Parallel processing method for coil formation and control cooling of hot-rolled steel wire

Abstract

To provide a parallel processing method for control cooling and Mandarin roll coil formation of a steel wire.SOLUTION: A hot-rolled steel wire is formed into a vertically helical ring by a laying winder, and dropped in an annular air duct having a center axis eccentric from a winder center axis. An annular stacking table that receives the ring to turn is provided in the air duct, and a coil having an outer / inner diameter of a ring diameter ±α (eccentric amount×2) is formed through eccentric stacking. A currently stacked ring row is blast-cooled by a strong suction duct connected to the lower end of the air duct. Cooling performance equal to or higher than boiling / cooling is acquired by an air speed of 20 m / s or higher and contamination of a mist spray. A rolling speed of 100 m / s or higher can also be dealt with.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for simultaneously subjecting steel wire rod produced by hot rolling to controlled cooling immediately after rolling and coiling. [Background technology]

[0002] In the manufacture of steel wire rods, some kind of deliberate cooling (called controlled cooling) is usually carried out immediately after hot rolling to adjust the metal structure and improve the mechanical and surface properties of the product. The development of this technology is summarized below. In the 1950s, the wire was simply wound after rolling, and coil formation was immediate. The outer edge of the coil was air-cooled, while the inside was tightly insulated, and the metal structure and mechanical properties were uneven within the coil, so the heat treatment required for processing into products was incorporated into the secondary processing of the wire. In order to improve uneven cooling and eliminate some of the heat treatment, Schlemann of Germany dropped spiral rings formed by a laying winder onto a moving conveyor to form a horizontal row of parallel rings, which succeeded in achieving almost uniform air cooling over the entire length. After cooling, the ring rows are bundled together to form a coil. In the early 1960s, Morgan of the United States and Stelco of Canada collaborated to incorporate an air blast device into the above conveyor, perfecting a controlled cooling method for high-carbon steel equivalent to air patenting (commonly known as the Stelmor Process), which eliminated the need for heat treatment in wire rope manufacturing. This process quickly became popular around the world. In the late 1960s, a method was developed in Japan to compete with the above process. In this method, vertical spiral rings formed by a vertical laying winder are dropped directly into a hot water tank and accumulated, whereby boiling cooling and coil formation are carried out simultaneously (commonly known as the ED process; Patent Document 1). This process has a greater cooling capacity than Stelmor, produces superior product strength, and is advantageous in terms of facility space, equipment costs, and operating costs. In the 1970s and 1980s, along with improvements to the Stelmor, the development and practical application of direct quenching, molten salt isothermal processing (commonly known as the DLP process; Non-Patent Document 1), and other controlled cooling methods progressed in Japan, leading to the production of a variety of products using hard and soft materials. Among them, DLP is a single-function process, but it has excellent performance equivalent to lead bath patenting, making it possible to eliminate the heat treatment that is essential for the production of piano wire and PC steel wire, and it has not been surpassed even today. The ED process was also improved by combining it with Stelmor (Patent Document 2, Non-Patent Document 2), and the parallel processing of coil formation and cooling in the old ED was eliminated. Since then, improvements have been made in various places.

[0003] The new process disclosed in Patent Document 3 uses molten salt as a refrigerant, similar to the DLP process, and combines a new cooling method that excels in uniform cooling, enabling high-quality and diverse heat treatments. Furthermore, it revives the method of processing coil formation and controlled cooling in parallel, and the coil shape is completely new, so it was highly anticipated for its new effects, but it has not yet been put into practice due to technical difficulty and other reasons.

