Hot-rolled steel strip and method of making it
AssigneeThyssen Stahl AG
InventorsManfred Espenhahn, Thomas Heller, Jürgen Esdohr
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Abstract
The invention concerns hot-rolled steel strip no more than 5 mm thick, optionally less than 2 mm thick, made of high-tensile steel, that contains 0.08%-0.25% carbon, 1.20% to 2.0% manganese, and 0.02% to 0.05% aluminum, and optionally up to 1.0% chromium, up to 0.1% copper, up to 0.5% molybdenum, up to 0.1% nickel, up to 0.009% nitrogen, up to 0.0025% B, and optionally a stoichiometric amount of titanium in relation to nitrogen. The steel strip has a greater than 95% martensitic structure, and a tensile strength of 800 to 1400 N/mm2.
Claims13
A hot steel strip having a thickness below 5 mm and a tensile strength from 800 to 1400 N/mm2, said hot steel strip comprising in mass percentage
- 0.08 to 0.25% of carbon,
- 1.20 to 2.0% of manganese,
- 0.02 to 0.05% of aluminum,
- and less than 0.07% silicon, the remainder being iron and unavoidable impurities, said impurities including up to 0.015% phosphorous and up to 0.003% sulfur, said hot steel strip having a greater than 95% martensitic structure.
A process for producing a hot steel strip having a final thickness of less than 5 mm and a tensile strength above 800 N/mm2, wherein said hot steel strip comprises in mass percentage:
- 0.08 to 0.25% carbon,
- 1.20 to 2.0% manganese,
- 0.02 to 0.05% aluminum,
- and less than 0.07% silicon, the remainder being iron and unavoidable impurities, said impurities including up to 0.015% phosphorous and up to 0.003% sulfur, said hot steel strip having a greater than 95% martensitic structure, said process comprising the steps of:
- heating a slab to a temperature in the range of 1000 to 1300° C.;
- pre-rolling said slab within a temperature range of 950 to 1150° C.;
- finishing said slab at a final rolling temperature above Ar3 to produce a rolled strip;
- cooling the rolled strip to a coiling temperature in the range of 20° C. to below the martensite start temperature;
- and coiling of the thus cooled rolled strip such that a structure with more than 95% martensite is obtained.
Dependencies are inferred from the claim text.