JP6539794B1 - Ni-based alloy and Ni-based alloy sheet - Google Patents

Abstract

An object of the present invention is to heat even a high Nb-containing Ni-based alloy in which 1.5 mass% or more of Nb is contained in a Ni-based alloy excellent in hot workability, cracking resistance and corrosion resistance. An object of the present invention is to provide a Ni-based alloy which is excellent in descalability, capable of easily pickling and removing oxide scale generated in a solution treatment heat treatment step after a processing step. SOLUTION: In mass%, carbon (C): 0.001 to 0.045%, silicon (Si): 0.05 to 0.45%, manganese (Mn): 0.10 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 0.10% Titanium (Ti): 0.001 to 0.08% 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 descalability characterized by satisfying the relationship of the content (mass%) of the element. 1401 × B + (Mo + W) + 3.0 × Mn−2.2 × Si−2.4 × Al−1.7 × Ti ≧ 3.20 【Selection Diagram】 None

Description

  The present invention is a Ni-based alloy excellent in stress corrosion cracking and intergranular corrosion resistance, and in particular, it is easy to pickle oxide scale formed by solution heat treatment subsequent to hot rolling process and hot rolling process. The present invention relates to a Ni-based alloy excellent in descalability and a plate material formed by rolling a Ni-based alloy, which can be removed to obtain a clean surface.

  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, an alloy is generally used 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.

  On the other hand, after producing a hot forged slab from an alloy ingot of cast Ni-based alloy, when producing a Ni-based alloy sheet through a hot working process and a solution heat treatment process, surface defects occur on the surface of the Ni-based alloy sheet I had something to do. When surface defects occur, a general method of removing surface defects includes a method of removing mechanically after the solution heat treatment step. As a method of mechanically removing surface defects, there may be mentioned, for example, a method of removing with a grindstone rotating at a high speed, or with a grit adhered to a belt rotating at a high speed. There is also a method of mechanically removing surface defects with a milling cutter or the like. Thus, mechanical removal of surface defects results in removal of oxide scale, which is one of surface defects.

  For example, as in Patent Document 4, when surface defects caused by hot working can be effectively prevented, the step of mechanically removing surface defects is unnecessary, and for example, it is adopted in general SUS 304. It has been carried out to pick up the oxide scale with a mixed acid consisting of nitric acid and hydrofluoric acid to obtain a clean alloy surface. However, in the case of a high Nb-containing Ni-based alloy in which Nb is contained in an amount of 1.5% by mass or more in the Ni-based alloy, oxidized scale still remains in the form of islands in the conventional pickling removal method. As a result, there has been a situation where a mechanical oxide scale removing step is required. The cause of this phenomenon is that a high Nb content Ni base alloy has a small content of Fe and densely forms Cr oxide scale and Ni oxide scale with high protection on the surface, high Nb content It can be considered that something has some effect.

  As mentioned above, if the oxidation scale can not be completely removed by acid pickling, as a result, a mechanical oxidation scale removing step is required, and the technology for preventing surface defects can not be fully utilized. It is necessary to remove the oxide scale by However, strengthening of pickling conditions is not appropriate in view of additional cost and environmental load due to the treatment of waste acid solution and the like.

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. An object of the present invention is to provide a Ni-based alloy which is excellent in descalability, capable of easily pickling and removing oxide scale produced in a solution heat treatment step after a hot working step.

  The inventors of the present invention conducted extensive studies to solve the above-mentioned problems, and in order to solve the above-mentioned problems, proceeded with studies so as to form the composition and structure of oxide scale which can be easily pickled and removed. That is, the present invention is directed to a high Nb-containing Ni-based alloy containing 1.5% by mass or more of Nb, and by forming a composition and structure of an oxide scale that can be easily pickled and removed, hot rolling It was decided to find a Ni-based alloy composition capable of easily pickling and removing the oxide scale formed in the solution heat treatment step after the hot working step such as, etc. to obtain a clean Ni-based alloy surface.

  Therefore, the inventors focused on the relationship between the degree of residual oxide scale and the alloy composition for a high Nb-containing Ni-based alloy. As a result, when the B content was high, the oxide scale tended to be pickled relatively well, so it was considered that the residual oxide scale could be reduced and prevented by the addition of trace elements. The inventors found Al, Ti, Si, Mn, Mo, and W as trace elements affecting formation of oxide scale, and clarified the influence of pickling removal of oxide scale when these trace elements are added. We studied to make it. The purpose of the small amount is to achieve the characteristics of the Ni-based alloy, such as cracking resistance, corrosion resistance, workability, structure stability, manufacturability, and the extent to which the influence on the cost can be prevented.

