Marine low-speed machine pre-combustion chamber mold strengthening method based on prestress additive manufacturing

Abstract

The invention discloses a marine low-speed machine pre-combustion chamber mold strengthening method based on prestress additive manufacturing, which comprises the following steps of: carrying out additive strengthening on a local position, which needs to be strengthened, of a mold by using an electric arc fuse wire additive process, and additionally arranging a stud at a local position, which needs to be strengthened, of a grinding tool to apply prestress; according to the pre-combustion chamber mold, stress can be effectively reduced when the reinforced pre-combustion chamber mold resists unbalance loading, the stud is melted through the temperature of the material adding layer in the material adding process, the stud and the mold are fused into a whole, the tensile strength and toughness of the protruding root area are improved, and the strength and hardness of the protruding head area are improved; and tempering heat treatment is further carried out after material adding, so that stable tempered martensite is obtained, the effect of improving the stability of the structure of the pre-combustion chamber mold is achieved, the mold does not generate structure transformation in the using process, the physical dimension and performance of the mold tend to be stable, meanwhile, internal stress can be eliminated, and the toughness is improved. And the comprehensive service performance and the service life of the die are obviously enhanced.

Description

Technical Field

[0001] The invention relates to the technical field of hot forging dies, and in particular to a method for strengthening a pre-combustion chamber die of a marine low-speed engine based on prestressed additive manufacturing. Background Art

[0002] The traditional manufacturing process of the nickel-based superalloy precombustion chamber of the marine dual-fuel low-speed engine is machining, which has the disadvantages of large machining allowance, low material utilization rate, and no continuous metal streamline formed inside the part, resulting in low service mechanical properties of the part. In contrast, the precision die forging of the precombustion chamber can obtain excellent part performance, high production efficiency and low manufacturing cost, but at the same time, the requirements for mold performance are also higher.

[0003] Due to the complex shape of the inner cavity of the precombustion chamber, the inclined deep hole inside is difficult to form, so the precombustion chamber forging die often has slender features. At the same time, the precombustion chamber often serves under high temperature conditions, and needs to be formed with high-temperature alloys that meet the service requirements, and high-temperature alloys still have large deformation resistance at high temperatures. This also causes the root of the die protrusion to be easily cracked by uneven friction during the forging process, and the protrusion head is prone to collapse and wear under high temperature and heavy load conditions, resulting in serious die failure. It is difficult to achieve mass production of precombustion chambers with forging dies made of ordinary forged steel.

[0004] Therefore, it is necessary to improve the forging processing method of the pre-combustion chamber mold of the marine low-speed engine to better meet the requirements of low cost, high performance and long life, which has important practical significance for the process technology progress of the pre-combustion chamber of the marine low-speed engine. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for strengthening the pre-combustion chamber mold of a marine low-speed engine based on prestressed additive manufacturing. This method can effectively avoid defects such as cracking and collapse of the pre-combustion chamber forging die under service conditions, and further improve the comprehensive performance and service life of the mold.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: The method for strengthening the pre-combustion chamber mold of a marine low-speed engine based on prestressed additive manufacturing includes the following steps: S1. According to the shape of the precombustion chamber forging and the stress condition of the precombustion chamber die during the forging process, determine the position where the precombustion chamber die needs to be prestressed and the prestress design requirements required at the corresponding position; S2. Processing a threaded blind hole at the position of the mold base where the pre-combustion chamber mold needs to apply prestress, wherein the processing depth of the threaded blind hole is not greater than the molten pool depth of the arc fuse additive process; S3. Screw a steel stud into the threaded blind hole at the mold base position where the prestress is required, and tighten the stud so that the axial prestress applied by the tightened stud to the mold base position where the threaded blind hole is located meets the design requirements; S4. An arc fuse additive layer is prepared on the surface of the side where the stud is screwed at the mold base position where the prestress needs to be applied to the pre-combustion chamber mold, and the stud is melted as the additive process is carried out during the arc fuse additive process. After each additive layer is added, the additive layer is hammered to make the surface of the additive layer smooth; S5. After the arc fuse additive processing is completed, the last additive layer is polished and the pre-combustion chamber forging is tempered to obtain the final strengthened pre-combustion chamber mold.

