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Showing papers on "Pearlite published in 1987"


Journal ArticleDOI
TL;DR: In this paper, an excellent combination of elongation over 30% and high strength about 100kgf/mm2 is achieved in processing of a 0.4C-1.8Mn steel by intercritical annealing, rapid cooling into bainite transformation temperature to soak several minutes.
Abstract: An excellent combination of elongation over 30% and high strength about 100kgf/mm2 is achieved in processing of a 0.4C-1.5Si-0.8Mn steel by intercritical annealing, rapid cooling into bainite transformation temperature to soak several minutes. This combination is caused by transformation induced plasticity of retained austenite. Sufficient amount of stable austenite is a requisite for the good ductility. For the rapid cooling after annealing, the soaking temperature for the best combination of strength and ductility is immediately above Ac1. On the other hand, a delay before rapid cooling provides good properties if the soaking temperature is near Ac3 and the subsequent cooling is performed at a lower rate before pearlite transformation; in this case the critical cooling rate is reduced. These phenomena are discussed in terms of the growth of ferrite and the diffusion of alloying elements inclusive of Mn during slow cooling.

349 citations


Journal ArticleDOI
TL;DR: In this paper, a study of the mechanisms of pearlite spheroidization under static annealing conditions was carried out in two materials, AISI 1080 steel and pure Fe-C alloy.
Abstract: A study of the mechanisms of pearlite spheroidization under static annealing conditions was carried out in two materials — AISI 1080 steel and pure Fe-C alloy. By electrolytically etching away the ferrite matrix, the morphology of the cementite phase was directly investigatedvia SEM and TEM techniques. It was clearly observed that the initiation and development of spheroidization are associated with morphological faults such as terminations, holes, and fissures in the cementite plates. During spheroidization the recession of terminations and the expansion of holes and fissures led to the break-up of large cementite plates into small segments. The migration of these faults is anisotropic. The preferred orientations, [010] and [210] directions in the (001) cementite plane, were determined by TEM analysis. This anisotropic morphological change is attributed to the anisotropy of the α/Fe3C interfacial energy. All the experimental evidence strongly supports the idea that the fault migration theory is the main mechanism governing spheroidization.

164 citations


Journal ArticleDOI
TL;DR: In this paper, the interphase boundary structure and interface processes at the pearlite-retained austenite growth interface in Fe-0.8 wt% C-12wt% Mn alloy were investigated by transmission electron microscopy.

96 citations


Journal ArticleDOI
TL;DR: In this paper, a model is developed to rationalize this observation and is applied to a number of pearlite growth phenomena, including lamellar curvature, laminate branching and hole formation, and synchronous growth.

74 citations


Journal ArticleDOI
TL;DR: In this article, the micromechanisms of cleavage fracture under notched-bend conditions for fully pearlitic microstructures are compared to those exhibited by simple ferrite-carbide micro structures and are shown to exhibit substantial differences to those of the simple micro structures.

61 citations


Journal ArticleDOI
TL;DR: Magnetoacoustic emission (MAE) and Barkhausen emission (BE) have been measured as a function of applied magnetic field and tensile stress from mild-steel samples in a wide range of heat treatments, to develop a technique to measure stress without prior knowledge of the microstructure as mentioned in this paper.
Abstract: Magnetoacoustic emission (MAE) and Barkhausen emission (BE) have been measured as a function of applied magnetic field and tensile stress from mild-steel samples in a wide range of heat treatments, to develop a technique to measure stress without prior knowledge of the microstructure. The results are supplemented by measurements of magnetic coercivity and mechanical hardness. MAE is found to decrease with increasing applied stress, whereas the variation of BE is more complicated. The amplitudes of both MAE and BE, as well as the coercivity and hardness are also found to depend on the microstructure to varying degrees. Thus in ferritic-pearlitic and ferritic-pearlitic-martensitic steel MAE is much more sensitive to stress than to changes in microstructure, whereas the sensitivity of BE to stress and microstructure is similar. Above 50 MPa MAE is also more sensitive to stress in ferrite containing cementite, whereas BE both lacks a monotonic dependence upon stress and is sensitive to microstructure. In martensite, however, there is no MAE, the BE increasing monotonically with stress. Tempered martensitic structures give a weak MAE signal that is more sensitive to tempering temperature than applied stress, whereas the BE increases with stress for tempers below 500°C and decreases above. The dependence of MAE and BE on magnetic field are discussed in terms of domain-wall nucleation and irreversible motion in ferrite at higher fields, and irreversible wall motion through martensite or pearlite at lower fields. The results imply that MAE can be used alone to measure stress provided the general form of the microstructure is known; otherwise BE can be used as an additional technique to resolve any ambiguity.

