Although there are allegedly over 3,500 different types of steel, it can be separated into four groups depending on its chemical content. Steel is a metal alloy composed of both iron and carbon. Still, it is the level of impurities and elements such as nickel, magnesium, molybdenum, silicon, copper, vanadium that help to determine the grade of each steel. The amount of carbon determines a steel’s grade, what other alloys it contains, and the way it has been processed. A widely used metal, varieties of steel are produced with different qualities in order to make them better suited for different applications.
Steel is graded as a way of classification and is often categorized into four groups—Carbon, Alloy, Stainless, and Tool.
What is carbon steel?
Carbon steels contain trace amounts of alloying elements and account for 90% of total steel production. Carbon steels can be further categorized into three groups depending on their carbon content.
Most of the steel around the globe is some form of carbon steel. It comprises iron, carbon and varying specific amounts of other alloying elements. As the main alloying element of carbon steels, carbon accounts for around 90% of all steel production. It helps create a stronger and a lot more rigid metal. This is because the atoms present in carbon allow it to travel through the iron’s crystal lattice, slightly distorting the lattice and filling the gaps between the metallic atoms.
Given this characteristic, the resultant carbon steel products are extremely hard. Carbon Steel can be segregated into three main categories: Low carbon steel (sometimes known as mild steel); Medium carbon steel; and High carbon steel.
Low Carbon Steel (Mild Steel): Typically contain 0.04% to 0.30% carbon content. This is one of the largest groups of Carbon Steel. It covers a great diversity of shapes; from Flat Sheet to Structural Beam. Depending on the desired properties needed, other elements are added or increased. For example, Drawing Quality (DQ) – The carbon level is kept low, and Aluminum is added, and for Structural Steel, the carbon level is higher, and the manganese content is increased. While it offers high malleability and ductility, low carbon steel is characterized by low tensile strength, which can certainly be improved through the process of cold-rolling. This involves rolling the steel between two polished rollers under high-pressure conditions. Among its most common uses include the production of metal sheets, boxes, pipes, chains, wires, cases, rivets, vehicle frames, etc.
Medium Carbon Steel: Typically has a carbon range of 0.31% to 0.60%, and a manganese content ranging from .060% to 1.65%. This product is stronger than low carbon steel, and it is more difficult to form, weld and cut. Medium carbon steels are quite often hardened and tempered using heat treatment. Because it is highly malleable and can be moulded into a variety of shapes and sizes, this type is the most commonly used among the three. From skyscrapers to fences, to bridges and homes, you’ll see it used everywhere.
High Carbon Steel: Commonly known as “carbon tool steel” it typically has a carbon range between 0.61% and 1.50%. High carbon steel is very difficult to cut, bend and weld. Once the heat is treated, it becomes extremely hard and brittle. To improve its wear resistance, it is taken through appropriate heat treatment. Besides being used for high strength wires and springs, it is a useful material for producing shock-absorbing machinery.
Manganese steel is a work hardening steel that is made up of 11 to 14% manganese content. Due to its excellent work hardening characteristics and wear resistance, manganese steel is used in manufacturing complex railway tracks. Other contemporary applications include shovel buckets, shot blast cabinets, scrapers, anti-drill security plates, etc.
What is alloy steel?
Alloy steels contain alloying elements like nickel, copper, chromium, and/or aluminium. These additional elements are used to influence the metal’s strength, ductility, corrosion resistance, and machinability.
While it is the carbon content of steel that determines the degree to which it can be hardened, certain alloying elements added to the steel can make heat treatment less traumatic, a benefit when it comes to reducing quenching distortion in complex, thin-walled parts, for example. The term hardenability refers to how deep steel can be hardened, and alloy steels loosely fall into two camps around this measure: carburizing steel, which mostly hardens near the surface, and through-hardening steel, which can extend the hardening down into the metal’s core.
In the AISI numbering system, manganese steels are designated 13xx, nickel steels, 2xxx, nickel-chromium steels, 3xxx, molybdenum steels, 4xxx, and so on up to 9xxx for silicon-manganese steels.
