JP6539795B1 - Ni-based alloy, Ni-based alloy ingot, slab for Ni-based alloy hot rolling and Ni-based alloy sheet - Google Patents

Abstract

The object of the present invention is to heat even a high Nb-containing Ni-based alloy which is excellent in hot workability, cracking resistance and corrosion resistance and which contains 1.5 mass% or more of Nb in the Ni-based alloy. It is possible to provide a Ni-based alloy excellent in scale removability, which can prevent the generation of dents and wrinkles on the surface of the alloy due to the pressing of the oxide scale generated in the in-process step, and obtain excellent yield before and after hot working. To aim. SOLUTION: 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) Aluminum: 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, and in the following formulas (wherein each element is described in Ni-based alloy A Ni-based alloy excellent in scale removability characterized by satisfying the relationship of the content (mass%) of the element. 4.2 × Mo + 3.6 × W + 355 × B ≧ 0.60 【Selection chart】 None

Description

  The present invention is a Ni-based alloy which is excellent in stress corrosion cracking and intergranular corrosion resistance, and in particular, is a recess formed due to indentation of oxide scale produced by a hot working process such as hot forging. The present invention relates to a Ni-based alloy, a Ni-based alloy block, a Ni-based alloy ingot, a slab for Ni-based alloy hot rolling, and a Ni-based alloy sheet which are capable of suppressing surface defects such as wrinkles.

  Ni-based alloys are applied in severe use environments because they are excellent in corrosion resistance and heat resistance. Among the Ni-based alloys, for example, JIS NCF 600 equivalent materials are used as core materials of nuclear reactors because they have excellent resistance to stress corrosion cracking and intergranular corrosion resistance. In a more severe environment, a Ni-based alloy is generally applied in which Nb or the like is added and carbon in solid solution is fixed as carbide.

  However, the Ni-based alloy to which Nb is added has a problem in hot workability. Then, in patent document 1, the solution heat treatment of NbC is proposed. Moreover, in patent document 2, improvement of the grain boundary strengthening by reduction of B addition and O content is proposed. However, although all have a certain effect, there is room for improvement in stress corrosion cracking and intergranular corrosion resistance. Therefore, in Patent Document 3, a Ni-based alloy excellent in hot workability and excellent in stress corrosion cracking, and in Patent Document 4, hot rolled so as not to generate surface defects in a slab containing B and A method of manufacturing a Ni-based alloy hot-rolled sheet is proposed. In particular, in patent documents 3 and 4, it was excellent in hot workability, crack resistance, and corrosion resistance.

  On the other hand, in the Ni-based alloy of the above-mentioned patent document, the oxidized scale formed in the hot working process such as hot forging partially remains on the surface of the Ni-based alloy and is directly pressed into the Ni-based alloy. Surface defects such as dents and wrinkles may occur on the surface of the base alloy. The surface defects such as dents and wrinkles, which are formed by pressing the partially remaining oxide scale into the Ni-based alloy, can be dealt with in terms of quality by grinding and removing the relevant portion.

  However, for example, when a Ni-based alloy is used as a material for nuclear reactors, extremely high quality is required, so it may be necessary to reliably remove surface defects such as the above-mentioned dents and wrinkles. . If a process such as grinding is carried out to reliably remove the surface defects such as the above-mentioned dents and wrinkles, the yield will be reduced, and an extra process will be added, making the production of the Ni-based alloy plate complicated. And the manufacturing cost will also rise.

Japanese Patent Application Laid-Open No. 63-53235 Japanese Patent Application Laid-Open No. 61-84348 Patent No. 4,993,327 Patent No. 4414588 gazette

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

  The inventors of the present invention have intensively studied in order to solve the above-mentioned problems, and in order to solve the above-mentioned problems, it was considered that the oxide scale should have a composition and structure which can be easily peeled off from the Ni-based alloy. On the other hand, the oxide scale also has the function 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 loss of the Ni-based alloy is caused by the oxidation during hot working. And the yield may be reduced. Therefore, during heating, while maintaining the close contact state of the oxide scale close to the conventional one with respect to the Ni-based alloy, during processing such as forging, many cracks are easily introduced into the oxide scale and peeled off from the Ni-based alloy. The investigation was advanced for the purpose of obtaining the oxidation scale. Since the composition and structure of the oxide scale are affected by the additive elements, from the viewpoint of the composition of the additive elements, the adhesion of the oxide scale is maintained at the time of heating, and an oxide scale having releasability is formed at processing such as forging. I decided to find a thing.

