JP3375817B2 - Welding wire for high chromium ferritic steel - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention
And a welding wire for high chromium ferrite steel containing Cr. 2. Description of the Related Art High chromium ferritic steels, in addition to good strength properties at high temperatures, also have excellent oxidation resistance, and have a lower coefficient of thermal expansion and a lower susceptibility to stress corrosion cracking than austenitic stainless steels. It is used for high temperature and high pressure thermal power plants and nuclear power equipment. In recent years, from the viewpoint of protecting the global environment, efficiency has been improved by increasing operating conditions to higher temperatures and pressures, and emission of carbon dioxide gas per unit energy has been suppressed. For this purpose, various new steel materials have been developed, and many of them have already been put into practical use. Some welding materials for welding the steel materials have already been proposed with some new components. ing. However, all of the conventional welding materials have insufficient properties. For example, in JP-A-1-215489 and JP-A-2-280993, Ca, La and, if necessary, La,
It has been proposed to improve the toughness by adding Ce to lower the oxygen of the weld metal. [0005] In addition, the following publications are known. JP-A-1-215490, JP-A-2-37989. JP-A-2-268977, JP-A-1-174998, JP-A-5
177383, JP-A-5-177384, JP-A-5-
212582, JP-A-5-285691, JP-A-6-1
42981, JP-A-6-277879, JP-A-7-80
680, JP-A-7-96390, JP-A-7-16418
2, JP-A-7-204885, JP-A-7-26856
3, JP-A-7-284986. [0006] However, these known welding wires for high chromium ferritic steel have poor welding workability and insufficient high temperature strength characteristics such as creep rupture strength. . The present invention has been made in view of the above-mentioned problems, and has a sufficient high-temperature strength characteristic mainly including creep rupture strength, excellent welding workability, and a characteristic of high chromium ferritic steel. It is an object of the present invention to provide a high chromium ferritic steel welding wire that can be applied to various fields. [0008] The welding wire for high chromium ferrite steel according to the present invention has a C: 0.01 to 0.19.
Wt%, Si: 0.01 to 1.50 wt%, Mn:
0.01 to 2.00% by weight, Cr: 7.00 to 1
3.00% by weight, Mo: 0.01 to 1.60% by weight,
Ni: 0.02 to 1.50% by weight, Nb + Ta: 0.
002 to 0.25% by weight, V: 0.01 to 0.50
% By weight, Ti: 0.001 to 0.100% by weight, A
l: 0.002 to 0.10% by weight, N: 0.003 to 0.100% by weight, O: 0.002 to 0.030% by weight, Ca: 0.0002 to 0.01% by weight and M
g: containing 0.0002 to 0.01% by weight;
The sum of Al + 10 × (Ca + Mg) is limited to 0.13% by weight or less, and further, W: 0.10 to 3.00% by weight, Cu: 0.005 to 4.00% by weight, Co:
It contains at least one selected from the group consisting of 0.005 to 5.00% by weight and B: 0.0005 to 0.01% by weight, with the balance being iron and unavoidable impurities. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The reasons for adding each component of the welding wire of the present invention and the reasons for limiting the composition will be described below. C: 0.01 to 0.19% by weight C is a component necessary for enhancing the hardenability of the weld metal and ensuring the strength at room temperature, and forms carbide by post-weld heat treatment to produce creep. It is also important from the viewpoint of securing high-temperature strength characteristics such as breaking strength. C is 0.01% by weight
If it is less than the above, the above strength cannot be sufficiently obtained. Further, when C is 0.
If it exceeds 19% by weight, the strength at room temperature is too high.
The susceptibility to cold cracking due to hydrogen increases. Further, if the amount of C is so large as to exceed 0.19% by weight, the susceptibility to hot cracking is increased, and it is not suitable as a welding wire. Desirable lower and upper limits are 0.05% by weight and 0.15%, respectively.
% By weight. Si: 0.01 to 1.50% by weight Si is a deoxidizing element and an important element from the viewpoint of adjusting the bead shape. Excessive addition causes embrittlement when kept at a high temperature for a long time. Care must be taken to increase the temper embrittlement susceptibility. From the above viewpoint, the range of Si is set to 0.01 to 1.50% by weight. Desirable lower and upper limits of Si are 0.10% by weight and 0.80% by weight, respectively. Mn: 0.01 to 2.00% by weight Mn also acts as a deoxidizing element like Si, but is effective for further improving the hardenability of the weld metal and improving the toughness. However, when Mn is added in a large amount, the creep rupture strength is reduced. Therefore, the addition amount of Mn is set to 0.01% by weight to 2.00% by weight. Desirable M
The lower and upper limits of n are 0.20% by weight and 1.20% by weight, respectively. [0013] Cr: 7.00 to 13.00% by weight Cr is an important component for securing oxidation resistance and high-temperature strength characteristics. From the viewpoints of oxidation resistance and high-temperature strength, the lower limit of Cr needs to be 7.00% by weight. However, when a large amount of Cr is added, δ ferrite tends to precipitate in the martensite structure, and accordingly, the toughness is reduced. From the viewpoint of toughness, the upper limit is set to 13.00% by weight. In addition, Cr
Are preferably 8.00% by weight and 1% by weight, respectively.