Hardening of alloy steels can usually be done in oil for a slower quench than with water as required for plain carbon steels. This can reduce distortion and permit hardening to penetrate deeper into the material’s core.
Alloy steels contain alloying elements (e.g. manganese, silicon, nickel, titanium, copper, chromium, and aluminium) in varying proportions in order to manipulate the steel’s properties, such as its hardenability, corrosion resistance, strength, formability, weldability or ductility. Applications for alloys steel include pipelines, auto parts, transformers, power generators and electric motors.
Low Alloy Steel – Sometimes called HSLA, or High-Strength Low-Alloy, steel, this metal offers improved strength over plain carbon steels and is used in settings where weight is a factor such as mobile equipment. It cold-forms well and is readily welded. It has better resistance to corrosion than plain steel, with good impact, fatigue, and abrasion resistance as well.
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Other low alloy steels, with designations such as HY 80 and HY 90, are used for ship hulls and off-highway equipment. Still, other low alloy steels are available for specific conditions such as low-temperature toughness or to produce protective, weathering layers on decorative steel used for building facades.
As a valuable alloying agent for steels, molybdenum helps improve the steel’s toughness, weldability, as well as its corrosion resistance. This makes it ideal for use in structural steels, and therefore, they are widely used in marine environment applications. Oil and gas pipelines and ball bearings also make use of molybdenum steel.
Nickel steel alloy is among the most commonly used steel alloy around the globe. Besides a high nickel content of around 3.5%, it comprises approximately 0.35% carbon content. Its specialty is that adding nickel strengthens structural steel without a proportionate decrease in elasticity. This increase in toughness helps resist fractures that may be caused by high impacts, shocks, and loads.
Nickel-chromium steel has high hardenability. This steel is resistant to corrosion because of chromium and has high abrasion resistance to oxidation and abrasion. It has high-temperature strength and offers much greater toughness at a specified carbon level. The amount of nickel in nickel-chromium steel is between 3.25 and 3.75 per cent, and that of chromium is 1.25 to 1.75 per cent.
Moreover, at the time of quenching, nickel decreases the value of distortion in steel. Nickel steel offers incredible responsiveness to heat treatment as the addition of nickel lowers the steel’s temperature, making it ideal for heat treatment.
When it comes to magnetic force, silicon steel is the most significant material used today. While small quantities of silicon steel are used in pulse transformers and small relays, applications like large motors and generators utilize tons of silicon steel. Among its properties, saturation reduction, resistivity, magnetostriction, and magneto-crystalline anisotropy are highly sought out. With a mere 1 to 2% addition of silicon, the steel is most widely used to produce permanent magnets.
What is stainless steel?
Steels contain 10–20% chromium as their alloying element and are valued for their high corrosion resistance. These steels are commonly used in medical equipment, piping, cutting tools, and food processing equipment.
Stainless steels generally contain between 10-20% chromium as the main alloying element and are valued for high corrosion resistance. With over 11% chromium, steel is about 200 times more resistant to corrosion than mild steel. These steels can be divided into three groups based on their crystalline structure:
Austenitic: Austenitic steels are non-magnetic and non-heat-treatable, and generally contain 18% chromium, 8% nickel and less than 0.8% carbon. Austenitic steels form the largest portion of the global stainless steel market and are often used in food processing equipment, kitchen utensils, and piping.
Ferritic: Ferritic steels contain trace amounts of nickel, 12-17% chromium, less than 0.1% carbon, along with other alloying elements, such as molybdenum, aluminium or titanium. These magnetic steels cannot be hardened by heat treatment but can be strengthened by cold working.
Martensitic: Martensitic steels contain 11-17% chromium, less than 0.4% nickel, and up to 1.2% carbon. These magnetic and heat-treatable steels are used in knives, cutting tools, as well as dental and surgical equipment.
Stainless steel is a steel alloy with increased corrosion resistance compared to carbon/alloy steel. Common alloying ingredients include chromium (usually at least 11%), nickel, or molybdenum. Alloy content often is on the order of 15-30%.
