The porosity formation mechanism in the laser-welded butt joint of 8 mm thickness Ti-6Al-4V alloy: Effect of welding speed on the metallurgical pore formation

2020 ◽  
Vol 34 (04) ◽  
pp. 2050056
Author(s):  
Deyong Tian ◽  
Zhuanni Gao ◽  
Feiyun Wang ◽  
Tingyan Yan ◽  
Min Yu ◽  
...  
Keyword(s):  
Welding Speed ◽  
Electron Beam Welding ◽  
Welding Process ◽  
High Energy ◽  
Industrial Applications ◽  
Butt Joint ◽  
Hydrogen Gas ◽  
High Energy Density ◽  
Porosity Formation ◽  
Alloy Effect

The high energy density beam welding techniques, such as laser and electron beam welding process, have been widely used in industrial applications. In this study, the butt structures of Ti-6Al-4V alloys with the thickness up to 8 mm are successfully joined by the laser welding process. The macromorphology and microstructures of the welded joints are investigated by a scanning electron microscope (SEM). The penetration increases from 5.91 mm to 9.37 mm with the decrease of welding speed from 1.2 m/min to 0.8 m/min under the condition of equal laser power. The acicular [Formula: see text] is formed in the fusion zone, resulting from high cooling rate during the process. The metallurgical porosity formation is proposed by investigating the distribution of Al and H elements around the pores. It is concluded that the pores in the weld bead are induced by aluminum vapor and hydrogen gas from the molten pool. The diameter of metallurgical pore has a tendency to increase with the decrease of welding speed.

Study of Metallurgical and Mechanical Behavior of Laser Butt-Welded Dissimilar Joint of Inconel and Stainless Steel

2019 ◽  
Author(s):  
Sanjib Jaypuria ◽  
Santosh Kumar Gupta ◽  
Sulthan Suresh-Fazeela ◽  
Dilip Kumar Pratihar ◽  
Debalay Chakrabarti ◽  
...  
Keyword(s):  
Laser Welding ◽  
Welding Speed ◽  
Inconel 718 ◽  
Electron Beam Welding ◽  
High Energy ◽  
High Energy Density ◽  
Laser Source ◽  
Laves Phases ◽  
Xrd Phase Analysis ◽  
Welding Processes

Abstract High energy density welding processes like laser and electron beam welding are capable of welding dissimilar plates with much ease due to high power density and low heat input in spite of the varying thermos-physical properties of the used alloys. The present work is aimed to check the feasibility of joint prepared with laser welding of SS 316L and Inconel 718 plates. The experiments are designed to study the effect of welding speed on the mechanical and metallurgical behavior of the joints without any offset to joint line. The formation of laves phases is confirmed by energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) phase analysis. These laves phase are micro-segregation of Nb, Fe, C and Cr, which is because of high temperature in a small area of fusion zone (FZ) due to intense heat of laser source. Micro-segregation of different elements has led to micro-fissures, which is detrimental for the joints operating at elevated temperature. Cooling rate and peak temperature during welding play the significant role in obtaining a sound quality joint. The present work gives an insight on feasibility of laser welded joint of SS 316L and Inconel 718 with suitable selection of welding speed during laser welding.

Effect of the temperature gradient on hot cracking susceptibility for electron beam welding Alloy 247 LC

2020 ◽  
Vol 62 (7) ◽  
pp. 721-726 ◽  
Author(s):  
A. Senger ◽  
T. Jokisch ◽  
S. Olschok ◽  
U. Reisgen
Keyword(s):  
Electron Beam ◽  
Temperature Gradient ◽  
Electron Beam Welding ◽  
Rupture Strength ◽  
Cast Alloy ◽  
Welding Process ◽  
High Energy ◽  
Hot Cracking ◽  
High Energy Density ◽  
Welding Parameter

Abstract Conventionally cast Alloy 247 LC is characterized by good creep rupture strength and corrosion resistance at high temperatures and is therefore frequently used for cast components in the aero-engine and power generation industries. From a welding technology point of view, the precipitation- hardening nickel-based alloy has an increased susceptibility to hot cracking. Due to its high segregation tendency and its γ’ precipitation formation, the material is even classified as non-weldable. However, electron beam welding in a vacuum as the method of choice for joining and repairing nickel-based components in industrial practice, provides a variable beam welding process with high energy density. This allows varied temperature gradients to be implemented. In this paper, results of welding parameter optimization with regard to hot crack reduction are presented. For this purpose, a comprehensive crack analysis was carried out using scanning electron microscopy, metallography and X-ray microtomography and was then compared with the temperature gradient along the fusion line. Two hot cracking phenomena were identified and differentiated. Thereby, a clear dependence between temperature gradient and crack reduction becomes obvious.