[0007] As a preferred solution, in step S4, the additive material for preparing the arc fuse additive layer is a nickel-based alloy or an iron-based alloy.

[0008] As a preferred solution, in step S3, the hardness of the steel material of the stud used is greater than the hardness of the additive material, and the melting point of the steel material is lower than the melting point of the additive material.

[0009] As a preferred solution, the steel material of the stud is high alloy structural steel.

[0010] As a preferred embodiment, in step S4, the processing parameters for hammering the additive layer are as follows: the hammering pressure on the additive layer is 0.5~1mm each time, the hammering pressure is 0.1~0.5Mpa, the moving speed of the hammer head is 1000~2000mm / min, and the hammering intervention temperature range is 20~550℃.

[0011] As a preferred solution, in step S5, the specific method of tempering the pre-combustion chamber forging is: S501. After the arc fuse additive processing is completed, the pre-combustion chamber forging is immediately returned to the furnace for the first time to heat up, and the heating temperature is 500-550°C; S502, after the first reheating is completed, the pre-combustion chamber forgings are placed in a heat preservation sand pit for the first slow cooling treatment, and the heat preservation temperature is 170~190℃; S503, after the first slow cooling treatment is completed, the pre-combustion chamber forgings are immediately returned to the furnace for a second heating, and the heating temperature is 500-550°C; S504, after the second reheating is completed, the pre-combustion chamber forgings are placed in a heat preservation sand pit for a second slow cooling treatment, and the heat preservation temperature is 170~190℃; S505. After the second slow cooling treatment is completed, the pre-combustion chamber forging is placed in the air to cool to room temperature, and the tempering treatment is completed to obtain the final strengthened pre-combustion chamber mold.

[0012] As a preferred solution, in step S501, the charging temperature of the pre-combustion chamber forgings before the first reheating is less than or equal to 450°C.

[0013] As a preferred solution, the tempering processing parameters of the first reheating in step S501 and the second reheating in step S503 are the same, the heating time is 0.3~0.5h, and the tempering holding time is determined according to the maximum geometric size of the precombustion chamber forging, and the holding time is 1h for every 50mm.

[0014] As a preferred solution, the slow cooling and heat preservation time of the first slow cooling treatment in step S502 and the second slow cooling treatment in step S504 are both greater than or equal to 12 hours.

[0015] As a preferred solution, for a newly manufactured pre-combustion chamber mold for a marine low-speed engine, a prestressed material reinforcement area is reserved at the local position where prestress needs to be applied, and then the method of steps S1 to S5 is used for reinforcement treatment; for a failed pre-combustion chamber mold for a marine low-speed engine, the failed part is cleaned and then the method of steps S1 to S5 is used for reinforcement treatment.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention is a method for strengthening the pre-combustion chamber mold of a marine low-speed engine based on prestressed additive manufacturing. The arc fuse additive process is used to perform additive reinforcement on the local position of the mold that needs to be strengthened, and studs are added to the local position of the mold that needs to be strengthened to apply prestress, so that the reinforced pre-combustion chamber mold can effectively reduce stress when resisting unbalanced loads, and the temperature of the additive layer is used to melt the studs during the additive process, so that the studs and the additive layer are fused into a whole. Since the hardness of the studs is greater than the hardness of the additive layer material, the overall hardness and strength can be improved after the screws are fused to the additive layer.

[0017] 2. In the method of the present invention, different prestresses are given to different areas by using studs according to the load conditions of the mold, and the studs are integrated with the mold during the additive process, thereby improving the tensile strength and toughness of the root area of ​​the protrusion, as well as the strength and hardness of the head area of ​​the protrusion, and significantly enhancing the comprehensive service performance and service life of the mold.