[0004] This method allows for a variety of cooling methods (from gentle to strong cooling), solves the problem of uneven cooling within a single ring or coil, and also produces a coil with a shape that has never been produced before: "a coil in which rings are continuously eccentrically arranged and accumulated (commonly known as a flower winding in the steel wire industry)." This coil brings various new effects to subsequent processes, such as 1) stable bundling (no bundle collapse), and 2) uniform and efficient pickling and coil heat treatment. The key to the process is to form vertical spiral rings using a vertical laying winder, which then drops them onto a horizontal rotating stacking table with an axis eccentric to the spiral ring axis to form a "flower-wrapped" coil. The stacking table is then lowered into a cooling tank for a special immersion cooling process. This process provides excellent cooling uniformity. As shown in Figure 4(b), 1) the ring pitch is larger than that of the conventional horizontal parallel ring array stacking coil (Figure 4(a)), resulting in less density on the inner and outer circumferences of the coil; 2) conversely, there are no independent rings in the center of the row; instead, the rings are moderately close together and intersect, minimizing the difference between the two. 3) The radially centrifugal flow of the refrigerant passes evenly through the gaps between the rings, which have a geometric regularity.

[0005] The problem is that, although the quality and various heat treatments that can be achieved are excellent because molten salt is mainly used as a refrigerant, there is a considerable burden in temperature control, treatment of adhering salt, equipment costs, maintenance costs, and management.

[0006] Patent Document 4 discloses appropriate manufacturing conditions when using cold water as the refrigerant in the above method (Patent Document 3) for direct quenching. If hot water is used, the known patenting method is achieved, and both the equipment and operation are simplified.

[0007] Patent Document 5 discloses an improvement over the operational problems of Patent Document 4. Patent documents 3, 4 and 5 all relate to the same system of "flower-wrapped" coil formation and the parallel process of immersion cooling in a liquid refrigerant, and share a common weakness. As the rolling speed increases, the rotation speed of the winder increases, and the number of revolutions of the accumulation table also increases. The rotating coil causes excessive vortexes in the liquid refrigerant, which can lead to overflow and cause danger and uneven cooling. This problem cannot be solved by simply improving the freeboard. For wire rod diameters of 7 mm or more, the rolling speed is not excessive, so with proper design it is possible to use a liquid refrigerant. However, at 5.5 mm, which is the maximum production volume ratio, the rolling speed increases to 100-150 m / s. The appropriate rotation speed is approximately 60 revolutions per minute, which would create abnormal vortexes and is thought to be difficult to use in practical use. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Tokkosho No. 45-8536 [Patent Document 2] Patent Publication No. 64-7139 [Patent Document 3] Patent 3890567 [Patent Document 4] Tokuhei 7-94693 [Patent Document 5] Patent 6050543 [Non-patent literature]

[0009] [Non-Patent Document 1] Wakimoto, Iron and Steel 69 (1983), S570 [Non-patent document 2] Yamada, Trans.ISIJ,Vol27,1987(42) Summary of the Invention [Problem to be solved by the invention]

[0010] The methods of Patent Documents 3, 4 and 5, which are the basis of the present invention, namely, forming a spiral ring from a hot-rolled wire rod using a laying-type winder, dropping it vertically onto a horizontally rotating accumulation table, and eccentrically stacking it to form a "flower-wound" coil, while lowering the accumulation table into a liquid refrigerant tank for immersion cooling, thereby performing coil formation and controlled cooling in parallel, have the following problems. As the rolling speed increases, the number of revolutions of the winder increases, and the number of revolutions of the collecting table also increases. The rotating coils cause excessive vortexes in the liquid refrigerant, which can lead to spillage, which is dangerous and can cause uneven cooling. Using a liquid refrigerant can be difficult in some cases. The problem to be solved by the present invention is to provide a method that can obtain the same effect, i.e., "flower winding" + "controlled cooling," without using a liquid refrigerant. [Means for solving the problem]

[0011] The first aspect of the present invention is a method for concurrently subjecting red-hot steel wire rod immediately after hot rolling to controlled cooling and coiling, the method comprising: forming a falling vertical spiral ring from a traveling wire rod using a vertical laying winder directly or via a horizontal laying winder and a horizontal conveyor; eccentrically stacking the vertical spiral ring at a constant phase angle and a constant falling speed on a ventilated annular stacking table that is provided in an annular wind tunnel having a vertical axis eccentric from the central axis of the vertical spiral ring and that rotates to receive the vertical spiral ring; forming a coil having predetermined inner and outer diameters and regular gaps; and applying air blast cooling to the coil through a suction duct connected to the lower end of the annular wind tunnel.

