Ceramic-iron composite, method of production and roll ring for a submerged roll

Abstract

The application discloses a ceramic-iron composite material, a preparation method and a roll ring for a submerged roll, and belongs to the field of composite materials. The preparation method of the ceramic-iron composite material comprises the following steps: uniformly mixing alumina powder and metal iron powder subjected to oxidation treatment to obtain a mixture; performing die pressing forming on the mixture to obtain a green compact; placing the green compact in a vacuum or a protective atmosphere, and pre-sintering the green compact at 900-950 DEG C for 60-90 min to obtain a sintered compact; after re-pressing the sintered compact, placing the sintered compact in a vacuum or a protective atmosphere, and sintering the sintered compact at 1250-1450 DEG C for 40-90 min, and cooling to obtain the ceramic-iron composite material. The ceramic-iron composite material has the advantages of excellent hardness, bending strength, compressive strength, fracture toughness and service life.

Description

Technical Field

[0001] This invention relates to a ceramic-iron composite material, its preparation method, and a roller ring for submerged rollers, belonging to the field of composite materials. Background Technology

[0002] Galvanized steel strip is a type of steel material made by coating cold-rolled or hot-rolled long steel sheets with zinc. It fully utilizes the high strength and low cost of steel and the excellent oxidation and corrosion resistance of zinc. Essentially, galvanized steel strip is a composite material and a widely used basic metal material. Galvanized steel strip is mainly used in the manufacture of steel pipe products such as greenhouse pipes and heating pipes, as well as building roof panels, automotive parts, and appliance casings. During the hot-dip galvanizing process, the base steel strip undergoes a series of physicochemical reactions with the molten high-temperature liquid zinc, fusing the alloy layer with the pure zinc layer and the steel strip base. The production cost of galvanized steel strip has a significant impact on downstream production stages and the supply chain.

[0003] The zinc pot is a key piece of equipment in a cold-rolled continuous hot-dip galvanizing unit used to produce galvanized steel strip. The "three rolls" (submerged roll, stabilizing roll, and straightening roll) are the core components of the zinc pot. The submerged roll is the core of the three rolls; it not only works while immersed in molten zinc for extended periods but also provides the main power for the steel strip. The submerged roll typically consists of a roll ring and a roll shaft, with the roll shaft passing through the roll ring (see CN105088121A). The roll ring is often made of ceramic material, or its surface is coated with a ceramic layer. The proper functioning of the submerged roll depends on the proper functioning of its roll ring. During the galvanizing process, the steel strip moves continuously. From a macroscopic perspective, the steel strip moves at a uniform speed; from a microscopic perspective, the movement is variable and impact-prone. Because ceramics are hard and wear-resistant but also brittle and easily broken, once a crack appears, it is irreparable and must be scrapped. During the operation of continuous hot-dip galvanizing units, the failure of existing roller rings has invariably been due to cracking, requiring replacement; there has never been a case of them being scrapped due to excessive wear. The roller rings function similarly to bearings on the submerged rollers. While the existing roller rings have sufficient wear resistance, their impact resistance (i.e., fracture toughness) is insufficient. Therefore, to improve the service life of the submerged roller rings, it is essential to focus on enhancing their toughness.

[0004] Generally, ceramics are materials and products made from clay as the main raw material and various natural minerals through crushing, mixing, molding, and calcination. Ceramic materials are usually sintered from oxides and typically have high hardness, low plasticity, and poor electrical and thermal conductivity. Metals, on the other hand, usually possess luster (i.e., strong reflection of visible light), ductility, and good electrical and thermal conductivity. The properties of ceramics and metals are almost opposite: ceramics are wear-resistant but not impact-resistant, while metals are impact-resistant but not wear-resistant. When a material that is both wear-resistant and impact-resistant is needed, the only solution is to use composite materials, combining the properties of both. Therefore, using metal-ceramic composite materials to prepare the roll rings of submerged rollers, endowing the roll rings with both wear-resistant and impact-resistant properties, is expected to improve the service life of the roll rings. Currently, in production sites, ceramic roll rings are widely used components of submerged rollers, and there are no known cases of manufacturers producing and using metal-ceramic roll rings.

