Showing papers on "Shielded metal arc welding published in 2010"

The effects of metal vapour in arc welding

Abstract: Metal vapour is formed in arc welding processes by the evaporation of molten metal in the weld pool, and in the case of gas–metal arc welding, in the wire electrode and droplets. The presence of metal vapour can have a major influence on the properties of the arc and the size and shape of the weld pool. Previous experimental and computational works on the production and transport of metal vapour in welding arcs, in particular those relevant to gas–metal arc welding and gas–tungsten arc welding, are reviewed. The influence of metal vapour on the thermodynamic, transport and radiative properties of plasmas is discussed. The effect of metal vapour on the distributions of temperature, current density and heat flux in arcs is examined in terms of these thermophysical properties. Different approaches to treating diffusion of metal vapour in plasmas, and the production of vapour from molten metal, are compared. The production of welding fume by the nucleation and subsequent condensation of metal vapour is considered. Recommendations are presented about subjects requiring further investigation, and the requirements for accurate computational modelling of welding arcs.

Welding and joining of magnesium alloys

Abstract: Part 1 General: Introduction to the welding and joining of magnesium Welding metallurgy of magnesium alloys Preparation for welding of magnesium alloys Welding materials for magnesium alloys Welding and joining of magnesium alloys to aluminium alloys The joining of magnesium alloys to steel Corrosion and protection of magnesium alloy welds. Part 2 Particular welding and joining techniques: Brazing and soldering of magnesium alloys Mechanical joining of magnesium alloys Adhesive bonding of magnesium alloys Gas-tungsten arc welding (GTAW) of magnesium alloys Metal inert gas welding (MIG) of magnesium alloys Variable polarity plasma arc welding of magnesium alloys Hybrid laser-arc welding of magnesium alloys Activating flux tungsten inert gas (A-TIG) of magnesium alloys Friction stir welding of magnesium alloys Laser welding of magnesium alloys Resistance spot welding of magnesium alloys Electro-magnetic welding of Mg alloys.

Arc welding control method and arc welding apparatus

Abstract: An arc welding control method carries out weld with a welding current and a welding speed different from those at a steady welding period according to intrinsic resistivity of a weld wire or a base material at a welding start period and a welding end period, so as to obtain a satisfactory welding quality.

The Influence of the Matrix Microstructure on Abrasive Wear Resistance of Heat-Treated Fe–32Cr–4.5C wt% Hardfacing Alloy

Abstract: The abrasion wear resistance of Fe–32Cr–4.5C wt% hardfacing alloy was investigated as a function of matrix microstructure. In this study, the alloy was deposited on ASTM A36 carbon steel plates by the shielded metal arc welding (SMAW) process and the as-welded matrix microstructure was changed into ferrite, martensite, and tempered martensite by heat treatment processes. The Pin-on-disk test results show that under low (5 N) and high (20 N) load conditions, the wear resistance behavior of the as-welded matrix sample is 20 and 15% higher, respectively, than the martensitic matrix sample, although the bulk hardness of the as-welded matrix is 5% lower. The ferritic matrix sample has the poorest wear resistance behavior which is less than half of that of the as-welded matrix one. Micro-ploughing, micro-cutting, and micro-cracking are recognized as the micro-mechanisms in the material removal in which the proportion of micro-ploughing mechanism increased by increasing matrix toughness.

Research on the activating flux gas tungsten arc welding and plasma arc welding for stainless steel

Abstract: A systematic study of the effects of activating flux in the weld morphology, arc profile, and angular distortion and microstructure of two different arc welding processes, namely, Gas Tungsten Arc Welding (GTAW) and Plasma Arc Welding (PAW), was carried out. The results showed that the activating fluxes affected the penetration capability of arc welding on stainless steel. An increase in energy density resulting from the arc constriction and anode spot reduction enhanced the penetration capability. The Depth/Width (D/W) ratio of the weld played a major role in causing angular distortion of the weldment. Also, changes in the cooling rate, due to different heat source characteristics, influenced the microstructure from the fusion line to the centre of the weld.

Internal exposure, effect monitoring, and lung function in welders after acute short-term exposure to welding fumes from different welding processes.

