Method of controlling the bend of a threaded steel bar

Abstract

The embodiment of the application provides a method for controlling the bending degree of screw thread steel, comprising the following steps in sequence: smelting, smelting raw materials to obtain molten steel; continuous casting, pouring the molten steel into a continuous casting machine to obtain a continuous casting billet; heating, transferring the continuous casting billet to a heating furnace for heating to obtain a rolling piece; rolling, rolling the rolling piece to obtain screw thread steel; cooling, cooling the screw thread steel by using a water penetrating box; and shearing, shearing the cooled screw thread steel by using a double-length shearing machine. In the application, the temperature difference between the upper surface and the lower surface of the rolling piece is controlled to be within 10 DEG C, so that the uniformity of the temperature distribution from the upper surface to the lower surface of the rolling piece is ensured, and the possibility of screw thread steel bending is reduced; a back-blowing air pipe is arranged in the water penetrating box, water on the surface of the screw thread steel can be blown dry, water drops are prevented from being concentrated on the lower surface of the screw thread steel, and the temperature difference between the upper surface and the lower surface of the screw thread steel is effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of threaded steel processing technology, and more specifically, to a method for controlling the curvature of threaded steel. Background Technology

[0002] During the processing of rebar, due to unreasonable process parameter settings or fluctuations in process and equipment stability, the finished rebar is prone to bends after being placed on the cooling bed. Bends in rebar can easily cause a series of problems such as disordered steel on the cooling bed, steel fork in the roller conveyor before shearing, and overlapping bends in fixed-length shearing, which seriously affect production quality and efficiency, and can also easily cause safety hazards.

[0003] Therefore, this application is hereby submitted. Summary of the Invention

[0004] The present invention includes, for example, providing a method for controlling the curvature of threaded steel bars, which can control the curvature of threaded steel bars and reduce the occurrence of bends.

[0005] The embodiments of the present invention can be implemented as follows:

[0006] In a first aspect, the present invention provides a method for controlling the curvature of threaded steel bars, comprising the following steps performed sequentially:

[0007] Smelting is the process of refining raw materials to obtain molten steel.

[0008] Continuous casting involves pouring the molten steel into a continuous casting machine to obtain a continuously cast billet.

[0009] Heating involves transferring the continuously cast billet to a heating furnace for heating to obtain a rolled piece, wherein the temperature difference between the upper and lower surfaces of the rolled piece is less than 10°C.

[0010] Rolling is the process of rolling a workpiece to obtain rebar.

[0011] Cooling is achieved by using a water tank to cool the rebar. The water tank is provided with a forward air seal, a first water cooler, a first reverse water seal, a second water cooler, a second reverse water seal, a third water cooler, a third reverse water seal, a first reverse air seal, and a second reverse air seal in sequence along the direction from steel inlet to steel outlet.

[0012] Shearing: Using long-length shears to cut cooled rebar;

[0013] The water tank between the third reverse water seal and the first reverse air seal is provided with an air inlet and an air outlet, and the air inlet is connected to a backflush air pipe facing the lower surface of the rebar.

[0014] An air inlet and an air outlet are provided in the water tank between the first and second reverse air seals, and a backflush air pipe is connected to the air inlet facing the lower surface of the threaded steel.

[0015] In an optional embodiment, the continuous casting billet outlet of the continuous casting machine and the continuous casting billet inlet of the heating furnace are connected by a conveying device, and the conveying device is equipped with a heat insulation cover.

[0016] In an optional embodiment, a feeding platform is provided outside the continuous casting billet inlet of the heating furnace, and a heat insulation cover is provided on the feeding platform.

[0017] In an optional embodiment, the method further includes transferring the continuously cast billet leaving the continuous casting machine to a feeding platform or a heating furnace via a conveying trolley equipped with a heat insulation cover.

[0018] In an optional embodiment, the first, second, and third water coolers are each provided with a cooling water inlet and a cooling water outlet, and the cooling water inlet is connected to an annular slit nozzle with an adjustable annular slit size.

[0019] In an optional embodiment, when shearing rebar, the cutting edge of the double-length shear moves in the same direction as the rebar, and the ratio of the linear velocity of the cutting edge of the double-length shear to the linear velocity of the rebar is 1.10-1.15.

