SiC reinforced nodular cast iron and preparation method thereof

Abstract

The invention discloses SiC reinforced nodular cast iron which comprises the following raw materials in percentage by mass: 3.4%-3.6% of C, 2.1%-2.7% of Si, less than or equal to 0.4% of Mn, less than or equal to 0.03% of S, 0.03%-0.06% of Mg, 0.02%-0.05% of RE and the balance of Fe, and the sum of the mass percentages of all the components is 100%. The material improves the hardness and wear resistance of nodular cast iron, and solves the problem of short service life of nodular cast iron. The invention further discloses a preparation method of the SiC reinforced nodular cast iron.

Description

Technical Field

[0001] The invention belongs to the field of metal composite materials, and in particular relates to SiC reinforced ductile iron, and also relates to a preparation method of the SiC reinforced ductile iron. Background Art

[0002] Wear, as one of the three forms of component material failure (wear, corrosion, and fracture), has had a serious impact on national life safety and national economic benefits. The annual consumption of materials in the fields of friction, wear, and lubrication accounts for about 3% to 5% of my country's GDP. According to incomplete statistics, my country's annual consumption of steel wear-resistant materials and wear-resistant parts is about 5 million tons, and the demand and output are both the highest in the world. Steel wear-resistant materials are widely used in mining, metallurgy, electricity, railways, construction, and mechanical industries, but the problem of component failure caused by their wear is also becoming increasingly prominent. Further improving the wear resistance of steel materials is an important way to solve the wear failure of component materials. Ductile iron, as a commonly used wear-resistant component material, can be regarded as a special composite material composed of spherical graphite with a volume fraction of nearly 10% distributed in a steel matrix. The graphite in the matrix is ​​spherical, which reduces stress concentration and makes it have good comprehensive mechanical properties. At the same time, during the friction and wear process, the graphite in the matrix will be dragged to the surface to play a lubricating effect, reducing the friction coefficient, so that ductile iron has good wear resistance. However, due to the distribution of low-hardness graphite with a volume fraction of nearly 10% in the matrix, the overall hardness of ductile iron is lower than that of cast steel, which weakens its wear resistance and makes it difficult to serve under harsh wear conditions (such as heavy load, high speed, and high wear). In recent years, in order to further improve the wear resistance of steel materials, ceramic particle reinforced steel-based composites have attracted widespread attention. The use of ceramic particles SiC as a reinforcement to compound with ductile iron to prepare particle-reinforced ductile iron composites is expected to further improve the wear resistance of ductile iron. Summary of the invention

[0003] The purpose of the present invention is to provide SiC reinforced ductile iron, improve the hardness and wear resistance of ductile iron, and solve the problem of short service life of ductile iron.

[0004] Another object of the present invention is to provide a method for preparing SiC reinforced ductile iron.

[0005] The first technical solution adopted by the present invention is SiC reinforced ductile iron, and the raw materials include, by mass percentage, C: 3.4%~3.6%, Si: 2.1%~2.7%, Mn: ≤0.4%, S: ≤0.03%, Mg: 0.03%~0.06%, RE: 0.02%~0.05%, and the balance is Fe, and the total mass percentage of each component content is 100%.

[0006] The second technical solution adopted by the present invention is a method for preparing SiC reinforced ductile iron, which is specifically: Step 1, weighing raw materials according to the mass percentage of each component of the composite material, including: breaded iron, scrap steel, carburizer, inoculant, spheroidizer and Fe / SiC cored wire; Step 2, placing the weighed bread iron, carburizer, and scrap steel into a medium frequency induction heating furnace in order for heating; Step 3, after removing the slag from the molten iron in step 2, adding the Fe / SiC cored wire into the melt, and continuing to heat to obtain molten iron of designed composition; Step 4: Remove impurities from the sand by sand casting, fill the mold with molding sand, and compact the molding sand by vibration or compaction to form a sand mold corresponding to the shape of the casting; Step 5, placing the spheroidizing agent and inoculant weighed in step 1 into a molten iron ladle, and covering it with a covering agent, wherein the covering agent is rust-free iron filings; Step 6, pour the molten iron finally obtained in step 3 into the iron ladle from slow to fast, and perform spheroidization inoculation treatment. After the spheroidization inoculation is completed, stir quickly until the temperature of the molten iron decreases, the fluidity becomes worse, the SiC powder is difficult to float in the molten iron, and is evenly distributed in the molten iron; Step 7: quickly and evenly pour the molten iron obtained in step 6 into the prefabricated sand mold so that the molten iron fills the entire mold cavity. After the molten metal solidifies, a casting blank is obtained.

[0007] The present invention is also characterized in that: Step 1 is specifically as follows: according to the mass percentage of each component of SiC reinforced ductile iron, the raw materials are weighed, including: breaded iron (Q10): 50%, scrap steel: 8.22%~28.22%, recarburizer: 0.58%~1.04%, spheroidizer: 0.6%~0.8%, inoculant: 0.6%~0.8%, Fe / SiC cored wire: 20%~40%, and the sum of the mass percentages of the above components is 100%; the carbon equivalent in the raw materials is 4.3wt.%.

