Ti-V-Nb微合金钢焊接热影响区中的沉淀物

本文对5种含Ti-V-N_b的微合金钢埋弧自动焊焊接热影响区中沉淀物溶解、沉淀及晶粒长大进行了考察。焊接线能量为3和6 kJ/mm.Ti钢(0.014% T_i)焊接中TiN粒子变化很少,与焊接热循环中TiN很有限的溶解计算结果相吻合.低Ti-V钢(0.002% Ti,0.093% V)和低Ti-Nb钢(0.002% Ti,0.029% Nb)中富V和富Nb粒子分别在母材中溶解,富Ti沉淀物在热循环的加热段形成,而富V粒子和富Nb粒子又在冷却段再沉淀.Ti-V钢(0.014% Ti,0.080% V)和Ti-V-Nb钢(0.016% Ti,0.082% V,0.027% Nb)中沉淀物粒子成分分布在较宽的范围内.焊接时富Ti立方体状沉淀物不溶解而富V、富Nb球状粒子溶解了.这两种钢冷却时无明显再沉淀。研究的5种钢的这些不同表现是与母材中沉淀物的溶解及冷却时发生的再沉淀可获得的热力学动力分不开的.

Precipitates in HAZ of Ti-V-Nb microalloy steels

The dissolution, precipitation and grain coarsening of precipitates in the HAZ of submerged are welds deposited at 3kJ/mm and 6kJ/mm heat input on five Ti, V,Nb containing microalloy steels were examined.The Ti-bearing steel (0.014% Ti) showed little change in the TiN particle distribution on welding, being in agreemetn with the calculated result of very limited TiN solution during the weld thermal cycle.For low Ti-V steel (0.002% Ti,0.093% V)and low Ti-Nb steel (0.002%Ti, 0.029% Nb),the V-rich particles and the Nb-rich particles in the base metal dissolved.During the heating leg of the cycle the Ti-rich particles formed,while on cooling,the V-rich and the Nb-rich particles precipitated again.Ti-V steel (0.014% Ti,0.08%V)and Ti-V-Nb steel (0.016% Ti,0.082% V,0.027% Nb) contained a wide distribution of particle compositions.On welding,the Ti-rich cuboidal precipitates did not dissolve while the V-rich and the Nb-rich spheroidal precipitates did dissolve.No reprecipitation was abserved on cooling in these two steels. The different behaviour of thc five steels was related to the dissolution of the precipitation in the basc metal and the available thermodynamic driving foree for reprecipitation on cooling.