JPH07331378A - Production of iron-chromium-aluminum sintered alloy - Google Patents

Abstract

PURPOSE:To produce a heat resistant material improved in the plastic working of a steel ingot by HIP forming of an Fe-Cr-Al alloy powder and capable of being forged without causing cracking. CONSTITUTION:A molten Fe-Cr-Al alloy is powdered by a gas atomizing method or a water atomizing method. The resulting powder is formed into a steel ingot by HIP forming or CIP forming. This steel ingot is red heated and then continuously forged by stages in a longitudinal direction by using a segmental die divided into three or more pieces in a diameter direction and having an angle of inclination in an axial direction. Then, hot rolling is done.

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 a Fe--Cr--Al sintered alloy, more specifically, a heater material,
The present invention relates to a method for producing a Fe—Cr—Al-based sintered alloy suitable for use in high temperature regions such as inner members of various industrial furnaces and heat resistant materials.

[0002]

2. Description of the Related Art Household appliances, which have been proposed so far,
A method for producing a Fe—Cr—Al based sintered alloy suitable for a high electric resistance material and a heat resistant material useful for a heating element of an industrial furnace or a precision resistance wire will be described with reference to FIG.

That is, in FIG. 5, an Fe-Cr-Al-based alloy is melted in the atmosphere or vacuum-melted, and an alloy powder is prepared by an atomizing method of an inert gas such as argon or a water atomizing method, followed by HIP molding. Hot extrusion or two-sided forging with two dies is performed with the mild steel layer attached to the outside, and hot rolling is performed to obtain a product. Then, as a result of conducting examinations on these two methods, it was found that the industrially effective forging method, step B in FIG. 5, has a problem as described below.

Generally, Fe-Cr-Al powder is HIPed.
Although a steel ingot is created by a molding method, Al oxynitride is present in a film form on the surface of the powder used,
Therefore, it hinders the true bonding (metal bonding) of the powders. Therefore, when the steel ingot produced by the HIP forming method is forged or rolled in the next step, the HIP steel ingot is often cracked and a sound product (billet) cannot be produced. Was.

Further, in the forging after the HIP molding in the prior art, as shown in FIG. 6, a billet M is installed between two molds 3 and 3 and the billet M is moved by the vertical movement of the upper mold 3.
When the forging is performed, tensile stress is generated in the central portion of the billet M and cracks 4 occur (this forging is called two-sided forging). Further, as shown in FIG. In the forging used, there is a problem that cracks 4 occur in the billet M between the dies 5 and 5.

In order to solve this problem, the techniques described below have been proposed. First, JP-A-62-280348
Japanese Patent Laid-Open Publication No. 2003-242242 discloses a method for manufacturing a Fe-Cr-Al alloy sintered body, in which Cr is 20 to 35 wt% and Al is 5 to 12 wt%.
Fe-Cr-Al alloy powder containing 0.02 wt% or less of oxygen and 0.03 wt% or less of nitrogen was produced by a vacuum melting / gas atomization method, and the Fe-Cr-Al alloy powder was filled and sealed in a metal container. Then, hot isostatic press molding is performed, and Fe-Cr-A having a specific resistance of 150 μΩ · cm or more is formed.
A method for producing an 1-based alloy sintered body has been proposed. After hot isostatic pressing, hot working is performed to remove the coated metal container.

[0007] Next, Japanese Patent Application Laid-Open No. 04-308064 discloses a high electric resistance material and a method for manufacturing the same.
-Cr-Al-based alloy, Cr 15 to 30 wt%,
Al5-30wt%, Ca + Mg 1.0wt% or less, F
e A high electric resistance material in the remaining range. Also, this Fe
-Cr-Al system alloy is Cr20-35wt%, Al5
~ 12 wt%, Si 2 wt% or less, Mn 1 wt% or less,
Ti can be 0.1 to 1 wt%, oxygen can be 0.02 wt% or less, nitrogen can be 0.03 wt% or less, and the balance can be Fe.

The manufacturing method is a method in which a container is filled with the alloy powder having the above-mentioned contained components and component ratios, and the powder in the container is hot compression molded. Then, by including Ca + Mg in a total amount of 1.0 wt% or less, the plastic workability of the steel ingot by HIP forming is improved, and forging can be performed without the occurrence of cracks.

