A hot rolling alloy tool steel X32 opening pouring production process of a vertical bending slab caster

Abstract

The present application relates to a kind of hot rolling alloy tool steel X32 opening production process of production process of vertical bending type slab caster, specifically as follows: step 1: vertical bending type caster head vertical bending section parameter setting before opening;Step 2: vertical bending type caster opening process;Step 3: opening process flow is ended.The present application is by innovating the arc parameter of the crystallizer and bending section of the head of vertical bending type slab caster and the opening degree control setting of bending section in vertical bending interval, reduce the drawing resistance caused by bending strain and drum strain, to solve the blanking hidden danger caused by the strength of opening head blank;By using low-silicon dry material tundish, set upper station liquid temperature interval to solve the quality defect of opening head blank.Finally through the crystallizer copper plate oiling of opening time period, opening sprout time interval setting, opening after specific water quantity optimization parameter setting, completely solve the problem of hot rolling alloy tool steel X32 in vertical bending type slab continuous casting opening production blanking hidden danger and angle transverse crack quality defect.

Description

Technical Field

[0001] This invention relates to a production process, specifically to a hot-rolled alloy tool steel X32 casting process for a vertical bending slab casting machine, belonging to the field of continuous casting technology in iron and steel metallurgy. Background Technology

[0002] In current continuous casting processes in the steel industry, hot-rolled alloy tool steel X32 is used as the backing material for bimetallic saw blades. It can be used to manufacture saw blades for cutting steel, non-ferrous metals, hard and precious woods, and polymer materials. Its alloy content is as high as 5.0% to 8.5%, resulting in a strength of 1800 MPa to 2000 MPa. The high strength, extremely high requirements for internal and surface quality, and the significant challenges in slab continuous casting production make it particularly difficult. Especially in vertical bending continuous casting machines, improper process settings during the initial casting stage can lead to serious casting slab stagnation accidents or batch quality defects.

[0003] According to the inventor's search, no production process for hot-rolled alloy tool steel X32 has been disclosed. The published application number 201510673626.3, "A method for producing and smelting saw blade steel," only describes and specifies the smelting technology for this steel, but does not address the control of key parameters in the continuous casting process. Other similar casting start-up processes, such as the method for improving the casting start-up effect of high-carbon steel continuous casting (publication number CN106270422A), mainly involve adding calcium silicate powder to the tundish before casting start-up. After the molten steel flows into the tundish, the oxygen in the molten steel reacts with the calcium silicate powder, releasing heat to reduce the temperature drop of the molten steel and eliminate the phenomenon of cold steel forming at the bottom of the tundish, thus improving the casting start-up effect. However, no such process is addressed for the casting start-up production of X32 slabs with high alloy content and strength approaching 2000 MPa. Application number CN114472836A discloses a method for preventing steel leakage during the initial casting of high-carbon steel slabs. This method addresses the issue of insufficient shell strength in the initial casting shell of high-carbon steel slabs due to solidification characteristics by setting appropriate initial casting process parameters. However, alloy tool steel X32 and high-carbon steel have different steel properties, and the high strength resulting from its high alloy content places entirely different demands on the slab continuous casting process. In the vertical bending casting machine involved, the initial casting shell is prone to corner transverse cracks, and the high strength can easily lead to slab stagnation and other production hazards, requiring a comprehensive process solution to resolve these issues.

[0004] In the continuous casting production of hot-rolled alloy tool steel X32 in vertical bending slabs, improper settings in the initial casting process can cause blockages due to the high-strength slab passing through the continuous casting mold and casting machine head. These blockages can range from minor fluctuations in the liquid level within the mold to severe accidents such as slab stagnation. Furthermore, given the extremely high smelting cost of X32 steel, poor control of quality defects at the initial casting head can result in significant cost losses. In view of these issues, this invention provides an initial casting process technology for the continuous casting production of hot-rolled alloy tool steel X32 in slabs. This technology primarily addresses the problems of slab stagnation and corner cracking defects in the initial casting production of hot-rolled alloy tool steel X32 in vertical bending slabs through the optimization and improvement of key continuous casting process parameters, including control of critical precision parameters at the casting machine head, control of molten steel superheat during initial casting, use of special materials in the continuous casting tundish, setting of key initial casting process parameters, and setting of casting machine cooling parameters. Summary of the Invention

