JPH0819482B2 - Carburized iron and its manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to carburized iron and a method for producing the same.

Prior art and problems When obtaining various steel products using reduced iron, a carbon source is added as a reducing agent for reducing coexisting iron oxide when the reduced iron is melted in an electric furnace. As the carbon source, natural gas is used in the Hill method, Midrex method, Fior method, etc., and coal is used in the Lulurgi method, Krupp method, DRC method, and King roll-Metter method. In the former case, the carbon content in the reduced iron is about 1.0 to 2.5% by weight, and in the latter, it is 0.1
~ 0.5% by weight. Generally, the amount of the reducing agent is required to be about 2.0% by weight with respect to the reduced iron, and therefore it is actually necessary to add carbon to the molten iron to adjust the carbon amount.

However, in the method of directly adding carbon to molten iron,
Since the difference in specific gravity between carbon and iron is significant, carbon floats on the surface and is surface-oxidized to be consumed as carbon dioxide gas, and a sufficient reducing effect is not exhibited, and in addition, it is difficult to uniformly disperse even deeper.

On the other hand, porous iron such as reduced iron pellets and lamp iron ore is porous and brittle, and is easily pulverized by friction between iron ingots, absorbs moisture, or is easily oxidized by contact with water or air. I have a problem to say.

Means for Solving the Problems The present invention coats a porous iron surface with a thermoplastic resin containing carbon powder to prevent pulverization of porous iron, moisture absorption and oxidation, and to add this to reduced iron and the like. , A method of controlling the carbon content is provided.

That is, the present invention relates to a carburized iron having a porous iron surface coated with a thermoplastic resin containing a carbon source, and a method for producing the same.

The carbon source used in the present invention is preferably powdery carbon, for example, coal powder, carbon black, coke powder, charcoal,
Petroleum pitch, petroleum coke, anthracite, electrode graphite scrap, graphite slap, waste carbon black, electrode graphite scrap, etc. are exemplified, but as an inexpensive raw material, for example, fine coke as a by-product of coke obtained by the cold breeze method or the like. There is.

The particle size of carbon powder is 100 when applied by the spray method etc.
It is suitable to be less than μm, and 1 mm or less for the dipping method.

The carbon source is preferably 30% by weight or less of the total amount of the thermoplastic resin and the carbon source, and when it is 30% by weight or more, the coating film strength is reduced.

Examples of the thermoplastic resin used in the present invention include polyolefin resins such as polyethylene, polypropylene, polybutylene, and methylpentene, olefin copolymers such as ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate (methyl) copolymer, and the like. Coalescing; poly-p-xylylene,
Examples thereof include polyvinyl acetate, polyacrylate, polymethacrylate, polyvinyl chloride, polyvinylidene chloride, polyvinyl ether, polyacrylonitrile, thermoplastic polyester, polycarbonate, polybutadiene and polyisoprene. Preferred thermoplastic resins are polyolefins, polyolefin-based copolymer resins, vinyl acetate and the like, and polyolefins, particularly polyethylene are preferred.

These resins have a viscosity at 200 ° C of 1 to 10,000 cp
s, especially 10-7000cps. Softening temperature of 60-200 ℃, especially 80-1
20 ° C is suitable.

When the viscosity of the thermoplastic resin is more than 10,000 cps, the mixture with the carbon source becomes non-uniform, and the surface of the porous iron is not coated uniformly, so that the effect of preventing moisture absorption by the resin coating is reduced. If the resin viscosity is less than 1 cps, the resin is absorbed by the pores on the iron surface, so a large amount of resin is required.

In the present invention, a recovery film of agricultural polyethylene, low molecular weight polyethylene, atactic polypropylene, and the like, which are by-products in the polyethylene manufacturing process, can be used, and these may be mixed in an appropriate ratio and used. Carbon content can be increased with atactic polypropylene.

As porous iron, reduced iron pellets (porosity about 50%
Degree), reduced iron briquette obtained by hot pressing it, (porosity 20-30%), lamp iron ore (porosity about 50
%) Etc., and these are usually used in a lump form of about 3 to 40 mm.

As a method for coating the carbon source-containing thermoplastic resin on the porous iron surface, there are a spray method and a dipping method, the former is suitable for thinning the resin coating, and the latter is a large amount of carbon on the porous iron surface. It is preferable to adhere to.

