Solid phase change modified nodular cast iron and preparation method and application thereof

Abstract

The invention discloses solid phase change modified nodular cast iron and a preparation method and application thereof, and belongs to the technical field of nodular cast iron modification. The method disclosed by the invention comprises the following steps: carrying out ferritization treatment on as-cast nodular cast iron to obtain ferritized nodular cast iron; the ferritized nodular cast iron is sequentially subjected to isothermal quenching, medium-temperature tempering and high-temperature tempering, and modified nodular cast iron is obtained; according to the method, a part of eutectic graphite nodules obtained through solidification are dissolved in a metal matrix through control of a solid-state phase change process, and then the precipitation position and the precipitation dynamic process of C dissolved in the metal matrix are controlled through control of a tempering process in solid-state phase change, so that the eutectic graphite nodules are obtained. And C dissolved in the metal matrix is separated into fine graphite nodules from a new position different from the position of the eutectic graphite nodules, so that the density number of the graphite nodules in the nodular cast iron is greatly increased, and the technical problem that the density number of the graphite nodules in the nodular cast iron cannot be effectively increased by an existing treatment method is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of ductile iron modification, and in particular relates to ductile iron modified by solid-state phase change, a preparation method and application thereof. Background Art

[0002] Increasing the number of graphite nodules in ductile iron and reducing their spacing have a crucial impact on significantly improving the various key properties of ductile iron. As the core component of the microstructure of ductile iron, the shape, quantity and distribution of graphite nodules are directly related to the macroscopic performance of the material. Through advanced casting technology and alloying treatment, the increase in the number of graphite nodules and the reduction in spacing can be effectively promoted. This process can not only greatly enhance the friction and wear resistance of ductile iron, but also make the friction pair parts made of this material, such as sliding bearings and gears, show longer service life and lower wear rate when subjected to high loads and frequent friction. At the same time, optimizing the graphite nodule structure can also significantly improve the ductile iron's resistance to aluminum liquid corrosion, which is particularly important for parts such as aluminum alloy die-casting molds and aluminum liquid siphons that need to be in long-term contact with molten aluminum liquid. Reducing the spacing between graphite nodules means that the internal defects of the material are reduced and the corrosion resistance is enhanced, thereby ensuring the stability and durability of the mold and siphon in harsh working environments, and reducing the risk of premature failure due to corrosion. In addition, the optimization of graphite nodule structure can effectively improve the mechanical properties of ductile iron, especially toughness, which is crucial to improving the safety and reliability of structural parts. In summary, this series of performance improvements not only broadens the application field of ductile iron, but also provides strong material support for technological innovation and product upgrades in related industries such as automobile manufacturing, aerospace, and precision machinery, and has far-reaching practical significance for promoting technological progress and sustainable development of the entire industrial chain.

[0003] However, the graphite nodules in ductile iron parts or profiles are generally obtained by solidification, and the graphite nodules are generally coarse and the distance between two adjacent graphite nodules is far, which is not conducive to the improvement of the performance of ductile iron materials. Although the Chinese patent application with publication number CN118207473A proposes a method for increasing the density of graphite nodules in ductile iron by decomposing eutectic carbides, for ordinary ductile iron materials or parts, there is no primary carbide in their solidified structure, so how to increase the density of graphite nodules is an urgent problem to be solved for ordinary ductile iron materials to improve their performance.

[0004] From the basic knowledge and practice of cast iron heat treatment (see page 240 of "Metal Materials Science" edited by Wang Xiaotian), we know that conventional cast iron heat treatment methods cannot change the number, shape and distribution of graphite nodules in cast iron, that is, they cannot effectively increase the density of graphite nodules. Summary of the invention

[0005] The purpose of the present invention is to provide a solid-state phase-change modified ductile iron and a preparation method and application thereof, so as to solve the technical problem that the existing treatment method cannot effectively improve the density of graphite nodules in ductile iron.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The invention discloses a method for preparing solid-state phase change modified ductile iron, comprising the following steps:

[0008] The as-cast ductile iron is subjected to ferritization treatment to obtain ferritized ductile iron;

[0009] The ferritized ductile iron is subjected to isothermal quenching, medium-temperature tempering and high-temperature tempering in sequence to obtain modified ductile iron.

