Gradient controlled forging and controlled cooling method and system for non-quenched and tempered steel for fractured connecting rod

Abstract

The invention relates to the technical field of metal material hot working, and discloses a gradient controlled forging and controlled cooling method and system for non-quenched and tempered steel for an expansion breaking connecting rod. A cooling assembly of the gradient controlled forging and controlled cooling system comprises a cooling die, and a first cooling cavity in the cooling die corresponds to a preset expansion breaking groove path; the temperature control module is used for controlling the temperature of a preset expansion-breaking groove path in a cooling stage; the second cooling cavities are formed in the two sides of the first cooling cavity and used for regulating and controlling the temperature of the two sides of the path of the preset expansion breaking groove in the cooling stage. The third cooling cavity is arranged on the outer side of the second cooling cavity and used for regulating and controlling the temperature of the large head, the rod body and the small head in the cooling stage. According to the gradient controlled forging and controlled cooling method and system, in the cooling process, differential cooling control is conducted on different parts of the expansion breaking connecting rod, a gradient temperature field is formed, a preset expansion breaking groove path obtains a higher-hardness and finer structure, and follow-up expansion breaking is facilitated; and meanwhile, the rod body, the small head and other areas keep high toughness.

Description

Technical Field

[0001] This invention relates to the field of hot working technology of metallic materials, and in particular to a gradient controlled forging and controlled cooling method and system for non-quenched and tempered steel used in fracture-resistant connecting rods. Background Technology

[0002] The fracture-extension connecting rod is a moving part of the engine, and its performance requirements are stringent: the big end needs to have high hardness and low toughness to ensure that the crack can expand neatly and smoothly along the preset V-shaped or U-shaped groove during the fracture process, so as to obtain a flat separation surface; while the rod body and the small end need to have excellent comprehensive strength and toughness to withstand the continuous alternating tensile and compressive loads during engine operation and prevent fatigue fracture.

[0003] The current mainstream production process involves first selecting a general-purpose non-quenched and tempered steel, and then developing a universal forging and cooling process. Under traditional uniform cooling processes, to ensure that the weakest part (usually the larger end, due to its slow cooling rate) reaches its performance limit, the overall alloy content of the steel (e.g., V, Nb) must be increased to enhance its hardenability. While this ensures the performance of the larger end, it directly leads to severe performance overcapacity in areas with higher toughness requirements, such as the shaft and smaller end. This means that hardness and strength far exceed actual needs, while the toughness potential is not fully realized, resulting in a waste of expensive microalloying elements and increased costs. Summary of the Invention

[0004] Therefore, the purpose of this invention is to overcome the problems of redundant material properties and waste of alloy resources caused by the uniform cooling process in the production of fracture-resistant connecting rods. This invention provides a gradient controlled forging and cooling method and system for non-quenched and tempered steel for fracture-resistant connecting rods. During the cooling process, different parts of the fracture-resistant connecting rod are subjected to differentiated cooling control to form a gradient temperature field, so that the preset fracture groove path obtains higher hardness and finer structure, which is convenient for subsequent fracture. At the same time, the rod body, small end and other areas maintain high toughness, improve the strength and toughness matching of the overall fracture-resistant connecting rod, thereby improving product quality and performance.

[0005] To solve the above-mentioned technical problems, the present invention provides a gradient controlled forging and controlled cooling system for non-quenched and tempered steel used in fracture-resistant connecting rods, comprising:

[0006] A gradient controlled forging and controlled cooling system for non-quenched and tempered steel used in fracture-resistant connecting rods, characterized in that it includes a cooling assembly, the cooling assembly including a cooling mold, the cooling mold comprising:

[0007] The first cooling chamber corresponds to a preset expansion groove path and is used to regulate the temperature of the preset expansion groove path during the cooling stage.

[0008] The second cooling chamber is disposed on both sides of the first cooling chamber and is used to regulate the temperature on both sides of the preset expansion groove path during the cooling stage.

[0009] A third cooling chamber is disposed outside the second cooling chamber and is used to regulate the temperature of the rod body and the small end during the cooling stage.

[0010] Each cooling chamber contains a cooling medium.

[0011] Preferably, the length of the first cooling cavity is greater than the total length of the preset expansion groove path; the width of the first cooling cavity is less than or equal to the width of the preset expansion groove; the first cooling cavity contains a first cooling medium, which is liquid nitrogen atomization, and the temperature of the first cooling medium is less than or equal to -30°C.

[0012] The width of the second cooling cavity is greater than or equal to the width of the first cooling cavity; the second cooling cavity contains a second cooling medium, which is air, and the temperature of the second cooling medium is 10°C to 50°C.

[0013] The third cooling chamber contains a third cooling medium, which is air, and the temperature of the third cooling medium is 20°C to 80°C.

[0014] Preferably, the cooling assembly further includes:

[0015] The first nozzle array, with its air outlet facing the first cooling cavity area, is used to regulate the temperature of the preset expansion groove path during the cooling stage.

[0016] The second nozzle array, with its outlet facing the second cooling cavity area, is used to regulate the temperature on both sides of the preset expansion groove path during the cooling stage.

[0017] The third nozzle array, with its air outlet facing the third cooling chamber area, is used to regulate the temperature of the rod body and the small end during the cooling phase.

[0018] Each nozzle array is connected to an external cold source.

[0019] Preferably, the angle between the spray direction of each nozzle array and the normal to the connecting rod surface is 0° to 45°;

[0020] The nozzle diameter of the first nozzle array is less than or equal to the nozzle diameter of the second nozzle array, and the nozzle diameter of the second nozzle array is less than or equal to the nozzle diameter of the third nozzle array.

[0021] The injection pressure of the first nozzle array is greater than or equal to the injection pressure of the second nozzle array, and the injection pressure of the second nozzle array is greater than or equal to the injection pressure of the third nozzle array.

[0022] The first injection medium sprayed by the first nozzle array is liquid nitrogen atomized gas, and the temperature of the first injection medium is less than or equal to -30℃;

[0023] The second jet medium injected by the second nozzle array is air, and the temperature of the second jet medium is 10°C to 50°C;

[0024] The third jet medium sprayed by the third nozzle array is air, and the temperature of the third jet medium is 20°C to 80°C.

[0025] Preferably, the gradient controlled forging and cooling system further includes a final forging assembly, which includes a first final forging die and a second final forging die arranged in a mirror image. The final forging die includes:

[0026] The first final forging cavity corresponds to a preset expansion groove path and is used to regulate the temperature of the preset expansion groove path during the final forging stage.

[0027] The second final forging cavity is disposed on both sides of the first final forging cavity and is used to regulate the temperature on both sides of the preset expansion groove path during the final forging stage.

