A gas nitriding furnace is used to form a very hard surface onto the extrusion dies. Both brand new dies and used dies are nitrided between each use as they get older. This is normally carried out a 535C in an ammonia rich atmosphere. Nitriding is initiated when gaseous ammonia is cracked or “dissociated” using a steel surface as the catalyst at about 480C. Active nitrogen produced during this reaction moves into the surface of the steel and combines with Chromium and other alloy constituents to form their respective “nitrides”. These nitrides are extremely hard (1200Hv to 1500Hv) and increase the average hardness of the surface layers of the steel. As a general rule, the processes will double the (surface) hardness of the original steel.
Thermserve has built and supplied the furnace in association with RGB Metallurgical Ltd, of Burntwood, UK.
Furnace characteristics include PLC/HMI control for fully automatic operation. Mass flow control is incorporated for accurate nitriding potential function; along with an accurate ammonia gas analyser. Multi-programme recipes are included and the furnace is equipped with fast cooling, hydraulic lid and complete dissociation control.
|Water cooled 'O' ring seals||Tight furnace - no sand seal|
|Automatic dissociation control||Best nitriding potential control|
|Automatic pressure control||Less operation intervention|
|Modular basket design||Ease of loading|
|Gas change over panel||Ease of bottle change|
|PLC recipes||Multi recipe storage|
|Larger recirculation fan||Better gas distribution|
|Cooling fan||Faster cycles|