions that are edge regions of an abutted portion of at least one of a sheet surface portion and a sheet thickness portion of one metal member and a sheet surface portion of the other metal member and have at least one turned portion at at least one portion thereof, the fillet arc welded joint comprising: a fillet bead formed with respect to a region containing the turned portion of the corner portion by the fillet arc welding; and a stiffening bead formed on one place or plural places of at least the one turned portion by arc welding different from the fillet arc welding, wherein the stiffening bead is formed so that a welding start point or a welding end point of the stiffening bead overlaps with the fillet bead, and is formed in a direction of, of the one metal member and the other metal member, the metal member in which a larger tensile stress occurs when, to a fillet arc welded joint formed under the same condition as that of the fillet arc welded joint except for the point that the stiffening bead is not formed, a cyclic load expected to be applied to the fillet arc welded joint is applied, the fillet bead is formed with respect to the corner portion of one side of the corner portions formed on both sides of the abutted portion, and at least one metal member of the one metal member and the other metal member is formed of a metal sheet having a sheet thickness of 3.2 mm or less. 10. The fillet arc welded joint according to claim 9, wherein the welding start point of the stiffening bead is at a position overlapping with another weld bead. 11. The fillet arc welded joint according to claim 10, wherein the welding start point of the stiffening bead is at a position overlapping with the fillet bead. 12. The fillet arc welded joint according to claim 9, wherein the turned portion contains at least one of a bent portion and a curved portion. 13. The fillet arc welded joint according to claim 9, wherein the stiffening bead is formed in a region that constitutes the turned portion and where magnitude of a maximum principal stress becomes larger than at a welding start position of the fillet bead when the cyclic load is applied to a fillet arc welded joint formed under the same condition as that of the fillet arc welded joint except for the point that the stiffening bead is not formed. 14. The fillet arc welded joint according to claim 9, wherein the stiffening bead is formed in a region that constitutes the turned portion and where the magnitude of the maximum principal stress becomes maximum when the cyclic load is applied to a fillet arc welded joint formed under the same condition as that of the fillet arc welded joint except for the point that the stiffening bead is not formed. 15. The fillet arc welded joint according to claim 9, wherein a hardness Hw of the stiffening bead exceeds a metal member maximum hardness Hb of, of the one metal member and the other metal member, the metal member on which the stiffening bead is formed. 16. The fillet arc welded joint according to claim 9, wherein a length La of the stiffening bead is two times or more of a width W of the fillet bead, a height Ha of the stiffening bead is 0.5 times or more of a thickness t of, of the one metal member and the other metal member, the metal member on which the stiffening bead is formed, a width Wa of the stiffening bead is 0.5 times or more of the width W of the fillet bead, and an angle γ of the stiffening bead with respect to the fillet bead is not less than 45° nor more than 135°."
  ],
  "description_excerpt": "The present invention relates to a method of forming a fillet arc welded joint and a fillet arc welded joint, and is preferred to be used particularly for fillet arc welding plural metal members.\n\nIn the automotive field, for example, improvement in collision safety is required together with improvement in fuel consumption by weight reduction of vehicle bodies for environmental conservation. Thus, use of high-strength steel sheets for thickness reduction and optimization of vehicle body structures have been practiced hitherto in various ways, so as to achieve weight reduction of vehicle bodies and improvement in collision safety.\n\nLarge fatigue strength is also required in the high-strength steel sheets for weight reduction of vehicle bodies. In general, the fatigue strength of a parent material to be used for a welded member increases in proportion to steel sheet strength, but it is known that the fatigue strength of a welded joint barely increases even when the steel sheet strength is increased. This hinders the weight reduction of vehicle bodies by use of the high-strength steel sheets.\n\nFor underbody members such as suspension arms and sub-frames in particular, the fatigue strength of welded portions becomes more important. Fillet arc welding is often used for welding of these underbody members. Thus, in order to achieve the weight reduction of underbody members, an increase in fatigue strength of fillet arc welded joints becomes an issue.\n\nFIG.",
  "cpc": [
    "B23K 9/0043",
    "B23K 2101/006",
    "B23K 2101/18",
    "B23K 2103/04",
    "B23K 2103/05",
    "B23K 31/00",
    "B23K 9/02",
    "B23K 9/025",
    "B23K 9/028",
    "B23K 9/16",
    "B23K 9/23",
    "B60G 2206/8201"
  ],
  "ipc": [
    "B23K 9/00",
    "B23K 9/025",
    "B23K 9/028",
    "B23K 9/02",
    "B23K 9/23"
  ],
  "assignees": [
    "Nippon Steel and Sumitomo Metal Corp"
  ],
  "inventors": [
    "Shoko Tsuchiya",
    "Shinji Kodama",
    "Yuuichi Yosida",
    "Yoshinari Ishida",
    "Masahiro Ogawa"
  ],
  "filing_date": "2013-11-28",
  "publication_date": "2015-07-16",
  "priority_date": "2012-11-29",
  "application_number": "US-201314408509-A",
  "family_id": "50827948",
  "cited_by_count": 9,
  "citations": [
    "US4280541A",
    "US5233149A",
    "US9227271B2"
  ]
}