The Research On The Hot-Push 45 Steel Elbow’s Forming Process

In recent years, with the development of ship and petrochemical, gas and other industries, as a liquid, gas pipeline elbow has been widely used. When the tube is bent, the load pressure of the inner and the outer side of the pipe wall is different because of the difference of the mechanical properties between the inner and outer sides of the pipe wall. Elbow as one of the main connecting parts of the pipe system, the safety operation of the whole system, so the structure design of the elbow is very important. The main content of the pipe production enterprises to accelerate the pace of key technological transformation is to improve the level and productivity of the forming of the elbow.Through a combination of numerical simulation and experimental verification of the method, using ABAQUS finite element simulation software on the elbow hot-push forming process is system simulated. According to the simulation results, the optimum forming process parameters are presented, and analyzed on the effect of the elbow’s forming quality under different technological parameters, such as push of temperature, of pushing speed, friction coefficient.The main research contents and results are as follows:(1)Using the involute variation as expanding mandrel diameter forming section of axis, The main design ideas is by infinite curvature radius decreases gradually to the plastic section radius of curvature, so that is conducive to the metal flow in the process of expanding, concave metal can fully flow to convexity, so as to avoid the wall thickness is uneven phenomenon which decrease of outer wall thickness increase of inner wall thickness and in the traditional deformation of elbow bending, which can ensure roundness of the diameter and wall thickness uniformity.(2)By using the control variable method, the design of the central axis is optimized, and the optimal design is simulated.(3)Through the finite element software ABAQUS and combined with orthogonal test method on different parameters of elbow hot-push forming process is simulated. The simulation results show that the temperature is too high will lead to the tube blank easily wrinkling, too low will lead to cracking. In this paper, the temperature is 700℃, at a suitable push speed the tube is in an ideal state of elastic and plastic, and the thickness of the elbow stays the same; In the orthogonal experiment, the temperature distribution is uniform, and the push velocity will not affect the distribution of temperature field. When the push speed is slow, it can provide sufficient time for the metal flow and improve the uniformity of the wall thickness, But in the industrial production, push speed too slow will increase the production cycle and affect the production efficiency, what we need to do is to balance the relationship between the push speed and production efficientcy and select an appropriate push velocity. The coefficient of friction between the mandrel and tube billet is related to the actual work environment. The friction coefficient increases, the friction between the tube wall and the mandrel is larger, and the inner side of the tube wall is thicker; The increase of friction can also restrain the metal flow, and to a certain extent, it can ensure the uniformity of the thickness of the wall.(4)The experiment on the machine is carried out, and the wall thickness of the elbow is compared with the simulation results, the experimental results and the finite element simulation results show that the wall thickness difference is within reasonable range, and verify the accuracy of the finite element analysis result.Through the above research, the effect of the elbow’s forming quality under different technological parameters is obtained, and the involute variation design as the axis, so as to avoid the wall thickness is uneven phenomenon which increase of inner wall thickness and decrease of outer wall thickness; through experiments to learn more about the elbow thick wall forming, and verify the accuracy of the finite element analysis model, provide a new research method for the elbow forming process.