Microstructure Of Carbon Steel Research Articles

普通炭素鋼の組織と基礎特性

普通炭素鋼の組織と基礎特性

Effect of Welding Parameters on Microstructure and Mechanical Properties of Friction Stir Welded Plain Carbon Steel

In the present investigation, friction stir welding was carried out for plain carbon steel under variable rotational and traversing speed of tool keeping all other welding parameters same. Microstructural characterization was carried out for welded samples along with determination of microhardness distribution and evaluation of mechanical properties. Weld nugget microstructure principally consisted of ferrite-pearlite, however ferrite grain size and pearlite area fraction were varied depending on welding parameters. Substantial grain growth was found in heat affected zone. Sub-size tensile specimens exhibited improvement in strength; whereas, standard tensile samples showed lowering in strength with respect to parent alloy. Ductility of subsize and standard specimens showed smaller value in comparison to parent alloy and dependent on local microstructural characteristics.

Evolution of Martensitic Microstructure of Carbon Steel Tempered at Low Temperatures

This work presents the microstructural changes of a carbon steel during tempering at low temperatures (first stage of tempering), and its effects in the second and third stages. These changes are determined by internal friction. Internal friction is measured in a forced vibration mode at 5Hz, in a temperature range from 300 to 600K. Four internal friction peaks appear: S1 at 350K, P1 at 380K, P2 at 440K, P3 at 480K. S1 only appears in the sample tempered at 380K for 20hours, and this can be related to the reduction of the martensite tetragonality. The height of P1 is lowest when the intensity of tempering is increased. This height can be related to the quantity of epsilon carbide than precipitate. The heights of P2 and P3 are not changed significantly, but the difference of temperature between both is lowest when the tempering intensity is increased. This suggests than the dissolution of epsilon carbide and formation of cementite takes places in a lowest range of temperature

Effects of rare earth oxide on hardfacing metal microstructure of medium carbon steel and its refinement mechanism

The electrodes for hardfacing medium carbon steel with six additions of rare earth oxide were developed in this work. By means of optical microscopy and scanning electron microscopy, the microstructure, inclusion and the fractograph of the hardfacing metal were observed. Then, the effects of rare earth oxide on microstructure and inclusions in hardfacing metal were analyzed. The effectiveness of rare earth oxide as heterogeneous nuclei of δ-Fe was calculated with the misfit theory. The results showed that, the microstructure of hardfacing metal was composed of ferrite and small amount of pearlite. The microstructure was refined at first and then coarsened with the increase of rare earth oxide addition. The fractograph was changed from brittle to equiaxed dimples, then became quasi-cleavage and cleavage gradually. The calculated results showed that, the ferrite grain size could be refined because that LaAlO 3 as heterogeneous nuclei of δFe was moderately effective, and the ferrite grain size was coarsened because the misfits between Ce 2O 3 and δFe, Ce 2O 2S and δFe were increased with futher increase of rare earth oxide addition.

Analysis of microstructure and mechanical properties of different high strength carbon steels after hot stamping

Usage of high strength steels may reduce the weight of automobiles and improve the crash safety and low down the gas emissions. Besides cold forming, hot stamping has gained much interest for the production of car body components. Boron alloyed steels have been the point of focus for the materials choice in hot stamping. In this paper, four high strength non-boron alloyed steels were hot stamped using water and nitrogen cooling media. Microstructural analyses, lateral and surface hardness profiling as well as tensile tests of hot stamped samples were performed. These steels provided yield strength (Y.S.) values of 600–1100MPa and ultimate tensile strength (U.T.S.) values of 900–1400MPa. Increasing cooling rates, i.e. by using nitrogen cooled punch (NCP) during hot stamping resulted in mostly martensitic microstructure and maximum strength, while hot stamping using water cooled punch (WCP) resulted in maximum formability index due to presence of some ferrite phase.

Effect of phosphorus on the microstructure and mechanical properties of strip cast carbon steel

Carbon steel strips with different phosphorus and carbon contents were produced by using the twin roll strip casting process. Fine grains and dendrite structure were observed in high-P steels. Negative phosphorus segregation was found in strip cast high-P and high-C steels. For the steels with different carbon contents, phosphorus distribution in the thickness direction of the strip is obviously different. This is because solutes are redistributed in the melting pool and the phosphorus segregation rate is associated with the length of the mushy zone and the phosphorus solubility in different phases. Phosphorus as a solute in ferrite can lead to the higher hardness and strength with lower plastic propertyies.

