A method of hot sawing low alloy round steel

Abstract

The present application relates to the technical field of metal smelting, and relates to a high-temperature sawing method of hot-rolled low-alloy round steel, after rolling and flying shear treatment of the hot-rolled low-alloy round steel are completed, the hot-rolled low-alloy round steel is sawed, and the sawing control parameters are as follows: the sawing temperature of the round steel is controlled to be less than 700 DEG C, the tooth shape parameters of the metal saw tooth are as follows: the tooth pitch is 16-17 mm, the tooth number is 340-350, and the wedge angle is 55-65 DEG; and the sawing speed is controlled to be 30 mm / s, and the control range is 55%-65%. Through a series of process improvement measures such as reducing the sawing temperature of the round steel surface, optimizing the metal saw tooth shape parameters and reducing the sawing speed, the generation of the round steel end edge is improved, the generation of the round steel end edge of the hot-rolled low-alloy steel is effectively improved, the sawing time is prolonged, the replacement frequency of the metal saw blade is reduced, the production operation efficiency is improved, the batch production of the product is facilitated, and the production cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of metal smelting technology, and more specifically, to a high-temperature sawing method for hot-rolled low-alloy round steel. Background Technology

[0002] The composition of hot-rolled low-alloy round steel is: carbon 0.18-0.23%, silicon 0.17-0.37%, manganese 0.55-0.9%, chromium 0.85-1.25%, molybdenum 0.35-0.45%, copper ≤0.2%, nickel ≤0.3%, sulfur ≤0.02%, phosphorus ≤0.025%, etc., with the balance being iron. This low-alloy steel not only needs to have good strength and toughness, withstand impact, bending and contact forces, but also needs to have small deformation, high precision and low noise. This steel is widely used in automobiles, railways, ships, engineering machinery and wind power as a special alloy steel.

[0003] This hot-rolled low-alloy steel round bar has high strength but relatively poor thermal conductivity, making it more prone to heat accumulation during sawing. When Ø100-Ø150 round bars are segmented using a metal saw, molten edges easily form at the ends. The essence of molten edges is that the heat generated by the friction between the saw teeth and the material cannot be dissipated in time, causing the metal temperature at the cut edge to rise to a melting or semi-molten state, and then being pressed against the cut edge by the saw blade. During high-temperature sawing, this hot-rolled low-alloy steel round bar experiences high resistance and generates a large amount of sawing heat. Its poor thermal conductivity makes heat difficult to dissipate, easily accumulating in the cut area and forming molten edges. After sawing 70 tons of this hot-rolled low-alloy steel round bar in less than 60 minutes, the metal saw blade had to be replaced due to molten edges exceeding the standard requirements. Each metal saw blade replacement takes 35 minutes, and the cost of saw blades per ton of steel exceeds 25 yuan. The severe molten edges during sawing lead to short sawing times and frequent metal saw blade replacements, severely restricting the mass production of this product. Therefore, it is necessary to propose a high-temperature sawing method for hot-rolled low-alloy steel round bars. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a high-temperature sawing method for hot-rolled low-alloy steel. By adopting a series of process improvement measures, such as reducing the sawing temperature of the round steel surface, optimizing the metal saw tooth profile parameters, and reducing the feed speed, the method improves the formation of molten edges at the ends of the round steel. This effectively reduces the formation of molten edges at the ends of the hot-rolled low-alloy steel round steel, extends the sawing time, reduces the frequency of metal saw blade replacement, improves production efficiency, facilitates mass production of the product, and reduces production costs.

[0005] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A high-temperature sawing method for hot-rolled low-alloy steel bars involves sawing the hot-rolled low-alloy steel bars after rolling and flying shearing. The sawing control parameters are as follows: Control the sawing temperature of round steel to <700℃; The tooth profile parameters for controlling the metal saw teeth are: tooth pitch of 16-17 mm, number of teeth of 340-350, and wedge angle of 55-65°. Control the feed speed of the saw to 55%-65% of 30 mm / s.

