MANUFACTURE OF THICK 50KG CLASS LOW YIELD RATIO-HIGH TENSILE STRENGTH STEEL PLATE SMALL IN DIFFERENCE OF HARDNESS IN PLATE THICKNESS DIRECTION

摘要

PURPOSE:To manufacture a thick 50kg class low yield ratio-high tensile strength steel plate small in the difference of hardness in the plate thickness direction by limiting chemical components, heating temp. and rolling finishing temp. as well as cooling starting temp., cooling velocity and cooling stopping temp. at the time of controlled cooling in a steel plate. CONSTITUTION:This is a method of heating a slab to =1100 deg.C, thereafter finishing its rolling in the temp. range of 850 to 900 deg.C and executing cooling to the temp. range of 500 to 400 deg.C at 3 to 12 deg.C/sec cooling velocity in which its cooling starting temp. is regulated to (the rolling finishing temp. -50 deg.C) or above.