High-aluminum steel and its continuous casting method

Abstract

The present application discloses a high-aluminum steel and its continuous casting method. The method includes providing molten high-aluminum steel; continuously casting the molten steel of the first steel type and the molten high-aluminum steel from the first ladle into the second ladle in sequence; the molten high-aluminum steel is not the molten steel in the first casting order, and the molten steel of the first steel type and the molten high-aluminum steel are continuously cast successively; using a pure steel covering agent to cover the liquid surface of the molten high-aluminum steel cast into the second ladle; casting the molten high-aluminum steel into a mold using mold powder for crust formation to form a slab containing a billet shell; pulling out the slab containing the billet shell from the mold for cooling to obtain a continuously cast slab of high-aluminum steel. The method of the present application can stably and smoothly cast molten high-aluminum steel with an Al content of 3.0 wt% to 6.0 wt%, the incidence rate of continuous casting sticking alarm and speed reduction is ≤ 0.25 times / furnace, and no breakout accident occurs. The continuously cast slab obtained by continuous casting has good internal quality, no surface cracks and slag inclusion defects, and well meets the requirements of rolling steel.

Description

Technical Field

[0001] This application belongs to the technical field of steel metallurgy, and particularly relates to a high-aluminum steel and its continuous casting method. Background Art

[0002] Research has found that when the content of aluminum added as an alloying element to steel is ≥ 3 wt%, it can cause passivation of the steel like chromium and has corrosion resistance in oxidizing acids. Therefore, aluminum, as the main alloying element of corrosion-resistant steel and low-density steel, has broad prospects.

[0003] When continuously casting high-aluminum steel, a mold powder is generally used to protect the molten steel to be cast, prevent the molten steel from oxidizing, and at the same time play a role in lubricating the molten steel and the inner surface of the mold. However, the mold powder is very easy to denature, and Al in the molten steel of high-aluminum steel and SiO in the liquid slag of the mold powder 2 as well as oxygen in the casting equipment are prone to redox reactions, which will cause clogging and breakout accidents at the tundish nozzle, seriously affecting the production efficiency of continuous casting. Summary of the Invention

[0004] The embodiment of this application provides a continuous casting method for high-aluminum steel, which can stably and smoothly cast molten high-aluminum steel with an Al content of 3.0 wt% - 6.0 wt%. The incidence of continuous casting adhesion alarm speed reduction is ≤ 0.25 times per heat, and no breakout accident occurs. The surface of the continuously cast slab has no crack and slag inclusion defects. The result of the macrostructure defect rating map of the continuously cast slab obtained by testing according to the YBT4003-2016 standard is that the macro central segregation C class is 0.5 - 1.0 level, indicating that the internal quality of the continuously cast slab prepared by the method of the embodiment of this application is good and well meets the requirements of rolling.

[0005] In the first aspect, this application provides a continuous casting method for high-aluminum steel, and the method includes:

[0006] Providing molten steel of a first steel grade and molten high-aluminum steel with an Al content of 3.0 wt% - 6.0 wt%;

[0007] Sequentially and continuously casting the molten steel of the first steel grade and the molten high-aluminum steel from a first ladle to a second ladle; wherein, the molten high-aluminum steel is not the molten steel for the first casting order. First, the molten steel of the first steel grade is cast, and then the molten high-aluminum steel is continuously cast;

[0008] Using a pure steel covering agent to cover the liquid surfaces of the molten steel of the first steel grade and the molten high-aluminum steel sequentially cast into the second ladle;

[0009] Casting the molten high-aluminum steel from the second ladle into a mold using a mold powder to form a shell, so as to form a slab containing a shell;

[0010] The cast slab containing the billet shell is pulled out from the mold for cooling to obtain a continuous casting slab of high-aluminum steel.

[0011] In one embodiment, a first long nozzle with a small upper opening and a large lower opening is used for continuous casting, so that the first long nozzle immerses from the first ladle into the second ladle.

[0012] For the continuous casting method of high-aluminum steel in the embodiment of the present application, the purpose of using the first water nozzle with a small upper and large lower shape for continuous casting is to prevent splashing when the molten steel in the first ladle begins to leak into the second ladle, play a role in partial pressure relief, and reduce secondary oxidation caused by the contact between the molten steel of high-aluminum steel and air.

[0013] In the continuous casting method of high-aluminum steel in the embodiment of the present application, the molten steel of the first steel type has a composition similar to that of the molten steel of high-aluminum steel, but its Al content is lower than that of the high-aluminum steel in the present application.

