HSLA Steel: Uses, Composition, and Its Properties

HSLA steels, also referred to as micro-alloyed steels, contain small amounts of alloying elements. This is done to improve mechanical properties such as strength and corrosion resistance compared to regular carbon steel.

In this article, we define HSLA steels and delve into their uses, manufacturing methods, chemical compositions, properties, and more.

What Is HSLA Steel?

HSLA stands for "High-Strength Low-Alloy" steel. As the name suggests, this type of steel is alloyed with only small amounts of alloying elements such as: sulfur, phosphorus, molybdenum, and silicon, in addition to the usual iron and carbon. These alloying elements enhance the strength and mechanical properties of the steel while maintaining a relatively low carbon content. HSLA steel can be significantly harder and more resistant to heat treatment than carbon steel, while simultaneously delivering better strength. Additionally, alloying elements can be incorporated to enhance the steel's resistance to corrosion. HSLA steel is known for its excellent combination of strength, toughness, and formability.

There are six different classifications of HSLA steels, each tailored to meet specific application and mechanical property requirements. They’re known as: inclusion-shape-controlled steel, micro-alloyed ferrite-pearlite steel, acicular ferrite steel, pearlitic steel, and weathering steel. The latter is also known as corten and is renowned for its atmospheric corrosion resistance and high tensile strength. 

What Is HSLA Steel Used For?

HSLA (High-Strength Low-Alloy) steel is used in a wide range of applications thanks to its excellent combination of strength, toughness, and other desirable properties. Some common uses for HSLA steel include:

1. Vehicle components such as: chassis, subframes, wheels, seat runners, and suspension systems.
2. Building construction, bridges, and infrastructure projects where high-strength materials must support heavy loads and withstand environmental conditions.
3. Pipelines for transporting oil, gas, and other fluids.
4. Ship hulls and other critical marine components.
5. Structural engineering applications, including: high-rise buildings, stadiums, and industrial facilities.
6. Equipment and structures in the oil and gas industry, including drilling rigs, storage tanks, and offshore platforms.

How Is HSLA Steel Made?

HSLA steel is produced in much the same way as other types of steel. The process begins by mixing iron ore and coal in a furnace. The heat melts the materials and removes some impurities. The specific alloying formula depends on which particular type of HSLA steel you’re making. After reaching the proper chemical composition, extra steps remove most remaining impurities left in the HSLA steel. Then, the steel is left to cool and solidify into a large rectangular shape called an ingot. Finally, this ingot is processed further to reach its final size and shape.

What Is the Most Common Type of HSLA Steel?

The most common type of HSLA (High-Strength Low-Alloy) steel can vary depending on the region and specific applications. However, one of the more popular styles is known as ASTM A572. ASTM A572 Grade 50, in particular, is widely used in the United States. It offers a balance of strength, weldability, and corrosion resistance, making it suitable for a wide range of structural applications in construction and other industries. Another very popular HSLA grade is ASTM A36, which is an all-purpose alloy. It is mainly used for structures and is affordable, easily weldable, and formable, with a wide range of mechanical uses. 

What Is the Chemical Composition of HSLA Steel?

HSLA steels typically have between 0.05-0.25% carbon, and up to 2% manganese. However, because there are so many different grades of HSLA steel on the market, each with its own alloying composition, there is no single chemical composition list. The chemical compositions of two common alloys in North America, ASTM A572 and A656 are given in Tables 1 and 2 below.  

The chemical composition of ASTM A572 is given in Table 1:

The chemical composition of ASTM A656 is outlined in Table 2:

What Is the Carbon Content of HSLA Steel?

HSLA steels are classified as low-carbon steels. They typically contain 0.05-0.25% carbon, which makes them formable and weldable. This is accompanied by small amounts of alloying elements such as molybdenum, manganese, vanadium, titanium, and others to achieve high yield strengths (more than 275 MPa) in the as-rolled condition. 

What Are the Properties of HSLA Steel?

The properties of HSLA steel grades A572-50 and A36 are outlined in Table 3:

What Is the Machinability Rating of HSLA Steel?

The machinability rating for different grades of HSLA steel varies based on their composition. However, to give an indication of what to expect, the machinability rating for A572 is between 55-80%, rated in comparison to the steel SAE1112, which has a hardness of 160 Brinell. 

