Effect Of Post-weld Heat Treatment Research Articles

Evaluation of the post-welding heat treatment effect on compatibility with hydrogen.

The article covers effect of post-weld heat treatment (PWHT) on the properties of thermo-mechanically treated (TMT) pipeline steel in interaction with hydrogen gas. The object of the study were specimens of the base metal and longitudinal welded joints of X65 large diameter pipes in the initial state (after TMT) and after PWHT. Tests in the hydrogen environment showed that PWHT conducted under ASME B 31.12 modes leads to a decrease in the plastic properties of X65 pipe steel when exposed to hydrogen gas, which is due to the fact that PWHT contributes to a signifi-cant increase in the number of hydrogen traps and concentration in the surface layer. Microstructure of the specimens after PWHT is characterized by a significant amount of highly dispersed precipitates, presumably carbides, which can act as low-energy hydrogen traps, increasing the amount of diffusionally mobile hydrogen and contributing to its movement into crack development zones. The specimens with PWHT showed a significant change in fracture pattern after hydrogen testing, indicating the embrittlement effect of hydrogen: multiple laminations, cracks, fracture consists mainly of quasi-cleavage facets. Thus, the post-welding heat treatment of X65 steel leads to a significant increase in the negative effect of hydrogen on steel: embrittlement of heat-treated steel when exposed to hydrogen gas is observed. Since the post-welding heat treatment negatively affects compatibility of X65 steel with hydrogen gas, PWHT may be cancelled in accordance with GR-3.7.1 of ASME B 31.12.

Effects of Postweld Heat Treatment on Interfacial Behavior and Mechanical Properties of Joints Welded with Cu/Ni-Cr Alloy.

Welded cable composed of nickel-chromium (Ni-Cr) alloy and copper is a crucial component in the resistance heating technology used for heavy oil production. Tungsten inert gas (TIG) welding was employed to join the copper and Ni-Cr alloy using copper filler wire, and the stability of the welded joint was analyzed under high-temperature service conditions. We examined the changes in the microstructure and properties of the welded joint after postweld heat treatment (PWHT) at 600 °C for 3, 6, and 12 days. The results showed that the welded joint was appropriately formed, with fractures occurring in the copper substrate. The average tensile strength of the welded joint was 240 MPa. The copper and nickel dissolved into each other, forming a Cu0.81Ni0.19 strengthening phase. A columnar crystal diffusion layer formed at the interface between the Ni-Cr alloy and the fusion zone after welding. Grain boundary migration promoted the continuous growth in the columnar crystals as the PWHT duration increased, eliminating the microdefects and inhomogeneities caused by welding. The microhardness progressively decreased from the Ni-Cr alloy side to the copper side. However, the nanoindentation results at the Ni-Cr fusion line initially decreased and then increased with increasing PWHT duration, which contrasted the overall hardness trend observed across the joint after PWHT.

Effect of post-weld heat treatment on microstructure and mechanical properties of induction roll welded joint for A283GRC steel and 5052 aluminum alloy

Steel-aluminum transition joints are commonly produced through explosive welding and friction welding techniques, serving to link aluminum pressure vessels with steel pipes within cold boxes in air separation unit. This study investigates the impact of post-weld heat treatment (PWHT) on the microstructure and mechanical properties of steel-aluminum transition joints created via induction roll welded (IRW), utilizing A283GRC steel and 5052 aluminum alloy as substrates. The findings suggest that the types of intermetallic compounds (IMCs) in IRW joints remain unchanged before and after heat treatment. The thickness of interfacial IMCs increases with higher annealing temperature and longer annealing time, with a faster growth rate at higher annealing temperatures. After PWHT, the grain size near the interface of the joint on the steel side decreased, with the most significant decrease observed when annealed at 300 °C for 2 h. While cracks in the interface zone gradually diminish or disappear with PWHT, excessive heat treatment temperature or duration may result in new transverse cracks. At an annealing temperature of 200 °C, there is limited growth range for IMCs and noticeable repair effect on cracks within the interface region. When annealed at 300 °C and 400 °C, there is a decrease in joint hardness compared to before heat treatment levels, and this decreasing rate accelerates with higher annealing temperature and longer duration. Following annealing at 300 °C for 2 h, the shear strength of the sample reached 70.52 MPa, which is 32 % higher than that before heat treatment. Overall findings suggest that the annealing temperature exerts a more pronounced impact on the mechanical properties of joints in comparison to the annealing duration across the investigated time and temperature ranges. The fracture mode exhibited by the samples before and after heat treatment in IRW is characterized by a mixed fracture mode. However, the predominant fracture mode observed without heat treatment is brittle fracture, whereas after heat treatment, ductile fracture becomes the primary mode of fracture.