[0010] Furthermore, the process parameters of the ferritization treatment are: firstly heat the cast ductile iron to 750-800°C at a heating rate of 400-600°C / h, then keep it warm for 0.5-1h, then cool it to 650°C within 3-5h, and then cool it to room temperature.

[0011] Furthermore, the cooling method is air cooling.

[0012] Furthermore, the process parameters of the isothermal quenching are: firstly, the ferritized ductile iron is heated to 850-950°C at a heating rate of 400-600°C / h and kept warm for 1-3h; then, the ductile iron is quenched into a 250-320°C salt bath and kept warm for 1-2h before being taken out of the furnace and cooled to room temperature.

[0013] Furthermore, the process parameters of the medium-temperature tempering are: first heating to 450-550° C. at a heating rate of 400-600° C. / h and keeping warm for 1-3 hours.

[0014] Furthermore, the process parameters of the high temperature tempering are: heating to 650-720°C at a heating rate of 400-600°C / h, keeping warm for 4-8h, and air cooling to room temperature after being taken out of the furnace.

[0015] Furthermore, the components of the cast ductile iron include, by mass percentage: 3.6% to 3.8% C, 2.2% to 2.8% Si, ≤0.50% Mn, ≤0.08% P, 0.04% to 0.06% Mg 残留 , 0.01%~0.03%Re and ≤0.02%S, the balance is Fe and unavoidable impurities.

[0016] The invention also discloses solid phase change modified ductile iron prepared by the preparation method.

[0017] Furthermore, the density of graphite nodules in the solid-state phase-change modified ductile iron is at least 25 times greater than the density of graphite nodules in the cast ductile iron.

[0018] The invention also discloses the application of the ductile iron modified by solid-state phase change in aluminum alloy die-casting molds and aluminum liquid siphons.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The invention discloses a preparation method of solid-state phase change modified ductile iron. The method comprises the following steps: sequentially performing ferritization treatment, isothermal quenching, medium-temperature tempering and high-temperature tempering on the cast ductile iron, and controlling the solid-state phase change process to firstly dissolve a part of the solidified eutectic graphite balls into a metal matrix. Then, the tempering process in the solid-state phase change is controlled to control the precipitation position and precipitation kinetics of C dissolved in the metal matrix, so that the C dissolved in the metal matrix is ​​re-precipitated as fine graphite balls from a new position different from the position of the eutectic graphite balls, thereby realizing a substantial improvement in the density of graphite balls in the ductile iron, and solving the technical problem that the existing treatment method cannot effectively improve the density of graphite balls in the ductile iron.

[0021] The present invention also discloses modified ductile iron prepared by the above method, which significantly improves the thermal conductivity, self-lubricating properties and aluminum liquid corrosion resistance of ordinary ductile iron materials, thereby solving the problem of short service life of parts and equipment such as aluminum liquid delivery pipes, aluminum alloy die-casting molds, glass molds, etc. due to corrosion and thermal fatigue, which has practical significance for promoting technological progress in the above fields, and at the same time has significant economic benefits for the industrial development of the above fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The metallographic structure diagram of as-cast ductile iron and ferritized ductile iron;

[0023] Among them: a-as-cast ductile iron; b-ferritized ductile iron;

[0024] Figure 2 The metallographic structure of the austempered ductile iron obtained by austempering;

[0025] Figure 3 This is the metallographic structure of the modified ductile iron. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0027] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0028] Herein, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0029] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0030] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0031] The present invention provides a preparation method of solid-state phase change modified ductile iron, which realizes a significant increase in the density of graphite nodules in ordinary ductile iron materials through solid-state phase change; by controlling the solid-state phase change process of ordinary ductile iron, a part of C in eutectic graphite nodules is transformed into solid solution C, and then re-precipitated as fine graphite nodules from a new position different from the position of the eutectic graphite nodules, thereby realizing a significant increase in the density of graphite nodules in ductile iron, and specifically comprises the following steps:

[0032] Step 1: ferritizing the as-cast ductile iron to obtain ferritized ductile iron; completely ferritizing the metal matrix of the ductile iron whose original metal matrix is ​​not a full ferrite matrix;

[0033] Step 2: Isothermal quenching of ferritized ductile iron; completely transforming the metal matrix of ductile iron into austenitic structure;

[0034] Step 3: Medium temperature tempering of ductile iron; completely transforming the austenitic metal matrix of ductile iron into troostite;

[0035] Step 4: High temperature tempering of the ductile iron is performed to achieve a significant increase in the density of graphite nodules in the ductile iron.

[0036] Preferably, the ductile iron material in step 1 comprises the following components by mass percentage: 3.6% to 3.8% C, 2.2% to 2.8% Si, ≤0.50% Mn, ≤0.08% P, 0.04% to 0.06% Mg 残留 , 0.01%~0.03%Re and ≤0.02%S, the balance is Fe and unavoidable impurities.

[0037] Preferably, the ferritization treatment process in step 1 is: first heat the cast ductile iron to 750-800°C at a heating rate of 400-600°C / h, then keep it warm for 0.5-1h, then cool it to 650°C within 3-5h, and then air-cool it to room temperature; after step 1, the metal matrix in the cast ductile iron is completely transformed into a ferrite matrix.

[0038] Preferably, the isothermal quenching process of the ductile iron in step 2 is: first, the ferritized ductile iron is heated to 850-950°C at a heating rate of 400-600°C / h and kept warm for 1-3h, and then the ductile iron is quickly quenched into a 250-320°C salt bath and kept warm for 1-2h before being taken out of the furnace and cooled to room temperature to obtain austempered ductile iron, thereby completing the isothermal quenching of the ductile iron.

[0039] Preferably, the medium-temperature tempering treatment process in step 3 is: first heat the ductile iron after isothermal quenching to 450-550°C at a heating rate of 400-600°C / h and keep it warm for 1-3h, so that the ductile iron of the austempered ductile iron is completely transformed into ductile iron with a troostite structure.

[0040] Preferably, the high temperature tempering process in step 4 is: after the medium temperature tempering insulation is completed, the ductile iron material is directly heated to 650-720°C at a heating rate of 400-600°C / h and kept for 4-8 hours, and finally taken out of the furnace and air-cooled to room temperature. After step 4, the density of graphite nodules in the ductile iron is increased by more than dozens of times compared with the original cast state and the ferrite state.

[0041] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0042] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0043] Example 1

[0044] A method for preparing solid-state phase change modified ductile iron comprises the following steps:

[0045] Step 1: ferritization treatment of cast ductile iron; the ferritization treatment process is: firstly heat the cast ductile iron to 750°C at a heating rate of 400°C / h, then keep it warm for 0.5h, then cool it to 650°C within 3h, then air cool it to room temperature; the ductile iron material includes the following components by mass percentage: 3.6% C, 2.2% Si, ≤0.50% Mn, ≤0.08% P, 0.04% Mg 残留 , 0.01%Re and ≤0.02%S, the balance is Fe and unavoidable impurities;

[0046] Step 2: Isothermal quenching of ferritized ductile iron; the isothermal quenching process is: firstly, the ferritized ductile iron is heated to 850°C at a heating rate of 400°C / h and kept at this temperature for 1 hour, then the ductile iron is quickly quenched into a 250°C salt bath and kept at this temperature for 1 hour before being taken out of the furnace and cooled to room temperature;

[0047] Step 3: Medium-temperature tempering of ductile iron; the medium-temperature tempering treatment process is: firstly, the ductile iron after isothermal quenching is heated to 450°C at a heating rate of 400°C / h and kept at this temperature for 1h;

[0048] Step 4: The ductile iron is subjected to high temperature tempering to obtain modified ductile iron; the high temperature tempering process is as follows: after the medium temperature tempering and insulation is completed, the ductile iron material is directly heated to 650°C at a heating rate of 400°C / h and kept warm for 8h, and finally taken out of the furnace and air-cooled to room temperature.

