Solid State Phenomena Vol. 328

Abstract: The reasons for the decrease in the operational resistance of high-pressure metal hoses made of austenitic steels are considered. The main cause of damage to metal high-pressure hoses was revealed, namely, the low performance of the metal protective braiding under the influence of an unfavorable environment. It has been established in the work that in the initial state the wire made of AISI 201 steel has a high strength (σ_0.2 = 1370 MPa and σ_T = 1650 MPa) and has relatively low plastic characteristics (δ = 15 % и ψ = 40 %), since up to 40–60% deformation martensite is present in its structure. The resistance of steels of the austenitic class AISI 201 and AISI 316 to intergranular corrosion has been investigated. The effect of heat treatment on the mechanical and plastic properties of wire samples of ø made of AISI 201 steel has been investigated. Optimal heat treatment modes have been determined that increase the durability of the braid in an unfavorable environment and, consequently, the operational durability of metal hoses in general.

Abstract: Welded flexible compensating elements made of austenitic stainless steels, such as metal hoses and bellows expansion joints, operate in a complex stress state; therefore, almost all corrosion damage of these products occurs in a stressed state. In addition, in welded joints, defects are possible associated with elastic-plastic deformations and stresses arising in the manufacturing process. Paper considers the defects of welded joints of multilayer bellows expansion joints made of stainless steels AISI 304 and AISI 316 types. The influence of the parameters of the argon tungsten electrode welding mode, with or without filler wire, on the mechanical characteristics of welded joints was studied. Mechanical tests of samples of welded joints were carried out on a tensile testing machine. The optimal range of variation of the parameters of the welding mode has been established, in which the plastic characteristics of the welded joints have maximum values. A metallographic study of the microstructure of welded joints of metal hoses and bellows expansion joints was carried out. The influence of the content of nonmetallic inclusions in the material of products on the conditions of melting and crystallization of the weld pool, contributing to the appearance of pores and hot cracks in the metal of the weld and the heat affected zone, has been established. To reduce the influence of the content of non-metallic inclusions in the weld metal and the heat-affected zone on the conditions of melting and crystallization of the weld pool, it is recommended to carry out preliminary heat treatment of the austenitic steel strip.

Abstract: The study looks at features the formation of the structure of the surface layer of pure-iron after hardening treatment with surface plastic deformation (SPD) by a multiradius roller (MP-roller). Earlier authors with the help of the method of finite-element modelling (FEM) of the MP-roller SPD process proved the possibility of creating high hydrostatic pressure in the deformation center of the part being processed. The methods of optical (OM) and atomic-force microscopy (AFM) and X-ray structural analysis have determined that the MR-roller SPD results in the formation of an intensively deformed surface layer of the component with characteristic ferrite grains, stretched in the direction of the current of the metal and an average size of 20-30 μm. Analysis of the results of the X-ray structural analysis showed that the processing of the SPD by the MP-roller results in a significant increase in the microdistortion of the crystal lattice, which is characteristic of the nanodimensional structure. The data obtained are well consistent with the results of the finite element modelling previously obtained.

Abstract: The metal workpiece Surface Layer (SL) Residual Stresses (RS) modeling and computational algorithms creation relevance is shown. The RS forming discrete elastoplastic finite element model at Surface Plastic Deformation (SPD) hardening treatment, including technological inheritance effect, is presented. A model feature is the complex non-monotonic types of metal loading and subsequent unloading and hardened body effect consideration, as well as residual stress tensor components evaluation as a result of these effects. Residual stress tensor components calculations in the workpiece hardened surface layer after treatment with different routines are performed. The metal hardening effect on the residual stresses values and distribution is established. The correlations between the residual stress tensor components and the main treatment routine parameters - the roller tension and profile radius are established.

