JPH11181507A - Production of iron base si-mn alloy powder good in pulverizability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a nonmagnetic iron base Si-Mn alloy powder excellent in pulverizability. SOLUTION: An alloy raw material is melted so as to form an iron alloy contg., by weight, 0.40 to 1.20% C, 5.0 to 12.0% Si, 19.0 to 42.0% Mn, and the balance Fe, after solidification, it is cooled in such a manner that the cooling time T (sec) at 1150 to 400 deg.C is regulated to the range of T<=3.41×10<-5> (X-6)<9.21> , and thereafter, it is mechanically pulverized to a prescribed grain size, where X is variables depending on the components, defined as X=Si+2.92C+0.077 Mn. Moreover, the alloy powder is the one satisfying Si<=8.3C+0.14 Mn and relative permeability (μ)<=1.10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an iron-based Si-Mn alloy powder having particularly excellent pulverizability.

[0002]

2. Description of the Related Art Conventionally, ferromanganese, ferrosilicon and silicomanganese, which are mainly used as deoxidation, desulfurization, slag-making and alloying components additives in steel production, are known as J
IS standard (G2301, G2302, G2304-19
86), the alloy components are high [Mn ≧ 73%, (Mn + Si) ≧ 74%, for example]
And the carbon content is extremely high (for example, FMnM
2: C ≦ 2.0%, SiMn0: C ≦ 1.5%). Then, these ferromagnetic irons are to be supplied as alloy powders or granules according to the prescribed particle size for the purpose of use. In other words, these ferromagnetic irons are characterized in that they are supplied in a large amount and in the form of powder and granules, as shown in the production method of lots in JIS. This is realized by the fact that the powder and the granular shape can be easily obtained by cooling after melting due to the high amount of carbon and the amount of carbon.

On the other hand, in recent years, with the diversification of steel products, the necessity of powdered ferromagnetic iron having a smaller amount of alloys such as Si and Mn and a lower carbon content than conventional JIS standards has been increasing. ing. For example, the flux of the flux-cored wire for arc welding applied to welding of structures includes various powder raw materials such as slag forming agents, deoxidizing agents, alloying agents, and iron powder depending on the purpose. Contains several tens% in total of the above powders of ferromanganese, ferrosilicon, silicomanganese, iron powder and the like. The segregation of the components generated from the mixed alloy flux may adversely affect the welding quality at the time of welding the steel material.

[0004] Therefore, there is a strong demand for a method of blending the above several kinds of powdery raw materials to produce in advance a single alloyed iron powder having the same components as the aligned components and using the same in a flux. However, in general, when Si, Mn and C in ferroalloys are reduced, their ductility and toughness are gradually improved, and it is difficult to obtain powdery products with ordinary production equipment. In addition, when component adjustment for improving this is performed, it becomes easy to take on magnetism, and using a flux mixed with magnetized alloy powder, for example, as shown in the proposal of Japanese Patent Publication No. 4-72840, When a flux-cored wire is made by continuously forming a strip, filling with a flux, and seam welding, depending on the manufacturing conditions, segregation of components, poor fusion of the seam, etc. may occur, resulting in a flux-cored wire. May adversely affect the production yield of steel and the welding quality when welding steel.

[0005]

Therefore, in producing iron-based Si-Mn alloy iron containing a large amount of iron as described above, in order to mass-produce the powder, it is possible to easily pulverize it in the production process. It is necessary to be. As alloy powders having a high iron content, Fe-Mn alloy powders are described in Japanese Patent Publication No. 4-62838 and Japanese Patent Laid-Open Publication No. Hei 5-31594. In fact, there is no iron-based Si-Mn alloy powder which is an alloy of these types and which can be easily pulverized and mass-produced. In addition, the fact that the alloy powder is non-magnetic can further expand various uses. Therefore, an object of the present invention is to provide a production method capable of easily pulverizing an iron-based Si-Mn alloy, which has conventionally been considered not to be easily pulverized.

