Medium Frequency Induction Heating Research Articles

Experimental study on induction heating generation for plastic deformation

The resistance heating system, or band heater, was usually used for deformation in the plastic recycling process and works on the principle of Joule heating: an electric current through a resistor converts electrical energy into heat energy. However, the main problem with resistance heating is heat conduction because some heat is lost in the transference from the wire to the body. According to this problem, induction heating was designed into the process because electromagnetic induction can directly produce heat in the object. This study provides a simple temperature control for a low-cost, high-efficiency, and high-power factor based on the Class-E DC-AC resonant inverter that was applied for operating under the zero-voltage switching (ZVS) condition to test the plastic deformation efficiency. The inverter was used to test the efficiency of the plastic deformation. The medium-frequency induction heating that has been proposed is designed to operate at a frequency ranging from 10 to 100 kHz, a line rms voltage of 220 V, a line frequency of 50 Hz, and an output power of 600 W. The experiment's results provide verification that supports the viability of the proposed induction heating method.

Study on Distribution of Heat Treatment Temperature Field of Long distance Oil and Gas Pipeline with High Steel Grade

In-service welding repair is important to ensure natural gas pipelines’ safe and reliable operation. The temperature distribution in the welding heat treatment process directly affects the pipeline’s bearing capacity and local stress distribution. This study studied the temperature distribution of a high steel pipeline generated by the heat treatment process for the long-term transportation of oil and gas was studied experimentally. The medium frequency induction heating method is applied to heat the tube body by winding a heating belt on the outer wall of the steel pipe to simulate pre-welding and post-welding heat treatment. At the same time, a thermocouple is used to record the temperature change of each position during the whole heating process to obtain data. Through numerical analysis and fitting, the distribution law of the temperature field in the heat treatment process of steel pipe is established to guide the field heating temperature control.

Experimental Study on Local Heat Treatment of Thick Plate with Medium Frequency Induction Heating in Pressure Equipment

Experimental Study on Local Heat Treatment of Thick Plate with Medium Frequency Induction Heating in Pressure Equipment

Study on Purification Technology of Silicon Carbide Crystal Growth Powder.

Silicon carbide (SiC) is a wide-bandgap (WBG) semiconductor material, and its preparation process has strict requirements on the purity of raw materials. A self-developed medium-frequency induction heating furnace was used to carry out powder heat treatment and purification experiments on SiC powder to improve the purity of the powder. Samples with 3.5N purity were analyzed using XRD and GDMS characterization methods. It was found that under conditions of high-temperature (2200 °C) and long-time (50 h) processing, the impurity removal effect was quite good, but the powder loss was as high as 53.42%. The powder loss during the low-temperature (less than 2050 °C) and short-time process was less than 1.5%, but the purification effect was not substantial. After a prolonged processing time, the purification effect of low-temperature heat treatment conditions was improved, but the powder loss was also increased to 30%. In contrast, segmented purification processing at a low temperature in the early stage and a high temperature in the later stage achieved a good purification effect. On the premise of maintaining the utilization rate of raw materials, a 5N-purity SiC source was successfully prepared. The test results show that the contents of free Si, free C and free oxygen impurities were reduced to less than 0.01%, and the contents of Al, B, Fe, Mg, Na, Ti and other impurities were less than 1.15 ppm, which is close to the ppb level.

Application of model-free adaptive temperature control in medium frequency induction heating

Induction heating has a series of advantages such as high heating efficiency, low energy consumption, and environmental protection. It is widely used in the heat treatment of metal workpieces. Only when the temperature of heat treatment meets the process requirements can the quality of workpiece be guaranteed, so the temperature control algorithm is very important. The heat treatment requirements of thick wall pipeline are more stringent than those of conventional workpieces, in order to better control the heat treatment temperature, a model-free adaptive temperature control algorithm based on data-driven is proposed. The principle and rationality of the algorithm were analyzed, and the previous process data were analyzed and fitted. Then the controller was designed and tested in the field of thick-wall pipe heat treatment. The results show that this method can improve the accuracy of temperature control, enhance the uniformity of temperature distribution, and meet the requirements of the production process.

Research on local compensation technology of large diameter steel pipe with heterogeneous structure and analysis of application

When large-diameter steel pipes have special structures with stiffening rings, grouting holes, etc., the electrostatic spray epoxy powder anti-corrosion process is likely to produce large temperature differences due to the sudden thickness changes during heating, which cannot meet the temperature requirements of powder spraying. This paper designs a set of automatic temperature compensation technology for large-diameter steel pipes with stiffening rings and grouting holes, which aims to solve the problem of uneven heating of stiffening rings and grouting holes in the medium frequency induction heating powder spraying process. Through the method of “intermediate frequency heating + stiffening ring temperature compensation”, the inner and outer parts of the steel pipe are heated evenly and the temperature difference is reduced. The temperature difference between the inner wall of the steel pipe is reduced to 3∼15°C in the area of the stiffening ring, and the temperature is reduced in the area of the grouting hole. The difference is reduced from 70°C to 57°C to 20°C, the temperature difference is controlled within the allowable range of technical requirements, and the temperature compensation effect is good. The process has the advantages of simple device structure, high work efficiency, and small temperature difference in the spraying area, and is suitable for use on similar large-diameter steel pipes or other hydraulic metal structures.

