Method for preventing groove blasting of rib anchor rod finished product hole

Abstract

The invention relates to a method for preventing groove explosion of a rib anchor rod finished product hole. The method comprises the steps that firstly, a spraying device of a rough and medium rolling mill is shut down before production; 2, a K1 roller of a phi 390 rolling mill is used for rolling, the rolling starting temperature ranges from 1050 DEG C to 1200 DEG C, in the rolling process, the temperature of a continuous casting blank is controlled to range from 900 DEG C to 1000 DEG C, the speed of the continuous casting blank fed into the rolling mill is controlled to range from 10 m / min to 20 m / min, and the material penetrating frequency is controlled to be within three times; after rolling is started, cooling water of the rollers K1 and K3 is temporarily closed; 3, controlling the transverse rib height of a finished product according to the middle and lower limits. According to the method, the technical parameters in the rolling procedure are regulated and controlled, groove explosion or block falling of the roller in the continuous rolling production process is effectively avoided, and stable production of the rib anchor rod is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of anchor bar steel rolling, and particularly relates to a method for preventing the bursting of finished holes of ribbed anchor bars. Background Art

[0002] The ribbed steel bar anchor is a supporting device that uses the mechanical biting effect between the thread structure and the anchor body to reinforce rock masses, soil bodies or concrete structures. In recent years, due to advantages such as high strength, high bonding performance and good construction flexibility, the ribbed steel bar anchor has become the mainstream choice in geotechnical anchoring projects. Besides playing an important role in the support of mine roadways, the ribbed steel bar anchor can also be used for the high-strength and durable roadway support of projects such as railways and hydropower. According to the processing technology and structural differences, the ribbed steel bar anchor can be divided into ordinary ribbed steel bar anchors, full-thread anchors, non-longitudinal ribbed steel bar anchors and fine-tooth ribbed anchors. The rolling process of ordinary ribbed steel bar anchors is simple and the cost is low, but there is stress concentration at the junction of the transverse ribs and longitudinal ribs, and the pull-out resistance is limited; the non-longitudinal ribbed steel bar anchor only retains the transverse thread ribs (transverse ribs), which has good corrosion resistance and fatigue resistance, but the initial bonding force and construction flexibility are poor; the full-thread anchor has uniform thread distribution, good construction flexibility and strong shear resistance, but due to the large thread pitch and shallow thread depth of the full-thread anchor, there are problems of insufficient durability and fatigue resistance; the fine-tooth ribbed anchor is processed from ribbed steel bars, its rib teeth are fine and dense, the shape is unique, and the bonding force is strong, which can form a strong support structure in the formation. Compared with traditional ribbed steel bar anchors, it has the characteristics of strong durability, strong bonding force and high tensile strength, and can withstand high stresses and deformations in the formation.

[0003] The fine-tooth ribbed anchor is also called the ribbed anchor. The geometric accuracy and mechanical properties of the rib pattern (raised stripe) on the surface of the fine-tooth ribbed anchor directly determine the bonding strength between the anchor and the grout / rock and soil mass. At present, the production of fine-tooth ribbed anchors mainly relies on the hot rolling forming process - the steel billet is rolled into a ribbed rod body at high temperature, and the groove design and durability of the rolling mill rolls are the core elements for controlling the rib pattern quality. However, during the continuous rolling process, local material spalling (i.e., "bursting" or "chunk dropping") often occurs on the surface of the rolling mill rolls due to the relatively dense rib spacing and extreme working conditions (high temperature, high stress, friction and wear). This will not only cause defects such as rib pattern defects and dimensional out-of-tolerance on the surface of the finished fine-tooth ribbed anchor, seriously reducing the physical properties of the fine-tooth ribbed anchor, but also affect the smooth progress of the production process of the anchor, and may even cause potential engineering safety hazards in severe cases. Summary of the Invention

[0004] Aiming at the technical problems of "bursting grooves" or "chunk dropping" that are likely to occur during the continuous rolling production of ribbed anchor bolts using the hot rolling forming process, the present invention provides a method for preventing the bursting of finished holes of ribbed anchor bolts. By regulating the process parameters in the rolling process, it effectively avoids "bursting grooves" or "chunk dropping" during the continuous rolling production process of the rolling mill, which is beneficial to the stable production of ribbed anchor bolts.

[0005] The technical solution of the present invention is as follows: A method for preventing the bursting of finished holes of ribbed anchor bolts, comprising the following steps: Step 1: Shut down the spray device of the rough and medium rolling mills before production; Step 2: Use the K1 roll of the Φ390 rolling mill for rolling, with the starting rolling temperature being 1050 - 1200 °C to prevent bursting grooves at low temperatures. During the rolling process, control the temperature of the continuous casting billet at 900 - 1000 °C, control the feeding speed of the continuous casting billet into the rolling mill at 10 - 20 m / min, and control the number of threading times at 1 - 3 times; after starting rolling, temporarily close the cooling water of the K1 roll - K3 roll; Step 3: Control the height of the transverse ribs of the finished product according to the middle and lower limits.

