Carbon Content Of Steel Research Articles

Pass schedule of wire drawing process to prevent delamination for high strength steel cord wire

The high-speed drawing of high carbon content steel wires is usually conducted at room temperature employing a number of passes or reductions through several dies. In the multipass drawing process, the temperature rise at each pass affects the mechanical properties of the final product (such as its bending and torsion properties, and its tensile strength). This temperature rise during deformation encourages delamination in the wire, which has a deleterious influence on the torsional properties and durability of the wire. In this study, we investigated the delamination of wires using torsion tests and evaluated the wire temperature during drawing. Our data shows that one of the main reasons for delamination was an excessive rise in wire temperature. Based on our experimental results, in order to prevent delamination due to an excessive rise in wire temperature, a new isothermal pass schedule that could control the wire temperature was designed. The pass redesign for the conventional high carbon (0.75 wt%C) steel cord wire drawing process with delamination was carried out by using the isothermal pass schedule to control the wire temperature. In order to verify the effectiveness of the proposed method, wire drawing and torsion test were conducted. From the results of experiments, it was possible to produce high carbon steel cord wire without delamination.

Measurement of Carbon Content in Steel by LIBS Which Transmits a Laser Beam in Optical Fiber

Utilizing new laser transmission technology, we have developed a laser induced breakdown spectrometer (LIBS) that allows to obtain uniform energy profile by transmitting high-energy laser emitted from GP-YAG through optical fiber, implemented measurement of carbon content in steel and demonstrated its capability of accurate and fast measurement. The spectrometer made it possible to measure both carbon content distribution in the depth direction and average carbon content in steel at the same time by setting the diameter of the laser light with energy of 90 mJ to 0.9 mm on samples after transmitting it by the optical fiber. In addition, we were able to find carbon content in steel in a coefficient of correlation over 0.99 by using 50 shots average data after 3.6 μm from surface.

Theoretical design and advanced microstructure in super high strength steels

A theoretical design procedure based on phase transformation theory alone has been successfully applied to design steels with a microstructure consisting of a mixture of bainitic ferrite and retained austenite. Using thermodynamics and kinetics models, a set of four carbide free bainitic steels with a 0.3 wt.% carbon content were designed and manufactured following a thermomechanical treatment consisting of hot rolling and two-step cooling. The designed steels present significant combinations of strength and ductility, with tensile strengths ranging from 1500 to 1800 MPa and total elongations over 15%. However, a carbon content of 0.3 wt.% is still high for in-use properties such as weldability. In this sense, a reduction in the average carbon content of advanced bainitic steels was proposed. Improved bainitic steels with a carbon content of 0.2 wt.% reached combinations of strength and ductility comparable to those in TRIP assisted steels.

Microstructure and of mechanics microwave boriding

Microwave boriding layer microstructure of carbon steels and its diffusion mechanics were studied. The results show that the existence of microwave field in the boriding can’t change the growth mechanics of boriding layer. Compared with conventional boriding, if the treatment temperature and time remain constantly, the descend rate of the boriding layer thickness with the increase of carbon content of steel is smaller. The diffusion activation energy of T8 steel is 2.6×105 J/mol between the temperature of 750 °C and 900 °C in microwave field, which is in the same order of conventional boriding.

Effect of scandium on structure and properties of corrosion-resistant steels

We determined the effect of scandium microadditives (in an amount equal to 0.1–0.2 wt.%) on the carbon, sulfur, phosphorus, and gas (N, O, and H) content of Kh18T and Kh18N10T steels, and on the tendency for grain growth, mechanical, and corrosion properties.

Frictional Heat-Induced Phase Transformation on Train Wheel Surface

By combining thermomechanical coupling finite element analysis with the characteristics of phase transformation [continuous cooling transformation (CCT) curve], the thermal fatigue behavior of train wheel steel under high speed and heavy load conditions was analyzed. The influence of different materials on the formation of the phase transformation zone of the wheel tread was discussed. The result showed that the peak temperature of wheel/track friction zone could be higher than the austenitizing temperature for braking. The depth of the austenitized region could reach a point of 0. 9 mm beneath the wheel tread surface. The supercooled austenite is transformed to a hard and brittle martensite layer during the following rapid cooling process, which may lead to cracking and then spalling on the wheel tread surface. The decrease in carbon contents of the train wheel steel helps inhibit the formation of martensite by increasing the austenitizing temperature of the train wheel steel. When the carbon contents decrease from 0.7% to 0.4%, the A c3 of the wheel steel is increased by 45 °C, and the thickness of the martensite layer is decreased by 30%, which is helpful in reducing the thermal cycling fatigue of the train wheel tread such as spalling.

