JP2023029224A - Heat-resistant alloy material and elastic member formed by processing the same - Google Patents

Abstract

To provide precipitation-strengthening heat-resistant alloy material for an elastic member for a device used at high temperature up to a maximum of 900°C, and to provide an elastic member formed by processing the same.SOLUTION: A heat-resistant alloy material comprises a Ni-Fe-based alloy. The alloy has a component composition comprising, by mass, Ni: 40-62%, Cr: 13-20%, Nb+Ta: 0.2-2.0%, Ti: 1.5-2.8%, Al: 1.0-2.0% (provided that Ti/Al:2.3 or less), W: 3.0% or less, Mo: 2.0% or less (provided that Mo+(1/2)W: 1.0-2.5%), Cu: 0.1-3.0%, B: 0.001-0.010%, Zr: 0.01-0.05%, and the balance consisting of Fe and unavoidable impurities, wherein the heat-resistant alloy material is a plate material with a thickness of 1.5 mm or less, which has a rolled and annealed structure with an average grain size of more than 100 μm but 250 μm or less. The elastic member is adjusted to Hv300-450 through an aging treatment after processing and forming the heat-resistant alloy material.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a precipitation-strengthened heat-resistant alloy material made of a Ni--Fe-based alloy and an elastic member formed by processing and molding the same for elastic members of equipment used at high temperatures.

In recent years, in turbochargers for automobiles, as the temperature of the exhaust gas rises, so does the operating temperature. For elastic members used in such a high-temperature environment, for example, a heat-resistant alloy material made of Inconel 718 (trade name) alloy, which is a precipitation-strengthened Ni—Fe-based alloy, is used. However, in this alloy, the strengthening phases γ″ phase and γ' phase change to the δ phase, which does not contribute to the enhancement of mechanical strength, in a high temperature range of 800°C or higher. It becomes impossible to maintain the spring characteristic as a member.

In addition, Nimonic 263 (trade name), which is a Ni--Cr alloy used for aircraft turbine components, exhibits excellent high-temperature mechanical strength at 800°C, but when exposed to a higher temperature range, a strengthening phase of γ The ' phase disappears, and spring characteristics at high temperatures cannot be expected. In addition, since it contains nearly 20% Co, it is disadvantageous in terms of material cost.

Here, Patent Document 1 discloses a heat-resistant alloy material composed of a Co-free Ni—Fe-based alloy, which can be used for metallic gaskets of automobile engine cylinder heads in place of austenitic stainless steel. By using an alloy sheet material that can be easily formed even by cold working without active aging treatment, the γ' phase precipitates in the austenite matrix during use at high temperatures, maintaining high high-temperature strength. It is possible.

Japanese Patent No. 6270194

In a heat-resistant alloy material made of Ni—Fe-based alloy, an elastic member that can be used at a temperature higher than the conventional temperature of 800° C., for example, up to 900° C. is required. On the other hand, in the heat-resistant alloy material composed of a Ni--Fe-based alloy that does not contain Co in Patent Document 1, the assumed use temperature as a gasket is 600 to 800°C, and it is not necessarily assumed to be used at 850°C or higher. do not have.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a Ni-Fe-based elastic member for equipment used at high temperatures, which can be used up to 900°C. An object of the present invention is to provide a precipitation-strengthened heat-resistant alloy material made of an alloy and an elastic member formed by processing the same.

The heat-resistant alloy material according to the present invention contains, in mass %, Ni: 40 to 62%, Cr: 13 to 20%, Nb+Ta: 0.2 to 2.0%, Ti: 1.5 to 2.8%, Al: 1.0 to 2.0% (however, Ti/Al: 2.3 or less), W: 3.0% or less, Mo: 2.0% or less (however, Mo + (1/2) W: 1.0 ~2.5%), Cu: 0.1 to 3.0%, B: 0.001 to 0.010%, Zr: 0.01 to 0.05%, C: 0.08% or less, Si: 1.0% or less, Mn: 1.0% or less, P: 0.02% or less, S: 0.01% or less, Ca: 0.01% or less, Mg: 0.01% or less, balance Fe and unavoidable It is characterized by being a sheet material having a thickness of 1.5 mm or less and having a roll-annealed structure with an average crystal grain size of more than 100 μm and 250 μm or less.

