CN106906491A - A kind of ferronickel base is anti-oxidant and corrosion resisting alloy inert anode material - Google Patents

Abstract

The invention belongs to the field of metallurgy, and specifically relates to a nickel-iron-based anti-oxidation and corrosion-resistant alloy inert anode material, which is suitable for molten salt electrolysis industries such as metal aluminum. The mass percent composition of the nickel-iron-based alloy inert anode material includes: 5-70% Ni, 10-70% Fe, 5-65% Cu, 3-55% Cr, 1-12% Co, 1-5% Al. The invention provides an alloy material suitable for an inert anode of a molten salt electrolytic cell, and is suitable for a high-temperature (700-960° C.) electrolyte system. The alloy material of the present invention has corrosion resistance and low solubility. At the same time, the nickel-iron-based alloy reacts with oxygen to form a dense and continuous oxide protective layer, which can effectively reduce the internal diffusion of oxygen and provide a stable anti-oxidation protective layer for the anode. And has good electrical conductivity.

Description

A nickel-iron-based anti-oxidation and corrosion-resistant alloy inert anode material

technical field

The invention belongs to the field of metallurgy, and specifically relates to a nickel-iron-based anti-oxidation and corrosion-resistant alloy inert anode material, which is suitable for molten salt electrolysis industries such as metal aluminum.

Background technique

Since the invention of aluminum electrolysis technology by Hall et al., there have been many major advances in the electrolysis process in aluminum smelting technology for more than 100 years. However, the expensive self-consumable carbon anode has not yet been replaced, which has brought great pressure to people. The disadvantages of existing carbon-consuming anodes are:

1. Consume a large amount of high-quality coke and petroleum coke;

2. Emission of large amounts of greenhouse gases and toxic gases, such as CO ₂ , CF ₄ , CF ₆ and HF;

3. The cost of anode replacement is high and the labor intensity is high.

When Hall invented the aluminum electrolysis process, he proposed the idea of using an inert anode. From the electrolytic formula: 2Al ₂ O ₃ → 4Al+3O ₂ , it can be seen that the use of an inert anode will avoid the emission of CO ₂ and other gases. There is a huge lure for the aluminum industry. The inert anode materials that are currently studied mainly include ceramic materials, cermet materials and metal alloy materials. Because ceramic materials and cermets have inherent defects that are difficult to overcome, such as poor electrical conductivity and thermal shock resistance, difficult to connect, difficult to process, etc., while metal alloys do not have the above defects, they are one of the most promising candidate materials for inert anodes. .

U.S. Patents US4956068 and US5069771 describe nickel-based superalloys (such as: In, Mo, etc.) % Cr, about 15% Al, Ti, Zr, Y, Hf, Nb, the outer metal coating forms an oxide ceramic layer after surface oxidation, which can prevent oxygen atoms from diffusing into the interior.

US Patent US6562224 describes a method for making an inert anode for an aluminum electrolytic cell. The anode is composed of a Ni-Fe matrix and is pre-oxidized in air or oxygen atmosphere at 1000-1100 ° C before being placed in the electrolytic cell. A layer of iron oxide layer (such as Fe ₂ O ₃ ) is formed on the surface of the Ni-Fe substrate. The outer layer has poor conductivity to oxygen ions and has unidirectional conductivity to free oxygen atoms. During the electrolysis process It can reduce the diffusion of oxygen into the Ni-Fe matrix.

US Patent US20050205431A1 describes a nickel-based alloy anode, the mass percentage of its constituent elements is: 20-60% nickel, 5-15% iron, 1.5-5% aluminum, 0-2% rare earth elements, 0-2% 2% of other elements, such as: Mn, Si, C, etc., and the rest is Cu, keeping the Cu/Ni ratio at 0.2-0.3. The alloy adopts sand casting, and an oxide protective film with a thickness of 0.1 to 1.0 mm is formed in situ during the electrolysis process.

Although extensive and in-depth research and exploration have been carried out on inert anode materials, there are still no successful inert anode materials for industrial applications. Although nickel-iron-based alloys are important corrosion-resistant materials, the nickel-iron spinel formed by oxidation has good local corrosion and stress corrosion properties in electrochemical corrosion, and its comprehensive corrosion resistance is suitable for harsh corrosion conditions under modern industrial technology. However, the oxidation resistance of the alloy inert anode material still needs to be improved.

