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- General Purpose - Generally, temperature of as trimmed forgings ranges between 950 to 1050 Deg. C. If all these jobs collected in pallet, it takes long time to cool. Micro-structure, hardness and other physical properties will vary from job to job. A slow moving conveyor after trimming press provides sufficient time to cool the job below eutectoid transformation temperature before collection in pallet.
- For Normalising. Being temperature of as trimmed forgings is well above Eutectoid transformation Temperature, forgings can be normalized on cooling conveyor in open atmosphere.
- For hardening by air quenching. Forgings can be air quenched by blowing air on forgings or by sucking out surrounding air.
- For getting improved micro-structure than Normalising. To improve the micro-structure, conveyor can be provided with hood, lined with ceramic cloth. This will reduce the cooling rate by increasing the air temperature inside the hood. The cooling process is slower than normalizing.
- For initial force cooling and slow cooling there after. This process resembles to hardening and tempering.
Length of controlled cooling conveyor is to be decided by multiplying
1. Speed of conveyor required for particular job ( e.g. 1Mtr/Min)
2. Residence time of forging on conveyor ( e.g. 8 Minutes)
From this data, conveyor length required is 8 Mtrs.
Speed of conveyor depends on dimensions of forging and cycle time of production. Suppose width of forging is 120 mm and cycle time is 6 seconds. Assume jobs are to place on conveyor width wise, then speed of conveyor required is 120 x 10 mm/min (i.e. 1.2 mtr/min). If width of conveyor is more, forgings can be placed side by side and speed can be reduced. We provide conveyors with Variable frequency drive to set the speed as per requirement.
The principle of controlled cooling conveyor is ‘Newton’s Law of Cooling’. As per this law cooling rate depends on ambient temperature, initial temperature, material to be cooled & geometry of particular jobs. On that basis, if jobs are to be cooled faster than getting cooled in open atmosphere then conveyor will be kept open, but if jobs are to be cooled slower than natural rate, then it will be kept closed. Open conveyors, gives variation in microstructure because ambient temperature in various seasons will be different.
Yes, microstructure is function of cooling rate for given material and it can be attained various adjustments given on conveyor. As forgings are already hot and soaked at elevated temperatures, experienced metallurgist can save the fuel and time required for heating and soaking in heat treatment of forgings.