Discussion on the Effect of Hydrogen Content on End Cracking of Bars
Baowu JFE produced 200 square meters of steel 45 without RH treatment in bulk.The bars were cold cut and segmented before being bundled and stored in the warehouse.After being stacked for 2-3 days,end cracks appeared in the batch of the steel.The bars with end cracks were repaired,and the polished,and still the bars showed secondary and terti-ary cracks.The depth of end cracks was about 0.1mm-5mm,posing a significant quality control risk.By analyzing the steelmaking process of the steel,it was found that the steel with RH treatment did not crack during shearing at any tempera-ture,but there were cracking defects at the sheared ends of the steel without RH treatment at 200 ℃-300 ℃;By comparing the distribution of shear residual stress in various diameters of bars,it was found that the residual stress at the rear end of large diameters is high,and the occurrence rate of end cracking is significantly higher.This indicates that the end cracking of bars is affected by residual hydrogen content and residual stress.To solve the problem of end cracking of rods,high-tem-perature shear is used to segment the bars.The hardness of high-temperature bars is small when shearing,which can signif-icantly reduce the shear stress on the bars.And after high-temperature shearing,there is a slow cooling process in the bars,which can remove residual hydrogen.This method effectively solves the problem of end cracking of the steel that has not had RH treatment.
end crackinghydrogen contentcold shearhigh temperature shearresidual stress
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