CN115475911A

CN115475911A - Casting method of engine body cover

Info

Publication number: CN115475911A
Application number: CN202211078103.0A
Authority: CN
Inventors: 王海涛; 王晓铭
Original assignee: Qingdao University of Technology
Current assignee: Qingdao University of Technology
Priority date: 2022-09-05
Filing date: 2022-09-05
Publication date: 2022-12-16

Abstract

The invention discloses a casting method of a machine body cover, relates to the technical field of casting, solves the problems that the casting of the machine body cover in the prior art is complex, the casting efficiency is low, cracks, shrinkage porosity and other defects are easy to generate, and the quality of a casting is difficult to ensure, has the beneficial effects of improving the casting efficiency and being high in the quality of the casting, and has the following specific scheme: a method of casting a body cover comprising the steps of: selecting the position of the maximum projection area of the part as a parting surface; designing a sand core: the core comprises an outer core and an inner cavity core, wherein the inner cavity core is molded by core assembly, a core head is arranged on the sand core, and a core bone is embedded in the sand core; designing a pouring system: an open center pouring type horizontal pouring system is adopted, a casting adopts four pieces in one die, and the sectional area of a pouring gate is as follows: the cross section area of the straight pouring channel is smaller than that of the horizontal pouring channel and is smaller than that of the inner pouring channel; designing a model: dividing the parting surface into two parts to manufacture an upper box pattern and a lower box pattern, and manufacturing a sand mold; pouring: and (5) closing the box after fixing the sand core, and pouring molten metal.

Description

Casting method of engine body cover

Technical Field

The invention relates to the technical field of casting, in particular to a casting method of a machine body cover.

Background

As shown in figure 1, the machine body cover part is made of ENAC-42100 aluminum alloy, and has good casting performance and small tendency of shrinkage porosity and thermal stress. The engine body cover is usually arranged on the upper part of a closed cylinder to form a combustion chamber and serve as a support for a cam shaft, a rocker shaft and an air inlet and exhaust pipe, air is mainly sucked into the cylinder, a spark plug ignites combustible mixed gas to drive a piston to do work, and waste gas is exhausted from the exhaust pipe.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a machine body cover casting method, which solves the technical problems that the casting complexity of the subsequent machine body cover is different, the defects of cracks, air holes, shrinkage porosity and the like are caused, the casting quality is difficult to ensure, the casting yield of the casting is low and the like due to the difference of the parting surface and the sand mold selection scheme in the prior art.

In order to achieve the purpose, the invention is realized by the following technical scheme:

a casting method of a machine body cover comprises the following steps:

and (3) selecting a parting surface: selecting the position of the maximum projection area of the part as a parting surface;

designing a sand core: the core comprises an outer core and an inner cavity core, wherein the outer core is used for forming the middle part of a reinforcing rib and the part, which is not easy to form a film, of a bottom heat dissipation rib, the inner cavity core is used for forming an inner cavity of a machine body cover, the inner cavity core is formed by core assembly, a core head is arranged on a sand core, and a core bone is embedded in the sand core;

designing a pouring system: an open center pouring type horizontal pouring system is adopted, a casting adopts four pieces, and the cross section area of a pouring gate is as follows: the cross section area of the straight pouring channel is smaller than that of the horizontal pouring channel and is smaller than that of the inner pouring channel;

designing a model: dividing the parting surface into two parts to manufacture an upper box pattern and a lower box pattern, and manufacturing a sand mold;

pouring: and (5) closing the box after fixing the sand core, and pouring molten metal.

According to the casting method of the engine body cover, the core print of the outer core is arranged at the bottom of the outer core, at least two core prints on the outer core are close to each other at a set distance, the inner cavity core is composed of the main body core and the connecting core, and the core print of the inner cavity core is arranged at the bottom of the connecting core and at the end of the main body core far away from the connecting core.

According to the casting method of the engine body cover, the sand core is provided with the air outlet hole, and the air outlet hole is formed in the core heads of the outer core and the inner cavity core.

In the above casting method for a body cover, the cross-sectional area of the sprue: cross-sectional area of runner: the cross section of the ingate = 1.

According to the casting method of the engine body cover, the cross sections of the cross runners and the inner runners are trapezoidal, the cross section of the straight runner is circular, and the cross runners are provided with the cross runner extension slag collecting bags for storing primary flow liquid.

