Flame Hardening Process: What Makes it Economical for Surface Hardening?

18 April 2018

Process economy is an ideal we chase in heat treatment technology. Masses of fuel and heat are devoured during a hard day’s work inside this manufacturing environment. How does the work retain a cost-efficient edge? Particularly in flame hardening, how do we surface harden a large workpiece while we’re also worrying about an economical processing approach? Well, flame hardening is selective, which means there’s already a frugal system in action.

Flame Hardened Frugality

Talk of affordability occupies the mind of a processing engineer. Certainly, there’s no shortage of techniques. Carburizing processes cook away inside some manufacturing facilities. Meanwhile, another factory has chosen a carbonitriding method. Both techniques have a common factor, the inclusion of a chemical alteration system. The chemicals are diffused, with the metal surface then altering as the furnace fills with gas. Feed systems and gases, they’re efficient but expensive. On the other hand, the flame hardening process doesn’t use chemicals. Mounted on a scanner mechanism, the focused heat source selectively hardens targeted workpiece sections. Gear teeth, for instance, only require hardening on their outer edges, not their entire form.

Dance of the Flame

Most of these facts have been covered in other articles. Flame hardened parts receive focused treatment, and that treatment further reduces costs by reducing post-treatment grinding and finishing. Furthermore, the treated parts don’t experience process distortion, not to the degree found in other surface hardening techniques. Beyond those cost-cutting benefits, there’s the manner in which the flame head discharges its thermal load. Scanning heads move in closely compressed scan lines across large surfaces. Elsewhere, a wheel or vehicle axle is spinning in a special mechanism. The flame is fixed, but the cylindrical piece is rotating at a carefully calculated velocity. In a truly advanced heat treatment station, both methods operate concurrently. The progressive scan is in motion, the part is rotating, and a quench operation immediately follows each stage.

Providing superior wear surfaces, the secret to economical case hardening lays in that three-dimensional control system. The gas and flame head is discharging a measured thermal envelope, one that’s sharply focused. It’s now up to the progressive scan velocity and rotating equipment to regulate the heat. When that head, or parts-moving mechanism, is properly regulated, travel speed combines with output temperature and flame shape to ensure calculated surface hardened depth. More cost-effective than chemical diffusion technology, flame hardened parts come in many shapes and sizes. As long as that selective treatment mechanism can get into the geometry of a workpiece, this is a supremely economical heat treatment solution.

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