The invention discloses a special test block for ultrasonic
creeping wave flaw detection of butt-jointed
welding seams of a special steel small-
diameter tube, which comprises a tool body and a tool shank, wherein the tool body comprises a
tool bit, a tool back and a tool edge, the tool shank is connected to the tool back side of the tool body through a connecting body, the tool back and the tool edge of the tool body are convex arc surfaces of which the curvatures are the same as that of an outer circle of the small-
diameter tube, and the side surface of the tool body is provided with three transverse through holes; the
tool bit is formed by concentrically and co-directionally overlapping two concentric sectors of which the diameters have one-
time difference, and one radial edge of each of the sectors is coincidently arranged with the tool back; and the thickness of the tool shank is the same as the wall thickness of the small-
diameter tube, the upper and lower surfaces of the tool shank are convex and concave arc surfaces of which the curvatures are the same as those of the outer circle and an inner circle of the small-diameter tube respectively, the convex and concave arc surfaces of the tool shank are provided with straight grooves with equal-depth openings respectively, and the side surface of the tool shank is provided with two transverse through holes. The special test block has a simple and practical structure, and can accurately test parameters of a
creeping wave probe, check monitoring process parameters, and be matched with a
creeping wave flaw detection process to realize the ultrasonic creeping wave flaw detection of the butt-jointed
welding seams of the special steel small-diameter tube.