[0018] 3. In the method of the present invention, the additive layer is hammered, which not only makes the surface of the additive layer smooth to facilitate the addition of the next layer, but also has a stress relief effect, reduces the residual stress of the additive layer, and improves the strength of the additive layer; at the same time, the integration of the studs enables the entire mold to effectively resist shear when subjected to shear force, thereby improving the strength and hardness of the mold.

[0019] 4. In the method of the present invention, tempering heat treatment is also carried out after material addition to obtain stable tempered martensite, so as to achieve the effect of improving the stability of the pre-combustion chamber mold structure, so that the mold does not undergo structural transformation during use, and its geometric dimensions and performance tend to be stable. At the same time, it can also eliminate internal stress, improve toughness, and achieve an effective reinforcement effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to make the purpose, technical solution and advantages of the invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings, in which: Figure 1 is a flow chart of the method of the present invention; Figure 2 This is a schematic diagram of the prestressed strengthening area of ​​the pre-combustion chamber forging die; Figure 3 The schematic diagram is a schematic diagram of the installation state of applying prestress to the mold base by using studs; Figure 4 This is a simulation diagram of the stress of the mold without prestressing simulated by CAE software; Figure 5 This is a simulation diagram of the mold load stress with a small prestress simulated by CAE software; Figure 6 This is a simulation diagram of the mold load stress with a large prestress simulated by CAE software. DETAILED DESCRIPTION

[0021] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0022] It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. In the description of the present invention, it should be noted that the orientation or position relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. is based on the orientation or position relationship of the drawings, or the orientation or position relationship in which the invention product is usually placed when used, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance. In addition, the terms "horizontal", "vertical", etc. do not mean that the components are absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted. In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0023] The present invention provides a method for strengthening a pre-combustion chamber mold of a marine low-speed engine based on prestressed additive manufacturing, such as Figure 1 As shown, the method comprises the following steps: S1. According to the shape of the precombustion chamber forging and the stress condition of the precombustion chamber die during the forging process, determine the positions in the precombustion chamber die where prestress needs to be applied and the prestress design requirements required at the corresponding positions.

[0024] In specific implementation, it is necessary to analyze the stress conditions of different parts of the forging die and their usage requirements according to the shape and size of the pre-combustion chamber forging, as well as the load conditions of the pre-combustion chamber die during the forging process. The root of the protrusion requires higher tensile strength and toughness, and the head of the protrusion requires higher strength and hardness and needs to relieve the peak stress. This can determine the position where the pre-combustion chamber die needs to be prestressed and the design requirements for the prestress size required at the corresponding position. For example, Figure 2 In the example shown, analysis can determine that the concave waist areas on both sides of the pre-combustion chamber forging, as well as the bottom area, are areas that require functional enhancement. They can be marked and reserved for additive space areas in preparation for the subsequent addition of additive layers.

[0025] S2. Processing a threaded blind hole at the position of the mold base where the pre-combustion chamber mold needs to apply prestress, wherein the processing depth of the threaded blind hole is not greater than the molten pool depth of the arc fuse additive process.

[0026] After determining the position for applying prestress, it is necessary to prepare the corresponding threaded blind hole on the mold base. In the specific implementation, the corresponding threaded blind hole is prepared in advance at the position where the mold needs to apply prestress, and the stud is screwed into it. Since the arc fuse additive process is prepared in the subsequent stage to enhance the local position where the precombustion chamber forging needs to be prestressed, and it is hoped that the stud screwed into the threaded blind hole will gradually melt along with the additive process, the processing depth of the threaded blind hole is required to be no greater than the molten pool depth of the arc fuse additive process to ensure that the stud can be effectively melted during the arc fuse additive process.

