Microstructure Of Low Carbon Steel Research Articles

Effect of Ti De-oxidation on Solidification and Post-solidification Microstructure in Low Carbon High Manganese Steel

This paper investigates the effect of de-oxidation inclusions on micro-structure in low-carbon steels. Low carbon (0.07 wt%), high Mn (0.9 wt%) steel in a Al2O3 or MgO crucible was deoxidized by ad ...

Comparison and analysis of dislocation density, morphology and evolution in microstructure of low-carbon steel produced using different technologies

Three kinds of specimens were produced from hot strips of similar composition and same thickness (nominal gauge 4.0 mm) but produced using different technologies, and the dislocation density of these strips was quantitatively measured by positron annihilation technique test. The dislocation morphology and evolution in microstructure of each pass for producing the 1.9 mm hot strip using CSP (compact strip production) technology were observed under an H-800 transmission electron microscope; its density was also quantitatively measured using the positron annihilation technique test, and the factors influencing the dislocation density during the production process were analyzed. The experimental results show that the dislocation density in the microstructure produced using CSP technology is higher than that in the microstructure produced using conventional technology. This result was discussed and confirmed on the basis of the finite element simulation and the theory relevant to dislocations.

Interaction of hydrogen with the microstructure of low-carbon steel

The interaction of hydrogen (H) with the microstructure of SAE 1008 type low-carbon steel is studied in this work. The objective is to determine the binding energy, Δ E, of H with the cementite (Fe 3C) for three different conditions of the carbide. Electrochemical permeation tests are combined with the numerical resolution of Fick's equations assuming that hydrogen is delayed during de transport by reversible trapping sites. Techniques of H vacuum desorption are also employed to describe irreversible trapping. From permeation tests, we obtain the density of reversible trapping sites and the probabilities of H capture and release from which Δ E is evaluated. From effusion test, weak and strong trapping sites with energies in the range of Δ E ≈ 10–50 kJ/mol H were observed.

Oxidation of 1018 carbon steel in borate medium by in situ EC-STM: Surface morphology of the oxidized ferrite and pearlite phases

Microstructures of low carbon steel are ferrite (Fe-α) and pearlite (alternate mixture of Fe-α and Fe 3C) and each one has its own oxidation mechanism. These two phases were identified using in situ electrochemical scanning tunneling microscopy (EC-STM). Real time images were obtained during the immersion of 1018 carbon steel probes in 0.642 M H 3BO 3 and 0.1 M NaOH, pH 7.8. Two different corrosion mechanisms (oxide characteristics) were identified and correlated with the observed surface changes.

Important factors to obtain homogeneous and ultrafine ferrite–pearlite microstructure in low carbon steel

The microstructural evolutions during compressions at different temperatures and strains were investigated using a Gleeble-1500 test machine for a low carbon steel, with and without the formation of pre-eutectoid ferrite. The physical processes that occurred during heavy deformation were discussed by observing the microstructure and analyzing the true stress–true strain responses. The important factors to obtain the equiaxed, homogeneous and ultrafine ferrite, include the initial microstructure before deformation, the deformation temperature and the true strain imposed. The refinement mechanisms for attaining the ultrafine-grained ferrite were discussed in terms of the strain-assisted transformation (SAT) of austenite to ferrite and the dynamic recrystallization of ferrite. The adequate ferritic microstructure has been obtained by deforming the undercooling austenite with a sufficient strain in a reasonable temperature range. The SAT should preferentially be considered in obtaining the ultrafine ferrite because it occurs more easily than the dynamic recrystallization of ferrite. Decreasing the recovery rate of ferrite and increasing the defect concentration in austenite is beneficial to the formation of ultrafine ferrite.

Effects of Titanium and Oxygen Content on Microstructure in Low Carbon Steels

The effects of the titanium and oxygen concentration on the characteristics of inclusions and microstructure in low carbon wrought steels were investigated. Increasing the titanium concentration from 48 to 120ppm promoted the formation of TiN particles and decreased the prior austenite grain size. The fraction of intragranular ferrite in the microstructure was relatively unchanged. When the oxygen concentration was increased from 50 to 130 ppm, the volume fraction and the number of inclusion increased. However, the fraction of intragranular ferrite in microstructures decreased abruptly above 80 ppm because the allotriomorph ferrite phase at the prior austenite grain boundary began to form.

A new low carbon steel microstructure: Ultrafine ferrite grains with homogeneously distributed fine cementite particles

Low carbon steels containing carbon less than 0.2 wt.% are the most widely used ferrous alloys in structural application. These steels consist of ferrite of large volume fraction with pearlite as the remainder and exhibit a strength of ∼400 MPa. To date, considerable effort has been devoted to enhancing the strength of these steels. However, existing methods of improving their strength are limited by the counter effect of loss of ductility and toughness. To overcome this deficiency, a new low carbon steel microstructure and its processing route are reported in this study. The steel with the new microstructure-submicrometer scale equiaxed ferrite grains with fine cementite particles distributed uniformly—was manufactured by imposing severe plastic deformation to introduce ultrafine ferrite grains and subsequent static annealing for uniform precipitation of nanosized cementite particles. The strength of the steel with the new microstructure increased nearly 100%, over 800 MPa, without significant loss of ductility.

