Carbon Steel Weld Research Articles

Oxide formation during electric resistance welding of low carbon steels

The influence of Mn and Cr on the formation of surface oxides and their entrapment during electric resistance welding of Si containing low carbon steels was studied using thermodynamic calculations and experimental investigation of the microstructure of the different oxide inclusions within welds on electric resistance welding-fabricated pipes. The process of oxidation during the welding process, its dependence on oxygen content, temperature of oxidation and the composition of ferrite within the parent steel were analysed. It was shown that the most important influence on the type of oxide inclusions formed during welding is the Mn/Si ratio, while Cr has an indirect influence via carbide formation, which increases the relative content of Mn in ferrite.

Current deflection NDE for the inspection and monitoring of pipes

Routine inspection of oil and gas pipes for time dependent degradation is essential. Pipelines are most commonly inspected using In-Line Inspection (ILI), however restrictions from pipe geometry, features or flow rate can prevent its use. Facility pipework rarely facilitates ILI, and external inspection often warrants the undesirable removal of the pipe insulation and cladding. This work investigates the applicability of a current deflection non-destructive evaluation technique for both the detection and growth monitoring of defects, particularly focusing on corrosion. Magnetic sensors are used to monitor variations in the spatial distribution of the induced magnetic flux density outside a pipe that arise from deflection of an injected electric current around inner or outer wall defects. An array of orthogonal magnetoresistive sensors has been used to measure the magnetic flux density surrounding six-inch schedule 40 seamless and welded carbon steel and austenitic steel pipes. The measurements were stable and repeatable to the order of 100pT which suggests that the defect detection or growth monitoring of corrosion-type defects may be possible with a few amps of injected current when measurements are taken at around 50mm lift-off. The sensitivity of the technique is dependent on factors including defect geometry, sensor lift-off, bends, variations in nominal pipe geometry or material properties, and the presence of ferromagnetic objects, each of which were investigated using either experiment or a validated finite element model.

Compressive Strength of Steel Frames after Welding with Micro-Jet Cooling

Low carbon steel weld structures generally exhibit a very linear stress-strain relationship. In the study of strength of materials, the compressive strength is the capacity of a material or structure to withstand loads tending to reduce size of structure. It is mainly measured by plotting applied force against deformation in a testing machine. Compressive strength is a main key value for design of welded structures.The main goal of that paper was analysing of plastic properties of frame welds which were made with various parameters of micro-jet cooling. New technology of micro-jet welding could be regarded as a new way to improve plastic properties of welds. It allows to obtain welds with better mechanical properties in comparison to ordinary welding method. Furthermore it is possible to steering of weld structure and properties of the weld. There were given main information about influence of various micro-jet gases on metallographic and properties of structure steel welds.

Multilayers of PAni/n-TiO2 and PAni on carbon steel and welded carbon steel for corrosion protection

Abstract Multilayers of polyaniline (PAni) and PAni/nanotubes-TiO2 composite were compared for corrosive protection on carbon steel and welded carbon steel. The layer porosity, morphology and thickness were characterized. PAni coating showed the best protection when a layer of 2 μm was deposited on steel surface. In spite of the good anticorrosive behaviour of PAni, when the layer thickness was increased up to 4.5 μm a decrease in the anticorrosive behaviour is detected due to the development of mechanical tensions which increase the porosity of the film. However, the addition of TiO2 nanotubes to PAni coatings shows an interesting ability to inhibit this undesirable mechanical effect, showing a good anticorrosive behaviour and lower porosity when thickness layer is increased. The morphological and electrochemical tests of the samples showed good resistance against degradation in chloride medium and in the salt spray analysis, promoting improvement of corrosion protection in an aggressive corrosion medium.

Effect of Welding Heat Input on the Corrosion Resistance of Carbon Steel Weld Metal

The corrosion resistance of carbon steel weld metal with three different microstructures has been systematically evaluated using electrochemical techniques with the simulated produced water containing CO2 at 90 °C. Microstructures include acicular ferrite, polygonal ferrite, and a small amount of pearlite. With welding heat input increasing, weld metal microstructure becomes more uniform. Electrochemical techniques including potentiodynamic polarization curve, linear polarization resistance, and electrochemical impedance spectroscopy were utilized to characterize the corrosion properties on weld joint, indicating that the best corrosion resistance corresponded to the weld metal with a polygonal ferrite microstructure, whereas the weld metal with the acicular ferrite + polygonal ferrite microstructure showed the worst corrosion resistance. The samples with high welding heat input possessed better corrosion resistance. Results were discussed in terms of crystal plane orientation, grain size, and grain boundary type found in each weld metal by electron backscatter diffraction test.