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 0.45%, manganese (Mn): 0.10 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 0.10%, titanium (Ti): 0.001 to 0.08%, 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 inevitable impurities,
A Ni-based alloy excellent in descalability characterized by satisfying the relationship of the following formula (wherein the notation of each element means the content (mass%) of the element).
1401 x B + (Mo + W) + 3.0 x Mn-2.2 x Si-2.4 x Al-1.7 x Ti 3. 3.20
[2] Ni excellent in descalability according to [1] characterized by satisfying the relationship of the following formula (wherein the notation of each element means the content (mass%) of the element) Base alloy.
1401 x B + (Mo + W) + 3.0 x Mn-2.2 x Si-2.4 x Al-1.7 x Ti 6.00 6.00
[3] A Ni-based alloy excellent in descaling properties according to [1] or [2], characterized in that it is, by mass%, boron (B): 0.0020 to 0.0070%.
[4] A Ni-based alloy sheet obtained by rolling the Ni-based alloy excellent in descalability according to any one of [1] to [3].

  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, it is possible to obtain a Ni-based alloy which is excellent in descalability, in which the oxide scale formed in the solution heat treatment step after the hot working step can be easily pickled and removed. Therefore, a clean surface state can be obtained without performing a mechanical removal step for oxide scale removal for a high Nb-containing Ni-based alloy that has a good surface state free of defects.

It is a graph showing the relationship between the content (%) of B and the residual scale area ratio (%). It is a graph showing the relationship between the content (%) of Mo + W and the residual scale area ratio (%). It is a graph showing the relation between the content (%) of Mn and the residual scale area rate (%). It is a graph showing the relationship between the content (%) of Si and the residual scale area ratio (%). It is a graph showing the relation between the content (%) of Al and the residual scale area ratio (%). It is a graph showing the relationship between the content (%) of Ti and the residual scale area ratio (%). 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, details of the Ni-based alloy which is excellent in the descaling property of the present invention will be described. The Ni-based alloy having excellent descalability 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 0.45%, manganese (Mn): 0.10 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 .10%, titanium (Ti): 0.001 to 0.08%, 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 remainder 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 with excellent de-scalability characterized by
1401 x B + (Mo + W) + 3.0 x Mn-2.2 x Si-2.4 x Al-1.7 x Ti 3. 3.20

C: 0.001 to 0.045%
C in the Ni-based alloy, which is excellent in descaling properties, is an essential element to stabilize the austenite phase and to ensure the 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 0.45%
Si in the Ni-based alloy, which is excellent in descaleability, is an element essential for 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. Also, it inhibits the efficient pickling of oxidized scale. Therefore, the upper limit of the content is 0.45%. The preferable lower limit of the content is 0.08%, and the particularly preferable lower limit is 0.10%. The upper limit of the content is preferably 0.40%, and particularly preferably 0.35%.

Mn: 0.10 to 1.00%
Mn in a Ni-based alloy, which is excellent in descaleability, is an element essential to 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 and contributes to the efficient pickling removal of the oxide scale. For this reason, addition of at least 0.10% 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 0.11%, and the particularly preferable lower limit is 0.12%. 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 descalability 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 descalability is an element which segregates in 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, which is excellent in descaleability, is an important element contributing to the improvement of the corrosion resistance, and is an element essential for use in severe environments. 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 which is excellent in descaleability has an 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, which is excellent in descaleability, 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 0.10%
Al in the Ni-based alloy, which is excellent in descaleability, is an element essential for deoxidation, and has the 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, if it is added in excess of 0.10%, removal of the oxide scale by pickling is inhibited to generate residual oxide scale. Therefore, the upper limit of the content is 0.10%. The preferable lower limit of the content is 0.02%, and the particularly preferable lower limit is 0.03%. The upper limit of the content is preferably 0.09%, particularly preferably 0.08%.

Ti: 0.001 to 0.08%
Ti in the Ni-based alloy, which is excellent in descaleability, is an element contributing to deoxidation, and has an effect of suppressing oxidation together with Al. Addition of at least 0.001% is necessary to obtain this effect. On the other hand, if it is added in excess of 0.08%, removal of the oxide scale by pickling is inhibited to generate residual oxide scale. Therefore, the upper limit of the content is 0.08%. The preferable lower limit of the content is 0.002%, and the particularly preferable lower limit is 0.003%. The upper limit of the content is preferably 0.07%, particularly preferably 0.06%.

