KR20010006648A - High pressure high temperature apparatus - Google Patents

Abstract

PURPOSE: To effectively perform the cooling of an annular die and to improve productivity of artificial diamond or the like in a mold device of a punch and a die by forming, on the annular die for high temperature and high pressure, cooling flow passages or cooling grooves extending from the top surface to the bottom surface thereof. CONSTITUTION: When manufacturing artificial diamond or cubic boron nitride (CBN) by a high temperature and high pressure method using a mold device consisting of a punch A and an annular die B, on the annular die B of cemented carbide, cooling flow passages extending in the axial direction of the die from top surface to the bottom surface thereof are formed. These flow passages are formed in straight lines, or in spirals, or in twists. By causing a coolant of temperature of not less than 10deg.C to flow in the cooling flow passages, the cooling of the annular die B is performed. By this cooling, the temperature of the die is preferably lowered to a prescribed critical point or less to attain the die performance about 10 times extra as compared with the conventional die.

Description

HIGH PRESSURE HIGH TEMPERATURE APPARATUS}

The present invention basically relates to a high pressure high temperature (HPHT) device comprising an annular die and a pair of tapered punches. By providing a cooling channel in the annular die, a dramatic and surprising increase in performance has been obtained.

Punch and die devices are industrially manufactured of synthetic diamond and cubic boron nitride (CBN) or polycrystalline diamond green compacts (PCDs) and PCBNs (polycrystalline cubic crystals) due to their simplicity in structure and relatively large sizes that can be used in the machining sector. Boron nitride green compact) is preferred. The punch and die apparatus consists of an annular die and a pair of tapered forming punches axially aligned oppositely. The inner diameter of the die is generally about 5 cm and the outer diameter is about 15 cm. Punch and die are usually made of cemented carbide. The composition of the die and punch is selected such that the hardness of the die exceeds 1100 HV and the hardness of the punch exceeds 1500 HV. The die and punch are both shrink fit into a steel ring with an outer diameter of about 35 cm. Such devices generally operate at temperatures and pressures at which diamond or cBN is stable, ie hundreds of degrees Celsius higher than 1000 degrees Celsius, and pressures of about 60 kbar. This process is referred to herein as the HPHT process. Heating is obtained by passing a current through a cemented carbide punch and a diamond or cBN charge. The heat generated in the diamond or cBN inputs is insulated and insulated from the die, but some temperature rise of the cemented carbide is unavoidable. The cemented carbide portion close to the input reaches a temperature of about 200 ° C. very easily. This may affect the cemented carbide tools used in the HPHT process, ie dies and punches. In order to maintain the temperature control of the die, the die is subjected to cooling by cooling water on the end face.

Because of the harsh conditions applied to punches and dies, the punches and dies can only be used for a limited number of cycles before changing. In general, the reason for the exchange is cracking or sparring of the outer portion of the die. Punch is relatively cheap and easy to change. However, dies are much more expensive than punches because of their size. Dies are also difficult to exchange.

It is therefore an object of the present invention to provide an annular die with improved properties.

1 is a photograph showing a punch and die device composed of a punch A and an annular die B;

Figure 2 is a photograph showing an annular die according to the present invention with the axially oriented cooling channel of the die placed in a cemented carbide die.

Figure 3 is a photograph showing an alternative arrangement of cooling channels on the outer cylindrical surface of the die.

<Description of the code | symbol about the principal part of drawing>

A: Punch

B: annular die

It has now been surprisingly found that when a die is provided with a cooling channel extending from the top to the bottom of the die, an unexpectedly 10 times increase in die performance is achieved. This cooling channel does not appear to affect the strength of the die, but lowers the temperature below the critical point. The cooling channel will be located at a distance from the center of the die. The cooling channel will not be too close because strength may be affected.

According to the present invention, the die will be provided with 5 to 25 cooling channels located equidistantly on a circle having a diameter in the range of ID: OD: OD. Channels located on the outer diameter of the die are of course present as grooves in the outer cylindrical surface. The dimensions of these channels will be such that the channels occupy up to 2000 mm 2 of the end face of the die having typical dimensions. The cooling channel may be straight, but may also be spiral or twisted.

Cooling channels can be obtained by various methods known in the art. The cooling channel is drilled or milled in a presintered state. The cooling channel may be made by placing some material or metal that melts during sintering. The cooling channel may be formed by making a die of two rings, the inside of which has a groove on the outer surface.

The invention also relates to a method for synthesizing diamond or cBN under high pressure / high temperature conditions using a cemented carbide annular die. This method is characterized by the use of an annular die which is cooled by providing cooling channels. Preferably the temperature of the cooling medium will be less than 10 ° C.

Example

Six annular dies were tested. The die was made of cemented carbide having dimensions outer diameter (OD) = 127 mm and inner diameter (ID) = 40 mm. The composition of the cemented carbide was 11% Co and 89% WC with a hardness of 1330 HV. In the pre-sintered state, 15 holes of 6 mm were drilled so as to be regularly distributed on a circle having a diameter of 105 mm.

The die was tested on a 1800 ton diamond press, which averaged 22,460 processes. A similar conventional die, i.e., a die without a cooling channel, could only go through 3200 processes.

The die according to the present invention is significantly increased in performance compared to conventional die in a high pressure high temperature operating environment by providing a cooling channel.

Claims (6)

An annular die for a high pressure, high temperature process, characterized in that a cooling channel or groove is provided extending from the top surface to the bottom surface. The annular die according to claim 1, which is made of cemented carbide. 3. The annular die of claim 1 or 2, wherein the channel is straight. 3. The annular die of claim 1, wherein the channel is helical or twisted. In a high pressure high temperature process performed in an apparatus consisting of an annular die and two opposing punches, The annular die is cooled by providing cooling channels. 6. The high pressure high temperature process according to claim 5, wherein the annular die is cooled by a cooling medium having a temperature of less than 10 ° C.