Very rarely does steel come in the shape or size needed. The plate is cut using one of the various methods available, usually thermal or erosion cutting. When steel is cut using a thermal process, heat is used to melt the metal. This is also known as burning. Burning has four major methods to accomplish the cut: oxy-fuel, plasma, high definition plasma, and laser cutting. While there are four options for thermal, there is one popular option for the erosion process- water jet cutting. Today we’re going to explore how each of these processes work and some of the benefits associated, starting with the thermal category.

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Oxy-fuel cutting

Oxy-fuel uses, as the name suggests, pure oxygen to react with steel that has been preheated. The reaction from the immense heat being met with pure oxygen creates iron oxide resulting in melting the steel. This process can be thought of as rapid, controlled rusting. Oxy-fuel needs a specific material to be successful, carbon steel. Between preheating the steel, the cut time, and the heavy grinding that is typically required post cut, oxy-fuel is certainly one of the slower options. You might be asking if it’s slow, why choose it? This is a great option if you’re looking to burn carbon steel greater than 2 inches thick while still keeping a tight tolerance. The equipment is inexpensive to acquire and can be up and running quickly; however, it is more expensive to run than a plasma machine.

Plasma cutting

Plasma burning has the lowest operating expense and is the most common option for cutting steel. While oxy-fuel needs carbon steel, plasma requires any type of conductive material. The most common include steel, stainless steel, aluminum, brass, and copper. Where oxy-fuel excels at cutting thick materials, a plasma burn can accommodate materials up to 1.25 inches. Now that we know the materials we can use, how does it work? A high temperature ionized gas is forced through a narrow nozzle while an electrical current adds energy to ionize the flow. This creates a plasma arc, which can reach 40,000° F. The continuous movement of the plasma arc blows away the melted metal creating the cut. Often times, there is no preheating required, which makes it a faster process than oxy-fuel. With these advantages, it’s clear to see why this is the most popular cut technique.

(Fig. 1: Plasma Cutting Diagram)

High definition plasma cutting

If you’re looking for a more precise cut, you might want to consider the plasma high definition method. As indicated by the name, the plasma arc is still utilized. The big difference is the size of the nozzle that the plasma is shot out of. Here we use a narrower nozzle to achieve cuts that are cleaner and have more squared edges. For the best results, you want to use metals between 3mm and 25mm thick. More precision means a tighter tolerance and a higher cost.

Laser cutting

To round out the burning techniques lets dive into laser cutting. Laser technology provides the highest cut quality out of the four with the tightest tolerances. This, of course, means it is also the highest cost between the thermal options. There are two main types of lasers: CO2 and fiber lasers. CO2 lasers apply high voltages to a mixture of CO2, N2, and HE to generate a laser beam, which is reflected through mirrors to the cutting head. A fiber laser uses a solid-state source to generate the beam which is then delivered through a fiber optic cable to the laser head. Ideally, mild steel, stainless steel, brass, copper, or aluminum are used when laser cutting. Each material has a different thickness recommended, all falling between .25 inch and 1 inch. This option is ideal for people looking for extremely precise cuts for fine features. If you’re looking to cut holes less than a 1:1 diameter-to-thickness ratio, this is a great cut option.

(Fig. 2: CO2 laser diagram)

Each cut that uses heat has what is known as a heat affected zone (HAZ). The HAZ is the area of the material that has been affected by the heat used to cut. This can lead to the metal being a little bit stronger or weaker in that area, or possibly less ductile. Each process has a different HAZ associated with it, which is something you will want to take into consideration when deciding what cut process to use.

Waterjet cutting

You don’t have to worry about the HAZ with waterjet cutting. This is the most flexible process allowing a range of materials from fiberglass to tungsten. Here we use an ultra-high water pressure ranging between 60,000 PSI and 90,000 PSI. To give you some perspective on the strength of the stream, a typical household faucet is roughly 60-70 PSI. Water is run through either an intensifier pump or a crankshaft pump. An intensifier pump uses a hydraulic oil to move a piston, which forces the water through a tiny hole. The crankshaft pump forces water through high-pressure tubing using crankshafts to move the plungers. Both pumps force the water through a nozzle, where abrasives can be added if you’re cutting stronger materials. The most common abrasive is garnet. The water is then formed into a thin, high-pressure beam ready to cut. This technique has the highest precision and tightest tolerances of all the processes we have talked about. It is also the most expensive option, but can certainly be worth it for the accuracy delivered.

(Fig. 3: Waterjet Cutting Diagram)

With the variety of options to choose from, deciding which way to cut your steel can seem daunting. Luckily, you don’t always have to choose. The company manufacturing your steel will usually choose the best option for your project. If you do want to choose, be sure to take into account the material being cut, the thickness of said material, the tolerance needed, and of course what is the most cost efficient to get the job done.

How to Cut Steel: 5 Different Methods Explained

| Categorized in: Production

Steel cutting is a critical step in steel fabrication, but why does steel need to be cut after it’s produced and why are there different ways of cutting it? There are a number of factors that inform these decisions, so let’s go through them.

Why does steel need to be cut?

