Hypereutectoid Steel Research Articles

Elastic Strains of Cementite in a Pearlite Steel during Tensile Deformation Measured by Neutron Diffraction

Lattice plane strain, i.e., elastic strain, in cementite plates embedded in the ferrite matrix was measured by in situ neutron diffraction during tensile deformation for a hypereutectoid pearlite steel. The employment of time-of-flight method and microstructure control enable us to measure the shift of cementite peaks along tensile and transverse directions at the applied stress up to 1.6 GPa. The highest elastic strains of cementite determined was approximately 0.015. Heterogeneous plastic deformation between ferrite and cementite as well as among ferrite blocks are discussed.

多重スキンパス伸線による過共析鋼線のデラミネーション抑制

多重スキンパス伸線による過共析鋼線のデラミネーション抑制

Metadynamic and Static Recrystallization of Hypereutectoid Steel

The metadynamic and static recrystallization behavior in hypereutectoid steel containing 1 % carbon was determined by hot compression testing. Compression tests were performed using double hit schedules at temperatures between 900 to 1 050°C, strain rates of 0.01 to is -1 and recrystallization times of 0.1 to 500s. The characteristics of static and metadynamic recrystallization are distinctly different. Results show that the metadynamic kinetics was twice as fast as the static kinetics. These data were used to generate equations to predict the kinetics of static and metadynamic recrystallization, as well as the evolution of grain size, after recrystallization.

Genuine Damascus steel: a type of banded microstructure in hypereutectoid steels

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Dynamic recrystallization of austenite in microalloyed high carbon steels

Hypereutectoid steels of 1% carbon, alloyed with high silicon and microalloying levels of vanadium were subjected to dynamic recrystallization. It was found that an increase in carbon and vanadium content leads to smaller grain size. To characterize the dynamic recrystallization behavior of these steels, compression tests were performed over the temperature range 900–1050 °C using strain rates of 0.01, 0.1 and 1 s −1. Equations were generated that can be used to predict the critical strain for dynamic recrystallization. Of interest is the finding that there is an activation energy for deformation specifically associated with dynamic recrystallization (i.e. peak strain). This activation energy associated with the peak strain is lower than that associated with the steady state stress. This is contrary to Sellar's original observation that the peak strain is a function of the activation energy for deformation according to the Zener–Hollomon relationship.

A Study of the Graphitization Process in the Annealing of Inoculated Hypereutectoid Steel

It is known that the processes of graphite formation in graphitizing inoculation of hypereutectoid steels are realized fully enough in crystallization of the alloy, and there is no need for graphitizing annealing of castings. However, the effect of graphitizing inoculation of these steels is transient, and the inoculated melt rapidly loses the acquired condition upon a hold. This limits the use of graphitizing inoculation in the production of castings from hypereutectoid steels. In some cases it is possible to use mold inoculation, when the graphitizing agent is introduced into the melt right in the mold and the graphitization ceases to be limited by the time required for the effect of graphitizing inoculation to be preserved in full measure under conventional conditions [1]. One more method of effective use of graphitizing inoculation can be applied to the production of castings from hypereutectoid steels. It has been shown in [2] that the susceptibility of intense graphitization is preserved in an alloy after the disappearance of the effect of graphitizing inoculation. Specifically, this property manifests itself in the substantially shorter time of graphitizing annealing needed for castings of deinoculated metal cast 6 – 12 min after the introduction of the inoculant into the melt. Consequently, it should be possible to use graphitizing inoculation of these steels for improving the heat treatment of castings. In this connection, we studied the process of graphitization in the annealing of inoculated hypereutectic steel.

Possibilities of Nondestructive Testing of Physico-Mechanical Characteristics of Hypereutectoid Carbon Steels with the Structures of Isothermal Austenite Decomposition

The possibilities of estimating the hardness, the wear resistance under abrasive action and sliding friction, the impact strength, and the internal stresses of the U9 steel (with 0.94% of carbon) with the initial fine-lamellar pearlite structure annealed at 650°C during 2–600 min on the basis of magnetic and electrical characteristics, readings of an eddy-current instrument, and parameters of electromagnetic-acoustic conversion are studied. A comparative analysis of the magnetic, electromagnetic, strength, and tribological characteristics of the U10 and U15 hypereutectoid steels (with 1% and 1.53% of carbon, respectively) subjected both to isothermal treatment at 330–650°C (with formation of pearlite and bainite structures) and to additional short-time annealing at 650°C is carried out.

Ancient blacksmiths, the Iron Age, Damascus steels, and modern metallurgy

The history of iron and Damascus steels is described through the eyes of ancient blacksmiths. For example, evidence is presented that questions why the Iron Age could not have begun at about the same time as the early Bronze Age (i.e. approximately 7000 b.c.). It is also clear that ancient blacksmiths had enough information from their forging work, together with their observation of color changes during heating and their estimate of hardness by scratch tests, to have determined some key parts of the present-day iron–carbon phase diagram. The blacksmiths’ greatest artistic accomplishments were the Damascus and Japanese steel swords. The Damascus sword was famous not only for its exceptional cutting edge and toughness, but also for its beautiful surface markings. Damascus steels are ultrahigh carbon steels (UHCSs) that contain from 1.0 to 2.1% carbon. The modern metallurgical understanding of UHCSs has revealed that remarkable properties can be obtained in these hypereutectoid steels. The results achieved in UHCSs are attributed to the ability to place the carbon, in excess of the eutectoid composition, to do useful work that enhances the high temperature processing of carbon steels and that improves the low and intermediate temperature mechanical properties.

