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Showing papers on "Tempering published in 1981"


Journal ArticleDOI
TL;DR: In this paper, the precipitation behavior of a PH 13-8 Mo stainless steel was investigated in the temperature range 450 − 575 °C using optical microscopy, transmission electron microscopy and X-ray diffraction techniques.

131 citations


Patent
01 Dec 1981
TL;DR: In this paper, an electric humidity detecting sensing element on the basis of a layer of porous aluminum oxide, treated by sealing in boiling water, passivation and tempering at 70° to 110° C, achieving a substantial reduction of subsequent variations of calibrating curves.
Abstract: Electric humidity detecting sensing element on the basis of a layer of porous aluminum oxide, treated by sealing in boiling water, passivation and tempering at 70° to 110° C., achieving thereby a substantial reduction of subsequent variations of calibrating curves. The time of tempering may range from 2 to 24 hours. A preferred average time of tempering is 8 hours, with a practical upper limit of 12 hours.

106 citations


Journal ArticleDOI
01 Sep 1981
TL;DR: In this article, the constitutive relations of thermoelastic-plastic bodies during heat treatment when considering phase transformation on the basis of continuum thermodynamics are discussed, and applications of the theory to the cases of quenching and low-temperature-tempering are also presented.
Abstract: The first part of the paper deals with the constitutive relations of thermoelastic-plastic bodies during heat treatment when considering phase transformation on the basis of continuum thermodynamics. Interaction between temperature and metallic structures is carefully discussed to obtain the heat conduction equation including latent heat due to phase transformation. Applications of the theory to the cases of quenching and low-temperature-tempering are also presented. Structure and temperature distributions are numerically calculated by a finite element technique after determining the physical properties from the data of dilatation-temperature-time diagrams. Variations of stress and strain are also analysed. Calculated results of the transformation kinetics and residual stress are compared with experimental data for plain carbon and chromium steels measured by micrographs and both method of X-ray diffraction and Sachs' boring out technique, respectively.

87 citations


Journal ArticleDOI
R. G. Davies1
TL;DR: In this paper, a study of dual-phase steels with tensile strength of about 690 MPa (100 ksi) has shown that these steels are susceptible to the presence of hydrogen.
Abstract: Reversible hydrogen embrittlement (HE) is usually only found in quenched and tempered steels with yield stresses in excess of 1035 MPa (150 ksi). A study of the HE phenomena in two dual-phase steels with tensile strengths of about 690 MPa (100 ksi) has shown that these steels are susceptible to the presence of hydrogen. HE results in a reduction in fracture strength, although no preyield failures are observed, and a change in fracture mode from ductile dimpling to transgranular cleavage. After prestraining and HE, it is found that the greater the prestrain the higher is the fracture stress. It is concluded that the presence of the 15 to 20 pct high carbon (0.6 pct C) high strength martensite in the dual-phase steels is responsible for the HE; tempering studies give results consistent with this idea. Delayed failure tests on notched specimens showed that for the as-received condition, the run-out stress (stress for no failures in 50 to 100 h) to be above the macroscopic flow stress. A condition for HE failure in dual-phase steels appears to be considerable macroscopic deformation.

48 citations


Journal ArticleDOI
TL;DR: In this paper, the microstructures developed after normalizing and tempering 0.5Cr0.25V ferritic steels and the changes which occur during service in electricity-generating plant.

47 citations


Journal ArticleDOI
A. R. Marder1
TL;DR: In this paper, the effect of the heat treating parameters on the properties and structure of molybdenum and vanadium bearing dual-phase steels was studied and the relationship between strength and ductility was independent of alloy addition.
Abstract: A systematic study was made of the effect of the heat treating parameters,(i.e., temperature, time, and cooling rate) on the properties and structure of molybdenum and vanadium bearing dual-phase steels. The volume percent martensite was found to be the major structural factor that controls the strength and ductility of these steels. The relationship between strength and ductility was independent of alloy addition for the alloys studied. Annealing temperature was shown to be very important in these alloys, especially at high quench rates. The molybdenum alloy exhibited better hardenability than the vanadium alloy for equivalent heat treating conditions. Therefore, for a given set of annealing conditions the molybdenum alloy generally had the highest tensile strength and lowest total elongation. A minimum in the 0.2 pct yield strength was found at a specific volume fraction martensite. The increase in yield strength at the lowest volume fraction studied can be related to a jog or discontinuity in the stress-strain curve during tensile testing. This jog was found to be the result of the lack of a sufficient amount of free dislocations. The causes of this deficiency of the dislocations may be: 1) an insufficient amount of transformed martensite, 2) a large martensite interparticle spacing, 3) dynamic recovery of dislocations during cooling, and 4) pinning of dislocations by precipitates during cooling.

