Production method of steel for non-quenched and tempered crankshaft
By precisely controlling the end-point components of the converter smelting and multi-stage refining treatment, the problems of complex quality and unstable quality in the traditional crankshaft steel production process are solved, and high-quality and low-energy-consuming steel production is achieved.
Patent Information
- Application Number
- CN202510189379.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-20
- Publication Date
- 2025-05-13
AI Technical Summary
The traditional crankshaft steel production process has problems such as complex quality treatment, high energy consumption and long cycle, which leads to the steel being prone to quality defects and difficult to meet production requirements.
The steel production method for non-temperature crankshafts is adopted to ensure the foundation quality and purity of the steel by precisely controlling the end-point components of the converter smelting, LF furnace refining and deoxygenation, RH furnace vacuum treatment and continuous casting stage.
It improves the strength, toughness and quality stability of steel, reduces production cycle and energy consumption, and enhances the stability and reliability of the production process.
Smart Images
Figure CN119979807A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of non-quenched and tempered crankshaft steel production methods, in particular to a non-quenched and tempered crankshaft steel production method. Background Art
[0002] With the rapid development of the automotive industry and other fields, the performance requirements for crankshaft steel are increasing. The traditional crankshaft steel production process has many shortcomings, such as complex tempering process, high energy consumption, and long cycle. In each production link, the converter smelting composition control accuracy is not enough, the steel-related operations are not fine enough, affecting the quality of molten steel, the LF furnace refining deoxidation and slag control are deficient, the RH furnace vacuum treatment is difficult to take into account the stability of nitrogen content, and the temperature control and cooling parameters of the molten steel in the continuous casting stage are unreasonable. These problems make steel prone to quality defects and make it difficult for the finished steel to meet production requirements. For this reason, we propose a non-tempered crankshaft steel production method. Summary of the invention
[0003] The object of the present invention is to provide a method for producing non-quenched and tempered crankshaft steel to solve the problems raised in the above background technology.
[0004] To achieve the above object, the present invention provides the following technical solution: a method for producing non-quenched and tempered crankshaft steel, the method comprising the following steps:
[0005] S1. During the converter smelting stage, the end-point composition of the converter smelting is precisely controlled to make the phosphorus content less than 0.012% and the carbon content greater than 0.08%. By closely monitoring the reaction in the furnace, finely adjusting the oxygen injection amount and the slag-making material addition parameters, the steel-out temperature is ensured to reach 1620°C or above. The furnace gas analysis system is used to monitor the chemical reaction process in the furnace in real time to ensure accurate control of the end-point composition.
[0006] S2, in the steel-making stage, the alloy is added in an accurate amount according to the composition requirements of the ladle furnace at the station, and the alloy is added to the molten steel evenly and orderly during the steel-making process, and slag washing, deoxidation, slag blocking and argon blowing operations are performed;
[0007] In the S3 and LF furnace refining stages, silicon carbide and a small amount of aluminum particles are used for diffusion deoxidation. According to the initial oxygen content of the molten steel and the target oxygen content, the amount of silicon carbide and aluminum particles added is precisely controlled and evenly sprinkled on the surface of the molten steel to make them fully contact the molten steel to improve the deoxidation efficiency. Close attention is paid to the reaction of the molten steel to prevent excessive deoxidation reaction from causing molten steel overflow or damage to the furnace lining. The refining white slag retention time is controlled at about 35 minutes, and the total slag volume is controlled at more than 12kg / t steel. After the molten steel temperature reaches 1590℃, nitrogen alloy wire is fed to increase nitrogen. After the refined slag becomes white slag, a small amount of silica sand is added to adjust the basicity of the refined slag to the target value, and the slag composition is strictly controlled according to the actual situation. , strictly control the white slag retention time and slag amount, accurately calculate the amount of silica sand added, and pay attention to the fluidity of the slag and the ability to absorb inclusions. After refining, feed 0.4-0.6m / t steel calcium wire into the molten steel for inclusion modification. The calcium wire feeding speed should be uniform to avoid excessive local calcium content. After the calcium wire is fed, soft blow for 6-8 minutes. The flow rate of soft blown argon should be strictly controlled. Excessive flow may destroy the environment that is conducive to the floating of inclusions. By slowly blowing argon, the molten steel is kept in a slightly stirred state, which is conducive to the floating of inclusions. Then feed the sulfur line to increase sulfur, and evenly control the sulfur line feeding speed to meet the sulfur content requirements of the steel grade;
