JPS61227103A - Production of iron powder - Google Patents

Abstract

PURPOSE:To grind coarse-grained pig which is difficult to be ground at a low cost by crushing and deforming plastically the coarse-grained pig obtd. in the stage of treating a molten iron to a plate shape at an ordinary temp. to generate many cracks then pulverizing said pig. CONSTITUTION:The coarse-grained pig 4 separated from the kish graphite and slag generated in the stage of treating the molten iron or casting the pig is stored into a storage hopper 1. Such coarse-grained pig 4 is fed via a chute 2 and a gate 3 to vertical multi-stage rolls 5 which rotate at a low speed. The upper rolls 6, middle rolls 6 and lower rolls 6 of the rolls 5 are gradually narrowed in the spacings therebetween. The coarse-grained pig 4 is successively crushed and fed downstream via guides 7 and is formed to plate shape of about 1mm. Such pig is changed to the crushed material in which the many cracks are generated. Such crushed material is fed via a conveyor 8 having a magnetic separator to a storage hopper 9 from which the crushed material is supplied to a pulverizer 10 and is thereby pulverized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing iron powder from coarse-grained pig iron separated from quiche graphite or slag.

[Prior art]

During blast furnace hot metal processing operations, amorphous coarse pig iron containing Quiche graphite is unavoidably generated, which accounts for approximately 1% of the amount of hot metal, which is a large amount. However, some of it is magnetically sorted and becomes scrap with low added value.

The reality is that it is recycled as a raw material for sintering.

However, about 50% of coarse-grained pig iron has a grain size of 2 mm or less, and is attracting attention as a raw material for iron powder. However, since it is granular and has considerable toughness, the impact load during crushing is dispersed, making it difficult to crush by mechanical crushing such as ball mills, hammer mills, and other conventional crushers. As a method of crushing solid metals that are difficult to crush, Chemical Industry Handbook (Maruzen Co., Ltd.) P, 1031-17゜3
．． There is a cryo-grinding method as described in 6.

In low-temperature pulverization, if the pulverized material is thermoplastic or tough at room temperature, it is cooled with a refrigerant such as dry ice or liquid nitrogen.
Since this is a method of grinding by imparting brittleness, when grinding iron, special materials must be used in consideration of the low-temperature brittleness of drums and ball materials.

In addition, bulky iron-based scraps are lightly pressed at room temperature as in JP-A-52-52482 (metal scrap processing method), and then the cooled scraps are crushed.

There is also a method of coarsely crushing and then finely crushing, but it is known that running costs and equipment costs are higher than mechanical crushing at room temperature.

On the other hand, mechanical crushing methods include (1) ball mill method, (2) hammer mill method, (3) vibration mill method, (4) stamp mill method, (5) edge mill method, (6) microteaser method, etc. Although it is known, methods (4) to (6) require large equipment costs and have relatively low pulverization efficiency, so pulverization using methods (1) to (3) is the most economical. However, as described above, the impact load during crushing of the coarse pig iron is dispersed due to both its shape and material, and in the ball mill method, the pulverization rate is low even if it is crushed for a long time. Moreover, the crushing mechanism only pulverizes the surface of the coarse particles due to wear, and volumetric pulverization due to impact is not performed.In addition, in the hammer mill method, even if the iron is coarsely crushed in advance with an edge mill, the screen wears out significantly, and the screen must be replaced before pulverization. The operating time of the machine is short, with intermittent operation of less than 10 minutes, resulting in poor workability and not being a good idea as a production facility.

In a vibrating mill, coarse pig iron with a wide particle size composition is separated, and fine grains of 3 mm or less can be pulverized in a laboratory-scale vibration mill, but coarse pig pigs of 3 mm or more are coarsely pulverized. It cannot be pulverized without crushing, and the iron powder has a spherical shape with few irregularities, making it as unsuitable as a raw material for body warmers as sintered metal, and no mill on a commercial scale has been found at present.

[Problem that the invention seeks to solve]

The coarse-grained pig iron of unspecified shape with a major axis of 15 mm or less that is generated during the hot metal treatment has a particle size composition as shown in Fig. 3 (a), although it has many fine particles of 2 mm or less, but it is not stable at room temperature. It is difficult to pulverize both sides of the material using mechanical pulverization methods. In other words, since the coarse-grained pig is granular and made of the same material as pig iron, it has toughness, so the impact load during crushing is dispersed, and the crushing mechanism is such that the surface layer of the coarse-grained pig is only slightly abraded and crushed. Therefore, a means for volumetric pulverization is required.

[Means to solve problems]

Since the material of coarse-grained pig is the same as pig iron, it has toughness.
% of graphite. Also, examples of its shape (3 to 10 mm
) has an unspecified granular shape as shown in FIG. 6, and since it is mixed with fine particles, the impact load during crushing is dispersed and it is difficult to crush, as described above. However, the coarse-grained pig iron has a property of being prone to cracking starting from graphite due to low stress. Furthermore, by crushing at room temperature and at low speed, countless cracks can be generated starting from the graphite contained.

