Use of a 3D Workpiece to Inductively Heat an Ammonia Cracking Reactor

One of the most important types of heat treatment that high-carbon steel wires are subjected to is the patenting treatment. This process is conducted with the aim of obtaining a fine-grained uniform pearlitic structure which will be susceptible to plastic deformation in drawing processes. Patenting involves two-stage heat treatment that includes heating the wire up to the temperature above Ac3 in a continuous heating furnace (in the temperature range of 850÷1050°C) followed by a rapid cooling in a tank with a lead bath down to the temperature range of 450÷550°C. The patenting process is most significantly influenced by the chemistry of the steel being treated, as well as by the temperature and the rate of heating and cooling of the wire rod or wire being patented. So far, heating up to the austenitizing temperature has been conducted in several-zone continuous gas-fired or electric furnaces. Recently, attempts have been made in a drawing mill to replace this type of furnace with fast induction heating, which should bring about an energy saving, as well as a reduced quantity of scale on the patented wire. This paper presents the analysis of the structure and mechanical properties of wires of high-carbon steel with a carbon content of 0.76%C after the patenting process using induction heating for different levels of the coil induction power.

We performed numerical simulations to determine the effect of the most influential operating parameters on the performance of a radio frequency (RF) induction-heating system in which RF magnetic fields inductively heat metal foils to grow graphene. The thermal efficiency of the system depends on the geometry as well as on the materials’ electrical conductivity and skin depth. The process is simulated under specific graphene and two-dimensional (2D) materials growth conditions using finite elements software in order to predict the transient temperature and magnetic field distribution during standard graphene and 2D materials growth conditions. The proposed model considers different coil Helmholtz-like geometries and 11 metal foils, including Ag, Au, Cu, Ni, Co, Pd, Pt, Rh, Ir, Mo, and W. In each case, an optimal window of process variables ensuring a temperature range of 1035 °C–1084 °C or 700 °C–750 °C suitable for graphene and MoS2 growth, respectively, was found. Temperature gradients calculated from the simulated profiles between the edge and the center of the substrate showed a thermal uniformity of less than ∼2% for coinage metals like Au, Ag, and Cu and up to 7% for Pd. Model validation was performed for graphene growth on copper. Due to its limited heat conductivity, good heating uniformity was obtained. As a consequence, full coverage of monolayer graphene on copper with few defects and a grain domain size of ∼2 µm was obtained. The substrate temperature reached ∼1035 °C from ambient after only ∼90 s, in excellent agreement with model predictions. This allows for improved process efficiency in terms of fast, localized, homogeneous, and precise heating with energy saving. Due to these advantages, inductive heating has great potential for large-scale and rapid manufacturing of graphene and 2D materials.

Electroheating by magnetically inducing high-power currents into metal has been an accepted industrial process for over half a century. During the last decade, rapid development in high-current solid-state devices has resulted in the gradual replacement of the motor generator by frequency converters for the generation of medium-frequency power (300 Hz to 10 kHz). Power at these frequencies is normally used for forging, forming and melting, and for deeper case hardening. Lower frequencies (50 to 200 Hz) are obtained straight from supply lines, or from magnetic multipliers; applications include forging and melting at high power levels. Higher frequencies between 100 kHz and 10 MHz are produced by radio-frequency systems, and processes include hardening and joining. This article summarises the main areas of induction heating and the systems used to generate and control these power sources, and includes extracts from a new book on induction heating by the authors, published this summer. Advantages of induction heating include fast and precise heating, clean and compact equipment and, in many instances, cost savings compared with traditional methods

The Resonant Induction Heating Method

The anti-/de-icing technology based on induction heating offers significant advantages regarding fast heating, high efficiency, safety and environmental protection. However, the reported methods require the modification of base materials, which lacks universal applicability. Here, a universal and facile anti-/de-icing method is proposed based on induction heating. The durable induction heating coating was prepared by one-step spin coating with micron-sized nickel powder, epoxy resin and silicone resin. The induction heating ability of this coating was investigated by adjusting the proportion of composition, particle size and thickness. An optimal induction heating ability was achieved with the mass ratio of nickel powder and resin, particle size of nickel powder and coating thickness being 1.5, 7 μm and 1070 μm, respectively. We further show this coating can be applied for anti-/de-icing, demonstrated by its excellent de-/anti-icing performances. Finally, the mechanical durability of the coating was verified by the tape peel and sandpaper friction.

