Speaking of spiral steel pipe fracture and crack problem, we have to refer to the relatively backward country in the above application and production of spiral steel pipe, so for spiral steel pipe fracture is relatively small. However, due to our existing buried pipeline, most are spiral steel pipe, and several large steel pipe factory in the production of spiral steel pipe. Therefore, the fracture characteristics of the spiral pipe is very necessary. The following Xiaobian do a brief study on the fracture characteristics of spiral steel.
First, in the direction of cis rolling straight, that is to say, the same direction as the spiral weld, the spiral pipe fracture resistance minimum, that is in this direction, the spiral steel pipe is easy to crack. Secondly, in the vertical direction of pressing, the fracture resistance of the spiral pipe is the largest, ie, the direction of spiral steel pipe is not easy to crack in the direction. Finally, along the direction of the axis, the fracture resistance is the range between the above two directions.
2 for spiral pipe fracture direction determination, to depend on its CVN value. In the same one on tubing, if the ratio of the maximum CVN value and minimum CVN value at 2 or smaller, the helical tube pipe cracks along the axial extension; while maximum CVN value and the minimum CVN value ratio of at least 2 and close to 4 when the spiral steel pipe cracks extended along the rolling direction, and the instability of the crack will be extended along the axis; when the ratio of the maximum the CVN value and minimum CVN value of about 4 or greater when occurs the fracture, the direction of the spiral steel pipe along the rolling direction, i.e. in the direction of the spiral weld extensions. ; Once the maximum the CVN value and minimum CVN value ratio reaches 3:1 when we must consider the spiral steel pipe along the rolling direction of crack initiation.