METHOD AND DEVICE FOR PREPARING ALUMINUM-COATED STEEL SHEETS INTENDED FOR BEING WELDED AND THEN HARDENED UNDER A PRESS; CORRESPONDING WELDED BLANK

• US 20170120391A1
• Filed: 04/17/2015
• Published: 05/04/2017
• Est. Priority Date: 04/25/2014
• Status: Active Grant

• Current Assignee: Arcelormittal (ArcelorMittal SA)
• Original Assignee: Arcelormittal (ArcelorMittal SA)
• Inventors: Schmit, Francis, Yin, Qingdong, Ehling, Wolfram, Vierstraete, Ren
• Granted Patent: US 10,668,570 B2
• Time in Patent Office: Days
• CPC Class Codes: B23K 2101/006 Vehicles
• 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 26/211 with interposition of special material to facilitate connection of the parts
• 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 26/348 in combination with arc heating, e.g. TIG [tungsten inert gas], MIG [metal inert gas] or plasma welding laser beam for starting a welding or cutting arc B23K9/067
• CPC Class Codes: B23K 26/361 for deburring or mechanical trimming B23K26/351 takes precedence
• CPC Class Codes: B23K 26/40 taking account of the properties of the material involved
• CPC Class Codes: B23K 26/60 Preliminary treatment
• CPC Class Codes: B23K 28/02 Combined welding or cutting procedures or apparatus
• CPC Class Codes: B23K 9/167 and of a non-consumable electrode
• CPC Class Codes: B23K 9/173 and of a consumable electrode

Abstract

The present invention provides a method for the preparation of steel sheets to be fabricated into a welded steel blank. The method includes procuring at least one pre-coated first steel sheet and one pre-coated second steel sheet, made up of a steel substrate and a pre-coating made up of an intermetallic alloy layer in contact with the steel substrate, topped by a layer of aluminum metal or aluminum alloy or aluminum-based alloy, the first sheet having a principal face, an opposite principal face, and at least one secondary face, the second sheet having a principal face, an opposite principal face and at least one secondary face, positioning the first and second sheets, leaving a gap of between 0.02 and 2 mm between the secondary faces and facing each other, the mating of the first and second sheets defining a median plane perpendicular to the principal faces of the first sheet and the second sheet, then removing the layers of metal alloy by melting and vaporization simultaneously on the principal faces, in a peripheral zone of the sheets, the peripheral zones being the zones of the principal faces closest in relation to the median plane located one on either side of it.

Claims

1-34. -34. (canceled)

35. :

A method for the preparation of sheets to be used for the fabrication of a welded steel blank, comprising the steps of;

procuring at least one pre-coated first steel sheet and one pre-coated second steel sheet, each sheet including;

a steel substrate and

a pre-coating including an intermetallic alloy layer in contact with the steel substrate, topped by a metal alloy layer of aluminum metal or aluminum alloy or aluminum-based alloy,

the first sheet comprising a principal face, an opposite principal face and at least one secondary face,

the second sheet comprising a principal face, an opposite principal face and at least one secondary face,

positioning the first and second sheets to form a gap from 0.02 and 2 mm between the secondary faces, the secondary faces facing each other, the positioning of the first and second sheets defining a median plane perpendicular to the principal faces of the first and second sheets; and

removing the metal alloy layers in first and second peripheral zones of the first and second sheets, respectively, by melting and vaporization simultaneously on the principal faces of the sheets, the peripheral zones being zones of the principal faces closest to the median plane and located one on either side of the median plane.

36. :

The preparation method as recited in claim 35, wherein the simultaneous removal by melting and evaporation is carried out by a laser beam that spans the median plane.

37. :

The preparation method as recited in claim 35, wherein widths of the first and second peripheral zones are from 0.25 to 2.5 mm.

38. :

The preparation method as recited in claim 35, wherein widths of the first and second peripheral zones are equal.

39. :

The preparation method as recited in claim 35, wherein widths of the first and second peripheral zones are different.

40. :

The preparation method as recited in claim 35, wherein the step of removal by melting and vaporization is carried out on the principal faces and on the opposite principal faces simultaneously.

41. :

The preparation method as recited in claim 35, wherein the intermetallic alloy layers remain in the first and second peripheral zones after the respective metal alloy layers are removed.

42. :

The preparation method as recited in claim 35, wherein the steel substrates of the first and second steel sheets have different compositions of steel.

43. :

The preparation method as recited in claim 35, wherein the pre-coatings on the first and second steel sheets have different thicknesses.

44. :

The preparation method as recited in claim 35, wherein the metal alloy layers include, with the percentages expressed by weight, from 8 to 11% silicon, from 2 to 4% iron, and the a balance of the composition including aluminum and unavoidable impurities.

45. :

The preparation method as recited in claim 35, wherein the gap is greater than 0.04 mm.

47. :

A method for fabricating a welded blank comprising the steps of;

procuring at least first and second sheets prepared by the method recited in claim 35; and

carrying out a welding operation of the first sheet and the second sheet in the peripheral zones, along a plane defined by the median plane, less than one minute after the removal of the metal alloy layer by melting and vaporization on the at least one first sheet and at least one second sheet.

