JP2020109199A - Ni-BASED ALLOY, Ni-BASED ALLOY INGOT, Ni-BASED ALLOY HOT-ROLLING SLAB AND Ni-BASED ALLOY SHEET - Google Patents

Abstract

To provide an Ni-based alloy, wherein, even though it is a high-Nb-content Ni-based alloy that contains Nb of 1.5 mass% or more in an Ni-based alloy having excellent hot workability, cracking resistance and corrosion resistance, it is possible to prevent the alloy surface from being dented or scratched when the oxidized scale occurring in a heat processing step is pushed in, and to give a good yield before and after the heat processing, offering excellent scale peelability.SOLUTION: An Ni-based alloy having excellent scale peelability comprises, in mass%, carbon (C): 0.001-0.045%, silicon (Si): 0.05-1.00%, manganese (Mn): 0.05-1.00%, phosphorus (P): 0.015% or less, sulfur (S): 0.0030% or less, chromium (Cr): 14-24%, niobium (Nb): 1.5-4.0%, iron (Fe): 3-25%, aluminum (Al): 0.01-0.20%, titanium (Ti): 0.001-0.20%, nitrogen (N): 0.003-0.020%, boron (B): 0.0010-0.0100%, oxygen (O): 0.0002-0.0020%, molybdenum (Mo) and/or tungsten (W): 0.005-0.25%, with the balance being nickel (Ni) and inevitable impurities, satisfying the relation of the following formula (where each element symbol denotes a content of the element (mass%) in the Ni-based alloy). 4.2×Mo+3.6×W+355×B≥0.60.SELECTED DRAWING: None

Description

The present invention is a Ni-based alloy excellent in stress corrosion cracking resistance and intergranular corrosion resistance, and in particular, a dent caused by the oxide scale produced by a hot working process such as hot forging being pressed. The present invention relates to a Ni-base alloy, a Ni-base alloy ingot, a slab for hot rolling of a Ni-base alloy, and a Ni-base alloy plate which can suppress surface defects such as scratches and have excellent scale releasability.

Ni-based alloys have excellent corrosion resistance and heat resistance, and are therefore used in severe operating environments. Among Ni-based alloys, for example, JIS NCF 600 equivalent material has excellent stress corrosion cracking resistance and intergranular corrosion resistance, and is therefore used as a core material of a nuclear reactor. In a more severe environment, a Ni-based alloy in which Nb or the like is added and solid solution carbon is fixed as a carbide is usually applied.

However, the Ni-based alloy containing Nb has a problem in hot workability. Then, in patent document 1, the solution heat treatment of NbC is proposed. Further, Patent Document 2 proposes improvement of grain boundary strengthening by addition of B and reduction of O content. However, although all have a certain effect, there is room for improvement in stress corrosion cracking resistance and intergranular corrosion resistance. Therefore, in Patent Document 3, a Ni-based alloy having excellent hot workability and excellent in stress corrosion cracking resistance is disclosed. In Patent Document 4, a slab containing B is hot-rolled so as to prevent surface defects from being formed into a thick plate. A method for manufacturing a hot-rolled Ni-based alloy sheet has been proposed. In particular, in Patent Documents 3 and 4, the hot workability, crack resistance and corrosion resistance were excellent.

On the other hand, in the Ni-based alloy of the above-mentioned patent document, the oxide scale generated in the hot working process such as hot forging partially remains on the surface of the Ni-based alloy and is directly pushed into the Ni-based alloy, so that Ni Surface defects such as dents and flaws sometimes occurred on the surface of the base alloy. Surface defects such as dents and scratches formed by partially remaining oxide scale being pressed into the Ni-based alloy can be dealt with in terms of quality by grinding and removing the part.

However, for example, when a Ni-based alloy is used as a material for a nuclear reactor, extremely high quality is required, and therefore it may be necessary to reliably remove the above-mentioned surface defects such as dents and flaws. .. In order to reliably remove the above-mentioned surface defects such as dents and scratches, if a step such as grinding is carried out, the yield will be reduced, and an extra step will be added, which makes the production of the Ni-based alloy plate complicated. And the manufacturing cost will increase.

JP-A-63-53235 JP-A-61-84348 Japanese Patent No. 499327 Japanese Patent No. 4414588

In view of the above circumstances, the present invention provides a high Nb-containing Ni-based alloy that is excellent in hot workability, crack resistance, and corrosion resistance, and that contains Nb in an amount of 1.5% by mass or more. , Ni base which is excellent in scale releasability, which can prevent generation of surface defects such as dents and scratches on the alloy surface due to indentation of oxide scale generated in the hot working process, and can obtain excellent yield before and after hot working. The purpose is to provide an alloy.

