Electric Arc Furnace Refractory Material Description
Electric arc furnace make use of waste steel to smelt steel. During steel smelting, furnace bottom will expose to steel liquid chemical corrosion, mechanical abrasion and impaction, thermal shock and so on. So the service life of electric furnace actually is furnace refractory material’s service life.
Based on bottom electrodes structure types, direct current electric arc furnaces can be classified into 3 types, ABB, Clecim and GHH. GHH furnace bottom electrodes are thin steel rods(20~50mm diameter), bottom surface is also cooled by air. Other types of direct current electric furnaces is developed on basis of these 3 types.
For GHH and VAI furnaces, Steel needles( discs) gap is tamped by dry ramming mass. Electricity is relatively dispersive, bottom electrodes consumption is relatively even, without patching, the service life of bottom electrodes is 300~1000 times. To increase service life, several methods can be adopted. 1. When furnace cools, clean residual slag, wed steel needles, and construct magnesia dry ramming mass between steel needles. 2. Hot patched by conductive refractory material. These methods all be tested before and got ideal effect. GHH also adopted movable electrodes zone furnace bottom, can quickly hot change bottom electrode within 8 hours.
Electric Arc Furnace Bottom Dry Ramming Mass Performance
Item
MgO %
CaO %
Fe2O3 %
SiO2 %
Density g/cm3
EAFRM-1
>77
>17
<4
<0.7
>2.5
EAFRM-2
84
8~12
5~8
1
>2.4
EAFRM-3
91
3
4.5
0.5
>2.4
EAFRM-4
84
6~10
4~7
<1.5
>2.5
For ABB direct current electric arc furnace, bottom electrodes adopt conductive magnesia carbon bricks, conductive magnesia calcia carbon bricks, conductive mortar, conductive MgO-Fe ramming mass, conductive magnesia carbon ramming mass, conductive magnesia calcia carbon ramming mass, etc. Although whole bottom is conductive and electricity is scattered, the bottom electrodes corrosion is not homogenous. If bottom center part’s corrosion is serious, this part will be thinner and have smaller resistance, so electricity will be greater and aggravate corrosion. So this type of bottom electrodes should be frequently patched. ABB furnaces can be hot patched at any time or be patched when cooled, so the service life is very long, max. service life is higher than 13,000 times.
ABB DC Electric Furnace Bottom Refractory Material Index
Item
Conductive magnesia carbon bricks-99
Conductive Magnesia calcia carbon bricks
Conductive Magnesia carbon bricks-60
Conductive Magnesia carbon bricks -80
Conductive mortar
MgO %
98.5
70
60
80
/
CaO %
1.0
10
19
1.0
/
SiO2 %
0.2
/
/
0.2
/
C %
14
12
15
10
50
Bulk density g/cm3
2.85
2.95
2.95
3.02
/
Apparent porosity %
13
10
10
8
/
Compression strength Mpa >
20
30
30
70
/
Specific resistance Ω/m <
2*10-4
2*10-4
2*10-4
2*10-4
2*10-5
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