Showing papers on "Pearlite published in 1986"
TL;DR: In this paper, the critical cleavage fracture stresses were measured on bluntly-notched bend specimens tested over the temperature range -125 °C to 23 °C, and the calculated values for σF were independent of both the type and location of initiation site(e.g., inclusion, pearlite colony).
Abstract: The microstructural parameter(s) controlling the critical cleavage fracture stress, σF, of fully pearlitic eutectoid steel have been investigated. Independent variation of the pearlite interlamellar spacing,Sp, and the prior austenite grain size were accomplished through heat treatment. Critical cleavage fracture stresses were measured on bluntly-notched bend specimens tested over the temperature range -125 °C to 23 °C. The cleavage fracture stress increased with decreasingSp, and was independent of prior austenite grain size. Fine pearlitic microstructures exhibited temperature, strain-rate, and notched-bar geometry independent values for σF, consistent with propagation-controlled cleavage fracture. Coarse pearlitic specimens exhibited temperature-dependent values for σF over a similar temperature range. Inclusion-initiated fractures were generally located at or beyond the location of the peak normal stress in the bend bar, while cracking associated with pearlite colonies was observed to be closer to the notch than the predicted peak stress location. The calculated values for σF were independent of both the type and location of initiation site(e. g., inclusion, pearlite colony). Thus, although inclusions may provide potent fracture initiation sites, their presence or absence does not necessarily change σF in fully pearlitic microstructures.
111 citations
TL;DR: In this paper, the role of large prior austenite grain sizes in promoting low ductility of fully pearlitic eutectoid steels has been investigated, and it appears that the prior grain size controls ductility through its influence prior to catastrophic failure.
Abstract: The role of large prior austenite grain sizes in promoting low ductility of fully pearlitic eutectoid steels has been investigated. Independent variation of the pearlite interlamellar spacing,S
p, and the prior austenite grain size enabled determination of the microstructural feature controlling ductility in these steels. Tests on a variety of specimens over the temperature range —196 °C to 310 °C showed that specimens heat treated to contain a large prior austenite grain size consistently exhibited lower fracture strains (i.e., ductility), regardless of the type of fracture present, than did fine grained specimens. It appears that the prior austenite grain size controls ductility through its influence prior to catastrophic failure.
85 citations
TL;DR: In this article, the influence of prior austenite grain size dγ and true interlamellar spacing of pearlite St on the strength and fracture toughness of a eutectoid rail steel has been investigated.
Abstract: The influence of prior austenite grain size dγ, and true interlamellar spacing of pearlite St on the strength and fracture toughness of a eutectoid rail steel has been investigated. Specimens were machined from rail sections and heat treated to produce a wide variation in dγ and st. Mechanical properties studied included 0·2% proof stress σ0·2, ultimate tensile strength σu, tensile ductility δ, cleavage fracture stress σf, and plane strain fracture toughness K1c. All tests were performed at a temperature of −80°C. The values of σ0·2 and σu increase as st decreases. The proof stress is related to the mean free distance λin the pearlitic ferrite by a Hall–Petch equation. A microstructural dependence similar to that of σ0·2 is shown by σf and for all but the finest pearlites σf is interpreted as a shear stress controlled cleavage nucleation stress. The value of K1c first decreases with decreasing st and then increases for the finest spacings. This behaviour is attributed to a change in the micromecha...
54 citations
TL;DR: In this article, a series of pure Fe-C alloys consisting of ferrite and pearlite was studied and it was shown that the ferrite/cementite lamella interface has little effect on the hydrogen occlusivity, but it does interfere with the hydrogen diffusion path across the pearlite colonies.
Abstract: Experiments on a series of pure Fe–C alloys consisting of ferrite and pearlite only have shown that the ferrite/pearlite and pearlite/pearlite interfaces are effective hydrogen trapping sites. The ferrite/cementite interfaces within the pearlite colonies, however, have little effect on the hydrogen occlusivity. With an increase in carbon content, more ferrite/pearlite interfaces are created and these increase the hydrogen occlusivity. Although the ferrite/cementite lamella interface has little effect on the hydrogen occlusivity, it does appear that the lamellae interfere with the hydrogen diffusion path across the pearlite colonies. Thus, the higher-carbon alloys in the pearlitic condition have a lower apparent hydrogen diffusivity. Hydrogen has little effect on the tensile strength, but significantly reduces the ductility. After hydrogen charging, high-carbon alloys suffer a lower ductility loss. However, in terms of absolute values, the low-carbon specimens are always more ductile than the high-...
