Research On Microstructure Evolution In Pre-heat Treatment And Cold Ring Rolling

Cold ring rolling is an advanced plastic forming technique by which manufacture seamless rings of different cross section. It is widely applied in fields of automobiles, trains, ships, aerospace and atomic energy owing to its advantage of less cost, high precision, high performance and so on; Combining finite element simulation and experiments, researched on microstructure evolution and deformation behavior in pre-heat treatment, rolling, and quenching of rings. It will provide the theoretical bases of improving the precision and properties of cold-rolled rings.Firstly, get mechanical properties of pre-heat treated 1045 steel by tensile test. Secondly, a rational FE model of cold ring rolling was set up in ABAQUS software environment, and the cold ring rolling was analyzed. Thirdly, practical experiment was carried out on D56G90 cold ring rolling mill with the same processing parameters used in FE simulation. Last, investigate the microstructures after every processes. The research shows that within the range measured in these experiments, the size of the grains in the rings becomes smaller as the annealing cooling rate increases, whereas the lamellar spacing of the pearlite decreases, which results in stronger materials with increased plasticity.At the same time, as the annealing cooling rate rises, the stress inside the rolled rings rises, while the strain becomes smaller, and the fragmentation of the pearlite lamellae increases and they become finer. All of these effects lead to improved rolled ring properties.Experiments of pre-heat treatment, cold ring rolling and quenching was conducted to rings of GCr15 steel, then simulated the cold ring rolling of GCr15 in ABAQUS software environment. The samples were researched in SEM, tensile test, XRD and micro-hardness. The results imply that GCr15 steel after annealing turned granular pearlite from lamellar and cementite grains become big, ultimate tensile strength increases, and percentage elongation decrease with the slower annealing cooling rate.The{111}<112>-fibre texture of cold ring rolled ring strengthen as quicker annealing cooling rate. The{111}<110> texture strengthen and the{111}<112> texture weaken from outside to middle of the GCrl5 steel ring. In the inside, the{111} <112> and the{111}<110> weaken. At the same time, the{100}<011> texture exists in the inside ring. After quenching, the martensite becomes smaller and the cementite smaller of quicker annealing cooling rate.In the whole process, the micro-hardness does not change much after normalizing, decrease after annealing, then increase after rolling and rise much too after quenching. But the micro-hardness of ring with the slowest annealing cooling rate is maximum after every process.