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The earliest known production of steel dates back to 1800 BC and is found in iron tools discovered at archaeological sites in Anatolia. This material has been in use for at least 4,000 years! For centuries, this product has helped construct and build civilization. It is used for basic construction materials and in the automotive or environmental industries. How can it be processed? What are its composition and mechanical properties? We write about it below!

Composition of steel

General-purpose structural steel is an alloy of iron and carbon, containing up to 2% carbon (a material with higher carbon content is called cast iron). Steel is the most popular material used in the construction of the world’s infrastructure and industry, used in manufacturing everything from sewing needles to oil tankers. In addition, the tools needed to build and manufacture such items are also made of steel. Analyzing its structure in more detail, one must point out that it is an iron-carbon alloy containing less than 2% carbon and 1% manganese with small amounts of: 

  • silicon, 
  • phosphorus, 
  • sulfur,
  • oxygen. 

Since it is an alloy and not a pure element, it does not belong to the field of metals. Although steel itself contains iron belonging to this group, carbon, and other parts, also contained in this alloying composition, exclude the possibility of classifying steel as a metal. Today, steel is the world’s most important construction material in every aspect of our lives. We can see its extensive use in, for example: 

  • automobiles, 
  • building products, 
  • refrigerators, 
  • washing machines, 
  • cargo ships, 
  • surgical knives, 
  • And, of course, in many other industrial fields. 

Properties of steel

Steel has many properties, including specific hardness, ductility, tensile strength, yield strength, elongation, fatigue strength, corrosion resistance, and others. 

Among the parameters that determine the properties of steel are:

  • Hardness – is the ability of the material to withstand friction and wear. It is worth noting that while everyday language means the same thing as strength and ductility, in the context of metal properties, it is quite different from strength and flexibility.
  • Strength – the ability to absorb energy, without cracking or tearing. It is also defined as a material’s resistance to cracking under stress. It is usually measured in joules per square centimeter. It is essential to distinguish this from hardness, because a material that deforms severely without cracking can be considered very strong but not rigid.
  • Expansion and ductility – This is expressed as a percentage of test length and falls between tensile strength and yield strength (i.e., the percentage of the material that bends before breaking). This characteristic of steel that allows it to be machined is a precious aspect for CNC operators. Yield strength is the point up to which the steel does not fail in tension.

The above mechanical properties of steel make it an efficient material.

Basic physical properties of steel

Steel has a density of 7,850 kg/m3, which means it is 7.85 times denser than water. It has a melting point of 1510 C, higher than most metals. By comparison, bronze has a melting point of 1040 C, copper 1083 C, cast iron 1300 C, and nickel 1453 C. Tungsten, on the other hand, has a melting point of 3410 degrees Celsius, which is not surprising since this element is used in light bulbs. The coefficient of linear expansion of steel (expressed in µm per meter per degree Celsius) is 11.1 at 20°C, making it stronger than copper (16.7), tin (21.4), or lead (29.1).

Metal alloys and steel

Iron, as the main steel component, is one of the most widespread elements in the Earth’s crust. In most alloy steels, the main component is iron, with 0.002-2.1% carbon by weight. In this range, carbon-iron bonds form a strong molecular structure. The resulting network microstructure helps achieve some of the steel properties we depend on, such as tensile strength and hardness. Although all steel is composed of iron and carbon, different types contain certain percentages of these elements. It can also contain other elements, such as: 

  • nickel, 
  • molybdenum, 
  • manganese
  • titanium, 
  • boron, 
  • cobalt 
  • vanadium. 

The addition of various elements to the „recipe” of a steel alloy affects its material properties. Methods of steel production and processing have further increased these possibilities. A notable group of steel alloys contains chromium. All these alloys are commonly referred to as stainless steel.

What is the melting point of steel?

The melting range for this alloy is between 2500-2800°F or 1370-1540°C. Why such a range? Because there are different types of alloys. The word „alloy” is almost always misused these days. In practice, the word means a mixture of metals, any metal. Almost all metals in use today are mixtures and, therefore, alloys. Other metals are added to most steels to fine-tune their properties, such as strength, corrosion resistance, or ease of production. Steel is simply iron that has been processed to control its carbon content. Iron melts at about 1510 degrees Celsius (2750 degrees Fahrenheit). Steel typically melts at about 1370 degrees Celsius (2500 degrees Fahrenheit).

