U.S. patent application number 10/392937 was filed with the patent office on 2003-10-02 for manufacturing technique of powder metallurgy.
Invention is credited to Chen, Chih-Cheng, Lin, Wen-Hao, Wang, Jenn-Shing.
Application Number | 20030185698 10/392937 |
Document ID | / |
Family ID | 28451366 |
Filed Date | 2003-10-02 |
United States Patent
Application |
20030185698 |
Kind Code |
A1 |
Wang, Jenn-Shing ; et
al. |
October 2, 2003 |
Manufacturing technique of powder metallurgy
Abstract
The manufacturing technique for powder metallurgy of the
invention includes the steps of: mixing ceramic powder with
binders, fillings or lubricants for casting a body; forming a
microwave-absorbent body using molding, extrusion, forging,
injection or doctor blade; placing the body into a microwave oven
for heating and debinding; placing the half-finished product after
debinding in a sintering oven for sintering the debinded
half-finished product; and finally obtaining a finished product
after sintering and temperature lowering.
Inventors: |
Wang, Jenn-Shing; (Yungkang
City, TW) ; Lin, Wen-Hao; (Kaohsiung, TW) ;
Chen, Chih-Cheng; (Fengshan City, TW) |
Correspondence
Address: |
Far East College
P.O. Box No. 6-57
Chung-Ho
Taipei
235
TW
|
Family ID: |
28451366 |
Appl. No.: |
10/392937 |
Filed: |
March 21, 2003 |
Current U.S.
Class: |
419/56 |
Current CPC
Class: |
C04B 35/64 20130101;
C04B 35/638 20130101; B22F 3/1025 20130101; C04B 2235/667 20130101;
C04B 35/62655 20130101 |
Class at
Publication: |
419/56 |
International
Class: |
B22F 003/105 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 28, 2002 |
TW |
91106098 |
Claims
What is claimed is:
1. A manufacturing technique for powder metallurgy comprising the
steps of: mixing ceramic powder with binders, fillings or
lubricants for casting a body; forming a microwave-absorbent body
using molding, extrusion, forging, injection or doctor blade;
placing the body into a microwave oven for heating and debinding;
placing the half-finished product after debinding in a sintering
oven for sintering the debinded half-finished product; obtaining a
finished product after sintering and temperature lowering; and the
characteristics thereof are: before the body enters the debinding
process, the body is placed in a microwave-absorbent medium, and
the body along with the medium are placed in the microwave and
debinded with adjusted temperature and time required.
2. The manufacturing technique for powder metallurgy in accordance
with claim 1, wherein the half-finished body after debinding or a
debinded body acquired from other methods is directly placed in the
microwave oven for heating to the sintering temperature, and is put
in a sintering oven having reached the sintering temperature for
sinetering therein using microwave.
3. The manufacturing technique for powder metallurgy in accordance
with claim 1, wherein ceramic microwave-absorbent medium containing
the microwave-absorbent body is powder mainly made of carbon,
carbide, nitride, nitanate, oxide, sulfide or a compound.
4. The manufacturing technique for powder metallurgy in accordance
with claim 3, wherein the carbide is SiC, TiC or WC.
5. The manufacturing technique for powder metallurgy in accordance
with claim 3, wherein the nitride is TiN, AlN or
Si.sub.3N.sub.4.
6. The manufacturing technique for powder metallurgy in accordance
with claim 3, wherein the titanate is barium titanate, calcium
titanate, strontium titanate or lead titanate.
7. The manufacturing technique for powder metallurgy in accordance
with claim 3, wherein the oxide is NiO, CoO, CaMnO.sub.3,
LaMnO.sub.3, SnO.sub.2, TiO.sub.2, MgWO.sub.4, MgO, NiO,
SrTiO.sub.3 or SrZrO.sub.3, ZrO.sub.2 or CaO.
8. The manufacturing technique for powder metallurgy in accordance
with claim 3, wherein the oxide is added with compounds such as
Li.sub.2O, La.sub.2O.sub.3, CaO, SrO, TiO.sub.2, Sb.sub.2O.sub.5,
Ta.sub.2O.sub.5 or Cr.sub.2O.sub.3 or ZnO.
9. The manufacturing technique for powder metallurgy in accordance
with claim 3, wherein the sulfide is FeS or MnS.
10. The manufacturing technique for powder metallurgy in accordance
with claim 3, wherein the compound is Fe.sub.2O.sub.3--MeO.
11. The manufacturing technique for powder metallurgy in accordance
with claim 3, wherein the compound is Fe.sub.2O.sub.3--MeO, and the
Fe.sub.2O.sub.3 may be mixed with NiO, CoO, MoO, MgO, ZnO, CuO,
Li.sub.2O, CaO, FeO, B.sub.2O, PbO, SrO, La.sub.2O.sub.3,
Cr2O.sub.3, SnO.sub.2 or WO.sub.3.