[0012] The second aspect of the present invention is 1) The turning is performed by a turning roller table having a rotation axis in the radial direction provided on the annular accumulation table, 2) The rotation direction is opposite to the winding direction, 3) The wind speed is 20 m / s or more, and if necessary, the mist spray is used along with the wind. 4) A method for concurrently processing coil formation and controlled cooling of steel wire rod as described in the first invention, characterized in that two annular wind tunnels containing annular accumulation tables are provided to enable rapid switching.

[0013] As a definition of a predicate, The phase angle is defined by the following formula and means the rotation angle per ring. Phase angle (rad) = 2π x number of revolutions on the accumulation table / number of revolutions of the winder The eccentric distance is the distance between the rotation axis of the accumulation table and the central axis of the vertical spiral ring. [Effects of the Invention]

[0014] First, it is possible to easily manufacture the "flower-wound coil" shown in Figure 4, which has never been manufactured before. Accurate "flower-wound coil" formation creates a nearly uniform gap within the coil, except on the inner and outer periphery of the coil. The lack of close contact between adjacent rings and uneven ventilation ensures highly uniform cooling. The orbiting ring array (Fig. 5b) is less densely packed on the inner and outer periphery than the parallel ring array (Fig. 5a), and also provides better cooling uniformity than the commonly used Stelmor process. The formation of regular voids improves the quality stability and processing efficiency in the subsequent pickling and heat treatment of the entire coil (batch processing).

[0015] Second, as shown in Figure 5(a), conventional coils are thin-walled (small difference between the inner and outer diameters) due to the simple accumulation of tightly packed rings, and the cylindrical inner and outer surfaces are uneven. Although the coil shape is maintained by forceful bundling, the cargo is prone to collapse during transportation. In particular, double bundling is unavoidable to deal with rocking during sea transport. The "flower-wrapped coil" (Fig. 5(b)) has a constant inner and outer diameter and is thick-walled and cylindrical, so it does not collapse even when simply bound. It is also resistant to scratches.

[0016] As an effect of the present invention itself, the refrigerant is blown by air in the wind tunnel, so the problem of vortex currents that occurs in the case of a liquid refrigerant is eliminated. The wind is drawn downward, in the same direction as the falling ring, so there is almost no disturbance when the ring lands. "Flower-wrapped coils" can be formed without any problems even at rolling speeds of 100 meters per second or more.

[0017] The airflow speed and mist volume can be easily adjusted with a single control mechanism, and various controlled cooling levels, from weak to strong, can be easily applied. The heat transfer coefficient is 200-300 due to the mist mixing and wind speed effect (30m / min or more). (kcal / m 2 h°C), providing a cooling capacity equal to or greater than that of boiling cooling.

[0018] When accumulating the vertical spiral rings, the coils on the accumulating table are rotated by a rotating roller conveyor, and the rotation direction is opposite to that of the winding machine. 1) The rings are pulled by the collecting platform as they fall (the ring diameter becomes smaller), which stabilizes the placement of the rings. If the rings are pushed in the same direction, they will tend to push freely, and the resistance will vary, which will lead to variations in the landing points. 2) The ring near the bottom end of the coil is no longer in fixed contact with the accumulation table, etc., so no excessive cooling points occur. 3) Even if the tip of the ring falls and gets caught in a gap in the ventilated accumulation table, it is pulled out immediately because it is facing the opposite direction, and no disturbance occurs in the coil formation.

