Machinery's Handbook, 31st Edition
412 Alloy Steels and toughness where section size is small enough to permit the desired physical proper- ties to be obtained with the customary heat treatment. Steels falling in this classification may be subdivided into two groups on the basis of hardenability: a) Low Hardenability: SAE 1330, 1335, 4037, 4042, 4130, 5130, 5132, 8630 b) Medium Hardenability: SAE 2330, 3130, 3135, 4137, 5135, 8632, 8635, 8637, 8735, 9437 0.40–0.42 Mean Carbon Content of SAE Specification: In general, these steels are used for medium and large parts requiring a high degree of strength and toughness. The choice of the proper steel depends on the section size and the mechanical properties that must be produced. The low and medium hardenabilty steels are used for average size automotive parts, such as steering knuckles, axle shafts, propeller shafts, etc. The high hardenability steels are used particularly for large axles and shafts for large aircraft parts. These steels are usually considered as oil quenching steels, although some large parts made of the low and medium hardenability classifications may be quenched in water under properly controlled conditions. These steels may be divided into three groups on the basis of hardenability: a) Low Hardenability: SAE 1340, 4047, 5140, 9440 b) Medium Hardenability: SAE 2340, 3140, 3141, 4053, 4063, 4140, 4640, 8640, 8641, 8642, 8740, 8742, 9442 c) High Hardenability: SAE 4340, 9840 0.45–0.50 Mean Carbon Content of SAE Specification: These steels are used primarily for gears and other parts requiring fairly high hardness as well as strength and toughness. Such parts are usually oil-quenched and a minimum of 90 percent martensite in the as- quenched condition is desirable. a) Low Hardenability: SAE 5045, 5046, 5145, 9747, 9763 b) Medium Hardenability: SAE 2345, 3145, 3150, 4145, 5147, 5150, 8645, 8647, 8650, 8745, 8747, 8750, 9445, 9845 c) High Hardenability: SAE 4150, 9850 0.50–0.63 Mean Carbon Content of SAE Specification: These steels are used primarily for springs and hand tools. The hardenability necessary depends on the thickness of the material and the quenching practice. a) Medium hardenability: SAE 4068, 5150, 5152, 6150, 8650, 9254, 9255, 9260, 9261 b) High Hardenability: SAE 8653, 8655, 8660, 9262 1.02 Mean Carbon Content of SAE Specification—SAE 50100, 51100, 52100: These straight chromium electric furnace steels are used primarily for the races and balls or rollers of antifriction bearings. They are also used for other parts requiring high hardness and wear resistance. The compositions of the three steels are identical, except for a varia - tion in chromium, with a corresponding variation in hardenability. a) Low Hardenability: SAE 50100 b) Medium Hardenability: SAE 51100, 52100 Resulfurized Steel: Some of the alloy steels, SAE 4024, 4028, and 8641, are made resul furized so as to give better machinability at a relatively high hardness. In general, increased sulfur results in decreased transverse ductility, notched impact toughness, and weldability. Characteristics and Typical Applications of Standard Stainless Steels.— Typical ap- plications of various stainless steel alloys are given in the following. The first number given is the AISI designation followed by the UNS number in parenthesis. (See also Num- bering Systems for Metals and Alloys on page 395) 201 (S20100): High work-hardening rate; low-nickel equivalent of type 301. Flatware; automobile wheel covers, trim.
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