Some samples of ore, coal and limestone, obtained in the Mittagong district, with pig-iron and castings manufactured therefrom, were exhibited at the Mining Exhibition in London and obtained a first award.
Sharp to indicate a stage in the life-history of an insect between two successive castings of the cuticle.
His grandfather had obtained from Venice an " artist " who undertook " to build churches and palaces, to cast big bells and cannons, to fire off the said cannons and to make every sort of castings very cunningly "; and with the aid of that clever Venetian he had become the proud possessor of a " cannon-house," subsequently dignified with the name of " arsenal."
During post-embryonic development - no insect being hatched with the smallest external rudiments of those organs - and on the necessity for successive castings or " moults " (ecdyses) of the cuticle.
Among the manufactures are charcoal, pig-iron, car wheels and general castings at Lime Rock, cutlery at Lakeville, and knife-handles and rubber brushes at Salisbury.
1 During the twelve years that followed Morse was engaged in a painful struggle to perfect his invention and secure for it a proper presentation to the public. In poverty he pursued his new enterprise, making his own models, moulds and castings, denying himself the common necessaries of life.
Among the manufactures are rubber goods, chemicals, iron castings, woollen goods, cutlery, &c. The value of the factory products increased from $8,886,676 in 1900 to $11,009,573 in 1905, or 23.9%.
Besides these there are gravestones, stelae with human heads, fragments of limestone, architectural designs as well as bronze castings of camels, horses, mice, serpents, &c. (cf.
They are frequently stated to be of beaten bronze, but they are really castings, apparently by the cire perdue process.
Japanese bronze is well suited for castings, not only because of its low melting-point, great fluidity and capacity for taking sharp impressions, but also because it has a particularly smooth surface and readily develops a fine patina.
But for very large castings the process had to be modified.
It has important iron and steel works and iron foundries, at which armour-plates, guns and projectiles are made for the Italian navy, also steel castings, machinery and rails, a royal arms factory, and lignite mining.
It has therefore been proposed, for greater depths, to put four columns of tubbings of smaller diameters, 82 and 52 ft., in the shaft, and fill up the remainder of the boring with concrete, so that with thinner and lighter castings a greater depth may be reached.
1877), two similar castings, A and B, each consisting.
The top flange consisted of cast iron hollow castings butted end to end, and the struts were of cast iron.
Hitherto it had been felt as a great difficulty in casting specula that the solidification did not begin at one surface and proceed gradually to the other, the common sand mould allowing the edges to cool first, so that the central parts were subject to great straining when their time of cooling came, and in large castings this generally caused cracking.
Specifically, it is cast iron in the form of castings other than pigs, or remelted cast iron suitable for such castings, as distinguished from pig iron, i.e.
Thus ornamental iron castings were made in Sussex in the 14th century, and in the 16th cannons weighing three tons each were cast.
In making malleable castings the annealing, i.e.
The castings, initially of white cast iron, are heated for about a week, to a temperature usually above 730° C. and often reaching 900° C. (1346° and 1652° F.).
The molecular freedom which this high temperature gives enables the cementite to change gradually into a mixture of graphite and austenite with the result that, after the castings have been cooled and their austenite has in cooling past Aci changed into pearlite and ferrite, the mixture of cementite and pearlite of which they originally consisted has now given place to one of fine or " temper " graphite and ferrite, with more or less pearlite according to the completeness of the transfer of the carbon to the state of graphite.
In carrying out this process the castings are packed in a mass of iron oxide, which at this temperature gradually removes the fine or " temper " graphite by oxidizing that in the outer crust to carbonic oxide, whereon the carbon farther in begins diffusing outwards by " molecular migration," to be itself oxidized on reaching the crust.
Steel castings have initially the extremely coarse structure due to cooling without mechanical distortion from their very high temperature of solidification; they are " annealed," i.e.
6, and then cast into castings of cast iron, or converted into wrought iron or steel by purifying it, following path 2.
If it is to follow path r the castings into which it is made may be either (a) grey or (b) chiiied or (c) malleable.
Grey iron castings are made by remelting the pig iron either in a small shaft of " cupola " furnace, or in a reverberatory or " air " furnace, with very little change of chemical composition, and then casting it directly into suitable moulds, usually of either " baked," i.e.
The general procedure in the manufacture of chilled and of malleable castings has been described in §§ 30 and 31.
Indeed, the remelting of cast iron to make grey iron castings belongs here.
