Spheroidal graphite cylinder body and preparation method thereof
By using specific raw material ingredients and process steps in the manufacturing process of ductile castings, including the use of low-reduced earth spheroidizers and silicon barium inoculant, problems such as graphite morphological distortion and intergranular slag inclusion in ductile castings are solved, and graphite spheres are realized Improvement of number and uniformity and stable production of cylinder performance.
Patent Information
- Application Number
- CN202411635762.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-15
- Publication Date
- 2025-02-18
AI Technical Summary
In the existing ductile casting manufacturing process, the product performance is unstable and graphite morphological distortion, intergranular slag inclusion and shrinkage are prone to problems, which affects the mechanical properties and usage performance of the cylinder.
A ductile ink cylinder preparation method is adopted, including raw material ingredients, molten iron smelting, deoxygenation pretreatment, pulping spheroidization, and condensation with flow, pouring and other steps. By injecting additives such as low-reduced earth spheroidizer, silicon barium inoculant, crushed steel sheets and antimony ingots, the chemical composition and graphitization process of molten iron are controlled to improve the number and uniformity of graphite spheres.
Effectively solve the problems of intergranular slag inclusions and intergranular shrinkage in metallographic phase, prevent component segregation, improve graphite sphere count and uniformity, realize stable production of casting performance, and improve the product qualification rate of cylinder production .
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Abstract
Description
Technical Field
[0001] The invention relates to the technical field of manufacturing technology of ductile iron castings, and in particular to a ductile iron cylinder body and a preparation method thereof. Background Art
[0002] The cylinder block of a low-speed engine is mainly used for power output of ship parts. The cylinder block supports the cylinder liner, cylinder head, piston, connecting rod and other components. It is the core component of the ship and is usually made of high-performance ductile iron.
[0003] In order to ensure the overall rigidity of the cylinder body, the cylinder body parts are often designed to be very thick, especially the cylinder head bolt hole mounting surface area, the wall thickness is often 230mm-300mm; in the prior art, high carbon equivalent is usually used to prevent shrinkage and shrinkage of castings, conventional spheroidizers are used for spheroidization, and silicon-barium inoculants are used for inoculation and post-casting.
[0004] The following problems are often associated with it: (1) Product performance is unstable, and performance problems may easily occur; (2) The graphite morphology is easily distorted, and problems such as broken graphite, blooming graphite, waterweed-like graphite, and graphite floating may easily occur; (3) Intergranular slag inclusions and shrinkage are prone to occur; (4) The matrix structure is unstable, the number of graphite nodules is relatively small, and the pearlite content is unstable, which seriously affects the mechanical properties and performance of the cylinder body. Summary of the invention
[0005] In view of the above problems in the prior art, the present invention provides a spheroidal graphite cylinder body and a preparation method thereof, the purpose of which is to improve the performance stability of the spheroidal graphite cylinder body and improve the production qualification rate of the cylinder body.
[0006] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is as follows:
[0007] On the one hand, a preparation method of a ductile iron cylinder body is provided, comprising the following steps: S1. raw material batching: ductile iron return material, pig iron and scrap steel are weighed according to a proportion to obtain raw materials; S2. molten iron smelting: the raw materials are sent to a smelting furnace for heating, and a carburizer and silicon carbide are added during the melting process to obtain molten iron; S3. deoxidation pretreatment: the molten iron is superheated and poured into an iron ladle, and silicon barium is added; S4. spheroidization and in-stream inoculation: low-rare earth spheroidizer, silicon-barium inoculant and broken steel sheets are laid in layers in a ladle, and the molten iron in the iron ladle is then flushed into the ladle; and during the molten iron discharge process, an antimony ingot is added into the ladle to obtain spheroidized molten iron; S5. pouring: the spheroidized molten iron is deslaged and poured into a casting mold, and a cerium oxysulfide inoculant is added in-stream to form a cylinder body.
[0008] Furthermore, in S1, the mass ratio of ductile iron recycled materials, pig iron and scrap steel is 5-15:45-55:35-45.
