Increase In Quenching Temperature Research Articles

Effect of quenching temperature on the austenite stability and mechanical properties of high-strength air-cooled TRIP steel prepared with hot-rolled C–Si–Mn sheets

This paper systematically studies the effect of quenching temperature on the microstructure evolution and the relationship between the microstructure and mechanical properties of air-cooled TRIP steel prepared with C–Si–Mn hot-rolled sheet. The results indicate that when the quenching temperature is lower than (200 °C) or close to (250 °C) the Ms temperature, the martensite transformation mainly occurs during quenching or at early stage of air cooling. When the quenching temperature reaches 300 °C, lathy bainite begins to form. As the quenching temperature increases, the morphology of bainite is transformed from lathy to granular. Bainite transformation during air cooling can promote the C enrichment in austenite, thus improving the thermal stability of the austenite. However, martensite transformation also occurs during subsequent air cooling, and the start temperature of martensite transformation first decreases and then increases with the increase of quenching temperature from 300 °C to 450 °C. The yield and tensile strength of TRIP specimens first decrease and then increase, while the retained austenite content, elongation and product of strength and elongation (PSE) first increase and then decrease. When the quenching temperature is 400 °C, the best elongation and PSE are obtained. The best elongation of 400TRIP specimen is mainly attributed to its highest content and suitable mechanical stability of retained austenite, which is favorable for the expansion of the TRIP effect range. The TRIP specimens prepared with hot-rolled sheet all exhibit ultra-high tensile strength (over 1050 MPa), which is related to the ultrafine ferrite grains, martensite transformation during air cooling and TRIP effect of retained austenite.

Effect of Heat Treatment on Microstructure and Properties of Quenched and Tempered Steel with High Vanadium Contents

After heat treatment, the microstructure of quenched and tempered (Q&T) steel with high vanadium (V) content was characterized using metallographic and scanning electron microscopes (SEM). The proto-austenite grains of the tested steel were compared at different quenching temperatures, and the precipitation behavior of precipitates and matrix microstructure characteristics at various tempering temperatures were studied. Tensile properties and low-temperature impact toughness of the tested steel with different heat treatments were measured using an electronic universal testing machine and an impact testing machine. The findings indicate that as the quenching temperature increases, the size of the proto-austenite grains gradually increases. When the quenching temperature surpasses 920 °C, the size of the proto-austenite grains obviously increases. With a constant tempering temperature, an increase in quenching temperature results in a decrease in the size of precipitates. With a constant quenching temperature, an increase in tempering temperature results in an increase in the size of precipitates. Therefore, the tested steel quenched at 920 °C for 1 hour and then tempered at 630 °C for 1.5 hours would obtain excellent comprehensive mechanical properties, with a tensile strength of 1233 MPa and a low-temperature impact value of 64 J.

Effect of heat treatment on microstructure and properties of modified hypereutectic high chromium cast iron

Abstract The effect of heat treatment on the microstructure, hardness and wear resistance of modified hypereutectic high chromium cast iron (HCCI) was investigated. The results show that the quenching treatment partially dissolves the edges of the primary carbides, and the sharp corners become rounded and blunt. As the quenching temperature increases, the carbide re-dissolves into the matrix, and the hardness and wear resistance first increase and then decrease. The hardness and wear resistance are the best when quenched at 1000 °C. After tempering, the martensite is transformed into tempered martensite, and the precipitation of secondary carbides increases. As the tempering temperature increases, the secondary carbides gradually become coarser. When the tempering temperature is 500 °C, the hypereutectic HCCI shows the highest hardness and the best wear resistance. When tempered at 400 °C, hypereutectic HCCI shows the best erosion and wear resistance.

The Effect of Ni Interlayer on the Hot-Rolled and Quenched Stainless Steel Clad Plate.