Controlled synthesis of monolayer graphene with a high quality by pyrolysis of silicon carbide

Monolayer graphene with high quality was synthesized by pyrolysis of 6H-silicon carbide single crystal in a medium frequency induction heating furnace. The obtained graphene was systematically studied via Raman spectroscopy, atomic force microscopy (AFM), and high-resolution transmission electron microscopy (HRTEM). The characterized results showed that monolayer graphene with high quality was obtained when the growth temperature, Ar flow, and growth pressure was 2000 °C, 150 sccm, and 15 Torr, respectively. Our results showed that growth temperature, Ar flow, and growth pressure had great influence on the quality of the obtained monolayer graphene. Compared with the conventional monolayer graphene preparation methods, our method is simple, controllable, and repeatable, which greatly expands the application prospect of graphene.

The Analysis of Numerical Simulation About Thermal Management on Frequency Converter

For the heat loss of frequency converter in 50KW class medium-frequency electron magnetic induction steam generator system, this study explored a new solution for inverter cooling and waste heat recovery, which solved the problem of coolant temperature rise while replacing the cooling water, meanwhile recovered part of the waste heat for re-production. The heat dissipation of the power device is simulated to analyze the rationality of the heat dissipation system structure, and the thermal resistance equivalent circuit is established to realize the accurate calculation of the temperature at each point in the system. Experimental research under different environmental temperatures, power, and total cooling water conditions has been done to test and verify its function, the findings show that the designed heat dissipation system for the medium frequency induction heating power supply device works well, which makes the temperature of all pivotal devices converge to normal operating temperature range and increases the energy efficiency of the system by about 4%. The proposed cooling scheme is suitable for promotion in heating projects with high power equipment.

Three-dimensional analysis of medium-frequency induction heating of steel pipes subject to motion factor

As hydrocarbon resource exploration will extend towards deep sea and alpine cold areas in future, the corresponding welded pipes for oilfield use will face increasingly adverse operating environment. Acquisition of more precise heat source for medium-frequency heat treatment of welded pipes is fundamental to postweld residual stress analysis, weld microstructure improvement and performance research. However, as a pipe billet is subjected to movement factor, it is very tough to solve for a three-dimensional heat source closer to real pattern with complex process parameters. In this paper, the authors utilized a computing method of sequential coupling combining electromagnetic-thermal coupling and relative motion between steel pipe and coils, and designed the corresponding computation flowchart, and by computing pipe billet heat treatment process, they found that the steady-state temperature field formed around a weld appears double ellipsoidal. Further analysis shows that the root cause of the double ellipsoidal temperature field is asymmetric distribution of magnetic flux density and induction current, generated in the weld zone due to electromagnetic effect, within the steel pipe in axial direction. Moreover, stability and hysteresis of pipe billet temperature field were studied. It’s found that there is a certain hysteresis between the maximum temperature of inner surface and that of outer surface, because of two different heat sources undergone by the inner and outer surfaces of the weld, as well as relative motion between induction coil and welded pipe. The unique heat transfer process and temperature distribution pattern in wall-thickness direction is the immediate cause of the double ellipsoidal three-dimensional temperature field. This study offers a referenceable analysis method for further exploring steel pipe induction heating process under complex process parameters and optimization of the process parameters.

Multi-objective Optimization of Medium Frequency Induction Heating Process for Large Diameter Pipe Bending

Medium frequency induction heating for large diameter pipe bending is an advanced technique that has been widely used. However, the thickness control of outer wall and inner wall of pipe is still difficult in the actual production: outer wall tends to be thinner and inner wall tends to be thicker. Therefore, it is necessary to optimize the process parameters of bending. Combined central composite experimental design and a proper selection of design parameters sample, an accurate response surface model was built in order to decrease ovality, thickness reduction ratio and forming load. The response value of objective function was analyzed; and important influence factors for system stability were found, i.e heating temperature, heating width and advance speed. The results indicate that the optimal value range were heating temperature of outer wall t=1030∼1070°C, while advance speed v=0.3∼0.4mm/sec. Practical results from multi-objective optimization could achieve qualified products.

Mechanical properties and hardness results of the medium frequency induction sintered iron based powder metal bushings

In this study; iron based powder metal (PM) bushing compacts were sintered via medium frequency induction heating system. Iron based powders were mixed with 2 wt.% copper (Cu), 0.3 wt.% carbon (C) and 1 wt.% zinc stearat (Zn-st) via V-Type mixer. PM compacts were sintered by 2 different sintering processes. One of them was conventional sintering method other was medium frequency induction sintering method. In conventional sintering process, PM bushing compacts were sintered under inert environmental at 1120?C for 30 minutes. In medium frequency induction sintering process, PM bushing compacts were sintered between 30-50 kHz frequency (Medium frequency) at 2 kW, 1120?C for 1 or 3 minutes under atmospheric environmental. Mechanical properties, densities and micro hardness? were investigated for all sintered processes. SEM and micro structural images were taken from polished broken surface of the sintered PM bushing compacts. 3 minutes induction sintered compacts were reached the compressive strength, microhardness and density values of the conventional sintered PM bushing compact.

