Optimal Heat Treatment Process Research Articles

Optimization of Heat Treatment Process for Mg-11Gd-2Y-3Sm-0.5Zr Alloy

Optimization of Heat Treatment Process for Mg-11Gd-2Y-3Sm-0.5Zr Alloy

Review of Scientific Results Obtained During Production of ITER TF and PF Conductors in Russia

The Russian Scientific R&D Cable Institute was obliged to produce and to deliver 20% toroidal field (TF) conductors and 20% poloidal field (PF) cables for the ITER magnet system. The task has been completed in October 2015. This work was a great technological challenge in the development of tricky technologies. Development of manufacturing processes was accompanied by extensive scientific studies directed to an improvement of technologies and a search of causes resulting in change of cables and conductors properties during manufacturing and testing. In this paper, we present the extended review and summary of results obtained for Russian superconductors that permitted improving technologies and finding out the reasons of changes of properties of cables and conductors during manufacturing and testing. The study of rotation and untwisting of TF cables during insertions into jackets allowed developing the model describing the rotation process and suggesting the device which keeps untwisting within demanded levels. Analyses of mandatory SULTAN high-field electromagnetic tests of PF and TF conductors from Russia confirmed good quality and adequacy of manufacturing processes. Micrographic studies of Nb 3Sn strands before and after SULTAN tests permitted qualitatively understanding the reason for the stability of RF TF conductor behavior during multiple electromagnetic and thermal cycling. Statistical studies of residual resistance ratio (RRR) of Nb 3Sn and NbTi strands permitted tracking of its degradation during manufacturing processes and SULTAN tests. The optimal heat treatment process for Nb 3Sn conductors has been confirmed after RRR statistical study. The hydraulic performance has been measured in the short samples of TF conductor. By using the parameters obtained, it is possible to predict hydraulic performance of helium flow in a conductor at any temperature. These results led to deeper understanding and to improving manufacturing processes and quality of TF and PF conductors for the ITER magnet system and could be useful for suppliers of superconducting cables and conductors using ITER-like technologies.

Study on Heat Treatment of the C-276/Q235-B Bimetallic Composite Plate

For the problem that stress relief annealing has a great effect on corrosion resistance and mechanical properties of the C-276/Q235-B bimetallic composite plate, the microstructure and mechanical properties of the C-276/Q235-B bimetallic composite plate at different heat treatment processes were investigated in the present investigation. The results showed that after 560°C,580°C and 600°C heat treatment, the tensile strength of composite plate was in 515-530MPa and elongation rate was in 25.6-33%, which could meet the requirements for industries. Corrosion tests were conducted according to A and B methods of ASTM G28 standard, corrosion resistance of composite plate after 560°C, 580°C and 600°C heat treatment exhibited a small difference with supplied C-276 alloy. Microstructure of composite plate after 580°C heat treatment exhibited a single austenite without intermediate phase and after 650°C heat treatment with small amounts of intermediate phase. The optimal heat treatment process for the C-276/Q235-B bimetallic composite plate was air cooling after 4 h heat treatment at 580°C.

Failure Analysis and Study on Heat Treatment Process of Grate Bars Used in Sintering Trolley

The as-cast grate bar structure used in sintering trolley is primarily comprised of austenite and eutectic (eutectic austenite and eutectic carbide).The austenite is dendrite, while the carbides are reticular and chrysanthemum-like. The failed grate bar structure primarily consists of ferrite, carbide, martensite and residual austenite; cavity shrinkage and shrinkage porosity exist in the structure, and the fracture exhibits typical cleavage fracture characteristics. The primary means of failure are abrasion and fracture. The secondary carbides precipitated in the sample (quenching (1050°C+2.5h)+ tempering (390°C+2.5h)) and the other one (quenching (1050°C+2.5h)+ tempering (420°C+2.5h) ) are dispersed and refined. Compared with the as-cast one, their relative abrasion resistance performances respectively are 0.8645 and 0.8752.The values of hardness and impact toughness of the samples heat-treated are greater than those of the as-cast grate bar. The optimum heat treatment process is as follows: quenching (1050°C,2.5h) + tempering (390°C~420°C,2.5h)

Microstructure and mechanical properties of Mg–6Gd–3Y–0.5Zr alloy processed by high-vacuum die-casting

