回転金型を用いた後方せん孔摩擦試験による厳しい温・熱間摩擦下での摩擦係数の測定

抄録

We have proposed a new friction test method under severe friction conditions. The method applies backward extrusion, which enables us to create high surface pressure, large surface area expansion and a long sliding distance. In addition, die temperature in the actual forging processes can be reproduced. The unique feature of the die set used in this method is a punch rotating at a very slow angular velocity. From the combination of measured load P and torque M, friction coefficients μ of the entire punch contact surface can be calculated. The equation between M/P and μ was derived using FEM analysis. This equation depends on the punch shape, not the flow stress of material. By this method, we measured friction coefficients at 900 ℃-1200 ℃, in which warm and hot forging conditions of steel were reproduced. As a result, we were able to quantitatively evaluate the lubricant combustion temperature, billet antioxidant coating, lubricant spray pressure, and billet initial temperature, which strongly affect friction coefficients.