According to the casting method of the engine body cover, the bottom of the sprue is provided with the sprue pit, the sprue pit is hemispherical, and the diameter of the sprue pit is larger than that of the lower end of the sprue.

According to the casting method of the engine body cover, a riser is arranged at the top of a casting before pouring, and the riser adopts a spherical top cylindrical atmospheric pressure blind riser.

According to the casting method of the engine body cover, before pouring, a plurality of chills are arranged on the annular surface at the bottom of the outer core, the chills are uniformly distributed on the annular surface, and a chiller is arranged on the bottom surface of a casting adjacent to each ingate.

According to the machine body cover casting method, when the sand core is fixed, the sand mold is provided with the core head seat, and the core head seat is arranged corresponding to the core head.

According to the casting method of the machine body cover, when the molten metal is poured, the pouring cup is installed in advance, and the funnel-shaped pouring cup is selected as the pouring cup.

The beneficial effects of the invention are as follows:

1. in order to improve the process yield of castings and the production efficiency of the castings, the invention adopts one-mold four-piece pouring, and simultaneously selects the position with the maximum projection area of the parts as a parting surface, thereby simplifying the complexity of pouring the machine body cover, requiring a small quantity of sand molds, having no loose blocks after the sand molds are fixed, simplifying the installation and the fixation of the sand molds, having high dimensional precision of the castings, requiring a low height of sand molds, being convenient for core setting and reducing the process difficulty.

2. The core frame is embedded in the sand core, so that the sand core is not deformed, cracked or broken in the manufacturing, transporting, assembling and pouring processes, and has enough rigidity and strength.

3. The horizontal pouring gate is provided with a horizontal pouring gate extension section slag collection bag to store primary flow liquid, prevent the end part from cooling in advance to block a pouring channel, and meanwhile, the slag collection bag plays a role of collecting slag and stopping slag to prevent the molten metal from flowing back, so that impurities and scum in the molten metal can be guaranteed to float in the horizontal pouring gate end slag collection bag when reaching the first inner pouring gate.

4. The open type horizontal injection pouring system has the advantages that the molten metal is smooth and unimpeded in the pouring process, a pouring gate cannot be blocked, scum is fully achieved, the sectional area of an inner pouring gate is largest, the filling stability is guaranteed, and the defects of insufficient cast-in-place, cold shut, cutoff and the like cannot occur.

5. Through the optimized design of the casting process, the process yield of the casting reaches 83.6 percent, the casting yield reaches 98 percent, and the casting yield reaches the upper limit level in the similar casting products.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are included to illustrate an exemplary embodiment of the invention and not to limit the invention.

Fig. 1 is a top view of a housing cover in a housing cover casting method according to an embodiment of the present invention.

Fig. 2 is a bottom view of a housing cover in a housing cover casting method according to an embodiment of the present invention.

Fig. 3 is a schematic illustration of the location of the parting plane of the body cover in an embodiment of the invention.

Figure 4 is a diagram of a one-mold four-piece molding layout for a sandbox in an embodiment of the present invention.

FIG. 5 is a schematic diagram of a design structure of a sand core in an embodiment of the present invention.

FIG. 6 (a) shows example 1 of the present invention ^# The structural schematic diagram of the positioning core head of the sand core.

FIG. 6 (b) shows example 2 of the present invention ^# The structural schematic diagram of the positioning core head of the sand core.

FIG. 7 shows example 2 of the present invention ^# The core assembly structure of the sand core is shown schematically.

FIG. 8 shows example 2 of the present invention ^# The structural schematic diagram of the core bone of the sand core.

FIG. 9 (a) shows example 1 of the present invention ^# The psammitolite core head exhaust structure sketch map.

FIG. 9 (b) shows example 2 of the present invention ^# The psammitolite core head exhaust structure sketch map.

Fig. 10 is a schematic view of an open type injection gating system in an embodiment of the present invention.

FIG. 11 is a cross-sectional view of a runner in an embodiment of the present invention.

FIG. 12 is a schematic cross-sectional view of an ingate in an embodiment of the present invention.

FIG. 13 is a schematic structural view of a direct casting runner nest in an embodiment of the invention.

FIG. 14 is a schematic view of a sprue slag trap configuration in an embodiment of the present invention.

