JP2009022989A - WELDING MATERIAL FOR Ni BASED HIGH Cr ALLOY - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a welding material for Ni based high Cr alloy having excellent resistance to weld cracking, in other words, excellent resistance to reheat cracking and excellent resistance to solidification cracking, and excellent welding workability and wire machinability. <P>SOLUTION: The welding material for Ni based high Cr alloy has the composition consisting of, by mass, for the total mass of a welding material, 28.0-31.5% Cr, 7.0-11.0% Fe, 2.0-6.0% Mn, 0.8-2.0% Nb, with the total of Mn and Nb being 2.8-7.5%, and the balance Ni with inevitable impurities, while the composition of the inevitable impurities being suppressed to be ≤0.04% C, ≤0.5% Si, ≤0.02% P, ≤0.004% S, ≤0.1% Al, ≤0.1% Ti, ≤0.01% O, and ≤0.02% N, and the total of Al and Ti being ≤0.11%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention mainly relates to a welding material for welding a Ni-based high Cr alloy used in a highly corrosive environment.

  At present, 600 alloys used in high-corrosion environments such as pressurized water reactors operating at high temperatures and reheating furnaces for nitric acid production are resistant to intergranular stress corrosion cracking in primary cooling water environments close to pure water. It has been known for a long time. On the other hand, in order to improve the intergranular stress corrosion cracking resistance, a material change to a 690 alloy newly developed in recent years is effective instead of the 600 alloy. Table 1 shows a typical base material alloy composition of 690 alloy.

  When manufacturing a structure using this 690 alloy, it is common to involve welding. After this welding, a welding material is required in order to maintain the strength and ensure the weld crack resistance. Regarding this welding material, there is an ASME boiler and pressure vessel code (ASME Code) of the American Society of Mechanical Engineers (ASME). The chemical components are shown in Table 2.

  The composition of the welding material shown in Table 2 is almost the same as that of the 690 alloy, as is apparent from comparison with Table 1 which is the composition of the 690 alloy base material. Table 2) limits the contents of P and Cu in order to prevent weld cracking, and limits the contents of Mo, Nb, Al, Ti, and the total content of Al and Ti to prevent a decrease in corrosion resistance. Added.

Moreover, in patent document 1 which is a prior art, C: 0.04% or less and Si: 0.01-0.0.0% by weight for the purpose of providing the welding material excellent in weld crack resistance similarly. 13%, Mn: 5% or less, Cr: 28-31.5%, Nb: 1.8% or less, Al: 0.5-1.1%, Ti: 0.5-1%, (Al + Ti : 1.6% or less), Fe: 7 to 11%, V: 0.5% or less, P: 0.02% or less, S: 0.015% or less, O: A welding material for a Ni-based high Cr alloy having a composition containing 0.01% or less, N: 0.002 to 0.03% and the balance being Ni is disclosed.
JP 2003-31473 A (paragraph 0009)

However, conventional 690 alloy and Ni-based high Cr alloy welding materials (hereinafter also referred to as wires) have the following problems.
Since 690 alloy is a single structure of austenite inferior in weld crack resistance, further improvement in performance has been demanded in terms of weld crack resistance. Also, even if the wire has improved weld crack resistance, it is practically difficult if the workability deteriorates due to the occurrence of cracks during hot working during wire manufacture, that is, if the hot workability is poor. Become. Here, the 690 alloy often generates cracks particularly during hot working, and the generation of cracks during the hot working causes a decrease in yield. For this reason, there is a problem that the wire processability is inferior.
In addition, as a problem at the time of manufacture of a wire, there exists a disconnection in wire drawing other than the crack at the time of hot processing. These are collectively referred to as wire workability in this application.

Regarding the welding material described in Patent Document 1, when a welding material having this composition range was created in the research process of the present invention, there were many cases in which cracking occurred particularly during hot rolling, resulting in a decrease in yield. . For this reason, the welding material described in Patent Document 1 has a problem that it is inferior in wire workability.
Furthermore, depending on the component composition of the wire, a large amount of slag may be generated at the time of welding, and the generation of this slag takes time and effort to remove this slag, which makes it difficult to perform the welding operation, that is, the welding workability is reduced. There was a thing. Moreover, the solidification crack which a welded part cracks by segregation may generate | occur | produce.

  The present invention has been made to solve the above technical problem, and its purpose is to provide weld crack resistance, that is, reheat crack resistance and solidification crack resistance, welding workability and wire workability. An object of the present invention is to provide a Ni-based high Cr alloy welding material excellent in the above-mentioned.

