Method For Laser Welding One Or More Workpieces Of Hardenable Steel In A Butt Joint

• US 20150306702A1
• Filed: 08/02/2013
• Published: 10/29/2015
• Est. Priority Date: 11/19/2012
• Status: Active Grant

• Current Assignee: Wisco Tailored Blanks GmbH
• Original Assignee: Wisco Tailored Blanks GmbH
• Inventors: Breuer, Arndt, Brandt, Max, Schaftinger, Dietmar
• Granted Patent: US 9,623,515 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B23K 2101/18 Sheet panels
• CPC Class Codes: B23K 2101/34 Coated articles , e.g. plated or painted; Surface treated articles
• CPC Class Codes: B23K 2103/04 Steel or steel alloys
• CPC Class Codes: B23K 2103/08 Non-ferrous metals or alloys
• CPC Class Codes: B23K 2103/50 Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
• CPC Class Codes: B23K 26/26 of rectilinear seams
• CPC Class Codes: B23K 26/32 taking account of the properties of the material involved
• CPC Class Codes: B23K 26/322 involving coated metal parts using absorbing layers on the workpiece B23K26/18
• CPC Class Codes: B23K 35/3066 with Ni as next major constituent
• CPC Class Codes: C22C 38/002 containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
• CPC Class Codes: C22C 38/06 containing aluminium
• CPC Class Codes: C22C 38/08 containing nickel C22C38/105 takes precedence
• CPC Class Codes: C22C 38/22 with molybdenum or tungsten
• CPC Class Codes: C22C 38/28 with titanium or zirconium
• CPC Class Codes: C22C 38/32 with boron
• CPC Class Codes: C22C 38/38 with more than 1.5% by weight of manganese

Abstract

A method for laser welding of one or more workpieces made from press hardenable steel, in a butt joint, in which the workpiece or the workpieces have a thickness of at least 1.8 mm and/or a jump in thickness of at least 0.4 mm arises at the butt joint including supplying filler wire into a molten bath generated by a laser beam. In order to ensure that the weld seam can reliably harden into a martensitic structure during the hot forming (press hardening), the filler wire contains at least one alloy element from the group of manganese, chromium, molybdenum, silicon and nickel, wherein the at least one alloy element is present in the filler wire with a mass proportion that is larger by 0.1% by weight than the mass proportion of the element in the press hardenable steel of the workpiece or the workpieces.

Claims

1. A method for laser welding of one or more workpieces made from press hardenable steel, particularly manganese-boron steel, in a butt joint, in which the workpiece or the workpieces (1, 2;

1, 2′

) have a thickness of at least 1.8 mm and/or a jump in thickness (d) of at least 0.4 mm arises at the butt joint (3), and in which the laser welding takes place with the supply of filler wire (10) into the molten bath (8) generated with a laser beam (6), characterised in that the filler wire (10) contains at least one alloy element from the group comprising manganese, chromium, molybdenum, silicon and/or nickel, which element promotes the formation of austenite in the molten bath (8) generated using the laser beam (6), wherein this at least one alloy element is present in the filler wire (10) with a mass proportion that is larger by 0.1% by weight than in the press hardenable steel of the workpiece or the workpieces (1, 2;

1, 2′

).

2. The method according to claim 1, characterised in that the steel of the workpiece or the workpieces (1, 2;

1, 2′

) has the following composition;

0.10-0.50% by weight C,

max. 0.40% by weight Si,

0.50-2.00% by weight Mn,

max. 0.025% by weight P,

max. 0.010% by weight S,

max. 0.60% by weight Cr,

max. 0.50% by weight Mo,

max. 0.050% by weight Ti,

max. 0.0008-0.0070% by weight B, and

min. 0.010% by weight Al,

remainder Fe and unavoidable impurities.

3. The method according to claim 1 or 2, characterised in that the filler wire (10) has the following composition:

0.05-0.15% by weight C,

0.5-2.0% by weight Si,

1.0-2.5% by weight Mn,

0.5-2.0% by weight Cr+Mo, and

1.0-4.0% by weight Ni,

remainder Fe and unavoidable impurities.

4. The method according to one of claims 1 to 3, characterised in that the filler wire (10) has a carbon mass proportion that is lower by at least 0.1% by weight than the press hardenable steel of the workpiece or the workpieces (1, 2;

1, 2′

).

5. The method according to one of claims 1 to 4, characterised in that the filler wire (10) is supplied to the molten bath (8) in a heated state.

6. The method according to claim 5, characterised in that the filler wire (10) is heated to a temperature of at least 50°

C., at least in a length section, before supply into the molten bath (8).

7. The method according to one of claims 1 to 6, characterised in that the molten bath (8) is loaded with protective gas during the laser welding.

8. The method according to claim 7, characterised in that pure argon or a mixture of argon and carbon dioxide is used as protective gas.

9. The method according to one of claims 1 to 8, characterised in that the workpiece used or the workpieces used (1, 2;

1, 2′

) have a surface layer with an aluminium or aluminium/silicon basis.

10. The method according to one of claims 1 to 8, characterised in that the workpiece used or the workpieces used (1, 2;

1, 2′

) are uncoated or partly de-layered.