Ultrafine Grained Material Produced by Machining

The evolution of microstructure of carbon steel subjected to large plastic strain machining was investigated. The microstructure generated in machined chips was ultrafine grains with an average size of 200 nm. A finite element model was established to study large plastic deformation in plain orthogonal cutting. The results show most of the grain refinement associated with the formation of ultrafine grained chip can be attributed to the large shear strain imposed in the deformation zone. It is feasible to take machining as a method to preparing ultrafine grained materials and a type of experiment method to study severe plastic deformation.

Microstructure and mechanical properties of UFG medium carbon steel processed by HPT at increased temperature

Using the high pressure torsion (HPT) deformation method the medium carbon steel (AISI 1045) was the experimental material used to conduct the deformation process. The torsion deformation experiment was performed at increased temperature of 400 °C. The influence of deformation processing parameters, resolved shear strain γ (number of turns N = 1–6) and applied pressure p (constant pressure of 7 GPa), was evaluated by microstructure analysis and mechanical properties. The strength behaviour was assessed by microhardness measurements across the disc to detect the positional hardening, by tensile tests and in situ measured torque. In situ measurement of torque during deformation allows characterizing the changes in mechanical properties due to the large shear deformation developed across the disc. To obtain absolute values of strength the ultimate tensile strength was measured in radial direction with respect to the deformed sample. From each deformed disc two sub-sized tensile test specimens with gauge length of 2.5 mm were machined. The tensile strength in samples increased markedly with the number of turns. The hardness measured at disc edge gradually increases as straining increases until it saturates after 2–3 turns. However, the hardness values at edge were different from those measured in disc centre and for applied straining no saturation was reached across the disc. The SEM and TEM investigations were carried out to analyze the fine microstructure evolution regarding the strain introduced. To follow the difference in strain distribution across the deformed disc the microstructure analysis was performed at edge and central site of the disc in order to evaluate the effect of the strain distribution. TEM investigation confirmed the increasing misorientation even in very small grains, the fragmentation and dissolution of the cementite lamellae, (diffuse cementite/ferrite boundaries), the alignment of the fragments to the shear plane with increasing deformation. Indistinct deformation of ferrite and preserved cementite lamellae morphology were found at the centre of the disc.

Effects of Si and Cr on Bainite Microstructure of Medium Carbon Steels

Effects of Si and Cr contents on bainite microstructure of medium carbon steels have been examined in order to obtain further information for good strength–ductility balanced spring steel. Four practical medium carbon steels, S55C, SUP9, SUP7 and SUP12 were isothermally transformed at temperatures between 300°C and 500°C after austenitized at 1000°C. The microstructure was observed by means of scanning electron microscopy and transition electron microscopy. While carbide was found rapidly with bainite transformation in S55C without Si and Cr, carbide precipitation was suppressed by the increase of Si and Cr concentration in SUP9, SUP7 and SUP12. The fraction of retained austenite was increased with increasing of Si and Cr at the intermediate stage of bainite transformation because of the increase of C concentration in retained austenite. Particularly, Si addition promoted carbide-free bainitic ferrite and leading to larger amounts of retained austenite by carbon enrichment.

Effects of Si and Cr on Bainite Microstructure of Medium Carbon Steels

Effects of Si and Cr contents on bainite microstructure of medium carbon steels have been examined in order to obtain important information for good strength–ductility balanced spring steel. Four practical medium carbon steels, JIS-S55C, SUP9, SUP7 and SUP12 were isothermally transformed at temperatures between 300°C and 500°C after austenitized at 1000°C. The microstructure was observed by means of scanning electron microscopy and transmission electron microscopy. While carbide was formed from the early stage of bainite transformation in S55C without Si and Cr, carbide precipitation was suppressed by the increase of Si particularly in SUP7 and SUP12. The fraction of retained austenite was increased with increasing of Si and Cr at the intermediate stage of bainite transformation because of the increase of C concentration in retained austenite. Particularly, Si addition promoted carbide-free bainitic ferrite and leading to larger amounts of retained austenite by carbon enrichment.

