Double-layer centrifugally cast rolls with working layer of high-chromium cast iron. Chemical composition, microstructure and properties.
The metal structure of the working layer of high-chromium rolls consists of eutectic colonies on the basis of Cr7C3 carbide and tempered bainitic matrix reinforced with special secondary carbides. Such structure, obtained after the heat treatment, provides high wear resistance and thermal fatigue crack propagation resistance.
The core material and necks made of ductile cast iron with nodular graphite and pearlite matrix.
Field of application of high-chromium cast iron rolls:
- Roughing and intermediate stands of hot strip mills and finishing stands F1-F3;
- Roughing stand Steckel mill
- Roughing stands of plate rolling mills
- Roughing stands of narrow strip and middle strip rolling mills.
The metal microstructure of high-chromium rolls.
 |
 |
| microstructure of the working layer, х100 | microstructure of the core, х100 |
Table 1. Chemical compound of metal of working layer and core of high-chromium rolls.
| Pos. | Roll execution |
Chemical compound, % |
||||||||
|
С |
Si |
Mn |
P |
S |
Cr |
Ni |
Mo |
V |
||
|
no more |
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|
1 |
ЛПХ17НМдц-63 (68) |
2,5-3,0 |
0,5-1,0 |
0,5-1,2 |
0,1 |
0,04 |
16,0-18,0 |
1,0-1,5 |
1,2-1,8 |
0,3-0,6 |
|
2 |
Core of high-strength cast iron |
3,0-3,4 |
1,6-2,4 |
0,5-1,0 |
0,1 |
0,02 |
до 0,5 |
0,5-1,5 |
Cu до 0,2 |
Mg 0,03-0,06 |
Table 2. Technological and physical-mechanical properties.
| Pos. | Roll execution | Working layer depths, mm | Hardness, HS |
Bending strength, МPа |
Coefficient of elasticity, GPa | Impact strength, Joule/cm2 | Heat conductivity, W/m*К | Heat capacity, Joule /kg*К |
Coefficient of linear extension (20?1000С) 106/°С |
|
1 |
ЛПХ17НМдц-63 (68) |
40-60 |
63-83 |
550-750 |
21-25 |
2,5-3,3 |
36-38 |
520-540 |
10-13 |
|
2 |
Core of high-strength cast iron |
- |
35-45 |
360-460 |
16-19 |
4,2-4,6 |
42-48 |
550-580 |
11-12 |
