Arcelormittal

Maria Poirier

Pascal Drillet

Francis Schmit

Ivan Viaux

Sujay Sarkar

Cristian Alvarez

Thierry Lizon

Sadok Gaied

Thierry David

Lucille Gouton

A process for manufacturing a press hardened laser welded steel part, includes providing at least one first steel sheet with a composition containing, by weight 0.062≤C≤0.095%, the at least one first steel sheet precoated with a metallic precoating of aluminum, or aluminum-based alloy, or aluminum alloy.

Process for manufacturing a press hardened laser welded steel part

A method for producing a welded blank () includes providing two precoated sheets (), butt welding the precoated sheets () using a filler wire. The precoating () entirely covers at least one face () of each sheet () at the time of butt welding. The filler wire () has a carbon content between 0.01 wt. % and 0.45 wt. %. The composition of the filler wire () and the proportion of filler wire () added to the weld pool is chosen such that the weld joint () has (a) a quenching factor FT: FT−0.9FT≥0, where FTis a quenching factor of the least hardenable substrate (), and FTand FTare determined: FT=128+1553×C+55×Mn+267×Si+49×Ni+5×Cr−79×Al−2×Ni−1532×C−5×Mn−127×Si−40×C×Ni−4×Ni×Mn, and (b) a carbon content C<0.15 wt. % or, if C≥0.15 wt. %, a softening factor FAsuch that FA>5000, where FA=10291+4384.1×Mo+3676.9Si−522.64×Al−2221.2×Cr−118.11×Ni−1565.1×C−246.67×Mn.

Method for producing a welded steel blank and associated welded blank

A method for producing a part includes providing a first and a second precoated sheet (), butt welding the first and second precoated sheets () to obtain a blank (), and heating the blank () to a heat treatment temperature at least 10° C. lower than the full austenitization temperature of the weld joint () and at least 15° C. higher than a minimum temperature T:

Method for producing a press-hardened laser welded steel part and press-hardened laser welded steel part

A press hardened steel part is provided. The steel of the part has a chemical composition including, in weight: 0.062%&#x2264;C&#x2264;0.095%, 1.4%&#x2264;Mn&#x2264;1.9%, 0.2%&#x2264;Si&#x2264;0.5%, 0.020%&#x2264;Al&#x2264;0.070%, 0.02%&#x2264;Cr&#x2264;0.1%, wherein: 1.5%&#x2264;(C+Mn+Si+Cr)&#x2264;2.7%, 0.040%&#x2264;Nb&#x2264;0.060%, 3.4&#xd7;N&#x2264;Ti&#x2264;8&#xd7;N wherein: 0.044%&#x2264;(Nb+Ti)&#x2264;0.090%, 0.0005&#x2264;B&#x2264;0.004%, 0.001%&#x2264;N&#x2264;0.009%, 0.0005%&#x2264;S&#x2264;0.003%, 0.001%&#x2264;P&#x2264;0.020%, optionally: 0.0001%&#x2264;Ca&#x2264;0.003%, and the remainder being Fe and unavoidable impurities. The microstructure of the part includes, in a majority of the part, in surface fractions: less than 40% of bainite, less than 5% of austenite, less than 5% of ferrite, and a remainder being martensite. The martensite is fresh martensite and self-tempered martensite.

Steel for press hardening and press hardened part manufactured from such steel

A process for manufacturing a press hardened steel part is provided. The steel of the part has a chemical composition including, in weight: 0.062%&#x2264;C&#x2264;0.095%, 1.4%&#x2264;Mn&#x2264;1.9%, 0.2%&#x2264;Si&#x2264;0.5%, 0.020%&#x2264;Al&#x2264;0.070%, 0.02%&#x2264;Cr&#x2264;0.1%, wherein: 1.5%&#x2264;(C+Mn+Si+Cr)&#x2264;2.7%, 0.040%&#x2264;Nb&#x2264;0.060%, 3.4&#xd7;N&#x2264;Ti&#x2264;8&#xd7;N wherein: 0.044%&#x2264;(Nb+Ti)&#x2264;0.090%, 0.0005&#x2264;B&#x2264;0.004%, 0.001%&#x2264;N&#x2264;0.009%, 0.0005%&#x2264;S&#x2264;0.003%, 0.001%&#x2264;P&#x2264;0.020%, optionally: 0.0001%&#x2264;Ca&#x2264;0.003%, and the remainder being Fe and unavoidable impurities. The process includes hot forming the heated blank in the forming press so as to obtain a formed part and cooling the formed part at a cooling rate CR1 between 40 and 360&#xb0;C/s in a temperature range from 750 to 450&#xb0;C. and at a cooling rate CR2 between 15 to 150&#xb0;C/s in a temperature range from 450&#xb0;C to 250&#xb0;C. wherein CR2&#x3c;CR1.

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Villers Saint Paul, France

Maria Poirier