Manufacturing method of low-carbon high-silicon chilled cast iron camshaft under same carbon equivalent

Abstract

The invention belongs to the technical field of chilled cast iron camshafts, and particularly relates to a manufacturing method of a low-carbon high-silicon chilled cast iron camshaft under the same carbon equivalent, and the manufacturing method comprises the steps of modeling, burdening, smelting, pouring, cooling and unboxing, sand cleaning and detection. Under the condition of the same carbon equivalent, the carbide content of the center of the camshaft can be effectively controlled by strictly controlling the ratio of carbon to silicon and matching with a special inoculant under the conditions of low carbon content and high silicon content, and the obtained chilled cast iron camshaft is good in carbide grade and high in hardness in a metallographic structure, especially excellent in shaft neck macrostructure performance and good in mechanical property. The processing performance and the service life of the chilled cast iron camshaft are greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of chilled cast iron camshafts, and in particular relates to a method for manufacturing a low-carbon and high-silicon chilled cast iron camshaft under the same carbon equivalent. Background Art

[0002] The camshaft is one of the key components of the engine and an important part for opening and closing the cylinder valves in the engine. The wear resistance of the cam parts directly affects the performance of the engine. Chilled cast iron has good wear resistance and abrasion resistance due to its high hardness carbides and ledeburite structure. Carbides also have a skeleton effect, and the pearlite in the ledeburite has an oil storage function. Therefore, chilled cast iron is widely used as the camshaft material of the engine.

[0003] Carbides play a vital role in chilled cast iron camshafts. Controlling the content of carbides can improve the use and processing performance of chilled cast iron camshafts. Carbides can not only improve the hardness and wear resistance of the camshaft, but also form a unique structure with pearlite to improve oil storage and wear resistance. They can also enhance the impact resistance and fatigue resistance of the camshaft, so that the camshaft can maintain a stable working state in a complex working environment. However, if the carbide content in the camshaft is too high, it is easy to increase the brittleness of the material and reduce the toughness, which makes the material more prone to cracks and peeling during the friction process; it is not the lower the better. If the carbide content is too low, the hardness of the chilled layer will be reduced accordingly, thereby affecting the wear resistance and service life of the camshaft, and it is easy to increase the shrinkage tendency, which seriously affects the quality and performance of the camshaft. Carbon equivalent is a crucial technical parameter in the manufacture of chilled cast iron camshafts, which involves many aspects of the casting process and the final performance of the product. Under the same carbon equivalent, the lower the carbide content, the higher the level, and the better the performance. Therefore, developing a manufacturing method for a chilled cast iron camshaft with an increased carbide level at the same carbon equivalent can improve the performance and service life of the camshaft. Summary of the invention

[0004] In view of the above-mentioned deficiencies mentioned in the background technology, the purpose of the present invention is to provide a method for manufacturing a low-carbon and high-silicon chilled cast iron camshaft under the same carbon equivalent. Under the condition of the same or similar carbon equivalent, by strictly controlling the ratio of carbon to silicon, at a low carbon and high silicon content, and in combination with a special inoculant, the carbide content in the camshaft can be effectively controlled. The obtained chilled cast iron camshaft has a good carbide level and high hardness in the metallographic structure, especially the excellent performance of the journal structure, which greatly improves the processing performance and service life of the chilled cast iron camshaft.

[0005] In order to achieve the above object, the present invention provides a method for manufacturing a low-carbon and high-silicon chilled cast iron camshaft with the same carbon equivalent, comprising the following steps: (1) Molding: Check and clean the coated sand, use the horizontal parting core shooting machine to simultaneously make the upper and lower shell molds in the shell making machine, place the forming chiller at the lower shell mold chiller seat just below the cam peach tip after demolding, and quickly squeeze the adhesive into the adhesive groove of the lower mold in a hot state, and place it in the press molding machine for pressing. After 2 hours of pressing, pour and mold; (2) Ingredients: 8-10% scrap steel, 25-30% pig iron, 55-65% recycled materials, and 4-5.5% other composite components; the C:Si ratio in the resulting molten iron is 1.4-1.8; (3) Melting: Pig iron, scrap steel, recycled materials and other composite components are added to the medium frequency induction furnace in the order of 660V and 600kW. When the temperature of the molten iron rises to 1480±10℃, a covering agent is added to remove the slag from the molten iron. When the temperature of the molten iron rises to 1520±10℃, a covering agent is added to continue heating. When the temperature of the molten iron rises to 1590-1640℃, the molten iron in the furnace is purified and the slag is removed 2-3 times. After the slag is removed, the power is turned off and the molten iron is taken out of the furnace. At the same time, the first inoculant is added to the ladle for inoculation. Then, a covering agent is added to the surface of the molten iron again to remove the slag and clean it. The molten iron is kept warm for standby use. (4) Pouring: The molten iron is divided into separate packages and the second inoculant is added into the hanging package. After the white mouth width is tested and found to be qualified, the hanging package is transferred to the shell casting area, and the temperature of the molten iron is reduced to 1350-1440℃ for pouring; (5) Cooling and unpacking: After cooling for ≥60 min, unpack and obtain the chilled cast iron camshaft casting; (6) Sand cleaning: Pull the blank to the shot blasting area for shot blasting; (7) Inspection: Before the blank is shipped out, an appearance inspection is carried out, including inspection for runout and casting defects.

