WO2012014541A1 - Free-cutting stainless-steel cast product and process for producing same - Google Patents
Free-cutting stainless-steel cast product and process for producing same Download PDFInfo
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- WO2012014541A1 WO2012014541A1 PCT/JP2011/059910 JP2011059910W WO2012014541A1 WO 2012014541 A1 WO2012014541 A1 WO 2012014541A1 JP 2011059910 W JP2011059910 W JP 2011059910W WO 2012014541 A1 WO2012014541 A1 WO 2012014541A1
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- C—CHEMISTRY; METALLURGY
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/002—Heat treatment of ferrous alloys containing Cr
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/56—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering characterised by the quenching agents
- C21D1/60—Aqueous agents
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D5/00—Heat treatments of cast-iron
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/02—Making non-ferrous alloys by melting
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/004—Dispersions; Precipitations
Definitions
- the present invention relates to a cast stainless steel product to which a free machinability imparting material is added and a method for producing the same.
- Stainless steel cast steel products where corrosion resistance is important for example, pipe joints (elbows, sockets, nipples, etc.) used in equipment piping, vacuum equipment, analytical equipment, etc., valves, joint flanges, etc. are made by casting. Although it is manufactured, plastic products such as forging and rolling are not performed on products with complicated shapes, and cutting (mechanical) processing such as planar processing, drilling processing, and threading processing is eventually performed with the cast structure. Necessary. Since these products are required to have excellent corrosion resistance, austenitic stainless steels such as SUS304 and SUS316 are often used.
- these austenitic stainless steels are known as hard-to-cut steels whose machinability deteriorates due to work hardening in the vicinity of the cut surface because work hardening easily proceeds. Therefore, there is a conventional free-cutting stainless steel to which S (sulfur), Pb (lead), Se (selenium), etc. are added as a free-cutting property imparting material for the purpose of improving machinability. From the viewpoint of safety and security, it is unsuitable as a joint for equipment for producing food and beverages. Se is known as an environmentally hazardous substance and has been withheld from use.
- SUS303 which is commercially available as sulfur-added free-cutting stainless steel, contains about 0.3% of S, which is known as an element that adversely affects corrosion resistance even in a small amount, and is a part of equipment where corrosion resistance is important. It is unsuitable for use.
- Patent Document 1 discloses a free-cutting stainless steel that can simultaneously satisfy excellent machinability, corrosion resistance, and mechanical properties, and a manufacturing method thereof.
- h-BN hexagonal boron nitride
- the present invention is a cast steel product that does not require much importance on mechanical properties and requires a complex shape, and is capable of satisfying not only excellent machinability and environmental performance but also corrosion resistance at the same time. It is an object of the present invention to provide a machined stainless steel cast steel product and a manufacturing method thereof.
- the present invention effectively uses the properties of h-BN (hexagonal boron nitride) particles that are excellent as a solid lubricant, chemically stable and not attacked by acid or alkali, and can be specified even in the state of a cast structure.
- h-BN hexagonal boron nitride
- the present inventors have found a stainless steel cast steel product excellent in machinability and corrosion resistance and a method for producing the same by utilizing the fact that h-BN precipitates or dissolves / reprecipitates by heat treatment.
- Invention 1 is a cast stainless steel product to which a free machinability imparting material is added, wherein the free machinability imparting material is h-BN (hexagonal boron nitride) particles, and the particle size is 200 nm to 10 ⁇ m.
- the spherical h-BN particles were uniformly dispersed and precipitated in the steel.
- Invention 2 is a method for producing a cast stainless steel product of Invention 1, characterized by controlling the cooling rate in the temperature range of 1250 ° C. to 850 ° C. during solidification of casting and dispersing and precipitating h-BN particles. The configuration to adopt was adopted.
- Invention 3 is a method for producing a cast stainless steel product of Invention 1, wherein the cast stainless steel on which h-BN particles are precipitated is heated and then rapidly cooled to cause the h-BN particles to dissolve and disappear.
- a configuration characterized by re-dispersing and precipitating the h-BN particles by returning is employed.
