Virtual study of conditions for occurrence of non-metallic inclusions under consumable-electrode multiple-pass welding of pipe-lines

2020 ◽  
pp. 488-493
Author(s):  
A.E. Filyakov ◽  
S.I. Poloskov ◽  
V.A. Erofeev ◽  
M.A. Sholokhov
Keyword(s):  
Arc Welding ◽  
Complex Oxides ◽  
Slag Inclusion ◽  
Causal Factors ◽  
Lack Of Fusion ◽  
Slag Inclusions ◽  
Diffi Cult ◽  
Metallic Inclusions ◽  
Side Face ◽  
Arc Current

The causal factors for the occurrence of non-metallic inclusions in the form of slags, complex oxides and sulfi des under multi-pass arc welding analyzed. It is assumed that lack of fusion in interlayers and slag inclusions are formed on the surface of the beads of previous passes if slag residues in craters exist arising from short interruptions of arc burning, or lack of fusion at bevelled edges. The virtual study is carried out using physical and mathematical model, the features of which are fi xing the level of the melt at the solidifi ed front of the weldpool and introducing into it description of non-metallic inclusions fi lling cavities in the surface crater or lack of fusion at the side face of the groove. The results of numerical simulation of the remelting process of slag residues in different welding modes and with different sizes of slag inclusion are presented. It is shown that, with signifi cant depth of craters or lack of fusion, comparable with the thickness of the deposited layer, it is diffi cult to create conditions for their rise to the surface of the weldpool even at the maximum permissible arc current.

Technological aspects for formation of defects during welding of main pipelines

2020 ◽  
pp. 343-348
Author(s):  
A.E. Filyakov
Keyword(s):  
Arc Welding ◽  
Welded Joint ◽  
Arc Voltage ◽  
Energy Parameters ◽  
Lack Of Fusion ◽  
Transverse Vibrations ◽  
Slag Inclusions ◽  
Effi Ciency ◽  
Main Pipelines ◽  
Welding Processes

During the construction of main pipelines, welding is the main source of the formation of defects, therefore, to minimize them, monitoring and documentation of welding are performed. Analysis of the characteristic defects of the welds showed the dominance of internal formation defects in the form of pores, slag inclusions and lack of fusion. It is established that the main reason for the formation of such defects is craters on the surface of previous passes, which are formed during arc breaks or underestimated range of electrode transverse vibrations. To increase the effi ciency of monitoring for the arc welding processes with fi xing the current and the arc voltage, it is proposed to develop special intelligent module that estimates the parameters of electrode transverse vibrations, change in the energy parameters of the arc, and based on these data predicts the probability and place of formation of defects in the welded joint.

scholarly journals Detection of slag inclusions using infrared thermal imagining system

2021 ◽  
Vol 338 ◽  
pp. 01012
Author(s):  
Wojciech Jamrozik ◽  
Jacek Górka
Keyword(s):  
Cross Section ◽  
Arc Welding ◽  
Infrared Camera ◽  
Slag Inclusion ◽  
Small Temperature ◽  
Radiographic Images ◽  
Slag Inclusions ◽  
Metal Arc Welding ◽  
Made In

Assuring high quality of welded joins is a vital task in many industrial branches also when joints are made manually. It is the case metal-arc welding with covered electrode. One of main imperfection, that can occur in this process is slag inclusion. In the paper an method for detection of slag inclusion in multipass manual welding is proposed and validated. The key idea of the method is that small temperature disturbances will be noticeable in consecutive cross-section of joint in the cooling pass. Temperature distribution weld face was measured with longwave infrared camera (LWIR). For consecutive cross-section made in IR representation of joint differences in mean temperature was calculated to assess the cooling rate directly after the elements were welded. It can be made because on each thermogram the whole joint is visible, thus position of electrode in time can be easily marked. Results of slag inclusion detection were compared with radiographic images of made joints. In the future additional studies will be performed in order to generalize proposed method to wider group of materials and for more complex welds.

