Casting method of high-compactness air-cooled diesel engine cylinder cover

Abstract

The invention discloses a casting method for a high-compactness air-cooled diesel engine cylinder cover. The casting method comprises the steps that 1, RR350 aluminum alloy is smelted into liquid, and after slag and gas are removed, an aluminum alloy solution is obtained; 2, an aluminum alloy solution is poured into the preheated metal mold; 3, a collaborative vibration rod is connected with the free end of an ultrasonic amplitude-change pole of the ultrasonic energy gathering device, and then the collaborative vibration rod penetrates through an oil spraying hole of the metal mold to be inserted into the metal mold, so that the aluminum alloy solution in the metal mold is driven by the ultrasonic amplitude-change pole and the collaborative vibration rod to vibrate till the aluminum alloy solution is completely solidified; fine and uniform crystal grains are formed when the aluminum alloy solution is solidified and crystallized; according to the multi-field auxiliary cylinder cover casting forming technology, solidification feeding on the casting thin-wall mold filling difficult position in the ultrasonic vibration mode is achieved, the ultrasonic field and gravity field coupled multi-field auxiliary cylinder cover casting forming technology is formed, feeding is promoted, the pinhole degree is reduced, grains are refined, and the yield and performance of castings are improved.

Description

Technical Field

[0001] The invention belongs to the field of metal smelting and casting, and in particular relates to a casting method for a highly compact air-cooled diesel engine cylinder head. Background Art

[0002] With the development of equipment technology, the specific power of air-cooled diesel engines continues to increase, and the service conditions of air-cooled diesel engines are becoming more severe. Under the service conditions of high compactness, high temperature, high pressure, high mechanical, high thermal load, high speed, and high friction, very high requirements are placed on the heat dissipation performance and load-bearing capacity of the diesel engine cylinder head. With the increase in engine power density and the high compactness of the structural layout, the thermal load and mechanical load of the cylinder head are more stringent, which not only requires the cylinder head material to have good strength, toughness and fatigue resistance, but also puts higher requirements on the casting of the high-compact air-cooled diesel engine cylinder head. Therefore, on the basis of improving the cylinder head material, the casting process is optimized and improved, in order to improve the performance of the high-compact air-cooled diesel engine cylinder head products and obtain high-quality, low-cost cylinder head castings.

[0003] The development process of aluminum alloy cylinder head castings has evolved from the initial sand casting to the semi-metal casting with the inner sand core of the metal mold to low-pressure casting. Metal mold gravity casting and metal mold low-pressure casting are the most commonly used aluminum alloy cylinder head casting process methods. In the actual production of most aluminum alloy cylinder heads in the world today, metal mold gravity casting is the most widely used casting process method. Using a gravity casting machine, the metal liquid fills the metal mold through the pouring system under the action of its own gravity to obtain the required casting. During the metal mold gravity casting process, due to the high thermal conductivity of the metal mold and the effect of the mold water cooling system, the casting cools quickly, the grain size is relatively small, and the mechanical properties are high. Moreover, the metal mold gravity casting equipment is simple and reliable in structure, simple and flexible in operation and maintenance. Compared with traditional pressure casting and vacuum casting, the gravity casting machine does not need to use high pressure and vacuum equipment, reducing complexity and energy consumption.

[0004] At present, due to the development trend of high compactness, refinement and thin-walled air-cooled diesel engine cylinder head castings, the requirements for casting performance are becoming higher and higher, especially for the problems of insufficient thin-wall filling of air-cooled cylinder head cooling blades, grain coarsening in thin-wall structures, local heat shrinkage, slow solidification in thick and large parts, and easy appearance of coarse grains, which in turn cause low alloy performance. Summary of the invention

[0005] The purpose of the present invention is to provide a casting method for a highly compact air-cooled diesel engine cylinder head, so as to solve the problems of insufficient thin-wall filling, grain coarsening at the thin-wall structure, and local heat shrinkage compensation of the cylinder head prepared by the traditional gravity metal mold casting process.

