Microstructure Of Carbon Steel Research Articles

The influence of microstructure on the rolling contact fatigue of steel for high-speed-train wheel

Rolling contact fatigue (RCF) is an important concern for the durability of railroad wheels and rails, especially when considering high-speed trains. In this work, the effect of microstructures on the RCF of high-speed-railway was studied under a simulated train speed of 500km/h. Two different carbon steel microstructures: spheroidized pearlite and lamellar pearlite, were achieved by different heat treatment. Results of rolling contact fatigue test demonstrated that the fatigue resistance of lamellar steel considerably exceeds that of spheroidized steel. The lamellar steel presented a more fragmentary surface but lower weight loss during the entire fatigue tests. Analysis of cross-section profiles of worn specimens suggests that cracks propagated near the surface of lamellar steel and may strengthen the fatigue resistance of the steel. Based on micro-indentation hardness data, it is suggested that greater energy dissipation induced by larger plastic deformation may also improve RCF resistance.

Effects of Filler Compositions on Mechanical and Physical Properties of the Dissimilar Resistance Spot Welded between Aluminium Alloy and Carbon Steel

The resistance spot weld (RSW) of dissimilar materials betweeen steel and aluminium is generally more complex than that of similar materials due to the extreme differences in the mechanical, physical and chemical properties of the base metals. This study proposed the use of filler material to connect the differences of their properties. Al-Alloy 5083 with thickness of 4 mm and 1.2 mm thick carbon steel SS400 were joined in lap joint types using RSW with the filler materials. The filler materials were a mixture of steel and aluminium in which weight composition variations (Fe:Al) were 90:10; 70:30; 30:70 and 90:10 in percent. The physical properties were examined based on the microstructure using optical microscope while the mechanical properties were measured with respect to the strength and hardness using Universal Testing Machine and Vickers Microhardness respectively. Results showed that weld metals with filler composition of 70:30% had highest shear-strength. The microstructure examinations showed that Microstructure of base metal and HAZ carbon steel was ferrite and perlite while that of weld metal was bainite. There were no significant differences in the microstructures and the hardness of weld metal, HAZ, and the base metal of aluminium alloy-5083 due to nonheat-treatable material.

Effect of nano-sized TiC particle addition on microstructure and mechanical properties of SA-106B carbon steel

The dispersion behavior of nano-sized TiC particles treated by different processes and its influence on microstructural and mechanical modification has been investigated in SA-106B carbon steel with different TiC contents. It was found that mechanically-activated TiC nanoparticles introduced into a carbon steel matrix were dissolved during hot rolling and re-precipitated vigorously during subsequent normalizing treatment at 920°C. The dispersed TiC particles were very fine (<20nm), giving a suppressing effect on the growth of recrystallized austenite to promote considerable grain refinement of final ferrite–pearlite structure. This fine microstructure (grain size: ~10μm) with a homogeneous distribution of TiC particles offers a higher strength level (yield strength: 372MPa, tensile strength: 544MPa) without sacrificing ductility (>30%) and impact energy (>250J) at the TiC content of 0.1wt%. Theoretical calculations showed that grain refinement plays a dominant role in enhancing the yield strength of TiC-bearing carbon steel, together with nanoparticle strengthening interacting on the solid solution strengthening and dislocation strengthening.

Microstructure and Tensile Properties of SS400 Carbon Steel and SUS430 Stainless Steel Butt Joint by Gas Metal Arc Welding

The application of SS400 carbon steel and AISI430 ferritic stainless steel joint has been increased in industries because of the advantage of both metals was able to increase the service lifetime of the important structures. Therefore, a fusion welding process that could produce a sound weld and good joint properties should be optimized. This research is aimed to weld a butt joint of SS400 carbon steel and AISI430 ferritic stainless steel using Gas Metal Arc Welding (GMAW) welding process and to study the effects of welding parameters on joint properties. The experimental results were concluded as follows. The optimized welding parameter that produced the tensile strength of 448 MPa was the welding current of 110A, the welding speed of 400 mm/min and the mixed gas of <TEX>$80%Ar+20%CO_2$</TEX>. Increase of the welding current affected to increase and decrease the tensile strength of the joint, respectively. Lower welding current produced the incomplete bonding of the metals and indicated the low tensile strength. Microstructure investigation of the welded joint showed a columnar grain in the weld metal and a coarse grain in the heat affected zone (HAZ). The unknown hard precipitated phases were also found at the grain boundaries of the weld metal and HAZ. The hardness profile did not show the difference of the hardness on the joint that was welded by various welding currents but the hardness of the weld metal was higher than that of the other location.

