The carburizing process has been successfully carried out in multipurpose furnace employing the drip-feed atmosphere with the addition of rare earth (RE). The carbon transfer coefficients (BRE) and mean diffusion coef...The carburizing process has been successfully carried out in multipurpose furnace employing the drip-feed atmosphere with the addition of rare earth (RE). The carbon transfer coefficients (BRE) and mean diffusion coefficient (DRE) were calculated respectively based on the kinetics of the specimens weigh gain per unit area and the carburized layer growth. The results show that the BRE and DRE are all increased on basis of the incorporation of rare earth. In addition, the mathematical models of the carbon concentration profile under different carburizing conditions and the carbon diffusion coefficient DSRE (at x=0 for carburizing time t>0) have been deduced using the profile simulation method. Computer simulation results show that the simulated curves coincide quite well with the experimental data.展开更多
IN the past five years the process combination of vacuum hardening, respectively vacuum carburizing with high-pressure gas quenching was successfully introduced to the market, especially in the manufacture of gears. I...IN the past five years the process combination of vacuum hardening, respectively vacuum carburizing with high-pressure gas quenching was successfully introduced to the market, especially in the manufacture of gears. In the meantime furnace concepts for various applications are available to the industry. In the following report three plant varieties are introduced, which differ in process flexibility and throughput. This report also explains criteria for the selection of a furnace in view of the existing application requirements. Besides this a short introduction is given into the vacuum carburizing process and the high-pressure gas quenching technology.展开更多
Steel is the most important metallic material used in industry. This is because of the versatility of its engineering properties under different conditions. In one condition it can be very mild, soft and suitable for ...Steel is the most important metallic material used in industry. This is because of the versatility of its engineering properties under different conditions. In one condition it can be very mild, soft and suitable for any forming operation. In another condition the same steel can be very hard and strong. This versatility is made possible by the different heat treatments that the steel can be subject to. One such treatment is Gas carburizing. This is the most widely used process for surface hardening of low carbon steels. In this method the surface composition of the steel changes by diffusion of carbon and or nitrogen and result in hard outer surface with good wear resistance properties. A striking feature of Gas Carburizing process is that in this process the original toughness and ductility remains unaffected even after heat treatment. 3% nickel chromium case hardened low carbon steels are widely used for critical automotive and machine applications such as rack and pinion, gears, camshaft, valve rocker shafts and axles which requires high fatigue resistance. Fatigue behaviour of case carburized parts depends to a great extent on the correct combination of Hardness Penetration Depth (HPD) and the magnitude of hardness at the surface and beneath the surface with low size and shape distortion. In order to reduce the manufacturing costs in terms of material consumption and elimination of the number of processing steps, the effect of Gas carburizing parameters on the fatigue behaviour should already be considered in the parameter design stage. Therefore it is of importance to optimize the gas carburizing process variables to attain quality products with respect to hardness and case depth. In the present paper, the evaluation of process capability was carried out through a Limit Design Concept called orthogonal array design of experiment. To optimize the process variables the influence of several parameters (Holding time, Carbon potential, Furnace temperature and Quench time) of the gas carburizing process on the micro hardness, total case depth, effective case depth and level of distortion of AISI 8620 steel were discussed.展开更多
文摘The carburizing process has been successfully carried out in multipurpose furnace employing the drip-feed atmosphere with the addition of rare earth (RE). The carbon transfer coefficients (BRE) and mean diffusion coefficient (DRE) were calculated respectively based on the kinetics of the specimens weigh gain per unit area and the carburized layer growth. The results show that the BRE and DRE are all increased on basis of the incorporation of rare earth. In addition, the mathematical models of the carbon concentration profile under different carburizing conditions and the carbon diffusion coefficient DSRE (at x=0 for carburizing time t>0) have been deduced using the profile simulation method. Computer simulation results show that the simulated curves coincide quite well with the experimental data.
文摘IN the past five years the process combination of vacuum hardening, respectively vacuum carburizing with high-pressure gas quenching was successfully introduced to the market, especially in the manufacture of gears. In the meantime furnace concepts for various applications are available to the industry. In the following report three plant varieties are introduced, which differ in process flexibility and throughput. This report also explains criteria for the selection of a furnace in view of the existing application requirements. Besides this a short introduction is given into the vacuum carburizing process and the high-pressure gas quenching technology.
文摘Steel is the most important metallic material used in industry. This is because of the versatility of its engineering properties under different conditions. In one condition it can be very mild, soft and suitable for any forming operation. In another condition the same steel can be very hard and strong. This versatility is made possible by the different heat treatments that the steel can be subject to. One such treatment is Gas carburizing. This is the most widely used process for surface hardening of low carbon steels. In this method the surface composition of the steel changes by diffusion of carbon and or nitrogen and result in hard outer surface with good wear resistance properties. A striking feature of Gas Carburizing process is that in this process the original toughness and ductility remains unaffected even after heat treatment. 3% nickel chromium case hardened low carbon steels are widely used for critical automotive and machine applications such as rack and pinion, gears, camshaft, valve rocker shafts and axles which requires high fatigue resistance. Fatigue behaviour of case carburized parts depends to a great extent on the correct combination of Hardness Penetration Depth (HPD) and the magnitude of hardness at the surface and beneath the surface with low size and shape distortion. In order to reduce the manufacturing costs in terms of material consumption and elimination of the number of processing steps, the effect of Gas carburizing parameters on the fatigue behaviour should already be considered in the parameter design stage. Therefore it is of importance to optimize the gas carburizing process variables to attain quality products with respect to hardness and case depth. In the present paper, the evaluation of process capability was carried out through a Limit Design Concept called orthogonal array design of experiment. To optimize the process variables the influence of several parameters (Holding time, Carbon potential, Furnace temperature and Quench time) of the gas carburizing process on the micro hardness, total case depth, effective case depth and level of distortion of AISI 8620 steel were discussed.
