The length of the furnace depends mainly on the nature of the lining material and whether the smelting sintering process is perfect.
1. Material of the lining:
Acidic lining, the bricks should be free of impurities such as a pure ( S I 0 2 content of greater than 99 . . 3% high-grade quartz sand) in which the impurity content of F. E 2O3 ≤ 0 . . 5% , C A 0 ≤ 0.25%; A l 203 ≤ 0.2%; moisture ≤ 0.5%. In the lining sintering process, the crystalline state of quartz sand at the sintering temperature should be changed to phosphorus quartz . Otherwise , when the furnace is smelting , the temperature of the lining will occur. severe frequent changes , prompting crystalline quartz has also undergone change , will have a huge impact on the furnace . so lining sintering include ovens , it is an important part of the crucible to obtain excellent high temperature performance. In general , in order to improve the strength of the lining , the amount of boric acid can be appropriately increased .Specific ratios refer to the table below .
Table 1 Relationship between the amount of boric acid added to the acid furnace lining and the smelting temperature
Casting temperature ( °C )
Smelting temperature ( °C )
Keep sintering time ( hours )
Gray iron and high carbon steel
0.5 or more
70.6% medium carbon steel
For the alkaline lining , magnesia is used as the main material . The formulation can be referred to Table 2 and Table 3. The large tonnage and high temperature bismuth are preferably prepared by fused magnesia and fused A i2 03 .
Table 2 ratio of alkaline lining materials
Electric furnace capacity ( kg )
Magnesium sand particle size composition (%)
A l2 03
<1( mm )
1-3 ( mm )
3-5 ( mm )
5-20 ( mm )
180 mesh 40%
50-140 mesh 32%
20-40 mesh 28%
Table 3 ratio of binder for alkaline lining
Water glass - boric acid
Clay - boric acid
Table 4 oven time reference table (150 kg )
Time ( minutes )
Oven time reference table (250-500 kg )
Time ( minutes )
Oven time reference table (1000 kg or more )
Time ( minutes )
2. Filling and tanning of the lining :
First, the quartz sand is dried ( temperature 300 °C , time ≥ 12 hours ). The quartz sand should be pure , and after magnetic separation , it should not be mixed into slag , wood chips , broken iron, etc. ) .
Then the induction coil against the inner wall of the sleeve into a circle 5 insulating layer cotton mm thick made of stone , in a mix of quartz sand mixture gradually into the stove-sand , lining should be layer by layer filling , each The thickness of the layer should not exceed 40-50 mm . Only the thickness of the first layer is more than 50 mm . After tamping with the tamping rod , tamping with a flat hammer . When filling the second layer , the surface of the first layer should be drawn . and clear residual material , before the insertion of the material stove-sand next layer. When filling the bottom of the furnace , the thickness of each packing is 30-40 mm , and then the upper part is removed, and then the hammer is leveled .
Discharge crucible mold , the crucible mold to be leveled , and measuring the crucible mold and the inductor internal radial clearance , to ensure the circumferential direction of the gap uniformly , After adjustment , increase was in the crucible mold , and with a wooden ramp wedge to four weeks administration is fixed , in order to prevent the stove- sand loose when . Therefore lining and filling ramming must have specialized tools . when the stove-sand when the roof , preferably stay 20 is mm height of about , the original stove-sand add material on the basis of 2-3% of boric acid In this way, a hard layer of sintered layer can be obtained . In addition , a layer of water glass is applied to the top of the die and the discharge port , and a small amount of water glass is added with 35% of quick-drying cement and 65% of the furnace sand . The composition is composed of a mixture of appropriate consistency and can be kneaded into a group. The furnace sand can also be used ( 10% water glass or 20% refractory clay can be added into the furnace sand with 10 % refractory clay for furnace sand ).
Low transmission power , slowly heated crucible mold , a moisture sufficiently evaporated , the specific time and shown in Table 4 carried out . , And optionally a crucible form is removed , when the temperature reaches 800-1200 after about degrees Celsius , can be divided into several charged return clean rust-free material , with 90% or so of the power charge is heated to melting , after heating to the sintering temperature in table 1 to maintain a certain time , and then continuous melting 2-3 furnace. In order to obtain a good glazed crucible , the first furnace can only be returned with clean and rust-free small pieces , then add appropriate amount of broken glass , 150 kg melting furnace plus 0.5k g ; 250 kg melting furnace plus 1.5 kg ; 500 kg melting Furnace plus 2k g , 1000k g melting furnace plus 4 kg ; 2000 kg melting furnace plus 8 kg is appropriate.
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