[0005] This invention addresses the problems existing in the prior art by providing a process for the initial casting of hot-rolled alloy tool steel X32 in a vertical bending slab casting machine. This invention solves the problem of billet stagnation caused by the high strength of the initial casting billet by innovating the parameters of the crystallizer and bending section at the head of the vertical bending slab casting machine, as well as controlling the opening degree of the bending section in the vertical bending zone. This reduces the pulling resistance caused by bending strain and bulging strain. Furthermore, it addresses the quality defects of the initial casting billet by using a low-silicon dry material tundish and setting a temperature range for the molten steel. Finally, by adjusting parameters such as applying oil to the crystallizer copper plate during the initial casting period, setting intervals for the initial casting emergence time, and optimizing the specific water content after initial casting, this invention completely solves the problems of billet stagnation and corner cracking defects in the initial casting of hot-rolled alloy tool steel X32 in vertical bending slab continuous casting.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: a hot-rolled alloy tool steel X32 casting process for a vertical bending slab casting machine, the process comprising the following steps:

[0007] Step 1: Setting parameters for the vertical bending section of the head of the vertical bending casting machine before pouring;

[0008] 1.1 Setting parameters for foot roller opening and copper plate thickness.

[0009] 1.1.1 The thickness of the copper plate at the bottom of the casting machine's crystallizer is set according to a shrinkage coefficient of 1.05. The opening of the foot rolls of the crystallizer is further reduced by 1mm based on the thickness of the copper plate at the bottom of the crystallizer. The purpose is to control the bulging of the high-strength alloy steel after it exits the bottom of the crystallizer and reduce the drawing resistance caused by the bulging stress.

[0010] 1.1.2 The deviation between the outer arc of the casting machine and the center baseline of the casting machine is set to -0.2mm to 0mm. The opening value of the curved section inlet is set to the same as the crystallizer foot roller setting value (the purpose is to ensure horizontality in the height direction). Before each production run, a horizontal ruler is used to calibrate the arc. If the arc deviation exceeds 0.3mm, alignment adjustment is performed. The purpose is to reduce the resistance caused by the misalignment strain of the high-strength slab during the height direction of the casting machine.

[0011] 1.2 Negative Tolerance Setting for Bending Section Opening: The entire bending section adopts a shrinkage setting of 1mm, and its shrinkage is evenly distributed across all rollers. The shrinkage amount for each pair of rollers is 1 / N (N represents the number of roller pairs in the bending section). The allowable offline tolerance for the bending section is -0.3mm to 0.10mm; the tolerance for the arc is -0.15mm to 0.2mm. The purpose is to reduce positive tolerances, utilize the bearing clearance under hot conditions to compensate for excessive deviations, and reduce the potential for corner transverse crack defects and slab running obstacles caused by bulging strain and arc strain during the operation of high-strength slabs.

[0012] Step 2: Initial casting process of the vertical bending casting machine;

[0013] 2.1 Use of Tundish in Initial Casting: A dry-material tundish with a special dry lining containing 50% inorganic salt and 50% resin binder is used. A 150-minute baking time is set, with a baking temperature exceeding 1300°C and maintained at 1300°C for more than 30 minutes. This aims to reduce the increase in hydrogen content in the molten steel caused by moisture and crystal water from the tundish refractory material at the slab head, thereby reducing slag inclusion defects in the first slab.

[0014] 2.2 Copper Plate Oiling in the Crystallizer: Ordinary rapeseed oil is used. Before casting, it is evenly applied to the copper plates on all four sides of the crystallizer within a 600mm radius from the top using a roller brush, following a top-to-bottom sequence. The purpose is to utilize the lubricating properties of rapeseed oil to provide excellent lubrication between the X32 slab and the copper plate, thus mitigating the potential for abnormal casting caused by excessive friction in the initial casting stage.

