Fig. 1. Double-retort pit furnace

Boeing has already spent more than $500 million on parts made in China and is expected to spend another $750 million in the next five years, according to the International Association of Machinists and Aerospace Workers. Based on these investment numbers, minimizing risk appears to be the key concern of aerospace manufacturers and suppliers. Of the risk profile, product integrity for performance ranks among the highest compared to security, regulatory, economic, intellectual property and disruptive events. One means of guaranteeing product integrity is to transfer proven-performance technology from U.S. assembly and production plants to offshore plants in China and India.

Keeping pace with aerospace requires companies like Alcoa Fastening Systems (AFS) to establish a full-service logistics center as it did in Shanghai, China earlier this year. They also have announced the creation of two new 50,000-square-foot manufacturing sites in the Suzhou Industrial Park (100 km from Shanghai) to support rapidly growing commercial aviation as well as railway/railcar production and sub-assembly in that market. Both facilities will incorporate the latest in available manu-facturing technology plus Alcoa Business System’s lean methodologies. One facility will be dedicated to the production of se-lect aerospace fastening systems, while the other will produce fasteners for AFS’ railcar and transportation custom-ers. Selection of the specific products to be produced is being carefully considered and coordinated with the company’s major customers around the world.

To minimize company, personnel and product risks, the selection of proven-performance technologies already in place en-sures a seamless transition in production. To perform to these expectations in heat treatment, AFS relied on BeaverMatic Incor-porated (the manufacturer) to ensure repeatable metallurgical results, dependable equipment, ease of installation and simplified controls. Faced with challenging aerospace combustion-system specifications, temperature-uniformity requirements and nu-merous other codes, the manufacturer recently designed, built and shipped a double-retort pit furnace for tempering fasteners (Fig. 1). A pit furnace is utilized for nitriding or tempering smaller intricate parts for superior strength. One pit furnace sent to China was designed to process 600-pound loads for quick turnaround. Although thousands of parts are heat treated daily to accommodate new aerospace players, the demand still surpasses supply.

Fig. 3. Honeywell controls and fan-fold recorder

Pit Furnace Benefits

Two specific reasons for choosing a pit furnace were the flexibility and simplicity of its application. The vessel design is round for structural strength, also allowing the vessel to be smaller and easier to utilize for loading and confined spaces. Since no external load cart is required, the loading and unloading of four 9-inch-high baskets is relatively simple for any operator. With the ability to run larger loads in a vertical design and gain more cycle time with a load cooling station, part uniformity is ensured in the tempering process.

Another benefit for choosing a pit furnace was the simplistic cycle sequences of operation. The operations are dependable, easy to understand and can be carried out by one of several operators by following basic parameters (see exhibit for details).

For ease of installation, the control panel is all prewired with controls, push buttons, signal lights, motor starter, purge timer and system-analyzing safety monitor for a plug-and-play scenario. Other furnace features include:
  • Honeywell controls and circular chart recorder/controller (Fig. 3)
  • Circulation blower mounted in heating chamber
  • Flame safety and gas shut-off valves comply with NFPA and FM guidelines
  • NEMA 12 control panel
  • Stainless-steel lining and duct work
  • Heating chamber and top cover insulated with mineral-fiber insulation (Fig. 2)


Fig. 2. Close-up of heating chamber

Global Supply

As companies continue to build manufacturing facilities in Asia, the best technology and manufacturing practices will be trans-ferred, allowing other regions to benefit. Located in Middle America is Rockford, Ill. – the once capital of fastener manufacturing – which now plays a role of supplying that same proven equipment to international manufacturers. BeaverMatic has tapped into this niche by supplying simple, proven and dependable furnaces. According to company president, Kary Peterson, “BeaverMatic furnaces are optimized for ease of operation, especially as more equipment is shipped internationally. Aerospace, in particular, has numerous safety regulations and code requirements for processing metals. It is our ability to meet these requirements with equipment reliability and service that places us on many preferred-vendor lists, which has launched us globally.” IH

For more information: Kary Peterson is president of BeaverMatic, Inc., 424 Buckbee St., Rockford, IL 61104; tel: 815-963-0005; fax: 815-963-5673; e-mail: kp@beavermatic.com. A.J. Gonzales is senior project engineer for Alcoa Fastening Systems HQ, 135 N. Unruh Ave, City of Industry CA 91744; tel: 626-937-5490; fax: 626-937-5410; e-mail: A.J.Gonzales@Alcoa.com

Additional related information may be found by searching for these (and other) key words/terms via BNP Media SEARCH at www.industrialheating.com: microscopy, metallography, delta ferrite: aerospace, pit furnace, nitriding, vacuum, retort, fastener

EXHIBIT: Designed for Ease

Cycle Sequence

Operator
  • Loads the baskets
  • Sets the baskets into the tree
  • Places the tree into the retort
  • Secures the retort to the fan assembly, thus sealing the retort
  • Connects - Water, Argon, Fan, Thermocouples, Vacuum lines to top of fan assembly
With pressure switches chosen and the fan/retort assembly still on the cooling station, the operator presses the retort purge-cycle push button. The vacuum pump runs, and the vacuum valve opens. The retort evacuates down to a set point then backfills by use of the vac-uum valve and the process argon solenoid valve. The evacuation/backfill repeats one time. Following the second pumpdown, the retort is backfilled up to ½-pound positive pressure. The retort purge-complete pilot light illuminates and, for the remainder of the automatic cycle, retort pressure will automatically regulate itself.

Operator interface is required for acknowledging when heat cycle is complete, allowing him/her to hoist the fan/retort assembly back over to the cooling station.