Application of orientation imaging microscopy to study phase transformations in steels

In this investigation, the methodology, advantages, and limitations of using Orientation Imaging Microscopy (OIM) to study microstructures in multiphase steels are examined. In particular, proeutectoid ferrite precipitation has been investigated in a hypoeutectoid steel (Fe–0.12%C–3%Ni), while the proeutectoid cementite transformation has been studied in a hypereutectoid steel (Fe–1.3%C–13%Mn). By utilizing misorientation maps and inverse pole figure maps to determine the orientation differences between individual crystals, the internal morphology of the solid-state precipitates has been determined. What appear by other types of imaging to be monolithic single crystals are shown to be aggregates of finer crystals with misorientations between them. The relative quality of the Electron Backscatter Diffraction (EBSD) patterns has been correlated to specific phases and to interphase and grain boundaries using pattern quality maps (also referred to as image quality maps). These techniques have been adapted for quantitative identification of different microconstituents, including volume fraction measurements. By making comparisons among optical micrographs, conventional SEM micrographs, pattern quality maps, inverse pole figure maps, and misorientation maps, the advantages and limitations of different types of OIM mapping for studying different aspects of phase transformations in steels are elucidated.

The precipitation of copper in abnormal ferrite and pearlite in hyper-eutectoid steels

The precipitation of copper within abnormal ferrite and pearlitic phases in hyper-eutectoid Fe-C-Cu and Fe-C-Mn-Cu experimental steels has been examined, principally by transmission electron microscopy, in terms of morphology, mechanism and crystallography. Interphase precipitation of copper during austenite decomposition was found to be a primary precipitation mechanism. However, precipitation due to ageing was also observed in both abnormal and pearlitic ferrite. The latter case appeared either as uniformly distributed precipitates within the ferrite or in association with dislocations. Copper precipitates adopted either the Kurdjumov–Sachs or the Nishiyama–Wasserman orientation relationship with respect to the ferrite. Disc-shaped precipitates thought to form by ageing within abnormal and pearlitic ferrite develop on {001} ferrite habit planes. Twinning observed within copper precipitates formed by interphase precipitation was attributed to a requirement to accommodate the growth of precipitates at the interphase boundary. Multi-twinned precipitates were found in pearlitic ferrite and may be evidence for an intermediate transitional state between b.c.c. and f.c.c. structure.

A Review of Microsegregation Induced Banding Phenomena in Steels

A review is presented of banding in hypoeutectoid and hypereutectoid steels. The data available on hypereutectoid steels are quite limited and therefore a study is presented on banding in a 52100 steel. Similarities and differences are identified in the banding that occurs in commercial hypoeutectoid versus hypereutectoid steels. The distinct surface patterns of Damascus steels, which are nearly pure hypereutectoid steels, have recently been shown to be due to carbide banding. It is shown that the carbide banding in the 52100 steel occurs by a distinctly different mechanism than the carbide banding of the Damascus composition steels.

Work Hardening of Hypereutectoid and Eutectoid Steels during Drawing.

Work hardening of pearlite and bainite during drawing of high-carbon steel wires was studied by using stress-strain curves of drawn wires and making a detailed observation of their microstructure. The study revealed the following relationship between flow stress and strain in high-carbon steel wires. Flow stress σ is represented by a weighted average of the strengths of ferrite and cementite. The amount of work hardening Δσ is represented by an equation corresponding to exp(Be) where B is a constant that depends on the initial microstructure of the steel wire and e is the strain. When the initial microstructure of steel wire is made up entirely of a pearlite lamellar structure, the value of B is 0.5. When the initial microstructure contains some bainite, the value of B is lower than 0.5. Finally the flow stress was formulated as a function of carbon content, supercooling degree, and e. The calculated maximum flow stress showed good correlation with the measured flow stress of 0.8 % C and 0.2%Cr-0.92%C steel wires during drawing.

Determination of the Temperature Dependence of the Lattice Parameters of Cementite by Neutron Diffraction

The structure and behavior of the cementite phase has a profound effect on the properties of steels and cast irons. For example, the size and distribution of cementite particles is known to influence the fracture and fatigue behavior of steels. Cementite plays a critical role in various phase transformations in the system, for example the pearlite and bainite reactions. Recently, it has been shown that cementite plays an important role in the process of austenite formation which occurs when the eutectoid temperature is exceeded. Despite the importance of the cementite phase in the context of ferrous metallurgy, it appears that little emphasis has been placed on determining the dependence of the lattice parameters on temperature. The results which are available have been determined using X-ray diffractometry, which can be subject to systematic errors arising from (i) specimen height misalignments, and (ii) temperature inhomogeneities. The purpose of the present paper is to report data from a high purity Fe-C hypereutectoid steel, which were obtained using high-resolution neutron diffractometry. The cementite is thus in equilibrium with the matrix phase, even above the eutectoid temperature, and this allows measurements to be obtained with a considerable degree of precision.