[0008] S4, RH furnace vacuum treatment stage, using RH furnace for vacuum treatment, ensure that the vacuum time is controlled to be more than 12 minutes, and through the operation of the vacuum system of the equipment, ensure that the H content in the steel is controlled below 1.5×10-6;
[0009] S5, in the continuous casting stage, the temperature of the molten steel in the tundish is controlled at 18-28°C. After the steel is tapped from the refining furnace, the ladle covering agent and heating device are used to reduce the temperature drop of the molten steel during transportation. At the same time, the tundish is fully preheated so that the molten steel can be kept in the superheat range of 18-28°C after entering the tundish. During the continuous casting process, the molten steel temperature change in the tundish is monitored and the flow rate of molten steel from the ladle to the tundish is adjusted in time to maintain a stable superheat. The temperature drop of the tundish is controlled within 10°C, and the continuous casting is subjected to secondary cooling;
[0010] S6. In the rolling stage, 280 square billets are selected to roll round steel with a diameter of 90mm. Before rolling, the billets are strictly inspected for quality to ensure that there are no obvious surface and internal defects in the billets, so as to ensure the smooth progress of the subsequent rolling process. During rolling heating, the billets are sent to the preheating section of the rolling heating furnace, and the temperature of the preheating section is strictly controlled below 680℃. The billets then enter the soaking section, and the temperature of the soaking section is set at 1180-1210℃ for high-temperature diffusion. The total time in the furnace is controlled at 200-300min. The temperature control system of the heating furnace is used to monitor the furnace temperature in real time with the help of a thermocouple temperature measuring device, and the fuel supply or combustion air volume is adjusted in time according to the temperature deviation to ensure that the billets are heated according to the set temperature curve to achieve uniform composition and organization. At the same time, attention should be paid to avoid oxidation, overheating or overburning caused by excessive heating temperature;
[0011] S7. In the subsequent processing stage, the round steel after rolling enters the online pickling link, and the round steel is immersed in a pickling solution of appropriate concentration. The surface oxide scale and possible minor defects are removed by chemical reaction, and then rinsed with clean water. During the pickling process, the pickling solution concentration, temperature and pickling time parameters are strictly controlled to effectively avoid excessive pickling corrosion on the steel surface and affect its dimensional accuracy and performance. After the pickling is completed, check whether there are obvious crack defects on the surface of the round steel. The round steel after pickling inspection is placed on the cooling bed, and the cooling bed plus insulation cover is used for insulation and slow cooling. The insulation cover covering time and the cooling speed of the cooling bed are controlled according to the round steel specifications and steel type factors, which can effectively reduce thermal stress, reduce the probability of cracks, prevent cold air from entering and affecting the slow cooling effect, and regularly check the operation of the cooling bed to ensure smooth cooling of the round steel.
[0012] Preferably, the slag washing, deoxidation, slag blocking and argon blowing in S2 include the following specific steps:
[0013] S2.1. During the steel-making process, 450-550kg of lime and 280-300kg of refined synthetic slag are added for slag washing to ensure that the alloy and molten steel are fully mixed, and the slag is fully in contact with the molten steel in the molten steel flow to play the role of absorbing impurities. Pay attention to the fluidity of the slag in real time to prevent the occurrence of crusting;
[0014] S2.2. Add about 300kg of aluminum iron along the steel flow for precipitation deoxidation, and control the amount and speed of addition to prevent the increase of inclusions due to excessive aluminum addition, or the violent reaction of molten steel and splashing due to too fast addition speed;
[0015] S2.3. Feeding 200m aluminum wire into the back of the furnace for further precipitation and deoxidation can effectively improve the deoxidation effect. Pay attention to the coordination of deoxidation operation and subsequent bottom blowing argon and other operations;
[0016] S2.4. In the later stage of steel tapping, the slag outflow is monitored by infrared automatic detection equipment. When slag outflow is detected, the slide slag blocking device will act quickly to control the slag thickness of the ladle top to be less than or equal to 20mm. The infrared detection equipment should be calibrated regularly to maintain the mechanical properties of the slide slag blocking device to ensure its sensitive and reliable action. The slag blocking time should be reasonably controlled to effectively avoid the normal steel tapping caused by premature slag blocking or the excessive thickness of the slag on the ladle top caused by late slag blocking.