Evaluation of corrosion properties of TA2-Q345 explosive composite plate at different heat treatment temperatures

This study investigated the effects of post-weld heat treatment (PWHT) at 500 °C, 600 °C, 700 °C, and 800 °C on the microstructure and corrosion performance of the TA2-Q345 explosive composite plate, with TA2 as the flyer plate and Q345 as the base plate. X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) analyses were performed, alongside electrochemical experiments. The explosive welding interface of the TA2-Q345 composite plate exhibited a characteristic wavy structure, which indicated high welding quality. The XRD results indicated that the PWHT temperature significantly affects both the phase structure and the intensity of the diffraction peaks of the oxide film. Additionally, the porosity calculations demonstrated that the sample subjected to PWHT at 500 °C exhibited the lowest porosity in the surface oxide film, resulting in a denser oxide film that effectively enhanced corrosion resistance. However, as the temperature continued to rise, defects such as craters, bulges, and delamination between the oxide film and the titanium matrix were observed. The results of the electrochemical analysis indicated that, compared to untreated samples, the PWHT samples demonstrated improved corrosion resistance. Specifically, the sample with PWHT at 500 °C has the lowest corrosion current density (icorr) of 6.1892E-06 A/cm2, while the untreated sample has the highest icorr of 6.3577E-05 A/cm2, indicating that 500 °C is the optimal temperature. The corrosion process involved the hydrolysis of titanium chloride to form a TiO2 film and localized corrosion of the TiO2 protective film. The corrosion products composed of mainly C, O, and Ti were dispersed on the surface of PWHT samples.

Design of explosively welded Fe–Al multilayer laminated composite pipes: A critical microscopy analysis of stand-off distance and post-weld heat treatment effects on interface properties

This study examined the microstructure and mechanical properties of explosively welded (EXW) Fe–Al multilayer laminated composite pipes, specifically SS321/AA1050/AA5083, with varying stand-off distances (SD) and post-weld heat treatments (PWHT). Findings revealed that higher collision forces at higher-SD produced a wavy interface with finer grains at the AA1050/AA5083 interface. In contrast, lower-SD yielded a smooth, flat interface. At the SS321/AA1050 interface, collision energy resulted in the formation of an uneven composite reaction layer comprising multiple intermetallics. Analysis of the SS321/AA1050 interface revealed that an increase in the PWHT temperature results in diffusion toward the reaction layer, transforming the unevenly Al-rich and Fe-rich phases into a uniform Al85(Fe,Cr,Ni)15 solid solution. The increase in the fraction of this phase made the reaction layer more brittle. At the AA1050/AA5083 interface, PWHT at higher temperatures caused a significant hardness decline extending further from the interface in samples with higher-SD. On the SS321 side of the laminated composite, higher SD resulted in higher kernel average misorientation (KAM) and increased hardness. Despite a decrease in hardness after PWHT at 350 °C, the hardness gradient from the matrix to the interface in laminates with higher SD remained relatively unaffected, whereas the lower SD counterparts experienced a noticeable stress relief.

Welding residual stress analysis based on ABAQUS direct coupling

Abstract Taking the welded joints of the drive axle shell and half shaft casing as the research object, based on the ABAQUS engineering software and its DFLUX subroutine, numerical simulation of the residual stresses of the welded joints before and after the heat treatment is carried out by adopting the direct coupling of temperature-displacement and the method of birth-death unit, to analyze the improvement effect of post-weld heat treatment on the residual stress of welded joints. The results show that the heat treatment process significantly reduces the equivalent peak stress of welded joints, from the original 195.25 MPa to 145.21 MPa, with a decrease of 25.6%. The axial peak stress of the welded joints decreased from 170.94 MPa to 130.84 MPa, with a decrease of 23.5%.

Effects of post-weld heat treatment on microstructure, tensile properties and linear expansion behavior of laser welded Invar alloy

To improve the ductility and toughness of 4J36 Invar alloy welded joints, this study investigates the microstructure evolution of laser welded 4J36 Invar alloy joints under different annealing temperatures, and evaluates the changes in the thermal expansion coefficient (TEC) of the joints after heat treatment. The results indicated that the 4J36 Invar alloy joints maintain a single austenitic phase after annealing at different temperatures, but the grain morphology and size change significantly. Compared to the welded joint without heat treatment, the ductility of the heat-treated one increased by 94 %, which reached 39.2 %. The TEC of the Invar joints increases with the increase of annealing temperature. The optimal process parameters are an annealing temperature of 650 °C and a holding time of 1.5 h. Under these conditions, the welded joint exhibits a strength close to that of the base material, with improved ductility and relatively low TEC.

