Post-weld Heat Research Articles

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.

Optimizing process parameters and a comparative study of post-weld heat treatments on the microstructure and mechanical properties of 0.3%C-Cr-Mo-V steel

Optimizing process parameters and a comparative study of post-weld heat treatments on the microstructure and mechanical properties of 0.3%C-Cr-Mo-V steel

Enhancing surface integrity in friction stir welding through deep rolling and post-weld heat treatment

This study aimed to investigate mechanical surface treatment through deep rolling (DR) and post-weld heat treatment (PWHT) to enhance the surface integrity of an AA7075-T651 aluminum alloy welded through friction stir welding (FSW). The surface integrity of the welded joint was evaluated by analyzing residual stress, microhardness, surface roughness, microstructure, and fatigue life. The experimental design comprised three sets: one set exclusively applied FSW, another set applied FSW followed by DR (FSW-DR), and the last set applied FSW followed by PWHT (FSW-PWHT). Fatigue testing (screening) was performed through a four-point bending test with a bending stress of approximately 300 MPa, test frequency of 2.5 Hz at room temperature, and stress ratio (R) of 0. The FSW parameters included a tool rotational speed of 1600 rpm, welding speed of 30 mm/min, immersion depth of 0.1 mm, dwell time of 15 s, and tool tilt angle of 0°. The DR parameters included a rolling pressure of 150 bar and rolling speed of 1400 mm/min. The results revealed that the residual stress significantly influenced fatigue life. The fatigue test demonstrated that FSW workpieces treated with the DR process (FSW-DR) exhibited the highest fatigue life, showing a remarkable increase of 33.5 % compared with that of untreated FSW workpieces. Moreover, the residual stress changed from tensile to compressive, accompanied by noticeable enhancements in microhardness and surface roughness. These results highlight that FSW followed by the DR process (FSW-DR) positively affects weld surface integrity, resulting in an extended service life for welded components.

PWHT influence on welding residual stress in 45 mm bridge steel butt-welded joint

To investigate the spatial distribution of welding residual stress (WRS) and effect of post welding heat treatment (PWHT) on WRS relaxation in the welded components of steel bridges, a 45 mm-thick Q345qD butt-welded specimen was manufactured. Experimental measurement and numerical simulation methods were employed to examine specimen surface and internal WRSs. The simulated results exhibited good agreement with the measured ones, confirming the rationality of the numerical simulation process. Subsequently, through the PWHT simulation in ABAQUS, the evolution of WRS during PWHT was comprehensively analyzed and the effect of PWHT parameters on the stress relaxation was studied. The measured and simulated results show that the longitudinal welding residual stresses (LWRSs) are tensile in the weld region and compressive away from the weld. High-value stresses are mainly concentrated on specimen surfaces and the mid-thickness. Transverse welding residual stresses (TWRSs) present multi-layered distribution, alternating between tension and compression within the weld region. WRS reduction mainly occurs during the heating stage of PWHT, with slight decrease during the holding stage and an increase during the cooling stage. Optimizing PWHT parameters, including temperature, and holding time, heating/cooling rates, proved effective in achieving substantial WRS relaxation.

The Effects of Post Weld Heat Treatment on Microstructure and Mechanical Properties of API X70 Linepipe using Submerged Arc Welding

API X70 steel requires high strength and toughness for safety in extreme environments like high pressure and low temperature. Submerged Arc Welding (SAW ) is effective for manufacturing thick steel pipes. However, the welding heat input during SAW alters the microstructure and mechanical properties of the heat affected zone (HAZ). Therefore, investigating the correlation between microstructure and mechanical properties in welded X70 pipes is important to address potential degradation of HAZ and weld metal (WM). In this study, post weld heat treatment (PWHT) was performed to improve mechanical properties of HAZ and WM and to reduce residual stress caused by the welding process. We performed PWHT at 640°C for 15 hours and followed by air cooling. After heat treatment, we observed the microstructure through OM and SEM analysis, and investigated the mechanical properties through tensile test, hardness test, and Charpy impact test.

