B在钢中的偏析及SS400含硼钢的重熔现象

Segregation of B in steel and remelting phenomenon after solidification of SS400 B-bearing steel

为了研究B在钢中的偏析及重熔特性，采用金属原位分析仪、二次离子质谱仪以及微观偏析模型研究了B在SS400含硼钢中的偏析行为，并利用高温激光共聚焦显微镜观察了SS400含硼钢连铸坯裂纹处的重熔现象。偏析模型计算结果表明，当凝固率达到0．96时，B元素的偏析比达到16以上；金属原位分析仪测试结果表明，所取的4个试样中B元素的最大偏析比分别为32．37、18．01、18．40、12．96，试验结果和模型计算都表明B在钢中具有很强的偏析性，也表明尽管SS400含硼钢中B的质量分数仅为0．0013％，但是由于B在钢中的偏析，局部区域中B的质量分数可能超过0．015％。二次离子质谱仪分析表明，B在裂纹区域存在明显的偏析现象。高温激光共聚焦显微镜观察结果表明，SS400含硼钢裂纹处在1008．4～1150．9℃、1294．8～1304．9℃、1325．8～1342．8℃、1379．8～1420．6℃均存在重熔现象。

To investigate the segregation and remelting properties of B-bearing steel, segregation of B in SS400 B- hearing steel was studied through original position analyzer for metal（OPA）, secondary ion mass spectrometry （SIMS）, micro-segregation model, and the retrograde melting phenomenon on cracks during casting of B-bearing steels was observed by eonfoeal scanning laser microscope （CSLM）. The micro-segregation model shows that when solidified fraction is 0.96, the segregation level of B is beyond 16. The OPA result indicates that the maxi- mum segregation levels of B come from 4 samples are 32.37, 18.01, 18.40 and 12.96. Model calculations and ex- perimental results show a strong segregation of B in steel, it also shows that although the mass fraction of B in SS400 B bearing steel is only 0. 0013~, but since B segregates in steel, mass fraction of B on local region may ex ceed 0. 015 ~. The analysis of SIMS shows that the serious segregation of element B occurs in the crack area. The results of CSLM studies show that the remelting phenomenon are found around surface crack in slab when the tem- peratures are 1008.4-1 150.9 ℃, 1294.8--1 304.9 ℃, 1 325.8--1 342.8 ℃, 1 379.8--1 420.6 ℃.