JPH09267190A - Welding wire for high crome ferrite wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a welding wire for high chrome ferrite wire being applicable to various fields wherein a high temperature strength property comprising creep rupture strength primarily is enough, or a welding workability is excellent. SOLUTION: By weight %, C: 0.01-0.19, Si: 0.01-1.50, Mn: 0.01-2.00 Cr: 7.00-13:00, Mo: 0.01-1.60, Ni: 0.02-1.50, Nb+Ta: 0.002-0.25, V: 0.01-0.50, Ti: 0.001-0.100, Al: 0.002-0.10, N: 0.003-0.100, O: 0.002-0.030, Ca: 0.0002-0.01 and Mg: 0.0002-0.01 are contained, and together with confining sum of Ti+Al+10×(Ca+ Mg) to <=0.13, at least one element selected from a group comprising W, Cu, Co and B is contained and the balance consists essentially of iron and unavoidable impurities.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is 7% to 12% by weight.
Of Cr-containing high-chromium ferritic steel welding wire.

[0002]

2. Description of the Related Art High-chromium ferritic steel has excellent strength characteristics at high temperatures and excellent oxidation resistance, and has a smaller coefficient of thermal expansion and less susceptibility to stress corrosion cracking than austenitic stainless steel. Therefore, it is used in high-temperature and high-pressure thermal power plants and nuclear equipment. In recent years, from the viewpoint of protecting the global environment, efforts have been made to improve efficiency by making operating conditions higher temperature and pressure, and to suppress carbon dioxide emission per unit energy.

To this end, various new steel materials have been developed and many have been put into practical use, and as a welding material for welding the steel materials, some new component systems have already been proposed. ing. However, all of these conventional welding materials have insufficient characteristics.

For example, in Japanese Patent Laid-Open Nos. 1-215489 and 2-280993, Ca and La, if necessary,
It proposes to improve toughness by adding Ce to reduce oxygen in the weld metal.

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-5-285969, JP-A6-1
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 steels have the drawbacks of 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 problems, and has sufficient high-temperature strength characteristics centering on creep rupture strength, excellent welding workability, and high chromium ferritic steel characteristics. It is an object of the present invention to provide a high-chromium ferritic steel welding wire that can be utilized in various fields.

[0008]

The welding wire for high chromium ferritic steel according to the present invention comprises C: 0.01 to 0.19.
% By weight, Si: 0.01 to 1.50% by weight, 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
1: 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: 0.0002 to 0.01% by weight, Ti +
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 is characterized by containing 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 inevitable impurities.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The reason for adding each component and the reason for limiting the composition of the welding wire of the present invention 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 also produces carbides by heat treatment after welding, which causes creep. It is also important from the viewpoint of ensuring high temperature strength characteristics such as breaking strength. 0.01% by weight of C
If it is less than the above range, the above strength cannot be sufficiently obtained. Also, C is 0.
If it exceeds 19% by weight, the strength at room temperature is too high.
The cold cracking susceptibility due to hydrogen becomes high. Further, if the amount of C exceeds 0.19% by weight, the susceptibility to hot cracking becomes high and it is unsuitable as a welding wire. The preferred lower and upper limits are 0.05% by weight and 0.15%, respectively.
% By weight.

Si: 0.01 to 1.50 wt% Si is an important element from the viewpoint of adjusting the deoxidizing element and the bead shape, but excessive addition causes embrittlement when held at high temperature for a long time and Care must be taken to increase the temper embrittlement susceptibility. From the above viewpoint, the range of Si is 0.01 to 1.50% by weight. The 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 acts as a deoxidizing element similarly to Si, but it is effective in further improving the hardenability of the weld metal and improving the toughness. However, if a large amount of Mn is added, the creep rupture strength will be reduced. Therefore, the addition amount of Mn is set to 0.01 wt% to 2.00 wt%. Desirable M
The lower limit and the upper limit of n are 0.20% by weight and 1.20% by weight, respectively.

Cr: 7.00 to 13.00 wt% Cr is an important component for ensuring the oxidation resistance and high temperature strength characteristics. From the viewpoint of oxidation resistance and high temperature strength, the lower limit of Cr is 7.00% by weight. However, when Cr is added in a large amount, δ ferrite is likely to precipitate in the structure of martensite, and the toughness decreases accordingly. From the viewpoint of toughness, the upper limit is 13.00% by weight. In addition, Cr
Desirable lower and upper limits of 8.00% by weight and 1 respectively
It is 2.00% by weight.

