High-performance corundum dry ramming mix for medium-frequency induction furnace and preparation method thereof

Abstract

The application discloses high-performance corundum dry ramming mix for medium-frequency induction furnace and a preparation method thereof, and belongs to the technical field of refractory material preparation. The dry ramming mix base material comprises the following components: white corundum aggregate, white corundum micro powder, magnesia aggregate, magnesia micro powder, alpha-alumina micro powder and magnesium aluminate spinel; an additive accounts for 0-5 wt.% of the total weight of the base material, and the additive is a compounded composite material of silicon nitride / metallic silicon / silicon-iron alloy. The added compounded composite material can promote in-situ generation of the magnesium aluminate spinel, and simultaneously make the in-situ magnesium alumina spinel transform into aluminum-rich magnesium alumina spinel; the high-activity silicon ions contained form a liquid phase, and simultaneously generate three-dimensional network mullite whiskers with high-energy state alumina, and the network structure of the composite material itself plays a reinforcing effect. Therefore, the prepared ramming mix has the characteristics of high mechanical strength, good thermal shock stability, excellent corrosion resistance and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of refractory material preparation, and more particularly relates to high-performance corundum dry ramming material for a medium-frequency induction furnace and a preparation method thereof. BACKGROUND

[0002] The medium-frequency induction furnace is widely used in the metallurgical and casting industries in recent years due to the fast heating speed, intermittent operation, convenient operation, small pollution, high efficiency and energy saving, and continuous development in the direction of high power, fast melting and large capacity, so higher requirements are put forward for the lining material of the medium-frequency induction furnace. At present, the dry ramming material for the medium-frequency induction furnace can be divided into neutral, alkaline and acidic dry ramming materials according to different compositions, among which the neutral dry ramming material is most widely used. The composition includes neutral oxides such as Al2O3 or neutral composite oxides; however, the existing corundum dry ramming material still has the following problems in the process of use:

[0003] (1) The sintering strength of the working layer is low, so that the anti-erosion performance is poor.

[0004] (2) The anti-slag erosion ability is poor, so that the service life is greatly reduced, and the normal production efficiency is affected.

[0005] (3) The bulk structure of the non-working layer is thin, which is not conducive to the absorption of thermal stress, so that the thermal shock stability is poor.

[0006] Among them, the anti-slag erosion performance is very important. In the use process of the medium-frequency induction furnace, the thickness of the refractory material used for the lining is only 70-110 mm, the inner side is in contact with the high-temperature metal liquid, and the outer side is close to the water-cooled coil. The refractory material has a large temperature difference between the inner and outer sides, and is used under the conditions of a relatively thin cross section and a strong erosive environment of many smelting operations. The main process conditions affecting the damage of the lining include: smelting temperature, degassing time, primary degassing amount, chemical composition of the slag and type of produced steel (iron). The main factors affecting the damage of the lining include: slag chemical erosion, refractory material structure spalling and thermal erosion. Therefore, the anti-slag performance directly affects whether the industrial production can proceed smoothly.

[0007] Through retrieval, Chinese patent application No. 202211375422.8 has an invention named "aluminum-magnesium dry ramming material and preparation method thereof". The application uses fused magnesia, anhydrous magnesium sulfate, fused white corundum, active Al2O3 micro powder, complexing agent, retarder and the like as raw materials, introduces a proper amount of titanium dioxide, and sets a proper heat treatment temperature to improve the phase, sintering performance and mechanical properties of the ramming material. However, the anti-slag erosion performance of the sample burned by the application is still not ideal.