[0014] In one embodiment of the present application, by mass percentage, the molten steel of the first steel type includes the following components: C: 0.030% - 0.100%, Si: ≤0.60%, Mn: ≤1.50%, P: ≤0.035%, S: ≤0.030%, Al ≤0.50%, and the rest are iron and inevitable impurities. This is to reduce the amount of molten steel for mixed casting, reduce mixed-cast slabs, and lower costs.

[0015] In one embodiment, the opening of the first long nozzle is in the shape of a horn with a small upper and large lower. Of course, the first long nozzle can also be set in the shape of a square step with a small upper and large lower at the opening, a multi-faceted tubular shape, etc. that can play a role in pressure relief.

[0016] In one embodiment, the steps of continuously casting the molten steel of the first steel type and the molten steel of the high-aluminum steel from the first ladle into the second ladle in sequence include:

[0017] Using high-Cr tapping slag to drain the molten steel of the first steel type and the molten steel of high-aluminum steel respectively; by mass percentage, the high-Cr tapping slag includes the following components: Cr 2 O 3 ≥31.0%, Al 2 O 3 8% - 15%, MgO 7 - 12%, SiO 2 18% - 25%. The high-Cr tapping slag is used as the filling material at the bottom of the first long nozzle of the first ladle. Its main function is to guide the molten steel to open automatically, ensure that the ladle of the molten steel can be opened automatically, avoid the molten steel from caking and causing the ladle of the molten steel to not open; prevent the first ladle from not opening automatically and resulting in the inability to insert the invasive first long nozzle, thereby causing a large contact area between the molten steel of high-aluminum steel and air and serious secondary oxidation. The high-Cr tapping slag is set at the bottom of the first ladle during use so that the molten steel can flow smoothly through the first long nozzle to the second ladle.

[0018] In one embodiment, the step of continuously casting the molten steel of the first steel type and the molten high-aluminum steel from the first ladle into the second ladle in sequence includes:

[0019] Performing continuous casting throughout under a protective atmosphere;

[0020] Wherein, before continuous casting, the second ladle is purged with a protective atmosphere for a time ≥ 5 min, and the purging flow rate of the protective atmosphere is 2800 L / min to 3000 L / min;

[0021] During the casting process, the flow rate of the protective atmosphere at the first long nozzle of the first ladle is 100 L / min to 150 L / min. Using a protective atmosphere for continuous casting can reduce the oxidation reaction between the molten high-aluminum steel and oxygen, and reduce the formation of Al 2 O 3 to avoid the accumulation of molten high-aluminum steel in the inner cavity of the nozzle, resulting in nozzle tumor formation and blockage, and causing the continuous casting to not proceed smoothly.

[0022] In one embodiment, the protective atmosphere is selected from argon, or a mixed gas of argon and nitrogen.

[0023] In one embodiment, the pure steel covering flux, by mass percentage, includes components with the following contents:

[0024] SiO 2 ≤3.0 wt%, CaO 50.0% - 55.0%, MgO 6.0% - 8.0%, Al 2 O 3 32.0% -

[0025] 36.0%, and the rest are other inevitable impurities. During continuous casting, it is necessary to add the pure steel covering flux in a timely and uniform manner to protect the molten steel surface from contacting oxygen as little as possible and reduce the oxidation reaction.

[0026] In one embodiment, the basicity of the mold powder is 0.38 - 0.58, the melting point is 820 °C - 900 °C, and the viscosity is 0.10 Pa·s - 0.20 Pa·s; the mold powder, by mass percentage, includes components with the following contents:

[0027] SiO 2 36.8% - 42.8%, CaO 16.1% - 22.1%, Al 2 O 3 1.7% - 4.7%, C 5.0% - 7.0%, Na 2 O 9.0% - 11.0%, Li 2 O 5.0% - 7.0%, and the rest are other inevitable impurities.

[0028] In one embodiment, the superheat of the molten steel of the high-aluminum steel in the second ladle is 50°C to 70°C. The second ladle is cast with molten steel having a high superheat to prevent the nozzle from being blocked, promote the melting and lubrication of the mold powder; meanwhile, it is beneficial to casting at a low casting speed.

[0029] In the continuous casting method of high-aluminum steel according to the embodiment of the present application, the superheat is a certain temperature range beyond the liquidus temperature of the molten steel. The liquidus temperature of the high-aluminum steel grade in the present application is 1518°C, and the temperature in the second ladle is 1568°C to 1588°C.

[0030] In one embodiment, the step of pouring the molten steel of high-aluminum steel from the second ladle into a mold using mold powder for shell formation to form a slab containing a billet shell, pouring the molten steel of high-aluminum steel from the second ladle into the mold using an invasive second nozzle, includes:

[0031] Opening the stopper rod of the second nozzle between the second ladle and the mold;

[0032] Blowing a protective atmosphere into the stopper rod, and the gas flow rate of the protective atmosphere is 2 L / min to 5 L / min.

