Effect Of Tempering Temperature Research Articles

Effect of tempering temperature on carbide precipitation behaviours in high strength low alloy steel under high magnetic field

The influence of high magnetic field on carbide precipitation behaviours during the tempering of a high strength low alloy steel was investigated by means of transmission electron microscopy. TEM analysis results indicated that the applied high field effectively promoted the precipitation of Fe5C2 type carbide at low temperature (200°C) and the precipitation of M6C type carbide at intermediate temperature (530°C). The promotion of specific carbides at low and intermediate temperature was caused by the reduction in magnetic Gibbs free energy. Regarding the magnetic Gibbs free energy of carbides, not only the magnetization but also the internal field induction related to the morphology of carbide was taken into consideration. It was observed that there was no pronounced effect of high magnetic field on the precipitation sequence of alloy carbides when specimens were tempered at 700°C, because they were changed into paramagnetic phases at this temperature.

The Microstructure and Properties of Low-Carbon PM Mn-Cr-Mo Steels Sintered under Different Conditions

Abstract The paper presents the effect of sintering conditions on the microstructure and mechanical properties of low-carbon Mn-Cr-Mo PM steels. It was proved there is no effect of tempering temperature on the properties of Astaloy CrL-base steels, sintered at 1250°C in 5%H2-95%N2 mixture as compared with the properties of those sintered at 1120°C. The properties of Astaloy CrM-based steels, sintered at 1250°C in air were comparable or higher to Astaloy CrL-based steels. The addition of lump of ferromanganese was not sufficient for metal oxides reduction. The structure investigation confirmed the earlier observations that Mn-Cr-Mo PM steels have predominantly martensitic or martensitic/bainitic microstructure.

Impact Toughness of 0.3 Mass% Carbon Tempered Martensitic Steels Evaluated by Instrumented Charpy Test

The effect of tempering temperature on the impact toughness of 0.3 mass% carbon martensitic steels with prior austenite grain (PAG) size of about 6 μm and 30 μm were investigated. Instrumented Charpy impact test (ICIT) method was used to evaluate the impact toughness. The tempering temperature of 723K gives the largest difference in the Charpy impact energy at room temperature (RT) between the specimens with two different PAG sizes. Investigation of the test temperature dependence of Charpy impact energy in the 723K tempered steels shows a steep transition at around 200 K for the 6 μm PAG specimen, while it shows a continuous slow transition in a wide range of temperature for the 60 μm PAG specimen. ICIT waveform analysis shows that the fracture propagation energy in stead of the fracture initiation energy mainly controls the temperature dependence of the impact energy. The carbide size distribution in these two specimens was investigated by SEM and TEM. The 60 μm PAG specimen shows the distribution of coarser carbides than does the 6 μm PAG specimen, which seems to be the main reason for the observed difference between them in the Charpy impact energy and the other properties of impact fracture.

Structure–mechanical property relationship in a high strength microalloyed steel with low yield ratio: The effect of tempering temperature

We elucidate here the significance of microstructure, in particular, martensite–austenite constituent, in influencing impact toughness and yield-to-tensile strength ratio in a low carbon low-alloyed steel processed via combination of thermo-mechanical controlled processing and tempering. The objective of the study described here is to explore the impact of tempering temperature on the stability of bainite in the attempt to obtain high strength steel with yield strength greater than 600MPa and yield ratio less than 0.85, together with superior impact toughness. An accompanying objective is to study the striking variation in toughness with tempering temperature, while the strength exhibited insignificant change. The microstructure of the studied steel primarily comprised of fine lath and granular bainite, small fraction of ferrite, together with some martensite–austenite constituent. The morphology of martensite–austenite constituent was granular and stringer-type, and was located between laths or at the bainite/ferrite boundary. With the increase in tempering temperature, the microstructure became coarse and martensite–austenite constituent was decomposed, leading to decrease in tensile strength and impact toughness, while the yield strength continued to remain stable. High strength, good toughness, and low yield ratio was obtained at lower tempering temperature and is attributed to the fine lath-type microstructure and stable martensite–austenite constituent.

Effect of Tempering Temperature on Mechanical Properties and Microstructures of 800MPa Microalloy Low Carbon Bainitic Steel

The effect of tempering temperature on the microstructures and mechanical properties of a microalloy low carbon bainitic steel was investigated by microscopic analysis and testing of mechanical properties. The results show that the microstructures of the tested steel primarily consists of lath bainite, granular bainite, quasipolygonal ferrite and little acicular ferrite at different tempering temperatures. With the tempering temperature increasing, the proportion of lath bainitie decreases, while the volume of granular bainite and quasipolygonal ferrite increases. At the tempering temperatures of 550-650°C and tempering time of 1 hour, the steel was mostly composed of granular bainite, quasipolygonal ferrite and a little lath bainite, which a good combination of strength and toughness can be obtained.