[0006] Further, in Step 1, the rough and medium rolling mills include the 1# rolling mill, 2# rolling mill, 3# rolling mill, 4# rolling mill, 5# rolling mill, 6# rolling mill, 7# rolling mill, 8# rolling mill, 9# rolling mill, 10# rolling mill, 11# rolling mill, and 12# rolling mill. Among them, the 1# rolling mill - 6# rolling mills are rough rolling mills, and the 1# rolling mill, 2# rolling mill, 3# rolling mill, 4# rolling mill, 5# rolling mill, and 6# rolling mills are connected end to end in sequence to form a six-stand rough rolling section; the 7# rolling mill - 12# rolling mills are medium rolling mills, and the 7# rolling mill, 8# rolling mill, 9# rolling mill, 10# rolling mill, 11# rolling mill, and 12# rolling mills are connected end to end in sequence to form a six-stand medium rolling section. A flying shear device can be set between the six-stand rough rolling section and the six-stand medium rolling section. The invention uses multiple rolling mills in the six-stand rough rolling section and the six-stand medium rolling section to cooperate to form a continuous rolling production line for producing ribbed anchor bolt products. On the one hand, the continuous casting billet does not need to stop in the middle during the production process, significantly shortening the rolling cycle; on the other hand, each rolling mill on the continuous rolling production line can achieve precise regulation. Through 12 passes of cumulative reduction, the error accumulation of a single pass is reduced, and the dimensional accuracy of the rolled piece is accurately controlled. After shutting down the spray devices of the 1# rolling mill - 12# rolling mills before production, the entire continuous rolling production line can form a gradient thermal insulation chain, which is beneficial to narrowing the temperature fluctuation range and improving the plastic stability of the material.

[0007] Furthermore, in step two, when rolling with the K1 roll of the Φ390 rolling mill, ordinary cooling water is used for cooling. The water pressure of the ordinary cooling water is 6 - 8 kg, preferably 7 kg, and it is strictly prohibited to use controlled rolling and controlled cooling high-pressure water for cooling. The material of the roll is preferably high-speed steel and / or semi-steel. Using ordinary cooling water for cooling can reduce the cooling rate of the surface of the rolled piece, narrow the temperature difference between the surface and the interior of the rolled piece, reduce the residual stress on the surface and in the interior of the rolled piece, and improve the quality stability of the finished ribbed anchor rod. High-speed steel (HSS) is a tool steel containing high alloying elements such as tungsten (W), molybdenum (Mo), chromium (Cr), vanadium (V), etc., and has the characteristics of high hardness, high wear resistance, and high heat resistance. The roll made of high-speed steel can maintain a high hardness during the hot rolling process, ensuring that the roll can effectively bite into the rolled piece at high temperatures, avoiding the roll gap deviation caused by thermal softening. The high rigidity of high-speed steel can also reduce the rolling force fluctuation and suppress surface defects including burst grooves. Semi-steel is a hypereutectic cast steel with a very high carbon content (1.4% - 2.4%). Such high-carbon cast steels actually extend into the cast iron category, so it is commonly called semi-steel. Semi-steel is an iron alloy material with relatively high strength, wear resistance, and corrosion resistance, and its main components are iron plus a small amount of elements such as carbon and manganese. Semi-steel has good mechanical properties and thermal fatigue resistance, and the roll made of semi-steel has relatively small thermal stress. In addition, the roll made of semi-steel has a moderate elastic modulus, which can provide good deformation coordination and reduce the fluctuation of the transverse rib height.

[0008] Further, in Step 2, the loop is cooled with cooling water. The cooling water for the loop is appropriately turned down slightly, and the flow rate of the loop cooling water is controlled within 20 - 35 m³ / h to ensure the cooling effect. During the cooling process, it is necessary to prevent the loop cooling water from splashing onto the red-hot steel. For the fine-thread ribs of the rib anchor rod, the geometric shape is complex and is prone to becoming a thermal stress concentration point. Using a small flow rate of cooling water to cool the loop can make the temperature change of the loop more gentle, avoiding thermal stress concentration in key components such as the loop due to sudden cooling, thereby reducing the risk of cracks or deformation. Controlling the flow rate of the loop cooling water within the range of 20 - 35 m³ / h can not only meet the cooling requirements of key components such as the loop but also stabilize the working temperature of the rolling mill, avoiding a decrease in surface hardness due to overheating, and thus reducing the accelerated wear of the rib anchor rod during rolling due to softening. If the cooling water splashes onto the surface of the red-hot steel, it may cause an increase in the thickness of the steel oxide scale or micro-cracks. Such defects will increase the local pressure on the rolling mill (especially in the contact area of the fine-thread ribs) during rolling, resulting in scratches, chipping, or bursting of the rolling mill surface. When the shutdown time of the rolling mill exceeds 2 hours due to reasons such as changing the continuous casting billet variety, waiting for gas, or peak-shaving production, the CP2 control system notifies the pump house to turn off all the cooling tower fans, and the temperature of the ordinary cooling water is controlled within 25 - 35 °C. After turning off the cooling tower fans, the active heat dissipation capacity of the cooling tower decreases, making the temperature of the ordinary cooling water higher than normal temperature. On the one hand, this can avoid excessive cold of the ordinary cooling water causing too large a temperature difference between the surface and the core of the rolling mill after the rolling mill is shut down, thereby reducing thermal stress concentration and the risk of micro-cracks in the rib anchor rod. On the other hand, controlling the temperature of the ordinary cooling water within 25 - 35 °C can not only avoid brittle fracture or spalling of the rib anchor rod caused by the temperature of the rolling mill dropping to the brittle range of the material, but also the relatively mild cooling environment is conducive to slowly releasing the residual stress and maintaining the shape stability of the rolling mill. When the rolling mill restarts, the temperature of the rolling mill can reach the steady-state rolling temperature faster, preventing thermo-mechanical fatigue damage to the rib anchor rod and playing a role in protecting the structure of the rib anchor rod.

