Grinding hardening is a new technology of hardening steel piece surfaces with grinding heat generated in the grinding process instead of with a high or medium frequency induction heating method,which can effectively i...Grinding hardening is a new technology of hardening steel piece surfaces with grinding heat generated in the grinding process instead of with a high or medium frequency induction heating method,which can effectively integrate grinding and surface hardening. Experimental studies were carried out on grinding hardening of non-quenched and tempered steel. Through grinding experiments with variable depths of cut and feeding rate,the variation in the depth of the hardening layer was studied and the microstructure of the hardening zone of the test pieces was subsequently ana-lyzed. In the end,the hardening effect of non-quenched and tempered steel was compared with that of 40Cr steel,which revealed the superiority of non-quenched and tempered steel in grinding hardening technology.展开更多
The grind-hardening method suitable for external grinding is proposed in this paper and the experiments are carried out on M1432B grinding machine. The hardened layer of the workpiece with cut depth 0.3 mm and speed 0...The grind-hardening method suitable for external grinding is proposed in this paper and the experiments are carried out on M1432B grinding machine. The hardened layer of the workpiece with cut depth 0.3 mm and speed 0.2 m/min is analyzed. The result indicates the metallurgical structure of the hardened layer is martensite and the top hardness value is 754 HV (about 62.3 HRC). At the same time, the grinding force, one of the most important factors of external grind-hardening process is modeled, and the measurement method is provided with elastic core clampers. The measurement result shows that the values of both the tangential force and the normal force increase when the cut depth increases, and the top value is 146 N and 656 N with the cut depth value of 0.4 mm. The increment speed and the value of the normal force are larger than the tangential force.展开更多
To shorten the process of face gears,the grinding-hardening effect experiment of face gears under minimum quantity lubrication(MQL)was carried out.Firstly,the grinding method of face gears was analyzed based on the en...To shorten the process of face gears,the grinding-hardening effect experiment of face gears under minimum quantity lubrication(MQL)was carried out.Firstly,the grinding method of face gears was analyzed based on the envelope principle,and the control equation of grinding movement was constructed.Secondly,the distribution ratio equation of heat flux density was established,and the theoretical calculation formula of triangle heat source was derived.Thirdly,since a MATLAB calculation program was compiled,the temperature change law under MQL grinding was analyzed.In the end,the influence of grinding parameters on the grinding-hardening layer depth was analyzed.The results demonstrate that MQL grinding achieves the grinding-hardening effect.展开更多
Engineering the surfaces of components to improve the life and performance of parts used in automotive and aerospace engineering is the active area of research. Suitable Thermal/ Mechanical/Thermo mechanical surface e...Engineering the surfaces of components to improve the life and performance of parts used in automotive and aerospace engineering is the active area of research. Suitable Thermal/ Mechanical/Thermo mechanical surface engineering treatments will produce extensive rearrangement of atoms in metals and alloys and corresponding marked variations in Physical, Chemical and Mechanical properties. Among the more important of these treatments are heat treatment processes such as hardening by Quenching, Induction hardening and Case Carburizing which rely on phase transformations to produce desired changes in mechanical properties. Other processes where phase transformation occur are casting, welding and machining etc. [1] Phase transformation may be homogeneous or heterogeneous. Homogeneous involves rearrangements in the structure of the material taking place simultaneously in all parts of the solid, while the heterogeneous transformation involves structural changes which are more localized. Alternatively they could be called as Isothermal and Nonisothermal transformation. But irrespective of the classification, these transformations alter the structure of the material giving rise to changes in the mechanical and physical properties of the processed material. It is of interest to review some consequences of surface modification in isothermal (Normalizing) and nonisothermal transformations (Machining) of low carbon steels.展开更多
