Steel 09G2S Research Articles

Impact Strength of Low-Carbon Steel 09G2S Welded Joint Metal

Impact Strength of Low-Carbon Steel 09G2S Welded Joint Metal

Structure and Magnetic Properties of 09G2S Steel Obtained by the Selective Laser Melting Method

Structure and Magnetic Properties of 09G2S Steel Obtained by the Selective Laser Melting Method

Study of the fatigue strength of steel 09G2S obtained by 3D printing based electric arc welding in a wide range of low temperatures

In this work, we consider the issues of obtaining workpieces from cold-resistant steel 09Mn2Si by a promising method of 3D-printing by electric arc surfacing (electric arc additive growing). The task of assessing the mechanical properties of the obtained material and understanding the process of its destruction is urgent. The assessment of the fatigue strength of the obtained material after deposition and after subsequent heat treatment (HT) (normalization) in a wide range of low temperatures is carried out. A fractographic analysis of fatigue fractures of 9Mn2Si steel using scanning electron microscopy was also carried out. Ultimately, this makes it possible to assess the reliability of parts manufactured by 3D-printing arc welding. In the course of the work, the mechanical properties were obtained and the analysis of the curves of low-cycle fatigue of the samples after 3D-printing and after further HT in the temperature range of -60 ... 20 °C was carried out. Metallographic studies have been carried out and structural changes have been established in the process of fatigue loading at different operating time of the sample. A relationship was established between the value of the maximum cycle stress and the operating time corresponding to the onset of the onset of the main crack and the moment of fracture of the sample for steel 9Mn2Si steel. The dependence of the average growth rate of the main crack on the applied stress during fatigue tests is obtained.

Plastic Strain Localization in Steel Composites Produced via Additive Manufacturing

In this work we report the kinetics of plasticity of St3 low-carbon steel-based composite alloy prepared via vacuum electron beam cladding of 09G2S steel wire. The digital image correlation method revealed the existence of macroscopic localization of plastic flow at the yield plateau and parabolic hardening stage. The kinetic characteristics of localized plasticity domains were measured in various composite layers, as well.

Development of equipment and technology for precision air-plasma cutting of plate steel

The authors have investigated the structure of cutting seams obtained after cutting steel 09G2S with a new narrow-jet plasma torch of PMVR-5.3 type which has a number of design features in gas dynamic stabilization system (GDS) of plasma arc. To increase the efficiency of GDS in PMVR-5.3 plasma torch, a symmetrical input of plasma-forming gas (PFG) into the flow division system and a gas-dynamic flow stabilizer using two (forming and stabilizing) swirlers with a variable number of swirl channels were used. It is shown that the achieved advantage in GDS efficiency makes it possible to obtain high cutting quality of steel 09G2S with thickness of 40 mm with high productivity and lower energy costs. Analytical methods have proved a high degree of cutting precision of the new torch– a small cut width, no melting and rounding of the upper edge, as well as a grate in the cut lower part and splashes in the cut upper part, almost zero angular deviation, minimum values of the surface microrelief and width of the thermal impact zone. Metallographic analysis and determination of hardness showed the presence of three subzones in the thermal impact zone with significant structural changes in two of them. A number of factors were noted influencing the revealed changes in the structure formation, as well as changes in the elemental composition of the cutting seam surface layer revealed during the X-ray spectral analysis. Attention is drawn to the surface microrelief after plasma cutting, which in all quality indicators is commensurate with machining of the surface after milling and corresponds to the second class of quality in terms of surface cleanliness. It was proved that the use of the new narrow-jet plasma torch allows high-quality cutting of plate steel in thickness range up to 40 mm or more. However, welding of blanks without pre-machining can be carried out with a cutting thickness of no more than 20 mm.

Study of the EDM Process of Bimetallic Materials Using a Composite Electrode Tool.

New types of profile products make complex use of bimetals. These materials possess a set of properties such as strength, corrosion resistance, thermal conductivity, heat resistance, wear resistance. For the processing of such products, it is advisable to use electrophysical processing methods, one of which is the technology of copy-piercing electrical discharge machining (EDM). Currently, EDM is one of the most common methods for processing products from modern bimetal materials. An urgent task is to study the EDM process of bimetallic materials. The aim of the work was to increase the efficiency and accuracy of the EDM process of bimetallic products using electrode-tools with different physical and mechanical properties. Bimetal—weld coated steel backing, base material—09G2S steel, surfacing material—M1 copper were used. The processing of the bimetallic workpiece was carried out on an Electronica Smart CNC copy-piercing EDM machine. EI used graphite, copper, and composite. A theoretical model was developed that allows calculation of the amount of removal of bimetallic material of steel–copper depending on the EDM modes and the ET (electrode tool) material. During the processing of the steel layer, regardless of the EI material, microcracks were formed along the grain boundaries, and during the processing of the copper layer, enlarged holes resulted.