44 citations


Journal ArticleDOI
TL;DR: In this paper, a study of tempered martensite embrittlement in Ni-Cr steel doped with 0.01 wt pct S was performed and it was shown that if the austenitizing temperature is below 1050 °C, the sulfide precipitates at the grain boundary and can lower the cohesive strength across the boundary.
Abstract: This paper reports a study of tempered martensite embrittlement in a Ni-Cr steel doped with 0.01 wt pct S. The segregation of sulfur to the grain boundaries and the associated embrittlement of this material are very dependent upon the austenitizing temperature. If the austenitizing temperature is below 1050 °C very little embrittlement and very little intergranular fracture are observed because sulfur remains precipitated as chromium sulfide. At higher austenitizing temperatures the sulfides dissolve and sulfur segregates to the grain boundaries. Because of the high bulk content, the sulfur concentration at the grain boundaries becomes great enough for the sulfides to reprecipitate there. This leads to low energy intergranular ductile fracture. However, some sulfur remains unprecipitated at the boundary and can lower the cohesive strength across the boundary. When plate-like cementite precipitates at the grain boundary during tempering heat treatments at 300 to 400 °C, the combination of the carbides and the unprecipitated sulfur causes intergranular fracture and tempered martensite embrittlement.

43 citations


Journal ArticleDOI
TL;DR: In this paper, the authors studied the effect of adding V and Nb to the 0.05C-10Cr-2Mo steels and their effects on the creep rupture strength and microstructure of the steels.
Abstract: The new ferritic heat-resisting steels of 0.05C-10Cr-2Mo-0.10V-0.05Nb (Cb) composition with high creep rupture strength and good ductility have already been reported. The optimum amounts of V and Nb that can be added to the 0.05C-10Cr-2Mo steels and their effects on the creep rupture strength and microstructure of the steels have been studied in this experiment. The optimum amounts of V and Nb are about 0.10 pct V and 0.05 pct Nb at 600 °C for 10,000 h, but shift to 0.18 pct V and 0.05 pct Nb at 650 °C. Nb-bearing steels are preferred to other grades on the short-time side, because NbC precipitation during initial tempering stages delays recovery of martensite. On the long-time side, however, V-bearing steels have higher creep rupture strength. By adding V to the steels, electron microscopic examination reveals a stable microstructure, retardation during creep of the softening of tempered martensite, fine and uniform distribution of precipitates, and promotion of the precipitation of Fe2Mo.

41 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of hydrogen on fracture of quenched and tempered 1045 steel were examined at room temperature on tensile, Charpy impact, and 4-point notched bend specimens.
Abstract: This work examined the effects of hydrogen on fracture of quenched and tempered 1045 steel Tests were made at room temperature on tensile, Charpy impact, and 4-point notched bend specimens This steel exhibits tempered martensite embrittlement (TME) for tempering temperatures between 300 and 375 °C Thus hydrogen in most cases affected fracture by increasing the amount of intergranular fracture In bend specimens, hydrogen also induced quasicleavage (QC) fracture at points of maximum normal stress below the notch root, points which appeared to be the locations of crack initiation Tear ridges on theseQC surfaces were at martensite lath packet boundaries Crack orientations were largely mode I in uncharged specimens, with mode II appearing at the notch root in most hydrogen-charged specimens These observations are in general agreement with earlier work on martensitic steel

37 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that the forbidden spots observed in electron diffraction patterns from the precipitates can reasonably be interpreted on the basis of the characteristic growth nature of the carbide phases.
Abstract: Application of the lattice and structure imaging techniques in electron microscopy has shown that θ-Fe3C and χ-Fe5C2 intergrow microsyntactically in the precipitated particles at the early third stage of martensite tempering (520~670K). Also is found the microsyntactic intergrowth of higher Carbides, θn-Fe2n+1Cn, having structures closely related With those of θ-Fe3C and χ-Fe5C2. All the forbidden spots observed in electron diffraction patterns from the precipitates can reasonably be interpreted on the basis of the characteristic growth nature of the carbide phases. At the later stage of tempering (720-870K), the precipitates are θ-Fe3C containing various kinds of planar defect. Amechanism is presented for the transformation from χ-Fe5C2 to θ-Fe3C.

