Inertia friction welding, or spin welding, is an eco-friendly, metal joining process used to bond similar or dissimilar metals together. This process is accomplished without the use of filler metals, fluxes, or shielding gases like conventional welding. It also minimizes energy consumption, produces no fumes, gases, smoke, or waste. Initially, friction welded components were, as a rule, circular. With today’s technologies, the applications, components, material types, sizes and shapes that can be joined are endless. Spinweld offers – direct-drive friction welding and inertia friction welding. (See Advantages of Friction Welding)
Friction welding, commonly known as spin welding, is a controlled machining process for joining SIMILAR or DISSIMILAR (Bi-Metal) combinations of materials. The ultimate goal of spin welding is to have a 100% weld throughout the full joint interface. This means, given suitable materials, the weld union or interface strength is equal in strength to that of the parent metals. This process yields a high-strength, low-stress, small heat-affected zone (HAZ) weld with no porosity, and in most cases, eliminates the need for costly pre-machining or costly tooling. You may have heard of this friction welding process or welding interface referred to as spinning, welding, fusing, bonding, marring, or union. Friction welding is a well-established process developed in the 1890’s and is widely accepted throughout many different industries and global markets.
A simple explanation defines the friction welding process as rotating one component against a fixed component under pressure. This action efficiently prepares and cleans the weld interface, and generates sufficient low temperature, frictional heat, for at least one of the materials to become plastic at the joint interface. This “Solid State” (non-melting), joining process produces a merging between the materials via the heat developed by the induced rubbing motion, and the applied load between the two surfaces.
At this point, rotation stops rapidly and the components are forged together.
What is the difference between direct drive and inertia friction welding?
Both direct drive and inertia friction welding provide a superior union of materials by rotating one component against a fixed component under pressure. The difference is the energy source, RPMs and timing/distance as pressure is applied.
Direct Drive Friction Welding
Energy is provided by an electric motor directly connected to the machine spindle. This energy source is infinite with respect to time and is applied to the interfacing materials until the proper total heat or plastatic state is obtained. Speed is held constant for a selected time and/or distance, as pressure is varied. When the desired plastatic state is achieved, the rotating component is stopped and a forging load is applied to complete the joining process, making the parts as one. Greater total heat is achievable over inertia friction welding which may slow the rate of cooling resulting in slightly longer cycle times.
Inertia Friction Welding
Energy is provided by the machine’s kinetic energy that is stored in a rotating system or mass. The energy available in a stored energy system is finite. This requires specific parameters of mass/weight, speed, and pressure to meet the requirements of the weld union. When the desired rotational speed is achieved, kinetic energy is transferred into the freely rotating part. Constant forge pressure is applied until a plastic state is reached. Rotation stops due to controlled pressure as the desired total displacement length of material (upset) is met. Rotational speeds are normally higher than direct drive friction welding. The majority of the total displacement comes at the very end of the weld cycle as compared to being spread out over the middle to the end of the cycle.
Spinweld Friction Welding, CNC Machining & Turn-key Solution
- Step 1: One component is loaded into a rotational “head” chuck and the other component is loaded into a fixed “tail” stock. The head is accelerated to a preset speed.
- Step 2: The rotating “head” component or the fixed “tail” stock (depending on machine style and desired pressure) is then forced against the remaining component.
- Step 3: Rotation stops and forge pressure completes the welding cycle. The result is a clean, strong, and full interface weld every time.
- Step 4: CNC machining is then performed for removal of difficult or hardened flash (if desired), rough machining, cell optimization, or for finish machining to provide a completed part. Additionally, other value-added services are offered to finish the project to exact print specifications.
Friction Welding Advantages
- Low-cost manufacturing alternative and machining process.
- Weld complex shapes or circular shapes at all stages of components: finished, semi-finished, and raw stock
- Optimizes material usage; near net-shapes or for cost containment
- Solution-based manufacturing and machining process to reduce material cost, reduce tooling cost, reduce R&D cost, reduce weight, and/or reduce machining cost.
- Solution-based manufacturing and machining process to increase quality, increase manufacturing throughput, and/or increase speed-to-market
- Readily join combinations of steels & non-ferrous metals
- Dissimilar metal combinations can be joined
- Powder metal components can be welded to other powder metals, forgings, casting or wrought materials
- High production rates
- Joint strength equal to or greater than the parent metal
- Self-cleaning action reduces or eliminates surface prep time and cost
- Joint preparation is not critical; machined, saw cut, and even sheared surfaces are weldable
- The integrity of welded joints is very reliable
- Cost reduction for complex forgings/castings
- Highly precise & repeatable process
- 1OO% of metal-to-metal joints yield parent metal properties
- Low welding stress
- Components can be stronger & lighter than what other welding methods yield
- Environmentally friendly, no fumes produced
- Simplification of component design
- Substitution of costly with less costly materials
- No filler metals, fluxes, or protective gases needed
- Can choose manual loading or optional automated loading
- Joints can withstand high-temperature variations
- Reduced scrap parts rate
- Reduced HAZ (heat affected zone)
- And more…