NADCA
Beta Heat Treatment
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Heat Treatment to NADCA requirements

As any heat treatment company will tell you, to process tooling in conformance with the NADCA (North American Die Casting Association) heat treatment specification is highly demanding and requires the use of extremely accurate and controllable equipment. The rate of heating and, more importantly, cooling must be closely controlled to achieve the optimum mechanical properties in any component. Any shortfall or compromise in the process will become evident when the finished item is in use.

Fluidised bed furnaces, used by Beta Heat Treatment, guarantee a temperature control of +/- 5oc throughout the entire process cycle, a tolerance that many other processes find difficult to match. If you are unable to control the temperature you will lose control of the process and it becomes impossible to repeat previous successes.

graph 4

Fig.1 shows an actual process graph. You will see four thermocouple traces, two from thermocouples attached to the component (surface and core), a third placed within the load and the fourth one to the furnace controller.The traces clearly show the thermocouple in the core lagging at each process phase, as one would expect.What is clear is the close proximity of temperature recordings from the four individual test thermocouples throughout the austenitising phase.

One of  the most critical parameters, when processing, can be the quench rate from the austenitising temperature. This must be carefully controlled to provide optimum metallurgical properties, whilst minimising distortion and the risk of cracking.

graph5

Fig. 2 shows the quench phase, scaled in minutes. The load couple is removed prior to quenching and placed into the quench furnace. The temperature differential between the core and surface is evident during the cooling period. The strict requirement to achieve a quench rate of 28ºC/min is easily achieved.

Quality

The exacting requirements of the NADCA specification include ‘HS’ rating of microstructure and grain size. Beta has a fully equipped laboratory capable of metallographic, hardness and micro hardness testing, with independent verification by Charpy test carried out by a UKAS approved test house.