[0033] In one embodiment, the protective atmosphere is selected from argon, or a mixed gas of argon and nitrogen, and the volume / mass ratio of argon to nitrogen is 1:0.4 to 1.8.

[0034] In one embodiment, the depth at which the second nozzle is inserted into the mold is 160 mm to 180 mm.

[0035] In the continuous casting method of high-aluminum steel according to the embodiment of the present application, blowing a protective atmosphere into the stopper rod to prevent the second nozzle from being blocked, and preventing the formation of negative pressure in the inner cavity of the second nozzle resulting in the absorption of gas by the nozzle refractory, reducing the slag-steel reaction between the molten high-aluminum steel in the mold and the mold powder surface caused by blowing the stopper rod, that is, reducing the reaction between Al in the molten steel and SiO in the mold powder 2 reaction. At the same time, during continuous casting, most of the nitrogen is absorbed by the molten high-aluminum steel, and the nitrogen increase in the molten steel will be 0.5 ppm to 1.5 ppm, which will not have a great impact on the quality of the molten steel.

[0036] In the present application, both the first long nozzle and the second nozzle are invasive nozzles, that is, they can receive molten steel from the previous device and insert it into the molten steel of the next device to reduce the oxidation of the molten steel.

[0037] In one embodiment, the step of pouring the molten steel of high-aluminum steel from the second ladle into a mold using mold powder for shell formation to form a slab containing a billet shell includes:

[0038] The mold uses strong cooling with cooling water to form a shell on the molten high-aluminum steel to form a billet shell. The process parameters are as follows: the flow rate of the cooling water on the wide face of the mold is 5500 L / min to 6500 L / min, and the flow rate on the narrow face is 700 L / min to 800 L / min.

[0039] In the continuous casting method of high-aluminum steel according to the embodiment of the present application, by strongly cooling the mold, it is ensured that the superheat of the tundish molten steel, that is, the molten steel in the second ladle, is within the range of 40°C to 70°C. Under this condition, the thickness of the billet shell when it exits the mold is within a safe range, that is, the thickness ≥ 14 mm, ensuring the safety of casting; at the same time, since the gap between the strongly cooled billet shell and the inner wall of the mold copper plate increases, the probability of adhesion between the billet shell and the copper plate is reduced, so that the continuous casting proceeds smoothly.

[0040] In one embodiment, the step of pulling out the billet containing the billet shell from the mold for cooling to obtain a continuous casting billet of high-aluminum steel, the pulling speed of pulling out the billet containing the billet shell from the mold is 0.4 m / min to 0.8 m / min.

[0041] In one embodiment, the step of pulling out the billet containing the billet shell from the mold for cooling to obtain a continuous casting billet of high-aluminum steel includes:

[0042] In at least the first 1 / 4 to 1 / 3 segments of the total number of segments of the secondary cooling segment, the billet is cooled with a specific water volume of 0.8 L / kg to 1.1 L / kg of steel;

[0043] In the remaining segments of the total number of segments of the secondary cooling segment, the billet is cooled with equipment cooling water to obtain a cooled billet.

[0044] In the continuous casting method of high-aluminum steel according to the embodiment of the present application, using a specific water volume of 0.8 L / kg to 1.1 L / kg of steel to strongly cool the billet in the secondary cooling segment can prevent the billet shell from bulging; in the remaining segments, indirect cooling is performed with equipment cooling water to prevent straightening cracks and deformation of the billet at low pulling speeds.

[0045] In a second aspect, the present application provides a high-aluminum steel, prepared according to the above continuous casting method of high-aluminum steel. By mass percentage, the high-aluminum steel includes the following components:

[0046] C: 0.030% to 0.080%, Si: 0.10% to 0.40%, Mn: 0.60% to 1.40%, P: ≤ 0.030%, S: ≤ 0.020%, Al: 3.0% to 6.0%, N ≤ 0.004%, and the rest are Fe and unavoidable impurities.

