Stress corrosion resistance of welded joints of low-alloy pipe steel produced by high frequency welding

Abstract

The paper presents the results of stress corrosion resistance studies of welded joints of low-alloy steel 17G1SU, obtained by high-frequency welding (HFW). The potentiometry method has established that the welded joint in the state after welding and after linear heat treatment is resistant to corrosion, because the potential difference between the weld and the base metal does not exceed (30-50) mV. According to the results of accelerated corrosion-mechanical tests in 3% NaCl under conditions of constant load under different stress, it was found that the rate of uniform corrosion of both types of welded joints is almost the same as the base metal. Slightly higher corrosion rate of the welded junction after linear heat treatment correlates with the electrochemical data. In general, the welded joint, made according to the factory technology, has resistance to corrosion and mechanical destruction in a solution of 3% NaCl at the level of the base metal, in the absence of weld defects. In the range of protective polarization potentials normalized by the standard of Ukraine, the ratio of the cathodic protection current to the diffusion current limit for the base metal and for the weld metal practically does not differ. It can be expected that under the conditions of cathodic protection, the predominant local flooding of the weld metal or the parent metal is not expected.