Can flux-cored wire be used for welding between pressure-bearing components of pressure vessels, as well as between pressure-bearing and non-pressure-bearing components?

When welding between the pressure-bearing components of a pressure vessel, or between pressure-bearing and non-pressure-bearing components, whether flux-cored wires can be used requires consideration of the following key factors: ### 1. **Adherence to Standards and Specifications** - **ASME Standards**: According to the ASME Boiler and Pressure Vessel Code (Section VIII), flux-cored wires are permitted, but it is necessary to meet the requirements of processes such as SAW, GMAW, or FCAW; furthermore, the wires must comply with the material standards specified in the code (such as SFA-5.20 or SFA-5.29). - **National standards (such as GB 150): Chinese standards also permit the use of flux-cored wires, but they must comply with regulations such as GB/T 10045 or GB/T 17493, and welding procedure qualification is required. ### 2. **Types and Properties of Flux-Cored Welding Wires** - **Gas-shielded flux-cored wires (such as FCAW-G)**: Require a shielding gas (such as CO₂ or a mixture of gases); they are used to produce high-quality welds and are suitable for critical areas of pressure vessels. - **Self-shielding flux-cored wires (such as FCAW-S): They rely on the gas-generation agent inside the wire for protection, which may limit their use in certain conditions (such as outdoor environments with strong winds); it is necessary to assess whether their crack resistance and impact toughness meet the required standards. ### 3. **Welding Procedure Qualification (WPS/PQR)** – The parameters (current, voltage, speed, etc.) must be verified through procedure qualification to ensure that the mechanical properties of the welds (strength, toughness) meet the design requirements. - Non-destructive testing (RT, UT) and destructive tests (bending, impact tests) are required to verify the quality. ### 4. **Application Scenarios and Limitations** - **Welding of stressed components**: High-toughness welding materials should be preferred, especially in low-temperature or cyclic loading conditions; it is necessary to ensure compatibility between the weld wire and the base material (such as following the equal-strength or high-compatibility principle). - **Welding of non-compressed components**: If the joint carries loads (such as the connection between a bracket and a housing), the standards for compressed components still must be followed. ### 5. **Post-weld treatment and inspection** – Depending on the material thickness and standard requirements, post-weld heat treatment (PWHT) may be necessary to eliminate residual stresses. - Strictly carry out visual inspections, non-destructive testing, and pressure tests to ensure that the welds are defect-free. ### Conclusion: Flux-cored wires **can** be used, but the following conditions must be met: – The wires must comply with relevant standards (such as ASME SFA or GB/T) ； - Through qualified welding procedure qualification ； - The properties of the welded joint (strength, toughness, corrosion resistance) meet the design requirements ； - Post-weld inspection passed. In practical applications, a comprehensive decision must be made by considering specific design documents, standard requirements, and engineering experience; consulting certification bodies or welding engineers may be necessary when required. -

It can be used, provided that it meets the requirements of Clause 7 of GB/T150.4.

GB150 does not prohibit its use; it’s just that quality control of flux-cored wires is difficult, which is why the standard adopts a more cautious approach regarding their use. Stringent requirements are applied to weld evaluation, wire retesting, welding process control, product weld specimens, and so on.