Fu Gang Yan

Cutting temperature and tool wear of hard turning hardened bearing steel

Abstract A study was undertaken to investigate the performance of PCBN tool in the finish turning of GCr15 bearing steel with different hardness between HRC30 and 64. A natural thermocouple was used to measure the cutting temperature, and tool life and cutting temperature were investigated and compared. The objective was to determine the influence of the workpiece hardness on changes in cutting temperature and tool wear characteristics. According to the experimental results, the critical hardness when turning hardened GCr15 bearing steel with a PCBN tool is about HRC50.

Research on the Application and Design of Special Tools of the Hydrogenated Cylindrical Shell

Both the heavy cutting process and the importance of the chip control are discussed. Through analyzing the characteristics of the rough machining of the hydrogenated cylindrical shell, both the structure and the material of the turning tool for rough machining are designed. To test and verify the feasibility study on them, the contrast experiment between the new-type turning tool and the reference substance in cutting the 2.25Cr-1Mo-0.25V steel which is the material of hydrogenated cylindrical shell is made, then the service life and the chip-breaking performance of the tool are compared. Finally, the technical reference to design the new-type turning tools is summarized.

Effect of Different Edge Preparation on High Speed Turning Hardened Steel Process

Through combining turning experiments and FE simulations, this paper studied the effects of force, temperature and residual stress of machined surface on high speed hard turning GCr15 bearing steel hardened to HRC60-62 with three kinds of ordinary edge preparation (sharp-edge, hone and chamfer). The experiment and simulation results indicated that the diathermanous proportion of chamfered edge preparation to tool and machined surface is less, and this distribution of cutting temperatures is useful for tool life and machined surface quality. The simulation results showed that cutting force had a descending tendency with increasing of cutting speed, which is in accordance with the change rules of machining general rigidity material, and it proved that FE simulations have good precision. The simulation results of residual stress of machined surface showed that residual tensile stress existed in machined surface using both honed and chamfered tools, and a highest compressive stress (about -200MPa) existed among 150-200μm of the depth into the workpiece surface. The difference was that the depth of superficial harden layer with honed tools is larger than that with chamfered tools.

Research on the Dynamic Mechanical Characteristics of the Tool Life in the Excessively Heavy-Duty Cutting Process

Basing the foundation on the cutting experiments of 2.25Cr-1Mo-0.25V steel which is the material of hydrogenated cylindrical shell, the dynamic mechanical characteristics of the excessively heavy-duty cutting were analyzed. Then through researching the influence that the dynamic mechanical characteristics had on tools failure in limited heavy-duty cutting process, and the model of dynamic shearing force in cutting area was established. However, the experimental results showed that the dynamic shear-flowing-stress in cutting area had great influence on tools fatigue, and the mainly damaged form of the heavy-duty cutting tool was shearing fracture. Analyzing the theory comprehensively, the critical condition of tools fracture which was under the terms of extreme loading had been established finally.

Research on the Fracture and Breakage of Heavy-Duty Turning Tool for Rough Machining Hydrogenated Cylindrical Shell

Analyzing and researching the main failure forms of the hard alloy turning tool in rough machining process of the hydrogenated cylindrical shell’s blank. Then the cutting experiments were done at the site, and the results showed that the main failure forms of the hard alloy turning tool in rough machining process of the blank were tools’ fracture. However the main reason leading into this phenomenon was the mechanical impact of variable frequency and variable load which was caused by the dynamic change of cutting dosage. Integrating the experiment results, and combining the principles of elasticity and the principles of fracture toughness of hard alloy, the measures of protecting the tools from being fractured prematurely in heavy cutting process were worked out, then the research result would provide reference database for practical production.