According to such characteristics, by processing and forming and aging, it is possible to provide a heat-resistant alloy material that can maintain mechanical strength as an elastic member even when used at high temperatures up to 900°C.

1 is a flowchart showing a method of manufacturing a heat-resistant alloy material and an elastic member according to the present invention; FIG. FIG. 3 is a schematic diagram of a cross section of a metal showing a white texture without γ' particles. 1 is a list of component compositions for Examples and Comparative Examples. 1 is a list of test results of examples and comparative examples. 10 is a photograph of a cross-sectional structure after a heating test in Example 9. FIG.

A heat-resistant alloy material and an elastic member formed by processing the same as one embodiment according to the present invention will be described with reference to FIGS. 1 and 2. FIG.

The heat-resistant alloy material according to this embodiment has, in terms of % by mass, Ni: 40 to 62%, Cr: 13 to 20%, Nb+Ta: 0.2 to 2.0%, Ti: 1.5 to 2.8%, Al : 1.0 to 2.0% (however, Ti/Al: 2.3 or less), W: 3.0% or less, Mo: 2.0% or less (however, Mo + (1/2) W: 1.0% or less) 0 to 2.5%), Cu: 0.1 to 3.0%, B: 0.001 to 0.010%, Zr: 0.01 to 0.05%, C: 0.08% or less, Si : 1.0% or less, Mn: 1.0% or less, P: 0.02% or less, S: 0.01% or less, Ca: 0.01% or less, Mg: 0.01% or less , and the balance is substantially Fe.

As shown in FIG. 1, such an Fe—Ni-based alloy is made into a slab or billet by hot forging or the like, and further formed into a desired shape by hot rolling (hot rolling: S1). Furthermore, cold rolling is performed to give work strain so as to obtain a predetermined rolling ratio (cold rolling: S2). Subsequently, annealing treatment is performed so as to partially relax the stress due to working strain by heating (annealing treatment: S3). In the cold rolling (S2), the rolling may be performed in a plurality of times, and the annealing treatment (S3) is similarly performed after each rolling. The conditions of each step are set so that after the final annealing treatment (S3), a rolled annealed structure having an average grain size of more than 100 μm and 250 μm or less is obtained, and a plate material having a thickness of 1.5 mm or less is obtained. be done.

It should be noted that the average crystal grain size is required to be relatively large in order to maintain a high creep strength at a temperature of 800° C. or higher, for example, a temperature of about 900° C., which is the operating environment. On the other hand, if it is too large, the ductility will be lowered and the workability will be impaired. Therefore, the average crystal grain size should be within the above-described range of more than 100 μm and 250 μm or less. It is more preferable to set the average crystal grain size within the range of 120 to 200 μm. The average crystal grain size is measured at the central portion in the thickness direction of a cross section (TD cross section) in the sheet width direction based on JIS G0551:2013.

As a result, a γ' precipitation hardening heat-resistant alloy material can be obtained. Thus, the heat-resistant alloy material in this embodiment is obtained by the annealing treatment (S3) as the final step.

Further, the obtained heat-resistant alloy material is processed and formed into a predetermined shape by cutting, machining, etc. (processing and forming: S4), and fine precipitates of the γ' phase are dispersed and precipitated in the crystal grains by aging treatment. By hardening (aging treatment: S5), elastic members such as metal gaskets, disk springs, and leaf springs can be obtained. At this time, the hardness of the elastic member is preferably adjusted within the range of Hv 300 to 450 by aging treatment (S5).

