JP2022185963A - Stainless steel-based alloy which can be mechanically pulverized, and method for manufacturing the same - Google Patents

Abstract

To provide a stainless steel-based alloy which can obtain an excellent product yield by mechanical pulverization without using a molten metal spray method with a poor product yield, in manufacture of stainless steel-based alloy powder.SOLUTION: A stainless steel-based alloy with a thickness of 15 μm or more and 120 μm or less which is manufactured with a single roll molten metal quenching device having a device constitution capable of preparing a stainless steel-based alloy molten metal added with a specific range of boron (B) and quenching and solidifying the alloy molten metal on a cooling roll obtains a fine metallic structure mainly containing α-Fe, and thereby can secure excellent pulverization property with a process yield of 80% or more in metallic powder compressive molding, metallic powder injection molding (MIM), and in pulverization of stainless steel-based alloy powder having a powder diameter optimal for a metallic 3D printer by a mechanical pulverization method such as a pin disc mill and a jet mill.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a stainless steel alloy suitable for producing stainless steel powder applied to powder sintering, metal powder injection molding, and metal 3D printers, and a method for producing the same.

Powder metallurgy technologies such as sintered products using metal powder compression molding (press molding) products, metal powder injection molding (MIM) products, and metal 3D printers are capable of producing complex shapes and high-precision parts in near net shape or net shape. It can be molded, and its high molding precision and economic efficiency have spread and developed widely in the industrial field centered on the automobile industry. Most of them use iron powder as the raw material, but in recent years, the use of alloy powder such as stainless steel and heat-resistant and corrosion-resistant superalloys has also been widely developed. The technical background of these developments is, first of all, the establishment of mass production technology for alloy powder production technology by the molten metal atomization method (atomization method), which has made it possible to mass produce high-quality metal powder for powder metallurgy. Therefore, all stainless steel powders that are mass-produced and sold at present are manufactured by a molten metal atomization method such as water atomization or gas atomization.

Methods for producing metal powders are roughly divided into mechanical methods, chemical methods, and atomization (spraying) methods. Mechanical methods are methods that use physical stress to pulverize metal lumps to obtain fine powder from coarse particles. Recently, in addition to the above methods, a mechanical alloying method has also been researched and developed in which mechanical energy is applied to a mixture of pure metal powders using a ball mill or the like, and the powders are repeatedly pressed and crushed to produce alloy powders. ing. Chemical methods produce powder through chemical reactions such as reduction and electrolysis, and are characterized by the ability to obtain extremely fine particles. Research and development is widely carried out on However, although the chemical method can, in principle, produce pure metal fine powder, it is difficult to produce alloy powder in a single process.

On the other hand, in the molten metal atomization method (atomization method), droplets of the molten alloy are scattered by the kinetic energy of the high-pressure atomizing medium such as gas or liquid and the centrifugal force due to the high-speed rotation of the disk, and the droplets are solidified and powdered. It is a method to mass-produce powder of stable quality, so it has become the mainstream as a metal powder manufacturing technology for powder metallurgy. In addition, the molten metal atomization method is gas atomization, in which the molten alloy is made to flow down from the pouring nozzle arranged at the bottom of the hot water storage container (tundish), and the atomizing medium (water or gas) is sprayed from the spray nozzles arranged around it to powder it. and the centrifugal atomization method, in which molten alloy is poured down onto a disk rotating at high speed and pulverized by centrifugal force.

The water atomization method tends to produce an irregular powder shape with many protrusions, while the gas atomization method and centrifugal atomization method produce a powder shape that is nearly spherical. The particle size of the powder (powder size) is adjusted by adjustment or by adjusting the disk rotation speed, and the powder is classified using a sieve to obtain a metal powder having a desired powder particle size according to the application.

However, in the molten metal atomization method, high-pressure water atomization that can obtain the finest powder (Non-Patent Document 1 “Production of fine stainless steel powder by high-pressure water atomization method and effect on sintered compact”). The average powder particle size of is about 10 μm, the average powder particle size of 30 μm in the water atomizer for general mass production, and the average powder particle size of about 50 μm in the gas atomizer, which is even coarser, and is used in metal powder injection molding (MIM) and In order to meet the requirements for metal 3D printers with a size of several tens of microns or less, the powder obtained by water atomization or gas atomization is sieved, the powder of several tens of microns is overcut, and the metal powder injection molding and metal 3D Since it is used as a metal powder for printers, it is the main reason why the prices of various metal powders such as stainless steel powders are increasing.

In addition, the metal powder obtained by the molten metal atomization method has a normal particle size distribution, but as described above, when overcutting several 10 μm or more, the powder particle size distribution is a normal distribution, which is a distribution without a coarse particle side of the particle size distribution. As a result, close-packing of the powder cannot be achieved, and this leads to a decrease in molding density in metal powder press molding and metal injection molding. Therefore, there is a strong demand for metal powder to improve its yield and particle size distribution.

Since stainless steel has high toughness and is difficult to crush mechanically, the manufacturing method of stainless steel powder is limited to the molten metal spraying method. At present, there is no stainless alloy that can be mechanically pulverized into a powder with an average particle size of 3 μm to 200 μm.

