Our knowledge of steel has come a long way in the more than 2,000 years since it was first developed. We understand the effects of adding carbon and a wide variety of other alloying elements on steel properties. We understand the microstructures that form in steel, how they are influenced by steel composition and mechanical and thermal treatments, and their influence on steel properties. This knowledge has enabled extensive engineering of steel alloys, steel production processes, and steel component design and fabrication.
This knowledge has enabled the development of different types of steels to meet different applications. This includes carbon steels, low-alloy steels, tool steels, high-strength low-alloy (HSLA) steels, and stainless steels. Adding various combinations of alloying elements enable us to tailor steel strength, ductility, and other properties to meet a wide range of requirements for a wide range of applications. Each of the different types of steels has a certain set of alloy compositions and range of properties that make them suitable for different applications.
Our understanding of steel metallurgy has also enabled the development of many processes used to alter steel shape and microstructure to achieve specific properties and to produce different forms of steel. Steel mills use hot-rolling, cold-rolling, three different annealing processes, and normalizing to create microstructures that result in desired mechanical properties, easier machining, and/or better response to further heat treatment.
Currently, mills worldwide use these processes to produce about two billion tons of plate, sheet, and bar a year. Some sheet is used to produce welded tubing and pipe and some bar is used to produce wire and seamless tubing and pipe. Regardless of the form, steel metallurgy knowledge has enabled most mills to develop robust production processes capable of producing steel that consistently meets customer requirements.
Then, companies that fabricate steel components from plate, sheet, bar, and tubing use through hardening heat treatments, such as quench and temper, to alter the steel microstructure to increase its strength and hardness. They also use case hardening heat treatments to alter the composition and/or microstructure of a component’s surface for increased strength and/or increased hardness. Because of their knowledge of steel metallurgy, most of the companies performing the heat treatments have developed processes capable of consistently meeting customer requirements.
Finally, companies that design steel components for use in their products can take advantage of steel metallurgy knowledge to optimize designs for performance, reliability, and cost. By understanding the effects of alloy composition, mill processing, and post-fabrication heat treatments on steel properties they can select the optimum alloy, mill condition, fabrication method, and post-fabrication heat treatment. Sometimes the considerations lead to innovations that give a competitive advantage in performance, reliability, and or cost.
Steel is an incredibly versatile material that is used in a wide range of applications across numerous industries. It has come a long way since its early beginnings and plays a crucial role in shaping our modern world.
Also, Michael Pfeifer just released a Metal Conversations podcast episode on Steel Metallurgy Knowledge. It's about 10 minutes long and covers factors that influence metal properties and the status of steel metallurgy knowledge.