  Therefore, the inventors focused on the adhesion of the oxide scale at the time of heating and the relationship between the peelability at the time of processing and the alloy composition for the high Nb-containing Ni-based alloy. As a result, the additive elements that improve the removability of the oxide scale at the time of heating are three elements of Mo, W, and B, and the effect of improving the removability of B is particularly remarkable. Excellent peelability at time was confirmed. Furthermore, the weight change due to the oxidation of the Ni-based alloy during hot working can be maintained substantially the same as in the prior art by the effects of Al and Ti, and the loss of the Ni-based alloy due to the oxidation action is also comparable to the conventional Found out.

  Although the mechanism of the above effect is unknown, Mo, W, B sublime and gasify when exposed to a high temperature oxidizing atmosphere, so that a small amount of Mo, W, B gas components exist between the oxide scale / matrix. Or promote separation during processing such as forging, or Mo, W, and B are released through the oxide scale as a gas, and a gas flow path is formed, so that a fragile oxide scale and It is thought that it became.

The summary 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 (B) ): 0.0010 to 0.0100%, oxygen (O): 0.0002 to 0.0020%, molybdenum (Mo) and / or tungsten (W) respectively 0.005 to 0.25%, balance nickel ( Ni) and inevitable impurities,
A Ni-based alloy excellent in scale removability characterized by satisfying 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] It is characterized in that, by mass%, boron (B): 0.0010 to 0.008%, molybdenum (Mo) and / or tungsten (W): 0.008 to 0.21% [1 ] The Ni-based alloy which is excellent in the scale exfoliation property as described in [].
[3] is characterized by satisfying the relationship of the following formula (wherein the notation of each element means the content (mass%) of the element in the Ni-based alloy) [1] or [2] The Ni-based alloy which is excellent in scale removability as described in.
4.2 × Mo + 3.6 × W + 355 × B ≧ 1.00
[4] A Ni-based alloy block comprising the Ni-based alloy according to any one of [1] to [3]. [5] A slab for Ni-based alloy hot rolling, in which the Ni-based alloy mass according to [4] is hot-forged.
The Ni-based alloy sheet by which the slab for Ni-based alloy hot rolling as described in [6] [5] was hot-rolled.

  According to the Ni-based alloy of the present invention, it is a high Nb-containing Ni-based alloy which is excellent in hot workability, cracking resistance and corrosion resistance and in which the N-based alloy contains 1.5% by mass or more of Nb Also, Ni which is excellent in scale removability can prevent generation of surface defects such as dents and wrinkles of the alloy surface by pressing of oxide scale generated in the hot working process and can obtain excellent yield before and after hot working Base alloys can be obtained. Therefore, for a high Nb-containing Ni-based alloy that has a good surface state free from defects, the reduction in yield after hot working is prevented, and fine defects such as dents and wrinkles are prevented without adding an extra step. It is possible to obtain a surface state which is also prevented from occurring.

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

Next, the Ni-based alloy excellent in the scale removability of the present invention will be described in detail. The Ni-based alloy having excellent scale removability according to the present invention has a carbon (C) content of 0.001% by mass (hereinafter, the mass% which is the content of each component of the Ni-based alloy is simply referred to as "%"). -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 %, The balance being nickel (Ni) and unavoidable impurities, and satisfying the relationship of the following formula (wherein the notation of each element means the content (mass%) of the element in the Ni-based alloy). Ni-based alloy excellent in scale removability characterized by
4.2 × Mo + 3.6 × W + 355 × B ≧ 0.60

C: 0.001 to 0.045%
C in a Ni-based alloy excellent in scale removability is an essential element to stabilize the austenite phase and to secure mechanical strength at room temperature. For this purpose, a content of 0.001% or more is required. On the other hand, the addition of an excessive amount forms a compound (carbide) mainly composed of Nb and C, forms a Cr-depleted part in the vicinity thereof, and significantly reduces the corrosion resistance. Moreover, the compound which has Nb and C as a main component increases, causes a crack, and reduces 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 upper limit of the content is preferably 0.040%, and particularly preferably 0.035%.

Si: 0.05 to 1.00%
Si in the Ni-based alloy, which is excellent in scale removability, is an element essential to deoxidation, and is further required to improve stress corrosion cracking resistance. This effect is obtained by addition of 0.05% or more. On the other hand, the addition of an excessive amount leads to the increase of inclusions and the associated generation 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%. Further, a preferable upper limit of the content is 0.80%, and a particularly preferable upper limit is 0.60%.