34 citations


Journal ArticleDOI
TL;DR: In this article, transmission electron microscopy and microhardness testing were used to examine the as-quenched structure and mechanical properties of a series of rapidly solidified (RS) iron-tungsten-carbon-alloys with a constant W:C atomic ratio of 2:1, and Tl high speed tool steel.
Abstract: Transmission electron microscopy, and microhardness testing were used to examine the as-quenched structure and mechanical properties of a series of rapidly solidified (RS) iron-tungsten-carbon-alloys ranging from 6 to 23 pct tungsten with a constant W:C atomic ratio of 2:1, and Tl high speed tool steel. The RS iron-tungsten-carbon alloys were found to exhibit a significant change in microstructure and hardness as the tungsten and carbon content was increased. The change in morphology was from lath martensite in the lower tungsten alloys to a solidification structure of δ-ferrite cells surrounded by austenite and M6C carbide, in the higher tungsten alloys. A model is proposed to explain the morphologicl change. In addition, the tempering behaviors of RS Fe-6.2 wt pct W-0.21 wt pct C, Fe-23 wt pct W-0.75 wt pct C and Tl high speed tool steel were examined and compared to those observed for the conventional solution-treated and quenched alloys. A discussion is also included on the microstructural dependence upon cooling rate of RS high speed tool steels.

Journal ArticleDOI
TL;DR: In this article, a steel containing 0.30% C, 0.95% Mn, 1.10% Si, 110% Cr, 0.,013%P, 0,008% Ni and 0.009% Cu and known for its susceptibility to reversible temper embrittlement was studied.

Journal ArticleDOI
TL;DR: In this article, the authors found that bolts made of 2 1/4 CrMoV steel became gradually embrittled and exhibited an increasing fraction of intercrystalline fracture after long exposure (more than 25,000 h).
Abstract: Bolts made of2 1/4 CrMoV steel became gradually embrittled and exhibited an increasing fraction of intercrystalline fracture after long exposure (more than 25,000 h) at 540 °C. This has been found to be caused by the segregation of phosphorus to the prior austenite grain boundaries. This was accompanied by the depletion of molybdenum in the ferrite down to about 0.3 pct owing to the formation of a molybdenum-containing carbide Fe3Mo3C(M6C). Reheating of the embrittled bolts to 680 °C removed the segregation of phosphorus at the grain boundaries and therefore also removed the intercrystalline embrittlement. However, the molybdenum content of the ferrite was lowered further to about 0.2 pct; hence the scavenging of phosphorus by molybdenum was further reduced, and therefore the embrittling tendency of these bolts during reuse was increased. Even after reaustenitizing, quenching and tempering, the service life of these bolts was found to be shorter than in the original condition; this is presumed to be due to an inhomogeneity of molybdenum in the austenite not removed by the reaustenitizing treatment.

Journal ArticleDOI
TL;DR: In this article, both scanning transmission electron microscopic (STEM) and chemical extraction techniques were used to analyze the chemical content of precipitated austenite in 5.5Ni steel as a function of heat treatment.
Abstract: Both scanning transmission electron microscopic (STEM) and chemical extraction techniques were used to analyze the chemical content of precipitated austenite in 5.5Ni steel as a function of heat treatment. Austenite was introduced into the steel by tempering at 600 °C for 2 h (QT2) or 100 h (QT100), by tempering for 1 h at 670 °C (QL), or by double tempering 1 h at 670 °C + 1 h at 600 °C (QLT). The two methods of chemical analysis employed for the analysis of this austenite differ quantitatively in the measured austenite composition but are in qualitative agreement; they show an austenite enrichment in Ni, Cr, Mn, and Mo which is most pronounced (and nearly equivalent) for the QT100 and QLT treatments. The similar enrichment of the QT100 and QLT material is interpreted in light of the sequence of reactions leading to the QLT structure. A good correlation is found between the apparent solute enrichment of the precipitated austenite and its thermal stability on cooling to 77 K.

