An apparatus and method for producing foamed steel

Abstract

This invention relates to the field of porous metal material preparation technology, and discloses an apparatus and method for preparing foamed steel. The apparatus includes a furnace body, a crucible, a heating element, a lifting mechanism, a stirring assembly, a feeding hopper, and a rotary joint. The stirring assembly includes a coaxial inner stirring tube, a coaxial outer stirring tube sleeved outside the inner stirring tube, and a hollow stirring paddle located at the bottom. The inner cavity of the coaxial inner stirring tube forms a powder conveying channel, and an annular channel is formed between the coaxial outer stirring tube and the inner stirring tube. The feeding hopper is connected to the powder conveying channel, and the rotary joint is connected to both the powder conveying channel and the annular channel. The hollow stirring paddle has a discharge port at its bottom and air jets on its sidewall. This apparatus can deliver thickeners and foaming agents into the molten steel and complete the stirring and foaming process under inert gas protection, improving the uniformity of powder dispersion and the stability of the foam cells.

Description

Technical Field

[0001] This invention relates to the field of porous metal material preparation technology, and in particular to an apparatus and method for preparing foamed steel. Background Technology

[0002] Foamed steel is a porous metallic material with a large number of pores distributed in a steel or iron-based alloy matrix. It combines the strength and heat resistance of metallic materials with the lightweight, sound absorption, heat insulation, and electromagnetic shielding properties of porous materials. It has application potential in aerospace, transportation, construction engineering, protective energy absorption and integrated functional structural components.

[0003] Melt foaming is one of the important methods for preparing foamed metals. For foamed steel, due to the high melting point of steel and iron-based alloys, the preparation process usually requires melting and foaming at around 1500℃ or even higher. High-temperature steel melt is characterized by high density, high temperature, and easy oxidation. The thickeners and foaming agents are mostly powdered carbides, nitrides, or carbonates, whose density, wettability, and thermal stability are significantly different from those of steel melt.

[0004] In existing processes, if thickeners or foaming agents are added to molten steel using a top-feeding method, the powder material tends to float on the surface of the molten steel, making it difficult to penetrate the melt and disperse evenly. Simultaneously, the powder is prone to burning, agglomeration, or failure near the high-temperature liquid surface, resulting in unstable thickening and foaming effects. If only a conventional agitator is used for stirring, the powder's delivery path into the melt is uncontrollable, leading to uneven dispersion of the foaming agent, easily forming bubbles with large pore sizes, and even causing localized bubble collapse, large pores, or concentrated inclusions.

[0005] Furthermore, molten steel is prone to oxidation at high temperatures, and the preparation process of foamed steel requires a relatively stable inert atmosphere for protection. Traditional melting furnaces and conventional stirring devices often cannot simultaneously meet the requirements of furnace sealing, dynamic ventilation protection, deep powder feeding, and high-speed stirring and dispersion. Therefore, there is a need for a foamed steel preparation apparatus and method that can deliver thickeners and foaming agents into the interior of molten steel and complete stirring and foaming under inert gas protection. Summary of the Invention

[0006] The purpose of this invention is to provide an apparatus and method for preparing foamed steel, so as to improve the problems of powdered thickeners and foaming agents being prone to floating, burning, uneven dispersion, and difficulty in controlling the protective atmosphere in the furnace in high-temperature steel melt.

[0007] To achieve the above objectives, the present invention provides an apparatus for preparing foamed steel, comprising a furnace body, a base, a crucible, a heating element, a lifting mechanism, a stirring assembly, a feeding hopper, and a rotary joint. The furnace body is provided with a base, the crucible is disposed on the base, the heating element is arranged around the crucible, the lifting mechanism is disposed on the outside of the furnace body, and the stirring assembly is mounted on the lifting mechanism and can move up and down relative to the crucible with the lifting mechanism.

[0008] The mixing assembly includes a mixing motor, a coaxial inner mixing tube, a coaxial outer mixing tube, and a hollow mixing paddle. The coaxial outer mixing tube is sleeved outside the coaxial inner mixing tube. The inner cavity of the coaxial inner mixing tube forms a powder conveying channel, and an annular channel is formed between the coaxial outer mixing tube and the coaxial inner mixing tube. The hollow mixing paddle is connected to the lower ends of the coaxial inner and outer mixing tubes. The bottom of the hollow mixing paddle has a discharge port communicating with the powder conveying channel, and the sidewall of the hollow mixing paddle has an air jet port communicating with the annular channel. The mixing motor is located at the other end of the coaxial inner and outer mixing tubes. The discharge end of the feeding hopper communicates with the powder conveying channel. The rotary joint is located outside the coaxial inner and outer mixing tubes and communicates with both the powder conveying channel and the annular channel.

[0009] Furthermore, the rotary joint is provided with a first gas flow channel and a second gas flow channel that are independent of each other. The first gas flow channel is connected to the powder conveying flow channel, and the second gas flow channel is connected to the annular gap flow channel. Thus, during the rotation of the stirring assembly, one path of inert gas can enter the powder conveying flow channel and assist in the downward conveying of powder, while another path of inert gas can enter the annular gap flow channel and be discharged through the jet nozzle on the side wall of the hollow stirring paddle.

[0010] Furthermore, the lifting mechanism includes a lifting slide rail, a lifting motor, and a horizontal support. The lifting slide rail is vertically arranged, and the horizontal support extends above the furnace body. The stirring assembly is mounted on the horizontal support, and the central axis of the stirring assembly coincides with the central axis of the crucible. The horizontal support moves along the lifting slide rail under the drive of the lifting motor. With this structure, the stirring assembly can switch between a standby position and a working position extending into the crucible.

