Properties and Applications of High Strength Cold-Rolled Steels; Plain Carbon and Killed Low Alloy

Four families of low-carbon, high-strength cold-rolled (HSCR) sheet are discussed, exhibiting minimum yield strengths of 40 to 140 ksi. The relative merits of the various grades are analyzed in terms of important fabricating and selection criteria: strengthening capability, planar anisotropy, formability, impact loading response, weldability and cost reduction. Paralleling the increase in strengthening capability in HSCR was an increased planar anisotropy and variation in formability within the various families. The impact loading of all cold-rolled grades showed increased yield strengths and energy absorption; the weldability of the different grades varied widely depending upon strengthening mechanisms, strength level, and chemistry; the cost reductions possible with the HSCR decreased as the degree of formability required in the finished part increased. Generally, gauge reductions of 6% to 34% were found to be necessary to offset cost extras for different grades of HSCR sheet. Continued work towards development of a full range of HSCR sheet with varying degrees of formability and cost appears necessary in light of the present and future expected needs of the steel buyer and designer.