JPH03204197A - High-ni alloy for highly corrosion resistant welding rod - Google Patents

Abstract

PURPOSE:To improve the hot workability of a blank material and to improve the corrosion resistance and mechanical properties of the deposited metal of a weld zone by incorporating specific ratios of C, Si, Mn, P, S, Ni, Cr, Mo, N, and O into the alloy and containing the balance substantially Fe. CONSTITUTION:The high-Ni alloy for highly corrosion resistant welding rods contains, by weight %, <=0.03 C, over 0.2 to 0.5 Si, <=0.5 Mn, <=0.03 P, <=0.003 S, 50 to 75 Ni, 17 to 25 Cr, 6 to 12 Mo, 0.05 to 0.2 N, <=0.006 O, and the balance substantially Fe. Further, at least >=1 kinds of Cu, V and W are incorporated into the alloy in such a manner that the total ratio thereof attains <=5%. The performance is additionally improved if 0.2 to 1.5 Nb and 0.002 to 0.01 B are further incorporated into the alloy. The hot workability of the blank material is improved and the corrosion resistance and mechanical properties of the deposited metal in the weld zone are improved. Weld defects are decreased.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a high Ni alloy for highly corrosion-resistant welding rods, and is particularly useful when welding materials (such as stainless steel mesh) that require corrosion resistance such as marine structures. The purpose is to provide materials for welding rods used in

[Conventional technology]

In recent years, higher quality seawater-resistant materials have been desired as the marine structures for which they are used have become larger. On the other hand, if we tried to provide something that could meet these demands, we could not avoid being disadvantaged in terms of cost.

Among these, high Cr,
High grade stainless steel with high MO content. For this material,
It is important to ensure corrosion resistance in the weld zone, and for this purpose, the welding rod (filler metal) used should contain more elements effective for corrosion resistance, such as Cr and Mo, than the base metal (base metal) composition. Ni-based alloys containing a large amount of metal, such as Inconel 625 alloy, are recommended.

Furthermore, recently, a high Ni alloy welding rod that overcomes the drawbacks of the above-mentioned Inconel 625 alloy has been published in Japanese Patent Application Laid-Open No. 63-21209.
This is proposed in Publication No. 1. This welding rod is intended to improve weldability and mechanical properties by inducing the component composition to be extremely low C1 and extremely low N, instead of containing Nb.

[Problem to be solved by the invention]

The alloy material used to manufacture welding rods is based on the properties of the weld metal that forms between the weld metal and the base metal when welding with the welding rod, that is, the corrosion resistance and mechanical properties of the weld metal. Even as it is (without any particular heat treatment etc.),
It is necessary to be excellent. Moreover, in terms of the hot workability of the material itself and the fluidity of the molten metal during welding, which are required when manufacturing this alloy to the state of filler metal,
The conventional alloys mentioned above are not necessarily sufficient.

The purpose of the present invention is to overcome the various problems of the conventional alloys for welding rods mentioned above, and in particular, when this alloy is used as filler metal, etc., the weld metal and the base metal weld metal part are It has excellent corrosion resistance and mechanical properties even after heat treatment, and the welded metal part has few defects and has excellent weldability. Furthermore, the material has excellent hot workability, so welding rods It is an object of the present invention to provide an alloy that can be manufactured with good yield even when manufacturing.

[Means to solve the problem]

While proceeding with research and development of an alloy capable of realizing the above-mentioned object of the present invention, the present inventors found that in an austenitic alloy with a high content of Cr and Mo, if the solidification structure is not a single austenite phase, σ phase etc. It was found that this precipitates and causes the structure to become unstable. Therefore, in order to make the solidified structure a completely austenitic structure, it is necessary to suppress S to a low level, since the presence of impurities such as S adversely affects hot workability. However, on the other hand, if this S is low, the fluidity of molten metal during welding etc. will be poor, and defects will occur in the weld metal part and heat affected zone.

Therefore, in the present invention, in order to satisfy the above characteristics, we first lower the S content and at the same time add a slightly larger amount of Si.If we design the alloy in this way, it will have excellent hot workability and weldability. It has been found that an alloy with excellent properties can be obtained.