[0006] Furthermore, the carbon equivalent CE% is controlled at 3.9-4.15%.

[0007] Furthermore, in step (2), the contents of the components in the molten iron are C 3.3-3.4%, Si 1.9-2.3%, Mn 0.6-0.9%, S < 0.1%, P < 0.1%, Mo 0.2-0.4%, Ni 0.2-0.4%, Sn 0.005-0.01%, Cr 0.4-0.6%, Cu 0.5-1.0%, and the remainder is Fe and unavoidable impurities.

[0008] The present invention optimizes the chemical composition of molten iron, maintains low carbon and high silicon under the condition of the same or similar carbon equivalent, and cooperates with two inoculations to eliminate the carbides in the center of the camshaft as much as possible while ensuring that the camshaft has no shrinkage cavity or shrinkage, so that the carbide level in the metallographic structure of the product is controlled at a relatively low level, the white castellation width is appropriate, and the overall performance is excellent.

[0009] Furthermore, in step (1) of the above technical solution, the width of the formed chill matches the cam peach.

[0010] Furthermore, in step (1) of the above technical solution, the particle size of the coated sand is 70-140 mesh, the strength at room temperature is 7.2 MPa, and the gas evolution at 850°C is 14.5 mL / g; the sand injection time in the shell making machine is 3-5 s, the curing time is 105-125 s, the mold temperature is 220-260°C, and the pressing time is >2 min.

[0011] Furthermore, in step (3) of the above technical solution, the amount of the first inoculant added is 0.2-0.4% of the total amount of molten iron; the first inoculant is a composite inoculant, comprising 5-6% barium, 0.1-0.5% calcium, 0.1-0.2% aluminum, 0.6-1% zirconium, 0.01-0.05% cerium, 65-69% silicon, and the remainder is iron; and the particle size is 6-8 mm. Barium is the most active element among alkaline earth metals. It has a good deoxidizing effect and can effectively promote the graphitization process, eliminate the tendency of white cast iron in castings, and at the same time prolong the action time of the inoculant and improve the strength of castings. Calcium can react with oxygen and sulfur in molten iron to form stable compounds to purify the molten iron and improve the impact performance of castings. Aluminum not only acts as a deoxidizer to improve the cleanliness of molten iron and prolong the inoculation time, but also can cooperate with silicon and calcium to promote the graphitization process. Zirconium can improve the fluidity of molten iron and improve the cleanliness of molten iron. Cerium purifies molten iron, refines the grain structure, improves the mechanical properties and processing properties of castings, and can also improve the graphite morphology in cast iron. Silicon, as the basis of composite inoculation, has a strong ability to promote graphitization, which can improve the uniformity of the cross-section of castings, reduce the tendency of molten iron to be overcooled, increase the number of eutectic clusters, etc., thereby improving the strength and mechanical properties of cast iron. In this technical solution, by optimizing the inoculant formula and adding it when the molten iron is out of the furnace, the chemical composition and solidification process of the molten iron can be affected earlier, which helps to form fine graphite structure, reduce carbide formation, improve the strength and toughness of castings, reduce the tendency of white cast iron, and improve the processing performance and service life of the product.

[0012] Furthermore, in step (3) of the above technical solution, the covering agent is expanded perlite or expanded graphite.

