Power angle steel for high-precision iron tower and production method of power angle steel

Abstract

The invention relates to electric angle steel for a high-precision iron tower and a production method thereof, and belongs to the technical field of steel for iron towers. The production method comprises the steps of steel billet heating, rolling forming, cooling, straightening, sawing and sizing and stacking. The invention further provides the electric angle steel for the iron tower prepared through the production method. According to the steel angle for the iron tower, a microalloying component system is adopted, a specific controlled rolling and controlled cooling process is matched, reduction addition of alloy elements such as Mn and V is achieved, expensive alloy is saved, meanwhile, the requirement for the steel purity (mainly inclusions in the components) is lowered, and the strength and impact toughness of the finally obtained steel angle for the iron tower can both exceed the standard requirements; and moreover, a large amount of surplus is achieved, and the production cost is greatly reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of steel for iron towers, and particularly relates to a high-precision electric power angle steel for iron towers and a production method thereof. Background Art

[0002] An angle steel tower is a plate tower with downcomers and is a type of electric power iron tower. Its bubbling area is composed of angle steels arranged side by side, and the arrangement direction of the angle steels is parallel to the liquid flow direction. The angle steel tower has the characteristics of simple structure, high strength, and good stability. Angle steel towers are widely used in various terrain environments.

[0003] During the construction of the power grid, the requirements for the dimensions, surface quality, and product performance of angle steel for iron towers are getting higher and higher. The existing production of angle steel all adopts the transverse or full continuous rolling process for rolling, and air cooling is used for cooling. There is no controlled rolling and controlled cooling process, no means for precise dimension control, and no high-precision straightening process. The assurance of product dimensions, angles, and bending is all ensured by manual measurement. The product performance is ensured by adding microalloys such as Nb, V, Ti, etc. to ensure strength and toughness, with a relatively high production cost, poor product quality assurance ability, and the low-temperature impact toughness cannot be stably qualified. The production efficiency of steelmaking and rolling is extremely low, and the smelting cost remains high. Patent CN109127724A provides a production process method for high-toughness angle steel. This method performs air-cooling treatment on the steel plate after rough and medium rolling to reduce the temperature of the steel plate when it enters the finishing mill, so that deformation-induced ferrite precipitation occurs during the finishing rolling of medium and large-sized angle steels with an angle of more than 10°, promoting the refinement of the grain size. Although Patent CN109127724A can improve the impact toughness of medium and large-sized angle steels, it does not have the effect of increasing the yield strength and tensile strength of angle steel. Summary of the Invention

[0004] Aiming at the problem that the existing production process cannot improve the yield strength and tensile strength of angle steel, the present invention provides a production method for high-precision electric power angle steel for iron towers to solve the above problems.

[0005] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a production method for high-precision electric power angle steel for iron towers, including steel billet heating, rolling into shape, cooling, straightening, sawing to a fixed length, and stacking; wherein, The chemical composition of the steel billet is one of the following: C: 0.13% - 0.19%, Mn: 1.20% - 1.45%, Si: 0.21% - 0.46%, V: 0.030% - 0.055%, S≤0.030%, P≤0.030%; the balance is Fe and unavoidable impurities.

[0006] Or, C: 0.13% - 0.19%, Mn: 1.20% - 1.45%, Si: 0.21% - 0.46%, Nb: 0.020% - 0.037%, S ≤ 0.030%, P ≤ 0.030%; the balance is Fe and inevitable impurities.

[0007] Or, C 0.13% - 0.19%, Mn: 1.25% - 1.65%, Si: 0.21% - 0.46%, V: 0.050% - 0.085%, S ≤ 0.030%, P ≤ 0.030%; the balance is Fe and inevitable impurities.

[0008] Or, C: 0.13% - 0.19%, Mn: 1.02% - 1.40%, Si: 0.21% - 0.46%, S ≤ 0.035%, P ≤ 0.035%; the balance is Fe and inevitable impurities.

[0009] Or, C: 0.14% - 0.20%, Mn: 1.20% - 1.40%, Si: 0.21% - 0.46%, S ≤ 0.035%, P ≤ 0.035%; the balance is Fe and inevitable impurities.

[0010] The rolling forming step is as follows: adopt double BD rolling + four - stand finishing rolling. The starting rolling temperature of BD1 is 970 °C - 1150 °C, rolling for 3 - 5 passes; BD2 rolls for 3 passes, and the final rolling temperature of BD2 is 900 °C - 1000 °C. Before finishing rolling, control the entry temperature of the finishing mill to be 800 °C - 900 °C and then roll, rolling for 4 passes, and the final rolling temperature of the finishing mill is 840 °C - 900 °C.

