A method for reducing friction of continuous casting mold of iron-nickel based alloy

Abstract

The present invention belongs to the field of steelmaking, and is a method for reducing the friction of the crystallizer in the pouring stage of continuous casting of iron-nickel-based alloy, comprising the following steps: step 1: temperature of molten steel in the tundish: 1408-1416°C; step 2: cooling water volume of the pouring crystallizer; step 3: using special pre-melted slag; step 4: injecting 170-180 tons of iron-nickel-based alloy melt meeting the composition of claim 1 into a tundish with a nominal capacity of 30 tons, and after the tundish is poured, the molten steel is injected into the crystallizer; step 5: after reaching the target pulling speed, adjusting the cooling water volume of the crystallizer, the wide surface water flow: 3650-3700Nl / min, the narrow surface water flow: 370-390 Nl / min. After adopting this pouring process, the friction of the iron-nickel-based alloy in the pouring stage is significantly reduced, the average value is reduced from the original 26.5KN to below 21.5KN, and the surface quality of the ingot is also significantly improved.

Description

Technical Field

[0001] The invention belongs to the field of steelmaking and relates to a method for reducing the friction of an iron-nickel based alloy continuous casting crystallizer. Background Art

[0002] As a highly corrosion-resistant alloy, the usage of iron-nickel-based alloy is increasing. The traditional die casting process cannot meet the needs of users, and it is necessary to develop an efficient and high-quality production process. Therefore, a continuous casting production process has been developed. However, the friction force in the pouring stage of the continuous casting process is relatively large, which can easily cause surface defects of the ingot, such as crack defects, which are usually more than 10 meters long, resulting in waste and seriously affecting the metal yield of the continuous casting ingot. For this reason, the high-temperature mechanical properties of the iron-nickel-based alloy were studied, and the continuous casting pouring process was redesigned to reduce the friction force in the pouring stage. The present invention provides a method for reducing the friction force of the continuous casting start-up crystallizer of the iron-nickel-based alloy, so as to solve the problem of the surface quality of the iron-nickel-based alloy ingot caused by the large friction force in the pouring stage, improve the metal yield, and reduce production costs. Summary of the invention

[0003] The purpose of the present invention is to provide a method for reducing the friction of the iron-nickel based alloy continuous casting mold in view of the above problems.

[0004] The object of the present invention is achieved in this way: a method for reducing the friction force of the crystallizer in the continuous casting start-up stage of an iron-nickel-based alloy, wherein the mass percentage of the steel grade of the produced iron-nickel-based alloy is: C: ≤0.15%, Si: ≤1.00%, Mn: ≤1.50%, P≤0.035%, S≤0.020%, Cr: 19.00-27.00%, Ni: 30.00-45.00%, Al: 0.03-0.65%, Ti: 0-1.20%, N: 0-0.26%, Nb: 0-0.60%, Mo: 0-3.5%, Cu: 0-3.0%, and the rest are Fe elements and other inevitable impurity elements.

[0005] A method for reducing the friction of the crystallizer in the pouring stage of continuous casting of an iron-nickel-based alloy, comprising the following steps: Step 1: The temperature of the molten steel in the tundish is 1408-1416°C; Step 2: The cooling water volume of the pouring crystallizer is 3550-3600Nl / min on the wide side and 350-370 on the narrow side. Nl / min; Step 3: Use special pre-melted slag, the special pre-melted slag composition: SiO2: 35-40%, CaO: 20-26%, Al2O3: 1.5-3.5%, Fe2O3: 9.0-11.0; Na2O: 10-13%, F: 5-12%, Li2O: 0.3-3.0%, C: ≤0.5%, the melting point of the special pre-melted slag is 850-900℃, the viscosity is 0.08-0.20Pa·s, and the amount of special pre-melted slag added is 8-15kg; Step 4: Pour 170~180 tons of iron-nickel-based alloy melt that meets the above composition requirements into a tundish with a nominal capacity of 30 tons. After the tundish is poured, the molten steel is injected into the crystallizer. After the molten steel submerges the side hole of the immersion nozzle, the molten steel level is 100~150mm away from the crystallizer. When the upper edge of the device is 150mm±20mm, start the straightening machine, increase the pulling speed to 0.3m / min at a speed of ≤0.005m / min / s, maintain the constant pulling speed of 0.3m / min for 40~80s, then increase the pulling speed to 0.6m / min at a speed of ≤0.005m / min / s, maintain it at a constant pulling speed of 0.6m / min for 5-10min, then increase the pulling speed to the set target pulling speed of 0.80-0.90m / min at a speed of ≤0.005m / min / s, and then maintain the constant pulling speed for stable casting; Step 5: After reaching the target pulling speed, adjust the cooling water volume of the crystallizer, the water flow rate on the wide side: 3650-3700Nl / min, the water flow rate on the narrow side: 370-390 Nl / min.