In Patent Document 1, an alloy product that has wear resistance equal to or higher than that of martensitic stainless steel and a Co-based alloy at high temperatures, and high-temperature strength, and that can be manufactured at a lower cost than the Co-based alloy, and a method for producing the same. is disclosed, but the Cr--Fe--Nii alloy powder is claimed to be obtained by an atomizing process.

Patent Document 2 discloses an Fe-based alloy powder that can be used as a cladding material for forming a cladding layer of martensitic stainless steel containing Cr. The method for producing the Fe-based alloy powder is a gas atomization method. Adopted.

In Patent Document 3, by attaching organic nanoparticles to the surface of stainless steel powder having an average particle size of 10 μm or more and 500 μm or less, a powder material having high fluidity and reduced influence due to the presence of organic substances is produced. Although disclosed, the method for producing stainless steel powder is the gas atomization method.

Patent Document 4 discloses a precipitation hardening stainless steel powder for powder metallurgy that can suppress deterioration of properties due to oxidation when subjected to degreasing by an acid degreasing method. It is disclosed that the maximum particle size of the powder is preferably 200 μm or less, and methods for producing the precipitation hardening stainless steel powder for powder metallurgy include a water atomization method, a gas atomization method, and a high-speed rotating water stream atomization method. Although various powdering methods such as the atomization method, the reduction method, the carbonyl method, and the pulverization method are described, the production method is preferably the atomization method, and more preferably the water atomization method or the high-speed rotating water jet atomization method. there is

Patent Document 5 discloses a precipitation hardening stainless steel powder capable of producing a sintered body having high mechanical strength and a method for producing the same. Atomization methods such as a high-speed rotary water jet atomization method, a reduction method, a carbonyl method, a pulverization method, and the like, but the production method is preferably an atomization method, and a water atomization method or a high-speed rotation method. Water atomization is said to be more preferred.

Non-Patent Document 1 introduces the relationship between the spraying conditions of the high-pressure water spraying method and the average particle size of the powder, and the effect on the sintered body.

Non-Patent Document 2 introduces the influence of the shape of a spray nozzle in high-pressure water atomization on metal powder.

Non-Patent Document 3 introduces the conditions for densification by hot die forging using water-atomized powder of typical stainless steel grades and the mechanical properties of the material after forging.

Patent application 2018-67379 Patent application 2018-162021 Patent application 2020-176818 Patent application 2019-36328 Patent application 2020-100714

Production of fine stainless steel powder by high-pressure water spray method and its application to sintered compacts, (Daido Special Steel Co., Ltd. Powder Division) Kiyohide Hayashi, Kiyoshi Suzuki, Takeo Hisada: Electric Steelmaking Vol.58 No.4, 243 pages (1987) Effect of shape of high-pressure water atomizing jet on properties of metal powder, (Daido Special Steel Co., Ltd., Technology Development Laboratory) Koichiro Sekimoto, Teppei Okumura, Chikao Nakagawa: Electric Steelmaking Vol.58 No.4, p.11( 2017) Powder Forging of Stainless Steel, (Mitsubishi Metals Central Research Institute, Ltd.) Kunio Obara, Rokuro Sato: Electric Steelmaking, Vol.48, No.2, p.128 (1977)

Powder metallurgy products such as metal powder compression molding (press molding) using stainless steel alloy powder, metal powder injection molding (MIM), and metal 3D printers can be used to form complex shapes and high-precision parts in near net shape or net shape. Therefore, it is widely applied to various industrial fields such as parts for various automobiles. This causes a steep rise in the price of stainless steel alloy powder, and is an obstacle to the spread of powder metallurgy products using stainless steel alloy powder. Therefore, there is a strong demand from the powder metallurgy industry for a method for producing stainless steel alloy powder with an average particle size of 3 μm to 200 μm that can be arbitrarily applied to various molding methods and with excellent product yield.

Mechanical pulverization methods such as hammer mills, feather mills, pin disk mills, and jet mills are examples of methods for producing metal powder with a high yield of average particle diameters of 3 μm to 200 μm that can be used in various molding methods. , Stainless steel alloys have high toughness, and the mechanical pulverization method described above has a limit of an average particle size of about 100 μm at most.
It is not possible to produce stainless steel alloy powder with an average particle size of 3 μm to 70 μm, which can be used for molding methods that are expected to become more widespread in the future, such as MIM and metal 3D printers.

Therefore, the present invention uses mechanical grinding methods such as hammer mills, feather mills, pin disc mills, and jet mills to achieve a product yield of 80% or more, while ensuring a product yield of 80% or more. It is an object of the present invention to provide a stainless steel alloy having excellent pulverizability and a method for producing the stainless steel alloy.

The stainless steel alloy with excellent grindability according to the present invention is
The compositional formula (Fe _1-xy Cr _x Ni _y ) _100-lmnqz Mn _l Si _m B _n Mo _q Cu _z is represented by atomic %, and the composition ratios x, y, l, m, n, q, and z are, respectively,
0.15≤x≤0.30
0.002≤y≤0.25
0.00≦l≦2.00 atomic %
0.00≤m≤3.00 atomic %
7.00≤n≤20.00 atomic %
0.00≤q≤3.50 atomic %
0.00≤z≤4.00 atomic %
and the contents of carbon C, nitrogen N, oxygen O, sulfur S, and phosphorus P, which are inevitable impurities mixed into the quenched alloy that satisfies this composition formula, are
C≤2000ppm
N≤3000ppm
O≤3000ppm
S≤2000ppm
P≤500ppm
and having a thickness of 15 μm or more and 120 μm or less.