[0011] The cooling step is as follows: adopt an ultra - fast cooling device. After cooling, the temperature of the angle steel is 600 °C - 700 °C. Use the walking - beam natural cooling in the front section of the cooling bed to cool to 450 °C - 550 °C, and use the walking - beam spray cooling + forced air cooling in the rear section of the cooling bed to cool to 80 °C - 100 °C.

[0012] The straightening step is as follows: use double straightening machines alternately. For angles with a size of ∠14° and below, use a φ800 straightening machine; for angles with a size of ∠16° and above, use a 1050 straightening machine. The diameter of the lower straightening rolls increases from small to large, with a diameter difference ≤ 5 mm, and the diameter of the upper straightening rolls decreases from large to small, with a diameter difference ≤ 40 mm.

[0013] Further, the steel billet heating steps are as follows: control the temperature of the first heating section at 790 °C - 1080 °C, the furnace pressure of the first heating section at 25 ± 10 Pa, the temperature of the second heating section at 1030 °C - 1300 °C, the furnace pressure of the second heating section at 30 ± 10 Pa, the temperature of the soaking section at 1030 °C - 1290 °C, the furnace pressure of the soaking section at 35 ± 10 Pa, and the temperature of the steel billet when it leaves the furnace at 970 °C - 1150 °C; Further, the sawing and sizing steps are as follows: adopt grouped row sawing, position the steel by a high-precision sizing machine, adjust the moving saw and the moving roller table, make the fixed saw and the moving saw run synchronously, the sizing length starts from 6 meters and increases by 0.1 meters to 12.5 meters, the deviation of sawing and sizing is within +20 mm - +30 mm, the cutting skew ≤ 2 mm, and the height of the sawing burr ≤ 5 mm; Further, the stacking steps are as follows: adopt a fully automatic stacker and stack in a positive and negative alternating pattern of 2 + 1 or 3 + 2 or 4 + 3.

[0014] Further, in the steel billet heating steps, the heating time is 60 - 70 min.

[0015] Further, in the rolling and forming steps, the finishing rolling speed is 0.9 - 3 m / s.

[0016] Further, in the cooling steps, 7 groups of ultra-fast cooling devices are arranged intermittently, the main pipe pressure is 7 - 12 bar, the flow rate is 700 - 1000 m 3 / h, the fast cooling water pumps operate in a double-pump mode and the frequency is 35 - 50 Hz, and the speed of the ultra-fast cooling roller table is 5% - 10% higher than the rolling speed.

[0017] Further, in the straightening steps, the straightening temperature ≤ 100 °C, the straightening speed is 1 - 4 m / s, the dimensional accuracy of rolling: the deviation of the leg length dimension is ±1.5 mm or ±2 mm, the angle deviation after straightening is ±35′, and the camber deviation ≤ 0.25%.

[0018] In the second aspect, the present invention provides a power angle steel for iron towers prepared by using the above production method.

[0019] Further, the grain size grade of the power angle steel for iron towers reaches above grade 8, the yield strength is between 485 - 525 MPa or 375 - 440 MPa, the tensile strength is between 550 - 650 MPa or 500 - 600 MPa, the longitudinal impact toughness is 70 - 110 J, the elongation after fracture > 22%, and preferably, the elongation after fracture > 23%.

[0020] The beneficial effects of the present invention are as follows: The 1+1+X process layout rolling mill layout and high-precision profiler detection means provided by the present invention are used to straighten different models on different straightening machines. The final angle steel for iron towers obtained has dimensional accuracy, camber, and angle within the standard range and small fluctuations.

[0021] The present invention provides a microalloying composition system, combined with a specific controlled rolling and controlled cooling process, to achieve a reduction in the addition of alloying elements such as Mn and V, saving expensive alloys. At the same time, the requirement for the steel purity (mainly inclusions in the composition) is reduced. The strength and impact toughness of the final angle steel for iron towers can exceed the standard requirements, with a large margin, and the production cost is greatly reduced.