[0019] An existing winding machine can also be used. Only the upstream section of the horizontal conveyor from the winding machine is reused, and the wire is dropped from the horizontal conveyor into the cooling tank (wind tunnel) mentioned above. Although the coil shape is somewhat inferior, it is possible to perform controlled cooling and coil formation simultaneously.

[0020] The time difference between the rear end of the leading wire and the front end of the following wire is less than 10 seconds. To avoid a drop in rolling efficiency, two cooling tanks must be quickly switched for one rolling line. The current Stelmor system allows for processing with one tank. While this may seem disadvantageous at first glance, it eliminates the need for a cooling conveyor of approximately 100 meters, and is simpler and less expensive. [Brief explanation of the drawings]

[0021] [Figure 1] 1 shows a schematic diagram of an apparatus for carrying out the controlled cooling method of the present invention. [Figure 2] 1 is a schematic diagram of a collection platform for collecting falling vertical spiral rings. [Figure 3] 1 shows the shape of an eccentric ring row of the present invention. [Figure 4] 1 shows the shape of the coil of the present invention. [Figure 5] The methods of forming the ring array into a coil are compared. (a) Comparative Example, (b) This invention [Figure 6] FIG. 1 is a diagram showing the relationship between the heat transfer coefficient, the wind speed, and the wire diameter in air jet cooling. [Figure 7] FIG. 10 is a diagram showing the relationship between the overall heat transfer coefficient including the radiation term, the wind speed, and the wire diameter. [Figure 8] This shows a structure in which a horizontal laying type winder and a horizontal conveyor are incorporated into the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] The method of the present invention for performing concurrent coil formation and controlled cooling will now be described with reference to FIG. The red-hot wire rod 2 that has passed through the final hot rolling mill 1 passes through pinch rolls 3 and is formed into a solenoid-type spiral ring 6 by a vertical laying type winder 4 consisting of a rotating spiral-type helical guide tube 5. The spiral ring 6 falls onto a horizontal ring accumulating stand 9 installed in an annular wind tunnel W consisting of a vertical outer cylinder 7 and a vertical inner cylinder 8, where it is accumulated and formed into a coil 10.

[0023] During accumulation, the ring array on the accumulation table 9 is rotated by a rotation mechanism 12 (rotation center axis Y) which rotates eccentrically with the rotation center axis X of the winder 4 at a slower speed than the winder 4 to form a coil 10 consisting of an eccentric accumulated ring array. The turning mechanism 12 comprises a rotary drive source 13, a spindle 14 for transmitting torque, a bevel gear (not shown), and a turning roller table 24 shown in FIG. The accumulation table 9 is equipped with an elevation mechanism 15 consisting of a spindle 14 and a hydraulic cylinder 16, which descends at a predetermined speed to maintain a constant falling distance, and ascends at a predetermined speed to quickly remove the coils.

[0024] In the wind tunnel W, a powerful blast of air passes vertically downward through the accumulated ring array (in the process of forming a coil), accelerating and cooling the ring array. At the bottom end of the wind tunnel W, a suction duct 17 is installed perpendicularly, and hot air 19 is powerfully exhausted by an axial fan 18. Wind tunnels are originally designed to be rectified, and the structure shown in the figure raises concerns about uneven blast of air, but uneven cooling is largely avoided by the swirling of the material to be cooled.

[0025] The cooling rate depends on the speed of the blast. In this invention, the wind speed is specified as 20 m / s or more. This achieves the same level of cooling as a normal Stelmor. It is desirable for the maximum wind speed to exceed 30 m / s. This results in a cooling capacity equivalent to boiling cooling. If even stronger cooling is desired, mist sprays 20 are installed above the wind tunnel or not only above it but also on the inside and outside walls of the wind tunnel, and mist is mixed into the blast. The cooling capacity is strengthened in proportion to the amount mixed in. It is effective for quality control if the amount of mist mixed in and the air volume are variable depending on the type of steel, wire diameter, load conditions, etc.