[0006] The present invention adopts the following technical solution: a casting method for a highly compact air-cooled diesel engine cylinder head, comprising:

[0007] Step 1: Melting the RR350 aluminum alloy into liquid and removing slag and gas to obtain an aluminum alloy solution;

[0008] Step 2: Pour the aluminum alloy solution into the preheated metal mold;

[0009] Step 3: Connect the cooperative vibration rod to the free end of the ultrasonic horn of the ultrasonic energy concentrator, and then insert the cooperative vibration rod into the metal mold through the oil injection hole of the metal mold, so that the aluminum alloy solution in the metal mold vibrates under the drive of the ultrasonic horn and the cooperative vibration rod until the aluminum alloy solution is completely solidified, so that the aluminum alloy solution forms fine and uniform grains when solidifying and crystallizing.

[0010] Further, the coordinated vibration rod comprises:

[0011] The cooperative rod has a square cross section, an outer end of which is threadedly connected to the free end of the ultrasonic horn of the ultrasonic energy concentrator, and an inner end of which is an inclined surface and is used to fit the outer side of the oil injection hole of the metal mold;

[0012] The vibrating insertion rod is columnar and fits the injection hole surface of the metal mold; the vibrating insertion rod and the cooperative rod are coaxially arranged, and the fixed end of the vibrating insertion rod is integrally connected with the inner end of the cooperative rod. The insertion end is used to insert into the metal mold and make the aluminum alloy solution vibrate under the drive of the ultrasonic amplitude transformer and the cooperative rod.

[0013] Furthermore, in step 3, the vibration frequency of the ultrasonic horn is 20-30 KHz and the power is 2-3 KW.

[0014] Furthermore, in step 3, the insertion depth of the vibrating extension rod is 50 to 60 mm, and the insertion angle is 30° to 60°.

[0015] Furthermore, in step 1, the RR350 aluminum alloy is smelted twice, the temperature of both smeltings is 750±20° C., 0.3-0.5% inorganic salt and 4%-6% Al-5Ti-B are added during the initial refining, and 1%-2% inorganic salt is added during the secondary refining.

[0016] Furthermore, in step 2, the preheating temperature of the metal mold is 250-280°C.

[0017] Furthermore, step 2 of pouring the aluminum alloy solution into the preheated metal mold is completed within 8 to 10 seconds.

[0018] The beneficial effects of the present invention are:

[0019] The present invention introduces an ultrasonic field into a cylinder head casting mold, applies ultrasonic vibration during the solidification process of the casting, and designs a vibration insertion rod according to the shape of the oil injection hole of the mold; thereby realizing the solidification and shrinkage compensation of the thin-walled casting where the casting is difficult to fill by the ultrasonic vibration mode, forming a multi-field assisted cylinder head casting molding process coupled with an ultrasonic field and a gravity field, promoting shrinkage compensation, reducing pinholes, refining grains, and improving the yield and performance of the casting;

[0020] The present invention introduces ultrasound to refine the grain size during alloy solidification. Compared with traditional gravity casting, the yield strength is increased by 15%, the elongation is increased by 73%, and the risk of engine cylinder head cracking is reduced.

[0021] In the present invention, during the casting process, the vibrating extension rod drives the aluminum alloy solution of the metal mold to realize ultrasonic vibration under certain power parameters, thereby changing the original alloy solidification characteristics, forming finer and more uniform grains and more optimized grain boundaries during crystallization, thereby improving the strength and toughness of the cylinder head material, and forming a certain residual stress field at the typical structural parts of the cylinder head, thereby improving the overall rigidity and stability of the cylinder head and having a certain shrinkage compensation function, reducing the occurrence of pores, improving the cylinder head yield, and realizing multi-field auxiliary casting molding of a highly compact air-cooled diesel engine cylinder head. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the structure of the cooperative vibration rod of the present invention;

[0023] Figure 2 It is the organizational morphology diagram of comparative example 1, embodiments 1, 2, and 3 of the present invention;

