A pre-packed porous reaction vessel for ductile cast iron production and spheroidizing method thereof

Abstract

This invention discloses a pre-assembled porous reaction vessel for ductile iron production and its spheroidizing treatment method, belonging to the field of casting technology. The reaction vessel includes a covered hollow structure made of high-temperature resistant metal sheet, with multiple through-holes for pressure relief in its walls. The internal chamber is filled along its height with a pre-compacted multi-layer metallurgical filler, including at least a spheroidizing agent layer and an inoculant layer. This invention also discloses a spheroidizing treatment method based on this vessel. This invention ensures precise ingredient mixing through factory pre-assembly, achieves physical pressure relief and explosion prevention through the porous structure, and pre-sets the temporal and spatial sequence of the reaction through the multi-layer filler, achieving a stable, continuous, and high-absorption spheroidizing reaction. This invention completely eliminates the safety risks of manual operation, requires no expensive equipment investment, and has significant economic and social benefits.

Description

Technical Field

[0001] This invention relates to the field of casting technology, and more specifically to a pre-loaded porous reaction vessel for ductile iron production and its spheroidizing treatment method. Background Technology

[0002] In ductile iron production, spheroidizing treatment is a key process that determines the quality of castings. Currently, the mainstream methods include: 1. Pouring Method: The spheroidizing agent, inoculant, and covering agent are manually laid sequentially in the pit at the bottom of the molten iron ladle. This method has inherent problems such as high risk of workers being burned by the high temperature during loading, large weighing errors, and inconsistent compaction, resulting in large fluctuations in the spheroidizing effect, with the magnesium absorption rate typically only 35%-45%.

[0003] 2. Wire feeding method: Although it improves operational safety, it requires high equipment investment and is difficult to achieve the ideal "multi-layer progressive" inoculation effect, which is not friendly to small and medium-sized foundry enterprises.

[0004] Existing technologies lack a solution that can precisely control reaction kinetics in a standardized and low-cost manner. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a green and energy-saving reaction vessel and method that is prefabricated in the factory, inherently safe, can precisely control the reaction sequence, improve magnesium absorption rate, reduce the amount of spheroidizing agent added, and reduce the consumption of rare earth magnesium mining.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A pre-loaded porous reaction vessel for ductile iron production includes: The container body is a covered cylindrical structure made of inexpensive metal sheets such as A3; The container body has multiple through-holes for pressure relief on its side walls and / or bottom. The internal cavity of the container body is filled with a pre-compacted multi-layer metallurgical filler along the height direction, and the multi-layer metallurgical filler includes at least a spheroidizing agent layer and an inoculant layer.

[0007] In some embodiments of the present invention, the diameter of the pressure relief through hole is Φ1.5mm-Φ2.5.0mm, and the opening ratio is 15%-35%.

[0008] In some embodiments of the present invention, the multilayer metallurgical filler layer is, from top to bottom, a first inoculant layer, a first spheroidizing agent layer, a second inoculant layer, a second spheroidizing agent layer, and a third inoculant layer.

[0009] Based on the different grades and requirements of ductile iron produced, and according to the different compositions of the original molten iron, various spheroidizing agents and inoculants can be flexibly pre-loaded, including but not limited to rare earth spheroidizing agents, magnesium-based spheroidizing agents, 75FeSi inoculants, silicon-barium inoculants, silicon-strontium inoculants, etc., as well as their number of layers, positions, particle sizes, etc.

[0010] In some embodiments of the present invention, the outer surface of the container body is provided with an anti-floating structure.

[0011] In some embodiments of the present invention, the anti-floating structure is a longitudinal groove or barb provided on the outer wall of the container body.

[0012] In some embodiments of the present invention, the cover and the container body are sealed by a fusible weak connection structure.

[0013] The present invention also provides a spheroidizing treatment method, comprising the following steps: 1. Place the pre-loaded reaction vessel described in any of the above schemes into the spheroidizing pit at the bottom of the preheated molten iron ladle; 2. Cover the top and sides of the container with a covering agent (slag remover, ductile iron shavings, etc.) and compact it; 3. Pour in molten iron to melt the container lid, and the multiple layers of metallurgical filler inside react with the molten iron in a preset order.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. Intrinsically safe: Eliminates the need for manual filling of spheroidizing agents and inoculants, reducing the risk of burns during filling; the porous pressure relief structure physically eliminates the risk of gas explosions and jets caused by pressure buildup.

[0015] 2. Precise and controllable: Factory pre-assembly ensures absolute precision in alloy weighing, proportioning, and compaction; the multi-layer structure pre-sets the temporal and spatial sequence of the reaction, making the spheroidization reaction stable and continuous.

[0016] 3. High efficiency and energy saving: The optimized reaction environment allows the magnesium absorption rate to be stably increased to over 60%, significantly saving the amount of spheroidizing agent and reducing production costs.

