METHOD FOR THE MANUFACTURE OF A SHAPED BODY AS WELL AS GREEN COMPACT

• US 20120114516A1
• Filed: 11/09/2011
• Published: 05/10/2012
• Est. Priority Date: 11/09/2010
• Status: Active Grant

• Current Assignee: Degudent GmbH (Astrazeneca PLC)
• Original Assignee: Degudent GmbH (Astrazeneca PLC)
• Inventors: STEINKE, Rudi, VOLLMANN, Markus, WISSEL, Irmgard, HACHENBERG, Jörg, ZELLMANN, Gerhard, HOCK, Elmar, FECHER, Stefan, VOLKL, Lothar
• Granted Patent: US 9,393,088 B2
• Time in Patent Office: Days
• US Class Current: 419/25
• CPC Class Codes: A61C 13/0022 Blanks or green, unfinished dental restoration parts
• CPC Class Codes: A61K 6/84 comprising metals or alloys
• CPC Class Codes: B22F 2003/247 Removing material: carving, cleaning, grinding, hobbing, honing, lapping, polishing, milling, shaving, skiving, turning the surface
• CPC Class Codes: B22F 2003/248 Thermal after-treatment
• CPC Class Codes: B22F 2301/15 Nickel or cobalt
• CPC Class Codes: B22F 3/02 Compacting only
• CPC Class Codes: B22F 3/1021 Removal of binder or filler removal of binder from ceramics C04B35/638
• CPC Class Codes: B22F 3/11 Making porous workpieces or articles
• CPC Class Codes: B22F 3/16 in successive or repeated steps
• CPC Class Codes: B22F 3/24 After-treatment of workpieces or articles B22F3/1146 takes precedence
• CPC Class Codes: C22C 19/05 with chromium
• CPC Class Codes: C22C 19/053 with the maximum Cr content being at least 30% but less than 40%
• CPC Class Codes: C22C 19/055 with the maximum Cr content being at least 20% but less than 30%
• CPC Class Codes: C22C 19/07 based on cobalt

Abstract

A method for manufacturing a shaped body, comprising creating a mixture of a metal powder and binding agent, compacting the mixture to form a green compact, heating the green compact to a debinding start temperature T₁, debinding the green compact by controlled heating of the green compact from start temperature T₁ to end temperature T₂ at a heat-up rate R₁, presintering the debindered green compact to the presinter end temperature T_VS at a heat-up rate R_HVS, cooling the green compact from the presinter end temperature T_VS at a cool-down rate R_KVS, whereby at least the heat-up rate R_HVS, the presinter end temperature T_VS, and the cool-down rate R_KVS are tuned relative to each other in such a way that the presintered green compact forming a blank has a surface porosity of 16% to 22% after presintering, and machining and sintering of the blank to form the shaped body.

Claims

1. A method for the manufacture of a shaped body, in particular a dental prosthesis or part thereof, characterized by the following processing steps:

preparing a mixture of a metal powder and a binding agent;

compacting the mixture to form a green compact;

heating the green compact from room temperature to a debinding start temperature T₁;

debinding the green compact by controlled heating of the green compact from the debinding start temperature T₁ to a debinding end temperature T₂ at a heat-up rate R₁ in such a way that the green compact suffers no damage;

presintering of the debindered green compact to a presinter end temperature T_VS at a heat-up rate R_HVS;

cooling the green compact from the presinter end temperature T_VS at a cooling rate R_KVS, whereby at least the heat-up rate R_HVS, the presinter end temperature T_VS, and the cooling rate R_KVS are tuned relative to each other in such a way that the presintered green compact, forming a blank, possesses a surface porosity between 16% and 22% after presintering,

material-removing machining of the blank; and

sintering to final density of the machined blank to form the shaped body.

2. The method of claim 1, characterized in that after being heated to the presinter end temperature T_VS, the green compact is held at the presinter end temperature T_VS for the duration of a holding time t_VS before it is cooled at the cooling rate R_KVS, whereby preferably the green compact is cooled at the cooling rate R_KVS to a temperature T₃, with 450°

C.≦

T₃≦

650°

C.

3. The method of claim 1, characterized in that for debinding purposes, the green compact at first is heated to the debinding start temperature T₁ with 350°

C.≦

T₁≦

550°

C. and subsequently is heated in the temperature range between T₁ and the debinding end temperature T₂, with 550°

C.<

T₂<

650°

C. and T₂>

T₁, at a heat-up rate R₁, with 1 K/min≦

R₁≦

5 K/min, to T₂, whereby in particular the green compact is held at the debinding end temperature T₂ for a time period t₂ with 1 min≦

t₂≦

20 min.

4. The method of claim 1, characterized in that the compacted green compact used is a green compact with a surface porosity between 16% and 27%, in particular between 18% and 22%.

5. The method of claim 1, characterized in that as metal powder one uses a nickel-chromium alloy or a cobalt-chromium alloy, whereby for a cobalt-chromium alloy one chooses the following composition:

Cobalt;

50% to 70% by weight

Chromium;

20% to 35% by weight

Molybdenum;

0% to 10% by weight

Tungsten;

0% to 20% by weight

Other elements;

less than 10% by weight,

whereby the sum total adds up to 100% by weight,

while for a nickel-chromium alloy one uses the following composition;

Nickel;

50% to 70% by weight

Chromium;

20% to 35% by weight

Molybdenum;

0% to 10% by weight

Tungsten;

0% to 20% by weight

Other elements;

less than 10% by weight

with a sum total of 100% by weight.