[0009] Further, in S2, the recarburizer and silicon carbide account for 0.6% and 0.8% of the raw material mass, respectively.
[0010] Furthermore, the mass proportions of the chemical elements in the molten iron produced in S2 are as follows: C content is 3.60-3.70%, Si content is 1.35-1.50%, Mn content is 0.24-0.30%, S content is ≤0.02%, P content is ≤0.03%, Cu content is 0.30-0.40%, and the rest is Fe and unavoidable impurities.
[0011] Furthermore, in S3, silicon barium accounts for 0.1-0.3% of the mass of the molten iron.
[0012] Furthermore, in S4, the low rare earth spheroidizer accounts for 1.15-1.20% of the mass of the molten iron, and the low rare earth spheroidizer is covered with a silicon-barium inoculant accounting for 0.1% of the mass of the molten iron and crushed steel sheets accounting for 0.5-0.6% of the mass of the molten iron.
[0013] Further, in S4, the antimony ingot accounts for 0.003% of the mass of the molten iron.
[0014] Furthermore, the mass proportions of the chemical elements in the spheroidized iron prepared in S4 are as follows: C content is 3.40-3.50%, Si content is 2.35-2.50%, Mn content is 0.24-0.30%, S content is ≤0.015%, P content is ≤0.03%, Cu content is 0.30-0.40%, Mg content is 0.035-0.05%, Sb content is 0.003-0.004%, and the rest is Fe and unavoidable impurities.
[0015] Furthermore, in S5, the cerium oxysulfide inoculant accounts for 0.1-0.2% of the mass of the spheroidized iron water.
[0016] On the other hand, a spheroidal graphite cylinder body is also provided, which is made by the above-mentioned preparation method of the spheroidal graphite cylinder body.
[0017] The beneficial effects of the present invention are as follows: by using the present invention, the problems of intergranular slag inclusions and intergranular shrinkage in the metallographic phase can be solved, the problem of component segregation can be prevented, and the number and uniformity of graphite nodules can be effectively improved; stable production of as-cast performance can be achieved, and the product qualification rate of cylinder body production can be improved. DETAILED DESCRIPTION
[0018] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with specific implementation methods.
[0019] Example 1
[0020] The embodiment of the present invention provides a preparation method of a ductile iron cylinder body, which includes the following steps: S1. raw material batching: ductile iron return material, pig iron and scrap steel are weighed according to a proportion to obtain raw materials; S2. molten iron smelting: the raw materials are sent to a smelting furnace for heating, and a carburizer and silicon carbide are added during the melting process to obtain molten iron; S3. deoxidation pretreatment: the molten iron is superheated and poured into an iron ladle, and silicon barium is added; S4. spheroidization and in-stream inoculation: low-rare earth spheroidizer, silicon-barium inoculant and broken steel sheets are laid in layers in a ladle, and the molten iron in the iron ladle is then flushed into the ladle; and during the molten iron discharge process, antimony ingots are added into the ladle to obtain spheroidized molten iron; S5. pouring: the spheroidized molten iron is deslaged and poured into a casting mold, and a cerium oxysulfide inoculant is added in-stream to form a cylinder body.
[0021] In the present invention, a low rare earth nodulizer is used to prevent the influence of rare earth on the graphite morphology of thick and large-section ductile iron, and to neutralize the harmful elements in the molten iron that affect the graphite morphology; a trace amount of Sb element, i.e., antimony ingot, is also added to neutralize the adverse factors in the rare earth, and the Sb element can also hinder graphitization and prevent excessive growth of graphite balls; silicon carbide is also added for pretreatment to control the oxygen content before the molten iron is formed, promote the retention of graphitized cores in the molten iron, improve the metallurgical quality of the molten iron, and increase the number of graphite balls and the uniformity of graphite ball distribution; and a high-efficiency sulfur oxide cerium inoculant is used for inoculum, which promotes the increase and retention time of graphite cores in the molten iron, and increases the number of graphite balls and the nodularity rate.
