What Is Steel?- Properties, Uses | Types Of Steels

What is a Steel?

Steel is an alloy made up of iron with typically a few tenths of a percent of carbon to improve its strength and fracture resistance compared to other forms of iron.

Many other elements may be present or added. Stainless steels that are corrosion– and oxidation-resistant need typically an additional 11% chromium.

Because of its high tensile strength and low cost, steel is used in buildings, infrastructure, tools, ships, trains, cars, machines, electrical appliances, and weapons. Iron is the base metal of steel.

Depending on the temperature, it can take two crystalline forms (allotropic forms): body center cubic and face center cubic. The interaction of the allotropes of iron with the alloying elements, primary carbon, gives steel and cast iron their range of unique properties.

In pure iron, the crystal structure has relatively little resistance to the iron atoms slipping past one another, and so pure iron is quite ductile, or soft and easily formed.

In steel, small amounts of carbon, other elements, and inclusions within the iron act as hardening agents that prevent the movement of dislocations.

When was steel invented?

The earliest known production of steel is seen in pieces of ironware excavated from an archaeological site in Anatolia (Kaman-Kalehöyük) and is nearly 4,000 years old, dating from 1800 BC. Horace identifies steel weapons such as the falcata in the Iberian Peninsula, while Noric steel was used by the Roman military.

Is Steel a metal?

As steel is an alloy, it is not a pure element and is, as a direct result, not a metal. Instead, it is a variant of a metal.

Although steel is composed of iron – which is metal – the non-metal carbon within its chemical makeup means that it is not a pure metal, so it cannot be classed as one.

So, there you have it. Steel is not a metal.

Composition of Steel

Steel is an alloy of iron and carbon in which the carbon content ranges up to 2 percent (with higher carbon content, the material is defined as cast iron).

By far the most widely used material for building the world’s infrastructure and industries, it is used to fabricate everything from sewing needles to oil tankers. In addition, the tools required to build and manufacture such articles are also made of steel.

Steel is an alloy of iron and carbon containing less than 2% carbon and 1% manganese and small amounts of silicon, phosphorus, Sulphur, and oxygen. Steel is the world’s most important engineering and construction material.

It is used in every aspect of our lives; in cars and construction products, refrigerators and washing machines, cargo ships, and surgical scalpels.

Properties of Steel

Steel has several properties, including hardness, toughness, tensile strength, yield strength, elongation, fatigue strength, corrosion, plasticity, malleability, and creep.

The properties that are most important in wear and abrasion-resistant steel are:

• HARDNESS is the material’s ability to withstand friction and abrasion. It is worth noting that, while it may mean the same as strength and toughness in colloquial language, this is very different from strength and toughness in the context of metal properties.
• TOUGHNESS is difficult to define but generally is the ability to absorb energy without fracturing or rupturing. It is also defined as a material’s resistance to fracture when stressed. It is usually measured in foot lbs. per sq. in or Joules per sq. centimeter. It is important to distinguish this from hardness as a material that severely deforms without breaking, could be considered extremely tough, but not hard.
• YEILD strength is a measurement of the force required to start the deformation of the material (i.e. bending or warping).
• TENSILE strength is a measurement of the force required to break the material.
• ELONGATION (or Ductility) is the “Degree” to which the material can be stretched or compressed before it breaks. It is expressed as a percent of the length being tested and is between the tensile strength and yield strength (i.e., what percent does the material bend before breaking).

Basic Physical Properties of Steel

Steel has a density of 7,850 kg/m³, making it 7.85 times as dense as water. Its melting point of 1,510 C is higher than that of most metals. In comparison, the melting point of bronze is 1,040 C, that of copper is 1,083 C, that of cast iron is 1,300 C, and that of nickel is 1,453 C.

Tungsten, however, melts at a searing 3,410 C, which is not surprising since this element is used in light bulb filaments.

Steel’s coefficient of linear expansion at 20 C, in µm per meter per degree Celsius, is 11.1, which makes it more resistant to changing size with changes in temperature than, for example, copper (16.7), tin (21.4), and lead (29.1).

What is steel made of?

Steel is made of an alloy of iron and carbon in which the carbon content ranges up to 2 percent (with higher carbon content, the material is defined as cast iron).