[0009] Further, in Step 2, multi-stand collaborative operation is used for rolling. The K1 roll of the Φ390 rolling mill is only the core roll of the finishing section. In the actual rolling process, 1 - 20 Φ390 rolling mills can be used for collaborative operation as needed. Using multi-stand collaborative operation for rolling can not only significantly shorten the total rolling time of a single anchor rod, achieving continuous high-speed production, but also avoid the entire production line from shutting down due to roll changing or maintenance of some rolling mills through the method of multi-stand rotation operation, ensuring production continuity. Multi-stand collaborative operation can avoid a single roll from being under high load for a long time. While avoiding temperature accumulation in the roll due to continuous operation, it reduces the wear rate of the roll and extends the service life of the roll.

[0010] Further, in step two, the continuous casting billet is a cylindrical steel, with a length of 1 - 1.5 meters and a diameter of 22 millimeters. There is no severe scale or defect on the surface of the continuous casting billet. The continuous casting billet with a length of 1 - 1.5 meters is convenient for clamping and pushing, reducing material jamming or positioning deviation caused by too long billets, and ensuring the continuous feeding rhythm of the rolling mill. Limiting the diameter of the continuous casting billet to 22 millimeters can make the continuous casting billet heat more evenly, avoid too large temperature difference between the core and the surface of the continuous casting billet due to too large cross-section, inhibit the concentration of residual stress in the fine tooth rib part, and improve the anti-fatigue performance of the rib anchor rod. The present invention feeds the continuous casting billet into the rolling mill at a low speed of 10 - 20 m / min, which can avoid the failure of the rolling mill to bite the continuous casting billet or steel jamming caused by too fast feeding speed. During the process of feeding the continuous casting billet into the rolling mill, observe the stability of the continuous casting billet when passing through the pass profiles of each pass (such as whether there is deviation or vibration). After rolling, use a caliper to measure the key dimensions of the rolled continuous casting billet, such as diameter, ovality, rib height, etc., and observe whether there is rib misalignment in the rolled continuous casting billet.

[0011] Further, in step two, control the standard roll gap within 1 - 3 millimeters, preferably 2 millimeters. Controlling the standard roll gap at 2 millimeters can ensure that the roll pattern is fully pressed into the surface of the steel, avoiding insufficient rib height or pitch deviation caused by too large roll gap. Adjust the consistency of the roll gaps on both sides of all rolling mills, and align the guide device with the rolling groove to prevent the continuous casting billet from having a sickle bend and uneven deformation at the head (or having a temperature difference) during rolling, resulting in the potential hazard of uneven deformation and bursting when the head of the continuous casting billet bites into the K1 roll of the 20# rolling mill.

[0012] Further, in step two, after starting rolling, when the heads of the first, second, and third continuous casting billets pass through the rolling mill, temporarily turn off the cooling water of the K1 roll of the 20# rolling mill, the K2 roll of the 19# rolling mill, and the K3 roll of the 18# rolling mill for 1 - 2 seconds. The rolls will accumulate heat during hot rolling. If they suddenly come into contact with low-temperature cooling water, great thermal stress will be generated on the roll surface due to sudden cooling, resulting in the expansion of microcracks on the roll surface and ultimately causing roll chipping or spalling. Temporarily turning off the cooling water can prevent the huge impact on the rolls caused by the sudden drop in the roll surface temperature, resulting in roll chipping and slipping accidents, avoid local shrinkage deformation of the rolls, affect the matching degree between the rolling groove and the rolled piece, and cause uneven rib depths. Temporarily turning off the cooling water can maintain the dimensional stability of the rolls and ensure uniform thread forming.

[0013] Further, in step three, the height of the transverse ribs of the finished product is 0 - 0.1 mm, preferably 0.05 - 0.1 mm. When designing the pass, the inclination angle of the transverse ribs is 60º. First, the pass design with a 60º inclination angle is beneficial to balance the rolling force and reduce the fluctuation of the rib height caused by uneven stress on the rolled piece. Second, the pass design with a 60º inclination angle enables the metal to flow uniformly along the roll groove during rolling, avoiding metal accumulation or tearing of the rolled piece surface caused by too large an inclination angle. Third, the pass design with a 60º inclination angle is easier to align during roll grinding and roll changing, reducing the downtime caused by pass misalignment and ensuring production continuity. The shallow groove design with a transverse rib height ≤ 0.1 mm reduces the local pressure on the roll. Combined with the optimized component force of the 60º inclination angle, it can reduce the wear at the edge of the roll groove and extend the service life of the roll.

[0014] Further, in step three, the strength grade of the finished product is any one of 335 MPa, 400 MPa, 500 MPa, and 600 MPa. If it is necessary to schedule the production of finished products with different strength grades, they shall be produced in the order from high to low in strength grade to match the differences in the cooling speed requirements of the water temperature and finished products with different strength grades. The requirements for the cooling speed of the ribbed anchor rods with different strength grades are different. Using cooling water at a higher temperature for slow cooling of the finished product with a lower strength grade can avoid the accumulation of residual stress caused by overcooling; using cooling water at a lower temperature for rapid cooling of the finished product with a higher strength grade can improve the strength and toughness through phase transformation strengthening.

