WO2011125901A1 - 常温靭性に優れたフェライト系耐熱鋳鋼及びそれからなる排気系部品 - Google Patents
常温靭性に優れたフェライト系耐熱鋳鋼及びそれからなる排気系部品 Download PDFInfo
- Publication number
- WO2011125901A1 WO2011125901A1 PCT/JP2011/058331 JP2011058331W WO2011125901A1 WO 2011125901 A1 WO2011125901 A1 WO 2011125901A1 JP 2011058331 W JP2011058331 W JP 2011058331W WO 2011125901 A1 WO2011125901 A1 WO 2011125901A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- phase
- cast steel
- resistant cast
- nbc
- heat
- Prior art date
Links
Images
Classifications
-
- 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
- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
-
- 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
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
-
- 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
- C21D6/002—Heat treatment of ferrous alloys containing Cr
-
- 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
-
- 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
-
- 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
-
- 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
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
-
- 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
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
-
- 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
- C21D2211/005—Ferrite
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
- F01N13/16—Selection of particular materials
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2530/00—Selection of materials for tubes, chambers or housings
Definitions
- the present invention relates to exhaust system parts for automobile gasoline engines and diesel engines, in particular, ferritic heat-resistant cast steels having excellent room temperature toughness suitable for exhaust manifolds, etc., and exhaust system parts comprising the same.
- heat-resistant cast iron such as high-Si spheroidal graphite cast iron and Ni-resist cast iron (Ni-Cr austenitic cast iron), ferritic heat-resistant cast steel, and austenitic heat-resistant cast steel Etc.
- Ferritic 4% Si-0.5% Mo spheroidal graphite cast iron shows relatively good heat resistance up to around 800 ° C, but is inferior in durability at temperatures above that.
- Heat-resistant cast iron such as Ni-resist cast iron and austenitic heat-resistant cast steel containing a large amount of rare metals such as Ni, Cr, and Co simultaneously satisfy oxidation resistance and heat crack resistance at 800 ° C or higher.
- Ni-resist cast iron is not only expensive because of its high Ni content, but also has a high coefficient of linear expansion due to the austenitic matrix structure, and the presence of graphite that is the starting point of fracture in the microstructure. Inferior to sex. Austenitic heat-resistant cast steel has no graphite as a starting point of fracture, but has a high coefficient of linear expansion, and therefore has insufficient heat cracking resistance near 900 ° C. In addition, since it contains a lot of rare metals, it is expensive, easily affected by the global economic situation, and there is concern about the stable supply of raw materials.
- heat-resistant cast steel for exhaust system parts it is desirable for heat-resistant cast steel for exhaust system parts to ensure necessary heat-resistant characteristics by suppressing the rare metal content as much as possible from the viewpoints of economy and stable supply of raw materials as well as effective utilization of resources.
- low-cost and high-performance exhaust system parts can be obtained, and fuel-saving technology can be applied to low-priced passenger cars, contributing to the reduction of CO 2 gas emissions.
- the ferritic heat-resistant cast steel has a smaller coefficient of linear expansion than the austenitic heat-resistant cast steel, the thermal stress generated upon starting and starting of the engine is small, and the heat-resistant crack resistance is excellent.
- Ferritic heat-resistant cast steel has poor toughness at room temperature because it contains a large amount of Cr for oxidation resistance. Exhaust system parts are subjected to mechanical vibrations and shocks during the production process and assembly process to the engine. Therefore, ferritic heat-resistant cast steel used for exhaust system parts needs to have sufficient room temperature toughness so that cracks and cracks do not occur even when mechanical vibrations and impacts occur.
- Japanese Patent Laid-Open No. 2007-254885 is mainly composed of Fe, 0.10 to 0.50 mass% C, 1.00 to 4.00 mass% Si, 0.10 to 3.00 mass% Mn, 8.0 to 30.0 mass% Cr, and 0.1 to 5.0 It is made of ferritic stainless cast steel containing Nb and / or V of mass%, has a thin part with a thickness of 1-5 mm, and the average crystal grain size of the ferrite phase in the structure of the thin part is 50-400 ⁇ m Discloses thin-walled cast parts with improved high-temperature strength. In the thin cast part, the thin part of 5 mm or less is rapidly cooled after casting, so that the average crystal grain size of the ferrite phase becomes small, and the yield strength at high temperature, tensile strength and elongation at break are high.
- the ferritic heat-resistant cast steel disclosed in JP 2007-254885 improves the fluidity of the melt by lowering the melting point due to the inclusion of a large amount of Si, as well as improving high-temperature strength, oxidation resistance, carburization resistance and machinability.
- Si since it contains a large amount of Si of 1.00 to 4.00 mass% (about 2% or more in the examples), Si dissolves in the ferrite matrix structure, and the room temperature toughness decreases.
- Japanese Patent Application Laid-Open No. 7-197209 describes 0.1 to 1.20% C by weight, 0.05 to 0.45% C-Nb / 8, 2% or less Si, 2% or less Mn, 16.0 to 25.0% Cr, 1.0 to It has a composition consisting of 5.0% W and / or Mo, 0.40 to 6.0% Nb, 0.1 to 2.0% Ni, 0.01 to 0.15% N, the balance Fe and inevitable impurities, and a normal ⁇ phase ( ⁇ ferrite) In addition to the phase), it has a phase ( ⁇ ′ phase) transformed from ⁇ phase (austenite phase) to ⁇ + carbide, and the area ratio ⁇ ′ / ( ⁇ + ⁇ ′) ⁇ of the ⁇ ′ phase is 20 to 70%.
- a ferritic heat-resistant cast steel having improved castability is disclosed. Since this ferritic heat-resistant cast steel contains more C (austenite element) than is necessary for the formation of NbC, a ⁇ phase is produced during solidification by C dissolved in the matrix structure, and during the cooling process the ⁇ phase becomes ⁇ ' It transforms into a phase, thereby improving ductility and oxidation resistance. Therefore, this ferritic heat-resistant cast steel is suitable for exhaust system parts used at 900 ° C. or higher.
- JP-A-11-61343 describes 0.05 to 1.00% C, 2% or less Si, 2% or less Mn, 16.0 to 25.0% Cr, 4.0 to 20.0% Nb, 1.0 to 5.0% W by weight ratio. And / or Mo, 0.1 to 2.0% Ni, 0.01 to 0.15% N, and the balance Fe and inevitable impurities, and having a Laves phase (Fe 2 M) in addition to the normal ⁇ phase
- a ferritic heat-resistant cast steel having excellent high-temperature strength, particularly creep rupture strength, is disclosed.
- This ferritic heat-resistant cast steel has a Laves phase due to the combination of Nb, W, Mo, Ni and N, thereby improving high-temperature strength, especially creep rupture strength. Toughness is not always sufficient.
- an object of the present invention is to provide an exhaust system component such as a ferritic heat resistant cast steel excellent in room temperature toughness and an exhaust manifold made of this ferritic heat resistant cast steel while ensuring oxidation resistance and heat cracking resistance near 900 ° C. Is to provide.
- the casting material When producing a thin and complex-shaped casting such as an exhaust system part, the casting material is required to have good hot water flowability.
- increasing the C content to lower the solidification start temperature is effective for improving the flow of molten metal, but simply increasing C increases the amount of Cr carbide precipitated or transforms into martensite. Toughness deteriorates due to phase crystallization.
