稀土和Ca、Mg元素对高强度钢焊接热影响区组织和韧性的影响

研究了低合金高强度非调质中厚板钢中添加稀土(REM)和Ca、Mg微量元素对大线高能焊接热影响区(HAZ)显微组织微细化和晶内针状铁素体(IAF)形成的影响.结果表明,添加REM和Ca、Mg元素可在钢的HAZ中形成弥散稳定的氧硫化物(CeCa)2O2S和(CeMg)2O2,热轧奥氏体化(1450℃)和焊接热输入10 kJ/mm时都十分稳定,比传统采用TiN强化的钢具有更优良的低温韧性.有效地控制细小弥散的氧硫化合物,能获得适中的奥氏体有效晶粒尺寸和提供HAZ中形成晶内针状铁素体及稳定活性的形核位置.促进晶内铁素体协同形核生长,有效地使得HAZ组织微细化.

Effect of Rare-earth Metal, Ca and Mg on Microstructure and Toughness of Heat Affected Zone of High Heat-Input Welding

The effect of addition rare-earth metal(REM),Ca and Mg elements on the microstructure,toughness of and the formation of intragranular acicular ferrite(IAF) in hot affect zone of large heat-input welded low alloy non quenched-tempered steel plate was investigated.Experimental results indicated that REM,Ca and Mg can promote formation of dispersive and stable oxy-sulphide(Ce,Ca)_2O_2S or(Ce,Mg)_2O_2 which are stable in hot-rolling process,austenitizing treatment and welding with a heat-input 10 kJ/mm,as a result the steel has better low temperature toughness comparing with the steel strengthened by TiN.The austenite grains of moderate and effective size and the stable and active nucleation sites for intra-granular acicular ferrite(IAF) in HAZ can be obtained by effective control of the dispersive oxy-sulphide,moreover the sympathetic intragranular nucleation and growth of ferrite are promoted for refining microstructure in HAZ.