Hot Rolled Silicon Steel VS Cold Rolled Silicon Steel

Whether you are involved in the manufacturing of transformers, motors, generators, inductors, or other electrical devices, understanding hot rolled silicon steel and cold rolled silicon steel can benefit you in selecting the most suitable magnetic material for your applications. By learning about the differences in the manufacturing process, grain structure, mechanical strength, magnetic properties, applications, and cost of these two types of silicon steel, you can make informed choices that optimize the performance and efficiency of your projects.

Introduction

Hot rolled silicon steel, commonly referred to as hot rolled electrical steel, is generated via a specific process that involves rolling the steel at high heat, commonly above the recrystallization temperature of the product. This technique imparts unique qualities to the steel, making it suitable for particular applications.

Cold rolled silicon steel, commonly known as cold rolled electrical steel, is produced by cold rolling process, which involves rolling the steel at or near room temperature level. The cold rolling procedure improves the steel’s surface, boosts its dimensional precision, and improves magnetic properties, making it perfect for applications requiring efficient electromagnetic efficiency.

Manufacturing Process

The manufacturing process of hot rolled silicon steel starts with the heating of pieces or billets at temperature levels usually ranging between 1100 ° C and 1250 ° C. This high-temperature process is vital as it transforms the steel into an extra malleable kind, enabling it to be easily shaped and formed. Once the steel reaches the desired temperature, it travels through a collection of rolling mills. The initial rolling phases, called roughing, lower the thickness of the steel while boosting its total uniformity. Subsequently, the steel undergoes an ending-up procedure where it is additionally thinned and smoothed. These competing mills enhance the surface quality and accomplish the precise measurements required.

In contrast, cold rolled silicon steel starts with hot rolled silicon steel and goes through additional actions to attain the wanted attributes. Firstly, the hot rolled silicon steel is pickled to remove surface oxides and impurities. Then, the steel passes through a collection of rollers at room temperature, which slowly decreases its thickness. This cold rolling process not only thins the steel but also gives much better mechanical properties.

Grain Structure

They also differ in grain structure, including grain size and grain orientation.

The high temperature in the hot rolling process enables the formation of larger grains, which can affect the steel’s magnetic characteristics. However, cold rolled silicon steel tends to have a smaller grain size due to room-temperature rolling.

As for grain orientation, Hot rolled silicon steel has no orientation while cold rolled silicon steel is available in two types: cold rolled oriented silicon steel and cold rolled non oriented silicon steel.

Annealing

Compared with hot rolled silicon steel, cold rolled silicon steel needs an additional annealing process after rolling, aiming to boost its magnetic properties and rust resistance. Furthermore, the annealing procedure can also relieve interior stresses and fine-tune the grain structure by heating the steel to a certain temperature and then slowly cooling it.

Magnetic Properties

Cold rolled silicon steel offers superior magnetic properties than hot rolled silicon steel, including low core loss and high magnetic permeability. As for the magnetic saturation point, the magnetic saturation point of cold rolled silicon steel is probably higher than 0.3T of hot rolled silicon steel. (the saturation point of cold rolled silicon steel begins at 1.9T (19000Gs); while the saturation point of hot rolled silicon steel starts at approximately 1.6T (16000Gs).)

These properties are crucial for cold rolled silicon steel to attain high efficiency in electromagnetic applications.

Mechanical Strength

The mechanical properties of hot rolled silicon steel and cold rolled silicon steel differ substantially as a result of their unique manufacturing processes. These differences make each kind ideal for specific applications and affect their performance in various industrial contexts.

Hot rolled silicon steel is commonly identified by its lower tensile toughness and yield strength contrasted to cold rolled silicon steel. This is mainly because the hot rolling procedure entails higher temperatures, which can lead to a more loosened-up and pliable microstructure. The heat additionally leads to larger grain dimensions, adding to its relatively softer and much more flexible nature.

On the other hand, cold rolled silicon steel undertakes a procedure at or near the area temperature level, leading to a finer microstructure with smaller sized grain dimensions. This causes greater tensile stamina and yield strength, making it more challenging and much more immune to contortion. The cool rolling procedure also improves the surface finish, offering a smoother and more uniform appearance.

Machinability & Formability

In addition, the mechanical properties also influence the machinability and formability of these two silicon steels.

When shearing or stamping, the performance of cold-rolled silicon steel is particularly affected, but the impact on hot-rolled silicon steel is smaller.

Besides, hot rolled silicon steel, being even more ductile, is easier to create and shape, whereas cold rolled silicon steel, with its higher stamina, is extra challenging to collaborate with but supplies premium dimensional accuracy and stability.

Surface Quality

HR silicon steel usually has a rough surface and inaccurate size due to the hot rolling process.

CR silicon steel usually has a smooth surface and precise dimension due to the cold rolling process.

Applications

Both hot rolled silicon steel and cold rolled silicon steel are used in electrical and electric applications due to their magnetic properties. But their emphasis is different.

Hot rolled silicon steel is mainly used in applications that require high magnetic properties but low finish aesthetics. For example:

In electrical fields, it can be used in the production of electrical transformers, activators, and magnetic amplifiers.

In the renewable resource field, it is utilized in wind generators.

In the automotive industry, hot rolled silicon steel finds applications in making components such as automotive members, chassis parts, and auto chassis parts.

Cold rolled silicon steel, renowned for its premium magnetic properties and surface finish, finds extensive application in numerous electrical and industrial markets.

In the electrical field, it can be used to fabricate transformers, electric motors, generators, inductors, relay cores, and magnetic shields.

In mechanical engineering, cold rolled silicon steel demonstrates good surface quality without edge cracks and can be tailored for specific yield strength and magnetic properties by using heat treatment. This makes them suitable for use in high-speed rotating mechanical machinery, such as turbochargers, mechanical turbo-compounding systems, aero-engine spools, and racing engines.

Cost

Due to the differences in manufacturing complexity and market availability, there is a noticeable disparity in the prices of hot rolled and cold rolled silicon steel.

Hot rolled silicon steel usually has a lower cost due to its minimized manufacturing costs and higher schedule. On the other hand, the precise manufacturing process and limited accessibility of cold rolled silicon steel cause greater costs. Below is a table sheet for reference:

HR VS CR Silicon Steel, Which one Suits my Projects Better?

In conclusion, when choosing between hot rolled silicon steel and cold rolled silicon steel, there are many aspects to consider, including the production, magnetic properties, mechanical strength, applications, prices, etc. While hot rolled silicon steel is much more cost-effective and widely readily available, cold rolled silicon steel provides superior magnetic properties that justify its greater cost and restricted schedule for specialized uses.

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