Further, Japanese Patent Application Laid-Open No. 04-308065 proposes a high electric resistance material and a method for producing the same, that is, a Fe-Cr-Al alloy, Cr1.
5-30 wt%, Al 5-30 wt%, rare earth element 1.
It is a high electric resistance material in the range of 0 wt% or less and the balance of Fe, and is a manufacturing method in which a container is filled with an alloy powder having this composition, and the powder in the container is hot compression molded. And
By containing the rare earth element in an amount of 1.0 wt% or less,
The plastic workability of the steel ingot by HIP forming is improved, cracks do not occur, and forging can be performed.

The technique disclosed in Japanese Patent Laid-Open No. 280348/1987 is not more than 0.02 wt% oxygen and 0.03 wt% nitrogen.
By restricting the following, JP-A-04-308
The technology of Japanese Patent No. 064 is such that Ca + Mg is 1.0 wt% or less, oxygen is 0.02 wt% or less, and nitrogen is 0.03 wt%.
Furthermore, by limiting to the following, JP-A-04-30
In the technique of Japanese Patent No. 8065, by limiting the rare earth element to 1.0 wt% or less, the plastic workability of the steel ingot by the HIP forming of the Fe-Cr-Al alloy powder is improved, the cracking does not occur, and the forging is performed. Processing can be performed.

However, although the composition of the Fe--Cr--Al alloy in the above-mentioned technique gives good results in terms of hot workability, it does not necessarily satisfy the target product characteristics. It was not possible to obtain such an effect.

Therefore, the method for producing the Fe--Cr--Al powder alloy excellent in creep resistance and oxidation resistance and the Fe--Cr--Al powder alloy previously proposed by the applicant include:
It is not possible to apply the above-mentioned conventional technique, and therefore, Fe is produced by an extrusion method which is technically limited in manufacturing.
A -Cr-Al-based powder alloy was manufactured. Hereinafter, the method for producing the Fe-Cr-Al-based powder alloy previously proposed by the applicant will be described.

First, Japanese Unexamined Patent Publication No. 05-043976 discloses a technique relating to a method for producing a Fe-Cr-Al powder alloy, which comprises 20 to 35 wt% of Cr and 4 to 12 wt% of Al.
A method of pulverizing a molten Fe-Cr-Al alloy containing Al by a gas atomizing method, preforming this alloy powder, and performing hot extrusion with an extrusion ratio of 2 or more without preforming, and then performing the forming. In this alloy powder, oxygen is controlled to be 0.10 wt% or less, nitrogen is controlled to 0.05 to 0.20 wt%, and one of Nb or Ti and Y, H are added.
One or more of f, Sc, and a rare earth element may be contained in a total amount of 1 wt% or less. And the manufactured material has improved toughness, and the hot workability becomes remarkably good,
Furthermore, it has good creep resistance and oxidation resistance.

Next, Japanese Patent Laid-Open No. 05-098401 relates to a Fe-Cr-Al powder alloy, which is manufactured by a hot extrusion method, and contains 20 to 35 wt% of Cr, A
14 to 12 wt%, oxygen 0.10 wt% or less, nitrogen 0.0
Fe-Cr-Al-based powder alloy containing 5 to 0.20 wt% and the balance unavoidable impurities and Fe, Y,
1w of 1 or more selected from Hf, Sc and rare earth elements
t% or less, or 0.001 wt% or more, solid solubility limit (0.0
1 wt%) or less, and at least one selected from Zr, Nb, and Ti can be contained. And Fe
The -Cr-Al powder alloy is extremely excellent in creep resistance and oxidation resistance.

[0015]

DISCLOSURE OF THE INVENTION The present invention solves various problems of the above-described conventional method for producing an Fe-Cr-Al-based powder alloy or a sintered alloy, and the applicant first In order to solve the problems in the method for producing a Fe-Cr-Al-based powder alloy having a composition to which the proposed conventional technique cannot be applied, the present inventor conducted extensive research and conducted extensive studies, and as a result, it was found that by atmospheric melting or vacuum melting Fe-Cr-A that can be performed without cracking when a steel ingot produced by HIP forming an alloy powder obtained by gas atomizing a molten metal and water atomizing the molten metal is forged
We have developed a manufacturing method for l-sintered alloys.