[0005] Typically, cermet materials are composite materials prepared using powder metallurgy. This method involves mixing ceramic particles and metal powder (such as ferroalloy powder), pressing them into a green body, and then sintering it at a temperature near the metal's melting point. This method is simple to operate, easy to implement, and can be used to prepare various ceramic / metal composite materials. Furthermore, by controlling the pressing pressure and sintering process, a dense body with a density exceeding 95% can be achieved.

[0006] In recent years, with technological advancements, advanced processes have been employed to prepare high-performance metal-ceramic materials, such as hot isostatic pressing (HIP) and spark plasma sintering (SPS). These processes have significantly improved the hardness, strength, and especially the toughness and impact resistance of metal-ceramic materials. While these new technologies primarily improve the density of sintered blanks or the sintering performance of the metal, they offer little improvement to the sintering performance between metal and ceramic particles, particularly the metal-ceramic interface. Therefore, their effectiveness in enhancing these properties remains limited. Furthermore, the high cost of these new technologies results in a low cost-performance ratio, restricting their widespread application. Summary of the Invention

[0007] To address the shortcomings of existing technologies, one objective of this invention is to provide a method for preparing a ceramic-iron composite material with excellent mechanical properties; another objective of this invention is to provide a ceramic-iron composite material; and a third objective of this invention is to provide a roller ring for a submerged roller.

[0008] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0009] A method for preparing a ceramic-iron composite material includes the following steps:

[0010] S1. Mix alumina powder and oxidized iron powder evenly to obtain a mixture;

[0011] The proportion of metallic iron powder in the mixture is 10-40 wt%.

[0012] S2. The mixture is molded into a compact;

[0013] S3. Place the pressed blank under vacuum or protective atmosphere conditions and pre-sinter at 900-950℃ for 60-90 minutes to obtain a sintered blank;

[0014] S4. After re-pressing the sintered blank, place it under vacuum or protective atmosphere and sinter at 1250-1450℃ for 40-90 minutes, then cool to obtain ceramic-iron composite material.

[0015] Optionally, in S1, the particle size of the alumina powder is -2500 to -1900 mesh, more specifically -2400 to -1950 mesh, for example, -2400 mesh, -2300 mesh, -2200 mesh, -2100 mesh, -2000 mesh, or -1950 mesh; the particle size of the iron powder is -250 to -190 mesh, more specifically -240 to -195 mesh, for example, -240 mesh, -230 mesh, -220 mesh, -210 mesh, or -200 mesh. Thus, the particle size of the iron powder is significantly larger than that of the alumina powder, and the amount of alumina powder added is significantly greater than the amount of iron powder added. Therefore, in practice, the iron powder in the mixture is dispersed within the alumina powder and is tightly "wrapped" by the alumina powder, which helps to form a compact with low porosity, laying a good foundation for subsequent sintering.

[0016] Optionally, in S1, the method for preparing oxidized iron powder includes the following steps: immersing unoxidized iron powder in a blackening agent solution, keeping it at 135-145℃ for 70-100 min, then separating the solid and liquid, washing, and drying to obtain the product.

[0017] In the blackening agent solution, the concentration of sodium hydroxide is 30-36 wt%, the concentration of sodium nitrite is 7-13 wt%, and the concentration of sodium phosphate is 1-3 wt%. This yields metallic iron powder with a suitable oxygen content (approximately 4-8 wt%).

[0018] Optionally, in the blackening agent solution, the concentration of sodium hydroxide is 32-34 wt%, the concentration of sodium nitrite is 9-11 wt%, and the concentration of sodium phosphate is 1.5-2.5 wt%.

[0019] Furthermore, maintain the temperature at 138-142℃ for 80-90 minutes.

[0020] Optionally, in S2, the compression molding pressure is 1.5-3 t / cm. 2 Further, it becomes 1.8-2.5 t / cm 2Furthermore, it is 2.1-2.4 t / cm 2 .

[0021] Optionally, in S3, pre-sintering is carried out at 910-940℃ for 70-80 min, and further, pre-sintering is carried out at 920-930℃ for 72-78 min.