[0026] Figure 2 shows the main features of the ring stacker. The ring stacker consists of a ventilated annular stacking plate 21, an outer ring 22, an inner ring 23, and a rotating roller table 24 with a rotation axis in the radial direction. The stacker 20 itself does not rotate; only the eccentric stacking ring row 10 on the table rotates. The lower end of the ring row is no longer in fixed contact with the steel structure of the stacker, preventing localized overcooling. In the Stelmor process, the same effect can be achieved as if all the original chain conveyors had been converted to roller conveyors.

[0027] Figure 3 shows the shape of an eccentrically integrated ring array. The figure shows 16 rings, and although the inner and outer peripheries are somewhat densely distributed, the middle portion forms a nearly uniform gap, allowing wind blasts to easily penetrate. Figure 4 shows the shape of the coil (mass approximately 2t) formed by eccentric accumulation. Geometrically, the inner and outer diameters of the coil are the ring diameter ±2 × eccentricity, and the ring pitch is the phase angle × coil diameter / 2. The actual shape is a thick cylinder with a constant inner and outer diameter. The height is 1.0 to 1.6 m. It can be seen that the air blast passes through more evenly. There is concern that the cooling effect will decrease if the cooled material forms a wall on the inner and outer circumferential surfaces, but by setting the gap between the wind tunnel wall appropriately, the air blast cooling can be strengthened and restored.

[0028] FIG. 5 shows a comparison of the coil formation between the conventional method (a) and the present invention (b). In the conventional method (a), when the cooled and hardened horizontal ring array is simply dropped into a concentrator to be coiled, unevenness occurs on the inner and outer surfaces as shown in the figure, the rings are closely packed, and the wall thickness is small. In the present invention (b), the individual rings are eccentrically assembled to form a thick coil with a nearly constant inner and outer diameter, as shown in the figure.

[0029] Explain the relationship between wind speed and cooling rate. Patent Document 5 discloses the relationship between the wind speed and the heat transfer coefficient in air blast cooling of hot-rolled steel bars. The present invention utilizes the disclosed analytical method. Figure 6 shows the recalculated results for the wire for convective heat transfer. Figure 7 shows the overall heat transfer coefficient (kcal / m) including the radiation term, which is more practical. 2 h℃). In the existing Stelmor process, the maximum wind speed is about 10 m / s, and the overall heat transfer coefficient is about 150, which is clearly inferior to boiling cooling (about 200-250). In the present invention, the radiation is reduced to some extent by the density, and the actual result is somewhere between the two (Figures 5 and 6). The above values ​​are useful as references, but the exact wind speed required will be optimized through actual implementation.

[0030] In the Stelmor process, where the conveyor length exceeds 50 m, applying a wind blast along the entire length is wasteful in terms of equipment and energy. A wind speed of 20 or more is extremely difficult. However, the present invention makes it possible to apply a powerful wind blast using a single small wind tunnel. In this invention, in order to obtain cooling power equivalent to or greater than that of boiling cooling, the wind speed should be set to 30 m / s or more. Mixing in mist is also effective. In either case, the key to this process is to design a powerful wind tunnel. The addition of an auxiliary fan is also envisioned. Once the heat transfer coefficient is known, the cooling rate can be calculated using the following formula: dθ / dt=4α·(θ-θr) / cρD ---(1) θ;Temperature t;Time α;Heat transfer coefficient θr;Refrigerant temperature c;Specific heat ρ;Density D;Wire diameter

[0031] FIG. 8 is not necessarily the best when the present invention is applied to an existing wire rod rolling mill, but it does not require the installation of a new winder as described above. Many existing factories use horizontal laying winders. Wire rod 72 that has passed through a final rolling mill 71 is pulled by pinch rolls 73 and formed into a spiral ring by a horizontal laying winder 74. The spiral ring that emerges from the winder lands on a horizontal conveyor 75 and continues on as a horizontal row of rings 76. In the conventional method (a), the wire is cooled by air blowing while traveling and heads to a concentrator (not shown), where it falls and becomes a coil.