[0017] 4. High versatility: No need to modify existing molten iron ladles, no need for expensive equipment investment, applicable to various pit-type processing processes. Attached Figure Description

[0018] Figure 1 This is a cross-sectional view of the overall structure of the reaction vessel in an embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram showing the reaction vessel of the present invention in use in a molten iron ladle. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in detail below.

[0021] like Figure 1 , Figure 2 As shown, a pre-assembled porous reaction vessel for ductile iron production includes: The container body 1 is a hollow structure with a lid, made of metal sheet. The container body has multiple through-holes 2 for pressure relief. The internal cavity of the container body is filled with a pre-compacted multi-layer metallurgical filler along the height direction, and the multi-layer metallurgical filler includes at least a spheroidizing agent layer and an inoculant layer.

[0022] The pressure relief through hole 2 has a diameter of Φ1.5mm-Φ2.5mm and an opening ratio of 15%-35%.

[0023] The multi-layer (two or more layers) metallurgical filler layers are, from top to bottom, the first inoculant layer 7, the first spheroidizing agent layer 6, the second inoculant layer 5, the second spheroidizing agent layer 4, and the third inoculant layer 3.

[0024] The outer surface of the container body is provided with an anti-buoyancy structure to prevent it from floating in molten iron.

[0025] The anti-floating structure is a longitudinal groove or barb set on the outer wall of the container body.

[0026] The lid of the container body is sealed to the container via a fusible weak connection structure.

[0027] The metal sheet is made of inexpensive materials such as A3, and the weak connection 8 is welded.

[0028] A method for spheroidizing a pre-loaded reaction vessel includes the following steps: Step 1: Place the reaction vessel 11, pre-filled with metallurgical packing, into the spheroidizing pit at the bottom of the preheated molten iron ladle; Step 2: Cover the top and sides of the reaction vessel with the covering agent 10 and compact it. Press the top of the reaction vessel with a pressure iron 9. Step 3: Pour molten iron into the ladle to melt the reaction vessel, and the multi-layered metallurgical packing material inside reacts with the molten iron in a predetermined order to form spheroids. Example 1:

[0029] This embodiment provides a reaction vessel for processing 600 kg of molten iron.

[0030] Container fabrication: 1.2mm thick A3 perforated steel sheet is stamped and stretched into a cylinder with a diameter of Φ200mm and a height of 280mm, resembling a filter cartridge. The A3 perforated steel sheet features evenly distributed circular holes with a diameter of Φ2.5mm and a hole spacing of 5mm, resulting in an opening rate of approximately 25%. A thin circular sheet is also stamped as the lid.

[0031] Pre-loading of filler: In a dry environment, open the cover and fill the cylinder with the following materials in sequence, then mechanically vibrate and compact them: • Bottom layer: Leak-proof and moisture-proof paper (the paper is also in a tube shape and is placed against the inner wall of the cylinder) • Bottom layer: Fine-particle silicon-strontium inoculant (1-3mm), 1.0kg; Secondary layer: Spheroidizing agent (grade 3-8, Re3Mg8), 2.5 kg; • Middle layer: Fine-particle barium silicate inoculant (1-3mm), 1.5kg; • Secondary top layer: Spheroidizing agent (grade 3-8, Re3Mg8), 3.5 kg; • Top layer: coarse-particle barium silicon inoculant (3-8mm), 3.5kg.

[0032] The total weight of the packing material is 12 kg.

[0033] Sealing: Cover the lid and apply three tiny spot welds at the connection between the lid edge and the cylinder opening to form a weak connection, ensuring that the material does not leak during transportation. It can be melted by heat or pushed open by a small pressure.

[0034] How to use: 1. Place the pre-assembled container into the spheroidizing pit at the bottom of the molten iron ladle, which is preheated to about 150-200°C, using long-handled pliers.

[0035] 2. Cover the top and sides of the container with a perlite covering agent with a thickness of not less than 80mm, and place a piece of scrap steel weighing not less than 10kg on top.

[0036] 3. Molten iron at a temperature of approximately 1450-1480℃ is poured in from the other side of the nozzle.

[0037] 4. The molten iron submerges the container, and the container lid melts rapidly. The lid is pushed open or melted by the slight internal pressure. The molten iron then contacts and melts each layer of filler in sequence, achieving a stable and continuous spheroidization reaction.

[0038] Direct cost calculation for spheroidization: The average price of high-quality spheroidizing agent is 9.5 yuan / kg, and the corresponding amount for 600 kg of molten iron is 57 yuan. Comparative Example 1:

[0039] In the traditional pouring method, spheroidizing agent is first placed at the bottom of one side of the dam-type spheroidizing treatment ladle, covered with ferrosilicon alloy and slightly compacted, and then covered with rust-free iron filings, steel plates or other covering agents. Then, molten iron is poured into the other side of the molten iron ladle at once, relying on the heat of the molten iron to melt the spheroidizing agent and react with the molten iron.

