Substitution: Technology

Conservation & Recycling, Vol. 7. No.

I, pp.15- 20.1534.

0361- 36ws4

Papmon

Printed in Great Britain.

s3.00+

.oo

Press Ltd.

REVIEW ARTICLE No. 5 SUBSTITUTION: TECHNOLOGY* T. D. SCHLABACH Bell Telephone Laboratories, Murray Hill, NJ 07974, U.S.A.

Substitution as a technological process is the replacement of one material, process, design or technology for another. These types of substitution occur at varying levels of complexity and under the principal responsibility of a design engineer. In general, substitution is an evolutionary process and one motivated by cost reduction, functional advantage or supply considerations. To these historical factors are now added regulatory constraints, strategic concerns, environmental issues and public attitudes. These, together with a quickened pace of innovation, have led to more abrupt substitution and a growing emphasis on the technological planning for substitution. Substitution is one facet of a broad conservation effort aimed at conserving scarce materials, reducing energy use and eliminating waste. By its very nature, substitution can have a substantial impact on related areas of technology. TYPES OF SUBSTITUTION There are four basic types of substitution: material, process, design and functional, They are closely related in that a substitution of one type may well cause others. Thus, for example, a material substitution often requires a modification of the process used and design changes almost invariably lead to material and process changes. Similarly, substitution stimulates competitive development and innovation in the material, process or system that it seeks to displace. Material substitution is probably the most familiar type and of greatest concern because of its relation to the supply of critical and strategic resources. Under this heading, three categories of materials substitution may be distinguished: physical, quantitative and invisible. Physical substitution is the replacement of one material for another and countless examples could be cited; aluminum for copper in electrical conductors, glass for steel in containers and synthetic detergents for soap to name but a few. Such substitutions only occur if the substitute material has properties which permit the function to be achieved at lower costs under the prevailing circumstances. Quantitative substitution involves a quantitative reduction in the amount of material used per unit of output. Examples would include using a thinner tin coating on tin-plated steel, less gold on an electrical contact or the use of a composite to replace a thicker, monolithic material. Invisible substitution is less obvious and occurs when a new product entering the market uses material(s) other than those traditionally used. This type is more difficult to trace although some examples are clear such as when a new car model or piece of sporting equipment is introduced. Substitution in the area of processing and fabrication is responsible for the majority of ongoing cost reductions realized in product manufacture. It can range from eliminating a manufacturing step to adopting a wholly new manufacturing process as in going from a *Article also to be published in Encyclopedia of Materials Science and Engineering (Pergamon Press. 1984). 15

T. D. SCHLABACH

16

machined to a powder-metallurgy part. This type of substitution is closely correlated with technical development and materials property improvement through processing. Design substitution involves alteration of the product. Miniaturization is one example. Others include redesigning a product for easier maintenance or to operate on a different mechanical or electrical principle. In functional substitution, a completely different approach to performing a needed function is found. A now classical example is the substitution represented by transistors for vacuum tubes. Jet engines replacing piston engines and propellers in aircraft and nuclear reactors replacing boilers fired by fossil fuels are other examples. Functional substitution can lead to the profound revision of consumption patterns for materials and energy and can inspire the creation of entirely new industries [l]. LEVELS OF SUBSTITUTION It is possible to identify several levels of substitution depending on the complexity of the substitution process involved and to attach typical development times for their implementation. These levels are adapted from Jantsch [2] and are listed in Table 1. A related ranking may be found in [3]. Noninteractive materials substitution is one that can be implemented easily while retaining product performance. It could be as simple as changing suppliers for a given- material but typically involves a different material. The development of a new material or chemical process is more common and interactive materials substitutions are so named because they often involve associated processing and design modification. The majority of substitution activity takes place in the first four levels listed which happen to correspond to the time frames for much of present corporate planning. Higher levels of substitution induce significant lower-level changes. Table 1. Levels of substitution and associated development times

Level 1 Noninteractive material substitutions Assembly or component change 2 Development of new material or chemical process 3 Interactive materials substitution Electronic technology change Subsystem or small system development 4 Systems of reasonable complexity 5 Complex weapon systems 6 Telephone exchange technology 7 Time for scientific discoveries to find largescale technical application

THE SUBSTITUTION

Development time (Yt.1 l-3 3-4 4-5 m7 mu10 ml3 ml5

PROCESS

Once a substitution need or opportunity has been identified and defined in terms of cost and performance objectives, the steps in its implementation are: (a) Draw on the available R & D stockpile. (b) Begin design and development.

