The selection and evaluation of materials for equipment designed and manufactured in accordance with elastic design criteria can be selected according to the materials that have been evaluated in ISO 15156-2(GB/T20972.2), ISO15153-6 (GB/T20972.3) or NACE_MR0175-2003. The environmental conditions to avoid stress corrosion have been defined in these standards. Only when these conditions are met can the materials be selected according to the requirements of the corresponding specifications. If these limiting conditions are not met, HIC and SSC tests shall be carried out to meet the corresponding standard requirements.

1. The materials used shall meet the requirements of NACEMR-0175/ISO 15156-2015

2. Material hardness shall not exceed 22 HRC (where: SA-105 shall not exceed 187 HBW).

3. The measured tensile strength of the material is not more than 630MPa, and the nominal yield strength stipulated in the standard is not more than 355MPa

4. Use vacuum degassing process or other alternative process, for fine grain calm steel

5. Materials should be supplied in normalizing state or normalizing + tempering state

6. Non-metallic inclusions A, B, C and D of materials shall not exceed grade 2, and the total number shall not exceed grade 4.0. The test method shall be in accordance with ASTME45 or ISO4967,

7. The austenite grain size of the material shall be tested according to ASTM E112, and the average grain size shall be 7 or finer.

8. Requirements for ultrasonic testing of materials

9. Chemical composition limitation:

C or less 0.20% S 0.012% or less 0.015% or less Ni P

10. Materials shall meet the impact test requirements under MDMT

11. Material Z direction tensile requirements (standard: SA-770 or EN10164 or GB/T5313 three sample average ≥35%, a single value ≥25%,)

12. HTC test

Specification: NACE TM0284-2016 solution: A solution test time: 96h Test evaluation: CLR≤15% CTR≤5% CSR≤2% 13. SSC test specification: NACE TM0177-2016 solution: A solution test time: 720H Threshold stress: 80% AYS(actual yield strength of material)

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