Arcelormittal

Sujay Sarkar

Pascal Drillet

Maria Poirier

Xavier Bano

Guillaume Marcireau

Blandine Oehler

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 hot rolled steel sheet having a composition including the elements, expressed in percentage by weight 0.11%≤Carbon≤0.16%, 1%≤Manganese≤2%, 0.1%≤Silicon≤0.7%, 0 02%≤Aluminum≤0.1%, 0.15%≤Molybdenum≤0.4%, 0.15%≤Vanadium≤0.4%, 0.002%≤Phosphorus≤0.02%, 0%≤Sulfur≤0.005%, 0%≤Nitrogen≤0.01%, and can contain one or more of the following optional elements 0%≤Chromium≤0.5%, 0%≤Niobium≤0.05%, 0.0001%≤Calcium≤0.005%, 0%≤Boron≤0.001%, 0%≤Magnesium≤0.0010%, 0%≤Titanium≤0.01%, with 0.3%≤Mo+V+Nb≤0.6%, the remainder composition being composed of iron and unavoidable impurities, the microstructure of steel sheet including in area fraction, 70% to 90% Bainite, 10% to 25% Ferrite wherein the cumulated amounts of Bainite and Ferrite is at least 90% and a cumulated amount of Residual Austenite and Martensite is between 0% and 10%.

Hot rolled steel sheet and a method of manufacturing thereof

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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Metz, France

Sujay Sarkar