[0020] In an optional implementation, when the tail of the sheared rebar does not bend at the end, but the tails of the remaining sections are somewhat bent, the lead rate of the multiple-length shear is reduced.

[0021] When the head of the first section of the sheared rebar is not bent, but the heads of the remaining sections are bent, the advance rate of the multiple-length shearing should be increased.

[0022] In an optional embodiment, the rolling step adopts three-line split rolling, and the rolled piece passes through a pre-finishing rolling equipment, which includes four 450 rolling mills and two 350 rolling mills arranged sequentially, numbered 11#, 12#, 13#, 14#, 15#, and 16# respectively; wherein, rolling mill 12# is a vertical rolling mill, and the other five are horizontal rolling mills; rolling mill 11# adopts a hole-less rolling, rolling mill 12# has a box-shaped hole, rolling mill 13# has a pre-splitting hole, rolling mill 14# has a split hole, rolling mill 15# has an elliptical hole, and rolling mill 16# has a finished round hole; the width of the rolled piece entering rolling mill 11# is 6-8mm larger than the height of the rolled piece entering rolling mill 12#, and the height of the rolled piece entering rolling mill 11# is adapted to the bottom width of the slot of the split hole of rolling mill 12#.

[0023] In an optional embodiment, after the rolled piece passes through the No. 12 rolling mill, the width of the black strip at the edge of the rolled piece accounts for 70%-80% of the width of the rolled piece.

[0024] Preferably, the area of ​​the middle hole of the No. 13 rolling mill cutting hole is 3% to 5% smaller than the area of ​​the two side holes;

[0025] Preferably, the feed side of the No. 13 rolling mill is provided with a double-row wheel guide, and the distance between the two vertical wheels of the guide should be 0.15-0.25mm greater than the height of the rolled piece after passing through the No. 12 rolling mill;

[0026] Preferably, the width of the cutting hole of the No. 13 rolling mill is 90 mm, and the width of the cutting hole of the No. 14 rolling mill is 94.46 mm.

[0027] In an optional implementation, for two adjacent mills in the roughing mill and intermediate mill, when the latter mill bites the steel, the rolling current or torque of the former mill is 2%-3% smaller than that of the latter mill.

[0028] The beneficial effects of the embodiments of the present invention include, for example:

[0029] The temperature difference between the upper and lower surfaces of the rolled steel is controlled within 10℃ to ensure the uniformity of temperature distribution from the upper to the lower surface of the rolled steel and reduce the possibility of bending of the rebar.

[0030] The water tank is equipped with a back-blowing air pipe, which can blow dry the water on the surface of the rebar, prevent water droplets from accumulating on the lower surface of the rebar, and effectively control the temperature difference between the upper and lower surfaces of the rebar. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the cutting holes for rolling mills #12 to #17. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0034] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0035] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0036] In the description of this invention, it should be noted that if terms such as "upper," "lower," "inner," or "outer" are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed, they are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0037] Furthermore, the terms "first" and "second" are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0038] It should be noted that, where there is no conflict, the features in the embodiments of the present invention can be combined with each other.

[0039] This invention provides a method for controlling the bending degree of rebar, comprising the following steps performed sequentially:

[0040] Smelting is the process of refining raw materials to obtain molten steel.

[0041] Continuous casting involves pouring the molten steel into a continuous casting machine to obtain a continuously cast billet.

[0042] Heating involves transferring the continuously cast billet to a heating furnace for heating to obtain a rolled piece, wherein the temperature difference between the upper and lower surfaces of the rolled piece is less than 10°C.

[0043] Rolling is the process of rolling a workpiece to obtain rebar.

[0044] Cooling is achieved by using a water tank to cool the rebar. The water tank is provided with a forward air seal, a first water cooler, a first reverse water seal, a second water cooler, a second reverse water seal, a third water cooler, a third reverse water seal, a first reverse air seal, and a second reverse air seal in sequence along the direction from steel inlet to steel outlet.

[0045] Shearing: Using long-length shears to cut cooled rebar;

[0046] The water tank between the third reverse water seal and the first reverse air seal is provided with an air inlet and an air outlet, and the air inlet is connected to a backflush air pipe facing the lower surface of the rebar.