56 citations



Journal ArticleDOI
TL;DR: In this paper, a study of the kinetics of pearlite spheroidization under static annealing conditions was carried out in two materials, AISI 1080 steel and pure Fe-C alloy.
Abstract: A study of the kinetics of pearlite spheroidization under static annealing conditions was carried out in two materials — AISI 1080 steel and pure Fe-C alloy. A stereological “shape factor”,F, defined asF =Svp/3• Km, was introduced for the kinetic study. The significance of this shape factor in relation to the geometrical characters of lamellar structures is discussed. For constant temperature a linear relation betweenF and the logarithm of time was obtained. Analysis of the time and temperature dependencies for a constant shape factor gave an activation energy of 70 kcal/mole for AISI 1080 steel and 58 kcal/mole for Fe-C alloy which indicates that volume diffusion of Fe in ferrite is the rate-controlling mechanism. The modified fault migration theory, which was developed from the mechanism study of this research, was applied to predict the kinetics of the pearlite spheroidization. For both the AISI 1080 and the Fe-C alloy experimental results have a good match with the theoretical prediction.

52 citations


Journal ArticleDOI
TL;DR: In this article, an interpretation of the Scheil's additivity rule for steels is proposed and its properties are studied, and a stable numerical discretization scheme is proposed.

45 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that the microstructural parameters that affect the coercivity most strongly are the volume fractions and grain sizes of ferrite and pearlite, and a simple model was derived from these observations, which correctly predicts the coercivities of a large number of steels.
Abstract: Pearlitic steels with volume fractions of pearlite from 5 to 100% have been studied using a high-voltage electron microscope and by measuring the Barkhausen activity. The results indicate that the microstructural parameters that affect the coercivity most strongly are the volume fractions and grain sizes of ferrite and pearlite. In electron microscope studies it was observed that domain walls were particularly strongly pinned in cementite lamellae in pearlite grains. A simple model is derived from these observations, which correctly predicts the coercivity of a large number of steels.

43 citations


Journal ArticleDOI
01 Jun 1987-Wear
TL;DR: In this article, the erosion behavior of AISI 4140 steel under various heat treatment conditions was investigated, and a variety of microstructures, such as the primary and tempered martensites, varying proportions of martensite and bainite, cementite spheroids embedded in a ferrite matrix and ferrite and pearlite were obtained.

Journal ArticleDOI
TL;DR: In the hydrogenated state, failure was almost entirely intergranular along prior austenite grain boundaries and cracking of martensitic laths as discussed by the authors, and the fracture surface of the ferrite-pearlite and ferrite bainite specimens consisted of small cleavage regions surrounding nonmetallic (oxide) inclusions.
Abstract: Hydrogen embrittlement (HE) tests were carried out on a carbon-manganese pipeline steel having a low sulphur content (<0.01%). It was shown that the susceptibility to HE increased as the microstructures changed from ferrite-pearlite to martensite. In the hydrogenated state the fracture surface of the ferrite-pearlite and ferrite-bainite specimens consisted of small cleavage regions surrounding non-metallic (oxide) inclusions; these were called rosettes and were a characteristic feature of the embrittled state. In hydrogenated martensitic specimens, failure was almost entirely intergranular along prior austenite grain boundaries and cracking of martensitic laths. In the martensitic specimens a relationship between inverse time to failure and prior austenite grain size was established.


