Production method for reducing deviation of residual magnesium content of spheroidal inoculated cast iron

Abstract

The present application relates to the production technology field of nodular cast iron, and discloses a production method for reducing the deviation of residual magnesium content of spheroidizing inoculated cast iron, comprising the following steps: S10: determining a spheroidizing temperature suggestion value according to the single-piece weight and wall thickness of a predetermined product, and determining a spheroidizing temperature median value T0 according to the spheroidizing temperature suggestion value; S20: determining a theoretical feeding amount L1 according to the actual tapping iron amount of a single ladle, T0 and the magnesium absorption rate of the spheroidizing line of the current production line; S30: measuring the temperature T1 at 5-13 cm below the center of the liquid surface of the ladle, correcting the actual feeding amount L2 based on T1, L2=L1+(T1-T0)*a*L1, wherein a is 0.0015-0.0023, the units of T1 and T0 are ℃, and the units of L1 and L2 are m. The corrected spheroidizing agent feeding amount not only reduces the overall use amount of the spheroidizing line, but also unexpectedly reduces the fluctuation range of residual magnesium content of different batches of ladles.

Description

Technical Field

[0001] This invention relates to the field of ductile iron production technology, specifically to a production method for reducing the deviation in residual magnesium content in spheroidized inoculated cast iron. Background Technology

[0002] Spheroidizing is one of the main steps in the production of ductile iron. Its principle involves continuously feeding a cored wire containing a spheroidizing agent into the deep molten iron using a wire feeder to achieve spheroidization of graphite, thereby improving the mechanical properties of the cast iron. The feed rate directly affects the final residual magnesium concentration in the molten iron; increasing the feed rate will increase the residual magnesium content, but excessive magnesium can lead to defects such as white cast iron and shrinkage cavities; reducing the feed rate may result in poor spheroidization. In actual production, fluctuations in the residual magnesium content between different batches (ladles) are a key factor affecting the consistency of performance of ductile iron products from different batches.

[0003] CN111842811A designs the length of wire used and the feed speed parameters for each ladle of molten iron based on the amount of molten iron produced and the temperature of the molten iron. The molten iron temperature is designed based on the product wall thickness and is divided into end cap products (molten iron temperature of 1520-1530℃), brake products (molten iron temperature of 1540-1550℃), pipe bending products (molten iron temperature of 1550-1560℃), and pipe clamp products (molten iron temperature of 1560-1570℃).

[0004] CN115466822A first obtains the temperature inside the ladle and determines the temperature difference between the upper and lower regions inside the ladle. Based on the magnitude of the temperature difference or the comparison between the temperature difference and a set threshold, the feeding speed of the guide device is increased or decreased to improve the uniformity of spheroidization treatment in a single ladle.

[0005] CN120828131A divides the molten iron temperature into temperature ranges and adjusts the basic amount of magnesium wire based on the different molten iron temperature ranges in the spheroidizing treatment batch, but does not mention the numerical difference between the ranges or how to adjust them.

[0006] None of the above solutions address the stability control of residual magnesium content in ladles across different batches from manufacturers producing products with similar wall thicknesses. Furthermore, while the spheroidizing feed rate is positively correlated with residual magnesium content within a certain range, there is also a saturation threshold; excessive magnesium fed into the spheroidizing line is prone to overflowing as vapor. Therefore, how to improve the stability of residual magnesium content while controlling the feed rate at a lower level is also one of the main research directions in the spheroidizing inoculation process. Summary of the Invention

[0007] One of the objectives of this invention is to overcome the deficiencies in the existing technology and provide a production method to reduce the deviation of residual magnesium content in spheroidized cast iron. By adjusting the feed amount of the spheroidizing line through measured temperature and correction formula, the production cost can be reduced and the fluctuation of residual magnesium content in different batches of molten iron can be minimized.

[0008] To achieve the above-mentioned technical effects, the technical solution of the present invention is as follows: a production method for reducing the residual magnesium content deviation in spheroidized inoculated cast iron, comprising the following steps: S10: The recommended point value or the midpoint value of the recommended range for determining the spheroidizing temperature is determined by the unit weight and wall thickness of the predetermined product, and is then set as the median value of the spheroidizing temperature T0. S20: The theoretical feed rate L1 is determined based on the actual iron output of a single ladle, T0, the magnesium absorption rate of the current production line spheroidizing line, the sulfur content before spheroidizing, the magnesium content per meter of the line, and the target sulfur content and target residual magnesium content after spheroidizing. S30: The measured temperature T1 is 5-13 cm below the center of the liquid surface in the ladle. The actual feed amount L2 of the spheroidization line is obtained based on T1. L2 = L1 + (T1 - T0) * a * L1, where a is 0.0015-0.0023, T1 and T0 are in °C, and L1 and L2 are in m.

