The microstructural evolution and toughness properties of simulated coarse‐grained heat‐affected zone (CGHAZ) in Ti–Ca killed steel with different heat input are studied and compared with Al–Ca killed steel. It is found that the impact toughness of CGHAZ in Ti–Ca killed steel with heat inputs of 50, 100, and 200 kJ cm⁻¹ is ≈129, ≈105, and ≈44 J, respectively. However, the toughness of Al–Ca killed steel decreases from ≈28 to ≈23 J and then to ≈18 J. In Ti–Ca killed steel, Ti–Ca–Al–Mn–S oxides with appropriate size of ≈0.3–2 μm effectively promote the nucleation of acicular ferrite (AF). In addition, the high‐density number of ≈1329 inclusions mm⁻² is one of the most important reasons for the formation of AF. However, dominant Al–Ca–Mn–S oxides in Al–Ca killed steel cannot effectively promote the nucleation of AF and mainly act as a potential propagation site of impact crack. In Ti–Ca killed steel, predominantly interlocked AF with high‐angle grain boundaries and high‐density of dislocations remarkably improves the toughness of CGHAZ.

中文翻译：

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热输入对Al-Ca和Ti-Ca镇静钢粗粒热影响区组织和冲击韧性的影响

研究了不同热量输入的Ti-Ca镇静钢中模拟粗晶粒热影响区（CGHAZ）的组织演变和韧性，并将其与Al-Ca镇静钢进行了比较。发现在热输入为50、100和200 kJ cm ^-1的Ti-Ca镇静钢中CGHAZ的冲击韧性分别为≈129，≈105和≈44J。但是，Al–Ca镇静钢的韧性从≈28降低到≈23J，然后降至≈18J。在Ti–Ca镇静钢中，Ti–Ca–Al–Mn–S氧化物的尺寸约为≈0.3–2 μm有效促进针状铁素体（AF）的形核。另外，≈1329夹杂物的高密度mm ^-2是形成房颤的最重要原因之一。但是，Al-Ca镇静钢中的主要Al-Ca-Mn-S氧化物不能有效地促进AF的成核，并且主要充当冲击裂纹的潜在传播点。在Ti-Ca镇静钢中，以高角度晶界和高位错为主的互锁AF显着提高了CGHAZ的韧性。