Mn: 0.05 to 1.00%
Mn in a Ni-based alloy, which is excellent in scale removability, is an element essential for deoxidation as with Si, and also contributes to the stability of the austenite phase. In particular, the increase in hardness due to the addition is small, and it is an element that can ensure the stability of the austenite phase while optimizing the mechanical strength. Furthermore, it acts on the oxide scale, contributes to the efficient peeling of the oxide scale, and suppresses the generation of dents and wrinkles on the surface of the Ni-based alloy due to the indentation of the oxide scale. For this reason, addition of at least 0.05% or more is necessary. On the other hand, the addition of an excessive amount lowers the 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%. Further, a preferable upper limit of the content is 0.80%, and a particularly preferable upper limit is 0.60%.

P: 0.015% or less P in a Ni-based alloy which is excellent in scale removability is an element which segregates in grain boundaries and reduces corrosion resistance and hot workability. For this reason, the upper limit needs to be strictly limited. In the present invention, the content is limited to 0.015% or less. The upper limit of the content is preferably 0.012%, and particularly preferably 0.010%. The lower limit of the content is preferably as close to 0% as, for example, 0.001%.

S: 0.0030% or less S in a Ni-based alloy excellent in scale removability is an element which segregates at grain boundaries to form a low melting point compound and causes a reduction in hot workability, and should be reduced as much as possible. is there. For this reason, the upper limit needs to be strictly limited. In the present invention, the content is limited to 0.0030% or less. Preferably it is 0.0025% or less, especially preferably 0.0020% or less. The lower limit of the content is preferably as close to 0% as, for example, 0.0001%.

Cr: 14 to 24%
Cr in a Ni-based alloy excellent in scale removability is an important element contributing to the improvement of the corrosion resistance, and an element essential for use in a severe environment. For this reason, an addition of at least 14% is necessary. On the other hand, if the content is more than 24%, the mechanical strength at high temperature becomes high and the processing becomes difficult. Furthermore, it causes destabilization 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 upper limit of the content is preferably 23.0%, and more preferably 22.0%.

Nb: 1.5 to 4.0%
Nb in a Ni-based alloy excellent in scale removability has the effect of precipitating C and N as carbides, nitrides or carbonitrides to improve corrosion resistance. In order to obtain this effect, addition of at least 1.5% or more is necessary. On the other hand, if the content is too large, intergranular brittleness may be caused by precipitates precipitated excessively, so the upper limit of the content is made 4.0%. The preferable lower limit of the content is 2.0%, and the particularly preferable lower limit is 2.1%. The upper limit of the content is preferably 3.7%, and particularly preferably 3.2%.

Fe: 3 to 25%
Fe in the Ni-based alloy excellent in scale removability is a component that contributes to the improvement of toughness. At least 3% addition is required to achieve this effect. On the other hand, if the content exceeds 25%, the corrosion resistance is lowered. 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 upper limit of the content is preferably 23%, particularly preferably 21%.

Al: 0.01 to 0.20%
Al in a Ni-based alloy excellent in scale removability is an element essential for deoxidation, and has an effect of suppressing oxidation together with Ti. Addition of at least 0.01% or more is necessary to obtain this effect. On the other hand, when it is added in excess of 0.20%, the hot workability is lowered, a large number of inclusions are formed in the base material of the Ni-based alloy, and the corrosion resistance is lowered. 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%. Further, a preferable upper limit of the content is 0.18%, and a particularly preferable upper limit is 0.16%.

Ti: 0.001 to 0.20%
Ti in the Ni-based alloy, which is excellent in scale removability, is an element contributing to deoxidation, and has an effect of suppressing oxidation together with Al. In the present invention, the scale removability during hot working is improved by the addition of B, Mo, etc., but the oxidation resistance is maintained at the time of heating, that is, at the stage of holding statically under heating conditions. Therefore, it is preferable to suppress the loss of the Ni-based alloy. Addition of at least 0.001% or more is necessary to maintain the oxidation resistance when held statically under heating conditions. On the other hand, when it is added in excess of 0.20%, the hot workability is lowered, a large number of inclusions are formed in the base material of the Ni-based alloy, and the corrosion resistance is lowered. 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%. Further, a preferable upper limit of the content is 0.18%, and a particularly preferable upper limit is 0.16%.

N: 0.003 to 0.020%
N in the Ni-based alloy excellent in scale removability improves the mechanical strength at room temperature, increases the stability of the austenite phase, and further improves the corrosion resistance. For this reason, addition of 0.003% or more is required. On the other hand, the formation of a compound with Nb reduces the amount of Nb that is effective, and blow holes are likely to occur. 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 upper limit of the content is preferably 0.014%, and more preferably 0.012%.