Common applications include food handling/processing, medical instruments, hardware, appliances, and structural/architectural uses.
For more information about the difference between Stainless and Aluminum, click here.
Stainless Steel can be purchased online and at any Metal Supermarkets location. It is available in a wide variety of shapes such as bar stock, channel, beam, angle and more. It can be cut to your exact specifications.
What are the different categories of stainless steel?
Ferritic Stainless Steel
Ferritic stainless steel contains about 12-17% chromium, up to 0.1% carbon, trace amounts of nickel and other alloy metals in small quantities such as aluminium, molybdenum, and titanium. While ferritic steels are tough, strong, and magnetic, they can be further strengthened by cold working. However, they aren’t responsive to heat treatment, which means they can’t be hardened through this technique.
Austenitic Stainless Steel
Austenitic steel is much higher in chromium content than its stainless steel counterparts. The chromium content in this type of steel can be as high as 18%, while other elements include nickel, constituting 8%, and carbon at 0.8%. Even though austenitic steel is unresponsive to heat treatments, it is popular for its non-magnetic properties, making this steel one of the most widely used steels worldwide. Some common uses include the manufacturing of pipes, food processing equipment, and kitchen utensils.
Martensitic Stainless Steel
Consisting of 11 to 17% chromium, martensitic steel contains approximately 1.2% carbon and less than 0.4% nickel. Martensitic steels are not only responsive to heat treatments but also encompass magnetic properties. Dental and surgical instruments, knives, blades, and other cutting tools make use of martensitic stainless steel.
Duplex Stainless Steel
Duplex steel is simply a combination of ferritic and austenitic steels, resulting in steel that’s much stronger than both individually. It is not only weldable but also corrosion-resistant. Yet, it’s not strong magnetically.
Precipitation Hardening Stainless Steel
This steel is made up of 17% chromium and 4% nickel, leading to a hardened steel variety. Additionally, some other metals are also added in varying quantities, including aluminium, copper, and niobium. This type can be moulded into different shapes, making them ideal for use in engine components and nuclear waste casks. It also offers moderate corrosion resistance.
What is tool steel?
Tool steel is a term used for a variety of high-hardness, abrasion-resistant steels. Specific tool applications are dies (stamping or extrusion), cutting, mould-making, or impact applications like hammers (personal or industrial). It is also a common material used to make knives.
Tool Steels are extremely hard and are quite often used to form other metal products.
Tool Steel is available in a wide variety of shapes including round bar, flat bar, square bar and more. It can be purchased online and at any Metal Supermarkets location. It can be cut to your exact specifications.
Tool steels contain tungsten, molybdenum, cobalt and vanadium in varying quantities to increase heat resistance and durability, making them ideal for cutting and drilling equipment. Steel products can also be divided by their shapes and related applications:
Long/Tubular Products include bars and rods, rails, wires, angles, pipes, and shapes and sections. These products are commonly used in the automotive and construction sectors.
Flat Products include plates, sheets, coils, and strips. These materials are mainly used in automotive parts, appliances, packaging, shipbuilding, and construction.
Cobalt alloys offer tremendous corrosion resistance, wear resistance, high-temperature strength, and magnetic properties. Some tougher cobalt applications include gas-turbine vanes and buckets. Yet, this type of steel is more commonly used to make cutting tools.
Tungsten, also known as wolfram, is basically a dull silver metal that boasts the highest melting point among all metal types in their purest form. What makes it stand out from other metal types is its strength and ability to withstand high temperatures. Owing to these characteristics, different steel alloys make use of this metal to enhance resistance to corrosion and wear.
Besides this, rocket engine nozzles make use of tungsten steel to achieve high heat resistance. If combined with cobalt, nickel, and iron, tungsten steel can be used to produce turbine blades for many types of aircraft. Besides, many other machines and tools require high heat resistance, and thus, make use of tungsten steel.
