| The large conical cylinder is one of main kinds of large forgings,with the characteristics of large diameter and wall thickness.For the particularity of its volume,the large conical cylinder is mainly applied under the environment of high temperature resistance,corrosion resistance and pressure resistance,such as used in petrochemical,nuclear power,aerospace and so on.Our country has come up with the perspective of paying great attention on developing basic parts and materials,and the large conical cylinder is the basic part in nuclear power,aerospace,and chemical industry.Therefore,along with the rapid development of these industries and the progress of technology,the demand of large conical cylindrical pieces is becoming higher and higher.Due to the special working environment,special size and shape,and its core role in the field of application,the quality requirements of large conical cylinder are very high,which also makes high requests for the corresponding manufacturing technology and level.So how to manufacture large conical cylinder with high efficiency and quality is to be the key issue of improving major technical equipment for our country.Rolling forming is a kind of highly efficient forming method,and compared with forging forming,it has the characteristics of shorter processing time,less material waste,better comprehensive mechanical performance and so on.However,there has been no public report and related research on the rolling technology of large conical cylinder at home and abroad.Therefore,this paper is to study on the material of large conical cylinder,determine the layout of the mill roll system and the optimal roll system,optimize some parameters like the roller speed's,and use the differential temperature rolling technology to further improve cylinder forming performance,by all of which the research on the rolling theories of large conical cylinder are carried out.First of all,by the isothermal compression experiment,the thermal deformation behavior and structural transformation of the 20MND5 steel was tested on the Gleeble-3800 thermal simulated test machine under the condition that the strain rate is0.001~10s-1 and the deformation temperature is 950~1 150?,which helped to study therules that deformation technology affects the thermal deformation flow stress and establish its thermal deformation constitutive equation.With the consideration of influences from both the strain rate and deformation temperature on the properties of material structure,this study made the 20MND5 steel hot working diagram,which is based on the constructive equation,and determined the rheological instability area of this steel and the optimum parameters during the thermal deformation process.This paper also analyzed the deformation characteristics of different areas of the 20MND5 steel,and found out the appropriate strain rate and its dependent variable when the deformation of 20MND5 steel happens under different temperature.Secondly,the method of determining the optimum size of roller was put forward by this paper through the way that the large conical cylinder and roller were placed vertically and then carried out the finite element numerical simulation under the conical roller system.Based on the SOLIDWORKS modeling software,the large conical cylinder rolling three-dimensional model was established,and the simulation of the rolling process of the large 20MND5 steel conical cylinder was carried out through DEFORM definite software,which illustrated the influential rules and mechanism of the strain field and temperature field on the roller size during the rolling process,and finally determined the optimal matching roll system.Finally,the differential temperature rolling simulation experiment was carried out and compared with the isothermal rolling,it strengthens the rolling effect and improves the rolling technology,which means that it achieves in improving the actual production. |
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