Nd,Yb:YAG Laser Crystal Production and its Property

To produce Nd, of Yb: YAG laser crystal by use of medium frequency induction heating Czochralski method.Taking advantage of the XRD, absorption spectra and fluorescence spectra on the crystal of the phase structure of and spectral to analyze the performance of structureshows that: Nd, Yb: YAG crystals belong to the cubic crystal system with the lattice parameters a = 1.2021 nm. There is a strong absorption in the 808nm but under the common temperature Nd, Yb: YAG crystal fluorescence spectra of the strongest fluorescence emission peak at 1030nm, attributable to the Yb3 +ion2F5/22F7/2level transition

The Development of Detection System for Three-Dimensional Alternating Electromagnetic Radiation

Medium frequency induction heating is a kind of energy-saving heating method. Now it has been applied to industrial heating craft, and it reveals that it has wide application prospect. However, due to the problem of electromagnetic radiation, it is extremely necessary to do some detection and protection. Based on this study background and according to the standards of EN62233:2008 Measurement Methods for Electromagnetic Fields of Household Appliances and Similar Apparatus with Regard to the Human Exposure in European Union, the guidelines of ICNIRP (the abbreviation of International Commission for Non-Ionizing Radiation Protection) with the international authority are adopted on the protection standards of electromagnetic field. And a new detection system for three-dimensional alternating electromagnetic radiation has been developed, and is used to detect electromagnetic radiation generated in industrial medium frequency induction heating. In the laboratory test, the precise instrument imported in Germany was a comparison of the equipment. And when testing the same heating object, the test results had better consistency between the precise instrument and the new detection system. On the basis of test requirements in EN62233, a comprehensive value of electromagnetic field intensity has been gotten after the superposition of every effective harmonic component in electromagnetic field, and the prompt of exceed standard is given in the paper, which gives a viable reference and guidance for electromagnetic radiation detection of medium frequency induction heating. After experimental debugging and system calibration in the laboratory, the detection system is running stably and accurately, and reaches the design requirements.

Study on Application and Realization of Integrated Control to Medium-Frequency Induction Heating

A integrated control strategy for medium-frequency (MF) induction heating system is presented in this paper. The output power regulation of MF-induction heating system used repetitive-Fuzzy PID integrated control, which can enhance the ability of the control system to withstand the parameter variations and nonlinear uncertain disturbances, and improve the dynamic characteristic of the control system; the digital phase-locked loop (DPLL) was applied to control the output frequency of MF-induction heating, which reduce the losses of switching components and improve the efficiency of the overall control system. The experimental results show that the proposed control scheme can endow the MF-induction heating power supply system with good steady state and dynamic performance and the power modulation control system can keep better precise control quality, output power adjustment quickly, high output power factor and verify the validity of the proposed integrated control strategy.

1.03μmYb: YAG Laser Crystal Production and its Property

In this paper, the crystal growth, ceramic preparation and performance of Yb: YAG was studied systematically. The new technics that is filling protective atmosphere in the lower vacuum has been presented firstly. The Yb: YAG laser with a dimension of Φ27mm×100mm was grown by Czochralski method to medium frequency induction heating. The performance of Yb: YAG crystal was investigated by using several measurements, such as absorption spectrum, fluorescence spectrum and so on.

Research into Grinding Hardening of Microalloyed Non-quenched and Tempered Steel

Grinding hardening is a new technology of hardening steel piece surfaces with grinding heat generated in the grinding process instead of with a high or medium frequency induction heating method, which can effectively integrate grinding and surface hardening. Experimental studies were carried out on grinding hardening of non-quenched and tempered steel. Through grinding experiments with variable depths of cut and feeding rate, the variation in the depth of the hardening layer was studied and the microstructure of the hardening zone of the test pieces was subsequently analyzed. In the end, the hardening effect of non-quenched and tempered steel was compared with that of 40Cr steel, which revealed the superiority of non-quenched and tempered steel in grinding hardening technology.

A Thyristor Inverter for Medium-Frequency Induction Heating

This paper is concerned with the development of a current-fed-type inverter suitable for induction heating and melting applications in the medium-frequency (1-5 kHz) range. The control circuitry, load power factor control, thyristor turn-off control, and protection techniques are discussed. A simple and reliable starting scheme has been developed which provides reliable start-up with all practical loads. The starting circuit has a main and an auxilliary part. The necessity of one or both of these starting circuits is discussed. Experimental results from a prototype unit are presented. The performance of the equipment has been found quite satisfactory.