Casting mold and process method of piston

Abstract

The invention discloses a casting mold and a process method of a piston, which are suitable for a ZL109 aluminum-silicon alloy gravity casting piston, and are particularly suitable for a product with a cylinder diameter of 135 mm and more than 135 mm. According to the method, a five-piece mold structure composed of an inner mold middle core, a front small core, a rear small core, a left large side core and a right large side core is adopted, a flushing cooling pipeline is arranged in the front small core, intermittent cooling is carried out after molten aluminum pouring is completed, and the cooling time is controlled within 50-60 seconds. And a reasonable temperature gradient is formed after cooling, so that the piston skirt part and the edge groove area are sequentially solidified. And in cooperation with the design of a small-size feeding head, the feeding time is shortened, and the feeding efficiency is improved. Compared with the traditional process, the method can effectively reduce the structure shrinkage porosity defect, improve the metallographic structure and mechanical property of the casting, and improve the production efficiency at the same time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of casting, in particular to a casting mold and process method of a piston. BACKGROUND

[0002] The present application relates to a casting process method of a large aluminum piston, in particular to a 5-piece mold structure cooling and feeding control gravity casting process method suitable for a piston with a bore diameter of 135mm or more, and belongs to the technical field of casting manufacturing.

[0003] As a core component of an internal combustion engine, the quality of a piston directly affects the performance of the engine and the reliability of the whole machine. Currently, the commonly used aluminum piston is made of ZL109 aluminum-silicon alloy material and is formed by gravity casting. Since the piston needs to be designed for weight reduction, the inner cavity usually has a concave structure, which is difficult to demold with a whole mold, so a five-piece inner mold structure composed of an inner mold middle core, a front small core, a rear small core, a left large edge core and a right large edge core is generally used.

[0004] In the prior art, only the inner mold middle core in the five-piece inner mold structure has a cooling channel, and the front small core is generally in a natural cooling state, which has low cooling efficiency, especially in the piston skirt gate area, the cooling capacity is insufficient, and it is easy to produce organization shrinkage defects. To make up for this problem, large-size feeding risers are often designed to extend the feeding time and transfer the hot spots to the riser, but this not only prolongs the production cycle, but also increases the thermal load of the mold, reduces the overall production efficiency and yield, and the piston skirt gate has poor metallographic structure and insufficient mechanical properties, which restricts the production quality and rhythm of large high-performance pistons. SUMMARY

[0005] The purpose of the present application is to provide a casting mold and process method of a piston, which solves the problems of piston skirt groove area organization shrinkage, poor metallographic structure, excessive feeding time, uneven mold temperature control and other problems in the prior art, thereby improving the quality of piston products, shortening the casting cycle and improving the production efficiency.

[0006] The application is implemented by adopting the following technical scheme: a casting mold of a piston, characterized by comprising an outer mold and five-piece structure inner molds arranged in the cavity of the outer mold, the inner molds comprising: a middle core arranged at the middle axis of the piston blank; a front small core and a rear small core arranged at the front and rear ends of the middle core respectively and connected and fixed with the middle core through dovetail grooves or T-shaped groove structures; a left large side core and a right large side core arranged at the left and right sides of the piston blank respectively; the middle core can be driven downward by an oil cylinder in the vertical direction and drive the front small core and the rear small core to move inwardly and shrink, the left large side core and the right large side core are driven to move inwardly and demold by the horizontal oil cylinder after the middle core demolds, and the front small core is internally provided with a water flushing cooling pipe. Through the above mold structure, the smooth demolding of the large and complex inner cavity aluminum piston can be realized, and the structural basis for the heat control of the key area is provided, which helps to improve the compactness of the casting and the use efficiency of the mold.

[0007] Further, the water flushing cooling pipe is connected to an external cooling water source and is configured to intermittently supply water after the aluminum liquid is poured, and the cooling time can be controlled to be between 50 to 60 seconds. Through the setting of intermittent cooling, the front small core can quickly absorb heat in the key cooling window, form the required temperature gradient, and facilitate the sequential solidification of the piston skirt area, thereby reducing the risk of shrinkage in this area.

