U.S. patent application number 16/716626 was filed with the patent office on 2020-04-30 for method for producing water-atomized prealloyed powder with high cold press formability.
The applicant listed for this patent is Henan Yingchuan New Material Co., Ltd. Invention is credited to Wenwen AN, Dagen DOU, Anding FAN, Xiaofeng LI, Yanan LU.
Application Number | 20200130065 16/716626 |
Document ID | / |
Family ID | 64809978 |
Filed Date | 2020-04-30 |
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United States Patent
Application |
20200130065 |
Kind Code |
A1 |
LI; Xiaofeng ; et
al. |
April 30, 2020 |
METHOD FOR PRODUCING WATER-ATOMIZED PREALLOYED POWDER WITH HIGH
COLD PRESS FORMABILITY
Abstract
A method for producing a water-atomized prealloyed powder with
high cold press formability, includes the following steps: (a)
preparing a -400 mesh semi-finished prealloyed powder; (b)
controlling the semi-finished prealloyed powder to have a moisture
content of 1 wt % to 2 wt % and an oxygen content of 0.6 wt % to
0.8 wt %, and then drying in a vacuum drying oven at 100.degree. C.
for 90 minutes to 120 minutes, so that a preliminary bond is
produced between powder particles; and (c) reducing, annealing,
crushing, and sieving an initially bonded powder particle. The
powder is changed from a spheroidal shape to more complex shapes
such as "rice ear shape", "grape shape", and "satellite powder",
which greatly improves the cold press formability of the prealloyed
powder; the method only performs simple surface modification of the
powder without changing other properties, and has wide
applicability.
Inventors: |
LI; Xiaofeng; (Luohe City,
CN) ; FAN; Anding; (Luohe City, CN) ; DOU;
Dagen; (Luohe City, CN) ; LU; Yanan; (Luohe
City, CN) ; AN; Wenwen; (Luohe City, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Henan Yingchuan New Material Co., Ltd |
Luohe City |
|
CN |
|
|
Family ID: |
64809978 |
Appl. No.: |
16/716626 |
Filed: |
December 17, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22F 2009/049 20130101;
B22F 2998/10 20130101; B22F 2009/0808 20130101; B22F 9/22 20130101;
B22F 2301/35 20130101; B22F 2009/086 20130101; B22F 2009/088
20130101; B22F 1/0081 20130101; B22F 9/08 20130101; B22F 9/082
20130101; B22F 2009/0828 20130101; B22F 1/0085 20130101; B22F
2998/10 20130101; B22F 9/082 20130101; B22F 9/22 20130101; B22F
9/04 20130101; B22F 1/0085 20130101 |
International
Class: |
B22F 9/08 20060101
B22F009/08; B22F 1/00 20060101 B22F001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 26, 2018 |
CN |
201811261373.9 |
Claims
1. A method for producing a water-atomized prealloyed powder with
high cold press formability, comprising the following steps: (a)
preparing a -400 mesh semi-finished prealloyed powder; (b)
controlling the semi-finished prealloyed powder to have a moisture
content of 1 wt % to 2 wt % and an oxygen content of 0.6 wt % to
0.8 wt %, and then drying in a vacuum drying oven at 100.degree. C.
for 90 minutes to 120 minutes, so that a preliminary bond is
produced between powder particles; and (c) reducing, annealing,
crushing, and sieving an initially bonded powder particle.
2. The method for producing a water-atomized prealloyed powder with
high cold press formability according to claim 1, wherein in step
(a), the semi-finished prealloyed powder adopts a water atomization
pulverizing process, and the specific operation thereof is: using
high-pressure water to crush a metallic solution into a micro
droplet in an atomizer, and filtering after cooling, wherein, the
temperature of the metallic solution is 1450 to 1750.degree. C.,
the diameter of a nozzle is 4 to 5 mm, a water flow intersection
angle is 40.degree., a water pressure is 65 Mpa to 80 Mpa, and a
water flow rate is 180 L/min to 200 L/min.
3. The method for producing a water-atomized prealloyed powder with
high cold press formability according to claim 2, wherein in step
(a), the metallic solution is any one or a combination of two or
more of iron, copper, nickel, tin, zinc, cobalt, tungsten,
molybdenum, vanadium, and chromium.
4. The method for producing a water-atomized prealloyed powder with
high cold press formability according to claim 2, wherein in step
(a), the semi-finished prealloyed powder is one of iron copper,
iron copper nickel, iron copper nickel tin, iron copper cobalt tin,
and iron tungsten molybdenum vanadium chromium.
5. The method for producing a water-atomized prealloyed powder with
high cold press formability according to claim 1, wherein in step
(c), the reduction temperature is 500 to 600.degree. C., and the
reduction time is 8 to 10 hours.