Steel products generally can be bought in standard sizes or dimensions, but many projects require different specifications for particular uses or situations. This is where steel cutting comes in handy and allows for even further modification and refinement of the steel you receive. For most projects using structural steel, raw steel arrives and undergoes precise cuts to transform into beams, plates, and pipes matching the final design. However, cutting steel can happen during multiple stages of a project:

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1. On-site construction often requires further cutting to fit steel elements together precisely or to accommodate existing structures.
2. Unexpected situations or design changes may necessitate cutting for adjustments or repairs. 
3. Cuts are also crucial for preparing steel for connections, such as creating bevels for welding.
4. Finally, demolition or renovation projects frequently involve strategically cutting and removing beams, tubing, and other steel shapes.

Best Ways to Cut Steel

Different methods might be used depending on certain aspects of the steel being cut and the tolerance or required precision of the cuts being made. The five primary methods used today are:

1. Laser Cutting
2. Waterjet Cutting
3. Plasma Cutting
4. Flame Cutting
5. Production Sawing

Laser Cutting

Typically employed for thinner steel (less than 1.25 inches), laser cutting is highly accurate and minimizes material loss. It uses an intense beam of light focused by mirrors in the head of the laser cutter to direct the extreme heat at the steel and melt it along predetermined cutting paths. However, laser cutting is also slower than some of the other cutting methods and can heat the surrounding area of the cut, leading to warping or thermal stress.

Waterjet Cutting

As its name suggests, waterjet cutting uses high-pressure water (or a mixture of water and an abrasive substance, such as garnet or aluminum oxide) to erode and cut away steel quickly. Unlike laser cutting, there is no heat distortion from this method and it can cut thicker pieces of steel, up to 8 inches. Because of this, waterjet cutting is also the most expensive type of steel cutting due to its versatility, accuracy, and expensive operating costs.

Plasma Cutting

Plasma, or superheated ionized gas, is directed through a fine nozzle at steel (or other electrically conductive materials) and uses an electric arc that passes through the conductive plasma to melt the steel. The high-pressure gas from the nozzle then cuts through the molten steel and blows it away, cutting the workpiece. This method is quick, but is usually limited by a thickness of around 1.5 inches (2.5 inches for CNC plasma cutters) and can have a lower-quality cutting edge than other methods.

Flame Cutting

Also called oxy-fuel cutting, flame cutting steel often involves preheating the piece around the area that’s going to be cut. A torch is then used to combine oxygen and fuel gasses (acetylene, propane, propylene, etc.) to oxidize and melt the metal away, cutting through large steel products. While flame cutting is slower than plasma cutting due to the preheating process, it’s generally the most cost-effective method and can cut through steel as thick as 48 inches. Flame cutting can also be less finely tuned than other methods — but at these sizes, the accuracy and tolerances are much less delicate and strict. Most of the steel cutting that we perform is flame cutting.

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Sawing

The final method of cutting steel is also the most basic, and that’s using a circular shop or band saw for the process. Saw cutting steel can allow for close tolerances, as well as reducing the waste material produced.  While not the most powerful method, it shines in situations where precision is key.

Depending on the size and shape of the metal being cut, most steel sawing will most likely use one of two types: 

• Chop saws (pictured above) are most often used with abrasive cut-off wheels, are portable, and make quick cuts on various steel shapes like pipes and beams making them ideal for fast on-site cuts or for smaller steel sections. However, they can get hot and leave rougher cuts.

• Band saws (pictured above) use a continuous blade for a more controlled metal cutting environment which results in clean, straight cuts and minimal waste. Additionally, they can handle a wide range of thicknesses and can even follow a template for more intricate shapes.

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Cutting Steel: FAQs

How to Cut Steel Pipes?

Cutting steel pipes can be done using a variety of different methods. Mechanical methods such as sawing are common for smaller diameter pipes, providing clean, straight cuts. For larger or thicker pipes, an oxy-fuel torch can be effective, especially for quick and rough cuts. A plasma cutter is also a suitable choice, offering clean and precise cuts while being able to handle varying wall thicknesses efficiently without heat-induced warping.

How to Cut Thick Steel?

Thick steel requires robust metal cutting methods such as oxy-fuel flame cutting. This cost-effective method uses a high temperature from a flame to melt and oxidize the steel. Due to its speed and precision, plasma cutting is also effective for precisely and quickly cutting medium-thick steel (usually up to two inches).

How to Cut Galvanized Steel?

Cutting galvanized steel presents a unique challenge as it requires metal cutting methods that will minimize damage to the zinc coating and preserve its corrosion resistance. In these cases, mechanical steel cutting methods like sawing are preferred, since they don’t generate heat that would vaporize the zinc. 

How to Cut Steel Plates?

Steel plates can be cut using a variety of methods depending on their thickness and the precision required. For thin to medium-thick plates, laser cutting is highly effective, offering high precision and clean edges. Plasma cutting is the most versatile as it can handle a wide range of thicknesses. For very thick plates, water jet cutting provides precise results without heat distortion. 

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Service Steel has the versatility to cut your steel products to size at a cost-effective rate and for any of your project’s needs. Whether you need flame cutting, sawing, or other finishing services such as galvanizing or impact testing, we can quickly supply you with the steel you need. Request a quote or give us a call today!

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