Iron, the major elemental component of steel, is one of the most plentiful elements in the earth’s crust. All steel alloys are primarily iron and 0.002–2.1 % carbon by weight. In this range, carbon bonds with iron create a strong molecular structure.

The resulting lattice microstructure helps achieve certain material properties, like tensile strength and hardness, that we rely on in steel.

Although all steel is made of iron and carbon, different types of steel contain different percentages of each element. Steel can also include other elements like nickel, molybdenum, manganese, titanium, boron, cobalt, or vanadium.

Adding different elements to the “recipe” for a steel alloy affects its material properties. The method of manufacture and treatment of the steel further enhances those abilities.

One notable group of steel alloys contains chromium. All such alloys are known commonly as stainless steel.

What is the Melting Point of steel?

The melting point of steel ranges from 2500-2800°F or 1371-1540°C. Why a range? Why not just a single point on the thermometer? Unlike a pure metal such as iron, steel is an alloy.

That depends on the alloy of steel you are talking about. The term alloy is almost always used incorrectly these days, especially amongst bicyclists.

They use the term to mean aluminum. What the term alloy means is a mixture of metals, any kind of metal. Almost all metal used today is a mixture and therefore an alloy.

Most steel has other metals added to tune its properties, like strength, corrosion resistance, or ease of fabrication. Steel is just the element iron that has been processed to control the amount of carbon.

Iron, out of the ground, melts at around 1510 degrees C (2750°F). Steel often melts at around 1370 degrees C (2500°F).

the melting point of carbon steel

The melting point of steel ranges from 2500-2800°F or 1371-1540°C. Why a range? Why not just a single point on the thermometer?

Unlike a pure metal such as iron, steel is an alloy. Pure metals have a precise temperature, which is their melting point. Alloys, however, include multiple elements with different melting points. Therefore, alloys do not melt or freeze at a fixed temperature.

Steel is an alloy of iron and carbon. Stainless steel also includes chromium and usually nickel and other elements in its alloy. The addition of each new element lowers the overall melting point. This is called melting point depression.

the melting point of stainless steel

Stainless steel’s melting point falls between 2550 and 2790°F or 1400 and 1530°C.

The melting point of a particular type of stainless steel depends upon its exact chemical composition. Each element brings its melting point into the equation. The major elements composing stainless steel are iron, chromium, and nickel.

Pure iron has a fixed melting point of 1535°C, chromium of 1890°C, and nickel of 1453°C. Compare those numbers to the 1400-1530°C range for stainless steel.

Each grade of stainless steel has a slightly different mix of elements. Consequently, the exact melting point varies across different grades.

How does the melting point vary across different grades?

Stainless steel comes in five families and has more than 150 grades. Only 15 of these grades are commonly used, however.

The two most popular grades of stainless steel are 304 and 316. Both grades are part of the austenitic stainless-steel family, which includes about two-thirds of the stainless steel produced.

Austenitic stainless steel features a face-centered cubic crystal structure, which remains constant across all temperatures from cryogenic to the melting point.

Stainless steel’s melting points can vary from a low of 1375°C for grade 316 steel to a high of 1510°C for grade 430. The most common grade, 304, has a melting point of 1400-1450°C.

Different Types of Steel

The Four Main Types of Steel:

• Carbon Steel
• Alloy Steel
• Stainless Steel
• Tool Steel

#1. Carbon Steel.

Carbon steel looks dull, matte-like, and is known to be vulnerable to corrosion. Overall, there are three subtypes to this one: low, medium, and high carbon steel, with low containing about .30% of carbon, medium at .60%, and high at 1.5%.

The name itself actually comes from the reality that they contain a very small amount of other alloying elements. They are exceptionally strong, which is why they are often used to make things like knives, high-tension wires, automotive parts, and other similar items.

• Steel that contains up to 2% carbon
• Steel that does not contain any standard amounts of elements that would classify it as an “alloy steel” (e.g., cobalt, nickel, tungsten, molybdenum, titanium, zirconium, vanadium, chromium, etc.)

You may also notice the term “carbon steel” applied to steels with less than 0.4% copper or steels that have certain magnesium-to-copper contents, though those definitions are contested across industries. For this, we’re talking about the first two definitions.

