Papers by Keyword: Post Weld Heat Treatment

Abstract: Recently, the fuel oil of diesel engines of marine ships is being changed to heavy oil of low quality as the oil price is getting higher and higher. Therefore, the wear and corrosion in all parts of the engine, such as cylinder liner, piston crown, and spindle and seat ring of exhaust valves has predominantly increased. Thus, the repair welding of the piston crown is a unique method to prolong its life in a economical point of view. In this case, filler metals with a high corrosion and wear resistance are mainly being used for repair welding. However, the piston crown on the ships job site is often actually being welded with mild filler metals. Therefore, in this study, mild filler metals, such as E4301, E431316, and E4316, were welded to the SS401 steel as the base metal, and the corrosion properties of their weld metals with and without post weld heat treatment were investigated with some electrochemical methods in 0.1% H₂SO₄ solution. The weld metal welded with E4301 filler metal exhibited the best corrosion resistance among the filler metals in the case of no heat treatment, however, its resistance was considerably decreased due to the post weld heat treatment (annealing:625°C, 2hr). In particular, the weld metal of E4316 exhibited relatively a good corrosion resistance by the post weld heat treatment.

Abstract: Recently, the fuel oil of diesel engine of marine ships has been changed with heavy oil of low quality as the oil price is getting higher and higher. Therefore, the wear and corrosion against all parts of the engine, such as cylinder liner, piston crown, and spindle and seat ring of exhaust valves has predominantly increased due to its consumption. Thus, the repair welding of the piston crown is a unique method to prolong its life in a economical point of view. In this case, filler metals having a better corrosion and wear resistance are mainly being used for repair welding. However, the piston crown on the ship’s job site is often actually being welded with mild filler metals. Therefore, in this study, the mild filler metals, such as E5016, E1216, and E2316, were welded to the SS401 steel as the base metal, and the corrosion properties of their weld metal zones with and without post weld heat treatment were investigated with some electrochemical methods in 0.1% H2SO4 solution. The weld metal zone welded with E1216 filler metal exhibited the best corrosion resistance among the filler metals with irrespective of heat treatment, however, its corrosion resistance was somewhat decreased due to the post weld heat treatment(annealing:625oC, 2hr). In particular, the weld metal of E2316 exhibited relatively a good corrosion resistances by the post weld heat treatment.

Abstract: The research was study the effect of post weld heat treatment parameters on microstructure and hardness in heat affected zone. The specimen was carbon steel AISI 1050 which thickness of 6 mm. The experiments with full factorial design. The factors used in this study were post weld heat treatment(PWHT) temperature of 500, 550, 600, 650 and post weld heat treatment time of 10 and 15 hour. The welded specimens were tested by tensile strength testing and hardness testing according to ASTM code. The result showed that both of post welds heat treatment temperature and post weld heat treatment time had interaction on hardness at 95% confidential (P value < 0.05). A factor affecting the hardness was the most PWHT temperature 550 ๐C and PWHT time 10 hr. of 279 HV. Microstructure can be concluded that low PWHT temperature and time effect on temper martensite with a coarse grain and martensite scattered throughout. Martensite was a smaller and greater fine grain, the ferrite and the volume decrease due to a higher temperature.This research can be used as data in the following appropriate PWHT parameters to carbon steel weld.

Abstract: In this research, post-weld heat treatment (PWHT) of dissimilar API 5CT C90 and ASTM A182 F22 welded pipe was carried out at temperatures of 500, 600, 700 and 800°C. The effects of PWHT on the microstructure and mechanical properties of the weldment were investigated. The mechanical tests and microstructure examinations were focused on the fusion line area of API 5CT C90 as this area is the most crucial part of the weldment. The main objective of this research is to assess the microstructure and mechanical properties of the dissimilar weldment. The results were then compared with NACE MR0175/ISO15156 code which requires hardness values below 275 Hv10 at a cap, below 250 Hv10 at a root and an average value 42 Joules at-20°C for charpy impact test [. The experimental results show that PWHT reduces the hardness value and increase the toughness of the weldment. Meanwhile, the optical microscopic examination shows that the higher the PWHT temperature, the coarser the grain size. The results showed that the 800°C PWHT specimen complied with the code.