[0015] 2.3 Flow control is achieved using a stopper rod in conjunction with an immersion nozzle.

[0016] 2.4 Casting process

[0017] 2.4.1 After the molten steel reaches the rotary table, the tundish is positioned at the casting stage, with the tundish submersible nozzle inserted to a depth of 130mm. The ladle is then opened for casting. 2.4.2 After the ladle opens for casting, the liquid level at both ends of the tundish flow control points reaches 350mm. The flow control mechanism (stopper rod) is then opened, allowing the molten steel to be injected into the crystallizer.

[0018] 2.4.3 Control the stopper opening to ensure that the molten steel injected into the crystallizer reaches the lower edge of the submerged entry nozzle within 20-25 seconds. The purpose is that, due to the large solidification range of high-alloy steel and insufficient billet shell strength, rapid filling allows the molten steel to flow sufficiently, maximizing contact with the coolant and ensuring the strength of the solidified shell.

[0019] 2.4.4 The time it takes for molten steel to rise from the bottom edge of the submerged entry nozzle to the normal liquid level in the crystallizer should be less than 60 seconds (emergence time). The purpose is to reduce the emergence time and the time spent at low casting speeds, thereby reducing the strength of the billet shell.

[0020] 2.4.5 After the molten steel in the crystallizer has submerged the side hole of the submerged entry nozzle, start the casting machine to draw the billet.

[0021] Step 3: The pouring process is now complete.

[0022] Compared to existing technologies, this invention has the following advantages: It primarily addresses the issue of billet stagnation caused by high initial billet strength by optimizing the parameters of the crystallizer and bending section at the head of the vertical bending slab casting machine, as well as the opening degree control of the bending section within the vertical bending range. This reduces the resistance to billet pulling caused by bending strain and bulging strain. Furthermore, it addresses quality defects in the initial billet by innovating the tundish material and the temperature range of the molten steel used in the upper stage. Finally, it solves the problems of billet stagnation and corner cracking defects in the initial casting production of hot-rolled alloy tool steel X32 in vertical bending slab continuous casting by optimizing parameters such as sealing and oiling the crystallizer, setting the initial casting emergence time in intervals, and optimizing the specific water volume after initial casting. This invention effectively solves the initial casting production problems of hot-rolled alloy tool steel X32 in vertical bending slab continuous casting machines. After adopting this technology in its continuous casting process, Meigang Steel Plant produced a total of 5903.4 tons of hot-rolled alloy tool steel X32 in 2022. Ten pouring attempts were made, with a 100% success rate, a zero-accident rate, and a first-round billet downgrade rate of less than 2.7%. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall process of the present invention. Detailed Implementation

[0024] To enhance understanding of the present invention, the embodiments will be described in detail below with reference to the accompanying drawings.

[0025] Example 1: See Figure 1 A process for the initial casting of hot-rolled alloy tool steel X32 on a vertical bending slab casting machine, the process comprising the following steps:

[0026] Step 1: Setting parameters for the vertical bending section of the head of the vertical bending casting machine before pouring;

[0027] 1.1 Setting parameters for foot roller opening and copper plate thickness.

[0028] 1.1.1 The thickness of the copper plate at the bottom of the casting machine's crystallizer is set according to a shrinkage coefficient of 1.05. The opening of the foot rolls of the crystallizer is further reduced by 1mm based on the thickness of the copper plate at the bottom of the crystallizer. The purpose is to control the bulging of the high-strength alloy steel after it exits the bottom of the crystallizer and reduce the drawing resistance caused by the bulging stress.

[0029] 1.1.2 The deviation between the outer arc of the casting machine and the center baseline of the casting machine is set to -0.2mm to 0mm. The opening value of the curved section inlet is set to the same as the crystallizer foot roller setting value (the purpose is to ensure horizontality in the height direction). Before each production run, a horizontal ruler is used to calibrate the arc. If the arc deviation exceeds 0.3mm, alignment adjustment is performed. The purpose is to reduce the resistance caused by the misalignment strain of the high-strength slab during the height direction of the casting machine.

