Short-process high-temperature alloy welding wire production system

Abstract

A short-process high-temperature alloy welding wire production system comprises a medium-frequency smelting furnace, a bottom blowing device, an upper blowing device, a crystallizer and a throwing machine. A heating element is arranged in an inner cavity of the medium-frequency smelting furnace, and an air inlet is formed in the bottom; the bottom blowing device is connected to an air inlet in the bottom of the medium-frequency smelting furnace. The upper blowing device is movably mounted on an opening in the upper end of the medium-frequency smelting furnace; two ends of the crystallizer are respectively an inlet and an outlet; the inlet of the crystallizer is hermetically connected with a water gap of the medium-frequency smelting furnace; a dummy bar is arranged at one end of the throwing machine, and the dummy bar of the throwing machine directly faces or extends into an outlet of the crystallizer. The device is used for casting blank manufacturing of the high-temperature alloy welding wire, and is matched with an original high-temperature alloy welding wire production process, so that short-process, continuous and low-cost production of the high-temperature alloy welding wire is realized.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of high temperature alloy welding wire manufacturing, especially a short process high temperature alloy welding wire production system. BACKGROUND

[0002] High temperature alloy welding wire has a wide range of applications in many fields due to its high temperature resistance, corrosion resistance, and high strength, etc. For example: I. In the field of aerospace, it is used for the connection and repair of key components such as engine parts, turbine blades, and combustion chambers, meeting the working requirements of aircraft in extreme environments; II. In the field of petroleum and chemical industry, it is used for the connection and repair of equipment such as pipelines, valves, and reactors, which can withstand high temperature, high pressure, and corrosive media; III. In the field of electric power industry, it is used for the connection and repair of key components of equipment such as gas turbines, steam turbines, and generators, ensuring the stable operation of power equipment.

[0003] As shown in Figure 5 , the current high temperature alloy welding wire production process mainly includes the following key steps:

[0004] S01, vacuum induction smelting: introducing raw materials into a vacuum induction smelting furnace, vacuumizing for smelting, due to the reduction of pressure, the solubility of oxygen in molten steel is reduced, and then it is precipitated, realizing deoxidation; then the molten steel is discharged into a mold, and after the molten steel is completely solidified, a primary smelting ingot is obtained; due to the inherent defects of the primary smelting ingot such as rough surface (dimple), shrinkage cavity, segregation, and slag entrapment, subsequent electric slag secondary remelting process is needed to eliminate them.

[0005] S02, electric slag secondary remelting: using an electric slag remelting furnace (the structure of a typical electric slag remelting furnace can refer to CN207016840U: single column double conductive cross arm ingot type electric slag remelting furnace device) to remelt the primary smelting ingot to manufacture a secondary remelting ingot, which basically eliminates the inherent defects of the primary smelting ingot, and the remaining small part of defects needs to be eliminated through subsequent forging process;

[0006] The equipment structure of electric slag secondary remelting is introduced: single column double conductive cross arm ingot type electric slag remelting furnace device, including a workbench erected above a bottom plate, an upper column located at the upper end of the workbench, a lower column located at the lower end of the workbench, and a crystallizer located at the side of the workbench; the upper column is provided with a first electrode clamping and conveying arm and a second electrode clamping and conveying arm; the first electrode clamping and conveying arm and the second electrode clamping and conveying arm are both vertically movable along the upper column; the ingot column is provided with a first slag ingot clamping and conveying arm and a second slag ingot clamping and conveying arm, and the first slag ingot clamping and conveying arm and the second slag ingot clamping and conveying arm are both vertically movable along the ingot column;

[0007] The operation process of the electric secondary remelting is introduced as follows: the arc agent is placed on the starter rod inserted from the bottom of the crystallizer, and the high-voltage switch is closed to arc; the first electrode clamp arm and the second electrode clamp arm are controlled to be powered on alternately to clamp the self-solubilizing electrode (the first melting ingot) to move downward continuously, at the same time, the first slag ingot clamp arm and the second slag ingot clamp arm are powered on alternately to clamp the electric slag ingot (the second remelting ingot) to move downward, and the slag is discharged through the groove on the bottom plate;

[0008] The working principle of the electric secondary remelting is introduced as follows: when the device works, the operator performs remelting preparation according to the process procedure, after the slag is ignited, the consumable electrode (the first melting ingot), the slag pool, the metal pool, the electric slag ingot and the starter cross arm form a loop through the short net lead and the transformer. During the power-on process, the slag pool releases Joule heat to gradually melt the end of the consumable electrode, the molten metal gathers into droplets, falls into the crystallization pool through the slag pool, forms a metal pool, and rapidly solidifies to form an electric slag ingot (a second remelting ingot) under the action of water cooling.

