氮微合金化HRB500E连铸坯高温力学性能的研究

Research on high temperature mechanical properties of nitrogen-microalloying steel HRB500E continuous casting billet

为了优化氮微合金化钢HRB500E的连铸冷却配水工艺,保证铸坯质量,采用Gleeble-1500D热模拟试验机测定了铸坯的高温力学性能,并对试样断口组织形貌进行了显微观察与分析,讨论了其在不同温度区间的断裂机理。研究表明:在应变速率为1.4×10-3/s时,铸坯第Ⅲ脆性温度区间出现在675~750℃,脆断主要原因是铁素体在奥氏体晶界析出、晶界处Mn S的偏析和大量V(C,N)的析出;铸坯未出现第Ⅱ脆性温度区,在1 000℃左右断裂方式为穿晶断裂;第Ⅰ脆性温度区在1 300℃以上,断裂方式为晶间断裂,主要原因是O,S,P在晶界富集促进形成液膜。

To optimize the CC water-cooling technology of nitrogen-microalloying steel HRB500 E continuous casting billet and guarantee the quality of the billet,the high temperature mechanical properties of the billet were measured by Gleeble-1500 D thermal simulator,the microstructure and morphology of specimen fracture were observed and analyzed,and the fracture mechanism of the billet in different temperature range was also discussed. The results showed that when the strain rate was 1. 4 × 10-3/s,the third brittle temperature range of HRB500 E billet was 675-750 ℃. The main cause of the brittle fracture was due to precipitation of ferrite at austenite grain boundary,Mn S segregation and precipitation of large amount of V（C,N） at grain boundary. The second brittle temperature range did not appear in the billet,and the fracture mode was transgranular fracture at about 1 000 ℃. The first brittle temperature range was above 1 300 ℃. The fracture mode was intergranular fracture,and the main cause was enrichment of O,S,P at the grain boundary,which led to form liquid film.