A STUDY ON THE WEAR AND FAILURE OF HOT FORGING DIES OF AUTOMOTIVE CONNECTING RODS
A STUDY ON THE WEAR AND FAILURE OF HOT FORGING DIES OF AUTOMOTIVE CONNECTING RODS
复制标题
汽车连杆热锻模磨损失效研究
DOI：
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发表时间：
2009
期刊：
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通讯作者：
S. Tonini
中科院分区：
文献类型：
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作者：
S. Tonini
锻件价格的很大一部分是由于锻模表面失效而返工的成本。为了在价格和生产时间方面寻求更高的竞争力，有必要了解模具故障的机制，以延长其工作寿命，避免风险情况和工具可能的完全故障，并降低返工，维护和设置的成本，实现更高的生产率。除了已知的增加锻模寿命的改变，例如锻造温度、冲程速度、润滑（摩擦）和模具表面上的表面冶金改性之外，还可以通过模具轮廓的几何改变来增加模具寿命。本文研究了弯角半径、飞边宽度、型腔深度、上杆半径、飞边厚度、锻模和工件温度的改变对连杆锻件在预成形模杆区磨损的影响。通过数值模拟和统计分析发现，对模具磨损过程影响最大的参数是影响模具型腔体积的参数，而模具型腔体积又直接影响锻件飞边的总宽度。因此，飞边的宽度是磨料磨损的比较量度。分析了连杆杆部锻造过程中的磨粒磨损、法向应力和锻造载荷的演变过程，得出了四个不同的阶段。通过该验证，发现工艺过程中的材料流动与现有参考文献中观察到的不同，并且还可以验证杆杆中的镦粗过程或轧制工件头部朝向杆杆的径向流动，这往往会增加工件杆的直径。较大的直径增加了磨料磨损的过程，因此是设计连杆模具时要考虑的一个重要因素。通过对锻造杆柄区域所需载荷的分析，验证了当型腔未完全填充时，载荷模式是不同的。最后通过加工图的构建，确定了一些无充填缺陷、磨损量较低的优化区域，从而提高了模具寿命，保证了产品质量，并可能减少原材料。
A significant part of forgings prices is due to costs from reworks of forging dies because of failures on their surfaces. In quest of a higher competitiveness in terms of prices and production times, it is necessary to understand the mechanisms of die failure to increase its working life, avoiding risk situations and a possible total failure of the tools, and also decreasing costs of reworks, maintenance and set-ups, achieving a higher productiveness. Besides known changes to increase forging die life such as forging temperature, stroke speed, lubrication (friction) and superficial metallurgical modification on dies surfaces, it is also possible to increase die life trough geometrical changes of the die profile. In this work it has been studied how the modification of the corner radius, flash land width, depth of cavity, radius of the upper stem, flash thickness and temperatures of forging dies and workpiece influence the wear of the forging of connecting rods in the stem region of the pre-form dies. Through numerical simulation and statistical analysis it was found that the parameters that most influence the process of die wear are the same that affect the die cavity volume which also influence directly the overall width of flash of the forged part. Therefore, the width of a flash is a comparative measure of abrasive wear. It was also analyzed the process of forging in the stem region of connecting rods and it could be verified four distinct stages in the evolution of the abrasive wear, normal stress and forging load. Through this validation it was found that material flow during the process differs from the observed in available bibliographic refererences and it could be also verified a process of upsetting in the rods stem or a radial flow of the rolled workpiece heads toward the rods stem, which tends to increase the diameter of the workpiece stem. Larger diameters increase the process of abrasive wear, therefore being an important factor to be considered in the design of connecting rods dies. From the analysis of the necessary load to forge the stem region of the rod it was verified that the loading pattern is different when the cavity is not completely filled. Finally through the construction of processing maps it can be determined some optimized regions without filling defects, with lower values of wear and thereby increasing die life, keeping the product quality and possibly reducing raw material.