Gas is key to removing molten metal, and this is where problems are most likely to occur.

1. Incorrect gas type:

Phenomenon: A large amount of hard slag hangs on the bottom of the cut.

Principle: Stainless steel is primarily cut using oxygen (O₂) or nitrogen (N₂).

Oxygen: Reacts exothermically with the metal, aiding combustion and improving cutting performance. The cut surface is a black oxide layer.

Nitrogen: Provides cooling and purging, resulting in a bright, oxidation-free silver cut surface.

Solution: Confirm your process requirements and select the correct gas. If cutting for speed, use oxygen.

2. Insufficient gas pressure:

Phenomenon: Excessive slag hangs on the bottom, preventing a thorough cut.

Solution:

When using oxygen: The pressure typically needs to be 1.0-1.5 MPa (approximately 10-15 bar). Higher pressures are required for thicker plates. When using nitrogen: The pressure requirement is higher, typically 1.4-2.5 MPa (approximately 14-25 bar). The thicker the plate, the higher the pressure requirement.

Action: Immediately check the pressure gauge on the machine tool to see if it reaches the set value. Check the gas line for leaks.

3. Insufficient Gas Purity:

Symptom: Even with sufficient pressure, the cut will not be thorough, resulting in poor cross-section quality.

Solution:

Oxygen purity: Should be ≥ 99.95%.

Nitrogen purity: Should be ≥ 99.995% (4.5 nines or higher). Using pipeline nitrogen or a nitrogen generator with insufficient purity will severely affect cutting results. Using a liquid nitrogen tank is recommended.