6. The method for producing a water-atomized prealloyed powder with
high cold press formability according to claim 1, wherein in step
(c), the annealing operation is: annealing at a temperature of 800
to 1050.degree. C. and a vacuum degree of 10.sup.-1 Kpa for 5 to 6
hours.
7. The method for producing a water-atomized prealloyed powder with
high cold press formability according to claim 1, wherein in step
(c), a continuous impact crusher is used to crush, and the crusher
has a speed of 2000 to 3000 rpm.
8. The method for producing a water-atomized prealloyed powder with
high cold press formability according to claim 1, wherein in step
(c), a 100 to 300 mesh screen is used to sieve.
Description
FIELD OF INVENTION
[0001] The present invention belongs to the technical field of
powder metallurgy, and in particular relates to a method for
producing a water-atomized prealloyed powder with high cold press
formability.
BACKGROUND
[0002] Prealloyed powders for powder metallurgy and diamond tools
are expected to have more complex particle shapes for good
formability and high green strength. However, at present, the most
easily mass-produced high-pressure water atomization pulverizing
technology on the market generally produces powders with a
spheroidal shape, an undeveloped surface structure, and poor cold
press formability. In recent years, the widespread use of fully
automatic machinery equipment have put forward higher requirements
for the cold press formability of prealloyed powders, and the
quality of cold press forming restricts the development of powder
manufacturers. The existing improvement methods are as follows:
[0003] 1. The morphology of powders is improved by controlling the
atomization process, including adjusting the surface tension,
viscosity and superheat degree of a metal, optimizing the
combination of nozzles during high-pressure atomization, adjusting
a spray medium, adjusting a spray angle, and adjusting the diameter
of a molten metal flow (the diameter of a discharge spout),
adjusting the flying distance and cooling time of a metal droplet,
etc. This method has an effect on an individual prealloyed powder,
but the scope of use is quite limited.
[0004] 2. The powder is post-treated to achieve the purpose of easy
cold press forming; there are two main ideas at present.
[0005] 2.1. One idea is that a forming agent and a lubricant are
directly added during the use of a prealloyed powder, but the
forming agent and the like mixed into the powder need to be
completely removed during a post-sintering process of a cutter head
and a part, otherwise a small amount of residue will have a fatal
effect.
[0006] 2.2. The other idea is that a copper-containing oxide or
salt is mixed into the prealloyed powder, then the non-metal
component is removed by pyrolysis, and finally some of the
remaining copper is plated on the surface of the prealloyed powder,
so that the surface of the original spheroidal prealloyed powder is
changed, producing a more complex structure and a larger specific
surface area; besides, the copper has low hardness and good
ductility, which greatly contributes to the cold press formability
of the prealloyed powder; however, since the plated powder and the
original powder are simply combined instead of being alloyed, in a
strict sense, the powder produced by such a method is a mixed
powder of a prealloyed powder and a simple powder, and its
properties are far less than those of purely alloyed powders.
SUMMARY
[0007] An objective of the present invention is to provide a method
for producing a water-atomized prealloyed powder with high cold
press formability.
[0008] To achieve the above objective, the present invention adopts
the following technical solution.
[0009] A method for producing a water-atomized prealloyed powder
with high cold press formability, including the following
steps:
[0010] 1) preparing a -400 mesh semi-finished prealloyed powder,
where the semi-finished prealloyed powder is required to be -400
mesh fine powder, because only a fine-grained powder particle has
strong surface activity and large surface energy, which are prone
to interface contact for the formation of a polymer;
[0011] 2) controlling the semi-finished prealloyed powder to have a
moisture content of 1 wt % to 2 wt % and an oxygen content of 0.6
wt % to 0.8 wt %, and then drying in a vacuum drying oven at
100.degree. C. for 90 min to 120 min, where during this process, a
preliminary bond is produced between powder particles by a
capillary force; in this step, the moisture content of the
semi-finished prealloyed powder is controlled to be 1 wt % to 2 wt
%, in order to ensure a short vacuum drying process and improve
production efficiency; the oxygen content is required to be 0.6 wt
% to 0.8 wt %, in order to ensure that a subsequent reduction
process can easily remove surface oxygen by using hydrogen, and
improve the surface morphology of the particle; if the oxygen
content is too low, the surface of the particle is not easy to form
a pit and a pore; if the oxygen content is too high, the subsequent
reduction process cannot reduce the oxygen content to a certain
range, failing to meet a requirement for use; and [0012] 3)
reducing, annealing, crushing, and sieving an initially bonded
powder particle. In step 1), the semi-finished prealloyed powder
adopts a water atomization pulverizing process, and the specific
operation thereof is: using high-pressure water to crush a metallic
solution into a micro droplet in an atomizer, and filtering after
cooling, where, the temperature of the metallic solution is 1450 to
1750.degree. C., the diameter of a nozzle is 4 to 5 mm, a water
flow intersection angle is 40.degree., a water pressure is 65 Mpa
to 80 Mpa, and a water flow rate is 180 L/min to 200 L/min.
