Rare earth ferrosilicon functional coating, preparation method and application thereof

Abstract

This invention discloses a rare-earth ferrosilicon functional coating, its preparation method, and its application, belonging to the field of refractory materials technology. The rare-earth ferrosilicon functional coating includes a transition layer and a functional layer. The transition layer comprises the following raw materials in parts by weight: 60-90 parts refractory filler, 5-20 parts binder, and 0-8 parts antioxidant / anti-corrosion component. The functional layer comprises the following raw materials in parts by weight: 20-70 parts rare-earth ferrosilicon alloy powder, 20-75 parts refractory filler, 3-20 parts binder, and 0-26 parts antioxidant / anti-corrosion component. This invention also discloses a rare-earth ferrosilicon (RE-FeSi) based functional coating for the working part of a stopper rod used for flow control in continuous casting tundishes, providing anti-nodulation, anti-clogging, and anti-corrosion properties. The coating's preparation method and application in the continuous casting process are also disclosed. Through the reaction and inclusion modification of rare-earth elements at high-temperature interfaces, a comprehensive protective system with anti-adhesion deposition, anti-corrosion, and anti-thermal shock spalling is formed, thereby improving the stability of flow control during casting and extending the service life of the stopper rod.

Description

Technical Field

[0001] This invention relates to the field of refractory materials technology, and more specifically to a rare earth silicon-iron functional coating, its preparation method, and its application. Background Technology

[0002] In continuous casting production, the tundish stopper rod works in conjunction with the tundish nozzle to regulate the molten steel flow. The stopper rod head (conical / end face) is constantly exposed to the combined effects of high-temperature molten steel, protective slag, and inclusions. Common problems include:

[0003] 1. Nodulation and sedimentation: Sediments mainly composed of Al2O3, All2O3-MgO (spinel) and other inclusions gradually accumulate at the head of the stopper rod and inlet area, resulting in a reduction in the effective flow area, flow fluctuations, and even blockage. 2. Interface reaction and corrosion: The molten steel and slag react and corrode the stopper rod refractory, causing changes in geometry and a decrease in control precision; 3. Thermal shock spalling during start-up and shutdown of casting: Temperature cycling causes the expansion and spalling of surface microcracks, leading to local turbulence and an increased risk of secondary oxidation.

[0004] The above problems are particularly prominent in aluminum-killed steel, high-Al steel, and long continuous casting conditions, directly affecting casting stability, bar changing frequency, and billet quality.

[0005] Currently, common solutions include: increasing the density of the refractory material, changing the material system of the stopper rod, using conventional anti-adhesion coatings (such as Al2O3 / ZrO2 systems, carbon-containing coatings, etc.), or adjusting the protective flux. However, the following shortcomings still exist: 1. Unstable anti-nodulation effect: It has limited inhibition on Al2O3 inclusions and deposits, and "hard nodules" are still easily generated after long-term casting, and the growth of nodules is uncontrollable; 2. Insufficient bonding strength between coating and substrate: Conventional coatings are prone to cracking and local peeling under thermal shock and erosion, which in turn induces flow field disturbance; 3. Lack of a synergistic mechanism of "inclusion modification + interface shielding": Most coatings rely solely on physical isolation or wettability adjustment, which cannot form a continuous and effective protective reaction layer at high-temperature interfaces; 4. Poor adaptability to different steel grades: When the content of Al, O, and S in the steel and the slag system change, the effect of existing coatings fluctuates significantly.

[0006] Therefore, how to improve the stability of flow control during the casting process and extend the service life of the stopper rod is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] In view of this, the purpose of this invention is to provide a rare earth silicon-iron functional coating and its preparation method and application, so as to solve the problems of easy nodule formation, easy clogging, easy corrosion and insufficient coating life in the prior art.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A rare-earth silicon-iron functional coating includes a transition layer and a functional layer; The transition layer comprises the following raw materials in parts by weight: 60-90 parts of refractory filler, 5-20 parts of binder, and 0-8 parts of antioxidant / anti-corrosion component; The functional layer comprises the following raw materials in parts by weight: 20-70 parts of rare earth ferrosilicon (RE-FeSi) powder, 20-75 parts of refractory filler, 3-20 parts of binder, and 0-26 parts of antioxidant / anti-corrosion component.