As a result of intensive studies, the inventors have found that a welding material for a Ni-based high Cr alloy having excellent reheat cracking resistance can be obtained by adding a predetermined amount of Mn and Nb to a Ni-based high Cr alloy. The present invention has been reached. Further, by restricting the contents of Al and Ti, the wire workability was not impaired, and by restricting the content of Nb, the coagulation cracking resistance was not impaired.
Here, reheat cracking refers to a cracking phenomenon in which cracking occurs due to the thermal effect of a bead newly welded to a previous weld bead when multilayer welding is performed.

  That is, in order to solve the above problems, the welding material for Ni-based high Cr alloy according to the present invention is Cr: 28.0 to 31.5 mass%, Fe: 7.0 to 11.0 per total mass of the welding material. Mass%, Mn: 2.0-6.0 mass%, Nb: 0.8-2.0 mass%, and the total of said Mn and said Nb is 2.8-7.5 mass% And the balance consists of Ni and unavoidable impurities. Among the unavoidable impurities, C: 0.04 mass% or less, Si: 0.5 mass% or less, P: 0.02 mass% or less, S: 0.0. 004% by mass or less, Al: 0.1% by mass or less, Ti: 0.1% by mass or less, O: 0.01% by mass or less, N: 0.02% by mass or less, and Al and the above The total Ti is 0.11% by mass or less.

  According to such a configuration, the reheat cracking resistance of the welding material for the Ni-based high Cr alloy is improved by containing a predetermined amount of Mn and Nb. Further, by adding a predetermined amount of Cr, the stress corrosion cracking resistance is improved, and by containing a predetermined amount of Fe, generation of scale is suppressed. Furthermore, among the inevitable impurities, by limiting the content of Al and Ti, the wire workability is prevented from being lowered, and by limiting the content of a predetermined element, resistance to weld cracking and stress corrosion cracking Etc. are suppressed.

  In the welding material for Ni-based high Cr alloy according to the present invention, the Mn is 4.0 to 5.9% by mass, the Nb is 1.0 to 1.8% by mass, and the Mn And Nb is 5.0 to 7.5% by mass.

  According to such a configuration, the reheat cracking resistance of the Ni-based high Cr alloy welding material is improved by further limiting the total content of Mn, Nb and Mn and Nb to a predetermined range. , Welding workability and wire workability are more difficult to decrease.

  According to the welding material for Ni-based high Cr alloy according to the present invention, reheat cracking resistance can be improved. Moreover, since generation | occurrence | production of the crack at the time of hot rolling can be suppressed, wire workability can be improved and, as a result, productivity can be improved. Furthermore, it is possible to improve welding workability.

Hereinafter, the welding material for Ni-based high Cr alloy according to the present invention (hereinafter referred to as welding material) will be described in detail.
The welding material contains a predetermined amount of Cr, Fe, Mn, and Nb, the total amount of Mn and Nb is a predetermined amount, and the balance is made of Ni and inevitable impurities. Among the inevitable impurities, C, Si, P, S, Al, Ti, O, N are suppressed to a predetermined amount or less, and the sum of the Al and the Ti is specified to be a predetermined amount or less. is there.
Hereinafter, the reasons for limiting the components of the welding material will be described. In addition, content of a component is the mass% per welding material total mass.

<Cr: 28.0 to 31.5% by mass>
Cr is an essential element for improving the corrosion resistance such as stress corrosion cracking resistance and pitting corrosion resistance. is necessary. On the other hand, when it exceeds 31.5 mass%, the hot workability at the time of manufacture of a welding material will fall remarkably. Therefore, the Cr content is 28.0 to 31.5 mass%.

<Fe: 7.0 to 11.0% by mass>
Fe prevents or suppresses the generation of scale that occurs when the amount of Cr is high, such as 690 alloy. When the Fe content is less than 7.0% by mass, scale generation becomes significant. On the other hand, when it exceeds 11.0 mass%, stress corrosion cracking resistance will fall. Therefore, the Fe content is 7.0 to 11.0% by mass.