- Nb needs to be increased together with C in order to improve the molten metal flowability while suppressing the decrease in toughness.
- the ⁇ phase consisting of a body-centered cubic (BCC) structure decreases the toughness when an alloying element is dissolved in the base structure for the purpose of improving the strength, etc., or a crystallized product or precipitate is formed.
- BCC body-centered cubic
- the content of C, Si, Nb, etc. is controlled within the desired range, and the optimal proportion of primary crystal ⁇ phase ( ⁇ ferrite phase) and eutectic ( ⁇ + NbC) phase of ⁇ phase and Nb carbide (NbC)
- ferritic heat-resistant cast steel having excellent room temperature toughness while ensuring oxidation resistance and heat cracking resistance near 900 ° C. can be obtained.
- the ferritic heat-resistant cast steel having excellent room temperature toughness has a mass ratio of 0.32 to 0.48% C, 0.85% or less of Si, Mn below 2%, Up to 1.5% Ni, 16 to 19.8% Cr, 3.2-5% Nb, 9 to 11.5 Nb / C, N of 0.15% or less, 0.002 to 0.2% S, and a total of 0.8% or less W and / or Mo And having a composition comprising the balance Fe and inevitable impurities, and having a structure in which the area ratio of the eutectic ( ⁇ + NbC) phase of ⁇ phase and Nb carbide (NbC) is 60 to 90% .
- the exhaust system part of the present invention is characterized by comprising the above-mentioned ferritic heat-resistant cast steel.
- the exhaust system parts include exhaust manifold, turbine housing, turbine housing integrated exhaust manifold, catalyst case, catalyst case integrated exhaust manifold, or exhaust outlet, especially exhaust manifold, catalyst case, catalyst case integrated exhaust manifold, exhaust outlet. Is preferred.
- the ferritic heat-resistant cast steel of the present invention has excellent room temperature toughness while ensuring oxidation resistance and heat cracking resistance near 900 ° C. without heat treatment, it is high performance and inexpensive. In addition, since the content of rare metals is suppressed, it contributes not only to reducing raw material costs but also to effective use and stable supply of resources. Exhaust system parts made of the ferritic heat-resistant cast steel of the present invention having such characteristics can be manufactured at low cost, thereby expanding the scope of application of fuel efficiency reduction technology and contributing to the reduction of CO 2 gas emissions from automobiles, etc. .
- FIG. 6 is an optical micrograph (100 ⁇ ) showing the microstructure of the ferritic heat-resistant cast steel of Example 8.
- 1 is a schematic diagram showing an ingot A of 1 inch Y block for cutting out a test piece.
- FIG. It is the schematic which shows the ingot B of the stepped Y block which cuts out a test piece.
- It is a graph which shows the relationship between Nb content and a normal temperature impact value.
- It is a graph which shows the relationship between Nb content and the area ratio of a eutectic ((delta) + NbC) phase.
- Ferritic heat-resistant cast steel The composition and structure of the ferritic heat-resistant cast steel of the present invention will be described in detail below. Note that “%” indicating the content of each element is “% by mass” unless otherwise specified.
- C (carbon): 0.32 to 0.48% C has an action of lowering the solidification start temperature to improve the fluidity of the molten metal, that is, the molten metal flowability (castability).
- C combines with Nb to form a eutectic ( ⁇ + NbC) phase of ⁇ phase and Nb carbide (NbC), and has the effect of increasing the high temperature strength.
- the C content needs to be 0.32% or more.
- the C content is set to 0.32 to 0.48%.
- the C content is preferably 0.32 to 0.45%, more preferably 0.32 to 0.44%, and most preferably 0.32 to 0.42%.
- Si 0.85% or less Si not only acts as a deoxidizer for molten metal but also improves oxidation resistance. However, when Si exceeds 0.85%, it dissolves in the ferrite of the base structure and causes the base structure to become brittle. Therefore, the Si content is 0.85% or less (excluding 0%).
- the Si content is preferably 0.2 to 0.85%, more preferably 0.3 to 0.85%, and most preferably 0.35 to 0.85%.
- Mn (manganese) 2% or less Mn is effective as a deoxidizer for molten metal, just like Si, but if it exceeds 2%, it degrades the oxidation resistance of ferritic heat-resistant cast steel. Therefore, the Mn content is 2% or less (excluding 0%). The Mn content is preferably 0.1 to 2%, more preferably 0.1 to 1.5%, and most preferably 0.2 to 1.2%.
- Ni is an austenite stabilizing element and forms a ⁇ phase. Austenite is transformed into martensite while it is cooled to room temperature, and martensite deteriorates room temperature toughness. Therefore, it is desirable that the Ni content is as low as possible. However, since Ni is usually contained in the raw material scrap material, it is inevitably mixed in the ferritic heat-resistant cast steel. Since the limit of Ni content that can prevent adverse effects on room temperature toughness is 1.5% or less, the Ni content is set to 0 to 1.5%. The Ni content is preferably 0 to 1.25%, more preferably 0 to 1.0%, and most preferably 0 to 0.9%.
- Cr 16 to 19.8% Cr is an element that improves oxidation resistance and stabilizes the ferrite structure. In order to ensure oxidation resistance near 900 ° C, Cr needs to be at least 16%. On the other hand, when the Cr content exceeds 19.8% in the ferrite base, sigma brittleness is likely to occur, the toughness is lowered, and the machinability is also deteriorated. Therefore, the Cr content is 16 to 19.8%.
- the Cr content is preferably 17 to 19.8%, more preferably 17 to 19.5%, and most preferably 17.5 to 19.0%.
- Nb (Niobium): 3.2-5% Nb combines with C to form a eutectic ( ⁇ + NbC) phase, improving the high-temperature strength and lowering the solidification start temperature.
- the decrease in the solidification start temperature improves the flowability of the hot water, which is important for the production of a thin and complex-shaped casting such as an exhaust system part.
- Nb also fixes C as crystallized carbide (NbC) during solidification, thus preventing C, a strong austenite stabilizing element, from dissolving in the ferrite of the base structure and crystallizing the ⁇ phase. Prevent toughness loss.
- Nb remarkably improves the room temperature toughness by refining the crystal grains of the primary crystal ⁇ phase and the eutectic ( ⁇ + NbC) phase.
- the Nb content needs to be 3.2% or more.
- the Nb content is set to 3.2 to 5%.
- the improvement effect of high temperature strength, molten metal flow and toughness by Nb can be almost achieved at about 4%, and since Nb is an expensive rare metal, the Nb content is preferably 3.2. It is ⁇ 4.0%.
- the Nb content is more preferably 3.2 to 3.9%, and most preferably 3.3 to 3.9%.
- Nb / C 9 to 11.5
- the regulation of the content ratio of Nb and C is most important for obtaining excellent room temperature toughness while ensuring oxidation resistance and thermal crack resistance near 900 ° C.
- Nb forms carbides with C, but if C is excessive (Nb / C ratio is small), excess C that did not form Nb carbides is dissolved in the base structure and the ⁇ phase is unstable. The ⁇ phase crystallizes out. The crystallized ⁇ phase transforms into martensite that lowers the room temperature toughness before reaching room temperature. If the Nb / C ratio is small, the growth of the primary ⁇ phase is promoted, so that the crystal grains of the primary ⁇ phase are not sufficiently refined and the toughness is not improved.
