Influence of longitudinal control magnetic field on efficiency of the arc process

Problematic. When surfacing and welding with the action of a longitudinal magnetic field (LMF), the productivity of melting of the electrode metal increases, it is possible to control the geometric dimensions of the cross-section of the surfaced beads and welds, the structure of the surfaced metal and welds is refined, the hardness increases, the strength and ductility of the weld metal increases, and the resistance of the welds hot cracking. Research objective. Analyze the literature data on the effect of LMF on the efficiency of the arc surfacing process of worn-out surfaces of parts and structures, taking into account the magnetic properties of electrode wires and base metal to increase the efficiency of this process. Realization technique. Experiments were performed on submerged-arc surfacing with Sv-08A wire with a diameter of 5 mm with the action of an alternating LMF. Investigated the effect of the LMF frequency on the depth of penetration of the base metal and the width of the surfaced beads. The results of research. It has been established that at frequencies of the LMF within the range f = 5...50 Hz, the penetration depth is less, and the width of the bead is greater than in surfacing without the action of the LMF. In the future, it is necessary to carry out studies on the effect of LMF during surfacing with flux-cored wires and strips on the metal structure of the surfaced beads and their service characteristics. Conclusions. It has been established that for grinding the structural components of the metal surfaced with the action of LMF, it is necessary to ensure effective mixing of the liquid metal in the weld pool, that is, along its entire length. In this case, it is necessary to ensure the optimal parameters of the control magnetic fields. There is no theory that would explain the mechanism of refinement of the weld structure during arc surfacing with the action of LMF, and the existing views on this mechanism are contradictory. The data presented in the literature refer to the process of arc surfacing and welding with solid wire, there are no data on surfacing using flux-cored wires and strip electrodes.

Selection of Weld Structure of Bogies Based on Sub-Model

In order to effectively deal with the problems in the allowable fatigue strength data of weld joints of steering structures, it is necessary to carry out comparative tests and analyses according to various structural stress methods and data. Therefore, on the basis of understanding the applied strength standard of bogie welded structure in China, and aiming at the application of weld structural stress at the present stage, this paper constructs the fatigue diagram and S-N curve of Q345 weld seam based on the actual tested structural stress, and starts with the result study.

Exploration on the Materials Quality Control of Railway Vehicle Weld Structure Based on Service Safety Demand

With the continuous increasing of service-rail-vehicle in China, some defects such as cracks appeared at different stages of service when they had not reached the design life, while current theories and methods cannot explain the appearance of defects, which brought risks and hidden dangers to the operation of the vehicles. It was found that the reasons were mainly caused by one or several factors such as material performances, design, manufacturing process and operating environment. Since more and more sensors being installed on the vehicles to supervise the health of structure, it is more improtant to focus on the performances of materials. Through comparing different material standards including international, national, railway industry and enterprise standards, as well as the technical delivery conditions of other industries, it was recommended that the fracture mechanical parameters such as fracture toughness and fatigue crack growth should be proposed into the materials quality control regulations of original equipment manufacturers (OEMs). Furthermore, based on the testing data of materials from OEMs, several suggestions were proposed on the basic performance of materials such as raising the requirements contained impact, metallography and corrosion resistance properties in order to provide guarantee for the service safety of vehicles.

A Cooks Distance Approach to Control the Haz and Arc Length of Tig Mild Steel Weld

The heat affected zone and arc length parameters have a vital role to play in determining the integrity of a weld structure. The cooks distance is a statistical diagnostic employed in this study to select the best optimum combination of welding process parameters. Mild steel plate was the choice material used to produce the weld specimen, which was welded with the Tungsten inert gas method. The RSM model was used to develop an optimal solution that can explain the behavior of the welded joint with respect to the heat affected zone and arc length, different diagnostic techniques were employed which includes the normal probability plot and cooks distance plot. The model developed has sufficient merit as the results obtained shows that the cooks distance values is within the range of 0 and 1 indicating the absence of outlier in the data making the optimal solution highly acceptable.

