稀土复合变质对新型铸造热锻模具钢组织与性能的影响

研究了稀土复合变质对新型铸造热锻模具钢（CHD钢）组织与性能的组织。结果表明，稀土复合变质能细化晶粒，并且随着稀土量的增加。细化效果明显；加入适量的稀土复合变质后，夹杂物数量明显减少，夹杂物趋于球化并均匀地分布在钢中，形态和分布得以了改善，向钢中加入稀土进行复合变质，能促进贝氏体、奥氏体和位错亚结构的形成，细化马氏体板条。当残留稀土含量为0.02%时，CHD钢的硬度、强度变化不大，断裂韧性（KIC）和疲劳裂纹扩展门槛值（△Kth）有所提高，冲击韧性、延伸率、断面收缩率提高了近一倍，抗热疲劳性能也最好。

Effect of Rare Earth Complex Modification on Microstructure and Properties of a New Cast Hot-Work Die Steel

The effects of rare earth (RE) complex modification on structure and the properties of a new cast hot-work die (CHD) steel were investigated. The results show that the grain of the CHD steel can be refined by the RE complex modification. With the increase of RE addition, the grain size is reduced. The amount of inclusions reduced, inclusions are inclined to sphericize and are distributed evenly, the morphology and distribution of inclusions are improved by the appropriate RE complex modification. Bainite, austenite and the sub structure with high dense dislocations are also promoted to form and the lath of martensite is also refine by the RE complex modification. When the retained RE content reached at 0.02 %, a little effects can be found on the strength and hardness, but the fracture toughness and the threshold of fatigue crack growth are improved meantime, impact toughness, elongation and total reduction in area are increased by over 1 time, and the resistance to thermal fatigue is also improved mostly too.