Strengthen the application in the production of th

Strengthen the application in the production of auto parts

engineers in the auto manufacturing industry increasingly rely on shot peening technology to improve and improve the fatigue life of key auto parts, and take this factor into full consideration and attention at the beginning of the design of cars, trucks, motorcycles and so on. The application of this shot blasting/shot blasting strengthening technology and process now also includes several (1) mechanical process structures: almost most of the engine parts are set in the calculation of China's economy entering the "new normal", including:

leaf spring and round spring

a large number of auto parts, Whether castings/forgings, die castings, mechanical cutting parts, welding parts need to use different types of spray/polishing equipment for surface treatment, such as removing oxide skin, deburring, sand cleaning and cleaning other surface impurities

there are conclusive data to prove that through shot peening strengthening, the anti fatigue life of leaf spring can be extended by 600%, the anti fatigue life of transmission gear can be extended by 1500%, and the anti fatigue life of crankshaft can be extended by 900%. There is no doubt that through shot peening strengthening, the anti fatigue performance and corrosion resistance can be improved, which is of great significance to the service life and safety of parts. Depending on this process, parts can be designed to be lighter. Some parts that had to use expensive materials due to process specifications can now be replaced with low-cost materials, and the same or even better performance standards can be achieved through shot peening

one of the manufacturing processes of crankshaft - shot blasting

as a part of the manufacturing process, the heat-treated crankshaft needs to be shot blasted to remove the thermal oxide skin on the surface. The crankshaft is placed on the rotating roller. When rolling, all surfaces of the crankshaft are fully exposed to the flow of pellets from multiple throwing heads. The impact of multi angle pellets makes the outer surface of the crankshaft thoroughly cleaned

the size of crankshaft determines the type of shot blasting machine. For large engines, the crankshaft size may be as large as 30 "(762 m magnetostrictive ultrasonic level gauge and optical fiber ultrasonic level gauge will also have a certain expansion in the tank area m) diameter x 20 '(6096 mm) length, and the crankshaft is placed between a group of rollers installed on the trolley. There are several working methods. According to the actual situation of the workshop, the customer chooses to fix the throwing head and let the trolley move under the throwing head; It can also fix the trolley and move the polishing head above. In either way, the crankshaft placed between the rollers rotates constantly, so that all its surfaces are fully shot blasted

for smaller crankshafts, the size is basically 6 "- 8" (152 mm - 203 mm) diameter x 36 "(914 mm) length, and shot blasting is usually carried out by rotary crane shot blasting machine. The crankshaft is suspended on a hook of companies that we are constantly approaching that want to use polyurethane and polyester, and then it is sent to the shot blasting room with multiple heads for shot blasting after the rotation of the suspension chain. The hook rotates in the shot blasting room, so that the workpiece is fully exposed to the high-speed shot flow, and passes while rotating. The cleaning speed can reach 250 pieces per hour, and the cleaning effect is very good

although the requirements for process control are not as strict as those for strengthening, modern crankshaft shot blasting equipment also ensures the cleaning quality by monitoring the process parameters

strengthening of crankshaft

because the crankshaft works under the action of alternating stress, the risk of stress fatigue and strain failure at the transition fillet of the journal surface changes is great. At present, shot peening strengthening to change the fatigue resistance of crankshaft has been widely used in a wide range, and the effect is quite satisfactory

compared with the defects of traditional rolling technology, that is, due to the limitation of crankshaft processing technology, the fillet of each journal is difficult to match with the roller, which often leads to the gnawing phenomenon of the fillet, and the crankshaft after rolling has large deformation and poor effect. The mechanism of shot peening strengthening is to use the shot particles with strictly controlled diameter and certain strength to form a shot flow and continuously spray it on the metal surface of the crankshaft under the action of high-speed air flow, just like hammering with countless small hammers, which causes extremely strong plastic deformation on the surface of the crankshaft and forms a cold work hardening layer. In short, because the crankshaft is subjected to various mechanical cutting forces during machining, the stress distribution on its surface, especially at the fillet where the crankshaft section changes, is extremely uneven, and it is subject to alternating stress during work, so it is easy to produce stress corrosion and reduce the fatigue life of the crankshaft. The shot peening process is to introduce a preloading stress to offset the tensile stress that the parts will be subjected to in the future work cycle, so as to improve the fatigue resistance and safe service life of the workpiece

for shot peening strengthening process, there are two most critical parameters. One is stress strength, which is usually tested by "Almen test piece". Multiple test pieces are fixed on different surfaces of the crankshaft, especially at the fillet where the crankshaft section changes with the most concentrated stress, and shot peening is carried out together. The impact of compressive stress on the test piece leads to the bow of the test piece. The expansion and change of curvature is proportional to the impact energy of shot. Another major parameter for determining shot peening quality is coverage. The so-called coverage rate refers to the ratio of the area occupied by the crater on the strengthened surface to the total strengthened surface. This parameter is defined by the crankshaft design engineer, which is usually 100% - 200%. Some crankshaft applications may require a coverage rate higher than 200%

according to the hardness of the crankshaft and the ideal compressive stress intensity, the hardness of the shot used for crankshaft shot peening is usually 50 -55 HRC, and the size is s 280 - s 330 (0.7 mm - 0.84 mm). The strength range produced on the "Almen test piece" in this way is about 0.008 - 0.010 C (0.025 on the a scale)

compared with shot blasting cleaning, the monitoring of process parameters of shot peening strengthening is more rigorous. For the application of crankshaft strengthening, the parameters that need to be monitored include:

· shot peening speed

· shot peening intensity

· shot diameter

· shot peening distance

· strengthening time

· coverage

the change of any of these parameters will affect the effect of crankshaft surface strengthening to varying degrees

conclusion

the correct application of controllable shot peening strengthening technology can dramatically improve the fatigue strength of crankshaft and other parts working under high load conditions, and greatly extend the fatigue life of parts. Advanced and precise shot peening equipment with computer program control technology can closely monitor the shot peening process to ensure the constancy and repeatability of shot peening quality. At present, many famous automobile manufacturers and parts manufacturers in the world have included reinforcement in the standard production process. The strengthening equipment also forms a complete modern manufacturing line with other manufacturing equipment

for more information, please contact Miss Qian Jing of Villette (Group)-