But, it also changes the important parameters of the process and brings a few additional variables into the process. There are several important factors about MIG welding that you need to be careful about. One such important factor is gas pressure, as the process heavily relies on gas. In this guide, we will discuss the importance of gas pressure in the MIG welding procedure and how you can calibrate the machine to offer the right gas pressure. We will also go over some standard gas flow rate values for common materials and also talk about the minimum and maximum gas flow rate requirements regarding various jobs. So make sure you don’t miss that out.
Gas Pressure Required For MIG Welding
Apart from ensuring whether you have the right nozzle or wire feed speed for the job, you also have to pay attention to the suitable gas pressure setting and make sure that you have selected the right pressure level before you start the process. The gas pressure is a crucial factor that deals with the reliability as well as the quality of the weld obtained via the MIG welding process. The best method is to set up gas pressure based on the material of the workpiece that you are working with. It will give you the best results if you simply refer to a reference chart for the workpiece material and set up the gas pressure accordingly. If the weld bead is excessively strong or weak, it won’t be able to join the parts efficiently. Apart from a damaged weld bead, you could also end up with a damaged workpiece. To avoid that, almost all MIG welders come with a pressure regulator gauge. In almost all regions, the pressure regulator gauge would have readings in pounds per square inch or PSI unit. The ideal pressure range for most standard MIG welding jobs is between 3 to 8 PSI. However, this range is pretty wide and you need to calibrate the pressure levels further to get the perfect results.
How To Control The Gas Flow Rate?
Setting up the gas flow rate on a MIG welder is quite easy. All gas regulators come with a valve that allows you to modify the flow rate allowed via the regulator. Thus, you can change the output gas flow rate directly by using this valve. In the case of a standard MIG welder gas regulator, you will find 2 gauges. Here, one gauge represents the gas pressure in the PSI unit whereas the other shows the gas flow rate. The gas flow rate is usually displayed in CFH or cubic feet per hour unit. Once you start releasing the gas from the valve, the regulator pointer will move according to the gas flow rate and will show the gas flow rate on the regulator. On some MIG welders, you would only get a single regulator for the gas bottle pressure. These are high-end options that feature a special vertical plastic chamber to represent the gas flow rate instead of a regulator. The chamber also has similar inscriptions in CFH like the gas flow regulator. But instead of a needle, there will be a small ball inside the chamber that will rise according to the pressure of the gas, representing the gas flow rate.
Suitable Flow Rate System
A lot of beginner welders probably get confused between CFH and LPM since these are 2 commonly available gas flow rate measurement systems. Even though the majority of pressure regulators have readings in CFH units, there are many manufacturers that prefer LPM or liters per minute measurement systems for gas flow rate. In comparison, we will recommend going with the standard CFH of cubic feet per hour regulators. Almost all regional welding guides and professionals use imperial measurement systems. The same goes for professional workshops also prefer the imperial system for ease of communication. So, it would be better to get a MIG welder that features a pressure regulator with a CFH flow rate measurement system. You can also convert the LPM readings to CFH readings, but it would be time-consuming and might produce calculation errors.
Are All Shielding Gasses The Same?
To put it simply, no. Not all shielding gasses are the same and all gasses are supposed to be measured differently based on their chemical and physical properties. Some shielding gasses are heavier, or rather denser than others. Therefore, you will have to check the regulator and make sure that the pressure reading is correct according to the shielding gas. For example, if you are using Argon as the shielding gas for welding and using a regulator which was previously calibrated for the Helium gas bottle, the readings will be inaccurate and you won’t get desirable welding results due to inaccurate gas pressure and flow rate. When it comes to MIG welding, it is not much of an issue since carbon dioxide and Argon are that far apart in terms of chemical or physical properties. Still, you should use a regulator designed for the specific gas to get accurate flow readings which is crucial for a flawless welding job.
Special Regulators For 100% CO2 Tanks
If you are using pure 100% carbon dioxide as a shielding gas, you need to be even more careful about the pressure regulator or flow meter. Standard gas regulators or flow meters may freeze while they are connected to pure 100% carbon dioxide due to the low gas temperature. It is caused by the gas’ expansion which drastically reduces its temperature. So, it would be ideal to use a special regulator specifically designed for carbon dioxide. Even if you have not faced a complete regulator freeze yet, you will start to notice a frost build-up overtime on the regulator. Another problem with standard regulators is the type of connector. While a carbon dioxide gas tank uses a CGA-320 connector, most other standard gas bottles use CGA-580 connectors. Thus, using a different connector pressure regulator or flow meter can cause gas leaks. If you still want to use the regulator, you can get a CGA-320 to CGA-580 adapter and then safely connect the device to the gas tank.
Correct MIG Gas Flow Rate Based On Material
Since there are a few metals that are mostly used for the MIG welding process, it would be right to learn the correct gas flow rate according to the material and then use the same for your process. The most commonly used metals for MIG welding are Mild Steel, Stainless Steel, and Aluminum. Each of these metals needs a different gas flow rate based on the nozzle diameter, wire feed speed, and the physical properties of the metal. Here’s what you need to know about different gas flow rates based on the material type.
