JP2010172952A - WELDING MATERIAL COMPOSED OF HIGH-Cr CONTAINING Ni-BASED ALLOY, AND WELDING METHOD USING THE SAME - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a welding material composed of a high-Cr containing Ni-based alloy capable of more enhancing tensile strength than heretofore, and to provide a welding method using the welding material. <P>SOLUTION: The welding material composed of a high-Cr containing Ni-based alloy has a composition composed of, by mass, ≤0.04% C, ≤0.50% Si, ≤1.00% Mn, 28.0-31.5% Cr, ≤0.50% Mo, 7.0-11.0% Fe, ≤0.30% Cu, ≤0.10% Nb+Ta, 0.5-3.0% Al, and 0.5-3.0% Ti, with inevitable impurities containing ≤0.020% P and ≤0.015% S and the balance Ni. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a high chromium (Cr) -containing nickel (Ni) based alloy welding material and a welding method using the same.

  Ni-base alloy welding materials are used for the inner surface welding of the pressure vessel of the boiling water reactor and the welded portion of the control rod drive mechanism stub tube and shroud support. Currently used Ni-based alloy welding material ASME (The American Society of Mechanical Engineers: ASME) SFA-5.14 The Cr content of ERNiCr-3 is about 20%.

  On the other hand, as a high Cr content Ni-base alloy welding material having a Cr content of about 30%, ASME SFA-5.14 ERNi-Cr-Fe-7 and ERNi-Cr-Fe-7A, which are Ni-Cr-Fe based alloys, are used. In order to further improve the corrosion resistance, application of these high Cr-containing Ni-based welding materials is being studied.

  Table 1 shows specified values relating to the chemical components of the above-mentioned welding materials. The unit of the numerical values shown in Table 1 is mass%.

  The tensile strengths of ERNi-Cr-Fe-7 and ERNi-Cr-Fe-7A described above are substantially equivalent to the tensile strength of NCF690, which is one of the counterpart materials during welding. For this reason, the further strength improvement of a welding part is desired.

  Therefore, development of a high Cr-containing Ni-based alloy welding material which is excellent in tensile strength by finely adjusting the additive element based on the above ERNi-Cr-Fe-7 or the like is underway. As one of such high Cr content Ni-base alloy welding materials, for example, a high Cr content Ni-base alloy whose tensile strength characteristics are improved by adding 0.03 to 0.3% of nitrogen (N) is used. A welding material is known (see, for example, Patent Document 1). Further, there is known a high Cr-containing Ni-based alloy welding material in which tensile strength characteristics are improved by composite addition of nitrogen (N), tungsten (W), and vanadium (V) (for example, Patent Document 2). reference).

Japanese Patent No. 3170166 Japanese Patent No. 3382834

  As described above, with regard to the high Cr content Ni-base alloy welding material, the tensile strength of the material can be obtained by adding nitrogen (N), tungsten (W), and vanadium (V) based on ERNi-Cr-Fe-7. Improvements are being made. In this case, nitrogen (N) forms nitrides (TiN) with titanium (Ti) and the like, and improves the tensile strength of the material. Tungsten (W) and vanadium (V) improve the tensile strength of the material by dissolving in the matrix.

  However, in the development of conventional high Cr content Ni-base alloy welding materials, the relationship between the influence of elements contributing to precipitation strengthening such as Al and Ti and the tensile strength is not mentioned.

  Therefore, the present invention clarifies the relationship between the content of Al and Ti in the ERNi-Cr-Fe-7 series high Cr content Ni-base alloy welding material and the tensile strength after heat treatment, and improves the tensile strength compared to the prior art. It is an object of the present invention to provide a high Cr content Ni-base alloy welding material and a welding method using the same.

  One aspect of the high Cr content Ni-based alloy welding material of the present invention is, in mass%, C: 0.04% or less, Si: 0.50% or less, Mn: 1.00% or less, Cr: 28.0%. -31.5%, Mo: 0.50% or less, Fe: 7.0% to 11.0%, Cu: 0.30% or less, Nb + Ta: 0.10% or less, Al: 0.5% to 3 0.0%, containing Ti: 0.5% to 3.0%, further containing P: 0.020% or less, S: 0.015 or less as unavoidable impurities, with the balance being Ni. It is characterized by that.

