A production control method for high-nickel austenitic ductile iron

Abstract

The present invention provides a production control method for high-nickel austenitic ductile iron, belonging to the technical field of cast iron production. A production control method for high-nickel austenitic ductile iron includes subjecting the molten iron after melting to spheroidizing treatment. The technological steps of the spheroidizing treatment include: providing a nickel-magnesium wire and an inoculant wire, putting the nickel-magnesium wire and the inoculant wire into a wire feeding device, and simultaneously adding the nickel-magnesium wire and the inoculant wire into a spheroidizing ladle through the wire feeding device for automatic spheroidizing, wherein the molten iron after melting is in the spheroidizing ladle. In the present invention, inoculation treatment is carried out simultaneously during the spheroidizing treatment to ensure that the graphite precipitated in the matrix structure is in a spherical shape, avoiding other shapes such as flaky and cluster-like shapes, and stabilizing and improving the spheroidizing quality.

Description

Technical Field

[0001] The present invention belongs to the technical field of cast iron production, and particularly relates to a production control method for high-nickel austenitic ductile iron. Background Art

[0002] High-nickel austenitic ductile iron is an alloy developed in recent years. This alloy can withstand high temperatures of 880 °C and is commonly used in the exhaust manifolds and supercharger housings of engines, and also as castings in a corrosion-resistant state. At present, the standard adopted in China is "High-Nickel Austenitic Cast Iron Parts" GB / T 26648-2011. This standard is divided into a total of 12 grades, including 2 gray iron grades and 10 ductile iron grades. Commonly used nodulizing alloys include nickel-magnesium alloy, silicon-magnesium alloy, and nickel-magnesium-silicon-iron alloy.

[0003] The metallographic structure of high-nickel austenitic ductile iron is spherical graphite distributed on an austenite matrix containing a small amount of carbide. This cast iron not only has high room-temperature mechanical properties, but also has good thermal shock resistance, high-temperature creep resistance, corrosion resistance, and high-temperature oxidation resistance, and at the same time has a low high-temperature thermal expansion.

[0004] At present, the entire industry uses the pressure-pack nodulizing method for producing high-nickel austenitic ductile iron: First, the nickel-magnesium nodulizer and inoculant are put into the ladle in a certain proportion, and then the molten iron in the furnace is poured into the ladle. After the nodulizing reaction is completed, casting is carried out manually or by a casting machine. This method has unstable magnesium absorption rate, extremely high requirements for tapping weight and temperature, unstable nodulization, and high failure risk.

[0005] Patent document CN105316564A provides a production process for high-nickel austenitic ductile iron using wire feeding nodulizing treatment. The production process for high-nickel austenitic ductile iron using wire feeding nodulizing treatment includes steps of batching, melting and composition adjustment, nodulizing treatment, casting, unpacking and post-treatment, and heat treatment; the nodulizing treatment is wire feeding nodulizing treatment; it can avoid the problem of poor metallography of castings, make the quality of castings stable, with low production cost and low defect rate; at the same time, it can improve the labor intensity and working conditions and improve work efficiency; the dust generated during the nodulizing process is easy to control and is more environmentally friendly. This technology uses a new nodulizer to achieve nodulizing treatment of high-nickel austenitic ductile iron through wire feeding nodulizing, so the nodulizing problems existing in the use of traditional nickel-magnesium nodulizer and inoculant still cannot be effectively solved. In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a production control method for high-nickel austenitic ductile iron to stabilize and improve the nodulizing quality in view of the deficiencies of the prior art.

[0007] To solve the above technical problem, the technical solution adopted by the present invention is:

[0008] A production control method for high-nickel austenitic ductile iron, including spheroidizing the molten iron after melting. The technological steps of the spheroidizing treatment include: providing nickel-magnesium wire and inoculating wire, putting the nickel-magnesium wire and inoculating wire into a wire feeding device, and simultaneously adding the nickel-magnesium wire and inoculating wire into a spheroidizing ladle through the wire feeding device for automatic spheroidization. The molten iron after melting is in the spheroidizing ladle;

[0009] The chemical composition of the nickel-magnesium wire is by weight percentage: nickel 80 - 85%, magnesium 15% - 20%;

[0010] The chemical composition of the inoculating wire is by weight percentage: silicon 68 - 75%, magnesium 5 - 10%, strontium 0.8 - 1.5%, and the balance is iron and inevitable impurities.

