A method for preparing a multi-alloy synergistically reinforced gray cast iron

Abstract

This invention relates to the field of gray cast iron material preparation technology, and particularly to a method for preparing multi-alloy synergistically strengthened gray cast iron, comprising: adding steel raw materials to a smelting apparatus and heating to form molten iron; adding a chromium alloy to the molten iron, heating and holding at that temperature to form a basic mixture; determining the degree of furnace lining peeling based on the vibration frequency of the smelting apparatus, and determining the overheating risk level of the basic mixture based on the degree of furnace lining peeling; determining a target heating temperature based on the overheating risk level; determining the eddy current risk level based on the actual rotation speed; adjusting the stirring intensity during the smelting process based on the eddy current risk level; detecting the mixing ratio of the basic mixture and adjusting the amount of steel raw materials or the chromium alloy added to form a target solution; and simultaneously adding manganese nitride, alloyed tin, and ferrous sulfide to the target solution in a specified ratio to form multi-alloy synergistically strengthened gray cast iron. This invention improves the strength, toughness, fluidity, and resistance to solidification defects of gray cast iron.

Description

Technical Field

[0001] This invention relates to the field of gray cast iron material preparation technology, and in particular to a method for preparing gray cast iron with multi-alloy synergistic strengthening. Background Technology

[0002] In existing technologies, gray cast iron has long been widely used in machinery manufacturing, automotive industries, and other fields due to its advantages such as low cost, excellent casting performance, convenient machining, and good vibration damping effect. To meet the mechanical property requirements of castings, traditional technologies often employ alloying strengthening schemes using chromium and copper. However, the relatively low chromium content makes it difficult to fully utilize its role in refining the matrix structure and forming reinforcing carbides, resulting in limited strength improvement and failing to meet higher performance requirements, thus affecting overall strength. Copper is a precious metal, and its extensive use significantly increases production costs. Furthermore, the use of nitrogen to enhance mechanical properties is not fully utilized. Therefore, existing technologies struggle to balance the strength, toughness, and casting performance of gray cast iron, failing to meet the high-performance requirements of high-end equipment for cast iron materials.

[0003] Chinese Patent Publication No. CN115584430A discloses a high-pearlite-content thick-section gray cast iron and its preparation method, including (1) adding scrap steel, recycled material and ferrosilicon into an electric furnace for smelting; (2) adding copper and tin to the molten iron ladle, tapping the molten iron, adding silicon-strontium-zirconium inoculant in the flow for in-flow inoculation, adding silicon-strontium-zirconium inoculant again to the molten iron ladle for inverted inoculation after tapping; (3) lifting and transferring the molten iron for pouring, adding silicon-strontium-zirconium inoculant, and obtaining high-pearlite-content thick-section gray cast iron after molding. Therefore, it can be seen that the aforementioned high-pearlite thick-section gray cast iron and its preparation method have the following problems: the furnace lining of the smelting equipment will be gradually eroded and peeled off during use, resulting in a reduction in its thickness. After the furnace lining becomes thinner, the heat insulation capacity decreases, which in turn leads to an excessively high actual heat load of the molten iron, resulting in excessive oxidation of the molten iron, loss of beneficial elements, and coarse grains, which leads to a decrease in the mechanical properties of the cast iron or the generation of shrinkage defects. Summary of the Invention

[0004] Therefore, this invention provides a method for preparing multi-alloy synergistically strengthened gray cast iron to overcome the problems in the prior art where the furnace lining of the smelting equipment is gradually eroded and peeled off during use, resulting in a reduction in its thickness. After the furnace lining becomes thinner, the heat insulation capacity decreases, leading to excessively high actual heat load of the molten iron, resulting in excessive oxidation of the molten iron, loss of beneficial elements, coarse grains, and a decrease in the mechanical properties of the cast iron, shrinkage defects, and purity of the molten iron.