scholarly journals Residual Stress in Laser Welding of TC4 Titanium Alloy Based on Ultrasonic laser Technology

2018 ◽  
Vol 8 (10) ◽  
pp. 1997 ◽  
Author(s):  
Yu Zhan ◽  
Enda Zhang ◽  
Yiming Ge ◽  
Changsheng Liu
Keyword(s):  
Residual Stress ◽  
Titanium Alloy ◽  
Laser Welding ◽  
Welding Speed ◽  
Heat Input ◽  
Welding Process ◽  
High Energy ◽  
High Energy Density ◽  
Tc4 Titanium Alloy ◽  
Longitudinal Residual Stress

Laser welding is widely used in titanium alloy welding due to its high energy density, small heat affected zone, and rapid processing ability. However, problems with laser welding, such as deformation and cracking caused by residual stress, need to be resolved. In this paper, the residual stress in laser welding of TC4 titanium alloy was studied using an ultrasonic laser. The residual stress in titanium alloy plates is considered a plane stress state. A pre-stress loading method is proposed and acoustoelastic coefficients are obtained. Based on the known acoustoelastic coefficients, the transverse and longitudinal residual stresses in laser welding are measured using an ultrasonic laser. The results show that longitudinal residual stress is greater than the transverse stress. The distribution regularity of the residual stress is similar to normal welding, but the tensile stress zone is much narrower. Then, the influence of heat input and welding speed on residual stress is discussed. With increasing heat input, the welding zone widens, and the peak value of the residual stress increases. A higher welding speed should be chosen when the welding power is constant. This research has important significance for the measurement and control of residual stress in the laser welding process.

scholarly journals Effect of Pre-Heating and Post-Heating on Electron Beam Welding of Reduced Activation Ferrite/Martensite Steel

2021 ◽  
Vol 2 (3) ◽  
pp. 225-238
Author(s):  
Yong Zhang ◽  
Jiefeng Wu ◽  
Zhihong Liu ◽  
Songlin Liu ◽  
Mingzhun Lei ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Electron Beam ◽  
Electron Beam Welding ◽  
Laser Beam Welding ◽  
Welding Process ◽  
High Energy ◽  
High Energy Density ◽  
Post Heat Treatment ◽  
Rafm Steel

Reduced activation ferritic/martensitic (RAFM) steels are considered the main candidate material for the water-cooled ceramic breeder (WCCB) in a fusion reactor. High-energy density welding approaches, such as electron beam welding (EBW) and laser beam welding (LBW), are frequently utilized in the welding of RAFM steels. During the welding process, cracks and other defects are prone to appear. In this paper, EBW was selected for the welding of RAFM steels. Those with and without pre-heat and post-heat treatment by electron beams are studied by finite element simulation and trials. The results show that the experimental results are consistent with the simulation. In particular, in the case of similar deformation, the residual stress after electron beam heat treatment is far less than that without heat treatment. Without heat treatment, the residual stress near the weld is more than 400 MPa, while the residual stress after heat treatment is about 350 MPa. As the reduction of residual stress is essential to prevent the occurrence of cracks and other defects after welding, pre-heat and post-heat treatment by the electron beam is deemed as an effective way to greatly improve the welding quality in RAFM steel welding.

scholarly journals A Compact Review of Laser Welding Technologies for Amorphous Alloys

Metals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1690
Author(s):  
Jian Qiao ◽  
Peng Yu ◽  
Yanxiong Wu ◽  
Taixi Chen ◽  
Yixin Du ◽  
...  
Keyword(s):  
Amorphous Alloy ◽  
Laser Welding ◽  
Amorphous Alloys ◽  
High Energy ◽  
Industrial Applications ◽  
High Energy Density ◽  
Current Status ◽  
Future Research ◽  
Technological Parameters ◽  
Fast Heating

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.

Study on Electron Beam Welding of AZ61 Magnesium Alloy

2010 ◽  
Vol 34-35 ◽  
pp. 1516-1520
Author(s):  
Hong Ye ◽  
Han Li Yang ◽  
Zhong Lin Yan
Keyword(s):  
Electron Beam ◽  
Magnesium Alloys ◽  
Welding Speed ◽  
Electron Beam Welding ◽  
Weld Zone ◽  
Welding Process ◽  
Processing Parameters ◽  
Beam Current ◽  
Fine Grained ◽  
Section Shape

Electron beam welding process of AZ61 with 10mm thickness magnesium alloys was investigated. The influence of processing parameters including focusing current, welding beam current and welding speed was researched. The results show that an ideal weld bead can be formed by choosing processing parameters properly. Focusing current is main parameter that determines cross section shape. The beam current and welding speed are main parameters that determine the weld width and dimensions. The test results for typical welds indicate that the microhardness of the weld zone is better than that of the base meta1. A fine-grained weld region has been observed and no obvious heat-affected zone is found. The fusion zone mainly consists of small α-Mg phase and β-Mg17A112. The small grains and β phases in the joint are believed to play an important role in the increase of the strength of weld for AZ61 magnesium alloys.

