« AnteriorContinuar »
The flowers resplendent to the visual sense
The verdant foliage a blooming-train,
Anon the direct process nature takes,
And now the cock doth sound his liquid lay;
So genial Spring doth all things put in gear; Eccentric there, with fly-wheel action here. Producers thrive, the merchant rolls in wealth ; And here's a ladle to our miners' health !
THE NOMENCLATURE OF IRON AND STEEL.
The following paper, read by Mr. Holley, before the American Institute of Mining Engineers, at Cleveland, in October, 1875, was called forth by a series of articles on the same subject, contributed by Mr. H. M. Howe to the Engineering and Mining Journal. These articles may be found in the numbers of that journal for August 28th, September 4th, September 11th, and September 18th, 1875. As is well known to the earlier members of the Institute, the discussion thus inaugurated acquired an absorbing interest, and was continued in many papers and speeches (see Transactions, iv., 138, 328; V., 10, 309, 311, 355, 515), involving the appointment of an International Committee, and a lively debate over its report. The present purpose being, not to present both sides of the question, but to illustrate Mr. Holley's style in controversy, only the paper with which he opened it is given in this place.
WHAT IS STEEL?
The general usage of engineers, manufacturers, and merchants, is gradually, but surely, fixing the answer to this question. In every country, rails, boiler-plates, and machinery bars, whether hard or soft, are almost universally called steel, when they are made from cast ingots. Other names for the softer steels, such as “homogeneous metal,” “Bessemer iron,” “Martin iron," and the like, have failed to obtain general recognition.
The meaning of the term steel, before it was enlarged to cover newly developing varieties, has been traced, by a recent writer, down through Percy, Shakespeare and the Bible, in a most interesting manner, from an archæological point of view. Undoubtedly it did characterize hardness and other qualities imparted by carbon. It is within the memory of most of us, that all steels were tool-steels, and that the soft, structural varieties were introduced—varieties which harden but little, which bend cold, and which, in many physical properties, are akin rather to wrought-iron than to tool-steel.
But, since both the hard and the soft steels are made by the same processes, and have their great distinguishing structural feature in common, viz., homogeneity resulting from fluidity, it has come to pass, despite every other proposed nomenclature, that all the compounds of iron which have been cast in malleable masses, are called steel, the term wrought-iron being still confined to malleable iron made from pasty masses, and hence laminated in structure.
No inconvenience has been found, so far, in distinguishing between the more or less carburized products, in general, by the terms
high-steel,” “ low-steel,” “ tool-steel,” etc., and, in particular, by prefixing the percentage of carbon and other ingredients, to the term steel. Steels which contain distinguishing ingredients other than carbon, are called “chrome-steel,” “titanium-steel," and the like, just as variously compounded bronzes are called "phosphor-bronze,” “aluminium-bronze," etc. Thus the combination of several words or symbols, and figures, may completely disclose the characters of the metal, in terms that are subject to no misunderstanding.
But inasmuch as several high metallurgical authorities and clever writers have of late proposed to disturb this natural and somewhat settled nomenclature, it seems important to consider the claims of the various classifications. I shall attempt, in this paper, to show that the existing classification is more scientific and more convenient than any other, and that those others which have been most prominently brought into public notice are radically defective.
The most common objection to the existing enlargement of the term “steel," so as to include the soft steels, is that it “pirates” a time-honored term, and applies it to a thing which is very different in many of its qualities. People who know nothing about steel, except as they use it in cutting instruments, or read about it in classic authors, say that it is brittle, hard, and resilient, and they are much shocked to hear that it may also be soft and ductile; just as any one who knows nothing about india-rubber, except in the form of springs, would be astonished to find that one change in manufacture turns it into water-proof clothing, and another, into hard crystalline instruments and jewelry. The terms “hard-rubber" and “soft-rubber,” as used in technical literature and commerce, have not given rise to any serious misunderstandings. People who do not know that the great bulk of the material made by steel-processes, and having every ingredient and structural arrangement of the old steels, is, nevertheless, soft and ductile, and that it would be unsuitable for rails, plates, and the like, if it were not soft and ductile, are not to be considered authorities in this discussion, any more than a decorative artist in coal-tar would for that reason be an authority on aniline colors.