12. The manufacturing technique for powder metallurgy in accordance
with claim 3, wherein the NiO, CoO, MoO, MgO, ZnO, CuO, Li.sub.2O,
CaO, FeO, B.sub.2O, PbO, SrO, La.sub.2O.sub.3, Cr.sub.2O.sub.3,
SnO.sub.2 or WO.sub.3 may be used independently or mixed with
others.
13. The manufacturing technique for powder metallurgy in accordance
with claim 3, wherein ceramic microwave-absorbent medium containing
the microwave-absorbent body may be compounds with any compound
ratios from carbon, carbide, nitride, titanate, oxide, sulfide or a
compound.
14. The manufacturing technique for powder metallurgy in accordance
with claim 1, wherein the non microwave-absorbent medium is a
compound having any compound ratio from Al.sub.2O.sub.3, SiO.sub.2
or ZrO.
15. The manufacturing technique for powder metallurgy in accordance
with claim 1, wherein the macromolecules are binders, fillings or
lubricant containing any from acrylic, ethyl cellulose,
hydroxypropyl cellulose, polypropylene, polyacetal polymer,
ethylene vinyl acetate, atactic polypropylene,
styrene-butadienecoplymer, methylcellulose, polyethylene, oxidized
polyethylene, cellulose acetate, nylon, polystyrenes, polybutylene,
polysulfone, polyethylene, paraffin, wax, mineral oil, vegetable
oil, fatty acid, fatty alcohols, fatty ester hydrocarbon wax,
epoxy, polyphenylene, phenol, stearic acid, ester wax, oleic acid,
diethyl phthalate, and formaldehyde.
Description
BACKGROUND OF THE INVENTION
[0001] (a) Field of the Invention
[0002] The invention relates to a manufacturing technique of powder
metallurgy, and more particularly, to a manufacturing technique of
powder metallurgy for accelerating the production procedure, and
reducing equipment and resource cost thereof, as well as being
capable of quickly drying and removing binders, fillings or
lubricants in order to suit ceramic material fabrications.
[0003] (b) Description of the Prior Art
[0004] In common manufacturing processes of powder metallurgy, in
order to facilitate ceramic powder to form a green body more
easily, macromolecules are frequently added as a forming additive.
Such type of forming additives includes binders, surfactants,
fillings or lubricants. The forming additives are mixed with
macromolecules for casting bodies that may be formed by such as
molding, forging, extrusion, injection molding or doctor blade
methods. Then the green bodies are placed into furnaces for
debinding as the next step.
[0005] Injection molding from ceramic powder possess properties of
general plastic injections, and are materials that can be used with
high efficiency. When injection moldings from ceramic powder are
adopted for products having complicated shapes in mass production,
the products have relatively better microstructures because sizes
thereof are evenly contracted. Therefore, the injection molding
products approach near net shapes or net shapes, and do not require
a great amount of subsequent processing, and thus significantly
saving production cost thereof by reducing the processing expenses.
However, the binder used come as high as 30 vol%, and defects
incurred are prone to arise during removing macromolecules in the
debinding process; to be more precise, the debinding process stands
as a rather major manufacturing process.
[0006] In the present invention, issues like green body forming,
sintering, materials of powder, or ingredients of additives shall
not be discussed. Instead, the invention is targeted at providing
another method for the debinding step in the manufacturing
process.
[0007] As described above, common debinding processes currently
used include solvent debinding and thermal debinding, wherein:
[0008] 1. Solvent debinding is implemented by the steps of dipping
a body into a solvent, and extracting dissolvable binders,
fillings, surfactants or lubricants from the body. However, such
means of solvent debinding brings about environmental and recycling
issues and thus further increases the processing expense
thereof.
[0009] 2. Thermal debinding is implemented by the steps of placing
a body into a furnace, and eliminating any binders using a high
temperature to remove binders, fillings, surfactants, lubricants or
macromolecules in sequence. This method may be used to remove
binders directly or after solvent debinding with only
human-friendly gases produced that give no environmental, recycling
or human-hazardous issues as the solvent debinding, and is
therefore the most extensively applied debinding process.
Nevertheless, it is necessary to pre-heat the furnaces to a
temperature required for thermal debinding, meaning that the time
and energy of pre-heating and the energy consumed during
maintaining the heat sum up to considerable amounts of money, and
thus resulting in an efficiency problem often abstained by the
manufacturing process. Also, defects are prone to occur during the
time-consuming thermal debinding process, and hence reforms with
respect to the above shortcomings can yet be advanced.