[0027] S3. A steel stud is screwed into the threaded blind hole at the mold base position where prestress is required, and the stud is tightened so that the axial prestress applied by the tightened stud to the mold base position where the threaded blind hole is located meets the design requirements.

[0028] In this step, different prestress design requirements are given to different areas using studs according to the load conditions of the mold. In specific implementation, tools such as torque wrenches or torque electrodes can be used to tighten the studs according to the prestress design requirements to apply corresponding prestress to the mold base, so that the reinforced pre-combustion chamber mold can effectively reduce stress when resisting eccentric loads.

[0029] At the same time, since the subsequent steps are to use the arc fuse additive process to strengthen the local positions of the pre-combustion chamber forgings that need to be prestressed, and it is hoped that the studs will gradually melt together with the additive process to play a role of joint reinforcement, therefore, steel studs are used in this step to ensure that the hardness of the steel material of the studs is greater than the hardness of the additive material, and the melting point of the selected steel material needs to be lower than the melting point of the additive material. The specific selection of the stud material is determined based on comprehensive considerations of the selection of additive materials. At the same time, in order to ensure that the studs are completely melted, after the studs are tightened, the length of the studs exposed in the threaded blind hole should not be greater than the depth of the molten pool of the arc fuse additive process. For an example of the installation state of applying prestress to the mold base by stud tightening, please refer to Figure 3 shown.

[0030] S4. An arc fuse additive layer is prepared on the surface of the side where the stud is screwed at the position of the mold base where prestress needs to be applied to the pre-combustion chamber mold, and the stud is melted as the additive process is carried out during the arc fuse additive process. After each additive layer is added, the additive layer is hammered to make the surface of the additive layer smooth.

[0031] In this step, the studs and the additive materials gradually melt together and merge with the mold, thereby improving the tensile strength and toughness of the root area of ​​the protrusion, as well as the strength and hardness of the head area of ​​the protrusion, and significantly enhancing the comprehensive service performance and service life of the mold. In the specific implementation, the additive material is preferably a nickel-based alloy or an iron-based alloy, which not only ensures good strength after the additive, but also expands the selection range of the additive layer material. Correspondingly, the steel material of the stud is preferably high-alloy structural steel, which can have both high material hardness and a lower melting point than the additive material, ensuring that the studs are melted together in the arc fuse additive. For example, in the specific implementation, the studs can be selected as M4×4 12-grade standard full-thread studs made of high-alloy structural steel. The integration of the studs allows the mold as a whole to effectively resist shearing when it is subjected to shear force, thereby improving the strength and hardness of the mold.

[0032] The processing technology for preparing the arc fuse additive layer belongs to the existing technology, and the arc fuse additive processing parameters can be set as: arc fuse additive current 400A, arc fuse additive voltage 32V, and the diameter range of the fuse can be selected as 0.5~3.0mm.

[0033] Hammering the additive layer can not only make the surface of the additive layer flat to facilitate the addition of the next layer, but also relieve stress, reduce the residual stress of the additive layer, and improve the strength of the additive layer. In the specific implementation, the processing parameters for hammering the additive layer are preferably: the hammering pressure on the additive layer is 0.5~1mm each time, the hammering pressure is 0.1~0.5Mpa, the moving speed of the hammer head is 1000~2000mm / min, and the hammering intervention temperature range is 20~550℃; this can better ensure the flatness and stress relief effect of the hammering treatment of the additive layer.

[0034] S5. After the arc fuse additive processing is completed, the last additive layer is polished and the pre-combustion chamber forging is tempered to obtain the final strengthened pre-combustion chamber mold.

[0035] This step also involves tempering heat treatment after material addition to obtain stable tempered martensite, so as to improve the stability of the pre-combustion chamber mold structure. This ensures that the mold does not undergo structural changes during use, and its geometric dimensions and performance tend to be stable. It can also eliminate internal stress, improve toughness, and achieve an effective reinforcement effect.

