A method for preparing synthetic cast iron based on a high proportion of scrap steel

Abstract

This invention relates to the field of cast iron production technology, and particularly to a method for preparing synthetic cast iron based on a high proportion of scrap steel. The method includes: obtaining synthetic cast iron molten iron by high-temperature melting of furnace charge; increasing the preset settling time when the synthetic cast iron molten iron preparation fails to meet the standard based on eutectic undercooling; adding silicon carbide to the synthetic cast iron molten iron that meets the preset standard and stirring to obtain a first inoculated molten iron; tapping the first inoculated molten iron and adding a first inoculant to obtain a second inoculated molten iron; determining whether the second inoculated molten iron preparation meets the preset standard again based on the eutectic recovery rate when the preparation of the second inoculated molten iron fails to meet the standard based on the eutectic solidification rate, or determining an adjustment strategy when the preparation of the second inoculated molten iron fails to meet the standard based on the relative deviation rate of carbon equivalent; and casting the second inoculated molten iron that meets the preset standard into a casting to obtain a synthetic cast iron casting. This invention improves the efficiency of synthetic cast iron preparation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cast iron production process, and particularly relates to a synthetic cast iron preparation method based on high proportion of scrap steel. BACKGROUND

[0002] Cast iron is one of the most widely used basic materials in manufacturing industry, and its performance directly relates to the quality and service life of various mechanical equipment. The smelting of traditional cast iron mainly uses pig iron as the main charge, supplemented by scrap steel and recycled materials. However, this traditional method has the following obvious disadvantages:

[0003] High dependence on pig iron and large cost fluctuation: The price of pig iron is greatly affected by the upstream iron ore and coke market, and the cost is difficult to control. In addition, pig iron itself contains a large amount of impurity elements, which can deteriorate the mechanical properties and casting properties of cast iron. In contrast, scrap steel has a wide source and a relatively low price. Increasing the proportion of scrap steel can significantly reduce the raw material cost.

[0004] Large environmental pressure: The production of pig iron is a typical high-energy and high-emission process.

[0005] In order to overcome the above problems, the industry has begun to explore synthetic cast iron technology, that is, using scrap steel as the main charge and adding carbon additive to adjust the carbon equivalent to simulate the chemical composition of pig iron. Although the high-proportion scrap steel process has obvious advantages, in actual production application, the fluctuation of high-proportion scrap steel raw materials leads to poor stability of the iron liquid, making it difficult for the industry to balance the dual demands of reducing cost by high-proportion scrap steel and stable quality of synthetic cast iron.

[0006] Chinese patent application publication No. CN114990419A discloses a scrap steel smelting cast iron method, which belongs to the technical field of cast iron production process. The method comprises the following steps: step S1, charge preparation: selecting low-carbon scrap steel with an average carbon content of 0.2%, selecting recycled pouring head and runner head cast iron recycled material, preparing carbon powder and silicon iron; step S2, furnace charging: the first batch of materials is 15% scrap steel + 30% carbon additive; the second batch of materials is 20% scrap steel + 50% carbon additive; step S3, preliminary smelting of metal liquid; step S4, iron liquid purification: adding slag collector for slagging treatment, then adding inoculant to adjust the composition, stirring uniformly, and sampling for testing; step S5, according to the spectral composition analysis data, the composition of the iron liquid is adjusted, and the adjustment sequence is: first increasing Mn, then increasing carbon, and finally increasing Si, until the as-cast composition and organization standard are reached; step S6, the iron liquid continues to be heated, and the temperature is measured by a thermocouple thermometer, and the furnace is discharged.

[0007] It can be seen that the above technical solution does not consider the metallurgical state of the iron liquid after smelting and the iron liquid after inoculation, which affects the undercooling tendency before solidification of the iron liquid and the inoculation effect, thereby causing the problem of poor preparation efficiency of synthetic cast iron. SUMMARY

[0008] To this end, the present application provides a synthetic cast iron preparation method based on a high proportion of scrap steel, to overcome the problem in the prior art that the metallurgical state of the molten iron after smelting and the molten iron after inoculation is not considered, affecting the supercooling tendency before solidification of the molten iron and the inoculation effect, thereby resulting in poor preparation efficiency of the synthetic cast iron.

[0009] To achieve the above-mentioned purpose, the present application provides a synthetic cast iron preparation method based on a high proportion of scrap steel, comprising:

[0010] After high-temperature smelting of the charge including scrap steel and a first preset amount of silicon carbide in an electric furnace, a synthetic cast iron molten iron is obtained, and after high-temperature standing for a preset standing time, a first cooling curve of the synthetic cast iron molten iron is collected, and the eutectic supercooling degree is determined based on the first cooling curve;

[0011] When it is determined that the preparation of the synthetic cast iron molten iron does not meet the preset standard according to the eutectic supercooling degree, the preset standing time of the next batch is increased or the value of the first preset amount of the next batch is increased;

[0012] A second preset amount of silicon carbide is added to the synthetic cast iron molten iron that meets the preset standard and stirred to obtain a first inoculated molten iron;

[0013] The first inoculated molten iron is tapped, and a first inoculant is added in a third preset amount in the iron stream to obtain a second inoculated molten iron; and the eutectic re-ascending rate of the second inoculated molten iron is determined based on a second cooling curve of the second inoculated molten iron;

[0014] When it is determined that the preparation of the second inoculated molten iron does not meet the preset standard according to the eutectic re-ascending rate of the second inoculated molten iron, it is determined whether the preparation of the second inoculated molten iron meets the preset standard according to the eutectic solidification rate of the second inoculated molten iron, or the adjustment strategy when the preparation of the second inoculated molten iron does not meet the preset standard is determined according to the relative deviation rate of the carbon equivalent of the second inoculated molten iron;

[0015] The second inoculated molten iron that meets the preset standard is poured into a cast, and a second inoculant is added during pouring to obtain a synthetic cast iron cast.

