Steel structure surface protection material and method for preparing steel claw protection layer by using same

Abstract

The invention discloses a steel structure surface protection material which comprises the following chemical components: chromium, boron, nickel, silicon, rare earth, 0.2-2% of carbon and the balance of iron and inevitable impurity elements. The invention discloses a method for preparing a steel claw protection layer by using a steel structure surface protection material. The method comprises the steps of preparing an alloy, preparing a high-performance alloy wire, pretreating the surface of a steel claw, manufacturing a hot-dip coating, manufacturing a sealing layer, drying and detecting. The method is suitable for the technical field of aluminum electrolysis production, the steel structure surface protection material manufactured by the method has the characteristics of high temperature resistance, high hardness, high steel base bonding strength, high wear resistance, low porosity, good thermal expansion and shrinkage performance and the like, and the oxidation corrosion rate of the anode group steel claw can be reduced by more than 90%.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum electrolysis production, and specifically relates to a steel structure surface protection material and a method for preparing a steel claw protection layer using the same. Background Art

[0002] Modern aluminum industry production generally adopts cryolite-alumina molten salt electrolysis method. Electrolytic aluminum production uses carbon material as anode, aluminum liquid as cathode, and electrolyte is molten cryolite dissolved with alumina. The main equipment is a prebaked electrolytic cell. The prebaked anode used is composed of anode carbon block, steel claw, and aluminum guide rod.

[0003] The material of steel claws of various manufacturers is ordinary steel. Every year, a large number of steel claws are scrapped, which is an indispensable part of production costs. The main reason affecting the service life of steel claws is oxidation corrosion. Analyzing the characteristics and environment of aluminum electrolysis production process, steel claw corrosion is mainly caused by the oxidation of Fe. From the perspective of chemical reaction, the oxidation of steel claws requires two conditions: high temperature and oxidizing gas. The higher the temperature, the faster the oxidation rate. The oxidizing substances in the electrolysis system are mainly oxygen, carbon dioxide, sulfur dioxide, fluoride, etc. When the aluminum electrolysis cell is in normal production, the surface temperature of the steel claw crossbeam is about 300℃, the temperature of the exposed part of the steel claw head is above 400℃, and the maximum temperature of the part buried in alumina can reach above 650℃. In this high temperature environment, oxidizing gases such as oxygen, carbon dioxide, sulfur dioxide, and fluoride react with Fe, causing Fe to be oxidized and corroded.

[0004] According to statistics, more than 35% of steel claws are scrapped due to oxidation corrosion. The oxidation of steel claws not only reduces the service life, but also causes an increase in the iron content in the electrolytic production material system, which has a great impact on the quality of raw aluminum, affects the conductivity of steel claws, and has many effects on aluminum electrolysis production. Therefore, how to protect steel claws from oxidation corrosion has also become a problem that plagues aluminum electrolysis production. Summary of the invention

[0005] One of the purposes of the present invention is to provide a steel structure surface protection material; The second object of the present invention is to provide a method for preparing a steel claw protective layer using a steel structure surface protection material.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: A steel structure surface protection material, the chemical composition of the material is as follows by mass percentage: chromium 12%-21%, boron 1.8%-4.8%, nickel 0.2%-0.95%, silicon 0.6%-1.8%, rare earth 0.2%-1%, carbon: 0.2%-2%, and the balance is iron and unavoidable impurity elements.

