1. Preliminary Annealing: During the preliminary annealing process, a scale which may have formed on the hot rolled steel is removed as delayed passing through scale breaker and a hydrochloric acid bath. This initial heat treatment process improves the cold rolling properties of steel as well as its magnetic properties.
2. Cold Rolling: In order to obtain specific thickness and material properties, a reduction ratio of 40-90% is applied normally. Rolling and edge trimming machines are automatically controlled to obtain uniform thickness and width.
3. Annealing: Annealing is a process in which cold rolled structures are converted to a recrystallized structure through heat treatment. For grain oriented electrical steel, two different annealing methods are available: decarbonization annealing and high-temperature annealing. Decarbonization annealing removes excess carbon from the steel and applies a MgO coating. High-temperature annealing produces secondary recrystallized structures having superior magnetic properties.
4. Insulation Coating: In this process, insulation coating is applied by a continuous coater roll in order to minimize eddy current losses, which are proportional to the sheet thickness. A series of coaters are used to apply insulation coating liquid to the top and bottom of a plate. Grain oriented electrical steel has two layers of coating, a base coating of dark brown Forsterite (Mg2SiO4) as the main ingredient and a transparent insulating coating containing phosphates. For non-oriented electrical steel, various coating methods with various thicknesses and ingredients are used depending on end usage and specific user’s requirements.

Cold Rolled Steel

1. Pickling: Hot rolled coils pass through a pickling line, where scale breaker machines and hydrochloric acid solutions are used to remove any surface scale and/or oxide film that which causes surface flaws during the final stage of cold rolled steel processing.
2. Cold Rolling: Pickled coils are cold rolled in tandem mills to a specified thickness, typically 40 to 90%, of original material dimensions. Fully automated shape adjustment is ensured through state of the art process machinery.
3. Electrolytic Cleaning: The purpose of electrolytic cleaning is to remove lubricant oil and contaminants on the cold rolled steel prior to the annealing process.
4. Annealing: This is a highly productive manufacturing method whereby steel products with extra deep drawing qualities and high tensile strength can be produced. Two annealing methods are commonly used: batch annealing and continuous annealing.
5. Skin Pass: This final rolling process is performed in order to remove minor surface defects such as stretch marks and to produce a smooth, lustrous surface. Skin Pass results in a further thickness reduction of about 1%.

1. Billet Conditioning: This process is intended for checking the surface quality of billet and removing any defects. Shot blast is used to remove any scale from the surface. Magnet particle testing and visual inspection are also used to identify any defects which must be removed using a grinder. Ultrasonic testing and dimension and geometry checking are also applied as part of the internal quality assurance process.
2. Reheating: The temperature within the furnace and the duration of reheating depend on where the product will be used. To avoid decarburization, which can affect the surface quality of the product, a billet is pre-heated sufficiently at a low temperature before being rolled within the reheating furnace. For this purpose, the fuel and air ratio are strictly controlled.
3. Rolling: The temperature, draft and speed of deformation with which the product is rolled are controlled to meet customer requirements for material features. Further measures to ensure the surface quality include the adjustment of roll roughness and gap, detection of any cracks and dimension correction.
4. Cooling: Coiling temperature at the laying head, the air flow and movement speed of the blower on the cooling bed and the cooling speed of the insulation cover are controlled to ensure that the product has the features required for each application. High carbon steel Wire rods are subject to fast cooling to achieve the microstructure required for successful drawing while low carbon steel is subject to slow cooling to ensure that the product provides the softness required for the customer to eliminate an annealing process.
5. Inspection: Samples are taken from the front and rear edges of the product after rolling and cooling for testing to identify any defects in the dimension or surface or material integrity. Packaging and tagging are also inspected according to customer requirements prior to shipping.