大功率内燃机车球铁曲轴中夹渣缺陷形成与防止的研究

An Investigation on the Formation and Prevention of the Dross in the Nodular Cast Iron Crankshaft of the Heavy Diesel Locomotive

本文研究内燃机车球墨铸铁曲轴中夹渣缺陷的形成机理及防止的方法。通过对曲轴中夹渣组成的分析，确定该缺陷主要是在低压铸造过程中所形成的氧化夹渣。在测定现场工艺参数的基础上，采用水模拟试验方法研究充型过程对夹渣形成的影响，发现开始于升液管内形成的“冷铁水” 及其随后的紊流流动是形成这种缺陷的主要原因。实验证明，使用“溢流室”改变型内温度竹市和撇除早期渣，是消除这种缺陷的有效方法。

This paper deals with the mechanism of forming the dross defect, which is shown after nitriding in the nodular cast iron crankshaft of the diesel locomotive, and its methods of prevention. By analysing the compositions of the drosses taken from the crankshaft, it has been found that this defect is mainly caused by the oxide dross, formed during the pouring process of the low pressure die casting. Based on the data measured in production,a hydrau- lic model is built to investigate the influence of the way of filling mould on the dross formation. It is found that "cold liquid metal"in the refractory tube and its turbulent flow within the mould is the main reason of the defect. Experiments indicate that using the "overflow chamber", which can equalize the temperature in the mould and skim off the early dross, is an effective way to prevent the defect.