Nickel alloy 718 tubing is one of many alloys with great properties that can make it applicable in many environments where heat will be involved. It is commonly used in offshore oil mining because of its corrosion resistance. One challenge new fabricators have when dealing with it however is welding.
Welders who have not worked with stainless steel before can make a few mistakes when working with nickel alloy 718 tubing. We have compiled some of the common mistakes made.
Using the Wrong Tools
It may be a surprise to some metalworkers that what they consider the right tools when working with carbon steel are the wrong tools when it comes to stainless steel. The thing about stainless steel is that it can be contaminated when you use the same tools for carbon steel. Particles from the ordinary steel can be introduced to the tubing and when you finally apply it, you realize it begins corroding prematurely.
Applying too Much Heat
Yes, alloys can withstand high temperatures, but at the same time, they have different levels at which they begin to get deformed. Some welders may simply believe because they used a particular amount of heat on one metal, they can do the same for another. This is a big mistake to make when dealing with stainless steel and it can result in the steel getting deformed in the process. The worst result of applying too much heat is depletion of the chromium layer which is essential for corrosion resistance. If this happens the steel will eventually lose its most favorable quality.
Using the Wrong Filler Metal
Stainless steel has different grades and because of that, the filler metal used to weld one grade may not work on another. Some welders do not take the time to find out what grade they are working on and because of that, they use the wrong filler which ends up in a waste of material as well as a poorly done job. It is important to always establish what grade of stainless steel you are working on and what would be the best approach.
Using the Wrong Amount of Shielding Gas
This is a mistake that can go unnoticed as the steel fabrication leaves the workshop because it may look just fine. This deception is why this mistake is made over and over until the clients start complaining. The mixture of oxygen and carbon dioxide used when welding carbon steel is not appropriate for stainless steel. Too much of it and you will have a fabrication that will corrode in just a few weeks. It may not look like you have made a mistake but this is just as bad as using too much heat.
This is a general mistake when welding. Some welders may forget or ignore safety guidelines when welding and that can result in an accident.
Before you begin welding stainless steel, ensure that you know what grade you are working with and what is the best approach to working on it. Never try to apply the same procedure used for carbon steel to stainless steel. It takes a bit of adjustment to get used to working with stainless steel but with practice, you can become perfect.