CRNO
Coils & Sheets
To meet the demands of
the electrical industry, Rourkela Steel Plant offers Cold Rolled
Non Oriented (CRNO) fully processed steel used in the manufacture
of magnetic
cores and components.
Standard Width: The
standard width of CRNO coils or sheets are 900, 950 and 1000 mm.
Slit coils can be
supplied in minimum width of 100 mm and then in multiples of 10
mm.
Other sizes are negotiable.
Standard Length: The
standard length of CRNO sheets is 2000, 2500 mm.
Coil Weight: 1
to 5 tonnes.
Tolerances
in dimensions and shape
|
Width
mm
|
Nominal Thickness
mm
|
Thickness Tolerance % on
Nominal |
Thickness Deviation in
Transverse Direction
mm
|
Width Tolerance
mm
|
Camber per 2m of length
mm
|
Flatness % max |
Maximum Bow Height at 0.5
m length
mm
|
|
|
|
|
|
|
|
|
|
|
£
150 |
0.50 |
± 8 |
£
0.03 |
+ 0.3 |
£
1.0 |
2
|
10 |
|
> 150 -500 |
0.50 |
± 8 |
£
0.03 |
+ 0.5 |
£
1.0 |
2 |
10 |
|
> 500 - 1000 |
0.50 |
± 8 |
£
0.03 |
+ 1.5 |
£
1.0 |
2 |
10 |
|
> 1000 |
0.50 |
± 8 |
£
0.03 |
+ 1.5 |
£
1.0 |
2 |
1 |
Flatness %: (Wave
height/ Wave length) x 100
Burr height: maximum
50 micron
Grades
and Specifications
Magnetic and
Mechanical Properties
CRNO steels from RSP
are graded on the basis of Epstein Core Loss Testing at an
induction
of 1.5 Tesla. These maximum core loss limits are based
upon the general procedures
established by the American Society
for Testing and Materials (ASTM A 34). For this purpose
RSP has
set up a fully equipped and modern testing laboratory consisting
of among
other equipment, a sophisticated Digital Core Loss
Testing Unit. Other test instruments
include Franklin Surface
Insulation Resistance Tester, Hay Bridge, DC Hysteresis Loop
Tracer etc.
Magnetic properties
and lamination factor of SAIL CRNO coils/ sheets are in
conformity with
AISI and Non-Oriented Fully Processed, ASTM A
677 specifications.
|
Grade |
Thickness
mm (in)
|
Assumed Density
kg/ dm3
|
Maximum Core Loss
Watts per kg at 50 HZ
& 1.5T
|
Maximum Magnetic Flux
Density at 5000 A/m |
Minimum Lamination @
Factor % |
|
M-27 |
0.50
(0.0197) |
7.70 |
3.31 |
1.60 |
96.0 |
|
M-36 |
7.70 |
3.57 |
1.60 |
|
M-43 |
7.70 |
4.01 |
1.61 |
|
M-45 |
7.75 |
5.31 |
1.62 |
|
M-47A |
7.75 |
6.98 |
1.64 |
|
M-47B |
7.75 |
8.01 |
1.65 |
|
M-27 |
0.65
(0.0256) |
7.70 |
3.92 |
1.60 |
96.5 |
|
M-36 |
7.70 |
4.18 |
1.60 |
|
M-43 |
7.70 |
4.70 |
1.61 |
|
M-45 |
7.75 |
6.27 |
1.63 |
|
M-47A |
7.75 |
8.73 |
1.65 |
|
M-47B |
7.75 |
10.01 |
1.66 |
The present
production range is in 0.50mm thickness.
The values are
measured in accordance with ASTM A34 / JIS C 2550 methods using
as
sheared specimens consisting of half of the strip parallel
and half sheared transverse to the
rolling directions.
Note Core Loss is in
Watts/ kg at 1.5 Tesla induction for 50 Hz.
Magnetic Ageing:
The Non-Oriented steels will have
less than 5% increase in core loss upon
a standard ageing
treatment (of as-sheared specimens) 2250 C for 24
hours. Grading is done
based on watt loss value obtained after
ageing.
Microstructure:
The CRNO steels from RSP, being in
decarburised and fully annealed
condition have large grain size
suitable for excellent magnetic properties.
Stacking factor:
The stacking factor is typically
95-98% for 0.5 mm thickness
depending on coating thickness.
Packing: The
material is first wrapped in stretch film over card board
protectors in the
eye and OD edges followed by an additional
layer of air-bubble polythene type covering.
It is then packed
in galvanised sheet metal envelope. Metallic collars are
provided in the
eye of the coil and on the OD to prevent
handling damages. The envelope with strapped
with 4 eye and 3 to
4 circumferential straps of special steel. Additional support is
provided
when warranted. No metallic packing is given on slit
coil.
Insulation
and Applications
|
Insulation Designation |
Description |
Applications |
|
C-0 |
Natural coating |
Fractional horsepower motors
and relays, small communication power transformers and
reactors. |
|
C-3 |
Organic coating |
Air/oil-cooled medium sized
power and distribution transformers, medium sized continuous
duty, high efficiency rotating electrical machinery. |
|
C-4 |
Inorganic coating |
Applications requiring
insulation similar to C-3 and a stress relief anneal. Used
extensively for small stamped laminations that require
higher resistance than what is provided by annealing oxides. |
|
C-6 |
Semi-organic coating |
Applications requiring
stress-relief anneal and burn-off treatment. Extremely
useful for stamped laminations of hermetically sealed
compressors used in refrigeration system |