- An Nb / C ratio of 9 or more is required to refine the crystal grains of the primary crystal ⁇ phase and the eutectic ( ⁇ + NbC) phase while suppressing the crystallization of the ⁇ phase.
- the Nb / C ratio is 9 to 11.5.
- the Nb / C ratio is preferably 9 to 11.3, more preferably 9.3 to 11, and most preferably 9.5 to 10.5.
- N nitrogen
- N is a strong austenite stabilizing element and forms a ⁇ phase. While the ⁇ phase is cooled to room temperature, it becomes martensite and deteriorates room temperature toughness. Therefore, it is desirable that the N content is as low as possible, but N is inevitably mixed in the raw material scrap. Since the limit of N that does not adversely affect room temperature toughness is 0.15% or less, the N content is set to 0 to 0.15%.
- the N content is preferably 0 to 0.13%, more preferably 0 to 0.11%, and most preferably 0 to 0.10%.
- S produces spherical or massive sulfides in cast steel and improves the machinability by the lubricating action of the sulfides. To obtain this effect, S must be 0.002% or more. However, if S exceeds 0.2%, the room temperature toughness of the ferritic heat-resistant cast steel decreases. Therefore, the S content is set to 0.002 to 0.2%.
- the S content is preferably 0.005 to 0.2%, more preferably 0.008 to 0.2%, and most preferably 0.01 to 0.2%.
- the total content of W and / or Mo is preferably 0 to 0.6%, more preferably 0 to 0.5%, and most preferably 0 to 0.3%.
- controlling the crystallization amount of the eutectic ( ⁇ + NbC) phase of ⁇ phase and Nb carbide (NbC) is important for ensuring excellent room temperature toughness.
- a relatively large amount of eutectic ( ⁇ + NbC) phase solidifies after a relatively short time after the ⁇ phase first solidifies as a primary crystal.
- the primary crystal ⁇ phase is suppressed by the solidified eutectic ( ⁇ + NbC) phase, and growth of the eutectic ( ⁇ + NbC) phase is also suppressed by the solidified primary crystal ⁇ phase.
- the primary ⁇ phase and the eutectic ( ⁇ + NbC) phase suppress the growth of each other, so it is assumed that the crystal grains of the primary ⁇ phase and the eutectic ( ⁇ + NbC) phase are both refined and the toughness is significantly improved Is done.
- the area ratio of the eutectic ( ⁇ + NbC) phase needs to be 60 to 90%, assuming that the area of the entire structure is 100%.
- the area ratio of the eutectic ( ⁇ + NbC) phase is less than 60%, the crystal grains of the primary crystal ⁇ phase become coarse, and a significant improvement effect of room temperature toughness cannot be obtained.
- the area ratio of the eutectic ( ⁇ + NbC) phase exceeds 90%, the eutectic ( ⁇ + NbC) phase becomes excessive, the crystal grains become coarse and become brittle, and the toughness of the ferritic heat-resistant cast steel decreases.
- the area ratio of the eutectic ( ⁇ + NbC) phase is preferably 60 to 87%, more preferably 60 to 85%, and most preferably 60 to 80%.
- Exhaust system parts Preferred examples of the exhaust system parts of the present invention made of the above ferritic heat-resistant cast steel include an exhaust manifold, a turbine housing, a turbine housing integrated exhaust manifold in which the turbine housing and the exhaust manifold are integrally cast, a catalyst case,
- the catalyst case-integrated exhaust manifold and the exhaust outlet, which are integrally casted from the catalyst case and the exhaust manifold, are not limited to these, and include, for example, a cast member that is used by welding to a sheet metal or pipe member.
- Exhaust system parts of the present invention are exposed to exhaust gas at a high temperature of 1000 ° C or higher, and the surface temperature reaches around 900 ° C. However, high oxidation resistance and thermal crack resistance are maintained, and excellent heat resistance and durability are achieved. Demonstrate. Therefore, it is particularly suitable for an exhaust manifold, a catalyst case, a catalyst case integrated exhaust manifold, and an exhaust outlet that require oxidation resistance and heat crack resistance. Furthermore, since it has excellent room temperature toughness, cracks and cracks do not occur even when subjected to mechanical vibrations and impacts in the production process of exhaust system parts, the assembly process to the engine and the like. Moreover, since the content of rare metals is suppressed, it is inexpensive. In other words, the exhaust system parts of the present invention can be used for mass-produced vehicles that have high heat resistance and durability, and can be expanded in fuel efficiency technology because they are inexpensive, thereby reducing CO 2 gas emissions. It is expected to contribute greatly.
- Examples 1 to 20 and Comparative Examples 1 to 21 Table 1 shows the chemical compositions of the cast steels of Examples 1 to 20 and Comparative Examples 1 to 21.
- Examples 1 to 20 are ferritic heat-resistant cast steels within the composition range of the present invention, and Comparative Examples 1 to 18 are cast steels outside the composition range of the present invention.
- the cast steel of Comparative Example 19 is an example of a ferritic stainless cast steel described in JP-A-2007-254885
- the cast steel of Comparative Example 20 is an example of a ferritic heat-resistant cast steel described in JP-A-7-197209
- the cast steel 21 is an example of a ferritic heat-resistant cast steel described in JP-A-11-61343.
- each cast steel was melted in the atmosphere using a high-frequency melting furnace (basic lining) with a capacity of 100kg, it was poured out at 1600-1650 ° C and immediately poured into two molds at 1530-1560 ° C.
- a 1-inch Y block ingot A shown in FIG. 3 and a stepped Y block ingot B shown in FIG. 3 were cast.
- the dimensions of each ingot are shown in FIGS.
- a test piece was cut from a portion of about 30 mm from the bottom of the ingot A, and a test piece was cut from a portion of the ingot B having a thickness of 10 mm, and used for the following evaluation tests.
- a test piece with a width of 7.5 mm was cut out from a 10 mm thick part of ingot B to obtain a JIS ZZ2242 Charpy impact test piece without a notch.
- a Charpy impact tester with a capacity of 50 J an impact test was performed on three test pieces under the same conditions at 23 ° C. according to JIS Z 2242, and the measured impact values were averaged. Table 2 shows the impact test results.
- the room temperature impact value is preferably 15 ⁇ 10 4 J / m 2 or more in order to have excellent toughness so that cracks and cracks do not occur during the production process of exhaust system parts. All of Examples 1 to 20 had a normal temperature impact value of 15 ⁇ 10 4 J / m 2 or more.
- FIG. 4 shows the relationship between the Nb content and the room temperature impact value ( ⁇ 10 4 J / m 2 ) for the test pieces of Examples 4 to 7 and Comparative Examples 1 to 4 having an Nb / C ratio of about 10. As is apparent from FIG. 4, the impact temperature at room temperature was 15 ⁇ 10 4 J / m 2 or more when the Nb content was 3.2 to 5%. As is clear from FIG.
- the area ratio of the eutectic ( ⁇ + NbC) phase is 60 to 60% when the Nb content is 3.2 to 5%. 90%.