[0011] Optionally, the wire feeding speed of the wire feeding device is 26 - 30 m / min.

[0012] Optionally, the inner core powder of the nickel-magnesium wire weighs 465 ± 15 g / m, the particle size is 0.1 - 2.5 mm, the outer wrapped special steel strip has a diameter of 13.3 ± 0.3 mm, and a thickness of 0.45 ± 0.02 mm.

[0013] Optionally, the nickel-magnesium wire is obtained by the processes of crushing, sieving and remixing magnesium ingots and electrolytic nickel. The magnesium content in the magnesium ingots is above 99.95%, and the nickel content in the electrolytic nickel is above 99.95%.

[0014] Optionally, the inner core particle size of the inoculating wire is 0.1 - 2.5 mm, the inner core powder weighs 240 ± 15 g / m, the outer wrapped special steel strip has a diameter of 13.3 ± 0.3 mm, and a thickness of 0.45 ± 0.02 mm.

[0015] Optionally, the addition amount of the nickel-magnesium wire relative to the molten iron is 7 - 8 m / 500 kg.

[0016] Optionally, the addition amount of the inoculating wire relative to the molten iron is 7 - 9 m / 500 kg.

[0017] Optionally, the technological steps of the spheroidizing treatment include: the spheroidizing treatment temperature is controlled at 1600 - 1640 °C, and the time is controlled at 20 - 30 s.

[0018] Optionally, the chemical composition mass percentage of the high-nickel austenitic ductile iron is: C: ≤2.3%, Si: 4.9 - 5.5%, Mn: 0.5 - 1.5%, P: ≤0.08%, S: ≤0.03%, Ni: 34.0 - 37.0%, Cr: 1.75 - 2.25%, Mg: ≥0.03%, and the balance is Fe.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] The present invention produces high-nickel austenitic ductile iron by improving the wire feeding spheroidizing process, which can significantly stabilize and improve the spheroidizing quality. During the spheroidizing treatment of the present invention, inoculation treatment is carried out simultaneously to ensure that the graphite precipitated in the matrix structure is in a spherical shape, avoiding other shapes such as flaky and cluster-like shapes, which may lead to spheroidizing failure. Generally, spheroidizing failure is determined as follows: the graphite morphology in the matrix structure does not meet the expectations; and the proportion of spherical graphite expected to reach is less than 90%. The spheroidizing quality of the improved process of the present invention is stable. Since its popularization and use, in nearly 10,000 batches, the number of spheroidizing failures is 0, the spheroidizing rate has increased by more than 10%, and the spheroidizing quality is more stable.

[0021] The magnesium absorption rate of the process of the present invention is high, reaching 50 - 70%. If the magnesium absorption rate is low, resulting in the residual magnesium content in the casting being lower than expected, it will cause a straight-line decline in the spheroidizing rate (standard requirement ≥ 90%), and even spheroidizing decay. Spheroidizing decay of high-nickel austenitic ductile iron will show regional flaky graphite clusters, and the mechanical functions of the casting (such as tensile strength and elongation) will deteriorate severely.

[0022] The process of the present invention is automated wire feeding spheroidizing. The dust collector of the spheroidizing station is directly connected to the cover of the spheroidizing ladle, achieving dust-free and magnesium-free spheroidizing, with strong environmental protection; at the same time, the labor intensity is small, there is no need for high-temperature pressing of the ladle, and only one person is required to complete the spheroidizing treatment and automatic pouring operations.

