Active Standard ASTM A768 / A768M | Developed by Subcommittee: A01.06
Book of Standards Volume: 01.05
Historical (view previous versions of standard)
This specification covers vacuum-treated 12% chromium alloy steel forgings for turbine rotors and shafts. Materials shall be manufactured by specified melting processes, heat treatment (quenching, tempering, and austenitizing), rough machining, boring, and stress relieving. Product analysis shall be used to evaluate if the elemental chemical compositions of the forgings are within specified range. Specimens shall also undergo tension and impact tests to evaluate their conformance to tensile and notch toughness requirements, which include tensile strength, yield strength, elongation, and reduction of area. Nondestructive tests, such as ultrasonic and internal inspection, and stability tests shall be performed as well. Forgings may be retreated one or more times, but not exceeding three additional times, if the results of mechanical tests fail to meet required values.
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1.1 This specification covers vacuum-treated 12 % chromium steel forgings for turbine rotors and shafts.
1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
A275/A275M Practice for Magnetic Particle Examination of Steel Forgings
A370 Test Methods and Definitions for Mechanical Testing of Steel Products
A418/A418M Practice for Ultrasonic Examination of Turbine and Generator Steel Rotor Forgings
A472/A472M Specification for Heat Stability of Steam Turbine Shafts and Rotor Forgings
A788/A788M Specification for Steel Forgings, General Requirements
ICS Number Code 77.140.85 (Iron and steel forgings)