[0047] The continuous casting method of high-aluminum steel in the embodiment of the present application involves continuously casting the molten steel of the first steel type and the molten high-aluminum steel, using the molten steel of the first steel type to remove oxygen in the casting equipment, and reducing the Al generated by the reaction of the molten high-aluminum steel with oxygen in the casting equipment. 2 O 3 To reduce the adhesion between the molten high-aluminum steel and the casting equipment; and by using a pure steel covering agent to reduce the contact between the molten high-aluminum steel and oxygen, further reducing the generation of Al 2 O 3 ; further, by blowing argon or a mixed gas of argon and nitrogen through a stopper rod to reduce the reaction between the molten high-aluminum steel and SiO in the protective slag 2 , reducing the slag-steel reaction; and by strongly cooling the continuous casting billet to ensure an increase in the gap between the shell of the continuous casting billet and the inner wall of the mold, reducing the probability of adhesion between the shell and the mold, so that the molten high-aluminum steel can be continuously cast stably and smoothly from the ladle to obtain a continuously cast billet, reducing crack and slag inclusion defects, and reducing the incidence of alarm speed reduction during the production process due to continuous casting adhesion. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required to be used in the embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0049] Figure 1 is a flow block diagram of the continuous casting method of high-aluminum steel provided by an embodiment of the present application;

[0050] Figure 2 is a structural diagram of the continuous casting equipment used in the continuous casting method of high-aluminum steel in the embodiment of the present application;

[0051] Description of the reference numerals:

[0052] 1, slewing tower; 100, first ladle; 101, first long nozzle; 102, second ladle; 103, second nozzle; 104, mold; 105, oscillating mold; 106, electromagnetic induction stirrer; 107, cooling nozzle; 108, supporting guide roll; 109, dummy bar; 110, flame cutter. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0053] The features and exemplary embodiments of various aspects of the present application will be described in detail below. To make the objectives, technical solutions, and advantages of the present application clearer and more understandable, the present application will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application and not to limit the present application. For those skilled in the art, the present application can be implemented without some of these specific details. The following description of the embodiments is only intended to provide a better understanding of the present application by showing examples of the present application.

[0054] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, the elements defined by the statement "including..." do not exclude the existence of additional identical elements in the process, method, article or device including the said elements.

[0055] As pointed out in the background art section, when continuous casting and pouring molten steel of high-aluminum steel, the mold powder in the mold is prone to redox reaction with Al in the high-aluminum steel molten steel, causing the alkalinity and melting point of the mold powder to rise sharply, the viscosity to increase, and the crystallization performance to be greatly improved; thick and wide slag strips are formed on the inner wall of the mold, affecting the normal flow of liquid slag into the gap between the billet shell and the mold copper plate. Without the mold powder as a lubricating substance between the mold copper plate and the billet shell, frequent sticking alarms and speed reduction are likely to occur, greatly affecting the production efficiency of continuous casting, and serious steel leakage accidents may occur.

[0056] In addition, the high Al content in the molten steel of high-aluminum steel is prone to secondary oxidation with oxygen in the air, forming a large amount of Al 2 O 3 , which accumulates in the inner cavity of the nozzle and causes nozzle clogging due to tumor formation. The nitrogen-aluminum product in the steel is high, and straightening cracks are likely to occur in continuous casting.

[0057] The above technical problems will occur in steel grades with 0.5wt% ≤ Al < 3wt%. At present, for the high-aluminum steel produced by slab continuous casting, the main purposes of aluminum as an alloying element in it are:

[0058] 1) Refine the essential grains of the steel and increase the temperature at which the steel grains coarsen;

[0059] 2) Improve the electrical and magnetic properties of the steel;

[0060] 3) Improve the wear resistance and fatigue strength of nitrided steel;

[0061] 4) Control the phase transformation temperature of steel.

[0062] For high-aluminum steel with an Al content of 3.0 wt% to 6.0 wt%, the above technical problems are more likely to occur. In this regard, this application will make improvements to it.

[0063] To solve the problems of the prior art, the embodiments of this application provide a continuous casting method for high-aluminum steel. First, the continuous casting method for high-aluminum steel provided by the embodiments of this application will be introduced in conjunction with the Figure 2 continuous casting equipment shown as follows.

[0064] Figure 1 The flowchart of the continuous casting method for high-aluminum steel provided by an embodiment of this application is shown. As Figure 1 shown, the method includes:

[0065] S1. Provide the molten steel of the first steel type and the molten steel of high-aluminum steel. By mass percentage, the molten steel of high-aluminum steel includes the following components:

[0066] C: 0.030% to 0.080%, Si: 0.10% to 0.40%, Mn: 0.60% to 1.40%, P: ≤0.030%, S: ≤0.020%, Al: 3.0% to 6.0%, N ≤0.004%, and the rest are Fe and inevitable impurities; As Figure 2 shown, the molten steel of the first steel type and the molten steel of high-aluminum steel are respectively and independently placed in two first ladles 100 on the rotary tower 1 of the continuous casting equipment, so that after the molten steel of the first steel type is cast, the molten steel of high-aluminum steel can be rotated to the molten steel pouring position to carry out continuous casting pouring with the molten steel of the first steel type. The molten steel of the first steel type includes the following components, C: 0.030% to 0.100%, Si: ≤0.60%, Mn: ≤1.50%, P: ≤0.035%, S: ≤0.030%, Al ≤0.50%, and the rest are iron and inevitable impurities.