  Another aspect of the high Cr content Ni-base alloy welding material of the present invention is, in mass%, C: 0.04% or less, Si: 0.50% or less, Mn: 1.00% or less, Cr: 28.0. % To 31.5%, Mo: 0.50% or less, Fe: 7.0% to 11.0%, Cu: 0.30% or less, Nb + Ta: 0.5% to 1.0%, Al: 0 0.5% to 3.0%, Ti: 0.5% to 3.0%, further containing P: 0.020% or less and S: 0.015 or less as inevitable impurities, the balance being Ni It has the composition which consists of.

  ADVANTAGE OF THE INVENTION According to this invention, the high Cr content Ni base alloy welding material which improved the tensile strength compared with the past, and the welding method using the same can be provided.

The figure which shows the relationship between the content of Al and Ti in high Cr content Ni base alloy welding material, and the normal temperature and high temperature tensile strength before and after heat processing after welding. The graph which shows the precipitation curve in Ni base alloy (Alloy718).

  Hereinafter, a high Cr content Ni-base alloy welding material and a welding method using the same according to an embodiment of the present invention will be described with reference to the drawings.

  The ERNi-Cr-Fe-7 high Cr-containing Ni-base alloy welding material according to the present embodiment is mass%, C: 0.04% or less, Si: 0.50% or less, Mn: 1.00% or less. Cr: 28.0% to 31.5%, Mo: 0.50% or less, Fe: 7.0% to 11.0%, Cu: 0.30% or less, Nb + Ta: 0.10% or less, Al : 0.5% to 3.0%, Ti: 0.5% to 3.0%, further, P: 0.020% or less, S: 0.015 or less as an inevitable impurity, the balance Has a composition of Ni.

  As shown in Table 1, in ASME SFA-5.14 ERNi-Cr-Fe-7, the Al content is 1.10% by mass or less and the Ti content is 1.0% by mass or less. . On the other hand, in this embodiment, the tensile strength is adjusted by setting the Al content to 0.5 mass% to 3.0 mass% and the Ti content to 0.5 mass% to 3.0 mass%. The ERNi-Cr-Fe-7 high Cr-containing Ni-base alloy welding material can be improved. In addition, except Al and Ti among said composition, it is the same as ERNi-Cr-Fe-7 shown in Table 1.

  Among the above compositions, C is a solid solution strengthening element, and the tensile strength increases with an increase in the amount of C. However, the stress corrosion cracking resistance is deteriorated, so the C amount exceeds 0% by mass considering both characteristics. It is 0.04 mass% or less.

  Si has a deoxidizing effect during welding, but when the amount of Si increases, the susceptibility to hot cracking at welding increases. Therefore, the amount of Si exceeds 0% by mass and is 0.50% by mass or less.

  Mn has a deoxidizing action and a desulfurizing action at the time of welding, but if the amount of Mn is added exceeding 1%, the hot water flow of slag is deteriorated at the time of welding and welding workability is deteriorated. 1 mass% or less.

  Cr is an essential element for improving corrosion resistance, and in order to sufficiently obtain the effect of stress corrosion cracking resistance, 28% by mass or more is necessary. On the other hand, if it exceeds 31.5% by mass, the filler material is produced. Therefore, the Cr content is 28% by mass to 31.5% by mass.

  Mo is dissolved in the matrix to improve the tensile strength, but an increase in the amount of Mo significantly degrades the hot workability during the production of the filler metal. For this reason, Mo amount exceeds 0 mass% and is 0.50 mass% or less.

  Fe prevents or suppresses the generation of scale that occurs when the amount of Cr is high, but scale generation becomes significant when the amount of Fe is less than 7% by mass, and stress corrosion cracking deteriorates when added in excess of 11% by mass. . For this reason, Fe is 7 mass%-11 mass%.

  When Cu is heated to a high temperature, it is finely dispersed and precipitated in the matrix to increase the tensile strength. However, when it is excessive, the resistance to weld cracking is increased, so the amount of Cu exceeds 0% by mass and is 0.30% by mass or less. Yes.

  Nb and Ta are elements that have a strong tendency to form carbides and improve tensile strength. However, an increase in the amount of Nb and Ta impairs workability, so the amount of Nb + Ta exceeds 0% by mass and is 0.10% by mass or less. It has become.

  P makes a low-melting point eutectic with Ni and increases the weld hot cracking susceptibility. Therefore, the lower the content, the better. However, excessive restriction causes a decrease in economic efficiency, so the P content is 0.020% by mass or less. It has become.

