A launder with multiple filters for vacuum induction melting furnace

Abstract

The present invention belongs to the field of metallurgy, and specifically relates to a launder with multiple filter screens for a vacuum induction melting furnace. According to weight percentage, the launder body material is a mixture of 54.5-56.5% magnesium oxide, 33-35% aluminum oxide, 8.8-9.0% calcium oxide, 1-1.2% aluminum, 0.3-0.6% boron nitride, and 0.3-0.6% boric acid; according to weight percentage, the filter screen material of the launder is 44.5-46.5% aluminum oxide, 33-35% magnesium oxide, 18.8-19% calcium oxide, 1-1.2% aluminum, and 0.4-0.6% boron nitride. The launder structure with multiple filter screens for the vacuum induction melting furnace provided by the present invention can not only realize multi-stage filtration of high-temperature alloys to improve the purity, but also realize deoxidation, desulfurization and denitrification during the pouring process of the vacuum induction melting furnace by improving the launder and filter screen formula, so that the purity of the molten steel is further improved, and the purity is improved by 50%, and the probability of the launder cracking will not occur until 10 times of use.

Description

Technical Field

[0001] The invention belongs to the field of metallurgy, and in particular relates to a launder with multiple filter screens for a vacuum induction smelting furnace. Background Art

[0002] The vacuum induction melting furnace is an important equipment for modern production of high alloying, easy segregation, difficult to control trace elements and extremely small amounts of inclusions. For materials used in important links such as aviation parts, from the perspective of safety, reliability and long life, the materials need to have good creep properties and long-term service material structure stability and deformation resistance. The realization of these properties requires very strict control of the content of inclusions such as oxygen, nitrogen and sulfur. In order to achieve high purity of alloy materials, the vacuum induction melting furnace needs to be matched with a molten steel filtration system to achieve the preparation of high-purity alloys, especially in the use of old material return materials considering the economic cost.

[0003] Different from small vacuum induction melting furnaces, large vacuum induction melting furnaces at home and abroad have the characteristics of multiple independent vacuum chambers to achieve complex process control. The structural characteristics of multiple independent vacuum chambers and the characteristics of large-scale equipment have formed another difficulty for the alloy liquid filtration system, that is, the long flow channel system and the large temperature drop increase the difficulty of filtration, which is easy to cause production pouring blockage accidents. This is why the alloy liquid multi-filter mesh filtration system is rarely used in large vacuum induction melting furnaces. It is very important to realize the filtration of molten steel with multiple filters in large equipment for high-purity high-temperature alloys.

[0004] The three-dimensional mesh structure of the ceramic foam net can block inclusion particles at the hole mouth, and smaller inclusions are deposited in the corners of the filter holes due to the tortuous and changeable channels of the filter when the molten liquid passes through the filter. At the same time, the ceramic surface has a strong adsorption force that can adsorb fine inclusions. When multiple foam ceramic nets are set up, the molten steel is filtered layer by layer, and high-purity alloys will be obtained. If foam ceramic filtration can be assisted on large vacuum melting furnace equipment, it is of great significance to even achieve multiple filter filtration.

[0005] With the extreme performance requirements of alloy materials, the control level of inclusion content in alloys is becoming more and more stringent. It is very important to filter the molten steel in the vacuum induction melting furnace during the pouring process and control the contact reaction between refractory materials and molten steel during the pouring process to reduce the oxygen content, nitrogen content and sulfur content. Unfortunately, due to the limitations of molten steel superheat and the filtering capacity of the filter, the use of filters in the flow trough often blocks the molten steel and causes production accidents. Therefore, the use of filters to reduce the process of molten steel inclusions is limited. The probability of molten steel blockage when using a primary filter in the actual production of large-scale equipment exceeds 50%, and the filter is basically not allowed to be used.

[0006] The thermal shock resistance of the flow channel (the number of times without cracking is the service life) is affected by the following indicators: material refractoriness, strength, linear thermal expansion coefficient, high-temperature porosity, and sintering layer formation temperature. The higher the material refractoriness, the higher the strength, the lower the linear thermal expansion coefficient, the higher the high-temperature porosity, and the lower the sintering layer formation temperature, the better the thermal shock resistance, the more times without cracking, and the longer the service life.

[0007] Ordinary material chutes and filter screens may crack during one use. Cracking will not only increase the impurities in the molten steel, making the previous filtering efforts useless, but also cause production safety accidents. Ordinary material chutes not only cannot remove oxygen and sulfur, but on the contrary, due to the influence of refractory impurities, they will increase the oxygen and sulfur content in the molten steel.