[0016]

Fe-Cr according to the present invention
The manufacturing method of the —Al-based sintered alloy is as follows: After powdering the molten Fe—Cr—Al alloy by the gas atomizing method or the water atomizing method, the powder is made into a steel ingot by HIP molding or CIP molding. After soaking, it has an angle of inclination in the axial direction, and the cross-sectional area becomes smaller as the steel ingot advances. The first invention is a method for producing a Fe—Cr—Al based sintered alloy, which is characterized by performing hot rolling after performing forging, and a Fe—Cr—Al based molten alloy is gas atomized or water atomized. After pulverizing by, the powder is sealed in a container and then heated, and the powder-sealed container has an inclination angle in the axial direction and has a cross-sectional area that decreases as the container advances. Use a mold to connect in the longitudinal direction. Manner, and, after a stepwise forging, Fe-Cr-Al which is characterized in that the hot rolling
The present invention comprises two inventions, the second invention being a method for producing a sintered sintered alloy.

The method for producing the Fe-Cr-Al sintered alloy according to the present invention will be described in detail below.

Note that Fe that can be used in the method for producing a Fe--Cr--Al system sintered alloy according to the present invention.
As the -Cr-Al alloy, Cr 20 to 35 wt%,
Al 4-12 wt%, oxygen 0.10 wt% or less, nitrogen 0.
An alloy containing 0.5 to 0.20 wt% and the balance being unavoidable impurities and Fe is preferable, and this alloy contains at least one selected from Y, Hf, Sc, and rare earth elements. 1 wt% or less, or 0.001 wt%
Above, solid solubility limit (0.1wt%,) below, Zr, N
One or more selected from b and Ti can be contained.

As shown in FIG. 3 (step C), the manufacturing method of the Fe-Cr-Al based sintered alloy according to the present invention is as follows. Melting temperature of alloy 1600 by atmospheric melting or vacuum melting
Molten steel obtained by melting at ~ 1650 ° C
30 to 50 after being flowed down from the tundish nozzle diameter
An alloy powder is produced by gas atomizing with nitrogen gas of kg / cm ² .

This powdered alloy powder is used to make a metal container,
For example, it was filled in a mild steel container, vacuum heated and deaerated, and then sealed. Then, HIP molding (temperature: 1100 to 1200
C, pressure: 700 to 2000 kg / cm ² , time: 3 to
7 hours, preferable condition is 1000 ° C. × 1000
kg / cm ² × 3 hours. ) [Or CIP molding (pressure: 3000 to 10000 kg / cm ₂ , time: 10
20 minutes, preferably 5000 kg / cm ²
× 10 minutes. )] Was carried out to produce a forging billet M.

This billet M is soaked (heating temperature: 110).
0-1200 degreeC, for example, 1150 degreeC. ) And then a plurality of dies, for example, four split dies 1 as shown in FIG.
Thus, the outer wall of the billet M is subjected to pressure forging in a stepwise manner continuously from the entire circumferential direction to the longitudinal direction at the same time (in this way, 3
The method of pressure forging the material from the entire circumference with more than one die is called multi-face forging. Multifaceted forging conditions in this case: 3 to 4 split molds, mold angle 5 to 20 degrees, preferably 5 to 1
It is 5 degrees. ). For example, as shown in FIGS. 1 and 2, it has an inclination angle in the axial direction, for example, an angle of 15 °, and the cross-sectional area decreases as the steel ingot advances.
The outer wall of the billet M is continuously and stepwise pressure-forged in the longitudinal direction by the individual split molds 2, 2. Then, the mild steel adhering to the outer peripheral portion of the obtained multifaceted forged body is removed to produce a billet for rolling, and thereafter, the heating temperature is 1000 to 12.
Hot rolling is performed at 00 ° C to obtain a product.

Next, in the method for producing a Fe-Cr-Al system sintered alloy according to the present invention, as shown in FIG. 3 (step E), first, Fe-Cr adjusted to a predetermined contained component and component ratio. −
A molten metal obtained by melting an Al-based alloy by atmospheric melting or vacuum melting is pulverized by gas atomization or water atomization to obtain an alloy powder.

