RU2496603C1 - Method for obtaining rectangular workpiece, and device for its implementation - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: liquid metal is supplied to an intermediate annular capacity installed in an annular cavity of a rotating crystalliser, formed with two horizontally adjacent cantilever rolls with concave end surfaces, with zones of formation and rolling of an ingot. Intermediate annular capacity consists of two parts in the form of annular inserts from heat-insulating material. Metal is supplied through an annular dosing channel of intermediate annular capacity, the width of which is changed by movement along rotation axis of crystalliser of lower part of the capacity, to formation zone of an annular ingot under action of centrifugal forces. The required level of liquid metal h_M in the formation zone is determined as per mathematical relationships and maintained as constant during pouring process. Crystallising sections of the annular ingot are directed to a gap formed by movement and turning of one cantilever roll relative to another one. In the rolling zone, the ingot is crimped till welding together and rolled till a workpiece of required sizes is obtained, and the workpiece is separated from the annular ingot.

EFFECT: improving quality and accuracy of workpiece dimensions.

3 cl, 2 ex, 4 dwg

Description

The invention relates to the field of metallurgy, and more particularly to continuous casting and production of honeycomb rolled products, mainly of small grades.

A known method of producing small sections in a combined casting and rolling unit (1), including steelmaking in a steelmaking furnace, casting steel into an initial billet, preheating the initial billet before rolling and rolling in a continuous rolling mill with a roughing, intermediate and finishing groups of rolling stands.

The disadvantages of this method are the low casting speed of 0.05 ÷ 0.12 m / s, the excess size of the original continuously cast billet in the production of small grades with a side of 6.5 ÷ 8.0 mm, the need for pre-heating the cast billet before rolling.

Closest to the invention is a method for producing a rectangular billet and a device for its implementation (2), comprising feeding liquid metal into an annular cavity of a mold formed by horizontal conjugation of cantilever rolls with concave end surfaces, one of which is with a hole for filling. The mold is rotated, forming a ring ingot in the radial direction. Liquid metal enters the formation zone. After the onset of growth of the crust of the solid phase, the second roll is moved and rotated relative to the first. Crystallized sections rush into the resulting gap (rolling zone), where they are crimped before welding and simultaneously rolled out by rolling sections to the required dimensions, holding onto the rolling line with at least three support rollers. After that, with a special mechanism, the workpiece is separated from the ring ingot for subsequent rolling in the finishing group of rolling stands.

The disadvantage of this method is the low reliability of operation, due to the inability to maintain a constant level of liquid metal in the zone of formation of the ring ingot, which leads to inconsistency of the thickness of the welded crusts of the solid phase in the zone of compression and rolling of the ring ingot, an increase in the forces of compression and rolling, the variation in the size of the workpiece after separation from ring ingot. In addition, when the level increases and the liquid metal fills the boundary of the ingot formation zone, sticking of the ingot at the boundary occurs and the likelihood of rupture of the crust of the solid phase and the stopping of the casting process increase. The lack of structural rigidity caused by the large diameters of the cantilever rolls and low-speed drives for adjusting the roll gap and the inaccuracy of setting the angle of rolling narrow the technological capabilities of the known method.

The purpose of the invention is the expansion of technological capabilities, improving the reliability.

The invention proposes, initially, to supply liquid metal to the zone of formation of the annular ingot through the annular dispenser channel of the intermediate annular capacity of the rotating mold, the width of the annular dispenser channel, it is proposed to adjust the relative displacement along the axis of rotation of the mating parts of the annular annular container. The required level of liquid metal h _m in the zone of formation of the crust of the solid phase of the ring ingot is proposed to be previously determined from the expression

h _m = t _f ^* b _zag ^* n,

where b _zag - the required width of the workpiece, mm;

n is the mold rotation frequency, r / s;

t _f - the time of formation of the crust of the solid phase, s;

t _f = 60 ^* t _cr

where t _cr - crystallization time, min;

T _cr = (0.5 ^* h _zag / K _cr ) ² , min,

where h _zag - the required thickness of the workpiece, mm;

To _cr - the crystallization coefficient for steels is in the range 27 ÷ 30;

and it is proposed to maintain constant during casting a change in the value of the annular channel of the dispenser.

In the inner cavity of the mold, a device for implementing the method, it is proposed to install an intermediate annular container with a metering channel, consisting of mating parts made in the form of annular inserts of heat insulating material, a metering channel is formed between the ring inserts. The lower part of the intermediate annular tank has a reciprocating drive along the axis of rotation of the mold with the possibility of changing the value of the annular channel-dispenser. It is proposed to install a liquid metal level sensor at the site of formation of the ring ingot, which is connected through the control unit to the drive for moving the lower part of the intermediate ring vessel.