[0007] A method for preparing a steel claw protective layer using the steel structure surface protection material according to claim 1, comprising the following steps: S1. Alloy preparation: (1) selecting a finished high carbon steel, wherein the chemical composition of the finished high carbon steel is as follows by mass percentage: C 0.9%-1.7%, Si≤0.70%, P≤0.15%, S≤0.055%, and the balance is iron and unavoidable impurity elements, adding the finished high carbon steel into a melting furnace and heating it to above 1600° C. to obtain high temperature molten steel; (2) The temperature of the high-temperature molten steel is controlled at 1600°C-1660°C, high-temperature smelting and oxygen blowing are used to assist melting, the alloy elements in the steel are calculated according to the amount of molten iron added and the amount of steel produced, ferrochromium, ferronickel, ferrosilicon, ferroboron and rare earth elements are added in sequence, and the mass percentage of each element in the molten steel is adjusted to the mass percentage of the chemical composition of the material to obtain an alloy liquid; S2. Preparation of high performance alloy wire: Using professional continuous casting equipment, the alloy liquid obtained from S1 is cast into high-performance alloy wire; S3. Surface preparation of steel claws: The surface of the steel claws is treated by manual sandblasting, with a treatment grade of Sa3.0, making the surface appear obviously frosted; S4. Hot-dip coating production: Using arc spraying technology, the high-performance alloy wire obtained by S3 is evenly thermally sprayed on the surface of the steel claw pretreated by S3 to form an amorphous hot-dip coating; S5. Sealing layer production: A high-performance coating is made with nano-transition sealing material as the base material, and the coating is evenly covered on the surface of the steel claw formed with the amorphous hot-dip coating obtained by S4 by thermal spraying or direct brushing to form a sealing layer; S6. Drying and testing: The steel claws obtained in S5 are naturally dried in an environment above 20°C for no less than 48 hours. After being thoroughly dried, the chemical composition is tested. If it meets the chemical composition mass percentage of the material, the performance test is then carried out.

[0008] In order to further realize the present invention, the ferrochrome described in S1 adopts refined ferrochrome, in which the mass percentage of chromium element is ≥60%, and the mass percentage of carbon element is ≤0.5%; the ferronickel adopts national standard FeNi40 and above, in which the mass percentage of carbon element is ≤0.6%; the ferrosilicon adopts national standard FeSi65 and above, in which the mass percentage of phosphorus element is ≤0.3%; the ferroboron adopts medium carbon ferroboron, in which the mass percentage of boron element is ≥15%, and the mass percentage of carbon element is ≤2%.

[0009] In order to further realize the present invention, after the steel claws described in S3 are manually sandblasted, the surface roughness of the steel claws reaches Rz60μm-120μm.

[0010] In order to further realize the present invention, the voltage of the arc spraying in S4 is 28V-32V, the current is 180A-220A, and the air pressure is 0.5MPa-0.6MPa.

[0011] In order to further realize the present invention, the nano transition sealing material in S5 includes 5%-8% bentonite, 10%-15% ceramic fiber, 6%-10% polyethylene glycol, and the balance is a high-purity silicate solution.

[0012] In order to further realize the present invention, the coating thickness in the performance test described in S6 is 280μm-300μm, the Rockwell hardness is ≥65HRC, the steel base bonding strength is ≥52MPa, the high temperature oxidation resistance at 800°C is more than 20 times that of Q235 steel, the wear resistance at 315°C is more than 17 times that of nickel-chromium alloy, and the porosity is ≤3%.

[0013] In order to further realize the present invention, the mass percentage of the impurity elements is less than 0.5%.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention is applicable to the technical field of aluminum electrolysis production. The steel structure surface protection material produced by the present invention, the protective layer produced on the surface of the steel claw, i.e. the coating, has the characteristics of high temperature resistance, high hardness, high steel base bonding strength, strong wear resistance, low porosity, good thermal expansion and contraction performance, etc., and can reduce the oxidation corrosion rate of the anode group steel claw by more than 90%.

[0015] The steel structure surface protection material designed by the present invention and the protective layer prepared using the same have the advantages of good high-temperature oxidation resistance, good thermal expansion and contraction performance, strong steel-based bonding and high density; (2) The protective layer and the preparation method are suitable for the aluminum electrolysis production environment, and can be hot-dipped on the surface of the anode group steel claw to effectively prevent the high-temperature oxidation of the steel claw. The use of the protective layer can reduce the oxidation corrosion rate of the anode group steel claw by more than 90%, greatly extend the service life of the steel claw, reduce production costs, reduce the iron impurity content in the electrolytic cell covering material from the source, effectively improve the quality of the original aluminum, and keep the size of the steel claw for a long time, the conductive cross-sectional area remains unchanged, and the conductive performance of the steel claw is always in an excellent state. DETAILED DESCRIPTION

[0016] The present invention will be further described below in conjunction with specific implementation modes.

