Study on Ultra-low Hydrogen High Strength CHE607GX Electrode for X70 Pipeline Welding

Study on Ultra-low Hydrogen High Strength CHE607GX Electrode for X70 Pipeline Welding
　　To meet need of welding requirement for X70 pipeline steel used in China’s nation-wide gas transferring project, the ways to improve the operation properties and the weld-toughness of welding electrodes with alkaline coating, as well as to improve the electrodes’resistance to moisture absorption, are thoroughly studied. Upon this, a new type of ultra-low-hydrogen Block neodymium magnet and high-toughness electrode, branded as CHE607GX, is developed and tested.With respect to the operation properties, the effect of chemical compositions of the coatings on various operation properties is examined by using a advanced GX high temperature physical analyzer a serious of welding procedures. It is found that the changes of marble, fluorite and quartz in coatings’composition may greatly affect the properties of the electrode, and the best result is achieved when these materials are in the range of marble/fluorite 2～2.5%(wt)and quartz 4～10%.
　　With respect to the microstructure and mechanical properties of the weld, the effect of C, Mn, Si and Ni is discussed, while the effect of the addition of Ti-B and rare earth is also examined. It is found that by strictly controlling the compositions C,Si and impure element S, as well as by maintaining Mn/Si at a ratio of 3.0~3.5 and adding small amount of Ni (0.3~2%) and http://www.chinamagnets.biz/ a micro addition of Ti-B and rare earth in the weld, the formation pro-eutectoid ferrite can be significantly suppressed while the formation of acicular ferrite can be promotedIn order to increase the electrodes’resistance to moisture absorption, all coating materials that might cause severe moisture absorption are carefully sorted out and closely tested. It is found that by replacing the moisture-prone materials with moisture-resistant materials, as well as by correctly selecting the adhesive materials, the moisture-resistance of the coatings can be greatly improved.With its excellent properties in welding operation as well as its outstanding mechanical properties of the weld, the new electrode has been successfully used in China’s nation-wide gas transferring project.