COLD ROLLED STEEL PLATE HAVING EXCELLENT BAKING HARDENABILITY NON-COLD AGEING CHARACTERISTICES AND MOLDABILITY, AND MOLTEN ZINC-PLATED COLD-ROLLED STEEL PLATE AND METHOD OF MANUFACTURING THE SAME

摘要

A cold rolled steel plate having excellent baking hardenability, non-cold-ageing characteristics and moldability, and a molten zinc-plated cold-rolled steel plate and a method of manufacturing the same. The structure of an annealed product is turned into mixed structure by positively adding Mn and Cr to a base material of very low carbon steel or very low carbon steel containing not less than one of Ti and Nb. This enables a steel plate having both a high paint-baking hardenability and a high non-cold-ageing characteristics as well as a high processability represented by an average r-value (deep drawing characteristics) to be obtained. Especially, the paint-baking hardenability is such that a cold-rolled steel plate and a molten zinc-plated cold-rolled steel plate which provide a BH amount as high as around 10 kgf/mm2 as necessary, and which also have excellent non-cold-ageing characteristics, can be provided. IMAGE