Research On Theory And Technology Of Rolling Of Non-circular Section Steel Wire

Non-circular section steel wire is a kind of precise profiled bar. It can be made into various products efficiently in related fields with less raw material and energy consumption for it doesn’t need cutting process. So it improves both the energy utilization and the resource utilization. The non-circular section steel wire has been widely used because it meets the demands of energy conservation and emission reduction and promotes the development of low-carbon economy. Therefore it has great development prospect. However, as a new product, there are many aspects need to be improved in manufacturing technique.This paper tries to make a comprehensive research on the key technical problems in the processing and manufacturing process of non-circular section steel wire. The discussions focus mainly on four aspects:Production equipment, Material molding processing technique, Plastic deformation micromechanism and Improvement of product performance using new technology. Some conclusions that have certain theoretical and practical values have been summarized.Then used the explicit finite element analysis software ANSYS/LS-DYNA, this paper researches and analyzes the rolling force、stress and metal flow behaviors on the rolling process which loads tensile stress from the front and back and take the most complicated special-shaped section of coil-spring loaded oil ring for example to design a rolling process which can roll a special-sized coil-spring loaded oil ring. Then,this paper simulates the traditional drawing process of coil-spring loaded oil ring in the same process step and compares the rolling process with it, the comparison demonstrates that in the same process step, the rolling process we have study on can get a good result, while traditional drawing process can not reach the purpose. It states clearly that rolling technology of Non-circular section steel wire is more efficient than conventional drawing.Based on the results of molding simulation technology and the key conclusions to use to make the relevant of the validation, this paper adopt 3D visual modeling technology and check it with finite element method, using the software of AutoCAD and Pro/Engineering to complete the whole series drawings and optimization, and the rolling mill that we design can satisfy the precision requirement in stiffness of special-shaped wire of piston ring.This paper also researches the plastic deformation mechanism of 9Cr18MoV which is a kind of high-carbon high-chromium stainless steel in the process of room temperature and warm working compared with 20# and 60Si2Mn. This is very important for the manufacture of non-circular section steel wire.9Cr18MoV is the mainstream material to manufacture special-shaped section steel strips used by piston ring in western countries. Domestic markets mainly import it from western countries because it is quite difficult to produce.Hydraulic universal material testing machine, Gleeble1500 thermal-mechanical testing system and SPS electropulsing compression experimental system designed by ourself were employed to investigated the plastic deformation behaviours at room temperature and 500℃,600℃and 700℃middle temperature of the low, middle and high-Carbon steels:20#,60Si2Mn and 9Cr18MoV. The parameters of SPS electropulsing compression experimental system:current of 0-5000A, on time/off time of 8/2, duration of 3ms. The strain rate of compression deformation process is 0.05/s, and the maximal deformation compression is 40%. The experimental results show that compared with room temperature compression, the maximum deformation resistance of middle temperature compression has been decreased 60-80%; Compared with the Gleeble compression experiments of the similar temperature range and the same deformation reduction, the electropulsing can significantly decrease the flow stress of compression process, and the maximal drop value of compression plastic deformation resistance can reach to 47.1%.Microhardness test results of 9Cr18MoV specimens show that:the microhardness of room temperature cpmpression samples is higher because the sample matrix is hardened; the microhardness of higher temperature cpmpression samples is lower because the sample matrix have softening tendency; The hardness of the higher temperature deformation samples with Electropulsing is higher than the Gleeble experimental samples under the same deformation conditions. It means that the material property heated by electropulsing is better because of hypoeutectic structure after dynamic recovery and grain refinement after dynamic recrystallization.With reference of the optical microscopy photos of the samples’microstructure, transmission electron microscopy has been employed to analysis the microstructure and the deformation dislocations structures of the center area at the middle cross-section of the samples, and dynamic recovery and dynamic recrystallization phenomenons of the middle temperature compression deformation samples have been observed; In order to achieve the bigger deformation reduction of high-hardness steels under lower temperature, electropulsing can facilitate the dynamic recovery and dynamic recrystallization of in the process of the middle temperature plastic deformation. It is found in the investigation process of mechanism of plastic deformation with electropulsing that the electropulsing can advance the dynamic recovery and dynamic recrystallization by promoting the dislocations’climb, the dislocation dipoles’ annihilation and recomposition, and increasing the movability dialocations’quantity, and promoting the thermal activated slip of dislocations, and the coalescence and turning process of the subcrystals, then advancing the dynamic recovery and dynamic recrystallization.A new method to obtain ultrafine grain microstructure with less energy consumption is proposed in this paper. The plastic processing with electropulsing proceeds in ferrite temperature range (under 700℃). And dynamic recrystallization will occur in lower temperature, which will reduce the deformation resistance greatly. What is more, the dynamically recrystallized grain size in this lower temperature range is smaller due to the influence of electropulsing and it saves more energy compared with traditional rolling processing in austenite temperature range. And the grain grows slowly in lower temperature and can be controlled easily. So ultrafine grain microstructure which is about 1μm can be obtained. Based on this theory, this paper designs a new technology to process non-circular section steel wire in lower temperature with less oxidation.