JP2018188686A - Alloy original sheet for heat-resistant member, alloy sheet for heat-resistant member, and gasket for exhaust system member of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alloy sheet for a heat-resistant member that has a smaller Ni content and has a 0.2% proof stress and settling resistance in a high temperature tensile test equal to or superior to those as compared with the conventional Ni-based heat-resistant alloy.SOLUTION: An alloy sheet for a heat-resistant member has a chemical composition containing C: 0.0020 to 0.10%, Si: 0.020 to 3.0%, Mn: 0.020 to 2.0%, P: less than 0.050%, S: less than 0.010%, Cr: not less than 12.0% to less than 25.0%, Ni: more than 35.0% to less than 50.0%, N: 0.0005 to 0.020%, Al: more than 3.0% to not more than 5.0%, Ti: more than 1.5% to less than 3.0%, Mo: 1.0 to 2.5%, Nb: 2.25 to 4.00% and Cu: less than 0.3% and satisfying the relationship of [Ti]/[Al]≥0.50 and [Nb]/[Al]≥0.75. The alloy sheet has a metal structure in which a Ni-based intermetallic compound is present in a host phase composed of austenite and has the chemical composition of Ni, Ti and Nb contained in the Ni-based intermetallic compound which occupies, by atom%, more than 60% of Ni, not less than 3.5% of Ti and not less than 0.8% of Nb, respectively, based on the entire chemical composition constituting the Ni-based intermetallic compound.SELECTED DRAWING: None

Description

  The present invention relates to an alloy original plate for a heat-resistant member, an alloy plate for a heat-resistant member, and a gasket for an engine exhaust system member.

  A gasket used as a heat-resistant member in an automobile engine or the like is a kind of sealing material (packing) in which a step portion called a bead is formed on a thin metal plate having a thickness of about 0.1 to 0.3 mm.

  The gasket seals the leakage of the exhaust gas from the connecting portion by the repulsive force of the elastically deformed bead when sandwiched between the connecting portions of the exhaust system member of the engine. Gaskets are used in harsh conditions where they are exposed to an environment where high-temperature exhaust gas is present for a long period of time, so the gasket material has high bead sag resistance at high temperatures and high strength. It must be maintained.

  Among gaskets used in automobile engines, turbo gasket materials used at a high temperature of about 700 ° C. are currently based on Ni, Cr and Fe, a considerable amount of Nb and Mo, and a smaller amount of Al and An expensive Ni-based alloy cold-rolled sheet such as precipitation hardening type Inconel (registered trademark) 718 containing an alloy element such as Ti is used.

  For this reason, there is a high need for an alternative material that has a lower Ni composition and is lower than heat-resistant Ni-based alloys such as Inconel 718 and Inconel 625, is excellent in high-temperature strength, and has high sag resistance.

  In Patent Document 1, in mass%, C: 0.15% or less, Si: 1.0% or less, Mn: 0.3% or less, Ni: 30 to 49%, Cr: 10 to 18%, Al: A chemical containing 1.6 to 3.0%, containing one or more elements selected from IVa group and Va group in total 1.5 to 8.0%, the balance being Fe and impurities An Fe—Ni—Cr based heat resistant alloy having a composition is disclosed.

In Patent Document 2, in mass%, C: 0.02 to 0.30%, Si: 0.02 to 3.5%, Mn: 0.02 to 2.5%, Ni: 10 to 50%, Cr: 12-25%, Ti: 1.0-5.0%, Al: 0.002-1.0%, Nb: 0.1-3.0%, B: 0.001- Containing one or more selected from 0.01%, Mo: 0.1-4.0%, the total content of Ti, Al and Nb is 3.0-7.0%, The weight ratio of the precipitated η phase (Ni ₃ Ti) and the gamma prime γ ′ phase (Ni ₃ (Al, Ti, Nb)) precipitated in the base γ phase crystal grains is 0.01 to 30.00%. , A heat resistant stainless steel having a hot tensile strength at 600 ° C. of 800 N / mm ² or more is disclosed.

JP-A-7-109539 JP 2000-109955 A

  However, these conventional techniques have the advantage that the Ni content is lower than Ni-based heat-resistant alloys such as Inconel 718 and can be manufactured at low cost, but they are inferior to Inconel 718 in terms of high-temperature strength and sag resistance. It was. There is a need for a gasket and its material that are comparable in quality to Inconel 718 and the like, while saving the amount of Ni added.

As a result of intensive studies in order to solve the above problems, the present inventors have reduced the Ni content, and Al, which is a formation element of the gamma prime γ ′ phase (Ni ₃ (Al, Ti, Nb)), It has been found that by optimizing the Ti and Nb contents, the heat resistance can be maintained and improved even if the Ni content is reduced.

  That is, since the mechanical properties after aging for 1 to 400 hours at 700 ° C., which is the operating temperature of the gasket for exhaust system members, are superior to those of Inconel 718 which is a conventional material, exhaust system members, particularly gaskets The present invention has been completed through further investigations after finding out that it can be used as a heat-resistant alloy plate for use. The present invention is listed below.

(1) By mass%, C: 0.0020 to 0.10%, Si: 0.020 to 3.0%, Mn: 0.020 to 2.0%, P: less than 0.050%, S: Less than 0.010%, Cr: 12.0% or more and less than 25.0%, Ni: more than 35.0% and less than 50.0%, N: 0.0005 to 0.020%, Al: more than 3.0% 5.0% or less, Ti: more than 1.5% and less than 3.0%, Mo: 1.0 to 2.5%, Nb: 2.25 to 4.00%, Cu: less than 0.3% When the contents (mass%) of Ti, Nb and Al are [Ti], [Nb] and [Al], respectively, [Ti] / [Al] ≧ 0.50, [Nb] / [Al] An alloy base plate for a heat-resistant member that satisfies a relationship of ≧ 0.75, has a chemical composition with the balance being Fe and impurities, and exhibits a metal structure consisting only of an austenite phase. ,
When heat-treated at 700 ° C. for 1 hour, the Ni-based intermetallic compound is present in the austenite matrix, and the Ni-based intermetallic compound is formed with respect to the entire chemical composition constituting the Ni-based intermetallic compound. An alloy base plate for a heat-resistant member, wherein the chemical composition of Ni, Ti and Nb contained in the compound occupies more than 60%, 3.5% or more and 0.8% or more, respectively, in atomic%.

