Papers by Keyword: High-Carbon Steel

Abstract: In this paper, the evolution of texture in the ferrite phase and mechanical behavior of cold-drawn pearlitic steel wires produced for strand manufacturing at Trefisoud company was investigated. Wire drawing induces the development of dislocation density, reduction of interlamellar spacing and the refinement of grains size which leads to a strong hardening of the wires. That explains the increase of the tensile strength from 1242 MPa to 2618 MPa with higher deformation. Also, the cementite lamellae are rotated toward the drawing axis and the thickness of lamellae further decreases when strain level increases, this phenomenon leads to a somewhat fibrous structure. The quantitative analysis obtained by EBSD data shows the development of a strong (<110> // ND) texture of the ferrite phase leading to a structural transformation from isotropic to anisotropic.

Abstract: Study of TiC interaction with low-and high-carbon steel is presented in this article. Was carried out interaction thermodynamic modeling in the temperature range of 900-1800 °C, which showed that titanium carbide would dissolve in melts with these compositions, regardless of melt’s carbon content at given parameters. The obtained thermodynamic results were verified by conducting an experiment with high-temperature complex in order to study substances interaction processes. The obtained experimental samples were studied with scanning microscope as well as structure and compounds composition, obtained as a result of experiment mentioned above.

Abstract: Medium-carbon, silicon-rich steels are commonly suggested to obtain a very fine bainitic microstructure at a low temperature slightly above Ms. Thereby, the resulted microstructure consists of slender bainitic-ferritic plates interwoven with retained austenite. The advanced strength and ductility package of this steel is much dependent on the fineness of bainitic ferrite, as well as the retained austenite phase. In this article, the aluminum to silicon ratio, and the isothermal transformation temperature have been adopted to obtain ultra-high strength high carbon steel. Optical and SEM investigation of the produced steels have been performed. XRD has been used to track the retained austenite development as a result of the change in the chemical composition of developed steels and heat treatment process. Mechanical properties in terms of hardness and microhardness of obtained phases and structure were investigated. Results show that the increment of aluminum to silicon ratio has a great effect in promoting the bainitic transformation, in tandem with improving the stability and the fineness of retained austenite. Such an advanced structure leads to enhancement in the whole mechanical properties of the high carbon steel.

Abstract: In this paper, critical temperature of phase transformation and continuous cooling transformation (CCT) curve of S87B were determined by hot uniaxial compression tests. At several of cooling speed, the microstructures were studied. The results indicate that the critical temperature of phase transformation become lower with cooling speed increasing, the min interlamellar spacing of pearlite was 0.125μm when the cooling speed was 4°C/s, the best cooling speed of phase transformation area was during (3-4)°C/s..

Abstract: The elements of railway turnouts made from rail sections of R260 high carbon steel must have a high resistance to abrasive and contact fatigue wear, as well as a good resistance to cracking under service loads. These mechanical properties largely determine the suitability of steel for use as railway track components. In this study, two groups of specimens were subjected to tests of mechanical properties and metallurgical analyses. The first group included material obtained from the hot-rolled block section, the rolling end temperature being T_kw = 950°C, while the second group was material after the rolling process with the subsequent 20-minute isothermal annealing at a temperature of 480°C. The microstructure of tested materials (R_m, R_p0.2, A₅, Z, HB) was characterized, and their basic mechanical properties and fracture toughness in the K_Ic plane strain condition were determined. Also the effect of temperature, ranging from-80°C to 100°C, on the KCU impact toughness of R260 steel was established. Based on the SEM observation using the Hitachi S-3400N scanning microscope, it was found that pearlitic structure with a varied distance between cementite plates, equal to 0.29 μm and 0.09 μm, respectively, appears in the hot-rolled R260 steel and in the steel subjected to additional isothermal annealing treatment. The impact of pearlite morphology on the cracking characteristics and basic mechanical properties of materials was analyzed. It was found that at room temperature, the higher fracture toughness (K_Ic = 66.4 MPa·m^1/2) is shown by the steel after isothermal annealing at 480°C, in which less distance between the plates of cementite has been observed in the perlite. The fracture toughness of R260 steel after hot rolling at 950°C was K_Ic = 48.3 MPa·m^1/2. As in the case of fracture toughness, the impact strength of R260 steel after isothermal annealing was significantly greater than the impact strength of steel only after hot rolling. The determined cracking characteristics of R260 steel make it possible to determine the effect of heat treatment on the formation of microstructure and material properties, which determine the service life of rail sections.

