Advancements in plasma cutting of stainless steel

Stainless steel accounts for a relatively small percentage of the world-wide steel consumption, but it is vitally important to economies, particularly in the energy and food processing markets. Where cutting stainless steel is concerned, there are several cutting technologies that manufacturers employ. The most common of these are plasma, band saws and waterjet that boast broad thickness ranges, and laser and sheers for thinner plates.

Amongst these systems, a plasma set-up presents numerous benefits. Plasma uses thermal energy and high velocity gas to melt and remove material from a cut surface, resulting in fast cut speeds when compared to band saws and waterjet systems. And unlike laser, plasma features a thicker cutting capability, and the flexibility to quickly switch from severing 160mm stainless steel plates to cutting fine features on thin stainless (0.8-6mm) and mild steel, as well as on aluminium.

Early plasma systems designed for cutting thick stainless steel used very high amperage and delivered slow cut speeds compared to recent technological developments. Modern plasma systems however allow end-users to select from an expanded range of gases and amperages to produce optimal cut speeds and desired cut quality for a variety of needs.

The challenge of cutting stainless steel with plasma

For customers with experience in cutting mild steel, expanding into cutting stainless steel brings new challenges, and several factors must be taken into consideration in order to ensure success.

Gas types and selection

When cutting mild steel, oxygen plasma gas and air shields can effectively deliver excellent cut quality across the full range of thicknesses. Success on stainless steel, however, requires a different type of gas and consumable technology for varying thickness ranges and grades. Proper gas selection is the first step toward success in plasma cutting stainless steel.

Technology requirements for different stainless steel types

Plasma processes engineered for a specific grade of stainless steel may not necessarily perform well on other types of the same metal. For example, a plasma system meant for use on 304L, an austenitic stainless steel that is the most commonly used grade world-wide, brings about dross and a rough cut edge when used on 316L. When used on 304L, cuts are clean with no visible dross. The 316L cut can be improved to the same cut quality of the 304L cut by increasing the cut speed and shield pressure slightly.

As the above instance illustrates, each material type responds differently to plasma cutting. In order to cut various grades of stainless steel, a wide range of cutting processes is necessary in order to attain the best results.

Molten material viscosity & piercing

Two other challenges presented by cutting stainless steel with plasma are molten material viscosity and piercing. Unlike cutting mild steel with oxygen or air, the viscosity of the molten material when working with stainless steel is much higher. As a result, secondary operations such as grinding often need to be carried out in order to remove the slag. Factors that can reduce, or even eliminate, the formation of dross on stAir Jordan XIII Slippers