[0024] Figure 3 It is the mechanical property diagram of comparative example 1 and embodiments 1, 2 and 3 in the present invention. DETAILED DESCRIPTION

[0025] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] The invention discloses a casting method for a highly compact air-cooled diesel engine cylinder head, comprising:

[0027] Step 1: Melting the RR350 aluminum alloy into liquid and removing slag and gas to obtain an aluminum alloy solution;

[0028] Step 2: Pour the aluminum alloy solution into the preheated metal mold;

[0029] Step 3: Connect the cooperative vibration rod to the free end of the ultrasonic horn of the ultrasonic energy concentrator, and then insert the cooperative vibration rod into the metal mold through the oil injection hole of the metal mold, so that the aluminum alloy solution in the metal mold vibrates under the drive of the ultrasonic horn and the cooperative vibration rod until the aluminum alloy solution is completely solidified, so that the aluminum alloy solution forms fine and uniform grains when solidifying and crystallizing.

[0030] Step 1: RR350 aluminum alloy is smelted twice, the temperature of both smeltings is 750±20° C., 0.3-0.5% inorganic salt and 4%-6% Al-5Ti-B are added during the initial refining; 1%-2% inorganic salt is added during the secondary refining.

[0031] The preheating temperature of the metal mold in step 2 is 250-280° C. Step 2 is completed within 8-10 seconds when pouring the aluminum alloy solution into the preheated metal mold.

[0032] The vibration frequency of the ultrasonic horn in step 3 is 20-30KHz and the power is 2-3KW. The insertion depth of the vibrating insertion rod 2 in step 3 is 50-60mm and the insertion angle is 30°-60°. The vibration time of the ultrasonic horn of the ultrasonic concentrator in step 3 is 3-5min.

[0033] Among them, the cooperative vibration rod includes: a cooperative rod 1 and a vibration extension rod 2.

[0034] The cross-section of the cooperative rod 1 is square, and the outer end of the cooperative rod 1 is threadedly connected to the free end of the ultrasonic amplitude rod of the ultrasonic energy concentrator, and the inner end of the cooperative rod 1 is an inclined surface and is used to fit the outer side of the oil injection hole of the metal mold; the vibration insertion rod 2 is columnar and fits the shape of the oil injection hole of the metal mold; the vibration insertion rod 2 is coaxially arranged with the cooperative rod 1, and the fixed end of the vibration insertion rod 2 is integrally connected with the inner end of the cooperative rod 1, and the insertion end of the vibration insertion rod 2 is used to insert into the metal mold, and make the aluminum alloy solution vibrate under the drive of the ultrasonic amplitude rod and the cooperative rod 1.

[0035] Comparative Example 1

[0036] This comparative example adopts a conventional gravity casting method, and the specific steps include:

[0037] Step 1: Melt the RR350 aluminum alloy into liquid and remove slag and gas to obtain an aluminum alloy solution.

[0038] RR350 aluminum alloy, calculated by atomic percentage, includes: Cu: 4.6%, Ni: 1.5%, Mn: 0.2%, Zr: 0.2%, Ti: 0.18%, Co: 0.3%, Sb: 0.3%, Fe≤0.50%, Si≤0.30%, Mg≤0.05%, and the rest is Al.

[0039] In step 1, two smeltings are performed, and the temperature of both smeltings is 760°C. 0.4% inorganic salt and 5% Al-5Ti-B are added in the first refining, and 1.5% inorganic salt is added in the second refining. In step 1, high-purity argon is used for degassing, and the argon flow rate is 0.5L / min. The standing time for slag removal is 15min.

[0040] Step 2: When the temperature of the aluminum alloy solution is 750°C, pour the aluminum alloy solution into a metal mold preheated at 280°C. The pouring of the aluminum alloy solution into the preheated metal mold is completed within 8 seconds.

[0041] Step 4: Take out the blank cylinder head 4 minutes after casting and carry out T6 heat treatment for solution aging. Solution treatment: keep at 545±5℃ for 8 hours, then heat up to 555±5℃ with the furnace, keep for 7 hours, then quench in 70-95℃ water; aging treatment: keep at 160℃ for 24 hours, then take out and cool in air.