[0022] The composition and process design of the angle steel for iron towers of the present invention are reasonable, the production control and process system are loose, and stable production can be achieved. Calculated based on an annual production of 500,000 tons of angle steel for power iron towers, the benefit per ton of steel is more than 200 yuan, and the annual benefit can reach more than 100 million yuan, with high economic benefits. At the same time, the production process is simple, with less energy consumption, green and low-carbon, and has positive social benefits. Detailed implementation manners

[0023] 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 of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0024] Embodiment 1 A high-precision angle steel for power iron towers (angle steel for power iron towers of Southern Power Grid Q355C∠160×10) is produced according to the following production process method: (1) Steel billet composition Using the converter high-efficiency smelting technology, a qualified 180 mm×220 mm rectangular billet of Q355C is obtained, with chemical components of C 0.16%, Si 0.31%, Mn 1.16%, P 0.025%, S 0.016%, and the balance being Fe and unavoidable impurities.

[0025] (2) Steel billet heating Control the temperature of the first heating section to 1000 °C, the furnace pressure of the first heating section to 22 Pa, the temperature of the second heating section to 1180 °C, the furnace pressure of the second heating section to 24 Pa, the temperature of the soaking section to 1150 °C, the furnace pressure of the soaking section to 26 Pa. The steel billet is heated for 63 minutes, and the tapping temperature of the steel billet is 1000 °C.

[0026] (3) Rolling and forming Rolled equal-leg angle steel ∠160×10, using double BD rolling + four-stand finishing rolling. The starting rolling temperature of BD1 is 1000 °C, rolling for 5 passes, turning the steel once in front of the mill, and passing through two 90° steel turnings during the rolling process. BD2 rolls for 3 passes, the final rolling temperature of BD2 is 950 °C, the entrance temperature of the finishing mill is 900 °C, rolling for 4 passes, the final rolling temperature of the finishing mill is 850 °C, and the rolling speed is controlled at 1.8 m / s during the finishing rolling process.

[0027] (4)Cooling Adopt an ultra-fast cooling device, control the main pipe pressure to be 10.5 bar, the flow rate to be 830 m 3 / h, the number of pumps started is 2, the frequency is 42 Hz, the speed of the ultra-fast cooling roller table is 1.95 m / s, the temperature of the angle steel after cooling is 670 °C, the front section of the cooling bed steps and cools naturally to 520 °C, the temperature is 85 °C after spray cooling, and the temperature when leaving the cooling bed is 76 °C.

[0028] Detect the grain size and mechanical properties of the Q355C tower power angle steel obtained in Example 1. The grain size grade of the angle steel is 8.5, the yield strength is 420 MPa, the tensile strength is 560 MPa, the longitudinal impact toughness at 0 °C is 105 J, and the elongation after fracture is 24%.

[0029] (5)Straightening Straighten using a 1050 straightening machine, the straightening speed is 2 m / s. The diameters of the lower straightening rolls from No. 1 to No. 5 are 979 mm, 980mm, 980.5 mm, 981 mm, 982 mm respectively, and the diameters of the upper straightening rolls from No. 1 to No. 5 are 995 mm, 990 mm, 985 mm, 983 mm, 980 mm respectively.

[0030] Detect the dimensions, angles, and cambers of the Q355C tower power angle steel obtained in Example 1. The leg lengths of the angle steel are 160.87mm / 160.92 mm, the leg thicknesses are 10.32 mm / 10.45 mm; the angle is 90°25′; the camber is 0.12%.

[0031] (6)Sawing Use a marshalling trolley and a marshalling bench to group the straightened tower power angle steel into groups of 4. The fixed-length machine is positioned at 8.7 meters, and at the same time, adjust the position of the moving saw, and the fixed saw and the moving saw run simultaneously for sawing and segmenting.

[0032] Measure the length, burr height, and sawing skew of the Q355C tower power angle steel obtained in Example 1. The fixed-length of the angle steel is 8.72 meters, the burr height is 2 mm, and the sawing skew is 1 mm.

[0033] (7)Stacking Stacked into bundles according to the stacking pattern of 2+(2+1) by a fully automatic palletizer. The number of pieces stacked in a single bundle is 23, the number of layers is 15, the size of the bundle after stacking is 453 mm×311 mm, and the weight of a single bundle is 4.948 t.

[0034] Example 2 A kind of high-precision electric power angle steel for iron towers (electric power angle steel for State Grid Q420C∠180×14 iron towers) is produced according to the following production process method: (1) Billet composition Adopt the converter high-efficiency smelting technology to obtain a qualified 220 mm×290 mm rectangular billet of Q420C. The chemical composition is C: 0.17%, Mn: 1.35%, Si: 0.30%, V: 0.061%, S: 0.012%, P: 0.020%; the balance is Fe and inevitable impurities.