The present invention was developed focusing on this point, and its manufacturing method involves crushing coarse pig iron separated from a mixture of quiche graphite and slag, which is generated during tapping of blast furnace hot metal and processing of hot metal such as cast iron, in advance at room temperature. This method of producing iron powder is characterized by generating a large number of cracks by plastically deforming it into a plate shape, and then pulverizing it into fine particles.

To explain the manufacturing process of the present invention, there is first a step of separating coarse-grained pig iron from Quiche graphite, in which the hot metal tapped from the blast furnace is transported to a casting machine or a mixed iron furnace, and the Quiche graphite generated at each location is mixed with the molten iron. Drain and retain the slag mixture.

The retained waste slag is classified using a bar screen.

Next, it is separated into sludge, small lumps, rough pig iron, and coarse pig iron using a trommen. The above separation method can also be performed dryly. Further, the above-mentioned coarse-grained pig iron includes those generated from sources other than tap iron, cast pig iron, and converter furnaces.

Next, the separated coarse-grained pig iron is crushed through a plurality of rolls and plastically deformed into a plate shape of about 1 mm, thereby generating a large number of cracks. Then, it is pulverized using a pulverizer.

[Effect]

First, a method for separating coarse-grained pig iron will be explained using an example. The coarse pig iron is mixed in the quiche graphite and waste slag and must be separated.

Figure 2 shows the separation method. Hot metal tapped from blast furnace A is received in hot metal ladle B and sent to caster C or mixer, and slag E- and F are removed during each hot metal treatment. It will be done. Since this slag contains a large amount of rough pig iron and granular pig iron, the iron source and graphite will be recovered. The sludge is temporarily retained and then classified using a bar screen H with a 300 m/m sieve mesh. +300m/m is sieve top rough ironwork and -300m/m
m is rough pig iron under the sieve, graphite, and sludge. After that, the sludge is first removed from -300m/m by Trommen K, which has water washing and sieving functions, and the rest is -300m/m/m.
m/m of coarse grain pig N and 15-300 m/m of small lump round iron M. Among the above, coarse pig pig N is finely pulverized using a device as described below.

FIG. 1 shows an example of an apparatus for crushing and pulverizing coarse pig iron.

The equipment consists of a coarse pig iron storage hopper1. Chute 2, multi-stage roll 5. Conveyor 8 and pulverizer 10 with magnetic separator
Consists of etc. Between the hopper 1 and the chute 2 there is a gate 3 for cutting out the necessary material. Further, the multistage roll 5 is composed of a plurality of rolls 6 and a guide 7, and the roll 5
The gap becomes narrower from the top to the bottom. In the subsequent process, a pulverizer 10 is provided via a conveyor 8 and a hopper 9 having a magnetic separator to remove impurities.

The above-mentioned pulverizer may be a ball mill, a hammer mill, a vibration mill, or the like. Preferably, a vibrating mill is used because of its obtainable iron powder particle shape and grinding efficiency.

In the present invention, by crushing the granular shape, which is the main cause of difficulty in crushing coarse-grained pig iron, with low-speed rotating rolls at room temperature, it is plastically deformed into a plate shape with countless cracks as shown in Figure 7. facilitates fine pulverization. This plastic deformation method is possible using rolls or a press, but press crushing has poor productivity because the material supply is intermittent, and is unsuitable for mass processing; however, roll crushing is continuous and the material supply is This makes it suitable for mass processing. It is preferable that the roll be of the vertical multi-stage type in order to allow granular raw materials to be bitten and to crush large granular materials to a predetermined thickness by increasing the number of passes.

The plate-shaped crushed material crushed to about 1 mm by the above method may be broken and split due to propagation of generated cracks because the larger the particle size is, the more roll passes are required.

The coarse pig iron with a particle size of 1 mm or more turns into crushed material with numerous cracks. The thus obtained crushed material does not disperse the impact load during crushing, and the volumetric crushing is significantly improved due to the synergistic effect of the simultaneously generated cracks, so it becomes possible to omit the coarse crushing step and perform fine crushing. .

In particular, the volume pulverization due to cracking during crushing results in a significantly uneven shape, resulting in iron powder suitable for use as a raw material for sintered metals and hand warmers.

The above-mentioned iron powder may be classified according to the purpose of use, and the particle size may be made uniform and mixed to obtain the optimum particle size. For example, it is possible to guarantee the same quality as that for commercially available iron powder body warmers.

An example of the operation of producing iron powder will be described below.

As shown in FIG. 1, a hopper 1 for storing the coarse pig iron
The coarse-grained pig iron 4 is rolled widely through a chute 2 attached to the chute 2 so that about 70% of the roll length of 40 cm is crushed.
kg/min, and passed through the crushing guide 7 at a rolling reduction rate of 50% by the upper roll 6 (gap between rolls 6 m/m) of the vertical multi-stage roll 5 rotating at a low speed of 10 m/min or less peripheral speed, and then passed through the crushing guide 7 at a reduction rate of 50%. Rolls (gap between rolls 2.5m/m
) 60%, lower roll (gap between rolls 1 m /
m ) under 60% pressure to form a plate shape of approximately 1 mm.

