Numerical Simulation Analysis Of Welding Temperature Field Of 15CrMoR Steel And Its Application In Welding Procedure Qualification

Nowadays,15 CrMoR steel is widely used in the production of pressure vessel,especially in the flame tube of heating system of Oil Producing station in oil field.After welding,Some defects such as hardening of heat Affected Zone,cold cracks and reheating crack have serious effect on the quality of products.Welding procedure qualification requires that welding parameter such as welding current,speed,the change of radius of heat source will affect the mechanical property and non-destructive inspection of welding joint,so it is important to take a best combination of these three kinds of parameters.Presently,Pressure Vessel Manufacture Enterprise adopts a changeable multi-sections welding parameter to conduct the experiment of Welding Procedure Qualification,later compares mechanical property and non-destructive inspection of each section.At last,choses the optimum welding parameter to conduct the production.we will spend much time and this method costs us much material and labor.Also we will spend a few days to determine the optimum welding parameter of each kind of material.With the rapid development of computer software,we should look for a simulation method to lessen scope of welding parameter,which is meaningful for enterprise to reduce the cost and Personnel input.the paper will use software to Analyze the temperature field which was resulted from three kinds of welding parameter under different circumstances.On this basis,we simulate the Weld stress and chose the optimum welding parameter to conduct the experiment of Welding Procedure Qualification.By this way,we can save cost and reduce the working time.The essay will apply ABAQUS to choose the model,look for the Physical parameters of thermal property of the material,Divide Grids and load boundary.And then simulate and analyze the welding of 15 CrMoR steel and obtain nephograms and curves under different currents,speed of welding and radius of heating,last we make a comparative analysis and come to the rules of affecting the property of welding.By simulation and analysis,we know the dynamic change of molten pool in welding by the use of Gaussian heat source in submerged arc welding.Under different welding techniques,the central temperature of weld seam all reaches the melting point,the satisfying shape of molten pool can be achieved by the welding.By double passes welding,we get the two high peaks at thermal cycle curves of different points.The change of electric current of welding only affects the highest temperature of central molten pool,and has no much influence on the temperature outside the molten pool.And we find that,with the increase of welding speed,a point can reach the peak of temperature within the shorter time by a contrast analysis of the distribution of temperature and the change of molten pool under different velocities of melding.At the same time,with the fast speed of welding,There isn't much difference in terms of central temperature of welding under 3 different velocities of welding.This indicates the limitedness of velocities of welding on the central temperature of molten pool.By a comparative analysis of the temperature distribution under different radiuses of heat source.We get that the smaller the radius of heat source,the higher the temperature of central weld seam,the narrower the weld seam.on the basis of temperature fields,we make a contrastive analysis of stress fields in the submerged arc welding of 15 CrMoR steel,By the analysis of stress nephograms and equivalent stress at different time under different typical welding techniques,and a contrastive analysis of stress-strain curve on different routes of welding testing plate,we get he following conclusions:By stress nephograms,we can see that the weld face of second pass has formed certain residual welding stress on the basis of the first one,the metals near the area o f weld seam will release partial stress under the high temperature of heat source,so residual welding stress on the weld face of second pass will be lower than the first one,but has a more extensive distribution.The residual stress come to its limit at t he beginning and end points of vertical routes of central weld seam,and there is less residual stress in other areas.Horizontal residual stress mainly concentrates on the weld seam or some places near it under typical techniques of welding.By the experimental results,we conclude that the most commonly used welding technique is that :welding voltage 34v;welding current 600A;welding velocity 30cm/min;the radius of heat source 8mm.the maximum equivalent stress in different routes are the minimum value by using this welding technique.This paper aims at validating the accuracy of simulation by comparing the mechanical property and non-destructive inspection of each group,get the optimum numerical simulation method of welding parameter and lays a theo retical basis for the choice of welding parameter of other material.