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Coated inserts for rough milling

a technology of cemented carbide and cutting tool, which is applied in the field of rough milling coated inserts, can solve the problems of thermal cracks, chipping and edge fractures, and increasing the tendency to form comb cracks

Inactive Publication Date: 2007-11-06
SANDVIK INTELLECTUAL PROPERTY AB
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

It is well known that for cemented carbide cutting tool inserts used in the machining of cast irons, the cutting edge is worn by different wear mechanisms such as chemical and abrasive wear but the cutting edge is generally also subjected to crack formation due to the intermittent cutting load, resulting in so called chippings and edge fractures caused by different types of cracks in the inserts.
In particular, the use of fluid coolant increases the tendency to form comb cracks, often also called thermal cracks.
The use of fluid coolant leads to large temperature gradients and thermal tensile stresses in the insert surface, increasing the tendency for formation of surface cracks, in particular in the case of coated cutting tool inserts where the hard but brittle ceramic surface coating is prone to crack under conditions involving unfavourable thermal tensile stresses.
Cracks in the coating increases the risk for chipping and edge fractures and for flaking of the coating.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0031]A. Cemented carbide milling inserts in accordance with the invention with the composition 7.6 wt. % Co, 1.25 wt. % TaC, 0.30 wt. % NbC and balance WC with average grain size of 1.8 μm, with a binder phase alloyed with W corresponding to a CW-ratio of 0.87 were coated with a 0.5 μm equiaxed TiC0.05N0.95-layer (with a high nitrogen content corresponding to an estimated C / N-ratio of 0.05) followed by a 2.6 μm thick TiC0.54N0.46-layer, with columnar grains by using MTCVD-technique (temperature 850-885° C. and CH3CN as the carbon / nitrogen source). In subsequent steps during the same coating cycle, a 1.3 μm thick layer of Al2O3 was deposited using a temperature 970° C. and a concentration of H2S dopant of 0.4% as disclosed in U.S. Pat. No. 5,674,564. A thin (0.5 μm) layer of TiN was deposited on top according to known CVD-technique. XRD-measurement showed that the Al2O3-layer consisted of 100% κ-phase.

[0032]The coated inserts were brushed using a nylon straw brush containing SiC gra...

example 2

[0037]D. Cemented carbide milling inserts in accordance with the invention with the composition 7.6 wt. % Co, 1.25 wt. % TaC, 0.30 wt. % NbC and balance WC with an average grain size of 1.75 μm, with a binder phase alloyed with W corresponding to a CW-ratio of 0.88 were coated with a 0.5 μm equiaxed TiC0.05N0.95-layer (with a high nitrogen content corresponding to an estimated C / N-ratio of 0.05) followed by a 2.0 μm thick TiC0.54N0.46-layer, with columnar grains by using MTCVD-technique (temperature 850-885° C. and CH3CN as the carbon / nitrogen source). In subsequent steps during the same coating cycle, a 1.4 μm thick layer of Al2O3 was deposited using a temperature 970° C. and a concentration of H2S dopant of 0.4% as disclosed in U.S. Pat. No. 5,674,564. A thin (0.5 μm) layer of TiN was deposited on top according to known CVD-technique. XRD-measurement showed that the Al2O3-layer consisted of 100% κ-phase.

[0038]The coated inserts were brushed using a nylon straw brush containing SiC...

example 3

[0041]E. Cemented carbide milling inserts in accordance with the invention, identical to the inserts described in D (Example 2), except for that the coating not was brushed.

[0042]Inserts from D and E were tested in face milling of grey cast iron cylinder heads.

[0043]

Operation:Face milling-roughingWork-piece:Cylinder headMaterial:Pearlitic grey cast iron, alloyed,Cutting speed:116 m / minFeed rate / tooth:0.32 μm / rev.Depth of cut:1.5-2 μmInsert-style:TNEF 1204AN-CANote:Wet, 13 teeth, unstable tendenciesResults:Tool-life, number of component per edge setGrade D: (invention)685Grade C:570(outside invention)Tool-life criterion was edge break-out on the work piece due to chipping and high flank wear of the edges.

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Abstract

Coated milling insert has a WC-Co cemented carbide with a low content of cubic carbides and a highly W-alloyed binder phase and a coating including an inner layer of TiCxNy with columnar grains followed by a layer of κ-Al2O3 and a top layer of TiN. The coated milling insert is particularly useful for milling of grey cast iron with or without cast skin under wet conditions at low and moderate cutting speeds and milling of nodular cast iron and compacted graphite iron with or without cast skin under wet conditions at moderate cutting speeds.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS[0001]The present application is a reissue of U.S. Pat. No. 6,638,609 B2, which claims the benefit of priority to Swedish Application No. 0004079-0 filed Nov. 8, 2000.FIELD OF THE INVENTION[0002]The present invention relates to coated cemented carbide cutting tool inserts, particularly useful for milling of grey cast under wet conditions, preferably at low and moderate cutting speeds but also for milling of nodular cast iron and compacted graphite iron under wet conditions at moderate cutting speeds.BACKGROUND OF THE INVENTION[0003]It is well known that for cemented carbide cutting tool inserts used in the machining of cast irons, the cutting edge is worn by different wear mechanisms such as chemical and abrasive wear but the cutting edge is generally also subjected to crack formation due to the intermittent cutting load, resulting in so called chippings and edge fractures caused by different types of cracks in the inserts.[0004]Different type...

Claims

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Application Information

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IPC IPC(8): C23C16/30C22C29/08C23C30/00
CPCC22C29/08C23C30/005B22F2003/247B22F2005/001Y10T428/252Y10T428/265Y10T428/24975
Inventor NORDGREN, ANDERSHESSMAN, INGEMARMIKUS, MARIAN
Owner SANDVIK INTELLECTUAL PROPERTY AB
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