[0023] The present invention strictly controls the composition and uniformity of the nickel-magnesium wire. The chemical composition of the nickel-magnesium wire is by weight percentage: nickel 80 - 85%, magnesium 15% - 20%, the inner core powder weight is 465 ± 15 g / m, the particle size is 0.1 - 2.5 mm, the outer wrapped special steel strip has a diameter of 13.3 ± 0.3 mm and a thickness of 0.45 ± 0.02 mm. On the one hand, it ensures that the composition is stable and qualified, and on the other hand, it ensures that the particle size distribution in the unit volume sample is uniform and the weight is within the design tolerance range. The nickel-magnesium wire is wound with a special wire reel, the inner core is filled evenly, and the outer is wrapped with a special steel strip, without phenomena such as virtual packages, open seams, cracks, material leakage, rust, and oil stains.

[0024] The present invention strictly controls the composition and uniformity of the inoculation wire. The chemical composition of the inoculation wire is by weight percentage: silicon 68 - 75%, magnesium 5 - 10%, strontium 0.8 - 1.5%, and the balance is iron and inevitable impurities. The inner core particle size is 0.1 - 2.5 mm, the inner core powder weight is 240 ± 15 g / m, the outer wrapped special steel strip has a diameter of 13.3 ± 0.3 mm and a thickness of 0.45 ± 0.02 mm. The inoculation wire is wound with a special wire reel, the inner core is filled evenly, and the outer is wrapped with a special steel strip, without phenomena such as virtual packages, open seams, cracks, material leakage, rust, and oil stains.

[0025] The process of the present invention can also accurately control the wire feeding spheroidizing time through the wire feeding equipment. The preferred wire feeding speed is 26 - 30 meters / min.

[0026] The production control method of high-nickel austenitic ductile iron of the present invention has stable spheroidizing quality, high automation degree, low labor cost, low labor intensity and strong environmental protection. Detailed implementation manners

[0027] To better understand the present invention, the content of the present invention will be further clearly elaborated below in conjunction with embodiments. However, the protected content of the present invention is not limited to the following embodiments. In the following description, a large number of specific details are given to provide a more thorough understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without one or more of these details.

[0028] The terms used herein are only for describing specific implementation manners and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of steps, operations, devices, components and / or combinations thereof.

[0029] Unless otherwise specified, all raw materials are commercially available products, and unless otherwise specified, they do not contain other components not clearly indicated except for inevitable impurities.

[0030] The present invention provides a production control method for high-nickel austenitic ductile iron, including spheroidizing the molten iron after melting, wherein:

[0031] The technological steps of the spheroidizing treatment include: providing nickel-magnesium wire and inoculant wire, putting the nickel-magnesium wire and inoculant wire into a wire feeding device, and simultaneously adding the nickel-magnesium wire and inoculant wire into a spheroidizing ladle through the wire feeding device for automatic spheroidizing. The spheroidizing ladle contains molten iron after melting;

[0032] The chemical composition of the nickel-magnesium wire is by weight percentage: nickel 80 - 85%, magnesium 15% - 20%;

[0033] As an example, the chemical composition of the nickel-magnesium wire by weight percentage can be selected as: nickel 80.6%, magnesium 19.4%; or nickel 84.7%, magnesium 15.3%; or nickel 83.5%, magnesium 16.5%; or nickel 82.4%, magnesium 17.6%;

[0034] Strictly controlling the chemical composition of the nickel-magnesium wire can ensure the stability of the composition and improve and stabilize the spheroidizing quality;

[0035] The chemical composition of the inoculant wire is by weight percentage: silicon 68 - 75%, magnesium 5 - 10%, strontium 0.8 - 1.5%, and the balance is iron and inevitable impurities;

[0036] As an example, the chemical composition of the inoculation wire can be selected as follows by weight percentage: 68.3% silicon, 9.8% magnesium, 1.5% strontium, and the balance is iron and inevitable impurities;

[0037] or, 70.4% silicon, 8.5% magnesium, 1.0% strontium, and the balance is iron and inevitable impurities;

[0038] or, 72.5% silicon, 6.3% magnesium, 1.2% strontium, and the balance is iron and inevitable impurities;

[0039] or, 74.8% silicon, 5.2% magnesium, 0.8% strontium, and the balance is iron and inevitable impurities.

