Finite Element Analysis Of Mechanical Expanding For X80 Longitudinal Welded Pipe

As the technology of pipeline steel manufacturing improved, the development of oil and gas transmission pipeline is moving in the direction of large flows and high-pressure transmission. At the same time, the initiation of west-east gas transmission project will also bring our country's pipeline manufacturing industry into a new era, which provides a good developing opportunity upon our nation's high grade longitudinal welded pipe manufacturing enterprises and it also proposes more requests for higher level of quality and property.Mechanical expanding is an important process to ensure the quality of the LSAW pipe production, mechanical expanding may eliminate the residual stress caused by forming and welding, improve the internal stress distribution of steel, but also have a negative impact, such as reduce the thickness of the tube wall, generate cracks nearby the heat affected zone and so on when the improper parameters are used. Mechanical expanding is the final process to achieve shape forming of the large-diameter longitudinal welded pipe, which plays an important role to the perfect size and appearance of the production.This paper put the nonlinear finite element software ABAQUS as a platform to build a model of two-dimensional finite element simulation of longitudinal welded pipe. Basing on this model, we can use small size hole enlargement mould to do experiment of expanding on the welded pipe under the laboratory condition. When comparing and analyzing the experimental result and the simulated result, it shows that the shapes of welded pipe are fitted well.In order to obtain the mechanical property parameters of the heat affected zone, using X80 pipeline steel to make the thermal simulation experiment, then we can get the mechanical properties which will be imported into the finite element model of pipe to simulate the pipe expanding. Using this method, we can comprehensively analysis the effect on the welded pipe forming caused by ovality and pouted quantity which are caused in the process of mechanical expanding. And we can also analysis how the ellipticity pouted quantity reverse turning angle, surplus height of weld reinforcement expanding rate and hardening index effect on the quality of the welded pipe. It reveals how each parameter effects the stress in the heat affected zone, and the primary and secondary factors show the regular pattern of how it goes. At last the measure of how to prevent crack in X80 welded pipe in the process of expanding will be given out.