Journal ArticleDOI
TL;DR: In this paper, the microstructures produced during continuous cooling of two particular non-oriented lamination steels have been examined using light microscopy, scanning electron microscopy and transmission electron microscope.
Abstract: The microstructures produced during continuous cooling of two particular non-oriented lamination steels have been examined using light microscopy, scanning electron microscopy and transmission electron microscopy. In addition to proeutectoid ferrite and pearlite, cementite was present on ferrite grain boundaries and on proeutectoid ferrite/ pearl ite interfaces. Mechanisms for the formation of these cementite films are presented. The microstructural results demonstrate that ferrite is the “active nucleus” for pearlite in these low-carbon steels. In addition, the data suggest that in addition to branching, the pearlite reaction can be initiated by the nucleation of a series of cementite precipitates on the proeutectoid ferrite/austenite interface.

Patent
30 Jun 1987
TL;DR: A wear resistant iron alloy article is preferably formed by compacting and sintering a predominantly iron powder mixture containing additions of carbon, copper and nickel boride as discussed by the authors, and the product microstructure comprises hard borocementite particles dispersed in a martensite or pearlite matrix.
Abstract: A wear resistant iron alloy article is preferably formed by compacting and sintering a predominantly iron powder mixture containing additions of carbon, copper and nickel boride. The product microstructure comprises hard borocementite particles dispersed in a martensite or pearlite matrix. The particles have a cross-sectional dimension greater than 1 micron and are present in an amount preferably between 10 and 30 volume percent to improve wear resistance.

Patent
Godfried Vanneste1
29 May 1987
TL;DR: In this paper, steel wires are processed by heating in a furnace 6 to the austenitization temperature and then cooled to a range in which austenite is transformed into pearlite by passing the wires through a water cooling device.
Abstract: Steel wires W are `patented` by heating in a furnace 6 to the austenitization temperature and then cooled to a range in which austenite is transformed into pearlite by passing the wires through a water cooling device 1. This cooling device comprises a tank 2 through which very pure water is continuously circulated at a temperature of at least 85° C. The high purity of the water permits very stable film boiling conditions to occur on the surface of the wire resulting in a soft pearlite structure of excellent drawability.

Patent
12 Mar 1987
TL;DR: In this paper, a steel composed of, by weight 0.55-0.85% C, 0.20-1.20% Si and 0.5-10.0 deg.C is hot rolled to rail and the surface or part less than 5mm from the surface of the top of the rail is cooled at the rate of 2-15 deg.
Abstract: PURPOSE:To deepen hardened depth and to provide good weldability, by hot rolling steel contg. specified quantities of C, Si, Mn, Cr to rail, and controlling apparent pearlite transformation and cooling condition of a range thereafter. CONSTITUTION:Steel composed of, by weight 0.55-0.85% C, 0.20-1.20% Si, 0.5-1.50% Mn, 0.10-0.80% Cr and the balance Fe with inevitable impurity, if necessary >=added one kind among 0.01-0.05% Nb, 0.05-0.20% V, 0.01-0.05% Ti is used and hot rolled to rail. Then the surface or part less than 5mm from the surface of the top of the rail is cooled at the rate of 2-15 deg.C/sec from 800 deg.C to starting temperature of apparent pearlite transformation. It is continuously cooled in transformation domain succeeding thereto while maintaining apparent transformation temp. Successively it is forcedly cooled by 0.5-10.0 deg.C/sec at temp. between apparent end temp. of pearlite transformation and 450 deg.C further lower than preceding step cooling. In this way, high strength rail superior in weldability is obtd. by adding a small quantity of alloy.

