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Show I ; HEAT TREATING I IMPOmiT STEP H Long Life of Steel Parts In- H sured by Carbonizing Pro- M cess in Motor Car M I Manufacturing. fl ' . One of the most important but least H 1 "understood processes connected with H i the manufacture of the modern motor H ' oar, is the science of heat treatment H I It is an old axiom that "No motor car H I ls stronger than its weakest point." H ! :Tbe motor is the heart of the car and fl , by that motor, the manufacturer's fl roputatlon must stand or fall. H The heat treating department stands fl out as the manufacturer's chief in- H surance against weak, faulty parts in ! t motor or chassis. In the Chalmers 'plant, for instance, every part that is subjected to severe strain must run the gauntlet of thirty furnaces in the heat treating department before it is m . ready for use. Among the parts treat- Hl pd in this department are steering H !' arms, crankshafts, connecting rods, h I camshafts and gears. H The camshaft, which must undergo H ( "a great share of the motor strain, is H lirst packed in a gas pipe about three H inches in diameter. A carbonizing Hl compound is then poured into the pipe Hl :nd tamped lightly about the cam- H r haft. After the camshaft is packed Hj snugly away in its steel container the H ends are securely plugged with fire Hj rlay and the camshaft is ready for H . the carbonizing furnace. H f When the furnace has been stacked H high with camshafts the doors are H i ( losed and the fire is turned on. i The heat generated In the carbonizing carboniz-ing furnaces rangea-from 1650 to 1700 degrees Fahrenheit and 1b regulated from a central control presided over by a tender whose sole business It is to keep tab on the temperature and timing. Each job which goes Into the fires is registered on a separate card which gives the tender a check on all work in process. Ovor each lurnace is a combination light-Indicator with three colored lenses blue, green and red. When the blue light shows the temperature is too low and more heat Is applied. When the Ted light shows It Is a danger signal, indicating that the heat is too Intense. The Ideal temperature tem-perature is indicated by the display of a green light. When all throe lights are burning the job Is done, and ready to come out of the furnace. Toughening the Steel. louring the process of carbonization a change takes place in the texture of the steel. In direct ratio to the length of time spent In the furnace the carbon compound which surrounds the camshaft penetrates the surface of the steel. The part which is carbonized car-bonized is called the case, and is much harder than the core, or Interior which has not been reached by the carbon. To carbonize the steel through to the core would mean a weakening of the entire camshaft, because the steel would, become brittle and lose its resiliency. After the carbonizing process, the shaft' is ready for its first heat treatment treat-ment totoughen the core. It is again placed In a furnace, this time without with-out Its gas pipe protector. Again the fire Is applied and the temperature tempera-ture raised to such a a degree that the core Is made tougher and more cap; able of standing severe strains. Al the correct time, the red hot shafts are lifted from the fire and shot down an incline that gives them a whirlins motion as they plunge into vat of water. This rotary motion assures that all parts will reach the water at the same time, so that cooling will be even. Bath Jn Boiling Oil. A third visit to tho furnace follows for the second heat-treatment for case hardening and closing the pores. Many makers omit the second treatment entirely, but Chalmers has Included It as an extra faotor of satety. After the final heating tho shaft Is again quenched In water. The last step In the Una of heat-treating heat-treating is a bath In boiling oil. This bath Is administered to release any strains or tension which the steel might have undergone in provlous ordeals or-deals by fire. From the oil vats, the camshafts are taken to the sandblast room. Here a surface scale, which has accumulated on tho steel, In removed re-moved by means of sand driven through a hose under high pressure. Not until the green camshaft huh passed through all these operations U it ready for the lathe work and finer machining operations which render it suitable for installation in the car |