[0035] (2) Billet heating Control the temperature of the first heating section to be 1080 °C, the furnace pressure of the first heating section to be 20 Pa, the temperature of the second heating section to be 1265 °C, the furnace pressure of the second heating section to be 25 Pa, the temperature of the soaking section to be 1270 °C, the furnace pressure of the soaking section to be 30 Pa. The billet is heated for 105 min, and the tapping temperature of the billet is 1085 °C.

[0036] (3) Rolling and forming Roll the ∠180×14 equal-angle steel. Adopt double BD rolling + four-stand finishing rolling. The starting rolling temperature of BD1 is 1085 °C, rolling for 5 passes, turning the steel once in front of the mill, and the steel is turned 90° twice during the rolling process. BD2 rolls for 3 passes, the final rolling temperature of BD2 is 985 °C, the entry temperature of the finishing mill is 879 °C, rolling for 4 passes, the final rolling temperature of the finishing mill is 863 °C, and the rolling speed is controlled at 1.41 m / s during the rolling process of the finishing mill.

[0037] (4) Cooling Adopt an ultra-fast cooling device, control the main pipe pressure to be 9.2 bar, the flow rate to be 824 m 3 / h, the number of pump units started is 2, the frequency is 42 Hz, the speed of the ultra-fast cooling roller table is 1.65 m / s, the temperature of the angle steel after cooling is 681 °C, the front section of the cooling bed steps and cools naturally to 485 °C, and the temperature is 86 °C after spray cooling, and the temperature of the lower cooling bed is 75 °C.

[0038] The grain size and mechanical properties of the Q420C electric power angle steel for iron towers obtained in Example 2 are detected. The grain size grade of the angle steel is 9.5, the yield strength is 505 MPa, the tensile strength is 638 MPa, the longitudinal impact toughness at 0 °C is 83 J, and the elongation after fracture is 24%.

[0039] (5) Straightening Straightened by a 1050 straightening machine with a straightening speed of 1.6 m / s. The diameters of the lower straightening rolls from No. 1 to No. 5 are 969 mm, 971 mm, 973 mm, 973.5 mm, and 974 mm respectively, and the diameters of the upper straightening rolls from No. 1 to No. 5 are 985 mm, 985 mm, 984.5 mm, 984 mm, and 983 mm respectively.

[0040] The dimensions, angles, and cambers of the Q420C power angle steel for iron towers obtained in Example 2 were measured. The leg lengths of the angle steel are 180.18 mm / 180.24 mm, the leg thicknesses are 13.86 mm / 13.89 mm; the angle is 90.2°; the camber is 0.08%.

[0041] (6) Sawing The straightened power angle steel for iron towers was grouped into bundles of 4 by using a grouping trolley and a grouping bench. The length sizing machine was positioned at the 9-meter position. At the same time, the position of the movable saw was adjusted, and the fixed saw and the movable saw ran simultaneously for sawing and segmenting.

[0042] The length, burr height, and sawing skew of the Q420C power angle steel for iron towers obtained in Example 2 were measured. The specified length of the angle steel is 9.02 meters, the burr height is 1.8 mm, and the sawing skew is 0.5 mm.

[0043] (7) Stacking Stacked into bundles according to the stacking rule of 2 + (2 + 1) by using a fully automatic stacking machine. The number of angle steels in a single bundle is 20, the number of layers is 13. After stacking, the bundle size is 535 mm × 332 mm, and the weight of a single bundle is 5.308 t.

[0044] Example 3 A high-precision power angle steel for iron towers (power angle steel for South Grid Q420B ∠125 × 10 iron towers) is produced according to the following production process: (1) Steel billet composition Adopt converter high-efficiency smelting technology to obtain a qualified 165 mm × 165 mm rectangular billet of Q420B. The chemical composition is C: 0.16%, Mn: 1.29%, Si: 0.28%, V: 0.045%, S: 0.018%, P: 0.022%; the balance is Fe and unavoidable impurities.

[0045] (2) Steel billet heating Control the temperature of the first heating section to be 905 °C, the furnace pressure of the first heating section to be 22 Pa, the temperature of the second heating section to be 1150 °C, the furnace pressure of the second heating section to be 23 Pa, the temperature of the soaking section to be 1180 °C, the furnace pressure of the soaking section to be 28 Pa. The steel billet is heated for 85 minutes, and the tapping temperature of the steel billet is 1040 °C.

[0046] (3)Rolling forming Roll angle steel ∠125×10 equal angle steel, using double BD rolling + four - stand finishing rolling. The starting rolling temperature of BD1 is 1040 °C, rolling for 3 passes, turning the steel 180° in front of the mill, without turning the steel during the rolling process. BD2 rolls for 3 passes, the final rolling temperature of BD2 is 990 °C, the entry temperature of the finishing mill is 890 °C, rolling for 4 passes, the final rolling temperature of the finishing mill is 878 °C, and the rolling speed during the finishing rolling process is controlled at 2.0 m / s.

