JPH10146692A - Inert-gas shielded arc welding material for nickel base alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide inert-gas shielded arc welding material for Ni base alloy capable of obtaining weld metal excellent in crack resistance, creep strength and sulfide corrosion resistance as well as in welding workability. SOLUTION: The inert-gas shielded arc welding material for Ni alloy contains, by weight, 0.02-0.20% C, 25-35% Cr, 1.5-3.0% Mo, 0.05-0.2% Al, 0.1-0.3% Ti, 0.01-0.05% Zr, 0.1-0.5% Si, 0.004-0.04% N, and the balance Ni with inevitable impurities. This inevitable impurities are regulated so as to include, by weight, <=0.002% B, <=0.02% P, <=0.02% S, <=0.2% Mn, and <=5.0% Fe.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inert gas arc welding material used for welding a Ni-base alloy, and more particularly to a weld metal having excellent weldability and excellent high-temperature strength and high-temperature corrosion resistance. The present invention relates to an inert gas arc welding material for a Ni-based alloy that can be obtained.

[0002]

2. Description of the Related Art Conventionally, Ni-based alloys have been widely used as heat-resistant alloys for materials such as thermal power plants and turbine plates. Various welding materials for welding these Ni-based alloys have been proposed (JP-A-61-11593, JP-A-62-102).
No. 35 and JP-A-1-122694).

In recent years, in such a thermal power plant made of a Ni-based alloy, in order to increase the efficiency and reduce the cost, the steam condition of a power generation boiler is increased to a high temperature and a high pressure, or a coal-fired boiler is used from a heavy oil fired boiler. Attempts have been made to change to a boiler. Therefore, with the change of these use conditions, there is a demand for the development of a welding material capable of obtaining a weld metal having better creep strength and higher temperature corrosion resistance (sulfide corrosion resistance) than before. The target values of the creep strength and the sulfide corrosion resistance of the weld metal are shown in Table 1 below.

[0004]

[Table 1]

[0005] When the target values of creep rupture strength and sulfide corrosion resistance shown in Table 1 can be achieved, it is possible to obtain a boiler for power generation corresponding to a change in use conditions.

[0006]

SUMMARY OF THE INVENTION The welding materials for Ni-base alloys disclosed in the above-mentioned prior art publications are intended to improve the creep strength and the high-temperature oxidation resistance, and have problems in coal-fired boilers. Sulfide corrosion due to S in coal ash cannot be prevented. That is, there is a problem that even when welding is performed using a conventional welding material, a weld metal satisfying the target values shown in Table 1 cannot be obtained.

The present invention has been made in view of the above-mentioned problems, and provides a weld metal having excellent welding workability, good crack resistance, and excellent creep strength and sulfide corrosion resistance. It is an object to provide an inert gas arc welding material for a Ni-based alloy that can be obtained.

[0008]

According to the present invention, an inert gas arc welding material for a Ni-based alloy according to the present invention comprises C: 0.02 to 0.
20% by weight, Cr: 25 to 35% by weight, Mo: 1.5
To 3.0% by weight, Al: 0.05 to 0.2% by weight,
Ti: 0.1 to 0.3% by weight, Zr: 0.01 to 0.05% by weight, Si: 0.1 to 0.5% by weight, and N: 0.004 to 0.04% by weight. , The rest is N
i and unavoidable impurities, wherein B as the unavoidable impurity is 0.002% by weight or less, P is 0.02% by weight or less, S is 0.02% by weight or less, Mn is 0.2% by weight or less, It is characterized in that Fe is regulated to 5.0% by weight or less.

The inert gas arc welding in the present invention refers to TIG welding and plasma welding in which a non-consumable electrode such as tungsten is used to generate a welding arc, and a consumable electrode in which the welding material itself is used as an electrode. MIG
Refers to welding.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION As a result of intensive experiments and research conducted by the present inventors to solve the above problems, the following findings have been obtained. That is, while the solidification structure at the time of welding, in order to weld metal to maintain the base material equivalent to the creep rupture life, by the addition of Al and Ti in the weld material, Ni ₃ Al and in the weld metal It is effective to precipitate Ni ₃ Ti or the like to improve the solidification structure. In addition, Zr
And Mo can increase the high-temperature strength.

