阅读说明：本技术 一种凸轮轴强化处理工艺 (Camshaft strengthening treatment process ) 是由 胡卫中 冯涛 王春燕 杜菲 吕国强 陈振晓 马风云 贾丽霞 焦丽 郝广杰 陈正虎 于 2021-07-15 设计创作，主要内容包括：本发明公开了一种凸轮轴强化处理工艺,属于机械加工领域,包括以下步骤：下料-正火-机械粗加工-校直-去应力回火-激光熔凝淬火强化-机械精加工-成品入库,凸轮轴整体采用正火处理,凸轮和轴径采用激光熔凝淬火进行强化。采用了本申请的处理工艺,既提高了凸轮轴表面硬度、耐磨性和抗接触疲劳能力,又满足高功率、高爆压、高可靠性重载发动机工况需求。(The invention discloses a camshaft strengthening treatment process, which belongs to the field of machining and comprises the following steps: blanking, normalizing, mechanically rough machining, straightening, stress-relieving tempering, laser melting quenching strengthening, mechanically finish machining, warehousing of finished products, normalizing the whole camshaft, and strengthening the cam and the shaft diameter by laser melting quenching. By adopting the treatment process, the surface hardness, the wear resistance and the contact fatigue resistance of the camshaft are improved, and the working condition requirements of a high-power, high-detonation pressure and high-reliability heavy-load engine are met.)

1. A camshaft strengthening treatment process comprises the following steps: blanking, normalizing, mechanical rough machining, straightening, destressing tempering, laser melting quenching strengthening, mechanical finish machining and finished product warehousing, and is characterized in that: the whole camshaft is subjected to normalizing treatment, and the cam and the shaft diameter are strengthened by laser melting and quenching.

2. The camshaft strengthening treatment process according to claim 1, wherein: the laser melting quenching process comprises the following steps:

s1: cleaning the surface of the camshaft;

s2: uniformly brushing a light absorption coating on the surface of the camshaft;

s3: fixing the processed camshaft on laser fusing equipment, rapidly scanning by laser beams, and heating the surface of the camshaft to be higher than the melting temperature;

s4: after the laser beam is scanned, the melting layer of the camshaft is subjected to self-condensation solid crystallization.

3. The camshaft strengthening treatment process according to claim 2, wherein: the laser melting equipment comprises a quenching numerical control system, the quenching numerical control system of the laser melting equipment controls a cam shaft to rotate and move, and a laser processing system adopts a helium-neon laser to perform accurate positioning and is matched with a light guide system to perform laser strengthening processing.

4. A camshaft reinforcement treatment process according to any one of claims 1 to 3, characterized in that: the laser fusing process parameters in step S3 are: the laser output power is 3kW, the defocusing amount is 220mm, and the scanning speed is 1.4-1.8 m/min.

5. The camshaft strengthening treatment process according to claim 3, wherein: in the step S3, the servo motor of the quenching numerical control system accurately controls the light guide system to follow up and down, and the defocusing amount is kept consistent.

6. The camshaft strengthening treatment process according to claim 2, wherein: the light absorbing coating in step S2 is a white silica light absorbing coating, and the ratio of alcohol is 1: dilution was carried out at a ratio of 2.

7. The camshaft strengthening treatment process according to claim 1, wherein: and (3) normalizing by heating in a trolley furnace at 850-890 ℃, keeping the temperature for 3h, discharging from the furnace, performing forced air cooling by adopting a spray and fan, and detecting the hardness.

8. The camshaft strengthening treatment process according to claim 2, wherein: the diameter of the light spot in the laser fusion quenching process in step S3 was 5 mm.

9. The camshaft strengthening treatment process according to claim 1, wherein: the allowance of mechanical finishing is 0.05-0.1 mm.

10. A camshaft reinforcing treatment process according to any one of claims 1 to 3 or 5 to 9, wherein: the cam and the shaft diameter of the finished camshaft are provided with a laser fusing scanning belt.

Technical Field

The invention belongs to the field of machining, and relates to a camshaft strengthening treatment process.

Background

The camshaft is an important driving and controlling part of the engine, and the main body of the camshaft is a cylindrical rod body with the same length as the cylinder group, and a plurality of cams and shaft diameters are arranged on the camshaft. It has a great influence on the reliability, the use efficiency and the service life of the engine. When the camshaft works, the intake and exhaust valves are accurately opened and closed at regular time according to the gas distribution phase, relative sliding friction is generated between the cam and the ejector rod, the profile of the cam is in a boundary lubrication or mixed lubrication state, and the formed lubrication film is thin and uneven, so that the cam surface often has failure modes such as scratch, pitting corrosion, rapid wear and the like. With the increasing power of engines and the increasing emission requirements of the environment, increasing the intake pressure by turbocharging has been one of the main ways to improve the performance of engines. The improvement of the air inlet and exhaust pressure of the engine also leads to the great improvement of the contact stress between the camshaft cam and the valve ejector rod. In order to ensure that the engine service performance, the service life and the emission index meet the regulations, the camshaft is required to have sufficient toughness and rigidity, and also have good contact fatigue resistance, scratch resistance and wear resistance.

