JPS5881901A - Method of making atomized iron powder having excellent formability and low apparent density for use in powder metallurgy - Google Patents

Abstract

PURPOSE:To obtain atomized iron powder having low apparent density equal to that of reduced iron powder and excellent formability, by reduction-annealing atomized green iron powder having defined apparent density while increasing sintering-coagulation between particles, and controlling impulsive force to crush and disintegrate sintered cake. CONSTITUTION:Atomized green iron powder having the relationship between its apparent density chi(g/cm<3>) and its particle size di(mum) represented by the arithmetic means of two meshes d1 and d2 of Tyler Standard screen scale which satisfies the formulaIand II (a and b are the constants of particle size with b<=1.5) as for a part having a particle size exceeding 150mum and a part having a particle size below 150mum, respectively, is used. Said green iron powder, directly or after subjected to the treatment to accelerate the coagulation of particles, is reduction-annealed at 800-1,100 deg.C in a reducing decarburizing atmosphere to accomplish sufficient reduction-annealing and sintering-coagulation between particles. The obtained sintered cake is crushed and disintegrated by applying impulsive force below 1X10<5>kgf.m/S<2> to it, so as to obtain iron powder containing more than 80wt% particles having a particle size below 150mum and having apparent density of 2.00-2.60g/cm<3>.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to (1) a method for producing atomized iron powder for powder metallurgy with excellent formability and low apparent density; The sintering and agglomeration of the particles can be enhanced, and the sintered cake can be pulverized and agglomerated (hereinafter referred to as pulverization and agglomeration). This paper aims to propose an advantageous manufacturing method for atomized iron powder for powder metallurgy, which has excellent formability and low apparent density, by limiting the cost and impact of the process (denoted as straightening and crushing). Water-sprayed iron powder usually has an apparent density of 23
0~J, -〇t415, which has excellent compressibility,
It is used as a raw material iron powder for high-density iron-based sintered materials, but the formability evaluated by Rattler value and compact transverse rupture strength is rather poor, and the mechanical strength of sintered materials is poor despite its high density. is also weak,
Its application to medium- and low-density iron-based sintered materials is inadvertent and is currently limited to the above-mentioned applications. There is a demand for atomized iron powder that also has the following properties:
Development is progressing @ For example, Tokkai Sho! As described in Dar // Sanji No. 17, high-pressure water is sprayed at an inverted conical jet angle t-10 to prevent reverse jetting while increasing the amount of fine powder in raw iron powder. A method has been proposed in which a sintered cake is annealed in a reducing atmosphere at a temperature of 1,000 or 1,200 degrees Celsius to obtain a particle size distribution larger than that of airborne iron powder. Also, Tokkai Showa 10-//! According to Publication No. 1, the particle size distribution y psc value is 100.2 according to the American standard.
00. For each line of Ko JO and 3 Ko J Meshes, add up the cumulative amount of particles on the sieve, the amount of the saucer, and the cumulative weight j1 ratio on the t needle side, and a. . Water atomized iron powder whose 9 value is in the range of i, o-co, 7 is reduced annealed at a temperature of 760 to //4 IY°C, and the sintered cake is prepared with a mill gap of 0. J reference j-2,
@J fnm, rotation speed J00~! 000r, crushed with p6m discuncle, apparent density is λ, to t4s
The following method for producing iron powder has also been proposed.

However, all of these methods simply increase the proportion of fine powder in the raw iron powder and cause the particles to sinter and agglomerate each other during reduction annealing.
The sintered cake is crushed under a relatively light (low) load.
The aim is to improve W density and formability.

In general, as the amount of fine powder in the water-sprayed iron powder increases and as the reduction annealing temperature increases, sintering between particles is promoted, and the apparent density of the crushed iron powder decreases. Although it is possible to improve one's performance, it is accompanied by the following problems.

In other words, if the reduction annealing temperature is too high (over 100°C), the sintered cake will be difficult to crush, and if you try to increase productivity by crushing it under high load, it will be more difficult to process it. Not only is it impossible to improve the formability due to the high hanging density, but the compressibility is also deteriorated, and the reduction annealing temperature is 11.
Even if the temperature is below 00℃, it is not foolish to use raw iron powder with a lower apparent density corresponding to the apparent density of the finished wax product iron powder, which is stable and benign. It is difficult to produce iron powder with a low apparent density.
If the temperature is too low, such as less than 0°C, deoxidation, decarburization, annealing, and recrystallization will be insufficient, making it impossible to ensure sufficient compressibility.

