Induction heating of workpieces forging and stamping

Determine the composition of the line

For short measuring blanks, a piece-by-piece or sequential feeding through a multi-turn inductor is used. If only the end of the bar is heated, the inductor and the stop form the zone of the desired length without heating the rest of the metal. For serial production, a drive, a pusher, a roller conveyor, a pyrometer, a rejection of an underheated part and communication with the press can be provided. UralInduktor forms the concept of the complex and the technical solution, and the Chinese plant performs detailed design and manufactures equipment according to the agreed concept.

The operating frequency is chosen primarily by the transverse size and the required uniformity. For relatively small workpieces, the ABB and AVZ series are considered. For a massive section, deep and through heating, as well as a long inductor, AVN is prioritized, including the 1–20 kHz range. AVVS is used for small parts and local areas where a higher concentration of heating is required. LN is convenient for manual operations and experienced work with the delivered inductor, but for a stable forging line stroke, stationary feeding is more often designed. The final range is confirmed by the test; the actual frequency inside it depends on the inductor and the part.

What data is needed to calculate

The more accurate the initial data, the more reliable it is possible to link the power, inductor length and performance. For several sizes indicate the entire range and share of each product in the program, and not only the largest position.

steel grade, initial and required workpiece temperature;

shape, diameter or sides of section, length and mass;

heating completely or only the area indicating the length of the zone;

required performance in pieces or kilograms per hour;

allowable temperature difference between the surface and the core;

loading method, feed direction, line height and transfer time to the press;

Network voltage, available electrical power and liquid cooling conditions.

Indicative example of calculation

The example is an evaluation and does not replace thermal calculation and trial heating. The steel cylindrical workpiece Ø 40 × 100 mm has a mass of approximately 0,99 kg. For heating from 20 to 1150 °C, take the average specific thermal capacity of 0,65 kJ/(kg·C): 0,99 × 0,65 × 1130 ox ≈ 727 kJ or 0,20 kWh heat per unit. With the conditionally accepted total CPD of the 55 process, it would take about 0,36 kWh of electricity per part. At the 60 rate, the average calculated load per hour would be approximately 22 kW.

For power supply, there is a reserve for starting a cold line, losses, interoperational pauses and holding the specified stroke. In this example, the subject of verification may be the power input of the order of 30–40 kW, but it is impossible to name the model only by calculated energy. The nominal output power of the converter is not equal to the power transferred to the part. At the test, the relationship of power, frequency, core length, heating time and temperature difference in cross-section is specified.

Inductor, temperature control and cooling

The inductor is designed taking into account the gap, alignment and method of removing the scale. A simple copper tube inductor is usually included. Complex profiles, sets for several sizes and quick-change inductors are calculated separately by agreement. For repeatability of the process, a pyrometer with a given measurement range and the logic of reaction to underheat or overheating is advisable. The emission ability and the viewing location are specified on the real surface: the reading of the pyrometer without setting cannot be considered an unconditional core temperature.

The converter and inductor are cooled by liquid. The cooling system is selected according to the thermal calculation, power, operating time and conditions of the workshop; air cooling is not used for such a task. With a correctly calculated contour, the equipment can work around the clock in compliance with the established load mode.

Verification and commissioning

The equipment comes with Russian-language control and documentation. After assembly, the factory checks the installation with the inductor ordered; UralInduktor receives photo and video materials in the agreed volume. Before shipment to the customer in Miass, a re-check is performed with full connection without load. The commissioning works take place at the customer’s site with its details: specialists check the regime, conduct trial cycles, train personnel and draw up acts.

Temperature, performance and evenness of heating are not guaranteed only by calculation: they are fixed after testing on parts or on an agreed analogue. Warranty - 18 months; the beginning of the term is determined by the contract from the date of shipment or the signing of the commission act.

What to send for selection

Send the drawing of the workpiece, the grade of steel, the required temperature and line stroke. We will prepare the heating concept, offer frequency range, power, inductor and mechanization. Price - on request after analysis of technical specifications.