Mechanical Properties Of Low Carbon Steel Research Articles

Recrystallization kinetics and the mechanical properties of low-carbon steel during high-temperature annealing in electric furnace

Recrystallization kinetics and the mechanical properties of low-carbon steel during high-temperature annealing in electric furnace

Structure and properties of steels for manufacture of core catcher vessel of nuclear reactor

The Russian new nuclear reactors are provided with a special core catcher vessel device (cc-vessel) designed to minimize the consequences of a severe beyond design basis accident at a nuclear power plant, when the reactor pressure vessel collapses and the core melts. For manufacture of the cc-vessel structural elements, low-carbon unalloyed or low-alloyed steels are used. When a severe beyond design basis accident develops, the cc-vessel’s body is subjected to extreme temperature and force loads, which can lead to degradation of the structure, loss of strength and failure of the entire cc-vessel. To calculate the strength characteristics of the cc-vessel, which ensure its safe and reliable operation, the detailed data are required on the structure and mechanical properties of low-carbon steels at high temperatures and after extreme thermal actions simulating the development of a severe beyond design basis accident. The paper analyzes data on the structure and mechanical properties (tensile strength, crack resistance, toughness and cyclic strength) of a number of low-carbon steels under extreme temperature and force actions, including conditions simulating the development of a severe beyond design basis accident at a nuclear power plant, in order to select the material for the design of cc-vessel of nuclear reactor. New data on the structure, mechanical properties, and thermal diffusivity in a wide temperature range of a Cr – Mo steel (Russian Standard – 15KhM) as a candidate structural material for the manufacture of the cc-vessel body are presented. The low content of manganese and alloying with molybdenum and vanadium in 15KhM steel provides a finer grained structure and eliminates the steel’s tendency to temper brittleness.

Studying the impact of multi-pass friction stir processing on microstructure and mechanical properties of low-carbon steel

Studying the impact of multi-pass friction stir processing on microstructure and mechanical properties of low-carbon steel

Microstructure and mechanical properties of low-carbon steel fabricated by electron-beam additive manufacturing

The microstructure and mechanical properties of a billet obtained by electron-beam additive manufacturing (EBAM) using an industrial welding wire of low-carbon steel were studied. After EBAM, the steel billet possesses the phase composition constant in volume (ferrite with carbides). Deformation behavior of samples of steel obtained by the additive methods depends on their position in the billet. In its lower part, which is characterized by a high cooling rate in the EBAM-process, predominantly equiaxed ferrite grains with an average size of 15 μm are formed. The mechanical properties and deformation behavior (the presence of a yield plateau, the stages of plastic flow) of this part of the billet are close to those of normalized low-carbon steel obtained by conventional methods of metallurgy and thermomechanical processing. In the middle and top parts of the billet, the coarse non-equiaxed ferritic grains (hundreds of micrometers) form. The mechanical properties in this part weakly depend on the position of the samples and their orientation relative to the building direction of the billet — the yield plateau disappears; the yield stress, the ultimate tensile strength, the elongation become lower than those of the normalized low-carbon steel obtained by the conventional method. Despite the predominance of ferritic grains (with carbides), a small portion of grains with a lamellar ferrite morphology resembling martensite or bainite is observed in all parts of the billet. The latter is the result of a complex thermal history of the billet, which can undergo multiple phase transformations during successive heating and cooling cycles.

High-temperature mechanical properties of low-carbon steel used for the manufacture of core catcher vessel

Direct experimental data had been obtained on the mechanical properties of 22 K low-carbon steel (ASTM Grade 1022), used for the manufacture of core catcher vessel, when tested for uniaxial static tension within the temperature range from room temperature to 1200 °C. A 60-mm thick steel sheet after hot rolling and normalization was used for investigation. It is shown that the sharpest decrease in strength properties is observed in the temperature range of 400–650°С. Long-term high-temperature heat treatment simulating conditions of a severe beyond design basis accident at a nuclear power plant, most noticeably changes the mechanical properties of 22 K steel in the test temperature range from room temperature to 700 °C, namely, it decreases the yield strength in the temperature range from room temperature to 300 °C and increases the yield strength and ultimate tensile strength in the temperature range from 400 up to 700°С. At higher temperatures, the effect of heat treatment is less significant. A wave-like shape of the stress-strain curves due to active dynamic recrystallization processes for as-received specimens and specimens after heat treatment appears, respectively, at temperature above 600°С and above 750°С.