Investigation of the Corrosion of Steels in Marine Environment Using Orientation Imaging Microscopy / Untersuchung der Korrosion von Stählen in Meeresumgebung mittels orientierungsabbildender Rasterelektronenmikroskopie

Steels find a wide application for constructions in marine environment, such as ships, platforms offshore and pipelines. Because of the see water being a highly aggressive medium, corrosion of these materials plays an important role with respect to security and economy. The corrosion behaviour is quite different in the different crystal directions in the case of a single crystal. In polycrystalline materials the chemical resistivity is dependant not only on the chemical composition, but also on the orientation of the grains and so on the texture of the sheet. The kind of the grain boundaries is another microstructural aspect of great importance here. In this paper Orientation Imaging Microscopy (OIM TM ) and White Light Interferometry (WLI) are used to investigate the correlation between corrosion behaviour and microstructure of low carbon steels for marine application.

Wear behaviour and microstructure of laser-processed low carbon steel with chromium

A 2.5 kW CO 2 continuous wave laser has been used to modify the surface microstructure of low carbon steel with chromium. The laser-induced surface microstructure has been studied as a function of processing parameters such as power density, laser beam-substrate interaction time and energy density (product of power density and beam-substrate interaction time). The effects of surface roughness, alloyed layers with various depths and hardness distribution on the abrasive wear properties were studied. Microstructural analysis performed by transmission electron microscopy, optical microscopy and X-ray diffraction of the alloyed layers showed two types of structure depending on composition and energy density. A block-on-ring test system was employed to evaluate the wear properties of the laser-surface-alloyed layers. The wear surface was examined with a scanning electron microscope. It was found that the laser radiation and rapid solidification changed the microstructure of the surface layers, resulting in an increase of surface hardness and resistance to abrasive wear compared with the bulk material. High energy density processing produced a martensite-ferrite mixture and some retained austenite structure exhibiting higher hardness than the austenite-ferrite structure produced by low energy density processing. The wear resistance increases with decreasing surface roughness and increasing surface hardness. The wear mechanism consists of the formation of grooves (ploughing by the abrasive particle) and the removal of chips during the repeated passes. The higher hardness permits shallow wear grooves in the worn surface.

Barkhausen jumps and microstructure in low carbon steel

A study of Barkhausen jumps (BJ) is carried out on samples of low carbon steel of different heat treatments. The formation of cementite lamellas, beside the dislocation density, may have an important role in controlling BJ. Spheroidization of the lamellas would decrease the number of jumps as well as the mean potential difference (UB) of jumps. The relative amount of produced eddy current depends on the microstructure of the sample. Spheroidization of the lamellas would increase the amount of produced eddy current. Barkhausensprunge (BJ) werden an Proben von kohlenstoffarmem Stahl nach verschiedenen Warmebehandlungen durchgefuhrt. Die Bildung von Zementitlamellen kann neben der Versetzungsdichte eine wesentliche Rolle bei der Steuerung der BJ spielen. Die Spharoidizierung der Lamellen erniedrigt sowohl die Zahl der Sprunge als auch die mittlere Potentialdifferenz (UB) der Sprunge. Die relative Grose des produzierten Wirbelstromes hangt von der Mikrostruktur der Probe ab. Die Spharoidisierung der Lamellen erhoht den produzierten Wirbelstrom.

Structure and properties of low-carbon steels and iron after deformation under superplasticity conditions

1. The superplasticity effect during upsetting of low-carbon steels develops in the temperature range Ac1S-Ac3S, to a greater extent close to Ac3S with deformation rates\(\dot \varepsilon\)≅ sec−1, and it is characterized by a simultaneous reduction in deformation resistance, absence of residual hardening for ferrite, and deformation predominantly by a grain boundary sliding mechanism. 2. After superplastic deformation in the temperature range Ac1S-Ac3S the microstructure of low-carbon steels is characterized by retention of the original grain size or refinement, presence of a developed subgrain structure, low dislocation density within the body of grains, and absence of pore type defects, which gives a high impact strength compared with that obtained after deformation at higher temperatures. 3. With an increase in carbon content in low-carbon steels (up to 0.3% C) the superplasticity effect develops to a lesser degree, and there is a reduction in the difference in impact strength after deformation in a superplasticity regime and at higher temperatures.

Ultrasonic attenuation and microstructure in low-carbon steels

AbstractUltrasonic attenuation measurements up to a frequency of 30 MHz have been made on a low-carbon steel. The microstructure was controlled to produce a series of specimens with varying ferrite grain size. Analysis of the attenuation data was not possible using a simple Rayleigh scattering model and the mean grain size. It was concluded that the grain size distribution is an important factor in determining the attenuation and that a relatively small number of large grains can dominate the scattering processes.

Laser shock processing of low carbon steel

The effect of laser shock processing (LSP) on the microstructure and mechanical properties of the low carbon (0.04 wt % C) steel was studied. LSP was performed with a 1.054 ^m wavelength Ndrphosphate laser operating in a pulse mode (600 ps duration and up to 200 J energy with a 3 mm diameter beam) with power densities above 10* * W/cmA Shock waves were generated by volume expansion of the plasma formed when the material was laser irradiated. Maximum shock wave intensities were obtained by not using a plasma-confining overlay. When an energy-absorbing black paint coating was used, the specimen surface yielded LSP-induced deformation without melting. The maximum pressure we were able to generate was approximately 2.5 GPa. The rise-time was about 25 ns and a generally 140 ns decay of the laser-shock wave followed. Mechanical properties of material such as surface hardness and residual stress were improved through modifying the microstructure by shock waves. The microstructure of low carbon steel was shown to be strain rate dependent; high density dislocation arrays (~10Wcm.2) were generated by LSP due to high strain-rate deformation and dislocation cell substructures were produced by the low strain rate deformation of shot peening and cold rolling. Strengthening of low carbon steel was a function of dislocation density regardless of processing method.