Zirconium Cutting And Welding Preparation And Welding Process

1. Cutting and Welding Preparation

Zirconium can be cut by machining, cold sawing, hack sawing, friction sawing, shearing, abrasive cutting, plasma cutting, oxygen cutting, laser and water jet cutting. Surfaces are not subject to thermal contamination during machining, sawing, shearing and water jet processes.

While oxygen or plasma cutting can be used for rough cutting, both methods require removal of at least 1/16" (1.5 mm) of material from the lowest point of the cut surface (either by machining or grinding) to ensure that all metal is contaminated The cutting process is removed. For example, for metal cuts 1/2 to 1 inch thick, the total cut allowance may be as high as 3/8 inch.

Grinding of zirconium usually involves the use of specialized alumina or silicon carbide grinding wheels. In these applications, it is important to protect adjacent zirconium surfaces and the surrounding environment from abrasive sparks, which are hot enough to pierce gas hoses and are sure to start a fire if they go directly into flammable debris.

During grinding or sanding, a rotary or traction file should be used on the grinding surface to remove abrasive particles that may be present on the joint surface. Likewise, filing or machine grinding the cut surface to remove abrasive grains and areas of minor contamination caused by localized heating. Abrasive water jet cutting is another suitable process for zirconium. Cut surfaces of any profile allow for economical production of part configurations that would be too expensive to produce by machining. Lower cutting speeds produce smooth surfaces and largely eliminate post-processing.

Abrasives can get trapped in overly rough surfaces, and abrasive grains can even stick to smooth cutting surfaces, so be sure to do any further work on any surfaces you're welding on, at least spinning or pulling files.

2. Welding process

The most commonly used zirconium welding process is GTAW. Manual GTAW allows all-position welding to any configuration that the welding torch has access to. Auto GTAW is usually limited to a flat or horizontal position. Seam welders with copper support bars and continuous compactors using copper bars are common for direct headers. Tube-to-tube sheet and small tube butt welds using automated orbital GTAW equipment are also common.

PAW is typically used for single-run welds prepared using automated equipment, copper backing, and square butt welds up to about 3/8" (9mm) thick. Typically, GTAW overlay channels are used to correct underfill, while the root side may require cosmetic fusion channels or mechanical removal of excess leakage.

For repetitive welding of heavy sections, a high current process such as keyhole GTAW should be considered. Electron beam and laser welding are also suitable.