[0005] To achieve the above objectives, the present invention provides a method for preparing multi-alloy synergistically strengthened gray cast iron, comprising:

[0006] Steel raw materials are added to smelting equipment and heated to form molten iron;

[0007] Chromium alloy is added to the molten iron, heated to the target heating temperature and held at that temperature for a period of time to form a basic mixture;

[0008] The degree of furnace lining peeling is determined based on the vibration frequency of the smelting equipment, and the degree of overheating risk of the base mixture is determined based on the degree of furnace lining peeling.

[0009] The target heating temperature is determined based on the degree of overheating risk.

[0010] Obtain the actual rotational speed under the adjusted target heating temperature condition, and determine the degree of eddy current risk based on the actual rotational speed;

[0011] Adjust the stirring intensity during the smelting process according to the level of eddy current risk;

[0012] The mixing ratio of the base mixture is detected, and the amount of steel raw material or chromium alloy added is adjusted according to the mixing ratio to form the target solution;

[0013] Manganese nitride, alloyed tin, and ferrous sulfide are added to the target solution in proportion to form multi-alloy synergistically strengthened gray cast iron.

[0014] Furthermore, determining the degree of furnace lining peeling based on the vibration frequency of the smelting equipment includes:

[0015] Obtain the vibration frequency of the device;

[0016] The vibration frequency of the device is compared with the preset vibration frequency;

[0017] If the vibration frequency of the equipment is greater than the preset vibration frequency, it is determined that the degree of furnace lining peeling exceeds the allowable range, and the change in the vibration frequency of furnace lining peeling is obtained.

[0018] Further, determining the degree of overheating risk of the base mixture based on the degree of furnace lining peeling includes:

[0019] The reduction in the actual thickness of the furnace lining is determined based on the change in the furnace lining peeling vibration frequency.

[0020] The actual thickness of the furnace lining is determined based on the amount of reduction in the actual thickness of the furnace lining.

[0021] Compare the actual thickness of the furnace lining with the preset thickness;

[0022] If the actual thickness of the furnace lining is less than the preset thickness, it is determined that the overheating risk of the base mixture exceeds the allowable range, and the target heating temperature is reduced.

[0023] Furthermore, the reduction in the actual thickness of the furnace lining is the product of the change in the furnace lining peeling vibration frequency and the conversion coefficient.

[0024] Furthermore, the degree of eddy current risk is determined based on the actual rotational speed, including:

[0025] Compare the actual rotational speed with the preset rotational speed;

[0026] If the actual rotational speed is greater than the preset rotational speed, the risk of eddy currents is determined to be beyond the allowable range, and the stirring intensity is reduced.

[0027] Furthermore, the target heating temperature is negatively correlated with the actual thickness of the furnace lining.

[0028] Furthermore, the stirring intensity is negatively correlated with the actual rotation speed.

[0029] Further, adjusting the amount of the steel raw material or the chromium alloy added according to the mixing ratio includes:

[0030] The mixing ratio of the base mixture is compared with the preset first ratio and the preset second ratio, respectively;

[0031] If the mixing ratio of the base mixture is greater than the preset second ratio, then the amount of steel raw material added is increased;

[0032] If the mixing ratio of the base mixture is less than the preset first ratio, the amount of chromium alloy added is increased.

[0033] Furthermore, the mixing ratio of the basic mixture is the ratio of the amount of chromium ions to iron ions.

[0034] Furthermore, the particle size of the manganese nitride is 35 mm.