Effect of Tempering Temperature on Mechanical Properties of 40CrMnSiB Steel

40CrMnSiB steel is a new type of B-containing structural steel. To research the effect of tempering temperature on mechanical properties of 40CrMnSiB steel, forging, normalizing and quenching are carried out on material firstly, then temper respectively at 350°C400°C450°C500°C550°C600°C650°C and 700°C. After tempering, mechanical properties are tested. Also the hardness, along a radius of section, of the material after tempering at 300°C is measured and the effect of tempering temperature on mechanical properties of 40CrMnSiB steel is analyzed. The results show that: the mechanical properties of 40CrMnSiB steel is sensitive to temper temperature, properties range a large scale with temper temperature; it has a strength of 1800MPa (or more) with good ductility, toughness and fine comprehensive mechanical properties; the hardness of the material after tempering at 300°C is over 50HRC, hardenability is fine, the main microstructure is martensite.

Effect of Tempering Temperature on the Microstructure and Hardness of a Super-bainitic Steel Containing Co and Al

The effect of tempering temperature, within the range of 400 to 700°C, on the microstructure and hardness of two super-bainitic steels, one as the control parent sample and the other with added Co & Al was investigated. Post-tempering examinations of the super-bainitic samples showed that low temperature tempering cycles (400–500°C) resulted in carbides formation, and some increases in the hardness possibly due to precipitation strengthening in the Co & Al contained steel. Once the tempering temperature increased to 600°C, the hardness plummeted in both steels due to the concurrent coarsening of the bainitic ferrite plates and more precipitation of carbides. At the higher tempering temperature of 700°C, further reduction in the hardness occurred because of the accelerated recovery of ferrite and spheroidization of carbides. This work clearly showed that the super-bainitic steel containing Co & Al had a superior tempering resistance particularly at low tempering temperatures (<500°C) due to reduced carbide precipitation in the presence of Co & Al.

回火温度对高强高韧钢组织及性能的影响

经系列试验，研究了调质过程不同回火温度对高强高韧钢组织及性能的影响。试验表明：在560℃~580℃温度范围内，各项性能指标变化不大；在580℃~670℃温度范围内，随回火温度升高，强度与硬度降低，韧性提高。原因分析：抗拉强度和屈服强度先增大后减小，延伸率先减小后增大，这源于索氏体组织和碳化物的共同作用。 After series of tests, the effects of tempering temperature on the microstructures and properties of steel with high strength and high tenacity during tempering were discussed. The result shows that: various performance indicators show little change in the temperature range of 560C - 580C; with the increase of tempering temperature, strength and hardness decrease and toughness increases in the temperature range 580C - 670C. Reason Analysis: due to the combined action of Sorbite and Carbide, the tensile strength and yield strength first increase and then decrease, on the contrary, the toughness descends first and then increases.

Optimization of the technological conditions of producing thin sheets and strips from corrosion-resistant VNS9-Sh steel

The technological conditions of producing thin sheets and strips from corrosion-resistant VNS9-Sh steel are optimized at the stages of casting, deformation, and heat treatment. The effect of the as-cast phase composition of VNS9-Sh steel on the ductility of the metal during cold rolling and on the mechanical properties of the end products in the form of thin sheets and strips is studied. It is shown that, for the required level of the mechanical properties of sheets and strips to be achieved, the magnetization of as-cast steel samples should be J = 3–10 mV on the scale of an IFSS (MKL) device, which corresponds to 1.5–5% martensite in the as-cast steel. It is also shown that the required level of mechanical properties (σu ≥ 1470 MPa, δ ≥ 12%) is achieved after work hardening of 17–35% and that 40–50% deformation martensite and 50–60% cold-worked austenite exist in a ready strip if the magnetization of as-cast steel samples is 3–10 mV and the strip is subjected to work hardening. The effect of tempering temperature in the range 100–450°C is studied to increase the yield strength of the steel in the form of a ready strip at low degrees of cold deformation (17–25%). The increase in the yield strength without a decrease in the ultimate tensile strength is maximal after tempering at 125°C for 1 h due to strain aging processes.

