WO2011013193A1 - Egrクーラー用フェライト系ステンレス鋼およびegrクーラー - Google Patents
Egrクーラー用フェライト系ステンレス鋼およびegrクーラー Download PDFInfo
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- WO2011013193A1 WO2011013193A1 PCT/JP2009/063370 JP2009063370W WO2011013193A1 WO 2011013193 A1 WO2011013193 A1 WO 2011013193A1 JP 2009063370 W JP2009063370 W JP 2009063370W WO 2011013193 A1 WO2011013193 A1 WO 2011013193A1
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- egr cooler
- brazing
- stainless steel
- ferritic stainless
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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
- C22C38/001—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
- C22C38/04—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
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
- F02M26/11—Manufacture or assembly of EGR systems; Materials or coatings specially adapted for EGR systems
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
- F02M26/13—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
- F02M26/22—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with coolers in the recirculation passage
- F02M26/29—Constructional details of the coolers, e.g. pipes, plates, ribs, insulation or materials
- F02M26/32—Liquid-cooled heat exchangers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
- F28D7/00—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall
- F28D7/16—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being arranged in parallel spaced relation
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F21/00—Constructions of heat-exchange apparatus characterised by the selection of particular materials
- F28F21/08—Constructions of heat-exchange apparatus characterised by the selection of particular materials of metal
- F28F21/081—Heat exchange elements made from metals or metal alloys
- F28F21/082—Heat exchange elements made from metals or metal alloys from steel or ferrous alloys
- F28F21/083—Heat exchange elements made from metals or metal alloys from steel or ferrous alloys from stainless steel
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F9/00—Casings; Header boxes; Auxiliary supports for elements; Auxiliary members within casings
- F28F9/02—Header boxes; End plates
- F28F2009/0285—Other particular headers or end plates
- F28F2009/029—Other particular headers or end plates with increasing or decreasing cross-section, e.g. having conical shape
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/12—Improving ICE efficiencies
Definitions
- This invention relates to the ferritic stainless steel used as a member which comprises an EGR cooler, and the EGR cooler comprised using the member.
- EGR exhaust Gas Recirculation exhaust gas recirculation
- the EGR cooler In the EGR system, a device for cooling the exhaust gas to a temperature at which it can be circulated is required. This is the EGR cooler.
- FIG. 1 and 2 schematically illustrate the structure of a general EGR cooler.
- a section partitioned by two partition plates is provided in a part of the exhaust gas flow path formed by the outer cylinder, and a heat exchanger that releases heat to the cooling water is configured in the section.
- This section partitioned by the partition plate is referred to herein as a “heat exchange section”.
- a vent pipe is joined to the partition plate at a location where a hole is provided, and exhaust gas flows through the vent pipe in the heat exchange section. Cooling water flows around the vent pipe.
- the EGR cooler is composed of a metal member such as an outer cylinder, a partition plate, a vent pipe, or a fin in the vent pipe, and these members are joined by brazing.
- the exhaust gas temperature on the side where the heat exchange section is entered may reach a maximum of about 800 ° C.
- the temperature on the outlet side may reach a maximum of about 200 ° C. Therefore, Cu brazing used for assembling a general heat exchanger has durability. Run short. Accordingly, Ni brazing (BNi-5, BNi-6, etc. of JIS Z3265) that is excellent in high temperature oxidation resistance and high temperature strength is applied to the EGR cooler.
- the metal member constituting the EGR cooler is required to have the following characteristics.
- Ni brazing property is good.
- (3) Corrosion resistance to LLC (long life coolant; for example, ethylene glycol) is good. This is because LLC is usually added to the cooling water of EGR.
- High temperature strength and high temperature oxidation resistance are good. This is because the EGR cooler is exposed to high-temperature exhaust gas.
- (5) Good corrosion resistance against condensation of condensed water This is because in the EGR cooler, condensation tends to occur near the exhaust gas outlet side during operation, and condensation tends to occur at the exhaust gas contact location after operation.
