Technological features of the production of welded beds from prefabricated base parts

The work is devoted to the problem of fatigue strength of welded-cast joints as applied to the operating conditions of body parts of machines. Such operating conditions are characterized by non-uniformity of intensity and concentration of the load on parts and assemblies during the operation of the equipment. This heterogeneity of the load actualizes production of precisely welded-cast base parts for metalworking equipment beds. This is of considerable technological and economic interest. The aim of the work is to study the strength of welded-cast bearing structures in relation to the work of beds of heavy lathes. Unalloyed medium-carbon structural steel 35L and steel of ordinary quality MCT3 in the form of rolled products were used as the main materials for research. The research methods are presented. The study of the structure and properties of the welded joint made it possible to assess the technical feasibility of using the studied metals in the manufacture of welded-cast bearing structures. It has been established that welding of steel castings with rolled steel causes significant structural and mechanical heterogeneity. The influence of processing technology on the nature of formation of the structure of welded-cast joints is presented. The influence of heat treatment on the value of the hardness of the welded seam and the heat-affected zone was investigated. The study of the fatigue resistance of welded-cast specimens was carried out in relation to the operating conditions of joints undergoing vibration loads at normal temperatures, which can be classified as fatigue with a symmetric load cycle. It was found that the use of heat treatment of welded-cast specimens significantly reduces the mechanical heterogeneity of the joint along the seam and the heat-affected zone. Based on the results of studying mechanical characteristics, the choice of technology for the production of welded-cast joints is justified.

Investigation of the gap bridgeability at high-power laser hybrid welding of plasma-cut thick mild steels with AC magnetic support

One of the challenges of the high-power hybrid laser welding of thick steels is the sensitivity of the process of the process to manufacturing tolerances. This usually leads to a time-consuming preparation of the welding edges, such as milling. The study deals with the influence of the edge quality of milled and plasma-cut steel made of S355J2 with a wall thickness of 20 mm on the laser hybrid welded seam quality. Furthermore, the gap bridgeability and the tolerances towards edge misalignment was investigated. An AC magnet was used as backing support to prevent sagging and positioned under the workpiece, to generate an upwards directed electromagnetic pressure. The profiles of the edges and the gap on the top and root side were measured using a digital camera. Single-pass laser hybrid welds of plasma-cut edges could be welded using a laser beam power of just 13.7 kW. A gap bridgeability up to 2 mm and misalignment of edges up to 2 mm could be achieved successful. Additionally, the independence of the cutting side and the welding side was shown, so that samples were welded to the opposite side to their cutting. For evaluation of internal defects or irregularities, X-ray images were carried out. Charpy impact strength tests were performed to determine the toughness of the welds.

Design of replaceable nozzles for connecting pipelines in electron beam welding

The article is devoted to the use of electron beam welding for connecting pipelines in the oil and gas industry. The analysis of the proposed approach and equipment for creating permanent pipe-flange connections is carried out. The advantages and disadvantages of the proposed approach are considered. During the work, the welded seam was calculated. A set of interchangeable attachments for the turntable has also been developed. Thus, the purpose of this work is to improve the quality of welded joints of oil and gas equipment through the use of electron-beam welding technology and design of replaceable nozzles for a turntable for an electron-beam welding unit.

Analysis of Defects at Laser Welding of Heat-Resistant Alloy KhN45VMTYuBR

The article presents the results of the impact of laser welding parameters on defect occurrence in the welded seam of the Ni-based heat-resistant alloy Kh45VMTYuBR applied for the manufacture of gas-turbine engines. On the basis of the research the authors conduct the analysis of dimensions as well as the number of pores and micro-cracks in the welded seam. The paper provides the recommendations on the selection of the laser welding mode for the heat-resistant alloy to reduce defect occurrence in a welding seam.

Microstructure and mechanical properties of 6082-T6 aluminum alloy–zinc coated steel braze-welded joints

The laser braze-welding technique was aimed to join a low alloyed zinc coated steel used in automotive industry, with a deformable, aging hardenable aluminum alloy from the 6xxx series using as filler material a AlSi12 wire. The heterogeneous joint was obtained by welding of aluminum alloy with the filler wire and by brazing of molten aluminum alloy together with the filler wire on the surface of a zinc coated steel which remained in solid state. The results showed that by using a proper heat input, the zinc coated steel was brazed without a melting process by the aluminum alloy which was in liquid state. On the interface between the zinc coated steel and the welded seam, a thin layer (the thickness was 6 to 8 μm) formed consisting of star (Al-Fe-Si) or needle shape (Mg-Al-Fe-Mn) intermetallic phases.