[0047] An air inlet and an air outlet are provided in the water tank between the first and second reverse air seals, and a backflush air pipe is connected to the air inlet facing the lower surface of the threaded steel.

[0048] The billet is heated in the furnace to increase its temperature, which aims to reduce the billet's deformation resistance, increase its plasticity, and facilitate large reduction deformation during rough rolling. An improper furnace heating regime can cause temperature differences between the upper and lower surfaces, head and tail temperatures, or uneven temperature distribution on both sides of the billet when hot billets and cold billets are alternately fed into the furnace. This can lead to bending of the rolled piece after shearing at multiple lengths. Therefore, the temperature difference between the upper and lower surfaces of the rolled piece exiting the furnace must be controlled within 10℃ to ensure uniform temperature distribution from the upper to the lower surface of the rolled piece.

[0049] After passing through three water coolers, the rebar is equipped with a reverse water seal and two reverse air seals. Reverse blowing is performed between the third reverse water seal and the first reverse air seal, and / or between the first and second reverse air seals, to remove cooling water adhering to the surface of the rebar. If the water on the surface of the rebar cannot be removed, after exiting the water tank, due to the presence of transverse ribs, the lower surface of the rolled piece will have water under gravity, while the upper surface will be dry. This results in a lower temperature on the lower surface compared to the upper surface, increasing the temperature difference and generating stress. During shearing with a long-length shear, the tail of the steel will bend towards the lower temperature direction. Reverse blowing effectively prevents bending of the rebar caused by uneven temperature between the upper and lower surfaces. Specifically, a valve can be installed on the reverse blowing pipe to adjust the air flow rate, ensuring sufficient pressure to thoroughly remove water from the surface of the rolled piece. Additionally, the temperature of the reverse blowing air should also be set as needed.

[0050] In other alternative embodiments of this application, the continuous casting billet outlet of the continuous casting machine and the continuous casting billet inlet of the heating furnace are connected by a conveying device, and the conveying device is equipped with a heat insulation cover.

[0051] In other optional embodiments of this application, a feeding platform is provided outside the continuous casting billet inlet of the heating furnace, and a heat insulation cover is provided on the feeding platform.

[0052] In other alternative embodiments of this application, the continuously cast billet leaving the continuous casting machine is transferred to a material conveying trolley in a loading platform or heating furnace, the material conveying trolley being equipped with a heat insulation cover.

[0053] The uneven temperature caused by alternating hot and cold billets entering the furnace is difficult to compensate for through heating regime adjustments. Therefore, this problem can be improved through the following three measures: 1. Add a heat insulation cover between the heating furnace and the continuous casting machine. This reduces heat dissipation from the continuously cast billets and decreases the temperature difference between the billets and the conveying device, thus improving the temperature uniformity of the billets. 2. Install a loading platform. One or more loading platforms can be installed according to process needs. The loading platform can store hot billets during slow rolling cycles and process downtime. The heat insulation cover also reduces heat dissipation. 3. Install flatbed carts and add heat insulation devices to the flatbed carts, reducing the temperature drop of the continuously cast billets from leaving the continuous casting machine to entering the furnace by more than 100°C. Through these modifications, the hot charging rate of the production line can be increased from 60% to 90%, solving the problem of low billet temperature entering the furnace during smooth production and reducing the number of cold billets entering the furnace.

[0054] In other optional embodiments of this application, the first water cooler, the second water cooler and the third water cooler are each provided with a cooling water inlet and a cooling water outlet, and the cooling water inlet is connected to an annular slit nozzle with an adjustable annular slit size.

[0055] When the nozzle circumferential gap of the water cooler is small, it is easy to reach the upper limit of the cooling capacity. When producing large-diameter rebar, the recovery temperature of the steel is too high, resulting in excessively low mechanical properties. A low water flow rate will cause insufficient water pressure inside the cooler, leading to uneven cooling of the rolled piece and the phenomenon of uneven cooling on both sides. The rolled piece will also bend under shear force at the multiple-length shearing point. When the circumferential gap is large, the high water flow rate can easily form a closed-loop tempered martensite structure, which does not meet national standards. This application uses nozzles with adjustable circumferential gap sizes to facilitate adjustment of the circumferential gap size according to process conditions. During adjustment, the circumferential gap of the cooler nozzle should be properly adjusted to ensure equal water flow around the circumferential gap.

