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Article
Publication date: 1 October 2018

Tunde Isaac Ogedengbe, Taiwo Ebenezer Abioye and Augusta Ijeoma Ekpemogu

The purpose of this study is to conduct gas tungsten arc dissimilar welding of AISI 304 stainless steel and low carbon steel within a process window so as to investigate…

Abstract

Purpose

The purpose of this study is to conduct gas tungsten arc dissimilar welding of AISI 304 stainless steel and low carbon steel within a process window so as to investigate the effects of current, speed and gas flow rate (GFR) on the microstructure and mechanical properties of the weldments.

Design/methodology/approach

The welding experiment was carried out at different combinations of parameters using WN-250S Kaierda electric welding machine. A combination of scanning electron microscopy and energy dispersive X-ray spectroscopy was used to examine the microstructure of the weldments. Micro-hardness and tensile tests were performed using Vickers hardness tester and Instron universal testing machine, respectively. ANOVA was used to analyze the significance of the parameters on the mechanical properties.

Findings

The microstructure of the weld region is characterized with dendritic structure with the existence of ferrite and austenite phases. The utilized parameters show significant effects on the ultimate tensile strength (UTS) of the weldments. The current and GFR were found to be the most and least significant factors, respectively. Both the grain size and weld penetration contributed to the UTS of the weldments. The UTS (427-886 MPa) increased with decreasing current and welding speed. In all samples, the weld region exhibited higher hardness (297-396 HV) than the HAZ in the base metals (maximum of 223 Â ± 6 HV). All the three factors show significant effect with the welding speed contributing mostly to the hardness of the weld region.

Originality/value

The parametric combination that gives the optimum mechanical performance of the dissimilar gas tungsten arc weldments of AISI 304 stainless steel and low carbon steel was established.

Details

World Journal of Engineering, vol. 15 no. 5
Type: Research Article
ISSN: 1708-5284

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Article
Publication date: 11 December 2018

Somrerk Chandra-Ambhorn, Sompong Chueaprakha and Thamrongsin Siripongsakul

The dissimilar welds between AISI 304L and Fe-15.6Cr-8.5Mn were investigated on oxidation at 700°C with the effects of dissolved nitrogen in the welds. This paper aims to…

Abstract

Purpose

The dissimilar welds between AISI 304L and Fe-15.6Cr-8.5Mn were investigated on oxidation at 700°C with the effects of dissolved nitrogen in the welds. This paper aims to clarify the oxidation behaviors to expand the range of application for Fe-Cr-Mn stainless steel.

Design/methodology/approach

Dissimilar welds between AISI 304L and Fe-15.6Cr-8.5Mn were fabricated using gas tungsten arc welding to investigate the oxidation behavior of the welds at 700°C. Pure Ar and Ar-4%N2 shielding gases were used to evaluate the effects of nitrogen gas. The welds were introduced to the cyclic oxidation test. In each cycle, the furnace was heated up to 700°C, and the temperature was kept at 700°C for 8 h, then the mass gain because of oxidation was examined. The scales after oxidation test were investigated by using scanning electron microscopy with EDX and X-ray diffraction analysis.

Findings

Addition of 4 per cent nitrogen to Ar shielding gas reduced delta-ferrite content in the weld. Ar-4%N2 shielding gas resulted in dissolved nitrogen which helped increase the diffusivities of chromium or oxygen vacancies in the oxide to facilitate the chromia formation at the inner part near the steel substrate. This protective layer can help reduce the Fe outward diffusion, thus reducing mass gain because of iron oxide formation.

Originality/value

The oxidation behavior of dissimilar welds between AISI 304L and Fe-15.6Cr-8.5Mn were investigated at 700°C. The evaluation is beneficial for expanding the range of application of Fe-Cr-Mn stainless steel at high temperature.

Details

Anti-Corrosion Methods and Materials, vol. 66 no. 2
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 18 November 2019

Vinoth Kumar M. and Balasubramanian V.

