Welded Joints Of Low-alloy Steels Research Articles

Features of Formation of Structure and Physical and Mechanical Properties of Permanent Welded Joints of Low-Alloy Steels by Methods of Adaptive Pulse Control of Energy Parameters of Welding Mode

The features of the formation of the structure and physical and mechanical properties of all-in-one compounds of low-alloy steels are studied. It is shown that the quality and strength properties of permanent joints depend on the energy parameters of the technological process of their manufacture. The technological process is accompanied by melting, transfer and crystallization of the weld metal from the melt, which has a dominant effect on the structure, indicators of static and dynamic strength of welded joints. The ranges of welding modes that have the greatest impact on the structural and mechanical properties of the zone of permanent joints in the temperature range from +20 degrees to minus 60 degrees Celsius. The results of the research can be widely used in the practice of repair and installation works of structures of the Northern design, working in conditions of naturally low climatic temperatures.

Development of electrodes for welding transmission pipelines and marine equipment made of high-strength low-alloy cold-resistant steels

The problems of production of welding electrodes with basic coatings in Russia is associated with the changes in the raw materials base used as components for electrode coatings, in particular, the electrodes of the UONII-13 series used extensively in industry in welding important structures made of cold-resistant low-alloy steels of different strength categories are examined. A promising composition of the electrode coating with a new deoxidation alloying system is proposed. The system results in high welding and technological characteristics of the electrodes and stable mechanical properties of the metal of welded joints in low-alloy steels with a strength of up to 560 MPa. The high-quality parameters are achieved as a result of using Minal (mineral alloy) in the electrode coating for adding through this coating the mineral and rare-earth components. The compositions of the coatings of the developed electrodes are calculated using the phase equilibrium diagrams of non-metallic systems.

Changes in the Structure and Properties of Welded Joints of Low-Alloy Steels, Subjected to Cyclic Loads

Time-varying loads negatively affect the properties and structure of materials. Structural failures typically occur at loads below the yield point. In this work, fatigue tests of welded joints of low-alloy steels were carried out in an asymmetric cycle at loads of 60 and 80% of the yield strength. The stress ratio was 0.8-0.9. On the basis of the results of the tests, equations linking the number of cycles to failure with test parameters were obtained. Such equations can be used for estimating the residual life of elements both under construction and in operation. It has been found that the failure is not instantaneous. Specimens of steels continue to resist variable loads for 4000 - 26000 cycles to failure, depending on steel grade and the parameters of the test. Under operating conditions, it gives an opportunity to discover the onset of failure and dispose of the defective part or to replace the entire structure. A standard technique was used to measure the microhardness on the fractured specimens. The distance between the nearest indentations was 0.2 mm. The results of the measurements were plotted in graphs of ahardness change characteristic for all steels under study. A microhardness “step” has been discovered in areas with high dislocation density, as evidenced by x-ray diffraction and transmission electron microscopy. An intermediate stage of the investigation is the development of recommendations for determining the moment of failure of welded constructions with a probability of 95%.

Control of Structure and Properties of Welded Connections of Alloy Steels by Application Highly Concentrated Pulse Energy Actions

We appraised welding modes influence on corrosion resistance of welded joints of the alloyed steels in this paper. Influence of frequency characteristics of the current on structure steel welded joints obtained by stationary modes and pulse change of their power parameters is investigated. It is established that at reduction of current frequency the structure is crushed. The conducted researches have shown that at use of pulse welding mode the mechanism of corrosion interaction of welded joints of low-alloy steels in hydrochloric acid changes: instead of intergranular corrosion proper to joints after a stationary mode pitting corrosion occurs.

Combined pulsed effect of shielding gases and welding current in consumable electrode welding

Methods of improving the process of consumable electrode welding using different types of metal transfer in welding of steels by the combined pulsed effect of shielding gases and welding current are described. Special features of the microstructure of the metal of the welded joints in low-alloy steels are discussed.

Effect of the energy parameters of the welding process on the structure and properties of welded joints in low-alloy steels

The results of investigations of the effect of the pulsed welding process on the structure and mechanical properties of welded joints in low-alloy steels are presented. It is shown that the pulsed welding conditions improve the homogeneity of the structure and reduce the grain size of the metal of the welded joint and the heat-affected zone (HAZ). Changes in the structure increase the ductility of the welded joint.

Influence of structural features of welded joints of low-alloy steels on magnetic and micromagnetic properties

Variations of magnetic (coercive force H c , residual induction B r , maximum magnetic permeability μmax, maximum magnetic-permeability field H μmax, saturation magnetization J max) and micromagnetic (number of pulses N and RMS Barkhausen-noise amplitude U) characteristics along the parent metal-welded joint direction were studied for welds of steels 10XCHД, 15XCHД, 09Γ2C, and X70.

Estimation of the Efficiency of Methods Aimed at Increasing the Fatigue Resistance of Welded Joints under Impact Loading at Low Temperatures

We analyze the experimental data on the influence of various types of hardening treatment (mechanical removal of reinforcement of the weld, argon-arc treatment, blasting, and ultrasonic surface cold working) on the fatigue resistance of welded joints of low-alloy steels under harmonic and impact loads at room and low (–60°C) temperatures. It is shown that the level of fatigue resistance increases after each type of treatment carried out under the same testing conditions. The comparison of the efficiency of the indicated types of treatment under impact loading at low temperature with the original state of the welded joint under harmonic loading at room temperature demonstrates that ultrasonic surface cold working is the most efficient procedure of hardening of welded structures operating at low climatic temperatures.

Corrosion cracking of welded joints in low-alloy steels in a hydrogen sulfide-bearing medium

Corrosion cracking of welded joints in low-alloy steels in a hydrogen sulfide-bearing medium

Effect of micro-additions of cerium and boron on the susceptibility of the weld zone of welded joints in lowalloy steels to cracking during tempering

Effect of micro-additions of cerium and boron on the susceptibility of the weld zone of welded joints in lowalloy steels to cracking during tempering