Heating Furnace Research Articles

Cast Alumina-Forming Austenitic Stainless Steels for High Temperature Heat Treatment Furnace Rolls

Abstract Alloy developers worldwide have struggled to create creep-resistant alumina-forming, iron-based austenitic stainless steels for use as high-temperature structural alloys, but with limited success in balancing alloy cost, oxidation, and creep resistance. This article describes the research and development of a novel cast alumina-forming austenitic stainless steel. This work won the prestigious Engineering Materials Achievement Award presented at IMAT 2023 in Detroit.

Thermal deflection in neutron scattering sample environments at Oak Ridge National Laboratory.

The neutron sources at Oak Ridge National Laboratory use a wide suite of sample environment equipment to deliver extreme conditions for a number of experiments. Much of this instrumentation focuses on extremes of temperature, such as cryostats, closed-cycle refrigerators in both low and high temperature configurations, and radiant heating furnaces. When the temperature is controlled across a large range, thermal deflection effects can notably move the sample and affect its alignment in the beam. Here, we combine these sample environments with neutron imaging and machine vision to determine the motion of a representative sample with respect to the neutron beam. We find vertical sample displacement on the order of 1-2mm and horizontal displacement that varies from near-negligible to 1.2mm. While these deflections are not relevant for some of the beamlines at the first target station at the spallation neutron source and the high flux isotope reactor, they will become critical for upcoming instrumentation at the second target station, as well as any instruments targeting sub-mm samples, as neutron sources and optics evolve to smaller and more focused beams. We discuss mitigation protocols and potential modifications to the environment to minimize the effect of misalignment due to thermal deflection.

Thermomechanical constitutive behaviour of 3D printed biomimetic polymer material under high strain rates

With the continuous technical breakthroughs of flexible electronics, materials with outstanding application potential are constantly being designed and optimized. Biomimetic polymer materials are particularly appealing due to their versatility and ease of fabrication, but their mechanical reliability, particularly their thermomechanical constitutive behaviour under extreme working loads, remains unclear. In this paper, the impact responses of a 3D printed biomimetic polymer material named “Tangoblack” are investigated under thermomechanical, focusing on the effect of strain rate. By adjusting the pressure of the gas gun in the split Hopkinson pressure bar, different strain rates are achieved, while the high temperature of the tested sample can be controlled using a heating furnace integrated into the experiment system. Materials for pulse shapers are carefully selected to ensure longer durations at nearly constant strain rates. The constitutive behaviour of the biomimetic polymer material is further investigated under a wide strain rate range from 958 s−1 to 2158 s−1 and three different temperatures (20 °C, 70 °C and 120 °C). The results demonstrate a significant dependence of the polymer material on both strain rate and temperature. A rapid increase in forming strain rate enhances the strain hardening process, while simultaneously revealing a substantial temperature softening effect. Then, an improved nonlinear thermoviscoelastic ZWT constitutive model is proposed utilizing the Vogel-Fulcher-Tammann equation and implemented as a user-defined material model in ABAQUS/Explicit. The proposed constitutive model is demonstrated to be distinctly advantageous, which suggests a novel pathway for describing the mechanical reliability of biomimetic polymer materials under extreme working conditions.

Comparison of Microwave Versus Conventional Furnace Heat Treatments of Carbide Composite Thermal Spray Coatings

Thermal spraying has become an industrial standard in the production of wear-resistant WC-Co and Cr3C2-NiCr composite coatings. However, generating optimum wear-resistant nano-reinforced carbide microstructures within the coatings remains challenging. The alternative two-step approach in this work involves coating formation under high energy conditions to generate maximum carbide dissolution, followed by heat treatment to precipitate nanocarbides. Microwave heating of particulate materials has been reported to offer several benefits over conventional furnace heating, including faster heating rates, internal rather than external heating, and acceleration of reactions/phase transformations at lower temperatures. This novel work explored the use of microwaves for heat treatment (as distinct from melting) of WC-Co and Cr3C2-NiCr thermal spray coatings and contrasted the rate of phase development with that from conventional furnace treatment. Coatings were successfully microwave heat-treated to generate the same phase composition as furnace treatment. Both treatments generated comparable results in the Cr3C2-NiCr system. The WC-Co system achieved a much more crystalline structure in a dramatically shorter time relative to the conventional furnace-treated sample. The results are contrasted as a function of material and microstructure interaction with microwaves and the critical phase transition temperatures to account for the observed responses.

