Abstract
High-volume water sprays and air-water mixtures have been used to shorten the holdperiod(HP) in the two-stage rolling of 0.08%Nb, 0.02%Nb, and 0.09%Ti steels. The effects of gentler diffuse sprays were also roughly determined. Highvolume sprays create pronounced temperature gradients through the thickness, and subsequent rolling can produce deformed, elongated surface grains in the finished plate, depending upon steel composition, plate thickness during the HP, and spraying time. It appears that the lesser temperature gradients imposed by air-water mixtures or gentler diffuse sprays are better suited to significantly lower hold times for thick plates with larger additions of Nb or Ti. High-volume sprays can, however, be used to lower finishing temperatures in two-stage rolling in plain C-Mn (0.18C-1.28Mn) steel if adequate time is allowed after spraying to permit temperature homogenization through the thickness. The bulk mechanical properties of the HSLA steels tested were relatively unaffected by length of HP, and the 0.02%Nb steel improved markedly in strength and toughness on being oil quenched after rolling.
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