JPH05179378A - Ni-base alloy excellent in room temperature and high temperature strength - Google Patents

Abstract

PURPOSE:To obtain an Ni-base alloy having high strength and toughness in a wide range from a room temp. to a high temp. by preparing an Ni-base alloy contg. specified rations of C, Si, Mn, Al, Fe, W, Mo, Nb, Ti, P and S. CONSTITUTION:An Ni-base alloy contg., by weight, <=0.1% C, <=1.0% Si, 0.1 to 2.0% Mn, 0.03 to 15.0% Al, <=10.0% Fe and 15.0 to 55.0% W independently or in combination with Mo (in the case of combination, the content of Mo is regulated to <=20.0%) and furthermore contg. one or two kinds of 3.0 to 15.0% Nb and >3.0 to 10.0% Ti, and the balance Ni with inevitable impurities and in which, in the impurities, the content of P is regulated to <=0.030% and that of S to <=0.010% is prepd. In this way, the objective Ni-base alloy excellent in strength, toughness and ductility in a wide temp. range from a room temp. to a high temp. of about >=1000 deg.C, preferably, to about 1200 deg.C can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is not limited to high temperature strength,
Various tools (mandrel bars, plugs, dies, rolls, etc.) that require high strength and toughness even at room temperature, valves for motors, structural members such as combustion chambers, heat treatment furnaces, boilers, etc. The present invention relates to an alloy suitable as a material for applications.

[0002]

2. Description of the Related Art Alloy 71, which is a typical existing Ni-based alloy
8 (trade name) exhibits excellent strength and toughness up to 800 ° C, but at a high temperature of 1000 ° C or higher, the strength is significantly lower than that of the Ni-W alloy. The hardness of this alloy 718 at room temperature has a limit of about 43 Rockwell (HRC), and this value is JIS ・ SKD61 of the existing representative hot work tool steel alloy.
Since it does not reach the level of, it does not have sufficient performance to be used in a wide range from room temperature to high temperature.

Japanese Unexamined Patent Publication No. 54-24214 proposes a heat-resistant steel containing Ni and Cr as main components. The steel of the present invention has excellent thermal fatigue properties, but the sum of Mo + W + Nb + Ta is relatively low at 10.0% or less, and therefore the high temperature strength is low, and its applicable range is estimated to be up to about 1100 ° C. The inventor of the present invention has found that Japanese Patent Application Laid-Open Nos. 2-153035 and 3-613
In Japanese Patent Laid-Open No. 45-45, an excellent Ni-W alloy having high strength and ductility even at a high temperature of 1200 ° C. was proposed, but these alloys of the prior inventions have a hardness at room temperature of at most HRC.
It has a room temperature strength lower than that of JIS / SKD61 for use as a mandrel bar or the like, and when used as a tool, there are problems such as dents, elongation or tearing.

As described above, an alloy which maintains a high strength from room temperature to a high temperature of about 1200 ° C. and has good toughness and ductility has not yet been developed.

[0005]

The object of the present invention is to be suitable as a material for various structural members and overlays having high strength in a wide range from room temperature to high temperature and also having toughness and ductility. To provide an alloy.

[0006]

The summary of the present invention is as follows.
It is in a Ni-based alloy. All% relating to the content of alloy components mean% by weight.

(1) C: 0.1% or less, Si: 1.0% or less, Mn: 0.1
~ 2.0%, Al: 0.03 to 15.0%, Fe: 10.0% or less, W alone or in combination with Mo 15.0 to 55.0% (However, in the case of composite
Mo is 20.0% or less), and further contains one or two of Nb: 3.0 to 15.0% and Ti: 3.0% to 10.0% or less, and the balance is Ni and inevitable impurities. Ni-based alloy excellent in room temperature and high temperature strength, characterized in that P is 0.030% or less and S is 0.010% or less.

(2) The alloy according to (1) above, further containing less than 15.0% Cr.

(3) In addition, 0.01% or less of each Mg, Y, L
The above (1) or (2) containing at least one of a, Ce and B
Alloy of.

[0010]

[Function] Materials with various uses as described above are
It is necessary to simultaneously provide strength, toughness and ductility in a wide temperature range of 1000 ° C or higher, preferably 1200 ° C.

That is, at room temperature, it has strength equivalent to that of die steel such as SKD61 and toughness equal to or higher than that of die steel, and further requires high strength of alloy 718 or higher at high temperature. The various characteristic values to be provided are specifically shown below.