[0009] Specifically, the temperature is measured at points 5, 6, 7, 8, 9, 10, 11, 12, and 13 cm below the center of the molten steel surface in the ladle, or at a range of two points representing the maximum and minimum values. Further, the temperature is measured at 8-12 cm below the center of the molten steel surface in the ladle, and even further, at 8-11 cm below the center of the molten steel surface in the ladle.

[0010] The preferred technical solution is that 'a' is 0.00175-0.0021. Specifically, 'a' can be a value of 0.00175, 0.0018, 0.00185, 0.0019, 0.00195, 0.0020, 0.00205, or 0.0021, or a range of two of these values ​​as the maximum and minimum values. Further, 'a' is 0.0018-0.00195.

[0011] A preferred technical solution further includes S11: sampling the molten iron after spheroidizing treatment on the production line and determining the residual magnesium content, and combining the spheroidizing line feed rate and the spheroidizing line magnesium content to obtain the magnesium absorption rate of the current production line spheroidizing line; The current magnesium absorption rate of the spheroidizing line is calculated as follows: [0.76 * (sulfur content before spheroidizing - sulfur content after spheroidizing) + residual magnesium content of the sample] * mass of molten iron / (feed amount of spheroidizing line * magnesium content of spheroidizing line) * 100%. The units for the mass of molten iron and the feed amount of spheroidizing line are kg. The sulfur content before spheroidizing, the sulfur content after spheroidizing, the residual magnesium content, the magnesium content of the spheroidizing line, and the current magnesium absorption rate of the spheroidizing line are all percentages.

[0012] The preferred technical solution is that the sulfur content of the molten iron before feeding into the spheroidizing line is not higher than 0.02%, and further, not higher than 0.015%.

[0013] The preferred technical solution is: L1 = [(sulfur content before spheroidization - target sulfur content) * 0.76 + target residual magnesium content] * actual iron output / (magnesium absorption rate of the current spheroidization line * magnesium content per meter of the current spheroidization line); The sulfur content before spheroidization, the target sulfur content, the target residual magnesium content, the current magnesium absorption rate of the spheroidizing line as a percentage, the actual iron output in kg, and the magnesium content per meter of the current spheroidizing line in kg / m are all listed.

[0014] The preferred technical solution is to add the inoculating wire and the spheroidizing wire to the molten iron simultaneously.

[0015] The preferred technical solution is that the feeding amount of inoculated wire L3 = (actual output iron amount * current inoculation percentage of inoculated wire in the production line) / current silicon content per meter of inoculated wire; where the unit of actual output iron amount is kg, and the unit of current silicon content per meter of inoculated wire is kg / m.

[0016] The preferred technical solution is that the spheroidized wire core powder comprises: 37%-54.5% Si, 2%-3% Ca, 17.5%-30% Mg, 1.5%-2.4% Ba, 1.5%-2.4% RE, 0.45%-1.2% Al and the balance iron, with a feeding speed of 26-36 m / min.

[0017] The preferred technical solution is that the core powder composition of the inoculated filament includes: 50%-60% Si, 1%-2% Ca, 2%-4% Ba and the balance iron, with a feeding speed of 30-40 m / min; the inoculation percentage of the inoculated filament is 22%-28%.

[0018] The advantages and beneficial effects of this invention are as follows: This production method for reducing the deviation of residual magnesium content in spheroidized cast iron is based on the difference between the measured temperature of molten iron and the median spheroidizing temperature to correct the spheroidizing line feed amount. The corrected spheroidizing agent feed amount not only reduces the overall amount of spheroidizing line used in the production line and lowers production costs, but also effectively reduces the fluctuation range of residual magnesium content in ladles of different batches, thereby improving the consistency of performance of different batches of ductile iron products and facilitating the high-quality mass production of ductile iron. Compared with multi-segment temperature testing of ladle depth, measuring the temperature 5-13cm below the center of the ladle liquid surface is more convenient and safer. Production practice has proven its high feasibility, and the cast iron products have no obvious defects such as white cast iron or shrinkage cavities. Attached Figure Description

[0019] Figure 1 It is a statistical curve of residual magnesium content in multiple batches of molten iron using the theoretical feed rate of Comparative Example 1 and the spheroidization line 1. Figure 2 The statistical curve of residual magnesium content in batches of molten iron with modified feed rate and spheroidization line 1 in Example 1 is used. Figure 3 It is a statistical curve of residual magnesium content in multiple batches of molten iron using the theoretical feed rate of Comparative Example 2 and the spheroidization line 2. Figure 4 The statistical curve of residual magnesium content in batches of molten iron using the modified feed rate and spheroidization line 2 in Example 2 is shown. Detailed Implementation