<Mn: 2.0 to 6.0% by mass>
Mn is effective as an element that brings about a deoxidizing action and a desulfurizing action at the time of welding, and also has an effect of fixing S and improving reheat cracking resistance. If the Mn content is less than 2.0% by mass, these sufficient effects cannot be obtained. On the other hand, in order to enhance these effects, it is preferable to increase the Mn content. However, if it exceeds 6.0 mass%, the slag generated at the time of welding deteriorates the hot water flow, and the welding workability decreases. Therefore, the Mn content is set to 2.0 to 6.0 mass%. Preferably, it is 4.0-5.9 mass%.

<Nb: 0.8-2.0 mass%>
Nb improves reheat cracking resistance, but if the Nb content is less than 0.8% by mass, sufficient effects cannot be obtained. On the other hand, if it exceeds 2.0% by mass, the resistance to solidification cracking deteriorates, and the hot workability during the production of the welding material is remarkably lowered. Therefore, Nb content shall be 0.8-2.0 mass%. Preferably, it is 1.0-1.8 mass%.

Here, in the present invention, the total content of Mn and Nb is defined within a predetermined range.
<Total of Mn and Nb: 2.8 to 7.5% by mass>
Addition of Mn and Nb improves the resistance to reheat cracking, but when the total content of Mn and Nb exceeds 7.5% by mass, the hot workability during the production of the welding material is significantly reduced. Moreover, slag is likely to be generated, and welding workability is reduced. Therefore, the total content of Mn and Nb is 2.8 to 7.5% by mass. Preferably, it is 5.0-7.5 mass%, More preferably, it is 5.0-7.0 mass%.

<Balance: Ni and inevitable impurities>
The welding material contains the above components as essential components, and the balance is made of Ni and inevitable impurities.
Hereinafter, the reason why C, Si, P, S, Al, Ti, O, N, and the total of Al and Ti, which are elements included as inevitable impurities, are suppressed to a predetermined amount or less will be described.

<C: 0.04 mass% or less>
C is a solid solution strengthening element, and the tensile strength increases with an increase in the C content, but an increase in the C content decreases the stress corrosion cracking resistance. Therefore, considering both characteristics, the C content is set to 0.04% by mass or less.

<Si: 0.5% by mass or less>
Since the reheat cracking resistance deteriorates when the Si content increases, the Si content is set to 0.5 mass% or less.

<P: 0.02 mass% or less>
P is an element that forms a low-melting point eutectic (Ni—Ni ₃ P or the like) with Ni and degrades reheat cracking resistance. Therefore, the smaller the content of P, the better. However, excessive limitation causes a decrease in economic efficiency. Therefore, the P content is 0.02% by mass or less.

<S: 0.004 mass% or less>
S, like P, forms a low-melting point eutectic (Ni—Ni ₃ S ₂ or the like) with Ni, and remarkably deteriorates the hot workability during production of the welding material. Therefore, the S content is 0.004% by mass or less.

<Al: 0.1% by mass or less>
If Al is contained excessively, wire workability is lowered, so the content is made 0.1% by mass or less.

<Ti: 0.1% by mass or less>
Ti, like Al, reduces wire workability when contained in excess, so is 0.1% by mass or less.

Here, in this invention, the sum total of content of Al and Ti is prescribed | regulated below to predetermined.
<Total of Al and Ti: 0.11% by mass or less>
Excessive inclusion of Al and Ti generates slag, reduces welding workability, and remarkably reduces wire workability. Therefore, the total content of Al and Ti is 0.11% by mass or less. Preferably, it is 0.10 mass% or less.

<O: 0.01% by mass or less>
O is an unavoidable impurity that enters from the atmosphere during the melting of the welding material, and reduces the stress corrosion cracking resistance. Accordingly, the content is 0.01% by mass or less.

<N: 0.02 mass% or less>
N, like O, is an unavoidable impurity that enters from the atmosphere during melting of the welding material, and causes defects such as blow holes. Therefore, it is 0.02 mass% or less.

  In addition to the above-mentioned C, Si, P, S, Al, Ti, O, and N, it is considered that unavoidable impurities include, for example, Mo and Cu. Even if Cu is contained in an amount of 0.3% by mass or less, Cu does not substantially affect the effect of the present invention.

  Next, the welding material according to the present invention will be specifically described by comparing an example that satisfies the requirements of the present invention with a comparative example that does not satisfy the requirements of the present invention.

[First embodiment]
First, a welding material having the composition shown in Table 3 was prepared, and then, using this welding material, the following reheat cracking resistance (weld cracking resistance) and welding workability were evaluated. . In addition, the wire workability was evaluated when the welding material was produced (manufactured).
Table 3 shows the component composition of the welding material. In Table 3, those not satisfying the configuration of the present invention are indicated by underlining the numerical values. The value of the total amount of Al and Ti (Al + Ti) is a value obtained by rounding off the third decimal place.