[0067] S2. Use argon protection throughout the process, and continuously cast the molten steel of the first steel type and the molten steel of high-aluminum steel from the first ladle 100 to the second ladle 102 in sequence with a first long nozzle 101 that is small at the top and large at the bottom and in a trumpet shape; among them, the molten steel of high-aluminum steel is not the molten steel of the first pouring order. First, pour the molten steel of the first steel type, and then continuously pour the molten steel of high-aluminum steel. When pouring the molten steel of the first steel type and the molten steel of high-aluminum steel, use high-Cr drainage slag placed at the bottom of the first ladle 100 to drain the molten steel of the first steel type and the molten steel of high-aluminum steel; by mass percentage, the high-Cr drainage slag includes the following components: Cr 2 O 3≥31.0%, Al 2 O 3 8% - 15%, MgO 7% - 12%, SiO 2 18% - 25%; Before continuous casting, the time for purging the second ladle 102 with argon is ≥5 min, and the argon purging flow rate is 2800 L / min - 3000 L / min; During casting, the argon flow rate of the first long nozzle 101 of the first ladle 100 is 100 L / min - 150 L / min;

[0068] S3. Use a pure steel covering agent to cover the liquid surfaces of the molten steel of the first steel grade and the high-aluminum steel molten steel poured into the second ladle 102 in sequence. By mass percentage, the pure steel covering agent includes the following components:

[0069] SiO 2 ≤3.0 wt%, CaO 50.0% - 55.0%, MgO 6.0% - 8.0%, Al 2 O 3 32.0% -

[0070] 36.0%, and the rest are other inevitable impurities;

[0071] S4. Use the second nozzle 103 to pour the high-aluminum steel molten steel from the second ladle 102 into the mold 104 with mold powder for crust formation to form a continuous casting billet containing a shell; Specifically include:

[0072] S41. Open the stopper rod of the second nozzle 103 between the second ladle 102 and the mold 104;

[0073] S42. Blow a nitrogen and argon mixed gas into the stopper rod, and the gas flow rate is 2 L / min - 5 L / min

[0074] Among them, the insertion depth of the second nozzle 103 into the mold 104 is 160 mm - 180 mm, the liquidus temperature of this steel grade is 1518 °C, and the superheat degree of the high-aluminum steel molten steel in the second ladle 102 is 50 °C - 70 °C, that is, the temperature of the high-aluminum steel molten steel in the second ladle is 1568 °C - 1588 °C;

[0075] The basicity of the mold powder is 0.38 - 0.58, the melting point is 820 °C - 900 °C, and the viscosity is 0.10 Pa·s - 0.20 Pa·s; By mass percentage, the mold powder includes the following components:

[0076] SiO 2 36.8% - 42.8%, CaO 16.1% - 22.1%, Al 2 O 31.7%~4.7%, C5.0%~7.0%, Na 2 O 9.0%~11.0%, Li 2 O 5.0%~7.0%, and the rest are other inevitable impurities; when the high aluminum steel liquid is crystallized in the crystallizer 104, a vibrating crystallizer 105 is used to vibrate to prevent the high aluminum steel liquid from sticking to the inner wall of the crystallizer.

[0077] S43, the crystallizer 104 uses cooling water to forcefully cool the high-aluminum steel liquid to form a shell, and the process parameters are: the wide surface flow rate of the cooling water in the crystallizer 104 is 6000L / min~6500L / min, and the narrow surface flow rate is 700L / min~800L / min, so as to obtain a casting with a shell thickness of ≥14 mm; and the uncooled and solidified molten steel in the shell of the casting with the shell is stirred by an electromagnetic induction stirrer to make the composition and structure uniform and the precipitated phase uniform.

[0078] S5. Pull the ingot containing the shell out of the crystallizer 104 at a pulling speed of 0.4 m / min to 0.8 m / min onto the supporting guide roller 108 and cool it by spraying water from the cooling nozzle 107 to obtain a continuous casting ingot of high aluminum steel; the cooling specifically includes:

[0079] S51. In the 0-3 sections of the secondary cooling sector, cooling nozzles 107 are used to cool the ingot with a water content of 0.8 L / kg to 1.1 L / kg of steel to prevent bulging of the ingot shell.

[0080] S51. Use equipment cooling water to cool the ingot in the remaining 4-16 sections of the secondary cooling sector to prevent straightening cracks in the ingot and deformation of the ingot at a low pulling speed, thereby obtaining a cooled ingot.