  (2) The alloy base plate for a heat-resistant member according to (1), wherein a heat reduction margin before and after holding at 700 ° C. for 400 hours after heat treatment at 700 ° C. for 1 hour is 40 HV or less.

  (3) The alloy base plate for a heat-resistant member according to (1) or (2), which contains one or more of Co: 3.0% or less and W: less than 3.0% by mass%.

  (4) In any one of (1) to (3), containing one or more of B: 0.01% or less, Ca: 0.005% or less, and Mg: 0.002% or less in mass% The alloy original plate for heat-resistant members as described.

  (5) By mass%, C: 0.0020 to 0.10%, Si: 0.020 to 3.0%, Mn: 0.020 to 2.0%, P: less than 0.050%, S: Less than 0.010%, Cr: 12.0% or more and less than 25.0%, Ni: more than 35.0% and less than 50.0%, N: 0.0005 to 0.020%, Al: more than 3.0% 5.0% or less, Ti: more than 1.5% and less than 3.0%, Mo: 1.0 to 2.5%, Nb: 2.25 to 4.00%, Cu: less than 0.3% When the contents (mass%) of Ti, Nb and Al are [Ti], [Nb] and [Al], respectively, [Ti] / [Al] ≧ 0.50, [Nb] / [Al] An alloy plate for a heat-resistant member that satisfies a relationship of ≧ 0.75 and has a chemical composition with the balance being Fe and impurities, and a Ni-based intermetallic compound is present in the austenite matrix. The chemical composition of Ni, Ti and Nb contained in the Ni-based intermetallic compound is more than 60% in atomic percent with respect to the entire chemical composition constituting the Ni-based intermetallic compound. , 3.5% or more and 0.8% or more, an alloy plate for heat-resistant members.

  (6) The alloy plate for a heat-resistant member according to (5), wherein a hardness reduction before and after holding at 700 ° C. for 400 hours is 40 HV or less.

  (7) The alloy plate for a heat-resistant member according to (5) or (6), which contains one or more of Co: 3.0% or less and W: less than 3.0% by mass%.

  (8) In any one of (5) to (7), containing at least one of B: 0.01% or less, Ca: 0.005% or less, and Mg: 0.002% or less, by mass% The alloy plate for heat-resistant members as described.

  (9) By mass%, C: 0.0020 to 0.10%, Si: 0.020 to 3.0%, Mn: 0.020 to 2.0%, P: less than 0.050%, S: Less than 0.010%, Cr: 12.0% or more and less than 25.0%, Ni: more than 35.0% and less than 50.0%, N: 0.0005 to 0.020%, Al: more than 3.0% 5.0% or less, Ti: more than 1.5% and less than 3.0%, Mo: 1.0 to 2.5%, Nb: 2.25 to 4.00%, Cu: less than 0.3% When the contents (mass%) of Ti, Nb and Al are [Ti], [Nb] and [Al], respectively, [Ti] / [Al] ≧ 0.50, [Nb] / [Al] A gasket for an exhaust system member of an engine having a chemical composition in which a relation of ≧ 0.75 is satisfied, and the balance is Fe and impurities, and N in the austenite matrix The chemical composition of Ni, Ti and Nb contained in the Ni-based intermetallic compound is expressed in atomic% with respect to the entire chemical composition constituting the Ni-based intermetallic compound. A gasket for an exhaust system member of an engine, characterized by occupying more than 60%, 3.5% or more and 0.8% or more, respectively.

  (10) The gasket for an exhaust system member of the engine according to (9), wherein a hardness reduction before and after holding at 700 ° C. for 400 hours is 40 HV or less.

  (11) The gasket for an exhaust system member of an engine according to (9) or (10), which contains at least one of Co: 3.0% or less and W: less than 3.0% by mass.

  (12) In any one of (9) to (11), containing at least one of B: 0.01% or less, Ca: 0.005% or less, and Mg: 0.002% or less The gasket for the exhaust system member of the described engine.

  According to the present invention, an alloy for a heat-resistant member that has a lower Ni content than conventional Ni-base heat-resistant alloys and has the same or better heat resistance (0.2% proof stress and sag resistance in a high-temperature tensile test). An original plate, an alloy plate for a heat-resistant member, and a gasket for an engine exhaust system member can be provided.

  An alloy base plate for a heat-resistant member, an alloy plate for a heat-resistant member, and a gasket for an engine exhaust system member according to the present invention will be described. In the following description, “%” regarding chemical composition or concentration means “% by mass” unless otherwise specified. In addition, “%” regarding each chemical composition of Ni, Ti, and Nb in the Ni-based intermetallic compound phase means “atomic%”.

1. Alloy base plate for heat-resistant member and alloy plate for heat-resistant member according to the present invention (1) Chemical composition First, essential elements will be described.

(1-1) C: 0.0020 to 0.10%
C is combined with Ti, Nb, Cr and the like to generate carbides, and the carbides work as a strengthening phase, but when the C content exceeds 0.10%, deterioration of workability of the alloy plate for heat-resistant members, The increase in Cr carbide causes a decrease in corrosion resistance. Therefore, the C content is 0.10% or less, and preferably 0.030% or less, and more preferably 0.020% or less when forming a heat-resistant member alloy plate with a high degree of workability. is there.