Figure 1 shows a view A of a device for implementing the proposed method; figure 2 is a view of B; figure 3 is a section A-A; figure 4 - place B.

Installation (Figure 1) for the implementation of the proposed technical solution comprises a frame 1, two conjugate cantilever rolls 2, 3 with vertical axes of rotation and concave end surfaces forming the inner cavity of the mold. On the end surface of the rolls 2, 3, a forming zone 6 and a rolling zone 7 of the annular ingot 16 are made. In the central region of the rolls 2 and 3, inserts 4 and 5 of heat-insulating material are installed. The coupling of the inserts 4 and 5 forms an intermediate annular container 14 with an annular channel-dispenser 15. The formation zone 6 of the annular ingot 16 is made of a heat-conducting material, such as copper. An open heat removal system is mounted on the outside of the rolls 2 and 3 on a liquid coolant, for example water, consisting of a pressure annular collector 12 with feeders 24, an annular tank 13 and radial channels 20 in zones 6 and 7. The rolling zone 7 is made of tool steel . The working surface of zone 6 has a wear-resistant coating, for example, chromium-nickel, which reduces the sliding wear of the crusts 18 of the solid phase of the ring ingot 16 (Figure 4). Cantilever rolls 2 and 3 are mounted in the frame 1 on spherical bearings 25, with the possibility of rotation relative to the vertical axis of rotation. The cantilever rolls 2 and 3 are driven in rotation from the backup rolls 19 (Figure 3), which have individual rotation drives and settings between the roll gap. The cantilever roll 3 has a drive 11 moving along the axis of rotation and a drive reciprocating movement 10 of the lower insert 5 with the possibility of adjusting the metering channel 15 of the intermediate annular tank 14. Along the perimeter of the mold mounted support rollers 8 (Figure 2), with the possibility of holding on line rolling the protruding part of the annular ingot 16, and the nozzle 21 for cooling the outer edges and working surfaces of the rolling zone 7 and the ingot 16. In the rolling zone 7, in the area with a minimum between the roll gap, a disk cutting device 9 (Figure 4) with the possibility of separating the rectangular billet 17 from the ring ingot 16. Along the path of the workpiece 17 mounted guide wiring 22 and the finishing group of rolling stands 23 (Figure 2). In the cases of the cantilever rolls 2 and 3, in the zone 6 of the formation of the annular ingot 16, a sensor 26 for determining the level pm of liquid metal, for example, radiation, is connected through the control unit to the drive 10 for moving the lower insert 5 of the intermediate ring container 14.

The method is as follows.

Before starting work, pre-drying and heating to a temperature of 850 ÷ 900 ° C of inserts 4 and 5 of the intermediate annular tank 14 and refractories of the working surfaces of the mold are performed. Based on the cast grade of steel, temperature, speed parameters of the process and the specified dimensions of the rectangular billet, the control computer selects a variant of the control model of the process, preliminary calculation of the required level of liquid metal h _m from the expression

h _m = t _f ^* b _zag ^* n,

where b _zag - the required width of the workpiece, mm;

n is the mold rotation frequency, r / s;

t _f - the time of formation of the crust of the solid phase, s;

t _f = 60 ^* t _cr

where t _cr - crystallization time, min;

t _cr = (0.5 ^* hsag / K _cr ) ² , min,

where h _zag - the required thickness of the workpiece, mm;

To _cr - the crystallization coefficient for steels is in the range 27 ÷ 30;

