Seamless line pipes are mainly used to transport high-pressure oil and gas near the wellhead. With the increasingly serious hydrogen sulfide corrosion problem, the development of anti-sulfur seamless line pipe is imminent, and the quality of sulfur resistance is the key. The media and material factors that affect the hydrogen-induced cracking (HIC) performance are discussed, and it is believed that the addition of Cu and Ni can improve the HIC performance of seamless line pipe materials and reduce the S content in steel, and it can also be reduced by spraying silicon calcium powder. Sensitivity to hydrogen bubbling.


        With the deepening of oil and natural gas exploitation, there are more and more oil and gas wells with complex exploitation conditions and sulfur-containing environments, and the problem of hydrogen sulfide corrosion is very acute. In recent years, domestic and foreign demand for sulfur-resistant seamless line pipes has been increasing. Seamless line pipes are mainly used to transport high-pressure oil and gas near the wellhead. They are steel pipes without welds made by seamless pipe production. This article intends to discuss the research and manufacture of anti-sulfur seamless line pipe.


1 Test method
        According to the ISO3183 standard, using the immersion method, 7 furnaces of 1 ton steel ingots are smelted in the laboratory, and then forged, perforated, pipe jacked, and stretched to produce tubes. The 20 mm×100 mm×5 mm plate thickness or tube thickness is cut on the steel pipe for test In this way, immerse it in the solution configured according to the standard, take it out after 96 h, and take the cross-section in the vertical rolling direction, and use the metallographic method to calculate 3 parameters (crack length rate CLR, crack thickness rate CTR, and crack sensitivity rate CSR). Compare the susceptibility to hydrogen induced cracking (HIC).


2 Factors affecting HIC performance


2.1 Media factors


1) pH value. A large number of research results show that in the range of pH 1 to 6, the sensitivity of hydrogen bubbling decreases with the increase of pH. When pH>6, hydrogen bubbling does not occur [1].
2) H2S concentration. The higher the concentration of hydrogen sulfide, the greater the sensitivity of hydrogen bubbling.
3) Chloride ion. In the pH range of 3.5 to 4.5, the presence of Cl- increases the corrosion rate and the sensitivity to hydrogen bubbling.
4) Temperature. The sensitivity of CLR and hydrogen bubbling at 25°C. When the temperature is lower than 25°C, the corrosion reaction and the hydrogen diffusion rate are accelerated by increasing the temperature, so that the susceptibility to hydrogen bubbling is increased. After the temperature is higher than 25°C, the H2S concentration decreases, which reduces the sensitivity of hydrogen bubbling.
5) Time. The test uses 96 h as a comparison. Generally, as the test time increases, the degree of corrosion tends to be serious.


2.2 Material factors


2.2.1 The influence of chemical composition
A round of steel grades designed according to different grades was smelted in the laboratory. The specific composition is shown in Table 1, and the HIC immersion test was carried out. Observed from the surface of the sample after soaking, the bubbling area of ​​B2, B6, and B7 is obviously larger than that of B9 and B10. The results of the crack sensitivity index are shown in Table 2. It can be seen from Table 2 that the anti-HIC performance of B2, B6, and B7 is significantly inferior to that of B9 and B10. In Table 1, the B2, B6, and B7 steel grades do not contain Cu and Ni, while the B9 and B10 steel grades contain Cu and Ni. It can be seen that the addition of Cu and Ni causes the corrosion products to form a protective film on the surface of the steel, inhibits the corrosion reaction on the surface, thereby reducing the escape of hydrogen, reducing the entry of hydrogen from the environment into the steel matrix, and reducing the hydrogen drum Bubble sensitivity increases the performance of anti-HIC, which is very consistent with Oriani's research results [2], and Oriani also pointed out that only adding 0.2% of Ni and more than 0.2% of Cu can produce an effect.