Factors That Affect Welding-Induced Residual Stress and Distortions in Pressure Vessel Steels and Their Mitigation Techniques: A Review

Abstract

Pressure vessels comprise critical plant equipment within industrial operations. The fact that the vessel operates under pressure, and may carry toxic, dangerous or hazardous contents, necessitates that care is taken to ensure safety of humans operating it and the environment within which it operates. Residual stress developed during welding of pressure vessel structures adversely affects fatigue life of such structure by reducing fracture toughness. Formation of residual stresses during welding occurs when nonuniform heating of the metallic surfaces produces substantial temperature gradients, which in turn cause plastic straining of the different portions of the weld-piece material, thereby subjecting it to postcooling internal stresses that are likely to weaken it. A number of studies have been performed on welding parametric analysis with the help of design of experiments (DoE), mathematical programming, evolutionary algorithms and finite element methods, with the intention to quantify effects of welding factors on resultant residual stress. The objective of this review is to organize such literature according to the specific areas of analysis in order to enhance access thereto and elucidate relevance thereof for purposes of reference work and further studies. The paper specifies three categories of influential factors as prewelding conditions, in-process parameters, and postwelding conditions. It is shown that prewelding conditions, such as the choice of welding process, must be chosen in line with the nature of materials to be welded, operational application of the structure, and trade-offs between service life and production costs. Heat input (which is the function of arc voltage, welding current, and travel speed) is the most influential machine-related in-process parameter in the residual stress generation during welding. It is also observed that when applying mitigating factors, care should be taken not to exacerbate the residual stress situation through suboptimal parametric set-up.

Evaluation of through-thickness residual stresses in conventional and narrow grooved stainless steel welds

“…It was suggested that an alternating weld pass sequence is beneficial compared to conventional continuous welding to reduce the residual stresses. 4 Teng et al studied the effect of high-speed welding on low carbon steel butt joints using finite element (FE) modeling and found that a higher welding speed led to a reduction in residual stresses. 5 Teng et al also studied the effect of the pipe wall thickness and the diameter of pipes made of SAE 1020 low carbon steel on the residual stress distribution.…”

Influence of Restraint Conditions on Welding Residual Stresses in H-Type Cracking Test Specimens

“…It is well known that the distribution and magnitude of WRS can be influenced by many factors such as joint types, plate geometry, material properties, welding parameters and restraint conditions [6]. Among those factors, the restraint condition of welded construction has a great influence on WRS [7].…”

Examining Stress Relaxation in a Dissimilar Metal Weld Subjected to Postweld Heat Treatment

“…Residual stresses are usually harmful for the service life of the component by contributing to brittle fracture, corrosive cracking, creep damage and although they are usually accounted for through a safety factor in the design of a pressure vessel, this may not be sufficient for every case [2][3][4][5]. Post weld heat treatment (PWHT) is often recommended in the codes and standards for pressure vessles or pipes, in order to achieve the required microstructure and mechanical properties of the joint, in terms of strength and toughness, and relax the residual stresses [6][7][8][9]. Modified 9Cr-1Mo (P91) is a creep strength enhanced ferritic/martensitic steel that is increasingly being considered as a suitable material for high temperature applications, such as steam generators and fast breeder reactors [10,11].…”