[0017] A steel structure surface protection material, the chemical composition of the material is as follows by mass percentage: chromium 12%-21%, boron 1.8%-4.8%, nickel 0.2%-0.95%, silicon 0.6%-1.8%, rare earth 0.2%-1%, carbon: 0.2%-2%, the remainder is iron and unavoidable impurity elements, and the mass percentage of the impurity elements is less than 0.5%.

[0018] A method for preparing a steel claw protective layer using the steel structure surface protection material according to claim 1, comprising the following steps: S1. Alloy preparation: (1) selecting a finished high carbon steel, wherein the chemical composition of the finished high carbon steel is as follows by mass percentage: C 0.9%-1.7%, Si≤0.70%, P≤0.15%, S≤0.055%, and the balance is iron and unavoidable impurity elements, adding the finished high carbon steel into a melting furnace and heating it to above 1600° C. to obtain high temperature molten steel; (2) The temperature of the high-temperature molten steel is controlled at 1600°C-1660°C, high-temperature smelting and oxygen blowing are used to assist melting, the alloy elements in the steel are calculated according to the amount of molten iron added and the amount of steel produced, ferrochromium, ferronickel, ferrosilicon, ferroboron and rare earth elements are added in sequence, and the mass percentage of each element in the molten steel is adjusted to the mass percentage of the chemical composition of the material to obtain an alloy liquid; Ferrochrome uses refined ferrochrome, in which the mass percentage of chromium is ≥60% and the mass percentage of carbon is ≤0.5%; ferronickel uses national standard FeNi40 and above, in which the mass percentage of carbon is ≤0.6%; ferrosilicon uses national standard FeSi65 and above, in which the mass percentage of phosphorus is ≤0.3%; ferroboron uses medium carbon ferroboron, in which the mass percentage of boron is ≥15% and the mass percentage of carbon is ≤2%; S2. Preparation of high performance alloy wire: Using professional continuous casting equipment, the alloy liquid obtained from S1 is cast into high-performance alloy wire; S3. Surface preparation of steel claws: After the surface of the steel claw is treated by manual sandblasting, the treatment level is Sa3.0, making the surface appear obviously frosted, and the surface roughness of the steel claw reaches Rz60μm-120μm; S4. Hot-dip coating production: The arc spraying technology is adopted, the voltage of the arc spraying is 28V-32V, the current is 180A-220A, and the air pressure is 0.5MPa-0.6MPa. The high-performance alloy wire obtained by S3 is evenly thermally sprayed on the surface of the steel claw pretreated by S3 to form an amorphous hot-dip coating; S5. Sealing layer production: A high-performance coating is prepared with a nano-transition sealing material as a base material. The nano-transition sealing material includes 5%-8% bentonite, 10%-15% ceramic fiber, 6%-10% polyethylene glycol, and the balance is a high-purity silicate solution. The high-performance coating is thermally sprayed or directly brushed to evenly cover the surface of the steel claw formed with the amorphous hot-dip coating obtained in S4 to form a sealing layer. S6. Drying and testing: The steel claws obtained from S5 are naturally dried in an environment above 20°C for no less than 48 hours. After being thoroughly dried, the chemical composition is tested. If the chemical composition mass percentage meets the requirements, performance testing is performed. In the performance testing, the coating thickness is 280μm-300μm, the Rockwell hardness is ≥65HRC, the steel base bonding strength is ≥52MPa, the high temperature oxidation resistance at 800°C is more than 20 times that of Q235 steel, the wear resistance at 315°C is more than 17 times that of nickel-chromium alloy, and the porosity is ≤3%.

[0019] Example: The technical solution provided by the present invention has been successfully implemented on a certain 500kA aluminum electrolysis series.

[0020] The protective layer preparation process is as follows: S1. Alloy preparation: (1) Prepare a certain amount of finished high carbon steel with a carbon mass percentage of 2.0% and other elements mass percentages of Si 0.60%, P 0.12%, and S 0.045%, add it into a melting furnace, heat it to above 1650°C, and obtain high-temperature molten steel.

