Welding Layer Research Articles

Impact of amplitude modulation of heteropolar square current pulses on formation of permanent joints in metal structures under residual magnetization

The work studies the impact of amplitude modulation of heteropolar current pulses on the formation of permanent joints of main pipelines done by manual shielded metal-arc welding. The results show that square pulsed current together with additional low-frequency current modulation facilitates formation of all weld layers in pipelines with residual magnetization. The work establishes that varying residual magnetization degree has no adverse effect on the quality of all layers of the permanent joints realized by modulated alternating square current, including their macrostructural and microstructural characteristics. This increases the technological stability of welding through elimination of electrode freezing during low-energy periods.

Operational factors of new flux cored wires of the Fe–C–Si–Mn–Cr–Ni–Mo system for surfacing of protective plates of shearer cutting drums

Evaluation of the joint effect of the chemical composition of flux cored wires on the wear and hardness of the deposited layer was carried out using mathematical-statistical methods, allowing the influence of the chemical composition of the flux cored wires on the performance of the weld layer of the mining equipment to be revealed. According to the results of the multifactor correlation analysis, the dependences of the hardness of the deposited layer and its wear resistance on the mass fraction of elements included in the flux cored wires composition of the Fe-C-Si-Mn-Cr-Ni-Mo system were determined. The obtained dependences are used to predict the hardness of the deposited layer and its wear resistance when the chemical composition of the weld metal is changed. New, protected by patents of the Russian Federation, flux cored wires of the system Fe-C-Si-Mn-Cr-Ni-Mo for surfacing the mining equipment were developed.

The evolution of microstructure and intergranular corrosion resistance of duplex stainless steel joint in multi-pass welding

Abstract This work focused on the microstructure and intergranular corrosion resistance of duplex stainless steel at different periods of multi-pass welding. Roots protected with pure Ar and Ar-N2 mixing gas were investigated. The austenite content of the root shielded by pure Ar raised with the increasing of welding layers, but its intergranular corrosion resistance was significantly deteriorated. The microstructure showed that much secondary austenite (γ2) formed after the root was reheated by the subsequent welding layer and in the final joint. Meanwhile, the results of the root shielded with Ar-3% N2 showed that its austenite content in the root of final joint was similar to the pure Ar shielded root, but its intergranular corrosion resistance was not obviously deteriorated in multi-pass welding process. It is suggested that a suitable austenite-ferrite phase ratio in the final DSS multi-pass joint cannot guarantee a good intergranular corrosion performance, the microstructural evolution process, e.g., the precipitation of chromium nitride and the formation of γ2, also affect the corrosion resistance.

Role of Bead Sequence in Underwater Welding.

This paper presents examinations of the role of the bead sequence in underwater welding. Two specimens of wet welded layers made by covered electrodes with the use of normalized S355G10+N steel were welded by a reasonable bead sequence. For each specimen, metallographic macro- and micro-scopic tests were done. Then, Vickers HV10 hardness measurements were conducted for each pad weld in the welded layer. The results show that welding in the water environment carries many problems in the stability of the welding arc, which influences the properties of the welds. The effects of refining and tempering the structure in heat-affected zones of earlier laid beads was observed, which provides a reduction of hardness. The possibility of applying two techniques while welding the layer by the wet method is described. It is stated that a reasonable bead sequence can decrease the hardness in heat-affected zones up to 40 HV10. Tempering by heat from next beads can also change the microstructure in this area by tempering martensite and can decrease susceptibility to cold cracking.

