Sand furnace lining process for stove

Technical

Equipment technical parameters

Sand furnace lining process for stove

Time: 2019-07-09

Sand furnace lining process for stove

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, it should be high-grade pure quartz sand free of impurities such as bricks (S i 0 2 content of greater than 99.3%), and 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 changes, 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 , the specific ratio is referred to the following table .

Table 1 Relationship between the amount of boric acid added to acid furnace lining and smelting temperature

Serial number	material	Casting temperature ( °C )	Boric acid	Quartz sand	Smelting temperature ( °C )	Keep sintering time ( hours )
1	Gray iron	1400	1.8- 2.5%	98.2- 97.5%	1450	3-4
2	Gray iron	1400-1450	1.2- 2.0%	98.8- 98.0%	1480	3-4
3	Gray iron	1450- 1500	1.0- 1.7%	99.0- 98.3%	1500-1525	2-3
4	Gray iron	1500-1550	1.0- 1.6%	99.0- 98.4%	1550	1-2
5	Gray iron and high carbon steel	1550- 1600	0.8- 1.5%	99.2- 98.5%	1600	0.5 or more
6	70.6% medium carbon steel	1600	0.5- 0.9%	99.5- 99.1%	Casting temperature	0.3-0.5

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 Alkaline lining material ratio

Serial number	Electric furnace capacity ( kg )	坩埚Materials (%)			Magnesium sand particle size composition (%)
Serial number	Electric furnace capacity ( kg )	Magnesia	Fused magnesia	Electrofusion A l2 03	<1( mm )	1-3 ( mm )	3-5 ( mm )	5-20 ( mm )
1	10-30	70-80	30-20		25	45	30
2	150-500	50-20	50-80		20	35	25	20
3	≥ 1000		70-80	30-40		180 mesh 40%	50-140 mesh 32%	20-40 mesh 28%

Table 3 ratio of binder for alkaline lining

Name	Binder composition
Name	Water glass	clay	Boric acid
Boric acid			1.5-2.5
Water glass	5
Water glass - boric acid	5
Clay - boric acid		2-2.5	1.5-1.8

Table 4 oven time reference table (150 kg )

Power (KW)	20	30	40	50	60
Time ( minutes )	60	60	60	120	120

Oven time reference table (250-500 kg )

Power (KW)	30	40	60	100	150
Time ( minutes )	60	60	60	120	120

Oven time reference table (1000 kg or more )

Power (KW)	50	60	70	80	100	120	140
Time ( minutes )	60-120	60-120	60-120	60-120	120-240	120-240	120-240

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 the circle from 5 mm thick insulating layer of cloth made of stone, quartz sand in the mix into the stove-phase mixture of sand, filling the lining layer by layer should 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 beforethe insertion of the stove-material layer of sand. 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, heavier material in the crucible mold and wood oblique conveyance to four weeks administration is fixed, in order to prevent the stove- when the loose sand. Therefore lining and filling ramming must have specialized tools. when the stove-top sand, preferably leaving about 20 mm height, then adding 2-3% of boric acid based on the original on the stove-abrasive 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 forfurnace sand ).

Low power transmission, the crucible mold was slowly heated to a moisture sufficiently evaporated, the specific time may be made with reference to Table 4, and optionally the crucible mold taken out when the temperature reached approximately 800-1200 degrees Celsius, can be divided into several charged return clean rust-free material, with about 90% of the power charge is heated to melting, after heating to the sintering temperature in table 1 to maintain a certain time, then 2-3 continuous melting 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.