Design of a Compliant Industrial Gripper Driven by a Bistable Shape Memory Alloy Actuator

2020 ◽  
Author(s):  
Dominik Scholtes ◽  
Stefan Seelecke ◽  
Gianluca Rizzello ◽  
Paul Motzki
Keyword(s):  
Shape Memory ◽  
High Energy ◽  
Industrial Applications ◽  
High Energy Density ◽  
Small Scale ◽  
Monitoring And Control ◽  
Actuation System ◽  
First Results ◽  
Functional Prototype ◽  
And Control

Abstract Within industrial manufacturing most processing steps are accompanied by transporting and positioning of workpieces. The active interfaces between handling system and workpiece are industrial grippers, which often are driven by pneumatics, especially in small scale areas. On the way to higher energy efficiency and digital factories, companies are looking for new actuation technologies with more sensor integration and better efficiencies. Commonly used actuators like solenoids and electric engines are in many cases too heavy and large for direct integration into the gripping system. Due to their high energy density shape memory alloys (SMA) are suited to overcome those drawbacks of conventional actuators. Additionally, they feature self-sensing abilities that lead to sensor-less monitoring and control of the actuation system. Another drawback of conventional grippers is their design, which is based on moving parts with linear guides and bearings. These parts are prone to wear, especially in abrasive environments. This can be overcome by a compliant gripper design that is based on flexure hinges and thus dispenses with joints, bearings and guides. In the presented work, the development process of a functional prototype for a compliant gripper driven by a bistable SMA actuation unit for industrial applications is outlined. The focus lies on the development of the SMA actuator, while the first design approach for the compliant gripper mechanism with solid state joints is proposed. The result is a working gripper-prototype which is mainly made of 3D-printed parts. First results of validation experiments are discussed.

Development of Cathode Filament Power Supply for EBW Based on ARM

2014 ◽  
Vol 960-961 ◽  
pp. 1300-1303
Author(s):  
Ze Ting Wang ◽  
Peng Liu ◽  
Sheng Wen Fan
Keyword(s):  
Electron Beam ◽  
Power Supply ◽  
Electron Beam Welding ◽  
High Volume ◽  
High Energy ◽  
High Energy Density ◽  
Shipping Industry ◽  
Soft Start ◽  
Power Frequency ◽  
Low Efficiency

The electron beam welding has high energy density, and has been widely applied in air space, the car and shipping industry. Traditional electron beam welding machine power supply system adopts the technology of the power frequency or medium frequency, with high volume, low efficiency and poor stability of electron beam. I put forward a digital filament power control scheme based on STM32, and introduce the hardware and software implementation method in detail. Experiments show that it can realize soft-start and soft-down process, and also be quickly identified and promptly forbid the output when filament fracture, which realize the intellectualization of filament power supply.

scholarly journals Effect of Electron Beam Welding Parameters on Temperature and Stress Field of AISI P20 Tool Steel in Vacuum Roll-cladding Process

2021 ◽  
Author(s):  
lanyu mao ◽  
Zongan Luo ◽  
Yingying Feng ◽  
Xiaoming Zhang
Keyword(s):  
Electron Beam ◽  
Stress Field ◽  
Tool Steel ◽  
Welding Speed ◽  
Electron Beam Welding ◽  
Welding Process ◽  
Welding Current ◽  
Temperature Fields ◽  
Welding Parameters ◽  
Aisi P20

Abstract Vacuum roll-cladding (VRC) is an effective method to produce high quality ultra-heavy AISI P20 plate steel. In the process of VRC, reasonable welding process of electron beam welding (EBW) can significantly avoid welding cracks and reduce the cost. In this paper, the electron beam welding process of AISI P20 tool steel was simulated by using a combined heat source model based on finite element method, and the temperature field and stress field under different welding parameters were studied respectively . The results showed that welding parameters have a greater effect on weld penetration than that of weld width, which making the aspect ratio increases with the increase of welding current, and decrease with the increase of welding speed. The weld morphologies were consistent with those of the modeling and the measured thermal heat curves were good agreement with those of simulated, which was verified the feasibility and effectiveness of temperature fields. The results of stress fields under different welding parameters indicat ed that lower welding speed and higher welding current resulting in lower residual stress at welded joint, which means lower risk of cracking after EBW. The results of this study have been successfully applied to industrial production.

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