[0008] In step 1, the spheroidizer is a rare earth magnesium spheroidizer, and the inoculant is a silicon-barium-calcium inoculant.

[0009] In step 1, the SiC particles in the Fe / SiC cored wire are spherical with an average particle size of 50 μm, the average particle size of the Fe powder is 100 μm, the mass fraction of the spherical SiC powder in the cored wire is 50%, and the mass fraction of the iron powder is 50%.

[0010] Step 2: Add the weighed bread iron, carburizer and scrap steel into the medium frequency induction heating furnace in sequence for heating, with a heating rate of 40°C / min~50°C / min, a smelting time of 30min~40min, and a high-temperature melting temperature of the smelting furnace of 1550°C~1600°C.

[0011] In step 2, the recarburizer is placed between the bread iron (Q10) and the scrap steel to ensure the absorption rate of the recarburizer and avoid the carbon content not meeting the design.

[0012] Step 3 is specifically as follows: after the molten iron in step 2 is deslagging, the Fe / SiC cored wire weighed in step 1 is added to the molten iron and heated for 160s~310s to decompose SiC accounting for 2.57%~3.43% of the total mass of all raw materials, increase the silicon content of the molten iron by 1.8%~2.4%, and increase the carbon content by 0.77%~1.03%. The mass of the remaining undecomposed SiC accounts for 6.57%~16.57% of the total mass of all raw materials, and the average particle size of the remaining SiC is 40.52μm~45.52μm. The carbon and silicon contents in the molten iron are measured using a PD-TY8 furnace-front molten iron management instrument. The silicon content in the molten iron is 2.1%~2.7%, and the carbon content is 3.4%~3.6%. When the molten iron reaches the designed composition, it is immediately discharged from the furnace.

[0013] In step 6, the temperature of the molten iron is reduced to 1300°C-1350°C and stirring is stopped.

[0014] In step 7, the interval time for pouring molten iron into the sand mold is 30s-50s.

[0015] The casting blank obtained in step 7 is the SiC reinforced ductile iron prepared by the present invention, wherein the mass percentage of each component is: C: 3.4%~3.6%, Si: 2.1%~2.7%, Mn: ≤0.4%, S: ≤0.03%, Mg: 0.03%~0.06%, RE: 0.02%~0.05%, and the balance is Fe; and the total carbon equivalent in this component should be maintained at 4.3 wt.%.

[0016] The beneficial effects of the present invention are: The method of the present invention strictly controls the proportion of each component in the raw material and each process link of the casting process, thereby obtaining SiC reinforced ductile iron. SiC has high hardness (microhardness of 2700HV) and a linear expansion coefficient close to that of iron. SiC is used as a reinforcing particle and has good preparation performance when combined with ductile iron, and can also improve the strength, hardness and wear resistance of ductile iron. Compared with other ceramic particles, SiC can avoid the formation of impurities, and silicon is a graphitization-promoting element. By controlling the degree of SiC decomposition by heating time to regulate the silicon content in the matrix, the formation of graphite in ductile iron can be promoted, the number and content of graphite balls can be increased, the friction coefficient can be effectively reduced, the self-lubricating properties of ductile iron can be brought into play, wear can be reduced, and the service life can be extended. Adding SiC particles to ductile iron so that they are evenly distributed in the iron matrix, thereby preparing SiC reinforced ductile iron with high hardness, low friction coefficient and high wear resistance, which is of great significance to improving the wear resistance of ductile iron and extending the service life of the component material. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a flow chart of preparation of SiC reinforced ductile iron in the method of the present invention; Figure 2 Schematic diagram of the decomposition process and microstructure of SiC after the SiC particles of Example 1 of the present invention are added to molten iron. DETAILED DESCRIPTION The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0018] The invention provides SiC reinforced ductile iron. The raw materials include, by mass percentage, C: 3.4%-3.6%, Si: 2.1%-2.7%, Mn: ≤0.4%, S: ≤0.03%, Mg: 0.03%-0.06%, RE: 0.02%-0.05%, the balance is Fe, and the total mass percentage of the contents of the various components is 100%.

[0019] The present invention also provides a method for preparing SiC reinforced ductile iron, such as Figure 1 As shown, specifically: Step 1, weighing raw materials according to the mass percentage of each component of the composite material, including: breaded iron, scrap steel, carburizer, inoculant, spheroidizer and Fe / SiC cored wire; Step 1 is specifically as follows: according to the mass percentage of each component of SiC reinforced ductile iron, the raw materials are weighed, including: breaded iron (Q10): 50%, scrap steel: 8.22%~28.22%, recarburizer: 0.58%~1.04%, spheroidizer: 0.6%~0.8%, inoculant: 0.6%~0.8%, Fe / SiC cored wire: 20%~40%, and the sum of the mass percentages of the above components is 100%; the carbon equivalent in the raw materials is 4.3wt.%.

