One of the oldest, and still very reliable, processes for making steel is the Bessemer process, which was perfected and brought into mainstream use in the mid- to late-1800s. This method uses an egg-shaped converter with several ton capacity to blow air through iron from the mouth of the converter and create steel. The acid Bessemer process (versus the basic process) was, for the most part, replaced by the acid open-hearth process, which was then replaced again by the electric arc process. There is a short window of only about 25 minutes when the steel is in the furnace, which makes it more difficult to get it just right.
The Siemens open hearth process, which also has an acid and basic variety, uses oil or natural gas to supply the heat for melting and working the charge. Raw materials, including cold or molten pig iron, scrap, and lime are in the furnace for anywhere from 6 to 14 hours, which makes it easier to control the outcome than in the Bessemer process.
Electric Arc Method
This method begins with heat generated from electric arcs struck between carbon electrodes and a metal bath. Steel scrap is melted to remove phosphorus and sulphur, and deoxidize it in the furnace. What remains is a purified steel, which is very high quality as long as there is very little gas absorption and the proper temperature is maintained. This processes is often used today to create highly alloyed steels, such as stainless steel or heat-resisting steel. For some special alloys, the electric arc method is combined with vacuum degassing, which removes hydrogen, atmospheric and volatile impurities for an exceptional quality steel.
Crucible and High Frequency
The crucible method was developed centuries ago, and refers to the process of making steel using a crucible, refining steel that has been consolidated and melting it to become more uniform. It has been replaced in most cases by the high frequency method, where heat is generated in the metal by eddy currents from a magnetic field. When the frequency increases, eddy currents travel closer to the surface of the charge and develop heat to carry the current. The high frequency method is advantageous for eliminating contamination, so high quality steels such as magnet, die, tool steel, and ball bearing steel can be made economically.
Once the steel is made, the next step is to create whatever end-user product you intend to get from the steel. Here are some examples of the different types of steel that are made, and you can find these end-user products at Wasatch Steel:
- Hot or cold strip steel – used for cars and consumer goods
- Coils – used for ship building and welded pipes
- Hot rolled bars – often used for rebar
- Rods – for wire, nuts, and bolts
- Tube rounds – for use in making pipes
- Structural steel – for use in construction and similar applications
- Rails – for use building railroads