B: 0.0010 to 0.0100%
B in a Ni-based alloy excellent in scale removability is an important element for improving hot workability. In hot working such as hot forging and hot rolling, exfoliation of oxide scale from a Ni-based alloy is promoted, and generation of surface defects such as dents and wrinkles resulting from indentation of oxide scale is surely suppressed. The addition of at least 0.0010% is necessary to obtain the above effect. On the other hand, if the content exceeds 0.0100%, the hot workability is rather reduced, 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 upper limit of the content is preferably 0.0080%, and particularly preferably 0.0070%.

O: 0.0002 to 0.0020%
O in the Ni-based alloy, which is excellent in scale removability, makes it easy to reduce the amount of N in the melting and refining processes. For this reason, it is necessary to contain at least 0.0002% or more. On the other hand, O bonds with Al, Ti, Si and Mn to form a deoxidized product. When it is contained in excess of 0.0020%, the deoxidation product causes a reduction in corrosion resistance and causes surface defects. For this reason, the upper limit of the content is made 0.0020%. The preferable lower limit of the content is 0.0003%, and the particularly preferable lower limit is 0.0004%. The upper limit of the content is preferably 0.0019%, and particularly preferably 0.0018%.

Mo and / or W: 0.005 to 0.25%
Mo and W in the Ni-based alloy excellent in scale removability improve the corrosion resistance, in particular, improve the pitting resistance, the crevice corrosion resistance, and also contribute to the improvement of intergranular corrosion. Furthermore, it acts on the oxide scale, promotes the exfoliation of the oxide scale from the Ni-based alloy during hot working, and reliably suppresses the occurrence of surface defects such as dents and wrinkles resulting from indentation of the oxide scale. In order to obtain these effects, it is necessary to add at least 0.005% of at least one of Mo and W, or 0.005% of each of Mo and W, respectively. On the other hand, the excessive addition of Mo and / or W reduces the oxidation resistance of the Ni-based alloy and promotes the oxidation, so the oxidation at the time of heating before hot working is promoted and the oxidation after hot working The reduction in yield due to the exfoliation of the scale, that is, the loss of the Ni-based alloy increases, and the cost increases. Therefore, the upper limit of the content of Mo and / or W is 0.25% for any one of Mo and W, or 0.25% for both Mo and W. The lower limit of the content of Mo and / or W is preferably 0.008% for Mo or W, or 0.008% for Mo or W, and the lower limit is particularly preferably 0.010%. . In addition, the upper limit of the content of Mo and / or W is preferably 0.21% of either Mo or W, or 0.21% for Mo and W, respectively, and the upper limit is particularly preferably 0.18%. It is.

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

The following formula 4.2 × Mo + 3.6 × W + 355 × B ≧ 0.60
The degree of the influence is shown as a formula by regression analysis about the element which affects the oxide scale exfoliation property. When the value of the above-mentioned formula is 0.60 or more, Nb is included in the Ni-based alloy which is improved in oxide scale removability during hot working and is excellent in hot workability, cracking resistance and corrosion resistance. Even in a high Nb-containing Ni-based alloy containing 1.5% by mass or more, the oxide scale exfoliates effectively 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 equation is 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 removability and the yield during hot working. On the other hand, the upper limit of the value of the above formula is not particularly limited, and an example is 5.50.

The specification method of the said formula is as follows.
Ni-20% Cr-2.3% Nb-7% Fe was made into the basic composition, the Ni base alloy which changed the addition amount of the said various elements to this was melted, and it cut | disconnected to 10 mmt x 100 mm x 150 mm. Thereafter, all surfaces of the cut Ni-based alloy were finished by wet polishing # 120 to obtain test pieces. The obtained test piece was placed in a heating device previously heated to 1200 ° C., held for 3 hours, and subjected to heat treatment 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, deformed by 15% with a hydraulic hammer, and the presence or absence of peeling of the oxide scale was evaluated. The evaluation of the presence or absence of peeling of the oxide scale was carried out by observing the surface of the test piece with a digital microscope (10 × magnification), for a total of 20 mm × 20 mm areas, and the area of the portion judged to have remained oxide scale The total area of the oxidation scale was calculated by approximation with a polygon. The total area of the places where the oxide scale remained was divided by the observation area, and the value obtained by further multiplying by 100 was taken as the residual scale area ratio (%).

