Electroplastic Rolling for Stainless Steel
Although my country’s stainless steel industry has developed rapidly, it still has high energy consumption, high pollution, and low efficiency compared with industrialized countries. Take 304 stainless steel as an example, because it is prone to severe work hardening during the production and processing process, and its forming performance is poor.
Therefore, multiple annealing treatments are required during rolling, drawing, and other processing processes to reduce or eliminate work hardening. , To facilitate subsequent processes. Multiple annealing is not only time-consuming and energy-consuming but also has serious environmental pollution and other problems. Therefore, it is of great significance to find a clean, environmentally friendly, energy-saving, and efficient production process.
Recently, Zheng Xingpeng and others from the Shenzhen Graduate School of Tsinghua University proposed to apply the electro-plastic rolling process to 304 stainless steel strips and verified its feasibility through experiments. The so-called “Electroplasticity” refers to the phenomenon that the resistance to deformation of materials decreases sharply and the plasticity increases significantly under the action of moving electrons (current or electric field).
Electroplastic processing technology can reduce the deformation resistance of the material, improve the plasticity of the material, and enhance the forming ability of the material. Zheng Xingpeng and others carried out multi-pass cold rolling and electro-plastic rolling of 304 stainless steel strips on the electro-plastic rolling mill developed by themselves.
Among them, high-energy pulses were generated when the stainless steel strip was rolled by elastoplasticity. The device continuously applies a high-energy pulse current (120 V) to the rolling strip. They contrasted and studied the deformation resistance, hardness, tensile strength, and elongation of the materials under different rolling methods, and conducted a systematic analysis of the microstructure.
Experiments have shown that the deformation resistance of the material is as high as 16.5 kN during cold rolling. After the pulse current is introduced, the deformation resistance of the material is significantly reduced, and the reduction is greater and greater with the increase of the electrical pulse frequency. When a 500 Hz pulse current is applied, the deformation resistance of the material drops to about 12.2 kN, which is as high as 26%.
The test results of the sample show that whether it is cold rolled or electric rolled, the hardness of the sample increases with the increase of deformation, but the degree of aggravation of cold rolling is much higher than that of electric rolling. In electric rolling, after reaching a certain amount of deformation, the hardness of the sample tends to a stable value.
In electro-rolling, as the frequency increases, the tensile strength of the sample basically shows a downward trend, while the corresponding elongation continues to increase. However, when the deformation is 20% to 50%, the tensile strength of the sample is greater than that at 500 Hz when an electric pulse of 600 Hz is applied, and the elongation rate is also very large at this time. The tensile strength of the sample rolled by 600 Hz pulse current increases gradually with the increase of deformation and then begins to decrease after reaching an extreme point.
Correspondingly, its elongation first shows a downward trend and reaches a minimum point. After slowly rising. This shows that there is an optimal frequency in the electro-rolling process, at which the best match of strength and plasticity can be achieved. At this time, compared with the original sample in the solid solution state, the electro-rolling test is 50% deformed. This not only has high tensile strength but also has good plasticity.
Their work shows that high-energy electric pulses can effectively reduce the degree of work hardening of the material and improve its plastic deformation performance so that it can increase the number of rolling passes, increase the total deformation, and easily obtain thinner materials without intermediate annealing. Sheet and strip. This is a clean, environmentally friendly, energy-saving, and efficient production process route.