[0081] The cooled ingot is pulled to subsequent working equipment through the dummy rod 109 for operation or processing, for example, it is pulled to a flame cutter for cutting the ingot.

[0082] The technical solution of the present application and its beneficial effects are further illustrated below through specific comparative examples and embodiments.

[0083] The molten steel of the first steel grade in the following comparative examples and embodiments is the molten steel of the first steel grade mentioned above, and a pure steel covering agent with the following content components is used:

[0084] SiO 2 2.0wt%, CaO 53.0%, MgO 7.0%, Al 2 O 3 34.0% and the rest are other inevitable impurities.

[0085] Comparative Example 1: This comparative example provides a continuous casting method for high-aluminum steel molten steel. Among them, the component and mass percentage content of the high-aluminum steel molten steel are as follows: C: 0.062%, Si: 0.16%, Mn: 1.01%, P: 0.020%, S: 0.004%, Al: 5.1%, N: 0.0028%, and the rest are Fe and inevitable impurities.

[0086] The molten steel of the first steel type and the high-aluminum steel molten steel are continuously cast from the first ladle to the second ladle; among them, the high-aluminum steel molten steel is the first furnace in the pouring order, and then the molten steel of the first steel type is continuously poured. That is, the first furnace of molten steel first pours the high-aluminum steel molten steel and then pours the molten steel of the first steel type; during pouring, the argon flow rate of the first long nozzle is 150 L / min;

[0087] Blow a nitrogen and argon mixed gas into the stopper rod, the volume ratio of argon to nitrogen is 1:1, and the gas flow rate is 4.8 L / min; the depth of the second nozzle inserted into the mold is 175 mm; pour the high-aluminum steel molten steel from the second ladle into the mold using mold powder for crust formation to form a continuous casting billet containing a shell; among them, the liquidus temperature of this steel type is 1518 °C, the temperature of the second ladle is 1555 °C, and the superheat is 37 °C; the basicity of the mold powder is 0.51, the melting point is 850 °C, and the viscosity is 0.11 Pa·s; the mold powder, by mass percentage, includes the following components: SiO 2 40.8%, CaO 20.1%, Al 2 O 3 3.7%, C 6.0%, Na 2 O 10.0%, Li 2 O 6.0%, and the rest are other inevitable impurities;

[0088] Pull out the continuous casting billet containing the shell from the mold for cooling. The water flow rate on the wide side of the mold water cooling is 6200 L / min, and the water flow rate on the narrow side is 750 L / min. The continuous casting drawing speed is 0.75 m / min; the specific water volume of the 0-4 sections of the secondary cooling segment is 1.1 L / kg steel, and the remaining sections of the segment close the secondary cooling water and only use equipment cooling water for cooling to obtain the continuous casting billet of high-aluminum steel.

[0089] In this comparative example, the incidence rate of bonding alarm speed reduction during the continuous casting of high-aluminum steel is 4 times per furnace, a bonding breakout accident occurs, and the low magnification center segregation rating is 1.0 level.

[0090] Example 1: This example provides a continuous casting method for high-aluminum steel. Among them, the component and mass percentage content of the high-aluminum steel molten steel are as follows: C: 0.042%, Si: 0.15%, Mn: 0.96%, P: 0.015%, S: 0.003%, Al: 4.8%, N: 0.0032%, and the rest are Fe and inevitable impurities.

[0091] Pour the molten steel of the first steel grade and the molten steel of the high-aluminum steel into the second ladle continuously from the first ladle in sequence; among them, pour the molten steel of the first steel grade first, and then pour the molten steel of the high-aluminum steel continuously. Pour the molten steel of the high-aluminum steel as the 3rd furnace in the pouring sequence. The argon flow rate in the first long tundish connecting the first ladle to the second ladle is 110 L / min;

[0092] Use a pure steel covering agent to cover the liquid surfaces of the molten steel of the first steel grade and the molten steel of the high-aluminum steel poured into the second ladle in sequence;

[0093] Pour the molten steel of the high-aluminum steel from the second ladle into a mold using mold powder for crust formation to form a continuous casting billet containing a solidified shell; among them, the liquidus temperature of this high-aluminum steel grade is 1518 °C, the temperature of the second ladle is 1578 °C, and the superheat is 60 °C; the basicity of the mold powder is 0.45, the melting point is 830 °C, and the viscosity is 0.12 Pa·s; the mold powder, by mass percentage, includes components with the following contents: SiO 2 40.8%, CaO 20.1%, Al 2 O 3 3.7%, C 6.0%, Na 2 O 10.0%, Li 2 O 6.0%, and the rest are other inevitable impurities; blow a nitrogen-argon mixed gas into the stopper rod, the volume ratio of argon to nitrogen is 1:1, and the gas flow rate is 4.0 L / min; the insertion depth of the second tundish into the mold is 165 mm;

[0094] Pull out the continuous casting billet containing the solidified shell from the mold for cooling. The wide-face flow rate of the mold cooling water is 6200 L / min, and the narrow-face flow rate is 750 L / min. The continuous casting speed is 0.7 m / min; the specific water ratio of the 0-4 sections of the secondary cooling segment is 1.0 L / kg of steel, and the remaining sections of the segment close the secondary cooling water and only use equipment cooling water for cooling to obtain a continuous casting billet of high-aluminum steel.

