Method of making a cemented carbide power with low compacting pressure

Abstract

The present invention relates to a method of making a cemented carbide with submicron WC grain size with a powder metallurgical technique including milling, pressing and sintering. The method includes milling all components except WC for about three hours, then adding the WC powder and milling for about ten additional hours. In this way a cemented carbide powder with acceptable low compacting pressure is obtained.

Description

where M_s is the measured saturation magnetization of the sintered cemented carbide body in kA/m hAm²/kg and wt % Co is the weight percentage of Co in the cemented carbide. The CW-ratio in inserts according to the invention shall preferably be 0.80-1.0, and most preferably 0.80-0.90. The amount of W dissolved in binder phase is controlled by adjustment of the carbon content by small additions of carbon black or pure tungsten powder.

According to the method of the present invention, the milling procedure is started with a >2 hours, preferably about 3 hours, pre-milling step including wet milling in ethanol with cemented carbide milling bodies of all components except of WC such as grain growth inhibitors, carbon black or tungsten powder, binder metal and pressing agent, respectively. The pre-milling step is followed by a further final milling step of about 10 hours with the WC powder included. The amount of milling bodies during the pre-milling and final milling shall be such that the weight ratio milling bodies: WC powder is about 4-7. The cemented carbide powder is then dried preferably by spray drying, pressed to inserts and sintered.

WC-powder with submicron grain size distribution according to the invention with no grains greater than 1.5 μm is prepared by milling/sieving such as in a jetmill-classifier. According to the present invention, a minimal change in grain size and/or grain size distribution results from the final milling step.

Claims

#2# 1. A method of making a submicron cemented carbide powder comprising a plurality of components including submicron WC and binder metal, the powder having a low compacting pressure, the method comprising the steps of:

(i) pre-milling a mixture of components which does not include the WC for more than 2 hours;

(ii) adding the WC to the mixture of step (i) and milling for approximately 10 hours; and

(iii) drying the milled mixture to obtain a powder.

2. #2# The method of claim 1, wherein the mixture of components in step (i) comprises grain growth inhibitors, at least one of carbon black and tungsten powder and a pressing agent.

3. #2# The method of claim 2, wherein the mixture of components in step (i) is wet milled in ethanol.

4. #2# The method of claim 1, wherein the premilling step (i) is performed for approximately 3 hours.

5. #2# The method of claim 1, wherein step (iii) comprises spray drying.