- Invention 4 is a method for producing a cast stainless steel product of Invention 1, wherein a temperature range of 1250 ° C. to 850 ° C. during casting solidification is rapidly cooled to obtain a cast structure in which no h-BN particles are precipitated, and then 950 A configuration characterized in that h-BN particles are dispersed and precipitated by performing a tempering heat treatment at a temperature of ⁇ 1100 ° C. is adopted.
- Invention 5 is a method for producing cast stainless steel products of Inventions 2 to 4, wherein the addition amount of B (boron) is 0.003 to 0.5 mass%, and the addition amount of N (nitrogen) A configuration characterized in that the ratio N / B is 1 or more was adopted.
- Invention 6 is a method for producing a cast stainless steel product of Invention 5, wherein B is added to ferroboron or metal boron, and N is added to the molten stainless steel by setting the melting atmosphere to (argon + nitrogen) or reduced pressure nitrogen. The structure characterized by doing is adopted.
- Invention 7 is a method for producing a cast stainless steel product of Invention 5, characterized in that B is added to the molten stainless steel by addition of ferroboron or metal boron, and N is added by a nitrogen-containing compound or ferroalloy. The configuration to adopt was adopted.
- H-BN particles that are chemically stable and not affected by acids or alkalis are uniformly dispersed and precipitated, and h-BN, which has excellent characteristics as a solid lubricant, improves machinability and deteriorates corrosion resistance.
- h-BN which has excellent characteristics as a solid lubricant, improves machinability and deteriorates corrosion resistance.
- the invention 1 can satisfy not only excellent machinability and environmental performance but also corrosion resistance.
- the improvement of machinability can reduce the power of the cutting machine, the carbon dioxide emission can be reduced by reducing the electric energy consumption, and the productivity can be expected to be improved because high-speed cutting is possible.
- FIG. 1 A photograph of the formation and distribution of precipitates by SEM observation of the developed material 1.
- the present invention has the features as described above, and an embodiment thereof will be described below.
- the melting of the cast stainless steel is performed using a melting furnace for melting ordinary stainless steel, in which the melting atmosphere can be adjusted.
- ferroboron or metal boron is used as the raw material for B.
- ferroboron having a low melting point is technically advantageous as the melting raw material, and economical because the price per unit weight of B is low. It is.
- the amount of B added is such that the final B content in the cast stainless steel product is generally 0.003 to 0.5 mass%, more preferably 0.01 to 0.2 mass%.
- a method of adding N there is an addition of a nitride of an alloy element that absorbs N in a melting atmosphere or constitutes stainless steel, such as chromium nitride or ferrochrome nitride.
- the N content in the stainless steel cast steel product should be N / B of 1 or more in terms of a molar ratio as a general guide. If the molar ratio of N to B in the stainless steel cast steel is less than 1, the amount of dissolved B increases and the precipitation amount of h-BN effective for machinability decreases, so it is necessary to increase N / B as much as possible. There is. Although the N content depends on the constituent elements of the cast stainless steel, since B increases the activity of N, the equilibrium N concentration in the steel decreases as B increases. In the component composition of SUS304, the N content is 0.25 mass% or less except for dissolution in a pressurized N atmosphere.
- the stainless steel molten steel containing B and N produced as described above is obtained by controlling the cooling rate in the precipitation temperature region of h-BN from 1250 ° C. to 850 ° C. during the solidification process in the mold. It is possible to deposit and distribute h-BN spherical particles having a particle size of 200 nm to 10 ⁇ m.
- h-BN which has grown coarsely to about 20 to 30 ⁇ m, may be unevenly distributed in a part of the material depending on the cooling rate during the cooling process after casting.
- H-BN precipitated in stainless steel cast steel products decomposes into B and N at a temperature of 1200 ° C or higher for a relatively short time (for example, 0.5 to 1 hour at 1250 ° C). Solid solution in the cast steel matrix.
- a cast stainless steel product containing B and N in a solid solution state in a supersaturated state is obtained.
- the quenching operation may be water cooling performed on ordinary stainless steel, but the cooling rate in the temperature range in which h-BN is deposited, which will be described later, needs to be a cooling rate that does not cause precipitation.
- the selection of the tempering temperature is important for precipitating h-BN having a particle size and a distribution state that provides good machinability.
- the tempering temperature at which a grain size and distribution state that provides good machinability are obtained is preferably in the range of 950 to 1100 ° C.