[0028] The third final forging cavity is located outside the second final forging cavity and is used to regulate the temperature of the rod body and the small end during the final forging stage.

[0029] Each final forging cavity is equipped with a heating module.

[0030] Preferably, the length of the first final forging cavity is greater than the total length of the preset expansion groove path; the width of the first final forging cavity is less than or equal to the width of the preset expansion groove; a row of heating device arrays is provided in the first final forging cavity for regulating the temperature of the preset expansion groove path during the final forging stage; the first heating temperature of the heating device array in the first final forging cavity is the sum of the first target final forging temperature and the first final forging compensation temperature difference.

[0031] The width of the second final forging cavity is greater than or equal to the width of the first final forging cavity; multiple rows of heating device arrays are sequentially arranged inside the second final forging cavity, and along the direction from the first final forging cavity to the third final forging cavity, the second heating temperature of each row of heating device arrays is: In the formula, From the first final forging cavity to the third final forging cavity, the second final forging cavity contains the first... Array of heating devices; For the second final forging cavity The second heating temperature of the array of heating devices; The first heating temperature is the heating device array inside the first final forging cavity. The third heating temperature is the heating element array inside the third final forging cavity. The number of rows of heating device arrays inside the second final forging cavity; To compensate for the temperature difference in the second final forging;

[0032] The third final forging cavity is equipped with an array of multiple rows of heating devices. The third heating temperature of the heating device array in the third final forging cavity is the sum of the third target final forging temperature and the third final forging compensation temperature difference.

[0033] On the other hand, the present invention provides a gradient controlled forging and controlled cooling method for non-quenched and tempered steel for fracture-resistant connecting rods, which is based on the gradient controlled forging and controlled cooling system for non-quenched and tempered steel for fracture-resistant connecting rods as described in claims;

[0034] The gradient controlled forging and controlled cooling method includes the following steps:

[0035] Step SS1: In the final forging stage of the fracture-resistant connecting rod, by controlling the temperature of the fracture-resistant connecting rod in the final forging die, the following conditions are achieved during the final forging process: the temperature of the preset fracture groove path of the fracture-resistant connecting rod is lower than the temperature on both sides of the preset fracture groove path, and the temperature of other areas of the fracture-resistant connecting rod is higher than the temperature on both sides of the preset fracture groove path.

[0036] Step SS2: After forging, by controlling the temperature of the fractured connecting rod in the cooling assembly, during the cooling process, the temperature of the preset fracture groove path of the fractured connecting rod is lower than the temperature on both sides of the preset fracture groove path, and the temperature of other areas of the fractured connecting rod is higher than the temperature on both sides of the preset fracture groove path.

[0037] Preferably, controlling the temperature of the fractured connecting rod in the final forging die during step SS1 includes:

[0038] Step SS11: Determine the Ar3 of the non-quenched and tempered steel based on its composition;

[0039] Step SS12: Based on the Ar3 of the non-quenched and tempered steel and the target performance of the fracture-resistant connecting rod, determine the target final forging temperatures of the first, second, and third regions of the fracture-resistant connecting rod; wherein, the first region corresponds to the first final forging cavity, the second region corresponds to the second final forging cavity, and the third region corresponds to the third final forging cavity;

[0040] Step SS13: Determine the heating temperature of each final forging cavity based on the target final forging temperatures of the first, second, and third regions of the expansion joint.

[0041] Preferably, the temperature of the fractured connecting rod in the controlled cooling assembly during step SS2 includes:

[0042] Step SS21: Determine the target cooling temperatures for the first, second, and third regions of the fracture-resistant connecting rod based on the composition of the non-quenched and tempered steel and the target performance of the fracture-resistant connecting rod.

[0043] Step SS22: Adjust the temperature and flow rate of the cooling medium in the cooling chamber according to the target cooling temperature and target performance of the first, second and third regions.

[0044] Preferably, the temperature of the fractured connecting rod in the cooling assembly during step SS2 further includes:

[0045] Step SS23: Obtain the actual surface temperature of the fractured connecting rod in the cooling mold;

[0046] Step SS24: Based on the actual surface temperature of the fractured connecting rod in the cooling mold and the target cooling temperatures of the first, second, and third regions, adjust the wind speed and temperature of each nozzle array to ensure that the actual surface temperature of the fractured connecting rod in the cooling mold is within the corresponding target cooling temperature.

[0047] Compared with the prior art, the above-described technical solution of the present invention has the following advantages:

[0048] The gradient controlled forging and cooling system for non-quenched and tempered steel used in fracture-resistant connecting rods described in this invention divides the cooling mold into a first cooling chamber, a second cooling chamber, and a third cooling chamber, corresponding to a preset fracture groove path, the areas on both sides of the preset fracture groove path, and the rod body and small end, respectively. This achieves differentiated cooling control for different parts of the fracture-resistant connecting rod. This facilitates the formation of a gradient temperature field during cooling, resulting in higher hardness and a finer microstructure for the preset fracture groove path, which is conducive to subsequent fracture. Simultaneously, it maintains high toughness in the rod body and small end, improving the overall strength-toughness matching of the connecting rod, thereby enhancing product quality and performance.

[0049] Furthermore, the gradient controlled forging and controlled cooling method for non-quenched and tempered steel used in the fracture-resistant connecting rod described in this invention uses dual gradient temperature control in the final forging stage and the cooling stage. First, a gradient temperature distribution is formed in the final forging stage, with a low temperature along the preset fracture groove path, medium temperature on both sides, and high temperature in other areas. Then, this gradient is maintained in the cooling stage, so that different areas obtain the most suitable microstructure during the phase transformation process. This is beneficial to improving the overall fatigue strength and reliability of the connecting rod while ensuring fracture performance. Attached Figure Description

[0050] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein:

[0051] Figure 1 This is a schematic diagram of a cooling mold in an embodiment of the present invention.

[0052] Figure 2 This is a schematic diagram of another structure of the cooling mold in an embodiment of the present invention.

[0053] Figure 3This is a schematic diagram of the structure of a final forging die in an embodiment of the present invention.

[0054] Figure 4 This is a schematic diagram of another structure of the final forging die in an embodiment of the present invention.

[0055] Figure 5 This is a schematic flowchart illustrating a gradient controlled forging and controlled cooling method for non-quenched and tempered steel used in a fracture-resistant connecting rod according to an embodiment of the present invention.

[0056] Figure 6 This is the microstructure of the first region of the fractured connecting rod in an embodiment of the present invention.

[0057] Figure 7 The microstructure of the first region of the fractured connecting rod obtained by the uniform cooling process.

