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condition of ductility, extensibility, or a certain grade of softness or hardness, with all that is involved in and follows from those Conditions. The effect may be See also:

MECHANICAL

mechanical only, or a chemical See also:

CHANGE (derived through the Fr. from the Late Lat. cambium, cambiare, to barter; the ultimate derivation is probably from the root which appears in the Gr. «a urmu', to bend)

change may take See also:

PLACE (through Fr. from Lat. platea, street; Gr. IrAar6s, wide)

place also. Sometimes the causes' are obvious, in other cases they are more or less obscure. But of the actual facts, and the immense importance of this operation as well as of the related ones of tempering and hardening in See also:

SHOP

shop processes, there is no question. When the treatment is of a mechanical See also:

CHARACTER (Gr. xapareri7p, from xap&crew, to scratch)

character only, there can be no reasonable doubt that the See also:

COMMON

common belief is correct, namely, that the metallic crystals or See also:

fibres undergo a molecular rearrangement of some See also:

KIND (O. E. ge-cynde, from the same root as is seen in " kin," supra)

kind. When it is of a chemical character, the process is one of cementation, due to the occlusion of gases in the molecules of the metals. Numerous examples of annealing due to molecular rearrangement might be selected from the extensive range of workshop operations. The following are a few only: when a See also:

BOILER

boiler-maker bends the edges of a See also:

PLATE

plate of See also:

STEEL, FLORA ANNIE (1847– )

steel or See also:

IRON [symbol Fe, atomic weight 55.85 (0=16)]

iron by See also:

HAMMER, FRIEDRICH JULIUS (1810-1862)

hammer blows (flanging), he does so in successive stages (heats), at each of which the plate has to be reheated, with inevitable cooling down during the See also:

time See also:

WORK

work is being done upon it. The result is that the plate becomes brittle over the parts. which have been subjected to this treatment; and this brittleness is not uniformly distributed, but is localized, and is a source of weakness, inducing a liability to crack. If, however, the plate when finished is raised to a full red heat, and allowed to cool down away from See also:

ACCESS (Lat. accessus)

access of cool See also:

air, as in a See also:

FURNACE

furnace, or underneath See also:

wood ashes, it resumes its old ductility.

The plate has been annealed, and is as safe as it was before it was flanged. Again, when a See also:

SHEET

sheet of thin metal is forced to assume a shape very widely different from its See also:

ORIGINAL

original See also:

PLANE

plane aspect, as by hammering, or by See also:

DRAWING

drawing out in a press—a See also:

CARTRIDGE (corruption of Fr. cartouche)

cartridge See also:

case being a See also:

FAMILIAR (through the Fr. familier, from Lat. familiaris, of or belonging to the familia, family)

familiar example—it is necessary to anneal it several times during the progress of the operation. Without such annealing it would never arrive at the final See also:

STAGE (Fr. 6/age; from Lat. stare, to stand)

stage desired, but would become torn asunder by the See also:

EXTENSION (Lat. ex, out ; tendere, to stretch)

extension of its metallic fibres. Cutting tools are made of steel having sufficient See also:

CARBON (symbol C, atomic weight 12)

carbon to afford capacity for hardening. Before the process is performed, the condition in which the carbon is See also:

PRESENT

present renders the steel so hard and tough as to render the preliminary turning or shaping necessary in many cases (e.g. in milling cutters) a tedious operation. Tolessen this labour, the steel is first annealed. In this case it is brought to a See also:

low red heat, and allowed to cool away from the air. It can then be machined with See also:

COMPARATIVE

comparative ease and be subsequently hardened or tempered. When a metallic structure has endured See also:

long service a See also:

state of fatigue results. Annealing is, where practicable, resorted to in See also:

order to restore the original strength. A familiar See also:

ILLUSTRATION

illustration is that of chains which are specially liable to succumb to See also:

CONSTANT, BENJAMIN (1845-1902)

constant overstrain if continued for only a See also:

YEAR

year or two. This is so well known that the practice is regularly adopted of annealing the chains at See also:

REGULAR

regular intervals.- They are put into a clear hot furnace and raised to a low red heat, continued for a few See also:

HOURS, CANONICAL

hours, and then allowed to cool down in the furnace after the withdrawal of the source of heat.