[0022] Preferably, in S1, the mass ratio of ductile iron recycled materials, pig iron and scrap steel is 5-15:45-55:35-45.
[0023] Specifically, QT500-7 grade ductile iron recycled material and Q10 grade pig iron can be used, and scrap steel can be the leftovers of automobile stamping sheet metal parts.
[0024] It should be noted that, in this embodiment, the chemical element composition requirements in Q10 pig iron are as follows: C ≥ 3.4%, Si = 0.5 ~ 1.0%, Mn ≤ 0.20%, P ≤ 0.04%, S ≤ 0.02%, Ti ≤ 0.03%, trace element B ≤ 0.0007%, Pb ≤ 0.002%, and the rest are Fe and unavoidable impurities.
[0025] The requirements for the chemical element composition in scrap steel are as follows: C≤0.5%, Si≤1.0%, Mn≤0.20%, P≤0.035%, S≤0.02%, Ti≤0.025%, Cr≤0.05%, B≤0.0007%, Pb≤0.001%, AL≤0.05%, and the rest are Fe and unavoidable impurities.
[0026] Preferably, in S2, the recarburizer and silicon carbide account for 0.6% and 0.8% of the raw material mass, respectively.
[0027] It should be noted that in this embodiment, the requirements for the recarburizer are: C ≥ 98.5%, S ≤ 0.3%, N < 0.02%, and the rest are inevitable impurities with a particle size of 5 to 10 mm. The requirements for silicon carbide are: SiC ≥ 90%, and the rest are inevitable impurities with a particle size of 1 to 5 mm.
[0028] Preferably, the mass proportions of the chemical elements in the molten iron produced in S2 are: C content is 3.60-3.70%, Si content is 1.35-1.50%, Mn content is 0.24-0.30%, S content is ≤0.02%, P content is ≤0.03%, Cu content is 0.30-0.40%, and the rest is Fe and unavoidable impurities.
[0029] It is worth mentioning that in S2, one or more of ferrosilicon, ferromanganese and cathode copper can be added according to the different mass proportions of various chemical elements in the molten iron, so as to adjust the mass proportions of various chemical elements in the molten iron.
[0030] Among them, the requirements for the composition of each chemical element in ferrosilicon are as follows: Si ≥ 72%, AL ≤ 1.5%; the requirements for the composition of each chemical element in ferromanganese are as follows: Mn ≥ 65%, and the particle size is 50-150mm; the requirements for the composition of each chemical element in cathode copper are as follows: Cu ≥ 99.95%, Pb ≤ 0.002%, and the rest are Fe and unavoidable impurities.
[0031] Preferably, in S3, silicon and barium account for 0.1-0.3% of the mass of the molten iron.
[0032] Preferably, in S4, the low rare earth spheroidizer accounts for 1.15-1.20% of the mass of the molten iron, and the low rare earth spheroidizer is covered with a silicon-barium inoculant accounting for 0.1% of the mass of the molten iron and broken steel pieces accounting for 0.5-0.6% of the mass of the molten iron.
[0033] In this embodiment, the requirements for low rare earth nodulizer are as follows: Mg 5.5-6.2%, RE 0.8-1.2%, Si 40-50%, Ca 1.0-2.0%, AL ≤ 1.0%, and the rest are inevitable impurities, with a particle size of 5-25 mm. The requirements for silicon-barium inoculant are as follows: Ba 4-6%, Si 62-72%, Ca 1.0-2.0%, AL 1.0-1.6%, and the rest are inevitable impurities, with a particle size of 3-12 mm.
[0034] Preferably, in S4, the antimony ingot accounts for 0.003% of the mass of the molten iron; the requirements for the antimony ingot are as follows: Sb≥99.65%, As<0.1%, and the total impurity content≤0.35%.