Effect of Cr Content on Microstructure and Mechanical Properties of Low Carbon Steel Welds

Effect of Cr Content on Microstructure and Mechanical Properties of Low Carbon Steel Welds

English

English

Process modeling and parameter optimization using radial basis function neural network and genetic algorithm for laser welding of dissimilar materials

The welded joints of dissimilar materials have been widely used in automotive, ship and space industries. The joint quality is often evaluated by weld seam geometry, microstructures and mechanical properties. To obtain the desired weld seam geometry and improve the quality of welded joints, this paper proposes a process modeling and parameter optimization method to obtain the weld seam with minimum width and desired depth of penetration for laser butt welding of dissimilar materials. During the process, Taguchi experiments are conducted on the laser welding of the low carbon steel (Q235) and stainless steel (SUS301L-HT). The experimental results are used to develop the radial basis function neural network model, and the process parameters are optimized by genetic algorithm. The proposed method is validated by a confirmation experiment. Simultaneously, the microstructures and mechanical properties of the weld seam generated from optimal process parameters are further studied by optical microscopy and tensile strength test. Compared with the unoptimized weld seam, the welding defects are eliminated in the optimized weld seam and the mechanical properties are improved. The results show that the proposed method is effective and reliable for improving the quality of welded joints in practical production.

Interface microstructure and fracture behavior of single/dual-beam laser welded steel-Al dissimilar joint produced with copper interlayer

Dissimilar metal welding of Q235 low carbon steel and 5052 aluminum alloy was carried out by a single/dual-beam laser in a steel-on-aluminum overlap configuration with a copper interlayer. The weld appearance, microstructure, and fracture behavior of the joints made by the single/dual-beam laser welding were investigated comparatively. The results showed that dual-beam laser welding, compared with single-beam laser welding, had better process stability which made better weld appearance and bigger effective joining width which enhanced tensile capacity. With a copper interlayer, a contact reaction zone appeared between the copper interlayer and aluminum matrix, which enlarged effective joining zone. The microstructures of the welding joint welded by a single/dual-beam laser were composed of the ligulate fusion zone with Fe-Al interface and the contact reaction brazing zone with Al-Cu interface. The Fe-Al interface mainly consisted of α-Al and Al2Cu eutectic structure, FeAl, FeAl2, and a certain amount of Al-Cu intermetallics, Fe2Al5 and FeAl3. The Al-Cu interface mainly consisted of eutectic phase Al2Cu and metastable phase of Al-Cu intermetallics. The tensile property was enhanced by a dual-beam laser, and the addition of the copper-foil interlayer might improve the metallurgical reaction of interfacial reaction region and promote the load-carrying ability of weld joint. An ideal joint with fewer defects could be obtained when the welding speed is 0.9–1.25 m/min of dual-beam laser welding and 1.5–1.75 m/min of single-beam laser welding.

Determination of the gross heat input in arc welding

A method to expurgate intrinsic errors from cryogenic calorimetric measurements is described. The sources of errors were identified and experimental procedures were devised to expurgate quantitatively the deviations from the true values, using extrapolation and linearization techniques. The methodology was applied to a case of MIG/MAG welding of carbon steel. The outcome of this approach represents the actual heat input (referred to here as gross heat input) and evidences that the commonly accepted conventional heat input measured by calorimetric methods represents only part of the heat input that is absorbed by the samples. It is expected that the gross heat input values can be successfully used in numerical simulations for better reliability in prediction models on welding.

Numerical simulation of alloy composition in dissimilar laser welding

A three-dimensional multiphase computational fluid dynamic model was developed to investigate the meltpool fluid dynamics, dilution and alloy composition in laser welding of low carbon steel and stainless steel. Using the developed model, independent predictions on weld properties are made for a range of laser parameters, and in all cases the results of the numerical model were found to be in close agreement with experimental observations. The investigation revealed that above certain specific point energy the materials within the melt pool are predominantly homogenous. A minimum meltpool convention is required in dissimilar laser welding to obtain weld bead properties suitable for industrial applications. The present model provides a simple yet effective method to predicting the weld bead alloying concentration and homogeneity encompassing wide range of materials.

