汽车法兰盘热锻模具磨损失效的实验分析和数值研究

Experimental and Numerical Study on the Wear Failure of Hot Forging Die of Automobile Flange

采用扫描白光干涉仪和扫描电镜对汽车法兰盘热锻模具的表面磨损形貌进行观察,分析其磨损失效机理.同时,基于Archard磨损模型,建立热模锻过程的热-力耦合有限元模型,研究模具预热温度、锻造速率和模具热处理工艺等因素对模具磨损的影响.结果表明,锻后模具表面出现黏着磨损、氧化磨损和磨粒磨损现象,其中磨粒磨损造成的模具损伤程度最高,最大磨损深度约为100μm;数值分析表明,当模具预热温度为250℃,锻造速率为300 mm/s时,锻后模具最高温度低于模具材料AISI H13钢的许用温度(620℃),且模具磨损深度达到最低水平;相比于淬回火热处理工艺,采用离子渗氮处理可使锻后模具最大磨损深度由7.2×10–5 mm下降至1.3×10–5 mm,磨损幅度降低82%,模具服役寿命提高约5.5倍,模拟结果与实际生产情况吻合.

Scanning white light interferometer and scanning electron microscope were used to observe the surface wear states of hot forging die of automobile flange and reveal its wear failure mechanism. In addition, based on the abrasive wear model developed by Archard, the thermo-mechanical coupled FE model of the hot forging process was built to estimate the influence of initial die temperatures, forging rate and heat treatment method on the wear depth of die. The results demonstrate that three types of wear mechanism were observed on the worn surface, namely adhesive wear,oxidation wear and abrasive wear. Abrasive wear was the most serious, which caused a maximum wear depth about100 μm. According to the numerical results, when the initial temperature of die was 250 ℃ and the forging rate was300 mm/s, the maximum die temperature after forging was lower than the allowable temperature of AISI H13（about620 ℃）, and it rendered the minimum wear depth of die after forging. Also, compared with the quenching and tempering method, by using plasma nitriding, the maximum wear depth of die dropped from 7.2×10^（-5） mm to 1.3×10^（-5） mm. The weardepth of die was reduced by 82% and the service life of die was improved by 5.5 times. The experimental result had a good agreement with the predicted one.