[0020] In step 1, the spheroidizer is a rare earth magnesium spheroidizer, and the inoculant is a silicon-barium-calcium inoculant.

[0021] In step 1, the SiC particles in the Fe / SiC cored wire are spherical with an average particle size of 50 μm, the average particle size of the Fe powder is 100 μm, the mass fraction of the spherical SiC powder in the cored wire is 50%, and the mass fraction of the iron powder is 50%.

[0022] Step 2, placing the weighed bread iron, carburizer, and scrap steel into a medium frequency induction heating furnace in order for heating; Step 2: Add the weighed bread iron, carburizer and scrap steel into the medium frequency induction heating furnace in sequence for heating, with a heating rate of 40°C / min~50°C / min, a smelting time of 30min~40min, and a high-temperature melting temperature of the smelting furnace of 1550°C~1600°C.

[0023] In step 2, the recarburizer is placed between the bread iron (Q10) and the scrap steel to ensure the absorption rate of the recarburizer and avoid the carbon content not meeting the design.

[0024] Step 3, after removing the slag from the molten iron in step 2, adding the Fe / SiC cored wire into the melt, and continuing to heat to obtain molten iron of designed composition; Step 3 is specifically as follows: after the molten iron in step 2 is deslagging, the Fe / SiC cored wire weighed in step 1 is added to the molten iron and heated for 160s~310s to decompose SiC accounting for 2.57%~3.43% of the total mass of all raw materials, increase the silicon content of the molten iron by 1.8%~2.4%, and increase the carbon content by 0.77%~1.03%. The mass of the remaining undecomposed SiC accounts for 6.57%~16.57% of the total mass of all raw materials, and the average particle size of the remaining SiC is 40.52μm~45.52μm. The carbon and silicon contents in the molten iron are measured using a PD-TY8 furnace-front molten iron management instrument. The silicon content in the molten iron is 2.1%~2.7%, and the carbon content is 3.4%~3.6%. When the molten iron reaches the designed composition, it is immediately discharged from the furnace.

[0025] Step 4: Remove impurities from the sand by sand casting, fill the mold with molding sand, and compact the molding sand by vibration or compaction to form a sand mold corresponding to the shape of the casting; Step 5, placing the spheroidizing agent and inoculant weighed in step 1 into a molten iron ladle, and covering it with a covering agent, wherein the covering agent is rust-free iron filings; Step 6, pour the molten iron finally obtained in step 3 into the iron ladle from slow to fast, and perform spheroidization inoculation treatment. After the spheroidization inoculation is completed, stir rapidly until the temperature of the molten iron decreases, the fluidity deteriorates, the SiC powder is difficult to float in the molten iron, and is evenly distributed in the molten iron; In step 6, the temperature of the molten iron is reduced to 1300°C-1350°C and stirring is stopped.

[0026] Step 7: quickly and evenly pour the molten iron obtained in step 6 into the prefabricated sand mold so that the molten iron fills the entire mold cavity. After the molten metal solidifies, a casting blank is obtained.

[0027] In step 7, the interval time for pouring molten iron into the sand mold is 30s-50s.

[0028] The casting blank obtained in step 7 is the SiC reinforced ductile iron prepared by the present invention, wherein the mass percentage of each component is: C: 3.4%~3.6%, Si: 2.1%~2.7%, Mn: ≤0.4%, S: ≤0.03%, Mg: 0.03%~0.06%, RE: 0.02%~0.05%, and the balance is Fe; and the total carbon equivalent in this component should be maintained at 4.3 wt.%.

[0029] Example 1 The preparation method of SiC reinforced ductile iron of the present invention is specifically implemented according to the following steps: Step 1. According to the mass percentage of each component of SiC reinforced ductile iron, the raw materials are weighed, including: bread iron (Q10): 50%, scrap steel: 27.36%, recarburizer: 1.04%, rare earth magnesium spheroidizer: 0.8%, silicon barium calcium inoculant: 0.8%, Fe / SiC cored wire: 20%, and the sum of the mass percentages of the above components is 100%; the carbon equivalent in the raw materials is 4.3wt.%.

[0030] The SiC particles in the Fe / SiC cored wire are spherical with an average particle size of 50 μm, the average particle size of the Fe powder is 100 μm, the mass fraction of the spherical SiC powder in the cored wire is 50%, and the mass fraction of the iron powder is 50%.

[0031] Step 2: Add the weighed bread iron, carburizer and scrap steel into the medium frequency induction heating furnace in sequence for heating. The heating rate is 40°C / min, the smelting time is 30min, and the high temperature melting temperature of the smelting furnace is 1550°C.