This can be used as an elastic member for equipment used at high temperatures, which can be used up to 900°C.

The component composition described above may further contain Co: 0.05 to 5.0% by mass. Addition of Co can improve the creep strength.

In addition, the component composition described above may contain either one or both of V: 0.05 to 1.0% by mass and REM: 0.005 to 0.05% by mass. The addition of V can improve the mechanical strength, and the addition of REM can improve the oxidation resistance of grain boundaries. REM is a rare earth element, and includes a total of 17 elements including Sc, Y and lanthanoids, and one or more of these elements can be added so that the sum of these elements is within the above range.

In addition, the above-described component composition allows N: 0.020% by mass or less and O: 0.005% by mass or less as impurities that are inevitably contained. It is preferable to ensure the

By the way, the fine precipitates of the γ' phase are important for improving the mechanical strength at high temperatures, and particularly when they are precipitated inside the crystal grains, they greatly contribute to the improvement of the creep strength. The volume fraction of the precipitated γ' phase is roughly proportional to the solid solution temperature of the γ' phase. Therefore, the solid solution temperature of the γ' phase is preferably 940°C or higher. As a result, the γ' phase can be sufficiently dissolved in the annealing treatment (S3), and the γ' phase can be sufficiently precipitated in the aging treatment (S5). On the other hand, if the solid solution temperature of the γ' phase is excessively high, the hot workability of the alloy is lowered. Therefore, the solid solution temperature of the γ' phase is preferably 1010°C or lower.

Note that the solid solution temperature of the γ' phase can be adjusted by the respective contents of Ni, Al, Ti, Nb, and Ta that constitute the γ' phase, and can be calculated by thermodynamic calculation. Therefore, it is also preferable to adjust the contents of these components so that the solid solution temperature of the γ' phase calculated by thermodynamic calculation is within the above range of 940 to 1010°C. For thermodynamic calculation, thermodynamic calculation software Thermo-Calc2020a, for example, can be used. The same software can be used to calculate the solid solution temperature of the γ' phase using TTNi8 as a thermodynamic database.

As described above, the fine precipitates of the γ' phase are important for improving the mechanical properties at high temperatures. In some cases, the mechanical strength as an elastic member is lowered by transforming to η phase or δ phase.

As shown in FIG. 2, when the γ' particles 1 due to the γ' phase precipitates are dispersed and precipitated, a white structure 2 (inside the dotted line) in which the γ' particles 1 do not exist may be generated. The white structure 2 contains plate-like precipitates 3 of η phase or δ phase, and sometimes contains carbonitrides 4 . That is, since the γ' particles 1 are transformed into the plate-like precipitates 3, it is thought that the γ' particles 1 around them are reduced. Such a white structure 2 becomes a portion where precipitation strengthening by the γ' particles 1 cannot be obtained, and thus may lead to a decrease in mechanical strength.

Therefore, in order to maintain the mechanical properties at high temperatures for a long time in a use environment of about 900° C., it is also preferable to have a component composition that suppresses the amount of white tissue generated. Whether or not such a composition is obtained can be confirmed by a heating test on the heat-resistant alloy material. As a heating test, for example, a test piece is cut out from a heat-resistant alloy material and exposed to an environment of 900° C. for 400 hours. After that, the cross-sectional area ratio of the white structure in which no γ' phase particles are present is measured. The cross-sectional area ratio of white tissue is preferably 10% or less, more preferably 5% or less.

[Manufacturing test]
Next, the results of actually manufacturing heat-resistant alloy materials and conducting various tests will be described.

First, heat-resistant alloy materials were obtained in the same manner as described above, using alloys having respective chemical compositions shown in Examples 1 to 9 and Comparative Examples 1 to 4 in FIGS. 3(a) and 3(b). All heat-resistant alloy materials were rolled to a thickness of 1 mm.