Contents of the invention

In view of the deficiencies in the prior art above, the purpose of the present invention is to provide an oxidation-resistant, corrosion-resistant nickel-iron-based oxidation-resistant and corrosion-resistant alloy inert anode material, which can reduce pollution and is suitable for inert anode materials in molten salt electrolytic cells.

Technical scheme of the present invention is:

A nickel-iron-based anti-oxidation and corrosion-resistant alloy inert anode material, characterized in that the mass percent composition of the anode material includes: 5-70% Ni, 10-70% Fe, 5-65% Cu, 3-55% Cr, 1-12% Co, 1-5% Al.

The nickel-iron-based anti-oxidation and corrosion-resistant alloy inert anode material, the mass percent composition of the anode material also includes 0.1 to 2% active elements, one or more of La, Y, Ce, Hf, etc. the mix of.

The nickel-iron-based anti-oxidation and corrosion-resistant alloy inert anode material, the mass percentage composition of the anode material also includes 0-10% alloying elements, and the alloying elements are Mo, W, Ti, Nb, V, Mn , Sn, Ag, Ta an alloy element or a combination of two or more.

The nickel-iron-based anti-oxidation and corrosion-resistant alloy inert anode material is further heat-treated to optimize the microstructure of the material, refine the grains, and improve the high-temperature oxidation resistance and electrolyte corrosion resistance of the alloy.

The nickel-iron-based anti-oxidation and corrosion-resistant alloy inert anode material, the anode material is pre-oxidized to form a uniform and dense oxide layer in the air or aerobic atmosphere at a high temperature of 800-1100 ° C, and the oxide layer is made of nickel ferrite , spinel structure of cobalt ferrite and nickel oxide, chromium oxide, copper oxide and iron oxide.

The nickel-iron-based anti-oxidation and corrosion-resistant alloy inert anode material, the corresponding metal oxide formed by oxidation, has semiconductor characteristics at high temperature.

Advantage of the present invention and beneficial effect are:

(1) The alloy material of the present invention has corrosion resistance and low solubility. At the same time, the nickel-iron-based alloy reacts with oxygen to form a dense and continuous oxide protective layer, which can effectively reduce the internal diffusion of oxygen and provide a stable anti-oxidation for the anode. protective layer, and has good electrical conductivity;

( ₂ ) when the present invention realizes green production, by-product O can produce economic benefits;

(3) The present invention is easy to process and easy to link electric poles;

(4) The present invention realizes the effects of saving resources and reducing costs.

Description of drawings

Fig. 1 is a comparison chart of weight gain of inert alloy anodes with two components in Example 1 and Example 2 of the present invention after oxidation at 960°C. In the figure, the abscissa Oxidation time is the oxidation time (h), and the ordinate Mass gain is the weight gain (mg/cm ² ).

Fig. 2 is a diagram of the area specific resistance (ASR) at 960°C after the inert alloy anodes with two components of Example 1 and Example 2 of the present invention were oxidized in air at 960°C for 30 hours. In the figure, the abscissa Temperature is the temperature (°C), and the ordinate ASR is the surface specific resistance (mΩ·cm ² ).

Fig. 3(a) and Fig. 3(b) are respectively the surface and cross-sectional morphology of the inert alloy anode in Example 2 of the present invention after oxidation at 960°C for 30 hours. Among them, Figure 3(a) is the surface topography; Figure 3(b) is the cross-sectional topography.

detailed description

In the specific implementation process, the nickel-iron base anti-oxidation and corrosion-resistant alloy inert anode material of the present invention, the mass percent composition of its alloy material comprises: 5～70% Ni, 10～70% Fe, 5～65% Cu, 3-55% Cr, 1-12% Co, 1-5% Al. Preferably, the mass percent composition of the alloy material includes: 20-60% Ni, 20-60% Fe, 5-30% Cu, 3-30% Cr, 6-12% Co, 2-5% % Al.