[0009] S03, forging: the second remelting ingot is forged under specific temperature conditions to a square billet of a specific size; this process includes annealing and grinding steps. This process is used to eliminate inherent defects such as porosity and segregation of the second remelting ingot, and to improve the density and refine the grains of the structure, providing a good foundation for subsequent hot rolling.

[0010] S04, post-processing: the square billet is prepared into a wire rod that meets the subsequent drawing requirements through a hot continuous rolling process. The wire rod successively passes through the solid solution, pickling, rough drawing and fine drawing processes, and the diameter of the welding wire is gradually reduced to the process requirement, i.e. a high-temperature alloy welding wire product is obtained.

[0011] Therefore, the current high-temperature alloy welding wire production process has the following shortcomings:

[0012] 1. Long process flow; the core processes before post-processing include two melting and one forging shaping, and the two melting processes are completed in different devices, making the process flow long.

[0013] 2. High production cost: the core processes before post-processing include two melting and one forging shaping, and waste, loss and labor cost are generated in each process, ultimately resulting in high production cost.

[0014] 3. Poor continuity: the core processes before post-processing include two melting and one forging shaping, and the ingot cannot be seamlessly connected between any two adjacent processes, but needs to be manually transported.

[0015] 4. High raw material requirement; the above process is difficult to remove phosphorus and sulfur in the raw material, and the phosphorus and sulfur in the raw material will be brought into the final product with each process, so only the source can be controlled, and only the raw material with phosphorus and sulfur content within the product requirement range can be purchased.

[0016] In summary, under the premise of ensuring the quality of high-temperature alloy welding wire products, simplifying the process flow, reducing production costs, and reducing raw material requirements have always been the research direction of related enterprises. The utility model discloses a short process high-temperature alloy welding wire production system

[0017] The utility model discloses a short process high-temperature alloy welding wire production system, which is matched with the unique short process high-temperature alloy welding wire production process, can realize the casting blank manufacturing of high-temperature alloy welding wire, and solves the problems of long production process, high production cost, poor continuity and high raw material requirement of the existing high-temperature alloy welding wire production process.

[0018] The utility model discloses a technical scheme: short process high-temperature alloy welding wire production system, including intermediate frequency smelting furnace, bottom blowing device, upper blowing device, crystallizer and drawbench, the heating element is equipped in the inner chamber of intermediate frequency smelting furnace, is equipped with the open mouth in the upper end, is equipped with the water gap in the lower end, is equipped with the air inlet in the bottom, bottom blowing device is connected on the air inlet of intermediate frequency smelting furnace bottom, is used to send inert gas to the inner chamber of intermediate frequency smelting furnace, upper blowing device is movably installed on the open mouth of the upper end of intermediate frequency smelting furnace, is used to send inert gas to the liquid level above the inner chamber of intermediate frequency smelting furnace, the crystallizer is water -cooling type horizontal continuous casting crystallizer, the both ends of crystallizer are import and export respectively, and the import of crystallizer is sealedly connected with the water gap of intermediate frequency smelting furnace, and one end of drawbench is equipped with the dummy bar, and the dummy bar of drawbench is opposite or extends into the export of crystallizer.

[0019] The utility model further discloses a technical scheme: the bottom of intermediate frequency smelting furnace is equipped with the installation mouth, and the air brick is fixedly installed in the installation mouth, and the upper end of air brick is located in the inner chamber of intermediate frequency smelting furnace, and the lower end of air brick is located in the outside of intermediate frequency smelting furnace, and the lower end of air brick is equipped with the steel pipe, and air brick has the characteristics of isolating molten steel and air permeability.