  On the other hand, reducing the C content to less than 0.0020% results in an increase in cost during refining and a decrease in the room temperature strength of the alloy plate for heat-resistant members. Therefore, the C content is 0.0020% or more, preferably 0.004% or more.

(1-2) Si: 0.020 to 3.0%
Si is an element added as a deoxidizing element during refining, and is an element that improves the oxidation resistance of the alloy plate for a heat-resistant member. When the Si content is less than 0.020%, the cost during refining increases and the oxidation resistance of the alloy plate for heat-resistant members decreases. Therefore, the Si content is 0.020% or more, preferably 0.03% or more.

  However, if the Si content exceeds 3.0%, the alloy plate for a heat-resistant member may be hardened and the workability may be deteriorated. Therefore, the Si content is 3.0% or less, and preferably 1.0% or less when forming a high-workability alloy sheet for a heat-resistant member.

(1-3) Mn: 0.020 to 2.0%
Mn, like Si, may be added as a deoxidizing element during refining. However, if the Mn content is less than 0.020%, the cost during refining is increased. Therefore, the Mn content is 0.020% or more, preferably 0.05% or more from the viewpoint of refining costs, and more preferably 0.07% or more.

  However, if the Mn content exceeds 2.0%, the oxidation resistance of the alloy plate for heat-resistant members at high temperatures is deteriorated and the material is hardened. Therefore, the Mn content is 2.0% or less, and preferably 1.5% or less from the viewpoint of the oxidation resistance of the alloy plate for a heat-resistant member and the production stability.

(1-4) P: Less than 0.050% P is an element harmful to hot workability and toughness. P is an impurity inevitably contained in ferrochrome as a raw material, but the content of less than 0.050% is allowed. Therefore, the P content is less than 0.050%, and preferably 0.035% or less from the viewpoint of improving the workability of the alloy plate for heat-resistant members.

  It is very difficult to remove P during refining, and in order to suppress the P content, it is preferable that the P concentration of the ferrochrome raw material is low. However, since the low P ferrochrome is expensive, the P content is preferably Is 0.005% or more, more preferably 0.010% or more.

(1-5) S: less than 0.010% S is an element harmful to the hot workability and corrosion resistance of the alloy plate for heat-resistant members. S is an impurity inevitably contained in the raw material, and the lower the S content, the better the hot workability and corrosion resistance, but the content of less than 0.010% is allowed. Accordingly, the S content is less than 0.010%, preferably less than 0.0030%, and more preferably less than 0.0010%.

  However, if the S content is reduced to less than 0.0002%, the desulfurization load increases and the refining cost increases. Therefore, the S content is preferably 0.0002% or more.

(1-6) Cr: 12.0 or more and less than 25.0% Cr is an essential element for ensuring the oxidation resistance and corrosion resistance of the alloy plate for heat-resistant members. When the Cr content is less than 12.0%, these effects are not achieved. Therefore, the Cr content is 12.0% or more, and is preferably 14.0% or more from the viewpoint of ensuring oxidation resistance and corrosion resistance of the alloy plate for heat-resistant members.

  On the other hand, when the Cr content is 25.0% or more, the workability of the alloy plate for heat-resistant members is deteriorated and the toughness is deteriorated. Therefore, the Cr content is less than 25.0%, preferably 24.1% or less, and more preferably 23.5% or less from the viewpoint of the stability of the production of the alloy plate for heat-resistant members.

(1-7) Ni: more than 35.0% and less than 50.0% Ni stabilizes the parent phase austenite and, at the same time, intermetallic compound gamma prime γ ′ (Ni ₃ (Al, Ti, Nb)), gamma double prime γ ″ (Ni ₃ (Nb, Ti)) and the like, which are extremely important elements for ensuring the oxidation resistance and heat resistance of the alloy plate for heat-resistant members. Is more than 35.0% in order to sufficiently secure the heat resistance of the alloy plate for a heat-resistant member, and is preferably 37.5% or more from the viewpoint of further improving the heat resistance.

  On the other hand, when the Ni content is 50.0% or more, hot workability is lowered in addition to an increase in alloy cost. Therefore, the Ni content is less than 50.0%, and is preferably 46.0% or less from the viewpoint of hot workability.

(1-8) N: 0.0005 to 0.020%
N may generate nitrides and reduce the workability of the alloy plate for heat-resistant members. Therefore, the N content is 0.020% or less, and is preferably less than 0.010% when the degree of processing required for the alloy plate for heat-resistant members is severe.

  On the other hand, reducing the N content to less than 0.0005% causes an increase in refining costs. Therefore, the N content is 0.0005% or less, and preferably 0.0010% or more from the viewpoint of the stability of manufacturing the alloy plate for heat-resistant members.

(1-9) Al: more than 3.0% to 5.0% or less Al is an element constituting Ni-based intermetallic compounds such as gamma prime γ ′ and gamma double prime γ ″ that contribute to precipitation strengthening, and Ti Therefore, the heat resistance of the alloy plate for a heat-resistant member is improved without degrading hot workability as compared with Nb, so the Al content is more than 3.0%, preferably 3.1% or more. .

  On the other hand, if the Al content exceeds 5.0%, the Ti and Nb composition in the Ni-based intermetallic compound may be reduced, and overaging may be promoted by coarsening, and the high temperature resistance of the alloy plate for heat-resistant members. Precipitation of sigma phase, which degrades fatigue properties, increases. Therefore, the Al content is 5.0% or less, and preferably less than 4.0% from the viewpoint of ensuring sufficient heat resistance.