51 citations
TL;DR: In this article, the limits of applicability of the additive principle for the prediction of continuous-cooling transformation kinetics from isothermal transformation data are clarified based on an analysis of recently measured austenite-to-pearlite transformation in a eutectoid, plain-carbon steel.
Abstract: The limits of applicability of the Additivity Principle, necessary for the prediction of continuous-cooling transformation kinetics from isothermal transformation data, are clarified based on an analysis of recently measured austenite-to-pearlite transformation kinetics in a eutectoid, plain-carbon steel. It has been found that additivity holds for the transformation event, exclusive of the incubation period, in this steel. But the isokinetic condition defined by Avrami, and the early site-saturation criteria postulated by Cahn as sufficient conditions for additivity are not satisfied. Thus a new condition, termed “effective site saturation”, is proposed in which the growth of pearlite nucleated early in the transformation dominates the overall kinetics of austenite decomposition. A criterion for effective site saturation has been established.
45 citations
TL;DR: In this paper, the micromechanism of cleavage fracture in a fully pearlitic steel has been investigated and the results indicate that pearlite can exhibit two different cleavage mechanisms which are dependent on the strength of the steel.
Abstract: The micromechanism of cleavage fracture in a fully pearlitic steel has been investigated Uniaxial tensile and compression test specimens, together with single notched bend (SNB) and double notched bend (DNB) specimens, were heat treated such that the prior austenite grain size remained constant while the pearlite interlamellar spacing was varied The SNB specimens were used to determine the cleavage fracture stress σfM, over the temperature range −25 to −196°C The DNB specimens were used to study the initial stages of crack nucleation The results indicate that pearlite can exhibit two different cleavage mechanisms which are dependent on the strength of the steel For cleavage fracture stresses below about 2100 MN m−2, fracture is nucleation controlled and involves shear linking of carbide nucleated microcracks before unstable cleavage can occur Under these conditions, the cleavage fracture stress is dependent on temperature and is proportional to the uniaxial proof stress For cleavage fractur
38 citations
TL;DR: In this article, the formation of austenite is associated initially with a migration of ferrite grain boundaries, and it is proposed that this boundary migration is induced by manganese diffusion along the boundaries.
Abstract: Manganese-containing ferritic–pearlitic steels have been studied after intercritical annealing for various times at temperatures of 700 and 725°C, during which austenite formation occurred at ferrite grain boundaries. Light and electron optical microscopy, and scanning transmission electron microanalysis and microdiffraction were employed for the study, in which both microstructural development and manganese redistribution were examined in detail. It was observed that the formation of austenite is associated initially with a migration of ferrite grain boundaries. It is proposed that this boundary migration is induced by manganese diffusion along the boundaries, and that this in turn provides the mechanism for rapidly transporting manganese to the growing austenite. On this basis, we find that austenite formation in these steels is associated with manganese-rich migrated ferrite boundaries, and is not dependent on the presence of cementite particles for nucleation.MST/467
32 citations
TL;DR: In this paper, two commercially produced linepipe steels were investigated with regard to HIC on cathodic charging, and they showed a high banded microstructure consisting of alternative layers of polygonal ferrite and a mixture of non-ferritic constituents (pearlite, bainite, and martensite-austenite).
Abstract: Linepipe steels are susceptible to hydrogen-induced cracking (HIC) in wet, sour gas environments. Two commercially produced linepipe steels were investigated with regard to HIC on cathodic charging. Both steels, B and C, showed a high banded microstructure consisting of alternative layers of polygonal ferrite and a mixture of non-ferritic constituents (pearlite, bainite, and martensite-austenite). The degree of banding was higher in Steel B than in Steel C. Also present were elongated inclusions in Steel B, while in Steel C they were more or less equiaxed. On cathodically hydrogen-charging in the absence of external stress, microvoids formed at low current densities at or around inclusions. On prolonged charging, these voids grew and propagated parallel to the bands, running along the interface between ferrite/non-ferrite constituents, along inclusions lodged in the non-ferritic consitituents, and at places through the non-ferritic constituents. Steel B, not unexpectedly, showed more severe permanent microstructural damage than Steel C, leading to the conclusion that a high banded structure and/or the presence of elongated inclusions is deleterious to resistance against HIC.