[0032] After the molten iron in step 3 and step 2 is deslagging, the Fe / SiC cored wire weighed in step 1 is added to the molten iron, and the mass of the Fe / SiC cored wire is 20%. After heating for 230s, SiC accounting for 2.57% of the total mass of all raw materials is decomposed, the silicon content of the molten iron increases by 1.8%, and the carbon content increases by 0.77%. The mass of the remaining undecomposed SiC accounts for 7.43% of the total mass of all raw materials, and the average particle size of the remaining SiC is 43.1μm. The carbon and silicon contents in the molten iron are measured using the PD-TY8 type furnace front molten iron management instrument. The silicon content in the molten iron is 2.1%, and the carbon content is 3.6%. When the molten iron reaches the designed composition, it is immediately discharged from the furnace.

[0033] Step 4: Remove impurities from the sand by sand casting, fill the mold with molding sand, and compact the molding sand by vibration or compaction to form a sand mold corresponding to the shape of the casting.

[0034] Step 5: Place the rare earth magnesium spheroidizer and silicon-barium-calcium inoculant weighed in step 1 into a molten iron ladle and cover it with a covering agent, which is rust-free iron filings.

[0035] Step 6: Pour the molten iron obtained in step 3 into the iron ladle slowly or quickly for spheroidization inoculation. After the spheroidization inoculation is completed, stir rapidly until the temperature of the molten iron drops to 1300°C, the fluidity deteriorates, the SiC powder is difficult to float in the molten iron, and is evenly distributed in the molten iron, and the stirring is stopped.

[0036] Step 7: Quickly and evenly pour the molten iron obtained in step 6 into the prefabricated sand mold, so that the molten iron fills the entire mold cavity, and after the molten metal solidifies, a casting blank is obtained. The interval time for pouring the molten iron into the sand mold is 30 seconds.

[0037] The casting blank obtained in step 7 is the SiC reinforced ductile iron prepared by the present invention, wherein the mass percentage of each component is: C: 3.6%, Si: 2.1%, Mn: 0.3%, S: 0.02%, Mg: 0.03%, RE: 0.02%, and the balance is Fe; and the total carbon equivalent in this component should be maintained at 4.3 wt.%.

[0038] like Figure 2 As shown in the figure, SiC particles are added to the molten iron and gradually decompose from the outside to the inside. The silicon atoms produced by the decomposition diffuse into the molten iron, inhibiting the formation of cementite and promoting the precipitation of carbon atoms in the form of graphite. The remaining SiC particles exist in the ductile iron as reinforcements, improving the hardness of the ductile iron, and giving full play to the supporting and protective role of the reinforcements, avoiding excessive wear of the matrix, improving its wear resistance, and reducing the volume of SiC particles, further improving its mechanical properties.

[0039] Example 2 The preparation method of SiC reinforced ductile iron of the present invention is specifically implemented according to the following steps: Step 1. According to the mass percentage of each component of SiC reinforced ductile iron, the raw materials are weighed, including: bread iron (Q10): 50%, scrap steel: 27.72%, recarburizer: 0.88%, rare earth magnesium spheroidizer: 0.6%, silicon barium calcium inoculant: 0.8%, Fe / SiC cored wire: 20%, and the sum of the mass percentages of the above components is 100%; the carbon equivalent in the raw materials is 4.3wt.%.

[0040] The SiC particles in the Fe / SiC cored wire are spherical with an average particle size of 50 μm, the average particle size of the Fe powder is 100 μm, the mass fraction of the spherical SiC powder in the cored wire is 50%, and the mass fraction of the iron powder is 50%.

[0041] Step 2: Add the weighed bread iron, carburizer and scrap steel into the medium frequency induction heating furnace in sequence for heating. The heating rate is 50°C / min, the smelting time is 40min, and the high temperature melting temperature of the smelting furnace is 1600°C.

[0042] After the molten iron in step 3 and step 2 is slag-removed, the Fe / SiC cored wire weighed in step 1 is added to the molten iron, and the mass of the Fe / SiC cored wire is 20%. Heating for 260s decomposes SiC, which accounts for 2.86% of the total mass of all raw materials, and the silicon content of the molten iron increases by 2.0%, and the carbon content increases by 0.86%. The mass of the remaining undecomposed SiC accounts for 7.43% of the total mass of all raw materials, and the average particle size of the remaining SiC is 43.24μm. The carbon and silicon contents in the molten iron are measured using the PD-TY8 type furnace front molten iron management instrument. The silicon content in the molten iron is 2.3%, and the carbon content is 3.53%. When the molten iron reaches the designed composition, it is immediately discharged from the furnace. Step 4: Remove impurities from the sand by sand casting, fill the mold with molding sand, and compact the molding sand by vibration or compaction to form a sand mold corresponding to the shape of the casting.

[0043] Step 5: Place the rare earth magnesium spheroidizer and silicon-barium-calcium inoculant weighed in step 1 in a molten iron ladle and cover them with a covering agent, wherein the covering agent is rust-free iron filings, the rare earth magnesium spheroidizer is 0.6% of the mass of the molten iron, and the silicon-barium-calcium inoculant is 0.8% of the mass of the molten iron.

