Vacuum Furnace Quenching System: The Role of Gas Quenching in Heat Treatment

06 August 2019

Using gaseous quenching mediums, new and improved cooling models are rippling through the heat treatment sector. However, not just any old cloud of gas is going to suit this role. For one thing, an inert element is mandatory. The synthetic atmosphere can’t be influenced by the heat, nor can an alloy workpiece be somehow altered by the gaseous substance, at least not beyond the heat treatment procedure’s desired effects.

Key Properties of Gas Quenching Mediums

If an inert gaseous atmosphere is to have any effect on a heat-soaked metal part, it needs to be dense and thick. Usually, the gas in question is delivered as a high-pressure mass. Referred to as High-Pressure Gas Quenching, the substance is propelled into a vacuum-sealed furnace. From here, convection currents and heat transference laws quickly cool a hardened metal item. Before proceeding any further, those inert gaseous mediums deserve a mention. They are, in order of preference, nitrogen, helium, argon and hydrogen. Argon yields poor quenching results, while hydrogen combusts when it comes into contact with oxygen.

The Benefits of Gas Quenching

So, hydrogen is a safety risk. Argon isn’t a good option either. Sticking with a high-pressure stream of nitrogen or helium, a vacuum furnace, one that’s equipped with a quenching chamber, receives its velocity-delivered stream of quenching gas. Of great benefit here, the gas cooling action doesn’t cause the metal to deform or experience dimensional changes. That’s a feature that liquid quenching can’t duplicate, by the way. Also, the process is significantly accelerated, so the hardened workpiece receives a more responsively applied cooling profile. Provided with perfectly timed quenching notches, high-pressure gas cooling systems are more governable than their oil or water facilitated quenching counterparts.

A Solution to a Martensite-Deprived Processing Conundrum

Industry-essential martensitic steels are viewed as structurally desirable alloys. These super-hard alloys are found in automobile components, crane pins and all sort fields, applications that require tough material backbones. Unfortunately, austenitic steel doesn’t readily transform into martensite, not unless the heat-treated alloy is rapidly quenched. Right there, that’s a job for a powerful, highly pressurized gas quenching system.

There’s no dried liquid runoff on a gas-cooled steel part, so there are no strange coatings to clean away after the process has completed. Liquid quenched parts tend to produce residues, so they don’t exit a vacuum furnace clean. Using gas quenching systems, a clean and dimensionally unchanged steel part slides out of the furnace after the heat treatment work finishes. No material deformation occurs, nor there are any weird coatings left over afterwards. Best of all, the gas-driven rapid cooling effect transforms heated austenitic structures into quenched martensite, which is super-hard and corrosion-resistant.

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