Super 304HCu super austenitic stainless steel tubes containing 2.3 to 3 (Wt.%) of copper (Cu) is used in superheaters and reheater tubings of nuclear power plants. In…

Abstract

Purpose

Super 304HCu super austenitic stainless steel tubes containing 2.3 to 3 (Wt.%) of copper (Cu) is used in superheaters and reheater tubings of nuclear power plants. In general, austenitic stainless steels welded by conventional constant current gas tungsten arc welding (CC-GTAW) produce coarse columnar grains, alloy segregation and may result in inferior mechanical properties. Pulsed current gas tungsten arc welding (PC-GTAW) can control the solidification structure by altering the prevailing thermal gradients in the weld pool.

Design/methodology/approach

Super 304HCu tubes of Ø 57.1 mm and the wall thickness of 3.5 mm were autogenously welded using CC and PC-GTAW processes. Joints are characterized using optical microscopy, electron microscopy, energy dispersive spectroscopy and electron backscatter diffraction (EBSD) techniques. Hot tensile properties of the weld joints were evaluated and correlated with their microstructural features.

Findings

Current pulsing in GTAW has resulted in minimal eutectic film segregation, lower volume % of delta ferrite and appreciable improvement in tensile properties than CC-GTAW joints.

Originality/value

The EBSD boundary map and inverse pole orientation map of Super 304HCu weld joints evidence the grain refinement and much frequent high angle grain boundaries achieved using weld current pulsing.

Details

World Journal of Engineering, vol. 16 no. 6
Type: Research Article
ISSN: 1708-5284

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Article
Publication date: 29 June 2010

S.N. Santillan, S.B. Valdez, W.M. Schorr, R.A. Martinez and S.J. Colton

The purpose of this paper is to investigate the corrosion of the heat‐affected zone (HAZ) and weld zone of austenitic stainless steels that have been welded using two…

Abstract

Purpose

The purpose of this paper is to investigate the corrosion of the heat‐affected zone (HAZ) and weld zone of austenitic stainless steels that have been welded using two different processes. The corrosion behavior is evaluated in synthetic seawater using the electrochemical polarization technique.

Design/methodology/approach

Welded and unwelded UNS S30403 specimens were welded by flux core arc, and gas tungsten arc welding (GTAW) techniques. The test equipment consisted of an electrochemical three‐electrode cell using synthetic seawater as the corrosive medium. The scan rate was 10 mV/s and the potential range was −500‐500 mV vs saturated calomel electrode. The pH for the synthetic seawater was around seven. The electrochemical tests were performed after 1, 2, 3, and, 11 weeks. The metal surface was characterized by examination using an inverted microscope and scanning electron microscopy.

Findings

The polarization measurements of the flux core arc welding‐HAZ showed a high corrosion susceptibility, while GTAW‐HAZ presented good corrosion performance.

Practical implications

With the application and correct interpretation of this electrochemical technique, designers, welding engineers, and manufactures can access important information and take correct decisions regarding welding processes to meet corrosion resistance requirements.

Originality/value

The methodology and approach of interpreting the polarization plots used in this research can be applied to study other welding techniques and different welded metals in specific corrosive media, which will be of value to the welding industry.

Details

Anti-Corrosion Methods and Materials, vol. 57 no. 4
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 8 March 2010

Bo Chen, Jifeng Wang and Shanben Chen

Welding sensor technology is the key technology in welding process, but a single sensor cannot acquire adequate information to describe welding status. This paper…

Abstract

Purpose

Welding sensor technology is the key technology in welding process, but a single sensor cannot acquire adequate information to describe welding status. This paper addresses arc sensor and sound sensor to acquire the voltage and sound information of pulsed gas tungsten arc welding (GTAW) simultaneously, and uses multi‐sensor information fusion technology to fuse the information acquired by the two sensors. The purpose of this paper is to explore the feasibility and effectiveness of multi‐sensor information fusion in pulsed GTAW.

