A marine low-speed engine cylinder liner casting method and cylinder liner

Abstract

The application relates to a marine low-speed engine cylinder liner casting method and a cylinder liner. The method comprises the following steps: inverting a sand mold used for casting the cylinder liner, so that the sand mold corresponding to a thick-wall end is located at the lower part, and the sand mold corresponding to a thin-wall end is located at the upper part; placing a core in the sand mold, and setting a riser at the upper end of the sand mold; setting an outer chill at the outer wall of the thick-wall end of the cylinder liner in the sand mold, and setting an inner chill at the end of the thick-wall end of the cylinder liner in the sand mold; setting a plurality of forced chills at the end of the thick-wall end of the cylinder liner at the lower end of the sand mold, the forced chills being connected with a cooling medium circulating system used for circulating and supplying the cooling medium to the forced chills; injecting molten metal along the riser during casting, starting the cooling medium circulating system before casting, and closing the cooling medium circulating system after the molten metal in the riser is solidified, so that the cylinder liner is obtained by solidification. The method can make the thick-wall end of the cylinder liner solidify preferentially, improve the mechanical performance and the fineness of the crystal grains of the thick-wall end, and help to improve the service life of the cylinder liner.

Description

Technical Field

[0001] This invention relates to the field of casting technology, specifically to a casting method and cylinder liner for marine low-speed engines, applicable to a casting method for improving the material properties of the combustion chamber end of high-power marine low-speed engine cylinder liners. Background Technology

[0002] As a crucial component of high-power marine low-speed engines, the cylinder liner has two main components. The upper part of the cylinder liner, as part of the combustion chamber, withstands high-temperature and high-pressure conditions and requires high mechanical strength, hence its thick-walled shape. The lower part of the cylinder liner, as the intake end, operates in a lower temperature and pressure environment, hence its thin-walled shape. In addition, the cylinder liner also constrains the piston, causing it to reciprocate, resulting in friction between the piston and piston rings. The upper, thick-walled end, in particular, experiences high temperatures, leading to poor lubrication. Furthermore, the material has coarse grains, resulting in more severe wear than the thin-walled end. All these factors directly affect the service life of the cylinder liner.

[0003] In conventional cylinder liner casting, a solidification sequence from far to near is followed to ensure successful casting. Natural cooling is used, with the thick-walled end positioned near the upper riser 7, and the thin-walled end placed at the lower end with cooling systems (internal chiller 3 and external chiller 2). This ensures solidification occurs in a far-to-near order during casting. Figure 1 As shown in the diagram, in this casting method, the mechanical properties and grain density of the thin-walled section are superior to those of the thick-walled section. The thick-walled section has lower mechanical properties and coarser grains compared to the thin-walled section, resulting in the thick-walled section failing to meet performance requirements during cylinder liner use. Furthermore, the thick-walled section is located close to the riser, and the riser at the thick-walled section is relatively large, leading to a lower molten iron yield. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for casting cylinder liners for marine low-speed engines and a cylinder liner that solves the problems of insufficient material properties at the thick-walled end and wasted material properties at the thin-walled end, thereby improving the mechanical properties and grain density of the thick-walled end of the cylinder liner, making the performance of the thick-walled end superior to that of the thin-walled end.

[0005] The technical objective of this invention is achieved through the following technical solution: A method for casting marine low-speed engine cylinder liners using inverted forced sequential solidification, the method comprising: The sand mold used for casting the inverted cylinder liner is positioned such that the sand mold corresponding to the thick-walled end is located at the bottom and the sand mold corresponding to the thin-walled end is located at the top; a core is placed inside the sand mold, and a casting cavity is formed between the core and the sand mold; a riser is set at the top of the sand mold. An external chill is provided on the outer wall of the thick-walled end of the cylinder liner inside the sand mold, and an internal chill is provided at the end of the thick-walled end of the cylinder liner inside the sand mold. The internal chill is located on the outer side of the core. Several forced chills are provided at the lower end of the sand mold corresponding to the thick-walled end of the cylinder liner. The forced chills are connected to a cooling medium circulation system for circulating cooling medium to the forced chills. During casting, molten metal is injected into the casting cavity through the riser. Before casting, the cooling medium circulation system is started, and after the molten metal in the riser solidifies, the cooling medium circulation system is turned off.

[0006] Furthermore, a cavity is provided inside the forced chill, and a refrigerant inlet and outlet connector connected to the internal cavity are provided on the outside of the forced chill; the cooling medium circulation system is connected to the refrigerant inlet and outlet connectors through pipelines to realize the circulation of the cooling medium.