Study on Deterioration Characteristics of Low-Carbon Steel’s Mechanical Properties and Fracture Mechanism under Marine Engineering Environment

In order to study the mechanical properties of low-carbon steel under the coupling effect of the overall environment and the loads, the tensile mechanical test was carried out. The results indicated that, as the sea water concentration and tensile deterioration increased, both the mass-loss rate and surface roughness of the low-carbon steel gradually increased, and the yield strength, tensile strength, elongation, and section shrinkage decreased gradually. The mechanical parameters of the low-carbon steel were affected by the joint actions of the sea water concentration and tensile deterioration. The established mechanical model of low-carbon steel under the marine engineering environment shows that tensile deterioration had no effects on the fracture toughness, while the increase of sea water concentration could reduce the fracture toughness remarkably.

Incompatible effects of B and B + Nb additions and inclusions' characteristics on the microstructures and mechanical properties of low-carbon steels

The influence of boron as well as boron with niobium additions on the phase transformation behaviour, resultant microstructures, and mechanical properties of thermomechanically controlled hot-rolled and direct-quenched low-carbon bainitic steel plates was investigated. Also, the probable factors that could inhibit their specific merits on hardenability, phase transformation behaviour and mechanical properties, were studied. Continuous cooling transformation diagrams of both deformed and non-deformed austenite were constructed for the investigated steels. Laser scanning confocal microscopy (LSCM) and field emission scanning electron microscopy (FESEM) were employed to examine the microstructures, besides detailed analyses of the non-metallic inclusions using FESEM combined with INCA software. Moreover, the precipitates were investigated qualitatively using both FESEM as well as transmission electron microscopy (TEM). The results showed that the addition of boron or boron with niobium led to an increase in the critical transformation temperatures (AC1 and AC3) covering the intercritical range. The addition of boron with niobium decreased the bainite start transformation temperature (Bs), while the lone addition of boron had a slight or insignificant effect on Bs. While the addition of boron alone had no effect on the hardness, ultimate tensile strength (UTS), yield strength (YS), and elongation to fracture, augmenting it with niobium led to a marginal increase in the UTS and YS. In general, the addition of boron with or without niobium deteriorated the impact toughness of the investigated steel. These were explained in terms of the slight changes in the chemical composition and cleanness of the investigated steels and considering various microstructural features i.e., prior austenite grain size, effective grain size, coarsest grain size and precipitates characteristics, particularly the formation of coarse (Fe,Cr)23(B,C)6.

FORMATION OF LOW-CARBON WIRE ROD STRUCTURE UNDER SHS CONDITIONS USING MAGNETIC COERCIMETRIC CONTROL

The article discusses the use of a self-propagating high-temperature synthesis of SHS ofsolid chemical compounds – it is a new technological process that possible to obtain a materialwith a given structure based on carrying out an exothermic reaction of interaction of reagents inthe combustion regime. The influence of cold deformation and intermediate annealing underSHS conditions on the structure, magnetic and mechanical properties of low-carbon steel is determined.The use of magnetic coercimetric control possible to control changes in the structureand mechanical properties of during technological cycle for low-carbon welded wire in productionconditions.