Types of Carbon Steel

There are three ways that carbon steel is classified — low, medium, and high

• Low Carbon Steel. Low carbon steel (or “mild carbon steel” or “plain carbon steel”) refers to carbon steel that has up to 0.30% carbon content. This is, by far, the most common type of steel on the metals market. There are a few reasons for this. For starters, low-carbon steel is relatively inexpensive. Also, since the carbon content is lower than medium and high steel, low-carbon steel is easy to form and is perfect for applications where tensile strength isn’t an immediate issue, such as structural beams.
• Medium Carbon Steel. Medium carbon steel refers to carbon steels that have between 0.31% and 0.60% carbon content and between 0.31% and 1.60% magnesium. One of the biggest benefits of medium carbon steel is its strength. However, that comes with some tradeoffs. Medium carbon steel has low ductility and toughness, making it more difficult to form and weld.
• High Carbon Steel. High carbon steel refers to carbon steels that have between 0.61% and 1.50% carbon content and between 0.31 and 0.90 magnesium. When it comes to hardness and toughness, high-carbon steel is the carbon steel of choice. However, this comes at a tradeoff. It’s very difficult to weld, cut, or form high-carbon steel.

#2. Alloy Steel.

The next type of steel is alloy steel, these are made by combining carbon steel with various alloying elements to provide unique properties to each steel.

There is an incredibly wide range of alloy steels, but some of the most common include Chromium, Cobalt, Molybdenum, Nickel, Tungsten, and Vanadium.

Due to the incredible variety of alloy steels, you can create steels with almost every possible property using alloy elements. That being said, some of these steels are relatively expensive.

These tend to be more resistant to corrosion and are favored for some car parts, pipelines, ship hulls, and mechanical projects. For this one, the strength depends on the concentration of the elements that it contains.

#3. Tool Steel.

Tool steel is famous for being hard and both heat and scrape-resistant. The name is derived from the fact that they are very commonly used to make metal tools, like hammers.

These are steels used for tooling activities such as drilling. Commonly made up of molybdenum, vanadium, tungsten, and cobalt, tooling steels are heat-resistant, durable, and strong.

There are 6 grades of tool steel:

• Air-hardening
• Water-hardening
• D-type
• Hot-working
• Shock-resisting types
• Oil-hardening

#4. Stainless Steel.

Last but not least, stainless steels is probably the most well-known type on the market. This type is shiny and generally has around 10 to 20% chromium, which is their main alloying element.

This combination, allows the steel to be resistant to corrosion and very easily molded into varying shapes.

Because of their easy manipulation, flexibility, and quality, stainless steel can be found in surgical equipment, home applications, and silverware, and even implemented as exterior cladding for commercial/industrial buildings.

Related Posts: What is Stainless Steel?

Uses of Steel

Iron and steel are used widely in the construction of roads, railways, other infrastructure, appliances, and buildings.

Most large modern structures, such as stadiums and skyscrapers, bridges, and airports, are supported by a steel skeleton. Even those with a concrete structure employ steel for reinforcing.

Some Uses of steel is given below:

• Steel is environment-friendly & sustainable. It possesses great durability.
• Compared to other materials, steel requires a low amount of energy to produce lightweight steel construction.
• Steel is the world’s most recycled material which can be recycled very easily. Its unique magnetic properties make it an easy material to recover from streams to be recycled.
• Steel can be designed in various forms. It gives a better shape and edge than iron which is used to make weapons. 
• Engineering steels are used for general engineering and manufacturing sectors. 
• Steel is highly used in the automobile industry. Different types of steel are used in a car’s body, doors, engine, suspension, and interior. The average 50% of a car is made of steel.
• Steel reduces CO2 emissions.
• All types of energy sectors demand steel for infrastructure and resource extraction. 
• Stainless steels are used to produce offshore platforms and pipelines. 
• Steels are used for packaging and protecting goods from water, air, and light exposure. 
• Most household appliances like fridges, TV, oven, sinks, etc are made of steel. 
• Steels are used for producing industrial goodies like farm vehicles and machines.
• Stainless steel is used as a cutlery material.
• Because of its easy welding capability and attractive finishing, steel has become a prominent feature in modern architecture.
• Stainless steel gives a hygienic environment. That’s why it is used for surgical implants.
• Steel has a wider range of temperatures which is used to make large sheets. 
• Renewable energy resources like solar, hydro, and wind power use stainless-steel components. 
• Mild steel is used for building construction. It is also a highly favored building frame material.

