喷射成形工模具钢沉积坯中冶金缺陷计算分析及其消除-中国材料进展

文章信息/Info

Title:: Computer Analysis and Elimination to Metallurgical Defects 
in ToolDie Steel Deposit Prepared by Spray Forming

摘要:: 用有限元方法计算分析了喷射成形工模具钢沉积坯内部疏松等冶金缺陷的成因，并计算、验证了热等静压或锻轧等热加工消除内部缺陷的过程。研究表明，喷射成形工模具钢沉积坯粥状层补缩不足和冷却收缩产生的热应力是造成坯体中疏松等冶金缺陷的重要原因。热等静压采用的温度为1 170 ℃，锻造加工温度也能达到1 150 ℃，在这样温度下，工模具钢表现出一定的塑性，高温高压的热加工过程，对材料内部的冶金缺陷起到了一定的弥和作用。试验结果表明，经历热加工过程后的工模具钢内部的冶金缺陷明显减少。热等静压或锻轧等热加工可有效减少喷射成形工模具钢坯体内部的疏松等缺陷，热锻、热轧是消除沉积坯内部冶金缺陷的重要方法。另外，与Ar气相比，采用N2做雾化气体的喷射成形工模具钢沉积坯，由于高温下气体和合金元素的反应，沉积坯内部的含气式疏松很少。因此，采用N2喷射成形制备的工模具钢经热加工后，沉积坯密度更接近理论密度。

Abstract:: With the help of finite element method computing, the formation of metallurgical defects, such as hot tear, porosity etc was analyzed and the process of reducing the defects was verified in the paper. We found that the hot tear and porosity in tooldie steel are caused by the pull stress engendered by cooling contract and insufficient feeding of liquid metal in local position in billet. The hot isostatic pressing temperature employed is 170 ℃，and forging processing temperature can reach 150 ℃, die steel exhibits a certain plasticity at these temperatures, the hot processing can close metallurgical defects inside of the material after the thermal processing of the high temperature and pressure. Forging and hot roll process are important method to decrease and eliminate the looseness and porosity in deposit of tooldie steel. Further, as compared with the Ar gas, for tool and die steel prepared by spray forming thermal processing with the N2, deposition green density can close to the theoretical density.