The present inventors have mainly clarified the relationship between the cooling rate during solidification and the easiness of pulverization, and
It succeeded in obtaining i-Mn alloy powder. When the structures at various cooling rates were compared, it was found that the growth state of the dendrite was greatly different depending on the cooling rate during solidification, and that the structure having a medium dendrite had good pulverizability. It has been found that the condition that the dendrite becomes medium can be obtained even at the medium cooling speed. Furthermore, high Mn, which has conventionally been considered not to be easily pulverized,
Nonmagnetic iron-based S with composition similar to that of austenitic alloys
It has been clarified that manufacturing conditions with good pulverizability also exist for the i-Mn alloy. In the case of a high cooling rate such as water atomization, a fine dendrite structure develops and can be crushed for the time being, but the dendrite is harder to grind than a medium dendrite, so the scope of the present invention Excluded from.

[0007]

The gist of the invention is as follows: (1) C: 0.40 to 1.20% by weight, Si:
The alloy raw material is melted and solidified to form an iron alloy containing 5.0 to 12.0% and Mn: 19.0 to 42.0% with the balance being Fe. When the cooling time T (sec) is T ≦ 3.41 × 10 ⁻⁵ (X−6)
^9. Cooling to a range of ^9.21 , and then mechanically pulverizing to a predetermined particle size.
Method for producing i-Mn alloy powder. Where X = Si + 2.9
Component dependent variable obtained at 2C + 0.077Mn.

(2) C: 0.40 to 1.20 by weight%
%, Si: 5.0 to 12.0%, Mn: 19.0 to 4
2.0%, with the balance being Fe and Si ≦ 8.
The alloy material is melted so that the iron alloy satisfies 3C + 0.14Mn and the relative magnetic permeability (μ) ≦ 1.10. After solidification, a cooling time T (sec) from 1150 ° C. to 400 ° C.
c) is cooled so that T ≦ 3.41 × 10 ⁻⁵ (X−6) ^9.21 , and then mechanically pulverized to a predetermined particle size. -Method for producing Mn alloy powder. Where X = Si + 2.92C + 0.0
Component dependent variable obtained at 77Mn.

(3) By weight%, P: 0.10 to 0.40
(1) or (2) above,
A method for producing an excellent iron-based Si-Mn alloy powder according to the above description. (4) The method for producing an iron-based Si-Mn alloy powder according to the above (1) to (3), wherein the particle diameter is 212 μm or less.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The present inventors conducted melting experiments by changing the composition and cooling time of the iron-based Si-Mn alloy in various ways. Melting was performed in a high-frequency furnace, and an alumina crucible (dissolution amount 2 kg) was used. After melting, the temperature was adjusted to a start temperature of 1500 ° C. by adjusting the load of the high-frequency furnace, and then cooled by six methods. FIG. 1 conceptually shows a cooling method and a cooling curve thereof. The solidification temperature of the iron-based Si-Mn alloy used for the experiment was approximately 1200 to 1350 ° C.
Was in the range. Incidentally, generally cooling rate is estimated to liquid quenching method ^{1 × 10 5 ~10 6 ℃ /} sec atomizing ^{5 × 10 3 ~10 5 ℃ /} sec Other casting 5 × 10 ³ ℃ / sec extent less .

The curve in FIG. 1 shows a liquid quenching process in which a melt is melted in a tundish type crucible having a slit at the bottom, and molten metal is dropped on the roll surface of an amorphous ribbon forming apparatus having a high-speed rotating roll. Although the ribbon made by this method is very easily pulverized, the cost of a modified tundish, roll equipment and the like is high, and the productivity is low. The curves are water atomized. The molten metal dissolved in the high frequency furnace was dropped into a water flow having a weight ratio of metal to water of 1:50. The resulting metal particles were used as a pulverization test and a resin-filled sample after draining and drying, and the microstructure of the cross section of the slab was observed under a microscope. The photograph shown in the circle in the figure is an example of the composition of Fe-0.6C-8Si-31Mn. A micrograph in the left circle shows a fine structure, and it was found that the pulverizability was poor.