- the tempering holding time the higher the temperature, the faster the diffusion rate of B and N, so that it takes only a short time.
- the range is 0.5 to 3 hours, preferably 1 to 2 hours. Quench quickly to stop h-BN growth.
- Example 1 A commercially available austenitic stainless steel (SUS304) round bar (weight 18 kg) was melted as a melting raw material using a vacuum induction melting furnace.
- the component composition (mass%) of the melting raw material is 0.04% C, 0.30% Si, 1.00% Mn, 0.030% P, 0.024% S, 8.09% Ni, 18.05. % Cr.
- 0.07 MPa of N was sealed in a vacuum induction melting furnace, and the N concentration in the molten steel was adjusted.
- the B content target values are 0.02 mass%, 0.05 mass%, and 0.1 mass%, respectively, and the N content target value is 0.2 mass%.
- Comparative material 1 was solidified under the same melting and casting conditions except that the melting raw material was melted in an Ar atmosphere (cast steel corresponding to SUS304 cast material and not containing h-BN), comparative material 2 Comparative material 1 containing 0.3 mass% of S (corresponding to SUS303 cast material, sulfur-added free-cutting stainless steel cast steel), as comparative material 3, N is developed in comparative materials 1 to 3 Similarly, 0.2 mass% contained was melted.
- the N partial pressure of the melting atmosphere was adjusted to 0.005 MPa, and the developed material 4 having the same N level as the comparative materials 1 and 2 was melted.
- the same material as the developed materials 1 to 3 was used as the melting raw material, and the target value of the B content was set to 0.05 mass% as in the developed material 2.
- Table 1 shows analytical values (unit: mass%) of B, N, and S after casting of the melted materials (developed materials 1 to 4, comparative materials 1 to 3).
- the ingot that had been cast and solidified was subjected to an h-BN solution heat treatment that was held in a resistance heating type electric furnace at a temperature of 1250 ° C. for 0.5 hours in an air atmosphere and then cooled with water outside the furnace.
- a resistance heating type electric furnace the water-cooled ingot was kept at 1050 ° C. for 1 hour in an air atmosphere, and then h-BN precipitation heat treatment was carried out by water cooling outside the furnace.
- This heat treatment was performed under the same conditions for both the developed material and the comparative material in order to make the conditions of the cast structure the same.
- FIG. 1 is a developed electron 1
- FIG. 2 is a developed material 3
- FIG. 3 is an SEM (scanning electron microscope) photograph showing the formation and distribution of precipitates in the comparative material 2.
- FIG. A round bar having a diameter of 3.6 mm was cut out from the sample after heat treatment, a notch was made in a part thereof, this part was bent and broken, and the fracture surface was observed with an SEM.
- This SEM is equipped with an EDS (energy dispersive X-ray analysis) device. Using this EDS device, elemental analysis of non-metallic inclusions that can be observed on the fracture surface was performed, and the inclusion species were identified. .
- EDS energy dispersive X-ray analysis
- FIG. 1 it was observed that several 200- ⁇ m or smaller h-BN particles (indicated by solid arrows) were dispersed on the entire fracture surface in the 200 ⁇ field of view at the bottom of the dimple.
- several spherical 10 ⁇ m MnS (indicated by broken line arrows) produced by a small amount of sulfur and manganese contained in the raw material for dissolution were also observed.
- FIG. 2 it was observed that h-BN particles of 10 ⁇ m or less were dispersed throughout the fracture surface in the 200 ⁇ field of view as in FIG.
- the number of h-BN particles is approximately 10 times that of the developed material 1 in proportion to the B concentration. From the shape of the h-BN particles observed in FIGS. 1 and 2, it can be considered that B and N dissolved in supersaturation in the molten steel are precipitated as h-BN in the solidification process.
- MnS spherical MnS of about 10 to 30 ⁇ m were observed at the bottom of the fracture surface dimple over the entire 200 ⁇ field of view. These MnS particles are also observed in FIG. 1 and are considered to be crystallized when the steel is in a molten state from the particle size and shape.
- FIG. 4 shows a result of a turning test performed on a round bar sample cut from a cast steel sample after heat treatment of the comparative materials 1 and 2 and the developed material 4. As shown in Table 1, these three materials have almost the same N content as about 0.06 mass%.