Abstract: Objective: In this study, the effect of short-term exposure to welding fumes emitted by different welding techniques on workers was investigated. Methods: In a 3-fold crossover study, six welders used three different welding techniques for 3 hours. Before and after welding, blood and urine samples were collected to perform biomonitoring of metals. Breath condensate was collected to assess inflammatory reactions, and lung function measurements were performed. Results: Welding led to a significant increase of chromium and nickel in blood and urine and of nitrate and nitrite in exhaled breath condensate. These increases were higher for manual metal arc welding with alloyed material (MAW-a). Several lung function parameters decreased after welding. This decrease was significantly higher after MAW-a. Conclusions: In respect to biological effects, MAW-a seems to be more important than other welding techniques.

Underwater arc welding of higher strength low-alloy steels

Abstract: Welding is used extensively in the construction and repair of underwater pipelines. Recently, the volume of application of underwater welding in these operations has been expanded considerably. Thi...

Characterization of boride-rich hardfacing on carbon steel by arc spray and GMAW processes

Abstract: This paper reports the hardfacing of low carbon steel using a boron-rich cored wire electrode. Arc spraying and gas metal arc welding (GMAW) techniques were employed to form a series of boride-rich coatings on the surface of St52 steel. Optical metallography, scanning electron microscopy, X-ray diffraction, and Vickers hardness testing were used to evaluate coatings structure and morphology, phase evolution and mechanical properties, respectively. The results showed that coatings produced by arc spraying composed of a uniform laminar morphology. In gas metal arc welding, a graded type coating was obtained and the microstructure consisted of a mixture of Fe 2 B, α-Fe and some FeB, with strong metallurgical bonding to the substrate. Identification of phases by XRD indicated that in both processes, the coatings possessed a high content of iron borides and some eutectic. These phases produced microhardness values in excess of 1600 HV on the coating surface. Indentation testing proved that boride coatings obtained by welding technique had better adhesion to steel substrate and were far more resistant to spalling.

Argon-Hydrogen Shielding Gas Mixtures for Activating Flux-Assisted Gas Tungsten Arc Welding

Abstract: Using activating flux for gas tungsten arc welding (GTAW) to improve penetration capability is a well-established technique. Argon is an inert gas and the one most widely used as a shielding gas for GTAW. For the most austenitic stainless steels, pure argon does not provide adequate weld penetration. Argon–hydrogen mixtures give a more even heat input to the workpiece, increasing the arc voltage, which tends to increase the volume of molten material in the weld pool as well as the weld depth-to-width ratio. Great interest has been shown in the interaction between activating flux and the hydrogen concentration in an argon-based shielding gas. In this study, the weld morphology, the arc profile, the retained delta ferrite content, the angular distortion, and the microstructures were examined. The application of an activating flux combining argon and hydrogen for GTAW is important in the industry. The results of this study are presented here.

Friction stir welding of ductile iron and low carbon steel

Abstract: Friction stir welding (FSW) is a low distortion, high quality solid welding. There is no melting during the welding process, which results in improved welding quality. Ductile iron has the advantages of being low cost, of excellent castability, and of being good mechanically. Therefore, it is generally used in many structural engineering parts. In this study, ferritic ductile iron and low carbon steel were used to explore the qualities of dissimilar metal welding under different conditions. The FSW process, changes in the microstructure of the welding area and the mechanical properties of joints were explored. According to the research, we found that when dissimilar metal welding is conducted at 982 rev min–1 with a travelling speed of 72 mm min–1, flawless welding quality can be obtained if the stir rod rotates counterclockwise with carbon steel fixed in the advancing side and with ductile iron in the retreating side. FSW successfully provided defect free welds. However, fine pearlite and martens...

Welding method of girth weld of inner cladding thin-walled stainless steel composite tube

Abstract: The invention relates to a welding method of a girth weld of an inner cladding thin-walled stainless steel composite tube. The welding method comprises the following steps: girth welds of the inner cladding stainless steel composite tube are respectively and gradually welded by three welding seams, an inner cladding layer welding seam and a transition layer welding seam are welded by argon tungsten-arc welding, the stainless steel inner cladding layer welding seam adopts welding wires with the same quality thereof, the transition layer welding seam adopts ER309 welding wires, and the base layer is welded by shielded metal arc welding or CO2 gas shielded welding and adopts a welding material matched with the strength of the base layer; and the inner cladding layer, the transition layer and the first layer of the base layer are welded under back argon gas protection. The welding method guarantees corrosion resistance of a joint of the inner cladding layer and mechanical property of a welding joint of the base layer; and the method plays an important role in promoting wide application of the inner cladding stainless steel composite tube in businesses such as oil-gas delivery, chemical industry, oil refining and the like, improving corrosion resistance of an inner wall of a pipe, and solving the problems of high cost and the like caused by adopting a full wall-thickness stainless steel pipe.