The vacuum hot-rolled SUS314/Q235 stainless steel clad plate has many drawbacks including serious interface alloy element diffusion, stainless steel cladding’s sensitization, and carbon steel substrate’s low strength. In this study, the comprehensive properties were systematically adjusted by changing the thickness of the Ni interlayer (0, 100, 200 μm) and the quenching temperature (1000~1150 °C). The results showed that the Ni interlayer can obviously hinder the diffusion of carbon element, so as to achieve the purpose of eliminating the decarburized layer and reducing the carbon content of the carburized layer. Meanwhile, the perfect metallurgical bonding between the substrate and cladding can be obtained, effectively improving the stainless steel clad plate’s tensile shear strength and comprehensive mechanical properties, and significantly reduce the brittleness of the carburized layer. As the quenching temperature increases, the grains coarsening of carbon steel and stainless steel became more and more serious, and the sensitization phenomenon and the thickness of the carburized layer are gradually decreased. The stainless steel clad plate (Ni layer thickness of 100 μm) quenched at 1050 °C had the best comprehensive mechanical properties. Herein, the interface shear strength, tensile strength and the fracture elongation reached 360.5 MPa, 867 MPa and 16.10%, respectively, achieving strengthening and toughening aim. This is attributed to the disappearance of the sensitization phenomenon, the grain refinement and the lower interface residual stress.

Quench Temperature-Dependent Phase Transformations During Nonisothermal Partitioning

An attempt has been made to estimate the amount and composition of different phases formed during the simulated quenching and nonisothermal partitioning (Q&P) process in a dilatometer by matching the experimental dilation data with empirically determined dilation curve. The result highlights the carbon enrichment of austenite, as well as its partial transformation to secondary martensite and/or bainite, during the partitioning step. Also, an increase in quench temperature (QT) led to enhanced bainite or secondary martensite formation, as a result of reduced carbon enrichment of remaining austenite. Further Q&P experiments on bulk samples were carried out to understand the dependence of carbon diffusion and subsequent microstructure evolution with QT. Although the change in experimentally obtained retained austenite (RA) content with QT corroborates with the existing model predictions, the maximum amount of RA was observed at QT lower than predicted. The half-thickness of RA films increased with increasing QT, which substantiates the theoretical prediction of the diffusion distance of carbon atoms in austenite.

The effect of TiN inclusions on the fracture mechanism of 20CrMnTi steel with lath martensite

This study aims to investigate the effect of TiN inclusions on the fracture mechanism of 20CrMnTi steel with martensite. Size of martensite packets, blocks and TiN inclusions were characterized, and the room-temperature tensile properties, impact toughness and fracture toughness were tested of 20CrMnTi steel quenched at different temperatures. The effects of TiN inclusions on the impact toughness and fracture toughness were investigated according to the Hall-Petch relationship. The results show that, TiN inclusions are high temperature stable phases which insoluble to the matrix, mostly squared in shape and dispersed. The impact toughness and fracture toughness of 20CrMnTi steel decrease with increasing sizes of the initial austenite grains, martensite packets and blocks as the quenching temperature increases. Interestingly, the TiN inclusions strongly affect the toughness of the 20CrMnTi steel in the fracture and the fine-grained sample has a better toughness. Under high-stress concentrations, TiN inclusion particles can initiate cleavage cracking.

Effect of Quenching Temperature on Microstructure and Properties of Al-Bearing High-Boron High-Speed Steel

Microstructure and properties of the alloys could be changed by heat treatment process. In this work, effect of quenching temperature on the microstructure of Al-bearing high-boron high-speed steel (AB-HSS) was investigated by means of optical microscopy, scanning electron microscopy and X-ray diffraction. Hardness and wear resistance of AB-HSS at different quenching temperatures were tested by rockwell hardness tester, microhardness tester and wear tester, respectively. The experimental results indicate that the microstructure of as-cast AB-HSS is mainly composed of pearlite, ferrite, M2B-type boride and M23(C, B)6-type borocarbide. After quenched treatment, the matrix transforms into the martensite and the type of boride has no obvious change. The morphology of boride changes from continuous network and fish-bone to isolate shape and granular distribution. As quenching temperature increases, the hardness of alloy increases. The hardness reaches 65.1 HRC when quenching temperature is 1110 °C. The wear resistance of alloy gradually increases with the increase in quenching temperature. The wear resistance is the best when the quenching temperature reaches 1110 °C.

