Showing papers on "Pearlite published in 1978"
TL;DR: In this paper, a study has been made of the mechanical properties of dual phase (martensite plus ferrite) structures produced when a V containing HSLA steel is cooled in a controlled manner from either the austenite or austenites plus ferrites phase fields, such a heat treatment results in the pearlite regions and carbide particles of the standard V steel being replaced by martensite; this leads to a decrease in the yield stress and an increase in ductility while the tensile strength is essentially unchanged.
Abstract: A study has been made of the mechanical properties of dual phase (martensite plus ferrite) structures produced when a V containing HSLA steel is cooled in a controlled manner from either the austenite or austenite plus ferrite phase fields Such a heat treatment results in the pearlite regions and carbide particles of the standard V steel being replaced by martensite; this leads to a decrease in the yield stress and an increase in ductility while the tensile strength is essentially unchanged The fatigue of dual phase steels is slightly superior in the high strain life (ductility controlled) region and slightly inferior in the low strain life (yield dominated) region when compared to standard V steel The replacement of the pearlite and cementite particles which can nucleate cracks, by more ductile martensite islands results in improved Charpy impact properties The strength and the ductility of the dual phase materials is shown to be in agreement with a theory of composites with two ductile phases This theory then allows one to understand the relative importance of various microstructural features in controlling strength and ductility In this way it is found that the key to the superior elongation (at a constant tensile strength) is largely due to the high strength (fine grained), highly ductile ferrite matrix
221 citations
TL;DR: In this article, a model is proposed to account for the differences in behaviour between coarse and fine pearlites, based upon a combination of pile-up and fibre loading stresses, in which the operating deformation mode is largely determined by which type of mechanism is dominant.
184 citations
Journal Article•
TL;DR: In this article, the tensile deformation and fracture of pearlite were studied using high-resolution 200-kV semi-volumetric sensors and a high-frequency 200-KV semiuser.
Abstract: Dynamic studies of the tensile deformation and fracture of pearlite using high-resolution 200-KV sem
178 citations
TL;DR: In this paper, the volume dilatation in the absence of stress is assumed to be a linear function of the separate specific volumes and weight fractions of the constituents (pearlite, austenite and martensite).
Abstract: T he problems of quenching-stress analysis are critically reviewed and an adequate simple theory is discussed. The theory accounts for both plasticity and volumetric changes due to phase transformation accompanying the thermal-hardening of a group of simple steels that are characterized by C-shaped time-temperature-transformation diagrams. The volume dilatation in the absence of stress is assumed to be a linear function of the separate specific volumes and weight fractions of the constituents (pearlite, austenite and martensite). With use of the classical relationships of a formal theory of transformation kinetics, the amounts of pearlite and martensite are expressed in terms of the temperature and the temperature-history. The specific forms of such functions are given. In order to account for the influence of phase transformation on plastic properties, the non-isothermal plastic flow-rule is generalized, and a thermal-hardening parameter is introduced which is identified with the amount of pearlite. Variational principles and bounding inequalities associated with the fundamental rate-problem are considered. As an example, the problem for a rapidly, uniformly-cooled half-space is solved. The variations of the residual stress and the final amount of martensite with distance from the outer surface are given, for several values of the rate-of-cooling. The results suggest that the residual stress vanishes on the plane containing approximately 30–35 per cent of martensite.
64 citations
TL;DR: In this article, transmission electron microscopy of an air-cooled medium carbon (0.5 wt pct) steel containing 0.1 wt 1 pct vanadium has shown that VC precipitates by the interphase mecha-nism during transformation to both proeutectoid and pearlitic ferrite.
Abstract: Transmission electron microscopy of an air-cooled medium carbon (0.5 wt pct) steel containing 0.1 wt pct vanadium has shown that VC precipitates by the interphase mecha-nism during transformation to both proeutectoid and pearlitic ferrite. Depending upon the rate of transformation, a considerable proportion of the available vanadium may remain in supersaturated solid solution and can be precipitated as VC upon subsequent aging at 700°C. It was found that the proportion of proeutectoid ferrite, the interlamellae pearlite spac-ings and the VC precipitate dispersion parameters all decreased with increasing cooling rate in as-transformed material.
