Prachya Peasura

Effect of Resistance Spot Welding Parameters on the Austenitic Stainless Steel 304 Grade by Using 23 Factorial Design

This research was study the effect of resistance spot welding process on physical properties. The specimen was austenitic stainless steel sheet of 1 mm. The experiments with 23 factorial design. The factors used in this study are welding current at 8,000 and 12,000 Amp, welding time at 8 and 12 cycle and electrode force were set at 1.5 and 2.5 kN. The welded specimens were tested by tensile shear testing according to JIS Z 3136: 1999 and macro structure testing according to JIS Z 3139: 1978. The result showed that the welding current, welding time and electrode force had interaction on tensile shear and nugget size at 95% confidential (P value < 0.05). Factors affecting the tensile shear are the most welding current of 12,000 amp., welding time of 8 cycle and electrode force of 2.5 kN. were tensile shear of 9.83 kN. The nugget size was maximum at 7.15 mm. on welding current of 12,000 amp., welding time of 12 cycle and electrode force of 1.5 kN This research can bring information to the foundation in choosing the appropriate parameters to resistance spot welding process.

Application of Response Surface Methodology for Modeling of Postweld Heat Treatment Process in a Pressure Vessel Steel ASTM A516 Grade 70.

This research studied the application of the response surface methodology (RSM) and central composite design (CCD) experiment in mathematical model and optimizes postweld heat treatment (PWHT). The material of study is a pressure vessel steel ASTM A516 grade 70 that is used for gas metal arc welding. PWHT parameters examined in this study included PWHT temperatures and time. The resulting materials were examined using CCD experiment and the RSM to determine the resulting material tensile strength test, observed with optical microscopy and scanning electron microscopy. The experimental results show that using a full quadratic model with the proposed mathematical model is Y TS = −285.521 + 15.706X 1 + 2.514X 2 − 0.004X 1 2 − 0.001X 2 2 − 0.029X 1 X 2. Tensile strength parameters of PWHT were optimized PWHT time of 5.00 hr and PWHT temperature of 645.75°C. The results show that the PWHT time is the dominant mechanism used to modify the tensile strength compared to the PWHT temperatures. This phenomenon could be explained by the fact that pearlite can contribute to higher tensile strength. Pearlite has an intensity, which results in increased material tensile strength. The research described here can be used as material data on PWHT parameters for an ASTM A516 grade 70 weld.

Investigation into the influence of post-weld heat treatment on the microstructure and hardness of Inconel X-750

This work describes a post-weld heat treatment for a precipitation-hardened nickel alloy. Inconel X-750 is a nickel-based superalloy for gas tungsten arc welding processes. The materials were heat-treated in two steps: solution and aging. The post-weld heat treatment variables examined in this study included post-weld heat treatment temperatures of 705°C, 775°C, and 845°C and post-weld heat treatment time of 2–24 h in 2-h increments. The resulting materials were examined using the full factorial design of experiments to determine the resulting material hardness and observed with optical microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy in the fusion zone and heat-affected zone. The results show that a longer post-weld heat treatment time corresponds to larger γ′ precipitates and a smaller amount of Cr23C6 at the grain boundaries, which can decrease the overall hardness. The post-weld heat treatment analysis indicates that an increase in the amount of γ′ results in better mechanical properties for particles with octagonal shapes and a small size. A factorial analysis, which was conducted on the relationship between the post-weld heat treatment temperature and time to the hardness of the fusion zone, had a 95% confidence level.

Effect of Post Weld Heat Treatment on Fusion and Heat Affected Zone Microstructure and Mechanical Properties of Inconel X-750 Welds

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.

Modelling and optimisation of the post-weld heat treatment of γ′ precipitation and hardness on Inconel X-750 using the response surface methodology

This work describes a post-weld heat treatment (PWHT) for Inconel X-750. The following PWHT variables were examined: the solution temperature, PWHT temperature, and PWHT time. In this research, the application of the response surface methodology and Box-Behnken design in a mathematical model was investigated and optimised. The resulting materials were examined using optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM) in the fusion zone (FZ). The experimental results reveal that using a full quadratic model with the proposed mathematical model of the γ′ precipitation size and γ′ hardness in the FZ, the obtained correlation of the hardness and γ′ precipitate size showed a reasonable linear relationship.

