The Effect of Tempering Temperature on Microstructure and the Mechanical Properties of Forged Steel Containing Chrome, Manganese and Molybdenum
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Steel bearings have plenty of usages in manufacturing different kinds of ball bearings, bearings and cold rolling rollers. Heat treatment has an important role in the properties of this group of steels. Therefore, in current research the effect of tempering temperature on the microstructure, hardness, impact energy and wear resistance in forged steel containing Chrome, Manganese and Molybdenum will be studied. For this purpose, the samples were tempered after austenitizing at 900ºC and quenching in the oil at 6 temperatures of 150, 250, 350, 450, 550 and 650 ºC for an hour. Then microstructural studies and mechanical properties of the samples including hardness, impact energy and wear resistance were surveyed on the samples. The results showed that the hardness was gradually decreased (impact energy gradually increased) at the temperature range of 150 - 250 ˚C and at temperature range of 350 -650ºC, the hardness would decrease and the impact energy would increase. Also, the wear resistance would decrease with an increase in the tempering temperature. The result should be justified considering the softening of the structure and the reduction in martensite tetragonality which stems from an increase in the tempering temperature. The study of the wear surface of the samples indicated that the dominant wear mechanism was adhesive wear in which with an increase the tempering temperature due to a reduction in the hardness of the samples, more sever adhesive wear was observed. DOI: http://dx.doi.org/10.5755/j01.mech.24.6.22478Keywords:
Tempering
Impact energy
Atmospheric temperature range
Adhesive wear
Quenched and tempered steels are needed for highly-stressed structures in military and non-military equipment. This paper was written for studying the structure and properties (hardness and impact energy absorbed) of medium-carbon and carbon-manganese steels before and after Quench+Temper and Double Quenched+Tempered. Because water is cheap and easy to control, it was used as a quenching medium. This study compares the hardness and impact energy absorbed of quenched plus tempered and double quenched plus tempered steels. The results showed that double quenched plus tempered steel hardness was higher than in quenched plus tempered steels. Besides, the grain structure is refiner than that of quenched plus tempered steel. The taking of the austenite temperature and holding time is essential because of the hardness at the end of the quenching process. The study aims to obtain hardness and impact energy from quenching+tempering and double quenching+tempering of medium-carbon and carbon-manganese steel for armor steel. In the first step, five specimens were heated at 900 ℃ (held for 30 minutes), cooled in freshwater and produced Q900 Steel. Then, these specimens were heated at 750 ℃, 800 ℃, 850 ℃, and 900 ℃, held for 30 minutes and provided Q900+750 Steel, Q900+800, Q900+850 Steel, and Q900+900 Steel. These specimens were tempered at 150 ℃ (held for 30 minutes) and produced Q900+750&T Steel, Q900+800&T Steel, Q900+850&T Steel, Q900+900&T Steel. Martensite reached the cooling period 357 ℃ to 182 ℃, tempered at 150 ℃ (held for 30 minutes). Hardness for double-quenching and tempering is higher than for conventional. The maximum impact energy of double-quenching and tempering heat treatment of Q900+850&T steel is suitable for armor steel used.
Tempering
Carbon steel
Carbon fibers
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The effects of intercritical treatment parameters,such as quenching temperature and tempering temperature on microstructure and mechanical properties of 17Ni4.5CrMoV cast steel were investigated.The results show that,after intercritical quenching treatment,the microstructure of cast steel is fined,meanwhile a mixed microstructure containing tempering martensite and ferrite as well as a small amount of precipitated austenite are obtained,which results in greater improvementer on the matching of strength and toughness of the cast steel.Moreover,the optimal intercritical quenching process for 17Ni4.5CrMoV cast steel is obtained.