50 citations
TL;DR: In this paper, the mechanism of eutectoid decomposition in ten Ti-X binary systems, wherein X was successively Bi, Co, Cr, Cu, Fe, Mn, Ni, Pb, Pd and Pt, has been investigated.
Abstract: The mechanism of eutectoid decomposition in ten Ti-X binary systems, wherein X was successively Bi, Co, Cr, Cu, Fe, Mn, Ni, Pb, Pd and Pt, has been investigated. In hypo-eutectoid alloys, the bainite reaction (defined in the present context as a nonlamellar dispersion of intermetallic compound particles amongst proeutectoid a) predominated in all alloys studied but Ti-Cu, where both bainite and pear lite were formed. In alloys of near eutectoid composition pearlite was the dominant product in some systems and bainite was in others. These results are essentially independent of reaction temperature. They are quite different from analogous ones in Fe-C alloys, where pearlite is the principal eutectoid structure formed at high temperatures and bainite plays this role at low tem-peratures. The difference between the Ti-X and Fe-C behaviors was explained in terms of the much more pronounced tendency for proeutectoid α plate formation in Ti-X than in Fe-C alloys and, on a theory due to Hillert, of the need for disordered interphase boundaries in order to develop the cooperative growth mode that leads to the evolution of pearlite.
48 citations
TL;DR: In this article, annealed and cold-worked coarse-grained coarse-grain poly crystalline oxide (PCO) alloys with 0.1, 0.5, and 1.0% C were oxidized in 1 atm O2 at 500°C.
Abstract: Fe-C alloys containing 0.1, 0.5, and 1.0% C were oxidized in 1 atm O2 at 500°C. Two specimen preparations were used: annealed followed by slow cooling to form coarse pearlite plus proeutectoid ferrite or cementite; and cold-worked by abrading after annealing. The cold-worked alloys oxidize more rapidly. Annealed pearlite oxidizes faster than annealed ferrite. The differences in oxidation rate are caused by differences in the Fe3O4 grain size, that is, by the number of oxide grain boundaries available to act as easy diffusion paths for the outward diffusion of Fe through the Fe3O4. The oxidation rate constant is 10 times larger for fine-grained poly crystalline oxide than for oxide in which the Fe3O4 is monocrystalline.
43 citations
TL;DR: In this paper, the effects of Mn, Sn, and Sb on the eutectoid transformation of ductile iron were shown to be consistent with their behavior in malleable iron.
Abstract: The eutectoid transformation of austenite in cast iron is known to proceed by both the meta-stable γ → α + Fe3C reaction common in Fe-C alloys of near eutectoid composition, and by the direct γ → α + Graphite reaction, with the graphite phase functioning as a car-bon sink. In addition, the meta-stable cementite constituent of the pearlite can dissolve near the graphite phase (Fe3C → α + Graphite), producing free ferrite. Isothermal trans-formation studies on a typical ductile iron (nodular cast iron) confirmed that all of these reaction mechanisms are normally operative. The addition of 1.3 pct Mn was found to substantially retard all stages of the transformation by retarding the onset of the eutectoid transformation, decreasing the diffusivity of carbon in ferrite, and stabilizing the cemen-tite. Minor additions of Sb (0.08 pct) or Sn (0.12 pct) were found to inhibit the γ →α + Graphite reaction path, as well as the Fe3C → α + Graphite dissolution step, but did not significantly affect the meta-stable γ → α + Fe3C reaction. Scanning Auger microprobe analysis indicated that Sn and Sb adsorb at the nodule/metal interphase boundaries during solidification. This adsorbed layer acts as a barrier to the carbon flow necessary for the direct γ → α + Graphite and Fe3C → α + Graphite reactions. With the graphite phase dis-abled as a sink for the excess carbon, the metal transforms like a nongraphitic steel. The effects of Mn, Sn, and Sb on the eutectoid transformation of ductile iron were shown to be consistent with their behavior in malleable iron.
