Performance of ERW Small Tubing of 3Cr Steel

The physicochemical properties, electrochemical properties, high-temperature and high-pressure CO₂ corrosion resistance and H₂S corrosion resistance for electrical resistance weld (ERW) small tubing of 3Cr steel were studied by physical and chemical property tests, electrochemical tests, high-temperature and high-pressure CO₂ corrosion test and hydrogen-induced cracking test. The results show that the physicochemical properties fully met the requirements of API SPEC 5CT-2018. The free corrosion potential and impedance value of 3Cr steel were higher than those of N80 steel. In high-temperature and high-pressure CO₂ corrosion environment, the corrosion rate was 0.93 mm/a for 3Cr steel and it was 1.29 mm/a for N80 steel. The base material of 3Cr steel ERW small tubing was not sensitive to hydrogen-induced cracking, while the welded seam was sensitive to hydrogen-induced cracking. Excessive hardness of the welded seam was the main reason for its sensitivity to hydrogen-induced cracking.