[0016] Further, the process of determining whether the preparation of the synthetic cast iron molten iron meets the preset standard according to the eutectic supercooling degree of the synthetic cast iron molten iron comprises:

[0017] The eutectic supercooling degree is compared with a first preset eutectic supercooling degree and a second preset eutectic supercooling degree, respectively;

[0018] If the eutectic supercooling degree is less than the first preset eutectic supercooling degree, it is determined that the preparation of the synthetic cast iron molten iron meets the preset standard;

[0019] If the eutectic undercooling degree is greater than or equal to the first preset eutectic undercooling degree and less than a second preset eutectic undercooling degree, it is determined that the preparation of the synthetic cast iron liquid does not meet the preset standard, and the preset standing time of the next batch is increased according to the difference between the eutectic undercooling degree and the first preset eutectic undercooling degree.

[0020] If the eutectic undercooling degree is greater than or equal to the second preset eutectic undercooling degree, it is determined that the preparation of the synthetic cast iron liquid does not meet the preset standard, and the value of the first preset addition amount of the next batch is increased according to the difference between the eutectic undercooling degree and the second preset eutectic undercooling degree.

[0021] Further, the process of obtaining the eutectic undercooling degree of the synthetic cast iron liquid comprises:

[0022] A first preset amount of the synthetic cast iron liquid is poured into a thermal analysis sample cup with a built-in thermocouple, and a temperature change curve from pouring to solidification of the synthetic cast iron liquid, i.e. a first cooling curve, is recorded. The first actual eutectic temperature is determined from the first cooling curve.

[0023] A first preset amount of the synthetic cast iron liquid is poured into a spectral standard test block, and based on the determination of the chemical composition of the synthetic cast iron liquid, the first theoretical eutectic temperature of the synthetic cast iron liquid is calculated.

[0024] The absolute value of the difference between the first actual eutectic temperature and the first theoretical eutectic temperature is the eutectic undercooling degree of the synthetic cast iron liquid.

[0025] Further, the increase in the value of the first preset addition amount of the next batch is provided with several adjustment methods, and each adjustment method has a different increase in the value of the first preset addition amount of the next batch.

[0026] Further, the process of determining whether the preparation of the second inoculation liquid meets the preset standard according to the eutectic rise rate of the second inoculation liquid comprises:

[0027] The eutectic rise rate is compared with a first preset eutectic rise rate and a second preset eutectic rise rate, respectively.

[0028] If the eutectic rise rate is less than the first preset eutectic rise rate, it is determined that the preparation of the second inoculation liquid does not meet the preset standard, and the adjustment strategy when the preparation of the second inoculation liquid does not meet the preset standard is determined according to the relative deviation rate of the carbon equivalent of the second inoculation liquid.

[0029] If the eutectic rebound rate is greater than or equal to the first preset eutectic rebound rate and less than a second preset eutectic rebound rate, it is determined that the preparation of the second inoculation iron liquid meets the preset standard, and whether the preparation of the second inoculation iron liquid meets the preset standard is determined again according to the eutectic solidification rate of the second inoculation iron liquid.

[0030] If the eutectic rebound rate is greater than or equal to the second preset eutectic rebound rate, it is determined that the preparation of the second inoculation iron liquid meets the preset standard.

[0031] Further, the process of obtaining the eutectic rebound rate of the second inoculation iron liquid comprises:

[0032] A second preset amount of the second inoculation iron liquid is poured into a thermal analysis sample cup with a built-in thermocouple;

[0033] The temperature change curve of the second inoculation iron liquid during the process of cooling from liquid to solid, i.e., a second cooling curve, is recorded;

[0034] The lowest temperature value of the eutectic transformation stage of the second inoculation iron liquid is identified and read from the second cooling curve, which is recorded as a eutectic lowest temperature;

[0035] The highest temperature value to which the temperature rebounds after supercooling due to the release of crystallization latent heat of the second inoculation iron liquid is identified and read from the second cooling curve, which is recorded as a second eutectic rebound temperature;

[0036] The second theoretical eutectic temperature of the second inoculation iron liquid is calculated according to the chemical composition of the second inoculation iron liquid;

[0037] The difference between the second eutectic rebound temperature and the eutectic lowest temperature is calculated, which is recorded as a first difference;

[0038] The difference between the second theoretical eutectic temperature and the eutectic lowest temperature is calculated, which is recorded as a second difference; the ratio of the first difference to the second difference is recorded as the eutectic rebound rate of the second inoculation iron liquid.

[0039] Further, when it is determined again according to the comparison result that the eutectic solidification rate of the second inoculation iron liquid is less than a preset eutectic solidification rate that the preparation of the second inoculation iron liquid does not meet the preset standard, the addition rate of the first inoculant of the next batch is increased according to the difference between the eutectic solidification rate and the preset eutectic solidification rate.