The engine camshaft generally adopts materials such as nodular cast iron, alloy cast iron, steel and the like, adopts strengthening treatment technologies such as an induction quenching treatment technology, a gas nitriding (carburizing) technology, surface vapor deposition and the like, and then is polished, but the processes have the problems of multiple process parameter influence factors, uneven quenching layer, large deformation, need of increasing subsequent processing, complex process, low efficiency, serious pollution and the like.

The whole quenching after carburization produces uneven depth of an effective hardened layer, the carburization time is as long as nearly 30 hours, the nitriding technology is adopted for a longer time, the camshaft can be greatly deformed due to long-time heating and heat preservation, and the surface can be decarburized in the cooling process. In order to ensure the product performance, the subsequent processing amount after induction quenching, carburizing quenching and the like is within the range of 0.5-1mm, the subsequent processing efficiency is low due to higher surface hardness, and the hardened layer with the most wear-resistant and optimal contact fatigue performance is removed due to the deformation problem, so that the finished product on the surface of the camshaft has lower hardness and poorer contact fatigue resistance. Oil quenching is adopted for integral quenching, a large amount of oil smoke is easily generated, and ammonia gas is adopted as a carrier of N atoms in the nitriding process, so that severe environmental pollution can be caused. The surface structure of the camshaft formed by quenching into an acicular martensite structure has the advantages of high hardness, good wear resistance and the like, but the surface structure cannot play the greatest advantage because of subsequent grinding and polishing removal, and simultaneously the core structure is not refined due to poor cooling conditions, so that a coarse ferrite structure generated by long-time carburization remains. Therefore, a processing technology for strengthening treatment of the camshaft is urgently needed at present, the surface hardness, the wear resistance and the contact fatigue resistance of the distribution camshaft can be improved, and the working condition requirements of a high-power, high-detonation pressure and high-reliability heavy-load engine are met.

Disclosure of Invention

The invention provides a camshaft processing technology with integral heat treatment and surface laser composite reinforcement, which improves the surface hardness, wear resistance and contact fatigue resistance of the camshaft and meets the working condition requirements of a heavy-load engine with high power, high detonation pressure and high reliability.

In order to achieve the purpose, the invention adopts the technical scheme that:

a camshaft strengthening treatment process comprises the following steps: blanking, normalizing, mechanically rough machining, straightening, stress-relieving tempering, laser melting quenching strengthening, mechanically finish machining, warehousing of finished products, normalizing the whole camshaft, and strengthening the cam and the shaft diameter by laser melting quenching.

The technical scheme of the invention is further improved as follows: the laser melting quenching process comprises the following steps:

s1: cleaning the surface of the camshaft;

s2: uniformly brushing a light absorption coating on the surface of the camshaft;

s3: fixing the processed camshaft on laser fusing equipment, rapidly scanning by laser beams, and heating the surface of the camshaft to be higher than the melting temperature;

s4: after the laser beam is scanned, the melting layer of the camshaft is subjected to self-condensation solid crystallization.

The technical scheme of the invention is further improved as follows: the quenching numerical control system of the laser fusing equipment controls the camshaft to rotate and move, and the laser processing system adopts a helium-neon laser to perform accurate positioning and is matched with a light guide system to perform laser strengthening processing.

The technical scheme of the invention is further improved as follows: the laser fusing process parameters in step S3 are: the laser output power is 3kW, the defocusing amount is 220mm, and the scanning speed is 1.4-1.8 m/min.

The technical scheme of the invention is further improved as follows: in the step S3, the servo motor of the quenching numerical control system accurately controls the light guide system to follow up and down, and the defocusing amount is kept consistent.

The technical scheme of the invention is further improved as follows: the light-absorbing paint in step S2 was a white silica light-absorbing paint, and was diluted with alcohol (dilution ratio 1: 2) and brushed.

The technical scheme of the invention is further improved as follows: and (3) normalizing by heating in a trolley furnace at 850-890 ℃, keeping the temperature for 3h, discharging from the furnace, performing forced air cooling by adopting a spray and fan, and detecting the hardness.

The technical scheme of the invention is further improved as follows: the diameter of the light spot in the laser fusion quenching process in step S3 was 5 mm.