Correlation of the Barkhausen Noise with Metallurgical and Mechanical Characteristics of Welded Low Carbon Steel

The influence of Electron Beam welding technique on the microstructure, mechanical and magnetic properties of low carbon steels was presented and evaluated. Samples with dimensions of 12 cm x 6 cm x 1.5 mm were prepared from stock plate, installed on the welding table and welded at welding speeds and pulsed currents following a predesigned protocol. In order to examine the influence of welding on the magnetizing behavior of low carbon steel, magnetic Barkhausen noise were conducted on the surface of the welded samples. The results were further evaluated by examining the microstructure and mechanical properties of the welded samples by using scanning electron microscopy and micro-hardness measurements, respectively.

Variations of the Magnetic Permeability and Barkhausen Noise in a Welded Low Carbon Steel

The present paper investigates the utilization of both the magnetic Barkhausen noise and permeability measurements for the nondestructive distinguish of the three welding zones in a welded low carbon steel.

Orientation changes near the interface of explosively bonded (carbon steel)/Zr700 sheets

The microstructure and texture of explosively welded carbon steel (base) and Zr700 (flyer) plates were characterized by means of scanning electron microscopy equipped with a high resolution electron backscattered diffraction facility. The orientation maps demonstrate that the deformed zones near-the-interface are composed of several layers, the width of which depends on the applied bonding parameters. For both metals, the very thin layer of ultra-fine grains directly adheres to the interface. In the areas more distanced from the interface, the structure evolution depends on the plate material. In the case of a Zr 700 sheet the second layer is formed by highly dislocated (sub)grains, which progressively evolve, towards the structure composed of only lightly deformed grains. In the case of a carbon steel sheet, the second layer near the interface was composed of flattened grains.

Comparação da Taxa e Eficiência de Deposição entre os Consumíveis ER70S-6 e E71T-1C

Na soldagem de aço de baixo carbono podem ser empregados diversos consumíveis, como o arame tubular e o arame maciço. Este trabalho compara a taxa e a eficiência de deposição em função da corrente de soldagem, da distância do bico de contato à peça (DBCP) e do tipo de gás de proteção, comparando-se o ER70S-6 com o E71T-1C. As taxas de deposição foram medidas usando-se uma sequência de cordões de solda sobre chapa de aço. As frequências de destacamento das gotas foram medidas a partir de equipamento de aquisição de dados, baseando-se nas variações de tensão do arco. O diâmetro da gota foi calculado teoricamente com base na velocidade de alimentação do arame. Foi utilizado um programa para análise estatística dos resultados produzidos pelos experimentos. Os resultados mostraram que a taxa de deposição aumenta com o aumento da corrente e com o aumento da DBCP. Da mesma maneira, a variável mais importante para controlar a eficiência de deposição foi a natureza do consumível. O ER70S-6 apresentou uma maior eficiência de deposição que o arame tubular E71T-1C, como era esperado, uma vez que o arame tubular gera escória que não é contabilizada na massa do cordão depositado.

Application of Differential Transform Method for Estimating Thermal Cycle Developed in GTA Welding of High Carbon Steel Joints

This article reveals a detailed study of temperature cycle formed during Gas Tungsten Arc welding of high carbon steel (AISI 1090) butt joints. Experimental work has been carried out to estimate the temperature distribution along fusion boundary to longitudinal direction of the weldment by mounting thermocouples on the plate along with Data Acquisition System. Heat flux distribution due to moving point heat source has been demonstrated by implementing Gaussian surface heat flux and Angular Torch model. Cooling rate has predicted by application of Adams cooling rate equation. Conduction-convection phenomena plays dominant role for evaluating heat loss from the weld joint and Differential Transform Method (DTM) has been applied to judge non-dimensional temperature distribution. Analytical studies has shown well agreement with experimental temperature distribution.