[0040] The eutectic solidification rate is the ratio of the first difference to a eutectic rebound duration, wherein the eutectic rebound duration is the duration experienced by the second inoculation iron liquid from the eutectic lowest temperature to the second eutectic rebound temperature obtained from the second cooling curve.

[0041] Further, the process of determining the adjustment strategy when the preparation of the second inoculation iron liquid does not meet the preset standard according to the relative deviation rate of the carbon equivalent of the second inoculation iron liquid comprises:

[0042] Comparing the relative deviation rate of the carbon equivalent with a preset relative deviation rate of the carbon equivalent;

[0043] If the relative deviation rate of the carbon equivalent is less than the preset relative deviation rate of the carbon equivalent, increasing the second preset amount of silicon carbide in the next batch according to the difference between the preset relative deviation rate of the carbon equivalent and the relative deviation rate of the carbon equivalent;

[0044] If the relative deviation rate of the carbon equivalent is greater than or equal to the preset relative deviation rate of the carbon equivalent, issuing an ingredient out-of-control alarm;

[0045] The relative deviation rate of the carbon equivalent is determined according to the carbon equivalent of the second inoculation iron liquid and a preset carbon equivalent.

[0046] Further, the furnace charge is composed of the following raw materials in mass percentage: 60%-80% of scrap steel, 20%-40% of shot-blasted recycled material, and silicon carbide added in a first preset amount, wherein the particle size range of the silicon carbide is 1-5 mm.

[0047] Further, the first inoculant is a silicon-barium inoculant, the amount of which is 0.3%-0.5% of the mass of the first inoculation iron liquid, and the particle size range of the first inoculant is 3 mm-10 mm; the second inoculant is a silicon-barium inoculant, the amount of which is 0.1%-0.2% of the mass of the second inoculation iron liquid, and the particle size range of the second inoculant is 0.2 mm-0.8 mm.

[0048] Compared with the prior art, the present application has the beneficial effects that the present application constructs a closed-loop quality control throughout the whole process of melting, inoculation and pouring, extracts the metallurgical state characteristic values such as eutectic undercooling degree, eutectic recovery rate, eutectic solidification rate and relative deviation rate of carbon equivalent by real-time acquisition and analysis of the cooling curve of the iron liquid at different process stages, and performs multi-level judgment and feedback adjustment accordingly, not only evaluates the eutectic undercooling degree of the iron liquid after melting, but also evaluates the inoculation effect again after tapping and inoculation, and provides two fine troubleshooting paths for unqualified conditions: one is to further judge according to the eutectic solidification rate, and the other is to trace the reasons for not meeting the standard according to the relative deviation rate of the carbon equivalent, so as to ensure that various preparation risks are discovered and addressed in time before final pouring, thereby improving the preparation efficiency of synthetic cast iron.

[0049] Furthermore, this invention achieves precise identification and differentiated processing of molten iron preparation effects by setting a graded judgment of eutectic undercooling and a dual-threshold graded judgment. Instead of using a single standard, the eutectic undercooling is compared with two preset eutectic undercooling values. Targeted measures can be taken based on the different degrees of defects in the graphitization capacity of the molten iron: when the eutectic undercooling is less than the first preset value, the molten iron is directly judged to be qualified without additional adjustment, ensuring production efficiency; when the eutectic undercooling is between the first and second preset values, it indicates that the graphitization capacity of the molten iron is only slightly insufficient, which can be improved by extending the preset standing time of the next batch; when the eutectic undercooling is greater than or equal to the second preset value, it indicates that the graphitization capacity of the molten iron is severely insufficient, which requires increasing the first preset amount of silicon carbide to supplement carbon and silicon elements, thereby improving the efficiency of process adjustment.

[0050] Furthermore, by measuring the actual temperature and calculating the theoretical temperature through spectral analysis, this invention eliminates the subjectivity and error of human experience-based judgment, making the abstract metallurgical concept of supercooling tendency measurable and comparable, thereby improving the reliability of the assessment.

[0051] Furthermore, the present invention provides multiple adjustment methods for increasing the amount of silicon carbide added, thereby achieving adaptive and precise control of the magnitude of the increase in the amount of silicon carbide added.

[0052] Furthermore, the present invention reflects the kinetic conditions of eutectic cluster growth in the second inoculated iron melt by setting the eutectic solidification rate; when the eutectic solidification rate is less than the preset value, it indicates that the first inoculant is dispersed in the iron melt. By increasing the addition rate of the first inoculant in the next batch, its dispersion in the iron flow is improved, thereby providing more effective crystallization nuclei, promoting faster and more uniform eutectic growth, and thus improving the level of intelligence in the evaluation. Attached Figure Description

[0053] Figure 1 This is a flowchart of a method for preparing synthetic cast iron based on a high proportion of scrap steel, as described in an embodiment of the present invention.

[0054] Figure 2 This is a flowchart illustrating how to determine whether the preparation of the synthetic cast iron molten metal meets a preset standard, as described in this embodiment of the invention.