Journal ArticleDOI
TL;DR: In this paper, a fracture toughness study was made on M-2 high speed steel and the major experimental variables included: melting processes (air-melted, ESR and AOD), austenitizing (single and dual) temperature, tempering temperature, and carbide distribution and morphology.
Abstract: A fracture toughness study was made on M-2 high speed steel. The major experimental variables included: melting processes (air-melted, ESR and AOD), austenitizing (single and dual) temperature, tempering temperature, and carbide distribution and morphology. Microstructural characterization was performed by using X-ray diffraction, optical microscopy, scanning electron microscopy and transmission electron microscopy of carbon extractive replica. It appears that undissolved carbides are the major microstructural constituents that control crack initiation and hence toughness. Retained austenite is believed to be responsible for the increasedKIc values observed in dually austenitized specimens. The large grain size resulting from this process apparently impaired impact toughness. Despite the variety of melting processes and heat treatments investigated, fracture toughness remained in the range of 11 to 27.5 MPa m1/2, inversely proportioned to the hardness in the range of 55 to 66 Rc.


Journal ArticleDOI
TL;DR: In this paper, the variation of retained austenite content in heat treated steels is studied by an X-ray diffraction technique, and the effects of surface preparation on the results of X-Ray diffraction measurements are also demonstrated.
Abstract: The variation of retained austenite content in heat treated steels is studied here by an X-ray diffraction technique. It is found that the retained austenite content in steel samples studied increases with the austenitizing temperature and decreases slowly with the tempering temperature up to 177 °C. Above this temperature, it decreases very rapidly until at the tempering temperature of 260 °C it becomes completely zero. The effects of surface preparation on the results of X-ray diffraction measurements are also demonstrated.

Journal ArticleDOI
TL;DR: In this article, a bead-on-plate gas tungsten-arc (GTA) and laser welds in a 12Cr-1Mo-0.3V (HT9) martensitic stainless steel were evaluated using both optical metallography and microhardness techniques.

Patent
12 Feb 1981
TL;DR: In this paper, a slab of 0.02W0.60 Si, 1.0W2.5 Mn, 0.005W 0.10 Nb, ≥ 1 kinds of limited amts, ≤ 0.008 S and F out of the balance unavoidable impurities is heated to 1,180°C or below temp.
Abstract: PURPOSE: To obtain titled high-tensile steel permitting additional intensification by making the temp. for stopping of the accelerated cooling after heating-rolling under adequate conditions for steel of composition having adequate content of Nb lower than that in the prior art. CONSTITUTION: A slab of 0.02W0.15 C, by %, 0.03W0.60 Si, 1.0W2.5 Mn, 0.005W 0.060 solAl, 0.01W0.10 Nb, ≥1 kinds of limited amts. of Ti, Ni, Cu, Mo, V, Cr, B, Ca, REM and ≤0.008 S and F out of the balance unavoidable impurities is heated to 1,180°C or below temp. at which Nb solutionizes at ≥0.01. Thereafter, it is rolled to ≥ 50% cumulative draft in an austenite recrystallization temp., in succession to which it is rolled to ≥50% cumulative draft at Ar 3 WAr 3 +150°C. Thereafter, it is cooled immediately down to 450W300°C at 2W20°C/sec. cooling rates, after which it is air-cooled. With the accelerated cooling temp. in excess of the upper limit, the two phase structure of ferrite and bainite is formed, and the effect of increasing strength is not large. Below the lower limit, the amt. of martensite increases and this decreases the effect of tempering. COPYRIGHT: (C)1982,JPO&Japio

Journal ArticleDOI
TL;DR: In this article, a study of the structure and mechanical properties of Fe-Cr-Mo-C martensitic steels with and without boron addition has been carried out.
Abstract: A study of the structure and mechanical properties of Fe-Cr-Mo-C martensitic steels with and without boron addition has been carried out. Nonconventional heat treatments have subsequently been designed to improve the mechanical properties of these steels. Boron has been known to be a very potent element in increasing the hardenability of steel, but its effect on structure and mechanical properties of quenched and tempered martensitic steels has not been clear. The present results show that the as-quenched structures of both steels consist mainly of dislocated martensite. In the boron-free steel, there are more lath boundary retained austenite films. The boron-treated steel shows higher strengths at all tempering temperatures but with lower Charpy V-notch impact energies. Both steels show tempered martensite embrittlement when tempered at 350 °C for 1 h. The properties above 500 °C tempering are significantly different in the two steels. While the boron-free steel shows a continuous increase in toughness when tempered above 500 °C, the boron-treated steel suffers a second drop in toughness at 600 °C tempering. Transmission electron microscopy studies show that in the 600 °C tempered boron-treated steel large, more or less continuous cementite films are present at the lath boundaries, which are probably responsible for the embrittlement. The differences in mechanical properties at tempering temperatures above 500 °C are rationalized in terms of the effect of boron-vacancy interactions on the recovery and recrystallization behavior of these steels. Although boron seems to impair room temperature impact toughness at low strength levels, it does not affect this property at high strength levels. By simple nonconventinal heat treatments of the present alloys, martensitic steels may be produced with quite good strength-toughness properties which are much superior to those of existing commercial ultra-high strength steels. It is also shown that very good combinations of strength and toughness can be obtained with as-quenched martensitic steels.

