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Flame Cutting vs. Plasma Cutting for Stainless Steel and Aluminum

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Anyone who works with metals knows the importance of understanding several different cutting methods. Unfortunately, the same manufacturers that might spend months researching, testing, and prototyping products with a wide variety of metal alloys, some of which are barely distinguishable from each other, in order to get just the right material, will use whatever cutting tool they have at hand. The smart producers know that what you use to cut your materials is just as important as the material itself.

That’s why it is critical for manufacturers to understand the differences between flame cutting and plasma cutting, and knowing which operations are best suited for each. Ultimately, the decision will come down to a number of factors, including what alloy you are using, its thickness, the location, the variety of work, your power resources, budget, and more.

We often get asked about the differences between flame cutting and plasma cutting. In the following paragraphs, we’ll take a look at both, and explain why when it comes to aluminum and stainless steel, plasma cutting is really the only viable option.

What Is Flame Cutting?

Flame cutting goes by many names, including oxy-fuel cutting, oxyacetylene cutting, and oxy cutting. It is a process that relies on fuel gases and oxygen to cut metals. It originated with French engineers Edmond Fouché and Charles Picard in 1903 as a method of flame welding. It relies on pure oxygen, rather than air, to increase the flame temperature. This allows for the localized melting of the workpiece material.

In oxy-fuel cutting, the flame is not intended to melt the metal, but rather is supposed to bring the material to its ignition temperature. Then, a stream of oxygen is aimed at the metal and cuts through it, creating a metal oxide slag. As a quick comparison, a common propane/air flame burns at about 3,590°F, a propane/oxygen flame burns at about 4,087°F, an oxyhydrogen flame burns at 5,072°F, and an acetylene/oxygen flame burns at about 6,332°F.

A cutting torch will generally have a 60- or 90-degree angled head with holes placed around a central jet. The outer jets are flames consisting of oxygen and acetylene that are intended for preheating. The central jet only has oxygen. By employing the preheating flames, it is possible to change the direction of the cut without having to change the position of the nozzle or the angle.

Cutting in this manner works very well with iron and steel. The cut is initiated by heating the edge of the metal to the ignition temperature. When the cutting valve releases the oxygen from the central jet, it chemically combines with the iron and turns into molten iron oxide, producing the cut.

Unfortunately, while flame cutting is a cheap, efficient option for working with ferrous metals such as iron and steel, it is nearly impossible to effectively use with aluminum or stainless steel. With aluminum, it doesn’t work because aluminum oxide melts at a higher temperature (this is the reason why high-grade aluminums are a popular choice in and around aerospace engines). On the other hand, because stainless steel doesn’t oxidize, it is also not a suitable choice.

For these reasons, when working with stainless steel and aluminum, manufacturers will generally turn to plasma cutting as an alternative to flame cutting.

What Is Plasma Cutting?

Plasma cutting, as with flame cutting, is a process that shoots a jet of ionized gas through an orifice at a high rate of speed. The gas, after being both superheated and electrically ionized by the electrical channel, forms a completed circuit back to the cutter via a grounding clamp. We refer to this ionized gas as plasma. The more electrical energy that is added, the hotter the plasma arc becomes. This arc is able to heat the metal and the gas blows away the material once it has melted, creating a cut at the desired point.

A plasma cutter is highly effective with any electrically conductive metal, including aluminum and stainless steel. The compressed gas that is used might be air, oxygen, inert, or some other gas, depending on what material is being cut. When the gas is forced through the nozzle, an electrical arc forms between the electrode in the nozzle and the material. The gas is then ionized with enough heat intensity to melt through the material.

What Are The Advantages Of Plasma Cutting?

Plasma cutting is known to work extremely well on materials that are less than a half inch in thickness. It can also be employed with stacked material or expanded metals. In these cases, hand-held torches are likely adequate. For thicker materials, as much as 6 inches, computer-controlled rigs are available. Additionally, the plasma generally forms an extremely localized cone that is effective at cutting sheet metal in angular or curved shapes.

Other advantages include that prep time is kept to a minimum with a plasma cutter, without a need for preheating. The cutter produces an extremely precise kerf. The versatility is tremendous, and it’s possible to use plasma cutters for stack cutting, beveling, shape cutting, gouging, and piercing. Furthermore, the heat-affected zone is small, so there is very little warping or other damage. Clean up is also relatively easy.

As for portability, this depends on the machine being used, the size of the power source required, and how big the air tanks are. There are many kinds of portable plasma cutters available that are perfect for field work and rely on engine-driven generators or primary power sources. For larger cuts, dedicated machines will be necessary.

Your Technical Resources Partner

While both flame cutting and plasma cutting have their place, if you are working with aluminum or stainless steel, then plasma will be your only option. At Clinton Aluminum and Steel we pride ourselves on helping manufacturers pair the right tool with the right material. We strive to be a technical resources partner to our clients, helping each one extract the maximum value from their purchasing decisions.

With a staff that averages nearly 13 years of working for us, Clinton is recognized as the Midwest’s leading supplier of aluminum and stainless steel products. Contact us today to learn more about what we can do for you.

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