新型耐磨钢NM400斜Y形坡口焊接抗裂性分析

Y-groove cracking test on the welding crack resistance of the NM400 steel

采用斜Y形坡口焊接抗裂性试验对NM400钢的焊接抗裂性进行了研究,通过测定其表面裂纹率、断面裂纹率及根部裂纹率,评定NM400的抗裂性能,并分析焊前预热对材料抗裂性的影响.同时,应用热弹塑性有限元法对斜Y形坡口试样进行了焊接过程的有限元数值模拟计算,得出横向焊接残余应力的分布情况及峰值位置.结果表明,常温下NM400的根部裂纹率较高,预热150℃时各裂纹率均降至0.因此,焊前预热能够提高NM400的焊接抗裂性.另斜Y形坡口根部产生较大的应力集中,局部横向残余应力超过材料的强度,是致使其产生裂纹的力学因素.

Y-groove cracking test was conducted to study the welding crack resistance of NM400 steel. Assessment of welding crack resistance of steel NM400 consists of the surface crack rate,section crack rate and root crack rate,and the effects of preheating on the crack resistance of steel NM400 has been analyzed. Thermal elastic-plastic finite element method was applied to carry out a finite numerical simulation of welding process for samples used in Y-groove cracking test and transverse welding residual stress distribution and peak position were obtained. The results indicated that the root crack rate of the steel NM400 at room temperature reached a high value,and it could be decreased to zero when preheating at 150 ℃. Therefore,preheating before welding can improve the welding crack resistance of steel NM400. Otherwise,stress concentration occured at the root of the Y-groove. Local transverse residual stress which was larger than the yield strength of materials is mechanical factors causing cracks.