Effect of Post Weld Heat Treatment on Carbon Steel AISI 1050 in Heat Effected Zone

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.

The Influence of Welding Parameters on Effected the Complete for Resistance Spot Welding on Mild Steel

This research was study the effect of resistance spot welding process on physical properties. The specimen was mild steel sheet metal. The experiments with full factorial design. The factors used in this study are welding current, welding time and electrode force. The welded specimens were tested by tensile shear testing according to JIS Z 3136: 1999 and macro structure testing according to JIS Z 3139: 1978. The result showed that both of welding current, welding time and electrode force had interaction on tensile shear and nugget size at 95% confidential (P value < 0.05). Factors affecting the tensile shear and nugget size are the most welding current 10,000 amp., welding time 10 cycle and electrode force 1 kN. were tensile shear 7.13 kN. and nugget size maximum 6.75 mm. This research can bring information to the foundation in choosing the appropriate parameters to resistance spot welding process.

Synthesis of Closed Cell Aluminum Foam Using the Compression Method

This research was to study the synthesis of aluminum foam with pure aluminum and its mechanical properties. The synthesis varied at 1% - 5% of TiH2 and mixed with 99.7 % aluminum powder size of 44 µm. then compressed by hydraulic at 25, 30 and 35 tons in the diameter 27 mm, high 60 mm molded. The Aluminum foams were produced by using heat treatment at 800 °C for 10 minutes then cool to room temperature and tested its mechanical properties. The results showed that aluminum foams which lowest bulk density (0.958 g/cm3) was 2% TiH2 synthesized, compressed at 35 tons and highest bulk density (1.393 g/cm3) was 1% TiH2 synthesized, compressed at 25 tons. Moreover, the highest compressive strength (847 kg/cm2) showed at 2% TiH2 synthesized and compressed at 35 tons. Thus, this research contributes to a body of knowledge that informs the application of aluminum foam.

Experiment Design with Full Factorial in Gas Tungsten Arc Welding Parameters on Aluminium Alloy 5083

This research was to study of gas tungsten arc welding (GTAW) welding parameters that affects to the mechanical properties of aluminum alloy AA5083 welding with GTAW. The full factorial design was experiment. The factors was study in type of polarity on alternating current (AC), direct current electrode negative (DCEN) and direct current electrode positive (DCEP), levels of welding current for 180,200,220 and 240 amp. The specimen to analyses the physical properties has microstructure and hardness of weld metal and heat affected zone. The result showed that type of welding current and levels of welding current interaction hardness at the level of confidence 95% (P-value<0.05). The factor hardness maximum of weld metal was alternating current at level of current 240 amp. and hardness of 136.53 HV. The factor hardness maximum of HAZ value was alternating current at level of welding 220 amp. and hardness of 169.43 HV. The welding parameters can result in increasing Mg2Si intensity in parent phase. It can also be observed that Mg2Si at the parent phase decreased due to high welding current in HAZ.This research can be used as information in choosing how to welding parameter for gas tungsten arc welding of aluminum alloy.

Application of Full Factorial Design for Post Weld Heat Treatment Parameters on Duplex Stainless Steel UNS31803

In this research, the post weld heat treatment (PWHT) of duplex stainless steel (DSS) was study. The PWHT process can be affected by differing parameters. The specimen was duplex stainless steel UNS31803 grade sheet of 10 mm thickness. The PWHT parameters were analyzed by application of full factorial design. The factors used in this study were PWHT temperature of 650, 750, and 850 ๐C with PWA time of 1, 2, 4 and 8 hours. The welded specimens were tested with micro vickers hardness and ferrite content testing according to ASTM E3-11 code. The result showed that both of PWHT temperature and PWHT time interaction on hardness and ferrite content for 95% confidential (P value < 0.05). The factor in most effect of hardness was the PWHT temperature of 850๐C and PWHT time for 4 hour at the hardness of 277.73 HV. The ferrite was the most ferrite content for 77.39% resulted in corrosion resistance due to suitable of PWHT temperature 750 ๐C and PWHT time for 8 hour. Finally, form PWHT process with the information was used choosing the appropriate for PWHT parameters to duplex stainless steel welds.