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When was it discovered? What types of steel do exist? Which are its applications?
It is resistant to corrosion, traction and wear. It was first discovered by some Hindu tribes, perfected in its use by the Japanese people and later discontinued for a long time; only to be rediscovered in England in 1740. What are we talking about? Obviously, we are talking about the most widely used metal alloy all over the world, Steel!
Skyscrapers, oil pipes, cars, appliances, all have one thing in common: each of these items is, or at least partially is, made out of steel. Steel is a material with multiple characteristics, formed by the union of iron and carbon.
Starting with some history facts, the first type of steel was made in India in 300 AD. It was called Wootz steel and it was wrought in sealed crucibles.
Shortly after the year 1000, the Indian technique arrived in the Middle East, where it was further refined to give rise to Damascus steel, which is an extremely flexible and resistant variety. Unfortunately, after 1300 there is no other recording of the usage of this amazing technique. In the following years, some Japanese artisans tried to reproduce it, creating something very similar.
At this point we should mention the most common “packet-steel”, the first to arrive in Europe; its manufacturing technique consists in creating a package of alternating layers of soft iron and cast iron, softened and then hammered together to weld them and diffuse the carbon from the cast iron to the soft iron, in order to obtain the desired percentage of carbon. This technique once fell out of use in the Middle Ages, only to be rediscovered in the Renaissance period.
After some experiments carried out in his furnace, in 1740 Benjamin Huntsman reinstated the crucible technique: he developed a furnace capable of reaching 1600 ºC and inside it he placed clay crucibles with 15 kg of iron. Then cast iron, which is rich in carbon, was added, thus obtaining steel. It was a revolution in the steel industry, this new technique allowed large quantities of steel to be produced in a short time, without compromising quality.
This way of producing steel remained the best option until the arrival of the Bessemer converter in 1856. Henry Bessemer designed a particular pear-shaped oven, used to reduce the excess carbon present in molten cast iron. This converter is able to convert liquid cast iron into steel, unique to the point of becoming the first furnace to allow steel production in a single processing step.
In 1865 a different type of procedure was developed. The Martin-Siemens process allowed the liquid cast iron to be purified from carbon halving the time expenditures. Through the irradiation of direct flames on the molten metal, the material reaches more than 1800 ° C, eliminating superfluous carbon molecules.
The technological breakthrough takes place with the LD process, conceived in Austria in 1949, which involved the use of pure oxygen to eliminate carbon molecules, resulting in a very pure steel using a smaller amount of fuel to raise the temperature of the liquid cast iron. Even today, the LD process is the most used for refining steel and covers 50% of world production.
Over 1.864 million tons of steel are produced each year worldwide and they are processed in various ways, such as rolling or stamping.
However, do you know what is steel made of? And how many types of it are there?
Steel, as we said earlier, is a metal alloy composed of iron and carbon, which must not exceed 2.1%, otherwise the iron would turn into cast iron. Steel is mainly a forging product, that is workable when it is hot, and unlike cast iron, its main feature is the resistance to traction, corrosion, wear and heat.
Steel can be divided into four main categories:
- Carbon steel
- Alloy steel
- Stainless steel (inox)
- Tool steel
Carbon steels, corresponding to 90% of total production, represent the most widespread type, as well as the least valuable. This type of steel with an opaque appearance has technical characteristics that make it malleable and easily workable, but also highly subject to corrosion and sensitive to high and low temperatures.
It is resistant to corrosion, traction and wear. It was first discovered by some Hindu tribes, perfected in its use by the Japanese people and later discontinued for a long time; only to be rediscovered in England in 1740. What are we talking about? Obviously, we are talking about the most widely used metal alloy all over the world, Steel!
Skyscrapers, oil pipes, cars, appliances, all have one thing in common: each of these items is, or at least partially is, made out of steel. Steel is a material with multiple characteristics, formed by the union of iron and carbon.
Starting with some history facts, the first type of steel was made in India in 300 AD. It was called Wootz steel and it was wrought in sealed crucibles.
Shortly after the year 1000, the Indian technique arrived in the Middle East, where it was further refined to give rise to Damascus steel, which is an extremely flexible and resistant variety. Unfortunately, after 1300 there is no other recording of the usage of this amazing technique. In the following years, some Japanese artisans tried to reproduce it, creating something very similar.