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

Metallurgical characteristics of aluminum-steel joints manufactured by rotary friction welding: A review and statistical analysis

Rotary friction welding (RFW) is a solid-state joining process that can be used to join different alloy systems such as aluminum-steel alloys. Rotary friction welding has become increasingly appealing for various industries due to the sustainable advantages that it offers, including overall cost reduction, weight minimization, and unique properties. However, the formation of brittle intermetallic compounds (IMCs) at the interface can be a challenge in the welding process of aluminum-steel alloys. This paper reviews the metallurgical characteristics of aluminum-steel alloy joints manufactured by rotary friction welding. The different types of intermetallic compounds that can form at the interface, as well as the factors that affect their formation, are discussed. The effects of rotary friction welding parameters on the microstructure and mechanical properties of the joints are also presented. Specifically, minimizing interfacial reaction layers via post-weld heat treatment and controlling the heat input during the process is crucial to suppressing the formation of intermetallic compounds. This study employed artificial intelligence modeling, specifically the artificial neural network - multilayer perceptron, to investigate the effect of various parameters on the ultimate properties of the parts welded together. Overall, this paper provides an excellent resource for industries looking to embrace rotary friction welding to tackle the challenge of dissimilar Al-steel joining.

Laser welding of ultra-high strength steel rocket engine shell

The microstructure and mechanical properties of 30Cr3-30CrMnSiA ultra-high strength steel rocket engine shell welded joint were investigated in detail. The results indicated that the microstructure of the fusion zone was martensite of columnar and equiaxial due to the fast cooling rate of the laser welding. At the as-weld (AW) state, the average grain size of the 30Cr3 base metal was 4.63 μm, which was much smaller than that of the 30CrMnSiA base metal, which averaged 6.85 μm. After the post-weld heat treatment (PWHT), all the microstructures of the base metal, fusion zone and heat affected zone (HAZ) of 30Cr3 were tempered martensite. Meanwhile, at both AW and PWHT state, the tensile specimens of the welded joints of dissimilar materials were all fractured in the 30CrMnSiA base metal side at both 25 °C and 800 °C. After the PWHT, the tensile strength of 30CrMnSiA and 30Cr3 base metal at 25 °C were 1517.4 MPa and 1795.3 MPa, respectively. The welded joints of dissimilar materials by laser welding also showed excellent tensile properties at high temperature (800 °C), because of the small average grain size.

Effect of Post-weld Heat Treatment on the Microstructure and Mechanical Properties of 2.25Cr-1Mo-0.25V Ultra-Thick Steel Plate

Effect of Post-weld Heat Treatment on the Microstructure and Mechanical Properties of 2.25Cr-1Mo-0.25V Ultra-Thick Steel Plate

Physical simulation of the underclad heat affected zone in a reactor pressure vessel to study intergranular cracking

Underclad cracking in nuclear pressure vessels was of significant concern in the 1970s and 1980s before mitigating adjustments were made both to steel compositions and manufacturing practice. Unfortunately, the cracking mechanisms are still not well understood, and this can undermine confidence when changes to cladding operations are under consideration. In this work, Charpy-sized test coupons of 18MND5 steel were subject to a range of thermal cycles that can be experienced by the substrate immediately adjacent to the interface with the overlay. The Charpy test results are considered in combination with analysis of the samples through field emission gun (FEG) scanning electron microscopy (SEM) and wavelength dispersive X-ray spectroscopy (WDXS). The findings suggest that the heat affected zone subject to the coarse grained plus intercritical thermal cycle, before post weld heat treatment, has a peculiar and potentially brittle microstructure. However, in a steel with no obvious macrosegregation, no clear evidence of intergranular cracking in the early stages of the post weld heat treatment could be found. The second part of the work focuses on the effects of segregation regions in large forgings, more specifically ghost lines, on the tendency for underclad cracking. Ghost line regions that subsequently form a coarse grained heat affected zone (CGHAZ), and are then heated to just under the A1 temperature, seem to be the most prone to intergranular cracking. Cracking susceptibility appears to be associated with elevated concentrations of alloying and impurity elements at grain boundaries.