The inventors of the present invention have made extensive studies to solve the above-mentioned problems, and thought that in order to solve the above-mentioned problems, the oxide scale should have a composition and structure that can be easily separated from the Ni-based alloy and cracked. On the other hand, the oxide scale also has an action of suppressing the progress of oxidation of the Ni-based alloy, and if the adhesion of the oxide scale to the Ni-based alloy is too low, the oxidation action during hot working causes loss of the Ni-based alloy. And the yield may decrease. Therefore, during heating, while maintaining a close adherence of the oxide scale to the Ni-based alloy, which is similar to the conventional state, during processing such as forging, many cracks are easily introduced into the oxide-scale and peel off from the Ni-based alloy. The study was advanced with the aim of obtaining an oxide scale. Since the composition and structure of the oxide scale is affected by the additive element, from the viewpoint of the composition of the additive element, while maintaining the adhesion of the oxide scale during heating, it forms an oxide scale that has peeling properties during processing such as forging. I decided to find a thing.

Therefore, the inventors have paid attention to the relationship between the adhesiveness of the oxide scale during heating and the peelability during processing and the alloy composition of the high Nb-containing Ni-based alloy. As a result, the additional elements that improve the peelability of the oxide scale during heating are Mo, W, and B, and the effect of improving the peelability of B is particularly remarkable. Excellent peelability was confirmed. Further, the weight change due to the oxidation of the Ni-based alloy during hot working can be maintained at about the same level as before due to the effect of Al and Ti, and the loss of the Ni-based alloy due to the oxidation effect will also be at the same level as before. Found.

Although the mechanism of the above effect is unknown, Mo, W, and B sublimate and gasify when exposed to a high-temperature oxidizing atmosphere, so that the gas components of Mo, W, and B are present in trace amounts between the oxide scale/mother phase. However, it promotes peeling at the time of processing such as forging, or Mo, W, and B are fragile oxide scales in which a gas flow path is formed by being released as gas through the oxide scales. It is possible that

The gist of the configuration of the present invention is as follows.
[1]% by mass, carbon (C): 0.001 to 0.045%, silicon (Si): 0.05 to 1.00%, manganese (Mn): 0.05 to 1.00%, phosphorus (P): 0.015% or less, sulfur (S): 0.0030% or less, chromium (Cr): 14 to 24%, niobium (Nb): 1.5 to 4.0%, iron (Fe): 3 to 25%, aluminum (Al): 0.01 to 0.20%, titanium (Ti): 0.001 to 0.20%, nitrogen (N): 0.003 to 0.020%, boron (B ): 0.0010 to 0.0100%, oxygen (O): 0.0002 to 0.0020%, molybdenum (Mo) and/or tungsten (W): 0.005 to 0.25%, balance nickel (Ni) ) And inevitable impurities,
A Ni-based alloy having excellent scale releasability, which satisfies the relationship of the following formula (wherein the notation of each element means the content (mass%) of the element in the Ni-based alloy).
4.2×Mo+3.6×W+355×B≧0.60
[2] Boron (B): 0.0010 to 0.008% and molybdenum (Mo) and/or tungsten (W): 0.008 to 0.21% by mass% [1] ] The Ni-based alloy excellent in scale releasability according to [1].
[3] [1] or [2] characterized by satisfying the following equation (wherein the notation of each element means the content (mass %) of the element in the Ni-based alloy)): A Ni-based alloy having excellent scale releasability according to 1.
4.2×Mo+3.6×W+355×B≧1.00
[4] A Ni-based alloy ingot made of the Ni-based alloy according to any one of [1] to [3].
[5] A slab for hot rolling of a Ni-based alloy obtained by hot forging the Ni-based alloy ingot according to [4].
[6] A Ni-base alloy sheet obtained by hot-rolling the slab for hot-rolling Ni-base alloy according to [5].

The Ni-based alloy of the present invention is a high Nb-containing Ni-based alloy that is excellent in hot workability, crack resistance and corrosion resistance, and that contains 1.5% by mass or more of Nb. Also, it is possible to prevent the generation of surface defects such as dents and scratches on the alloy surface due to the indentation of the oxide scale generated in the hot working step, and to obtain an excellent yield before and after hot working. A base alloy can be obtained. Therefore, for a high Nb-containing Ni-based alloy having a good surface condition without defects, it is possible to prevent a decrease in yield after hot working, and to add fine defects such as dents and scratches without adding an extra step. It is possible to obtain a surface state in which generation is prevented.

