In simplest terms, innovation is the introduction of a new method, idea or product into the marketplace that represents a revolutionary (as opposed to evolutionary) change or breakthrough, often leading to a technological advance within its targeted industry. The Doctor loves innovation, and while this article is not intended to be an endorsement of, nor a commercial for, a particular company or product, a few vacuum-furnace designs have recently caught the Doctor’s eye and are deserving of our attention. Let’s learn more.
As we all know, the criticality of today’s applications demands absolute control, process repeatability and the highest possible quality. The following equipment innovations – in no particular order – help heat treaters do just that.
Innovation 1: Large/Heavy, Complex Parts Processing Solutions
Car-bottom-type vacuum furnaces (Fig. 1) were developed to handle large, heavy product workloads as well as long, horizontal components. These furnaces initially started at 3.6-m (12-foot) hot-zone length, progressed to 7.2-m (24-foot) length and eventually were built to handle 11-m (36 foot) lengths. The major advantage of this type of furnace is to process loads up to 45 tons (100,000 pounds) while incorporating heating elements under the workload as well as heating elements around the circle of the hot zone.
Recent demands from the aerospace and nuclear industries have extended designs to 14.6 m (48 feet) by 2.1 m (7 feet) in diameter; units capable of handling loads up to 68 tons (150,000 pounds) at 1315˚C (2400˚F).Dual-loading cars are provided for loading/unloading from both ends of this furnace to minimize lost production time (proven to increase capacity by up to 30%) when loading/unloading large loads.
Car-bottom furnaces offer a unique ability to thermally process sensitive materials such as titanium, zirconium, precipitation-hardening stainless steels and nickel alloys while meeting the demands for surface cleanliness. This is achieved in part by:
- A highly efficient vacuum system that includes triple mechanical pumps, vacuum boosters, and (Varian 35-inch) diffusion pumps
- A stainless steel inner cold wall, which inherently remains cleaner than a carbon-steel cold wall
- A load car (the portion of the hot zone exposed to air on loading) consisting of less graphite-felt insulation, resulting in less moisture pickup when outside the furnace
Innovation 2: Near-Net-Shape Processing Solutions
Powder metallurgy represents one of a number of niche markets whose identifying characteristics include rapid growth and product diversity. Within this industry, metal injection molding is one of the near-net-shape technologies used to produce high-performance, precision components such as medical and orthodontic devices, mobile-phone parts, firearms and door-lock internals to name a few. Materials include stainless steels (e.g., 316L, 17-4); low-alloy steels; tool steels and specialty alloys for implantable and magnetic applications; hard metals (e.g., WC-50, WC-10Co); and refractory alloys.
Uniquely designed single-chamber batch vacuum furnaces (Fig. 2) are one solution (continuous vacuum being the other) that allows the processing of the wide range of materials required from the many different types of feedstock available. These designs offer cycle (recipe) flexibility, choices of process atmospheres (e.g., hydrogen, argon) and the ability to do secondary debinding and sintering in one self-contained unit.
Innovation 3: Lean Manufacturing via Small-Batch Processing Solutions
Integration of heat treatment directly into the mainstream of the manufacturing process has been the goal of heat treaters for a very long time. This enables synchronization with soft-machining operations to produce a small batch of production parts in-line and on-demand to meet the needs of the other manufacturing centers. The goal is to reduce unit cost to produce and improve efficiency.
Important benefits include short cycle times (achieved by optimizing hardening or case-hardening processes for small-batch loads), part surface control, minimizing distortion while maintaining precise temperature uniformity, and cycle reproducibility so as to achieve consistent quality in a 24/7 manufacturing environment.
Parts are loaded onto a single grid, which is transported through the system (Fig. 3) for hardening or case hardening (carburizing or carbonitriding). In the example shown, high-speed-steel saw blades are hardened at 1150-1200˚C (2100-2200˚F) soaking at temperature for 5-7 minutes to produce the desired microstructure on both the high-speed-steel teeth and backing materials. In other applications, such as carburizing of gears, austenitizing temperatures of 1040˚C (1900˚F) are utilized.
Innovation 4: Single-Piece Part Processing Solutions
Manufacturers continue to strive for true single-piece part flow, and the Unicase Master® (Fig. 4) is designed for hardening or case hardening high volumes of automotive gears and bearing races. The design transports single parts through the entire process to allow individualized part heating and 4D Quenching® where the quench gas follows the contour of a single component part in the quench. The way in which this is done represents a possible breakthrough in quenching deformation control.
This green, lean and agile design meets the productivity demands of high-volume gear and bearing manufacturers while optimizing process flexibility and operational speed by applying cutting-edge low-pressure carburizing (LPC) and high-pressure gas-quenching (HPGQ) technologies.
Progress is the movement toward achieving a specific goal, which in the case of the heat-treatment industry is offering the most price-competitive technology solutions to industry. Progress can only be achieved by innovation and the exchange of ideas by those in the heat-treating community. If your product or service was not mentioned here, set the goal of being here next time. The Doctor will be watching.
- Herring, Daniel H., Vacuum Heat Treatment, BNP Media, 2012
- Mr. William R. Jones, Solar Atmospheres, technical contributions and private correspondence
- Mr. Stefan Joens, Elnik Systems, technical contributions and private correspondence
- Mr. William Gornicki, ALD-Holcroft, technical contributions and private correspondence
- Mr. Maciej Korecki, SECO/WARWICK Corporation, technical contributions and private correspondence
- Loser, Klaus and Volker Heuer, “Syncrotherm® - Heat Treatment System and Processes for Lean Production,” 2015 Heat Treat Conference & Exposition, Conference Proceedings, ASM International, Oct. 2015
- Korecki, Maciej, “In-line, Low Distortion, Precision Case Hardening for the Automotive Transmission and Bearing Industries,” Conference Proceedings, Heat Treat Summit North America, SECO/WARWICK Corporation, Sept. 2015