Effect of microstructure of carbon steel on magnetite formation in simulated Hot Conditioning environment of nuclear reactors

The objective of present investigation is to establish the role of starting microstructure of carbon steel on the magnetite formation behaviour in Hot Conditioning simulated environment. Two grades of carbon steel (low and high carbon) were subjected to selective heat-treatments to generate different microstructures: martensite, tempered martensite and modified ferrite–pearlite. Oxidation was carried out in lithiated water of pH 10–10.2 in a static autoclave at 270°C. The results of the investigation clearly establish that: (a) high carbon steel (0.63% C) showed a relatively higher rate of oxidation over the low carbon (0.08% C) grade at all the test durations and (b) the oxidation rates for both the grades were sensitive to microstructural differences at initial stages of oxidation while the differences narrowed down after 72h of exposure. The oxide formed was established to be magnetite on all the specimens.

Effect of cooling rate on the microstructure and mechanical properties of a C–Mn–Cr–B steel

The microstructure and mechanical properties of a low carbon steel containing 30 ppm boron have been investigated. The steel was subjected to various cooling conditions in a thermo-mechanical simulator to generate continuous cooling transformation (CCT) diagram. Similar cooling conditions were also applied to tensile samples in order to evaluate their mechanical properties. The results indicate profuse banding in the hot strip of thickness 2.5 mm. This effect is attributed to the presence of manganese. In addition, variation in cooling rate led to increase in strength but severely affected percentage elongation albeit in an acceptable limit of 6%. This effect is discussed in the light of degree of banding of strips and microstructural constituents generated during heat treatment of steel strips of different thicknesses.

Effect of Velocity of Impact on Mechanical Properties and Microstructure of Medium Carbon Steel during Quenching Operations

Theoretical analysis of the effects of velocity of impact using suitable heat transfer equations expressed in forms of finite difference method was developed and used to determine their effects on the characteristic cooling parameters during quenching process. Various velocities of impact obtained by varying the heights of specimen drops were also used to experimentally determine their effects on characteristic cooling parameters and mechanical properties of medium carbon steel using water as the quenching medium. At height of drop of 0.5 m, 1.0 m, 1.5 m, and 2.0 m, the tensile strength of the material is 410.4, 496.12, 530.56, and 560.40 N/mm2 respectively. The corresponding hardness values are 42.4, 45.2, 46.2, 50.5 HRC respectively. It is found that as the velocity of impact increases, maximum cooling rate increases. Hardness and ultimate tensile strength also increase. There are good agreements between theoretical and experimentally determined values of critical cooling parameters of water during quenching operations.

Investigating the effects of short time austenitizing and cooling rate on pearlitic microstructure and mechanical properties of a hot rolled plain eutectoid carbon steel

In this research, the effects of transformation temperature, time and cooling rate during continuous and isothermal heat treatment processes on microstructure evolutions and mechanical properties of a hot rolled plain eutectoid steel rod were investigated. Austenitizing was performed at the temperatures of 850 and 950 °C for 5 min. Cooling rate was selected between 7 and 26 °C/s for the continuous cooling and isothermal cooling was conducted in a salt bath furnace at the temperature range of 520 and 560 °C. The results showed that the finest pearlite microstructure and a good combination of strength and ductility were achieved by isothermal heat treatment at 560 °C. On the other hand, continuous cooling from 850 °C at the rate of 26 °C/s resulted in an adequate tensile strength (1040 MPa) and substantial increase in the ductility (elongation: 21% and reduction area: 51%).