[0009] The present invention discloses a rare earth ferrosilicon functional coating disposed in at least one working area (preferably the stopper head) of an intermediate tundish stopper rod. The coating includes a transition layer and a functional layer. Specifically, to improve adhesion and thermal shock resistance, a transition layer is first coated on the substrate surface to improve thermal expansion matching and adhesion strength with the stopper rod substrate (such as Al2O3-C, Mg-C, etc.), reducing the risk of thermal shock peeling. The functional layer uses rare earth ferrosilicon alloy powder as the functional phase, combined with refractory fillers, antioxidant / anti-corrosion components, and binders to form a sinterable or in-situ densified coating.

[0010] Among them, the functional layer is poured at high temperatures: 1. Rare earth elements (Ce / La, etc.) interact with O, S and oxide inclusions at the interface, making the inclusions tend to be more complex, rounded, have a lower melting point, or be more fluid, thus reducing the tendency of "hard Al2O3 nodules" to continue growing. 2. A denser and more stable reaction / protective layer is formed on the coating surface, reducing the direct reaction between steel and refractory and slag and refractory, thus slowing down erosion; 3. By controlling the microstructure and wettability of the coating, the deposited layer is made more difficult to adhere firmly and more easily washed away by the steel flow, thus achieving anti-nodulation and anti-clogging.

[0011] Key points and areas to be protected in this invention: 1. Coating material system: RE-FeSi powder is used as the functional phase, combined with refractory fillers and binders to form a curable / sinterable stopper rod anti-nodulation coating; 2. Coating objects and areas: The coating is applied to the stopper rod of the continuous casting tundish, and should at least cover the conical surface and end face of the stopper rod head; 3. Structural design: A dual-layer or gradient structure with a transition bonding layer and a functional layer is adopted to improve adhesion and resistance to thermal shock peeling; 4. Process methods: including specific steps and parameter ranges for surface pretreatment, slurry preparation, multiple coatings and drying / curing / firing.

[0012] Furthermore, the aforementioned functional layer comprises the following raw materials in parts by weight: 35-60 parts of rare earth ferrosilicon alloy powder, 30-55 parts of refractory filler, 6-15 parts of binder, 3-12 parts of SiC, and 0.5-3 parts of B4C.

[0013] Furthermore, the above-mentioned rare earth ferrosilicon alloy powder comprises the following raw materials in parts by weight: 8-12 parts of rare earth RE, 40-50 parts of Si and 38-52 parts of Fe, with D50 in the range of 10-80 μm.

[0014] Furthermore, the aforementioned rare earth elements (RE) include Ce and La.

[0015] Furthermore, the aforementioned rare earth elements (RE) also include Pr and Nd.

[0016] Furthermore, the aforementioned refractory filler is at least one of Al2O3, ZrO2, MgO and spinel (MgAl2O4), and is arranged in a 5-200μm multi-gradation to improve density and erosion resistance.

[0017] Furthermore, the aforementioned binder is a phosphate binder (aluminum dihydrogen phosphate, aluminum phosphate sol, etc.) or a silica sol / water glass system.

[0018] Furthermore, the aforementioned antioxidant / anti-corrosion component is at least one of SiC, B4C, Si, and Al.

[0019] Furthermore, the rare earth silicon-iron functional coating of the present invention also includes additives, preferably at least one of dispersants, thixotropic agents and defoamers.

[0020] A method for preparing a rare-earth silicon-iron functional coating specifically includes the following steps: (1) Weigh each raw material according to the above-mentioned rare earth silicon iron functional coating parts by weight; (2) Mix the refractory filler, binder and antioxidant / anti-corrosion component evenly, add ethanol aqueous solution, ball mill or high speed stir for 10-60 min to make it evenly dispersed, and the transition layer is obtained. (3) Mix rare earth silicon iron alloy powder, refractory filler, binder, SiC and B4C evenly, add ethanol aqueous solution, ball mill or high speed stirring for 10-60 min to make it evenly dispersed, and the functional layer is obtained.

[0021] This invention also claims protection for the application of the above-described rare earth ferrosilicon functional coating or the rare earth ferrosilicon functional coating prepared by the above-described method in the continuous casting process.

