A 27si mn hot-rolled wire rod and a production method thereof

Abstract

The present application belongs to the technical field of hot-rolled steel preparation, and particularly relates to a 27SiMn hot-rolled wire rod and a production method thereof. The chemical component mass percentage of the 27SiMn hot-rolled wire rod is as follows: C: 0.28-0.29%, Si: 0.85-0.94%, Mn: 0.90-0.99%, P≤0.020%, S≤0.020%, Cr≤0.150%, Ni≤0.080%, Cu≤0.150%, O≤0.003%, N≤0.006%, H≤0.0002%, and the rest is Fe and inevitable impurities. The specific steps are as follows: S1: adding molten iron and scrap steel into a converter, and performing converter smelting on the molten iron and scrap steel to obtain primary smelting molten steel; S2: performing LF refining on the converter primary smelting molten steel; S3: performing continuous casting on the refined molten steel to obtain a square billet; S4: performing eighteen-mechanism hot rolling on the square billet to obtain an initial hot-rolled wire rod; and S5: performing pit stack cold heat treatment on the initial hot-rolled wire rod to obtain a final hot-rolled wire rod. The method can ensure the stability of the performance of the 27SiMn hot-rolled wire rod product by precisely controlling the process parameters, and the product has the characteristics of small chemical component fluctuation and few inclusions in the steel.

Description

Technical Field

[0001] This invention belongs to the field of hot-rolled steel preparation technology, and particularly relates to a 27SiMn hot-rolled wire rod and its production method. Background Technology

[0002] 27SiMn hot-rolled wire rod is a commonly used metallic material, widely applied due to its high tensile strength. However, current production processes result in significant fluctuations in the chemical composition and a high level of impurities in the 27SiMn hot-rolled wire rod, leading to instability in its tensile strength, yield strength, plasticity, and toughness. Furthermore, 27SiMn hot-rolled wire rod exhibits delayed fracture during storage, meaning it spontaneously fractures after a period of time without significant external force, resulting in low yield and resource waste. Summary of the Invention

[0003] The purpose of this invention is to provide a 27SiMn hot-rolled wire rod and its production method, which solves the problems of large fluctuations in chemical composition, many impurities, and delayed fracture of 27SiMn hot-rolled wire rod during storage caused by existing production processes.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A 27SiMn hot-rolled wire rod has the following chemical composition by mass percentage: C: 0.28-0.29%, Si: 0.85-0.94%, Mn: 0.90-0.99%, P≤0.020%, S≤0.020%, Cr≤0.150%, Ni≤0.080%, Cu≤0.150%, O≤0.003%, N≤0.006%, H≤0.0002%, with the remainder being Fe and unavoidable impurities.

[0005] Furthermore, the chemical composition by mass percentage is as follows: C: 0.28%, Si: 0.89%, Mn: 0.92%, P: 0.008%, S: 0.017%, Cr: 0.040%, Ni: 0.030%, Cu: 0.028%, O: 0.0025%, N: 0.0058%, H: 0.0001%, with the remainder being Fe and unavoidable impurities.

[0006] The specific steps of the above-mentioned production method for 27SiMn hot-rolled wire rod are as follows: S1: Add molten iron and scrap steel to the converter. One furnace produces 110-120t of molten steel, 100-115t of molten iron, and 10-30t of scrap steel. The molten iron and scrap steel are then smelted in the converter to obtain primary molten steel. S2: LF refining of primary molten steel in converter. During refining, the atmosphere inside the furnace is kept at a slightly positive pressure. The refining time is 30-40 minutes, the calcium wire is 140-160 meters long, and the white slag stabilization time is ≥15 minutes to obtain refined molten steel with Als ≤0.006%. S3: Refined molten steel is continuously cast using 27SiMn protective slag. The ladle casing, tundish liquid level, submerged entry nozzle, and crystallizer liquid level are all protected during the entire casting process. The secondary cooling mode adopts a weak cooling mode, and the casting speed is controlled at 2.9 to 3.1 m / s to obtain a square billet. S4: Hot rolling of square billets on an 18-stand mill to obtain initial hot-rolled wire rod; S5: Perform hot and cold treatment on the initial hot-rolled wire rod in a pit to obtain the final hot-rolled wire rod; The temperature control process during the thermal treatment of the sump pile is as follows: S51: Obtain pit temperature data The pit has six faces Xi, which are the top, bottom, left, right, front, and back of the pit, i∈[1,6]. Temperature detectors are installed on each face. The temperature detectors acquire the air temperature data of the six faces Xi at each sampling time and construct the average air temperature data sequence Zi, i∈[1,6] within each preset sub-time period sequence Yn of the six faces Xi. S52: Constructing the heating model data sequence Based on the difference between the above average air temperature data sequences Zi and Z6, we obtain ΔZi = Zi - Z6, i ∈ [1, 6], where Z6 is the air temperature at the bottom of the pit; if Zi < Z6, then we construct a preset heating device heating model data sequence Mi, i ∈ [1, 6], Mi = k * ΔZi, where k is the scaling factor. S53: Heating hot-rolled wire rod based on heating device model data sequence Mi and heating device start-up heating mode sequence Ni, i∈[1,6]; S54: Repeat steps S51 to S53; S55: When Zi=Z6 in step S52, the temperature control system stops building the preset heating device heating model data sequence Mi and stops the heating device.