Furthermore, it has been found that by adding a combination of Nb and B to the alloy components, even better corrosion resistance, mechanical properties, and hot workability can be obtained. Generally, Nb is effective in improving corrosion resistance, but has the effect of degrading hot workability. Therefore, in the alloy of the present invention, B is added to address the deterioration factor to suppress deterioration of hot workability. Furthermore, the mechanical properties of the alloy deteriorated by the addition of B, so it was decided to suppress the negative factors by adding Nb in combination.

The present invention, which was completed based on this idea, has a C≦0.03
wt%, Si >0.2~0.5%wt%.

Mn<0.5wt%, P≦0.030111
t%.

S≦0.003 wt%, Ni=50-75 wt%
.

Cr=17.0~25.0wt%, Ao=6.
0-12. h+t%.

N=0.05-0.20wt% and O≦0.006
It is a high Ni-based alloy for highly corrosion-resistant welding rods, with the remainder substantially consisting of Fe, C≦0.03wt%, and Si over 0.2 to 0.5wt%.
below.

Mn≦0.5wt%, P≦0.030wt%, S≦
0.003wt%.

Ni=50~75wt%, Cr=17.0~25.0
wt%.

Mo=6.0~12.0wt%, N=0.05~0
．． 20wt%.

0≦0.006 wt%, a high Ni alloy for highly corrosion-resistant welding rods containing at least one of Cu, V and W within a range where the total amount thereof is 5 wt% or less, and the remainder substantially consisting of Fe, provided that , the Cu content is 2% or less, and the W content is 3%.
% or less and V contains 2% or less, and the above alloy further contains Nb = 0.2 to 1.5 wt% and B = 0
．． This is a high Ni alloy for highly corrosion resistant welding rods containing 002% to 0.010%++1%.

[For production]

The reason why the alloy of the present invention must be constructed as described above will be explained below.

C: This C combines with Cr etc. and precipitates as carbide at grain boundaries, causing deterioration of corrosion resistance, so the lower the content, the better.

The upper limit allowed in the present invention is 0.03 wt% (hereinafter simply expressed as "%").

Si: This Si is effective in improving the fluidity of molten metal, but it is ineffective at extremely low S levels below 0.2%, and when it exceeds 0.5%, it forms precipitates such as σ phase. This causes deterioration of mechanical properties and corrosion resistance. Therefore, the range is set to more than 0.2% to 0.5%.

Mn: This Mn is an element that forms the σ phase, etc., but 0.
If it is less than 5%, the influence of σ phase bioacid will be reduced, so 0.5
% as the upper limit.

P: Since P is an element that increases hot cracking sensitivity and deteriorates weldability, it is contained with an upper limit of 0.030%.

S: In a fully austenitic structure, S significantly reduces hot workability and therefore needs to be low. Therefore, the upper limit was set at 0.003%. Preferably 0.002%
It is as follows.

Ni: In order to maintain corrosion resistance (in the present alloy containing a large amount of Cr and Mo, it is necessary to increase the Ni content in order to suppress the precipitation of these elements as intermetallic compounds. The amount needs to be at least 55%.

Cr: This Cr is 1 to maintain corrosion resistance in the present invention.
It is necessary to add 7% or more. However, if the amount is too large, the structure becomes unstable due to precipitation of σ phase, so the upper limit of addition is 25%.

Mo=This MO is added to maintain corrosion resistance like the above-mentioned Cr, and needs to be added in an amount of 6% or more. However, from the viewpoint of structure stability, 12% or more is not preferable, so 12% was set as the upper limit.

N: This N acts effectively on corrosion resistance and structure stabilization in the present invention. For this purpose, a significant effect cannot be obtained unless the content is 0.05% or more; on the other hand, 0.3%
If the amount added exceeds 0.3%, the solid solubility limit will be exceeded and defects such as blowholes will occur.

Nb: This Nb acts as a C stabilizing element in the alloy,
It is also effective for intergranular corrosion resistance. Furthermore, this N
b has the effect of reducing corrosion resistance deterioration caused by reverse segregation of Cr and Mo during solidification.

This effect cannot be obtained unless the content is 0.5% or more.

