The main difficulty in ultrasonic testing of large annular forgings is to consider both the detection sensitivity and the detection blind area. The detection sensitivity of different depths of the forging must meet the requirements of the technical conditions.
The detection blind area on the surface of the forging should be smaller than the machining allowance, but it is difficult to consider both at the same time. , the surface blind area of ultrasonic testing increases with the increase of the initial wave occupation width of the flaw detector, and the initial wave occupation width increases with the increase of sensitivity. For large size (300mm~400mm) forgings ultrasonic testing reaches 1.2mm flat bottom hole equivalent, the width of the initial wave has reached tens to hundreds of millimeters, and it is difficult to meet the requirement of a machining allowance of several millimeters.
Therefore, it is difficult to achieve the requirements of taking into account the sensitivity and detection of the blind areas through one detection in the detection of large-size forgings.
It can be considered to detect large-size forgings in-depth zones, that is, on the premise of satisfying the surface blind area, the combined performance of the measuring instrument and the probe shall be the maximum detection depth that can meet the detection sensitivity requirements as the surface area, in order to ensure the surface area.
The detection meets the requirements of detection sensitivity and blind area. It is necessary to make the reflected wave height of the flat-bottomed hole with the buried depth equal to the machining allowance and the maximum depth of the surface area reach the reference wave height.
The surface area is hereinafter referred to as the depth area. In order to ensure that the detection of the depth area meets the requirements of detection sensitivity and blind area, it is necessary to make the reflected wave height of the flat-bottomed hole with the buried depth equal to the maximum depth of the depth area and the surface area reach the reference wave height.
Large-scale annular forgings solve the problem of ultrasonic testing of large-scale and complex forgings according to the above ideas.
Considering that the detection blind area of the water immersion method is better than the contact method, and it is not sensitive to the surface roughness and shape of the forging, the water immersion method can be selected to detect the surface area; the sensitivity of the contact method is better than that of the water immersion method, and the contact method or the water immersion method can be considered.
The method to improve the sensitivity of the method can detect the depth area. According to the specific situation, on the premise of satisfying the sensitivity and blind area, the combined detection of the water immersion method and the contact method can be selected.
