Do you need shielding gas for a plasma cutter?

No, a plasma cutter can operate without shielding gas, but using it improves cut quality and extends torch life.

How Plasma Cutters Work

The Basic Mechanism of Plasma Cutting

Plasma cutting is a process that cuts through electrically conductive materials by means of an accelerated jet of hot plasma. Typically, materials cut by plasma cutters include steel, stainless steel, aluminum, brass, and copper, although other conductive metals may also be cut using this process.

Here’s a basic rundown of how the process works:

• Creation of Plasma: At its core, a plasma cutter works by sending an electric arc through a gas (often air) that is passing through a constricted opening. This electric arc elevates the temperature of the gas, transforming it into the fourth state of matter, known as plasma.
• Directing the Plasma: The plasma is then directed towards the metal to be cut. The tight opening (usually a nozzle) through which the gas passes causes it to squeeze out at a high speed, like air passing through a venturi in a carburetor.
• Cutting the Metal: The super-hot plasma effectively melts the metal being cut, while the high-speed gas blows the molten metal away, resulting in a clean cut.

Importance of Gas in Plasma Cutting

Gas plays an integral role in plasma cutting and determines the quality, speed, and type of cut. Here’s why gas is so important:

• Gas Type Affects the Cut: The type of gas used can influence the speed of the cut, the thickness of the metal that can be cut, and the smoothness of the cut edge. For instance, using argon can produce different results compared to using nitrogen.
• Cooling and Protection: The gas also acts as a cooling agent. After the plasma melts the metal, the gas rapidly cools the cut edges, which reduces warping and distortion of the metal. Additionally, the gas shields the cut from atmospheric contamination.
• Gas Pressure and Flow: The pressure and flow rate of the gas can also be adjusted to optimize cut quality. Different metals and thicknesses may require adjustments to these settings to achieve the best results.

Role of Shielding Gas in Plasma Cutting

Shielding Gas vs. Plasma Gas

While both shielding gas and plasma gas are integral to the plasma cutting process, they serve distinct purposes:

MIG

TIG

• Plasma Gas: This is the primary gas used to generate the plasma arc. It flows between the electrode and the nozzle and, when ignited by the power supply, becomes ionized, turning into plasma. Common plasma gases include nitrogen, oxygen, and argon-hydrogen mixtures.
• Shielding Gas: Surrounding the plasma gas, the shielding gas flows around the outer perimeter of the nozzle. Its primary purpose is to shield the cutting area from atmospheric contamination, which could negatively impact cut quality. Additionally, it helps in cooling and protecting the torch components. Common shielding gases include air, argon, and nitrogen, though the best gas often depends on the specific metal being cut.

It’s important to note that in some plasma cutting setups, the plasma gas doubles as the shielding gas, especially when cutting with air.

Purpose of Shielding Gas

Shielding gas plays a critical role in ensuring the plasma cutting process is both efficient and produces high-quality results:

• Preventing Atmospheric Contamination: As its name implies, shielding gas creates a shield around the cutting area, preventing impurities in the atmosphere from mixing with the molten metal. This is vital because contaminants can adversely affect the cut’s integrity and appearance.
• Cooling and Protecting the Torch: The flow of the shielding gas also helps to cool the torch components, extending their life and ensuring consistent performance. Without adequate cooling, the torch’s wear components might degrade more rapidly.

Benefits of Using Shielding Gas

Utilizing the right shielding gas can elevate the quality of plasma cuts. Some of the key benefits include:

• Enhanced Cut Quality: Shielding gas can significantly improve the edge quality of the cuts, resulting in smoother edges free from excessive dross or imperfections.
• Increased Cutting Speed: In certain applications, using the right shielding gas can boost cutting speeds, allowing for more efficient operations.
• Longer Consumable Life: As the shielding gas helps cool and protect the torch components, using it correctly can extend the lifespan of these components, saving costs in the long run.
• Better Weldability: For projects where the cut pieces will later be welded, a clean cut achieved with proper shielding gas use ensures easier and more effective welding.

Common Shielding Gases Used in Plasma Cutting

Argon and its Mixtures

Argon is a noble gas that’s frequently used in plasma cutting, either on its own or mixed with other gases. Here’s why it’s a popular choice:

• Inert Nature: Being a noble gas, argon doesn’t easily react with metals at high temperatures. This means it can help produce cleaner cuts with minimal oxidation or other reactions.
• Argon-Hydrogen Mixtures: Often, argon is mixed with hydrogen, especially for cutting thicker stainless steel and aluminum. The addition of hydrogen enhances the cutting capability by making the plasma hotter.

Nitrogen

Nitrogen is another common shielding and plasma gas:

• Versatility: Nitrogen can be used both as a primary plasma gas and a shielding gas. It’s particularly useful when cutting stainless steel or aluminum.
• Clean Cuts: Using nitrogen can result in oxide-free edges, especially on stainless steel. This can be beneficial if the cut piece is intended for welding, as it’ll require minimal post-cut cleanup.

Oxygen and its Mixtures

Oxygen plays a critical role in plasma cutting, especially for metals like mild steel:

• Faster Cutting: For materials like mild steel, oxygen as a plasma gas can increase the cutting speed, thanks to its exothermic reaction with the metal.
• Mixtures with Argon: Sometimes, oxygen is mixed with argon for cutting thicker materials. This mixture can offer a balance between speed and cut quality.

