Research On The Precision Forming Technology And Theory Of The Big Thickness Difference Ring With Conical Section

With the rapid development of global economy,the domestic and overseas research in ring rolling is gradually increasing,and a considerable amount of research results is achieved.Improvement of ring rolling technology makes ring parts used in manned spaceflight,manufacturing,machinery,energy and other fields,which is playing an increasingly important role.The big wall thickness difference ring with conical section is the representative of the special-shaped cross-section ring,which the biggest characteristic is with big variation of wall thickness.Moreover,its external surface is straight wall and the inner surface is conical section shape.The forming and manufacturing of such parts plays a very important role for the equipment reliability,operation life,stability,so it is the key point to guarantee the forming uniformity and stability in the forming process.A type high-speed bearing outer ring(the important application of big wall thickness difference ring with conical section)was taken as the research object,due to its complex structure,it is difficult for the traditional forging method to forming its internal structure,and the forming defects such as the spread and the filling defect influence the final quality of rings,so in order to eliminate the above defects,the precision rolling ring was put forward.Based on the theories of ring rolling,plastic mechanics and other basic theory knowledge,the precision forming technology and theory of a certain type high-speed bearing outer ring has been studied by the methods of the finite element simulation and experimental verification,theoretical analysis and numerical calculation,which provides reference and guidance in order to improve rolling forming defects of this kind of rings.In this paper,based on the Simufact finite element simulation software platform,the high-speed bearing outer ring precision coupled thermo-mechanical model has been established.After that,it was analyzed about equivalent plastic strain of the forming ring,and the actual experiment has been carried out.It was found the ring forming quality was good and size error was not more than 2.6%,which has been verified the reliability of the finite element simulation.The microstructure of outer ring after rolling was martensite and carbide,and the dispersion of carbide distribution was promoted with the hot and cold composite treatment,which the hardness was improved.With the method of single variable,it has been respectively studied that the effect of the process parameters of ring rolling(driven roller speed,feed rate,coefficient of friction)and the angle of outer-ring raceway on the deformation uniformity of raceway area.The study showed that with the increase of friction factor,deformation uniformity firstly became good,then got bad;The feed speed increased,deformation uniformity was good first,and then behaved a little bad;And it was clear larger the adrive roller rotation speed,the worse deformation uniformity of the ring;In additional,with increase of the receway angle,the deformation inhomogeneity slowly increased,when it was 11°,the deformation inhomogeneity increased significantly.Based on the blank of this kind of ring used in practical production(unilateral inclination),it has been researched and summarized about the effects of the blank angle ? and straight wall length h on ring contour filling and dimensional precision,its impact was analyzed on the stability of rolling at the same time.With increase of the blank angle ? and straight wall length h,the stability of ring rolling gradually improves.In addition,the blank design of bilateral slope symmetrical structure was put forward,and optimum blank design of h =75 mm was gotten.Taking the blank with h=75 mm as research objects,it was investigated about the finite element simulation and the analysis of relevant laws(equivalent plastic strain,temperature,dynamic recrystallization volume fraction,grain size,etc),and then through the orthogonal design method,the process parameters optimization is made.The conclusion was as follows: 1)Based on ring overall deformation uniformity,optimal process parameters combination was: the driven roller speed: 1.0 r/s,the friction factor: 1.2,the feed speed: 3.0 mm/s;2)According to the average grain size,the combination of the optimization process parameters was: drive roller rotation speed: 1.6 r/s,the friction factor: 1.0,the feed speed: 2.5 mm/s.