Effect Of Post-weld Treatment Research Articles

Recent update of the IIW-recommendations for fatigue assessment of welded joints and components

The IIW-Recommendations for Fatigue Design of Welded Components and Structures is an international guideline that contains all relevant information to design welded structures under cyclic loading. Within the recommendations, all relevant assessment approaches, i.e., nominal, structural and notch stresses as well as fracture mechanics, are included. In addition, the relevant infu-ences are covered, such as the effect of post-weld treatment, mean resp. residual stresses and wall thickness. In the current update, the structure is enhanced and straightened and with it the applicability is improved. As completely new content, the assessment of welded thin joints with the notch stress approach and the impact of post-weld treatment procedures on the endurable stresses and the slope of the S-N curve is added. It is expected that the new update will have the same impact on design and other codes as the old one.

Effect of Post-Welding Treatment on Corrosion Behavior of Laser and Gas Tungsten Arc-Welded (Fe50Mn30Co10Cr10)99C1 Interstitial High-Entropy Alloy

Effect of Post-Welding Treatment on Corrosion Behavior of Laser and Gas Tungsten Arc-Welded (Fe50Mn30Co10Cr10)99C1 Interstitial High-Entropy Alloy

On the design of fillet welds made of ultra-high-strength steel

Current static design approaches for fillet arc welds made of high- or ultra-high-strength steel (UHSS) do not differ from the design of welds made of conventional steels. However, important issues such as potential softening in heat-affected zone (HAZ), strength at fusion lines, optimal reinforcement geometry, load capacity changes due to local bending moment, and the effect of post-weld treatments on the joint strength require careful consideration in order to ensure optimum performance from these steels. This paper reprises results of previous research works and recent findings and summarizes key aspects of weld design specific to UHSS welds.

Microstructure, Mechanical and Corrosion Behaviour of AA7075 Aluminium Alloy Friction Stir Welds

Friction stir welding (FSW) is emerging as an alternative technique for joining high strength aluminium alloys as it eliminates the problems during fusion welding. In this work, the effect of post weld treatments (PWHT), viz., peak aging (T6) and retrogression and reaging (RRA) on the microstructure, mechanical properties, pitting corrosion and stress corrosion cracking (SCC) resistance of AA7075 aluminium alloy friction stir welds has been studied. An attempt also has been made to change the chemical composition of the weld nugget by adding boron carbide (B 4 C) nano powder with the aid of the FSW. Hardness and tensile properties were found to be better in PWHT – T6. Pitting corrosion and SCC resistances were improved in PWHT-RRA condition with negligible loss of strength when compared to PWHT-T6. RRA promotes coarse precipitation of the equilibrium phase η in the grains and sub grain boundaries, while maintaining a fine distribution of η' in the grain interiors. The increased strength and hardness in the peak aged (T6) condition was attributed to the presence of semi-coherent intermediate η' (MgZn 2 ). With the addition of B 4 C nano powder to the weld nugget, hardness, tensile properties, pitting corrosion resistance and SCC resistance were further improved significantly when compared to the unreinforced weld nugget. PWHT-RRA treatment on the welds with B 4 C nano powder addition resulted in improved hardness of weld nugget which is attributed to the uniform distribution of strengthening precipitates in the matrix and powder strengthening. Pitting corrosion resistance, Tensile strength and SCC resistance was improved significantly in B 4 C added welds after RRA treatment when compared to the same welds without B 4 C addition.

Microstructure, mechanical and corrosion behavior of high strength AA7075 aluminium alloy friction stir welds – Effect of post weld heat treatment

