Milling with ceramic inserts of austempered ductile iron (ADI): process conditions and performance
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ORIGINAL ARTICLE
Milling with ceramic inserts of austempered ductile iron (ADI): process conditions and performance L. N. López de Lacalle 1 & A. Fernández Valdivielso 1 & F. J. Amigo 1 & L. Sastoque 1 Received: 17 May 2020 / Accepted: 11 August 2020 / Published online: 17 August 2020 # Springer-Verlag London Ltd., part of Springer Nature 2020
Abstract In the work here presented, the high performance of ceramic insert tools in milling of ADI 1000 iron casting is analyzed. Austempered ductile irons (ADI) are ductile iron castings with strength and mechanical properties enhanced after specific heat treatment, achieving 1000 MPa or even more. Sintered carbide tools are state of the art in many industrial applications, including iron casting machining, but ceramic inserts are a feasible and promising option since cutting speed can be improved by 5 or even 10 times. A complete testing campaign was performed, starting with coated sintered carbides and aiming at the use of whisker reinforced Al2O3 ceramics and Si3N4 tools. The two most important conclusions are as follows: firstly, that the milling type socalled up-milling (or conventional) is more recommended than down-milling, also known as climb milling, and secondly, that dry machining enhances ceramics performance in comparison with using emulsion coolants (oil in water). Finally, results regarding economic aspects were analyzed based on the tools cost-performance ratio. Keywords ADI . Ductile iron . Milling . Machining . Ceramic tools
1 Introduction Ductile cast iron, also known as nodular cast iron or spheroidal graphite cast iron, was developed and patented around 1948. Graphite spheroids in metal matrix, different from graphite layers of gray casts, lead to castings with superior characteristics. Thus, ductile casting was quickly introduced in industrial designs to make lightweight components [1, 2]. Afterward, ADI (austempered ductile iron) castings represented a new evolution step. In ADI, graphite still appears spheroidal, but the big difference lies in the rest of the microstructure (Fe-C), which forms the so-called ausferrite. Hence, the ADI casting 5-stage heat treatment (heating, time, quenching, austempering, and cooling) causes a matrix structure, in which the acicular ferrite retains the carbon-stabilized austenite. So after this heat treatment so-called austempering, the ausferrite microstructure grows and develops. The austempering
* L. N. López de Lacalle [email protected] 1
Department of Mechanical Engineering, Aeronautics Advanced Manufacturing Center (CFAA), Faculty of Engineering of Bilbao, Alameda de Urquijo s/n, 48013 Bilbao, Spain
temperature determines the casting microstructure and its mechanical properties, resulting in different ADI grades. The understanding and control of heat treatment led to the introduction of ADI castings in a variety of industrial sectors. This material was and is increasingly demanded by engineers in terms of strength, wear, or fatigue resistance. ADI mechanical properties are superior to pearlite ducti
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