Journal ArticleDOI
TL;DR: In this paper, the authors examined the erosive behavior of plain carbon steels as a function of carbon content and microstructure, and found a good correlation exists among the hardness, deformability, and errosive wear characteristics of plain Carbon steels for the experimental conditions of the present study.

Patent
27 Nov 1981
TL;DR: In this paper, a seamless steel pipe for 80kg/mm is produced by hot rolling a steel contg. class structure having excellent toughness in weld zone by hot-rolling steel specific ratios of C, Si, Mn, Cr, Mo, Cu, Al, N, B, and subjecting the steel to cooling, heating, hardening and tempering under specific conditions.
Abstract: PURPOSE:To produce a seamless steel pipe for 80kg/mm. class structure having excellent toughness in weld zone by hot-rolling steel contg. specific ratios of C, Si, Mn, Cr, Mo, Cu, Al, N, B, and subjecting the steel to cooling, heating, hardening and tempering under specific conditions. CONSTITUTION:Steel contg. 0.07-0.16 % c, 0.1-1.0% Si, 0.5-1.5% Mn, <=0.30% Cr, 0.1-0.7% Mo, <=0.30% Cu, 0.07-0.11% Al, 0.0020-0.0040% N, and 0.0005- 0.0020% B, and consisting of the balance Fe with unavoidable impurities is formed by hot rolling. After the hot rolled plate is cooled down to temp. lower than the Ar 1, the same is heated and hardened at 1-30 deg.C/sec. heating rate at 850-1,000 deg.C, and is then tempered to temp. lower than Ac 1 point. If necessary, 0.2-1.5% Ni can be contained and the P contained as unavoidable impurities is preferably kept at <=0.020% and S at <=0.010%.

Journal ArticleDOI
TL;DR: In this paper, a new type of cold-rolled dual phase steel sheet with good formability and dent-resistance has been developed for automobile outer body panels, which is manufactured by means of hot rolling with high temperature coiling, cold rolling, and continuous annealing with water-quenching and tempering.
Abstract: A new type of cold rolled dual phase steel sheet with good formability and dent-resistance has been developed for automobile outer body panels. The steel, basically a low carbon and manganese aluminum killed steel, is manufactured by means of hot rolling with high temperature coiling, cold rolling, and continuous annealing with water-quenching and tempering. The mechanical properties after temper rolling are characterized by yield strength lower than 24kgf/mm2, total elongation larger than 40% and r-value higher than 1.5. Moreover the steel sheet has not only high bake hardenability but also high anti-aging property.

Journal ArticleDOI
TL;DR: In this article, a quenched and tempered marine steel has been cooled at different rates after tempering and low frequency fatigue crack growth rates in air and seawater compared, and water quenching was shown to result in significantly lower fatigue cracks growth rates compared to furnace cooling.

Journal ArticleDOI
TL;DR: In this paper, the effects of cold work on the further tempering characteristics of three carbon steels which had previously been quenched and tempered for a short period have been investigated.
Abstract: The effects of cold work upon the further tempering characteristics of three carbon steels which had previously been quenched and tempered for a short period have been investigated. Recrystallization of the ferrite has been observed and with the low-carbon steel the ferrite grain size may become much larger than that found after direct tempering. Cold work also seems to increase the rate of Ostwald ripening of the cementite. The results obtained are discussed in relation to previous work on the role of dispersed phases upon recrystallization behaviour.

Patent
07 Dec 1981
TL;DR: In this article, a high tensile hot-rolled steel plate which maintains high strength and high toughness even at cryogenic temp. is obtained by rolling steel contg. specific contents of C, Si, Mn, SolAl at specific temp. conditions and reduction rates of areas.
Abstract: PURPOSE:To obtain a high tensile hot-rolled steel material having high strength and high toughness by rolling steel contg. specific contents of C, Si, Mn, SolAl at specific temp. conditions and reduction rates of areas and subjecting the same to hardening and tempering during the course of cooling. CONSTITUTION:The steel contg. 0.02-0.30wt% C, =60% total reduction rate of area or total draft, >=10% reduction rate of area or draft per pass at >=900 deg.C and 950-800 deg.C rolling finishing temp. Thereafter the steel is subjected to direct hardening and the tempering treatment at temp. lower than the AC1 transformation point at a short time during the course of cooling. According to this method the high tensile hot-rolled steel plate which maintains high strength and high toughness even at cryogenic temp. is obtained.