22 citations
TL;DR: In this paper, the authors showed that cementite particles were retained as three different morphologies in the fine-grained austenite formed during the 850 °C intercritical austenitizing treatment.
Abstract: Two 52100 steels, one containing 0.009 pct P, the other 0.023 pct P, were homogenized at 1150 °C, slowly cooled to form proeutectoid carbides and pearlite, partially spheroidized, austenitized at 850 °C for one hour, oil quenched, and tempered at 200 °C. Light microscopy and transmission electron microscopy of carbon extraction replicas showed that cementite particles were retained as three different morphologies in the fine-grained austenite formed during the 850 °C intercritical austenitizing treatment. The morphologies are characterized as follows: (1) closely spaced intragranular carbides most of which are less than 0.25 μm in diameter, (2) carbides about 1 μm in diameter, located on austenite grain boundaries, and (3) branched proeutectoid carbides arranged in networks corresponding to the coarse, 130 μm diameter austenite grains formed during homogenizing. The major effect of high phosphorus content was to retard the spheroidization of the retained carbides.
20 citations
TL;DR: In this paper, fracture surfaces are observed using a scanning electron microscope to correlate fracture toughness with the fracture surface and to understand the mechanism of crack growth at different stress intensity factor ranges.
Abstract: Fracture toughness and fatigue crack growth data of four nodular cast irons with different pearlite fractions are studied. The influence of temperature on fracture toughness is also investigated. Fracture surfaces are observed using a scanning electron microscope to correlate fracture toughness with the fracture surface and to understand the mechanism of crack growth at different stress intensity factor ranges. It is shown that the upper shelf fracture toughness increases with pearlite fraction. The existence of nodular void regions on the fracture surface plays an important role in fracture toughness. The fatigue crack growth rate is less sensible to stress intensity factor range when pearlite fraction increases.
17 citations
TL;DR: In this paper, the power spectra exhibit clustering in elementary magnetic transitions, which can be expressed in terms of the mean pulse duration ϱ τ 0, inversely proportional to coercivity, incrasing as a function of grain size D approximately as D 1 2.
TL;DR: In this paper, it was shown that deformed rail steels and associated weld metal exhibited fatigue crack growth rates that are slightly faster than undeformed rail steel and weld metal growth data are appreciably faster than rail steel growth results and exhibit growth rate plateaux that reside above the upper bound reported for rail steel fatigue crack.
Patent•
24 Sep 1986TL;DR: In this article, a water cooling device consisting of a tank of very pure water is continuously circulated at a temperature of at least 85°C, which permits very stable film boiling conditions to occur on the surface of the wire resulting in a soft pearlite structure of excellent drawability.
Abstract: Steel wires Ware "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.
TL;DR: In this paper, the influence of grain boundary carbide density on impact behavior has been examined for C-Mn-Nb-Al steels by normalizing at increasing temperatures above the Ac3 and tempering for long times below the AC1.
Abstract: The influence of grain boundary carbide density on impact behaviour has been examined for C–Mn–Nb–Al steels by (i) normalizing at increasing temperatures above the Ac3, and (ii) tempering for long times below the AC1. Low normalizing temperatures (i) resulted in a large number of grain boundary carbides possibly because incomplete homogenization on austenitizing produces a high concentration of carbon at the boundaries. Raising the normalizing temperature reduced the number of grain boundary carbides as well as refining their size, but the expected improvement in impact behaviour was not realized because grain size also increased. Tempering at 680°C raised the grain boundary carbide density considerably and completely destroyed the pearlite colonies; tempering at 600°C (ii) gave a lower increase in carbide density and destroyed fewer pearlite colonies. Only small changes in grain size and grain boundary carbide thickness were noted so that the deterioration in impact behaviour obtained on temperin...
Patent•
04 Mar 1986TL;DR: In this paper, the wires from an austenitizing furnace are first quenched in a fluidized bed (Q), which is fluidized by hot gases from the furnace and is also provided with a cooling system.