CHAMBER FURNACE FOR SIMULATION OF CARBON MATERIALS HEAT TREATMENT IN ELECTROTHERMAL FLUIDIZED BED

Existing laboratory furnaces for high-temperature heat treatment of materials at around 3000°C, which have graphite heaters, allow samples to be heated at a rate two orders of magnitude lower than in electrothermal fluidized bed furnaces. This makes it impossible to use them in the research into the heat treatment of carbon materials because they do not meet the conditions of shock heating and do not allow to keep accurate residence time. The paper presents the research into the use of low-density composite carbon materials as heaters. Based on the results obtained, a high-temperature chamber furnace was designed, studied, and the temperature field in the heater was simulated. As a result, a high-temperature laboratory furnace was created with a sample heating rate of 20 °C/s - 100 °C/s, which made it possible to use it to simulate the heating process in the electrothermal fluidized bed furnace. Comparison of energy consumption in the furnace with a traditional graphite heater and a low-density carbon composite heater showed that heat loss in the furnace is reduced by 1.7 to 1.8 times.

Enhancing the Tensile Properties and Ductile-Brittle Transition Behavior of the EN S355 Grade Rolled Steel via Cost-Saving Processing Routes.

Structural rolled steels are the primary products of modern ferrous metallurgy. Consequently, enhancing the mechanical properties of rolled steel using energy-saving processing routes without furnace heating for additional heat treatment is advisable. This study compared the effect on the mechanical properties of structural steel for different processing routes, like conventional hot rolling, normalizing rolling, thermo-mechanically controlled processing (TMCP), and TMCP with accelerating cooling (AC) to 550 °C or 460 °C. The material studied was a 20 mm-thick sheet of S355N grade (EN 10025) made of low-carbon (V+Nb+Al)-micro-alloyed steel. The research methodology included standard mechanical testing and microstructure characterization using optical microscopy, scanning and transmission electronic microscopies, energy dispersive X-ray spectrometry, and X-ray diffraction. It was found that using different processing routes could increase the mechanical properties of the steel sheets from S355N to S550QL1 grade without additional heat treatment costs. TMCP followed by AC to 550 °C ensured the best combination of strength and cold-temperature resistance due to formation of a quasi-polygonal/acicular ferrite structure with minor fractions of dispersed pearlite and martensite/austenite islands. The contribution of different structural factors to the yield tensile strength and ductile-brittle transition temperature of steel was analyzed using theoretical calculations. The calculated results complied well with the experimental data. The effectiveness of the cost-saving processing routes which may bring definite economic benefits is concluded.

NPK Biofertilizer Production from Banana Peel, Feather and Bone Ashes and their Comparative Advantage to 20:10:10 Inorganic Fertilizer

The possibility of formulating nitrogen, phosphorus and potassium (NPK) biofertilizer from ashes of waste organic materials such as chicken feathers, bone and banana peels is investigated in this study by first subjecting the agricultural waste to 80-250 heat in a muffle furnace to produce ash. Kjeldatherm block digestion unit, UV spectrophotometer, and flame photometers, respectively helped in measuring the concentrations of N, P and K inherent in the fertilizer precursors as well as in 5 formulated blends (i.e., A, B, C, D & E). It was discovered that NPK in the single substrate and blends favorably compared with standard NPK 20:10:10 chemical fertilizer to some extent. Among single material fertilizer sources, feather ash with 0.179:1:0.134 NPK and bone ash with 0.009:1:0.021 NPK had the closest nutrient content with the standard, showing potential promise. On the other hand, Blend E is the same as the standard, followed by Blend A, B, D and C, which are hierarchically close in elemental composition to the standard. The choice of these biofertilizers is dependent on their nutrient compositions, the type of crops to be grown, and the soil mineral requirements. Most importantly, different NPK ratio organic fertilizers produced in this study can competitively be produced in a large scale to address huge costs associated with the NPK 20:10:10 standard commercial fertilizer. Blend E (NPK 20:10:10) can be formulated locally by farmers in rural areas easily using this particular agricultural residue or a host of other confirmed farm wastes.

