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Jackson Edwards
Jackson Edwards

New Cutting Edge Pre-intermediate Book Download



"1. A coated cutting insert for milling of gray cast iron alloys, comprising: a tungsten carbide-based substrate having a rake surface and a flank surface, the rake surface and the flank surface intersect to form a substrate cutting edge; the substrate consisting of 5.9 weight percent to 6.1 weight percent cobalt, and 0.4 weight percent to 0.6 weight percent chromium, the remainder being tungsten and carbon, apart from impurities; and




New Cutting Edge Pre-intermediate Book Download



a tungsten carbide-based substrate having a rake surface and a flank surface, the rake surface and the flank surface intersect to form a substrate cutting edge; the substrate consisting of between 5.9 weight percent and 6.1 weight percent cobalt, and between 0.3 weight percent and 0.7 weight percent chromium, the [remainder] balance being tungsten and carbon, apart from impurities; and


The Board's view expressed in the annex to the summons to oral proceedings, that D2 represents the closest prior art, is disagreed with. Firstly, the disclosure in D6 and D5 does not justify this position and secondly, reliable technical evidence supports the position that the machining characteristics of ductile cast iron are fundamentally different from those of gray cast iron. Therefore a cutting insert useful for milling ductile cast iron is not conclusively suitable for milling gray cast iron. D6 is silent about the machinability of ductile cast iron which is termed "Spheroidal Graphite (SG) Cast Iron" (see page 71, the paragraph bridging the left- and the right-hand column) while with respect to gray cast iron it reveals only "its good machining properties" (see page 71, left-hand column, 2nd full paragraph). D5 does also not support the Board's position since it mentions "Alloyed tungsten carbide grades (letter M, yellow color, generally with less TiC than the corresponding P series) for multipurpose use, such as steels, nickel-base superalloys, and ductile cast irons" and "Straight tungsten carbide grades (letter K, red color) for cutting gray cast iron, nonferrous metals, and non-metallic materials" (see page 75) so that ductile cast iron uses one grade of cutting inserts while gray cast iron uses another grade. Consequently, D5 does not teach or suggest that one cutting insert is suitable for machining both types of materials. The same conclusion is valid with respect to the passage under the heading "Machining Applications" at page 86 of D5 only mentioning gray cast iron and the use of uncoated straight WC-Co grades. There is no common technical knowledge that WC grades used for milling ductile cast irons are suitable for milling gray cast irons, too. Furthermore, D7 and D8 prove that the mechanism of chip formation in the machining of these two types of materials having different graphite morphologies is fundamentally different (see D7, page 655) so that ductile cast iron is easier to machine (see D7, page 660; see D8, pages 568 and 572). Accordingly, although D2 is also concerned with milling operations, the person skilled in the art would not take D2 as a springboard when aiming at improved cutting tools for the milling of gray cast iron. In this context it is admitted that the problem underlying D2 with respect to the thermal and mechanical shocks of the cutting inserts is similar to that of the present application. However, the present application relates to gray cast iron and all examples were made with gray cast iron (see page 1, lines 23 to 26 and the examples given on pages 6 to 12).


The distinguishing features of the cutting inserts based on composition 1 of D2 have been correctly mentioned in the annex. But even if the skilled person would apply the steps referred to by the Board with respect to the common general knowledge he would not arrive at the improved cutting insert according to claim 1 of the main request but only at an inferior one, as proven by the test results according to Annex 1.


Furthermore, it needs to be considered that the person skilled in the art will select a particular coating scheme in view of the desired application and the nature of the substrate to be coated. Therefore, although D5 seems to disclose that an alumina outer coating may have some advantages over a TiC outer coating, it is clear for the skilled person that these advantages do not come into play for each and any cutting application and/or substrate. D5 appears to teach that alumina has a higher hardness at about 1000ºC than TiC which does not necessarily mean that the coating is suitable to withstand thermal and mechanical shocks. D5 also shows that alumina has a higher coefficient of thermal expansion than TiC (see page 81, table 8) which would also cause a higher thermal expansion mismatch between the substrate and the alumina coating. Accordingly, D5 does also not support any common general knowledge that overlying a TiC layer with an alumina outer coating would result in an improved tool life for each and any machining operation, in particular in the milling of gray cast iron. The skilled person has no reasonable expectation of success, nor any other motivation to modify the teaching of D2 being directed to the milling of ductile cast iron, by using a different substrate and different coating scheme to adapt it for the machining of workpieces of different material. Therefore the subject-matter of claim 1 of the main request involves inventive step.


