Steel for pipeline steel tube with excellent hydrogen sulfide breakage resistance

Abstract

The invention discloses a pipe steel to prevent hydrogen sulfide fracture, which comprises the following parts: 0.02-0.15% C, 0.01-0.50% Si, 0.50- 1.20% Mn, less than 0.0012% P, less than 0.003% S, 0.20-0.50% Cu, 0.01-0.10% Al, 0.001-0.10% V, 0.01-0.05% Nb (2<=Ca% / S%<=10; C%+Si% / 30+ Mn% / 20+Cu% / 20<=0.20%) and Fe, wherein the pure degree of non-metal inclusion is below 40*10-3%.

Description

technical field [0001] The present invention relates to a steel for pipeline steel pipes that is extremely excellent in fracture resistance in an environment containing moist hydrogen sulfide. Background technique [0002] In recent years, the use of pipeline steel pipes in the transportation of crude oil and natural gas has been increasing. However, hydrogen sulfide is often contained in crude oil and natural gas. The coexistence of water such as seawater or groundwater and hydrogen sulfide has a high probability of corroding the steel surface. , the embrittlement of materials due to corrosion has become a big problem. Among the defects generated by steel in a humid hydrogen sulfide environment, there are hydrogen-induced cracking and sulfide stress corrosion cracking, which are collectively referred to as hydrogen sulfide cracking. [0003] Hydrogen-induced cracking is a crack that occurs even in the absence of external stress, and can be seen in both high-strength materi...

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Problems solved by technology

However, in this method, the specific gravity of rare earth elements is large, and it is difficult to float and remove inclusions when the molten steel is solidified, so it is difficult to prevent cracks caused by the dense presence of inclusions in the precipitated grain portion at the bottom of a large steel ingot.

In addition, the addition of a large amount of rare earth elements may easily cause problems in industrial production such as nozzle clogging during casting.

In addition, the high-temperature long-time soaking treatment before hot rolling and the controlled cooling rate after hot rolling are well known as countermeasures against abnormal structures, but it is difficult to achieve sufficient effects with such a complicated process.

In addition, restrictions on manganese and phosphorus are also effective, but this alone cannot fully exert the effect of preventing hydrogen-induced cracking. Adding copper is effective in suppressing the intrusion of hydrogen in steel, but the effect is not sufficient in harsh environments.

[0010] On the other hand, for sulfide stress cracking, it is effective to reduce the hardness of high-strength materials, and there are restrictions such as Rockwell hardness HRC ≤ 22, but only reducing the hardness cannot completely prevent cracking in harsh environments

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