Microstructure Of Medium Carbon Steel Research Articles

Analisis Pengaruh Arus Pengelasan Dan Jenis Elektroda Pada Struktur Mikro Material Baja Karbon Rendah

The purpose of this study was to determine the changes in the microstructure that occur in low carbon steel due to welding using the type of electrodes E6013 and E7016 with a diameter of 2.6 with a current of 60-110. This research was carried out by several processes, namely specimen making, testing process and data analysis. In the specimen test, the microstructure of medium carbon steel was observed in the base metal region, the HAZ metal region, and the weld metal region. Microstructure testing was carried out to see the occurrence of changes in the microstructure of the specimen as a result of the welding process and the test results obtained were in the form of microstructure images with 500x magnification. The results showed that the changes in the microstructure that occurred in the HAZ region. This is found in the type of electrode E6013 indicating the higher the current used, the finer the grain size of the resulting structure. Meanwhile, for the E7016 electrode, it is the opposite where the higher the current used, the coarser the grain size of the resulting structure. Keywords: HAZ area, microstructure, type of electrode

Monitoring the microstructural changes of heat treated medium carbon steel by Barkhausen noise and hysteresis loop techniques

Heat treatment plays an important role to improve the thermo-mechanical properties of different carbon steel. This paper focus on a study the effect of different heat treatment process i.e. annealing, normalising, and quenching on the microstructure of medium carbon steel using non-destructive techniques like Barkhausen Noise (BN) and Hysteresis Loop (HL). Microstructural behavior was evaluated in terms of phase transformation, BN-peak value, differential permeability, and core loss at different austenitizing temperature. BN and HL analysis indicated that higher BN-peak and differential permeability were obtained in annealed sample. Further, higher core loss was obtained in quenched sample.

Modelling of overload effects on fatigue crack initiation in case of carbon steel

AbstractThis paper deals with the modelling of short crack initiation within a microstructure of medium carbon steel under fatigue loading, as well as with the influence of overload on the crack initiation period. Studies on the long crack growth show that the overload introduces first an increase in the crack growth rate that is then followed with a decrease, a so‐called retardation. A micro‐model containing the microstructure of the material is analysed using the finite element method in combination with a model for crack development – the assessment of number of cycles needed for crack initiation was based on the Tanaka–Mura equation. The analysis brings in a correlation between the crack growth rate and the crack length together with the effects of the overload on the crack growth rate. The overload is found to accelerate the short crack growth; however, the following retardation could not be captured due to the inability of the model to produce residual stresses, which are considered to be the main cause of the retardation effect.

Influence of on-line tempering parameters on microstructure of medium-carbon steel

A new process involving ultra-fast cooling (UFC) and on-line tempering (OLT) was proposed to displace austempering process, which usually implements in a salt/lead bath and brings out serious pollution in the industrial application. The optimization of the new process, involving the evolution of the microstructure of medium-carbon steel during various cooling paths, was studied. The results show that the cooling path affected the final microstructure in terms of the fraction of pearlite, grain size and distribution of cementite in pearlite. Increasing the cooling rate or decreasing the OLT temperature contributes to restraining the transformation from austenite to ferrite, and simultaneously retains more austenite for the transformation of pearlite. It is also noted that bainite was observed in the microstructure at the cooling rate of 45 °C/s and the OLT temperature of 500 °C. Through either increasing the cooling rate or decreasing the OLT temperature, the distribution of cementite in pearlite is more dispersed and grain is refined. Taking the possibility of industrial applications into account, the optimal process of cooling at 45 °C/s followed by OLT at 600 °C after hot rolling was determined, which achieves a microstructure containing nearly full pearlite with an average grain size of approximately 7 μm and a homogeneously dispersed distribution of cementite in pearlite.

The Influence of Quench Tempering and Carburazing Treatment towards Mechanical Properties and Microstructure of Medium Carbon Steel for Automotive Application

Gear is one of the machine components that is widely used in industrial and automotive fields. In machinery process, gear has a very important function to forward speed, power, or torque from one engine component to other components as a mechanical drive. Today a lot of development to obtain a good quality of gear, due to many gears were damage, worn out, and broken because they were not strong enough to resist friction and pressure. In addition, broken gears due to pressure and friction make them did not last long. To increase the hardness value of gear, then it needs though material that can be used when the gear reach optimum rotation. The material that is widely used for gear application is medium carbon steel. The medium carbon steel is a metal material that has carbon composition ranging from 0.30 to 0.59%. This medium carbon steel has hardness value of 174.501 HVN without treatment. The process of quench tempering and carburizing are conducted to increase hardness and toughness value of the material. The hardness value of gear is 140 HVN. The result of the research showed the hardness value at various temperature 780°C, 810°C, and 840°C. The optimum hardness values ​is 165.355 HVN at the temperature of 840°C. Medium carbon steel is expected to be an alternative to produce steel material with certain mechanical properties. This research also conducted heat treatment in austenite area and then detained with holding time of 20, 40, and 60 minutes. Furthermore, quench tempering was conducted and followed by carburizing to obtain a ferrite phase and coarse pearlite and to increase hardness value after quech tempering. It is expected that after quech tempering and carburizing process, steel with better mechanical properties can be produced. This research obtained the increase of hardness value and the number of pearlite and ferrite.

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.

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 (<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.

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.

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.

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.

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.

Investigation on microstructure of medium carbon steel deformed at strain rates of upto 10 5 per second at −30°C to 235°C

Investigation was carried out to study the microstructural changes (if any) in medium carbon steel (En-8) deformed at low strain rate (quasistatic) and very high strain rates employing different temperatures. A dynamic compression test rig was used for firing a flat ended cylindrical tool steel projectile against disc shaped specimen placed upon a comparatively rigid anvil. Metallographic specimens were prepared from as-received material as well as from the specimens deformed at low and very high strain rates. The mode of deformation was revealed by metallographic examination of all the deformed specimens. When the specimens were compressed, deformed grains were obtained. No deformation twins were observed in the steel used in the present study which deformed at various strain rates and at sub-zero, room and warm temperatures. It is envisaged that the initiation of twinning during impact was affected by the presence of alloying elements and inclusions in the medium carbon steel, despite its high strain rate sensitivity.