JP2686499B2 - Manufacturing method of iron-based ceramic materials - Google Patents

Description

The present invention relates to a method for producing a ceramic material that can be used as a refractory or the like.

[Prior Art] As a ceramic material having heat resistance and abrasion resistance, materials mainly composed of various carbides, borides, and silicides, including oxides such as alumina, are widely used.

[Problems to be Solved by the Invention] Conventional ceramic materials all have excellent heat resistance and abrasion resistance, but generally the raw materials are expensive and the production cost is high. In addition, it has been almost impossible to recycle the conventional ceramics once used.

In order to solve such a problem, the applicant of the present invention has invented a high carbon iron-based ceramic material and has already applied for a patent (Japanese Patent Application No. 63-26195). It is an object of the present invention to increase the strength of this material and make it practically superior.

[Means for Solving the Problems] The method for manufacturing an iron-based ceramic material according to the present invention is mainly composed of iron, and contains 4.3% or more and 6.7% or less of carbon as an essential component and 4.5% or more and 25% or less by weight ratio. Chrome and 4% or more 1
It contains 0% or less vanadium. Cerium in the melt,
It is characterized in that it is cast after adding one or more of the group of graphite spheroidizing agents consisting of misch metal, calcium and calcium silicon.

Conventionally, iron-carbon alloys were industrially used only for carbon contents of 4.3% or less, and those with more carbon than this were not used. Further, in an iron-carbon alloy, it is extremely difficult to increase the carbon content to 4% or more without crystallizing a large amount of graphite, and it was almost impossible industrially.

Kawano, who is one of the inventors of the present invention, paid attention to the high carbon region which has not been industrially used in the past, and as a result of various researches, practically excellent in heat resistance and wear resistance in these high carbon regions. As mentioned above, the inventors have applied for a patent as described above. However, the present invention further improves the strength by spheroidizing the graphite crystallized in the iron-based ceramic material in the high carbon region. . Hereinafter, this will be described in detail.

First, a method of increasing the amount of bound carbon without crystallizing a large amount of graphite in an iron-carbon system is problematic. This problem is caused by an appropriate cementite stabilizing element such as chromium (C
It was found that the addition of r) solved the problem. The reason for this is that chromium thermodynamically lowers the activity of carbon (C), and thus it is considered that even if the amount of carbon increases, it is difficult to crystallize as graphite.

As described above, the ceramic material according to the present invention contains iron as a main component, and carbon, chromium, and vanadium as essential components, and other elements are added to this, depending on the application. In the above carbon amount range, that is, in the carbon amount of 4.3% (% by weight, the same applies hereinafter) to 6.7%, the amount of cementite increases as the amount of carbon increases. On the contrary, the smaller the carbon content, the larger the amount of ledeburite. In the iron-carbon system, theoretically, when the carbon content is 4.3%, all of them are ledeburite. At 6.7%, everything becomes cementite. When the carbon content is 5.5%, the ratio between the cementite content and the redeburite content is about 50:50 in terms of both weight ratio and volume ratio. The more preferable range of the amount of carbon is 4.8 to 5.8%. Within this range, a mixed structure of cementite and ledeburite or a mixed structure of ledeburite and two phases is mainly formed.

If the crystallized amount of graphite is 1.0% or less, it is practically acceptable.
It is particularly preferable that the content be ˜0.6%. Note that the amount of graphite may be slightly larger than this depending on the application. In addition, since it is necessary to make the crystallized graphite spherical, for strength development,
Prior to pouring, the graphite spheroidizing agent described below is added.

As an additive other than the above-mentioned carbon, chromium and vanadium, in addition to the spheroidizing agent, other elements such as molybdenum (Mo), tungsten (W), manganese (Mn), boron (B) as necessary as described above. 1 type or 2 types or more of these can be added. All of these are cementite stabilizing elements, and not only prevent carbon from crystallizing as graphite, but also improve hardness and strength.

Chromium (Cr), which is an essential element, is an element that dissolves in cementite up to about 90%, and is an element that is particularly effective in forming cementite. If the amount is small, not only is it difficult to form cementite, but also the stability of the obtained ceramics at high temperatures is deteriorated. Conversely, if the added amount of chromium is too large, the product becomes brittle and the raw material cost increases. The preferable amount of chromium added is 0.1 to 40%, more preferably 0.1 to 25%, and particularly preferably 7 ± 2%.

Molybdenum (Mo) is an element that is difficult to dissolve in cementite because it forms MoC at high temperature in advance, and tends to crystallize at the interface between primary crystallite and reedebrite.
When added alone, it is not much different from the case where chromium is added alone, but when added together with chromium, it increases the hardness at room temperature and high temperatures of 1000 ° C or less, and significantly increases wear resistance and high temperature strength. It is considered that addition of a large amount of molybdenum is not preferable for plastic working at high temperature (for example, 1100 ° C.) because it increases high temperature strength. The preferable addition amount of molybdenum is 0 to 10%, more preferably 0 to 5.0%, and further preferably 0.1 to 4%. In the above range, when the amount of molybdenum is small, the abrasion resistance, high-temperature strength and corrosion resistance tend to decrease. When the amount is too large, the raw material cost increases and the ligature tends to deteriorate.