[0022] A method for using a rare-earth silicon-iron functional coating specifically includes the following steps: (1) Surface pretreatment Sandblasting or grinding is performed on the area of ​​the stopper rod substrate to be coated to create roughness and remove dust; preheating to 60-150℃ removes surface moisture. (2) Preparation of coating slurry Take the above-mentioned rare earth ferrosilicon functional coating or the rare earth ferrosilicon functional coating prepared by the above preparation method (the viscosity is adjusted according to the construction method). (3) Coating Apply the coating in multiple layers using brushing, spraying, or dipping methods. First, apply a transition layer, and then apply the functional layer after it dries. After each application, allow the coating to stand and level to avoid sagging and pinholes, thus achieving the target thickness. (4) Drying and curing / firing Curing: Dry at 80-120℃ for 1-4 hours, then keep warm at 200-350℃ for 1-3 hours; Firing: Hold at 600-1000℃ for 0.5-2 hours.

[0023] Furthermore, in step (1) above, the stopper rod substrate is Al2O3-C, ZrOl2-C, MgO-C or carbon-containing composite refractory stopper rod; the coating area is the head cone surface and end face of the stopper rod substrate, and optionally covers the neck area 30-150mm above the head of the stopper rod.

[0024] Furthermore, in step (3) above, the thickness of the transition layer is 0.2-0.6 mm; the thickness of the functional layer is 0.2-3.0 mm, preferably 0.4-1.5 mm.

[0025] As can be seen from the above technical solution, compared with the prior art, the beneficial effects of the present invention are as follows: 1. Significantly reduces the risk of nodule formation and blockage. Through the synergistic effect of rare earth elements on inclusions and interfacial reactions, the continuous growth of deposits such as Al2O3 is inhibited, resulting in a more stable flow area. 2. Improve the stability of pouring flow control Reduce the drift in the opening-flow relationship caused by deposition or local peeling, making the control of liquid level and pulling speed more stable; 3. Improve erosion resistance The coating forms a protective reactive layer, reducing the direct erosion of the base refractory by molten steel / slag; 4. Improves resistance to thermal shock and spalling. The transition layer improves adhesion and matches thermal expansion, reducing crack propagation and localized spalling; 5. Extend the service life of the stopper rod The benefits are more pronounced under conditions such as continuous casting and high-Al steel, thereby improving production line stability and overall cost performance.

[0026] In summary, this invention discloses a rare earth ferrosilicon (RE-FeSi) based functional coating for the working part of a stopper rod used for flow control in continuous casting tundish, which is anti-nodulation, anti-clogging, and anti-erosion. It also discloses the preparation method of the coating and its application in the continuous casting process. Through the reaction and inclusion modification of rare earth elements at the high-temperature interface, a comprehensive protective system with anti-adhesion deposition, anti-erosion, and anti-thermal shock spalling is formed, thereby improving the stability of flow control during the casting process and extending the service life of the stopper rod. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1 Rare earth silicon-iron functional coating, including a transition layer and a functional layer; The transition layer comprises the following raw materials by weight: 75g Al2O3, 12g silica sol, and 5g SiC; The functional layer comprises the following raw materials by weight: 45g rare earth ferrosilicon alloy powder, 35g ZrO2, 8g silica sol, 10g SiC and 2g B4C; The rare earth ferrosilicon alloy powder comprises the following raw materials by weight: 10g of rare earth RE (mainly Ce+La), 45g of Si, and 45g of Fe; The preparation method of the above-mentioned rare earth silicon-iron functional coating specifically includes the following steps: (1) Weigh each raw material according to the weight of the above rare earth ferrosilicon functional coating; (2) Mix Al2O3, silica sol and SiC evenly, add ethanol aqueous solution, and ball mill for 10 min to disperse it evenly, thus obtaining the transition layer; (3) Mix rare earth silicon iron alloy powder, ZrO2, silica sol, SiC and B4C evenly, add ethanol aqueous solution, and ball mill for 10 min to disperse it evenly, thus obtaining the functional layer.

[0029] Example 2 Rare earth silicon-iron functional coating, including a transition layer and a functional layer; The transition layer comprises the following raw materials by weight: 60g ZrO2, 20g silica sol, and 8g B4C; The functional layer comprises the following raw materials by weight: 40g rare earth silicon-iron alloy powder, 30g Al2O3, 15g silica sol, 12g SiC and 3g B4C; The rare earth ferrosilicon alloy powder comprises the following raw materials by weight: 8g of rare earth RE (mainly Ce+La), 40g of Si, and 52g of Fe; The preparation method of the above-mentioned rare earth silicon-iron functional coating specifically includes the following steps: (1) Weigh each raw material according to the weight of the above rare earth ferrosilicon functional coating; (2) Mix ZrO2, silica sol and B4C evenly, add ethanol aqueous solution, and ball mill for 60 min to disperse it evenly, thus obtaining the transition layer; (3) Mix rare earth silicon iron alloy powder, Al2O3, silica sol, SiC and B4C evenly, add ethanol aqueous solution, and ball mill for 60 min to disperse it evenly, thus obtaining the functional layer.