2.00% by weight. Mo: 0.01 to 1.60% by weight Mo is also an important element for forming carbides and securing high-temperature strength. However, excessive addition of Mo increases the room temperature strength, increases the susceptibility to cold cracking due to hydrogen, and further reduces the toughness. From this viewpoint, the addition amount of Mo is set to 0.01% by weight to 1.60% by weight. Desirable lower and upper limits of Mo are 0.20% by weight and 1.20% by weight, respectively. Ni: 0.02 to 1.50% by Weight Ni is an important and effective element for suppressing the precipitation of δ ferrite in a high chromium ferritic steel and improving the toughness of a weld metal. However, when a large amount of Ni is added, there is a disadvantage that the creep rupture strength is reduced.
Therefore, the addition amount of Ni is set to 0.02 to 1.50% by weight. Desirable lower and upper limits of Ni are 0.10% by weight and 1.00% by weight, respectively. Nb and Ta: 0.002 to 0.25 weight
% Nb and Ta are both effective elements that undergo heat treatment after welding to form fine carbides and increase the creep rupture strength. However, when these elements are added excessively, excessive precipitates are generated, and the toughness is reduced. Since Nb and Ta both have the same action, either one or both of them may be added. Therefore, Nb and Ta
Is defined by the sum thereof, and is 0.002% by weight to 0.1% by weight.
25% by weight. Desirable lower and upper limits of the sum of Nb and Ta are 0.005% by weight and 0.15% by weight, respectively. V: 0.01 to 0.50% by weight V is an element effective in forming fine carbides and increasing creep rupture strength by undergoing heat treatment after welding in a state where V is also present with Nb or Ta. is there. However, if it is added in excess of an appropriate range, the strength at room temperature increases, and the sensitivity to cold cracking due to hydrogen decreases, which is not preferable. A suitable amount of V is 0.01 to 0.50% by weight. Desirable lower and upper limits of V are 0.05% by weight and 0.30% by weight, respectively. Ti: 0.001 to 0.100% by weight In the presence of Ti, Nb, Ta or V, Ti is also subjected to a heat treatment after welding to form fine carbides and is effective for increasing the creep rupture strength. Element. Excessive addition of Ti not only causes a decrease in toughness due to intragranular precipitation of carbides,
It causes slag with poor removability, and reduces welding workability. Therefore, the addition amount of Ti is set to 0.001% by weight to 0.100% by weight. Desirable lower and upper limits of Ti are 0.005% by weight and 0.050% by weight, respectively. Al: 0.002 to 0.10% by weight Al acts as a deoxidizing material and becomes a fine nitride in the coexistence with N, which promotes the refinement of the structure of the weld metal and is effective in improving the toughness. It is. However, excessive addition of Al generates slag having a high melting point, and significantly impairs welding workability.
Therefore, the addition amount of Al is 0.002% by weight to 0.10% by weight.
% By weight. Desirable lower and upper limits of Al are 0.005% by weight and 0.050% by weight, respectively. N: 0.003 to 0.100% by weight N forms nitrides with Al as described above and contributes not only to the improvement of the toughness of the weld metal but also to the improvement of the creep rupture strength. is there. However, when N is added excessively, it appears as a spherical defect in the weld metal. Therefore, N
Suitable range is 0.003% to 0.100% by weight
And The desirable lower limit and upper limit of N are respectively 0.0
05% by weight and 0.070% by weight. O: 0.002 to 0.030 wt% O determines the fluidity of the weld metal in a molten state, and is an extremely important element for obtaining a sound weld. In order to obtain good appearance and familiarity of the weld metal, it is necessary to add O in an amount of 0.002% by weight or more. However, when O is increased, the toughness is significantly reduced, and 0.030
It is not preferable to exceed the weight%. Desirable lower and upper limits of O are 0.003% by weight and 0.020% by weight, respectively. Ca: 0.0002 to 0.01% by weight Ca acts as a strong deoxidizing agent, reduces the amount of oxygen in the weld metal, and is effective in improving toughness. However, when Ca is added in a large amount, the amount of slag generated increases, and welding workability is impaired. The appropriate amount of Ca added is 0.0002% by weight.