Induction heating has important applications in science and industry. The method of induction heating can be successfully used for melting and heat treatment of titanium and zirconium alloys. Different applications using induction precise heating before plastic deformation are discussed in this paper. For alloys of many metals such as titanium, zirconium, niobium, tantalum, etc., it is important to provide precision heating with a high degree of homogeneity of the temperature field and strict adherence to the condition of heating. This is explained by polymorphism of the alloys based on these metals, their chemical activity at high temperatures and the specific thermal and electrical properties. It is very important for induction heating to define the extreme achievable unevenness of the temperature field. For special alloys it is necessary to use resistance furnaces for homogenization of billets’ temperature after heating in the inductors. Optimal control can be used for massive billets to reduce significantly the heating time, energy expenses and to improve the quality of the temperature field distribution. Optimization of induction heating process can be achieved by synchronous solution of the problem of optimal control and design with specially developed models.

Sintering is a vital technology used for consolidation of metal and ceramic powders. The process is generally long and energy consuming because of the way in which heat transfer happens in electrical and gas furnaces. This study focuses on optimizing the sintering process of metallic powders, in particular titanium, using high frequency induction heating as alternative sintering method. Using electromagnetic induction and the associated Eddy current effect, the heat is generated directly into the electrically conductive object. Consequently, faster heating rates and lower heat loses are achieved. The purpose of this study is to understand the effect of process parameters, such as the powder compact density, on the efficiency of the induction heating and the properties of the sintered materials. The average heating rates recorded while heating to 1300oC are in the range of 3.5o to 15.3o C per second. Significant densification and consolidation, evident by the amount of closed porosity and increase in tensile strength was found in spite of the short heating time. The results show that the powder compact density plays a crucial role on the heating efficiency as well on the properties of the sintered material such as final density, porosity distribution and tensile properties. The samples with higher initial density showed tensile strength and ductility values comparable to those of high vacuum sintered and those specified by international standards for powder metallurgy Ti products.

The term electric furnace applies to all furnaces that use electrical energy as their sole source of heat. Electric furnaces are used for heating solid materials to desired temperatures below their melting points for subsequent processing, or melting materials for subsequent casting into desired shapes. Classification is by the manner in which the electrical energy is converted into heat. Three types of furnaces are widely used in industry: electric resistance furnaces, arc furnaces, and electric induction furnaces. The most widely used and best known resistance furnaces are indirect‐heat resistance furnaces or electric resistor furnaces. They are categorized by a combination of four factors: batch or continuous; protective atmosphere or air atmosphere; method of heat transfer; and operating temperature. The primary method of heat transfer in an electric furnace is usually a function of the operating temperature range. The three methods of heat transfer are radiation, convection, and conduction. Radiation and convection apply to all of the furnaces described. Conductive heat transfer is limited to special types of furnaces. Operating temperature ranges are classified as low, medium, and high; there is no standard or precise definition of these ranges. Arc furnaces used in electric melting, smelting, and electrochemical operations are of two basic designs; indirect and direct arc. The arc of the indirect‐arc furnace is maintained between two electrodes and radiates heat to the charge. The arcs of the direct‐arc furnace are maintained between the charge and the electrodes, making the charge a part of the electrical power circuit. Not only is heat radiated to the charge, but the charge is heated directly by the arc and the current passing through the charge. Direct‐arc furnaces include open‐arc furnaces, d‐c arc furnaces; submerged arc‐furnaces; and arc‐resistance furnaces. All new furnace installations require pollution control equipment. This normally consists of off‐gas afterburning (sometimes with energy recovery), and dust collection equipment, typically a baghouse. Induction furnaces utilize the phenomena of electromagnetic induction to produce an electric current in the load or workpiece. This current is a result of a varying magnetic field created by an alternating current in a coil that typically surrounds the workpiece. Power to heat the load results from the passage of the electric current through the resistance of the load. Physical contact between the electric system and the material to be heated is not essential and is usually avoided. Nonconducting materials cannot be heated directly by induction fields. The efficiency of an induction furnace installation is determined by the ratio of the load useful power to the input power drawn from the utility. Losses that must be considered include those in the power converter transmission lines, coil electrical losses, and thermal loss from the furnace. A unique capability of induction heating is apparent in its ability to heat the surface of a part to a high temperature while the interior remains at room temperature. Electric furnaces are used for annealing, brazing, carburizing, galvanizing, forging, hardening, melting, sintering, enameling, and tempering metals, most notably aluminum, copper, iron and steel, and magnesium alloys.