Effect of Current Variation on Microstructure and Properties of B4C Nickel-base Alloy by Plasma Surfacing

In order to study the hardness of nickel-based alloys and the effect of different mass fraction boron Carbide on the microstructure of nickel-based alloys. In this paper, different amounts of boron carbide are added to the nickel alloy powder. A layer of nickel alloy surface layer is welded on the surface of the Q235 steel plate by plasma surfacing technology. The microstructure of the laminate is observed and analyzed by using Caisijinxiang tissue microscope. The hardness of the welding layer was tested by microhardness meter and the influence of boron Carbide on nickel alloy was obtained. The results show that boron carbide and nickel base alloy are well fused. The surfacing layer is mainly composed of fine dendrites and herbaceous eutectic structures. The addition of boron carbide can significantly improve the hardness andfine structure of the surfacing layer. With the increase of the content of boron carbide, the hardness of the surfacing layer first increases and then decreases. The experimental data show that when the mass fraction contentof boron carbide is 6% and the current is 110A, the hardness of the welding parts is higher.

Effect of Molybdenum on Metallurgical and Wear Properties of Fe–Cr–C Hard facing alloy

In this research, Surface hardening was performed by two types of Flux Cored Arc Welding (FCAW) filler metals based on Fe–Cr–C and Fe–Cr–C–Mo at the single, two and three- pass modes on the plain carbon steel. To evaluate the metallurgical and mechanical properties of hard facing layers, the optical microscope metallography, Scanning Electronic microscope, X-ray Diffraction test, hardness testing, Microhardness test and abrasion test was applied. Adding (1.1– 1.3) molybdenum to the Fe–Cr–C filler rod led to the formation of complex carbides of M7C3, in the microstructure. By increasing molybdenum, the wear resistance and hardness of the weld layers increased so that three-layers weld hardness reached to 62 HRC. Also, the hardness of complex carbides is 1299 HV which increased to 1596 HV by adding molybdenum.

Usage of Gray Cast Iron for Hardening of Agricultural Machines’ Soil-Tilling Implement

Research of gray cast iron was established to study physical-mechanical properties in microstructure while apply a layer on steel basis of work tool’s soil-tilling. Gray cast iron went through preliminary heat treatment, where gray cast iron hardening with temperature of 750…1050 °C with following water quenching. Research program including: comparison analysis of reference specimen and specimens which were went through heat treatment. Researching material was applied on work tool’s soil-tilling with two methods: arc surfacing and elcetrosparck surfacing. Microstructure of welding layer after arc welding and electrospark welding was studied. Therefore was found out that elecrosparck method gave opportunity to obtain wear resistant layer for a few run, also structure and basis of gray cast iron doesn’t change. Coarse graining doesn’t spot in pad weld, which is beneficial for properties. Measurement of welding layer’s hardness is bigger than base metal and there is no softening of basis. Field tests of hardened products which have shown that to use effectively gray cast iron with heat treatment for hardening, because quality and coating thickness is meeting the requirements of abrasive resistance and there are no spotted significant changes of geometrical dimension for soil-tilling implement.

Microstructural Changes and Impact Toughness of Fill Pass in X80 Steel Weld Metal

Multi-pass welding is used in high-pressure and thick-walled pipes in natural gas and oil pipelines. When a welding layer of a welded joint is subjected to different welding thermal cycles, its microstructure and properties change, thereby affecting the overall welding performance. In this study, the temperature and microstructural variations of the fill pass 2 (FP2) in the entire welding process were investigated by combining the thermal cycle with the cascade welding method. The original FP2 and FP2 after double thermal cycles had the worse deformation ability by tensile test. The toughness of FP2 improved after a single thermal cycle, decreased after double thermal cycles, and improved again after triple thermal cycles. The content of martensite–austenite (M–A) constituents and the average grain size of FP2 in the cascade samples were inversely proportional to FP2 toughness. Massive M–A constituents and their unique distribution at the inter-critical temperature were harmful to weld metal toughness. Controlling the size and fraction of M–A constituents can improve weld metal toughness.

