Quench Temperature Research Articles

Quenching and partitioning treatment of a low-carbon martensitic stainless steel

► The amount of retained austenite was increased by Q&P treatment in 12Cr–0.1C steel. ► Ideal carbon concentrations in austenite and ferrite were calculated assuming CCE condition. ► The optimum partitioning treatment condition for 12Cr–0.1C steel was found. ► The strength–ductility balance of 12Cr–0.1C steel was improved by TRIP effect. Quenching and partitioning (Q&P) treatment was applied to a commercial low-carbon martensitic stainless steel, AISI Type 410 (Fe–12Cr–0.1C). The quench interruption temperature was optimized with consideration of the ideal carbon concentration in untransformed austenite after partitioning to lower the Ms temperature to room temperature. After partitioning at an appropriate temperature, a significant fraction of austenite was retained through the enrichment of carbon into the untransformed austenite. It was also suggested that the addition of silicon is not necessarily required for the Q&P treatment of 12Cr steel because of the retardation of carbide precipitation at the partitioning temperature owing to the large amount of chromium. Tensile testing revealed that the Q&P-treated material exhibited a significantly improved strength–ductility balance compared with conventional quench-and-tempered materials due to the transformation-induced plasticity (TRIP) effect by the retained austenite.

’Quenching and Partitioning’ - An <i>In Situ</i> Approach to Characterize the Process Kinetics and the Final Microstructure of TRIP-Assisted Steel

The ‘Quenching and Partitioning’ (Q&P) concept aims to increase the strength level of conventional TRIP-assisted advanced high strength steel (AHSS) by replacing ferritic constituents by tempered martensite. The Q&P heat treatment process involves austenitization and interrupted quenching followed by carbon partitioning from martensite to austenite at elevated temperatures. The final microstructure is traditionally investigated at room temperature after metallographic preparation by microscopy and x-ray analysis with laboratory tubes. Besides other disadvantages the established characterization methods are not adequate to observe the development of the microstructure during Q&P treatment. In the present work the microstructural evolution during Q&P processing was monitored by in-situ diffraction experiments using very hard (100 keV) synchrotron x-ray radiation. Debye-Scherrer rings were recorded as a function of time and temperature during the heat treatment in a state-of-the-art dilatometer (type Bähr DIL805AD) at the Engineering Materials Science beamline HARWI-II (HZG outstation at Deutsches Elektronensynchrotron (DESY), Hamburg). The diffraction patterns contain quantitative information on the phases present in the sample (for more details cf. Abstract Carmele et al, this conference). The evolution of the austenite phase fraction during the partitioning treatment at the quench temperature (1-step Q&P) is discussed exemplarily for a Si-based TRIP steel with additions of Ni.

Simulation of Multifilament Superfine Denier Polyester Melt Spinning

Based on melt spinning dynamic model and theory, a basic model of superfine denier polyester multifilament was established. Besides the expressions of quench air temperature and quench air velocity for superfine denier filament spinning process have been established in this paper. In different conditions of diameters of spinneret holes, spinning temperature and the quenching process, the degree of orientation, crystallinity and spinning stress of polyester filament in the spinning process was simulated, respectively. The variation of quench air temperature and air velocity of multifilament in different circles of spinneret was mainly discussed. The research was expected to provide basic theory for optimizing production technique and manufacturing high quality superfine denier polyester filament.

Study of Chemical Quench of High Temperature Syngas

Quench of high temperature raw syngas to a certain degree is of great importance for the availability of a gasifier, and it influences the economical running of whole energy utilization system. Chemical quench is one of the best choices for high temperature syngas quench. Based on the Gibbs free energy minimization approach, thermodynamic analyses are carried out to elucidate the quench process of high temperature syngas. The optimal quench temperature and optimal feeding rate of coal are achieved with the consideration of effects such as inlet syngas temperature, steam input and moisture content in the coal. The results show that chemical quench is an effective way for high temperature syngas quench. The higher the temperature of syngas is, the better the chemical quench effect is. Steam input to the syngas can enhance the chemical quench reaction for the same coal feeding rate, while the effect of moisture content in coal on chemical quench is negligible.