The curve is obtained by casting a molten metal melted in a high-frequency furnace on a horizontal iron mold whose back surface has a water cooling jacket. The pulverizability of the slab was as good as the following curve. The curve is a mold in which a molten metal melted by a high-frequency furnace is cast into a non-water-cooled mold, while a large amount of water spray is applied when the molten metal surface solidifies in the mold. Air cooled inside. The micrograph at the center in the figure shows a structure where the dendrite has grown to a medium size and then the matrix has solidified without phase separation. When non-water cooled and the mold ratio is small or cooled in the furnace as it is, crushing is difficult because the component segregation between the dendrite and the matrix is leveled as shown in the micrograph in the right circle in the figure It turned out to be. This boundary is located between the curves, which is inferred from the fact that the dendrite area ratio of the curve tends to be smaller than that of the curve.

The method of determining the friability is the same as in the embodiment described later. 100 g of the slab is crushed by a disk-type ring mill (amplitude: 100 mm, frequency: 1,
800 times / min) and pulverized for 60 seconds to obtain a particle size of 212.
A case where the value of μm or less was 50% or more was judged to be good. In addition,
FIG. 1 is a conceptual diagram, but FIG. 2 shows a measured value in a case where a thermocouple is set in a mold in a case of water cooling after casting a mold in the case of a curve. The present inventors have repeatedly performed melting experiments of iron-based Si-Mn alloys having various compositions changed in the above cooling methods. As a result, iron-based Si-
It has been found that the grindability of a Mn alloy can be greatly improved by selecting an appropriate cooling rate depending on its composition.

The reasons for limiting the cooling rate, which is the basis of the present invention, will be described below. Dissolve iron-based Si-Mn alloy,
The Vickers hardness (Hv) of the solidified slab is approximately 55
When it is 0 or more, the pulverizability becomes good even in ordinary mechanical pulverization. At this time, it was found from many experimental results that the measured value of the Vickers hardness (Hv) was very close to the calculated value of Hv obtained by the following equation (1). Hv = 380C + 130Si + 10Mn + [P] -1076 (1) where [P] = 0 (P <0.10%), [P] = 80
(P ≧ 0.10%).

However, even with an iron-based Si—Mn alloy having a composition in which the value of Hv calculated by the equation (1) is 550 or more, the pulverizability deteriorates depending on the cooling rate, and conversely, H
Good pulverizability was sometimes obtained with a composition in which the calculated value of v was less than 550. The present inventors have paid attention to the behavior of such an iron-based Si-Mn alloy with respect to grindability. Therefore, first, a component-dependent variable X that entirely represents the composition of the iron-based Si-Mn alloy is defined by the following equation (2). X = Si + 2.92C + 0.077Mn (2) In the equation (2), the value of X is correlated with the value of Hv in the above equation (1), and the coefficient ratio between the components is Hv in the equation (1). Equal to the contribution of

In FIG. 3, the vertical axis represents X = Si + 2.92C + 0.
077Mn, the horizontal axis shows the descent time (sec) from the start of cooling of the molten metal to 400 ° C. when various cooling rates were changed. In FIG. 3, the dashed line is a line indicating X = 11.89, and this value indicates that the value of Hv according to equation (1) is 550 (where P ≧
0.10%), which is a standard for obtaining good pulverizability. However, as shown in FIG. 3, even with a composition in which the value of X is less than 11.89, if the cooling rate is high, there is a good pulverization area, and X ≒
If the cooling rate is low even in the vicinity of 11.89, it can be seen that there is a pulverization defective area.