Replacement working body material as a way to increase reliability of road construction machines

Introduction. On the example of a motor grader knife, ways of increasing the reliability of road construction machines (RCM) operation are evaluated. For this purpose, the analysis of force effects nature on the working body of the RCM is carried out and its design features are highlighted (the presence of a welded joint). Based on the analysis, the range of characteristics necessary for making a decision on the possibility of replacement the material of the RCM working body is determined. Additionally, its thermocyclic treatment (TCT) is carried out. Experimental studies of the effect of this thermal impact type on the structure and properties of steels are described.Materials and methods. With the help of metallographic analysis, the author investigates the influence of the number of thermal effects cycles on the grain size and the complex of various materials physical and mechanical characteristics of road construction machines working body at various stages of the thermocyclic treatment.Results. It is determined that an increase in the level of the investigated steels physical and mechanical characteristics is possible through the use of TCT due to the obtaining of a fine-grained metal structure. The dependences of the main physical and mechanical characteristics of the investigated steels (ultimate strength and yield strength) on the number of thermal effects cycles are considered. Correlation relationships are selected to describe these dependencies. The relationship between the yield strength and ultimate strength of 09G2S and 30MnB5 steels and the grain size is considered. In addition, studies of the steels fatigue characteristics are carried out; data on determining the microhardness are presented for the welded joint. For various operating temperatures, fractographic studies are carried out on samples after cyclic loading.Discussion and conclusion. Based on a comparative analysis of the complex of physical and mechanical characteristics, the author made a conclusion about the possibility of replacing steel 09G2S with steel 30MnB5.

ИССЛЕДОВАНИЕ СВОЙСТВ СТАЛЬНОЙ ЭМАЛИРОВАННОЙ ПОВЕРХНОСТИ ДЛЯ СИЛОСНЫХ БАШЕН

One of the technologies for obtaining and storing high-quality silage and haylage is the use of silo towers. The authors propose to manufacture silo towers from high-strength and corrosion-resistant steel sheets, coated with glass enamel, which has a lower coefficient of sliding friction than steel and concrete, as well as high resistance to aggressive environments. The aim of the study was to determine the properties of the glass-enamel coating of steel parts for the manufacturing of tower-type storages. A glass-enamel coating from a frit of glass-enamel brand MK-5 was applied to prepared sheets of steel 09G2S using a spray gun. The total thickness of the enameled coating ranged from 200 to 350 nm. Steel sheets were baked at a temperature of 850°C for 30 minutes. The thickness of the enamel coating was determined with an Olympus GX51 microscope. The roughness was determined using a TAYLOR HOBSON Surtronic 25 profilometer. The adhesive properties of the coating were studied using a Positest AT-M adhesive meter. Each test piece was tested twice. The tests were carried out on a sheet of 0.06 m2. The coefficient of sliding friction was determined on an adapted test bench. Laboratory tests with silage mass were carried out according to the developed methodology. Studies of the steel surface with a glass-enamel coating showed that the average thickness of the enameled layer was 690 nm, the roughness was 0.01 μm, and the adhesion was 5.25 MPa. The sliding friction coefficient of sliced plant materials on the enameled steel surface was 0.15, which is 2.6 and 3.2 times lower than that of non-enamelled steel and concrete, respectively. The authors have made conclusions about the possibility of using steel 09G2S in silo towers as a suitable sustitute for steel 65G and the sufficient efficiency of the chosen enameling technology.

Исследование макроскопической локализации пластического течения в аддитивно изготовленном биметалле

The paper studies the kinetics of macroscopic localization of plastic deformation in a bimetal obtained by electron-beam surfacing of wire from low-carbon steel 09G2S on a substrate of St.3. Mechanical tests according to the scheme of uniaxial tension of flat ones were carried out at a constant rate at room temperature. The mechanical properties and stages of the plastic flow of the bimetal are compared with those of the starting materials. The kinetics of plastic deformation localization zones in different bimetal layers was studied by digital speckle photography.