It is a graph showing the relationship between the value of the relational expression of the component composition of the Ni-based alloy and the residual scale area ratio (%).

Next, the Ni-based alloy excellent in scale releasability of the present invention will be described in detail. The Ni-based alloy excellent in scale releasability of the present invention is mass% (hereinafter, mass% which is the content of each component of the Ni-based alloy is simply referred to as “%”), and carbon (C): 0.001. -0.045%, silicon (Si): 0.05-1.00%, manganese (Mn): 0.05-1.00%, phosphorus (P): 0.015% or less, sulfur (S): 0.0030% or less, chromium (Cr): 14 to 24%, niobium (Nb): 1.5 to 4.0%, iron (Fe): 3 to 25%, aluminum (Al): 0.01 to 0. .20%, titanium (Ti): 0.001 to 0.20%, nitrogen (N): 0.003 to 0.020%, boron (B): 0.0010 to 0.0100%, oxygen (O). : 0.0002 to 0.0020%, molybdenum (Mo) and/or tungsten (W): 0.005 to 0.25%, balance nickel (Ni) and unavoidable impurities. The description of the element means the content (mass %) of the element in the Ni-based alloy.) A Ni-based alloy having excellent scale releasability, which is characterized by satisfying the relationship.
4.2×Mo+3.6×W+355×B≧0.60

C: 0.001-0.045%
C in the Ni-based alloy, which is excellent in scale releasability, is an essential element for stabilizing the austenite phase and ensuring mechanical strength at room temperature. For this purpose, the content of 0.001% or more is required. On the other hand, addition of an excessive amount forms a compound (carbide) containing Nb and C as main components, forms a Cr-deficient portion in the vicinity thereof, and significantly reduces corrosion resistance. Further, the amount of the compound containing Nb and C as the main components is increased to cause cracking and reduce the crack resistance. Therefore, the upper limit of the content is 0.045%. The preferable lower limit of the content is 0.003%, and the particularly preferable lower limit is 0.005%. The preferable upper limit of the content is 0.040%, and the particularly preferable upper limit is 0.035%.

Si: 0.05-1.00%
Si in the Ni-based alloy, which is excellent in scale releasability, is an essential element for deoxidizing and is necessary for improving the stress corrosion cracking resistance. This effect is obtained by adding 0.05% or more. On the other hand, the addition of an excessive amount causes an increase in inclusions and, in connection with this, the occurrence of surface defects. Therefore, the upper limit of the content is 1.00%. The preferable lower limit of the content is 0.08%, and the particularly preferable lower limit is 0.10%. The preferable upper limit of the content is 0.80%, and the particularly preferable upper limit is 0.60%.

Mn: 0.05-1.00%
Mn in the Ni-based alloy, which is excellent in scale releasability, is an essential element for performing deoxidation like Si, and also contributes to the stability of the austenite phase. In particular, it is an element that has a small increase in hardness due to addition and can secure the stability of the austenite phase while optimizing the mechanical strength. Furthermore, it acts on the oxide scale, contributes to efficient exfoliation of the oxide scale, and suppresses the occurrence of dents and flaws on the surface of the Ni-based alloy due to the indentation of the oxide scale. Therefore, addition of at least 0.05% is necessary. On the other hand, addition of an excessive amount reduces corrosion resistance, so the upper limit of the content is 1.00%. The preferable lower limit of the content is 0.08%, and the particularly preferable lower limit is 0.10%. The preferable upper limit of the content is 0.80%, and the particularly preferable upper limit is 0.60%.

P: 0.015% or less P in the Ni-based alloy, which is excellent in scale releasability, is an element that segregates at grain boundaries and reduces corrosion resistance and hot workability. Therefore, the upper limit must be strictly limited. In the present invention, it is limited to 0.015% or less. The preferable upper limit of the content is 0.012%, and the particularly preferable upper limit is 0.010%. Further, the lower limit of the content is more preferable as it approaches 0%, but for example, 0.001% can be mentioned.

S: 0.0030% or less S in the Ni-based alloy, which is excellent in scale releasability, is an element that segregates at grain boundaries to form a low-melting point compound and causes deterioration of hot workability, and should be reduced as much as possible. is there. Therefore, the upper limit must be strictly limited. In the present invention, it is limited to 0.0030% or less. It is preferably 0.0025% or less, and particularly preferably 0.0020% or less. Further, the lower limit of the content is more preferable as it approaches 0%, but, for example, 0.0001% can be mentioned.