Effect of Post-Weld heat treatment on residual stress in deck-rib double-side welded joints and process optimization

Post-weld heat treatment (PWHT) is expected to release the welding residual stress (WRS) of deck-rib double-side welded joints in orthotropic steel decks (OSDs). In this paper, the WRS distribution of deck-rib double-side welded joints before and after PWHT is evaluated by hole drilling method and numerical simulation, and the effect of PWHT parameters on WRS relaxation is further compared, and reasonable parameters are suggested. Based on the principle of WRS relaxation by PWHT, the feasibility of secondary continuous PWHT was explored. The results show that PWHT can effectively release the WRS and make the distribution more uniform. Extending the heat preservation time and increasing the temperature can release more WRS, and the heating and cooling rate has little influence on the WRS, so it is recommended to use the specified maximum value. The effect of secondary continuous PWHT is slight, and it is not recommended for use.

Influence of Post-Weld Heat Treatment on Mechanical Properties and Microstructure of Plasma Arc-Welded 316 Stainless Steel.

This study investigates the effects of post-weld heat treatment (PWHT) on the microstructures and mechanical properties of plasma arc-welded 316 stainless steel. The experimental parameters included the solid solution temperatures of 650 °C and 1050 °C, solid solution durations of 1 h and 4 h, and quenching media of water and air. The mechanical properties were evaluated using Vickers hardness testing, tensile testing, scanning electron microscopy (SEM), and optical microscopy (OM). The highest ultimate tensile strength (UTS) of 693.93 MPa and Vickers hardness of 196.4 in the welded zone were achieved by heat-treating at 650 °C for one hour, quenching in water, and aging at 500 °C for 24 h. Heat-treating at 650 °C for one hour, followed by quenching in water and aging at 500 °C for 24 h results in larger dendritic δ grains and contains more σ phase compared to the other conditions, resulting in increased strength and hardness. Additionally, it shows wider and shallower dimple structures, which account for its reduced impact toughness.

Effects of Post-Weld Heat Treatment on the Microstructure and Mechanical Properties of Automatic Laser-Arc Hybrid Welded AZ31B Magnesium Alloys

Effects of Post-Weld Heat Treatment on the Microstructure and Mechanical Properties of Automatic Laser-Arc Hybrid Welded AZ31B Magnesium Alloys

Effect of post-weld heat treatment on microstructure and mechanical properties of twinning-induced plasticity (TWIP) steel joints

The effect of post-weld heat treatment on microstructure and mechanical properties of twinning-induced plasticity (TWIP) steel joints obtained by melting electrode inert gas-shielded welding (MIG welding) was systematic studied. A total of two post-weld heat treatment processes are proposed, i.e., post-weld annealing treatment (PWAT) with temperature/time of 1100 ℃/1 h and subsequent furnace cooling and post-weld solution treatment (PWST) with temperature/time of 1100 ℃/1 h and subsequent water quenching, which were compared with the case of post-weld non-treatment (PWNT). Following annealing treatment at 1100°C, the joint tensile strength dropped by 6.6 % (from 845.46 MPa to 789.85 MPa), while its elongation at break increased by 40.87 % (from 29.80 % to 41.98 %). The significant increase in plasticity was due to the significant elimination of weld stresses in the joints after annealing. Moreover, the stresses in the weld metal of the PWST joints were instead significantly elevated and the carbides were solidified, which resulted in the lower strength. When post-weld heat treatment was applied, the impact toughness of the joints was lower than when untreated. This was primarily due to the greater percentage of the low-angle grain boundaries and the precipitation of MC-type carbides. Consequently, post-weld annealing treatment was an effective method to further enhance the strong plasticity of new twinning-induced plastic steel joints.

Coupling effect of post-weld heat treatment and fatigue damage on the hydrogen embrittlement of X80 steel welded joints

The influence of post-weld heat treatment (PWHT) and fatigue damage on the hydrogen embrittlement sensitivity of X80 steel welded joints, obtained using flux-cored arc welding method, was investigated in the study. Compared to the as-welded specimens, the sensitivity of hydrogen embrittlement after PWHT was decreased. However, the coupling effect of PWHT and fatigue damage improved significantly the HE sensitivity. Furthermore, the fracture site of the PWHT + pre-fatigue specimens with hydrogen-charged was transferred to the weld metal, and the fracture was characterized by intergranular fracture, quasi-cleavage (QC) and shallow dimples ductile fracture. The increase of the hydrogen content might be attributed to the evolutions of dislocation and the proportion of high-angle grain boundary caused by fatigue damage. Meanwhile, the size of QC for the hydrogen-charged welded joints was related to the degree of fatigue damage, hydrogen content and microstructure strength.

