Steel has existed for over a millennia, since blacksmiths discovered they could modify iron by adding carbon under elevated temperatures, resulting in steel. Its history is rooted in the ancient Middle East and Europe. China was the first country to start mass-producing steel in the 19th century, and Sir Henry Bessemer’s technique revolutionized the steel-making process. The Bessemer process was considered the most important technique for producing steel in the 19th century.
Steel is widely used in various industries due to its tensile strength, corrosion resistance, cost-effectiveness, durability, and malleability. It has been a popular choice for structural engineering applications for many years. The versatility of steel has led to its use in building trains, pipes, turbines, ships, cars, bicycles, knives, weapons, planes, tankers, doors, propellers, and industrial machines. Yet, it holds potential for so much more.
Together, we’ll explore the dynamic aspects of steel, and discover answers to the following:
● What is steel making?
● The major steps in steel production
● Types of steel alloys
● Technological innovations in steel processing and manufacturing
● The economic impact of steel production
● The environmental impact of steel production
What is Steel Making?
Steelmaking is an oxidation process that involves fabricating steel from iron ores or scraps. Steel is a unique combination of iron and carbon oxides, and a host of selected minerals. It’s usually fabricated using two major methods: Blast Furnace–Basic Oxygen Furnace (BF–BOF) and Electric Arc Furnace (EAF). Unlike most metals, steel cannot be extracted naturally from the earth’s crust.
However, iron ores can be extracted from the earth. When heated, iron ores can produce metallic iron. This mineral is regarded as one of the most abundant elements on the planet, taking up 5% of the earth’s crust. According to the U.S. Geological Survey, iron ore is mined in over 50 countries. A total of 98% of iron ores were consumed by the steel-making industry in the United States in 2022.
Steel Making: What are the Major Steps in Steel Production?
Iron making
The steelmaking process most widely used is the Blast Furnace–Basic Oxygen Furnace (BF–BOF). It is most preferred when working with iron ore. For scrap iron or directly reduced iron, the Electric Arc Furnace is preferred. The process of creating pure steel starts with smelting the iron ore, coke, and limestone into molten liquid. The iron ore, coke, and limestone as a flux is introduced into the blast furnace where it separates the iron from its ore and carbon from coke.
They interact with oxygen, which is introduced as hot air to incinerate the coke to produce CO and CO2. The carbon monoxide sheds off some of the iron oxides and the composition is regarded as liquid iron or pig iron, as it contains about 4% of carbon along with a host of impurities. This is the iron-making process. To process steel, you must refine the pig iron to eliminate impurities.
Primary Steel Making
The Bessemer process which was patented in 1856 was the first industrial process for refining molten pig iron in the 19th century. An improved process for refining pig iron is the basic oxygen steelmaking process. The refining phase involves eliminating the impurities (graphite, manganese, silicon, phosphorus, and sulfur) in the pig iron by blowing oxygen or electricity to improve its properties.
The pig iron is introduced into the basic oxygen furnace (BOF) or electric arc furnace (EAF) and oxygen or electrical energy is blown at high velocity to reduce the excess carbon to 2% by rotation.
Secondary Steel Making
The molten liquid iron is then regarded as low-carbon steel and may be further refined in a ladle. In the second refining stage, oxygen is also blown into the ladle containing the liquid steel. The next step is deoxidization. This involves removing excess oxygen from the molten steel. It’s done by adding deoxidizing elements such as aluminum, manganese, silicon, and calcium carbide which have an affinity for oxygen.
This treatment often forms slags. This by-product can be easily scraped off from molten iron by tilting the ladle, as the slag floats on the surface. Desulfurization agents (lime flux) can be injected to dilute sulfur and form basic slag. The slag formed prevents reoxidation or heat loss. Alloying elements (aluminum and silicon) in moderate quantities can be added to the liquid steel to further eliminate oxygen.
If needed, vacuum oxygen decarburization can be done to lower the carbon content remaining in the mix. The final composition is stainless steel and is then poured out into the desired mold for casting.
