Analysis of Characteristics of Mg Alloy Welded Joint by Laser Welding

2011 ◽  
Vol 314-316 ◽  
pp. 949-952
Author(s):  
Hong Jian Xiu ◽  
Jun Liu ◽  
Jun Hui Dong ◽  
Ping Xu
Keyword(s):  
Heat Conduction ◽  
Laser Welding ◽  
Weld Metal ◽  
Welding Speed ◽  
Heat Input ◽  
Welded Joint ◽  
Mg Alloy ◽  
Deep Penetration ◽  
Deep Penetration Welding ◽  
Main Factor

The microstructure, the regular and mechanism of various parameters on formation of weld bead of Mg alloy AMCa403 using a laser welding were investigated. The results show that sound welds without major defects can be produced. Two welding modes of deep penetration welding, heat conduction welding were found, and heat input was found to be the main factor for welding mode and shape. The microstructure of weld metal is significantly finer than the base metal. At the same power, with the increase of welding speed, the microstructure of weld metal is much finer.

Numerical Analysis of Solidification Behavior during Laser Welding Nickel-Based Single-Crystal Superalloy Part: II Crystallography-Dependent Supersaturation of Liquid Aluminum

2021 ◽  
Vol 1018 ◽  
pp. 13-22
Author(s):  
Zhi Guo Gao
Keyword(s):  
Laser Welding ◽  
Single Crystal ◽  
Weld Pool ◽  
Welding Speed ◽  
Heat Input ◽  
Laser Power ◽  
Liquid Aluminum ◽  
Dendrite Growth ◽  
Solidification Cracking ◽  
Solid Liquid Interface

The thermal metallurgical modeling of liquid aluminum supersaturation was further developed through couple of heat transfer model, dendrite selection model, multicomponent dendrite growth model and nonequilibrium solidification model during three-dimensional nickel-based single-crystal superalloy weld pool solidification. The welding configuration plays more important role in supersaturation of liquid aluminum, morphology instability and nonequilibrium partition behavior. The bimodal distribution of liquid aluminum supersaturation along the solid/liquid interface is crystallographically symmetrical about the weld pool centerline in (001) and [100] welding configuration. The distribution of liquid aluminum supersaturation along the solid/liquid interface is crystallographically asymmetrical throughout the weld pool in (001) and [110] welding configuration. Optimum low heat input (low laser power and high welding speed) with (001) and [100] welding configuration is more favored to predominantly promote epitaxial [001] dendrite growth to reduce the metallurgical factors for solidification cracking than that of high heat input (high laser power and slow welding speed) with (001) and [110] welding configuration. The lower the heat input is used, the lower supersaturation of liquid aluminum is imposed, and the smaller size of vulnerable [100] dendrite growth region is incurred to ameliorate solidification cracking susceptibility and vice versa. The overall supersaturation of liquid aluminum in (001) and [100] welding configuration is beneficially smaller than that of (001) and [110] welding configuration regardless of heat input, and is not thermodynamically relieved by gamma prime γˊ phase. (001) and [110] welding configuration is detrimental to weldability and deteriorates the solidification cracking susceptibility because of unfavorable crystallographic orientations and alloying aluminum enrichment. The mechanism of asymmetrical solidification cracking because of crystallography-dependent supersaturation of liquid aluminum is proposed. The eligible solidification cracking location is particularly confined in [100] dendrite growth region. Moreover, the theoretical predictions agree well with the experiment results. The useful modeling is also applicable to other single-crystal superalloys with similar metallurgical properties for laser welding or laser cladding. The thorough numerical analyses facilitate the understanding of weld pool solidification behavior, microstructure development and solidification cracking phenomena in the primary γ phase, and thereby optimize the welding conditions (laser power, welding speed and welding configuration) for successful crack-free laser welding.

