1,
SSAW steel pipe in different directions taken specimens tensile and impact tests, found that test different directions of yield strength and ultimate strength difference is small, generally only in the 5-10% range, and different direction of the sample cvn values vary greatly, cvn value entirely with the angle changes. Spiral although yield strength and ultimate strength in different directions difference is small, showing a very slight strength anisotropy, however cvn value in different directions is a big difference, that exhibit very serious impact toughness anisotropy the consequences of this serious cvn anisotropy values generated by the fracture resistance is different in different directions: straight along the rolling direction, that is the same as the spiral weld direction, the fracture of least resistance, that is easy along cracking in this direction; perpendicular to the rolling direction of the fracture resistance of the maximum; in the axial direction, the fracture resistance in between.
2, The line, the maximum principal stress is the hoop stress, that is the biggest driver of cracking along the axial direction. In other words, just from the stress situation, genetic defects most likely to crack the axial direction. For straight seam pipe, the direction of maximum and minimum driving directions crack fracture resistance is the same, and therefore the fracture must be carried out in the axial direction. However, the spiral, the two are not the same.
3, Spiral fracture propagation direction depending on whether the spiral pipe for CVN value anisotropic size.
4, Pipe defects are rarely found in the base material, generally in the weld or heat affected zone, and defects in the weld or heat affected zone is most consistent with the trend of the weld, ie straight seam tube defects in the axial direction, the spiral ramp of the defects.
