Method for continuous casting, continuous rolling and continuous straightening of steel rail

Abstract

The invention is suitable for the technical field of metallurgical processes, and provides a continuous casting, continuous rolling and continuous straightening method for a steel rail. Comprising the following steps that a continuous casting billet is produced through a continuous casting machine; performing scanning, typical defect judgment and alarm on the surface of the continuous casting blank through a 2D surface defect detection system so as to obtain the position of a defect on the surface of the casting blank; carrying out follow-up targeted cleaning according to the surface defect position of the continuous casting billet; the continuous casting billet is subjected to induction supplementary heat treatment; the continuous casting billet is subjected to descaling treatment through high-pressure water; rolling the continuous casting billet by using a rolling mill to obtain an initial steel rail; marking the initial steel rail; waste heat quenching treatment is conducted on the initial steel rail, and deformation limiting is conducted on the rail bottom / rail head of the steel rail; straightening the initial steel rail by using a straightening machine; the initial steel rail is subjected to rough fixed-length cutting treatment of any length; the cut initial steel rail is subjected to quality detection; and performing fixed-length cutting treatment on the initial steel rail subjected to quality detection to obtain a finished steel rail.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgical process, in particular to a method for continuous casting, continuous rolling and continuous straightening of rails. Background Art

[0002] In recent years, the headless continuous casting and rolling process has made great progress in the industrial application of plates, bars and wires, and has been widely used, but it has not yet been involved in the field of profile rolling. For example, the traditional heavy rail hot rolling process generally adopts a universal mode, and its basic process flow is: continuous casting billet → walking furnace heating → high-pressure water descaling → BD1 billet opening → BD2 billet opening → high-pressure water descaling → universal rolling (five-frame or three-frame) → thermal printing → hot saw cutting → pre-bending walking cooling bed → horizontal and vertical composite straightening → inspection center → processing → storage; Therefore, traditional rolling has many disadvantages: Traditional rail hot rolling mills roll single intermediate billets, so they inevitably go through a series of processes such as accelerated rolling, decelerated rolling, steel throwing, and tail swinging when entering the billet, primary rolling, and finishing rolling mills. The resulting dimensional tolerances and uneven mechanical properties are difficult to solve within the original process framework. The continuous casting billets need to be stacked and flame cleaned offline. This process wastes the heat of the billets, increases the cost of manual cleaning, and occupies the stacking space; the heating furnace heats the cleaned room temperature billets to above 1200℃, which is a major energy consumer in rolling production, and the energy consumption accounts for more than 60% of the entire process; the surface of the billet will be severely decarburized after high-temperature heating, and the decarburization of the rail surface will cause the physical properties of the rail hardness, wear resistance, and fatigue strength to decrease. At the same time, it will cause serious oxidation and burning. The rolling mills are relatively independent, and some of the stands are reversible rolling mills, which need to continuously turn the steel over for reciprocating rolling, increasing the rolling interval time; when the universal rolling mill produces rails, during the continuous rolling stage, the "steel piling" phenomenon will occur at the moment of steel feeding, and the "tail swinging" phenomenon will occur at the moment of separation, all of which will cause fluctuations in rail specifications; in order to ensure that the end specifications of the rolled rails do not meet the requirements, the head and tail of the rails need to be cut as much as possible after rolling, resulting in serious waste of materials; since the rails are in a lying state during the rolling process, they are affected by gravity and rolling, and the specifications and straightness are difficult to control; during the cooling process of the rails, the cooling speeds of various parts of the cross section are inconsistent, which will produce repeated cooling stresses. Due to the asymmetry of the rails in the lying state, the rails will form a pre-straightening bend, and it is difficult to form a good straightness during straightening through the pre-bending model, which is also the main reason for the fluctuations in straightening specifications and residual stress fluctuations.

