High Carbon Low Alloy Steel Research Articles

The Effect of Low-Quantity Cr Addition on the Corrosion Behaviour of Dual-Phase High Carbon Steel

Industrial application of high carbon low alloy steel with the dual-phase structure of martensite and austenite has increased drastically in recent years. Due to its excellent compression strength and its high abrasion resistance, this grade of steel has used as a high performance cutting tool and in press machinery applications. By increasing the usage of more corrosive media in industrial practice and increasing the demand for reducing the production cost, it is crucial to understand the effect of the small addition of Cr on the corrosion behaviour of this grade of steel. In this study, this effect was investigated using Secondary Electron Microscopy (SEM) and in-situ Atomic Force Microscopy (AFM) in the sodium chloride solution. Also, the corrosion rate was measured using the Tafel polarisation curve. It has been found that the small addition of Cr increased the stability of retained austenite, thus improving its corrosion resistance and reducing its corrosion rate. This effect has been acquired through in-situ high resolution topography images in which the samples were submerged in a corrosive solution. It has been demonstrated that the corrosion rate was reduced when the stability of austenite enhanced.

Study on Corrosion Behavior of Heat Treated High Carbon Low Alloy Steel

India is a developing country where agriculture acts as a major contributor about 27.4% to the gross domestic product (GDP), and accounts for about 18% share, of total value of country’s export. In the recent days, there is a remarkable change in production of agricultural tools of different kind which are used accessories in farming. Most often farming tools are made of high strength low alloy steel such as EN42 grade steel has been selected for present investigation for it’s wide availability. Wear resistance is one of the major mechanical factors for ploughing. But, role of corrosion cannot be minimized being it is directly related to surface deterioration phenomena. So, heat treatment is considered to one of the ways to mitigate corrosion issue and keeping wear resistance as major requirement, Presence of morphological variation due to heat treatment becoming the source for studying pitting potential corrosion. Annealing, normalizing, hardening of base metal has been conducted for selected grade of steel and systematically examined for hardness and determining pitting potential of heat treated sample. Among all the samples, annealed sample exhibited low hardness and it may be accounted to reliving of internal stresses of received rolled but exhibited higher corrosion resistance. While as, hardened steel has shown higher hardness and less corrosion resistance. It is attributed to existence of marten site and chances of more prone to inter granular corrosion. As, the present investigate aims at studying corrosion behavior of heat treated steel, it is recommended to practice normalizing from both the requirements of corrosion and wear resistance.

Effects of ausforming strain on bainite transformation in nanostructured bainite steel

The effects of ausforming strain on bainite transformation in high-carbon low-alloy nanobainite steel were investigated using a Gleeble 3500 thermomechanical simulator machine. The bainite transformation speed at 300°C was found to be accelerated by ausforming at 300, 600, and 700°C under applied strains ranging from 10% to 50% followed by isothermal transformation at 300°C. The ausformed bainite volume fraction varied with the ausforming strain because of the mechanical stabilization of the deformed austenite. Ausforming at low temperatures not only enhanced the bainite ferrite volume fraction but also refined the microstructure substantially. Although the amount of bainite ferrite might have been reduced with increasing strain, the microstructures were refined by ausforming.

Effects of Mn and Cr contents on microstructures and mechanical properties of low temperature bainitic steel

The effects of Mn and Cr contents on bainitic transformation kinetics, microstructures and mechanical properties of high-carbon low alloy steels after austempered at 230, 300 and 350 °C were determined by dilatometry, optical microscopy, scanning electron microscopy, X-ray diffraction and tensile tests. The results showed that Mn and Cr can extend bainitic incubation period and completion time, and with the increase of Mn and Cr content, the bainitic ferrite plate thickness decreased and the volume fraction of retained austenite increased. TRIP (transformation induced plasticity) effect was observed during tensile testing which improved the overall mechanical property. The increase of Mn concentration can improve the strength to a certain extent, but reduce the ductility. The increase of Cr concentration can improve the ductility of bainitic steels which transformed at a low temperature. The low temperature bainitic steel austempered at 230 °C exhibited excellent mechanical properties with ultimate tensile strength of (2146 ± 11) MPa and total elongation of (12.95 ± 0.15) %.

