Steel 09G2S Research Articles

INFLUENCE OF THE TEMPERATURE OF A ZINC MELT ON THE COATING THICKNESS AND STRUCTURE DURING HIGH-TEMPERATURE ZINCPLATING STEELS WITH A HIGH SILICON CONTENT

The experimental results on the fabrication of zinc coatings during high-temperature hot-dip zinc-plating the samples made of steel 09G2S are presented. Coating microstructure and phase composition are investigated by scanning electron microscopy and energy dispersive electron probe microanalysis. It is established that the coating thickness decreases at zinc-plating temperatures of 535–565 °C and reaches the minimum at 555 °C. The ratio of phases in coating at various temperatures is analyzed. It is noted that the coating thickness is minimal when its phase composition does not contain pure ζ-phase. Recommendations for selecting the process temperature of steel with a high silicon content are given.

INFLUENCE OF INTRODUCTION OF CARBON-FLUORINE CONTAINING ADDITIVES IN AN-67 FLUX ON PROPERTIES OF METAL WELDS IN 09G2S STEEL

Experimental study of the effect of introduction of carbon-fluorine containing additives in AN-67 flux welding of 09G2S steel. It is shown that the use of supplements reduces the total oxygen content in the weld, reduces pollution by oxide non-metallic inclusions and the level of gas saturation of the weld metal, increases required mechanical properties and toughness of the weld. The concentration of carbon in the weld remains at the base metal.

Ultrasonic estimation of the residual stresses

A method for estimating the residual stresses in the weld joint material is described. The results of acoustic examination of the samples made from structural plate steels 15, 20, 08ps, 15G2SF, and 09G2S are presented. A linear relationship between the Poisson ratios of the studied orthotropic materials is found when no residual mechanical stresses are present. Using the example of a weld joint of a pipe element made from steel 15G2SF, it is shown that the linear relationship between the Poisson ratios is violated in the presence of residual stresses. An algorithm for monitoring the residual mechanical stresses in the depressed-zero acoustic tensometry regime based on the deviation of the Poisson ratio of the material from the linear relationship is proposed. The results of measurements of the principal stress difference in a weld joint of a pipe made from steel 09G2S are detailed.

Metallographic study of construction materials with atomic force microscopy method

The results of atomic force microscopy (AFM) investigation of the micro- and nanostructure of 09G2S steel are presented. The method was developed for investigation of construction steel with AFM which allowed improving the quality and reliability of metallographic studies. Identification of the phase state of a material and determination of such microstructure parameters as grain size, pearlite fraction, the size of pearlite colonies, pearlite structural characteristics, and the width of intergrain boundary areas were performed on the basis of AFM images of 09G2S steel.

High-rate deformation and fracture of steel 09G2S

The results of experimental and theoretical studies of steel 09G2S deformation and fracture laws in a wide range of strain rates and temperature variations are given. The dynamic deformation curves and the ultimate characteristics of plasticity in high-rate strain were determined by the Kolsky method in compression, extension, and shear tests. The elastoplastic properties and spall strength were studied by using the gaseous gun of calibre 57 mm and the interferometer VISAR according to the plane-wave experiment technique. The data obtained by the Kolsky method were used to determine the parameters of the Johnson-Cook model which, in the framework of the theory of flow, describes how the yield surface radius depends on the strain, strain rate, and temperature.

FATIGUE LIFE OF WELDED JOINTS STUDS BRIDGE DECK RAILWAY BRIDGE

Purpose. To determine the conditions of use of weld studs in the construction and repair of railway bridges carry out a set of relevant studies. Methodology. Study of determining fatigue resistance of welded specimens of welded structures carried out by their fatigue tests at zero cyclic tension. To test the model used samples of the welded jointstuds BMP plates with T-section beam, and performed numerical analysis of these compounds. On the basis of the got results the graphs are built and dependences of tunnels support deformation at the substantial change of engineering and geological terms are established. Findings. The results of studies of fatigue resistance of the new design mounting plates ballastless bridge deck (BMP) of railway bridges with welded studs. Originality. It is shown that the design is promising, but its implementation needs to be improved welding techniques and the use of new materials for cushioning layer for attaching plates BMP. Practical value. Cal-defined cyclic durability of welded joints in steel studs09G2S with top chord T-bar manufac-pared from low-carbon steel St3sp and low alloy steel 09G2S who received welding.