[0013] Furthermore, in step (4) of the above technical solution, the second inoculant is added when 1 / 3 of the molten iron is added to the hanging ladle, and the time from the addition of the second inoculant to the completion of pouring is controlled within 9-10 minutes. In this technical solution, by adding the second inoculant in the middle of adding molten iron to the hanging ladle, the impact of the liquid flow can be utilized to achieve the effect of stirring, so that the inoculant is completely dissolved in the high-temperature molten iron, thereby improving the inoculation effect.

[0014] Furthermore, in step (4) of the above technical solution, the amount of the second inoculant added is 0.1-0.2% of the total molten iron in the ladle; the second inoculant is a strontium-silicon-iron composite inoculant, comprising 0.8-1.2% strontium, 0.05-0.1% calcium, 0.1-0.2% aluminum, 70-75% silicon, and the remainder is iron, and the particle size is 2-4 mm. Strontium has a strong ability to promote graphitization, and can significantly improve the morphology and distribution of graphite in castings. It also has a special effect of reducing the number of eutectic clusters, which helps to reduce shrinkage cavities and shrinkage defects in castings. It can also effectively reduce the tendency of cast iron to have white cast iron and improve the strength and toughness of castings. Adding a small amount of calcium to the strontium ferrosilicon composite inoculant can further enhance the inoculation effect of the inoculant and improve the microstructure of the casting. In the present technical solution, adding the inoculant again to the ladle can further promote graphitization, refine the grains, improve the uniformity of the cross-sectional structure of the cast iron, increase the number of eutectic clusters, reduce defects such as segregation, thereby improving the strength and toughness of the casting and improving the stability of the casting.

[0015] Furthermore, in step (4) of the above technical solution, after the hanging bag is packed, a sample is taken, a sand mold test block is cast, the white width of the triangular sample is determined, and adjustments are made according to the result. The white width of the triangular sample is adjusted in the following manner: if the white width is too deep, an appropriate amount of the second inoculant can be added to the molten iron surface for adjustment; if the white width is too shallow, an appropriate amount of scrap steel can be added for adjustment, thereby improving the yield of finished products.

[0016] Compared with the prior art, the present invention has the following beneficial effects: Under the condition of the same carbon equivalent, the present invention can effectively control the carbide content in the center of the camshaft by strictly controlling the ratio of carbon to silicon, under the condition of low carbon and high silicon, and using a special inoculant. The obtained chilled cast iron camshaft has a carbide quantity of level 2 in the metallographic structure, high hardness, and especially excellent journal structure performance, which greatly improves the processing performance and service life of the chilled cast iron camshaft. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 This is a macroscopic structure diagram of the non-cold shock zone of the journal in Example 1 of the present invention; Figure 2 This is the macroscopic microstructure of the non-cold shock zone of the journal of Example 1 of the present invention (×100); Figure 3This is the macroscopic structure diagram of the non-cold shock area of ​​the journal of Comparative Example 1 of the present invention; Figure 4 This is the macroscopic microstructure diagram (×100) of the non-cold shock zone of the journal of comparative example 1 of the present invention. DETAILED DESCRIPTION

[0019] The experimental methods in the following examples are conventional methods unless otherwise specified. The raw materials involved in the following examples are common commercial products and can be purchased from the market unless otherwise specified.

[0020] The above-mentioned technical features of the present invention and the technical features specifically described below (such as implementation cases) can be combined with each other to form a new or preferred technical solution.

[0021] The raw materials involved in the embodiments of the present invention are either existing commercially available products or can be prepared according to existing methods.

[0022] The shell mold equipment is a horizontal parting core shooting machine produced by Weizhong Machinery Technology Co., Ltd. in Wenzhou City, Zhejiang Province, model: HX-600B; the adhesive used is a conventional adhesive such as silica sol.

[0023] The specific contents of the present invention are further explained below in conjunction with embodiments.

[0024] Example 1 A method for manufacturing a chilled cast iron camshaft comprises the following steps: (1) Molding: Check and clean the coated sand, use the horizontal parting core shooting machine to simultaneously produce the upper and lower shell molds in the shell making machine, and place the molded chiller at the lower shell mold chiller seat just below the cam peach tip after demolding. The width of the molded chiller should match the cam, and the adhesive should be quickly squeezed into the adhesive groove of the lower mold in a hot state, and then placed in a press machine for pressing. After 2 hours of pressing, pour and mold. Among them, the particle size of the coated sand is 100 mesh, the strength at room temperature is 7.2MPa, and the gas evolution at 850℃ is 14.5mL / g; the sand shooting time in the shell making machine is 3-5s, the curing time is 105-125s, the mold temperature is 220-260℃, and the pressing time is more than 2min.

