RU2345854C2 - Manufacturing method of heavy-walled tubes - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method includes double-line screw rolling of heated tubular billet plug rolling by three rollers and screw calibration by three rollers. In the capacity of blank there are used coupling fittings of served drill pipes. Thread on fitting is removed by mechanical operation, places of abrupt junction of wall thickness are beveled, heated, specified into rollers and deformed on plug with rolling-out 1.4 at the first passage and with rolling-out 2.0 at the second passage, after what tube is calibrated.

EFFECT: widening of manufacturing capabilities and reduction of manufacturing costs.

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Description

The invention relates to pipe rolling production, namely, to obtain hot-rolled thick-walled pipes by screw rolling.

It is known in the pipe rolling industry to produce thick-walled tubes by screw rolling on units with three-roll rolling mills and a screw rolling calibration mill / cm. I.E. Siege and others. Modern pipe shops. M .: "Metallurgy", 1977, p.65-68, p.193-194, p.206-209 /.

A known method for the production of thick-walled pipes (with the ratio D / S = 4-l 1,5), including screw rolling with three rolls on the mandrel of a hollow heated billet and screw calibration with three rolls / cm N.F. Ermolaev. Pipe rolling production. M .: Metallurgizdat, 1958, p. 274-277 /.

Both methods are limited to the use of one type of preform having a constant wall in length.

However, the use of alternative types of the initial blank is relevant. Such, for example, are connecting fittings from waste drill pipes having a variable wall thickness along the length. These items due to significant losses of material due to corrosive effects during operation are deprived of the opportunity to be used for their intended purpose and are exclusively recycled. There are two ways for processing such recyclables into suitable products: a) remelting, characterized by low metal losses, but requiring additional redistribution, incl. and rolling; b) machining, allowing you to directly receive finished products, but characterized by significant losses of metal in the chips.

The task is to directly process the connecting fittings of used drill pipes into finished products in the form of thick-walled pipes.

The problem is solved by creating a method for the production of thick-walled pipes from connecting fittings from waste drill pipes, according to which connecting fittings having a variable wall length and thread are machined to remove thread and mow the places of sharp transition of wall thickness, then the fittings are heated and screw rolled on a cylindrical mandrel with three double-cone rolls with a hood of 1.4 in the first pass and with a hood of 2.0 in the second pass, after which screw calibration is carried out at the mandrel with three rolls.

An example of the method

Used as a workpiece was a used drill pipe nipple with a largest outer diameter of 152 mm, an inner diameter of 70 mm, a length of 250 mm, and a variable-length wall thickness with sharp transitions and threads. Before rolling by machining, the threads were removed and the places of a sharp transition of the wall were mowed to a slope of the generatrix of 25 °. Then the workpiece was heated to 1180 ° C and set with the smallest diameter of 120 mm into the deformation zone formed by three rolls with an inclination angle of the generatrix of the deforming section of 4.5 ° and a cylindrical mandrel with a diameter of 67 mm. With a draw ratio of 1.4 at a feed angle of 5 ° and a rolling angle of 4 °, a semi-finished product with a diameter of 116 mm and a wall thickness of 24.5 mm was obtained. Then, by rolling by three rolls on a cylindrical mandrel, the semi-finished product with a diameter of 116 mm and a length of 350 mm was re-deformed at a feed angle of 8 ° and a rolling angle of 3 ° with a compression of 20% and a draw ratio of 2.0. A pipe with a diameter of 96 mm and a wall thickness of 14.5 mm was obtained. After that, the pipe was calibrated with three rolls on a mandrel with a compression of 2% and a draw ratio of 1.15. A short length of 700 mm and an equal wall pipe of 92x13.5 mm were obtained. Rolling was carried out with one heating.

The finished pipe has accurate dimensions and high surface quality.

Thus, due to the use of screw rolling, the proposed method allows direct processing of recycled materials in the form of connecting fittings from used drill pipes into finished products in the form of hot-rolled thick-walled pipes that satisfy all quality requirements with minimal metal losses.

Since the connecting fittings are made of steels of a special composition designed for oil pipes, the resulting thick-walled pipes can be used, for example, as blanks for the manufacture of couplings for tubing according to GOST 633-80.

Claims (1)

A method of manufacturing thick-walled pipes from connecting fittings from used drill pipes, characterized in that for connecting fittings having a wall thickness and a thread that are variable in length, the threads are machined and the places of abrupt transition of the wall thickness are mowed, then the fittings are heated and screw rolling is carried out on a cylindrical the mandrel with three double-cone rolls with an exhaust hood of 1.4 at the first pass and with a hood of 2.0 at the second pass, after which screw calibration is performed on the mandrel with three shaft kami.