2.2.1 It is correct that D2 relates to cutting inserts for milling of ductile iron alloys, a material which is different from gray cast iron. However, D2 mentions the micro-chipping problems associated with mechanical and thermal shock, particularly in high speed milling operation between about 600 and about 800 surface feet per minute (see column 1, lines 13 to 67) in exactly the same way as the present application (according to its examples cutting speeds of about 900 and 1200 surface feet per minute were applied; see WO-A-02 14578, page 8, lines 9 and 37; page 9, line 19; page 10, line 11; page 11, line 5) wherein it is generally mentioned that thermal shocks and mechanical shocks of the milling operation result in micro-chipping of the cutting edge of the cutting tool (see the published WO-A-02 14578 corresponding the application as originally filed, page 1, lines 11 to 17). Thus the problems mentioned above are considered to be the same for both materials. This finding has not been objected to by the appellant at the oral proceedings.


2.2.3 D5 is an excerpt of a text book and concerns cemented carbides in general. D5 discloses the ISO R513 classification of carbides according to their use for machining by chip removal (see page 75, table 4). It mentions in the text "Alloyed tungsten carbide grades (letter M, yellow color, generally with less TiC than the corresponding P series) for multipurpose use, such as steels, nickel-base superalloys, and ductile cast iron" (see page 75, left-hand column, second and third full paragraph), i.e. the M-series is suitable for machining ductile cast iron, while it discloses with respect to grades M 10, M 20 and M 30 in said table 4 gray cast iron among the materials to be machined and milling as one use of these alloyed WC-based carbide substrate materials (see page 75, table 4). Hence the appellant's argument that ductile cast iron uses one grade of cutting insert while gray cast iron uses another grade cannot hold.


Document D2 discloses a coated cutting tool for the milling of ductile iron comprising a rake face and a flank face, a cutting edge at the juncture of the rake and flank face and a coating on the substrate; the substrate comprising a WC based cemented carbide having a bulk composition of no more than 7 wt.% Ta, no more than 3 wt.% Nb, no more than 5 wt.% Ti, no more than 1 wt.% Cr, between about 5 and about 13 wt.% Co and the balance WC; the coating comprising an innermost coating scheme including at least one layer adjacent to the substrate, and the coating further including an outermost layer comprising TiC applied by CVD (see column 4, lines 14 to 38 and claim 1). According to claims 4 and 5 - both referring to claim 1 - the innermost coating scheme comprises a single innermost TiCN layer applied at a temperature between about 900 and about 1050ºC and the CVD layer of TiC is adjacent to the CVD layer of TiCN; this two-layer embodiment corresponds to that of figure 2.


4.1.3 With respect to feature iii) the Board remarks that it belongs to the common general knowledge that an (additional) outermost alumina layer provides an improved tool life at higher cutting speeds as compared to an outermost TiC layer, due to a better temperature stability and hardness (abrasion resistance) of the alumina coating (see D5, page 81, left hand column, second paragraph to middle column, second paragraph and figures 19 and 20b). By overlying the TiC layer with an alumina layer the latter prevents the oxidation of the TiC layer at high temperatures of about 1000ºC which are easily reached at high cutting speeds.


4.4.1 As already mentioned, it belongs to the common general knowledge of the person skilled in the art that an alumina coating has a higher hardness than TiC at a temperature of 1000ºC - which is easily reached at the rake face of the tool during high-speed machining - and provides a better abrasion resistance at higher cutting speeds and thereby provides an improved tool life, e.g. when turning gray cast iron (see D5, page 81, left-hand column, first full paragraph to middle column, second full paragraph; and figures 19 and 20). Such an improved tool life is also due to the fact that an outermost alumina layer prevents or suppresses the oxidation of the underlying TiC layer at such high temperatures of about 1000ºC.


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