[0044] Step 6: Pour the molten iron obtained in step 3 into the iron ladle slowly or quickly for spheroidization inoculation. After the spheroidization inoculation is completed, stir rapidly until the temperature of the molten iron drops to 1350°C, the fluidity deteriorates, the SiC powder is difficult to float in the molten iron, and is evenly distributed in the molten iron, and the stirring is stopped.

[0045] Step 7: Quickly and evenly pour the molten iron obtained in step 6 into the prefabricated sand mold, so that the molten iron fills the entire mold cavity, and after the molten metal solidifies, a casting blank is obtained. The interval time for pouring the molten iron into the sand mold is 50 seconds.

[0046] The casting blank obtained in step 7 is the SiC reinforced ductile iron prepared by the present invention, wherein the mass percentage of each component is: C: 3.53%, Si: 2.3%, Mn: 0.2%, S: 0.01%, Mg: 0.06%, RE: 0.05%, and the balance is Fe; and the total carbon equivalent in this component should be maintained at 4.3 wt.%.

[0047] Example 3 The preparation method of SiC reinforced ductile iron of the present invention is specifically implemented according to the following steps: Step 1. According to the mass percentage of each component of SiC reinforced ductile iron, the raw materials are weighed, including: bread iron (Q10): 50%, scrap steel: 27.87%, recarburizer: 0.73%, rare earth magnesium spheroidizer: 0.8%, silicon barium calcium inoculant: 0.6%, Fe / SiC cored wire: 20%, and the sum of the mass percentages of the above components is 100%; the carbon equivalent in the raw materials is 4.3wt.%.

[0048] The SiC particles in the Fe / SiC cored wire are spherical with an average particle size of 50 μm, the average particle size of the Fe powder is 100 μm, the mass fraction of the spherical SiC powder in the cored wire is 50%, and the mass fraction of the iron powder is 50%.

[0049] Step 2: Add the weighed bread iron, carburizer and scrap steel into the medium frequency induction heating furnace in sequence for heating. The heating rate is 45°C / min, the smelting time is 35min, and the high temperature melting temperature of the smelting furnace is 1600°C.

[0050] After the molten iron in step 3 and step 2 is slag-removed, the Fe / SiC cored wire weighed in step 1 is added to the molten iron, and the mass of the Fe / SiC cored wire is 20%. Heating for 280s, the SiC accounting for 3.14% of the total mass of all raw materials is decomposed, the silicon content of the molten iron increases by 2.2%, the carbon content increases by 0.94%, the mass of the remaining undecomposed SiC accounts for 6.86% of the total mass of all raw materials, and the average particle size of the remaining SiC is 41.42μm. The carbon and silicon contents in the molten iron are measured using the PD-TY8 type furnace front molten iron management instrument. The silicon content in the molten iron is 2.5%, and the carbon content is 3.46%. When the molten iron reaches the designed composition, it is immediately discharged from the furnace. In step 6, the temperature of the molten iron is reduced to 1320℃ and stirring is stopped.

[0051] Step 4: Remove impurities from the sand by sand casting, fill the mold with molding sand, and compact the molding sand by vibration or compaction to form a sand mold corresponding to the shape of the casting.

[0052] Step 5: Place the rare earth magnesium spheroidizer and silicon-barium-calcium inoculant weighed in step 1 into a molten iron ladle and cover it with a covering agent, which is rust-free iron filings.

[0053] Step 6: Pour the molten iron obtained in step 3 into the iron ladle slowly or quickly for spheroidization inoculation. After the spheroidization inoculation is completed, stir rapidly until the temperature of the molten iron drops to 1350°C, the fluidity deteriorates, the SiC powder is difficult to float in the molten iron, and is evenly distributed in the molten iron, and the stirring is stopped.

[0054] Step 7: Quickly and evenly pour the molten iron obtained in step 6 into the prefabricated sand mold, so that the molten iron fills the entire mold cavity, and after the molten metal solidifies, a casting blank is obtained. The interval time for pouring the molten iron into the sand mold is 40 seconds.

[0055] The casting blank obtained in step 7 is the SiC reinforced ductile iron prepared by the present invention, wherein the mass percentage of each component is: C: 3.46%, Si: 2.5%, Mn: 0.4%, S: 0.03%, Mg: 0.05%, RE: 0.04%, and the balance is Fe; and the total carbon equivalent in this component should be maintained at 4.3 wt.%.

[0056] Example 4 The preparation method of SiC reinforced ductile iron of the present invention is specifically implemented according to the following steps: Step 1. According to the mass percentage of each component of SiC reinforced ductile iron, the raw materials are weighed, including: bread iron (Q10): 50%, scrap steel: 28.22%, recarburizer: 0.58%, rare earth magnesium spheroidizer: 0.6%, silicon barium calcium inoculant: 0.6%, Fe / SiC cored wire: 20%, and the sum of the mass percentages of the above components is 100%; the carbon equivalent in the raw materials is 4.3wt.%.