37 citations
29 citations
TL;DR: In this paper, the creep and rupture properties of 2 1/4 Cr-1 Mo steel were determined for steel plates (from a single heat) given three different annealing treatments: two were fully annealed, but cooled at different rates from the austenitizing temperature.
Abstract: The strength of 2 1/4 Cr-1 Mo steel depends on the microstructure, which, in turn, de-pends on the heat treatment. In the fully annealed and isothermally annealed conditions, the microstructure is primarily proeutectoid ferrite with varying amounts of bainite and pearlite. The relative amounts of the latter constituents depend on the cooling rates during the anneal. The creep and rupture properties were determined for steel plates (from a single heat) given three different annealing treatments: two were fully annealed, but cooled at different rates from the austenitizing temperature, and the third was iso-thermally annealed. Properties were determined at 454, 510, and 566°C. At 454 and 510°C, the cooling rate had a significant effect on the creep and rupture properties, with the ma-terial cooled fastest being the strongest. Although at 510°C strengths at short rupture times differed widely, the properties approached a common value at longer rupture times. The properties differed very little at 566°C, even for short rupture times. The effect of heat treatment was concluded to be the result of interaction solid solution hardening, a dislocation-drag process. This process gave rise to nonclassical creep curves (as op-posed to classical curves with single primary, secondary, and tertiary stages). By examining the creep-curve shape, it was possible to interpret the heat treatment effects on the creep-rupture properties.
25 citations
TL;DR: In this article, a statistical analysis was performed to evaluate possible correlations with fatigue crack growth properties and microstructural parameters, including carbon, manganese and oxygen content, and the fraction of pearlite.
Abstract: In order to establish safe inspection periods of railroad rails, information on fatigue crack growth rates is required. These data should come from a sufficiently large sample of rails presently in service. The reported research consisted of the generation and analysis of fatigue crack growth data of 66 rail samples taken from existing track all over the United States. Additional information concerns mechanical properties, chemical composition, microstructure, and fractographic features. A statistical analysis was performed to evaluate possible correlations with fatigue crack growth properties and microstructural parameters. Weak correlations were found with carbon, manganese and oxygen content, and with the fraction of pearlite. A subsequent phase of this research program is discussed.
TL;DR: In this article, the diffusional transformations of austenite were examined and it was shown that separate C-curves are required for pearlite, upper bainite, lower bainites, and isothermal martensite.
Abstract: This paper examines the diffusional transformations of austenite and concludes that separateC-curves are required for pearlite, upper bainite, lower bainite and isothermal martensite. A schematic isothermal transformation diagram incorporating the four curves is presented for a plain carbon eutectoid steel and used to develop a schematic continuous cooling transformation diagram. These diagrams are shown to be more compatible with the available experimental information than are the usual diagrams based on a single transformation curve.
Patent•
24 Apr 1978
TL;DR: An iron-base sintered alloy especially suitable for valve seat manufacture having excellent wear resistance and being able to be machine-cut is provided in this paper, where the alloy is produced by combining specifically atomized pre-alloyed powder, iron powder, nickel powder and graphite powder by means of compacting and sintering processes.
Abstract: An iron-base sintered alloy especially suitable for valve seat manufacture having excellent wear resistance and being able to be machine-cut is provided. The alloy is produced by combining specifically atomized pre-alloyed powder, iron powder, nickel powder and graphite powder by means of compacting and sintering processes, and has a microstructure comprising pearlite and globular hard alloy phase formed with said atomized pre-alloyed hard alloy powder uniformly dispersed in said pearlite and martensite surrounding said hard alloy phase.
TL;DR: In this article, the enthalpies of Cu-Al and Cu-In lamellar pearlites were found to be 1183 mJ m −2 and 1156 mJm −2 respectively, with an error of ± 10%.
Patent•
31 Aug 1978
TL;DR: In this paper, a steel sheet consisting of C 0.05-0.25, Mn 0.1-2, Si 0.2, and balance Fe and inevitable impurities is treated under the following conditions and coiled: at the time of hot rolling the temp. is regulated to below the equilibrium ferrite transformation start temp. (T1), and a reduction ratio of 20- 80% is applied.