Cr: 14-24%
Cr in the Ni-based alloy, which is excellent in scale releasability, is an important element that contributes to the improvement of corrosion resistance, and is an element essential for use in severe environments. For this reason, addition of at least 14% is necessary. On the other hand, if the content exceeds 24%, the mechanical strength at high temperature becomes high and processing becomes difficult. Further, it causes instability of the austenite phase and promotes precipitation of carbides. Therefore, the upper limit of the content is 24%. The preferable lower limit of the content is 15.0%, and the particularly preferable lower limit is 15.5%. The preferable upper limit of the content is 23.0%, and the particularly preferable upper limit is 22.0%.

Nb: 1.5-4.0%
Nb in the Ni-based alloy, which is excellent in scale releasability, has the effect of precipitating C and N as carbides, nitrides, or carbonitrides to improve corrosion resistance. In order to obtain this effect, it is necessary to add at least 1.5% or more. On the other hand, if the content is too large, grain boundary brittleness may occur due to excessively precipitated precipitates, so the upper limit of the content is 4.0%. The preferable lower limit of the content is 2.0%, and the particularly preferable lower limit is 2.1%. Moreover, the preferable upper limit of the content is 3.7%, and the particularly preferable upper limit is 3.2%.

Fe: 3 to 25%
Fe in the Ni-based alloy, which is excellent in scale releasability, is a component that contributes to improvement in toughness. To obtain this effect, at least 3% must be added. On the other hand, if the content exceeds 25%, the corrosion resistance decreases. Therefore, the upper limit of the content is 25%. The preferable lower limit of the content is 5%, and the particularly preferable lower limit is 6%. The preferable upper limit of the content is 23%, and the particularly preferable upper limit is 21%.

Al: 0.01 to 0.20%
Al in the Ni-based alloy, which is excellent in scale releasability, is an essential element for deoxidizing, and also has an effect of suppressing oxidation together with Ti. In order to obtain this effect, it is necessary to add at least 0.01% or more. On the other hand, if added in excess of 0.20%, the hot workability is deteriorated, a large number of inclusions are formed in the base material of the Ni-based alloy, and the corrosion resistance is deteriorated. Therefore, the upper limit of the content is 0.20%. The preferable lower limit of the content is 0.02%, and the particularly preferable lower limit is 0.03%. The preferable upper limit of the content is 0.18%, and the particularly preferable upper limit is 0.16%.

Ti: 0.001 to 0.20%
Ti in the Ni-based alloy, which is excellent in scale releasability, is an element that contributes to deoxidation and has an effect of suppressing oxidation together with Al. In the present invention, addition of B, Mo, etc. improves scale peelability during hot working, but retains oxidation resistance during heating, that is, at the stage of statically holding under heating conditions. Therefore, it is preferable to suppress the loss of the Ni-based alloy. In order to maintain the oxidation resistance when statically held under heating conditions, it is necessary to add at least 0.001% or more. On the other hand, if added in excess of 0.20%, the hot workability is deteriorated, a large number of inclusions are formed in the base material of the Ni-based alloy, and the corrosion resistance is deteriorated. Therefore, the upper limit of the content is 0.20%. The preferable lower limit of the content is 0.002%, and the particularly preferable lower limit is 0.003%. The preferable upper limit of the content is 0.18%, and the particularly preferable upper limit is 0.16%.

N: 0.003 to 0.020%
N in the Ni-based alloy, which is excellent in scale releasability, improves the mechanical strength at room temperature, increases the stability of the austenite phase, and further improves the corrosion resistance. Therefore, it is necessary to add 0.003% or more. On the other hand, since a compound is formed with Nb, the effective amount of Nb is reduced and blowholes are easily generated. Therefore, the upper limit of the content is 0.020%. The preferable lower limit of the content is 0.005%, and the particularly preferable lower limit is 0.008%. The preferable upper limit of the content is 0.014%, and the particularly preferable upper limit is 0.012%.