Mathematical Modelling of Non‐equilibrium Decarburization Process during Vacuum Circulation Refining of Molten Steel: Application of the Model and Results (I) ‐ Decarburization Process and Influences of Some Technological Factors

A novel three‐dimensional mathematical model proposed and developed for the non‐equilibrium decarburization process during the vacuum circulation (RH) refining of molten steel has been applied to the refining process of molten steel in a 90‐t multifunction RH degasser. The decarburization processes of molten steel in the degasser under the conditions of RH and RH‐KTB operations have been modelled and analysed, respectively, using the model. The results demonstrate that the changes in the carbon and oxygen contents of liquid steel with the treatment time during the RH and RH‐KTB refining processes can be precisely modelled and predicted by use of the model. The distribution patterns of the carbon and oxygen concentrations in the steel are governed by the flow characteristics of molten steel in the whole degasser. When the initial carbon concentration in the steel is higher than 400 · 10−4 mass%, the top oxygen blowing (KTB) operation can supply the oxygen lacking for the decarburization process, and accelerate the carbon removal, thus reaching a specified carbon level in a shorter time. Moreover, a lower oxygen content is attained at the decarburization endpoint. The average contributions at the up‐snorkel zone, the bath bulk and the free surface with the droplets in the vacuum vessel in the refining process are about 11, 46 and 42% of the overall amount of decarburization, respectively. The decarburization roles at the gas bubble‐molten steel interface in the up‐snorkel and the droplets in the vacuum vessel should not be ignored for the RH and RH‐KTB refining processes. For the refining process in the 90‐t RH degasser, a better efficiency of decarburization can be obtained using an argon blow rate of 417 I(STP)/min, and a further increase in the argon blowing rate cannot obviously improve the effectiveness in the RH refining process of molten steel under the conditions of the present work.

Modeling of the Barkhausen jump in low carbon steel

This work presents a model for the magnetic Barkhausen jump in low carbon content steels. The outcomes of the model evidence that the Barkhausen jump height depends on the coercive field of the pinning site and on the mean free path of the domain wall between pinning sites. These results are used to deduce the influence of the microstructural features and of the magnetizing parameters on the amplitude and duration of the Barkhausen jumps. In particular, a theoretical expression, establishing the dependence of the Barkhausen jump height on the carbon content and grain size, is obtained. The model also reveals the dependence of the Barkhausen jump on the applied frequency and amplitude. Theoretical and experimental results are presented and compared, being in good agreement.

Effect of B/N ratio on plastic anisotropy behaviour in low carbon aluminium killed steel

Effect of B/N ratio on plastic anisotropy behaviour in low carbon aluminium killed steel

Investigação do efeito do teor de intersticiais sobre o grau de sensitização em aços inoxidáveis ferríticos a 600ºC

O objetivo do presente trabalho foi investigar o efeito do teor de carbono e nitrogênio em aços inoxidáveis ferríticos com 17%Cr (16%Cr-0,04%C-0,032%N; 17,2%Cr-0,02%C-0,0062%N; 18,5%Cr-0,008%C-0,0213%N) sobre o grau de sensitização (GS). Os aços foram solubilizados a 1200°C e resfriados em água. Tratamentos isotérmicos foram realizados a 600°C entre 5 minutos e 16 horas. Foi realizado o ensaio de reativação eletroquímica potenciodinâmica de ciclo duplo (DL-EPR) em solução 0,5M H2SO4 a (25 ± 2)°C. O GS foi medido através da relação entre as densidades de correntes anódicas máximas nas etapas de reversão, i r, e ativação, i a. O exame microestrutural dos corpos-de-prova foi realizado nos microscópios óptico e eletrônico de varredura após ataque metalográfico com reagente Vilella. Os resultados mostram variação do GS com o tempo. Um máximo de GS foi obtido para cada aço e, posteriormente, foi observada diminuição do GS. A intensidade do GS e o tempo de ocorrência variaram em função dos teores de carbono e nitrogênio nos aços.