Process Parameter Optimization in ARC Welding of Dissimilar Metals

Abstract: Welding is a basic manufacturing process for making components or assemblies. Recent welding economics research has focused on developing the reliable machinery database to ensure optimum production. In this paper, the optimization of welding input process parameters for obtaining greater weld strength in the manual metal arc (MMA) welding of dissimilar metals like stainless steel and carbon steel is presented. The Taguchi method is adopted to analyze the effect of each welding process parameter on the weld strength, and the optimal process parameters are obtained to achieve greater weld strength. Experimental results are provided to illustrate the proposed approach.

Parametric Optimization of Gas Metal Arc Welding Processes by Using Factorial Design Approach

Abstract: Gas Metal Arc Welding is a process in which the source of heat is an arc format between consumable metal electrode and the work piece with an externally supplied gaseous shield of gas either inert such as argon, helium. This experimental study aims at optimizing various Gas Metal Arc welding parameters including welding voltage, welding current, welding speed and nozzle to plate distance (NPD) by developing a mathematical model for sound weld deposit area of a mild steel specimen. Factorial design approach has been applied for finding the relationship between the various process parameters and weld deposit area. The study revealed that the welding voltage and NPD varies directly with weld deposit area and inverse relationship is found between welding current and speed with weld deposit area.

900MPa high-strength steel preheating-free combined welding method

Abstract: The invention discloses a 900MPa high-strength steel preheating-free combined welding method 700-800 MPa low-hydrogen type high-tenacity shielded metal arc welding is adopted for backing welding, then a 900MPa high-tenacity solid wire is matched with Ar+CO2 mixed gas shielded welding for implementing filling welding, and a 800MPa flux-cored wire is matched with CO2 gas shielded welding for cosmetic welding A crack-free welding joint can be obtained by welding 900MPa high-strength steel through adopting a preheating-free and postweld heat treatment free combined welding process, and a joint region is smooth and clean, and can meet operating requirements on a high-strength steel welding structure for higher bearing capacity because the room temperature tensile strength of weld metal is more than 860MPa and the damping power of a V-shaped notch of the weld metal with the test temperature of 0 DEG C is more than 90J; and meanwhile, the method has welding cost reduced by about 25 percent, simple and convenient operation and easy popularization

Study of weld joint strength using sensor signals for various torch angles in pulsed MIG welding

Abstract: The present work focuses on the influence of pulse parameters at various torch angles on the tensile properties of low carbon steel butt weld in pulsed metal inert gas welding. The interface of weld zone and heat affected zone was found to be the weakest area due to significant variation of weld microstructure. The weld bead characteristics strongly influenced the joint strength. An infrared pyrometer and sound sensor have also been used along with arc sensors to monitor the weld quality. The arc power and arc sound kurtosis were found to be strongly correlated with weld quality.

Dynamic fracture toughness of armour grade quenched and tempered steel joints fabricated using low hydrogen ferritic fillers

Abstract: The armour grade quenched and tempered steel joints fabricated using low hydrogen ferritic steel (LHF) filler exhibited superior joint efficiency owing to preferential ferrite microstructure in the welds and also they offered required resistance to HIC. However, the combat vehicles used in military operations will be required to operate under a wide range of road conditions ranging from first class to cross country. Structural components in combat vehicles are subjected to dynamic loading with high strain rates during operation. Stress loadings within the vehicle hull of these vehicles are expected to fluctuate considerably and structural cracking especially in welds during the service life of these vehicles can lead to catastrophic failures. Under these conditions, fracture behaviour of high strain rate sensitive structural steels can be better understood by dynamic fracture toughness (K1d). Hence, an attempt was made to study dynamic fracture toughness of the armour grade quenched and tempered steel and their welds fabricated using LHF consumables. The experimental results indicate that the K1d values of the joints fabricated by shielded metal arc welding (SMAW) are higher than those of the joints fabricated using flux cored arc welding (FCAW) process.