[0047] (4)Cooling Adopt an ultra - fast cooling device, control the main pipe pressure at 8.7 bar, the flow rate at 795 m 3 / h, the number of pump units in operation is 2, the frequency is 39 Hz, the speed of the ultra - fast cooling roller table is 2.25 m / s, the temperature of the angle steel after cooling is 676 °C, the front section of the cooling bed steps for natural cooling to 488 °C, the temperature is 75 °C after spray cooling, and the temperature when leaving the cooling bed is 43 °C.

[0048] Detect the grain size and mechanical properties of the Q420B power angle steel for tower obtained in Example 3. The grain size grade of the angle steel is 9.0, the yield strength is 495 MPa, the tensile strength is 635 MPa, the longitudinal impact toughness at 20 °C is 96 J, and the elongation after fracture is 25%.

[0049] (5)Straightening Adopt an 800 straightening machine for straightening, the straightening speed is 3 m / s. The diameters of the lower straightening rolls from No. 1 to No. 5 are 765 mm, 766 mm, 766 mm, 766.5 mm, and 768 mm respectively, and the diameters of the upper straightening rolls from No. 1 to No. 5 are 755 mm, 753 mm, 753 mm, 952 mm, and 952 mm respectively.

[0050] Detect the dimensions, angles, and cambers of the Q420B ∠125×10 power angle steel for tower obtained in Example 3. The leg lengths of the angle steel are 125.86 mm / 125.92 mm, the leg thicknesses are 10.24 mm / 10.30 mm; the angle is 90.2°; the camber is 0.13%.

[0051] (6)Sawing Use a marshalling trolley and a marshalling bench to group the straightened power angle steel for tower into groups of 6. The length - setting machine is positioned at the 11.5 - meter position, and at the same time, adjust the position of the moving saw. The fixed saw and the moving saw run simultaneously for sawing and segmenting.

[0052] Measure the length, burr height, and sawing skew of the Q420B power angle steel for tower obtained in Example 3. The specified length of the angle steel is 11.525 meters, the burr height is 1.5 mm, and the sawing skew is 1 mm.

[0053] (7) Palletizing Using a fully automatic palletizer, bales are formed according to the palletizing rule of 3+(3+2). The number of pieces in a single bale is 23, the number of layers is 9, the size of the bale after palletizing is 552 mm×215 mm, and the weight of a single bale is 5.061 t.

[0054] Example 4 A kind of high-precision electric power angle steel for iron towers (electric power angle steel for iron towers of national standard Q355B ∠140×12) is produced according to the following production process method: (1) Steel billet composition Adopting the converter efficient smelting technology, a qualified 180 mm×220 mm rectangular billet of Q355B is obtained, and the chemical composition is C: 1.17%, Mn: 1.05%, Si: 0.32%, S: 0.025%, P: 0.28%; the balance is Fe and inevitable impurities.

[0055] (2) Steel billet heating Controlling the temperature of the first heating section to be 1010 °C, the furnace pressure of the first heating section to be 19 Pa, the temperature of the second heating section to be 1125 °C, the furnace pressure of the second heating section to be 21 Pa, the temperature of the soaking section to be 1145 °C, the furnace pressure of the soaking section to be 26 Pa, heating the steel billet for 90 min, and the tapping temperature of the steel billet to be 1035 °C.

[0056] (3) Rolling and forming Rolling ∠140×12 equal-angle steel, adopting double BD rolling + four-stand finishing rolling. The starting rolling temperature of BD1 is 1035 °C, rolling 5 passes, 180° steel turning once in front of the mill, and the steel turning process passes through two 90° steel turnings. BD2 rolls 3 passes, the final rolling temperature of BD2 is 905 °C, the entry temperature of the finishing mill is 860 °C, rolling 4 passes, the final rolling temperature of the finishing mill is 850 °C, and the rolling speed is controlled to be 1.6 m / s during the rolling process of the finishing mill.

[0057] (4) Cooling Using an ultra-fast cooling device, controlling the main pipe pressure to be 8.9 bar, the flow rate to be 820 m 3 / h, the number of pump units started is 2, the frequency is 41 Hz, the speed of the ultra-fast cooling roller table is 1.75 m / s, the temperature of the angle steel after cooling is 670 °C, the front section of the cooling bed steps and cools naturally to 467 °C, the temperature is 82 °C after spray cooling, and the temperature of getting off the cooling bed is 53 °C.