[0042] The cylinder head obtained in Comparative Example 1 was dissected to detect the grain size. The grain size of the aluminum alloy cylinder head under conventional gravity casting conditions was 98±15μm. Its microstructure is as follows: Figure 2 As shown in Comparative Example 1, the mechanical properties results are shown in Tables 1 and Figure 3 shown.

[0043] Example 1

[0044] Step 1: Melt the RR350 heat-resistant aluminum alloy into liquid and remove slag and gas to obtain an aluminum alloy solution.

[0045] RR350 aluminum alloy, calculated by atomic percentage, includes: Cu: 4.6%, Ni: 1.5%, Mn: 0.2%, Zr: 0.2%, Ti: 0.18%, Co: 0.3%, Sb: 0.3%, Fe≤0.50%, Si≤0.30%, Mg≤0.05%, and the rest is Al.

[0046] In step 1, two smeltings are performed at a temperature of 750°C for both times. 0.3% inorganic salt and 4% Al-5Ti-B are added during the first refining, and 1% inorganic salt is added during the second refining. In step 1, high-purity argon is used for degassing, with an argon flow rate of 0.6L / min, and the slag removal standing time is 18min.

[0047] Step 2: When the temperature of the aluminum alloy solution is 755°C, pour the aluminum alloy solution into a metal mold preheated at 250°C. The pouring of the aluminum alloy solution into the preheated metal mold is completed in 8 seconds.

[0048] In step 3: the insertion depth of the coordinated vibration rod is 50 mm, the insertion angle is 30°, the vibration frequency of the ultrasonic horn is 20 KHz, the ultrasonic generator power of the ultrasonic horn is 2 KW, and the ultrasonic vibration coagulation time is 4 min.

[0049] The cylinder head obtained in Example 1 was dissected to detect the grain size. The grain size of the aluminum alloy cylinder head in Example 1 was 75±8 μm. Its microstructure was as follows: Figure 2 As shown in Example 1, the mechanical properties results are shown in Tables 1 and Figure 3 shown.

[0050] Example 2

[0051] The specific steps of this embodiment are the same as those of Embodiment 2, except that:

[0052] In step 1, 0.45% inorganic salt and 5% Al-5Ti-B are added during the primary refining; and 1.5% inorganic salt is added during the secondary refining.

[0053] In step 2, the aluminum alloy solution is poured into a metal mold preheated at 260° C. and the process is completed in 9 seconds.

[0054] In step 3, the insertion depth of the cooperative vibration rod is 55 mm, the insertion angle is 45°, the vibration frequency of the ultrasonic horn is 25 KHz, the ultrasonic generator power of the ultrasonic horn is 2.5 KW, and the ultrasonic vibration coagulation time is 4 minutes.

[0055] The cylinder head obtained in Example 2 was dissected to detect the grain size. The grain size of the aluminum alloy cylinder head in Example 2 was 56±10 μm. Its microstructure was as follows: Figure 2 As shown in Example 2, the mechanical properties results are shown in Tables 1 and Figure 3 shown.

[0056] Example 3

[0057] The specific steps of this embodiment are the same as those of Embodiment 1, except that:

[0058] In step 1, 0.5% inorganic salt and 6% Al-5Ti-B are added during the primary refining; and 2% inorganic salt is added during the secondary refining.

[0059] In step 2, the aluminum alloy solution is poured into a metal mold preheated at 280° C. and the process is completed in 10 seconds.

[0060] In step 3, the insertion depth of the cooperative vibration rod is 60 mm, the insertion angle is 60°, the vibration frequency of the ultrasonic horn is 30 KHz, the ultrasonic generator power of the ultrasonic horn is 3.0 KW, and the ultrasonic vibration coagulation time is 4 min.

[0061] The cylinder head obtained in Example 3 was dissected to detect the grain size. The grain size of the aluminum alloy cylinder head in Example 3 was 43±10 μm. Its microstructure was as follows: Figure 2 As shown in Example 3, the mechanical properties results are shown in Tables 1 and Figure 3 shown.