Abstract High strength aluminium alloy AA7075 (Al–Zn–Mg–Cu) is a precipitate hardenable alloy widely used in the aerospace, defense, marine and automobile industries. Use of the heat treatable aluminium alloys in all these sectors is ever-increasing owing to their excellent strength-to-weight ratio and reasonably good corrosion resistance. The shortage in corrosion resistance, however, usually poses negative concern about their reliability and lifetime when they service in the variable marine environments. These alloys also exhibit low weldability due to poor solidification microstructure, porosity in fusion zone and lose their mechanical properties when they are welded by fusion welding techniques. Friction stir welding (FSW) is a reliable technique to retain the properties of the alloy as the joining takes place in the solid state. The welds are susceptible to corrosion due to the microstructural changes in the weld nugget during FSW. In this work, the effect of post weld treatments, viz., peak aging (T6) and retrogression & reaging (RRA), on the microstructure, mechanical properties and pitting corrosion has been studied. Friction stir welding of 8 mm-thick AA7075 alloy was carried out. The microstructural changes of base metal and nugget zone of friction stir welds were studied using optical microscopy, scanning electron microscopy and transmission electron microscopy. Tensile and hardness test of base metal and welds has been carried out. Pitting corrosion resistance was determined through dynamic polarization test. It was observed that the hardness and strength of weld were observed to be comparatively high in peak aged (T6) condition but the welds showed poor corrosion resistance. The resistance to pitting corrosion was improved and the mechanical properties were maintained by RRA treatment. The resistance to pitting corrosion was improved in RRA condition with the minimum loss of weld strength.

Effect of post weld treatment on cracking behaviors of beam-column connections in steel bridge piers

A great number of moment-resisting steel structures collapsed due to ductile crack initiation at welded beam-column connections, followed by explosive brittle fracture in the Kobe (Hyogoken-Nanbu) earthquake in 1995. A series of experimental and numerical studies on cracking behaviors of beam-column connections in steel bridge piers were carried out by the authors

Effect of Post Weld Heat Treatments on Mechanical and Stress Corrosion Cracking Behaviour of Aa7075 Friction Stir Welds

The high strength aluminium alloys exhibits low weldability due to poor solidification microstructure, porosity in the fusion zone and lose their mechanical properties when they are welded by fusion welding techniques. Friction stir welding (FSW) is a promising technique to retain the properties of the alloy as the joining take place in the solid state. Even though mechanical properties of the welds are better, corrosion resistance of welds gets affected by the microstructural changes that occur during welding. In the present work the effect of post weld treatments viz. peak ageing (T6), overaging (T73), retrogression and retrogression & reaging (RRA) on the mechanical properties and stress corrosion resistance is studied. It was observed that Retrogression and RRA treatments improved the resistance to stress corrosion cracking and maintained the mechanical properties. The resistance to stress corrosion is improved in RRA and Retrogression condition with the minimum loss of weld strength. This is attributed to the dissolution, re-precipitation and re-distribution of precipitates.

Design of Electrical Panels of Naval Vessels for Improved Fatigue, Shock and Vibration Performance

Structural reliability of electrical panels installed in naval vessels is of critical importance from the structural performance viewpoint. The electrical panels may be exposed to vibration and fatigue loadings from internal and external sources as well as wave loadings that result into fatigue crack and fracture due to the decrease of fatigue strength. In this regard, electrical outfitting equipments on naval vessels are required to comply with capabilities against vibration and shock tests, normally tested according to Military Standard. This study introduces the effect of post welding treatment, such as toe grinding as well as post welding heat treatment (PWHT), are examined through a series of fatigue and impact tests according to military standards. On the other hand, the use of elastic mounts that are capable of isolating and mitigating shock and vibration toward electrical panels are investigated. Both experimental and numerical results are presented based on the analysis according to military standards.

Effect of postweld treatment on the fatigue crack growth rate of electron-beam-welded AISI 4130 steel

This article studies the effect ofin-chamber electron beam and ex-chamber furnace postweld treatments on the fatigue crack growth rate of electron-beam-welded AISI 4130 steel. Mechanical properties of the weldment are evaluated by tensile testing, while the fatigue properties are investigated by a fatigue crack propagation method. Microstructural examination shows that both postweld treatments temper the weldment by the appropriate control of beam pattern width, input beam energy, and furnace temperature. In addition, the ductility, strength, and microhardness of the weldment also reflect this tempering effect. The fatigue crack growth rate is decreased after both postweld treatments. This is mainly caused by the existence of a toughened microstructure and relief of the residual stress due to the fact that (1) the residual stress becomes more compressive as more beam energy is delivered into the samples and (2) postweld furnace tempering effectively releases the tensile stress into a compressive stress state.