[0040] Loading weight and time The amount of molten iron to be processed is 600 kg. Spheroidizing agent: Grade 3-8, Re3Mg8, addition amount 1.4%, 8.4 kg Inoculant: Coarse-particle barium silicate inoculant (3-8mm), 6kg Manual filling time: approximately 5 minutes Direct cost calculation for spheroidization: The average price of high-quality spheroidizing agent is 9.5 yuan / kg, and the corresponding amount for 600 kg of molten iron is 82.2 yuan. Comparative Example 2:

[0041] The wire feeding spheroidizing method involves wrapping a spheroidizing agent (such as pure magnesium or magnesium alloy) into a cored wire using cold-rolled low-carbon steel strip. The cored wire is then fed directly into the bottom of the molten iron ladle using a wire feeder at a constant speed and in a measured manner to initiate the spheroidizing reaction. The spheroidizing reaction occurs at the bottom third of the ladle, and the molten iron is stirred as it boils.

[0042] Feeding thread addition amount Cored wire: 30Mg spheroidized wire (Mg 29-31%, RE 2-3%, Ca 2-4%, Si 40-44%), usage method is 2 meters / ton, the amount added is 12 meters for 600 kg of molten iron.

[0043] Direct cost calculation for spheroidization: The average price of spheroidizing wire is 4.5 yuan / m, and the corresponding amount for 600 kg of molten iron is 54 yuan.

[0044] Comparison of overall costs for spheroidizing 600kg of molten iron:

[0045] Note: Depreciation and maintenance of wire feeding equipment: 18.3 yuan (the wire feeding equipment and wire feeding station are calculated based on an investment of 400,000 yuan, a 5-year depreciation period, and an annual basic saturation production of 5,000 ladles of 3,000 tons of molten iron balls. Maintenance costs are calculated at 10% of the depreciation).

[0046] Performance verification:

[0047] Note: The molten iron from the same furnace contains the same amount of sulfur (0.012%), the spheroidizing agent contains 7.9% magnesium, and the wire feed contains 62 g / m of magnesium.

[0048] Preliminary tests conducted at the inventor's foundry on the container method described in Example 1 showed that, compared with the conventional flushing method under the same conditions, the flame height during the reaction process was reduced by about 30%, the reaction duration was extended by about 20 seconds, and the magnesium absorption rate was calculated to reach 62.3% through spectral analysis. The absorption rate was significantly better than that of the conventional flushing method, and the stability of the residual magnesium content was higher than that of the wire feeding balling method.

[0049] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A pre-assembled porous reaction vessel for ductile iron production, characterized in that, include: The container body (1) is a hollow structure with a lid made of metal sheet; The container body has multiple through-holes (2) in its wall. The internal cavity of the container body is filled with a pre-compacted multi-layer metallurgical filler along the height direction, and the multi-layer metallurgical filler includes at least a spheroidizing agent layer and an inoculant layer.

2. The pre-assembled porous reaction vessel according to claim 1, characterized in that, The pressure relief through hole (2) has a diameter of Φ1.5mm-Φ2.5mm and an opening rate of 15%-35%.

3. The pre-assembled porous reaction vessel according to claim 1, characterized in that, The multilayer metallurgical filler layers are arranged from top to bottom as follows: first inoculant layer (7), first spheroidizing agent layer (6), second inoculant layer (5), second spheroidizing agent layer (4), and third inoculant layer (3).

4. The pre-assembled porous reaction vessel according to claim 1, characterized in that, The outer surface of the container body is provided with an anti-buoyancy structure to prevent it from floating in molten iron.

5. The pre-assembled porous reaction vessel according to claim 4, characterized in that, The anti-floating structure is a longitudinal groove or barb set on the outer wall of the container body.

6. The pre-assembled porous reaction vessel according to claim 1, characterized in that, The lid of the container body is sealed to the container through a fusible weak connection (8) structure.

7. The pre-assembled porous reaction vessel according to claim 6, characterized in that, The metal sheet is made of A3 inexpensive material, and the weak connection (8) is welding.

8. A spheroidization treatment method using the pre-assembled porous reaction vessel according to any one of claims 1-6, characterized in that, Includes the following steps: Step 1: Place the reaction vessel (11) pre-loaded with metallurgical packing layer into the spheroidizing pit at the bottom of the preheated molten iron ladle; Step 2: Cover the top and sides of the reaction vessel with a covering agent (10) and compact it. A pressure iron (9) is placed on top of the reaction vessel. Step 3: Pour molten iron into the ladle to melt the reaction vessel, and the multi-layered metallurgical packing material inside reacts with the molten iron in a predetermined order to form spheroids.

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