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

A process for manufacturing a press hardened laser welded steel part, comprising the successive steps of:

• providing at least one first steel sheet with a composition containing, by weight:
• 0.062≤C≤0.095%;
• 1.4%≤Mn≤1.9%;
• 0.2%≤Si≤0.5%;
• 0.020%≤Al≤0.070%;
• 0.02%≤Cr≤0.1%;
• wherein:
• 1.5%≤(C+Mn+Si+Cr)≤2.7%;
• 0.040%≤Nb≤0.060%;
• 3.4×N≤Ti≤8×N;
• wherein:
• 0.044%≤(Nb+Ti)≤0.090%;
• 0.0005≤B≤0.004%;
• 0.001%≤N≤0.009%;
• 0.0005%≤S≤0.003%;
• 0.001%≤P≤0.020%;
• and
• a remainder being Fe and unavoidable impurities,
• the at least one first steel sheet precoated with a metallic precoating of aluminum, or aluminum-based alloy, or aluminum alloy;
• providing at least one second steel sheet with a composition containing, by weight, from 0.065 to 0.38% of carbon, the at least one second steel sheet precoated with a metallic precoating of aluminum, or aluminum-based alloy, or aluminum alloy;
• removing a portion of a thickness of the aluminum precoating at upper and lower sides along one side of a periphery of the at least one first steel sheet and the at least one second steel sheet;
• creating a welded blank by laser welding the at least one first steel sheet and the at least one second steel sheet, such that an aluminum content in a weld metal is lower than 0.3% by weight, the laser welding being performed along the periphery wherein the portion of the thickness of the aluminum precoating has been removed;
• heating the welded blank and holding the welded blank at a temperature Tm between 890 and 950° C., a holding duration Dm at the temperature being between 1 and 10 minutes, so as to obtain a heated welded blank;
• transferring the heated welded blank within a forming press, the transfer duration Dt being less than 10 s;
• hot forming the heated welded blank in the forming press so as to obtain a welded formed part;
• and
• cooling the welded formed part at a first cooling rate CR1 between 40 and 360° C./s in a temperature range between 750 and 450° C., and at a second cooling rate CR2 between 15 to 150° C./s in a temperature range between 450° C. and 250° C., wherein CR2<CR1.