To 0.01% by weight. Desirable lower and upper limits of Ca are 0.0005% by weight and 0.005% by weight, respectively. Mg: 0.0002 to 0.01% by weight Mg also acts as a strong deoxidizer when added in combination with Ca.
It is effective in reducing the oxygen content of the weld metal and improving the toughness.
When Mg is added in a large amount like Ca, the amount of slag generated increases, and welding workability is impaired. For this reason,
Mg added in an amount of 0.0002% to 0.01% by weight
And Desirable lower and upper limits of Mg are each set to 0.1.
0005% by weight and 0.005% by weight. Ti + Al + 10 × (Ca + Mg): 0.
13% by weight or less It is important to regulate the sum of Ti + Al + 10 × (Ca + Mg) to 0.13% by weight or less. As mentioned above, T
The elements i, Al, Ca, and Mg have a small amount of effective action when added in combination. However, it is necessary to regulate not only the amount of each element added alone but also the total amount of each element added. That is, as a result of studying the reduction in workability due to the generation of slag, the present inventor found that Ti + Al + 10 × (C
It has been found that it is effective to regulate the sum of (a + Mg) to 0.13% by weight or less. In addition, lanthanoid elements (eg, La and Ce) can be added in addition to these four elements.
It is desirable to keep the content to 01% by weight or less. The wire of the present invention can be further enhanced by adding a component having the following action as a selective component. W: 0.10 to 3.00% by weight W has an effect of improving the high-temperature strength characteristics of the weld metal by solid solution strengthening. However, if W is less than 0.10% by weight, this effect cannot be obtained. On the other hand, W is 3.00% by weight.
If it exceeds 300, the room temperature strength increases, and the cold cracking susceptibility due to hydrogen increases. Note that a desirable upper limit of W is
2.00% by weight. Cu: 0.005 to 4.00% by weight Cu can increase the creep rupture strength of the weld metal due to the precipitation effect. However, no effect was observed when Cu was less than 0.005% by weight. Further, when the Cu content exceeds 4.00% by weight, the room-temperature strength increases, the susceptibility to cold cracking due to hydrogen increases, and the susceptibility to hot cracking also increases. Note that a desirable upper limit of Cu is
2.50% by weight. Co: 0.005 to 5.00% by weight Co is an important and effective element for suppressing the precipitation of δ ferrite in the high chromium ferritic steel and improving the toughness of the weld metal. If the Co content is less than 0.005% by weight, no effect is observed. If the Co content exceeds 5.00% by weight, the room temperature strength increases, and the sensitivity to cold cracking due to hydrogen increases. Note that a desirable upper limit of Co is 3.50% by weight. B: 0.0005 to 0.01% by weight B has the effect of reducing the size of the weld metal, increasing the toughness, and increasing the creep rupture strength. However, B is 0.00
No effect is observed at less than 05% by weight, and 0.01% by weight
If added in excess of, the room temperature strength increases and the sensitivity to cold cracking and hot cracking due to hydrogen increases. Note that a desirable upper limit of B is 0.007% by weight. Others This wire is applicable to TIG welding, MAG welding and submerged arc welding. It is also possible to apply Cu, Ni or other metal plating on the wire surface,
In that case, it is necessary to consider the alloy component including the amount of plating. In addition, various surface treatment agents and various residues other than plating may be present on the surface of the wire, but it is necessary to define each element including the above elements contained therein. Not even. Further, although P, S, As, Sb, Sn and the like are usually contained as impurity elements, it is desirable that each of them is suppressed to 0.010% by weight or less. The present invention will be described below in more detail with reference to Examples and Comparative Examples. Tables 1 and 2 below show the chemical composition of the welding wire. This welding wire was finished to a diameter of 1.2 mm to be used for automatic TIG welding. The surface of the welding wire was not plated with Cu. Table 3 shows welding conditions for a mechanical test of the weld metal. Except as shown in Table 3, it was based on JISZ3316 (TIG welding rod and wire for mild steel and low alloy steel). The test plate is SS4 of JIS G3101 (rolled steel for general structure)
At 00, buttering was performed with a test wire and used. Table 4 shows the results of the welding test. The low-temperature cracking test was based on JISZ3157 (U-type welding cracking test method), and the preheating temperature was set to 150 ° C. After welding, it was left for 72 hours, and one in which no crack occurred was judged to be good. The hot cracking test was based on JISZ3155 (C-type jig restraint butt welding test method). Route interval is 2m
m. Those which did not crack other than craters were determined to be good. The base material used for both the low-temperature cracking test and the high-temperature cracking test was ASTMA387Gr91 steel with a thickness of 2
The thing of 5 mm was used. In addition, the welding conditions used were those shown in Table 3 below. However, this excludes the preheating temperature in the low-temperature cracking test. Further, in the mechanical test, after performing heat treatment after welding at 740 ° C. for 4 hours, various test pieces were processed and tested. The specimen for creep rupture test has a parallel part diameter of 6.
