JPH0245959B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a Ni-base composite wire for gas-shielded arc welding that exhibits excellent properties that allow a Ni-Cr-Nb/Ta alloy weld metal to be obtained. [Prior Art] Ni-Cr-Nb/Ta alloys have excellent corrosion resistance and heat resistance, and are therefore widely used in nuclear reactors, pressure vessels, and the like. However, AWS A5・14, ERNiCr−3, ERNiCrMo− used for welding these alloys
Grade 3 solid wire for welding has a poor production yield during forging and rolling, and is also difficult to draw, especially welding wire for gas shielding is usually 1.2 to 1.6 mm.
Since φ was required, the price was also very high. In order to improve this, a composite wire using Ni, which has good wire drawability, as the base metal for the outer sheath was first proposed and disclosed (Japanese Patent Application Laid-Open No. 1986-
28697). [Problems to be solved by the invention] However, these Ni-based composite wires have poor arc stability, generate a large amount of spatter, and have problems with welding workability, so they have not been widely used. It's not working. Therefore, the present inventors investigated and traced these causes from the perspective of arc phenomena. As a result, the Ni-based metal sheath, which is used for the purpose of obtaining a stable austenitic structure, has a melting point approximately 150°C lower than that of the mild steel sheath, so the sheath melts before the flux during welding.
It was found that the flux column was very long. It was also found that a long flux column obstructs the concentration of the arc, causing variations in arc length and an increase in the amount of spatter, resulting in a deterioration of welding workability. This phenomenon was particularly noticeable in the low welding current range of 100 to 250A. The present invention has been made in view of these circumstances, and its purpose is to provide a Ni-base composite wire for gas shielded arc welding that has excellent corrosion resistance, heat resistance, and cracking resistance as well as welding workability. That is. [Means for solving the problems] The present invention contains P and S in the flux.
It is a Ni-Cr-Nb/Ta composite wire and has the following main points. In a composite wire formed by filling flux into a metal sheath, the metal sheath contains Ni: 60% or more based on the total weight of the metal sheath, and P: 0.015% or less and S: 0.015% or less, respectively. The included flux contains P: 0.002 to 0.05% and S: 0.002 to 0.1% based on the total weight of the flux,
In addition, Ni: 50% or more based on the total weight of the wire,
Cr: 10~25%, Nb+Ta: 0.8~4.5% [However, Cr
+1.5 (Nb+Ta)≧15%] and C: suppressed to 0.2% or less, a Ni-based composite wire for gas shielded arc welding. If it is necessary to further improve the cracking resistance, in addition to the above structural requirements, add Mg to the metal shell:
0.0005-0.03%, Al: 0.001-0.2%, B: 0.00005
~0.04% of one or more selected from the group can be added, which is also an important component of the present invention. [Function] The present invention is configured as described above, but in short, by regulating the content of Ni, Cr, Nb, and Ta in the wire, corrosion resistance and heat resistance are improved while maintaining wire productivity. At the same time, it was previously said that it was necessary to limit the addition of P to flux as much as possible because it degrades cracking resistance.
We aim to improve welding workability by actively adding and S to the flux, and if necessary,
By adding one or more selected from the group consisting of Mg, Al and B, the cracking resistance is further improved. Below are the effects of each additive component and reasons for numerical limitations: (a) Additives whose content is regulated relative to the total weight of the wire, (b) Additives whose content in the flux is regulated, (c) Containment in the outer sheath metal. We will explain each additive separately, the amount of which is regulated. (a) Additives whose content is regulated based on the total weight of the wire: Ni: 50% or more Ni-based wire is used for co-metal welding of Ni alloys, as well as for dissimilar metal welding with carbon steel.
However, when welding dissimilar materials, dilution by the base metal is necessary.
Since the content is about 20 to 40%, a content of 50% or more is required to form a stable austenite structure and maintain good corrosion resistance even in such cases. Cr: 10-25% Cr is an element that provides excellent corrosion resistance and heat resistance, and is an essential additive component along with Nb and Ta. It also contributes to improving strength, but with a content of less than 10%, these elements I can't expect much of an effect. On the other hand, when it exceeds 25%, the ductility of the weld metal decreases significantly. Nb + Ta: 0.8 to 4.5% Nb and Ta improve the corrosion resistance and heat resistance of the wire as described above, and also act as a strong deoxidizing agent in Ni-Cr alloys. However, if the total amount of Nb and Ta added is less than 0.8%, deoxidation is insufficient and blowholes cannot be prevented. On the other hand, if the total amount added exceeds 4.5%, solidification cracking becomes extremely likely to occur. Note that Nb and Ta are often used in combination, and it is sufficient that the above numerical conditions are satisfied as a total. However, Nb≧
By satisfying the conditions of 0.6% and Ta≧0.1%, the above effect becomes even more stable. Cr+1.5 (Nb+Ta): 15% or more Nb and Ta affect the corrosion resistance of composite wire.