[0020] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and examples. The following examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0021] Median spheroidization temperature The median spheroidizing temperature is determined based on various influencing factors such as the product and steel grade of ductile iron. When the spheroidizing temperature of the recommended casting temperature is a point value, that point value is the median spheroidizing temperature. When the spheroidizing temperature of the recommended casting temperature is a range value, the median spheroidizing temperature is half the sum of the upper and lower limits of the range (the midpoint of the range).

[0022] For example, the recommended casting temperatures for centrifugal ductile iron pipes used in cast iron pipes and cast iron cylinder liners are as follows: For a nominal diameter of 100mm, the median spheroidizing temperature is 1520℃; for a nominal diameter of 200-300mm, the median spheroidizing temperature is 1500℃; for a nominal diameter of 400-1000mm, the median spheroidizing temperature is 1460℃; for a nominal diameter of 1200-1400mm, the median spheroidizing temperature is 1450-1480℃; for a nominal diameter of 1600mm, the median spheroidizing temperature is 1410-1460℃; and for a nominal diameter of 1800-2200mm, the median spheroidizing temperature is 1420-1450℃. For example, the spheroidizing temperature of isothermally quenched ductile iron castings (copper-molybdenum ADJ) used to produce automobile timing gears is 1430-1450℃, and the median spheroidizing temperature is 1440℃.

[0023] Example 1

[0024] The core powder composition of spheroidizing line 1 is: Si 44.6%, Ca 2.6%, Mg 29%, Ba 2.13%, RE 2.15%, Al 0.74%, Ti 0.06%, Cr 0.06%, MgO 1%, with the balance being Fe and unavoidable impurities. The core powder mass is 239 g / m. By sampling the molten iron after spheroidizing treatment and determining the residual magnesium content, combined with the spheroidizing line feed rate and residual magnesium content, the magnesium absorption rate of this spheroidizing line was found to be 52%, and the feed rate was 35 m / min.

[0025] The core powder composition of the inoculated yarn is: Si 55.25%, Ca 1.45%, Ba 2.37%, with a powder weight of 260 g / m. The inoculated yarn used in the current production line has an inoculation percentage of 25% and a feeding speed of 38 m / min.

[0026] The target residual magnesium content is 0.045%, and the actual residual magnesium content can range from 0.032% to 0.05%. The sulfur content of the molten iron before feeding into the spheroidizing line is controlled to be below 0.02%.

[0027] The production method for reducing the residual magnesium content deviation in spheroidized cast iron was applied to the production of cast iron raw materials with a nominal diameter of 1200-1400 mm, with a spheroidizing temperature of 1450-1480℃ and a median spheroidizing temperature T0 of 1465℃.

[0028] The production method for reducing the residual magnesium content deviation in spheroidized inoculated cast iron includes the following steps: S1: Calculate the theoretical feed rate L1, with the molten iron mass of the ladle being 730kg, the sulfur content before spheroidization being 0.015%, the target sulfur content after spheroidization being 0.009%, and the target residual magnesium content being 0.045%. L1 = [(sulfur content before spheroidization - target sulfur content) * 0.76 + target residual magnesium content] * actual iron output / (magnesium absorption rate of the current spheroidization line * magnesium content per meter of the current spheroidization line) = [(0.015% - 0.009%) * 0.76 + 0.045%] * 730 / (52% * 0.239 * 29%) = 10.038m.

[0029] S2: A handheld rapid thermocouple thermometer is used. The thermometer is manually inserted into the molten iron in the ladle to measure the temperature. The measured temperature T1 at 10cm below the center of the liquid surface in the ladle is 1440℃. The value of a is taken as 0.0019. Based on the measured temperature, the actual feed rate L2 is corrected to L1+(T1-T0)*a*L1=10.038+(1440-1465)*0.0019*10.038=9.561m; Based on the theoretical feed rate L1 being 100%, the actual feed rate L2 saves 4.75% of the spheroidization line.

[0030] S3: Calculate the feed rate L3 of the inoculated wire. With the molten iron in the ladle as 730kg, L3 = (actual amount of iron produced * current percentage of inoculated wire in the production line) / current silicon content per meter of inoculated wire = (730 * 25%) / (0.26 * 55.25%) = 12.704m.

