The forging method with horizontal V-shaped anvils (HVA) is effective in the control of inner stress states, metal tissue, etc. FEM numerical simulation is conducted for the HVA forging method, under various processing parameters. The results show that during HVA forging, the transversal and axial stress states in the middle part of forgings are influenced by not only the ratio of the anvil width to billet height (anvil-width ratio )but also the ratio of the blank width to billet height (blank-width ratio) and the reduction ratio, while the end parts are influenced little. Among those processing parameters, the reduction ratio plays an important role. When the reduction ratio is 5% or 10%, it is possible to obtain axial and transversal tensile stress. When the reduction ratio is larger than 15%, it is easy to obtain two-way compressive stress. Therefore, in order to control the two-way tensile stress, big reduction ratio should be adopted. Small blank-width ratios result in the forgings cracks because of transversal tensile stress in common flat-anvil stretching method. On the contrary, even if the blank-width ratio is small, transversal compressive stress can be generated in forgings for the HVA forging method, only if the matching of the anvil-width ratio and the reduction ratio is suitable. The feature of the HVA forging method benefits the preventing forgings from inner cracks. The results provide the theoretical foundation for the application of the HVA forging method.
Considering the difficulty for the dynamic recrystallization to happen in Steel 26Cr2Ni4MoV, which was used to manufacture low-pressure steam turbine rotors generally, after-forging static recrystallization was studied with the thermo-torsion method. In order to investigate the influence of multi-step cumulative deformation on after-forging static recrystallization of Steel 26Cr2Ni4MoV, the thermo-torsion method was adopted to conduct a constant-temperature four-step torsion test at 900°C. The time gap between each step in the test agreed with that in real production. Results show that the influence of multi-step cumulative deformation on after-forging static recrystallization is almost the same with that of single-step deformation. It means that the nucleation and the growth of after-forging static recrystallization are related mainly to the last deformation and temperature-keeping time. Grain size can be controlled through the last deformation and temperature-keeping time. The findings supply the theoretical foundation for the said-steel controlled forging processes.
The structure and processing of car holders castings were analyzed. Die-casting molding process scheme was established. The design of mold includes three core-drawing mechanisms. the gate of the gating system was arranged on the casting bottom surface. For economy and die easy maintenance considerations, die-casting machine, mold, and mold standard parts should be standard parts. The designs of mold gating system and non-standard pieces were completed with the aid of PROE. Proved by actual production, the mold operated smoothly, without clamping stagnation, and the production of die castings meet delivery requirements.
Shooting nails are mainly applied to fix thin reinforced concrete and steel plate, so the nails should have high hardness and high toughness. Unreasonable heat treatment process could possibly cause too high hardness and decreased toughness, leading to nail cracking and fracture in the course of production and use. Research on heat treatment process through experimental study on the nail determines the reasonable heat treatment process of nail. The feasible quenching heating temperature was 847~840 °C, and the temperature of salt bath during isothermal cooling was 292 °C. Its resultant hardness was 680HV, meeting the requirements of the use of nails. The shoot nail cracking and fracture in the course of use can be avoided effectively. The microstructure of shooting nails after heat treatment showed lower bainite, which contributed to good mechanical properties.
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