Dynamic process control and monitoring of novel S3RS based hydrogen cooling system

Aluminum-lithium alloy prepared by a solid-state route applying an alternative fast sintering route based on induction heating

Induction heating is a fast, reproducible, and efficient heating method used in various manufacturing processes. However, there is no established additive manufacturing (AM) process based on induction heating using wire as feedstock. This study investigates a novel approach to AM based on inductive heating, where a steel wire is melted and droplets are detached periodically using a two-winding induction coil. The process parameters and energy input into the droplets are characterized. The induction generator exhibits a sluggish response to the excitation voltage, resulting in a lag in the coil current. The process is captured using a high-speed camera, revealing a regular droplet formation of 14 Hz and uniform shapes and sizes between 2.11 and 2.65 mm in diameter when operated within an appropriate process window. Larger drops and increased spatter formation occur outside this window. The proposed method allows for the production of droplets with almost spherical shapes. Further analysis and characterization of droplet formation and energy input provide insights into process optimization and indicate an overall efficiency of approximately 10%.

Imported oil, nuclear and coal now contribute about 55% of the energy the USA consumes, and those forms of energy are under environmental, social and legal scrutiny. There are limits to which non-“clouded” natural gas and renewables can replace these sources. This has motivated the CCTL to pursue R&D on blending domestically available fuels in thermal reactors to produce more useful gaseous or liquid fuels. Feedstock blending results with batch-fed indirectly heated gasifiers (IHGs) were reported at the three previous Turbo Expo meetings. This is a progress report on initial work with a continuously fed IHG scaled to potentially give a gaseous output suitable for a 5–20 kW microturbine or a reciprocating engine. An electric tube furnace is now used rather than a combustor fueled by the residual char or part of the gaseous or liquid output. Some novel features of this current effort are: a) Biomass blends are auger-fed through a reactor tube fabricated out of available components to simulate a conical shape, b) The output gas is filtered and partially cooled by the incoming biomass feedstock, c) The system has been designed to facilitate feedstock blending studies, d) A trap and external heat exchanger condenses the residual tar, water vapor, and volatile metals, e) The char-ash is collected and stored in a pressure vessel, f) Gas output volume is measured with an orifice dividing system and respirometer. The results of runs in a semi-continuously fed system with various biomass particle sizes and with various blends of biomass and coal are presented. The fate of volatile metals contained in the input feedstock is assessed. With the completion of an external hopper-feeder and the replacement of the electric tube furnace by an output gas or charcoal combustor, a later application to microturbines is within reach.