Characteristics of CO2 Laser Welded TRIP Steel Sheet

2011 ◽  
Vol 189-193 ◽  
pp. 3764-3767
Author(s):  
Wen Quan Wang ◽  
Shi Ming Huang ◽  
Qun You ◽  
Chung Yun Kang
Keyword(s):  
Tensile Strength ◽  
Weld Metal ◽  
Welding Speed ◽  
Steel Plate ◽  
Welded Joint ◽  
Raw Material ◽  
Maximum Hardness ◽  
Transformation Induced Plasticity ◽  
Trip Steel Sheet ◽  
Lower Elongation

Characteristics of CO2 laser welded 1000 MPa grade Transformation Induced Plasticity steel plate were investigated under different welding power, welding speed and shield gas. Decreasing welding power, increasing welding speed or using mixed shield gas (Ar+He) all reduced the porosity in the weld metal (WM). The weld metal and HAZ near the WM had maximum hardness. In tensile strength test of load perpendicular to the weld axis, the specimens had same tensile properties as that of the raw material. For the load parallel with the weld axis, the specimens prepared with Ar had equal yield strength (YS) and tensile strength (TS) to that of the raw material. But the elongation was lower than that of the raw material. The specimens prepared with shield gas He had higher YS, TS and lower elongation compared with that of the raw material. The welded joint had lower formability than that of the raw material. The formability of specimens prepared with low welding power or mixed shield gas Ar+He was improved compared with that of the specimens prepared using high power or single shield gas Ar.

Laser Welding on Material Used for Automobile Lightweight

2012 ◽  
Vol 442 ◽  
pp. 389-392
Author(s):  
Qiang Wu ◽  
Lan Ying Xu ◽  
Yu Zhong Li
Keyword(s):  
Laser Welding ◽  
Heat Affected Zone ◽  
High Strength ◽  
Deep Penetration ◽  
Technological Parameters ◽  
Welding Stability ◽  
Zinc Coated Steel ◽  
Protective Gas ◽  
Deep Penetration Welding ◽  
The Relationship

Based on a large number of welding tests to automotive lightweight material by CO2 laser, the microstructures of welded joint were tested related to performance. on the condition of welding technology, the relationship between the lower critical power of stabile deep penetration welding and welding speed and the focus position is deduced, In a coaxial and side protective gas conditions, through the optimization of technological parameters laser deep penetration welding can effectively avoid heat affected zone of high strength zinc coated steel becomes soft, welded comprehensive quality has been effectively controlled. Zinc evaporates unsteadily, which leads to expansion of heat affected zone and reduction of welding stability, so in this paper effective measures are taken to control it. Experimental results show that a qualified welding quality can be obtained by optimized process parameters of laser welding and adopting argon as shielding gas.

Effect of Heat Input on Structure and Mechanical Properties of Low Matched Welded Joint in a 1000MPa Grade Steel

2011 ◽  
Vol 418-420 ◽  
pp. 1184-1187 ◽  
Author(s):  
Zheng Jun Liu ◽  
Chu Ao Wang ◽  
Yun Hai Su ◽  
Fu Dong Zhao ◽  
Le Cheng Li
Keyword(s):  
Mechanical Properties ◽  
Weld Metal ◽  
Heat Input ◽  
Welded Joint ◽  
Optical Microscope ◽  
Metallurgical Structure ◽  
Weld Metal Microstructure ◽  
Optimal Values ◽  
Metal Microstructure ◽  
Grade Steel

In order to investigate the effect of heat input on the microstructure and mechanical properties of low matched high-tensile steel welded joint, the metallurgical structure and mechanical properties of welded joint obtained with different heat input were analyzed using optical microscope , welded joint tensile test and impact test of weld metal. The results show that the optimal values are obtained when the heat input is 11.9KJ/cm,where the tensile strength is 798.45MPa and ballistic work is 69J; Weld metal microstructure is mainly composed by the primary ferrite and acicular ferrite. The width of the dendrite and grain size of the weld metal microstructure increase with the increasing of the heat input.

scholarly journals High-Power Fiber Laser Welding of High-Strength AA7075-T6 Aluminum Alloy Welds for Mechanical Properties Research

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7498
Author(s):  
Abdel-Monem El-Batahgy ◽  
Olga Klimova-Korsmik ◽  
Aleksandr Akhmetov ◽  
Gleb Turichin
Keyword(s):  
Mechanical Properties ◽  
Laser Welding ◽  
Fiber Laser ◽  
Fusion Zone ◽  
High Power ◽  
Heat Input ◽  
Welded Joint ◽  
High Strength ◽  
Residual Tensile Stress ◽  
Fiber Laser Welding

