Method of producing non-ageing cold rolled steel sheets
AssigneeKawasaki Steel Corporation
InventorsOsamu Hashimoto, Susumu Sato, Tomoo Tanaka
Life of this patent
Estimating the term…
Abstract
A method of producing substantially non-ageing cold rolled steel sheets having a remarkably excellent deep drawing property, wherein an extra low-carbon steel is melted together with niobium in an amount of less than the necessary amount for fixing completely carbon contained in the extra low-carbon steel to prepare a molten steel, the molten steel is made into an ingot and then the ingot is slabbed, or the molten steel is continuously cast to produce a slab, the slab is subjected to a hot rolling and a cold rolling to produce a cold rolled sheet according to an ordinary method, and the cold rolled sheet is subjected to a box annealing.
Claims6
A method of producing non-ageing cold rolled steel sheets having a remarkably excellent deep drawing property or r value of not lower than 1.86, an elongation that is not lower than 50%, and an ageing index that is not more than 1.0 KG/mm.sup.2, the method comprising preparing a steel consisting of, in % by weight, not more than 0.01% of carbon, not more than 0.2% of silicon, 0.05-0.40% of manganese, not more than 0.02% of phosphorus, not more than 0.02% of sulfur, not more than 0.01% of nitrogen, acid-soluble aluminum in an amount not less than 0.005%, and of at least 1.8 times amount of nitrogen, niobium in an amount less than the necessary amount for completely fixing carbon and not less than 0.001%, and in an amount of log (Nb/C) of within the range of 0.10-1.00, and the remainder being iron and incidental impurities, and subjecting the steel to a hot rolling, a cold rolling and box annealing.
Dependencies are inferred from the claim text.