This alloy powder was filled in a metal container (made of mild steel), vacuum heated and deaerated, and then sealed. Next, the alloy powder enclosing container is subjected to continuous and stepwise forging in the longitudinal direction by using three or more dies, for example, four divided dies 1 and 1 as shown in FIG. As shown in FIGS. 1 and 2, the filled metal container has an inclination angle in the axial direction,
For example, four split molds 2 and 2 having an angle of 5 to 20 ° and having a smaller cross-sectional area as the container advances.
Thus, the outer wall of the metal container is continuously and stepwise pressure-forged in the longitudinal direction. The billet obtained by cutting and removing the metal container after multi-face forging is heated and hot rolled to obtain a product.

Thus, Fe-Cr-A according to the present invention
Since the production method of the l-sintered alloy does not employ the hot extrusion method of the prior art, the unit weight and diameter after extrusion can be increased, and the production cost is considerably lower than that of the extrusion method. End

[0025]

[Examples] Examples of the method for producing a Fe-Cr-Al sintered alloy according to the present invention will be described together with comparative examples.

[0026]

[Example 1] Table 1 shows Fe-Cr-Al according to the present invention.
The contents and ratios of the Fe-Cr-Al-based alloys used in Examples and Comparative Examples of the method for producing a sintered sintered alloy are shown. In Table 1, No. 1 to No. 4 are comparative examples, and No. 5 to No. 12 are Fe-Cr- according to the present invention.
It is an example of a manufacturing method of an Al-based sintered alloy.

After the Fe-Cr-Al alloys of No. 5 to No. 8 in Table 1 and the ratio of the components are melted by atmospheric melting (vacuum melting is also possible), the molten metal is nitrogen atomizer (Argon atomizer is also possible). Alloy powder was manufactured by. That is, 200 kg of raw materials were charged using a high frequency melting furnace, melted at a temperature of 1650 ° C., dropped from a 5 mmφ tundish nozzle, and nitrogen gas was blown to this molten steel to produce a gas atomized powder.

This alloy powder was used after sieving with a 35-mesh sieve. The oxygen content of this powder is 50-
100 ppm, nitrogen content is 600-800 ppm. Next, this gas atomized powder is treated with an inner diameter of 300φ ×
It was filled in a mild steel container having a length of 2000 mm, deaerated by heating under vacuum, and then sealed. Then, HIP treatment was performed at a temperature of 1100 ° C. and a pressure of 1000 atm to prepare a HIP molded steel ingot having a diameter of 280φ and a length of 1800 mm.

This HIP molded steel ingot was soaked at a temperature of 1150 ° C. according to step C of FIG.
Diameter 14 by 5 sided forging method with 4 split dies at 5 °
A billet of 0φ × 7200 mm in length was produced. next,
After removing the mild steel part on the billet outer periphery, it was heated to a temperature of 1100 ° C. and then hot-rolled, but a sound rolled material without cracks in any billet could be produced.

FIG. 4 shows the relationship between the processing temperature and the drawing, and when the Fe-Cr-Al alloy powder having the same content and ratio of components is used, the Fe-Cr- according to the present invention is used.
In the multifaceted forged material by the split mold according to the manufacturing method of the Al-based sintered alloy, the drawing value is 80% or more at any temperature, and the workability is greatly improved.
It can be seen that the P-molded body has an extremely low aperture value of 20% or less at any temperature.

[0031]

[Comparative Example] Fe-Cr-Al based alloys of No. 1 to No. 4 in Table 1 having the composition and ratio of components were processed by the same method as in Example 1 to obtain HIP of diameter 280φ × length 1800 mm.
A formed steel ingot was produced.

This HIP steel ingot was subjected to the step B shown in FIG.
After heating to a temperature of 1150 ° C., two-sided forging was performed using two dies. As a result of ultrasonic flaw detection, it was found that cracks had occurred in any billet, and the hot rolling of the next step was performed. Could not be done.

[0033]

[Example 2] Ingredients and ingredient ratios in Table 1 No. 9-
The Fe-Cr-Al-based alloy of No. 10 was melted in the air (vacuum melting was also possible), and the resulting melt was pulverized with a nitrogen atomizer (argon atomizer is also available) to prepare an alloy powder. The alloy powder was filled in a mild steel container having an inner diameter of 300φ and a length of 2000 mm, heated and deaerated, and then sealed. (That is, the process of producing the gas atomized powder is the same processing method as in Example 1.)