Patent
19 Oct 1987
TL;DR: In this article, a steel of grain size No.1W 0.8% C is hot rolled into a bar steel or a wire rod, and the steel stock is cooled from this temp. down to 720°C at ≥30°C/h cooling rate.
Abstract: PURPOSE: To efficiently manufacture a bar stock or wire rod for cold forging having superior quality at a low cost by forming a steel of a specific C content into a mixed structure of fine ferrite and pearlite by means of final finish rolling at a specific temp. and then applying annealing to the above for a specific short time. CONSTITUTION: A steel containing 0.1W0.8% C is hot rolled into a bar steel or a wire rod. At this time, the final finish rolling of the steel stock is carried out at 700W800°C, by which the steel stock is formed into a mixed structure of ferrite and pearlite of grain size No.8 or above. Subsequently, this steel stock is reheated to (Ac 1 +15±10)°C at a heating rate, preferably, of ≥300°C/h and held for 5W60min. The steel stock is cooled, preferably, from this temp. down to 720°C at ≥30°C/h cooling rate, and then cooled from 720°C to 680°C at a cooling rate lower than 10W30°C/h. By this method, the bar stock or wire rod for cold forging having superior characteristics, such as hardness and degree of spheroidizing, can be obtained. COPYRIGHT: (C)1989,JPO&Japio

Patent
21 Oct 1987
TL;DR: In this article, the authors proposed to obtain a ferrous casting excellent in castability and having high strength and high hardness by adding specific amounts of B to a Ferrous casting material so as to spheroidize graphite.
Abstract: PURPOSE: To obtain a ferrous casting excellent in castability and having high strength and high hardness by adding specific amounts of B to a ferrous casting material so as to spheroidize graphite and uniformly disperse this spheroidal graphite and also forming a matrix structure into a hypereutectoid composition consisting of pearlite. CONSTITUTION: As a stock for casting ember requiring light weight, high strength, and high hardness, such as automobile cracnkshaft, connecting rod, and camshaft, a ferrous casting containing,by weight, 0.5W2.5% C, 1.0W4.0% Si, <0.6% Mn, <0.05% S, and 0.01W0.1% B is used. Since superior castability due too high Si content is provided and spheroidal graphite is formed by the addition of B, and further, the structure is formed into a hypereutectoid composition consisting of pearlite, the ferrous casting member having high strength and high hardness can be obtained. COPYRIGHT: (C)1989,JPO&Japio

Journal ArticleDOI
TL;DR: In this paper, the thermal fatigue resistance of flake graphite irons was evaluated in four different thermal cycles (700-40°C, 600-40 °C, 500-40ºC and 720-290°C) using a fully automatic thermal fatigue testing machine.

01 Jan 1987
TL;DR: In this paper, the authors investigated the rolling contact fatigue behavior of a Japanese head hardened (HE) premium rail steel in North America and found that it exhibits premature surface spalling, however no controlled field experiments have been carried out to support this view.
Abstract: Rolling Contact Fatigue Behavior of Three Eutectoid Rail Steels Xiaonong Qiu Oregon Graduate Center, 1987 Supervising Professor: Dr. Paul. Clayton In recent years a Japanese head hardened (HE) premium rail steel in North America has experienced rolling contact fatigue (RCF) problems. Field observations suggest that this material exhibits premature surface spalling, however no controlled field experiments have been carried out to support this view. The current work was undertaken on behalf of a major railroad which uses the HE rail steel. The rolling contact fatigue behavior of this and two other rail steels used by the company, namely a standard carbon (STD) rail steel and a second premium rail steel alloyed with chromium and molybodenum (CrMo), was evaluated in laboratory tests. The experiments were conducted using an Amsler wear testing machine under water lubricated, rolling-sliding conditions over a range of contact pressures. It was found that the HE rail steel possesses the best RCF resistance of the three steels. Further, an attempt was made to characterize the fatigue crack appearance and to correlate it to RCF resistance. The results suggest that HE rail steel and CrMo rail steels are superior to STD rail steel in terms of both crack initiation and propagation. xiv Supporting microstructural and mechanical test evaluations show that HH rail steel has the smallest pearlite interlamellar spacing, lowest inclusion content, and the highest tensile strength, ductility, impact resistance and wear resistance. It is therefore concluded that the investigation has revealed no metallurgical deficiency that could explain why HH rail should experience a RCF problem in practice with respect to other rail steels. While it is not possible, from the small number of mechanical tests on only three materials, to draw any firm conclusions about the correlation between RCF resistance, microstructure, and mechanical properties, the data does suggest that RCF resistance correlates directly with tensile strength, and wear resistance.