Design/methodology/approach

The weld voltage and weld sound information are first acquired by arc sensor and sound sensor, then the features of the two signals are extracted, and the features are fused by weighted mean method to predict the changes of arc length. The weights of each feature are determined by optional distribution method.

Findings

The research findings show that multi‐sensor information fusion technology can effectively utilize the information of different sensors and get better result than single sensor.

Originality/value

The arc sensor and sound sensor are first used at the same time to get information about pulsed GTAW and the fusion result shows its advantages over single sensor; this reveals that multi‐sensor fusion technology is a valuable research area in welding process.

Details

Industrial Robot: An International Journal, vol. 37 no. 2
Type: Research Article
ISSN: 0143-991X

Keywords

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Article
Publication date: 26 June 2009

Bo Chen, Jifeng Wang and Shanben Chen

Welding process is a complicated process influenced by many interference factors, a single sensor cannot get information describing welding process roundly. This paper…

Abstract

Purpose

Welding process is a complicated process influenced by many interference factors, a single sensor cannot get information describing welding process roundly. This paper simultaneously uses different sensors to get different information about the welding process, and uses multi‐sensor information fusion technology to fuse the different information. By using multi‐sensors, this paper aims to describe the welding process more precisely.

Design/methodology/approach

Electronic and welding pool image information are, respectively, obtained by arc sensor and image sensor, then electronic signal processing and image processing algorithms are used to extract the features of the signals, the features are then fused by neural network to predict the backside width of weld pool.

Findings

Comparative experiments show that the multi‐sensor fusion technology can predict the weld pool backside width more precisely.

Originality/value

The multi‐sensor fusion technology is used to fuse the different information obtained by different sensors in a gas tungsten arc welding process. This method gives a new approach to obtaining information and describing the welding process.

Details

Sensor Review, vol. 29 no. 3
Type: Research Article
ISSN: 0260-2288

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Article
Publication date: 1 May 2009

J.F. Wang, W.Y. Wang and S.B. Chen

The control of weld penetration in gas tungsten‐arc welding (GTAW) is required for fully automated systems to overcome variations in the welding process. The surface…

Abstract

Purpose

The control of weld penetration in gas tungsten‐arc welding (GTAW) is required for fully automated systems to overcome variations in the welding process. The surface depression of weld pool, or weld pool height, has a close relationship with width of the backside bead in the full‐penetrated weld. The purpose of this paper is to inspect the pool height.

Design/methodology/approach

A fast linear approach, based on shape from shading (SFS) algorithm, was employed to reconstruct a 3D shape of welding pool from a 2D image, which was obtained from a real welding pool. Then the pool height can be extracted. Furthermore, three methods were introduced to improve the above algorithm.

Findings

The reconstructed pool height was in good agreement with the real height of weld pool from experiments.

Research limitations/implications

The algorithm requires a uniform reflection on the pool surface.

Practical implications

This method is applicable to inspect weld pool height in GTAW. It is a basis for future work on control of weld penetration.

Originality/value

A faster SFS algorithm has been introduced to extract weld pool height in real‐time. Moreover, the algorithm was improved to fit for extracting the surface shape of weld pool.

Details

Industrial Robot: An International Journal, vol. 36 no. 3
Type: Research Article
ISSN: 0143-991X

Keywords

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Article
Publication date: 19 February 2013

M. Dewan, J. Liang, M. Wahab and A. Okeil

Heat-treatable AA-6061-T651 Aluminum alloys (Al-Mg-Si) have found considerable importance in structural and aerospace applications for their high strength to weight ratio…