[0040] Strictly controlling the chemical composition of the inoculation wire can ensure the stability of the composition, improve and stabilize the spheroidization quality; during spheroidization, inoculation treatment is carried out to make the graphite precipitation in the product matrix structure spherical, and the spheroidization rate is increased.

[0041] As an example, the wire feeding device in the present invention can select a commercially available automatic spheroidizing wire feeder.

[0042] As an example, the molten iron after melting is the molten iron obtained by batching and melting according to the requirements of high-nickel austenitic ductile iron.

[0043] In some preferred embodiments of the present invention, the wire feeding speed of the wire feeding device is 26 - 30 m / min. For example, 26 m / min, 28 m / min or 30 m / min can be selected. In the following examples, 28 m / min is set and will not be repeated.

[0044] In some preferred embodiments of the present invention, the technological steps of spheroidization treatment include: the spheroidization treatment temperature is controlled at 1600 - 1640 °C, and the time is controlled at 20 - 30 s.

[0045] In some preferred embodiments of the present invention, the inner core powder of the nickel-magnesium wire weighs 465 ± 15 g / m, the particle size is 0.1 - 2.5 mm, the outer wrapped special steel strip has a diameter of 13.3 ± 0.3 mm, and a thickness of 0.45 ± 0.02 mm. The nickel-magnesium wire in the following examples all meets the above conditions.

[0046] Strictly controlling the physical state of the nickel-magnesium wire, including the particle size and single powder weight of the nickel-magnesium wire, etc., to ensure the uniform particle size distribution of the raw materials per unit volume and further improve the spheroidization quality.

[0047] In some preferred embodiments of the present invention, the nickel-magnesium wire is obtained by the processes of crushing, sieving and remixing magnesium ingots and electrolytic nickel. The magnesium content in the magnesium ingots is above 99.95%, and the nickel content in the electrolytic nickel is above 99.95%. The following examples will not be repeated.

[0048] In some preferred embodiments of the present invention, the addition amount of the nickel-magnesium wire relative to the molten iron is 7 - 8 m / 500 kg, or 14 - 16 m / 1000 kg; alternatively, it can be 7 m / 500 kg, 7.2 m / 500 kg, 7.5 m / 500 kg, 7.8 m / 500 kg or 8 m / 500 kg, and is not limited thereto. In the following examples, 7.5 m / 500 kg is used in all cases.

[0049] In some preferred embodiments of the present invention, the core particle size of the inoculating wire is 0.1 - 2.5 mm, the core powder weight is 240 ± 15 g / m, the diameter of the special steel strip wrapped outside is 13.3 ± 0.3 mm, and the thickness is 0.45 ± 0.02 mm. In the following examples, the inoculating wires all meet the above conditions.

[0050] Strictly control the physical state of the inoculating wire, including the particle size of the inoculating wire, the powder weight per unit length, etc., to ensure that the particle size distribution of the raw materials per unit volume is uniform, thereby improving the spheroidization quality and spheroidization rate.

[0051] In some preferred embodiments of the present invention, the addition amount of the inoculating wire relative to the molten iron is 7 - 9 m / 500 kg; alternatively, it can be 7 m / 500 kg, 7.5 m / 500 kg, 8 m / 500 kg, 8.5 m / 500 kg or 9 m / 500 kg, and is not limited thereto; it can also be adjusted according to the inoculation requirements, including different product structures, silicon content in the molten iron in the furnace, etc. In the following examples, 8 m / 500 kg is used in all cases.

