Study On The Nodularity And Thickness Of Centrifugal Nodular Cast Iron Pipe Using Ultrasonic Testing Method

Centrifugal Nodular Iron Pipe has been widely used in urban water supply, gas supply etc. project for its advandages such as thiner wall, better toughness, higher strength and better corrosion resistance and so on than Iron Pipe made from other process. With the expand of production increasingly, people pay more attention to the quality inspection and control of Centrifugal Nodular Iron Pipe. It is particularly important to test nodularity and the thickness for nodularity has impact on mechanical properties of Iron Pipe directly and thickness of pipe wall is uneven or part of pipe wall is too thin will cause the partial load capacity decline, then lead to accident of explosion.With the temperature fixed,the linear relationship between the nodularity and ultrasonic velocity have already been identification by people. For a long time,people were trying to test the nodularity of the centrifugate spheroidal graphite iron pipe.But,there are multiple of difficulties as the special shape of the pipe in the settlement of the sound travel and the sound path.This paper test the ultrasonic transversal wave velocity of the centrifugate spheroidal graphite iron pipe, making the main wave transmitting through the chord of the pipe by the specific designing probe device.The linear relationship of the nodularity and the transversal velocity in room temperature is obtained,and this method is used in the ultrasonic non-destructive test of the nodularity of centrifugate spheroidal graphite iron pipe.This method againsts the influence of the pipe thickness to the test of the velocity. Considering the effect of the temperature to the velocity,this study also test the law between the velocity and the temperature from room temperature to 160°C.The result shows that,the velocity linearly declined as the rising of the temperature and the temperature coefficient of velocity seems to no relationship with the nodularity .According to this,the velocity of various temperature can be converted to the velocity of room temperature,then the nodularity without temperature effect can be obtained.The thickness is also a important factor of the pipe quality,but the thickness of the pipe is difficult to measure with measuring tool unless two end of the pipe. So we measure transversal wave velocity and longital wave velocity of nodular iron pipe separately which product under certain production conditions(the same ingredients of iron liquid, the same state of matrix etc.), and get its transfer coefficient of transversal wave velocity and longital wave velocity, we convert the transversal velocity to longital velocity,then measure the thickness of the pipe using the reflection method.So we convert the transversal velocity to longital velocity,then measure the thickness of the pipe using the reflection method.The nodularity and thickness are measured at the same time,then the quality of the pipe is intergrate evaluated. The results show that it meet production requirements by mesuring the nodularity and the thickness employed this device in the production field.