Abstract: PURPOSE:To obtain the title sheet with low yield ratio by treating a steel sheet consisting of a specified amt. of C, Mn, Si, and the balance Fe and inevitable impurities while specifying the temp. in hot rolling and the cooling rate and by coiling the treated sheet. CONSTITUTION:A steel sheet consisting of C 0.05-0.25%, Mn 0.1-2%, Si <=1%, and the balance Fe and inevitable impurities is treated under the following conditions and coiled: at the time of hot rolling the temp. is regulated to below the equilibrium ferrite transformation start temp. (T1), and a reduction ratio of 20- 80% is applied. The hot rolled sheet is then cooled from T1 to the ferrite transformation start temp. (T2) at an average cooling rate above 30 deg.C/sec and from T2 to above the pearlite transformation start temp. at an average cooling rate below 30 deg.C/sec for above 2 sec. The cooled sheet is further cooled at a cooling rate above 50 deg.C/sec and coiled at below the bainite transformation start temp. Thus, a high tensile steel sheet is obtd. having a mixed structure of bainite phase and/or martensite phase and ferrite phase and an yield ratio below 80%.
TL;DR: In this paper, the effect of compositional variations on strength and toughness of 17 experimental rail alloys was studied, where carbon, manganese, and silicon levels were varied over ranges to yield eutectoid or hypoeutectoidal microstructures.
Abstract: Previous studies on eutectoid steel have demonstrated that strength and toughness are essentially independently varying parameters, with the former primarily controlled by the pearlite interlamellar spacing and the latterprimarily controlled by the prior austenite grain size. The work has now been extended to study the effect of modest compositional variations on strength and toughness of 17 experimental rail alloys. Carbon, manganese, and silicon levels were varied over ranges to yield eutectoid or hypoeutectoid microstructures. Vanadium was added to some of these compositions, primarily as a grain refiner. These steels were heat treated to produce varying austenite grain sizes and a reasonably constant, fine pearlite spacing. Instrumented impact tests on precracked Charpy bars were performed to determine both the dynamic fracture toughness (K 1 d), and the Charpy transition temperature. Tensile tests were used to monitor strength and ductility. Mechanical test data were correlated with observed microstructural variations, particularly the austenite grain size and pearlite spacing as'well as fractographic studies of the variation of fracture facet size with austenite grain size. These studies led to a general description of the fracture process in such steels.
TL;DR: In this paper, the temperature dependence of the coercive force for medium and high-carbon pearlitic steels is investigated and it is shown that with increasing temperature the coercivity initially decreases to a minimum value near 100°C, then increases through a maximum near the Fe 3 C Curie temperature, and then decreases to zero as the temperature approaches the magnetic or crystallographic transformation temperature for the ferrite.
Patent•
25 Sep 1978
TL;DR: In this paper, a high tension hot-rolled steel plate of low yield ratios and superior ductility in a coiled state after hot rolling is produced by applying the specific heat treatment to the steel plate, which is then cooled between 1 second and 30 seconds from the hot rolling end temperature down to 600 deg.
Abstract: PURPOSE:To produce the high tension hot rolled steel plate of low yield ratios and superior ductility in a coiled state after hot rolling by applying the specific heat treatment to the steel plate of C<0.20% containing the specific amounts of Mn, N for forming composite structure. CONSTITUTION:The steel plate is produced by ending hot rolling at tmperatures between 700-820 deg.C from the slab containing C<0.20%, Mn; 0.5-2.5%, N< 0.03%. When the hot rolling is ended within this temperature range, the ideal material of low yield ratios and high elongation is obtainable. Next, it is cooled between 1 second and 30 seconds from the hot rolling end temperature down to 600 deg.C, then the austenite having been accumulated with stresses immediately after hot rolling becomes a large number of polygonal ferrites and the pearlite transformation in which C, Mn, N are concentrated in the non-transformed austenite is suppressed, becoming martensite residual austenite. Next, the mean cooling speed from 600 deg.C down to coiling is made 5 deg.C/sec. or higher and coiling is done at 400 deg.C or under.