[0017] S2.5. Carry out bottom blowing of argon throughout the furnace. Blow an appropriate amount of argon through the air bricks at the bottom of the ladle. The argon flow rate should be moderate to prevent excessive flow from causing violent churning of the molten steel, resulting in oxidation and excessive heat loss, or too small flow to achieve a good stirring effect. Check the air permeability of the air bricks regularly to ensure the normal operation of the bottom blowing of argon, promote the melting of the alloy and the floating and removal of deoxidation products.
[0018] Preferably, in the RH furnace vacuum treatment stage in S4, circulating nitrogen blowing is used to increase nitrogen so as to maintain a stable nitrogen content in the steel.
[0019] Preferably, the temperature drop of the tundish in S5 is controlled by adopting high-quality tundish refractory materials, while reducing the residence time of the molten steel in the tundish, reducing the temperature drop amplitude, and in the continuous casting process, the ladle replacement is arranged compactly to avoid the molten steel waiting for casting in the tundish for a long time. The superheat of the molten steel in the tundish is controlled by controlling the temperature of the molten steel and the preheating temperature of the tundish.
[0020] Preferably, in the S5, the continuous casting adopts crystallizer cooling for the first time. When the molten steel starts to be poured into the crystallizer, the changes in the molten steel level in the crystallizer are closely observed, and the liquid level is kept stable by the liquid level control system. At the same time, the temperature difference between the inlet and outlet water of the crystallizer is observed. The temperature difference cannot exceed 10-15°C. If the temperature difference is too large, it means that the cooling intensity is too high or the local cooling is uneven, and the cooling water volume needs to be adjusted in time. Protective slag is added to the surface of the molten steel in the crystallizer. The protective slag forms a layer of liquid slag film on the surface of the molten steel, which plays a role in lubricating the ingot and preventing the oxidation of the molten steel. The thickness of the slag layer is controlled to be 5-10mm. Protective slag is added to the surface of the molten steel in the crystallizer. The protective slag forms a layer of liquid slag film on the surface of the molten steel, which plays a role in lubricating the ingot and preventing the oxidation of the molten steel.
[0021] Preferably, the second cooling of continuous casting in S5 adopts a relatively high water content of 0.35L / kg and a constant drawing speed of 0.80m / min for casting steel. Through a precise water flow control system, the flow of cooling water is adjusted according to the weight parameters of the ingot to ensure that the set water content requirement is met. At the same time, through the precise control of the billet drawing machine, the billet drawing speed is kept stable at 0.80m / min, the billet drawing speed is monitored in real time and compared with the set value. Once a deviation is found, the output power of the billet drawing motor is adjusted immediately to restore the billet drawing speed to 0.80m / min.
[0022] Preferably, in S6, precise temperature control is achieved by adjusting the flame intensity and fuel flow parameters of the heating furnace burner.
[0023] Preferably, in S6, when the ingot is heated and taken out of the furnace, it immediately enters the high-pressure water descaling process, and the high-pressure water descaling pressure is controlled at about 28 MPa. The water is pressurized by a high-pressure water pump, and then the high-pressure water is sprayed onto the surface of the steel billet from the nozzle to remove the surface oxidized iron scale. During operation, the parameters such as the spray angle and spray distance of the high-pressure water must be correct, and the high-pressure water descaling system equipment, including the water pump operating performance and nozzle wear, must be checked regularly to ensure a good descaling effect and no oxidized iron scale remains on the surface after descaling.
[0024] Preferably, in the S6 rolling stage, the finishing rolling inlet temperature is controlled at 950-1000°C by controlling the amount of cooling water in the rolling mill, and the reduction amount is adjusted by accurately controlling the gap between the rollers during the rolling process to ensure smooth finishing rolling and stable quality of finished steel products, and to prevent uneven deformation, dimensional deviation or surface quality problems due to improper temperature, as well as damage to the rolling mill equipment or uneven internal structure of the steel due to excessive deformation resistance.
[0025] Compared with the prior art, the present invention provides a method for producing non-quenched and tempered crankshaft steel, which has the following beneficial effects:
[0026] 1. The production method of non-quenched and tempered crankshaft steel, through the precise control of the final composition in the converter smelting stage, makes the phosphorus content less than 0.012%, the carbon content greater than 0.08%, and uses the furnace gas analysis system to ensure the precise control of the final composition, thereby ensuring the basic quality of the steel, providing a high-quality raw material basis for subsequent processes, and is conducive to improving the comprehensive properties of the steel such as strength and toughness.