[0058] Explanation of reference numerals in the accompanying drawings: 11. Large end; 110. Preset fracture groove path; 111. Preset fracture groove; 12. Rod body; 13. Small end; 2. Cooling mold; 21. First cooling chamber; 22. Second cooling chamber; 23. Third cooling chamber; 3. Final forging assembly; 301. First final forging chamber; 302. Second final forging chamber; 303. Third final forging chamber; 31. First final forging mold; 32. Second final forging mold; 33. Heating device array. Detailed Implementation

[0059] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0060] The large end 11, the shaft 12, and the small end 13 of the fracture-extension connecting rod have different performance requirements. The pre-set fracture groove path 110 of the large end 11 requires high hardness and low toughness to facilitate smooth fracture; other areas (such as the shaft 12) require high strength and toughness to withstand alternating loads. The properties of steel fundamentally depend on its microstructure (e.g., the morphology, size, and proportion of ferrite, pearlite, and bainite). The microstructure is determined by the transformation behavior of supercooled austenite within a specific temperature range. The cooling rate is a key external variable controlling phase transformation. This invention proposes a gradient controlled forging and controlled cooling method and system for non-quenched and tempered steel used in fracture-extension connecting rods. By segmented temperature control, different final forging and cooling processes can be applied to different parts of the fracture-extension connecting rod, thereby forming a microstructure optimally suited to its function within the connecting rod.

[0061] In application, this invention can improve the product yield by controlling the temperature of the final forging process and the cooling process in stages, based on the composition of the billet and the target performance of the product. Furthermore, based on the effects of the gradient controlled forging and cooling method and system according to this invention, the composition of the billet can be designed according to the target performance of the product, thereby ensuring the product yield while also achieving cost savings (reducing the addition or weight percentage of expensive metals).

[0062] Example 1: This example introduces a gradient controlled forging and controlled cooling system for non-quenched and tempered steel used in fracture-resistant connecting rods.

[0063] The gradient forging and cooling system of this embodiment includes a cooling component, which is used to regulate the temperature of each region of the billet (i.e., the fracture-resistant connecting rod) during the cooling stage. Furthermore, the gradient forging and cooling system of this embodiment may also include a final forging component 3, which is used to regulate the temperature of each region of the billet (i.e., the fracture-resistant connecting rod) during the final forging stage.

[0064] The final forging assembly 3 in this embodiment includes a first final forging mold 31 and a second final forging mold 32 arranged in a mirror image. Further, both the first final forging mold 31 and the second final forging mold 32 include a first final forging cavity 301, a second final forging cavity 302, and a third final forging cavity 303.

[0065] In application, the first final forging cavity 301, the second final forging cavity 302, and the third final forging cavity 303 are arranged side by side, and each final forging cavity has the same length. Furthermore, each final forging cavity is equipped with a heating module to regulate the temperature of each final forging cavity, thereby regulating the temperature of each region of the billet (i.e., the fracture connecting rod) in the final forging stage.

[0066] In practical applications, the fracture-resistant connecting rod includes a large end 11, a rod body 12, and a small end 13 connected sequentially. Further, the fracture-resistant connecting rod of this embodiment includes a first region, a second region, and a third region. The first region corresponds to the first cooling cavity 21, the second region corresponds to the second cooling cavity 22, and the third region corresponds to the third cooling cavity 23. Further, the first region can be a preset fracture groove path 110 of the fracture-resistant connecting rod; the second region can be both sides of the preset fracture groove path 110; and the third region can be other regions of the fracture-resistant connecting rod (including at least the rod body 12 and the small end 13).

[0067] In actual implementation, the pre-cut fracture groove 111 is a V-shaped or U-shaped groove pre-machined on the fracture-resistant connecting rod. It serves as a stress concentration point, guiding the crack to propagate neatly at a specific location, thereby achieving fracture-type separation of the connecting rod cap and the connecting rod body 12. The pre-cut fracture groove path 110 refers to a virtual line running along the bottom of this V-shaped or U-shaped groove, which is the pre-cut path for fracture to occur.

[0068] It is worth noting that the target microstructures formed in the first, second, and third regions of the fractured connecting rod obtained based on the gradient controlled forging and cooling system of the present invention are different.

[0069] In this embodiment, the first final forging cavity 301 corresponds to the preset expansion fracture groove path 110, which is used to regulate the temperature of the first region (i.e., the preset expansion fracture groove path 110) in the final forging stage.

[0070] In application, the length of the first final forging cavity 301 is greater than the total length of the preset fracture groove path 110 to ensure that the entire preset fracture groove path 110 is uniformly controlled. Simultaneously, the width of the first final forging cavity 301 is less than or equal to the width of the preset fracture groove. Further, the width of the first final forging cavity 301 is greater than the width of the preset fracture groove path 110, but less than or equal to the width of the preset fracture groove. Preferably, the width of the first final forging cavity 301 is half the width of the preset fracture groove, which avoids excessive temperature influence on the lateral areas and covers the preset fracture groove path 110, facilitating control of the low-temperature state of the preset fracture groove path 110.

[0071] In practical applications, a row of heating device arrays 33 is provided in the first final forging cavity 301 to regulate the temperature of the preset expansion groove path 110 during the final forging stage. Furthermore, the first heating temperature of the heating device array 33 in the first final forging cavity 301 is the sum of the first target final forging temperature and the first final forging compensation temperature difference.

[0072] In some embodiments, due to the presence of contact thermal resistance and the short contact time during final forging, compensation of the final forging die temperature is required to ensure that specific portions (first region, second region, and / or third region) of the fracture-resistant connecting rod reach the target final forging temperature (e.g., first target final forging temperature, second target final forging temperature, and / or third target final forging temperature) during final forging. For regions requiring cooling, the final forging die temperature needs to be significantly lower than the target final forging temperature (e.g., 100°C to 300°C lower); for regions requiring heat preservation, the final forging die temperature needs to be close to or slightly higher (e.g., 50°C higher) than the target final forging temperature of the workpiece.

[0073] In some embodiments, the specific temperature difference compensation range can be determined experimentally based on forging pressure, contact time, and billet thermophysical properties. Generally, for areas requiring cooling, the final forging die temperature is more than 100°C lower than the target final forging temperature; for areas requiring heat preservation, the final forging die temperature is 0°C to 100°C higher than the target final forging temperature.

[0074] In some embodiments, the final forging temperature difference compensation includes the following formula:

[0075] ;

[0076] In the formula, the subscript One, two, or three; For the first Final forging compensates for temperature differences; For the first Target final forging temperature; The compensation coefficient is typically set between 0.5 and 2.0. Further, the compensation coefficient is determined based on the thermal properties of the billet material, the contact heat transfer coefficient, and the holding time of the final forging pressure. If the contact heat transfer coefficient is large and the holding time of the final forging pressure is short, the compensation coefficient can be between 0.5 and 1.0; if the heat penetration depth is large and the material has strong heat storage capacity, the compensation coefficient can be between 1.0 and 2.0.