[0008] The present invention realizes deoxidation, desulfurization and denitrification in the pouring process of the vacuum induction melting furnace by improving the formula of the launder and the filter screen, so that the purity of the molten steel is further improved. Summary of the invention

[0009] The object of the present invention is to provide a launder with multiple filter screens for a vacuum induction melting furnace, which can realize multi-stage filtration and achieve deoxidation, desulfurization and denitrification during the pouring process of the vacuum induction melting furnace by improving the filter screen formula, so that the purity of the molten steel is improved by more than 50%, and the probability of the launder cracking occurs after 10 uses.

[0010] The technical solution of the present invention is as follows:

[0011] A flow trough with multiple filter screens for a vacuum induction melting furnace comprises: a trough body, a water outlet, and a filter screen. The specific structure is as follows: the trough body is a rectangular cylindrical structure arranged in the horizontal direction, the front end of the trough body is connected to the molten steel outlet of the vacuum induction melting furnace, the rear end of the trough body is a closed end, the water outlet is arranged at the lower part of the rear end of the trough body, and the filter screens are arranged at the front, middle and rear parts of the inner cavity of the trough body along the rectangular longitudinal section of the inner cavity of the trough body.

[0012] The vacuum induction melting furnace uses a flow trough with multiple filter screens. The trough body material of the flow trough is a uniform mixture of 54.5-56.5% magnesium oxide, 33-35% aluminum oxide, 8.8-9.0% calcium oxide, 1-1.2% aluminum, 0.3-0.6% boron nitride and 0.3-0.6% boric acid by weight percentage; the filter screen material of the flow trough is a uniform mixture of 44.5-46.5% aluminum oxide, 33-35% magnesium oxide, 18.8-19% calcium oxide, 1-1.2% aluminum and 0.4-0.6% boron nitride by weight percentage.

[0013] The vacuum induction melting furnace uses a flow channel with multiple filter screens, and the filter screens include long screens and short screens parallel to each other, and both the long screens and the short screens are rectangular mesh structures.

[0014] The vacuum induction melting furnace uses a launder with multiple filter screens, the long screen size is: width 120mm×height 130mm×thickness 20mm, and the short screen size is: width 120mm×height 40mm×thickness 20mm.

[0015] The vacuum induction melting furnace uses a flow trough with multiple filter screens, and the number of long screens is two, wherein: one long screen is arranged at the front part of the inner cavity of the trough body along the rectangular longitudinal section of the inner cavity of the trough body, and only a gap one is left between its lower end plane and the bottom of the inner cavity of the trough body, and the other parts of the long screen are tightly fitted with the inner wall surface of the trough body; the other long screen is arranged at the rear part of the inner cavity of the trough body along the rectangular longitudinal section of the inner cavity of the trough body and in front of the water inlet, and only a gap four is left between its upper end plane and the top of the inner cavity of the trough body, and the other parts of the long screen are tightly fitted with the inner wall surface of the trough body.

[0016] The vacuum induction melting furnace uses a flow trough with multiple filter screens, with two short screens in a group, a total of four groups, and the first to fourth groups of short screens are respectively arranged along the four rectangular longitudinal sections of the inner cavity of the trough body, and are staggered in sequence between two long screens.

[0017] The vacuum induction melting furnace uses a flow trough with multiple filter screens. The first and third groups of short screens are respectively provided with two short screens in an upper and lower position. A gap is left between the two short screen structures in each group. The short screen located at the lower part is tightly fitted with the inner wall surface of the trough body, and a gap is left between the short screen located at the upper part and the top of the inner cavity of the trough body.

[0018] The vacuum induction melting furnace uses a flow trough with multiple filter screens. The second and fourth groups of short screens are respectively provided with two short screens in an upper and a lower manner. A gap is left between the two short screen structures in each group. The short screen located at the upper part is tightly fitted with the inner wall surface of the trough body, and a gap is left between the short screen located at the lower part and the bottom of the inner cavity of the trough body.

[0019] The vacuum induction melting furnace uses a launder with multiple filter screens, and the preparation method of the launder is as follows:

[0020] (1) In a mixing barrel, the magnesium oxide, aluminum oxide and calcium oxide of the launder body refractory material are uniformly mixed according to the following particle size weight percentages;

[0021] The particle size distribution is as follows by weight percentage: 9-11% of particles have a particle size of <0.07mm, 12-14% of particles have a particle size of 0.07mm≤<1mm, 11-13% of particles have a particle size of 1mm≤<1.5mm, 14-16% of particles have a particle size of 1.5mm≤<2.5mm, 24-26% of particles have a particle size of 2.5mm≤<4mm, 19-21% of particles have a particle size of 4mm≤<7mm, and 4-6% of particles have a particle size of 7mm≤<15mm.

