Researchers from the University of Witwatersrand in South Africa have reported a review of research on residual stresses in carbon steel welding: formation mechanisms, mitigation strategies, and advances in advanced post weld heat treatment technologies. The relevant paper titled "A comprehensive review of residual stresses in carbon steel welding: formation mechanisms, mitigation strategies, and advanced post heat treatment techniques" was published in The International Journal of Advanced Manufacturing Technology.
Residual stress is a key factor affecting the service performance, reliability, and durability of carbon steel welded joints. These stresses can make the joint prone to brittle fracture, fatigue failure, and stress corrosion cracking, especially in the heat affected zone (HAZ). Uneven thermal expansion and contraction during the welding process lead to residual stress generation. The thicker the plate and the stronger the structural constraints, the more prominent the residual stress problem becomes. Post weld heat treatment (PWHT) plays an important role in relieving residual stress by tempering martensitic structure, refining microstructure, improving toughness and ductility, and other mechanical properties. This article systematically explains the formation mechanism of residual stress, evaluates the effectiveness of PWHT technology, and focuses on advanced methods such as neutron diffraction, computational modeling, and composite welding processes. Although PWHT can significantly reduce residual stress, complete stress elimination still cannot be achieved, highlighting the necessity of innovative strategies such as composite welding processes, computational modeling, and advanced heat treatment. This study combines metallurgical principles with experimental results to provide a systematic solution for improving the performance and reliability optimization of welded joints in high demand industrial applications.
Figure 1: Examples of residual stresses at macro and micro scales. Macroscopic stress is generated between different regions of the material, while microscopic stress exists between different phases of the material's microstructure
Figure 2 Schematic diagram of laser welding process
Figure 3 Schematic diagram of laser arc composite welding process
Figure 4 shows a schematic diagram of the heat affected zone (HAZ) and its sub regions, overlaid with relevant phase diagrams of microstructural transformations in this area during welding or thermal cutting processes
Figure 5 shows the iron carbon equilibrium phase diagram, indicating the temperature ranges for different heat treatment processes
Figure 6 Microstructure of Coarse Grain Heat Affected Zone (CGHAZ): (a) Welded joint; (b) After heat treatment; (c) EBSD analysis of welded joints; (d) EBSD analysis of heat-treated joints
Figure 7A516: Optical microstructure of different regions of the welded joint of steel: (a) Base metal; (b) Fusion line; (c) Heat affected zone; (d) Fusion zone
Figure 8 SEM micrographs of various regions of the welded joint under different post weld heat treatment conditions
Figure 9: The morphology of the fusion zone after different welding parameters and post weld heat treatment
Figure 10: Morphology of Welding Fusion Zone without Post weld Heat Treatment
Figure 11: Crack morphology in the welding fusion zone without post weld heat treatment
Figure 12: Optical images of weld metal in different post weld heat treatment states: (a) as welded state; (b) Stress relief; (c) Normalization treatment
Figure 13: Optical images of the heat affected zone under different post weld heat treatment states: (a) as welded state; (b) Stress relief; (c) Normalization treatment
Figure 14: Optical images of the base metal under different post weld heat treatment states: (a) as welded state; (b) Stress relief; (c) Normalization treatment
SEM micrograph of the marked area in Figure 15
This review systematically investigates the effects of residual stress and post weld heat treatment on the microstructure evolution, mechanical properties, and corrosion resistance of carbon steel welded joints. The relevant findings provide important basis for a deeper understanding of these mechanisms.
Despite some progress, the current residual stress management technology still faces bottlenecks such as high cost, complex processes, and insufficient scalability, and urgently needs to develop innovative, economically efficient, and environmentally sustainable solutions.
The key directions for future research to focus on breakthroughs can be improved through the following suggestions to enhance the efficiency, reliability, and optimization level of post weld heat treatment processes for carbon steel, thereby significantly improving the quality and performance of welded components in industrial applications:
Welding parameter optimization: By precisely controlling parameters such as heat input, welding speed, and joint geometry, residual stress levels are effectively reduced, thermal deformation and stress concentration defects are minimized, and weld integrity is improved;
Advanced PWHT technology development: Customize heat treatment solutions for specific materials and application requirements, achieve martensitic tempering, reduce hydrogen content, and homogenize microstructure through controllable heating/cooling cycles, and improve fatigue resistance;
Application of advanced stress detection technology: incorporating neutron diffraction, X-ray diffraction, and computational modeling into standard welding practices, and developing data-driven stress relief strategies through precise stress characterization and predictive analysis;
Promotion of composite welding technology: Leveraging the advantages of laser arc composite technology in reducing residual stress gradients, narrowing the heat affected zone, and achieving uniform stress distribution, to enhance the efficiency and economy of industrial applications;
Standardization system construction: Establish a standardized framework that integrates computational modeling, experimental verification, and PWHT practice to ensure consistency and repeatability of residual stress control effects under different materials and application scenarios;
Research on Green Manufacturing Technology: Developing energy-saving welding and post weld treatment processes in response to global sustainable development initiatives, including reducing welding carbon footprint, exploring recyclable materials, and adopting circular economy models.
Source: Yangtze River Delta Laser Alliance
