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Elemental Research on Die Design for Achieving High Quality Products in Hot Extrusion

热挤压高质量产品模具设计的基础研究

基本信息

批准号：
01550536
负责人：
NAKANISHI Kenji
金额：
$ 0.51万
依托单位：
Kagoshima University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1990
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-01550536/
关键词：
Hot Extrusion Aluminum Alloy Flow Stress at Elevated Temperature Metal Flow Peripheral Recrystallization Work-Hardening Rate Equation Extrusion Die Ceramic Die デッドメタルゾ-ン

项目摘要

Die design considering the elastic deformation of die itself and achieving the sound product without defect in hot extrusion requires detailed and realistic stress analysis. Mechanistic interpretation of run-out direction, which is closely connected with distortion of the cross section of the product and that of peripheral recrystallization in hot extrusion of some aluminum alloys, which causes streaks after anodizing, are also required to optimize the extrusion process and die design. In the present investigation, some uniaxial compressive testings of Al-Mg-Si (6063) aluminum alloy, plane strain hot extrusion experiments of the same alloy using the symmetric and non-symmetric dies and numerical analyses concerning with the above subjects were performed. Those results are summarized below.1) The work-hardening rate equations proposed by the investigator previously were introduced to predict the distributions of effective stress and temperature rise due to plastic working energy with taking into account the complex distributions of effective strain-rate, effective strain and temperature in the deformation zone in hot extrusion. 2). Run-out direction of the extruded product could be related to the angle between the u=0 line and the extrusion direction. (Velocity component, u, is directed to normal direction to the extrusion direction.) The angle of u=0 line can be controlled by both die configuration and dead metal zone. 3). The peripheral recrystallized grain structure is not generated in hot extruded product when the effective strain, epsilon, is less than 1.55 or the effective strain gradient is less than 0.44epsilon is satisfied. Those values, 1.55 and 0.44, are obtained at 473^ﾟC and become smaller at higher temperature. 4) The metal flow patterns involving thin dead metal zones were observed in extrusion using ceramic dies having smooth surface and low heat conductivity.

模具设计要考虑模具本身的弹性变形，实现热挤压过程中产品的完好无缺陷，需要对模具进行详细的、真实的应力分析。对某些铝合金热挤压成形过程中产生的横截面变形和外围再结晶的变形方向进行力学解释，是优化挤压工艺和模具设计的重要依据。本文对Al-Mg-Si（6063）铝合金进行了单轴压缩试验，对该合金进行了对称模和非对称模的平面应变热挤压试验，并进行了数值分析。这些结果总结如下。1)引入前人提出的加工硬化速率方程，考虑热挤压变形区有效应变率、有效应变和温度的复杂分布，预测塑性能引起的有效应力和温升的分布。2）. 挤出制品的跳动方向与u=0线与挤出方向的夹角有关。（速度分量u指向挤压方向的法向。）u=0线的角度可以通过模具结构和死区来控制。3）. 当有效应变epsilon小于1.55或满足有效应变梯度epsilon小于0.44时，热挤压制品不产生外围再结晶晶粒组织。这些值为1.55和0.44，在473^ C时得到，在更高的温度下变得更小。4)采用表面光滑、导热系数低的陶瓷模具，观察了挤压过程中涉及薄死金属区的金属流动模式。