GW63K (Mg–6Gd–3Y–0.5Zr) magnesium alloys were prepared successfully by high-vacuum die-casting. Effects of fast shot speed and vacuum level on the grain size and mechanical properties of this alloy were studied. Microstructure of the alloys was analyzed by SEM, EDX and optical microscope (OM). The effect of heat treatment on high vacuum die-casting (HVDC) GW63K alloy was also studied. The results indicate that with the increase of fast velocity, the tensile yield strength hardly changes, but the elongation first increases, then decreases. The optimum heat treatment process is solution treatment at 748 K for 2 h and aging at 473 K for 80 h. Under this condition, GW63K magnesium alloy exhibits a maximum tensile strength and elongation of 308 MPa and 9.45%. There is significant correlation between ductility and the presence of external solidified cells (ESCs). The as-cast GW63K alloy consists of α-Mg and Mg24(Gd,Y)5 particles. After heat treatment, Gd and Y atoms dissolve into α-Mg matrix.

In situ neutron diffraction analysis of stress-free d-spacing during solution heat treatment of modified 319 Al alloy engine blocks

Aluminium alloy engine blocks have successfully replaced ferrous materials in order to maximise weight savings and improve vehicle fuel efficiency. However, the development of an optimal heat treatment process is required to improve engine block casting integrity and prevent potential problems such as in-service cylinder distortion. Optimisation of heat treatment parameters requires an in-depth study to determine how residual stresses are relieved with time during solution heat treatment. In order to perform this analysis, however, in situ neutron diffraction must first be carried out on stress-free samples of the same composition and processing history as the engine blocks to account for factors such as thermal expansion and changes in lattice parameter due to dissolution of secondary phases. The results from this study suggest that thermal expansion caused the largest change in d0 spacing, while prolonged exposure at the solutionising temperature resulted in relatively small changes in {311} and {331} d0 spacing due to phase dissolution.

Heat treatment effect on microstructure, hardness and wear resistance of Cr26 white cast iron

High chromium cast iron(HCCI) is taken as material of coal water slurry pump impeller, but it is susceptible to produce serious abrasive wear and erosion wear because of souring of hard coal particles. The research on optimization of heat treatments to improve abrasive wear properties of HCCI is insufficient, so effect of heat treatments on the microstructure, hardness, toughness, and wear resistance of Cr26 HCCI is investigated to determine the optimal heat treatment process for HCCI. A series of heat treatments are employed. The microstructures of HCCI specimens are examined by using optical microscopy and scanning electron microscopy. The hardness and impact fracture toughness of as-cast and heat treated specimens are measured. The wear tests are assessed by a Type M200 ring-on block wear tester. The results show the following: With increase of the quenching temperature from 950 °C to 1050 °C, the hardness of Cr26 HCCI increased to a certain value, kept for a time and then decreased. The optimal heat treatment process is 2 h quenching treatment at 1000 °C, followed by a subsequent 2 h tempering at 400 °C. The hardness of HCCI is related to the precipitation and redissolution of secondary carbides in the process of heat treatment. The subsequent tempering treatment would result in a slight decrease of hardness but increase of toughness. The wear resistance is much related to the “supporting” effect of the matrix and the “protective” effect of the hard carbide embedded in the matrix, and the wear resistance is further dependent on the hardness and the toughness of the matrix. This research can provide an important insight on developing an optimized heat treatment method to improve the wear resistance of HCCI.

Microstructure and Mechanical Properties of a Spray-Formed Superalloy

The microstructural evolution and mechanical properties of a spray-formed superalloy were studied in this paper. Based on a better understanding of the microstructural evolution of the spray-formed superalloy during solution treatment, an optimum solution treatment process was obtained, namely, at 1,140 °C for 6 h, and air cooling (AC). The effects of the ageing treatments on the mechanical properties of the post-solution-treated spray-formed superalloy were evaluated using ageing harden curves and tensile testing. The results indicated that the maximum hardness value was achieved at 850 °C for 8 h, AC. Due to co-precipitation of primary and secondary γ′ precipitates during the heat treatment, the spray-formed superalloy obtained an excellent combination of yield strength (YS = 1,110 MPa), ultimate tensile strength (UTS = 1,503 MPa), ductility (elongation, EL = 21%) and excellent stress rupture properties at 650 °C (UTS = 1,209 MPa, EL = 15.8%). The heat treatment also improved the rupture life at 650 °C/950 MPa and 750 °C/539 MPa up to 140 h without rupturing. The tensile-fractured surfaces exhibit ductile transgranular failure feature. The optimum heat treatment process was determined to be 1,140 °C/6 h + 850 °C/8 h + AC.