[0006] The beneficial effect of the present invention is that after adopting the pouring process, the friction force of the iron-nickel based alloy in the pouring stage is significantly reduced, the average value is reduced from the original 26.5KN to below 21.5KN, and the surface quality of the casting billet is also significantly improved. DETAILED DESCRIPTION

[0007] Due to its excellent corrosion resistance, iron-nickel based alloys are widely used in petrochemical, marine engineering, aerospace and other fields. However, due to its high alloy content, the content of nickel-chromium and other alloys exceeds 50%, which leads to poor thermal conductivity and poor high-temperature plasticity. In the crystallizer, the temperature of the solidified shell is around 1200°C. Under the same process conditions, due to its poor thermal conductivity, the initial solidified shell is thinner than conventional steel grades, the shrinkage of the ingot is small, and the friction between the ingot and the crystallizer wall is large, so it is necessary to design and develop different pouring processes.

[0008] Based on the solidification characteristics of iron-nickel-based alloys, the present invention proposes to reduce the cooling water intensity of the crystallizer in the pouring stage, use special pre-melted slag and a three-stage pouring speed-up process. That is, 1) Continuous casting slab specifications: thickness 200mm, width 1000-2100mm; pouring crystallizer cooling water volume, pouring stage: wide side: 3550-3600Nl / min, narrow side: 350-370Nl / min; after reaching the target pulling speed: the cooling water volume is adjusted to wide side: 3650-3700Nl / min, narrow side: 370-390 Nl / min; 2) Use special pre-melted slag, the special pre-melted slag composition: SiO2: 35-40%, CaO: 20-26%, Al2O3: 1.5-3.5%, Fe2O3: 9.0-11.0; Na2O: 10-13%, F: 5-12%, Li2O: 0.3-3.0%, C: ≤0.5%, the melting point of the special pre-melted slag is 850-900℃, the viscosity is 0.08-0.20Pa·s, and the amount of special pre-melted slag added is 8~15kg; 3) The iron-nickel base alloy melt is injected into a tundish with a nominal capacity of 30 tons, the tundish is opened to pour molten steel into the crystallizer, and after the molten steel submerges the side hole of the submerged nozzle, a three-stage speed-up process is adopted to gradually increase the pulling speed to the target pulling speed at a certain speed. That is, qualified iron-nickel based molten steel is poured into the tundish, and the molten steel is poured into the crystallizer. After the molten steel submerges the side hole of the immersion nozzle, the straightening machine is started when the molten steel level is 150mm±20mm away from the upper edge of the crystallizer, and the pulling speed is increased to 0.3m / min at a speed of ≤0.005m / min / s, and the constant pulling speed of 0.3m / min is maintained for 60s±20s, and then the pulling speed is increased to 0.6m / min at a speed of ≤0.005m / min / s, and maintained at a constant pulling speed of 0.6m / min for 5-10min, and then the pulling speed is increased to the set target pulling speed (0.80-0.90m / min) at a speed of ≤0.005m / min / s, and then the constant pulling speed is maintained for stable casting; 4) After reaching the target pulling speed, the cooling water volume of the crystallizer is adjusted, the water flow rate of the wide surface is: 3650-3700Nl / min, and the water flow rate of the narrow surface is: 370-390 Nl / min.

[0009] A method for reducing the friction of a crystallizer in a continuous casting start-up stage of an iron-nickel-based alloy comprises the following steps:

[0010] Step 1: The main composition range of the iron-nickel based alloy steel produced is: C: ≤0.15%, Si: ≤1.00%, Mn: ≤1.50%, P≤0.035%, S≤0.020%, Cr: 19.00~27.00%, Ni: 30.00~45.00%, Al: 0.03~0.65%, Ti: 0~1.20%, N: 0~0.26%, Nb: 0-0.60%, Mo: 0-3.5%, Cu: 0-3.0%, and the rest are Fe elements and other unavoidable impurity elements;

[0011] Step 2: Casting size of iron-nickel alloy slab: thickness 200mm × width 1000-2100mm

[0012] Step 3: The iron-nickel based alloy is austenite solidified in a single phase with small shrinkage. The taper of the narrow copper plate of the crystallizer is set to 0.90~1.20% to reduce the extrusion of the copper plate on the solidified shell;

