Effects of tool path strategies and thermochemical treatments on the surface roughness of hardened punches for hot stamping

Author(s)

Castanhera, Isabela ^[1] ; Diniz, Anselmo Eduardo ^[1] ; Button, Sergio Tonini ^[1]

Affiliation

^[1] Univ Estadual Campinas, Sch Mech Engn, Mendeleyev St, 200 Cidade Univ, Campinas, SP - Brazil

• Document type: Journal article
• Source: Journal of the Brazilian Society of Mechanical Sciences and Engineering; v. 42, n. 5 APR 4 2020.
• Web of Science Citations: 0

Abstract

The surfaces of molds and dies need to present a good quality because their roughness profiles are transferred to either cast or formed products. Dies and molds are frequently made of complex surfaces, and consequently, an adequate milling strategy is important to result in a proper workpiece surface. To evaluate the adequacy of a surface to be used as forming tool involves the use of roughness parameters like S-a, S-sk, S-ku, S-p and S-v. These parameters influence some surface properties like wear resistance and lubrication capacity. In this work, different tool paths of milling and turning processes were chosen to machine a typical spherical surface used as die (punch) of hot stamping, in order to analyze the surface parameters S-a, S-sk, S-ku, S-p and S-v of hardened steel samples. The used milling strategies were circular (upward and downward), radial (upward and downward), parallel contours and spiral (upward). Punches machined by all strategies were submitted to thermochemical treatments, plasma nitriding and nitrocarburizing Tenifer(R) process. The cited roughness parameters were measured in both moments, before and after the thermochemical treatments. There was similarity between milled and turned results, and thermochemical treatments presented significant influence on measured surface parameters. Machining marks were smoothed by thermochemical treatments which altered surface parameters. Thermochemical treatments effects were affected by the combination of machining marks and micro-burrs from machining processes. All tests resulted in S-ku parameter either close or above 3. At 45 degrees position of the workpiece, plasma nitriding tended to decrease roughness S-a, S-p and S-v values and present positive values of parameter S-sk. Nitrocarburizing process tended to increase roughness S-a, S-p and S-v values and present negative values of parameter S-sk, while not treated samples presented positive and negative S-sk values, depending on the machining strategy. (AU)

• FAPESP's process: 13/00551-7 - Milling of dies and moulds: vibration in the process and milling of complex profiles
• Grantee: Anselmo Eduardo Diniz
• Support Opportunities: Research Projects - Thematic Grants