Study on the Crack Forming during Cold Forging Process of ML25Mn Steel

2012 ◽  
Vol 184-185 ◽  
pp. 1255-1258
Author(s):  
Zhuang Li ◽  
Di Wu ◽  
Wei Lv
Keyword(s):  
Chemical Composition ◽  
Surface Quality ◽  
High Hardness ◽  
Complex Oxides ◽  
Cold Forging ◽  
Internal Defects ◽  
Forging Process ◽  
Sem Observation ◽  
Metallic Inclusions ◽  
The Matrix

The important factors that affect the formability of the cold forging steel are its surface quality and internal defects. The cracking phenomenon was taken place during cold forging of ML25Mn steel. In this study, microstructural analyses were made on around the cracked regions of the steel. The reason of cracking, which occurred during cold forging for ML25Mn steel, was investigated based on SEM observation in detail. The results have shown that the crack forming during cold forging process is not related to the chemical composition for ML25Mn steel. Cracking is not resulted from high hardness of the steel rods. There are some non-metallic inclusions in the matrix of ML25Mn steel, and the film-like inclusions are composed of MnS, CaS and complex oxides containing Mg, Al, Mn, Fe, S, Ca and O. The formation of non-metallic inclusions is the result of the deoxidation and the solidification during smelting and casting of steel.

Argon-Arc Welding of Cu/Ti3AlC2 Cermet

2008 ◽  
Vol 368-372 ◽  
pp. 1001-1003
Author(s):  
Hua Zhang ◽  
Hong Xiang Zhai ◽  
Zhen Ying Huang ◽  
Shi Bo Li
Keyword(s):  
Network Structure ◽  
Arc Welding ◽  
Room Temperature ◽  
Applied Pressure ◽  
Al Alloys ◽  
Welding Parameters ◽  
Arc Voltage ◽  
Arc Current ◽  
Joining Strength ◽  
Welding Technique

Joining of Cu/Ti3AlC2 cermet by an argon-arc welding technique without filler was firstly investigated. The results show that the Cu/Ti3AlC2 cermet can be joined firmly. The joining strength at room temperature was measured to be 851 MPa after optimization of the welding parameters with 2.6 A/mm2 for arc current density, 5 s for arc time, 10.8 kPa for applied pressure and 12 V for arc voltage. The microstructure in welded zone shows that fine TiCx particles uniformly dispersed in a network structure of Cu-Al alloys. This feature endows the Cu/Ti3AlC2 cermet with the high joining strength.

Effect of Arc Current Ultrasonic-Frequency Pulsation on Underwater Wet Arc Welding Quality

2013 ◽  
Vol 763 ◽  
pp. 174-178 ◽  
Author(s):  
Jie Zhu ◽  
Jia Cheng Guo ◽  
Wei Wang ◽  
Jia You Wang
Keyword(s):  
Arc Welding ◽  
Axial Direction ◽  
Pulse Frequency ◽  
Ultrasonic Frequency ◽  
Weld Penetration ◽  
Welding Quality ◽  
Underwater Welding ◽  
Joint Properties ◽  
Ultrasonic Assisted ◽  
Arc Current

A novel process of ultrasonic-assisted underwater wet arc welding was proposed to improve the joint properties, a number of ultrasonic-assisted underwater welding experiments were then carried out, and the effects of pulse frequency on weld formation, joint hardness and microstructure were investigated. Experimental results show that the ultrasonic frequency pulsation of arc can improve weld penetration while reducing effectively the hardness of joint HAZ in the arc axial direction and refining the grain of microstructure, and the effects of which are related closely to the pulse frequency.

Arc Characteristics and Droplet Transfer Analysis of Disconnect Impulse Arc Welding for Repairing Surface Default of Metal Parts

2014 ◽  
Vol 941-944 ◽  
pp. 2026-2029 ◽  
Author(s):  
Jun Wei Yang ◽  
Jia Xu Teng ◽  
Qing Zhang ◽  
Ling Dong Meng
Keyword(s):  
Arc Welding ◽  
Droplet Transfer ◽  
Metal Parts ◽  
Transfer Characteristics ◽  
Camera Systems ◽  
Arc Characteristics ◽  
Wire Material ◽  
Metallurgical Bonding ◽  
Arc Current ◽  
The Wire

The wire material and the workpiece was fused together by the transient arc heat from disconnect impulse, to achieve metallurgical bonding. The process of arc striking and the arc was very short in disconnect impulse arc welding. The image signals of disconnect impulse arc and droplet transfer were acquired using speed camera systems. Then, the arc and the droplet transfer characteristics in repairing the metal defects process were discussed. The results showed that the process of arc striking was only 0.5-1ms in disconnect impulse arc welding. The maintain arc time must be matched with the arc current, the longer maintain arc time the less the arc current was likely to be.