- the primary ⁇ phase and the eutectic ( ⁇ + NbC) phase coexist in an optimal ratio, so that the primary ⁇ phase and It is considered that the crystal grains of the eutectic ( ⁇ + NbC) phase are all refined and have a high normal temperature impact value.
- Comparative Example 9 is a solidification of the matrix structure in which the strong austenitizing element C is excessive and excessive C is dissolved. This is because the austenite produced sometimes transformed into martensite with low toughness during cooling to room temperature.
- Comparative Example 11 Nb with a large atomic radius is excessive, and excess Nb is dissolved in the ferrite matrix.
- Comparative Example 12 the Nb / C ratio was too large, and Nb was excessive as in Comparative Example 11.
- Comparative Examples 13 and 14 are because the Nb / C ratio was too small, and the strong austenitizing element C was surplus as in Comparative Example 9, and (9) Comparative Examples 15 and 16 were This is because the ferrite in the base structure has become brittle due to too much Si.
- Comparative Examples 17 and 18 there are too many W or Mo having a large atomic radius, and W or Mo is dissolved in the ferrite of the base structure. This is probably due to lattice distortion.
- Comparative Example 19 which is a ferritic stainless cast steel described in Japanese Patent Application Laid-Open No. 2007-254885 contains Si in a large amount of 2.8%, Si embrittles the ferrite of the base structure and has a low impact value.
- Comparative Example 20 which is a ferritic heat-resistant cast steel described in JP-A-7-197209, has a Nb / C ratio that is too small, so that the eutectic ( ⁇ + NbC) phase is insufficient and, as in Comparative Example 9, it is strong austenite. Element C is excessive and impact value is low.
- Comparative Example 21 which is a ferritic heat-resistant cast steel described in JP-A No.
- Comparative Example 5 with a low Cr content has a sufficient impact value, but has a large amount of oxidation loss and insufficient oxidation resistance.
- FIG. 1 shows the microstructure (100 times) of the ferritic heat-resistant cast steel of Example 8.
- the microstructure consists of a primary ⁇ phase 2 and a lamellar eutectic ( ⁇ + NbC) phase 1.
- the area ratio of the eutectic ( ⁇ + NbC) phase was 62%.
- Oxidation loss Exhaust system parts are exposed to oxidizing high-temperature exhaust gas containing nitrogen oxides and so on, so oxidation resistance is required.
- the temperature of the exhaust gas exhausted from the engine is about 1000 ° C, and the temperature of exhaust system parts such as the exhaust manifold and the catalyst case reaches nearly 900 ° C, so the oxidation resistance at 900 ° C was evaluated.
- As oxidation resistance a round bar-shaped test piece with a diameter of 10 mm and a length of 20 mm cut out from a portion of about 30 mm from the bottom of the ingot A was held at 900 ° C. for 200 hours in the atmosphere, and then shot blasted. Then, the oxidation scale was removed, and the mass change per unit area before and after the oxidation test, that is, the oxidation loss (mg / cm 2 ) was determined. Table 2 shows the measurement results of the weight loss.
- the oxidation loss of ferritic heat-resistant cast steel used for exhaust system parts that reach temperatures near 900 ° C. is 20 mg / cm 2 or less.
- the oxidation weight loss exceeds 20 mg / cm 2 the generation of an oxide film as a starting point of cracks increases, resulting in insufficient oxidation resistance.
- the ferritic heat-resistant cast steels of Examples 1 to 20 contain 16% or more of Cr, which is important for ensuring oxidation resistance. Therefore, the oxidation weight loss is all 20 mg / cm 2.
- High temperature strength and heat distortion resistance In general, the strength of metal materials decreases as the temperature rises, and thermal deformation easily occurs.
- Ferritic heat-resistant cast steel having a body-centered cubic (BCC) structure has lower high-temperature strength and heat-deformability than austenitic heat-resistant cast steel having a face-centered cubic (FCC) structure.
- the main factor affecting the high temperature strength and heat distortion resistance is the high temperature strength in addition to the shape and dimensions.
- the 0.2% proof stress at 900 ° C. is preferably 20 MPa or more.
- the 0.2% proof stress (high temperature proof stress) at 900 ° C. of Examples 1 to 20 was as high as 20 mm MPa or more.
- the high-temperature proof stress of Comparative Examples 1, 2, 8 and 10 having a low C and / or Nb content and Comparative Examples 13 and 14 having a small Nb / C ratio was less than 20 MPa.
- the area ratio of the eutectic ( ⁇ + NbC) phase Examples 1 to 20 were 60% or more, while Comparative Examples 1, 2, 8, 10, 13, and 14 were less than 60%. From this, it was found that not only toughness but also high temperature strength and heat distortion resistance are improved by crystallizing a relatively large amount of eutectic ( ⁇ + NbC) phase.
- Comparative Example 19 Since Comparative Example 19 has a low C content, the high temperature yield strength is high despite the lack of the eutectic ( ⁇ + NbC) phase. The reason for this is considered that Comparative Example 19 contains a large amount of Si. In addition, Comparative Example 20 has a high Nb content, so that the high-temperature proof stress is high despite the lack of the eutectic ( ⁇ + NbC) phase. The reason for this is considered that Comparative Example 20 contains a large amount of W.
- the ferritic heat-resistant cast steel of the present invention in which a large amount of eutectic ( ⁇ + NbC) phase is crystallized has a high-temperature strength equivalent to that of Comparative Examples 19 and 20 in which high-temperature strength is improved by containing a large amount of Si or W. .
- Thermal fatigue life Exhaust system parts are required to be resistant to thermal cracking (long thermal fatigue life) due to repeated operation (heating) and stop (cooling) of the engine. It can be said that the greater the number of cycles until thermal fatigue failure is caused by cracks and deformation caused by repeated heating and cooling, the longer the thermal fatigue life, and the better the heat resistance (heat crack resistance) and durability.
- thermal fatigue life After attaching a smooth round bar test piece (diameter: 10 mm, distance between gauge points: 20 mm) cut from a portion of approximately 30 mm from the bottom of ingot A to an electro-hydraulic servo type testing machine, Heating / cooling cycle in air, with a minimum cooling temperature of 150 ° C, a maximum heating temperature of 900 ° C, and a temperature amplitude of 750 ° C.
- the thermal fatigue life was measured by mechanically constraining the expansion and contraction accompanying heating and cooling to cause thermal fatigue failure. Thermal fatigue life is the cycle until the maximum tensile load drops to 75% with the maximum tensile load of the second cycle as the reference (100%) in the load-temperature diagram obtained from the load change due to repeated heating and cooling. It was a number. Table 2 shows the measurement results of the thermal fatigue life.
- the degree of mechanical restraint is expressed by a restraint rate defined by (free thermal expansion elongation ⁇ elongation under mechanical restraint) / (free thermal expansion elongation).
- the constraint ratio of 1.0 refers to a mechanical constraint condition that does not allow elongation at all when the test piece is heated from 150 ° C. to 900 ° C., for example.
- the restraint ratio of 0.5 means a mechanical restraint condition that allows only 1 mm of elongation when the free expansion and elongation is 2 mm, for example. Therefore, at a restraint factor of 0.5, a compressive load is applied during temperature rise, and a tensile load is applied during temperature drop. Since the restraint rate of exhaust system parts of an actual automobile engine is about 0.1 to 0.5 that allows a certain degree of elongation, the restraint rate is set to 0.5 here.