Different phenomenological equations based on plasticity, primary creep (as a viscoplastic mechanism), secondary creep (as another viscoplastic mechanism) and different combinations of these equations are presente...Different phenomenological equations based on plasticity, primary creep (as a viscoplastic mechanism), secondary creep (as another viscoplastic mechanism) and different combinations of these equations are presented and used to describe the material inelastic deformation in uniaxial test. Agreement of the models with experimental results and with the theoretical concepts and physical realities is the criterion of choosing the most appropriate formulation for uniaxial test. A model is thus proposed in which plastic deformation, primary creep and secondary creep contribute to the inelastic deformation. However, it is believed that the hardening parameter is composed of plastic and primary creep parts. Accordingly, the axial plastic strain in a uniaxial test may no longer be considered as the hardening parameter. Therefore, a proportionality concept is proposed to calculate the plastic contribution of deformation.展开更多
The YC 31125 hardened gear hobbingmachine was developed by theChongqing Machine Tools Works. Itworks according to the principle of continuousscale division: it can cut spur and helicalgears, and chain and worm wheels....The YC 31125 hardened gear hobbingmachine was developed by theChongqing Machine Tools Works. Itworks according to the principle of continuousscale division: it can cut spur and helicalgears, and chain and worm wheels. Thanksto its rigidness, it can semi-finish or finishhardened gears by the hobbing method usinga carbide hob. In this way, hardened gearscan be efficiently finished by hobbingoperation instead of the grinding method,with higher precision and productionefficiency. When hobbing spur gears,展开更多
Microstructure transformation and aging hardening behavior of 15-5 PH stainless steel were studied by optical microscopy (OM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show...Microstructure transformation and aging hardening behavior of 15-5 PH stainless steel were studied by optical microscopy (OM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results showed that the 15-5 PH stainless steel consists of NbC precipitates and lath matensite with a high dislocation density after solution treatment. With increasing aging temperature and aging time, the martensitic laths were resolved gradually. Meanwhile, the nanometric-sized Cu precipitates gradually coarsened and lost their coherency with'the martensite matrix, which exhibited an elliptical shape finally. Fine Cu precipitates can lead to significant dispersion hardening effect, while the coarsened Cu precipitates have no contribution to strengthening. The reversed austenite was observed in the speci- mens aged at 550 ℃ and above; moreover, the amount of reversed austenite increased as aging temperature in- creased. The precipitation hardening behavior of 15-5 PH stainless steel may depend on the balance between the softening caused by the formation of reversed austenite and the hardening caused by the precipitation of copper.展开更多
基金Projects JH03-001 supported by the High and New Technology Foundation of Jiangsu High School2006B009 by the Science Foundation of China University ofMining & Technology
文摘Grinding hardening is a new technology of hardening steel piece surfaces with grinding heat generated in the grinding process instead of with a high or medium frequency induction heating method,which can effectively integrate grinding and surface hardening. Experimental studies were carried out on grinding hardening of non-quenched and tempered steel. Through grinding experiments with variable depths of cut and feeding rate,the variation in the depth of the hardening layer was studied and the microstructure of the hardening zone of the test pieces was subsequently ana-lyzed. In the end,the hardening effect of non-quenched and tempered steel was compared with that of 40Cr steel,which revealed the superiority of non-quenched and tempered steel in grinding hardening technology.
文摘The grind-hardening method suitable for external grinding is proposed in this paper and the experiments are carried out on M1432B grinding machine. The hardened layer of the workpiece with cut depth 0.3 mm and speed 0.2 m/min is analyzed. The result indicates the metallurgical structure of the hardened layer is martensite and the top hardness value is 754 HV (about 62.3 HRC). At the same time, the grinding force, one of the most important factors of external grind-hardening process is modeled, and the measurement method is provided with elastic core clampers. The measurement result shows that the values of both the tangential force and the normal force increase when the cut depth increases, and the top value is 146 N and 656 N with the cut depth value of 0.4 mm. The increment speed and the value of the normal force are larger than the tangential force.