A new approach for improving the quality of the carbon anode for aluminum electrolysis – An impregnation-baking process

Prebaked carbon anode is the primary consumable material in the aluminum reduction cell, and its quality directly affects the energy consumption of aluminum production. An impregnation-baking process of the anode was proposed to reduce the anode porosity, improve the quality of the anodes, and reduce additional carbon consumption. The theoretical analysis and industrial testing on the impregnation-baking process were carried out. Firstly, the coal tar pitch was immersed into the anode carbon block through the impregnation process. An anode impregnation model was developed and used for theoretical calculations to analyze the effects of pressure and temperature on the impregnation process. The accuracy of the model was verified experimentally. Secondly, the impregnated anodes were placed in an electromagnetic induction heating furnace for baking to carbonize the immersed pitch. The thermogravimetric and pyrolysis kinetics methods were used to analyze the baking process of the impregnated anodes. Finally, the impregnated-baked anodes were compared with common anodes regarding their impact on the technical and economic indicators of the aluminum electrolysis process in industrial tests. The results showed that the physicochemical properties of the impregnated-baked anodes were significantly improved, with the bulk density increase of 0.1 g/cm3, air permeability reduction of 0.54 nPm, compressive strength enhancement of 9.43 MPa, and electrical resistivity decrease of 10 uΩ·m. The anode service life was increased from 31 to 35 days, the current efficiency was increased by 0.44 %, and the operating voltage was reduced by 17 mV, which improved economic benefit significantly.

The Optimization of Distribution and Fan Parameters in Heat Treatment Furnaces Through the Integration of Numerical Simulation and Machine Learning

Abstract The present study employed numerical simulation technology to investigate the distribution of workpieces within a low-temperature trolley heat furnace and analyze the influence of circulating fan parameters on heat treatment quality. This analysis was integrated with machine learning technology to guide heat treatment production. The research findings indicate that when the number of workpieces remains constant, their position has a significant impact on airflow velocity distribution, heating rate, and temperature uniformity within the furnace. Additionally, wind pressure from the circulating fan affects both fluid field and temperature field; the increasing wind pressure leads to higher flow rates in the furnace as well as increases heating rates for workpieces. Heating efficiency exhibits a nonlinear relationship with wind pressure increment. By adjusting air pressure distribution from the circulating fan, workpiece temperature uniformity can be improved by 64%. Furthermore, machine learning technique demonstrates excellent performance in predicting workpiece temperatures with a maximum relative error of 2.4%, while maintaining consistent trends in temperature uniformity.

High-precision microcline 40Ar/39Ar dating by combined techniques

K-feldspar is one of the most common minerals applied for 40Ar/39Ar dating because of its high K content and ubiquitous presence. Excess 40Ar in K-feldspar resulting in unreliable ages has long been reported, however, its occurrence and trapping time are still inconclusive. Combined argon extraction techniques, including laser step heating, and step crushing, as well as succedent furnace incremental heating, have been applied to six microcline samples from two hydrothermal ore deposits in South China, to address these issues. Two microcline samples (09SZ37 & 39) measured by all the above three gas extraction techniques yield flat age spectra and concordant inverse isochron ages respectively. However, one sample (09NL10) produces a flat spectrum but with abnormally low radiogenic 40Ar, and the other three samples obtain uneven age spectra, by laser heating. All six samples measured by step crushing yield quite similar age spectra characterized with declining staircases for the first several steps, and followed with very flat plateaus of high-precision plateau ages for the subsequent later crushing steps. The declining sections with abnormally old ages indicate that excess 40Ar (and obvious atmospheric argon) was trapped in the microcracks and the secondary fluid inclusions. The data points corresponding to age plateaus well define inverse isochron ages which are in consistence with their plateau ages respectively. Furthermore, the crushed powders of all six samples by further furnace step heating also yield very flat age spectra, whose plateau ages are well concordant with those obtained by the foregoing step crushing experiments. The trapped excess 40Ar caused the total fusion ages of laser heating 0.7–17.8% older than their true ages. Mineral grains of ca. 0.10 mm may effectively remove excess 40Ar in microcracks and secondary fluid inclusions, proposed for direct 40Ar/39Ar step heating. Stepwise crushing, combined with furnace heating, is not only very useful to date fluid inclusions, but also robust to remove excess 40Ar and obtain more precise true ages for K-bearing minerals, e.g., K-feldspar, amphibole, tourmaline, and so on.