<Reheat cracking resistance>
The reheat cracking resistance was evaluated by a surface bending test based on JIS Z 3224. Good resistance to reheat cracking when cracks did not occur (◯). Some when cracks of 2.4 mm or less were 2 or less, resistance to reheat cracking was slightly poor (Δ), and many cracks occurred. The product was judged to have poor reheat cracking resistance (x).

<Welding workability>
The welding workability was evaluated by actually performing the welding work using the produced welding material. During welding, the generation of slag was small and the welding work was performed normally, but the welding workability was good (○), and the welding work could be performed. Those that were difficult were judged to have poor welding workability (△), and those that could not be welded due to a lot of slag generation were judged to be poor (x).

<Wire workability>
The wire workability was evaluated by confirming the processing status at the time of wire production. Good wire workability (◎) when processed without problems, few cracks during hot working, but good wire workability (○) when heat breakage is likely to occur. It was judged that the wire workability was poor (x) when many cracks occurred during the inter-working and there were many breaks during wire drawing.
These results are shown in Table 4.

As shown in Table 4, Examples 1 to 5 were satisfactory in all of reheat cracking resistance, welding workability, and wire workability because the component composition satisfied the scope of the present invention.
In Example 4 in wire workability, Nb was 2.0% by mass or less, but exceeded 1.8% by mass, and therefore was slightly inferior to wire processability as compared with other examples. .
On the other hand, Comparative Examples 6 to 19 had the following problems because the component composition did not satisfy the scope of the present invention.

  In Comparative Example 6, Mn, Nb and the total amount of Mn and Nb (Mn + Nb) deviated from the lower limit values, so that welding workability and wire workability were good, but reheat cracking resistance was poor. In Comparative Example 7, since the total amount of Mn and Mn and Nb deviated from the lower limit value, the welding workability and the wire workability were good, but the reheat cracking resistance was poor. In Comparative Example 8, Mn, and the total amount of Mn and Nb deviated from the lower limit value, and the total amount of Nb, Al and Ti (Al + Ti) exceeded the upper limit value, so reheat cracking resistance, welding workability And it was inferior to wire workability.

  In Comparative Example 9, the total amount of Nb, Mn, and Nb deviated from the lower limit value, and the total amount of Al and Ti exceeded the upper limit value. Therefore, the reheat crack resistance, welding workability, and wire workability were inferior. In Comparative Example 10, since the total amount of Nb, Ti, and Al and Ti exceeded the upper limit value, the reheat cracking resistance was good, but the welding workability and wire workability were poor. In Comparative Example 11, since the total amount of S, Nb and Mn and Nb exceeded the upper limit value, the reheat cracking resistance was good, but the welding workability and wire workability were poor.

  In Comparative Example 12, Nb deviated from the lower limit value, and the total amount of Mn and Al and Ti exceeded the upper limit value. Therefore, the reheat crack resistance, welding workability, and wire workability were inferior. In Comparative Example 13, Mn deviated from the lower limit value, and the total amount of Nb, Ti, and Al and Ti exceeded the upper limit value.

  In Comparative Example 14 and Comparative Example 15, since Nb deviated from the lower limit, welding workability and wire workability were good, but the reheat cracking resistance was poor. In Comparative Example 16, since the total amount of Nb, Al, and Al and Ti exceeded the upper limit value, the reheat cracking resistance was good, but the welding workability and wire workability were poor. In Comparative Example 17, since the total amount of Ti, Al, and Al and Ti exceeded the upper limit value, the reheat cracking resistance was good, but the welding workability and wire workability were poor.

  In Comparative Example 18, since the total amount of Ti and Al and Ti exceeded the upper limit value, the reheat cracking resistance was good, but the welding workability and wire workability were poor. In Comparative Example 19, since the total amount of S, Ti, Al, and Al and Ti exceeded the upper limit value, the reheat cracking resistance was good, but the welding workability and wire workability were poor.

Next, based on the above results, appropriate values of Mn, Nb, Al, and Ti contents will be described with reference to the drawings.
FIG. 1 is a graph showing the relationship between the Mn and Nb contents in the alloy in the first example and reheat cracking resistance (weld cracking resistance), and FIG. 2 shows the relationship between Mn in the alloy in the first example and FIG. 3 is a graph showing the relationship between the total amount of Nb (Mn + Nb) and the total amount of Al and Ti (Al + Ti) and welding workability. FIG. 3 shows the total amount of Mn and Nb in the alloy in the first embodiment (Mn + Nb). And it is a graph which shows the total amount (Al + Ti) of Al and Ti, and the relationship of wire workability.