Effect of cooling-rate during solidification on the structure-property relationship of hot deformed low-carbon steel

The present study investigates the combined effect of cooling-rate during solidification and hot deformation on the microstructure and mechanical properties of low-carbon steel, especially considering the beneficial effect of acicular ferrite. Low-carbon steel was cast in two different moulds to vary the cooling-rate during solidification. The cast ingots were soaked and hot forged at different temperatures. Relatively slower cooling-rate during solidification and deformation at relatively lower temperature were found to be beneficial for the acicular ferrite formation, which increased the hardness and strength without hampering the ductility. The difference in solute contents at the dendrite center and the interdendritic regions of the cast-ingots, as a result of microsegregation, and the compositional homogenization during soaking were predicted. Based on the predicted compositions, the microstructures of the cast and hot forged ingots were explained considering the effect of prior-austenite grain size, austenite conditioning during deformation, fraction of non-metallic inclusions and the segregation of Nb along the prior-austenite grain boundaries on the phase transformation.

Study of the influence of thecomposition and structure of ст3псsteel on hardness

Formulation of theproblem. The use of indirect methods of quality control of metal rolling is due to many factors, among which the influence of the chemical composition and technological regimes should be noted. These factors affect the structure and the mechanical characteristics, in particular, low carbon steels. In the work for the prediction of hardness indicators of Ст3псsteel, it is proposed to apply the methodology of planning experiments, taking into account the influence of elements of chemical composition and structure. To estimate the ferrite-pearlite structure, it is proposed to use the fractal formalism, the use of which allows you to track changes in the structure by determining the fractal dimension of its elements. Materials and methods. Using the methodology of planning experiments, the effect of the chemical composition and structure on the mechanical properties of low-carbon Ст3пс lowalloyed steel was investigated. Results. By implementing the experiment planning matrix, a mathematical model was obtained for evaluating the hardness of Ст3псsteel, taking into account the influence of elements of chemical composition and the fractal dimension of perlite. The model is adequate according to the criteria of Cochran's and Fisher. Based on the analysis of the coefficients of the regression equation, a histogram of the influence of the elements of the chemical composition of the studied steel on the hardness indicators was constructed. The growth of the fractal dimension of perlite from 1,785 to 1,946 with an increase in the carbon content from 0,14 to 0,22 % was recorded, which indicates the possibility of its use in assessing the structure of low-carbon steels. Conclusions. A method for assessing the hardness of St3ps steel has been developed, taking into account the influence of elements of chemical composition and fractal dimension of perlite. The results indicate the prospects forthe application of the theory of fractals in the prediction of the mechanical properties of low-carbon steels.

The effect of beam oscillations on the microstructure and mechanical properties of electron beam welded steel joints

The influence of beam oscillations on the microstructure and mechanical properties of low-carbon steels, subjected to electron beam welding, was investigated. Beam oscillations created a dynamic distribution of power around the stationary position of the beam resulting in the enhanced flow of heat inside the keyhole and yielded wider fusion and heat-affected zones. A reduction in the undercutting at the weld root was also achieved through beam oscillation. The weld microstructure consisted of large columnar grains in the fusion zone and equiaxed grains of varying sizes in the heat-affected zone. The variation in grain size across the weld joint was attributed to the steep temperature gradients produced during electron beam welding. High hardness was seen in the fusion and heat-affected zones due to the occurrence of martensite. Weld samples fabricated using beam oscillations showed lower microhardness compared with joints produced by stationary beam welding. This decrease in hardness arose from enhanced grain growth and additional diffusion of carbon out of the austenite lattice due to beam oscillations. Beam oscillations did not introduce any significant morphological changes to the weld microstructure, but resulted in enhanced tensile strength and lower microhardness in the weld joints.