B: 0.0010 to 0.0100%
B in the Ni-based alloy, which is excellent in scale releasability, is an important element that improves hot workability. In hot working such as hot forging and hot rolling, separation of the oxide scale from the Ni-based alloy is promoted, and occurrence of surface defects such as dents and scratches due to indentation of the oxide scale is reliably suppressed. To obtain the above effect, addition of at least 0.0010% is necessary. On the other hand, if the content exceeds 0.0100%, the hot workability is rather deteriorated, and cracking occurs during hot forging and hot rolling. Therefore, the upper limit of the content is 0.0100%. The preferable lower limit of the content is 0.0012%, and the particularly preferable lower limit is 0.0015%. The preferable upper limit of the content is 0.0080%, and the particularly preferable upper limit is 0.0070%.

O: 0.0002 to 0.0020%
O in the Ni-based alloy, which is excellent in scale releasability, facilitates the reduction of the N content in the melting and refining processes. Therefore, it is necessary to contain at least 0.0002% or more. On the other hand, O combines with Al, Ti, Si, and Mn to form a deoxidized product. If it is contained in excess of 0.0020%, it may cause deterioration of corrosion resistance and surface defects due to deoxidized products. Therefore, the upper limit of the content is 0.0020%. The preferable lower limit of the content is 0.0003%, and the particularly preferable lower limit is 0.0004%. The preferable upper limit of the content is 0.0019%, and the particularly preferable upper limit is 0.0018%.

Mo and/or W: 0.005-0.25%
Mo and W in the Ni-based alloy, which are excellent in scale releasability, improve corrosion resistance, particularly pitting corrosion resistance and crevice corrosion resistance, and also contribute to intergranular corrosion resistance. Further, it acts on the oxide scale, promotes peeling of the oxide scale from the Ni-based alloy during hot working, and surely suppresses the occurrence of surface defects such as dents and scratches due to indentation of the oxide scale. To obtain these effects, it is necessary to add at least one of Mo and W by 0.005%, or both Mo and W by 0.005%. On the other hand, excessive addition of Mo and/or W lowers the oxidation resistance of the Ni-based alloy and promotes the oxidation, so that the oxidation during heating before hot working is promoted and the oxidation after hot working is accelerated. The yield due to scale peeling decreases, that is, the loss of the Ni-based alloy increases, resulting in an increase in cost. Therefore, the upper limit of the content of Mo and/or W is 0.25% for either one of Mo and W, or 0.25% for both Mo and W. A preferable lower limit of the content of Mo and/or W is 0.008% of any one of Mo and W, or 0.008% of each of Mo and W, and the particularly preferable lower limit is 0.010%. .. The preferable upper limit of the content of Mo and/or W is 0.21% of any one of Mo and W, or 0.21% of each of Mo and W, and the particularly preferable upper limit is 0.18%. Is.

In the Ni-based alloy excellent in scale releasability of the present invention, the balance other than the above components is Ni and inevitable impurities. The Ni-based alloy excellent in scale releasability of the present invention contains Ni as a main component.

The following formula 4.2×Mo+3.6×W+355×B≧0.60
Regarding the elements that affect the oxide scale releasability, the degree of the effect is expressed as a formula by regression analysis. When the value of the above equation is 0.60 or more, the oxide scale peeling property during hot working is improved, and Nb is contained in the Ni-based alloy excellent in hot workability, crack resistance and corrosion resistance. Even with a high Nb-containing Ni-based alloy that is contained in an amount of 1.5 mass% or more, the oxide scale is effectively separated from the Ni-based alloy during hot working. Therefore, it is necessary to control the component composition of the Ni-based alloy so that the value of the above formula becomes 0.60 or more. The value of the above formula is preferably 0.80 or more, more preferably 1.00 or more, and particularly preferably 1.40 or more from the viewpoint of further improving the oxide scale peeling property and the yield during hot working. On the other hand, the upper limit of the value of the above formula is not particularly limited, but may be, for example, 5.50.

The method of specifying the above formula is as follows.
Ni-20%Cr-2.3%Nb-7%Fe was used as a basic composition, and a Ni-based alloy in which the addition amount of each of the above various elements was changed was melted and cut into 10 mmt×100 mm×150 mm. Then, all surfaces of the cut Ni-based alloy were finished by wet polishing #120 to obtain test pieces. The obtained test piece was put in a heating device which was previously heated to 1200° C., and was held for 3 hours to be heat-treated to form an oxide scale on the surface of the Ni-based alloy. After the heat treatment, the test piece was taken out of the heating device and deformed by 15% with a hydraulic hammer to evaluate the presence or absence of peeling of the oxide scale. The evaluation of the presence or absence of peeling of the oxide scale was carried out by observing a 20 mm×20 mm area on the surface of the test piece with a digital microscope (magnification: 10 times) at a total of 20 locations, and determining the area of the area where the oxide scale remained. The total area of the oxide scale was calculated by approximation with a polygon. The total area of the places where the oxide scale remained was divided by the observed area, and the value obtained by multiplying by 100 was taken as the residual scale area ratio (%).