[0003] In order to solve the above problems, a method for continuous casting, continuous rolling and continuous straightening of rails is proposed. Summary of the invention

[0004] The object of the present invention is to provide a method for continuous casting, continuous rolling and continuous straightening of rails to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions: A method for continuous casting, continuous rolling and continuous straightening of rails, comprising the following steps: Producing continuous casting billets using a continuous casting machine; Through the 2D surface defect detection system, the continuous casting billet surface is scanned, typical defects are determined, and alarms are issued to obtain the location of surface defects on the billet; Carry out follow-up targeted cleaning according to the position of surface defects of continuous casting billet; Conduct induction heat treatment on continuous casting billets; Descaling the continuous casting slab using high pressure water; The continuous casting billet is rolled by a rolling mill to obtain an initial steel rail; Marking the initial rails; Perform residual heat quenching on the initial rails and limit deformation of the rail bottom / rail head; The initial rails are straightened using a straightening machine; Roughly cut the initial rails into any length; Conduct quality inspection on the initial rails after cutting; The initial rails that have passed the quality inspection are cut to length to obtain finished rails.

[0006] As a further solution of the present invention: the continuous casting machine is a straight arc continuous casting machine.

[0007] As a further solution of the present invention: the following targeted cleaning according to the position of the surface defects of the continuous casting billet comprises: Adopt online artificial flame following targeted cleaning.

[0008] As a further solution of the present invention: the descaling treatment of the continuous casting billet by using high-pressure water comprises: The continuous casting billet is descaled using high-pressure water sprayed by a descaling machine.

[0009] As a further solution of the present invention: using a rolling mill to roll the continuous casting billet to obtain an initial rail, comprising: The entire production line rolling mill layout adopts a continuous rolling mill with a spacing of 4-6 meters between frames. The unit consists of alternating two-roller horizontal and vertical rolling mills, universal rolling mills and edge rolling mills.

[0010] As a further solution of the present invention: the residual heat quenching treatment of the initial rail and the limiting deformation of the rail bottom / rail head include: The initial rail final rolling temperature is 900±50℃, and the final cooling temperature is 60℃; the cooling is controlled in two temperature sections.

[0011] As a further solution of the present invention: the final rolling temperature of the initial rail is 900±50°C, and the final cooling temperature is 60°C; the cooling is controlled in two temperature sections, including: The first stage cooling medium is water mist, the cooling temperature range is 950-520℃, the average cooling rate is 4.83℃ / s, the cooling time is 89s, and the cooling line length is 169m; The second stage cooling medium is air cooling, the cooling temperature range is 520-60℃, the average cooling rate is 3℃ / s, the cooling time is 153s, and the cooling line length is 292m.

[0012] As a further solution of the present invention: the rough cutting of the initial rail into any length comprises: The quick-cut system is used to roughly cut the initial rails into any length.

[0013] As a further solution of the present invention, the quality of the initial rail after cutting is tested, including: Send the cut initial rails to two inspection centers for steel separation / delivery; The testing center tests a number of initial rails; the testing center includes a cold 3D profiler, a flatness tester, a 2D surface quality testing device, an ultrasonic testing system and an eddy current testing system.

[0014] As a further solution of the present invention: the initial rails that have completed quality inspection are cut to a fixed length to obtain finished rails, including: The steel separation stand transports the initial rails after testing to the cut-to-length sawing production line; The cut-to-length sawing production line cuts the initial rails to a fixed length; The rail collection stand collects the finished rails after cutting.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention has a whole process from continuous casting to straightening, and adopts vertical continuous rolling of rails; the heating furnace, which is a large energy consumer, is eliminated, and the problems of decarburization layer and oxidation burning are solved; the fully symmetrical rolling solves the problem of metal deviation, eliminates the specification fluctuation caused by the impact of the inlet and outlet steel ends, eliminates the pre-straightening bending caused by uneven temperature during pre-bending, eliminates the straightening blind area, and has the advantages of almost no fluctuation in the overall specifications, and can be cut to length according to needs, saving more than 40% of energy compared with traditional processes, and increasing the yield rate by more than 6%, bringing huge economic and social benefits to industrial energy conservation and emission reduction and product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention is a schematic diagram of the layout of a method for continuous casting, continuous rolling and continuous straightening of rails. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] Example 1 See also Figure 1 , a flow chart of a method for continuous casting, continuous rolling and continuous straightening of rails provided in Example 1 of the present invention comprises the following steps S1 to S12. The overall layout of the production line of this process: 3 plant spans, each span is 40 meters, and the middle main rolling span. Both sides are detection and collection spans, and this production line is designed to produce 500 meters of rails at most. The main rolling span covers the continuous casting machine, induction heating system, descaling system, continuous rolling unit, printer and continuous straightening unit, and the detection and collection span includes the detection center, sawing processing, finished product collection, etc.