Before the annealing the fracture of a See also:

LINK

link would be more crystalline than afterwards. In these examples, and others of which these are typical, two conditions are essential, one being the grade of temperature, the other the cooling. The temperature must never be so high as to cause the metal to become overheated, with See also:

RISK

risk of burning, nor so low as to prevent the penetration of the substance with a See also:

GOOD, JOHN MASON (1764-1827)

good See also:

VOLUME

volume of heat. It must also he continued for sufficient time. More than this cannot be said. Each particular piece of work requires its own treatment and See also:

period, and nothing but experience of similar work will help the craftsman. The cooling must always be See also:

GRADUAL (Med. Lat. gradualis, of or belonging to steps or degrees; gradus, step)

gradual, such as that which results from removing the source of heat, as by drawing a furnace See also:

FIRE (in O. Eng. f j'r; the word is common to West German languages, cf. Dutch vuur, Ger. Feuer; the pre-Teutonic form is seen in Sanskrit pu, pavaka, and Gr. irup; the ultimate origin is usually taken to be a root meaning to purify, cf. Lat. purus)

fire, or covering with non-conducting substances. The chemical kind of annealing is specifically that employed in the manufacture of malleable See also:

CAST (from the verb meaning " to throw "; the word is Scand. in origin, cf. Dan. kaste, and Swed. kasta; " cast " in Middle Eng. took the place of the A.S. weor pan, cf. Ger. werf en)

cast iron. In this process, castings are made of See also:

white iron,—a brittle quality which has its carbon wholly in the combined state. These castings, when subjected to heat for a period of ten days or a fortnight, in closed boxes, in the presence of substances containing See also:

OXYGEN (symbol 0, atomic weight 16)

oxygen, becomehighly ductile. This change is due to the absorption of the carbon by the oxygen in the cementing material, a comparatively pure soft iron being See also:

LEFT

left behind. The result is that the originally hard, brittle castings after this treatment may be cut with a See also:

KNIFE (0. E. cuff, a word appearing in different forms in many Teutonic languages, cf. Du. knijf, Ger. Kneif, a shoe-maker's knife, Swed. knif; the ultimate origin is unknown; Skeat finds the origin in the root of " nip," formerly " knip "; Fr. canif is a

knife, and be See also:

bent See also:

double and See also:

TWISTED

twisted into spirals without fracturing.

The distinction between hardening and tempering is one of degree only, and both are of an opposite character to annealing. Hardening, in the shop sense, signifies the making of a piece of steel about as hard as it can be made—" See also:

glass hard "—while tempering indicates some stage in an See also:

INFINITE (from Lat. in, not, finis, end or limit; cf. findere, to deave)

infinite range between the fully hardened and the annealed or softened condition. As a See also:

MATTER

matter of convenience only, hardening is usually a stage in the work of tempering. It is easier to harden first, and " let down " to the See also:

TEMPER (from Lat. temperare, to mingle or compound in due proportion, to qualify, rule, regulate, to be moderate, formed from tempos, time, fit or due season)

temper required, than to secure the exact heat for tempering by raising the material to it. This is partly due to the long established practice of estimating temperature by See also:

COLOUR (Lat. color, connected with celare, to hide, the root meaning, therefore, being that of a covering)

colour tints; but this is being rapidly invaded by new methods in which the temper heat is obtained in furnaces provided with pyrometers, by means of which exact heat regulation is readily secured, and in which the See also:

HEATING

heating up is done gradually. Such furnaces are used for hardening balls for See also:

BEARINGS

bearings, cams, small toothed wheels and similar work, as well as for tempering springs, milling cutters and other- kinds of cutting tools. But for the cutting tools having single edges, as used in See also:

ENGINEERS, MILITARY

engineers' shops, the colour test is still generally retained. In the practice of hardening and tempering tools by colour, experience is the only safe See also:

GUIDE (in Mid. Eng. gyde, from the Fr. guide; the earlier French form was guie, English " guy," the d was due to the Italian form guida; the ultimate origin is probably Teutonic, the word being connected with the base seen in O. Eng. witan, to know)

guide. Colour tints vary with degrees of See also:

LIGHT

light; steels of different brands require different treatment in regard to temperature and quenching; and steels even of identical chemical See also:

composition do not always behave alike when tempered. Every fresh See also:

brand of steel has, therefore, to be treated at first in a tentative and experimental See also:

FASHION (adapted from Fr. facon, agon, Lat. factio, making, facere, to do or make)

fashion in order to secure the best possible results. The larger the-masses of steel, and the greater the disparity in dimensions of adjacent parts, the greater is the risk of cracking and distortion. Excessive length and the presence of keen angles increase the difficulties of hardening.