Comparing Different Shielding Gases

When it comes to selecting the right shielding gas for a plasma cutting project, several factors come into play:

• Material Type: The kind of metal you’re cutting can dictate the best gas choice. For example, nitrogen might be better suited for stainless steel, while oxygen is often preferred for mild steel.
• Cut Quality: If you need a super-smooth, high-quality cut, the choice of shielding gas can make a significant difference. Argon mixtures, for instance, often produce smoother cuts on certain metals.
• Cost Considerations: Some gases are more expensive than others. Depending on the project scale, cost can be a deciding factor.
• Availability: Not all gases are readily available everywhere. It’s essential to consider what gases are easily accessible in your region.

Plasma Cutting Without Shielding Gas

Possible Complications and Drawbacks

Cutting without the use of a shielding gas can introduce several challenges and risks:

• Oxidation: Without a shielding gas to protect the cut, metals, especially those like steel, can oxidize rapidly. This oxidation can degrade the quality of the cut and lead to rougher edges.
• Increased Dross: Dross is the molten metal residue left behind after cutting. Without shielding gas, there’s a higher likelihood of more dross forming, which requires post-cut cleanup.
• Reduced Torch Life: The absence of shielding gas can cause the torch and its components to experience greater wear and tear, as they aren’t adequately cooled and protected.
• Atmospheric Contamination: Without the protective barrier that a shielding gas provides, contaminants in the air, such as moisture or other gases, can interact with the molten metal, potentially affecting the integrity of the cut.

Situations Where Shielding Gas Might Not Be Necessary

While there are definite advantages to using shielding gas in plasma cutting, there are scenarios where it might not be crucial:

• Cutting with Air: Some plasma cutters use air as both the plasma and shielding gas. In these setups, an external shielding gas might not be necessary, as the air serves a dual purpose.
• Less Critical Applications: For projects where cut quality isn’t a top priority, or if post-cut cleanup isn’t a concern, skipping shielding gas might be acceptable.
• Specific Metal Types: Some metals are less prone to issues like oxidation or atmospheric contamination. In such cases, the benefits of shielding gas might be less pronounced.
• Short, Quick Cuts: For rapid, short-duration cuts, especially in well-ventilated areas, the complications from not using a shielding gas might be minimal.

Safety Precautions When Using Shielding Gas

Handling and Storage Tips

Proper handling and storage of shielding gas cylinders are paramount for safety:

• Upright Storage: Always store gas cylinders in an upright position, secured with chains or straps to prevent them from falling.
• Cap Protection: When not in use, ensure that the protective cap is in place to guard the cylinder’s valve from potential damage.
• Regular Inspections: Periodically inspect the cylinders for any signs of damage, leaks, or corrosion. Ensure that the labeling is legible to avoid any mix-up of gases.
• Away from Extreme Conditions: Store gas cylinders in a cool, dry place, away from direct sunlight, heat sources, or any potential source of ignition.
• Transport Safely: When moving gas cylinders, use a cylinder cart and ensure they are secured. Avoid dragging, rolling, or sliding the cylinders.

Ventilation and Workspace Considerations

Proper ventilation is crucial when using shielding gases:

• Adequate Air Flow: Ensure your workspace has enough ventilation to prevent the buildup of gases, which can be hazardous if inhaled in large quantities.
• Monitor Oxygen Levels: Some shielding gases, like argon, can displace oxygen, leading to potential asphyxiation. It’s crucial to monitor oxygen levels in confined spaces.
• Extraction Systems: If available, use extraction systems to remove gases and fumes from the cutting area.

Potential Hazards and How to Avoid Them

Using shielding gas involves several potential hazards, but with awareness, these can be mitigated:

• Gas Leaks: Regularly inspect hoses, connections, and regulators for leaks. Use soapy water to detect any leaks; bubbles will form if gas is escaping.
• Pressure Concerns: Shielding gas cylinders are under high pressure. Ensure that regulators and pressure-relief devices are in good working condition.
• Fire Hazards: Gases like oxygen can accelerate combustion. Keep flammable materials away from the cutting area and have a fire extinguisher readily available.
• Health Risks: Inhaling certain shielding gases can be harmful. Always wear appropriate respiratory protection if working in confined spaces or if there’s a risk of inhaling the gas.

Cost Implications of Using Shielding Gas

Expense Breakdown

Understanding the expenses associated with using shielding gas can help businesses and individuals budget more effectively:

• Gas Prices: As of 2022, a standard-sized cylinder (around 250 cubic feet) of argon might cost anywhere from $30 to $60, depending on the region and supplier. Prices for other gases, like nitrogen or oxygen, can vary, but are generally in a similar range.
• Rental or Purchase of Cylinders: Some suppliers charge a monthly rental fee for the gas cylinder, which can range from $5 to $25 per month. Purchasing a cylinder outright can cost between $100 and $300, but this can be more cost-effective in the long run if you use shielding gas regularly.
• Equipment and Accessories: Regulators, hoses, and other related equipment are additional costs. A good quality regulator, for instance, might set you back $50 to $100.
• Delivery Fees: Depending on the supplier, there might be delivery charges for transporting the cylinders to your location.

Evaluating Cost vs. Benefit

While the use of shielding gas incurs costs, evaluating these expenses in light of the benefits can provide a clearer picture:

• Improved Cut Quality: Using shielding gas can result in smoother, cleaner cuts. This means less post-cut cleanup, which can save time and further expenses in labor.
• Extended Equipment Life: Shielding gas can extend the life of plasma cutter torch components, reducing maintenance and replacement costs.
• Efficiency and Speed: Certain shielding gases can increase the speed of the cutting process, leading to faster project completion and potentially reduced labor costs.
• Potential for Increased Revenue: For businesses, the ability to produce high-quality cuts can lead to increased customer satisfaction and more business opportunities.