[0013] Step 4: Use special pre-melted slag for pouring and increase the usage. Use special slag with low melting point and fast melting speed. The slag forming speed is fast, and liquid slag is quickly formed and flows into the crystallizer and the shell. This special slag has good lubrication properties and reduces the friction of the shell in the crystallizer. Special pre-melted slag composition: SiO2: 35-40%, CaO: 20-26%, Al2O3: 1.5-3.5%, Fe2O3: 9.0-11.0; Na2O: 10-13%, F: 5-12%, Li2O: 0.3-3.0%, C: ≤0.5%, special pre-melted slag melting point 850-900℃, viscosity 0.08-0.20Pa·s, special pre-melted slag addition amount 8~15kg,

[0014] Step 5: Set the cooling water volume of the crystallizer in stages: during the pouring process, the wide side: 3500-3600 Nl / min, the narrow side: 350-370 Nl / min; after reaching the target casting speed, the stabilization process: the wide side: 3650-3750 Nl / min, the narrow side: 370-400 Nl / min;

[0015] Step 6: The iron-nickel-based high-temperature alloy has a high alloy content, poor plasticity, poor thermal conductivity, slow solidification speed, and a thin shell. The process of increasing the pouring speed is designed: qualified iron-nickel-based molten steel is injected into the tundish. After the tundish reaches the pouring liquid level, the molten steel is injected into the crystallizer. After the molten steel submerges the side holes of the immersion nozzle, a special pouring pre-molten slag is added. When the molten steel level is 150mm±20mm away from the upper edge of the crystallizer, the straightening machine is started, and the pulling speed is increased to 0.3m / min at a speed of ≤0.005m / min / s, and the constant pulling speed of 0.3m / min is maintained for 60s, and then the pulling speed is increased to 0.6m / min at a speed of ≤0.005m / min / s, and maintained at a constant pulling speed of 0.6m / min for 5-10min, and then the pulling speed is increased to 0.8-0.85m / min (target pulling speed) at a speed of ≤0.005m / min / s, and then the constant pulling speed is maintained for stable casting. Embodiment 1

[0016] Steel grade N08810

[0017] (1) Qualified molten steel after smelting: Qualified molten steel is obtained through smelting. The mass percentage of each element in the molten steel is: C=0.053; Si=0.22; Mn=0.0.56; P=0.022; S=0.001; Cr=20.30; Ni=30.50; Al=0.31; Ti=0.25; N=0.011, and the rest are iron and unavoidable elements.

[0018] (2) Main process parameters of casting process: 1) Molten steel temperature in tundish: 1408-1413℃, liquidus temperature of this steel grade is 1385℃. 2) Specifications of continuous casting slab: thickness 200mm×width 2040mm. 3) Water flow rate of crystallizer in the pouring stage: 3550-3580Nl / min on the wide side, 350-360Nl / min on the narrow side. 4) The amount of pre-molten slag used in the pouring is 10kg. 5) During the pouring and speed-up process, molten steel is injected into the crystallizer. After the molten steel submerges the side holes of the immersion nozzle, the straightening machine is started when the molten steel level is 160 mm from the upper edge of the crystallizer. The pulling speed is increased to 0.3 m / min at a rate of 0.005 m / min / s, and the constant pulling speed of 0.3 m / min is maintained for 60 s. The pulling speed is then increased to 0.6 m / min at a rate of 0.005 m / min / s, and maintained at a constant pulling speed of 0.6 m / min for 10 min. Then, the pulling speed is increased to 0.8 m / min (target pulling speed) at a rate of 0.005 m / min / s, and then the constant pulling speed is maintained for stable casting.

[0019] (3) Comparison of implementation effects: The friction force data during the pouring stage were statistically analyzed, and the average friction force value was 18.9 KN. After the continuous casting billet came out of the secondary cooling chamber, the surface of the billet was checked and no cracks were found on the surface of the billet. Embodiment 2

[0020] Steel grade N08120

[0021] Qualified molten steel after smelting: Qualified molten steel is obtained through smelting, and the mass percentage of each element in the molten steel is: C=0.058; Si=0.25; Mn=0.63; P=0.025; S=0.001; Cr=24.80; Ni=36.6; Al=0.056; Nb=0.55; N=0.18, and the rest are iron and unavoidable elements.