[0007] Furthermore, the cooling medium circulation system includes a cooling medium storage tank, a heat exchange system, and a conveying system. The cooling medium storage tank stores cooling medium liquid. The cooling medium storage tank conveys the cooling medium along the pipeline to the refrigerant inlet joint through the conveying system. After the cooling medium is output from the refrigerant outlet joint, it enters the heat exchange system along the pipeline for heat exchange and then flows back to the cooling medium storage tank.

[0008] Furthermore, before casting begins, the cooling medium circulation system is turned on to allow the cooling medium to circulate and fill the cavity of the forced chill. After confirming that the cooling medium circulation system is working properly, the cooling medium circulation system is turned off. During the actual casting, the cooling medium circulation system is turned on first, and then molten metal is injected into the casting cavity through the riser.

[0009] Furthermore, the boiling point of the cooling medium at normal pressure is greater than 200°C.

[0010] Furthermore, the cooling medium storage tank, heat exchange system, and conveying system are detachably connected.

[0011] Furthermore, the riser is a riser that adapts to the outer diameter and height of the scavenging end of the cylinder liner.

[0012] Furthermore, when the molten metal solidifies in the casting cavity, the lower region solidifies preferentially, and the solidified region absorbs heat from the adjacent upper region, achieving gradual upward solidification until the molten metal in the riser solidifies, at which point the cooling medium circulation system is shut off.

[0013] The present invention also provides a marine low-speed engine cylinder liner, comprising a thin-walled end and a thick-walled end, wherein the cylinder liner is cast by the above-described method.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The casting method of the present invention enables the thick-walled end region of the cylinder liner to solidify preferentially, and the mechanical properties of the thick-walled end are better than those of the thin-walled end. The grains of the thick-walled end are finer and more uniform than those of the thin-walled end, which improves the wear resistance of the thick-walled end of the cylinder liner, helps to extend the service life of the cylinder liner, and avoids the problem of insufficient material properties of the thick-walled end and waste of material properties of the thin-walled end.

[0015] 2. In the casting method of the present invention, the riser is set in the thin-walled end region, which greatly reduces the diameter of the riser and the height of the riser is also relatively reduced. Compared with the riser being set in the thick-walled end, the mass ratio of the riser is reduced by about 60%, which reduces the demand for molten metal and the energy consumption of smelting, increases the yield of molten metal, and reduces manufacturing costs.

[0016] 3. The casting method of the present invention does not change the smelting process of molten metal compared with conventional methods, but can reduce the outlet water temperature and reduce the energy consumption required for melting. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a conventional marine low-speed engine cylinder liner casting.

[0018] Figure 2 This is a schematic diagram of the inverted forced sequential solidification casting of marine low-speed engine cylinder liners according to the present invention.

[0019] Figure 3 This is a schematic diagram of the cooling medium circulation system connection in an embodiment of the present invention.

[0020] Figure 4 This is a schematic diagram of the internal cooling channel arrangement of the forced chiller in an embodiment of the present invention.

[0021] In the picture: 1. Sand mold; 2. External chill; 3. Internal chill; 4. Cooling medium circulation system; 5. Forced chill; 6. Core frame; 7. Riser; 8. Gating system; 41. Cooling medium storage tank; 42. Heat exchange system; 43. Conveying system; 51. Refrigerant inlet connector; 52. Refrigerant outlet connector. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to specific embodiments: During the conventional casting of marine low-speed engine cylinder liners, such as Figure 1As shown, the sand mold 1 required for cylinder liner casting is placed in a normal configuration, with the sand mold corresponding to the thick-walled end at the top and the sand mold corresponding to the thin-walled end at the bottom. The core 6 is placed inside the sand mold 1, forming a casting cavity between the sand mold 1 and the core 6. A riser 7 is set at the upper end of the sand mold 1, i.e., near the thin-walled end. An external chill 2 is set inside the sand mold 1 corresponding to the outer wall of the thick-walled end of the cylinder liner, and an internal chill 3 is set inside the sand mold 1 corresponding to the thin-walled end of the cylinder liner. The internal chill 3 is located outside the core 6. During casting, the casting system 8 injects molten metal, i.e., molten iron, into the casting cavity from the riser 7 at the top. The thin-walled end region at the bottom will solidify first, while the thick-walled end at the top will solidify last. This results in poor mechanical properties and coarser grains at the thick-walled end, which cannot be adapted to the high temperature and high pressure conditions of the thick-walled end when the cylinder liner is used.