What is the melting point of stainless steel?

The melting point of stainless steel ranges from 2550 to 2790°F or 1400 to 1530°C. The melting point of a particular type of stainless steel depends on its exact chemical composition. Each element brings its melting point into the equation. Iron, chromium, and nickel are the main elements that make up stainless steel. Pure iron has a constant melting point of 1535°C, chromium 1890°C, and nickel 1453°C. Compare these numbers with stainless steel’s 1400-1530°C temperature range. Each grade of stainless steel has a slightly different combination of elements. Hence, the exact melting point varies from grade to grade. Remember that are a few kinds stainless steels: duplex stainless steels, ferritic stainless steels, martensitic stainless steels.

How does the melting point differ in different grades?

There are five series and more than 150 grades of stainless steel. However, in practice, only 15 of these categories are used on a daily basis in various constructions. The two most popular grades are:

  • 304 
  • 316. 

They belong to the austenitic stainless steels, characterized by a cubic crystalline structure concentrated on the surface and the fact that they remain solid at all temperatures from cryogenic to melting. The melting point of 316 stainless steel ranges from 1375 ° C to 1510 ° C for 430-grade steel. The most common grade, 304, has a melting point of 1400-1450 ° C.

Different types of steel

The four primary grades of steel are as follows:

  • Carbon
  • Alloyed
  • Stainless 
  • Tool steel
  • Carbon steel

It looks dull and is very susceptible to corrosion. In general, this steel is divided into three subtypes: 

  • low-carbon steel, 
  • medium carbon, 
  • high-carbon steel. 

The first subtype contains about 0.30% carbon, in the second, the amount of this element is 0.60%, and in the case of high-carbon steel, it is 1.5%. The name itself comes from the fact that it contains tiny amounts of other alloying elements. 

Alloy steel

Another type is alloyed steel, which combines carbon steel with various alloying elements that give it unique properties. There are many types of alloy steels. Because of the wide range of alloy steels, elements can be used to create steels with almost any property imaginable. That being said, some of them are relatively expensive. They tend to be more resistant to corrosion and are sometimes the preferred choice for some automotive parts, pipes, boat hulls, and mechanical components. 

Tool steels

Tool steels are known for their strength, heat, and scratch resistance. They got their name because they are very commonly used to make metal tools, such as hammers. They usually consist of molybdenum, vanadium, tungsten, and cobalt. It is worth noting that tool steels are: 

  • heat resistant, 
  • durable 
  • strong.

There are five grades of tool steel:

  • Carbon steels.
  • Steels used for cold working.
  • Steels are used for hot work.
  • Sintered alloy steels.
  • High-speed steels.

Stainless steel

Stainless steel is the most popular type of this material on the market. This type is shiny and generally contains 10% to 20% chromium, its main alloying element. The above combination makes the steel resistant to corrosion and can be easily molded into various shapes. Because of its ease of handling, flexibility, and quality, stainless steel is used in surgical equipment, household applications, cutlery, and even as exterior cladding in commercial or industrial buildings.

Applications of steel 

Steel is environmentally friendly and sustainable. It is characterized by high strength. It requires very little energy to produce lightweight steel structures compared to other materials. Steel is the most recycled material in the world and can be easily recycled. Its unique magnetic properties make it a material easily extracted from the bottom of water bodies, for example. Structures made of steel are used in general engineering and manufacturing industries. It is also widely used in the automotive industry. Various types of steel are used in a car’s body, doors, engine, suspension, and interior. On average, 50% of common car parts are made of it. Virtually all energy sectors require steel for infrastructure construction and resource extraction. 

Its stainless counterpart is used in offshore platforms and pipelines, but also renewable energy sources such as:

  • solar energy, 
  • hydropower 
  • wind energy, 

Where specific components are made of this material; on top of that, stainless steel provides a hygienic environment. Hence its use is revealed, especially in surgical implants. Most household appliances, such as refrigerators, televisions, ovens, sinks, etc., are also steel. Due to its ease of welding and aesthetic finish, steel has become a distinctive element of modern architecture. These parameters characterizing the usefulness of steel make it the most popular construction material.