[0021] (2) After the molten steel is smelted, the composition is adjusted and the temperature is controlled at 1600℃-1660℃. Through high-temperature smelting and oxygen blowing to assist melting, the alloy elements in the steel are calculated according to the amount of molten iron added and the amount of steel produced. Ferrochromium, ferronickel, ferrosilicon, borax and rare earth elements are added in sequence to control the mass percentage of each alloy element in the molten steel to meet the following requirements: chromium: 12%-21%; boron: 1.8%-4.8%; nickel: 0.2%-0.95%; silicon: 0.6%-1.8%; rare earth: 0.2%-1%; carbon: 0.2%-2%; the balance is iron, and the mass percentage of other impurity elements is <0.5%.

[0022] Among them, the ferrochrome used is refined ferrochrome, with the mass percentage of chromium element ≥60% and the mass percentage of carbon element ≤0.5%; the ferronickel is the national standard FeNi50 (45%~60%Ni), with the mass percentage of carbon element ≤0.6%; the ferrosilicon is the national standard FeSi75-A (74.0~80.0Si), with the mass percentage of phosphorus element ≤0.3%; the ferroboron is medium carbon ferroboron (the main raw material for the preparation of amorphous materials), with the mass percentage of boron element ≥15%, and the mass percentage of carbon element ≤2%.

[0023] S2. Preparation of high performance alloy wire: Using professional continuous casting equipment, the alloy liquid is cast into high-performance alloy wire.

[0024] The alloy wire is amorphous and has the following characteristics: excellent tensile erosion resistance, wear resistance and high temperature resistance, strong adhesion of the coating, and strong oxidation resistance; the high-performance composite wire is divided into two parts, the hard phase and the plastic phase, so the coating has strong plasticity and has a roughly consistent thermal expansion coefficient with the base material.

[0025] S3. Surface preparation of steel claws: The surface of the steel claw is treated by manual sandblasting, with a treatment grade of Sa3.0, making the surface appear obviously frosted, and the surface roughness of the steel claw reaches Rz60um~120um.

[0026] S4. Hot-dip coating production The arc spraying technology is used to evenly thermally spray the high-performance alloy wire onto the pre-treated surface of the steel claw to form an amorphous hot-dip coating. The arc spraying voltage is 32V, the current is 220A, and the air pressure is 0.55MPa.

[0027] S5. Sealing layer production: High-purity silicate solution is finely processed into a film-forming material, including 5%-8% bentonite, 10%-15% ceramic fiber, 6%-10% polyethylene glycol, and the remainder is high-purity silicate solution. Nano transition sealing material is made, and the surface of the hot-dip layer made of S4 is evenly covered with a coating by thermal spraying to form a sealing layer.

[0028] S6. Drying and testing: After the coating is completed, it is naturally dried for 60 hours in an environment above 25°C to make the coating dry thoroughly.

[0029] Then the chemical composition and coating performance tests were carried out. The chemical composition test results are as follows: The performance test results are as follows: The steel claws with anti-oxidation coating were used on 500kA aluminum electrolytic cells, and the results were as follows: After three anode replacement cycles (96 days) in the electrolytic cell, the average width of the steel claw decreased by 0.59 mm, and the average height decreased by 0.61 mm (the data was measured by averaging 4 points). Among them, 3 points had basically no change, and 1 point decreased by less than 3 mm. The data details are shown in the table below.

[0030] At the same time, data collection was done on the size of unprotected steel claws. Using an anode replacement cycle (32 days), the average width or height reduction was 3.62mm. From this comparative analysis, it can be seen that after the anti-oxidation coating is made on the surface of the steel claw, the anti-oxidation corrosion ability is greatly improved, and the oxidation rate of the steel claw is reduced by 94.5%.

Claims

1. A steel structure surface protection material, characterized in that: The chemical composition of the material is as follows by mass percentage: chromium 12%-21%, boron 1.8%-4.8%, nickel 0.2%-0.95%, silicon 0.6%-1.8%, rare earth 0.2%-1%, carbon: 0.2%-2%, and the remainder is iron and unavoidable impurity elements.

