Experimental study of the lubrication by soaps in stainless steel wire drawing

Formulation of efficient lubrication procedures for multi-pass steel wire drawing is a problem of prime importance. One studies the performances of industrial soaps in stainless steel wire drawing by experiments. Before drawing, the wire is pickled and covered with salt. One measures the drawing force, die average temperature, and the total residual film surface weight and observes the drawn wire surface by scanning electron microscope. The influence of the drawing velocity u in the range 0.1–10 m/s, the nature of the stearate (Na, Ca) and the filler amount, the salt surface weight, the wire roughness and yield stress, and the die angle are studied. Results demonstrate that quasi-hydrodynamic lubrication is induced by a mixture of salt and soap; calcium stearate is well adapted to the lowest velocities, whereas sodium stearate has better performances at the highest velocities. Rheological origins of these differences are discussed.