[0008] Further, the front small core is provided with a spring mounting hole, and the hole length of the spring mounting hole is less than 90 mm to reserve space for the cooling pipe. Through the compact design of the structure, the cooling pipe space is reserved, the cooling capacity of the front small core is enhanced, the structural strength and arrangement rationality of the mold are ensured, and the assembly flexibility of the mold is improved.

[0009] Further, a feeding riser is arranged on the outer mold, the feeding riser is connected with the gate area of the piston skirt, and is used for feeding the shrinkage area. This structure helps to control the hot spot position, directs the shrinkage compensation behavior to the feeding riser, avoids defects concentrated in the key parts of the finished product, and improves the quality stability of the casting.

[0010] Further, the width of the feeding riser is 30-35 mm, and the height of the static pressure head is 20-25 mm. Compared with the traditional riser, the size design is greatly reduced, which is beneficial to reduce the feeding heat capacity, shorten the feeding time, improve the production efficiency, reduce the aluminum consumption and the scrap rate.

[0011] Further, the middle core of the inner mold has a continuous water cooling structure. The continuous cooling mode can maintain the constant temperature state of the middle core, improve the service life of the mold, slow down the thermal fatigue, and create conditions for temperature control balance.

[0012] Further, the mold is suitable for gravity casting of ZL109 aluminum-silicon alloy and casting of aluminum pistons with a cylinder diameter of 135 mm or more. The structure is particularly suitable for manufacturing pistons for large heavy-duty engines and can meet multiple requirements for mold rigidity, thermal conductivity, demolding method, and cooling capacity, and has good industrialization promotion value.

[0013] A casting process method of a piston, comprising the following steps: Step one: installing the mold The core, the front small core, the rear small core, the left large edge core, and the right large edge core in the inner mold are sequentially installed in the outer mold cavity to form a complete mold cavity structure, connect the cooling water channel, and check the water supply state.

[0014] Step two: melting and pouring the alloy The ZL109 aluminum-silicon alloy is melted at a temperature in the range of 720-740 DEG C, and the molten aluminum is poured into the mold cavity through the sprue.

[0015] Step three: cooling operation After pouring is completed, water is supplied to the inside of the front small core through the water cooling pipe, and the cooling time is controlled to be between 50-60 seconds, while the core is continuously cooled.

[0016] Step four: feeding During the cooling process, the feeding riser is used to provide feeding aluminum liquid, and the feeding time is controlled to be 180 seconds to maintain internal pressure compensation for solidification shrinkage.

[0017] Step five: demolding The middle core in the inner mold is driven to move in the vertical direction, the front small core and the rear small core are driven to shrink inward, and when the overall shrinkage size is smaller than the inner diameter of the piston stop, the mold is demolded, and then the left large edge core and the right large edge core are driven to move inward along the horizontal direction to realize complete demolding of the inner mold assembly.

[0018] Step six: mold resetting The cooling water supply of the front small core is turned off, and after the mold temperature returns to the preset range, the next pouring cycle is prepared.

[0019] The piston casting mold and process method have the following beneficial effects: In the five-piece mold structure, the front small core has an independent water cooling pipe, and intermittent cooling of 50-60 seconds is implemented after the aluminum liquid is poured, so that a reasonable temperature gradient is formed in the piston skirt sprue area, sequential solidification is realized, and shrinkage defects are reduced.

[0020] The compact design of the front small core structure reserves installation space for the cooling water channel, and the cooling capacity is improved without increasing the size of the mold.

[0021] By increasing the cooling rate, the feeding riser size can be reduced significantly, the hot spot volume can be reduced, the feeding riser width can be reduced from 50-60mm to 30-35mm, and the static pressure head height can be reduced from 50-55mm to 20-25mm.

[0022] The overall feeding time is shortened from 210 seconds to 180 seconds, and the average saving of each blank is about 30 seconds, and the production rhythm is increased by about 10%.