A robot welding approach for the sphere-pipe joints with swing and multi-layer planning

Sphere-pipe joints welding is widely used in industrial applications. This paper presents a robot welding approach for the sphere-pipe joints with swing and multi-layer planning. Firstly, various coordinate systems are used to describe the geometric relationship between weld seam and robot welding torch. The sphere-pipe intersecting curve welding process is basically uphill and downhill welding. Therefore, this paper establishes a description model of the welding torch attitude, which parameterizes the attitude description and automatically adjusts the torch attitude during the welding process according to the change of weld inclination angle. To overcome the negative effects of gravity, such as deepening of the molten pool and reduction of the weld width, this paper integrates the swing welding technology into trajectory planning and gives a solving algorithm for the welding torch swing curve. The swing welding also can reduce the number of weld pass. Therefore, multi-layer single-pass swing welding is an economical and efficient way for thicker weldments. In this paper, a multi-layer single-pass swing welding planning algorithm is proposed, which can automatically determine the height and swing amplitude of each welding layer. Finally, the industrial robot Puma560 is used to carry out experimental simulation, and the simulation results are used to verify the feasibility and accuracy of this approach.

Evaluation of double-layer weld deposition technique on ASTM A182 F22 steel without post-weld heat treatment

The present work evaluates the mechanical and metallurgical behavior of ASTM A182 F22 steel heat-affected zone (HAZ) through the double-layer weld deposition technique, with different welding energies between the first and second layers. This methodology leads to the reduction of hardness levels in the HAZ and can exempt the need for post-weld heat treatment on low-alloy steel after buttering welding. The welding was performed by the automated GMAW process in flat position. As the filler metal, the AWS ER309L, ER 80S-G and ER NiCrMo-3 (Inconel 625) alloys were applied on ASTM A182 F22 steel. The analysis of the refining and/or tempering in coarse-grained HAZ (CGHAZ) of the first layer was performed by metallographic tests and microhardness measurements. The tempering of the first-layer CGHAZ is dependent on the correct overlap of the weld layers, weld bead geometry and the highest imposed heat of the second layer. The results revealed that the Higuchi technique is effective for obtaining welding parameters for the second-layer deposition that promotes thermal treating of the hard region of the first-layer HAZ. However, this technique was not able to reduce the hardness values at the 250 HV level required by NACE 0175 for the test conditions in this work.

Microstructure and Characterization of Overlay Welding Layer using Fe-based Composite Powders

Microstructure and Characterization of Overlay Welding Layer using Fe-based Composite Powders

Strengthening mechanism and properties of Co–WC composite coatings deposited by plasma‐transferred arc welding

Cobalt (Co)-based tungsten carbide (WC) wear-resistant coatings with different content of WC were prepared on the surface of Q235 low carbon steel by plasma-transferred arc welding. The properties of the coatings such as strengthening mechanism, microhardness and wear properties were tested by using a metallurgical microscope, scanning electron microscope, energy dispersive spectrometer, X-ray diffraction, Rockwell hardness tester, and friction wear equipment. The results show that the main reasons for the strengthening of spray welding layer are the solution strengthening formed by α-Co with supersaturated tungsten (W) and the dispersion strengthening caused by eutectic precipitated carbide and silicide. The proportion of the solid solution of W in α-Co steadily ranges from 18.00 to 19.59%. The morphologies of rich W-phase are mainly related to the content of W. With the content of W increasing, the evolution process of the shape is the amorphous form→damascene shape→star-like shape→the polygon. Amorphous W-rich phase can be obtained when the content of WC ranges from 20 to 30%, evenly distributed W-rich phase in the shape of damascene or star can be obtained when the WC content ranges from 30 to 40%, and the polygonal W-rich phase can be obtained at the percentage of 40-50%.