[0006] In one embodiment, the round steel in the grouping area is held for 2-4 minutes when it enters the metal saw cutting area.

[0007] In one embodiment, the sawing temperature of the round steel is controlled at 600-700°C.

[0008] In one embodiment, the tooth pitch is 16.51 mm.

[0009] In one embodiment, the number of teeth is 342.

[0010] In one embodiment, the wedge angle is 60°.

[0011] In one embodiment, the target temperature for homogenization during the heating stage of the hot-rolled low-alloy round is 1200°C.

[0012] In one embodiment, during the preparation of hot-rolled low-alloy steel balls, the cooling water flow rate is controlled to be 170-190 m³ / h during rough rolling. 3 / h.

[0013] In one embodiment, during the preparation of the hot-rolled low-alloy round, the intermediate rolling and finishing rolling temperatures are both ≥900°C.

[0014] In summary, the present invention has the following beneficial effects: This invention improves the formation of molten edges at the ends of round steel bars by adopting a series of process improvements, such as reducing the sawing temperature of the round steel surface, optimizing the metal saw tooth profile parameters, and reducing the feed speed. After implementation, the sawing time can reach 200 minutes to saw more than 230 tons of hot-rolled low-alloy steel round steel bars, and the saw blade consumption per ton of steel is less than 7 yuan. This invention effectively improves the formation of molten edges at the ends of hot-rolled low-alloy steel round steel bars, extends the sawing time, reduces the frequency of metal saw blade replacement, improves production efficiency, facilitates the mass production of this product, reduces production costs, and enhances the market competitiveness of special steel. This invention can be promoted and applied in similar production lines of high-quality special steel. Detailed Implementation

[0015] The present invention will now be described in detail with reference to the embodiments.

[0016] This invention proposes a high-temperature sawing method for hot-rolled low-alloy steel bars, employing a series of process improvements such as reducing the sawing temperature on the steel surface, optimizing the metal saw tooth profile parameters, and reducing the feed speed to mitigate the formation of molten edges. The specific improvements are as follows: The sawing temperature of the round steel is controlled at 600-700℃. Preferably, the round steel in the grouping area is held for 2-4 minutes when it enters the metal sawing area to ensure that the surface temperature of the round steel entering the metal sawing area is below 700℃, i.e., <700℃. Lowering the sawing temperature requires higher heat to produce a melted edge, thus reducing the formation of melted edges. In existing processes, the sawing temperature of the round steel exceeds 700℃, generally 700-950℃. The higher round steel temperature promotes the formation of melted edges. Moreover, the round steel in the grouping area is not held before entering the metal sawing area and is directly sawn, resulting in a high surface temperature and easy formation of melted edges.

[0017] The tooth profile parameters of the metal saw teeth are controlled as follows: tooth pitch of 16-17 mm, number of teeth of 340-350, and wedge angle of 55-65°. Preferably, the tooth pitch is 16.51 mm, the number of teeth is 342, and the wedge angle is 60°. This invention uses metal saw teeth with a larger number of teeth. Fewer teeth mean fewer teeth participating in cutting simultaneously, resulting in a very high load on each tooth. This generates enormous cutting heat that cannot be quickly dissipated through the tooth body, causing the tooth tip temperature to rise sharply, exceeding the melting point of steel (approximately 1400-1500°C). This melts the metal and adheres to the tooth tip or the cut surface, forming severe melted edges. Increasing the number of teeth means more teeth participating in cutting simultaneously, reducing the load on each tooth, reducing cutting heat, and allowing it to be quickly dissipated through the tooth body. This reduces the tooth tip temperature, and dispersing heat helps reduce melted edges. In addition, increasing the wedge angle increases the heat dissipation volume, which also helps reduce the formation of melted edges. In comparison, in the existing technology, the parameters of the metal sawtooth shape are: tooth pitch of 17.67mm, number of teeth of 320, and wedge angle of 55°, which results in severe melting edges during the sawing process.