[0023] The metallographic grade of the casting is improved from 4 to 3, the room temperature tensile strength is improved from 240MPa to 258MPa, and the overall performance of the piston is significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows. The drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the structures shown in the drawings.

[0025] Figure 1 is a schematic diagram of the overall structure of the mold of the present application; Figure 2 is a schematic diagram of the piston blank; Figure 3 is a schematic diagram of the outer mold structure; Figure 4 is a schematic diagram of the inner mold from the bottom; Figure 5 is Figure 4 is a schematic diagram of the D-D cross section; In the figure, 1 is a piston blank; 2 is an inner mold core; 3 is a front small core; 4 is a rear small core; 5 is a left large edge core; 6 is a right large edge core; 7 is a feeding riser; 8 is a water flushing cooling pipe; 9 is a gate; 10 is a piston skirt; 11 is a rib groove; and 12 is an outer mold. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, but not all embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0027] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention. Example

[0028] like Figures 1-5 As shown, this embodiment provides a piston casting mold, including an outer mold 12 for forming the shape of the piston blank 1, and five structural inner molds disposed inside the mold cavity. The inner molds include five components: inner mold core 2, front small core 3, rear small core 4, left large side core 5, and right large side core 6.

[0029] Specifically, the inner mold core 2 is located at the central axis of the piston blank 1 and is the core component for demolding the entire inner cavity. The front small core 3 and the rear small core 4 are respectively arranged at the front and rear ends of the core 2 and are connected and fixed to the core through dovetail grooves or T-slot structures. During demolding, the core 2 is driven downward by a vertical hydraulic cylinder, which drives the front small core 3 and the rear small core 4 to retract and move inward, thereby realizing the smooth demolding of the inner cavity of the piston blank 1. The left large side core 5 and the right large side core 6 are arranged on the left and right sides of the piston blank 1 and are driven by horizontal hydraulic cylinders respectively. After the inner mold core 2 is removed, they move horizontally towards the center of the piston for demolding.

[0030] In this embodiment, a water-cooling pipe 8 is added inside the front core 3. This water-cooling structure is connected to an external cooling water source and adopts an intermittent cooling method. Water cooling begins after the aluminum liquid is poured, and the cooling time is adjustable, usually controlled at 50-60 seconds. Through this cooling system, the front core 3 can quickly reduce its temperature and further absorb heat from the skirt 10 and groove 11 of the piston blank 1, forming a temperature gradient for sequential solidification.

[0031] In addition, the structural improvements to the front core 3 also include the optimization of its length. By shortening the mounting hole for the lifting spring from 114mm to 70mm, the overall size of the front core 3 is made more compact, freeing up more space for cooling pipes, thereby improving cooling efficiency and installation operability.

[0032] Regarding the feeding system, a feeding riser 7 is designed on the outer mold 12. Compared to the larger feeding riser in the original design, the feeding riser 7 in this embodiment can be reduced in size due to the optimized cooling structure. Its width B is 30-35mm, and the static pressure head height H is 20-25mm, which is significantly better than the traditional design with a width B of 50-60mm and a static pressure head height H of 50-55mm. The feeding riser 7 is connected to the gate 9 area of ​​the piston skirt 10, which can form a heat joint during the cooling and solidification process of the molten aluminum, thus promoting smooth feeding.

[0033] Through the above structural design and improvement, the embodiment effectively solves the problem of loose structure at the piston skirt groove 11 caused by uneven cooling in traditional molds, improves the metallographic quality and mechanical properties of the overall casting, and reduces the scrap rate and improves the production efficiency. Embodiment

[0034] The embodiment provides a casting process method of a casting mold of a piston based on the piston in the embodiment 1, which is suitable for a gravity casting piston made of ZL109 aluminum-silicon alloy material, and is particularly suitable for casting of large aluminum pistons with a cylinder diameter of 135 mm or more.

