IN690合金管材热挤压中玻璃垫润滑行为的仿真研究

Theoretical Study on Lubrication Behavior of Glass Pad during Hot Extrusion Process of IN690 Superalloy Tubes

润滑对镍基高温合金管材热挤压过程具有重要影响。通过建立玻璃垫熔融流动的解析润滑模型,研究61MG178、A5和Up68/2886玻璃垫在IN690合金管材热挤压过程中的润滑行为。结果表明,熔融玻璃膜厚度随着挤压速度的增大和玻璃垫倾角的增大而减小,温度对膜厚的影响由温度本身和相应的玻璃高温粘度梯度共同决定。玻璃膜的流动稳定性随挤压速度的增大、温度的减小而升高。61MG178具有最优的润滑性能,Up68/2886玻璃垫次之,A5玻璃垫仅适用于低速挤压。为达到理想润滑效果并节能减耗,针对挤压工艺规程中对死区倾角的限定,玻璃垫横截面可相应地设计为三角形或梯形。经过合理的倾角和尺寸设计,在全温度、挤压速度区间内,61MG178玻璃垫可实现理想的润滑效果,能够很好地应用于实际生产。

Lubrication plays an important role in hot extrusion of Ni-based superalloy tubes.A theoretical model is applied in this paper to investigate lubrication behavior of 61MG718,A5 and Up68/2886 glass pad during hot extrusion process of IN690 superalloy tubes.The results indicate that the thickness of melted glass film declines with rise of extrusion speed and angle of glass pad.The influence of temperature depends on both the value of temperature and corresponding viscosity gradient of glass.Glass film shows better flow stability with rise of extrusion speed and decline of temperature.61MG178 glass pad performs the best lubrication behavior among three kinds of pads and A5 pad is only suitable for low speed extrusion.Given lubrication and the cost of production,glass pad can be made to be triangular or trapezoidal shape at cross section according to the angle of it.After rational geometry design,61MG178 pad can show excellent lubrication effect at the whole temperature and extrusion speed in industry production.