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| SAE Metals and Carbon Steels By Larry Stevens Understanding S.A.E. Metals The purpose of this article is not develop an expertise, but rather to provide your thinking to a point where you can con- verse with experts and not be considered a novice. Most often we are speaking of alloys, which are simply a mixture of elements or compounds. The same in liquids are called solu- tions. Metals are generally mixed to change the strenth, machinabillity, forging characteristics, wearibiliy, hardness, melting points, etc. Melting point change is called cutictic change. For example; Navy Brass, consists of 70% copper which melts at 1981 degrees F, and 30% zinc which melts at 788 degrees. Combined they melt at 1706 degrees F. In the case of solutions, fresh water freezes at 32 degrees F. When salt is added the freezing point (and melting point) lowers The following are metals most often used to alloy steel we generally use. Carbon is not mentioned since this is already present in the base metal in the most desirable amount. The examples given refer to gear steels. Knowing the stress on gear teeth, one can judge the desirable effects on a particular application. Nickel- Increases hardness and strenth with effect on ductility. Chromium-Increases hardness and strenth over that obtained with nickel, but loss of ductility. Manganese- Greater strenth than that of nickel and more toughness than chromium. Likely to flow under unit pressure. Vanadium- Similar effects of those of manganese, Higher impact strenth,. Difficult to machine. Molybdenum-Increased strenth without afecting ductibility. High impact strenth, easily machined. Tungsten- Used in high speed cutting tools and magnets. There are two popular methods used to classify metals. A.S.T.M. ( American Society for testing Materials ) covers iron casting and shapes used in constrution produced by the hot rolling prosesses. S.A.E. (Society of Automobile Engineers). These are often called "Automotive Steels". Most of the S.A.E. steels a Blacksmith will be probably encounter will be of the junkyard variety used for tools, jigs,and fixtures to be used in trade. Basically the S.A.E. numbered system consists of four digits. The first digit of one through seven idenitifies the main alloy it contains. The second digit identifies the amount of alloy or what higher amounts or both. Example 1020 indicates plain carbon steel with.20% carbon 11XXwould indicate some magnese is present 20XX is a nickelsteel with 0.5%. 23XX has somewhat higher nickel content 3XXX is a nickel chromiun steel,33XX has somewhat higher content of both. 41XX is a chromium molybdenum steel. 43XX chromium, nickel, molybdenum steel 46XX nickel molybdenum steek 51XX low chromium steel. 515XX corrosion and heat risistent steel. (stanless) 61XX chromium vanadium steel 71XX tungsten steel All of this is nice to know, but what good is it while at a salvage yard with a truck cylinder head, studs in one hand and a rear axle in the other? The following is a list of truck steels which most American manufactures adhere to. Conecting rods SAE 2340 Connecting rod boles SAE 3135 cylinder head studs SAE 2330 Main bearing studs SAE 2330 Transmission shifting rods SAE 3120 Rear axle shafts SAE 4340 Rear axle studs SAE 2330 Rear axle wheel studs SAE 3135 Front axle centers SAE 3130 Spindle and steering arms SAE 3130 Leaf springs SAE 1085 Coil Springs SAE 1095 In summary, this article was written so that the next time acquire na piece of automotive scrap you will have a fair idea as to which SAE classification it belongs. A spark test compared to known steel sample will give an idea of its carbon content. This way an approximate determination can be made to see if it will serve the intended use. |
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