- FIG. 4 shows that h-BN particles or MnS particles dispersed in the materials have an effect on the machinability. Shows the impact.
- the cutting test conditions were a cutting depth of 1.0 mm, a tool feed of 0.1 mm / rev, a tool material M30 (without chip breaker), no cutting oil, and a turning speed in the range of 12 to 200 m / min. It is a measured value.
- the developed material 4 Compared to Comparative Material 1 (corresponding to SUS304 cast material), the developed material 4 has a cutting force reduction of 20% in the medium cutting speed region and 11% in the high speed cutting region, and the machinability is greatly improved.
- the comparative material 2 is a sulfur-added free-cutting stainless steel cast steel. Compared with this, the developed material is inferior in machinability, but the comparative material 2 cannot be used when corrosion resistance is important. Only the developed material can satisfy both good machinability and corrosion resistance, and the superiority of the developed material cannot be denied.
- FIG. 5 shows the relationship between the cutting speed and the resultant force of cutting resistance in the turning of the samples of the developed materials 1 to 3 and the comparative material 3 (without B addition) with different B addition amounts. As shown in Table 1, these four materials have almost the same N content as about 0.2 mass%, and FIG. 5 shows the effect of B addition on machinability. In the developed material in which B was added to the comparative material 3 having a B concentration of 0 mass%, a decrease in cutting resistance was observed in most cutting speed regions, and an improvement in machinability due to the addition of B was recognized.
- FIG. 6 shows the result of the corrosion test by the sulfuric acid corrosion test method (JIS G 0591). The test conditions were immersed in boiling 5% H 2 SO 4 for 6 hours continuously, and compared with the amount of corrosion obtained by dividing the weight loss by the initial surface area of the sample.
- JIS G 0591 sulfuric acid corrosion test method
- this invention makes it possible to easily provide a stainless steel cast steel product that is environmentally friendly and has improved machinability without deteriorating corrosion resistance, and is excellent in various processing fields using stainless steel cast steel products. Was able to bring about usability.
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Abstract
Description
そこで、従来、切削性を向上する目的で、快削性付与材としてS(硫黄)、Pb(鉛)、Se(セレン)などを添加した快削ステンレス鋼があるが、Pbには地球環境問題があり、安全・安心の観点から食品や飲料を生産する機器用の継手等としては不適当である。Seは環境負荷物質として知られ、使用を差し控えるようになっている。また、硫黄添加快削ステンレス鋼として市販されている鋼種のSUS303では、微量でも耐食性に対し悪影響を及ぼす元素として知られるSが0.3%程度含まれており、耐食性が重視される機器の部位に使用することは不適当である。 Stainless steel cast steel products where corrosion resistance is important, for example, pipe joints (elbows, sockets, nipples, etc.) used in equipment piping, vacuum equipment, analytical equipment, etc., valves, joint flanges, etc. are made by casting. Although it is manufactured, plastic products such as forging and rolling are not performed on products with complicated shapes, and cutting (mechanical) processing such as planar processing, drilling processing, and threading processing is eventually performed with the cast structure. Necessary. Since these products are required to have excellent corrosion resistance, austenitic stainless steels such as SUS304 and SUS316 are often used. However, these austenitic stainless steels are known as hard-to-cut steels whose machinability deteriorates due to work hardening in the vicinity of the cut surface because work hardening easily proceeds.
Therefore, there is a conventional free-cutting stainless steel to which S (sulfur), Pb (lead), Se (selenium), etc. are added as a free-cutting property imparting material for the purpose of improving machinability. From the viewpoint of safety and security, it is unsuitable as a joint for equipment for producing food and beverages. Se is known as an environmentally hazardous substance and has been withheld from use. In addition, SUS303, which is commercially available as sulfur-added free-cutting stainless steel, contains about 0.3% of S, which is known as an element that adversely affects corrosion resistance even in a small amount, and is a part of equipment where corrosion resistance is important. It is unsuitable for use.
