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连续挤压机挤压轮使用寿命研究

Study on Extrusion Wheel Service Life of Continuous Extrusion Machine

【作者】 卢培民

【导师】 王延辉;

【作者基本信息】 大连交通大学 , 材料加工工程, 2010, 硕士

【摘要】 挤压轮是连续挤压成型(CONFORM, Continuous Extrusion Forming)机的关键部件,由于其在工作中承受压力、热应力及摩擦力的综合作用,所以对模具材质有较高要求,要求很高的强韧性配合,一般选择H13热作模具钢作为CONFORM连续挤压机挤压轮用钢,但有一部分挤压轮的寿命较短,发生非正常损坏失效,严重的降低了生产效率,增加了生产成本。了解其早期失效的原因对进一步改进挤压轮的制造工艺、提高寿命有很大的指导作用。本文围绕挤压轮寿命这一问题,主要从失效分析、受力及材料上来展开研究工作。首先,分析非正常损坏失效原因。在连续挤压生产现场取回新鲜断口试样,主要采用光学金相显微镜和扫描电子显微镜等仪器,对挤压轮的断口进行了宏观分析、化学成分分析、硬度分析、金相分析和开裂面电子形貌分析研究。试验研究结果表明,挤压轮槽表面留有肉眼可见加工划痕,在划痕处先形成热疲劳裂纹,萌生了裂纹源,在高应力集中下最终使挤压轮产生疲劳断裂。然后,对应力集中产生断裂的过程进行研究。结合挤压轮实际生产中的受力情况,建立ANSYS有限元模型,分析挤压轮轮槽、键槽部位在实际生产过程中应力及变形情况,对结果进行总结得出挤压轮工作区与挡料块接触部位的应力、变形较大,在这样的应力下轮槽发生形变,工作区与非工作区轮槽处于来回弯曲状态下,与实际发生断裂的部位相吻合。最后,根据裂纹萌生扩展与组织性能的关系,对挤压轮材料组织性能进行研究。主要与超细化材料的组织性能做对比分析,比较两者组织性能上的差异,分析主要原因,对挤压轮材料进行改进。降低回火温度能显著提高挤压轮的强度,韧性略有下降。

【Abstract】 Extrusion wheel is a key die in the continuous extrusion forming Machine,because of its work under Comprehensive role of pressure, thermal stress and friction, so has high requirements to the die materials, demanding moreStrength and toughness, generally, we selected hot work die steel of H13 as the continuous extrusion wheel’s material, but some of them have the low life,damaged in adnormally failure, a serious result in reducting production efficiency and increasing production cost.Analysys the reasons for its early failure hasa great guide for further improve the extrusion wheel manufacturing process.This text around extrusion wheel life this problem,primarily from failure analysis materials and force to study.First,failure analysis to non-normal damage fracture. Collecting fresh fracture sample from continuous extrusion production. Optical microscope and scanning electron microscope and other instruments were carried out Macro-examination, chemical composition analysis, hardness testing, microstructure examination and fracture analysis on the cracked die. Experimental results show that the extrusion wheel groove have visible machining scratches in the surface, and first formed thermal fatigue crack in the scratch, source of crack initiation, the extrusion wheel happened fatigue fracture under the high stress concentration.Then, study on the process of fracture under stress.Combination of extrusion wheel force in the actual production situation,estabblish ANSYS finite element model to analyze the stress and deformation in the wheel groove and keyway position which in the normal work force state,come to the work area at the extrusion wheel gauge quick access to parts of the stress has the largest stress, round groove has deformed on this stress, a alternate loading work on non-working and working area which consistent with the actual site of fracture.Finally, acorrding to the relationship between crack iniation expansion and microstructure, to research on extrusion wheel’s miscrostructure and properties. Mainly to do comparative analysis with ultrafine material’s microstructure and properties, comparing the difference of miscrostructure and properties between the them, and analyze the main reason to improve the extrusion wheel’s material.Lower tempering temperature can significantly improve the extrusion wheel strength,toughness decreased slightly.

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