[0007] Furthermore, in step S1, during converter smelting, the amount of molten iron added is 40 to 60 tons, a low-nitrogen silicon-manganese alloy is used, and the endpoint control targets are: C≥0.15%, P≤0.012%, T≥1610℃.

[0008] Furthermore, in step S1, after smelting, 100-200 kg of deoxidizer, 1500-2500 kg of silicon-manganese alloy, and 150-300 kg of carbon raiser are added to finally obtain primary molten steel.

[0009] Furthermore, in step S2, a deoxidizer, silicon-manganese alloy, and carbon raiser are added during the refining process to finally obtain refined molten steel.

[0010] Further, the mass composition of the 27SiMn protective slag in step S3 is as follows: SiO2: 25.7-30.7%, CaO: 27.7-32.7%, Al2O3: 3.0-6.0%, Fe2O3≤2.5%, MgO: 4.0-6.4%, R2O(Na2O+K2O): 6.8-9.8%, F⁻: 2.0-4.0%, C 全 : 12.0-16.0%.

[0011] Furthermore, during the eighteen-stand hot rolling process in step S4, the heating section temperature is controlled as follows: preheating section ≤1080℃, heating section 1140±30℃, soaking section 1120±30℃; the rolling temperature is controlled as follows: initial rolling temperature 1100±20℃, finishing rolling temperature 1020±20℃, wire drawing temperature 870±20℃; and the rolling speed is controlled as follows: 54~72m / s.

[0012] Furthermore, in step S53, the heating power is set to be proportional to Mi, with each unit Mi corresponding to QW of heating power. Therefore, the heating power of the pit Xi surface is Ni = Mi * Q.

[0013] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: (1) The production process of 27SiMn hot-rolled wire rod adopts the converter-refining-continuous casting-rolling mode, which breaks through the traditional converter-continuous casting-rolling production mode and provides a new production method for this steel grade. Through precise control of process parameters, the chemical composition of the product fluctuates little and the steel contains few inclusions, thus ensuring the stability of the performance of 27SiMn hot-rolled wire rod. (2) After rolling, the initial hot-rolled wire rod is subjected to a pit-piled cold and heat treatment. Through a temperature control strategy—using temperature detectors to monitor the temperature of each surface of the pit in real time, and combining temperature control algorithms with local heating devices to adjust the temperature difference, the 27SiMn hot-rolled wire rod is cooled uniformly during the pit-piled cold and heat treatment process. This series of improvements greatly reduces the risk of delayed fracture of 27SiMn hot-rolled wire rod and effectively improves the yield. Attached Figure Description

[0014] Figure 1 This is a six-sided schematic diagram of the temperature detector installed during the cold and heat treatment of the sump pile in an embodiment of the present invention. Detailed Implementation

[0015] The technical solution of the present invention will be described in detail below with reference to the embodiments. Example 1