[0035] Compared with existing technologies, the beneficial effects of this invention are that by monitoring the vibration frequency changes of the smelting equipment, the degree of peeling and actual thickness of the furnace lining can be diagnosed indirectly and in real time. Based on this, the target heating temperature can be adjusted, thereby offsetting the increased thermal efficiency caused by the thinning of the furnace lining. This achieves precise and stable control of the molten iron temperature, reduces overheating defects caused by furnace lining wear, and improves production safety. Traditionally, the electromagnetic stirring intensity in medium-frequency furnaces is set by fixed electrical parameters, which cannot respond to fluctuations caused by changes in molten iron quantity and temperature. Insufficient stirring leads to uneven composition and temperature, while excessive stirring generates deep vortices, entraining slag and gas, resulting in inclusions and porosity defects in the castings. This invention, by acquiring the actual rotational speed signal reflecting the stirring intensity in real time, determines the degree of eddy current risk and reduces the stirring intensity to maintain the molten liquid in a state of forming shallow vortices. This effectively prevents the entrainment of slag and gas, improves the purity of the molten iron, and reduces the casting scrap rate. Traditional processes require a lengthy waiting period for sampling and analysis after alloy addition to confirm the composition. This delay leads to significant fluctuations in chemical composition between different furnace runs, resulting in unstable mechanical properties of the final product. This invention performs rapid pre-furnace composition analysis immediately after the chromium alloy is added and the furnace is held at room temperature. Based on the mixing ratio analysis results, the amount of subsequent steel raw materials and chromium alloy added is finely adjusted, ensuring that the composition of the molten iron, as the base mixture, remains stable within the target range. Simply adding elements such as chromium, tin, and nitrogen, if the proportions are inappropriate or the process is poor, has limited strengthening effects and can easily cause side effects such as brittleness and deteriorated processing performance. By simultaneously adding manganese nitride, alloyed tin, and ferrous sulfide, Cr, Sn, N, and S elements exert a synergistic strengthening effect on an ideal basis: chromium provides matrix strengthening, tin refines pearlite, and nitrogen forms nitrides with chromium for dispersion strengthening. Ultimately, this allows gray cast iron to achieve high strength, high hardness, and high wear resistance while maintaining good processing performance and toughness.

[0036] Furthermore, the method described in this invention obtains the actual thickness change, realizing a non-contact assessment of the degree of furnace lining peeling. Since the furnace lining will gradually thin due to thermal shock and chemical erosion during long-term high-temperature smelting, the relationship between vibration frequency and furnace lining thickness can be used to continuously monitor the health status of the furnace lining without shutting down the furnace, provide timely warnings of potential furnace penetration risks, and avoid overheating risks by automatically reducing the target heating temperature, thereby improving production continuity.

[0037] Furthermore, the method of the present invention improves the microstructure uniformity and chemical stability of the basic mixture by lowering the set temperature when the furnace lining becomes thinner, thereby avoiding metallurgical defects such as carbon burn-off, alloy element volatilization and grain coarsening caused by overheating of molten iron.

[0038] Furthermore, the method described in this invention determines the degree of eddy current risk. Since the actual rotational speed is directly related to the internal flow field morphology of the molten pool, excessively high rotational speeds can easily form deep eddies, causing slag gas entrainment and refractory material erosion. By adjusting the stirring intensity, the dissolution rate and distribution uniformity of alloying elements are improved, while the generation of gas inclusions and non-metallic inclusions is reduced, thereby improving the purity and density of cast iron.

[0039] Furthermore, the method described in this invention reduces the problem of structural instability caused by compositional deviation by comparing a preset first ratio and a preset second ratio. Deviations in chromium content will affect the pearlite content and matrix hardness. This invention ensures the consistency of the composition of each batch of molten iron through real-time fine-tuning.

[0040] Furthermore, the method described in this invention optimizes the dissolution kinetics of manganese nitride in high-temperature molten iron by limiting the particle size to 35 mm. If the particle size is too small, nitrogen will be released prematurely and lost due to oxidation. If the particle size is too large, dissolution will be insufficient, resulting in component segregation. The 35 mm particle size takes into account both settling velocity and dissolution rate, and can fully dissolve and distribute evenly in molten iron, maximizing the strengthening effect of nitrogen, while reducing the generation of undissolved residues, improving alloy utilization and the internal quality of castings. Attached Figure Description

[0041] Figure 1 This is a flowchart illustrating the preparation method of multi-alloy synergistically strengthened gray cast iron according to an embodiment of the present invention.