[0062] Table 1

[0063] Tensile strength / MPa Yield strength / MPa Elongation / % Comparative Example 1 262 225 1.85 Example 1 276 234 2.21 Example 2 281 245 2.8 Example 3 298 260 3.2

[0064] According to the alloy microstructure morphology and grain size results of the cylinder heads prepared by Comparative Example 1 and Examples 1, 2 and 3, it can be seen that the grain size of the aluminum alloy of Examples 1, 2 and 3 is significantly reduced, and the grain size is refined from 98±15μm in Comparative Example 1 to 43±10μm, and the amount of precipitation strengthening phase is increased by 8% at most, the tensile strength is increased to 298MPa, the yield strength is increased to 260MPa, and the elongation is increased to 3.2%.

[0065] The results of the cylinder head thin-wall area dissection show that under the auxiliary effect of gravity field and ultrasonic field multi-field coupling, the thin-wall structure shrinkage compensation and microstructure refinement effects are achieved, pores and cracks are reduced, and the cylinder head casting quality is improved. Figure 3 It can be seen that pores and cracks do not appear in the metallographic structure.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A casting method for a highly compact air-cooled diesel engine cylinder head, characterized in that: include: Step 1: Melting the RR350 aluminum alloy into liquid and removing slag and gas to obtain an aluminum alloy solution; Step 2: Pour the aluminum alloy solution into the preheated metal mold; Step 3: Connect the cooperative vibration rod to the free end of the ultrasonic horn of the ultrasonic energy concentrator, and then insert the cooperative vibration rod into the metal mold through the oil injection hole of the metal mold, so that the aluminum alloy solution in the metal mold vibrates under the drive of the ultrasonic horn and the cooperative vibration rod until the aluminum alloy solution is completely solidified, so that the aluminum alloy solution forms fine and uniform grains when solidifying and crystallizing.

2. A casting method for a highly compact air-cooled diesel engine cylinder head according to claim 1, characterized in that: The coordinated vibration rod comprises: The cooperative rod (1) has a square cross section, an outer end of which is threadedly connected to the free end of the ultrasonic horn of the ultrasonic energy concentrator, and an inner end of which is an inclined surface and is used to fit the outer side of the oil injection hole of the metal mold; The vibrating insertion rod (2) is columnar and fits the injection hole-shaped surface of the metal mold; the vibrating insertion rod (2) is coaxially arranged with the coordination rod (1), the fixed end of the vibrating insertion rod (2) is integrally connected with the inner end of the coordination rod (1), and the insertion end is used to be inserted into the metal mold and make the aluminum alloy solution vibrate under the drive of the ultrasonic amplitude transformer and the coordination rod (1).

3. The casting method of a highly compact air-cooled diesel engine cylinder head according to claim 1, characterized in that: In step 3, the vibration frequency of the ultrasonic horn is 20-30 KHz and the power is 2-3 KW.

4. The casting method of a highly compact air-cooled diesel engine cylinder head according to claim 1, characterized in that: The insertion depth of the vibrating insertion rod (2) in step 3 is 50 to 60 mm, and the insertion angle is 30° to 60°.

5. The casting method of a highly compact air-cooled diesel engine cylinder head according to claim 1, characterized in that: Step 1: RR350 aluminum alloy is smelted twice, the temperature of both smeltings is 750±20° C., 0.3-0.5% inorganic salt and 4%-6% Al-5Ti-B are added during the initial refining; 1%-2% inorganic salt is added during the secondary refining.

6. The casting method of a highly compact air-cooled diesel engine cylinder head according to claim 1, characterized in that: The preheating temperature of the metal mold in step 2 is 250-280°C.

7. The casting method of a highly compact air-cooled diesel engine cylinder head according to claim 1, characterized in that: Step 2 is completed within 8 to 10 seconds when pouring the aluminum alloy solution into the preheated metal mold.

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