Further, the inventors of the present application have found that Cr
By adding Mn, Al, and Mn, Mo, and Fe in the welding material, sulfide corrosion resistance can be improved, and by reducing P, S, and B in the welding material, welding can be performed. It was found to be effective in preventing hot cracking. Since P and B can be uniformly dispersed in a base material subjected to a tempering treatment such as rolling or heat treatment, these may be added to the base material, thereby increasing the creep rupture strength. be able to. However, when P and B are added to the welding material, they tend to be concentrated in the final solidified portion of the weld metal, as in S, causing hot cracking of the weld. Therefore, in order to prevent hot cracking, it is necessary to reduce P, B and S in the welding material.

As a means for improving the weldability, it is effective to add a small amount of Si to the welding material to improve the flowability of the molten metal. Further, by limiting the contents of Al and Ti in the welding material, it is possible to suppress the generation of slag on the surface of the welding metal and to keep the conformability of the welding bead good. If N is excessively added to the welding material, blow holes will be generated.

Hereinafter, the chemical components contained in the inert gas arc welding material for a Ni-based alloy according to the present invention and the reasons for limiting the composition will be described.

C: 0.02 to 0.20% by weight When C is added to the welding material, Ti in the weld metal becomes
By the precipitation strengthening as C and ZrC, the tensile strength and creep strength of the weld metal can be improved. If C in the welding material is less than 0.02% by weight based on the total weight of the welding material, the desired strength cannot be obtained. On the other hand, when C in the welding material exceeds 0.20% by weight, a large amount of carbide is generated, and sulfide corrosion resistance and ductility are reduced. Therefore, the C content in the welding material is set to 0.02 to 0.20% by weight.

[0015] Cr: 25 to 35 wt% Figure 1 takes a corrosion weight loss on the vertical axis, Cr in the welding material to the horizontal axis
It is a graph which shows the relationship between the Cr content in welding material and sulfide corrosion resistance taking content. As shown in FIG. 1, when the Cr content in the welding material increases, the corrosion weight loss decreases, that is, the sulfide corrosion resistance of the obtained weld metal improves. This is because the bonding strength between Cr and S is strong, so that Cr ₂ S ₃ is formed on the surface of the weld metal, so that penetration of Ni sulfide can be prevented. If the Cr in the welding material is less than 25% by weight, the sulfide corrosion resistance of the weld metal cannot be improved. On the other hand, if Cr in the welding material exceeds 35% by weight, the crack resistance of the weld metal decreases. Therefore, the Cr content in the welding material is 25 to 3
5% by weight.

Mo: 1.5 to 3.0% by weight Mo is a component that can improve the creep strength because it solid-solution strengthens the matrix in the weld metal. If Mo in the welding material is less than 1.5% by weight, the effect cannot be sufficiently obtained. On the other hand, if Mo in the welding material exceeds 3.0% by weight, high-temperature cracking may occur or sulfide corrosion resistance may decrease. Therefore, the Mo content in the welding material is set to 1.5 to 3.0% by weight.

Al: 0.05 to 0.2 wt% Al significantly improves sulfide corrosion resistance by coexisting with Cr in the weld metal. If the Al content in the welding material is less than 0.05% by weight, the effect cannot be sufficiently obtained. On the other hand, Al in the welding material
If the content is more than the weight percentage, slag is generated in the molten metal, and the conformability is reduced. Therefore, the Al content in the welding material is set to 0.05 to 0.2% by weight.

Ti: 0.1 to 0.3% by weight As described above, Ti precipitates Ni ₃ Ti, TiC or TiN in the weld metal, strengthens the solidified structure, and acts as a deoxidizing agent. If the content of Ti in the welding material is less than 0.1% by weight, the effect cannot be sufficiently obtained. On the other hand, when the Ti in the welding material exceeds 0.3% by weight, slag is generated in the molten metal, and the conformability is reduced.
Therefore, the Ti content in the welding material is set to 0.1 to 0.3% by weight.

Zr: 0.01 to 0.05% by weight Zr is a component that strengthens the solidified structure and acts as a deoxidizing agent, like Ti. If Zr in the welding material is less than 0.01% by weight, the effect cannot be sufficiently obtained. On the other hand, when Zr in the welding material exceeds 0.05% by weight, slag is generated in the molten metal, and the conformability is reduced. Therefore, the Zr content in the welding material is set to 0.01 to 0.05% by weight.