[0019] S1. Producing continuous casting billets using a continuous casting machine; In an embodiment of the present invention, the continuous casting machine is a straight arc continuous casting machine, wherein the straight arc continuous casting machine can produce steel billets with a cross-section of 200-450 mm after dynamic light reduction at a maximum pulling speed of 8-12 m / min. Heavy rail billets generally use square billets of 380 (width) * 280 (height) mm. The specific width, thickness and pulling speed depend on the required rolling variety.

[0020] S2. Scan the surface of the continuous casting billet, determine typical defects, and give an alarm through the 2D surface defect detection system to obtain the position of the surface defects of the billet; S3, performing follow-up targeted cleaning according to the position of surface defects of the continuous casting billet; In the embodiment of the present invention, the step S3, performing follow-up targeted cleaning according to the position of the surface defects of the continuous casting billet, comprises: Adopt online artificial flame following targeted cleaning.

[0021] S4. Perform induction heat treatment on the continuous casting billet. Since the temperature of the billet is still 900-1000℃ after it is discharged from the continuous casting machine and before it is descaled, the billet needs to be heated before rolling.

[0022] In the embodiment of the present invention, online artificial flame following targeted cleaning is adopted. Each group of heat supplement device is 1.5-2 meters.

[0023] S5, descaling the continuous casting billet using high pressure water; In the embodiment of the present invention, the step S5, descaling the continuous casting billet using high pressure water, comprises: The high-pressure water sprayed by the descaling machine is used to descale the continuous casting billet. There can be four descaling machines. The first descaling machine is installed at the entrance of the billet mill. The first descaling ring structure adopts a double ring structure, descaling on four sides, the descaling pressure is greater than 22MPa, the descaling roller speed is 0.8-1.2m / s, and the descaling temperature drop is less than 20℃.

[0024] The other three machines are nested between the universal units, adopting a simple descaling structure, descaling on the left and right, with a descaling pressure of >22MPa, and the descaling roller speed is matched according to the extension of the rolled piece, and the descaling temperature drop is <10℃.

[0025] The high-pressure water flow generated by the high-pressure water descaling system is used to remove the iron oxide scale. In the process of billet descaling, the high-pressure water flow passes through the nozzle installed on the descaling billet to form a fan-shaped water jet to impact the billet surface that needs to be descaled. Under the impact of the high-pressure water flow, the shear force formed by the contraction of the iron oxide scale when it is cooled, and the steam explosion formed by the rapid evaporation of the water flow, the iron oxide scale is peeled off and washed away from the billet surface.

[0026] S6, rolling the continuous casting billet by a rolling mill to obtain an initial steel rail; It should be noted that the entire production line rolling mill layout adopts a continuous rolling unit with a frame interval of 4-6 meters. The unit is composed of alternating two-roller flat vertical rolling mills, universal rolling mills and edge rolling mills; in order: box-shaped hole (2 sets of vertical two-rollers) → box-shaped hole (1 set of flat two-rollers) → trapezoidal hole (1 set of flat two-rollers) → hat-shaped hole (1 set of flat two-rollers) → rail-shaped hole (3 sets of vertical two-rollers) → universal rough rolling hole (3 sets of vertical universal) → edge rolling hole (2 sets of vertical edge rolling) → universal medium rolling hole (1 set of vertical universal) → edge rolling hole (1 set of vertical edge rolling) → universal finishing rolling hole (1 set of vertical universal).