[0052] The present invention will be specifically described by taking a certain type of austenitic ductile iron material as the research object. The chemical composition (mass fraction) of the austenitic ductile iron material is shown in the following table:

[0053] C% Si% Mn% Ni% Cr% Mg% Fe ≤2.3 4.9-5.5 0.5-1.5 34.0-37.0 1.75-2.25 ≥0.03 Balance

[0054] The raw material ratio (mass fraction) of the high-nickel austenitic ductile iron is shown in the following table:

[0055] Material Name Ratio Same-material Returned Materials (Gating System, Scrap Parts) 50-70 High-purity Pig Iron Grade C2 14-23 Low-carbon Scrap Steel 3.2-5.2 Electrolytic Manganese 0.18-0.3 Electrolytic Nickel 10.4-17.3 Low-carbon Ferrochrome FeCr55C0.25 1.0-1.7 72 Ferrosilicon 1-2.5

[0056] The melting process of the above raw materials includes: controlling the melting temperature at 1600 - 1650 °C, and controlling the melting time per single furnace at 40 - 60 min.

[0057] The matrix structure of the austenitic ductile iron material: austenite + a small amount of grain boundary carbides + spherical graphite. Graphite type: spherical. Graphite size: 4 - 8. Spheroidization level: 1 - 3 levels.

[0058] In the following tests, the raw material ratio (mass fraction) of the austenitic ductile iron is shown in the following table:

[0059] Material Name Ratio Same-material Returned Materials (Gating System, Scrap Parts) 62 High-purity Pig Iron Grade C2 17 Low-carbon Scrap Steel 4.5 Electrolytic Manganese 0.20 Electrolytic Nickel 13.5 Low-carbon Ferrochrome FeCr55C0.25 1.3 72 Ferrosilicon 1.5

[0060] The smelting process includes: controlling the smelting temperature at 1630 ± 20 °C and the smelting time per furnace at 50 ± 5 min.

[0061] The molten iron is obtained by smelting with the same raw materials and smelting process as above, and the molten iron is spheroidized through the following implementation examples.

[0062] Example 1

[0063] The molten iron after smelting the above austenitic ductile iron material is spheroidized by the wire feeding spheroidizing method. A nickel-magnesium wire and an inoculating wire are provided. The nickel-magnesium wire and the inoculating wire are put into the wire feeding equipment, and the nickel-magnesium wire and the inoculating wire are simultaneously added into the spheroidizing ladle through the wire feeding equipment for automatic spheroidization. The molten iron in the spheroidizing ladle is the molten iron after smelting. Among them: the chemical composition of the nickel-magnesium wire is 80.6% nickel and 19.4% magnesium by weight percentage; the chemical composition of the inoculating wire is 68.3% silicon, 9.8% magnesium, 1.5% strontium, and the balance is iron and unavoidable impurities.

[0064] Example 2

[0065] The molten iron after smelting the above austenitic ductile iron material is spheroidized by the wire feeding spheroidizing method. A nickel-magnesium wire and an inoculating wire are provided. The nickel-magnesium wire and the inoculating wire are put into the wire feeding equipment, and the nickel-magnesium wire and the inoculating wire are simultaneously added into the spheroidizing ladle through the wire feeding equipment for automatic spheroidization. The molten iron in the spheroidizing ladle is the molten iron after smelting. Among them: the chemical composition of the nickel-magnesium wire is 84.7% nickel and 15.3% magnesium by weight percentage; the chemical composition of the inoculating wire is 74.8% silicon, 5.2% magnesium, 0.8% strontium, and the balance is iron and unavoidable impurities.

[0066] Example 3

[0067] The molten iron after smelting the above austenitic ductile iron material is spheroidized by the wire feeding spheroidizing method. A nickel-magnesium wire and an inoculating wire are provided. The nickel-magnesium wire and the inoculating wire are put into the wire feeding equipment, and the nickel-magnesium wire and the inoculating wire are simultaneously added into the spheroidizing ladle through the wire feeding equipment for automatic spheroidization. The molten iron in the spheroidizing ladle is the molten iron after smelting. Among them: the chemical composition of the nickel-magnesium wire is 83.5% nickel and 16.5% magnesium by weight percentage; the chemical composition of the inoculating wire is 72.5% silicon, 6.3% magnesium, 1.2% strontium, and the balance is iron and unavoidable impurities.

