HEAT TREATING ALUMINUM FOR THE AEROSPACE INDUSTRY

Wisconsin Oven (East Troy, WI) designed and manufactured a natural gas-fired batch oven with a quench tank to solution treat aluminum for the aerospace industry. The equipment is designed to accept a 4 ft wide x 4 ft high x 4 ft long basket.

The oven is rated for a 1,250 deg F maximum operating temperature and a 1,100 deg F normal operating temperature. The system achieves a customer-required temperature uniformity of ±10 deg F at 600 deg F and 1,100 deg F per AMS 2750D Class 2 furnaces and Type C Instrumentation. A nine-point temperature uniformity survey (TUS) using calibrated wire in an empty oven chamber under static operating conditions was conducted with the results exceeding their requirements (+5.4 deg F/ ?1.8 deg F at 600 deg F and +5.3 deg F / ?6.1 deg F at 1,100 deg F). A System Accuracy Test (SAT) was also performed using temporary thermocouples to further insure proper operation.

The oven is fabricated with 6 in of insulation in a CAN-style construction. The inner shell and ductwork are fabricated with 18 ga 304 stainless steel. The hearth consists of two rows of wheels, rated at a capacity of 3,600 lbs gross loading weight. The heating system features a 500,000 BTU per hour air heat burner and includes a motorized gas control valve, flame detector and flame relay with alarm horn.

WHAT IS SOLUTION HEAT TREATING?
Solution heat treating is a process used to treat non-ferrous alloys. Aluminum is a non-ferrous alloy that commonly undergoes solution heat treating. By changing the internal structure of the alloy, solution heat treating increases the alloy?s overall tensile strength.

The process of solution treating requires the alloy to be heated up to an appropriate temperature that will allow all of the added (now in solution) alloying metals to be in solution in the primary metal. Once the alloy metal has reached the "solutionizing temperature", the alloying elements are ?frozen? in the solution by cooling rapidly from the solutionizing temperature down to room temperature.

The metal is now in its softest condition and requires strengthening. This is accomplished by time. Some alloy metals will age naturally at room temperature. Some alloy metals will require (because of expediency) strengthening by accelerating the procedure. This is done through artificial aging or artificial strengthening that requires the alloy metal to be raised to a specific temperature for a specific amount of time.

The recirculation system provides combination air flow and utilizes a 10,000 cfm @ 15 hp blower. The majority of the air is delivered under the work to flow vertically upward past and through the product to provide even heating.

The non-heated manual quench tank is fabricated with low maintenance, corrosive resistant 12 ga 304 stainless steel. Water level control is provided for make-up water. Water agitation of the quench tank is provided by an agitation pump with a manifold for more uniform cooling, pulling the heated quenchant from the load. A push button station allows the oven operator to raise and lower the basket into and out of the quench tank and open and close the vertical lift door. Automated systems with heating and/or cooling are also available.

The horizontal solution treat system includes a UL certified, NEMA 12 rated control panel with IEC style push buttons and pilot lights. The oven temperature is controlled by a Honeywell DCP100 programmable temperature controller and recorded by a Honeywell DPR100 strip chart recorder. Both the oven temperature controller and recorder meet AMS 2750D accuracy requirements and provide the flexibility to heat treat a wide range of parts with multiple recipes.

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Jim Lucas is a senior sales engineer for Wisconsin Oven Corporation, 2675 Main Street, East Troy, WI 53120, 262-642-6010, www.wisoven.com, jlucas@wisoven.com

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