[0058] The grain size and mechanical properties of the electric power angle steel for the South China Grid Q355B ∠140 × 12 tower obtained in Example 4 were detected. The grain size grade of the angle steel was 9.5, the yield strength was 415 MPa, the tensile strength was 585 MPa, the longitudinal impact toughness at 20 °C was 115 J, and the elongation after fracture was 25%.

[0059] (5)Straightening An 800 straightening machine was used for straightening, with a straightening speed of 2.5 m / s. The diameters of the lower straightening rolls from No. 1 to No. 5 were 772 mm, 773 mm, 773.5 mm, 774.5 mm, and 775 mm respectively, and the diameters of the upper straightening rolls from No. 1 to No. 5 were 768 mm, 767 mm, 767 mm, 766.5 mm, and 765 mm respectively.

[0060] The dimensions, angles, and cambers of the electric power angle steel for the South China Grid Q355B ∠140×12 tower obtained in Example 4 were detected. The leg lengths of the angle steel were 141.02 mm / 140.96 mm, the leg thicknesses were 12.28 mm / 12.32 mm; the angle was 90.3°; the camber was 0.12%.

[0061] (6)Sawing The straightening electric power angle steel for the tower was grouped into bundles of 5 by using a marshalling trolley and a marshalling gantry. The sizing machine was positioned at 8.5 meters, and at the same time, the position of the moving saw was adjusted, and the fixed saw and the moving saw ran simultaneously for sawing and segmenting.

[0062] The length, burr height, and sawing skew of the electric power angle steel for the South China Grid Q355B ∠ 140 × 12 tower obtained in Example 4 were measured. The specified length of the angle steel was 8.52 meters, the burr height was 2 mm, and the sawing skew was 1 mm.

[0063] (7)Stacking An automatic stacking machine was used to stack them into bundles according to the stacking rule of 3+(3+2). The number of angle steels in a single bundle was 23, the number of layers was 15, the size of the bundle after stacking was 600 mm×315 mm, and the weight of a single bundle was 4.99 t.

[0064] Example 5 A kind of high-precision electric power angle steel for tower (electric power angle steel for national standard ∠ 140 × 10 tower) was produced according to the following production process method: (1)Steel billet composition By using the converter high-efficiency smelting technology, a qualified 180 mm×220 mm rectangular billet of Q420B was obtained, and the chemical composition was C: 0.17%, Mn: 1.29%, Si: 0.29%, Nb: 0.035%, S: 0.016%, P: 0.020%; the balance was Fe and unavoidable impurities.

[0065] (2)Billet heating Control the temperature of the first heating section at 990 °C, the furnace pressure of the first heating section at 20 Pa, the temperature of the second heating section at 1120 °C, the furnace pressure of the second heating section at 21 Pa, the temperature of the soaking section at 1135 °C, the furnace pressure of the soaking section at 28 Pa. The billet is heated for 105 minutes, and the billet discharge temperature is 1030 °C.

[0066] (3)Rolling and forming Roll the equal - angle steel ∠140×10. Adopt double BD rolling + four - stand finishing rolling. The starting rolling temperature of BD1 is 1030 °C, and it is rolled for 5 passes. The steel is turned over 180° once in front of the machine, and the steel is turned over 90° twice during the rolling process. BD2 is rolled for 3 passes, the final rolling temperature of BD2 is 900 °C, the entrance temperature of the finishing mill is 850 °C, and it is rolled for 4 passes. The final rolling temperature of the finishing mill is 840 °C. During the rolling process of the finishing mill, control the rolling speed at 1.8 m / s.

[0067] (4)Cooling Adopt an ultra - fast cooling device. Control the main pipe pressure at 8.9 bar, the flow rate at 842 m 3 / h, the number of pumps started is 2, the frequency is 42 Hz, the speed of the ultra - fast cooling roller table is 1.92 m / s. The temperature of the angle steel after cooling is 680 °C. The front section of the cooling bed steps and cools naturally to 456 °C, and the temperature is 90 °C after spray cooling, and the temperature when leaving the cooling bed is 60 °C.

[0068] Detect the grain size and mechanical properties of the national standard Q420B ∠140×10 power angle steel for towers obtained in Example 5. The grain size grade of the angle steel is 9.5, the yield strength is 515 MPa, the tensile strength is 640 MPa, the longitudinal impact toughness at 20 °C is 102 J, and the elongation after fracture is 24%.