In this crushing process, the coarse grained piglet smaller than the gap between the lower rolls passes under no pressure, but the coarse grained piglet larger than the gap between each flute roll is crushed. be divided. The material of the crushing roll is preferably a chilled roll, which has an HRB of 140 or less and is soft so that the crushed material does not stick to the roll during crushing because the coarse grained pig iron is not whitened.

The crushed material is stored in a hopper 9 by a conveyor 8 having a magnetic separator, and is supplied to a pulverizer 10. 10 kg of the crushed material was charged into a ball mill with a drum diameter of 30 cm and a drum length of 20 cm, and pulverized at a rotational speed of 5 Orpm for 1 hour. The particle size structure after crushing is as shown in Figure 3 (b), and the particle size configuration after 7 hours of ball mill crushing without crushing is shown in Figure 3 (c). The crushing rate is the best compared to the particle size configuration (d) in which the particles were then finely pulverized using an atomizer for 50 minutes.

Further, the iron powder pulverized by the method according to the present invention is
The particle shape classified by 97μ is a rectangular polygon as shown in FIG. 8, which is an ideal shape as a raw material for sintered metal scraps and body warmers. This iron powder was classified into -297~149μ and -149μ, mixed at 50% of each in the same way as commercially available products, and a heat generation test was conducted.As shown in Figure 4, the heat generation temperature was similar to that of a commercially available disposable body warmer. It was confirmed that they had similar characteristics such as duration.

Further, as a result of classifying the iron powder pulverized according to the present invention into particles of 297 μm or less and testing whether or not they can be used as iron powder for sintered metals, particles having the particle size configuration shown in Table 1 were obtained and molded without the addition of a binder. As mentioned above, this iron powder contains 3 to 4% graphite, so it does not require the addition of a binder and has a yield of 3 t/c.
RD Excellent moldability with no problems in handling after mold removal even at low pressure.

Figure 5 shows the density of a green compact molded into a 40φ sample using the iron powder in Table 1, and it can be seen that iron powder 2 has better moldability than cast iron powder 1, which is made by ball milling powder. . The reason for this is that the particle shape of the cast iron powder 1 causes directional cracks during cutting to be inherited by the powder and has a large particle size coefficient (Q/d), which causes a bridging phenomenon and deteriorates compressibility. On the other hand, the iron powder has non-directional cracks, has an appropriate particle size coefficient, and does not cause the bridging phenomenon, so it has good compressibility.

〔Effect of the invention〕

In this way, the material properties of coarse-grained pig, which had been conventionally recovered as scrap, were crushed by rolls or presses to generate a large number of cracks, making it possible to crush coarse-grained pig which was difficult to crush at a low cost.

In addition, by making the iron powder suitable as a raw material for body warmers, the quality of which is comparable to that of sintered metals, not only is the added value increased several times, but it can also be used as a raw material for iron powder body warmers, which has been in short supply due to increased demand in recent years. It can be supplied at low cost and has significant economic effects.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing the iron powder manufacturing method of the present invention, and FIG. 2 is a flowchart showing the separation and separation of coarse grained pig iron from Kish graphite. Figure 3 shows the particle size distribution of coarse pig iron before crushing and the particle size distribution of iron powder obtained by various crushing methods. (a) Particle size distribution of coarse grained pig before crushing (b) Particle size distribution after crushing according to the present invention (c) Particle size distribution of uncrushed coarse grained pig crushed for 7 hours in a ball mill (d) Particle size distribution of uncrushed coarse grained pig using a hammer crusher Particle size distribution after coarse crushing for 15 minutes with an atomizer and finely crushing with an atomizer for 50 minutes. Figure 4 shows the results of an exothermic test to determine the suitability of the iron powder obtained in the present invention as a raw material for body warmers. FIG. 5 shows the green compact density measured by molding a 4oφ sample using the iron powder obtained according to the present invention. (1) Green density of cast iron powder obtained by crushing dull powder (2) Green density of iron powder according to the present invention Figure 6 shows the density of coarse-grained iron (
3 to 10 mm), Figure 7 is an example of the appearance of a crack generated by crushing Figure 6 with a roll, Figure 8 is an example of the shape of iron powder particles obtained by the present invention, 1: Coarse pig iron storage hopper 2: Same chute 3: Gate 4: Coarse pig iron 5: Multistage roll 6: Roll 7: Guide 8: Conveyor 9: Crushed material storage hopper 10: Fine crusher A: Blast furnace B: Hot metal pot C: Cast iron machine D: Mixed pig iron furnace E: Slag F: Slag G: Detention H: Bar screen (sieving) Work: Round iron above the sieve J: Nitron mening on the round iron below the sieve (washing with water, sieving) L: Sludge M: Small lumps Round Iron N: Coarse Pig No. 2 To, Unskinned Layer Volume No. 3 At and 4 (μn#-Run (〃r) Thick f! Pressure (fhys')), 罎No. 6vR to 1 Figure 1i7f: Figure 8

Claims (1)

[Claims] An iron that is characterized in that coarse pig iron separated from quiche graphite and slag generated during hot metal processing or cast iron is crushed in advance at room temperature, plastically deformed into a plate shape to generate a large number of cracks, and then finely pulverized. Method of manufacturing powder.