Induction Shrink Fitting Steel Tube With IGBT Heating Units
Objective Heating a steel tube to 500-1000ยฐF for a shrink-fittingย application. Determine expansion (growth) of ID at varyingย temperatures.
Material Steel tubes 7โ OD x 4.75โ ID x 5โ heat zone
Type โKโ thermocouple to measure temperature
Thermal blanket
Temperature 500, 800, 1000 ยฐF (260, 427, 538ยฐ C)
Frequency 66 kHz
Equipment DW-HF-7.5, 7.5 kW, 150-400 kHz induction power supply,ย equipped with a remote heat station containing two 1.5 ฮผFย capacitors (for a total of 0.75 ฮผF)
A multi-turn, special series-parallel induction heating coilย designed and developed specifically for this application.
Process Initial tests were completed on a sample without a thermalย blanket. A thermocouple is slipped between the copper ringย and the steel tube to measure temperature. The part measured
4.940โ (at room temperature with an ID gauge.) The partย reaches 1000ยฐF (538ยฐC) in about 10 minutes.
The chart below shows the comparison between theoreticalย and experimental measured results
Results/Benefits The part measures 4.975โ at 1000ยฐF yielding an expansion ofย 0.035โ (4.975 minus 4.94). At 500 and 800ยฐF the expansionย numbers were 4.950 and 4.964 respectively. When using a
thermal blanket the heat time is reduced by about 90 secondsย (8.5 minutes as opposed to 10 minutes).
