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Classification & Diameter Expansion Requirements of ERW Steel Pipe
Sep 24, 2020
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This news mainly talks about the classification and expanding requirements of straight seam steel pipe (ERW steel pipe).
Classification of ERW Steel Pipe:
According to the section shape, straight seam steel pipe (ERW steel pipe) can be divided into round steel pipe and special-shaped steel pipe.
Special shaped steel pipe refers to all kinds of steel pipes with non-circular cross-section, mainly including square pipe, rectangular pipe, elliptical pipe, flat elliptical pipe, semicircular pipe, hexagonal pipe, octagonal pipe, convex pipe and doubly convex pipe. It also contains multi concave tube, melon seed tube, flat tube, unequal hexagon tube, equilateral triangle tube, rhombic tube, star tube, double concave tube, pentagonal tube, parallelogram tube, drop tube, inner finned tube, ribbed tube, twisted tube, B-TUBE, d-tube and multi-layer tube.
Classification of cross section shape of straight seam steel pipe (ERW steel pipe)
According to the shape of vertical section, steel pipe can be divided into equal section steel pipe and variable section steel pipe. Variable cross-section (or variable cross-section) steel pipe refers to the steel pipe whose section shape, inner diameter, outer diameter and wall thickness change periodically or aperiodically along the pipe length. It mainly includes: outer stepped pipe, inner stepped pipe, outer conical pipe, inner conical pipe, corrugated pipe, periodic section pipe, spiral pipe and steel pipe with heat sink.
Diameter Expansion Requirements of ERW Steel Pipe:
The diameter expansion of straight seam steel pipe (ERW steel pipe) is a kind of pressure processing technology. It increases the force from the inner wall of the steel pipe by hydraulic or mechanical means to make the steel pipe expand along the radial direction. The mechanical method is simpler and more efficient than the hydraulic method. The mechanical expanding process of several large-diameter straight welded pipe is mechanical expanding. The process is as follows: the mechanical expanding adopts the segmented sector block at the end of the expanding machine. In order to realize the plastic deformation of the whole tube along the length direction. It is divided into five stages.
1. Initial round stage
At this time, the radius of the round pipe in the steel pipe is almost the same in the range of step size, and the steel pipe reaches the initial circle.
2. Nominal inner diameter stage
The sector block starts from the front and decelerates until it reaches the required position, which is the circumferential position of finished pipe with quality requirements.
3. Rebound compensation stage
The position of the sector block in the second stage will be further reduced until the required position is reached, that is, the circumferential position of the steel pipe before elasticity required by the process design.
4. Pressure maintaining stable stage
Before springback, the sector block at the circumferential position of the steel pipe remains unchanged for a period of time, which is the stable pressure maintaining stage required by the equipment and expanding process.
5. Unloading return stage
Before the elastic recovery, the fan-shaped block shrinks rapidly from the circumferential position of the steel pipe until it reaches the initial diameter position of the minimum shrinkage diameter of the fan-shaped block required in the expanding process. In practical application, 2 and 3 steps can be combined and simplified in the simplification process, which has no effect on the diameter expansion quality of the steel pipe.
Classification of ERW Steel Pipe:
According to the section shape, straight seam steel pipe (ERW steel pipe) can be divided into round steel pipe and special-shaped steel pipe.
Special shaped steel pipe refers to all kinds of steel pipes with non-circular cross-section, mainly including square pipe, rectangular pipe, elliptical pipe, flat elliptical pipe, semicircular pipe, hexagonal pipe, octagonal pipe, convex pipe and doubly convex pipe. It also contains multi concave tube, melon seed tube, flat tube, unequal hexagon tube, equilateral triangle tube, rhombic tube, star tube, double concave tube, pentagonal tube, parallelogram tube, drop tube, inner finned tube, ribbed tube, twisted tube, B-TUBE, d-tube and multi-layer tube.
Classification of cross section shape of straight seam steel pipe (ERW steel pipe)
According to the shape of vertical section, steel pipe can be divided into equal section steel pipe and variable section steel pipe. Variable cross-section (or variable cross-section) steel pipe refers to the steel pipe whose section shape, inner diameter, outer diameter and wall thickness change periodically or aperiodically along the pipe length. It mainly includes: outer stepped pipe, inner stepped pipe, outer conical pipe, inner conical pipe, corrugated pipe, periodic section pipe, spiral pipe and steel pipe with heat sink.
Diameter Expansion Requirements of ERW Steel Pipe:
The diameter expansion of straight seam steel pipe (ERW steel pipe) is a kind of pressure processing technology. It increases the force from the inner wall of the steel pipe by hydraulic or mechanical means to make the steel pipe expand along the radial direction. The mechanical method is simpler and more efficient than the hydraulic method. The mechanical expanding process of several large-diameter straight welded pipe is mechanical expanding. The process is as follows: the mechanical expanding adopts the segmented sector block at the end of the expanding machine. In order to realize the plastic deformation of the whole tube along the length direction. It is divided into five stages.
1. Initial round stage
At this time, the radius of the round pipe in the steel pipe is almost the same in the range of step size, and the steel pipe reaches the initial circle.
2. Nominal inner diameter stage
The sector block starts from the front and decelerates until it reaches the required position, which is the circumferential position of finished pipe with quality requirements.
3. Rebound compensation stage
The position of the sector block in the second stage will be further reduced until the required position is reached, that is, the circumferential position of the steel pipe before elasticity required by the process design.
4. Pressure maintaining stable stage
Before springback, the sector block at the circumferential position of the steel pipe remains unchanged for a period of time, which is the stable pressure maintaining stage required by the equipment and expanding process.
5. Unloading return stage
Before the elastic recovery, the fan-shaped block shrinks rapidly from the circumferential position of the steel pipe until it reaches the initial diameter position of the minimum shrinkage diameter of the fan-shaped block required in the expanding process. In practical application, 2 and 3 steps can be combined and simplified in the simplification process, which has no effect on the diameter expansion quality of the steel pipe.