Abstract: Continuous casting process parameters such as casting speed, superheat, secondary cooling water flow rate have greatly affections to central defects in SWRH82B billet. These parameters were investigated by the methods of chemical content analysis and etch test for macrostructure in some steel plant of china. The results shows that the central defect of SWRH82B billet can be improved when the superheat is controlled at the range of 15~25°C, casting speed is 1.80m•min-1 and secondary cooling water flow rate is 0.72 L•kg-1.

Abstract: The effects and mechanism of cerium, lanthanum and cerium-lanthanum alloys on microstructure and the impact toughness of high-carbon steel were studied in the present work. For high-carbon steel, the state and the content of RE were measured, and the effects and the mechanism of RE on sulfide inclusions, microstructure and the impact toughness of steel were determined. With increasing the RE addition, the sulfide inclusion can be changed from strip-like, spindle, ellipsoidal and spheric in shape. Strip-like sulfide disappears in high-carbon steel with the RE addition being 0.05%. A small quantity of RE can fine the austenitic grain, decrease the height of the SKK peak of the internal friction curve, and improve the impact toughness of high-carbon steel evidently. And the effects of lanthanum on fining the austenitic grain and improving the impact toughness is the largest, next to that of cerium-lanthanum alloys, and that of cerium is the least, which can be verified by the internal friction experiments.

Abstract: The eutectoid transformation of austenite can occur cooperatively (pearlite transformation) or by means of a non-cooperative mode (Divorced Eutectoid Transformation). In the cooperative mode, ferrite and cementite grow together, leading to the typical lamellar microstructure of pearlite. In the non-cooperative mode, spheroidal cementite particles grow directly from the undissolved carbides in the austenite phase. The transformation product is a fully spheroidized microstructure. In this study, the parameters promoting the occurrence of DET in a hypereutectoid steel (austenitization temperature, cooling rate, presence of proeutectoid cementite in the initial microstructure) were investigated. It is shown that low undercooling levels and a homogenous distribution of fine carbides in the austenite promote the DET over the lamellar transformation mode. The spheroidized microstructures produced by DET lead to larger ductilities comparing to those obtained by the lamellar transformation mode.

Abstract: Isothermal constant strain rate compression tests on high-carbon steel are carried out under deformation temperation of 850°C, 950°C, 1050°C、1150°C and 1250°C respectively and deformation of 0.7 using the THERMECMASTOR-Z thermal simulator at a strain rate of 1s-1. The austenite grain morphology before and after deformation and the true stress-strain curves during the deformation process are analyzed. The experimental results show that increased deformation temperation can obviously contribute to the grain refinement. And under the same strain rate conditions, as the deformation temperation rises, peak stress will move toward the opposite direction of strain increment，thus the dynamic recrystallization is apt to occur.

Abstract: Effect of ultrasonic treatment time on inclusions in high carbon steel with the addition of pure rare earth Ce was investigated. The results showed that ultrasonic treatment could disperse, refine and remove inclusions in molten high carbon steel with rare earth. With the increase of ultrasonic treatment time, total oxygen content of high carbon steel and average diameter of inclusions decreased evidently, inclusions in high carbon steel could be removed in a certain degree, but the number of the inclusions increased significantly. Total oxygen content (mass fraction) of high carbon steel, equivalent number I and average diameter d of inclusions in ingot was respectively 59×10⁶, 134 entries•mm^-2 and 2.91 μm when the ultrasonic treatment time was 60 s, at the same time, the percentage of inclusions with diameter D＜2.31 μm is up to more than 43 % of the total.