The existing researches of hot ring rolling process are mainly based on forged billet. Compared with the existing process, the new ring casting-rolling compound forming process has significant advantages in saving materials and energy, reducing emission and reducing the production cost. The microstructure evolution of the casting materials during hot deformation is the basis of the research of the new process. However, the researches on the casting materials are rare. The metadynamic recrystallization of the as-cast 42CrMo steel after normalizing and tempering during the hot compression is investigated. The tests are performed on the Gleeble-1500 thermal-mechanical simulator. The influence rule of the deformation parameters on the metadynamic recrystallization is obtained by analyzing the experimental data. The kinetic model of the metadynamic recrystallization is deduced. The analysis results show that the metadynamic recrystallization fraction increases with the increase of the deformation temperature and the strain rate. The metallographic experiments are used to investigate the influence rule of the deformation parameters on the grain size of the metadynamic recrystallization. The experimental results show that the grain of the metadynamic recrystallization could be refined with the increase of the strain rate and the decrease of the deformation temperature during hot compression. The occurrence of the metadynamic recrystallization during the hot deformation is more difficult in as-cast 42CrMo steel than in forged 42CrMo steel. The research can provide the foundation for the further research of the hot deformation behaviors of the as-cast structure and theoretical support for the new ring casting-rolling compound process.

The precipitation, dissolution, and coarsening of different carbides at 680 °C in G18CrMo2–6 steel was investigated experimentally combined with Jmatpro simulation. The G18CrMo2–6 steel was normalized at 940 °C, followed by tempering at different times at a constant temperature of 680 °C. During the tempering process, there are mainly two kinds of carbide, namely M₃C and M₂₃C₆. Through characterization of microstructural evolution, thermodynamic calculation, and kinetic simulation, it was observed that during the tempering process, the stable M₂₃C₆ carbide was growing, whereas the metastable M₃C carbide was disappearing. At the end, the M₃C carbide was dissolved and the M₂₃C₆ carbide was in equilibrium with the matrix.

Bearing ring is the crucial component of bearing. With regard to such problems as material waste, low efficiency and high energy consumption in current process of producing large bearing ring, a new process named “casting-rolling compound forming technology” is researched by taking the typical 42CrMo slew bearing as object. Through theoretical analysis, the design criteria of the main casting-rolling forming parameters are put forward at first. Then the constitutive relationship model of as-cast 42CrMo steel and its mathematical model of dynamic recrystallization are obtained according to the results of the hot compression experiment. By a coupled thermal-mechanical finite element model for radial-axial rolling of bearing ring, the fraction of dynamic recrystallization is calculated and recrystallized grains size are predicated. Meanwhile, the effects of the initial rolling temperature and feed rate of idle roll on material microstructure evolution are analyzed. Finally, the industrial rolling experiment is designed and performed, based on the simulation results. In addition, mechanical and metallographic tests are conducted on rolled bearing ring to get the mechanical parameters and metallographic structure. The experimental data and results show that the mechanical properties of bearing ring produced by casting-rolling compound forming technology are up to industrial standard, and a qualified bearing ring can be successfully formed by employing this new technology. Through the study, a process of forming large bearing ring directly by using casting ring blank is obtained, which could provide an effective theoretical guidance for manufacturing large ring parts. It also has an edge in saving material, lowering energy and improving efficiency.

The compact cast-rolling compound forming of bimetallic ring is an efficient process for manufacturing large bimetallic rings. The difference in hot deformation behavior of the two metals directly affects the coordinated deformation of bimetals during hot rolling. In this paper, hot compression tests of 40Cr/Q345B bimetallic blank produced by centrifugal casting were carried out at temperatures of 950–1200 °C and strain rates of 0.005–5 s⁻¹. Based on the comparisons of flow stress behavior, activation energy, and activation volume, hot deformation behavior coordination of 40Cr/Q345B bimetallic blank was investigated. Processing maps were established to study the optimum processing windows for 40Cr/Q345B bimetallic blank. Under the same deformation conditions, 40Cr shows lower overall flow stress than Q345B, which facilitate the coordinated deformation of the bimetallic blank during rolling, and the flow stress difference between 40Cr and Q345B decreases with the increase of temperature. It was connected with the increase in the second phase particles pinning effect for higher MnS content in Q345B. The common rate-controlling mechanism for 40Cr and Q345B is the thermal breaking of attractive junctions and movement of jogged screw dislocations. The bimetallic blanks exhibit good deformation coordination in the optimum processing window (1030–1100 °C and 0.5–1 s⁻¹ with a strain of 0.6).