Influence of solid solution treatment on microstructure and mechanical properties of 2219 aluminium alloy

The influence of solid solution treatment on the microstructure and mechanical properties of 2219 aluminium alloy was investigated by means of analysis of differential scanning calorimetry curve; observation of SEM microstructures; and measurement of hardness, conductivity and mechanical properties. Results showed that the hardness of the solid solution treated alloy increased first and then descended with increasing heating rate from 10 to 30°C min−1 or the extension of solid solution time from 30 to 70 min, whereas an opposite tendency was found for the electrical conductivity. The optimal heat treatment process, that is the heating rate of solid solution treatment of 20°C min−1, solid solution temperature of 535°C for 50 min and aging temperature of 180°C for 24 h, is determined. In addition, the best mechanical performances of the alloy were obtained. Yield strength is 279·13 MPa, tensile strength is 421·99 MPa and elongation is 15·6%.

Study on Microstructure and Property of Al-Si-Cu-Mg Casting Alloy during Solution and Aging Treatment

The effect of the alloying elements Cu and Mg, the solution and artificial aging process on the microstructure and property were investigated. Solution treatment was carried out at 535 ± 5°C in different time for the Al-Si-Cu-Mg casting alloy, and the artificial aging was carried out at 160 ± 5°C and 175 ± 5°C and190 ± 5°C in different time. The microstructure has been investigated by Optical Microscopy, Scanning Electron Microscopy (SEM). We found that most of Cu and Mg element in the alloy gathered and formed multivariate composite phase at grain boundaries. With the increasing of solid solution time, the intermetallic phases will be dissolution into the matrix, and if the solid solution time is long enough, they will be distributed uniformly in alloy. With the increase of the aging temperature, the time for aging peak will be shorter, but the peak will be lower. Finally, we determine the optimum heat treatment process is 535°C × 12h + 175°C × 8h。

Influence of Heat Treatment Temperature on Microstructure and Property of 00Crl3Ni5Mo2 Supermartensitic Stainless Steel

The microstructural evolution and mechanical property of 00Crl3Ni5Mo2 supermartcnsitic stainless steel (SMSS) subjected to different heat treatments were investigated. Room tensile tests, hardness tests, scanning electron microscopy, transmission electron microscopy and X-ray diffraction were conducted on the heat-treated steels. It is found that the microstructure of the heat-treated steel is composed of tempered lath martensite, retained austenite and δ-ferrite. The austenitizing temperature and tempering temperature have a significant effect on the microstructural changes, which leads to the complex variations of mechanical properties. The fine tempered lath martensite and more dispersed reversed austenite in the microstructure facilitate improving the comprehensive mechanical properties of the studied steel. The optimal heat treatment process of 00Crl3Ni5Mo2 SMSS is obtained by austenitizing at 1000 °C for 0.5 h + hair cooling followed by tempering at 630 °C for 2 h + hair cooling, where the excellent combination of tensile strength, elongation and hardness can be achieved.

Influences of material processing on the microstructure and inter-granular current properties of polycrystalline bulk Ba(Fe,Co)2As2

The phase formation, microstructure, magnetic, and transport properties of Ba(Fe,Co)2As2 polycrystalline bulks prepared by systematically varied synthesis conditions were studied to clarify the key issues for intergranular critical current properties. After optimization of heat treatment process, Ba(Fe0.92Co0.08)2As2 samples with high phase purity and Tc>25K were reproducibly obtained. Electron microscopy analyses showed that the use of refined starting powder by high-energy ball-milling yield microstructure with improved uniformity and Ba(Fe,Co)2As2 phase can be synthesized at lower temperature down to 500°C owing to an increased reactivity. The samples synthesized at low temperature showed well-connected microstructure with fine grain size and intergranular critical current density progressively improved with lowering the heating temperature. Our results suggest that fine grain size and grain boundary structure formed at low temperature are favorable for increasing the area of effective transport current path, while they are electromagnetically weakly coupled and suppressed under external magnetic field.

