RSP : Electrical Steels

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

Notes

1. The values were measured in accordance with ASTM A 34 methods using fully processed specimens consisting of half the strip sheared parallel and half sheared transverse to the rolling direction.

2. W _15/50 indicates core loss at 1.5T and 50 Hz.

3. B ₅₀ indicates the magnetic flux density at 5000 AT/m.

4. Core loss values are measured after accelerated ageing at 225^O C for 24 hours.

5. The above values are typical ones and not for guarantee.

Notes

1. Nominal thickness 0.50 mm or 0.0197 inches. Number of bends: more than 25.

2. The values were measured on traverse samples of fully processed material.

3. The tensile tests were conducted in accordance with JIS Z 2201.

4. The above values are typical ones and not for guarantee