[0022] (2) adding aluminum with a particle size of less than 0.07 mm, boron nitride with a particle size of less than 0.07 mm, and boric acid with a particle size of less than 0.07 mm to the launder body refractory material mixed in step (1), and mixing them evenly again;

[0023] (3) Pour the mixture obtained in step (2) into the flow channel body mold and tamp it into shape, adding the mixture to a height of 10 to 15 mm each time, tamping it with a tool, and then adding the next layer one by one;

[0024] (4) Take a flow trough filter screen made of a uniform mixture of aluminum oxide, magnesium oxide, calcium oxide, aluminum, and boron nitride, and glue and assemble the filter screen into the flow trough body;

[0025] (5) Wrap the formed and assembled flow channel filter body with plastic cloth and place it at room temperature for 1 to 1.5 hours;

[0026] (6) The stopped flow channel is transferred to the sintering electric furnace for sintering and forming. The sintering process is as follows:

[0027] When the furnace temperature is lower than 50℃, start heating up at a heating rate of 70±5℃ / hour, and heat up to 250℃ and keep it for 1 hour; continue heating up at a heating rate of 120±10℃ / hour, and heat up to 700℃ and keep it for 0.5 hour; continue heating up at a heating rate of 120±10℃ / hour to 900℃ and keep it for 1.5 hours; continue heating up at a heating rate of 180±10℃ / hour to 1150℃ and keep it for 1 hour; cool down to 650℃ at a cooling rate of 130±10℃ / hour, and air cool to room temperature after taking out of the furnace;

[0028] (7) When using the launder, preheat it to 950-1050°C using a gas flame jet furnace and use it immediately.

[0029] The design concept of the present invention is:

[0030] In the present invention, the trough body material is mainly magnesium oxide, supplemented by aluminum oxide, calcium oxide, aluminum, boron nitride and boric acid; the trough filter material is mainly aluminum oxide, supplemented by magnesium oxide, calcium oxide, aluminum and boron nitride. Since calcium oxide and aluminum are added to the trough body and the filter, they can remove oxygen, sulfur and nitrogen from the molten steel. The synergistic mechanism between calcium oxide and aluminum is:

[0031] 2Al+3CaO+3S=3CaS+Al2O3

[0032] 2Al+3O=Al2O3

[0033] n Al2O3+m CaO=n Al2O3·m CaO

[0034] n Al2O3·m CaO is a large particle and easy to be suspended slag, which is easy to remove from the molten steel, thus deep deoxidation, while reducing the density of fine Al2O3 and CaO slag, resulting in reduced resistance to N2 rising in the molten steel, accelerating vacuum volatilization, and effectively removing nitrogen. CaS slag is easy to remove, thus removing sulfur.

[0035] In the trough body material of the flow trough, when calcium oxide is less than 8.8wt%, the deoxidation and desulfurization effect is insufficient; when calcium oxide is greater than 9wt%, the flow trough is easy to absorb moisture in the air due to calcium oxide and hydrate, reducing the heat shock resistance of the flow trough. When aluminum is less than 1wt%, the deoxidation and desulfurization effect is insufficient; when aluminum is greater than 1.2wt%, excessive Al2O3 is generated and inclusions are increased. Therefore, the trough body material of the present invention is controlled as follows: calcium oxide 8.8-9.0wt%, aluminum 1-1.2wt%.

[0036] In the trough body material of the flow trough, when magnesium oxide <54.5wt% or magnesium oxide >56.5wt%, the thermal expansion coefficient of the flow trough increases and is prone to cracking. When aluminum oxide <33wt% or aluminum oxide >35wt%, the thermal expansion coefficient of the flow trough increases and is prone to cracking. When boron nitride <0.3wt% or boron nitride >0.6wt%, the thermal expansion coefficient of the flow trough increases and is prone to cracking. When boric acid <0.3wt%, insufficient adhesion will occur, resulting in a decrease in the thermal shock resistance of the flow trough; when boric acid >0.6wt%, the residual boron is too high to pollute the molten steel, increase the boron content of the alloy material, and cause the alloy's creep resistance to decrease. Therefore, the trough body material of the present invention is controlled as follows: magnesium oxide 54.5-56.5wt%, aluminum oxide 33-35wt%, boron nitride 0.3-0.6wt%, and boric acid 0.3-0.6wt%.

