Preparation process of high-temperature-resistant strong-power cam shaft

Abstract

The invention discloses a high-temperature-resistant strong-power camshaft, which is characterized in that the camshaft comprises the following raw materials in percentage by weight: 0.35%-0.45% of C, 12%-15% of Cr, 3%-5% of Ni, 0.8%-1.2% of Mo, 0.2%-0.4% of V, 0.8%-1.2% of Si, 0.5%-0.8% of Mn, 1.5%-2.0% of W, 0.1%-0.3% of Nb and 0.05%-0.15% of Ti. Through combination of optimized component design, unique subzero treatment and other processes, the comprehensive mechanical property of the camshaft is remarkably improved, the camshaft can still keep extremely high surface hardness and fatigue strength in a high-temperature environment, and the camshaft is particularly suitable for high-pressurization and high-horsepower strong-power engines.

Description

Technical Field

[0001] This invention belongs to the field of camshafts, and more specifically, relates to a high-temperature resistant, high-power camshaft. Background Technology

[0002] As a core transmission component in power equipment such as internal combustion engines and compressors, the camshaft's performance directly determines the equipment's power output efficiency and service life. Under high-load conditions, the camshaft must withstand cyclic impact loads and friction for extended periods, while also facing the high-temperature environment generated during equipment operation. This places stringent requirements on its high-temperature resistance, wear resistance, and toughness. Existing camshafts are mostly made of conventional alloy materials such as 45# steel and 20CrMnTi, manufactured through tempering and surface hardening processes. However, conventional materials have low contents of high-temperature resistant elements such as Cr and Mo (generally Cr≤5%, Mo≤0.5%), which easily lead to softening of the microstructure under high-temperature environments. This results in decreased surface hardness and accelerated wear on the camshaft, which in turn causes reduced power transmission accuracy and increased equipment failure rate. For example, after operating at 500℃ for 1000 hours, the tensile strength of a certain type of internal combustion engine camshaft can decrease by more than 15%, failing to meet the requirements of long-term high-load use. To improve high-temperature resistance, some technologies attempt to increase the content of alloying elements or optimize heat treatment processes, but these have significant limitations: On the one hand, blindly increasing the Cr and Ni content can easily lead to increased material brittleness, causing cracks during forging; on the other hand, existing processes mostly use air cooling or ordinary oil cooling, resulting in uneven cooling rates and excessive differences in hardness between the camshaft substrate and its surface, which can easily lead to internal stress concentration and the risk of fracture during use. Furthermore, conventional casting processes do not strictly control impurity content, leading to the enrichment of impurity elements at grain boundaries, further reducing the material's high-temperature stability. In summary, current camshafts, in terms of material composition and manufacturing process, cannot simultaneously meet the comprehensive requirements of high temperature resistance, high power and long service life. There is an urgent need to develop a camshaft that takes into account both high temperature stability and mechanical properties, as well as the corresponding manufacturing technology. Summary of the Invention

[0003] In view of this, the technical problem to be solved by the present invention is to provide a high-temperature resistant and high-power camshaft manufacturing process to solve the problems of poor high-temperature resistance, insufficient hardness, easy breakage of existing camshafts, and difficulty in balancing high-temperature stability and mechanical properties in materials and processes.

[0004] To address the aforementioned technical problems, this invention discloses a high-temperature resistant, high-power camshaft. The raw material composition of this camshaft includes: C: 0.35%-0.45%, Cr: 12%-15%, Ni: 3%-5%, Mo: 0.8%-1.2%, V: 0.2%-0.4%, Si: 0.8%-1.2%, Mn: 0.5%-0.8%, W: 1.5%-2.0%, Nb: 0.1%-0.3%, and Ti: 0.05%-0.15%.

[0005] According to one embodiment of the present invention, the raw material composition of the camshaft includes: C: 0.35%, Cr: 12%, Ni: 3%, Mo: 0.8%, V: 0.2%, Si: 0.8%, Mn: 0.5%, W: 1.5%, Nb: 0.1%, Ti: 0.05%.

[0006] According to one embodiment of the present invention, the raw material composition of the camshaft includes: C: 0.4%, Cr: 14%, Ni: 4%, Mo: 1%, V: 0.3%, Si: 1%, Mn: 0.65%, W: 1.75%, Nb: 0.2%, Ti: 0.10%.

[0007] According to one embodiment of the present invention, the raw material composition of the camshaft includes: C: 0.45%, Cr: 15%, Ni: 5%, Mo: 1.2%, V: 0.4%, Si: 1.2%, Mn: 0.8%, W: 2.0%, Nb: 0.3%, Ti: 0.15%.