[0025] (2) Ingredients: scrap steel 9%, pig iron 26%, recycled materials 60%, other composite components such as chromium, manganese, nickel, copper and other alloys 5%; the C / Si ratio of the obtained molten iron is 1.71, and the carbon equivalent CE% is controlled at 4.063%; among which, the obtained molten iron contains C3.4%, Si1.99%, Mn0.65%, S<0.1%, P<0.1%, Mo0.3%, Ni0.25%, Sn0.006%, Cr0.42%, Cu 0.53%, and the balance is Fe and unavoidable impurities.

[0026] (3) Melting: Pig iron, scrap steel, recycled materials and other alloy components are added to the medium frequency induction furnace in the order of 660V and 600kW. When the temperature of the molten iron rises to 1480±10℃, expanded perlite or expanded graphite is added to remove the slag from the molten iron. When the temperature of the molten iron rises to 1520±10℃, a covering agent is added to continue heating. When the temperature of the molten iron rises to 1620℃, the molten iron in the furnace is purified and the slag is removed 2-3 times. After the slag is removed, the power is turned off, the molten iron is taken out of the furnace, and at the same time, a first inoculant of 0.2% of the total amount of the molten iron is added to the ladle for inoculation. Then, a covering agent is added again to the surface of the molten iron for slag removal and cleaning, and the molten iron is kept warm for use. The first inoculant contains 6% barium, 0.4% calcium, 0.2% aluminum, 0.6% zirconium, 0.04% cerium, 67% silicon, and the remainder is iron. The particle size is 6-8mm.

[0027] (4) Pouring: The molten iron is divided into packages, and when 1 / 3 of the molten iron is added to the ladle, a second inoculant is added, which accounts for 0.2% of the total molten iron in the ladle. After the white mouth width is tested to be qualified, the ladle is transferred to the shell casting area, and the molten iron temperature is reduced to 1350-1440°C for pouring. The time from the addition of the second inoculant to the completion of pouring is controlled within 9-10 minutes; wherein, the second inoculant is a strontium-silicon-iron composite inoculant, which contains 0.8% strontium, 0.05% calcium, 0.15% aluminum, 72% silicon, and the balance is iron, and the particle size is 2-4mm.

[0028] (5) Cooling and unpacking: After cooling for ≥60 min, unpack the box to obtain the chilled cast iron camshaft casting.

[0029] (6) Sand cleaning: Pull the blank to the shot blasting area for shot blasting.

[0030] (7) Inspection: Before the blank is shipped out, an appearance inspection is carried out, including inspection for runout and casting defects.

[0031] Example 2 A method for manufacturing a chilled cast iron camshaft comprises the following steps: (1) Molding: Check and clean the coated sand, use the horizontal parting core shooting machine to simultaneously make the upper and lower shell molds in the shell making machine, and place the molding chiller at the lower shell mold chiller seat just below the cam peach tip after demolding. The width of the molding chiller should match the cam, and the adhesive should be quickly squeezed into the adhesive groove of the lower mold in a hot state, and then placed in a press machine for molding. After 2 hours of molding, pour and mold. Among them, the particle size of the coated sand is 110 mesh, the strength at room temperature is 7.2MPa, and the gas evolution at 850℃ is 14.5mL / g; the sand shooting time in the shell making machine is 3-5s, the curing time is 105-125s, the mold temperature is 220-260℃, and the molding time is more than 2min.

[0032] (2) Ingredients: 8% scrap steel, 30% pig iron, 58% recycled materials, and 4% other composite components such as chromium, manganese, nickel, copper and other alloys; the C:Si ratio in the obtained molten iron is 1.6, and the carbon equivalent CE% is controlled at 4.05%; among which, the obtained molten iron contains 3.35% C, 2.1% Si, 0.66% Mn, less than 0.1%, less than 0.1% P, 0.25% Mo, 0.3% Ni, 0.007% Sn, 0.5% Cr, 0.65% Cu, and the remainder is Fe and unavoidable impurities.