[0049] Example 2

[0050] A method for preparing solid-state phase change modified ductile iron comprises the following steps:

[0051] Step 1: ferritization treatment of cast ductile iron; the ferritization treatment process is: firstly heat the cast ductile iron to 800°C at a heating rate of 600°C / h, then keep it warm for 1h, then cool it to 650°C within 5h, then air-cool it to room temperature; the ductile iron material includes the following components by mass percentage: 3.8% C, 2.8% Si, ≤0.50% Mn, ≤0.08% P, 0.06% Mg 残留 , 0.03%Re and ≤0.02%S, the balance is Fe and unavoidable impurities;

[0052] Step 2: Isothermal quenching of ferritized ductile iron; the isothermal quenching process is: firstly, the ferritized ductile iron is heated to 950°C at a heating rate of 600°C / h and kept at this temperature for 3h, then the ductile iron is quickly quenched into a 320°C salt bath and kept at this temperature for 2h before being taken out of the furnace and cooled to room temperature;

[0053] Step 3: Medium-temperature tempering of ductile iron; the medium-temperature tempering treatment process is: firstly, the ductile iron after isothermal quenching is heated to 550°C at a heating rate of 600°C / h and kept at this temperature for 3h;

[0054] Step 4: The ductile iron is subjected to high temperature tempering to obtain modified ductile iron; after the medium temperature tempering and insulation is completed, the ductile iron material is directly heated to 720°C at a heating rate of 600°C / h and kept for 8h, and finally taken out of the furnace and air-cooled to room temperature.

[0055] Example 3

[0056] A method for preparing solid-state phase change modified ductile iron comprises the following steps:

[0057] Step 1: ferritization treatment of cast ductile iron; the ferritization treatment process is: firstly heat the cast ductile iron to 780°C at a heating rate of 500°C / h, then keep it warm for 45 minutes, then cool it to 650°C within 4 hours, then air cool it to room temperature; the ductile iron material includes the following components by mass percentage: 3.7% C, 2.5% Si, ≤0.50% Mn, ≤0.08% P, 0.05% Mg 残留 , 0.02%Re and ≤0.02%S, the balance is Fe and unavoidable impurities;

[0058] Step 2: Isothermal quenching of ferritized ductile iron; the isothermal quenching process is: firstly, the ferritized ductile iron is heated to 900°C at a heating rate of 500°C / h and kept at this temperature for 2h, then the ductile iron is quickly quenched into a 300°C salt bath and kept at this temperature for 1.5h before being taken out of the furnace and cooled to room temperature;

[0059] Step 3: Medium-temperature tempering of ductile iron; the medium-temperature tempering treatment process is: firstly, the ductile iron after isothermal quenching is heated to 500°C at a heating rate of 500°C / h and kept at this temperature for 2h;

[0060] Step 4: The ductile iron is subjected to high temperature tempering to obtain modified ductile iron; after the medium temperature tempering and insulation is completed, the ductile iron material is directly heated to 700°C at a heating rate of 500°C / h and kept at this temperature for 6h, and finally taken out of the furnace and air-cooled to room temperature.