The following points have to be observed in the work of hardening and tempering. A grade of steel must be selected of suitable quality for the purpose for which it has to be used. There are a number of such grades, ranging from about 11 to z % content of carbon, and each having its See also:

SPECIAL

special utility. Overheating must be avoided, as that See also:

burns the steel and injures or ruins it. A safe See also:

RULE

rule is never to heat any grade of steel to a temperature higher than that at which experience proves it will take the temper required. Heating must be regular and thorough throughout, and must therefore be slowly done when dealing with thick masses. Contact with sulphurous See also:

FUEL (O. Fr. feuaile, popular Lat. focalia, from focus, hearth, fire)

fuel must be avoided. See also:

BATHS

Baths of molten See also:

ALLOYS (through the Fr. aloyer, from Lat. alligare, to combine)

alloys of See also:

lead and See also:

TIN (Lat.- stannum, whence the chemical symbol " Sn "; atomic weight =117.6, 0=16)

tin are used when very exact temperatures are required, and when articles have thick and thin parts adjacent. But the See also:

gas furnaces have the same advantages in a more handy See also:

FORM (Lat. forma)

form. Quenching is done in See also:

WATER

water, oil, or in various hardening mixtures, and sometimes in solids. See also:

RAIN (O.E. regn; the word is common to Teutonic languages, cf. Ger. Regen, Swed. and Dan. regn; it has been connected with Lat. rigare, to wet, Gr. 13pixeav)

Rain water is the See also:

PRINCIPAL

principal hardening See also:

AGENT (from Lat. agere, to act)

agent, but various saline compounds are often added to intensify its See also:

ACTION

action. Water that has been long in use is preferred to fresh.

Water is generally used See also:

COLD (in O. Eng. cald and ceald, a word coming ultimately from a root cognate with the Lat. gelu, gelidus, and common in the Teutonic languages, which usually have two distinct forms for the substantive and the adjective, cf. Ger. Kolte, kalt, Dutch koude

cold, but in many cases it is warmed to about 8o° F., as for milling cutters and taps, warmed water being less liable to crack the cutters than cold. Oil is preferred to water for small springs, for guns and for many cutters. See also:

Mercury hardens most intensely, because it does not evaporate, and so does lead or See also:

wax for the same See also:

REASON (Lat. ratio, through French raison)

reason; water evaporates, and in the spheroidal state, as See also:

steam, leaves contact with the steel. This is the reason why long and large See also:

OBJECTS

objects are moved vertically about in the water during quenching, to bring them into contact with fresh cold water. There is a good See also:

DEAL

deal of See also:

MYSTERY (Gr. µw(Trilpcov, from tcuvrm, an initiate, µfew, to shut the mouth)

mystery affected by many of the hardeners, who are very particular about the composition of their baths, various See also:

OILS (adopted from the Fr. oile, mod. huile, Lat. oleum, olive oil)

oils and salts being used in an infinity of combinations. Many of these are the result of long and successful experience, some are of the nature of " fads." A change of See also:

bath may involve injury to the steel. The most difficult articles to harden are springs, miffing cutters, taps, reamers. It would be easy to give scores of hardening compositions. Hardening is performed the more efficiently the more rapidly the quenching is done. In the case of thick objects, however, especially milling cutters, there is risk of cracking, due to the difference of temperature on the outside and in the central See also:

BODY

body of metal. Rapid hardening is impracticable in such objects. This is the cause of the distortion of long taps and reamers, and of their cracking, and explains why their See also:

TEETH (O.E. Eel); plural of tooth, O.E. top)

teeth are often protected with soft See also:

SOAP

soap and other substances.

The presence of the body of heat in a See also:

TOOL (0. Eng. tdl, generally referred to a root seen in the Goth. taujan, to make, or in the English word " taw," to work or dress leather)

tool is taken See also:

ADVANTAGE

advantage of in the work of tempering. The tool, say a See also:

CHISEL (from the O. Fr. cisel, modern ciseau, Late Lat. cisellum, a cutting tool, from caedere, to cut)

chisel, is dipped, a length of 2 in. or more being thus hardened and blackened. It is then removed, and a small See also:

AREA

area rubbed rapidly with a See also:

hit of grindstone, observations being made of the changing tints which gradually appear as the heat is communicated from the hot shank to the cooled end. The heat becomes equalized, and at the same time the approximate temperature for quenching for temper is estimated by the See also:

APPEARANCE (from Lat. apparere, to appear)

appearance of a certain tint; at that instant the See also:

ARTICLE (from Lat. articulus, a joint)

article is plunged and allowed to remain until quite cold. For every different class of tool a. different tint is required. " Blazing off " is a particular method of hardening applied to small springs. The springs are heated and plunged in oils, fats, or See also:

TALLOW (M.E. talugh, talg, cf. Du. talk, L. Ger. talg ; the connexion with O.E. taelg, dye, or Goth, tulgus, firm, is doubtful)

tallow, which is burned off previous to cooling in air, or in the ashes of the forge, or in oil, or water usually. They are hardened, reheated and tempered, and the tempering by blazing off is repeated for heavy springs. The practice varies almost infinitely with dimensions, quality of steel, and purpose to which the springs have to be applied. The range of temper for most cutting tools lies between a See also:

PALE (through Fr. pal, from Lat. palms, a stake, for paglus, from the stem pag- of pangere, to fix; " pole " is from the same original source)

pale See also:

STRAW

straw or yellow, and a light See also:

PURPLE

purple or See also:

PLUM

plum colour. The corresponding range of temperatures is about 4300 F. to 5300 F., respectively. " See also:

SPRING (from " to spring," " to leap or jump up," " burst out," O. Eng., springau, a common Teut. word, cf. Ger. springer, possibly allied to Gr. QnrFpxecOac, to move rapidly)

Spring temper " is higher, from dark purple to See also:

BLUE (common in different forms to most European languages)

blue, or 5.50 F. to 63o° F.

In many See also:

FINE

fine tools the range of temperature possible between good and poor results lies within from 5° to To° F. There is another kind of hardening which is of a superficial character only—" case hardening." It is employed in cases where toughness has to be combined with durability of See also:

SURFACE

surface. It is a cementation process, practised on wrought iron and mild steel, and applied to the link motions of engines, to many pins and studs, eyes of levers, &c. The articles are hermetically luted in an iron See also:

box, packed with nitrogenous and saline substances such as potash, See also:

bone dust, See also:

leather cuttings, and See also:

salt. The box is placed in a furnace, and allowed to remain for periods of from twelve to See also:

THIRTY

thirty-six hours, during which period the surface of the metal, to a See also:

DEPTH

depth of to in., is penetrated by the cementing materials, and converted into steel. The work is then thrown into water and quenched. A muffle furnace, _employed for annealing, hardening and tempering is shown in fig. 1; the heat being obtained by means of See also:

PETROLEUM (Lat. Petra, rock, and oleuin, oil)

petroleum, which is contained in the tank A, and is kept under pressure by pumping at intervals with the wooden handle, so that when the See also:

VALVE (Lat. valva, a leaf of a double or folding door, allied to volvere, to roll, as of a door on its hinges)

valve B is opened the oil is vaporized by passing through a heating coil at the furnace entrance, and when ignited burns fiercely as a gas See also:

FLAME (Lat. flamma; the root flag- appears in flagrare, to burn, blaze, and Gr. d, XEryew)

flame. This passes into the furnace through the two holes, C, C, and plays under and up around the See also:

ANNELIDA

ANNELIDA muffle D, See also:

STANDING

standing on a fireclay slab. The See also:

DOORWAY (corresponding to the Gr. Iran, Lat. porte)

doorway is closed by two fireclay blocks at E. A temperature of over 20000 F. can be obtained in furnaces of this class, and the heat is of course under perfect See also:

CONTROL (Fr. contrdle, older form contre rolle, from Med. Lat. contra-rotulus, a counter roll or copy of a document used to check the original; there is no instance in English of the use of " control " in this, its literal, meaning)

control. A reverberatory type of gas furnace, shown in fig.

2, differs from the oil furnace in having the flames brought down through the roof, by pipes A,A,A, playing on work laid on the fireclay slab B, thence passing under this and out through the See also:

ELBOW

elbow- 1.1 „c " See also:

PIPE

pipe C. The hinged doors, D, give a full opening to the interior of the furnace. It will be noticed in both these furnaces (by Messrs See also:

Fletcher, See also:

Russell & Co., Ltd.) that the iron casing is a See also:

mere See also:

shell, enclosing very thick See also:

FIREBRICK

firebrick linings, to retain the heat effectively. (J. G.

End of Article: ANNEALING, HARDENING AND

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