Continuous Casting
The continuous casting method has become the preferred method for casting steel as it offers high quality and yield. Using continuous casting, the liquid steel is solidified into semi-finished billets, beams, slabs, or blooms. The liquid steel is poured from the ladle, into the tundish, and then into the mold through a submerged entry nozzle.
The copper mold is water-cooled and as soon as the molten liquid hits the lubricated cold wall of the mold, it begins to freeze and form thin solid steel shells containing liquid. The seal is pulled off and the shells are pushed gradually out of the mold through spray chambers to solidify with the help of water sprays.
Metal Forming and Rolling
The process involves passing the steel through a series of rollers at a uniform speed to reduce its wall thickness and shape into desired forms, including rods, bars, wires, and rails. Rolling helps to improve the mechanical properties of the steel such as its strength, machinability, surface finish, ductility, and size of the steel. Rolling can be done on hot or cold steel.
Fabrication
The final process involves transforming the raw or semi-finished steel into final products. There are several techniques for converting the steel to the desired products. The steel may go through some or all of these processes: cutting, shearing, bending, drawing, punching, drilling, stamping, forging, and assembling. On most occasions, steels are assembled by welding the parts together.
Advanced methods for fabricating steel include injection molding, machining, and additive manufacturing.
Types of Steel Alloys
- Stainless Steel: Stainless steel is a recyclable iron alloy composed of iron ore, chromium, carbon, nitrogen, manganese, and other metals like nickel, silicon, titanium, and molybdenum. This material is known for its excellent rust and corrosion resistance. When exposed to oxygen, stainless steel can self-heal due to the presence of chromium. There are five types of stainless steel, classified according to their crystalline structures: austenitic, duplex, ferritic, martensitic, and precipitation-hardening. Austenitic and duplex stainless steel are the most common types. The main difference between them is their composition. Duplex stainless steels have higher corrosion resistance and strength compared to their austenitic counterparts.
- Carbon Steel: As the name suggests, carbon steel comprises iron ore and under 2% of carbon by weight. Carbon steels may contain small amounts of copper, manganese, sulfur, phosphorus, and silicon. It may be made from stainless steel. Carbon Steel is one of the most common steel alloys in the world. Carbon steels can be low, medium, and high. Carbon steels with higher carbon content have a lower melting point and weldability. Under high moisture, carbon steel may become susceptible to corrosion and rust. However, when combined with chromium, it builds resistance.
- Tool Steel: Tool steels are carbon steel alloys made primarily from varying levels of carbide-forming metal scraps such as tungsten, vanadium, chromium, and molybdenum under controlled conditions. These alloys are produced using the electric arc furnace process. These specialty steels are usually produced in small batches and are used for making cutting and shaping tools. Tool steels possess hardness and abrasion resistance. When combined with nickel, it improves its temperature performance.
- Alloy Steel: Alloy steels are carbon steels combined with one or more metal weights to improve their mechanical properties. Alloy steels may comprise unique levels of manganese, nickel, vanadium, copper, aluminum, silicon, zinc, titanium, tungsten, molybdenum, cobalt, and chromium. Compared to carbon steels, alloy steels have higher strength, wear resistance, hardness, corrosion resistance, machinability, weldability, and toughness when subjected to heat treatments. It is mostly used to facilitate building and construction projects.
The Future of Steel Making: Top 5 Technological Innovations to Look Out for in Steel Processing and Manufacturing
The steel manufacturing industry is one of the most lucrative industries in the world, as such, researchers and scientists are constantly looking for ways to optimize its potential and minimize its negative impact on the environment. Below are some of the advancements in steel technology in recent years.
1. Automated Robotic Application
Using robotics in steel fabrication has enhanced the precision and speed in performing several steel fabrication processes. Automated robots can now predict and facilitate uniform material handling, process control, and parts assembly to facilitate the process reliability, production cycle, and safety of the workers. In steel mills, robotic workstations can be implemented and regulated by technical personnel. These workstations can help you manage fixturing during welding, with only simple instructions.