[0027] 2. The non-quenched and tempered crankshaft steel production method effectively improves the deoxidation efficiency, reduces the oxygen content and the number of inclusions in the molten steel, and significantly improves the purity of the steel, thereby improving the quality stability and mechanical properties of the steel. In the RH furnace vacuum treatment stage, the circulating nitrogen blowing is used to increase the nitrogen, while the hydrogen content in the steel is effectively reduced, and the stability of the nitrogen content in the steel is maintained, thereby avoiding the influence of nitrogen content fluctuations caused by vacuum treatment on the steel performance, improving the stability and reliability of the production process, and facilitating large-scale and efficient production.
[0028] 3. The production method of non-quenched and tempered crankshaft steel reasonably arranges slag washing, deoxidation, slag blocking and argon blowing operations in the steel-making stage, such as adding a specific amount of lime and refined synthetic slag for slag washing, accurately controlling the deoxidation of aluminum iron and aluminum wire, effectively blocking slag and reasonably blowing argon at the bottom, which promotes the melting of alloy and the floating removal of deoxidation products, improves the efficiency of the steel-making process and the quality of molten steel, reduces the burden of subsequent refining, and shortens the production cycle.
[0029] 4. The production method of non-quenched and tempered crankshaft steel controls the temperature of the molten steel in the ladle through a variety of measures during the continuous casting stage, such as using ladle covering agents, heating devices, and compact arrangement of ladle replacement to control superheat and temperature drop, combined with reasonable parameter settings of crystallizer cooling and secondary cooling, so that the solidification process of the ingot is more stable, the internal structure is uniform, the defects of the ingot are reduced, the continuous casting production efficiency and the quality of the ingot are improved, and high-quality ingots are provided for subsequent rolling. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Figure 1 It is a schematic diagram of the production method of the present invention. DETAILED DESCRIPTION
[0031] like Figure 1 As shown, the present invention provides a technical solution: a method for producing non-quenched and tempered crankshaft steel, the method for producing non-quenched and tempered crankshaft steel comprising the following steps:
[0032] S1. During the converter smelting stage, the end-point composition of the converter smelting is precisely controlled to make the phosphorus content less than 0.012% and the carbon content greater than 0.08%. By closely monitoring the reaction in the furnace, finely adjusting the oxygen injection amount and the slag-making material addition parameters, the steel-out temperature is ensured to reach 1620°C or above. The furnace gas analysis system is used to monitor the chemical reaction process in the furnace in real time to ensure accurate control of the end-point composition.
[0033] S2, in the steel-making stage, according to the composition requirements of the ladle furnace at the station, the alloy is accurately added, and the alloy is added to the molten steel evenly and orderly during the steel-making process, and slag washing, deoxidation, slag blocking and argon blowing operations are performed, wherein slag washing, deoxidation, slag blocking and argon blowing include the following specific steps:
[0034] S2.1. During the steel-making process, 450-550kg of lime and 280-300kg of refined synthetic slag are added for slag washing to ensure that the alloy and molten steel are fully mixed, and the slag is fully in contact with the molten steel in the molten steel flow to play the role of absorbing impurities. Pay attention to the fluidity of the slag in real time to prevent the occurrence of crusting;
[0035] S2.2. Add about 300kg of aluminum iron along the steel flow for precipitation deoxidation, and control the amount and speed of addition to prevent the increase of inclusions due to excessive aluminum addition, or the violent reaction of molten steel and splashing due to too fast addition speed;
[0036] S2.3. Feeding 200m aluminum wire into the back of the furnace for further precipitation and deoxidation can effectively improve the deoxidation effect. Pay attention to the coordination of deoxidation operation and subsequent bottom blowing argon and other operations;
[0037] S2.4. In the later stage of steel tapping, the slag outflow is monitored by infrared automatic detection equipment. When slag outflow is detected, the slide slag blocking device will act quickly to control the slag thickness of the ladle top to be less than or equal to 20mm. The infrared detection equipment should be calibrated regularly to maintain the mechanical properties of the slide slag blocking device to ensure its sensitive and reliable action. The slag blocking time should be reasonably controlled to effectively avoid the normal steel tapping caused by premature slag blocking or the excessive thickness of the slag on the ladle top caused by late slag blocking.