the optimal rolling angle is determined, the backup rolls 19 are adjusted. At the operator's command, the rotation rolls of the backup rolls 19 and the displacement drive 11 of the lower cantilever roll 3 are turned on. The lower cantilever 3 is pressed along the rolling zone 7 to the upper cantilever roll 2 without a gap, while the upper cantilever roll 2 relies on the upper group of backup rolls 19 and its axis of rotation is deviated from the vertical axis by an angle equal to ½ of the rolling angle, comprising 0.3 ÷ 0.5 degrees. The mold is rotated at a frequency of 250 ÷ 400 rpm. The drive 10 is turned on, the lower insert 5 is pressed against the upper insert 4 without a gap. Liquid metal begins to be fed into the intermediate annular container 14 of the mold. Upon filling the intermediate annular tank 14, a command is issued for the reverse inclusion of the drive 10, the insert 5 is lowered by a predetermined amount. An annular channel 15 is formed between inserts 4 and 5 and, under the action of centrifugal forces, the liquid metal, without touching the walls of the internal cavity of the mold, begins to be fed into the zone 6 of the formation of the ring ingot 16. When the liquid metal interacts with the working heat sink surface of the zone 6 of the formation of the ring ingot 16 , as it fills up, the crusts of the solid phase 18 immediately begin to grow. Upon reaching the desired level pm of liquid metal, a command is issued from the level sensor 26 through the control unit to reverse turn on of the displacement drive 11, the roll 3 is lowered down, and, clinging to the lower group of support rolls 19, is turned around the rolling angle, forming between the roll gap of the required size. An annular ingot 16, under the action of centrifugal forces, is squeezed out into the roll gap, and its peripheral ring part of the ingot 16 enters the rolling zone 7. Since the axis of rotation of the cantilever rolls 2 and 3 are deployed, the inter-roll gap changes depending on the angle of rotation of the mold, and the rolling zone 7 has a narrowing sector between the roll gap, where the solid phase of the ring ingot 16 is compressed until the crusts 18 are welded, and subsequent plastic deformation by rolling to the required thickness Nzag of the workpiece 17. Under the action of the layer 1.5 to 3% of the rolling expansion, the ring ingot 16 increases in diameter and, in the increase sector of the inter-roll gap of the rolling zone 7, extends beyond the outer edge of the mold, where it is picked up and held by the support rollers 8 on the rolling line, which define the protruding path part of the annular ingot 16 to the sector of reducing the inter-roll gap of the rolling zone 7. The width of the protruding part of the annular workpiece is equal to the required width b _{zag of the} workpiece 17. In the sector of the minimum inter-roll gap equal to the required thickness h _{zag of the} workpiece 17, a disk cutting device 9 is installed, which separates the workpiece 17 from the annular ingot 16. The presence of pre-configured backup rolls 19 allows to obtain the workpiece 17 with higher accuracy, in addition, the central region of the cantilever rolls 2, 3 is unloaded in which the parts are concentrated made of refractory materials, sensitive to deformation. When changing the temperature and speed parameters of the process, the roll gap is controlled by individual adjustment roll backup drives 19. When the liquid metal level deviates from the given h _m , a control command is issued to change the width of the annular dispensing channel 15, by turning on the drive 10. Thus it becomes possible to control the thickness of the crusts of the solid phase 18 without changing the frequency n of rotation of the mold, this significantly expands the technological capabilities of the process, and improves the quality GUT preform reduce cut head and tail parts of the blank 17. To improve the speed and accuracy of positioning of the lower roll 3 and the insert 5, with process control, applied in the installation speed linear servo motors. Regulation time is reduced to 0.1 ÷ 0.15 s.

Heat is removed from the formation zone 6 and the rolling zone 7 of the annular ingot by the flow of water in the radial channels 20 made in cantilever rolls 2 and 3. The speed of water in the radial channel 20 is 8 ÷ 10 m / s. The required pressure is created from the action of centrifugal forces, when the mold is rotated, in an open annular tank 13. A constant water level in the annular tank 13 is maintained through the feeders 24 from the pressure annular collectors 12.

At the same time as the breeding and rotation of the roll 3, nozzles 21 are turned on, which prevent overheating of the working surfaces of the rolling zone 7 and form a secondary cooling zone (ZVO) of the protruding part of the ring ingot 16. A drain pan is mounted in the lower part of the bed 1 to drain the water into the system water recycling installation. Bearing bearings 25 of the cantilever rolls 2 and 3 also have water cooling loops.

The workpiece 17 separated by a disk cutting device 9, with a speed of 15 ÷ 25 m / s, is sent through the wiring 22 to the finishing group of the stand 23, where it is rolled to the required size of rolled products, then passes through the accelerated cooling line and wound into a riot on the coiler. The weight of the revolt in this case may be equal to the weight of the melting supplied to the installation in the steel ladle.

Example 1

Steel 40X was cast, on the cross-section of the profile of a rectangular billet -10 × 16 mm, followed by rolling into a wire rod with a diameter of 8.0 mm.

The smelting weight was one ton. The diameter of the cantilever rolls is 2 and 3-1200 mm, the length of the ingot forming zone 6 is 160 mm, the mold rotation speed is 250 ÷ 300 rpm, the rolling angle is 0.38 degrees.

The casting speed was 16 ÷ 18 m / s, the level h _{m of} metal was determined from the expression

h _m = 60 ^* (0.5 ^* 10/28) ^{2 *} 16 ^* 4.5 = 138 mm

The casting and rolling time of one ton is 53 s.

The rolling line consisted of a finishing block of rolling stands 180 with a group drive. In rolling, 4 block stands were involved.

Hourly installation capacity of 60 tons per hour.