Welding solid wire and weld metal

Abstract: The objective of the present invention is to provide a similar-metal-composition welding solid wire, and weld metals therefor, with which both excellent bead shape and high ultralow-temperature toughness for the weld joints can be achieved when welding 9% Ni steels together by means of a high-efficiency MIG welding method. A fixed ratio of a REM and O are included in a similar-metal-composition welding solid wire of a 9% NI steel base material, and oxygen is supplied in a trace amount in a range that does not hinder the ultralow-temperature toughness of the weld joint ( 1 a ) but that is capable of forming fine REM oxides in the weld metal ( 3 ) and of controlling the weld metal to produce an excellent bead shape. In addition, both Al and Ti are regulated and an argon gas that contains little or no carbon dioxide gas is used as the shield gas in the MIG welding method. Thus, both an excellent bead shape and high ultralow-temperature toughness for the weld joint ( 1 a ) can be achieved.

Welding method of thick steel plate

Abstract: PROBLEM TO BE SOLVED: To provide a welding method of a thick steel plate which is suitable for pipe making welding of large diameter steel pipes such as UOE steel pipe with a thickness of ≥30 mm and spiral steel pipe. SOLUTION: In welding a steel material with a thickness of ≥30 mm or more from both sides, an electrode for gas shielded arc welding is arranged, as multi-electrode welding as necessary, in the front in the welding direction of the first electrode in multi-electrode submerged arc welding for hybrid welding. In the hybrid welding, the multi-electrode submerged arc welding is performed with a heat input to satisfy an expression (1) while, desirably, the gas shielded arc welding is performed with a heat input to satisfy an expression (2). If the gas shielded arc welding is multi-electrode welding, the wire diameter to be applied for the first electrode is ≥1.4 mm, with a current density set at ≥500 A/mm 2 . Provided that 0.18t-3≤Q S ≤0.35t-5.5 (1), where t is the thickness (mm) of the steel material and Q S is a welding heat input (KJ/mm) of multi-electrode submerged arc welding, and that Q G ≤0.17t-1.5 (2), where t is the thickness (mm) of the steel material and Q G is a welding heat input (KJ/mm) of gas shielded arc welding. COPYRIGHT: (C)2011,JPO&INPIT

Contribution of precipitate on migrated grain boundaries to ductility-dip cracking in Alloy 625 weld joints

Abstract: We investigated the crack properties in Alloy 625 weld metals and their characteristics using experimentally designed filler wires fabricated by varying the niobium and manganese contents in the flux with the shield metal arc welding (SMAW) process. The fast diffusivity of niobium on the migrated grain boundary (MGB) under strong restraint tensile stress, which was induced by the hardened matrix in weld metal containing high niobium and manganese, accelerated the growth of niobium carbide (NbC) in multipass deposits. Coalescence of microvoids along with incoherent NbC and further propagation induced ductility-dip cracking (DDC) on MGB.

Novel method of thermite welding

Abstract: This article presents a novel method of thermite welding. A hand operated portable welding can be conveniently realised using self-made thermite welding pencil without any welding equipments. A butt junction was obtained between two low carbon steel plates. Morphological, microstructure and mechanical analyses of the weld bead were carried out. The results demonstrated that the two steel plates were jointed by fusion bonding with the filler. No defects such as porosity and microcrack were found. The hardness test showed the low hardness of the fusion zone compared with the base material. In addition, the grain growth in HAZ did not affect the hardness of the base material. The average tensile strength of welds was 285·4 MPa, ∼70% of the average tensile strength of low carbon steel.

Comparative study of high-strength steel weld metals obtained by the SMAW and FCAW processes for offshore applications and mooring chains

Abstract: A comparative study of the clad electrode and tubular wire processes was carried out, looking at the mechanical and micro-structural properties of weld metals of high-resistance steel, in the ‘as-welded’ and ‘stress-relief heat treatment’ (PWHT) conditions. The results show that the procedures adopted for welding with tubular wire and clad electrodes allow satisfactory levels of mechanical resistance to be obtained, with the exception of the value of percentage lengthening of the tubular wire, in the as-welded condition. The impact tests show that both the weld metals showed satisfactory impact resistance, in both the as-welded and PWHT conditions, observing that, for the tubular wire, the impact resistance is lower for the clad electrode in both conditions, lying close to the limit applied for the acceptance criterion of 50 J at 0°C in the PWHT condition. It was confirmed that the productivity achieved by the tubular wire process was approximately twice as high as that for the clad electrode process. As ...