FIG. 15 is a schematic view of riser placement in an embodiment of the present invention.

Fig. 16 is a schematic diagram of the arrangement of the chiller in the embodiment of the invention.

FIG. 17 (a) is a schematic view showing the design of a cope flask pattern in the embodiment of the present invention.

FIG. 17 (b) is a schematic view showing the design of a drag flask pattern in the embodiment of the present invention

Fig. 18 (a) is a schematic view showing the production of a cope mold in the example of the present invention.

FIG. 18 (b) is a schematic view of the manufacturing of a drag sand mold in the embodiment of the present invention.

FIG. 19 is a flow chart of sand mold making, core setting and mold assembling in the embodiment of the invention.

In the figure: the spacing or dimensions between each other are exaggerated to show the location of the various parts, and the schematic is shown only schematically.

Wherein: 1.1 ^# Sand core, 2.2 ^# Sand core, 3.1 ^# Positioning core head of sand core, 4.2 ^# The method comprises the following steps of (1) positioning a core head of the sand core, 5) a sprue, 6 a cross gate, 7 an ingate, 8 a sprue pit, 9 a slag collecting ladle, 10 a riser and 11 chilling blocks.

Detailed Description

It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

As introduced by the background art, the difference of the parting surface and the selection of the sand mold scheme in the prior art causes different casting complexity of the subsequent machine body cover, and simultaneously, the problems of low casting efficiency, easy generation of defects such as cracks, shrinkage porosity and the like and difficult guarantee of the casting quality are solved.

Example one

In an exemplary embodiment of the present invention, referring to fig. 1, a method of casting a housing cover includes the steps of:

1. parting surface selection

As shown in fig. 1 and 2, the block cover is a schematic structural diagram, a parting surface is selected according to structural characteristics of the block cover, and as shown in fig. 3, a position of a maximum projected area of a part is selected as the parting surface, so that complexity of casting the block cover is simplified, the parting surface is a surface where two half molds contact each other, and the position of the maximum projected area of the part is selected as the parting surface, which has the advantages that: the required sand mould is small in quantity, the sand mould is fixed without loose pieces, the installation and fixation of the sand mould are simpler, the size precision of a casting is high, the height of the required sand box is low, the core setting is convenient, and the process difficulty is reduced.

2. Sand box casting arrangement

In order to improve the casting process yield in view of the small casting volume, a one-box four-piece arrangement is adopted, as shown in fig. 4, to improve the casting efficiency.

3. Sand core design

After the parting surface is determined, the sand core is designed, and the required sand core comprises an outer core and an inner cavity core based on the structural characteristics of the machine body cover and the selection of the parting surface.

The requirement of the sand core is that the shape, the size and the position in the sand mold of the sand mold are required to ensure that the shape and the size of the casting meet the requirements, the outer core is used for forming the middle part of the reinforcing rib and the part which is not easy to lift at the heat dissipation rib at the bottom, and the inner cavity core is used for forming the inner cavity of the engine body cover.

Considering that the aluminum alloy castings have the problems of air holes and pinholes and influence on the quality of the castings, the molding sand should have a small gas evolution, the molding material of the embodiment adopts alkaline phenolic resin self-hardening sand, as shown in fig. 5, the outer core is 1 ^# The sand core forms the part which is not easy to be stripped at the middle part of the reinforcing rib and the heat dissipation rib at the bottom, and the inner cavity core is 2 ^# The sand core is used for forming an inner cavity of the machine body cover. The sand core is designed into the outer core and the inner cavity core, so that the yield of the cast machine body cover is high, and the product has no flaws.

In order to ensure the core setting and mould assembling accuracy, 1 ^#

Sand core

1, 2 ^# The core 2 is provided with a core head structure as shown in figure 6, which is 1 respectively ^# Sand core positioning core heads 3 and 2 ^#

Positioning core head

4,1 of sand core ^# The positioning core head of the sand core is arranged at 1 ^# The bottom of psammitolite, outer core head are two, locate outer core bottom on the annular surface, the line of the two passes through the annular surface center, can not exert an influence to the pouring process.

