Wave springs and disc springs: applications and manufacture

A wave spring is an annular elastic element with crests and troughs formed in a metal ring; a multilayer wave spring is built from many single-layer springs stacked together. Wave springs are used in electric motors, textile machinery, general machinery manufacturing, petrochemical, hydraulic and automotive applications. Installed at nominal size in a bearing chamber or bore, they need little space, damp noise and vibration, and suit large and small strokes.

Space and load advantages

At a similar load a wave spring saves at least half the space of an ordinary coil compression spring, reducing equipment volume and cross-section at a comparable cost, and is ideal where axial space is limited. Different load requirements can be met by changing the material thickness and width, or by stacking two or three overlapping wave springs.

Disc spring classes and manufacture

A disc spring, also known as a disc spring washer or belleville washer, is a conical, disc-shaped spring that carries load along its axis. Disc springs are divided into three classes by thickness: Type 1, below 1.25 mm; Type 2, 1.25 mm to 6 mm; and Type 3, 6 mm to 14 mm. Each class has its own process route. Type 1: stamp forming, quenching, tempering, polishing, strong-pressure treatment, surface treatment, inspection. Type 2: punched ring blank, grinding both sides, turning and chamfering inner and outer diameters, conical cold forming, high-temperature normalizing, heat treatment, shot peening, strong pressure, surface treatment, inspection. Type 3: round-steel blanking, forged cone, turning to size, high-temperature normalizing, quenching, tempering, shot-peening strengthening, strong surface treatment, inspection.

Type 1 stamping needs no machining allowance, while Type 2 and Type 3 blanks generally require about 4 mm of allowance. Forming in a die holds concentricity; shot peening raises fatigue strength, strong-pressure treatment reduces creep and extends life, and surface treatment prevents corrosion failure.

Surface treatments for disc springs

Bluing (blackening) heats the steel in air or in an oxidizing solution to form a thin oxide film. Electrophoresis removes oil, rust spots and scale that would impair film adhesion. Phosphating forms a stable phosphate film with phosphoric acid or phosphate salts, typically on carbon-steel coil spring washers. Electroplating deposits a metal or alloy by electrolysis, most commonly zinc or nickel. Mechanical plating deposits metal powder by adsorption and mechanical collision at room temperature and pressure; ordinary disc washers are mechanically galvanized.

Function and applications

A disc spring is tapered in the axial direction and stores potential energy under the bolt when loaded. On relaxation it releases part of that energy to keep flange connections under the pressure the seal requires. Stress distribution is uniform from inside to outside, giving a low-stroke, high-compensation-force effect. Disc springs are used alone or stacked in series or parallel, carrying static and dynamic loads along the axis on the upper inner and lower outer edges; they deform until flat, storing energy that converts automatically into sealing force where needed, reducing the additional compression and retightening otherwise required for gaskets and packing.

High-temperature disc springs suit hot working environments and offer excellent corrosion resistance. They are used in high-temperature valves and for preloading pipe-bolt and anchor-bolt connections, and widely in power plants, petrochemical plants and steel mills on pipe flanges, valves, heat exchangers and electric furnaces.

Advantages of disc springs

Disc (butterfly) springs are an essential part of modern industrial production. They offer good wear resistance and long service life, as the material is carefully selected and repeatedly tested during manufacture, along with good high-temperature resistance and strong environmental adaptability.