ACCURATE ORIENTATION RELATIONSHIPS BETWEEN FERRITE AND CEMENTITE IN PEARLITE

In most previous work, the interlamellar interface between pearlitic ferrite and cementite is considered to have a low energy and dislocations have been observed at the interfacial boundary, in both plain carbon steels and high manganese steels. Here, four new orientation relationships (ORs) between pearlitic ferrite and cementite have been determined using the more accurate CBKLDP technique. In eutectoid steel the pearlite obeys the New-2, New-3 and New-4 ORs; in hypoeutectoid steel only the Isaichev OR is observed; in hypereutectoid steel the New-5 OR is followed. The two widely accepted ORs, the Pitsch-Petch OR and the Bagaryatskii OR have never been observed. They probably do not exist.

Pearlite morphology in the hypereutectoid steels

The variation of pearlite morphology with carbon content in hypereutectoid steels was examined analytically. It was shown that the cementite thickness decreases with increasing carbon content if (S/S°) < (C°/C); that it remains unchanged if (S/S°) = (C°/C); and that it increases with increasing carbon content if (S/S°) > (C°/C). In addition, the significance of these conditions on improving the drawability of the hypereutectoid steels was discussed.

Use of hypereutectoid high-speed steel 11M5F for the production of cutting and cold-stamping tools in the Avtovaz Joint-Stock Company

The development of low-alloy high-speed steels that reduce the production cost of cutting tools and dies can present practical interest for plants and small enterprises manufacturing tools for their special purposes. The present paper gives the results of an investigation of hypereutectoid low-alloy high-speed steel 11M5F and a widely used steel of grade R6M5. The basic and technological properties of these steels are compared, and the results of industrial tests of cutting, thread-rolling, cold-stamping tools and tools for semihot deformation operating under various conditions are described.

Monitoring the microstructure of pearlitic steels by magnetoacoustic emission

Magnetoacoustic emission (MAE) and Barkhausen emission (BE) measurements have been made on hypereutectoid steel samples heat treated to produce completely pearlitic microstructures with various interlamellar spacings. Both the peak height ratio of the MAE profile and the amplitude of the BE profile were found to increase with increasing interlamellar spacing. These results can be explained in the context of the domain structure and the domain wall processes observed by Lorentz microscopy. The correlation of the spacing with the shape of the MAE and BE profiles shows that both techniques are useful for monitoring the pearlite interlamellar spacing.

Research on the wear characteristics of hypereutectoid steel

In this research, the wear behavior of hyper-eutectoid steel was examined at ambient temperature ranging from room temperature to a high temperature of 400 °C. A common asymmetric test rig was used, where a pin specimen of hyper-eutectoid steel is pressed against a disk of carbon steel for machine structure use. Two types of pin specimen were prepared: an as-received specimen and a quenched specimen.. As a result, the following was clarified. The protective surface film of iron oxide is not a main factor in determining the wear behavior of the hyper-eutectoid steel of as-received pin specimens. The wear behavior is closely related to the separation of the oxide film from bulk material when the sliding conditions are severe. The wear behavior of a quenched pin specimen is strongly influenced by a microstructural transition and a reduction in hardness of the pin specimen at elevated temperature.

Fabricación del acero de Damasco: estudio metalográfico

Damascus Steel is the denomination that the Europeans gave to the material with which the musulman swords were manufactured during the Era of the Crusades. This hypereutectoid steel presents a high content in carbon, more than 0.8 %, and in some cases up to 2 % in weight. The secret of its good mechanical characteristics is based in the hot forging process in the temperatures interval between 650 and 850 °C. The final quenching in water, brine or other aqueous solutions, confers to the swords manufactured with this steel a good resistance to its cutting edge and a high toughness. In the present investigation, the manufacture processes of this type of steel are studied. Electronic scanning microscopy has been applied to the study of materials manufactured by the authors following the ancient craftsmen methods of forging and quenching.

Micromechanical modelling of the elastoplastic behavior of polycrystals containing precipitates— Application to hypo- and hyper-eutectoid steels

This study, based on micro-macro transitions, deals with the modelling of elastoplastic behavior of metallic polycrystals containing intracrystalline non-shearable precipitates. At first, we recall the usual elastoplastic description of pure single crystals based on crystallographic gliding on slip systems. For single crystals containing precipitates, a new hardening matrix is developed based on the Orowan mechanism, taking into account the dislocation-dislocation and dislocation-precipitate interactions. Applications to hypo- and hyper-eutectoid polycrystalline steels containing spherical isotropic cementite particles are presented. A good agreement with experimental results is observed for the overall behavior and the residual stresses after a given amount of plastic strain.