Weldability evaluation of in-service ethylene cracking furnace tubes after small punch sampling

The small punch test technique facilitates the convenient acquisition of the mechanical properties of in-service equipment materials and the assessment of their remaining service life through sampling. However, the weldability of components with thin walls after small punch sampling, such as ethylene cracking furnace tubes, requires further investigation. Therefore, the weldability of in-service ethylene cracking furnace tubes following small punch sampling was investigated through nondestructive testing, microstructural characterization, and mechanical testing. Additionally, the impact of small punch sampling size and residual stress on the creep performance of the specimens was studied using an improved ductility exhaustion model. The results indicate that both the surface and interior of the weld repair areas on new furnace tubes and service-exposed furnace tubes after small-punch sampling are defect-free, exhibiting good weld quality. The strength of the specimens after weld repair was higher than that before sampling, whereas toughness decreased. Weld repair following small punch sampling of furnace tubes is both feasible and necessary. Furthermore, a linear relationship was observed between specimen thickness, diameter, and creep fracture time. The residual stress of welding affects the creep performance of the specimen under different stresses.