As shown in FIG. 4, the obtained heat-resistant alloy material was examined for crystal grain size, solid solution temperature of γ′ phase, cross-sectional area ratio of white structure, and 90° bending workability. Further, the obtained heat-resistant alloy material was subjected to an aging treatment of air cooling after holding at 800° C. for 8 hours, and the creep strength was investigated.

Based on JIS G0551:2013, the grain size was the average grain size measured at the central portion in the thickness direction of the cross section (TD cross section) in the plate width direction.

The solid solution temperature of the γ' phase can be calculated with thermodynamic calculation software, but here it was calculated using Thermo-Calc2020a and TTNi8 as a thermodynamic database.

The cross-sectional area ratio of the white structure was determined by observing the cross-sectional structure with an optical microscope after conducting a heating test in which the obtained heat-resistant alloy material was exposed to 900° C. for 400 hours.

For creep strength, a creep test was performed with a tensile load of 50 MPa in an atmosphere of 900 ° C. If the time until rupture was 50 hours or more, it was judged as "excellent" and "O" was recorded, and 40 hours or more. Those of less than 50 hours were judged to be "good" and recorded "Δ", and those of less than 40 hours were judged to be "poor" and recorded "x".

For the 90° bending workability, the heat-resistant alloy material was bent at 90° and the surface was observed. It was judged as "defective" and "x" was recorded.

In Examples 1 to 9, the average crystal grain size is in the range of more than 100 μm and 250 μm or less, the solid solution temperature of the γ′ phase is in the range of 940 to 1010° C., and the cross-sectional area ratio of the white structure is 10% or less. I was able to The creep strength was rated as "excellent" except for Example 9, which was rated as "good", and the 90° bending workability was all rated as "good".

As shown in FIG. 5, in Example 9, a slight white structure was generated, and the cross-sectional area ratio was 7%. Compared to other examples, the relatively high Ti/Al ratio of 2.09 slightly lowered the stability of the γ' phase, and it was thought that the creep strength was slightly lowered due to the formation of the white microstructure.

In Comparative Example 1, the solid solution temperature of the γ' phase was as low as 861°C, so it was considered that the precipitates of the γ' phase could not be sufficiently maintained. As a result, the cross-sectional area ratio of the white tissue was as high as 90% or more, and the creep strength was "poor".

In Comparative Examples 2 and 3, an alloy having the same chemical composition as in Example 2 was used, and the conditions of cold rolling (S2) and annealing treatment (S3) were changed to change the average grain size. be. The average crystal grain size was as small as 53 μm in Comparative Example 2 and as large as 303 μm in Comparative Example 3, compared to 145 μm in Example 2. As a result, in Comparative Example 2, the creep strength was "bad" due to the small crystal grain size. On the other hand, in Comparative Example 3, the creep strength was "excellent" due to the large crystal grain size, but the 90° bending workability was "poor".

In Comparative Example 4, since the solid solution temperature of the γ' phase was as low as 842°C, the cross-sectional area ratio of the white structure was increased to 90% or more as in Comparative Example 1, and the creep strength was "poor".

By the way, the range of the composition of the alloy that can provide the same mechanical properties and good judgment as those of the above-described examples is determined as follows.

Ni is an element necessary to improve heat resistance and corrosion resistance by making the matrix austenite, generate the γ' phase, which is a precipitation strengthening phase, and obtain phase stability and mechanical strength to ensure hot workability. is. On the other hand, an excessive content causes an increase in cost. Taking these into consideration, Ni is in the range of 40 to 62% by mass, preferably 40 to 54%, more preferably 45 to 54%.

Cr is an element necessary to ensure heat resistance. On the other hand, if it is contained excessively, it precipitates the σ phase and lowers toughness and mechanical strength at high temperatures. Considering these, Cr is in the range of 13 to 20%, preferably in the range of 13 to 18% by mass.

