IIW blocks of different steels and manufacturing processes can have different
velocity and attenuation characteristics. This in turn may impact the results
obtained from ultrasonic nondestructive examinations. The American Society of
Testing Materials (ASTM) needs your help in developing realistic tolerances
for IIW carbon steel calibration blocks. Can you loan ASTM one or more of
your companys blocks for a couple of months so that the National Institute of
Standards and Technology (NIST) can make specific parametric measurements?
BACKGROUND
The International Institute of Welding (IIW) calibration blocks are used as a
standard reference for establishing some of the operating characteristics of
contact straight-beam and angle-beam search units. ASTM's Volume 3.03 on
Nondestructive Testing contains a document (E 164) titled, "Standard Practice
for Ultrasonic Contact Examination of Weldments." Annex A1 of this Standard
Practice describes the design of IIW blocks and details dimensional tolerances
for the manufacture of these blocks. It states that "materials must be
selected by the using parties." It also states that "unless otherwise
specified, a low carbon steel such as UNS G10180 is suggested." As a result,
there are a variety of reference blocks (manufactured to tight mechanical
tolerances but of different materials) being used in industry that may have
different ultrasonic characteristics.
ASTM-E 164 does not specify the requirements or tolerances for either
ultrasonic velocity or attenuation. As carbon steel IIW blocks are being made
of various materials (e.g. A36, 1018, 4340, etc.), acoustic velocity and
attenuation of the various materials can different. Further, the acoustic
parameters may vary due to heat treatment, rolling direction, texture and
whether the block is made from rolled plate or cast billet. The extent of
ultrasonic variability and its affect on the characterization of ultrasonic
search units has not been documented. However, differences in measurement
results between various users of the IIW blocks has generated questions that
need attention and resolution. At issue is the need to define realistic
acoustic parameters. Establishing acoustic tolerances would benefit all
parties by helping reduce potential ambiguity or errors in the analysis of
data obtained by ultrasonic testing.
ACOUSTIC PARAMETER MEASUREMENTS
NIST, Boulder, Colorado Division, has agreed to provide an independent
assessment of the acoustic velocity and attenuation of IIW blocks that are
manufactured and/or used in the United States. These data are to be used to
gain a better understanding of velocity and attenuation variances that might
affect ultrasonic nondestructive examination results. NIST has studied
various techniques and has selected procedures for making these ultrasonic
measurements. Now it needs to get a quantity of steel IIW blocks that are
representative of those being used by industry. These measurements are an
important part of NIST's collaborative materials characterization program with
ASTM. Once measurements are made, your blocks will be returned to you along
with measurement data.
ACTION REQUESTED
Would it be possible for your organization to provide NIST with one or more
steel IIW blocks for their tests. If so, please contact me, G. J. Posakony,
at GJPos@AOL.com and I can provide information and detailed shipping
instructions.