Abstract: In the heat treatment of steel wires (W) in a patenting operation, the wires from an austenitizing furnace (1) are first quenched in a fluidized bed (Q). This bed (Q) is fluidized by hot gases from the furnace (1) and is also provided with a cooling system (28). The wires are then passed into a second fluidized bed (TR-S) where transformation takes place. This bed is fluidized by an independent source of hot gas (21) and is divided into regions (13) along its length which have independently controllable auxiliary heaters (14). The temperatures in the zone (Q) and the region (13) along zone (TR-S) are controlled to give a fine pearlite microstructure in the wire.
TL;DR: Mesure statistique par microscopie electronique a transmission de l'espace interlamellaire durant la croissance de perlite dans l'acier perlitique microallie de composition (% poids) as mentioned in this paper.
Patent•
15 Dec 1986
TL;DR: In this article, an ingot of a low-alloy steel contg., by weight, 0.05-0.20% C, <0.05% Si, 1.0-2.0% Mn, < 0.015% S, S 0.15% V, V 0.1% Nb and 0.50% Cr is heated to 950-1,150 deg.C and worked into a wire rod for a bolt by hot rolling.
Abstract: PURPOSE:To obtain an alloy steel for an unrefined bolt or the like having superior toughness by hot working a low-alloy steel having a specified composition and by cooling it under specified conditions. CONSTITUTION:An ingot of a low-alloy steel contg., by weight, 0.05-0.20% C, <0.05% Si, 1.0-2.0% Mn, <0.015% S, 0.01-0.05% Al and at least one among <0.15% V, <0.1% Nb and 0.05-0.50% Cr is heated to 950-1,150 deg.C and worked into a wire rod for a bolt by hot rolling. The wire rod is finish- rolled and cooled to <=500 deg.C at <=10 deg.C/sec cooling rate to form a dense ferrite- pearlite structure. A steel material having the desired strength and toughness and suitable for use as a material for an unrefined bolt or the like is obtd.
TL;DR: In this paper, the influence of hot deformation and austenization temperature on the subsequent isothermal transformation to pearlite was studied for 40Cr steel, which contains 0.38%C and 0.89%Cr.
Patent•
01 Jul 1986
TL;DR: In this article, the authors proposed a matrix structure for surface hardening of a cast iron material composed of, by weight, 2.5-4% C, 2-3.5% Si, 0.5 -11.5 % Mn, =70% pearlite.
Abstract: PURPOSE:To provide superior strength, castability and soundness after casting by adding Ca as well as one or more among cu, Sn and Cr and forming a matrix structure contg. a specified percentage of pearlite. CONSTITUTION:The composition of a cast iron material for surface hardening is composed of, by weight, 2.5-4% C, 2-3.5% Si, 0.5-11.5% Mn, =70% pearlite.
TL;DR: In this paper, the effects of manganese, chromium, and molybdenum on the transformation behavior of eutectoid steels were evaluated by multiple linear regression analysis of the isothermal transformation diagram data.
Abstract: Isothermal transformation diagrams of a series of eutectoid steels alloyed with 0.75% C, 0.28% Si, 0.43 to 0.91% Mn, 0 to 0.76% Cr, and 0 to 0.34% Mo were determined using a dilatometer. The effects of manganese, chromium, and molybdenum on the transformation behavior of these eutectoid steels were then evaluated by multiple linear regression analysis of the isothermal transformation diagram data. The regression analysis shows that molybdenum has its greatest effect in delaying the austenite decomposition at high temperatures (650 to 500° C), chromium at intermediate temperatures (550 to 500° C), and manganese at low temperatures (350 to 300° C). The results imply that molybdenum has a much greater effect in suppressing the formation of pearlite than it has in suppressing bainite, while manganese suppresses both the pearlite and the bainite transformation.
Patent•
28 Jan 1986
TL;DR: In this article, the authors proposed a method to improve the wear resistance and heat resistance of a disk rotor by disposing a metal having a high tendency to form carbide on the sliding surface and irradiating high-density energy thereto, then subjecting the surface to the heat treatment under specific conditions.