[0037] In the filter material of the flow trough, when calcium oxide <18.8wt% or calcium oxide >19wt%, the thermal shock resistance of the filter decreases. When aluminum <1wt%, the deoxidation and desulfurization effect is insufficient; when aluminum >1.2wt%, excessive Al2O3 is generated and inclusions are increased. Therefore, the filter material of the present invention is controlled as follows: calcium oxide 18.8-19wt%, aluminum 1-1.2wt%.

[0038] In the filter material of the flow trough, when aluminum oxide <44.5wt% or aluminum oxide >46.5wt%, the thermal expansion coefficient of the filter increases and the mesh is easily blocked. When magnesium oxide <33wt% or magnesium oxide >35wt%, the thermal expansion coefficient of the filter increases and the mesh is easily blocked. When boron nitride <0.4wt% or boron nitride >0.6wt%, the adhesion decreases and the filter is prone to cracking. Therefore, the filter material of the present invention is controlled as follows: aluminum oxide 44.5-46.5wt%, magnesium oxide 33-35wt%, and boron nitride 0.4-0.6wt%.

[0039] The advantages and beneficial effects of the present invention are:

[0040] 1. The trough body material of the flow trough of the present invention is a mixture of 54.5-56.5wt% magnesium oxide, 33-35wt% aluminum oxide, 8.8-9.0wt% calcium oxide, 1-1.2wt% aluminum, 0.3-0.6wt% boron nitride and 0.3-0.6wt% boric acid, which can improve the thermal shock resistance of the trough body of the flow trough (the service life is not the number of cracking resistance). The thermal shock resistance is affected by the following indicators: material refractoriness, strength, linear thermal expansion coefficient, high-temperature porosity and sintering layer formation temperature. The trough body material of the flow trough of the present invention has high refractoriness, high strength, low linear thermal expansion coefficient, high-temperature porosity and low sintering layer formation temperature, so it has good thermal shock resistance, many non-cracking times and long service life.

[0041] 2. The filter material of the flow trough of the present invention is a mixture of 44.5-46.5wt% aluminum oxide, 33-35wt% magnesium oxide, 18.8-19wt% calcium oxide, 1-1.2wt% aluminum, and 0.4-0.6wt% boron nitride, which can reduce the gas and impurity content of molten alloy steel. Compared with ordinary filter screens (such as aluminum oxide, silicon carbide, zirconium oxide, and magnesium oxide), the oxygen content of molten alloy steel can be reduced by more than 40wt%, the sulfur content by more than 30wt%, and the nitrogen content by more than 15wt%.

[0042] 3. The arrangement structure of the filter screen of the present invention can achieve multiple filtration of molten steel without clogging. The molten steel passes through the flow channel arranged in the S-shaped structure of the filter screen, avoiding the molten steel blocking failure caused by the resistance of the conventional closed filter screen, which not only allows the molten steel to pass smoothly but also achieves multiple filtration, which improves the filtering effect and increases the safety performance, and can achieve zero-fault production and operation. The conventional filter screen has a production failure rate of 50% when filtering molten steel on one layer, and a failure rate of 100% on a two-layer filter screen, and it is even more impossible to achieve more layers of filtration. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The front view (section view) of the launder structure with multiple filters for vacuum induction melting furnace;

[0044] Figure 2 A top view (section view) of a launder structure with multiple filters for a vacuum induction melting furnace;

[0045] In the figure, 1 is the trough body, 2 is the water outlet, 3 is the long net, 4 is the short net, 5 is the gap one, 6 is the gap two, 7 is the gap three, and 8 is the gap four. DETAILED DESCRIPTION

[0046] Below, the present invention is further described in detail by examples.

[0047] Example 1

[0048] In this embodiment, the preparation method of the launder with multiple filter screens for the vacuum induction melting furnace is as follows:

[0049] (1) In a mixing barrel, 55.0 wt% magnesium oxide, 34.0 wt% aluminum oxide, and 8.8 wt% calcium oxide of the launder body refractory material are uniformly mixed according to the following particle size weight percentages.

[0050] The particle size distribution by weight percentage is: particle size <0.07mm accounts for 10%, 0.07mm≤particle size <1mm accounts for 13%, 1mm≤particle size <1.5mm accounts for 12%, 1.5mm≤particle size <2.5mm accounts for 15%, 2.5mm≤particle size <4mm accounts for 25%, 4mm≤particle size <7mm accounts for 20%, 7mm≤particle size <15mm accounts for 5%;

[0051] The purpose of selecting specific proportions of the above-mentioned refractory materials according to different particle size segments is to balance the strength, density, porosity, thermal expansion performance, and thermal shock resistance of the refractory molding, thereby ensuring the service life and cracking frequency.