[0077] In some other embodiments, the compensation coefficient includes the following formula:

[0078] ;

[0079] In the formula, The material density of the fracture-resistant connecting rod is expressed in kg / m³. 3 ; The specific heat capacity of the connecting rod after expansion is expressed in J / (kg·℃). This refers to the depth of heat penetration, measured in meters (m). The contact heat transfer coefficient is expressed in W / (m²). 2 ·℃); The holding time for final forging pressure is expressed in seconds (s).

[0080] In this embodiment, the second final forging cavity 302 is disposed on both sides of the first final forging cavity 301, and is used to regulate the temperature on both sides of the preset expansion groove path 110 during the final forging stage. Preferably, there are two second final forging cavities 302, which are respectively disposed on both sides of the first final forging cavity 301.

[0081] In application, the width of each second final forging cavity 302 is greater than or equal to the width of the first final forging cavity 301. Further, the width of the second final forging cavity 302 is... The width of the first final forging cavity 301 is twice that of the first final forging cavity. Wherein, The number of rows of heating device array 33 inside the second final forging cavity 302.

[0082] In practical applications, to ensure a linear temperature increase within the second final forging cavity 302 from the first final forging cavity 301 to the third final forging cavity 303, a smooth temperature gradient transition is achieved within the second region (transition zone). This avoids abrupt temperature changes that could lead to uneven microstructure or stress concentration, ensuring the continuity of the microstructure and stable performance changes in the transition zone. In this embodiment, the second final forging cavity 302 is sequentially equipped with multiple rows of heating device arrays 33, and along the direction from the first final forging cavity 301 to the third final forging cavity 303, each row of heating device arrays 33 has a different second heating temperature.

[0083] Specifically, the second heating temperature of each row of heating device array 33 is: In the formula, From the first final forging cavity to the third final forging cavity, the second final forging cavity contains the first... Array of heating devices; For the second final forging cavity The second heating temperature of the array of heating devices; The first heating temperature is the heating device array inside the first final forging cavity. The third heating temperature is the heating element array inside the third final forging cavity. This refers to the number of rows of the heating device array within the second final forging cavity, typically... ; This is to compensate for the temperature difference during the second final forging.

[0084] In this embodiment, the third final forging cavity 303 is disposed outside the second final forging cavity 302, and is used to at least regulate the temperature of the rod body 12 and the small end 13 during the final forging stage.

[0085] In application, the third final forging cavity 303 includes two parts, one of which is located outside a second final forging cavity 302, and the other is located outside another second final forging cavity 302. The side of the second final forging cavity 302 adjacent to the first final forging cavity 301 is the inner side, and the side away from the first final forging cavity 301 is the outer side, forming a cavity gradient of low temperature, medium temperature, and high temperature from the middle (first final forging cavity 301) to the outside. This facilitates the formation of a gradient layout of low temperature, medium temperature, and high temperature along the preset fracture groove path 110 to both sides of the connecting rod.

[0086] In practical applications, the third final forging cavity 303 is equipped with a multi-row heating device array 33. The third heating temperature of the heating device array 33 in the third final forging cavity 303 is the sum of the third target final forging temperature and the third final forging compensation temperature difference. The cooling assembly in this embodiment includes a cooling mold 2, which is used to regulate the temperature of each region of the billet (i.e., the fractured connecting rod) during the cooling stage. Furthermore, the cooling assembly in this embodiment may also include a nozzle array, which is used to assist in regulating the temperature of each region of the billet (i.e., the fractured connecting rod) during the cooling stage.

[0087] The cooling mold 2 in this embodiment includes a first cooling cavity 21, a second cooling cavity 22 and a third cooling cavity 23, and each cooling cavity contains a cooling medium for regulating the temperature of each region of the blank (i.e., the expansion joint) during the cooling stage.

[0088] In application, the dimensions of the cooling chambers are similar to those of the corresponding final forging chambers. The first cooling chamber 21 corresponds to the first final forging chamber 301, the second cooling chamber 22 corresponds to the second final forging chamber 302, and the third cooling chamber 23 corresponds to the third final forging chamber 303. Specifically: the length of the first cooling chamber 21 is greater than the total length of the preset expansion groove path 110, the width of the first cooling chamber 21 is less than or equal to the width of the preset expansion groove 111, and the width of the second cooling chamber 22 is greater than or equal to the width of the first cooling chamber 21.

[0089] In practical applications, each cavity is connected to a cooling medium supply end on one side and a cooling medium recovery end on the other side. Specifically, the first cooling cavity 21 is connected to the first cooling medium supply end, the second cooling cavity 22 is connected to the second cooling medium supply end, and the third cooling cavity 23 is connected to the third cooling medium supply end.

[0090] In this embodiment, the first cooling cavity 21 corresponds to the preset expansion groove path 110, which is used to regulate the temperature of the preset expansion groove path 110 during the cooling stage.

[0091] In application, the first cooling medium within the first cooling chamber 21 is liquid nitrogen atomized gas, and the temperature of the first cooling medium is less than or equal to -30°C. Furthermore, the first cooling rate of the first region is controlled by controlling the flow rate of the first cooling medium within the first cooling chamber 21. Even further, the first cooling rate is ≥15°C / s.

[0092] In this embodiment, the second cooling chamber 22 is disposed on both sides of the first cooling chamber 21, and is used to regulate the temperature on both sides of the preset expansion groove path 110 during the cooling stage. Preferably, there are two second cooling chambers 22, which are respectively disposed on both sides of the first cooling chamber 21, and are used to regulate the temperature on both sides of the preset expansion groove path 110 during the cooling stage.

[0093] In application, the width of the second cooling chamber 22 is greater than or equal to the width of the transition zone caused by the temperature difference between the first cooling chamber 21 and the third cooling chamber 23, ensuring that the transition zone is completely within the cooling range of the second cooling chamber 22 and avoiding cooling blind spots or sudden temperature changes. The width of the transition zone can be determined based on the cooling time, the thermal diffusivity of the blank, and the temperature difference between the first and third regions.

[0094] Furthermore, the width of each second cooling cavity 22 is greater than or equal to the width of the first cooling cavity 21. Furthermore, the width of the second cooling cavity 22 is... The width of the first cooling cavity 21 is twice that of the first cooling cavity 21. Wherein, The number of rows of heating device array 33 inside the second final forging cavity 302.

[0095] In practical applications, the second cooling medium within the second cooling chamber 22 is air, and its temperature ranges from 10°C to 50°C. Furthermore, the second cooling rate of the second region is controlled by controlling the flow rate of the second cooling medium within the second cooling chamber 22. Even further, the second cooling rate is between 5°C / s and 15°C / s.