特許文献1には、優れた切削性、耐食性、機械的特性を同時に満足することができる快削ステンレス鋼とその製造方法が開示されている。この発明では、切削性、耐食性、機械的特性の全てを満足するため、鋳造後のインゴットに鍛造・圧延の塑性加工を行い鋳造組織を消去した後、h-BN(六方晶系窒化ホウ素)粒子を再析出することで、従来のステンレス鋼材料に比較し25%程度の切削性の改良が行われた。
しかしながら、特許文献1に開示されるように、鍛造・圧延した後熱処理により切削性が改善されたステンレス鋼は開発されたものの、鋳造組織のままで切削性が改善されたステンレス鋳鋼製品及びその製造方法は、開示されていない。 Sulfur-added free-cutting stainless steel can be used only in an atmosphere that is weakly corrosive or only for the manufacture of products that do not require corrosion resistance. For these reasons, no free-cutting stainless steel product that satisfies both excellent machinability and corrosion resistance at the same time has been obtained.
However, as disclosed in
発明1により、優れた切削性と環境性のみならず耐食性も満足させることができた。 H-BN particles that are chemically stable and not affected by acids or alkalis are uniformly dispersed and precipitated, and h-BN, which has excellent characteristics as a solid lubricant, improves machinability and deteriorates corrosion resistance. We could provide no stainless steel cast steel product and its manufacturing method.
The
この発明の製造方法において、ステンレス鋼鋳鋼の溶解は、溶解雰囲気の調整が可能な、通常のステンレス鋼を溶製する溶解炉を使用して行われる。この溶解において、Bの原料としては、フェロボロンあるいは金属ボロンが使用されるが、溶融点の低いフェロボロンのほうが溶解原料としては技術的に有利であり、Bの単位重量当たりの価格が低いため経済的である。 The present invention has the features as described above, and an embodiment thereof will be described below.
In the production method of the present invention, the melting of the cast stainless steel is performed using a melting furnace for melting ordinary stainless steel, in which the melting atmosphere can be adjusted. In this melting, ferroboron or metal boron is used as the raw material for B. However, ferroboron having a low melting point is technically advantageous as the melting raw material, and economical because the price per unit weight of B is low. It is.
(1)鋳造後の冷却速度を制御する。
(2)金型鋳型を使用する。
(3)注湯位置、押湯形状等の鋳型の設計を考慮する。
などが考えられる。 In a cast stainless steel product, h-BN, which has grown coarsely to about 20 to 30 μm, may be unevenly distributed in a part of the material depending on the cooling rate during the cooling process after casting. To avoid this,
(1) Control the cooling rate after casting.
(2) Use a mold mold.
(3) Consider the mold design such as pouring position and shape of the feeder.
And so on.
この状態から急冷することにより、過飽和に固溶した状態のBとNを含有するステンレス鋼鋳鋼製品が得られる。急冷の操作は、通常のステンレス鋼に対して行われる水冷で構わないが、後述のh-BNを析出する温度範囲での冷却速度を、析出を起こさない冷却速度とする必要がある。 H-BN precipitated in stainless steel cast steel products decomposes into B and N at a temperature of 1200 ° C or higher for a relatively short time (for example, 0.5 to 1 hour at 1250 ° C). Solid solution in the cast steel matrix. In addition, since such a process is impossible when a cast stainless steel product is melted, it is necessary to process at a temperature lower than the melting temperature.
By rapidly cooling from this state, a cast stainless steel product containing B and N in a solid solution state in a supersaturated state is obtained. The quenching operation may be water cooling performed on ordinary stainless steel, but the cooling rate in the temperature range in which h-BN is deposited, which will be described later, needs to be a cooling rate that does not cause precipitation.
