Heat treatment and casting are the salient processes in Steel making. Heat is a part of the process from the point when raw material is washed till the final outcome is moulded to a desired shape. If casting is given a rating of 3 points on a scale of 5, Heat treatment in the entire manufacturing cycle has to be given a full 5 out of 5. But, generating heat was never at an easy cost. The Global Steel Industry has been gradually improving their methods of heating the substance. Red hot furnaces use a lot of fuel and try to add some pollution agents in both air and water media. Air and water treatment has hence, been an integral part of Steel making.
Apart from pollution control, heat distribution and outcome quality are keen topics for steel industry experts to be answered. Heat treatment process improvement has been in discourse and evolution from about the last decade. Use of graphite material in heat crucibles, automated & low pressure carburizing, pack carburizing and vaccum heat treating are all topics of recent interest for steel process innovators. Subsiding reinforced steel making sector, the other steel sector which demanded a more efficient and robust outcome in automotive components manufacturing.
Gear shafts in particular, demand increased strength, fatigue resistance and low surface hardness. To fulfill these qualities the heat treatment procedure which has been under gradual development evolved into a novel process named as pack-carburising. In the recent past, Limavady Gear Company, Northern Ireland became the first company to test pack carburising in order to reduce manufacturing distortions in the gears and shafts produced. This latest process used carbon on component’s surface before the routine heating and cooling procedure is performed.
The results explored new challenges as the method produced different results for same material in several tests, hence, proving unpredictable. Yet, achieving the desired quality was a point of delight for several automotive metallurgy partisans. In fact, the trend of heat treatment process improvement has been in action since a couple of years ago, in automotive industry component making. The topic is in discussion at several top-notch Steel Industry events since then. Russia’s Heat Treatment 2011 is one such industry gathering where Automotive Metallurgy specialists around the globe exchange technological insights for the past year.
To wrap up the issue of Limavady Gear Company’s latest trial, involvement of InterTrade Ireland’s “Fusion” Programme and ITT Dublin has to be adverted. The trial of pack carburising at Limavady was funded by InterTrade Ireland and collaborative involvement of Mechanical Engineering Department at Institute of Technology Tallaght, Dublin.
Another heat treatment named Austempering process was introduced by Michigan based Applied Process Inc. In the process material is heated to “red heat” in a controlled atmosphere, but, quenching is done in a bath of molten salt maintaining the temperature at 450°F (232°C) to 750°F (399°C). This process addressed the non-uniform heat phase transformation during quenching.
