焊接气瓶钢HP295热塑性研究
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摘要
采用Gleeble 3500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R_A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.
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.
引文
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[3] 鲁永剑.低合金钢中厚板连铸坯热送裂纹形成及预防机理研究[D].重庆:重庆大学,2013.
[4] Jia Y C,Guo H R,Ran L I,et al.Effects of rolling processes on yield ratio and formability of hot rolled gas cylinder steel[J].Journal of Iron and Steel Research (International),2012,19(3):52-55.
[5] 陈毛川,王福明,陶素芬,等.40Cr钢的高温热塑性[J].材料热处理学报,2014,35(S1):119-125.
[6] 王志刚,余驰斌,鲍思前,等.Q345C连铸坯高温热塑性的研究[J].南方金属,2010(176):22-25.
[7] 范倚,王明林,张慧,等.第三代汽车钢的热塑性及断裂机理[J].北京科技大学学报,2013,35(5):607-612.
[8] 耿明山,张炯明.含钒低合金钢铸坯高温延塑性研究[J].中国冶金,2010,20(3):11-17.
[9] 杨小刚,张立峰,任英,等.含钛微合金钢的高温热塑性及断裂机理[J].工程科学学报,2016,38(6):805-811.
[10] Mintz B,Crowther D N.Hot ductility of steels and its relationship to the problem of transverse cracking in continuous casting[J].International Materials Reviews,2010,55(3):168-196.
[11] Banks K M,Tuling A,Mintz B.Influence of thermal history on hot ductility of steel and its relationship to the problem of cracking in continuous casting[J].Materials Science and Technology,2012,28(5):536-542.
[12] 赵明,刘继恒,杨晓燕.低碳锰钢魏氏组织的形成及力学性能[J].金属热处理学报,1995,16(1):53-57.
[13] Mintz B,Arrowsmith J M.Hot-ductility behaviour of C-Mn-Nb-Al steels and its relationship to crack propagation during the straightening of continuously cast strand[J].Metals Technology,1979,6(1):24-32.
[14] 鈴木洋夫,西村哲,山口重裕.凝固組織を持つ種々の鋼の高温域における脆化特性[J].鉄と鋼,1979,65(14):2038-2046.
[15] Won Y M,Kim K H,Yeo T J,et al.Effect of cooling rate on ZST,LIT and ZDT of carbon steels near melting point[J].ISIJ International,1998,38(10):1093-1099.
[16] 鈴木洋夫,西村哲,今村淳,等.900～600 ℃温度域における鋼の脆化特性:連鋳々片の表面横割れに関連して[J].鉄と鋼,1981,67(8):1180-1189.