Abstract: PURPOSE: To improve the wear resistance and heat resistance of the sliding surface of a disk rotor by disposing a metal (alloy) having a high tendency to form carbide on the sliding surface and irradiating high-density energy thereto, then subjecting the surface to the heat treatment under specific conditions. CONSTITUTION: The metallic element such as Cr or Mo or the alloy thereof having the higher tendency to form the carbide than Fe is disposed to the place of a cast iron disk rotor to be formed as the sliding surface. The high density energy is then irradiated thereto to quickly melt and quickly resolidify the metal or the alloy and to form the chilled alloy layer with 0.2W10wt% concn. of the above-mentioned metallic element. The chilled alloy layer is heated to the A 1 transformation point or above and the solidus phase temp. or below and is then cooled. The alloyed cast iron layer of 250W400 HV hardness in which the base is pearlite or consists essentially of pearlite, the residual cementite exists at 2W15% and the lumped graphite is crystallized is formed to ≥0.2mm depth. The disk rotor having the resistance to heat and wear and excellent workability and rust preventiveness is obtd. by the above-mentioned method. COPYRIGHT: (C)1987,JPO&Japio
Patent•
22 Nov 1986
TL;DR: In this paper, a steel contg, by weight, 0.25-0.6%, 0.1-1%, Si, 1-2% Mn and 0.3-1% Cr, is heated to the Ac3 transformation point - 1,050 deg.C and cooled so as to form a steel structure contg.
Abstract: PURPOSE:To provide superior strength and toughness to a hot forged article by heating a steel obtd. by adding prescribed amounts of Mn and Cr to a machine structural carbon steel to a prescribed low temp., hot forging the heated steel and cooling the resulting hot forged article so as to reduce the amount of proeutectoid ferrite in the article. CONSTITUTION:A steel contg., by weight, 0.25-0.6% C, 0.1-1% Si, 1-2% Mn and 0.3-1% Cr is heated to the Ac3 transformation point - 1,050 deg.C and hot forged. The resulting hot forged article is cooled so as to form a steel structure contg. proeutectoid ferrite by an amount F(%) represented by the formula [where C% is the C content (wt%) in the steel]. The structure is a ferrite-pearlite structure having <=0.2mum space between pearlite lamellae.
TL;DR: The sharpness of the diffraction line peak can be measured by using a constant of the Gaussian curve fitted to the peak of the peak as mentioned in this paper, which can be used to measure the extent of hardening of slack quenched steels.
Abstract: An X-ray diffraction line will broaden considerably when steels transform to martensite on quenching Slack quenched steels contain a mixed martensite and fine pearlite structure which produces an anomalous diffraction line profile with a sharp peak superimposed on a broad base The sharpness of the diffraction line peak can be measured by using a constant of the Gaussian curve fitted to the peak This constant (denoted GCP) for completely hardened steels increases with increasing carbon content up to 07 wt% carbon At higher carbon contents, the GCP becomes almost constant Also, the GCP increases with increasing hardness along a single curve independently of carbon content The GCP for the slack quenched steels is smaller than that for the completely hardened steels Extent of hardening of the slack quenched steels having a sharp diffraction line peak can be evaluated rapidly and nondestructively by comparing their GCP value with that for the completely hardened steels
Patent•
29 May 1986
TL;DR: In this article, the authors obtain as-cast pearlite-base CV graphite cast iron having superior mechanical properties and wear resistance by specifying a composition consisting of C, Si, Mn, Mg, Cu, Mo and Fe.
Abstract: PURPOSE:To obtain as-cast pearlite-base CV graphite cast iron having superior mechanical properties and wear resistance by specifying a composition consisting of C, Si, Mn, Mg, Cu, Mo and Fe. CONSTITUTION:This pearlite-base CV graphite cast iron consists of, by weight, 3.5-4.2% C, 2.0-3.3% Si, =about 70% pearlite and the balance ferrite. The cast iron has superior mechanical properties and wear resistance, causes hardly shrinkage defects and dross defects, and also has superior castability, so the thickness and weight of a casting can be reduced.
TL;DR: The mechanism of localized corrosion and the initiation of corrosion fatigue cracks were investigated metallographically on HT50-CR steel by testing it with a rotating beam fatigue machine in artificial sea water as discussed by the authors.
