5.1 Reference blocks fabricated in accordance with this practice will exhibit specific area-amplitude and distance-amplitude relationships only with an immersion test at 5 MHz using the search unit, test instrument and test parameters described in this practice. Comparison test at other frequencies or with uncalibrated instruments will not necessarily give the same relationships shown in this practice. See Reference ( 1 ) for area-amplitude limitations at other frequencies and transducer diameters. Also see Reference ( 2 ) for cautions regarding use of standard blocks for test standardizations.

1.1 This practice covers a procedure for fabrication and control of metal alloy reference blocks used in ultrasonic examination that have a flat-surface sound entry, are cylindrical in shape, and contain flat-bottom holes (FBH) which may be used for checking the performance of ultrasonic examination instrumentation and search units and for standardization and control of ultrasonic examination of metal alloy products. The reference blocks described are suitable for use with either the direct-contact method or immersion pulse-echo ultrasonic methods.

1.2 While this procedure is basically designed for the fabrication and control of carbon and alloy steel blocks to be used in conjunction with the examination of these materials, the fabrication and control procedures may also be suitable for the preparation of blocks for other types of materials such as nickel-base alloys, certain types of aluminum alloys, and so forth. Additional procedures and controls may be required when fabricating reference blocks from other than carbon or alloy steel material. This practice shall in no way preclude the specification or addition of any supplemented requirements as deemed necessary for the specific application. This practice, however, must not be confused with, nor does it supersede Practice E127 , specifically governing the fabrication and evaluation of 7075-T6 aluminum alloy ultrasonic standard reference blocks.

1.3 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.

1.4 This standard does not purport to address all of the safety problems, 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.