[0042] Figure 2 This is a flowchart illustrating the process for determining the degree of furnace lining peeling in the preparation method of multi-alloy synergistically strengthened gray cast iron according to an embodiment of the present invention.

[0043] Figure 3 A flowchart illustrating the determination of the overheating risk level of the basic mixture in the preparation method of multi-alloy synergistically strengthened gray cast iron according to embodiments of the present invention;

[0044] Figure 4 This is a flowchart illustrating the adjustment of the amount of steel raw material or chromium alloy added in the preparation method of multi-alloy synergistically strengthened gray cast iron according to an embodiment of the present invention. Detailed Implementation

[0045] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0046] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0047] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0048] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" 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 mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0049] Please see Figure 1 , Figure 2 , Figure 3 as well as Figure 4 The flowcharts shown are, respectively, the preparation process of the multi-alloy synergistically strengthened gray cast iron according to an embodiment of the present invention, the process for determining the degree of furnace lining peeling, the process for determining the degree of overheating risk of the base mixture, and the process for adjusting the amount of steel raw materials or chromium alloys added; an embodiment of the present invention provides a method for preparing multi-alloy synergistically strengthened gray cast iron, comprising:

[0050] Step S1: Add the steel raw material into the smelting equipment and heat it to form molten iron;

[0051] In practice, a medium-frequency induction furnace was used for smelting.

[0052] In this embodiment, 3000 kg of Q235 steel raw material is added to a medium-frequency induction furnace with a nominal capacity of 5 tons. The initial thickness of the furnace lining is 150 mm, and the furnace lining material is magnesium aluminum spinel dry ramming material. The initial set temperature for step S1 to heat up to form molten iron is 1620°C.

[0053] Step S2: Add the chromium alloy to the molten iron, heat it to the target heating temperature and hold it at that temperature for a first time to form a basic mixture;

[0054] Step S3: Determine the degree of furnace lining peeling based on the vibration frequency of the smelting equipment, and determine the degree of overheating risk of the base mixture based on the degree of furnace lining peeling;

[0055] Obtain the vibration frequency of the device;

[0056] The vibration frequency of the device is compared with the preset vibration frequency;

[0057] If the vibration frequency of the equipment is greater than the preset vibration frequency, it is determined that the degree of furnace lining peeling exceeds the allowable range, and the change in the vibration frequency of furnace lining peeling is obtained.

[0058] Specifically, an ICP-type triaxial acceleration vibration sensor was installed on the tilting shaft bearing housing of the smelting equipment to collect vibration signals during equipment operation.

[0059] Optionally, the preset vibration frequency can be selected within the range of [1000Hz, 1100Hz], and the preferred embodiment of the preset vibration frequency is 1050Hz.

[0060] Specifically, the degree of overheating risk of the base mixture is determined based on the degree of furnace lining peeling;

[0061] The reduction in the actual thickness of the furnace lining is determined based on the change in the furnace lining peeling vibration frequency.

[0062] The actual thickness of the furnace lining is determined based on the amount of reduction in the actual thickness of the furnace lining.

[0063] Compare the actual thickness of the furnace lining with the preset thickness;

[0064] If the actual thickness of the furnace lining is less than the preset thickness, it is determined that the overheating risk of the base mixture exceeds the allowable range, and the target heating temperature is reduced.

[0065] The reduction in the actual thickness of the furnace lining is the product of the change in the furnace lining peeling vibration frequency and the conversion coefficient.

[0066] Specifically, the change in the vibration frequency of furnace lining peeling = the vibration frequency of the equipment - the preset vibration frequency.

[0067] Specifically, the actual thickness of the furnace lining = the initial thickness of the furnace lining - the reduction in the actual thickness of the furnace lining.

[0068] Specifically, the selectable range of the conversion factor is [0.2mm / Hz, 0.4mm / Hz], and the preferred embodiment of the conversion factor is 0.3mm / Hz.