Patent
28 Apr 1987
TL;DR: In this paper, a non-heattreated steel wire for bolt excellent in workability and toughness and having high strength by subjecting a steel stock containing additive components such as Nb, V, etc., to hot rolling and cooling each under specific conditions and then by wire-drawing the above.
Abstract: PURPOSE:To develop a non-heattreated steel wire for bolt excellent in workability and toughness and having high strength by subjecting a steel stock containing additive components such as Nb, V, etc., to hot rolling and cooling each under specific conditions and then by wire-drawing the above. CONSTITUTION:The steel stock contain, by weight, 0.1-0.2% C, =2 kinds among 0.05-0.5% Ni, 0.05-0.5% Cr and 0.05-0.5% Mo is heated to 1,000-1,120 deg.C and ten hot-rolled in such a way that finish rolling temp. is 750-950 deg.C. This hot-rolled steel stock is cooled at an average cooling rate of >=5 deg.C/sec through the temp. range from 800 down to 500 deg.C to have a structure of ferrite + bainite or of ferrite + pearlite + bainite, which is subjected to wire drawing so as to manufacture the non-heattreated wire for bolt having a tensile strength as high as 90-110kgf/ mm .

Journal ArticleDOI
TL;DR: In this article, a difference exists in the Rayleigh wave velocity of martensite and pearlite and the difference in velocity can be used to characterize the hardness of a surface modified layer on a pearlite substrate.
Abstract: Nondestructive techniques are required for the in-process characterization of rapidly solidified and surface modified layers to fulfill the role of sensors in emerging intelligent materials processing technologies In steels, where surface modificationvia directed high energy sources is being investigated for surface hardening, it has been found that a difference exists in the Rayleigh wave velocity of martensite and pearlite The difference in velocity can be used to characterize the hardness of a surface modified layer on a pearlite substrate By varying the Rayleigh wave frequency (and thus the depth of wave penetration) and measuring velocity dispersion, it has also been possible to determine nondestructively the depth of modified surface layers on both AISI 1053 and 1044 steels produced by electron beam melting


Journal ArticleDOI
TL;DR: In this article, the effects of various methods for increasing the strength and reducing the proneness to brittle failure (cold resistance) of steels used in construction and engineering are evaluated.
Abstract: Methods are discussed for increasing the strength and reducing the proneness to brittle failure (cold resistance) of steels used in construction and engineering. The chief strengthening methods--solid-solution, dislocation, dispersion, and grain-boundary strengthening--are evaluated. The effects of these methods and the increase in yield strength provided by them on the ductile and brittle properties and fracture toughness of carbon and other steels are comparatively evaluated, taking into account the microstructural routes of these changes and the ferritic-pearlitic and martensitic structural differences of the steels. Methods are given for calculating the relative contributions of the different strengthening mechanisms to the embrittlement process. Dispersion strengthening caused minimal embrittlement in comparison with other strengthening methods. The advantages of steels strengthened with carbonitride was compared to those strengthened with carbon and low alloy steels. Diagrams of structural strength are included for hot-rolled and heat-treated carbon steels.