[0027] The continuous casting billet is firstly opened by alternating horizontal and vertical two-roller opening mill (6-9 frames) to form the heavy rail prototype, and then rolled by universal primary rolling mill, edge rolling mill, universal intermediate rolling mill, edge rolling mill, universal finishing rolling mill, etc. (6-8 frames). The whole hole design adopts symmetrical hole shape, and the rolled piece is in a standing state. This rolling method ensures the balance of metal flow and the stability of rolling, and there is no problem of metal deviation and asymmetry.

[0028] S7, marking the initial rails; It should be noted that rail trademarks are pressed on the waist of the rails according to regulations. The marking content includes steel grade code, production year and month, furnace number, flow number, billet number, rail serial number, etc. The spacing between rail trademarks is adjusted according to the fixed length.

[0029] S8, performing residual heat quenching treatment on the initial rails and limiting deformation of the rail bottom / rail head; In the embodiment of the present invention, the step S8, performing residual heat quenching treatment on the initial rail and limiting deformation of the rail bottom / rail head, includes: The initial rail final rolling temperature is 900±50℃, and the final cooling temperature is 60℃; the cooling is controlled in two temperature sections.

[0030] Specifically, the first stage cooling medium is water mist, the cooling temperature range is 950-520°C, the average cooling rate is 4.83°C / s, the cooling time is 89s, and the cooling line length is 169m; The second stage cooling medium is air cooling, the cooling temperature range is 520-60℃, the average cooling speed is 3℃ / s, the cooling time is 153s, and the cooling line length is 292m; The rail running speed is 1.9m / s, the average cooling rate is 3.67℃ / s, the total cooling time is 242s, and the total length of the cooling line is 461m.

[0031] S9, straightening the initial rail using a straightening machine; In the embodiment of the present invention, the straightening machine is a horizontal and vertical composite straightening machine, with horizontal 9-roller straightening, flat roll pitch of 1600mm, vertical 7-roller straightening, vertical roll pitch of 1100mm, and the straightening speed matches the final rolling speed.

[0032] S10, performing a rough cutting process of arbitrary length on the initial rail; In the embodiment of the present invention, the step S10, performing a rough sizing process of cutting the initial rail into any length, comprises: The quick-cut system is used to roughly cut the initial rails into any length.

[0033] Specifically, the rails are roughly cut to any length, with a length range of 9-500m; the quick cutting system needs to run along with the rails, with a cutting accuracy of ±100mm.

[0034] S11, performing quality inspection on the initial rail after cutting; In the embodiment of the present invention, the step S11, performing quality inspection on the initial rail after cutting, includes: Send the cut initial rails to two inspection centers for steel separation / delivery; The testing center tests a number of initial rails; the testing center includes a cold 3D profiler, a flatness tester, a 2D surface quality testing device, an ultrasonic testing system, and an eddy current testing system; The straightness test of the testing center completes the detection and identification of the straightness of the entire length of the rail; the 2D surface quality testing equipment completes the detection and identification of surface defects of the rail; the ultrasonic testing system completes the detection and identification of internal defects of the rail; and the eddy current testing system completes the detection and identification of near-surface defects at the head and bottom of the rail.

[0035] S12, cutting the initial steel rails that have completed quality inspection to a fixed length to obtain finished steel rails.

[0036] In the embodiment of the present invention, the step S12, cutting the initial rails that have completed the quality inspection to a fixed length to obtain finished rails, includes: The steel separation stand transports the initial rails after testing to the cut-to-length sawing production line; The steel racks are divided into two.

[0037] The cut-to-length sawing production line cuts the initial rails to a fixed length; It should be noted that there are 4 fixed-length sawing production lines (the shortest fixed-length is considered to be 100m, if it is less than 100 meters, there must be more than 4 production lines), and every 2 lines are responsible for completing the precise length production of the rails tested by a testing center line.

[0038] The rail collection stand collects the finished rails after cutting.

