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17 pages, 7717 KiB

Open AccessArticle

MAG Welding Process with Micro-Jet Cooling as the Effective Method for Manufacturing Joints for S700MC Steel

by Tomasz Węgrzyn, Tadeusz Szymczak, Bożena Szczucka-Lasota and Bogusław Łazarz

Metals 2021, 11(2), 276; https://doi.org/10.3390/met11020276 - 05 Feb 2021

Cited by 11 | Viewed by 2113

Abstract

Advanced high-strength steel (AHSS) steels are relatively not very well weldable because of the dominant martensitic structure with coarse ferrite and bainite. The utmost difficulty in welding these steels is their tendency to crack both in the heat affected zone (HAZ) and in [...] Read more.

Advanced high-strength steel (AHSS) steels are relatively not very well weldable because of the dominant martensitic structure with coarse ferrite and bainite. The utmost difficulty in welding these steels is their tendency to crack both in the heat affected zone (HAZ) and in weld. The significant disadvantage is that the strength of the welded joint is much lower in comparison to base material. Adopting the new technology regarding micro-jet cooling (MJC) after welding with micro-jet cooling could be the way to steer the microstructure of weld metal deposit. Welding with micro-jet cooling might be treated as a very promising welding S700MC steel process. Tensile and fatigue tests were mainly carried out as the main destructive experiments for examining the weld. Also bending probes, metallographic structure analysis, and some non-destructive measurements were performed. The welds were created using innovative technology by MAG welding with micro-jet cooling. The paper aims to verify the fatigue and tensile properties of the thin-walled S700MC steel structure after welding with various parameters of micro-cooling. For the first time, micro-jet cooling was used to weld S700MC steel in order to check the proper mechanical properties of the joint. The main results are processed in the form of the Wöhler’s S–N curves (alternating stress versus number cycles to failure). Full article

(This article belongs to the Special Issue Technology of Welding and Joining)

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17 pages, 11958 KiB

Open AccessArticle

Recrystallization Behavior of a Pure Cu Connection Interface with Ultrasonic Welding

by Zhanzhan Su, Zhengqiang Zhu, Yifu Zhang, Hua Zhang and Qiankun Xiao

Metals 2021, 11(1), 61; https://doi.org/10.3390/met11010061 - 30 Dec 2020

Cited by 20 | Viewed by 3073

Abstract

Three-dimensional metal waveguide components are key components in the next generation of radio telescopes. Ultrasonic additive manufacturing technology combining ultrasonic welding and micro electrical discharge machining (micro-EDM) provides a new method for the overall manufacturing of waveguide elements, and the effective welding of [...] Read more.

Three-dimensional metal waveguide components are key components in the next generation of radio telescopes. Ultrasonic additive manufacturing technology combining ultrasonic welding and micro electrical discharge machining (micro-EDM) provides a new method for the overall manufacturing of waveguide elements, and the effective welding of Electrolytic Tough Pitch copper (Cu-ETP) sheets is the key process of this method. This study demonstrates that the orthogonal test optimization method is used to conduct ultrasonic welding tests on Cu-ETP. Specifically, electron backscattered diffraction (EBSD) technology is used to analyze the crystal grains, grain boundary types and texture changes during interface recrystallization. In addition, the finite element software ABAQUS 6.13 is employed to calculate the temperature field in order to determine the possibility of recrystallization of the welding interface. The results showed that the average grain size of the welding interface decreased from 20 to 1~2 μm. The Cu-ETP matrix is mainly composed of coarse grains with high-angle grain boundaries (HAGBs), while a large number of low-angle grain boundaries (LAGBs), subcrystals and fine equiaxed grains appear in the welded joint. At the same time, discontinuous dynamic recrystallization (DDRX) occurs in the less strained area, and continuous dynamic recrystallization (CDRX) is predominant in the greater strain area. The temperature field calculation shows that the peak temperature of the welding interface exceeds the recrystallization temperature of Cu-ETP from 379.05 to 433.2 °C. Full article

(This article belongs to the Special Issue Technology of Welding and Joining)

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24 pages, 14711 KiB

Open AccessArticle

The Weldability of Duplex Stainless-Steel in Structural Components to Withstand Corrosive Marine Environments

by Iñigo Calderon-Uriszar-Aldaca, Estibaliz Briz, Harkaitz Garcia and Amaia Matanza

Metals 2020, 10(11), 1475; https://doi.org/10.3390/met10111475 - 05 Nov 2020

Cited by 7 | Viewed by 2684

Abstract

There is still a considerable gap in the definition of the weldability of Duplex Stainless Steel (DSS). A lack of clarity that is explained by the standard specification of the maximum content of equivalent carbon that defines a “weldable” steel coupled with the [...] Read more.