[0036] In a specific implementation, the specific method of performing tempering treatment on the pre-combustion chamber forging in step S5 is: S501. After the arc fuse additive processing is completed, the pre-combustion chamber forging is immediately returned to the furnace for the first time to heat up at a heating temperature of 500-550°C.

[0037] In this step, the charging temperature of the precombustion chamber forgings before the first reheating is less than or equal to 450°C; the tempering processing parameters of the first reheating are: the heating time is 0.3~0.5h, the tempering holding time is determined according to the maximum geometric size of the precombustion chamber forgings, and the holding time is 1h for every 50mm.

[0038] S502. After the first re-melting and heating is completed, the pre-combustion chamber forgings are placed in a heat-insulating sand pit for the first slow cooling treatment, and the heat-insulating temperature is 170~190℃.

[0039] In this step, the slow cooling and heat preservation time of the first slow cooling treatment is greater than or equal to 12 hours. During this process, an infrared thermometer can be used to measure the temperature to detect the temperature of the slow cooling process.

[0040] S503, after the first slow cooling treatment is completed, the pre-combustion chamber forgings are immediately returned to the furnace for a second heating, and the heating temperature is 500-550°C; In this step, the tempering processing parameters of the second reheating and heating are the same as those of the first reheating and heating.

[0041] S504, after the second reheating is completed, the pre-combustion chamber forgings are placed in a heat preservation sand pit for a second slow cooling treatment, and the heat preservation temperature is 170~190℃; In this step, the slow cooling and heat preservation time of the second slow cooling treatment must also be greater than or equal to 12 hours. During this process, an infrared thermometer can be used to measure the temperature to detect the temperature of the slow cooling process.

[0042] S505. After the second slow cooling treatment is completed, the pre-combustion chamber forging is placed in the air to cool to room temperature, and the tempering treatment is completed to obtain the final strengthened pre-combustion chamber mold.

[0043] After the second slow cooling treatment, the temperature of the pre-combustion chamber forging is about 170~180℃, and then it is placed in the air to cool to room temperature to obtain stable tempered martensite, so as to achieve the effect of improving the stability of the pre-combustion chamber mold structure, thereby obtaining the final strengthened pre-combustion chamber mold.

[0044] The present invention provides a method for strengthening a pre-combustion chamber mold for a marine low-speed engine based on prestressed additive manufacturing. The method comprises the following steps: a corresponding threaded blind hole is prepared in advance at a position where the mold needs to apply prestress, and a prepared steel stud is screwed into the hole. When the stud is tightened, the axial preload applied by the stud to the position of the mold base body meets the design requirements, thereby applying a certain prestress to the mold base body. Then, the mold base body is subjected to arc fuse additive manufacturing. Each time an additive layer is formed, the additive layer is hammered to make the surface of the additive layer smooth. In this process, the hardness of the stud material is greater than The hardness of the additive material and the melting point of the stud material are lower than that of the additive material, so that the stud gradually melts as the additive process proceeds, and finally combines with the additive layer as a whole; the threaded blind hole is based on the molten pool depth of the arc fuse additive to ensure that the stud can gradually melt during the additive process; finally, tempering heat treatment is performed to improve the stability of the pre-combustion chamber mold structure, so that the mold does not undergo organizational changes during use, and its geometric size and performance tend to be stable. At the same time, it can also eliminate internal stress, improve toughness, and achieve an effective reinforcement effect.

[0045] In the specific application implementation, for the newly manufactured marine low-speed engine pre-combustion chamber mold, a prestressed additive reinforcement area is reserved at the local position where prestress needs to be applied, and then the method of steps S1 to S5 is used for strengthening treatment; for the failed marine low-speed engine pre-combustion chamber mold, the failed part is cleaned and then the method of steps S1 to S5 is used for strengthening treatment.

