Friction Welding is a “solid-state joint process that produces coalescence of materials under compressive force contact of workpieces rotating or moving relative to one another to produce heat and to plastically displace material from the faying surfaces.”*
Used in the United States and Europe for more than 50 years, friction welding has been a well-kept secret. Sometimes it is referred to as spin weld or spin welding, because one part is rotated in process. As customers learn and understand the process, benefits become clear.
Reduce material consumption and shorten machine cycle time
The ability to create near-net shape blanks offers manufacturers an opportunity to reduce material consumption and shorten machining cycle time. Joining dissimilar metals like stainless steel alloys to other metals provides unique design flexibility.
Friction Welding Methods
Computer controlled Direct-Drive Rotary Friction Welding: provides continuous speed control through the cycle, and stops according to a computer parameter developed specific to the part.
Inertia Friction Welding: this uses part rotation under pressure to heat the fraying surfaces.
- This uses a flywheel to generate the rotational momentum in the part-holding chuck.
- The flywheel driven chuck spins until it stops when the weld zone seizes. This inertia method is also sometimes described by the colloquial term, spin weld.
* The Friction Welding Process was formally defined by the AWS on Oct 15, 2008 in the Recommended Practices AWS C6.1 for the Welding Industry.
Is the weld process computer controlled for repeatability and quality assurance?
Yes. Hand-set manual controls can introduce variables into the process that prevent repeatability from lot to lot over time.
Machine Set Up
- Parts are loaded into the friction welding equipment.
- Experienced operators setup the machine for each job to control the 3-step process with a series of parameters unique to each job: Rotational Speed, Axial Force and Length. You can see images of friction welding’s three stages in the photos below.
- After the three parameters are established, they’re recorded and stored for use throughout the entire project.
Using this quality approach ensures repeatable consistency for each additional weld produced on the machine. The results are represented visually on the Playback Graph shown below the three steps.
One component is positioned in a stationary clamp. The second part is positioned in the rotating spindle, which is then brought up to a pre-defined rotational speed (blue line on graph). At the right moment, pre-defined axial force (red line on graph) is applied.
These conditions are maintained for a predetermined time. A second step of pressure is applied (second step on red line on graph at about 1 seconds in this example) until the desired temperatures and material conditions exist. It’s during this stage that the two materials are plasticized (become malleable). The green line signifies measurement of “length loss” and triggers the stopping point when the part reaches planned Overall Length.
Rotational speed is stopped. Then increased axial force (third step in the red line at 9.5 seconds) is applied to create “forge pressure” for another predetermined time – completing the weld. This provides molecular bonding and grain refinement through the weld zone.