[0020] The utility model still further discloses a technical scheme: upper blowing device includes furnace cover and air pipe A, and the furnace cover includes fireproof lining and the stainless steel shell that is wrapped in the outer layer of fireproof lining, and the movable cover of furnace cover is established in the open mouth of the upper end of intermediate frequency smelting furnace, to form the closed interval between the inner chamber of furnace cover and the liquid level of molten steel in the inner chamber of intermediate frequency smelting furnace, and the lower end of furnace cover is along the annular isolation ring of asbestos material between the outer wall of the upper end of intermediate frequency smelting furnace along the mouth, and one end of air pipe A is communicated to the closed interval, and the other end of air pipe A is communicated to the gas source.

[0021] The utility model still further discloses a technical scheme: bottom blowing device includes air pipe B, and the middle part of air pipe B is equipped with flow control valve, and one end of air pipe B is connected on the steel pipe of the lower end of air brick, and the other end of air pipe B is communicated to the gas source.

[0022] Compared with the prior art, the utility model has the following advantages:

[0023] 1. Its billet manufacturing for high-temperature alloy welding wire, with the unique high-temperature alloy welding wire production process, realizes the short process, continuous and low-cost production of high-temperature alloy welding wire. Based on the production system and the production process, the high-temperature alloy welding wire product has high purity, good density, uniform crystal structure, low center crack and shrinkage. The short process is reflected in: the electric secondary remelting and forging process are omitted, which is equivalent to shortening the core process before post-processing. The continuous is reflected in: the core process before post-processing realizes seamless docking and continuous discharge. The low cost is reflected in: the shortening of the process and the continuous of the process, which reduces the labor cost, waste and loss.

[0024] 2. It realizes the argon stirring at the bottom of the furnace by using the bottom blowing device, and realizes the argon sealing above the liquid surface by using the upper blowing device, which ensures the high purity of the high-temperature alloy material; and the whole smelting process is completed in the same furnace, which effectively solves the problem of secondary oxidation of molten steel.

[0025] 3. It effectively reduces the inclusions (inclusions are divided into four categories: sulfides, aluminum oxides, silicates and spherical oxides) and gases (dissolved oxygen and dissolved nitrogen) in the molten steel in the refining operation, greatly improves the purity of the molten steel, and then makes the various indicators of the subsequent continuous casting billet equivalent to those of the traditional "vacuum induction melting + electric secondary remelting" process. The principle of removing inclusions is as follows: the bubbles generated by the bottom blowing of inert gas (blowing argon from the bottom of the intermediate frequency melting furnace) float up in the molten steel, contact the inclusions in the molten steel and adsorb the inclusions on the bubble wall, and finally transfer to the liquid slag material with the bubble floating up; non-metallic inclusions are directly adsorbed by the liquid slag material to form composite inclusions; the oxides in the molten steel first react with the deoxidizer, and then the reaction product reacts with the liquid slag material to form composite inclusions; the above two types of composite inclusions are insoluble in molten steel and have a specific gravity less than that of molten steel, and float on the surface of the molten steel. The principle of removing gas is as follows: the bubbles generated by the bottom blowing of inert gas (blowing argon from the bottom of the intermediate frequency melting furnace) form a local vacuum in the molten steel, and a pressure difference is formed at the interface between the bubble and the molten steel, which causes the dissolved oxygen and dissolved nitrogen in the molten steel to be continuously absorbed into the bubble, causing the bubble to continuously grow, float up and overflow the surface of the liquid slag material, and finally greatly reducing the gas content in the molten steel.

[0026] 4. It effectively reduces the phosphorus and sulfur content in the molten steel by argon stirring at the bottom of the furnace (achieved based on the bottom blowing device), which reduces the requirement for the phosphorus and sulfur content in the raw materials.

[0027] The utility model will be further described in conjunction with the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 This is a schematic diagram of the structure of this utility model;

[0029] Figure 2 This is a flow chart of the production process for high-temperature alloy welding wire.

[0030] Figure 3 This is a state diagram of the medium-frequency melting furnace in step S01 of the production process.

[0031] Figure 4 Metallographic image of the cross section of the finished high-temperature alloy welding wire;

[0032] Figure 5 This is a flowchart of the existing high-temperature alloy welding wire production process.

[0033] Legend: Medium frequency melting furnace 1; Opening 11; Water inlet 12; Permeable brick 13; Steel pipe 14; Bottom blowing device 2; Air inlet pipe B21; Flow control valve 22; Upper blowing device 3; Furnace cover 31; Air inlet pipe A32; Annular isolation ring 33; Crystallizer 4; Roller 5. Detailed Implementation

[0034] Example 1:

[0035] like Figure 1 As shown, the short-process high-temperature alloy welding wire production system includes a medium-frequency melting furnace 1, a bottom blowing device 2, an upper blowing device 3, a crystallizer 4, and a billet puller 5.

