Helical and straight weldment pipes (diameter 1420 mm, wall thickness 21.6 mm) made of Ch70 (API) low-alloy steels (Mn content 1.62%) doped with Nb (0.05%) or Nb, Mo and V (0.05%, 0.24% and 0.068%, respectively) were electropolished to remove 20 micrometer thick surface layer, subsequently heated at 200 deg C to 600 deg C for 12 h, then studied for residual stress by X-ray diffraction analysis and for changes in magnetic characteristics after tension 2 mm/min and twisting 30 deg of angle/min ( up to 650 MPa). Pipe specimens of diameter 6 mm and length 120 mm (working part) were used for the study. Content of microdeformations in crystalline network, coercive force and residual induction decreased while maximum magnetic permeability and its field increased with increasing annealing temperature in the range 400 deg C to 600 deg C. The coercive force showed a minimum while the residual induction and magnetic permeability field a maximum at a stress of about 200 MPa. The magnetic measurements were found efficient in determination of microdeformations of the crystalline network of the pipeline steels.
Use of magnetic methods for evaluation of stresses and deformations in pipeline steels
Titel russisch
Tjazeloe Masinostroenie ; 10 ; 2-6
2010
5 Seiten, 4 Bilder, 2 Tabellen, 6 Quellen
Aufsatz (Zeitschrift)
Russisch
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