[0015] The beneficial effects of the present invention are as follows: A method for preventing the bursting of the finished product holes of ribbed anchor rods provided by the present invention is beneficial to forming a stable high-temperature rolling environment by shutting down the spray device of the rough and medium rolling mills before production and temporarily closing the cooling water of the K1 - K3 rolls after rolling starts, enabling the continuous casting billet to be in the best plastic state and reducing the phase transformation stress caused by sudden temperature changes; by controlling the temperature of the continuous casting billet at 900 - 1000°C and the rolling start temperature at 1050 - 1200°C, a thermodynamic equilibrium system is constructed, effectively avoiding brittle fracture caused by low-temperature rolling; by selecting the K1 roll of the Φ390 mill for rolling, controlling the speed of feeding the continuous casting billet into the mill at 10 - 20 m / min, and controlling the number of threading times within 3 times, the accumulated strain energy is reduced, and at the same time, the work hardening effect is reduced; controlling the height of the transverse ribs of the finished product according to the middle and lower limits can make the surface stress distribution of the finished product more uniform. Finite element analysis shows that the maximum principal stress can be reduced by 25 - 30 MPa, fundamentally eliminating the risk of bursting caused by stress concentration. Specific embodiments

[0016] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0017] Embodiment 1 A method for preventing the finished hole of the ribbed anchor rod of model MG600X(Z)Φ22 from bursting, comprising the following steps: Step 1: Before production, confirm that the water temperature of the cooling water is 25-35°C, and shut down all the spray devices of the rough and intermediate rolling mills. The rough and intermediate rolling mills include No. 1 rolling mill, No. 2 rolling mill, No. 3 rolling mill, No. 4 rolling mill, No. 5 rolling mill, No. 6 rolling mill, No. 7 rolling mill, No. 8 rolling mill, No. 9 rolling mill, No. 10 rolling mill, No. 11 rolling mill and No. 12 rolling mill. Among them, No. 1 rolling mill - No. 6 rolling mills are rough rolling mills, and No. 1 rolling mill, No. 2 rolling mill, No. 3 rolling mill, No. 4 rolling mill, No. 5 rolling mill and No. 6 rolling mill are connected end to end in sequence to form a six-stand rough rolling section; No. 7 rolling mill - No. 12 rolling mills are intermediate rolling mills, and No. 7 rolling mill, No. 8 rolling mill, No. 9 rolling mill, No. 10 rolling mill, No. 11 rolling mill and No. 12 rolling mill are connected end to end in sequence to form a six-stand intermediate rolling section. A flying shear device is arranged between the six-stand rough rolling section and the six-stand intermediate rolling section. After the continuous casting billet is loaded, it is successively subjected to heating furnace heating, high-pressure water descaling, rough rolling in the six-stand rough rolling section, flying shear cutting of the head and tail, and intermediate rolling in the six-stand intermediate rolling section. The present invention adopts multiple rolling mills in the six-stand rough rolling section and the six-stand intermediate rolling section to cooperate to form a continuous rolling production line to produce the finished ribbed anchor rod. On the one hand, the continuous casting billet does not need to pause during the production process, significantly shortening the rolling cycle; on the other hand, each rolling mill on the continuous rolling production line can achieve precise regulation. Through 12 passes of cumulative reduction, the error accumulation of a single pass is reduced, and the dimensional accuracy of the rolled piece is accurately controlled. After shutting down the spray devices of No. 1 rolling mill - No. 12 rolling mills before production, the entire continuous rolling production line can form a gradient heat preservation chain, which is beneficial to narrowing the temperature fluctuation range and improving the plastic stability of the material.

[0018] Step 2: Use the K1 roll of the Φ390 rolling mill for rolling. The starting rolling temperature is 1050-1200°C to prevent bursting at low temperature. During the rolling process, control the temperature of the continuous casting billet at 900-1000°C, control the speed of feeding the continuous casting billet into the rolling mill at 10-20 m / min, and control the number of threading times at two; after starting rolling, temporarily close the cooling water of the K1 roll - K3 roll.

[0019] When rolling with the K1 roll of the Φ390 rolling mill, ordinary cooling water is used for cooling. The water pressure of the ordinary cooling water is 7 kg, and the use of controlled rolling and controlled cooling high-pressure water for cooling is prohibited. The roll material is high-speed steel. Using ordinary cooling water for cooling can reduce the cooling rate of the rolled piece surface, narrow the temperature difference between the rolled piece surface and the inside of the rolled piece, reduce the residual stress on the rolled piece surface and inside the rolled piece, and improve the quality stability of the ribbed anchor rod finished product. High-speed steel (HSS) is a tool steel containing high alloy elements such as tungsten (W), molybdenum (Mo), chromium (Cr), vanadium (V), etc., and has the characteristics of high hardness, high wear resistance, and high heat resistance. The roll made of high-speed steel can maintain a high hardness during the hot rolling process, ensuring that the roll can effectively bite into the rolled piece at high temperatures, avoiding roll gap deviation caused by thermal softening. The high rigidity of high-speed steel can also reduce the rolling force fluctuation and suppress surface defects including bursting. Semi-steel is a hypereutectic cast steel with a very high carbon content (1.4% - 2.4%). Such high-carbon cast steels actually extend into the cast iron category, so it is commonly called semi-steel. Semi-steel is an iron alloy material with relatively high strength, wear resistance, and corrosion resistance. Its main components are iron plus a small amount of elements such as carbon and manganese. Semi-steel has good mechanical properties and thermal fatigue resistance. The roll made of semi-steel has relatively small thermal stress. In addition, the roll made of semi-steel has a moderate elastic modulus, can provide good deformation coordination, and reduce the fluctuation of the transverse rib height.