In the spraying method, a thermoplastic resin in which a carbon source is dispersed is atomized and its mist is sprayed onto porous iron kept at a temperature lower than the softening temperature of the resin. The mist may be either a molten mist of resin or a powder mist, but the particle size is preferably 100 μm or less. The atomized mist solidifies on the iron surface even when it is a molten mist. As a result, the resin is not impregnated into the voids of the porous iron, and it is effective for coating the surface with a small amount. Therefore, the surface temperature of porous iron, etc. is preferably lower than the softening temperature of the resin.
Degree is general. Since reduced iron pellets are usually obtained at 50 to 60 ° C., they can be used as they are.

The adhesion amount of carbon-containing thermoplastic resin to porous iron is iron
Suitable is 0.1 to 4 parts by weight, especially 0.5 to 3 parts by weight, of the carbon-containing thermoplastic resin per 100 parts by weight. If it is less than 0.1 part by weight, the coating thickness becomes insufficient, and conversely if it is used in excess of 4 parts by weight, it is uneconomical. When the method of the present invention is adopted, it is possible to uniformly coat the porous iron with a small amount of the resin as described above.

The porous iron obtained by the above method is in a state in which the mist of the carbon-containing thermoplastic resin is attached to its surface,
Many uncoated portions remain on the surface. Therefore, the resin-attached porous irons are rotated in contact with each other in an appropriate rotating body to uniformly attach the resin to the surface thereof. At that time, it is preferable to maintain the treatment atmosphere temperature at a low temperature, particularly, a temperature lower than the softening temperature of the resin. By doing so, there is no risk that the iron surface not covered with the resin will be exposed to high temperature and oxidized, and in addition, the resin will not be impregnated into the voids of the porous iron more than necessary and consumed. . As a result, the continuous treatment in which the treatment is performed in an inert gas atmosphere becomes easy, and the structure of the treatment device becomes simple.

The carbon-containing resin-coated porous iron obtained by the above method is still sufficiently resistant to oxidation, has a small amount of water absorption, and is difficult to be dusted, but if necessary, further soften the resin by coating the coated porous iron. You may heat above temperature. in this case,
Since the porous iron is coated with resin, it can be prevented from being oxidized by heating. Post-heating is preferable for achieving adhesion and homogenization of the resin.

When using this method, it is preferable to use pulverized coal having a carbon source of 100 μm or less. If it exceeds 100 μm, the spray nozzle may be clogged.

An example of a method for producing porous iron coated with a carbon-containing thermoplastic resin by the above-mentioned spray method will be described below with reference to FIGS. 1 to 4.

FIG. 1 is a schematic cross-sectional view of the apparatus for producing carburized iron of the present invention, FIG. 2 is a left side view of the apparatus of FIG. 1, and FIG. 3 is II.
A sectional view and FIG. 4 show a right side view. The cylindrical difficult horizontal rotation drum (1) is rotatably installed by a rotation support base (3) rotated by a motor (2), and a supply port (5) for supplying porous iron is provided on the left side surface of the drum. A heating spray device is provided, and a discharge port (6) for discharging porous iron is provided on the right side surface of the drum. In order to use the continuous production method (overflow method), the discharge port is made larger than the supply port, and the height (l) to the discharge port (6) of the outlet side drum wall is set to be higher than the height (l ') to the supply port. You can make it smaller. A blade (4) is provided inside the drum.

A certain amount of porous iron and a carbon-containing thermoplastic resin for coating the iron are charged by a heat spray from a supply port, and a drum is rotated. The rotation of the porous irons is hindered by the blades, so that they are in good contact with each other and are pressed against each other by the co-rubbing effect, so that the resin is uniformly attached. At that time, the porous iron itself may be heated by the heater (9) above the softening temperature of the resin.

The resin coating of porous iron may be performed in two steps. That is,
If necessary, the carbon-containing thermoplastic resin-coated porous iron surface is then heated if necessary. In this case, since the resin film is formed in the first step, reoxidation due to heating can be suppressed.

The carbon-containing thermoplastic resin may be further coated on the surface of the porous iron coated with the carbon-containing thermoplastic resin in the same manner as described above by repeating the same operation as in the second step. At that time, the first
The resin used in the step and the resin used in the second step may be changed. For example, in the first step, a resin that is difficult to be impregnated into the porous iron, for example, a thermoplastic resin having a molecular weight of about 5000 may be used, and in the second step, a resin having a molecular weight of about 1500 may be used. Moreover, you may use resin with high abrasion resistance in a 2nd process.

The second step does not necessarily have to employ the above method, and may employ the dipping method. In this case, since the resin film is formed in the first step, the resin is prevented from entering the porous iron due to the immersion. However, even in such a case, the condition that the resin film formed in the first step does not remelt should be adopted.