ЕФЕКТИВНІСТЬ ВИКОРИСТАННЯ НИЗЬКОКАЛОРІЙНОГО ПАЛИВА В ПРОТИТОЧНИХ ВАПНЯНО-ВИПАЛЮВАЛЬНИХ ПЕЧАХ

Highly expensive energy carriers require revision of the existing engineering approaches in heating of industrial furnaces. The paper presents the results of research into the performance of a shaft kiln for lime-stone burning, which was fired with mixtures of natural gas and a fuel gas of a low calorific value. On the basis of studying various schemes of fuel distribution between the burners, the optimal operation mode of the kiln with reduced consumption of natural gas by 30% was identified. The lime quality indicators increase when the blast furnace gas is supplied to the central burner and improve when supplied to the peripheral burners. The joint supply of blast furnace gas in the calorific value section of the natural blast furnace mixture 9.4 ÷ 35 MJ/m3 allows keeping the performance of the furnace unchanged. At the same time, the coefficient of replacing natural gas with blast furnace gas is close to unity The proposed mode of heating the furnace with a capacity of 200 t/day with a natural blast furnace mixture provides 30% natural gas savings

Varied directions of heat flow and emission of volatiles impact evolution of products in pyrolysis of wet and dry pine needles

In pyrolysis of biomass via furnace heating, directions for travel of volatiles and heat flow are opposite. This is drastically different from simultaneously heating surface/inner core of a biomass particle with microwave heating. Changing direction of heat flow and volatiles affects volatiles-char interactions and evolution of pyrolytic products. This was investigated herein by pyrolysis of wet and dry pine needles via furnace or microwave heating at 600 °C. The results indicated that microwave heating induced intensive cracking of outer/inner structures of pine needles. This promoted gasification, decreased production of biochar/bio-oil, diminished formation of both light and heavy organics in bio-oil. Microwave heating also accelerated aromatization, forming biochar of higher C/O and C/H ratios and thermal stability. Additionally, formation of “hot spot” in pyrolysis of wet pine needles via microwave heating was evidenced by the phenomenon of decomposition of CaCO3 to CaO in pyrolysis, which also contributed to enhanced aromatic degree of biochar. Besides, pyrolysis of wet pine needles via microwave heating also generated developed pore structures in biochar (151.4 m2 g−1), as the inherent water and carbonaceous organics were heated simultaneously. Hydrogen bonding from inherent water was largely cracked only above 500 °C. Prolonged retention time of H2O reacted with carbonaceous intermediates, generating more aliphatic structures. Additionally, microwave heating also induced formation of unique morphology like massive thorn-like particulate matters on biochar.

Temperature Measurement in Rolling Mill Heating Furnaces

Temperature Measurement in Rolling Mill Heating Furnaces

Thermal strengthening of seamless steel pipes grades 13KhFA for oil and gas industry

The present study focuses on grade 13KhFА steel alloyed with chromium and vanadium for the production of seamless pipes. The pipes were subjected to heat treatment throughout their body and along their entire length. They were fed individually into the furnace, end-to-end, consecutively. The heat treatment furnace was fueled by natural gas. Cooling of the pipes from the quenching temperature was achieved using water in a jet cooling multi-hole device (sprayer). This was followed by high self-tempering due to the heat retained after exiting the quenching furnace. Following quenching and high tempering, the structure of the 13KhFА steel on the surface of the pipe consisted of a mixture of ferrite and carbides with a granular carbide morphology (tempered sorbite). This structure enhances the corrosion resistance of the steel and provides an optimal combination of strength and toughness. The hardening temperature for seamless pipes made of 13KhFА steel was set within the range of 915–920 °C, while the tempering temperature was maintained at 720–730 °C. This careful selection of quenching and tempering temperatures within the specified limits makes it possible to obtain an improved structure of the 13KhFА steel. Keywords: pipe steel; thermal hardening; economically alloyed steel; regulatory standards; corrosion resistance.