[0056] The QTB (Quenehing Tempering Bars) process typically uses turbid circulating water cooling, which is prone to blockage of the annular cooling water inlet by contaminants. This results in incomplete cooling water filling of the cooling water pipes, causing uneven cooling of the upper and lower surfaces as the steel passes through the nozzles, and potentially leading to bending of the steel on the upper cooling bed. Therefore, it is essential to thoroughly clean the quenching bar during maintenance to ensure a clean environment and guarantee the stability of the quenching process.

[0057] In other optional embodiments of this application, when shearing threaded steel, the cutting edge of the double-length shear moves in the same direction as the threaded steel, and the ratio of the linear velocity of the cutting edge of the double-length shear to the linear velocity of the threaded steel is 1.10-1.15.

[0058] In other optional embodiments of this application, when the tail of the sheared rebar does not bend but the tails of the remaining sections are somewhat bent, the lead rate of the multiple-length shear is reduced.

[0059] When the head of the first section of the sheared rebar is not bent, but the heads of the remaining sections are bent, the advance rate of the multiple-length shearing should be increased.

[0060] The multiple-length shear is a segmenting shear used before the workpiece enters the cooling bed. Its blade speed setting is related to the speed of the workpiece exiting the last stand of the mill. The linear speed of the multiple-length shear is slightly greater than the speed of the workpiece exiting the mill, meaning there is a certain lead ratio. The typical setting is between 1.10 and 1.15, and this setting is closely related to the mill speed. When the mill speed increases or decreases significantly, the lead ratio of the multiple-length shear needs to be slightly adjusted. If the lead ratio of the multiple-length shear is set too high, meaning the shear linear speed is much greater than the final mill exit speed of the workpiece, the tail of the first segment of the workpiece is easily bent by the rotating shear blade, causing bending at the tail of the workpiece. If the lead ratio of the multiple-length shear is set too low, the head of the second segment of the workpiece will collide with the shear blade, resulting in bending at the head of the workpiece, and in severe cases, causing disorder on the skirt roller table.

[0061] In other optional embodiments of this application, the rolling step adopts three-line split rolling, and the rolled piece passes through a pre-finishing rolling equipment. The pre-finishing rolling equipment includes four 450 mill stands and two 350 mill stands arranged sequentially, numbered 11#, 12#, 13#, 14#, 15#, and 16# respectively; wherein, mill 12# is a vertical mill, and the other five are horizontal mills; mill 11# uses a no-hole rolling, mill 12# has a box-shaped hole, mill 13# has a pre-splitting hole, mill 14# has a split hole, mill 15# has an elliptical hole, and mill 16# has a finished round hole; the width of the rolled piece entering mill 11# is 6-8 mm larger than the height of the rolled piece entering mill 12#, and the height of the rolled piece entering mill 11# is adapted to the bottom width of the slot of the split hole of mill 12#. Figure 1 As shown.

[0062] Stable line difference is the core of slitting rolling technology. When the line difference is stable, the exit speed of the rolled pieces on each line is consistent, and production proceeds smoothly. When the line difference is unstable, that is, the exit speed of the rolled pieces on each line is inconsistent, when the rolled pieces reach the multiple-length shearing stage, the rolled pieces with a longer line difference will have a faster speed, which may cause the head of the rolled piece to bend due to impact with the shear blade; the rolled pieces with a shorter line difference will have a slower speed, which may cause the tail of the rolled piece to bend due to impact with the shear blade. Therefore, it is necessary to adjust the position of the pre-slitting guide and the size of the material before pre-slitting according to the length of the line difference to ensure that the line differences are aligned.

[0063] The No. 11 rolling mill is selected without a perforation. Compared with the perforated roll, the flat roll is characterized by its unrestricted width, mainly free width, with drum-shaped width on both sides, and relatively small elongation and section reduction rate.