As described above, in the spray method, it is possible to apply the carbon-containing resin uniformly to the surface of the porous iron while suppressing the absorption as much as possible, and it is also possible to supply the carburized iron without causing oxidation, pulverization, breakage, etc. It will be.

The second method of the present invention is a dipping method. In the spraying method, it is possible to carburize while positively suppressing the absorption of resin into the porous iron, but it is necessary to carburize pig iron, steel, soft iron, etc., which requires a large amount of carburizing. It is desirable that the iron itself contains many carbon sources. The dipping method can also be used for that purpose.

In the dipping method, a low viscosity resin is melted and a carbon source is dispersed therein. As the carbon source, it is preferable to use carbon powder of about 1 mm or less. If the particle size of the carbon powder is larger than 1 mm, the carbon powder itself may cause dust due to friction and collision of the porous iron during handling and transportation.

Porous iron is dipped in this carbon-containing resin liquid, lifted, and cooled if desired.

 Hereinafter, the present invention will be described with reference to examples.

Example 1 As shown in FIG. 1, reduced iron pellets (porosity 55%, water absorption 15%) that had been heated to 75 ° C. in advance were continuously supplied from a supply device (7) in a fixed amount as shown in FIG. (1)
20% by weight of carbon black (particle size 50 μm) mixed resin (molecular weight 1400, polyethylene resin 34% by weight of softening point 83 ° C., atactic polypropylene resin 34% by weight of softening point 110 ° C. and molecular weight 330,000). , 12 wt% of high-molecular-weight polyethylene resin having a softening point of 86 ° C. is made into a liquid mist by a heating spray device (8) and continuously supplied at a ratio of 2 wt% to the pellets, while the inner wall of the drum heater (9) is used. ) And heated to 180 ° C to obtain carburized iron by the rotary overflow method. The obtained carburized iron was left outdoors for one month, and changes in metallization rate, water absorption rate during rainfall, and rotational strength were observed. The results are shown in Table 1.

Metallization rate: Measured by wet analysis based on JIS-M-8202.

Water absorption rate: 100 g of the sample was exposed for 5 hours when the average rainfall was 2 mm / Hr, and the moisture adhering to the surface was absorbed by the filter paper, and immediately weighed.

Rotational strength: The rotational strength index and abrasion strength index are calculated based on JIS-M-8712.

Example 2 In the same manner as in Example 1, reduced iron pellets (porosity 55%, water absorption 15%) that had been heated to 75 ° C. in advance were continuously charged into a rotating drum in a fixed amount, and Mixed resin containing 20% by weight of carbon black (particle size 50 μm) (molecular weight
1400, 34 wt% polyethylene resin with a softening point of 83 ° C and a softening point of 1
34% by weight of atactic polypropylene resin at 10 ° C and 12% by weight of high molecular weight polyethylene resin with a molecular weight of 330,000 and a softening point of 86 ° C) are made into a liquid mist by heat spraying and continuously supplied at a ratio of 4% by weight to pellets. Meanwhile, the inner wall of the drum was heated to 180 ° C. and rotated to obtain carburized iron by the overflow method. The obtained carburized iron was left outdoors for one month, and changes in metallization rate, water absorption rate during rainfall, and rotational strength were observed. The results are shown in Table 1.

Example 3 Reduced iron pellets (porosity: 55%, water absorption rate: 15%) that had been heated to 75 ° C. in advance were continuously charged into a rotary drum in the same manner as in Example 1, and the reduced iron pellets were continuously charged. Mixed resin containing 30% by weight of carbon black (particle size 50 μm) (molecular weight
Polyethylene resin with a softening point of 1400 and a softening point of 83 ° C 30% by weight and a softening point of 1
30 wt% atactic polypropylene resin at 10 ° C and high molecular weight polyethylene resin with a molecular weight of 330,000 and a softening point of 86 ° C (10 wt%) are heated and sprayed into a liquid mist, which is continuously supplied at a ratio of 2 wt% to pellets. Meanwhile, the inner wall of the drum was heated to 180 ° C., the drum was rotated, and carburized iron was obtained by the overflow method. 1 of the obtained carburized iron outdoors
After being left for a month, changes in metallization rate, water absorption rate during rainfall, and rotational strength were observed. The results are shown in Table 1.