[0011] Furthermore, flanges are provided at the top and bottom openings of the furnace body, and the coaxial stirring outer tube passes through the flange at the top opening of the furnace body and extends downward into the crucible. The flange at the top opening of the furnace body has an outlet communicating with the inner cavity of the furnace, and the flange at the bottom opening of the furnace body has an inlet communicating with the inner cavity of the furnace. Through the combined action of the furnace inlet, outlet, and annular flow channel, an inert atmosphere environment can be formed inside the furnace.

[0012] Furthermore, the foamed steel preparation apparatus also includes at least two thermocouples. One thermocouple extends from the flange at the bottom opening of the furnace body, passes through the base, and approaches the crucible. The other thermocouple extends from the side of the furnace body and approaches the heating element. By monitoring at least two temperature points, the melt temperature and the temperature of the furnace heating zone can be separately determined, thereby improving the stability of foaming temperature control.

[0013] The present invention also provides a method for preparing foamed steel, which is implemented using the above-mentioned foamed steel preparation apparatus and includes the following steps: S1. Under an inert atmosphere, steel is placed in the crucible and heated until it melts to obtain molten steel. S2. A thickening agent is added to the steel melt through the feeding bin and the powder conveying channel, and the steel melt after adding the thickening agent is stirred and thickened by the hollow stirring paddle. S3. Cool the thickened steel melt to the foaming temperature range and keep it at that temperature; S4. Foaming agent is added into the cooled steel melt through the feeding hopper and the powder conveying channel, and the steel melt after adding foaming agent is stirred and foamed by the hollow stirring paddle. S5. Cool and solidify the stirred and foamed steel melt to obtain foamed steel.

[0014] Further, in step S1, the steel is carbon steel, alloy steel, or iron-based alloy; in step S1, the heating temperature is 1600℃ and the holding time is 1h; in step S3, the foaming temperature range is 1350℃~1550℃ and the holding time is 0.5h.

[0015] Further, the tackifier is SiC or VC, the particle size of the tackifier is 5μm to 15μm, and the amount added is 1% to 10% of the mass of the steel; the foaming agent is Cr2N or SrCO3, the particle size of the foaming agent is 5μm to 15μm, and the amount added is 1% to 10% of the mass of the steel.

[0016] Further, the inert atmosphere is argon; in steps S1 to S4, argon is introduced through the air inlet at the bottom of the furnace body and the annular flow channel at a flow rate of 0.5 L / min to 2 L / min; in steps S2 and S4, argon is introduced through the powder conveying channel at a flow rate of 0.5 L / min to 2 L / min; the stirring rate in steps S2 and S4 is 1500 r / min to 2500 r / min, and the stirring time is 8 min to 15 min.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: First, the present invention forms a powder conveying channel through a coaxial stirring inner tube and connects the powder conveying channel with the discharge port at the bottom of the hollow stirring paddle, which can convey the thickener and foaming agent to the interior of the steel melt, reducing the situation where the powder floats, burns or agglomerates on the surface of the steel melt.

[0018] Secondly, the present invention forms an annular flow channel between the coaxial outer stirring tube and the coaxial inner stirring tube, and connects the annular flow channel with the jet port on the side wall of the hollow stirring paddle, so that inert gas can be discharged into the steel melt and its surrounding area at the stirring paddle, thereby improving the atmosphere protection state of the stirring area and reducing the risk of high temperature steel melt backflow and blockage of the pipeline.

[0019] Third, the present invention introduces inert gas into the coaxial pipeline in a rotating state through a rotary joint, so that powder conveying, inert gas protection and high-speed stirring can be realized on the same stirring component, which is suitable for the requirements of deep feeding and dynamic atmosphere protection in the foaming process of foamed steel melt.

[0020] Fourth, the present invention adds a foaming agent after cooling to the foaming temperature range after thickening, which helps to match the viscosity of the steel melt with the process of bubble generation, growth and retention, thereby improving the uniformity of the internal pore structure of the foam steel. Attached Figure Description

[0021] Figure 1 This is a schematic cross-sectional view of the overall structure of the apparatus for preparing foamed steel according to the present invention; Figure 2 This is a schematic diagram of the feeding hopper in the device of the present invention; Figure 3 This is a top view of the feeding hopper in the device of the present invention; Figure 4 This is a schematic diagram of the internal gas flow channel of the rotary joint in the device of the present invention; Figure 5 This is a bottom cross-sectional view of the rotary joint in the device of the present invention; Figure 6 This is a schematic diagram of the internal flow channel structure of the hollow stirring paddle in the device of the present invention; Figure 7 This is a side view of the internal flow channel of the hollow stirring paddle in the device of the present invention.

[0022] Explanation of reference numerals in the attached figures: 1: Stirring motor; 2: Solid outer tube; 3: Feeding bin; 4: Coaxial stirring inner tube; 5: Rotary joint; 6: Coaxial stirring outer tube; 7: Air outlet; 8: Flange; 9: Lifting slide rail; 10: Heating element; 11: Lifting motor; 12: Crucible; 13: Hollow stirring paddle; 14: Base; 15: Air inlet; 16: Thermocouple. Detailed Implementation

[0023] These embodiments are provided to make the invention thorough and complete, and to fully express the scope of the invention to those skilled in the art. It should be noted that, unless otherwise specifically stated, the relative arrangement of components and steps, material composition, numerical expressions, and values ​​set forth in these embodiments should be interpreted as merely exemplary and not as limiting.

[0024] In the following embodiments, the foamed steel preparation device mainly achieves the conveying of powdered thickener or foaming agent into the steel melt through the cooperation between the coaxial stirring inner tube 4, the coaxial stirring outer tube 6, the rotary joint 5, and the hollow stirring paddle 13, while maintaining inert gas protection during the conveying process. Specifically, the inner cavity of the coaxial stirring inner tube 4 serves as a powder conveying channel, used to guide the thickener or foaming agent from the feeding bin 3 to the hollow stirring paddle 13, and discharge it into the steel melt through the discharge port at the bottom of the hollow stirring paddle 13; the annular channel formed between the coaxial stirring outer tube 6 and the coaxial stirring inner tube 4 serves as a gas conveying channel, used to guide the inert gas to the hollow stirring paddle 13, and discharge it through the jet nozzle on the side wall of the hollow stirring paddle 13.