[0038] S2.5. Perform bottom blowing of argon throughout the furnace. Blow an appropriate amount of argon through the air-permeable bricks at the bottom of the ladle. The argon flow rate should be moderate to prevent excessive flow from causing violent churning of the molten steel, resulting in oxidation and excessive heat loss, or too small flow to achieve a good stirring effect. Check the air-permeable performance of the air-permeable bricks regularly to ensure the normal operation of the bottom blowing of argon and promote the melting of the alloy and the floating and removal of the deoxidation products.
[0039] In the S3 and LF furnace refining stages, silicon carbide and a small amount of aluminum particles are used for diffusion deoxidation. According to the initial oxygen content of the molten steel and the target oxygen content, the amount of silicon carbide and aluminum particles added is precisely controlled and evenly sprinkled on the surface of the molten steel to make them fully contact the molten steel to improve the deoxidation efficiency. Close attention is paid to the reaction of the molten steel to prevent excessive deoxidation reaction from causing molten steel overflow or damage to the furnace lining. The refining white slag retention time is controlled at about 35 minutes, and the total slag volume is controlled at more than 12kg / t steel. After the molten steel temperature reaches 1590℃, nitrogen alloy wire is fed to increase nitrogen. After the refined slag becomes white slag, a small amount of silica sand is added to adjust the basicity of the refined slag to the target value, and the slag composition is strictly controlled according to the actual situation. , strictly control the white slag retention time and slag amount, accurately calculate the amount of silica sand added, and pay attention to the fluidity of the slag and the ability to absorb inclusions. After refining, feed 0.4-0.6m / t steel calcium wire into the molten steel for inclusion modification. The calcium wire feeding speed should be uniform to avoid excessive local calcium content. After the calcium wire is fed, soft blow for 6-8 minutes. The flow rate of soft blown argon should be strictly controlled. Excessive flow may destroy the environment that is conducive to the floating of inclusions. By slowly blowing argon, the molten steel is kept in a slightly stirred state, which is conducive to the floating of inclusions. Then feed the sulfur line to increase sulfur, and evenly control the sulfur line feeding speed to meet the sulfur content requirements of the steel grade;
[0040] S4, RH furnace vacuum treatment stage, the RH furnace is used for vacuum treatment, ensuring that the vacuum time is controlled at more than 12 minutes, and the vacuum system of the equipment is operated to ensure that the H content in the steel is controlled below 1.5×10-6, and circulating nitrogen blowing is used to increase nitrogen to maintain a stable nitrogen content in the steel;
[0041] S5. During the continuous casting stage, the temperature of the molten steel in the middle ladle is controlled at 18-28℃. After the steel is tapped from the refining furnace, the ladle covering agent and heating device are used to reduce the temperature drop of the molten steel during transportation. At the same time, the middle ladle is fully preheated so that the molten steel can be kept in the superheat range of 18-28℃ after entering the middle ladle. During the continuous casting process, the temperature change of the molten steel in the middle ladle is monitored and the flow rate of molten steel from the ladle to the middle ladle is adjusted in time to maintain the superheat stable. The temperature drop of the middle ladle is controlled within 10℃. The temperature drop of the middle ladle is controlled by using high-quality The refractory material of the tundish is used to reduce the residence time of the molten steel in the tundish and the temperature drop. During the continuous casting process, the ladle replacement is arranged compactly to avoid the molten steel waiting for casting in the tundish for a long time. The superheat of the molten steel in the tundish is controlled by controlling the temperature of the molten steel and the preheating temperature of the tundish. The crystallizer cooling is used for the first time in continuous casting. When the molten steel begins to be poured into the crystallizer, the changes in the molten steel level in the crystallizer are closely observed and the liquid level is kept stable through the liquid level control system. At the same time, the temperature difference between the inlet and outlet water of the crystallizer is observed. The temperature difference is not It can exceed 10-15℃. If the temperature difference is too large, it means that the cooling intensity is too high or the local cooling is uneven. It is necessary to adjust the cooling water volume in time, add protective slag on the surface of molten steel in the crystallizer, and the protective slag forms a layer of liquid slag film on the surface of molten steel, which plays a role in lubricating the billet and preventing the oxidation of molten steel. The thickness of the slag layer is controlled at 5-10mm. Add protective slag on the surface of molten steel in the crystallizer, and the protective slag forms a layer of liquid slag film on the surface of molten steel, which plays a role in lubricating the billet and preventing the oxidation of molten steel. The second cooling of continuous casting adopts a relatively high specific water volume of 0.35L / kg and a constant drawing speed of 0.80m / min for steel casting. Through the precise water flow control system, the flow of cooling water is adjusted according to the weight parameters of the billet to ensure that the set specific water volume requirements are met. At the same time, through the precise control of the billet drawing machine, the billet drawing speed is kept stable at 0.80m / min, the billet drawing speed is monitored in real time and compared with the set value. Once a deviation is found, the output power of the billet drawing motor is adjusted immediately to restore the billet drawing speed to 0.80m / min.