Accordingly, a boundary line shown by a solid line is drawn between the good pulverization area and the poor pulverization area in FIG. 3, and this is read assuming that it is a power equation. Limited time. T ≦ 3.41 × 10 ⁻⁵ (X−6) ^9.21 (3) Equation (3) is obtained based on the temperature drop time from solidification to 1150 ° C. to 400 ° C. But,
It was confirmed that the cooling rate at a temperature lower than 400 ° C. hardly affected the pulverizability.

Next, the reasons for the regulation of the components will be described from the viewpoint of pulverizability and demagnetization. The relationship between the cooling rate (T), which has an important effect on the pulverizability, and the chemical components was determined by a series of experiments, and could be expressed by the equation (3). C, Si, Mn and P for obtaining an iron-based Si-Mn alloy having good pulverizability
Is determined by the formula (3), which is limited in terms of the composition in terms of the content of each component and is limited in terms of the cooling rate as described above.

The reasons for limiting the range of each component from the aspect of composition of the iron-based Si-Mn alloy of the present invention will be described below. C: 0.40 to 1.20% C is a component that improves the pulverizability and effectively acts on demagnetization, and is required to be 0.40% or more. C is 0.
If it is less than 40%, the Vickers hardness (Hv) of the slab is 550.
And pulverization becomes difficult. Regarding the upper limit of C, even if this value exceeds 1.20%, the effect on pulverizability and demagnetization hardly changes. Therefore, the range of C is set to 0.40 to 1.20%.

Si: 5.0 to 12.0% By containing 5.0% or more of Si, pulverizability is remarkably improved, but pulverizability hardly changes even if it exceeds 12%. Further, from the viewpoint of magnetism, Si needs to be controlled by the content of other components as described later, and therefore the upper limit is limited to 12.0%. When the content of Si is less than 5.0%, the pulverizability rapidly deteriorates.

Mn: 19.0-42.0% Since Mn has a small contribution to Vickers hardness (Hv), its grindability is not as strong as that of C or Si. Is required to be 19.0% or more in order to maintain the stable austenite phase. on the other hand,
Si with strong ferrite forming ability to improve pulverizability
Is increased to near the upper limit, Mn needs to be 40% or more. Therefore, the range of Mn is set to 19.0 to 42.0%.

Further, when a small amount of P is added to the ferroalloy of the present invention, it is extremely effective in increasing the hardness (Hv), that is, improving the pulverizability. In summary, based on the examples, when P is added in an amount of 0.10% or more, the Vickers hardness (Hv) increases by about 80 and the pulverizability is improved. However, if added in an excessively large amount, there is a risk of embrittlement of the material of a steel product using the alloy powder of the present invention. Therefore, in the present invention, the range of P is set to 0.10 to 0.40%. As described above, the reasons for limiting the components of C, Si, Mn, and P which affect the pulverizability of the iron-based Si-Mn alloy have been described, but each component is within the above-defined range of the content and the cooling rate. By satisfying the expression (3), good pulverizability can be ensured.

Next, the reason why the relative magnetic permeability (μ) of the iron-based Si—Mn alloy powder is set to 1.10 or less is that the value of 1.10 indicates that the magnetic material has a slight magnetic property. It is a critical value that has a non-magnetic permeability (μ) of 1.10 or less in consideration of, for example, the use when used as a flux raw material in a flux-cored wire for welding, if the non-magnetic permeability (μ) is 1.10 or less. No welding defects occur during seam welding. In terms of the amount of ferrite in the slab measured to obtain a measure of demagnetization, the relative magnetic permeability (μ) becomes 1.10 or less when the amount of ferrite is 1 to 10.
It became clear that it corresponded to 2% or less.