[0069] Specifically, the initial thickness of the furnace lining is 150mm, the selectable range of the preset thickness is [130mm, 140mm], and the preferred embodiment of the preset thickness is 135mm.

[0070] Step S4: Determine the target heating temperature based on the degree of overheating risk;

[0071] The target heating temperature is negatively correlated with the actual thickness of the furnace lining.

[0072] Specifically, when the overheating risk exceeds the allowable range, if the actual thickness is less than the preset thickness by less than 2 mm, the target heating temperature will be reduced by 2℃. If the difference between the actual thickness and the preset thickness exceeds 2 mm, the target heating temperature will be reduced by 0.5℃ for every 1 mm exceeding the difference. In a specific embodiment, the actual thickness is 130 mm, the preset thickness is 135 mm, and the current target heating temperature is 1620℃. Then, the reduced target heating temperature is 1620-2-(135-130-2)÷1×0.5=1616.5℃.

[0073] In practice, the method described in this invention obtains the actual thickness change, realizing a non-contact assessment of the degree of furnace lining peeling. Since the furnace lining will gradually thin due to thermal shock and chemical erosion during long-term high-temperature smelting, the relationship between vibration frequency and furnace lining thickness can be used to continuously monitor the health status of the furnace lining without shutting down the furnace, provide timely warning of potential furnace penetration risks, and avoid overheating risks by automatically reducing the target heating temperature, thereby improving production continuity.

[0074] In practice, the method of the present invention improves the uniformity of the structure and chemical stability of the basic mixture by lowering the set temperature when the heat transfer efficiency increases due to the thinning of the furnace lining, thus avoiding metallurgical defects such as carbon burn-off, volatilization of alloying elements and grain coarsening caused by overheating of molten iron.

[0075] Step S5: Obtain the actual rotational speed under the adjusted target heating temperature condition, and determine the degree of eddy current risk based on the actual rotational speed;

[0076] Compare the actual rotational speed with the preset rotational speed;

[0077] If the actual rotational speed is greater than the preset rotational speed, the risk of eddy currents is determined to be beyond the allowable range, and the stirring intensity is reduced.

[0078] Specifically, a high-speed industrial camera located above the observation hole on the furnace cover records a 10-second video stream of the molten pool surface at a frame rate of 100fps. The video stream is transmitted to an industrial control computer and processed by machine vision algorithms to calculate the rotational angular velocity by tracking the movement trajectory of slag or feature points at the edge of the central vortex of the molten pool.

[0079] Specifically, the selectable implementation range of the preset speed is [30 rpm, 40 rpm], and the preferred embodiment of the preset speed is 35 rpm.

[0080] In practice, the method of the present invention determines the degree of eddy current risk. Since the actual rotation speed is directly related to the internal flow field morphology of the molten pool, excessively high rotation speed is prone to forming deep eddies, causing slag gas entrainment and refractory material erosion. By adjusting the stirring intensity, the dissolution rate and distribution uniformity of alloying elements are improved, while reducing the generation of gas inclusions and non-metallic inclusions, thereby improving the purity and density of cast iron.

[0081] Step S6: Adjust the stirring intensity during the smelting process according to the degree of eddy current risk;

[0082] The stirring intensity is negatively correlated with the actual rotation speed.

[0083] In practice, the stirring intensity is adjusted by the industrial control computer from the intermediate frequency power control unit, which adjusts the frequency of the alternating current input to the induction furnace coil.

[0084] Specifically, when the eddy current exceeds the allowable range, if the actual rotational speed is within 2 rpm of the preset rotational speed, the frequency of the alternating current is reduced by 1 Hz. If the difference between the actual rotational speed and the preset rotational speed exceeds 2 rpm, the frequency of the alternating current is reduced by 0.1 Hz for every 1 rpm difference. In a specific embodiment, the actual rotational speed is 40 rpm, the preset rotational speed is 35 rpm, and the current frequency of the alternating current is 250 Hz. Therefore, the frequency of the reduced alternating current is 250 - 1 - (40 - 35 - 2) ÷ 1 × 0.1 = 248.7 Hz.

