The Processes Used in Steelmaking
Basic oxygen process
The basic oxygen process for steel fabricatormaking (also called Linz-Donawitz steelmaking or the oxygen converter process) is a process used to convert carbon-rich pig iron into steel. The process involves blowing oxygen into the molten pig iron to reduce the carbon content and change it into a low-carbon steel. The oxygen used during this process is derived from oxygen, which is present in the atmosphere.
The first step in the process is to mix lime with oxygen. A typical basic oxygen furnace is a vertical vessel with an open upper cone. This vessel is lined with magnesite and is mounted on trunnions. Injecting the oxygen and lime mixture through the nozzles cools the steel to a desired temperature. Then, the steel is tapped into the ladle at temperatures of about 1,600 deg C or 2,900deg F. This process takes about thirty to forty-five minutes to complete.
Electric arc furnace
Electric arc furnaces are used to produce steel from scrap iron. They can heat scrap metal to a temperature of about 1,500 degrees Celsius, which is sufficient to make steel. The scrap is then replaced with pig iron or direct reduced iron. However, these furnaces are highly energy-intensive and produce large quantities of carbon dioxide. This can negatively impact the stability of the power grid.
The basic structure of an electric arc furnace is shown in Figure 1. It comprises a roof 206, a shell 102, and a refractory system. The electrodes protrude through a hole in the roof. The electrodes 122 may be single or several and may be placed in a triangular configuration. A mast structure may be provided for raising and lowering the electrodes.
Continuous casting
Continuous casting is a process where liquid steel is poured into a mould at a controlled rate. This liquid steel contains solid inclusions, such as alumina, which move through the flow field. These inclusions may attach to bubbles and form larger clusters. Then, they circulate up into the mould flux at the top surface.
The entire casting process has many challenges, including the need to control solidification for optimum surface and internal quality. Solidification quality is largely determined by the previous operations in the tundish and ladle, but can also be influenced during the casting process. Some important control parameters include steel chemistry, casting speed, and mold powder.
Open-hearth furnace
An open-hearth furnace is an industrial furnace used to produce steel. It burns out excess carbon and other impurities in pig iron, thereby transforming it into steel. Open-hearth furnaces are an efficient way to produce high-quality steel. In addition to steelmaking, they are also used in other industrial processes.
Unlike Bessemer converters, open-hearth furnaces are more efficient and less expensive. Moreover, they can use scrap steel from the Bessemer process. Several open-hearth furnaces were used at the Pittsburgh Works of Jones & Laughlin Steel Corporation.
Bessemer converter
The Bessemer steel converter was invented by Henry Bessemer and became a major innovation in the steel making process. In the past, steel was scarce and extremely expensive, so Bessemer’s converter allowed a large number of people to produce steel cheaply. This invention changed the way steel was manufactured and sparked a manufacturing revolution.
The Bessemer steel converter has a cylindrical top and a number of openings at the bottom. These perforations allow air to enter the converter and cause the steel to create oxides of carbon, manganese, and silicon. In just 15 to 20 minutes, the process is complete.
Low-carbon steel
Low-carbon steel is a versatile material that can be used in various applications. Its low cost and easy fabrication processes make it an ideal choice for many different industrial uses. Its many benefits include the ability to form complicated shapes and a variety of tensile strengths. Low-carbon steel is also resistant to rot, wind and earthquakes, making it an excellent choice for building frames in construction projects.
Low-carbon steel is a good candidate for joining processes such as GTAW and GMAW. While these traditional processes can greatly increase productivity, laser welding of plain carbon steel is not limited to these applications. In fact, laser welding has been successfully applied to fabricate carriages for CNC punch presses. In one application, a CO2 laser with a 5 kW power rating was used to limit distortion and weld finishing operations.