[0013] In step 1), the metallic solution is any one or a
combination of two or more of iron, copper, nickel, tin, zinc,
cobalt, tungsten, molybdenum, vanadium, and chromium.
[0014] In step 1), the semi-finished prealloyed powder is one of
iron copper, iron copper nickel, iron copper nickel tin, iron
copper cobalt tin, and iron tungsten molybdenum vanadium
chromium.
[0015] In step 3), the reduction temperature is 500 to 600.degree.
C., and the reduction time is 8 h to 10 h, ensuring that the powder
particle is slowly and fully reduced under a low temperature
condition, and hydrogen and oxygen are effectively combined to
achieve the effect of deoxidation; besides, the removal of oxygen
in the powder particle makes it easy to form the pit and the pore
on the surface, thereby increasing the specific surface area; the
reduction can be carried out by putting into a push boat type or
steel belt type reduction furnace.
[0016] In step 3), the annealing operation is: annealing at a
temperature of 800 to 1050.degree. C. and a vacuum degree of
10.sup.-1 Kpa for 5 to 6 h; after the vacuum high-temperature
annealing step, the powder particle polymer produced in the
previous steps can be transformed into a crystal interface with a
slight atomic bond. The transformation is more likely to occur at a
vacuum degree of 10.sup.-1 Kpa or below. The choice of temperature
is important. If the temperature is low, the particles will not be
bonded to form an agglomerate or have a certain strength; if the
temperature is too high, the powder particles will be sintered, and
mechanical properties and physical properties will be changed,
which is contrary to the original intention of powder
treatment.
[0017] In step 3), a continuous impact crusher is used to crush;
the crusher has a speed of 2000 to 3000 rpm; this speed ensures
that a powder particle after the crushing is microscopically an
agglomerate of several powder particles and macroscopically has a
more complex surface and have excellent cold press formability,
ensuring that the crushed powder is not a single particle, but an
agglomerate of several particles, so that the agglomerate
macroscopically has a complex surface and is "rice ear-shaped" or
"grape-shaped".
[0018] In step 3), a 100 to 300 mesh screen is used to sieve to
remove a coarse particle, so as to ensure the cold press
formability of the finished powder, because an excessively coarse
particle will break bonding uniformity between particles during the
cold press forming process.
[0019] Compared with the prior art, the present invention has the
following positive effects.
[0020] The present invention discloses a method for producing a
water-atomized prealloyed powder with high cold press formability,
which has the characteristics of simple and easy process, low cost
and easy scale production. The present invention first uses a
physical reaction to bond produced spheroidal powder particles, and
then controls the crushing condition to crush the bonded bulk
powder into a granular shape, and this process changes the powder
from a spheroidal shape to more complex shapes such as "rice ear
shape", "grape shape", and "satellite powder", which greatly
improves the cold press formability of the prealloyed powder; the
method of the present invention only performs simple surface
modification of the powder without changing the other properties,
and has wide applicability.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a schematic diagram of a process flow of the
present invention;
[0022] FIG. 2 is a comparative scanning electron microscope image
of an iron-copper prealloyed powder before and after being treated
by the present invention (Embodiment 1); and
[0023] FIG. 3 is a comparative scanning electron microscope image
of an iron-based prealloyed powder before and after being treated
by the present invention (Embodiment 2).
DETAILED DESCRIPTION
[0024] The present invention is described in more detail below with
reference to the embodiments and accompanying drawings.
Embodiment 1
[0025] A method for producing a water-atomized prealloyed powder
with high cold press formability, with a process flow shown in FIG.
1, including the following steps:
[0026] 1) weigh 50 kg of raw material required for the prealloyed
powder production, including 70 wt % of iron and 30 wt % of copper;
prepare a semi-finished prealloyed powder by a water atomization
pulverizing process, where the temperature of a metallic solution
is 1550 to 1600.degree. C., the diameter of a nozzle is 5 mm, a
water flow intersection angle is 40.degree., a water pressure is 80
Mpa, and a water flow rate is 200 L/min; use high-pressure water to
crush a steel liquid into a micro droplet in an atomizer, and
filter after cooling to obtain a -400 mesh semi-finished
iron-copper prealloyed powder. In other embodiments, the metallic
solution is any one or a combination of two or more of iron,
copper, nickel, tin, zinc, cobalt, tungsten, molybdenum, vanadium,
and chromium; preferably, the prealloyed powder is one of iron
copper, iron copper nickel, iron copper nickel tin, iron copper
cobalt tin, and iron tungsten molybdenum vanadium chromium.