[0085] Step S7: Detect the mixing ratio of the base mixture, and adjust the amount of steel raw material or chromium alloy added according to the mixing ratio to form the target solution;

[0086] The mixing ratio of the basic mixture is the ratio of the amount of chromium ions to iron ions.

[0087] In practice, a preheated sampling steel cup is used to extract approximately 1000 grams of molten iron from the sampling port of the smelting furnace. The molten iron is then rapidly poured into a rapidly cooling mold to form a disc-shaped spectral sample with a thickness of approximately 3-4 mm. The disc-shaped spectral sample is designed to allow for rapid solidification. After the sample cools, the surface is gently polished using a grinding machine to expose a fresh, smooth, and oxidation-free metal surface. The prepared sample is then placed on the sample stage of a mobile direct-reading spectrometer, and the detection program is started. After 25 seconds, the spectrometer completes the analysis and displays the mass percentage results of each element directly on the screen.

[0088] Specifically, the chromium alloy is a high-carbon ferrochrome with a Cr content of 60%; the first time is 15 minutes.

[0089] Specifically, adjusting the amount of the steel raw material or the chromium alloy added according to the mixing ratio includes:

[0090] The mixing ratio of the base mixture is compared with the preset first ratio and the preset second ratio, respectively;

[0091] If the mixing ratio of the base mixture is greater than the preset second ratio, then the amount of steel raw material added is increased;

[0092] If the mixing ratio of the base mixture is less than the preset first ratio, the amount of chromium alloy added is increased.

[0093] Specifically, the optional implementation range of the preset second ratio is [0.35%, 0.45%], the preferred embodiment of the preset second ratio is 0.40%, the optional implementation range of the preset first ratio is [0.23%, 0.30%], and the preferred embodiment of the preset first ratio is 0.25%.

[0094] If the mixing ratio of the base mixture is greater than the preset second ratio, the amount of steel raw material to be added is calculated based on the value greater than the preset second ratio.

[0095] If the mixing ratio of the base mixture is less than the preset first ratio, the amount of chromium alloy to be added is calculated based on the value that is less than the preset first ratio.

[0096] In practice, if the mixing ratio of the base mixture is measured to be 0.43%, which is greater than 0.40%, the amount of steel raw material needs to be increased. After adding steel raw material, the total mass of chromium remains unchanged, but the total mass of the base mixture increases. The new chromium content process is: new chromium content = current chromium content × total mass of base mixture / total mass of base mixture + mass of added steel raw material.

[0097] In practice, the method of the present invention compares the preset first ratio and the preset second ratio, which reduces the problem of structural instability caused by composition deviation. The deviation of chromium content will affect the pearlite content and matrix hardness. The present invention ensures the consistency of the composition of each batch of molten iron by real-time fine adjustment.

[0098] Step S8: Add manganese nitride, alloyed tin, and ferrous sulfide to the target solution in proportion to form multi-alloy synergistically strengthened gray cast iron.

[0099] In practice, a jaw crusher was used to crush manganese nitride into 35mm particles.

[0100] Specifically, large pieces of raw manganese nitride are added to the feed inlet of a jaw crusher. By adjusting the discharge gap of the jaw crusher, the particle size of the material after the first crushing is controlled to be approximately between 20mm and 45mm. The gap between the two rollers is precisely adjusted to 35mm. The target particle size material that meets the requirement of 35mm ± 5mm is accurately separated from the crushed mixture, and excessively large pieces and powder are removed.

[0101] In practice, the method described in this invention optimizes the dissolution kinetics of manganese nitride in high-temperature molten iron by limiting the particle size to 35 mm. If the particle size is too small, nitrogen will be released prematurely and lost due to oxidation. If the particle size is too large, dissolution will be insufficient, resulting in component segregation. The particle size of 35 mm takes into account both settling speed and dissolution rate, which can fully dissolve and distribute evenly in molten iron, maximizing the strengthening effect of nitrogen, while reducing the generation of undissolved residues, improving alloy utilization and the internal quality of castings.

