Aerospace parts special strengthening thread rolling wheel: rolling method is a kind of plastic processing technology, it is predicated on metal fiber, metal body made of plastic displacement, so that no chip makes the metal forming, so as to improve the mechanical properties by thread processing, but also greatly reduces the special material of aviation aerospace parts used.

　　 As the aerospace parts generally use high thermal strength, good thermal stability, corrosion resistance of high temperature alloy, titanium and its alloy, stainless steel and other materials. These materials is a salient feature of high strength, heat resistance, good corrosion resistance, high chemical activity, low thermal conductivity, low elastic modulus, are difficult to machine materials, the characteristics of machining deformation coefficient, cutting deformation, work hardening, cutting force, high cutting temperature, * easy to wear, surface quality and precision. The connecting forms of aerospace components are various, and the thread is an important form of connection. The common thread connection is widely used to strengthen MJ thread, thread tooth bottom for workpiece requirements increased thread arc, and after quenching the rolling thread, the screw bolt can get high mechanical performance.

　　 　　Aerospace MJ the best solution for strengthening external threads

　　 　　The aerospace titanium alloy, superalloy MJ strengthen the external thread, the general * is not good to meet the requirements of the parts, and to provide the best processing scheme from design, manufacturing and other sectors, which relates to the selection of materials, process improvement, * * chooses the appropriate cutting speed. The rolling method is a kind of plastic processing technology, it is predicated on metal fiber, metal body made of plastic displacement, so that no chip makes the metal forming, so as to improve the mechanical properties by thread processing, but also greatly reduces the special materials for aerospace parts. After the plastic parts are deformed by rolling, the strength and hardness of the outer thread parts have been improved, while the plasticity has been reduced. The metal fibers in the thread have not been cut off, but they have been deformed along the thread type. After rolling the material, material density, and the surface of the cold work hardening layer, and the existence of residual stress and wear resistance after rolling parts have a relatively large increase, the fatigue strength of 20%~40%. can be improved by thread rolling parts, thread surface roughness is greatly improved, excellent surface quality can be to improve the cyclic strength of thread. The plastic deformation of materials, with the increase of deformation degree, strength is more and more high, so the thread rolling, the tensile strength of 20%~30% can be improved, the shear strength of 5%. MJ at the same time, strengthen the external thread requirement for high strength, by means of the principle of plastic deformation of metal rolling screw can solve the tooth bottom in order to increase the problem of arc. Therefore, the rolling stock is the best choice for the aerospace enterprises to strengthen the processing of external thread parts of titanium alloy and high temperature alloy MJ.

　　 　　Design and application points of thread rolling wheel

　　 　1 titanium alloy, high temperature alloy MJ external thread characteristic

　　 　　(1)Part materials are often difficult to process materials such as titanium alloys and superalloys.

　　 　　(2)The only difference between the thread and the ordinary thread is that the external thread adopts a big arc tooth bottom, and the bottom of the tooth is a continuous and smooth curve. The radius of the arc on the curve is 0.18P.

　　 　　(3)High precision screw, selection of tolerance zone threads 4h6h and 4g6g in diameter in the tolerance range, corresponding to the pitch error, angle error, roundness error, taper error and any other error in the shape effect of thread diameter equivalent sum shall not exceed half in diameter tolerance. Pitch deviation limit Delta P=0.4Td2/1.7321, Delta a/2=arctan angle limit deviation (0.3Td2/1.125P).

　　 　　2 design of rolling wheel

　　 　　(1)*Material Science。 First of all, good performance * material should be chosen. W6Mo5Cr4V2 has good rigidity and toughness, and its surface hardness is up to HRC64~66 after quenching. It is a widely used low tungsten high speed tool steel with molybdenum. W6Mo5Cr4V2Al (501) is a kind of aluminum containing super hard high speed steel, high temperature hardness at 600 DEG C has reached HRC54, higher strength and toughness, excellent cutting ability, in most cases the cutting performance of M42 steel and the same, wide application. Processing titanium alloy, high temperature alloy MJ external thread, choose W6Mo5Cr4V2Al (501) better, hardness control at HRC65~67, can effectively meet the requirements of the workpiece, but also guarantee the rolling wheel has better life.

　　 　　(2)Shape structure of rolling wheel. The commonly used rolling machine spindle: Phi 45, Phi 54, Phi 75, Phi 80 and some special diameter spindle rolling machine, the model selection of thread rolling wheel diameter range, determine the specific thread number, thickness of the part length threaded part made of unilateral or bilateral use according to the.