[0064] To accommodate the correction allowance for the box-shaped pass of the 12# mill in the next pass, the material width of the 11# mill should be 6-8mm greater than the material height of the 12# mill. If the material width is too small, the rolled piece will not fill the pass completely when slit in the 13# mill, resulting in a line difference where the middle is longer than the sides. If the material width is too large, the head is prone to lateral bending, and may even cause steel piling at the exit. The material height of the 11# mill should be consistent with the bottom width of the box-shaped pass of the 12# mill. If the material height is too small, the rolled piece will be rolled diagonally within the box-shaped pass, affecting the service life of the 12# mill inlet.

[0065] In other optional embodiments of this application, after the rolled piece passes through the No. 12 rolling mill, the width of the black strip at the edge of the rolled piece accounts for 70%-80% of the width of the rolled piece; the No. 12 rolling mill's cutting hole is a vertical box-shaped hole with a certain sidewall slope, the purpose of which is to smooth and even out the drum-shaped widening produced in the K8 pass, providing good conditions for the pre-cutting of the next pass. In actual production, the reduction of the No. 12 rolling mill needs to be strictly controlled. If the reduction is too small, it will not play a corrective role; if the reduction is too large, it will easily cause double drum deformation on both sides, resulting in irregular material shape and affecting the stability of rolling.

[0066] In actual production, because the rolls are cooled by cooling water, the temperature of the rolls is much lower than that of the workpiece. The part of the workpiece that deforms when it comes into contact with the rolls will undergo heat conduction, and a "black band" will appear on the edge of the workpiece that is different from the undeformed area. When viewed from the same horizontal line, it is ideal for the width of this black band to be 70%-80%.

[0067] Preferably, the area of ​​the middle hole of the No. 13 mill cutting pass is 3% to 5% smaller than the area of ​​the two side holes. The pre-cutting pass is a crucial factor in determining the metal flow rate in each pass and is also the most direct factor affecting the line difference. When designing the pre-cutting pass, if the areas of the three holes are designed to be the same size, the line difference is difficult to adjust; if the area of ​​the side holes is designed to be too large, the line difference on both sides will be too long and cannot be adjusted. Therefore, the area of ​​the middle hole is 3% to 5% smaller than the area of ​​the two side holes. The degree of filling of the rolled piece in the pass is fully considered. When the rolled piece does not fully fill the pass, the sidewalls of the pass do not provide support, resulting in fluctuations in the dimensions of the two sides of the rolled piece after cutting, causing random changes in the dimensions of the two finished products, making it difficult to control the "three-line difference". Excessive reduction will accelerate pass wear; insufficient reduction will increase the load on the subsequent mill.

[0068] Preferably, the feed side of the No. 13 rolling mill is equipped with a double-row wheel guide. The distance between the two vertical wheels of the guide should be 0.15-0.25 mm greater than the height of the rolled piece after passing through the No. 12 rolling mill. The No. 13 rolling mill inlet uses a double-row wheel guide. In actual control, the distance between the vertical wheels should be approximately 0.2 mm greater than the material height of the No. 12 rolling mill, allowing for slight movement of the rolled piece inside the No. 13 rolling mill inlet. If the distance is too large, the vertical wheels of the No. 12 rolling mill inlet guide will not be able to guide the rolled piece into the center of the pass, and the rolled piece is prone to deviation or twisting, making it difficult to control. If the distance is too small, the vertical wheels of the No. 12 rolling mill inlet guide will be subjected to excessive force, shortening the service life of the inlet guide.

[0069] Preferably, for rolling No. 18 rebar, the width of the cutting hole of the No. 13 rolling mill is 90mm, and the width of the cutting hole of the No. 14 rolling mill is 94.46mm.

[0070] This application includes a comparative example. Based on the aforementioned embodiments, the width of the cutting hole of the No. 13 rolling mill is 91.6 mm, and the width of the cutting hole of the No. 14 rolling mill is 96.01 mm.

