Method for producing variable-thickness variable-diameter steel pipes

Abstract

The invention discloses a method for producing variable-thickness variable-diameter steel pipes. The method comprises the following four steps: unidirectionally fixing a mother pipe through a mother pipe feeding end; pushing the mother pipe through a pushing device to pre-expand the diameter of a mother pipe output end; bidirectionally fixing the mother pipe through the mother pipe feeding end and the mother pipe output end; expanding the diameter of the whole mother pipe through the pushing device and a drawing device. The method substantially changes the wall thickness of the steel pipe and also precisely controls the wall thickness of the steel pipe after diameter expanding, and the produced big-caliber seamless steel pipe has a good mechanical property and good appearance quality.

Description

technical field [0001] The invention relates to the technical field of production of large-diameter seamless steel pipes, in particular to a method for producing steel pipes with variable thickness and variable diameters. Background technique [0002] Seamless steel pipe is a commonly used fluid conveying pipe. Compared with solid round steel, when the bending and torsional strength is the same, its manufacturing material is less, its weight is lighter, and it is easy to process and shape. It is widely used in the manufacture of structural parts and mechanical parts. The production of seamless steel pipes mainly includes the piercing process in which the tube blank is gradually formed into a hollow thick-walled capillary under the action of the roll and the plug on the piercing machine, and the capillary is rolled on the automatic rolling machine to be close to the wall thickness of the finished product. The rolling process of the waste pipe, the sizing and reducing process...

AI Technical Summary

Problems solved by technology

[0009] To sum up, the diameter expansion production method of large-diameter seamless steel pipes with a diameter greater than 400mm and cross-rolling diameter expansion production methods have complex diameter expansion production methods and large equipment investment, and are only suitable for large-scale production of large-diameter seamless steel pipes. There are technical problems such as helical patterns inside the product and poor surface quality; the steel pipe continues to be in a tensioned state after diameter expansion and deformation in the production method of drawing and diameter expansion, which may expand the original defects of the steel pipe, and may cause the steel pipe to break if not properly controlled

In addition, although the wall thickness can be reduced, the wall thickness is uncontrollable, the outer diameter accuracy is low, and the steel pipe surface is not smooth. The production method of pushing and expanding the diameter is difficult to greatly change the wall thickness through process optimization while expanding the diameter. The length of the large-diameter seamless steel pipe is relatively short, and the production speed of a single machine is slow; therefore, it is necessary to expand the diameter of a large-diameter seamless steel pipe that can not only expand the diameter but also change the thickness of the pipe wall, the thickness of the pipe wall is controllable, and the production cost is low. production method

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