[0055] Figure 3 This is a flowchart illustrating how the preparation of the second inoculated iron liquid is determined based on the eutectic recovery rate of the second inoculated iron liquid according to an embodiment of the present invention to determine whether the preparation of the second inoculated iron liquid meets a preset standard;

[0056] Figure 4 This is a flowchart illustrating the adjustment strategy for determining when the preparation of the second inoculated iron liquid does not meet the preset standard, as described in an embodiment of the present invention. Detailed Implementation

[0057] In order to make the objects, technical schemes and advantages of the present application clearer, the following further describes the present application with reference to the embodiments; it should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0058] The preferred embodiments of the present application are described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present application and not to limit the protection scope of the present application.

[0059] It should be pointed out that the data in the present embodiment are obtained by comprehensive analysis and evaluation of historical detection data and corresponding historical detection results of the present application in the three months before the present detection. Those skilled in the art can understand that the determination method of the present application for a single parameter can be to select the value with the highest proportion as the preset standard parameter according to the data distribution, to use weighted summation to obtain the value as the preset standard parameter, to substitute each historical data into a specific formula and to obtain the value by using the formula as the preset standard parameter, or other selection methods, as long as the present application can clearly define different specific situations in the single determination process by using the obtained value.

[0060] Please refer to Figure 1 , Figure 2 , Figure 3 and Figure 4 , which are respectively a flowchart of a preparation method of synthetic cast iron based on high proportion of scrap steel according to an embodiment of the present application; a flowchart of determining whether the preparation of the synthetic cast iron melt conforms to the preset standard according to an embodiment of the present application; a flowchart of determining whether the preparation of the second inoculation melt conforms to the preset standard according to the eutectic re-ascending rate of the second inoculation melt according to an embodiment of the present application; and a flowchart of adjustment strategy when the preparation of the second inoculation melt does not conform to the preset standard according to an embodiment of the present application.

[0061] The present embodiment provides a preparation method of synthetic cast iron based on high proportion of scrap steel, comprising:

[0062] Step S1, adding furnace charge including 70% of scrap steel, 28% of the same kind of cast iron re-melted material treated by shot blasting, 0.2% of silicon carbide with a particle size of 2 mm in a first preset amount of furnace charge mass into a medium-frequency induction furnace, and obtaining a synthetic cast iron melt after melting at 1510℃, and obtaining a first cooling curve of the synthetic cast iron melt after high-temperature standing for a preset standing time of 8 min, and obtaining a eutectic undercooling degree based on the first cooling curve, wherein the furnace temperature is kept at 1505℃ during the standing.

[0063] Step S2, when it is determined that the preparation of the synthetic cast iron melt does not conform to the preset standard according to the eutectic undercooling degree, increasing the preset standing time of the next batch or increasing the value of the first preset amount of the next batch;

[0064] Step S3, adding silicon carbide with a second preset adding amount of 0.1% of the mass of the synthetic cast iron liquid to the synthetic cast iron liquid meeting the preset standard and stirring to obtain a first inoculation liquid;

[0065] Step S4, tapping the first inoculation liquid and adding a first inoculant with a third preset adding amount of 0.4% of the mass of the first inoculation liquid to the iron stream to obtain a second inoculation liquid; determining the eutectic re-ascending rate of the second inoculation liquid based on a second cooling curve of the second inoculation liquid;

[0066] Step S5, when the preparation of the second inoculation liquid is determined not to meet the preset standard according to the eutectic re-ascending rate of the second inoculation liquid, determining whether the preparation of the second inoculation liquid meets the preset standard according to the eutectic solidification rate of the second inoculation liquid for a second time, or determining the adjustment strategy when the preparation of the second inoculation liquid does not meet the preset standard according to the relative deviation rate of the carbon equivalent;

[0067] Step S6, pouring the second inoculation liquid meeting the preset standard into a cast piece, and adding a second inoculant with a mass of 0.1% of the mass of the second inoculation liquid during pouring to obtain a synthetic cast iron cast piece.

[0068] It should be noted that the data in the present embodiment are results obtained through preliminary experiments before the present detection by the method of the present application, and each preset value can be adjusted according to specific use conditions, as long as the method of the present application can determine different specific conditions in the single determination process through the obtained numerical values. The preset values set in the present embodiment are obtained according to preliminary experiments, and each correction coefficient is also selected through experimental verification.

[0069] In the present embodiment, tapping is a conventional operation in the field of casting, that is, the process of discharging liquid iron liquid from a smelting furnace and transferring it into a ladle.

[0070] Specifically, the process of determining whether the preparation of the synthetic cast iron liquid meets the preset standard according to the eutectic supercooling degree of the synthetic cast iron liquid includes:

[0071] Comparing the eutectic supercooling degree with a first preset eutectic supercooling degree of 10℃ and a second preset eutectic supercooling degree of 20℃, respectively;

[0072] If the eutectic supercooling degree is less than the first preset eutectic supercooling degree, it is determined that the preparation of the synthetic cast iron liquid meets the preset standard;

[0073] If the eutectic undercooling is greater than or equal to the first preset eutectic undercooling and less than a second preset eutectic undercooling, it is determined that the preparation of the synthetic cast iron melt does not meet the preset standard, and the preset standing time of the next batch is increased according to the difference between the eutectic undercooling and the first preset eutectic undercooling.