Si: 0.1 to 0.5% by weight Si is a component that can improve the flowability of molten metal. If the content of Si in the welding material is less than 0.1% by weight, the effect cannot be sufficiently obtained. On the other hand, if Si in the welding material exceeds 0.5% by weight, the hot metal cracking sensitivity of the weld metal increases. Therefore, the Si content in the welding material is set to 0.1 to 0.5% by weight.

N: 0.004 to 0.04% by weight N is a component that combines with Ti, Zr and the like to form nitrides and strengthen the structure. If the N in the welding material is less than 0.004% by weight, the effect cannot be sufficiently obtained. On the other hand, when N in the welding material exceeds 0.04% by weight, blow holes are generated. Therefore, the N content in the welding material is set to 0.004 to 0.04% by weight.

P: 0.02% by weight or less, S: 0.02 weight
Less than% of P and S are present in the welding material as unavoidable impurities. If P and S in the welding material each exceed 0.02% by weight, the susceptibility of the weld metal to hot cracking will increase. Therefore, the P content in the welding material is regulated to 0.02% by weight or less, and the S content is regulated to 0.02% by weight or less.

B: 0.002 wt% or less B may be added to the base metal Ni-base alloy in order to improve the creep strength of the weld metal by precipitation of boride. However, in the case of weld metal with a solidified structure,
It is difficult to uniformly disperse and precipitate B. When B in the welding material exceeds 0.002% by weight, the B is concentrated in the final solidified portion of the weld metal together with B mixed in the weld metal by dilution from the base metal during welding, and hot cracking is prevented. Cause it. Therefore, the B content in the welding material is restricted to 0.002% by weight or less.

Mn: 0.2 wt% or less Mn is present in the welding material as an inevitable impurity. If Mn in the welding material exceeds 0.2% by weight, the sulfide corrosion resistance of the weld metal will be reduced. Therefore, the Mn content in the welding material is restricted to 0.2% by weight or less.

Fe: 5.0 wt% or less If the Fe content in the welding material exceeds 5.0 wt%, the high-temperature strength and sulfide corrosion resistance of the weld metal will decrease. Therefore, the Fe content in the welding material is restricted to 5.0% by weight or less.

[0026]

EXAMPLES Examples of the inert gas arc welding material for a Ni-based alloy according to the present invention will be specifically described in comparison with comparative examples.

First, welding materials having various chemical compositions are prepared, and a welding metal is formed by welding a steel material using the welding materials. Weldability was evaluated by investigating the occurrence of slag. The obtained weld metal was subjected to a creep rupture test and a sulfide corrosion test to evaluate creep strength and sulfide corrosion resistance.

FIG. 2A is a plan view showing a groove shape of a welding base metal used in a creep rupture test and a sulfide corrosion test, and FIG. 2B is a sectional view thereof. The two carbon steel sheets 1 are notched at their end faces and have inclined surfaces 1a. The two carbon steel plates 1 are arranged with their inclined surfaces 1a facing each other, and form a V-shaped groove portion 2 that opens upward. The back surface of the V-shaped groove portion 2 is slightly separated, and a backing metal 3 is arranged on the back surface side. In this embodiment, a carbon steel plate 1 having a thickness of 20 mm, a length in a welding direction of 200 mm, and a width in a direction perpendicular to the welding direction of 120 mm is used. The distance (route interval) is 6 mm,
Both were arranged with a groove angle of 45 °. The surface of the inclined surface 1a and the surface of the backing metal 3 were subjected to three layers of buttering with a welding material to be used, thereby forming a metal layer 4 having the same composition as the welding material.

A weld metal is formed by performing multi-layer welding on the groove 2 of the carbon steel sheet 1 arranged as described above, and a creep rupture test piece and a sulfide corrosion test piece are formed from the weld metal. Collected.

FIG. 3 is a cross-sectional view showing the location of the creep rupture test specimen from the weld metal, and FIG. 4 is a side view showing the shape and size of the creep rupture test specimen used in this example. At the V-shaped groove 2 of the carbon steel sheet 1, from the weld metal 5 formed in the longitudinal direction along the welding direction,
A round bar-shaped test piece 6 was sampled along the longitudinal direction.
At this time, the test piece 6 was sampled such that the center of the circle which was the cross-sectional shape of the test piece 6 was positioned at the center of the formed weld metal 5 and at the center of the thickness of the steel sheet 1.