[0012] room temperature Hardness (HRC) 40 or more (preferably 45 or higher) at room temperature toughness _(V E ₂₀₎ 2kgm / cm tensile strength at 1200 ° C. Tensile strength 40 kgf / mm ² or more at ² or more 1000 ° C. 30 kgf / mm ² Ductility at 1200 ° C 60% or more The present inventor
Various investigations were conducted with the inclusion of b: 5.5% and Ti: 1.5% in the ranges exceeding the upper limits, but in this range, the toughness and hot workability deteriorate, and room temperature and high temperature strength cannot be improved. I couldn't do it. However, limiting the content of Cr and Fe,
Moreover, the above mechanical properties can be obtained by containing a large amount of W or W + Mo, Nb, Ti, and Al. In alloys of such composition, Nb increases its melting point,
It was confirmed that the toughness also exhibits a preferable improving effect.

The present invention has been made based on the above new findings. Hereinafter, the function and effect and the proper content of the components constituting the alloy of the present invention will be described.

C: When it exceeds 0.1%, the melting point of the alloy is lowered, which causes problems such as cracking and segregation during casting. Further, since the high temperature ductility and the room temperature ductility are significantly deteriorated, C
Is 0.1% or less.

Si: As a deoxidizing agent for the alloy, it is an effective component for improving various properties of the alloy. However, if it exceeds 1.0%, it promotes segregation during casting and formation of nonmetallic inclusions.
The upper limit is 1.0%.

Mn: It is effective as a deoxidizing agent for the alloy and one of the components that basically maintain the alloy of the present invention in the γ (austenite) structure. In addition, Mn fixes S in the alloy as MnS and improves hot workability. If it is less than 0.1%, these effects cannot be expected. When Mn exceeds 2.0%, the melting point of the alloy decreases, so that the hot workability deteriorates again. Therefore, the proper range of Mn is 0.1% to 2.0%.

Al: added as a deoxidizing agent for the alloy. further
When the Al content is 0.03% or more, the intermetallic compound (Ni ₃ Al) phase is effectively precipitated in the matrix in the composition range of the alloy of the present invention, and the room temperature and high temperature strength are improved. If it exceeds 15.0%, the melting point of the alloy is lowered and the embrittlement phase and inclusions are precipitated, and the mechanical properties such as ductility and toughness deteriorate. Therefore, the proper range of Al is 0.03% to 15.0%.

In the Fe: Ni based alloy, it is substituted with Ni and is effective in increasing the economic efficiency of the alloy. Also, a small amount of Ni reduces the hot workability and crack susceptibility during overlay welding. Although effective, if it exceeds 10.0%, an embrittlement phase precipitates and toughness deteriorates. Therefore, the Fe content is 10.0% or less.

Cr: Cr causes precipitation of an embrittlement phase when it contains a large amount of Nb, Ti or Al like the alloy of the present invention,
On the contrary, it does not have to be contained because it hinders the strength improving effect of Nb, Ti, and Al. However, when it is necessary to consider prevention of high-temperature oxidation, it is necessary to suppress precipitation of the embrittlement phase and to contain it in a range that does not cause a decrease in strength.
The Cr range is less than 15.0%.

W: Even if contained in a large amount, the strength of the matrix is remarkably increased without deteriorating the toughness at room temperature, and further, the effect of suppressing the precipitation of the embrittlement phase even when used for a long time such as in a boiler tube. However, if it is less than 15.0%, the desired strength cannot be obtained.

On the other hand, if it exceeds 55.0%, the Ni content is reduced as a result, so that it is difficult to maintain the γ phase and the precipitation of the brittle phase is promoted. Furthermore, since the melting point of the alloy becomes high, melting by ordinary means is impossible, but up to 55.0% W, the melting point can be suppressed to 1650 ° C or less, and melting by a general electric furnace is possible. Is possible. Therefore, the proper range of W is from 15.0% to 55.0%.

Since it has the same effect as Mo: W, it can be used by substituting a part of W. However, the melting point of the alloy is lower than that of W, so that if it is contained in excess, the high temperature ductility also decreases. Further, the upper limit of the Mo content is 20.0% because it promotes precipitation of an embrittlement phase during use for a long time and deteriorates toughness and corrosion resistance.

Nb and Ti: Nb contribute to the improvement of the room temperature toughness when the Fe and Cr contents are within the proper ranges. Further, the melting point of the alloy is maintained at a relatively high temperature, and it precipitates in the matrix as a carbide / nitride, contributing to the maintenance of high temperature strength. Ti is an intermetallic compound (Ni ₃ Ti), similar to the above Al.
Also, it precipitates as carbides / nitrides like Nb and contributes to improvement of high temperature strength. However, when Nb is less than 3.0% and Ti is 3.0% or less, neither effect is obtained.
If the Nb content exceeds 15.0% and the Ti content exceeds 10.0%, the melting point of the alloy is lowered and the embrittlement phase precipitates, resulting in deterioration of ductility, toughness, and workability. Therefore, Nb is 3.0% to 15.0%, Ti
Is more than 3.0% up to 10.0%, which is the proper range for each.

Generally, Ta is often contained in the raw material Nb, but the effect of Ta is equivalent to that of Nb. Therefore, Ta may be contained together with Nb.