[0061] Example 4

[0062] A method for preparing solid-state phase change modified ductile iron comprises the following steps:

[0063] Step 1: ferritization treatment of cast ductile iron; the ferritization treatment process is: firstly heat the cast ductile iron to 750°C at a heating rate of 400°C / h, then keep it warm for 1h, then cool it to 650°C within 5h, then air-cool it to room temperature; the ductile iron material includes the following components by mass percentage: 3.6% C, 2.2% Si, ≤0.50% Mn, ≤0.08% P, 0.05% Mg 残留 , 0.02%Re and ≤0.02%S, the balance is Fe and unavoidable impurities;

[0064] Step 2: Isothermal quenching of ferritized ductile iron; the isothermal quenching process is: firstly, the ferritized ductile iron is heated to 850°C at a heating rate of 400°C / h and kept at this temperature for 1 hour, then the ductile iron is quickly quenched into a 250°C salt bath and kept at this temperature for 1 hour before being taken out of the furnace and cooled to room temperature;

[0065] Step 3: Medium-temperature tempering of ductile iron; the medium-temperature tempering treatment process is: firstly, the ductile iron after isothermal quenching is heated to 550°C at a heating rate of 400°C / h and kept at this temperature for 3h;

[0066] Step 4: The ductile iron is subjected to high temperature tempering to obtain modified ductile iron; after the medium temperature tempering and insulation is completed, the ductile iron material is directly heated to 720°C at a heating rate of 400°C / h and kept warm for 4h, and finally taken out of the furnace and air-cooled to room temperature.

[0067] Example 5

[0068] A method for preparing solid-state phase change modified ductile iron comprises the following steps:

[0069] Step 1: ferritization treatment of cast ductile iron; the ferritization treatment process is: firstly heat the cast ductile iron to 750°C at a heating rate of 400°C / h, then keep it warm for 1h, then cool it to 650°C within 3h, then air-cool it to room temperature; the ductile iron material includes the following components by mass percentage: 3.6% C, 2.8% Si, ≤0.50% Mn, ≤0.08% P, 0.05% Mg 残留 , 0.01%Re and ≤0.02%S, the balance is Fe and unavoidable impurities;

[0070] Step 2: Isothermal quenching of ferritized ductile iron; the isothermal quenching process is: firstly, the ferritized ductile iron is heated to 950°C at a heating rate of 400°C / h and kept at this temperature for 3h, then the ductile iron is quickly quenched into a 320°C salt bath and kept at this temperature for 1h before being taken out of the furnace and cooled to room temperature;

[0071] Step 3: Medium-temperature tempering of ductile iron; the medium-temperature tempering treatment process is: firstly heat the ductile iron after isothermal quenching to 450°C at a heating rate of 600°C / h and keep it at that temperature for 1h;

[0072] Step 4: The ductile iron is subjected to high temperature tempering to obtain modified ductile iron; after the medium temperature tempering and insulation is completed, the ductile iron material is directly heated to 650°C at a heating rate of 600°C / h and kept at this temperature for 8h, and finally taken out of the furnace and air-cooled to room temperature.

[0073] Example 6

[0074] A method for preparing solid-state phase change modified ductile iron comprises the following steps:

[0075] Step 1: ferritization treatment of cast ductile iron; the ferritization treatment process is: firstly heat the cast ductile iron to 780°C at a heating rate of 400°C / h, then keep it warm for 1h, then cool it to 650°C in 4h, then air cool it to room temperature; the ductile iron material includes the following components by mass percentage: 3.6% C, 2.5% Si, ≤0.50% Mn, ≤0.08% P, 0.06% Mg 残留 , 0.01%Re and ≤0.02%S, the balance is Fe and unavoidable impurities;

[0076] Step 2: Isothermal quenching of ferritized ductile iron; the isothermal quenching process is: firstly, the ferritized ductile iron is heated to 880°C at a heating rate of 550°C / h and kept at this temperature for 2h, then the ductile iron is quickly quenched into a 250°C salt bath and kept at this temperature for 1h before being taken out of the furnace and cooled to room temperature;

[0077] Step 3: Medium-temperature tempering of ductile iron; the medium-temperature tempering treatment process is: firstly, the ductile iron after isothermal quenching is heated to 450°C at a heating rate of 400°C / h and kept at this temperature for 1h;

[0078] Step 4: The ductile iron is subjected to high temperature tempering to obtain modified ductile iron; the high temperature tempering process is as follows: after the medium temperature tempering and insulation is completed, the ductile iron material is directly heated to 650°C at a heating rate of 400°C / h and kept warm for 8h, and finally taken out of the furnace and air-cooled to room temperature.