  S, like P, forms a low-melting eutectic with Ni and increases the weld hot cracking susceptibility, so the smaller the content, the better. For this reason, the amount of S is 0.015 mass% or less.

  The reason why the Al content is 0.5 mass% to 3.0 mass% and the Ti content is 0.5 mass% to 3.0 mass% will be described later.

  As an example, an ERNi-Cr-Fe-7 high Cr-containing Ni-based alloy welding material having an Al content of 0.67% by mass and a Ti content of 0.53% by mass was produced. As a comparative example, an ERNi-Cr-Fe-7 high Cr-containing Ni-based alloy welding material having an Al content of 0.10% by mass and a Ti content of 0.21% by mass was produced. Table 2 shows the components of the ERNi-Cr-Fe-7 series high Cr-containing Ni-base alloy welding materials of these examples and comparative examples. The unit of the numerical values shown in Table 2 is mass%.

  FIG. 1 shows the results of examining the tensile strength at normal temperature and high temperature before and after heat treatment after welding for the above-described examples and comparative examples. 1A shows normal temperature tensile strength (MPa), and FIG. 1B shows high temperature (302 ° C.) tensile strength (MPa). The conditions for the post-weld heat treatment at this time were approximately 615 ° C. (about 615 ± 20 ° C.) and 45 hours.

  As shown in FIG. 1A, in the case of the comparative example in which the Al content is 0.10% by mass and the Ti content is 0.21% by mass, there is hardly any increase in the room temperature tensile strength due to the heat treatment after welding. The normal temperature tensile strength before and after heat treatment is about 600 MPa, and the tensile strength of NCF690 alloy, which is a comparative material, at normal temperature is 586 MPa (JSME power generation nuclear equipment standard design and construction standard (2005 version) JSMES NC1-2005 Appendix Chart Part5 Design tensile strength at temperature (Su (MPa)).

  On the other hand, in the case of the example in which the Al content is 0.67% and the Ti content is 0.53%, the normal temperature tensile strength is increased from about 570 MPa to about 680 MPa by the heat treatment after welding, The tensile strength showed a value larger than the tensile strength 586 MPa at normal temperature of the NCF690 alloy as a comparative material.

  Further, as shown in FIG. 1B, in the case of the comparative example in which the Al content is 0.10% and the Ti content is 0.21%, the high temperature (302 ° C.) tensile strength is about The high-temperature tensile strength after heat treatment is reduced from 550 MPa to about 490 MPa, and the tensile strength at high temperature (302 ° C.) of the NCF690 alloy, which is a comparative material, is 540 MPa (JSME Power Generation Nuclear Equipment Standard Design and Construction Standard (2005 edition) JSME S NC1-2005 Appendix Chart Part 5 Designed to a value lower than the material design tensile strength Su (MPa) at each temperature.

On the other hand, in the case of the example in which the Al content is 0.67% and the Ti content is 0.53%, the high temperature (302 ° C.) tensile strength is increased from about 530 MPa to about 560 MPa by the heat treatment after welding. The subsequent high temperature (302 ° C.) tensile strength was higher than the tensile strength of 540 MPa at the high temperature (302 ° C.) of the comparative NCF690 alloy. Thus, it is thought that the reason why the tensile strength at normal temperature and high temperature is improved after heat treatment in the examples is that precipitates such as Ni ₃ Al and Ni ₃ Ti are precipitated in the crystal grains.

  From the above results, in the ERNi-Cr-Fe-7 series high Cr content Ni-base alloy welding material, by increasing the Al content and Ti content, normal temperature tensile strength and high temperature (302 ° C) by heat treatment after welding. It was shown that the tensile strength was increased. That is, Al content of ERNi-Cr-Fe-7 series high Cr content Ni-base alloy welding material is 0.57% or more 0.67%, Ti content is 0.50% or more 0.53%, It was found that a tensile strength greater than the tensile strength of NCF690 alloy can be obtained by performing a heat treatment for 45 hours at a temperature of about 615 ° C. after welding.

  On the other hand, when Al is added too much, other characteristics may be deteriorated, for example, welding workability may be deteriorated. For this reason, it is preferable that Al content shall be about 3.0 mass% or less. The Ti content is preferably about 3.0% by mass or less for the same reason.

