When you think about steel, you probably imagine that it’s pretty heavy, right? After all, something as strong as steel would have to be heavy due to its density.
Cue high-strength low-alloy steel.
This high-strength metal is made specifically to provide certain mechanical properties while also providing one unique advantage: It’s lightweight for the same strength equivalent of standard steels.
But what exactly is high-strength low-alloy steel and what advantages does it offer in the roll forming process over standard carbon steel? Let’s take a closer look!
What Is High-Strength Low-Alloy Steel?
High-strength low-alloy steel, also referred to as HSLA steel, is popular among manufacturers for its enhanced mechanical properties and increased ability to resist corrosion compared to standard carbon steel (aka mild steel). This alone is one of the most important roll forming design considerations.
HSLA steel is different from other steel because of its properties and unique capabilities. Many standard steels are made to meet a specific chemical composition. HSLA steel is made to achieve specific mechanical properties.
The term “low-alloy” means that the metal has between 1.5% and 5% total alloy content. This gives high-strength low-alloy steel unique advantages over standard carbon steel and other metals.
What Are the Advantages of HSLA Steel?
There are many advantages to using HSLA steel, and HSLA steel suppliers can highlight certain properties based on what other metals are added to the mix. Notable advantages of HSLA steel include:
- High yield strength
- Improved formability and weldability
- Better corrosion resistance
High Yield Strength
HSLA steel provides a high yield strength. This refers to the amount of force you can put on the steel before it starts to bend (aka, plastic deformation) and doesn’t rebound back into place (aka, elastic deformation).
Most high-strength low-alloy steel can take on high stress loads and spring back into place with ease. Many engineers call this the ability to bend “elastically.” This high yield strength gives the steel an ability to resist bending or breaking. You can imagine the benefits this provides in structural applications. (More on them shortly.)
It’s important not to confuse strength with hardness. A steel can have a high level of strength and still be able to withstand applied loads without cracking or bending. A metal with increased hardness doesn’t absorb impact as well, and will typically crack when enough force is applied.
To summarize, for purposes of applied loading, strength is a measure of how much force is applied before a material deforms. Hardness is a measure of a material’s resistance to deformation also, but cracking or breaking are more likely to occur under too much force. They go hand-in-hand, but are separate characteristics better suited for differing tasks.
Improved Formability and Weldability
One of the components that makes HSLA steel valuable in the manufacturing industry is that its increased strength still allows for formability and weldability. Many believe that the alloying process would cause these properties to suffer, but HSLA steel is equal to, if not better than, standard carbon steel when it comes to forming and welding.
The formability of high-strength low-alloy steel is improved due to its ability to bend without breaking. This makes it easy for manufacturers to bend it at any angle up to 180 degrees (meaning formed back on itself) without any cracking or “crazing”.
When talking about welding HSLA steel, many manufacturers will alloy the metal with ingredients that possess high weldability. It’s not uncommon for the engineer designing a project to request specific HSLA steel properties that match the needs of their specific application.
Increasing the carbon content of steel is the most cost-effective way to increase its strength.
On a general basis, the costs associated with creating HSLA steel are typically higher than with other metals. However, due to the strength to weight ratio you gain by using HSLA, you’ll use less material and actually decrease your costs.
This reduction in cost makes the steel suitable for any budget. Bigger companies can buy HSLA steel in bulk to accommodate large orders, and it provides smaller companies access to high-quality metal fit for several industries.
Better Corrosion Resistance
HSLA material properties won’t match red metals such as copper, brass, and bronze; or the high chromium stainless steels in corrosion resistance. However, HSLA steel has a slightly higher resistance to corrosion than standard carbon steel.
This is because of the microstructure that comprises high-strength low-alloy steel. And by adding chromium, you can make HSLA steel even more resistant to corrosion.
In Which Industries Will You Find HSLA Steel?
Due to its relatively low weight and high strength, there are certain industries that favor HSLA steel over other roll formed metals. For example, the solar industry prefers to use HSLA steel for solar racking systems on commercial buildings. Higher strength can be obtained with thinner gage steel reducing the additional static load these systems apply to roof structures. No loss in capability is realized with systems still being able to support the panels themselves as well as wind and snow loads.
Here are a couple of other industries that favor high-strength low-alloy steel:
One of the most common places to find high-strength low-alloy steel is in the automotive industry. And it’s not hard to guess why.
HSLA’s material properties make it great for the automotive industry. One of the areas that has benefited most is fuel efficiency. The lighter the car is, the easier it is for the engine to move the car, resulting in better mileage.
Strength is also important in auto applications. Referred to as “toughness” in steel specifications, it’s common to find HSLA steel in the doors and side panels of vehicles. This serves two purposes:
- To provide the vehicle with enough strength to carry its passengers
- To increase the vehicle’s ability to absorb impact, resulting in a safer driving experience
Common construction projects like commercial, institutional, and residential buildings, travel infrastructure, and others use some form of HSLA steel.
As with sheet metal applications, HSLA steels can be hot rolled into bars, plates, and structural shapes used for construction. The same benefits of strength to weight ratio still apply, making these grades of steel popular with engineering firms designing these projects..
Fun fact: High-strength low-alloy steel is the material of choice for many roller coasters.
The Steel That’s a Steal
High-strength low-alloy steel is a valuable commodity for many industries, and offers plenty of adantanges throughout the roll forming process. Its relatively low weight and high level of strength strikes a perfect balance -- one that’s suitable for numerous construction and architectural projects. (Not to mention it’s cheaper than many alternatives.)
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