The addition of carbon content in steel can improve hardness (hardness) and tensile strength (tensile strength), but on the other hand makes it brittle (brittle) and lower ductility (ductility).
Although steel has previously been manufactured by blacksmiths for thousands of years, when the use becomes increasingly more efficient production methods discovered in the 17th century. With the invention of the Bessemer process in the mid-19th century, mass production of steel into material that makes the price of production becomes cheaper. Currently, steel is one of the most common materials in the world, with production of more than 1.3 billion tons annually. Steel is a major component in buildings, infrastructure, ships, automobiles, machinery, tools, and weapons. Modern steel are generally classified based on its quality by some standards institutions.
Material characteristics.
Iron can be found in the earth's crust only in the form of ore, usually in the form of iron oxides such as magnetite and hematite. Iron is extracted from iron ore by removing oxygen atoms and then combine again with other atoms such as carbon. This process is called smelting. There is a small amount of iron that has been through this process in the past by heating the ore planted on the coals, and then combine the two metals to forge hammer. Embodied carbon content can also be controlled.High temperatures in the smelting process can be achieved with an ancient method that has been used since the days of Copper. Because the iron oxidation level is increasing very fast temperature above 800 ° C (1,470 ° F), it should be noted that the smelting process should be conducted in an environment with low oxygen levels. Smelting processes will produce alloy steel called. Excess carbon and other impurities can be removed with some gradual process.
Some material was also added to the mixture of iron / steel with carbon to obtain the desired characteristics. Nickel and manganese is added for added strength, chrome added to increase hardness and the boiling point, and the addition of vanadium also add violence and mitigate the effects of metal fatigue.
To prevent corrosion, chromium is added at least 11% wt thus forming a hard oxide on the surface of the steel; This steel is known as stainless steel (anti-stain steel). Tungsten is added to cementit formation, resulting in a lower quench rate will form martensite. On the other hand, sulfur, nitrogen, and phosphorus make steel becomes brittle, so that these elements must be separated when processing.
The density of steel varies depending on its constituent elements, but generally is between 7.750 and 8.050 kg / m3 (484 and 503 lb / cu ft), or 7.75 and 8:05 g / cm3 (4:48 and 4.65 oz / cu in).
Despite the low concentration range mixture of iron and carbon steel form, but can form a wide variety of different metallurgical structures with properties that are very different. Understanding these properties are very important in the production of steel. At room temperature, the most stable form of iron is body-centered cubic structure (BCC), called ferrite or iron-α. This iron is a soft metal that can only dissolve the carbon in small concentrations, not more than 0.021 wt% at 723 ° C (1,333 ° F), and only 0.005% at 0 ° C (32 ° F). At 910 ° C pure iron turned into a face-centered cubic structure (FCC), called austenite or iron-γ. FCC austenite structure can dissolve more carbon, up to 2.1% [5] (carbon 38 times ferrite) at 1,148 ° C (2,098 ° F), which is called cast iron (cast iron).
When steel with a carbon content of less than 0.8% is heated, then the austenitic phase (FCC) tried to turn into a mixture of ferrite phase (BCC), generates excess carbon.
Heat treatment.
There are a variety of heat treatments commonly used in the processing of steel. The heat treatment is most often used is annealing, quenching, and tempering. Annealing is a heat treatment of the steel that is done by heating the steel to a temperature high enough to make a soft steel. This process occurs in three stages, recovery, recrystallization and grain growth. Annealing temperature required for annealing depends on the type and content of alloying element in steel.Quenching and tempering first involves heating the steel to turn into the austenite phase then cooling is done using a cooling medium oil or water. A decrease in temperature suddenly produce a martensitic structure which is hard and brittle. Steel is then processed through a tempering process which is one type of annealing. In this process a portion of the martensitic structure will change to cementite, or Spheroidite to reduce internal stress and defects in steel, so steel is more resilient and more resistant to cracking.
Steel production.
Understanding the process of erection of steel construction in general is a process that consists of the assembly of the steel components so that it becomes an integral and implemented in the field. The erection process consists of the appointment process and put the steel components to the desired position, and then connectthem together.
After going through the process of smelting iron from ore, carbon containing excess. To make steel, need to be melted and reprocessed to reduce the carbon content to achieve the desired amount, then after that the other elements can be added. This liquid is then poured continuously forming a long plate or cast iron into steel bars. Approximately 96% of steel is poured continuously and 4% is produced in the form of bullion.
The steel industry.
Already commonly heard term "iron and steel industry" as a whole, but from a historical perspective they are different products. The steel industry is often used as an indicator of economic development, because the role of steel to meet the needs of infrastructure and economic development as a whole.In 1980, more than 500,000 workers in the steel industry. In 2000, workers in the steel industry decreased to 224,000.
Economic development in India and China are rapidly lead to an increase in demand for steel in recent years. Between 2000 to 2005, the global demand for steel increased by approximately 6%. Since 2000, several steel companies of China and India have become major companies in the industry, such as Tata Steel, Shanghai Baosteel Group Corporation and Shagang. The world's largest steel producer is ArcelorMittal.
In 2005, the British Geological Survey stated that China is the largest steel producer in the world, about a third of the world's steel production comes from China, followed by Japan, Russia and the United States.
In 2008, the steel becomes a commodity trading on the London Metal Exchange. In late 2008, the steel industry had fallen so much lead to termination of employment.
History.
Prior to the introduction of production methods Bessmer and various production techniques other modern, steel including materials that are expensive and only used when no alternative materials that are cheaper, especially to the sharp part of the knife, razor, and a sword, and various tools and utensils that require parts hard and sharp. Steel when it is also used for springs, including springs used in clock.With the development of production methods more quickly and economically, the steel becomes more readily available and become much cheaper. Steel has replaced the use of pig iron in various ways. In the 20th century with the invention of plastic, the use of steel for some applications can be replaced, because the plastic is cheaper and lighter. Carbon fiber also replace steel for various applications to prioritize their light weight than an economical price, such as on airplanes, sports equipment and luxury vehicles.
Classification of steel.
* Based on composition.
- Carbon steel- Low alloy steel
- Stainless steel
* Based on the manufacturing process.
- Open steel furnace- Electric kitchen
- The process of oxidation base
* Based on the shape of the product.
- Plates bars- Tube
- Gazette
- Pita
- Structural Shapes
* Based on the microstructure.
- Ferritic- Pearlitic
- Martensitic
- Austenitic
* Based on the usability in construction
- Structural Steel- Non-Structural Steel
Compared with excess Steel Concrete.
What are the advantages of steel as a building construction? Concrete and steel are the materials that are used as building construction familiar. Sturdy structure makes the material able to support the building with a strong and resistant to earthquake shocks.But you know, if the steel has many advantages compared to concrete. What are they?
Easier installation process.
On the construction of the building with concrete construction design, required a series of the process is quite long. Call it, ranging from the selection of raw materials, forming concrete mix design, and manufacture of concrete structures. Meanwhile if we use the construction of the steel, the steel products will be obtained already in the form of ready to install. His installation is relatively easy because quite stringing it with the help of bolts only.Power Quality Stay Awake.
If we compare the stability of the quality of the steel and concrete, the steel quality is arguably remain stable. This is because the manufacture of steel products is done in a special factory with direct supervision of experts. Instead, the concrete quality is often changed either due to the composition of the raw materials used and the method of manufacture, for example, from K225 transformed into K175. If you have this, like it or not the construction that has been created should be dismantled again so worth taking. As a result, the development costs will increase.More Environmentally Friendly.
As we know, the raw material for making concrete comprising a mixture of cement, sand, water, and rocks. Mining activities of these ingredients lead to more environmentally disturbed. Meanwhile, the process of mining iron ore as a raw material for steel actually disturb the environment. However, levels are relatively smaller than the mining was done in a concrete-making materials.More Reduce Costs execution.
Although steel prices more expensive than concrete. But if we take into account the processing time of development, we can save costs in terms of this budget. Steel construction is easily installed and easily repaired as well, resulting in a long process is relatively faster. Instead, the concrete construction requires more time considering there are many stages to go through when we build building construction with this material. Thank you for reading this article.Written and posted by Bambang Sunarno. sunarnobambang86@gmail.com
author:
https://plus.google.com/105319704331231770941.
name: Bambang Sunarno.
http://primadonablog.blogspot.com/2015/09/do-you-know-about-steel.html
DatePublished: September 7, 2015 at 10:40
Tag : Do You Know About Steel.
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