[0030] 1.2 Negative Tolerance Setting for Bending Section Opening: The entire bending section adopts a shrinkage setting of 1mm, and its shrinkage is evenly distributed across all rollers. The shrinkage amount for each pair of rollers is 1 / N (N represents the number of roller pairs in the bending section). The allowable offline tolerance for the bending section is -0.3mm to 0.10mm; the tolerance for the arc is -0.15mm to 0.2mm. The purpose is to reduce positive tolerances, utilize the bearing clearance under hot conditions to compensate for excessive deviations, and reduce the potential for corner transverse crack defects and slab running obstacles caused by bulging strain and arc strain during the operation of high-strength slabs.

[0031] Step 2: Initial casting process of the vertical bending casting machine;

[0032] 2.1 Use of Tundish in Initial Casting: A dry-material tundish with a special dry lining containing 50% inorganic salt and 50% resin binder is used. A 150-minute baking time is set, with a baking temperature exceeding 1300°C and maintained at 1300°C for more than 30 minutes. This aims to reduce the increase in hydrogen content in the molten steel caused by moisture and crystal water from the tundish refractory material at the slab head, thereby reducing slag inclusion defects in the first slab.

[0033] 2.2 Copper Plate Oiling in the Crystallizer: Ordinary rapeseed oil is used. Before casting, it is evenly applied to the copper plates on all four sides of the crystallizer within a 600mm radius from the top using a roller brush, following a top-to-bottom sequence. The purpose is to utilize the lubricating properties of rapeseed oil to provide excellent lubrication between the X32 slab and the copper plate, thus mitigating the potential for abnormal casting caused by excessive friction in the initial casting stage.

[0034] 2.3 Flow control is achieved using a stopper rod in conjunction with an immersion nozzle.

[0035] 2.4 Casting process

[0036] 2.4.1 After the molten steel reaches the rotary table, the tundish is positioned at the casting stage, with the tundish submersible nozzle inserted to a depth of 130mm. The ladle is then opened for casting. 2.4.2 After the ladle opens for casting, the liquid level at both ends of the tundish flow control points reaches 350mm. The flow control mechanism (stopper rod) is then opened, allowing the molten steel to be injected into the crystallizer.

[0037] 2.4.3 Control the stopper opening to ensure that the molten steel injected into the crystallizer reaches the lower edge of the submerged entry nozzle within 20-25 seconds. The purpose is that, due to the large solidification range of high-alloy steel and insufficient billet shell strength, rapid filling allows the molten steel to flow sufficiently, maximizing contact with the coolant and ensuring the strength of the solidified shell.

[0038] 2.4.4 The time it takes for molten steel to rise from the bottom edge of the submerged entry nozzle to the normal liquid level in the crystallizer should be less than 60 seconds (emergence time). The purpose is to reduce the emergence time and the time spent at low casting speeds, thereby reducing the strength of the billet shell.

[0039] 2.4.5 After the molten steel in the crystallizer has submerged the side hole of the submerged entry nozzle, start the casting machine to draw the billet.

[0040] Step 3: The pouring process is now complete.

[0041] Example 2: See Figure 1 A certain factory is continuously casting vertically bent slabs. The slab thickness is 230mm. The bending section is equipped with 18 pairs of rollers. Flow control is achieved using stopper rods and submerged entry nozzles. The continuous casting process for producing hot-rolled alloy tool steel X32 is as follows:

[0042] Step 1. Setting parameters for the vertical bending section of the head of the vertical bending casting machine before casting begins;

[0043] 1.1 Setting parameters for foot roller opening and copper plate thickness.

[0044] 1.1.1 The thickness of the copper plate at the bottom of the casting machine's crystallizer is set according to a shrinkage coefficient of 1.05. In this embodiment, the thickness is 230mm, so the thickness at the bottom of the crystallizer is 230 * 1.05 = 241.5mm. The opening of the foot rolls of the crystallizer is reduced by 1mm based on the thickness of the copper plate at the bottom of the crystallizer, so the actual setting is 240.5mm. The purpose is to control the bulging of the high-strength alloy steel after it exits the bottom of the crystallizer and reduce the drawing resistance caused by the bulging stress.