(1-10) Ti: more than 1.5% and less than 3.0% Ti is an element constituting a Ni-based intermetallic compound such as gamma prime γ ′ and gamma double prime γ ″ that contributes to precipitation strengthening. In addition to Al, Nb, it is an important element for securing the heat resistance of the alloy plate for heat-resistant members.To ensure the heat resistance that the alloy plate for heat-resistant members can withstand use at 700 ° C., the Ti content is Over 1.5%, preferably over 1.8%.

  On the other hand, if the Ti content exceeds 3.0%, the hot workability is deteriorated and the rolling load is increased, and the formation of an intermetallic compound phase that does not contribute to the high temperature strength of the alloy plate for heat-resistant members is promoted. Therefore, the Ti content is less than 3.0%, and preferably less than 2.5% from the viewpoint of ensuring the stability of manufacturing the alloy plate for heat-resistant members and ensuring the high temperature strength.

(1-11) Mo: 1.0 to 2.5%
Mo is an element that greatly improves the heat resistance of the alloy plate for a heat-resistant member as a solid solution strengthening element of the parent phase austenite without greatly impairing hot workability. In order to ensure heat resistance that the alloy plate for heat-resistant members can withstand use at a high temperature of about 700 ° C., the Mo content is 1.0% or more, and preferably 1.1% or more.

  On the other hand, if the Mo content exceeds 2.5%, the rolling load may increase and casting cracks may occur. Therefore, the Mo content is 2.5% or less, preferably 2.0% or less.

(1-12) Nb: 2.25 to 4.00%
Nb, together with Ti, is an element constituting a Ni-based intermetallic compound such as gamma prime γ ′ and gamma double prime γ ″ that contributes to precipitation strengthening. The heat-resistant member alloy plate can withstand use at 700 ° C. In order to ensure the properties, the Nb content is 2.25% or more, preferably 2.31% or more.

  On the other hand, Nb tends to segregate in the vicinity of the dendritic grain boundaries during solidification, and lowers hot workability due to a local increase in strength and an increase in precipitates at the grain boundaries. Therefore, the Nb content is 4.00% or less, and preferably 3.50% or less from the viewpoint of hot workability.

(1-13) Cu: Less than 0.3% When Cu has a low melting point and exists in a high concentration, it causes melt embrittlement during hot forging and hot rolling, thereby reducing hot workability. Accordingly, the Cu content is less than 0.3%, and the hot workability is improved as the Cu content is lower, and therefore preferably less than 0.10%.

(1-14) [Ti] / [Al] ≧ 0.50, [Nb] / [Al] ≧ 0.75
When the contents (mass%) of Ti, Nb, and Al are [Ti], [Nb], and [Al], respectively, the above relationship is satisfied. The reason for this will be explained.

  In order to solve the above-mentioned problems, the present inventors have studied a chemical composition utilizing a Ni-based intermetallic compound phase such as gamma prime γ ′ or gamma double prime γ ″ effective for high-temperature strengthening of an alloy plate for a heat-resistant member. A cold-rolled sheet was prototyped.

  As a result, depending on the chemical composition in the gamma prime γ ′ or gamma double prime γ ″ of Al, Ti, Nb, which are constituent elements of the Ni-based intermetallic compound phase such as gamma prime γ ′ and gamma double prime γ ″, Despite reducing the Ni content, the high-temperature use performance of the alloy plate for heat-resistant members indicated by 0.2% proof stress at 700 ° C. and hardness change (sag resistance) before and after aging at 700 ° C. is that of Inconel 718. It was found to be equal to or better than the high temperature use performance.

  Specifically, the chemical composition of the alloy plate for heat-resistant members is within a predetermined range, and the Ni composition in the deposited Ni-based intermetallic compound phase is more than 60% in atomic%, and the Ti composition is 3.5%. As described above, when the Nb composition is 0.8% or more, the hardness reduction allowance before and after aging at 700 ° C. × 400 hours is 40 HV or less.

  In order to make the Ni composition, the Ti composition and the Nb composition in the Ni-based intermetallic compound phase in this way, the chemical composition of the alloy plate for a heat-resistant member is set to A value: [Ti] / [Al] ≧ 0.50, B Value: [Nb] / [Al] ≧ 0.75, and a material to be rolled using an induction heating (IH) apparatus or the like between rough rolling and finish rolling in the hot rolling step of the alloy plate for heat-resistant members The whole is reheated, the cold rolling rate of the final cold rolling is set to 70% or less, and an aging treatment at 700 ° C. for 1 hour or longer is further performed after the cold rolling.

  For this reason, in this invention, A value: [Ti] / [Al] is 0.50 or more, Preferably it is 0.51 or more, More preferably, it is 0.53 or more. Moreover, B value: [Nb] / [Al] is 0.75 or more, Preferably it is 0.76 or more, More preferably, it is 0.77 or more.

Next, the optional elements contained as necessary will be described.
(1-15) Co: 3.0% or less, and W: less than 3.0% One type Co acts as a solid solution strengthening element in the parent phase austenite, and in the operating temperature range of the alloy plate for heat-resistant members It is an element that promotes the formation of gamma prime γ 'that contributes to precipitation strengthening. However, if the Co content exceeds 3.0%, in addition to an increase in alloy costs, casting cracks are caused. Therefore, the Co content is 3.0% or less, preferably 2.5% or less. In order to surely obtain the above-described effect by containing Co, the Co content is preferably 0.10% or more.

W, like Co, is an element that improves the high-temperature strength as a solid solution strengthening element in the parent phase austenite. However, if the W content is 3.0% or more, in addition to an increase in alloy cost, an increase in rolling load and casting cracks are caused. Therefore, the W content is less than 3.0%, preferably 2.0% or less. In order to surely obtain the above-described effect by containing W, the W content is preferably 0.02% or more.
Co and W may be contained alone or in combination of two.