Mo: 0.01 to 1.60 wt% Mo is also an important element for forming carbides and ensuring high temperature strength. However, excessive addition of Mo increases the room temperature strength, increases the cold crack sensitivity due to hydrogen, and further reduces the toughness. From this point of view, the addition amount of Mo is set to 0.01 wt% to 1.60 wt%. The desirable lower and upper limits of Mo are 0.20% by weight and 1.20% by weight, respectively.

Ni: 0.02 to 1.50 wt% Ni 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. However, if a large amount of Ni is added, there is an adverse effect that the creep rupture strength is reduced.
Therefore, the addition amount of Ni is set to 0.02% to 1.50% by weight. The 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
Both % Nb and Ta are elements effective in forming a fine carbide by heat treatment after welding and increasing creep rupture strength. However, if these elements are added excessively, excessive precipitates are generated, and the toughness is lowered. Since Nb and Ta have the same action, either one or both may be added. Therefore, Nb and Ta
The addition amount is defined by the sum, and 0.002% by weight to 0.
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 wt% V is also an element effective in forming a fine carbide by heat treatment after welding in the state of coexisting with Nb or Ta to enhance creep rupture strength. is there. However, if it is added in excess of the appropriate range, the room temperature strength increases and the cold cracking susceptibility due to hydrogen decreases, which is not preferable. A suitable addition amount of V is 0.01% by weight to 0.50% by weight. The 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 Ti is also effective to form a fine carbide by heat treatment after welding in the coexistence of Nb, Ta or V to enhance creep rupture strength. It is an element. Excessive addition of Ti not only causes deterioration of toughness due to precipitation of carbide in the grain, but
This causes the generation of slag with poor peelability and reduces the welding workability. Therefore, the addition amount of Ti is set to 0.001% by weight to 0.100% by weight. The desirable lower and upper limits of Ti are 0.005% by weight and 0.050% by weight, respectively.

Al: 0.002 to 0.10 wt% Al acts as a deoxidizing agent and becomes a fine nitride in the coexistence of N, which promotes the refinement of the structure of the weld metal and is effective in improving the toughness. Is. However, excessive addition of Al causes slag having a high melting point to be generated, which significantly impairs welding workability.
Therefore, the addition amount of Al is 0.002% by weight to 0.10%.
% By weight. The desirable lower and upper limits of Al are 0.005% by weight and 0.050% by weight, respectively.

N: 0.003 to 0.100 wt% N forms nitrides with Al as described above, not only contributes to the improvement of toughness of the weld metal, but is also effective in improving creep rupture strength. is there. However, when N is added excessively, it appears as spherical defects in the weld metal. Therefore, N
Suitable range of 0.003% to 0.100% by weight
And In addition, the desirable lower limit and upper limit of N are 0.0, respectively.
05% and 0.070% by weight.

O: 0.002 to 0.030 wt% O is an extremely important element in order to obtain a sound welded part because the weld metal influences the fluidity in the molten state. In order to obtain a good weld metal appearance and familiarity, it is necessary to add O in an amount of 0.002 wt% or more. However, when the content of O is large, the toughness is remarkably reduced, and 0.030
It is not preferable if it exceeds the weight%. The desirable lower and upper limits of O are 0.003% by weight and 0.020% by weight, respectively.

Ca: 0.0002 to 0.01 wt% Ca acts as a strong deoxidizer, reduces the oxygen content of 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 the workability of welding is impaired. The appropriate amount of Ca added is 0.0002% by weight.
To 0.01% by weight. The desirable lower and upper limits of Ca are 0.0005% by weight and 0.005% by weight, respectively.

Mg: 0.0002 to 0.01 wt% Mg also acts as a strong deoxidizer when added together with Ca,
It is effective in reducing the amount of oxygen in the weld metal and improving toughness.
When Mg is added in a large amount like Ca, the amount of slag generated is increased and the welding workability is impaired. For this reason,
Addition amount of Mg is 0.0002% by weight to 0.01% by weight
And The desirable lower limit and the upper limit of Mg are 0.
% And 0.005% by weight.

Ti + Al + 10 × (Ca + Mg): 0.
13 wt% or less It is important to regulate the sum of Ti + Al + 10 × (Ca + Mg) to 0.13 wt% or less. As mentioned above, T
Although the elements of i, Al, Ca, and Mg have an effective effect by adding a small amount in combination, it is necessary to regulate not only the addition amount of each element but the total addition amount of each element. That is, as a result of examining the workability deterioration 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 to these four elements, it is possible to add a lanthanoid element (for example, La and Ce, etc.), but in that case, each element should also have a concentration of 0.
It is desirable to suppress it to 01% by weight or less.