Quench Analysis of a High-Current Forced-Flow HTS Conductor Model for Fusion Magnets

A fundamental understanding of the quench phenomenon is particularly important in the design and operation of magnets using High Temperature Superconductors because the quench propagation velocity is low due to high specific heat at high temperature. We have performed the simulations of a high-current forced-flow conductor model to assess the key quench parameters, e.g. the temperature increase of the normal zone and its propagation velocity, using the CryoSoft code THEA. The sensitivity of these results on conductor design and operation parameters was assessed with a variational analysis. Results show that the helium flow has a beneficial impact on the longitudinal propagation of the normal zone and the resulting reduction of the peak quench temperature.

Polypropylene/polyamide 6/polypropylene-g-maleic anhydride blending monofilaments: effects of quench temperature

We describe the effects of quench temperature on the structure and mechanical properties of polypropylene/polyamide 6/polypropylene grafted maleic anhydride (PP/PA6/PP-g-PAH) blend monofilaments. The monofilaments were prepared by melt-spinning under different quench temperatures. The thermal properties were investigated by Differential scanning calorimetry (DSC) and the morphologies were observed using Scanning electron microscope (SEM). We measured the tensile strength, the loop strength, and the elongation at break of the monofilaments. Results demonstrated that the quench temperature had strong effects on the structure and mechanical properties of the PP/PA6/PP-g-MAH blend monofilaments. With the decrease of quench temperature, the tensile strength and the loop strength of the blend monofilaments increased obviously, which could be attributed to the different crystallization processes and orientation structures induced by changing quench temperatures.

Phase‐Separation Kinetics and Mechanism in a Methylcellulose/Salt Aqueous Solution Studied by Time‐Resolved Small‐Angle Light Scattering (SALS)

AbstractPhase‐separation dynamics are investigated by SALS in aqueous MC solutions in the presence of 5% NaCl, promoted by a quench temperature. The observed scattering peak indicates that the phase separation occurs by the SD mechanism, leading to a bicontinuous structure. A semilog plot of I(q) against time in the early stage of SD gives a straight line, but the position of qmax varies; also, a Cahn–Hilliard plot indicates that diffusive processes dominate and the data can be described by linear CHC theory. Dapp shows a kinetic dependency on the quench temperature. The spinodal temperature of the sample is 41 °C. In the late stages, S(q,t) collapses into a universally time‐independent curve. magnified image

Test results and analyses of conductor short samples for China first PF conductor

The first China PF conductor sample (CNPF1) which was made of one single cable section with hairpin configuration and without bottom joint was fabricated with Chinese NbTi strands and assembled at ENEA and CEA according to the requirements of the SULTAN test facility. The sample was equipped with temperature sensors and voltage taps at CEA according to the test program. The test program included DC performance, cyclic loading, AC loss, and MQE test. The sample exhibited a good performance which fit well with the requirement in the procurement arrangement (PA). But most of the current sharing temperature ( T cs ) tests showed a suddenly voltage take-off or fast voltage transition with take-off electric field below the threshold of 10 μV/m. The temperature could be considered as quench temperature ( T q ) but not exactly T cs . At 35 kA and background field of 3.5 T, the temperature T q was 6.94 K. Even after 2000 cycles at the condition of 6.5 T and 19 kA, the T q remained unchanged.