FIG. 4 is a graph showing the relationship between the composition of the cast slab and the magnetism of the iron-based Si-Mn alloy iron. The vertical axis represents the value of the amount of ferrite (α) (%) obtained by measuring the ferromagnetic component contained in the slab by a ferrite meter, and the austenite index (A / F) on the horizontal axis represents the slab as shown in the figure. C, S
This is a value obtained from the contents of i and Mn, and means that the larger the value, the stronger the austenitizing tendency. From this FIG. 4, the austenite index (A
/ F) increases, the amount of ferrite exhibiting magnetism increases.
It can be seen that when the austenite index (A / F) becomes 2.40 to 2.80 even if the variation is considered, the amount of ferrite almost disappears and the material becomes non-magnetic.

Therefore, based on the relationship between the austenite index (A / F) and the amount of ferrite (α) shown in FIG. 4, the austenite index (A / F) was set to 2.40, which is a practically non-magnetic material and has no practical problem. The relational expression between the two cases is obtained by the following expression (4). α = 114−47.4 (A / F) (4) When a non-magnetic condition (α ≦ 0) is added to the equation (4),
Equation (4) becomes the following equation (5) and regulates the composition of the iron-based Si-Mn alloy. Si ≦ 8.3C + 0.14Mn (5)

In the present invention, along with the regulation of the relative magnetic permeability, the expression (5) is a requirement for producing a nonmagnetic iron-based Si-Mn alloy powder. Restricting the demagnetization from the aspect of composition was effective in improving the quality of the iron-based Si-Mn alloy and improving the production yield. It should be noted that, with respect to the iron-based Si—Mn alloy having the composition regulated by the formula (5), if the alloy is manufactured with the cooling rate regulated by the above-described formula (3), sufficiently good grindability can be obtained. It was confirmed that substantial non-magnetism was obtained even after the test.

As described above, according to the present invention, by controlling the composition and selecting a cooling rate suitable for the composition, it is possible to produce a nonmagnetic iron-based Si-Mn alloy powder having good crushability. In addition, the applications of these alloy powders are, for example, the productivity (disconnection) and welding workability (particularly arc stability) of a flux-cored wire having a finished wire diameter of 1.2 mm.
Even if it is a fine particle having a particle diameter of 212 μm or less for improving the crushing property, it has a sufficiently crushable property.

[0028]

(Example 1) A raw material blended so as to have predetermined components is melted using a high-frequency induction melting furnace (melting amount 2 kg), cast into a mold, solidified, and then cooled with water to form a slab. Obtained. The slab was roughly pulverized with a hammer, and the pulverizability was evaluated using a ring mill pulverizer having the shape shown in FIG. 5A is a plan view of the ring mill pulverizer taken along the line BB ′ of FIG. 5B, and FIG. 5B is a cross-sectional view of the ring mill pulverizer taken along the line AA ′ of FIG. When the inner ring 2 is inserted into the inner ring 1 and the bottom member 3 is horizontally vibrated under predetermined conditions, the inner ring 2 moves, and the slab inserted between the outer cylinder 1 and the inner ring 2 is formed. Is crushed by impact. The crushability was evaluated by using the above-mentioned ring mill crusher to coarsely pulverize slabs (average size 10 to 10).
After putting about 100 g of a 20 mm lump and applying an impact for 60 seconds at an amplitude of 100 mm and a frequency of 1800 times / minute, the particle size becomes 2
When the ratio of 12 μm or less is 90% or more, the evaluation symbol ◎ (very good), when it is 50% or more, ○ (good), 50%
When the value was less than △, it was marked with a mark (insufficient). Table 1 shows the test results.
No. 1 was a comparative example, and Nos. 2 to 5 were examples of the present invention, in which good crushability was obtained.