scholarly journals Characteristics of Welding and Arc Pressure in the Plasma–TIG Hybrid Welding Process

2018 ◽  
Author(s):  
Bo Wang ◽  
Xunming Zhu ◽  
Hongchang Zhang ◽  
Hongtao Zhang ◽  
Jicai Feng
Keyword(s):  
Arc Welding ◽  
Gas Flow ◽  
Welding Process ◽  
Hybrid Welding ◽  
Plasma Arc ◽  
Arc Pressure ◽  
Arc Current ◽  
Arc Welding Process ◽  
Welding Processes

In this article, a novel hybrid welding process called plasma-TIG coupled arc welding was proposed to improve the efficiency and quality of welding by utilizing the full advantage of plasma and TIG welding processes. The two arcs of plasma and TIG were pulled into each other into one coupled arc under the effect of Lorentz force and plasma flow force during welding experiments. The arc behavior of coupled arc was studied by means of it’s arc profile, arc pressure and arc force conditions. The coupled arc pressure distribution measurements were performed. The effects of welding conditions on coupled arc pressure were evaluated and the maximum coupled arc pressure was improved compared with single-plasma arc and single-TIG arc. It was found that the maximum arc pressure was mainly determined by plasma arc current and plasma gas flow. According to the results, the proposed coupled arc welding process have both advantages of plasma arc and TIG method, and it has a broad application prospect.

Effect of arc breaks and short circuits on lack of fusion formation at sidewalls of groove during multi-pass weaving of pipelines

2021 ◽  
pp. 343-347
Author(s):  
A.E. Filyakov
Keyword(s):  
Mathematical Model ◽  
Arc Welding ◽  
Welding Process ◽  
Lack Of Fusion ◽  
Arc Power ◽  
Side Walls ◽  
Short Circuits ◽  
Arc Welding Process ◽  
Short Time ◽  
Transverse Oscillations

To evaluate the effect of the short-time arc breaks along the side-walls of grove during multi-pass welding virtual study of this effect is performed using deterministic mathematical model of arc welding process. It is established that breaks in arc burning lead to the appearance of craters, which may not be remelted during the subsequent pass. It is shown that the effect of the duration of the arc breaks on the craters depth increases with increase in the amplitude and period of oscillations. The effect of breaks is more noticeable if they occur when approaching the groove face than if they occur when moving from the groove face to the center of the pass. When analyzing the welding monitoring data, it is necessary to take into account not only the arc power, but also the parameters of transverse oscillations of the torch, including the phase of arc breaks relative to these oscillations.

Technological Aspects Regarding Manual Metal Arc Welding Using Pulsed Current for Fillet Joints Applications

2016 ◽  
Vol 1138 ◽  
pp. 56-61
Author(s):  
Mircea Burcă ◽  
Aurelian Vasile Magda ◽  
Ioan Lucaciu
Keyword(s):  
Weld Pool ◽  
Arc Welding ◽  
Pulse Current ◽  
Filler Materials ◽  
Pulsed Current ◽  
Welding Equipment ◽  
Lack Of Fusion ◽  
Metal Arc Welding ◽  
Research Findings ◽  
Fillet Joint

The idea of using electrical pulse current at manual arc welding with coated electrode starts from the observation of frequency influence, unchanging in manual TIG welding with filler materials, on weld pool volume, by partial solidification of the weld pool in base time of the pulse current, thus being able to control its volume.This paper presents for the first time this new challenge of inverter modern sources: manual metal arc welding using pulsed current.Experimental research findings highlight the technological aspects when using pulsed current in manual metal arc welding, using STEL welding equipment that has this option. The application - concerns the establishment the lack of fusion welded joints in fillet positions. It highlights the beneficial effect of pulsed current, in particular by the joint penetration.Experiments have pursued highlighting of welding pulsed current and frequency of the pulses by the appearance of the joint and the influence by weld geometry for lack of fusion fillet joint. Also, the influence of frequency pulsed current by arc stability, sprays, etc. compared with standard welding was observed.

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