高效愈合钢锭内部缺陷的锻造工艺设计

DESIGN OF FORGING METHODS OF HEALING DEFECTS IN INGOTS EFFECTIVELY

总结了宽砧径向压实工艺(WRF法),该工艺可使应变集中于钢锭中心区域,并满足孔洞闭合所需的最佳高径比条件,因此可高效愈合钢锭的中心缩孔、疏松.基于该方法,针对压机压力较小的情况,提出了单向大变形压实法.该方法通过两个道次的单方向变形将坯料锻造成扁方状,可以使用小压力实现较大钢锭内缺陷的有效愈合.基于界面焊合原理,针对管板类锻件探伤合格率较低的问题,提出了管板类锻件的锻间保温锻造法.利用该方法成功进行了含缺陷管板的修复实验.以上各锻造工艺均经过工业实验验证,证明其可以顺利愈合锻件内的孔洞型缺陷,提高锻件合格率.

Large forgings are the fundamental parts of many kinds of key equipment, and large ingots are the basis of large forgings. There are severe metallurgical defects in large ingots, such as porosities, shrinkage cavities and gas cavities. The continuity of material is damaged by the defects, which must be eliminated during forging process. Using FEM simulation, it is found that void shape is the most important parameter affecting void closing during hot forging. Height-diameter ratio of the void is defined to describe the effect of void shape. The simulation results show that the larger height-diameter ratio of the void, the harder it is for the void to close. Based on these results, wide anvil radial forging（WRF） method is proposed. WRF method can concentrate the strain on the center of the ingot; make the height-diameter ratio of the voids smallest and heal shrinkage cavities effectively. Another one direction heavy forging method is proposed to be used on smaller forging machines. Using this method, the billet is forged along the same direction for two passes. This method can heal defects effectively with small pressure. Based on interface healing rules, temperature dwelling forging method for forging tube plates are proposed. A tube plate with defects is repaired using this method. These forging methods have been used on industrial experiments, and have been proved to be able to heal the defects in the billets and increase qualified rate of the forgings.