6. The method of claim 1, characterized in that the green compact is held for the duration of a holding time t_VS at the presinter end temperature T_VS, in particular with 650°

C.≦

T_VS≦

1100°

C., whereby the higher one selects T_VS the shorter one should set the holding time t_VS.

7. The method of claim 1, characterized in that for a presinter end temperature T_VS of 650°

C.≦

T_VS≦

750°

C., one selects a holding time t_VS with 10 min≦

t_VS≦

200 min, in particular 30 min≦

t_vs≦

100 min, and particularly preferred 50 min≦

80 min, and preferably sets the heat-up rate R_HVS and the cool-down rate R_KVS to 1 K/min≦

R_HVS≦

200 K/min, in particular 1 K/min≦

R_HVS≦

50 K/min, particularly preferred 1 K/min≦

R_HVS≦

20 K/min, and 1 K/min≦

R_KVS≦

200 K/min, in particular 1 K/min≦

R_KVS≦

50 K/min, particularly preferred 1 K/min≦

R_KVS≦

20 K/min.

8. The method of claim 1, characterized in that for a presinter end temperature T_VS of 750°

C.≦

T_VS≦

850°

C., one selects a holding time t_VS of 5 min≦

t_VS≦

60 min. preferably 10 min≦

t_vs≦

30 min, and sets the heat-up rate R_HVS and the cool-down rate R_KVS to 5 K/min≦

R_HVS≦

200 K/min, preferably 5 K/min≦

R_HVS≦

20 K/min, and 5 K/min≦

R_KVS≦

200 K/min, particularly preferred 5 K/min≦

R_KVS≦

20 K/min.

9. The method of claim 1, characterized in that, for a presinter end temperature T_VS with 850°

C.≦

T_VS≦

950°

C., the holding time t_VS is set to 5 min≦

t_VS≦

30 min, in particular 10 min≦

t_vs≦

20 min, and the heat-up rate R_HVS and the cool-down rate R_KVS are preferably set to 15 K/min≦

R_HVS≦

200 K/min, in particular 15 K/min≦

R_HVS≦

50 K/min, and 15 K/min≦

R_KVS≦

200 K/min, in particular 15 K/min≦

R_KVS≦

50 K/min.

10. The method of claim 1, characterized in that for a presinter end temperature T_VS with 950°

C.≦

T_VS≦

1100°

C. the holding time t_VS is set to 5 min≦

t_VS≦

20 min and the heat-up rate R_HVS and the cool-down rate R_KVS preferably are set to 30 K/min≦

R_HVS≦

200, in particular 30 K/min≦

R_HVS≦

100 K/min, and 30 K/min≦

R_KVS≦

200 K/min, in particular 30 K/min≦

R_KVS≦

100 K/min.

11. The method of claim 1, characterized in that the green compact is kept at a presinter end temperature (in K) for a time period t_VS whereby

t/2<

t_VS<

2t

with;

12. The method of claim 11, characterized in that the heating time with an approximately constant heat-up rate R_HVS and the cooling time with an approximately constant cool-down rate R_KVS are set within the range between 650°

C. and the presinter end temperature T_VS, specified in degree Celsius, in a way so that they satisfy the condition;

13. The method of claim 1, characterized in that the metal alloy is atomized into a powder and is mixed with a wax- and/or cellulose-based binding agent to produce a mixture, that preferably the green compact is produced by way of isostatic or axial pressing of the mixture consisting of the metal powder and the binding agent, at a pressure p with 100 MPa≦

p≦

1,000 MPa, in particular 200 MPa≦

p≦

600 MPa, or using a metal powder injection moulding process, and that preferably the debinding and presintering and preferably the cooling is performed in the absence of oxygen, in particular under an inert-gas atmosphere or a reducing atmosphere such as a forming gas atmosphere or in vacuum.

14. A green compact intended for the manufacture of a dental prosthesis or a part thereof, characterized in that the green compact is a presintered green compact that consists of a dental metal alloy and possesses a surface porosity between 16% and 22%.

15. The green compact of claim 14, characterized in that the presintered green compact possesses a surface porosity between 18% and 20%.

16. The green compact of claim 14, characterized in that the dental metal alloy is a nickel-chromium alloy or a cobalt-chromium alloy, whereby the dental alloy in the form of the nickel-chromium alloy preferably consists of:

Nickel;

50 to 70% by weight

Chromium;

20 to 35% by weight

Molybdenum;

0 to 10% by weight

Tungsten;

0 to 20% by weight

Other elements;

less than 10% by weight,

and the dental alloy in the form of the cobalt-chromium alloy preferably contains;

Cobalt;

50 to 70% by weight

Chromium;

20 to 35% by weight

Molybdenum;

0 to 10% by weight

Tungsten;

0 to 20% by weight

other elements;

less than 10% by weight,

whereby the respective sum totals of the elements add up to 100% by weight.