It is generally believed that the non metallic inclusions in the steel pipe can destroy the continuity and compactness of the steel pipe, and the serious inclusions will lead to the emergence of the phenomenon of steel tube delamination. Another idea is hydrogen induced cracking, which is due to the formation of white spots in the circular tube, the formation of white spots in the circular tube, the formation of layer defects in the rolling process. In addition, the stress exceeds the plastic rotation of the two roller is not uniform deformation, can also lead to the strength of the layered.
Control measures of internal layer of steel pipe:
1, improve the plastic toughness of steel tube
Improving the cleanliness of molten steel, reduce harmful impurities; increase the proportion of the axis of the floor, reduce the central segregation and central porosity; the reasonable cooling system, avoid cracks in plate; billet rolling plate or offline slow cooling process, reduce internal stress, so as to ensure the organization performance and billet and finished products meet the technical standards.
2, reasonable control of heating temperature
The best heating temperature is selected by measuring the thermo plastic curve. Also note that there is enough time to heat the heating pipe to reduce the plastic deformation resistance, improve the toughness.
3, reduce the roll speed
Speed is a key parameter for the roll piercing process, in which the rolling speed changes from low to high, and there is a critical delamination starting to roll speed. At lower roll speeds, it is easy to form the lumen; the higher the roller speed, and the delamination defects of the capillary formation are easy to form. In order to eliminate the delamination defects and the capillary, the roll speed should be reduced to the critical delamination starting at the roll speed.
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