  (1-16) B: 0.01% or less, Ca: 0.005% or less, and Mg: 0.002% or less

  B, Ca, and Mg are all elements that contribute to improvement of hot workability and formability of the alloy plate for a heat-resistant member. However, if the contents of B, Ca, and Mg are excessive, not only the hot workability is decreased, but there is a possibility of causing casting cracks and clogging of the molten metal nozzle in the casting equipment. Therefore, the B content is 0.01% or less, the Ca content is 0.005% or less, and the Mg content is 0.002% or less. In order to reliably obtain the above-described effects by containing B, Ca, and Mg, the B content is preferably 0.0002% or more, the Ca content is preferably 0.0002% or more, and Mg content is contained. The amount is preferably 0.0002% or more.

  B, Ca and Mg may be contained singly or in combination of two or more.

(1-17) Balance The balance other than the above is Fe and impurities. Impurities include those contained in raw materials such as ore and scrap and those contained in the manufacturing process.

(2) Each chemical composition of Ni, Ti, and Nb in the Ni-based intermetallic compound phase As described above, the alloy plate for a heat-resistant member according to the present invention is subjected to aging treatment at 700 ° C. for 1 hour or more, and then the austenite matrix phase. From this, Ni-based intermetallic compounds are precipitated. And the chemical composition of Ni, Ti, and Nb is more than 60%, 3.5% or more and 0.8% or more, respectively, with respect to the entire chemical composition constituting the Ni-based intermetallic compound. Therefore, the hardness reduction allowance in the cross section of the alloy plate for heat-resistant members before and after aging at 700 ° C. × 400 h is 40 HV or less.

  Elements constituting the Ni-based intermetallic compound other than Ni, Ti, and Nb are Fe, Cr, Al, Mo, Cu, and the like, and include the above-described optional elements (Co, W, B, Ca, Mg). In some cases, these elements are also included. In addition, about an austenite phase and Ni type | system | group intermetallic compound, a phase is identified by the electron beam diffraction image of a transmission electron microscope (TEM). Regarding the chemical composition of Ni, Ti and Nb contained in the Ni-based intermetallic compound, the Ni-based metal observed for each sample using an X-ray detector attached to a scanning electron microscope (SEM) Five intercalation compounds are arbitrarily selected, point analysis is performed, and the content of each element is determined by the arithmetic average value of the atomic%.

(3) Hardness reduction allowance before and after holding at 700 ° C. for 400 hours The hardness reduction allowance before and after holding at 700 ° C. for 400 hours indicates the high temperature sag resistance of the alloy plate for heat resistant members and gasket according to the present invention. It is an indicator. A turbo gasket, which is a kind of gasket, is exposed to a high-temperature exhaust gas near 700 ° C. for a long period of time. Therefore, sufficient high-temperature sag resistance with less bead sag is required even in such an environment.

  Alloy plates used for gaskets exhibit a reduction in hardness due to the coarsening of Ni-based intermetallic compounds during use, and the decrease in hardness causes the gasket to sag, thus exhibiting sag resistance when used at high temperatures. As an index, a reduction in hardness before and after holding at 700 ° C. for 400 hours is used.

  The reason for limiting the holding time to 400 hours is that the decrease in hardness when held at 700 ° C. may change particularly after 200 to 300 hours have elapsed, and the amount of change after 400 hours has elapsed. This is because the hardness tends to decrease and the hardness gradually decreases with time.

  In the gasket and the alloy plate for a heat-resistant member according to the present invention, the hardness reduction when subjected to aging heat treatment at 700 ° C. for 400 hours is set to 40 HV or less in terms of Vickers hardness. When the hardness reduction allowance is more than 40 HV, the sag during use as a gasket is large, which causes a decrease in fuel consumption, generation of abnormal noise, and the like.

  The decrease in hardness during use is caused by the coarsening of the Ni-based intermetallic compound responsible for strengthening and the change to another intermetallic compound that does not contribute to strengthening. The rate of sag at this time hardly changes even in a material that has been subjected to aging heat treatment at a high temperature in advance or a material that has been used for a certain period of time as a gasket.

  For this reason, a material that simulates the exhaust gas environment by performing an aging heat treatment in the range of 600 to 800 ° C. and a gasket that is used in various exhaust gas environments are kept at 700 ° C. for 400 hours, respectively. Even if it investigates, the hardness reduction allowance does not exceed 40HV.

  In order to suppress the increase in the speed of sag in this way, the structure control for suppressing the coarsening of the Ni-based intermetallic compound responsible for strengthening γ ′ and the like is an important element. The chemical composition of Ni, Ti and Nb contained has a great influence.

2. Production method of alloy base plate for heat-resistant member and alloy plate for heat-resistant member according to the present invention A hot-rolled alloy plate is obtained by subjecting the slab having the above-described chemical composition to hot rough rolling and finish rolling. The alloy base plate for heat-resistant members according to the present invention is manufactured by repeatedly performing annealing (including solution heat treatment) and cold rolling. The final plate thickness of the alloy base plate for heat-resistant members is about 0.1 to 0.3 mm.

  At this time, the material to be rolled is heated (reheated) between rough rolling and finish rolling, and the cold rolling rate of the final cold rolling is set to 70% or less. The alloy plate for heat-resistant members according to the present invention is produced by subjecting the alloy original plate for heat-resistant members to aging treatment. An aging treatment is good to heat at 700 degreeC for 1 hour or more, for example.

