The importance of metal in today’s industry

Today’s world is unimaginable without the metal structures whose application spreads from the car industry to building bridges. Although concepts such as iron, metal, and steel are being used every day, the question arises as to whether there is a difference between them? One of the common mistakes that appears daily is to equalize or use the terms iron, metal, and steel as synonyms.

However, there is a certain difference in the aforementioned terms, ranging from the conceptual definition itself to the way in which steel or iron is obtained in the first place.

What’s the difference between metal iron and steel?

What are metals?

Metals, ie, metallic elements are the chemical elements that got their name thanks to the metal link through which the atoms in the crystal grid are connected. Looked through the prism of chemistry, metals found in nature can be found in pure form, without any additives. Furthermore, each metal has its physical and chemical properties that shape its behavior.

In addition to the above-mentioned division, metals can be divided into precious, semi-precious and common metals. The classification of metals with respect to the preciousness depends on its corrosion resistance. Precious metals are therefore resistant to all types of corrosion while the common metals are on the other hand subject to corrosive action.

All metals have a glossy surface and excellent processing properties. However, due to the reflexive properties, there are problems with laser cutting.  Mainly, in nature, they can be found most often in a solid state, except mercury which is liquid.

Is there a difference between metal and steel?

There is. Due to its chemical properties, stainless steel can’t be classified as metal, but as alloy. Thus, metals as such in their structure don’t have any admixtures as opposed to the steel which has.

However, despite the fact that steel is not a metal, it possesses properties that have metals. For example, steel plates can have a glossy surface just like metals. Observed through the prism of the properties, steel is a good electric power and heat generator just like all metals. Nonetheless, because of its composition, it can’t  be placed in the metals category, in a periodic system of elements.

And what about the difference between iron and steel?

Željezo se kao takvo može klasificirati kao sirovina koje se upotrebljava u izradi kako slitina tako i komponenti poput vijaka. Sukladno tome i činjenici da čelik ima udio željeza do čak 99% izvire glavna razlika između ova dva elementa.

In addition, another thing that affects the significant difference between steel and iron are its properties. That is just why stainless steel (inox) is corrosion-resistant, has good thermal conductivity and properties that make it one of the most widely used constructional metals .

Iron is an important raw material for component making

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The emergence of stainless steel alloy

Today’s world of construction, car industry, mechanical engineering and many other branches can hardly be imagined without inox or stainless steel. Inox was created in 1821 when French Berthier added 1.5% chromium to steel, in order to make cutlery. During the 20th century, the approach to the development of steel production technology was systematical; and a number of new ways and techniques have that have greatly contributed to and enhanced the production of the same have been discovered.

The importance of this material is reflected in the fact that during 2011, a total of 1 490.06 million tonnes of steel was produced in the world, and this figure is increasing over the years. The leading stainless steel manufacturer is China, followed by Japan, the United States and India. The special importance of stainless steel is that it can be completely recycled and the proportion of recycled stainless steel is up to 80%.

Chemical composition of inox

As it has already been said, in the production of stainless steel, a certain percentage of chromium or nickel is added to the mentioned. These materials make steel resistant to corrosion. Chromium, whose share can rise up to 20% is added to the iron and carbon. In addition to chromium, nickel is added to the mixture as well. However, different standards in stainless steel production require different proportions of chemical elements. For example, the steel of the standard X13 NiCr Si 35-16 contains up to 37% nickel and 17% chromium while other elements such as nitrogen come in a proportion of a 0.11% maximum. However, the most important metal in the chemical composition is chrome, which creates an oxidized layer on the steel surface, that protects it against corrosion and external influences.

Production process

The process of stainless steel production begins with loading the recycled material by large cranes or magnets into containers that are then transported to the high furnaces. In high furnaces, with the addition of nickel, or chromium, recycled steel is left to melt. There are different stoves that can be used in this process, and among the best is an electric furnace which produces the best and the fines steel as well. However, prior to the melting, the steel should be grinded or cleaned from impurities to make the quality as good as possible.

The production process is continued in the refining furnace after melting. Since molten steel itself contains many other chemical elements, these elements need to be removed, which is achieved by the refining process, after which the molten steel flows from the refining furnace and is formed into pieces of about 64 meters long. These pieces are further rolled to finally obtain a rolled steel strip that then goes to further purification, or where a protective layer is formed through the contact of chromium and atmosphere. After that, the steel is shaped or cut according to customer’s requirements, and later pipes, fences, and other things can be made of it.

Apart from the fact that steel can be produced by recycling an old steel, it can also be produced by the purification of crude iron, which is a process that in some segments differs from the production process done with recycled steel.

High furnaces

The process of steel production, as well as of other metals, happens in high furnaces. The electric furnace serves for the melting of the steel and is made on the basis of the electrical arc or induction. The electric arc-based blades function in a way that a high temperature is being created between the electrode and the metal by means of electric energy, and that’s how the steel melts. There are several basic reasons why an electric furnace is used, and the main reasons are an easy achievement of high temperature, an easier control of the chemical composition, no combustion product, and much less coating on the stove itself is being consumed.

Types of stainless steels

There are different types of stainless steels or inox, which can be divided into:

• Ferritic stainless steels – This kind of stainless steel contains 13 to 17% of chromium. This kind of steel is highly resistant to acids, is very soft, possesses the properties of the magnet but there is a problem of poor weldability

• Austenitic inox – the chromium content in this type of steel ranges from 15 to 20%. Its main characteristics are self-magnetism, bigger deformation in welding, plasticity and good properties at low temperatures

• Austenitic ferrite inox– chromium content ranges from 22 to 24%. This kind of steel is often used in mining, ie petroleum, petrochemical and chemical industry

• Martensitic inox – inox which has an increased carbon content, and is mainly used in the production of tools

• Soft martensitic inox – these steels are high-strength. They are used to make parts that are in an environment where unclean air is well present

Stainless steel processing techniques

Inox as one of the most common metals in today’s industry has various processing techniques. However, to make the positions made of stainless steel, processable, it is necessary to cut them. One of the most economical cutting techniques is laser cutting. In addition to laser cutting, inox can be cutted with the following techniques:

• Plasma cutting
• Water jet cutting
• Autogenous cutting
• Cutting steel by using cutting plates

However, of all the above mentioned cutting metal processing techniques, laser inox cutting represents a technique in which the ratio of the cutting quality, the speed and the economy of the cutting is the best.

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