[0016] S1: Add 100t of molten iron and 25t of scrap steel to the converter for converter smelting. Use low-nitrogen silicon-manganese alloy. The endpoint control targets are: C: 0.18%, P: 0.010%, T: 1615℃. Add 125kg of deoxidizer, 2100kg of silicon-manganese alloy, and 160kg of carbon raiser to obtain primary molten steel. S2: The primary steel from the converter is subjected to LF refining. During refining, the atmosphere inside the furnace is kept under a slight positive pressure. The refining time is 38 minutes, the calcium wire is 150 meters long, the white slag stabilization time is ≥17 minutes, and 25 kg of deoxidizer, 126 kg of silicon-manganese alloy, and 32 kg of carbon raiser are added to obtain refined steel with an Al content of 0.040%. S3: Refined steel is continuously cast using 27SiMn protective slag. The mass composition of the 27SiMn protective slag is: SiO2: 26.4%, CaO: 28.9%, Al2O3: 4.0%, Fe2O3: 1.2%, MgO: 4.8%, R2O(Na2O+K2O): 7.5%, F⁻: 2.5%, C 全 : 13.2%, the tundish casing, the liquid level of the tundish, the submerged nozzle, and the liquid level of the crystallizer are all protected during the entire pouring process. The secondary cooling mode adopts the weak cooling mode, and the casting speed is controlled at 3.0 m / s to obtain a square billet. S4: The square billet is hot rolled on an 18-stand mill. The heating section temperature is controlled as follows: preheating section: 1070℃, heating section: 1150℃, soaking section: 1130℃; the rolling temperature is controlled as follows: initial rolling temperature: 1110℃, finishing rolling temperature: 1030℃, wire drawing temperature: 880℃, and the rolling speed is controlled at 65m / s to obtain the initial hot-rolled wire rod. S5: Perform hot and cold treatment on the initial hot-rolled wire rod in a pit to obtain the final hot-rolled wire rod; The temperature control process during the thermal treatment of the sump is as follows: S51: Obtain pit temperature data The pit has six faces Xi, i∈[1,6], as shown below. Figure 1 As shown, X1 is the top, X2 is the left, X3 is the back, X4 is the right, X5 is the front, and X6 is the bottom. Temperature detectors are installed on each face. These detectors acquire air temperature data at various sampling times for each of the six faces Xi of the pit, constructing an average air temperature data sequence Zi, i ∈ [1, 6], within each preset sub-time period sequence Yn, n ∈ [1, ∞]. The average air temperature data sequence for each face within the first preset sub-time period Y1 (0–10 minutes) is set as follows: Z1 = 18℃ (average temperature of the X1 surface of the pit). Z2 = 19℃ (average temperature of the X2 surface of the pit). Z3 = 17℃ (average temperature of the X3 surface of the pit). Z4 = 18.5℃ (average temperature of the X4 surface of the pit). Z5 = 20℃ (average temperature of the X5th surface of the pit); Z6 = 20℃ (average temperature of the pit floor, used as a reference temperature). S52: Constructing the heating model data sequence Based on the difference between the above average air temperature data sequences Zi and Z6, we obtain ΔZi=Zi-Z6, i∈[1,6], where Z1 to Z4 are all less than Z6. Therefore, a preset heating device heating model data sequence Mi is constructed for Z1, Z2, Z3 and Z4. Assuming the heating model data sequence Mi is proportional to the temperature difference, Mi = k * ΔZi, and setting the proportionality coefficient k = 1, then: M1=ΔZ1=Z6-Z1=20℃-18℃=2; M2=ΔZ2=Z6-Z2=20℃-19℃=1; M3=ΔZ3=Z6-Z3=20℃-17℃=3; M4=ΔZ4=Z6-Z4=20℃-18.5℃=1.5; M5=0 (No heating required for the fifth side); M6=0 (No ground heating required); S53: Based on the heating device heating model data sequence Mi, the heating device starts the heating mode sequence Ni, i∈[1,6] to heat the hot-rolled wire rod; set the heating power to be proportional to Mi, each unit Mi corresponds to QW heating power, then the heating power of the pit Xi surface is Ni=Mi*Q, set each unit Mi corresponds to 100W heating power, then: The heating power of the heating device on the first side (X1) is N1 = M1 * 100W = 200W; The heating power of the heating device on the second side (X2) is N2 = M2 * 100W = 100W; The heating power of the heating device on the third side (X3) is N3 = M3 * 100W = 300W; The heating power of the heating device on the fourth side (X4) is N4 = M4 * 100W = 150W; The heating device does not start on the ground (X5, X6); S54: Repeat steps S51 to S53; In each preset sub-time period, such as Y2 (10-20 minutes), Y3 (20-30 minutes), ..., temperature data is reacquired, a new heating model data sequence is constructed, and the heating method of the heating device is adjusted; S55: When Zi=Z6 in step S52, the temperature control system stops building the preset heating device heating model data sequence Mi and stops the heating device heating mode sequence Ni from heating the hot-rolled wire rod. During the second preset sub-time period Y2, the average air temperature data sequence obtained by the temperature detector is as follows: Z1=19℃, Z2=20℃, Z3=19℃, Z4=19.5℃, Z5=20℃, Z6=20℃. At this point, the average temperature of all surfaces has reached the pit floor temperature Z6. Therefore, the temperature control system stops building the heating model data sequence Mi and stops heating.

[0017] The chemical element mass percentages of the 27SiMn hot-rolled wire rod obtained in this embodiment are as follows: C: 0.28%, Si: 0.89%, Mn: 0.92%, P: 0.008%, S: 0.017%, Cr: 0.040%, Ni: 0.030%, Cu: 0.028%, O: 0.0025%, N: 0.0058%, H: 0.0001%, with the remainder being Fe and unavoidable impurities.

