材料期刊网

用金相、电子探针、膨胀分析等对12AlMoV钢焊接接头第一类碳迁移过程进行了研究.结果证明,发生这类碳迁移是由于在碳快速扩散的温度范围,熔合线一侧较早地析出先共析铁素体,使熔合线两侧存在显著的碳活度差所产生.从而验证了作者等提出的焊接接头碳迁移的活度原理. 对这类接头,晶体结构的不同所引起碳活度系数的差别,较之合金成分的不同引起的差别为大.前者是发生第一类碳迁移的主要的热力学条件.从动力学方面考虑,碳迁移进行的程度,与一定温度下的保持时间有关. 为减弱和抑制12AlMoV钢焊接接头碳迁移,并提出了合金化和焊接工艺措施.

An investigation of the first kind migration process of carbon has been carriedout on the welded joints of a 12AlMoV steel by means of microscopy, EPMA anddilatometry. It is shown that this carbon migration is caused by the existance ofa significant activity gradient of carbon between the two sides of fusion line. Thismay take place as a result of the earlier precipitation of pro-eutectoid ferrite onone side of the fusion line within a temperature range that rapid diffusion ofcarbon atoms occurs. This confirms the activity reasoning proposed by the authorfor carbon migration. The difference of the activity coefficient of carbon caused by different crystalstructures is larger than that caused by different compositions of the alloys forthese welded joints. Hence, it is the main thermodynamic condition accountingfor this kind of carbon migration. From kinetic point of view, the degree ofcarbon migration increases with the duration under certain temperatures. Changingthe composition as well as modification of welding technology have been proposedso as to retard or suppress the carbon migration in the welded joints of the steel.