Induction heating is widely used for heat treatment, providing fast and precise heating effect. A wide range of electromagnetic parameters, such as the structure parameters of coil and the electrical operating parameters, have significant influences on the temperature distribution of the workpiece in induction heating process, which is important for the subsequent heat treatment process. In this work, the main factors including exciting current, power frequency, coil inner diameter and coil spacing are chosen to be studied by numerical simulation. Meanwhile the single-factor experimental design and the Fuzzy Gray Relational Analysis are combined to investigate the impacts of the four factors on the temperature distribution, providing great reference value for further research of induction heating. The result shows that, for axial temperature difference of specimen, the impacts of the four factors are ranked from the most important to the least important as coil inner diameter, coil spacing, power frequency and exciting current. While for radial temperature difference, the ranking list of importance becomes exciting current, power frequency, coil inner diameter and coil spacing.

The results of obtaining borated layers on 15H11MF high-alloy steel under equilibrium and non-equilibrium heating conditions are presented. Equilibrium conditions were achieved by slow furnace heating (with a heating rate of 0.1 oC/s), non-equilibrium – by induction heating (with a heating rate of 100 oC/s). The heating was controlled by measuring the thermoelectric power by a thermocouple welded to the surface of the sample by electric contact welding. The signal from the thermocouple was digitized by the ADC and transmitted to a computer where, at high speed, an array of data of temperature-time dependence of the process was formed. Furnace heating was carried out in a laboratory electric furnace at 1130 оС ± 5 оС, 1150 оС ± 5 оС and 1160 оС ± 5 оС. Induction heating was carried out to temperatures of 1180 oC ± 20oC, 1200 oC ± 20oC, 1220 oC ± 20oC. The possibility of significant reduction of the treatment process from 3 hours to 2 minutes due to the intensifying action in non-equilibrium conditions of structure formation is shown. Boron saturation came from the paste. Saturating paste consisted of 60% boron carbide, 30% NaF, 10% CaF2. The method of metallographic research shows not only the morphological differences of the obtained surface layers, but also established the predominant mechanism of boron diffusion into high-alloy martensitic steel. During furnace heating (1150оС), a solid boron with a thickness of up to 50 μm and a hardness of 15100 MPa is formed. At a depth of up to 150 μm, grain boundary diffusion is noticeable, which obviously dominates in the processes of boron saturation of high-alloy steels. At temperatures of 1160 oC and furnace heating under a solid layer of boride with a thickness of 110 μm, a two-phase zone is formed, which consists of boride and a solid solution with a thickness of 70 μm. This layer is more defective. Induction heating with boron saturation forms a thick (up to 200 μm) layer of coarse boride crystallites (18900 – 9270 MPa) with an eutectic structure (6440 MPa), which becomes coarser with increasing temperature from 1180 to 1220 оС. The ability to obtain solid hardened layers in a short treatment time makes boron saturation from pastes a more attractive alternative among other chemical-heat treatment technologies.

Aircraft CFRP parts as sharklets are produced in resin transfer molding (RTM) tooling. The parts need to be heated up homogenously over the whole area with a constant temperature. The complex shape and accessibility of the tooling make it hard to introduce a common heating system. In addition, the heat must be transferred through the Invar metal tooling structure onto the CFRP. Infrared lamp, air fan and microwave heating are concepts in development. Electrical heating layer mats and cages are laborious in applying. Induction has the advantage of contact-less, efficient, and fast heating. Induction heating was tested for the structural bonding of CFRP frames and stringers showing high bonding strengths. To apply this technology for the RTM tooling, the placement and distance of the induction coils is important. Simulation can help to find the right adjustments and power needed for induction heating. With the program COMSOL the surface and the coils are modeled, and the numerically structured net is divided in small tetrahedron and quadratic sub elements. Since there is no magnetic streamline in the middle of the coil-section, a symmetric halving of the structure is applied as a boundary condition. The temperature-time development and the distance of the coils are simulated in 2D and 3D. Due to the material properties of the magnetic flux concentrator (MFC), higher flux concentration of the magnetic field occurred only in 2D. The results are validated by experiments and are in good agreement.