2. Internet of Things
Internet of Things (IoT) sensors can measure the various aspects of material selection and process parameters to facilitate the production of quality parts. By attaching these sensors to equipment and tools, you enable them to monitor and gather data in real-time and analyze those data to provide actionable insights to the manufacturing team on quality control and process optimization. IoT sensors also reduce machine downtimes and ensure no breaks in the production cycle.
3. Structural Health Monitoring Systems
Innovations in data analytics, modeling, and simulation technology allow fabricators to ascertain the health of installed steel structures to optimize their performance, detect material deterioration, and prevent structural damage such as cracks and rust. Fabricators and engineers can now derive quantitative values about the behavior of steel products such as bridges using structural health monitoring sensors.
4. Eco-Friendly Surface Treatment and Coating Technology
Advancements in eco-friendly steel surface treatments have helped enhance steel products’ shelf life. Using bio-based or ceramic-based coating can minimize the negative environmental impact on the products. Tradition conversion coating has received backlash over the years for its toxicity. Modern low-foam metal cleaning additives ensure low bath temperatures, hence conserving energy. Using powder coating and oil-based epoxy coating prevents corrosion.
5. Sustainable Design Techniques
Steel fabricators and designers are turning to practices such as green design and green material selection to promote the fabrication of sustainable steel products that minimize waste, energy consumption, and greenhouse emissions. Manufacturers can further promote sustainability in steel design, by using recycled steel and prefabrication techniques, as steel is a sustainable material. Using advanced computer-aided design (CAD) tools allows designers to work with complex 3D and 2D technologies to improve the accuracy of the final products.
Steel Making and its Economic Impact: Is Steelmaking a Viable Investment?
Yes, steelmaking is a viable investment. Steel materials are the metal of choice for several commercial applications because of their cost-efficiency, durability, malleability, energy efficiency, economic value, and versatility. Steel is used across major industries in the United States: construction, energy, transportation, automotive, aviation, medical, defense, and packaging. In 2022, the United States was recorded as the fourth major steel-producing country in the world. It produced 80.5 million tonnes of crude steel in 2022.
According to the 2023 Steel Market Outlook report from Future Market Insights, the global steel market is projected to increase from $1,893.9 billion in 2023 to $2,901.9 in 2033, following a 4.4% compounded annual growth. Data from IBIS World revealed that the U.S. generated $82.4 billion in revenue in 2023, even though the market declined by -22.7% in the same year. In 2021, the OEC World data placed the United States at the 9th position on the list of global steel exporters and 2nd on the steel importers’ list.
Steel Making and its Environmental Impact: Does Steel Making Affect Carbon Emissions?
Yes, steel production causes carbon emissions. During the coming, coal combustion releases harmful pollutants such as particulate matter (PM), sulfur oxides, carbon monoxides, carbon dioxides, nitrogen oxides, wastewater, and other hazardous wastes. These pollutants can be detrimental to both aquatic and terrestrial life. While there are talks that bio-sourced materials like Bamboo and fiber-reinforced polymers might replace Steel in the future, we believe that only steel will replace steel in the future.
Active reinforcements are underway to improve the eco-friendliness and strength of steel to ensure it remains relevant for a long time. One of the reinforcements to look out for is Green steel. Green steel focuses on producing zero-carbon steel from renewable energy sources rather than fossil fuels. An example is the hydrogen-direct reduced iron-electric arc furnace (H2-DRI-EAF).
Final Thoughts
At PTI. Tech, we employ sustainable steel technologies, processes, and personnel to ensure our partners receive the best service. As a company that cares deeply about the well-being of our environment, we ensure our clients can look forward to tailor-made solutions that facilitate their corporate social needs.
Schedule a consultation today to discover how our capabilities can bring your innovative ideas to life. We offer advanced and personalized design and engineering, metal injection molding, prototyping, additive manufacturing, specialty tooling, and quality control solutions to all our clients.