Therefore, the purpose of this invention is to expand the application of sprayed iron powder to #1, which has excellent high compressibility by nature, and especially to medium and low density iron-based sintered materials. To provide inexpensively atomized iron powder which has an apparent density of 2.00 to 40115, which is the same as that of reduced iron powder (reduced iron powder), is rich in fluidity, and has moldability superior to that of original iron powder. However, the invention of ``Sprayed Iron Powder'' is to produce atomized raw iron powder with a correspondingly low apparent density corresponding to the apparent density of the final product, atomized iron powder, or to further reduce the apparent density and improve formability. In order to achieve this, it is necessary to perform a treatment that promotes the agglomeration of particles and use raw iron powder as a raw material, to achieve sufficient reduction annealing and sintering agglomeration of particles, and to achieve reduction annealing temperature range that achieves sintering and sintering. In crushing the cake, the above object is advantageously achieved by satisfying the conditions that the iron powder maintains the irregular grain shape inherent in liquid I!JtIl and the aggregate irregular grain shape formed by sintering and agglomeration. As shown in Figure 1, the apparent density of water atomized iron powder is 8.
x(f/, 13] and its single particle size! di(#tl)
For grain sizes exceeding izopm, χ= is constant and l! 0
For grain sizes less than or equal to
And this relationship is especially true for reduction annealed round sintered cakes.
The inventors have found that the same holds true for water-sprayed iron powder crushed by an impact force of x 105 f-m/2 or less.

According to Jin's knowledge, the apparent density of reduction annealed iron powder is limited by the apparent density of raw iron powder.

In other words, it is difficult to make the apparent density of the reduction-annealed nine-iron powder lower than the apparent density of the atomized raw iron powder at a particle size exceeding /jOfim, and the harder the crushing, the higher the apparent density. On the other hand, for particle sizes smaller than Japan, the apparent density of reduction-annealed iron powder is lower than that of atomized raw iron powder because the particles sinter and agglomerate each other to form irregular grain shapes. However, the grain size index b has a positive value, and it is difficult to realize a negative value industrially.

Therefore, after reduction annealing, the apparent density was 2. In order to produce atomized iron powder of tot7s or less, the apparent density (f/s), χ≦here, is required at a particle size exceeding izopm. 0゜Cπ /#fif'l&d giant 96-bX
However, d1g Tyler standard casting average diameter of two sieves (da-rihiki) (μm) @, b5 particle size constant b≧/,
It is necessary to use raw atomized iron powder that satisfies the relationship j as a raw material.In the particle size of /jOwn or less, the particles are sintered and agglomerated together to form an irregular grain shape, which further reduces the apparent density. We have found that particle size, mixing of liquids, and magnetization are effective for promoting magnetization for the following reasons.

Sprayed raw iron powder can be efficiently aggregated into coarse particles by sintering and agglomerating the fine powders by first sorting them by particle size, and considering reduction workability, it is actually best to use 200 mesh:L as the boundary. If necessary, it is recommended to perform pre-throwing after reduction annealing.

As the liquid fills the interparticle spaces in the packed bed of atomized raw iron powder and evaporates, the liquid level moves and its surface tension causes the particles to move, and the effect of agglomerating local FMK fine powder, especially coarse powder, is caused by the ib system. , water, oil, organic compounds such as alcohol, and mixtures thereof are used as the 5 liquids mixed here.
It will be done. J~J17 weight range f! is effective and practical. Liquid-sprayed raw iron powder is rapidly cooled by high-pressure liquid and the lattice is distorted, so it is easily magnetized and has residual magnetism, which is especially noticeable in water-sprayed raw iron powder. This is because they attract each other and agglomerate.Next, there are important factors that determine the reduction annealing temperature in a reducing and decarburizing atmosphere, the crushing impact force of the sintered cake, and the apparent density of the crushed iron powder. The cause @ If the reduction annealing temperature is lower than 100℃, the reduction, annealing, and mutual sintering agglomeration of particles are insufficient, resulting in a decrease in apparent density and failure to ensure compressibility.・Reduction annealing temperature higher than 7100℃ In such cases, it is difficult to crush the grains, and if the grains are forcibly crushed under a high load, they become smooth polyhedral grains with a high apparent density, and at the same time undergo work hardening and deteriorate their compressibility.

Therefore, the reduction annealing temperature is suitably in the range of too -1ioo°C, and the time for holding and soaking after papermaking is not particularly limited as long as the time sufficient for the above-mentioned heat treatment is appropriately selected.

As a crusher for sintered cakes, machines that cut the particles, make the surface of the particles into flat polyhedrons or flat plates, and crush them into balls should be avoided; for example, machines that use repulsion type or impact type hammers Ol, Demain Integrator (adopts various forms such as roux in a cage.