[0018] Example 2 S1: Add 105t of molten iron and 20t of scrap steel to the converter for converter smelting. Use low-nitrogen silicon-manganese alloy. The endpoint control targets are: C: 0.16%, P: 0.011%, T: 1620℃. Add 129kg of deoxidizer, 2006kg of silicon-manganese alloy, and 166kg of carbon raiser to obtain primary molten steel. S2: The primary steel from the converter is subjected to LF refining. During refining, the atmosphere inside the furnace is kept under a slight positive pressure. The refining time is 30 minutes, the calcium wire is 140 meters long, the white slag stabilization time is ≥16 minutes, and 26 kg of deoxidizer, 121 kg of silicon-manganese alloy, and 33 kg of carburizer are added to obtain refined steel with an Als of 0.005%. S3: Refined steel is continuously cast using 27SiMn protective slag. The mass composition of the 27SiMn protective slag is: SiO2: 27.7%, CaO: 29.5%, Al2O3: 4.9%, Fe2O3: 1.9%, MgO: 5.4%, R2O(Na2O+K2O): 8.4%, F... - 2.9%, C 全 The yield was 14.8%. The molten metal in the tundish, the submerged nozzle, and the liquid level in the crystallizer were all protected during the entire casting process. The secondary cooling mode adopted a weak cooling mode, and the casting speed was controlled at 2.9 m / s to obtain a square billet. S4: The square billet is hot rolled on an 18-stand mill. The heating section temperature is controlled as follows: preheating section: 1080℃, heating section: 1160℃, soaking section: 1140℃. The rolling temperature is controlled as follows: initial rolling temperature: 1120℃, finishing rolling temperature: 1040℃, wire drawing temperature: 890℃. The rolling speed is controlled as follows: 72m / s, to obtain the initial hot-rolled wire rod. S5: Perform hot and cold treatment on the initial hot-rolled wire rod in a pit to obtain the final hot-rolled wire rod; The temperature control process during the thermal treatment of the sump is as follows: S51: Obtain pit temperature data The pit has six faces Xi, i∈[1,6], as shown below. Figure 1 As shown, X1 is the top, X2 is the left, X3 is the back, X4 is the right, X5 is the front, and X6 is the bottom. Temperature detectors are installed on each face. These detectors acquire air temperature data at various sampling times for each of the six faces Xi of the pit, constructing an average air temperature data sequence Zi, i ∈ [1, 6], within each preset sub-time period sequence Yn, n ∈ [1, ∞]. The average air temperature data sequence for each face within the first preset sub-time period Y1 (0–10 minutes) is set as follows: Z1 = 18℃ (average temperature of the X1 surface of the pit). Z2 = 19℃ (average temperature of the X2 surface of the pit). Z3 = 17℃ (average temperature of the X3 surface of the pit). Z4 = 18.5℃ (average temperature of the X4 surface of the pit). Z5 = 20℃ (average temperature of the X5th surface of the pit); Z6 = 20℃ (average temperature of the pit floor, used as a reference temperature). S52: Constructing the heating model data sequence Based on the difference between the above average air temperature data sequences Zi and Z6, we obtain ΔZi=Zi-Z6, i∈[1,6], where Z1 to Z4 are all less than Z6. Therefore, a preset heating device heating model data sequence Mi is constructed for Z1, Z2, Z3 and Z4. Assuming the heating model data sequence Mi is proportional to the temperature difference, Mi = k * ΔZi, and setting the proportionality coefficient k = 1, then: M1=ΔZ1=Z6-Z1=20℃-18℃=2; M2=ΔZ2=Z6-Z2=20℃-19℃=1; M3=ΔZ3=Z6-Z3=20℃-17℃=3; M4=ΔZ4=Z6-Z4=20℃-18.5℃=1.5; M5=0 (No heating required for the fifth side); M6=0 (No ground heating required); S53: Based on the heating device heating model data sequence Mi, the heating device starts the heating mode sequence Ni, i∈[1,6] to heat the hot-rolled wire rod; set the heating power to be proportional to Mi, each unit Mi corresponds to QW heating power, then the heating power of the pit Xi surface is Ni=Mi*Q, set each unit Mi corresponds to 100W heating power, then: The heating power of the heating device on the first side (X1) is N1 = M1 * 100W = 200W; The heating power of the heating device on the second side (X2) is N2 = M2 * 100W = 100W; The heating power of the heating device on the third side (X3) is N3 = M3 * 100W = 300W; The heating power of the heating device on the fourth side (X4) is N4 = M4 * 100W = 150W; The heating device does not start on the ground (X5, X6); S54: Repeat steps S51 to S53; In each preset sub-time period, such as Y2 (10-20 minutes), Y3 (20-30 minutes), ..., temperature data is reacquired, a new heating model data sequence is constructed, and the heating method of the heating device is adjusted; S55: When Zi=Z6 in step S52, the temperature control system stops building the preset heating device heating model data sequence Mi and stops the heating device heating mode sequence Ni from heating the hot-rolled wire rod. During the second preset sub-time period Y2, the average air temperature data sequence obtained by the temperature detector is as follows: Z1=19℃, Z2=20℃, Z3=19℃, Z4=19.5℃, Z5=20℃, Z6=20℃. At this point, the average temperature of all surfaces has reached the pit floor temperature Z6. Therefore, the temperature control system stops building the heating model data sequence Mi and stops heating.