[0023] To address the aforementioned problems, this embodiment provides a method for casting marine low-speed engine cylinder liners using inverted forced sequential solidification, such as... Figure 2 As shown, the method includes: The sand mold 1 used for casting the inverted cylinder liner is positioned such that the sand mold corresponding to the thick-walled end is located at the bottom and the sand mold corresponding to the thin-walled end is located at the top; a core 6 is placed inside the sand mold 1, and a casting cavity is formed between the core 6 and the sand mold 1; a riser 7 is provided at the upper end of the sand mold 1, and the riser 7 is a riser adapted to the outer diameter and height of the scavenging end (thin-walled end) of the cylinder liner; An external chill 2 is provided on the outer wall of the thick-walled end of the cylinder liner inside the sand mold 1, and an internal chill 3 is provided on the end of the thick-walled end of the cylinder liner inside the sand mold 1. The internal chill 3 is located on the outside of the core 6. Several forced chills 5 are provided at the lower end of the sand mold 1 corresponding to the thick-walled end of the cylinder liner. The forced chills 5 are connected to a cooling medium circulation system 4 for circulating cooling medium to the forced chills 5. During casting, molten metal (iron) is injected into the casting cavity through the casting system 8 along the riser 7. Before casting, the cooling medium circulation system 4 is started, and the cooling medium circulation system 4 is turned off after the molten metal in the riser 7 has solidified.

[0024] More specifically, such as Figure 3 As shown, the forced chill 5 has a cavity inside, and a refrigerant inlet 51 and a refrigerant outlet 52 communicating with the internal cavity are provided on the outside of the forced chill 5. The cooling medium circulation system 4 is connected to the refrigerant inlet 51 and the refrigerant outlet 52 through pipelines to realize the circulation of the cooling medium. A cooling channel can also be provided inside the forced chill 5. The cooling channel can be reciprocated to increase the contact heat exchange area. The refrigerant inlet 51 and the refrigerant outlet 52 are connected to the two ends of the cooling channel, such as... Figure 4 As shown.

[0025] The cooling medium circulation system 4 includes a cooling medium storage tank 41, a heat exchange system 42, and a conveying system 43. The cooling medium storage tank 41 stores cooling medium liquid. The cooling medium is preferably a coolant with a boiling point greater than 200°C at normal pressure, such as non-toxic and non-flammable PFPE (perfluoropolyether oil) or dimethyl silicone oil. The conveying system 43 includes a liquid conveying pump. The cooling medium storage tank 41 conveys the cooling medium along the pipeline to the refrigerant inlet joint 51 through the conveying system 43. After the cooling medium is output from the refrigerant outlet joint 52, it enters the heat exchange system 42 along the pipeline for heat exchange and cooling, and then flows back to the cooling medium storage tank 41.

[0026] The cooling medium circulation system 4 is located outside the sand mold 1. The cooling medium storage tank 41, heat exchange system 42, and conveying system 43 are detachably connected. All the pipelines of the forced chill iron 5 are connected in parallel to the cooling medium circulation system 4.

[0027] More specifically, before casting, confirm that the cylinder liner model for production matches the process, turn on the cooling medium circulation system 4, check whether the cooling medium circulation system 4 and its pipeline connections are normal, and whether all parameters match the process parameters. Ensure that the cooling medium flows and fills the cavity of the forced chill 5, and then turn off the cooling medium circulation system 4.

[0028] During the formal casting process, the cooling medium circulation system 4 is first turned on, and the outlet temperature of the cooling medium circulation system 5 is checked to see if it is within the process requirements. Once the outlet temperature of the cooling medium in the cooling medium circulation system 4 is within the process requirements, molten iron is injected into the casting cavity through the casting system 8 along the riser 7. The molten iron fills the riser 7 to its full height. After the molten iron in the riser 7 solidifies, the cooling medium circulation system 4 is turned off, and the cooling medium in the forced chill 5 cavity is discharged.

[0029] Molten iron solidifies in the casting cavity to form a casting. Sand mold 1, riser 7, external chill 2 and core 6 are removed to obtain a marine low-speed engine cylinder liner. The thick-walled end of the cylinder liner has a finer grain and better mechanical properties than the thin-walled end.