Standard Gauge for Sheet And Plate Iron And Steel

Number of gauges	Thickness in fractions of an inch	Thickness in decimal parts of an inch	Thickness in mm	Weight per square foot in ounces avoirdupois	Weight per square foot in pounds avoirdupois	Weight per square foot in Kg	Weight per square meter in Kg	Weight per square meter in pounds avoirdupois
0000000	1/2	.5	12.7	320	20.00	9.072	97.65	215.28
000000	15/32	.46875	11.90625	300	18.75	8.505	91.55	201.82
00000	7/16	.4375	11.1125	280	17.50	7.983	85.44	188.37
0000	13/32	.40625	10.31875	260	16.25	7.371	79.33	174.91
000	3/8	.375	9.525	240	15	6.804	73.24	161.46
00	11/32	.34375	8.73125	220	13.75	6.237	67.13	148.00
0	5/16	.3125	7.9375	200	12.50	5.67	61.03	134.55
1	9/32	.28125	7.14375	180	11.25	5.103	54.93	121.09
2	17/64	.265625	6.746875	170	10.625	4.819	51.88	114.37
3	1/4	.25	6.35	160	10	4.536	48.82	107.64
4	15/64	.234375	5.953125	150	9.375	4.252	45.77	100.91
5	7/32	.21875	5.55625	140	8.75	3.969	42.72	94.18
6	13/64	.203125	5.159375	130	8.125	3.685	39.67	87.45
7	3/16	.1875	4.7625	120	7.5	3.402	36.62	80.72
8	11/64	.171875	4.365625	110	6.875	3.118	33.57	74.00
9	5/32	.15625	3.96875	100	6.25	2.835	30.52	67.27
10	9/64	.140625	3.571875	90	5.625	2.552	27.46	60.55
11	1/8	.125	3.175	80	5	2.268	24.41	53.82
12	7/64	.109375	2.778125	70	4.375	1.984	21.36	47.09
13	3/32	.09375	2.38125	60	3.75	1.701	18.31	40.36
14	5/64	.078125	1.984375	50	3.125	1.417	15.26	33.64
15	9/128	.0703125	1.7859375	45	2.8125	1.276	13.73	30.27
16	1/16	.0625	1.5875	40	2.5	1.134	12.21	26.91
17	9/160	.05625	1.42875	36	2.25	1.021	10.99	24.22
18	1/20	.05	1.27	32	2	.9072	9.765	21.53
19	7/160	.04375	1.11125	28	1.75	.7938	8.544	18.84
20	3/80	.0375	.9525	24	1.50	.6804	7.324	16.15
21	11/320	.034375	.873125	22	1.375	.6237	6.713	14.80
22	1/32	.03125	.793750	20	1.25	.567	6.103	13.46
23	9/320	.028125	.714375	18	1.125	.5103	5.493	12.11
24	1/40	.025	.635	16	1	.4536	4.882	10.76
25	7/320	.021875	.555625	14	.875	.3969	4.272	9.42
26	3/160	.01875	.47625	12	.75	.3402	3.662	8.07
27	11/640	.0171875	.4365625	11	.6875	.3119	3.357	7.40
28	1/64	.015625	.396875	10	.625	.2835	3.052	6.73
29	9/640	.0140625	.3571875	9	.5625	.2551	2.746	6.05
30	1/80	.0125	.3175	8	.5	.2268	2.441	5.38
31	7/640	.0109375	.2778125	7	.4375	.1984	2.136	4.71
32	13/1280	.01015625	.25796875	6½	.40625	.1843	1.983	4.37
33	3/320	.009375	.238125	6	.375	.1701	1.831	4.04
34	11/1280	.00859375	.21828125	5½	.34375	.1559	1.678	3.70
35	5/640	.0078125	.1984375	5	.3125	.1417	1.526	3.36
36	9/1280	.00703125	.17859375	4½	.28125	.1276	1.373	3.03
37	17/2560	.006640625	.168671875	4¼	.265625	.1205	1.297	2.87
38	1/160	.00625	.15875	4	.25	.1134	1.221	2.69

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