What is Shot Peening?

What is Shot Peening?

It is a type of cold working, usually metal beads (glass or ceramic particles are also used, also known as short balls or pinning balls) are impinged on the surface to undergo plastic deformation and generate compressive residual stresses to change mechanical properties.

In particular, shot peening improves fatigue performance and may produce more than 10 times fatigue performance.

Shot Peening is similar to sandblasting, but it uses shot balls without any surface wear, so less raw material is removed.

Shot pinning has been applied to increase the fatigue life of valve springs but is now used in various applications. Currently used in gears, cams, camshafts, clutch springs, coil springs, rods, gear wheels, turbine blades, etc.

Shot Peening principle

When small particles collide on the metal surface, deformation occurs at the collision site, and when the strength exceeds a certain energy, plastic deformation occurs in which the deformation cannot be restored.

In order to balance the force with the metal interior that is not affected by collision with this deformation layer, a compressive residual stress is generated on the surface, and a tensile residual stress is generated directly below the deformation layer, resulting in an overall equilibrium state.

Shot Peening effect

Short pinning treatment has the effect of increasing fatigue life and surface strength of metal materials, and is widely used as a technology to alleviate tensile residual stress generated in the weld area.

In general, it is known that the oxidation properties of metals are improved through surface treatment by short pinning, which is because the compressive residual stress formed on the metal surface suppresses the elution of metal components, and the reaction with the external medium on the metal surface is reduced.

Shot Peening Machine

A short pinning machine is a device that sprays small particles (pinning balls) with compressed air and causes them to hit the workpiece.

The short pinning machine consists of a blast chamber, a cyclone tank, a blast unit tank, a dust collector, a control panel, a hopper, and an air control system.

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