[0025] With the above structure, powdered materials are no longer added directly from above the surface of the molten steel. Instead, they can enter the deep region of the molten steel from the bottom of the hollow stirring paddle 13 after the stirring assembly extends into the molten steel. Simultaneously, the hollow stirring paddle 13 rotates under the drive of the stirring motor 1, causing the thickener or foaming agent entering the molten steel to be dispersed by stirring and shearing. The inert gas discharged from the annular channel forms a gas protection near the stirring paddle and reduces the risk of blockage caused by high-temperature molten steel entering the channel. Therefore, in the following embodiments, regardless of whether carbon steel, alloy steel, or iron-based alloy is used as the matrix material, or different types of thickeners and foaming agents are used, foamed steel can be prepared through this deep feeding, simultaneous aeration, and rotary stirring method.

[0026] It should be noted that the parameters listed in the following embodiments, such as matrix material, thickener, foaming agent, particle size, dosage, temperature, stirring rate, stirring time, and argon flow rate, are all used to illustrate specific implementation methods of the technical solution of the present invention. Without departing from the technical concept of the present invention, those skilled in the art can make appropriate adjustments to the relevant parameters based on the steel type, crucible capacity, target porosity, target pore size, and equipment dimensions.

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the following embodiments are only used to illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention. Where there is no structural conflict, the technical features in the following embodiments can be combined with each other.

[0028] Example 1 This embodiment provides a foamed steel preparation apparatus.

[0029] like Figures 1 to 7 As shown, the foamed steel preparation apparatus includes a furnace body, a base 14, a crucible 12, a heating element 10, a lifting mechanism, a stirring assembly, a feeding bin 3, and a rotary joint 5. The base 14 is disposed within the furnace body, forming a space to accommodate the crucible 12 and the heating element 10. The crucible 12 is placed on the base 14 and is used to hold the steel or iron-based alloy material to be melted. The heating element 10 is arranged around the crucible 12 to heat the metal material inside the crucible 12, causing it to form molten steel.

[0030] Flanges 8 are installed at the top and bottom openings of the furnace body. When fitted together, the flanges 8 create a relatively enclosed working space within the furnace cavity. An air inlet 15 is located at the bottom opening of the furnace body, and an air outlet 7 is located at the top opening. During the foamed steel preparation process, inert gas enters the furnace cavity through the air inlet 15 and exits through the air outlet 7, thereby creating an inert atmosphere within the furnace and reducing oxidation of the molten steel at high temperatures.

[0031] The lifting mechanism is located on the outside of the furnace body and includes a lifting slide rail 9, a lifting motor 11, and a horizontal support. The lifting slide rail 9 extends vertically, and the horizontal support has a right-angled structure. One end of the horizontal support engages with the lifting slide rail 9, and the other end extends above the furnace body. The stirring assembly is mounted on the horizontal support. The lifting motor 11 drives the horizontal support to move up and down along the lifting slide rail 9, thereby moving the stirring assembly between the standby position and the working position. When the stirring assembly is in the standby position, the hollow stirring paddle 13 is located above the crucible 12 or above the surface of the molten steel; when the stirring assembly is in the working position, the hollow stirring paddle 13 extends into the molten steel inside the crucible 12.

[0032] The stirring assembly includes a stirring motor 1, a solid outer tube 2, a coaxial inner stirring tube 4, a coaxial outer stirring tube 6, and a hollow stirring paddle 13. The coaxial inner stirring tube 4 and the coaxial outer stirring tube 6 are mounted on a transverse support. The solid outer tube 2 is located at the end of the coaxial inner stirring tube 4 and the coaxial outer stirring tube 6 furthest from the crucible 12, facilitating connection to the stirring motor 1 and torque transmission. The hollow stirring paddle 13 is connected to the end of the coaxial inner stirring tube 4 and the coaxial outer stirring tube 6 closest to the crucible 12. The stirring motor 1, connected to the solid outer tube 2, drives the coaxial inner stirring tube 4, the coaxial outer stirring tube 6, and the hollow stirring paddle 13 to rotate synchronously.

[0033] The coaxial stirring outer tube 6 is sleeved on the outside of the coaxial stirring inner tube 4. The inner cavity of the coaxial stirring inner tube 4 forms a powder conveying channel, and the inner wall of the coaxial stirring outer tube 6 and the outer wall of the coaxial stirring inner tube 4 form an annular channel. The powder conveying channel is mainly used to convey powdered materials such as thickeners or foaming agents, while the annular channel is mainly used to convey inert gases.

[0034] The feeding bin 3 is located below the solid outer tube 2, and its discharge end is connected to the inner cavity of the coaxial stirring inner tube 4. Exemplarily, a through hole is formed in both the coaxial stirring outer tube 6 and the coaxial stirring inner tube 4. A corresponding through hole is also formed in the feeding bin 3. When the coaxial stirring outer tube 6 and the coaxial stirring inner tube 4 rotate, and the two through holes align and overlap, the material can enter the inner cavity of the coaxial stirring inner tube 4 through the discharge end of the feeding bin 3, completing the feeding process. After the thickener or foaming agent is added to the feeding bin 3, it can enter the inner cavity of the coaxial stirring inner tube 4 and move downwards along the powder conveying channel. The feeding bin 3 can be filled with thickener and foaming agent at different process stages, or it can be cleaned or replaced after one type of powder is added before adding another type of powder.

