Low Carbon Steel Cold Extrusion Phosphide - Saponification Research

In this article, the friction mechanism of soft steel cold extrusion process is investigated in detail. The forming mechanism of phosphate coating and saponification coating, lubricate mechanism, the influencing factors of coating quality are analyzed theoretically. Zinc phosphate coating and saponification coating at mid-temperature are researched by metallographic microscope, SEM, EPMA and XRD. Its surface topography, cross-section topography, structure and element constituents are obtained. The main discoveries are:(1) The components of zinc phosphate coating at mid-temperature are mainly zinc phosphate (H film), has accompanied with a little zinc iron phosphate (P film); There are two kinds of surface topographies, including clubbed and spherical particulate. The structure of phosphate coating cross-section is layer structure and the space length between layers is slightly different. The thickness of phosphate coating is about 20 μ m.(2) Phosphate-saponification coating can be divided into three layers, including sodium stearate,zinc stearate and zinc phosphate. The outer layer is sodium stearate, which presents a structure of flocculence. The sequences are zinc stearate and zinc phosphate in turn.(3) It has a good lubrication effect where phosphate-saponification coating remains after cold extrusion process.(4) The transmutation extent of phosphate-saponification coating surface is different in forming process. The attenuation rate of coating outer surface changes from small to big, then again to small along height direction, while inner surface changes from small to big along height direction.(5) The transmutation extent in various parts is different in forming process. The upside and bottom are relatively smaller, the middle part (the exit of cavity die) is the biggest. The transmutation extent becomes small gradually along with the height direction going down.(6) The friction of the middle part is bigger, where the effect of lubrication is bad, so it tends to have scuffing.It is indicated from the research results that it would obtain good lubrication effect if using zinc phosphate coating at mid-temperature in soft steel cold extrusion...