Papers by Keyword: Base Metal

Abstract: Modeling of the temperature distribution during electric arc surfacing with a strip electrode is carried out in relation to the design scheme of a semi-infinite body. Also, in the work, the temperature distribution was calculated when a flat layer was heated by a linear source, which made it possible to compare the temperature distribution data without and taking into account the heat release conditions at the product boundaries. The simulation results showed that the control of heat input into the base metal when using mechanical control actions makes it possible to reduce the overheating of the weld pool, reduce the area of the melting isotherm, and reduce the cooling rate of the heat-affected zone. By calculation, the previously determined optimal range of values of the frequency of control actions of 40÷60 Hz was confirmed, which makes it possible to ensure the minimum depth of penetration of the base metal and obtain a favorable structure in the heat-affected zone, prone to the formation of a coarse-grained structure.

Abstract: By the non-destructive testing of a dissimilar weld joint (DWJ) of cold collector DN 1100 (CC) on a steam generator, indications were found on inner-side cold collector’s surface at the root position of the examined weld. All the identified indications were very similar in shape and form, therefore, it was decided to cut out a part of the damaged site from this type of DWJ DN 1100 and get the obtained ring (real piece of material) for complex metallographic analysis. This paper briefly describes the results and recommendations found for the future reference during the next long‑term operation induced ageing and degradation of critical steam generator parts in NPP Bohunice Unit 4. There are summarized the results obtained from evaluation of original DWJ material.

Abstract: In this paper, the properties of the base metal of the low-alloy high-strength steel 20MnTiB, the welding process and the microstructure and properties of the welded joints were studied. The results are as follows: post-heat treatment below 400°C, the strength change of the steel decreases slowly, the elongation does not change significantly, and the metallographic structure is not obvious. When the temperature is above 400, the strength is greatly reduced. And its plasticity increases remarkably, and precipitates on the grain boundary are precipitated and grown on the metallographic structure. When the line energy is in the range of 9.6~12.0kJ/cm, the mechanical properties and microstructure of the welded joints meet the requirements, and the welding process that meets the requirements is studied. Finally, the mechanical properties and microstructure of the welded joint are studied. Provide a reference for the research and application of steel.

Abstract: It was experimentally established earlier that the increment of the electrode wire melting coefficient at submerged arc welding and surfacing with magnetic fields action (with equal parameters of the welding mode) depends on the chemical composition of the wires. It is suggested that this effect depends on the magnetic properties of the welding materials, i.e. electrode wire and base metal. To measure the magnetic properties of welding materials, a method has been developed in which the magnetic properties of welding materials on samples are investigated. The samples were made in the form of tori, on which the primary and secondary windings were placed. The primary circuit contains an ammeter and a voltmeter, as well as a wattmeter that allows to take into account losses in the sample on hysteresis and Foucault currents, and the secondary circuit contains a voltmeter. Experimental data on the magnetic properties of some welding and surfacing wires, as well as of base metals, are obtained. A simplified method is proposed, in which torus samples are also used, but on which only one winding is placed, over which a direct current is flowed. The value of the increment of the electrode wire melting coefficient at arc welding with the action of magnetic fields increases with increasing their magnetic permeability.

Abstract: Due to the difficulty of manufacturing complex small pieces ofthe new bearing steel0.30C-Cr-W with high-performance in the aviation industry, the electron beam welding process are usually used for preparing the complex parts.Thewelding performance of 0.30C-Cr-W steelwas calculated by theory and confirmedby actual experiments.The base metal was preheated,then welded and heattreated for weldments.The purpose of this work is to study the properties and the microstructure changes of base metal after heat treatment, weldments before heat treatment and weldments after heat treatment.The results show that the base metalafter heat treatment is sorbitic,weldzone of weldments after heat treatmentismartensite and austenite, theprecipitated M₂₃C₆ and M₆C in latter (the weld zoneof weldmentsafter heat treatment) were more thanthe former (the base metalafter heat treatment), and the strengthof the latter is 23.4%lower than the former, theroom temperature impact absorbing energy and hardness of the latter increased 13.5% and 6.6%. It may be considered that0.30-C-Cr-W steel is not suitablefor welding by the theoretical calculations, but after reasonable preheat and post-weld heat treatment, the mechanical properties of the weld afterheat treatment can satisfy the requirements.

Abstract: A rear cradle as one of the suspension system takes a role to connect a tie rod, suspension arm, transmissions and rubber bush. It consists of the side member and cross member which are joined by welding process. However, the rear cradle may be distorted due to thermal deformation during welding process, which cause dimensional tolerance problem when assembling. So, it is necessary to predict the thermal deformation and the optimal welding conditions should be suggested to reduce the dimensional tolerances. In this paper, MAG(metal active gas) welding process was applied in the simulation model using the SYSWELD^R, commercial S/W for welding simulation. And then, It should be predicted on the results about the gap and thermal deformation of main cylinder and derived the phase transformation, temperature distribution, residual stress and thermal deformation of total model shape.

Abstract: In order to determine the heavy plate structure have sufficient fracture toughness, based on BS7448 fracture toughness test experiment standard,the study of the typical bridge steel material were extended to CTOD( crack tip open displacement) fracture toughness test at 20 °C, The average CTOD value of base metal which was more than the allowable value of CTOD were obtained,so the structure can satisfy the design need .

Abstract: The fatigue crack growth of longitudinal SAW welds of a API 5L X42 steel pipe was evaluated using curved three point bend test specimens, where the radius of curvature of the specimens was equal to the pipe radius, so that no extensive machining or flattening was required. The fatigue crack growth tests were done in a servohydraulic closed loop machine under load control, in air at room temperature. The da/dN vs ∆K plots and Paris’s equation constants were obtained for the base metal, deposited metal and heat affected zone in the CR orientation, which corresponds to the short transverse direction of the pipe. The greater resistance to fatigue crack growth was the base metal, whereas the deposited metal showed the least resistance to the fatigue crack propagation. The deposited metal and the heat affected zone behaved according to Paris’s law, unlike the base metal, that showed a high dispersion of the fatigue crack growth rates. This behavior was due to the propagation of the crack in the direction transverse to the banded microstructure. Furthermore, the differences in fatigue crack growth rates among each zone were also related to the roughness of the fracture surfaces and fracture toughness.

Abstract: In order to understand the influence of Heat-Affected Zone (HAZ) on fatigue properties of 16Mn steel, a series of cyclic torsional tests were conducted on 16Mn weld metal, the base metal, and the HAZ metal. The specimens of 2mm diameter were uniformly-spaced taken from a bulk 16Mn plate, which included a V-style welded joint in the center, and the space for each specimen was 4mm. From cyclic fatigue tests performed on specimens at different positions, one can observe that the fatigue damage evolution in the HAZ is faster than those in the weld and the base metal, i.e., HAZ has a significant effect on fatigue life of 16Mn. In addition, the peak stress decline curves of HAZ specimens in different rows are considerably diversified, but the damage evolution and fatigue properties of HAZ metal are similar in spite of their locations.