RU2564194C2 - Hot-rolled tube manufacturing method - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method involves piercing of a billet, tube rolling in two in-series located mills for longitudinal rolling in rolls with many-sided grooves with a number of sides that exceeds six and with height of the groove of the first mill, which is bigger than that of the groove of the second mill by 1-2 mm, on short mandrels, with outer diameters equal to outer diameter of the mandrel of the first mill or outer diameter of the mandrel of the second mill is by 1-2 mm smaller than outer diameter of the mandrel of the first mill with first mill drawing µ=1.1-1.5 and µ=1.05-1.15 in the second mill, tube grooving is performed with drawing µ=1.1-1.3 in a sizing mill with the groove diameter in the last stand of 114.0-117.0 mm.

EFFECT: possibility of manufacturing tubes with reduction of defects along a longitudinal rolling mark on the tube inner surface.

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Description

The invention relates to pipe rolling production and can be used in the production of hot-rolled pipes with a diameter of 114 mm from continuously cast billets with a diameter of 150 and 156 mm on pipe-rolling units with two longitudinal rolling mills.

A known method for the production of hot-rolled pipes from a workpiece with a diameter of 150 and 160 mm, including flashing the workpiece in a piercing mill with a diameter increase of up to 166 mm, rolling a sleeve-tube in an automatic mill in two passes with an exhaust hood µ = 1.26-1.98 in rolls with an oval calibration with equal caliber height in both passes on a short mandrel, the diameter of which for the first pass is less than 2 mm in diameter of the mandrel for the second pass, and the calibration of the pipe, the outer diameter of which in the hot state is 127-129 mm, is carried out in a calibration mill with exhaust hood th µ = 1.00-1.026 (Danilov F.A. et al. “Hot rolling of pipes”, Metallurgizdat, M., 1962, Table 16 “Rolling table of an average automatic plant”).

The disadvantage of this method is the production of billets with a diameter of 150 and 156 mm hot rolled pipes with a diameter of 127-129 mm

The closest in technical essence and the achieved results is a method for the production of seamless hot-rolled pipes, in which the sleeve-tubes are rolled in two consecutive longitudinal rolling mills in rolls with multifaceted calibration with equal caliber heights in both mills on short mandrels that have equal outer diameters or the outer diameter of the mandrel of the second mill is 1 mm larger than the outer diameter of the mandrel of the first mill, with an extract in the first mill µ = 1.2-1.9 and µ = 1.00-1.07 in the second mill (Pat. RF №233227 1, published on August 27, 2008).

The disadvantage of the prototype method is the production of pipes with a diameter of 114 mm only from a workpiece with a diameter of 120 mm and a significant level of defectiveness of the pipes along the longitudinal rolled risk on the inner surface formed when rolling the sleeve-tubes in longitudinal rolling mills in rolls with polyhedral (hexagonal) calibration.

The technical problem solved by the invention consists in the production of hot-rolled pipes with a diameter of 114 mm from a continuously cast billet with a diameter of 150 and 156 mm on a tube rolling unit with two successive rolling mills with a decrease in the level of defect along the longitudinal welded risk on the inner surface of the pipes.

The solution to the technical problem is achieved by the fact that in the method for the production of hot-rolled pipes with a diameter of 114 mm from a continuously cast billet with a diameter of 150 and 156 mm, which includes piercing the billet in a piercing mill with a diameter increase of up to 162 mm, rolling the pipe in two successive longitudinal rolling mills in rolls with multifaceted gauges on short mandrels, rolling in a rolling mill and calibration in a calibration mill, rolling a pipe in two consecutive longitudinal rolling mills is performed in rolls with many face gauges with the number of faces more than 6 and the height of the caliber of the first mill is greater than the height of the caliber of the second mill by 1-2 mm on short mandrels that have external diameters equal to the outer diameter of the mandrel of the first mill or the outer diameter of the mandrel of the second mill by 1-2 mm smaller than the outer diameter of the mandrel of the first mill with the hood in the first mill µ = 1.1-1.5 and µ = 1.05-1.15 in the second mill, and the calibration of the pipe with the hood µ = 1.1-1.3 is performed in a calibration mill with a caliber diameter in the last stand of 114.0-117.0 mm.

The production method is as follows.

A continuously cast billet with a diameter of 150 or 156 mm, heated to a temperature of plasticity in a ring furnace, is fed into a two-roll piercing mill, where a sleeve with an outer diameter of up to 162 mm with a hood µ = 2.4-3.5 is flashed. After axial delivery from the output side of the piercing mill, the sleeve is rolled in two successive longitudinal rolling mills on a short mandrel. Both mills have the same design and rolls with multifaceted calibers with more than 6 faces. The height of the caliber of the first mill is 1-2 mm greater than the height of the caliber of the second mill, and the short mandrels of both mills have outer diameters equal to the outer diameter of the mandrel of the first mill, or the outer diameter of the mandrel of the second mill, 1-2 mm less than the outer diameter of the mandrel of the first mill. The caliber width of the first mill is determined by the diameter of the sleeve, and the second mill by the diameter of the rough pipe after the first mill. Rolling is carried out with an extract µ = 1.1-1.5 in the first mill and µ = 1.05-1.15 in the second mill.