[0033] (3) Melting: Pig iron, scrap steel, recycled materials and other alloy components are added to the medium frequency induction furnace in the order of 660V and 600kW. When the temperature of the molten iron rises to 1480±10℃, expanded perlite or expanded graphite is added to remove slag from the molten iron. When the temperature of the molten iron rises to 1520±10℃, a covering agent is added to continue heating. When the temperature of the molten iron rises to 1600℃, the molten iron in the furnace is purified and the slag is removed 2-3 times. After the slag is removed, the power is turned off, the molten iron is taken out of the furnace, and at the same time, a first inoculant of 0.3% of the total amount of the molten iron is added to the ladle for inoculation. Then, a covering agent is added again to the surface of the molten iron for slag removal and cleaning, and the molten iron is kept warm for use. The first inoculant contains 5.5% barium, 0.2% calcium, 0.15% aluminum, 0.8% zirconium, 0.03% cerium, 69% silicon, and the remainder is iron. The particle size is 6-8mm.

[0034] (4) Pouring: The molten iron is divided into packages, and when 1 / 3 of the molten iron is added to the ladle, a second inoculant is added, which accounts for 0.15% of the total molten iron in the ladle. After the white mouth width is tested to be qualified, the ladle is transferred to the shell casting area, and the molten iron temperature is reduced to 1350-1440°C for pouring. The time from adding the second inoculant to the completion of pouring is controlled within 9-10 minutes; wherein the second inoculant is a strontium-silicon-iron composite inoculant, which contains 1.0% strontium, 0.06% calcium, 0.1% aluminum, 70% silicon, and the balance is iron, and the particle size is 2-4mm.

[0035] (5) Cooling and unpacking: After cooling for ≥60 min, unpack the box to obtain the chilled cast iron camshaft casting.

[0036] (6) Sand cleaning: Pull the blank to the shot blasting area for shot blasting.

[0037] (7) Inspection: Before the blank is shipped out, an appearance inspection is carried out, including inspection for runout and casting defects.

[0038] Example 3 A method for manufacturing a chilled cast iron camshaft comprises the following steps: (1) Molding: Check and clean the coated sand, use the horizontal parting core shooting machine to simultaneously make the upper and lower shell molds in the shell making machine, and place the molding chiller at the lower shell mold chiller seat just below the cam peach tip after demolding. The width of the molding chiller should match the cam, and the adhesive should be quickly squeezed into the adhesive groove of the lower mold in a hot state, and then placed in a press machine for molding. After 2 hours of molding, pour and mold. Among them, the particle size of the coated sand is 140 mesh, the strength at room temperature is 7.2MPa, and the gas evolution at 850℃ is 14.5mL / g; the sand shooting time in the shell making machine is 3-5s, the curing time is 105-125s, the mold temperature is 220-260℃, and the molding time is more than 2min.

[0039] (2) Ingredients: scrap steel 10%, pig iron 23.5%, recycled materials 62%, other composite components such as chromium, manganese, nickel, copper and other alloys 4.5%; the C:Si ratio in the obtained molten iron is 1.4, and the carbon equivalent CE% is controlled at 4.067%; among which, the obtained molten iron contains C3.3%, Si2.3%, Mn0.8%, S<0.1%, P<0.1%, Mo0.4%, Ni0.35%, Sn0.008%, Cr0.55%, Cu 1.0%, and the balance is Fe and unavoidable impurities.

[0040] (3) Melting: Pig iron, scrap steel, recycled materials and other alloy components are added to the medium frequency induction furnace in the order of 660V and 600kW. When the temperature of the molten iron rises to 1480±10℃, expanded perlite or expanded graphite is added to remove the slag from the molten iron. When the temperature of the molten iron rises to 1520±10℃, a covering agent is added to continue heating. When the temperature of the molten iron rises to 1640℃, the molten iron in the furnace is purified and the slag is removed 2-3 times. After the slag is removed, the power is turned off, the molten iron is taken out of the furnace, and at the same time, a first inoculant of 0.4% of the total amount of the molten iron is added to the ladle for inoculation. Then, a covering agent is added again to the surface of the molten iron for slag removal and cleaning, and the molten iron is kept warm for use. The first inoculant contains 5% barium, 0.3% calcium, 0.1% aluminum, 0.65% zirconium, 0.02% cerium, 66% silicon, and the remainder is iron. The particle size is 6-8mm.

