Materials of Pipe Fittings for Resisting Hydrogen Sulfide Stress Corrosion
Posted: 04/22/2022 09:27:49 Hits: 7
For the selection and evaluation of materials used in equipment designed and manufactured according to the elastic design criteria, the materials that have been evaluated in accordance with ISO 15156-2 (GB/T20972.2) and ISO15156-3 (GB/T20972.3) or NACE MR0175-2003 standards can be used. The environmental conditions to avoid stress corrosion have been limited by these standards. Only when the limited conditions are met, can the materials be selected according to the requirements of the corresponding specifications; if these limited conditions are not met, HIC and SSC tests are required to meet the requirements of the corresponding standards.
The following requirements should be met:
1. The materials used for pipe fittings must meet the requirements of NACEMR-0175 OR ISO 15156-2015.
2. The hardness of the material does not exceed 22 HRC. SA-105 should not exceed 187 HBW.
3. The measured tensile strength of the material is not greater than 630MPa, and the nominal yield strength specified by the standard is not more than 355MPa.
4. Use vacuum degassing process or other alternative processes to produce fine-grain killed steel.
5. The material should be supplied in a normalized state or normalized plus tempered state.
6. The material non-metallic inclusions A, B, C and D shall not exceed grade 2, and the total amount shall not exceed grade 4.0. The test method shall be in accordance with ASTM E45 or ISO 4967.
7. The material is tested for austenite grain sizes according to ASTM E112, and the average grain size is required to be grade 7 or finer.
8. The material should meet the requirements of ultrasonic tests.
9. Chemical composition restrictions:
C is less than and equal to 0.20%, S 0.012%, P 0.015%, Mn 1.0%, CE 0.43, and Ni is less than 1.0%.
10. The material should meet the impact test requirements under MDMT.
11. Requirements for Z-direction tensile for the material: the average value of three samples of SA-770, EN10164 or GB/T5313 is greater than and equal to 35%, and the single value is greater than and equal to 25%.
12. HIC tests
Specifications: NACE TM0284-2016
Solution: solution A
Test time: 96 hours
Test evaluation: CLR being greater than and equal to 15%, CTR being greater than and equal to 5%, CSR being greater than and equal to 2%
13. SSC
Test specifications: NACE TM0177-2016
Solution: solution A
Test time: 720 hours
Threshold stress: 80% AYS (the actual yield strength of the material)
The following requirements should be met:
1. The materials used for pipe fittings must meet the requirements of NACEMR-0175 OR ISO 15156-2015.
2. The hardness of the material does not exceed 22 HRC. SA-105 should not exceed 187 HBW.
3. The measured tensile strength of the material is not greater than 630MPa, and the nominal yield strength specified by the standard is not more than 355MPa.
4. Use vacuum degassing process or other alternative processes to produce fine-grain killed steel.
5. The material should be supplied in a normalized state or normalized plus tempered state.
6. The material non-metallic inclusions A, B, C and D shall not exceed grade 2, and the total amount shall not exceed grade 4.0. The test method shall be in accordance with ASTM E45 or ISO 4967.
7. The material is tested for austenite grain sizes according to ASTM E112, and the average grain size is required to be grade 7 or finer.
8. The material should meet the requirements of ultrasonic tests.
9. Chemical composition restrictions:
C is less than and equal to 0.20%, S 0.012%, P 0.015%, Mn 1.0%, CE 0.43, and Ni is less than 1.0%.
10. The material should meet the impact test requirements under MDMT.
11. Requirements for Z-direction tensile for the material: the average value of three samples of SA-770, EN10164 or GB/T5313 is greater than and equal to 35%, and the single value is greater than and equal to 25%.
12. HIC tests
Specifications: NACE TM0284-2016
Solution: solution A
Test time: 96 hours
Test evaluation: CLR being greater than and equal to 15%, CTR being greater than and equal to 5%, CSR being greater than and equal to 2%
13. SSC
Test specifications: NACE TM0177-2016
Solution: solution A
Test time: 720 hours
Threshold stress: 80% AYS (the actual yield strength of the material)
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