Effect of tempering temperature on the toughness of 9Cr–3W–3Co martensitic heat resistant steel

Effect of tempering temperature on the toughness of 9Cr–3W–3Co martensitic heat resistant steel was studied on the basis of the microstructures after normalized at 1100°C for 1h and then tempered at 740–780°C for 3h. With increasing tempering temperature from 740°C to 780°C, the absorbed energy of the 9Cr–3W–3Co steel increased greatly from 26J to 115J. The change of the toughness with increasing tempering temperature was attributed to the softening of the base metal and the increase of the crack propagation path. The softening of the base metal was caused by the decrease of the dislocation density and the supersaturation of the interstitial atoms. The reason for the increase of the crack propagation path was that the length of the large angle boundaries increased and then the propagation direction of the cleavage crack was deflected more frequently.

Microstructure and XRD of Ductile Iron Using Annealing-Tempering Heat Treatment Process

In this present study, the effect of tempering temperature of annealing-tempering combination processes, on microstructure as well as exploring the phase constituents of ductile iron through XRD analysis were performed. Ductile iron produced through conventional CO2sand casting method was performed annealing-tempering heat treatment processes by using change furnace method. Three different temperatures were investigated ranging from (i) 250 °C, (ii) 300 °C and (iii) 350 °C for 1.5 hours respectively. Standard metallographic observation and XRD analysis were done to characterize the microstructure and the constituents respectively. It is found that the graphite structure exist in both treated and untreated samples. Pearlitic structure was formed in the microstructure for heat treated samples. Ferritic-pearlitic matrix structure surrounding the graphite nodule has been shown in as-cast sample. Annealing-tempering process does not change the BCC ferrite peak in (200), (211), (220) and (310) planes shown in as-cast.

Effect of tempering temperature on microstructure and mechanical properties of AISI 6150 steel

Effect of tempering temperature on the microstructure and mechanical properties of AISI 6150 steel was investigated. All samples were austenitized at 870 °C for 45 min followed by oil quenching, and then tempered at temperatures between 200 and 600 °C for 60 min. The results show that the microstructure of tempered sample at 200 °C mainly consists of tempered martensite. With increasing the tempered temperature, the martensite transforms to the ferrite and carbides. The ultimate tensile strength, the hardness and the retained austenite decrease with increasing tempered temperature, and 0.2% yield strength increases when the temperature increases from 200 to 300 °C and then decreases with increasing the temperature, but the elongation and impact energy increase with increasing the tempering temperature.

Effect of tempering temperature on isothermal decomposition product formed below Ms

Recent papers have shown that bainitic ferrite plates can be produced by transformation at low temperatures, resulting in enhanced mechanical properties of martensitic steels and increased resistance to tempering. To that end, experimental investigations were performed on the formation of the microstructure in SAE 9254 steel during isothermal heat-treatment below the martensite start (Ms) temperature. After the isothermal heat-treatment, the same steel was subjected to tempering at various temperatures. Vickers microhardness measurements were performed on the isothermally heat-treated and tempered samples, and microhardness values for the samples were compared with those for quenched and tempered samples of the same steel. All the isothermally treated samples contained the martensite (αμ), bainitic ferrite (αb), and retained austenite (γr) phases. The retained austenite blocks (γb) decomposed in the samples tempered at 400°C. A significant decrease in the microhardness value for the sample heat-treated at 270°C can only be observed after the sample was tempered at 450°C, because bainite was the predominant phase in the microstructure, which self-tempers as it forms.

Effect of tempering temperature and microstructure on the corrosion behavior of a tempered steel

In this study, a tempered martensitic matrix was obtained in a low carbon steel, by applying austenization, quenching and tempering heat treatments. After austenization at 1000°C for 30 minutes, steel samples were quenched in water and then tempered at 200, 540 and 600°C for 30 minutes. Hardness measurements were done and then immersion tests were carried out in a 3.5 wt % NaCl solution for periods ranging between 1–7 days. Weight losses of the samples were determined after each immersion period and microstructural studies were performed on the corroded surfaces. Corrosion rates were calculated using weight loss data and verified by potentiodynamic tests. Results revealed that corrosion behavior of the experimental steels was directly affected by tempering temperature, hardness and microstructure.