Even after deforming the test piece, when comparing the area where the oxide scale did not peel and remained, it was found that the oxide scale slightly peeled from the test piece even if it contained a small amount of a specific element. If the residual scale area ratio was 30% or less, surface defects such as dents and scratches due to indentation of the oxide scale were not recognized. As a result of the above-mentioned test, the elements in which the effect of the oxide scale releasability is recognized are Mo, W, and B. Among Mo, W, and B, the effect of B is particularly remarkable, and even if a small amount is added, The effect of oxide scale releasability was confirmed. Furthermore, it has been found that the weight change due to the oxidation of the Ni-based alloy can be maintained at about the same level as in the conventional case due to the effect of Al and Ti, and the loss of the Ni-based alloy due to the oxidation effect is also at the same level as in the conventional case.

From the above test results, the degree of influence of the additional element on the oxide scale peeling property due to the deformation of the Ni-based alloy was clarified, and the value obtained by multiple regression analysis was expressed as 4.2×Mo+3.6×W+355×B. It is a relational expression of the component composition of the Ni-based alloy, and by setting 4.2×Mo+3.6×W+355×B to 0.6 or more, the Ni-based alloy surface of the Ni-based alloy surface due to indentation of the oxide scale generated in the hot working step is It was found that the occurrence of dents and flaws can be prevented.

A graph showing the relationship between the value of the relational expression of the component composition of the Ni-based alloy and the residual scale area ratio (%) is shown in FIG. From FIG. 1, it is understood that when the value of the above formula is 0.60 or more, the oxide scale peeling property due to the deformation of the Ni-based alloy can be effectively obtained. The dotted line in FIG. 1 indicates the residual scale area ratio of 30%.

According to the Ni-based alloy excellent in scale releasability of the present invention, the high Nb-containing Ni containing 1.5% by mass or more of Nb in the Ni-based alloy is excellent in hot workability, crack resistance and corrosion resistance. Even for base alloys, it is possible to prevent the occurrence of dents and flaws on the alloy surface due to the indentation of the oxide scale generated in the hot working process, and to obtain excellent yield before and after hot working. It is possible to obtain a Ni-based alloy having excellent properties. Therefore, with respect to the high Nb-containing Ni-based alloy having a good surface condition without defects, it is possible to prevent a decrease in yield after hot working, and to perform even after hot working without adding an extra step. It is possible to obtain a surface state in which the generation of minute defects such as dents and scratches is prevented.

Further, the Ni-based alloy excellent in scale releasability of the present invention is a Ni-based alloy ingot, and the Ni-based alloy ingot is subjected to hot forging to form a Ni-based alloy hot rolling slab, thereby pushing in oxide scale. It is possible to prevent the generation of fine dents and flaws on the alloy surface due to the above, and it is possible to obtain a slab for hot rolling of a Ni-based alloy that has an excellent yield before and after hot forging. In addition, by rolling the Ni-based alloy hot rolling slab by hot rolling, etc., it is possible to prevent the generation of fine dents and flaws on the alloy surface due to the indentation of the oxide scale, and also to improve the yield before and after rolling. It is possible to obtain a Ni-based alloy plate having

Therefore, the Ni-based alloy of the present invention can be applied to, for example, materials for nuclear reactors with strict quality requirements and can be manufactured at low cost.

Next, examples of the present invention will be described, but the present invention is not limited to these examples unless the gist thereof is exceeded.

Examples 1 to 19 and Comparative Examples 1 to 13
Production of Ni-based alloy ingot First, in a 60t electric furnace, a predetermined amount of a predetermined raw material such as scrap, nickel, chromium, and niobium is charged and melted, and then AOD (Argon Oxygen Decarburization) or VOD (Vacuum Oxygen Decarburization). At this point, a mixed gas of oxygen and Ar was blown to decarburize. Then, ferrosilicon alloy and/or aluminum was added to reduce Cr, and then limestone and fluorite were added to perform deoxidation and desulfurization. Then, in a so-called normal ingot making method, molten metal was injected from the lower side of the mold to cast into a rectangular Ni-based alloy ingot, and Examples 1 to 19 and Comparative Example 1 having various component compositions shown in Table 1 below. ~13 Ni-based alloys were obtained. The mass of the rectangular Ni-based alloy ingot was 8 tons, and the cross-sectional dimensions were 280 mm×850 mm on the injection side and 550 mm×1100 mm on the feeder side. The Ni-based alloy ingot, which has been cooled and solidified after casting, is heated and held at 1030° C. for 2 hours, and then reheated to 1200° C. to perform 20% upset forging (hot forging) to obtain a sample Ni. A base alloy was produced. The content of each component in Table 1 means% by mass, and the balance is nickel (Ni) and inevitable impurities. Further, in Table 1 below, the underlined numerical values mean values outside the scope of the present invention.

