A control method for preventing hole wall thinning of high-line deformed steel bar finished product

Abstract

The application discloses a control method for preventing hole meat loss of high-line screw thread steel finished products, and belongs to the technical field of metallurgy. The control method for preventing hole meat loss of high-line screw thread steel finished products provided by the application mainly comprises the following steps: the temperature of a control roller ring is controlled below 50 DEG C by using cooling water; the temperature of a rolled piece head entering a reducing mill train is ensured to be 820-850 DEG C by controlling water operation of the rolled piece; the pre-precision rolling and 8-rack incoming materials are controlled within the lower limit of a process requirement size; and a 76-degree milling cutter tip angle is used to process a thread roller ring. By the above method, the hole meat loss phenomenon of the high-line screw thread steel finished products can be greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and more specifically, to a control method for preventing the loss of wire rod from the finished product holes of high-strength wire rod. Background Technology

[0002] The Shaogang high-speed wire rod production line was completed and put into operation at the end of 2004. Its main product specifications are: medium 5.5-16mm smooth coils and medium 6-16mm threaded coils. The guaranteed speed is 80m / s, with a maximum speed of 102m / s. The reduction sizing mill uses cemented carbide rollers made of WC75. Frequent material loss from the finished threaded steel holes severely restricts normal and stable production and affects product quality. Therefore, it is necessary to provide a control method to prevent material loss from the finished threaded steel holes.

[0003] Therefore, this invention is proposed. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects of the prior art and provide a control method for preventing the loss of wire rod from the finished product hole of high-strength threaded steel.

[0005] The technical problem solved by this invention is achieved by the following technical solution.

[0006] This invention provides a method for controlling the loss of filler material from the finished wire rod rebar. The rebar production line includes, sequentially arranged along the rolling direction, roughing mills 1#-6#, flying shear 1#, intermediate mills 7#-12#, flying shear 2#, pre-finishing mills 13#-18#, water tank 1#, water tank 2#, flying shear 3#, finishing mills 19#-26#, water tank 3#, water tank 4#, and reducing mills 27#-30# and water tank 5#. The control method for preventing filler loss from the finished wire rod rebar mainly includes: using cooling water to control the surface temperature of the rolls below 50°C; controlling the water-passing operation of the rolled piece to ensure that the temperature of the rolled piece head entering the reducing mill is 820-850°C; and controlling the out-of-roundness and tolerance diameter of the rolled piece entering the pre-finishing mill and finishing mill to be within the lower limit of the process requirements.

[0007] The present invention has the following beneficial effects:

[0008] This invention provides a method for controlling material loss from the finished product holes of high-strength wire rod rebar. The method mainly includes: using cooling water to control the surface temperature of the rolls below 50°C; controlling the water-passing operation of the rolled piece to ensure the temperature of the head of the rolled piece entering the reducing and sizing mill is 820-850°C; and controlling the out-of-roundness and tolerance diameter of the rolled piece entering the pre-finishing and finishing mills to be within the lower limit of the process requirements. These measures reduce the phenomenon of material loss from the finished product holes of high-strength wire rod rebar. Attached Figure Description

[0009] 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.

[0010] Figure 1 This is a schematic diagram showing the coverage area and spray angle of the water pipe. Detailed Implementation

[0011] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0012] The following is a detailed description of a control method for preventing the loss of wire rod from the finished product hole of high-strength threaded steel, provided by an embodiment of the present invention.

[0013] Due to the high hardness and impact force of rolled steel, the crescent and lettering on the thread roll are constantly impacted, making it difficult to demold during rolling. This causes pieces to easily chip off from the lettering and crescent areas of the finished threaded steel roll. To reduce chipping from the finished threaded steel roll, this invention provides a method for preventing chipping from the finished threaded steel roll, which mainly includes the following methods:

[0014] 1. Roller ring cooling requirements:

[0015] Cooling is essential for reducing the effects of hot corrosion, thermal fatigue, and thermal stress on the roll ring during rolling, preventing roll ring breakage and material loss, slowing crack propagation, and extending groove life. It is crucial for maximizing the effectiveness of cemented carbide roll rings, as detailed below:

[0016] (1) The temperature of the cooling water is below 35℃.

