| China is a traditional agricultural country,the number of people engaged in agriculture and related industries is large.At present,China's total agricultural output value has reached 10 trillion yuan.In addition,by increasing capacity,reducing production costs and improving product quality,there is room for about 10% annual growth.Promoting the development of agricultural mechanization is an important means to realize the sustainable and healthy growth of agricultural output value.As one of the most widely used agricultural machinery and tools in China,combine harvester can greatly simplify the harvesting process.The full automation of harvesting a variety of crops can effectively increase production capacity,improve efficiency and improve product quality.However,the design and manufacturing level of agricultural machinery and tools in China is still relatively low,and the gap with the world level is large,the performance and reliability of the combined harvester produced are relatively poor.As an important part of combine harvester,the quality of cutting tool has an important influence on the service life,performance,adaptability and reliability of combine harvester.Such as cutting tools in the process of work will frequently appear deformation,wear,corrosion and other conditions,not only cause a lot of economic losses,but also limit the further use of combine harvester.In order to break the monopoly of the world's giants on agricultural machinery industry,effectively improve the service life of cutting tools of combine harvester.Using laser cladding technology to improve the performance of cutting tools,the main research contents are as follows:1.COMSOL simulation software was used to simulate the process of laser beam acting on the substrate,and the variation law of temperature field and molten pool size of the substrate under different laser process parameters was studied.2.According to the change rule of different process parameters on cladding layer,an orthogonal experiment is used to design and conduct laser cladding experiments,so as to determine the optimal combination of laser process parameters: Output current 130 A,scanning speed 300mm/min,spot diameter 0.8mm,pulse frequency 35 Hz,pulse width2.5ms,powder preset thickness 1.0mm,overlap rate 25%.3.In order to design the cladding alloy powder required by the actual working condition,a monocrystalline silicon powder was added to the iron-based alloy powder.The laser cladding experiment was carried out with the optimum technological parameters to study the influence of different Si elements on the iron-based cladding layer.The samples were tested by Shanghai SIOMM mhvd-1000 at microhardness tester,it was found that as the proportion of Si elements in the alloy powder increased,the microhardness of the cladding layer gradually increased.When the mass ratio was 20:1,the hardness of the cladding layer was the maximum.The cladding layer was detected by Hitachi TM4000 plus scanning electron microscope,Hitachi 550 i energy spectrum analyzer and other advanced characterization equipment.It is found that if the content of Si element is too high,it has a great negative effect on the structure and quality of cladding layer.Therefore,adding an appropriate amount of monocrystalline silicon can effectively improve the performance of cladding coating,but too much monocrystalline silicon will affect the microstructure of cladding layer.Experimental results show that when the mass ratio of iron-based alloy cladding powder to monocrystalline silicon is 40:1,the hardness of cladding layer is relatively high,and the microstructure is uniform and the flatness is high.4.Finally,in order to optimize the laser process flow,different scanning paths were used for laser cladding experiments to study the effect of laser cladding on the cutting tool deformation,so as to avoid the increase of errors caused by laser processing and the influence on the performance of the cutting tool. |
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