[0071] The size of the mill's slitting hole has a significant impact on the line deviation. If the slitting hole is too large, the line deviation in the comparison will be longer in the middle and shorter at the sides. To ensure the line deviation is even, operators will excessively reduce the size of the pre-slitting pass material, increasing the amount of metal flowing to the sides within the middle hole. This leads to excessive wear of the slitting wedge, and the line deviation will again exhibit the situation of being longer in the middle and shorter at the sides. Operators will then continue to reduce the size of the pre-slitting hole material, creating a vicious cycle that results in the hole's inefficiency. In addition, an excessively large pre-slitting hole material will also make it difficult for subsequent passes to process, resulting in a heavier finished product, difficulty in controlling negative deviation, and increased production costs per ton of steel. The aforementioned embodiment, by resetting the slitting hole, effectively improves the problems of inefficiency in the hole and high negative deviation. In other embodiments of this application, before passing through the pre-finishing rolling mill, the rolled piece passes through the roughing rolling mill and the intermediate rolling mill in sequence. The roughing rolling mill includes six 650 mill stands arranged in sequence, numbered 1#, 2#, 3#, 4#, 5#, and 6# respectively; the intermediate rolling mill includes four 550 mill stands arranged in sequence, numbered 7#, 8#, 9#, and 10# respectively.

[0072] In other alternative embodiments of this application, for two adjacent mills in the roughing mill and intermediate mill, when the latter mill bites the steel, the rolling current or torque of the former mill is 2%-3% smaller than that of the latter mill.

[0073] In actual control, when tension adjustment is poor, the line difference will manifest as a large line difference in the first few sections of multiple lengths, followed by a uniform line difference in the last section. In this case, adjustments need to be made using stands with unequal flow rates per second on the rolling line. For roughing and intermediate rolling, the optimal tension can be judged based on the rolling current; ideally, the current (torque) of the current stand should be 2%-3% lower after the next stand bites the steel. For pre-finishing and finishing rolling, the tension can be judged based on the condition of the workpiece within the looper. A good tension is indicated when there is a symmetrical curvature between the starting and pressing rollers. If the workpiece changes from a certain curvature to a straight line after the looper starts rolling, it indicates that the looper setting height is too low and there is steel pulling; the looper setting height needs to be increased. If the workpiece is straight during starting rolling, it indicates that the speed of the preceding mill is too low; the speed of the preceding mill needs to be increased. When the second stand before the looper throws the steel, if the workpiece does not vibrate, the tension is good; if the workpiece vibrates, the tension is too high; the speed of the preceding stand or the looper height needs to be increased. When the cross-sectional area of ​​the rolled piece is small and there is no looper, a steel bar can be used to move the rolled piece. When the rolled piece can be moved easily, the tension is good. When it is difficult to move the rolled piece, it indicates that there is a large tension between the front and rear mills, and the speed of the front stand needs to be increased.

[0074] The distance between the shearing channel and the shearing post-cutting channel is also crucial. During the shearing process, the upper shear blade applies a downward force to the front part of the rolled piece. If the distance between them is too great, the tail of the rolled piece will impact the edge of the bottom plate of the shearing channel, causing impact bending. This is characterized by a large degree of bending and scratches at the bend. If impact marks are found at the bend of bent steel, check whether the improper positioning of the shearing channel and the post-cutting channel is the cause and adjust accordingly.

[0075] From March to April, the factory's production line experienced 212 minutes of downtime due to bending and forking of steel. From May to June, after using the method described in this application to control the bending of rebar, downtime due to bending and forking was reduced to 55 minutes, resulting in an average monthly saving of 78 minutes. Taking a machine-hour output of 200 tons as an example, this translates to an average monthly increase of 240 tons. The degree and frequency of bending at the cooling bed were significantly reduced, and the bending situation on the cooling bed was noticeably improved, saving unnecessary downtime for production. In addition, the steel can be aligned at the alignment rollers, eliminating the need for workers to adjust the bent steel back to its original position, thus reducing the labor intensity of employees. The cut length was reduced from 400mm to below 100mm, increasing the yield rate by 0.3%.