[0010] Furthermore, the modern times is an environmental-friendly
era, especially regarding to uses and recycling of resources. It
shall be taken into consideration that chemical solvent, which is
non-eco-friendly and is limited to a certain number of times to be
used, is adopted for solvent debinding; and furnaces employed for
thermal debinding are quite energy consuming. Therefore, it is a
vital task as how to provide a manufacturing technique for
debinding capable of rapidly accomplishing the debinding process
and reducing resource wastage, as well as being
environmental-friendly.
[0011] With respect of the aforesaid shortcomings, domestic and
international patent publications or related information are taken
into reference. Referring to Patent Publication No. 333482,
"Manufacturing Process for Carbon Chromium/Aluminum Oxide Ceramic
Devices Having Complicated Shapes Using Injection Molding
Technique", it is observed that several defects are derived from
the debinding process thereof:
[0012] 1. The furnaces are troublesome and time-consuming in
raising and lowering the temperatures thereof. The production cost
can be reduced and the manufacturing efficiency can be elevated if
the time of heating from room temperature to a temperature required
for debinding and lowering temperature after debinding completed
can be shortened.
[0013] 2. Energy cannot be concentrated entirely on the body.
During heating of a common furnace, a major part of the energy is
absorbed through the furnace body and dissipated into the
atmosphere, and thus leaving as little as 30 percent of the
original energy for debinding the body. It is indeed uneconomical
to waste such great amounts of energy for merely achieving the
purpose of debinding.
[0014] 3. Common furnaces take up large spaces for that they are
massive in volume and heavy in weight, and difficulties may arise
for moving such furnaces, thus lacking mobility.
[0015] 4. Furnaces have high equipment cost. Expense burdens and
maintenance fees thereof may be worsened by problems and shortening
of lifespan of heating bodies and heat-resistant materials caused
by any contamination of binder decompositions in the furnaces.
[0016] 5. Chemical solvents are limited to certain expiration
periods. In solvent debinding, chemical extraction properties of
chemical solvents are inevitably lowered after using for a period
of time or when increasing the number of bodies. Besides, expired
chemical solvents may become another environmental dilemma.
[0017] In addition, referring to Patent Publication No. 167524
disclosing a method for thermal processing unstable ceramics using
microwave, wherein microwave technique is applied during the
sintering process of ceramics. In the prior invention, a microwave
sensor is formed from an appropriate powder bed that is
characterized regarding to heating, protection, deoxidization and
thermal conductance as required. However, the characteristics are
provided for the requirements of the "sintering" process of
ceramics; that is, this prior invention confers nothing upon the
"debinding" process of ceramic bodies before the sintering process.
Therefore, the shortcomings of the aforesaid debinding means
(solvent debinding and thermal debinding) are not resolved by the
Patent Publication No. 167524.
[0018] Conclusive from the above, as described by shortcomings and
issues of the conventional debinding means, the handling of the
solvent used are troublesome, uneconomical and non-eco-friendly,
and furnaces adopted for thermal debinding are time-consuming for
heating and temperature lowering. Therefore, it is a vital task of
the invention as how to provide a manufacturing technique for
powder metallurgy capable of overcoming the prior disadvantages
such as having high production and equipment cost, lack of mobility
and being unable to concentrate energy.
SUMMARY OF THE INVENTION
[0019] The primary object of the invention is to provide
manufacturing technique capable of accelerating production
procedure, reducing production cost, and rapidly drying and
removing binders, fillings or lubricants. The technique is suitable
for debinding of cast bodies after powder materials are mixed with
binders, fillings or lubricants, and is able to avoid energy waste
in heating and temperature lowering as well as keeping away from
being bulky in size.
[0020] Another object of the invention is to provide manufacturing
equipment and method for elevating manufacturing efficiency by
shortening the time of heating and temperature lowering.
[0021] Another object of the invention is to provide manufacturing
equipment and method with energy concentration for saving
energy.
[0022] The other object of the invention is to provide
manufacturing equipment and method with low equipment cost and
mobility for reducing production cost and facilitating the moving
thereof.
[0023] To better understand the manufacturing process and functions
of the present invention, descriptions shall be given with the
accompanying drawings below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 shows a schematic drawing illustrating the
manufacturing process according to the invention.
[0025] FIG. 2 shows a comparison diagram illustrating the time
required for heating to sintering temperatures of the invention and
a prior art.
[0026] FIG. 3 shows a comparison table illustrating the compressive
resistance of relative densities after sintering by the present
invention and a prior art.