The shape of the inner cavity of the body cover is complex, so 2 ^# The core is made of core assembly and is divided into 2-1 parts ^# Sand core, 2-2 ^# Sand core, 2 ^# The combined shape of the sand core is shown in FIG. 7, 2 ^# The positioning core heads of the sand cores are respectively arranged at 2-1 ^# Sand core, 2-2 ^# The outer end part of the sand core does not influence the pouring process.

In order to ensure that the sand core does not deform, crack or break during manufacture, transport, assembly and casting, the sand core should have sufficient rigidity and strength. The core ribs are arranged in the sand core to improve the strength and rigidity of the sand core. As shown in figure 8, the core rod material of the casting adopts Q235 carbon steel, and the core rods are combined together through threaded connection. The casting is convenient to be detached and drawn out from the casting hole after the casting is cast, formed, cooled and shaked out.

The casting adopts phenolic resin sand to make the core, and in the pouring process, the high-temperature molten metal vaporizes the moisture in the sand core, and organic matters are volatilized, decomposed and combusted, so that a large amount of gas is generated in a short time. These gases, once introduced into the molten metal, can cause porosity in the casting. Therefore, in the whole process of designing and manufacturing the sand core, setting the sand core and assembling the box, attention is paid to the exhaust of the sand core, so that the gas generated in the sand core can be timely exhausted from the core head.

In order to ensure the exhaust of the sand core, an exhaust passage is arranged in the sand core during core making, so that defects of air holes, insufficient casting and the like of a casting are prevented, a wax line is buried in the sand core, an air outlet hole is arranged at a core head and is communicated with the exhaust passage in the sand core, and the air outlet hole of the core head is not blocked during core setting so as to lead gas in the sand core out of a mold. The design of the sand core exhaust passage is shown in figure 9.

4. Gating system design

The ENAC-42100 aluminum alloy has active property, a layer of oxide film is formed on the surface of molten metal during smelting, and the defects of air holes, slag inclusion and the like are easily induced after the liquid alloy solution is rolled into an oxide film interlayer. Therefore, the pouring system should select a stable technological scheme with less disturbance and molten metal filling.

The open type pouring system is adopted because the molten metal is in a non-pressure flowing state in the pouring system, the mold filling is stable, the scouring force to the cavity is small, and the oxidation of the molten metal during the pouring of the aluminum alloy casting can be reduced.

In the middle injection type pouring system, a cavity below an ingate is equivalent to a top injection type pouring system; the cavity below the ingate corresponds to a bottom-pouring gating system. Therefore, the pouring system has the advantages of a top pouring type pouring system and a bottom pouring type pouring system, the molten metal is stably filled, and splashing, oxidization and casting defects caused by the splashing and oxidization can be avoided; and the horizontal pouring channel is basically in a full state, so that slag blocking is facilitated, and air in the cavity is easily and sequentially discharged.

Comprehensive analysis the body cover casting adopts an open pour type horizontal pouring system, as shown in figure 10, a sprue is arranged at the central position, and due to the fact that the viscosity of aluminum alloy liquid is large, the open pouring system is adopted, the molten metal pouring process is smooth and unimpeded, a pouring channel cannot be blocked, scum is sufficient, and the sectional area of the inner pouring channel is smallThe maximum, guarantee to fill the type steady, can not appear cast-in-place deficiency, cold shut, cutoff defect etc. and water the sectional area and be: the cross section area of the straight pouring channel is smaller than that of the horizontal pouring channel and is smaller than that of the inner pouring channel; the ratio of the gate cross-sectional area is ∑ F _{Straight bar} :∑F _{Cross bar} :∑F _{Inner part} And 2, molten metal enters the cavity horizontally from the bottom of the pouring channel.

(1) And (3) calculating the size of each part of the gating system:

τ＝3δ ^0.33 G ^0.33

wherein A is the area of the dam-flow resistance, i.e. the sprue area ∑ F _{Straight bar} ；

G is the mass of the molten metal (12 Kg);

rho-molten Metal Density (2.68 g/cm) ³ )；

τ -fill time;

delta-minimum wall thickness of casting (5 mm);

hp-average calculated pressure head when filling all cavities;

H ₀ -total height (135 mm) of the casting (cavity);

p is the height of the cavity above the choked flow (45 mm);

c-casting height (51 mm);

calculating the pouring time tau =12 seconds, hp =115mm, A resistance =4cm ² 。

Thus, Σ F _{Straight bar} ＝4cm ² From Σ F _{Straight bar} :∑F _{Horizontal bar} :∑F _{Inner part} 3, obtaining Σ F _{Horizontal bar} ＝8cm ² ，∑F _{Inner part} ＝12cm ² 。

The sprue is a straight pipe section, and is designed to have 2% -4% of drawing slope for convenient drawing without sand, the height of the sprue is 40mm, the diameter of the top part is phi 22mm, and the diameter of the lower end is phi 24mm.