It is characterized in that the stainless alloy can be obtained in a pulverization process using a pin disc mill to obtain a stainless alloy pulverized powder having an average particle size of 50 μm or more and 200 μm or less with a pulverization process yield of 80% or more.

In the pulverization process using a jet mill, the stainless alloy pulverized powder having an average particle size of 3 μm or more and 50 μm or less can be obtained with a pulverization process yield of 80% or more.

In addition, the method for producing a stainless steel alloy with excellent grindability of the present invention includes:
The compositional formula (Fe _1-xy Cr _x Ni _y ) _100-lmnqz Mn _l Si _m B _n Mo _q Cu _z is represented by atomic %, and the composition ratios x, y and l, m, n, q, z are respectively
0.15≤x≤0.30
0.002≤y≤0.25
0.00≦l≦2.00 atomic %
0.00≤m≤3.00 atomic %
7.00≤n≤20.00 atomic %
0.00≤q≤3.50 atomic %
0.00≤z≤4.00 atomic %
a step of preparing a molten stainless steel alloy having a composition satisfying the above; In the rapid solidification step, the molten alloy is applied to the surface of the cooling roll while rotating the cooling roll at a roll surface speed of 10 m / sec or more and 40 m / sec or less, boron nitride (BN), quartz (SiO2), silicon carbide (SiC ), and alumina (Al2O3), and the injection nozzle has a single hole at the tip of the nozzle, or one direction perpendicular to the rotation direction of the cooling roll. having a plurality of apertures of two or more that are spaced apart, the diameter of the apertures being 0.5 mm or more and 2.0 mm or less, and the spacing between the apertures constituting the apertures being 2.0 mm It is characterized by being more than or equal to 30.0 mm or less.

In the method for producing a stainless steel alloy, the atmosphere in the rapid solidification step is atmospheric pressure (101.3 kPa) or an inert gas of 1 kPa or more and 100 kPa or less, and the molten alloy is injected from the injection nozzle. The injection pressure is 2 kPa or more and 60 kPa or less.

The method for producing a stainless steel alloy is characterized in that, in the rapid solidification step, the distance between the chill roll surface and the tip of the injection nozzle (nozzle/roll gap) is 0.3 mm or more and 20 mm or less.

In the method for producing a stainless steel alloy, the chill roll has an outer diameter of 200 mm or more and 1500 mm or less, and the arithmetic mean roughness Ra of the chill roll surface is 10 nm or more and 20 μm or less.

According to the present invention, unlike a stainless steel alloy mainly composed of γ-Fe that forms an austenite phase having high toughness, a stainless steel alloy having a fine metal structure with an average grain size of 5 μm or less mainly composed of α-Fe Therefore, in mechanical pulverization such as hammer mills, feather mills, pin disk mills and jet mills, it is possible to support various molding methods used in powder metallurgy while ensuring a pulverization process yield of 80% or more. A stainless steel alloy suitable for producing stainless steel alloy powder with an average particle size of 3 μm to 200 μm, which provides a high compacting density, can be obtained.

Furthermore, in the single roll quenching method used as a method for producing a stainless steel alloy with excellent grindability according to the present invention, the above-mentioned Since the raw material yield until obtaining the stainless steel alloy is 95% or more and 99% or less, the direct rate of the raw material in the total process to the stainless steel alloy pulverized powder combined with the mechanical pulverization process is 76% or more, and in addition, since all steps up to the production of the pulverized powder of the stainless steel alloy can be performed by a dry process, it is possible to achieve a significant improvement in yield compared to the molten metal spray method, and a reduction in manufacturing costs due to this.

(a) is a cross-sectional view showing an example of the overall configuration of a single-roll molten metal rapid cooling apparatus used when producing the stainless steel alloy according to the present invention, and (b) is a portion where the molten alloy is rapidly solidified. It is an enlarged view. (c) is an enlarged view of the bottom surface of the injection nozzle, (c-1) is a single-hole injection nozzle having a single-hole opening, and (c-2) is a multiple-hole injection nozzle having multiple openings. Examples of nozzles are shown respectively. FIG. 2 shows a block diagram of a pin disk mill used for pulverizing the stainless steel alloy according to the present invention. In the pin disk mill, the pins arranged on the fixed disk and the disk rotating at high speed collide with the crushed raw material (stainless alloy according to the present invention), and the impact causes the crushed raw material to rotate at the speed of the disk rotating at high speed. Then, by appropriately adjusting the number of pins, the powder is pulverized to a desired powder particle size. 2 is an X-ray diffraction profile of the stainless steel alloy obtained in Example 1 on the free surface side (opposite side to the contact surface of the chill roll). 2 shows X-ray diffraction profiles of the stainless steel alloys obtained in Examples 3 and 4 on the free surface side (the side opposite to the contact surface of the chill roll). 3 is an X-ray diffraction profile of the free surface of the stainless steel alloy obtained in Comparative Example 11 (the side opposite to the contact surface of the cooling roll). 13 is an X-ray diffraction profile of the free surface of the stainless steel alloy obtained in Comparative Example 13 (the side opposite to the contact surface of the chill roll).

