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Tin Plate

plates, pot, placed, heated, production and rolls

TIN PLATE, Manufacture of. The manu facture of tin plate was probably begun in Bohemia, about the beginning of the 16th cen tury, and was first attempted in England about 1670. The crude methods consisted of the simple expedient of dipping the plates of iron into a vat of molten tin and allowing the surplus metal to drain off. In 1865 Mr. More wood, of South Wales, England, invented a machine which gave tin plate manufacture its start, greatly reducing the cost of production. At the surface of the pot he placed a pair of steel rods which seized the plate as it came up and rolled off the superfluous tin; thus leaving.. the coating of the plate smooth and even. Since then many improvements have been made in the methods of manufacture, making the product more serviceable and reducing materi ally the manufacturing expenses. The modern method is as follows: After the bars of steel have reached the rolling mill they are first cut into accurate lengths, then placed in the sheet-mill furnace, brought to a cherry-red heat, taken out in pairs and given three or four passes through rough ing rolls, each bar being fed through sidewise and rolled singly. After cooling they are again heated, placed one upon the other, and in pairs are again rolled. The doubler then grasps the plates at one end with a pair of large tongs and brings the two ends together. The loose ends are then shorn off square, and the fold is flat tened by means of a powerful press, thus mak ing four thicknesses or plates, one end of each being free, the other still forming the bend. The plates are again heated, passed through the roughing rolls, taken by the doubler, opened back to the bend, and once more doubled. The first bend is snipped off when the ends are squared, thus making one free end for each sheet in the pack. This is done to prevent buckling and to insure a perfect finished plate. They are then heated for the fourth time, passed two or three times more through the finishing rolls and are then ready for the pickier.

After the sheets have been separated and examined for possible flaws, they are sent to the black pickier, where they are immersed in a strong solution of acid and hot water to re move all dirt, after which they are rinsed and allowed to drain. All perfect plates, in order

to make them sufficiently soft for general use, are sent to the annealing furnace, which opens the pores and toughens the plate. After be ing heated there thoroughly for a period of about 12 hours the plates are cooled off and carried to the cold rolls through which they are passed singly. The re-squarer then trims the four edges and restacks the plates in the annealing box; they are again annealed and put into the white pickier, in which the acid solu tion is much weaker than in the first bath.

Having been pickled and rinsed, the plates are placed in water boshes; immersed in a bath of melted palm-oil; placed in a pot con taining molten tin and lead; and finally dipped into another pot of tin of lower temperature than the previous one. From the tinning pot they are put into the grease pot, the thickness of the coating being determined by the length of time they remain therein. After cooling they are cleaned by passing through bran and dust. This completes the process and the plates are ready for the market.

According to the census of 1905 there were in the United States 36 establishments engaged in the manufacture of tin plate, employing $10,813,239 capital and 4,847 persons; paying $2,383,070 for wages and $31,375,714 for mate rials; and having an aggregate output valued 'Th at $35,283,360. e business has largely in creased since, and the present method of figur ing the production is by boxes. Of these the production in 1914 was 20,271,683, 1915 22,925, 437, 1916 26,979,994 and 1917 32,898,597. The tremendous increase, due to war orders, can not be maintained unless there is an increase in the production of tin, which is not expected.

Consult Louis, H., 'Metallurgy of Tin' (1911); • Schnabel, C., 'Handbook of Metal lurgy' (2d ed., 2 vols., London 1905-07).