VOLUMETRIC CHANGES AT HEATING IN STEEL 60Si2CrV SUBJECTED TO Q&P TREATMENT

The paper presents results of the investigation of phasestructural transformations and volumetric changes that occur during heating in high-silicon spring steel 60Si2CrV subjected to Q&P(quenching and partition) treatment. Chemical composition of the steel was: 0.53 % C; 1.46 % Si; 0.44 % Mn; 0.95 % Cr; 0.10 % V; 0.016 % S; 0.013 % P. Steel samples were subjected to Q-n-P treatment as follows: a) austenitization at 880 °C; b) quenching with the cooling stop at 120, 160, 200 and 240 °C; c) subsequent holding at 220, 250 and 300 °С with duration from 10 to 3600 s; d) final cooling in water. The volumetric changes during heating were studied using an optical differential dilatometer at a heating rate of 1 K/s. As a reference, a sample of the same steel stabilized by high tempering was used. The amount of retained austenite was determined by X-ray diffraction using a diffractometer DRON-3 with Fe-radiation. It is found that on the heating curves of Q&P samples, the sections corresponding to different transformations during tempering are clearly identified. On dilatograms of the Q&P samples, dilatometric effect corresponding to the second transformation during tempering (270 – 430 °C) was found to be increased dramatically, indicating an increase in retained austenite amount compared to the quenched state as a result of Q&P treatment (as confirmed by Xray study). At the same time, value of the effect corresponding to the third transformation during tempering was found to be decreased. To obtain the maximum amount of retained austenite in 60Si2CrV steel, the partitioning temperature should be of 260 – 300 °С, while the quenching completion temperature should be of 160 – 240 °С. The amount of retained austenite rises substantially as the quenching temperature increases. Duration of the partitioning stage should be selected taking into account the extreme character of austenite dependence on the partitioning time. As a result of the work, an effective applicability of the dilatometric method for analyzing the steel structural state and choosing the optimal mode of Q&P treatment was demonstrated.

Microstructure and Properties of Fe–Cr–B–Al Alloy After Heat Treatment

By means of optical microscope, scanning electron microscope, X-ray diffraction, energy dispersive spectrometer, Rockwell and Vickers hardness tester, and wear tester, the microstructure and properties of Fe–10Cr–1B–4Al alloy quenched in different temperature has been studied. The results show that the microstructure of as-cast Fe–10Cr–1B–4Al are composed of pearlite, ferrite and the eutectic borocarbide which shows a network distribution along grain boundaries. The eutectic borocarbides are composed of M7(C, B)3, M2(B, C) and M23(C, B)6. As the quenching temperature increases, the network structure of eutectic borocarbide breaks, but the type of eutectic borocarbide has no obvious change, and the matrix structure changes gradually from ferrite to pearlite. As the quenching temperature increases, the macro-hardness and the matrix micro-hardness of Fe–10Cr–1B–4Al alloy increases gradually. The macro-hardness and matrix micro-hardness of alloy reach the highest value of 45.7 HRC and 388.1 HV, respectively when the quenching temperature is 1150 °C. The hardness of alloy decreases slightly when the quenching temperature is too high. While quenching at 1150 °C, the alloy has the highest wear resistance and good comprehensive properties.

Effect of Bath Temperature on Cooling Performance of Molten Eutectic NaNO3-KNO3 Quench Medium for Martempering of Steels

Martempering is an industrial heat treatment process that requires a quench bath that can operate without undergoing degradation in the temperature range of 423 K to 873 K (150 °C to 600 °C). The quench bath is expected to cool the steel part from the austenizing temperature to quench bath temperature rapidly and uniformly. Molten eutectic NaNO3-KNO3 mixture has been widely used in industry to martemper steel parts. In the present work, the effect of quench bath temperature on the cooling performance of a molten eutectic NaNO3-KNO3 mixture has been studied. An Inconel ASTM D-6200 probe was heated to 1133 K (860 °C) and subsequently quenched in the quench bath maintained at different temperatures. Spatially dependent transient heat flux at the metal–quenchant interface for each bath temperature was calculated using inverse heat conduction technique. Heat transfer occurred only in two stages, namely, nucleate boiling and convective cooling. The mean peak heat flux (q max) decreased with increase in quench bath temperature, whereas the mean surface temperature corresponding to q max and mean surface temperature at the start of convective cooling stage increased with increase in quench bath temperature. The variation in normalized cooling parameter t 85 along the length of the probe increased with increase in quench bath temperature.