Abstract: The mechanism of localized corrosion and the initiation of corrosion fatigue cracks were investigated metallographically on HT50-CR steel by testing it with a rotating beam fatigue machine in artificial sea water. Two types of localized corrosion, i.e., pitting and grooving, were observed on the specimen surface. The sites of grooving were restricted to the area which was equivalent to the center region of the received plate. Quantitative metallographic data of pit distribution indicated that the pit growth rate in this area was significantly faster than that in the other area, and many cracks nucleated at the grooving sites. Degenerate or banitic pearlite and elongated inclusions (MnS) were observed in this area. SEM and EPMA examinations showed that the preferential dissolution of ferrite around the degenerate pearlite and MnS resulted in the growth of pitting and grooving corrosion. These inhomogeneous structures in the material had a significant role on the corrosion fatigue life.
TL;DR: A pearlitic nodular iron with a bull's-eye structure was studied in this paper, and the fracture surfaces were observed by using both optical and scanning electron microscopy, showing that the fracture growth occurred transgranularly in the pearlite matrix.
Patent•
22 Nov 1986
TL;DR: In this paper, a steel composed of, by weight 0.25-0.60% C, 0.30-1.00% Cr and the balance Fe with inevitable impurities is hot rolled or tempered or normallizing treated.
Abstract: PURPOSE:To obtain the titled steel in which tempering heat treatment after forging is not required, by treating suitably a steel in which specified quantities of Mn and Cr are added to steel for machinery structure, to decrease a quantity of pro-eutectoid ferrite and refine pearlitic structure. CONSTITUTION:Steel composed of, by weight 0.25-0.60% C, 0.10-1.00% Si, 1.00-2.00% Mn, 0.30-1.00% Cr and the balance Fe with inevitable impurities is hot rolled or tempered or normallizing treated. In the structure obtd. thereby, denoting pro-eutectoid ferrite quantity as F%, pearlitic lamellar spacing as Dmum, the titled steel composed of ferrite and pearlite structure under F<=90-140 C% and D<=0.20mum is obtd. In the component compsn., toughness is improved by further adding <=0.1% Ti or 0.1% Nb, or machinability can be improved by adding at least one kind among <=0.15% S, <=0.30% Pb, <=0.010% Ca.
Patent•
15 Mar 1986
TL;DR: In this paper, a large diameter steel bar with high strength and high tensile strength is used to obtain a rolled steel bar which has high strength, toughness and to which addition of expensive element for improving quenchability is suppressed as low as possible, by controlling pearlite transformation temp.
Abstract: PURPOSE:To obtain a rolled steel bar which has a large diameter, high strength, the toughness and to which addition of expensive element for improving quenchability is suppressed as low as possible, by controlling pearlite transformation temp. in patenting large diameter steel bar. CONSTITUTION:The steel bar consists of, by weight 0.6-0.9% C, 0.25-2.0 Si, 0.5-2.0% Mn, 0.3-1.0% Cr and the balance Fe, and has >=20mm. diameter, >=120kg/mm. tensile strength, >=20% reduction of area. In case the steel bar heated to austenite temp. range is cooled at equal rate for obtaining said bar, critical temp. in contact with pearlite transformation starting line in continuous cooling transformation curve thereof is denoted as Tc. Pearlite transformation is started in Tc-(Tc+40 deg.C) temp. range, and said bar is cooled to control so that max. temp. during said transformation is suppressed in <=Tc+80 deg.C.
TL;DR: In this article, the effect of austenitizing temperature on the fracture toughness of machine structural steels, SCM440 and S45C, was investigated, and the results obtained are summarized as follows.
Abstract: The effect of austenitizing temperature on the fracture toughness of machine structural steels, SCM440 and S45C was investigated. Steels were austenitized at 780°C or 760°C, 1050°C and 1200°C and then quenched and tempered. The elastic-plastic fracture toughness JIc tests by the stretched zone method were performed to obtain the fracture toughness. Also the cross section of the stretched zone was observed to evaluate the effect of the microstructure.The results obtained are summarized as follows.(1) For SCM440 steel the fracture toughness decreased with increasing the austenitizing temperature, while it increased slightly for S45C steel.(2) The decrease of the fracture toughness of SCM440 steel at high austenitizing temperature was caused by embrittlement of the grain-, martensite- and acicular ferrite·pearlite-boundaries.(3) The critical stretched zone width, SZWc of S45C steel hardly changed because the variation of the strength of pearlite grains was very small under the present heat treatment conditions.