[Alloy composition]
In stainless steel alloys, Cr is an essential main element for ensuring corrosion resistance, and if the substitution rate for Fe is 15% or less, good corrosion resistance cannot be maintained. In addition, if the substitution ratio of Cr to Fe is 30% or more, the hardness of the stainless steel alloy is significantly increased and the grindability is deteriorated. The following are good. The substitution ratio of Cr to Fe is preferably 17% or more and 29% or less, more preferably 18% or more and 28% or less.

Like Cr, Ni, which is an essential element in stainless steel alloys, plays a role in stabilizing the austenitic structure of the stainless steel in the sintered product produced by the powder metallurgy method using the pulverized powder of the stainless steel alloy according to the present invention. This austenitic structure contributes to the improvement of the mechanical strength of the sintered body by the powder metallurgy method using the pulverized powder of the stainless alloy. Strength decreases. In addition, if the substitution amount of Ni with respect to Fe is 25% or more, the corrosion resistance is lowered and the cost is increased. The substitution ratio of Ni to Fe is preferably 2% or more and 23% or less, more preferably 5% or more and 21% or less.

Like Ni, the addition of Mn works to increase the mechanical strength of the sintered product obtained by powder metallurgy using the pulverized powder of the stainless steel alloy according to the present invention. Therefore, the amount of Mn added to the stainless steel alloy according to the present invention is preferably 0.0% or more and 2.0 atomic % or less. It is preferably 0.5 atomic % or more and 2.0 atomic % or less, more preferably 0.5 atomic % or more and 1.8 atomic % or less.

The addition of Si serves to prevent scale during melting in the single roll molten metal quenching process in the present invention and refines the structure of the stainless steel alloy. Therefore, the amount of Si added to the stainless steel alloy according to the present invention is preferably 0.0% or more and 3.0 atomic % or less. It is preferably 0.4 atomic % or more and 3.0 atomic % or less, more preferably 0.4 atomic % or more and 2.8 atomic % or less.

Addition of B is an essential element for changing the metal structure of the stainless steel alloy of the present invention produced by a single roll molten metal quenching apparatus from γ-Fe mainly to α-Fe, and in addition, the single roll molten metal quenching By reducing the viscosity of the molten alloy in the process and improving the adhesion between the chill roll and the molten alloy, the cooling rate of the molten metal is improved, the glass-forming ability of the alloy is increased, and the metal structure of the stainless-based alloy according to the present invention is improved. Although it contributes to refinement, if the amount added is 7.0 atomic % or less, the formation of the α-Fe phase is insufficient. The amount of B added to the stainless steel alloy according to the present invention is preferably 7.0% or more and 20.0 atomic % or less. It is preferably 8.0 atomic % or more and 15.0 atomic % or less, more preferably 8.0 atomic % or more and 13.0 atomic % or less.

The addition of Mo contributes to the corrosion resistance of the stainless steel alloy according to the present invention, as with Cr, but if added by 3.5 atomic % or more, the hardness of the stainless steel alloy increases and the grindability deteriorates. The amount of Mo added to the alloy is preferably 0.0% or more and 3.5 atomic % or less. It is preferably 0.0 atomic % or more and 3.0 atomic % or less, more preferably 0.0 atomic % or more and 2.0 atomic % or less.

Addition of Cu, like addition of Si, contributes to refinement of the structure of the stainless steel alloy obtained in the single roll molten metal quenching process in the present invention. The amount of Cu added to the stainless steel alloy according to the present invention is preferably 0.0% or more and 4.0 atomic % or less. It is preferably 0.0 atomic % or more and 3.0 atomic % or less, more preferably 0.0 atomic % or more and 2.0 atomic % or less.

In the stainless steel alloy according to the present invention, carbon C, nitrogen N, oxygen O, sulfur S, and phosphorus P, which are unavoidable impurities, are C ≤ 2000 ppm, N ≤ 3000 ppm, respectively, in order to maintain the corrosion resistance of the stainless steel alloy. O ≤ 3000 ppm, S ≤ 2000 ppm, and P ≤ 500 ppm. If so, you can actively add it. Similarly, N also contributes to the formation of the austenite phase in the sintered body, so it may be positively added up to N≦1700 ppm. Furthermore, since S and P contribute to the improvement of the machinability of the sintered body, they may be positively added with the upper limits of S≦1500 ppm and P≦450 ppm.

[Metal structure]
General stainless steel is mainly composed of γ-Fe which constitutes an austenitic phase with excellent toughness, but the stainless steel alloy obtained by the present invention has a metal structure mainly composed of α-Fe. However, when the volume ratio of α-Fe is 50% or less, the toughness of the stainless steel alloy increases and the grindability when mechanical pulverization is employed decreases. Since a pulverization process yield of 80% or more cannot be ensured, the α-Fe contained in the stainless steel alloy is preferably 50% by volume or more. It is preferably 60% by volume or more, more preferably 80% by volume or more.

