Electric welding rod for welding X70-grade pipeline steel

Abstract

The invention belongs to an electric welding rod for welding X70-grade pipeline steel. Components of a core wire (wt%) include 0.02-0.10% of C (carbon), 0.30-0.55% of Mn (manganese), 0.015-0.03% of Si (silicon), 0.01-0.20% of Cr (chromium), 0.01-0.30% of Ni (nickel), 0.005% or less than 0.005% of S (sulphur), 0.010% or less than 0.010% of P (phosphorus), 98.675-99.47% of Fe (ferrum) and the rest impurities. Components of a coating measured by weight of the core wire (wt%) include 16.0-20.0% of marble, 7.5-9.0% of fluorite, 2.0-3.0% of feldspar, 1.5-2.0% of quartz, 3.0-3.8% of electrolytic manganese, 1.5-2.58% of silicon iron, 3.0-4.0% of ferrotitanium, 0.3-0.6% of sodium carbonate, 1.5-2.5% of ferrous powder, 0.5-0.58% of nickel powder and 0.1-0.2% of ferromolybdenum. The weight of binder is 10-20% of that of the powder, and the binder is mixed and coated on the core wire and then baked at a low temperature and a high temperature, so that the electric welding rod is formed. During welding, the electric welding rod with stable arc is fine in slag spreadability and less in splash, weld shaping is bright, weld metal has fine corrosion resistance, low-temperature toughness and crack resistance, the tensile strength is 630MPa, the yield strength is 510MPa, the elongation is 24%, the average value of ballistic work at the temperature of -20 DEG C is 160J, and the minimum single value of the ballistic work is 120J.

Description

technical field [0001] The invention relates to an electric welding rod for welding, in particular to an electric welding rod for X70 grade pipeline steel welding and having good corrosion resistance, high strength and low temperature toughness, and the welding rod can be widely used for X60 grade pipeline steel Welding of steel and other low-alloy steels that have the same composition and strength grade as X70 pipeline steel, and have higher requirements for parathion and low-temperature toughness. Background technique [0002] Pipeline steel is mainly used for the transportation of crude oil, refined oil, natural gas and coal-water slurry. With the adjustment of my country's energy structure and the change of logistics transportation mode, pipeline steel has broad application prospects in my country. [0003] The complex operating environment is an important feature of oil and gas transmission projects, which makes the damage caused by corrosion of oil and gas pipelines d...

AI Technical Summary

Problems solved by technology

Comparing the chemical composition and performance of the above two, it can be seen that the deposited metal of ordinary basic electrode (J607) has poor matching with the X70 pipeline steel alloy system, and the main alloying elements are silicon (Si), molybdenum (Mo) and so on. There is a large difference between the content of the content and the content of X70 grade steel coils, but the content of sulfur and phosphorus is high, especially the content of sulfur is high, and there is a lack of elements such as Ti, Ni, Cr, etc. After X70 pipeline steel is welded, its deposited metal greatly reduces the corrosion resistance, crack resistance and low temperature toughness of the weld

At the same time, according to the theory, a large number of experiments and the analysis of some engineering accidents, it is believed that the welding of X70 pipeline steel with ordinary alkaline low-hydrogen electrode (J607) can hardly meet the welding requirements of X70 pipeline steel, especially Requirements for corrosion resistance, crack resistance and low temperature toughness