It was found that the contribution rate was 1.5 times. In other words, as shown in Figure 1, the relationship between Cr + 1.5 (Nb + Ta) and corrosion resistance [according to JIS G 0572 (sulfuric acid/ferric sulfate corrosion test method)], Cr + 1.5 (Nb + Ta)
If it is less than 15%, corrosion resistance deteriorates. C: 0.2% or less C contributes to improving the strength of weld metal, and also Nb
Like Ta and Ta, it is effective as a deoxidizing agent. However, if the amount added exceeds 0.2%, the ductility of the weld metal will decrease significantly. (b) Additives whose content in flux is regulated: As mentioned above, the main reason for the deterioration of welding workability in conventional Ni-based composite wires is that the flux column becomes extremely long during welding. Therefore, the present inventors conducted various studies on how to easily melt the embedded flux. All numerical values are percentages of the total flux weight. First, NaF, KF, _MgF2 , etc., which have relatively low melting points, and their composite compounds (melting point 800-1400℃)
An experiment was carried out in which the following was added to the flux. As a result, the flux column became slightly shorter and the effect of reducing spatter was also observed. These effects were greater as the melting point of the metal fluoride added was lower. The lower limit at which the addition effect is recognized is 0.01% in terms of fluorine amount, and the more preferable range is 0.5%.
That's all. However, simply adding metal fluoride to flux merely assists in the action of facilitating flux removal.
It has not yet reached the point where the flux itself can be easily melted and separated. P: 0.002 to 0.1% S: 0.002 to 0.05% Therefore, as a result of various changes in additives, it was found that the most excellent effect could be obtained when a flux containing P and S was used. Ta. That is, by adding P and S to flux, the melting point of the flux grains themselves decreases, making it easier to melt individual flux grains, but generally flux grains begin to melt from the surface; As a result of the coexistence of these, the viscosity of the molten zone on the grain surface is significantly reduced, which promotes separation from the flux, and these effects work synergistically to significantly shorten the flux column and drastically reduce the amount of spatter. It has been found. In order to obtain the above effects, the amount of P and S added must be at least 0.002%, while in order to prevent cracking, P must be at most 0.05% and S at least 0.1%. It was found that it was necessary to limit each of these. (c) Additives whose content in the shell metal is regulated: All values are percentages of the total weight of the shell metal. P, S: Both 0.015% or less, preferably
0.005% or less P and S are added to the flux to lower the melting point of the flux as described above, but from the perspective of preventing cracking, P and S are pure impurities, so adding P and S to the entire wire is important. It is necessary to limit the amount. For this reason, the amounts of P and S added to the outer shell metal are also limited. However, since P and S in the outer skin metal have a higher yield in the weld metal than P and S in the flux, their addition ratio is more limited than the content in the flux, and both P and S are each 0.015% or less,
Preferably, it needs to be 0.005% or less. Mg: 0.0005 to 0.03% Al: 0.001 to 0.2% B: 0.00005 to 0.04% As mentioned above, since P and S in the entire wire are limited, a weld metal with good crack resistance can be formed. However, if it is necessary to further improve the cracking resistance, Mg, Al and B
It is effective to add one or more selected from the group of: The amount of Mg required to achieve this effect is 0.0005% or more.