The stainless steel alloy according to the present invention, which is produced by rapid solidification of a molten alloy using a single roll molten metal rapid cooling method, has a fine metal structure composed of α-Fe with an average crystal grain size of 0.1 μm to 10 μm. When the grain size is 0.1 µm or less and when the average crystal grain size is 10 µm or more, the grindability of the stainless steel alloy is lowered. Below. It is preferably 0.3 μm or more and 5 μm or less, more preferably 0.5 μm or more and 3 μm or less.

[Alloy thickness]
The stainless steel alloy obtained by the present invention, which has 50% by volume or more of α-Fe and has a fine structure with an average crystal grain size of 0.1 μm to 10 μm, has an alloy thickness of 15 μm or more and 120 μm or less. It is possible to secure a pulverization yield of 80% or more in pulverization, but if the alloy thickness is 15 μm or less, the production efficiency of the stainless alloy decreases during rapid cooling of the molten metal on a single roll, which causes an increase in manufacturing costs. On the other hand, if the thickness is 120 μm or more, the average crystal grain size is 10 μm or more, and the grindability deteriorates. It is preferably 18 μm or more and 100 μm or less, more preferably 20 μm or more and 80 μm or less.

[Oxide film]
In the stainless steel alloy obtained in the present invention, an oxide film of 20 nm or less is formed on the surface of the quenched alloy during rapid cooling of molten metal on a single roll. is required to be 1 nm or more, and the thickness of the oxide film is preferably 2 nm or more and 20 nm or less, more preferably 5 nm or more and 20 nm or less.

[Pulverization particle size]
The stainless steel alloy obtained by the present invention has a pulverization process yield of 80% or more in the pulverization process using a pin disc mill. cannot be guaranteed. On the other hand, if the average pulverized particle size is 200 μm or more, the molding density in metal compression molding and metal injection molding (MIM) will decrease, so the average pulverized particle size of the stainless alloy using a pin disc mill is 50 μm. More than 200μm or less is good. Preferably, it is 60 μm or more and 160 μm or less. More preferably, the thickness is 60 μm or more and 130 μm or less.

The stainless steel alloy obtained by the present invention can obtain a pulverization process yield of 80% or more in the pulverization process using a jet mill. cannot be guaranteed. On the other hand, if the average pulverized particle size is 50 μm or more, the printer nozzle will be clogged when manufacturing a molded product with a metal 3D printer. More than 50μm or less is good. Preferably, the thickness is 3 μm or more and 40 μm or less. More preferably, the thickness is 4 μm or more and 30 μm or less.

[Molten metal rapid cooling]
The nozzle for injecting the molten alloy in the single roll molten metal quenching process of the present invention is an injection nozzle having a single opening at the bottom of the nozzle, or an injection nozzle spaced in one direction perpendicular to the rotation direction of the cooling roll. A multi-hole injection nozzle having two or more openings arranged at intervals may be used as shown in the drawing (c-2), but if the diameter of the opening is 0.5 mm or less, the molten alloy will not flow through the nozzle. When the molten metal is ejected, the amount of molten metal discharged per unit time decreases, and the opening is blocked by the cooled and solidified molten alloy. On the other hand, if the diameter of the opening hole is 2.0 mm or more, the amount of molten metal discharged per unit time is too large, so that the cooling roll is not able to remove the heat from the molten alloy in time, and the cooling roll surface is locally melted. The diameter of the opening hole is preferably 0.5 mm or more and 2.0 mm or less because the quenched alloy (stainless alloy) sticks to the cooling roll and the quenching of the molten metal cannot be continued. It is preferably 0.5 mm or more and 1.5 mm or less, more preferably 0.7 mm or more and 1.2 mm or less.

The distance between the slits in the multi-hole injection nozzle should be 2.0 mm or more in order to prevent the openings from falling off when the molten alloy is injected from the injection nozzle. Also, in consideration of increasing the production efficiency of the quenched alloy (stainless alloy), the distance between the plurality of open holes is preferably 30.0 mm or less.

Using the above-mentioned single-hole type injection nozzle and multi-hole type injection nozzle, the alloy composition of the present invention was blended on the surface of the chill roll mainly made of copper, copper alloy, Mo, or W. By spraying the molten alloy, it is possible to obtain a stainless steel alloy with a thickness of 15 μm or more and 120 μm or less. The metallographic structure of the alloy is coarsened, impairing the grindability. On the other hand, when the roll surface speed is 40 m/sec or more, the molten alloy supplied from the injection nozzle onto the chill roll surface cannot adhere to the chill roll surface, and the formation of the quenched alloy (stainless alloy) becomes unstable. The surface speed should be between 10m/sec and 40m/sec. In order to refine the stainless steel alloy structure and stabilize the formation of the stainless steel alloy, the roll surface speed is preferably 15 m/sec or more and 40 m/sec or less, more preferably 18 m/sec or more and 38 m/sec or less. good.

The material of the injection nozzle that supplies the molten alloy onto the surface of the quench roll may be composed mainly of quartz (SiO2), boron nitride (BN), silicon carbide (SiC), or alumina (Al2O3). preferable.

