Research

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15 pages, 7082 KiB

Open AccessArticle

Numerical and Experimental Investigations of Solidification Parameters and Mechanical Property during Laser Dissimilar Welding

by Zhiyong Li, Gang Yu, Xiuli He, Shaoxia Li and Yao Zhao

Metals 2018, 8(10), 799; https://doi.org/10.3390/met8100799 - 05 Oct 2018

Cited by 14 | Viewed by 3274

Abstract

Laser beam welding (LBW) has been considered an effective fusion welding method for the dissimilar welding of 304 stainless steel and Ni. However, the principles governing the correlations between the heat input, weld dimension, solidified microstructure and mechanical properties have not been fully [...] Read more.

Laser beam welding (LBW) has been considered an effective fusion welding method for the dissimilar welding of 304 stainless steel and Ni. However, the principles governing the correlations between the heat input, weld dimension, solidified microstructure and mechanical properties have not been fully studied before. Therefore, LBW experiments with variable heat input were carried out. A transient, three-dimensional model considering liquid metal convection was developed, and solidification parameters such as temperature gradient (G), growth rate (R), and cooling rate (GR) were calculated through thermal analysis to validate the experimental results. Then, microhardness tests were carried out to verify the predications made by the simulation. Energy dispersive spectroscopy (EDS) measurements were performed to study the mass transfer. The results indicate that the joints produced by LBW were nearly defect-free. The heat input per unit length is more effective at characterizing the influence of heat input on weld dimensions. The heat input has a greater influence on the cooling rate (GR) than the morphology parameter (G/R). The results demonstrate that both the solidification characteristics and mechanical property are greatly affected by the thermal behavior in the molten pool. Full article

(This article belongs to the Special Issue Laser Welding of Industrial Metal Alloys)

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21 pages, 8827 KiB

Open AccessArticle

Laser Welding Dissimilar High-Strength Steel Alloys with Complex Geometries

by Panos Efthymiadis and Khalid Nor

Metals 2018, 8(10), 792; https://doi.org/10.3390/met8100792 - 03 Oct 2018

Cited by 5 | Viewed by 4099

Abstract

Laser welding of dissimilar high-strength steels was performed in this study for two different geometries, flat and circular samples with material thicknesses of 5 and 8 mm. The material combinations were a low carbon to a medium or high carbon steel. Three different [...] Read more.

Laser welding of dissimilar high-strength steels was performed in this study for two different geometries, flat and circular samples with material thicknesses of 5 and 8 mm. The material combinations were a low carbon to a medium or high carbon steel. Three different welding systems were employed: a Nd:YAG, a CO₂ and a fiber laser. The process stability was evaluated for all the experiments. The resulting full penetration welds were inspected for their surface quality at the top and bottom of the specimens. Cross sections were taken to investigate the resulting microstructures and the metallurgical defects of the welds, such as cracks and pores. Significant hardening occurred in the weld region and the highest hardness values occurred in the Heat Affected Zone (HAZ) of the high carbon steel. The occurrence of weld defects depends strongly on the component geometry. The resulting microstructures within the weld were also predicted using neural network-simulated Continuous Cooling Transformation (CCT) diagrams and predicted the occurrence of a mixture of microstructures, such as bainite, martensite and pearlite, depending on the material chemistry. The thermal fields were measured with thermocouples and revealed the strong influence of component geometry on the cooling rate which in term defines the microstructures forming in the weld and the occurring hardness. Full article

(This article belongs to the Special Issue Laser Welding of Industrial Metal Alloys)

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15 pages, 5363 KiB

Open AccessArticle

Study of Solidification Cracking Susceptibility during Laser Welding in an Advanced High Strength Automotive Steel

by Gautam Agarwal, He Gao, Murugaiyan Amirthalingam and Marcel Hermans

Metals 2018, 8(9), 673; https://doi.org/10.3390/met8090673 - 28 Aug 2018

Cited by 20 | Viewed by 6294

Abstract

Susceptibility to weld solidification cracking in transformation-induced plasticity steel sheets was studied using a modified standard hot cracking test used in the automotive industry. To vary the amount of self-restraint, bead-on-plate laser welding was carried out on a single-sided clamped specimen at increasing [...] Read more.