The influence of welding condition on the microstructure of WC hardfacing coating on carbon steel substrate

Tungsten carbide (WC) hardfacing coating technique is widely used to improve the performance of carbon steel blade exposed to acidic and abrasive conditions during production. This paper deals with the influence of welding parameters on the microstructure and carbide distribution of WC. WC hardfacing was deposited onto carbon steel by shielded metal arc welding (SMAW). Welding parameters such as welding current, number of weld layers, electrode drying and base material preheat were the focus of this work. Coating hardness, microstructure and elemental composition were analysed in detail. The effects of the welding parameters on WC hardfacing coating microstructure and hardness value were characterized by scanning electron microscope (SEM) and micro-Vickers hardness tester respectively. The larger carbide growth in overall coating region is mainly dictated by high current (200 A), increased number of weld layers (3 layers) and presence of base material preheat due to sufficient heat energy initiating carbide growth. The investigation also revealed that high current affected the growth of smaller carbide particles in matrix region significantly. Meanwhile, number of weld layers and base material preheat influences were seen during hardfacing with lower welding current. The absence of electrode drying led to uniform smaller carbide distribution in matrix region. It was found that increased number of large carbides and uniformly distributed smaller carbides in WC hardfacing deposit increased the hardness value of the coating.

Wear analysis of welded layers containing node carbide, in the abrasive soil mass

The paper presents the research of the wear intensity of welded layers in natural soil abrasive mass. The samples made of 38GSA steel with the welded surface layers contains carbide forming elements. In case of the test abrasive mass, XHD 6715 material showed the wear 2.5 times lower than El-Hard 61 and twice smaller than El-Hard 65. The analysis of the wear indicates that the welding layer containing vanadium and chromium carbides, molybdenum and niobium carbides has proven to be the most resistant to wear in the test abrasive mass.

High performance and thermal stress analysis of a segmented annular thermoelectric generator

Annular thermoelectric generators can eliminate the thermal contact resistance formed due to geometry mismatch when flat-plate thermoelectric generators are used with round shaped heat source or heat sink. Therefore, in this study, the numerical simulation of a segmented annular thermoelectric generator (SATEG) is investigated using three-dimensional finite element analysis. The thermoelectric and mechanical performance of the segmented annular thermoelectric generator is studied by considering temperature dependent thermoelectric material properties and elastoplastic behaviour of copper and the welding layer (solder). The influence of segmented pin geometry on the performance of the segmented annular thermoelectric generator is investigated and comparison is made with non-segmented annular thermoelectric generators. COMSOL 5.3 Multiphysics software is used to investigate the effects of heat source temperature, thermoelectric leg length and leg angle on the electrical and mechanical performance of the segmented and non-segmented annular thermoelectric generators. Results show that the segmented annular thermoelectric generator has a greater efficiency compared to the annular thermoelectric generator (ATEG) with Bismuth telluride material when the temperature difference is greater than 100 K. In addition, the efficiency of the SATEG is found to be 21.7% and 82.9% greater than that of the Bismuth telluride ATEG and Skutterudite ATEG respectively at 200 K temperature difference. Finally, the results show that increase in thermoelectric leg length can reduce the thermal stress and electrical performance of the segmented and non-segmented thermoelectric generators. Results obtained from this study would influence the design and optimization of segmented annular thermoelectric generators.

The effect of cold work on the transformation kinetics and texture of a zirconium alloy during fast thermal cycling

The effect of cold-work on the transformation kinetics and texture evolution after fast temperature cycling were studied in a dilute zirconium alloy. It was found that cold-work delays the onset of phase transformation and helps randomise the texture after the transformation. Samples of Zircaloy-4 in two conditions, cold-rolled to 70% reduction and fully recrystallised, were heated above the β-transus at a fast rate of 100 °C s−1 using resistive heating and without constraint. Electrical resistivity was used to measure the phase fraction during heating and electron back-scatter diffraction was used to measure the texture before and after the thermal cycle. Whereas previous work on titanium suggested that cold-work leads to texture strengthening after transformation, these new experiments show that, when the heating rate is fast enough, recrystallisation is incomplete on heating, which slows down the start of transformation, leading to a random α-texture after cooling. The texture in the recrystallised material after β heat-treatment is non-random but different from the start, a consequence of both a stronger β-texture after grain growth and stronger variant selection on cooling. This variant selection can be mostly explained by α-nucleation at special β-grain boundaries. These results demonstrate that prior deformation has a strong effect on the textures produced after β-heat treatment when heating rates are fast. This has implications for the anisotropy of nuclear cladding components after loss-of-coolant (LOCA) and reactivity-initiated accidents (RIA) but also more widely for the manufacturing of zirconium and titanium using welding or additive layer manufacturing where the heating rates are high.