[0030] Forced chill 5 is kept at a low temperature by an external cooling medium circulation system 4, maintaining a large temperature difference with the cylinder liner casting in the sand mold 1. This allows the cylinder liner casting to continuously release heat to the forced chill 5, causing the thick-walled end of the cylinder liner to solidify first. Under the action of the forced chill 5, the already solidified area is continuously cooled, and the low temperature is transferred upwards, causing the adjacent upper area to gradually cool down. This achieves forced sequential solidification, ensuring that the cylinder liner solidifies in a sequence from far to near. The relatively faster solidification and cooling of the thick-walled end, coupled with the maximum pressure of molten iron at the thick-walled end due to the height difference, results in higher mechanical properties, finer and more uniform grains, and a denser material in the thick-walled end area, making it less prone to loose, large grains.

[0031] This embodiment is merely a further explanation of the present invention and is not intended to limit the present invention. Those skilled in the art can make non-inventive modifications to this embodiment as needed after reading this specification, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for casting marine low-speed engine cylinder liners using inverted forced sequential solidification, characterized in that, The method includes: The sand mold used for casting the inverted cylinder liner is positioned such that the sand mold corresponding to the thick-walled end is located at the bottom and the sand mold corresponding to the thin-walled end is located at the top; a core is placed inside the sand mold, and a casting cavity is formed between the core and the sand mold; a riser is set at the top of the sand mold. An external chill is provided on the outer wall of the thick-walled end of the cylinder liner inside the sand mold, and an internal chill is provided at the end of the thick-walled end of the cylinder liner inside the sand mold. The internal chill is located on the outer side of the core. Several forced chills are provided at the lower end of the sand mold corresponding to the thick-walled end of the cylinder liner. The forced chills are connected to a cooling medium circulation system for circulatingly supplying cooling medium to the forced chills. During casting, molten metal is injected into the casting cavity through the riser. Before casting, the cooling medium circulation system is started, and after the molten metal in the riser solidifies, the cooling medium circulation system is turned off.

2. The method for casting marine low-speed engine cylinder liners using inverted forced sequential solidification according to claim 1, characterized in that, The forced chiller has a cavity inside, and a refrigerant inlet and a refrigerant outlet are provided on the outside of the forced chiller to communicate with the cavity. The cooling medium circulation system is connected to the refrigerant inlet and the refrigerant outlet through pipelines to realize the circulation of the cooling medium.

3. The method for casting marine low-speed engine cylinder liners using inverted forced sequential solidification according to claim 2, characterized in that, The cooling medium circulation system includes a cooling medium storage tank, a heat exchange system, and a conveying system. The cooling medium storage tank stores cooling medium liquid. The cooling medium storage tank is conveyed to the refrigerant inlet joint along the pipeline through the conveying system. After the cooling medium is output from the refrigerant outlet joint, it enters the heat exchange system along the pipeline for heat exchange and then flows back to the cooling medium storage tank.

4. The method for casting marine low-speed engine cylinder liners using a reverse-sequence solidification process according to claim 3, characterized in that, Before casting begins, the cooling medium circulation system is turned on to allow the cooling medium to circulate and fill the cavity of the forced chill. After confirming that the cooling medium circulation system is working properly, the cooling medium circulation system is turned off. During the actual casting, the cooling medium circulation system is turned on first, and then molten metal is injected into the casting cavity through the riser.

5. The method for casting marine low-speed engine cylinder liners using a reverse-sequence solidification process according to claim 3, characterized in that, The boiling point of the cooling medium at normal pressure is greater than 200℃.

6. The method for casting marine low-speed engine cylinder liners using a reverse-sequence solidification process according to claim 3, characterized in that, The cooling medium storage tank, heat exchange system, and conveying system are detachably connected.

7. The method for casting marine low-speed engine cylinder liners using a reverse-sequence solidification process according to claim 1, characterized in that, The riser is a riser that adapts to the outer diameter and height of the scavenging end of the cylinder liner.

8. The method for casting marine low-speed engine cylinder liners using a reverse-sequence solidification process according to claim 1, characterized in that, When the molten metal solidifies in the casting cavity, the lower region solidifies first, and the solidified region absorbs heat from the adjacent upper region, achieving gradual upward solidification until the molten metal in the riser solidifies, at which point the cooling medium circulation system is shut off.

9. A marine low-speed engine cylinder liner, characterized in that, The cylinder liner includes a thin-walled end and a thick-walled end, and is cast by the method described in any one of claims 1 to 8.

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