Distribution of residual stresses in welded joints in 09G2S steel produced by adaptive pulsed-arc welding

Results of investigations into the effect of conditions of adaptive pulsed-arc welding on the mechanical properties and distribution of residual stresses in welded joints in plates of 09G2S low-alloy steel are presented. Pulsed-arc welding increases the impact toughness of the weld metal at subzero temperatures in comparison with the stationary conditions, and compressive residual welding stresses were detected.

Determination of the Parameters of Crack Resistance for 17g1s Steel Under Transverse Shear

We determine the static crack resistance of compact Richard’s specimens made of 17G1S steel and the critical crack opening displacement under the conditions of transverse shear (mode II). The specimens are tested under cyclic loading. Richard’s specimens are modernized with an aim to improve the conditions for the initiation and growth of mode II cracks. By using the digital image correlation method, we determine the distribution of strains near the notch tip.

Developing a Flat-Rolled Product for the Metal Structures of Vertical Oil Storage Tanks

The material traditionally used for the structures of oil storage tanks – hot-rolled low-alloy plate steel 09G2S – rapidly decreases in strength with an increase in the thickness of the plates and becomes more susceptible to brittle fracture. The material does not provide the necessary resistance to the initiation of hydrogen-induced corrosion cracking and is not reliable or safe enough for use in storage tanks. The low strength of this steel makes it impossible to blast-proof these structures. The solution to these problems is the development and use of new rolled plates with excellent service properties. One steel that meets these needs is steel 08G2NMFB, of strength class 390. This steel has good weldability and is highly resistant to brittle fracture. Its use will ensure a high degree of reliability and safety in the operation of large storage tanks and provide significant technical-economic benefits.

Evaluation of the parameters of texture components of fractures of high-toughness structural steel 09G2S after dynamic tests

Profiles of ductile fractures obtained in dynamic tests of steel 09G2S after quenching and tempering at 200, 400, 500, and 650°C are studied with the help of a scanning electron microscope and the optical module of an automated microhardness meter. The size parameters of microscopic dimples in the fractures are determined. It is suggested to classify the dimples in terms of their width-to-height ratio. The law of variation of the sizes of microscopic dimples of various types upon growth in the tempering temperature is determined.

Structure, dynamic crack resistance and fracture mechanisms of quenched and tempered structural steels

The structure of steels 09G2S, 25 and 40 after quenching and tempering at from 200 to 650°C is studied. An own method of the authors is used to estimate the impact toughness and the dynamic crack resistance of structural steels in various structural states. The micromechanisms of crack growth are studied in steels with various structures.

Ways of improving the quality of the surface of rolled products made of low-carbon structural steel ingots

Study of the nature of low-carbon structural steel rolled product surface defects by a metallographic method makes it possible to establish that formation of flaws in rolled product in the bottom part of ingots is connected with the presence of gas bubbles and extraneous inclusions. The effect of aluminum on rolled product surface quality is analyzed. The optimum aluminum content in steels 09G2S – 0.011–0.015%, S355j2G3 – 0.021–0.025% is established, and this makes it possible to improve metal ductility, reduce the degree of ingot defect development, and reduce rolled product rejection for surface defects.

Fracture strength of steels under biaxial loading in hydrogen

We have studied the stress-strain state of material in the process zone, near the crack tip in cruciform specimens made of 09G2S steel under non-proportional biaxial loading. We have obtained the strain distribution in this zone, in a domain of size 6 × 4.5 mm by the method of digital correlation of speckle images. We have compared the strain distributions and critical parameters obtained in air and hydrogen. It has been established that, under biaxial loading, the critical stress intensity factor K C , critical crack opening δ C , and critical strain e C near its tip vary within the limits of 15, 47, and 40%, respectively, depending on the parameter of loading rigidity κ. For hydrogen, we have detected a shift of the maximum of the dependence P C vs. parameter κ to the side of its positive values. The maximal effect of hydrogen on δ C and eС is observed under uniaxial tension (κ = 0).

Optimizing the composition of mixtures made by the company Tekhmet for casting steel ingots at the Chusovoi Metallurgical Plant

In the course of mastering a technology that uses heat-insulating inserts to cast steels (09G2S, rim steel 15, 50KhGFA, 62PP, etc.) into 1.94-ton ingots by bottom-pouring at linear speeds of 0.25–0.7 m/min, specialists at the Chusovoi Metallurgical Plant worked with the company Tekhmet (in Ukraine) to test different mixtures that could be used for the entire product mix. Mixture TSK-20(O) was ultimately recommended for practical use and can be employed without additional heating of the top part of the ingot. At a consumption of 1.5–1.6 kg/ton, this mixture ensures the level of quality required for ingots cast with fireclay-lined hot tops and heat-insulating inserts, regardless of the grade of steel.