ВПЛИВ СПОСОБУ НАПЛАВЛЕННЯ НА ЧАСТКУ УЧАСТІ ОСНОВНОГО МЕТАЛУ В НАПЛАВЛЕНОМУ

The article presents the methods of wide-layer mechanized surfacing using various electrode materials, as well as the influence of technological factors on the participation of the base metal in the weld metal. An analysis was made of the influence of the method of surfacing on the proportion of the participation of the base metal in the weld metal. Widespread is the method of welding with overlapping the previous roller next. This scheme of surfacing allows, depending on the amount of overlap (step of surfacing), to reduce the participation of the base metal in the weld metal.When surfacing with continuous electrode section electrodes, it is possible to obtain wide weld layers with a small share of the base metal in the weld metal, which ensures the formation of a wear-resistant phase simultaneously over the entire width of the weld layer from the total pool throughout the entire volume. The influence of the methods of wide-layer surfacing under a layer of flux using a tape electrode material of different sizes on the participation of the base metal in the weld metal is considered.In mechanized electric arc surfacing of wear-resistant alloys of the required size using powder strip electrode materials, various schemes were used.It is possible to obtain wide-layer cladding in one pass using an oscillating electrode or an oscillating device on which the weldable product is fixed.The use of multi-electrode mechanized arc surfacing of wear-resistant alloys with powder strip electrode materials in one pass allows to obtain a weld layer up to 300 mm wide using an external magnetic field.To obtain the desired chemical composition of the deposited wear-resistant layer with the required wear-resistant phase, use mechanized surfacing methods that provide the deposited layers of the required width.The use of wide-layer mechanized surfacing with the use of powder strip electrode materials allows to obtain the required chemical composition in a single pass with a minimum share of the base metal in the weld metal, reduce the consumption of the electrode material, reduce energy costs, improve performance.

Determination of ballistic properties on ARMOX 500T steel welded joint

In this paper, the effect of different hardness filler materials and sequence of welding on the ballistic performance has been investigated. Also, besides the optimization of the ballistic properties, other mechanical testing was carried out in order to achieve wanted mechanical properties along the entire welded joint. The experimental work includes macrostructure analysis, ballistic testing, and hardness testing of steel welded joint. The base material used in the experiment were ARMOX® 500T plates. In this experiment 3 different filler materials were used. Based on the testing results, it was found out that best ballistic performance of the welded joint is achieved if capping layer is welded with a hardfacing filler material. This distributes the impact energy to a greater area and transfers it to the lower hardness weld layer underneath which then absorbs the rest of the energy.

Effects of welding layer on continuous induction welding behavior of woven CF/PPS laminates

Effects of welding layer on continuous induction welding behavior of woven CF/PPS laminates

Effect of chemical dilution and the number of weld layers on residual stresses in a multi-pass low-transformation-temperature weld

Influences of chemical dilution and the number of weld layers on residual stresses in a multi-pass low-transformation-temperature (LTT) weld were investigated by finite element modelling and neutron diffraction. A coupled thermal-metallurgical-mechanical (TMM) model that took into account the chemical dilution effect was developed to simulate the complex LTT welding phenomena. The model was strictly validated by comparing the predictions with experimental measurements and the results found good agreement between them. The results showed that a transformation strain caused by LTT martensitic transformation introduced large compressive residual stresses (−500 MPa) into the weld zone and the quantities were closely related to the chemical dilution between welding layers. Simulation results revealed that the chemical dilution helped mitigate the large localized tensile residual stresses by modulating the phase transformation process and a single LTT layer was sufficient to generate high compression near the weld surface (~2.5 mm), which suggests a great importance for repair welding.