Research on the High-Efficiency Turning Tool for Rough Machining of Large Hydrogenated Cylindrical Shell Forging

The large hydrogenated cylindrical shell is an important part of petrochemical pressure vessels. From the macroscopic aspects, the influence that the surface defects of the large hydrogenated cylindrical shells forging blank has on the high efficiency machining was analyzed in the paper firstly. Then, through the chemical point of view, the new chemical components of the shells material were known, and the shells material physical properties were also dissected. The phenomenon of compatibility between the Co element which is in tools material and the siderophile element of the 2.25Cr-1Mo-0.25V steel which is the material of the large hydrogenated cylindrical shell was found. Therefore, the technical performance requirements of the heavy-duty turning tool which is to achieve the goal of high efficiency cutting were put forward. Through researching the chemical and the physical properties of the shell, the new high-efficiency turning tool was designed from the aspects of the tools material and the tools geometric structure. Finally, the comparative test between the new heavy-duty turning tool which was named XF8 and the YT5 tool which was being used in factory was made, and by way of comparing both the service life and the chip-breaking performance of XF8 with YT5s, the test results showed that the XF8 met the requirements of high-efficiency heavy-duty turning, and the feasibility of the tools design scheme was further verified.

Investigations of Surface Roughness with Cutting Speed and Cooling in the Wear Process during Turing GH4133 with PCBN Tool

The high temperature strength of Ni-based superalloys coupled with excellent corrosion resistance make them ideal for aerospace applications. However, the difficulty in finish machining superalloys with the carbide tools presents the short tool-life. Polycrystalline Cubic Boron Nitride (PCBN) is potential to machine superalloys. To data, there are many researches about PCBN tool wear, but only little papers showing how the surface roughness and the wear speed are influenced by cutting parameter and the coolant during the differences periods of PCBN tool wear. This investigation has been conducted to show that the PCBN tool wear is slower with cooling that without cooling during cutting superalloys with PCBN tool especially in VB up to a certain value. It is shown that tool fracture can be reduced by using the cooling. In the process of PCBN tool wear, in addition, there are some differences of the effect of the cooling for roughness Ra values.

Tool Life Evaluation Methods of Heavy Forging Hogging Machining Based on Image Processing Technology

In practical production, the evaluation method of tool life that heavy forging shell ring is in hogging machining compare the length of its processing surface in a single direction, the method considers neither the actual cutting distance of cutting tool, nor the impact times sustained by the cutting tool, this paper provides a new method of tool life evaluation based on image processing technology. Through collecting images of processing surface of the work-piece, which contains the different colors and brightness caused by processed and unprocessed, and image processing, analysis and calculation, the new method can accomplish the calculation about the effective cutting distance of cutting tool and the number of impact force about cutting tool, it will be more scientific and more reasonable evaluation method of tool life. Finally, one example is given. New method can be used to provide accurate evaluation of tool life and material machinability for the machining of large forgings.

Application of Continuous Wavelet Features and Multi-Class Sphere SVM to Chatter Prediction

A cutting chatter forecast method based on continuous wavelet feature and multi-class spherical Support Vector Machines is studied in this paper. The method based on continuous wavelet transform extracts the cutting vibration signal feature and uses multi-class spherical Support Vector Machines to discern the chatter. In order to simplify computational complexity when binary classification SVM turn to multi-class classification, the algorithm makes every kind of samples have a spherical SVM. In the feature space identified the test sample and spherical SVM centre distance as a decision-making function. Experiments show that using combine spherical SVM with continuous wavelet feature Vector has good recognition effect in the milling chatter recognition system. Chatter inoculation forecast accuracy reaches 95%, and chatter outbreak forecast accuracy reaches 97.5%.

Layer Face Milling Cutter Parametric Modeling and Modal Analysis

Performance-based parametric design method for improving the face milling cutter design efficiency and ensuring the use of performance has an important significance. Three kinds of parameter design method are described in this paper, and parametric design of series of layer milling cutter is completed by modeling parametric design method with UG software. Also, modal analysis is made with FEM. Therefore the study results provide examples for optimization of tool structural and analysis of restrain vibration.