A mild steel container sealed with this alloy powder is kept at room temperature,
CIP treatment was performed at a pressure of 5000 atm to produce a CIP molded steel ingot. Then, the lump CIP molded steel ingot is soaked to a temperature of 1100 ° C. according to the step D, and then the mold angle is 7 °.
Three-sided forging with three divided dies, and a diameter of 140φ x
A bar material having a length of 7200 mm was used. Next, after heating the surface of the bar material to a temperature of 1100 ° C., hot rolling was performed, but no crack was generated in any of them, and a sound rolled material could be manufactured.

[0035]

[Example 3] Fe-Cr-Al-based alloys of No. 11 to No. 12 in Table 1 having the content and ratio of components were melted by atmospheric melting, and the melt was pulverized by a nitrogen gas atomizer to obtain alloy powder. It was made. The inner diameter of this alloy powder is 300φ
× A 2000 mm long mild steel container was filled, heated and deaerated, and then sealed. (That is, the process of producing the gas atomized powder is the same processing method as in Example 1.)

A mild steel container filled with this alloy powder
After heating to a temperature of 100 ° C, a forging ratio of 4 and a mold angle of 7 °
Four-sided forging was performed by using individual split molds to produce a steel ingot.
Then, a mild steel container was cut and removed from this steel ingot to form a billet. This billet was heated to a temperature of 1150 ° C. and then hot-rolled, but neither cracked,
A sound rolled material could be manufactured.

Table 1 shows F used in Examples of the method for producing the Fe-Cr-Al system sintered alloy according to the present invention in the comparative example.
It shows the contained components and component ratios of the e-Cr-Al alloy, and shows the manufacturing process and the presence or absence of cracks.

[0038]

[Table 1]

[0039]

As described above, Fe according to the present invention
Since the method for producing the —Cr—Al-based sintered alloy has the above-described configuration, a plurality of Fe-Cr—Al-based alloy powders (two are included without using the hot extrusion method as in the conventional technique). No.), for example, by performing multifaceted forging with three or more split dies, there is an excellent effect that cracks are not generated even if hot working is performed at a high temperature. The unit weight and diameter of the billet after multi-face forging can be increased as compared with the extrusion method, and
It is a low-cost and excellent manufacturing method that can be mass-produced industrially.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a split mold used in a method for producing a Fe—Cr—Al based sintered alloy according to the present invention.

FIG. 2 is a vertical cross-sectional view of the mold of FIG. 1 used in the method for producing a Fe—Cr—Al based sintered alloy according to the present invention.

FIG. 3 is a diagram showing various steps in a method for producing a Fe—Cr—Al based sintered alloy according to the present invention.

FIG. 4 is a diagram showing a relationship between a processing temperature and a drawing of a multifaceted forged material and a HIP material.

FIG. 5 is a diagram showing various steps of a conventional Fe—Cr—Al based sintered alloy.

FIG. 6 is a cross-sectional view of a mold used in the related art.

FIG. 7 is a cross-sectional view of another mold used in the related art.

[Explanation of symbols]

 1 ... Split mold 2, 3, 5 ... Mold 4 ... Crack M ... Billet

Claims (2)

[Claims] 1. An Fe-Cr-Al alloy melt is pulverized by a gas atomizing method or a water atomizing method, and then the powder is HIP molded or CIP molded to produce a steel ingot,
This steel ingot has a tilt angle in the axial direction after soaking, and the die is divided into a plurality of parts in the radial direction whose cross-sectional area decreases as the steel ingot advances. A method for producing a Fe-Cr-Al-based sintered alloy, which comprises performing stepwise forging and then hot rolling. 2. A Fe-Cr-Al alloy melt is pulverized by a gas atomizing method or a water atomizing method, and the powder is sealed in a container and then heated to have an inclination angle in the axial direction of the powder-sealed container. Using a die that is divided into multiple parts in the radial direction whose cross-sectional area becomes smaller as the container progresses, continuously and stepwise forging in the longitudinal direction, and then performing hot rolling. A method for producing a Fe-Cr-Al-based sintered alloy, which is characterized.