There is still a considerable gap in the definition of the weldability of Duplex Stainless Steel (DSS). A lack of clarity that is explained by the standard specification of the maximum content of equivalent carbon that defines a “weldable” steel coupled with the fact that the alloying elements of DSS exceed this defined limit of weldability. In this paper, welding quality in an inert environment and in presence of chlorides is analyzed with the aim of defining optimum welding conditions of 2001, 2304, and 2205 DSS. The same procedure is followed for a hybrid weld between DSS 2205 and a low carbon mild steel, S275JR. As main output, this study defined the optimal welding conditions with tungsten inert gas without filler for each type of DSS weld that showed excellent anti-corrosion performance, with the exception of the DSS 2205-S275JR weld where widespread corrosion was observed. Additionally, this study established a relationship between the thermal input during welding and the content of alloying elements in defect-free joints. Furthermore, it demonstrated that an increase in ferrite content did not lead to a worse corrosion resistance, as expected after passivation. Full article

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10 pages, 7461 KiB

Open AccessArticle

Improvement in Weldment of Dissimilar 9% CR Heat-Resistant Steels by Post-Weld Heat Treatment

by Jiankun Xiong, Ting Li, Xinjian Yuan, Guijun Mao, Jianping Yang, Lin Yang and Jian Xu

Metals 2020, 10(10), 1321; https://doi.org/10.3390/met10101321 - 02 Oct 2020

Cited by 3 | Viewed by 1562

Abstract

The effect of the post-weld heat treatment on the microstructures and mechanical properties of the dissimilar joint of G115, a novel developed martensite heat resistant steel, and CB2 steel, currently used in an ultra-super-critical power unit, was investigated. The results indicate that the [...] Read more.

The effect of the post-weld heat treatment on the microstructures and mechanical properties of the dissimilar joint of G115, a novel developed martensite heat resistant steel, and CB2 steel, currently used in an ultra-super-critical power unit, was investigated. The results indicate that the quenched martensite underwent decomposition and transformation, and the amount of dislocations were sharply decreased in the weld metal after post-weld heat treatment (PWHT). Many nano-scale M₂₃C₆ precipitates present in the weldment were distributed on the grain and grain boundary in a dispersed manner with PWHT. The average microhardness of the weldment decreased from about 400 HV to 265–290 HV after PWHT and only a slight decrease in the microhardness of CB2 steel was detected after PWHT at 760 °C. In contrast to the case of the as-received joint, the tensile strength of the joint was improved from 630 MPa to 694 MPa and the fracture location moved from the weld metal to the base metal after PWHT. The fracture surface consisted of a cleavage fracture mode without PWHT, whereas many dimples were observed on the fracture surface with PWHT. Full article

(This article belongs to the Special Issue Technology of Welding and Joining)

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11 pages, 4278 KiB

Open AccessArticle

Microstructure and Performance Analysis of Welded Joint of Spray-Deposited 2195 Al-Cu-Li Alloy Using GTAW

by Chuanguang Luo, Huan Li, Yonglun Song, Lijun Yang and Yuanhua Wen

Metals 2020, 10(9), 1236; https://doi.org/10.3390/met10091236 - 14 Sep 2020

Cited by 2 | Viewed by 1905

Abstract

High-strength aluminum alloy fabricated using spray deposition technology possesses many advantages, such as fine crystal grains, low component segregation, uniform microstructure, and small internal stress. In this study, spray-deposited 2195 Al-Cu-Li alloy in forged state was used and welded using the gas tungsten [...] Read more.