What Are the Characteristics of HSLA Steel?

HSLA steels have several key characteristics that make them valuable, including:

1. are significantly stronger than standard carbon steel of similar thickness. This favorable strength-to-weight ratio is one of their most important characteristics, making them suitable for lightweight yet robust designs.
2. Have good toughness and resistance to fracture, making them durable and capable of withstanding impacts and stress without fracturing.
3. Often designed to be easily formed and fabricated into various shapes without sacrificing strength or structural integrity.
4. Typically weldable.
5. Some HSLA steel grades are designed to resist corrosion, making them suitable for outdoor or corrosive environments.
6. Depending on the grade, HSLA steel is often ductile, enabling parts to be stretched or deformed without breaking.
7. available in various grades, each with its own combination of properties, allowing for precise selection based on specific requirements.

What Is the Ultimate Tensile Stress of HSLA steel?

The ultimate tensile strength for different grades of HSLA will vary, but these steels typically reach up to 450 MPa with ductility as high as 30%. To learn more, see our guide on Ultimate Tensile Strength (UTS).

What Is the Yield Strength of HSLA Steel?

In the as-rolled condition, most HSLA steels have high yield strengths that exceed 275 MPa. The exact yield strength values will differ for the various HSLA steel grades. To learn more, see our guide on the Yield Strength of Materials.

Is HSLA Steel Hard or Soft?

HSLA steels can have varying levels of hardness, depending on their specific grade and heat treatment. They are not classified as inherently "hard" or "soft" because the hardness of HSLA steel can be tailored to meet specific requirements.

Some grades of HSLA steel are designed for hardness and strength, making them suitable for applications where those are the critical factors such as in the manufacturing of cutting tools. These grades typically undergo heat treatment processes to achieve the desired hardness.

On the other hand, there are also HSLA steel grades that are engineered to maintain good formability and toughness while providing adequate strength. These grades may not have exceptionally high hardness values and are considered to be relatively "soft" in comparison to the harder varieties.

Is HSLA Steel Weldable?

In general, the weldability of these materials is fairly good. Nonetheless, certain considerations should be taken into account when working with HSLA steels. Always adhere to best practices such as: preparing the material surface, appropriate preheating, and maintenance of essential interpass temperatures.

Is HSLA Steel Magnetic?

Yes, HSLA steel is typically magnetic. The magnetic properties of steel are primarily influenced by its iron content, and since HSLA steels contain significant amounts of iron, they are generally magnetic. However, the degree of magnetism can vary depending on the specific composition and processing of the HSLA steel.

What Are the Common Forms of HSLA Steel Material?

HSLA steel can be purchased in various forms and shapes to suit different applications. Common forms of HSLA steel include:

Sheet and Coil

HSLA steel is often produced in the form of sheets or coils, which are used for things like: automotive body panels, construction components, and general fabrication.

Plate

HSLA steel plates are thicker than sheets and are commonly used in structural applications, such as: building construction, bridges, and large equipment components.

Bars

HSLA steel bars are available in various shapes, including: round, square, and flat bars. They are used in applications that demand high strength and good formability, such as in shafts, fasteners, and structural components.

Tubes and Pipes

HSLA steel can be formed into tubes and pipes for applications in: automobiles, infrastructure construction, and oil and gas pipelines.

Structural Shapes

HSLA steel is used to produce various structural shapes, including I-beams, channels, and angles. These often show up in building construction and other structural applications.

What Are the Equivalents of HSLA Steel?

The equivalents to some common HSLA steel grades are listed in Table 4:

What Are the Advantages of HSLA Steel?

The advantages of HSLA steels include:

1. They offer significantly higher strength than conventional steel of similar thickness. 
2. The high strength-to-weight ratio of HSLA steel enables weight reduction in applications such as automotive manufacturing, aerospace, and construction.
3. They’re engineered to maintain good toughness and impact resistance.
4. Despite the high strength, HSLA steel remains ductile and formable. 
5. Some HSLA steel grades are designed specifically for corrosion resistance.

What Are the Disadvantages of HSLA Steel?

The disadvantages of HSLA steel include:

1. In some cases, HSLA steel can be more expensive than conventional steel due to expensive alloying elements and specialized manufacturing processes.
2. The increased strength of HSLA steel comes at the expense of reduced flexibility, resulting in a lower capacity to bend or stretch without failing. 