Adhesion between the molten alloy and the cooling roll is important when producing the stainless steel alloy. The adhesion of the molten alloy is also affected by the material of the cooling roll. Considering the above, either copper or an alloy with copper as the main component, Mo or an alloy with Mo as the main component, or W or an alloy with W as the main component is preferable, but equipment related to the production of stainless steel alloys And in view of running costs, copper or an alloy containing copper as a main component is preferable. In addition, since the surface roughness of the chill roll surface also affects the adhesion between the molten alloy and the chill roll, it is preferable that the arithmetic mean roughness Ra of the chill roll surface is 10 nm or more and 20 μm or less, which improves production efficiency and quality. Taking this into account, Ra is preferably 50 nm or more and 10 μm or less, more preferably 100 nm or more and 10 μm or less.

The adhesion between the molten alloy and the chill roll in the present invention affects not only the surface roughness of the chill roll but also the injection pressure of the molten alloy supplied from the injection nozzle to the chill roll surface. If the injection pressure is 2 kPa or less, the molten alloy cannot be pressed against the chill roll surface so weakly that the molten alloy cannot be brought into close contact with the chill roll surface, so that the molten alloy cannot be rapidly solidified. On the other hand, when the injection pressure is 60 kPa or more, the pressure of the molten alloy pressed against the chill roll surface is too strong, so the molten alloy is splashed on the chill roll and the molten metal cannot be quenched. The following are good. It is preferably 5 kPa or more and 40 kPa or less, more preferably 10 kPa or more and 30 kPa or less.

Further, the adhesion between the molten alloy and the chill roll, which is important in the present invention, also affects the amount and temperature of the roll cooling water flowing inside the chill roll. When the roll cooling water is 0.1m3/min or less, the heat quantity of the molten alloy sprayed onto the chill roll surface from the nozzle cannot be removed by the chill roll, and the surface temperature of the chill roll rises gradually, causing localized damage to the chill roll surface. Rapid cooling of molten metal cannot be implemented because it melts to On the other hand, when the roll cooling water flow rate is 20 cubic meters/min or more, the temperature difference ΔT between the roll cooling water IN side and the roll cooling water OUT side becomes 1°C or less, and the surface temperature of the cooling roll during molten metal cooling does not rise. Since the adhesion between the roll surface and the molten alloy becomes unstable, a roll cooling water flow rate of 0.1 m3/min or more and 20 m3/min or less is preferable. It is preferably 0.2 cubic meters/min or more and 15 cubic meters/min or less, more preferably 0.3 cubic meters/min or more and 15 cubic meters/min or less.

The temperature of the roll cooling water is preferably 5°C or higher and 60°C or lower. If the temperature is 5°C or less, the adhesion between the molten alloy and the chill roll cannot be ensured, and if the temperature is 60°C or more, separation of the stainless steel alloy from the chill roll becomes unstable. The temperature is preferably 10°C or higher and 60°C or lower, and more preferably 15°C or higher and 55°C or lower.

In the method for producing a stainless steel alloy, the cooling roll preferably has an outer diameter of 200 mm or more and 1500 mm or less. When the outer diameter is 200 mm or less, the time required for the stainless steel alloy to separate from the chill roll after the stainless steel alloy is formed on the chill roll surface is short, and the molten metal is not sufficiently quenched, resulting in a fine metal structure. can't On the other hand, it is difficult to produce a chill roll with an outer diameter of 1500 mm or more by forging. The outer diameter is preferably 230 mm or more and 1300 mm or less, more preferably 280 mm or more and 1200 mm or less.

In the method for producing a stainless steel alloy according to the present invention, the total length of the cooling roll is the total length of the openings of the multiple-hole type nozzle (the distance from the outermost of one of the openings to the outermost of the other opening of the nozzle The total length of the roll is preferably 20 mm or more and less than 400 mm in addition to the total length of the opening holes), and the thickness of the cooling roll is preferably 5 mm or more and 100 mm or less. When considering the total length of the cooling roll obtained by adding the length of 20 mm or less to the total length of the opening hole, and the heat capacity of the cooling roll as a heat sink when the thickness of the cooling roll is 5 mm or less, the heat is supplied from the injection nozzle to the cooling roll. Since the temperature of the cooling roll rises too much before the heat of the molten alloy is removed by the roll cooling water, stable rapid cooling of the molten alloy cannot be performed. On the other hand, if the total length of the roll obtained by adding 400 mm or more to the total length of the opening holes and the thickness of the cooling roll are 100 mm or more, the processing cost of the cooling roll increases significantly, and the roll cooling water The heat conduction is slow, and the surface temperature of the cooling roll rises too much, making it impossible to stably quench the molten metal. A preferable length of the cooling roll is a length obtained by adding a length of 30 mm or more and 300 mm or less to the total length of the opening hole, and a thickness of the cooling roll is preferably 5 mm or more and 70 mm or less. More preferably, the length is the total length of the opening hole plus 40 mm or more and 300 mm or less, and the thickness of the cooling roll is preferably 7 mm or more and 50 mm or less.

In the positional relationship between the cooling roll and the injection nozzle of the single roll molten metal quenching apparatus of the present invention, the molten alloy is supplied from the injection nozzle to the cooling roll while reciprocating horizontally (traversing) the injection nozzle in the longitudinal direction of the cooling roll. As a result, it is possible to reduce the roughness of the chill roll surface due to local melting, so that the rapid solidification time can be extended compared to the case where the jet nozzle does not traverse. , preferably within 90% of the length of the chill roll, more preferably within 80%.