4 transverse runners are provided, and each casting is 1, sigma F _{Horizontal bar} ＝8cm ² Therefore F is _{Horizontal bar} ＝2cm ² . For the convenience of stripping, the cross section of the runner is designed to be trapezoidal, and the specific dimension is shown in fig. 11.

4 ingates in total, one ingate for each casting, sigma F _{Inner part} ＝12cm ² Therefore F is _{Inner part} ＝3cm ² . For the convenience of stripping, the ingate is designed into a trapezoid, and the specific dimension is shown in fig. 12.

For facilitating core setting, the cross-sectional shapes of the runner 6 and the ingate 7 are trapezoidal, the cross-sectional shape of the sprue 5 is circular, and the runner 6 distributes molten metal mainly to the ingate 7 and stores low-temperature molten metal containing gas and inclusions poured at first. The cross gate 6 is designed to ensure that impurities in the molten metal float to the top of the cross gate when reaching the first ingate, and a cross gate extension section of 80-120 mm is designed to store the primary flow liquid so as to prevent the backflow of the molten metal.

(2) Design of direct-pouring channel pit

The molten metal has strong impact on the bottom of the sprue, generates a vortex and a highly turbulent flow region, and often causes casting defects such as sand washing, slag holes, a large amount of oxide inclusions and the like. The flow condition of molten metal can be improved by arranging the straight pouring way nest. The bottom of the sprue is provided with a straight-pouring pit 8, the straight-pouring pit 8 is designed to be hemispherical, the diameter of the straight-pouring pit 8 is 1.4-2.0 times of the diameter of the lower end of the sprue, namely S phi 40mm, and the straight-pouring pit is shown in figure 13.

(3) Slag trap design

The tail end of the cross gate 6 is provided with a cross gate extension slag collecting ladle 9 to store primary flow liquid and prevent the end part from being cooled in advance to block a pouring channel, and meanwhile, the slag collecting ladle 9 plays roles in slag collection, slag blocking and turbulence prevention, as shown in figure 14. The height of the slag collecting bag is 1.5 times of that of the horizontal pouring gate.

(4) Riser design

The riser 10 is designed to improve the molten metal feeding effect, and in order to reduce the heat dissipation speed of the riser 10, prolong the solidification time of the riser and reduce the surface area of the riser as much as possible, the riser is designed to be a spherical-top cylindrical atmospheric pressure blind riser.

Calculating the diameter and the height of a riser according to a modulus method, and repeatedly simulating, verifying, calculating and correcting, wherein the riser is designed at the position of a cross gate close to an ingate, and has the diameter of 32mm and the height of 45mm; a riser with a diameter of 26mm and a height of 40mm was provided at a position away from the gate in each casting. As shown in fig. 15, two sizes of risers were designed, 4 each, for a total of 8.

(5) Chill design

According to pouring simulation analysis, a hot spot exists near a casting close to an inner pouring gate, a large shrinkage cavity defect occurs, a chilling block 11 needs to be arranged, the solidification sequence of molten metal is improved, the defect is eliminated, crystal grains are refined, and the mechanical performance is optimized.

The chilling block is a graphite chilling block with moderate chilling effect.

G _{Cooling by cooling} ＝ρ _Cold V _{Cooling by cooling} ＝ρ _Cold S _{Cooling by cooling} δ _Cold

Wherein: g _{Cooling by cooling} Weight of chill (g)

V ₀ Casting requires chilled volume (cm) ³ )；

M ₀ The modulus (cm) of the casting at the location where chilling is required;

mr-casting modulus (cm) of adjacent part of the chill;

S _cold Area of chill (cm) ² )；

δ _Cold -chill thickness (cm);

ρ _{cooling by cooling} Density of graphite chill (2.25 g/cm) ³ )。

The volume V of the casting needing chilling is calculated by the simulation analysis of the metal liquid pouring ₀ ＝75.42cm ³ Casting modulus M of parts needing chilling ₀ =4.01cm; casting mode Mr =2.4cm adjacent to the chill.