[0042] S6. In the rolling stage, 280 square billets are used to roll round steel with a diameter of 90mm. Before rolling, the billets are strictly inspected for quality to ensure that there are no obvious surface and internal defects in the billets, so as to ensure the smooth progress of the subsequent rolling process. During rolling heating, the billets are sent to the preheating section of the rolling heating furnace, and the temperature of the preheating section is strictly controlled below 680℃. Accurate temperature control is achieved by adjusting the flame intensity and fuel flow parameters of the heating furnace burner. The billets then enter the soaking section, and the soaking section temperature is set at 1180-1210℃ for high-temperature diffusion. The total time in the furnace is controlled at 200-300min. The temperature control system of the heating furnace is used to monitor the furnace temperature in real time with the help of a thermocouple temperature measuring device, and the fuel supply or combustion air volume is adjusted in time according to the temperature deviation to ensure that the billets are heated according to the set temperature curve to achieve uniform composition and organization. At the same time, attention should be paid to avoid oxidation caused by excessive heating temperature. Overheating or overburning problem: when the billet is heated and taken out of the furnace, it will immediately enter the high-pressure water descaling process. The high-pressure water descaling pressure is controlled at about 28MPa. The water is pressurized by a high-pressure water pump, and then the high-pressure water is sprayed to the billet surface by the nozzle to remove the surface oxidized iron scale. During operation, the parameters such as the spray angle and spray distance of the high-pressure water must be correct, and the high-pressure water descaling system equipment, including the water pump operation performance and nozzle wear, must be checked regularly to ensure good descaling effect, so that there is no oxidized iron scale left on the surface after descaling. The finishing rolling inlet temperature is controlled at 950-1000℃ by controlling the cooling water volume in the rolling mill. During the rolling process, the roll gap is precisely controlled to adjust the reduction amount to ensure the smooth progress of the finishing rolling process and the stable quality of the finished steel products, and to prevent uneven deformation, dimensional deviation or surface quality problems caused by improper temperature, as well as damage to the rolling mill equipment or uneven internal structure of the steel due to excessive deformation resistance;
[0043] S7. In the subsequent processing stage, the round steel after rolling enters the online pickling link, and the round steel is immersed in a pickling solution of appropriate concentration. The surface oxide scale and possible minor defects are removed by chemical reaction, and then rinsed with clean water. During the pickling process, the pickling solution concentration, temperature and pickling time parameters are strictly controlled to effectively avoid excessive pickling corrosion on the steel surface and affect its dimensional accuracy and performance. After the pickling is completed, check whether there are obvious crack defects on the surface of the round steel. The round steel after pickling inspection is placed on the cooling bed, and the cooling bed plus insulation cover is used for insulation and slow cooling. The insulation cover covering time and the cooling speed of the cooling bed are controlled according to the round steel specifications and steel type factors, which can effectively reduce thermal stress, reduce the probability of cracks, prevent cold air from entering and affecting the slow cooling effect, and regularly check the operation of the cooling bed to ensure smooth cooling of the round steel.
[0044] The above generally describes the present invention in detail, but it is obvious to a person skilled in the art that some modifications or improvements can be made to the present invention. Therefore, modifications or improvements that do not depart from the spirit of the present invention are within the scope of protection of the present invention.