Susceptibility to weld solidification cracking in transformation-induced plasticity steel sheets was studied using a modified standard hot cracking test used in the automotive industry. To vary the amount of self-restraint, bead-on-plate laser welding was carried out on a single-sided clamped specimen at increasing distances from the free edge. Solidification cracking was observed when welding was carried out close to the free edge. With increasing amount of restraint, the crack length showed a decreasing trend, and at a certain distance, no cracking was observed. With the aid of a finite element-based model, dynamic thermal and mechanical conditions that prevail along the transverse direction of the mushy zone are used to explain the cracking susceptibility obtained experimentally. The results indicate that the transverse strain close to the fusion boundary can be used as a criterion to predict the cracking behavior. The outcome of the study shows that optimum processing parameters can be used to weld steels closer to the free edge without solidification cracking. Full article

(This article belongs to the Special Issue Laser Welding of Industrial Metal Alloys)

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16 pages, 10842 KiB

Open AccessArticle

Minimization of the Thermal Impact in the Laser Welding of Dissimilar Stainless Steels

by Francisco Cordovilla, Alejandro Tur, Ángel García-Beltrán, Marcos Diaz, Ignacio Angulo and José L. Ocaña

Metals 2018, 8(8), 650; https://doi.org/10.3390/met8080650 - 18 Aug 2018

Cited by 4 | Viewed by 3512

Abstract

Laser welding of dissimilar stainless steels is of interest when mechanical, corrosion, or esthetical requirements impose the use of a high-performance stainless steels, while production-cost requirements prevent using expensive materials in all the parts of a given device. The compromise may lead to [...] Read more.

Laser welding of dissimilar stainless steels is of interest when mechanical, corrosion, or esthetical requirements impose the use of a high-performance stainless steels, while production-cost requirements prevent using expensive materials in all the parts of a given device. The compromise may lead to the use of the most expensive material in critical areas and the cheapest one in the remaining. Their union can be materialized by laser-pulsed welding. It has intrinsic difficulties derived from the different physical and chemical properties of the steels, and from the need of preserving the protective passive layer. The present work achieves a welded joint with minimum thermal impact by means of laser pulses, capable of preserving the corrosion resistance of the involved stainless steels. The influence of the parameters to define static and dynamic pulses on the material and on the welding regime, keyhole, or heat conduction, is studied. It is used to calculate the overlapping factor of the pulses on the basis of the real dimensions of the melted area. A continuous joint has been built with dynamic pulses. The corrosion resistance of it has been checked showing a similar behavior to the non-heated material. The microstructure of the optimized joint is associated with a reduced HAZ while its mechanical behavior is suitable for its real application. Full article

(This article belongs to the Special Issue Laser Welding of Industrial Metal Alloys)

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17 pages, 6848 KiB

Open AccessArticle

Numerical Model for Predicting Bead Geometry and Microstructure in Laser Beam Welding of Inconel 718 Sheets

by Iñigo Hernando, Jon Iñaki Arrizubieta, Aitzol Lamikiz and Eneko Ukar

Metals 2018, 8(7), 536; https://doi.org/10.3390/met8070536 - 12 Jul 2018

Cited by 11 | Viewed by 5894

Abstract

A numerical model was developed for predicting the bead geometry and microstructure in laser beam welding of 2 mm thickness Inconel 718 sheets. The experiments were carried out with a 1 kW maximum power fiber laser coupled with a galvanometric scanner. Wobble strategy [...] Read more.