Resistance Spot Weldability of High Strength Steel Sheets for Automobiles and the Quality Assurance of Joints

Resistance spot weldability of high strength steel (HSS) sheets for automobiles and the quality assurance technique of joints were investigated. The suitable welding current range in spot welding of HSS sheets shifted to the lower current side compared with that of mild steel sheets and it was affected by the electrode force. Vickers hardness at the welded zone increased with an increase of base steel carbon content. Tensile shear strength (TSS) of joints increased with an increase of nugget diameter, sheet thickness, and base steel strength. The cross tension strength (CTS) of joints increased with an increase of nugget diameter and sheet thickness. However, it showed a peak for base steel strength and carbon equivalent. Fatigue strength didn’t increase with base steel strength. The suitable welding current range in spot welding of galvannealed HSS sheets shifted to the higher current side compared with that of bare HSS sheets. Electrode tip life for galvannealed HSS sheets was over 3 000 points and it was a practical use level. It’s possible to assure the joint strength by estimating the nugget diameter using current and voltage during spot welding.

The influence of orientation and aluminium content on the deformation mechanisms of Hadfield steel single crystals

Abstract The low stacking fault energy and high carbon content in Hadfield steel make twinning the basic deformation mechanism from the onset of plastic deformation in [1¯11] and [011] oriented single crystals in tension at T = 77 – 300 K. Alloying with aluminium (2.7 Al in wt.%) results in an increase of stacking fault energy from 0.03 J · m2 to 0.05 J · m−2 and moves twinning to higher degrees of deformation (∊pl > 15 %). In aluminium-free [1¯23] crystals twinning starts after 20 % strain. For [1¯23], [001] orientations, aluminium additions change the dislocation arrangement from a uniform distribution to a planar dislocation arrangment and also suppress twinning. Intersections of dislocation pile-ups were found to be the governing factor for hardening in the aluminium-alloyed [001] crystals.

伝統的鍛錬工程における日本刀材料の炭素量変化

The Japanese sword has excellent strength-toughness balance given by two traditional processes. One process is compounding of inner tough iron and outer strong steel. And the other process is cooling-rate control quenching by using thickness of clay-coating before quenching. However, it is a precondition for acquiring high strength-toughness that carbon content of sword parts are regulated in proper quantities. Carbon content of sword parts is very important and controlled under forging process which contains TSUMI-WAKASHI (forge-welding piled steel chips) work and fold-forging.Therefore, changes in carbon content of TAMA-HAGANE steels and carbon steels under traditional forging process were investigated in this study. Changes in carbon content depended on enclosing decarburized or carburized surface in steel as forge-weld interface. Total changes in carbon content were proportional to total layers of included surface in steel. Changes in carbon content per one forge-welded layer. “d (mass%/layer)” was ruled by carbon content of raw materials “C0 (mass%)”. When C0 is over 0.2 mass%, carbon content of forged steel is decreasing and the more C0, the more |d |. C0 is under 0.2 mass%, carbon content is increasing. The mass of forged steels is 4% increasing per one fold-forging cycle, but d is not affected by changes in mass of them.

Mould Heat Transfer in the Continuous Casting of Round Billet

Mould heat transfer behaviors during the continuous casting of round billets are elucidated in this paper. Round copper moulds were instrumented with 72 thermocouples and mould temperature together with heat flux were monitored simultaneously with mould powder lubrication during continuous casting of a diameter 178 mm round billets. The profiles of the temperature and heat flux were analyzed based on the longitudinal and circumferential monitoring data under different installation status of moulds. The influences of steel carbon content, casting speed, and mould oscillation frequency on heat transfer have been discussed especially at position 70–110 mm below the meniscus where the heat transfer was the highest and most sensitive to operational parameters. Eventually, the correlation coefficient, defined as the correlation of local heat flux and temperature (CCHT) in the hot face of mould around the mould circumference at the same mould height, has proved to be a good characteristic parameter for analyzing the influence of scale on abnormal heat transfer in quantity.

INFLUENCE OF HEAT-TREATMENT ON WORKABILITY FOR ENLARGING PARTIAL DIAMETER OF CARBON STEEL SHAFT

A novel processing method to enlarge a partial diameter in the middle of shaft by means of combining a rotational-bending stress and an axial-compressive stress, can work various kinds of structural carbon steel without temperature-rise above 20K at room temperature. However, it was found that the maximum diameter-enlargement rate D f /D0 without initiating a fatigue damage crack decreased with increase in carbon contents of steel with mixed microstructure of ferrite and pearlite. It is thought that the mixed microstructure causes initiating the fatigue damage crack. In the present research, six kinds of heat-treatments of 823K-948K×5.4ks-tempering after 1153K×7.2ks-quenching were conducted for carbon steel shafts. The heat-treatments with change from mixed microstructure to uniform minute microstructures, are useful in increasing the diameter-enlargement rate [Formula: see text].