[0041] (4) Pouring: The molten iron is divided into packages, and when 1 / 3 of the molten iron is added to the ladle, a second inoculant is added, which accounts for 0.1% of the total molten iron in the ladle. After the white mouth width is tested to be qualified, the ladle is transferred to the shell casting area, and the molten iron temperature is reduced to 1350-1440℃ for pouring. The time from adding the second inoculant to the completion of pouring is controlled within 9-10 minutes. The second inoculant is a strontium-silicon-iron composite inoculant, which contains 1.2% strontium, 0.1% calcium, 0.1% aluminum, 75% silicon, and the balance is iron, and the particle size is 2-4mm.

[0042] (5) Cooling and unpacking: After cooling for ≥60 min, unpack the box to obtain the chilled cast iron camshaft casting.

[0043] (6) Sand cleaning: Pull the blank to the shot blasting area for shot blasting.

[0044] (7) Inspection: Before the blank is shipped out, an appearance inspection is carried out, including inspection for runout and casting defects.

[0045] Comparative Example 1 A method for manufacturing a chilled cast iron camshaft, which differs from Example 1 in that the C content in the molten iron is 3.5% and the silicon content is 1.70%.

[0046] Comparative Example 2 A method for manufacturing a chilled cast iron camshaft, which differs from Example 1 in that the C content in the molten iron is 3.5% and the silicon content is 2.1%.

[0047] Comparative Example 3 A method for manufacturing a chilled cast iron camshaft, which differs from Example 1 in that the C content in the molten iron is 3.4% and the silicon content is 2.4%.

[0048] Comparative Example 4 A method for manufacturing a chilled cast iron camshaft, which differs from Example 1 in that the first inoculant in step (4) is a common silicon-calcium-barium composite inoculant having a composition of 6% barium, 0.4% calcium, 67% silicon, and the remainder being iron.

[0049] Comparative Example 5 A method for manufacturing a chilled cast iron camshaft, which differs from Example 1 in that the second inoculant in step (5) is a common silicon-calcium-barium composite inoculant having a composition of 6% barium, 0.4% calcium, 67% silicon, and the remainder being iron.

[0050] Comparative Example 6 A method for manufacturing a chilled cast iron camshaft, which differs from Example 1 in that a second inoculant is not used in step (5).

[0051] Test example 1. The components before the furnace in Examples 1-3 and Comparative Examples 1-6 were analyzed by spectral analysis. The results are shown in Table 1.

[0052] Table 1 Spectral component analysis (%)

[0053] 2. The width of the triangular specimens of Examples 1-3 and Comparative Examples 1-6 before casting was tested. The results are shown in Table 2.

[0054] Table 2 White mouth width

[0055] 3. According to QC / T554-2018, the metallographic structures of the camshaft bodies obtained in Examples 1-3 and Comparative Examples 1-6 were tested respectively, and the macrostructure and microstructure (×100) of the non-cold shock zone of the journal of Example 1 and Comparative Example 1 were tested. The results are as follows: Figure 1-4 The metallographic structure and hardness test results are shown in Table 3.

[0056] Table 3 Performance test results

[0057] From the results in Tables 1 to 3, it can be seen that the present invention can effectively control the carbide content in the camshaft by strictly controlling the ratio of carbon to silicon under the condition of the same or similar carbon equivalent, under the condition of low carbon and high silicon, and using a special inoculant. The obtained chilled cast iron camshaft has a good carbide grade in the metallographic structure, reaching grade 2, high hardness, and especially excellent journal structure performance (such as Figure 1-Figure 2 ). In Comparative Example 1, when the carbon equivalent is equivalent to that of Example 1, when high carbon and low silicon are used, the carbide level is significantly reduced, and the hardness is significantly reduced. At the same time, from the metallographic structure Figure 3 and Figure 4 It can be seen that the camshaft macrostructure is uneven, with white spots, and the microstructure is obviously worse. In Comparative Examples 2 and 3, the carbon equivalent is too high, and both high carbon and low silicon and low carbon and high silicon are not conducive to the elimination of carbides, and have a certain impact on other properties; in Comparative Examples 4-6, ordinary silicon-calcium-barium composite inoculant is used for inoculation or no inoculation is performed before pouring, which not only affects the elimination of carbides, but also has different degrees of impact on properties such as hardness.

