Avoid all sharp angles-

Shrinkage in Castings.

Steel-castings.

Manufacture of Wrought-iron.

Refining and Puddling.

When beams or other rolled-iron shapes are to be rolled the cold muck bars arc sheared off to convenient lengths and sufficient of them tied together with wire into bundles to make the desired length of beam or other shape This is called piling. Usually from five to nine muck bars are piled on top of each other in each bundle.

The details of piling and size of muck bars, of course, vary in different shops. The Phoenix Iron Company form their pile for beams over nine inches deep very ingeniously, by rolling bars of different shapes, which are keyed and fitted into each other and are driven and held firmly together by wedges, as shown in Figure 160.

From puddle ball to muck bar.

System of Piling.

The writer believes that there are only a few mills using this method, which is to be regretted, as the advantage of having the grain or joints of the rolled-section longitudinal to each part is very great over the method where the seams run at right angles to the web, as is the case in the ordinary pilinc.

Table XXVII Densities And Weights Of Cast Irons 2001

Fig. 160.

These bundles or piles are put into the fire and heated to an almost white heat. They are then put on barrows or trucks and run as fast as possible to the rolls. These are arranged in pairs or in threes in a long line. The rollers are about eight feet long, the ends supported in cast-iron stanchions (called housings) of tremendous strength, the pressure against them being very great when the iron is forcing its way between two rollers. In "two-high mills" there are two rows of rollers over each other, in "three-high mills" there are three rows of rollers over each other. Each row of rollers revolves in opposite direction to the next row over, the result being that the iron is drawn in and squeezed between them. The roller has cut along its surface grooves which gradually shape the heated mass to its final section. The first set of teeth shape the iron roughly to the shape desired, the next pair come a little nearer to the shape, and so on till the last pair which give it the exact shape ; for large sections it sometimes requires two sets of three-high rollers for each piece, but usually one set answers to roughen and finish the piece. Of course the length of the piece increases as its cross-section is diminished by the squeezing process of the rollers. Where the rollers are three-high, the heated bundle or pile is run through the first set of grooves in the lower pair of rollers in one direction; as it comes out on the other side, it is picked up by a pair of tongs (usually manipulated by hand, but by steam when large pieces are being rolled), and carried to the upper pair of rollers, where it runs back through their first pair of grooves but in the opposite direction. It is then carried to the second pair of grooves in the lower rollers where it runs through in the same direction as through the first, then back through the second pair of grooves in the upper rollers and so on to the end. Where the mill is only two high the rolling is all done in the same direction, the iron being run back over the upper roll, its friction on and the turning of the roll facilitating greatly the work of getting it back quickly. The operation of rolling continues during the one heating of the bundle or pile of refined iron, as, of course, the furnaces would not be large enough to re-heat long pieces. The rolling must, therefore, be very rapid, and no delay should take place. The pressure of the rolls is so great that if the mass meets with any obstacle, instead of stopping and wedging in the roll the balance will run on out and curl the piece all up, sometimes even pushing the end up through the roof. When the iron has made its final passage through the rollers and is properly shaped in section, it usually is all curled up lengthways in both directions. It is still at a cherry red heat and is, therefore (after having the defective parts at the ends cut off by a circular saw), either run onto or quickly carried by a gang of men and placed lengthwise across a long series of skids or rollers. At the other ends of these skids are iron upright stops. A gang of men armed with heavy wooden mauls or mallets belabor the fiat side of the section its entire length till it touches the skids at every point. They now move it over against the stops and belabor the short edge or flat side of flange, till the flat side of the other flange touches the stops at every point. This, of course, straightens the beam or other section lengthwise in both directions. It is now allowed to cool and is ready to sell for use. Plate-iron is straightened as above. Beams and channels are straightened cold by being run through a gag press. Angles are straightened cold by running through straightening rolls.

Rolling out the Piles.

Description of Rollers.

Process of

Rolling.

Iron rolled as above is the ordinary rolled-iron of commerce and is known as merchantable or "single refined-iron."

For better qualities the muck liars are heated and rolled into plates of single refined-iron. When Forming the bundle or pile tin-top and bottom layers consist of the single refined plates, the intermediate layers being muck bars. Or the top, bottom and centre layers are of single refined-iron plates, the other layers being muck bars. This is generally known as "extra refined-iron" and a small advance is charged for it over single refined-iron. For the best work all the layers in the pile or bundle are made of single refined plates, no muck bars at all being used. This is known as "double refined-iron" and a considerable extra price is charged for it over the cost of single refined-iron.