SUBSTITUTION: TECHNOLOGY (c)

17

Conduct screening tests of viable alternatives.

(d) Develop hard design and reliability data. (e) Evaluate on a pilot scale in the manufacturing

environment.

These steps are the same as those for an original design process; differing only in being more narrowly focused for low-level substitution. The design engineer has the principal responsibility for the substitution process and the critical nature of his role can be seen by considering Fig. 1. At each stage, alternatives exist for the material and the part showing that there is no unique path to a material for use nor to the behavior of a part to meet its intended use. The choices made, then, at these various stages determine the kinds and amounts of materials (and energy) used, attendant pollution, reuse and recycling possibilities and the related technologies to be impacted. Design guides are seldom available to help make these choices wise ones for our resources and environment. It is useful to remember that design engineers are conservative in their technical judgements and are usually rewarded on the basis of the initial effectiveness of their designs and not on end-oflife considerations such as ease of recycling.

Ores,natural products and their refining

_

Ing;$knts prepamtion

*

Materials with specific composition structure and defects

w

Properties

-

Uses

-

Behavior or response

_

Intended use

Materials Parts

Materials of construction

-

Processing and fabrication

Structure * p,“:t

Fig. 1. Schematicrelationship between SUBSTITUTION

starting

materials and their final uses.

AND TECHNOLOGY

PLANNING

The critical element in facilitating future substitution is to ensure that an adequate technology stockpile exists on which to draw. This first step in the substitution process allows for the widest range of options to be considered. On a narrower basis, technological forecasting is used to identify likely future directions and products, and the substitution opportunities they present. A substantial methodology exists for doing this [4]. On yet a narrower level, the materials and components most critical to the product(s) are identified and specific substitution strategies developed to deal with their potential unavailability. The economics of substitution is dealt with by Tilton [S]. SUBSTITUTION

CONSTRAINTS

Many factors act to inhibit substitution. At the design level, there may be a lack of property or reliability data. In manufacturing, there are retooling and start-up costs to consider. Within

T. D. SCHLABACH

18

the organization, there is inertia to continue the past and delay in converting to the new. Government, society and individuals can also act to block or delay substitution. A particular constraint arises when a design depends on a unique property or material. For example, superconducting systems uniquely require liquid helium. In this, and less stringent examples, design lock-in occurs that prevents substitution. Lock-in can also occur with dedicated manufacturing facilities inflexible to change. For these reasons, substitution offers little hope for mitigating short-term, unanticipated shortages. These are constrained by the inplace technology and must be a direct fit in order to work. Substitution can also be inhibited because of its impact on related areas of technology. For example, demand for a substitute material could exceed known supply. Or, the substitution may require developments in several related areas before it itself could be implemented. ALUMINUM

VS COPPER:

COST-DRIVEN

SUBSTITUTION

These last four sections illustrate some of the principles cited and identify certain important driving forces for substitution. The mutual substitutability of aluminum and copper in electrical applications receives wide study and close monitoring. It is a substitution driven principally by cost considerations that begins with the relative cost required for equivalent electrical conductivity. As seen in Table 2, aluminum is more attractive than copper on that basis and sodium is more attractive than either. The choice, however, is dictated by many other factors including relative availability, ease of manufacture, size, connector technology, performance in the field and customer acceptance. On the basis of these, sodium is rejected for all but a very few special cases while aluminum finds uses in many instances [6]. Table 2. Electrical conductor materials

Resistivity @Q cm) Specific gravity Price (% kg-‘)* Relative cost per mho

Copper (ETP grade)

Aluminum (EC grade)

Sodium

1.71 8.89 1.92 1.00

2.83 2.70 1.67 0.44

4.88 0.97 1.19 0.19

*American Metal Market, March 1981

In the specific instance of substituting aluminum for copper in communications cables, it required some five years to accomplish because new alloys, connectors, cable constructions and manufacturing methods had to be developed and tested. This is a case where now either could be used depending on overall economics but there are other cases where only copper or only aluminum can be used for technical reasons. COBALT: AVAILABILITY-DRIVEN

