STAINLESS STEEL OVERVIEW
With advancements in the steel industry and the evolving fields of metallurgy and materials science, the production and use of stainless steels have significantly expanded. Its superior features include corrosion resistance, aesthetic appeal, low life cycle cost, full recyclability, and heat resistance. These material properties and advantages make stainless steel stand out among other types of steel. Stainless steel is widely used not only in industrial sectors such as kitchen utensils, construction, automotive, food industry, and white goods but also in everyday life for making decorative items and artworks.
Although the demand is high, stainless steel production in Turkey remains at relatively low levels. The most important raw material for stainless steel is chromite ore. While chromite ore is produced in Turkey, a significant amount of stainless steel is imported from abroad. At this point, the responsibility falls not only on disciplines such as Ore Processing Engineering, Metallurgy, and Materials Engineering but also on all of us, including businessmen from both the public and private sectors.
The production of stainless steel is a long and complex process. Roughly, the process begins with the collection and stocking of scrap metals. The stocked scrap is melted in metal melting furnaces. Various elements are added to the molten metal to achieve the desired quality. Once the desired quality is reached, the mixture is taken from the furnace and poured into a large holding ladle. This ladle is then transported by crane to the continuous casting machine. The material is continuously cast from the continuous casting machine. The continuously cast stainless steel is cut into billets of specific lengths and transported with cranes. These billets are reheated through heat treatment to be shaped properly. After heating, the billets are sent to different production lines according to their cross-sectional area to be formed into the desired shapes. The stainless steel, after taking its final shape, is annealed and heat-treated according to the properties it needs to exhibit. Finally, it is cut, packaged, straightened, and subjected to various surface treatments, completing this challenging and labor-intensive production process.
Paslanmaz Çelik Üretimi Video – ArcelorMittal Tesisleri
Stainless steel is the most recycled material in the world. It is estimated that 82% of the stainless steel used will be converted into new steel. Moreover, the quality of stainless steel does not degrade when recycled; remelted and recycled steel retains the same quality and properties as the original steel. Due to the attractiveness and high value of stainless steel scrap, there is no need for assistance to sustain the processing scrap market. In principle, stainless steel can be recycled infinitely. However, an annual production increase of 6% in stainless steel, combined with the durability of stainless steel products, indicates a shortage of stainless steel scrap. This means that although today’s production relies mainly on recycled steel, there is still a need for raw materials in the form of alloying elements. Currently, approximately 60% of the raw materials used to make new stainless steel are recycled steel.
Stainless steel is a steel containing 10.5% or more chromium and 1.2% or less carbon. The high chromium [Cr] content in stainless steel gives it its corrosion-resistant properties. Chromium forms a thin chromium oxide layer on the surface, which protects the steel from rusting. Nickel [Ni] is also used as an alloying element in stainless steel and provides corrosion resistance. Additionally, alloying elements such as molybdenum, tungsten, vanadium, selenium, and nitrogen may be present.
Stainless steels can exhibit different microstructures depending on the amounts of alloying elements they contain. Based on these microstructures, stainless steels can be roughly divided into five groups: austenitic stainless steels, ferritic stainless steels, martensitic stainless steels, ferritic-austenitic (duplex) stainless steels, and precipitation-hardened stainless steels. Selecting the appropriate stainless steel group for an application contributes to low maintenance costs and long service life. For example, high-strength stainless steels provide economic and resource efficiency benefits in construction by reducing material usage. High-strength steels can absorb more energy in the event of a collision, enhancing safety in vehicles and many other structural components and systems.