High-strength aluminum alloy fabricated using spray deposition technology possesses many advantages, such as fine crystal grains, low component segregation, uniform microstructure, and small internal stress. In this study, spray-deposited 2195 Al-Cu-Li alloy in forged state was used and welded using the gas tungsten arc welding (GTAW) process to test and verify the features of the fusion joint. Quantitative analysis was carried out to evaluate the relationship between the local microstructures and performances of the fusion joint, which was composed of four zones: weld metal, fusion zone, heat-affected zone, and base metal. The characteristic quantities of each zone, including recrystallized grain fraction, grain sizes, grain misorientation angle, and Vickers hardness, and their distributions were considered as the key factors affecting the performance of the joint because of welding thermal cycle impact on the fusion joint. To recognize the metallurgical characteristics of spray-deposited alloy 2195, a statistical algorithm based on the concept of the Hall–Petch relationship was proposed to validate the actual test results, which include the correlation effects of both the filler wire and welding process. The correlation between the microstructures and performances of several characteristic quantities were evaluated by integrating the above characteristic information of the fusion joint under the strong coupling of multiple factors. Thus, the advantages of weldability of spray-deposited alloy 2195 using GTAW could be understood in detail. Full article

(This article belongs to the Special Issue Technology of Welding and Joining)

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14 pages, 3121 KiB

Open AccessArticle

Low Temperature Cu/Ga Solid–Liquid Inter-Diffusion Bonding Used for Interfacial Heat Transfer in High-Power Devices

by Guoqian Mu, Wenqing Qu, Haiyun Zhu, Hongshou Zhuang and Yanhua Zhang

Metals 2020, 10(9), 1223; https://doi.org/10.3390/met10091223 - 10 Sep 2020

Cited by 7 | Viewed by 3331

Abstract

Interfacial heat transfer is essential for the development of high-power devices with high heat flux. The metallurgical bonding of Cu substrates is successfully realized by using a self-made interlayer at 10 °C, without any flux, by Cu/Ga solid-liquid inter-diffusion bonding (SLID), which can [...] Read more.

Interfacial heat transfer is essential for the development of high-power devices with high heat flux. The metallurgical bonding of Cu substrates is successfully realized by using a self-made interlayer at 10 °C, without any flux, by Cu/Ga solid-liquid inter-diffusion bonding (SLID), which can be used for the joining of heat sinks and power devices. The microstructure and properties of the joints were investigated, and the mechanism of Cu/Ga SLID bonding was discussed. The results show that the average shear strength of the joints is 7.9 MPa, the heat-resistant temperature is 200 °C, and the thermal contact conductance is 83,541 W/(m²·K) with a holding time of 30 h at the bonding temperature of 100 °C. The fracture occurs on one side of the copper wire mesh which is caused by the residual gallium. The microstructure is mainly composed of uniform θ-CuGa₂ phase, in addition to a small amount of residual copper, residual gallium and γ₃-Cu₉Ga₄ phase. The interaction product of Cu and Ga is mainly θ-CuGa₂ phase, with only a small amount of γ₃-Cu₉Ga₄ phase occurring at the temperature of 100 °C for 20 h. The process of Cu/Ga SLID bonding can be divided into three stages as follows: the pressurization stage, the reaction diffusion stage and the isothermal solidification stage. This technology can meet our requirements of low temperature bonding, high reliability service and interfacial heat transfer enhancement. Full article

(This article belongs to the Special Issue Technology of Welding and Joining)

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12 pages, 38203 KiB

Open AccessArticle

Electrochemical Migration Inhibition of Tin by Disodium Hydrogen Phosphate in Water Drop Test

by Bokai Liao, Hong Wang, Shan Wan, Weiping Xiao and Xingpeng Guo

Metals 2020, 10(7), 942; https://doi.org/10.3390/met10070942 - 14 Jul 2020

Cited by 8 | Viewed by 2886

Abstract

The inhibition effect of Na₂HPO₄ on the electrochemical migration (ECM) of pure tin was investigated by means of water drop testing and surface characterizations. The effects of concentration of Na₂HPO₄ and applied direct current (DC) bias voltage [...] Read more.