[0058] Finally, it should be emphasized that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various changes and modifications. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for manufacturing a low-carbon, high-silicon chilled cast iron camshaft at the same carbon equivalent, characterized in that: The following steps are involved: (1) Molding: Check and clean the coated sand, use the horizontal parting core shooting machine to simultaneously make the upper and lower shell molds in the shell making machine, place the forming chiller at the lower shell mold chiller seat just below the cam peach tip after demolding, and quickly squeeze the adhesive into the adhesive groove of the lower mold in a hot state, and place it in the press molding machine for pressing. After 2 hours of pressing, pour and mold; (2) Ingredients: 8-10% scrap steel, 25-30% pig iron, 55-65% recycled materials, and 4-5.5% other composite components; the C:Si ratio in the resulting molten iron is 1.4-1.8; (3) Melting: Pig iron, scrap steel, recycled materials and other composite components are added to the medium frequency induction furnace in the order of 660V and 600kW. When the temperature of the molten iron rises to 1480±10℃, a covering agent is added to remove the slag from the molten iron. When the temperature of the molten iron rises to 1520±10℃, a covering agent is added to continue heating. When the temperature of the molten iron rises to 1590-1640℃, the molten iron in the furnace is purified and the slag is removed 2-3 times. After the slag is removed, the power is turned off, the molten iron is taken out of the furnace, and the first inoculant is added to the ladle for inoculation. Then, a covering agent is added to the surface of the molten iron again to remove the slag and clean it up. The molten iron is kept warm for standby use. (4) Pouring: The molten iron is divided into separate packages and the second inoculant is added into the hanging package. After the white mouth width is tested and found to be qualified, the hanging package is transferred to the shell casting area, and the temperature of the molten iron is reduced to 1350-1440℃ for pouring; (5) Cooling and unpacking: After cooling for ≥60 min, unpack the box to obtain the chilled cast iron camshaft casting; (6) Sand cleaning: Pull the blank to the shot blasting area for shot blasting; (7) Inspection: Before the blank is shipped out, an appearance inspection is carried out, including inspection for runout and casting defects.

2. The manufacturing method according to claim 1, characterized in that: The carbon equivalent CE% is controlled at 3.9-4.15%.

3. The manufacturing method according to claim 1, characterized in that: In step (2), the contents of the components in the molten iron are C 3.3-3.4%, Si 1.9-2.3%, Mn 0.6-0.9%, S < 0.1%, P < 0.1%, Mo 0.2-0.4%, Ni 0.2-0.4%, Sn 0.005-0.01%, Cr 0.4-0.6%, Cu 0.5-1.0%, and the balance is Fe.

4. The manufacturing method according to claim 1, characterized in that: In step (1), the width of the formed chill matches the cam.

5. The manufacturing method according to claim 1, characterized in that: In step (1), the particle size of the coated sand is 70-140 mesh, the strength at room temperature is 7.2 MPa, and the gas evolution at 850°C is 14.5 mL / g; the sand injection time in the shell making machine is 3-5 s, the curing time is 105-125 s, the mold temperature is 220-260°C, and the pressing time is >2 min.

6. The manufacturing method according to claim 1, characterized in that: In step (3), the amount of the first inoculant added is 0.2-0.4% of the total amount of molten iron; the first inoculant is a composite inoculant, comprising 5-6% barium, 0.1-0.5% calcium, 0.1-0.2% aluminum, 0.6-1% zirconium, 0.01-0.05% cerium, 65-69% silicon, and the remainder is iron; the particle size is 6-8 mm.

7. The manufacturing method according to claim 1, characterized in that: In step (3), the covering agent is expanded perlite or expanded graphite.

8. The manufacturing method according to claim 1, characterized in that: In step (4), the second inoculant is added when 1 / 3 of the molten iron is added to the ladle, and the time from the addition of the second inoculant to the completion of pouring is controlled within 9-10 minutes.

9. The manufacturing method according to claim 1, characterized in that: In step (4), the amount of the second inoculant added is 0.1-0.2% of the total molten iron in the ladle; the second inoculant is a strontium-silicon-iron composite inoculant, comprising 0.8-1.2% strontium, 0.05-0.1% calcium, 0.1-0.2% aluminum, 70-75% silicon, and the remainder is iron, and the particle size is 2-4 mm.

10. The manufacturing method according to claim 1, characterized in that: In step (4), after the hanging bag is packed, a sample is taken, a sand mold test block is cast, and the white width of the triangular sample is determined. Adjustments are made based on the results. The white width of the triangular sample is adjusted in the following ways: if the white width is too deep, an appropriate amount of the second inoculant can be added to the molten iron surface for adjustment; if the white width is too shallow, an appropriate amount of scrap steel can be added for adjustment.

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