Drop Bottom furnaces/ovens and belt furnaces are used for solution heat treatment of aluminum. This furnace construction type allows quench delay times of 5 seconds needed for thin wrought aluminum alloys and ALCLAD.
When heating alloys above a certain temperature, it goes into a "solid solution". When held at this temperature long enough, all the alloy will have gone into solution, hence "solution heat treatment". To preserve this state, the material needs to be quenched within seconds in a drop bottom furnace. Specifications such as AMS 2750H/CQI-9 or NADCAP specify the pyrometric requirements for the furnace. Material specifications such as AMS 2770, AMS 2771, BAC 5621, Milspec 6088 specify for each material the heat treatment process such as soak temperature, drop times and quench temperature. The solution heat treat process is followed by a precipitation hardening process done in separate coolers or ovens.
Bottom drop furnaces can be heated by electricity or fired by gas. If the process specification allows direct fuel gas firing, this technology has an economic advantage. If process specifications do not allow products of combustion in the air stream, then electric or indirect gas fired furnaces are the choice. Keith company has built class 1 furnaces according to AMS 2750H (formerly AMS2750G) process specifications using all these technologies. To insure best temperature uniformity over a long period of time, we often choose downdraft designs for gas fired bottom drop furnaces. In any case, the load is shielded from direct heating radiation.
AMS 2750H Specifications:
Covers pyrometric requirements for thermal processing equipment used for heat treatment. It covers temperature sensors, instrumentation, thermal processing equipment, system accuracy tests and temperature uniformity surveys.
General Capabilities:
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Meets pyrometric specifications AMS 2750H (formerly AMS2750G)
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Meets AMS 2770, AMS 2771, AMS 2772, BAC-5621, RPS-953, MIL-H-6088, NADCAP AC1702
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Quench delay time of parts 5 - 15 seconds
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temperature control and recording requirements per AMS 2750H / CQI-9
Special Options
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Many different control / recording options available
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Data acquisition and integration with remote monitoring
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Customized load baskets, racks and external hoists
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heated and/or cooled insulated quench tanks
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Gas (indirect or direct) fired or electric heated systems
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Custom sizes are available
Periodic redesigns assure these furnaces are always cost effective and efficient and will meet the most rigorous heat-treating specifications in effect. To best suit a shop layout, the quench tank may roll beneath the door or from side to side. Moreover, a single quench may service two or more furnaces