[0008] According to an embodiment of the present invention, the manufacturing process of the above-mentioned high-temperature resistant and high-power camshaft is characterized by comprising the following steps: 1) Raw material proportioning and smelting: The alloy raw materials are provided by mass percentage as follows: C: 0.35%-0.45%, Cr: 12%-15%, Ni: 3%-5%, Mo: 0.8%-1.2%, V: 0.2%-0.4%, Si: 0.8%-1.2%, Mn: 0.5%-0.8%, W: 1.5%-2.0%, Nb: 0.1%-0.3%, Ti: 0.05%-0.15%; the balance being Fe and unavoidable impurities; the above alloy raw materials are placed in a medium-frequency induction furnace and smelted into molten steel with uniform composition at 1580~1650℃; 2) Refining and casting: The molten steel obtained in step 1) is transferred to an LF refining furnace under argon protection for refining, adjusting the composition and reducing the sulfur and oxygen content, and then cast into camshaft billets; 3) Forging and pretreatment: The camshaft billet is heated to 1150~1200℃ for multi-directional die forging to form a camshaft blank; after forging, the blank is normalized at a temperature of 900~930℃, and then air-cooled to room temperature. 4) Rough machining: Rough turning and drilling of the center hole are performed on the pre-treated camshaft blank; 5) Heat treatment: The rough-machined camshaft blank is subjected to quenching, cryogenic treatment and tempering in sequence; Quenching: Under a protective atmosphere, the workpiece is heated to 860~890℃, held at that temperature for a period of time and then rapidly oil-quenched; Cryogenic treatment: The quenched workpiece is immediately transferred to a cryogenic environment of -80℃ ~ -196℃ and held for 1-4 hours; Tempering: The cryogenically treated workpiece is heated to 520~580℃, held at that temperature and then air-cooled. 6) Finishing and surface treatment: The heat-treated workpiece is precision ground to the design dimensions, then the cam part is subjected to ultrasonic induction hardening, and finally all surfaces are shot peened for strengthening.

[0009] According to one embodiment of the present invention, in step (1) above, the heating rate of the vacuum induction melting furnace is 10℃-15℃ / min, and electromagnetic stirring is used during the melting process, with a stirring speed of 300-500r / min.

[0010] According to one embodiment of the present invention, in step (3) above, after surface quenching, a low-temperature tempering treatment is performed. The low-temperature tempering temperature is 180℃-220℃, the holding time is 1-1.5h, and the cam is air-cooled to reduce the internal stress on the cam surface.

[0011] According to one embodiment of the present invention, in step (4) above, stress-relief annealing is performed after finishing, with an annealing temperature of 300℃-350℃ and a holding time of 1-1.5h, followed by furnace cooling to room temperature.

[0012] Compared with the prior art, the present invention can achieve the following technical effects: By combining optimized composition design with unique cryogenic treatment and other processes, the overall mechanical properties of the camshaft are significantly improved, enabling it to maintain extremely high surface hardness and fatigue strength even in high-temperature environments. It is particularly suitable for high-boost, high-horsepower engines.

[0013] Of course, any product implementing this invention does not necessarily need to achieve all of the technical effects described above at the same time. Detailed Implementation

[0014] The following examples illustrate the implementation of the present invention in detail, thereby enabling a full understanding of how the present invention uses technical means to solve technical problems and achieve technical effects, and allowing for its implementation.

[0015] A high-temperature resistant, high-power camshaft, the raw material composition of which includes: C: 0.35%-0.45%, Cr: 12%-15%, Ni: 3%-5%, Mo: 0.8%-1.2%, V: 0.2%-0.4%, Si: 0.8%-1.2%, Mn: 0.5%-0.8%, W: 1.5%-2.0%, Nb: 0.1%-0.3%, Ti: 0.05%-0.15%.

[0016] Therefore, three sets of embodiments with different proportions were carried out according to the above method.

