Research Of The Tribological Characteristics Of The Sand Reclamation Machinery Wear-resistant Component Manufactured By WAAM

In the field of casting industry,sand casting accounts for 60～70%of casting production,which has the characteristics of simple production process,low cost and wide variety of applied alloys.Since the 17th century,foundry sand is still the main molding material in foundry production,and foundry waste sand has always been the bulk of waste produced in foundry industry.Therefore,the comprehensive development and utilization of foundry waste sand has been widely concerned by all countries in the world.At present,the most commonly used recycling method of used foundry sand is dry mechanical recycling of used foundry sand,and the centrifugal recycling technology of used foundry sand is widely used.In the process of the regeneration of the used foundry sand,the used foundry sand has obvious impact behavior on the equipment,which causes the wear of the key parts of the equipment and affects the stable operation life of the equipment.The material of the key wear-resistant parts of the equipment is white wear-resistant cast iron produced by foundry.Due to the influence of material characteristics and casting defects,the mechanical properties of castings are poor,the impact wear resistance is low,and the long-term stable operation of the equipment can not be guaranteed.Through the discrete element simulation analysis of the centrifugal regenerator of casting sand,it is found that the parts of the centrifugal regenerator that are easy to wear appear on the inclined inner side of the impact plate and the inner surface of the lower gear ring at the inclined inner side.The surface normal cumulative contact energy is obviously higher than the tangential cumulative contact capacity,which shows that the wear of the lower retaining ring is mainly caused by impact wear,while the sliding wear effect is relatively weak.The structure of the centrifugal regenerator is further improved,and the static simulation of the impact plate parts is carried out by ANSYS to analyze the stress change.In order to solve the above problems,this paper uses EDEM simulation software to carry out discrete element simulation analysis on the working process of key components of centrifugal regenerator,analyze the parts that are easy to be worn during the working process,and optimize the structure of centrifugal regenerator.Aiming at the parts that are easy to wear in the equipment and the possible failure modes,a centrifugal regenerator impact plate component with gradient structure is proposed.The core is made of carbon steel and the outside is made of high chromium cast iron wear-resistant layer,which is made by wire arc additive manufacture（WAAM,Wire Arc additive Manufacture）for additive manufacturing.The primary and secondary laws of the influence of welding current,hot wire current,welding speed and wire feeding speed on the width-height ratio and penetration depth in the additive process were determined by orthogonal experiments.Finally,the carbon steel core plate and outer wear-resistant layer were prepared by hot wire-assisted arc additive manufacturing technology,and the microstructure,mechanical properties and wear-resistant performance were experimentally explored.Through the discrete element simulation analysis of the centrifugal regenerator of casting sand,it is found that the parts that are easy to be worn by the centrifugal regenerator appear on the inclined inner side of the impact plate and the inner surface of the lower retainer ring at the inclined inner side,and the surface normal cumulative contact energy is obviously higher than the tangential cumulative contact capacity,indicating that the wear of the lower retainer ring is mainly caused by impact wear,and the sliding wear effect is relatively weak.The structure of the centrifugal regenerator is improved according to the wear position and wear mode.Using ANSYS finite element analysis,the static simulation analysis of the impact plate parts is carried out,and the stress changes of the impact plate blades caused by gradient structure design and changing the contact position between the core parts and the lower retaining ring are analyzed.A series of experiments were carried out by hot wire TIG additive manufacturing technology,and the primary and secondary laws of experimental factors affecting indexes were determined by range analysis method.The best additive process parameters were obtained by observing the weld surface morphology and measuring the cross-section morphology.The optimal parameters were used to collect the temperature field,and the distribution of current in the main arc and hot wire was changed.The influence of different current distribution on the substrate temperature during the process of adding materials was studied.The carbon steel core plate of impact plate was made by hot wire TIG additive manufacturing technology,and its microstructure,hardness change along the direction of additive manufactured and mechanical properties of different orientation addition parts were studied and analyzed.The results show that the ferrite grains in the previous weld bead are mainly equiaxed,and the coarse columnar grains and dendrites in the top weld bead are mainly used.Vickers hardness of core additive parts ranges from 170～200 HV,and the highest hardness appears at the top layer of additive parts.The additive parts show similar tensile strength in transverse and longitudinal directions,and there are a lot of dimples in the tensile fracture surface,which shows the characteristics of ductile fracture.The external wear-resistant layer was made by TIG additive manufacturing technology,and the effect of arc additive on the microstructure,phase composition,hardness and wear resistance of the wear-resistant layer was studied.The results show that the microstructure of the wear-resistant layer is mainly composed of austenite matrix and M₇C₃carbide,with a small amount of martensite.With the increase of the distance from the matrix,the microstructure changes from dendrite to bundle.The Rockwell hardness of wear-resistant layer made by arc additive is 64.2HRC.The dynamic abrasive wear test was carried out on the wear-resistant layer.With the impact energy increasing from 1J to 5J,the wear rate of the wear-resistant layer in unit sliding distance increased obviously,from 0.214 to 0.643mg/mm,and the wear form changed from micro-cutting wear to micro-peeling and fatigue wear.The abrasive wear test of the wear-resistant layer was carried out.With the increase of impact angle and impact time,the mass loss of the wear-resistant layer increased.When the impact angle was 90 and the impact time was 40min,the mass loss was 0.162g,which was about26.5%lower than that of Cr26 material.With the increase of impact angle,the wear form of quartz sand abrasive particles on wear-resistant layer changes from micro-cutting to material fracture and spalling pit.