Process of making a high strength cold reduced steel sheet having high bake-hardenability and excellent non-aging property

A process of making a high strength cold reduced steel having both high bake-hardenability and excellent non-aging property consisting essentially of controlling the chemical composition of the steel within the following range in the steel making stage:

• ______________________________________ C 0.02 to 0.12% Mn 10 .times. [S] to 2.00% [N] [N] 0.003 to 0.02% Al <5 .times. 10.sup.-4 /[N] % [S] [S] 0.005 to 0.023%, ______________________________________
• the steel is hot rolled, pickled and cold reduced, and the cold-reduced steel strip so obtained is subjected to the following full continuous annealing process:
• ______________________________________ heating-up step Ac.sub.1 to 900.degree. C. holding time 5 to 180 seconds at a temperature of from Ac.sub.1 to 900.degree. C. rapid cooling quenching to room temperature from step Ac.sub.1 to 900.degree. C. in a water jet stream reheating step from the room temperature to a temperature of from 150 to 450.degree. C. tempering step holding at a temperature of from 150 to 450.degree. C. for from 5 to 300 seconds, and final step cooling from 150 to 450.degree. C. to room temperature and coiling. ______________________________________