[0029]

[Table 1]

(Example 2) A small high-frequency induction melting furnace (melting amount 2 kg) and a large high-frequency induction heating furnace (melting amount 250 k
Table 2 shows the results of mass dissolution using g). The cooling rate was varied depending on the size of the casting mold, small size, water cooling, air cooling, furnace cooling, casting thickness, and the like. No1 ~ 11 and No17
Nos. To 19 show that the non-magnetic iron-based Si-Mn alloy has good pulverizability and can be produced in the examples of the present invention.
Nos. 3 and 5 are examples of the present invention. It was also confirmed that the large amount dissolution shown in Nos. 17 to 19 coincided with the small amount dissolution result. In contrast,
Nos. 12 to 16 are comparative examples, each of which does not satisfy the expression (3) representing the cooling rate limited by the present invention, and thus has poor pulverizability. The method for evaluating the grindability was the same as that in the above-described example, and the relative magnetic permeability (μ) of the alloy powder was measured using a vibrating sample magnetometer.

[0031]

[Table 2]

[0032]

As described above, according to the present invention, it is possible to produce a large amount of substantially non-magnetic iron-based Si-Mn alloy powder having a high iron content in a production process with extremely good pulverizability. It has become possible.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram for explaining a cooling curve and a structure of an alloy at that time in a melting experiment according to the present invention;

FIG. 2 is a diagram showing an example of a cooling curve of the present invention up to 400 ° C.

FIG. 3 is a diagram showing the relationship between the composition of iron-based SiMn alloy, cooling rate, and grindability,

FIG. 4 is a diagram showing the relationship between the chemical composition of the slab and the magnetism in the Si—Mn alloy iron including the present invention.

FIG. 5 is a schematic view showing a ring mill pulverizer used for pulverizability evaluation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Outer cylinder 2 Inner ring 3 Bottom member 4 Top lid 5 Cast piece

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C22C 38/04 C22C 38/04 // C22C 33/04 33/04 A (72) Inventor Shizuo Kawaguchi 1-Yoshihisa, Takaoka-shi, Toyama 1-1 Nippon Heavy Chemical Industry Co., Ltd. Takaoka Plant (72) Inventor Toshishi Kikuchi 8-4 Nihonbashi Koamicho, Chuo-ku, Tokyo Nippon Heavy Industries Co., Ltd. (72) Inventor Koichi Aoki 3-chome Tsukiji, Chuo-ku, Tokyo 5-4 Inside Nippon Steel Welding Industry Co., Ltd. (72) Inventor Masao Kamata 3-4-4 Tsukiji, Chuo-ku, Tokyo Inside Nippon Steel Welding Industry Co., Ltd.

Claims (4)

[Claims] 1. An iron alloy containing 0.40 to 1.20% by weight of C, 5.0 to 12.0% of Si, 19.0 to 42.0% of Mn, and the balance Fe After melting and solidifying the alloy raw material, the cooling time T (sec) from 1150 ° C. to 400 ° C. is T ≦ 3.41 × 10 ⁻⁵ (X-6) ^9.21
, And then mechanically pulverized to a predetermined particle size.
Method for producing Mn alloy powder. Where X = Si + 2.92C
+ Component dependent variable obtained at 0.077 Mn. 2. The composition according to claim 1, comprising 0.40 to 1.20% of C, 5.0 to 12.0% of Si, and 19.0 to 42.0% of Mn, with the balance being Fe. , Si ≦ 8.3C + 0.14M
After melting and solidifying the alloy raw material so as to obtain an iron alloy satisfying n and the relative magnetic permeability (μ) ≦ 1.10, the cooling time T (sec) from 1150 ° C. to 400 ° C. is T ≦ 3. 4
Cooled so that 1 × 10 ^-5 range (X-6) ^9.21,
Thereafter, a method for producing an iron-based Si-Mn alloy powder having good pulverizability, comprising mechanically pulverizing to a predetermined particle size. Here, X is a component-dependent variable obtained by Si + 2.92C + 0.077Mn. 3. The method for producing an iron-based Si—Mn alloy having good pulverizability according to claim 1, wherein the content of P is 0.10 to 0.40% by weight. 4. The method for producing an iron-based Si—Mn alloy powder according to claim 1, wherein the particle size is 212 μm or less.