TL;DR: In this paper, a laboratory study was conducted on a broad range of compositional variations of chromium-molybdenum steels for application as high-strength, as-rolled rails.
Abstract: A laboratory study was conducted on a broad range of compositional variations of chromium--molybdenum steels for application as high-strength, as-rolled rails. A series of experimental heats was prepared and processed to simulate commercial production of as-rolled 65-kg/m (132-lb/yd) rail, with regard to cooling rate and transformation characteristics. Test specimens were evaluated in terms of hardness, tensile properties, and microstructure. The mechanical properties are related to the observed microstructures. Increasing the molybdenum content of the steel is highly effective in increasing yield strength by refining the pearlite; the appearance of coarse bainite reduces the yield strength. Vanadium contributes additional strengthening, but only under certain conditions where the pearlite is refined. Lowering carbon and adding columbium produces microstructural changes that are not beneficial to the mechanical properties. These results make possible some tentative conclusions regarding the optimization of composition for the commercial production of as-rolled rails in the 760 to 1170 N/mm/sup 2/ (110 to 170 ksi) yield strength range.
Patent•
[...]
23 Jun 1978
TL;DR: In this paper, a high tensile rail provided with the fine pearlite structure and the deep uniform hardened layer is manufactured by heating the steel of a specified component to a temperature above Ac3 point, and by cooling under a limited condition for causing the isothermal transformation.
Abstract: PURPOSE:To manufacture the high tensile rail provided with the fine pearlite structure and the deep uniform hardened layer, by heating the steel of a specified component, which stably forms the pearlite structure, to a temperature above Ac3 point, and by cooling under a limited condition for causing the isothermal transformation. CONSTITUTION:The steel, containing 0.60-0.82wt% C, 0.1-1.0% Si, 0.40- 0.60% Mn, and the balance consisting of iron and inevitable impurities, as the fundamental component, and besides, if necessary, containing one or more of 0.2- 1.0 % Cr and 0.02-0.10% V, is heated to above Ac3 point. Next, the steel is cooled from above austenitic region to the temperature range 450-600 deg.C, at a cooling speed 3-30 deg.C/sec, and the isothermal transformation is caused in the temperature range 450-600 deg.C. Hereby, the high tensile rail can be manufactured being provided with the fine pearlite structure of Hv+340, and the uniform hardened layer of above 10 mm depth. Depending on this rail, the reduction of abrasion due to the heavy weight of axle, and the prevention of the shelly cracks to be generated at high speed running, can be contrived.
Patent•
12 May 1978
TL;DR: In this paper, a high tensile high carbon steel wire rod with excellent drawability is produced by finish rolling a steel billet of a specified compsn. contg. C, Mn, Si, and V after which the wire rod is cooled from a temp. above a specified temp. at a specified rate to form fine pearlite structure.
Abstract: PURPOSE:To produce a high tensile high carbon steel wire rod with excellent drawability by finish rolling a steel billet of a specified compsn. contg. C, Mn, Si, and V after which the wire rod is cooled from a temp. above a specified temp. at a specified rate to form fine pearlite structure.
TL;DR: In this article, the mechanism of impact-initiated cleavage fracture has been studied in fully pearlitic rail steel and it has been shown that the early stages of cracking probably occur by strain localization in the ferritic lamellae.
Abstract: Under service conditions, final failure of rails is usually caused by impact. To elucidate the phenomenon, the mechanism of impact-initiated cleavage fracture has been studied in fully pearlitic rail steel. The study has demonstrated that the early stages of cracking probably occur by strain localization in the ferritic lamellae. By direct correlation studies of fracture surface and microstructure, it has been further shown that a crack usually does not change direction at pearlite colony boundaries. Rather, the prior austenite grain size is the controlling agent for the more effective obstacle to crack propagation, namely, the cleavage facet size. The data show that the facet size is dependent on the prior austenite grain size, although it is always somewhat less, particularly for the larger grain size materials. The reasons why it is an effective parameter to represent the toughness of eutectoid steels are discussed.