Al: 0.001% or more, B: 0.00005% or more, but if the amount added is excessive, welding workability will deteriorate. From this point of view, Mg: 0.03% or less, Al: 0.2
% or less, B: It is necessary to limit the amount added to 0.04% or less. Ni: 60% or more In order to obtain a stable austenitic weld metal and to ensure good wire drawability during wire production, the Ni content in the outer shell metal must be 60% or more. At this time, Cr, Nb + Ta, and C may be added to the outer shell, but excessive addition will significantly impair wire drawability, so limit the amounts added to Cr: 30% or less, Nb + Ta: 5% or less, and C: 0.25% or less. There is a need to. [Example] Using the Ni-based alloy shown in Table 1 as the outer skin, the second
Composite wires shown in the table were manufactured. Wire diameter is 1.2
mmφ. Regarding P and S in the contained flux, raw materials containing P and S in the range of Tr. to 0.2% were selected, and the amounts of P and S in the total flux were adjusted. Furthermore, the second
In the table, the flux composition is Fe-Nb・Ta: 60%
Nb/Ta, Re-Si: 50% Si, Fe-Ti: 50%
Ti, Fe-Al: 45% Al, NaF: 45% F,
CaF ₂ :Contains 50% F, and in the test result column, ○ mark indicates good quality, and × mark indicates poor quality. <Welding conditions> Power source: DC/constant voltage characteristics (reverse polarity) Shielding gas: Pure Ar (25/min) Current: 250A Voltage: 27~28V Speed: 30cm/min <Corrosion test method> JIS G0572 (sulfuric acid/sulfuric acid No. 2 Iron corrosion test method) <Bending test method> JIS Z3124 (Roller bending test method for butt welded joints) Test piece thickness: 9.5mm ^tBending radius: 19mm Bending angle: 180°

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[Table] The test results were as follows. [Comparative example] <W-1> Cr in wire is 7.5%, {Cr+1.5
(Nb+Ta)} is low at 12.9% in both cases, resulting in poor corrosion resistance. <W-5> The C content in the wire was high at 0.23%, and cracking occurred due to insufficient ductility during the bending test. <W-13> The Cr content in the wire was high at 26.4%, and cracking occurred due to insufficient ductility during the bending test. <W-6> (Nb+Ta) in the wire is as low as 0.54%, and corrosion resistance is poor. Also, blowholes occur due to insufficient deoxidation. <W-7> (Nb+Ta) in the wire was high at 5.4%, and solidification cracking occurred. <W-11> P in the flux is high at 0.076%,
Solidification cracking occurred. <W-15> S content in the outer shell metal is as high as 0.018%,
Solidification cracking occurred. Also, P in flux is 0.0008
% and S were low at 0.0006%, resulting in poor workability. <W-8> P in the flux was low at 0.0005%, resulting in poor workability. <W-10> S content in flux is as low as 0.001%,
Poor workability. <W-16> Ni content in the wire is low at 48%, and corrosion resistance is poor. <W-18> Ni content in the outer skin metal is low at 57.2%.
Cr is high at 32.3%, and wire breakage occurs during wire drawing. In addition, the P content in the outer skin metal was as high as 0.017%, which caused solidification cracking. [Examples] <W-2, 3, 4, 9, 12, and 17> are examples of the present invention, and all of the performances of welding workability, corrosion resistance, and bending performance are good. [Effects of the Invention] The Ni-base composite wire for gas-shielded arc welding of the present invention configured as described above allows welding work to be performed extremely efficiently, and at the same time has excellent corrosion resistance, heat resistance, and cracking resistance. You can get welded metal.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the influence of Cr and Nb+Ta on the corrosion resistance of wire.

Claims (1)

[Claims] 1. In a composite wire formed by filling a metal sheath with flux, the metal sheath contains Ni: 60% or more (the meaning of weight %, the same applies hereinafter) based on the total weight of the metal sheath, and P. : 0.015% or less and S: 0.015%
On the other hand, the included flux is P: 0.002 to 0.05 relative to the total flux weight.
% and S: 0.002 to 0.1%, and based on the total weight of the wire, Ni: 50% or more, Cr: 10 to 25%, Nb
+Ta: 0.8 to 4.5% [However, Cr+1.5 (Nb+Ta)≧
Ni for gas shielded arc welding, characterized by containing 15%] and suppressing C to 0.2% or less.
Basic composite wire. 2. In a composite wire formed by filling a metal sheath with flux, the metal sheath contains Ni: 60% or more based on the total weight of the metal sheath, and is suppressed to P: 0.015% or less and S: 0.015% or less, and further
Mg: 0.0005-0.03%, Al: 0.001-0.2%, B:
Contains one or more types selected from the group of 0.00005 to 0.04%, while the included flux contains P: 0.002 to 0.05% and S: 0.002 to 0.1% based on the total weight of the flux.
Ni: 50% or more, Cr: 10-25%, Nb + Ta: 0.8-4.5% [However,
Cr+1.5 (Nb+Ta)≧15%] and C: 0.2%
A Ni-based composite wire for gas-shielded arc welding, which is characterized by having the following properties: