What is Steel? Hey Engineering Lovers, my name is Igor Felipe and today we are going to talk about steel. And before continuing, if you're watching this video and you're not subscribed, take the opportunity now to subscribe, leave your like and activate the bell, and with that, you'll be part of the largest community of engineering lovers on youtube.
But then, what is steel? Steel is a metallic material widely used in industry and civil construction due to its mechanical properties and strength. It is a metallic alloy composed mainly of iron and carbon, in addition to other elements in smaller amounts, such as manganese, silicon and chromium.
Iron, in its pure form, is relatively soft and does not have the desired characteristics for many applications. However, when carbon and other elements are added to iron in certain proportions, steel is formed. This addition of carbon and other elements allows steel to have a wide range of mechanical properties, such as tensile strength, hardness, toughness and ductility.
The steelmaking process involves melting ingredients such as iron ore, coal and other materials at high temperatures. This process is known as steelmaking and is usually carried out in large furnaces called blast furnaces. The liquid steel resulting from the blast furnaces is then molded into different shapes, such as bars, plates or wires, through rolling, casting or extrusion processes.
But when was steel discovered? The discovery and use of steel goes back to ancient times. Although it is difficult to determine an exact date, it is believed that steel production began around the 12th century BC in regions of Asia Minor, present-day Turkey and the Middle East.
In the beginning, steel was produced by a process known as smelting directly from iron ore, heated in furnaces with charcoal. This method produced low-carbon steel known as "wrought iron", which was stronger than pure iron. This technique was widely used in various ancient civilizations such as the Hittites, Assyrians and Egyptians.
However, it was during the Industrial Revolution in the 18th century that significant advances in steel production took place. The steelmaking process was improved with the development of blast furnaces and large-scale production methods. A major milestone was the invention of the steelmaking process known as the Bessemer process in the mid-19th century.
This process was the first low-cost industrial process for the mass production of steel from molten pig iron. Since then, there have been technological advances and refinements in steelmaking methods, resulting in a wide variety of steel types and grades available today. But why is steel so used and what is its advantage over other metals?
Steel is widely used in various industries and applications due to several advantages it has over other metals. Steel is known for its high mechanical strength, which means it can withstand heavy loads without warping or breaking. This resistance is important in structural applications, such as civil construction, vehicles and various equipment.
Steel is highly durable and depending on its composition, it can be resistant to corrosion, which means it can withstand harsh conditions such as exposure to moisture, chemicals and temperature fluctuations. Iron, which is the main component of steel, is one of the most abundant elements in the earth's crust and this makes steel widely available and relatively inexpensive compared to other metals. An interesting point is that steel is a highly recyclable material.
It can be melted down and recycled several times by controlling its composition without losing its mechanical properties. And that's why many steel industries use scrap metal to reuse the material in new steel production. This contributes to sustainability and reduced environmental impact, as the use of recycled steel reduces the need for iron ore extraction and saves energy.
In addition to these advantages, steel also offers other beneficial characteristics such as good conductivity. thermal and electrical resistance, fire resistance, wear resistance and ease of welding. Today, the iron and steel industry offers a wide variety of alloys, classified and cataloged based on national and international standards, such as ABNT, which is the Brazilian standard, SAE, which is the American standard, and DIN, which is the German standard.
. In some cases, specifications from ASTM, which is the American Society for Testing and Materials) or AISI, which is the American Iron and Steel Institute, which also classifies the types of steel, can be used. But then, what types of steel do we have?
Steel can be found in different groups, the 3 main ones being carbon steel, alloy steel and stainless steel. Carbon steel is a metallic alloy that basically contains iron, carbon and some alloying elements, but without significant amounts. They are the most produced in the world, constituting about 90% of world production and can be divided into subgroups: high carbon, medium carbon, low carbon, extra low carbon and ultra low carbon.
• High carbon steel – above 0. 50% up to the limit of 2. 11% carbon content • Medium carbon steel – between 0.
20% and 0. 49% carbon content • Low carbon steel – between 0. 05% and 0.
20% carbon content • Extra low carbon steel – between 0. 015% and 0. 05% carbon content • Ultra low carbon steel – below 0.
015% carbon content An example of this type of steel is SAE 1020 low carbon steel. It is quite common in the market, and it is cost-effective. It is widely applied in various sectors of industry such as light gears, shafts, crankshafts, pins and is also used in the construction industry as metallic inserts in concrete and even anchor bolts.
We also have ASTM A36 steel which is also a low carbon steel, which in terms of composition is very similar to SAE1020, but they are more used in metal profiles, angles, round bars and many others. Another example of steel that we can know is the SAE 1045 medium carbon steel, which is widely used in hydraulic cylinders, clamps and even screws and nails that we have in our homes. Alloyed steels, in addition to iron and carbon, have other elements in significant proportions that can alter the chemical or mechanical properties of the material.
It is important to understand that alloy steel is different from alloy steel. Thus, both carbon steel and alloy steel are steel alloys, as they have an alloy of iron and carbon. But alloyed steel is a type of alloy that has other elements that alter its characteristics and that is what separates it into another group.
These alloying elements can include manganese, chromium, silicon, nickel, molybdenum, vanadium, aluminum and even niobium. Alloy steels tend to be named according to the most predominant element, such as chromium-vanadium steel, chromium-molybdenum steel or chromium-nickel-molybdenum steel. As with carbon steel, alloyed steel is classified into different subgroups, which are determined by the sum of the levels of alloying elements added to its composition, with low-alloy, medium-alloy and high-alloy steel.
• Low alloy steels: up to 5% alloy elements. • Medium alloy steels: between 5% and 10% of alloying elements. • High alloy steels: from 10% of alloy elements.
An example of this type of steel is low alloy steel SAE 4140, which is a chrome-molybdenum steel and SAE 4340, which is chrome-nickel-molybdenum steel, which are used in wheels and casters in trains for freight transport or bridge wheels. rollers. And lastly we have stainless steel or stainless steel.
As the name itself says, they are steels that are resistant to oxidation, but they are not eternal as many people imagine. Stainless steel is also considered a type of alloyed steel, but technically, stainless steel is a metal alloy consisting of a mixture of carbon iron with at least 10. 5% of the element chromium, which makes it more resistant than steel.
than ordinary steel. When this type of steel comes into contact with oxygen in the air, the chromium forms a thin layer of oxide on the surface of the steel, and this is what protects it against corrosion. Despite being very thin, this film adheres very well to stainless steel, and this protects it against aggressive agents, such as sea water, temperature variations and oxygen itself, which is the main cause of metal oxidation.
Other elements can be added to the alloy such as nickel, molybdenum, vanadium and tungsten, and this can change the resistance of the material in addition to keeping it stainless. Thus, it is possible to classify stainless steels into five basic categories: Ferritic, Austenitic, Martensitic, Duplex and precipitation hardenable. An example is AISI 409 ferritic stainless steel, which is used in motorcycle exhausts and car exhaust systems and even in capacitor casings.
Another example is the AISI 430 ferritic stainless steel , which is widely used in car decorations and domestic utensils ranging from stoves and refrigerators to the stainless steel cutlery we know. Now the question you don't want to shut up, what is the best type of steel? The answer may be a little vague, but the truth is, it depends.
Each type of steel has specific characteristics, so saying that one steel is better than the other will depend a lot on where it will be used and its characteristics, so it really depends. Trust me, choosing the type of steel is a very complex topic and I could talk for hours here and it still wouldn't be enough. But hey, did you know all these steel features?
Do you have any equipment that contains steel near you? Have you had the opportunity to work with steel welding things around? Leave it here in the comments, I want to know I'm going to leave two videos on the side that you might also like and that's cool, it's worth checking out.
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