Shaft muffle electric furnaces, type SShZM
Purpose and application
Shaft muffle furnaces are used for heating under light or clean annealing of steels or non-ferrous alloys. Depending on the supplied atmosphere, the surface of the workpieces can be clean or even bright, even with prolonged annealing. These electric furnaces are similar in application to the purpose of bell-type furnaces.
As a protective atmosphere, it is possible to use inert or generator gases, and even hydrogen. A fan for stirring the protective atmosphere and a cooling system are available as options. The protective atmosphere is fed directly into the muffle and, depending on the density, downward or upward.
Frame made by welding profiles into a truss with upholstery in sheets, in the form of a vertical chamber (shaft). From above, the frame is covered with a steel sheet with an opening for the passage of the muffle. Outside, part of the frame is covered with protective covers. A hinge is attached to the frame for installing the swing frame under the cover or guides for rolling back the cover. The traditional color of the frame is blue, the panels are light gray, it is allowed to agree on the color of the coating under the Customer's brand.
Thermal insulation. A lining is mounted inside the frame, forming a heated space. Thermal insulation of the side walls is made of a combination of fibrous, microporous materials of various brands (fiber boards, bricks, sheets, cotton wool). The furnace is lined with durable refractories. On the inner surfaces of the walls of the heating chamber, there are special combs for fixing the heater supports. The shaft is covered from above by ballscrew slabs with an opening for the passage of the muffle. B through the lining, as an option, it is possible make a hole for the possibility of forced air supply by a fan at the stage of cooling the workpieces.
Muffle is obtained by rolling a sheet of heat-resistant nickel steel 20X23H18 into a cylinder, with one vertical seam. On the one hand, the bottom is welded to the cylinder, on the other, the supporting and sealing flanges. At the bottom, there is a horizontal stand. The shielding gas supply pipe is led to the bottom, and the outlet pipe is connected to the supply line. The support flange of the muffle is installed on the ceiling of the heating module through a heat-insulating fiber gasket. The sealing flange is grooved with fixed flexible heat-resistant seals.
Oven cover formed from a supporting frame with a heat-insulating insert that fits into the muffle. On the side of the furnace, the heat-insulating insert is covered with a metal casing. Sealing the working space is achieved by pressing against the flexible elements of the sealing flange. Tubes pass through the cover, branch exhaust gases, turning into a candle. The candle has a flow valve, a pressure indicator, a branch pipe with oxygen sensor "Lambda probe". The cover is suspended on a cantilever swing or retractable frame. Rise or rise, and the rollback is carried out by an electric drive controlled from a remote button post.
Electric heaters are located along the perimeter of the lining and in the grooves of the hearth masonry. Heaters are wound in in the form of zigzags made of Superfechral precision wire and fixed on special nails of the inner plates. Electric heaters are divided between phases and into several heating zones. Circular heating of the oven ensures uniform temperature field and reduces warm-up time.
Gas rack designed for dosing and supplying gases to the muffle. The post is a welded structure, on which the inert gas supply line and the reductant (hydrogen) gas supply line, including the necessary fittings, are located. The pressure regulators equalize the pressure and, before mixing, the gas mixture, dosed, along the sleeves, is fed to the muffle tube.
This system can be useful in case you need to regulate or accelerate the speed. cooling workpieces in a protective atmosphere. The air is supplied by the gas blower to the heating chamber, and the cooling speed is regulated by the fan capacity or the position of the dampers.
Electric furnace heating control produced by signals from thermocouples inserted behind the heaters, a little short of the muffle. The thermostat controls the current using the “pulse width modulation” method. Heat treatment is allowed according to the temperature-time schedule. The operation modes are registered, the magnitude of the current and voltage on the heaters is monitored. Overheating protections available, break of thermocouple and other necessary interlocks.
|Designation||Working dimensions, mm (dia × depth)||Gab. dimensions (length × height × bs)||Power, kWt||Furnace weight||Max. loading, t|
View design sketch
The optimal ratio of dense refractories on the hearth and fibrous thermal insulation along the side walls increases it service life, minimizes heat loss by heat transfer and accumulation. Increased total thickness thermal insulation minimizes heat loss through the walls. Cast hearth plates made of steel no worse than 15Kh23N18L. Application of a direct mesh sprocket mounted on the drive and a rack rigidly mounted on the bottom eliminates jerking and coasting during start and stop.