Effect of small addition of Cr on stability of retained austenite in high carbon steel

High carbon steels with dual phase structures of martensite and austenite have considerable potential for industrial application in high abrasion environments due to their hardness, strength and relatively low cost. To design cost effective high carbon steels with superior properties, it is crucial to identify the effect of Chromium (Cr) on the stability of retained austenite (RA) and to fully understand its effect on solid-state phase transition. This study addresses this important knowledge gap. Using standard compression tests on bulk material, quantitative X-ray diffraction analysis, nano-indentation on individual austenitic grains, transmission electron microscopy and electron backscatter diffraction–based orientation microscopy techniques, the authors investigated the effect of Cr on the microstructure, transformation behaviour and mechanical stability of retained austenite in high carbon steel, with varying Cr contents. The results revealed that increasing the Cr %, altered the morphology of the RA and increased its stability, consequently, increasing the critical pressure for martensitic transformation. This study has critically addressed the elastoplastic behaviour of retained austenite – and provides a deep understanding of the effect of small additions of Cr on the metastable austenite of high carbon steel from the macro- to nano-level. Consequently, it paves the way for new applications for high carbon low alloy steels.

Effects of Alloying Elements on Static Recrystallization Behavior of Work-Hardened Austenite of High Carbon Low Alloy Steel

Effects of Alloying Elements on Static Recrystallization Behavior of Work-Hardened Austenite of High Carbon Low Alloy Steel

Transition between alloy–element partitioned and non-partitioned growth of austenite from a ferrite and cementite mixture in a high-carbon low-alloy steel

The growth of austenite from a mixture of ferrite and cementite in low-alloy steels can be classified into three temperature ranges above the eutectoid temperature. In the first range, the austenite growth and cementite dissolution are controlled by alloy element diffusion from the beginning. In the second, they are controlled by carbon diffusion and switch to alloy element diffusion control at a later stage. In the third, the cementite dissolution, if the ferrite matrix has transformed to austenite upon heating, is controlled by carbon diffusion until completion. The transition temperatures between these ranges are evaluated in a quaternary alloy containing Mn and Cr by Thermo-calc and DICTRA simulation, and are in essential agreement with earlier experimental results. The proposed simple approach of calculating the transition temperatures may facilitate our understanding of austenitization kinetics and the design of heat treatment, for example, homogenization and soaking, of high-carbon steels.

Cracking mechanisms in large size ingots of high nickel content low alloyed steel

This study is focused on determining the possible root causes for cracking after open die forging of large size ingots made of high nickel medium carbon low alloy steels. Optical and scanning electron microscopies as well as Energy Dispersion Spectroscopy (EDS) were used to examine the microstructure of the samples taken out of a cracked forged ingot. The large size of the samples permitted to investigate microstructure at different locations at the surface and in depth. Chemical analysis revealed chromium and oxygen enrichment at the grain boundaries. Grain size measurement indicated clear differences between “clean” surface zones and cracked ones, and between surface and in depth regions. The analyses indicated that fracture phenomena may be due to abnormal grain size which promotes oxide penetration into grain boundaries, resulting in their embrittlement and cracking upon cooling.

