中文摘要：

通过调整冶炼工艺,研究钢中氧化钛和氮化钛的数量、尺寸及分布规律,并利用热力模拟试验机对试验钢的大热输入焊接热影响区韧性进行分析。试验结果表明：实施新的冶炼工艺能够使钢中形成大量细小的氧化钛和氮化钛类夹杂物;在熔合线部位温度为1 400℃时,钢中的TiN因溶解而失去钉扎作用。尺寸小于5μm的含Ti2O3和MnS的复合夹杂物,其形成IAF的能力强;尺寸为5～6μm的这类夹杂物具有IPF的形核能力。新的冶炼工艺能够大幅度提高大热输入焊接热影响区韧性。

英文摘要：

Quantities,sizes and distribution of titanium oxide and nitride in steels obtained by different smelting processes were investigated.Toughness in heat-affected zone（HAZ） of tested steels was researched through thermal-mechanical simulation machine.The results show that numerous finely titanium oxide and nitride inclusions were acquired by a new smelting process.TiN inclusions in fusion line were dissolved in matrix when heated above 1 400 ℃,and then the pinning grain boundaries and inhibiting grain growth effects of TiN inclusions disappear.When the size of Ti2O3-MnS complex inclusions is less than 5 μm,these inclusions have a strong effect on promoting the formation of intragranular acicular ferrites（IAF）.When the size is larger than 5-6 μm,some these inclusions also can promote the formation of intragranular polygonal ferrite（IPF）.The toughness of steel in HAZ with high heat input can be improved by the new smelting process.