[0008] Chinese patent application No. 202310060815.8, entitled "Aluminum-magnesium dry ramming mix for medium-frequency induction furnace and preparation method thereof", the dry ramming mix of the application case uses fused white corundum as aggregate, magnesia, tabular corundum, calcined alumina powder and spinel-calcium aluminate composite material as matrix, and all raw materials are uniformly mixed. The application case optimizes the microstructure of the aluminum-magnesium dry ramming mix, strengthens the combination of substances, reduces the expansion caused by in-situ spinelization reaction, forms vacancy defects to improve the slag absorption capacity, so that the strength and linear change of the aluminum-magnesium dry ramming mix after firing and the slag penetration resistance are obviously improved. However, the dry ramming mix of the application case has low room temperature strength and large linear change rate. SUMMARY

[0009] 1. Technical problems to be solved by the invention

[0010] Based on the existing corundum dry ramming mix for medium-frequency induction furnace, the sintering strength is low, the thermal shock performance and the anti-molten slag erosion performance are poor, and other problems, the present application provides a modified corundum dry ramming mix for medium-frequency induction furnace with silicon nitride / metallic silicon / silicon-iron alloy composite material as additive and a preparation method thereof. The high-performance corundum dry ramming mix for medium-frequency induction furnace prepared by the present application has excellent strength, excellent erosion resistance, thermal shock stability and low linear change rate, and can be used for medium-frequency induction furnace lining, which can effectively improve the production efficiency of medium-frequency induction furnace.

[0011] 2. Technical solutions

[0012] To achieve the above-mentioned purposes, the technical solutions provided by the present application are as follows:

[0013] The high-performance corundum dry ramming mix for medium-frequency induction furnace of the present application comprises the following components and weight percentages in the dry ramming mix base material: 65-85wt.% white corundum aggregate, 6-10wt.% white corundum powder, 2-6wt.% magnesia aggregate, 2-5wt.% magnesia powder, 2-5wt.% alpha-alumina powder, and 3-9wt.% magnesium aluminate spinel; the additive is 0-5wt.% of the total weight of the dry ramming mix base material, and the additive is a compounded composite material of silicon nitride / metallic silicon / silicon-iron alloy.

[0014] Further, the particle size distribution of the white corundum aggregate is as follows: 8-5mm white corundum aggregate accounts for 5-30wt.%, 5-3mm white corundum aggregate accounts for 20-30wt.%, 3-1mm white corundum aggregate accounts for 25-35wt.%, and 1-0.28mm white corundum aggregate accounts for 25-30wt.%.

[0015] Further, the magnesium sand aggregate particle gradation is that the magnesium sand aggregate of 1-0.5mm accounts for 40-52wt.%, and the magnesium sand aggregate of 0.5-0.088mm accounts for 48-60wt.%.

[0016] Further, the alpha-alumina micro powder is selected from the alpha-alumina micro powder with Al2O3 content ≥98wt.% and a bimodal structure of particle size distribution curve, and the bimodal peak values are 1.12um and 2.13um respectively.

[0017] Further, the mass ratio of the silicon nitride powder, the metal silicon powder and the silicon-iron alloy powder in the silicon nitride / metal silicon / silicon-iron alloy compound composite material is (0.15-0.3):0.2:1.

[0018] Further, the white corundum micro powder is a mixture of fine powder with a particle size of 50-200 meshes and fine powder with a particle size of less than 325 meshes.

[0019] Further, the magnesium sand micro powder is fine powder with a particle size of less than 300 meshes.

[0020] Further, the magnesium-aluminum spinel includes but is not limited to the spinel with a label of MA-66, MA-78 and MA-90 specified in GB / T 26564-2011, and the fine powder with a particle size of less than 0.032mm.

[0021] The preparation method of the high-performance corundum dry ramming mixture for a medium-frequency induction furnace of the application is as follows: the white corundum aggregate, the white corundum micro powder, the magnesium sand aggregate, the magnesium sand micro powder, the alpha-alumina micro powder, the magnesium-aluminum spinel and the silicon nitride / metal silicon / silicon-iron alloy compound composite material are uniformly stirred in a stirrer for 3min and are pressed and formed, and after room temperature curing, the high-performance corundum dry ramming mixture is prepared by being kept at 1600℃ for 3h.