  Comparison of the area in which the oxide scale remains without peeling even after deformation of the test piece shows that the oxide scale peels off from the test piece smoothly even though it contains a small amount of a specific element. Also, when the residual scale area ratio was 30% or less, surface defects such as dents and wrinkles due to indentation of oxide scale were not observed. As a result of the above test, in particular, the elements in which the effect of the oxide scale removability is recognized are Mo, W, B, and the effect of B among Mo, W, B is particularly remarkable, and the addition of a small amount is also possible. The effect of the oxide scale removability was confirmed. Furthermore, it has been found that the weight change due to the oxidation of the Ni-based alloy can be maintained substantially the same as the conventional one by the effects of Al and Ti, and the loss of the Ni-based alloy due to the oxidation action is also comparable to the conventional one.

  From the above test results, the degree of influence of the additive element on the oxide scale removability due to the deformation of the Ni-based alloy is clarified, and the value obtained by multiple regression analysis is represented by 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 be 0.6 or more, the Ni-based alloy surface is formed by pressing the oxide scale formed in the hot working process. It turned out that it is possible to prevent the occurrence of dents and wrinkles.

  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. It can be seen from FIG. 1 that when the value of the above equation is 0.60 or more, oxide scale removability by deformation of the Ni-based alloy can be obtained effectively. The dotted line in FIG. 1 indicates a residual scale area ratio of 30%.

  According to the Ni-based alloy having excellent scale removability according to the present invention, high Nb-containing Ni having 1.5% by mass or more of Nb contained in the Ni-based alloy excellent in hot workability, cracking resistance and corrosion resistance Even in the base alloy, it is possible to prevent the generation of dents and wrinkles on the surface of the alloy due to the pressing of the oxide scale generated in the hot working process, and also to obtain excellent yield before and after hot working. Ni-based alloy excellent in Therefore, for the high Nb-containing Ni-based alloy which has a good surface state free from defects, the reduction in yield after hot working is prevented, and even after hot working without adding an extra step. It is possible to obtain a surface state in which the occurrence of minute defects such as dents and wrinkles is also prevented.

  In addition, the Ni-based alloy having excellent scale removability according to the present invention is a Ni-based alloy ingot, and the Ni-based alloy ingot is hot-forged to form a slab for Ni-based alloy hot rolling, thereby pushing oxide scale. It is possible to prevent the occurrence of fine dents and wrinkles on the surface of the alloy and to obtain a Ni-based alloy hot rolling slab having an excellent yield before and after hot forging. In addition, by rolling the Ni-based alloy hot rolling slab by hot rolling or the like, it is possible to prevent the generation of fine dents and wrinkles on the surface of the alloy due to pressing of oxide scale, and excellent yield before and after rolling. It is possible to obtain a Ni-based alloy sheet having

  For this reason, the Ni-based alloy of the present invention can be applied to, for example, nuclear reactor materials with strict requirements, and nuclear reactor materials can be manufactured inexpensively.

  EXAMPLES Next, examples of the present invention will be described, but the present invention is not limited to these examples as long as the purpose of the present invention is not exceeded.

Examples 1-19, comparative examples 1-13
Production of an alloy ingot of Ni-based alloy First, predetermined amounts of predetermined raw materials such as scrap, nickel, chromium, niobium and the like are charged in a 60 t electric furnace and melted, and then AOD (Argon Oxygen Decarburization) or VOD (Vacuum Oxygen Decarburization) Then, a mixed gas of oxygen and Ar was blown to decarburize. Thereafter, ferrosilicon alloy and / or aluminum were added to reduce Cr, and then limestone and fluorite were added to perform deoxidation and desulfurization. Thereafter, the so-called ordinary ingot forming method injects a molten metal from the lower side of the mold and casts it into a rectangular Ni-based alloy mass, and Examples 1 to 19 and Comparative Example 1 having various component compositions shown in Table 1 below. We obtained ~ 13 Ni-based alloys. The mass of the flat rectangular Ni-based alloy block was 8 tons, and the cross-sectional dimensions were 280 mm × 850 mm for the injection side and 550 mm × 1100 mm for the feeder side. The cast and solidified Ni base alloy block after cooling and heating is heated and held at 1030 ° C. for 2 hours, and then reheated to 1200 ° C. to perform upset forging (hot forging) at 20% to obtain Ni as a sample. A base alloy was manufactured. In addition, content of each component in Table 1 means mass%, and remainder consists of nickel (Ni) and an unavoidable impurity. Further, in Table 1 below, the underlined numerical value means that it is a numerical value outside the scope of the present invention.