- the thermal fatigue life is 1000 cycles or more under the conditions of a heating upper limit temperature of 900 ° C, a temperature amplitude of 750 ° C or higher, and a constraint factor of 0.5. Is preferred. If the thermal fatigue life is 1000 cycles or more, it can be said that the ferritic heat resistant cast steel has excellent heat crack resistance. As can be seen from Table 2, the thermal fatigue lives of Examples 1 to 20 were all sufficiently long at 1400 cycles or more. From this, it can be seen that the ferritic heat resistant cast steel of the present invention has sufficient heat cracking resistance necessary for exhaust system parts reaching a temperature of around 900 ° C.
- the ferritic heat-resistant cast steel of the present invention has excellent heat resistance characteristics (oxidation resistance, high-temperature strength, heat distortion resistance, and heat crack resistance) required for exhaust system parts that reach temperatures near 900 ° C. Has room temperature toughness.
- Example 21 After casting an automotive exhaust manifold (main wall thickness: 4.0 to 6.0 mm) using the ferritic heat-resistant cast steel of Example 6, the mold release (unframe) process, casting design part (without heat treatment) Machine processing was performed through a cutting process of the weir part), a cleaning process by shot blasting, and a casting finishing process such as casting burr.
- the resulting exhaust manifold was free of cracks and cracks, and no casting defects such as shrinkage cavities, poor hot water, and gas defects were observed. In addition, there were no cutting defects in machining and abnormal wear and damage of the cutting tool.
- This exhaust manifold was assembled in an exhaust simulator equivalent to an inline 4-cylinder high-performance gasoline engine with a displacement of 2000 cc.
- Exhaust gas temperature at full load is about 1000 ° C at the exhaust manifold outlet (downstream of exhaust gas), exhaust manifold surface to investigate the life until through-crack generation and crack and oxidation occurrence
- An endurance test was conducted.
- the target for the heating and cooling cycle is 1200 cycles.
- the exhaust system part made of the ferritic heat-resistant cast steel of the present invention has high oxidation resistance and heat cracking resistance even near 900 ° C., and has excellent room temperature toughness.
- the exhaust system parts of the present invention are inexpensive because they are made of ferritic heat-resistant cast steel with a low content of rare metals, and contribute to the reduction of CO 2 gas emissions by expanding the scope of application of low fuel consumption technology.
- ferritic heat-resistant cast steel of the present invention is not limited to this, for example, combustion engines such as construction machines, ships, and aircraft, melting furnaces, etc. , Heat treatment furnaces, incinerators, kilns, boilers, cogeneration equipment and other thermal equipment, petrochemical plants, gas plants, thermal power plants, nuclear power plants, etc. It can also be used for various casting parts that require room temperature toughness as well as high performance.
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Combustion & Propulsion (AREA)
- General Engineering & Computer Science (AREA)
- Exhaust Silencers (AREA)
- Heat Treatment Of Articles (AREA)
Abstract
Description
0.32~0.48%のC、
0.85%以下のSi、
2%以下のMn、
1.5%以下のNi、
16~19.8%のCr、
3.2~5%のNb、
9~11.5のNb/C、
0.15%以下のN、
0.002~0.2%のS、及び
合計で0.8%以下のW及び/又はMo
を含有し、残部Fe及び不可避不純物からなる組成を有し、δ相とNb炭化物(NbC)との共晶(δ+NbC)相の面積率が60~90%である組織を有することを特徴とする。
本発明のフェライト系耐熱鋳鋼の組成及び組織を以下詳細に説明する。なお、各元素の含有量を示す「%」は特に断りのない限り「質量%」である。
(1) C(炭素):0.32~0.48%
Cは、凝固開始温度を降下させて溶湯の流動性、すなわち湯流れ性(鋳造性)を良くする作用を有する。またCはNbと結合してδ相とNb炭化物(NbC)との共晶(δ+NbC)相を形成し、高温強度を高める作用を有する。このような作用を有効に発揮するために、C含有量は0.32%以上必要である。しかし、C含有量が0.48%を超えると共晶(δ+NbC)相が多くなり過ぎて、フェライト系耐熱鋳鋼は脆化し、常温靭性が低下する。このため、C含有量は0.32~0.48%とする。C含有量は好ましくは0.32~0.45%であり、より好ましくは0.32~0.44%であり、最も好ましくは0.32~0.42%である。
Siは溶湯の脱酸剤としての作用する他、耐酸化性を改善する作用を有する。しかし、Siは0.85%を超えると基地組織のフェライトに固溶し、基地組織を著しく脆化させる。このため、Siの含有量は0.85%以下(0%を含まず)とする。Si含有量は好ましくは0.2~0.85%であり、より好ましくは0.3~0.85%であり、最も好ましくは0.35~0.85%である。