Mg, Ca, Y, La, Ce, B: Inclusion of these components is effective in lowering O (oxygen) and fixing S in the alloy, and as a result, improves toughness at room temperature and high temperature ductility. Therefore, one or more kinds may be contained. However, in order to prevent the deterioration of ductility at high temperature, it should be suppressed to 0.01% or less.

Impurities: In addition to Ta, P, S, N, O (oxygen), and Co associated with Ni, and the like are inevitably mixed as impurities in the alloy of the present invention.

P and S are components that segregate during casting and cause cracking, and also deteriorate hot workability. Therefore, in the alloys of the present invention aiming at a higher level in room temperature toughness and high temperature strength, the smaller the better, the more preferable P is 0.030% or less (desirably 0.01% or less) and S 0.010% or less (desirably).
0.005% or less).

N may be contained up to about 0.2% by weight depending on the melting raw material, the manufacturing method, etc. of the alloy of the present invention, but if it is this amount, the performance of the alloy of the present invention is not deteriorated.

O (oxygen) is preferably 0.01% by weight or less in order to maintain the performance of the alloy of the present invention.

The alloy of the present invention is melted in a usual melting and refining step and then cast, and as-cast or forged, rolled,
Although it is manufactured as the above product through processing steps such as extrusion, it reduces or avoids segregation or cracking of the ingot,
Further, it is desirable to carry out a secondary melting step such as ESR and VAR in order to improve the internal cleanliness and the performance of the product. 1050-12 as well as normal Ni-based and Co-based alloys
The solution heat treatment at 50 ° C and the age hardening heat treatment at 600 to 800 ° C contribute to the improvement of the properties of the alloy of the present invention, but they can be used as they are.

[0031]

[Example] A 150 kg alloy ingot having the composition shown in Table 1 (1) to Table 1 (3) was vacuum induction melted (VIM) and manufactured by vacuum casting. The plate material was forged and subjected to solution treatment at 1050 to 1200 ° C. Among these, a part of the alloys containing a large amount of Nb, Ti and Al was additionally subjected to age hardening treatment at 650 to 750 ° C for 2 to 50 hours. Nos. 1 to 35 in Tables 1 (1) and 1 (2) are alloys of the present invention, and Nos. 36 to 51 in Table 1 (3) are comparative alloys. Nos. 52 and 53 in Table 1 (2) are existing alloys, and No. 5
2 corresponds to Alloy 718 and No. 53 corresponds to SKD61.

Using these test materials, Rockwell hardness (HRC) and toughness at room temperature, tensile strength at 1000 ° C. and tensile strength and ductility (drawing) at 1200 ° C.
Each was measured. These test results are shown in Table 2 (1) to Table 2
Shown in (3).

When this result is compared with the alloy of the present invention, the comparative alloy and the existing alloy, it is clear from Tables 2 (1) and 2 (2) that the alloys of the present invention all have any of the above characteristics. At the same time, the comparative alloys and existing alloys shown in Table 2 (3) have room temperature toughness and 10
The tensile strength at 00 ° C is insufficient, and none of them simultaneously satisfy the properties of.

The difference in the characteristics of the alloy of the present invention between Cr-containing and Cr-free is as shown in Table 2 (1) and Table 2 (2).
Not so big. However, alloy N with high Cr content
In o.6, No.10 and No.16, the mechanical property values at 1000 ° C and 1200 ° C tend to decrease to near the target lower limit. Further, in Comparative Alloy No. 45 in which the Cr content exceeds the upper limit value of the present invention, as shown in Table 2 (3), all the characteristic values except the room temperature toughness do not reach the target values.

[0035]

[Table 1 (1)]

[0036]

[Table 1 (2)]

[0037]

[Table 1 (3)]

[0038]

[Table 2 (1)]

[0039]

[Table 2 (2)]

[0040]

[Table 2 (3)]

[0041]

The alloy of the present invention has all the properties of room temperature toughness, high temperature tensile strength and high temperature ductility, and can be applied to various structural members in a wide range from room temperature to 1200 ° C.

[0042]

Claims (3)

[Claims] 1. By weight%, C: 0.1% or less, Si: 1.0% or less,
Mn: 0.1-2.0%, Al: 0.03-15.0%, Fe: 10.0% or less,
W alone or in combination with Mo contains 15.0 to 55.0% (however, in the case of composite, Mo is 20.0% or less), and Nb: 3.0 to 15.0.
% And Ti: more than 3.0% but not more than 10.0% and one or two kinds, and the balance is Ni and inevitable impurities. P in the impurities is 0.030% or less and S is 0.010% or less. A Ni-based alloy with excellent room temperature and high temperature strength. 2. The alloy of claim 1 further comprising less than 15.0% Cr by weight. 3. Further, 0.01% by weight or less of each Mg,
The alloy according to claim 1 or 2, containing at least one of Y, La, Ce and B.