[0052] (2) Add 1.2 wt% aluminum with a particle size of <0.07 mm, 0.5 wt% boron nitride with a particle size of <0.07 mm, and 0.5 wt% boric acid with a particle size of <0.07 mm to the mixed launder body refractory material, and mix them evenly again.

[0053] (3) Pour the mixture obtained in step (2) into the launder body mold and tamp it into shape. Note that the height of the mixture added each time is 10 to 15 mm. After tamping it with a tool, add the next layer one by one. Do not add too much refractory material at one time.

[0054] (4) a flow trough filter screen made by uniformly mixing 45% aluminum oxide, 34.5% magnesium oxide, 19% calcium oxide, 1% aluminum, and 0.5% boron nitride according to weight percentage is bonded and assembled into the flow trough body;

[0055] (5) Wrap the formed and assembled flow channel filter body with plastic cloth and place it at room temperature for 1.2 hours;

[0056] (6) The stopped flow channel is transferred to the sintering electric furnace for sintering and forming. The sintering process is as follows:

[0057] When the furnace temperature is lower than 50℃, start heating up at a heating rate of 70±5℃ / hour, and heat up to 250℃ and keep it for 1 hour; continue heating up at a heating rate of 120±10℃ / hour, and heat up to 700℃ and keep it for 0.5 hour; continue heating up at a heating rate of 120±10℃ / hour to 900℃ and keep it for 1.5 hours; continue heating up at a heating rate of 180±10℃ / hour to 1150℃ and keep it for 1 hour; cool down to 650℃ at a cooling rate of 130±10℃ / hour, and air cool to room temperature after taking out of the furnace;

[0058] During the above-mentioned sintering and forming process, the role of heating and insulation at different temperature steps is to ensure that the chemical reaction expansion control and water vapor evaporation in the process of refractory material forming objects from mixture to sintering to form ceramics will not form a source of cracking, and to ensure that the most stable and dense sintering layer is formed as quickly as possible under the lowest temperature and time cost conditions.

[0059] (7) When using the launder, preheat it to 980°C using a gas flame jet furnace and use it immediately.

[0060] Example 2

[0061] In this embodiment, the preparation method of the launder with multiple filter screens for the vacuum induction melting furnace is as follows:

[0062] (1) In a mixing barrel, 56.0 wt% magnesium oxide, 33 wt% aluminum oxide, and 9.0 wt% boron nitride of the launder body refractory material are uniformly mixed according to the following particle size weight percentages.

[0063] The particle size distribution by weight percentage is: particle size < 0.07mm accounts for 9%, 0.07mm≤particle size < 1mm accounts for 14%, 1mm≤particle size < 1.5mm accounts for 11%, 1.5mm≤particle size < 2.5mm accounts for 16%, 2.5mm≤particle size < 4mm accounts for 24%, 4mm≤particle size < 7mm accounts for 21%, 7mm≤particle size < 15mm accounts for 5%;

[0064] (2) 1.1 wt% aluminum with a particle size of <0.07 mm, 0.45 wt% boron nitride with a particle size of <0.07 mm, and 0.45 wt% boric acid with a particle size of <0.07 mm are added to the mixed launder refractory material and mixed evenly again.

[0065] (3) Pour the mixture obtained in step (2) into the launder body mold and tamp it into shape. Note that the height of the mixture added each time is 10 to 15 mm. After tamping it with a tool, add the next layer one by one. Do not add too much refractory material at one time.

[0066] (4) a flow trough filter screen made by uniformly mixing 44.5% aluminum oxide, 35% magnesium oxide, 18.9% calcium oxide, 1.2% aluminum, and 0.4% boron nitride according to weight percentage is bonded and assembled into the flow trough body;

[0067] (5) Wrap the formed and assembled flow channel filter body with plastic cloth and place it at room temperature for 1 hour;

[0068] (6) The stopped flow channel is transferred to the sintering electric furnace for sintering and forming. The sintering process is as follows:

[0069] When the furnace temperature is lower than 50℃, start heating up at a heating rate of 70±5℃ / hour, and heat up to 250℃ and keep it for 1 hour; continue heating up at a heating rate of 120±10℃ / hour, and heat up to 700℃ and keep it for 0.5 hour; continue heating up at a heating rate of 120±10℃ / hour to 900℃ and keep it for 1.5 hours; continue heating up at a heating rate of 180±10℃ / hour to 1150℃ and keep it for 1 hour; cool down to 650℃ at a cooling rate of 130±10℃ / hour, and air cool to room temperature after taking out of the furnace;

[0070] (7) When using the launder, preheat it to 1000°C using a gas flame jet furnace and use it immediately.