[0022] Further, the silicon nitride / metal silicon / silicon-iron alloy compound composite material is synthesized and treated by a high-temperature solid phase method, and the specific steps are as follows:

[0023] Step 1: different mass ratios of the silicon nitride powder, the metal silicon powder and the silicon-iron alloy powder are added into anhydrous ethanol, and a planetary ball mill is used for wet ball milling for 48h, wherein the ball-to-material ratio is 2:1, and the ball milling speed is 400r / min;

[0024] Step 2: the mixed material after ball milling is vacuum dried and is kept at 1400℃ for 3h in high-purity nitrogen;

[0025] Step 3: the compound composite material after high-temperature sintering is crushed and screened, and the powder with a particle size of ≤0.074um is selected.

[0026] 3. Beneficial effects

[0027] Compared with the prior art, the technical scheme provided by the application has the following remarkable effects:

[0028] (1) The application determines the best particle gradation of aggregate and powder according to the principle of "big at both ends and small in the middle" and industrial actual conditions, the addition of large aggregate can play a good supporting role, and the powder can play the role of filling the voids of aggregate and improving the workability and the like. The aggregate and powder with different particle gradations can make the dry ramming material tightly packed in the ramming forming stage to improve the sintering performance. The magnesia-alumina spinel micro powder can guide the in-situ nucleation and growth of magnesia-alumina spinel under high temperature conditions, the alpha-alumina with bimodal particle size composition fills the gaps between aggregates, and the alpha-alumina has high activity due to the small particle size, so that the sample is more easily sintered.

[0029] (2) The prepared composite material is in the form of hexagonal prism or fiber, the two structures are interwoven to form a three-dimensional space network structure, which can play a fiber reinforcing effect on the dry ramming material and improve the strength. After heat treatment, the composite material can precipitate silicon ions with high activity in the dry ramming material, and particle rearrangement occurs on the surface of alumina. The precipitation of silicon ions generates mullite whiskers in-situ, which further strengthens the reinforcing effect. With the increase of the composite material, the content of iron ions and silicon ions precipitated from the composite material increases, and part of the silicon ions form a liquid phase to promote the transmission rate of substances in the process of generating magnesia-alumina spinel, thereby greatly promoting the in-situ generation of magnesia-alumina spinel. A large amount of fine in-situ magnesia-alumina spinel low-melting phase generated can produce a Kurnakdal effect to offset the shrinkage caused by sintering, so that the product is more dense; the increase of grain boundaries also strengthens the micro-crack toughening mechanism, greatly enhancing the thermal shock stability of the dry ramming material. The presence of iron ions promotes the lattice activation of in-situ generated magnesia-alumina spinel, and guides the in-situ generated magnesia-alumina spinel to change to aluminum-rich magnesia-alumina spinel. At the same time, the composite material can activate Al2O3 in the matrix to make it more easily react to generate magnesia-alumina spinel, which is also beneficial to greatly improving the subsequent slag resistance and ensuring the normal operation of the medium-frequency induction furnace.

[0030] (3) The composite material of the application activates the crystal lattice by causing lattice defects in alumina. Alumina is in a high-energy state and can easily absorb cations in the molten slag, increase the viscosity of the molten slag and hinder the corrosion of the molten slag. At the same time, the high-energy alumina absorbs calcium ions in the molten slag to form a large amount of calcium hexaluminate and other high-melting substances at the defects in the sample, and the interlocking structure of the flaky calcium hexaluminate (see Figure 1 ) further hinders the corrosion of the sample by the molten slag and enhances the slag corrosion resistance of the dry ramming material.

[0031] (4) the linear change of the sample after heat treatment is 0.8-1.6%, the erosion index of the high-performance corundum-based dry ramming mixture for medium-frequency induction furnaces is 11-18% by using image analysis, the cold compressive strength is 25.5-50.5 MPa, the linear change and the erosion index are kept at a low level, and the high-performance corundum-based dry ramming mixture has excellent slag erosion resistance and excellent strength. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 A sheet-shaped calcium hexaluminate interlocking structure formed at an internal defect of a ramming mixture sample in the application;

[0033] Figure 2 A microstructure and a phase diagram of a silicon nitride / metallic silicon / silicon-iron alloy composite material. DETAILED DESCRIPTION

[0034] In order to further understand the content of the application, the application is described in detail in combination with the drawings and examples.

