A kiln company’s lining materials for electric furnaces, after determining the production process, among which special-shaped magnesia-chrome bricks are directly combined, are produced by refractory prefabricated parts, using wooden molds, vibration molding, drying, and high-temperature heat treatment to obtain finished products. The sample after drying and the sample after high temperature firing are shown in the figure above. It can be seen from the figure that the surface of the product is smooth after demoulding and molding, which can meet the requirements of production and use. The production control points of magnesia-chromium refractory prefabricated parts are as follows:
(1) Mix and stir.
The ingredients are required to be accurate, the mixing time must be guaranteed, the amount of binder added must be controlled, and the amount of binder added should be reduced as much as possible under the premise of ensuring fluidity and construction operability.
(2) Forming method.
According to the requirements of the product, ramming construction, vibration construction, vibration pressurization construction, etc. can be adopted. According to different construction methods, the amount of binder to be added is determined. Participate in: ramming construction<vibration pressurization construction<vibration construction, and choose at the same time Suitable moulds, such as: wooden moulds, plastic moulds, metal moulds, etc.;
(3) Release and dry.
Since magnesium-chromium castables are alkaline materials, there will be hydration reactions, so in the case of ensuring the demoulding strength, demoulding should be done as soon as possible (guarantee 4 hours in production), and reducing the demoulding time can also increase the utilization rate of the mold , to reduce costs; the curing time in the air after demoulding should also be strictly limited, try to maintain in a space with a temperature of 20°C, so as to remove moisture as soon as possible and prevent “hydration cracks” For the fired samples (as shown in Figure 3, the curing time in the air is too long), the drying time is determined according to the unit weight of the sample to ensure that the drying time is long enough to ensure that the residual moisture of the dried brick is <1.5% , so as to ensure that no cracking will occur during high temperature heat treatment;
(4) High temperature heat treatment.
The firing system is determined according to the chemical composition of the sample. At the same time, because the porosity of the refractory preform is larger than that of the shaped product, factors such as the line change rate should also be considered.