Mnは、Siと同様に溶湯の脱酸剤として有効であるが、2%を超えるとフェライト系耐熱鋳鋼の耐酸化性を劣化させる。このため、Mn含有量は2%以下(0%を含まず)とする。Mn含有量は好ましくは0.1~2%であり、より好ましくは0.1~1.5%であり、最も好ましくは0.2~1.2%である。
Niはオーステナイト安定化元素でγ相を形成し、オーステナイトは常温まで冷却される間にマルテンサイトに変態し、マルテンサイトは常温靭性を悪化させる。従って、Ni含有量は極力少ないのが望ましいが、Niは通常原料スクラップ材に含有されているので、不可避的にフェライト系耐熱鋳鋼に混入する。常温靭性への悪影響を防止し得るNi含有量の限界は1.5%以下であるので、Ni含有量を0~1.5%とする。Ni含有量は好ましくは0~1.25%であり、より好ましくは0~1.0%であり、最も好ましくは0~0.9%である。
Crは耐酸化性を改善し、フェライト組織を安定にする元素である。900℃付近での耐酸化性を確保するために、Crは少なくとも16%必要である。一方、フェライト基地においてCrが19.8%超になると、シグマ脆性が発生しやすくなって靭性が低下し、被削性も悪化する。そのため、Cr含有量は16~19.8%とする。Cr含有量は好ましくは17~19.8%であり、より好ましくは17~19.5%であり、最も好ましくは17.5~19.0%である。
NbはCと結合して共晶(δ+NbC)相を形成し、高温強度を向上させるとともに、凝固開始温度を低下させる。凝固開始温度の低下により、排気系部品のような薄肉で複雑形状の鋳物の製造に重要な湯流れ性が向上する。またNbは、凝固時に晶出炭化物(NbC)としてCを固定するので、強力なオーステナイト安定化元素であるCが基地組織のフェライトに固溶してγ相を晶出するのを防止し、もって靭性の低下を防止する。またNbは、初晶δ相及び共晶(δ+NbC)相の結晶粒の微細化により、常温靭性を著しく向上させる。Nbの上記効果を発揮するために、Nb含有量は3.2%以上が必要である。しかし、Nbが5%を超えると、共晶(δ+NbC)相の晶出量が過剰となり、フェライト系耐熱鋳鋼は脆化する。従って、Nb含有量は3.2~5%とする。なお、本発明のフェライト系耐熱鋳鋼においてNbによる高温強度、湯流れ性及び靭性の向上効果は約4%でほぼ達成でき、またNbは高価な希少金属であるので、Nb含有量は好ましくは3.2~4.0%である。Nb含有量はより好ましくは3.2~3.9%であり、最も好ましくは3.3~3.9%である。
NbとCの含有量比(Nb/C)の規制は、900℃付近での耐酸化性及び耐熱亀裂性を確保しつつ優れた常温靭性を得るために最も重要である。NbはCと炭化物を形成するが、Cが過剰であると(Nb/C比が小さいと)、Nb炭化物を形成しなかった余剰のCは基地組織に固溶し、δ相が不安定となってγ相が晶出する。晶出したγ相は常温に達するまでに常温靭性を低下させるマルテンサイトに変態する。またNb/C比が小さいと、初晶δ相の成長が促進されるので、初晶δ相の結晶粒の微細化が不十分となり、靭性が向上しない。γ相の晶出を抑制しつつ初晶δ相と共晶(δ+NbC)相の結晶粒を微細化するには、Nb/C比は9以上必要である。
Nは強力なオーステナイト安定化元素であり、γ相を形成する。γ相は常温まで冷却される間にマルテンサイト化して、常温靭性を悪化させる。そのため、N含有量は極力少ない方が望ましいが、Nは原料スクラップに不可避的に混入している。常温靭性への悪影響が出ないNの限界は0.15%以下であるので、N含有量を0~0.15%とする。N含有量は好ましくは0~0.13%であり、より好ましくは0~0.11%であり、最も好ましくは0~0.10%である。
Sは鋳鋼中で球状又は塊状の硫化物を生成し、硫化物の潤滑作用により被削性を向上させる。この効果を得るには、Sは0.002%以上必要である。しかし、Sが0.2%を超えると、フェライト系耐熱鋳鋼の常温靭性が低下する。そのため、S含有量は0.002~0.2%とする。S含有量は好ましくは0.005~0.2%であり、より好ましくは0.008~0.2%であり、最も好ましくは0.01~0.2%である。
W及びMoは基地組織のδ相に固溶して、フェライト基地に格子歪みを与え、常温靭性を悪化させるので、極力少ない方が望ましい。しかし、W及びMoは通常原料スクラップに含有されている。W及びMoがともに含有されている場合、それらの合計(W+Mo)含有量が0.8%を超えると、粗大な炭化物が生成し、常温靭性が低下する。従って、W及び/又はMoの含有量を合計で0~0.8%とする。W及び/又はMoの含有量は合計で好ましくは0~0.6%であり、より好ましくは0~0.5%であり、最も好ましくは0~0.3%である。
本発明のフェライト系耐熱鋳鋼においてδ相とNb炭化物(NbC)との共晶(δ+NbC)相の晶出量を制御することは、優れた常温靭性を確保するうえで重要である。本発明のフェライト系耐熱鋳鋼の鋳造時の凝固では、δ相が先に初晶として凝固した後比較的短時間後に、比較的多量の共晶(δ+NbC)相が凝固する。凝固した共晶(δ+NbC)相により初晶δ相の成長は抑制され、また共晶(δ+NbC)相の成長も凝固した初晶δ相により抑制される。このように初晶δ相及び共晶(δ+NbC)相が相互に成長を抑制し合うので、初晶δ相と共晶(δ+NbC)相の結晶粒はいずれも微細化し、靭性が著しく向上すると推測される。この効果を得るには、組織全体の面積を100%として、共晶(δ+NbC)相の面積率は60~90%である必要がある。共晶(δ+NbC)相の面積率が60%未満では、初晶δ相の結晶粒が粗大となり、常温靭性の大幅な向上効果が得られない。共晶(δ+NbC)相の面積率が90%を超えると、共晶(δ+NbC)相が過剰となり、その結晶粒が粗大するとともに脆化し、フェライト系耐熱鋳鋼の靭性は低下する。共晶(δ+NbC)相の面積率を60~90%に制御するには、C及びNbの含有量及びNb/C比を上記範囲に規制する必要がある。共晶(δ+NbC)相の面積率は好ましくは60~87%であり、より好ましくは60~85%であり、最も好ましくは60~80%である。
上記フェライト系耐熱鋳鋼からなる本発明の排気系部品の好ましい例は、エキゾーストマニホールド、タービンハウジング、タービンハウジングとエキゾーストマニホールドとを一体に鋳造したタービンハウジング一体エキゾーストマニホールド、触媒ケース、触媒ケースとエキゾーストマニホールドとを一体に鋳造した触媒ケース一体エキゾーストマニホールド、及びエキゾーストアウトレットであるが、これらに限定されず、例えば板金製又はパイプ製の部材と溶接して使用される鋳物部材も含む。
実施例1~20及び比較例1~21の鋳鋼の化学組成を表1に示す。実施例1~20は本発明の組成範囲内のフェライト系耐熱鋳鋼であり、比較例1~18は本発明の組成範囲外の鋳鋼である。比較例1及び2ではC及びNbの含有量が少なすぎ、比較例3及び4の鋳鋼はC及びNbの含有量が多すぎ、比較例5の鋳鋼はCr含有量が少なすぎ、比較例6及び7の鋳鋼はCr含有量が多すぎ、比較例8の鋳鋼はC含有量が少なすぎ、比較例9の鋳鋼はC含有量が多すぎ、比較例10の鋳鋼はNb含有量が少なすぎ、比較例11の鋳鋼はNb含有量が多すぎ、比較例12の鋳鋼はNb/C比が大きすぎ、比較例13及び14の鋳鋼はNb/C比が小さすぎ、比較例15及び16の鋳鋼はSi含有量が多すぎ、比較例17の鋳鋼はW含有量が多すぎ、比較例18の鋳鋼はMo含有量が多すぎる。比較例19の鋳鋼は特開2007-254885号に記載のフェライト系ステンレス鋳鋼の一例であり、比較例20の鋳鋼は特開平7-197209号に記載のフェライト系耐熱鋳鋼の一例であり、比較例21の鋳鋼は特開平11-61343号に記載のフェライト系耐熱鋳鋼の一例である。
常温靭性を評価するため、シャルピー衝撃試験による衝撃値を測定した。靭性の評価に引張伸び(延性)を測定することもあるが、機械的振動及び衝撃に対する抵抗力(亀裂及び割れの発生しにくさ)を評価するには、伸びではなく亀裂の進展速度が速い割れに対する感受性を評価した方が実態に則している。従って、引張試験より亀裂の進展速度が速いシャルピー衝撃試験により、靭性を評価した。
衝撃試験実施後の各試験片の端部から切り出したサンプルを鏡面研磨し、腐食エッチング処理した後、倍率100倍の光学顕微鏡により任意の5視野の写真を撮り、画像解析により共晶(δ+NbC)相の面積率を測定し、平均した。共晶(δ+NbC)相の面積率を表2に示す。図1は実施例8のフェライト系耐熱鋳鋼のミクロ組織(100倍)を示す。ミクロ組織は初晶δ相2と、ラメラー状の共晶(δ+NbC)相1とからなる。実施例8では、共晶(δ+NbC)相の面積率は62%であった。
排気系部品は、窒素酸化物等を含む酸化性の高温の排気ガスに曝されるため、耐酸化性が要求される。エンジンから排出される排気ガスの温度は約1000℃であり、エキゾーストマニホールドや触媒ケース等の排気系部品の温度は900℃近くに達するので、900℃における耐酸化性を評価した。耐酸化性として、インゴットAの底面から約30 mmの部分から切り出した直径10 mm及び長さ20 mmの丸棒状の試験片を大気中で900℃に200時間保持した後、ショットブラスト処理を施して酸化スケールを除去し、酸化試験前後の単位面積当たりの質量変化、すなわち酸化減量(mg/cm2)を求めた。酸化減量の測定結果を表2に示す。
一般に金属材料は高温になるほど強度が低下し、熱変形しやすくなる。体心立方晶(BCC)構造のフェライト系耐熱鋳鋼は、面心立方晶(FCC)構造のオーステナイト系耐熱鋳鋼より高温強度及び耐熱変形性が低い。高温強度及び耐熱変形性に影響を及ぼす主な要因として、形状や寸法の他に高温耐力がある。900℃付近の温度に到達する排気系部品に使用するには、900℃における0.2%耐力が20 MPa以上であるのが好ましい。