[0074] If the eutectic undercooling is greater than or equal to the second preset eutectic undercooling, it is determined that the preparation of the synthetic cast iron melt does not meet the preset standard, and the value of the first preset addition amount of the next batch is increased according to the difference between the eutectic undercooling and the second preset eutectic undercooling.

[0075] Specifically, the first preset eutectic undercooling has a value range of [5℃, 12℃], and the second preset eutectic undercooling has a value range of [15℃, 25℃], preferably, the first preset eutectic undercooling has a value of 10℃, and the second preset eutectic undercooling has a value of 20℃.

[0076] Specifically, the eutectic undercooling directly reflects the number of effective crystallization cores inside the melt, and the greater the eutectic undercooling, the fewer the cores, and the greater the tendency of white mouth.

[0077] Specifically, the increase in the preset standing time of the next batch is positively correlated with the difference between the eutectic undercooling and the first preset eutectic undercooling, wherein the positive correlation is, for example, a linear positive correlation or a nonlinear positive correlation, and the linear slope of the linear positive correlation is not particularly limited. It can be understood that the greater the difference between the eutectic undercooling and the first preset eutectic undercooling, the greater the increase in the preset standing time of the next batch.

[0078] Specifically, the process of obtaining the eutectic undercooling of the synthetic cast iron melt comprises:

[0079] A first preset amount 150g of the synthetic cast iron melt is poured into a heat analysis sample cup with a built-in thermocouple, and a temperature acquisition instrument is started to record the temperature change curve of the synthetic cast iron melt from pouring to solidification, i.e. a first cooling curve. The eutectic platform region is identified from the first cooling curve, and the lowest temperature point of the platform region is determined as the first actual eutectic temperature. Wherein, when hypoeutectic gray cast iron cools down, primary austenite is first precipitated, and the temperature continues to drop. When the eutectic transformation temperature is reached, austenite and graphite are simultaneously precipitated from the liquid. This process is carried out at constant or near constant temperature, and a large amount of latent heat of crystallization is released, forming a eutectic platform on the cooling curve.

[0080] A first preset amount of the synthetic cast iron melt is poured into a spectral standard test block, and based on the determination of the chemical composition of the synthetic cast iron melt: C=3.25%, Si=1.85%, P=0.06%, according to the formula: T 理1=1153+4.25×Si%-2.5×P%, the first theoretical eutectic temperature of the synthetic cast iron liquid is calculated;

[0081] The absolute value of the difference between the first actual eutectic temperature and the first theoretical eutectic temperature is the eutectic undercooling degree of the synthetic cast iron liquid.

[0082] Specifically, the increase of the numerical value of the first preset addition amount for the next batch is provided with several adjustment modes, wherein,

[0083] If the eutectic undercooling degree difference is less than the first preset eutectic undercooling degree difference 6℃, the numerical value of the first preset addition amount is increased to the corresponding value by using the first adjustment coefficient 1.04;

[0084] If the eutectic undercooling degree difference is greater than or equal to the first preset eutectic undercooling degree difference and less than the second preset eutectic undercooling degree difference 11℃, the numerical value of the first preset addition amount is increased to the corresponding value by using the second adjustment coefficient 1.06;

[0085] If the eutectic undercooling degree difference is greater than or equal to the second preset eutectic undercooling degree difference, the numerical value of the first preset addition amount is increased to the corresponding value by using the third adjustment coefficient 1.08;

[0086] The eutectic undercooling degree difference is the difference between the eutectic undercooling degree and the second preset eutectic undercooling degree.

[0087] Specifically, the process of determining whether the preparation of the second inoculation liquid meets the preset standard according to the eutectic rise rate of the second inoculation liquid comprises:

[0088] The eutectic rise rate is compared with the first preset eutectic rise rate 0.51 and the second preset eutectic rise rate 0.81 respectively;

[0089] If the eutectic rise rate is less than the first preset eutectic rise rate, it is determined that the preparation of the second inoculation liquid does not meet the preset standard, and the adjustment strategy when the preparation of the second inoculation liquid does not meet the preset standard is determined according to the relative deviation rate of the carbon equivalent of the second inoculation liquid;

[0090] If the eutectic rise rate is greater than or equal to the first preset eutectic rise rate and less than the second preset eutectic rise rate, it is determined that the preparation of the second inoculation liquid meets the preset standard, and whether the preparation of the second inoculation liquid meets the preset standard is determined according to the secondary determination of the eutectic solidification rate of the second inoculation liquid;

[0091] If the eutectic rise rate is greater than or equal to the second preset eutectic rise rate, it is determined that the preparation of the second inoculation liquid meets the preset standard.

[0092] Specifically, the first preset eutectic rebound rate is in the range of [0.35, 0.55], and the second preset eutectic rebound rate is in the range of [0.65, 0.85], preferably, the first preset eutectic rebound rate is 0.51, and the second preset eutectic rebound rate is 0.81.

[0093] Specifically, the eutectic rebound rate reflects the strength of the graphitization dynamics triggered by the inoculation behavior. The higher the eutectic rebound rate, the more the core created by inoculation is active and the more sufficient the graphitization is.

