Annealing

“ In annealing steels the operation is similar to hardening, as far as heating is concerned. The critical temperatures are the proper ones for annealing as well as hardening. From this point on there is a difference, for annealing consists in cooling as slowly as possible. The slower the cooling the softer will be the steel.
Annealing may be done in the open air, in furnaces, in hot ashes or lime, in powdered charcoal, in burnt bone, in charred leather and in water. Open-air annealing will do as a crude measure in cases where it is desired to take the internal stresses out of a piece. ”

“ In the process of annealing, the heat of the oven keeps the surfaces of the glass articles from absolutely becoming rigid, so that they yield sufficiently to the strain of the contracting interior portions; and if the whole substance of each article cools exactly together, the exterior and interior all the time at the same temperature, there is no strain and the ware is perfectly annealed. ”

“ Effect of Proper Annealing.—Proper annealing of low-carbon steels causes a complete solution or combination to take place between the ferrite and pearlite, producing a homogeneous mass of small grains of each, the grains of the pearlite being surrounded Page 117 by grains of ferrite. A steel of this refinement will machine to good advantage, due to the fact that the cutting tool will at all times be in contact with metal of uniform composition. ”

“ Better annealing is secured and harder metal may be annealed if the cooling is extended over a number of hours by placing the work in a bed of non-heat-conducting material, such as ashes, charred bone, asbestos fibre, lime, sand or fire clay. ”

“ Hot water was then substituted, and the cell was allowed to cool down to its original temperature. The six following pairs of responses were then taken. That this beneficial effect of annealing was not due to any accidental circumstance will be seen from the fact that both wires have their sensitiveness equally enhanced.
(4) In addition to this mode of annealing, both wires may be short-circuited and vibrated for a time. Lastly (5) slight stretching in situ will also sometimes be found beneficial. ”

“ If the annealing is to increase ductility to the maximum extent it should be slowly heated to slightly over the upper critical temperature and kept at this heat for a length of time necessary for a thorough penetration to the core, after which it can be cooled to about 1,200°F., then reheated to about 1,360°F., when it can be removed and put in an ash pit or covered with lime. If the annealing is just to relieve strains, slow heating is not necessary, but the steel must be brought up to a temperature not much less than a forging or rolling heat and gradually cooled. ”

“ In the manufacture of steel goods, which are first formed by the hammer, and require to be filed or otherwise treated, and in which softness and flexibility are essential to the change, annealing is absolutely necessary. This is particularly the case in making files and scissors; that the metal may be left sufficiently soft for cutting the teeth, and for filing off those parts which cannot be ground. Annealing is not less necessary in the drawing of wire, whether iron, copper, brass, silver, or gold. ”

“ Page 122 Annealing Method.—Forgings which are too hard to machine are put in pots with a little charcoal to cause a reducing atmosphere and to prevent scale. The covers are then luted on and the pots placed in the furnace. Carbon steel from 15 to 25 points is annealed at 1,600°F. Nickel steel of the same carbon and containing in addition 31⁄2 per cent nickel is annealed at 1,450°F. When the pots are heated through, they are rolled to the yard and allowed to cool. This method of annealing gives the best hardness for quick machining. ”

“ The experimental coining procedures are detailed in Appendix C. The alloys were blanked from strip without difficulty. A softening treatment prior to coining is necessary for any of these alloys. The temperature and time required to soften the blanks is greater as zinc content is increased beyond 5 percent. (See Annealing Summary - Table 4) As a result the annealing treatment for any of the experimental alloys would be more costly than for gilding metal blanks. ”

“ In addition to softening the steel, annealing benefits the metal by relieving strains in the piece. Should a particularly accurate job be called for, the steel should be annealed again after the roughing cuts have been taken and before machining to the final size. ”

“ In the electrical annealing of metals, case-hardened steel plates are locally softened where rivet-holes, &c., are required by passing an electric current through copper poles placed 1 or 2 inches apart on the smooth surface. Metallic wire is frequently heated to the annealing temperature between drawing operations, and various types of annealing furnaces are also electrically heated. ”

“ Annealing (an-ēl ́ing) , a process to which many articles of metal and glass are subjected after making, in order to render them more tenacious and which consists in heating them and allowing them to cool slowly. When the metals are worked by the hammer, or rolled into plates, or drawn into wire, they acquire a certain amount of brittleness, which destroys their usefulness, and has to be remedied by annealing. The tempering of steel is one kind of annealing. ”

“ Annealing Railway Wheels.—The leading and trailing wheels of locomotives, and railway carriage wheels, are commonly hollow cast-iron disc wheels.
The process of annealing adopted in a large manufactory in Philadelphia is as follows:—
The wheels are taken from the moulds, as soon after they are cast as they can bear moving without changing their form, and before they have become strained while cooling. In this state they are put into a circular furnace or chamber, which has been previously heated to a temperature about as high as that of the wheels when taken from the mould ”

“ In the production of very fine wire, the metal, after passing a few times through the draw-plate, requires annealing, as its fibres become so condensed and hardened that it is impossible to repeat the operation without some risk of the wire breaking. ”

“ In the manufacture and working of the various metals, annealing is frequently employed to reduce the brittle- ness usually resulting from a rapid or important change of molecular structure, such as is produced by hammering, long-continued vibration, rolling, and sudden cooling. ”

“ If it is desired to give a higher or more thorough tempering to iron or soft steel, the annealing process is repeated 2 or 3 times. The surface of the tool must, of course, be entirely free from scale. ”

“ We will say that the sawdust thickness on each side must be proportional to the dimensions of the speculum, or may even increase faster with advantage if time is of no moment.
The process of annealing may be considered successful if the disc does not fly to pieces in working; it is to be worked on the chilled side. The object of giving the chill the approximate counterpart form will now appear; it saves some rough grinding, and causes the finished surface to be more homogeneous than it would be if the centre were sunk by grinding through the chilled surface. ”