Evaluation (1) Residual scale area A test piece of 10 mm thickness x 100 mm width x 150 mm length was cut out from the obtained Ni-based alloy, the surface was finished by wet polishing #120 to obtain a test piece, and the surface of the test piece was digital microscope ( A total of 10 areas of 20 mm x 20 mm were observed with a VHX-2000 manufactured by Keyence Co., Ltd. (magnification: 10 times), and the area of the area where it was judged that the oxide scale remained was approximated by a polygon to obtain an oxide scale. The total area (A1) was calculated. From the total area (A1) of the oxidized scale and the total area (A2) of the observed area, the residual scale area ratio (%) was calculated by (A1/A2)×100 and evaluated in the following three stages.
◎: Remaining scale area ratio is 20% or less ○: Remaining scale area ratio is more than 20% and 30% or less ×: Remaining scale area ratio is more than 30%

(2) Yield before and after hot forging Regarding the Ni-based alloy ingot solidified by cooling as described above, the mass (a) before hot forging and the defects caused by the removal of oxide scale and the indentation of oxide scale after hot forging The mass (b) after the removal of the above was measured, and the yield (%) was calculated by (b/a)×100, and evaluated in the following three stages.
◎: Yield 99% or more ○: Yield 96% or more and less than 99% ×: Yield less than 96%

Table 2 below shows the evaluation results of the residual scale area and the yield before and after hot forging.

From Table 2 above, carbon (C): 0.001 to 0.045%, silicon (Si): 0.05 to 1.00%, manganese (Mn): 0.05 to 1.00%, phosphorus (P ): 0.015% or less, sulfur (S): 0.0030% or less, chromium (Cr): 14 to 24%, niobium (Nb): 1.5 to 4.0%, iron (Fe): 3 to. 25%, aluminum (Al): 0.01 to 0.20%, titanium (Ti): 0.001 to 0.20%, nitrogen (N): 0.003 to 0.020%, boron (B): 0.0010 to 0.0100%, oxygen (O): 0.0002 to 0.0020%, molybdenum (Mo) and/or tungsten (W): 0.005 to 0.25%, balance nickel (Ni) and It consists of unavoidable impurities and has the following formula (in the formula, the notation of each element means the content (mass %) of the element in the Ni-based alloy).
4.2×Mo+3.6×W+355×B≧0.60
In the Ni-based alloys of Examples 1 to 19 satisfying the relationship of, the residual scale area is ◯ or more, and the yield before and after hot forging is also ◯ or more, and the hot forging is performed while reducing the residual scale area in the hot forging. The front and rear yields have also improved. Therefore, in the Ni-based alloys of Examples 1 to 19, it is possible to prevent the occurrence of dents and flaws on the alloy surface due to the indentation of the oxide scale produced by hot working, and it is possible to obtain an excellent yield before and after hot working. found.

In particular, in Examples 1, 2, 4, 5, 7, 8, 10, 17 and 19 in which the value of the above formula is 1.00 or more, the residual scale area ratio is further reduced and the yield is further improved. In Examples 2, 4, 5, 7, 8, 10 to 17, 19 in which the value of the expression is 1.15 or more, the yield was further improved while the residual scale area ratio was further reduced. Further, in Examples 2, 4, 5, 7, 8, 11 to 15, 17, and 19 in which the value of the above formula is 1.40 or more, particularly excellent residual scale area ratio and yield could be obtained.

On the other hand, B is less than 0.0010%, Mo and W are less than 0.005%, the value of the above formula is less than 0.60, Comparative Example 1, B is less than 0.0010%, and the value of the above formula is Comparative Examples 2, 3, 4, Mo and W of less than 0.60, less than 0.005%, Comparative Example 5 of which the value of the above formula is less than 0.60, Values of the above formula are less than 0.60 In Comparative Example 6 and Comparative Example 7 in which Mo and W were less than 0.005%, the residual scale area was evaluated x, and the yield before and after hot forging was evaluated x.