  As described above, the Ni composition in the Ni-based intermetallic compound phase is more than 60% in atomic%, the Ti composition is made 3.5% or more in atomic%, and the Nb composition is 0.8% or more in atomic%. Therefore, the above-described A value: [Ti] / [Al] ≧ 0.50, B value: [Nb] / [Al] ≧ 0.75, and rough rolling and finish rolling in the hot rolling process In the meantime, the whole material is reheated using an induction heating (IH) device or the like, the cold rolling rate of the final cold rolling is set to 70% or less, and further, an aging treatment at 700 ° C. for 1 hour or more is performed after the cold rolling. Do.

  Reheating after rough rolling suppresses temperature drop during hot rolling to prevent ear cracks, and affects the chemical composition of the Ni-based intermetallic compound phase that precipitates after cold rolling. That is, by using reheating, the finish rolling temperature of hot rolling can be increased. Thereby, crystal grains coarsen in the metal structure after hot rolling and after final cold rolling or after final annealing, and the dislocation density after hot rolling is reduced.

  Since such a metal structure has a low dislocation density, the generation rate of the Ni-based intermetallic compound phase at the grain boundary increases. Further, it is considered that Ti and Nb are segregated at the crystal grain boundaries, and the amount of Ti and Nb segregation per unit area of the grain boundaries is increased by the coarsening. For this reason, a Ni-based intermetallic compound phase having a higher Ti and Nb composition is generated from the crystal grain boundary.

  At this time, the Ni-based intermetallic compound phase having a low Ti and Nb composition precipitated from within the crystal grains does not affect the heat resistance of the alloy plate for the heat-resistant member even if it is precipitated up to a certain amount. The alloy plate for heat-resistant members softens due to overaging when aging for a long time. For this reason, the final cold rolling rate is set to 70% or less, and dislocations serving as nucleation sites in the crystal grains are suppressed to a certain amount or less.

  The reason why the chemical composition of the alloy plate for heat-resistant members and the Ti and Nb composition in the Ni-based intermetallic compound phase affect the hardness change before and after aging at 700 ° C. is not clear, but the Al content should be a certain amount or more. As a result, the amount of precipitation of the Ni-based intermetallic compound phase is greatly increased, and elements such as Ti, Nb and the like that have a slow diffusion rate in the parent phase at 700 ° C. are included in the precipitated Ni-based intermetallic compound phase. It is presumed that the growth rate of the Ni-based intermetallic compound phase is slowed by the synergistic effect of the solid solution, and thereby the change in hardness before and after aging at 700 ° C. is reduced.

3. Gasket according to the present invention The gasket according to the present invention is processed into a predetermined gasket shape using the above-described alloy base plate for heat-resistant members according to the present invention as a raw material, and is attached as a part of an exhaust system member of the engine. Since the exhaust system member is heated to around 700 ° C. by using the engine, the processed alloy original plate for a heat-resistant member is subjected to an aging treatment to become a gasket according to the present invention. That is, the gasket according to the present invention has the above-described chemical composition, and each composition of Ni, Ti and Nb in the Ni-based intermetallic compound phase is more than 60% in atomic percent, 3.5% or more and 0%, respectively. It has more than 8% characteristics.

  Furthermore, in the gasket according to the present invention, the hardness reduction margin of the cross-sectional hardness before and after being held at 700 ° C. for 400 hours is 40 HV or less.

  In the gasket according to the present invention, a bead such as a so-called half bead or full bead is formed in the same manner as other gaskets. The gasket according to the present invention seals the leakage of exhaust gas from the connecting portion by the repulsive force of the elastically deformed bead when sandwiched between the connecting portions of the exhaust system member of the engine.

  The alloy base plate for a heat-resistant member, which is a material for the gasket, has a good workability because it exhibits a state before the Ni-based intermetallic compound is precipitated, that is, an austenite single-phase metal structure. The alloy base plate for heat-resistant members according to the present invention is less susceptible to cracking or the like when machining the gasket shape or forming a bead, contributing to the manufacturing quality of the gasket.

  The gasket according to the present invention has a lower Ni content and heat resistance (0.2% proof stress at 700 ° C. and hardness before and after aging at 700 ° C. compared to conventional gaskets made of Ni-based heat resistant alloys such as Inconel 718. High temperature use performance indicated by change in thickness (sag resistance) is equivalent or better.

The present invention will be described more specifically with reference to examples.
A 25 kg alloy lump having the chemical composition shown in Tables 1 and 2 (mass%, the balance being Fe and impurities) was melted. Tables 1 and 2 show the A and B values described above.

  This alloy lump was hot forged to form an alloy lump having a thickness of 45 mm, and further hot-rolled to obtain a hot rolled sheet having a thickness of 5.0 mm. At this time, in order to simulate reheating (IH heating) after rough rolling with an actual machine, a part of the sample was immediately placed in an atmospheric furnace at 1100 ° C. and heated for 30 minutes, and then extracted. Then, finish rolling was performed immediately.

  The hot-rolled sheet thus obtained was subjected to solution treatment at 1100 ° C. and cold rolling to produce a cold-rolled sheet having a thickness of 0.2 mm.

The cold-rolled sheet thus obtained was subjected to a tensile test at 700 ° C., as it was cold-rolled, and measured for the hardness of the cross section after aging at 700 ° C. for 400 hours. The tensile test at 700 ° C. was performed by a test method based on JIS G 0567. Regarding the hardness measurement of the cross section, the Vickers hardness test in accordance with JIS Z 2244 is performed under the condition of a load of 500 grams (in the L cross section of the cold rolled sheet (thickness cross section parallel to the rolling direction)). HV _0.5 ). At this time, the cross-sectional hardness is 425 HV or higher, 0.2% proof stress at a hardness of 350 HV or higher after being held at 700 ° C. for 400 hours: 1100 MPa or higher, and a reduction allowance before and after aging: 40 HV or lower is satisfied. Judgment was good. In the heat treatment after cold rolling and heat treatment at 700 ° C., the rate of temperature increase was 3 ° C./s, and cooling was air cooling.