[0035] Specifically, the method adopts a 5-piece structure inner mold for demolding operation, and combines an improved cooling system and an optimized feeding riser design to improve the compactness of the casting and the production efficiency. The casting process mainly includes the following steps: Step one: mold installation and preparation The mold structure is assembled according to the standard, and the inner mold core 2, the front small core 3, the rear small core 4, the left large edge core 5 and the right large edge core 6 are assembled in the outer mold 12 in sequence to form a complete mold cavity structure. It is confirmed that the connection between the inner mold parts is tight, the cooling waterway is unobstructed, and the cooling water pipe of the inner mold core 2 is in continuous water supply state, and the cooling waterway of the front small core 3 is standby for intermittent cooling.

[0036] Step two: alloy smelting and pouring ZL109 aluminum-silicon alloy material is used for smelting, and the smelting temperature is controlled in the range of 720-740℃. After the aluminum liquid is smelted, it is poured into the mold cavity through the sprue 9, so that the aluminum liquid fills the mold cavity, and the aluminum piston blank 1 is formed. The aluminum liquid flows through the front small core 3 and the surrounding area, and the heat is accumulated at the piston skirt 10 and the groove 11.

[0037] Step three: water flushing cooling After the aluminum liquid is poured, the water flushing cooling device of the front small core 3 is started immediately, and the cooling water is injected into the front small core 3 through the water flushing cooling pipe 8. The cooling time is controlled to be 50-60 seconds, so that the front small core 3 quickly absorbs the heat of the aluminum liquid in the surrounding area, forms a temperature gradient from top to bottom and from outside to inside in the piston blank 1, promotes the advance solidification of the sprue 9 and the skirt 10 area, and is beneficial to realize the sequential solidification.

[0038] In addition, the process parameters of the embodiment are also optimized and adjusted compared to the previous improvement, making the entire casting process more efficient and stable. Specifically, before the improvement, the feeding time was 210 seconds, the outer mold started to flush water after a delay of 30 seconds, the flushing time was 160 seconds, the middle core 2 continuously flushed water, the top mold delayed for 180 seconds and flushed for 10 seconds, and the pin core delayed for 10 seconds and flushed for 30 seconds. In this embodiment, the feeding time is optimized to 180 seconds, the outer mold still starts to flush water after a delay of 30 seconds, but the flushing time is shortened to 130 seconds, the middle core 2 still continuously flushes water, the newly added front small core 3 flushes water and cools within 0-50 seconds after the aluminum liquid is poured, the top mold delays for 140 seconds and flushes for 30 seconds, and the pin core delays for 5 seconds and flushes for 30 seconds.

[0039] Through this series of cooling time and sequence adjustment, the heat balance of the casting system is more reasonable, especially through the precise control of the cooling time of the front small core 3, the heat at the piston skirt 10 and the rib groove 11 can be quickly removed, the risk of shrinkage is reduced, and the organization consistency is improved. At the same time, the overall feeding time is shortened by 30 seconds, improving the single-piece production efficiency without sacrificing the feeding effect.

[0040] Step four: feeding and holding During the cooling process, the aluminum liquid in the feeding riser 7 maintains a flowing state, playing a feeding role to the solidification shrinkage area. In this embodiment, the size of the feeding riser 7 is optimized, with a width controlled between 30-35mm and a static pressure head height controlled between 20-25mm, effectively reducing the volume of the feeding area and improving the feeding efficiency. The entire feeding duration is 180 seconds.

[0041] Step five: mold demolding After feeding is completed, the inner mold middle core 2 is driven to move downward in the vertical direction by the oil cylinder, driving the front small core 3 and the rear small core 4 to move inward and shrink. When the total width of the inner mold middle core 2 and the front and rear small cores is less than the inner diameter of the piston stop, demolding can be achieved. Subsequently, the left large edge core 5 and the right large edge core 6 are respectively driven by horizontal oil cylinders to move towards the center of the piston to be removed, realizing complete demolding of the entire inner mold system.

[0042] Step six: mold resetting and recycling After demolding is completed, the cooling water of the front small core 3 is turned off, and the hot aluminum piston blank 1 quickly raises the temperature of the mold to above 300°C under the wrapping action, providing temperature protection for the pouring of the next blank. The entire mold system completes a production cycle, and the production turnover time of a single piston blank 1 is about 240 seconds.