At this point we should mention the most common “packet-steel”, the first to arrive in Europe; its manufacturing technique consists in creating a package of alternating layers of soft iron and cast iron, softened and then hammered together to weld them and diffuse the carbon from the cast iron to the soft iron, in order to obtain the desired percentage of carbon. This technique once fell out of use in the Middle Ages, only to be rediscovered in the Renaissance period.
After some experiments carried out in his furnace, in 1740 Benjamin Huntsman reinstated the crucible technique: he developed a furnace capable of reaching 1600 ºC and inside it he placed clay crucibles with 15 kg of iron. Then cast iron, which is rich in carbon, was added, thus obtaining steel. It was a revolution in the steel industry, this new technique allowed large quantities of steel to be produced in a short time, without compromising quality.
This way of producing steel remained the best option until the arrival of the Bessemer converter in 1856. Henry Bessemer designed a particular pear-shaped oven, used to reduce the excess carbon present in molten cast iron. This converter is able to convert liquid cast iron into steel, unique to the point of becoming the first furnace to allow steel production in a single processing step.
In 1865 a different type of procedure was developed. The Martin-Siemens process allowed the liquid cast iron to be purified from carbon halving the time expenditures. Through the irradiation of direct flames on the molten metal, the material reaches more than 1800 ° C, eliminating superfluous carbon molecules.
The technological breakthrough takes place with the LD process, conceived in Austria in 1949, which involved the use of pure oxygen to eliminate carbon molecules, resulting in a very pure steel using a smaller amount of fuel to raise the temperature of the liquid cast iron. Even today, the LD process is the most used for refining steel and covers 50% of world production.
Over 1.864 million tons of steel are produced each year worldwide and they are processed in various ways, such as rolling or stamping.
However, do you know what is steel made of? And how many types of it are there?
Steel, as we said earlier, is a metal alloy composed of iron and carbon, which must not exceed 2.1%, otherwise the iron would turn into cast iron. Steel is mainly a forging product, that is workable when it is hot, and unlike cast iron, its main feature is the resistance to traction, corrosion, wear and heat.
Steel can be divided into four main categories:
- Carbon steel
- Alloy steel
- Stainless steel (inox)
- Tool steel
Carbon steels, corresponding to 90% of total production, represent the most widespread type, as well as the least valuable. This type of steel with an opaque appearance has technical characteristics that make it malleable and easily workable, but also highly subject to corrosion and sensitive to high and low temperatures.
A steel with a high presence of carbon in the alloy would be harder, but at the same time less versatile than a steel with a low percentage of carbon; for this reason the types of carbon steel are divided according to the carbon content in the alloy, from extra soft, with percentages of carbon ranging from 0.05% to 0.15%, to extra hard, with percentages of carbon that range from 0.80% to 0.85%.
Another category is represented by alloyed steels, characterized by the mixture of different metals, which give the steel different characteristics. For instance: silicon increases elasticity, while molybdenum increases hardenability and resistance to heat. A further example consists in adding vanadium in the alloy. This chemical component increases mechanical strength and wear resistance of the final product. Their use is in great demand in the field of mechanics and for the construction of pipelines.
Let’s move on to stainless steel, characterized by greater resistance to oxidation and corrosion. This particular characteristic is obtained by adding to the chromium alloy (usually between 12% and 18%) the chromium molecules that, combining with molecules of carbon, form chromium carbides, thus creating a protective layer against corrosion. Stainless steels can be used for making surgical and domestic instruments, silverware and as exterior coatings for commercial and industrial buildings.
The category of tool steels, on the other hand, is obtained by inserting tungsten, molybdenum, cobalt and vanadium in variable quantities in the mixture to increase heat resistance and durability. They are well suited to withstand machining such as cutting and drilling and can be classified according to their shapes and related applications:
- Long or tubular products include bars, rails, cables, corners, tubes and beams and are commonly used in the automotive and construction industries.
- Flat products include plates, sheets, coils and strips and are mainly used in automotive parts, appliances, packaging, shipbuilding and construction.