排気系部品は、エンジンの運転(加熱)と停止(冷却)の繰り返しにより熱亀裂を生じにくい(熱疲労寿命が長い)ことが要求される。加熱冷却の繰り返しにより生じる亀裂や変形により熱疲労破壊に至るまでのサイクル数が多いほど熱疲労寿命が長く、耐熱性(耐熱亀裂性)及び耐久性に優れていると言える。
実施例6のフェライト系耐熱鋳鋼を用いて自動車用エキゾーストマニホルド(主要肉厚4.0~6.0 mm)を鋳造した後、熱処理を施さず鋳放しのまま、型ばらし(解枠)工程、鋳造方案部(堰部)の切断工程、ショットブラストによる清浄工程、及び鋳バリ等の鋳仕上げ工程を経て、機械加工を施した。得られたエキゾーストマニホルドには、亀裂及び割れは発生しておらず、引け巣、湯廻り不良、ガス欠陥等の鋳造欠陥も認められなかた。また機械加工での切削不具合や切削工具の異常摩耗、損傷等もなかった。
Claims (2)
- 質量比で、
0.32~0.48%のC、
0.85%以下のSi、
2%以下のMn、
1.5%以下のNi、
16~19.8%のCr、
3.2~5%のNb、
9~11.5のNb/C、
0.15%以下のN、
0.002~0.2%のS、及び
合計で0.8%以下のW及び/又はMo
を含有し、残部Fe及び不可避的不純物からなる組成を有し、δ相とNb炭化物(NbC)との共晶(δ+NbC)相の面積率が60~90%である組織を有することを特徴とする常温靭性に優れたフェライト系耐熱鋳鋼。 - 請求項1に記載の常温靭性に優れたフェライト系耐熱鋳鋼からなる排気系部品。
Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CN201180016272.5A CN102822370B (zh) | 2010-03-31 | 2011-03-31 | 常温韧性优异的铁素体系耐热铸钢和由其构成的排气系统零件 |
EP11765801.3A EP2554703B8 (en) | 2010-03-31 | 2011-03-31 | Ferrite heat-resistant cast steel having excellent normal-temperature toughness and exhaust system component formed from the same |
US13/637,927 US8900510B2 (en) | 2010-03-31 | 2011-03-31 | Heat-resistant, ferritic cast steel having excellent room-temperature toughness, and exhaust member made thereof |
JP2012509611A JP5626338B2 (ja) | 2010-03-31 | 2011-03-31 | 常温靭性に優れたフェライト系耐熱鋳鋼及びそれからなる排気系部品 |
KR1020127028477A KR101745927B1 (ko) | 2010-03-31 | 2011-03-31 | 상온 인성이 우수한 페라이트계 내열 주강 및 그것으로 이루어진 배기계 부품 |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2010081710 | 2010-03-31 | ||
JP2010-081710 | 2010-03-31 | ||
JP2010-194543 | 2010-08-31 | ||
JP2010194543 | 2010-08-31 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2011125901A1 true WO2011125901A1 (ja) | 2011-10-13 |
Family
ID=44762839
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP2011/058331 WO2011125901A1 (ja) | 2010-03-31 | 2011-03-31 | 常温靭性に優れたフェライト系耐熱鋳鋼及びそれからなる排気系部品 |
Country Status (6)
Country | Link |
---|---|
US (1) | US8900510B2 (ja) |
EP (1) | EP2554703B8 (ja) |
JP (1) | JP5626338B2 (ja) |
KR (1) | KR101745927B1 (ja) |
CN (1) | CN102822370B (ja) |
WO (1) | WO2011125901A1 (ja) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR20150065870A (ko) * | 2012-10-10 | 2015-06-15 | 히타치 긴조쿠 가부시키가이샤 | 피삭성이 우수한 페라이트계 내열 주강 및 그것으로 이루어지는 배기계 부품 |
JP2018197391A (ja) * | 2017-05-24 | 2018-12-13 | 大同特殊鋼株式会社 | メッキ浴用フェライト系ステンレス鋼 |
CN112143981A (zh) * | 2020-09-29 | 2020-12-29 | 泰州鑫宇精工股份有限公司 | 一种高强度耐热钢汽车用铸件制备方法 |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN103820739B (zh) * | 2014-02-28 | 2017-10-27 | 中车戚墅堰机车车辆工艺研究所有限公司 | 铁素体耐热铸钢及其制备方法和应用 |
KR102255111B1 (ko) * | 2019-07-31 | 2021-05-24 | 주식회사 포스코 | 내식성이 우수한 배기계용 페라이트계 강판 |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5348916A (en) * | 1976-10-15 | 1978-05-02 | Toyota Motor Corp | Free cutting heat-and corrosion resistant cast steel |
JPH04218645A (ja) * | 1990-03-27 | 1992-08-10 | Hitachi Metals Ltd | 熱疲労寿命に優れたフェライト系耐熱鋳鋼 |
JPH07197209A (ja) | 1993-11-25 | 1995-08-01 | Hitachi Metals Ltd | 鋳造性の優れたフェライト系耐熱鋳鋼およびそれからなる排気系部品 |
JPH1161343A (ja) | 1997-08-11 | 1999-03-05 | Hitachi Metals Ltd | 高温強度とくにクリープ破断強度の優れたフェライト系耐熱鋳鋼およびそれからなる排気系部品 |
JP2002309935A (ja) * | 2001-02-08 | 2002-10-23 | Hitachi Metals Ltd | 耐熱鋳鋼製排気系部品 |
JP2007254885A (ja) | 2006-02-23 | 2007-10-04 | Daido Steel Co Ltd | 薄肉鋳物部品及びその製造方法 |
Family Cites Families (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2225730A (en) * | 1939-08-15 | 1940-12-24 | Percy A E Armstrong | Corrosion resistant steel article comprising silicon and columbium |
US3029171A (en) * | 1959-03-23 | 1962-04-10 | Atlas Steels Ltd | Age hardening of stainless steels with niobium silicides |
US3963532A (en) * | 1974-05-30 | 1976-06-15 | E. I. Du Pont De Nemours And Company | Fe, Cr ferritic alloys containing Al and Nb |
JPH05140700A (ja) * | 1991-11-15 | 1993-06-08 | Mazda Motor Corp | フエライト系耐熱鋳鋼部材及びその製造法 |
US5582657A (en) | 1993-11-25 | 1996-12-10 | Hitachi Metals, Ltd. | Heat-resistant, ferritic cast steel having high castability and exhaust equipment member made thereof |
EP1826288B1 (en) * | 2006-02-23 | 2012-04-04 | Daido Tokushuko Kabushiki Kaisha | Ferritic stainless steel cast iron, cast part using the ferritic stainless steel cast iron, and process for producing the cast part |
JP5178157B2 (ja) * | 2007-11-13 | 2013-04-10 | 日新製鋼株式会社 | 自動車排ガス経路部材用フェライト系ステンレス鋼材 |