A Study of the Influence of Local Heat Treatment on the Structure of Welded Titanium Pipelines

The article analyzes the results of a study of the influence of zonal heat treatment on the structure of welded joints of pipeline elements made of titanium alloys Ti-3.5Al-1.5Mn. In the manufacture of such structures, the TIG welding method is used to join pipe elements, after which the heat treatment method can be used to relieve residual stresses. The experiments have confirmed the effectiveness of zonal heat treatment preceded by welding. It was revealed that for welded joints made of titanium alloys, heat treatment can stabilize the structure. In experiments conducted by the method of optical metallography, the structure of heat treated and untreated welded joints was investigated. The influence of heat treatment on the weld structure and heat-affected zone was identified.

ABOUT THE CLUSTER MECHANISM OF WELDS CRYSTALLIZATION IN ARC WELDING OF METALS AND ALLOYS

In this work, the task was set to analyze the literature data on the cluster mechanism of crystallization of alloys in the field of foundry and metallurgical production and the possibility of its application for the process of crystallization of metal in a weld pool during arc welding and surfacing of metals and alloys. Literature data have shown that the cluster mechanism of their crystallization is widely used to explain many properties of castings and ingots in metallurgical production. It is shown that the previously used diffusion mechanism of crystallization of melts of steels and alloys, that is, the mechanism of crystal growth as the attachment of atoms of a substance from the melt to the solid phase (substrate), does not stand up to criticism. However, this old approach is used in all work on weld solidification in electric arc welding and surfacing. The same approach has always been used in works devoted to the study of the effect of magnetic fields (MF) during arc welding on the refinement of the weld structure. In modern research in the field of foundry and metallurgical industries, it is assumed that there are already clusters in the molten metal. Clusters are centers of crystallization. The process of crystallization of melts is represented as the attachment to larger crystals (clusters) of smaller ones. Earlier it was found that the refinement of the structural components of the weld metal during welding under the influence of MF occurs at the stage of their primary crystallization. Surfacing was performed without and with the influence of a control alternating transverse magnetic field with a frequency of 6 Hz. At the same time, in the structure of the bead deposited with the action of the field, a 2-fold grain refinement was observed. This refinement of the structure of the deposited metal occurred during its primary crystallization. It was assumed that this happened by the cluster crystallization mechanism.

Effect of weld structure on fracture mode of heat-temperature HP40NbTi alloy

The microstructure and phase composition of pipe welded joint made of HP40NbTi alloy are studied. The short-term and long-term mechanical properties of the pipe base metal and the welded joint are determined. It is shown that the structural heterogeneity of the weld and the formation of G-phase in the heat-affected zone significantly reduce the long-term strength of the alloy. The fracture mode and the role of G-phase in the cracks formation during the operation of the welded joint are studied.

Welding procedure research of titanium heat exchangers

In order to manufacture Gr.1 titanium heat exchangers, the welding property and weld structure of titanium tube-to-tubesheet are analyzed. The procedure of Pulse GTAW is used and the visual inspection, dimensional inspection, chemical composition, mechanical properties and metallographic structures are tested and analyzed. The results show that the weld joint can get ideal structure and good chemical composition, mechanical properties and corrosion resistance. The successful welding qualification has accumulated valuable experience for manufacture of titanium heat exchangers.

Fatigue Property and Improvement of a Rounded Welding Region between the Diaphragm Plate and Closed Rib of an Orthotropic Steel Bridge Deck

By means of finite element modeling (FEM) and fatigue experiments, we study the fatigue performance of the rounded welding region between the diaphragm plate and closed rib of orthotropic steel bridge deck in this work. A local sub-model of the rounded welding region from the orthotropic steel bridge deck was developed to analyze the stress distributions. Based on the analysis results we designed the fatigue specimen for the fatigue test of this detailed structure. The fatigue experimental results revealed that the crack initiates from the weld toe of the rounded welding region and the stress concentration at the rounded welding region is the main mechanism of fatigue crack initiation. In addition, we propose three improvements to reduce the stress concentration of the rounded welding region, and the local structure optimization scheme of the diaphragm–rib weld can effectively improve the fatigue resistance of the detailed weld structure.