Hot roll forming system for high strength component production

A method for forming a part by roll forming, the method comprising:

• loading coating-free press-hardened steel (CFPHS) into a roll forming system, the CFPHS including:
• an alloy matrix of carbon (C) at a concentration of greater than or equal to about 0.05 wt.% to less than or equal to about 0.35 wt.%, chromium (Cr) at a concentration of greater than or equal to about 0.6 wt.% to less than or equal to about 4.0 wt.%, silicon (Si) at a concentration of greater than or equal to about 0.5 wt.% to less than or equal to about 2.0 wt.%, manganese (Mn) at a concentration of greater than or equal to about 0.5 wt.% to less than or equal to about 5.0 wt.%, niobium (Nb) at a concentration of greater than or equal to about 0.0 wt.% to less than or equal to about 0.05 wt.%, and a balance of iron (Fe), the alloy matrix being greater than or equal to about 95 vol.% martensite when fully hardened;
• a first layer directly on the alloy matrix, the first layer is continuous, has a first thickness of greater than or equal to about 0.01 µm to less than or equal to about 10 µm, and including an oxide enriched with Cr and Si;
• and
• a second layer disposed directly on the first layer, the second layer is continuous, has a second thickness of greater than or equal to about 0.01 µm to less than or equal to about 30 µm, and including an oxide enriched with Fe;
• heating the CFPHS with an induction heater prior to roll forming the CFPHS into the part, the heating includes heating a first portion of the CFPHS to a first temperature and heating a second portion of the CFPHS to a second temperature that is different from the first temperature;
• roll forming the CFPHS into the part with rollers after heating the CFPHS, the part defining a gap between a first surface and a second surface of the part that is less than, or equal to, 1.5 mm;
• and
• welding the first surface and the second surface together at the gap to close the gap,
• wherein the heating is performed inline with the roll forming on a common roll forming line.

A system for forming a part by roll forming, the system comprising:

• coating-free press-hardened steel (CFPHS) including:
• an alloy matrix of carbon (C) at a concentration of greater than or equal to about 0.05 wt.% to less than or equal to about 0.35 wt.%, chromium (Cr) at a concentration of greater than or equal to about 0.6 wt.% to less than or equal to about 4.0 wt.%, silicon (Si) at a concentration of greater than or equal to about 0.5 wt.% to less than or equal to about 2.0 wt.%, and a balance of iron (Fe), the alloy matrix being greater than or equal to about 95 vol.% martensite when fully hardened;
• a first layer directly on the alloy matrix, the first layer is continuous, has a first thickness of greater than or equal to about 0.01 µm to less than or equal to about 10 µm, and including an oxide enriched with Cr and Si;
• and
• a second layer disposed directly on the first layer, the second layer is continuous, has a second thickness of greater than or equal to about 0.01 µm to less than or equal to about 30 µm, and including an oxide enriched with Fe;
• an uncoiling device configured to uncoil the CFPHS;
• a flattening device configured to flatten the CFPHS;
• a punching device configured to punch openings in the CFPHS;
• a plurality of rollers configured to roll form the CFPHS into the part;
• and
• a heater between, the punching device and the plurality of rollers, the heater configured to heat the CFPHS after bring punched by the punching device and prior to being roll formed by the plurality of rollers,
• wherein the uncoiling device, the flattening device, the punching device, the plurality of rollers, and the heater are all on a common roll forming line.