Parachuting after heat treatment
N.B.: The information contained in this sheet comes from reliable sources. Nevertheless, it is provided without any guarantee, express or implied, of its accuracy.
CLEANING BY PARTICLE BLASTING
The purpose is to eliminate from the surface the pollution brought by the treatment, most often oxides (scale) or carbon residues (soot) coming from the atmospheres of treatment or cooking of mineral oils.
The different means are according to the nature of the projected particles:
BLASTING: Spraying of steel or cast iron shot, round or angular (cut wire) by spraying with a lance (hand blasting), by turbines in machines of the type plate, barrel, belt or scales.
Different sizes of shot are selected to achieve an appropriate surface finish.
CORINDONATION (or SANDBLASTING) Angular mineral particles are used as a projectile which have an effective stripping effect, with the risk of creating an unfavorable surface condition.
WET BLASTING: Spraying a mixture of water spray and corundum (without protection, this process leaves surfaces vulnerable to corrosion).
GLASS BALL PROJECTION, the shot is replaced by fine glass balls of small granulometry.
The resulting surface finish is well suited for finished parts.
The blasting machines are either manual (the operator holds the blasting nozzle by means of cuffs that access the box) or automatic, the projectiles being dispersed by a turbine or by nozzles.
CLEANING BY WIPING / POLISHING with the help of barrels or tanks animated by rotational movements and or vibrations, receiving the parts in bulk with polishing or wiping products of various natures: corn cob, walnut husks, crushed apricot stones etc. .
Mechanical or chemical-mechanical grinding: also known as vibratory grinding processes. They consist of repeated rubbing actions intended to deoxidize, polish, deburr or shine bulk parts in the presence of suitable abrasives (round mineral pebbles) and chemical agents in aqueous phase. The operation takes place in a vibrator: a functional tank with rotating and vibrating movements where parts and abrasives work in an aqueous medium. In the case of chemical-mechanical tribofinishing, the mechanical action is combined with a chemical action by means of additives that act simultaneously or separately on the fatty substances, oxides, solid particles and the base metal, with generally passivating actions.
Greasing or application of temporary protection products.
WET SURFACE TREATMENT
It is common to carry out a wet surface treatment on previously treated parts:
- chemical conversion: phosphating, chemical burnishing
- electrolytic deposition: electro-galvanizing, zinc flake...
The difficulties lie in the surface preparation in order to ensure satisfactory adhesion.
The risks lie mainly in the use of acid processes with hydrogen release on high strength steels.
Implementation
Main equipment (furnace, reactor, line, machine...)
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