マルテンサイト鋼の曲げ加工性におよぼす焼戻し温度の影響

Effect of tempering temperature on bendability of ultra-high-strength steel sheets with fully martensitic structure having tensile strength ranging from 1100 to 1650 MPa was investigated. In this study, cold-rolled steel sheets with carbon content ranging from 0.15 to 0.4% were quenched from austenite region and subsequently tempered at various temperatures below 500°C. Bendability seriously deteriorated at tempering temperature around 300°C when the tempered martensite embrittlement occurs. Under the same tensile strength level, steel sheets tempered below 200°C were superior in bendability to those tempered at even over 400°C when the ductility recovered. Minimum bending radius was well correlated with the elongated cementite particle number density in the tempered martensite matrix. In the cross section of the bent specimens, cracks along the elongated cementite particles were frequently observed. These results suggested that deterioration in bendability in steels tempered at higher temperature over 200°C was caused by the acceleration of crack propagation during bending deformation due to the elongated cementite precipitates. On the other hand, bendability of fully martensitic steels could not be clarified by the uniform elongation obtained by a tensile testing. Uniqueness of the material deformation behavior in bending was also discussed from the viewpoint of plastic working theory.

Microstructure evolution of an ultra-high strength metal alloy with tempering temperature

Optical microscopy (OM) and transmission electron microscopy (TEM) were used to investigate the effect of tempering temperature on the experimental extra-high carbon steels. It is found that tempering reaction can reduce austenite content and influence the stability of the austenite. As-normalized microstructure is a mixture of twinned martensite and retained austenite. Tempered at 250 °C for 2 h, lath martensite can occasionally be found nearby the diffusionally decomposed austenite area. It also is found that tempering at 650 °C for 2 h, nanoparticles of carbides precipitate in the martensite and decomposed austenite.

Mechanical property and irradiation damage of China Low Activation Martensitic (CLAM) steel

China Low Activation Martensitic (CLAM) steel is being studied to develop the structural materials for a fusion reactor, which has been designed based on the well-known 9Cr1.5WVTa steel. The effect of tempering temperature on hardness and microstructure of CLAM steel was studied. The strength of CLAM steel increased by adding silicon, and the ductility remained constant. Conversely, while CLAM steel maintained good ductility with the addition of yttrium, its tensile strengths were greatly degraded. Behaviors under electron irradiation of CLAM steel were examined using the high voltage electron microscope. Electron irradiation at 450°C formed many voids in CLAM steel with basic composition, whereas CLAM with silicon steel did not change the microstructure significantly.

The Tempering on Microstructure and the Yield-to-Tensile Ratio of High Performance Steels

The effects of tempering temperature on the microstructure and mechanical properties of 600MPa grade low carbon bainitic steel were investigated. The cause for the microstructure evolution has been investigated and the best tempering process was chosen to decrease the yield ratio of the steel. The influence of tempering process on the yield-to-tensile ratio of steels has been investigated by the aid of optical microscopy, SEM and XRD. The results show that after the TMCP processing the microstructure of steels mainly consist of lath martensite and bainite. The bainite and martensite have been refined markedly after the relaxation processing, therefore the properties of steels has been improved evidently. In order to decrease the yield-to-tensile ratio the steels underwent high temperature tempering. It has been found that during the tempering with the tempering temperature increased the yield-to-tensile ratio of steels decreased. The XRD and EBSD results show tempering temperature has considerable influence on the yield strength, but the influence on the tensile strength is not considerable. With the increase in tempering temperature, the low temperature toughness of steel can be improved considerably. The yield ratio of the steel was reduced after tempering at 650 °C and higher temperatures due to reversed austenitic phase transformation.

Effect of tempering temperature on failure resistance of wheel steel with a structure of martensite and lower bainite

The effect of wheel steel structural condition on mechanical properties with static and impact loading is studied. It is shown that steel with a lower bainite structure with low-temperature tempering has greater work for failure than steel with a martensitic structure. The superiority of a bainitic over a martensitic structure on toughness in impact tests is established. A difference is revealed in the brittle failure mechanism for martensitic and bainitic high-carbon steel.

Effect of Tempering on Mechanical Properties and Microstructure of a 9% Cr Heat Resistant Steel

Effect of tempering temperature ranged from 400 to 720°C on mechanical properties and microstructure of a P92-type creep resistant steel was investigated. The hardness value of 400 HB, which was obtained after solution treatment, increased to 430 HB with increasing the tempering temperature to 525°С. Further increase in the tempering temperature resulted in gradual decrease in hardness, which approached a level of about 220 HB after tempering at 720°С. The equiaxed particles of MX-type carbonitrides with a size of about 30 nm were precipitated randomly after tempering under all conditions. At temperatures below 525°C, the tempered martensite lath structure (TMLS) was characterized by a random distribution of fine M3C-type carbides and MX-type carbonitrides. The precipitation of M23C6 was observed after tempering at T ≥ 525°C. At 525°C, the M23C6 carbides appeared as thin films on high-angle boundaries (HAB), while M23C6 particles having almost equiaxed shape and located on various boundaries including low-angle lath boundaries precipitate at higher temperatures.