Ti, along with Al, Nb, and Ta, is an element necessary to combine with Ni to form a γ' phase effective for improving mechanical strength at high temperatures and to maintain a high solid solution temperature of the γ' phase. be. On the other hand, if it is contained excessively, workability is lowered, and plate-like η phase (Ni ₃ (Ti, Nb)) is likely to be precipitated, thereby lowering mechanical strength and toughness at high temperatures. Considering these, Ti is in the range of 1.5 to 2.8% by mass.

Al is an element necessary for bonding with Ni to form a γ' phase and ensuring mechanical strength at high temperatures. Considering these, Al is in the range of 1.0 to 2.0% by mass.

Here, Ti/Al governs the phase stability of the γ' phase, which is fine precipitates precipitated for precipitation hardening. Such phase stability is obtained at 2.3 or less, but if it exceeds 2.3, precipitation of plate-like η phase is induced. Therefore, Ti/Al is set to 2.3 or less. Moreover, it is preferably 2.0 or less.

Nb is a γ' phase-forming element and has the effect of promoting hardening by the γ' phase. On the other hand, if it is contained excessively, the η phase (Ni ₃ (Ti, Nb)) tends to precipitate, resulting in a decrease in mechanical strength at high temperatures. Ta is also a γ' phase-forming element and has the effect of promoting hardening by the γ' phase. On the other hand, if it is contained excessively, the η phase (Ni ₃ (Ti, Ta)) tends to be precipitated, and likewise the mechanical strength at high temperatures is lowered. In consideration of these, in mass %, Nb is in the range of 2.0% or less, and Ta is in the range of 2.0% or less. However, Nb+Ta should be within the range of 0.2 to 2.0%.

W and Mo are elements necessary for strengthening the matrix phase and improving the mechanical strength at high temperatures by forming a solid solution. On the other hand, an excessive content causes an increase in cost and a decrease in workability. Considering these, in mass%, W is 3.0% or less, Mo is 2.0% or less, and Mo + (1/2) W is 1.0 to 2.5% Within range.

Cu is an element that improves cold workability and is also effective in improving oxidation resistance. On the other hand, if it is contained excessively, the hot workability is lowered. Considering these, Cu is in the range of 0.1 to 3.0% by mass.

B is an element that contributes to the improvement of hot workability, suppresses the formation of η phase, prevents deterioration of mechanical strength and toughness at high temperature, and further improves high temperature creep strength. On the other hand, an excessive content lowers the melting point of the alloy and degrades the hot workability. Considering these, B is in the range of 0.001 to 0.010% by mass.

Zr is an element effective for segregating at grain boundaries to strengthen the grain boundaries and improve mechanical strength at high temperatures. On the other hand, if it is contained excessively, the hot workability is lowered. Considering these, Zr is in the range of 0.01 to 0.05% by mass.

C is an element that combines with Cr, Ti, Nb, and Ta to form carbides and is effective in improving mechanical strength at high temperatures, and can be optionally added. On the other hand, if it is contained in excess, carbides are excessively formed, which impairs hot workability, cold workability, toughness, and ductility. It's gone. Considering these, C is within the range of 0.08% or less in mass%.

Si is an element that mainly acts as a deoxidizing agent during melting and refining, and can be optionally added. On the other hand, excessive content lowers the toughness and impairs workability. Considering these, Si is within the range of 1.0% or less in mass %.

Mn, like Si, is an element that acts as a deoxidizing agent and can be optionally added. On the other hand, an excessive content impairs workability and oxidation resistance at high temperatures. Considering these, Mn is within the range of 1.0% or less in mass %.

Mg and Ca fix S and contribute to the improvement of hot workability. On the other hand, if it is contained excessively, a compound of each element is formed, which causes deterioration of hot workability. In consideration of these, Mg and Ca are each within the range of 0.01% or less in terms of mass %. One of these elements may be added, or both of them may be added.

P and S are impurities that are inevitably contained and deteriorate hot workability. Therefore, in mass %, P is 0.02% or less and S is 0.01% or less.