[0036] The medium-frequency melting furnace 1 has a heating element (not shown in the figure) in its inner cavity, an opening 11 at the upper end, a water inlet 12 at the lower end, and an air inlet at the bottom.

[0037] The bottom blowing device 2 is connected to the air inlet at the bottom of the medium-frequency melting furnace 1 and is used to blow inert gas into the inner cavity of the medium-frequency melting furnace 1.

[0038] The upper blowing device 3 is movably installed on the opening 11 at the upper end of the medium-frequency melting furnace 1, and is used to blow inert gas above the liquid surface in the inner cavity of the medium-frequency melting furnace 1.

[0039] The crystallizer 4 has an inlet and an outlet at its two ends. The inlet of the crystallizer 4 is connected to the water outlet 12 of the medium frequency melting furnace 1. The billet pulling machine 5 has a dummy bar at one end, which is directly opposite the outlet of the crystallizer 4 and is used to pull out the billet.

[0040] Preferably, the bottom of the medium-frequency melting furnace 1 is provided with an installation port, in which a permeable brick 13 is sealed and fixedly installed. The upper end of the permeable brick 13 is located in the inner cavity of the medium-frequency melting furnace 1, and the lower end of the permeable brick 13 is located outside the medium-frequency melting furnace 1. A steel pipe 14 is provided at the lower end of the permeable brick 13, and the end of the steel pipe 14 is the air inlet. The permeable brick 13 has the characteristics of isolating molten steel and allowing air to pass through.

[0041] Preferably, the upper air blowing device 3 includes a furnace cover 31 and an air inlet pipe A32. The furnace cover 31 is movably installed at the opening 11 at the upper end of the medium-frequency melting furnace 1, thereby forming a closed area between the inner cavity of the furnace cover 31 and the molten steel surface in the inner cavity of the medium-frequency melting furnace 1. An asbestos-made annular insulating ring 33 is provided between the inner wall of the lower edge of the furnace cover 31 and the outer wall of the upper edge of the medium-frequency melting furnace 1. One end of the air inlet pipe A32 is connected to the closed area, and the other end of the air inlet pipe A32 is connected to the gas source (inert gas source).

[0042] Preferably, the bottom air blowing device 2 includes an air inlet pipe B21; a flow control valve 22 is provided in the middle of the air inlet pipe B21, one end of the air inlet pipe B21 is connected to the steel pipe 14 at the lower end of the permeable brick 13, and the other end of the air inlet pipe B21 is connected to the air source (inert gas source).

[0043] like Figures 1-3 As shown, the short-process high-temperature alloy welding wire production process is based on the aforementioned short-process high-temperature alloy welding wire production system. The grades of high-temperature alloys include, but are not limited to, GH3536, GH4090, GH3625, NS3103, and NS3105.

[0044] The process steps are as follows:

[0045] S01, bottom-blown inert gas medium-frequency smelting:

[0046] A. Smelting: Before feeding the high-temperature alloy raw materials into the furnace, they are weighed again and the batching ratio is checked. Based on the batching ratio of the final product, additional alloy materials are selected and added. The slag-forming material and the high-temperature alloy raw materials are fed into the medium-frequency melting furnace in sequence. The medium-frequency melting furnace is started to melt the high-temperature alloy raw materials into molten steel and the solid slag-forming material into liquid slag. The liquid slag is insoluble in molten steel and has a lower specific gravity than molten steel. It floats on the surface of the molten steel, isolates the air, and adsorbs (some) inclusions in the molten steel.