Next, the rolling is performed in a 3-roll rolling mill with a hood µ = 1.01-1.02. After axial delivery from the output side of the rolling mill and induction heating, the pipe is rolled in a calibration mill, the diameter of the caliber of the last stand of which is 114.0-117.0 mm with a hood µ = 1.1-1.3.

After rolling in the first longitudinal rolling mill, the inner surface of the pipe has an oval cross-section, pipe sections in the gauge outlets that have not been crimped on a short mandrel have longitudinal folds of metal that can be rolled at longitudinal risk when rolling in the second mill. The proposed shape of the gauge minimizes the overflow of the gauge with metal and its getting into the gaps between the rollers by increasing the number of so-called "pockets" formed at the intersection of faces filled with excess metal during rolling.

The volume of metal that is used to fill the outlet zone is reduced, which helps to align the wall thickness in the outlets with a wall at the top of the caliber.

Due to the fact that the rolls of longitudinal rolling mills have multifaceted calibers with the number of faces more than 6, the height of which on the first mill is more than 1-2 mm than on the second, and the short mandrels of both mills have outer diameters equal to the outer diameter of the mandrel of the first mill, or the outer diameter of the mandrel of the second mill, 1-2 mm less than the outer diameter of the mandrel of the first mill, with an extract in the first mill µ = 1.1-1.5 and µ = 1.05-1.15 in the second mill, rolling pipes with a more uniform distribution of deformation along the perimeter of the gauge without overfilling I, prevents the formation of longitudinal rolled risks.

Calibration of the pipe in the calibration mill, the diameter of which in the last stand, which determines the size of the finished pipe, is 114.0-117.0 mm, due to the general deformation with the hood µ = 1.1-1.3.

The specific features of the continuously cast metal of the billet include the developed dendritic structure, pores and discontinuities in the axial zone of the billet. Rational rolling technology in this case is based on increased deformation - exhaust for the passage at each TPA rolling mill. Under such conditions, a gradual “healing” of discontinuities and pores occurs during rolling, which ensures a pipe with a dense and uniform structure. In the proposed method, the completion of "healing" occurs precisely on the calibration mill due to the general deformation with the hood µ = 1.1-1.3.

The method is tested in an industrial environment. The results are presented in table No. 1 "Data on the rental and quality of pipes", from which it follows that the use of the proposed method on TPA-140 with two consecutive longitudinal rolling mills allows you to master the production of hot rolled pipes with a diameter of 114 mm from a continuously cast billet with a diameter of 150 and 156 mm with a minimum level of defects in the form of longitudinal rolled risks.

Rental and pipe quality data Table 1 steel grade Pipe size mm Rental volume, t Diameter of the workpiece, mm Piercing mill Longitudinal rolling mill No. 1 Longitudinal rolling mill No. 2 Rolling mill Calibration mill Inconsistency longitudinal production prikat. risk,% The diameter of the sleeve, mm Coef. hoods Caliber height mm Diameter of mandrel, mm Coef. hoods Caliber height mm Diameter of mandrel, mm Coef. hoods Pipe size mm Coef. hoods Last caliber diameter stands, mm Coef. hoods Total def.,% 20-3 114 × 9 62.7 150 159 3,1 149 131 1.37 147 130 1.13 155 × 7.75 1,02 115.0 1.20 25.8 0.76 20-3 114 × 11 58.84 150 159 2.65 149 127 1.35 147 127 1.13 155 × 9.49 1,02 115.3 1.20 25.6 0.93 13XFA 114 × 11 115.39 156 159 2.83 149 127 1.34 147 127 1.13 155 × 9.49 1,02 115.3 1.20 25.6 1,60 13XFA 114 × 12 336.57 150 159 2.45 149 125 1.32 147 125 1.13 155 × 10.36 1,02 115.5 1.21 25.5 1.80

Claims (1)

A method of manufacturing hot rolled pipes with a diameter of 114 mm from continuously cast billets with a diameter of 150 and 156 mm, including piercing the billet, rolling the pipe and calibrating, characterized in that the pipe is rolled in two successive longitudinal rolling mills in rolls with multifaceted calibers with more faces 6 and a height of the caliber of the first mill is greater than the height of the caliber of the second mill by 1-2 mm, while rolling is carried out on short mandrels that have outer diameters equal to the outer diameter of the mandrel of the first tan, or the outer diameter of the mandrel of the second mill is 1-2 mm less than the outer diameter of the mandrel of the first mill, with a hood in the first mill µ = 1.1-1.5 and a hood µ = 1.05-1.15 in the second mill, and pipe calibration is carried out with an extract of μ = 1.1-1.3 in a calibration mill with a caliber diameter of 114.0-117.0 mm in the last stand.