[0027] 2) control the semi-finished prealloyed powder to have a
moisture content of 2 wt % and an oxygen content of 0.8 wt %, and
then dry in a vacuum drying oven at 100.degree. C. for 120 min,
where during this process, a preliminary bond is produced between
powder particles by a capillary force; in other embodiments, the
semi-finished prealloyed powder may be controlled to have a
moisture content of 1% to 2% and an oxygen content of 0.6 to 0.8%,
and then dried in a vacuum drying oven at 100.degree. C. for 90 min
to 120 min.
[0028] 3) put an initially bonded powder particle into a reduction
furnace, which is a push boat type reduction furnace, select a
reduction temperature of 550.degree. C., reduce the powder particle
under a hydrogen atmosphere, and treat for 8 h to remove surface
oxygen, making the surface of the spheroidal metal particle covered
with a pit and a pore to increase the specific surface area; then
put the powder in a high-temperature vacuum annealing furnace, and
treat for 5 h at an annealing temperature of 800.degree. C. and a
vacuum degree of 10.sup.-1 Kpa, so that the powder is fully
polymerized into a bulk; and use a continuous impact crusher to
crush a powder agglomerate into a powder at a speed of 2000 rpm,
and sieve through a 300 mesh screen to obtain a finished powder.
The prealloyed powder obtained by the present invention and a
comparative image are shown in FIG. 2. It can be seen from FIG. 2
that after an original particle of the prealloyed powder is treated
by the method of the present invention, agglomeration occurs, and a
single particle with complicated morphology is macroscopically
displayed, which is actually an agglomerate formed by bonding a
plurality of particles, and has excellent cold press formability.
In other embodiments, in step 3), a steel belt type reduction
furnace may be selected to treat at a reduction temperature of 500
to 600.degree. C. for 8 to 10 h; then, the annealing process is
adjusted to treat at a temperature of 800 to 1050.degree. C. and a
vacuum degree of 10.sup.-1 Kpa for 5 to 6 h to sufficiently
polymerize the powder into a bulk.
Embodiment 2
[0029] A method for producing a water-atomized prealloyed powder
with high cold press formability, with a process flow shown in FIG.
1, including the following steps:
[0030] 1) weigh 50 kg of raw material required for the production
of an iron-based prealloyed powder for powder metallurgy, including
82 wt % of iron, 13 wt % of chromium, 1 wt % of molybdenum, 1 wt %
of tungsten, 1 wt % of vanadium, and 2 wt % of carbon; prepare a
semi-finished prealloyed powder by a water atomization pulverizing
process, where the temperature of a metallic solution is 1650 to
1700.degree. C., the diameter of a nozzle is 4.5 mm, a water flow
intersection angle is 40.degree., a water pressure is 65 Mpa, and a
water flow rate is 180 L/min; use high-pressure water to crush a
steel liquid into a micro droplet in an atomizer, and filter after
cooling to obtain a -400 mesh semi-finished iron-based prealloyed
powder.
[0031] 2) control the semi-finished prealloyed powder to have a
moisture content of 1 wt % and an oxygen content of 0.6 wt %, and
then dry in a vacuum drying oven at 100.degree. C. for 100 min,
where during this process, a preliminary bond is produced between
powder particles by a capillary force.
[0032] 3) put an initially bonded powder particle into a reduction
furnace, which is a push boat type reduction furnace, select a
reduction temperature of 600.degree. C., reduce the powder particle
under a hydrogen atmosphere, and treat for 10 h to remove surface
oxygen, making the surface of the spheroidal metal particle covered
with a pit and a pore to increase the specific surface area; then
put the powder in a high-temperature vacuum annealing furnace, and
treat for 6 h at an annealing temperature of 1050.degree. C. and a
vacuum degree of 10.sup.-1 Kpa, so that the powder is fully
polymerized into a bulk; and use a continuous impact crusher to
crush a powder agglomerate into a powder at a speed of 3000 rpm,
and sieve through a 100 mesh screen to obtain a finished powder.
The prealloyed powder obtained by the present invention and a
comparative image are shown in FIG. 3. It can be seen from FIG. 3
that after an original particle of the prealloyed powder is treated
by the method of the present invention, agglomeration occurs, and a
single particle with complicated morphology is macroscopically
displayed, which is actually an agglomerate formed by bonding a
plurality of particles, and has excellent cold press formability.
The above embodiments are preferred implementations of the present
invention, but the implementations of the present invention are not
limited to the above embodiments. Changes, retouches, replacements,
combinations and simplifications made without departing from the
spiritual essence and principle of the present invention should be
equivalent substitution manners, and should all be included in the
protection scope of the present invention.
* * * * *