[0046] In order to verify the anti-eccentric load effect of the pre-combustion chamber mold after the prestressed material is strengthened by the present invention, the CAE software is used for simulation. The simulation results are as follows: Figure 4 , 5 As shown in Figure 6, all three figures are additive layers with the same material and thickness. The difference is Figure 4 The mold base in the mold is not prestressed by studs. Figure 5 and Figure 6 The studs in the method of the present invention are used to apply a certain amount of prestress to the mold base, wherein Figure 4 The prestress applied is small. Figure 5 The prestress applied is greater. Then the same stress is applied to the additive layer (that is, the pressure of the additive layer in the three figures is the same), and it is found that the additive layer with prestress applied ( Figure 5 , Figure 6 ) can effectively reduce stress when resisting eccentric load, while the additive layer without prestress ( Figure 4 ) The overall stress is too large, from which it is concluded that applying prestress can reduce the stress of the mold when it is loaded.

[0047] In summary, the present invention is a method for strengthening the pre-combustion chamber mold of a marine low-speed engine based on prestressed additive manufacturing. The arc fuse additive process is used to perform additive reinforcement on the local position of the mold that needs to be strengthened, and studs are added to the local position of the mold that needs to be strengthened to apply prestress, so that the reinforced pre-combustion chamber mold can effectively reduce stress when resisting offset loads, and the temperature of the additive layer is used to melt the studs during the additive process, so that the studs and the additive layer are fused into a whole. Since the hardness of the studs is greater than the hardness of the additive layer material, the overall hardness and strength can be improved after the screws are fused to the additive layer. In implementation, different prestresses are given to different areas by studs according to the load conditions of the mold, and the studs are integrated with the mold during the additive process, thereby improving the tensile strength and toughness of the root area of ​​the protrusion, as well as the strength and hardness of the head area of ​​the protrusion, and significantly enhancing the comprehensive service performance and service life of the mold. Hammering the additive layer can not only make the surface of the additive layer smooth for the next layer of additive, but also relieve stress, reduce the residual stress of the additive layer, and improve the strength of the additive layer; at the same time, the integration of the studs can effectively resist shear when the mold is subjected to shear force, thereby improving the strength and hardness of the mold. After the additive, tempering heat treatment is also performed to obtain stable tempered martensite to achieve the effect of improving the stability of the pre-combustion chamber mold structure, so that the mold does not undergo organizational changes during use, and its geometric dimensions and performance tend to be stable. At the same time, it can also eliminate internal stress, improve toughness, and achieve an effective reinforcement effect.

[0048] It can be understood that the present invention is described by some embodiments, and those skilled in the art are aware that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the present invention. Under the guidance of the present invention, these features and embodiments can be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. The embodiments described in the present invention are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all other embodiments obtained by ordinary technicians in the field without making creative work based on the embodiments in the present invention belong to the scope of protection of the present invention.

Claims

1. A method for strengthening a pre-combustion chamber mold for a marine low-speed engine based on prestressed additive manufacturing, characterized in that: The steps include: S1. According to the shape of the precombustion chamber forging and the stress condition of the precombustion chamber die during the forging process, determine the position where the precombustion chamber die needs to be prestressed and the prestress design requirements required at the corresponding position; S2. Processing a threaded blind hole at the position of the mold base where the pre-combustion chamber mold needs to apply prestress, wherein the processing depth of the threaded blind hole is not greater than the molten pool depth of the arc fuse additive process; S3. Screw a steel stud into the threaded blind hole at the mold base position where the prestress is required, and tighten the stud so that the axial prestress applied by the tightened stud to the mold base position where the threaded blind hole is located meets the design requirements; S4. An arc fuse additive layer is prepared on the surface of the side where the stud is screwed at the mold base position where the prestress needs to be applied to the pre-combustion chamber mold, and the stud is melted as the additive process is carried out during the arc fuse additive process. After each additive layer is added, the additive layer is hammered to make the surface of the additive layer smooth; S5. After the arc fuse additive processing is completed, the last additive layer is polished and the pre-combustion chamber forging is tempered to obtain the final strengthened pre-combustion chamber mold.