We investigated the relationship between the impact force and the apparent density of the crushed iron powder and found that as the impact force increases, the apparent density increases over the entire particle size range. If it exceeds ζ, the apparent density of the raw material atomized iron powder becomes higher. Therefore, the impact force is 10"ky, /'# m/@
@ζ2 □ is the upper limit. For example, it is necessary to take into consideration the diameter of the Rossdol gap or screen hole installed in a hammer mill so as not to lose the inherent irregularity of liquid/body sprayed raw iron powder and the aggregated irregularity due to sintered agglomeration. There is no need to limit the factor contribution rate to the coating density because it is small. The chemical composition of the sprayed iron powder invented by Jin is equal to or higher than that of transparent iron powder (building scale reduced iron powder, ore reduced iron powder), i.e. , /-Za・8t (zinc stearate if weight 11F・Mixed powder! Ensure green density at t/2 molding pressure is 4.70175 or more 0
The stomach is minimally necessary, from this point of view, the weight - o:
o, below Js, c 3 o, below or, N j 00
01 or less, 81 f 0010 or less, Mn i 008
0 or less, P: 0.01 or less, 8 J 0010 or less, 8 mouths 5 o, to or less, and the remainder is substantially composed of iron, of course unavoidable impurities are allowed. Regarding grain size, if there are too many coarse grains in iron-based sintered materials, there will be many irregularly shaped coarse pores, which will lead to embrittlement of mechanical strength, which will eventually lead to poor iron powder for powder metallurgy. It is limited to the general range, i.e. iron powder containing at least 10 particles with a particle size of /10 #m or less.

Next, the present invention will be described in detail based on examples.

Special meeting regarding patent No. fPJjjF! Ko/ri! According to the molten metal atomization and crushing device described in Publication No. , water pressure 4
cO-/10kgf/2G O range, molten metal/S#a
Adjust the diameter of the feces appropriately within the range of I-/mWLφ,
Under water spraying conditions in which the amount of water was 27,077 mIn, type J water-sprayed raw iron powder having the relationship ts between d and +d2 in FIG. 1 and the single particle diameter -di-(μm) was produced.

Next, the Tyler standard line is set to -100, and reduction annealing is performed by soaking for 10 to 20 minutes at a temperature of 700 to 10 degrees Celsius in ammonia decomposition gas, and the temperature is set to a temperature that does not cause re-distillation in the atmosphere, i.e. After cooling in the furnace to below iro℃, the sintered cake was taken out into the atmosphere and crushed with a hammer mill.
It was sieved using a ROM caster.

In addition, for water-sprayed raw iron powder having the relationship between apparent density and single particle size indicated by the middle symbol I in Figure 1, it is mixed with 10 weight drops of water and magnetized by a magnetic separator with a maximum magnetic force of 100 Gauss. ,
Then, the 10 to -00 mesh and the 100 mesh were subjected to different treatments for the sieved particles, and then reduced annealed under the same conditions as above and crushed to create a sintering agglomeration effect between the particles. Peku.

The rotation speed for crushing the sintered cake is: jIoot, p, m,
e Distance from the main shaft axis to the tip of the 71 inch i/
jOvm.

Number of hammers; JO book, unit weight of hammer; zoof
First, JtMn
Attach a screen with a hole diameter of φ and crush it, and cast it by 10 mesh casting. For tightening, the amount of tightening is 9'O. In the same way, attach a screen with a hole diameter of 0.3mmφ to O0 and 1φ, repeat the crushing and sieving process, and blend each batch of 110 mesh iron powder. I did O, j
The sintered cakes reduced and annealed according to grain size of ON CoOO Metsushi and -JOO Metsushi are respectively crushed, cast and blended under the same conditions and procedures as above, and water-sprayed raw iron powder tO ~ - Particle size ratio of 〇〇 mesh and 1100 mesh, that is, 10. The mO mesh was re-blended at a ratio of 5/1o and -100 mesh at a ratio of 0. Powder properties of the nine-sprayed raw iron powder described above, powder properties of reduction annealed iron powder, and green compact The properties are shown in Table 1 together with the particle agglomeration treatment and reduction annealing conditions.

As shown in Table 1, χ = 1.40°/jO for particle diameters exceeding 110 μm.
In particle sizes below am (II se 4 x 10”
110 mesh iron powder (test number 1) obtained by reduction annealing of water-sprayed raw iron powder having the relationship e - "" is shown in the same table (2).
As shown in Figure 7, the apparent density is 10 t/3, and the symbol 0 stomach;! As shown in , for particle diameters exceeding /jOμm, χ2.40.For particle diameters less than 110μm, dmax = i, z
x,,7. -4,471, and there is a limit to the reduction in apparent density due to mutual sintering and agglomeration of particles. It can be seen that the formability of the mixed powder is inferior to that of the comparative material (mill scale reduced iron powder).