Comparative example 8 in which Mo and W are more than 0.25%, comparative example 9 in which Mo is more than 0.25%, comparative example 10 in which W is more than 0.25%, and Al is less than 0.01%. In Comparative Example 11, Comparative Example 12 in which Ti is less than 0.001%, and Comparative Example 13 in which B is more than 0.0100%, the residual scale area was ◯ or more, but the yield before and after hot forging was The evaluation was x, and the yields before and after hot forging could not be obtained.

In the present invention, it is possible to prevent the occurrence of dents and scratches on the alloy surface due to the indentation of the oxide scale generated in the hot working step, and it is possible to obtain an excellent yield before and after hot working, so it can be used in a wide range of fields. Therefore, for example, it can be applied as a material for a nuclear reactor which has a strict required quality.

The gist of the configuration of the present invention is as follows.
[1]% by mass, carbon (C): 0.001 to 0.045%, silicon (Si): 0.05 to 1.00%, manganese (Mn): 0.05 to 1.00%, phosphorus (P): 0.015% or less, sulfur (S): 0.0030% or less, chromium (Cr): 14 to 24%, niobium (Nb): 1.5 to 4.0%, iron (Fe): 3 to 25%, aluminum (Al): 0.01 to 0.20%, titanium (Ti): 0.001 to 0.20%, nitrogen (N): 0.003 to 0.020%, boron (B ): 0.0010 to 0.0100%, oxygen (O): 0.0002 to 0.0020%, molybdenum (Mo) and/or tungsten (W) 0.005 to 0.25%, and the balance nickel ( Ni) and inevitable impurities,
A Ni-based alloy having excellent scale releasability, which satisfies the relationship of the following formula (wherein the notation of each element means the content (mass%) of the element in the Ni-based alloy).
4.2×Mo+3.6×W+355×B≧0.60
[2] Boron (B): 0.0010 to 0.008% and molybdenum (Mo) and/or tungsten (W): 0.008 to 0.21% by mass% [1] ] The Ni-based alloy excellent in scale releasability according to [1].
[3] [1] or [2] characterized by satisfying the following equation (wherein the notation of each element means the content (mass %) of the element in the Ni-based alloy)): A Ni-based alloy having excellent scale releasability according to 1.
4.2×Mo+3.6×W+355×B≧1.00
[4] A Ni-based alloy ingot made of the Ni-based alloy according to any one of [1] to [3]. [5] A slab for hot rolling of a Ni-based alloy obtained by hot forging the Ni-based alloy ingot according to [4].
[6] A Ni-base alloy sheet obtained by hot-rolling the slab for hot-rolling Ni-base alloy according to [5].

Claims (6)

In mass%, carbon (C): 0.001 to 0.045%, silicon (Si): 0.05 to 1.00%, manganese (Mn): 0.05 to 1.00%, phosphorus (P) : 0.015% or less, sulfur (S): 0.0030% or less, chromium (Cr): 14 to 24%, niobium (Nb): 1.5 to 4.0%, iron (Fe): 3 to 25 %, aluminum (Al): 0.01 to 0.20%, titanium (Ti): 0.001 to 0.20%, nitrogen (N): 0.003 to 0.020%, boron (B): 0 0.0010 to 0.0100%, oxygen (O): 0.0002 to 0.0020%, molybdenum (Mo) and/or tungsten (W): 0.005 to 0.25%, balance nickel (Ni) and unavoidable It consists of
A Ni-based alloy having excellent scale releasability, which satisfies the relationship of the following formula (wherein the notation of each element means the content (mass%) of the element in the Ni-based alloy).
4.2×Mo+3.6×W+355×B≧0.60 The boron (B): 0.0010 to 0.008% and the molybdenum (Mo) and/or the tungsten (W): 0.008 to 0.21% in mass%. Ni-based alloy with excellent scale releasability. The scale exfoliation according to claim 1 or 2, wherein the following formula (wherein the notation of each element means the content (mass %) of the element in the Ni-based alloy) is satisfied. Ni-based alloy with excellent properties.
4.2×Mo+3.6×W+355×B≧1.00 A Ni-based alloy ingot made of the Ni-based alloy according to claim 1. A slab for hot rolling of a Ni-base alloy obtained by hot forging the Ni-base alloy ingot according to claim 4. A Ni-based alloy sheet obtained by hot-rolling the slab for hot rolling of the Ni-based alloy according to claim 5.

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