Weld purging is the process of removing an unwanted gas or fluid from a weld joint and welding equipment.
Purging can range from the use of natural products like soapstone to more advanced chemical methods like acid etching. In this blog post, we will discuss how to purge weld using both traditional and chemical methods of purging.
How to Purge Weld
Purging is a necessary process when you are welding. It helps to prevent the formation of slag and other impurities on your weld bead or in your finished product.
Traditional Way Of Purging
Traditional purging involves using soapstone as a heat sink so that slag does not form during welding.
Slag forms when impurities are combined with melted metal or filler material at extremely high temperatures (such as those produced by arc welding). There are steps that you can take to ensure your welded piece is properly purged in a traditional way, including:
Step 1: Clean the Metal
The first step to purging your welded piece is to clean it. This will help enable the soapstone (or other heat sink material) to absorb excess slag and impurities from around the weld bead during welding so that you can achieve a high-quality, finished product.
To accomplish this step, use wire brushes or sandpaper to remove dirt and grime from your metal before applying soapstone as a heat sink medium.
Step 2: Soapstone Application and Burn-Off
After you have cleaned the metal, you will want to apply soapstone as a heat sink. To do this, first warm up your pieces of metal using an acetylene torch or other welding equipment before applying the soapstone.
Apply it at the edge where you began welding and allow it to cool for about 30 seconds; then reapply if necessary until enough soapstone covers your welded piece (but not so much that it causes excess smoke).
Step 3: Welding Your Piece
Once you have applied a sufficient amount of soapstone to your metal, proceed with welding. This will melt the slag and impurities on the metal so that they can be drawn into the soapstone as it melts.
When finished welding, allow your piece to burn off any excess soapstone before quenching it in water or removing it from its heat source.
Chemical Purging Methods of Purge Welding
Chemical purging is also a popular method used to purge weld. The benefit of chemical purging methods is that there are no heat losses like you would experience with traditional purging methods like soapstoning, which means more energy for your finished product.
Additionally, chemicals can be added in precise quantities to make sure they only remove specific impurities while minimizing the degradation of material properties. To do this, here are some steps you can take:
Step 1: Clean the Metal
Just like with traditional purging methods, it is important to clean your metal before chemical purging. When using chemicals as a purge medium, there are certain impurities that will be most effective at removing.
Therefore, you should remove any dirt or grime from the area of your weld so that these impurities do not interfere with chemical purging.
Step 2: Flux Application and Heat Treatment
Once your metal has been cleaned, apply flux (a combination of borax and water) in an even coating over the surface of where you intend to weld.
This could include fillet welding joints between two steel plates if making a signpost outside, for example. Then, heat the area of your weld to a temperature of about 400°F. This will melt any impurities that are on or just below your metal’s surface so that they can be drawn into the flux.
Step 3: Welding Your Pieces
Once you have applied flux, proceed with welding as normal (i.e., preheat if necessary and use soapstone). After completing your welds, allow them to cool until no longer hot before removing all traces of flux using water or another solution. This is important because harmful residues from residual borax could remain after cleaning otherwise.
Chemical purging has many benefits over traditional purging methods like soaps toning. However, one downside is that it requires more precise measurements in order for the chemicals to only remove impurities without damaging material properties.
Now that you know how to purge weld, you can confidently clean and prepare your metal before welding it together. Make sure to follow safety tips to prevent any injuries or accidents. You can also check our post on how to remove welding spatter from glass and how to tack weld aluminum.