Assessment of hydrogen effect on fracture resistance under complex-mode loading

Deformation and force criteria of the limiting-equilibrium state for a plate with an arbitrarily oriented crack under tension and under the influence of hydrogen-containing environment are proposed. The experimental investigations of the limiting-equilibrium state of lamellar specimens made of 09G2S steel with a central inclined crack in hydrogen environment and also in air under tension with different initial crack inclination angles were performed to check the criteria. Under specimen fracture the forces of the crack start were recorded. Experimental data agree well with calculation dependences.

Studies on the effect of high-temperature and pressure hydrogen environments on 09G2s steel properties

The susceptibility of 09G2S steel to hydrogen corrosion after the saturation of specimens with gaseous hydrogen under a 5-MPa uniform pressure at 300, 400, and 500°C was investigated during different holding times. This effect on the metal structure and properties was studied. It was shown that the saturation of specimens with hydrogen caused gradual carbon depletion of steel, the metal structure displayed a larger number of ferrite grains with well-defined boundaries. The onset of intense hydrogen corrosion appears as a smaller number of pearlite grains in the metal structure. The experimental data resulted in establishing the incubation period of hydrogen corrosion of 09G2S steel, i.e., time to the onset of decarbonization under preset conditions of the metal saturation with gaseous hydrogen under a 10-MPa pressure at ° , which is 90 and 17 h, 500 and 580°C respectively. The reserve of 09G2S steel hydrogen stability within the incubation period is the basis for adding to safe service life of equipment for petrochemical and oil refining industries in hydrogenation processes.

Evaluation of the concentration of hydrogen in the process zone near the crack tip

We construct, in the closed form, an analytic solution of the problem of diffusion of hydrogen in the process zone near the crack tip operating in contact with the ambient hydrogen-containing medium with regard for the preliminary hydrogenation of the material and the gradient of the field of mechanical stresses in this zone. It is shown that the hydrogenation of the material and the gradient of the hydrostatic component of the tensor of mechanical stresses induced in the material near the crack tip under loading may lead to the formation of the concentrations of hydrogen in this zone several times higher than in the medium. We also perform the experimental investigations and determine the local concentration of hydrogen in the process zone for specimens of 09G2S steel.

Evaluation of the effect of production and operating parameters on the durability and safety of assembled welded joints of valve fittings

Questions are considered of the reliability of assembled welded joints of valve fittings. It is proposed to use impact strength as a criterion of welded metal durability for welded joints. The effect of welding heating cycle on the structure and phase composition, and properties of metal around the joint (MAJ) of the heataffected zone (HAZ) of welded joints made from steel of strength categories K42 and K52 is studied. The effect of strain ageing on impact strength characteristics of the MAJ of the HAZ is analyzed for steel 17GS with different structure and phase compositions. It is shown that metal of the MAJ of the HAZ with a predominantly bainitic structure is most resistant to strain ageing. Dependences are plotted for evaluating welded joint material endurance and determination of the duration of the operating period, during which there is no critical fall in impact strength, and rational welding regimes are also established that make it possible to prolong safe operation of valve equipment to 30-35 years.

Study of adiabatic localized shear in metals by split Hopkinson pressure bar method

This paper is devoted to the technique for study of localized shear using hat-shaped samples by the split Hopkinson pressure bar (SHPB) method. Also it is devoted to results obtained in tests with samples of copper M1 and steel 09G2S. The tests were performed using hat-shaped samples with beforehand-determined direction of forced shear. Sizes of samples were thoroughly selected in order to minimize plastic deformation of the hat-shaped part and the ring base, which are in contact with the bar ends. Results of testing of copper M1 and steel 09G2S were obtained; “shear stress-displacement” diagrams were plotted. Values of amplitudes and durations of loading pulses were determined. Also shear stresses were determined when adiabatic localized shear was formed in case of this geometry of samples.

Analysis of the integrity of welded pipes of gas mains by the FITNET procedures

We have evaluated the integrity of a rectilinear element of a welded pipe of a gas main after its operation for 40 years with the use of the FITNET procedures according to the Failure-Assessment-Diagram approach. We have determined the critical sizes of defects in the base (17G1S steel) and weld metal of a longitudinal welded joint of a reserve pipe. Two levels of the gas pressure in the pipeline (4.5 and 7.0 MPa) are taken as critical values. It has been shown that, in the absence of corrosion and hydrogenating influence of the transported medium, the base metal of pipes both in as-received state and after long-term operation is more susceptible to fracture due to reaching the critical stressed state than the weld metal.