As shown in FIG. 4, the test piece 6 is formed such that its central portion in the longitudinal direction has a smaller diameter than both ends, and both ends having a large diameter have grip portions. 6
a, the outer peripheral surface is threaded,
The narrow central portion having a uniform diameter is the parallel portion 6b. In this embodiment, the diameter of the parallel portion 6b is 6 mm.
And the gauge length in the parallel portion 6b was 30 mm.
Then, using this creep rupture test piece 6, JIS
The test temperature was 750 ° C and the stress was 1 according to Z 2272.
2 (kgf / mm ² ), a tensile creep rupture test was performed, and the creep strength was measured by measuring the rupture life.

FIG. 5 is a cross-sectional view showing a sampling position of a sulfide corrosion test specimen from a weld metal, and FIG. 6 is a perspective view showing the shape and size of the sulfide corrosion test specimen used in this embodiment. Similarly to the creep rupture test piece, in the V-shaped groove portion 2 of the carbon steel sheet 1, from the weld metal 5 formed in the longitudinal direction along the welding direction, the length in the direction parallel to the longitudinal direction is 20 mm, and the width is 20 mm. Was 7 mm, and a rectangular parallelepiped test piece 7 having a height of 5 mm in the thickness direction of the carbon steel sheet 1 was collected.

Then, coal ash was applied to the test piece 7,
The sulfide corrosion resistance was evaluated by measuring the corrosion weight loss after standing at 700 ° C. for 100 hours in a predetermined atmosphere. The coal ash used in this example was 34% Na ₂ SO ₄ -41% K ₂ SO ₄ -25% Fe ₂
SO ₄ , 1% SO ₂ -5% O ₂ -10% CO ₂ -ba
l. The test was performed under an atmosphere of N ₂ .

Next, using the same various welding materials as those used in the creep rupture test and the sulfide corrosion test, other shapes of carbon steel were welded, and a C-shaped jig butt welding restraint cracking test was conducted. Then, the hot cracking resistance was evaluated.

FIG. 7A is a plan view showing a groove shape of a welding base material used in a C-shaped jig butt welding restraint crack test, and FIG. 7B is a sectional view thereof. Two carbon steel sheets 1
1 has a notched corner at the end face thereof,
1a. The two carbon steel plates 11 are arranged so that the end faces 11b on which the notched surfaces 11a are formed face each other, and have a Y-shaped groove 12 that opens upward.
Is formed. In addition, the back surface of the Y-shaped groove 12 is slightly separated. In the present embodiment, a carbon steel plate 11 having a plate thickness of 12 mm, a length in the welding direction of 200 mm, and a width in a direction perpendicular to the welding direction of 120 mm is used, and the height of the end face 11b is 6 mm. The notch surface 11a was formed. The two carbon steel plates 11 were arranged with a distance (route interval) between the back surfaces of 2 mm and a groove angle of 90 °. The surfaces of the notch surface 11a and the end surface 11b were subjected to three layers of buttering with a welding material to be used, thereby forming a metal layer 14 having the same composition as the welding material.

Then, the carbon steel sheet 1 thus arranged
TIG welding was carried out on the groove 12 of
A high-temperature cracking resistance was evaluated by performing a cracking test according to the C-type jig restraint butt welding cracking test method of Z3155. In TIG welding, the welding current is set to 1
50 A, welding voltage was 12 V, and welding speed was 8 cm / min.

The chemical components of the welding material used in this example are shown in Tables 2 to 5 below, and the evaluation results are shown in Tables 6 and 7 below. However, the target value of the creep rupture life shown in Tables 6 and 7 is 200 hours or more, and the target value of the sulfide corrosion weight loss is 40 (mg / cm ² ) or less. In the column for evaluating hot cracking resistance, ○ indicates that no cracks occurred, and X indicates that cracks occurred. Further, in the evaluation column of each item of the welding workability, ○ indicates good, and × indicates poor.

[0038]

[Table 2]

[0039]

[Table 3]

[0040]

[Table 4]

[0041]

[Table 5]

[0042]

[Table 6]

[0043]

[Table 7]

As shown in Tables 2 to 7 above, in Example No. 1 in which all the component compositions in the welding material were within the scope of the present invention.
With respect to Nos. 1 to 5, a weld metal excellent in creep rupture strength, sulfide corrosion resistance, and hot crack resistance was obtained, and welding workability was excellent.

