Research

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20 pages, 6021 KiB

Open AccessArticle

Optimization of GMAW Process Parameters in Ultra-High-Strength Steel Based on Prediction

by Alnecino Netto, Francois Miterand Njock Bayock and Paul Kah

Metals 2023, 13(8), 1447; https://doi.org/10.3390/met13081447 - 11 Aug 2023

Cited by 3 | Viewed by 967

Ultra-high-strength steel (UHSS) is a complex and sophisticated material that allows the development of products with reduced weight but increased strength and can assist, for example, in the automotive industry, saving fuel in vehicles and decreasing greenhouse gas emissions. Welding UHSS has a [...] Read more.

Ultra-high-strength steel (UHSS) is a complex and sophisticated material that allows the development of products with reduced weight but increased strength and can assist, for example, in the automotive industry, saving fuel in vehicles and decreasing greenhouse gas emissions. Welding UHSS has a certain complexity, mainly due to the higher alloys and heat treatments involved, which can result in a microstructure with higher sensitivity to welding. The primary purpose of the current work was to select the best parameters of the gas metal arc welding (GMAW) for welding the S960 material based on prediction methods. To achieve the expected results, a finite element analysis (FEA) was used to simulate and evaluate the results. It was found that the welding parameters and, consequently, the heat input derived from the process greatly affected the UHSS microstructure. Using FEA and estimating the extension of the heat-affected zone (HAZ), the peak temperature, and even the effect of distortion and shrinkage was possible. With an increase in the heat input of 8.4 kJ/cm, the estimated cooling rate was around 70 °C/s. The presence of a softening area in the coarse grain heat-affected zone (CGHAZ) of welded joints was identified. These results led to an increase in the carbon content (3.4%) compared to the base metal. These results could help predict behaviors or microstructures based on a few changes in the welding parameters. Full article

(This article belongs to the Special Issue Welding and Joining of Advanced High-Strength Steels)

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18 pages, 6117 KiB

Open AccessArticle

Test on Compressive Performance of Hollow Concrete-Filled Sandwich Circular Steel Tubes Connected by Thread

by Qingli Wang, Jie Zhao and Kuan Peng

Metals 2023, 13(7), 1207; https://doi.org/10.3390/met13071207 - 29 Jun 2023

Viewed by 928

Abstract

The connection method of lengthening the steel tube of hollow concrete-filled sandwich circular steel tubes and threaded connections is proposed. The length, depth and position are the basic parameters. Twelve hollow concrete sandwich circular steel pipes with threaded connections were designed and subjected [...] Read more.

The connection method of lengthening the steel tube of hollow concrete-filled sandwich circular steel tubes and threaded connections is proposed. The length, depth and position are the basic parameters. Twelve hollow concrete sandwich circular steel pipes with threaded connections were designed and subjected to axial compression tests. The axial compressive loading–longitudinal compressive displacement curves, axial compressive loading strain of steel tube curves and failure mode of the specimens are analyzed, and the effects of different parameters on the axial compressive-bearing capacity and stiffness of the specimens are studied. The results showed that within the range of parameters studied, the axial compression load–longitudinal compression displacement curves of the specimens were the linear elastic stage and the elastic–plastic stage, which can be divided into a yield-strengthening stage and a decreasing stage. The bearing capacity and strength of the lined threaded connection specimen are not inferior to those of the ordinary specimen or the welded specimen. The bearing capacity and strength of the specimen increase with the increase of the thread length. The bearing capacity and strength of the specimens connected with inner liner screws at the ends are higher than those connected with inner liner bolts at the middle. Full article

(This article belongs to the Special Issue Welding and Joining of Advanced High-Strength Steels)

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12 pages, 3312 KiB

Open AccessArticle

Effects of PWHT on the Residual Stress and Microstructure of Bisalloy 80 Steel Welds

by Houman Alipooramirabad, Anna Paradowska, Mark Reid and Reza Ghomashchi

Metals 2022, 12(10), 1569; https://doi.org/10.3390/met12101569 - 21 Sep 2022

Cited by 7 | Viewed by 1877

Abstract

Quenched and tempered (Q & T) steels have numerous applications, particularly in the defence industry with welding as the main fabrication route. Since welding imparts stresses due to thermal gradients development during welding, plus the fact that the Q & T fabricated structures [...] Read more.

Quenched and tempered (Q & T) steels have numerous applications, particularly in the defence industry with welding as the main fabrication route. Since welding imparts stresses due to thermal gradients development during welding, plus the fact that the Q & T fabricated structures are expected to function in a complex loading environment, it is critically important to relax the welding stresses before exposing the parts to service conditions. The present study reports on the generated residual stresses when Bisalloy 80 is welded by pulsed gas metal arc welding (GMAW-P) and verifies the effects of post-weld heat treatment (PWHT) on the microstructural changes, removal or reduction of residual stresses and the resulting mechanical properties of the welded Q & T steel joints. Neutron diffraction was utilized to measure the residual stresses in the as-welded and after PWHT of the Bisalloy 80 steel weldments. High levels of tensile residual stresses reaching to the yield strength of the weld metal were present (642 ± 24 MPa) in the as-welded joints but were substantially reduced after PWHT (145 MPa ± 21 MPa, which is ~23% of the yield strength of the weld metal). PWHT led to microstructural changes in different regions of the parent and weld metals, including the formation of coarsened polygonal ferrite grains and bainitic ferrite laths. This finding is in line with hardness measurements, where hardness reductions were evident in the heat-affected zone (HAZ) and the weld metal (WM) of the heat-treated specimens. Full article