[0069] (5)Straightening Adopt an 800 - type straightening machine for straightening. The straightening speed is 2.5 m / s. The diameters of the lower straightening rolls from No. 1 to No. 5 are 772 mm, 773 mm, 773.5 mm, 774.5 mm, 775 mm respectively, and the diameters of the upper straightening rolls from No. 1 to No. 5 are 768 mm, 767 mm, 767 mm, 766.5 mm, 765 mm respectively.

[0070] Detect the size, angle, and camber of the national standard Q420B ∠140×10 power angle steel for towers obtained in Example 5. The leg length size of the angle steel is 140.13 mm / 140.08 mm, the leg thickness size is 9.34 mm / 9.28 mm; the angle is 90.2°; the camber is 0.11%.

[0071] (6) Sawing Use the marshalling trolley and marshalling gantry to group the straightened power angle steel for the iron tower into groups of 5. The sizing machine is positioned at the 12-meter position. At the same time, adjust the position of the moving saw, and the fixed saw and the moving saw run simultaneously for sawing and segmentation.

[0072] Measure the length, burr height, and cutting skew of the national standard Q420B ∠140×10 power angle steel for the iron tower obtained in Example 5. The specified length of the angle steel is 12.022 meters, the burr height is 1.5 mm, and the sawing skew is 0.5 mm.

[0073] (7) Stacking Use a fully automatic stacking machine to stack into bundles according to the stacking rule of 2+(2 + 1). The number of pieces stacked in a single bundle is 20, the number of layers is 13, the size of the stacked bundle is 400 mm×235 mm, and the weight of a single bundle is 5.157 t.

[0074] Comparative Example Prepare a batch of power angle steel (∠200×200×24) for the iron tower according to the method disclosed in Patent CN109127724A. The specific method is as follows: (1) Chemical composition: C: 0.16%, Mn: 1.32%, Si: 0.42%, V: 0.042%, S: 0.030%, P: 0.030%.

[0075] (2) Rolling process: Rolling mill speed setting: The rolling speed of the finished product K1 rolling mill is set to 1.0 m / s, the rolling speed of the I-frame 750 rolling mill is set to 3.5 m / s, and the rolling speed of the II-frame rolling mill is set to 4.0 m / s.

[0076] The reheating furnace heats the billet to a high temperature of 1140 °C~1180 °C, rolls 5 passes (rough rolling) on the I-frame 750 two-high reversing rolling mill, and 3 passes (medium rolling) on the II-frame 750 two-high reversing rolling mill. Then stop at the transfer roller table between the finishing mill and the II-frame 750 rolling mill for 2.5~3 minutes. When the online pyrometer detects that the temperature at the front end of the steel drops below 850 °C, the PLC control system automatically starts the transfer roller table and sends the rolled piece into the 4-frame finishing mill for 4 passes. The final rolling temperature of the finished product after leaving the rolling mill reaches 780 °C~830 °C.

[0077] The entire rolling rhythm is set to 260 seconds.

[0078] The grain size and mechanical properties of the electric power angle steel (∠200 × 200 × 24) for iron towers produced in the comparative example were detected. The grain size grade of the angle steel was 8.5, the yield strength was 470 MPa, the tensile strength was 653 MPa, the longitudinal impact toughness at 0 °C was 82 J, and the elongation after fracture was 23%. The angle steels prepared in Examples 1 to 5 had finer grain sizes than those in the comparative example, and the yield strength, tensile strength, impact toughness, and elongation after fracture were all significantly improved, mainly because the in-furnace time was shortened, the rolling start temperature was reduced, the ultra-fast cooling pressure was increased, and the cooling intensity was increased.

[0079] 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 of the present invention. / Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered by the protection scope of the present invention.

