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 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.

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 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 C., the diameter of a nozzle is 4 to 5 mm, a water flow intersection angle is 40, 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 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 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

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 C., the diameter of a nozzle is 5 mm, a water flow intersection angle is 40, 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 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 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 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 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 C. for 8 to 10 h; then, the annealing process is adjusted to treat at a temperature of 800 to 1050 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 C., the diameter of a nozzle is 4.5 mm, a water flow intersection angle is 40, 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 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 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 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.