Therefore, the number of the first and second electrodes is increased,

consider thatThe thickness of the common chilling block in a factory is 10mm, 20mm and 30mm, the thickness of the chilling block at the position is delta 20mm, so S _{Cooling by cooling} ＝G _{Cooling by cooling} /(ρ _Cold δ _{Cooling by cooling} )＝16.44cm ² The casting bottom surface adjacent to each ingate is provided with a chilling block, 4 chilling blocks are arranged as shown in figure 16, a plurality of chilling blocks 11 are uniformly distributed on the annular surface of the bottom of the 1# sand core, and the casting bottom surface adjacent to each ingate is provided with a chilling block 11.

In the embodiment, the graphite chilling block with high refractoriness and high heat conductivity coefficient is selected, although the cost is slightly higher than that of the cast iron chilling block. However, through comparison of simulation results of the graphite chiller and the cast iron chiller, the effect of eliminating defects of the graphite chiller is found to be superior to that of the cast iron chiller, so that although the cost is slightly higher, the improvement of the qualified rate of castings is facilitated.

5. Pattern design

The pattern is used for forming a cavity of a casting mold and is indispensable technological equipment in sand casting. The mass production of the castings is not large, and in order to save the manufacturing cost, a wood pattern is adopted. And (3) lofting the casting, filling the hole groove, adding a pouring system, and dividing the wood type pattern into two parts from a parting surface to manufacture an upper box pattern and a lower box pattern by considering core head positioning, as shown in fig. 17.

6. Manufacture of sand mold

And respectively manufacturing an upper box sand mold and a lower box sand mold through the upper box mold sample and the lower box mold sample, wherein phenolic resin sand is used as molding sand as shown in figure 18.

7. Core box design

The core box is special technological equipment for manufacturing the sand core. Whether the size precision and the structure of the core box are reasonable or not will influence the quality and the molding efficiency of the sand core to a great extent. And designing a core box according to the structure of the sand core, and manufacturing the phenolic resin sand core by adopting a hot core box method.

8. Core setting sequence and mould assembling

The reasonable core setting sequence can reduce the labor intensity of workers and ensure the smooth casting process, after a pattern, a sand mold and a sand core are manufactured, core setting, mold assembling, positioning and fastening of the sand box are carried out according to the sequence shown in the figure 19, and then the next procedure of pouring molten metal is carried out.

Specifically, the method comprises the following steps:

the upper box and the lower box are stably placed on the molten iron casting site with the parting surfaces of the sand moulds upward, the outer core is accurately placed by aligning to the core head seat of the upper box, and the sand core is firmly bonded with the sand mould by using a bonding agent;

accurately positioning and placing the assembled inner cavity core to align to a core print seat of the lower box sand mold;

the case is gone up in the upset, will go up lower case lock, notice can not collide with the psammitolite that has installed, can not miss and bump the sand mould, arouse and fall the sand, prevent that the foreign matter from falling into the sand mould, go up lower case and pass through the accurate location lock of pin. And a sand core print seat of the inner cavity core of the upper box sand mould is accurately positioned and matched with the core print.

Adopt bolt fastening upper and lower case, notice the diagonal angle fastening, the symmetry order is fastened, and even power is exerted, prevents that upper and lower case die joint lock is not tight, warp the unevenness even.

And (4) placing a pouring cup, paying attention to the fact that an outlet at the bottom of the pouring cup is aligned with an inlet of a straight pouring channel of the upper box, completing a box closing process, and waiting for aluminum alloy liquid pouring in the next process.

It should be noted that, in the flat casting process, the sand box needs to complete the horizontal position molding to meet the requirements of normal upper and lower box molding, and a series of processes such as casting, exhausting, feeding and the like are completed after the horizontal position molding, core setting and mould assembling positioning.

Pouring: pouring the molten aluminum alloy, and boxing and shakeout after the molten aluminum alloy is cooled.