[0035] The rotary joint 5 is located at the lower part of the feeding hopper 3 and is disposed outside the coaxial inner stirring tube 4 and the coaxial outer stirring tube 6. The rotary joint 5 has independent first and second gas flow channels. The first gas flow channel communicates with the inner cavity of the coaxial inner stirring tube 4, and the second gas flow channel communicates with the annular flow channel formed between the coaxial outer stirring tube 6 and the coaxial inner stirring tube 4. Through the rotary joint 5, inert gas can still enter the powder conveying flow channel and the annular flow channel respectively during the rotation of the coaxial inner stirring tube 4, the coaxial outer stirring tube 6, and the hollow stirring paddle 13.

[0036] In an exemplary configuration, the first air passage is equipped with a retaining ring, which is fitted onto the coaxial stirring outer tube 6. Several vent holes are circumferentially formed at the locations covered by the retaining ring on both the coaxial stirring outer tube 6 and the coaxial stirring inner tube 4. In the annular flow channel section where the vent holes are located, two annular plates are fixedly connected to the upper and lower sections of the vent holes, respectively, to isolate the first air passage from the annular flow channel. Gas from the first air passage passes through the vent holes of the coaxial stirring outer tube 6, then through the vent holes of the coaxial stirring inner tube 4, and finally enters the inner cavity of the coaxial stirring inner tube 4. Because of the two annular plates in the annular flow channel, gas can only enter the inner cavity of the coaxial stirring inner tube 4 after entering the coaxial stirring outer tube 6, and cannot enter the annular flow channel itself.

[0037] Exemplary, such as Figure 4 and Figure 5As shown, after the coaxial inner stirring tube 4 and the coaxial outer stirring tube 6 enter the rotary joint 5, the coaxial outer stirring tube 6 is divided into upper and lower sections. The first air passage is equipped with a retaining ring, which is fitted onto the coaxial inner stirring tube 4. Several vent holes are circumferentially formed at the position of the coaxial inner stirring tube 4 covered by the retaining ring. The retaining ring supplies air circumferentially, supplying air to the inner cavity of the coaxial inner stirring tube 4 through the vent holes. The second gas flow passage is connected to the annular gap flow passage formed between the lower half of the coaxial outer stirring tube 6 and the coaxial inner stirring tube 4. A ring plate is fixedly connected between the lower half of the coaxial outer stirring tube 6 and the coaxial inner stirring tube 4. The function of this ring plate is to transmit the torque of the coaxial inner stirring tube 4, driving the lower half of the coaxial outer stirring tube 6 to rotate synchronously. Simultaneously, multiple vent holes are circumferentially formed on the ring plate, allowing the second gas flow passage to connect with the annular gap flow passage formed between the coaxial outer stirring tube 6 and the coaxial inner stirring tube 4.

[0038] The hollow impeller 13 has a hollow cavity inside. The inner cavity of the coaxial inner stirring tube 4 is connected to the discharge port at the bottom of the hollow impeller 13, and the annular flow channel between the coaxial outer stirring tube 6 and the coaxial inner stirring tube 4 is connected to the jet port on the side wall of the hollow impeller 13. Thus, the thickener or foaming agent entering the powder conveying channel can be discharged into the steel melt through the bottom of the hollow impeller 13; and the inert gas entering the annular flow channel can be discharged through the jet port on the side wall of the hollow impeller 13.

[0039] During operation, the powdered material is not directly sprinkled into the molten steel from above, but is conveyed into the molten steel through the feeding bin 3, the coaxial stirring inner tube 4, and the discharge port at the bottom of the hollow stirring paddle 13. Since the hollow stirring paddle 13 is simultaneously rotating, the discharged powder can be quickly dispersed in the molten steel under the stirring action, reducing the possibility of powder floating on the surface of the molten steel, agglomerating, or burning. At the same time, the inert gas in the annular channel is discharged through the jet nozzle on the side wall of the hollow stirring paddle 13, forming a gas protection near the stirring paddle and disturbing the melt near the side wall of the hollow stirring paddle 13, while also reducing the risk of molten steel flowing back into the annular channel.

[0040] In this embodiment, the equipment for preparing foamed steel also includes flanges 8 respectively located at the top and bottom openings of the furnace body. A coaxial stirring outer tube 6 passes through the flange 8 located at the top opening of the furnace body. The flange 8 at the top opening of the furnace body has an outlet 7 communicating with the inner cavity of the furnace body, and the flange 8 at the bottom opening of the furnace body has an inlet 15 communicating with the inner cavity of the furnace body. Through the combined action of the furnace body inlet 15, outlet 7, and annular flow channel, an inert atmosphere environment can be formed inside the furnace.

[0041] In this embodiment, the apparatus for preparing foamed steel also includes at least two thermocouples 16. One thermocouple 16 extends from the flange 8 at the bottom opening of the furnace body and passes through the base close to the crucible 12 to monitor the temperature of the crucible 12 and the molten steel inside it; the other thermocouple 16 extends from the side of the furnace body and close to the heating element 10 to monitor the temperature of the heating zone of the furnace body. With these two temperature monitoring points, the temperature can be controlled during melting, thickening, cooling, and foaming processes, keeping the molten steel within the temperature range required for each process stage.

[0042] Example 2 This embodiment provides a method for preparing foamed steel using the apparatus described in Embodiment 1.

[0043] First, prepare the base material, carbon steel, and place it in crucible 12. Check the flanges 8 at the top and bottom of the furnace body to ensure the furnace body is sealed. Adjust the lifting mechanism to the ready-to-work position, so that the hollow stirring paddle 13 is temporarily positioned above crucible 12. Open the gas inlet 15 to introduce argon gas into the furnace body at a flow rate of 0.5 L / min. The gas inside the furnace body is discharged through the gas outlet 7, thereby gradually forming an argon protective atmosphere in the furnace cavity.