[0018] The original feed rate was 30 mm / s. Appropriately reducing the feed rate to 55%-65% of the original feed rate can decrease the single-tooth cutting amount, reduce instantaneous frictional heat, and help reduce the formation of melted edges. In contrast, in existing technologies, the feed rate is controlled at 70%-100%. A faster feed rate increases the single-tooth cutting amount, increases instantaneous frictional heat, and easily leads to melted edges.

[0019] This invention improves the formation of molten edges at the ends of round steel bars by adopting a series of process improvements, such as reducing the sawing temperature of the round steel surface, optimizing the metal saw tooth profile parameters, and reducing the feed speed. After implementation, the sawing time can reach 200 minutes to saw more than 230 tons of hot-rolled low-alloy steel round steel bars, and the saw blade consumption per ton of steel is less than 7 yuan. This invention effectively improves the formation of molten edges at the ends of hot-rolled low-alloy steel round steel bars, extends the sawing time, reduces the frequency of metal saw blade replacement, improves production efficiency, facilitates the mass production of this product, reduces production costs, and enhances the market competitiveness of special steel. This invention can be promoted and applied in similar production lines of high-quality special steel.

[0020] The high-temperature sawing method of the present invention is used after the round steel is rolled, and more specifically, after the flying shear. One applicable production process is proposed below: S1. Heat the continuously cast billet, with a target soaking temperature of 1200℃; S2. High-pressure water descaling, with descaling pressure controlled at 23±1MPa, uses high-pressure water to remove iron oxide scale from the surface of the steel billet. S3. Control the cooling water flow rate of the two-roll reversible rolling mill rolls: 170-190 m³ / h 3 / h, rolled by a two-roll reversible rolling mill (φ1100*2500), rolling 9 passes, and rolling intermediate billets; S4, 1# hydraulic shearing head, cutting head length ≥100 mm, to remove end defects of rolled billet; S5, medium rolling mill, preferably, the medium rolling mill has 6 continuous rolling stands, all of which are arranged alternately in horizontal and vertical positions. The rolling mill consists of φ750x6, all of which are fifth-generation short-stress rolling mills, with a rolling temperature ≥900℃ and a round bar specification of Φ110mm ≤Φ220mm. The maximum shearing section of S6 and No. 1 flying shears is Φ142mm, the shearing temperature is ≥900℃, Φ132mm < round steel specification ≤ Φ142mm, No. 1 flying shears are used for multiple-length segmentation, round steel specification ≤ Φ110mm, head cutting length ≥ 100mm, tail cutting length ≥ 100mm, and head and tail defects are removed. S7. Finishing mill, preferably, consists of four consecutive horizontal and vertical stands arranged in alternating configurations. The mill comprises four φ550mm steel sections and is a fifth-generation short-stress mill. Rolling temperature ≥900℃, round steel specification Φ70mm ≤ Φ105mm; The maximum shearing section of S8 and No. 2 flying shears is Φ132mm. When the shearing temperature is ≥900℃ and the round steel specification is ≤φ132mm, No. 2 flying shears are used for multiple-length segmentation. S9. Grouping: Group the flying shear multiples together. When the round steel enters the metal saw cutting area, keep the round steel in the grouped area for 2-4 minutes to ensure that the surface temperature of the round steel entering the metal saw cutting area is below 700℃, thereby reducing the cutting temperature. S10. Three Φ1800mm metal saws (saw #1, moving saw, and saw #2) are used for segment cutting. The sawing temperature is 700℃-600℃, and the feed speed is 55%-65%. The metal saw tooth parameters are: tooth pitch 16.51mm, number of teeth 342, and wedge angle 60°. S11. Stepping straightening on a cooling bed, slow cooling in the pit, the temperature upon entering the slow cooling pit should be ≥450℃, and the temperature upon exiting the slow cooling pit should be ≤200℃. S12, straighten, then manually bevele the material after slow cooling; S13, Flaw detection, magnetic leakage: 0.3mm, ultrasonic flaw detection grade A; S14. Sampling and testing the performance of the finished product; S15. Bundling, weighing, and warehousing.