There are many types of steel, and its denominations and technical standards are established by national and international bodies, such as the ISO, International standard institute. The steels can be classified in group I, for basic and quality steels, and in group II for special steels.
Even if contemporary technology has reached unimaginable heights, steel still remains the most widely used material for every type of processing and product. A sector that still prefers the use of steel today is certainly the Automotive one. It often happens that leading companies in the automotive sector collaborate with steel mills to develop new alloys capable of giving more and more performing characteristics to their cars. For example, the steel giant AccerlorMittal, has founded a specific department for the automotive sector, called Global R&D for Automotive, which collaborates with the largest companies in the transport sector to improve the quality of special steels, AHSS, high strength steels, or UHSS, ultra-strength steels. These particular steels have the ability to have a high breaking point while maintaining a low weight, which is an essential factor for the performances of a vehicle.
The advantages of using these steels are several:
- They offer greater protection and safety against impact, meeting the rigorous standards of the automotive industry.
- They are lighter, thus they offer greater energy efficiency, reducing fuel costs.
- Vehicles using AHSS / UHSS steel can withstand higher payloads by increasing the carrying capacity.
- They increase torsional stiffness, improving vehicle handling and responsiveness.
- They also offer greater sustainability. Indeed, by choosing these steels, replacing aluminum or carbon fiber materials, the company makes a choice for the ecosystem, because aluminum and carbon fiber involve high emissions for production and recycling.
We have reached the end of our video! We talked about steel, its characteristics and its applications depending on the variety used for each of the different productive sectors.
Another category is represented by alloyed steels, characterized by the mixture of different metals, which give the steel different characteristics. For instance: silicon increases elasticity, while molybdenum increases hardenability and resistance to heat. A further example consists in adding vanadium in the alloy. This chemical component increases mechanical strength and wear resistance of the final product. Their use is in great demand in the field of mechanics and for the construction of pipelines.
Let’s move on to stainless steel, characterized by greater resistance to oxidation and corrosion. This particular characteristic is obtained by adding to the chromium alloy (usually between 12% and 18%) the chromium molecules that, combining with molecules of carbon, form chromium carbides, thus creating a protective layer against corrosion. Stainless steels can be used for making surgical and domestic instruments, silverware and as exterior coatings for commercial and industrial buildings.
The category of tool steels, on the other hand, is obtained by inserting tungsten, molybdenum, cobalt and vanadium in variable quantities in the mixture to increase heat resistance and durability. They are well suited to withstand machining such as cutting and drilling and can be classified according to their shapes and related applications:
- Long or tubular products include bars, rails, cables, corners, tubes and beams and are commonly used in the automotive and construction industries.
- Flat products include plates, sheets, coils and strips and are mainly used in automotive parts, appliances, packaging, shipbuilding and construction.
There are many types of steel, and its denominations and technical standards are established by national and international bodies, such as the ISO, International standard institute. The steels can be classified in group I, for basic and quality steels, and in group II for special steels.
Even if contemporary technology has reached unimaginable heights, steel still remains the most widely used material for every type of processing and product. A sector that still prefers the use of steel today is certainly the Automotive one. It often happens that leading companies in the automotive sector collaborate with steel mills to develop new alloys capable of giving more and more performing characteristics to their cars. For example, the steel giant AccerlorMittal, has founded a specific department for the automotive sector, called Global R&D for Automotive, which collaborates with the largest companies in the transport sector to improve the quality of special steels, AHSS, high strength steels, or UHSS, ultra-strength steels. These particular steels have the ability to have a high breaking point while maintaining a low weight, which is an essential factor for the performances of a vehicle.
The advantages of using these steels are several:
- They offer greater protection and safety against impact, meeting the rigorous standards of the automotive industry.
- They are lighter, thus they offer greater energy efficiency, reducing fuel costs.
- Vehicles using AHSS / UHSS steel can withstand higher payloads by increasing the carrying capacity.
- They increase torsional stiffness, improving vehicle handling and responsiveness.
- They also offer greater sustainability. Indeed, by choosing these steels, replacing aluminum or carbon fiber materials, the company makes a choice for the ecosystem, because aluminum and carbon fiber involve high emissions for production and recycling.
We have reached the end of our video! We talked about steel, its characteristics and its applications depending on the variety used for each of the different productive sectors.