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carbide insert cross reference 4

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ISO insert codes that describe the insert geometry are good reference but ISO code of grades is of no use. Here are some of my comments on

STANDARD ISO 513:1991

Application of hard cutting materials for machining by chip removal – Designations of the main groups of chip removal and groups of application


General comments:
The main concern in the use of this standard is how to assign the group of application for a given hard cutting material provided that the chemical composition, mechanical and physical properties of this material are known. The standard states (clause 4.3) that “working conditions expressed in table 5 in very general terms and manufactures of hard cutting materials may possibly describe them, for their own purposes, in terms more directly related to the fields of use for the hard cutting material they manufacture.” In reality, this is not the case. Manufacturers of hard cutting materials do not know the physics of the contact processes taking place at too-chip and tool-workpiece interfaces and thus cannot describe properly these working conditions. Although the may provide a user with a detailed list of the mechanical and physical properties of the hard cutting materials they produced (for example, in the USA, these properties are determined using ASTM and ASM standards), they cannot correlate these properties with those involved in the cutting process.
Two characteristics of hard cutting materials are used in the standard, namely, wear resistance and toughness. Moreover, according to the standard, they vary in opposite directions. For example, if toughness increases then wear resistance decreases and vise versa. Problems start when one asks what is the meaning of these wear resistance and toughness.
Wear resistance is not a defined characteristic of the tool material as well as the methodology of its measurement. The nature of tool wear, unfortunately, is not clear enough yet in spite of numerous investigations. Although various theories have been introduced hitherto to explain the wear mechanism, the complicity of the processes in the cutting zone hampers formulation of a sound theory of cutting tool wear. Cutting tool wear is a result of complicated physical, chemical, and thermomechanical phenomena. Because different “simple” mechanisms of wear (adhesion, abrasion, diffusion, oxidation, etc.) act simultaneously with predominant influence of one or more of them in different situations, identification of the dominant mechanism is far from simple, and most interpretations are subject to controversy. As a result, experimental, or post process methods are still dominant in the studies of tool wear and only topological or simply, geometrical parameters of tool wear are selected and thus reported in tool life consideration.
The most common experimental technique used by hard tool material manufacture to characterize wear resistance is a FALEX-type pin-on-disk tribometer. The main problem is that in this tribometer, the continuous sliding contact occurs by cyclic reintroduction of the same surface element from the countermaterial. Repeated contact occurs between many machine elements, such as journal bearings, rotating seals and engine pistons. By contrast, metal cutting tools generally slide against a fresh, not previously encountered surface. Therefore, in laboratory wear testing it is important to reproduce the contact conditions peculiar to those at the tool-chip interface. The standard laboratory test set-ups for sliding wear are either of pin-on-disk or pin-on-ring type, both characterized by repeated contact between the surfaces. This design has obvious experimental advantages but the resulting contact conditions differ from those at the tool-chip interface. Thus most attempts to use controversial testing for prediction of the contact conditions at the tool-chip interface have been unsuccessful. Moreover, it is impossible to account for a particular tool geometry (rake, flank, inclination angles, radius of the cutting edge, etc), regime parameters (feed, depth of cut), and the dynamic properties of the machining system.
Even specialists on hard materials (for example, G.S. Upadhyaya, Cemented Tungsten Carbides: Production, Properties, and Testing, Noyes Publication, Westwood, New Jersey USA, 1998) point out that the results of the standard (ASTM standard B 611-85) abrasive wear resistance test “should not be understood as wear characteristics of carbide” (p. 279)
Toughness of a hard tool material is even less relevant characteristics bearing in mind the methods used in its determination. In cemented carbides, “Short Rod Fracture Toughness” measurement is common, as described in ASTM standard B771-87. The test procedure involves testing of chevron-slotted specimens and recording the loading versus specimen mouth opening displacement during the test.
To understand why the obtained in this way toughness is not relevant in machining, one should recall that fracture toughness is not only a characteristic of the material but also a unction of the lading conditions. As shown by Astakhov (V.P. Astakhov, Metal Cutting Mechanics, CRC Press, Boca Raton, 1998/1999, page 150, Fig. 4.8), fracture toughness can vary by 300% depending on loading conditions (the state of stress, strain rate, temperature).


Viktor
 
Excellent explanation. Do you have anything published I could purchase?

Have you heard about the following?
ICSHM8: A Special Tribute to Joseph Gurland
8th International Conference on the Science of Hard Materials
San Juan, Puerto Rico, November 8-12, 2004


Thanks,
Tom

 
Tom

I haven’t heard anything about this conference though I wouldn’t mind to read its proceedings. Just as bed (or bad?) time stories with the corresponding pictures of the other side of the Moon (sorry, micrographs SEM images of structures which nobody normally can understand).
As for my comments, I have them for many ISO standards related to metal cutting. The above is a “mild’ one. Others are mush more harsh. The good news is that nobody cares about these standards even in professional writing not to mention research papers and reports. The bad one is that the selection of the proper carbide grade and tool geometry is still a mater of experience because almost nothing is available to make this selection a bit more intelligent.

Regards
Viktor


Viktor
 
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