Claims

1. A method for producing high-precision electric angle steel for iron tower, characterized in that: The process includes heating, rolling, cooling, straightening, sawing, sizing and stacking of steel billets; wherein: The chemical composition of the steel billet is one of the following: C: 0.13%~0.19%, Mn: 1.20%~1.45%, Si: 0.21%~0.46%, V: 0.030%~0.055%, S≤0.030%, P≤0.030%; the balance is Fe and unavoidable impurities; Or, C: 0.13%~0.19%, Mn: 1.20%~1.45%, Si: 0.21%~0.46%, Nb: 0.020%~0.037%, S≤0.030%, P≤0.030%; the balance is Fe and unavoidable impurities; Or, C 0.13%~0.19%, Mn: 1.25%~1.65%, Si: 0.21%~0.46%, V: 0.050%~0.085%, S≤0.030%, P≤0.030%; the balance is Fe and unavoidable impurities; Or, C: 0.13%~0.19%, Mn: 1.02%~1.40%, Si: 0.21%~0.46%, S≤0.035%, P≤0.035%; the balance is Fe and unavoidable impurities; Or, C: 0.14%~0.20%, Mn: 1.20%~1.40%, Si: 0.21%~0.46%, S≤0.035%, P≤0.035%; the balance is Fe and unavoidable impurities; The rolling forming steps are: double BD rolling + four-pass finishing rolling, BD1 starting rolling temperature is 970℃~1150℃, rolling 3~5 times, BD2 rolling 3 times, BD2 final rolling temperature is 900℃~1000℃, before finishing rolling, the finishing inlet temperature is controlled to be 800℃~900℃ before rolling; rolling 4 times, the finishing final rolling temperature is 840℃~900℃; The cooling steps are as follows: using an ultra-fast cooling device, the angle steel temperature after cooling is 600 ℃ ~ 700 ℃, using the front section of the cooling bed for step-by-step natural cooling to 450 ℃ ~ 550 ℃, and using the back section of the cooling bed for step-by-step spray cooling + forced air cooling to 80 ℃ ~ 100 ℃; The straightening steps are as follows: use double straightening machines alternately, use φ800 straightening machine for models of ∠14° and below, use 1050 straightening machine for models of ∠16° and above, the diameter of the lower straightening roller is from small to large, the diameter difference is ≤5 mm, the diameter of the upper straightening roller is from large to small, the diameter difference is ≤40 mm.

2. The method for producing a high-precision electric angle steel for an iron tower as claimed in claim 1, characterized in that: The billet heating steps are as follows: control the temperature of the first heating stage to 790 ℃ ~ 1080 ℃, the furnace pressure of the first heating stage to 25±10 Pa, the temperature of the second heating stage to 1030 ℃ ~ 1300 ℃, the furnace pressure of the second heating stage to 30±10 Pa, the temperature of the soaking section to 1030 ℃ ~ 1290 ℃, the furnace pressure of the soaking section to 35±10 Pa, and the billet out-of-furnace temperature to 970 ℃ ~ 1150 ℃.

3. The method for producing a high-precision electric angle steel for an iron tower as claimed in claim 1, characterized in that: The sawing and sizing steps are as follows: use grouped row sawing, use high-precision sizing machine to locate the steel position, adjust the mobile saw and mobile roller, the fixed saw and mobile saw run synchronously, the sizing length increases from 6 meters to 12.5 meters by 0.1 meters, the sawing sizing deviation is +20 mm~+30 mm, the cutting bevel is ≤2 mm, and the sawing burr height is ≤5 mm.

4. The method for producing a high-precision electric angle steel for an iron tower as claimed in claim 1, characterized in that: The palletizing steps are as follows: use a fully automatic palletizer to palletize alternately in forward and reverse directions according to 2+1, 3+2 or 4+3.

5. The method for producing a high-precision electric angle steel for an iron tower as claimed in claim 1, characterized in that: In the billet heating step, the heating time is 60~70 min.

6. The method for producing a high-precision electric angle steel for an iron tower as claimed in claim 1, characterized in that: In the rolling forming step, the finishing rolling speed is 0.9~3 m / s.

7. The method for producing a high-precision electric angle steel for an iron tower as claimed in claim 1, characterized in that: In the cooling step, 7 groups of ultrafast cooling devices are arranged intermittently, with a total pipe pressure of 7-12 bar and a flow rate of 700-1000 m 3 / h, the fast cooling water pump runs in pairs and the frequency is 35~50 Hz, and the ultra-fast cooling roller speed is 5%~10% higher than the rolling speed.

8. The method for producing a high-precision electric angle steel for an iron tower as claimed in claim 1, characterized in that: In the straightening step, the straightening temperature is ≤100 °C, the straightening speed is 1~4 m / s, the rolling size accuracy leg length size deviation is ±1.5 mm or ±2 mm, the angle deviation after straightening is ±35′, and the curvature deviation is ≤0.25%.

9. An electric angle steel for an iron tower prepared by using the production method of high-precision electric angle steel for an iron tower as claimed in claim 1.

10. The power angle steel for iron tower according to claim 9, characterized in that: The grain size grade of power angle steel for tower is >8, the yield strength is 485~525 MPa or 375~440 MPa, the tensile strength is 550~650 MPa or 500~600 MPa, the longitudinal impact toughness is 70~110 J, and the elongation after fracture is >22%.