Study On Ultrasonic Vibration Extrusion Forming Technology Of 20 Steel Pipe Billet

Traditional seamless steel pipe forming methods mainly include thermal extrusion forming,cold pressure forming,drilling forming and centrifugal casting,but to varying degrees there are high energy consumption,material loss,complex equipment technology and other shortcomings,and product surface quality and performance need to be further improved.Applying ultrasonic vibration in the process of plastic forming of metal materials can improve its mechanical properties,reduce the flow stress in the forming process,reduce frictional wear,improve the surface quality of parts and improve the forming accuracy.At present,ultrasonic vibration-assisted plastic forming technology has been applied to rolling,pulling,pulling deep,rotary forging and other processes,and obtained a good forming effect,has become a metal plastic forming research hot spot.Therefore,this thesis puts forward in the process of seamless steel pipe forming supplemented by appropriate ultrasonic vibration,taking 20 steel which is widely used in oil drilling,boilers and other industries as the research object,utilizing the method which is combined of experiments and finite element simulation,to study the performance of the mechanics of 20 steel in the ultrasonic vibration and ultrasonic vibration on the pipe blank forming process.Based on the material universal tester,an experimental platform for ultrasonic vibration mechanics is set up,the influence of ultrasonic vibration field on the performance of 20 steel mechanics under different ultrasonic power and strain rate is studied,the material structure model based on Johnson-Cook type is established,and the model parameters are identified and the corresponding error analysis is carried out in combination with the experimental results.The results of the mechanics test show that the volume effect caused by the auxiliary ultrasonic vibration field can reduce the flow stress by up to 10%in the range of strain rate and ultrasonic vibration power.Experiments on intermittent loading of ultrasonic vibration show that ultrasonic vibration only affects the forming process of 20 steel,and does not affect its post-forming mechanics.Based on the plastic forming finite element analysis software DEFORM,a three-dimensional model of ultrasonic vibration pipe blank extrusion is established,and the influence of ultrasonic vibration field on mold wear,stress and strain of tube blank forming process is studied in combination with the established material-based model.The forming process,supplemented by ultrasonic vibration,causes the surface effect of the material,reduces the friction between the mold and the tube blank and reduces the wear of the mold.Utilizing the developed ultrasonic vibration pipe blank extrusion forming experimental platform,the influence of ultrasonic vibration field on the load-displacement of 20 steel pipe billet forming process is studied,and the experimental results show that after loading ultrasonic vibration,the forming load decreases by 11%to 13%,and the load is lower when the mold displacement speed is small.The micromorphology of the inner surface of the tube blank is observed,and it is found that ultrasonic vibration can improve its surface quality,and the effect is more obvious at the large feed speed.Therefore,the research of this paper can provide a new forming method for 20 steel seamless steel pipe extrusion forming,and lay the foundation for the establishment of its complete set of new processes.