[0035] Example 1

[0036] The high-performance corundum-based dry ramming mixture for medium-frequency induction furnaces in the embodiment comprises the following components and the weight percentages of the components are as follows: 65wt.% of white corundum aggregate, 10wt.% of white corundum micro powder, 6wt.% of magnesia aggregate, 5wt.% of magnesia micro powder, 5wt.% of alpha-alumina micro powder, and 9wt.% of magnesium aluminate spinel. The additive is 1wt.% of a silicon nitride / metallic silicon / silicon-iron alloy composite material based on the total weight of the dry ramming mixture base (100%).

[0037] The particle size distribution of the white corundum aggregate is as follows: 8-5mm accounts for 5wt.% of the white corundum aggregate, 5-3mm accounts for 30wt.% of the white corundum aggregate, 3-1mm accounts for 35wt.% of the white corundum aggregate, and 1-0.28mm accounts for 30wt.% of the white corundum aggregate.

[0038] The particle size distribution of the magnesia aggregate is as follows: 1-0.5mm accounts for 52wt.% of the magnesia aggregate, and 0.5-0.088mm accounts for 48wt.% of the magnesia aggregate.

[0039] The white corundum micro powder is a mixture of a particle size of 50-200 mesh and a fine powder with a particle size of less than 325 mesh.

[0040] The alpha-alumina micro powder is selected from alpha-alumina micro powder with an Al2O3 content of ≥98wt.% and a particle size distribution curve with a bimodal structure, and the bimodal peak values are 1.12μm and 2.13μm, respectively.

[0041] The magnesium aluminate spinel is labeled as MA-66, and the particle size of the fine powder is less than 0.032mm.

[0042] The mass ratio of the silicon nitride powder, the metal silicon powder, and the ferrosilicon alloy powder in the silicon nitride / metal silicon / ferrosilicon alloy compound composite material is 0.15:0.2:1, and the microstructure and phase composition are shown in Figure 2 The preparation method is as follows:

[0043] Step 1: Different mass ratios of silicon nitride powder, metal silicon powder, and ferrosilicon alloy powder are added to anhydrous ethanol, and a planetary ball mill is used for wet ball milling for 48 h, wherein the ball-to-material ratio is 2:1, and the ball milling speed is 400 r / min.

[0044] Step 2: The mixed material after ball milling is vacuum dried, and to prevent the mixed material from being oxidized, it is placed in high-purity nitrogen at 1400°C for 3 h.

[0045] Step 3: The high-temperature sintered compound composite material is crushed and sieved, and the powder with a particle size of ≤0.074 μm is selected.

[0046] The preparation process of the corundum dry ramming material in this embodiment is as follows:

[0047] White corundum aggregate, white corundum powder, magnesia aggregate, magnesia powder, α-alumina powder, magnesium aluminate spinel, and the silicon nitride / metal silicon / ferrosilicon alloy compound composite material are uniformly stirred in a mixer for 3 min and are pressed into a shape, and after room temperature curing, a high-temperature sintering process is performed at 1600°C for 3 h.

[0048] The physical and chemical properties of the high-performance corundum dry ramming material for medium-frequency induction furnaces prepared in this embodiment are as follows: the bulk density is 2.97 g / cm3, the porosity is 22.4%, the linear change rate is 1.56%, the compressive strength is 37.1 MPa, the bending strength is 9.9 MPa, and the slag corrosion index is 17.4% at 1600°C for 3 h.

[0049] Example 2

[0050] The high-performance corundum dry ramming material for medium-frequency induction furnaces in this embodiment comprises the following components and their weight percentages: 85 wt.% of white corundum aggregate, 6 wt.% of white corundum powder, 2 wt.% of magnesia aggregate, 2 wt.% of magnesia powder, 2 wt.% of α-alumina powder, and 3 wt.% of magnesium aluminate spinel. The additive is measured based on the total weight of the dry ramming material base (100%), and 5 wt.% of the silicon nitride / metal silicon / ferrosilicon alloy compound composite material is added.

