Understanding Steel Properties and The Materials

In the world of steel construction and fabrication, there are four main types that are used on most projects and each has its own steel properties:

— Carbon steel

— Alloy steel

— Stainless steel

— Tool steel

All of these fall in the steel category, but if you were to try and use, say, stainless steel in a situation that called for carbon steel, you would realize the error of your ways very quickly. The reason for this is that each type has different steel properties that impact the jobs that it is suitable for, as well as other factors like durability and cost. So, with this said, here are some of the key steel properties any contractor, fabricator, or builder will need to understand and master to get the most out of the material.

Weldability

As the name implies, weldability determines exactly how well a piece of steel can be welded. If weldability is low, then the chances are higher for it to crack due to heating at the weld joint. There are a variety of different welding practices out there, but the weldability has the same impact on each type. There are some methods available in order to try and weld steel with lower weldability. This includes heat treatment processes, though you may need to apply one before and after the actual welding.

Hardenability

This metric has an inverse correlation to weldability and determines how easy it is to harden a material through thermal treatment. Generally, hardness levels will be laid out in the design phase. This is because knowing and controlling how hard the steel gets gives you more flexibility in terms of design. Hardenability in a given type of steel is impacted by alloys and carbon content. As an added note here, the bulk of steels are only capable of surface hardening, not through hardening.

Machinability

The name here may be a bit confusing, but machinability essentially covers how easy it is to cut (machine) a piece of steel. This is something key for fabricators, who will likely have to cut down pieces of base steel to meet design metrics. Machinability can be a difficult property to work with because so many different factors play a role. For example, if a piece is too ductile, it can spring back after getting cut. If it’s too hard, it can create greater wear and tear on your tools. The ideal combination is low hardness and medium ductility. Many steel fabricators also heat treat the steel before cutting to try and manipulate the hardness.

Workability 

Workability is a metric that determines how easy it is to bend or form a given material. This means that any project that requires bending steel or stamping needs to have a strong metric here. Generally, hardness and ductility play the largest roles out of the other steel properties in terms of workability. If you’re using stronger steel such as high carbon steel, you’re not going to have the ductility to bend the steel to your need. Steelworkers keep track of this with a stress-strain curve. This metric helps determine how much you can bend/form a given type of steel before it fails. There is also a term called hot workability, which refers to how workable it is when heated, increasing ductility.

Wear Resistance 

When we talk about wear resistance in regards to steel properties, we are talking about resistance to any surface material loss. This includes:

— Fatigue

— Abrasion

— Erosion

— Adhesion

Surface hardness is the defining factor when it comes to a given wear resistance for steel. This lets it wear down other metals that are not as hard, without having much wear or tear. 

Corrosion Resistance

Corrosion resistance is a metric that’s important if your steel structures are going to be exposed to rain, water, humidity, or anything that can cause oxidation of the surface. The best options to minimize damage here are using stainless or galvanized steel. However, these are very expensive, so most steel builders will opt for a sealer (paint) or concrete to cover the steel instead. With this said, corrosion, at some level, will happen to any exposed metal. This is why it’s important to monitor the steel after the installation as well as during.

Yield Strength

Yield strength is the key point where steel will start to show much more strain when dealing with stress. If the type of steel you are working on has higher ductility, like low carbon steel, it may begin to deform. In many cases, yield strength serves as a hard limit on how much design work you can do on a given piece of steel. Another notable metric is tensile/ultimate stress. This serves as at what point deflection will continue until the actual steel fracture happens. If you start to approach this limit, you will need to either lower the load, add reinforcement, or use a material with higher strength.

Steel is an extremely versatile and durable material, which makes it a staple in construction sites across the country. However, part of understanding the material is also making sure that you’re getting the most out of it in terms of profitability. Investing in a more expensive steel variety that you don’t necessarily need could turn a given job into a money loser rather than a profit. There are many other issues that could result in a steel construction job being less efficient and effective than usual.

Collecting as much data on your past steel jobs and other information is key to make sure that this doesn’t happen to you. But how do you get the data on the steelwork that you need? The answer is using project management software such as eSub. This is key because you not only have data on your materials and team members but also on your financial history. If you find one area is costing you an excess of money and time, you can refine your work process.