N: 0.003 to 0.020%
N in the Ni-based alloy, which is excellent in descaleability, 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 the Ni-based alloy, which is excellent in descaleability, is an important element that improves the hot workability. In hot forging and hot rolling, stably prevent cracking. In addition, it affects the structure of the oxide scale and improves the removal characteristics of the oxide scale by pickling. It is necessary to add at least 0.0010% to obtain these effects. On the other hand, if the content is more than 0.0100%, the hot workability is rather reduced. Therefore, the upper limit of the content is 0.0100%. The preferable lower limit of the content is 0.0015%, and the particularly preferable lower limit is 0.0020%. 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 descaleability, facilitates reduction of 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, which is excellent in descaling properties, improve the corrosion resistance, particularly the pitting resistance, the crevice corrosion resistance, and also contribute to the improvement of intergranular corrosion. Furthermore, it acts on the oxide scale and improves the removal characteristics of the oxide scale by pickling. 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, excessive addition of Mo and / or W causes cost increase and also reduces the stability of the austenite phase. 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 excellent in the descalability of the present invention, the balance other than the above components is Ni and an unavoidable impurity. In the Ni-based alloy which is excellent in the descaling property of the present invention, Ni is contained as a main component.

Following formula 1401 x B + (Mo + W) + 3.0 x Mn-2.2 x Si-2.4 x Al-1.7 x Ti 3. 3.20
About the element which influences the oxide scale removal characteristic by pickling, the grade of the influence is expressed as a formula by regression analysis. When the value of the above formula is 3.20 or more, the balance between the element promoting oxide scale removal characteristics by pickling and the element suppressing oxide scale removal characteristics by pickling is optimized, and the hot workability and the resistance Even with a high Nb-containing Ni-based alloy containing 1.5% by mass or more of Nb in a Ni-based alloy, which is excellent in cracking resistance and corrosion resistance, oxide scale can be effectively removed by pickling. . Therefore, it is necessary to control the component composition of the Ni-based alloy so that the value of the above equation is 3.20 or more. The value of the above formula is preferably 4.50 or more, more preferably 5.50 or more, and particularly preferably 6.00 or more, from the viewpoint of further improving the removal property of oxide scale by pickling. On the other hand, the upper limit of the value of the above formula is not particularly limited, and an example is 17.34.

The specification method of the said formula is as follows.
A sample of Ni-based alloy which has Ni-20% Cr-2.3% Nb-7% Fe as its basic composition and in which the addition amounts of the above-mentioned various elements are changed and which is hot-forged and cold-rolled Were cut into 3 mm t × 40 mm × 60 mm. Then, after finishing the entire surface of the cut Ni-based alloy by wet polishing # 120, it is heated to 1025 ° C in a burning atmosphere of city gas with an oxygen concentration of 2.5%, held for 30 minutes, and heat treated The oxide scale was formed on the surface of the Ni-based alloy. After the heat treatment, the Ni-based alloy was taken out of the heating apparatus and cooled, and then the Ni-based alloy was immersed in a mixed acid (1 mol of nitric acid, 1 mol of hydrofluoric acid) at a temperature of 30 ° C. for 15 minutes. Next, the Ni-based alloy was taken out of the mixed acid and washed with water, and then the degree of residual oxide scale was evaluated. In the evaluation, the area of the surface of the Ni-based alloy of 40 mm × 60 mm is photographed with a digital microscope, the scale of the obtained digital image is black, the portion from which the scale is removed is binarized to white, and the area ratio of the remaining scale I asked.

  Descaling was evaluated as complete when scale was removed from the surface of the Ni-based alloy and the area ratio of residual scale was less than 3%. Here, it is judged that the unevenness due to the pickling is also in a state in which the scale remains or a slight dotted scale remains on the digital image. As the descaling state, it is preferable that (1) the surface is slightly darkened by smut when exposed and rubbed, but the removal of the slight point-like scale is also completed, and (2) the slight point-like scale is It is particularly preferred that the removal is also complete and does not become black when exposed to rubbing.