[0051] The particle size distribution of the white corundum aggregate is: 8-5mm accounts for 20wt.% of the white corundum aggregate, 5-3mm accounts for 25wt.% of the white corundum aggregate, 3-1mm accounts for 30wt.% of the white corundum aggregate, and 1-0.28mm accounts for 25wt.% of the white corundum aggregate.

[0052] The particle size distribution of the magnesia aggregate is: 1-0.5mm accounts for 40wt.% of the magnesia aggregate, and 0.5-0.088mm accounts for 60wt.% of the magnesia aggregate.

[0053] The white corundum powder is a mixture of 50-200 mesh and fine powder with particle size less than 325 mesh.

[0054] The α-alumina powder is selected from α-alumina powder with Al2O3 content ≥98wt.% and bimodal structure of particle size distribution curve, and the bimodal peak values are 1.12μm and 2.13μm respectively.

[0055] The magnesium aluminate spinel has a label of MA-78, and the fine powder has a particle size less than 0.032mm.

[0056] The mass ratio of the silicon nitride powder, the metal silicon powder, and the silicon-iron alloy powder in the silicon nitride / metal silicon / silicon-iron alloy composite material is 0.3:0.2:1.

[0057] The physical and chemical properties of the high-performance corundum dry ramming mix for medium-frequency induction furnace prepared in this embodiment are: 1600℃×3h bulk density is 2.68g / cm3, porosity is 24.1%, linear change rate is 1.60%, compressive strength is 25.5MPa, flexural strength is 5.6MPa, and slag corrosion index is 18.0%.

[0058] Example 3

[0059] The high-performance corundum dry ramming mix for medium-frequency induction furnace in this embodiment comprises the following components and their weight percentages: 75wt.% of white corundum aggregate, 8wt.% of white corundum powder, 4wt.% of magnesia aggregate, 4wt.% of magnesia powder, 4wt.% of α-alumina powder, and 5wt.% of magnesium aluminate spinel. The additive is measured based on the total weight of the dry ramming mix base (100%), and 3wt.% of the silicon nitride / metal silicon / silicon-iron alloy composite material is added.

[0060] The particle size distribution of the white corundum aggregate is: 8-5mm accounts for 20wt.% of the white corundum aggregate, 5-3mm accounts for 25wt.% of the white corundum aggregate, 3-1mm accounts for 30wt.% of the white corundum aggregate, and 1-0.28mm accounts for 25wt.% of the white corundum aggregate.

[0061] The particle size distribution of the magnesia aggregate is that the 1-0.5mm accounts for 46wt.% of the magnesia aggregate, and the 0.5-0.088mm accounts for 54wt.% of the magnesia aggregate.

[0062] The white corundum micro powder is a mixture of 50-200 mesh and less than 325 mesh fine powder.

[0063] The α-alumina micro powder is selected from the α-alumina micro powder with Al2O3 content ≥98wt.% and bimodal structure of particle size distribution curve, and the bimodal peak values are 1.12μm and 2.13μm respectively.

[0064] The magnesium aluminate spinel is MA-90, and the fine powder with particle size less than 0.032mm.

[0065] The mass ratio of the silicon nitride powder, the metal silicon powder and the silicon-iron alloy powder in the compound composite material of silicon nitride / metal silicon / silicon-iron alloy is 0.2:0.2:1.