The technical scheme of the invention is further improved as follows: the allowance of mechanical finishing is 0.05-0.1 mm.

The technical scheme of the invention is further improved as follows: the cam and the shaft diameter of the finished camshaft are provided with 2-3 laser fusing scanning belts.

Due to the adoption of the technical scheme, the invention has the following technical effects:

the camshaft integral heat treatment and surface laser melting quenching composite strengthening process method replaces carburizing quenching and medium frequency induction quenching, and the metallographic structure of the surface layer of the camshaft treated by the process obtains superfine hidden needle martensite, so that the surface of the finished camshaft obtains high hardness and uniform depth of a hardened layer, the high wear resistance and high fatigue resistance of the product are ensured, meanwhile, the oil smoke environmental pollution caused by integral quenching is eliminated, and the risk factor of early failure of the engine caused by abnormal wear of the gas distribution camshaft in the prior art is completely eliminated.

The cam of the finished camshaft is provided with 3 laser melting scanning belts, the friction surface of the whole cam is hard and soft, the hardening belt can play a role of a hard framework and is wear-resistant, and the soft belt can store oil to play a role of lubrication and reduce the wear loss. Because the friction surface of the cam is in surface contact, the soft belt existing between the laser scanning belts is favorable for oil storage, cooling and lubrication.

Drawings

FIG. 1 is a metallographic structure of a laser hardened layer of the camshaft shaft diameter after being treated by the strengthening process of the invention;

FIG. 2 is a metallographic structure diagram of a laser hardened layer of a camshaft cam after being treated by the strengthening process.

Detailed Description

The technical solution of the present invention will be described in detail with reference to specific examples.

A camshaft strengthening treatment process comprises the following steps: blanking, normalizing, mechanically rough machining, straightening, stress-relieving tempering, laser melting quenching strengthening, mechanically finish machining, warehousing of finished products, normalizing the whole camshaft, and strengthening the cam and the shaft diameter by laser melting quenching.

The laser melting quenching process comprises the following steps:

s1: cleaning the surface of the camshaft;

s2: uniformly brushing a light absorption coating on the surface of the camshaft;

s3: the quenching numerical control system is used for controlling the camshaft to rotate and move, and the laser processing system adopts a helium-neon laser for accurate positioning and is matched with the light guide system for laser strengthening processing.

The quenching numerical control system of the laser melting equipment controls the camshaft to rotate and move through the turntable and the supporting frame, and the laser processing system adopts a helium-neon laser to perform accurate positioning and is matched with a light guide system to perform laser strengthening processing. In the step S3, the servo motor of the quenching numerical control system accurately controls the light guide system to follow up and down, and the defocusing amount is kept consistent.

The laser fusing process parameters are as follows: the laser output power is 3kW, the defocusing amount is 220mm, and the scanning speed is 1.4-1.8 m/min.

In step S2, the light absorbing coating is a white silica light absorbing coating, and the ratio of alcohol to water is 1: 2, carrying out diluted brushing, namely, the using amount of the alcohol is 2 times of the mass of the coating.

Example 1

Blanking a camshaft, integrally heating the camshaft by adopting a trolley furnace in a normalizing way, keeping the heating temperature at 850 ℃ for 3h, forcibly cooling the camshaft by adopting a spraying and air-blowing machine after discharging, detecting the hardness of 229HB, machining the camshaft and the diameter of the camshaft, straightening and stress relieving and tempering at 200 ℃. The laser melting quenching adopts 5kW carbon dioxide laser equipment, diluted white silica light absorption coating is uniformly coated on the cam and shaft diameter surfaces of the cam shaft after cleaning, melting strengthening processing is started after laser positioning, and the process parameters are as follows: the laser power is 3kW, the defocusing amount is 220mm, the scanning speed is 1.4m/min, and the diameter of a light spot is 5 mm. And air cooling is carried out after the laser fusing, and the step is finished. The surface hardness of the camshaft is measured to be 657HV, and the depth of a hardened layer is 0.94 mm. And (5) fine grinding to the size of a finished product, wherein the machining allowance is 0.07 mm.

Example 2

Blanking a camshaft, integrally heating the camshaft by adopting a trolley furnace in a normalizing way, keeping the heating temperature at 890 ℃, keeping the temperature for 3h, forcibly cooling the camshaft by adopting a spraying and air-blowing machine after discharging, detecting the hardness to be 235HB, machining the camshaft and the diameter of the camshaft, straightening and stress-relieving tempering at 200 ℃. The laser melting quenching adopts 5kW carbon dioxide laser equipment, diluted white silica light absorption coating is uniformly coated on the cam and shaft diameter surfaces of the cam shaft after cleaning, melting strengthening processing is started after laser positioning, and the process parameters are as follows: the laser power is 3kW, the defocusing amount is 220mm, the scanning speed is 1.5m/min, and the diameter of a light spot is 5 mm. And air cooling is carried out after the laser fusing, and the step is finished. The surface hardness of the camshaft was measured to be 661HV, and the depth of the hardened layer was 1.0 mm. And (5) performing fine grinding until the size of a finished product is obtained, wherein the machining allowance is 0.05 mm.