[0094] Specifically, the process of obtaining the eutectic rebound rate of the second inoculated iron liquid comprises:

[0095] A second preset amount of 80g of the second inoculated iron liquid is poured into a heat analysis sample cup with a built-in thermocouple;

[0096] The temperature change curve of the second inoculated iron liquid from liquid cooling to solid state, i.e. the second cooling curve, is recorded;

[0097] The lowest temperature value of the eutectic transformation stage of the second inoculated iron liquid is identified and read from the second cooling curve, which is recorded as the eutectic lowest temperature;

[0098] The highest temperature value of the second inoculated iron liquid after the temperature rises due to the release of crystallization latent heat is identified and read from the second cooling curve, which is recorded as the second eutectic rebound temperature;

[0099] According to the chemical composition of the second inoculated iron liquid: carbon content C%=3.28%, silicon content Si%=1.92%, and phosphorus content P%=0.05%, the second theoretical eutectic temperature of the second inoculated iron liquid is calculated according to the formula T 理2 =1153+4.25×Si%-2.5×P%.

[0100] The difference between the second eutectic rebound temperature and the eutectic lowest temperature is calculated, which is recorded as the first difference;

[0101] The difference between the second theoretical eutectic temperature and the eutectic lowest temperature is calculated, which is recorded as the second difference; the ratio of the first difference to the second difference is recorded as the eutectic rebound rate of the second inoculated iron liquid.

[0102] Specifically, the preparation of the second inoculated iron liquid is determined according to the eutectic solidification rate of the second inoculated iron liquid, wherein,

[0103] If the eutectic solidification rate is less than the preset eutectic solidification rate 0.6℃ / s, it is determined that the preparation of the second inoculated iron liquid does not meet the preset standard, and the addition rate of the first inoculant of the next batch is increased according to the difference between the eutectic solidification rate and the preset eutectic solidification rate.

[0104] If the eutectic solidification rate is greater than or equal to the preset eutectic solidification rate, it is determined that the preparation of the second inoculation molten iron meets the preset standard;

[0105] The eutectic solidification rate is a ratio of the first difference and a eutectic temperature rising duration, wherein the eutectic temperature rising duration is a duration experienced by the second inoculation molten iron from the eutectic minimum temperature to the second eutectic temperature rising temperature obtained from the second cooling curve.

[0106] Specifically, the eutectic solidification rate characterizes the intensity and rate of graphitization process of the molten iron after eutectic undercooling, essentially reflects the overall activity of the crystallization core created by inoculation treatment and the kinetic characteristics of graphite growth. The eutectic solidification rate is the temperature rising value per unit time, the higher the value, the more graphite cores are simultaneously and rapidly precipitated and release latent heat per unit time, and the more healthy and rapid the solidification process is. On the contrary, it indicates that the graphite growth dynamics is insufficient and the process is slow. Based on this, when the measured eutectic solidification rate is less than the preset value, it is determined that the molten iron preparation does not meet the preset standard, because the slow solidification rate directly indicates that the number of nucleation is insufficient or the core activity is low, and the risk of graphite morphology deterioration is high. At this time, the first inoculant addition rate of the next batch is increased according to the difference, aiming to increase the nucleation point input intensity per unit time to inoculate the undercooled molten iron, so as to forcibly stimulate more intense and more synchronous graphitization reaction.

[0107] Specifically, the preset eutectic solidification rate is 0.6℃ / s, but the above value is not limited thereto, and the person skilled in the art can also adjust the value according to actual needs.

[0108] Specifically, the process of determining the adjustment strategy when it is determined that the preparation of the second inoculation molten iron does not meet the preset standard according to the relative deviation rate of the carbon equivalent of the second inoculation molten iron comprises:

[0109] Comparing the relative deviation rate of the carbon equivalent with a preset relative deviation rate of the carbon equivalent 2%;

[0110] If the relative deviation rate of the carbon equivalent is less than the preset relative deviation rate of the carbon equivalent, the second preset addition amount of silicon carbide of the next batch is increased according to the difference between the preset relative deviation rate of the carbon equivalent and the relative deviation rate of the carbon equivalent;

[0111] If the relative deviation rate of the carbon equivalent is greater than or equal to the preset relative deviation rate of the carbon equivalent, an ingredient out-of-control alarm is issued.

[0112] Specifically, the preset relative deviation rate of the carbon equivalent is 2%, but the above value is not limited thereto, and the person skilled in the art can also adjust the value according to actual needs.

[0113] The obtaining process of the carbon equivalent relative deviation rate comprises:

[0114] The carbon content (C%) and silicon content (Si%) of the second inoculation iron liquid are determined by using a direct-reading spectrometer;

[0115] Based on the determined carbon content (C%) and silicon content (Si%) of the second inoculation iron liquid, the actual carbon equivalent of the second inoculation iron liquid is calculated according to a carbon equivalent calculation formula: CE = C% + (1 / 3)Si%.

[0116] The difference between the calculated actual carbon equivalent and the preset carbon equivalent 4.3% is calculated, and is recorded as a carbon equivalent difference value.

[0117] The absolute value of the carbon equivalent difference value and the percentage of the preset carbon equivalent are recorded as a carbon equivalent relative deviation rate.

[0118] Specifically, the increasing range of the second preset addition amount of silicon carbide in the next batch is positively correlated with the difference between the preset carbon equivalent relative deviation rate and the carbon equivalent relative deviation rate, wherein the positive correlation is, for example, linear positive correlation or nonlinear positive correlation, and the linear slope of the linear positive correlation is not specifically limited. It can be understood that the greater the difference between the preset carbon equivalent relative deviation rate and the carbon equivalent relative deviation rate, the greater the increasing range of the second preset addition amount of silicon carbide in the next batch.