[0071] Example 3

[0072] In this embodiment, the preparation method of the launder with multiple filter screens for the vacuum induction melting furnace is as follows:

[0073] (1) In a mixing barrel, 54.5 wt% magnesium oxide, 34.5 wt% aluminum oxide, and 8.9 wt% boron nitride of the launder body refractory material are uniformly mixed according to the following particle size weight percentages.

[0074] The particle size distribution by weight percentage is: particle size < 0.07mm accounts for 10%, 0.07mm≤particle size < 1mm accounts for 12%, 1mm≤particle size < 1.5mm accounts for 13%, 1.5mm≤particle size < 2.5mm accounts for 14%, 2.5mm≤particle size < 4mm accounts for 26%, 4mm≤particle size < 7mm accounts for 19%, 7mm≤particle size < 15mm accounts for 6%;

[0075] (2) 1.0 wt% aluminum with a particle size of <0.07 mm, 0.54 wt% boron nitride with a particle size of <0.07 mm, and 0.56 wt% boric acid with a particle size of <0.07 mm are added to the mixed launder refractory material and mixed evenly again.

[0076] (3) Pour the mixture obtained in step (2) into the launder body mold and tamp it into shape. Note that the height of the mixture added each time is 10 to 15 mm. After tamping it with a tool, add the next layer one by one. Do not add too much refractory material at one time.

[0077] (4) a flow trough filter screen made by uniformly mixing 46.5% aluminum oxide, 33% magnesium oxide, 18.8% calcium oxide, 1.1% aluminum, and 0.6% boron nitride according to weight percentage is bonded and assembled into the flow trough body;

[0078] (5) Wrap the formed and assembled flow channel filter body with plastic cloth and place it at room temperature for 1.5 hours;

[0079] (6) The stopped flow channel is transferred to the sintering electric furnace for sintering and forming. The sintering process is as follows:

[0080] When the furnace temperature is lower than 50℃, start heating up at a heating rate of 70±5℃ / hour, and heat up to 250℃ and keep it for 1 hour; continue heating up at a heating rate of 120±10℃ / hour, and heat up to 700℃ and keep it for 0.5 hour; continue heating up at a heating rate of 120±10℃ / hour to 900℃ and keep it for 1.5 hours; continue heating up at a heating rate of 180±10℃ / hour to 1150℃ and keep it for 1 hour; cool down to 650℃ at a cooling rate of 130±10℃ / hour, and air cool to room temperature after taking out of the furnace;

[0081] (7) When using the launder, preheat it to 1050°C using a gas flame jet furnace and use it immediately.

[0082] Table 1 shows the material components of the tank body of Examples 1 to 3 as follows:

[0083] Table 1

[0084] wt% Magnesium Oxide Alumina Calcium Oxide aluminum Boron Nitride Boric acid Example 1 55.0 34.0 8.8 1.2 0.5 0.5 Example 2 56.0 33.0 9.0 1.1 0.45 0.45 Example 3 54.5 34.5 8.9 1.0 0.54 0.56

[0085] Table 2 is a comparison of the performance indicators of the tank body of the present invention and tank bodies made of several commonly used ordinary materials:

[0086] Table 2

[0087]

[0088] Table 3 shows the filter material components of Examples 1 to 3 as follows:

[0089] Table 3

[0090] wt% Alumina Magnesium Oxide Calcium Oxide aluminum Boron Nitride Example 1 45 34.5 19.0 1.0 0.5 Example 2 44.5 35 18.9 1.2 0.4 Example 3 46.5 33 18.8 1.1 0.6

[0091] Table 4 is the comparison data of the filter materials of Examples 1 to 3 and the ordinary filter as follows:

[0092] Table 4

[0093] ppm Oxygen content of molten steel after filtration Sulfur content of molten steel after filtration Nitrogen content of molten steel after filtration Ordinary filter 12 9 27 Example 1 5 5 18 Example 2 4.5 5 20 Example 3 5 4.8 20

[0094] Table 5

[0095]

[0096] like Figure 1-Figure 2 As shown, the launder with multiple filter screens for the vacuum induction melting furnace of the present invention mainly comprises: a launder body 1, a water inlet 2, a long screen 3, and a short screen 4, and the specific structure is as follows:

[0097] The tank body 1 is a rectangular cylindrical structure arranged in the horizontal direction. The front end of the tank body 1 is connected to the molten steel outlet of the vacuum induction melting furnace. The rear end of the tank body 1 is a closed end. A water inlet 2 is arranged at the lower part of the rear end of the tank body 1. The front, middle and rear parts of the inner cavity of the tank body 1 are provided with filter screens along the rectangular longitudinal section of the inner cavity of the tank body 1. The filter screen includes a long net 3 and a short net 4 parallel to each other, wherein: the long net 3 is a rectangular net structure, and the dimensions of the long net 3 are: width 120mm×height 130mm×thickness 20mm; the short net 4 is a rectangular net structure, and the dimensions of the short net 4 are: width 120mm×height 40mm×thickness 20mm.

[0098] There are two long nets 3, among which: one long net 3 is arranged at the front part of the inner cavity of the tank body 1 along the rectangular longitudinal section of the inner cavity of the tank body 1, and only a gap 5 is left between its lower end plane and the bottom of the inner cavity of the tank body 1, and the other parts of the long net 3 are tightly fitted with the inner wall surface of the tank body 1; the other long net 3 is arranged at the rear part of the inner cavity of the tank body 1 along the rectangular longitudinal section of the inner cavity of the tank body 1 and in front of the water inlet 2, and only a gap 298 is left between its upper end plane and the top of the inner cavity of the tank body 1, and the other parts of the long net 3 are tightly fitted with the inner wall surface of the tank body 1.

[0099] The short nets 4 are grouped in pairs, with a total of four groups, each group of short nets 4 includes two short nets, and the first to fourth groups of short nets 4 are respectively arranged between two long nets 3 along the four rectangular longitudinal sections of the inner cavity of the tank body 1. Among them:

[0100] The first and third groups of short nets 4 are respectively provided with two short nets in upper and lower parts, and a gap 6 is left between the two short net structures of each group, the short net located at the lower part is closely fitted with the inner wall surface of the tank body 1, and a gap is left between the short net located at the upper part and the top of the inner cavity of the tank body 1. The second and fourth groups of short nets 4 are respectively provided with two short nets in upper and lower parts, and a gap 7 is left between the two short net structures of each group, the short net located at the upper part is closely fitted with the inner wall surface of the tank body 1, and a gap is left between the short net located at the lower part and the bottom of the inner cavity of the tank body 1.

[0101] In the present invention, the function of the long net 3 is to filter more than 2 / 3 of the molten steel area, and at the same time, reserve a notch to quickly transport the molten steel through, so as to avoid the temperature drop blocking the flow channel and the failure of filtering; the function of the short net 4 is to alternate the notch with the short net and quickly transport the molten steel through, so as to avoid blocking, and the filter nets arranged between the short net groups are staggered to ensure that 100% of the molten steel area is filtered.

[0102] The results of the embodiments show that the trough body material of the flow trough of the present invention has higher refractoriness, higher strength, lower linear thermal expansion coefficient, higher high-temperature porosity, and lower sintering layer formation temperature than the conventional flow trough, so it has good thermal shock resistance, greatly increases the number of times without cracking, and has a long service life (see Table 2). Compared with the structure and material of the ordinary filter screen, the structure and material of the flow trough filter screen of the present invention can reduce the oxygen content of alloy steel water by more than 40wt%, the sulfur content by more than 30wt%, and the nitrogen content by more than 15wt% (see Table 4). The feasibility comparison of the flow trough of the present invention and the conventional flow trough filtration shows that the failure rate of one group of filtration is reduced from 50% to 0%, and the feasibility of filtration from two to six groups is improved from infeasible to feasible, thereby realizing deep filtration and purification of molten steel in a large vacuum induction furnace (see Table 5).

