-70 degrees centigrade low-temperature steel welding bar

Abstract

The invention discloses a -70 degrees centigrade low-temperature steel welding bar. The -70 degrees centigrade low-temperature steel welding bar comprises a welding core and a coating, the coating of the welding bar is composed of 44-54% of marble, 15-24% of fluorite, 3-6% of barium carbonate, 2-5% of quartz, 2-5% of dehydration potassium titanate, 0.5-1.5% of borax, 1-3% of manganese metal, 3-6% of atomized ferrosilicon, 1-3% of rare earth ferrosilicon, 3-6% of ferrotitanium, 0.5-1.0% of silicon calcium alloy, 6.0-8.0% of nickel powder and 0.2-1.0% of Teflon. The -70 degrees centigrade low-temperature steel welding bar is featured with low nickel content, less splashing, good molten bath fluidity, uniform slag cover, soft electric arc sound, beautiful weld joint appearance, easiness in sediment separation and good welding technique, the content of diffusible hydrogen in the weld joint metal is within 5ml / 100 g (mercury process), and this meets the standard super-low-hydrogen welding bar requirement.

Description

technical field [0001] The invention relates to a -70°C low-temperature steel electrode, in particular to a -70°C low-temperature steel electrode suitable for welding 09MnNiDR steel, and belongs to the technical field of welding materials. Background technique [0002] Petroleum, chemical and other energy industries need a large amount of low-temperature steel to manufacture various production and storage equipment for liquefied petroleum gas, liquid ammonia, liquid oxygen, and liquid nitrogen. At present, the materials used in the energy industry at -70 to -196°C are mostly Ni-based low-temperature steels, and the Ni content is between 0.5% and 9%. The Ni-series steel with a Ni content of 0.5% to 2.3% is mainly used to manufacture low-temperature pressure vessels at -60 to -70°C. The 0.5% Ni low-temperature steel in my country is based on the corresponding foreign steel grades, and the chemical composition is optimized accordingly. The standard grade is 09MnNiDR, which has ...

AI Technical Summary

Problems solved by technology

[0003] Although many manufacturers can produce -70°C low-temperature steel electrodes, they all have the problem of low low-temperature impact value and instability, and it is difficult to meet the requirements, and some -70°C low-temperature steel electrodes still use 3.5% Ni route, Ni solid solution In ferrite, the toughness of the matrix can be improved, but fine-grained ferrite must be obtained in order to obtain excellent low-temperature toughness. However, when the nickel content of the weld is greater than 2.5%, as the nickel content increases, instead Coarse bainite structure is easy to appear in the weld, which leads to certain problems in the use of welding rods; especially 09MnNiDR steel contains a small amount of Nb, which plays a role in refining grains and precipitation strengthening in the steel, which is beneficial to reduce the steel However, when the Nb content of the weld metal exceeds 0.01%, NbC can be precipitated during the phase transformation process of post-weld cooling, which promotes the precipitation of martensite on the grain boundary and the formation of M-A structure. The formation of lath structure reduces the weld toughness

Images