[0020] Cool the loop with cooling water. Appropriately reduce the flow of the loop cooling water, and control the flow rate of the loop cooling water within 20 - 35 m³ / h to ensure the cooling effect. During the cooling process, prevent the loop cooling water from splashing onto the red-hot steel. The fine-tooth rib structure of the rib anchor rod has a complex geometry and is prone to becoming a heat stress concentration point. Using a small flow rate of cooling water to cool the loop can make the temperature change of the loop more gentle, avoid heat stress concentration in key components such as the loop due to sudden cooling, thereby reducing the risk of cracks or deformation. Controlling the flow rate of the loop cooling water within the range of 20 - 35 m³ / h can not only meet the cooling requirements of key components such as the loop but also stabilize the working temperature of the roll, avoid a decrease in surface hardness due to overheating, and thus reduce the accelerated wear of the rib anchor rod during rolling due to softening. If the cooling water splashes onto the surface of the red-hot steel, it may cause an increase in the thickness of the steel scale or micro-cracks. Such defects will increase the local pressure on the roll (especially in the contact area of the fine-tooth ribs) during rolling, resulting in scratches, chipping, or bursting of the roll surface. When the shutdown time of the rolling mill exceeds 2 hours due to reasons such as changing the continuous casting billet variety, waiting for gas, or peak-shaving production, the CP2 control system notifies the pump house to turn off all cooling tower fans and control the temperature of the ordinary cooling water within 25 - 35 °C. After turning off the cooling tower fans, the active heat dissipation capacity of the cooling tower decreases, making the temperature of the ordinary cooling water higher than normal temperature. On the one hand, it can avoid excessive temperature difference between the surface and the core of the roll due to the over-cooling of the ordinary cooling water after the rolling mill is shut down, thereby reducing heat stress concentration and the risk of micro-cracks in the rib anchor rod. On the other hand, controlling the temperature of the ordinary cooling water within 25 - 35 °C can not only avoid brittle fracture or spalling of the rib anchor rod caused by the roll temperature dropping to the brittle range of the material, but also the relatively mild cooling environment is conducive to slowly releasing the residual stress and maintaining the shape stability of the roll. When the rolling mill restarts, the roll temperature can reach the steady-state rolling temperature faster, preventing thermo-mechanical fatigue damage to the rib anchor rod and playing a role in protecting the structure of the rib anchor rod.

[0021] Use multi-stand coordinated operation for rolling. The K1 roll of the Φ390 rolling mill is only the core roll of the finishing section. In the actual rolling process, 20 Φ390 rolling mills are used for coordinated operation. Using multi-stand coordinated operation for rolling can not only significantly shorten the total rolling time of a single anchor rod, achieve continuous high-speed production, but also avoid the entire production line from shutting down due to roll changing or maintenance of some rolling mills through the method of multi-stand rotation operation, ensuring production continuity. Multi-stand coordinated operation can avoid a single roll from bearing high loads for a long time. While avoiding the temperature accumulation of the roll due to continuous operation, it reduces the wear rate of the roll and extends the service life of the roll.

[0022] The continuous casting billet is a cylindrical steel product. The length of the continuous casting billet is 1 - 1.5 meters, and the diameter is 22 millimeters. There is no severe scale or defect on the surface of the continuous casting billet. The continuous casting billet with a length of 1 - 1.5 meters is convenient for clamping and pushing, reducing jamming or positioning deviation caused by the excessive length of the billet, and ensuring the continuous feeding rhythm of the rolling mill. Limiting the diameter of the continuous casting billet to 22 millimeters can make the continuous casting billet heat more evenly, avoid excessive temperature difference between the core and the surface of the continuous casting billet due to too large a cross-section, inhibit the concentration of residual stress in the fine tooth rib part, and improve the anti-fatigue performance of the ribbed anchor rod. The present invention feeds the continuous casting billet into the rolling mill at a low speed of 10 - 20 m / min, which can avoid the failure of the rolling mill to bite the continuous casting billet or steel jamming caused by too fast feeding speed. During the process of feeding the continuous casting billet into the rolling mill, observe the stability of the continuous casting billet when passing through the pass grooves of each pass (such as whether there is deviation or vibration). After rolling, use a caliper to measure the key dimensions of the rolled continuous casting billet, such as diameter, ovality, rib height, etc., and observe whether there is misalignment of ribs in the rolled continuous casting billet.

[0023] Control the standard roll gap at 2 millimeters, control the material shape of the whole line, and ensure that the roll gaps on both sides of all rolling mills used are the same. Controlling the standard roll gap at 2 millimeters can ensure that the roll patterns are fully pressed into the surface of the steel, avoiding insufficient rib height or pitch deviation caused by too large a roll gap. Adjust the consistency of the roll gaps on both sides of all rolling mills, align the guide guard with the rolling groove, and prevent the continuous casting billet from having a sickle bend and uneven deformation at the head (or having a temperature difference) during the rolling process, which may cause the hidden danger of uneven deformation and bursting of the head of the continuous casting billet when biting into the K1 roll.

[0024] After starting rolling, when the heads of the first, second, and third continuous casting billets pass through the rolling mill, temporarily turn off the cooling water of the K1 roll, K2 roll, and K3 roll for 1 - 2 seconds. The rolls will accumulate heat during hot rolling. If they suddenly come into contact with low-temperature cooling water, great thermal stress will be generated on the roll surface due to sudden cooling, resulting in the expansion of microcracks on the roll surface and eventually causing roll chipping or spalling. Temporarily turning off the cooling water can prevent the huge impact on the rolls caused by the sudden drop in the roll surface temperature, resulting in roll chipping and slipping accidents, avoid local shrinkage deformation of the rolls, affect the matching degree between the rolling groove and the rolled piece, and cause uneven rib depths. Temporarily turning off the cooling water can maintain the stability of the roll dimensions and ensure uniform thread forming.

[0025] Step 3: Control the transverse rib height of the finished product according to the middle and lower limits to produce a ribbed anchor rod of model MG500X(Y)Φ22, and the rib interval of the ribbed anchor rod is 4 millimeters.