Comparative study of microstructural evolution in W-3Re alloy under high-temperature conditions: High heat flux loading versus furnace heating

In tokamak devices, tungsten (W), as the main candidate for plasma facing material, will suffer from the simultaneous challenges of high heat flux (HHF) and neutron irradiation. This study involved annealing experiments on W-3Re alloy using two distinct heating methods: furnace heating and electron beam heating. The evolution of hardness and microstrure of tungsten-rhenium (W-3Re) alloy after isochronous annealing and isothermal annealing has been analyzed and compared with pure tungsten (PW). The recrystallization kinetics of W-3Re alloy have been obtained employing the Johnson Mehl-Avrami Kolmogorov (JMAK) equation. Experimental results showed that recrystallization kinetics during electron beam annealing were faster than those in furnace annealing. This phenomenon can be attributed to the rapid heating process of electron beam annealing, which preserved more deformation energy within the material, thus providing more driving force for recrystallization at high temperatures. Additionally, Re appeared to inhibit grain boundary migration in W-3Re alloy, causing the recrystallization temperature to be approximately 100 °C higher than in pure tungsten, and also resulted in a smaller average grain size compared to pure tungsten. This research provides experimental data and reference for predicting the microstructural evolution of tungsten-rhenium alloy in future fusion reactor environments.

A Comprehensive Assessment of Al-Si Coating Growth at Various Heating Rates, Soaking Temperatures, and Times

In conventional hot stamping, an Al-Si-coated blank is first heated above the austenitization temperature and then soaked for a period of time within a furnace, prior to the stamping operation. In this work, the impacts of furnace heating rate, soaking temperature, and soaking time on the Al-Si coating evolution were investigated for two commercial coating weights, 80 and 150 g/m2. These heat treatment parameters during heating and soaking affect the coating microstructure and the thickness of the interdiffusion layer, which affect the properties of the as-formed coatings. The transformation and growth of binary Fe-Al and ternary Fe-Al-Si intermetallic layers were characterized and quantified for soak times up to 240 s. The results show that the effect of the heating rate on the Al-Si intermetallic distribution and ternary phase morphology was more severe than the soaking time and soaking temperature. The Fe2Al5 (η) phase was the dominant layer at the beginning of the soaking stage with a Fe3Al2Si3 (τ1) layer formed within it, and then the Fe3Al2Si3 layer transformed into FeAl (β2) as the soaking time increased due to the interdiffusion of Fe and Al. The transformation of Fe3Al2Si3 to FeAl occurred at a higher rate for elevated soaking temperatures due to the greater diffusivity of Al and Fe. The interdiffusion layer (IDL) consisted of FeAl,Fe3Al(β1) and α−Fe. Higher soaking temperatures of 1000 °C resulted in a thicker IDL for the same soak time when compared with 900 °C and 950 °C, but when the heating rate was lower, the IDL was thicker than that at the higher heating rate since a longer heating time was required to reach the soaking temperature of 900 °C, which prolonged the diffusion time during the heating stage. The findings were similar for AS80.

Analysis and control of surface cracks in a B-bearing continuous casting blooms

Abstract In this work, normal manufacture of a B-bearing steel was hampered by cracks in steel. In order to control these cracks, the formation mechanism has been examined through a comprehensive analysis of crack morphology, element segregation, high temperature mechanical properties, and precipitates. The high-temperature thermoplastic capabilities of the steel were found to be reduced by boron nitride particles precipitated at grain boundary. This led to the formation of a brittle zone in the straightening zone of the continuous casting process, which in turn caused cracks. Based on the formation mechanism of these cracks, the cracks were successfully controlled by adding an appropriate amount of Ti element to the steel and reducing the charging temperature of the heating furnace.

