RU2817810C1 - Five-stand sizing mill for calibration of longitudinal electric-welded pipes - Google Patents

Abstract

FIELD: pipe welding production.

SUBSTANCE: invention can be used for calibration of longitudinal electric-welded pipes. Sizing mill comprises stand with two sizing rolls and four stands with four sizing rolls following it. Calibration rolls of the stand with two rolls are located horizontally at the bottom and on top of the pipe at angle of 90° to the pipe forming plane. Said rolls have the possibility of converging and separating relative to the pipe with the initial diameter with provision of transfer of residual internal stresses of pipe into plastic deformation by means of its flattening with formation of oval. Rolls have concave surface, radius of which is 2–10 times greater than radius of produced pipe, and arc of pipe circumference has maximum angle of 120°.

EFFECT: as a result, deviation of the diameter value at the ends of the pipe from the requirements of the normative documentation is ensured.

1 cl, 2 dwg

Description

The invention relates to pipe welding production and can be used for calibrating straight-seam electric-welded pipes with a range of over 325 mm from various grades of steel during their production by forming the pipe body in closed stands with split washers, used in various branches of mechanical engineering.

A four-stand four-roll calibration mill (manufactured by Torrens, USA) is known, which is an analogue used for calibrating the diameter of electric-welded straight-seam pipes, containing the bodies of four stands with four calibration rolls installed in them, providing full girth of the pipe body during calibration, (“Welded pipes", Yu.M. Vatkin, E.M. Krichevsky, ed. "Metallurgy", Moscow, 1972; "Calibration of pipe mill tools", Yu.Ya. Vatkin, ed. "Metallurgy", Moscow, 1970) with four calibration rolls installed in them, ensuring full coverage of the pipe body during calibration.

The disadvantage of the analogue is that plastic deformation of the pipe wall occurs almost only in the space between the rolls, where the pipe does not come into contact with the working surface of the sizing rolls, and there is no friction with the rolls. In this case, the areas of maximum deformation of the mill are located in a very narrow zone at an angle of 60°. The calibration mill does not allow, due to the lack of sufficient free space between the rolls, plastic deformation of pipe sections at an angle of 90°, therefore elastic stresses located in this zone, according to the laws of metal forming, cannot transform into movements, that is, they cannot pass deformation of about 0.2% to eliminate vertical ovalization of the ends after cutting a continuous pipe into measured lengths.

The technical challenge is to create a sizing mill with a sufficiently free space between the rolls, allowing plastic deformation of pipe sections at an angle of 90°.

The technical result is the elimination of deviations in the diameter at the ends of the pipe from the requirements of regulatory documentation.

The technical result is achieved by the fact that a five-stand calibration mill for calibrating straight-seam electric-welded pipes contains a stand with two calibration rolls and four subsequent stands with four calibration rolls, while the calibration rolls of the stand with two rolls are located horizontally at the bottom and top of the pipe at an angle of 90° to plane of pipe forming with the possibility of bringing together and moving apart relative to the pipe with the original diameter, ensuring the transfer of residual internal stresses of the pipe into plastic deformation by flattening it to form an oval, while the mentioned rolls are made with a concave surface, the radius of which is 2–10 times greater than the radius of the produced pipe , and the arc of the pipe has a maximum angle of 120°.

The calibrating rolls of a stand with two rolls are designed to be reduced by a value Δ, which is calculated using the following formula:

Δ=Rtr × 2 -B, where

Rtr - outer radius of the finished pipe;

B is the vertical dimension of a pipe flattened in a stand by two calibrating rollers to form an oval, where

R _MAL - small (lateral) radius of the oval caliber when flattening the pipe

in a two-roll gauge;

t - pipe wall thickness;

ΔLtr is the relative difference in the length of the middle and inner fiber of the cross-section of the pipe in percent.

4. The large radius of the oval pipe profile in stand 5 (Fig. 1) is calculated using the formula, taking into account the angle of the large radius arc, for a four-roll sizing mill:

Where

Rbol - large (upper and lower) radius of the oval pipe when flattening the pipe in a two-roll caliber;

Lcp is the length of the metal fiber along the center line of the pipe in cross section;

Rsmall - small (lateral) radius of the oval caliber when the pipe is flattened

in a two-roll gauge;

t is the thickness of the pipe wall.

5. Calculate the vertical size of the oval B:

Where

B is the vertical dimension of the pipe, flattened in a stand by two calibrating rolls to form an oval;

Rbol - large (upper and lower) radius of the oval pipe when flattening the pipe in a two-roll caliber;

Rsmall - small (lateral) radius of an oval pass when flattening a pipe in a two-roll pass.

6. Calculate the amount by which it is necessary to reduce the axes of the upper and lower rolls to each other, relative to the initial diameter of the pipe, for the transition of residual internal elastic stresses into plastic deformation of the metal:

Δ is the amount of convergence of the upper and lower rolls when flattening a pipe of size R _TR × 2 located in the caliber;

_RTR - outer radius of the finished pipe;

B is the vertical dimension of the pipe, flattened in a stand by two calibrating rolls to form an oval.

The proposed five-stand mill is easy to use and allows you to adjust the diameter of the body and the ends of a continuous pipe formed in closed calibers with split washers. At the same time, it is important to eliminate the need to straighten the vertical end oval of pipes cut into measured lengths, as well as to ensure that the geometry of the ends of these pipes strictly corresponds to the requirements of regulatory documentation.

The use of the mill allows for significant savings in material, energy and financial resources when manufacturing orders with increased requirements for the geometric parameters of the pipe.

Claims (5)

1. A five-stand sizing mill for sizing straight-seam electric-welded pipes, characterized in that it contains a stand with two sizing rolls and four subsequent stands with four sizing rolls, while the sizing rolls of the stand with two rolls are located horizontally at the bottom and top of the pipe at an angle of 90 ° to the pipe forming plane with the possibility of bringing together and moving apart relative to the pipe with the original diameter, ensuring that the residual internal stresses of the pipe are converted into plastic deformation by flattening it to form an oval, while the mentioned rolls are made with a concave surface, the radius of which is 2-10 times greater than the radius produced pipe, and the arc of the pipe has a maximum angle of 120°. 2. A five-stand sizing mill according to claim 1, characterized in that the sizing rolls of a stand with two rolls are designed to be reduced by a value Δ, which is calculated using the following formula: Δ=Rtr×2 -B, where Rtr - outer radius of the finished pipe; B is the vertical dimension of the pipe, flattened in the stand by two calibrating rolls to form an oval.

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