Minimum design metal temperature for 15CrMoR

The minimum design metal temperature for 15CrMoR steel generally depends on the specific design codes and application requirements; a typical value might be -20°C or lower, with reference to relevant design specifications being necessary. The welding performance assessment (weld evaluation) and the impact test temperature for welded specimens are usually determined based on the design temperature or service conditions of the steel. If there are no special requirements, the impact test temperature for the welded specimens may be the same as or lower than the material’s minimum design metal temperature, in order to verify the material’s impact toughness at that temperature. Typically, the temperatures for impact testing include room temperature (20°C) and the lowest design temperature (e.g., -20°C); sometimes even lower temperatures are used to meet specific requirements. The specific temperature must be determined based on design specifications and engineering requirements. .

The welding procedure qualification (WPS/PQR) for 15CrMoR (chromium-molybdenum steel for pressure vessels) and the impact test temperature for the welded specimens must be determined in accordance with relevant standards (such as ASME, GB/T, or EN) and specific application conditions. The following are the standard recommendations: 1. Impact test temperature for welding procedure qualification (PQR) • Standard reference: Generally, ASME BPVC Section IX or GB/T 19866 (national standard) is followed. • Test temperature: ◦ Design temperature or minimum operating temperature: The impact test temperature shall be ≤ the container’s minimum design metal temperature (MDMT). ◦ In the absence of special requirements: generally in accordance with the material standards, the impact test temperature for 15CrMoR is usually 0°C or -20°C (refer to GB/T 713 or ASME SA387 Gr.12). ◦ Low-temperature containers: If used in low-temperature environments, lower temperatures may be required (such as -30°C or even -40°C), and adjustments must be made in accordance with the design specifications. 2. Impact test temperature for welded test pieces (product test plates) • Consistent with PQR: Usually the same as the impact temperature for welding procedure qualification, unless otherwise specified in the design documents. • Standard examples: ◦ GB/T 150.4 (Pressure vessels): Requires that the impact test temperature be ≤ the MDMT of the vessel. ◦ ASME VIII Div.1: Determines whether impact testing and temperature are required based on UCS-66. 3. Key considerations • Material thickness: If the thickness is ≥16 mm (ASME) or a specific value (GB/T), an impact test is usually required. • Welding material matching: Use a welding material that is compatible with the base material (such as R307), and its impact performance must meet the required standards. • Effect of heat treatment: Post-weld heat treatment (PWHT) may affect impact properties, and this should be reflected in the PQR. 4. Typical value reference • Normal operating conditions: 0°C or -20°C (common in non-low-temperature vessels). • Severe conditions: As low as -40°C depending on MDMT. Conclusion: The specific temperature should be determined based on design conditions, standard specifications, and customer requirements; it is recommended to consult the project’s technical agreement or the design department.

In accordance with the requirements of the new version GB/T150.2-2024, the minimum operating temperature for 15CrMoR is now 20°C; tests are conducted at 20°C according to GB/T713.2-2023