中厚钢板探伤不合格的原因及预防

针对邯钢Q345RT中厚板生产中出现的钢板探伤不合格缺陷,并且在钢板缺陷处取样,断口有时存在层状现象.采用化学分析、气体含量检验、铸坯低倍检验、金相组织分析和扫描电镜、断口形貌分析等方法,分析钢板探伤不合格的原因.结果表明：铸坯中心偏析严重,因偏析产生的少量马氏体、贝氏体组织导致轧后应力集中,在冷却速度较快的条件下钢板产生微裂纹,以条状MnS和CaO-A12O3为基体的硫化物夹杂和硅酸盐类夹杂物较高,铸坯中氢含量偏高引起氢致裂纹,均可导致钢板探伤不合格.通过控制炼钢工艺过程,减少了铸坯中的夹杂物和氢含量,该中厚板探伤合格率由92％提高到98.2％.

REASON AND PREVENTION FOR DEFECTS IN FLAW DETECTION OF PLATE

There are unqualifi.ed defects appeared in flaw detection of plate Q345RT in Han Steel, and layers in fracture surface of defect sample. The reason is analyzed with chemical analysis, gas content examination, casting billet macro - structure inspection, metallographic structure analysis, scanning electron microscope and fracture surface morphology analysis. It is showed that serious segregation in center of casting billet pro- duces a Little quantity of martensite and bainite, which causes after - roiling stress concentration, and then un- der faster cooling speed some micro cracks are brought about in steel plate; the sulfide and silicate inclusions in plate with strip - like MnS and CaO - A1203 as matrix are too much; hydrogen induced cracking caused by too high hydrogen content in billet, all above factors can lead to qualified defects in flaw detection. By con- trolling the steel making process procedure, the inclusions and hydrogen content in billet are reduced, and the qualified rate in flaw detection is raised from 92 to 98.2 percent.