Vanadium (V) is an element that dissolves well in cementite, and when used alone, it has almost no difference from that of chromium alone, and in some cases, it tends to crystallize a small amount of graphite. If graphite crystallizes in the product, not only wear resistance and strength decrease, but also the interface between graphite and iron is easily immersed, so that corrosion resistance decreases. Together with chromium, it improves the shape of cementite and promotes acicular or granular crystal formation. The preferred range of vanadium is 4 to 10%, more preferably 7 ± 2%. If the amount of vanadium is small within this range, the wear resistance, corrosion resistance and high temperature strength tend to decrease, and if it is large, the raw material cost increases. Rises. In addition, the ligature tends to be improved when the amount of vanadium is large.

Tungsten (W) alone has almost the same effect as chromium, and cooperates with chromium in a similar tendency to molybdenum. The preferred range of tungsten is 0-10%,
More preferably 0 to 3.0%, further preferably 2 ± 0.5%
Before and after, the smaller the amount, the lower the abrasion resistance, corrosion resistance and high-temperature strength tend to be.
Shows a tendency to degrade ligability.

Manganese (Mn) is an element that dissolves in cementite by about 60%, and when added alone, it shows almost the same tendency as chromium,
Corrosion resistance seems to be inferior to chromium. In cooperation with chromium, it shows the same tendency as molybdenum, vanadium, tungsten, etc., but it is not so remarkable. The preferred amount of manganese added is 0 to 10%, more preferably 0 to 5.0.
%, And more preferably 0 to 1.5%. When the manganese content is low within this range, the tendency is almost similar to that of chromium, but the tendency is not so remarkable as that of chromium. Also,
The more manganese, the more brittle and the corrosion resistance and oxidation resistance tend to deteriorate.

Boron (B) cannot be expected to be effective when added alone, and on the contrary, the product may be too hard.
Together with chrome, it has the effect of refining the cementite crystals and improving the durability. The same applies to the case where not only chromium but also chromium and molybdenum and chromium and vanadium are added together. The preferred addition amount of boron is 0
~ 1.0%, more preferably 0-0.5%, even more preferably
It is 0.1 ± 0.05%, and if it is too small, the grain refining effect is insufficient, and if it is too large, it becomes extremely brittle.

Depending on the case, 0.1% or less of Te or Bi can be used as an element for refining or preventing crystallization of graphite. Further, in addition to these additional elements, other elements that do not inhibit the stabilization of cementite, such as rhenium (Re), niobium (Nb), tantalum (Ta), and technetium (Tc) may be added. Further, other elements may be contained as long as they do not hinder practical use, and impurities that are unavoidably mixed and small amounts of graphite as described above may be present. To prevent casting and hot cracking, add phosphorus (P) to 0.3
It is preferable to add ± 0.2%.

Next, regarding the graphite spheroidizing agent, cerium (Ce), misch metal (Mishmetal), calcium (C
It was effective to add one or more of a) and calcium silicon (CaSi) to the molten metal. Misch metal is a naturally occurring cerium and lantern (La)
Is a relatively inexpensive alloy with a cerium content of approximately 40
It is about 90%. Calcium silicon has a calcium content of about 30 to 35%, and the balance is substantially silicon.

The addition amount of these graphite spheroidizing agents is preferably 0.005 to 1.0% in the case of cerium, and 0.4 to 0.8%.
Was even better. The preferable addition amount of the misch metal is the same as that of the cerium. It is considered that this is because 4-lanthanum (La), which is a rare element similar to cerium, has the same effect as cerium. Cerium occludes hydrogen (H ₂ ), and when it is added to the molten metal, this hydrogen gas is released as bubbles, so it is thought that graphite will crystallize in the bubbles in these bubbles. It was also preferable that the amount of calcium silicon added was 0.6 to 1.2%. In the case of adding calcium alone, an amount corresponding to the calcium content in the calcium silicon may be added. However, it was preferable to add calcium silicon in the form of calcium silicon rather than calcium alone. In order to generate bubbles of calcium in the molten metal, it is more effective to use calcium, which has a high boiling point and is less soluble in molten iron.

As described above, these graphite spheroidizing agents can be added alone or in combination of two or more. Of these, it is more preferable to add a combination of one containing cerium and one containing calcium, and among them, the combination of misch metal and calcium silicon was most effective.

These graphite spheroidizing agents are, for example, wrapped in a granular form and wrapped in paper, and rapidly added to the molten metal at 1700 ° C. or higher by a phosphorizer. At this time, the added spheroidizing agent evaporates,
It is preferred to cast quickly. A small amount of spheroidized graphite crystallizes in the obtained iron-based ceramic material, but a thin layer of Fe is formed around the spheroidized graphite. It is speculated that this will improve.

This iron-based ceramic material is preferably used as a refractory, a mechanical part, a structural material, etc., which is used at a temperature of 1000 ° C. or lower. Further, since it has high hardness at room temperature or high temperature, it can be used as a material for parts and structures having wear resistance.