Adapting a mathematical model of the end of the blow of a converter heat to existing conditions in the oxygen-converter shop at the Magnitogorsk Metallurgical Combine

The authors have constructed a deterministic dynamic model that makes it possible to predict the carbon content and temperature of steel at the end of the blow in oxygen converter steelmaking. Instrument measurements of different parameters of the heat are used to calculate the deviations of the parameters’ prescribed values from their actual values. Calculations are performed to determine the corrective additions that need to be made to a heat to synchronize the decarbonization and heating of the bath.

Analysis of variability and non-uniformity of mould heat extraction for round billet continuous casting in plant trials

Maintaining a stable and uniform heat transfer from steel shell to mould is important to produce high quality casting billet. In the present paper, a large amount of measured data of heat flux and temperature for round billet continuous casting mould from a plant trial has been analysed to shed light on the variability and non-uniformity of mould heat transfer around the perimeter. The results show that the variability and non-uniformity of heat extraction from the steel through the mould is affected slightly by operational parameters, such as pouring temperature, casting speed, meniscus, electromagnetic stirring current, but strongly by the steel carbon content and mould powder type. The installation of the mould in caster machine determines the magnitude of non-uniformity of heat transfer to a great extent. The relative root mean square (rRMS) of mould heat flux, presenting the variability and non-uniformity of mould heat transfer around the perimeter in transverse section, has wider range of variation and higher mean value compared with that of temperature. When the abnormality of heat transfer happens, such as deposit, the non-uniformity of mould heat transfer is also studied.

Influences of the Precooling Treatment in the Heat Affected Zone of the Welding in a Used Hadfield-Type Steel

The effects of precooling on the structural conditions of the heat affected zone (HAZ) of high manganese and high carbon content steel were studied. The steel samples were welded, homogenized at 1100°C for 45 minutes, and quenched in water. These samples were precooled to temperatures of 0°, − 30°, and − 60°C. Carbides, microfissures, cracks, or fractures in grain boundary were not found after the welding process. In the case of the homogenized samples with and without any precooling treatment, voids and microvoids were found at the grain boundary. No variations were observed in form and size of voids and microvoids in all samples. A significant increase in the hardness of the grain and grain boundaries located next to the fusion line of the heat affected zone of the precooled steel samples was found in relation to the homogenized samples. X-ray diffraction was used to study the evolution of the crystalline quality of the homogenized and precooled samples. It was found that the lattice parameter decreased and the crystalline quality increased as a result of the precooled conditions and welding process.

Consequences of magnetic aging for iron losses in electrical steels

Electrical steels, when submitted to operation, present continuous decrease of their magnetic properties, depending on the carbon content. This effect is attributed to the increase of the size of carbides, a process also known as coarsening or Ostwald Ripening. Loss separation can offer a better understanding of this phenomenon. Experimental results show that all effect of aging is inside the hysteresis loss component, with the excess losses unaffected. The carbon content in electrical steels should be less than 25 ppm to avoid magnetic aging.

High-temperature and high-pressurein situSCC device for synchrotron radiation diffraction experiments and application using an austenitic stainless steel

Suppressing the stress corrosion cracking (SCC) by reducing the carbon content in austenitic stainless steels is apparently not effective on core shrouds used in boiling water reactors in Japan: trans-granular cracking was found in the shrouds. To clarify the mechanism of the cracking, in situ stress measurements on specimens under stretched conditions in hot water have been attempted in the present study. An in situ device for diffraction measurements at synchrotron radiation facilities has been developed, and in situ experiments have been carried out at SPring-8. The SUS316L steel specimen was solution heat-treated, surface-ground and then placed in the in situ device. Sapphire windows were used for the light path in the device. A sufficient diffracted beam intensity was obtained through two sapphire windows and water. The side-inclination method was used for measuring the stress exerted on the specimen. A 2theta-sin2psi plot showed that a tensile stress was induced. The measured stress value is considered to be the summation of stresses owing to pre-straining, in situ loading and residual stress owing to surface grinding.