The Influence of Ultra Fast Cooling Processing on Tensile and Charpy Impact Properties of Low-Carbon High-Strength Steel

Low-carbon high-strength steel was investigated by ultra fast cooling (UFC) processing. The results have shown that the microstructures of both steels were all composed of quasi polygonal (QF), acicular ferrite (AF) and granular bainite (GB). The mechanical properties of low-carbon steel all meet the standard requirements of linepipe steels, this is attributed to the effect of the ferrite grain refinement which is resulted in UFC processing. MA islands are more finely dispersed in steel B. Nanoprecipitates which were likely to form at lower temperatures during or after UFC in steel B are finer and more dispersed than those in steel A. Therefore, steel B has higher ultimate tensile strength (UTS) and yield strength (YS). The Charpy absorbed energy (AK) of steel B exhibited a high value. This is because the amount of AF in steel B is much more than that in steel A. A great deal of acicular ferrite grain boundary inhibit growing cleavage crack in steel B.

Enhancing the mechanical properties of low-carbon steel by a graded dislocation microstructure

ABSTRACTIn the present paper, the microstructures and mechanical properties of a low-carbon steel processed by graded pre-torsion (PTO) and homogeneous pre-tension (PTE), respectively, have been investigated. Experimental results demonstrate that both PTO and PTE can improve the strength of the low-carbon steel, but at a loss of ductility and toughness. However, a much better strength–ductility–toughness synergy is achieved in samples processed by graded PTO than that in samples subjected to PTE. This enhancement of comprehensive mechanical properties is due to the formation of a graded microstructure, that is, the dislocation-density increases gradually with decreasing the depth from the sample surface. This study provides a strategy for enhancing the mechanical properties of metallic materials by graded plastic deformation.

Влияние цинкового покрытия на механические свойства низкоуглеродистой стали, микролегированной ниобием

Влияние цинкового покрытия на механические свойства низкоуглеродистой стали, микролегированной ниобием

Combined effects of high-temperature rolling and ultrafast cooling on the mechanical properties of low-carbon steel

ABSTRACTThe role of ultrafast cooling (UFC) on the grain refinement of ferrite, the precipitation behavior of cementite particles and the mechanical properties of a mild steel (Q235 grade) was evaluated by applying laminar cooling and UFC and varying the finish cooling temperature ranges during UFC after hot rolling. While UFC refined the ferrite grains, it accumulated the degeneration of pearlite, resulting in complete disappearance of the laminar pearlite at relatively low finish cooling temperatures. The minimum mean size of spheroidized cementite particles reached ~110 nm. Meanwhile, the enhancement of UFC on tensile strengths of mild steels mainly resulted from the grain refinement of ferrite and the precipitation strengthening of cementite particles; however, the contribution varied with the finish cooling temperature of UFC. A modified Ashby–Orowan model was also used for evaluating the yield strength increment of medium plates. This work will provide a theoretical basis for the diversity control of microstructure and for developing stronger and tougher mild steels by introducing UFC technology after high-temperature rolling.

Effects of Heat Treatment on the Microstructure and Mechanical Properties of Low-Carbon Steel with Magnesium-Based Inclusions

The effects of heat treatment on the microstructure and mechanical properties of Mg-containing (7 ppm), low-carbon commercial steel (SS400) were investigated. Twenty different heat treatment paths were performed using a Gleeble 1500 thermomechanical simulator. It was observed by using an optical microscope that as the cooling rate increased and holding temperature decreased, the volume fractions of pearlite, Widmanstatten ferrite, and grain boundary allotriomorphs ferrite fell, whereas that of acicular ferrite (AF) increased. Quantifying the fractions of AF and other phases by using electron backscatter diffraction shows that the heat treatment path with a cooling rate of 20 K/s and holding temperature of 723 K (450 °C) induced the highest volume fraction (44 pct) of AF. As such, the toughness of the sample was increased 12.4 times compared with that observed in the sample containing 4 pct AF. Typical inclusions were analyzed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy. The results showed that the magnesium-based complex inclusions could act as nucleation sites of AF. Inclusions with a size of about 5 μm can serve as heterogeneous nucleation sites for AF. Mg-containing SS400 steel also has excellent hot-ductility in the temperature range of 973 K to 1273 K (700 °C to 1000 °C), and the minimum percentage reduction in area (R.A pct) value of around 63 pct at 1073 K (800 °C).