[0119] Specifically, the charge is composed of the following raw materials in mass percentage: 60%-80% of scrap steel, 20%-40% of the same type of cast iron treated by shot blasting as a recycled material, and silicon carbide added in a first preset addition amount, wherein the particle size range of the silicon carbide is 1-5mm.

[0120] Specifically, the first inoculant is a silicon-barium inoculant, and the addition amount of the first inoculant is 0.3%-0.5% of the mass of the first inoculation iron liquid, and the particle size range of the first inoculant is 3mm-10mm; the second inoculant is a silicon-barium inoculant, and the addition amount of the second inoculant is 0.1%-0.2% of the mass of the second inoculation iron liquid, and the particle size range of the second inoculant is 0.2mm-0.8mm.

[0121] So far, the technical solutions of the present application have been described in combination with the preferred embodiments shown in the drawings, but those skilled in the art can easily understand that the protection scope of the present application is obviously not limited to these specific embodiments. Those skilled in the art can make equivalent changes or replacements to the related technical features without departing from the principles of the present application, and the technical solutions after these changes or replacements will all fall within the protection scope of the present application.

Claims

1. A method for producing a synthetic cast iron based on a high proportion of scrap steel, characterized in that, The method comprises the following steps: adding a charge including scrap steel with a charge ratio of 60%-80% and a first preset amount of silicon carbide into an electric furnace for high-temperature smelting to obtain a synthetic cast iron melt, obtaining a first cooling curve of the synthetic cast iron melt after high-temperature static setting for a preset static setting time, and determining a eutectic undercooling degree based on the first cooling curve; when it is determined that the preparation of the synthetic cast iron melt does not meet a preset standard according to the eutectic undercooling degree, increasing a preset static setting time of a next batch or increasing a value of the first preset amount of the next batch; adding a second preset amount of silicon carbide to the synthetic cast iron melt meeting the preset standard and stirring to obtain a first inoculation melt; tapping the first inoculation melt and adding a first inoculant in a third preset amount in the iron stream to obtain a second inoculation melt; determining a eutectic re-ascending rate of the second inoculation melt based on a second cooling curve of the second inoculation melt; when it is determined that the preparation of the second inoculation melt does not meet the preset standard according to the eutectic re-ascending rate of the second inoculation melt, determining whether the preparation of the second inoculation melt meets the preset standard according to a eutectic solidification rate of the second inoculation melt, or determining an adjustment strategy when the preparation of the second inoculation melt does not meet the preset standard according to a carbon equivalent relative deviation rate of the second inoculation melt; casting the second inoculation melt meeting the preset standard into a cast piece, and adding a second inoculant during the casting process to obtain a synthetic cast iron cast piece.

2. The method for producing a synthetic cast iron based on a high proportion of scrap according to claim 1, characterized in that, The process of determining whether the preparation of the synthetic cast iron melt meets the preset standard according to the eutectic undercooling degree of the synthetic cast iron melt comprises: comparing the eutectic undercooling degree with a first preset eutectic undercooling degree and a second preset eutectic undercooling degree respectively; if the eutectic undercooling degree is less than the first preset eutectic undercooling degree, it is determined that the preparation of the synthetic cast iron melt meets the preset standard; if the eutectic undercooling degree is greater than or equal to the first preset eutectic undercooling degree and less than the second preset eutectic undercooling degree, it is determined that the preparation of the synthetic cast iron melt does not meet the preset standard, and the preset static setting time of the next batch is increased according to a difference between the eutectic undercooling degree and the first preset eutectic undercooling degree; if the eutectic undercooling degree is greater than or equal to the second preset eutectic undercooling degree, it is determined that the preparation of the synthetic cast iron melt does not meet the preset standard, and the value of the first preset amount of the next batch is increased according to a difference between the eutectic undercooling degree and the second preset eutectic undercooling degree.

3. The method for producing a synthetic cast iron based on a high proportion of scrap according to claim 2, characterized in that, The process of obtaining the eutectic undercooling degree of the synthetic cast iron melt comprises: pouring a first preset amount of the synthetic cast iron melt into a thermal analysis sample cup with a built-in thermocouple, recording a temperature change curve of the synthetic cast iron melt from pouring to solidification, i.e. a first cooling curve, and determining a first actual eutectic temperature from the first cooling curve; pouring a first preset amount of the synthetic cast iron melt into a spectroscopic standard test block, calculating a first theoretical eutectic temperature of the synthetic cast iron melt based on the determination of the chemical composition of the synthetic cast iron melt; an absolute value of a difference between the first actual eutectic temperature and the first theoretical eutectic temperature is the eutectic undercooling degree of the synthetic cast iron melt.

4. The method for producing a synthetic cast iron based on a high proportion of scrap according to claim 3, characterized in that, The increase of the first preset addition amount for the next batch is provided with several adjustment modes, wherein, If the eutectic undercooling difference value is less than the first preset eutectic undercooling difference value, the first preset addition amount is increased to a corresponding value by using a first adjustment coefficient; If the eutectic undercooling difference value is greater than or equal to the first preset eutectic undercooling difference value and less than the second preset eutectic undercooling difference value, the first preset addition amount is increased to a corresponding value by using a second adjustment coefficient; If the eutectic undercooling difference value is greater than or equal to the second preset eutectic undercooling difference value, the first preset addition amount is increased to a corresponding value by using a third adjustment coefficient; The eutectic undercooling difference value is the difference between the eutectic undercooling and the second preset eutectic undercooling.