[0022] Optionally, in S4, the pressure of the secondary compression is 2.5-4 t / cm. 2 Further, it is 3-3.5 t / cm 2 .

[0023] Optionally, in S4, sintering is carried out at 1300-1400℃ for 45-80 min, and further, sintering is carried out at 1330-1380℃ for 50-75 min.

[0024] Optionally, in S3 and / or S4, the protective atmosphere is an argon atmosphere.

[0025] Optionally, the ceramic-iron composite material is in the form of a ring.

[0026] Optionally, the ceramic-iron composite material has a hardness ≥75HRA, flexural strength ≥370MPa, compressive strength ≥1018MPa, and fracture toughness ≥18MPa·m. 1 / 2 .

[0027] Based on the same inventive concept, the present invention also provides: a ceramic-iron composite material, prepared by the preparation method described above.

[0028] Based on the same inventive concept, the present invention also provides: a roller ring for a submerged roller, said roller ring being made of the ceramic-iron composite material as described above.

[0029] For composite materials, the most critical issue, or rather the primary problem to be solved, is the interfacial bonding between the different phases of the raw materials used to construct the composite. In other words, to improve the performance of ceramic-iron composites, the interfacial bonding between the metal powder (iron powder) and the ceramic particle phase (alumina powder) must be fundamentally addressed. Improving the bonding strength at the interface between the metal and ceramic particle phases is crucial to fundamentally improving the performance of ceramic-iron composites. The metal (iron powder) and the ceramic particle phase (alumina powder) are two completely different materials, and their interface is inherently incoherent. To improve their bonding strength, an interface must be introduced that can form a coherent bond (i.e., coherent atomic bond) with both the metal and the ceramic particle phase. The ceramic particle phase is a metal oxide. This means that an interfacial material must be introduced that can form a coherent interface, or at least a semi-coherent interface, with both the metal and the metal oxide. Only in this way can the performance of ceramic-iron composites be effectively improved, thereby extending the service life of the submerged roller ring.

[0030] The products of metal oxidation, except for metals with an oxide film density coefficient less than 1, show that the oxides of other metals with an oxide film density coefficient greater than 1 are generally coherently bonded to the base metal, or even completely coherently bonded. Many different oxides can form coherently bonded composite salts at high temperatures. Based on this principle, this invention uses surface-oxidized iron powder mixed with ceramic particles (alumina powder), pressed into a compact, and then sintered. Thus, the metal oxides on the surface of the iron powder are coherently bonded to the iron, and simultaneously, the metal oxides on the surface of the iron powder are also coherently bonded to the ceramic particles. This structure significantly improves the performance of ceramic-iron composite materials and extends their service life. Based on this idea, this invention has developed a novel ceramic-iron composite material and its preparation method. This ceramic-iron composite material is well-suited for use in the roll rings of submerged rollers, laying a solid foundation for the application of ceramic-iron composite materials in the roll rings of submerged rollers in hot-dip galvanized strip steel production units.

[0031] In this invention, the iron oxide on the surface of the metallic iron powder is generated by the oxidation of the matrix iron. They are coherent, with no external impurities present, resulting in a very clean interface and high interfacial bonding strength. Both iron oxide and alumina are oxides. These two oxides are first pressed, pre-sintered, and then re-pressed to bond tightly together. Then, during high-temperature sintering at 1250-1450℃, the two oxides react to form ferric aluminate. Ferric aluminate bonds to both iron oxide and alumina through a coherent interface, with no impurities present or generated at the interface, resulting in a very clean interface and high interfacial bonding strength. This method effectively solves the interfacial bonding problem between metallic iron powder and ceramic particles (alumina powder). The aforementioned coherent interface transforms the weak bonding of a single metal / ceramic interface into a strong bonding of multiple metal / metal oxide / metal salt / ceramic interfaces, improving the performance of the ceramic-iron composite material, particularly its toughness and impact resistance. Comparative experiments under the same working conditions demonstrate that the service life of the ceramic-iron composite material prepared according to this invention is significantly improved.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] (1) The present invention transforms the weak bonding of metal / ceramic into a strong bonding of multiple interfaces of metal / metal oxide / metal salt / ceramic, which can obtain a ceramic iron composite material with excellent hardness, bending strength, compressive strength, fracture toughness and service life.

