Evolution of Welding Residual Stresses within Cladding and Substrate during Electroslag Strip Cladding

Area of Science:

• Materials Science and Engineering
• Mechanical Engineering
• Chemical Engineering

Background:

• Hydrogenation reactors, vital in oil refining, face harsh conditions (high temp/pressure H2).
• Their common material, 2.25Cr-1Mo-0.25V steel, is susceptible to welding residual stress (WRS) in complex plate-welding structures.
• WRS significantly impacts equipment service life and integrity.

Purpose of the Study:

• To investigate the evolution of WRS during weld-overlay cladding for hydrogenation reactors.
• To analyze WRS distribution in distinct regions: cladding layer, stress-affected layer (SAL), and substrate.
• To evaluate the impact of substrate thickness and preheat temperature on WRS.

Main Methods:

• Finite Element Method (FEM) simulation to model WRS evolution.
• Blind hole method for experimental validation of the FEM model.
• Analysis of WRS in three defined regions based on plastic-strain state.

Main Results:

• WRS distribution identified in three regions: cladding, SAL, and substrate.
• SAL defined as a coupled stress region.
• Rapid stress generation in Stage 1 (approx. -440 MPa in SAL after 2.5s).
• WRS distribution largely established by Stage 2 (154s cooling).
• Interface between cladding and substrate identified as the most damaged region due to stress gradients.
• WRS in cladding layer initially increases with substrate thickness, then decreases.
• WRS in substrate and SAL decrease with increasing preheat temperature and substrate thickness.
• Compressive WRS in cladding layer increases with preheat temperature.

Conclusions:

• The study provides a detailed understanding of WRS evolution in hydrogenation reactor cladding.
• Identified critical factors (substrate thickness, preheat temperature) influencing WRS and equipment integrity.
• The findings are crucial for optimizing welding procedures and ensuring the longevity of high-pressure refining equipment.