  As a result, addition of B is very effective in obtaining oxide scale removal characteristics by pickling, and addition of Mo, W, and Mn also tends to contribute to improvement of oxide scale removal characteristics by pickling. Was confirmed. On the other hand, when the addition amount of Al increases, removal of the oxide scale by pickling is inhibited, and when Si and Ti are also added to the Ni-based alloy, the residual oxide scale tends to be generated in the acid washing. A graph showing the relationship between the B content (%) and the residual scale area ratio (%) is shown in FIG. 1, a graph showing the relationship between the Mo + W content (%) and the residual scale area ratio (%) is shown in FIG. A graph showing the relationship between the content of Mn (%) and the residual scale area ratio (%) is shown in FIG. 3, and the graph showing the relationship between the content of Si (%) and the residual scale area ratio (%) is shown in FIG. A graph showing the relationship between the Al content (%) and the residual scale area ratio (%) is shown in FIG. 5, and a graph showing the relationship between the Ti content (%) and the residual scale area ratio (%) is shown in FIG. , Respectively.

From the results of FIGS. 1 to 6, the degree of influence of the pickling of the additive element on the oxide scale removal characteristics becomes clear, and the relationship between the residual scale area ratio (%) and the component composition of the Ni base alloy is determined by regression analysis Is the following formula.
1401 x B + (Mo + W) + 3.0 x Mn-2.2 x Si-2.4 x Al-1.7 x Ti 3. 3.20

  Moreover, the graph showing the relationship between the value of the relational expression of the component composition of said Ni-based alloy, and a residual-scale area ratio (%) is shown in FIG. It is understood from FIG. 7 that when the value of the above formula is 3.20 or more, the oxide scale removing characteristic by the pickling can be effectively obtained. The dotted line in FIG. 7 indicates the residual scale area ratio (%) of 3%.

  According to the Ni-based alloy excellent in descaling properties of the present invention, high Nb-containing Ni containing 1.5 mass% or more of Nb in the Ni-based alloy excellent in hot workability, cracking resistance and corrosion resistance Even if it is a base alloy, it is possible to obtain a Ni-based alloy which is excellent in descalability, in which the oxide scale formed in the solution heat treatment step after the hot working step can be easily pickled and removed. Therefore, a clean surface state can be obtained without performing a mechanical removal step for oxide scale removal for a high Nb-containing Ni-based alloy that has a good surface state free of defects. In addition, by rolling the Ni-based alloy having excellent descaling properties of the present invention by hot rolling or the like, it is possible to obtain a surface-clean Ni-based alloy plate from which oxide scale has been removed.

  For this reason, the Ni-based alloy of the present invention can be applied, for example, to nuclear reactor materials that have stringent requirements.

  Also, prior to acid washing, there is known a method in which oxidation scale is mechanically cracked or partially removed by bending with a leveler, shot blasting or the like to promote acid washing. It does not reduce the effects of the present invention.

  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 to 17 and Comparative Examples 1 to 7
Production of Hot Forged Slab of Ni-Based Alloy The Ni-based alloys of Examples 1 to 17 and Comparative Examples 1 to 7 having various component compositions shown in Table 1 below are first scrapped in a 60 t electric furnace, nickel, chromium A predetermined amount of a predetermined raw material such as niobium was added and dissolved, and then a mixed gas of oxygen and Ar was blown in at AOD (Argon Oxygen Decarburization) or VOD (Vacuum Oxygen Decarburization) 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. The mass of the rectangular Ni-based alloy mass was 8 tons. After casting, the cooled and solidified Ni-based alloy block was heated and held at 1030 ° C. for 2 hours, and then reheated to 1200 ° C. to perform upset forging of 20%. After upset forging of 20%, it is further heated to 1200 ° C. as a first stage press, and forged three times at a forging rate of 7% for each press, followed by 1250 ° C. as a second stage press. Forging in the range of 5 to 75% three times, followed by heating to 1150 ° C., forging at 15% as a final pressing step, and hot working of a Ni-based alloy having a thickness of 150 mm as a sample A forged slab was manufactured. In addition, content of each component in Table 1 means mass%.