[0034] (2) Compared with existing roller rings involving ceramic materials or ceramic layers, the roller ring of the present invention has a longer service life. Attached Figure Description

[0035] Figure 1 This is a summary table of relevant process parameters for Examples 1-9 and Comparative Examples 1-10.

[0036] Figure 2 This is a summary table of relevant process parameters for Examples 10-19 and Comparative Examples 11-20.

[0037] Figure 3 The table shows the performance of the materials obtained in Examples 1-11 and Comparative Examples 1-12.

[0038] Figure 4 The table shows the performance of the materials obtained in Examples 12-19 and Comparative Examples 13-28. Detailed Implementation

[0039] The present invention will be described in detail below with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0040] Example 1

[0041] The preparation method of the ceramic-iron composite material in this embodiment includes the following steps:

[0042] S1. Mix alumina powder and oxidized iron powder in a V-type mixer for 25 minutes to obtain a mixture;

[0043] In the mixture, the proportion (W) of metallic iron powder is 25wt%; the particle size (D1) of the alumina powder is -2000 mesh; and the particle size (D2) of the metallic iron powder is -200 mesh. The preparation method of the oxidized metallic iron powder is as follows: the unoxidized metallic iron powder is immersed in a blackening agent solution, kept at 140℃ (T3) for 85 min (t3), filtered, washed with water, and dried to obtain the final product.

[0044] The blackening agent solution is composed of sodium hydroxide, sodium nitrite, sodium phosphate and water; the concentration of sodium hydroxide in the blackening agent solution is 33 wt%, the concentration of sodium nitrite is 10 wt%, and the concentration of sodium phosphate is 2 wt%.

[0045] S2. The mixture is molded on a hydraulic press using a steel mold to obtain a ring-shaped blank;

[0046] The compression molding pressure (P1) is 2.3 t / cm. 2 .

[0047] S3. Place the pressed billet in a vacuum furnace and pre-sinter it at 930°C (T1) for 75 min (t1) under vacuum conditions to obtain a sintered billet;

[0048] S4. After the sintered blank is repressed on a hydraulic press using a steel mold, it is placed under vacuum and sintered at 1350℃ (T2) for 65 min (t2), and then cooled to obtain a ring-shaped ceramic-iron composite material.

[0049] The pressure of the secondary pressure (P2) is 3.2 t / cm. 2 .

[0050] Examples 2-19, Comparative Examples 1-20

[0051] Repeat Example 1, except that: Figure 1 or Figure 2 The differences are shown.

[0052] Comparative Example 21

[0053] Example 1 is repeated, except that in S1, an equal amount of unoxidized iron powder is used instead of oxidized iron powder; after S2, the compact is subjected to hot isostatic pressing sintering, wherein the specific process of hot isostatic pressing sintering is: holding at 130MPa and 1200℃ for 60min.

[0054] Comparative Example 22

[0055] Example 1 is repeated, except that in S1, an equal amount of unoxidized iron powder is used instead of oxidized iron powder; after S2, the compact is subjected to hot isostatic pressing sintering, wherein the specific process of hot isostatic pressing sintering is: holding at 130MPa and 1350℃ for 65min.

[0056] Comparative Example 23

[0057] Example 1 is repeated, except that in S1, an equal amount of unoxidized iron powder is used instead of oxidized iron powder; after S2, the compact is subjected to spark plasma sintering. The specific process of spark plasma sintering is to hold the compact at 40 MPa and 1100°C for 20 minutes.

[0058] Comparative Example 24

[0059] Example 1 is repeated, except that in S1, an equal amount of unoxidized iron powder is used instead of oxidized iron powder; after S2, the compact is subjected to spark plasma sintering, wherein the specific process of spark plasma sintering is: holding at 40MPa and 1350℃ for 65 minutes.

[0060] Comparative Example 25

[0061] Example 1 is repeated, except that the proportion of iron powder in the mixture is 0 (i.e., only alumina powder is added).