[0096] In this embodiment, the third cooling chamber 23 is disposed outside the second cooling chamber 22, and is used to regulate the temperature of at least the rod body 12 and the small end 13 during the cooling stage. Preferably, it can also regulate the temperature of the large end 11 during the cooling stage.

[0097] In application, the third cooling chamber 23 includes two chambers, one of which is located outside one second cooling chamber 22, and the other is located outside the other second cooling chamber 22. The side of the second cooling chamber 22 adjacent to the first cooling chamber 21 is the inner side, and the side away from the first cooling chamber 21 is the outer side, forming a cooling gradient from the middle (first cooling chamber 21) to the outside in the form of low temperature, medium temperature, and high temperature. This facilitates the formation of a gradient structure along the preset fracture groove path 110 on both sides of the connecting rod, thereby ensuring high toughness and fatigue resistance.

[0098] In practical applications, the third cooling medium in the third cooling chamber 23 of this embodiment is air, and the temperature of the third cooling medium is between 20°C and 80°C. Furthermore, the third cooling rate of the third region is controlled by controlling the flow rate of the third cooling medium within the third cooling chamber 23. Even further, the third cooling rate is between 1°C / s and 5°C / s.

[0099] The nozzle array in this embodiment includes a first nozzle array, a second nozzle array, and a third nozzle array, and each nozzle array is connected to an external cold source to assist the cooling mold 2 in regulating the temperature of each area of ​​the blank (i.e., the expansion joint) during the cooling stage.

[0100] In application, the angle between the spray direction of each nozzle array and the normal to the connecting rod surface is 0° to 45°. Preferably, the angle between the spray direction and the normal to the connecting rod surface is 15° to 45°. More preferably, the angle between the spray direction and the normal to the connecting rod surface is 30°, which can enhance the impact and coverage effect of the airflow on the surface of the fractured connecting rod, and improve the heat exchange efficiency. Furthermore, the vertical projection of the spray direction on the cooling mold 2 is parallel to the first direction. The first direction is parallel to the extension direction of the long side of the first cooling cavity 21, which is beneficial for uniform cooling along the preset fractured groove path 110 and reduces the non-uniformity of temperature distribution.

[0101] In practical applications, the nozzle diameter of the first nozzle array is less than or equal to the nozzle diameter of the second nozzle array, and the nozzle diameter of the second nozzle array is less than or equal to the nozzle diameter of the third nozzle array. Preferably, the nozzle diameter of the first nozzle array is smaller than the nozzle diameter of the second nozzle array, and the nozzle diameter of the second nozzle array is smaller than the nozzle diameter of the third nozzle array. In some embodiments, the nozzle diameter of the first nozzle array is 0.1 mm to 0.5 mm, the nozzle diameter of the second nozzle array is 0.5 mm to 3 mm, and the nozzle diameter of the third nozzle array is 3 mm to 6 mm.

[0102] In actual implementation, the injection pressure of the first nozzle array is greater than or equal to the injection pressure of the second nozzle array, and the injection pressure of the second nozzle array is greater than or equal to the injection pressure of the third nozzle array. In some embodiments, the injection pressure of the third nozzle array is 0.5 MPa to 2.0 MPa, the second nozzle array is 0.2 MPa to 1.0 MPa, and the first nozzle array is 0.1 MPa to 0.5 MPa.

[0103] In this embodiment, the air outlet of the first nozzle array is aligned with the area of ​​the first cooling cavity 21 to regulate the temperature of the preset expansion groove path 110 during the cooling stage.

[0104] In application, the first nozzle array includes a row of nozzles arranged along a first direction, with the nozzles spaced at equal intervals. Furthermore, the first injection medium sprayed by the first nozzle array is liquid nitrogen atomized gas, and the temperature of the first injection medium is less than or equal to -30°C.

[0105] In this embodiment, the air outlet of the second nozzle array is aligned with the area of ​​the second cooling cavity 22 to regulate the temperature on both sides of the preset expansion groove path 110 during the cooling stage.

[0106] In application, two sets of second nozzle arrays are provided. One set of second nozzle arrays is aligned with the area of ​​the second cooling chamber 22 on one side of the second cooling chamber 22; the other set of second nozzle arrays is aligned with the area of ​​the second cooling chamber 22 on the other side of the second cooling chamber 22. Further, each set of second nozzle arrays includes at least one row of nozzles arranged along a first direction, with the nozzles evenly spaced. When each set of second nozzle arrays includes multiple rows of nozzles, the rows of nozzles are parallel to each other. Even further, the second spray medium sprayed by the second nozzle array is air, and the temperature of the second spray medium is between 10°C and 50°C.

[0107] In this embodiment, the air outlet of the third nozzle array is aligned with the area of ​​the third cooling chamber 23 to regulate the temperature of the large end 11, the shaft 12, and the small end 13 during the cooling phase.

[0108] In application, the third nozzle array comprises two sets, one set positioned outside a second nozzle array and the other positioned outside another second nozzle array. The side of the second nozzle array adjacent to the first nozzle array is designated as the inner side, and the side facing away from the first nozzle array is designated as the outer side. Furthermore, the third nozzle array sprays air as the third spray medium, and the temperature of the third spray medium is between 20°C and 80°C.

[0109] Example 2: This example introduces a gradient controlled forging and controlled cooling method for non-quenched and tempered steel used in fracture-resistant connecting rods.

[0110] The gradient controlled forging and cooling method of this embodiment can be implemented based on the gradient controlled forging and cooling system for non-quenched and tempered steel used in the fracture-resistant connecting rod described in Embodiment 1.

[0111] The gradient controlled forging and controlled cooling method of this embodiment includes step SS2. Further, refer to... Figure 5 Step SS1 may be included before step SS2.

[0112] Step SS1: In the final forging stage of the fracture-resistant connecting rod, by controlling the temperature of the fracture-resistant connecting rod in the final forging die, the following conditions are achieved during the final forging process: the temperature of the preset fracture groove path 110 (i.e., the first region) of the fracture-resistant connecting rod is lower than the temperature of both sides of the preset fracture groove path 110 (i.e., the second region), and the temperature of other regions of the fracture-resistant connecting rod (i.e., the third region) is higher than the temperature of both sides of the preset fracture groove path 110.

[0113] In application, during the final forging process: the temperature of the first zone is the first target final forging temperature; the temperature of the second zone is the second target final forging temperature; and the temperature of the third zone is the third target final forging temperature. Wherein, the first target final forging temperature < the second target final forging temperature < the third target final forging temperature.

[0114] In some embodiments, controlling the temperature of the fractured connecting rod in the final forging die during step SS1 includes steps SS11 to SS13.

[0115] Step SS11: Determine the Ar3 of the non-quenched and tempered steel based on its composition.

