. The Iron and steel magazine. ther constituent, pearlite,docs not sensibly yield until a tension of about twice theseamounts is reached, excepting when its structure is composedof broad sheets of ferrite and carbide of iron, for in such case the * Impact Tests on Wrought Steels of Commerce. Proceedings ofthe Institution of Mechanical Engineers, 1904, p. 1135. Overheated Steel 401 ferrite behaves as if it were massive, and the yield point isnecessarily nuioh lower. (6) The weakness of a steel under stress in any givendirection depends on the manner in which the ferrite and pearliteare arranged
. The Iron and steel magazine. ther constituent, pearlite,docs not sensibly yield until a tension of about twice theseamounts is reached, excepting when its structure is composedof broad sheets of ferrite and carbide of iron, for in such case the * Impact Tests on Wrought Steels of Commerce. Proceedings ofthe Institution of Mechanical Engineers, 1904, p. 1135. Overheated Steel 401 ferrite behaves as if it were massive, and the yield point isnecessarily nuioh lower. (6) The weakness of a steel under stress in any givendirection depends on the manner in which the ferrite and pearliteare arranged with relation to the stresses applied. For in-stance, in large forgings it not infrequently happens that theferrite and pearlite are arranged in more or less continuous bandsor sheets. If a polished and etched section is bent slightly atright angles to the plane of these, and is then examined, it willbe found that the ferrite bands are depressed below the surface,whilst the lines of pearlite remain in relief. On attempting to. Fig. 8. Broken Axle after Heat Treatment; section cut from a fatigue test piece. Magnified 50 diameters. Fig. 9. Broken Axle in Normal State; sec-tion cut from a fatigue test 50 diameters. bend to any great extent, the piece will break at a very poorangle. If, however, bending is effected with the fiber, the steelwill bend quite close without fracturing. If such a steel isheated to a sufficient temperature so as to cause the carbon to beregularly diffused through what was originally massive ferrite,and it is then quenched in water and reheated to 650° C, it willbend close equally in each direction, provided that there is acomplete aVjsence of strings or plates of sulphide or silicate ofmanganese. 402 The Iron and Steel Magazine To make the point clearer by a hypothetical case, let usassume that a bar of pearlite is divided midway between itsends by a plate of ferrite i-io inch in thickness, and is per-fectty united with the pearlite on e
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Keywords: ., bo, bookcentury1800, bookdecade1890, booksubjectiron, bookyear1898