[0017] (2) Sufficient pressure cooling water serves to quickly remove heat, flush away the black scale adhering to the roll surface, reduce roll wear and material loss from the groove, and ensure that the roll ring does not lose material. When the rolled workpiece enters the reducing and sizing unit, the cooling water pressure is 0.4-0.6 MPa. For reference, the cooling water pressure can be 0.4 MPa, 0.45 MPa, 0.5 MPa, 0.51 MPa, 0.52 MPa, 0.53 MPa, 0.55 MPa, 0.57 MPa, 0.6 MPa, etc., or any other value within the range of 0.4-0.6 MPa.

[0018] (3) Water requirements:

[0019]

[0020] (4) For the arrangement of cooling water, please refer to Figure 1 The cooling water should ideally be arranged from approximately one-third of the roll circumference starting at the taphole, with the water volume increasing at the taphole and gradually decreasing, especially important for taphole cooling. The water volume at the taphole nozzles should account for 20-30% of the total water volume in the annular water pipes, and the water jet from the taphole nozzles should be as close to the roll ring as possible. The water spray should be radially distributed, forming an angle of 15°-30° with the direction of roll ring rotation. For reference, the angle can be 15°, 20°, 25°, 30°, or any other value within the 15-30° range. The water jet width should be twice the width of the trough, and it should be sprayed directly into the trough, without scattering or forming a mist.

[0021] (5) Water quality requirements:

[0022] ① The suitable water pH for use with carbide roller rings is: 7.5≤pH≤7.8.

[0023] In a weakly alkaline environment with pH ≥ 7.2, roller rings with pure cobalt binder, such as YGH series and YGHT series roller rings, are preferred; in a slightly acidic environment with pH < 7.2, the corrosion of cobalt is aggravated, and roller rings containing cobalt nickel chromium binder, such as YGR series and PA series roller rings, are preferred.

[0024] ②The solid particle content in the cooling water should be less than 15mg / L, and the maximum particle size should be less than 40μm.

[0025] ③ The requirements for the chemical composition of cooling water are as follows:

[0026] Element chloride calcium ions sulfates Content, mg / L ≤40 ≤400 ≤75

[0027] The final cooling effect obtained by controlling water pressure, water volume and nozzle angle should be based on the roll surface temperature. The roll surface temperature should be controlled below 50℃. For reference, the roll surface temperature should be controlled at 45℃, 46℃, 47℃, 48℃, 49℃, etc.

[0028] By effectively cooling the roll ring grooves, the heat can be removed in time, reducing the thermal corrosion of the groove surface caused by high heat during rolling and lowering the probability of roll ring chipping.

[0029] 2. Currently, the β angle corresponding to a 70-degree cutter tip angle used for machining threaded roller rings is 55 degrees, which is too small. This makes it difficult to "demold" during rolling, and water cannot easily reach the groove, affecting the cooling effect of the roller ring. During high-speed rolling, it is easy to cause chipping and material loss. Moreover, the small cutter tip angle results in insufficient blade rigidity, making it prone to chipping. Chipping creates old grooves, leading to low efficiency and even the production of unusable grooves. Changing the cutter tip angle for machining threaded roller rings to a 76-degree cutter tip angle will widen the crescent, making it easier to "demold" during rolling. Water can easily reach the groove, resulting in better cooling of the roller ring. During high-speed rolling, it is less likely to cause chipping and material loss. The 76-degree cutter width also provides stronger blade rigidity, reducing the risk of chipping and improving operational efficiency.