[0035] Preferably, the mass proportions of the chemical elements in the spheroidized iron water prepared in S4 are as follows: C content is 3.40-3.50%, Si content is 2.35-2.50%, Mn content is 0.24-0.30%, S content is ≤0.015%, P content is ≤0.03%, Cu content is 0.30-0.40%, Mg content is 0.035-0.05%, Sb content is 0.003-0.004%, and the rest is Fe and unavoidable impurities.
[0036] Preferably, in S3, the molten iron is superheated to 1500°C and then allowed to stand for 8 minutes before being poured into a ladle; and the molten iron is taken out of the furnace for spheroidization and inoculation after the temperature of the molten iron is between 1440 and 1450°C.
[0037] In S4, silicon-barium inoculant and crushed steel flakes are covered on top of the low rare earth spheroidizer.
[0038] In addition, taking each ladle of 12 tons as an example, the spheroidization reaction time is controlled at 90-120S, and during the spheroidization process, 0.4% silicon-barium inoculant is introduced into the molten iron ladle along with the flow to achieve spheroidization and inoculation.
[0039] Of course, the spheroidized iron should be removed immediately, and the molten iron casting spectrum sample, carbon-sulfur sample and triangular test piece should be extracted.
[0040] In S5, the spheroidized iron water is poured into the nozzle basin, and the cerium oxysulfide inoculant is added in the process of pouring into the nozzle basin for flow inoculation; the spheroidized iron water is then allowed to stand for 1 minute until the inclusions fully float up, and the temperature is measured to be between 1320 and 1340°C, and then the plug is pulled out for pouring; taking 24 tons of molten iron as an example, the pouring time should be controlled within 80 seconds, and after the pouring is completed, the mold is cooled for 12 days and then the sand is removed from the box to obtain the cylinder body.
[0041] In this embodiment, a low-temperature fast pouring process is adopted to prevent cold shut, shorten the solidification time, and prevent element segregation from affecting the graphite morphology and intergranular shrinkage; the spheroidized iron liquid is poured into a large pouring basin and then left to stand before pouring, thereby preventing the problem of slag and air entrainment during the pouring process; the casting is cooled in the mold for 12 days to allow the casting to cool slowly and release the casting stress. The performance of the casting is completely obtained by the alloying and heat storage and heat dissipation conditions of the mold, thereby stabilizing the mechanical properties.
[0042] In S5, the cerium oxysulfide inoculant accounts for 0.1-0.2% of the mass of the spheroidized iron water; the chemical element composition requirements of the cerium oxysulfide inoculant are: Si70-76%, Ca0.75-1.25%, Al0.75-1.25%, Ce1.5-2.0%, and the rest are inevitable impurities, with a particle size of 0.1-0.8mm.
[0043] By using the present invention, the problems of intergranular slag inclusions and intergranular shrinkage in metallographic phase can be solved, component segregation can be prevented, and the number and uniformity of graphite nodules can be effectively improved; stable production of as-cast performance can be achieved, and the product qualification rate of cylinder body production can be improved.
[0044] Example 2
[0045] In this embodiment, three cylinder blocks are manufactured using the preparation method in Embodiment 1 and are numbered 1#, 2# and 3# respectively.
[0046] It is worth mentioning that, in this embodiment, in S1, the mass ratio of ductile iron recycled materials, pig iron and scrap steel is 1:5:4.
[0047] Among them, furan sand process is selected for manual core making and shaping; and cold iron made of HT200 and 150mm thick is spread on the wall surface of the casting and sand core with bolt holes.
[0048] Referring to Table 1 below, in actual production, the composition of molten iron before spheroidizing inoculation is as follows:
[0049] Table 1 Composition of molten iron before spheroidization
[0050]
[0051] Specifically, in this embodiment, the cerium oxysulfide inoculant added accounts for 0.15% of the mass of the spheroidized iron water. The spheroidized iron water is poured after being allowed to stand at 1339° C., and the pouring time is completed in 78 seconds.
