The Steel Manufacturing Process
Steel is composed of a mixture of metals, and there are several different processes used to produce it. While it has been produced for about two thousand years, it's made in a different way than it was in earlier times. While bloomery furnaces were originally used for the production of steel, it's now created through a different method called the bessemer process. This steel making process has been around in since the mid-1800s, but similar processes were used to make steel in Asia during the 11th century. The modern day process for how steel is made is far more effective than methods used in the past, and technological developments have further improved upon the steel manufacturing process.
Traditional Methods Of Steel Making:
In the traditional form of steel making, steel comes from a material known as pig iron. Pig iron is raw, unrefined iron that has not been mixed with other metals. The pig iron is loaded into an open hearth furnace, and this furnace combines the pig iron with other materials.
Limestone and iron ore go into the open hearth furnace with the pig iron. The furnace is then heated to a temperature of 1,600 degrees Fahrenheit. This is enough to cause the impurities to separate from the mixture. The impurities float to the top of the resulting material, which is referred to as slag.
Unfortunately, this process is significantly slower than newer methods of making steel. In fact, steel that is produced through this traditional method takes about 10 times longer to make than steel created through the bessemer method. As a result, this traditional method of steel making is rarely used today.
The Bessemer Method:
When the bessemer method is used, pig iron is oxidized in a bessemer converter. This is used to oxidize the iron. As the iron is being oxidized, it remains at the right to temperature to keep the steel molten. During this process, impurities in the iron combine with the oxygen. This creates a variety of oxides, and the impurities can be removed this way. Carbon monoxide is created in the process, but it simply burns off.
What Type Of Furnace Is Used For The Bessemer Process?
While there are different ways that the bessemer process can be utilized, a basic oxygen furnace is often used to create steel using the bessemer process. In other cases, a different type of furnace, called an electric arc furnace is used. This is especially common, and electric arc furnaces are used to create around sixty percent of the steel that is available today. When this type of furnace is used, electricity passes through the charge material.
Where Does The Iron Come From?
While much of the iron that is used in steel making comes directly from iron ore, it is also possible to manufacture steel from recycled materials. Recycled steel can be turned into high quality steel products, and it is a common source of iron for steel making. There are many potential sources of recycled steel, such as used vehicles, tools, parts, and even electronics.
What Else Can Be Added To The Mixture?
In addition, chemical cleaning agents are often added to the mixtures of modern day steel production furnaces. These chemical cleaning agents are referred to as fluxes, and they are highly effective at removing phosphorus and sulfur from the mixture.
However, it is also common for steel makers nowadays to add additional materials to the mixture used to make steel. One material that is often added to steel is chromium. Steel that contains chromium is called chrome. In some cases, the chromium is used as a plating over the steel. This is referred to as chrome plating. One advantage of adding chromium into the mixture is that it can make the steel resistant to staining. This is often called stainless steel, and it is very widely used.
It is also common for steel makers to add other metals, such as molybendum. Molybendum can improve corrosion resistance, and it is also often used in stainless steel mixtures. Some types of steel also include a certain trace amount of carbon, which can alter the properties of the final product. This is one of the most common additions in steel mixtures.
Other common addition materials include, silicon, titanium, nickel, copper, and aluminum. Each of these metals have unique properties that can help to improve the strength, corrosion resistance, or make it easier to weld the steel.
In other cases, additional metals are added to improve the heat resistance of the steel. Some examples of metals that are used include vanadium, cobalt, and tungsten. These materials are commonly added into steel mixtures that are used for the making of tools that will be exposed to high levels of heat.
While there are certain predetermined ratios of metals that are used by manufacturers, some manufacturers will experiment with a different mixture. Therefore, the specific amounts of non-iron metals that are added to steel may change over the course of time.
How Is Steel Formed Into The Correct Shape?
After the steel leaves the furnace, it has to be formed using a mold. This is referred to as the casting process. Nowadays, most steel mills use continuous casting. This means that molten steel is continuously fed into the casting mold. The casting process can form the steel into a variety of different shapes, such as beams, rounds, slabs, billets, and blooms.
After the casting process, the steel goes to a finishing mill. At the finishing mill, any coatings that are applied to the steel are put on. This includes chrome finishes and other coatings to prevent rust and staining.
What Happens After The Steel Leaves The Finishing Mill?
Once the steel is finished, it generally goes through a series of inspections to ensure that it can be sold. These inspections can include visual and dimensional inspection, spectro-chemical analysis, eddy current inspection, magnetic particle inspection, and any other necessary checks that must be done prior to the sale of the steel.