[0019] In this embodiment, the mass percentage of each chemical element in the 27SiMn hot-rolled wire rod is as follows: C: 0.29%, Si: 0.85%, Mn: 0.93%, P: 0.010%, S: 0.015%, Cr: 0.038%, Ni: 0.032%, Cu: 0.029%, O: 0.0022%, N: 0.0055%, H: 0.0001%, with the remainder being Fe and unavoidable impurities.

[0020] Example 3 S1: Add 110t of molten iron and 15t of scrap steel to the converter for converter smelting. Use low-nitrogen silicon-manganese alloy. The endpoint control targets are: C: 0.17%, P: 0.010%, T: 1630℃. Add 125kg of deoxidizer, 2053kg of silicon-manganese alloy, and 160kg of carbon raiser to obtain primary molten steel. S2: LF refining is performed on the primary molten steel from the converter. During refining, the atmosphere inside the furnace is kept under slight positive pressure. The refining time is 40 minutes, the calcium wire is 160 meters long, the white slag stabilization time is ≥18 minutes, and 25 kg of deoxidizer, 123 kg of silicon-manganese alloy, and 32 kg of carbon raiser are added to obtain refined molten steel with an Als content of 0.005%. S3: Refined steel is continuously cast using 27SiMn protective slag. The mass composition of the 27SiMn protective slag is: SiO2: 29.1%, CaO: 31.2%, Al2O3: 5.5%, Fe2O3: 2.4%, MgO: 6.1%, R2O(Na2O+K2O): 9.1%, F... - 3.4%, C 全 The casting process is 15.5%, with full protection for the molten metal in the tundish, the submerged nozzle, and the crystallizer. The secondary cooling mode is a weak cooling mode, and the casting speed is controlled at 3.1 m / s to obtain a square billet. S4: The square billet is hot rolled on an 18-stand mill. The heating section temperature is controlled as follows: preheating section: 1060℃, heating section: 1130℃, soaking section: 1110℃. The rolling temperature is controlled as follows: initial rolling temperature: 1100℃, finishing rolling temperature: 1010℃, wire drawing temperature: 860℃. The rolling speed is controlled as follows: 54m / s, to obtain the initial hot-rolled wire rod. S5: Perform hot and cold treatment on the initial hot-rolled wire rod in a pit to obtain the final hot-rolled wire rod; The temperature control process during the thermal treatment of the sump is as follows: S51: Obtain pit temperature data The pit has six faces Xi, i∈[1,6], as shown below. Figure 1 As shown, X1 is the top, X2 is the left, X3 is the back, X4 is the right, X5 is the front, and X6 is the bottom. Temperature detectors are installed on each face. These detectors acquire air temperature data at various sampling times for each of the six faces Xi of the pit, constructing an average air temperature data sequence Zi, i ∈ [1, 6], within each preset sub-time period sequence Yn, n ∈ [1, ∞]. The average air temperature data sequence for each face within the first preset sub-time period Y1 (0–10 minutes) is set as follows: Z1 = 18℃ (average temperature of the X1 surface of the pit). Z2 = 19℃ (average temperature of the X2 surface of the pit). Z3 = 17℃ (average temperature of the X3 surface of the pit). Z4 = 18.5℃ (average temperature of the X4 surface of the pit). Z5 = 20℃ (average temperature of the X5th surface of the pit); Z6 = 20℃ (average temperature of the pit floor, used as a reference temperature). S52: Constructing the heating model data sequence Based on the difference between the above average air temperature data sequences Zi and Z6, we obtain ΔZi=Zi-Z6, i∈[1,6], where Z1 to Z4 are all less than Z6. Therefore, a preset heating device heating model data sequence Mi is constructed for Z1, Z2, Z3 and Z4. Assuming the heating model data sequence Mi is proportional to the temperature difference, Mi = k * ΔZi, and setting the proportionality coefficient k = 1, then: M1=ΔZ1=Z6-Z1=20℃-18℃=2; M2=ΔZ2=Z6-Z2=20℃-19℃=1; M3=ΔZ3=Z6-Z3=20℃-17℃=3; M4=ΔZ4=Z6-Z4=20℃-18.5℃=1.5; M5=0 (No heating required for the fifth side); M6=0 (No ground heating required); S53: Based on the heating device heating model data sequence Mi, the heating device starts the heating mode sequence Ni, i∈[1,6] to heat the hot-rolled wire rod; set the heating power to be proportional to Mi, each unit Mi corresponds to QW heating power, then the heating power of the pit Xi surface is Ni=Mi*Q, set each unit Mi corresponds to 100W heating power, then: The heating power of the heating device on the first side (X1) is N1 = M1 * 100W = 200W; The heating power of the heating device on the second side (X2) is N2 = M2 * 100W = 100W; The heating power of the heating device on the third side (X3) is N3 = M3 * 100W = 300W; The heating power of the heating device on the fourth side (X4) is N4 = M4 * 100W = 150W; The heating device does not start on the ground (X5, X6); S54: Repeat steps S51 to S53; In each preset sub-time period, such as Y2 (10-20 minutes), Y3 (20-30 minutes), ..., temperature data is reacquired, a new heating model data sequence is constructed, and the heating method of the heating device is adjusted; S55: When Zi=Z6 in step S52, the temperature control system stops building the preset heating device heating model data sequence Mi and stops the heating device heating mode sequence Ni from heating the hot-rolled wire rod. During the second preset sub-time period Y2, the average air temperature data sequence obtained by the temperature detector is as follows: Z1=19℃, Z2=20℃, Z3=19℃, Z4=19.5℃, Z5=20℃, Z6=20℃. At this point, the average temperature of all surfaces has reached the pit floor temperature Z6. Therefore, the temperature control system stops building the heating model data sequence Mi and stops heating.