[0030] 3. Rolling Temperature Control: The cooling sections at the head of water tanks #1, #2, #3, and #4 are appropriately set. The cooling water holes of the outlet guide seats in the finishing mill and reducing / sizing mill are sealed to ensure that the water tanks are only opened after the head of the rolled piece has exited each tank. A water cut-off function for the head of the rolled piece is added between the #3 shear and the #8 stand to ensure that the head of the rolled piece enters the reducing / sizing mill within a certain high-temperature range (820°C-850°C). Practice has shown that when the head temperature of the rolled piece is below 820°C, the rolled piece has high hardness, resulting in a large impact force on the roll rings and making it prone to chipping. Above 850°C, the steel temperature is conducted into the roll ring grooves, easily causing thermal cracks and affecting the roll ring life.

[0031] The settings for the non-cooling section at the head of water tanks #1, #2, #3, and #4 are as follows:

[0032]

[0033] Practice has shown that: If the value of the non-cooling section at the head of water tanks #1, #2, #3, and #4 is higher than the set value, the head cooling process temperature will exceed the process requirements, increasing trimming and cost. If it is lower than the set minimum value, the steel head will be cooled by water penetration. If the steel head temperature is too low, the instantaneous impact force when biting into the finished roller ring will be large, increasing the roller ring load and easily causing the roller ring to break. For reference, the design of the non-cooling section at the head of water tank #1 can be 15mm, 16mm, 17mm, 18mm, etc., while the value of the non-cooling section at the head of water tanks #2, #3, and #4 can be any value within the range of 12-15mm, 12-15mm, and 10-15mm.

[0034] The temperature requirements for the head of the rolled piece entering the finishing mill and for the sizing process are as follows:

[0035] Specification Pre-finishing mill reducer and sizing unit 6mm ≥900 ≥850 8mm ≥900 ≥850 10mm ≥880 ≥820 12mm ≥880 ≥820

[0036] To ensure the temperature of the steel head during the high-speed rolling process, a high-temperature gauge is installed before entering the finishing mill and the sizing mill to measure the steel head temperature in real time. If the temperature is higher than the temperature of the steel head after the water tank is opened, it means that the steel head is not being saturated with water in the water tank.

[0037] 4. Control the out-of-roundness and tolerance diameter of the incoming material to the pre-finishing and finishing mills to the lower limit of the process requirements (out-of-roundness close to grade C) to avoid excessive head material exacerbating the impact force on the finished rolls. The tolerance diameter requirements for critical passes of each specification are specified. Diameter gauges are installed after stands #18 and #8 to monitor tolerance values ​​in real time. All four specifications of stands #18 use the same set of roll rings with identical tolerance diameters and out-of-roundness. Stand #8 has different diameters and out-of-roundness due to the different number of stands used.

[0038] The data for the key pass material type in thread rolling are as follows:

[0039]

[0040] 5. Determine a reasonable rolling mill tonnage.

[0041] Specification tonnage 6mm 500 8mm 900 10mm 1000 12mm 1200 .

[0042] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0043] Due to the high hardness and impact force of rolled steel, the crescent and lettering on the thread roll are constantly impacted, making it difficult to demold during rolling. This causes pieces to easily chip off from the lettering and crescent areas of the finished threaded steel roll. To reduce chipping from the finished threaded steel roll, this invention provides a method for preventing chipping from the finished threaded steel roll, which mainly includes the following methods:

[0044] 2. Roller ring cooling requirements:

[0045] Cooling is essential for reducing the effects of hot corrosion, thermal fatigue, and thermal stress on the roll ring during rolling, preventing roll ring breakage and material loss, slowing crack propagation, and extending groove life. It is crucial for maximizing the effectiveness of cemented carbide roll rings, as detailed below:

[0046] (1) The temperature of the cooling water is below 35℃.

[0047] (2) Sufficient pressure cooling water is essential to quickly remove heat, flush away the black scale adhering to the surface of the rolls, reduce roll wear and material loss from the grooves, and ensure that the roll rings do not lose material. When the rolled workpiece enters the reducing and sizing mill, the cooling water pressure is 0.4-0.6 MPa.

