Disclosure of Invention
The object of the present invention is to provide a method for manufacturing a casting mould for casting components of an aircraft engine casing, which reduces or avoids the aforementioned technical problems.
In order to solve at least one technical problem, the invention provides a casting process of a large aluminum alloy engine case part, wherein the basic outline dimension of the case part is 1400 mm x460 mm x195 mm, the thickness of a main body wall is 5-7 mm, the entire case is a semi-closed large cavity structure, the outline is slender, and an inner casting oil way is formed, and the casting process route comprises the following steps:
s1, initially designing a casting blank structure by adopting an anti-gravity investment precision casting process, and adjusting structural parameters such as process ribs, wall thickness, boss positions and the like on the premise of not influencing the use of parts, so that the casting blank structure is more suitable for casting production;
s2, casting a casing casting, wherein a copper pipe and a P L M-polycarbon gypsum core are adopted to manufacture a composite core, namely, a zinc alloy outer support is adopted to manufacture a semicircular core bar, the shape and structure of the core bar are consistent with the shape and structure of a slender three-dimensional structure core, the copper pipe and the zinc alloy are firmly cast together by an investment precision casting process, and the P L M-polycarbon gypsum core is pressed to enable the zinc alloy outer support and the P L M-polycarbon gypsum core to be integrated, so that the casing casting is ensured not to be dislocated in the casting process;
designing and manufacturing a set of wax pattern, fixing the P L M-polycarbonate gypsum core composite core in the wax pattern, pressing the wax pattern to realize the manufacture of the wax pattern, and obtaining a casing shell through coating, dewaxing and roasting;
s3, casing casting is carried out by adopting a counter-pressure casting process, firstly, a casting construction diagram is simulated by using MAGMA casting simulation software, a flow field, a temperature field and a stress field of a casting are analyzed, the structure, a pouring system and casting process parameter design of the casting are optimized, a roasted casing shell is placed in a sand box, and sodium silicate sand is filled around the casing shell for counter-pressure casting of the casting;
s4, molten aluminum smelting and pouring control, wherein in the pouring process, a reasonable mold filling speed and a differential pressure tank pressure maintaining pressure are determined, a reasonable pouring temperature is determined, and a signal lamp is arranged at the highest point of each casting to ensure that the mold filling time of each casting is within +/-2S;
s5, performing heat treatment on the castings, namely simulating by using heat treatment software to determine the optimal heat treatment process scheme of the castings, such as the placement position, the water inlet direction, the water inlet time, the water temperature and the like of the castings, and designing a reasonable fixture for heat treatment of the castings to ensure that the heat treatment of the castings is not deformed; marking off the casting, machining an auxiliary clamping table according to a line, locking and fixing the auxiliary clamping table with a heat treatment clamp, and placing the auxiliary clamping table perpendicular to the quenching medium surface to reduce the deformation generated by heat treatment of the casting as much as possible; and hot isostatic pressing is adopted, so that the dimensional stability of the casting is improved, and the mechanical property of the casting is improved.
Further, the zinc alloy described in S2 is ZA-27 zinc-based alloy, and its mechanical properties are: sigma b is 350-400 MPa,5 is 2.0-3.0%, HB = 100-120, and the melting point is about 380 ℃; the shell is roasted to the temperature of about 900 ℃, and the zinc alloy can be completely melted and even boiled.
Furthermore, the content of Fe in the aluminum ingot or alloy ingot used as the raw material of the aluminum liquid in S4 is less than 0.1%, and the chemical components of the cast aluminum alloy comprise Si 6.8-7.2%, Mg0.5-0.6%, Ti0.15-0.20%, Be0.1-0.2% and Fe less than 0.1%.
Further, the aluminum liquid in the S4 adopts long-acting alterant metal strontium (0.04-0.06%) and rare earth (0.2-0.3%) to modify the aluminum liquid, and the modification process has the advantages that the secondary dendrite spacing of the sample is minimum, the air holes are few, and silicon particles are punctiform or vermicular, small eutectic clusters and dispersed; and determining the modification effect of the aluminum liquid by combining an observation fracture (phi 15) method and a processing test block high-power metallographic observation method.
Further, the mold filling speed in S4 is 0.0014-0.004 MPa/S, and the pressure maintaining difference of the differential pressure tank is not less than 0.5 MPa. The pouring temperature is 690-710 ℃.
The invention has the following beneficial effects:
1. the casing casting adopts a composite core of a copper pipe and a P L M-polycarbonate gypsum core to realize a whole core, so that the core assembly precision is greatly improved, the casting has good deformability, the stress and deformation of the casting are greatly reduced, and the casting metallurgical defects such as size deformation and cracks of the casting are greatly reduced;
2. because the casting is in a semi-circular arc shape, the casting structure is slender. By adopting uniform casting shrinkage rate, the semi-arc shape has larger deviation with the theoretical size, and the reverse deformation process design is needed, so the casting construction drawing is simulated by adopting MAGMA5 casting simulation software, the flow field, the temperature field and the stress field of the casting are analyzed, and the casting structure is optimized;
3. the casing casting adopts a counter-pressure casting process, wherein the counter-pressure casting is that a casting mold is solidified under a large pressure difference, namely, a compact structure can be obtained because a casting is solidified under a high pressure (the feeding capacity is 4-5 times that of low-pressure casting and 7-8 times that of gravity casting); and because the pressure of the differential pressure casting is higher, the solubility of hydrogen in the aluminum liquid is increased, and the metal solidification speed is increased under high pressure, so that the hydrogen cannot be separated out in time and exists in the casting in the original state when the alloy is solidified, thereby greatly reducing the separated-out air holes (pin holes); simultaneously, external pressure can also participate in feeding, when the casting is solidified under high pressure, shrinkage cavities and microcracks which appear can be filled in time, the hidden danger of some cracks is eliminated by welding to a certain extent, the mechanical property of the casting is correspondingly improved, and the casting has the following outstanding advantages: (1) the casting defects of casting air hole shrinkage, shrinkage porosity and the like are eliminated; (2) improving the surface roughness of the casting; (3) the hot cracking tendency of the large complex casting during solidification is obviously reduced; (4) the counter-pressure casting has strong feeding pressure; (5) the differential pressure casting can reduce the solidification time by 20-25%, correspondingly reduce the deterioration and decline phenomenon in the solidification period, and refine the crystal grains, thereby being the best method for obtaining high-quality aluminum alloy castings at present.