[0076] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for controlling the curvature of threaded steel bars, characterized in that, This includes the following steps performed sequentially: Smelting is the process of refining raw materials to obtain molten steel. Continuous casting involves pouring the molten steel into a continuous casting machine to obtain a continuously cast billet. Heating involves transferring the continuously cast billet to a heating furnace for heating to obtain a rolled piece, wherein the temperature difference between the upper and lower surfaces of the rolled piece is less than 10°C. Rolling is the process of rolling a workpiece to obtain rebar. Cooling is achieved by using a water tank to cool the rebar. The water tank is provided with a forward air seal, a first water cooler, a first reverse water seal, a second water cooler, a second reverse water seal, a third water cooler, a third reverse water seal, a first reverse air seal, and a second reverse air seal in sequence along the direction from steel inlet to steel outlet. Shearing: Using long-length shears to cut cooled rebar; The water tank between the third reverse water seal and the first reverse air seal is provided with an air inlet and an air outlet, and the air inlet is connected to a backflush air pipe facing the lower surface of the rebar. An air inlet and an air outlet are provided in the water tank between the first and second reverse air seals. A backflush air pipe is connected to the air inlet and faces the lower surface of the threaded steel. The continuous casting billet outlet of the continuous casting machine and the continuous casting billet inlet of the heating furnace are connected by a conveying device, and the conveying device is equipped with a heat insulation cover. A feeding platform is provided on the outside of the continuous casting billet inlet of the heating furnace, and a heat insulation cover is provided on the feeding platform. It also includes a conveying trolley that transfers the continuously cast billet leaving the continuous casting machine to a feeding platform or heating furnace, the conveying trolley being equipped with a heat insulation cover; The first, second, and third water coolers are each equipped with a cooling water inlet and a cooling water outlet. The cooling water inlet is connected to an annular nozzle with an adjustable annular slit size.

2. The method for controlling the curvature of threaded steel bars according to claim 1, characterized in that, When shearing threaded steel, the cutting edge of the multiple-length shear moves in the same direction as the threaded steel, and the ratio of the linear velocity of the cutting edge of the multiple-length shear to the linear velocity of the threaded steel is 1.10-1.

15.

3. The method for controlling the curvature of threaded steel bars according to claim 2, characterized in that, When the tail section of the sheared rebar does not bend, but the tail sections of the remaining sections are somewhat bent, reduce the lead rate of the multiple-length shearing. When the head of the first section of the sheared rebar is not bent, but the heads of the remaining sections are bent, the advance rate of the multiple-length shearing should be increased.

4. The method for controlling the curvature of threaded steel bars according to claim 1, characterized in that, The rolling process employs a three-line split rolling method. The rolled piece passes through a pre-finishing rolling mill, which includes four 450mm mill stands and two 350mm mill stands arranged sequentially, numbered 11#, 12#, 13#, 14#, 15#, and 16# respectively. Among them, mill 12# is a vertical mill, and the other five are horizontal mills. Mill 11# uses a hole-free rolling method, mill 12# uses a box-shaped hole, mill 13# uses a pre-splitting hole, mill 14# uses a split hole, mill 15# uses an elliptical hole, and mill 16# uses a finished round hole. The width of the rolled piece entering mill 11# is 6-8mm greater than the height of the rolled piece entering mill 12#, and the height of the rolled piece entering mill 11# is adapted to the bottom width of the split hole of mill 12#.

5. The method for controlling the curvature of threaded steel bars according to claim 4, characterized in that, After passing through the No. 12 rolling mill, the width of the black strip on the edge of the rolled piece accounts for 70%-80% of the width of the rolled piece.

6. The method for controlling the curvature of threaded steel bars according to claim 4, characterized in that, The area of ​​the middle hole of the No. 13 rolling mill cutting hole is 3% to 5% smaller than the area of ​​the two side holes.

7. The method for controlling the curvature of threaded steel bars according to claim 4, characterized in that, The feed side of the No. 13 rolling mill is equipped with a double-row wheel guide. The distance between the two vertical wheels of the guide should be 0.15-0.25mm greater than the height of the rolled piece after passing through the No. 12 rolling mill.

8. The method for controlling the curvature of threaded steel bars according to claim 4, characterized in that, The width of the cutting hole of the No. 13 rolling mill is 90mm, and the width of the cutting hole of the No. 14 rolling mill is 94.46mm.

9. The method for controlling the curvature of threaded steel bars according to claim 5, characterized in that, For two adjacent mills in roughing and intermediate rolling mills, when the latter mill bites the steel, the rolling current or torque of the former mill is 2%-3% smaller than that of the latter mill.

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