Claims
1. A method for producing non-quenched and tempered crankshaft steel, characterized in that: The method for producing non-quenched and tempered crankshaft steel comprises the following steps: S1. During the converter smelting stage, the end-point composition of the converter smelting is precisely controlled to make the phosphorus content less than 0.012% and the carbon content greater than 0.08%. By closely monitoring the reaction in the furnace, finely adjusting the oxygen injection amount and the slag-making material addition parameters, the steel-out temperature is ensured to reach 1620°C or above. The furnace gas analysis system is used to monitor the chemical reaction process in the furnace in real time to ensure accurate control of the end-point composition. S2, in the steel-making stage, the alloy is added in an accurate amount according to the composition requirements of the ladle furnace at the station, and the alloy is added to the molten steel evenly and orderly during the steel-making process, and slag washing, deoxidation, slag blocking and argon blowing operations are performed; In the S3 and LF furnace refining stages, silicon carbide and a small amount of aluminum particles are used for diffusion deoxidation. According to the initial oxygen content of the molten steel and the target oxygen content, the amount of silicon carbide and aluminum particles added is precisely controlled and evenly sprinkled on the surface of the molten steel to fully contact the molten steel to improve the deoxidation efficiency. Close attention is paid to the reaction of the molten steel to prevent excessive deoxidation reaction from causing molten steel overflow or damage to the furnace lining. The refining white slag retention time is controlled at about 35 minutes, and the total slag volume is controlled at more than 12kg / t steel. After the molten steel temperature reaches 1590℃, nitrogen alloy wire is fed to increase nitrogen. After the refined slag becomes white slag, a small amount of silica sand is added to adjust the refined slag alkali The degree is adjusted to the target value, and the slag composition is strictly controlled according to the actual situation. The white slag retention time and slag amount are strictly controlled, and the amount of silica sand added is accurately calculated. At the same time, attention is paid to the fluidity and inclusion absorption capacity of the slag. After refining, 0.4-0.6m / t steel calcium wire is fed into the molten steel for inclusion modification. The calcium wire feeding speed should be uniform to avoid excessive local calcium content. After the calcium wire is fed, soft blowing is performed for 6-8 minutes. The flow rate of soft blowing argon should be strictly controlled. Excessive flow may destroy the environment that has been formed to facilitate the floating of inclusions. Then the sulfur line is fed to increase sulfur, and the sulfur line feeding speed is evenly controlled; S4, RH furnace vacuum treatment stage, using RH furnace for vacuum treatment, ensure that the vacuum time is controlled to be more than 12 minutes, and through the operation of the vacuum system of the equipment, ensure that the H content in the steel is controlled below 1.5×10-6; S5, in the continuous casting stage, the temperature of the molten steel in the tundish is controlled at 18-28°C. After the steel is tapped from the refining furnace, a ladle covering agent and a heating device are used. During the continuous casting process, the temperature change of the molten steel in the tundish is monitored and the flow rate of the molten steel from the ladle to the tundish is adjusted in time to maintain a stable superheat. The temperature drop of the tundish is controlled within 10°C, and the continuous casting is subjected to secondary cooling; S6. In the rolling stage, 280 square billets are selected to roll round steel with a diameter of 90mm. Before rolling, the billets are strictly inspected for quality to ensure that the billets have no obvious surface and internal defects. During rolling heating, the billets are sent to the preheating section of the rolling heating furnace, and the temperature of the preheating section is strictly controlled below 680℃. The billets then enter the soaking section, and the temperature of the soaking section is set at 1180-1210℃ for high-temperature diffusion. The total time in the furnace is controlled at 200-300min. The temperature control system of the heating furnace is used to monitor the furnace temperature in real time with the help of a thermocouple temperature measuring device, and the fuel supply or combustion air volume is adjusted in time according to the temperature deviation. At the same time, attention should be paid to avoid oxidation, overheating or overburning caused by excessive heating temperature; S7. In the subsequent processing stage, the round steel after rolling enters the online pickling link, and the round steel is immersed in a pickling solution of appropriate concentration, and the surface oxide scale and possible minor defects are removed by chemical reaction, and then rinsed with clean water. During the pickling process, the pickling solution concentration, temperature and pickling time parameters are strictly controlled. After the pickling is completed, check whether there are obvious crack defects on the surface of the round steel. The round steel after pickling inspection is placed on the cooling bed, and the cooling bed and insulation cover are used for insulation and slow cooling. The insulation cover covering time and the cooling speed of the cooling bed are controlled according to the round steel specifications and steel type factors.
