Thermal Pipe Expansion The induction heating Temperature and pushing speed

Induction heating temperature

The steel grade and wall thickness and pushing speed and heating coil will decide the temperature. Different steel grade wall thicknesses will be the different induction heating temperatures.The same wall thickness, low alloy steel temperature will be higher than the carbon steel, heavy pipe temperature will be higher than the thin steel pipe. Thermal pipe expansion adopts the medium frequency induction heating, Under the action of the alternating magnetic field, eddy currents are generated inside the steel pipe to convert electrical energy into heat energy. The penetration capacity of the eddy current is related to the frequency, the lower the frequency, the higher the penetration capacity, the higher the heating temperature, and the faster the speed. According to the empirical formula, the coil diameter

D=D4+(120mm----150mm), heating coil length L:??L2+250mm≤L≤L1+L2, each turn gap: when the wall thickness ＜25mm, gap ＜45mm, when the wall thickness is bigger than 25mm， the gap is 60mm----85mm.once the gap and length are confirmed, the more turns, the higher temperature induction heating.

So far, almost all the thermal expansion tubes produced are hypereutectoid steel, and the heating temperature should be higher than Ac3 50℃---100℃. difficult, the heating temperature should be appropriately increased. When heating the hot-expanded steel pipe, the heating temperature with the deviation of the wall thickness shall be taken. Because the higher the temperature, the smaller the deformation resistance, the faster the selectable pushing speed and the higher the production efficiency. On the contrary, the lower the temperature, the greater the deformation resistance, the slower the selectable pushing speed and the lower the production efficiency. However, if the heating temperature is too high and the heating time is too long, the austenite grains will become longer, and the bonding force between the grains will be weakened, thereby reducing the mechanical properties. melted, resulting in overburning. The heating temperature should not be too low. Too low temperature not only reduces the thermal expansion rate but also increases the hydraulic thrust and the wear of the core head. Therefore, the heating temperature must be selected moderately.

6.2 Pushing Speed

The pushing speed is related to the amount of diameter expansion, pushing times, heating temperature, friction force, and equipment capacity. Large diameter expansion, large friction resistance, and slow pushing speed. On the contrary, the expansion amount is small, the frictional resistance is small, and the pushing speed is fast. In order to reduce frictional resistance, first remove impurities such as iron filings on the inner wall of the raw steel pipe. Then evenly apply high-quality lubricant graphite, the number of pushing and pushing increases, the pushing diameter increases, the pushing force increases, the plasticity of the steel pipe decreases, and the pushing speed also decreases. All factors that affect the heating temperature affect the thermal expansion rate. The higher the temperature, the faster the thermal expansion rate. In addition, equipment capability is also very important. If the hydraulic press has enough thrust and the intermediate frequency power supply has enough power output, the pushing speed will be fast.

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