Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade.
Steel is iron that has most of the impurities removed. Steel also has a consistent concentration of carbon throughout (0.5 to 1.5 percent). Impurities like silica, phosphorous and sulfur weaken steel tremendously, so they must be eliminated. The advantage of steel over iron is greatly improved strength.
Modern steels are made with varying combinations of alloy metals to fulfill many purposes. Carbon steel, composed simply of iron and carbon, accounts for 90% of steel production. High strength low alloy steel has small additions (usually < 2% by weight) of other elements, typically 1.5% manganese, to provide additional strength for a modest price increase. Low alloy steel is alloyed with other elements, usually molybdenum, manganese, chromium, or nickel, in amounts of up to 10% by weight to improve the hardenability of thick sections. Stainless steels and surgical stainless steels contain a minimum of 11% chromium, often combined with nickel, to resist corrosion (rust). Some stainless steels are magnetic, while others are nonmagnetic.
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[edit] Production
In 2010, total world crude steel production was 1,413.6 million metric tonnes (mmt). The biggest steel producing country is currently China, which accounted for 44.3% of world steel production in 2010.
[edit] Recycling
The most commonly recycled items are containers, cans, automobiles, appliances, and construction materials. The steel industry has been actively recycling for more than 150 years, in large part because it is economically advantageous to do so. It is cheaper to recycle steel than to mine iron ore and manipulate it through the production process to form new steel. Steel does not lose any of its inherent physical properties during the recycling process, and has drastically reduced energy and material requirements compared with refinement from iron ore. The energy saved by recycling reduces the annual energy consumption of the industry by about 75%, which is enough to power eighteen million homes for one year.
Stainless steel is theoretically 100% recyclability and its long term life makes it an ideal environmental performer much better than many other materials. Stainless steel products are designed to have a long life; often spanning over several decades. This long term life generally is the reason for choosing stainless steel in the first place.
[edit] Environmental Impact
The quantity of energy required for manufacture of a product, the embodied energy, is of growing concern to environmentalists. More efficient process technology has allowed steelmakers to significantly reduce the amount of energy used in the production of stainless steel over the past two decades. Stainless steel's low thermal conductivity makes soldering and welding more energy efficient than with many other metals.
[edit] Environmental Benefits of Stainless Steels
Stainless steel has many environmental and social benefits. Stainless steel products enable us to lead a healthier life and are cleaner for the environment as well.
New catalytic converters use stainless steel for the holding and transportation of catalytic substances. The newest versions are much lighter and stronger than traditional ceramic versions as well as being much more energy efficient. Catalytic substances are usually highly corrosive and are active within a high temperature environment, thus being the reason for stainless steel being the chosen material. These stainless steel converters help to decrease pollution on motor vehicles, generator sets, forklifts, mining equipment, trucks, buses and trains etc.
Diesel filters are designed to remove smoke and soot particles from the exhaust gas of a diesel engine. Newer versions can consist of up to 90% stainless steel. Diesel filters can filter out 95% of black smoke and 85% of soot particles from the gas produced. Stainless steels excellent temperature resistance, manufacturability and economic properties make it the best option for the filter.
Stainless steel pipes for drinking systems help to keep water clean and quality standards high. Stainless steel guarantees lasting hygiene and prevents the formation of any medium on which bacteria can grow. Correct grade selection will minimise the risk of any localised corrosion, meaning there is practically no contamination of water in contact with the stainless steel.
Stainless steel is being used for the recycling of cardboard and paper, meaning it makes a major contribution to the reduction of the waste steam as well as the protection to trees.
[edit] Hygiene
The excellent hygienic properties of stainless steel are recognised by its use for surgical instruments and medical implants, as well as in food and drink processing, catering and washroom installations. Its smooth, neutral surface makes it difficult for bacteria to adhere and survive, and it is also very easy to clean, so strict standards of hygiene are possible at every stage of the process.