[0027] FIG. 4 shows manufacturing flow diagrams for comparing time
required for debinding in the present invention and a prior
art.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] Referring to FIG. 1, the manufacturing method implementing
the manufacturing technique for powder metallurgy according to the
invention comprises the steps of:
[0029] a. forming a body 1; the body 1 is formed by mixing ceramic
powder with binders, fillings or lubricants, and then by performing
cast methods such as molding, extrusion, injection or scraping;
[0030] b. heating and debinding; the body 1 is embedded into a non
microwave-absorbent medium 2 placed in a crucible 3 so as to
promote capillarity thereof using the medium 2, and is then placed
into a microwave oven 4 for heating and debinding according to time
and temperature required for heating and debinding;
[0031] c. sintering; a half-finished product 4 is put in a
sintering oven 6 for sintering the degreased, half-finished product
4;
[0032] d. finishing product; temperature is lowered according to
general procedures, and a finished product 7 is obtained from the
originally half-finished product 5 placed in the sintering oven
6.
[0033] According to the invention, the technique provided lies
mainly in the heating and debinding stage, and the characteristics
thereof are:
[0034] before entering the debinding process, the
microwave-absorbent body 1 is placed in the microwave oven 4 and
debinded by using adjusted microwave frequency required, and direct
observations through a window may be carried out during the
debinding process; in addition, the degreased half-finished product
5 using microwave or a degreased body obtained by other methods is
directly heated to the sintering temperature using microwave, and
is then placed into the sintering oven 6 after having reached the
sintering temperature or sintered directly by microwave, and thus
saving time and resources for gradual heating; referring to FIGS. 2
showing a comparison diagram illustrating the time required for
heating to sintering temperatures of the invention and a prior art,
and FIG. 3, tests at sintering temperatures 1400.degree.0 C. and
145020 C. are performed for a duration of two hours, and when
comparing the relative densities of the present invention to the
prior art, it is clearly observed that the product from the
invention has excellent sintering densities; also, referring to
FIG. 4 showing time differences for debinding in the manufacturing
process, the time for debinding according to the invention is
merely half of that of the prior art, and thus effectively reducing
the production time thereof.
[0035] It is perceived from the above that, the appeal according to
the invention is aimed at heating by microwave for accomplishing
the debinding process. The technique provided by the invention is
capable of overcoming disadvantages existing in the prior art: 1.
inconvenient heating and temperature lowering of furnaces, and
lengthened production time; 2. distracted heating energy, and
uneconomical; 3. furnaces bulky in size with poor mobility; 4.
inefficiency and environmental issues of chemical solvent.
According to the invention, the method and equipment provided are
able to accelerate production process, reduce production cost,
rapidly remove binders, fillings or lubricants, as well as being
environmental friendly for that the medium can be used for
absorbing microwave for a multiple of times. Therefore, the
invention is totally suitable for debinding process of cast bodies
from mixing ceramic powder with binders, fillings or
lubricants.
[0036] In addition, the microwave-absorbent cast bodies mentioned
above, the ceramic powder contained therein may be carbon, carbide,
nitride, titanate, oxide, sulfide or a compound: wherein the
carbide may be SiC, TiC or WC; the nitride may be TiN, AIN or
Si.sub.3N.sub.4; the titanate may be barium titanate, calcium
titanate, strontium titanate or lead titanate; the oxide may be
NiO, CoO, CaMnO.sub.3, LaMnO.sub.3, SnO.sub.2, TiO.sub.2,
MgWO.sub.4, MgO, NiO, SrTiO.sub.3 or SrZrO.sub.3; the sulfide may
be FeS or MnS; the compound may be Fe.sub.2O.sub.3--MeO, wherein
the Fe.sub.2O.sub.3 may be mixed with NiO, CoO, MoO, MgO, ZnO, CuO,
Li.sub.2O, CaO, FeO, B.sub.2O, PbO, SrO, La.sub.2O.sub.3,
Cr.sub.2O.sub.3, SnO.sub.2 or WO.sub.3, and NiO, CoO, MoO, MgO,
ZnO, CuO, Li.sub.2O, CaO, FeO, B.sub.2O, PbO, SrO, La.sub.2O.sub.3,
Cr.sub.2O.sub.3, SnO.sub.2 or WO.sub.3 may be used independently or
mixed with others; in addition, the aforesaid nitride may be added
with compounds such as Li.sub.2O, La.sub.2O.sub.3, CaO, SrO,
TiO.sub.2, Sb.sub.2O.sub.5, Ta.sub.2O.sub.5 or Cr.sub.2O.sub.3.
[0037] It is of course to be understood that the embodiment
described herein is merely illustrative of the principles of the
invention and that a wide variety of modifications thereto may be
effected by persons skilled in the art without departing from the
spirit and scope of the invention as set forth in the following
claims.
* * * * *