[0068] Example 4

[0069] The molten iron obtained by melting the above austenitic ductile iron material is spheroidized by the wire feeding spheroidizing method. A nickel-magnesium wire and an inoculant wire are provided, and the nickel-magnesium wire and the inoculant wire are put into a wire feeding device. The nickel-magnesium wire and the inoculant wire are simultaneously added into the spheroidizing ladle through the wire feeding device for automatic spheroidization. The spheroidizing ladle contains the molten iron after melting. Among them: The chemical composition of the nickel-magnesium wire is 82.6% nickel and 17.4% magnesium by weight percentage; the chemical composition of the inoculant wire is 70.4% silicon, 8.5% magnesium, 1.0% strontium, and the balance is iron and unavoidable impurities.

[0070] Comparative Example 1

[0071] The molten iron obtained by melting the above austenitic ductile iron material is spheroidized by the pressure-packing spheroidizing method. A nickel-magnesium spheroidizing agent and an inoculant are provided. The nickel-magnesium spheroidizing agent and the inoculant are pre-put into the spheroidizing ladle, and then the molten iron is poured into the spheroidizing ladle for spheroidization. Among them: The chemical composition of the nickel-magnesium spheroidizing agent and the inoculant is the same as that in Example 1.

[0072] Comparative Example 2

[0073] The molten iron obtained by melting the above austenitic ductile iron material is spheroidized by the wire feeding spheroidizing method. A nickel-magnesium wire and an inoculant are provided. The inoculant is put into the spheroidizing ladle, and then the molten iron is tapped; the nickel-magnesium wire is put into the wire feeding device, and the nickel-magnesium wire is added into the spheroidizing ladle through the wire feeding device for automatic spheroidization. The spheroidizing ladle contains a mixture of the inoculant and the molten iron after melting. Among them: The chemical composition of the nickel-magnesium spheroidizing agent and the inoculant is the same as that in Example 1..

[0074] Comparative Example 3

[0075] The molten iron obtained by melting the above austenitic ductile iron material is spheroidized by the wire feeding spheroidizing method. A nickel-magnesium wire and an inoculant wire are provided, and the nickel-magnesium wire and the inoculant wire are put into a wire feeding device. The nickel-magnesium wire and the inoculant wire are simultaneously added into the spheroidizing ladle through the wire feeding device for automatic spheroidization. The spheroidizing ladle contains the molten iron after melting. Among them: The chemical composition of the nickel-magnesium wire is 80.6% nickel and 19.4% magnesium by weight percentage; the chemical composition of the inoculant wire is 77.5% silicon, 1.5% strontium, and the balance is iron and unavoidable impurities.

[0076] The molten iron after spheroidization treatment in Examples 1 - 4 and Comparative Examples 1 - 3 is skimmed, and then cast by a casting machine to obtain castings; the castings are cooled for 1 h, then held at 950 °C for 4 hours, taken out of the furnace and cooled to room temperature to obtain finished products.

[0077] The metallographic structure and mechanical properties of the finished products prepared in Examples 1 - 4 and Comparative Examples 1 - 3 are detected, and the detection results are shown in the following table:

[0078] Serial Number / Item Standard Requirements Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Number of Nodular Graphite <![CDATA[Greater than 100 / mm 2 > 383 402 370 394 268 281 289 Spheroidization Rate ≥90% 97 95 95 96 86 88 85 Tensile Strength ≥370 MPa 510 504 496 490 425 417 431 Elongation ≥10% 24.0 25.5 24.5 26.5 20.0 19.5 18.3

[0079] As can be seen from the above test results, the spheroidization rate of the finished product obtained by the spheroidizing treatment of the present invention is stable above 90%, and both the tensile strength and elongation are significantly better than the standard requirements.

[0080] Under the same conditions of the spheroidizing agent and inoculant of the present invention, the spheroidization rate of the conventional pressure-packing method for spheroidization (Comparative Example 1) is relatively low and does not meet the requirements, and the tensile strength and elongation of the finished product are significantly inferior to those of Example 1.