[0045] 1.1.2 The deviation between the outer arc of the casting machine and the center baseline of the casting machine is set to -0.2mm to 0mm. The opening value of the inlet of the bending section is set to the same as that of the crystallizer foot roll (the purpose of which is to ensure horizontality in the height direction), which is also 240.5mm. Before each production run, a level ruler is used to calibrate the arc, and if the arc deviation exceeds 0.3mm, alignment adjustment is performed. The purpose is to reduce the resistance caused by the misalignment strain of the high-strength slab during the height direction of the casting machine.

[0046] 1.2 Negative Tolerance Setting for Bending Section Opening: The entire bending section adopts a shrinkage setting of 1mm, and its shrinkage is evenly distributed across all rollers. In this embodiment, the bending section has 18 pairs of rollers, with each pair having a shrinkage of 1 / 18, resulting in a shrinkage of 0.056mm per pair. The offline allowable tolerance for the bending section is -0.3mm to 0.10mm; the tolerance for the arc is -0.15mm to 0.2mm. The purpose is to reduce positive tolerances, utilize the bearing clearance under hot conditions to compensate for excessive deviations, and reduce the potential for corner transverse crack defects and slab running obstacles caused by bulging strain and arc strain during the operation of high-strength slabs. According to the settings of this invention, the actual results of the opening setting of the casting machine head for hot-rolled alloy tool steel X32 are as follows:

[0047]

[0048] Step 2. Setting up the casting process for the vertical bending casting machine.

[0049] 2.1 Use of a dry-material tundish with a special dry lining containing 50% inorganic salt and 50% resin binder. A baking time of 150 minutes is set, with a baking temperature of 1318°C and a holding time of 1300°C for 32 minutes. The purpose is to reduce the increase in hydrogen content in the molten steel caused by moisture and crystal water from the tundish refractory material at the slab head, thus reducing slag inclusion defects in the first slab.

[0050] 2.2 Copper Plate Oiling in the Crystallizer: Ordinary rapeseed oil is used. Before casting, it is evenly applied to the copper plates on all four sides of the crystallizer within a 600mm radius from the top using a roller brush, following a top-to-bottom sequence. The purpose is to utilize the lubricating properties of rapeseed oil to provide excellent lubrication between the X32 slab and the copper plate, thus mitigating the potential for abnormal casting caused by excessive friction in the initial casting stage.

[0051] 2.3 Flow control is achieved by using a stopper rod in conjunction with an immersion nozzle.

[0052] 2.4 Casting process

[0053] 2.4.1 After the molten steel reaches the rotary table, the tundish is positioned for casting, with the tundish submersible nozzle inserted to a depth of 130mm. The ladle is then opened for casting. 2.4.2 After the ladle is opened for casting, the liquid level at both ends of the tundish flow control points reaches 350mm. The flow control mechanism (stopper rod) is then opened, injecting the molten steel into the crystallizer.

[0054] 2.4.3 Control the stopper opening to ensure that the molten steel injected into the crystallizer reaches the lower edge of the submerged entry nozzle within 20-25 seconds. The purpose is that, due to the large solidification range of high-alloy steel and insufficient billet shell strength, rapid filling allows the high-alloy steel to flow sufficiently, maximize contact with the coolant, and ensure the strength of the solidified shell.

[0055] 2.4.4 Control the time for molten steel to rise from the bottom edge of the submerged entry nozzle to the normal liquid level in the crystallizer to be less than 60 seconds (emergence time). The purpose is to reduce the emergence time and the time spent at low casting speeds to reduce the strength of the billet shell.

[0056] 2.4.5 After the molten steel in the crystallizer has submerged the side hole of the submerged entry nozzle, start the casting machine to pull the billet.

[0057] Step 3. The pouring process is now complete.

