| As a large-scale mode of transportation,the pipeline conveys oil and gas,has the characteristics of economicy,safety and uninterrupted.the development trend of pipeline steel construction is developing towards long distance,large diameter and high pressure direction.Therefore,in the actual welding conditions,not only do ensure that the weld metal has the excellent welding process,but also it is more important to improve the welding speed and strength and toughness of the weld metal.The selection of sintering flux determines the improvement of welding speed and weld strengh and toughness.As for the high-grade pipeline steel,the researchment on match sintered welding flux is still less.Therefore,the research objective of this paper is to develop sintered flux that is matched to the X120 pipeline steel,and to expound the interdependence between flux composition and welding process,it summarized the methods of how to improve the strength and toughness of the weld,thus put forward the theoretical basis for the subsequent welding materials production of X120 high grade pipeline steel.Based on a large number of test data in the research on the CaF2-MgO-Al2O3-CaO-TiO2 type sintering flux,the results showed that:when the basicity of flux is between 1.6?2.2,the sintered flux with good sex of deslagging can obtain.When the content of deoxidizing SiFe is in 2%,can make the bead showed bright metallic luster,the welding manufacturability is best and can improve pitting phenomenon.Simultaneously,in the tests,effect of primary components containing in raw materials of the sintered flux on detachability,are stability,gas hole in weld,and other processing property were carried out.And by using the DPS software,the influence of flux component on weld forming was quantified and a reasonable mathematical model was given.the interaction between the flux component had a great influence on the process of welding.The results showed that the interaction of the CaF2 and ZrO2 had a negative effect on appearance of weld,the interaction of the CaF2 and CaO just the opposite,and when the ratio of CaF2 and CaO in the 2.2 to 2.8,the flux of the arc stability effect was best,and arc ending stage appears crater disappeared;and when the ratio of(MgO + CaO)/SiO2 is not greater than 3,that the desulfurization ability of the welding molten pool would be enhanced,the flux was added to a small amount of TiO2 could improve slag fluidity,thereby improving the formability of weld.To research the optimization of the mechanical properties for the joint finded that MnO is helpful to improve the penetration and welding speed and reduce the flux sensitivity of stomata.When the flux formula of adding MnO content is controlled at about 6%and adding 2%of the rare earth CeO2 at the same time,under the condition of the high-speed welding,the weld metal can get a lot of acicular ferrite and granular bainite,and the grains are small and uniform.At the same time,it can also effectively inhibit the precipitation of proeutectoid ferrite,so as to improve the impact toughness of weld metal. |
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