A numerical model was developed for predicting the bead geometry and microstructure in laser beam welding of 2 mm thickness Inconel 718 sheets. The experiments were carried out with a 1 kW maximum power fiber laser coupled with a galvanometric scanner. Wobble strategy was employed for sweeping 1 mm wide circular areas for creating the weld seams, and a specific tooling was manufactured for supplying protective argon gas during the welding process. The numerical model takes into account both the laser beam absorption and the melt-pool fluid movement along the bead section, resulting in a weld geometry that depends on the process input parameters, such as feed rate and laser power. The microstructure of the beads was also estimated based on the cooling rate of the material. Features such as bead upper and bottom final shapes, weld penetration, and dendritic arm spacing, were numerically and experimentally analyzed and discussed. The results given by the numerical analysis agree with the tests, making the model a robust predictive tool. Full article

(This article belongs to the Special Issue Laser Welding of Industrial Metal Alloys)

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15 pages, 5326 KiB

Open AccessArticle

Tensile–Shear Fracture Behavior Prediction of High-Strength Steel Laser Overlap Welds

by Minjung Kang, In-Hwan Jeon, Heung Nam Han and Cheolhee Kim

Metals 2018, 8(5), 365; https://doi.org/10.3390/met8050365 - 18 May 2018

Cited by 16 | Viewed by 6514

Abstract

A wider interface bead width is required for laser overlap welding by increasing the strength of the base material (BM) because the strength difference between the weld metal (WM) and the BM decreases. An insufficient interface bead width leads to interface fracturing rather [...] Read more.

A wider interface bead width is required for laser overlap welding by increasing the strength of the base material (BM) because the strength difference between the weld metal (WM) and the BM decreases. An insufficient interface bead width leads to interface fracturing rather than to the fracture of the BM and heat-affected zone (HAZ) during a tensile–shear test. An analytic model was developed to predict the tensile–shear fracture location without destructive testing. The model estimated the hardness of the WM and HAZ by using information such as the chemical composition and tensile strength of the BM provided by the steel makers. The strength of the weldments was calculated from the estimated hardness. The developed model considered overlap weldments with similar and dissimilar material combinations of various steel grades from 590 to 1500 MPa. The critical interface bead width for avoiding interface fracturing was suggested with an accuracy higher than 90%. Under all the experimental conditions, a bead width that was only 5% larger than the calculated value could prevent the fracture of the interface. Full article

(This article belongs to the Special Issue Laser Welding of Industrial Metal Alloys)

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14 pages, 6234 KiB

Open AccessArticle

Interface Characteristic of Explosive-Welded and Hot-Rolled TA1/X65 Bimetallic Plate

by Miao-Xia Xie, Xiang-Tao Shang, Lin-Jie Zhang, Qing-Lin Bai and Ting-Ting Xu

Metals 2018, 8(3), 159; https://doi.org/10.3390/met8030159 - 04 Mar 2018

Cited by 22 | Viewed by 4535

Abstract

TA1/X65 bimetallic plate has a bright future of application by combining the excellent corrosion resistance of TA1 and the high strength of inexpensive X65 steel, while manufacturing large size TA1/X65 bimetallic plate is still a challenging task. Multi-pass hot-rolling is the most common [...] Read more.

TA1/X65 bimetallic plate has a bright future of application by combining the excellent corrosion resistance of TA1 and the high strength of inexpensive X65 steel, while manufacturing large size TA1/X65 bimetallic plate is still a challenging task. Multi-pass hot-rolling is the most common way to achieve a large size bimetallic plate. In this work, interface characteristic of explosive-welded and multi-pass hot-rolled TA1/X65 bimetallic plate is experimentally studied. The microstructure, composition and microhardness distribution across the TA1/X65 interface are investigated by optical metallographic observation, scanning electron microscope (SEM) observation, energy dispersive spectrometer (EDS) analysis, and Vickers hardness test. Shear tests and stratified tensile tests are conducted with emphasis on impacts of the angle between loading direction and detonation wave propagation direction on interface strength. A straight TA1/X65 interface with periodic morphology of residual peninsula could be observed on the cross section parallel to detonation wave propagation direction, while in most cases there is no residual peninsula morphology on the straight TA1/X65 interface when the cross section is perpendicular to detonation wave propagation direction. TA1/X65 interface of explosive-welded and multi-pass hot-rolled bimetallic plate presents higher bearing capacity for the load perpendicular to detonation wave propagation direction than that for the load parallel to detonation wave propagation direction. The results of this paper have a certain guiding significance for the fabrication of pipes and containers made of explosive-welded and hot-rolled TA1/X65 bimetallic plate. Full article