[0052] Referring to Table 2 below, in actual production, the composition of molten iron after spheroidization inoculation is as follows:
[0053] Table 2 Composition of molten iron after spheroidization
[0054]
[0055] In this embodiment, a cylindrical specimen is obtained by nesting at the bolt hole position of the cylinder body. The diameter of the specimen is φ30 mm and the length is 230 mm.
[0056] The samples were subjected to: tensile test, metallographic test and hardness test.
[0057] Referring to Table 3 below, in actual production, the test results of sample performance are as follows:
[0058] Table 3 Sample performance test results
[0059]
[0060] It should be understood by those skilled in the art that, although preferred embodiments of the present invention have been described, additional changes and modifications may be made to these embodiments once those skilled in the art are aware of the basic inventive concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention. Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and the equivalent technology, the present invention is also intended to include these modifications and variations.
Claims
1. A method for preparing a spherical ink cylinder body, characterized in that: The following steps are involved: S1. Raw material batching: weigh ductile iron recycled materials, pig iron and scrap steel according to the proportion to obtain raw materials; S2. Hot metal smelting: The raw materials are fed into a smelting furnace for heating, and a carburizer and silicon carbide are added during the melting process to obtain hot metal; S3. Deoxidation pretreatment: Pour the superheated molten iron into the ladle and add silicon barium; S4. Pour into the spheroidizing and inoculating with the flow: Lay low rare earth spheroidizing agent, silicon-barium inoculant and broken steel pieces in the ladle, and then pour the molten iron out of the ladle into the ladle; and in the process of molten iron out of the water, put antimony ingots into the ladle to obtain spheroidized molten iron; S5. Pouring: After removing the slag from the spheroidized iron, pour it into a casting mold, and add cerium oxysulfide inoculant along the flow to form a cylinder body.
2. The method for preparing a spherical ink cylinder body according to claim 1, characterized in that: In S1, the mass ratio of ductile iron recycled materials, pig iron and scrap steel is 5-15:45-55:35-45.
3. The method for preparing a spherical ink cylinder body according to claim 1, characterized in that: In S2, the recarburizer and silicon carbide account for 0.6% and 0.8% of the raw material mass, respectively.
4. The method for preparing a spherical ink cylinder body according to claim 1, characterized in that: The mass proportions of the chemical elements in the molten iron produced in S2 are as follows: C content is 3.60-3.70%, Si content is 1.35-1.50%, Mn content is 0.24-0.30%, S content is ≤0.02%, P content is ≤0.03%, Cu content is 0.30-0.40%, and the rest is Fe and unavoidable impurities.
5. The method for preparing a spherical ink cylinder body according to claim 1, characterized in that: In S3, silicon and barium account for 0.1 to 0.3% of the mass of the molten iron.
6. The method for preparing a spherical ink cylinder body according to claim 1, characterized in that: In S4, the low rare earth spheroidizer accounts for 1.15-1.20% of the mass of the molten iron, and the low rare earth spheroidizer is covered with a silicon-barium inoculant accounting for 0.1% of the mass of the molten iron and broken steel pieces accounting for 0.5-0.6% of the mass of the molten iron.
7. The method for preparing a spherical ink cylinder body according to claim 1, characterized in that: In S4, antimony ingots account for 0.003% of the mass of molten iron.
8. The method for preparing a spherical ink cylinder body according to claim 1, characterized in that: The mass proportions of the chemical elements in the spheroidized iron produced in S4 are as follows: C content is 3.40-3.50%, Si content is 2.35-2.50%, Mn content is 0.24-0.30%, S content is ≤0.015%, P content is ≤0.03%, Cu content is 0.30-0.40%, Mg content is 0.035-0.05%, Sb content is 0.003-0.004%, and the rest is Fe and unavoidable impurities.
9. The method for preparing a spherical ink cylinder body according to claim 1, characterized in that: In S5, the cerium oxysulfide inoculant accounts for 0.1-0.2% of the mass of the spheroidized iron water.
10. A spherical ink cylinder body, characterized in that: The spheroidal graphite cylinder body is manufactured by the preparation method of any one of claims 1 to 9.