[0030] Example 3 Rare earth silicon-iron functional coating, including a transition layer and a functional layer; The transition layer comprises the following raw materials by weight: 90g MgO, 5g aluminum dihydrogen phosphate, and 5g Si; The functional layer comprises the following raw materials by weight: 35g rare earth silicon iron alloy powder, 55g MgAl2O4, 6g aluminum dihydrogen phosphate, 3g SiC and 1g B4C. The rare earth ferrosilicon alloy powder comprises the following raw materials by weight: 12g of rare earth RE (mainly Ce+La), 50g of Si, and 38g of Fe; The preparation method of the above-mentioned rare earth silicon-iron functional coating specifically includes the following steps: (1) Weigh each raw material according to the weight of the above rare earth ferrosilicon functional coating; (2) Mix MgO, aluminum dihydrogen phosphate and Si evenly, add ethanol aqueous solution, and stir at high speed for 60 min to make it evenly dispersed, thus obtaining the transition layer; (3) Mix rare earth silicon iron alloy powder, MgAl2O4, aluminum dihydrogen phosphate, SiC and B4C evenly, add ethanol aqueous solution, and stir at high speed for 60 min to make it evenly dispersed, thus obtaining the functional layer.

[0031] Performance testing The rare earth silicon-iron functional coatings prepared in Examples 1-3 were applied to the stopper rod substrate, specifically including the following steps: (1) Surface pretreatment The head cone and end faces of the Al2O3-C stopper rod substrate are sandblasted to create roughness and remove dust; preheat to 150℃ to remove surface moisture. (2) Preparation of coating slurry Take the rare earth silicon-iron functional coatings prepared in Examples 1-3 respectively; (3) Coating The coating is applied in multiple layers using a spraying method. First, a transition layer is applied, and after it dries, the functional layer is applied. After each application, the coating is allowed to stand and level to avoid sagging and pinholes, achieving the target thickness. The thickness of the transition layer is 1.0 mm, and the thickness of the functional layer is 0.3 mm. (4) Drying and curing / firing Curing: Dry at 120℃ for 4 hours, then keep warm at 350℃ for 3 hours; Firing: Hold at 1000℃ for 2 hours.

[0032] Performance testing Two types of samples were prepared: aluminum carbon (Al2O3-C) and aluminum spinel carbon (Al2O3-MgAl2O4-C), with a sample size of Φ20 mm × 20 mm. Two groups were set up for each type of material: the control group was coated with a commercially available conventional protective coating; the experimental group was coated with the rare earth silicon iron functional coating (RE-FeSi coating) of Example 1.

[0033] The coated samples were evaluated using a high-temperature static deposition method, and the specific steps are as follows: (1) Dry the sample at 120℃ for 2 h and then weigh it; (2) Preparation of simulated melt system: Al2O3 powder + CaO-SiO2-Al2O3 slag system; (3) Heat the melt to 1550°C and keep it stable; (4) Immerse the sample completely in the melt and keep it at that temperature for 30 min; (5) Remove the sample and allow it to cool naturally; (6) After gently brushing away any loosely attached material, weigh the product. (7) Calculate the sediment weight (sediment weight = mass after experiment - mass before experiment).

[0034] The evaluation results are shown in Table 1.

[0035] Table 1 Evaluation results of the samples after coating

[0036] As shown in Table 1, for aluminum-carbon materials, the RE-FeSi coating of this invention reduces the deposition weight from 2.3 g to 1.2 g, a reduction of approximately 48%. For aluminum spinel-carbon materials, the RE-FeSi coating reduces the deposition weight from 1.8 g to 0.6 g, a reduction of approximately 66.7%. In both different substrate systems, the RE-FeSi coating of this invention exhibits a significant effect in inhibiting Al2O3 deposition, indicating its good versatility.

