PLATE CXXII.
DETAILS OF HOME-STOYE AND FENDER,
BY STUART AND SMITH OF SHEFFIELD.
In considering the more striking and characteristic manufactures of Sheffield , we are necessarily led, inthe first instance, to the processes by which iron, when brought into the form of bars, rods, and sheets, isconverted into steel; the material which forms the great staple of the local trade. This change is producedby a series of operations, in the course of which a certain amount of carbon is imbibed or absorbed by theiron while subjected to the action of intense heat.
We may premise that the best description of steel is made from the iron imported from Sweden , beingchiefly the product of some mines at Dannemora, about thirty miles from Upsala , which have been workedfor more than four centuries, and yield upwards of 4000 tons annually. The well-known superiority of theDannemora iron has been by some writers ascribed to the presence of manganese, or silica in the ore, and byothers to the processes employed in smelting it, particularly the use of wood fuel. The bar-iron of thislocality is distinguished by its being marked with the letter L within a circle (“hoop L,” as it is commonlytermed); and other foreign varieties are in like manner known and valued as “ C C N D,” “ double bullet/'“gridiron,” “C and Crown,” &c.
The extensive steel works of Sheffield are of different kinds, and each bear distinctive appellations,—comprising,—“converting works,” in which steel in its crudest form is produced; “tilts,” or tilt works, in whichthe quality of the steel is further developed; “ casting furnaces,” in which the purest steel is produced bymelting and pouring the metal into moulds; and “ rolling mills,” by which the steel is formed into everyvariety of bars and sheet: and in some, though comparatively few establishments, these different processes areall carried on.
The office of the converting-furnace, as its name denotes, is that of combining bar-iron with a sufficientamount of carbon to entitle it to the name of steel. It is, in fact, a large oven, containing tw T o receptacles,or troughs, in which charcoal and iron bars are placed in alternate layers, covered at the top with a cementmade of the particles worn by abrasion from the numerous grindstones used in Sheffield . The bars are subjectedto a fierce heat for several days; more or less, according to the purposes for which the metal is intended.For files and similar articles, and for casting, a high degree of conversion is required. The metal thusconverted for ordinary purposes is denominated “blister steel.” After being again heated and toughened bythe blows of a ponderous hammer, it is termed “ common steel.” “ Shear steel ” is a name originallyemployed to denote that kind which is adapted for making shears; and the process for bringing it to thatstate is called “ shearing.” Though an important operation, this may be simply described by stating that theblister steel is broken into pieces of about a foot in length, heated to a high degree, and subjected to theaction of hammers worked by steam, so as to form a compact and uniform mass without flaws or blisters,and more malleable and tenacious than before. This action is for some purposes repeated; and according tothe extent to which the metal is welded or sheared it is termed “ half-shear,” “ single-shear, or double-shear.
The application of heat is one of the most important and frequently recurring processes in the productionof fine steel; and in no other manufacture is it required to so great an extent as in reducing this metal to a