On the other hand, the symbols in FIG.
χ≦2.40 for particle sizes exceeding m. /! dl = a6-'', b')
-10 mesh iron powder (test number! 5.4.6.7.8., 9 and 10 )
As shown in Table (2), the apparent density is 1. BuQ f/B
The compressibility and formability of the J Cu-0,tC-/Zn・8t-tat,2wt-□Fe mixed powder were as low as the comparative material (mill scale reduced iron powder; Test No. 11). It can be seen that it is equivalent to or better than .12) ・In addition, the symbol: Iron powder obtained by applying a particle agglomeration treatment to the atomized raw iron powder and reducing annealing (Test numbers 6, 7 and 8) It can be seen that the apparent density is further reduced and the moldability is improved.

On the other hand, when the reduction annealing temperature is too low, such as 7'OO℃ (test number 2), the reduction annealed -to-mesh iron powder is The apparent density did not decrease completely, and both the compressibility and formability of
) has not reached the level of trench 9 reduction annealing temperature of 1110
If the temperature is too high (℃).

Test No. 5) is the apparent density of reduction annealed nine-iron powder, which is difficult to break up the sintered cake due to sintering between the particles, resulting in smooth, multifaceted particles. IFij1 sprayed raw iron powder rose and hardened during crushing, resulting in poor compressibility and formability compared to comparative materials (Mill Scale Reduced Iron Powder 1 Test Nos. 11 and 121).

Figure 1 shows water-sprayed raw iron powder with symbol I in Figure 1 in ammonia decomposition gas! These are the results of investigating the relationship between the impact force when a sintered cake soaked at 0°C x 4Ajrrtin and reduction annealed is crushed in a hammer mill and the apparent density of 110 mesh iron powder. As is clear from this, the impact force affects the apparent density of the crushed iron powder, and the io5f-m/se
If an impact force exceeding c is adopted, the apparent density will be higher than the apparent density of raw iron powder.

Although the above embodiments have been explained using water-sprayed raw iron powder as an example, the present invention can be applied to all raw iron powders that are produced using a liquid as the spray medium and require atomization or annealing. can.

As described above, with this invention, a manufacturing technology for atomized iron powder for powder and carbon removal metallurgy, which has excellent formability and an apparent density as low as , QO ~ , and toe/s, has been established. Such low apparent density sprayed iron powder can be advantageously used as a raw material for medium to low density iron-based sintered materials, and can be used as a substitute for reduced iron materials (mill scale reduced iron powder, ore reduced iron powder). Not only is it possible, but it can also be used to ensure high compressibility.

[Brief explanation of the drawing]

Figure #I1 is a graph showing the relationship between the apparent density and single particle size of water-sprayed raw iron powder and reduction annealed and crushed product iron powder, and Figure 1 is a graph showing the relationship between water-sprayed raw iron powder with symbol JII in Figure 1. This is a graph showing the relationship between the impact force of the hammer mill and the apparent density of -to mesh product iron powder when a sintered cake obtained by reduction annealing the powder is crushed with a hammer mill.〇Patent applicant Kawasaki Steel Corporation

Claims (1)

[Claims] 1. The relationship between the apparent density χ(4s) and the arithmetic mean d1 of one @I(1, d) of the Tyler standard density (#9 grains in the shrine) is as follows. Both conditions of formula (2) are met. Raw iron powder is directly processed by liquid spraying, or the raw iron powder is subjected to particle aggregation treatment, and then heated to 100 to 100% in a reducing and decarburizing atmosphere.
Reduction annealing is carried out at a temperature in the range of 1 too°C, and the resulting sintered coo is crushed and disintegrated by applying an impact force of ix to ky/-m7g2 or less to obtain particles 1 with a particle size of tzostn or less.
Apparent density, including go weight or higher, 00-w2,40
A method for producing atomized iron powder for powder metallurgy with excellent formability and low apparent density, comprising obtaining iron powder with f/, -.
...(dI for particles smaller than particle diameter/IOa)!
1#c! ...(2) Here 1. 2. The method according to claim 1, wherein bH grain shape constant is b≧/, j2, and the atomized raw iron powder to be subjected to reduction annealing is classified powder classified in advance according to particle size. 5. Claim I in which blending is performed after crushing and disintegrating the sintered cake! Method 04 according to claim 12, wherein the particle aggregation treatment is addition and mixing of a liquid, or claim 81.2;
Method 05 according to IS, the particle aggregation treatment is magnetization. Method 0 according to claim 1.2 or 3, in which the atomized iron powder that has undergone reduction annealing has oxygen θ, CO!
Below T1 carbon 0.0j or less, nitrogen o, oi or less, silicon θ
,・10 or less, manganese 0. f-0 or less, a little 0, # or less, and sulfur 0.10 or less, or even tin O0
! Claim 1.2.
3.4 is the method described in 5.