The casting process requirements have strict requirements on the casting slag inclusion defect, so molten metal is required to be filtered in the pouring process, and in the actual production of a factory, a fiber filter screen and a ceramic filter (a grid type and a foam type) are mainly used, wherein the porosity of the ceramic filter, especially the foam ceramic filter, is higher and can reach 92%, and the capability of removing slag inclusion and non-metallic impurities is far stronger than that of the fiber filter screen. The foam filter is a deep filter, which takes ceramics as net racks, and the net racks are fully distributed with communicated three-dimensional small holes, when in pouring, large impurities are intercepted on the outer surface of the filter, and tiny impurities are adsorbed on the wall surface of a channel. And the flow mode of the molten metal is changed from turbulent flow to laminar flow, so that the possibility of further oxidation of the filtered metal is reduced, and therefore, the filter screen of the embodiment adopts a foam ceramic filter and is arranged at the inlet of the sprue.

9 smelting process

After the furnace burden is prepared, adding the furnace burden into a 1t gas furnace, wherein the smelting temperature is 740-760 ℃, after the furnace burden is completely melted, opening a furnace mouth, enabling alloy melt to flow into a tundish, carrying out modification and refinement in the tundish, respectively adding 0.5% of Al-10Sr and Al-5Ti intermediate alloys at the temperature of 700-720 ℃, stirring, blowing nitrogen to refine and degas aluminum liquid, adding a covering agent, standing and standing for 10-20 min, detecting the hydrogen content of the aluminum liquid by a hydrogen detector, and pouring after the hydrogen content is qualified, wherein the pouring temperature is 720 +/-10 ℃.

The alterant is modified by Sr, has the advantages of less Sr burning loss, high yield, long-acting modification, good remelting property, no equipment corrosion and no environmental pollution, and has obvious advantages. Al-10Sr intermediate alloy with Sr content of 8-10% is selected as smelting alterant. However, al-10Sr alterant has a latency of about 40min and has a tendency to increase to be close to gas absorption, so refining and degassing are carried out after the modification process. In order to ensure that the addition of Sr is between 0.02 and 0.06 percent, the addition of Al-10Sr is selected to be 5 percent.

The sand casting is different from pressure casting, and the filling is carried out by self gravity, so as to achieve higher mechanical property, during smelting, a refiner is added to refine grains, al-5Ti intermediate alloy is selected as the smelting refiner, the Ti content is higher, the grain refining effect is good, meanwhile, the introduction of B element is avoided, and the adverse effect is eliminated.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement 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 of a machine body cover is characterized by comprising the following steps:

2. The method for casting the engine body cover according to claim 1, wherein the core prints of the outer core are arranged at the bottom of the outer core, at least two core prints of the outer core are arranged close to each other at a set distance, the inner cavity core is composed of a main body core and a connecting core, and the core prints of the inner cavity core are arranged at the bottom of the connecting core and at the end of the main body core far away from the connecting core.

3. The method of casting a body cover as in claim 2, wherein the sand core is provided with air outlet holes, and the air outlet holes are provided at the core heads of the outer core and the inner cavity core.

4. A body cover casting method as claimed in claim 1, wherein the sprue cross-sectional area: cross-sectional area of runner: the cross section of the ingate = 1.

5. A body cover casting method according to claim 4, wherein the cross-sectional shapes of the cross runner and the ingate are trapezoidal, the cross-sectional shape of the sprue is circular, and the cross runner is provided with a sprue extension slag collection pocket for storing primary flow liquid.

6. A method for casting a body cover according to claim 5, wherein the sprue bottom is provided with a sprue recess, the sprue recess is hemispherical in shape, and the diameter of the sprue recess is greater than that of the lower end of the sprue.

7. The method for casting the engine body cover as claimed in claim 6, wherein a riser is arranged at the top of the casting before pouring, and the riser is a spherical top cylindrical atmospheric pressure blind riser.

8. A method for casting a body cover according to claim 7, wherein before casting, a plurality of chills are disposed on the annular surface of the bottom of the outer core, the chills are uniformly distributed on the annular surface of the bottom of the outer core, and a chill is disposed on the bottom of the casting adjacent to each ingate.

9. The machine body cover casting method according to claim 1, wherein a core head seat is provided on the sand mold in fixing the sand core, the core head seat being provided corresponding to the core head.

10. The machine body cover casting method according to claim 1, wherein a pouring cup is installed in advance when molten metal is poured, and the pouring cup is a funnel-shaped pouring cup.