Effect of carbon steel microstructure and molecular structure of two new Schiff base compounds on inhibition performance in 1M HCl solution by DC, SEM and XRD studies

In this investigation, attempts have been made to study the inhibitive effect of N,N′-ortho-phenylen acetyle acetone imine (S1) and 4-[(3-{[1-(2-hydroxy phenyl) methylidene] amino} propyl) ethanemidol]-1,3-benzenediol (S2) in the concentration range of 50–400 ppm for mild steel with two different microstructures resulted from two different heat treatments (annealed (A) and quenched and tempered (Q&T)) in 1 M hydrochloric acid solution. Both Schiff bases acted as a mixed type inhibitors. The S1 inhibitor for both microstructures showed better inhibition efficiency than S2. The A samples indicated slightly less corrosion than Q&T samples in 1 M HCl solution in absence of inhibitor due to the formation of duplex γ-Fe 2 O 3 /Fe 3 O 4 .

Vegetable oils as quenchants for hardening medium carbon steel

Groundnut (Arachia hypoge) oil and palm (Elaeis guineeness) kernel oil were investigated as vegetable quench-ing media for carbon steel (0.45 % C) by determining the characteristic temperature-time cooling curves and rel-ated mechanical properties. The three stages of cooling examined during quenching were vapour blanket, boili-ng and convection. The study was conducted to find vegetable oil alternatives to the commonly used synthetic polymer quenchants, which are considered hazardous, costly and not readily available. The influence of cooling rates of the quenching media on microstructure, tensile strength, yield stress and hardness of medium carbon steel were also investigated. The mechanical properties of groundnut oil quenched steel were higher than palm oil quenched steel, but the wear resistance measured by hardness testing was higher when quenched in palm kernel oil than in groundnut oil.

Erratum to "Effect of carbon steel microstructures and molecular structure of two new Schiff base compounds on inhibition performance in 1M HCl solution by EIS"

Erratum to "Effect of carbon steel microstructures and molecular structure of two new Schiff base compounds on inhibition performance in 1M HCl solution by EIS"

Effect of carbon steel microstructures and molecular structure of two new Schiff base compounds on inhibition performance in 1 M HCl solution by EIS

In this investigation, attempts have been made to study the inhibitive effect of N, N′- ortho-phenylen acetyle acetone imine (S1) and 4-[(3-{[1-(2-hydroxy phenyl) methylidene] amino} propyl] ethanemidol]-1,3-benzenediol (S2) in the concentration range of 50–400 ppm for mild steel with two different microstructures resulted from two different heat treatments (annealed (A) and quenched and tempered (Q&T)) in 1 M hydrochloric acid by ac impedance spectroscopy. The tests were conducted in acid solutions in the absence and presence of different concentrations of S1 and S2 Schiff bases for both microstructures. A sole time constant was observed from Bode-phase angle plots in the presence of inhibitors which reveals that the action of inhibitors is through adsorption on the surface. The charge transfer resistance and inhibition efficiency increases with the increase in Schiff bases concentration for both microstructures. The perlite samples in the absence of inhibitors in 1 M hydrochloric acid indicated slightly less corrosion than martensite ones, which was because of more protective oxide layers. Furthermore in the presence of S1 and S2, these samples showed better adsorption than martensite one. Schiff base S1 showed a better inhibition against corrosion in comparison with S2. Both S1 and S2 adsorbed on steel surface according to a Langmuir adsorption isotherm model. The associated Gibbs free energies for S1 on both microstructures are more than S2.

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.

Discontinuous transformation in the steel under hot deformation conditions

Purposeful effect of hot deformation process and transformation – austenite (A) to ferrite (F) and to pearlite (P) – interaction on the carbon steel microstructure was studied. Hot compression tests at various strain rates were performed during controlled cooling of the sample within the temperature range related to the start and finish of the phase transformation. Attention was paid to structural effects of dynamic precipitation and resulted morphology of structural components depended on expected localisation of phase transformation. The findings of carbide precipitates development along ferrite grain boundaries was the most noticeable effect of the hot deformation and subsequent transformation for tested samples. However, the flow localisation and preferred growth of the discontinuous transformation product-pearlite at shear bands was very limited. [Received on 25 October 2006; Accepted on 21 February 2007]