Microstructural Refinement and Mechanical Properties of High‐Speed Niobium‐Microalloyed Railway Wheel Steel

The relationship between microstructure and mechanical properties was studied in a Nb‐bearing high‐speed railway wheel steel and compared with a traditional low‐alloyed medium carbon steel. The microstructure of medium carbon steel comprised of ferrite and pearlite and the percentage of ferrite was increased from 4 to 24% on the addition of 0.06 wt% Nb and the grain size was refined. The addition of Nb inhibited mixed microstructure and delayed the coarsening temperature of austenite grains from 880 to 960 °C. The yield strength of Nb‐bearing steel was increased from 385 to 455 MPa and the Charpy v‐notch energy at −20 °C was increased from 7.0 to 19.0 J with no apparent reduction in tensile strength. Niobium formulates grain refinement and transformation of austenite to ferrite and pearlite over a wide region of cooling rate (&lt;10 °C s−1) and temperature range (530–690 °C) in the medium carbon steel. With the calculation of Thermal‐Calc software and solid solubility formula, Nb exists in the form of precipitates. The grain refining and precipitation strengthening are roles of niobium in promoting ferrite–pearlite transformation and improve toughness in the medium carbon steel.

Microstructure and properties of SA 106B carbon steel after treatment of the melt with nano-sized TiC particles

Carbon steel dispersed with nano-sized TiC ceramic particles was fabricated using the liquid metal casting process by means of their ex-situ introduction. For this purpose, the nano-sized TiC powders with an initial average size of 40nm were first mechanically activated with two metal powders (Fe, Ni) and then introduced externally into the molten carbon steel during the casting process. According to the chemical composition analysis, 90% of the initial TiC nanoparticles were discovered within the cast carbon steel. Compared to cast carbon steel without TiC nanoparticles, the grain size refinement and mechanical property enhancement were achieved. Atom probe tomographic analysis revealed that the TiC nanoparticles were approximately 30nm in size in the carbon steel matrix with a number density of 1.49×1021m−3.

Effects of Properties on S45C Carbon Steel by Electroless NiP Adding Al2O3 Powder of Composite Deposition and Various Heat Treatments

This research studies the effects on the surface microstructure and mechanical properties of S45C carbon steel via electroless Ni-P, by adding αAl2O3 powder via composite deposition and various heat treatments. The plating specimens were treated with pH5 and pH8 baths heated to 350°C and 300°C, respectively, and soaked for 1 hr. Meanwhile, two different particle sizes of Al2O3 powder were added to the electroless Ni-P plating: 0.3 μm of αAl2O3 and 0.05 μm of γAl2O3 powder, respectively. The experimental results show that, after 1 hr of heat treatment at 300°C, the optimal hardness for the specimens using the pH8 of Ni-P with αAl2O3 and γAl2O3 added by composite deposition are HV0.05 1237 and HV0.05 1145, respectively. All of the specimens underwent the main precipitate phase of Ni3P after heat treatment.

The Full Immersion Test Research of Refractory Weathering Steel

The paper mainly studied the corrosion properties of refractory weathering steel under chloride ion erosion environment. The full immersion tests on refractory weathering steel and carbon steel Q235 were conducted; and then a comparative analysis from the perspective of the corrosion weightlessness, the macro and micro morphology of rust layers have been made. Results indicated that refractory weathering steel and carbon steel corrosion weightlessness is relatively close to the early stage of corrosion, but the trend is reversed in the mid to late; refractory weathering steel corrosion weightlessness gradually decline, but the carbon steel’s is first increase then decrease. The carbon steel is mainly pitting corrosion, while refractory weathering steel develops general corrosion under chloride ion erosion environment. Rust layers of carbon steel are loose, hollow, and uneven. As the corrosion time goes on, the thickness of refractory weathering steel’s rust layers continuously thickening and the rust layers’ integrity are gradually increasing. The corrosion depth of refractory weathering steel is less than carbon steel’s; so does the longitudinal corrosion. This is because the microstructure of carbon steel is coarse pearlite and ferrite while the refractory weathering steel is granular bainite; the grain boundaries of carbon steel have more inclusions, especially MnS that is easily dissolved in chloride ion erosion environment. It is found that alloying elements Cr, Cu are enriched in the rust layers of refractory weathering steel by means of energy dispersive X-ray spectroscopy (EDS). The enrichment of these alloy elements in the rust layers improves the rust layer density, so that the uniform, dense, smooth rust layers formed on the surface of refractory weathering steel play a significant protective film to improve the substrate resistance corrosion.