[0017] Example 1 Raw material ratio: By mass percentage, the raw material composition of the camshaft in this embodiment is as follows: C: 0.35%, Cr: 12%, Ni: 3%, Mo: 0.8%, V: 0.2%, Si: 0.8%, Mn: 0.5%, W: 1.5%, Nb: 0.1%, Ti: 0.05%, with the balance being Fe and unavoidable impurities, wherein P≤0.03%, S≤0.02%, and Cu≤0.2%. Manufacturing process: (1) Raw material proportioning and smelting: Weigh the alloy raw materials according to the above proportions, place them in a medium frequency induction furnace, heat them to 1580℃ at 10℃ / min, and stir them electromagnetically at 300r / min during the smelting process. Keep them at the temperature for 2.5h to obtain molten steel with uniform composition. (2) Refining and casting: The molten steel is transferred to the LF refining furnace protected by argon gas, and the refining time is 1.5h. After adjusting the composition, it is cast into a camshaft billet. (3) Forging and pretreatment: The billet is heated to 1150℃ for multi-directional die forging, and then normalized at 900℃. After holding at 900℃ for 1.5h, it is air-cooled to room temperature. (4) Rough machining: Rough turning and drilling of the center hole are performed on the blank, with a machining allowance of 2mm; (5) Heat treatment: Heat the workpiece to 860℃ under a protective atmosphere, hold for 1 hour and then quickly oil quench; then transfer to a -80℃ cryogenic environment and hold for 4 hours; then heat to 520℃ for tempering, hold for 2 hours and then air cool. (6) Finishing and surface treatment: Grind to the design size, perform ultrasonic induction hardening on the cam part, and finally perform shot peening on the entire surface. Example 2 Raw material ratio: By mass percentage, the raw material composition is as follows: C: 0.4%, Cr: 14%, Ni: 4%, Mo: 1%, V: 0.3%, Si: 1%, Mn: 0.65%, W: 1.75%, Nb: 0.2%, Ti: 0.10%, with the balance being Fe and unavoidable impurities (P≤0.03%, S≤0.02%, Cu≤0.2%). Manufacturing process: (1) Raw material proportioning and smelting: The raw materials are placed in a medium frequency induction furnace, heated to 1620℃ at 12℃ / min, and electromagnetically stirred at 400r / min for 2 hours to obtain molten steel; (2) Refining and casting: Refining in an LF refining furnace under argon protection for 2 hours, and then casting into a billet; (3) Forging and pretreatment: The billet is forged at 1180℃ in a multi-directional die, then normalized at 920℃ after forging, held at the temperature for 1.8h and air-cooled; (4) Rough machining: Rough turn and drill the center hole, leaving a machining allowance of 1.5mm; (5) Heat treatment: Heating at 875℃ in a protective atmosphere and holding for 1.2h followed by oil quenching; cryogenic holding at -120℃ for 2.5h; tempering at 550℃ and holding for 2.2h followed by air cooling; (6) Finishing and surface treatment: After fine grinding, the cam is subjected to ultrasonic induction hardening, full-surface shot peening, and after surface hardening, it is tempered at 180℃ for 1 hour and then air-cooled to reduce internal stress. Example 3 Raw material ratio: By mass percentage, the raw material composition is as follows: C: 0.45%, Cr: 15%, Ni: 5%, Mo: 1.2%, V: 0.4%, Si: 1.2%, Mn: 0.8%, W: 2.0%, Nb: 0.3%, Ti: 0.15%, with the balance being Fe and unavoidable impurities (P≤0.03%, S≤0.02%, Cu≤0.2%). Manufacturing process: (1) Raw material proportioning and smelting: The temperature is raised to 1650℃ in a medium frequency induction furnace at 15℃ / min, and the mixture is stirred electromagnetically at 500r / min and kept at the temperature for 1.8h to obtain molten steel; (2) Refining and casting: Refining in an LF refining furnace under argon protection for 2.2 hours, then casting the billet; (3) Forging and pretreatment: The billet is forged at 1200℃ in a multi-directional die, then normalized at 930℃ after forging, held at the temperature for 2 hours and air-cooled; (4) Rough machining: rough turning and drilling of the center hole, leaving a machining allowance of 1mm; (5) Heat treatment: Heating at 890℃ in a protective atmosphere and holding for 1.5h followed by oil quenching; cryogenic holding at -196℃ for 1h; tempering at 580℃ and holding for 2.5h followed by air cooling; (6) Finishing and surface treatment: After finishing, the cam is subjected to ultrasonic induction hardening and full-surface shot peening. After finishing, it is stress-relief annealed at 300℃ for 1 hour and then cooled to room temperature in the furnace. In summary, in Example 1, the camshaft base hardness is 28 HRC and the cam surface hardness is 58 HRC. After holding at 600℃ for 1000 hours, the tensile strength decreases by 4.8% and the yield strength decreases by 7.5%, with no defects such as cracks or wear, meeting the requirements for high-load power equipment. In Example 2, the camshaft base hardness is 30 HRC and the surface hardness is 60 HRC. After holding at 620℃ for 800 hours, the tensile strength decreases by 3.2% and the yield strength decreases by 5.8%, exhibiting superior mechanical properties and high-temperature resistance, suitable for higher load conditions. In Example 3, the camshaft base hardness is 32 HRC and the surface hardness is 62 HRC. After holding at 650℃ for 500 hours, the tensile strength decreases by 2.5% and the yield strength decreases by 4.2%, exhibiting optimal high-temperature resistance and mechanical properties, suitable for application in extremely high-load and high-temperature power equipment scenarios.