Effect of hydrogen on plastic strain localization and fracture of steels

The effect of interstitial hydrogen atoms on the mechanical properties and plastic strain localization patterns in tensile tested specimens of low-carbon steels have been studied using a double exposure speckle photography technique. It is found that the mechanical properties of low-carbon steels are affected adversely by hydrogen embrittlement. The deformation diagrams were examined for the deformed samples of low-carbon steels. These are found to show all the plastic flow stages: the linear, parabolic and pre-failure stages would occur for the respective values of the exponent n from the Ludwik-Holomon equation.

Microstructural evolution and mechanical properties of low-carbon steel treated by a two-step quenching and partitioning process

The quenching and partitioning (Q&P) process is studied in Ti-bearing low-carbon steel. Detailed characterization of the microstructural evolution is performed by means of optical microscopy, scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results indicate that the investigated steel subjected to the Q&P process forms a multiphase microstructure of primarily lath martensite, with small amounts of plate-type martensite and retained austenite. The distribution and morphology of the retained austenite are observed; moreover the relationship between the phase fraction of the retained austenite, its carbon concentration, and the partitioning conditions is established. Carbides preferentially precipitate within the plate-type martensite at first, and gradually form in the martensitic laths over time during the partitioning step. Additionally, titanium precipitations contribute to both the refinement of prior austenite grains and the improvement of strength by precipitation strengthening. The results of mechanical properties testing indicate that the samples partitioned at 400°C exhibit a superior combination of strength and elongation, with products of the two properties ranging between 19.6 and 20.9GPa%. Based on analysis of work hardening behavior it is determined that the higher ductility is closely related to the higher phase fraction and/or stability of retained austenite.

Studies on Effects of Welding Parameters on the Mechanical Properties of Welded Low-Carbon Steel

In this work, the effect of heat input on the mechanical properties of low-carbon steel was studied using two welding processes: Oxy-Acetylene Welding (OAW) and Shielded Metal Arc Welding (SMAW). Two different edge preparations on a specific size, 10-mm thick low-carbon steel, with the following welding parameters: dual welding voltage of 100 V and 220 V, various welding currents at 100, 120, and 150 Amperes and different mild steel electrode gauges of 10 and 12 were investigated. The tensile strength, hardness and impact strength of the welded joint were carried out and it was discovered that the tensile strength and hardness reduce with the increase in heat input into the weld. However, the impact strength of the weldment increases with the increase in heat input. Besides it was also discovered that V-grooved edge preparation has better mechanical properties as compared with straight edge preparation under the same conditions. Microstructural examinations conducted revealed that the cooling rate in different media has significant effect on the microstructure of the weldment. Pearlite and ferrite were observed in the microstructure, but the proportion of ferrite to pearlite varied under different conditions.

Effect of carbon content on formation of bimodal microstructure and mechanical properties of low-carbon steels subjected to heavy-reduction single-pass hot/warm deformation

A compression test simulating heavy-reduction single-pass rolling was conducted to investigate the microstructural evolution based on the formation of a bimodal structure and the mechanical properties of 0.01% and 0.1% carbon steels and niobium steel. When thermomechanical processing was conducted near and above the critical transformation temperature (Ac3), microstructures of all steels were significantly refined and consisted of equiaxed grains without elongated grains. Nevertheless, these microstructures showed weak or no formation of the bimodal structure or coarse grains with decreasing carbon content, while they showed bimodal structure formation when 0.2% carbon steel was used in our previous research. The average grain size of Nb steel was about 2μm and its microstructure was uniformly refined. These may be attributed to a decrease in the number of nucleation sites with decreasing carbon content in low-carbon steels and the occurrence of nucleation at grain boundaries as well as in grain interiors in Nb steel during processing. Mechanical properties of all steels deformed above the critical transformation temperature exhibited high performance characteristics with superior strength and marked elongation. Their fractographs indicated ductile fracture, which was revealed by SEM observation after a tensile test.