(This article belongs to the Special Issue Welding and Joining of Advanced High-Strength Steels)

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20 pages, 4372 KiB

Open AccessArticle

Low-Temperature Deformation Mechanism and Strain-Hardening Behaviour of Laser Welded Dual-Phase Steels

by Isiaka Aderibigbe, Patricia Popoola, Emmanuel Sadiku and Elliot Biro

Metals 2022, 12(8), 1317; https://doi.org/10.3390/met12081317 - 05 Aug 2022

Cited by 1 | Viewed by 1624

Abstract

This paper analysed the change in microstructure after laser welding DP800 and DP1000, the effect of the laser welds on low temperatures deformation, and strain hardening behaviour when loaded at temperatures between −40 °C and 20 °C using quasi-static strain rates (1.7 × [...] Read more.

This paper analysed the change in microstructure after laser welding DP800 and DP1000, the effect of the laser welds on low temperatures deformation, and strain hardening behaviour when loaded at temperatures between −40 °C and 20 °C using quasi-static strain rates (1.7 × 10⁻² s⁻¹). The results showed that the fusion zone (FZ) was fully martensitic due to the rapid cooling during welding. Owing to the severity of the heat-affected zone, the joint efficiencies of DP800-DP800 and DP1000-DP1000 welds were 99.0% and 88.7%, respectively. The UTS, YS, and work hardening exponents of the welded joints increased slightly, while the strain hardening capacity of the base metals was much higher than those of the welded joints with decreasing temperatures. The evaluated work hardening exponents of the welded joints were determined using the Hollomon equation, Afrin equation, and Crussard-Jaoul analysis are in the range of 0.2–0.47, 0.24–0.59, and 0.45–0.71, respectively. The welded joints and the base metals demonstrated only stage III strain hardening, with DP800 joints exhibited excellent uniform and total elongation ranging between 8.0–8.7% and 10.4–14.2%, respectively. Fractures were located in the base metal of welded DP800 and SCHAZ of DP1000 welds, respectfully. The fracture surfaces demonstrated characteristic dimple fractures. The uniqueness of this study is found in its design, as there is currently no known literature on the low-temperature deformation mechanism and strain-hardening behaviour of similar DP800 and DP1000 welds. Full article

(This article belongs to the Special Issue Welding and Joining of Advanced High-Strength Steels)

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14 pages, 6240 KiB

Open AccessArticle

On the Measurability and Predictability of HAZ Softening in GMAW of Automotive DP980 Steel

by Cecilio J. Martínez-González, Enrique A. López-Baltazar, Francisco Alvarado-Hernández, Víctor H. Baltazar-Hernández, Dulal C. Saha, Elliot Biro and Norman Zhou

Metals 2022, 12(6), 1009; https://doi.org/10.3390/met12061009 - 14 Jun 2022

Viewed by 1248

Abstract

Dual Phase (DP) steel, composed of a ferrite matrix with dispersed islands of martensite, has become popular in auto-body car construction due to its outstanding mechanical properties (i.e., high strength and good ductility). DP steel softens at the sub-critical heat-affected zone (SC-HAZ) when [...] Read more.

Dual Phase (DP) steel, composed of a ferrite matrix with dispersed islands of martensite, has become popular in auto-body car construction due to its outstanding mechanical properties (i.e., high strength and good ductility). DP steel softens at the sub-critical heat-affected zone (SC-HAZ) when subjected to welding thermal cycles, owing to the tempering of the martensite phase. In this work, DP980 steel was subjected to varied thermal cycles: (a) furnace-tempering treatment, (b) gas metal arc welding (GMAW), and (c) resistance spot welding (RSW), in order to characterize the tempering of martensite below the Ac₁ critical temperature and at the sub-critical heat-affected zone (SC-HAZ) in the case of the welded specimens. The coarsening stage of cementite phase was characterized through microstructure observations and hardness measurements. As expected, the comparative results indicated an advanced stage of the martensite tempering in the furnace heat-treated specimens, followed by the GMAW and the RSW specimens. Further, developed softening kinetic models have been suitably employed and adjusted in order to predict the extent of softening along the SC-HAZ of the GMAW specimen. Finally, as the advanced stage of cementite coarsening is due to the influence of the arc welded thermal cycle, a reasonable estimation of the hardness profile was obtained, particularly for tempering temperatures above 400 °C. Full article

(This article belongs to the Special Issue Welding and Joining of Advanced High-Strength Steels)

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16 pages, 7679 KiB

Open AccessArticle

Surface Residual Stress Analysis in GMAW and LBW of the Dissimilar TRIP-DP Steels Joint: An Experimental Approach

by Víctor H. Baltazar-Hernández, Enrique A. López-Baltazar, Francisco Alvarado-Hernández, Salvador Gómez-Jiménez, José Jorge Ruiz-Mondragón, Elliot Biro and Norman Zhou

Metals 2022, 12(5), 880; https://doi.org/10.3390/met12050880 - 23 May 2022

Cited by 2 | Viewed by 1801

Abstract

A transformation-induced plasticity (TRIP) steel and a dual-phase (DP) steel were paired together by employing gas metal arc welding (GMAW) and laser beam welding (LBW) processes. The post-weld microstructure, the hardness profile, and the uniaxial tensile behavior of the welded steels have been [...] Read more.

