| "Remanufacturing" is the general name of a series of technical measures or engineering activities to repair and transform waste products with the goal of improving the performance of waste products and by means of advanced technology and industrialized production.At present,China’s remanufacturing technology is mainly used in automobile,engineering machinery,mining machinery and other fields.However,it is still basically blank in the field of agricultural machinery and equipment,so that a large number of retired or scrapped agricultural machinery and their parts and components are not reasonably reused every year,resulting in a great waste of resources.Therefore,remanufacturing of agricultural machinery and equipment is an important way to promote the transformation and upgrading of agricultural machinery industry and realize green development.In this paper,the key component of farming machinery-rotary tillage cutter is taken as the object,the wire remanufacturing characteristics and wear-resistant modification of damaged rotary tillage cutter are studied by taking arc additive remanufacturing as a means and by changing the powder core composition of powder core wire with "skin encloses powder " structure as the modification way.The purpose of this study is to provide theoretical basis and technical support for the development of powder cored wire for additive remanufacturing with good performance and promoting the remanufacturing of rotary tillage cutter and other agricultural machinery.The main work and achievements of this paper are as follows:(1)Research on the process of arc additive remanufacturing of rotary tillage cutter.The three-dimensional transient finite element model of arc additive remanufacturing was established and verified by experiments.Based on the verified model,the forming process parameters were optimized by orthogonal design with stress,deformation and penetration as optimization objectives;Under the condition of single pass and multi-layer arc additive remanufacturing,the optimal arc scanning path and the variation law of temperature,stress and strain are explored through the analysis of temperature field and stress field.The results show that the optimal forming parameters are voltage of 16 V,current of 180 A and speed of 2mm/s;Under the condition of single pass multi-layer arc additive remanufacturing,the "back and forth" arc scanning path is better than the "zigzag" arc scanning path;The variation law of temperature,stress and strain of cladding layer in arc additive remanufacturing was analyzed by using the optimal process parameters and "back and forth" arc scanning path,which provided a theoretical basis for the experiment of arc additive remanufacturing.(2)Research on the arc additive remanufacturing characteristics of different kinds of wire with same composition.The original 65 Mn base material was used as contrast samples,the macro morphology,microstructure and dry friction and wear behavior under different loads of commercially purchased solid wire,commercially purchased flux cored wire and selfmade powder cored wire arc additive remanufacturing samples were compared.The remanufacturing characteristics of powder cored wire,a new material for arc additive remanufacturing,were expounded.The results show that the remanufactured sample of powder cored wire has fine structure,good uniformity,less precipitates or inclusions,more Fe3 C in the structure,higher surface hardness,and better wear resistance under small load(5N,10N),but worse wear resistance under large load(15N,20N).The analysis shows that the matrix of remanufactured sample of powder cored wire is too soft to support large load,so its wear resistance under large load is not ideal.the performance can be further improved by adding functional particles to meet the requirements of the large load.(3)Research on the arc additive Remanufacturing characteristics of Ce O2 p modified powder cored wireThe remanufacturing samples of powder cored wire were used as contrast samples.the macro morphology,microstructure and dry friction and wear behavior under different loads of three kinds of remanufactured samples modified by Ce O2p(1%,2%,3%)were compared,The effects of rare earth on the macro morphology,microstructure and wear resistance of remanufacturing samples were discussed.The results show that: after adding rare earth,the surface of the sample is smooth and even,the defects such as holes and welding slag are less,and the surface hardness is increased;2% Ce O2 p showed the best wear resistance,followed by 1% and 3%.The analysis shows that in order to give full play to the properties of Ce O2 p modified powder core wire,it is necessary to control the amount of rare earth.An appropriate amount of rare earth can refine the grain,reduce the content of residual austenite and improve the hardness,so as to improve the wear resistance.(4)Research on the arc additive remanufacturing characteristics of WCp modified powder cored wire.The remanufacturing samples of powder cored wire were used as contrast samples.the macro morphology,microstructure and dry friction and wear behavior under different loads of three kinds of remanufactured samples modified by WCp(3%,6%,9%)were compared,The effects of ceramic particles on the macro morphology,microstructure and wear resistance of remanufacturing samples were discussed.The results show that :after adding WCp,the surface of the sample is smooth and uniform,the surface hardness increases by 40%-67%,and 6% sample is the best;The improvement of wear resistance is consistent with the increase of hardness,which indicates that hardness is one of the main factors for WCp to improve wear resistance.The analysis shows that when adding nano WCp for powder core wire material modification,the amount of addition must be paid attention to.The addition of excessive nano WCp will cause the agglomeration of nano powder,which is not conducive to the exertion of strengthening effect.The appropriate amount of WCp makes its dispersion strengthening effect better,the overall strength of the sample higher,the surface hardness increased and the wear resistance improved.To sum up,the modified powder cored wire arc additive remanufacturing method presented in this work has good engineering adaptability and application prospect.The samples prepared by this technology show good wear resistance,indicating that it can better meet the performance and application requirements after remanufacturing and repairing of damaged rotary tillage tools. |
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