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Method of making a fine grained cemented carbide

a cemented carbide, fine grain technology, applied in the direction of turning machines, turning apparatus, turning tools, etc., can solve the problems of limiting grain growth, unfavorable affecting toughness behavior, and particularly detrimental additions of vanadium or chromium, and achieve high deformation resistance and high toughness

Inactive Publication Date: 2006-02-09
SANDVIK AB
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0007] It is an object of the present invention to avoid or alleviate the problems of the prior art. It is further an object of the present invention to provide a cemented carbide insert with a combination of high toughness and high deformation resistance along with a method for making the same.

Problems solved by technology

When added, generally as carbides, they limit grain growth during sintering, but they also have undesirable side effects such as unfavorably affecting the toughness behavior.
Additions of vanadium or chromium are particularly detrimental and have to be kept on a very low level in order to limit their negative influence on the sintering behavior.
Both vanadium and chromium reduce the sintering activity often resulting in an uneven binder phase distribution and toughness reducing defects in the sintered structure.
Such production route, of course, increases the production cost.

Method used

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  • Method of making a fine grained cemented carbide
  • Method of making a fine grained cemented carbide
  • Method of making a fine grained cemented carbide

Examples

Experimental program
Comparison scheme
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example 1

[0034] From a powder mixture consisting of 6.0 weight-% Co, and balance WC with an average grain size of about 1 μm with 0.01 weight-% overstoichiometric carbon content, turning the inserts CNMG120408 were pressed. The inserts were sintered in H2 up to 450° C. for dewaxing. At 450° C., the furnace was evacuated and refilled with nitrogen up to a pressure of 0.8 atm. The temperature was kept constant at 450° C. during the nitrogen filling procedure. After completed filling, the temperature was increased to 1370° C. with a speed of 15° C. / min, keeping the nitrogen pressure constant. At 1370° C., the furnace was evacuated and refilled with a protective atmosphere of 10 mbar Argon and kept at 1370° C. for 30 minutes followed by an increased Ar pressure of 40 mbar and a temperature increase up to the final sintering temperature of 1410° C. where the temperature was kept for an additional hour before cooling and opening of the furnace.

[0035] The structure in the cutting inserts consisted...

example 2

Reference Example to Example 1

[0036] Pressed inserts from Example 1 were sintered in H2 up to 450° C. for dewaxing, further in vacuum to 1370° C., then filled with a protective gas of 10 mbar of Ar and kept at 1370° C. for 30 minutes followed by an increased Ar pressure of 40 mbar and a temperature increase up to the final sintering temperature of 1410° C. where the temperature was kept for an additional hour before cooling and opening of the furnace.

[0037] The structure in the cutting inserts consisted of a comparably less fine and uniform tungsten carbide grain size in combination with a acceptable binder phase distribution, FIG. 2.

example 3

[0038] Pressed inserts from Example 1 were sintered in H2 up to 450° C. for dewaxing. At 450° C., the furnace was evacuated and refilled with nitrogen up to a pressure of 0.8 atm. The temperature was kept constant at 450° C. during the nitrogen filling procedure. After completed filling, the temperature was increased to 1370° C. with a speed of 15° C. / min, keeping the nitrogen pressure constant. At 1370° C. the furnace was evacuated and refilled with a protective atmosphere of 10 mbar Argon. The actual sintering was limited to a 30 min hold at 1370° C. followed by cooling and opening of the furnace.

[0039] The structure in the cutting inserts consisted of comparably fine and uniform tungsten carbide grain size in combination with an acceptable binder phase distribution, FIG. 3.

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Abstract

According to the present invention there is provided a method of making a finegrained tungsten carbide—cobalt cemented carbide comprising mixing, milling according to standard practice followed by sintering. By introducing nitrogen at a pressure of more than 0.5 atm into the sintering atmosphere after dewaxing but before pore closure a grain refinement including reduced grain size and less abnormal grains can be obtained.

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates to a method of making a fine grained cemented carbide. By performing the sintering at least partly in a nitrogen-containing atmosphere, a grain refined cemented carbide structure has been obtained. [0002] Cemented carbide inserts with a grain refined structure are today used to a great extent for machining of steel, stainless steels and heat resistant alloys in applications with high demands on both toughness and wear resistance. Another important application is in microdrills for the machining of printed circuit board so called PCB-drills. [0003] Common grain growth inhibitors include vanadium, chromium, tantalum, niobium and / or titanium or compounds involving these. When added, generally as carbides, they limit grain growth during sintering, but they also have undesirable side effects such as unfavorably affecting the toughness behavior. Additions of vanadium or chromium are particularly detrimental and have to be ke...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): B22F3/10B23B27/14C22C1/05C22C29/08
CPCB22F2005/001B22F2998/10B22F2999/00C22C1/051C22C29/08B22F9/04B22F3/1007B22F2201/02B22F3/10
Inventor GUSTAFSON, PERNORGREN, SUSANNEWALDENSTROM, MATS
Owner SANDVIK AB
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