Control of microhardness of nickel-phosphorus coatings in amorphous and crystal states, taking into account requirements to quality of supplied products

The microhardness of a nickel-phosphorus coating 60 μm thick chemically applied to a steel substrate from an alkaline solution was determined at loads from 0,1 to 0,5 kgf. The control was carried out on preliminarily prepared samples of steel 09G2S, which passed the stage of crystallization annealing of the coating to the required hardness. The quality of the coating after the control and after 24 hours was evaluated with a reagent consisting of potassium synergistic and sodium chloride. It is established that the load is 0,2; 0,3 and 0,5 kgf are not suitable for reliable measurement of the microhardness of the coating due to a violation of its integrity and distortion of the microhardness indicators. A load of 0,05 kgf is unacceptable due to obtaining diagonals that are a multiple of the smaller confidence interval of 0,02 mm. The conducted studies and the revealed patterns made it possible to select the optimal load (0.1 kgf) used in determining the microhardness of a 60 μm thick coating, which guarantees the preservation of the quality of parts used in the oil and gas industry in the hardness range of 1000 HV and more.

Lüders deformation in specimens made of normalized 09G2S steel

The features of Lüders deformation in the normalized 09G2S steel are studied by the methods of digital image correlation, topography, and scanning electron microscopy of specimen faces. The paper studies the appearance, growth, structure, and location of deformation bands, as well as plastic strain in them.

Experimental validation of safety coefficient values of 09G2S steel by X-ray diffraction method

The present work demonstrates that FWHM profile broadening of the diffraction line reflected from a system of crystallographic planes is observed under short-term static loading of flat samples of 09G2S structural steel within the limits of Hooke’s law by the X-ray diffraction method. It has been established that the experimentally revealed change in the FWHM profile broadening of the diffraction line can indicate the development of elastic deformations of the crystal lattice of structural steels. It will allow physical substantiating of defined values of the safety coefficient based on new theoretical concepts of localized vibrational modes that are discrete breathers caused by distortions of the crystal lattice

Regularities of Stress-Corrosion Cracking of Pipe Steel 09G2S at Cathodic Polarization in a Model Soil Environment

Peculiarities of corrosion-mechanical fracture of 09G2S pipe steel samples in the conditions of cathodic protection were investigated. It was established that depending on the level of protective potential, stress-corrosion cracking of pipe steel of a ferrite-pearlite class 09G2S can occur by different mechanisms. The range of protective potentials was determined, at which the anodic dissolution and hydrogen embrittlement occur simultaneously during the fracture of steel, namely from -0.85 V to -1.0 V. The existence of the above mechanisms is confirmed by the change in the strength and viscosity properties of the steel and the morphology of the fractures. For steels of other manufacturing technology and grades, these potential areas may differ.

Study of mechanical properties of C-Mn-Si composition metal after wire-arc additive manufacturing (WAAM)

Wire-arc additive manufacturing (WAAM) is considered as a rather promising alternative to conventional subtracting production process for manufacture of large expensive metal components with complicated geometrical shape. Up-todate direction of WAAM investigations is aimed on production of functional metallic components with complicated geometrical shape and high accuracy, surface processing and mechanical properties meeting the strict requirements of aerospace, automotive and instrumental industries. At the same time, structural application of metal components based on their mechanical properties is studied insufficiently. It is necessary to understand additionally influence of technological conditions (such as energy input, protective gas role, speed of wire feed, welding speed, facing features and its sequence etc.) on the thermal initial parameters and finishing mechanical properties. The paper displays that mechanical properties of low-alloyed silicon-manganese composition of C-Mn-Si type with ferrite-pearlite structure is higher comparing with conventional steel 09G2S. It is shown that impact strength values for C-Mn-Si-type composition, which id formed via WAAM method, is higher by 2 times in comparison with welded joints which are faced by Sv-08G2S wire. 