[0057] The SiC particles in the Fe / SiC cored wire are spherical with an average particle size of 50 μm, the average particle size of the Fe powder is 100 μm, the mass fraction of the spherical SiC powder in the cored wire is 50%, and the mass fraction of the iron powder is 50%.

[0058] Step 2: Add the weighed bread iron, carburizer and scrap steel into the medium frequency induction heating furnace in sequence for heating. The heating rate is 45°C / min, the smelting time is 35min, and the high temperature melting temperature of the smelting furnace is 1590°C.

[0059] After the molten iron in step 3 and step 2 is deslagging, the Fe / SiC cored wire weighed in step 1 is added to the molten iron, and the mass of the Fe / SiC cored wire is 20%. After heating for 310s, SiC accounting for 3.43% of the total mass of all raw materials is decomposed, the silicon content of the molten iron increases by 2.4%, the carbon content increases by 1.03%, the mass of the remaining undecomposed SiC accounts for 6.57% of the total mass of all raw materials, and the average particle size of the remaining SiC is 40.52μm. The carbon and silicon contents in the molten iron are measured using the PD-TY8 type furnace front molten iron management instrument. The silicon content in the molten iron is 2.7%, and the carbon content is 3.4%. When the molten iron reaches the designed composition, it is immediately discharged from the furnace.

[0060] Step 4: Remove impurities from the sand by sand casting, fill the mold with molding sand, and compact the molding sand by vibration or compaction to form a sand mold corresponding to the shape of the casting.

[0061] Step 5: weigh the rare earth magnesium spheroidizer and silicon-barium-calcium inoculant taken in step 1 in proportion, place them in a molten iron ladle, and cover them with a covering agent, which is rust-free iron filings.

[0062] Step 6: Pour the molten iron finally obtained in step 3 into the iron ladle slowly or quickly for spheroidization inoculation. After the spheroidization inoculation is completed, stir rapidly until the temperature of the molten iron drops to 1310°C, the fluidity becomes worse, the SiC powder is difficult to float in the molten iron, and is evenly distributed in the molten iron, and the stirring is stopped.

[0063] Step 7: Quickly and evenly pour the molten iron obtained in step 6 into the prefabricated sand mold, so that the molten iron fills the entire mold cavity, and after the molten metal solidifies, a casting blank is obtained. The interval time for pouring the molten iron into the sand mold is 40 seconds.

[0064] The casting blank obtained in step 7 is the SiC reinforced ductile iron prepared by the present invention, wherein the mass percentage of each component is: C: 3.4%, Si: 2.7%, Mn: 0.35%, S: 0.025%, Mg: 0.06%, RE: 0.02%, and the balance is Fe; and the total carbon equivalent in this component should be maintained at 4.3 wt.%.

[0065] Example 5 The preparation method of SiC reinforced ductile iron of the present invention is specifically implemented according to the following steps: Step 1. According to the mass percentage of each component of SiC reinforced ductile iron, the raw materials are weighed, including: bread iron (Q10): 50%, scrap steel: 8.22%, recarburizer: 0.58%, rare earth magnesium spheroidizer: 0.6%, silicon barium calcium inoculant: 0.6%, Fe / SiC cored wire: 40%, and the sum of the mass percentages of the above components is 100%; the carbon equivalent in the raw materials is 4.3wt.%.

[0066] The SiC particles in the Fe / SiC cored wire are spherical with an average particle size of 50 μm, the average particle size of the Fe powder is 100 μm, the mass fraction of the spherical SiC powder in the cored wire is 50%, and the mass fraction of the iron powder is 50%.

[0067] Step 2: Add the weighed bread iron, carburizer and scrap steel into the medium frequency induction heating furnace in sequence for heating. The heating rate is 40°C / min, the smelting time is 40min, and the high temperature melting temperature of the smelting furnace is 1550°C.

[0068] After the molten iron in step 3 and step 2 is deslagging, the Fe / SiC cored wire weighed in step 1 is added to the molten iron, and the mass of the Fe / SiC cored wire is 40%. Heating for 160s, the SiC accounting for 3.43% of the total mass of all raw materials is decomposed, the silicon content of the molten iron increases by 2.4%, the carbon content increases by 1.03%, the mass of the remaining undecomposed SiC accounts for 16.57% of the total mass of all raw materials, and the average particle size of the remaining SiC is 45.52μm. The carbon and silicon contents in the molten iron are measured using the PD-TY8 type furnace front molten iron management instrument. The silicon content in the molten iron is 2.7%, and the carbon content is 3.4%. When the molten iron reaches the designed composition, it is immediately discharged from the furnace.

[0069] Step 4: Remove impurities from the sand by sand casting, fill the mold with molding sand, and compact the molding sand by vibration or compaction to form a sand mold corresponding to the shape of the casting.

[0070] Step 5: weigh the rare earth magnesium spheroidizer and silicon-barium-calcium inoculant taken in step 1 in proportion, place them in a molten iron ladle, and cover them with a covering agent, which is rust-free iron filings.

