SY/T 0599-2018 in English

Analysis of the core requirements of the standard

SY/T 0599-2018 proposes systematic technical requirements for material selection for natural gas surface facilities in hydrogen sulfide environments, focusing on controlling the risks of sulfide stress cracking (SSC) and stress corrosion cracking (SCC).

Material Zone Application Specifications

Key Technical Points

1. Chemical Composition Control

The standard stipulates that the nickel content should be less than 1% and the manganese mass fraction should be ≤1.4%. Free-cutting steel is prohibited. The stability of the material in an acidic environment is ensured by limiting the composition.

2. Hardness management

A three-level hardness control system is adopted:

• Base material hardness ≤ 22HRC
• Weld zone ≤ 250HV10
• Heat affected zone shall not exceed the base material limit

Special requirements for welding process

Implementation suggestions

1. Material selection strategy

It is recommended to give priority to the steel recommended in Appendix A. Materials in different SSC zones can be upwardly compatible (e.g. Zone 1 can use Zone 2 materials).

2. Key points of on-site control

Key control links:

• Stress relief of ≥595℃ must be performed when the cold deformation is ＞5%
• Mechanical cutting technology should be used for thread processing
• Hardness testing points should be distributed in different positions

3. Special working condition processing

For high sulfur environment (H₂S volume fraction ≥5%), additional assessment is required in accordance with GB/T 20972 series standards.