In welding, we usually do not directly set and monitor the pressure of CO ₂, but focus more on and control the flow rate.
This is because the pressure during transportation will vary due to the length of the pipeline and the number of joints, while the flow rate directly determines whether the amount of gas reaching the welding area is sufficient to form effective protection.
Here is a detailed explanation and the parameters you need to set:
Core concept: Flow vs. Pressure
Flow rate: The unit is liters per minute (L/min or LPM). This indicates how much protective gas flows out of the welding gun every minute, forming a gas shield to protect the molten pool. This is the core parameter that we need to set and monitor.
Pressure: The unit is megapascals (MPa) or bars (Bar). This refers to the pressure of gas in the pipeline.
Why is traffic more important? Even if the outlet pressure setting of the pressure reducer is the same, if the gas pipe is long, bent, or leaking, the gas pressure reaching the welding gun nozzle will decrease, and the flow rate will also decrease, resulting in poor protection effect. Therefore, directly monitoring and setting traffic is the most reliable method.
What does the numerical value represent
When the bottle is full: the pressure is about 5-7 MPa (about 50-70 kgf/cm2). This pressure will vary with the ambient temperature.
Pressure drop: With use, the pressure inside the bottle will gradually decrease.
Important reminder: This pressure value does not represent the supply pressure, but only represents how much gas is left in the cylinder. When the pressure drops below 1 MPa, it should be considered to replace the gas cylinder with a new one, otherwise the flow rate will be unstable.
2. Output pressure/flow rate (displayed on low pressure gauge)
What is this: The small range gauge on the pressure regulator (usually 0-0.6 MPa or 0-4 Bar), which either displays the output pressure or directly displays the flow rate (float flowmeter).
How to set:
If you are using a pressure reducer with a flow meter (with a float in the glass tube):
You can directly rotate the knob to adjust the top of the float to the flow scale line you need. For example, adjust to 15 L/min.
At this point, the pressure regulator will automatically maintain a stable output pressure (usually between 0.2-0.4 MPa) to ensure this flow rate. You don’t need to worry about the specific pressure value, just make sure the flow rate is correct.
If you are using a simple pressure regulator with only a pressure gauge:
You need to rotate the knob to set the output pressure at a fixed value, such as 0.3 MPa.