48. :

The fabrication method as recited in claim 47, wherein the welding operation is carried out by at least one laser beam.

49. :

The fabrication method as recited in claim 47, wherein the welding operation is carried out simultaneously by two laser beams, one effecting a welding of the side of the principal faces, and the other effecting a welding of the side of the opposite principal faces.

50. :

The fabrication method as recited claim 47, wherein the removing by melting and vaporization is carried out by a laser beam, and the devices for the removal and the welding operation are combined in a single piece of equipment, a relative speed of displacement in relation to that of the at least one first sheet and that of at least one second sheet is identical.

51. :

The fabrication method as recited in claim 47, wherein the welding operation is carried out using simultaneously at least one laser beam and one filler rod.

52. :

The fabrication method as recited in claim 47, wherein the removing step is guided by a device that tracks the median plan and wherein coordinates (x-y) defining a location of the plane at an instant t are recorded by a controller and used to guide the welding operation that is subsequently carried out.

53. :

The fabrication method as recited in claim 47, wherein the removing step is guided by a first device that tracks the median plane and the welding operation is guided by a second device that tracks the median plane and is separate from the first device.

54. :

The fabrication method as recited in claim 47, wherein the first and second sheets are clamped by a clamping device during the removing step, the clamping being kept constant until the welding operation and at least during the welding operation.

55. :

A method for fabricating a press-hardened part from a welded blank, comprising the following steps;

procuring at least one welded blank fabricated as recited in claim 47;

heating the at least one welded blank to create, by alloying between the steel substrate and the pre-coating an intermetallic alloy compound, and to confer a partially or totally austenitic structure on the substrate;

hot-forming the at least one welded blank to obtain a part;

cooling the part at a rate sufficient to form at least martensite or bainite in the substrate, thus obtaining a press hardening.

56. :

The fabrication method as recited in claim 55, wherein the hot forming of the at least one welded blank is carried out by a hot stamping operation.

57. :

A welded blank fabricated by an assembly comprising;

at least one first and second pre-coated steel sheet prepared by the method recited in claim 35;

at least one welded joint defining the median plane perpendicular to the principal faces of the at least one first and second sheets; and

cross sections perpendicular to the median plane wherein the first sheet has at least one first cross section on one side of the median plane and the second sheet has at least one second cross section on the other side of the median plane;

morphological characteristics of the intermetallic alloy layers of the at least one first and second sheets resulting from solidification after melting and vaporization of the pre-coating in the peripheral zones being identical in the at least one first cross section and at least one second cross section.

58. :

The welded blank as recited in claim 57, wherein a sum of the widths of the peripheral zones varies by less than 10% along the welded joint.

59. :

The welded blank as recited in claim 57, wherein the metal alloy layer includes, with concentrations expressed by weight, from 8 to 11% silicon and from 2 to 4% iron, the balance of the composition comprising aluminum and unavoidable impurities.

68. :

Use of a steel part fabricated as recited in claim 55 for the fabrication of structural, anti-intrusion or impact absorption parts in vehicles, in particular automobiles.

69. :

The preparation method as recited in claim 35, wherein the step of procuring is followed by the step of positioning which is followed by the step of removing.

70. :

The preparation method as recited in claim 35, wherein the intermetallic alloy layer remains in the peripheral areas after the removal of the metal alloy layer.

60. :

A device for the fabrication of welded blanks comprising;

a delivery device that delivers at least one first and one second steel sheets pre-coated with aluminum, aluminum alloy or an aluminum-based alloy;

a positioning device for the sheets, to obtain a median plane between the sheets;

a clamping device for the sheets;

at least one source for generating a first laser beam to remove the metal alloy layer of aluminum metal, aluminum alloy or aluminum-based alloy by melting and vaporization simultaneously in a peripheral zone of the at least one first and second sheets;

at least one guidance device positioning the first laser beam in relation to the median plane;

at least one source for generating a second laser beam for the welding of the sheets, in the peripheral zone from which the metal alloy layer was removed, to obtain a welded joint; and

at least one device for obtaining a relative displacement of the first and second sheets in relation to the first and second laser beams;

the first and second laser beams being located on a single line with reference to the median plane and at a fixed distance from each other.

61. :

The device as recited in claim 60, wherein the fixed distance is from 0.5 mm to 2 m.

62. :

The device as recited in claim 60, wherein the fixed distance is less than 600 mm.

63. :

The device as recited in claim 60, wherein the fixed distance is less than 5 mm.

64. :

The device as recited in claim 60, wherein the first laser beam is emitted from an ablation head and the second laser beam is emitted from a welding head, the heads forming a compact element and a focusing device being common to both the first and second laser beams.

65. :

The device as recited in claim 60, wherein the guidance device is able to position the second laser beam with reference to the median plane.

66. :

The device as recited in claim 60, further comprising a filler rod device for realization of the welded joint.

67. :

The device as recited in claim 60, further comprising a further laser beam to effect a weld on the face opposite to the face where the second laser beam operates.