Over the years, the phrase “to be square” has had negative connotations. In the world of orbital tube welding, nothing could be better.
For autogenous butt-welding of high purity stainless tubing, the squareness of tube ends is critically important for reliably producing repeatable, accurate welds.
“Squareness” is defined as a uniformly flat tube face that is perfectly perpendicular with the centerline of the ID bore.
In this kind of mechanized welding, there is no bevel typically performed by pipe beveling machines for most tube and pipe welding. Instead, the tube ends must be sharp, burr free, and perfectly square to each other in order to achieve an optimal fit-up without any gaps.
“Autogenous” welding means that there will be no additional filler metal introduced into the weld puddle.
Typically, autogenous welding is performed in closed weld heads that provide an oxygen controlled chamber and accurate in-line tube alignment. The typical tubing material used for high-purity tubing systems is small diameter stainless steel with a mirror-bright electro-polished ID surface throughout.
All metal required for an autogenous weld is drawn from the opposing tube faces. The arc power is adjusted to melt the two flatly joined ends into each other and penetrate to precisely reach the tube ID.
Gaps caused by out-of-square ends would draw metal into the weld joint from the tube ends inconsistently. This can lead to lack of fusion that could create minute pockets in the weld joint, excess penetration to create blow-throughs, or weld intrusion into the tube ID. All of these conditions have the potential to introduce physical contamination sources to a high purity tubing system.
The best, proven method to prevent these critical autogenous welding problems is to utilize precision tube squaring tools that guarantee tube ends that are exactly square and burr free. The use of squaring equipment will ensure that you get perfect, high purity weld joints each and every time that are so important for constructing and maintaining the integrity of your ultra-pure tubing systems.
Precision tube cutting and squaring machines face both straight tube and micro-fittings with either collet or saddle mounting systems that are specifically designed to prevent distortion of thin walled high purity tubing while simultaneously compensating for out-of-round conditions.
Additionally, tube squaring equipment offers “Short Perch” clamping which means you get secure mounting with the very short straight lengths usually encountered when working with micro-fittings.
It’s easy to see that when it comes to welding high-purity tubing, it’s good to be square.