[0039] It should be noted that there are 4 collecting racks, the shortest length is 100 meters and the maximum length is 500 meters; lifting / stacking: the lifting and stacking methods refer to the existing 100-meter rails and 500-meter rails in the welded rail factory.

[0040] The present invention improves the surface quality of the rail. The continuous casting-continuous rolling process reduces the frequent impact of the head and tail parts of the rolled piece with lower temperature on the rollers and guides, reduces the wear of the rollers, and is conducive to the smooth operation of the rolling mill and its transmission device; at the same time, it avoids the impact of steel feeding and tail swinging of steel out, reduces the impact of the rolled piece with the rollers, guides, side linings, etc., avoids the adhesion of the oxide scale on the surface of the roller and the defects of the oxide scale pressed into the surface of the rolled piece; improves the uniformity of the specifications of the rail throughout the length. The vertical continuous casting-continuous rolling rail method is adopted. The rolled piece is always in a vertical symmetrical state during the rolling process. The rolling process is continuous and the force on the same plane is symmetrical and balanced, avoiding the influence of the temperature difference between the front and rear ends and the middle of the rolled piece, eliminating the influence of the uneven cooling of the external roller cooling water, and eliminating the influence of the sinking of the head of the self-gravity on the forming of the rail, so that the uniformity of the specifications of the rail throughout the length is guaranteed; and the straightness of the rail throughout the length is improved. The rail straightening method of vertical continuous rolling and continuous straightening eliminates the straightening blind area where the three-point bending deformation of the local deformation area in contact between the straightening roller and the rail is not penetrated during the roller straightening process. The length of the straightening blind area is affected by the roller diameter and the amount of reduction. The continuous straightening process includes horizontal straightening, vertical straightening, and light reduction in one machine. Since there is no end of the rolled piece and the double-staggered small roller diameter high-strength roller straightening technology is adopted, the straightening blind area is eliminated and the residual stress of the rail is reduced. Due to vertical continuous rolling and cooling, the full-length specifications are stable, the rail is straight, and there is no residual stress caused by the temperature difference between the head and the tail and the irregular metal flow in the cross section. At the same time, the high-rigidity universal light reduction rolling mill after the straightening machine reduces the residual stress of the rail to within ±50MPa through the full-length fixed load method, thereby improving production efficiency. Since the dynamic deceleration and impact caused by each rolled piece at the moment of biting into each stand are eliminated, the continuous rolling process is stable and the tension fluctuation is small, thus creating conditions for further increasing the rolling speed; at the same time, the gap time between two adjacent rolled pieces is eliminated, and the utilization rate of the rolling mill is significantly improved. Except for roll replacement and maintenance, the continuous rolling time can reach several days and nights, the rolling mill operation rate can reach more than 90%, and the production capacity can be increased by 10% to 12%; it can greatly improve production efficiency and improve the yield rate of rails. It eliminates the cross-sectional size tolerance and intermediate rolling waste caused by piled steel during biting, and greatly reduces the metal consumption of cutting heads and tails, thereby increasing the metal recovery rate by more than 3% and improving product quality. When continuous casting and rolling are used, all performance indicators are consistent throughout the entire length, and there is no performance fluctuation; the continuous rolling and straightening process effectively eliminates the end specification fluctuation caused by the straightening blind area, and eliminates the metal consumption of cutting the head and tail after straightening, thereby increasing the metal recovery rate by more than 3%, the product quality and specifications are stable throughout the entire length, and the comprehensive yield rate is increased by more than 6%; the length of the finished rail can be arbitrarily determined according to user needs. The method of continuous casting, continuous rolling and continuous straightening ensures that the theoretical length of the finished product can be extended infinitely. Through the follow-up fast cutting system and precise reprocessing process, it can be cut to size and transported according to user needs; the welding process of the welding rail factory is eliminated to shorten the process. The base welding rail production line uses welding technology and linear processing flow to weld 100-meter short rails into 500-meter long rails.This process includes a series of processes such as hoisting, rail supply, rust removal, welding, rough grinding, normalizing, straightening, fine grinding, flaw detection, storage and transportation, which consumes a lot of resources. However, this process can directly produce 500-meter-long rails and directly process them, eliminating the complicated process of 500-meter rail welding.

