Al、Ti处理对低合金钢焊接粗晶区组织的影响

Effect of Al and Ti Treatment on Microstructure of Coarse-Grain HAZ in HSLA Steel

研究了Al、Ti处理对低合金钢焊接粗晶区组织的影响。研究发现：用A1处理时，钢中形成的夹杂物为A1的氧化物和细小的TiN。A1的氧化物和TiN不能促进晶内铁素体的形成，焊接粗晶区主要由粗大的晶界铁素体和平行排列的侧板条铁素体组成。用Ti处理时，钢中形成大量的Al、Ti、Mg、Ca复合氧化物夹杂，其颗粒大小为0．5～3．0μm，同时还有一定量细小的Ti的氮化物。复合Ti的氧化物具有促进晶内针状铁素体形核的能力，焊接粗晶区主要由晶界铁素体、少量的侧板条铁素体和大量的晶内针状铁素体组成。随焊接热循环高温保温时间增长，晶界铁素体粗大，侧板条铁素体数量减少。相变区的冷却速度减慢，晶界铁素体数量增多，针状铁素体的尺寸显著增大。

The Effect of Al and Ti treatment on coarse-grain HAZ microstructure in HSLA steel was investigated. The results showed that the inclusions in Al treated steel are mainly aluminum oxides and titanium nitrides. Aluminum oxide and Titanium nitride could not promote the formation of acicular ferrite. Microstructure of coarse-grain HAZ of Al treated steels consists of heavy ferrite in grain boundaries and ferrite side plate. The inclusions in Ti treated steel are Al,Ti, Mg,Ca composite oxides with size in the range of 0.5-3 μm and titanium nitride. Ti composite oxide could promote the formation of acicular ferrite and microstructure of coarse-grain HAZ of Ti treated steel consists of ferrit in grain boundaries, ferrite side plate and large amount of intragranular acicular ferrite. The size of ferrite in grain boundaries is increased and the amount of ferrite side plate is decreased with the increase of soaking time at the peak temperature. The amount of ferrite in grain boundaries and the size of acicular ferrite is increased with the increase of cooling rate during phase formation.