Stress Assisted Corrosion of Waterwall Tubes in Recovery Boiler Tubes: Failure Analysis

Waterside cracking of carbon-steel boiler tubes is one of the major safety and efficiency concerns in kraft recovery boilers in the pulp and paper industry, because any water leak into the furnace could cause a smelt-water explosion in the boiler. Failed carbon-steel boiler tubes from different kraft recovery boilers were examined to understand the role of carbon-steel microstructure on crack initiation and crack morphology. A number of carbon-steel tubes showed a deep decarburized layer on the inner surface (water-touched) and also an unusually large grain size at the inner tube surface. In some boiler tubes, cracks were found to initiate in areas with large-grained-decarburized microstructure. However, tubes without such microstructure were also found to have stress assisted corrosion (SAC) cracks. It was found that the decarburization and large grained microstructure may facilitate initiation and growth, but it is not necessary for SAC of carbon-steel boiler tubes.

Mechanical Properties and Microstructures of Ferritic-Rolled Ultra-Low Carbon (ULC) and Ti-Stabilized Interstitial-Free (Ti-IF) Steels

In this paper, effects of ferritic rolling process on microstructures and mechanical properties especially drawability of ultra-low carbon (ULC) and Ti-stabilized interstitial-free (Ti-IF) steels were investigated and the precipitates of ferritic-rolled Ti-IF steels were also analyzed. The results show that good deep drawability are achieved as IF steels are ferritic rolled in good lubricant condition; on the contrary, lubricant condition has less influence on the deep drawability of ULC steels. And with the decrease of rolling temperature in ferrite region, deep drawability of Ti-IF steels are improved, but for ULC steels, when ferritic rolled at low temperature, the r-value is still less than one, which means insignificant deep drawability.

Evaluation of Nanocrystalline Microstructure, Abrasion, and Corrosion Properties of Carbon Steel Treated by Plasma Electrolytic Boriding

Plasma electrolytic boriding (PEB) is a kind of plasma electrolytic saturation (PES) which is a relatively new surface engineering treatment to produce nanocrystalline coatings. This method of treatment provides high abrasion and corrosion resistance because of the nanocrystalline interlayer formation. In this study, PEB was applied on low alloy steel substrates, and the surface morphology and phase composition of the internal nanocrystalline layer formed has been studied using X-ray diffraction and scanning electron microscopy. Coating wear properties were assessed by conducting pin-on-disk wear tests. The corrosion resistance and electrochemical properties of the nanocrystalline coating were investigated by measuring the linear polarization resistance and also electrochemical impedance spectroscopy (EIS).

Study on the Formation of Ferrite-Cementite Microstructure by Strain Induced Dynamic Transformation in Medium Carbon Steels

Cold heading quality (hereafter CHQ) steels are widely used in automobile and construction industries. The various processes involved in the production of wire rod from CHQ steels are drawing, spheroidization annealing, forming, and quenching/tempering. Especially, the spheroidization annealing is inevitably used to soften the wire rod before severe forming. However, due to the economical constraints, many efforts have been made to shorten or avoid the spheroidization annealing process. One of the possible ways is to produce the ferrite-cementite (FC) microstructure directly after the drawing (rolling) process without performing any subsequent spheroidization annealing. In the present study, the effect of SIDT (Strain Induced Dynamic Transformation) on the microstructure of medium carbon steels was investigated to develop spheroidized annealing-free steel wire rods. When 0.45%C steels were hot deformed by heavy reduction at low temperatures conditions, deformed microstructures were quite different from conventional ferrite-pearlite structure. For example, the microstructure containing 57 vol. % of ferrite, which is far beyond the equilibrium ferrite fraction of 43 vol. % of 0.45%C steel was obtained by deformation at 700°C. Moreover, as deformation temperature decreased to 675°C, the pearlite structure disappeared completely and new microstructure composed of ferrite and cementite appeared. It was considered that this FC microstructure was obtained owing to small retained austenite grains existing between fine SIDT ferrites prefer to transform to cementite and ferrite instead of pearlite during cooling. Finally, the optimum conditions for producing the ferrite-cementite microstructure have been identified.