Tips To Successfully Weld Alloy 20 Pipes
Alloy 20 pipes are made with a combination of several metals, like nickel, copper, chromium, and molybdenum, which make this metal stronger than steel and harder to weld. But, it's not impossible to weld alloy 20 pipes. Keep reading to learn a few tips to make it easier to weld alloy pipes together, or to other materials.
Why Is It So Hard To Weld Alloy 20 Pipes?
Before you learn how to weld alloy pipes, you should first understand what metals this type of pipe is made of. Alloy 20 is a specific combination of nickel, chromium, and molybdenum stainless steel, and sometimes includes other metals like copper. But, it isn't considered to be stainless steel. It's a nickel alloy. This type of pipe is most commonly used for applications that involve sulfuric acid, because of it's high corrosion resistance. Alloy 20 pipe is also found in food, chemical, pharmaceutical and plastics industries.
GTA Welding Alloy Metals
Gas tungsten arc welding, also called GTA welding for short, is often considered to be the most challenging welding method to master. It is more time consuming, but it produces a much stronger weld than other methods. It's a type of arch welding using a non-consumable tungsten electrode and an inert gas like helium or argon. GTA welding is also considered to be a cleaner method of welding because it doesn't produce welding slag, which is bits of metal that chip off welds.
While it may be obvious to more experienced welders, alloy 20 pipe is much stronger than most metal piping. This is why welding alloy 20 metals requires some special considerations when welding it.
1. Go Slow
The most important thing you can do to improve your alloy 20 GTA welding technique is to slow down. Alloy 20 pipes have a lower thermal conductivity than steel and molten alloy weld puddles have a lower viscosity. This means you have to go much slower than if you were welding stainless steel or duplex stainless steel. If you travel too quickly while welding alloy 20 metal, then you have a good chance of having cold lap problems.
2. Don't Compensate By Increasing Weld Current
Some welders will try and compensate for a sluggish puddle by increasing the weld current. This will vaporize the alloying elements and make the metal corrode much quicker, thus greatly reducing the product's self life. You should always use low to moderate heat output and continuously check for excess heat input, which is typically a change of color.
3. Use Argon Gas
If you are welding alloy 20 pipes less than 1/8-inch thick, then use argon gas as your shielding gas. The flow rate should be set at 10 to 20 cubic feet per hour. If you're working with nickel alloy pipes more than 1/8-inch thick, then add helium to your gas because it allows for faster travel speeds. When mixing helium to argon, increase the flow rate by 1 ½ to 3 times in order to compensate for the helium's buoyancy.
4. Use A Gas Lens
Using a gas lens will ensure a smoother and more stable flow of shielding gas, which will then create a far superior gas envelope. Choose one that has the largest cup practical for the project.
5. Clean The Filter Rod
Before you begin to weld, put on some gloves and use isopropyl alcohol to clean the filler rod. Then, make sure all the alcohol has been removed from the filler prior to striking an arch. Also, always make sure the filler you use is made of the higher alloy parent material found in your alloy 20 pipe.
If you have a welding project that requires alloy 20 pipes, contact your local pipe distributor to purchase your pipes. Then follow the tips listed above to make sure you have a perfect GTA weld. If you have any questions, your pipe distributor at a site like http://www.jamesduva.com/ would be happy to answer them for you.