Research on the Optimization of Heat Treatment Process and the Abrasive Impact Wear Mechanism of 70Mn Steel

This research was conducted on the influence of heat treatment parameters on the mechanical properties and abrasive wear resistance of 70Mn steel through experimental results. Orthogonal experiment was applied for designing heat treatment process and acquired optimal heat treatment parameters. The experimental results showed that the optimum heat treatment process was firstly heated to 830°C preserved for 60min, and rapidly quenched, then tempered at 200°C for 80min. Abrasive impact wear experiment was performed on MLD-10 tester, under which the wear surface and the subsurface were observed through scanning electron microscope and optical microscope. According to the experimental result, abrasive impact wear mechanism was analyzed. The results showed that plastic deformation fatigue and gouging wear were the primary mechanisms of abrasive impact wear, together with a small amount of furrow and cutting.

The Effect of Heat Treatment on the Performances of Inconel690 Heat Transfer Tube

This article mainly studied the influence rule of heat treatment temperature on the performances of Inconel690 heat transfer tube. The microstructure, mechanical performances and corrosion properties were studied under different heat treated conditions. The optimized heat treatment process was obtained. The conclusions was as follows: with the increase of solution temperature from 1050°C to 1150°C, the mean grain size varied from 12μm to 58μm, the room temperature tensile strength and yield strength reduced gradually, while the elongation elevated gradually. The alloy had a good resistance to pitting corrosion after solutionization during 1090~1100°C.The massive carbides (M23C6) were precipitated along grain boundaries after sensitization processing. And with the increase of sensitization temperature, its morphology transform from tiny semicontinuous to coarsening continuously, multi-layered distribution emerged during higher sensitization temperature range. Along with the sensitization temperature rising, alloy 690 has better resistance to intergranular corrosion. As the sensitization temperature was higher than 750°C with isothermal holding for 2 hours, the desensitization phenomenon occurred, and the ability of anti-intergranular corrosion for alloy 690 could be enhanced distinctly.

Improvement in Mechanical Properties of Microalloyed Steel 30MSV6 by a Precipitation Hardening Process

The microstructural evolutions and mechanical properties of vanadium microalloyed steel (30MSV6) during precipitation hardening were studied. The effects of aging temperature and cooling rate on mechanical strength (yield strength and ultimate tensile strength) were similar. Increasing aging temperature or cooling rate firstly increased the mechanical strength of specimens up to their maximum values, which then decreased with further increase in aging temperature or cooling rate. Microstructural evolutions revealed that cooling rate had significant effects on the pearlite interlamellar spacing and size of pre-eutectoid ferrite. Unlike the effect of austenitizing temperature, the pearlite interlamellar spacing and pre-eutectoid ferrite size were decreased by increasing the cooling rate from austenitizing temperature. According to the microstructural evolutions and mechanical properties, the optimal heat treatment process of microalloyed steel 30MSV6 was austenitizing at 950 °C for 1 h, air cooling (3. 8 °C/s) and aging at 600 °C for 1. 5 h. This optimal heat treatment process resulted in a good combination of elongation and yield strength.

Effect of Heat Treatment on Microstructure and Properties of Cu-3Ti-1Al Alloy

The effect of heat treatment on the microstructure and properties of Cu-3Ti-1Al alloy was investigated. The microstructure was characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM), and the hardness and electrical conductivity were tested as well. The results showed that the hardness and electrical conductivity of Cu-3Ti-1Al alloy increased significantly after solid solution and ageing treatment. The strengthening effect of Cu-3Ti-1Al alloy was attributed to the formation of intermetallic phase such as Ti3Al and fine precipitates of coherent β-Cu4Ti. With increase of the aging time and the temperature, the precipitates became coarse and incoherent with Cu matrix, and the discontinuous precipitate β started to grow from grain boundaries toward grain interior, which decreased hardness. As the formation of Ti3Al, β-Cu3Ti and β-Cu4Ti phase can efficiently reduce Ti concentration in Cu matrix. The electrical conductivity of Cu-3Ti-1Al alloy increases. In the range of experiments, the optimal heat treatment process for Cu-3Ti-1Al alloy is solid solution at 850°C for 4h and ageing 500°C for 2h, and the hardness and electrical conductivity are 227HV and 12.3%IACS, respectively.

