RU2571029C1 - Production method of high-stiffness tongue-and-groove section - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, and namely to production of large tongue-and-groove Larsen sections. Claimed process comprises the billet heating, section rolling and cooling. Said billet is produced by longitudinal slitting of dismantled large-diameter main line pipe to two-four parts with transverse bulge. The billet is heated in pusher-type roller heating furnace to 570÷650°C and subjected to multipass rolling to tongue-and-groove section. Directly before every rolling pass the billet longitudinal zones are subjected to local heating to 950÷1050°C at the rate of 450÷600°C/sec. In the next rolling pass, said zones are subjected to high-intensity deformation of 15÷45% to curve the angles of rolled tongue-and-groove section. After every rolling pass geometrical sizes and relative location of the section horizontal and vertical flanges are fixed by accelerated local cooling of the said zones. In second rolling pass the periodic convexo-concave surface of increased bending strength can be formed at the medium horizontal flange.

EFFECT: higher precision of sizes and bending strength.

2 cl, 2 dwg, 1 ex

Description

The invention relates to the field of metallurgy, and in particular to methods of producing large-sized sheet pile profiles of the Larsen type when disposing of a dismantled DB main pipe and its reuse in rolled steel without steelmaking in a compact mobile metallurgical complex located on a repaired main pipeline thread.

A known method for the production of sheet piles (RU 2064350, B21B 1/08, publ. 07.27.1996), in which the sheet pile profile is produced on a universal beam mill from a continuously cast or rolled slab billet, the first stage includes preparatory and rough rolling, which is carried out on a crimping stand in reverse mode for 7 or 9 passes, and the second stage includes pre-finishing and finishing rolling, which is carried out in continuous mode, for 4 pre-finishing passes, using trough gauges with rough, pre-finishing finish rolling, with a wall slope close to the finished profile slope shelves. Starting from the first pre-finishing gauge, rolling is carried out with a straightened profile wall.

The disadvantage of this method is the excess dimensions of the original continuously cast billet 255 × 520 mm, leading to the need for a powerful rolling crimp stand 1300 with a drive of 2500 ÷ 3000 kW. The total number of rolling passes in the known technology is 12-14, which leads to the need for a high rolling speed to prevent cooling of the tackle, especially its tail, and the uneven temperature along the length of the tackle reduces the accuracy of the profile, its curvature during rolling, the need to edit the profile in a cold state. The use of a powerful rolling mill, high capital costs for construction and launch increase the payback period, and excessive total rolling deformation leads to increased production costs.

There is also a method of rolling Z-shaped sheet piles from an H-shaped semi-finished product (RU 2145263, B21B 1/08, publ. 10.02.2000). The method consists in the fact that the semi-finished product is processed using rolling means that determine the rolling plane with the provision of the jumper position of the H-shaped section of the semi-finished product mainly parallel to this rolling plane, and a pile with a Z-shaped section having a flat bridge forming an angle α ₀ s is obtained the rolling plane, two side wings forming an angle β ₀ with the rolling plane, and tacks made at the end of each wing.

The disadvantage of this method is the excessive number of rolling passes 9 ÷ 10 and the high power of the rolling mill, the presence of complex calibration of the rolls, low accuracy of the final profile.

The invention is aimed at eliminating these disadvantages.

The technical result of the invention is to increase the dimensional accuracy and rigidity of the tongue and groove profile, while reducing its specific gravity and the total cost of its production.

The specified technical result is achieved by the fact that in the method, including heating the workpiece, rolling the tongue and groove profile, its accelerated cooling, dressing and cutting to the required length, it is proposed to use the workpiece obtained by longitudinal dissolution of the dismantled main pipe of large diameter into 2 ÷ 4 parts with transverse convexity , heat the workpiece in a continuous heating furnace to a temperature of 570 ÷ 650 ° C and multi-pass rolling into a tongue-and-groove profile, and in the first pass, pre-roll profile, symmetrical with respect to the vertical axis, with three horizontal shelves and two inclined shelves, in the second pass, unclip the free fayes of the horizontal shelves to obtain two vertical longitudinal sides, in the third pass, upright the sides to be sharpened, in the fourth pass, fold the sides into the tongue and groove lock direction of the inclined shelves, while immediately before each rolling pass to produce local heating to a temperature of 950 ÷ 1050 ° C, at a speed of 450 ÷ 600 ° C / s, longitudinal zones of the workpiece, s the width of the local heating zone ZLN = (1.5 ÷ 3.5) ∗ h, where h is the thickness of the workpiece subjected to intense deformation of 15 ÷ 45% in the subsequent rolling pass, with the formation of radii in the corners of the sheet pile profile with radii R = (0.05 ÷ 0.15) ∗ h, where h is the thickness of the workpiece, and after each rolling pass, fix the geometric dimensions and the relative positions of the horizontal and vertical shelves of the rolled sheet pile profile by means of accelerated local cooling to the temperature of 350 ÷ 460 ° C of these zones at a speed of 180 ÷ 250 ° C / s In addition, in the second rolling passage, on the middle horizontal shelf, by rolling rolls, on one of which periodic convexes are applied, and on the second - periodic concavities, to roll a periodic convex-concave surface with increased bending stiffness.

