The core lies in precisely adjusting the oxygen-acetylene ratio to obtain a neutral flame, and adjusting flame parameters according to the thickness and material of the sheet metal to ensure cutting quality and efficiency. The following explains flame type identification, specific adjustment steps, adaptation methods for different sheet metals, and safety precautions.

Flame Types and Characteristics

Flame cutting machines can produce three types of flames by adjusting the oxygen-acetylene ratio, each with different shapes and applicable scenarios:

Neutral Flame (Normal Flame): The flame core has a clear, cylindrical outline, the reduction zone is relatively dim, and the outer flame temperature is between 1200 and 2500℃. Using a neutral flame when cutting steel plates under 200mm can produce a smooth cut; it is the "golden ratio" for gas cutting.

Oxidizing Flame: The flame core is short and the outline is blurred; the flame is purplish-blue and accompanied by a hissing sound. Excess oxygen leads to excessive metal oxidation, causing the cut to become brittle and deteriorating in quality; its use is generally avoided. Reducing Flame (Carburizing Flame): The flame core has a green edge at the end, the inner flame blends with the reducing zone and emits black smoke. When acetylene is in excess, the flame is longer, suitable for preheating thick plates (flame length needs to be at least 1.2 times the plate thickness), but the cutting speed is slower.

Ignition Adjustment Procedure

 Ignition and Initial Adjustment: First, slightly open the acetylene valve to ignite the flame (initially a yellow carburizing flame), then slowly open the oxygen valve.

Observe Flame Changes: When a bluish-white inner flame appears about 10-12mm outside the flame core, and the flame outline is clear, it is a neutral flame.

Fine Adjustment: Fine-tune the gas ratio through the torch valves to ensure the cutting oxygen jet is a uniform cylindrical shape. If the flame emits black smoke, increase the oxygen; if the outer flame is too bright and shortened, decrease the oxygen. CNC equipment can automatically control the gas valves through the "test flame" function, but the cutting oxygen pressure must be set according to the cutting table to avoid arbitrary adjustments.

Pre-cutting Verification: Check the cutting nozzle for blockages and remove any obstructions using a specialized tool. The cut surface should be visually smooth and free of defects, with a surface roughness of Ra12.5 being ideal.

Adaptation Techniques for Different Plate Materials

Thin Plates (<5mm): Use a low flame, with oxygen slightly less than acetylene to reduce oxidation. Keep the cutting nozzle high above the plate, at a large angle, and cut at a high speed to prevent deformation.

Thick Plates (>200mm): Use a reducing flame for preheating; the flame length should exceed 1/3 of the plate thickness. Keep the cutting nozzle at a 10°~20° angle to the workpiece and move it at a uniform speed (2-5mm) to ensure even heating of the edges.

Special Materials: Flame cutting is prohibited for stainless steel and non-ferrous metals to avoid affecting the plate's properties.