[0102] Specifically, high-purity tin ingots are used, which are broken into small pieces weighing less than 5 kg, and weighed according to the target tin content of 0.07%.

[0103] Specifically, 5 to 10 minutes before tapping, manganese nitride and tin alloy are added to the target solution together using a feeding hopper. Manganese nitride is mainly composed of combined nitrogen and contains a small amount of dissolved nitrogen, which can stably release nitrogen elements in the molten iron. The manganese elements it contains can also replenish the manganese content of the molten iron, stabilize pearlite, and increase the proportion of pearlite. The simultaneous addition of tin alloy can directly refine the pearlite and form a synergistic effect with the manganese and nitrogen elements of manganese nitride.

[0104] Specifically, the alloy tin uses tin ingots with grades Sn99.90, Sn99.95, or higher.

[0105] After the heat treatment period, a final composition verification was conducted. Direct-reading spectrometer analysis confirmed that the key alloying elements met the target range.

[0106] N: 90ppm~110ppm, Sn: 0.06%~0.08%, Cr: 0.25%~0.45%, Mn: 0.5%~0.7%, S: 0.07%~0.10%.

[0107] At this point, the target solution has been successfully transformed into multi-alloy synergistically strengthened gray cast iron.

[0108] Specifically, the preparation conditions for step S8 include:

[0109] The preparation temperature range is [1570℃, 1590℃];

[0110] Manganese nitride with a particle size of 35 mm, a manganese molar mass content of ≥75%, and a nitrogen molar mass content of ≥5%;

[0111] The mass of a single piece of alloy tin is less than 5kg, and the alloy tin needs to be preheated to 250℃~300℃ in advance;

[0112] The particle size of ferrous sulfide is 15 mm;

[0113] After adding manganese nitride, tin alloy, and ferrous sulfide, let stand for 6 to 10 minutes within the preparation temperature range.

[0114] In practice, this invention indirectly and in real-time diagnoses the degree of lining peeling and the actual thickness of the furnace lining by monitoring the vibration frequency changes of the smelting equipment. Based on this, the target heating temperature is adjusted to offset the increased thermal efficiency caused by the thinning of the furnace lining, achieving precise and stable control of the molten iron temperature, reducing overheating defects caused by furnace lining wear, and improving production safety. Traditionally, the electromagnetic stirring intensity in medium-frequency furnaces is set by fixed electrical parameters, which cannot respond to fluctuations caused by changes in molten iron quantity and temperature. Insufficient stirring leads to uneven composition and temperature, while excessive stirring generates deep vortices, entraining slag and gas, resulting in inclusions and porosity defects in the castings. This invention acquires the actual rotational speed signal reflecting the stirring intensity in real-time, determines the eddy current risk level, and reduces the stirring intensity to maintain the molten liquid in a state of shallow vortex formation. This effectively prevents the entrainment of slag and gas, significantly improves the purity of the molten iron, and reduces the casting scrap rate. Traditional processes require a long waiting time for sampling and analysis after adding alloys to confirm the composition. The results are delayed, and adjustments are not timely, leading to large fluctuations in chemical composition between different furnace runs, and ultimately unstable mechanical properties of the final product. This invention performs rapid pre-furnace composition analysis immediately after the chromium alloy is added and kept at a constant temperature. Based on the test results of the mixing ratio, the amount of subsequent steel raw materials and chromium alloy added is finely adjusted to ensure that the composition of the molten iron as the base mixture remains stable within the target range. Simply adding elements such as chromium, tin, and nitrogen, if the ratio is improper or the process is poor, will have limited strengthening effect and may easily produce side effects such as brittleness and deterioration of processing performance. By simultaneously adding manganese nitride, alloyed tin, and ferrous sulfide, elements such as Cr, Sn, N, and S can play a synergistic strengthening role on an ideal basis: chromium provides matrix strengthening, tin refines pearlite, and nitrogen forms nitride dispersion strengthening with chromium. Ultimately, gray cast iron achieves high strength, high hardness, and high wear resistance while maintaining good processing performance and toughness.