  The final cold rolling ratio of the cold-rolled sheet thus manufactured, the reheating conditions after hot rough rolling, the Ni composition in the Ni-based intermetallic phase after aging at 700 ° C. for 1 hour, the Ti composition, and the Nb Compositions and evaluation results are shown in Tables 3-5. The underline in Tables 1-5 indicates that it is outside the scope of the present invention or that the test results are not good.

  No. in Table 3 Nos. 1 to 23 are examples of the present invention that satisfy all the conditions defined in the present invention. 24 to 60 are comparative examples that do not satisfy the conditions defined in the present invention.

No. 1 to 23, 700 ° C. high temperature tensile test 0.2% proof stress: 1168 to 1373 MPa, cross-sectional hardness at room temperature: 406 to 531 HV _0.5 , cross-sectional hardness measured at room temperature after holding at 700 ° C. for 400 hours: 372 ~ 612HV _0.5 , reduction in cross-section hardness (sag resistance): -120 ~ 38HV, compared with conventional Ni-based heat-resistant alloys, the Ni content is reduced to 35.2-49.7% Nevertheless, it can be seen that the heat resistance (0.2% proof stress and sag resistance of the high-temperature tensile test) is equivalent or superior.

  On the other hand, N0.24-60 does not satisfy the chemical composition, A and B values specified in the present invention, or does not satisfy the final cold rolling rate, or does not perform reheating. Ti composition in the compound phase: less than 3.5% in atomic%, Nb composition: less than 0.8% in atomic%, hardness after 700-hour aging heat treatment at 700 ° C. and hardness reduction before and after aging Either was not good. This will be specifically described.

No. In Nos. 24 and 26, since the A value was below the lower limit of the range of the present invention, the Ti content in the Ni-based intermetallic compound phase was below the lower limit of the range of the present invention, and the sag resistance was low.
No. No. 25, the B value was below the lower limit of the range of the present invention, so the Nb content in the Ni-based intermetallic compound phase was below the lower limit of the range of the present invention, and the sag resistance was low.

No. No. 27 had a low 0.2% yield strength at 700 ° C. high temperature tensile test because the C content exceeded the upper limit of the present invention.
No. No. 28 had a low 0.2% yield strength at 700 ° C high temperature tensile test because the C content was below the lower limit of the present invention.

No. No. 29 had low sag resistance because the Si content exceeded the upper limit of the range of the present invention.
No. No. 30, since the Si content was below the lower limit of the range of the present invention, the 700 ° C high temperature tensile test 0.2% proof stress was low.

No. No. 31 had low sag resistance because the Mn content exceeded the upper limit of the range of the present invention.
No. No. 32 had a Mn content lower than the lower limit of the range of the present invention, and the 700 ° C. high temperature tensile test 0.2% proof stress was low.

No. No. 33 had a low 0.2% yield strength at 700 ° C. high temperature tensile test because the P content exceeded the upper limit of the range of the present invention.
No. No. 34 had a low 0.2% yield strength at 700 ° C. high temperature tensile test because the S content exceeded the upper limit of the range of the present invention.

No. No. 35 had low sag resistance because the Cr content exceeded the upper limit of the range of the present invention.
No. No. 36 had a low 0.2% yield strength at 700 ° C. high temperature tensile test because the Cr content was below the lower limit of the range of the present invention.

No. No. 37 had a low 0.2% yield strength at 700 ° C. high temperature tensile test because the Ni content exceeded the upper limit of the range of the present invention.
No. No. 38 had a low 0.2% yield strength at 700 ° C. high temperature tensile test because the Ni content was below the lower limit of the range of the present invention.

No. No. 39 had low sag resistance because the N content exceeded the upper limit of the range of the present invention.
No. No. 40 had a low 0.2% yield strength at 700 ° C high temperature tensile test because the N content was below the lower limit of the range of the present invention.

No. No. 41 had low sag resistance because the Al content exceeded the upper limit of the range of the present invention.
No. No. 42 had a low 0.2% yield strength at 700 ° C high temperature tensile test because the Al content was below the lower limit of the range of the present invention.

No. No. 43 had low sag resistance because the Ti content exceeded the upper limit of the range of the present invention.
No. 44, since the Ti content falls below the lower limit of the range of the present invention, the Ti content in the Ni-based intermetallic compound phase falls below the lower limit of the range of the present invention, and the 700 ° C. high temperature tensile test 0.2% yield strength and resistance It was not very lean.

No. No. 45 had low sag resistance because the Mo content exceeded the upper limit of the range of the present invention.
No. No. 46 had a Mo content of less than the lower limit of the range of the present invention, so the 700 ° C. high temperature tensile test 0.2% proof stress and sag resistance were low.

No. No. 47 had low sag resistance because the Nb content exceeded the upper limit of the range of the present invention.
No. In No. 48, the Nb content was below the lower limit of the range of the present invention, so the 700 ° C. high temperature tensile test 0.2% proof stress and sag resistance were low.

No. In No. 49, the Cu content exceeded the upper limit of the range of the present invention, so the 700 ° C. high temperature tensile test 0.2% proof stress and sag resistance were low.
No. 50, the Ni and Nb content exceeds the upper limit of the range of the present invention, and the Al and Ti content falls below the lower limit of the range of the present invention, so the Ti content in the Ni-based intermetallic compound phase is within the range of the present invention. The 700% high temperature tensile test 0.2% proof stress was low.