Vanadium steel is known for its corrosion-resistant properties as well as the ability to absorb shocks. Besides being used for chemical-carrying pipes and tubes, vanadium steel is used in the form of a thin layer to bond titanium to steel for aerospace applications. As little as 1% vanadium and chromium are sufficient to achieve shock and vibration resistance, making it ideal for automobile applications.
The addition of chromium lowers the critical cooling rate and increases the scaling resistance, wear resistance, and high-temperature strength of steel. It is primarily used to increase corrosion resistance. Featuring high elasticity and tensile strength, chromium steel is often used to manufacture machine and auto parts, rock crushers and safes.
Chromium steel has high hardenability and high resistance to corrosion and oxidation. This steel can withstand high temperature and has high abrasion resistance. Chromium steel can be brittle and contains chromium in the range of 0.15 per cent and above.
Chromium and molybdenum both individually add to the hardenability of alloy steel. This steel is highly resistant to corrosion and oxidation. It can withstand high temperature and is abrasion-resistant. Molybdenum in the steel maintains hardenability in the required range and increases high temperature working strength. The amount of chromium in this steel is kept between 0.40 and 1.10 per cent, and molybdenum is in between 0.08 and 0.25 per cent.
Chromium-vanadium steel makes use of both chromium and vanadium, combining the features of each. Featuring extremely high tensile strength, the steel can be easily cut but is not brittle. Common uses include gears, axles, connecting rods, vehicular frames, and so on.
What are the different tool steel categories?
Shock Resistant Tool Steel
As the name suggests, this tool steel variant is designed to offer high resistance to shocks at varying temperature levels. Comprising low contents of carbon, silicon, and molybdenum, it is abrasive and moderately tough. This steel is mostly used to manufacture tools such as screwdrivers, punches, chisels, and tools used in riveting.
Special-Purpose Tool Steel
This tool steel is specifically designed to achieve moderate toughness and malleability, using a low alloy class of steel. They are often used for producing wrenches, arbours, and taps.
Hot-Work Tool Steel
Hot-work tool steel is used to produce tools that require high resistance to heat for prolonged time periods, such as those utilized in forging, extrusion, punching, casting, and hot-shearing blades.
Water-Hardening Tool Steel
As the cheapest type, water-hardening tool steel is the most widely used tool steel in the production of tools. To incorporate hardness into the objects or tools, this steel is water quenched. Featuring high resistance to surface wear, this steel is often used to make files, cutters, hammers, blades and similar items.
High-Speed Tool Steel
High-speed tool steel is composed of tungsten, molybdenum, and vanadium steel alloys. These components are hard and retain their hardness when exposed to high temperatures, helping produce steel that’s perfect for high-speed machinery such as drills, reamers, saws, punches, taps, etc.
Cold-Work Tool Steel
This tool steel variant incorporates a high chromium content to achieve low distortion property while hardening, which may be done through air or oil. This feature means that the tools produced do not crack easily. As highly sturdy steel, cold-work tool steel is ideal for making knife blades, stamping dies, coining tools, etc.
Mould steel makes use of carbon steels to make injection and compression moulds for plastics. Plus, another common application is zinc die casting.
What are the different grades of steel?
Rolled steel grading systems provide a way to categorize steel based on all the different factors that can influence its properties and uses.
For instance, the rate of steel is cooled can impact how its molecules are joined together, as can the amount of time the steel is held at several critical temperature points during the cooling process. Two sheets of steel with the same alloy content can have different grades based on this heat-treatment process.
- The ASTM Grading System assigns each metal a letter prefix based on its overall category (“A” is the designation for iron and steel materials), as well as a sequentially-assigned number that corresponds with that metal’s specific properties.
- The SAE Grading System uses a four-digit number for classification. The first two digits denote the steel type and alloying element concentration, and the last two digits indicate the carbon concentration of the metal.
Steel grading standards are widely used by scientists, engineers, architects, and government agencies to ensure the quality and consistency of materials. These standards provide a common language to communicate the properties of steel with great specificity, and guide product manufacturers toward proper processing and application procedures.