市販のオーステナイト系ステンレス鋼(SUS304)丸棒(重量18kg)を溶解原料として真空誘導溶解炉を用いて溶解した。溶解原料の成分組成(mass%)は、0.04%C、0.30%Si、1.00%Mn、0.030%P、0.024%S、8.09%Ni、18.05%Crであった。溶融時に真空誘導溶解炉にNを0.07MPa封入し、溶鋼中のN濃度の調整を行った。溶融後、溶湯に市販のフェロボロン(19.2mass%B)を所定量添加し、B濃度の調整を行い、弱減圧N雰囲気中で20分間保持し、1600℃で出湯し、鋳鉄鋳型に鋳込み、インゴットを製造した。開発材1~3は、B含有量の目標値を、それぞれ、0.02mass%、0.05mass%、0.1mass%とし、N含有量の目標値を0.2mass%としたものである。 Example 1
A commercially available austenitic stainless steel (SUS304) round bar (weight 18 kg) was melted as a melting raw material using a vacuum induction melting furnace. The component composition (mass%) of the melting raw material is 0.04% C, 0.30% Si, 1.00% Mn, 0.030% P, 0.024% S, 8.09% Ni, 18.05. % Cr. At the time of melting, 0.07 MPa of N was sealed in a vacuum induction melting furnace, and the N concentration in the molten steel was adjusted. After melting, a predetermined amount of commercially available ferroboron (19.2 mass% B) is added to the molten metal, the B concentration is adjusted, held in a weakly reduced N atmosphere for 20 minutes, heated at 1600 ° C., poured into a cast iron mold, An ingot was manufactured. In the developed
開発材4は、比較材1(SUS304鋳造材に相当)に比べ、中切削速度域では20%、高速切削域で11%も切削抵抗合力が低下し、切削性が大きく改善されている。
比較材2は、硫黄添加快削ステンレス鋼鋳鋼であり、これに比較すると、開発材の切削性は劣っているものの、耐食性が重要となる場合には、比較材2は使用できない。良好な切削性及び耐食性の双方を満足できるのは開発材だけであり、開発材の優位性は否定できない。 As a machinability evaluation test, FIG. 4 shows a result of a turning test performed on a round bar sample cut from a cast steel sample after heat treatment of the
Compared to Comparative Material 1 (corresponding to SUS304 cast material), the developed material 4 has a cutting force reduction of 20% in the medium cutting speed region and 11% in the high speed cutting region, and the machinability is greatly improved.
The comparative material 2 is a sulfur-added free-cutting stainless steel cast steel. Compared with this, the developed material is inferior in machinability, but the comparative material 2 cannot be used when corrosion resistance is important. Only the developed material can satisfy both good machinability and corrosion resistance, and the superiority of the developed material cannot be denied.
h-BN添加の有無による耐食性を比較すると、開発材4と比較材1との差はほとんど観察されず、耐食性の劣化は認められなかった。一方、比較材2では、腐食量が、開発材4、比較材1と比べて著しく増加しており、耐食性が要求される場合には、比較材2は使用できないことを示している。 As an evaluation test of the corrosion resistance of the stainless steel, the results of a corrosion resistance test performed on the sample after the heat treatment of the cast material are shown in FIG. Since N contributes to the corrosion resistance of stainless steel, a comparison was made for materials with the same N concentration level. FIG. 6 shows the result of the corrosion test by the sulfuric acid corrosion test method (JIS G 0591). The test conditions were immersed in boiling 5% H 2 SO 4 for 6 hours continuously, and compared with the amount of corrosion obtained by dividing the weight loss by the initial surface area of the sample.
When the corrosion resistance with and without h-BN was compared, the difference between the developed material 4 and the
Claims (7)
- 快削性付与材を添加してなるステンレス鋼鋳鋼製品であって、前記快削性付与材がh-BN(六方晶系窒化ホウ素)粒子であって、粒径が200nmから10μmの球状の前記h-BN粒子が鋼中に均一に分散析出していることを特徴とするステンレス鋼鋳鋼製品。 A stainless steel cast steel product to which a free-cutting property imparting material is added, wherein the free-cutting property imparting material is h-BN (hexagonal boron nitride) particles and has a spherical shape with a particle size of 200 nm to 10 μm. A cast stainless steel product characterized in that h-BN particles are uniformly dispersed and precipitated in the steel.
- 請求項1に記載のステンレス鋼鋳鋼製品の製造方法であって、鋳造凝固時の1250℃から850℃の温度域での冷却速度を制御し、h-BN粒子を分散析出させることを特徴とするステンレス鋼鋳鋼製品の製造方法。 2. The method for producing a cast stainless steel product according to claim 1, wherein the cooling rate is controlled in a temperature range of 1250 ° C. to 850 ° C. during casting solidification, and h-BN particles are dispersed and precipitated. Manufacturing method for stainless steel cast steel products.