However, if it exceeds 1.5%, the ductility will actually decrease. In addition, since the hot workability of the material decreases when Nb is added, it is necessary to use it in combination with B.
While improving the hot workability described above, adding Nb suppresses the decrease in ductility due to the addition of B.
We aim to improve alloy properties through a mutually complementary relationship through their combined addition.

B: This B is added to alloys containing Nb especially for the purpose of improving hot workability. However, when added alone without Nb, the ductility decreases, but when added in combination with Nb, the B This toxicity will disappear.

These effects can only be obtained at 0.002% or more,
On the other hand, if the content exceeds 0.01%, ductility decreases and corrosion resistance deteriorates, so the content was set at 0.002 to 0.01%.

Cu, W, V: All of these are elements that effectively act on acid resistance, and one or more of them are optionally selected and used. As for Cu, if the amount added exceeds 2%, pitting corrosion resistance deteriorates.

On the other hand, W and V have the same effect as Mo on general corrosion resistance and are effective. However, if too much is added, the structure becomes unstable, so when adding W alone, the amount is 3% or less, and when using ① alone, it is 2% or less, but Cu.

Since it is not preferable for the upper limit to exceed 5% in mutual addition of W and (2), this 5% is set as the upper limit.

0: This content of 0 affects hot workability, which is a big problem in fully austenitic alloys. Therefore, in the present invention, this 0 is suppressed to 0.006% or less. This is because if it exceeds 0.006%, workability deteriorates.

〔Example〕

The alloy with the composition shown in Table 1 was rolled and drawn into a 2Hφ welding wire rod, which was used as filler metal for welding, and the stainless steel plate with the composition shown in Table 2 was prepared with the grooves shown in Fig. 1. , butt welded.

The evaluation method and test results for this welding test result are shown in Table 1 above.

As can be seen from the above results, in Invention Alloys 1 to 5, no pitting corrosion was observed, and there were no cracks due to bending after welding, no cracks due to forging, and no defects in welded parts. On the other hand, in the comparative alloy, in addition to bending cracks and cracks due to hot working, welding defects due to insufficient penetration of the grooved tip at the welded part were observed.

In particular, Comparative Alloy 2 has low Si and S content, so defects due to insufficient penetration are observed in the welded parts. In addition, it can be seen that Comparative Alloy 3 has poor hot workability, and Comparative Alloy 4 has poor ductility and weldability.

〔Effect of the invention〕

As shown above, according to the present invention, as a highly corrosion-resistant welding rod alloy, a Ni-based alloy containing high Cr and high ribs is used as a base composition, and the Si content is adjusted to be high, and at the same time, low S and low O Or, by adding Nb in combination with B, it is possible to provide a welding rod that not only has excellent hot workability of the material, but also has excellent corrosion resistance and mechanical properties of the weld metal in the weld zone, and has fewer weld defects. A suitable alloy is obtained.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the shape of a welding test piece used in Examples.

Claims (1)

[Claims] 1. C≦0.03wt%, Si more than 0.2 to 0.5%wt
%, Mn≦0.5wt%, P≦0.030wt%, S≦
0.003wt%, Ni=50-75wt%, Cr=1
7.0-25.0wt%, Mo=6.0-12.0wt
%, N=0.05-0.20wt% and O≦0.00
A high Ni alloy for highly corrosion resistant welding rods, containing 6 wt% and the remainder substantially consisting of Fe. 2, C≦0.03wt%, Si0
．． More than 2 to 0.5wt% or less, Mn≦0.5wt%, P≦
0.030wt%, S≦0.003wt%, Ni=50
~75wt%, Cr=17.0~25.0wt%, Mo
=6.0~12.0wt%, N=0.05~0.20w
t%, O≦0.006wt%, a high Ni alloy for highly corrosion-resistant welding rods, containing at least one of Cu, V and W within a range where the total amount thereof is 5wt% or less, and the remainder substantially consisting of Fe. . 3. The alloy according to claim 1 or 2 further contains Nb=0
．． 2-1.5wt% and B=0.002-0.010
High N for highly corrosion resistant welding rods containing wt%
i-alloy.