Authors: Kirschner, Marko
Title: Tiefbohren von hochfesten und schwer zerspanbaren Werkstoffen mit kleinsten Durchmessern
Language (ISO): de
Abstract: In industrial practice, high strength and performance-orientated materials contribute to enhance component properties and to improve resource efficiency. Consequently, these materials are constantly in demand and used more and more frequently in challenging applications. Within this context, high-strength bainitic steels as well as high temperature proof nickel based alloys are two of these material groups which are focused increasingly by automotive, aerospace and other applications sectors. The excellent material properties are linked to a sophisticated machining ability. Nevertheless, an economical manufacturing is an essential requirement to exploit the full potential of the use of high strength bainitic steels and high temperature-proof nickel based alloys. Therefore, it is absolutely indispensable to adopt and optimize existing manu¬facturing technologies. The research activities described in this thesis focus on the production of deep bore holes with smallest diameters and high length to diameter ratios based on mechanical processes. However, additional difficulties arise when single lip and twist deep hole drilling with smallest tool diameters are applied. Mentionable examples are very low tool rigidities, high mechanical tool loads owing to the limitedly realizable feed rates and the subsequently strong material squeezing and friction in the rounding of the cutting edge as well as the complicated chip removal through the small cross-sections of the chip flutes. In order to encounter the material and process specific challenges and to achieve a stable and productive deep hole drilling, a determined tool and process design for both materials is carried out. In the course of the experimental investigations the influence of the cutting data, the tool design with respect to the cutting tip design, the tool coating composition and the coating thickness as well as the cooling lubricant in single lip deep hole drilling is evaluated. Furthermore, a comparison of single lip and twist deep hole drilling shows the advantages and disad¬vantages of both manufacturing processes. A comprehensive analysis of the mechanical tool loads, chip formation, tool wear and bore hole quality regarding the dimension and form tolerances as well as the surface quality is made to evaluate the various influencing variables. Additionally, a newly developed methodology of analysis allows a closer look on the chip formation at the corresponding cutting edges and the chip removal along the chip flutes in smallest diameter deep hole drilling for the very first time. Here, samples made of the particular test materials are inserted in transparent acrylic glass carriers and the chip formation in the operating zone is documented by high speed microscopy. At the same time, the findings of this high speed chip formation analysis contribute to a substantial increase in fundamental process knowledge. A concluding comparison of the representative process characteristics and the technological correlations in deep hole drilling of high strength bainitic steels and high temperature proof nickel based alloys with smallest diameters clarifies the significantly divergent tribological application behavior. The differing mechanisms of tool wear as well as the related wear forms result in very individual and particular requirements on an efficient tool and process design. Based on the achieved knowledge, recommendations for the industrial practice are derived which facilitate a reliable and cost-efficient mechanical manufacturing of deep bore holes with smallest diameters for both materials, while simultaneously ensuring high bore hole quality in future.
Subject Headings: Mikrotiefbohren
Schwer zerspanbare Werkstoffe
Subject Headings (RSWK): Tiefbohren
Spanende Bearbeitung
Issue Date: 2016
Provenance: Vulkan-Verlag
Appears in Collections:Institut für Spanende Fertigung

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