Design And Manufacturing Of PM Gear With High Strength And Complexity

Gear is widely utilized in kinds of machine as one of the most importanttransmission parts. Because it is so difficult, and its production efficiency is so low,and raw materials are wasted, conventional cutting processing technique makeenterprises' benefits affected;when processing, part fiber of gear teeth is cut, sogear strength is not high, load capacity is affected. So people are thirsty for newproduction technology of gear with superior quality, higher efficiency and nowasted material. PM (Powder metallurgy) that takes metals as raw materials is usedto manufacture materials and products through sintering. PM is used widely asclose shape, and it has some advantages, such as low energy consumption, closeshape, small manufacturing tolerance about large launch parts compared with othermanufacturing technology. PM is a technology science that study metals, metalalloy, non-metal and compound powders and their properties, manufacturing theoryand technology;it is one of the most rapid advanced material and engineering areas.In this paper, PM gear replaced conventional mechanical processing 40Cr gear thatis appointed.Near 20 years, PM new technology, new technique emerged one after another,high performance and compound solve is one of the results that accelerate PMmaterials. Some new technique and new technology have some breakthroughs fordeveloping PM material and products. Developing PM materials with highperformance (including compound materials) is always development direction andresearch emphasis. Especiallly latest years, overseas strengthened PM developmentwith high density, high strength, high accuracy and high complexity. According tothose, some developed new technique about PM with high effiency, low energy,close shape made a great progress for PM parts application in depth and width.Performance and accuracies are two important index signs of iron base PMproduct quality. Although the requirements of different parts to both sides are notsame, technique factors to influence product performance and accuracies are notsame, high performance and high accuracies are always developement direction ofiron PM. To normal manufacturing industries, high mould-pressing density,appropriate alloy and heat-treatment after sintering are key factors to improveperformance, but suitable selection of alloys, compaction, sintering process andprecise green samples shrinkage control in sintering process are necessaryconditions to improve parts' accuracies.Performance of iron base PM materials is mainly decided by relative density,alloys kinds and quantities, microstructure and heat-treatment etc. In the study ofhigh performance PM materials, the relationship among compositions,microstructure and performance was emphasized formerly, and manufacturing,shape and application were usually ignored. In fact, whether a kind of material canbe applied is relative with performance, microstructure, processing closely. In thisreasearch, on the base of manufacturing cost, raw materials resource, economicalpress, PM press feasibility and sintering temperature and so on are considered,manufacturing technique and theory research of iron base PM materials with highperformance and high accuracies are studied, and suitable technique parameters,alloy microstructure and technology equipements are studied. Moreover, therelationship among alloy microstructure, green product density, sintering techniqueand alloy performance, sintering compactibility are indicated. At the same time,this paper has an important role in theory and application for more predictinginfluence of manufacturing technique to dynamics performance and dimensiondiversification of sintering parts, and has an important social significance andeconomics benefits.This thesis based on collabrating with Zhejiang JiaHe Co. Ltd. is completed.Its contens include design of PM gear profile, mould design, materialsmicrostructure research, manufacturing technique and dynamic performanceresearch, and according to design requirements and PM specification, it obtainedappropriate gear profile, and validated teeth contact strength and teeth bendstrength in theory, used parameters are gotten through weighted average of 40Cr.Validated results are that PM gear can meet design requirements. Design of PMgear mould is completed according as designed gear profile, and these moulds canpress qualified gear.Through dynamic performance and microstructure research of gear materials,appropriate materials ingredients Fe-XNi-XMo-XCu-XC can be obtained. Theresearch indictas the materials microsturcture can meet design requirements of gear.Gear profile of electric tools is "Olicon". PM gear's sintering process is followed as:pressing is 600~700MPa, green product is pre-sintering for 45min;H2 and N2 areas protecting atmosphere, double press occurs on the auto-mould, and doublepressing is 600~700MPa, sintering temperature is 1150℃ , sintering time is 1~1.5hours(workpieces stay in the area of high temperature), quenching temperature is740~850℃ , keeping temperature 15 min, tempering temperature is 200~300℃ ,keeping temperature 45min.This paper integrates practical production, and makes an avaliable explorationfor shape and manufacturing of PM gear, and offers valuable reference process.Due to limited time, there are some aspects needed further to be study orientationsas follows:1. computer simulation about powder flow in the process of, pressing,intuitionistic understanding and detailed analysis for complicated presseingprocess;2. computer simulation dynamic about gear, now only validate it throughpractical testing.If mould can be created , and computer simulation can be done, testing timeswill be decrease, cost is down and more time is saved, all those will be the keypoints of study in the future.