[0041] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0042] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for continuous casting, rolling and straightening of rails, characterized in that: The steps include: Utilizing a continuous casting machine to produce continuous casting billets; Through the 2D surface defect detection system, the continuous casting billet surface is scanned, typical defects are determined, and alarms are issued to obtain the location of surface defects on the billet; Carry out follow-up targeted cleaning according to the position of surface defects of continuous casting billet; Perform induction heat treatment on continuous casting billets; Use high-pressure water to descale the continuous casting billet; The continuous casting billet is rolled using a rolling mill to obtain an initial steel rail; Marking the initial rails; Perform residual heat quenching on the initial rails and limit deformation of the rail bottom / rail head; Use a straightening machine to straighten the initial rails; Rough cutting of the initial rails into any length; Conduct quality inspection on the initial rails after cutting; The initial steel rails that have completed quality inspection are cut to length to obtain finished steel rails.

2. The method for continuous casting, rolling and straightening of rails according to claim 1, characterized in that: The continuous casting machine is a straight arc continuous casting machine.

3. The method for continuous casting, rolling and straightening of rails according to claim 1, characterized in that: The following targeted cleaning according to the position of the surface defects of the continuous casting billet includes: Adopt online artificial flame following targeted cleaning.

4. The method for continuous casting, rolling and straightening of rails according to claim 1, characterized in that: The method of descaling the continuous casting slab by using high-pressure water comprises: The continuous casting billet is descaled using high-pressure water sprayed by a descaling machine.

5. The method for continuous casting, rolling and straightening of rails according to claim 1, characterized in that: The continuous casting billet is rolled using a rolling mill to obtain the initial rail, including: The entire production line rolling mill layout adopts a continuous rolling mill with a spacing of 4-6 meters between frames. The unit consists of alternating two-roller horizontal and vertical rolling mills, universal rolling mills and edge rolling mills.

6. The method for continuous casting, rolling and straightening of rails according to claim 1, characterized in that: The residual heat quenching treatment of the initial rail and the deformation restriction of the rail foot / rail head include: The initial rail final rolling temperature is 900±50℃, and the final cooling temperature is 60℃; the cooling is controlled in two temperature sections.

7. The method for continuous casting, rolling and straightening of rails according to claim 6, characterized in that: The final rolling temperature of the initial rail is 900±50°C, and the final cooling temperature is 60°C; the cooling is controlled in two temperature sections, including: The first stage cooling medium is water mist, with a cooling temperature range of 950-520°C, an average cooling rate of 4.83°C / s, a cooling time of 89s, and a cooling line length of 169m; The second section cooling medium is air cooling, the cooling temperature range is 520-60℃, the average cooling rate is 3℃ / s, the cooling time is 153s, and the cooling line length is 292m.

8. The method for continuous casting, rolling and straightening of rails according to claim 1, characterized in that: The rough cutting of the initial rails into any length comprises: The quick-cut system is used to roughly cut the initial rails into any length.

9. The method for continuous casting, rolling and straightening of rails according to claim 8, characterized in that: The quality inspection of the initial rail after cutting is carried out, including: Send the cut rails to two inspection centers for steel separation / delivery; The testing center tests a number of initial rails; the testing center includes a cold 3D cross-section profiler, a flatness tester, a 2D surface quality testing device, an ultrasonic testing system, and an eddy current testing system.

10. The method for continuous casting, rolling and straightening of rails according to claim 9, characterized in that: The process of cutting the initial steel rails that have completed quality inspection to a fixed length to obtain finished steel rails includes: The steel separation platform transports the initial rails after inspection to the cut-to-length sawing production line; The cut-to-length sawing production line cuts the initial rails to a fixed length; The rail collection stand collects the finished rails after cutting.

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