Microstructure of Cast Ultrahigh Carbon Steel (UHCS) Modified via Fe–Si–Mg–Ca–RE

In this study, effect of modification treatment via Fe–Si–Mg–Ca–RE modifier on microstructure of ultrahigh carbon steel containing 1.5 wt% C was investigated. Microstructure characterization was performed by optical microscopy. It was found that as-cast proeutectoid carbide network tend to break after the modification treatment, and the carbides changed to discontinuous and spherical shape and uniformly distributed in matrix. Also, grain size, porosity and inclusions content decreased by modification treatment.

Study on microstructure and mechanical characteristics of low-carbon steel and ferritic stainless steel joints

In this work, examinations on the microstructure and mechanical properties of plain carbon steel and AISI 430 ferritic stainless steel dissimilar welds are carried out. Welding is conducted in both autogenous and using ER309L austenitic filler rod conditions through gas tungsten arc welding process. The results indicate that fully-ferritic and duplex ferritic–martensitic microstructures are formed for autogenous and filler-added welds, respectively. Carbide precipitation and formation of martensite at ferrite grain boundaries (intergranular martensite) as well as grain growth occur in the heat affected zone (HAZ) of AISI 430 steel. It is found that weld heat input can strongly affect grain growth phenomenon along with the amount and the composition of carbides and intergranular martensite. Acquired mechanical characteristics of weld in the case of using filler metal are significantly higher than those of autogenous one. Accordingly, ultimate tensile strength (UTS), hardness, and absorbed energy during tensile test of weld metal are increased from 662MPa to 910MPa, 140Hv to 385Hv, and 53.6Jm−3 to 79Jm−3, respectively by filler metal addition. From fracture surfaces, predominantly ductile fracture is observed in the specimen welded with filler metal while mainly cleavage fracture occurs in the autogenous weld metal.

Heat Treatment Recycling of Dual Phase Region and its Effect on Hardness, Microstructure and Corrosion Rate of Medium Carbon Steel

In this work, the investigations were carried out to study the effect of heat treatment at dual phase of austenite and ferrite on mechanical properties , microstructure and corrosion rate of low alloyed medium carbon steel. The specimens were divided into five groups, first group, specimens were heated to the duel phase region at temperature of 740°C soaked for 30 minutes and quenched in water. The second group, The specimens were heated to 740°C soaked for 30 minutes and quenched in water, then tempered to 480°C soaked for 20 minutes. The third group the specimens were heated to austenizing temperature of 840°C soaked for 30 minutes and quenched in water, then the specimens reheated to the dual phase region at 740°C, soaked for 30 minutes and quenched in water, then the specimens were tempered at temperature 480°C for 30 minutes. The forth group, the specimens were heated to austenizing temperature of 840°C soaked for 30 minutes and quenched in water, this process were repeated again before the specimens were thereafter heated to the dual phase region at temperature of 740°C, soaked for 20 minutes and quenched in water, then the specimens were tempered at temperature 480°C for 20 minutes. The fifth group, the specimens were heated to austenizing temperature of 840°C soaked for 20 minutes and quenched in water, this process were repeated two times again before the specimens were thereafter heated to the dual phase region at temperature of 740°C, soaked for 20 minutes and quenched in water, then the specimens finally tempered at temperature 480°C for 20 minutes. The results proved the hardness increase after heat treatment at first and second group, at third group the highest hardness value was due to formation of martensite and ferrite, but at fourth and fifth groups hardness decreases due to appearance of carbides particles, also corrosion rate usually increases with two phase at microstructure than stable one phase, third group have less corrosion rate than fourth and fifth due to carbides particles formation which lead to more corrosion rate due to three phases presents.

