The nature of elastoplastic transition in low-carbon steel samples with and without welds

This paper describes the influence of a weld on elastoplastic transition in low-carbon steels. Depending on the level of internal stresses in the zone of the weld, the formation of Chernov-Lüders bands can occur either exactly in the weld or near it. In the second case, the influence of the weld is detected only when the front of the Chernov-Lüders band reaches it. In both cases, the features of kinetics for the fronts of the Chernov-Lüders bands are caused by the structural and phase inhomogeneity of a heat-affected zone and deposited metal

Elastic-plastic invariant of localized deformation autowaves

The parameters of localization patterns emerging at the linear stage of work hardening are discussed in the frame of autowave concept. The stress-strain diagrams have been plotted for the test samples of metals exposed to active loading. It is found that the product of phase autowave velocity and length has the same order of magnitude as the product of elastic wave rate and the lattice constant of the respective metal; hence, this quantity can be regarded aselastic-plastic invariant. The invariant is found to vary in a regular manner with the shear modulus, modulus of dilatation and interplanar spacing. The data obtained for elements of one and the same period of Mendeleev's table of elements are found to vary monotonically; however, after changing over to the next period, a jump-wise variation in the data would occur. It can thus be concluded that the elastic-plastic invariant is a dominant characteristic of plasticity;the nature of the invariant is related to the lattice properties and the phonon density of crystal lattice

The Structure and Mechanical Properties of Bridge Steel Weldings With Glass-Steel Liners

A new technology is developed for welding multi-span bridge constructions. The mechanical properties and structure of the low-carbon bridge steel welds have been studied. The welding parameters and application of steel-glass liners provide for long-term service of steel constructions in conformity with the welding industry specifications

Physical Nature of the Processes in Structure Forming, Phase and Chemical Composition of pipe Permanent Joints when MMA Welding

The paper outlines peculiarities of structure formation, phase and chemical composition in regard to heat content in molten electrode metal beads when pipe steel (steel 09G2S) welding using power sources with various energy characteristics. Mathematical calculations indicate an inverter power source provides minor heat content into the bead of electrode metal when welding. Experimental research has pointed at 4-9 % increase in impact strength of joints produced using an inverter power source in comparison with samples produced applying a diode rectifier. The following factors can possibly give rise to the increasing impact strength: difference in microstructures of weld joints, up to 50% shortening ferritic plates in metal of weld joint, change in dimensions of ferritic grains in the heat-affected zone by as much as 17.5 %, and decrease in the extent of heat-affected zone by 50%

The distinctive features of plastic deformation localization in polycrystalline aluminum by creep

The research was performed for polycrystalline aluminum by steady-state creep. It is known that at the macro-scale level, deformation exhibits localized behavior. The localization patterns would propagate over the deforming sample by steady-state creep, forming thereby a kind of phase autowave. The rate of phase autowave increases with the growing extent of straining. It is demonstrated that the processes controlling the autowave rate have the same activation volume as the processes controlling the creep rate

Corrosion and Mechanical Properties of Austenic Steel Weld Joints

This paper presents results of experiments on how tungsten, molybdenum and aluminum oxyhydroxide nanopowders, imbedded into the weld pool, affect corrosion resistance and mechanical properties of welded joints. It is shown that nanopowders have a significant effect on the intergranular corrosion of the weld

Microconstituents of the Modified Surface Layer of Austenitic Steel With Nanofibres of Aluminium Oxyhydroxide

In the paper the authors provide the results of experimental study of the effect caused by introduction of nanostructured fibres of aluminium oxyhydroxide into the surface layer of austenitic steel upon its microconstituents. The authors show that, due to introduction of given fibres dendrite size is reduced and equilibrium structure is formed

Microstructure of Modified Layer Produced Using Aluminum Oxy-Hydroxide Nanostructured Powders

The paper provides the results of experimental research into the influence of aluminum oxy-hydroxide nano-structured powders on the microstructure of modified layers. It has been demonstrated aluminum oxy-hydroxide nano-structured powders AlO(OH) applied as modifiers bring about the decrease in dendrite dimensions, support equilibrium microstructure formation, and cause the growth of microhardness

Physical Nature of the Processes in Forming Structures, Phase and Chemical Compositions of Medium-Carbon Steel Welds

This work presents peculiarities of forming a structure, phase and chemical composition while welding medium-carbon steels (Steel 45) depending on a heat content of molten electrode metal droplets when using welding power sources having different power parameters. It was experimentally established that the power inverter provides the decreased heat input into droplets of electrode metal during the welding process. This stimulates obtaining a fine-grained structure of the deposited metal and heat affected zone, reduces the extent of the HAZ that enhances working properties of welded joints

Increasing Strength and Operational Reliability of Fixed Joints of Tubes by ММА Welding

This paper presents peculiar properties of structure formation, phase and chemical composition while welding of low-alloy steel 09MnSi2-1 depending on the dynamic characteristics of power sources of different types. Proper selection of power sources enables to decrease burning of alloy elements in metal of weld (Mn by 14% and Si by 17% of the weight ratio), to obtain more homogenous structure of deposited metal, to reduce length of heat-affected zone by 50% and to improve impact strength by 4-9%