The ingots arc reheated in an open fire much like that of the common forge, and are passed under a heavy hammer weighing several tons, such as those of iron works; the blows are given gently at first, owing to the crystalline nature of the mass, but as the fibre is eliminated the strength of the blows is increased.
Steel is reduced under the heavy hammer to sizes as small as there -quarters of an inch square. Smaller bars arc finished under tilt hammers, which are much lighter than the preceding, move considerably quicker, and are actuated by springs instead of gravity alone; these condeuse the steel to the utmost. Rollers are also used, especially for steel of round, half-round, and tringular sections, but the tilt hammer is greatly preferred.
Cast-steel is the most uniform in quality, the hardest, and altogether the best adapted to the formation of cutting tools, especially those made entirely of steel; but much of the cast-steel will not endure the ordinary process of welding, but will fly in pares under the hammer when struck.
Mr. Mushet took out a patent in 1800, for the manufacture of cast- steel, by the direct fusion of malleable iron, charcoal, and other carbonaceous agents, in the respective proportions; and same process was likewise extended to some of the superior varieties of iron ores, so as to arrive at one step from the ore to cast-steel; but the method appears to have been only applicable to limited and common purposes, and not to have entered into serious competition with the ordinary mode just described.
In respect to steel, the same general remarks offered upon iron may be repeated, namely, that price in a great measure governs quality. Steel when broken does not show the fibrous character of iron, and in general the harder or harsher the steel,the more irregular or the less nearly flat will he its fracture.
The blished-steel should appear throughout its substance of an uniform appearance, namely, crystalline and coarse, much like inferior iron, but with less lustre and less of the bluish tint; when but partially converted, the film of iron will be readily distinguished in the center. The blistered-steel when it has been once passed through the fire and well hammered, assumes as may be supposed, a much finer grain, as in fact the operation converts it, (although in the small way,) into shear steel.
Shear steel breaks with a much finer fracture, but the crystalline appearance is still readily distinguished. Cast-steel is in general the finest of all in its fracture, and unless closely inspected, its separate crystals or granulations should be scarcely observable, but the appearance should be that of a fine, light, slaty-grey tint, almost without lustre.
The quality of steel is considerably improved, especially as regards cutting tools, when after being forged it is hammer-hardened, or well worked with the hammer until quite cold, as this tends to close the "pores" and to make the material more dense; above all things excess of heat should be avoided, as it makes the grain coarse and shining, almost like that of bad iron, and which deterioration can be only partially restored, by good sound hammering under a peculiar management. The particular degrees of heat at which different samples of iron and steel, bearing the same name, should be worked, can only be found by trial; and it would be hardly possible to describe the shades of difference.*
* The reader desirous to examine the several conditions of iron, from its state of ore to that of cast-steel, should visit the Museum of Economic Geology before referred to, which contains a good series of specimens.
It would have been incompatible with the nature of this work to have entered more largely into the manufacture of iron and steel, or to have attempted the notice of the various alloys of steel which have received many attractive denominations, especially when 80 much has been already written on the subject by those possessing superior opportunities.
Of all the works published on the manufacture of iron and steel, the one of the most grand importance is the collection of Mr. Mushet's papers, which have appeared in the Philosophical Magazine at various times subsequent to 1798, and were recently collected and published by himself under the title " Papers on Iron and Steel:" the labour and research therein recorded are almost beyond belief.
Of the more brief and popular accounts of this subject, perhaps the best is 106 of the Library of Useful Knowledge, " On the Manufacture of Iron," published by the Society for the Diffusion of Useful Knowledge. Aikin's Dictionary of Chemistry and Mineralogy, etc.; three volumes on the Manufactures in Metal, in Lardner's Cyclopedia; and Ure's Dictionary of Manufactures and Mines, contain likewise a very large store of information on the metals generally. The reader will also consult with advantage, Aikin's " Illustrations of Arts and Manufactures," and various articles in the Encyclopedias, etc. etc.