SUBSTITUTION

In 1978, due to production difficulties in Zaire, the producer price for cobalt quadrupled and a user allocation of 70% was imposed temporarily. Since Zaire supplies about 40% of the world’s cobalt and since most countries are heavily dependent on imports for cobalt, these events sparked a wide effort to find substitutes. As seen in Table 3 and discussed in [7], magnetic alloys were one area where several commercially viable substitutes were found. These

SUBSTITUTION: TECHNOLOGY Table 3. U.S. cobalt consumption (O/o)*

Superalloys Magnetic alloys Cutting and wear tools Catalysts and driers Other

1977

1980

26 25 16 24 9

45 15 15 20 5

*U.S. Bureau of Mines, Mineral Commodity Summaries

and other substitutes served to markedly alter the pattern of cobalt consumption between 1977 and 1980 in the U.S.A. The continued high use of cobalt in superalloys reflects the difficulty of substitution [8]. CARS: REGULATORY-DRIVEN

SUBSTITUTION

Government-mandated fuel-economy requirements in the U.S.A. are acting to substantially reduce the weight of cars and to alter their pattern of materials use. The weight reduction required is being achieved through smaller cars and greater use of light-weight, high-strength materials. This has meant an increased use of high-strength steels, aluminum and plastics as seen in Table 4 and as discussed in [3,9]. By 1985, some 30% of the car’s weight will be in these materials selected according to cost per unit fuel saved. Table 4. Projected material usage in U.S. passenger cars (W) Material Cast iron Steel: high-strength other Aluminum Plastics Other

1977

1981

1985

17

13

10

2 60 3 4 14

9 52 4 7 15

12 46 8 9 15

Since the automotive industry is a large user of materials, this changing pattern has a major impact on materials suppliers and on recycling. In addition, these newer materials require significant changes in manufacturing and assembly. LIGHT-WAVE

COMMUNICATION:

TECHNOLOGY-DRIVEN

SUBSTITUTION

In the 197Os, optical fibers having very low optical signal attenuation and good mechanical strength were developed and offered commercially. Reliable, long-lived, light-emitting and laser diode sources also became available at about the same time. Combining this transmission medium with reliable sources and detectors led to light-wave communication systems of high information-carrying capacity or bandwidth. Such systems joined with current integrated chip technology have created a communicationscomputer environment that promises to have a major commercial and social impact. The availability and anticipated low cost of these systems facilitates electronic mail, teleconferencing and electronic meetings, electronic journals and books, robotics and computer-aided design, and the wired city as noted in [l]. Functional substitution of this breadth and depth profoundly alters our use of materials and energy.

20

T. D. SCHLABACH

REFERENCES 1. A. G. Chynoweth, Electronic materials: functional substitution, in Materials: Renewable and Nonrenewable Resources (Edited by P. H. Abelson and A. L. Hammond), pp. 123 - 130. Association for the Advancement of Science, Washington, DC (1976). 2. E. Jantsch, Technological Forecasting in Perspective. Elsevier. North Holland, New York (1976). 3. D. G. Altenpohl, Materials in World Perspective. Springer, Berlin (1980). 4. H. A. Linstone and D. Sahal (eds) Technological Substitution. Elsevier. North Holland, New York (1976). 5. J. E. Tilton, Substitution: economics, in Encyclopedia of Materials Science and Engineering (Edited by M. B. Bever). Pergamon Press, New York (in press). Conservation & Recycling 7, 21-26 (1984). 6. National Materials Advisory Board, Mutual Substitutability of Aluminum and Copper, NTIS PB-211-727. National Technical Information Service, Springfield, VA (1972). 7. G. Y. Chin, S. Sibley, J. C. Betts, T. D. Schlabach, F. E. Werner and D. L. Martin, Impact of recent cobalt supply situation on magnetic materials and applications, IEEE Trans. Magn. MAC-B, 1685- 1691 (1979). 8. J. K. Tien, T. E. Howson, G. L. Chen and X. S. Xie, Cobalt availability and superalloys, J. Met. 32, 12-20 (1980). 9. J. J. Harwood and G. F. Bolling, Planning for changing materials utilization patterns, Mater. .Soc. 4, 239- 246 (1980).