[0037] Experimental results show that the RE-FeSi coating of this invention can significantly reduce the deposition of Al2O3 on the surface of refractory materials, with a reduction of approximately 50%-65%, effectively inhibiting nodule formation. The RE-FeSi coating of this invention significantly weakens the adhesion and enrichment ability of Al2O3 by altering interfacial reaction behavior and deposit adhesion characteristics, thereby inhibiting nodule formation at its source.

[0038] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A rare-earth silicon-iron functional coating, characterized in that, Includes a transition layer and a functional layer; The transition layer comprises the following raw materials in parts by weight: 60-90 parts of refractory filler, 5-20 parts of binder, and 0-8 parts of antioxidant / anti-corrosion component; The functional layer comprises the following raw materials in parts by weight: 20-70 parts of rare earth ferrosilicon alloy powder, 20-75 parts of refractory filler, 3-20 parts of binder, and 0-26 parts of antioxidant / anti-corrosion component.

2. The rare earth silicon-iron functional coating according to claim 1, characterized in that, The functional layer comprises the following raw materials in parts by weight: 35-60 parts of rare earth ferrosilicon alloy powder, 30-55 parts of refractory filler, 6-15 parts of binder, 3-12 parts of SiC and 0.5-3 parts of B4C.

3. A rare-earth silicon-iron functional coating according to claim 1 or 2, characterized in that, The rare earth ferrosilicon alloy powder comprises the following raw materials in parts by weight: 8-12 parts of rare earth RE, 40-50 parts of Si, and 38-52 parts of Fe.

4. The rare earth silicon-iron functional coating according to claim 3, characterized in that, The rare earth elements RE include Ce and La.

5. The rare earth silicon-iron functional coating according to claim 4, characterized in that, The rare earth elements RE also include Pr and Nd.

6. A rare-earth silicon-iron functional coating according to claim 1 or 2, characterized in that, The refractory filler is at least one selected from Al2O3, ZrO2, MgO, and MgAl2O4; The binder is a phosphate binder or a silica sol / water glass system; The antioxidant / anti-erosion component is at least one of SiC, B4C, Si, and Al.

7. A method for preparing a rare earth silicon-iron functional coating, characterized in that, Specifically, the following steps are included: (1) Weigh each raw material according to the weight proportions of the rare earth silicon-iron functional coating as described in any one of claims 1-6; (2) Mix the refractory filler, binder and antioxidant / anti-corrosion component evenly, add ethanol aqueous solution, ball mill or high speed stir for 10-60 min to disperse it evenly, and the transition layer is obtained; (3) Mix rare earth silicon iron alloy powder, refractory filler, binder, SiC and B4C evenly, add ethanol aqueous solution, ball mill or high speed stirring for 10-60 min to make it evenly dispersed, and the functional layer is obtained.

8. The application of a rare earth ferrosilicon functional coating as described in any one of claims 1-6 or a rare earth ferrosilicon functional coating prepared by the preparation method as described in claim 7 in the continuous casting process.

9. A method for using a rare earth silicon-iron functional coating, characterized in that, Specifically, the following steps are included: (1) Surface pretreatment Sandblasting or grinding is performed on the area of ​​the stopper rod substrate to be coated to create roughness and remove dust; preheating to 60-150℃ removes surface moisture. (2) Preparation of coating slurry The rare earth silicon-iron functional coating as described in any one of claims 1-6 or the rare earth silicon-iron functional coating prepared by the preparation method as described in claim 7; (3) Coating Apply the coating in multiple layers using brushing, spraying, or dipping methods. First, apply a transition layer, and then apply the functional layer after it dries. After each application, allow the coating to stand and level to avoid sagging and pinholes, thus achieving the target thickness. (4) Drying and curing / firing Curing: Dry at 80-120℃ for 1-4 hours, then keep warm at 200-350℃ for 1-3 hours; Firing: Hold at 600-1000℃ for 0.5-2 hours.

10. The method of using the rare earth silicon-iron functional coating according to claim 9, characterized in that, In step (1), the stopper rod substrate is Al2O3-C, ZrOl2-C, MgO-C or a carbon-containing composite refractory stopper rod; the coating area is the head cone surface and end face of the stopper rod substrate; In step (3), the thickness of the transition layer is 0.2-0.6 mm; the thickness of the functional layer is 0.2-3.0 mm.

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