What is Inertia Welding?

It is a solid-state welding technique that forges metal together without causing or requiring a melt product to occur.

Inertia/Friction Welding, a proven metalworking process developed in the early 60’s by Caterpillar Tractor Co., has gained widespread interest and acceptance. It is a solid state metals joining process capable of joining many metals and combinations of metals including many that the experts say “can’t be joined”. In most metals, the welds produced by the process are full strength and extremely repeatable. Rejects, if any, are basically negligible. Therefore, it has great potential for the designer and manufacturing engineer.
If you are wondering how you can apply inertia/friction welding profitably in your business, click here to review some of the possible product applications.
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:

Excellent Repeatability

Process is machine-controlled so results are highly repeatable

Joint strength

Bond strength is comparable or greater than parent material 

High weld integrity

It is a solid state process that does not suffer from inclusions and gas porosity

Bonds dissimilar metals

Dissimilar metals can be joined with no alloying of the metals

Cost reduction

Replaces costly forging castings
Minimum deflections provides excellent concentricity

Interlocked cycle
No hazardous light or spatter – 10:1 safety factor on flywheel design

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

Since the material factors have been determined, one can easily calculate the amount of flywheel, speed, and pressure to be applied to each diameter

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.

Maintenance of tooling and energy costs are higher with flash butt welding

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.

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