[0021] In this embodiment, the mass percentage of each chemical element in the 27SiMn hot-rolled wire rod is as follows: C: 0.28%, Si: 0.87%, Mn: 0.91%, P: 0.011%, S: 0.012%, Cr: 0.032%, Ni: 0.035%, Cu: 0.023%, O: 0.0026%, N: 0.0055%, H: 0.0002%, with the remainder being Fe and unavoidable impurities.

[0022] Comparative Example 1 S1: Add 100t of molten iron and 15t of scrap steel to the converter for converter smelting. Use low-nitrogen silicon-manganese alloy. The endpoint control targets are: C: 0.14%, P: 0.015%, T: 1590℃. Add 116kg of deoxidizer, 1960kg of silicon-manganese alloy, and 148kg of carbon raiser to obtain primary molten steel. S2: The primary steel from the converter is subjected to LF refining. During refining, the atmosphere inside the furnace is kept under a slight positive pressure. The refining time is 25 minutes, the calcium wire is 130 meters long, the white slag stabilization time is 14 minutes, and 23 kg of deoxidizer, 118 kg of silicon-manganese alloy, and 30 kg of carbon raiser are added to obtain refined steel with an Als of 0.008%. S3: Refined steel is continuously cast using 27SiMn protective slag. The mass composition of the 27SiMn protective slag is: SiO2: 23.4%, CaO: 24.1%, Al2O3: 2.1%, Fe2O3: 2.3%, MgO: 4.2%, R2O(Na2O+K2O): 10.1%, F - 4.2%, C 全 The casting process is 10.5% complete, with full protection for the molten tubing, tundish liquid level, submerged nozzle, and crystallizer liquid level. The secondary cooling mode adopts a weak cooling mode, and the casting speed is controlled at 3.0 m / s to obtain a square billet. S4: The square billet is hot rolled on an 18-stand mill. The heating section temperature is controlled as follows: preheating section: 1090℃, heating section: 1100℃, soaking section: 1080℃. The rolling temperature is controlled as follows: initial rolling temperature: 1090℃, finishing rolling temperature: 1000℃, wire drawing temperature: 850℃. The rolling speed is controlled as follows: 52m / s, to obtain the initial hot-rolled wire rod. S5: Finally, the initial hot-rolled wire rod is air-cooled to obtain the final hot-rolled wire rod.

[0023] In this comparative example, the mass percentages of each chemical element in the 27SiMn hot-rolled wire rod are as follows: C: 0.26%, Si: 0.83%, Mn: 0.88%, P: 0.03%, S: 0.030%, Cr: 0.170%, Ni: 0.010%, Cu: 0.170%, with the remainder being Fe and unavoidable impurities.

[0024] Comparative Example 2 S1: Add 95t of molten iron and 20t of scrap steel to the converter for converter smelting. Use low-nitrogen silicon-manganese alloy. The endpoint control targets are: C: 0.13%, P: 0.014%, T: 1620℃. Add 143kg of deoxidizer, 2289kg of silicon-manganese alloy, and 183kg of carburizer to obtain primary molten steel. S2: The primary steel from the converter is subjected to LF refining. During refining, the atmosphere inside the furnace is kept at a slightly positive pressure. The refining time is 38 minutes, the calcium wire is 150 meters long, the white slag stabilization time is ≥17 minutes, and 29 kg of deoxidizer, 137 kg of silicon-manganese alloy, and 37 kg of carbon raiser are added to obtain refined steel with an Als of 0.004%. S3: Refined steel is continuously cast using 27SiMn protective slag. The mass composition of the 27SiMn protective slag is: SiO2: 24.2%, CaO: 25.7%, Al2O3: 2.3%, Fe2O3: 2.1%, MgO: 4.5%, R2O(Na2O+K2O): 10.8%, F - 4.5%, C 全 The yield was 10.9%. The molten metal in the tundish, the submerged nozzle, and the liquid level in the crystallizer were all protected during the casting process. The secondary cooling mode adopted a weak cooling mode, and the casting speed was controlled at 3.0 m / s to obtain a square billet. S4: The square billet is hot rolled on an 18-stand mill. The heating section temperature is controlled as follows: preheating section: 1100℃, heating section: 1180℃, soaking section: 1160℃. The rolling temperature is controlled as follows: initial rolling temperature: 1130℃, finishing rolling temperature: 1050℃, wire drawing temperature: 900℃. The rolling speed is controlled as follows: 75m / s, to obtain the initial hot-rolled wire rod. S5: Finally, the initial hot-rolled wire rod is air-cooled to obtain the final hot-rolled wire rod.