Abstract: This paper presents the results of a study of the search and detection of iron ore minerals in the dumps of mining enterprises by the method of georadiolocation. The possibilities and technologies of the development of a technogenic deposit with low costs for the production of iron ore are shown. The main advantage is the presence of minerals already on the surface and does not require complex mining technology. The next stage considers the issues related to the problems of the technology of preparation of the charge for the production of cast iron when using the raw materials of technogenic deposits. Special attention is paid to the content of various alloying additives, an assessment of their influence on the properties of gray cast iron is given.

Abstract: The article considers the features of the technology of iron smelting in small foundries. The paper presents data on the sulfur content in the metal, various options for metal desulfurization are considered. These technologies allow us to obtain high-quality metal. The use of such cast iron will significantly improve the quality of metal products.

Abstract: Currently, two main methods of applying abrasive grains to the surface of a flexible backing - mechanical and electrostatic - are used for the manufacture of grinding tools. The mechanical method of abrasive applying involves pouring an abrasive onto a backing, on which an adhesive has been previously applied. In this case, grains are fixed on the surface of a backing in a non-optimal way in a chaotic manner without taking into account their geometric parameters. This subsequently leads to rather low performance of such tools, thereby not allowing the full use of their capabilities. In the electrostatic coating, abrasive grains are oriented along their major axis perpendicular to a backing. A large number of studies show that grain orientation by this method improves the cutting performance of an abrasive paper. At the same time, the mechanism of the effect of an electrostatic field on abrasives of various grain sizes, depending on the interelectrode space, has not been fully studied. Based on this, studies aimed at scientific substantiation of the process of orientation of abrasive grains on the working surface of an elastic tool in an electrostatic field are of great relevance. This work is devoted to the study of the effect of an electrostatic field on abrasive grains. The article presents some results of studies of the susceptibility of brown aluminium oxide 14A of various grain sizes to the electrostatic effect.

Abstract: Four various methods of powder feedstock preparation for laser powder bed fusion are compared. Application of commercial spherical powder leads to the formation of single-phased state. Powder mechanically alloyed during 14 minutes in air atmosphere provides conditions for the formation of double-phased state with nonuniform distribution of components in the samples. Mechanical alloying in Ar-atmosphere during 30 minutes leads to the formation of double-phased state with more uniform distribution of components and precipitations of Cr₂O₃. Preliminary mechanical sieving of the powder allows to produce double-phased samples with nonuniform distribution of components comparable with that in samples produced from powder mechanically alloyed during 14 minutes in air atmosphere. Microhardness of all the studied samples produced from all the studied powders was comparable. All the proposed methods of powder feedstock preparation are applicable in laser powder bed fusion depending on the required properties, elemental and phase composition of the final product.

Abstract: The analysis of factors affecting the state of the metal of pipelines of heating networks on the territory of hazardous production facilities is carried out, of which the effect of mechanical loads should be especially distinguished. The necessity of carrying out additional types of control along with visual and measuring control during routine inspections and after repairs of pipelines of heating networks has been substantiated. The method for measuring the coercive force and its measurement methods are considered, and a decision is made to develop a technique for studying pipelines of a heating network using this method. Samples for laboratory research have been prepared, namely, a fragment of a heating network pipeline, which has worked for over 10 years, and a fragment of a new pipeline with a similar steel grade. A plan for conducting experimental studies of the prepared samples has been prepared, including the developed methods of experimental studies of samples in accordance with the regulatory documentation, including: a method for studying samples of pipelines of heating networks by measuring the coercive force; method for determining the chemical composition of metals and alloys; methodology for carrying out metallographic studies. Measurements of the coercive force were carried out during the loading of the samples. A change in the coercive force with loading was recorded, mainly towards large values. In this case, the values of the coercive force on the sample, which worked in the territory of hazardous production facilities, are higher than those of the sample of the new pipeline. The complex of the studies carried out indicates that it is advisable at enterprises to measure the coercive force of the metal of pipelines of heating networks on the territory of a hazardous production facility during a routine inspection along with visual and measuring, as well as after repair and restoration work.