**Steel Composition and Properties**: – Steel contains 0.02% to 2.14% carbon by weight. – Alloy steel includes intentional alloying elements like manganese, nickel, and chromium. – Steel has improved strength and fracture resistance compared to iron. – Various elements like chromium and nickel are added to modify steel’s properties. – Steel can be heat-treated to enhance its properties. – Pure iron exists in BCC alpha iron structure at room temperature. – Carbon can form cementite when it moves out of solution with iron. – Different metallurgical structures form in steel based on carbon and iron concentrations. – Steel density ranges between 7,750 and 8,050kg/m^3 or 7.75 and 8.05g/cm^3. – Heat treating processes for steel include annealing, quenching, and tempering. **Steel Production and Recycling**: – Iron is commonly found in the Earth’s crust as an ore. – Iron is extracted through smelting, where oxygen is removed. – Impurities are removed from pig iron to produce steel. – Steel production involves reducing carbon content in smelted iron. – Various elements are added to steel to achieve desired properties. – Steel is one of the most recycled materials globally. – In the United States in 2008, over 82,000,000 metric tons of steel were recycled, with an overall rate of 83%. – Recycled raw materials account for about 40% of the total steel produced. – Steel production exceeds the amount that is scrapped. – Steel’s recyclability contributes to its sustainability. **Historical Evolution of Steel**: – Steel production dates back to antiquity with bloomeries and crucibles. – Steel was produced in Celtic Europe from 800BC and in Britain from 490-375BC. – High-carbon steel was produced in the Netherlands from the 2nd-4th centuries AD. – Evidence of early high carbon steel production in South Asia. – Wootz steel known for its durability and global exportation. – Introduction of Henry Bessemer’s steelmaking process in 1855. – Development of the Gilchrist-Thomas process to remove phosphorus. – Siemens-Martin process as a complement to the Bessemer process. – Use of electric arc furnaces (EAF) for reprocessing scrap metal and pig iron into new steel. – Bethlehem Steel in Pennsylvania was one of the world’s largest steel manufacturers before closing in 2003. **Steel Industry and Global Impact**: – The steel industry contributes 8% of global greenhouse gas emissions. – Major steel producers include ArcelorMittal, Tata Steel, Baosteel Group. – Increase in global steel demand due to economic growth in China and India. – Steel is one of the most commonly manufactured materials worldwide. – China is the top steel producer with one-third of the world share. – Ranking of other major steel producers like Japan, Russia, and the United States. – Significant carbon dioxide emissions associated with steel production. – Downturn in the steel industry at the end of 2008. – Global greenhouse gas emissions attributed to the steel industry in 2021. **Types of Steel and Applications**: – Stainless steel contains at least 11% chromium for corrosion resistance. – Carbon steel makes up 90% of steel production. – High strength low alloy steel provides additional strength at a modest price increase. – Advanced High Strength Steel (AHSS) is a new variety meeting CAFE regulations. – Stainless steels resist corrosion with added elements like chromium and vanadium. – Tool steels are alloyed for maximum solution hardening. – Steel is widely used in construction, infrastructure, appliances, and buildings. – Major structures like stadiums and skyscrapers are supported by steel skeletons. – Steel is used in car bodies, shipbuilding, aerospace, and white goods. – Applications include reinforcing concrete, mining, and office furniture.https://en.wikipedia.org/wiki/Steel