In addition, in the rapid solidification process of the molten alloy using the single roll molten metal quenching apparatus of the present invention, as a method of reducing roughness due to local melting on the chill roll surface, the chill roll surface is polished or ground during the molten metal quenching. It is also possible to extend the rapid solidification time by applying and removing roughness.

Examples of the present invention will be described below.

(Example)
After inserting 100 kg of raw materials containing each element of Fe, Cr, Ni, Mn, Si, B, Mo, and Cu with a purity of 99.5% or more into an alumina crucible so as to obtain each alloy composition shown in Table 1, high-frequency After melting by induction heating and preparing a molten alloy, alumina with an inner diameter of 200 mm and a height of 400 mm with a BN injection nozzle (hole diameter, hole spacing, and number of holes shown in Table 1) at the bottom. 50 kg of the molten alloy was poured into the hot water storage container. A cooling roll made of chromium zircon copper (outer diameter 600 mm×width 200 mm) is arranged at the nozzle/roll gap shown in Table 1 immediately below the injection nozzle.

After that, by energizing the high-frequency heating coil installed around the hot water storage container, 50 kg of the molten alloy is further heated, and the molten metal temperature is about 100 ° C or higher than the melting point of the alloy composition shown in Table 1. After reaching , pull out the alumina molten metal stopper arranged at the top of the injection nozzle, and the molten alloy is injected from the injection nozzle arranged at the bottom of the hot water storage container at the injection pressure shown in Table 2, and the roll surface speed shown in Table 2. spouted onto the surface of the cooling roll rotating at . The surface roughness of the cooling roll was adjusted in advance so as to have the arithmetic mean roughness (Ra) shown in Table 2 before the rapid solidification step.

The molten alloy jetted to the surface of the chill roll and pressed onto the roll forms a pool (paddle) on the chill roll surface, is rapidly solidified at the interface between the paddle and the chill roll, and has an average thickness shown in Table 3. , and a ribbon-shaped rapidly solidified alloy (stainless alloy according to the present invention) having an average width. The stainless steel alloy thus obtained was immediately coarsely pulverized by a feather mill to obtain stainless steel alloy flakes having a longitudinal direction of 5 mm to 50 mm. In all of Examples 1 to 10, the yield of the stainless alloy flakes having a length of 50 mm or less in the longitudinal direction of the stainless alloy was 99% or more by coarse pulverization using a feather mill. .

The stainless steel alloy flakes were pulverized using a pin disk mill or a jet mill. Table 4 shows the pulverization yield (yield of pulverized powder) and the average particle size of the pulverized powder. In addition, the volume ratio of the α-Fe phase was evaluated by X-ray diffraction (XRD) evaluation of each stainless steel alloy produced in Examples. In addition, the average crystal grain size of the crystal grains constituting each stainless steel alloy was observed with a transmission electron microscope (TEM), and binarization was performed on the image of the bright field image, and the JIS standard (JIS G 0551 : 2005). Table 4 shows the volume % of α-Fe and the average crystal grain size obtained in the above evaluation. As representative examples, FIG. 3 shows the X-ray diffraction profiles of Example 1, and FIG. 4 shows the X-ray diffraction profiles of Examples 3 and 4.

In addition, when the cross-sections of the stainless steel alloys of Examples 1 to 10 were analyzed for oxygen concentration by a transmission electron microscope, oxygen was concentrated in a thickness of 20 nm or less from the surface of the stainless steel alloy, and the surface of the stainless steel alloy It was confirmed that an oxide film phase was formed in the

(Comparative example)
After inserting 100 kg of raw materials containing each element of Fe, Cr, Ni, Mn, Si, and B with a purity of 99.5% or more into an alumina crucible so as to obtain each alloy composition shown in Table 1, it is melted by high-frequency induction heating. After preparing the molten alloy, the BN injection nozzle (hole diameter, hole spacing, and number of holes are shown in Table 1) described in Table 1 is placed in the bottom of the alumina hot water storage container with an inner diameter of 200 mm and a height of 400 mm. 50 kg of molten alloy was poured. A cooling roll made of chromium zircon copper (outer diameter 600 mm×width 200 mm) is arranged at the nozzle/roll gap shown in Table 1 immediately below the injection nozzle.

After that, by energizing the high-frequency heating coil installed around the hot water storage container, 50 kg of the molten alloy is further heated, and after the molten metal temperature reaches a temperature of about 100 ° C. or higher than the melting point of the alloy composition, Pull out the alumina molten metal stopper placed on the top of the hot water nozzle, and rotate the molten alloy from the injection nozzle placed on the bottom of the hot water storage container at the injection pressure shown in Table 2 and at the roll surface speed shown in Table 2. It spurted onto the surface of the cooling roll that was being held. The surface roughness of the cooling roll was adjusted in advance so as to have the arithmetic mean roughness (Ra) shown in Table 2 before the rapid solidification step.