Improved preparation technology of color-tunable long afterglow phosphors Sr1.94-xCaxMgSi2O7: Eu2+0.01, Dy3+0.05

Tetragonal long afterglow silicates, Sr1.94-xCaxMgSi2O7: Eu2+0.01, Dy3+0.05 (x=0, 0.388, 0.776, 1.164, 1.552, 1.94), are successfully synthesized by high-temperature solid-state reaction at 1300°C and 1350°C, respectively. Addition of excess silicon dioxide can reduce the sintering temperature from 1350°C to 1300°C, and photoluminescence performances and afterglow properties are improved. All samples have the same tetragonal structure, but the diffraction peaks shift to higher angles when smaller Ca2+ ions gradually substitute Sr2+ sites in the host. The reduced interplanar spacing leads to increscent crystal field strength. As a result, a red shift phenomenon is observed in the emission spectra with the increase of Ca2+ content. The afterglow emission bands also change from 466 to 529nm when the proportion of Ca2+ ions increases in the host. Both luminescence and afterglow colors can continuously vary from blue to green by adjusting the Ca/Sr ratio in the host, and emission wavelength is linear with the concentration of Ca2+(x). With increasing the concentration of Ca2+, the thermal stability is improved and the quenching temperature increases, but the afterglow properties deteriorate.

Microstructure evolution, fracture and hardening mechanisms of quenched and tempered steel for large sized bearing rings at elevated quenching temperatures

Based on 42CrMo steel, a steel with a higher C and Ni content is developed for use in large sized bearing rings. The impact energy and hardness of the quenched and tempered steel increase with the quenching temperature, but then decrease when the temperature is above 925 °C. When the temperature is below 925 °C, some larger M23C6-type carbides (with average diameters of 255.6 μm) exist in the quenched and tempered microstructure. The number of carbides is reduced as the quenching temperature increases. At the same time, the fracture modes change from microvoid coalescence and quasi-cleavage to microvoid coalescence. The number of round quasi-cleavage fractures, which are formed around the carbides, decrease as the number of carbides decrease. The existence of larger M23C6-type carbides leads to round quasi-cleavage fractures and decrease the impact energy. The precipitation strengthening of M23C6-type carbides increases the hardness at a quenching temperature of 925 °C.

Effects of synthesis conditions on the structural, stability and ion conducting properties of Li0.30(La0.50Ln0.50)0.567TiO3 (Ln=La, Pr, Nd) solid electrolytes for rechargeable lithium batteries

The structure, thermal stability, morphology and ion conductivity of titanium perovskites with the general formula Li3xLn2/3−xTiO3 (Ln=rare earth element; 3x=0.30) are studied in the context of their possible use as solid electrolyte materials for lithium ion batteries. Materials are prepared by a glycine–nitrate method using different sintering treatments, with a cation-disorder-induced structural transition from tetragonal to cubic symmetry, and are detected as quenching temperature increases. SEM images show that the average grain size increases with increasing sintering temperature and time. Slightly higher bulk conductivity values have been observed for quenched samples sintered at high temperature. Bulk conductivity decreases with the lanthanide ion size. A slight conductivity enhancement, always limited by grain boundaries, is observed for longer sintering times. TDX measurements of the electrolyte/cathode mixtures also show a good stability of the electrolytes in the temperature range of 30–1100°C.

Internal Friction Study of Vacancy Hardening in B2 Fe Al Alloys

nternal friction behaviour of B2 FeAl alloys has been examined to reveal the correlation of the microplasticity and thermal vacancies. The internal friction peak for Fe60Al40 appears at around 550 K, and the peak height increases with increasing quenching temperature. The curves of internal friction against the strain amplitude shift to larger strain amplitude as the quenching temperature increases. Analysis of the amplitude-dependent internal friction provides the plastic strain of the order of 10-9 as a function of effective stress on dislocation motion. It is found that the microflow stress at the plastic strain of 1×10-9 increases linearly with the square root of the net peak height. Remarkably, the microflow stress decreases with rising temperature but turns to increase above 500 K when measured after holding for 1 h at test temperatures. The anomalous increase in the microflow stress is caused by the creation of thermal vacancies at intermediate temperatures.

Molecular dynamics simulations of a molten Cu55 cluster embedded in face-centred cubic bulk during

The structural evolution of a molten Cu55 cluster embedded in face-centred cubic （FCC） bulk is simulated by molecular dynamics method based on the embedded-atom method potential through mean square displacement, pair analysis indices, and the average energy of atoms. The simulated results show that final structure of the embedded Cu55 cluster mainly presents local FCC structure at the quenching temperatures. During solidification, the atoms continuously interchange their positions, and the rearrangement of atom positions is sensitive to the temperature change. As the quenching temperature increases, diffusion abilities of the atoms increase. At 100—500 K, the formed FCC structures are stable, whereas at 700—1100 K, the local structures of the clusters fluctuate with time step increasing.

