Aerospace is the last place any welder or metallurgist would expect to come across stainless steel. Nevertheless, what is set to be humanity’s first interstellar space ship—SpaceX’s Starship—is designed with a hull of stainless steel due to the metal’s ability to retain strength under extremes of heat and cold. The Airforce’s XB70 Valkyrie bomber made heavy use of stainless steel in its wings and fuselage for similar reasons. That ability to resist extremes of heat and cold, along with stainless steel’s corrosion resistance and reasonable price compared to alternative materials, has made stainless steel the first choice for industries from aerospace to food production.
However, stainless steel is not the easiest material to weld while still preserving the alloy’s full range of strength and corrosion resistance. Stainless steel’s special properties can be lost when welded with the incorrect amperage settings, inadequate shielding gas, or incorrect filler wire. Tungsten inert gas (TIG) arc welding (also known as gas tungsten arc welding or GTAW) is widely considered to provide the highest quality stainless steel welds. Orbital TIG for wire feed stainless steel welding has all of the advantages of TIG while minimizing the disadvantages of more typical manual processes.
The Disadvantages of Wire Feed GTAW
Wire feed TIG welding is something that most welders have dreamed about at some point, as it promises to combine the ease and speed of wire feed gas metal arc welding (GMAW) with the quality and strength of TIG welding. While manual wire feed TIG welders do exist, these machines tend to fall short of their promise.
The following issues prevent manual wire feed TIG from wider use:
- Wire feed TIG does not offer the same precise control that manual TIG welding is famous for. Usually in manual TIG, a filler rod that the welder can help use to guide the molten puddle is used. Changing that to a wire feed gives up some of this control.
- The overall weight of the torch is heavier. Since the wire feed allows a TIG welding machine to perform welds that are longer than the duty cycle most tungsten electrode types and other parts of the weld head are designed for, liquid cooling systems are needed to keep these parts within temperature parameters. These systems add weight to the machine.
- Manual wire feed TIG requires much higher amperages than manual welding with a hand-fed rod. This means that heat levels are higher and there is a limit to how thin a workpiece can be welded using manual wire feed TIG.
- Manual cold wire TIG welding proceeds at approximately the same pace as TIG welding without a wire feed. Cold fill wire cools the weld pool, creating a hard limit to welding speed that a wire feed doesn’t change. Adding filler wire requires an increase in current, but will still usually end up reducing travel speed.
Often, welds created by manually operated wire feed TIG machines don’t have the usual cleanliness of form because of the loss of very fine control over the molten puddle caused by automating the fill wire combined with the fatigue of being able to weld for longer periods. This is especially true for stainless steel welding, as the travel rate for TIG welding stainless steel is very slow, and welder fatigue magnifies issues with weld formation. As a result, those who purchase these machines—generally home hobbyists—often increase the level of automation with mounts and turntables. This reduces fatigue and allows the completion of acceptable, very long TIG welds even for slower processes like TIG welding stainless steel.
When it comes to TIG wire feed stainless steel welding for aviation or power generation applications, automation is likely to be the only way to create a stainless steel weld that meets requirements.
Industries that choose stainless steel to meet more specific and much more exacting criteria turn to more sophisticated ways of automating TIG welding. When it comes to TIG wire feed stainless steel welding for aviation or power generation applications, automation is likely to be the only way to create a stainless steel weld that meets requirements. This is especially true when welding stainless steel pipes or tubing, where automated orbital welding is the only way to complete a continuous stainless steel weld around the whole circumference of the pipe.
Why Choose Orbital TIG Wire Feed Stainless Steel Welding
Stainless steel actually refers to a wide range of iron alloys with a high chromium content that makes them resistant to corrosion. When industries like aerospace or power generation choose a type of stainless steel for a project, they choose it to meet very specific criteria. Stainless steel piping used in the power generation industry is chosen for its ability to channel highly pressurized steam and to maintain that strength over decades in a highly corrosive environment. The stainless steel used for food, beverage, or biopharmaceutical process piping is chosen for its ability to be easily sanitized.
Orbital welding, along with additional prep work like the use of interior purge gas, is often the only way to ensure that a stainless steel wire feed TIG weld can meet requirements.
The welds that join these stainless steel pipes must also meet project requirements. In industries like power generation, where strength over time is required, the wire used for wire feed stainless steel welding must closely match the properties of the alloy being used for the project. The welds themselves and how they are formed must also conform to project specifications. The welds that join food process piping, for instance, must be free of crevices and porosity that can form pockets where microbial growth can occur. Often, the only way to meet these requirements in a timely manner is with orbital TIG wire feed stainless steel welding, which removes variability from the welding process due to welder fatigue and inattention. Orbital welding, along with additional prep work like the use of interior purge gas, is often the only way to ensure that a stainless steel wire feed TIG weld can meet requirements.
Orbital welding also offers ways to speed up the TIG welding process overall and increase welding productivity. High-strength stainless steel applications such as piping for power generation often demand very thick-walled pipe. This can take an extraordinarily long time to weld with manual TIG wire feed stainless steel welding. Automated orbital TIG wire feed stainless steel welding is a faster process due to automation allowing it to proceed continuously. In scenarios where the TIG torch is stationary and the workpiece can be rotated, the wire can be preheated before it enters the molten puddle, speeding up the welding process still further.
Arc Machines, Inc. provides orbital TIG welders for stainless steel welding with available accessories for hot wire TIG and purging of pipes and pressure vessels. For inquiries regarding products, contact sales@arcmachines.com. For service inquiries, contact service@arcmachines.com. Arc Machines welcomes the opportunity to discuss your specific needs. Contact us to arrange a meeting.