[0048] (3) Water requirements:

[0049]

[0050] (4) The cooling water should ideally be arranged from about one-third of the roll circumference starting from the taphole. The water volume should be at its maximum at the taphole and gradually decrease, with taphole cooling being particularly important. The water volume at the taphole nozzles should account for 20-30% of the total water volume in the annular water pipes, and the water jet from the taphole nozzles should be as close to the roll ring as possible. The water spray should be radially distributed, forming an angle of 15°-30° with the rotation direction of the roll ring; the water jet width should be twice the width of the trough, and it should be sprayed directly into the trough, without scattering or forming a mist.

[0051] (5) Water quality requirements:

[0052] ① The suitable water pH for use with carbide roller rings is: 7.5≤pH≤7.8.

[0053] In a weakly alkaline environment with pH ≥ 7.2, roller rings with pure cobalt binder, such as YGH series and YGHT series roller rings, are preferred; in a slightly acidic environment with pH < 7.2, the corrosion of cobalt is aggravated, and roller rings containing cobalt nickel chromium binder, such as YGR series and PA series roller rings, are preferred.

[0054] ②The solid particle content in the cooling water should be less than 15mg / L, and the maximum particle size should be less than 40μm.

[0055] ③ The requirements for the chemical composition of cooling water are as follows:

[0056] Element chloride calcium ions sulfates Content, mg / L ≤40 ≤400 ≤75

[0057] The final cooling effect obtained by controlling water pressure, water volume and nozzle angle should be based on the roll surface temperature, which should be controlled below 50℃.

[0058] By effectively cooling the roll ring grooves, the heat can be removed in time, reducing the thermal corrosion of the groove surface caused by high heat during rolling and lowering the probability of roll ring chipping.

[0059] 2. Use a 76-degree milling cutter tip angle to machine the threaded roller ring.

[0060] 3. Rolling Temperature Control: The cooling sections at the heads of water tanks #1, #2, #3, and #4 are appropriately set. The cooling water holes of the outlet guide seats in the finishing mill and reducing and sizing mill are sealed to ensure that the water tanks are only opened after the head of the rolled piece has exited each tank. A water cut-off function for the head of the rolled piece is added between the #3 shear and the #8 stand to ensure that the head of the rolled piece enters the reducing and sizing mill within a certain high-temperature range (820°C-850°C). This reduces the impact force of the rolled piece head on the roll ring and lowers the probability of material loss from the roll ring.

[0061] The settings for the non-cooling section at the head of water tanks #1, #2, #3, and #4 are as follows:

[0062]

[0063] The temperature requirements for the head of the rolled piece entering the finishing mill and for the sizing process are as follows:

[0064] Specification Pre-finishing mill reducer and sizing unit 6mm ≥900 ≥850 8mm ≥900 ≥850 10mm ≥880 ≥820 12mm ≥880 ≥820

[0065] To ensure the temperature of the steel head during the high-speed rolling process, a high-temperature gauge is installed before entering the finishing mill and the sizing mill to measure the steel head temperature in real time. If the temperature is higher than the temperature of the steel head after the water tank is opened, it means that the steel head is not being saturated with water in the water tank.

[0066] 4. Control the out-of-roundness and tolerance diameter of the incoming material to the pre-finishing and finishing mills to the lower limit of the process requirements (out-of-roundness close to grade C). The data for the material type in the key passes of thread rolling are as follows:

[0067]

[0068] 5. Determine a reasonable rolling mill tonnage.

[0069] Specification tonnage 6mm 500 8mm 900 10mm 1000 12mm 1200 .