Regulating the partially mixed zone via post-weld heat treatment to enhance sulfide stress corrosion cracking resistance of the Inconel 625/X80 weld overlay

This paper investigated the effect of post-weld heat treatment (PWHT) on microstructure evolution and sulfide stress corrosion cracking (SSCC) behavior of the fusion boundary (FB) region of Inconel 625/X80 weld overlay, with a focus on the partially mixed zone (PMZ). Three heat treatment regimens were designed, namely 620 °C/10 h, 620 °C/20 h, and 670 °C/10 h, in which 620 °C/20 h was proved to be the optimal parameter. The 10-hour PWHT conditions might induce heterogeneous carbon distribution owing to insufficient tempering duration, exacerbating the hardness mismatch in the FB region and thus promoting the development of SSCC. Following the 620 °C/20 h treatment, most of the brittle phase with high hardness in the FB region was eliminated, reducing the nucleation site for SSCC. More importantly, martensite in the PMZ was transformed into austenite with rod morphology, while cementite adjacent to the PMZ might evolve into dispersed refined austenite. Austenite shows low hydrogen sensitivity, enhancing the SSCC resistance of the PMZ. On the other hand, the carbides in the X80 matrix might restrict the diffusion of hydrogen toward the PMZ, thereby reducing the susceptibility of the PMZ to SSCC.

Effect of post-weld heat treatment on the microstructure and mechanical properties of CWW GMAW

This study aims to investigate the impact of heat treatment on the microstructure and welding properties of cable-type welding wire gas metal arc welding (GMAW) in shipping steel. In contrast to the untreated weld, the width of the heat-affected zone of the weld after heat treatment decreased. The microstructure of welded joints following heat treatment and air cooling is relatively and finer compared to the grain structure after furnace cooling and without heat treatment. The tensile strength of welded joints decreases compared to that of untreated weld, while it is higher than that of joints after heat treatment and furnace cooling. The impact toughness of heat treatment is higher than that of the weld seam, heat-affected zone, and fusion line without heating treatment, and the impact performance is higher than that of post-weld heat treatment with furnace cooling.

Effect of PWHT on microstructure and mechanical properties of welded joint of a new Fe-Ni-based superalloy

In this study, the effect post weld heat treatment (PWHT) on microstructural evolution and mechanical properties of weld metal of HT700P alloy with Inconel 617 filler metal was investigated. After welding, columnar grain, dendritic microstructure and segregation of Mo, Co and Ti elements related to the equilibrium distribution coefficient were observed in the weld metal. The PWHT was conducted in both direct-aging treatment with different time and solution treatment with different cooling methods. The results showed that direct-aging treatment had a limit impact on homogenization of weld metal, while microstructural homogenization and elemental segregation were significantly improved after solution treatment and massive M6C and M23C6 carbides precipitated at the grain boundaries and interdendritic region of weld metal. It was found that the elongation at 700 °C of welded joints after solution treatment was relatively increased, which was related to the decrease of residual stress and the precipitation of Mo-rich carbides at the grain boundaries. The fracture occurred in the weld metal presented interdendritic fracture characteristics, and the fracture mechanism for stress relaxation cracking was the strong grain interior induced by the precipitation of γ′ phase, leading to the stress concentration and nucleation of cavities at grain boundaries. After solution treatment, the creep lifetime of furnace cooling was much greater than that of water quenching. The superior creep properties of furnace-cooled joint could be attributed to the lower residual stress and the migration of carbon element in the fusion line, which inhibited the nucleation and aggregation of cavities in the partially melted zone.