[0026] The height of the transverse ribs of the finished product is 0.05 - 0.1 mm. When designing the pass shape, the inclination angle of the transverse ribs is 60º. First, the pass shape design with a 60º inclination angle is beneficial to balancing the rolling force and reducing the fluctuation of the rib height caused by uneven stress on the rolled piece. Second, the pass shape design with a 60º inclination angle can make the metal flow uniformly along the roll groove during rolling, avoiding metal accumulation or tearing of the surface of the rolled piece caused by too large an inclination angle. Third, the pass shape design with a 60º inclination angle is easier to align during roll grinding and roll change, reducing the downtime caused by pass misalignment and ensuring the continuity of production. The shallow groove design with a transverse rib height ≤ 0.1 mm reduces the local pressure on the roll. Combined with the optimization of the component force with a 60º inclination angle, it can reduce the wear at the edge of the roll groove and extend the service life of the roll.

[0027] (1) Production situation: When producing MG600X(Z) Φ22, the fourth roll groove that has already produced 215 tons was continued to be used. After a total of 415 tons of steel passed through, there was a slight explosion at the notch of the pass shape. The surface of the finished product had no pitting, the end of the transverse rib had no obvious jerks, the rib spacing was still clear and bright, and the surface gloss was bright. After changing the pass, the production continued for 200 tons with good surface quality and could be continued to be used. Since the total production plan for this time was 400 tons and there was no subsequent plan, it was not continued to be used.

[0028] (2) Roll groove situation: After 415 tons of steel passed through the fourth pass, there were small explosion points. After 200 tons of steel passed through the fifth pass, the surface quality was good and could be continued to be used next time.

[0029] Example 2 A method for preventing the explosion of the finished product pass of the ribbed anchor rod of model MG500Y Φ22 includes the following steps: Step 1: Before production, confirm that the water temperature of the cooling water is 25 - 35°C, and shut down all the spray devices of the rough and intermediate rolling mills. The rough and intermediate rolling mills include No. 1 rolling mill, No. 2 rolling mill, No. 3 rolling mill, No. 4 rolling mill, No. 5 rolling mill, No. 6 rolling mill, No. 7 rolling mill, No. 8 rolling mill, No. 9 rolling mill, No. 10 rolling mill, No. 11 rolling mill, and No. 12 rolling mill. Among them, No. 1 - No. 6 rolling mills are rough rolling mills, and No. 1 rolling mill, No. 2 rolling mill, No. 3 rolling mill, No. 4 rolling mill, No. 5 rolling mill, and No. 6 rolling mill are connected end to end in sequence to form a six-stand rough rolling section; No. 7 - No. 12 rolling mills are intermediate rolling mills, and No. 7 rolling mill, No. 8 rolling mill, No. 9 rolling mill, No. 10 rolling mill, No. 11 rolling mill, and No. 12 rolling mill are connected end to end in sequence to form a six-stand intermediate rolling section. A flying shear device is arranged between the six-stand rough rolling section and the six-stand intermediate rolling section. After the continuous casting billet is loaded, it is heated in the heating furnace, descaled by high-pressure water, rough rolled in the six-stand rough rolling section, the head and tail are cut by the flying shear, and then intermediate rolled in the six-stand intermediate rolling section. The present invention uses multiple rolling mills in the rough rolling mill section and the intermediate rolling mill section to cooperate to form a continuous rolling production line to produce the finished product of the ribbed anchor rod. On the one hand, the continuous casting billet does not need to stop in the middle during production, significantly shortening the rolling cycle; on the other hand, each rolling mill on the continuous rolling production line can achieve precise control. Through 12 passes of cumulative reduction, the error accumulation of a single pass is reduced, and the dimensional accuracy of the rolled piece is accurately controlled. After shutting down the spray devices of No. 1 - No. 12 rolling mills before production, the entire continuous rolling production line can form a gradient heat preservation chain, which is beneficial to narrowing the temperature fluctuation range and improving the plastic stability of the material.

[0030] Step 2: Use the K1 roll of the Φ390 rolling mill for rolling. The starting rolling temperature is 1050 - 1200°C to prevent low-temperature bursting. During the rolling process, control the temperature of the continuous casting billet at 900 - 1000°C, control the feeding speed of the continuous casting billet into the rolling mill at 10 - 20 m / min, and control the number of threading times at two; after starting rolling, temporarily turn off the cooling water of the K1 roll - K3 roll.

[0031] When rolling with the K1 roll of the Φ390 rolling mill, ordinary cooling water is used for cooling. The water pressure of the ordinary cooling water is 7 kg, and the use of controlled rolling and controlled cooling high-pressure water for cooling is prohibited. The roll material is high-speed steel. Using ordinary cooling water for cooling can reduce the cooling rate of the rolled piece surface, narrow the temperature difference between the rolled piece surface and the inside of the rolled piece, reduce the residual stress on the rolled piece surface and inside the rolled piece, and improve the quality stability of the finished ribbed anchor rod. High-speed steel (HSS) is a tool steel containing high alloying elements such as tungsten (W), molybdenum (Mo), chromium (Cr), vanadium (V), etc., and has the characteristics of high hardness, high wear resistance, and high heat resistance. The roll made of high-speed steel can maintain a high hardness during the hot rolling process, ensuring that the roll can effectively bite into the rolled piece at high temperatures and avoiding the roll gap deviation caused by thermal softening. The high rigidity of high-speed steel can also reduce the rolling force fluctuation and suppress surface defects including burst grooves. Semi-steel is a hypereutectic cast steel with a very high carbon content (1.4% - 2.4%). This type of high-carbon cast steel actually extends into the cast iron category, so it is commonly called semi-steel. Semi-steel is an iron alloy material with relatively high strength, wear resistance, and corrosion resistance, and its main components are iron plus a small amount of elements such as carbon and manganese. Semi-steel has good mechanical properties and thermal fatigue resistance, and the roll made of semi-steel has relatively small thermal stress. In addition, the roll made of semi-steel has a moderate elastic modulus, which can provide good deformation coordination and reduce the fluctuation of the transverse rib height.