On the other hand, Comparative Example No. 11, 19, 23, 2
In Nos. 5 and 30, since the content of C, Mo, Ti, Zr or N was less than the lower limit of the range of the present invention, the target creep rupture life of 200 hours or more could not be obtained. Comparative Example No. In Comparative Examples Nos. 12, 15 and 20, the content of C, Mn or Mo exceeded the upper limit of the range of the present invention. 1
In Nos. 6 and 21, since the content of Cr or Al was less than the lower limit of the range of the present invention, both values exceeded the target value of sulfide corrosion weight loss. Comparative Example No. In No. 13, since the Si content was less than the lower limit of the range of the present invention, the flowability of the molten metal was reduced. Comparative Example No. In No. 14, since the Si content exceeded the upper limit of the range of the present invention, the hot metal crack resistance was reduced and slag was generated.

Also, in Comparative Example No. In No. 17, since the Cr content exceeded the upper limit of the range of the present invention, the creep rupture strength and hot crack resistance of the weld metal were reduced. Comparative Example No. 1
8 has an Fe content exceeding the upper limit of the range of the present invention,
The creep rupture strength and sulfide corrosion resistance of the weld metal decreased. Comparative Example No. Since 22, 24 and 26 have contents of Al, Ti or Zr exceeding the upper limit of the range of the present invention,
Slag was generated in the weld metal. Comparative Example No. 27, 28
In Nos. And 29, the P, B or S content exceeded the upper limit of the range of the present invention, so that the hot cracking resistance was reduced. Comparative Example No.
31 is such that the N content exceeds the upper limit of the range of the present invention,
Blow hole occurred.

[0047]

As described in detail above, according to the present invention,
Since the chemical composition of the welding material and its content are properly specified, welding workability is excellent, crack resistance is good, and weld metal with excellent creep strength and sulfide corrosion resistance is obtained. be able to.

[Brief description of the drawings]

FIG. 1 shows the corrosion weight loss on the vertical axis and C in the welding material on the horizontal axis.
It is a graph which shows the relationship between Cr content in welding material and sulfide corrosion resistance taking r content.

2A is a plan view showing a groove shape of a welding base metal used in a creep rupture test and a sulfide corrosion test, and FIG. 2B is a cross-sectional view thereof.

FIG. 3 is a cross-sectional view showing a sampling position of a creep rupture test piece from a weld metal.

FIG. 4 is a side view showing the shape and size of a creep rupture test piece used in this example.

FIG. 5 is a cross-sectional view showing a sampling position of a sulfide corrosion test specimen from a weld metal.

FIG. 6 is a perspective view showing the shape and size of a sulfide corrosion test piece used in this example.

FIG. 7A is a plan view showing a groove shape of a welding base metal used in a C-shaped jig butt welding restraint cracking test,
(B) is a sectional view thereof.

[Explanation of symbols]

 1, 11; carbon steel sheet 2, 12; groove 3; backing metal 4, 14; metal layer 5; weld metal 6, 7;

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshizo Hashimoto 100-1 Urakawachi, Miyama-shi, Fujisawa-shi, Kanagawa Prefecture Inside the Kobe Steel Fujisawa Works (72) Inventor Shintaro Ozaki Urakawachi, Miyama-shi, Fujisawa-shi, Kanagawa 1001 Co., Ltd. Kobe Steel Fujisawa Plant

Claims (1)

[Claims] 1. C: 0.02 to 0.20% by weight, C
r: 25 to 35% by weight, Mo: 1.5 to 3.0% by weight, Al: 0.05 to 0.2% by weight, Ti: 0.1 to 0.3% by weight, Zr: 0.01 to 0.05% by weight,
Si: 0.1 to 0.5% by weight and N: 0.004 to 0.04% by weight, the balance being Ni and inevitable impurities, and B as the inevitable impurity is 0.002%.
Ni-base, wherein P is regulated to not more than 0.02 wt%, S is regulated to not more than 0.02 wt%, Mn is regulated to not more than 0.2 wt%, and Fe is regulated to not more than 5.0 wt%. Inert gas arc welding material for alloys.