[0044] Subsequently, the heating element 10 is activated, and the carbon steel is heated to 1600℃ under argon protection and held at that temperature for 1 hour to completely melt the carbon steel, resulting in a steel melt with a relatively uniform temperature. During the heating and holding process, the temperature near the crucible 12 and the temperature of the furnace heating area are monitored by thermocouples 16 to determine whether the steel melt has reached the predetermined melting state. At the same time, argon gas is introduced into the annular flow channel through the rotary joint 5 at a flow rate of 0.5 L / min. The argon gas flows downward into the hollow stirring paddle 13 along the annular flow channel between the coaxial stirring outer tube 6 and the coaxial stirring inner tube 4, and is discharged from the jet port on the side wall of the hollow stirring paddle 13.

[0045] After the steel melt is melted and held at a constant temperature, 5% of the steel mass and 10μm of SiC powder are weighed out as a thickener and added to the feeding hopper 3. The horizontal support is driven by the lifting motor 11 to descend along the lifting slide rail 9, so that the hollow stirring paddle 13 gradually extends into the interior of the steel melt. After the hollow stirring paddle 13 reaches the predetermined working position, the stirring motor 1 is started and the stirring speed is set to 2000 r / min.

[0046] Driven by the stirring motor 1, the coaxial inner stirring tube 4, the coaxial outer stirring tube 6, and the hollow stirring paddle 13 rotate synchronously. Then, argon gas is introduced into the inner cavity of the coaxial inner stirring tube 4 through the rotary joint 5 at a flow rate of 0.5 L / min. The SiC powder in the feeding bin 3 enters the inner cavity of the coaxial inner stirring tube 4 under its own weight and with the assistance of argon gas, and moves downwards along the powder conveying channel. After reaching the hollow stirring paddle 13, the SiC powder enters the molten steel through the outlet at the bottom of the hollow stirring paddle 13.

[0047] Because the SiC powder is discharged from inside the molten steel where the hollow stirring paddle 13 is located, rather than being added from the surface of the molten steel, the possibility of powder floating on the liquid surface and burning off is reduced. After the hollow stirring paddle 13 rotates at high speed, it can shear and disperse the SiC powder that has just entered the molten steel, allowing the SiC powder to disperse quickly within the molten steel. Stirring is maintained at 2000 r / min for 10 minutes to complete the thickening treatment of the molten steel. After the thickening treatment is complete, the introduction of argon gas into the coaxial stirring inner tube 4 is stopped, the feeding state of the feeding chamber 3 is closed or paused, and the stirring assembly is lifted to the ready-to-work position using the lifting mechanism.

[0048] Then, the heating power of the heating element 10 is reduced, and the temperature of the molten steel in the crucible 12 is monitored by thermocouple 16. The thickened molten steel is cooled to 1450°C and held at 1450°C for 0.5 hours. This cooling and holding process ensures that the thickened molten steel reaches a temperature suitable for subsequent addition of the foaming agent and retention of bubbles. During this process, argon gas continues to be introduced through the gas inlet 15 and the annular flow channel to maintain an inert atmosphere in the furnace cavity and near the lower end of the stirring assembly.

[0049] Subsequently, Cr2N powder with a particle size of 10μm, accounting for 5% of the steel mass, is weighed out as a foaming agent and added to the feeding hopper 3. The horizontal support is then lowered along the lifting rail 9 by the lifting motor 11, allowing the hollow stirring paddle 13 to extend into the cooled molten steel. The stirring motor 1 is started, the stirring speed is set to 2000 r / min, and argon gas is introduced into the inner cavity of the coaxial stirring inner tube 4 through the rotary joint 5 at a flow rate of 0.5 L / min.

[0050] Cr2N powder is conveyed downwards along the powder conveying channel of the coaxial stirring inner tube 4 with argon assistance, and enters the interior of the molten steel through the discharge port at the bottom of the hollow stirring paddle 13. After entering the molten steel, the Cr2N powder is dispersed in the molten steel under the rotation of the hollow stirring paddle 13 and gradually participates in the foaming process. At the same time, argon gas continuously introduced into the annular channel is discharged through the jet port on the side wall of the hollow stirring paddle 13, which on the one hand forms a gas protection for the area near the stirring paddle, and on the other hand reduces the possibility of the molten steel flowing back into the hollow stirring paddle 13 and the coaxial pipeline.

[0051] Maintain stirring at 2000 rpm for 10 minutes to disperse the foaming agent in the molten steel and form bubbles. After stirring and foaming are complete, stop introducing argon gas into the coaxial stirring inner tube 4, turn off the stirring motor 1, and lift the stirring assembly to the ready-to-work position using the lifting mechanism. Then turn off the heating element 10 and allow the stirred and foamed molten steel to cool naturally in the crucible 12 until solidification, obtaining foamed steel.

[0052] The foam steel prepared in this embodiment has a relatively uniform internal cell distribution, with a pore size distribution deviation of no more than 20%, an average pore size of 2.2 mm to 2.6 mm, and a porosity of 70% to 80%.

[0053] Example 3 This embodiment is basically the same as embodiment 2, except that the matrix material is alloy steel, the particle size of the tackifier and the foaming agent is 12μm, and the amount of tackifier and foaming agent added is 3% of the mass of alloy steel.

[0054] Specifically, the alloy steel is placed in crucible 12 and heated to 1600℃ under an argon protective atmosphere and held for 1 hour to completely melt the alloy steel. During the melting process, argon gas is continuously introduced into the gas inlet 15 at the bottom of the furnace and the annular flow channel. After the alloy steel forms a steel melt, SiC powder with a particle size of 12μm is added to the feeding bin 3 and transported into the steel melt through the coaxial stirring inner tube 4 and the discharge port at the bottom of the hollow stirring paddle 13. The mixture is stirred at 1500r / min for 8 minutes to complete the thickening of the steel melt.