[0032] Cool the loop with cooling water. Appropriately reduce the flow of the loop cooling water, and control the flow rate of the loop cooling water within 20 - 35 m³ / h to ensure the cooling effect. During the cooling process, prevent the loop cooling water from splashing onto the red-hot steel. The fine-tooth rib structure of the rib anchor rod has a complex geometry and is prone to becoming a thermal stress concentration point. Using a small flow rate of cooling water to cool the loop can make the temperature change of the loop more gentle, avoid thermal stress concentration in key components such as the loop due to sudden cooling, thereby reducing the risk of cracks or deformation. Controlling the flow rate of the loop cooling water within the range of 20 - 35 m³ / h can not only meet the cooling requirements of key components such as the loop but also stabilize the working temperature of the rolling mill, avoid a decrease in surface hardness due to overheating, and thus reduce the accelerated wear of the rib anchor rod during rolling due to softening. If the cooling water splashes onto the surface of the red-hot steel, it may cause an increase in the thickness of the steel scale or microcracks. Such defects will increase the local pressure on the rolling mill (especially in the contact area of the fine-tooth ribs) during rolling, resulting in scratches, chipping, or bursting of the rolling mill surface. When the shutdown time of the rolling mill exceeds 2 hours due to reasons such as changing the continuous casting billet variety, waiting for gas, or peak-shaving production, the CP2 control system notifies the pump house to turn off all cooling tower fans. Control the temperature of the ordinary cooling water within 25 - 35 °C. After turning off the cooling tower fans, the active heat dissipation capacity of the cooling tower decreases, making the temperature of the ordinary cooling water higher than normal temperature. On the one hand, it can avoid excessive temperature difference between the surface and the core of the rolling mill due to the overcooling of the ordinary cooling water after the rolling mill is shut down, thereby reducing thermal stress concentration and the risk of microcracks in the rib anchor rod. On the other hand, controlling the temperature of the ordinary cooling water within 25 - 35 °C can not only avoid brittle fracture or spalling of the rib anchor rod caused by the temperature of the rolling mill dropping to the brittle range of the material but also the relatively mild cooling environment is conducive to slowly releasing the residual stress and maintaining the shape stability of the rolling mill. When the rolling mill restarts, the temperature of the rolling mill can reach the steady-state rolling temperature faster, preventing thermo-mechanical fatigue damage to the rib anchor rod and playing a role in protecting the structure of the rib anchor rod.

[0033] Use multi-stand coordinated operation for rolling. The K1 roll of the Φ390 rolling mill is only the core roll of the finishing section. In the actual rolling process, 20 Φ390 rolling mills are used for coordinated operation. Using multi-stand coordinated operation for rolling can not only significantly shorten the total rolling time of a single anchor rod, achieve continuous high-speed production, but also avoid the entire production line from shutting down due to roll changing or maintenance of some rolling mills through the multi-stand rotation operation method, ensuring production continuity. Multi-stand coordinated operation can avoid a single roll from being under high load for a long time. While avoiding temperature accumulation of the roll due to continuous operation, it reduces the wear rate of the roll and extends the service life of the roll.

[0034] The continuous casting billet is a cylindrical steel product. The length of the continuous casting billet is 1 - 1.5 meters, and the diameter is 22 millimeters. There is no serious scale or defect on the surface of the continuous casting billet. The continuous casting billet with a length of 1 - 1.5 meters is convenient for clamping and pushing, reducing material jamming or positioning deviation caused by too long billets, and ensuring the continuous feeding rhythm of the rolling mill. Limiting the diameter of the continuous casting billet to 22 millimeters can make the continuous casting billet heat more evenly, avoid excessive temperature difference between the core and the surface of the continuous casting billet due to too large cross-section, inhibit the concentration of residual stress in the fine tooth rib part, and improve the anti-fatigue performance of the ribbed anchor rod. The present invention feeds the continuous casting billet into the rolling mill at a low speed of 10 - 20 m / min, which can avoid the failure of the rolling mill to bite the continuous casting billet or steel jamming caused by too fast feeding speed. During the process of feeding the continuous casting billet into the rolling mill, observe the stability of the continuous casting billet when passing through the pass grooves of each pass (such as whether there is deviation or vibration). After rolling, use a caliper to measure the key dimensions of the rolled continuous casting billet, such as diameter, ovality, rib height, etc., and observe whether there is rib misalignment in the rolled continuous casting billet.

[0035] Control the standard roll gap at 2 millimeters, control the material shape of the whole line, and ensure that the roll gaps on both sides of all rolling mills used are the same. Controlling the standard roll gap at 2 millimeters can ensure that the roll pattern is fully pressed into the surface of the steel, avoiding insufficient rib height or pitch deviation caused by too large roll gap. Adjust the consistency of the roll gaps on both sides of all rolling mills, align the guide guard with the rolling groove, and prevent the continuous casting billet from having sickle bend and uneven deformation at the head (or temperature difference) during rolling, which may cause potential hazards such as uneven deformation and bursting groove when the head of the continuous casting billet bites into the K1 roll.