  For the above reasons, in the ERNi-Cr-Fe-7 high Cr content Ni-base alloy welding material, the Al content Al content is 0.5 mass% to 3.0 mass%, and the Ti content is 0.00. 5 mass% to 3.0 mass%. After welding, the tensile strength at normal temperature and high temperature can be improved by subjecting the welded portion to heat treatment at a temperature of approximately 615 ° C. (for example, a temperature of 615 ± 20 ° C.) for at least 45 hours. As a welding method, TIG welding, MIG welding, or the like can be used.

In the above embodiment, after the welding, heat treatment is performed at a temperature of about 615 ° C. (for example, a temperature of 615 ± 20 ° C.) for at least 45 hours, thereby depositing precipitates such as Ni ₃ Al and Ni ₃ Ti in the crystal grains. The tensile strength at room temperature and high temperature was improved by precipitation. However, the conditions for such heat treatment are not limited to such conditions, and are conditions under which precipitates such as Ni ₃ Al and Ni ₃ Ti can be precipitated in the crystal grains to improve the normal temperature and high temperature tensile strength. I just need it.

The vertical axis of aging temperature and the horizontal axis of aging time are shown in the graph of Fig. 2. The precipitation curve in Ni-based alloy (Alloy 718) (SCC SUSCEPTIBILITY OF ALLOY 718, M. Tsubota et.al, Workshop on Advanced High-Strength Materials) , EPRI, 1986). From FIG. 2, it can be seen that Ni ₃ Al and Ni ₃ Ti are precipitated in the Ni-based alloy by applying a heat treatment at a temperature of about 750 ° C. to about 850 ° C. for 5 hours or more.

  Therefore, the Al content of the ERNi-Cr-Fe-7 high Cr content Ni-base alloy welding material is 0.5 mass% to 3.0 mass%, and the Ti content is 0.5 mass% to 3.0 mass%. Then, after welding, this weld is heat-treated at a temperature in the range of about 750 ° C. to about 850 ° C. for 5 hours or more. Thereby, the tensile strength at normal temperature and high temperature of ERNi-Cr-Fe-7 system high Cr content Ni base alloy welding material can be improved.

  In the above-described embodiments and examples, the ERNi—Cr—Fe-7 high Cr content Ni-based alloy welding material having a Nb + Ta content of 0.10% by mass or less has been described. However, the present invention can also be applied in the same manner to an ERNi—Cr—Fe-7A-based high Cr-containing Ni-base alloy welding material having a Nb + Ta content of 0.5 mass% to 1.0 mass%.

Claims (6)

  In mass%, C: 0.04% or less, Si: 0.50% or less, Mn: 1.00% or less, Cr: 28.0% to 31.5%, Mo: 0.50% or less, Fe: 7.0% to 11.0%, Cu: 0.30% or less, Nb + Ta: 0.10% or less, Al: 0.5% to 3.0%, Ti: 0.5% to 3.0% A high Cr-containing Ni-base alloy welding material containing a composition containing P: 0.020% or less and S: 0.015 or less as an inevitable impurity, with the balance being made of Ni.   After welding using the high Cr content Ni-base alloy welding material according to claim 1, the welded portion subjected to the welding is subjected to a heat treatment at a temperature of about 615 ° C. for 45 hours or more, and A welding method characterized by improving tensile strength.   After welding using the high Cr content Ni-base alloy welding material according to claim 1, the welded portion subjected to the welding is subjected to a heat treatment at a temperature of 750 ° C. to 850 ° C. for 5 hours or more to perform the welding. The welding method characterized by improving the tensile strength of a part.   In mass%, C: 0.04% or less, Si: 0.50% or less, Mn: 1.00% or less, Cr: 28.0% to 31.5%, Mo: 0.50% or less, Fe: 7.0% to 11.0%, Cu: 0.30% or less, Nb + Ta: 0.5% to 1.0%, Al: 0.5% to 3.0%, Ti: 0.5% to 3 High Cr content Ni-base alloy welding characterized by containing 0.0% and further containing P: 0.020% or less and S: 0.015 or less as unavoidable impurities, with the balance being made of Ni. material.   After performing welding using the high Cr content Ni-base alloy welding material according to claim 4, the welded portion subjected to the welding is subjected to a heat treatment at a temperature of about 615 ° C for 45 hours or more, and A welding method characterized by improving tensile strength.   After welding using the high Cr content Ni-base alloy welding material according to claim 4, the welded portion subjected to the welding is subjected to a heat treatment at a temperature of 750 ° C to 850 ° C for 5 hours or more, and the welding is performed. The welding method characterized by improving the tensile strength of a part.

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