  As shown in FIG. 1, the reheat cracking resistance is improved by the addition of Mn and Nb. However, when the content of Mn or Nb is small, the reheat cracking resistance is not improved.

  Moreover, as shown in FIGS. 2 and 3, when an appropriate amount of Mn and Nb is added, welding workability and wire workability tend to be impaired by the addition of Al and Ti. In addition, when the total addition of Al and Ti and the total addition of Mn and Nb was excessive, deterioration in welding workability and wire workability due to slag were observed. 2 and 3, “total of Mn and Nb: 0.00 mass%, total of Al and Ti: 0.02 mass%” (Comparative Example 6) and “total of Mn and Nb: 1.97 mass%. , The total of Al and Ti: 0.03 mass% (Comparative Example 7) is “◯”, but this is the content of “total of Mn and Nb” and “total of Al and Ti”. This is because if the amount is small, welding workability and wire workability are not affected.

[Second Embodiment]
In order to confirm the influence of the solidification cracking resistance due to the addition of Nb, the welding materials 1 to 4 having the components shown in Table 5 were prepared, and the solidification cracking resistance was evaluated by a ballast train test.
The component composition of the welding material is shown in Table 5. In Table 5, those not satisfying the configuration of the present invention are indicated by underlining the numerical values. The value of the total amount of Al and Ti (Al + Ti) is a value obtained by rounding off the third decimal place. Moreover, while showing welding conditions in Table 6, Fig.4 (a) shows a welding shape and (b) shows a test piece shape.

The produced welding materials 1 to 4 were adjusted so that only the Nb content was changed and the other elements were at the same level as much as possible. And the total value (total crack length) of the weld crack length which arose in the test piece 1 by the ballast rain test was calculated | required.
FIG. 5 shows the correlation between the Nb content of the welding materials 1 to 4 and the total crack length.
As shown in FIG. 5, as the Nb content increases, the total crack length increases, and if the Nb content is 2.0% by mass or less, the total value of solidification cracks tends to be stable at a low level. I found out.

  As mentioned above, although the best embodiment and the Example were shown and demonstrated in detail about the welding material which concerns on this invention, the meaning of this invention is not limited to an above-described content. Needless to say, the contents of the present invention can be widely modified and changed based on the above description.

It is a graph which shows the relationship of Mn and Nb content in the alloy in 1st Example, and reheat cracking resistance (weld cracking resistance). It is a graph which shows the relationship between the total amount (Mn + Nb) of Mn and Nb in the alloy in 1st Example, the total amount of Al and Ti (Al + Ti), and welding workability | operativity. It is a graph which shows the total amount (Mn + Nb) of Mn and Nb in the alloy in 1st Example, the relationship between the total amount of Al and Ti (Al + Ti), and wire workability. (A) is a schematic diagram which shows the welding shape in a ballest rain test, (b) is a schematic diagram which shows the test piece shape in a ballest rain test. It is a graph which shows the correlation with Nb content in a ballast train test, and the total value (total crack length) of weld crack length.

Explanation of symbols

1 Test plate R Bending radius

Claims (2)

Based on the total mass of the welding material, Cr: 28.0 to 31.5 mass%, Fe: 7.0 to 11.0 mass%, Mn: 2.0 to 6.0 mass%, Nb: 0.8 to 2. 0% by mass, and the total of Mn and Nb is 2.8 to 7.5% by mass, and the balance is made of Ni and inevitable impurities.
Among the inevitable impurities, C: 0.04 mass% or less, Si: 0.5 mass% or less, P: 0.02 mass% or less, S: 0.004 mass% or less, Al: 0.1 mass% Hereinafter, Ti: 0.1% by mass or less, O: 0.01% by mass or less, N: 0.02% by mass or less, and the total of Al and Ti is 0.11% by mass or less. A welding material for a Ni-based high Cr alloy, characterized in that:   The Mn is 4.0 to 5.9% by mass, the Nb is 1.0 to 1.8% by mass, and the total of the Mn and the Nb is 5.0 to 7.5% by mass. The welding material for a Ni-based high Cr alloy according to claim 1, wherein:

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