Effect of Gelatin Gelation Kinetics on Probe Diffusion Determined by FRAP and Rheology

The time-dependent diffusion and mechanical properties of gelatin in solution, in the gel state, and during the sol/gel transition were determined using fluorescence recovery after photobleaching (FRAP) and rheology. The parameters in the experimental design were 2% w/w and 5% w/w gelatin concentration; 15, 20, and 25 °C end quench temperatures; and Na(2)-fluorescein, 10 kDa FITC-dextran, and 500 kDa FITC-dextran as diffusion probes. The samples were monitored in solution at 60 °C, during quenching, for 75 min at end quench temperatures and after 1, 7, and 14 days of storage at the end quench temperature. The effect of temperature on the probe diffusion was normalized by determining the free diffusion of the probes in pure water for the different temperatures. The results gained by comparing FRAP and rheology showed that FRAP is able to capture structural changes in the gelatin before gelation occurs, which was interpreted as a formation of transient networks. This was clearly seen for 2% w/w gelatin and 20 and 25 °C end quench temperatures. The structural changes during sol/gel transition are detected only by the larger probes, giving information about the typical length scales in the gelatin structure. The normalized diffusion rate increased after 7 and 14 days of storage. This increase was most pronounced for fluorescein but was also seen for the larger probes.

Quench rate and temperature effects on boron coordination in aluminoborosilicate melts

The effect of temperature on the structure of aluminoborosilicate liquids has been studied by 11B MAS NMR, 11B 3QMAS NMR, 23Na and 27Al MAS NMR spectroscopies using glass samples prepared with different cooling rates and thus different fictive temperatures. The abundance of BO 3 group and non-bridging oxygen (NBO) increases with increasing fictive temperature, indicating that the reaction BO 4 ↔ BO 3 + NBO shifts to the right with increasing temperature. The observed temperature dependence of BO 4 species abundance allows us to estimate the ∆ H of this reaction to be 24 to 50 kJ mol −1 in different glass compositions, and closely related with the amount of NBOs in the glass. Configurational heat capacities have been measured by differential scanning calorimetry (DSC). We found that the redistribution of boron species (BO 4/BO 3) contributes a varying range of configurational heat capacity, from 7% to 30%, with different glass compositions. 11B 3QMAS NMR indicates two different BO 3 sites, the populations of which are also affected by fictive temperature. The exchange between two different BO 3 sites should also contribute to configurational heat capacity.

Influence of Solution Treatment on Microstructure and Quench Cracking in a Water-Quenched Aluminium Alloy 7150

In this work, the influence of multi-step solution (MSS) treatments on the constituent particle dissolution, overheating and associated quench cracking behaviour in room temperature water-quenched 7150 Al alloy has been investigated. For comparison, the microstructure and quench cracking behaviour of single step solution treated samples water-quenched from 505°C were also investigated. Based on optical microscopy of differently quenched samples, the quench cracking mode and the influence of overheating of constituents on the quench cracking behaviour have been demonstrated. The results reveal that the constituent particles can be effectively dissolved in the MSS-505°C samples. When the quench temperature of MSS-505°C samples is equal to or higher than 485°C , macro quench cracks can be clearly observed. Moreover, the density and length of the quench cracks increase with increasing quench temperature. Etched microstructures indicate that the quench crack propagation mode is intergranular. However, for samples directly heated to 505°C , typical overheating can be observed at the triple junctions and these regions preferentially act as crack propagation routes.

Nucleation of an Oil Phase in a Nonionic Microemulsion-Containing Chlorinated Oil upon Systematic Temperature Quench