CN101403073B (zh) * | 2008-11-14 | 2010-06-02 | 济南济钢铁合金厂 | 自生碳化物粒子强化铁素体耐热钢的制造方法 |
JP5862570B2 (ja) * | 2010-10-01 | 2016-02-16 | 日立金属株式会社 | 優れた湯流れ性、耐ガス欠陥性、靭性及び被削性を有するフェライト系耐熱鋳鋼、及びそれからなる排気系部品 |
DE102012002637B4 (de) * | 2012-02-10 | 2014-01-02 | Faurecia Emissions Control Technologies, Germany Gmbh | Abgasanlage |
-
2011
- 2011-03-31 EP EP11765801.3A patent/EP2554703B8/en active Active
- 2011-03-31 US US13/637,927 patent/US8900510B2/en active Active
- 2011-03-31 KR KR1020127028477A patent/KR101745927B1/ko active IP Right Grant
- 2011-03-31 WO PCT/JP2011/058331 patent/WO2011125901A1/ja active Application Filing
- 2011-03-31 CN CN201180016272.5A patent/CN102822370B/zh active Active
- 2011-03-31 JP JP2012509611A patent/JP5626338B2/ja active Active
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5348916A (en) * | 1976-10-15 | 1978-05-02 | Toyota Motor Corp | Free cutting heat-and corrosion resistant cast steel |
JPH04218645A (ja) * | 1990-03-27 | 1992-08-10 | Hitachi Metals Ltd | 熱疲労寿命に優れたフェライト系耐熱鋳鋼 |
JPH07197209A (ja) | 1993-11-25 | 1995-08-01 | Hitachi Metals Ltd | 鋳造性の優れたフェライト系耐熱鋳鋼およびそれからなる排気系部品 |
JPH1161343A (ja) | 1997-08-11 | 1999-03-05 | Hitachi Metals Ltd | 高温強度とくにクリープ破断強度の優れたフェライト系耐熱鋳鋼およびそれからなる排気系部品 |
JP2002309935A (ja) * | 2001-02-08 | 2002-10-23 | Hitachi Metals Ltd | 耐熱鋳鋼製排気系部品 |
JP2007254885A (ja) | 2006-02-23 | 2007-10-04 | Daido Steel Co Ltd | 薄肉鋳物部品及びその製造方法 |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR20150065870A (ko) * | 2012-10-10 | 2015-06-15 | 히타치 긴조쿠 가부시키가이샤 | 피삭성이 우수한 페라이트계 내열 주강 및 그것으로 이루어지는 배기계 부품 |
CN104718304A (zh) * | 2012-10-10 | 2015-06-17 | 日立金属株式会社 | 切削性优异的铁素体系耐热铸钢和由其构成的排气系统部件 |
EP2907885A4 (en) * | 2012-10-10 | 2016-07-13 | Hitachi Metals Ltd | HEAT-RESISTANT FERRITIC MOLDED STEEL WITH EXCELLENT MACHINING CAPACITY AND EXHAUST COMPONENT THEREOF |
US9758851B2 (en) | 2012-10-10 | 2017-09-12 | Hitachi Metals, Ltd. | Heat-resistant, cast ferritic steel having excellent machinability and exhaust member made thereof |
KR102087129B1 (ko) | 2012-10-10 | 2020-03-10 | 히타치 긴조쿠 가부시키가이샤 | 피삭성이 우수한 페라이트계 내열 주강 및 그것으로 이루어지는 배기계 부품 |
JP2018197391A (ja) * | 2017-05-24 | 2018-12-13 | 大同特殊鋼株式会社 | メッキ浴用フェライト系ステンレス鋼 |
CN112143981A (zh) * | 2020-09-29 | 2020-12-29 | 泰州鑫宇精工股份有限公司 | 一种高强度耐热钢汽车用铸件制备方法 |
Also Published As
Publication number | Publication date |
---|---|
CN102822370B (zh) | 2014-09-03 |
JPWO2011125901A1 (ja) | 2013-07-11 |
JP5626338B2 (ja) | 2014-11-19 |
US8900510B2 (en) | 2014-12-02 |
EP2554703B1 (en) | 2018-08-08 |
US20130022489A1 (en) | 2013-01-24 |
KR20130012957A (ko) | 2013-02-05 |
EP2554703A4 (en) | 2017-10-04 |
CN102822370A (zh) | 2012-12-12 |
EP2554703B8 (en) | 2018-10-31 |
EP2554703A1 (en) | 2013-02-06 |
KR101745927B1 (ko) | 2017-06-12 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
JP4985941B2 (ja) | 高Cr高Niオーステナイト系耐熱鋳鋼及びそれからなる排気系部品 | |
JP5353716B2 (ja) | オーステナイト系耐熱鋳鋼及びそれからなる排気系部品 | |
JP5862570B2 (ja) | 優れた湯流れ性、耐ガス欠陥性、靭性及び被削性を有するフェライト系耐熱鋳鋼、及びそれからなる排気系部品 | |
JPWO2005007914A1 (ja) | オーステナイト系耐熱球状黒鉛鋳鉄 | |
JP5626338B2 (ja) | 常温靭性に優れたフェライト系耐熱鋳鋼及びそれからなる排気系部品 | |
KR102453685B1 (ko) | 열피로 특성이 우수한 오스테나이트계 내열 주강 및 그것으로 이루어지는 배기계 부품 | |
JP6160625B2 (ja) | 被削性に優れたフェライト系耐熱鋳鋼及びそれからなる排気系部品 | |
JP6098637B2 (ja) | 被削性に優れたオーステナイト系耐熱鋳鋼及びそれからなる排気系部品 |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
WWE | Wipo information: entry into national phase |
Ref document number: 201180016272.5 Country of ref document: CN |
|
121 | Ep: the epo has been informed by wipo that ep was designated in this application |
Ref document number: 11765801 Country of ref document: EP Kind code of ref document: A1 |
|
WWE | Wipo information: entry into national phase |
Ref document number: 2012509611 Country of ref document: JP |
|
WWE | Wipo information: entry into national phase |
Ref document number: 13637927 Country of ref document: US |
|
NENP | Non-entry into the national phase |
Ref country code: DE |
|
WWE | Wipo information: entry into national phase |
Ref document number: 8612/DELNP/2012 Country of ref document: IN |
|
WWE | Wipo information: entry into national phase |
Ref document number: 2011765801 Country of ref document: EP |
|
ENP | Entry into the national phase |
Ref document number: 20127028477 Country of ref document: KR Kind code of ref document: A |