| As the key connection,transmission and base parts of slewing support,ring members have many kinds,large amount and wide applications.In deep space exploration,petrochemical and wind power and other extreme harsh environment applications,the inner and outer performance of the ring put forward different requirements,bimetallic composite ring has the advantages of the two metal materials,to maximize the performance of the advantages of complementary,so as to improve the ring performance and reliability.At present,the manufacturing method of bimetallic composite ring is complicated,time-consuming and labored,and the bonding strength is poor.In this paper,a short process manufacturing technology of bimetallic composite ring is studied.The bimetallic ring billet is directly hot rolled into bimetallic ring member by centrifugal casting,and the inner and outer layers of metal are metallurgical combined.It can provide an energy saving and efficient production method for large bimetallic ring member(diameter over 1 meter).In the compound forming process of bimetallic casting and rolling,the bimetallic ring casting billet is used to roll directly.In the process of rolling,not only the shape of the billet is formed,but also the structure and properties of the billet are improved,so that the cast structure is transformed into the forged structure,and the inner and outer layers of the metal are combined well.So the research of bimetallic centrifugal casting slab hot deformation behavior and microstructure evolution rule,analysis of as-cast organization(especially the bimetal combining layer metal as-cast organization)broken in the hot rolling process refinement mechanism and regularity,determine the internal and external and bimetal combining layer of microstructure of as-cast organization into forging thermodynamic conditions,It is particularly important to reveal the influence mechanism of key process parameters on microstructure evolution and to realize the integrated fabrication of bimetallic composite annular member with short flow program control and shape control.In this paper,through the development of reasonable technological parameters to obtain a good combination of centrifugal casting 40Cr/Q345B bimetal ring billet,both 40Cr wear resistance and Q345B weldability.The true stress-true strain curves of bimetallic(BCBL)with bonded layer obtained by Gleeble-3500,and the influence of different hot working parameters on flow stress was studied.On this basis,the constitutive relationship model and state recrystallization model were constructed.The effects of different thermal processing parameters on microstructure and atomic diffusion were studied by combining the true stress-strain curves.Based on the dynamic material model,the thermal working map of bimetallic(BCBL)with bonded layer was constructed,and the microstructure of the safety zone and instability zone identified by the thermal working map was analyzed.The main conclusions are as follows:(1)The centrifugal casting 40Cr/Q345B bimetal ring billet bonding layer has good metallurgical bonding,the thickness of diffusion layer reaches 3.69mm,and the mechanical properties approach to the mechanical properties of Q345B.(2)When the strain rate is constant,increasing the deformation temperature,the rheological stress decreases and the dynamic recrystallization feature is significant;when the deformation temperature is constant,accelerating the strain rate,the rheological stress rises and the dynamic reversion feature is weakened.(3)Temperature is the most important factor affecting atomic diffusion,the higher the temperature is.The wider the width of the binding layer.(4)Under the condition of high temperature and low rate,the dynamic recrystallization is easy to proceed,the grain growth rate is fast,and the coarsening phenomenon is serious,so the strain rate should be appropriately increased.(5)The optimum parameters of centrifugal casting 40Cr/Q345B bimetal ring billet are as follows:deformation temperature1150?1250?,strain rate 0.4?1-1. |
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