A transformation-induced plasticity (TRIP) steel and a dual-phase (DP) steel were paired together by employing gas metal arc welding (GMAW) and laser beam welding (LBW) processes. The post-weld microstructure, the hardness profile, and the uniaxial tensile behavior of the welded steels have been analyzed in detail. The experimental surface residual stress distribution across the weldment was measured through the X-ray diffraction sin²Ψ technique. The results indicate that although a harder microstructure composed of predominant martensite was observed along the weldment, the uniaxial tensile behavior resulted in better elongation properties and a higher UTS in the LBW specimen as compared to the GMAW specimen. The resultant residual stress distribution in the heat-affected zone (HAZ) had an increase to a maximum value, followed by a steady decrease up to the base metal following the trend: upper-critical UC-HAZ (maximum) → inter-critical IC-HAZ (moderated) → subcritical SC-HAZ (lowered), which was particularly more evident on the GMAW specimen. Overall, the resultant residual stresses along the weldment were lower on the LBW specimen (172 MPa maximum) which clearly contrasts to the GMAW specimen (421 MPa maximum). Finally, the tensile residual stresses in both the GMAW or LBW did not influence the overall tensile properties of the weldments. Full article

(This article belongs to the Special Issue Welding and Joining of Advanced High-Strength Steels)

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13 pages, 6365 KiB

Open AccessArticle

Influence of Inclusions on Mechanical Properties in Flash Butt Welding Joint of High-Strength Low-Alloy Steel

by Shih-Chen Shi, Wei-Cheng Wang and Dun-Kai Ko

Metals 2022, 12(2), 242; https://doi.org/10.3390/met12020242 - 27 Jan 2022

Cited by 8 | Viewed by 3263

Abstract

Flash butt welding is a high-efficiency welding technology that is widely used in industrial development. However, the inclusions and defects generated during the process are unacceptable. The presence of inclusions is one of the main factors affecting the quality of flash butt welding. [...] Read more.

Flash butt welding is a high-efficiency welding technology that is widely used in industrial development. However, the inclusions and defects generated during the process are unacceptable. The presence of inclusions is one of the main factors affecting the quality of flash butt welding. Suitable flash butt welding parameters such as the preheating temperature and upset distance are essential to eliminate inclusions. In this study, because the number of inclusions on the end face is greatly affected by the flash welding time and upset distance, the impact of different upset distances on the number of inclusions was studied by fixing the flash welding time. Further observations were conducted using a scanning electron microscope. Image analysis software was used on the obtained photos to quantitatively analyze the inclusions on the welding surface. A statistical analysis of the experimental data showed that the upset distance was related to the number of inclusions, and the total number of inclusions on the welding surface had a negative impact on the strength of the product. Full article

(This article belongs to the Special Issue Welding and Joining of Advanced High-Strength Steels)

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Review

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32 pages, 6047 KiB

Open AccessReview

Advanced High-Strength Steels for Automotive Applications: Arc and Laser Welding Process, Properties, and Challenges

by Ashok Kumar Perka, Merbin John, Udaya Bhat Kuruveri and Pradeep L. Menezes

Metals 2022, 12(6), 1051; https://doi.org/10.3390/met12061051 - 20 Jun 2022

Cited by 22 | Viewed by 5697

Abstract

In recent years, the demand for advanced high-strength steel (AHSS) has increased to improve the durability and service life of steel structures. The development of these steels involves innovative processing technologies and steel alloy design concepts. Joining these steels is predominantly conducted by [...] Read more.

In recent years, the demand for advanced high-strength steel (AHSS) has increased to improve the durability and service life of steel structures. The development of these steels involves innovative processing technologies and steel alloy design concepts. Joining these steels is predominantly conducted by following fusion welding techniques, such as gas metal arc welding, tungsten inert gas welding, and laser welding. These fusion welding techniques often lead to a loss of mechanical properties due to the weld thermal cycles in the heat-affected zone (HAZ) and the deposited filler wire chemistry. This review paper elucidates the current studies on the state-of-the-art of weldability on AHSS, with ultimate strength levels above 800 MPa. The effects of alloy designs on the HAZ softening, microstructure evolution, and the mechanical properties of the weld joints corresponding to different welding techniques and filler wire chemistry are discussed. More specifically, the fusion welding techniques used for the welding of AHSS were summarized. This review article gives an insight into the issues while selecting a particular fusion welding technique for the welding of AHSS. Full article

(This article belongs to the Special Issue Welding and Joining of Advanced High-Strength Steels)

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