基金Supported by the Innovative Research Project of Basic Products of State Administration of Science,Technology and Industry for National Defense(237099000000170006)。
文摘To shorten the process of face gears,the grinding-hardening effect experiment of face gears under minimum quantity lubrication(MQL)was carried out.Firstly,the grinding method of face gears was analyzed based on the envelope principle,and the control equation of grinding movement was constructed.Secondly,the distribution ratio equation of heat flux density was established,and the theoretical calculation formula of triangle heat source was derived.Thirdly,since a MATLAB calculation program was compiled,the temperature change law under MQL grinding was analyzed.In the end,the influence of grinding parameters on the grinding-hardening layer depth was analyzed.The results demonstrate that MQL grinding achieves the grinding-hardening effect.
文摘Engineering the surfaces of components to improve the life and performance of parts used in automotive and aerospace engineering is the active area of research. Suitable Thermal/ Mechanical/Thermo mechanical surface engineering treatments will produce extensive rearrangement of atoms in metals and alloys and corresponding marked variations in Physical, Chemical and Mechanical properties. Among the more important of these treatments are heat treatment processes such as hardening by Quenching, Induction hardening and Case Carburizing which rely on phase transformations to produce desired changes in mechanical properties. Other processes where phase transformation occur are casting, welding and machining etc. [1] Phase transformation may be homogeneous or heterogeneous. Homogeneous involves rearrangements in the structure of the material taking place simultaneously in all parts of the solid, while the heterogeneous transformation involves structural changes which are more localized. Alternatively they could be called as Isothermal and Nonisothermal transformation. But irrespective of the classification, these transformations alter the structure of the material giving rise to changes in the mechanical and physical properties of the processed material. It is of interest to review some consequences of surface modification in isothermal (Normalizing) and nonisothermal transformations (Machining) of low carbon steels.
文摘Different phenomenological equations based on plasticity, primary creep (as a viscoplastic mechanism), secondary creep (as another viscoplastic mechanism) and different combinations of these equations are presented and used to describe the material inelastic deformation in uniaxial test. Agreement of the models with experimental results and with the theoretical concepts and physical realities is the criterion of choosing the most appropriate formulation for uniaxial test. A model is thus proposed in which plastic deformation, primary creep and secondary creep contribute to the inelastic deformation. However, it is believed that the hardening parameter is composed of plastic and primary creep parts. Accordingly, the axial plastic strain in a uniaxial test may no longer be considered as the hardening parameter. Therefore, a proportionality concept is proposed to calculate the plastic contribution of deformation.
文摘The YC 31125 hardened gear hobbingmachine was developed by theChongqing Machine Tools Works. Itworks according to the principle of continuousscale division: it can cut spur and helicalgears, and chain and worm wheels. Thanksto its rigidness, it can semi-finish or finishhardened gears by the hobbing method usinga carbide hob. In this way, hardened gearscan be efficiently finished by hobbingoperation instead of the grinding method,with higher precision and productionefficiency. When hobbing spur gears,
基金Item Sponsored by National High Technology Research and Development Program of China(2012AA03A507)Key Laboratory Foundation of Metal Material Microstructure Control of Jiangxi Province of China(JW201223001)Foundation of Jiangxi Educational Committee of China(GJJ14534)
文摘Microstructure transformation and aging hardening behavior of 15-5 PH stainless steel were studied by optical microscopy (OM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results showed that the 15-5 PH stainless steel consists of NbC precipitates and lath matensite with a high dislocation density after solution treatment. With increasing aging temperature and aging time, the martensitic laths were resolved gradually. Meanwhile, the nanometric-sized Cu precipitates gradually coarsened and lost their coherency with'the martensite matrix, which exhibited an elliptical shape finally. Fine Cu precipitates can lead to significant dispersion hardening effect, while the coarsened Cu precipitates have no contribution to strengthening. The reversed austenite was observed in the speci- mens aged at 550 ℃ and above; moreover, the amount of reversed austenite increased as aging temperature in- creased. The precipitation hardening behavior of 15-5 PH stainless steel may depend on the balance between the softening caused by the formation of reversed austenite and the hardening caused by the precipitation of copper.