摘要
采用Gleeble-1500型热模拟试验机测试了Q345B和Q345C钢连铸板坯的高温力学性能,用扫描电镜观察了断口形貌,并分析了脆化机理。结果表明:Q345B和Q345C钢的第Ⅲ脆性区温度范围为700～825℃和600～980℃,在600～1 350℃下的抗拉强度均随温度的升高而降低,Q345C钢在780～840℃内断面收缩率小于30%,Q345B钢断面收缩率均大于30%;两种钢在1 350℃时均发生过熔断裂,1 000℃时均发生塑性穿晶断裂,而900℃时Q345B仍为塑性穿晶断裂,Q345C为穿晶与沿晶混合断裂,两种钢在800℃为脆性断裂,600℃时转化为塑性断裂;Q345钢脆化原因有两个,一是细小Nb(CN)等第二相在奥氏体单相区晶界处析出导致应力集中产生脆化;二是原奥氏体晶界处析出的网状铁素体强度低导致脆化。
High temperature mechanical properties of Q345B and Q345C steel continuously cast slabs were tested by Gleeble-1500 thermal simulation machine.The morphology of the fracture surface was analyzed by SEM.And the embrittlement mechanism was studied.The results show that the embrittlement temperature region Ⅲ of the Q345B steel was 700-825 ℃,and the Q345C steel was 600-980 ℃.Tensile strength of both the steels reduced with increasing the temperature in 600-1 350 ℃,and the reduction of area of Q345C steel was less than 30% in 780-840 ℃ and Q345B steel was always higher than 30% in all temperatures.Both the two steels occured transfusion fracture at 1 350 ℃,and plastic transcrystalline fracture at 1 000 ℃.The Q345B steel still occured transcrystalline fracture at 900 ℃,while the Q345C steel occured mixed fracture of transcrystalline and intergranular fracture at 900 ℃.The fracture mode of the two steels changed from brittle fracture at 800 ℃ to plastic fracture at 600 ℃.Causes of embrittlement of the Q345 steel existed in two aspects,one was that superfine Nb（CN） second phase particles precipitated at the austenite single phase region led to the embrittlement occured which was resulted from the strain concentration at the grain boundary,and the other was that the strength of reticulate ferrite precipated from original austenite grain boundaries was low,that resulted in the embrittlement.
出处
《机械工程材料》
CAS
CSCD
北大核心
2010年第11期91-94,共4页
Materials For Mechanical Engineering
基金
江西省教育厅科学基金资助项目(GJJ09519)
关键词
高温力学性能
Q345钢
连铸板坯
high temperature mechanical property
Q345 steel
continuously cast slab