(This article belongs to the Special Issue Laser Welding of Industrial Metal Alloys)

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10760 KiB

Open AccessArticle

Effect of Cobalt on Microstructure and Wear Resistance of Ni-Based Alloy Coating Fabricated by Laser Cladding

by Kaiming Wang, Baohua Chang, Yongping Lei, Hanguang Fu and Yinghua Lin

Metals 2017, 7(12), 551; https://doi.org/10.3390/met7120551 - 07 Dec 2017

Cited by 37 | Viewed by 5615

Abstract

Ni-based alloy powders with different contents of cobalt (Co) have been deposited on a 42CrMo steel substrate surface using a fiber laser. The effects of Co content on the microstructure, composition, hardness, and wear properties of the claddings were studied by scanning electron [...] Read more.

Ni-based alloy powders with different contents of cobalt (Co) have been deposited on a 42CrMo steel substrate surface using a fiber laser. The effects of Co content on the microstructure, composition, hardness, and wear properties of the claddings were studied by scanning electron microscopy (SEM), an electron probe microanalyzer (EPMA), X-ray diffraction (XRD), a hardness tester, and a wear tester. The results show that the phases in the cladding layers are mainly γ, M₇(C, B)₃, M₂₃(C, B)₆, and M₂B. With the increase in Co content, the amounts of M₇(C, B)₃, M₂₃(C, B)₆, and M₂B gradually decrease, and the width of the eutectic structure in the cladding layer also gradually decreases. The microhardness decreases but the wear resistance of the cladding layer gradually improves with the increase of Co content. The wear resistance of the NiCo30 cladding layer is 3.6 times that of the NiCo00 cladding layer. With the increase of Co content, the wear mechanism of the cladding layer is changed from abrasive wear to adhesive wear. Full article

(This article belongs to the Special Issue Laser Welding of Industrial Metal Alloys)

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Review

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30 pages, 30277 KiB

Open AccessReview

Laser Hybrid Butt Welding of Large Thickness Naval Steel

by Cristina Churiaque, Mariane Chludzinski, Manuel Porrua-Lara, Antonio Dominguez-Abecia, Francisco Abad-Fraga and Jose Maria Sánchez-Amaya

Metals 2019, 9(1), 100; https://doi.org/10.3390/met9010100 - 18 Jan 2019

Cited by 28 | Viewed by 9062

Abstract

Plates joining is one of the first stage at large vessels manufacturing line, process conditioning the whole shipbuilding production. Laser Arc Hybrid Welding (LAHW) process is nowadays providing promising results for large thickness naval steel, being primarily used for welding plates with thicknesses [...] Read more.

Plates joining is one of the first stage at large vessels manufacturing line, process conditioning the whole shipbuilding production. Laser Arc Hybrid Welding (LAHW) process is nowadays providing promising results for large thickness naval steel, being primarily used for welding plates with thicknesses between 6 to 15 mm, reaching up to 51 mm. In addition to this high penetration ability, LAHW allows increasing the production rates. Therefore, this technology is proposed as an alternative to conventional welding processes in shipbuilding, as it integrates the advantages of laser and arc welding, providing high process stability, high welding speed and penetration, narrow weld beads with a low heat input and good metallurgical properties. The present review reports the most representative investigation regarding the use of this technology to join large thickness flat panels of naval steel. It includes a summary of the most influential process variables, equipment characteristics, material properties, naval regulations, as well as microstructural characterisation and mechanical properties of joints. This review is thought to help readers from different backgrounds, covering from non-expert on welding or on naval sector, to industrial LAHW applicators and researchers. The industrial need of performing one single pass procedure to assure high quality welds of high thickness is suggested as one of the key aspects for future investigations. Full article

(This article belongs to the Special Issue Laser Welding of Industrial Metal Alloys)

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