Effect of post-weld heat treatment on the microstructure, phase composition and mechanical properties of dissimilar Al-Mg-Li/Al-Cu-Li laser welded joints

Butt joints of the V-1461 and 1424 heat treated aluminum–lithium alloys of the third generation were welded with a CO2 laser and studied in detail for the first time. In particular, spatial distributions of the formed phases and their evolution upon post-weld heat treatment (PWHT), determining the mechanical properties of the joints, were investigated. The PWHT included quenching and subsequent artificial aging. The key factors, affecting the metallurgical processes in a weld pool, were the following: 1) the alloying elements and the thermal properties of the alloys, 2) the dynamics of the local non-equilibrium melting, the convective transfer of the molten metal in the weld pool and its subsequent solidification, 3) the cooling rate, and 4) the PWHT procedure. By using synchrotron radiation and scanning electron microscopy, new θ(Al2Cu), T1(Al2CuLi) and S1(Al2MgLi) phases were found in the weld metal that were absent in both base metals. This phenomenon reduced the mechanical properties of the joints to the levels, corresponding to about 50 % of the 1424 alloy as the weakest one. Quenching contributed to the formation of the δ′(Al3Li) strengthening phase in the weld metal. As a result, the ultimate tensile strength increased up to 70 % and elongation up to 95 % of the corresponding levels of the 1424 alloy. Artificial aging made it possible to form the T1(Al2CuLi) strengthening phase, to increase the content of the δ′(Al3Li) one, as well as to improve the mechanical properties of the joint. In this case, the ultimate tensile strength was 411 MPa, the yield point was 327 MPa and elongation was 1.7 %. These values were close to those for the 1424 alloy (about 80 %, 89 % and 23 %, respectively).

Microstructure and corrosion behavior of A390-10 wt% SiC composite-AA2024-T6 aluminum alloy dissimilar joint: Effect of post-weld heat treatment

The weldability of aluminum matrix composites to other materials, such as aluminum alloys, is an essential point in expanding the use of these materials. This study investigated the effect of rotational speed and post-weld heat treatment on the microstructure, mechanical properties, and corrosion behavior of A390-10 wt% SiC composite/AA2024-T6 aluminum alloy dissimilar joint. Friction stir welding is performed using a square frustum pyramid pin tool with a rotational speed of 400–1200 rpm and a traverse speed of 40 mm/min. Results found that a surface groove formed on the weld crown at a rotational speed lower than 800 rpm due to insufficient material flow. Also, the tunnel defect formed on the advancing side at a rotational speed higher than 1000 rpm due to the turbulent flow of material. By increasing rotational speed from 800 to 1200 rpm, the average grain size of the advancing and retreating sides increased by 41.1 and 46.3 %, respectively. Compared to AA2024-T6 and A390-10 wt% SiC composite base metals, the average hardness of the stir zone of the joint fabricated by the rotational speed of 800 rpm increased by 8.4 and 38.2 %, respectively. By increasing the rotation speed from 800 to 1000 rpm, the yield strength and ultimate tensile strength decreased by 6.8 and 6.5 %, respectively. By decreasing rotational speed from 1000 to 800 rpm, the elongation and corrosion resistance decreased by 5.4 % and 34.7 %, respectively. After post-weld heat treatment, the hardness, yield strength, ultimate tensile strength, and corrosion resistance increase 15.9, 12.7, 7.8, and 28.9 %, respectively.

Effect of post-weld heat treatment on mechanical and microstructural properties of high strength steel weld metal

The usage of high strength steel (HSS) is steadily increasing, primarily driven by the pursuit of weight reduction, leading to a subsequent decrease in greenhouse gas emissions. This paper investigates the impact of various post-weld heat treatment (PWHT) temperatures of 525 °C, 550 °C and 575 °C with a holding time of 2 h on both the microstructure and mechanical properties of weld metal produced using a HSS metal cored wire. The investigation reveals that PWHT does not significantly alter strength but has a more pronounced influence on toughness. The as-welded condition exhibited the highest toughness. Among the samples subjected to the PWHT, the one treated at 575 °C showed the highest impact energy, reaching 69 J at −60 °C. This outcome is attributed to the increased presence of acicular ferrite in the microstructure, surpassing that of samples subjected to PWHT at different temperatures.

A Review on The Effect of Post-Weld Heat Treatment (PWHT) on Its Thermal Analysis and Mechanical Properties of Welded Metallic Pipe

Welding is a commonly used process in manufacturing and engineering, and it may create residual stress in the welded region that can cause problems during service. Thermal expansion of the post-weld heat treatment (PWHT) of steel carbon induces residual stress. To relieve the internal stresses in the weld zone, PWHT is used to soften the hardening zone, improve microstructures, and lower hydrogen content in the welded region. The pipe size, heating width, insulation conditions, heating rates, soaking temperature, and holding time are factors that influence PWHT procedures. This paper will explain clearly about the PWHT process and the effect of PWHT on the metallic metal.

Effect of Post-weld Heat Treatment on Microstructure and Mechanical Properties of P91 Heat-Resistant Steel Coating on Mild Steel

Effect of Post-weld Heat Treatment on Microstructure and Mechanical Properties of P91 Heat-Resistant Steel Coating on Mild Steel