[0071] Step 6: Pour the molten iron obtained in step 3 into the iron ladle slowly or quickly for spheroidization inoculation. After the spheroidization inoculation is completed, stir rapidly until the temperature of the molten iron drops to 1300°C, the fluidity deteriorates, the SiC powder is difficult to float in the molten iron, and is evenly distributed in the molten iron, and the stirring is stopped.

[0072] Step 7: Quickly and evenly pour the molten iron obtained in step 6 into the prefabricated sand mold, so that the molten iron fills the entire mold cavity, and after the molten metal solidifies, a casting blank is obtained. The interval time for pouring the molten iron into the sand mold is 40 seconds.

[0073] The casting blank obtained in step 7 is the SiC reinforced ductile iron prepared by the present invention, wherein the mass percentage of each component is: C: 3.4%, Si: 2.7%, Mn: 0.2%, S: 0.02%, Mg: 0.05%, RE: 0.04%, and the balance is Fe; and the total carbon equivalent in this component should be maintained at 4.3 wt.%.

[0074] Example 6 The preparation method of SiC reinforced ductile iron of the present invention is specifically implemented according to the following steps: Step 1. According to the mass percentage of each component of SiC reinforced ductile iron, the raw materials are weighed, including: bread iron (Q10): 50%, scrap steel: 8.22%, recarburizer: 0.58%, rare earth magnesium spheroidizer: 0.6%, silicon barium calcium inoculant: 0.6%, Fe / SiC cored wire: 40%, and the sum of the mass percentages of the above components is 100%; the carbon equivalent in the raw materials is 4.3wt.%.

[0075] The SiC particles in the Fe / SiC cored wire are spherical with an average particle size of 50 μm, the average particle size of the Fe powder is 100 μm, the mass fraction of the spherical SiC powder in the cored wire is 50%, and the mass fraction of the iron powder is 50%.

[0076] Step 2: Add the weighed bread iron, carburizer and scrap steel into the medium frequency induction heating furnace in sequence for heating. The heating rate is 35°C / min, the smelting time is 40min, and the high temperature melting temperature of the smelting furnace is 1550°C.

[0077] After the molten iron in step 3 and step 2 is deslagging, the Fe / SiC cored wire weighed in step 1 is added to the molten iron, and the mass of the Fe / SiC cored wire is 40%. Heating for 160s, the SiC accounting for 3.43% of the total mass of all raw materials is decomposed, the silicon content of the molten iron increases by 2.4%, the carbon content increases by 1.03%, the mass of the remaining undecomposed SiC accounts for 16.57% of the total mass of all raw materials, and the average particle size of the remaining SiC is 45.52μm. The carbon and silicon contents in the molten iron are measured using the PD-TY8 type furnace front molten iron management instrument. The silicon content in the molten iron is 2.7%, and the carbon content is 3.4%. When the molten iron reaches the designed composition, it is immediately discharged from the furnace.

[0078] Step 4: Remove impurities from the sand by sand casting, fill the mold with molding sand, and compact the molding sand by vibration or compaction to form a sand mold corresponding to the shape of the casting.

[0079] Step 5: Place the rare earth magnesium spheroidizer and silicon-barium-calcium inoculant weighed in step 1 into a molten iron ladle and cover it with a covering agent, which is rust-free iron filings.

[0080] Step 6: Pour the molten iron obtained in step 3 into the iron ladle slowly or quickly for spheroidization inoculation. After the spheroidization inoculation is completed, stir rapidly until the temperature of the molten iron drops to 1350°C, the fluidity deteriorates, the SiC powder is difficult to float in the molten iron, and is evenly distributed in the molten iron, and the stirring is stopped.

[0081] Step 7: Quickly and evenly pour the molten iron obtained in step 6 into the prefabricated sand mold, so that the molten iron fills the entire mold cavity, and after the molten metal solidifies, a casting blank is obtained. The interval time for pouring the molten iron into the sand mold is 50 seconds.

[0082] The casting blank obtained in step 7 is the SiC reinforced ductile iron prepared by the present invention, wherein the mass percentage of each component is: C: 3.4%, Si: 2.7%, Mn: 0.2%, S: 0.02%, Mg: 0.05%, RE: 0.04%, and the balance is Fe; and the total carbon equivalent in this component should be maintained at 4.3 wt.%.

[0083] Embodiments 1-6 of the present invention strictly control the ratio of each component in the raw materials and each process link of the casting process, thereby obtaining SiC reinforced ductile iron. The degree of SiC decomposition is controlled by heating time, the silicon content in the molten iron is increased, the number and spheroidization rate of graphite balls in the material are guaranteed, the self-lubricating properties of ductile iron are brought into play, and SiC is evenly distributed in the matrix, thereby improving the strength, hardness and wear resistance of the composite material, reducing wear and extending the service life.