[0115] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A method for producing a multi-alloy synergistically strengthened gray cast iron, characterized by, include: Steel raw materials are added to smelting equipment and heated to form molten iron; A chromium alloy is added to the molten iron, heated to the target heating temperature and held at that temperature for a period of time to form a basic mixture; The degree of furnace lining peeling is determined based on the vibration frequency of the smelting equipment, and the degree of overheating risk of the base mixture is determined based on the degree of furnace lining peeling. The target heating temperature is determined based on the degree of overheating risk. Obtain the actual rotational speed under the adjusted target heating temperature condition, and determine the degree of eddy current risk based on the actual rotational speed; Adjust the stirring intensity during the smelting process according to the level of eddy current risk; The mixing ratio of the base mixture is detected, and the amount of steel raw material or chromium alloy added is adjusted according to the mixing ratio to form the target melt; Manganese nitride, alloyed tin, and ferrous sulfide are added to the target melt in a specific ratio to form multi-alloy synergistically strengthened gray cast iron; The target ranges for alloying elements in the multi-alloy synergistic strengthened gray cast iron are: N: 90ppm~110ppm, Sn: 0.06%~0.08%, Cr: 0.25%~0.45%, Mn: 0.5%~0.7%, S: 0.07%~0.10%; The determination of the degree of furnace lining peeling based on the vibration frequency of the smelting equipment includes: Obtain the vibration frequency of the device; The vibration frequency of the device is compared with the preset vibration frequency; If the vibration frequency of the equipment is greater than the preset vibration frequency, it is determined that the degree of furnace lining peeling exceeds the allowable range, and the change in the vibration frequency of furnace lining peeling is obtained; Determining the degree of overheating risk of the base mixture based on the degree of furnace lining peeling includes: The reduction in the actual thickness of the furnace lining is determined based on the change in the furnace lining peeling vibration frequency. The actual thickness of the furnace lining is determined based on the amount of reduction in the actual thickness of the furnace lining. Compare the actual thickness of the furnace lining with the preset thickness; If the actual thickness of the furnace lining is less than the preset thickness, it is determined that the overheating risk of the base mixture exceeds the allowable range, and the target heating temperature is reduced; The degree of eddy current risk is determined based on the actual rotational speed, including: Compare the actual rotational speed with the preset rotational speed; If the actual rotational speed is greater than the preset rotational speed, the eddy current risk level is determined to be beyond the allowable range, and the stirring intensity is reduced. Adjusting the amount of the steel raw material or the chromium alloy added according to the mixing ratio includes: The mixing ratio of the base mixture is compared with the preset first ratio and the preset second ratio, respectively; If the mixing ratio of the base mixture is greater than the preset second ratio, then the amount of steel raw material added is increased; If the mixing ratio of the base mixture is less than the preset first ratio, the amount of chromium alloy added is increased.

2. The method of producing a multi-alloy synergistically strengthened gray cast iron according to claim 1, characterized by, The reduction in the actual thickness of the furnace lining is the product of the change in the furnace lining peeling vibration frequency and the conversion coefficient.

3. The method for preparing multi-alloy synergistically strengthened gray cast iron according to claim 2, characterized in that, The target heating temperature is negatively correlated with the actual thickness of the furnace lining.

4. The method for preparing multi-alloy synergistically strengthened gray cast iron according to claim 3, characterized in that, The stirring intensity is negatively correlated with the actual rotation speed.

5. The method for preparing multi-alloy synergistically strengthened gray cast iron according to claim 4, characterized in that, The mixing ratio of the basic mixture is the ratio of the amount of chromium ions to iron ions.

6. The method for preparing multi-alloy synergistically strengthened gray cast iron according to claim 5, characterized in that, The particle size of the manganese nitride is 35 mm.

Images