A series of 20 castings was carried out. The rental yield was 98.5%. Example 2

20X13 steel was cast into a profile section of a rectangular billet of 8 × 14 mm, followed by rolling onto a wire rod with a diameter of 6.5 mm.

The smelting weight was one ton. The diameter of the cantilever rolls 2 and 3 is 1200 mm, the length of the zone 6 of the ingot formation is 160 mm, the mold rotation speed is 250 ÷ 300 rpm, the rolling angle is 0.29 degrees.

The casting speed was 16 ÷ 18 m / s, the level h _{m of} metal was determined from the expression

h _m = 60 ^* (0.5 ^* 9/27) ^{2 *} 14 ^* 4.8 = 112 mm

The casting and rolling time of one ton is 67 s.

Hourly installation capacity of 54 tons per hour.

Measurement of the diameter along the length of the wire rod in the batch showed its high stability. The deviation did not exceed 0.25 of the size tolerance field, at the same time, the variation in the size of the wire rod produced by the known method reached 0.5-0.75 from the size tolerance field.

Tests for yield strength, elongation, toughness of the resulting wire rod showed an increased level of 10 ÷ 12% with respect to the wire rod produced in a known manner.

The yield by the known method did not exceed 0.92%, because in a series of 20 castings, one crashed.

The technical result of the proposed method is the expansion of technological capabilities and increased reliability by maintaining a constant level of liquid metal in the formation zone of the ingot and the independence of adjusting the size of the second volume of liquid metal entering the formation zone of the ring ingot from the speed of the mold.

Information sources

(1) A method for producing a short rolled product in a combined casting and rolling unit. RU 2134179 C1 IPC B22D 11/12. Published on August 10th, 1999.

(2) A method for producing a rectangular blank and a device for its implementation. RU 2198064 C2 IPC B22D 11/10, 11/12 Published on 02/10/2003.

Claims (3)

1. A method of obtaining a rectangular billet, including the supply of liquid metal into a rotating mold with an annular cavity formed by two horizontally conjugated cantilever rolls with concave end surfaces with zones of formation and rolling of the ingot, and the formation of an annular ingot in the radial direction under the action of centrifugal forces, while the zone of formation after the onset of growth of the crust of the solid phase, the crystallizing sections of the ring ingot are sent to the gap formed by moving and turning one of a roll relative to another, moreover, in the rolling zone, the annular ingot is squeezed before welding and simultaneously rolled to obtain the workpiece of the required size, and the ingot is held on the rolling line using at least three support rollers, after which the workpiece is separated from the annular ingot by a cutting mechanism, which differs the fact that the liquid metal is fed into an intermediate annular container, which is installed in the annular cavity of the mold, consisting of two parts, made in the form of annular inserts of heat coating material, from which through the annular channel-dispenser, the width of which is controlled by relative movement along the axis of rotation of the mold of the lower part of the intermediate annular container, while the required level of liquid metal h _m in the zone of formation of the annular ingot is preliminarily determined based on the following relationships
h _m = t _f · b _zag · n, t _f = 60 · t _kr , and t _kr = (0.5 · h _zag / K _kr ) ² ,
where b _zag - the required width of the workpiece, mm,
n is the frequency of rotation of the mold, r / s,
t _f - the time of formation of the crust of the solid phase, s,
t _cr - crystallization time, min,
h _zag - the required thickness of the workpiece, mm,
To _cr - the crystallization coefficient, which for steels is 27 ÷ 30, and maintain constant during casting by changing the width of the annular channel-dispenser. 2. A device for producing a rectangular billet containing a bed, a rotating mold with an annular cavity formed by two conjugate cantilever rolls with concave end surfaces with zones of formation and rolling of the ring ingot, made with the possibility of movement and rotation of one roll relative to another, drives for mutual movement and rotation rolls, a cutting mechanism, characterized in that it is equipped with an intermediate annular tank installed in the annular cavity of the mold consisting of two parts made in the form of annular inserts of heat insulating material, the lower of which is equipped with a reciprocating drive along the axis of rotation of the mold and configured to form an annular dispenser channel between the annular inserts and change the width of the annular dispenser channel when moving along the axis rotation of the mold, while in the zone of formation of the ring ingot a sensor is installed to determine the level of liquid metal, connected through the control unit with Odom reciprocating movement of the bottom portion of the intermediate annular container. 3. The device according to claim 2, characterized in that the cantilever rolls are mounted in a frame on spherical bearings with the possibility of rotation relative to the vertical axis of rotation and are driven into rotation by means of backup rolls having individual rotation drives and adjust the clearance between the cantilever rolls.

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