The molten alloy jetted to the surface of the chill roll and pressed onto the roll forms a pool (paddle) on the chill roll surface, is rapidly solidified at the interface between the paddle and the chill roll, and has an average thickness shown in Table 3. and a ribbon-shaped rapidly solidified alloy (stainless alloy according to the present invention) having an average width. Immediately after, the obtained stainless steel alloy was coarsely pulverized by a feather mill to obtain stainless steel alloy flakes having a longitudinal direction of 5 mm to 50 mm. In Comparative Examples 11, 12, and 13, the yield of the stainless steel alloy flakes having a longitudinal direction of 50 mm or less by coarse pulverization using a feather mill was 70% or less. there were.

The stainless steel alloy flakes were pulverized using a pin disk mill or a jet mill. Table 4 shows the pulverization yield (yield of pulverized powder) and the average particle size of the pulverized powder. Further, the presence or absence of the α-Fe phase and the volume ratio were evaluated by X-ray diffraction (XRD) evaluation of each stainless steel alloy produced in Examples. In addition, the average crystal grain size of the crystal grains constituting each stainless steel alloy was observed with a transmission electron microscope (TEM), and binarization was performed on the image of the bright field image, and the JIS standard (JIS G 0551 : 2005). Table 4 shows the volume % of α-Fe and the average crystal grain size obtained in the above evaluation. As representative examples, FIG. 5 shows the X-ray diffraction profile of Comparative Example 11, and FIG. 6 shows the X-ray diffraction profile of Comparative Example 13.

1 melting crucible 2 induction heating coil for melting (work coil)
3 melting crucible tilting shaft 4 hot water storage container (tundish)
5 Hot water storage container induction heating coil (work coil)
6 injection nozzle 7 stopper 8 molten alloy 9 chill roll 10 rapidly solidified alloy (stainless alloy)
12 single hole injection nozzle 13 multiple hole injection nozzle 14 cooling roll rotation direction 15 disk drive motor
16 Rotation side pin disk 17 Fixed side pin disk 18 Crushing pin 19 Raw material before crushing 20 Crushed product 21 Seal air

Claims (7)

The compositional formula (Fe _1-xy Cr _x Ni _y ) _100-lmnqz Mn _l Si _m B _n Mo _q Cu _z is represented by atomic %, and the composition ratios x, y, l, m, n, q, and z are, respectively,
0.15≤x≤0.30
0.002≤y≤0.25
0.00≦l≦2.00 atomic %
0.00≤m≤3.00 atomic %
7.00≤n≤20.00 atomic %
0.00≤q≤3.50 atomic %
0.00≤z≤4.00 atomic %
and the contents of carbon C, nitrogen N, oxygen O, sulfur S, and phosphorus P, which are inevitable impurities mixed into the quenched alloy that satisfies this composition formula, are
C≤2000ppm
N≤3000ppm
O≤3000ppm
S≤2000ppm
P≤500ppm
A stainless steel alloy having a thickness of 15 μm or more and 120 μm or less. 2. The stainless alloy according to claim 1, wherein the stainless alloy pulverized powder having an average particle size of 50 μm or more and 200 μm or less can be obtained at a pulverization process yield of 80% or more by a pulverization process using a pin disc mill. 2. The stainless alloy according to claim 1, wherein the stainless alloy pulverized powder having an average particle size of 3 μm or more and 50 μm or less can be obtained by a pulverization process using a jet mill with a pulverization process yield of 80% or more. The compositional formula (Fe _1-xy Cr _x Ni _y ) _100-lmnqz Mn _l Si _m B _n Mo _q Cu _z is represented by atomic %, and the composition ratios x, y and l, m, n, q, z are respectively
0.15≤x≤0.30
0.002≤y≤0.25
0.00≦l≦2.00 atomic %
0.00≤m≤3.00 atomic %
7.00≤n≤20.00 atomic %
0.00≤q≤3.50 atomic %
0.00≤z≤4.00 atomic %
A step of preparing a molten stainless steel alloy having a composition satisfying In the solidification process, while rotating the chill roll at a roll surface speed of 10 m/sec or more and 40 m/sec or less, boron nitride (BN), quartz (SiO2), silicon carbide (SiC), and alumina are applied to the surface of the chill roll. (Al2O3) is provided as a main component, and the injection nozzle has a single opening hole at the tip of the nozzle, or is spaced in one direction perpendicular to the rotation direction of the cooling roll. It has a plurality of apertures of two or more arranged, the diameter of said apertures is 0.5 mm or more and 2.0 mm or less, and in the plurality of apertures, the distance between each aperture constituting the aperture is 2.0 mm. The method for producing a stainless steel alloy according to claims 1, 2, and 3, wherein the thickness is 30.0 mm or more. In claim 4, the atmosphere in the rapid solidification step is normal pressure (101.3 kPa) or inert gas of 1 kPa or more and 100 kPa or less, and the injection pressure of the molten alloy injected from the injection nozzle is 2 kPa or more and 60 kPa or less. The method for producing a stainless steel alloy according to claim 1, claim 2, and claim 3. In claim 4, the distance between the cooling roll surface and the tip of the injection nozzle (nozzle/roll gap) in the rapid solidification process is 0.3 mm or more and 20 mm or less. A method of manufacturing an alloy. In claim 4, the outer diameter of the chill roll is 200 mm or more and 1500 mm or less, and the arithmetic mean roughness Ra of the chill roll surface is 10 nm or more and 20 μm or less. A method for producing a stainless steel alloy.

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