[0055] After the thickening treatment, the molten steel is cooled to 1400℃ and held at that temperature for 0.5 hours. Then, Cr2N powder with a particle size of 12μm is added to the feeding hopper 3 and conveyed to the hollow stirring paddle 13 through the coaxial stirring inner tube 4, entering the molten steel through the outlet at the bottom of the hollow stirring paddle 13. During the foaming process, the stirring rate is 1500 r / min, the stirring time is 8 min, and the argon gas flow rate through the coaxial stirring inner tube 4 is 1 L / min. After the foaming process is completed, the stirring assembly is raised, and the molten steel is cooled and solidified in the furnace to obtain foamed steel.

[0056] In this embodiment, the pore size distribution deviation at different locations inside the foamed steel does not exceed 20%, the average pore size is 2.2mm to 2.6mm, and the porosity is 71% to 79%.

[0057] Example 4 This embodiment is basically the same as embodiment 2, except that the matrix material is an iron-based alloy, the particle size of the thickener and the foaming agent is 15μm, and the amount of thickener and foaming agent added is 2% of the mass of the iron-based alloy.

[0058] Specifically, the iron-based alloy is placed in crucible 12 and heated to 1600°C under an argon protective atmosphere and held for 1 hour to completely melt the iron-based alloy. During melting, argon gas is continuously introduced into the gas inlet 15 at the bottom of the furnace and the annular flow channel to maintain an inert atmosphere inside the furnace and keep the area near the hollow stirring paddle 13 under gas protection.

[0059] After the iron-based alloy forms a melt, SiC powder with a particle size of 15μm is added to the feeding bin 3. The hollow stirring paddle 13 is lowered into the iron-based alloy melt using a lifting mechanism. The stirring motor 1 is started, and the stirring speed is set to 1500 r / min. Argon gas is introduced into the coaxial stirring inner tube 4 at a flow rate of 1.5 L / min, causing the SiC powder to flow downwards along the powder conveying channel into the hollow stirring paddle 13 and then into the iron-based alloy melt through the outlet at the bottom of the hollow stirring paddle 13. After continuous stirring for 8 minutes, the thickening treatment is completed.

[0060] After the thickening treatment, the iron-based alloy melt was cooled to 1380℃ and held at that temperature for 0.5 h. Then, Cr2N powder with a particle size of 15 μm was added to the feeding bin 3, and the hollow stirring paddle 13 was lowered to the working position again, and stirred at 1500 r / min for 8 min. The Cr2N powder entered the melt through the coaxial stirring inner tube 4 and the bottom outlet of the hollow stirring paddle 13. During the foaming process, argon gas in the annular flow channel was continuously discharged through the jet nozzle on the side wall of the hollow stirring paddle 13. After the stirring and foaming were completed, the stirring assembly was raised and the melt was cooled and solidified in the furnace to obtain foamed steel.

[0061] The pore size distribution deviation at different locations inside the foamed steel prepared in this embodiment does not exceed 20%, the average pore size is 2.5mm to 2.8mm, and the porosity is 73% to 80%.

[0062] Example 5 This embodiment is basically the same as embodiment 2, except that the tackifier is VC powder and the foaming agent is SrCO3 powder.

[0063] Specifically, carbon steel is placed in crucible 12 and heated to 1600℃ under argon protection and held for 1 hour to obtain molten steel. During the melting process, argon gas is continuously introduced into the gas inlet 15 at the bottom of the furnace and into the annular flow channel. The argon gas is discharged through the jet nozzle on the side wall of the hollow stirring paddle 13.

[0064] Subsequently, VC powder with a particle size of 5μm to 15μm is added as a thickener to the feeding hopper 3, with the amount of VC powder added being 1% to 10% of the steel mass. The hollow stirring paddle 13 is lowered into the molten steel using a lifting mechanism, and the stirring motor 1 is started, causing the hollow stirring paddle 13 to rotate at 1500 r / min to 2500 r / min. Argon gas is introduced into the coaxial stirring inner tube 4, causing the VC powder to move downwards along the powder conveying channel and enter the molten steel through the outlet at the bottom of the hollow stirring paddle 13. After continuous stirring for 8 to 15 minutes, the thickening treatment is completed.

[0065] After the thickening treatment, the molten steel is cooled to 1350℃~1550℃ and held at that temperature for 0.5h. Then, SrCO3 powder with a particle size of 5μm~15μm is added as a foaming agent to the feeding bin 3, with the amount of SrCO3 powder added being 1%~10% of the steel mass. The hollow stirring paddle 13 is lowered into the interior of the molten steel again, and argon gas is introduced into the coaxial stirring inner tube 4, allowing the SrCO3 powder to enter the interior of the molten steel through the powder conveying channel and the bottom outlet of the hollow stirring paddle 13. During the stirring and foaming process, the stirring speed is 1500r / min~2500r / min, and the stirring time is 8min~15min.

[0066] After the stirring and foaming process is completed, the argon gas supply to the coaxial stirring inner tube 4 is stopped, the stirring motor 1 is turned off, the stirring assembly is lifted to the ready-to-work position via the lifting mechanism, and the heating element 10 is turned off, allowing the molten steel to cool and solidify with the furnace, thus obtaining foamed steel. This embodiment illustrates that, in addition to the combination of SiC and Cr2N, VC and SrCO3 can also be added to the molten steel through the same deep feeding, inert gas protection, and high-speed stirring path, thereby completing the preparation of foamed steel.

[0067] Example 6 This embodiment illustrates the cooperative use of the powder conveying channel and the annular gap channel in the device of the present invention.