- 請求項1に記載のステンレス鋼鋳鋼製品の製造方法であって、鋳造組織中にh-BN粒子が不均一に析出しているステンレス鋼を1200℃以上の温度まで加熱した後に急冷して、h-BN粒子を固溶消滅させ、その後950~1100℃の温度での焼もどし熱処理を行うことにより、h-BN粒子を再度分散析出させることを特徴とするステンレス鋼鋳鋼製品の製造方法。 The method for producing a cast stainless steel product according to claim 1, wherein the stainless steel in which h-BN particles are non-uniformly precipitated in the cast structure is heated to a temperature of 1200 ° C or higher and then rapidly cooled. A method for producing a cast stainless steel product, characterized in that h-BN particles are dispersed and precipitated again by eliminating solid solution of BN particles and then performing a tempering heat treatment at a temperature of 950 to 1100 ° C.
- 請求項1に記載のステンレス鋼鋳鋼製品の製造方法であって、鋳造凝固時の1250℃から850℃の温度域を急冷し、h-BN粒子が析出していない鋳造組織とした後、950~1100℃の温度での焼もどし熱処理を行うことにより、h-BN粒子を分散析出させることを特徴とするステンレス鋼鋳鋼製品の製造方法。 A method for producing a cast stainless steel product according to claim 1, wherein a temperature range from 1250 ° C. to 850 ° C. at the time of casting solidification is rapidly cooled to obtain a cast structure in which h-BN particles are not precipitated, A method for producing a cast stainless steel product, characterized in that h-BN particles are dispersed and precipitated by performing a tempering heat treatment at a temperature of 1100 ° C.
- 請求項2~4に記載のステンレス鋼鋳鋼製品の製造方法であって、B(ホウ素)の添加量が0.003~0.5mass%であり、N(窒素)の添加量については、モル比でN/Bが1以上にすることを特徴とするステンレス鋼鋳鋼製品の製造方法。 5. The method for producing a cast stainless steel product according to claim 2, wherein the addition amount of B (boron) is 0.003 to 0.5 mass%, and the addition amount of N (nitrogen) is a molar ratio. A method for producing a cast stainless steel product, wherein N / B is 1 or more.
- 請求項5に記載のステンレス鋼鋳鋼製品の製造方法であって、Bはフェロボロン又は金属ボロンの添加により、Nは溶解雰囲気を(アルゴン+窒素)あるいは減圧窒素とすることにより、ステンレス溶鋼に添加することを特徴とするステンレス鋼鋳鋼製品の製造方法。 6. The method for producing a cast stainless steel product according to claim 5, wherein B is added to the molten stainless steel by adding ferroboron or metal boron, and N is a molten atmosphere (argon + nitrogen) or reduced pressure nitrogen. A method for producing a cast stainless steel product characterized by the above.
- 請求項5に記載のステンレス鋼鋳鋼製品の製造方法であって、Bはフェロボロン又は金属ボロンの添加により、Nは窒素を含有する化合物又はフェロアロイの添加により、ステンレス溶鋼に添加することを特徴とするステンレス鋼鋳鋼製品の製造方法。 6. The method for producing a cast stainless steel product according to claim 5, wherein B is added to the molten stainless steel by addition of ferroboron or metal boron, and N is added by a nitrogen-containing compound or ferroalloy. Manufacturing method for stainless steel cast steel products.
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JP2014040645A (en) * | 2012-08-23 | 2014-03-06 | National Institute For Materials Science | Free-cutting iron based shape memory alloy |
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WO2022211930A1 (en) | 2021-03-31 | 2022-10-06 | Dow Technology Investments Llc | Hydroformylation processes |
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JP2003129191A (en) * | 2001-10-24 | 2003-05-08 | Nisshin Steel Co Ltd | Boron nitride-containing stainless steel material with free-machinability, and manufacturing method therefor |
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JP2003129191A (en) * | 2001-10-24 | 2003-05-08 | Nisshin Steel Co Ltd | Boron nitride-containing stainless steel material with free-machinability, and manufacturing method therefor |
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JP2014040645A (en) * | 2012-08-23 | 2014-03-06 | National Institute For Materials Science | Free-cutting iron based shape memory alloy |
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US9670122B2 (en) | 2013-09-26 | 2017-06-06 | Dow Technology Investments Llc | Hydroformylation process |
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