Patent
09 Jul 1981
TL;DR: In this paper, the cooling, coiling and tempering conditions for the steel strip are specified and the rolling is concluded at the Ar3 transformation point -650 deg.C within 60sec to 60% draft.
Abstract: PURPOSE:To obtain a high tensile hot rolled steel strip of superior low temp. toughness by subjecting a continuously cast slag of a specific compsn. to rough rolling by avoiding long-time heating in a low temp. region then to finish rolling at low temps. and high drafts and specifying the cooling, coiling and tempering conditions for the steel strip. CONSTITUTION:The steel slab contg., by wt%, =1 kind among 0.01-0.15 V, 0.005-0.150 Ti, 0.005-0.150 Zr, 0.05-0.50 Mo, 0.10-1.00 Cu, 0.10- 4.00 Ni, 0.10-1.00 Cr, <=0.020 rare earth elements, and <=0.010 Ca and the balance substantially Fe is subjected to controlled rolling from 300mm. up to 3 times thickness of the product. Rough rolling of such material is begun as it is or after heat insulation in 20min or when the surface temp. attains 1,000-800 deg.C after heating. After the end thereof, finish rolling is begun at 950-750 deg.C within 60sec to 60% draft. The rolling is finished at the Ar3 transformation point -650 deg.C. The steel strip is coiled at <=MS point +50 deg.C, and after cooling down to the coiling MF point, the strip is tempered at the Ac1 transformation point or below.

Patent
04 Sep 1981
TL;DR: In this article, a work roll for hot rolling is manufactured with a cast steel contg. 0.6-1.2% C, = 0.65, and the roll is heat treated by oil hardening at 1,050-1,075 deg.
Abstract: PURPOSE:To make a work roll for hot rolling withstand large Hertz stress during rolling and to enhance the wear resistance by manufacturing the roll with a Cr-Mo-V cast steel contg. a specified amount of V. CONSTITUTION:A work roll for hot rolling is manufactured with a cast steel contg. 0.6-1.2% C, =0.65. The roll is heat treated by oil hardening at 1,050-1,075 deg.C and tempering at 510 or 550 deg.C. Fine V carbide particles are uniformly dispersed in the tempered martensite structure, and a work roll for hot rolling with >=61 HRC hardness and superior wear resistance is obtd. This roll withstands >=200kg/ mm. Hertz stress.

Patent
20 Jan 1981
TL;DR: In this paper, a process for the thermal tempering of glass is described, where the hot glass is immersed in a vessel in which there are two mutually immiscible liquids, and a glass is precooled for a specific time in the lower density and then is brought into the higher density.
Abstract: A process for the thermal tempering of glass wherein the hot glass is immersed in a vessel in which there are two mutually immiscible liquids. The liquid of lower density is above the liquid of higher density. The glass is precooled for a specific time in the liquid of lower density and then is brought into the liquid of higher density.

Patent
12 Sep 1981
TL;DR: In this article, a steel material, containing 0.10-0.15% C, < 0.50% Si, 0.30-1.70% Mn, and at least one of <5.00% Ni, <2.00%, Cr, and <1.040% N, is used as a material gears.
Abstract: PURPOSE:To manufacture a steel material for gears which is less in heat treatment strain and of a stable property in addition to the same hardenability as the conventional ones by regulating the amounts of Al and N present in the steel material within a specifically proper range. CONSTITUTION:A steel material, containing 0.10-0.50% C, <0.50% Si, 0.30- 1.70% Mn, and at least one of <5.00% Ni, <2.00% Cr, and <1.00% Mo, together with 0.015-0.055% Al and 0.010-0.040% N, is used as a material gears. The crystal grain size of the steel material is refined by regulating Al/N ratio to 0.5-2.5, lowering the oxygen content of the steel by deoxidation with Al, and existing N together. Thus, because no strain occurs in the steel material during such heat treatments as carburizing, hardening, tempering, etc., gears having excellent shape accuracy can be easily manufactured.