No abstract

Radial-axial ring rolling, which is widely used to manufacture large scale seamless rings, is an advanced but complicated plastic forming technique with multiprocess factors coupling with interactive effects. During the radial-axial ring rolling process, the blank size is a decisive parameter because it influences directly the degree of deformation of the ring and the rolling parameters of the process. In this paper, the blank size design method of the radial-axial ring rolling process is first proposed, then a valid three-dimensional (3D) coupled thermomechanical FE model of the process is explored under ABAQUS software environment. Based on the valid 3D FE model, the blank size effects on radial-axial ring rolling are investigated. The research results provide valuable guidelines for blank size design and optimisation in the actual radial-axial ring rolling production.

Ring rolling is a process for creating seamless ring-shaped components using specialized equipment and forming process because of its technological superiorities of high quality, high efficiency and low consuming in energies and materials [1]. According to the international trend of cooperative control of the geometric accuracy and microstructure performance in ring rolling, rolling forming criteria such as biting-in condition, plastic penetrating condition, and plastic deformation were considered comprehensively to manufacture the bearing rings [2,3]. The evolution rules of grain refinement, plastic damage, and texture of bearing ring in ring rolling compatible with the rolling forming criteria are required for the cooperative control of the geometric accuracy and microstructure performance [4,5].To realize the cooperative control of the geometric accuracy and microstructure performance of the bearing ring, several rules of the bearing ring formation need to be revealed. Firstly, the constitutive equation of the material used for the bearing ring manufacture is crucial to study the deformation and microstructure evolution of bearings. At present, the high temperature flow stress strain relation, austenite grain growth behaviour, volume fraction and grain size of the recrystallization are still the most important research points for the constitutive equation of the material.The mechanical conditions of rolling forming and the rules of geometric formation of bearing rings are also important and widely studied such as ring rolling theory [6,7], rolling forming process [8], process tooling [9], and forming equipment [10]. Moreover, many studies revealed the evolution rules of grain refinement, content and stability of retained austenite, and micro texture of bearing rings in ring rolling [11][12][13]. The effect mechanism of the rolling process parameters on the microstructure evolution and mechanical properties of bearing rings is also established [14,15]. Thirdly, some studies reported how the heat treatment process effects the microstructure evolution and mechanical properties of bearing rings [16,17].The above research results could hardly provide the optimal rolling technical route to realize the cooperative control of the geometric accuracy and microstructure performance of bearing rings. Further experimental and theoretical studies and numerical calculation may be needed for establishing the quantitative correlation mechanism of rolling technical route with geometric formation, fine crystalline microstructure and high toughness of bearing rings.Further, it is important to form the cooperative control mechanism of ring rolling process and heat treatment process to obtain the fine crystalline microstructure and high toughness of bearing rings. Future studies should be carried on along the above ideas to solve the optimal ring rolling-heat treatment route realizing the cooperative control of the geometric accuracy and microstructure performance of bearing rings.

The influence of different initiation manners on the forming features of reactive material jets was investigated using the AUTODYN-3D simulation software. The numerical simulation findings demonstrate that, as compared to center point initiation, annular multi-point initiation greatly improves the velocity of the reactive material jet head created, but the expansion impact is more noticeable during the jet generating process. At the head and axis of the jet, there are noticeable low density zones (density less than 1.2 g/ cm3) and high temperature zones (temperature greater than 1000 K) with annular multi-point initiation. This is due to the superposition of several detonation waves, which raises the detonation pressure pressing on the reactive material liner, resulting in faster liner crushing. Furthermore, when the number of initiation points and the distance between initiation positions increases, the range of low density and high temperature regions extends, reducing the reactive material jet’s penetration capabilities.

Bearing ring blanks of the high-speed rail bearings, machine tool spindle bearings and wind power bearings have been manufactured through the ring rolling technology. Yet, the microstructure evolution of bearing ring in cold ring rolling remains unclear. In this work, the plastic strain distribution of the rolled ring is first simulated. Then, the microstructure of bearing ring is studied by the electron backscatter diffraction technique. Furthermore, the microstructure changes in cold ring rolling are investigated through band contrast images, and the texture evolutions after various deformation ratios are analysed by the technique of 3D-Euler space distribution. This work provides valuable guidelines for enhanced understanding the role of the cold ring rolling technology on the microstructure evolution of bearing rings.