[0070] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for controlling the loss of wire rod material from finished wire rod holes, characterized in that, The rebar production line includes, sequentially arranged along the rolling direction, roughing mills #1-6, flying shear #1, intermediate mills #7-12, flying shear #2, pre-finishing mills #13-18, water tank #1, water tank #2, flying shear #3, finishing mills #19-26, water tank #3, water tank #4, and reducing mills #27-30 and water tank #5. Control methods to prevent material loss from the finished wire rod rebar include: using cooling water to control the roll surface temperature below 50℃; controlling the water-passing operation of the rolled piece to ensure the temperature of the rolled piece head entering the reducing mill is 820-850℃; and controlling the out-of-roundness and tolerance diameter of the rolled piece entering the pre-finishing and finishing mills to be within the lower limit of the process requirements, as follows: The cooling water volume is controlled as follows: 。 2. The control method for preventing wire rod from chipping off the finished product hole of high-strength wire rod according to claim 1, characterized in that, By controlling the water temperature, water pressure, water volume, spray angle, and water quality, the surface temperature of the roll is kept below 50°C.

3. The control method for preventing wire rod from chipping off the finished product hole of high-strength wire rod according to claim 2, characterized in that, Control the temperature of the cooling water to be below 35℃.

4. The method for controlling the loss of wire rod in finished wire rod holes according to claim 2, characterized in that, The cooling water pressure entering the reducing and sizing unit is controlled to be 0.4-0.6 MPa.

5. The control method for preventing wire rod from chipping off the finished product hole of high-strength wire rod according to claim 2, characterized in that, The cooling water is controlled to be arranged from one-third of the roll circumference starting from the steel outlet. The water volume is the largest at the steel outlet and then gradually decreases. The water volume of the water nozzle at the steel outlet accounts for 20-30% of the total water volume of the ring water pipe. The water is sprayed radially, and the spray angle is 15°-30° with the rotation direction of the roll ring. The width of the water column is twice that of the rolling groove, and it is sprayed directly into the rolling groove. The water does not scatter or mist.

6. The control method for preventing wire rod from chipping off the finished product hole of high-strength wire rod according to claim 5, characterized in that, The pH of the cooling water is 7.5≤pH≤7.8, the solid particle content in the cooling water is less than 15mg / L, the maximum particle size is less than 40μm, the chloride content in the cooling water is ≤40 mg / L, the calcium ion content is ≤400 mg / L, and the sulfate content is ≤75 mg / L.

7. The control method for preventing wire rod from chipping off the finished product hole of high-strength wire rod according to claim 1, characterized in that, The rolling temperature control of the head of the rolled piece is as follows: the head of water tanks No. 1, No. 2, No. 3 and No. 4 are set to be non-cooled, and the cooling water holes of the outlet guide seats in the finishing mill and reducing and sizing mill are blocked so that the water tanks are opened only after the head of the rolled piece has exited each water tank. The water cut-off function of the horizontal looper between the No. 3 flying shear and the finishing mill is added to make the temperature of the head of the rolled piece entering the reducing and sizing mill 820-850℃.

8. The method for controlling the loss of wire rod in finished product holes according to claim 7, characterized in that, The non-cooling section at the head of water tanks No. 1, No. 2, No. 3, and No. 4 is configured as follows: 。 9. The control method for preventing wire rod from chipping off the finished product hole of high-strength wire rod according to claim 7, characterized in that, The temperature control for the head of the rolled piece entering the finishing mill and the sizing mill is as follows: 。 10. The method for controlling the loss of wire rod in finished product holes according to claim 9, characterized in that, Also includes: A pyrometer is installed before the finishing mill and the reducing mill to measure the temperature of the steel head of the rolled piece in real time.

11. The control method for preventing wire rod from losing material from finished wire rod holes according to claim 10, wherein a diameter measuring instrument is installed before the finishing mill and the sizing mill to detect the tolerance diameter of the rolled piece in real time.

12. The method for controlling the loss of wire rod in finished product holes according to claim 1, characterized in that, Also includes: Use a 76-degree milling cutter tip angle to machine threaded roller rings.

13. The method for controlling the loss of wire rod in finished wire rod holes according to claim 1, characterized in that, Also includes: The tonnage of the rolling groove is controlled as follows during the rolling process: 。

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