Investigation of the fracture resistance of high strength ferritic steel welds in gaseous hydrogen environment

Hydrogen is expected to play a major role in the decarbonization of the energy grid. As a fuel, it possesses an elevated energy density per unit mass, about twice as much as natural gas but also a very low mass density; for this reason, it is preferably stored and transported at elevated pressures in the gas phase to achieve a comparable volumetric energy density. High strength quenched and tempered ferritic steels are widely used for gaseous hydrogen storage despite the fact that hydrogen affects material properties and result in higher fatigue crack growth rate and lower fracture toughness.This work presents the results of a comprehensive fracture toughness test program in gaseous hydrogen for the characterization of base metal, heat affected zone and weld metal on a high strength, quenched and tempered steel, suitable for the construction of hydrogen pressure equipment.Full penetration, butt welded joints were made using partly mechanized gas metal arc welding technique on a weldable, high strength steel, namely EN 101216-3 grade P690 QL2. Two different welding procedures were evaluated, and fracture toughness tests were conducted according to ASTM E1820 requirements, in high purity (99.9995%) hydrogen gas at a pressure of 200 bar on specimens extracted from base metal, heat affected zone and weld metal. While base metal and weld metal exhibited stable crack growth behavior, heat affected zone showed variable behavior as a function of the post-weld heat treatment conditions. It was found that local micro-hardness spots are a concern and should be controlled through dedicated post weld heat treatment operation to limit hardness values for use of welds in H2 gas conditions.

Microstructure and Fatigue Behavior of Cr-Mo Steel Weld Joints with Automatic TIG Welding

This research focused on how filler metal and post-weld heat treatment (PWHT) affected the microstructure and mechanical properties of 2.25Cr-1Mo steel welds, especially the fatigue behavior. Automatic TIG welding was used to fabricate the weld samples, and both AWS A5.28 ER90S-B3 (also known as B3) and AWS A5.14 ERNiCrMo-3 (commonly known as Inconel 625) were used as filler metals. The PWHT was performed at 690°C for one hour. That was the ideal condition for reducing the hardness of the heat affected zone (HAZ). The microstructure of the B3 weld metal and the HAZ was observed to alter from bainite to tempered bainite due to PWHT, resulting in a decrease in hardness (B3 WM: from 299.7 to 243.5 HV0.2 and HAZ: from 294.5 to 234.7 HV0.2). On the other hand, Inconel 625 weld metal showed an austenite microstructure: after PWHT, the formation of gamma prime increased its hardness (from 263.2 to 299.8 HV0.2). According to the tensile test results, the tensile strength of the welded samples was slightly lower than that of the original base metal, such as the UTS of the BM was 633.0 ± 3.0 MPa and that of the B3-PWHT sample was 601.4 ± 2.0 MPa. The effect of PWHT on tensile strength was negligible, but it significantly affected fatigue strength. For both filler metals, PWHT resulted in a decrease in fatigue strength. The fatigue strength of the B3 sample decreased from 290 to 120 MPa, while that of the IN625 sample reduced from 290 to 240 MPa. In comparison between two different materials, the fatigue strength of the Inconel 625 sample was greater than that of the B3 sample. Fatigue fracture surfaces can be classified into three stages: crack initiation, propagation, and fast fracture. The fatigue rupture was mostly initiated at the weld interface. The final fracture revealed a dimple appearance.

Microstructural-mechanical property evolution of AA7075 welds with different filler during heat treatment

This study investigated the changes in microstructure and mechanical properties of gas tungsten arc welded 7075 aluminum alloy joints using ER5356 and ER7150 filler wire subjected to post-weld heat treatment. The microstructure and mechanical property evolution of the welds was analyzed by both thermodynamics calculations and experimental methods. After welding, alloying elements segregated in the inter-dendritic regions, resulting in the formation of excessive intermetallic compounds. Within the welds of 7075 aluminum alloy with ER5356 filler material, the inter-dendritic region was primarily composed of the T-AlCuMgZn phase. In contrast, in the welds of 7075 aluminum alloy with ER7150 filler material, this region consisted of a eutectic mixture containing α-Al, T-AlCuMgZn, and η-MgZn2 phases. The α-Al matrix experienced limited supersaturation due to the presence of these inter-dendritic intermetallic compounds, which could not dissolve during the post-weld aging treatment. As a comparison, post-weld solutioning and aging treatment significantly improved the ultimate tensile strength of the joints. Among all the samples, the 7075 + ER7150 sample subjected to post-weld solutioning and aging treatment exhibited the highest strength and elongation, primarily attributed to the complete dissolution of the inter-dendritic intermetallic compounds and the formation of fine precipitates.

