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Wire chain forms an intermediate product between plate and welded load chain. The links either are in the form of an oval made of wire bent around a form with both ends butting against each other, or they are shaped like the figure eight with two openings, the ends butting against the sides of the wire piece near the middle.
Welded Chains
Welded chains are by far the most important, as the greater part of all chains in use are welded. They may be either hand or machine-made.
The hand-made chain is formed and welded by hand and is finished by blows of hand hammers, while the machine-made is wound into shape by machinery from coils or bars, cut into links by the same power, and is welded by dies operated by power or foot-driven hammers.
Machine-made chains cover sizes varying from 3/16 to1.25 inches in diameter, and are sold per 100-pound casks in three qualities, namely, proof coil chain, B.B. coil chain and B.B.B. coil chain.
Hand-made chains cover all sizes, 1.5 inch and heavier, and include stud link chains, which have an iron separator or stud pressed into the sides of the link; the latter are used largely for marine service. Hand-made chains are known and sold as crane or dredge chain and stud link chain.
Open-hearth steel is used largely in chain manufacture, but the better grades are made of the best refined iron. Nearly all chains are tested by the manufacturer before being shipped. The chains are subjected to a test strain, one-third in excess of that at which they should be worked in safety.
Weldless chains are either rolled or cast. There are numer-ous patented processes for producing rolled weldless chains, one of the most notable being a German invention, known as the Klatte process. Cast chains, even when cast from steel and sub-sequently rolled, have not found ordinary industrial application. Chains are shipped plain, or blackened if it is desired to pro-tect them from rust during transit.
Driving chains such as link belt, roller, rocker, silent drive, etc.,are of special design, requiring accurate machine finish, and in conjunction with suitable sprocket or gear wheels,form a part of the driving mechanism of some machines.
Tube and Pipe Industry
Tubes and pipes are interchangeable names given to long,hollow, metallic cylinders, open at both ends. Tubes are generally rated by their outside diameter, and pipes accord-ing to their nominal inside diameter. They are made from vari-ous materials, the most important being wrought steel, cast iron and wrought iron.
Cast iron pipes are used mainly for the conveyance of water having pressures less than 100 pounds per square inch. They are frequently cast with a bell mouth at one end, into which fits the plain end of the pipe to which it is connected. The space be-tween the plain pipe and bell is caulked with some pliable material, such as lead, to make it a tight joint. For high pressure, flanges are cast on the ends, which are connected with bolts. Cast pipes are manufactured in foundries specially built for this purpose. After being cast, they are usually dipped in hot asphalt before shipping.
Wrought steel pipes may be divided into riveted and welded. Riveted pipes are generally of diameters larger than 30 inches and are used for hydraulic purposes. They are made from plates overlapping each other and are united by means of rivets.
Welded pipes may be either butt-welded or lap-welded. Welded wrought steel pipe is used most extensively and enters into the construction of oil, gas and water lines. It is used in railroad cars for brake beams, air brake cylinders, for house heat-ing, plumbing, gas fitting and electric conduits, boiler flues，trolley poles, railings, posts, bent coils, air lines, etc.
Butt-welded tubes are made from skelp, heated to a welding temperature by pulling it through a bell-shaped die, which curls the plate and welds the edges together. Butt-welded tubes are only made up to 3 inches in diameter inclusive and are not as strong as lap-welded.