- austenitic stainless steel represented by SUS304 and SUS316 is mainly used as the metal member constituting the EGR cooler.
- austenitic stainless steel has a large coefficient of thermal expansion, the oxide scale generated at high temperature is liable to peel off during cooling and flow into the engine, or thermal fatigue failure due to repeated heating and cooling is likely to occur. Further improvement in high temperature strength is also desired.
- the material cost is high because a large amount of expensive Ni is contained.
- ferritic stainless steel has a thermal expansion coefficient smaller than that of austenitic steel, and the material cost is generally lower than that of austenitic steel.
- Ferritic stainless steel is frequently used for exhaust manifolds and mufflers that constitute the exhaust gas path.
- it is necessary to expose the material to a high temperature such as 1100 ° C. or higher. At such high temperatures, ferritic stainless steel usually causes coarsening of crystal grains and tends to reduce toughness.
- Patent Document 1 discloses ferritic stainless steel for heat exchangers with good brazing properties. However, as for brazing, Cu brazing is assumed, and improvement of Ni brazing and suppression of crystal grain coarsening at that time are not intended.
- the present invention is to provide a ferritic stainless steel suitable as an EGR cooler member used for Ni brazing, and an EGR cooler using the same.
- the above purpose is, in mass%, C: 0.03% or less, Si: more than 0.1 to 3%, Mn: 0.1 to 2%, Cr: 10 to 25%, Nb: 0.3 to 0.3. 8%, N: 0.03% or less, preferably the total content of C and N is 0.01% or more, and other if necessary, (A) A range of 4% or less in total of at least one of Mo, Cu, V and W; (B) a range of one or more of Ti, Al and Zr in a total range of 0.3% or less, (C) at least one of Ni and Co in a total range of 5% or less, (D) a range in which at least one of REM (rare earth element) and Ca is 0.2% or less in total; And is achieved by a ferritic stainless steel for an EGR cooler member, which is selectively contained in each of the remaining Fe and unavoidable impurities.
- the present invention provides an EGR cooler having a structure in which a steel member made of the above steel is held as a constituent member and at least the member is joined to another member by Ni brazing.
- the member include an outer cylinder, a partition plate, a vent pipe, and a fin attached to the vent pipe.
- an EGR cooler having a structure in which a steel material made of the above steel is held in a member that comes into contact with both automobile exhaust gas and cooling water and at least the member is joined to another member by Ni brazing is provided.
- the member that contacts both the automobile exhaust gas and the cooling water include an outer cylinder, a partition plate, and a vent pipe.
- ferritic stainless steel having good Ni brazing and toughness is provided.
- an EGR cooler having higher high-temperature strength, less oxide scale peeling, and lower material cost than a conventional EGR cooler using austenitic stainless steel as a member is realized.
- the figure which illustrated the structure of the EGR cooler typically.
- the figure which illustrated typically the structure of the type of EGR cooler which has a fin in a vent pipe.
- the components may be exposed to a high temperature of 700 ° C. or higher and a maximum of about 800 ° C. In this case, especially for ferritic steel types, a measure for preventing a decrease in high-temperature strength is important.
- Ni brazing is maintained at a high temperature of about 1050 to 1150 ° C., component design for suppressing coarsening of crystal grains is important.
- ferritic stainless steel exhibits a higher strength level than austenitic stainless steel in a medium temperature range from room temperature to about 600 ° C.
- the strength level decreases greatly at high temperatures such as 700 ° C. or higher.
- Nb addition is effective as a technique for preventing such a decrease in high-temperature strength. That is, the high temperature strength is remarkably improved by adding about 0.2% by mass of Nb to ferritic stainless steel.
- the improvement of the high temperature strength by Nb is mainly due to “solid solution Nb”. Therefore, in ferritic stainless steel used for high temperature applications, in order to ensure a sufficient amount of solute Nb, component design is usually made to reduce the C and N contents as much as possible.