Effects of post-weld heat treatments in microstructure, mechanical properties, and corrosion resistance of simulated heat-affected zone of supermartensitic steel UNS S41426

Effects of post-weld heat treatments in microstructure, mechanical properties, and corrosion resistance of simulated heat-affected zone of supermartensitic steel UNS S41426

Effect of post-weld heat treatment on corrosion resistance of X90 pipeline steel joints

Abstract In order to improve the corrosion resistance of welded joints, X90 pipeline steel joints were subjected to post-weld heat treatment at 610 °C, 640 °C, and 670 °C (holding time was 1 h). Through electrochemical corrosion and full immersion corrosion experiments, the corrosion resistance of welded joints under various conditions was tested, and the surface morphology and corrosion products of the corroded samples were analyzed by scanning electron microscopy and X-ray diffraction analysis. The experimental results show that the corrosion products of X90 pipeline steel welded joints in simulated soil solution mainly include Fe(OH)3, γ-FeOOH, α-Fe2O3, γ-Fe2O3, and a small amount of Fe3O4, FeCl3 and Fe. After heat treatment at 610 °C, the corrosion current density of the parent metal, heat-affected zone, and weld metal of the joint changes from 1.081, 2.889, 2.079 (×10−5 A cm−2) to 0.977, 2.211, 1.810 (×10−5 A cm−2), respectively, the corrosion resistance is improved.

The Role of Welding Parameters in Hydrogen Embrittlement Mitigation: A Case Study in Steel

This research investigates the mitigation of hydrogen embrittlement in steel, focusing on the effects of metallurgical hydrogen and the efficacy of various reduction techniques. Key findings demonstrate that vacuum treatment during steel casting combined with thermal treatment significantly lowers hydrogen content, enhancing steel's resistance to embrittlement. Welding processes differ in susceptibility to hydrogen-induced cracking, with submerged arc welding (SAW) showing the least and shielded metal arc welding (SMAW) the most susceptibility. Employing multipass welding, along with preheating and post-weld heat treatments, effectively minimizes hydrogen-related cracking by promoting even hydrogen distribution and desorption. The study highlights the successful application of fluoride-ion-containing welding fluxes, such as CaF2 and KF, to reduce weld hydrogen levels through chemical reactions. Furthermore, the choice of welding parameters, particularly the arc voltage, substantially impacts the hydrogen concentration in the welds. Additionally, the incorporation of hydrogen-binding elements such as yttrium significantly reduces the level of free hydrogen, thereby enhancing resistance to hydrogen corrosion. The research underlines the need for selecting appropriate welding methods and parameters to effectively reduce the adverse effects on welded joints. In conclusion, optimizing vacuum and thermal treatments, along with developing innovative welding materials, is imperative to control hydrogen content, crucial to the longevity and reliability of steel products in hydrogen-sensitive applications such as the oil and gas sector.

Effect of welding state on the re-precipitation behavior of Cu-rich and NiAl nanoparticles in HAZ of 1100 MPa grade low carbon ultra-high strength steel

The influence of multi-layer multi-pass welding and post-weld heat treatment (PWHT) on the co-precipitation behavior of Cu-rich and B2–NiAl, microstructural characteristics, grain size and mechanical properties of the coarse grain heat affected zone (CGHAZ) were systematically investigated for low-carbon ultra-high-strength steel with different Ni/Cu ratio. The results show that the CGHAZ microstructure of both high (1.5Cu) and low (2.0Cu) Ni/Cu ratio steel are composed of LB and GB, the grain size increases from 10.1 ± 1.1 μm and 9.5 ± 0.7 μm to 32.1 ± 1.0 μm and 32.2 ± 2.7 μm, and the nanoparticles are dissolved and subsequently re-precipitated during the welding process, with an average radius 1.56 nm and 1.71 nm, respectively. The hardness profile of the joint shows softening at CGHAZ and the tensile strength reaches 1218 MPa and 1056 MPa respectively. After PWHT, the re-precipitated behavior of the nanoparticles was enhanced, with average radius of 1.53 nm and 1.55 nm, and the number density increases from 1.55 × 1023 m−3 and 1.06 × 1023 m−3 to 4.01 × 1023 m−3 and 3.33 × 1023 m−3, respectively. The co-precipitation evolution mechanism shows that the typical core-shell structure is transformed into individual 9 R–Cu and B2–NiAl particles, and a large number of small-sized B2–NiAl particles were re-precipitated during the aging process. The strengthening mechanism shows that martensite strengthening and grain size strengthening are weakened in the as-welded CGHAZ, and only part of the nanoparticles was re-precipitated leading to the softening of CGHAZ during welding. After PWHT, a large number of small-sized nanoparticles were re-precipitated to restore the contribution of precipitation strengthening, while small-sized nanoparticles interacted with dislocations and entangled near the M-A constituents to promote the formation of microvoids and microcracks, thus seriously deteriorating the ductility.

