September/October 1989
The “super” in superalloy scrap could refer to several things: supercomplicated equipment, superexacting specifications, superdemanding quality requirements, and superparticular consumers. These aspects and more put superalloy scrap processing in a class by itself.
By David Borg
David Borg is manager of high-temperature alloy sales at Suisman and Blumenthal, Hartford, Connecticut.
Superalloy scrap processing is one of the most demanding forms of recycling today. Only a handful of companies have been able to combine the necessary ingredients successfully and become approved suppliers. Mastering this complex task requires balancing a host of factors, some at odds with each other, in a competitive market.
Successful superalloy scrap processors have made an unwavering commitment to quality over the long term. Taking shortcuts in processing or having a short-term business outlook are inconsistent with these processors’ “total quality” philosophy. Quality is the basis of a superalloy scrap processor’s reputation. The stakes are high in the superalloy business: some of the turbomachinery of most jet aircraft flying today is partially made from superalloy scrap.
Supertrained Employees
Employees are a major part of the quality philosophy. Numerous and complex alloy systems, that is large numbers of different alloys and subtle variations within certain alloys, make superalloy scrap processors extremely reliant on a conscientious, knowledgeable work force. Meticulous attention to detail must be maintained at all times. Some processors have formalized training and testing programs to qualify sorters and to certify that high standards are maintained. Initial training may take several months and complete qualifications may take a year or more. Both the employee and the company make a long-term commitment.
Equipment Systems Complex; Analysis Crucial
Because of the equipment used by superalloy scrap processors, they are at the pinnacle of technical complexity in the recycling industry. Equipment is used for processing, sorting and analysis.
The list of processing equipment is long and varied and includes, but is not limited to, shears, plasma torches, degreasers, shot-blasting equipment, pickling equipment, fragmentizers, crushers, magnetic separators, sieves, washers, and distributors. Most of this equipment is commercially available. The true test for the superalloy scrap processor is integrating the types of processing equipment in such a way as to create a product with the required quality at a competitive price.
Sorting equipment can range from the useful but limited magnet and grindstone to chemical spot testing and thermal conductivity meters to technologically intricate emission spectrographic and x-ray energy dispersive devices. It is important to realize that purchase of a high-tech sorting device does not guarantee results. Proper interpretation of all available information is central to production of quality products. Experience carries a lot of weight when making sorting decisions. New alloys are always entering the system. Couple that with the subtle variations between certain alloys and sorting becomes an extremely complex task.
Some superalloy scrap processors--particularly those heavily involved in turnings production--maintain full-service analysis laboratories staffed with chemists and technicians. Instrument-based methods of analysis are common. Some types of equipment used are flame and furnace atomic absorption spectrophotometers, X-ray wavelength dispersive spectrometers, inductively coupled plasma spectrophotometers, gas analyzers, carbon sulphur determinators, and emission spectrophotometers.
Quality turnings processing is dependent not only on a qualified laboratory but on the sampling system employed. Sampling is critical to the superalloy scrap processor: without a representative sample the best lab in existence can't provide useful data. Sampling is typically given a high priority in the superalloy scrap processing plant and may involve continuous or static devices, depending on the situation. The processors who specialize in turnings have, for the most part, developed their own sampling systems, which are derived through experimentation since sampling apparatus is not commercially available. To understand the importance of representative sampling, consider that some specifications require content guarantees down to one-half part per million for certain elements. (One-half part per million is equivalent to one penny in $20,000.)
Specifications Especially Stringent
Conformance to specifications and procedures is the goal of every superalloy scrap processor. Specifications originate from the consumer (external) and within a processor's organization (internal).
External specifications are numerous and varied. Since each consumer has slightly different requirements governing the same alloy, the processor is essentially performing customized preparation for each consumer.
Written internal specifications and procedures are also necessary for the completely integrated scrap processor. These specifications and procedures govern most aspects of the processing system including receiving, sorting, inventory, training, quality assurance, equipment cleanliness, material cleanliness, sizing, density, and packaging. Consistent material integrity and conformance to customer specifications require a highly structured system-internal specifications enable superalloy scrap processors to provide the required quality. Statistical process control, whether external or internal in origin, is becoming increasingly important for many superalloy processors. Control systems are most applicable to turnings operations.
Superalloy melters require superalloy scrap processors to guarantee the material provided (consider the one-half part per million). This makes the processors liable for problems the melter might encounter. In other words, if the problem material is traceable to the processor, the processor not only owns the material but must pay all incurred costs. Specifications give the industry a reference point for determining a processor's capabilities. Most consumers formally track a processor's performance and processors who consistently perform well are likely given more business.
Surveillance and Inspection Common
Superalloy scrap processors are subject to periodic surveillance and approval by major turbine engine producers and rotor-grade superalloy melters. Rotor-quality material approvals are broken down into solids and turnings. There are fewer approved turnings processors due to the overall system complexity and the investment required for things such as washers, crushers, and laboratories.
Surveillance involves a visit to the superalloy scrap processor's facility, where records are reviewed, procedure is studied, equipment is inspected, employees are questioned--all in an effort to ensure that the processor can consistently deliver the required quality. Rotor-grade specs also require that source identity of all scrap be maintained in the event of an accountability problem in the future. In the past, non-rotor-melters have generally not participated in surveillance programs; informal approval has been the norm. Currently however, they, too, have been incorporating surveillance programs into their systems.
All this attention to the minutest detail ensures the product generated by the superalloy scrap processor is of a high quality and can withstand the demands put on it by consuming industries.•