CN102497688B - Induction Heating Technology for Double-sided Roll Forming of Disc Parts - Google Patents

Abstract

The invention provides a discal-part induction heating technique used in the double-sided roll forming of discal parts. The technique is implemented by using a conventional induction heating power supply, a temperature controller, a water-cooling machine and a specially-designed induction coil and a method for controlling a heating process. Compared with the conventional batch-type furnace heating mode, the technique has the characteristics of short deformation-free heating time, capability of avoiding the growth of crystal grains of materials for discal parts, low heat loss and convenience in operation. In addition, because a rolling head is not arranged in the induction coil, the temperature of the rolling head is far lower than the temperature of a deformed discal part, thereby lowering the requirement on the high-temperature strength of materials of the rolling head, and reducing the material and processing cost of the rolling head, so that the isothermal roll forming of some high temperature alloy discal parts which are difficult to deform becomes feasible.

Description

Induction Heating Technology for Double-sided Roll Forming of Disc Parts

technical field

The invention relates to a heating technology for a disc shape in double-sided rolling forming of the disc shape.

Background technique

The existing double-sided rolling forming of disc-shaped parts uses a box-type furnace to heat the disc-shaped parts to be formed, as shown in Figure 1. In this type of heating, both the rolling head and the rotating spindle of the disc are heated in the furnace simultaneously with the disc shape. Although this heating method can achieve isothermal rolling forming, the four rolling heads and both ends of the main shaft are water-cooled outside the furnace, which will take away a lot of heat, which not only wastes energy but also increases the difficulty of water-cooling design; On the one hand, the rolling head and the plate are in the same heating furnace. To make the plate deform plastically through the rolling head, the high temperature strength of the material of the rolling head must be much higher than that of the plate material. In this way, when the disc material is a hard-to-deform superalloy, it is difficult to find a suitable material for the rolling head. Therefore, it is difficult to realize the rolling forming of a hard-to-deform material superalloy disc with the existing heating method. Third, for large disc blanks, the heating time of the box furnace is longer, which may cause grain growth for some materials.

Contents of the invention

The invention relates to an induction heating technology for a disk-shaped piece used in double-sided rolling forming of the disk-shaped piece.

The hardware equipment included in the induction heating technology adopted by the present invention is: induction heating power supply, special induction coil for heating plate, temperature controller for temperature rise speed and heat preservation control, water cooler for power supply and induction coil cooling. The current frequency for induction heating can be high frequency, medium frequency or low frequency, which mainly depends on the resistivity and thickness of the formed disc blank. The selected frequency range is approximately: (10 ⁶ × resistivity ÷ thickness ² ) between 3 times and 6 times, where the unit of resistivity is Ω/m, the unit of thickness is m, and the unit of frequency is HZ. For example, if the thickness of the blank is less than 40mm, high-frequency induction heating should be used. When the thickness of the blank is 40-100mm, medium-frequency induction heating should be used, and thicker blanks should be heated by power frequency induction. The power of the induction heating power supply is related to the type of material and the size of the plate. The estimation method is: (blank weight × heating temperature × specific heat) ÷ total efficiency. The high temperature efficiency of steel is 0.6-0.8, and the efficiency of aluminum alloy heating is about 0.5. The technical parameters of the water cooler are determined by the power and efficiency of the power supply. Assuming that the heat generated by the induction coil, inverter and capacitor is equal to 50%, 7.5% and 1.5% of the total power, the temperature difference between the inlet and outlet is 20°C, the specific heat of water=4.2kj/kg/°C, and the safety factor=1.15, then cooling is required The water flow rate is about w=0.03×the total power of the power supply, where the power unit is KW, and the flow unit is m ³ /hour. Increasing the temperature difference between the inlet and outlet water can reduce the water flow. In order to keep the disc at a constant temperature during the rolling process, a temperature controller is required, which includes an infrared thermometer for non-contact measurement of the disc temperature and a regulator for closed-loop temperature control. Referring to the existing induction heating theory and empirical formula, the special design of the heating induction coil of the disc is carried out according to the material properties of the disc and the geometric dimensions of the disc. The induction coil is divided into upper and lower parts, which are symmetrically placed on the upper and lower sides of the disk, and separated by a certain distance, and the heated disk is covered in the induction coil. The rolling head is placed horizontally between the upper and lower induction coils, and the disk is loaded outside the induction coil to achieve rolling forming. In order to minimize the influence of the magnetic field of the induction coil on the rolling head, so that the rolling head is not heated by induction, and in order to prevent the induction coil from affecting the movement of the rolling head, the distance between the upper and lower induction coils should be slightly larger than the diameter of the rolling head. as shown in picture 2. Although there is an area between the upper and lower induction coils that is not covered by the induction coil, because the disc is constantly rotating during the rolling process, the mass point of the disc is in the constant alternation of induction heating and plastic deformation, so through reasonable control of the disc The rotation speed of the parts can ensure that the deformation zone of the disc is in a state of isothermal and uniform temperature. During the rolling forming process, the rolling head is always outside the induction coil, and the effect of induction heating is very small. Only the heat transfer with the workpiece makes the local temperature rise, so the temperature of the rolling head is much lower than the temperature of the disc. This reduces the requirements on the high temperature strength of the rolling head material.