[0066] The physicochemical properties of the high-performance corundum dry ramming mix for medium-frequency induction furnace prepared in the embodiment are as follows: the bulk density is 3.01g / cm3, the porosity is 19.6%, the linear change rate is 0.8%, the compressive strength is 50.2MPa, the bending strength is 10.2MPa, and the slag erosion index is 11.1%. 3

[0067] The above description of the present application and its embodiments is illustrative, and is not restrictive, and the embodiment shown in the drawings is only one of the embodiments of the present application, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by the above description, and without departing from the spirit of the present application, similar structural modes and embodiments can be designed without creative design, and all of them should belong to the protection scope of the present application.​

Claims

1. A high-performance corundum dry ramming mix for intermediate frequency induction furnace, characterized in that: The dry ramming material base comprises the following components and weight percentages: 65-85 wt.% white corundum aggregate, 6-10 wt.% white corundum powder, 2-6 wt.% magnesia aggregate, 2-5 wt.% magnesia powder, 2-5 wt.% α-alumina powder, and 3-9 wt.% magnesium aluminate spinel; the additive is a compound composite of silicon nitride / metallic silicon / silicon-iron alloy, and the weight percentage of the additive in the total weight of the dry ramming material base is 1-5 wt.%. ​ The mass ratio of the silicon nitride powder, the metallic silicon powder, and the silicon-iron alloy powder in the compound composite of silicon nitride / metallic silicon / silicon-iron alloy is (0.15-0.3):0.2:

1. The compound composite of silicon nitride / metallic silicon / silicon-iron alloy is synthesized by a high-temperature solid-phase method, and the specific steps are as follows: Step 1: different mass ratios of silicon nitride powder, metallic silicon powder, and silicon-iron alloy powder are added to anhydrous ethanol, and wet ball milling is performed by using a planetary ball mill for 48 h, wherein the ball-to-material ratio is 2:1, and the ball milling speed is 400 r / min; Step 2: the mixed material after ball milling is vacuum dried and placed in high-purity nitrogen at 1400℃ for 3 h; Step 3: the compound composite after high-temperature sintering is crushed and sieved, and the powder with a particle size of ≤0.074 μm is selected. The magnesium aluminate spinel includes spinels of MA-66, MA-78, and MA-90, and the particle size of the fine powder is less than 0.032 mm.

2. The high-performance corundum dry ramming mix for medium-frequency induction furnace according to claim 1, characterized in that: The particle size distribution of the white corundum aggregate is as follows: the white corundum aggregate with a particle size of 8-5 mm accounts for 5-30 wt.%, the white corundum aggregate with a particle size of 5-3 mm accounts for 20-30 wt.%, the white corundum aggregate with a particle size of 3-1 mm accounts for 25-35 wt.%, and the white corundum aggregate with a particle size of 1-0.28 mm accounts for 25-30 wt.%.

3. The high-performance corundum dry ramming mix for medium-frequency induction furnace according to claim 2, characterized in that: The particle size distribution of the magnesia aggregate is as follows: the magnesia aggregate with a particle size of 1-0.5 mm accounts for 40-52 wt.%, and the magnesia aggregate with a particle size of 0.5-0.088 mm accounts for 48-60 wt.%.

4. The high-performance tabular corundum dry ramming mix for medium frequency induction furnace according to claim 3, characterized in that: The α-alumina powder is selected from α-alumina powder with an Al2O3 content of ≥98 wt.% and a particle size distribution curve of a bimodal structure, and the bimodal peak values are 1.12 μm and 2.13 μm, respectively.

5. The high-performance tabular corundum dry ramming mix for medium frequency induction furnace according to claim 4, characterized in that: The white corundum powder is a mixture of fine powder with a particle size of 50-200 mesh and fine powder with a particle size of less than 325 mesh.

6. The high-performance corundum dry ramming mix for medium-frequency induction furnace according to claim 5, characterized in that: The magnesia powder is fine powder with a particle size of less than 300 mesh.

7. A method for preparing high-performance corundum dry ramming mix for intermediate frequency induction furnace, characterized in that: The white corundum aggregate, the white corundum powder, the magnesia aggregate, the magnesia powder, the α-alumina powder, the magnesium aluminate spinel, and the compound composite of silicon nitride / metallic silicon / silicon-iron alloy in the dry ramming material according to any one of claims 1-6 are uniformly stirred in a mixer for 3 min and then pressed and formed, and after room temperature curing, a product is obtained by maintaining the temperature at 1600℃ for 3 h.

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