高炭素低合金鋼における加工オーステナイトの静的再結晶挙動に及ぼす合金元素の影響

高炭素低合金鋼における加工オーステナイトの静的再結晶挙動に及ぼす合金元素の影響

低合金鋼における加工オーステナイトの静的再結晶挙動に及ぼす炭素量の影響および合金元素による再結晶抑制機構

Many studies have investigated the effect of alloying elements on the recrystallization behavior of work hardened austenite. However, the recrystallization behavior of high carbon low alloy steel has not been systematically investigated yet. In this study, the effects of alloying elements, focusing on the carbon content, are examined by means of double hit compression test. The following conclusions were obtained: (1) The independent effect of carbon content on recrystallization behavior is not observed. (2) The effects of Nb, Ti and V addition on inhibiting recrystallization are promoted when carbon content is increased from 0.1% to 0.55%. (3) The carbon content dependency of the effects of Nb and Ti addition on recrystallization becomes weaker when deformation and holding temperature become lower. (4) C-V complexes or very fine VC clusters are postulated to be responsible for retarding recovery and recrystallization of 0.55%C-0.1%V steel, which shows the very strong inhibition effect.

Effect of Alloying Element Partition in Pearlite on the Growth of Austenite in High-Carbon Low Alloy Steel

The growth of austenite from pearlite in high-carbon low alloy steel occurs with and without alloy element redistribution depending on the amount of superheating above the eutectoid temperature. The transition temperature of austenite growth (denoted PNTT) is calculated as a function of pearlite transformation temperature and subsequent holding time, which affect the degree of partitioning in pearlite, using experimental partition coefficients k θ/α of Mn, Cr, Co, Si, and Ni reported in the literature. PNTT is the highest in Cr-containing alloys which have the largest k θ/α in pearlite. Post-transformation aging, usually accompanied by cementite spheroidization, leads to a marked increase of PNTT in Mn and Cr alloys. PNTT of Ni alloy does not depend on pearlite transformation temperature because practically the formation of partitioned pearlite is severely limited in this alloy for kinetic reasons. Above PNTT, austenite growth occurs fast initially, but slows down in the order of ten seconds when the ferrite disappears, and the remaining small carbide particles dissolve very slowly under the control of alloy element diffusion.

Effect of Ausforming Temperature on Bainite Transformation of High Carbon Low Alloy Steel

The effect of ausforming temperature on bainite transformation of high carbon low alloy steel was studied by in situ experiments using a Gleeble 3500 thermal and mechanical testing system. Morphology and crystallography of ausforming bainite were examined by scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD). It has been found that deformation at all temperatures range from 230°C to 600°C can accelerate low temperature bainite transformation, and transformation rate increased with deformation temperature reduced. Quantitative X-ray analysis shows that the volume fraction of retained austenite was about 35.84% after deformation and isothermal transformation for 20 hours, it was approximately the same amount with austempering bainite transformation process (no strain) which austenite volume fraction was about 32.01%. Low temperature bainite formation can be accelerated with a smaller increase amount of retained austenite by deformation at a low temperature range of 230~600 oC.

Effect of Austenitizing Temperature on Formation of Hard Bainite

The conditions of formation of what is known as “hard bainite” in the form of packets containing long thin ferrite crystals of a nanosize thickness are determined for a high-carbon low-alloy steel. The effect of the temperature of austenitizing before isothermal holds on the conditions of formation of such structure and on the hardness of the steel is studied. The austenitizing temperature corresponding to the highest hardening effect is determined.

초 고 탄소 저합금강의 경도와 인성에 미치는 열간단조의 영향

Abstract: This study was carried out to investigate the effect of hot forging on the hardness and impact value of ultra high carbon low alloy steel. With increasing hot forging ratio, thickness of the network and acicular proeutectoid cementite decreased, and than were broken up into particle shapes, when the forging ratio was 80%, the network and acicular shape of the as-cast state disappeared. Interlamellar spacing and the thickness of eutectoid cementite decreased with increasing forging ratio, and were broken up into particle shapes, which then became spheroidized. With increasing hot forging ratio, hardness, tensile strength, elongation and impact value were not changed up 50%, and then hardness rapidly decreased, while impact value rapidly increased. Hardness and impact value was greatly affected by the disappeared of network and acicular shape of proeutectoid cementite, and became particle shape than thickness reduction of proeutectoid and eutectoid cementite. Key Words ：Ultra High Carbon, Hot Forging, Hardness, Impact Value, Proeutectoid and Eutectoid Cementite.