1. Steel
Steel or mild steel is very easy to weld. So if you are welding on mild steel using either pure carbon dioxide or other inert gasses, you should keep the gas flow rate between 10 to 15 CFH. And if you start noticing porosity or other welding defects, you should increase the flow rate up to 20 or 30 CFH. The flow rate of your machine should be based on your welding speed. For higher welding speed, the gas flow rate should also be high enough to match the speed. A higher gas flow rate is also crucial to generate a wider welding bead since the shielding gas coverage would be insufficient with a lower gas flow rate. Based on the nozzle size, if the nozzle diameter is larger than 0.5 inch, the right gas flow rate should be between 22 to 55 CFH. But, that wouldn’t be the case for many users since standard MIG welding gun nozzles have a 0.5-inch nozzle, if not smaller.
2. Stainless Steel
Stainless steel on the other hand is more difficult to weld, even compared to mild steel. There are many different types of stainless steel available on the market which would produce different welding results on different heat levels. So, the gas shielding also affects differently for different stainless steels, and thus the gas flow rate which is responsible for the gas shielding. When you are starting with stainless steel, you should start around 20 to 25 CFH gas flow rate and keep an eye on the results to manage the gas flow rate as you move. If you start noticing porosity with the weld, you can start increasing the flow rate until you find the right level. On the other hand, if you are using Helium instead of pure carbon dioxide, you will need a much higher gas flow rate. It is because Helium is significantly lighter than carbon dioxide and there won’t be enough Helium available around the flame to create sufficient coverage without the right gas flow rate. It could also result in various welding defects such as porosity. So, make sure you start with a higher gas flow rate when you are using Helium with stainless steel.
3. Aluminum
Aluminum is a great conductor of heat and it can dissipate heat very quickly. Therefore, you will need a faster travel speed with a higher gas flow rate, around 30 CFH to be approximate. Also, you will have to use a completely inert gas while welding Aluminum, and the best choice would be Argon. You can also add Helium if you are working with a rather thicker workpiece made up of Aluminum. Even though Helium improves the heat transfer rate and penetration of the material, it is still lighter than Argon. Therefore, you will have to increase the gas flow rate even higher when working with a mixture of Argon and Helium. The flow rate should be based on the added helium percentage with Argon. For example, if you are mixing 75% Helium with 25% Argon, you will need about 50 CFH gas flow rate.
What Should Be The Minimum Gas Flow Rate?
The minimum gas flow rate also depends upon the material that you are working with. For Aluminum, the minimum gas flow rate required is 20 CFH. So if your MIG welder does not offer 20 CFH or above gas flow rate, it would not be a good option for Aluminum welding. On the other hand, up to 10 CFH gas flow rate is enough to obtain a reliable weld on mild steel. The minimum required flow rate also changes based on the surrounding environment. If you are performing the welding outside, you will have to use a higher flow rate since the effect of the surrounding wind is quite drastic on the welding bead. However, you can also shield the welding area from external wind and perform it with a moderate gas flow rate without any severe effect on the process. To be on the safe side, make sure that the gas flow rate is always higher than or equal to 15 to 15 CFH. While you may still notice welding defects like porosity, the chances of occurrence for such a defect is quite low with this minimum gas flow rate. And apart from that, you will have to increase the gas flow rate based on the width of the welding bead as well as the welding speed.
What Should Be The Maximum Gas Flow Rate?
Just like there is a limit on what the minimum gas flow rate should be, there is also a limit on the maximum gas flow rate for MIG welding that you need to follow if you wish to avoid welding defects. If the gas flow rate is overly strong, it can create turbulence while welding, causing the shielding gas to break and create contact with the surrounding atmosphere as well as contaminants. The maximum flow rate depends on the MIG welder nozzle size. Due to the venturi effect, the surrounding air gets trapped inside the shielding gas coverage in case of an excessively high gas flow rate. But, if too much surrounding air is mixed with the shielding gas, it would result in surface or subsurface porosity due to the entrapment of air bubbles, causing the weld bead to be brittle and weak. Here’s a simple reference table to understand the minimum or maximum gas flow rate suitable for your job. In this table, we have compared the gas flow rate according to the nozzle diameter so that you can choose the exact values and test the welds before making any changes.
Conclusion
That’s pretty much it. This is all you need to know about gas pressure and flow rate levels regarding MIG welding. The main reason behind achieving the right gas pressure and gas flow rate levels is obtaining the perfect gas shielding coverage around the welding area to prevent its contact with the surrounding air as well as with the contaminants present in the air. You cannot use very low or very high gas flow rates since you will face welding defects in both cases. Instead, you can simply go through our guide and ensure that you are using the values based on the information provided here. Source: MIG Welding Gas Pressure Settings Comment * Name * Email * Website
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