2. The method for producing non-quenched and tempered crankshaft steel according to claim 1, characterized in that: The slag washing, deoxidation, slag blocking and argon blowing in S2 include the following specific steps: S2.
1. During the steel-making process, 450-550kg of lime and 280-300kg of refined synthetic slag are added for slag washing to ensure that the alloy and molten steel are fully mixed, and the slag is fully in contact with the molten steel in the molten steel flow to play the role of absorbing impurities. Pay attention to the fluidity of the slag in real time to prevent the occurrence of crusting; S2.2, add about 300kg of aluminum iron along the steel flow for precipitation and deoxidation, and control the amount and speed of addition; S2.3, feed 200m aluminum wire into the back of the furnace for further precipitation and deoxidation; S2.
4. In the later stage of steel tapping, the slag infrared automatic detection equipment is used to monitor the slag outflow. When the slag outflow is detected, the slide slag blocking device will act quickly to control the slag thickness of the ladle top to be less than or equal to 20mm, and reasonably control the slag blocking time; S2.
5. Carry out argon blowing at the bottom of the furnace, and blow an appropriate amount of argon gas through the air-permeable bricks at the bottom of the ladle.
3. The method for producing non-quenched and tempered crankshaft steel according to claim 1, characterized in that: During the RH furnace vacuum treatment stage in S4, circulating nitrogen blowing is used to increase nitrogen so as to maintain a stable nitrogen content in the steel.
4. The method for producing non-quenched and tempered crankshaft steel according to claim 1, characterized in that: The temperature drop of the tundish in S5 is controlled by using high-quality tundish refractory materials, while reducing the residence time of the molten steel in the tundish, reducing the temperature drop amplitude, and arranging the replacement of the ladles in a compact manner during the continuous casting process. The superheat of the molten steel in the tundish is controlled by controlling the temperature of the molten steel and the preheating temperature of the tundish.
5. The method for producing non-quenched and tempered crankshaft steel according to claim 1, characterized in that: In the S5, the continuous casting adopts the crystallizer cooling for the first time. When the molten steel starts to be poured into the crystallizer, the change of the molten steel level in the crystallizer is closely observed, and the liquid level is kept stable by the liquid level control system. At the same time, the temperature difference of the water at the inlet and outlet of the crystallizer is observed. The temperature difference cannot exceed 10-15°C. If the temperature difference is too large, it means that the cooling intensity is too high or the local cooling is uneven. It is necessary to adjust the cooling water volume in time, add protective slag on the surface of the molten steel in the crystallizer, and the protective slag forms a layer of liquid slag film on the surface of the molten steel. The thickness of the slag layer is controlled at 5-10mm. Add protective slag on the surface of the molten steel in the crystallizer, and the protective slag forms a layer of liquid slag film on the surface of the molten steel.
6. The method for producing non-quenched and tempered crankshaft steel according to claim 5, characterized in that: The second cooling of continuous casting in S5 adopts a relatively high specific water volume of 0.35L / kg and a constant drawing speed of 0.80m / min for casting steel. Through an accurate water flow control system and precise control of the billet drawing machine, the billet drawing speed is kept stable at 0.80m / min. The billet drawing speed is monitored in real time and compared with the set value. Once a deviation is found, the output power of the billet drawing motor is immediately adjusted to restore the billet drawing speed to 0.80m / min.
7. The method for producing non-quenched and tempered crankshaft steel according to claim 1, characterized in that: In S6, precise temperature control is achieved by adjusting the flame intensity and fuel flow parameters of the heating furnace burner.
8. The method for producing non-quenched and tempered crankshaft steel according to claim 1, characterized in that: In S6, when the ingot is heated and taken out of the furnace, it immediately enters the high-pressure water descaling process, and the high-pressure water descaling pressure is controlled at about 28MPa. The water is pressurized by a high-pressure water pump, and then the high-pressure water is sprayed onto the surface of the steel billet through a nozzle to remove the surface oxide scale, so that no oxide scale remains on the surface after descaling.
9. The method for producing non-quenched and tempered crankshaft steel according to claim 1, characterized in that: In the S6 rolling stage, the finishing rolling inlet temperature is controlled at 950-1000° C. by controlling the amount of cooling water between the rolling mills, and the reduction amount is adjusted by accurately controlling the gap between the rolls during the rolling process.