[0025] In this comparative example, the mass percentages of each chemical element in the 27SiMn hot-rolled wire rod are as follows: C: 0.32%, Si: 0.97%, Mn: 1.00%, P: 0.040%, S: 0.030%, Cr: 0.180%, Ni: 0.100%, Cu: 0.160%, with the remainder being Fe and unavoidable impurities.

[0026] Comparative Example 3 S1: Add 90t of molten iron and 25t of scrap steel to the converter for converter smelting. Use low-nitrogen silicon-manganese alloy. The endpoint control targets are: C: 0.13%, P: 0.014%, T: 1680℃. Add 161kg of deoxidizer, 2327kg of silicon-manganese alloy, and 205kg of carburizer. Argon blowing time at the argon station is 18 minutes. Add 150 meters of calcium wire. The white slag stabilization time is ≥10 minutes to obtain refined molten steel with an Als of 0.003%. S2: Refined steel is continuously cast using 27SiMn protective slag. The mass composition of the 27SiMn protective slag is: SiO2: 25.5%, CaO: 26.8%, Al2O3: 2.8%, Fe2O3: 1.9%, MgO: 4.3%, R2O(Na2O+K2O): 11.4%, F - 4.9%, C 全 The casting process is 11.3%, with full protection for the molten tubing, tundish liquid level, submerged nozzle, and crystallizer liquid level. The secondary cooling mode adopts a weak cooling mode, and the casting speed is controlled at 3.0 m / s to obtain a square billet. S3: The square billet is hot rolled on an 18-stand mill. The heating section temperature is controlled as follows: preheating section: 1100℃, heating section: 1180℃, soaking section: 1160℃. The rolling temperature is controlled as follows: initial rolling temperature: 1130℃, finishing rolling temperature: 1050℃, wire drawing temperature: 900℃. The rolling speed is controlled as follows: 75m / s, to obtain the initial hot-rolled wire rod. S4: Finally, the initial hot-rolled wire rod is air-cooled to obtain the final hot-rolled wire rod.

[0027] In this comparative example, the mass percentages of each chemical element in the 27SiMn hot-rolled wire rod are as follows: C: 0.32%, Si: 0.97%, Mn: 1.00%, P: 0.040%, S: 0.030%, Cr: 0.180%, Ni: 0.100%, Cu: 0.160%, with the remainder being Fe and unavoidable impurities.

[0028] The 27SiMn hot-rolled wire rods produced by the methods of each embodiment and comparative example were tested, and the results are shown in the table below:

[0029] As can be seen from the table, compared with the comparative production method, the 27SiMn hot-rolled wire rod produced by the production method of the present invention has less fluctuation in chemical composition, fewer inclusions in steel, low fracture rate after long-term storage in warehouse, and high yield.

[0030] The method provided in this invention, through precise control of process parameters, ensures that the chemical composition of the product fluctuates within ±0.01%, resulting in fewer inclusions in the steel and guaranteeing the stability of the performance of 27SiMn hot-rolled wire rod. The method of performing a pit-piling cooling and heat treatment on the initial hot-rolled wire rod after rolling allows for uniform cooling within the pit, effectively reducing the risk of delayed fracture in the warehouse. As shown in the data from the examples and comparative examples in the table, the 27SiMn hot-rolled wire rod produced by the method of this invention exhibits a significantly reduced risk of delayed fracture. The fracture rate is less than or equal to 0.10%, and remains below 0.90% after 6 months of warehouse storage and below 0.10% after 12 months of warehouse storage. The total yield is greater than or equal to 98.9%, and the total yield has increased by more than 3.40%. However, the 27SiMn hot-rolled wire rod produced by the comparative production method has a delayed fracture risk of greater than or equal to 5.10%, a fracture rate of greater than or equal to 5.00% after 6 months of warehouse storage and greater than or equal to 5.10% after 12 months of warehouse storage, and a low total yield of less than or equal to 94.5%.

[0031] The above description is only a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention. All equivalent changes made to the technical solution of the present invention shall fall within the protection scope of the present invention.

Claims

1. A 27SiMn hot-rolled wire rod, characterized in that, Its chemical composition by mass percentage is as follows: C: 0.28–0.29%, Si: 0.85–0.94%, Mn: 0.90–0.99%, P≤0.020%, S≤0.020%, Cr≤0.150%, Ni≤0.080%, Cu≤0.150%, O≤0.003%, N≤0.006%, H≤0.0002%, with the remainder being Fe and unavoidable impurities.

