Tests show that 300M steel should be austenitized at temperatures above 1,800 deg. F to yield best combintion of strength and thickness. Tempering should be performed at temperatures between 400 and 600 deg. 

Raghavan, M.

Youngblood, J. L.

English

NASA Technical Reports Server

October 1975	 B75-10271 
NASA TECH BRIEF 
Lyndon B. Johnson Space Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Influence of Heat Treatment on

Mechanical Properties of 300M Steel 
Tests have been conducted on 300M steel to 
determine the heat treatment that yields the best 
combination of strength and thicknes. Bar stock with 
thicknesses of 0.5 in. (1.27 cm) and 1 in. (2.54 cm) 
was evaluated. The specimens were austenitized for 1 
hour in a vertical tube furnace in a continuously-
flowing helium atmosphere. They were then quenched 
in oil at room temperature and were double tempered 
(2 hours each time) in a salt bath. Austenitizing and 
tempering were conducted under the following 
temperatures: 
Austenitizing	 Tempering 
OF (K) OF (K) 
1,600 (1,140) Untempered 
1,800 (1,260) 400 (480) 
2,000 (1,370) 600 (590) 
2,200 (1,480) 800 (700) 
1.000 (810)
Test results for both bar stock thicknesses were 
similar. Data indicated that tensile strength decreased 
monotonically with tempering temperature for all 
austenitizing treatments. Yield strength, on the other 
hand, rose rapidly with tempering to approximately 
600° F (590 K) after which it decreased. Fracture 
toughness for samples austenitized at 1,600° F (1,140 
K) rose slowly and monotonically with tempering 
temperature. Maximum toughness was obtained from 
samples austenitized at temperatures exceeding
1,800'F (1,260 K), using a tempering temperature of 
494° F (530 K). Thereafter, the toughness decreased 
as the tempering temperature was raised, reaching a 
minimum at 800° F (700 K). 
On the basis of the observed results, it is concluded 
that the 300M steel should be austenitized at 
temperatures above 1,800° F (1,260 K). Tempering 
should be performed at temperatures between 4000 
and 600° F (480 and 590 K). Tempering at 
temperatures of 800° F (700 K) or over should be 
avoided. These results apply to steel section 
thicknesses of tin. (2.54 cm) or less. Additional work 
is required to establish these characteristics for 
thicker sections. 
Note: 
• Requests for further information may be directed 
to:
Technology Utilization Officer 
Johnson Space Center 
Code AT3 
Houston, Texas 77058 
Reference: TSP75-10271 
Patent status: 
NASA has decided not to apply for a patent. 
Source: J. L. Youngblood
Johnson Space Center and

M. Raghavan of

National Research Council

(MSC-14 792) 
Categories: 04 (Materials) 
06 (Mechanics) 
This document was prepared under the sponsorship of the National
	
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Influence of heat treatment on mechanical properties of 300M steel

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