A clear and stable nonionic model microemulsion consisting of pentaoxyethylene glycol dodecyl ether (C(12)E(5)), water, and 1-chlorotetradecane (CLTD) was prepared. This system was subjected to a systematic temperature quench (perturbation out of equilibrium) in steps of 1.0 degrees C from 20.4 to 15.3 degrees C in the unstable region of its phase diagram. The change in turbidity (for droplet volume fractions of 0.02 and 0.08) and hydrodynamic radius (R(h)) (for a droplet volume fraction of 0.02) of the system on its way to its new equilibrium was measured at each quench temperature. For small systematic temperature quenches just below the emulsification failure boundary (EFB) the turbidity decreases and remains constant indicating quick changes in the microstructures. Further lowering of temperature brings the system to the unstable region where the turbidity and light scattering increase sharply as function of time because of expulsion of excess oil from the microemulsion droplets. The newly formed oil-rich droplets grow in size as a function of time. These observations indicate the existence of a narrow but observable metastable region en route to the new equilibrium where both microemulsion droplets and larger oil-rich droplets coexist. The region in which microemulsion droplets are metastable is very narrow and is concentration-dependent. The presence of a metastable region is as for other similar systems attributed to the presence of a free energy barrier for the formation of the larger oil-rich droplets associated with curvature free energy of the surfactant film. The turbidity-time curves were converted to the radius-time curves using a model assuming monodisperse spherical droplets. The obtained results are in good agreement with the results for the hydrodynamic radius. The observed average radius from both type of measurements decreases in the metastable region. By performing calculation of the influence of eccentricity and size polydispersity on the observed radius, we have shown that the distribution of the microemulsion droplets becomes more homogeneous in the metastable region.

Influence of the experimental technique on the quench temperature dependence of the martensitic transformation temperature in Cu–Zn–Al alloys

The shift of the martensitic transformation temperatures has been measured in a Cu–Zn–Al alloy as a function of the quenching temperature using different experimental techniques. Results from temperature and stress induced transformations were compared. It was found that the spread of the results is related to the geometry as also to the preparation time characteristic of each experimental method. The evidence of Zn loss by volatilization during the high temperature anneals is also reported.

Modelling and confocal microscopy of biopolymer mixtures in confined geometries

The morphology of a phase separating and gelling biopolymer mixture (gelatin-maltodextrin) is strongly affected not only by thermodynamic conditions, but also by the presence of a restricted geometry. Phase separation within droplets is analysed using confocal laser scanning microscopy and image analysis by varying concentration (4% gelatin and 4%-7.3% maltodextrin), quench temperature (10 degrees C to 25 degrees C) and droplet diameters (10 mu m-120 mu m). The effects of confinement as well as quench temperature increase with increasing maltodextrin concentration in 120 mu m sized droplets. In small droplets below 20 mu m, the confinement and surface dominate the microstructure. The trends observed show good agreement with predictions of the elastic Lennard-Jones (ELJ) model, adapted to handle confinement, that is solved via conventional molecular dynamics. A one-dimensional spin-chain with variable bond length is furthermore introduced and shown to capture a number of qualitative behaviors. The findings reveal that the confined biopolymer mixture can be characterized by the very few parameters of the ELJ model, which incorporates the basic mechanism of short range attraction (collapse, crystallization) versus long range elastic repulsion (osmotic penalty). Accordingly, the study suggests that the model provides a handle towards the morphological design of binary polymer mixtures in microcapsules, droplets or other geometries of well defined size and shape.

Preparation of spherulites from amylose–palmitic acid complexes

We conducted a systematic study of the formation of spherulites from amylose–palmitic acid complexes. The independent variables included final heating temperature, intermediate quench temperature, final quench temperature and cooling rates. Spherulites were characterized by different techniques: optical microscopy, scanning electron microscopy, differential scanning calorimetry, X-ray diffraction, transmission electron microscopy and resistant starch content. Three distinct types of spherulite morphology were observed: spherical, sintered (“snowball”) and torus/disc shaped. Spherical-shaped particles were formed at higher endpoint heating temperatures and exhibited mixed B+V-type XRD patterns. Torus-shaped spherulites formed from samples heated to 140 °C followed by slow cooling, and exhibited V-6 I type XRD patterns. Resistant starch estimated for spherulites formed by heating to 180 °C followed by cooling to 40 °C at 1 °C/min vs. those formed by heating to 140 °C, cooled to 90 °C at 1 °C/min then to 40 °C at 0.04 °C/min was 28% and 39%, respectively. Morphology of the amylose–PA spherulites after resistant starch determination for spherical spherulite shows distinct pores and uneven surface texture. In contrast, the torus-shaped spherulites were degraded with evidence of recrystallization.