2. The 27SiMn hot-rolled wire rod according to claim 1, characterized in that, The chemical composition by mass percentage is as follows: C: 0.28%, Si: 0.89%, Mn: 0.92%, P: 0.008%, S: 0.017%, Cr: 0.040%, Ni: 0.030%, Cu: 0.028%, O: 0.0025%, N: 0.0058%, H: 0.0001%, with the remainder being Fe and unavoidable impurities.

3. The method for producing 27SiMn hot-rolled wire rod according to claim 1, characterized in that, The specific steps are as follows: S1: Add molten iron and scrap steel to the converter. One furnace produces 110-120t of molten steel, 100-115t of molten iron, and 10-30t of scrap steel. The molten iron and scrap steel are then smelted in the converter to obtain primary molten steel. S2: LF refining of primary molten steel in converter. During refining, the atmosphere inside the furnace is kept at a slightly positive pressure. The refining time is 30-40 minutes, the calcium wire is 140-160 meters long, and the white slag stabilization time is ≥15 minutes to obtain refined molten steel with Als ≤0.006%. S3: Refined molten steel is continuously cast using 27SiMn protective slag. The ladle casing, tundish liquid level, submerged entry nozzle, and crystallizer liquid level are all protected during the entire casting process. The secondary cooling mode adopts a weak cooling mode, and the casting speed is controlled at 2.9 to 3.1 m / s to obtain a square billet. S4: Hot rolling of square billets on an 18-stand mill to obtain initial hot-rolled wire rod; S5: Perform hot and cold treatment on the initial hot-rolled wire rod in a pit to obtain the final hot-rolled wire rod; The temperature control process during the thermal treatment of the sump pile is as follows: S51: Obtain pit temperature data The pit has six faces Xi, which are the top, bottom, left, right, front, and back of the pit, i∈[1,6]. Temperature detectors are installed on each face. The temperature detectors acquire the air temperature data of the six faces Xi at each sampling time and construct the average air temperature data sequence Zi, i∈[1,6] within each preset sub-time period sequence Yn of the six faces Xi. S52: Constructing the heating model data sequence Based on the difference between the above average air temperature data sequences Zi and Z6, we obtain ΔZi = Zi - Z6, i ∈ [1, 6], where Z6 is the air temperature at the bottom of the pit; if Zi < Z6, then we construct a preset heating device heating model data sequence Mi, i ∈ [1, 6], Mi = k * ΔZi, where k is the scaling factor. S53: Heating hot-rolled wire rod based on heating device model data sequence Mi and heating device start-up heating mode sequence Ni, i∈[1,6]; S54: Repeat steps S51 to S53; S55: When Zi=Z6 in step S52, the temperature control system stops building the preset heating device heating model data sequence Mi and stops the heating device.

4. The method for producing 27SiMn hot-rolled wire rod according to claim 3, characterized in that, In step S1, during converter smelting, the amount of molten iron added is 40-60 tons, and a low-nitrogen silicon-manganese alloy is used. The endpoint control targets are: C≥0.15%, P≤0.012%, T≥1610℃.

5. The method for producing 27SiMn hot-rolled wire rod according to claim 3, characterized in that, In step S1, after smelting, 100-200 kg of deoxidizer, 1500-2500 kg of silicon-manganese alloy, and 150-300 kg of carbon raiser are added to finally obtain primary molten steel.

6. The method for producing 27SiMn hot-rolled wire rod according to claim 3, characterized in that, In step S2, deoxidizers, silicon-manganese alloys, and carbon raisers are added during the refining process to finally obtain refined molten steel.

7. The method for producing 27SiMn hot-rolled wire rod according to claim 3, characterized in that, The mass composition of the 27SiMn protective slag in step S3 is as follows: SiO2: 25.7-30.7%, CaO: 27.7-32.7%, Al2O3: 3.0-6.0%, Fe2O3≤2.5%, MgO: 4.0-6.4%, R2O(Na2O+K2O): 6.8-9.8%, F⁻: 2.0-4.0%, C 全 : 12.0-16.0%.

8. The method for producing 27SiMn hot-rolled wire rod according to claim 3, characterized in that, When performing 18-stand hot rolling in step S4, the heating section temperature is controlled as follows: preheating section ≤1080℃, heating section 1140±30℃, soaking section 1120±30℃; the rolling temperature is controlled as follows: initial rolling temperature 1100±20℃, finishing rolling temperature 1020±20℃, wire drawing temperature 870±20℃; and the rolling speed is controlled as follows: 54~72m / s.

9. The method for producing 27SiMn hot-rolled wire rod according to claim 3, characterized in that, In step S53, the heating power is set to be proportional to Mi, and each unit Mi corresponds to QW of heating power. Therefore, the heating power of the pit Xi surface is Ni = Mi * Q.

Images