Is HSLA Steel Expensive?

Yes, compared to ordinary steel, HSLA can be more pricey. This is because of the unique properties obtained through the alloying elements and also the unique manufacturing requirements. 

How Does HSLA Steel Differ From Ordinary Steel?

HSLA steel stands apart from ordinary (conventional) steel in several significant ways. For one thing, it incorporates small quantities of alloying elements such as: niobium, vanadium, and titanium, in addition to iron and carbon. These elements enhance the steel's strength while maintaining a relatively low carbon content. This results in HSLA steel's remarkable strength-to-weight ratio compared to ordinary steel. Despite its high strength, HSLA steel retains good ductility and formability, so you can form it into complex shapes and still depend on its strength. It is commonly used for automotive components, construction equipment, and structural elements. In contrast, ordinary steel consists almost entirely of iron and carbon as the primary components and lacks the alloying elements and enhanced properties found in HSLA steel. It is used in many general-purpose applications where exceptional strength is not the primary requirement.

Is HSLA Steel Stainless Steel?

No, HSLA steel is not the same as stainless steel. The two are distinct types of steel with different compositions and properties.

HSLA steel, as the name suggests, is characterized by its high strength and low alloying content. It typically contains carbon and manganese alongside small amounts of alloying elements like niobium, vanadium, titanium, and others. HSLA steel is designed to offer better strength and toughness than standard carbon steel while maintaining good weldability and formability. It is commonly used in applications that need to balance strength with other properties, such as in construction, automotive manufacturing, and structural components.

Stainless steel, on the other hand, is a corrosion-resistant steel alloy that contains a significant amount of chromium (usually at least 10.5%). The high chromium content forms a protective layer of chromium oxide on the surface of the steel, which gives stainless steel its corrosion resistance. Stainless steel comes in various grades and types, such as austenitic, ferritic, and martensitic, each with its own properties and applications. It is widely used in applications where resistance to corrosion, staining, and rust is essential, such as in: kitchen appliances, cutlery, medical equipment, and architectural structures.

Is 4140 Steel an HSLA Steel?

Yes, 4140 is an HSLA steel that finds application in shafts, gears, and structural components. It is also a good structural material for gas and oil plants thanks to its hardenability, high strength, low cost, and weldability. To learn more, see our article on 4140 Steel.

What Is the Difference Between HSLA Steel and DP Steel?

DP (Dual-Phase) steels possess distinctive characteristics that differentiate them from HSLA steels. DP steels consist of two primary phases: a soft ferrite phase surrounding islands of harder martensite-phase inclusions. Ferrite makes DP steels highly ductile while the martensite contributes to their impressive tensile strength.

One significant distinction is in the manufacturing process. DP steels require specialized equipment and precise control over chemistry, cooling, and processing, which only certain mills can achieve. Meanwhile, HSLA steels can be produced in most sheet steel mills.

Another difference lies in material consistency among different steelmakers. HSLA steel grades maintain consistent properties and composition across manufacturers. The production of DP steel microstructure varies based on equipment and capabilities, leading to differences in steel melt chemistry, particularly in terms of carbon equivalent and weldability.

Formability is also a key differentiator. DP steels are easier to form, as indicated by their lower yield-strength-to-tensile-strength (YS/TS) ratio and higher strain-hardening exponent (n-value) over a lower strain range. Those properties cause the metal to distribute strain uniformly during forming. DP steels also benefit from bake hardening, increasing their yield strength through work hardening during forming and a subsequent paint curing cycle.

Summary

This article presented HSLA steel, explained it, and discussed its various uses and composition. To learn more about HSLA steel, contact a Xometry representative.

Xometry provides a wide range of manufacturing capabilities and other value-added services for all of your prototyping and production needs. Visit our website to learn more or to request a free, no-obligation quote.

Disclaimer

The content appearing on this webpage is for informational purposes only. Xometry makes no representation or warranty of any kind, be it expressed or implied, as to the accuracy, completeness, or validity of the information. Any performance parameters, geometric tolerances, specific design features, quality and types of materials, or processes should not be inferred to represent what will be delivered by third-party suppliers or manufacturers through Xometry’s network. Buyers seeking quotes for parts are responsible for defining the specific requirements for those parts. Please refer to our terms and conditions for more information.