Steel is one of the most widely used metals in the modern world. It’s cheap, powerful and incredibly versatile. In the world, the annual production volume of steel is about 750 million tons, and steel is the second largest volume production product after cement.
Steel is completely recyclable and requires only relatively little energy to produce. Because of the efforts of the steel industry, the current energy consumption and carbon dioxide emissions are only half of the CO2 emissions of the 1960s. This makes steel production very environmentally friendly and sustainable.
There are too many steel products, such as railways, oil and gas pipelines, skyscrapers, elevators, subways, bridges, cars, ships, knives and forks, razors and surgical instruments.
Before you understand steel, you need to understand the history of iron. Iron is the fourth largest element, accounting for more than 5% of the earth’s crust. The beginning of human iron production began around 2000 BC in the southwest or south central Asia. This marks the beginning of the iron age, and these tools and weapons have widely replaced copper and iron. In this era, wrought iron was produced by blacksmiths who heated the iron and crushed the impurities on the anvil. The iron produced is tough. It was not until the Middle Ages that new types of iron were developed using higher temperatures. This is called cast iron and it is harder than wrought iron but it is also more fragile. It was not until 1870 that a large amount of steel began mass production.
Composition of steel
Steel is an alloy of iron and carbon. It can contain small amounts of silicon, phosphorus, sulfur, and oxygen. The carbon content of steel is between 0.08-1.5%. This makes it harder than wrought iron but not as brittle as cast iron. Steel also has a unique balance of hardness, flexibility and tensile strength. It is also more durable and more rigid than softer wrought iron. At the same time it is more resistant to impact than the more brittle cast iron.
Steel is mainly produced in blast furnaces or electric arc furnaces.
The blast furnace mainly uses raw materials (iron ore, limestone and coke) and some scrap steel to make steel. The blast was invented by an Englishman in the mid-1850s and was named Henry Lisbemer. He designed a method for producing steel by blowing molten iron into the air to oxidize the material and separate impurities.
The modern blast furnace is a large steel shell shaped like a cylinder and lined with heat-resistant bricks. Iron ore, coke, and limestone enter the furnace from the top, sinking gradually to the bottom, and warming as they descend. In the upper half of the furnace, the gas from the combustion coke releases oxygen from the iron ore. At the bottom of the furnace, limestone begins to react with impurities in the ore and coke forms slag. At the bottom of the furnace, the temperature reached 3000 degrees Fahrenheit. The slag floats on top of the molten steel and is discharged through the slag in the furnace. The molten steel is discharged from the furnace wall through the drainage hole.
The electric arc furnace is mainly used for the production of special steels for other metal alloys. Scrap is poured into the EAF from a bridge crane. When the furnace is full, the lid is covered on the top of the furnace. The lid contains electrodes placed in the oven. The electrode carries a powerful current, generating heat, which melts the waste. As the scrap melts, other metals, called iron alloys, are added to the steel to obtain the desired chemical composition. Oxygen is blown into the furnace to purify the steel. Lime and fluorite are added and the impurities are melted to form a slag. The slag floats on top of the molten steel and can be poured out by tilting the furnace. By combining other metals to form steel alloys, a series of special steels can be manufactured in EAF. The most widely used of these is stainless steel, which has added chromium and nickel to give it corrosion resistance. Other special steels manufactured in EAF include steels for engineering, aerospace and armor plating.
Source: China Pipe Fittings Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)