The inhibition effect of Na₂HPO₄ on the electrochemical migration (ECM) of pure tin was investigated by means of water drop testing and surface characterizations. The effects of concentration of Na₂HPO₄ and applied direct current (DC) bias voltage on the ECM were also studied. Results showed that the mean time to failure caused by ECM decreased with the increasing bias voltage. Upon addition of relative high concentrations of Na₂HPO₄, Na₂HPO₄ can react with metallic tin or tin ions to form a protective film on the surface of anode and increase the pitting potential. The rate of anodic dissolution can be slowed down and thus ECM of tin was retarded. Fractal-like dendrites formed after ECM tests in the absence and presence of low concentrations of Na₂HPO₄ mainly consisted of tin elements. Relevant reactions were proposed to explain the inhibitory effect of Na₂HPO₄ on the ECM of tin. Full article

(This article belongs to the Special Issue Technology of Welding and Joining)

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13 pages, 4367 KiB

Open AccessArticle

Low Temperature Sealing Process and Properties of Kovar Alloy to DM305 Electronic Glass

by Zhenjiang Wang, Zeng Gao, Junlong Chu, Dechao Qiu and Jitai Niu

Metals 2020, 10(7), 941; https://doi.org/10.3390/met10070941 - 13 Jul 2020

Cited by 11 | Viewed by 3693

Abstract

The low temperature sealing of Kovar alloy to DM305 electronic glass was realized by using lead-free glass solder of the Bi₂O₃-ZnO-B₂O₃ system in atmospheric environment. The sealing process was optimized by pre-oxidation of Kovar alloy and [...] Read more.

The low temperature sealing of Kovar alloy to DM305 electronic glass was realized by using lead-free glass solder of the Bi₂O₃-ZnO-B₂O₃ system in atmospheric environment. The sealing process was optimized by pre-oxidation of Kovar alloy and low temperature founding of flake glass solder. The effects of sealing temperature and holding time on the properties of sealing joint were studied by means of X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), etc. The results showed that the pre-oxidized Kovar alloy and DM305 electronic glass were successfully sealed with flake glass solder at the sealing temperature of 500 °C for 20 min. Meanwhile, the joint interface had no pores, cracks, and other defects, the shear strength was 12.24 MPa, and the leakage rate of air tightness was 8 × 10⁻⁹ Pa·m³/s. During the sealing process, element Bi in glass solder diffused into the oxide layer of Kovar alloy and DM305 electronic glass about 1 μm, respectively. Full article

(This article belongs to the Special Issue Technology of Welding and Joining)

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11 pages, 1844 KiB

Open AccessArticle

Solderability, Microstructure, and Thermal Characteristics of Sn-0.7Cu Alloy Processed by High-Energy Ball Milling

by Ashutosh Sharma, Min Chul Oh, Myoung Jin Chae, Hyungtak Seo and Byungmin Ahn

Metals 2020, 10(3), 370; https://doi.org/10.3390/met10030370 - 13 Mar 2020

Cited by 2 | Viewed by 2591

Abstract

In this work, we have investigated the role of high-energy ball milling (HEBM) on the evolution of microstructure, thermal, and wetting properties of an Sn-0.7Cu alloy. We ball-milled the constituent Sn and Cu powders in eutectic composition for 45 h. The microstructural studies [...] Read more.

In this work, we have investigated the role of high-energy ball milling (HEBM) on the evolution of microstructure, thermal, and wetting properties of an Sn-0.7Cu alloy. We ball-milled the constituent Sn and Cu powders in eutectic composition for 45 h. The microstructural studies were carried out using optical and scanning electron microscopy. The melting behavior of the powder was examined using differential scanning calorimetry (DSC). We observed a considerable depression in the melting point of the Sn-0.7Cu alloy (≈7 °C) as compared to standard cast Sn-0.7Cu alloys. The resultant crystallite size and lattice strain of the ball-milled Sn-0.7Cu alloy were 76 nm and 1.87%, respectively. The solderability of the Sn-0.7Cu alloy was also improved with the milling time, due to the basic processes occurring during the HEBM. Full article

(This article belongs to the Special Issue Technology of Welding and Joining)

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20 pages, 15010 KiB

Open AccessArticle

Hybrid Laser Deposition of Fe-Based Metallic Powder under Cryogenic Conditions

by Aleksander Lisiecki and Dawid Ślizak

Metals 2020, 10(2), 190; https://doi.org/10.3390/met10020190 - 28 Jan 2020

Cited by 13 | Viewed by 2625

Abstract

The purpose of this study was to demonstrate the novel technique of laser deposition of Fe-based powder under cryogenic conditions provided by a liquid nitrogen bath. Comparative clad layers were produced by conventional laser cladding at free cooling conditions in ambient air and [...] Read more.