2. According to claim 1, the method for strengthening the pre-combustion chamber mold of a marine low-speed engine based on prestressed additive manufacturing is characterized in that: In the step S4, the additive material for preparing the arc fuse additive layer is a nickel-based alloy or an iron-based alloy.

3. The method for strengthening the pre-combustion chamber mold of a marine low-speed engine based on prestressed additive manufacturing according to claim 1 is characterized in that: In the step S3, the hardness of the steel material of the stud used is greater than the hardness of the additive material, and the melting point of the steel material is lower than the melting point of the additive material.

4. According to claim 3, the method for strengthening the pre-combustion chamber mold of a marine low-speed engine based on prestressed additive manufacturing is characterized in that: The steel material of the stud is high alloy structural steel.

5. According to claim 1, the method for strengthening the pre-combustion chamber mold of a marine low-speed engine based on prestressed additive manufacturing is characterized in that: In step S4, the processing parameters for hammering the additive layer are: the hammering pressure on the additive layer each time is 0.5~1mm, the hammering pressure is 0.1~0.5Mpa, the moving speed of the hammer head is 1000~2000mm / min, and the hammering intervention temperature range is 20~550℃.

6. According to claim 1, the method for strengthening the pre-combustion chamber mold of a marine low-speed engine based on prestressed additive manufacturing is characterized in that: In step S5, the specific method of tempering the pre-combustion chamber forging is: S501. After the arc fuse additive processing is completed, the pre-combustion chamber forging is immediately returned to the furnace for the first time to heat up, and the heating temperature is 500-550°C; S502, after the first reheating is completed, the pre-combustion chamber forgings are placed in a heat preservation sand pit for the first slow cooling treatment, and the heat preservation temperature is 170~190℃; S503, after the first slow cooling treatment is completed, the pre-combustion chamber forgings are immediately returned to the furnace for a second heating, and the heating temperature is 500-550°C; S504, after the second reheating is completed, the pre-combustion chamber forgings are placed in a heat preservation sand pit for a second slow cooling treatment, and the heat preservation temperature is 170~190℃; S505. After the second slow cooling treatment is completed, the pre-combustion chamber forging is placed in the air to cool to room temperature, and the tempering treatment is completed to obtain the final strengthened pre-combustion chamber mold.

7. The method for strengthening the pre-combustion chamber mold of a marine low-speed engine based on prestressed additive manufacturing according to claim 6 is characterized in that: In the step S501, the charging temperature of the pre-combustion chamber forgings before the first reheating is less than or equal to 450°C.

8. The method for strengthening the pre-combustion chamber mold of a marine low-speed engine based on prestressed additive manufacturing according to claim 6 is characterized in that: The tempering processing parameters of the first reheating in step S501 and the second reheating in step S503 are the same, the heating time is 0.3-0.5h, and the tempering holding time is determined according to the maximum geometric size of the pre-combustion chamber forging, and the holding time is 1h for every 50mm.

9. The method for strengthening the pre-combustion chamber mold of a marine low-speed engine based on prestressed additive manufacturing according to claim 6, characterized in that: The slow cooling and heat preservation time of the first slow cooling treatment in step S502 and the second slow cooling treatment in step S504 are both greater than or equal to 12 hours.

10. The method for strengthening the pre-combustion chamber mold of a marine low-speed engine based on prestressed additive manufacturing according to claim 1, characterized in that: For a newly manufactured pre-combustion chamber mold for a marine low-speed engine, a prestressed material reinforcement area is reserved at the local position where prestress needs to be applied, and then the method of steps S1 to S5 is used for reinforcement treatment; for a failed pre-combustion chamber mold for a marine low-speed engine, the failed part is cleaned and then the method of steps S1 to S5 is used for reinforcement treatment.

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