Modeling arrested cluster growth in quenched nanoparticle solutions

We have carried out numerical simulations on a model of phase separation in a binary mixture in the presence of a third, surface-active component. Based on this model we study phase separation in a quenched solution of gold nanoparticles with dodecane thiol ligands in a mixed solvent of butanone and toluene. In our model gold nanoparticles-butanone correspond to the generic binary mixture, while toluene is modeled as a surface-active third component. Our results show that the surface-active component acts as an inhibitor for the phase separation process but its effect decreases with the increase in quench temperature. Simulation results are consistent with two major findings in recent experiments: (a) growth of gold nanoparticle clusters gets arrested at late times and (b) the saturation value of the cluster size is smaller at lower temperatures of quench.

A Study of Boron-Bearing Wear-Resistant Alloy Steel Liner

This article reports the results of an experimental program aimed at improving ball mill availability by increasing the wear resistance of ball mill liners. The ball mill liners made from the wear-resistant alloy steel containing 0.8–2.0 wt%B (viz. boron alloy steel) have been developed. The effects of quenching temperature on the microstructural modification, mechanical properties, and wear resistance of boron alloy steel have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, impact tester, hardness tester, and impact wear tester. The results show that the hardness of boron alloy steel increases, and impact toughness has no obvious change, when the quenching temperature increases. When the quenching temperature reaches 1000°C, the matrix of boron alloy steel transforms into the lath martensite, and there is excellent wear resistance. After quenching at 1000°C and tempering at 220°C, boron alloy steel liners have excellent wear resistance and do not break in the use. Its servicing cycle is 1.6 times longer than that of high manganese steel liner. Boron alloy steel liner does not contain valuable alloy elements and has simple production process and low production cost.

Effect of quenching temperature on the microstructure and mechanical properties of Fe–B–Ti alloy

Abstract The effects of quenching temperature on the microstructure and mechanical properties of a cast Fe – B – Ti alloy containing 2.0 wt.% of boron and 1.0 wt.% of titanium were investigated. No clear influence on microstructure has been observed unless the quenching temperature is above 900 °C. As the quenching temperature exceeds 950 °C, most of the boride networks are broken and a large quantity of irregular borides appears. When the quenching temperature reaches 1050 °C, the networks disappear completely. The mechanical properties of the cast Fe – B – Ti alloy begin to improve when the quenching temperature increases. The hardness, impact toughness and bend strength have no obvious change when the quenching temperature exceeds 1000 °C. The cast Fe – B – Ti alloy quenching at 1000 °C has excellent comprehensive mechanical properties, its hardness, bend strength and impact toughness are 58.3 HRC, 2.39 GPa, 17.5 J cm−2 respectively.

Mechanical Properties of Cr2AlC Ceramics

Dense and predominantly single‐phase samples of Cr2AlC, together with a trace amount of Cr7C3, were fabricated by hot pressing of a mixture of chromium, aluminum, and graphite powders at 1400°C for 1 h. The hardness, Young's modulus, flexural strength, and compressive strength of Cr2AlC samples were 5.2, 288 GPa, 483±29, and 1159±23 MPa, respectively, which are comparable with those of Ti3AlC2 and Nb2AlC. The material exhibits good damage tolerance. For indentation loads up to 50 N, the post‐indentation flexural strengths decrease by approximately 10% and by 31% for a load of 100 N. The flexural strengths of Cr2AlC samples quenched from 300°C to room temperature decrease from 483 to 455 MPa, while the retained strengths decrease quickly to 199 MPa when the quench temperature increases to 500°C. A further increase in quench temperature to 700°, 900°, and 1100°C results in a small reduction of strength.

Glass ceramic foams from coal ash and waste glass: production and characterisation

Lightweight glass ceramic foams have been produced from a mixture of silicate wastes, namely 20 wt-% coal pond ash and 80 wt-% bottle glass cullet. A powder sintering route with the incorporation of 2 wt-%SiC as foaming agent was used. The pore morphology achieved under different sintering conditions was investigated in detail using X-ray microtomography. The apparent density of the foams ranged from 0·2 to 0·4 g cm−3, and the porosity ranged from 70 to 90%. Other variables, such as pore wall thickness, pore size and roundness, all behaved consistently with sintering temperature. The optimum sintering temperature was found to be in the range 1000–1050°C, at which porosity was about 75% and was the most uniform. Foams produced under this condition exhibit satisfactory compressive strength of about 1·5 MPa and show relatively high thermal shock resistance, with compressive strength gradually decreasing as quenching temperature increases.