Enhanced benzene vapor adsorption through microwave-assisted fabrication of activated carbon from peanut shells using ZnCl2 as an activating agent

Herein, microwave-assisted activated carbon (MW-AC) was fabricated from peanut shells using a ZnCl2 activator and utilized for the first time to eliminate benzene vapor as a volatile organic compound (VOC). During the MW-AC production process, which involved two steps—microwave treatment and muffle furnace heating—we investigated the effects of various factors and achieved the highest iodine number of 1250 mg/g. This was achieved under optimal operating conditions, which included a 100% impregnation ratio, CO2 as the gas in the microwave environment, a microwave power set at 500 W, a microwave duration of 10 min, an activation temperature of 500 °C and an activation time of 45 min. The structural and morphological properties of the optimized MW-AC were assessed through SEM, FTIR, and BET analysis. The dynamic adsorption process of benzene on the optimized MW-AC adsorbent, which has a significant BET surface area of 1204.90 m2/g, was designed using the Box-Behnken approach within the response surface methodology. Under optimal experimental conditions, including a contact duration of 80 min, an inlet concentration of 18 ppm, and a temperature of 26 °C, the maximum adsorption capacity reached was 568.34 mg/g. The experimental data are better described by the pseudo-second-order kinetic model, while it is concluded that the equilibrium data are better described by the Langmuir isotherm model. MW-AC exhibited a reuse efficiency of 86.54% for benzene vapor after five consecutive recycling processes. The motivation of the study highlights the high adsorption capacity and superior reuse efficiency of MW-AC adsorbent with high BET surface area against benzene pollutant. According to our results, the developed MW-AC presents itself as a promising adsorbent candidate for the treatment of VOCs in various industrial applications.

Effect of electric current on microstructure and texture evolution of the Ti2AlNb alloy during hot deformation

In this study, the stress-strain behavior of sintered Ti2AlNb alloy obtained at the temperatures of 980 °C and 1080 °C with a strain rate of 0.5 s−1 was investigated using compression tests under furnace heating and current heating. When deformed at 980 °C, the B2 phase texture orientation all exhibited <001>//ND and <101>//ND during current-assisted hot compression (CAHC) and furnace hot compression (FHC). With the deformation temperature increased to 1080 °C, the texture <001>//ND gradually moved towards the <111> texture direction during CAHC. The results were ascribed to the different microstructure evolution that dynamic globularization and DRX by electric current. It indicated that the current promoted the spheroidization of the O phase which did not change the texture orientation. However, as the temperature increased to 1080 °C, the current promoted dynamic recrystallization which resulted in big changes in B2 phase texture orientation. The current promoted the spheroidization of lath by accelerating the phase transformation of O→B2. The current affected the dynamic recrystallization (DRX) mechanisms by promoting the transformation of low-angle grain boundaries (LAGBs) into high-angle grain boundaries (HAGBs) through continuous absorption of dislocations. The true stain-stress curves indicated the reduction of the deformation resistance and enhancement of the deformability of the Ti2AlNb alloy, which was closely related to the microstructure evolution.

A combined theoretical, computational, and experimental investigation to evaluate performance of suitable thermocouple for microwave processing

Accurate temperature measurement during any microwave processing of material is a contentious issue. While thermocouples are routinely utilized in conventional heat furnaces, their presence in microwave cavities may cause complications such as localized distortion of electromagnetic field, heat dissipation, thermal instabilities, microwave breakdown, and significant inaccuracies in temperature measurement. Therefore, in the present investigation thermocouple effects are discussed by providing the results of temperature estimation by various thermocouples for microwave cladding systems. The present study theoretically and experimentally explored the impact of multiple thermocouples on temperature measurements during microwave heating. COMSOL simulation models were developed to explore microwave and thermocouple interaction during microwave heating. Simulation models were used to assess the effects of the microwave power intensity, thermocouple orientation, and geometry on temperature measurement. The investigation outcomes can be utilized as a guide for selecting appropriate thermocouples in the applications of microwave cladding and other microwave-based manufacturing processes.