- Nb carbide / nitride Nb carbide / nitride
- the pinning effect is also considered to contribute greatly. Therefore, in the component design in the steel of the present invention, it is rather advantageous to secure the C and N contents to some extent. Specifically, it is more effective to set the total content of C and N to 0.01% by mass or more.
- the pinning effect by precipitates such as Fe 2 Nb (Laves) and Fe 3 NbC (M6X) is also considered to act effectively on suppressing the grain coarsening. Suppressing the coarsening of crystal grains is particularly effective in preventing a decrease in low temperature toughness.
- alloy components other than Nb As for alloy components other than Nb, it was found that each element of Mo, Cu, V, and W also contributes to improvement of high-temperature strength as the amount of solid solution increases. Ni and Co were also found to be extremely effective in suppressing toughness degradation when the crystal grains were slightly coarsened. On the other hand, it has been clarified that Ti, Al, Zr, REM, and Ca have a factor that deteriorates the flow (wetting property) of the Ni brazing material on the surface of the steel material when Ni brazing is performed. This is thought to be due to the fact that oxides of these elements are likely to be formed on the steel surface during heating of the Ni brazing. However, there is no problem if the content of these elements is regulated to an appropriate range as described later.
- C and N are elements that form Nb carbide / nitride when combined with Nb.
- Nb is consumed by these precipitates and the solid solution Nb is reduced, the effect of improving the high temperature strength and the effect of suppressing the coarsening of the crystal grains due to the solid solution Nb are inhibited. Therefore, in the present invention, the C content needs to be limited to 0.03% by mass or less, and is preferably 0.025% by mass or less. Moreover, it is necessary to restrict N content to 0.03 mass% or less, and it is preferable that it is 0.025 mass% or less.
- the pinning effect by Nb carbide / nitride can also contribute to the suppression of grain coarsening during Ni brazing. Therefore, it is advantageous to secure a certain amount of C and N.
- the total content of C and N is 0.01% by mass or more.
- Si is an element that improves high-temperature oxidation characteristics.
- excessive Si content hardens the ferrite phase and causes deterioration of workability.
- Ni brazing property wetting property with Ni brazing material
- the Si content is limited to the range of more than 0.1 to 3% by mass, and more preferably in the range of 0.3 to 2.5% by mass.
- the upper limit can be regulated to 1.5% by mass.
- Mn is an element that improves high-temperature oxidation characteristics, particularly scale peel resistance. However, excessive addition promotes the formation of an austenite phase at high temperatures.
- the Mn content is specified in the range of 0.1 to 2% by mass.
- Cr has the effect of stabilizing the oxidation resistance at high temperatures. For this purpose, it is necessary to secure a Cr content of 10% by mass or more. However, excessive Cr content impairs manufacturability and workability of the steel material. Therefore, the Cr content is limited to a range of 25% by mass or less.
- Nb is an important element in the present invention and, as described above, effectively acts to increase the high-temperature strength and suppress the grain coarsening during Ni brazing.
- the solid solution strengthening of Nb largely contributes, but the precipitation strengthening by Nb carbide / nitride finely dispersed in the ferrite matrix is also effective for improving the high temperature strength.
- the pinning effect by Nb carbide / nitride works effectively together with the solid solution strengthening of Nb. In order to fully exhibit these actions, it is important to secure the Nb content at 0.3 mass% or more after restricting the C and N contents to the above ranges.
- the Nb content in order to suppress the coarsening of crystal grains during Ni brazing, it is effective to increase the Nb content, and it is preferable to set the Nb content to 0.4% or more or even 0.5% or more.
- the Nb content is limited to a range of 0.8% by mass or less.
- Mo, Cu, V, and W also contribute to improvement of high temperature strength mainly by solid solution strengthening. Therefore, one or more of these elements can be contained as necessary. In particular, it is more effective to secure a total content of these elements of 0.05% by mass or more. However, when these elements are added excessively, the hot workability is adversely affected. Moreover, it becomes a factor which inhibits low temperature toughness. As a result of various studies, when adding one or more of Mo, Cu, V, and W, the total content needs to be suppressed to 4% by mass or less.