In the former case there is no later chance to remove sulphur, a minute quantity of which does great harm by leading to the formation of cementite instead of graphite and ferrite, and thus making the cast-iron castings too hard to be cut to exact shape with steel tools; in the latter case the converting or purifying processes, which are essentially oxidizing ones, though they remove the other impurities, carbon, silicon, phosphorus and manganese, are not well adapted to desulphurizing, which needs rather deoxidizing conditions, so as to cause the formation of calcium sulphide, than oxidizing ones.
This has been particularly true in the manufacture of steel castings, i.e.
For making castings, especially those which are so thin and intricate that, in order that the molten steel may remain molten long enough to run into the thin parts of the mould, it must be heated initially very far above its melting-point, the Bessemer process has a very great advantage in that it can develop a much higher temperature than is attainable in either of its competitors, the crucible and the openhearth processes.
Charges in closed crucibles, and then casting it into ingots or other castings, though in addition the metal while melting may be carburized.
The manufacture of castings of cast iron, consists essentially in pouring the molten cast iron into, moulds, and, as preparatory steps, melting the cast iron itself and preparing the moulds.
For making castings of cast iron.
I), it can be melted and run even into narrow and intricate moulds, castings made of it are very often more economical, i.e.
- Different kinds of castings need very different sets of qualities, and the composition of the cast iron itself must vary from case to case so as to give each the qualities needed.
5) causes a sudden and permanent expansion, which forces the metal into even the finest crevices in its mould, a fact which is taken advantage of in making ornamental castings and others which need great sharpness of detail, by making them rich in graphite.
The expense of cutting castings accurately to shape, cutting on them screw threads and what not, called " machining " in trade parlance, is often a very large part of their total cost; and it increases rapidly with the hardness of the metal.
Beyond this, rapid cooling and the presence of sulphur both oppose the formation of graphite, and hence in cast iron rich in sulphur, and in thin and therefore rapidly cooling castings, the silicon-content must be greater than in thick ones and in those freer from sulphur.
Thus thick machinery castings usually contain between 1.50 and 2.25% of silicon, whereas thin castings and ornamental ones which must reproduce the finest details of the mould accurately may have as much as 3 or even 3.4 0% of it.
Castings which, like hydraulic press cylinders and steam radiators, must be dense and hence must have but little graphite lest their contents leak through their walls, should not have more than 1.75% of silicon and may have even as little as 1% if impenetrability is so important that softness and consequent ease of machining must be sacrificed to it.
The sulphur-content should not exceed 0.12%, and it is better that it should not exceed 0.08% in castings which have to be soft enough to be machined, nor 0.05% in thin castings the metal for which must be very fluid.
In the better classes of castings it is usually between 0.40 and 0.70%, and in chilled railroad car-wheels it may well be between 0.15 and 0.30%; but skilful founders, confronted with the task of making use of cast iron rich in manganese, have succeeded in making good grey iron castings with even as much as 2.20% of this element.
Fortunately its embrittling effect on cast iron is very much less than on steel, so that the upper limit or greatest tolerable proportion of phosphorus, instead of being o.10 or better 0.08% as in the case of rail steel, may be put at 0.50% in case of machinery castings even if they are exposed to moderate shocks; at 1.60% for gas and water mains in spite of the gravity of the disasters which extreme brittleness here might cause; and even higher for castings which are not exposed to shock, and are so thin that the iron of which they are made must needs be very fluid.
The permissible phosphorus-content is lessened by the presence of either much sulphur or much manganese, and by rapid cooling, as for instance in case of thin castings, because each of these three things, by leading to the formation of the brittle cementite, in itself creates brittleness which aggravates that caused by phosphorus.
Steel ingots and other steel castings are subject to three kinds of defects so serious as to deserve notice here.
In making castings of steel this same difficulty arises; and much of the steel-founder's skill consists either in preventing these pipes, or in so placing them that they shall not occur in the finished casting, or at least not in a harmful position.
But in addition to the greater cost of steel founding as compared with rolling there are two facts which limit the use of steel castings: (1) they are not so good as rolled products, because the kneading which the metal undergoes in rolling improves its quality, and closes up its cavities; and (2) it would be extremely difficult and in most cases impracticable to cast the metal directly into any of the forms in which the great bulk of the steel of commerce is needed, such as rails, plates, beams, angles, rods, bars, and wire, because the metal would become so cool as to solidify before running far in such thin sections, and because even the short pieces which could thus be made would pucker or warp on account of their aeolotachic contraction.
When we come to pieces of very irregular shape, such as crank-shafts, anchors, trunnions, &c., we must resort to forging, except for purposes for which unforged castings are good enough.
They include worsted spinning mills; collieries, ironstone mines, quarries and brickworks; the manufacture of iron and steel, both in the rough and in the form of finished articles, as locomotives, bridge castings, ships' engines, gun castings and shells, &c. The parliamentary borough returns one member.