[0116] In application, Ar3 of non-quenched and tempered steel is the temperature at which austenite begins to precipitate proeutectoid ferrite upon cooling, while Ar1 is the temperature at which austenite completes its transformation to pearlite upon cooling (i.e., the temperature at which austenite disappears). Ar3 and Ar1 of non-quenched and tempered steel can be estimated based on chemical composition using empirical formulas. Specifically, Ar3 of non-quenched and tempered steel includes the following formula:

[0117] ;

[0118] In the formula, The eutectoid temperature of pure iron (or very low carbon steel) can be obtained from the Fe-C equilibrium diagram; This refers to the types and quantities of elements added to non-quenched and tempered steel. ; The first non-quenched and tempered steel Adding elements, and An integer in the range [1, Q]. The first non-quenched and tempered steel The weight percentage of each added element, in wt% The first non-quenched and tempered steel The strength of the effect of each added element on the temperature of proeutectoid ferrite precipitation, in °C / wt%.

[0119] ;

[0120] In the formula, The temperature at which austenite disappears (i.e., phase transformation) in pure iron (or very low carbon steel) can be obtained from the Fe-C equilibrium diagram.

[0121] It is worth noting that the added elements in non-quenched and tempered steel are elements other than Fe and impurities in non-quenched and tempered steel, such as: C, Si, Mn, Ni, P, S, Al, N, Cr, V, Nb and / or Ti. as well as This can be determined through multiple linear regression analysis. Specifically, the added element is used as the independent variable, and the measured temperature of proeutectoid ferrite precipitation / phase transformation temperature is used as the dependent variable for multiple linear regression analysis.

[0122] Step SS12: Determine the target final forging temperatures of the first, second, and third regions of the fracture-resistant connecting rod based on the Ar3 of the non-quenched and tempered steel and the target properties (e.g., target hardness) of the fracture-resistant connecting rod.

[0123] When applied, the target final forging temperature can be flexibly adjusted according to different steel grades and performance requirements to improve process adaptability.

[0124] Furthermore, the target performance of the fracture-resistant connecting rod in this embodiment includes target hardness: (1) For the preset fracture groove path 110 (first region): high hardness and low toughness are required to ensure a smooth fracture surface and controllable crack propagation during fracture; for example, the first target hardness range can be 280HB to 320HB. (2) For both sides of the preset fracture groove path 110 (second region): as a transition zone, it needs to have a certain strength, toughness and crack propagation resistance; for example, the second target hardness range can be 240HB to 270HB. (3) For other regions (third region, including at least the rod body 12 and the small end 13): high strength and toughness are required to withstand alternating loads; for example, the third target hardness range can be 220HB to 250HB.

[0125] In practical applications, the target final forging temperature includes the following formula:

[0126] ;

[0127] In the formula, the subscript One, two, or three; For the first The first in the region Target final forging temperature; For the first The first in the region Target hardness; The base hardness is, for example, 220HB; This is the hardness sensitivity coefficient, which can be determined based on the steel grade or the content of added elements, and is expressed in °C / HB; in some embodiments, The value ranges from 0.8℃ / HB to 1.2℃ / HB.

[0128] Step SS13: Determine the heating temperature of each final forging cavity based on the target final forging temperatures of the first, second, and third regions of the expansion joint.

[0129] In application, the first heating temperature of the heating device array 33 in the first final forging cavity 301 is the sum of the first final forging temperature of the first final forging cavity 301 and the first final forging compensation temperature difference; the second heating temperature of the heating device array 33 in the second final forging cavity 302 is the sum of the second final forging temperature of the second final forging cavity 302 and the third final forging compensation temperature difference; and the third heating temperature of the heating device array 33 in the third final forging cavity 303 is the sum of the third final forging temperature of the third final forging cavity 303 and the third final forging compensation temperature difference.

[0130] In practical applications, the temperature difference compensation for final forging is determined based on the aforementioned content, and will not be repeated here.

[0131] In some embodiments, multiple rows of heating device arrays 33 are sequentially arranged in the second final forging cavity 302. Along the direction from the first final forging cavity 301 to the third final forging cavity 303, the second heating temperature of each row of heating device arrays 33 is determined according to the foregoing, and will not be repeated here.

[0132] Step SS2: After forging, by controlling the temperature of the fractured connecting rod in the cooling assembly, during the cooling process, the temperature of the preset fracture groove path 110 of the fractured connecting rod is lower than the temperature on both sides of the preset fracture groove path 110, and the temperature of other areas of the fractured connecting rod is higher than the temperature on both sides of the preset fracture groove path 110.

[0133] In application, after forging, the fracture-breaking connecting rod is transferred from the final forging die to the cooling die 2.

[0134] In practical applications, during the cooling process: the temperature of the first zone is the first target cooling temperature; the temperature of the second zone is the second target cooling temperature; and the temperature of the third zone is the third target cooling temperature.

[0135] In some embodiments, in order to obtain the target cooling rate in different regions and thereby enable the fractured connecting rod to form an ideal microstructure, the temperature control of the fractured connecting rod in the cooling assembly during step SS2 of this embodiment includes steps SS21 to SS22.

[0136] Step SS21: Determine the target cooling temperatures for the first, second, and third regions of the fracture-resistant connecting rod based on the composition of the non-quenched and tempered steel and the target performance of the fracture-resistant connecting rod.

[0137] In application, for the first region (preset fracture groove path 110): rapid cooling to a lower temperature is required to suppress the precipitation of proeutectoid ferrite and promote the formation of fine pearlite or bainite to achieve the first target hardness and ensure high hardness. For the second region (both sides of the preset fracture groove path 110): a moderate cooling rate is required to obtain a ferrite + pearlite mixed structure to achieve the second target hardness, balancing hardness and toughness. For the third region (at least the shaft 12, small end 13, etc.): slower cooling is required to promote the full precipitation of proeutectoid ferrite, forming a mixed structure of coarse ferrite and pearlite to achieve the third target hardness and ensure high toughness.

[0138] In practical applications, the target cooling temperature includes the following formula:

[0139] ;

[0140] In the formula, the subscript One, two, or three; For the first The first in the region Target cooling temperature For the first The first in the region Target hardness; For reference temperature, Ar3 or Ar1 is generally used: under the subscript When the subscript is 1 or 2, take Ar3 as the index. When the value is three, take Ar1; The base hardness is, for example, 220HB; The hardness temperature coefficient can be determined based on the steel grade and cooling medium, and its unit is °C / HB; in some embodiments, The range is from 1.℃ / HB to 2.0℃ / HB.

[0141] Step SS22: Adjust the temperature and flow rate of the cooling medium in the cooling chamber according to the target cooling temperature and target performance (e.g., hardness) of the first, second, and third regions.