Ultrafast cooling of medium carbon steel strip by air atomised water sprays with dissolved additives

Ultrafast cooling is a newly developing heat treatment technique that can be used for the production of advanced high strength steels. Conventional laminar jet cooling is generally fitted in the runout table; however, it cannot provide the higher cooling rates necessary, and air atomised spray cooling can be the best alternative for ultrafast cooling rates. As water is the commonly used coolant, it is beneficial to know the effect of surface active or volatile additives on the cooling characteristics for high heat flux applications. Thus, this study examines the two aspects of the use of enhancement of air atomised water spray cooling process with a mixture of ethanol and surfactant additives. First, additive based cooling of stainless steel strip was evaluated to optimise the cooling rate, then these optimum parameters were used to study the improvement in mechanical properties and microstructure of medium carbon steel compared to pure water ultrafast cooling. The cooling experiments were carried out at a temperature above the Leidenfrost point of the hot strip. A commercial inverse solver called INTEMP was used for the calculation of surface temperature and heat fluxes. It was observed that the addition of surfactants and alcohol enhanced the cooling rate and critical heat flux of the test strip and has higher impact on martensite phase evolution.

Microstructure and corrosion behaviour of plain carbon steel–B4C composite produced by GTAW method in 3·5 wt-%NaCl solution

In this work, the corrosion behaviour of metal matrix composite plain carbon steel–B4C was studied in 3·5 wt-%NaCl solution. The composite was locally produced as weld band on plain carbon steel by means of gas tungsten arc welding process and using nickel as wetting agent. Samples from weld band, heat affected zone and base regions were extracted precisely, and electrochemical techniques including open circuit potential, linear polarisation resistance, electrochemical impedance spectroscopy, potentiodynamic polarisation in combination with SEM-EDX surface analysis and microhardness were used for characterisation. The results showed that hardness value of made composite increased significantly to 642 HV10. However, the corrosion resistance of composite region during 7 days (168 h) of exposure to 3·5 wt-%NaCl solution was slightly reduced. This was attributed to the fact that B4C particles play as cathode site for oxygen reduction; therefore, they increase the corrosion rate slightly.

Effect of recalescence on microstructure and phase transformation in high carbon steel

This paper deals with the effect of recalescence on the microstructure of high carbon steels. Controlled experiments are conducted with varying cooling rates and different specimen geometries in a thermomechanical simulator to completely or partially suppress the transformation enthalpy. Different amounts of recalescence obtained from various experiments are then correlated with the final microstructures. The results clearly indicate the importance of recalescence and also show the limitations of using thermomechanical simulators in predicting the characteristics of γ→pearlite transformation in high carbon steels. A mathematical model has been developed to predict the phase transformation in high carbon steels under continuous cooling conditions incorporating the influence of recalescence. The newly developed model gives better prediction of microstructure than currently available models in high carbon steels under higher cooling rates.

EFFECT OF COOLING PATH ON THE HOLE--EXPANSION PROPERTY OF MEDIUM CARBON STEEL

In the present paper, ultra fast cooling (UFC) technology was applied in the cooling process to treat medium carbon steels after hot strip rolling, and the finish rolling temperature and UFC stop temperature are controlled as the important parameters. The effects of cooling path on the microstructure and hole-expansion property of annealing medium carbon steels were investigated. The results show that finely dispersed spherical cementite could be formed in ferrite matrix after annealing treatment. With decreasing the fininsh rolling temperature and UFC stop temperature, the spheroidized cementites after annealing were more homogeneous and dispersed finely. During hole- expansion test, cracks were observed to form usually in the edge region around the punched hole when the tangential elongation exceeded the forming limit, and cracks are mainly formed in the way of micro-voids coalescence. Fine and homogeneous microstructure comprised of ferrite and spheroidized cementite could improve the elongation of the experimental sheets, suppressing the coalescence of micro-voids, and improving the hole-expansion property.

Effects of laser shock processing on surface microstructure and mechanical properties of ultrafine-grained high carbon steel

Ultrafine micro-duplex structure (ferrite (α)+cementite (θ)) formed in a pearlitic Fe–0.8C steel after four passes of equal channel angular pressing (ECAP) at 923K via route Bc. Subsequently the surface of the ultra-micro-duplex structure was treated by multiple laser shock processing (LSP) impacts with different laser pulse energies. The microstructure was obviously refined due to the ultra-high plastic strain induced by LSP. The lattice parameter of α-Fe increased with the laser pulse energy, indicating that the cementite dissolution was enhanced. In addition, residual stress and microhardness increased with the LSP pulse energy.