In a high temperature environment, the alloy inert anode forms a uniform and dense oxide layer through pre-oxidation. The oxide layer is mainly nickel ferrite, cobalt ferrite spinel structure and nickel oxide, chromium oxide, copper oxide, nickel oxide, iron oxide, etc. The oxide layer is composed of uniform, dense and continuous, and the corresponding metal oxide formed by oxidation has semiconductor characteristics at high temperature. Cryolite molten salt has a low solubility, prevents the electrolyte from entering the matrix, and has excellent thermal conductivity, electrical conductivity, and uniform current distribution, which is convenient for machining. At the same time, the nickel-iron-based alloy reacts with oxygen to form a dense and continuous oxide protective layer, which can effectively reduce the internal diffusion of oxygen and provide a stable anti-oxidation protective layer for the anode. During the electrolysis process of the nickel-iron-based inert anode material, the corresponding metal oxide that can react with the fresh oxygen precipitated on the surface of the anode can also conduct electricity. After being oxidized in air at 960°C for 30 hours, the thickness of the oxide layer on the surface of the anode is about 30-60 μm.

In order to increase the adhesion of the oxide film, improve thermal shock resistance, and reduce spalling, active elements with a mass percentage of 0.1 to 2% must be added to the alloy material. Active elements include La, Y, Ce, Hf, etc. The addition of active elements can also refine the grains and increase the uniformity of the microstructure of the material. The composition of the alloy material also includes appropriate alloying elements, the elements include: Mo, W, Ti, Nb, V, Mn, Sn, Ag, Ta one alloy element or a combination of two or more, the above elements The sum of mass percentages is 0-6%, and its main purpose is to improve the plasticity and physical strength of the film layer. The anode material can be further heat-treated to optimize the microstructure of the material, refine the grains, and improve the high-temperature oxidation resistance and electrolyte corrosion resistance of the alloy. The alloy material has excellent electrical conductivity and mechanical properties, and is suitable for copper connection and bonding.

The metal alloy anode provided by the embodiment of the present invention is suitable for high-temperature (700-960°C) electrolyte system. After the anode is oxidized in the air, a uniform and dense spinel structure such as nickel ferrite and cobalt ferrite and other oxides are formed on the surface. A protective layer to prevent further oxidation inside the anode, and the surface oxide has a low solubility in cryolite molten salt to keep the inside of the anode electrochemically inert.

In the following, the present invention will be further supplemented with descriptions through embodiments and accompanying drawings.

Example 1

A nickel-iron anti-oxidation and corrosion-resistant alloy material suitable for the inert anode of metal molten salt electrolysis, the alloy composition (mass percentage) is: 5-70% Ni, 10-70% Fe, 5-65% Cu, 3-55% Cr, 1-12% Co, 1-5% Al. The alloying elements include: Mo, W, Ti, Nb, V, Mn, Sn, Ag, Ta and the active elements include: at least one of La, Y, Ce, Hf and the like. The alloy is melted in a vacuum induction furnace, then cooled and cast in a water-cooled mold. Ingots were cut into samples.

By mass percentage, the concrete chemical composition of present embodiment anode material is as follows: nickel (Ni) 41%, iron (Fe) 38%, copper (Cu) 5%, Cr (chromium) 4%, Co (cobalt) 6% , aluminum (Al) 3%, niobium (Nb) 1.5%, vanadium (V) 1%, hafnium (Hf) 0.5%.

As shown in Figure 1 and Figure 2, the oxidation test results at 960°C for 30 hours show that the weight gain of the alloy is about 5.12 mg/cm ² , and the oxide layer is only slightly peeled off after cooling in the furnace, indicating that there is a gap between the alloy and the oxide. Good adhesion.

Example 2:

A nickel-iron anti-oxidation and corrosion-resistant alloy material suitable for the inert anode of metal molten salt electrolysis, the alloy composition (mass percentage) is: 5-70% Ni, 10-70% Fe, 5-65% Cu, 3-55% Cr, 1-12% Co, 1-5% Al. The alloying elements include: Mo, W, Ti, Nb, V, Mn, Sn, Ag, Ta and the active elements include: at least one of La, Y, Ce, Hf and the like. The alloy is melted in a vacuum induction furnace, then cooled and cast in a water-cooled mold. Ingots were cut into samples.