Abstract

Heat-treatable AA-6061-T651 Aluminum alloys (Al-Mg-Si) have found considerable importance in structural and aerospace applications for their high strength to weight ratio and improved corrosion resistance properties. Intrinsic weld defects, post-weld residual stresses, and microstructural changes are the key factors for performance reductions and failures of welded structures. Gas-Tungsten-Arc-Welding (TIG/GTAW) was carried out on AA-6061-T651 plates with Argon/Helium (50/50) as the shielding gases. Non-destructive Phased-Array-Ultrasonic-Testing (PAUT) was applied for the detection and characterization of weld defects and mechanical performances. Ultrasonic technique was used for the evaluation of post-weld residual stresses in welded components. The approach is based on the acoustoelastic effect, in which ultrasonic wave propagation speed corresponds to the magnitude of stresses present within the materials. To verify the PAUT's residual stress results, a semi-destructive hole-drilling technique was used; and observed analogous results. The effects of post-weld-heat-treatment (PWHT) on the residual stresses, grain size, micro-hardness, and tensile properties are also studied. The grain size and micro-hardness values are studied through Heyn's method and Vickers hardness test, respectively. Lower residual stresses are observed in post-weld heat-treated specimens, which are also confirmed from microstructural and micro-hardness studies. The PWHT enhanced tensile properties for the redistribution of microstructures and residual stresses.

Details

World Journal of Engineering, vol. 10 no. 1
Type: Research Article
ISSN: 1708-5284

Keywords

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Abstract

Purpose

Traditional gas tungsten arc welding (GTAW) and GTAW-based wire and arc additive manufacturing (WAAM) are notably different. These differences are crucial to the process stability and surface quality in GTAW WAAM. This paper addresses special characteristics and the process control method of GTAW WAAM. The purpose of this paper is to improve the process stability with sensor information fusion in omnidirectional GTAW WAAM process.

Design/methodology/approach

A wire feed strategy is proposed to achieve an omnidirectional GTAW WAAM process. Thus, a model of welding voltage with welding current and arc length is established. An automatic control system fit to the entire GTAW WAAM process is established using both welding voltage and welding current. The effect of several types of commonly used controllers is examined. To assess the validity of this system, an arc length step experiment, various wire feed speed experiments and a square sample experiment were performed.

Findings

The research findings show that the resented wire feed strategy and arc length control system can effectively guarantee the stability of the GTAW WAAM process.

Originality/value

This paper tries to make a foundation work to achieve omnidirectional welding and process stability of GTAW WAAM through wire feed geometry analysis and sensor information fusion control model. The proposed wire feed strategy is implementable and practical, and a novel sensor fusion control method has been developed in the study for varying current GTAW WAAM process.

Details

Rapid Prototyping Journal, vol. 25 no. 5
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 10 August 2012

De‐Xing Peng

The purpose of this paper is to test whether TiC clad layer deposited on carbon steel by gas tungsten arc welding (GTAW) improves carbon steel substrate wear resistance.

Abstract

Purpose

The purpose of this paper is to test whether TiC clad layer deposited on carbon steel by gas tungsten arc welding (GTAW) improves carbon steel substrate wear resistance.

Design/methodology/approach

Cladding microstructure and cladded surface hardness were tested in samples prepared under varying welding parameters. The chemical composition, microstructure and surface morphology of the cladded layer were analyzed by optical microscope, scanning electron microscopy and energy dispersive X‐ray spectroscopy. The wear behavior of the cladded layer was studied with a block‐on‐ring tribometer. Wear mechanisms in the specimens are discussed based on microscopic study of wear surface characteristics.

Findings

The experimental results revealed an excellent metallurgical bond between the composite coating and substrate. Hardness was increased from HRb 6.6 in the substrate to HRb 65 in the modified layer due to the presence of the hard TiC phase. Experimental comparison of varying welding parameters revealed that welding speed and current had the largest effect on the hardness and wear resistance of the cladded layer.

Originality/value

The paper shows that by using cladding techniques to improve surface properties such as resistances to wear, corrosion, and oxidation, service life can be increased, and machinery costs can be reduced.

Details

Industrial Lubrication and Tribology, vol. 64 no. 5
Type: Research Article
ISSN: 0036-8792

Keywords

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