Application of High-Frequency Induction Heating Apparatus to Heat Treatment of 6061 Aluminum Alloy

Abstract

A high-frequency induction heating apparatus was used for the heat treatment of a commercial 6061 aluminum alloy bar with the objective of improving the mechanical properties and productivity. Heating states of the 6061 alloy bar were examined in terms of temperature distribution, heating rate, overheating and temperature fluctuation; moreover, the mechanical properties of the alloy after heat treatment were also investigated. The results of this study are as follows. When the 6061 alloy bar was rapidly heated to the heat treatment temperature using the induction heating apparatus, temperature distribution and overheating of the sample were small as well as the temperature fluctuations in the holding process. A rapid heating rate of about 21 C/s heated the sample to the heat treatment temperature of 560 C in 26 s. The sample showed equivalent or superior mechanical properties compared with a sample heated by conventional electric furnace. Temperature and time of the heat treatment process greatly influenced the mechanical properties of the 6061 alloy, while there was no significant difference in mechanical properties of the sample heat-treated at various heating rates.

Comprehensive Power Control Performance Investigations of Resonant Inverter for Induction Metal Surface Hardening

“…In addition, induction techniques are sought for their fasthardening cycles, accurate heating pattern and cores that remain relatively cold and stable [2]. To achieve high temperature solution treatment, it is important to ensure rapid treatment, no overheating during the temperature transition [1][2]. Such characteristics minimize distortion and make heating outcomes extremely repeatable.…”

“…This type of hardening is becoming one of the preferred heating technologies, due to its advantages regarding efficiency, fast heating, safety, cleanness and accurate control, when compared with other classical heating techniques. In addition, induction techniques are sought for their fasthardening cycles, accurate heating pattern and cores that remain relatively cold and stable [2]. To achieve high temperature solution treatment, it is important to ensure rapid treatment, no overheating during the temperature transition [1][2].…”

Local Reinforcement of 6061 Aluminum Alloy Bar Using High-Frequency Induction Heating Apparatus

“…The hardness increase at each position resulted from the extension of the holding time, while the quantity of hardness increase became lower for a holding time of 5 min or more. A previous report 13) on heat treatment with rapid heating pointed out that a sample must be heated to more than 713 K to increase the mechanical properties. The findings shown in Figs.…”

“…The frequency and power of the induction heating apparatus were 2 MHz and 10 kW, respectively. The surface of the sample was sprayed with a black coating to ensure precise temperature measurement using a radiation thermometer with a measurable temperature range of more than 523 K. Based on a previous study, 13) the emissivity value of the radiation thermometer was set to 0.78 to accurately measure the temperature. The radiation thermometer measured the temperature at the tip of the bar.…”

“…In addition, because a conventional thermocouple cannot be used because of the magnetic fields generated by the induction heating coil and the emissivity of aluminum alloys is unstable for temperature measurement using a radiation thermometer, it is difficult to measure the temperature of an aluminum alloy during heating by induction heating apparatus. Our previous study 13) showed that aluminum alloy bars with a 10-mm diameter can be heated efficiently using the induction heating apparatus with a higher frequency (2 MHz) than a conventional induction heating apparatus (less than 400 kHz). Furthermore, surface coating of the aluminum alloy with a black spray also leads to precision temperature measurement using a radiation thermometer.…”