[0043] Compared with the traditional process, the casting rejection rate is reduced from 4% to 2.5%, the metallographic structure grade of the skirt is improved from 4 to 3, and the tensile strength is increased from 240 MPa to 258 MPa. At the same time, due to the optimization of the shrinkage feeding riser and the cooling process, the production time of each piston is saved by about 30 seconds, and the production efficiency is improved by about 10%.

[0044] In the above embodiments, the basic principles and main features of the present application and the advantages of the present application are described. It should be understood by those skilled in the art that the present application is not limited to the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the present application. Any modification and change made by those skilled in the art without departing from the spirit and scope of the present application shall be within the protection scope of the claims of the present application.

Claims

1. A casting mold for a piston, characterized by, The piston core includes an outer mold (12) and five structural inner molds arranged in the cavity of the outer mold (12), which comprises: an inner mold middle core (2) located at the center axis of the piston blank (1); a front small core (3) and a rear small core (4) arranged at the front and rear ends of the middle core (2) respectively and connected and fixed with the middle core (2) through dovetail grooves or T-shaped groove structures; a left large side core (5) and a right large side core (6) arranged on the left and right sides of the piston blank (1) respectively; the middle core (2) can be driven by an oil cylinder to move downward in the vertical direction and drive the front small core (3) and the rear small core (4) to move inwardly and shrink, and the left large side core (5) and the right large side core (6) are driven by a horizontal oil cylinder to move inwardly and demold after the middle core (2) is demolded, and the front small core (3) is internally provided with a water flushing cooling pipe (8).

2. A casting mold for a piston according to claim 1, characterized in that The water flushing cooling pipe (8) is connected to an external cooling water source and is configured to intermittently supply water after the aluminum liquid is poured, and the cooling time can be controlled to be between 50 to 60 seconds.

3. A casting mold for a piston according to claim 2, characterized in that The front small core (3) is provided with a spring mounting hole, and the hole length of the spring mounting hole is less than 90mm to reserve space for the cooling pipe.

4. A casting mold for a piston according to claim 1, wherein The outer mold (12) is provided with a feeding riser (7) connected with the gate (9) area of the piston skirt (10) for feeding the shrinkage area.

5. A casting mold for a piston according to claim 4, wherein The width of the feeding riser (7) is 30-35mm, and the static pressure head height is 20-25mm.

6. A casting mold for a piston according to claim 1, wherein The middle core (2) of the inner mold has a continuous water cooling structure.

7. A casting mold for a piston according to claim 1, wherein The mold is suitable for gravity casting of ZL109 aluminum silicon alloy and is suitable for casting aluminum pistons with a cylinder diameter of 135mm or more.

8. A casting process method of a piston, realized on the basis of the casting mold of any of claims 1-7, characterized in that, The method comprises the following steps: Step one: install the mold Install the inner mold middle core, front small core, rear small core, left large side core and right large side core in the outer mold cavity in sequence to form a complete mold cavity structure, connect the cooling water channel and check the water supply state; Step two: melt the alloy and pour Melt the ZL109 aluminum silicon alloy at a temperature of 720-740℃, and pour the molten aluminum liquid into the mold cavity through the gate; Step three: cooling operation After pouring is completed, water is supplied to the inside of the front small core through the water flushing cooling pipe, and the cooling time is controlled to be between 50 to 60 seconds, and the middle core is continuously cooled at the same time; Step four: feeding During the cooling process, feeding aluminum liquid is provided through the feeding riser, and the feeding time is controlled to be 180 seconds to maintain internal pressure compensation for solidification shrinkage; Step five: demolding Drive the inner mold middle core to move in the vertical direction, drive the front small core and the rear small core to shrink inwardly, and when the overall shrinkage size is smaller than the inner diameter of the piston stop, demold, then drive the left large side core and the right large side core to move inwardly along the horizontal direction to realize complete demolding of the inner mold assembly; Step six: mold resetting Close the front small core cooling water supply, and after the mold temperature returns to the preset range, prepare for the next pouring cycle.

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