焊接气瓶钢HP295热塑性研究

Hot ductility of welded cylinder steel HP295

采用Gleeble3500热模拟试验机对焊接气瓶钢HP295的高温热塑性能进行测试,利用OM、SEM、EDS对实验钢热变形后的微观组织、断口形貌及微区成分进行表征,并对断裂类型及影响因素进行分析。结果表明,在500~1100℃的温度范围内,实验钢的断面收缩率RA均超过了77%,整体表现出了良好的高温塑性;实验钢的热塑性曲线在700~900℃之间出现了一个“塑性凹槽”,在800℃时试样的断面收缩率达到极小值77.98%,故实际生产中应避开这一温度范围,在铸坯表面温度高于900℃时进行矫直。HP295钢在900℃以上的高温塑性区,表现为穿晶韧性断裂;在800℃塑性极小值时,铁素体在奥氏体晶界的析出降低了实验钢的塑性,表现为沿晶韧性断裂。

The hot ductility of welded cylinder steel HP295 at high temperature was tested on a Gleeble 3500 thermal simulator. The fracture morphology,microstructure and composition were characterized by OM,SEM and EDS,and the fracture mechanism as well as influencing factors were analyzed. The results show that in the experimental temperature range of 500~1100 ℃,the measured reduction areas ( R A) of the samples exceed 77%,exhibiting overall good plasticity at high temperature. The curve of high temperature hot ductility shows a plastic groove between 700 ℃ and 900 ℃,and the area of reduction of the sample reaches a minimum value of 77.98% at 800 ℃.Therefore,it is vital to avoid this temperature range for slab straightening in the actual production and the steel should be straightened at a temperature above 900 ℃.HP295 steel shows the characteristic of transgranular ductile fracture at high temperature plastic zone above 900 ℃;on the other hand,the precipitation of ferrite at the austenite grain boundary weakens the ductility of HP295 steel at 800 ℃ with the minimum plasticity,and the fracture type is characterized as the intergranular ductile fracture.