ArcelorMittal S.A.
Method for producing a press-hardened laser welded steel part and press-hardened laser welded steel part

Abstract:

A method for producing a part includes providing a first and a second precoated sheet (1,2), butt welding the first and second precoated sheets (1) to obtain a blank (15), and heating the blank (15) to a heat treatment temperature at least 10.degree. C. lower than the full austenitization temperature of the weld joint (22) and at least 15.degree. C. higher than a minimum temperature T T min ( .degree. C . ) = AC 3 ( WJ ) - .alpha. IC max 100 ( Ac 3 ( WJ ) - 673 - 40 .times. Al ) . ##EQU00001## where Ac3(WJ) is the full austenitization temperature of the weld joint (22) .alpha. IC max = ( 1 - ( 1 + .rho. ) ( max ( 1 ; .rho. ) Ts 2 - 350 ) ( 1 - .beta. ) ( .rho. Ts 2 + Ts 1 ) + .beta. ( 1 + .rho. ) ( 3130 C FW + 750 ) - 350 .times. ( 1 + .rho. ) ) .times. 100 , ##EQU00002## where T.sub.S1 and T.sub.S2 are the ultimate tensile strengths of the strongest and the weakest substrate after press-hardening C.sup.FW is the carbon content of the filler material .beta. is the proportion of filler material .rho. is the ratio between the thicknesses of the weakest and the strongest substrate The method also includes holding the blank (15) at the heat treatment temperature for a time between 2 and 10 minutes; and press-forming the blank (15) into a part and cooling.