[0095] During the continuous casting process of the high-aluminum steel in this example, no sticking alarm and speed reduction occurred, the slab quality was good, and the low-magnification center segregation rating was 0.5 level.

[0096] Example 2: This example provides a continuous casting method for high-aluminum steel, in which the molten steel of the high-aluminum steel and its mass percentage contents are: C: 0.068%, Si: 0.18%, Mn: 1.02%, P: 0.023%, S: 0.005%, Al: 5.2%, N: 0.0035%, and the rest are Fe and inevitable impurities.

[0097] Pour the molten steel of the first steel grade and the high-aluminum steel molten steel from the first ladle into the second ladle in sequence continuously; among them, the high-aluminum steel molten steel is not the molten steel of the first casting order. First, pour the molten steel of the first steel grade, and then continuously pour the high-aluminum steel molten steel. Pour the high-aluminum steel molten steel as the 6th furnace of the casting order. The argon flow rate of the first long nozzle connecting the first ladle to the second ladle is 150 L / min;

[0098] Use a pure steel covering agent to cover the liquid surfaces of the molten steel of the first steel grade and the high-aluminum steel molten steel poured into the second ladle in sequence;

[0099] In this embodiment, the liquidus temperature of the high-aluminum steel is 1518 °C, the temperature of the second ladle is 1565 °C, and the superheat is 47 °C; Blow a nitrogen-argon mixed gas into the stopper rod. The volume ratio of argon to nitrogen is 1:1.2, and the gas flow rate is 4.6 L / min. The depth of the second nozzle inserted into the mold is 170 mm; Pour the high-aluminum steel molten steel from the second ladle into the mold using mold powder to form a shell to form a slab containing a billet shell; among them, the basicity of the mold powder is 0.52, the melting point is 860 °C, and the viscosity is 0.13 Pa·s; The mold powder, by mass percentage, includes the following components: SiO 2 40.8%, CaO 20.1%, Al 2 O 3 3.7%, C 6.0%, Na 2 O 10.0%, Li 2 O 6.0%, and the rest are other inevitable impurities;

[0100] Pull out the slab containing the billet shell from the mold for cooling. The wide-face flow rate of the mold cooling water is 6200 L / min, and the narrow-face flow rate is 750 L / min. The continuous casting speed is 0.8 m / min; The specific water volume of the 0-4 sections of the secondary cooling segment is 1.1 L / kg steel. The remaining sections of the segment close the secondary cooling water and only use equipment cooling water for cooling to obtain a continuously cast slab of high-aluminum steel.

[0101] In this embodiment, the incidence rate of sticking alarm speed reduction during the continuous casting of high-aluminum steel is 0.25 times / furnace, the slab quality is good, and the low-magnification center segregation rating is 0.5 level.

[0102] From the comparison content of the above Comparative Example 1 and Examples 1-3, it can be seen that for the continuous casting method of high-aluminum steel in the embodiments of the present application, by using the method of not taking the high-aluminum steel molten steel as the first casting furnace and increasing the treatment of pure steel covering agent, mold powder, first long nozzle, and introducing protective gas into the second nozzle, the incidence rate of sticking alarm speed reduction during the continuous casting of high-aluminum steel molten steel can be effectively improved, from 4 times / furnace to 0 times / furnace to 0.25 times / furnace.

[0103] As described above, this is only the specific implementation manner of the present application. Those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working processes of the systems, modules, and units described above can refer to the corresponding processes in the foregoing method embodiments, and will not be elaborated herein. It should be understood that the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present application.