Journal ArticleDOI
TL;DR: In this paper, the content of rare earth metals alloyed in steels was determined in the as-cast state and the accuracy of the results provided by this method was very satisfactory.
Abstract: Further experiments have been made to ascertain the conditions under which the method previously developed by the authors for determining the content of rare earth metals alloyed in steels can be applied. The accuracy of the results provided by this method is very satisfactory. The content of Ce alloyed in AISI 1518, AISI 1524 + B + Ti, SAE EV15, AISI Tl, and INCOLOY MA956 in the as-cast state have been determined. Autoradiographic studies show that Ce dissolves to a greater extent in pearlite than in ferrite in steels AISI 1518 and AISI 1524 + B + Ti. When Ce contents in the heat-resistant alloy INCOLOY MA956 and in SAE EV15 steel are high, the Ce segregate along grain boundaries. The content of Ce differs between grains; i.e., its distribution in steel is microscopically inhomogeneous.


Patent
28 Oct 1987
TL;DR: In this paper, the sub-eutectoid steel of original constitution of pearlite and ferrite was first heated up to a temperature about 20deg.C above Ac3 and quenched it, then, it was reheated to about 50 degrees.
Abstract: This technology is characterized by first heating the sub-eutectoid steel of original constitution of pearlite and ferrite up to a temperature about 20deg.C-30deg.C above Ac3 and quenching it, Then, reheating it to a temperature 10~50deg.C below Ac3 and requenching it. The equipment consists of a heating furnace and a quenching equipment, together with a reheating furnace and a requenching equipment.

Patent
15 Aug 1987
TL;DR: In this paper, a non-refining forgings whose tensile strength is >=70kgf/mm and whose Charpy absorption energy at a room temperature is >=5kgfm is obtained.
Abstract: PURPOSE:To improve the fatigue strength and toughness in a state of non- refining, after forging, by bringing steel for machine structure or low alloy steel to hot rolling, and thereafter, quenching it, forming a quench hardening depth layer on the surface by a prescribed sectional area rate, and thereafter, executing the forging in a specified temperature range. CONSTITUTION:Steel for machine structure, etc., are brought to hot rolling, and thereafter, only the surface layer is quenched by cooling in a short time by comparatively small quantity of water, and a quench hardening depth layer is generated on the surface, by 20-70% by a sectional area rate. Also, the inside is made to remain ferrite and pearlite structures. Subsequently, by bringing the steel for machine structure, etc., which have been quenched, to forging at a temperature between 550 deg.C-Ac1, a non-refining forgings whose tensile strength is >=70kgf/mm and whose Charpy absorption energy at a room temperature is >=5kgfm is obtained. This non-refining forgings has characteristics which are excellent in the fatigue strength and toughness, even if the subsequent heat treatment is omitted.

Patent
04 Aug 1987
TL;DR: In this paper, the authors proposed to improve the wear resistance and heat resistance of a valve seat part by forming a cast iron layer contg. metallic elements having the higher tendency to the formation of carbide than Fe on the surface of the part corresponding to the valve seat under specific conditions and forming the same into specific structure.
Abstract: PURPOSE:To improve the wear resistance and heat resistance of a valve seat part by forming a cast iron layer contg. metallic elements having the higher tendency to the formation of carbide than Fe on the surface of the part corresponding to the valve seat part under specific conditions and forming the same into specific structure. CONSTITUTION:1 Or >=2 kinds of the metals (Cr, Mo, W, etc.) having the higher tendency to the formation of carbide than Fe or the alloys thereof are disposed on the surface of the part corresponding to the valve seat part of a cylinder head body consisting of a cast iron. High-density energy is irradiated thereto from above to quickly melt the metals or alloys. The molten metals or alloys are quickly cooled to resolidify by which the alloyed cast iron layer is formed to have 0.2-10wt% total concn. of the above-mentioned metallic elements. Such alloyed layer is then heated to a temp. region above the A1 transformation point and below the solidus liquid line temp. and is subjected to a cooling treatment to convert the base to pearlite or the structure essentially consisting of pearlite (about >=50%). The alloyed cast iron layer of 250-400 Hv hardness consisting of the structure in which 2-15% residual cementite exists and lump graphite is crystallized is formed to >=0.2mm depth.