[0031] S4: Based on the calculated values ​​of L2 and L3 above, the wire feeding device simultaneously introduces the spheroidized wire and the inoculated wire into the ladle; S5: After the wire feeding is completed, the spheroidization and inoculation process ends, and the ladle is removed from the spheroidization wire feeding station; S6: After spheroidization and inoculation are completed, the ladle is introduced to the casting station, and the residual magnesium content is sampled and tested.

[0032] Example 2

[0033] Example 2 is based on Example 1, except that it uses spheroidized wire 2: Si 51.6%, Ca 2.1%, Mg 20%, Ba 1.83%, La 1.75%, Al 0.87%, MgO 1%, with the balance being Fe and unavoidable impurities. The core powder mass is 251 g / m, the magnesium absorption rate of this spheroidized wire is 45%, and the wire feeding speed is 35 m / min.

[0034] Comparative Example Comparative Example 1 is based on Example 1, except that: the uncorrected theoretical spheroidizing line feed amount L1 and the inoculated silk feed amount L3 are used.

[0035] Comparative Example 2 is based on Example 2, except that it uses the uncorrected theoretical spheroidizing line feed amount L1 and the inoculated silk feed amount L3.

[0036] Comparison of data from Example 1 and Comparative Example 1: 1. Usage of 1 ton of molten iron spheroidizing line in Example 1 and Comparative Example Based on the spheroidizing line and inoculation line of the embodiment, the monthly statistics of the number of ladles, the usage of spheroidizing lines (Mg28 - spheroidizing line 1, Mg20 - spheroidizing line 2), and the usage per ton of molten iron for spheroidizing line 1 before and after the adoption of the correction method for the two production lines are shown in the table below: Comparison of monthly statistics on the number of ladles, usage of spheroidizing line 1, and usage per ton of molten iron in Example 1 and Comparative Example 1:

[0037] *: The method for correcting the sphericity line was adopted starting in June 25.

[0038] As shown in the table above, taking the usage of 1 ton of molten iron spheroidizing line 1 from 24 / 1 to 25 / 2 as 100%, the usage of 1 ton of molten iron spheroidizing line 1 from 25 / 7, 11, and 12 is reduced by 13.5%.

[0039] 2. Stability of residual magnesium in ductile iron in Example 1 and Comparative Example 1 Spectral test data of molten iron samples after spheroidization and inoculation: Line graph of residual magnesium data from 46 sets of comparative example 1 is shown below. Figure 1 As shown in the figure, the line graph of residual magnesium data from 46 sets of Example 1 is as follows: Figure 2 As shown, the residual magnesium statistics for Comparative Example 1 and Example 1 are as follows: In Comparative Example 1, the 10 sets of residual magnesium data were greater than 0.05% (the number of data points greater than 0.05% accounted for 21.74% of the total data), with an average of 0.048% (represented as N%), and the variance of N was 7.33 × 10⁻⁶. -6 ; In Example 1, no residual magnesium data greater than 0.05% were found. The average of the first 46 groups was taken as 0.046% (denoted as M%), and the variance of M was 4.64 × 10⁻⁶. -6 .

[0040] Statistical analysis of data from Comparative Example 1 and Example 1 shows that the residual magnesium data of different batches of cast iron based on the modified spheroidizing line feed amount (Example 1) fluctuates less around the average value. In other words, the residual magnesium of multiple batches of ductile iron produced on the same production line fluctuates less and has higher stability.

[0041] When a is 0.0016, the amount of molten iron used in the spheroidizing line 1 is larger than in Example 1. 46 sets of residual magnesium data were collected, of which 7 sets had residual magnesium exceeding 0.05%, with an average of 0.04723% (denoted as Q%). The variance of Q is 9.27 × 10⁻⁶.-6 ; When a is 0.0018, the amount of molten iron used in line 1 is slightly larger than in Example 1. 46 sets of residual magnesium data were collected, and no residual magnesium exceeded 0.05%, with an average value of 0.0459% (referred to as J%). The variance of the J value is 7.23 × 10⁻⁶. -6 ; When 'a' is 0.0022, the amount of molten iron used in the spheroidizing line 1 is relatively small. 46 sets of residual magnesium data were taken, of which three sets had residual magnesium exceeding 0.05%, with an average of 0.04567% (denoted as P%). The variance of the P-value is 9.70 × 10⁻⁶. -6 ; According to statistics, the closer the a value is to 0.0019, the smaller the fluctuation range of residual magnesium in cast iron, and the higher the stability of residual magnesium value.