[0022] The main process parameters of the casting process: 1) Molten steel temperature in the tundish: 1412-1416℃, the liquidus temperature of this steel grade is 1388℃. 2) Specifications of continuous casting slab: thickness 200mm×width 2040mm. 3) Water flow rate of crystallizer in the pouring stage: 3550-3580Nl / min on the wide side, 350-360Nl / min on the narrow side. 4) The amount of pre-molten slag used in the pouring is 10kg. 5) During the pouring and speed-up process, molten steel is injected into the crystallizer. After the molten steel submerges the side holes of the immersion nozzle, the straightening machine is started when the molten steel level is 170 mm from the upper edge of the crystallizer. The pulling speed is increased to 0.3 m / min at a rate of 0.005 m / min / s, and the constant pulling speed of 0.3 m / min is maintained for 60 s. The pulling speed is then increased to 0.6 m / min at a rate of 0.005 m / min / s, and maintained at a constant pulling speed of 0.6 m / min for 10 min. The pulling speed is then increased to 0.8 m / min (target pulling speed) at a rate of 0.005 m / min / s, and then the constant pulling speed is maintained for stable casting.

[0023] (3) Comparison of implementation effects: The friction data during the pouring stage were statistically analyzed, and the average friction value was 20.4KN. After the continuous casting billet came out of the second cooling chamber, the surface condition of the billet was checked, and the surface cracks of the billet were reduced to 3m, which was significantly reduced by about 5m compared with the conventional process.

[0024] The present invention belongs to the field of steelmaking and continuous casting, and is more specifically mainly applied to iron-nickel-based high-alloy steel, to solve the problem of excessive friction in the continuous casting process of the original process of this type of steel. The present invention provides a method that can effectively reduce the friction between the ingot and the wall of the crystallizer during the pouring stage. Specifically, qualified molten steel is injected into the crystallizer, the amount of cooling water in the pouring stage is reduced, and special pre-molten slag is added. After the straightening machine is started, a three-stage pulling speed increase process is adopted. After the ingot shell is gradually stabilized, the pulling speed is increased to the target pulling speed. The present invention has been proven through application to effectively reduce the friction value of the iron-nickel-based alloy in the pouring stage, significantly improve the surface quality of the ingot, and significantly improve the metal yield, thereby achieving greater economic benefits.

[0025] The above description is only a specific embodiment of the present invention, but the structural features of the protection scope of the present invention are not limited thereto. Any changes or modifications made by any technician in the field of the present invention are all covered by the patent scope of the present invention.

Claims

1. A method for reducing the friction of the crystallizer during the initial pouring stage of continuous casting of an iron-nickel-based alloy, characterized in that: The mass percentage of the iron-nickel based alloy steel produced is: C:≤0.15%, Si: ≤1.00%, Mn: ≤1.50%, P≤0.035%, S≤0.020%, Cr: 19.00-27.00%, Ni: 30.00-45.00%, Al: 0.03-0.65%, Ti: 0-1.20%, N: 0-0.26%, Nb: 0-0.60%, Mo: 0-3.5%, Cu: 0-3.0%, and the rest are Fe element and other inevitable impurity elements; method The process comprises the following steps: Step 1: Temperature of molten steel in the tundish: 1408-1416°C; Step 2: Cooling water volume of the casting crystallizer: wide side: 3550-3600 Nl / min, narrow side: 350-370 Nl / min; Step 3: Use special pre-melted slag, the special pre-melted slag composition: SiO2: 35-40%, CaO: 20-26%, Al2O3: 1.5-3.5%, Fe2O3: 9.0-11.0; Na2O: 10-13%, F: 5-12%, Li2O: 0.3-3.0%, C: ≤0.5%, the melting point of the special pre-melted slag is 850-900℃, the viscosity is 0.08-0.20Pa·s, and the amount of special pre-melted slag added is 8-15kg; Step 4: Pour 170-180 tons of iron-nickel alloy melt into a 30-ton tundish with a nominal capacity. After the tundish is poured, the molten steel is poured into the crystallizer. After the molten steel submerges the side hole of the immersion nozzle, the straightening machine is started when the molten steel level is 150mm±20mm from the upper edge of the crystallizer. The pulling speed is increased to 0.3m / min at a speed of ≤0.005m / min per second, and the constant pulling speed of 0.3m / min is maintained for 40-80s, and then the pulling speed is increased to 0.6m / min at a speed of ≤0.005m / min per second, and maintained at a constant pulling speed of 0.6m / min for 5-10min, and then the pulling speed is increased to the set target pulling speed of 0.80-0.90m / min at a speed of ≤0.005m / min per second, and then the constant pulling speed is maintained for stable casting; Step 5: After reaching the target casting speed, adjust the cooling water volume of the crystallizer: wide surface water flow rate: 3650-3700 Nl / min, narrow surface water flow rate: 370-390 Nl / min.