American Malleable Cast Iron (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1922 Excerpt: ... melting operation one of the hoped for advantages from the use of the more elaborate method is a better control of the product, in this case arising from the greater uniformity of the heat cycle to be expected in a tunnel kiln operation as compared with the operation of a furnace which has temperatures "varying widely, not only from time to time, but also from place to place in the furnace. Touceda has designed annealing furnaces of the usual form in which attempts are made to carry the elimination of heat losses as far as practicable. He has also suggested a furnace heated by fuel in which the temperature once readied would be maintained electrically by nearly automatic means. Such a furnace if practicable would be very interesting. At least one concern is attempting to introduce an electrically heated furnace. This, however, is decidedly in the experimental stage. So much for the practical execution of the annealing operation. Controlling Annealing Temperatures In any annealing operation pyrometric control will be required. Thermocouples are somewhat frequently introduced in nichrome or ceramic tubes througli the furnace wall or roof. The practice has the advantage of a quick response to changes of firing conditions and is the only one possible in the continuous furnace. However, it does not give any data as to the temperature of the metal itself and accordingly it is advantageous to have one or more couples actually within the pot. The interior of a good sized pot may lag 15 or 20 hours behind the furnace temperature. The lag is less the more solidly the pot is filled with iron and more the greater the per cent of packing. These figures apply when the furnace temperature is known and uniform. If the space into which the couple penetrates is filled ...