How Strong is Steel? Different Types of Steel Strength Measurements

May 3, 2022 | Categorized in: Properties

Steel is one of the strongest and most commonly used materials on the planet, but when we say that steel is “strong,” what does that actually mean? There are a number of different forces and situations that require different measurements of strength, so which ones are the most important to know?

Why is steel so strong?

Steel’s chemical composition of iron, carbon, and other alloying elements creates a microstructure that is great at resisting deformation and fracture. In more technical terms, carbon atoms distort the original iron’s crystal lattice to create compounds like cementite or martensite. These form a very hard and strong microstructure with a smaller grain size, resulting in a stronger and tougher material. These factors can be further enhanced by other elements like manganese, nickel, chromium, and silicon.

Learn more about how alloys work here.

Importance of using different strengths

Different steel products and different applications provide or require different forms of strength. For instance, strength against compression isn’t as important in a situation where the only forces acting on the steel are pulling outward. However, knowing the different types of strength and which grades or shapes of steel meet the requirements for a certain job is crucial for safety and reliability purposes.

Different types of steel strength measurements

“Strength” (when used for metals like steel) can refer to measuring the resistance against a number of different forces. The most common strength measurements used in steel manufacturing are tensile, yield, and compressive strength. We’ll discuss these three, as well as some other examples that can be used to define a steel product’s characteristics.

Tensile strength of steel

This measure of a material’s strength refers to its ability to resist tension, or forces pulling and stretching it apart. A material with low tensile strength would pull apart more easily than one with high tensile strength, such as steel. Products like steel cables are a good representation of this measure of strength, as they’re usually under high levels of tension and need to resist this stress without breaking or stretching. A572-50, a steel grade that we frequently use for our structural shapes, has an ultimate tensile strength of over 70,000 psi (450 MPa).

Yield strength of steel

Another common measure of a material’s strength yield strength, is the amount of force that can be resisted before being permanently deformed. Essentially, this describes the maximum force that can be applied to deform a material, where it will still return to its original shape once the force is removed. Steel also has incredibly high yield strength, with another one of our common grades, A36, having a minimum yield strength of over 36,000 psi (250 MPa).

Compressive strength of steel

The opposite of tensile strength, compressive strength measures how much a material can be squeezed together and reduced in size. This is often tested with a machine that applies an increasing load to the material until a certain amount of deformation or compression occurs. Materials like concrete tend to have very high compressive strength, but much lower tensile strength. Steel can not only match these materials’ compressive strength with a thinner profile, but also has very high tensile and yield strength to complement its compression resistance.

Impact strength of steel

As you might guess from the name, this type of strength measures a material’s ability to withstand a blow without breaking. It can also be thought of as the amount of energy that can be absorbed (without fracturing) when a sudden force is applied. Sometimes referred to as toughness, it’s most frequently measured by the Charpy impact test, which we discuss in more detail here.

Flexural (bending) strength of steel

The flexural strength of steel refers to how much stress it can withstand from a bending force before breaking or permanently deforming. This is a critical measurement for evaluating load-bearing capacity in products like beams. Think of flexural strength as how much force it takes before a piece of steel snaps.

Shear strength of steel 

This type of strength defines the resistance to unaligned forces pushing one part of the material in one direction, while another part of the material is pushed in the opposite direction. Shear force is how scissors cut, because the piece of paper is pushed down by one blade and up by another blade. Materials with high shear strength are difficult to cut with scissors and are more resistant to these opposing and parallel forces on an object.

Torsional (twisting) strength of steel

Defined as the resistance against torque, this measurement describes the ability of a material to withstand a twisting stress without rupturing. Hollow tubing (round, square, or rectangular) has incredibly high torsional resistance, while shapes such as beams have a comparatively lower torsional resistance and strength because their shape doesn’t distribute forces as evenly along this axis.

Corrosion resistance of steel

While corrision resistance might not seem like a measurement of physical strength that fits with the others, it is still a measure of how strong a material is against being worn away or deteriorated. This mostly occurs due to environmental factors like water or gases (e.g. chlorine and ammonia). Galvanizing is a common process to increase steel’s corrosion resistance for harsh environments.

Learn more about galvanization here.

How do different factors affect steel’s strength?

So far, we’ve covered the different ways that strength is measured, but what factors can contribute to higher (or lower) measurements in different types of strength?

Composition

The chemical composition of your steel has the largest impact on how strong it will be. Some compositions, especially high-carbon grades such as 1095 steel, can have higher tensile strength (but at the cost of ductility). Other alloying elements like nickel (as seen in A514 steel) can be added to the steel’s composition to improve other characteristics like impact strength/toughness.

Learn more about the different steel grades and their compositions here.

Shape

The shape of your steel sections plays a significant role in flexural and torsional strength. For example, round tubular shapes will be better at resisting rotational forces than a beam due to their more even distribution of stress. However, the I-shape of a beam gives it enhanced resistance against bending and buckling, primarily along the axis of its web. Because of this, it’s important to consider which direction forces will be acting on your steel sections and plan for the right structural shapes accordingly.

Learn more about the various structural steel shapes here.

Manufacturing process

How your steel is manufactured also influences the different strength measurements that the final product exhibits. Steel is typically either hot rolled or cold rolled, each enhancing distinct characteristics. Hot rolling technically decreases the “strength” of the steel, making it more ductile and flexible. Cold rolling boosts the material’s hardness and yield strength by deforming the metal’s crystal structure at room temperature.

Learn more about hot rolled vs. cold rolled steel here.

Temperature

This might seem obvious, but the closer you get to steel’s melting point, the weaker it gets. In other words, higher environmental temperatures that your steel sections are exposed to reduce the material’s overall strength. This typically results in deformation and decreased load-bearing capacity. However, the opposite end of the spectrum is also relevant, with low temperatures increasing material brittleness and making it more susceptible to breaking.

Coating

Coatings can improve steel’s resistance to wear and corrosion, which may suppress crack propagation. The most well-known coating that relates to the strength measurements discussed above is galvanization, which applies a zinc coating to steel that bolsters its corrosion resistance. This is especially important for structural steel in damp, acidic, or abrasive environments like bridges over water, agricultural structures, industrial pipelines, and more.

Learn more about the different types of steel coatings here.

Get high-quality & high-strength steel today

Service Steel Warehouse is a leading supplier of premium steel products that fit a variety of applications. Whether you need steel with high yield strength, torsional strength, or anything in between, our ready-to-ship inventory has structural sections, piling, and everything your need for large-scale projects. Even better, our inventory is one of the largest in the country, so you never have to worry about delays in procurement. This doesn’t slow us down, though, and we ship as soon as the next-day, with delivery and distribution across the United States from our warehouses. Request a free quote for steel online, or contact our sales team directly to speak with a representative.