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Vacuum Heat Treatment Furnace

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Development of aluminum foil vacuum annealing furnace

1 Introduction to structure

The aluminum foil vacuum annealing furnace unit is mainly used for the finished annealing of aluminum foil coils. The surface of the workpiece after vacuum heat treatment is not oxidized and decarburized, with small deformation and good mechanical properties. The main components of the unit are a 4.5-ton aluminum foil vacuum annealing furnace, a vacuum system, a composite feeding and discharging car and a material rack, a compressed air system and a temperature control system. The following mainly outlines the structure of the 4.5-ton aluminum foil vacuum annealing furnace.

The effective working space of this aluminum foil vacuum annealing furnace is 3000 x 1200 x 1200mm, which is mainly composed of a vacuum chamber, a vacuum furnace door, a damper, a heating chamber, a heat exchanger, a cooling circulation fan and an air charging system, and the overall shape is a cube.

1.1 The vacuum chamber is a double-layer water-cooled sandwich structure. The outer shell is welded from carbon steel plates and profiles, and the inner shell is welded from stainless steel plates, and the inner wall is polished with high precision to reduce the amount of outgassing and enhance heat reflection.

1.2 The door of the vacuum furnace is a double-layer water-cooled sandwich structure with a circular shape. A heating chamber door is installed on the inner side of the furnace door to seal the heating chamber, and the opening and closing of the heating chamber door is controlled by a cylinder installed on the outer side of the furnace door. The furnace door is suspended by a 2-ton electric trolley and a 2-ton driven trolley, and the furnace door is opened and closed by driving the furnace door left and right by the electric trolley. There are two travel switches in the furnace door suspension device to achieve accurate positioning of the furnace door, and a manual control button is provided at the same time, which can control the walking of the furnace door by jogging. The furnace door is pressed by four sets of handwheel pressing devices. The furnace mouth seal between the vacuum furnace door and the vacuum chamber is sealed with a vacuum sealing rubber strip, that is, an inner and outer pressure strip is inlaid on the flange of the furnace door shell, and a vacuum sealing rubber strip is arranged between the inner and outer pressure strips. The structure of the furnace mouth sealing device is characterized by good sealing effect and compact structure.

1.3 The air door is composed of shell, heat preservation furnace lining and air door transmission components. The movement of the air door is realized by the motor driving the worm gear reducer and the screw drive.

1.4 The heating chamber is mainly composed of a cuboid frame formed by welding section steel and steel plate, a heat preservation furnace lining, a heating part and a copper strip connection. The front and rear of the heating chamber are respectively provided with a door, the sealing groove of the front door is inlaid with a sealing strip to seal against the heating chamber door inside the furnace door, and the sealing groove of the rear door is also inlaid with a sealing strip to be sealed by the air door.

The thermal insulation furnace lining is laid with aluminum silicate refractory fiber needle-punched blankets. The thermal insulation furnace lining is fixed on the rectangular frame formed by welding section steel and steel plate. The inner and outer lining plates of the thermal insulation furnace lining are made of heat-resistant steel plates.

Heating part: The heating element adopts Cr20Ni80 resistance belt, which is suspended on the inner wall of the heating chamber with a porcelain piece, and the external wiring between the heating elements is connected by a copper belt. The outlet end is drawn out of the furnace through a water-cooled electrode and connected to the secondary phase of the thyristor voltage regulator. In order to ensure the uniformity of furnace temperature and the accuracy of temperature control, electric heaters are evenly distributed on both sides of the furnace, and the electric heaters are divided into three zones for control. The thyristor voltage regulator is used with the control method to realize the stepless regulation of the output voltage, so as to achieve the purpose of regulating the power.

1.5 Heat exchanger: It is mainly composed of a finned heat exchanger with cooling water inside.

1.6 Cooling circulating fan: It is composed of stainless steel centrifugal impeller and electric motor.

1.7 Air charging system (workpiece cooling system). The system mainly provides cooling medium by argon contact, and the inflation pressure is less than 0.2Mpa. It relies on pneumatic high vacuum pressure ball valve and manual valve to realize the opening and closing of air supply. The flow control is performed by the mass flow controller in the inflation pipeline and the manual valve. accomplish. There is also a manual valve in the pipeline of the inflation system for rapid deflation under high vacuum. The cooling of the cooling medium is carried out by the heat exchanger at the rear of the furnace. In order to speed up the cooling speed and uniform cooling, the fan at the rear of the furnace body is forced to circulate the cooling medium.

2 Furnace door opening and improvement of sealing device

The traditionally designed vacuum furnace door adopts the rotary opening method, which has the following disadvantages: firstly, it occupies a large space, wastes plant resources, and has poor mobility; secondly, the sealing of the rotating shaft is not strict, the service life of the sealing ring is short, and the sealing ring Aging causes the furnace gas to escape and reduces the thermal efficiency. Based on the above problems, it is proposed to develop and design a new type of furnace door opening and sealing device.

2.1 The furnace door is opened by traversing and self-traveling. The furnace door is opened by horizontal movement. The furnace door is connected to the self-propelled trolley through hinges. The track of the trolley is fixed parallel to the top of the furnace door. In the free state, there is a certain gap between the furnace door and the door to ensure that the furnace door does not move with the furnace door. contact occurs.

2.2 The furnace door is pressed by four-point pressing method. The furnace door of the aluminum foil vacuum annealing furnace produced in the traditional way is generally opened by means of the rotating shaft at one end of the furnace door. The disadvantages of this structure are mainly concentrated on the problem of poor sealing on the rotating shaft side of the furnace door, and the rubber ring is not in contact with the furnace door. Synchronization leads to the first wear of the rubber ring on the side of the rotary shaft of the furnace door. The new furnace door opening and furnace mouth sealing method avoids a series of drawbacks caused by the rotating furnace door, and does not require strict positioning accuracy, which makes the installation, use and maintenance of the equipment more convenient and quick. In order to ensure good sealing of the furnace mouth, the furnace door is pressed by four-point pressing method, that is, there is a pressing point on each of the four corners of the furnace door. When the furnace door needs to be closed, the trolley drives the furnace door to walk to the furnace mouth for four Point pressing, the pressing force is even. When opening, the four sets of handwheel pressing devices are opened at the same time, and the furnace door is separated from the furnace door by its own weight. Its characteristics are that the rubber ring is evenly stressed and avoids wear.

2.3 Recommended technical parameters. The power of the traversing trolley is 0.4kW, the moving speed is 4m/min, and the pressing method: four-point manual screw pressing.

3 Postscript

After the above design improvements and repeated demonstration experiments, the new furnace door opening method, furnace mouth sealing device, furnace door pressing and walking mechanism are easy to install and disassemble, and the overall structure is compact, which can meet the various performance indicators required by the equipment. After on-site installation, commissioning and operation, it has been proved that the equipment has improved significantly: first, the furnace door system is more compact than the traditionally designed rotary furnace door system, the floor space is significantly reduced, and plant resources are saved; The furnace thermal efficiency is improved.

Equipment selection of vacuum annealing furnace: RVA vacuum annealing furnace produced by SIMUWU is an excellent choice for completing this type of process. Its process performance can fully meet the needs of such thermal processing, with good temperature control accuracy, temperature uniformity and annealing uniformity. High process repeatability, stable production, quality output can be guaranteed.