In terms of mass percentage, the specific chemical composition of the anode material of the present embodiment is as follows: nickel (Ni) 39%, iron (Fe) 32%, copper (Cu) 5%, Cr (chromium) 10%, Co (cobalt) 6% , aluminum (Al) 5%, niobium (Nb) 1.5%, vanadium (V) 1%, hafnium (Hf) 0.5%.

As shown in Figures 1 and 2, the oxidation test results at 960°C for 30 hours show that the weight gain of the alloy after oxidation is about 2.61 mg/cm ² , and the oxide layer only slightly peels off with furnace cooling.

Example 3

As shown in Figure 3(a) and Figure 3(b), the alloy anode of Example 2 was oxidized at a high temperature of 960°C for 30 hours, and the alloy anode was taken out, and the surface oxides were analyzed by X-ray diffraction and scanning electron microscope, which showed that the surface oxides of the alloy were mainly sharp Crystal structure, the thickness of the oxide is about 25-30μm; the oxide is a dense and continuous mixed oxide layer. It shows that the oxide formed in the oxidation process improves the high temperature oxidation resistance of the anode.

Example 4

Carry out resistance measurement (temperature is 960 ℃) to the alloy anode of embodiment 1, 2 alloy after high-temperature oxidation 30h respectively, test result: Corresponding to embodiment 1 and 2 alloy anode surface specific resistance (ASR) is respectively: 10.91mΩ. cm ² and 30.13mΩ﹒ cm ² . It shows that the oxide formed after oxidation of the alloy has better electrical conductivity.

Example 5

For the alloy anode of Example 2, pre-oxidation is used to form an oxide protective film on the surface of the alloy anode. The electrolytic application was carried out for several 10 hours at 960° C. with an anodic current density of 0.8 A/cm ² in an electrolyte composed of Na ₃ AlF ₆ —5% CaF ₂ —5% Al ₂ O ₃ . During electrolysis, high-purity graphite is used as the cathode, and the anode is vertically inserted into a graphite crucible lined with corundum, with a pole distance of 3.0 cm. The results show that the electrolysis process is stable, the cell voltage is 4.1-4.5 volts, the anode corrosion rate is low during the aluminum electrolysis process, and good electrical conductivity can be maintained. It shows that the alloy anode has good high temperature oxidation resistance and electrochemical corrosion resistance in molten salt cryolite.

Claims (6)

1. a kind of ferronickel base is anti-oxidant and corrosion resisting alloy inert anode material, it is characterised in that the quality hundred of the anode material Be grouped into including：5~70% Ni, 10~70% Fe, 5~65% Cu, 3~55% Cr, 1~12% Co, 1~ 5% Al.

2. ferronickel base according to claim 1 is anti-oxidant and corrosion resisting alloy inert anode material, it is characterised in that the sun The quality percentage composition of pole material also includes 0.1~2% active element, active element be one kind in La, Y, Ce, Hf etc. or Two or more mixing.

3. ferronickel base according to claim 1 is anti-oxidant and corrosion resisting alloy inert anode material, it is characterised in that the sun The quality percentage composition of pole material also include 0~10% alloy element, alloy element be Mo, W, Ti, Nb, V, Mn, Sn, A kind of alloying element or two or more combinations in Ag, Ta.

4. ferronickel base according to claim 1 is anti-oxidant and corrosion resisting alloy inert anode material, it is characterised in that the sun Pole material is further heat-treated, and to optimize Fine Texture of Material, crystal grain thinning improves the high-temperature oxidation resistance and resistance to electricity of alloy Solution matter corrosive nature.

5. ferronickel base according to claim 1 is anti-oxidant and corrosion resisting alloy inert anode material, it is characterised in that the sun Pole material generates the oxide layer of even compact by pre-oxidizing in 800~1100 DEG C of air or aerobic atmosphere of high temperature, Oxide layer is made up of nickel ferrite based magnetic loaded, the spinel structure of cobalt ferrite and nickel oxide, chromium oxide, cupric oxide and iron oxide.

6. ferronickel base according to claim 5 is anti-oxidant and corrosion resisting alloy inert anode material, it is characterised in that oxidation The respective metal oxide of formation, there is characteristic of semiconductor during high temperature.