5. The method for producing a synthetic cast iron based on a high proportion of scrap according to claim 4, characterized in that, The process of determining whether the preparation of the second inoculation iron liquid meets the preset standard according to the eutectic reversion rate of the second inoculation iron liquid includes: The eutectic reversion rate is compared with a first preset eutectic reversion rate and a second preset eutectic reversion rate, respectively; If the eutectic reversion rate is less than the first preset eutectic reversion rate, it is determined that the preparation of the second inoculation iron liquid does not meet the preset standard, and the adjustment strategy when the preparation of the second inoculation iron liquid does not meet the preset standard is determined according to the relative deviation rate of the carbon equivalent of the second inoculation iron liquid; If the eutectic reversion rate is greater than or equal to the first preset eutectic reversion rate and less than the second preset eutectic reversion rate, it is determined that the preparation of the second inoculation iron liquid does not meet the preset standard, and whether the preparation of the second inoculation iron liquid meets the preset standard is determined according to the secondary determination of the eutectic solidification rate of the second inoculation iron liquid; If the eutectic reversion rate is greater than or equal to the second preset eutectic reversion rate, it is determined that the preparation of the second inoculation iron liquid meets the preset standard.

6. The method for producing a synthetic cast iron based on a high proportion of scrap according to claim 5, characterized in that, The process of obtaining the eutectic reversion rate of the second inoculation iron liquid includes: A second preset amount of the second inoculation iron liquid is poured into a thermal analysis sample cup with a built-in thermocouple; The temperature change curve of the second inoculation iron liquid during the process of cooling from liquid to solid, i.e. the second cooling curve, is recorded; The lowest temperature value of the eutectic transformation stage of the second inoculation iron liquid is identified and read from the second cooling curve, which is recorded as the eutectic minimum temperature; The highest temperature value of the second inoculation iron liquid after the temperature rises due to the release of crystallization latent heat after supercooling is identified and read from the second cooling curve, which is recorded as the second eutectic reversion temperature; The second theoretical eutectic temperature of the second inoculation iron liquid is calculated according to the chemical composition of the second inoculation iron liquid; The difference between the second eutectic reversion temperature and the eutectic minimum temperature is calculated, which is recorded as the first difference; The difference between the second theoretical eutectic temperature and the eutectic minimum temperature is calculated, which is recorded as the second difference; the ratio of the first difference to the second difference is recorded as the eutectic reversion rate of the second inoculation iron liquid.

7. The method for producing a synthetic cast iron based on a high proportion of scrap according to claim 6, characterized in that, According to the secondary determination of the preparation of the second inoculation iron liquid when the eutectic solidification rate of the second inoculation iron liquid is less than the preset eutectic solidification rate, the addition rate of the first inoculant for the next batch is increased according to the difference between the eutectic solidification rate and the preset eutectic solidification rate. The eutectic solidification rate is a ratio of the first difference and a eutectic re-ascending time length, wherein the eutectic re-ascending time length is a time length experienced by the second inoculation molten iron from the eutectic minimum temperature to the second eutectic re-ascending temperature, which is obtained from the second cooling curve.

8. The method for producing a synthetic cast iron based on a high proportion of scrap according to claim 7, characterized in that, The process of determining the adjustment strategy when the preparation of the second inoculation molten iron does not meet the preset standard according to the relative deviation rate of the carbon equivalent of the second inoculation molten iron comprises: comparing the relative deviation rate of the carbon equivalent with a preset relative deviation rate of the carbon equivalent; if the relative deviation rate of the carbon equivalent is less than the preset relative deviation rate of the carbon equivalent, increasing the second preset addition amount of silicon carbide in the next batch according to a difference between the preset relative deviation rate of the carbon equivalent and the relative deviation rate of the carbon equivalent; if the relative deviation rate of the carbon equivalent is greater than or equal to the preset relative deviation rate of the carbon equivalent, issuing an ingredient out-of-control alarm; the relative deviation rate of the carbon equivalent is determined according to the carbon equivalent of the second inoculation molten iron and a preset carbon equivalent.

9. The method for producing a synthetic cast iron based on a high proportion of scrap according to claim 1, characterized in that, The furnace charge is composed of raw materials with the following mass percentages: 60%-80% of scrap steel, 20%-40% of the same type of cast iron return material treated by shot blasting, and silicon carbide added in a first preset addition amount, wherein the particle size range of the silicon carbide is 1-5 mm.

10. The method for producing a synthetic cast iron based on a high proportion of scrap according to claim 1, characterized in that, The first inoculant is a silicon-barium inoculant, and the addition amount of the first inoculant is 0.3%-0.5% of the mass of the first inoculation molten iron, and the particle size range of the first inoculant is 3 mm-10 mm; the second inoculant is a silicon-barium inoculant, and the addition amount of the second inoculant is 0.1%-0.2% of the mass of the second inoculation molten iron, and the particle size range of the second inoculant is 0.2 mm-0.8 mm.

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