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Induction furnace lining procedure determines the quality of the furnace and the efficiency of the production process.
The induction furnace lining plays the role of containing the molten metal, isolating the contact between the molten metal and the outer structure of the lining such as the coil, and protecting the furnace body during the work of the induction furnace. It is the most important part of the induction furnaces.
1. Introduction of induction furnace lining
In the induction furnaces lining procedure, the furnace lining is an important component of the furnace body. The furnace body parts of the induction furnaces are insulating mica, alarm net, asbestos insulation board and refractory lining from outside to inside. The insulating mica plays the role of insulation, the alarm network plays the role of alarm and warning, and the asbestos insulation board plays the role of heat insulation.
In actual production, induction furnaces linings have several different structures, among which coreless induction furnace linings are generally more demanded by customers.
2.Process characteristics
Characteristics of induction furnace lining procedure
Masonry of furnace lining
When building a furnace, it is necessary to pay attention to:
(1) Remove the original mica paper laid.
(2) Perform certain treatments on the selected refractory raw materials:
①Hand selection: Hand selection is to remove lumps and other impurities in raw materials:
②Magnetic separation, completely remove magnetic impurities, prevent accidents such as leakage or breakdown induction furnace:
③ The raw materials are dried slowly at a temperature above 200°C and kept warm for a period of time.
Asbestos boards are used to separate the refractory crucible and the induction coil to ensure the insulation and heat insulation performance of the furnace lining; some small holes for draining water are drilled on the asbestos boards to facilitate the drying of raw materials.
The bonding agent for the furnace lining, the tamping method and the baking process will all have a great impact on the lining of the induction furnace. Using a reasonable oven process when building the furnace lining can save energy and improve the production efficiency of the induction furnaces. The pressure plate above the furnace mouth can prevent the thermal expansion of the furnace lining and improve the service life of the furnace lining.
The construction of the furnace lining has the following methods:
(1) Masonry type: It is suitable for induction furnaces for continuous production, and the furnace lining is built with specific fillers and refractory bricks;
(2) Out-of-furnace molding method: suitable for small-capacity induction furnaces, pressed and formed outside the furnace, dried and built in the induction furnace;
(3) In-furnace forming method: It is suitable for induction furnaces with different capacities, and the furnace lining is formed in the furnace by mechanical or manual methods.
3.Sintering of induction furnace lining
Induction furnace lining sintering is the process of forming the lining into a solid whole. A good sintering process can make the lining obtain a good microstructure, so as to obtain good performance.
Factors that affect lining sintering include sintering temperature and process, chemical composition and particle size ratio of materials, etc. The sintered crucible structure is the basis for the induction furnace lining. People in the industry attach great importance to the quality of induction furnace lining.
The sintered furnace lining should have a three-layer structure, and the process of building a reasonable three-layer structure is divided into three stages:
(1) Baking stage: Heat the refractory crucible to 600°C at a certain heating rate, keep it warm for a period of time, and remove all the moisture in the furnace lining (during the firing process, adding 1.5wt%~1.8wt% boric acid can improve the sintering effect of the furnace lining optimal);
(2) Semi-sintering stage: heat up to 900°C, hold for a period of time, then raise the temperature to 1200°C t a higher heating rate, and hold for a period of time;
(3) Complete sintering stage: The firing temperature will affect the service life of the furnace lining.
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