| Feed pellet machine ring mold is the core part of feed granulator,and it is a circular and easily worn component that covers all the holes.In the process of pellet granulating,the pore size of the mold hole caused by wear becomes larger,and the molding rate of the feed particles is also decreased.When the molding rate falls to 75%,it means the ring die is invalid and needs to be replaced.With the continuous development of China's economy,market demand for ring mold is bigger and bigger.In our country,the martensitic stainless steel,which is used for 4Cr13,is generally used as a martensitic stainless steel.The service life is generally 600-800 hours,and the life span is short and lower than that of the foreign imported ring mold 1000 hours.And the replacement and maintenance also cost a lot of human cost and time cost,which have greatly improved the production cost of feed particles,and at the same time,it also caused a great waste of energy in China.Therefore,improving the service life of China's ring mold has important engineering application value and scientific significance.From the point of view of developing new ring mold materials,this paper tries to use two kinds of materials,H13 and 3Cr2W8 V,to replace the matrix of 4Cr13 martensitic stainless steel and two ways to improve the service life of the ring die by using the hot spraying process on the surface of the 4Cr13 stainless steel,and to reduce the production cost and reduce the feed grain.The purpose of the waste of national resources is less.The work of this paper has the following aspects:(1)sampling the 4Cr13 martensitic stainless steel,which is a scrap ring mold material for a feed grain factory in China.By observing and analyzing the failure structure,microstructure and surface wear morphology,the failure analysis of the ring die is carried out.(2)according to the failure mechanism of the ring die,the test platform is designed to simulate the wear condition of the ring die.(3)try to use hot die steel H13 steel and 3Cr2W8 V steel commonly used in the market and replace 4Cr13 stainless steel materials by spraying WC coating and CrC coating on 4Cr13 surface by thermal spraying process.(4)use the test platform to do the simulation,ring die wear test,mechanical test and corrosion test for the above four materials.(5)comprehensively analyze the data and verify the feasibility of the above four materials instead of 4Cr13 for making ring mold materials.The results show that:(1)the material selection of the ring die material is very important.The non-metallic oxidation inclusions and a large number of carbide particles will affect the mechanical properties of the ring die and lead to the decrease of the ring die strength.(2)the most serious part of the ring die wear is the ring die hole inlet.The main failure mechanism is the carbide stripping from the furrow,wear and fatigue interaction formed by the wear and the corrosion pits caused by the interaction of fatigue and corrosion.(3)set up a set of test platform to evaluate ring mold materials through experiments.(4)by comparing the mechanical properties of the hot working die steel H13 steel and the 3Cr2W8 V steel to the 4Cr13 stainless steel,it is found that the toughness of the 3Cr2W8 V steel is the best,the H13 steel is the second,and the 4Cr13 stainless steel is the worst.(5)the wear resistance of the five materials is low to high: 3Cr2W8 V steel,H13 steel,4Cr13 stainless steel,CrC coating and WC coating.(6)from the corrosion morphology,4Cr13 stainless steel is better than 3Cr2W8 V steel and H13 steel.WC coating and CrC coating can hardly see corrosion.(7)the thermal spraying of WC coating on the surface of the ring die surface produced by 4Cr13 can improve its wear resistance and corrosion resistance.The wear resistance of the surface can reach 15 times that of the original. |
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