内螺纹冷挤压成形过程仿真及试验研究

Simulation and experimental study on cold extrusion forming process of internal thread

为了获得较好的内螺纹冷挤压成形质量,对内螺纹冷挤压工艺进行研究,寻求内螺纹冷挤压最优的工艺参数组合。建立了内螺纹冷挤压三维模型,采用有限元模拟和试验相结合的方法研究了内螺纹底孔直径、挤压速度和摩擦系数与成形质量及工作扭矩之间的关系。通过数值模拟得到内螺纹底孔直径与牙高率的关系,获得了4种不同挤压速度下挤压扭矩和挤压温度的对比曲线,以及摩擦系数对挤压扭矩和挤压温度的影响规律。仿真和试验结果表明:挤压M8 mm×1.25 mm的内螺纹时,预制底孔直径为Φ7.37~Φ7.42 mm,挤压速度为15~30 r·min^-1,挤压成形的内螺纹的牙形饱满,连接强度好;此外,挤压过程中采用矿物油润滑,可以降低挤压扭矩,且挤压成形的内螺纹表面质量好。

To obtain better cold extrusion forming quality of internal thread,the cold extrusion technology of internal thread was studied and the optimal combination of process parameters was sought.A three-dimensional model of cold extrusion for internal thread was established,and the relationship between the bottom hole diameter of internal thread,extrusion speed and friction coefficient with forming quality and working torque was studied by finite element simulation and test.The relationship between the bottom hole diameter of internal thread and tooth height rate was obtained by numerical simulation;the comparison curves of the extrusion torque and extrusion temperature at four different extrusion speeds were obtained and the effect law of friction coefficient on extrusion torque and extrusion temperature was obtained.Simulation and test results show that when the internal thread of M8 mm×1.25 mm is squeezed,the diameter of the prefabricated bottom hole isΦ7.37-Φ7.42 mm,the extrusion speed is 15-30 r·min^-1,the internal thread formed by extrusion has full tooth shape and good connection strength.In addition,using mineral oil lubrication in the extrusion process can reduce the extrusion torque,and the surface quality of internal thread formed by extrusion is good.