It should be a simple choice for Metal Fabricators…but the devil is in the details
Isn’t Oxy-Acetylene Old School?
When Thomas Edison invented the light bulb, people continued to use candles.
When the first PC (the Altair) was introduced, people continued to use calculators.
When cell phones started integrating cameras, people continued to use DSLRs.
But in each case, each of the original solutions continued to be useful in a niche. Candles became useful for setting a romantic mood rather than reading a book. You couldn’t take an Altair with you to class to take a test. And, if you’re a professional photographer, you would trust your reputation to your iPhone’s camera…even with its gazillion pixels.
The same can be said for the place Oxy-Acetylene currently plays in a Metal Fabricator’s life.
Electric welding processes have almost completely taken over production welding applications. In most cases, an electric welding process which will turn out good welds faster than the oxy-acetylene torch.
If that is true, why bother with oxy-acetylene gas at all?
To paraphrase in the classic movie The Graduate where Mr. McGuire advises to young Benjamin: OXYFUEL CUTTING.
Oxyfuel Cutting has never been exclusively an oxy-acetylene process. Other fuel gases are also commonly used. However, when operators use cutting torches, they use acetylene more often than with all other fuel gases combined.
This blog post is meant for trainees and new operators who want to quickly understand some of the “why’s” of Oxyfuel Cutting. Future blog posts will describe the “how’s”.
What is Oxyfuel Cutting?
Oxyfuel Cutting begins by using preheating flames to raise the surface or edge of the steel to approximately 1,800º F. The operator then directs pure oxygen toward the heated area in a high pressure stream. A cavity forms and steel oxidizes and is blown away. A continuous cut forms as the preheated flame and oxygen stream are moved at constant speed.
Cutting Torches + Steel = Oxyfuel
While Oxyfuel Cutting can address many applications. Oxyfuel cuts ferrous (iron-containing) steels up to 24 in. thick. But only metals whose oxides have a lower melting point than the base metal itself can be cut with this process.
Metals such as aluminum and stainless steel cannot be cut with Oxyfuel due to the formation of an oxide that prevents oxidation from fully occurring.
What about Cutting Stainless Steel, Aluminum and Other Non-ferrous Metals?
Operators have proven that Plasma Arc Cutting is a great solution when you need to cut thin metals quickly, neatly, and with a minimal heat-affected zone. Plasma Arc Cutting systems can cut all electrically-conductive metals, including aluminum and stainless steel.
Plasma is an ionized gas that conducts electricity. In cutting applications you create plasma by adding electricity to an electrically-neutral gas. By adding electricity through an electrode (often made out of hafnium), the gas becomes imbalanced and conducts electricity. As you add more electrical energy, the plasma arc becomes hotter. Plasma arc cutting machines control this energy by constricting the arc and forcing it through a nozzle. Increasing air pressure and voltage make the arc hotter, and more capable of cutting through thicker metals while blowing away the cuttings.
Should you use Plasma or Oxyfuel?
With plasma technology today, you can cut all the way to the 3-inch mark. This advancement flies in the face of one of the industry’s longstanding rules of thumb: anything thicker than 1 inch should be cut with Oxyfuel.
So, just because it can, should you?
In the real world, you probably would not buy a piece of equipment just for its cutting abilities. That may be the primary objective, but both Plasma and Oxyfuel have benefits outside of cutting steel.
If you need to gouge-out steel, edge preparation, or remove an imperfection in a weld, handheld plasma arc cutting machines are extremely effective.
Oxyfuel cutting equipment have even more versatility. Combination torches allow operators to braze, solder, and fusion weld. While the cutting capacity (8-12 inches) of combination torches is reduced, the cutting capabilities matched with the added benefits are likely to satisfy most metalworkers' needs.
So at the end of the day, the answer to the Great Debate: Plasma Cutter or Oxyfuel Torch, comes down to your answers to three simple questions:
- What do you cut on a day-to-day basis?
- What is the thickest metal, within reason, that you'll ever cut?
- What else do you need to do besides cutting?
The How’s are Just as Important as the Why’s
Some people think that Oxyfuel Cutting is a mature uncomplicated process. But operators who work with it realize that making it perform properly is no simple matter.
Experienced operators can achieve a level of cut-quality that rivals a machined-surface, and do it in less time and at a fraction of the cost of hard-tooling. But reaching such levels of performance requires an understanding of many factors that can usually be gained only after years of hands-on experience.
But look to this blog for WestAir to information ways to improve cut-quality and performance in Oxyfuel Cutting operations.