　　Tooth profile design of rolling wheel

　　 　When the parts are strengthened with MJ, the circular arc tooth bottom of the external screw can greatly reduce the stress concentration, thereby increasing the fatigue life of the parts, and improving the fatigue life by more than two times. So the rolling tooth top must be processed into a circular arc shape, arc transfer must be smooth, not sharp point, the size of the parts to ensure the rolling tooth bottom arc radius of 0.15~0.18P, considering the external thread rolling workpiece after tooth bottom arc is smaller than the rolling wheel tooth top arc, so rolling the tooth top arc and arc defined as 0.16~0.18P. in the actual processing, when the rolling pressure is eliminated, the material will occur elastic recovery, thread top arc parts will become large, rounded root will become smaller, especially the external thread parts of titanium alloy, high temperature alloy and other hard materials, the relatively low elastic modulus that tendency of elastic deformation, easy to produce elastic deformation and elastic recovery, and each elastic recovery of the material is different, corresponding with rolling wheel rolling tooth top arc requirements are also different, so The top arc and chamfer arc of the rolling gear must be modified so as to ensure the arc requirement of the tooth shape of the workpiece. When the titanium alloy is rolled, the elasticity of the material is recovered between 0.005~0.012mm. When rolling the high temperature alloy, the elasticity of the material is restored between 0~0.005mm. The rolling of titanium alloy, rolling tooth top arc and chamfer need correction for 0.17~0.185P high temperature alloy; rolling, rolling and tooth top arc chamfer need correction for 0.165~0.18P. roll tooth size round wire is determined as: the upper high =H/2-5H/24=0.433P-0.180P=0.253P (reduced higher than ordinary 0.289P thread tooth), tolerances of rolling wheels circular minimum 0.16P, namely +0.02P. is rolling of titanium alloy, superalloy, high tolerance and proper teeth are determined according to the modified arc size. Under the tooth height and common thread in the same =H/2-H/8=0.433P-0.108P=0.325P. in the same way, after rolling parts tooth type angle also shrink, MJ thread diameter tolerance precision grade is higher and more stringent requirements, so the tooth type angle changes should also be considered. In order to ensure the accuracy of the workpiece on the pitch of the thread, and half angle of thread rolling wheel also provides a range of error, pitch error is 0.25Td2 in diameter equivalent value, P=0.25Td2/1.7321, accounting for 62.5% of the error of workpiece, the equivalent diameter of angle error is taken as 0.12Td2 + a/2=arctan (0.12Td2/0.75P), Delta a/2=arctan (0.12Td2/1.5P) the error of the 30%., accounting for the other according to 0.2Td2 given, the three part is 0.45Td2, 0.5Td2. does not exceed the rolling wheels must be chamfered, otherwise it will damage the thread rolling wheel edge in the rolling process, especially rolling high strength and hard material is more significant. Chamfer size should meet the requirements of MJ and the screw thread winding length requirements, considering rolling wheel life and avoid collapse teeth, so the chamfer angle is 16 degrees, the width is 1.3~1.5P. a good design of the rolling wheels, in order to ensure the rolling effect is good, in use must pay attention to several points:

　　 　　(1)The reasonable selection of blank diameter before rolling. Rolling hard processing material blank diameter d1=d-0.67P, calculated by the formula before rolling diameter of blank is approximate, according to the actual thread most after rolling in diameter, modified by test. Especially the mechanical properties of titanium alloy and high temperature alloy material are different, which greatly influences the rolling thread, and the influence on the MJ thread with higher precision is also obvious.

　　 　　(2)Difficult to machining materials when rolling thread speed with the material and material strength of rolling of titanium alloy, high-temperature alloy hard materials, rolling wheels rolling faster than ordinary steel, titanium alloy, high temperature alloy relative elongation of 5=10%~20%, rolling wheels when rolling thread speed is 7~12m/min.

　　 　　(3)Strict control of the rolling process, the rolling method is correct and with good rigidity, high precision equipment, otherwise the thread surface will appear wrinkles, creases, scratch, crack, fracture, rolling tool life is very low, in addition to the rolling tool life will be drastically reduced, the thread of stress concentration is more sensitive after rolling also, will make the workpiece thread premature fatigue damage.

　　 　　Development trend of roller wheel

　　 　　We are committed to military research and development, manufacturing, testing and thread gauge test. Process for the production of titanium alloy, superalloy aerospace industry MJ to strengthen the external thread with rolling wheels, has accumulated rich experience, strict production, processing, testing process, ensure the aerospace enterprises to strengthen the bottom thread workpiece tooth thread connection requirements. At the same time, with the advantage of enterprise processing, the special rolling wheel for ring groove rivet used for processing titanium alloy has been settled in a large number of aerospace enterprises. In order to better serve the aerospace enterprise, we will continue to strengthen technological innovation, because only research design for hard machining materials to become the preferred supplier of * *, modern aerospace manufacturing enterprises.

　　 　　The rapid development of high-speed cutting technology in our country, in the cutting principle is a breakthrough in the traditional cutting knowledge, in the cutting mechanism and conventional cutting is different, has its own characteristics and scope of application. At present, the domestic and foreign materials used for ultra high speed cutting are suitable for processing titanium alloy mainly with high performance high speed steel, powder high speed steel, YG type hard alloy, polycrystalline diamond PCD and cubic boron nitride.

　　 　　High speed cutting technology and * material are used in the processing of titanium alloy external thread. The best matching of titanium alloy and titanium alloy should be obtained from many factors, such as technology, machine tool support and auxiliary unit manufacturing technology, processing and testing technology, etc.. Solving the difficult problem of processing titanium alloy not only ensures the quality of processing, but also greatly improves the productivity, and has a good prospect of development. Ultra high speed machining technology is becoming mature for the processing of difficult to machine materials, but how to further improve the rolling technology of ultra high speed cutting titanium alloy has yet to be further studied.