These rolls have less
wear per campaign with negligible drop hardness
having a good resistance to thermal shock and
thermal fatigue with higher level of resistance to
slippage & surface oxidation at high temperatures of
operation in the mill. The shell matrix contains
martensite, bainite and finely dispersed carbides
which imparts excellent wear resistance and high
thermal fatigue resistance with resistance to
cracking & spalling. Core material is always SG Iron
imparting better strength for application in hot
strip mills. These rolls require high degree of
cooling in the mill during operation. The higher
requirement of roll cooling and mill discipline is
important for optimising the performance. It also
requires proper monitoring o cracks during dressing
through Eddy Current & Ultrasonic Testing.
The primary benefit using these rolls commensurate
with high campaign life compared to Hi Cr Steel
rolls. |
|
CHEMICAL COMPOSITION (SHELL) |
|
C |
Si |
Ni |
Cr |
Mo |
V |
W |
Nb |
|
2.00 |
0.70 |
0.70 |
5.50 |
3.00 |
2.80 |
- |
0.60 |
|
2.50 |
1.30 |
1.30 |
6.50 |
3.80 |
3.60 |
- |
1.20 |
|
CHEMICAL COMPOSITION (SC CORE) |
|
C |
Si |
Ni |
Cr |
Mo |
V |
W |
Nb |
|
2.90 |
1.90 |
1.00 |
0.60 |
- |
0.03 |
- |
- |
|
3.20 |
2.70 |
Max |
Max |
- |
0.07 |
- |
- |
|
MECHANICAL PROPERTIES |
|
|
|
60-70(In steps of 5°ShC)
|
|
70-80(In steps of 5°ShC) |
|
|
Neck Properties
(SG Core) |
|
Hardness (°Sh-C) |
U.T.S (N/mm2 |
Impact (J/cm2) |
|
35-45 |
400-500 |
3.50 max |
|