Example 3

Blanking a cam shaft, integrally heating the cam shaft by adopting a trolley furnace in a normalizing way, keeping the heating temperature at 880 ℃, preserving the heat for 3 hours, forcibly cooling the cam shaft by adopting a spraying and air-blowing machine after discharging, detecting the hardness to be 232HB, machining the cam shaft and the shaft diameter, straightening and tempering at 200 ℃ for stress relief. The laser melting quenching adopts 5kW carbon dioxide laser equipment, diluted white silica light absorption coating is uniformly coated on the cam and shaft diameter surfaces of the cam shaft after cleaning, melting strengthening processing is started after laser positioning, and the process parameters are as follows: the laser power is 3kW, the defocusing amount is 220mm, the scanning speed is 1.8m/min, and the diameter of a light spot is 5 mm. And air cooling is carried out after the laser fusing, and the step is finished. The surface hardness of the camshaft was measured at 670HV, and the depth of the hardened layer was 1.0 mm. And (5) performing fine grinding until the size of a finished product is obtained, wherein the machining allowance is 0.1 mm.

Example 4

Blanking a camshaft, integrally heating the camshaft by adopting a trolley furnace in a normalizing way, keeping the heating temperature at 890 ℃, keeping the temperature for 3h, forcibly cooling the camshaft by adopting a spraying and air-blowing machine after discharging, detecting the hardness of 240HB, machining the camshaft and the diameter of the camshaft, straightening and stress relieving and tempering at 200 ℃. The laser melting quenching adopts 5kW carbon dioxide laser equipment, diluted white silica light absorption coating is uniformly coated on the cam and shaft diameter surfaces of the cam shaft after cleaning, melting strengthening processing is started after laser positioning, and the process parameters are as follows: the laser power is 3kW, the defocusing amount is 220mm, the scanning speed is 1.6m/min, and the diameter of a light spot is 5 mm. When the laser fusing is carried out, the displacement between the scanning belts is controlled, for example, the interval between two scanning belts is set to be 3mm, the second scanning belt is started, the third scanning belt is controlled to be air-cooled after the laser fusing is carried out, and the steps of laser fusing and scanning are sequentially carried out. The surface hardness of the camshaft is detected to be 660HV, and the depth of a hardened layer is 0.96 mm. And (5) performing fine grinding until the size of a finished product is obtained, wherein the machining allowance is 0.1 mm. The cam of the finished camshaft is provided with three laser scanning belts, the friction surface of the whole cam is hard and soft, the hardened belt can play a role in hardness and abrasion resistance, the soft belt can store oil to play a role in lubrication and reduce the abrasion loss, and the soft belts between the scanning belts are in surface contact, so that the oil storage, cooling and lubrication are facilitated.

The gas distribution camshaft adopts the technical scheme of integral normalizing and laser melting quenching composite strengthening heat treatment, and is subjected to multi-round process parameter optimization, processing and detection. The surface hardness, effective hardening layer depth, deformation, subsequent processing amount, metallographic structure and other technical indexes are analyzed and compared, and the method is obviously superior to carburizing quenching and medium frequency induction quenching. As shown in fig. 1 and 2, the metallographic structure of the camshaft prepared in example 1 is shown in the drawings, it can be seen from the drawings that the central structure of the camshaft treated by the process of the present application is pearlite + ferrite, the intermediate transition structure is martensite + troostite + ferrite, and the surface structure is ultra-fine martensite, the gas distribution camshaft adopts the process scheme of the overall normalizing and laser melting quenching composite strengthening heat treatment, so that the surface hardness of the finished camshaft can reach above 650HV, the effective hardening depth reaches above 0.9mm, the deformation is only 0.02mm, the subsequent machining allowance is only 0.05-0.1mm, the surface metallographic structure obtains ultra-fine needle-like martensite, and the oil smoke environmental pollution caused by the overall quenching is eliminated. The surface of the finished distribution camshaft obtains high hardness and uniform depth of a hardened layer, and high wear resistance and high fatigue resistance of the product are ensured.

The invention can also be popularized and applied to the improvement of the quality reliability of other parts similar to slender shafts using carburizing quenching and induction quenching processes, and has wider popularization and application range.