FIELD: welding.
SUBSTANCE: invention relates to welding and namely to the production of a welded steel workpiece used for the production of parts of the anti-intrusion system or energy-absorbing parts of a motor vehicle. Two pre-coated sheets are used to produce a welded workpiece. Each of the sheets has a steel substrate pre-coated on at least one of its main faces. The precoating consists of an intermetallic alloy layer containing at least iron and aluminum and optionally a metal alloy layer extending over the intermetallic alloy layer. The metal alloy layer is an aluminum layer, an aluminum alloy layer or an aluminum base alloy layer, and the substrate is made of press hardened steel. The substrate steel of at least one of the sheets contains, wt%: 0,10≤С≤0,5, 0,5≤Mn≤3, 0,1≤Si≤1, 0,01≤Сr≤1, Ti≤0,2, Al≤0,1, S≤0,05, P≤0,1, B≤0,010, the rest is iron and inevitable impurities. Butt welding of the sheets is carried out with the use of a filler wire containing 0.01-0.45 wt% of carbon to obtain a welded joint at the junction between the sheets. During butt welding, the pre-applied coating completely covers at least one major face of each sheet. The composition of the filler wire and the proportion of the filler wire added to the weld pool are selected so that the resulting weld has a hardening factor FTWJ of the welded joint and the level of carbon CWJ in the welded joint. The hardening factor FTWJ can be calculated in accordance with this formula: FTWJ - 0.9FTBM 0 where FTBM is the hardening factor for the least hardened steel substrate, while the hardening factors FTWJ and FTBM are determined with the help of the following formula: FT=128 + 1553×C + 55×Mn + 267×Si + 49×Ni + 5×Cr – 79×Al – 2×Ni2 – 1532×C2 – 5×Mn2 – 127×Si2 – 40×C×Ni – 4×Ni×Mn. The carbon content CWJ is strictly less than 0.15 wt%. If the carbon content CWJ in the welded joint is 0.15 wt% or more, the welded joint has a softening factor FAWJ of the welded joint which is more than 5000 where the softening factor FAWJ of the welded joint is (22) calculated depending on the average content of aluminum, chromium, nickel, molybdenum, carbon, manganese and silicon in the welded joint according to the following formula: FA = 10291 + 4384,1×Mo + 3676,9Si – 522,64×Al – 2221,2×Cr – 118,11×Ni – 1565,1×C – 246,67×Mn. A part is produced by forming in a hot press and cooling the welded steel workpiece which is made of two pre-coated sheets and which has the required safety characteristics in a collision of vehicles.
EFFECT: invention enables production of parts of the anti-intrusion system or energy-absorbing parts of a motor vehicle.
25 cl, 6 tbl, 5 dwg