Modeling the material of the cylindrical work with welded seam at compression distribution of vehicle parts

It is shown that the distribution of the ends of tubular billets, which are the main connecting elements of the vehicle brake system, is accompanied by a loss of stability in the circumferential and axial directions, as well as localization of deformations, followed by destruction in the form of a longitudinal crack that occurs at the end of the preform. The presence of the weld complicates the general conditions of deformation during crimping and distribution and leads to the destruction of the workpiece along the weld. To prevent cracking, it is necessary to tighten the crimping and distributing factors, which inevitably leads to an increase in the number of transitions, the complexity of the process and the cost of manufacturing the part as a whole. The issue of deformation of welded structures is of interest with the development of new materials for the automotive industry, such as joining two or more steel sheets with different mechanical properties, thickness or type of coating, which are important for reducing weight, minimizing costs and reducing scrap. It is shown that the deformation of the pipe billet will depend not only on the plasticity characteristics of the base metal and the weld metal, which is obvious, but also on the ratio of the squares of the pipe billet. The increase in the above modulus of plasticity is accompanied by hardening of the welded joint compared with the initial metal of the workpiece, respectively, a decrease in the value of the secant modulus in both directions – a decrease in the strength characteristics of the weld metal. Further analysis of the deformation of the welded workpiece should be carried out taking into account the local anisotropy caused by the welding seam, which will make it possible to determine the conditions of sustained plastic deformation and create an additional effect on the weakened area.

Influence of Shielding Gas on Microstructure and Properties of GMAW DSS2205 Welded Joints

In the present study, the microstructures and properties of DSS 2205 solid wire MIG welded samples prepared in different shielding gases (pure Ar gas, 98%Ar + 2%O2 and 98%Ar + 2%N2) were investigated for improving the weldability of DSS 2205 welded joint. The work was conducted by mechanical property tests (hardness and tensile test) and corrosion resistance property tests (immersion and electrochemical tests). The results show that adding 2%O2 into pure Ar gas as the shielding gas decreases crystal defects (faults) and improves the mechanical properties and corrosion resistance of the welded joints. Phase equilibrium and microstructural homogeneity in welded seam (WS) and heat-affected zone (HAZ) can be adjusted and the strength and corrosion resistance of welded joints increased obviously by adding 2%N2 to pure Ar gas as the shielding gas. Compared with DSS 2205 solid wire MIG welding in 98%Ar + 2%O2 mixed atmosphere, the strength and corrosion resistance of welded joints are improved more obviously in 98%Ar + 2%N2 mixed atmosphere.

Non-Destructive Testing of Dissimilar Welded Joints

This paper presents research’s results of non-destructive examination of dissimilar welded samples. The samples were made using sheets of austenitic stainless steel and carbon steel welded through the method of MAG welding with tubular wire. The samples were subjected to non-destructive testing in order to analyse the integrity of the welded seam, heat affected zone and the adjacent area of the weld.

SPECIAL ASPECTS OF ARC WELDING OF A LAMINATED CORROSION-RESISTANT MATERIAL

The paper shows the demand of the chemical industry for corrosion-resistant materials, as well as the prospects of the creation of laminated metal materials with internal protectors (LMM with IP). The authors offer the architecture and composition of layers of LMM with IP ensuring stable operation within the highly aggressive environment. The study identified the possibility of improving corrosion resistance ten and more times compared to high-alloy austenitic stainless steels. The authors show the efficiency of the application of explosion welding to produce LMM with IP. The paper considers the example of the production of a four-layer material with one internal protector made of low-alloyed, low-carbon steel of the following architecture: 2-mm layers of 12H18N10T + 09G2S + 12H18N10T plates of steel and the base 10-mm layer of 09G2S. The authors developed the process diagrams for performing butt-welded joints of such material, identified special aspects of the formation of its microstructure and properties. To obtain the maps of specific chemical elements distribution in the layers and interlayer boundaries, the authors used the energy-dispersive microanalysis method. Peculiarities of corrosion damage of a welded seam and weld-adjacent area are studied. The study showed the necessity of using a facing layer in a welded seam. Microstructural, X-ray tomographic, and gravity-measuring studies proved the obtained results. To evaluate the quality of welded joint, the authors performed the corrosion tests of a welded seam and weld-adjacent area, carried out visual inspection control and X-ray tomography. The corrosion tests were carried out using 10-% III ferrous chloride water solution. The paper presents the results of the static bending tests of a welded joint. The absence of fracture, lamination, and cracks served as an estimation criterion. The study identified the possibility of obtaining a defect-free welded joint of LMM with IP with high corrosion resistance and advanced mechanical properties.