In FIG. 1 shows a rolling scheme with a ZLN sheet pile profile along rolling passes, FIG. 2 shows a top view of a rolling stand in a first rolling passage.

The method is as follows.

Dismantled from the old insulation, the dismantled main pipe from the repaired line of the main pipeline is transported to the production site of a compact mobile metallurgical complex, deployed in the immediate vicinity of the repaired pipeline section. At the pipe acceptance site, it is subjected to an incoming inspection for surface defects. In the presence of surface defects, repair and restoration of damaged pipe sections is carried out. Prepared for processing, a pipe with a length of 10.5 ÷ 11.0 meters is fed to a thermal cutting unit and longitudinally expanded into 2 ÷ 4 billets 1 in the form of strips with transverse convexity (Fig. 1). The blanks 1 are successively stacked on the furnace roller table with a bulge upwards and are fed along the roller table to the continuous heating furnace. In the heating furnace, the workpieces 1 are heated to a temperature of 570 ÷ 650 ° C. The heated billet 1 without changing the spatial position along the roller table is set in a rolling mill and rolled into a sheet pile profile for 4 rolling passes with a rolling speed of 0.15 ÷ 1.5 m / s and a total exhaust of 8 ÷ 12%. In FIG. 1 shows a scheme for rolling a workpiece 1 into a tongue-and-groove profile along rolling passages. In the first pass, a preliminary profile is rolled, symmetrical with respect to the vertical axis with three horizontal shelves 2 and two inclined shelves 3, in the second pass, free fairies of horizontal shelves 2 are unbent to obtain two vertical longitudinal sides 4, in the third pass, the vertical sides 4 are upset with a taper of 5, in the fourth pass, the sides 4 are bent into the tongue-and-groove lock 6 in the direction of the inclined shelves 7. In this case, immediately before each rolling pass, local heating is performed to a temperature of 950 ÷ 1050 ° C, n example, with gas burners 10, with a speed of 450 ÷ 600 ° C / sec, longitudinal zones of the workpiece 1, with the width of the local heating zone ZLN = (1,5 ÷ 3,5) ∗ h, where h is the thickness of the workpiece 1, subjected to intense deformation 15 ÷ 45% in the subsequent rolling pass, with the formation of radii R = (0.05 ÷ 0.15) ∗ h in the corners of the rolled sheet pile profile, where h is the thickness of the workpiece 1, and after each rolling pass, the geometric dimensions and relative position are fixed horizontal and inclined shelves of rolled sheet pile profile by means of accelerated locale cooling to a temperature of 350 ÷ 460 ° C of said zones by air-air nozzles 9 at a speed of 180 ÷ 250 ° C / s (Fig. 2). In addition, in the second rolling passage, on the middle horizontal flange 8, the rolling rolls 11, on one of which periodic convexes are applied, and on the second - periodic concavities, a periodic convex-concave surface is rolled with increased bending stiffness.

The optimum thermomechanical processing modes provide a tongue and groove profile with the following mechanical characteristics: σ _in = 540 ÷ 600 N / mm ^2, σ _m = 325 ÷ 415 N / mm ^2, δ ₅ = 16 ÷ 20%, which corresponds to GOST 19281-89 " Rolled steel of increased strength. " Low rolling speed and overall exhaust provide low metal and energy consumption of the rolling mill, the power of the main drive of the rolling mill is 500 ÷ 750 kW, which is 7 ÷ 8 times lower than the drive power of the rolling mill by a known method (RU 2064350, B21B 1/08, publ. July 27, 1996). Preheating to 570 ÷ 650 ° C and local heating to 950 ÷ 1050 ° C reduce the total gas consumption for heating the workpiece by 1.8 ÷ 2.0 times. In addition, local heating concentrates plastic deformation during rolling and allows one to obtain radii R = (0.05 ÷ 0.15) ∗ h in the corners of the sheet pile profile, where h is the thickness of the workpiece, which increases the bending stiffness of the sheet pile profile. The accelerated cooling at the exit of the rolling stand according to ZLN provides high precision sheet pile profile along the entire length. The wall thickness with respect to the height and width of the tongue and groove profile guarantee a decrease in its specific gravity with respect to the tongue and groove profile obtained by a known method (RU 2145263, B21B 1/08, publ. 10.02.2000).