Claims

1. A continuous casting method for high-aluminum steel, characterized in that, it includes: providing molten steel of a first steel grade and molten steel of high-aluminum steel with an Al content of 3.0 wt% to 6.0 wt%; by mass percentage, the high-aluminum steel includes the following components: C: 0.030% to 0.080%, Si: 0.10% to 0.40%, Mn: 0.60% to 1.40%, P: ≤0.030%, S: ≤0.020%, Al: 3.0% to 6.0%, N ≤ 0.004%, and the rest are Fe and inevitable impurities; continuously casting the molten steel of the first steel grade and the molten steel of the high-aluminum steel from a first ladle to a second ladle in sequence, including: continuously casting throughout under a protective atmosphere; wherein, before continuous casting, the second ladle is purged with a protective atmosphere for a time ≥ 5 min, and the purge flow rate of the protective atmosphere is 2800 L / min to 3000 L / min; during casting, the protective atmosphere flow rate of the first long nozzle of the first ladle is 100 L / min to 150 L / min; wherein, a first long nozzle with a smaller upper part and a larger lower part is used for continuous casting so that the first long nozzle immerses from the first ladle into the second ladle; the molten steel of the high-aluminum steel is not the molten steel for the first casting order, the molten steel of the first steel grade is cast first, and then the molten steel of the high-aluminum steel is continuously cast; Cover the liquid surfaces of the molten steel of the first steel grade and the molten high-aluminum steel that are successively poured into the second ladle with a pure steel covering agent; the pure steel covering agent, by mass percentage, comprises components with the following contents: SiO 2 ≤3.0 wt%, CaO 50.0% - 55.0%, MgO 6.0% - 8.0%, Al 2 O 3 32.0% - 36.0%, and the balance are other inevitable impurities; Pour the high-aluminum steel molten steel from the second ladle into a mold using mold powder for crust formation to form a slab containing a billet shell; the basicity of the mold powder is 0.38 to 0.58, the melting point is 820 °C to 900 °C, and the viscosity is 0.10 Pa•s to 0.20 Pa•s. The mold powder, by mass percentage, includes components with the following contents: SiO 2 36.8% - 42.8%, CaO 16.1% - 22.1%, Al 2 O 3 1.7% - 4.7%, C 5.0% - 7.0%, Na 2 O 9.0% - 11.0%, Li 2 O 5.0% - 7.0%, and the balance is other inevitable impurities; pulling out the cast slab containing a shell from the mold for cooling to obtain a continuously cast slab of high-aluminum steel.

2. The continuous casting method according to claim 1, characterized in that, the step of continuously casting the molten steel of the first steel grade and the molten steel of the high-aluminum steel from the first ladle to the second ladle in sequence includes: Use high-Cr drainage slag to drain the molten steel of the first steel grade and the high-aluminum steel molten steel; by mass percentage, the high-Cr drainage slag includes components with the following contents: Cr 2 O 3 ≥31.0%, Al 2 O 3 8% - 15%, MgO 7% - 12%, SiO 2 18% - 25%.

3. The continuous casting method according to claim 1, characterized in that, the superheat degree of the molten steel of the high-aluminum steel in the second ladle is 50°C to 70°C.

4. The continuous casting method according to claim 1, characterized in that, the step of casting the molten steel of the high-aluminum steel from the second ladle into a mold using mold powder for shell formation to form a cast slab containing a shell, and casting the molten steel of the high-aluminum steel from the second ladle into the mold using an invasive second nozzle, includes: opening the stopper rod of the second nozzle between the second ladle and the mold; blowing a nitrogen and argon mixed gas into the stopper rod, and the gas flow rate is 2 L / min to 5 L / min.

5. The continuous casting method according to claim 4, characterized in that, the depth of insertion of the second nozzle into the mold is 160 mm to 180 mm.

6. The continuous casting method according to claim 1, characterized in that, the step of casting the molten steel of the high-aluminum steel from the second ladle into a mold using mold powder for shell formation to form a cast slab containing a shell includes: the mold uses strong cooling with cooling water to make the molten steel of the high-aluminum steel form a shell to form a shell, and its process parameters are: the wide-face flow rate of the mold cooling water is 5500 L / min to 6500 L / min, and the narrow-face flow rate is 700 L / min to 800 L / min.

7. The continuous casting method according to claim 1, wherein, in the step of pulling out the slab containing the shell from the mold for cooling to obtain a continuous casting slab of high-aluminum steel, the pulling speed of pulling out the slab containing the shell from the mold is 0.4 m / min to 0.8 m / min.

8. The continuous casting method according to claim 1, wherein, the step of pulling out the slab containing the shell from the mold for cooling to obtain a continuous casting slab of high-aluminum steel includes: cooling the slab with a water ratio of 0.8 L / kg to 1.1 L / kg of steel in at least the first 1 / 4 to 1 / 3 segments of the total number of segments of the secondary cooling sector segments; cooling the slab with equipment cooling water in the remaining segments of the total number of segments of the secondary cooling sector segments to obtain a cooled slab.

9. A high-aluminum steel, wherein, it is prepared by the continuous casting method of high-aluminum steel according to any one of claims 1 to 8.

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