Hot-annealed cold rolled steel sheet excellent in formability and hardening hardening and its manufacturing method

摘要

The present invention relates to an annealing cold rolled steel sheet having excellent formability and hardening hardening property used in interior and exterior sheet materials of automobiles, and a method of manufacturing the same. The alloy composition and content of P-added low carbon steel Al-kilted steel are controlled and manufacturing conditions are controlled. It is excellent in formability by forming microstructures of coaxial grains different from those of conventional annealing materials, and has a method of manufacturing cold rolled steel sheets having a tensile strength of 30 to 35 kgf / mm2 with a hardening hardness of 4.0 kgf / mm2 or more. The purpose is to provide.;The present invention for achieving the above object is by weight%, C: 0.005 to 0.025%, Mn: 0.1 to 0.4%, P: 0.04 to 0.09%, S: 0.013% or less, Sol.Al: 0.02 to 0.08%, N: 0.0012% or less, the remaining annealing-type cold-rolled steel sheet composed of the remaining Fe and other unavoidable impurities, and excellent in formability and hardening hardenability, whose structure is equiaxed, and the steel formed as described above, after homogenizing heat treatment at a temperature of 1200 ° C or higher, After hot-rolled at 950 ° C in the temperature range, it is wound up and cold-rolled at a temperature in the range of 600 ° C or less, and then annealed and temper-rolled in the temperature range of 650-740 ° C. Its main purpose is to provide a method for producing the same.