Harmonic analysis of measured initial geometric imperfections in large spiral welded carbon steel tubes

Geometric imperfections have long been known to play an important role in determining the buckling resistance of metal cylindrical shells and tubes. Though the effect is more important in thin shells rather than thicker tubular members, it may still have a significant impact on the strength of tubulars where buckling occurs in the plastic range.Spiral welded carbon steel tubes with D/t ratios in the approximate range 50–150 are often used as primary load-bearing members together with sheet piling in deep retaining walls. A recent European study on such tubes aimed to devise improved and more economical design guidelines for their use. As a central part of this project, a representative selection of 18 tubes was subject to a laser survey to obtain detailed scans of the initial imperfections found on their outer surfaces, in addition to careful wall thickness measurements. The resulting high quality data set is considered to be the first of its kind.The surface imperfections of the full set of 18 tubes were collectively analysed using a combination of single and double Fourier series to assess the dominant imperfection modes and their amplitudes. It was found that the spiral welding process results in a very unique pattern of surface imperfections which is here characterised algebraically. The systematic peak geometric deviations of the tube surfaces were found to be modest and consistent with the imperfection amplitudes defined by EN 1993-1-6 for this D/t range.

Role of inclusions for formation of acicular ferit in low carbonsteel weld deposits

Acicular ferit was investigated from the viewpoint of orientation relationships among acicular ferit, prior austenite, and inclusions. The Baker-Nutting orientation relationship was observed between acicular ferit and a TiO layer forming at inclusion surfaces. Meanwhile, the Kurdjumov-Sachs orientation relationship was observed between acicular ferit and prior austenite. The results indicate that acicular ferit is considered to nucleate due to a low misfit with TiO layers; however, there is still doubt. In case the TiO layer form at molten steel, its orientation would be random with austenite. Thus, acicular ferit nucleating with the Baker-Nutting orientation relationship should have no orientation relationship with austenite. In order to address the issue, the inclusion formation process was investigated by using the liquid-tin quenching technique and the thermodynamic calculation. The results reveal that TiO form not at the high temperature such as molten steel temperature but at below the solid phase temperature such as austenite or ferit temperature. As the result of orientation analysis between prior austenite and TiO, TiO is not considered to form in austenite. It can be assumed that TiO layers form in order to match interface with acicular ferit. Additionally, the Mn depleted zone were also not observed. Therefore, acicular ferit is considered to nucleate not due to the low misfit or the Mn depleted zone but due to another mechanism.

Analysis of variance of tensile tests from spiral welded carbon steel tubes

Thick tubular carbon steel members are commonly used in combination with sheet piles in large retaining walls where they provide the necessary bending stiffness. A current international research project aims to provide safe and efficient design rules for such ‘Combitubes’. These tubes are usually manufactured by continuous spiral welding from a carbon steel coil. One of the key concerns is the possible influence of material anisotropy on the bending resistance of the resulting fabricated tube. Standard tensile tests were performed on several specimens extracted from such tubes, exploring the stress–strain behaviour in different orientations relative to the tube axes and the spiral directions. An analysis of variance (ANOVA) was then carried out to compare the mean values of properties deduced from these tests. This short paper offers statistical evidence that supports the view that an isotropic treatment may be acceptable for computational analyses and design of spiral welded steel tubes. It also illustrates how a standard statistical method may be applied to attempt such a validation, even though the data set may be too small for a rigorous statistical verification.

CREVICE CORROSION BEHAVIORS OF Q235 WELD JOINT

As a candidate package material for high level radiation waste disposal, the crevice corrosion behavior of Q235 low carbon steel weld joint was investigated in a solution simulated to the groundwater in the northwest part of China. The influences of temperature and oxygen content were evaluated. The microstructure of the weld joint was observed by OM, and SEM and surface profile were employed to analyze the crevice corrosion behavior of the weld joint. Open circuit potential of different regions of the weld joint was measured by electrochemical method. Experimental results indicated that the increases of temperature and oxygen content could promote the occurrence of crevice corrosion, and facilitate the corrosion processes both inside and outside the crevice. Fusion zone with a microstructure of clustered ferrite was the most severe corroded area in the weld joint, followed by weld metal, which was characterized by a coarse widmanstaetten structure. The microstructures of base metal and heat affected zone were fine and homogeneous, so these two regions underwent slighter corrosion.