[0142] When applied, step SS22 includes steps SS221 to SS222.

[0143] Step SS221: Determine the target cooling rate for the first, second, and third regions based on the target properties (e.g., hardness) of the first, second, and third regions.

[0144] In application, based on the CCT curve and / or the cooling rate and hardness relationship curve, the target cooling rate of the first, second and third regions is determined according to the target performance of the first, second and third regions.

[0145] Step SS222: Adjust the temperature and flow rate of the cooling medium in the cooling chamber according to the target cooling temperature and target cooling rate of the first, second and third regions.

[0146] In application, the temperature and flow rate of the cooling medium within the cooling chamber are defined by the following formula:

[0147] ;

[0148] In the formula, the subscript One, two, or three; For the first The first in the cooling chamber The first cooling medium Flow rate For the first The first in the region Target cooling rate, For the first The thickness of the cooling cavity, For the first The convective heat transfer coefficient of the cooling cavity is expressed in W / (m³). 2 ·℃); For the first The first cooling medium Flow rate; For the first Material density of the region; For the first Specific heat capacity of the region.

[0149] In some embodiments, the cooling mold 2 includes an upper cooling mold 2 and a lower cooling mold 2. In some other embodiments, the cooling mold 2 is an open mold, consisting only of the lower cooling mold 2. When the cooling mold 2 is an open mold...

[0150] Furthermore, in order to improve the accuracy of temperature control and compensate for cooling deviations caused by factors such as workpiece shape and initial temperature fluctuations, the temperature control of the cooling component in step SS2 of this embodiment may also include steps SS23 to SS24.

[0151] Step SS23: Obtain the actual surface temperature of the fractured connecting rod in the cooling mold 2.

[0152] In application, an infrared thermal imager is used to scan the surface of the fractured connecting rod in the open cooling mold 2 to obtain a two-dimensional temperature distribution. Based on the two-dimensional temperature distribution, the actual surface temperatures of the first, second, and third regions of the fractured connecting rod are determined.

[0153] Step SS24: Based on the actual surface temperature of the fractured connecting rod in the cooling mold 2 and the target cooling temperatures of the first, second, and third regions, adjust the wind speed and temperature of each nozzle array so that the actual surface temperature of the fractured connecting rod in the cooling mold 2 is within the corresponding target cooling temperature.

[0154] When applying this method, calculate the difference between the actual surface temperature and the target cooling temperature of the first, second, and third regions: In the formula, the subscript One, two, or three; For the first Difference; For the first The first in the region Actual surface temperature; For the first The first in the region Target cooling temperature.

[0155] When the difference is negative, it indicates that the actual surface temperature of the corresponding area is lower than the target cooling temperature, and cooling needs to be reduced. The adjustment strategy is to first reduce the injection pressure of the corresponding nozzle array to reduce the air velocity; if the injection pressure has reached the lower limit, then increase the temperature of the injection medium to increase the air temperature.

[0156] When the difference is positive, it indicates that the actual surface temperature of the corresponding area is higher than the target cooling temperature, and cooling needs to be enhanced. The adjustment strategy is to prioritize increasing the injection pressure of the corresponding nozzle array to increase the air velocity; if the injection pressure has reached its upper limit, then reduce the temperature of the injection medium to reduce the air temperature.

[0157] Example 3: This example, using the system described in Example 1 and the method described in Example 2, obtains a fracture-resistant connecting rod with a round steel specification of φ60mm to φ80mm. The ferrite content in the first region can reach 55%, and the ferrite content in the first region is less than 15%. (Reference) Figure 6 .

[0158] In this embodiment, the tensile strength of the second region of the fracture-resistant connecting rod is 1150 MPa to 1250 MPa, the yield strength is 830 MPa to 900 MPa, the elongation after fracture is 12.5% ​​to 14.5%, and the reduction of area is 35% to 40%; the tensile strength of the third region is 1200 MPa to 1300 MPa, the yield strength is 850 MPa to 950 MPa, the elongation after fracture is 14% to 17%, and the reduction of area is 35% to 40%; the decarburized layer depth on the connecting rod surface is less than or equal to 0.2 μm, and the slag shedding rate of the part during fracture is less than or equal to 8 ppm.

[0159] Meanwhile, by employing a uniform final forging process and a uniform cooling process on the billet of this embodiment, the resulting φ60mm to φ80mm fracture-resistant connecting rod has a ferrite content of less than 30% in the first region and a ferrite content of greater than 21% in the second region, as referenced. Figure 7 The tensile strength of both the second and third regions is less than 1150 MPa, and the yield strength is less than 800 MPa.

[0160] In summary, the present invention, without increasing alloy costs or performing subsequent heat treatment, achieves differentiated and gradient microstructure and mechanical property matching in different functional areas (preset fracture groove path 110, its two side transition areas, rod body 12 and small end 13 (or also including part of the large end 11 area)) within the same fracture-resistant connecting rod part through the coordinated control of forging and cooling processes. This simultaneously meets the performance requirements of easy fracture in the large end 11 (high hardness, low toughness) and strong and tough load-bearing capacity (high strength, high toughness) in the rod body 12 and small end 13 parts, and overcomes the problems of material property redundancy, alloy resource waste and insufficient process strength and toughness matching caused by traditional uniform cooling processes.

[0161] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A gradient controlled forging and controlled cooling system for non-quenched and tempered steel used in fracture-resistant connecting rods, characterized in that, Includes a cooling assembly, the cooling assembly including a cooling mold, the cooling mold comprising: The first cooling chamber corresponds to a preset expansion groove path and is used to regulate the temperature of the preset expansion groove path during the cooling stage. The second cooling chamber is disposed on both sides of the first cooling chamber and is used to regulate the temperature on both sides of the preset expansion groove path during the cooling stage. A third cooling chamber is disposed outside the second cooling chamber and is used to regulate the temperature of the rod body and the small end during the cooling stage. Each cooling chamber contains a cooling medium.

2. The gradient controlled forging and controlled cooling system for non-quenched and tempered steel used in fracture-resistant connecting rods according to claim 1, characterized in that, The length of the first cooling cavity is greater than the total length of the preset expansion groove path; the width of the first cooling cavity is less than or equal to the width of the preset expansion groove; the first cooling cavity contains a first cooling medium, which is liquid nitrogen atomization, and the temperature of the first cooling medium is less than or equal to -30°C. The width of the second cooling cavity is greater than or equal to the width of the first cooling cavity; the second cooling cavity contains a second cooling medium, which is air, and the temperature of the second cooling medium is 10°C to 50°C. The third cooling chamber contains a third cooling medium, which is air, and the temperature of the third cooling medium is 20°C to 80°C.

