Effect of Si Content and Hardness on the Machinability of Hot Working Die Steels

Abstract

This study has been carried out to clarify the effect of Si content and hardness on the machinability of 5 Cr-3 Mo type hot working die steel. With decreasing Si content, the amount of adhesion of work to carbide tools increase, which results in the shorter life of carbide tools. The effect of hardness on the amount of adhesion and the tool life is smaller than that of Si content. With decreasing Si content and increasing hardness, cutting forces, calculated friction angle, and cutting temperature at early stage increase. It is difficult, however, to explain the shorter tool life of the steels with lower Si content in different hardness by cutting forces, friction angle and cutting temperature. It is considered due to the difference of diffusivity of the steels or their oxide layers with carbide tools.

A review of surface integrity in machining and its impact on functional performance and life of machined products

“…We briefly review the current status of hard milling of mainly steels (300-650 HV30) with the focus on the SI aspects. As mentioned earlier, we shall look into three groups of materials, namely plastform type P20 steels (Umino et al, 2004;Persson and Chandrasekaran, 2002;Ghanem et al, 2002;Rahman et al, 2002), hot-working type H13 steels (Umino et al, 2003;Fujii and Matsuda, 2003;Mativenga and Hon, 2003;Axinte and Dewes, 2002;Chandrasekaran et al, 2005) and cold-working D2 type steels (Rao and Shin, 2001;Becze et al, 2000), respectively, with decreasing application potential for hard milling today. The indicated reservation as we go from 300 HV30 to 650 HV30 in hardness is both due to technical problems of viable tool life as well as SI.…”

“…Reduction in chip adhesion with increasing Si content is indicated as the main cause for machinability improvement, but a corresponding effect on SI was not investigated. Fujii and Matsuda (2003) studied end milling of hot worked die steels (type 5% Cr-3% Mo) in the hardness range of 35-50 HRc using uncoated carbide tools at a constant cutting speed of V = 100 m/min. The Si content of the steels varied from 0.1% to 1.01%.…”