4. The P L M-poly carbon gypsum core is made of new generation fire resistant poly carbon gypsum, the core is high temperature resistant, soluble, can be made into various complex shapes, is easy to clean, has the highest fire resistance of 2800 ℃, has obvious superiority compared with the traditional core, becomes loose after casting, can be easily removed, can clean the ultra complex inner cavity by vibration and simple tools, can clean the ultra complex inner cavity by soaking at normal temperature and washing with water, has excellent deformability, does not need any treatment on the joint with the silica sol shell, does not deform and crack the joint, and has size precision and surface luminosity superior to the silica sol shell.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and the described embodiments are only some embodiments, not all embodiments, of the present invention.
The basic outline dimension of the casing component prepared in the embodiment is 1400 mm, x460 mm, x195 mm, and the main body wall thickness is 5-7 mm, the whole casing is a semi-closed large-scale cavity structure, the outline is elongated, and the casting process route comprises the following steps:
firstly, a casting blank structure is preliminarily designed by adopting an anti-gravity method investment precision casting process, and structural parameters such as process ribs, wall thickness, boss positions and the like are adjusted on the premise of not influencing the use of parts, so that the casting blank structure is more suitable for casting production; on the premise of not influencing the use of parts, structural parameters such as process ribs, wall thickness, boss positions and the like are adjusted, so that the casting blank structure is more suitable for casting production.
Secondly, casting a casing casting, namely, manufacturing a composite core by adopting a copper pipe and a P L M-polycarbon gypsum core, namely, manufacturing a semicircular core bone by adopting a zinc alloy outer support, wherein the shape and the structure of the core bone are consistent with the shape of a slender three-dimensional structure core, firmly casting the copper pipe and the zinc alloy together by an investment precision casting process, pressing the P L M-polycarbon gypsum core to enable the zinc alloy outer support and the P L M-polycarbon gypsum core to be integrated, so that the casing casting is not dislocated in the casting process, melting and separating the zinc alloy when roasting a shell, wherein the zinc alloy, such as ZA-27 zinc-based alloy, has the mechanical properties that sigma b is 350-400 MPa,5 is 2.0-3.0%, HB = 100-120 and the melting point is about 380 ℃, roasting the shell to the temperature of about 900 ℃, the zinc alloy can be completely melted and even boiled, corroding through chemical reaction, and thus obtaining a compact copper pipe casting with accurate size, smooth inner wall and aluminum structure;
designing and manufacturing a set of wax pattern, fixing the P L M-polycarbonate gypsum core composite core in the wax pattern, pressing the wax pattern to realize the manufacture of the wax pattern, and obtaining the casing shell through coating, dewaxing and roasting.
Thirdly, casing casting is carried out by adopting a counter-pressure casting process, firstly, a casting construction diagram is simulated by using MAGMA (Magma casting simulation software), a flow field, a temperature field and a stress field of a casting are analyzed, the structure, a pouring system and casting process parameter design of the casting are optimized, a roasted casing shell is placed in a sand box, and sodium silicate sand is filled around the casing shell for counter-pressure casting of the casting;
fourthly, molten aluminum smelting and pouring control are carried out, the content of Fe in an aluminum ingot or an alloy ingot which is used as a raw material of the molten aluminum is required to be less than 0.1%, the chemical components of cast aluminum alloy comprise Si 6.8-7.2%, Mg0.5-0.6%, Ti0.15-0.20%, Be0.1-0.2% and Fe <0.1%, in the pouring process, the filling speed is determined to be 0.0014-0.004 MPa/s, the pressure maintaining difference of a differential pressure tank is not less than 0.5MPa, the pouring temperature is 690-710 ℃, a signal lamp is arranged at the highest point of the casting, and the filling time of each casting is guaranteed to be within +/-2 s. The aluminum liquid is modified by long-acting modifier metal strontium (0.04-0.06%) and rare earth (0.2-0.3%), and the modification process has the advantages that the secondary dendrite spacing of a sample is minimum, the air holes are few, silicon particles are dotted or worm-shaped, eutectic clusters are small and dispersed; and determining the modification effect of the aluminum liquid by combining an observation fracture (phi 15) method and a processing test block high-power metallographic observation method.
Fifthly, performing heat treatment on the casting, namely simulating by using heat treatment software to determine the optimal heat treatment process scheme of the casting, such as the placement position, the water inlet direction, the water inlet time, the water temperature and the like of the casting, and designing a reasonable casting heat treatment clamp to ensure that the casting is not deformed during heat treatment; marking off the casting, machining an auxiliary clamping table according to a line, locking and fixing the auxiliary clamping table with a heat treatment clamp, and placing the auxiliary clamping table perpendicular to the quenching medium surface to reduce the deformation generated by heat treatment of the casting as much as possible; and hot isostatic pressing is adopted, so that the dimensional stability of the casting is improved, and the mechanical property of the casting is improved.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.