Analysis and improvement of wide band edge crack defect in Q235B steel
By tracking the continuous casting billet,it is found that the distribution of the upper edge crack of the hot rolled strip is very consistent with the distribution of the transverse corner crack of the continuous casting billet.The results of energy spectrum analysis showed that K and Na were typical components of mold powder,which proved that the defect originated in the mold of continuous casting machine.Then take Q235B molten steel as an example,the carbon content should be controlled in the range of 0.15％-0.20％,w([Mn])/w([S])＞20 standard.By avoi-ding the crack sensitive region of carbon content and w([Mn])/w([S]),the proportion of furnace times in the crack sensitive region of carbon content and w([Mn])/w([S])and the value of the opening of the foot roll of continuous casting mold are adjusted to 0 mm、0.4 mm、0.8 mm.Two-side and middle-three-point tests were used to test the arc-foot roller and sector roller in the mould.Each checkpoint detects four sets of values,and the test control stand-ard was(1±0.15)mm The edge crack rate of hot rolled steel strip was reduced from 0.46％to 0.04％by optimi-zing and improving the nozzle insertion depth of continuous casting mold to 120-150 mm.
hot rolled strip coiledge crackcarbon contentMn/S ratiofoot roll opening
万方数据
维普