Study on Bainitic Microstructure under Low Austempering Temperature and its Wear Resistance of Low-Alloy High-Carbon Steel

A new low-alloy high-carbon steel was designed to obtain the carbide-free bainite under low-temperature austempering. The microstructure, wear resistance under dry sliding friction and the wear mechanism were comparatively studied between samples austempered and low-temperature tempered. Results show that the carbide-free bainitic microstructure composed of bainitic ferrite laths with mean thickness of 120 nm and retained austenite films can be achieved by austempering at 220 °C for 120 h in salt bath after austenitizing at 1000 °C. The wear resistance under dry sliding friction of austempered sample is 19% more than that of low-temperature tempered sample. The wear mechanism of the low-temperature austempered sample is determined as the adhesive wear.

A Transmission Electron Microscopy Study of Plate Martensite Formation in High-carbon Low Alloy Steels

The martensitic microstructures in two high-carbon low alloy steels have been investigated by classical and automated crystallographic analysis under a transmission electron microscope. It is found ...

Structure and properties of CrxN coating

In the present study, an attempt has been made to produce a coating of mixed nitride (CrN and Cr2N) of ultrafine size on a low alloy high carbon steel by a two-stage hybrid process comprising electrodeposition of Cr (45–85 μm) followed by gas nitriding in controlled atmosphere (using a gas mixture of NH3/Ar = 1∶3) in the temperature range 750–950°C for 2–6 h. The nitrided surface records extremely high hardness (∼19 GPa), enhanced wear resistance and residual compressive stress. Potentiodynamic polarisation test in a 3·56 wt-% NaCl solution shows an improvement in corrosion resistance due to formation of noble nitride. However, presence of brittle nitride phases and related surface roughness seems to deteriorate both tribological and corrosion properties.

Variant Selection of Low Carbon High Alloy Steel in an Austenite Grain during Martensite Transformation

In this study, the development of a lath martensite structure in low carbon high alloy steel was observed in situ using high-temperature laser scanning confocal microscopy. The crystallography of the martensite structure was analyzed using electron backscatter diffraction patterns. It was observed that martensite transformation starts from the prior austenite grain boundary. Then, the variant (Σ1) of another packet belonging to the same bain correspondence was observed in the early stage of martensite transformation. Another block in the same packet was observed in the next stage of martensite transformation. Finally, transformation occurred among the neighbors of the transformed martensite block.

Variant Selection of Low Carbon High Alloy Steel within an Austenite Grain during Martensite Transformation

Development of lath martensite structure in low carbon high alloy steel was in-situ observed using high temperature laser scanning confocal microscopy. The crystallography of the martensite structure was analyzed using electron backscatter diffraction patterns. It was observed that martensite transformation starts from the prior austenite grain boundary. Then, transformation proceeds along the growth direction of martensite block formed initially in the prior austenite grain. Finally, transformation takes place in the neighbors of transformed martensite block.

Microstructural Refinement of Bainite and Martensite for Enhanced Strength and Toughness in High-Carbon Low-Alloy Steel

This study attempts to determine the scope and extent of microstructural refinement through complete/partial recrystallization of prior cold deformed ferrite during austenitizing (1223 K (950 °C), 15 minutes) and/or austempering (543 K (270 °C), 30 minutes) followed by water quenching to obtain ultrafine bainitic sheaves along with thin martensitic plates in SAE 52100 steel. The volume fraction and sheaf/plate dimension (thickness/length) of bainitic ferrite and martensite were determined by optical and scanning/transmission electron microscopy studies coupled with compositional microanalysis. Marginal improvement in the tensile strength and significant improvement in the impact properties is obtained at an optimum level of prior cold deformation by tension in comparison to that recorded in austempered condition without prior deformation.