N is an impurity element that is inevitably contained, and combines with Ti and Al to form nitrides, which lowers cold workability. Therefore, N is preferably in the range of 0.020% or less in mass %.

O is an impurity element that is inevitably contained, and combines with Al, Ca, etc. to form inclusions, which lowers the cold workability. Therefore, O is preferably in the range of 0.005% or less in mass %.

Co is effective for improving creep strength at high temperatures. On the other hand, an excessive content not only leads to an increase in cost, but also lowers the phase stability of the γ' phase. Taking these into consideration, Co can be optionally contained within the range of 0.05 to 5% by mass.

V is an effective element for forming carbides and improving mechanical strength at high temperatures. On the other hand, if it is contained excessively, it causes deterioration of oxidation resistance. Considering these, V can be arbitrarily contained within the range of 0.05 to 1.0% by mass.

A rare earth element (REM) is an element that segregates at grain boundaries and is effective in improving oxidation resistance. On the other hand, if it is contained excessively, it causes deterioration of hot workability. Taking these into consideration, REM can be arbitrarily contained within the range of 0.005 to 0.05% by mass.

Other unavoidable impurity elements include Te, As, Sn, Sb, Se, Pb, Bi and the like. When these elements are excessively contained, the hot workability and high temperature strength of the alloy are remarkably lowered. Therefore, it is preferable that the content of these elements is limited to 0.0050% or less by mass % for each element. Examples of unavoidable impurities further include less than 0.05% by mass of Co, less than 0.05% by mass of V, and less than 0.005% by mass of REM.

Although representative embodiments of the present invention have been described above, the present invention is not necessarily limited thereto, and a person skilled in the art will be able to make modifications without departing from the spirit of the present invention or the scope of the appended claims. , one may find various alternatives and modifications.

1 γ' particles 2 White texture 3 Plate-like precipitates 4 Carbonitride

Claims (7)

in % by mass,
Ni: 40-62%,
Cr: 13-20%,
Nb + Ta: 0.2 to 2.0%,
Ti: 1.5-2.8%,
Al: 1.0 to 2.0% (Ti/Al: 2.3 or less),
W: 3.0% or less,
Mo: 2.0% or less (however, Mo + (1/2) W: 1.0 to 2.5%),
Cu: 0.1 to 3.0%,
B: 0.001 to 0.010%,
Zr: 0.01 to 0.05%,
C: 0.08% or less,
Si: 1.0% or less,
Mn: 1.0% or less,
P: 0.02% or less,
S: 0.01% or less,
Ca: 0.01% or less,
Mg: 0.01% or less,
Made of an alloy with a component composition consisting of the balance Fe and unavoidable impurities,
A heat-resistant alloy material characterized by being a plate material having a thickness of 1.5 mm or less and having a rolling-annealed structure with an average crystal grain size of more than 100 μm and 250 μm or less. 2. The heat-resistant alloy material according to claim 1, wherein the composition contains Co: 0.05 to 5.0%. 3. The heat-resistant alloy material according to claim 1, wherein the component composition contains either or both of V: 0.05 to 1.0% and REM: 0.005 to 0.05%. 4. The heat-resistant alloy material according to claim 1, wherein N: 0.020% or less and O: 0.005% or less. The heat-resistant alloy material according to any one of claims 1 to 4, wherein the solid solution temperature of the γ' phase calculated by thermodynamic calculation for the composition is within the range of 940 to 1010°C. The heat-resistant alloy material according to any one of claims 1 to 5, wherein the cross-sectional area ratio of the white microstructures containing no γ' phase particles is 10% or less after being exposed to 900°C for 400 hours. A metal gasket, disk spring, or leaf spring formed by processing and molding the heat-resistant alloy material according to any one of claims 1 to 6, wherein Hv is adjusted to 300 to 450 by aging treatment after processing and molding. An elastic member characterized by:

Images