“ This was passed again and again between gradually approximated rollers, with occasional annealing, until the desired thickness had been attained. The great extension of surface thus produced had the drawback of exaggerating any small defect in the union of the two metals, increasing it to a blister of an inch or more in diameter. ”

“ It is usual in England to soften the dies by annealing, previous to restoring their shape, and again hardening them subsequently. The shape may be thus more perfectly restored but at a greater cost, and the operation of softening and re-hardening deteriorates the quality of the steel. ”

“ The story was intended to teach all workers in brass and other metals, that they must be very patient, especially in annealing. Annealing oxidizes and softens the metal. While hammering cold sheet brass, the oft repeated blows harden the metal and cause brittleness. ”

“ In annealing, the steel should be brought up to the right color, medium orange, and left at that heat until it is hot through, care being taken that the heat does not run any higher in any part of the piece. If the corners or edges or any part be allowed to run up to bright orange, or to medium or bright lemon, as is often done, then there is bad work; the result will be uneven grain and internal strains. ”

“ For breech-pieces each ingot must be reduced in diameter by forging at least 40 per cent.; in case tubes are forged upon a mandrel from bored ingots, the walls must be reduced in thickness by forging at least 50 per cent. Forgings are to be annealed, oil tempered under such conditions as will assure their resistance and again annealed, and no piece will be accepted unless the last process has been an annealing one. ”

“ It is recommended to the reader who wants to know the nature and uses of these and other tools in a smithy that he become an apprentice to the nearest blacksmith; there is no better way to learn.
Certainly no one can learn to anneal, braze, case-harden, temper, lay, and weld iron just by reading about it. But we can at least offer some definitions:
Annealing is the process of softening steel so that it can be worked by cutting tools. It is done by heating the piece in the fire to blood-red heat, then allowing it to cool slowly. ”

“ TOOL OR CRUCIBLE STEEL Crucible steel can be annealed either in muffled furnace or by being packed. Packing is by far the most satisfactory method as it prevents scaling, local hard spots, uneven annealing, or violent changes in shape. ”

“ A piece of unannealed barometer-tube, forty inches long, measured when just drawn, will become about one-fourth of an inch shorter if annealed; whereas, if quickly cooled without annealing, it will only contract about one-eighth of an inch. ”

“ If any parts are required to be tempered or hardened it must be remembered that they become brittle and can not afterward be bent without annealing or softening. Tool or drill steel is a name given to uniform or rather reliable grades of steel adapted to heat treatment as tempering or annealing. ”

“ In the manufactures, in which the malleable metals are employed, annealing is used to soften a metal after it has been rendered hard by the hammer, and also to soften cast-iron, which is rendered very hard and brittle by rapid cooling. ”

“ When a metallic structure has endured long service a state of fatigue results. Annealing is, where practicable, resorted to in order to restore the original strength. A familiar illustration is that of chains which are specially liable to succumb to constant overstrain if continued for only a year or two. ”

“ In proportion as this brittleness and hardness are reduced by annealing, the flexibility is increased, which allows of the employment of steel for an infinite variety of purposes. A bath of oil, which boils at about 600 Fahr., is often used for the annealing of steel tools, when a tem perature between the boiling-point of water and 500 or 600 Fahr. is required. Annealing is also employed to render cast-iron malleable or less brittle than it is naturally, so that a dozen of small articles such as buckles and knife- blades can be manufactiircd at less cost than a single article can be otherwise. ”

“ As the load is further augmented, there is in general a clearly marked yield-point, at which a sudden large extension ensues. In metals which have been annealed or in any way brought into a condition which is independent of the effects of earlier applications of stress, this clastic stage is well marked, and the limit of elasticity is as a rule sharply defined. But if the metal has been previously overstrained, without having had its elasticity restored by annealing or other appropriate treatment, a very different
behaviour is exhibited. ”

“ Sometimes, however, a second tempering will bring a long pitch nearer correct.”
“Do you soften your taps after roughing them out in the lathe?”
Answer.—“Never, if we can possibly avoid it. Sometimes it is necessary because of improper annealing at first. The more times steel is annealed the worse the results obtained in making the tool, and the less durable the tool.”
The following are answers to similar questions addressed to the Morse Twist Drill and Machine Co.:—
“The expansion of taps during hardening varies with the diameter. ”

“ It is to me most interesting to find that the very group of annelids, the Polychæta, which possess solenocytes so remarkably resembling those of the excretory organs of Amphioxus, are the highest and most developed of all the Annelida. I have argued throughout that the law of evolution consists in the origination of successive forms from the dominant group then alive, dominance signifying the highest type of brain-power achieved up to that time. ”

“ Very definite and comparatively uniform, are the relations between shapes and circumstances among the Annulosa: including under that title the Annelida and the Arthropoda. The agreements and the disagreements are equally instructive.
At one time or other of its life, if not throughout its life, every annulose animal is locomotive; and its temporary or permanent locomotion, being carried on with one end habitually foremost and one surface habitually uppermost, it fulfils those conditions under which bilateral symmetry arises. ”

“ The soft bodies of certain species are protected by a coat, or tube, formed by the agglutination of sand, or other foreign substances, as in the Sabella (Lign. 123, fig. 6, p. 385) .
The fossil remains of the testaceous Annelides are very abundant in some deposits; and even the naked, flexible, soft-bodied forms have left proofs of their existence in some of the most ancient sedimentary rocks. Traces of nine species, belonging to five genera of these soft, naked Annelides, have been observed in the Silurian strata of Britain.
Lign. 166. Fossil impression of Nereis. Silurian strata. ”