Effect of Lubrication and Forging Load on Surface Roughness, Residual Stress, and Deformation of Cold Forging Tools

Karunathilaka Karunathilaka,Uemori Uemori,Hanamitsu Hanamitsu,Tada Tada,Omiya Omiya,Kawano Kawano,Fujii Fujii

doi:10.3390/met9070783

Karunathilaka Karunathilaka, Uemori Uemori + Show 5 more

Open Access

https://doi.org/10.3390/met9070783

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Journal: Metals	Publication Date: Jul 12, 2019
Citations: 7	License type: CC BY 4.0

Affiliation: Okayama University, Zenyaku Kogyo (Japan)

Abstract

Cold forging is a metal forming that which uses localized compressive force at room temperature. During the cold forging process, the tool is subjected to extremely high loads and abrasive wear. Lubrication plays an important role in cold forging to improve product quality and tool life by preventing direct metallic contact. Surface roughness and residual stress also greatly affects the service life of a tool. In this study, variations in surface roughness, residual stress, and specimen deformation with the number of cold forging cycles were investigated under different forging conditions. Specimens that were made of heat-treated SKH51 (59–61 HRC), a high-speed tool steel with a polished working surface, were used. The specimens were subjected to an upsetting process. Compressive residual stress, surface roughness, and specimen deformation showed a positive relationship with the number of forging cycles up to a certain limit and became almost constant in most of the forging conditions. A larger change in residual stress and surface roughness was observed at the center of the specimens in all the forging conditions. The effect of the magnitude of the forging load on the above discussed parameters is large when compared to the effect of the lubrication conditions.

Highlights

Forging is one of the well-known manufacturing methods that have been used to produce high quality and tough products under temperature-controlled conditions by shaping metal while using localized compressive forces
Cold forging, which is performed at room temperature, has gained importance in the field of steel-based products over the last sixty years [1]
The cold forging tools are subjected to a combination of abrasive wear and very high mechanical loads, which generates a surface pressure of up to 3000 MPa that is caused by high flow stress of the billet material at room temperature [2,3]

Summary

Introduction

Forging is one of the well-known manufacturing methods that have been used to produce high quality and tough products under temperature-controlled conditions by shaping metal while using localized compressive forces. Based on the temperature at which the forging process is performed, it is divided into three categories: hot, warm, and cold. Cold forging, which is performed at room temperature, has gained importance in the field of steel-based products over the last sixty years [1]. The cold forging tools are subjected to a combination of abrasive wear and very high mechanical loads, which generates a surface pressure of up to 3000 MPa that is caused by high flow stress of the billet material at room temperature [2,3]. The cyclic loading of tools causes’ fatigue, and a combination of high contact stress and cumulating sliding strength causes the wear [5]

Methods

Results

Conclusion