大型管板锻件夹杂性裂纹形成机理探讨

STUDY ON MECHANISM OF CRACKS ORIGINATED FROM INCLUSIONS IN HEAVY DISC FORGINGS

本文针对大型管板锻件内部产生夹杂性裂纹的机理进行了分析研究。认为产生锻造质量缺陷的主要原因为：非金属夹杂物经较大的变形而成为薄片状。这种片状夹杂在一定的力学条件作用下，产生微观乃至宏观裂纹；夹杂性裂纹的产生与夹杂物的自身特性及变形工艺密切相关。通过改变锻造工艺和工艺参数，可有效地控制夹杂物的形貌，减少夹杂性裂纹的生成。根据研究结论，作者从控制夹杂物形貌的角度出发，提出了直拔制坯十双凸成形的管板锻件锻造新工艺，生产实践证明，这种工艺可大大提高管板锻件的内部质量。

In this paper, authors analysed the mechanism of crack originated from inclusion in heavy disc forgings. They believe that the main reason of quality defects in heavy disc forgings is: the inclusions changed into thin slices after large upsetting deformation; and then, the inclusion slices coalesced into microcracks and up to rnacrocracks in a certain mechanical condition. Formation of cracks originated rom inclusions is relating to inclusion behaviors and deformation process. By changing the forging process and its parameters, the shape of inclusion can be effectively controlled, which can decrease the formation of cracks. From the view point of controlling inclusion shape, authors put forward a new process for disc forging which combined pre forming by direct drawing out and forming by upsetting of double side hub of pre form forgings. It had been proved that the new process can improve inner quality of disc forgings in a large range.