- Ti and Zr combine with C and N to form fine precipitates, which are dispersed in the steel, thereby exhibiting an effect of improving the high temperature strength.
- Al exhibits the effect of improving the high temperature oxidation characteristics. Therefore, one or more of these elements can be contained as necessary. However, if any of these elements is contained in a large amount, it causes a decrease in hot workability and surface quality characteristics. Moreover, since it is an element which forms a strong oxide film on the steel material surface, the flow of Ni brazing may be deteriorated by the oxide film.
- it is necessary to suppress the total content to 0.3% by mass or less. In particular, it is effective to set the total content in the range of 0.03 to 0.3% by mass, and more preferably 0.03 to 0.25% by mass.
- Ni and Co are remarkably effective in suppressing toughness deterioration when crystal grains are slightly coarsened by Ni brazing. These elements are also advantageous for improving the high temperature strength. Therefore, it is possible to contain one or more of these elements as required, and it is more effective to secure a total content of Ni and Co of 0.5% by mass or more. However, excessive addition of Ni and Co is not preferable because it causes formation of an austenite phase in a high temperature range. When adding 1 or more types of Ni and Co, it is necessary to suppress the total content of Ni and Co to the range of 5 mass% or less.
- REM rare earth element
- Ca are elements that improve high-temperature oxidation characteristics like Al, and in the present invention, one or more of them can be added as necessary. In particular, it is more effective to secure a total content of REM and Ca of 0.01% by mass or more. However, if it is added in a large amount, the manufacturability is lowered due to a decrease in toughness. Therefore, when adding 1 or more types of REM and Ca, it is necessary to suppress the total content to the range of 0.2 mass% or less.
- the ferritic stainless steel having the above composition has no problem with respect to the corrosion resistance against snow melting salt, the corrosion resistance against LLC, and the corrosion resistance against condensed water compared to the austenitic steel types used in conventional EGR coolers. Was confirmed.
- the high temperature strength (0.2% proof stress) and scale peel resistance in the exhaust gas environment are improved over the austenitic steel grade.
- Ferritic stainless steel having the above composition is made into a steel plate by a normal method, and is processed into members such as an outer cylinder, a partition plate, a vent pipe, and a fin attached to the vent pipe constituting the EGR cooler. These members are joined by Ni brazing, and an EGR cooler is constructed. It is not necessary that all the constituent members of the EGR cooler are made of the steel of the present invention. However, the steel member of the present invention has sufficiently secured corrosion resistance to LLC, and at the same time, improved high temperature oxidation characteristics in exhaust gas environment, resistance to crystal grain coarsening during Ni brazing, and wettability. It is a thing. For this reason, it is particularly effective to use the steel of the present invention for a member that contacts both automobile exhaust gas and cooling water and is subjected to Ni brazing. Examples of such a member include an outer cylinder, a partition plate, and a vent pipe.
- the steel having the chemical composition shown in Table 1 was melted, and the resulting steel ingot was hot-forged into a round bar and a plate to be processed into a round bar having a diameter of 15 mm and a plate having a thickness of 30 mm.
- the round bar was subjected to a solution treatment at a holding temperature set in the range of 1000 to 1100 ° C.
- the sheet is hot rolled into a hot rolled sheet having a thickness of 4 mm, annealed, and then cold rolled to a thickness of 1.5 mm, and then the holding temperature is set within a range of 1000 to 1100 ° C.
- the final annealing was performed.
- B4 and B5 are austenitic stainless steels.
- a high-temperature tensile test piece having a parallel part diameter of 10 mm was prepared from the round bar after solution treatment, a high-temperature tensile test at 700 ° C. was performed in accordance with JIS G056, and a 0.2% yield strength was measured. Since those having a 0.2% proof stress at 700 ° C. of 100 N / mm 2 or more exhibit characteristics superior to those of conventional austenitic steel types as EGR coolers, those having such characteristics were determined to be acceptable.
