SAE 4140 H/RH Steel - Hardenability Diagram

SAE 4140 H/RH Steel

Steel name: SAE 4140 H/RH
Diagram No.: 1594
AISI/SAE designation: 4140
Chemical composition in weight %: Steel 4140 H: 0.37-0.44% C, 0.65-1.10% Mn, 0.15-0.0.30% Si, 0.75-1.20% Cr, 0.15-0.25% Mo. Steel 4140 RH: 0.38-0.43% C, 0.75-1.10% Mn, 0.15-0.35% Si, 0.80-1.10% Cr, 0.15-0.25% Mo.
Steel group: Alloy steels
Applications: No data
Comment: Restricted hardenability (RH) steels are desirable to provide more controlled heat treatment response and dimensional control for critical parts. In general, 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 in the inflection region. Generally, the RH-band follows the middle of the corresponding standard H-band. An example of the RH-band compared with the standard H-band is given for a standard SAE 4140.
RH-band steels shall be within the minimum and maximum HRC range specified at the J1 position and shall meet one additional minimum and one additional maximum HRC value. In the following tables, the two additional hardness values shall represent the approximate hardness for 50% martensite for the minimum and maximum specified carbon content, respectively (except where hardenability is too high to exhibit 50% martensite hardness; then the two points shall be 5 HRC below the minimum and maximum hardness specified at the J1 position.
Reference: Not shown in this demo version.

Heat Treatment

Hardenability Diagram

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