[0068] In the process of preparing foamed steel, the inner cavity of the coaxial stirring inner tube 4 is used as a powder conveying channel. When it is necessary to add thickeners or foaming agents, the powdered material is added to the feeding bin 3, and argon gas is introduced into the coaxial stirring inner tube 4 through the rotary joint 5. The argon gas flows downward along the powder conveying channel, which can help the powdered material enter the hollow stirring paddle 13, and enter the interior of the steel melt through the bottom outlet of the hollow stirring paddle 13.

[0069] Argon gas is continuously introduced into the annular channel between the coaxial outer stirring tube 6 and the coaxial inner stirring tube 4 during the heating, thickening, and foaming processes. The argon gas in the annular channel flows downward into the hollow stirring paddle 13 and is discharged through the jet nozzle on the side wall of the hollow stirring paddle 13. Since this gas outlet is located inside the molten steel or near the working area of ​​the stirring paddle, the discharged argon gas can form a local gas protection for the high-temperature molten steel area near the hollow stirring paddle 13, and can reduce the risk of high-temperature molten steel flowing back upward along the jet nozzle or channel.

[0070] In the stirring and thickening steps and the stirring and foaming steps, the powder conveying channel and the annular channel operate simultaneously. The powder conveying channel is used to transport powdered materials into the molten steel, while the annular channel is used to discharge inert gas in the stirring zone. The two are independent of each other, which reduces the possibility of powder clogging the gas protection channel and also allows for separate control of powder addition and gas protection.

[0071] Example 7 This embodiment is used to illustrate the lifting operation process of the device of the present invention.

[0072] During the heating and melting stage, the stirring assembly can be held in the ready-to-work position, with the hollow stirring paddle 13 positioned above the crucible 12 or above the surface of the molten steel. Once the steel or iron-based alloy has completely melted and reached the predetermined holding time, the horizontal support is driven by the lifting motor 11 to descend along the lifting rail 9, allowing the hollow stirring paddle 13 to gradually enter the molten steel. During the descent, argon gas can be continuously introduced into the annular flow channel, allowing argon gas to be continuously discharged from the vents on the sidewall of the hollow stirring paddle 13, thereby reducing the possibility of the molten steel entering the vents or annular flow channel.

[0073] After the hollow stirring paddle 13 descends to the predetermined working position, the stirring motor 1 is started for stirring. After the thickening or foaming step is completed, the feeding is stopped and the argon gas used to assist in powder conveying is stopped from entering the coaxial stirring inner tube 4. Then, the stirring motor 1 is turned off or the stirring speed is reduced. Subsequently, the stirring assembly is lifted to the working position by the lifting mechanism. During the lifting process, argon gas can continue to be introduced into the annular channel to keep the gas exhaust port on the side wall of the hollow stirring paddle 13 in a gas discharge state, thereby reducing the risk of adhering melt entering the channel. After the stirring assembly leaves the molten steel, the gas supply to the annular channel is maintained or stopped according to the needs of subsequent processes.

[0074] Through the above lifting operation, the stirring component can enter the steel melt when it needs to be fed and stirred, and leave the steel melt after completing the corresponding operation. This reduces the risk of the stirring component being damaged due to being in the high-temperature steel melt for a long time, and also facilitates the subsequent switching, cleaning or replenishment of the feeding bin 3.

[0075] Example 8 This embodiment illustrates the cooling and sampling process of foamed steel.

[0076] After the stirring and foaming process is complete, stop introducing argon gas into the coaxial stirring inner tube 4, stop adding foaming agent, and turn off the stirring motor 1. After raising the hollow stirring paddle 13 to the ready-to-work position using the lifting mechanism, turn off the heating element 10, allowing the foamed steel melt in the crucible 12 to cool naturally with the furnace. During the furnace cooling process, argon gas can continue to be introduced through the gas inlet 15 for a period of time to maintain an inert atmosphere in the furnace cavity and reduce oxidation of the foamed steel surface during the initial high-temperature cooling phase.

[0077] After the molten metal in crucible 12 has completely solidified and cooled to a temperature suitable for removal, open furnace flange 8 and remove the solidified foamed steel from crucible 12. After cutting the foamed steel, the distribution of bubbles in its cross-section can be observed, and the uniformity and porosity of the bubbles can be evaluated using methods such as pore size statistics, bulk density measurement, or image analysis in different regions. By comparing the pore size differences in different regions of the upper, middle, and lower parts of the foamed steel, the dispersion effect of the foaming agent in the molten steel can be determined.

[0078] When preparing foamed steel using the apparatus of this invention, the foaming agent enters the interior of the molten steel from the bottom of the hollow stirring paddle 13 and disperses under high-speed stirring; simultaneously, argon gas in the annular flow channel is discharged from the side wall of the hollow stirring paddle 13, ensuring a relatively stable gas protection environment in the foaming area. Therefore, compared with the top-spreading method, this invention is more advantageous in reducing the problem of uneven cell structure caused by the foaming agent floating on the liquid surface or local concentration.

[0079] The various embodiments of the present invention have now been described in detail. To avoid obscuring the concept of the invention, some details known in the art have not been described. Those skilled in the art can fully understand how to implement the technical solutions of this invention based on the above description.

[0080] The above embodiments are merely specific implementations of the present invention and are not intended to limit the present invention. Any equivalent substitutions or conventional adjustments made to the coaxial stirring inner tube 4, coaxial stirring outer tube 6, rotary joint 5, hollow stirring paddle 13, feeding bin 3, furnace atmosphere control method, or preparation process parameters under the concept of the present invention shall fall within the protection scope of the present invention.

[0081] It should be noted that, in the description of this invention, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientation or positional relationships, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0082] Furthermore, the terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different parts. "Vertical" is not strictly vertical, but within the permissible range of error. "Parallel" is not strictly parallel, but within the permissible range of error. Terms such as "including" or "comprising" mean that the element preceding the word encompasses the element listed after the word, and do not exclude the possibility of encompassing other elements as well.

