The test block is designed according to the requirements of the standard NB/T47013-2015 non-destructive testing standard for the ultrasonic testing of carbon steel and low alloy steel forgings used in pressure equipment. It is suitable for the detection of carbon steel and low alloy steel forgings with thickness greater than 45mm by single crystal straight probe and the axial detection of carbon steel and low alloy steel bolt billets with diameter greater than or equal to M36 by straight probe.

Test method: According to the thickness of the workpiece to be tested and the standard requirements, select a group of suitable test blocks. The tested straight probe is placed on the detection surface shown in the diagram, and a group of φ2mm or φ3mm or φ4mm flat bottom holes (at least 3) with different detection distances are tested successively to make a straight probe range-amplitude curve, and this is used as the reference sensitivity. On this basis, a gain of 6dB is used as the scanning sensitivity.