The operation steps of using the induction heating method to implement the rolling forming of the disk shape are as follows: 1) Install the disk blank and the upper and lower induction coils; 2) The rolling head contacts the disk piece, and after applying a certain pressure, start the motor to let the rolling head drive the cold disk blank to rotate; 3) Set the heating temperature, turn on the induction heating power supply, and start induction heating of the rotating disk; 3) In order to ensure that the rolling deformation is in an isothermal state, a certain heating time and heat preservation should be left before the rolling deformation is officially carried out. The time is related to the blank material and the set heating temperature. Generally, it takes 5-10 minutes for the surface temperature to reach the set temperature. The purpose of heat preservation is to overcome the skin effect of induction heating, and make the temperature in the thickness direction uniform through heat conduction. The thicker the plate, the longer the heat preservation time is required. For most disc materials and discs with a thickness not greater than 100 mm, the required heating and holding time before rolling is 6-15 minutes. The plate is kept at a constant temperature by means of a temperature controller throughout the rolling process. After the rolling is completed, the power is turned off to stop heating, and the disc is taken out. Due to the short heating and holding time of the plate before rolling deformation, for most materials, this induction heating method will not cause significant grain growth.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be described in further detail below in conjunction with the accompanying drawings

Figure 1 Schematic diagram of the installation of the heating plate, rolling head, and spindle of the double-sided rolling box furnace for disc-shaped parts.

Figure 2 Schematic diagram of the shape and installation of the induction coil for double-sided rolling induction heating of disc-shaped parts. The rolling head is placed between the two induction coils.

Figure 3 Practical induction coil.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Here is an induction heating system for double-sided roll forming of small disk-shaped parts (diameter less than 200mm, thickness less than 30mm). This system includes a 40KW high-frequency induction heating power supply, a 4-horsepower air-cooled chiller, a water pipe with a diameter of 1 inch, and a temperature controller with a non-contact infrared temperature sensor. The shape and size of an induction coil for heating the disk is shown in Figure 3, wherein the induction coil is square and larger than the disk. The distance between the upper and lower induction coils is adjustable within the range of 65-80mm. The coil interval of the induction coil is 8mm, the copper pipe is a rectangular section, the size is 12×10mm, and the wall thickness is 1-2mm. For the heating of the titanium alloy disc blank with a diameter of 200mm and a thickness of 20mm, the set forming temperature is 927°C, and after heating and holding for 6-15 minutes, the rolling head can start loading for rolling forming. During the rolling process, the temperature controller ensures that the disc is in the isothermal process until the rolling is completed and the disc is unloaded.

Claims (1)

1. for a dish-type part induction heating technology for dish-type part two-sided roll milling forming, it is characterized in that: in two-sided roll milling forming process, heat dish-type part, the heating of diskware, distortion and rotational synchronization are carried out; According to dish-type part material property and physical dimension, be that dish-type part designs special induction coil, induction coil is divided into upper and lower two parts, and heated diskware is enclosed within induction coil, and ram is placed between two induction coils; Designed induction coil will guarantee ram working space and diskware deformation space, guarantees that the induction heating temperature rise of ram does not cause its plastic deformation, coordinates rotating speed and guarantees that diskware is out of shape under predetermined state of temperature; According to the heating-up temperature of diskware material and setting, determine the suitable heating and thermal insulation time, be less than the diskware of 100mm for thickness, before roll milling forming, the needed heating and thermal insulation time is 6-15 minute.

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