[0083] It should also be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention depending on the specific circumstances. When a specific device is described as being located between a first device and a second device, an intermediary device may or may not be present between the specific device and the first or second device.

[0084] All terms used in this invention have the same meaning as understood by one of ordinary skill in the art to which this invention pertains, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant art, and not as idealized or highly formalized, unless expressly defined herein.

[0085] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0086] While specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art should understand that modifications can be made to the above embodiments or equivalent substitutions can be made to some technical features without departing from the scope and spirit of the invention. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any manner.

Claims

1. An apparatus for preparing foamed steel, comprising a furnace body, a base (14), a crucible (12), a heating element (10), a lifting mechanism, a stirring assembly, a feeding bin (3), and a rotary joint (5), wherein the base (14) is disposed inside the furnace body, the crucible (12) is disposed on the base (14), the heating element (10) is arranged around the crucible (12), the lifting mechanism is disposed outside the furnace body, and the stirring assembly is mounted on the lifting mechanism and is capable of moving up and down relative to the crucible (12) with the lifting mechanism, characterized in that: The stirring assembly includes a stirring motor (1), a coaxial stirring inner tube (4), a coaxial stirring outer tube (6), and a hollow stirring paddle (13). The coaxial stirring outer tube (6) is sleeved on the outside of the coaxial stirring inner tube (4). The inner cavity of the coaxial stirring inner tube (4) forms a powder conveying channel. An annular flow channel is formed between the coaxial stirring outer tube (6) and the coaxial stirring inner tube (4). The hollow stirring paddle (13) is connected to the lower end of the coaxial stirring inner tube (4) and the coaxial stirring outer tube (6). The bottom of the hollow stirring paddle (13) is provided with a discharge port that communicates with the powder conveying channel. The side wall of the hollow stirring paddle (13) is provided with a jet nozzle that communicates with the annular channel. The stirring motor (1) is located at the other end of the coaxial stirring inner tube (4) and the coaxial stirring outer tube (6). The discharge end of the feeding bin (3) is connected to the powder conveying channel; The rotary joint (5) is sleeved on the outside of the coaxial stirring outer tube (6) and the coaxial stirring inner tube (4), and the rotary joint (5) has fluid channels that are respectively connected to the powder conveying channel and the annular gap channel.

2. The apparatus for preparing foamed steel according to claim 1, characterized in that: The rotary joint (5) is provided with a first gas flow channel and a second gas flow channel that are independent of each other. The first gas flow channel is connected to the powder conveying flow channel, and the second gas flow channel is connected to the annular gap flow channel.

3. The apparatus for preparing foamed steel according to claim 1, characterized in that: The lifting mechanism includes a lifting slide rail (9), a lifting motor (11), and a horizontal support. The lifting slide rail (9) is arranged vertically, and the horizontal support extends above the furnace body. The stirring assembly is arranged on the horizontal support, and the central axis of the stirring assembly coincides with the central axis of the crucible (12). The horizontal support can move along the lifting slide rail (9) under the drive of the lifting motor (11).

4. The apparatus for preparing foamed steel according to claim 1, characterized in that: Flanges (8) are provided at the top and bottom openings of the furnace body, and the coaxial stirring outer tube (6) passes through the flange (8) located at the top opening of the furnace body.

5. The apparatus for preparing foamed steel according to claim 4, characterized in that: The flange (8) at the top opening of the furnace body is provided with an air outlet (7) that communicates with the inner cavity of the furnace body, and the flange (8) at the bottom opening of the furnace body is provided with an air inlet (15) that communicates with the inner cavity of the furnace body.

6. The apparatus for preparing foamed steel according to claim 1, characterized in that: The device also includes at least two thermocouples (16), one of which extends from the flange (8) at the bottom opening of the furnace body and passes through the base close to the crucible (12), and the other thermocouple (16) extends from the side of the furnace body and close to the heating element (10).

7. A method for preparing foamed steel, characterized in that, The apparatus for preparing foamed steel according to any one of claims 1 to 6 is used, comprising the following steps: S1. Under an inert atmosphere, steel is placed in the crucible (12) and heated until it melts to obtain a steel melt; S2. Add a thickener to the inside of the steel melt through the feeding bin (3) and the powder conveying channel, and stir and thicken the steel melt after adding the thickener through the hollow stirring paddle (13); S3. Cool the thickened steel melt to the foaming temperature range and keep it at that temperature; S4. Foaming agent is added into the cooled steel melt through the feeding bin (3) and the powder conveying channel, and the steel melt after adding foaming agent is stirred and foamed by the hollow stirring paddle (13). S5. Cool and solidify the stirred and foamed steel melt to obtain foamed steel.

8. The method for preparing foamed steel according to claim 7, characterized in that: In step S1, the steel is carbon steel, alloy steel, or iron-based alloy; in step S1, the heating temperature is 1550℃~1650℃, and the holding time is 0.5h~1h; in step S3, the foaming temperature range is 1350℃~1550℃, and the holding time is 0.5h.

9. The method for preparing foamed steel according to claim 7, characterized in that: The thickener is SiC or VC, the particle size of the thickener is 5μm to 15μm, and the amount added is 1% to 10% of the mass of the steel; the foaming agent is Cr2N or SrCO3, the particle size of the foaming agent is 5μm to 15μm, and the amount added is 1% to 10% of the mass of the steel.

10. The method for preparing foamed steel according to claim 7, characterized in that: The inert atmosphere is argon; in steps S2 to S4, argon is introduced through the air inlet (15) at the bottom of the furnace body and the annular flow channel, with a flow rate of 0.5 L / min to 2 L / min; in steps S2 and S4, argon is introduced through the powder conveying channel, with a flow rate of 0.5 L / min to 2 L / min; the stirring rate in steps S2 and S4 is 1500 r / min to 2500 r / min, and the stirring time is 8 min to 15 min.

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