Optimization of Heat Treatment Process on Vacuum Die-Casting AT72 Magnesium Alloy

The effect of heat treatment on vacuum die-casting (VDC) AT72 magnesium alloy was studied. The optimal process of heat treatment was obtained. The result shows that the alloy was composed of α-Mg, Mg17Al12 and Mg2Sn. After solution treatment at 686K for 24h, Mg17Al12 completely dissolved in α-Mg matrix. With the aging treatment following solution treatment, Mg17Al12 kept precipitating in the matrix and along grain boundary. Moreover, Mg2Sn distributed along the grain boundary did not disappear after solution treatment at 686K. This indicates that Mg2Sn phase exhibits very high thermal stability. The heat treatment process was optimized with solution at 686K for 24h plus ageing at 473K for 18h, in the condition of which AT72 magnesium alloy exhibits a maximum hardness with value of 90.8Hv. The successful application of heat treatment for AT72 magnesium alloy could be attributed to the elimination of the air bubble in the casing through VDC. However, the porosity in the cast couldnt be efficiently eliminated by VDC, which result in the growth of shrinkage pore.

Preparation of benzene adsorption materials using waste activated alumina

A new type of benzene adsorption material was prepared by using the airtight heat treatment method. This method can directly transform the organic impurities of the activated alumina waste into carbon with adsorption capability. The microstructure and carbon content of materials were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), BET (Brunauer Emmett Teller) surface area analysis and elemental analysis. The influences of heat treatment temperature on the properties of the composite materials were discussed. The benzene adsorption capability of the material was investigated. The experimental results show that the optimal heat treatment process condition is airtight heating at 400°C for 2 h. The resulting sample has carbon mass fraction of 3.57%, specific surface area of 234.70m2/g, pore volume of 0.41m3/g, and average pore size of 6.59 nm. The samples show excellent benzene adsorption capability with an adsorption rate of 21.80%.

Selection of Heat Treatment Process and Wear Mechanism of High Wear Resistant Cast Hot-Forging Die Steel

AbstractDry sliding wear tests of a Cr-Mo-V cast hot-forging die steel was carried out within a load range of 50–300 N at 400 °C by a pin-on-disc high-temperature wear machine. The effect of heat treatment process on wear resistance was systematically studied in order to select heat treatment processes of the steel with high wear resistance. The morphology, structure and composition were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS); wear mechanism was also discussed. Tribo-oxide layer was found to form on worn surfaces to reduce wear under low loads, but appear inside the matrix to increase wear under high loads. The tribo-oxides were mainly consisted of Fe3O4 and Fe2O3, FeO only appeared under a high load. Oxidative mild wear, transition of mild-severe wear in oxidative wear and extrusive wear took turns to operate with increasing the load. The wear resistance strongly depended on the selection of heat treatment processes or microstructures. It was found that bainite presented a better wear resistance than martensite plus bainite duplex structure, martensite structure was of the poorest wear resistance. The wear resistance increased with increasing austenizing temperature in the range of 920 to 1120 °C, then decreased at up to 1220 °C. As for tempering temperature and microstructure, the wear resistance increased in following order: 700 °C (tempered sorbite), 200 °C (tempered martensite), 440 to 650 °C (tempered troostite). An appropriate combination of hardness, toughness, microstructural thermal stability was required for a good wear resistance in high-temperature wear. The optimized heat treatment process was suggested for the cast hot-forging steel to be austenized at 1020 to 1120 °C, quenched in oil, then tempered at 440 to 650 °C for 2 h.

Research on Hot-Work Die Steel Used for Extrusion Wheel

A set of new nitrogen-containing hot work die steels were designed. The best experimental steels and their heat treatment processes were optimized by microstructures, mechanical properties and thermal fatigue tests. The results show that the best compositions of V, Cr, N are 1.0 wt％, 3.75 wt％ and 0.01 wt％, respectively. The optimized heat treatment process is that quenching at 1080°C, first tempering at 550°C and second tempering at 530°C.