Evaluation (1) Residual scale area A test piece of 10 mm thickness × 100 mm width × 150 mm length is cut out from the obtained Ni-based alloy, the surface is finished by wet polishing # 120 to make a test piece, and the surface of the test piece is digital microscope ( The area of 20 mm × 20 mm is observed at a total of 10 places with Keyence Co., Ltd. (VHX-2000, magnification: 10 times), and the area of the place judged to be an oxide scale is approximated by a polygon to obtain an oxide scale The total area (A1) was calculated. From the total area (A1) of the oxide scale and the total (A2) of the observation area, the residual scale area ratio (%) was calculated by (A1 / A2) × 100, and evaluated in the following three stages.
:: Residual scale area ratio not more than 20% ○: Residual scale area ratio not less than 20% and not more than 30% ×: Residual scale area ratio not less than 30%

(2) Yield before and after hot forging For the Ni-based alloy block cooled and solidified as described above, the mass (a) before hot forging and defects caused by removal of oxide scale and indentation of oxide scale after hot forging The mass (b) after removal of 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%

  The evaluation results of the residual scale area and the yield before and after hot forging are shown in Table 2 below.

From the above Table 2, 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 3 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 in the following formula (wherein the notation of each element is the element in the Ni-based alloy Mean the content (% by mass) of
4.2 × Mo + 3.6 × W + 355 × B ≧ 0.60
In the Ni-based alloys of Examples 1 to 19 satisfying the following relationship, the residual scale area is ○ or more, the yield before and after hot forging is also ○ or more, while reducing the residual scale area in hot forging, hot forging The yield before and after was also improved. Therefore, in the Ni-based alloys of Examples 1 to 19, the generation of dents and wrinkles on the surface of the alloy due to pressing of the oxide scale formed by the hot working can be prevented, and an excellent yield can be obtained before and after the hot working found.

  In particular, in Examples 1, 2, 4, 5, 7, 8, 10 to 17 and 19 in which the value of the above equation is 1.00 or more, the yield is further improved while the residual scale area ratio is further reduced, In Examples 2, 4, 5, 7, 8, 10 to 17 and 19 in which the value of the equation is 1.15 or more, the yield was further improved while the residual scale area ratio was further reduced. Moreover, in Example 2, 4, 5, 7, 8, 11-15, 17 and 19 whose value of said Formula is 1.40 or more, the outstanding outstanding scale area ratio and the yield were able to be obtained.

  On the other hand, Comparative Example 1 in which B is less than 0.0010%, Mo and W are less than 0.005%, and the value of the above equation is less than 0.60, B is less than 0.0010%, the value of the above equation is Comparative Examples 2 and 3 which are less than 0.60, Comparative Example 5 wherein the value of Mo and W is less than 0.005%, the value of the above formula is less than 0.60, the value of the above formula is less than 0.60 In Comparative Example 6 and Comparative Example 7 in which Mo and W are less than 0.005%, the residual scale area is evaluated as x, and the yield before and after hot forging is also evaluated as 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 is ○ or more, but the yield before and after hot forging is It was evaluated as x, and the yield before and after hot forging could not be obtained.

  In the present invention, since generation of dents and wrinkles on the surface of the alloy due to pressing of oxide scale formed in the hot working process can be prevented and excellent yield can be obtained before and after hot working, it can be used in a wide range of fields. For example, it can be applied as a material for nuclear reactors with strict requirements.

Claims (6)

% 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) respectively 0.005 to 0.25%, balance nickel (Ni) and It consists of unavoidable impurities,
A Ni-based alloy excellent in scale removability characterized by satisfying 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 composition according to claim 1, characterized in that, in mass%, boron (B): 0.0010 to 0.008%, molybdenum (Mo) and / or tungsten (W): 0.008 to 0.21%. Ni base alloy with excellent scale removability. The scale exfoliation according to claim 1 or 2, characterized by satisfying the relationship of the following formula (wherein the notation of each element means the content (mass%) of the element in the Ni-based alloy). Ni-based alloy with excellent properties.
4.2 × Mo + 3.6 × W + 355 × B ≧ 1.00   A Ni-based alloy block comprising the Ni-based alloy according to any one of claims 1 to 3.   A slab for Ni-based alloy hot rolling, wherein the Ni-based alloy mass according to claim 4 is hot-forged.   The Ni-based alloy sheet by which the slab for Ni-based alloy hot rolling according to claim 5 was hot-rolled.

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