[0047] B, refining: b1, slag removal and addition: after the molten steel temperature reaches the refining temperature (the corresponding refining temperature of different grades of high-temperature alloy is common knowledge), the liquid slag material (which has absorbed impurities and become waste material) on the surface of the molten steel is removed, and new slag material is added; b2, slagging and slagging: inert gas is blown into the cavity of the intermediate frequency melting furnace through the bottom blowing device, the molten steel is stirred by the bubbles (manual stirring with a slagging rod is an alternative stirring method), the slagging material is broken and the heat in the molten steel is fully transferred to the slagging material, and the solid slagging material is melted into liquid slagging material (industry term: slagging and slagging); b3, deoxidizing slagging: deoxidizing agent is added to the liquid slagging material, and stirring is maintained during the addition process. The bubbles generated by the bottom blowing of inert gas contact the inclusions in the molten steel during the floating process and adsorb the inclusions (inclusions are divided into four categories: sulfides, aluminum oxides, silicates, and spherical oxides) on the bubble wall, and finally transfer to the liquid slagging material as the bubbles float. Non-metallic inclusions are directly adsorbed by the liquid slagging material to form composite inclusions, and the oxides in the molten steel first react with the deoxidizing agent, and then the reduced reaction product reacts with the liquid slagging material to produce composite inclusions (industry term: slagging). Both types of composite inclusions are insoluble in molten steel and have a specific gravity less than that of molten steel, and float on the surface of the molten steel.

[0048] S02, horizontal continuous casting with inert gas:

[0049] After the temperature of the molten steel reaches the casting temperature (the corresponding casting temperature of different grades of high-temperature alloy is common knowledge), the cover 31 is placed on the opening 11 of the intermediate frequency melting furnace 1, inert gas is supplied to the cavity between the liquid slagging material and the lower part of the cover through the upper blowing device, which can remove air (air leaks from the annular isolation ring) and prevent the molten steel from being oxidized. The intermediate frequency melting furnace 1 discharges the refined molten steel through the water gap 12, the molten steel enters the crystallizer 4, and the billet shell is formed. The billet is continuously pulled out of the crystallizer 4 by the horizontal movement of the dummy bar driven by the billet pulling machine 5, realizing horizontal continuous casting.

[0050] S03, post-processing:

[0051] The pulled billet is cut to the required length (i.e. the length required by the process), and the high-temperature alloy welding wire semi-finished product is obtained. The high-temperature alloy welding wire semi-finished product is peeled by a lathe to remove surface defects (horizontal continuous casting inherent defects: cold grid) on the outer circular surface. The disc is then prepared by hot continuous rolling process to meet the subsequent drawing requirements. The disc is sequentially subjected to solid solution, pickling, rough drawing and fine drawing processes, and the wire diameter is gradually reduced to the process requirement, i.e. the high-temperature alloy welding wire product is obtained.

[0052] Preferably, in the deoxidation slagging operation of the refining step in S01, the deoxidizer is added once every 0.5-5 minutes, and the number of additions is more than 50 times, and after each addition of the deoxidizer, the slag is melted into a liquid slag by point slagging operation, so as to ensure the continuity of deoxidation and the uniformity of deoxidizer distribution during the whole refining process.

[0053] Preferably, in the deoxidation slagging operation of the refining step in S01, after adding the deoxidizer at least 40 times, the composition of the molten steel is detected by sampling with a sampler, and according to the detection result, the additional alloying material is added for melting; then the composition of the molten steel is detected by sampling with a sampler, and when the composition of the molten steel is qualified, the deoxidizer is finally added at least 10 times.

[0054] Preferably, in S01, the amount of slagging material added twice is determined according to the amount of liquid slag formed after melting, which can completely cover the surface of the molten steel.

[0055] Preferably, in S01, the amount of slagging material added twice is determined according to the amount of liquid slag formed after melting, which can completely cover the surface of the molten steel.

[0056] Preferably, in S01, after the additional alloying material is selected and matched, it is placed in a drying box and kept at 100-150℃ for standby.

[0057] Preferably, in S01, after the high-temperature alloy raw material is added to the furnace, it is heated to 450-550℃ and baked for 4h to ensure dryness and no water vapor.

[0058] Preferably, in S01, this step is only performed when the air humidity is ≤60%, so as to reduce the influence of the external environment on the product quality.

[0059] Preferably, in S01, the static air height during smelting of the molten steel is ≥20cm, so as to ensure that the molten steel and the slagging material do not overflow when they are stirred and fluctuated by the inert gas.

[0060] Preferably, in S01, the deoxidizer is one or a combination of aluminum powder, aluminum particles, nickel-magnesium alloy, and silicon-calcium alloy.

