Forming Mechanism of High-Speed Cold Roll Beating of Spline Tooth

Ting Niu,Zhi-Qi Liu,Yong-Tang Li,Hui-Ping Qi

doi:10.1155/2018/2892361

Abstract

The spline tooth of ASTM 1045 was fabricated by high-speed cold roll-beating (HSCRB) process at room temperature. Microhardness of the spline tooth was examined by a nanoindenter. The grains and misorientation angle distributions were measured by electron backscatter diffraction (EBSD). The results showed that the microhardness was improved up to 1280 μm deep from the surface of the spine tooth. The microhardness and the grain sizes gradually decreased in the direction away from the surface. On the surface, the fraction of ultrafine grains increased up to about 90%, and the average grain diameter (which was ∼0.56 µm) decreased by 71.4%. The model of grain evolution during HSCRB process is proposed in this work. New grains appear first on the boundaries of the elongated grains within numerous subgrains. The elongated grains are refined as a result of subgrain rotation. By analyzing the HSCRB technical principle, we concluded that the process parameters affect the refinement degree of studied steel by determining beating pass, beating pass interval time, and strain rate.

Highlights

With the development of important industries, such as aircrafts, wind turbines, and nuclear power, a spline formed by current cutting methods fails to meet their high requirements. e spline formed by high-speed cold roll-beating (HSCRB) process possesses many advantages, such as higher strength and hardness and wear resistance
In region 2, the average grain diameter was 0.75 μm, and the fraction of ultrafine grains was >77%. e average grain diameter decreased by 63.1% comparing to the initial sample
In region 3, the average grain diameter was 0.56 μm, and the fraction of ultrafine grains reached up to 90% and 100% in fraction of all the fine grains. e average grain diameter decreased by approximately 71.4% comparing to the initial sample

Summary

Introduction

With the development of important industries, such as aircrafts, wind turbines, and nuclear power, a spline formed by current cutting methods fails to meet their high requirements. e spline formed by high-speed cold roll-beating (HSCRB) process possesses many advantages, such as higher strength and hardness and wear resistance. With the development of important industries, such as aircrafts, wind turbines, and nuclear power, a spline formed by current cutting methods fails to meet their high requirements. E spline formed by high-speed cold roll-beating (HSCRB) process possesses many advantages, such as higher strength and hardness and wear resistance. In our opinion, HSCRB process has not been studied in detail. Many studies were dedicated to material flow, dislocation density, residual stress, and cold working hardening during HSCRB process. Cui et al analyzed the trend of material flow based on the principle of constant volume and minimum moving resistance [4]. Lei studied the flow path trends of the special nodes by using the finite element simulation [5]. Wang et al obtained dislocation density curve of 40Cr under various strain rates [6]

Results

Discussion

Conclusion