Thus, the use of the invention provides energy efficiency in the production of tongue and groove profiles with increased dimensional accuracy and flexural rigidity, while reducing its specific gravity and the total cost of its production.

Example

According to the proposed method, a tongue-and-groove profile of Larsen type was produced with a height of 250 mm, a width of 550 mm from a dismantled main pipe GOST R 52079-2003, strength class K60, diameter 1420 mm, with a wall thickness of 16 mm, a length of 11.0 meters. The productivity of the complex is 50 thousand tons of sheet pile profile per year. The dismantled main pipe underwent preliminary preparation: they removed the old insulation, diagnosed the condition of the pipe body using ultrasonic testing, and if defects were detected in the form of surface corrosion cracking, the cracks were cut with their subsequent welding and cleaning of the weld joint. The pipe prepared for processing arrived at the thermal cutting unit. In a thermal cutting installation, the pipe was longitudinally unfurled into four strip billets with transverse convexity. The resulting billets were successively stacked on the furnace rolling table with a bulge upward and fed along the rolling table to a continuous heating furnace. In the heating furnace, the preforms were heated to a temperature of 610 ° C. The heated billet without changing the spatial position along the conveyor was set into a rolling mill and rolled into a sheet pile profile for 4 rolling passes with a rolling speed of 0.28 m / s and a total exhaust of 10%. In the first pass, a preliminary profile was rolled, symmetrical with respect to the vertical axis with three horizontal shelves and two inclined shelves, in the second pass, the free edges of the horizontal shelves were bent to obtain two vertical longitudinal sides, in the third pass, the vertical sides were besieged with a sharp edge, and in the fourth pass, the sides were bent into the tongue and groove in the direction of the inclined shelves. In this case, immediately before each rolling pass, local heating of the longitudinal zones of the billet, with a speed of 500 ° C / s, with the width of the local heating zone ZLN = (1.5 ÷ 3.5) ∗ h, where h is the thickness of the workpiece subjected to intense deformation of 15 ÷ 45% in the subsequent rolling pass, with the formation of radii R = 1.5 mm in the corners of the rolled sheet pile profile, and after each rolling pass, the geometric dimensions and the relative positions of the horizontal and inclined shelves effusions sheet pile profile by rapid local cooling to a temperature of 400 ° C zones of said water-air nozzles at a rate of 210 ° C / sec. In addition, in the second rolling passage, on the middle horizontal shelf, by rolling rolls, on one of which periodic convexes are applied, on the second - periodic concavities, a periodic convex-concave surface was rolled with increased bending stiffness. The tongue-and-groove profile cooled to a temperature of 380 ° C was folded into a bag of 4 pieces and cut off at the ends in a bag on a band saw to the required length. In the package, the rolled products cooled in air to a temperature of 20 ° C for 2.5 hours. Thermomechanical treatment regimens provides a sheet pile profile with the following mechanical characteristics: σ _in = 580 N / mm ^2, σ _m = 410 N / mm ^2, δ ₅ = 20%.

Claims (2)

1. A method of manufacturing a tongue-and-groove profile, including heating the workpiece, rolling the tongue and groove profile, its accelerated cooling, dressing and cutting to the required length, characterized in that they use the workpiece obtained by longitudinal dissolution of the dismantled main pipe of large diameter into 2 ÷ 4 parts with transverse convexity the billet is heated in a continuous heating furnace to a temperature of 570 ÷ 650 ° C and multi-pass rolling into a tongue-and-groove profile, with a preliminary profile being rolled in the first pass, metric with respect to the vertical axis, with three horizontal shelves and two inclined shelves, in the second pass the free edges of the horizontal shelves are folded down to obtain two vertical longitudinal sides, in the third pass the vertical sides are sharpened, in the fourth pass the sides are folded into the tongue-and-groove lock in the direction of the inclined shelves in this case, immediately before each rolling pass, local heating is performed to a temperature of 950 ÷ 1050 ° C with a speed of 450 ÷ 600 ° C / s of longitudinal zones of the workpiece with a width of ZLN = (1.5 ÷ 3.5) h, where h is the thickness of the workpiece subjected to intense deformation in the subsequent rolling pass 15 ÷ 45% with the formation of radii in the corners of the sheet pile profile with radii R = (0.05 ÷ 0.15) ∗ h, where h is the thickness of the workpiece, and after each the rolling passage fix the geometric dimensions and the relative positions of the horizontal and vertical shelves of the rolled sheet pile profile by means of accelerated local cooling of the said zones to a temperature of 350 ÷ 460 ° C at a speed of 180 ÷ 250 ° C / s. 2. The method according to p. 1, characterized in that in the second rolling passage by rolling rolls, on one of which periodic convexes are applied, and on the second - periodic concavities, a periodic convex-concave surface with increased bending stiffness is formed on the middle horizontal shelf of the profile .

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