Claims

1. SiC reinforced ductile iron, characterized in that: The raw materials include, by mass percentage, C: 3.4%~3.6%, Si: 2.1%~2.7%, Mn: ≤0.4%, S: ≤0.03%, Mg: 0.03%~0.06%, RE: 0.02%~0.05%, and the balance is Fe.

2. The method for preparing SiC reinforced ductile iron according to claim 1, characterized in that: Specifically: Step 1, weighing raw materials according to the mass percentage of each component of the composite material, including: breaded iron, scrap steel, carburizer, inoculant, spheroidizer and Fe / SiC cored wire; Step 2, placing the weighed bread iron, carburizer, and scrap steel into a medium frequency induction heating furnace in order for heating; Step 3, after removing the slag from the molten iron in step 2, adding the Fe / SiC cored wire into the melt, and continuing to heat to obtain molten iron of designed composition; Step 4: Remove impurities from the sand by sand casting, fill the mold with molding sand, and compact the molding sand by vibration or compaction to form a sand mold corresponding to the shape of the casting; Step 5, placing the spheroidizing agent and inoculant weighed in step 1 into a molten iron ladle, and covering it with a covering agent, wherein the covering agent is rust-free iron filings; Step 6, pour the molten iron finally obtained in step 3 into the iron ladle from slow to fast, and perform spheroidization inoculation treatment. After the spheroidization inoculation is completed, stir until the temperature of the molten iron decreases, the fluidity becomes worse, the SiC powder is difficult to float in the molten iron, and is evenly distributed in the molten iron, and the stirring is stopped; Step 7: quickly and evenly pour the molten iron obtained in step 6 into the prefabricated sand mold so that the molten iron fills the entire mold cavity. After the molten metal solidifies, a casting blank is obtained.

3. The method for preparing SiC reinforced ductile iron according to claim 2, characterized in that: Step 1 is specifically as follows: according to the mass percentage of each component of SiC reinforced ductile iron, the raw materials are weighed, including: breaded iron: 50%, scrap steel: 8.22%~28.22%, recarburizer: 0.58%~1.04%, spheroidizer: 0.6%~0.8%, inoculant: 0.6%~0.8%, Fe / SiC cored wire: 20%~40%, and the sum of the mass percentages of the above components is 100%; the carbon equivalent in the raw materials is 4.3wt.%.

4. The method for preparing SiC reinforced ductile iron according to claim 3, characterized in that: In step 1, the spheroidizer is a rare earth magnesium spheroidizer, and the inoculant is a silicon-barium-calcium inoculant.

5. The method for preparing SiC reinforced ductile iron according to claim 3, characterized in that: In step 1, the SiC particles in the Fe / SiC cored wire are spherical with an average particle size of 50 μm, the average particle size of the Fe powder is 100 μm, the mass fraction of the spherical SiC powder in the cored wire is 50%, and the mass fraction of the iron powder is 50%.

6. The method for preparing SiC reinforced ductile iron according to claim 2, characterized in that: Step 2: Add the weighed bread iron, carburizer and scrap steel into the medium frequency induction heating furnace in sequence for heating, with a heating rate of 40°C / min~50°C / min, a smelting time of 30min~40min, and a high-temperature melting temperature of the smelting furnace of 1550°C~1600°C.

7. The method for preparing SiC reinforced ductile iron according to claim 2, characterized in that: Step 3 is specifically as follows: after the molten iron in step 2 is deslagging, the Fe / SiC cored wire weighed in step 1 is added to the molten iron and heated for 160s to 310s to decompose SiC accounting for 2.57% to 3.43% of the total mass of all raw materials, increase the silicon content of the molten iron by 1.8% to 2.4%, and increase the carbon content by 0.77% to 1.03%. The mass of the remaining undecomposed SiC accounts for 6.57% to 16.57% of the total mass of all raw materials. The carbon and silicon contents in the molten iron are measured using a PD-TY8 furnace-front molten iron management instrument. The silicon content in the molten iron is 2.1% to 2.7%, and the carbon content is 3.4% to 3.6%. When the molten iron reaches the designed composition, it is immediately discharged from the furnace.

8. The method for preparing SiC reinforced ductile iron according to claim 2, characterized in that: In step 6, the temperature of the molten iron is reduced to 1300°C-1350°C and stirring is stopped.

9. The method for preparing SiC reinforced ductile iron according to claim 2, characterized in that: In step 7, the interval time for pouring molten iron into the sand mold is 30s-50s.

10. The method for preparing SiC reinforced ductile iron according to claim 2, characterized in that: The casting blank obtained in step 7 is the SiC reinforced ductile iron prepared by the present invention, wherein the mass percentage of each component is: C: 3.4%~3.6%, Si: 2.1%~2.7%, Mn: ≤0.4%, S: ≤0.03%, Mg: 0.03%~0.06%, RE: 0.02%~0.05%, and the balance is Fe; and the total carbon equivalent in this component should be maintained at 4.3 wt.%.

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