[0021] The technical solution of the present invention will be described below with reference to specific embodiments.

[0022] The following examples and comparative examples use the production of 130mm diameter round bars from low-alloy steel continuous casting billets as an example, and specifically include the following steps: Select 100 gear continuous casting billets, with billet serial numbers from 1 to 100, and billet dimensions of 320mm*425mm*9000mm; One hundred gear casting billets with good surface quality were divided into two groups of 50 billets each. The first group used the process of this invention, and the second group used the existing process. Example 1

[0023] The first batch of continuous casting billets, 320*425*9000, was heated in a walking beam furnace with a target temperature of 1200℃. High-pressure water descaling, with the descaling pressure controlled at 23 MPa; Control the cooling water flow rate of the two-roll reversible rolling mill rolls: 180m³ 3 / h; Two-roll reversible rolling mill (φ1100*2500) rolls 9 passes, billet size: 205*205; #1 hydraulic shearing head, cutting length 100mm, removes end defects of rolled billets; The 6-stand continuous rolling mill in the intermediate rolling mill is arranged alternately in horizontal and vertical configurations. The mill consists of φ750x6 mills and is a fifth-generation short-stress mill. The rolling temperature is 935℃ and the round bar specification is Φ130mm. Shear section of No. 1 flying shear: Φ130mm, shearing temperature: 930℃, No. 1 flying shear multiple length segmentation.

[0024] Grouping: Group the flying shear multiples together. When the round steel enters the metal saw cutting area, keep the round steel in the grouped area for 3.2 minutes. The surface temperature of the round steel entering the metal saw cutting area is 650℃-690℃.

[0025] Three Φ1800mm metal saws (saw #1, mobile saw, and saw #2) are used for segment cutting. The sawing temperature is 620℃-680℃, and the feed speed is 60%. The metal saw tooth parameters are: tooth pitch: 16.51mm, number of teeth: 342, wedge angle: 60°. The sawing time and sawing tonnage for each saw blade are shown in Table 1.

[0026] Step straightening on a cooling bed, slow cooling in a pit (entry temperature should be 490℃-550℃, exit temperature ≤200℃); straightening; manual chamfering of the slow-cooled material; flaw detection, magnetic flux leakage: 0.3mm, ultrasonic testing according to Class A flaw detection; sampling, testing of finished product performance; bundling and warehousing.

[0027] Table 1. Saw blade cutting time and cutting tonnage data for Example 1

[0028] Comparative Example 1 The second batch of continuous casting billets, 320*425*9000, were heated in a walking beam furnace with a target temperature of 1200℃. High-pressure water descaling, with a descaling pressure of 23 MPa; Cooling water flow rate of the rolls in the two-roll reversible rolling mill: 180 m³ / h 3 / h; A two-roll reversible rolling mill (φ1100*2500) rolls 9 passes, with a billet size of 205*205. #1 hydraulic shearing head, cutting length 100mm, removes end defects of rolled billet; The 6-stand continuous rolling mill in the intermediate rolling mill is arranged alternately in horizontal and vertical configurations. The mill consists of φ750x6 mills and is a fifth-generation short-stress mill. The rolling temperature is 930℃ and the round bar specification is Φ130mm. Shear section of No. 1 flying shear: Φ130mm, shearing temperature: 930℃, No. 1 flying shear multiple length segmentation.

[0029] Grouping: Group the flying shears together; once they leave the group, they enter the sawing zone at a temperature of 780-890℃.