[0062] Comparative Example 26

[0063] Repeat Example 1, except that in S1, an equal amount of unoxidized iron powder is used instead of oxidized iron powder.

[0064] Comparative Example 27

[0065] Repeat Example 1, except that: S3 is omitted; and sintering is performed for 140 min in S4.

[0066] Comparative Example 28

[0067] Repeat Example 1, except that the recompression step in S4 is omitted.

[0068] A summary table of relevant process parameters for Examples 1-19 and Comparative Examples 1-20 is shown below. Figure 1 and Figure 2 As shown.

[0069] The Rockwell hardness of the material was tested according to GB / T 230.1~3-2012 Metallic materials Rockwell hardness test - Parts 1~3; the bending strength of the material was tested according to GB / T 232-2024 Metallic materials bending test method; the compressive strength of the material was tested according to GB / T 6525-2019 Sintered metallic materials room temperature compressive strength test method; and the fracture toughness of the material was tested according to GB / T 21143-2014 Metallic materials quasi-static fracture toughness test method.

[0070] The test method for the service life of the prepared material is as follows: The sample is immersed in molten zinc at 460°C in a high-purity graphite crucible. The sample is taken out of the zinc liquid every 24 hours for observation. If the surface cracks, the experiment is terminated and the time (i.e., service life) is recorded. The high-purity graphite crucible is placed on a vibration platform with a frequency of 5Hz and an amplitude of 5mm in both the front-to-back and left-to-right directions.

[0071] The properties of the materials obtained in each embodiment and comparative example are as follows: Figure 3 and Figure 4 As shown.

[0072] As can be seen from the comparison, the ceramic-iron composite material prepared by the method of the present invention has high hardness, flexural strength, compressive strength, fracture toughness and long service life.

[0073] The above embodiments should be understood as being used only to illustrate the present invention more clearly, and not to limit the scope of the present invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art fall within the scope defined by the appended claims.

Claims

1. A method for preparing a ceramic-iron composite material, characterized in that, Includes the following steps: S1. Mix alumina powder and oxidized iron powder evenly to obtain a mixture; In the mixture, the proportion of metallic iron powder is 10-40 wt%; the particle size of the alumina powder is -2500 to -1900 mesh; and the particle size of the metallic iron powder is -250 to -190 mesh. S2. The mixture is molded into a compact; S3. Place the pressed blank under vacuum or protective atmosphere conditions and pre-sinter at 900-950℃ for 60-90 minutes to obtain a sintered blank; S4. After re-pressing the sintered blank, place it under vacuum or protective atmosphere and sinter at 1250-1450℃ for 40-90 minutes, then cool to obtain ceramic-iron composite material.

2. The method for preparing the ceramic-iron composite material according to claim 1, characterized in that, In S1, the preparation method of oxidized iron powder includes the following steps: immersing unoxidized iron powder in a blackening agent solution, keeping it at 135-145℃ for 70-100 min, then separating the solid and liquid, washing, and drying to obtain the product. In the blackening agent solution, the concentration of sodium hydroxide is 30-36 wt%, the concentration of sodium nitrite is 7-13 wt%, and the concentration of sodium phosphate is 1-3 wt%.

3. The method for preparing the ceramic-iron composite material according to claim 1, characterized in that, In S2, the compression molding pressure is 1.5-3 t / cm. 2 .

4. The method for preparing the ceramic-iron composite material according to any one of claims 1-3, characterized in that, In S3, pre-sintering is carried out at 910-940℃ for 70-80 minutes.

5. The method for preparing the ceramic-iron composite material according to any one of claims 1-3, characterized in that, In S4, the pressure of the secondary compression is 2.5-4 t / cm. 2 .

6. The method for preparing the ceramic-iron composite material according to any one of claims 1-3, characterized in that, In S4, sinter at 1300-1400℃ for 45-80 minutes.

7. The method for preparing the ceramic-iron composite material according to any one of claims 1-3, characterized in that, In S3 and / or S4, the protective atmosphere is argon.

8. A ceramic-iron composite material, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.

9. A roller ring for a submerged roller, characterized in that, The roller ring is made of the ceramic-iron composite material as described in claim 8.

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