- Ni brazing (wetting) Two 10 mm ⁇ 20 mm ⁇ 1.5 mm brazing specimens were cut out from each cold rolled annealed plate. One of the test pieces was placed horizontally, and a paste-like Ni solder was applied to the entire surface of the test piece with a thickness of 0.5 mm. A test piece / Ni brazing / test piece three-layered laminate was formed by stacking another test piece thereon, and placed in a vacuum furnace while keeping it horizontal. Heated for minutes. Take out the laminate after cooling, observe the surface of the test piece that was superposed on the upper surface (the one that was not coated with Ni brazing), and divide the area wetted with Ni brazing by the total area of the test piece surface Thus, the Ni brazing coverage was determined.
- Ni brazing rate of 50% or more was evaluated as A, 20% or more and less than 50% was evaluated as B, and less than 20% was evaluated as C.
- the Ni brazing filler used was a 19 mass% Cr-10 mass% Si-71 mass% Ni composition (equivalent to BNi-5 in JIS Z3265).
- the ferritic stainless steel of the present invention has a much smaller coefficient of thermal expansion than the austenitic stainless steels of Comparative Examples B4 and B5, 0.2% proof stress at 700 ° C. and repeated cycles. It was also superior in high-temperature oxidation characteristics. Further, it was confirmed that the Ni-brazing property (wetting property), the resistance against coarsening of crystal grains, and the low temperature toughness were sufficiently satisfactory as an EGR cooler member.
- Comparative Example B1 has a high C content and a low Nb content, so that the amount of dissolved Nb is insufficient, high temperature strength (0.2% proof stress at 700 ° C.), and resistance to coarsening of crystal grains. Inferior to Moreover, since the Mn content was high, an austenite phase was generated at a high temperature, and it was considered that this was partly transformed into a martensite phase, and the low temperature toughness was inferior. Although B2 had a low Nb content, since the C and N contents were also relatively low, the solid solution Nb content was adequately secured and the high-temperature strength (0.2% yield strength at 700 ° C.) was good.
- B3 had an excessive Ti content, an oxide film was likely to be formed on the surface during Ni brazing, and the Ni brazing property was inferior. Moreover, it was inferior to low-temperature toughness because the total content of Mo, Cu, V, and W was too high.