[0032] In the present invention, a collection table is placed immediately after the entrance of the horizontal conveyor, and the horizontal ring row 76 is dropped onto an annular collection table 79 as a vertical ring row 77 to form a coil 78. The annular collection table 79 is installed in an annular wind tunnel consisting of an outer cylinder 80 and an inner cylinder 81, and is rotated and raised and lowered at a predetermined speed by a coil rotation and elevation mechanism 82. A suction duct 83 is connected to the bottom of the wind tunnel, and a powerful suction is applied by an axial fan 84 installed inside the duct, performing the cooling process described above. Although the accuracy of the coil shape is somewhat reduced, this method is practical.

[0033] In both the methods shown in Figures 1 and 8, after the rear end of the rolled material is unwound, the front end of the next rolled material approaches a few seconds later. The previous coil is still cooling. To avoid a loss of efficiency, the wind tunnel must immediately be quickly replaced with a second wind tunnel. The second wind tunnel has its accumulation table rotated in advance and is waiting at a specified speed. [Example]

[0034] Specific examples of suitable implementation of the method of the present invention are summarized in Table 1. Particularly problematic is the 5.5 mm diameter, where the rolling speed is at its maximum. It is clear that the basic design and implementation would not be particularly difficult for a person skilled in the art.

[0035] [Table 1] [Industrial Applicability]

[0036] The present invention can be easily implemented in new and existing rolling mills by retrofitting. [Explanation of symbols]

[0037] 1; Final rolling mill 2; Red-hot wire rod 3; Pinch roll 4; Winder 5; Spiral-type helical guide tube 6; Spiral ring 7; Vertical outer cylinder 8; Vertical inner cylinder 9; Accumulation table 10; Coil 12; Swivel mechanism 13; Rotation drive source 14; Spindle 15; Lifting mechanism 16; Hydraulic cylinder 17; Duct 18; Axial fan 19; Hot air 20; Mist spray W; Wind tunnel X; Winder central axis Y; Accumulation table rotation axis 21; Annular accumulation plate 22; Outer ring 23; Inner ring 24; Swivel roller table 71; Final rolling mill 72; Red-hot wire rod 73; Pinch roll 74; Horizontal laying type winder 75; Horizontal conveyor 76; Horizontal ring row 77; Vertical ring row 78; Coil 79; Annular accumulation table 80; Outer cylinder 81; Inner cylinder 82; Swivel lifting mechanism 83; Suction duct 84; Axial flow fan

Claims

1. 1. A method for concurrently subjecting red-hot steel wire rod immediately after hot rolling to controlled cooling and coil formation, the method comprising: forming a falling vertical spiral ring from a traveling wire rod by a vertical laying winder directly or via a horizontal laying winder and a horizontal conveyor; eccentrically accumulating the vertical spiral ring at a constant phase angle and a constant falling speed on a ventilated annular accumulation table that receives and rotates the vertical spiral ring and is provided in an annular wind tunnel having a vertical axis eccentric from the central axis of the vertical spiral ring; forming a coil having predetermined inner and outer diameters and regular gaps; and applying air blast cooling to the coil through a suction duct connected to the lower end of the annular wind tunnel.

2. 1) The turning is performed by a turning roller table having a rotation axis in the radial direction provided on the annular accumulation table; 2) The turning direction is opposite to the winding direction, 3) The wind speed of the wind blast is 20 m / s or more, and if necessary, the mist spray is carried along with the wind blast; 4) A method for simultaneously processing coil formation and controlled cooling of steel wire rod as described in claim 1, characterized in that two annular wind tunnels containing annular accumulation tables are provided to enable rapid switching.

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