METHODICAL APPROACH TO THE STUDY OF STRESS CORROSION CRACKING MECHANISM OF PIPELINE STEEL AT CATHODIC PROTECTION BY LINEAR SWEEP VOLTAMETRY

A methodological approach to the rapid assessment by linear sweep voltammetry method stress corrosion cracking (SCC) mechanism of pipeline steels of various grades under cathodic protection has been developed. The proposed approach serves as the basis for the electrochemical study of the mechanism of stress corrosion cracking of pipeline steel at various protective potentials for laboratory conditions. The ratio of polarization currents at fast () and slow () scanning potential rate was determined, its analysis was carried out depending on the polarization potential for steels of various grades. It was established that polarization potentials at which the difference between corrosion rate of the crack’s tip and the other surface is the maximum (maximum value of ) and the rapid development of stress corrosion cracks begin, which is differ for steels of various grades and equal near -0.75 V for X70 steel, -0.85 V for 09G2S steel and -0.8 V for 17G1S steel. The boundaries of the polarization potentials are established, beyond which the SCC mechanism of the investigated steels in the model soil environment NS4 changes, namely: from -0.75 V to -1.05 V for X70; -0.85 V to -1.0 V for 09G2S; from -0.8 V to -0.98 V for 17G1S. This indicates the possibility of SCC development with different rates and patterns, all other things being equal. The results of the work can be useful both for a theoretical understanding of the SCC mechanism and for an express assessment of the SCC mechanism in a soil environment and, in particular, in underfilm electrolyte under a disbanded coating.

Methodology for testing pipeline steels for resistance to grooving corrosion

The methodology for testing pipeline steels is suggested on the assumption that for the destruction of pipes in field oil pipelines by the mechanism of grooving corrosion the simultaneous fulfillment of such conditions as the occurrence of scratches on the lower generatrix of the pipe, eventually growing into a channel in the form of a groove, emulsion enrichment with oxygen, presence of pipe wall metal in a stressed state, presence of chlorine-ion in the oil-water emulsion is required. Tests are suggested to be carried out in 3 % aqueous solution of NaCl with continuous aeration by air on bent plates 150×15×3 mm, made of the analyzed steel, the middle part of which is under the action of residual stresses σres, close to the level of maximum equivalent stresses σeqv in the wall of the oil pipeline, with the presence of a cut on this part on the inner side of the plate as an initiator of additional mechanical stresses. Using the value of the modulus of normal elasticity of the analyzed steel, the degree of residual strain of the elastic-plastic body from this material, corresponding to the value σres ≈ σeqv is calculated, based on which the plates are bent to the required deflection angle, after which the cut is applied to them. After keeping the plates in the corrosive medium for each of them the increase in depth of the cut as a result of corrosion of the walls by the corrosive medium is analyzed, from which the rate of steel K by the mechanism of grooving corrosion is calculated taking into account the duration of tests. Corrosion rate values for two pipe steel grades determined by the suggested procedure are given. The comparison of K values obtained leads to the conclusion about the higher resistance to grooving corrosion of 09G2S steel.

Influence of nanomodication on structure for-mation and properties of structural steel

The state of the problem of grinding the grain structure and improving the mechanical properties of low-alloy structural steels has been studied. The state of the problem of grain structure refinement and improving the mechanical properties of low-alloy structural steels has been studied. The role of nanodispersed additives is reduced to the creation of additional artificial crystallization centers in the melt. They must be consistent with the critical radiuses of the embryos. According to our calculations, for the grinding of primary austenite grains in castings, the size of the introduced particles should be 40–50 nm. Output and modified castings of 09G2 and 09G2S steels were subjected to severe plastic deformation by equal-channel angular pressing followed by low-temperature annealing at 350 °C. In the initial state, cast steels 09G2 and 09G2S had a ferrite-pearlite structure with an average primary austenite grain size of 30 μm; after modification and deformation, the grain size was 10 μm. After quenching and cooling in water, the structure has changed insignificantly - ferritic-reed, with an average grain size of ~ 8...10 microns. After cooling the quenched samples in a solution of 20 % NaCl in water, the structure of packet martensite was obtained. In the initial state, the studied steels have insufficiently high property values: microhardness Нμ up to 3000 MPa, yield point σ 0,2 up to 800 MPa. When quenching in water, the hardness somewhat increases, the most significant increase is observed when the samples are cooled in a NaCl solution. Due to the significant grinding of martensite crystals, accelerated cooling provides a greater increase in hardness. A nanodispersed powder of titanium carbonitride Ti (CN) with a fraction of 50...100 nm was obtained by the method of plasma-chemical synthesis, the process technology was developed. Intensive plastic deformation of 09G2 and 09G2S steel castings was carried out. The structure and properties of steels before and after treatments have been studied. As a result of the combination of hardening methods, the grain size of the steels was reduced by 3 times and the yield strength increased from 3000 to 4000 MPa. Nanodispersed powder of titanium carbonitride Ti (CN) with a fraction of 50...100 nm was obtained by the method of plasma chemical synthesis, and a process technology was developed. Intensive plastic deformation of castings of 09G2 and 09G2S steels was carried out. The structure and properties of steels before and after treatments were studied. As a result of a combination of hardening methods, grinding of steel grains by 3 times and increasing the yield strength from 3000 to 4000 MPa was achieved