Comparative Example 1 Reduced iron pellets (porosity 55%, water absorption 15%) that had been heated to 75 ° C. in advance were continuously charged into a rotary drum in a constant amount in the same manner as in Example 1 Mixed resin (Molecular weight 1400, softening point 83 ° C polyethylene resin 42.5% by weight and softening point 110 ° C atactic polypropylene resin 42.
5 wt%, high molecular weight polyethylene resin with a molecular weight of 330,000 and a softening point of 86 ° C (15% by weight) is made into a liquid mist by heating spray, and while continuously supplying it at a rate of 2% by weight to the pellets, the inner wall of the drum is 180 ° C. Heated to and rotated. Obtained carburized iron by the overflow method, and leave the obtained carburized iron outdoors for one month to change the metallization rate, water absorption rate during rainfall,
The rotation strength was observed. The results are shown in Table 1.

Comparative Example 2 In the same manner as in Example 1, reduced iron pellets (porosity 55%, water absorption 15%) that had been heated to 75 ° C. in advance were continuously charged into a rotary drum in a fixed amount, and Mixed resin containing 40% by weight of carbon black (particle size 50 μm) (molecular weight
1400, 25.5 wt% polyethylene resin with a softening point of 83 ° C and 25.5 wt% atactic polypropylene resin with a softening point of 110 ° C
And a high-molecular-weight polyethylene resin with a molecular weight of 330,000 and a softening point of 86 ° C (9% by weight) is sprayed into a liquid mist, and while continuously supplying 2% by weight to the pellets, the inner wall of the drum is heated to 180 ° C. Then, the carburized iron was obtained by rotating and overflowing, and the obtained carburized iron was left outdoors for one month to observe changes in metallization rate, water absorption rate during rainfall, and rotational strength. The results are shown in Table 1.

Comparative Example 3 The uncoated reduced iron pellets were left outdoors for one month, the change in metallization rate was examined, and the water absorption rate and rotational strength during rainfall were observed. The results are shown in Table 1.

Example 4 Lamp iron ore (porosity: 50%, water absorption rate: 9.6%) that had been heated to 75 ° C. in advance was continuously charged into the rotary drum in a constant amount in the same manner as in Example 1, and carbon was added thereto. 20% by weight black (particle size 50 μm) mixed resin (molecular weight 140
0, 34 wt% polyethylene resin with a softening point of 83 ° C and a softening point of 110
34% by weight of atactic polypropylene resin at ℃ and molecular weight
330,000, high-molecular-weight polyethylene resin with a softening point of 86 ° C (12% by weight) was heated and sprayed into a liquid mist, which was continuously supplied at a rate of 2% by weight to the inner wall of the drum.
Heated to 180 ° C and rotated. Carburized iron was obtained by the overflow method, and the drop strength of the obtained carburized iron was evaluated. Table 2 shows the results.

Drop strength: Drop strength (%) was calculated based on JIS-M-8711 Example 5 Lamp iron ore (porosity 50%, water absorption 9.6%) that had been heated to 75 ° C. in advance was used as Example 1. In the same manner, a fixed amount was continuously charged into the rotary drum, and a mixed resin containing 20% by weight of carbon black (particle size 50 μm) (molecular weight 140
0, 34 wt% polyethylene resin with a softening point of 83 ° C and a softening point of 110
34% by weight of atactic polypropylene resin at ℃ and molecular weight
330,000, high-molecular-weight polyethylene resin with a softening point of 86 ° C (12% by weight) is sprayed into a liquid mist and continuously supplied at a rate of 4% by weight to the inner wall of the drum.
Heated to 180 ° C and rotated. Carburized iron was obtained by the overflow method, and the drop strength of the obtained carburized iron was evaluated. Table 2 shows the results.

Example 6 Lamp iron ore (porosity: 50%, water absorption rate: 9.6%) that had been heated to 75 ° C. in advance was continuously charged into the rotating drum in the same manner as in Example 1, and carbon was added thereto. 30% by weight of black (particle size 50 μm) mixed resin (molecular weight 140
0, polyethylene resin 30% by weight with softening point 83 ° C and softening point 110
30% by weight of atactic polypropylene resin at ℃ and molecular weight
330,000, high-molecular-weight polyethylene resin with a softening point of 86 ° C (10% by weight) was heated and sprayed into a liquid mist, which was continuously supplied at a rate of 2% by weight to the inner wall of the drum.
Heated to 180 ° C and rotated. Carburized iron was obtained by the overflow method, and the drop strength of the obtained carburized iron was evaluated. Table 2 shows the results.

