How to Friction Weld Thin-wall Tubes for Pressure Containment

Posted May 18, 2015 In Manufacturing Efficiency, Strength of Bond

Manufacturing Challenge for Metal Part Fabricators

Several years ago, an industrial manufacturer of electric utility components was experiencing fallout with its cylinder fabrication process. Five employees produced sealed cylinders on the plant floor by hand welding thin-wall tubes to solid caps. The variation in quality led to persistent pressure test failures. Order volume was increasing, and that led to an increasing failure rate correlated to a rise in working hours to meet the demand.

Silencer Tube to Machined End Cap Friction Welded

Cylinders made from thin-wall tubes

The manufacturer launched a plan to research alternative methods for fabricating the cylinders using two materials featured in the company’s product design. One type was made from 1026 D.O.M. steel tube joined to a 1018 base. The other type was made from 304L stainless steel tube joined to a 304L stainless steel base. Options included upgrades to the existing operation compared to various outsourced methods.

Project Requirements

The cylinders had to pass an internal air pressure test to meet proprietary design requirements. If weld joints were to be used in fabrication, a full strength, full penetration bond would be necessary. Carving the cylinders out of solid material would have been price prohibitive, so a method to join the tubes to caps was needed.

Thinwall Tube to Solid Friction Welded

Cross section view of tube wall and end-cap prototype

Research indicated that friction welding would provide a full strength, full penetration solution with the added benefit of controlled repeatability. The right friction welding equipment would include computer controls with playback graph recording to assure the application of identical weld parameters from one assembly to the next. This would create parts with the full measure of friction welding strength.

This manufacturer evaluated the capital expense to implement its own friction welding cell but found that although volumes were growing, volumes did not support the capital expense and educational undertaking. The sourcing team decided to locate a sub-contract provider with the expertise and correct equipment to provide the fabrication service. A six-month timeline was given to test output and implement a sourcing solution.

Fabrication Solution Delivered

Cylinder Petal Bend Test

This “Petal” bend test shows the strength of the friction welded cylinder joint.

Our production team proposed a computer-controlled friction welding solution to assure repeatability of weld parameters to eliminate the fallout problem in the manufacturer’s plant. This took the operator variables out of the weld interface. The product development plan provided samples of the full strength, full penetration welded cylinder prototypes for approval within the six-month time frame. This allowed the production change to take place on schedule.

The friction welded cylinders are now standard procedure at the company. Quality benchmarks have been met for several years running. Furthermore, plant floor space and employees were re-allocated to higher value internal applications.