The purpose of this study was to demonstrate the novel technique of laser deposition of Fe-based powder under cryogenic conditions provided by a liquid nitrogen bath. Comparative clad layers were produced by conventional laser cladding at free cooling conditions in ambient air and by the developed process combining laser cladding and laser gas nitriding (hybrid) under cryogenic conditions. The influence of process parameters and cooling conditions on the geometry, microstructure, and hardness profiles of the clad layers was determined. The optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive spectrometer (EDS), and XRD test methods were used to determine the microstructure and phase composition. The results indicate that the proposed technique of forced cooling the substrate in a nitrogen bath during the laser deposition of Fe-based powder is advantageous because it provides favorable geometry of the clad, low dilution, a narrow heat-affected zone, a high hardness and uniform profile on the cross-sections, homogeneity, and refinement of the microstructure. The influence of the forced cooling on microstructure refinement was quantitatively determined by measuring the secondary dendrite arm spacing (SDAS). Additionally, highly dispersed nanometric-sized (200–360 nm) precipitations of complex carbides were identified in interdendritic regions. Full article

(This article belongs to the Special Issue Technology of Welding and Joining)

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Review

Jump to: Research

13 pages, 4990 KiB

Open AccessReview

A Compact Review of Laser Welding Technologies for Amorphous Alloys

by Jian Qiao, Peng Yu, Yanxiong Wu, Taixi Chen, Yixin Du and Jingwei Yang

Metals 2020, 10(12), 1690; https://doi.org/10.3390/met10121690 - 18 Dec 2020

Cited by 8 | Viewed by 2574

Abstract

Amorphous alloys have emerged as important materials for precision machinery, energy conversion, information processing, and aerospace components. This is due to their unique structure and excellent properties, including superior strength, high elasticity, and excellent corrosion resistance, which have attracted the attention of many [...] Read more.

Amorphous alloys have emerged as important materials for precision machinery, energy conversion, information processing, and aerospace components. This is due to their unique structure and excellent properties, including superior strength, high elasticity, and excellent corrosion resistance, which have attracted the attention of many researchers. However, the size of the amorphous alloy components remains limited, which affects industrial applications. Significant developments in connection with this technology are urgently needed. Laser welding represents an efficient welding method that uses a laser beam with high energy-density for heating. Laser welding has gradually become a research hotspot as a joining method for amorphous alloys due to its fast heating and cooling rates. In this compact review, the current status of research into amorphous-alloy laser welding technology is discussed, the influence of technological parameters and other welding conditions on welding quality is analyzed, and an outlook on future research and development is provided. This paper can serve as a useful reference for both fundamental research and engineering applications in this field. Full article

(This article belongs to the Special Issue Technology of Welding and Joining)

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16 pages, 8152 KiB

Open AccessReview

Research Status and Progress of Welding Technologies for Molybdenum and Molybdenum Alloys

by Qi Zhu, Miaoxia Xie, Xiangtao Shang, Geng An, Jun Sun, Na Wang, Sha Xi, Chunyang Bu and Juping Zhang

Metals 2020, 10(2), 279; https://doi.org/10.3390/met10020279 - 20 Feb 2020

Cited by 18 | Viewed by 4485

Abstract

Owing to its potential application prospect in novel accident tolerant fuel, molybdenum alloys and their welding technologies have gained great importance in recent years. The challenges of welding molybdenum alloys come from two aspects: one is related to its powder metallurgy manufacturing process, [...] Read more.

Owing to its potential application prospect in novel accident tolerant fuel, molybdenum alloys and their welding technologies have gained great importance in recent years. The challenges of welding molybdenum alloys come from two aspects: one is related to its powder metallurgy manufacturing process, and the other is its inherent characteristics of refractory metal. The welding of powder metallurgy materials has been associated with issues such as porosity, contamination, and inclusions, at levels which tend to degrade the service performances of a welded joint. Refractory metals usually present poor weldability due to embrittlement of the fusion zone as a result of impurities segregation and the grain coarsening in the heat-affected zone. A critical review of the current state of the art of welding Mo alloys components is presented. The advantages and disadvantages of the various methods, i.e., electron-beam welding (EBW), tungsten-arc inert gas (TIG) welding, laser welding (LW), electric resistance welding (ERW), and brazing and friction welding (FW) in joining Mo and Mo alloys, are discussed with a view to imagine future directions. This review suggests that more attention should be paid to high energy density laser welding and the mechanism and technology of welding Mo alloys under hyperbaric environment. Full article

(This article belongs to the Special Issue Technology of Welding and Joining)

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