Cold rolled grain oriented (CRGO) silicon steel is a soft magnetic polycrystalline metallic alloy that is used to manufacture electric motors and transformer cores. First manufactured in 1933 by N. P. Gross, CRGO steel is a highly useful material in modern-day electronics.
Silicon steel is used to manufacture transformers because it keeps eddy current losses at low levels due to the presence of high silicon content in it. Also, silicon steel reduces coercive forces that help minimise losses of reverse magnetization in transformers.
But before using it in making transformers, this silicon steel is cold rolled at room temperature. This allows its grains to orient themselves in a specific direction. This process also reduces the thickness of silicon steel between the range of 0.1-2 mm which makes it harder and stronger.
On the contrary, hot rolled steel refers to the steel that has been rolled at temperatures over 1,700 Fahrenheit. But, they are less beneficial as compared to cold rolled steel. Due to its high usefulness, CRGO silicon is a costly material.
Properties of CRGO Steel
A number of properties make CRGO steel the right choice for making transformer cores as well as other things such as automobile components, axles, motors, etc.
So, let's have a look at some of the most significant properties offered by cold-rolled grain-oriented (CRGO) silicon steel.
High magnetism
CRGO silicon steel has great magnetic properties in the direction of rolling. This increased magnetism is because, in grain-oriented silicon steel, the overall magnetic properties of the material are dependent on those of the individual grains.
This magnetism confines and guides the magnetic field in the transformers. Therefore less magnetizing current is used to magnetize this steel.
High resistivity
Another important property of CRGO silicon steel is its high resistivity levels. When silicon is added to the steel, it increases its resistivity which is otherwise quite low.
This high resistivity then reduces the core losses by minimizing the eddy current components there. Thus, the overall transformer working gets optimized.
High mechanical elasticity
Additionally, CRGO silicon steel offers exceptionally high mechanical elasticity. So when it is used in the core of transformers or in any other motor or component, they add to their life. Mechanical elasticity helps when the object comes under strain, thereby allowing it to retain its shape.
Reduced magnetostriction
Magnetostriction is an important property as it helps in the conversion of electrical energy into mechanical, which is what transformers do. But high magnetostriction leads to high vibration levels. So, raising the silicon content in the steel helps lower magnetostriction, although it can't be eliminated completely.
High lamination factors
Another important property of CRGO silicon steel is that it offers high lamination factors. CRGO laminations help with minimizing eddy currents and hysteresis losses in transformers.
When a transformer's core is laminated with CRGO steel material parallel to the magnetic field, it controls the induced electromagnetic flux and eventually the eddy currents.
Low power losses
As the CRGO silicon steel offers high permeability, therefore it preserves power. And we know that an efficient transformer's core should ideally allow low power losses. Therefore, cold-rolled grain-oriented silicon steel is used to make the transformers' core.
Reduced curie temperature
As we know that pure iron has a high curie temperature. So, if transformed into an alloy by adding silicon contents in it, the curie temperature of steel can be reduced.
So, in the case of transformers and motors, it is important to keep the temperature below curie temperature. This can help activate spontaneous magnetism which is an essential element of transformers.
CRGO Grain Oriented Silicon Steel