[0042] 3. Stability of residual magnesium in ductile iron in Example 2 Spectral test data of molten iron samples after spheroidization and inoculation: Line graphs of residual magnesium data from 23 comparative examples are shown below. Figure 3 As shown, three groups of residual magnesium data are greater than 0.05%; the line graph of residual magnesium data for 60 groups of Example 2 in Comparative Example 2 is shown below. Figure 4 As shown, the residual magnesium content is concentrated between 0.038% and 0.047%, none of which is greater than 0.05%.

[0043] Data from Example 2 shows that the method for correcting the feed amount of the spheroidizing line is also applicable to spheroidizing line 2.

[0044] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A production method for reducing the deviation in residual magnesium content in spheroidized inoculated cast iron, characterized in that, Includes the following steps: S10: The recommended point value or the midpoint value of the recommended range for determining the spheroidizing temperature is determined by the unit weight and wall thickness of the predetermined product, and is then set as the median value of the spheroidizing temperature T0. S20: The theoretical feed rate L1 is determined based on the actual iron output of a single ladle, T0, the magnesium absorption rate of the current production line spheroidizing line, the sulfur content before spheroidizing, the magnesium content per meter of the line, and the target sulfur content and target residual magnesium content after spheroidizing. S30: The measured temperature T1 is 5-13 cm below the center of the liquid surface in the ladle. The actual feed amount L2 of the spheroidization line is obtained based on T1. L2 = L1 + (T1 - T0) * a * L1, where a is 0.0015-0.0023, T1 and T0 are in °C, and L1 and L2 are in m.

2. The production method for reducing the residual magnesium content deviation in spheroidized inoculated cast iron according to claim 1, characterized in that, a is 0.00175-0.0021.

3. The production method for reducing the residual magnesium content deviation in spheroidized inoculated cast iron according to claim 1, characterized in that, It also includes S11: sampling the molten iron after spheroidizing treatment on the production line and determining the residual magnesium content, and combining the spheroidizing line feed rate and the spheroidizing line magnesium content to obtain the magnesium absorption rate of the current production line spheroidizing line; The current magnesium absorption rate of the spheroidizing line is calculated as follows: [0.76 * (sulfur content before spheroidizing - sulfur content after spheroidizing) + residual magnesium content of the sample] * mass of molten iron / (feed amount of spheroidizing line * magnesium content of spheroidizing line) * 100%. The units for the mass of molten iron and the feed amount of spheroidizing line are kg. The sulfur content before spheroidizing, the sulfur content after spheroidizing, the residual magnesium content, the magnesium content of the spheroidizing line, and the current magnesium absorption rate of the spheroidizing line are all percentages.

4. The production method for reducing the residual magnesium content deviation in spheroidized inoculated cast iron according to claim 1, characterized in that, The sulfur content of the molten iron before feeding into the spheroidizing line should not exceed 0.02%.

5. The production method for reducing the residual magnesium content deviation in spheroidized inoculated cast iron according to claim 1, characterized in that, L1 = [(Sulfur content before spheroidization - Target sulfur content) * 0.76 + Target residual magnesium content] * Actual amount of iron produced / (Magnesium absorption rate of the current spheroidization line * Magnesium content per meter of the current spheroidization line); The sulfur content before spheroidization, the target sulfur content, the target residual magnesium content, the current magnesium absorption rate of the spheroidizing line as a percentage, the actual iron output in kg, and the magnesium content per meter of the current spheroidizing line in kg / m are all listed.

6. The production method for reducing the residual magnesium content deviation in spheroidized inoculated cast iron according to claim 1, characterized in that, The inoculating wire and the spheroidizing wire are added to the molten iron at the same time.

7. The production method for reducing the residual magnesium content deviation in spheroidized inoculated cast iron according to claim 6, characterized in that, The feed rate of the inoculated wire L3 = (actual output iron amount * current inoculation percentage of the inoculated wire on the production line) / current silicon content per meter of inoculated wire; where the actual output iron amount is in kg and the current silicon content per meter of inoculated wire is in kg / m.

8. The production method for reducing the residual magnesium content deviation in spheroidized inoculated cast iron according to claim 7, characterized in that, The spheroidized wire core powder comprises: 37%-54.5% Si, 2%-3% Ca, 17.5%-30% Mg, 1.5%-2.4% Ba, 1.5%-2.4% RE, 0.45%-1.2% Al, and the balance iron, with a feeding speed of 26-36 m / min.

9. The production method for reducing the residual magnesium content deviation in spheroidized inoculated cast iron according to claim 7 or 8, characterized in that, The core powder composition of the inoculated filament includes: 50%-60% Si, 1%-2% Ca, 2%-4% Ba and the balance iron, with a feeding speed of 30-40 m / min; the inoculation percentage of the inoculated filament is 22%-28%.

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