3. The gradient controlled forging and controlled cooling system for non-quenched and tempered steel used in fracture-resistant connecting rods according to claim 1, characterized in that, The cooling assembly also includes: The first nozzle array, with its air outlet facing the first cooling cavity area, is used to regulate the temperature of the preset expansion groove path during the cooling stage. The second nozzle array, with its outlet facing the second cooling cavity area, is used to regulate the temperature on both sides of the preset expansion groove path during the cooling stage. The third nozzle array, with its air outlet facing the third cooling chamber area, is used to regulate the temperature of the rod body and the small end during the cooling phase. Each nozzle array is connected to an external cold source.

4. The gradient controlled forging and controlled cooling system for non-quenched and tempered steel used in fracture-resistant connecting rods according to claim 3, characterized in that, The angle between the spray direction of each nozzle array and the normal to the connecting rod surface is 0° to 45°; The nozzle diameter of the first nozzle array is less than or equal to the nozzle diameter of the second nozzle array, and the nozzle diameter of the second nozzle array is less than or equal to the nozzle diameter of the third nozzle array. The injection pressure of the first nozzle array is greater than or equal to the injection pressure of the second nozzle array, and the injection pressure of the second nozzle array is greater than or equal to the injection pressure of the third nozzle array. The first injection medium sprayed by the first nozzle array is liquid nitrogen atomized gas, and the temperature of the first injection medium is less than or equal to -30℃; The second jet medium injected by the second nozzle array is air, and the temperature of the second jet medium is 10°C to 50°C; The third jet medium sprayed by the third nozzle array is air, and the temperature of the third jet medium is 20°C to 80°C.

5. The gradient controlled forging and controlled cooling system for non-quenched and tempered steel used in fracture-resistant connecting rods according to claim 1, characterized in that, The gradient controlled forging and cooling system further includes a final forging assembly, which includes a first final forging die and a second final forging die arranged in a mirror image. The final forging die includes: The first final forging cavity corresponds to a preset expansion groove path and is used to regulate the temperature of the preset expansion groove path during the final forging stage. The second final forging cavity is disposed on both sides of the first final forging cavity and is used to regulate the temperature on both sides of the preset expansion groove path during the final forging stage. The third final forging cavity is located outside the second final forging cavity and is used to regulate the temperature of the rod body and the small end during the final forging stage. Each final forging cavity is equipped with a heating module.

6. The gradient controlled forging and controlled cooling system for non-quenched and tempered steel used in fracture-resistant connecting rods according to claim 5, characterized in that, The length of the first final forging cavity is greater than the total length of the preset expansion groove path; the width of the first final forging cavity is less than or equal to the width of the preset expansion groove; a row of heating device arrays is provided in the first final forging cavity to regulate the temperature of the preset expansion groove path during the final forging stage; the first heating temperature of the heating device array in the first final forging cavity is the sum of the first target final forging temperature and the first final forging compensation temperature difference. The width of the second final forging cavity is greater than or equal to the width of the first final forging cavity; multiple rows of heating device arrays are sequentially arranged inside the second final forging cavity, and along the direction from the first final forging cavity to the third final forging cavity, the second heating temperature of each row of heating device arrays is: In the formula, From the first final forging cavity to the third final forging cavity, the second final forging cavity contains the first... Array of heating devices; For the second final forging cavity The second heating temperature of the array of heating devices; The first heating temperature is the heating device array inside the first final forging cavity. The third heating temperature is the heating element array inside the third final forging cavity. The number of rows of heating device arrays inside the second final forging cavity; To compensate for the temperature difference in the second final forging; The third final forging cavity is equipped with an array of multiple rows of heating devices. The third heating temperature of the heating device array in the third final forging cavity is the sum of the third target final forging temperature and the third final forging compensation temperature difference.

7. A gradient controlled forging and controlled cooling method for non-quenched and tempered steel used in fracture-resistant connecting rods, characterized in that, This is achieved based on the gradient controlled forging and controlled cooling system for non-quenched and tempered steel used in fracture-resistant connecting rods as described in any one of claims 1 to 6; The gradient controlled forging and controlled cooling method includes the following steps: Step SS1: In the final forging stage of the fracture-resistant connecting rod, by controlling the temperature of the fracture-resistant connecting rod in the final forging die, the following conditions are achieved during the final forging process: the temperature of the preset fracture groove path of the fracture-resistant connecting rod is lower than the temperature on both sides of the preset fracture groove path, and the temperature of other areas of the fracture-resistant connecting rod is higher than the temperature on both sides of the preset fracture groove path. Step SS2: After forging, by controlling the temperature of the fractured connecting rod in the cooling assembly, during the cooling process, the temperature of the preset fracture groove path of the fractured connecting rod is lower than the temperature on both sides of the preset fracture groove path, and the temperature of other areas of the fractured connecting rod is higher than the temperature on both sides of the preset fracture groove path.

8. The gradient controlled forging and controlled cooling method for non-quenched and tempered steel used in fracture-resistant connecting rods according to claim 7, characterized in that, The temperature control of the fractured connecting rod in the final forging die during step SS1 includes: Step SS11: Determine the Ar3 of the non-quenched and tempered steel based on its composition; Step SS12: Based on the Ar3 of the non-quenched and tempered steel and the target performance of the fracture-resistant connecting rod, determine the target final forging temperatures of the first, second, and third regions of the fracture-resistant connecting rod; wherein, the first region corresponds to the first final forging cavity, the second region corresponds to the second final forging cavity, and the third region corresponds to the third final forging cavity; Step SS13: Determine the heating temperature of each final forging cavity based on the target final forging temperatures of the first, second, and third regions of the expansion joint.

9. The gradient controlled forging and controlled cooling method for non-quenched and tempered steel used in fracture-resistant connecting rods according to claim 8, characterized in that, The temperature of the fractured connecting rod in the controlled cooling assembly during step SS2 includes: Step SS21: Determine the target cooling temperatures for the first, second, and third regions of the fracture-resistant connecting rod based on the composition of the non-quenched and tempered steel and the target performance of the fracture-resistant connecting rod. Step SS22: Adjust the temperature and flow rate of the cooling medium in the cooling chamber according to the target cooling temperature and target performance of the first, second and third regions.

10. The gradient controlled forging and controlled cooling method for non-quenched and tempered steel used in fracture-resistant connecting rods according to claim 9, characterized in that, The temperature control of the fractured connecting rod in the cooling assembly during step SS2 also includes: Step SS23: Obtain the actual surface temperature of the fractured connecting rod in the cooling mold; Step SS24: Based on the actual surface temperature of the fractured connecting rod in the cooling mold and the target cooling temperatures of the first, second, and third regions, adjust the wind speed and temperature of each nozzle array to ensure that the actual surface temperature of the fractured connecting rod in the cooling mold is within the corresponding target cooling temperature.

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