| 摘要 |
PURPOSE:To enable considerable adjustment of the quality of hot rolled steel material contg. specific equiv. of C with a titled method which rolls and cools said material under limited conditions by setting the grain size of austenite prior to transformation and cooling conditions in such a way that the specific equation for estimating elongation is satisfied. CONSTITUTION:A hot rolled steel material contg. 0.10-0.50% equiv. C is rolled at the temp. above the Ar3 transformation point and is then immediately cooled to <=700 deg.C at a cooling rate of <=150 deg.C/sec to adjust the quality of said material. The target elongation is obtd. here by satisfying the equation [El: elongation (%), Ceq: C equiv. (={(%C+%Mn)/6}X100), CT: coiling temp. or cooling stop temp. ( deg.C), CR: cooling rate ( deg.C/sec), t: plate thickness (mm.), e0: the correction term if there is precipitation hardening or the like, A1-A6: constant, m, n: both 0 or 1, B: f(dgamma) or dgamma<-1/2> or constant, dgamma: grain size of austenite (mu), C: g(CR) or logCR]. |