This iron-based ceramic material can be relatively easily manufactured by a forging method using iron, graphite, and an additional element (or a compound thereof) as raw materials. Since the main raw materials are iron, carbon and chromium, the raw materials are easily available and the raw material cost is low. Further, since it is structurally composed of a compound of iron and carbon, iron can be easily recovered from the used one by a method such as blowing oxygen at a high temperature and can be recycled. There is little risk of pollution in the manufacturing process and recovery process.

[Example] Next, an example of the present invention will be described.

Using the raw materials shown in Table 1, test pieces of various compositions were manufactured by a known forging method. An example of a centrifugal forging device used for trial production is shown in FIG. In this forging device 1, a crucible 4 and a mold 5 are supported by one supporting member 3 provided on a rotary shaft 2 so as to project in the horizontal direction, and a refractory ring 6 is interposed between the two. A coil 7 for high frequency induction heating is wound around the outer periphery of the crucible 4, and the upper opening of the crucible 4 is covered with a quartz dome 8. Argon gas from the outside is supplied into the crucible 4 through the core of the rotary shaft 2. A counterweight 10 is attached to the other support member 9 protruding from the rotating shaft 2. The rotating shaft 2 is rotationally driven by a motor 11, and the raw material melted in the crucible 4 is centrifugally cast. The sample weight is about 40 g.

2 and 3 show examples of molds that can be used. FIG. 2 shows iron and ceramic molds, and FIG. 3 shows copper-chromium alloy centrifugal casting molds. In this embodiment, the mold shown in FIG. 2 was not used. Also in Fig. 3, A is 44 mm, B is 24 mm, C is 10 mm, D is 54 mm, E is 20 mm, F
Was 70 mm and G was 53 mm. A ceramic foam may be used on the upper part of the casting.

The microscopic structure of the obtained test piece is shown in FIG.
The magnification is displayed below each photo. The analysis values of composition are C5.78%, Si0.5%, Cr4.46%, V6.55%, Ni6.97
%, Mo0.98%, P0.3%, B0.1%. In this photo,
The white one is cementite (Fe ₃ C) and the gray one is redebrite. It can be seen that a small amount of spheroidized graphite (black) crystallized in these structures. The diameter of the cementite needle crystal is preferably 50 μm or less, 20
More preferably, it is less than or equal to μm. It is easily inferred that high strength can be obtained by making the crystallizing directions of such needle crystals uniform. In addition, redebrite has a higher limb property than cementite, and the strength is improved by making cementite finer.

Next, the results of examining the relationship between composition and strength are shown in Table 2. This iron-based ceramic material has excellent corrosion resistance. For example, if the iron-based ceramic material contains iron, carbon, and chromium 5 to 7%, the weight loss when immersed in a 1: 1 hydrochloric acid solution at 20 ° C is 96 hours. Was less than 10 mg / cm ² and was comparable to 18-8 stainless steel. Regarding heat resistance, it was possible to use it as a refractory material exposed to a high temperature of about 1000 ° C. The acid resistance (1: 1 hydrochloric acid solution) deteriorates when vanadium is used, but recovers when Ni is added at 6 ± 2%.

[Effects of the Invention] As is clear from the above description, the iron-based ceramic material obtained by the present invention has fire resistance, high hardness, and corrosion resistance sufficient to withstand use at a temperature of 1000 ° C or less, It can be used in a wide range of fields such as refractories and wear-resistant parts. Further, since the strength of the crystallized graphite is improved by making it spherical, it can be used as a constituent material that requires a certain level of strength. Moreover, since this ceramic material is mainly composed of iron, the raw material cost is low and the raw material is easily available. In addition, since both cementite and reedbrite that compose this ceramic material are compounds of iron and carbon,
It is also possible to recycle the used product, and it has high industrial utility value in various respects.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a casting apparatus, FIGS. 2 (a) and 2 (b) are plan views and side cross-sectional views of a used atmosphere melting mold, and FIGS. 3 (a), 3 (b) and 3 (c). ) Is a plan view, a front view, a side view of the centrifugal casting mold, and FIGS. 4 (a), (b), and (c) are micrographs showing the crystal structure. 1 ... Centrifugal casting device, 2 ... Rotating shaft 4 ... Crucible, 5 ... Mold

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Seisuke Sugawara 2-5-28, Mikuraminami, Higashi-Osaka City, Osaka Prefecture (56) References JP-A-60-174846 (JP, A) JP-B 59-29100 (JP) , B2) Japanese Patent Publication Sho 61-43408 (JP, B2)

Claims (1)

(57) [Claims] 1. A main component of iron, which is an essential component in a weight ratio.
Graphite spheroidizing agent consisting of cerium, misch metal, calcium and calcium silicon in a molten metal containing 4.3% to 6.7% carbon, 4.5% to 25% chromium and 4% to 10% vanadium A method for producing an iron-based ceramic material, comprising adding one or more of the above and then casting to obtain a ceramic material having a desired shape.