[0058] It should be noted that the above embodiments are not intended to limit the scope of protection of the present invention. Equivalent transformations or substitutions made based on the above technical solutions all fall within the scope of protection of the claims of the present invention.

Claims

1. A hot-rolled alloy tool steel X32 casting process for a vertical bending slab casting machine, characterized in that the process includes the following steps: Step 1: Setting parameters for the vertical bending section of the head of the vertical bending casting machine before pouring; Step 2: Initial casting process of the vertical bending casting machine; Step 3: The initial pouring process is complete; Step 1 is as follows: 1.1 Setting parameters for foot roller opening and copper plate thickness 1.1.1 The thickness of the copper plate at the bottom of the casting machine's crystallizer is set according to a shrinkage coefficient of 1.

05. The opening of the crystallizer's foot rolls is reduced by 1mm based on the thickness of the copper plate at the bottom of the crystallizer. The purpose of this is to control the bulging of the high-strength alloy steel after it exits the bottom of the crystallizer, and to reduce the resistance to billet pulling caused by the bulging stress. 1.1.2 The deviation between the outer arc of the casting machine and the center baseline of the casting machine is set to -0.2mm to 0mm. The opening value of the inlet of the curved section is the same as the setting value of the crystallizer foot roller. Before each production run, a horizontal ruler is used to calibrate the arc. If the arc deviation exceeds 0.3mm, alignment adjustment is performed. 1.2 Negative tolerance setting for the opening of the bending section: The entire bending section is set to shrink by 1mm, and the shrinkage is evenly distributed across all rollers. The shrinkage of each pair of rollers is 1 / N, where N represents the number of roller pairs in the bending section. The allowable offline tolerance for the bending section is -0.3mm to 0.10mm; the tolerance for the arc is -0.15mm to 0.2mm. Its purpose is to reduce positive tolerances, use bearing clearance under hot conditions to compensate for excessive deviations, and reduce the risk of corner transverse cracks and slab running obstacles caused by bulging strain and arc strain during operation of high-strength slabs. Step 2 is as follows: 2.1 Use in tundishes during initial casting: Use a dry-material tundish with a special dry lining containing 50% inorganic salt and 50% resin binder. Set a baking time of 150 minutes, with a baking temperature exceeding 1300°C and a holding time at 1300°C greater than 30 minutes. 2.2 Coating the copper plates of the crystallizer: Ordinary rapeseed oil is used. Before casting, it is evenly applied to the copper plates on all four sides of the crystallizer within a 600mm radius from the top edge using a roller brush, following a top-to-bottom sequence. The purpose is to utilize the lubricating properties of rapeseed oil to provide excellent lubrication between the X32 slab and the copper plates, thus mitigating the potential for abnormal casting caused by excessive friction in the initial casting stage. 2.3 Flow control is achieved using a stopper rod in conjunction with an immersion nozzle. 2.4 Casting process 2.4.1 After the molten steel is placed on the rotary table, the tundish is positioned at the pouring position, with the tundish submersible nozzle inserted to a depth of 130mm. Pouring begins from the ladle. 2.4.2 After the ladle starts pouring, when the liquid level reaches 350mm at both ends of the tundish flow control point, the flow control mechanism opens, and the molten steel is injected into the crystallizer. 2.4.3 Control the stopper opening to ensure that the molten steel injected into the crystallizer reaches the lower edge of the submerged entry nozzle within 20-25 seconds. The purpose is that, due to the large solidification range of high-alloy steel and insufficient billet shell strength, rapid filling allows the molten steel to flow sufficiently, maximizing contact with the coolant and ensuring the strength of the solidified shell. 2.4.4 The time it takes for molten steel to rise from the bottom edge of the submerged entry nozzle to the normal liquid level in the crystallizer should be less than 60 seconds. The purpose of this is to reduce the emergence time and the time spent at low casting speeds, thereby reducing the strength of the billet shell. 2.4.5 After the molten steel in the crystallizer has submerged the side hole of the submerged entry nozzle, start the casting machine to pull the billet.

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