# US 10,500,681 B2 · Arc spot welding method and welding apparatus for working the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,500,681 B2 - Document ID: US10500681B2 - Status: Granted - Kind: B2 - Application number: 15/517,095 - Filed: 2015-10-06 - Published: 2017-10-19 - Granted: 2019-12-10 - Earliest claimed: 2014-10-06 - Assignees: Nippon Steel Corporation - Applicants: Nippon Steel & Sumitomo Metal Corporation - Inventors: Shinji Kodama; Seiji Furusako; Yasunobu Miyazaki - Web page: https://patentgrep.com/patent/US10500681B2 ## CPC - B23K 37/06: for positioning the molten material, e.g. confining it to a desired area - B23K 9/0035: {of thin articles} - B23K 9/007: Spot arc welding - B23K 9/02: Seam welding; Backing means; Inserts - 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 ## Abstract An arc spot welding method able to give a predetermined weld bead diameter or excess metal height in a back surface weld bead of arc spot welding and able to give a welded joint excellent in both strengths of TSS and CTS and a welding apparatus for working the same are provided. Steel sheets containing carbon in 0.2 mass % or more and having sheet thicknesses “t” or more are arranged overlaid. A backing plate including a non-contact part and a contact part maintaining the back surface of the lower side steel sheet is provided. An arc generation and short-circuit conduction where the welding voltage between the welding wire and upper side steel sheet becomes 10V or less are alternately repeated so that the time period of the short-circuit conduction becomes over 30% to less than 60% per cycle to thereby weld the steel sheets. ## Claims ### Claim 1 An arc spot welding method arranging a plurality of steel sheets containing carbon in amounts of 0.2 mass % or more overlaid and performing lap welding while arranging a backing plate in contact with a lower side steel sheet at an opposite side to a welding torch, said backing plate comprising a non-contact part and a contact part, wherein the non-contact part faces said lower side steel sheet without contacting said lower side steel sheet and the contacting part contacts said lower side steel sheet, said arc spot welding method comprising: arranging the backing plate so that said contact part contacts the lower side steel sheet at a position exceeding 3 t from a circle equivalent center of a back surface weld bead and alternately and continuously repeating arc generation and short-circuit conduction so that a short-circuiting time where a welding voltage becomes 10V or less becomes over 30% to less than 60% per conduction cycle, where “t” is defined as the sheet thickness of the steel sheet with the thinnest sheet thickness among said plurality of steel sheets. ### Claim 2 (depends on 1) The arc spot welding method according to claim 1, wherein a value of a mean welding voltage (unit: V)/mean welding current (unit: A) in an arc spot welding time period in a time period of alternately and continuously repeating arc generation and short-circuit conduction is 0.07 to 0.10 (V/A) per cycle. ### Claim 3 (depends on 2) The arc spot welding method according to claim 2, wherein one cycle is made 5 msec to 20 msec and arc generation and short-circuit conduction are performed during that cycle. ### Claim 4 (depends on 2) The arc spot welding method according to claim 2, wherein said contact part maintains a clearance between a back surface of said lower side steel sheet and said non-contact part at 0.2 t to 3 t. ### Claim 5 (depends on 2) The arc spot welding method according to claim 2, forming a back surface weld bead having a weld bead diameter of a circle equivalent diameter of 3 t to 10 t and having an excess metal height of 0.2 t to 3 t. ### Claim 6 (depends on 2) The arc spot welding method according to claim 2, wherein the contact between said contact part and a back surface of said lower side steel sheet is at least one of point contact, line contact, and planar contact. ### Claim 7 (depends on 1) The arc spot welding method according to claim 1, wherein one cycle is made 5 msec to 20 msec and arc generation and short-circuit conduction are performed during that cycle. ### Claim 8 (depends on 7) The arc spot welding method according to claim 7, wherein said contact part maintains a clearance between a back surface of said lower side steel sheet and said non-contact part at 0.2 t to 3 t. ### Claim 9 (depends on 7) The arc spot welding method according to claim 7, forming a back surface weld bead having a weld bead diameter of a circle equivalent diameter of 3 t to 10 t and having an excess metal height of 0.2 t to 3 t. ### Claim 10 (depends on 7) The arc spot welding method according to claim 7, wherein the contact between said contact part and a back surface of said lower side steel sheet is at least one of point contact, line contact, and planar contact. ### Claim 11 (depends on 1) The arc spot welding method according to claim 1, wherein said contact part maintains a clearance between a back surface of said lower side steel sheet and said non-contact part at 0.2 t to 3 t. ### Claim 12 (depends on 11) The arc spot welding method according to claim 11, forming a back surface weld bead having a weld bead diameter of a circle equivalent diameter of 3 t to 10 t and having an excess metal height of 0.2 t to 3 t. ### Claim 13 (depends on 11) The arc spot welding method according to claim 11, wherein the contact between said contact part and a back surface of said lower side steel sheet is at least one of point contact, line contact, and planar contact. ### Claim 14 (depends on 1) The arc spot welding method according to claim 1, forming a back surface weld bead having a weld bead diameter of a circle equivalent diameter of 3 t to 10 t and having an excess metal height of 0.2 t to 3 t. ### Claim 15 (depends on 1) The arc spot welding method according to claim 1, wherein the contact between said contact part and a back surface of said lower side steel sheet is at least one of point contact, line contact, and planar contact. ### Claim 16 (depends on 1) The arc spot welding method according to claim 1, wherein when forming a back surface weld bead with a circle equivalent weld bead diameter of said back surface weld bead of over 5 t, said backing plate is formed by copper or a copper alloy and the contact between said contact part and a back surface of said lower side steel sheet is planar contact. ### Claim 17 (depends on 1) The arc spot welding method according to claim 1, wherein when forming a back surface weld bead with a circle equivalent weld bead diameter of said back surface weld bead of over 5 t, said backing plate is formed by a steel material and the contact between said contact part and a back surface of said lower side steel sheet is planar contact. ### Claim 18 (depends on 1) The arc spot welding method according to claim 1, wherein a contact area of said contact part and a back surface of said lower side steel sheet is 10 cm2 or less. ### Claim 19 An arc spot welding apparatus comprising; a backing plate provided with a non-contact part arranged separated from a back surface of said lower side steel sheet; and a contact part contacting the back surface of the lower side steel sheet maintaining a clearance of 0.2 t to 3 t between the back surface of said lower side steel sheet and said non-contact part, wherein the arc spot welding apparatus is configured to perform a method of arranging a plurality of steel sheets containing carbon in amounts of 0.2 mass % or more overlaid and performing lap welding while arranging the backing plate in contact with the lower side steel sheet at an opposite side to a welding torch, arranging the backing plate so that said contact part contacts the lower side steel sheet at a position exceeding 3 t from a circle equivalent center of a back surface weld bead and alternately and continuously repeating arc generation and short-circuit conduction so that a short-circuiting time where a welding voltage becomes 10V or less becomes over 30% to less than 60% per conduction cycle, where “t” is defined as the sheet thickness of the steel sheet with the thinnest sheet thickness among said plurality of steel sheets. ### Claim 20 (depends on 19) The arc spot welding apparatus according to claim 19, wherein said arc spot welding apparatus is a welding robot at which a welding torch and said backing plate are mounted.