  No. Nos. 51 to 56 are more particularly No. 51 because no reheating after rough rolling is performed. 55, the B value is below the lower limit of the range of the present invention. In No. 56, since the Ni and Nb contents exceed the upper limit of the range of the present invention and the Al and Ti contents are lower than the lower limit of the range of the present invention, the Ti and Nb contents in the Ni-based intermetallic compound phase are the present invention. It was below the lower limit of the range, and the sag resistance was low.

  Furthermore, no. In 57-60, since the final cold rolling rate was too high, the Ti and Nb contents in the Ni-based intermetallic compound phase were below the lower limit of the range of the present invention, and the sag resistance was low.

Claims (12)

In mass%, C: 0.0020 to 0.10%, Si: 0.020 to 3.0%, Mn: 0.020 to 2.0%, P: less than 0.050%, S: 0.010 %: Cr: 12.0% or more and less than 25.0%, Ni: more than 35.0% and less than 50.0%, N: 0.0005 to 0.020%, Al: more than 3.0% 5.0 %, Ti: more than 1.5% and less than 3.0%, Mo: 1.0 to 2.5%, Nb: 2.25 to 4.00%, Cu: less than 0.3%, Ti , Nb and Al content (% by mass) are [Ti], [Nb] and [Al], respectively, [Ti] / [Al] ≧ 0.50, [Nb] / [Al] ≧ 0. An alloy base plate for a heat-resistant member that satisfies the relationship of 75, has a chemical composition in which the balance is Fe and impurities, and exhibits a metal structure consisting only of an austenite phase,
When heat-treated at 700 ° C. for 1 hour, the Ni-based intermetallic compound is present in the austenite matrix, and the Ni-based intermetallic compound is formed with respect to the entire chemical composition constituting the Ni-based intermetallic compound. An alloy base plate for a heat-resistant member, wherein the chemical composition of Ni, Ti and Nb contained in the compound occupies more than 60%, 3.5% or more and 0.8% or more, respectively, in atomic%.   The alloy base plate for a heat-resistant member according to claim 1, wherein after the heat treatment at 700 ° C. for 1 hour, the hardness reduction before and after holding at 700 ° C. for 400 hours is 40 HV or less.   The alloy base plate for a heat-resistant member according to claim 1 or 2, comprising at least one of Co: 3.0% or less and W: less than 3.0% by mass.   The heat-resistant member according to any one of claims 1 to 3, comprising at least one of B: 0.01% or less, Ca: 0.005% or less, and Mg: 0.002% or less in mass%. Alloy base plate. In mass%, C: 0.0020 to 0.10%, Si: 0.020 to 3.0%, Mn: 0.020 to 2.0%, P: less than 0.050%, S: 0.010 %: Cr: 12.0% or more and less than 25.0%, Ni: more than 35.0% and less than 50.0%, N: 0.0005 to 0.020%, Al: more than 3.0% 5.0 %, Ti: more than 1.5% and less than 3.0%, Mo: 1.0 to 2.5%, Nb: 2.25 to 4.00%, Cu: less than 0.3%, Ti , Nb and Al content (% by mass) are [Ti], [Nb] and [Al], respectively, [Ti] / [Al] ≧ 0.50, [Nb] / [Al] ≧ 0. 75, an alloy plate for a heat-resistant member having a chemical composition with the balance of 75 and the balance being Fe and impurities,
Presents a metal structure in which a Ni-based intermetallic compound exists in the austenite matrix,
The chemical composition of Ni, Ti, and Nb contained in the Ni-based intermetallic compound with respect to the entire chemical composition that constitutes the Ni-based intermetallic compound is atomic%, more than 60%, 3.5% or more, respectively. An alloy plate for a heat-resistant member, which occupies 0.8% or more.   The alloy plate for a heat-resistant member according to claim 5, wherein a hardness reduction margin before and after holding at 700 ° C. for 400 hours is 40 HV or less.   The alloy plate for a heat-resistant member according to claim 5 or 6, comprising at least one of Co: 3.0% or less and W: less than 3.0% by mass%.   For heat-resistant members according to any one of claims 5 to 7, containing at least one of B: 0.01% or less, Ca: 0.005% or less, and Mg: 0.002% or less in mass%. Alloy plate. In mass%, C: 0.0020 to 0.10%, Si: 0.020 to 3.0%, Mn: 0.020 to 2.0%, P: less than 0.050%, S: 0.010 %: Cr: 12.0% or more and less than 25.0%, Ni: more than 35.0% and less than 50.0%, N: 0.0005 to 0.020%, Al: more than 3.0% 5.0 %, Ti: more than 1.5% and less than 3.0%, Mo: 1.0 to 2.5%, Nb: 2.25 to 4.00%, Cu: less than 0.3%, Ti , Nb and Al content (% by mass) are [Ti], [Nb] and [Al], respectively, [Ti] / [Al] ≧ 0.50, [Nb] / [Al] ≧ 0. A gasket for an exhaust system member of an engine having a chemical composition satisfying the relationship of 75, the balance being Fe and impurities,
Presents a metal structure in which a Ni-based intermetallic compound exists in the austenite matrix,
The chemical composition of Ni, Ti, and Nb contained in the Ni-based intermetallic compound with respect to the entire chemical composition that constitutes the Ni-based intermetallic compound is atomic%, more than 60%, 3.5% or more, respectively. A gasket for an exhaust member of an engine characterized by occupying 0.8% or more.   The gasket for exhaust system members of an engine according to claim 9, wherein a hardness reduction before and after holding at 700 ° C for 400 hours is 40 HV or less.   The gasket for an exhaust system member of an engine according to claim 9 or 10, wherein the gasket contains at least one of Co: 3.0% or less and W: less than 3.0% by mass. The exhaust of an engine according to any one of claims 9 to 11, containing at least one of B: 0.01% or less, Ca: 0.005% or less, and Mg: 0.002% or less in mass%. Gasket for system members.