- B4 and B5 are austenitic stainless steels and have a high coefficient of thermal expansion. High temperature strength (0.2% proof stress at 700 ° C.) was also lower than other ferritic steel types. In addition, due to the high coefficient of thermal expansion, the scale easily peeled off in repeated cycles, and the mass change became a large negative value. B6 had an excessively high total content of Ti, Al, and Zr, so that an oxide film was liable to be formed on the surface during Ni brazing, resulting in poor Ni brazing.
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Abstract
Description
(1)Niろう付け性が良好であること。
(2)融雪塩に対する耐食性が良好であること。EGRクーラーはエンジンルーム内に設置され、路面にまかれた融雪塩が付着しやすい環境にあるからである。
(3)LLC(ロングライフクーラント;例えばエチレングリコール)に対する耐食性が良好であること。EGRの冷却水には通常LLCが添加されるからである。
(4)高温強度と耐高温酸化性が良好であること。EGRクーラーは高温の排ガスに曝されるからである。
(5)凝結水の結露に対する耐食性が良好であること。EGRクーラーにおいては、運転中は排ガス出側付近に結露が生じやすく、また運転後は排ガス接触箇所に結露が生じやすいからである。
(a)Mo、Cu、VおよびWの1種以上を合計4%以下の範囲、
(b)Ti、AlおよびZrの1種以上を合計0.3%以下の範囲、
(c)NiおよびCoの1種以上を合計5%以下の範囲、
(d)REM(希土類元素)およびCaの1種以上を合計0.2%以下の範囲、
でそれぞれ選択的に含有し、残部Feおよび不可避的不純物からなるEGRクーラー部材用フェライト系ステンレス鋼によって達成される。
結晶粒の粗大化が抑制されることによって特に低温靭性の低下防止に効果がある。
そのような部材としては、例えば外筒、仕切り板、通気管が挙げられる。
〔熱膨張係数〕
溶体化処理後の丸棒から5mm角×50mm長さの試験片を作製し、熱膨張測定装置にセットして昇温速度2℃/分にて常温(25℃)から700℃までの平均熱膨張係数を求めた。
溶体化処理後の丸棒から平行部の直径が10mmの高温引張試験片を作製し、JIS G056に準拠して700℃の高温引張試験を実施し、0.2%耐力を測定した。700℃における0.2%耐力が100N/mm2以上であるものはEGRクーラーとして従来のオーステナイト系鋼種を上回る特性を呈することから、ここではそのような特性を具備するものを合格と判定した。
冷延焼鈍板から25mm×35mm×1.5mmの試料を切り出し、全面を#400湿式研磨仕上とした高温酸化試験片を作製した。この試験片について、EGRクーラー部材としての繰り返し使用を模擬して、大気+60℃飽和水蒸気の雰囲気において「900℃×25分加熱→常温で10分間放冷」のサイクルを1000サイクル実施し、試験片の試験前と試験後の質量変化(プラスは増加、マイナスは減少)を試験前の試験片の表面積で除することにより、単位面積あたりの質量変化を求めた。この質量変化の絶対値が10mg/m2以下であれば、EGRクーラー部材として優れた高温酸化特性を有していると評価され、5mg/m2以下であるものは特に優れている。
冷延焼鈍板から10mm×20mm×1.5mmのろう付け試験片を各鋼種2枚ずつ切り出した。うち1枚の試験片を水平に置いた状態で、その表面の全面にペースト状のNiろうを0.5mm厚で塗布した。その上にもう1枚の試験片を重ね、試験片/Niろう/試験片の3層からなる積層体を構成し、これを水平に保ったまま真空炉に入れ、真空引き後に1150℃で30分加熱した。冷却後に積層体を取り出し、上面に重ねた方(Niろうを塗布しなかった方)の試験片表面を観察し、表面のうちNiろうで濡れた面積を試験片表面の全面積で除することによりNiろう被覆率を求めた。Niろう被覆率が50%以上のものをA、20%以上50%未満のものをB、20%未満のものをCと評価し、B評価以上を合格とした。なお、Niろうは19質量%Cr-10質量%Si-71質量%Ni組成のもの(JIS Z3265のBNi-5相当品)を使用した。
上記のNiろう付け性を評価した試験片について、その断面(圧延方向および板厚方向に平行な断面;L断面)の金属組織を光学顕微鏡で観察した。エッチングは弗酸+硝酸の混酸で行った。平均結晶粒径が200μm以下のものをA、200μm超え500μm以下のものをB、500μm超えのものをCと評価し、B評価以上を合格と判定した。
1.5mm厚の冷延焼鈍板を上記Niろう付け性評価と同等のヒートパターンで熱処理したのち、その鋼板からVノッチシャルピー衝撃試験片を作製し、JIS Z2242に準拠して0℃でのシャルピー衝撃試験を実施した。試験片はハンマーのぶつかる方向が圧延方向に対して直角方向(C方向)となるように採取した。0℃でのシャルピー衝撃値が100J/cm2以上のものをA、50J/cm2以上100J/cm2未満のものをB、50J/cm2未満のものをCと評価し、B評価以上を合格と判定した。
これらの結果を表2に示す。
Claims (8)
- 質量%で、C:0.03%以下、Si:0.1超え~3%、Mn:0.1~2%、Cr:10~25%、Nb:0.3~0.8%、N:0.03%以下、残部Feおよび不可避的不純物からなるEGRクーラー部材用フェライト系ステンレス鋼。