Foaming behavior of high‐melt strength polypropylene/clay nanocomposites

AbstractThe foaming behavior of high‐melt strength polypropylene (HMS‐PP) and HMS‐PP/Cloisite 20A nanocomposites (PPNC) was studied in a batch process. PPNCs with 2, 4, 8, and 10 wt% clay were prepared in a twin screw extruder. The morphology of the nanocomposites was studied using XRD and TEM. Subsequently, foaming experiments were conducted using supercritical CO2 as the blowing agent in a batch process, and foams with cell sizes varying from the sub micrometer to the micro meter range were prepared. The effect of variation in saturation pressure and temperature, foaming temperature, foaming time, and quench temperature was determined experimentally. Dynamic rheological measurements were conducted to relate the influence of nanocomposites morphology with foam cell growth and nucleation. Extensional rheological measurements were also conducted to detect the presence of strain hardening effect at the foaming temperatures used in the experiment. It was found that the nucleation efficiency of clay reduces with increase in clay loading. Also, the optimum amount of filler for generation of fine celled foams was found to be around the percolation threshold of the polymer. The extended strain hardening effect shown by the polymer in presence of clay plays an important role in stabilizing foam cell sizes. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

Quench Margin Measurement in ${\rm Nb}_{3}{\rm Sn}$ Quadrupole Magnet

One of the possible practical applications of the Nb3Sn accelerator magnets is the LHC luminosity upgrade that involves replacing the present NbTi focusing quadrupoles in two high-luminosity interaction regions (IR). The IR magnets are exposed to strong radiation from the interaction point that requires a detailed investigation of the magnet operating margins under the expected radiation-induced heat depositions. This paper presents the results of simulation and measurement of quench limits and temperature margins for a Nb3Sn model magnet using a special midplane strip heater.

Thermal Shock Resistance of an AlN–BN–SiC Ceramic

Mechanical and thermal properties of AlN–BN–SiC (ABS) ceramics were used to calculate the R, R′, and R″″ thermal shock parameters. The R parameter values ranged from ∼400° to 450°C. Specimens were thermal shocked by water quenching and the critical quench temperatures (ΔTC) were compared with those of a baseline SiC composition. The behavior of the ABS was predicted by R parameter calculations while the behavior of the baseline material was predicted by the R′ calculations due to its higher thermal conductivity (87 W·(m·K)‐1) as compared with the ABS materials (∼30 W·(m·K)−1). The highest critical quench temperature for ABS was ∼415°C with the lowest at 360°C, while the critical quench temperature for the baseline material was 450°C. Using temperature dependent data over an appropriate temperature range (room temperature to the predicted ΔTC), the R parameters of the ABS materials were within 15°C of predictions. The baseline material was ∼1.7 times higher than predicted and this was attributed to the high‐thermal conductivity of the material resulting in soft thermal shock during quench testing.

Influence of carbon partitioning kinetics on final austenite fraction during quenching and partitioning

The quenching and partitioning (Q&P) process is a two-stage heat-treatment procedure proposed for producing steel microstructures that contain carbon-enriched retained austenite . In Q&P processing, austenite stabilization is accomplished by carbon partitioning from supersaturated martensite. A quench temperature selection methodology was developed to predict an optimum process quench temperature; extension of this methodology to include carbon partitioning kinetics is developed here. The final austenite fraction is less sensitive to quench temperature than previously predicted, in agreement with experimental results.

Glassy states in the stochastic Potts model

We have studied by numerical simulations the relaxation of the stochastic seven-state Potts model after a quench from a high temperature down to a temperature below the first-order transition. For quench temperatures just below the transition temperature the phase ordering occurs by simple coarsening under the action of surface tension. For sufficient low temperatures however the straightening of the interface between domains drives the system toward a metastable disordered state, identified as a glassy state. Escaping from this state occurs, if the quench temperature is nonzero, by a thermal activated dynamics that eventually drives the system toward the equilibrium state.