Claims

1. A launder with multiple filters for a vacuum induction melting furnace, characterized in that: include: The tank body, the nozzle, and the filter screen have the following specific structures: the tank body is a rectangular cylindrical structure arranged in the horizontal direction, the front end of the tank body is connected to the molten steel outlet of the vacuum induction melting furnace, the rear end of the tank body is a closed end, the nozzle is arranged at the lower part of the rear end of the tank body, and the filter screen is arranged at the front, middle, and rear of the tank body cavity along the rectangular longitudinal section of the tank body cavity; The body material of the flow trough is a uniform mixture of 54.5-56.5% magnesium oxide, 33-35% aluminum oxide, 8.8-9.0% calcium oxide, 1-1.2% aluminum, 0.3-0.6% boron nitride and 0.3-0.6% boric acid by weight percentage; the filter screen material of the flow trough is a uniform mixture of 44.5-46.5% aluminum oxide, 33-35% magnesium oxide, 18.8-19% calcium oxide, 1-1.2% aluminum and 0.4-0.6% boron nitride by weight percentage; The filter screen includes a long screen and a short screen which are parallel to each other, and both the long screen and the short screen are rectangular mesh structures; There are two long nets, wherein: one long net is arranged at the front of the inner cavity of the tank body along the rectangular longitudinal section of the inner cavity of the tank body, and only a gap one is left between the plane of its lower end and the bottom of the inner cavity of the tank body, and the other parts of the long net are closely fitted with the inner wall surface of the tank body; the other long net is arranged at the rear of the inner cavity of the tank body and in front of the water outlet along the rectangular longitudinal section of the inner cavity of the tank body, and only a gap four is left between the plane of its upper end and the top of the inner cavity of the tank body, and the other parts of the long net are closely fitted with the inner wall surface of the tank body; The short nets are grouped in pairs, with a total of four groups. The first to fourth groups of short nets are respectively arranged along the four rectangular longitudinal sections of the inner cavity of the tank body, and are staggered between the two long nets in sequence.

2. The launder with multiple filters for a vacuum induction melting furnace according to claim 1, characterized in that: The dimensions of the long net are: width 120 mm × height 130 mm × thickness 20 mm, and the dimensions of the short net are: width 120 mm × height 40 mm × thickness 20 mm.

3. The launder with multiple filters for a vacuum induction melting furnace according to claim 1, characterized in that: The first and third groups of short nets are respectively provided with two short nets in upper and lower parts, and a gap is left between the two short net structures in each group. The short net at the lower part is tightly fitted with the inner wall surface of the tank body, and a gap is left between the short net at the upper part and the top of the inner cavity of the tank body.

4. The launder with multiple filters for a vacuum induction melting furnace according to claim 1, characterized in that: The second and fourth groups of short nets are respectively provided with two short nets in an upper and a lower manner, and a gap is left between the two short net structures in each group. The short net located at the upper part is tightly fitted with the inner wall surface of the trough body, and a gap is left between the short net located at the lower part and the bottom of the inner cavity of the trough body.

5. The launder with multiple filters for a vacuum induction melting furnace according to claim 1, characterized in that: The preparation method of the flow trough is as follows: (1) In a mixing barrel, the magnesium oxide, aluminum oxide and calcium oxide of the launder body refractory material are uniformly mixed according to the following particle size weight percentages; The particle size distribution by weight percentage is as follows: particle size < 0.07 mm accounts for 9-11%, particle size 0.07 mm ≤ < 1 mm accounts for 12-14%, particle size 1 mm ≤ < 1.5 mm accounts for 11-13%, particle size 1.5 mm ≤ < 2.5 mm accounts for 14-16%, particle size 2.5 mm ≤ < 4 mm accounts for 24-26%, particle size 4 mm ≤ < 7 mm accounts for 19-21%, particle size 7 mm ≤ < 15 mm accounts for 4-6%; (2) adding aluminum with a particle size of less than 0.07 mm, boron nitride with a particle size of less than 0.07 mm, and boric acid with a particle size of less than 0.07 mm to the launder body refractory material mixed in step (1), and mixing them evenly again; (3) Pour the mixture obtained in step (2) into the flow trough body mold and tamp it into shape, adding the mixture to a height of 10 to 15 mm each time, tamping it with a tool before adding the next layer one by one; (4) Take a flow trough filter screen made of a uniform mixture of aluminum oxide, magnesium oxide, calcium oxide, aluminum and boron nitride, and glue and assemble the filter screen into the flow trough body; (5) Wrap the formed and assembled flow channel filter body with plastic cloth and place it at room temperature for 1 to 1.5 hours; (6) The stopped flow channel is transferred to the sintering electric furnace for sintering and forming. The sintering process is as follows: When the furnace temperature is lower than 50℃, start heating up at a heating rate of 70±5℃ / hour, and heat up to 250℃ and keep it for 1 hour; continue heating up at a heating rate of 120±10℃ / hour, and heat up to 700℃ and keep it for 0.5 hour; continue heating up at a heating rate of 120±10℃ / hour to 900℃ and keep it for 1.5 hours; continue heating up at a heating rate of 180±10℃ / hour to 1150℃ and keep it for 1 hour; cool down to 650℃ at a cooling rate of 130±10℃ / hour, and air cool down to room temperature after taking out of the furnace; (7) When using the launder, preheat it to 950~1050℃ with a gas flame jet furnace and use it immediately.

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