Evaluation Descalability The hot forged slab of the Ni-based alloy obtained as described above was heated at 1200 ° C. and hot-rolled to form a 25 mm-thick hot-rolled sheet. Next, the obtained Ni-based alloy hot-rolled sheet is put into a heating furnace, heated to 1025 ° C. in a combustion atmosphere of city gas with an oxygen concentration of 2.5%, and held for 30 minutes to obtain Ni-based. An oxide scale was formed on the surface of the hot-rolled sheet of the alloy. After the heat treatment, the hot-rolled sheet was removed from the heating furnace and cooled, and then the hot-rolled sheet was immersed in mixed acid (1 mol of nitric acid, 1 mol of hydrofluoric acid) at a temperature of 40 ° C. for 15 minutes. Next, the hot-rolled sheet was taken out from the mixed acid, washed with water, and the degree of remaining oxide scale was evaluated.
For evaluation, a test piece having an area of 100 mm × 150 mm is cut out, and the cut out test piece is photographed with a digital microscope (VHX-2000 manufactured by Keyence Corporation, 20 × magnification), and the scale of the obtained digital image is black, scale The part from which B was removed was binarized to white to calculate the residual scale area ratio (%), and the evaluation was made in the following five grades, and the evaluations 1 to 3 were judged as pass.
Evaluation 1: There is no residual scale, and it does not become black even if it is scratched Evaluation 2: There is no residual scale, but it becomes slightly dark due to smut when it is rubbed Evaluation 3: The scale portion is less than 3% of the whole There is a slight point-like residual scale Evaluation 4: The scale part is 3% or more and less than 25% of the whole Evaluation 5: The scale part remains 25% or more of the whole

  The evaluation results of the descalability are shown in Table 1 below. In Table 1 below, the underlined numerical values mean that they are out of the scope of the present invention.

From the above Table 1, carbon (C): 0.001 to 0.045%, silicon (Si): 0.05 to 0.45%, manganese (Mn): 0.10 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 0.10%, titanium (Ti): 0.001 to 0.08%, 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
1401 x B + (Mo + W) + 3.0 x Mn-2.2 x Si-2.4 x Al-1.7 x Ti 3. 3.20
In the Ni-based alloys of Examples 1 to 17 which satisfy the following relationship, the descalability evaluations were as good as 1 to 3, and it was possible to obtain excellent oxide scale removal characteristics by pickling. Therefore, in the case of the Ni-based alloys of Examples 1 to 17, it is not necessary to add a preliminary step such as mechanical oxide scale removal to remove the oxide scale.

  In particular, in Examples 1, 3, 5, 7, 8, 10, 11, 14 and 17 in which the value of the above formula is more than 5.83, the descalability evaluation is 1 or 2, and the pickling is more excellent In Examples 1, 3, 5, 8 and 17 where the removal characteristics of the oxide scale can be obtained and the value of the above formula is 9.82 or more, the descalability evaluation is 1 and further excellent oxidation by pickling The scale removal characteristics could be obtained.

  On the other hand, Comparative Example 1 in which aluminum (Al) exceeds 0.10%, Comparative Example 2 in which boron (B) is less than 0.0010%, 0.005% of molybdenum (Mo) and tungsten (W) Comparative Example 3 which is less than, Comparative Example 4 which satisfies various component compositions but the value of the above formula is less than 3.20, Comparative Example 5 which has silicon (Si) exceeding 0.45%, manganese (Mn) 0 . In Comparative Example 6 which is less than 10%, and Comparative Example 7 in which titanium (Ti) is more than 0.08%, the descalability evaluation is 4 or 5, and the removal property of oxide scale by acid washing is obtained. I could not.

  In the present invention, since it is possible to obtain a Ni-based alloy excellent in descaling ability that can be easily pickled and removed the oxide scale formed in the solution heat treatment step after the hot working step, 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 (4)

% By mass, carbon (C): 0.001 to 0.045%, silicon (Si): 0.05 to 0.45%, manganese (Mn): 0.10 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 0.10%, titanium (Ti): 0.001 to 0.08%, 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 descalability 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).
1401 x B + (Mo + W) + 3.0 x Mn-2.2 x Si-2.4 x Al-1.7 x Ti 3. 3.20 The Ni-based alloy excellent in descalability according to claim 1, characterized in that it satisfies the relationship of the following formula (wherein the notation of each element means the content (mass%) of the element).
1401 x B + (Mo + W) + 3.0 x Mn-2.2 x Si-2.4 x Al-1.7 x Ti 6.00 6.00   The Ni-based alloy excellent in descalability according to claim 1 or 2, characterized in that it is, by mass%, boron (B): 0.0020 to 0.0070%.   The Ni-based alloy board which the Ni-based alloy excellent in the descalability of any one of Claims 1 thru | or 3 rolled.

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