What is Inertia Welding?
It is a solid-state welding technique that forges metal together without causing or requiring a melt product to occur.
Although Inertia/Friction Welding is simple in principle and application, specific situations are many and varied. No attempt is made here to establish criteria for all of them.
Inertia Advantages
Along with its primary advantage of being able to join dissimilar metals, inertia welding also has the following benefits:
Minimum deflections provides excellent concentricity
SAFETY
Interlocked cycle
No hazardous light or spatter – 10:1 safety factor on flywheel design
MINIMUM TEST EQUIPMENT
With Inertia Welder Process, the amount of upset is utilized by the operator as a quality control check. Upset can be measured on the machine during the welding process.
No clutches, no belts
COMPUTED WELD
Since the material factors have been determined, one can easily calculate the amount of flywheel, speed, and pressure to be applied to each diameter
PROVEN PROCESS
Interface Welding has been welding pre-combustion chambers for decades. No field failures.
Model 100 up to 7000 RPM – Model 250 up to 4000 RPM.
Provides optimum surface velocity.
LOWER OPERATING COSTS
Maintenance of tooling and energy costs are higher with flash butt welding
GREATER FLEXIBILITY IN TOOLING
Axial pressure applied thru spindle leaving the machine bed free and uncluttered to tool
Inertia Welding Process
Inertia welding actually forges metal together by utilizing the kinetic energy stored in a flywheel system.
An inertia machine looks much like a conventional shop lathe. In a chuck attached to a flywheel of precisely measured mass, the machine holds one part for welding. A non-rotated chuck that moves axially under hydraulic pressure holds the other.
The machine spins part and flywheel to a predetermined speed, providing the inertia needed for welding, and then releasing them from the drive mechanism. At the same time, hydraulics move the non-spinning part forward, pressing it against the spinning part. Friction heats the contacting surfaces and slows part and flywheel until, having spent the kinetic energy in the flywheel, they stop. Increased hydraulic pressure pushes the heat-softened parts together until they cool, welded together.
Precise rotational speed and hydraulic pressure govern the rate of heat buildup and rate of compression of the joint for process repeatability. Measuring the overall length of the welded parts gives a quick check of process repeatability and indicates weld quality.
Upset material forms a flash that may require removal.
STEP 1
PRE-CONTACT:
One workpiece is fixed in a stationary holding device. The other, clamped in a spindle chuck, usually with attached flywheel, is accelerated rapidly.
STEP 2
FRICTION:
Once the flywheel reaches a predetermined speed, one part is thrust against the other piece. Friction between the parts decelerates the flywheel, converting stored energy to frictional heat – enough to soften, but not melt, faces of the parts.
STEP 3
FORGE:
Just before rotation ceases, the two parts bond. Remaining flywheel energy hot works the metal interface, expelling any impurities or voids and refining grain structure.
STEP 4
COMPLETION:
The weld is complete when the flywheel stops.
FULL VIDEO
STEP 5: Torque, Speed & Upset
A curve of speed, torque and upset (change in workpiece length) during the weld period shows what happens. The curve starts when the two pieces come together, after flywheel acceleration.
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