Comparative Example 4 Lamp iron ore (porosity 50%, water absorption 9.6%) that had been heated to 75 ° C. in advance was continuously charged into the rotary drum in the same manner as in Example 1 and mixed therein. A resin (4400 wt% polyethylene resin with a molecular weight of 1400 and a softening point of 83 ° C and 42.5 wt% atactic polypropylene resin with a softening point of 110 ° C and a molecular weight of 330,000 and a high molecular weight polyethylene resin with a softening point of 86 ° C and 15 wt%) are heated and sprayed. Liquid mist,
While continuously supplying 2% by weight to the lamp, the inner wall of the drum was heated to 180 ° C. and rotated. Carburized iron was obtained by the overflow method, and the drop strength of the obtained carburized iron was evaluated. Table 2 shows the results.

Comparative Example 5 Lamp iron ore (porosity: 50%, water absorption: 9.6%) that had been heated to 75 ° C. in advance was continuously charged into the rotary drum in a constant amount in the same manner as in Example 1, and carbon was added thereto. Mixed resin containing 40% by weight of black (particle size 50 μm) (molecular weight 140
0, 25.5 wt% polyethylene resin with a softening point of 83 ° C and a softening point of 11
25.5% by weight of atactic polypropylene resin at 0 ° C and 930,000 by weight of high molecular weight polyethylene resin having a molecular weight of 330,000 and a softening point of 86 ° C) are made into a liquid mist by heating and continuously supplied to the lamp at a ratio of 2% by weight. Meanwhile, the inner wall of the drum was heated to 180 ° C and rotated. Carburized iron was obtained by the overflow method, and the drop strength of the obtained carburized iron was evaluated. Table 2 shows the results.

Comparative Example 6 The drop strength of uncoated lamp iron ore was observed. Table 2 shows the results.

Advantageous Effects of Invention The carburized iron of the present invention has a surface coated with a resin, and therefore the porous iron is difficult to be finely pulverized during transportation, and is carburized. It can be adjusted to an appropriate carbon content by blending with other low iron. Further, since the carburized iron itself has a considerable specific gravity, even if it is put into the molten iron, it is easily mixed uniformly and does not disappear on the surface of the molten iron, so that it can be effectively used. Further, when the spray method is adopted, the resin is hardly absorbed inside the porous iron, and the porous iron can be coated with a small amount of resin.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a reduced iron pellet continuous production apparatus of the present invention, FIG. 2 is a left side view of the apparatus shown in FIG. 1 (feeding port for reduced iron pellets), and FIG. FIG. 4 shows a right side view (a discharge port for reduced iron pellets). (1) rotary drum, (2) motor, (3) rotary support, (4) blade, (5) supply port, (6) discharge port, (7) reduced iron pellet continuous supply device, (8) heated spray Equipment, (9) Drum heater.

Claims (17)

[Claims] 1. A carburized iron having a porous iron surface coated with a thermoplastic resin containing a carbon source. 2. The carburized iron according to claim 1, wherein the carbon source is coal powder, carbon black or coke powder. 3. The carburized iron according to claim 1, wherein the thermoplastic resin is a polyolefin resin. 4. The carburized iron according to claim 1, wherein the carbon content in the coating component is 30% by weight or less. 5. The carburized iron according to claim 1, wherein the porous iron is reduced iron pellets or lamp iron ore. 6. A method for producing carburized iron, characterized in that a thermoplastic resin containing a carbon source is melt-sprayed onto a porous iron surface kept at a temperature lower than about 10 ° C. lower than the softening temperature of the thermoplastic resin. . 7. The method for producing carburized iron according to claim 6, wherein the carbon source is coal powder, carbon black or coke powder. 8. The method according to claim 6, wherein the particle size of the carbon source is 100 μm or less. 9. The method according to claim 6, wherein the thermoplastic resin is a polyolefin resin. 10. The method according to claim 6, wherein the carbon content in the coating component is 30% by weight or less. 11. The method according to claim 6, wherein the porous iron is reduced iron pellets or lamp iron ore. 12. A method for producing carburized iron, wherein porous iron is impregnated in a thermoplastic resin liquid containing a carbon source to form a carbon-containing coating on the iron surface. 13. The method according to claim 12, wherein the carbon source is coal powder, carbon black or coke powder. 14. The method according to claim 12, wherein the particle size of the carbon source is 1 mm or less. 15. The method according to claim 12, wherein the thermoplastic resin is a polyolefin resin. 16. The method according to claim 12, wherein the carbon content in the coating component is 30% by weight or less. 17. The method according to claim 12, wherein the porous iron is reduced iron pellets or lamp iron ore.