Influence of Ni and PWHT on microstructure evolution and mechanical properties of GTA-welded duplex stainless steel and super duplex stainless steel joints: A comparative investigation

In the present investigation, a new endeavor has been made to analyze the impact of the secondary process (post-weld heat treatment (PWHT)) as well as Ni addition on the microstructure and mechanical characteristics of welds. Welds between similar joining materials from duplex stainless steels (DSS), as well as super DSS (SDSS), were made by the gas tungsten arc welding (GTAW) process. For DSS, after PWHT with the addition of Ni element, the amount of austenite rises and becomes more uniformly distributed with curved boundaries, while for SDSS, the microstructure mainly consists of intergranular and Widmanstätten austenite. According to the comparison of phase percentages obtained based on both ASTM E1245 and ASTM E562, a good balance between ferrite and austenite phases of joint materials was achieved. X-ray diffraction analyses on both joints revealed that phases are mainly ferrite and austenite with different lattice parameters without evidence of unwanted intermetallic phases. The addition of Ni increases the hardness values of DSS weld metal compared to the base metal due to an increased amount of Widmanstätten austenite and ferrite in the microstructure. The lowest ductility was obtained for the SDSS weld sample with the addition of Ni and PWHT because of the existence of secondary austenite in the weld metal and the Widmanstätten morphology of the austenite. The effect of PWHT on the development of microstructure and mechanical behaviors was more than the effect of nickel powder on weld samples.

Dissimilar friction stir welding and post-weld heat treatment of Ti-6Al-4V and AA7075 producing joints of unprecedented strength

Dissimilar welding of Ti and Al alloys is challenging due to the potential formation of brittle intermetallics, which can compromise weld strength. Friction stir welding (FSW) is an advanced joining method with the potential to drastically reduce or prevent the formation of intermetallic phases because melting is avoided. However, in previous studies, dissimilar joints of Ti-6Al-4V and EN AW-7075 with satisfactory strength could not be achieved. Thus, we investigated friction stir welding of these two materials in a butt configuration, and analyzed the effects of post-weld heat treatments on the mechanical properties. Tensile strengths of 441 MPa in the as-welded condition and 505 MPa after heat treatment were achieved, significantly surpassing strength values reported in earlier studies. Microscopic investigations showed no evidence of formation of brittle intermetallic phases, and ductile fracture was observed. Our results show that FSW is a very promising candidate for future aerospace applications requiring dissimilar joining of Ti and Al alloys.

PENGARUH QUENCHING SETELAH PENGELASAN TERHADAP KOROSI DI BAWAH INSULASI MEDIA AIR LAUT PADA BAJA A36

Corrosion in low-carbon steel is a significant issue in the industrial world, particularly in the oil, gas, refining, and chemical industries, as it leads to substantial financial losses. The total losses experienced by companies in Indonesia are estimated to reach 2-5% of the country's GDP. Corrosion arising from insulation damage, known as Corrosion Under Insulation (CUI), is challenging to detect but has a profound impact on industrial processes. Welding quality and corrosion resistance can be improved through post-weld heat treatment (PWHT). This research aims to investigate the influence of rapid cooling after welding low-carbon ASTM A36 steel on corrosion events under insulation using the "Water Immersion" method with seawater from the Muntok area, Bangka Belitung Islands Province, for 7 and 14 days. The welding process is performed using shielded metal arc welding (SMAW). Heat treatment is applied at 880°C for 60 minutes, as determined by the carbon equivalent calculation, followed by rapid cooling in seawater. Testing includes chemical composition analysis, non-destructive testing with dye penetrant on the welds, Brinell hardness testing, corrosion rate calculations, charpy impact testing, and metallography observations. The research results indicate that quenching enhances hardness and toughness while affecting the corrosion rate of the material after corrosion immersion, both with and without insulation. Material immersion exhibits a corrosion rate inhibition on the 14th day due to the formation of an oxide layer that hinders further degradation. Metallography observations reveal that after welding, phases formed include pearlite, acicular ferrite, and widmanstatten structures.