The results disclosed that both the microstructure and mechanical properties of AA7075-T6 laser welds are considerably influenced by the heat input. In comparison with high heat input (arc welding), a smaller weld fusion zone with a finer dendrite arm spacing, limited loss of alloying elements, less intergranular segregation, and reduced residual tensile stress was obtained using low heat input. This resulted in a lower tendency of porosity and hot cracking, which improved the welded metal’s soundness. Subsequently, higher hardness as well as higher tensile strength for the welded joint was obtained with lower heat input. A welded joint with better mechanical properties and less mechanical discrepancy is important for better productivity. The implemented high-power fiber laser has enabled the production of a low heat input welded joint using a high welding speed, which is of considerable importance for minimizing not only the fusion zone size but also the deterioration of its properties. In other words, high-power fiber laser welding is a viable solution for recovering the mechanical properties of the high-strength AA 7075-T6 welds. These results are encouraging to build upon for further improvement of the mechanical properties to be comparable with the base metal.

Effect of Heat Input on Microstructure and Properties of Microalloyed C-Mn Steel Full Penetration Welded Joint Using Laser Welding

2016 ◽  
Vol 43 (1) ◽  
pp. 0103003
Author(s):  
王海生 Wang Haisheng ◽  
王晓南 Wang Xiaonan ◽  
张敏 Zhang Min ◽  
王卫 Wang Wei ◽  
朱国辉 Zhu Guohui ◽  
...  
Keyword(s):  
Laser Welding ◽  
Heat Input ◽  
Welded Joint ◽  
Microstructure And Properties ◽  
Full Penetration ◽  
Mn Steel

Microstructure and Toughness of 1000 MPa High Strength Weld Metal

2010 ◽  
Vol 638-642 ◽  
pp. 3441-3446 ◽  
Author(s):  
Wan Sheng Du ◽  
Yun Peng ◽  
Hong Jun Xiao ◽  
Chang Hong He ◽  
Zhi Ling Tian
Keyword(s):  
Electron Microscope ◽  
Weld Metal ◽  
Heat Input ◽  
Welded Joint ◽  
Lath Martensite ◽  
Charpy Impact ◽  
High Strength ◽  
Hardness Test ◽  
Optical Microscope ◽  
Carbon Equivalent

Welding of 1000 MPa high strength alloy steel is difficult because of its welding cold cracking sensitivity and the difficulty in maintaining high joint toughness. In this paper the effects of alloy elements on welding cracking tendency are analyzed, and measures to prevent cold crack are proposed. Welding wires with high strength was deposited into weld metal and welded into joint. Tensile test, micro-hardness test and Charpy impact test were used to evaluate the strength and toughness of weld metal and heat affected zone. Optical microscope, transmission electron microscope and scanning electron microscope were used to analyze the microstructure. It is shown that the weld metal mainly consists of lath martensite, lath bainite, and residual austenite which exists between the laths. The strength of weld metal increases in a small degree with increasing carbon equivalent and its toughness and ductility are not related to carbon equivalent. The toughness and ductility are much sensitive to nonmetallic inclusions. The welded joint has tensile strength of higher than 1000 MPa when welded at heat input of 11 kJ/cm and 15 kJ/cm and the mechanical properties are little influenced by the amount of heat input in this range. The whole welded joint has good comprehensive properties.

Effect of Bead Deposition by Repair Welding on Residual Stress in Pipe Welds

2004 ◽  
Author(s):  
Masahito Mochizuki ◽  
Masao Toyoda
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Weld Metal ◽  
Initial Stress ◽  
Heat Input ◽  
Welded Joint ◽  
Repair Process ◽  
Residual Stress Distribution ◽  
Initial Residual Stress ◽  
Plastic Analysis

Residual stress by repair welds in a pipe weld is computed using the thermal elastic-plastic analysis. Weld bond and heat-affected zone of a butt-welded joint is gouged and then deposited by weld metal in repair process. Heat source is synchronously moved with the deposition of the finite-element as the weld deposition. The effects of initial stress, heat input, and weld length on residual stress distribution are studied from the organic results of numerical analysis. Initial residual stress before repair weld has no influence on the residual stress after repair treatment near weld metal, because the initial stress near weld metal releases due to high temperature of repair weld and then stress by repair weld regenerates. Heat input has an effect for residual stress distribution, for not its magnitude but distribution zone. Weld length should be considered for reducing the magnitude of residual stress in the edge of weld bead; short bead induces high tensile residual stress.

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