2. A method for preparing a steel claw protective layer using the steel structure surface protection material according to claim 1, characterized in that The steps include: S1. Alloy preparation: (1) selecting a finished high carbon steel, wherein the chemical composition of the finished high carbon steel is as follows by mass percentage: C 0.9%-1.7%, Si≤0.70%, P≤0.15%, S≤0.055%, and the balance is iron and unavoidable impurity elements, adding the finished high carbon steel into a melting furnace and heating it to above 1600° C. to obtain high temperature molten steel; (2) The temperature of the high-temperature molten steel is controlled at 1600°C-1660°C, high-temperature smelting and oxygen blowing are used to assist melting, the alloy elements in the steel are calculated according to the amount of molten iron added and the amount of steel produced, ferrochromium, ferronickel, ferrosilicon, ferroboron and rare earth elements are added in sequence, and the mass percentage of each element in the molten steel is adjusted to the mass percentage of the chemical composition of the material to obtain an alloy liquid; S2. Preparation of high performance alloy wire: Using professional continuous casting equipment, the alloy liquid obtained from S1 is cast into high-performance alloy wire; S3. Surface preparation of steel claws: The surface of the steel claws is treated by manual sandblasting, with a treatment grade of Sa3.0, making the surface appear obviously frosted; S4. Hot-dip coating production: Using arc spraying technology, the high-performance alloy wire obtained by S3 is evenly thermally sprayed on the surface of the steel claw pretreated by S3 to form an amorphous hot-dip coating; S5. Sealing layer production: A high-performance coating is made with nano-transition sealing material as the base material, and the coating is evenly covered on the surface of the steel claw formed with the amorphous hot-dip coating obtained by S4 by thermal spraying or direct brushing to form a sealing layer; S6. Drying and testing: The steel claws obtained in S5 are naturally dried in an environment above 20°C for no less than 48 hours. After being thoroughly dried, the chemical composition is tested. If it meets the chemical composition mass percentage of the material, the performance test is then carried out.

3. The method for preparing a steel claw protective layer using a steel structure surface protective material as claimed in claim 2, characterized in that: The ferrochrome described in S1 adopts refined ferrochrome, in which the mass percentage of chromium element is ≥60%, and the mass percentage of carbon element is ≤0.5%; the ferronickel adopts national standard FeNi40 and above, in which the mass percentage of carbon element is ≤0.6%; the ferrosilicon adopts national standard FeSi65 and above, in which the mass percentage of phosphorus element is ≤0.3%; the ferroboron adopts medium carbon ferroboron, in which the mass percentage of boron element is ≥15%, and the mass percentage of carbon element is ≤2%.

4. The method for preparing a steel claw protective layer using the steel structure surface protection material as claimed in claim 3, characterized in that: After the steel claws described in S3 are manually sandblasted, the surface roughness of the steel claws reaches Rz60μm-120μm.

5. The method for preparing a steel claw protective layer using the steel structure surface protection material as claimed in claim 4, characterized in that: The voltage of the arc spraying in S4 is 28V-32V, the current is 180A-220A, and the air pressure is 0.5MPa-0.6MPa.

6. The method for preparing a steel claw protective layer using the steel structure surface protection material as claimed in claim 5, characterized in that: The nano transition sealing material described in S5 includes 5%-8% bentonite, 10%-15% ceramic fiber, 6%-10% polyethylene glycol, and the balance is a high-purity silicate solution.

7. The method for preparing a steel claw protective layer using the steel structure surface protection material as claimed in claim 6, characterized in that: In the performance test described in S6, the coating thickness is 280μm-300μm, the Rockwell hardness is ≥65HRC, the steel base bonding strength is ≥52MPa, the high temperature oxidation resistance at 800℃ is more than 20 times that of Q235 steel, the wear resistance at 315℃ is more than 17 times that of nickel-chromium alloy, and the porosity is ≤3%.

8. The method for preparing a steel claw protective layer using the steel structure surface protection material as claimed in claim 1, characterized in that: The mass percentage of the impurity elements is less than 0.5%.

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