Where a material is gradually developed into new forms and qualities, there must be some general name to cover the various classes of metal; and whether it is better to enlarge the boundaries of the old one, or to arbitrarily make a new one, which new one must, from the nature of the case, merge into the old one, there being no natural dividing line, will be further considered throughout this paper. I venture to assert here that the charge, specially brought by the inventors of new definitions, against the existing use of the term “steel” —the charge of upsetting the recognized order of things—is wholly without foundation. Nobody invented the terin "steel,” as applied to the soft homogeneous products. There has been no natural or obvious place in the gradual gradation from hard to soft steels, to inject a new definition. As the possibilities of the crucible process were enlarged, the first soft product was hardly more than a variation from standard carburization; the early Bessemer and Martin steels, as produced in a successful commercial way, were hard; and, in fact, it is only quite recently that refractory materials have been adopted, by means of which the slowly receding standard of carbon in cheap steels has reached a tenth of one per cent. The same general name has been thus necessarily preserved for the products of the same process; but its boundaries have been enlarged to admit new varieties, and a gradual growth of subclassification. So that whatever the merits of any arbitrarily devised nomenclature may be, it must bear the demerit, whatever that is, of upsetting existing order and development.
A more common form of this objection is that a blacksmith would not recognize the soft metal as steel. “A blacksmith,” it is said, “calls that steel which will harden and temper, and blacksmiths ought to know what steel is.” There are various answers to this objection :
If familiarity with soft coking coal teaches a blacksmith how to burn highly carburized anthracite in his smithy, then his knowledge of highly carburized tool-steel ought to teach him what soft steel is. Hard coal is none the less coal because it does not respond, like soft coal, to a blacksmith's coking process, nor is soft steel any the less steel, because it does not respond, like tool-steel, to his hardening process. Anthracite coal was introduced long after bituminous coal was in general use, and the “pirating” of the time
honored name “coal,” to describe this material which is so different in many of its qualities, has not led to any vast inconveniences. It may be said that the parallel is incomplete, because both hard and soft coals are really the same thing only changed in composition and structure by natural processes, and that they both respond to the practical test-the influences of heat and oxygen. So are hard and soft steel the same thing, only changed in composition and structure by natural laws; and so do they both respond to the influences of heat and oxygen. Coals are, in fact, more diverse than steels in their carburization, structure, and strength, and in their requirements of treatment. If old nomenclature is to be held as a final criterion, then the modern condensing steam-engine should be a “low-pressure engine.” The fact is, on the contrary, that it is as often “highpressure” as any non-condensing engine.
The determination of previously unknown intermediate forms and functions is constantly enlarging the boundaries of all general classifications, and introducing subdivisions; hence the criterion of old classifications is inadequate and worthless.
If hardening in water is the determining characteristic of steel, who is to define “hardening ?” As a matter of fact, all products of the crucible, Bessemer vessel, open-hearth furnace, and puddling furnace, containing about a quarter of one per cent. of carbon, will perceptibly harden in water, just in proportion to the carbon contained; and every one of them, however little carbon it contains, will harden in some degree, as far as existing tests can determine. “If the product will make a tool, it is steel,” says the blacksmith. What kind of a tool ? Is an agricultural tool iron, and a cold-chisel steel; or does steel begin between cold-chisels and razors, and if so, where? A water-hardened tool perfectly adapted to certain uses may be made of Bessemer steel containing a half per cent. of carbon. The same Bessemer ingot may make a good rail. If one-half the ingot is steel, why is the other half iron ? The line must be so defined that people will agree upon it. Does it lie between thirty hundredths and thirty-one hundredths of carbon, or between ninetynine hundredths and one per cent.?
Obviously, no two men can agree on the amount of any hardening element which may constitute steel. And if they could agree, it would only be after a quantitative analysis had been made in all close cases.
A recent writer in the Engineering and Mining Journal (August 28th to September 18th, 1875) makes a number of ingenious objec