All About Carbon Steel Casting

Posted by hardikaegis on May 15th, 2019

Carbon steel is a type of steel where the main element in the alloy is carbon. It is the most common type of steel, accounting for more than 80-85% of total steel production. The property of the carbon steel depends on the proportion of carbon in the steel. Carbon steel casting manufacturers often add other elements like copper, silicone and manganese can also be added to enhance certain qualities.

Stages in Carbon Steel Manufacturing

Carbon steel is used in many forms and is present all around us. From the nails to the beams — carbon steel is used to make small as well as big objects. Steelmaking has evolved in many ways since the 19th century, but the basic principle remains the same. Modern steelmaking uses a lot of recycled material apart from the more traditional elements.

The two main processes we use in steelmaking are:

-    Basic oxygen steelmaking (BOF)

-    Electric arc furnaces (EAF)

There are six stages in the manufacturing of carbon steel. It includes finishing processes to make it suitable for commercial purposes. These six steps are:

Ironmaking

The main component of steel is iron. So, we start with ironmaking. We use iron ore, lime and coke — melting these in a blast furnace. High heat of the furnace, close to 3000°F, melts the raw material to give us molten iron. We use further to make the steel. This molten iron contains impurities.

Primary steelmaking

There are two methods used in primary steelmaking: BOF and EAF. The EAF is a more modern process. In the BOF process, the impurities are absorbed by lime. At this point, the steel will have about 4% carbon and some impurities. This virgin steel is then moved to a basic oxygen furnace or BOF, which contains recycled scrap metal. To oxidise the excess carbon, pure oxygen is blown through the liquid steel. What we get is steel with approximately 0-1.5% carbon content.

In the EAF methods recycled steel scrap is fed through high-power electric arc furnaces. The temperature inside these arcs is close to 3000º F. The high temperature melts the scrap. More scraps is added to keep the furnace running up to its full capacity and for quick production. Like the BOF method, oxygen is blown through the molten metal to oxidise the carbon.

Both processes give us a slag on the surface, which contains the impurities. This is removed. The molten steel, on the other hand, is tapped into huge steel baths or ladles for further processing by carbon steel casting manufacturers.

Secondary steelmaking

In this stage we add, remove or manipulate certain elements to adjust the composition of the steel as per our choice. There are different processes used here and the choice depends on the type of steel you want. These are ladle furnace, stirring, degassing, ladle injection and CAS-OB. These are further explained:

Ladle furnace: Alloy components are injected under extremely precise temperatures. The ladle here acts as an electron furnace.

Stirring: In this method we use electromagnetic fields to separate the non-metallic impurities. Turbulent currents are created in the ladle which pull out the impurities and bring them to surface. We get the homogeneous mixture we want.

Degassing: In this method we remove gases like hydrogen, nitrogen, and oxygen. At the same time we also reduce the sulphur in the product. Apart from inert gas injection we also use techniques like vacuums and temperature control.

Ladle injection: We inject an inert gas into the steel bath. The gas heats up and starts to move up through the molten steel. It leaves a stirring effect.

CAS-OB: Short for Composition Adjustment (with oxygen blowing), this method uses the stirring technique by injecting argon gas into the steel bath. The slag is left undisturbed. The hydrogen in the mix is reduced, while the oxide floats to the surface. Oxygen and aluminium is added. We get more control on the temperature to reach a more precise final composition.

Once the steel goes through these processes, we remove the oxygen. A controlled deoxidation is used to get the desired type of steel.

Casting and finishing

This is where an experienced carbon steel casting manufacturercomes in. The steel is poured into individual moulds in traditional method. Today we have casting machines which uses the same method in a more efficient and controlled manner. It then undergoes finishing to improve its functionality, surface finish and composition.

Also See: Carbon Steel, Steel Casting, Steel Bath, Primary Steelmaking, Steel, Carbon, Oxygen
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