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Steel MakingFatigue TestsIt has been known for fifty years that a beam or rod would fa... Annealing Method Forgings which are too hard to machine are put in pots with ... Chromium Chromium when alloyed with steel, has the characteristic func... Vanadium Vanadium has a very marked effect upon alloy steels rich in c... Suggestions For Handling High-speed Steels The following suggestions for handling high-speed steels are ... Testing And Inspection Of Heat Treatment The hard parts of the gear must be so hard that a new mill f... William Kelly's Air-boiling Process An account of Bessemer's address to the British Association w... Separating The Work From The Compound During the pulling of the heat, the pots are dumped upon a ca... Quenching Tool Steel To secure proper hardness, the cooling of quenching of steel ... Temperature Recording And Regulation Each furnace is equipped with pyrometers, but the reading an... Silicon SILICON is a very widespread element (symbol Si), being an es... Annealing ANNEALING can be done by heating to temperatures ranging from... Carburizing Material The simplest carburizing substance is charcoal. It is also th... Preventing Decarbonization Of Tool Steel It is especially important to prevent decarbonization in such... Molybdenum Molybdenum steels have been made commercially for twenty-five... Properties Of Alloy Steels The following table shows the percentages of carbon, manganes... Mushet And Bessemer That Mushet was "used" by Ebbw Vale against Bessemer is, perh... Tempering Round Dies A number of circular dies of carbon tool steel for use in too... Knowing What Takes Place How are we to know if we have given a piece of steel the ver... Refining The Grain This is remedied by reheating the piece to a temperature slig... |
Highly Stressed PartsCategory: APPLICATION OF LIBERTY ENGINE MATERIALS TO THE AUTOMOTIVE INDUSTRY The highly stressed parts on the Liberty engine consisted of the connecting-rod bolt, the main-bearing bolt, the propeller-hub key, etc. The material used for parts of this type was selected at the option of the manufacturer from standard S. A. E. steels, the composition of which are given in Table 11. TABLE 11.--COMPOSITION OF S. A. E. STEELS Nos. 2,330, 3,135 AND 6,130 Steel No 2,330 3,135 6,130 Carbon, minimum 0.250 0.300 0.250 Carbon, maximum 0.350 0.400 0.450 Manganese, minimum 0.500 0.500 0.500 Manganese, maximum 0.800 0.800 0.800 Phosphorus, maximum 0.045 0.040 0.040 Sulphur, maximum 0.045 0.045 0.045 Nickel, minimum 3.250 1.000 Nickel, maximum 3.750 1.500 Chromium, minimum 0.450 0.800 Chromium, maximum 0.750 1.100 Vanadium, minimum 0.150 All highly stressed parts on the Liberty engine must show, after heat treatment, the following minimum physical properties: Elastic limit, 100,000 lb. per square inch; elongation in 2 in., 16 per cent; reduction of area, 45 per cent; scleroscope hardness, 40 to 50. The heat treatment employed to obtain these physical properties consisted in quenching from a temperature of 1,525 to 1,575 deg.F., in oil, followed by tempering at a temperature of from 925 to 975 deg.F. Due to the extremely fine limits used on all threaded parts for the Liberty engine, a large percentage of rejection was due to warpage and scaling of parts. To eliminate this objection, many of the Liberty engine builders adopted the use of heat-treated and cold-drawn alloy steel for their highly stressed parts. On all sizes up to and including 3/8 in. in diameter, the physical properties were secured by merely normalizing the hot-rolled bars by heating to a temperature of from 1,525 to 1,575 deg.F., and cooling in air, followed by the usual cold-drawing reductions. For parts requiring stock over 3/8 in. in diameter, the physical properties desired were obtained by quenching and tempering the hot-rolled bars before cold-drawing. It is the opinion that the use of heat-treated and cold-drawn bars is very good practice, provided proper inspection is made to guarantee the uniformity of heat treatment and, therefore, the uniformity of the physical properties of the finished parts. The question has been asked many times by different manufacturers, as to which alloy steel offers the best machineability when heat-treated to a given Brinell hardness. The general consensus of opinion among the screw-machine manufacturers is that S. A. E. No. 6,130 steel gives the best machineability and that S. A. E. No. 2,330 steel would receive second choice of the three specified. In the finishing of highly stressed parts for aviation engines, extreme care must be taken to see that all tool marks are eliminated, unless they are parallel to the axis of strain, and that proper radii are maintained at all changes of section. This is of the utmost importance to give proper fatigue resistance to the part in question. Next: Gears Previous: Carbon-steel Forgings
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