Оценка влияния дисперсности структуры стали на магнитные и механические свойства

Introduction: The control of the mechanical properties of structural steels is one of the main processes that regulate the service life of equipment. In most technical processes (pressure treatment, welding, rolling, thermal exposure), structure changes both in local areas and in the entire volume. Changes in the steel structure entail changes in its properties and as a result in local areas, at various stages of operation, the likelihood of the occurrence and development of critical defects increases. Its presence significantly affects the performance of the equipment, and leads to premature aging of the material and its failure. Precisely because the control of the mechanical properties of steel remains one of the urgent problems, new control methods are being developed. It is known that all properties of steel depend on the structure of the substance, however, studies on the effect of the dispersion of the structure under consideration on the mechanical properties are presented in an insignificant amount. Purpose: to analyze from a mathematical point of view the influence of the factor of different grain size, as a parameter reflecting the dispersity of the system, on the mechanical properties of structural steel. The paper studies a heat-treated planar samples of steels 15KhSND, 09G2S and St3. Methods of research: scanning electron and optical microscopes are used to study the grain structure and grain boundaries; SIAMS 700 software package is used for finding the boundaries and average data of the grain structure; portable X-ray fluorescence analyzer of metals and alloys X-MET 7000 is used to determine the chemical composition of the test samples in percentage; tensile testing machine IR-50 is used for measuring the tensile strength of samples; Vickers hardness tester is used to determine the hardness of samples. Results and discussion: it is found that there is a satisfactory correlation for the mechanical properties of structural steels (hardness and ultimate strength) and the grain size factor, which can be used to predict the hazardous states of structures and the operating time. The analysis of variance and regression of the detected dependencies is carried out. It is noted that the dropout of some values from the general regression dependence can most likely be associated with a decrease in the value of internal stresses as a result of a decrease in the distortions of the crystal lattice of steel occurring during heat treatment. It should be noted that the processes occurring and the degree of its influence on the properties of the structural steels under consideration can be different due to the presence of different amounts of alloying elements in the composition of the studied steels.

The inhibitory properties of ion-modified zeolite for priming paint coatings

The anticorrosion environmentally friendly pigments based on synthetic zeolite for paint coatings were obtained by liquid-phase ion exchange method. Zeolite was modified with zinc, calcium and manganese ions. The corrosion resistance of 09G2C steel in 0.1% NaCl solution and in suspensions of modified zeolite was investigated by potentiodynamic polarization method. It was shown that the use of zeolite modified with cations of divalent metals contributes to the reduction of corrosion currents. It was found that the zeolite modified with zinc cations exhibits the most anticorrosion effect relative to 09G2C steel, as indicated by the values of corrosion currents (which are ~2 times smaller than in the non-inhibited solution) and the results of electrochemical impedance spectroscopy. The surface morphology of 09G2S steel after exposure to the inhibited media was determined by scanning electron microscopy. Protection mechanism of the modified zeolite was suggested.

Features of structure and mechanical properties formation in shaped rolled products made of 09G2S steel in accelerated water cooling process

The article provides an analysis of methods for strengthening structural shapes in a stream of section mills, a series of active experiments was carried out, and a calculation of predictive regression equations for the dependence of mechanical properties and microstructure indicators on the geometry of profile dimensions and technological parameters of cooling. An algorithm has been developed for iterative refinement of the forecast accuracy using such equations, which provides the minimum error in determining the specified characteristics. Metal microstructure at various modes of accelerated cooling in calm water of shaped rolled in the flow of a section mill confirms the patterns of structure formation and corresponds to the theory and practice of science of metals and heat treatment of metals. The developed techno logy of accelerated water cooling provides for shaped rolling increase in strength to a class of 600 MPa and higher for a wide assortment of structural shapes and for critical purposes for pipe and ship-car building. The use of accelerated cooling in calm water of shaped rolled gives a significant economic effect (80-100 USD per 1 ton of rolled steel) instead of using microalloying steel with elements such as vanadium and niobium, which reduce the size of the austenitic and then the real grain of the metal and thereby increase the yild point and its relation to the ultimate tensile strength, providing substantial strengthening of rolled products. As a result, an efficient technology have been developed for thermal hardening of structural shapes in the flow of a section mill.