New  Standard NB/T47019-2021! New Material 10HSC,New Application Environment

At the beginning of the New Year of 2022, our company successfully delivered the order of heat exchange tubes for 10# (HSC) wet hydrogen sulfide corrosion resistant environment with 19, 25 series to a large petrochemical enterprise.

The proportion of high-sulfur crude oil in China's imported crude oil is increasing under the background of the increasing degree of inferior oil resources in the world.   At the same time, the proportion of high-sulfur crude oil in China is increasing, and the processing of high-sulfur crude oil has become the main task of petroleum refining industry in China.   Hydrogen sulfide is the main form of sulfide in the processing of high-sulfur crude oil which brings increasingly serious corrosion problems of low temperature, moderate and high temperature to equipments. In particular, low-temperature hydrogen sulfide corrosion belongs to the local damage of materials which is more difficult to detect and prevent.   

On July 1, 2021, the National Energy Administration formally revised the NB/T47019-2011 standard, and specified the technical requirements of 10 (HSC) seamless heat exchange tubes in Appendix B of the new standard NB/T47019.2-2021.   Our company has maintained communication with each design institute with paying attention to the research direction of corrosion resistant heat exchange tube. We set up "wet hydrogen sulfide corrosion resistant heat exchange tube engineering technology development team” joint by technology department, sales department, purchasing department and domestic large state-owned steel mills and established the concrete steelmaking methods of raw materials according to the latest NB/T47019-2021 standards required in appendix B, in which specially added rare earth elements (Re) to improve its corrosion resistance.   Our company finished this batch of heat exchange tubes by optimizing the process and made a series of tests, and obtained the following results:

Advantages：

1.The micro-alloyed non-oxidation heat treatment seamless tubes with low carbon, ultra-low sulfur phosphorus improve their corrosion resistance by adding rare earth elements;

2.It has excellent comprehensive mechanical properties and low hardness, especially the extension at room temperature and impact toughness at low temperature is much higher than that of conventional carbon steel materials.   

3.Fine grain and high purity.   Based on repeat experiments, the grain size of the material is not more than grade 6.   The sum of non-metallic inclusions is less than 4.0.   

4.It has excellent resistance to sulfide stress cracking (SSCC).   According to the third-party inspection report, the cracking threshold stress of the material is much higher than the standard value requirements;

5.It has excellent resistance to hydrogen induced cracking (HIC, SOHIC).   The cracking length ratio (CLR), cracking thickness ratio (CTR) and cracking sensitivity ratio (CSR) of the material are all lower than the maximum values of NB/T47019-2021 standard according to several A solution tests by third-party, which means the experiment was a complete success.

6.Excellent resistance to uniform corrosion. According to the test analysis of 48h full immersion corrosion in the reagent of pH=3.0 4.5 H2S saturated 0.5% acetic acid +5%NaCl mixed solution in laboratory, the corrosion resistance of our new product 10 (HSC) is far superior to the corrosion resistance requirements of the latest NB/T47019-2021 standard and meet the technical requirements of several petrochemical design institutes.