[0081] Under the same conditions of the spheroidizing agent and inoculant of the present invention, changing the feeding method of the spheroidizing agent and inoculant will significantly affect the spheroidization rate of the finished product, and at the same time, the decrease in tensile strength and elongation is significantly different from that of Example 1.

[0082] Under the same conditions of the spheroidizing process of the present invention, changing the chemical composition of the inoculant results in obvious changes in the corresponding indexes of the finished product, indicating that the compatibility of the inoculant and the spheroidizing agent decreases, affecting the spheroidization rate and mechanical properties of the finished product.

[0083] The present invention conducts an installation test on the finished product obtained by the spheroidizing treatment of Example 1. For a production volume of 2,000 pieces, the statistical results show that the defective conditions of the castings, including sand holes and cold shuts, are both 0.

[0084] Since the spheroidizing treatment process of the present invention was put into use, in nearly 10,000 batches, the number of spheroidizing failures is 0, the raw materials are fully utilized, the product quality is effectively controlled, the cost is balanced, and the economic benefits are obvious.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Other modifications or equivalent replacements made by those of ordinary skill in the art to the technical solutions of the present invention should be covered within the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solutions of the present invention.

Claims

1. A production control method for high-nickel austenitic ductile iron, characterized in that: The chemical composition of the high-nickel austenitic ductile iron is as follows by mass percentage: C: ≤2.3%, Si: 4.9 - 5.5%, Mn: 0.5 - 1.5%, P: ≤0.08%, S: ≤0.03%, Ni: 34.0 - 37.0%, Cr: 1.75 - 2.25%, Mg: 0.03%, and the balance is Fe. It includes spheroidizing the molten iron after melting. The technological steps of the spheroidizing treatment include: providing a nickel-magnesium wire and an inoculant wire, putting the nickel-magnesium wire and the inoculant wire into a wire feeding device, and simultaneously adding the nickel-magnesium wire and the inoculant wire into the spheroidizing ladle through the wire feeding device for automatic spheroidization. The molten iron in the spheroidizing ladle is the molten iron after melting; The chemical composition of the nickel-magnesium wire is by weight percentage: nickel 80 - 85%, magnesium 15% - 20%; The chemical composition of the inoculant wire is by weight percentage: silicon 68 - 75%, magnesium 5 - 10%, strontium 0.8 - 1.5%, and the balance is iron and inevitable impurities; The spheroidizing treatment temperature is controlled at 1600 - 1640 °C, and the time is controlled at 20 - 30 s.

2. The production control method of a high-nickel austenitic ductile iron according to claim 1, characterized in that: The wire feeding speed of the wire feeding device is 26 - 30 m / min.

3. The production control method of a high-nickel austenitic ductile iron according to claim 1, characterized in that: The inner core powder of the nickel-magnesium wire weighs 465 ± 15 g / m, the particle size is 0.1 - 2.5 mm, the outer wrapped special steel strip has a diameter of 13.3 ± 0.3 mm, and a thickness of 0.45 ± 0.02 mm.

4. The production control method of a high-nickel austenitic ductile iron according to claim 3, characterized in that: The nickel-magnesium wire is obtained by the processes of crushing, sieving and remixing magnesium ingots and electrolytic nickel. The magnesium content in the magnesium ingots is above 99.95%, and the nickel content in the electrolytic nickel is above 99.95%.

5. The production control method of a high-nickel austenitic ductile iron according to claim 1, characterized in that: The inner core particle size of the inoculant wire is 0.1 - 2.5 mm, the inner core powder weighs 240 ± 15 g / m, the outer wrapped special steel strip has a diameter of 13.3 ± 0.3 mm, and a thickness of 0.45 ± 0.02 mm.

6. The production control method of a high-nickel austenitic ductile iron according to claim 1, characterized in that: The addition amount of the nickel-magnesium wire relative to the molten iron is 7 - 8 m / 500 kg.

7. The production control method of a high-nickel austenitic ductile iron according to claim 1, characterized in that: The addition amount of the inoculant wire relative to the molten iron is 7 - 9 m / 500 kg.