[0030] Three Φ1800mm metal saws (saw #1, mobile saw, and saw #2) are used for sawing in sections. The sawing temperature is 740℃-875℃, the feed speed is 75%, the tooth pitch is 17.67mm, the number of teeth is 320, and the wedge angle is 55°. The sawing time and sawing tonnage for each saw blade are shown in Table 2. Step straightening on a cooling bed, slow cooling in a pit (entry temperature should be 490℃-550℃, exit temperature ≤200℃); straightening; manual chamfering of the slow-cooled material; flaw detection, magnetic flux leakage: 0.3mm, ultrasonic testing according to Class A flaw detection; sampling, testing of finished product performance; bundling and warehousing.

[0031] Table 2. Saw blade cutting time and cutting tonnage data for Comparative Example 1

[0032] Analysis of the two sets of data shows that for the first group of ￠130 round steel, the average sawing time after each saw blade change was 209.5 minutes, with an average sawing weight of 241 tons per batch. A total of 6 saw blades were replaced, and the saw blade cost per ton of steel was 6.22 yuan. For the second group of ￠130 round steel, the average sawing time after each saw blade change was 49.7 minutes, with an average sawing weight of 59.4 tons per batch. A total of 24 saw blades were replaced, and the saw blade cost per ton of steel was 25.25 yuan. Compared with the original process, the saw blade of this invention can achieve a sawing time of 209.5 minutes and a sawing weight of 241 tons per batch of hot-rolled low-alloy steel round steel. After replacing the saw blade, the sawing time increased by 159.8 minutes, the sawing tonnage increased by 181.6 tons, and the saw blade consumption per ton of steel decreased by 19.03 yuan. This invention effectively improves the formation of melted edges at the ends of the hot-rolled low-alloy steel round bars, significantly extends the sawing time after each saw blade replacement, increases the sawing tonnage, reduces the frequency of metal saw blade replacement, improves production efficiency, facilitates the mass production of this product, reduces production costs, and enhances the market competitiveness of special steel. This invention can be promoted and applied in similar production lines of high-quality special steel.

[0033] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A high-temperature sawing method for hot-rolled low-alloy steel round bars, characterized in that, After the hot-rolled low-alloy round steel is rolled and subjected to flying shearing, it is sawn. The sawing control parameters are as follows: Control the sawing temperature of round steel to <700℃; The tooth profile parameters for controlling the metal saw teeth are: tooth pitch of 16-17 mm, number of teeth of 340-350, and wedge angle of 55-65°. Control the feed speed of the saw to 55%-65% of 30 mm / s.

2. The high-temperature sawing method for hot-rolled low-alloy round steel as described in claim 1, characterized in that, When the round steel enters the metal saw cutting area, the round steel in the grouping area should remain for 2-4 minutes.

3. The high-temperature sawing method for hot-rolled low-alloy round steel as described in claim 1, characterized in that, The sawing temperature of the round steel should be controlled at 600-700℃.

4. The high-temperature sawing method for hot-rolled low-alloy round steel as described in claim 1, characterized in that, The tooth pitch is 16.51 mm.

5. The high-temperature sawing method for hot-rolled low-alloy round steel as described in claim 1, characterized in that, It has 342 teeth.

6. The high-temperature sawing method for hot-rolled low-alloy round steel as described in claim 1, characterized in that, The wedge angle is 60°.

7. The high-temperature sawing method for hot-rolled low-alloy round steel as described in claim 1, characterized in that, During the preparation of hot-rolled low-alloy steel balls, the target temperature for homogenization during the heating stage is 1200℃.

8. The high-temperature sawing method for hot-rolled low-alloy round steel as described in claim 1, characterized in that, During the preparation of hot-rolled low-alloy steel rounds, the cooling water flow rate is controlled at 170-190 m³ / h during rough rolling. 3 / h.

9. The high-temperature sawing method for hot-rolled low-alloy round steel as described in claim 1, characterized in that, During the preparation of hot-rolled low-alloy steel balls, the intermediate rolling and finishing rolling temperatures are both ≥900℃.

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