To address the existing defects in the processing of magnesium alloy seamless tubes (MASTs), a new technology for producing AZ31 alloy tubes using a rotary piercing process was studied. Through the finite-element method and experimental analyses, the distributions of stress and strain and the temperature fields were analysed. The effects of temperature, radial reduction, plug diameter, and advance on the penetration rate, diameter, and wall thickness of the tube were studied. The results showed that temperature is the most important parameter; the penetration rate of the tube was >90% for rolling temperatures of 350–450°C. There was complete dynamic recrystallisation and a uniform distribution of equiaxed grains. This process can potentially replace the traditional extrusion process to produce MASTs.
As a process for producing seamless tubes, the tandem skew rolling (TSR) process was proposed. In order to study deformation characteristics and mechanism on tubes obtained by the TSR process, a numerical simulation of the process was analyzed using Deform-3D software. Simulation results demonstrated the distribution of stress, strain, velocity, and temperature of a seamless tube in the stable stage during the TSR process. Actual experiments of carbon steel 1045, high strength steel 42CrMo, and magnesium alloy AZ31 were carried out in a TSR testing mill. The results demonstrated that the TSR process is qualified for producing tubes of high quality, with an accuracy of ±0.2 mm in wall thickness and ±0.35 mm in diameter. This process is suitable for manufacturing seamless tubes that are difficult to deform or that have been deformed in a narrow range of temperature.
Abstract:Tandem skew rolling process is a new process for producing seamless steel tubes, which combines the piercing and the rolling in traditional production of seamless steel tube and rolls the billet into the tube by the method of continuous skew rolling directly. The process implements continuous rolling,such as piercing and rolling extension,piercing and secondary perforation and multi-channel skew rolling deformation. Aiming at the particularity of tandem skew rolling process, the method of stream function is adopted to establish the deformation model in the process. The velocity fields are obtained under the boundary conditions of the velocity as well as constant volume conditions,which is the basis of plastic deformation theory for solving the strain rate, deformation power, process parameters. Tandem Skew Rolling testing mill is developed and the corresponding process experiments are carried out. It is proved that the process is feasible and the accuracy of the mathematical model, which establish the groundwork for the further production application.
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