Development Of PP-Ni620 Nickel Based Electrode With New Slag System

In recent years,Chinese LNG industry has been developing vigorously.In the construction of LNG ships,warehouses(B,C)and land storage tanks,9% Ni steel is widely used,while ENiCrMo-6,a complete welding material,is entirely dependent on imports and subject to human beings.This is an urgent problem to be solved.Therefore,it has great political significance and economic benefit to develop domestic 9%Ni steel welding consumables independently.In this paper,a new kind of nickel-base electrode for 9% Ni steel with weak alkaline slag system is proposed.The effects of chemical composition of coating on arc stability,slag removal,slag fluidity,spatter rate and alloy transition coefficient are systematically studied by orthogonal design method of three factors and five levels.The further optimization design of electrode is realized..Through the experiment,it founds that when the ratio of carbonate and fluoride is 1.2-1.5,the slag removal performance is the best;when the total amount of titanium iron,rutile and cryolite is about 19-22%,the fluidity and covering performance of the slag is the best.Subsequently,the arc stability,slag removal,coverage and other properties of PP-Ni620 nickel-based electrodes with different slag systems were tested by using a comprehensive welding parameter tester.Finally,a new slag system formula was optimized and confirmed as the final formula of the subject,and a 9% Ni steel PP-Ni620 electrode was developed.In order to control the amount of alloy added in the formula,the transition coefficients of the alloy are calculated as follows: the transition coefficients of Cr,Mo,Mn,Nb + Ta and W are 0.59,0.61,0.44,0.41 and 0.52 respectively.The yield strength,tensile strength and elongation of deposited metal of the electrode are 434 MPa,708 MPa and 43%,which meet GB/T 13814,AWS A5.11 M and EN IOS 14172 standards.The performance of the electrode is similar to that of the mainstream imported Lincoln brand NYLOID2(the yield strength of deposited metal of imported electrode is 468 MPa,the tensile strength is 730 MPa,and the elongation is 41%).The low temperature impact properties of the deposited metal are different under different welding lines.Experiments show that the impact energy of deposited metal deposited between 9-10KJ/cm is the best at low temperature.Finally,the effects of strontium carbonate(carbonate)and cryolite(fluoride)on the transition coefficient and process properties of the alloy were investigated.The results show that substitution of strontium carbonate for part of marble can effectively reduce the oxidizing atmosphere,facilitate the transition of alloy elements and obtain softer technological properties(improve splash etc.);substitution of cryolite for part of fluorite can improve the fluidity of slag,and play a better role in the melting of metal powder.