Abstract: The aerospace industry strives to develop materials allowing an increase in payload and reducing fuel consumption. Al-Li alloys, with their low density and high strength are currently in use for such applications and have potential for additional applications. When compared to composites, utilizing Al-Li alloy products is cost effective for aerospace companies as they do not need to redesign pre-existing fabrication facilities. The joining of these alloys by conventional methods is limited by segregation of alloying elements and the formation of oxides during high temperature exposure. This study focuses on solid state joining method that has the potential to generate low heat and be defect free - Friction Stir Welding (FSW). AA2199 sheets were joined by FSW. Process variables included table force, tool rotation speed and weld travel speed. A post weld heat treatment (PWHT) was applied to improve the mechanical properties by precipitation of strengthening phases. An increase in hardness of the weld zone from 95HV to 125HV upon PWHT was recorded for selected welding conditions. The type and morphology of second phase precipitates is deemed responsible for this effect. It is suggested that the high temperature and high strain levels characteristic of welds with fast tool rotation allow for the dissolution of precipitates during welding. The re-precipitation of these second phases during PWHT allowed the welds to recover strength to the level of the base material.

Abstract: The Inconel X-750 indicates good hot corrosion resistance, high stability and strength at high temperatures and for this reason the alloy is used in manufacturing of gas turbine hot components. The objective of this research was study the effect of post weld heat treatment (PWHT) on fusion zone and heat affected zone microstructure and mechanical properties of Inconel X-750 weld. After welding, samples were solutionized at 1500 0C. Various aging temperature and times were studied. The results show that aging temperature and time during PWHT can greatly affect microstructure and hardness in fusion zone and heat affected zone. As high aging temperature was used, the grain size also increased and M23C6 at the grain boundary decreased. This can result in decreased of hardness. Moreover excessive aging temperature can result in increasing MC carbide intensity in parent phase (austenite). It can also be observed that M23C6 at the grain boundary decreased due to high aging temperature. This resulted in decreasing of hardness of weld metal and heat affected zone. Experimental results showed that the aging temperature 705 0C aging time of 24 hours provided smaller grain size, suitable size and intensity of MC carbide resulting in higher hardness both in weld metal and HAZ.

Abstract: The effect of post weld heat treatment on microstructures, tensile and corrosion properties of Inconel601 weld seam was investigated. The results indicated that the microstructure of weld metal consisted of coarser columnar grains with (Nb, Ti)-rich precipitations and laves phase distributed in them. Tensile and corrosion test displayed that the weld seam without any heat treatment exhibit the lowest mechanical and corrosion properties. Solution treatment at 1050°C was found to result in the considerable refinement of grain size and finally the improvement of mechanical and corrosion properties. It was also found that the specimens had the best mechanical and corrosion properties after heat treatment at 1150°C. However, with the treatment temperature increasing to 1200°C, the grain began to grow up, leading to the decrease of tensile strength and corrosion resistance.

Abstract: Presented work analyses the impact of heat treatment parameters on the mechanical properties and operational reliability of P5 (5%Cr0.5%Mo) steel welded joints. The key objects of research are heat-treated chrome-molybdenum steel welded joints and piping elements operated at high temperature for an extensive period of time, where degradation of mechanical properties has been observed. The main objective is to investigate the causes of degradation of alloy steel mechanical properties during fabrication and operation of the equipment, and to develop a methodology for identification of optimum heat treatment parameters for chrome-molybdenum steel welded joints. A few key issues are addressed herein: identification of dependence of chrome-molybdenum (5%Cr-0.5%Mo) steel welded joint mechanical properties on heat treatment parameters, identification of the optimum value of temperature/time parameter, and identification of causes of mechanical property changes and degradation of the steel.

Abstract: The cracking sensitivity of weldments in electron beam welded (EBW) Rene 41 with Incoloy 907 superalloy was studied under various welding and post-weld heat treatment condition. The results revealed that the optimum heat input for the weldments was about 714 J/cm. The weldments exhibited relatively higher cracking sensitivity when the post-weld heat treatments were carried out at 760°C for 16hrs. In this case, the carbides in the grain boundaries commonly distributed as thin film. It is found that the lower heating rate is favor to the formation of thin carbide film, which results in the increased cracking sensitivity in the heat affected zone (HAZ). When the weldments were heated at 950°C for 12h followed with furnace cooling to 620°Cand holding for 12hrs, then air cooling to room temperature, no cracks were observed in the HAZ of Rene 41. In this case, the carbides precipitated as stagger and refined granules in the grain boundaries. When the heat treatment temperature was up to 1040°C, some overfiring cracks occurred on the grain boundary of HAZ.

Abstract: The effects of post-weld heat treatment on 3.05-mm thick Ti-6Al-4V alloy were investigated using a 4 kW Nd:YAG laser. Two main defects, underfill and porosity, were observed. The use of filler wire reduced underfill defects but slightly increased porosity. No cracks were detected. The as-welded and stress-relief annealed welds had very similar microstructures, hardness, and tensile properties. However, the post-weld solution heat treatment and aging transformed the martensite in the fusion zone into a coarse interlamellar α-β structure, causing a decrease in ductility but a more homogeneous distribution in the hardness of the welds.