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Quenching Hardness Calculation and Tempering Hardness Characteristic of Cr-W-Mo-V Medium-alloy Steel
The changes of quenching and tempering hardness and the microstructure transformation of four kinds of Cr-W-Mo-V medium-alloy steels were investigated. On the basis of matrix composition calculation,the formula of the quenching hardness of the steels have been put forward according to austenite compositions at some austenitizing temperature. The good temper-resistance of the steels was obtained at tempering. With the increase of Cr,W,Mo and V content, secondary hardening or platform at low tempering temperature, even secondary hardening at high temperature appear with different types of carbides precipitated. Above quenching hardness formula implies the corresponding relation between rockwell hardness measurement and the mechanism of martensite strengthening. The formula is suitable for other steels.
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Rockwell scale
Hardening (computing)
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The influences of quenching(800 ℃,900 ℃,1000 ℃) and tempering(200 ℃,400 ℃,600 ℃) processes on microstructure and the mechanical properties of Medium Manganese Nodular Cast Iron with 6% Mn were studied.The results show that the optimized heat treatment of Nodular Cast Iron is austenitic treated at 900 ℃ for 2 h followed by water quenching,and then tempered at 200 ℃ for 2 h before water quenching.Quenching microstructure of Nodular Cast Iron is major martensite+bainite+retained austenite+spheroidal graphite.Microstructure of Nodular Cast Iron after quenching and tempering is tempered martensite+bainite+a small amount of retained austenite+carbide+spheroidal graphite.After heat treatment,hardness of samples decreased,impact toughness improved,wear resistance decreased.Quenching temperature has greater impact on the mechanical properties than tempering temperature.
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Heat treating
Austempering
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The microstructure and mechanical properties of Cr15 super martensitic stainless steel after different heat treatment were studied by SEM and XRD. The results show that the microstructure of steel A and B are lath martensite and retained austenite after quenching. The original austenite grain size increases with the increasing quenching temperature. The microstructure is composed by tempered martensite and reversed austenite after tempering. The amount of reversed austenite in both steels increases first and then decreases with the increasing tempering temperature. Both of the tested steels have the best mechanical properties at 650°C tempering temperature.
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Lath
Heat treating
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High vanadium high speed steel was carried out two groups of heat treatment,one was quenching at 900℃ to 1100℃ then tempering at 550℃,and the other was quenching at 1100℃ then tempering at 250℃ to 550℃.The rolling wear properties of high vanadium high speed steel were studied using WM-1 rolling wear tester and its microstructure was analysed by SEM.The results show that matrix is mainly tempered martensite under the condition of quenching at low temperature and tempering at 550℃;retained austenite content increases and martensite content relatively decreases along with the increase of quenching temperature,meanwhile,the wear resistance improves.Under the condition of quenching at 1100℃ and tempering at low temperature,the matrix is mainly retained austenite,and with the increase of tempering temperature,retained austenite content decreases while its wear resistance increases till a determinate value then decreases.The research results show the optimal technology of heat treatment is quenching at 1050℃ then tempering at 450℃ or 550℃;and proper content of retained austenite profits to improve the rolling wear properties.
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High Speed Steel
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This paper presents the research results on the microstructure changes of SKD61 steel after quenching at 1050[Formula: see text]C and then tempering at 580[Formula: see text]C. After quenching and tempering, the microstructure of this steel is determined by various moieties, including tempering martensite, residual austenite, and carbides dispersed within the matrix. Scanning electron microscopy, X-ray, and energy-dispersive spectroscopic analysis reveal that the presence of the carbides Cr 7 C 3 , Mo 3 C 2 and MoC determines the mechanical properties of steel during high-temperature operations.
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Quenching and tempering transformations of 23MnNiCrMo steel for the chains of coal machines were investigated. After being heated up to austenite range, the steel pieces were cooled separately in air, water and oil, then the cooled steel pieces were tempered at different temperature and time. It is showed that, when the quenching temperature is 860?℃, the microstructure of the steel quenched by water and oil are lath martensite + a little bainite + some residual austenite + some residual cabide. As the effect of the alloy elements, the tempering transformation of this steel is diferent from carbon-steel.When tempered at mid-temperature, the microstructure of this steel is transformed into a kind of composite structure composed mainly of tempering martensite with some bainite and residual carbide instead of complete tempering troostite structure.
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Lath
Alloy steel
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