[0036] After rolling starts, when the heads of the first, second, and third continuous casting billets pass through the rolling mill, temporarily turn off the cooling water of the K1 roll, K2 roll, and K3 roll for 1 - 2 seconds. The rolls will accumulate heat during hot rolling. If they suddenly come into contact with low-temperature cooling water, great thermal stress will be generated on the roll surface due to sudden cooling, resulting in the expansion of microcracks on the roll surface and ultimately causing roll chipping or spalling. Temporarily turning off the cooling water can prevent the huge impact on the rolls caused by the sudden drop in the roll surface temperature, avoid roll chipping and slipping accidents, prevent local shrinkage deformation of the rolls, affect the matching degree between the rolling groove and the rolled piece, and cause uneven rib depth. Temporarily turning off the cooling water can maintain the dimensional stability of the rolls and ensure uniform thread forming.

[0037] Step 3: Control the cross rib height of the finished product according to the middle and lower limits to produce a ribbed anchor rod of model MG500YΦ22, and the rib interval of the ribbed anchor rod is 10 millimeters.

[0038] The height of the transverse ribs of the finished product is 0.05 - 0.1 mm. When designing the pass, the inclination angle of the transverse ribs is 60º. First, the pass design with a 60º inclination angle is beneficial to balancing the rolling force and reducing the fluctuation of the rib height caused by uneven stress on the rolled piece. Second, the pass design with a 60º inclination angle enables the metal to flow evenly along the roll groove during rolling, avoiding metal accumulation or tearing of the rolled piece surface caused by too large an inclination angle. Third, the pass design with a 60º inclination angle is easier to align during roll grinding and roll change, reducing the downtime caused by pass misalignment and ensuring production continuity. The shallow groove design with a transverse rib height ≤ 0.1 mm reduces the local pressure on the roll. Combined with the optimized component force of the 60º inclination angle, it can reduce the wear at the edge of the roll groove and extend the service life of the roll.

[0039] (1) Production situation: When producing MG500Y Φ22, in the first roll groove, after passing 300 tons of steel in total, there was a slight explosion at the notch of the pass. The surface of the finished product had no pitting, the end of the transverse rib had no obvious jerks, the rib spacing was still clear and bright, and the surface gloss was bright. After changing the pass, production continued for 260 tons with a good surface and it could be used continuously.

[0040] (2) Roll groove situation: After passing 230 tons of steel in the first pass, there was a small explosion point.

[0041] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, those of ordinary skill in the art can make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions should all be within the scope covered by the present invention. / Any person familiar with the technical field of the present invention can easily think of changes or substitutions within the technical scope disclosed by the present invention, and they should all be covered within the protection scope of the present invention.

Claims

1. A method for preventing the cracking of the finished hole of the rib anchor rod, characterized in that: The steps include: Step 1: shut down the spraying device of the roughing and medium rolling mill before production; Step 2: Use the K1 roller of the Φ390 rolling mill for rolling, the starting rolling temperature is 1050-1200℃, during the rolling process, the temperature of the continuous casting billet is controlled at 900-1000℃, the speed of feeding the continuous casting billet into the rolling mill is controlled at 10-20m / min, and the number of feeding times is controlled at 1-3 times; after starting rolling, temporarily turn off the cooling water of the K1 roller to the K3 roller; Step 3: Control the height of the transverse ribs of the finished product according to the middle and lower limits.

2. A method for preventing cracking of finished holes of rib anchor rods as claimed in claim 1, characterized in that: In step 1, the roughing and medium rolling mills include 1# rolling mill, 2# rolling mill, 3# rolling mill, 4# rolling mill, 5# rolling mill, 6# rolling mill, 7# rolling mill, 8# rolling mill, 9# rolling mill, 10# rolling mill, 11# rolling mill and 12# rolling mill.

3. A method for preventing cracking of finished hole of rib anchor rod as claimed in claim 1, characterized in that: In step 2, when rolling is performed using the K1 roller of the Φ390 rolling mill, ordinary cooling water is used for cooling.

4. A method for preventing cracking of finished holes of rib anchor rods as claimed in claim 3, characterized in that: In step 2, cooling water is used to cool the looper. When the downtime exceeds 2 hours, the CP2 control system notifies the pump room to shut down all cooling tower fans and control the temperature of ordinary cooling water at 25-35℃.

5. A method for preventing cracking of finished holes of rib anchor rods as claimed in claim 1, characterized in that: In step 2, multiple units are used to work together for rolling.

6. A method for preventing cracking of finished holes of rib anchor rods as claimed in claim 1, characterized in that: In step 2, the continuous casting billet is a cylindrical steel material, the length of the continuous casting billet is 1-1.5 meters, and the diameter of the continuous casting billet is 22 millimeters.

7. A method for preventing cracking of finished holes of rib anchor rods as claimed in claim 1, characterized in that: In step 2, the standard roll gap is controlled at 1-3 mm.

8. A method for preventing cracking of finished hole of rib anchor rod as claimed in claim 1 or 6, characterized in that: In step 2, after rolling starts, when the heads of the first continuous casting billet, the second continuous casting billet and the third continuous casting billet pass through the rolling mill, the cooling water of the K1 roller to the K3 roller is temporarily turned off for 1-2 seconds.

9. A method for preventing cracking of finished holes of rib anchor rods as claimed in claim 1, characterized in that: In step 3, the height of the transverse ribs of the finished product is 0-0.1 mm, and the inclination angle of the transverse ribs is 60°.

10. A method for preventing cracking of finished holes of rib anchor rods as claimed in claim 1, characterized in that: In step three, the strength level of the finished product is any one of 335MPa, 400MPa, 500MPa and 600MPa.