[0079] Figure 1 Figure 2 is the metallographic structure diagram of cast ductile iron and ferritized ductile iron. It can be seen from the figure that the cast structure is composed of a large amount of ferrite, a small amount of eutectoid pearlite and a large amount of coarse eutectic graphite nodules, and there are no primary eutectic carbides and secondary carbides; after ferritization treatment, a small amount of eutectoid pearlite in the structure disappears and transforms into ferrite and graphite deposited on the eutectic graphite nodules. The final structure is composed of ferrite and eutectic graphite nodules, and there are no fine non-eutectic graphite nodules in the structure.

[0080] Figure 2 This is the metallographic structure of the austempered ductile iron obtained by austempering. As can be seen from the figure, the austempered structure consists of aubae matrix and coarse eutectic graphite nodules.

[0081] Figure 3 This is the metallographic structure of the modified ductile iron. As can be seen from the figure, there are about 5 original eutectic graphite nodules in the field of view, while the number of fine graphite nodules is at least over 100, which is increased by at least 25 times, indicating that the method of the present invention can achieve a significant increase in the density of graphite nodules in ductile iron.

[0082] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing solid-state phase change modified ductile iron, characterized in that: The following steps are involved: The as-cast ductile iron is subjected to ferritization treatment to obtain ferritized ductile iron; The ferritized ductile iron is subjected to isothermal quenching, medium-temperature tempering and high-temperature tempering in sequence to obtain modified ductile iron.

2. The method for preparing a solid-state phase change modified ductile iron according to claim 1, characterized in that: The process parameters of the ferritization treatment are: firstly heat the cast ductile iron to 750-800°C at a heating rate of 400-600°C / h, then keep it warm for 0.5-1h, then cool it to 650°C within 3-5h, and then cool it to room temperature.

3. The method for preparing a solid-state phase change modified ductile iron according to claim 2, characterized in that: The cooling method is air cooling.

4. The method for preparing a solid phase change modified ductile iron according to claim 1, characterized in that: The process parameters of the isothermal quenching are: firstly, the ferritized ductile iron is heated to 850-950°C at a heating rate of 400-600°C / h and kept at this temperature for 1-3h; then, the ductile iron is quenched into a salt bath at 250-320°C and kept at this temperature for 1-2h before being taken out of the furnace and cooled to room temperature.

5. The method for preparing a solid-state phase change modified ductile iron according to claim 1, characterized in that: The process parameters of the medium-temperature tempering are: firstly heating to 450-550°C at a heating rate of 400-600°C / h and keeping the temperature for 1-3h.

6. The method for preparing solid-state phase change modified ductile iron according to claim 1, characterized in that: The process parameters of the high temperature tempering are: heating to 650-720° C. at a heating rate of 400-600° C. / h, keeping the temperature for 4-8 hours, and air cooling to room temperature after being taken out of the furnace.

7. The method for preparing solid-state phase change modified ductile iron according to claim 1, characterized in that: In terms of mass percentage, the components of the cast ductile iron include: 3.6% to 3.8% C, 2.2% to 2.8% Si, ≤0.50% Mn, ≤0.08% P, 0.04% to 0.06% Mg 残留 , 0.01%~0.03%Re and ≤0.02%S, the balance is Fe and unavoidable impurities.

8. A solid-state phase-change modified ductile iron, characterized in that: The method can be prepared by any one of claims 1 to 6.

9. The solid state phase change modified ductile iron according to claim 8, characterized in that: The density of graphite nodules in the solid-state phase-changed ductile iron is at least 25 times greater than the density of graphite nodules in the as-cast ductile iron.

10. Use of the solid-state phase-change modified ductile iron according to claim 8 in aluminum alloy die-casting molds and aluminum liquid siphons.

Images