One having a distance of 0 mm and a distance between gauge points of 30 mm was used. In addition, the mechanical test was not implemented about the thing with poor crack resistance and workability. As criteria for the mechanical test, the Charpy absorbed energy was judged to be good when the embrittlement promoting heat treatment (step cooling) was 55 J or more, and the creep rupture time was 1000 hours or more. Since Examples 1 to 4 all fall within the scope of the present invention, satisfactory results were obtained in all of the welding workability, high-temperature and low-temperature crack resistance, and mechanical performance. Comparative Example 7 had low Si, and Comparative Examples 21 and 23
Are high in Ti and Al, Comparative Example 25 is high in N, Comparative Example 26 is low in O, and Comparative Examples 29 and 31 are Ca and Mg respectively.
Therefore, the welding workability is poor and is unsuitable as a welding wire. In Comparative Example 36, although the individual components were within the range of the present invention, the value calculated by the formula of Ti + Al + 10 × (Ca + Mg) exceeded 0.13% by weight. Was bad. Comparative Example 6 was C, Comparative Example 11 was Cr, Comparative Example 13 was Mo, Comparative Example 19 was V, and Comparative Example 32 was W.
However, since Comparative Example 33 contained Cu, Comparative Example 34 contained Co, and Comparative Example 35 contained B exceeded the range of the present invention, it was found that cracks occurred and were unsuitable as welding wires. Comparative Example 5 has C, Comparative Example 8 has Si, Comparative Example 9 has Mn,
Comparative Example 14 was Ni, Comparative Example 17 was Nb + Ta, Comparative Example 22 was Al, Comparative Example 24 was N, and Comparative Example 27 was O.
However, in Comparative Example 28, Ca was not included in the range of the present invention, and in Comparative Example 30, Mg was not included in the range of the present invention. Further, Comparative Example 5 contains C, and Comparative Example 10 contains Mn.
However, Comparative Example 12 was Mo, Comparative Example 15 was Ni, Comparative Example 16 was Nb + Ta, Comparative Example 18 was V, Comparative Example 20 was Ti, Comparative Example 22 was Al, and Comparative Example 24 was N. Since it did not fall within the range of the present invention, a sufficient creep rupture life could not be obtained. From the above results, it is apparent that the present invention is a welding material having good welding workability and crack resistance and capable of obtaining further excellent mechanical performance. [Table 1] [Table 2] [Table 3] [Table 4] As described above, according to the present invention, high-temperature strength characteristics mainly including creep rupture strength are extremely excellent, and good welding workability and crack resistance can be obtained.
Further, excellent mechanical performance can be obtained. For this reason, if the welding wire of the present invention is used, high chromium ferritic steel can be applied to various fields utilizing its characteristics, and the present invention exhibits excellent effects.

Claims (1)

(57) [Claims 1] C: 0.01 to 0.19% by weight, S
i: 0.01 to 1.50% by weight, Mn: 0.01 to 2.00% by weight, Cr: 7.00 to 13.00% by weight, Mo: 0.01 to 1.60% by weight, Ni: 0.0
2 to 1.50% by weight, Nb + Ta: 0.002 to 0.25% by weight, V: 0.01 to 0.50% by weight, T
i: 0.001 to 0.100% by weight, Al: 0.00
2 to 0.10% by weight, N: 0.003 to 0.100
% By weight, O: 0.002 to 0.030% by weight, Ca:
0.0002 to 0.01% by weight and Mg: 0.000
2 to 0.01% by weight, Ti + Al + 10 ×
The sum of (Ca + Mg) is limited to 0.13% by weight or less, and W: 0.10 to 3.00% by weight;
0.005 to 4.00% by weight, Co: 0.005 to 5.00% by weight, and B: at least one selected from the group consisting of 0.0005 to 0.01% by weight,
Welding wire for high chromium ferritic steel characterized by the balance consisting of iron and unavoidable impurities.