01 Jan 1978
TL;DR: In this paper, a rolling contact fatigue test was conducted in order to investigate the influence of load and slip on the contact fatigue behavior, and the lifetime to initiations of linear crack and spalling (defect very similar to'shelling' in rail) decreases remarkably, furthermore the angle between contact surface and crack propagating into subsurface also decreases, as load or slip increases.
Abstract: Both contact fatigue defect occurred on the running surface in high speed tracks and wear in heavy axle load railways have come into problem for rail performance. Rolling contact fatigue test was conducted in order to investigate the influence of load and slip on the contact fatigue behaviour. The lifetime to initiations of linear crack and spalling (defect very similar to 'shelling' in rail) decreases remarkably, furthermore the angle between contact surface and crack propagating into subsurface also decreases and spalling depth increases, as load or slip increase. Plastic flow formed at subsurface is concerned with crack initiation and partial crack propagation at early stage. The depth at which crack propagates in stable state corresponds to the hardness distribution under contact surface. Wear resistance of rail steels with different microstructures but the same hardness is arranged in order of microstructure as follows: pearlite, tempered martensite, bainite. This difference is mainly derived from the distribution, shape, and size of carbide in microstructure. As for the pearlitic steels, the wear resistance is improved as the interlamellar spacing decreases.
Patent•
11 Aug 1978
TL;DR: In this article, the steel material of above composition is heated to temperature above 1000°C to render Nb, Ti, Zr into solid solution, then hot rolled to be followed either by continuous cooling under the condition ferrite + pearlite structure is formed, or subjected to isothermal transformation.
Abstract: PURPOSE: Not thermally refined steel is provided with excellent strength equal to that obtained by quenching and annealing, by cooling process after forging or rolling, to obtain ferrite + pearlite structure. CONSTITUTION: Steel contains C: 0.30 to 0.60%, Si: 0.10 to 1.0%, Mn: 0.20 to 1.70%, N: 0.005 to 0.025% as essential components, one or more of each less than 0.20% of Nb, Ti, and Zr, and further either one or more of Ni<3.5%, Cr<2.0%, and Mo<0.7%, or one or more of S<0.15%, Pb<0.30%, Ca<0.01%, Se< 0.30%, and Te<0.3%. The steel material of above composition is heated to temperature above 1000°C to render Nb, Ti, Zr into solid solution, then hot rolled to be followed either by continuous cooling under the condition ferrite + pearlite structure is formed, or subjected to isothermal transformation. COPYRIGHT: (C)1980,JPO&Japio
TL;DR: In this article, electron microscopy examinations of surfaces damaged by fretting fatigue were performed to establish variations in microstructural and environmental effects on the fatigue process of ferrite/pearlite and martensite microstructures.
Patent•
30 Aug 1978
TL;DR: The corrosion behavior of hot-rolled C-Mn steels has been studied and compared in de-aerated 0·1 N sulphuric (lcid) and 0· 1 N hydrochloric acid as mentioned in this paper.
Abstract: The corrosion behaviour of two hot-rolled C–Mn steels (API 5LX X70 and API 5LX X52) has been studied and compared in de-aerated 0·1 N sulphuric (lcid and in de-aerated 0·1 N hydrochloric acid The influence of certain metallurgical factors (chemical composition, textures of three planes relative to the rolling direction, ratio of ferrite–pearlite area, ferritic grain size, shape and composition of non-metallic inclusions, extent of banded structures and work-hardening) on the morphology of the attack has been examined both during and after galvanokinetic polarisation, followed by galvanostatic polarisation (corresponding to a total of 22·5 × 104 Cm−2)The galvanokinetic polarisation curves of each of the two steels were virtually unaffected by the plastic deformation produced by the Charpy impact test The pearlite distribution, the Cu content and the shape and composition of non-metallic inclusions have an important effect on the anodic dissolution process that showed a strong tendency to start
Patent•
02 Nov 1978