- さらに、Mo、Cu、VおよびWの1種以上を合計4%以下の範囲で含有する請求項1に記載のフェライト系ステンレス鋼。
- さらに、Ti、AlおよびZrの1種以上を合計0.3%以下の範囲で含有する請求項1または2に記載のフェライト系ステンレス鋼。
- さらに、NiおよびCoの1種以上を合計5%以下の範囲で含有する請求項1~3のいずれかに記載のフェライト系ステンレス鋼。
- さらに、REM(希土類元素)およびCaの1種以上を合計0.2%以下の範囲で含有する請求項1~4のいずれかに記載のフェライト系ステンレス鋼。
- CおよびNの合計含有量が0.01質量%以上である請求項1~5に記載のフェライト系ステンレス鋼。
- 請求項1~6のいずれかに記載の鋼からなる鋼材を、構成部材に持ち、少なくともその部材を他の部材にNiろう付けにて接合した構造を有するEGRクーラー。
- 請求項1~6のいずれかに記載の鋼からなる鋼材を、自動車排ガスおよび冷却水の両方に接触する部材に持ち、少なくともその部材を他の部材にNiろう付けにて接合した構造を有するEGRクーラー。
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EP09847785.4A EP2460899A4 (en) | 2009-07-27 | 2009-07-27 | FERRITIC STAINLESS STEEL FOR EGR COOLER AND EGR COOLER |
KR1020127000631A KR20120036959A (ko) | 2009-07-27 | 2009-07-27 | Egr 쿨러용 페라이트계 스테인리스강 및 egr 쿨러 |
KR1020167026760A KR20160119255A (ko) | 2009-07-27 | 2009-07-27 | Egr 쿨러용 페라이트계 스테인리스강 및 egr 쿨러 |
US13/382,375 US20120111529A1 (en) | 2009-07-27 | 2009-07-27 | Ferritic stainless steel for egr cooler and egr cooler |
CN2009801606251A CN102471840A (zh) | 2009-07-27 | 2009-07-27 | Egr冷却器用铁素体系不锈钢及egr冷却器 |
PCT/JP2009/063370 WO2011013193A1 (ja) | 2009-07-27 | 2009-07-27 | Egrクーラー用フェライト系ステンレス鋼およびegrクーラー |
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JP2019533084A (ja) * | 2016-09-28 | 2019-11-14 | ポスコPosco | 吸音性に優れた排気系熱交換器用フェライト系ステンレス鋼およびその製造方法 |
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CN104364404B (zh) * | 2012-05-28 | 2020-07-28 | 杰富意钢铁株式会社 | 铁素体系不锈钢 |
FI125855B (fi) * | 2012-06-26 | 2016-03-15 | Outokumpu Oy | Ferriittinen ruostumaton teräs |
SI2893049T1 (sl) | 2012-09-03 | 2021-03-31 | Aperam Stainless France, | Feritna nerjavna jeklena pločevina, postopek za njeno izdelavo in njena uporaba, zlasti v izpušnih vodih |
KR20140087887A (ko) * | 2012-12-31 | 2014-07-09 | 현대자동차주식회사 | Egr 시스템용 페라이트계 스테인리스강 |
JP6370276B2 (ja) * | 2015-08-17 | 2018-08-08 | 日新製鋼株式会社 | 高Al含有制振性フェライト系ステンレス鋼材および製造方法 |
KR101697093B1 (ko) * | 2015-09-22 | 2017-01-18 | 주식회사 포스코 | 페라이트계 스테인리스강 및 이의 제조 방법 |
JP6895787B2 (ja) * | 2017-03-31 | 2021-06-30 | 日鉄ステンレス株式会社 | オーステナイト系ステンレス鋼、ろう付け構造体、ろう付け構造部品および排気ガス熱交換部品 |
CN110678567A (zh) * | 2017-05-24 | 2020-01-10 | 东华隆株式会社 | 熔融金属镀浴用部件 |
US10400714B2 (en) * | 2017-09-28 | 2019-09-03 | Senior Ip Gmbh | Heat exchanger with annular coolant chamber |
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US20120111529A1 (en) | 2012-05-10 |
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KR20120036959A (ko) | 2012-04-18 |
EP2460899A4 (en) | 2014-07-09 |
CN102471840A (zh) | 2012-05-23 |
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