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1.1 This specification covers hot-worked alloy and carbon-boron steels designed to attain restricted depth of hardening in the end-quench test. These steel compositions are identified by the suffix letter "RH" added to the conventional grade number.
1.2 In general, steels with restricted hardenability (RH steels) will exhibit a hardness range not greater than 5 HRC at the initial position on the end-quench hardenability bar and not greater than 65% of the hardness range for standard H-band steels (Specification A304) in the inflection region. Generally the restricted hardenability band follows the middle of the corresponding standard H-band. An example of the RH band compared with the H band is given for Grade 4140 in Fig. 1.
1.3 This specification is expressed in both inch-pound units and SI units. However, the material will be supplied to inch-pound units unless the purchase order specifies the "M" specification designation.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
A29/A29M Specification for Steel Bars, Carbon and Alloy, Hot-Wrought, General Requirements for
A255 Test Methods for Determining Hardenability of Steel
A304 Specification for Carbon and Alloy Steel Bars Subject to End-Quench Hardenability Requirements
E112 Test Methods for Determining Average Grain Size
SAE StandardsJ1868 Restricted Hardenability Bands for Selected Alloy Steels