[0018] In summary, this invention, through optimized component design and unique cryogenic treatment processes, significantly improves the overall mechanical properties of the camshaft, enabling it to maintain extremely high surface hardness and fatigue strength even in high-temperature environments. It is particularly suitable for high-boost, high-horsepower engines.

[0019] The foregoing description illustrates and describes several preferred embodiments of the present invention. However, as previously stated, it should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the inventive concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A high temperature resistant high power camshaft, characterized in that, The raw material composition of the camshaft comprises: C: 0.35%-0.45%, Cr: 12%-15%, Ni: 3%-5%, Mo: 0.8%-1.2%, V: 0.2%-0.4%, Si: 0.8%-1.2%, Mn: 0.5%-0.8%, W: 1.5%-2.0%, Nb: 0.1%-0.3%, Ti: 0.05%-0.15%.

2. The high-temperature-resistant, high-strength power camshaft of claim 1, wherein, The raw material composition of the camshaft comprises: C: 0.35%, Cr: 12%, Ni: 3%, Mo: 0.8%, V: 0.2%, Si: 0.8%, Mn: 0.5%, W: 1.5%, Nb: 0.1%, Ti: 0.05%.

3. The high-temperature-resistant, high-stress camshaft of claim 1, wherein, The raw material composition of the camshaft comprises: C: 0.4%, Cr: 14%, Ni: 4%, Mo: 1%, V: 0.3%, Si: 1%, Mn: 0.65%, W: 1.75%, Nb: 0.2%, Ti: 0.10%.

4. The high-temperature-resistant, high-stress camshaft of claim 1, wherein, The raw material composition of the camshaft comprises: C: 0.45%, Cr: 15%, Ni: 5%, Mo: 1.2%, V: 0.4%, Si: 1.2%, Mn: 0.8%, W: 2.0%, Nb: 0.3%, Ti: 0.15%.

5. The process of making high temperature resistant high strength power camshaft as claimed in claim 1 wherein, The method comprises the following steps: 1) Raw material proportioning and smelting: providing alloy raw materials with the following components in percentage by mass: C: 0.35%-0.45%, Cr: 12%-15%, Ni: 3%-5%, Mo: 0.8%-1.2%, V: 0.2%-0.4%, Si: 0.8%-1.2%, Mn: 0.5%-0.8%, W: 1.5%-2.0%, Nb: 0.1%-0.3%, Ti: 0.05%-0.15%; the balance is Fe and inevitable impurities; placing the above alloy raw materials in a medium-frequency induction furnace and smelting into molten steel with uniform components at 1580-1650℃; 2) Refining and pouring: transferring the molten steel obtained in step 1) into a LF refining furnace under argon protection for refining, adjusting the components and reducing the contents of sulfur and oxygen, and then pouring into a camshaft casting blank; 3) Forging and pretreatment: heating the camshaft casting blank to 1150-1200℃ for multi-directional die forging to form a camshaft blank; after forging, performing normalizing treatment on the blank at a normalizing temperature of 900-930℃, and then air cooling to room temperature; 4) Rough machining: rough turning and drilling a center hole on the pretreated camshaft blank; 5) Heat treatment: sequentially performing quenching, deep cryogenic treatment and tempering treatment on the rough machined camshaft blank; wherein the quenching treatment: heating the workpiece to 860-890℃ under a protective atmosphere, maintaining for a period of time, and then rapidly oil quenching; the deep cryogenic treatment: immediately transferring the quenched workpiece into a deep cryogenic environment of -80℃ to -196℃ for 1-4 hours; the tempering treatment: heating the deep cryogenic treated workpiece to 520-580℃, maintaining, and then air cooling. 6) Finishing and surface treatment: the workpiece after heat treatment is finished to the design size, then the cam part is super audio frequency induction hardened, and finally the whole surface is treated by shot peening.

6. The process for making high temperature resistant high dynamic force camshaft as claimed in claim 5 wherein, In step (1), the temperature rising rate of the vacuum induction melting furnace is 10-15℃ / min, and electromagnetic stirring is used during the melting process with a stirring speed of 300-500r / min.

7. The process of making high temperature resistant high dynamic force camshaft as claimed in claim 5 wherein, In step (3), low-temperature tempering treatment is further conducted after the surface quenching treatment, the low-temperature tempering temperature is 180-220℃, the holding time is 1-1.5h, and the air cooling is used to reduce the internal stress of the cam surface.

8. The process of making high temperature resistant high dynamic force camshaft as claimed in claim 5 wherein, In step (4), stress relief annealing treatment is further conducted after the finishing, the annealing temperature is 300-350℃, the holding time is 1-1.5h, and the furnace cooling to room temperature is used.