Transactions of Materials and Heat Treatment

Title：Effect of workpiece bottom hole diameter on tooth height rate in cold extrusion process of internal thread

Authors： Hou Hongling Chen Xin Chang Xianglong Zhao Yongqiang Wu Lang

Unit： Shaanxi University of Technology

KeyWords： cold extrusion internal thread bottom hole diameter tooth height rate fitting curve

ClassificationCode：TG376.3

year,vol(issue):pagenumber：2021,46(8):231-238

Abstract：

In order to establish the relationship between bottom hole diameter and tooth height rate, for 40Cr alloy steel, the change laws of extrusion torque and extrusion temperature during the extrusion process and the influences of bottom hole diameter on the fullness of internal thread and the tooth height rate were analyzed by numerical simulation, and the relationship equation between tooth height rate and bottom hole diameter for internal thread were obtained by MATLAB to fit the test results. Then, the reliability of numerical simulation results and the accuracy of fitting formula were verified by the cold extrusion test of internal thread. The research results show that the extrusion torque and extrusion temperature rise rapidly at the initial stage of cold extrusion for internal thread, and during the extrusion correction stage, the extrusion torque decreases rapidly and the extrusion temperature decreases slowly. For the internal thread with M8×1.25 mm, when the bottom hole diameter of workpiece is controlled at Φ7.33-Φ7.40 mm, the tooth height rate of internal thread after cold extrusion meets the connection strength requirements, and when the bottom hole diameter is Φ7.33 mm, the thread connection strength can be guaranteed to be 100%, while reducing the processing difficulty and increasing the service life of extrusion tap.

Funds：

陕西省自然科学基础研究计划项目(2019JM-466)；陕西省教育厅专项科研计划项目(18JK0148)；陕西理工大学研究生创新基金资助项目（SLGYCX2027）

侯红玲（1976-），女，博士，教授 E-mail：xjtuhhl@163.com 通信作者：赵永强（1976-），男，博士，教授 E-mail：zyq0620@163.com

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