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Hexagonal boron nitride (h-BN) is an excellent solid lubricant that can be used to improve the processability of difficult-to-cut materials. We tried to solve the processing difficulty of vermicular graphite cast iron (VGI) by adding 0.0144 wt% of h-BN micro-powders into VGI (tensile strength Rm ≥ 450 MPa). Then, we use coated cemented carbide tools (CCC tools, coatings TiC + Al2O3) to carry out the turning test on VGI. By analyzing the maximum wear maxVB of the flank face, the wear morphology characteristics of rake face, and the residue on rake face, the wear mechanisms of the tool are studied. Finally, the role of h-BN in the processing process is assumed and the Gray-Markov model of maxVB is modeled. It can be found that: when v = 100~200 m/min, the tool life of cutting VGI with h-BN (sample A) was twice that of cutting VGI without h-BN (sample B). In particular, when v = 200 m/min, the tool life of cutting sample A is as high as 8 min. It is shown that h-BN can make CCC tools have the same advantages as PCBN tools in cutting VGI. In cutting sample A, the wear mechanisms of rake face are abrasive wear, adhesive wear, and oxidation wear, and adhesive wear is the main cause of tool failure. Given the cutting speed, when t ≥ 2 min, the adhesive wear of the rake face in cutting sample A is slighter than that in cutting sample B. h-BN can effectively reduce the adhesive wear. The error of maxVB predicted by Gray-Markov model is Δ ≤ 1.25%, which can be used to analyze and predict the tool wear of VGI with h-BN.

In the dry and hard cutting process of hardened steel, the white layer of the machined surface has a great influence on the service performance and life of the part. The cutting force and cutting heat produced in the process are among the important factors affecting the white layer characteristics. In the process of machining, in addition to the cutting parameters, the characteristics of cutting tools can also lead to significant changes in both service performance and part lifetime. Therefore, it is necessary to further study the changes in the cutting force, cutting heat, and white layer characteristics under the influence of the tool characteristics. In this paper, hard cutting tests of hardened steel were carried out by cutting tools (including PCBN tools and ceramic tools) with different thermal conductivities and flank wear under different cutting speeds. The influence of the cutting speed and tool characteristics on the cutting force, flank temperature and white layer characteristics was analyzed, and a prediction model for the white layer thickness was established. It was found that the cutting speed, tool wear degree, and tool thermal conductivity all have a significant influence on the cutting force, cutting temperature, and white layer thickness. Among the results, the thickness of the white layer first increases and then decreases with increasing flank temperature, and the critical temperature at the maximum thickness of the white layer is the actual final temperature of austenite transformation. Changes in the cutting force indirectly affect the temperatures of the austenite and martensite phase transitions, thus affecting the thickness of the white layer. The prediction results show that a fuzzy neural network based on particle swarm optimization can effectively predict the thickness of the white layer.

In this study, RuT400(σb ≥ 500 MPa) was milled with different cutting speeds, feeding rates and cutting depths to construct cutting force and surface roughness prediction models via response surfac...

Vermicular graphite cast iron is not used widely because of the challenges associated with to processing. This study investigates the tool wear morphology and main wear mechanism during the turning of high-strength vermicular graphite cast iron using coated ceramic tools. Further, it develops a tool life prediction model, based on the grey theory, for the flank face of the tool. The results show that coated ceramic tools are more suitable than cemented carbide tools for the turning of vermicular graphite cast iron. Coated ceramic tools mainly exhibit adhesive, abrasive, and diffusion wear during low-speed cutting wherein the turning speed V c ≤ 200 m / min . The FeO layer formed by the oxidation of the workpiece attached to the tool tip can appropriately reduce the tool wear. During high-speed cutting ( V c > 400 m / min ), coated ceramic tools mainly show oxidative and diffusion wear and a certain degree of abrasive wear. As the turning speed increases, the diffusion wear of coated ceramic tools initially increases and then decreases. The analysis of the model prediction results shows that the short-term prediction error of the grey model is less than 5%.

The white layer formed in hard cutting is widespread due to the intensive property of hardened steels and it also has important effects on machined surface integrity and service performance. In order to study the issue about the formation of white layer and concluding the relationship between the characteristics of white layer, tool flank temperature and the thermal conductivity, we used SCM415 (carburizing and quenching) as the object to carry out a series of high-speed dry cutting tests and observing the white layer by using optical microscope Axio Scope A1 in this paper. By analyzed these results we found that the temperature of tools is lower when the thermal conductivity of tool is higher and the greater the thermal conductivity of tool is, the more obvious the influence of the temperature change on the flank face is. When the flank temperature increased, the thickness of white layer increased. However, the white layer thickness is reduced, when the flank temperature are more than a certain range. Flank wear in a certain range can reduce the thickness of white layer and improve the surface quality.

金沢大学理工研究域機械工学系, This study deals with the machinability of steels in turning with additional current. Tested work materials were plane carbon steel JIS S45C and BN added steel which has good machinability at high cutting speed. Turning tests were performed by carbide tool P30 in order to investigate the influence of electrical conditions of closed circuit system on the cutting mechanism of BN added steel. The tool life and cutting force was investigated practically and these results were discussed. 従来,鋼の被削性を改善するために快削性添加物や鋼中の介在物の組成や形態を制御するなど多くの快削鋼が研究·開発がされてきた.その中のひとつであるBN添加鋼は切削中にベラーグと呼ばれる保護膜を摩耗面上に形成し,高速域で標準鋼に比べ工具摩耗を大幅に抑制する.本研究ではこのBN添加鋼を最大20mAの微量通電下で超硬工具による旋削加工を行い電流量と摩耗量の関係を調べ,その摩耗抑制効果について検討を行った., 出版者照会後に全文公開

金沢大学理工研究域機械工学系, 炭素鋼の旋削加工における切りくず処理性の向上の目的で，S45Cに半導体レーザを用いて長手方向にライン状に熱処理を行い，超硬，サーメットおよびセラミック工具を用いて旋削を行い，その有効性について検討を行った．その結果，切りくず処理性に改善が見られ，レーザ熱処理により切りくず処理性の改善が可能であることがわかった．また，仕上げ面粗さ，切削抵抗や切りくず厚さもわずかながら影響を受けることがわかった．, 出版者照会後に全文公開

金沢大学理工研究域機械工学系, This study deals with the machinability of steels in turning with additional current. Tested work materials were plane carbon steel JIS S45C and BN added steel which has good machinability in turning at high cutting speed. Turning tests were performed by carbide tool K10, P10, P20, P30, Cemet tool and TiCN coated carbide tool to clarify the influence of chemical compositions of tool materials on the cutting mechanism of BN added steel. The cutting force was investigated practically and these results were discussed., 著者らはこれまでに，超硬合金P30を用いた高速対応型快削鋼であるBN添加鋼の旋削加工において，切削中における工具-被削材間への外部通電が工具摩耗に影響を与えることを報告した．そこで本報では，工具材種の影響を調べるために，化学成分が異なる種々の工具を用いたBN添加鋼の旋削加工を行い，工具-被削材間に流れる電流の大きさおよび方向と切削抵抗の関係について調査し，標準鋼切削時と比較し検討を加えた．, 出版者照会後に全文公開