Effect of structure and texture on the anisotropy of strength properties arising in the rolling of steel tubes

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Studies are made of the laws governing changes in the structure and crystallographic texture of tubes of austenitic (12Kh18N10T) and martensitic (38Kh5MSFA, 42Kh2N5SMA) steels that affect the anisotropy of the ultimate and yield strengths of these materials. These changes take place with a directional change in the strain characteristics of the rolled tubes. Features of transformation of the main components of texture in relation to initial structure and level and direction of plastic deformation are examined for rolled thin-walled tubes of austenitic and the same tubes when also heat-treated after rolling. The anisotropy of the strength properties is substantiated from the viewpoint of the effect of the crystalline orientation of the tension axis on the rate of strain-hardening of the material. For high-strength tubes made of martensitic steels, the measure of anisotropy of ultimate strength in longitudinal and transverse tension is determined to be dependent on the volume fraction of crystallites that form the secondary texture. The volume fraction of crystallites is determined by a quantitative relation linking the strain components over the diameter and wall thickness of the tube during rolling.