[0061] Preferably, in S01, the slagging material is quicklime, or a mixture of quicklime and fluorite; in the mixture, the weight percentage of quicklime is 90-95%, and the balance is fluorite. The addition of fluorite is used to increase the fluidity of the liquid slag (the name of the liquid slag after the slagging material is melted into a liquid).

[0062] Preferably, in S01, the inert gas is argon with a purity of more than 99.99%, or krypton with a purity of more than 99.99%, or helium with a purity of more than 99.99%.

[0063] Preferably, in the S03 step, the peeling depth is determined by the removal of defects on the outer cylindrical surface of the superalloy welding wire semi-finished product.

[0064] In this embodiment, the superalloy welding wire is made of superalloy of GH3625 brand. In the process of using the above process, the parameters of the key process nodes are as follows:

[0065] In the A sub-step of the S01 step, the smelting temperature is 1450±20℃; in the B sub-step of the S01 step, the refining temperature is 1540-1590℃.

[0066] In the S02 step, the start casting temperature is 1590±10℃, the continuous casting temperature is 1530-1580℃, and the casting blank pulling speed is 0.5-1.5m / min.

[0067] The molten steel obtained after the B sub-step of the S01 step is sampled to detect the contents of phosphorus and sulfur elements, and the detection results are compared with the contents of phosphorus and sulfur elements in the raw materials. The results are shown in Table 1, which shows that the process can effectively remove the phosphorus and sulfur elements in the raw materials.

[0068] Table 1:

[0069]

[0070]

[0071] The oxygen content of the casting blank obtained in the S02 step is detected, and the detection results are compared with the oxygen content in the raw materials. The results are shown in Table 2, which shows that the process can effectively remove the oxygen element in the raw materials.

[0072] Table 2:

[0073] Element O element (ppm) Raw material 117 Internal control value 50 Detection value 11

[0074] The metallographic detection of the cross section of the superalloy welding wire product prepared in the S03 step is carried out, as shown in Figure 4 The detection results show that the product grain reaches 8-10 levels, meeting the process requirements. It can be seen that the superalloy welding wire prepared by the process has fine grains, which indirectly proves that the material has high yield strength and good plasticity and toughness.

[0075] The high-temperature alloy welding wire product prepared in the S03 step is detected for inclusion content according to GB / T10561-2005 / ISO 4967:1998(E) (Standard Rating Diagram Microscope Detection Method for Determination of Non-metallic Inclusion Content in Steel), and the detection result is compared with the inclusions in the molten steel before the refining stage in the S01 step, and the result is shown in Table 3. Among them, the A-type inclusions (sulfides) reach 0.5 level (the highest level), the B-type inclusions (aluminum oxide) reach 0.5 level (the highest level), the C-type inclusions (silicate) reach 0.5 level (the highest level), and the D-type inclusions (spherical oxides) reach 1 level (the second level). It can be seen that the present process can effectively purify and remove inclusions.

[0076] Table 3:

[0077] Inclusion class Grade A (sulfide) 0.5 B (alumina) 0.5 C (silicate) 0.5

[0078]

[0079] After the high-temperature alloy welding wire product is prepared according to the above process, mechanical property detection is performed. Among them, the tensile strength is 874 Mpa, the yield strength is 430 Mpa, the elongation (under tensile test) is 55%, the shrinkage (under compression test) is 46%, and the hardness is 322 HB, which meets the process requirements.

Claims

1. A short process superalloy welding wire production system characterized by: The utility model relates to a horizontal continuous casting crystallizer and its production method, which comprises a medium-frequency smelting furnace, a bottom blowing device, an upper blowing device, a crystallizer and a drawing machine.

2. The short process superalloy welding wire production system of claim 1, wherein: The bottom blowing device is connected to the air inlet at the bottom of the medium-frequency smelting furnace and is used to blow inert gas into the inner cavity of the medium-frequency smelting furnace.

3. The short process superalloy welding wire production system of claim 2, wherein: The upper blowing device is movably installed on the open top of the medium-frequency smelting furnace and is used to blow inert gas above the liquid surface in the inner cavity of the medium-frequency smelting furnace.

4. The short process superalloy welding wire production system of claim 3, wherein: The bottom blowing device comprises an air inlet pipe B, and the middle part of the air inlet pipe B is provided with a flow control valve. One end of the air inlet pipe B is connected to the steel pipe at the lower end of the air brick, and the other end of the air inlet pipe B is connected to a gas source.

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