Further, the wire of the present invention can be further improved in performance by adding a component having the following action as a selective component.

W: 0.10 to 3.00 wt% W has the 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
When it exceeds, the room temperature strength becomes high and the cold cracking susceptibility due to hydrogen becomes high. In addition, the desirable upper limit of W is
It is 2.00% by weight.

Cu: 0.005 to 4.00 wt% Cu can increase the creep rupture strength of the weld metal due to the precipitation effect. However, the effect was not recognized when Cu was less than 0.005% by weight. Further, if the Cu content exceeds 4.00% by weight, the room temperature strength becomes high, the susceptibility to cold cracking due to hydrogen becomes high, and the susceptibility to hot cracking also increases. The desirable upper limit of Cu is
It is 2.50% by weight.

Co: 0.005 to 5.00 wt% Co is an important and effective element for suppressing the precipitation of δ ferrite in 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, and if it exceeds 5.00% by weight, the room temperature strength is high and the cold cracking susceptibility due to hydrogen is high. The desirable upper limit of Co is 3.50% by weight.

B: 0.0005 to 0.01% by Weight B has the effects of refining the weld metal, increasing the toughness, and increasing the creep rupture strength. However, B is 0.00
If less than 05% by weight, no effect is observed and 0.01% by weight
If added in excess of 1, the room temperature strength will be high, and the cold crack sensitivity and hot crack sensitivity due to hydrogen will be high. The 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 plate the surface of the wire with a metal such as Cu or Ni,
In that case, it is necessary to consider the alloy composition including the plating amount. There are cases where various surface treatment agents and various residues other than plating are present on the surface of the wire, but it is necessary to specify each element including the above-mentioned elements contained therein. There is no end. Furthermore, although P, S, As, Sb, Sn, and the like are usually included as impurity elements, it is desirable to suppress these to 0.010% by weight or less, respectively.

[0030]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples to explain the effectiveness of the present invention. Tables 1 and 2 below show the chemical composition of the welding wire. This welding wire was finished to have a diameter of 1.2 mm for use in automatic TIG welding. The surface of the welding wire was not plated with Cu.

Table 3 shows the welding conditions for the mechanical test of the weld metal. Other than those shown in Table 3, it was based on JIS Z3316 (TIG welding rod and wire for mild steel and low alloy steel). The test plate is SS4 of JISG3101 (rolled steel for general structure)
No. 00 was used by buttering with a test wire.

Table 4 shows the welding test results. The cold crack test was based on JISZ3157 (U-type weld crack test method), and the preheating temperature was 150 ° C. After welding, it was left for 72 hours, and when no crack was generated, it was judged as good. The hot cracking test was based on JISZ3155 (C-type jig constraint butt welding test method). Route interval is 2m
m. Then, other than the crater, those having no cracks were judged to be good. The base material used for both the cold cracking test and the hot cracking test is ASTM A387 Gr91 steel sheet thickness 2
A 5 mm one was used. The welding conditions used are those shown in Table 3 below. However, the preheating temperature of the cold crack test is excluded.

In the mechanical test, after 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 with a diameter of 6.
0 mm and a gauge length of 30 mm were used. A mechanical test was not carried out for those having poor crack resistance and workability. As the criteria for the mechanical test, it was determined that the Charpy absorbed energy was 55 J or more for heat treatment for embrittlement (step cooling) and the creep rupture time was 1000 hours or more.

Since all of Examples 1 to 4 are within the scope of the present invention, satisfactory results are obtained in terms of welding workability, high temperature and low temperature crack resistance, and mechanical performance.

Comparative Example 7 has a low Si content, and Comparative Examples 21 and 23
Have high Ti and Al, Comparative Example 25 has high N, Comparative Example 26 has low O, Comparative Examples 29 and 31 have Ca and Mg, respectively.
Therefore, the welding workability is poor and it is not suitable as a welding wire. Further, in Comparative Example 36, the individual components are within the scope of the present invention, but the value calculated by the formula of Ti + Al + 10 × (Ca + Mg) exceeds 0.13% by weight, so that a large amount of slag is generated and the workability of welding is also high. 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 Cu in Comparative Example 33, Co in Comparative Example 34, and B in Comparative Example 35 exceeded the range of the present invention, cracking occurred, and it was found that they are unsuitable as welding wires. Comparative Example 5 is C, Comparative Example 8 is Si, Comparative Example 9 is Mn,
Comparative Example 14 is Ni, Comparative Example 17 is Nb + Ta, Comparative Example 22 is Al, Comparative Example 24 is N, and Comparative Example 27 is O.
However, since Comparative Example 28 contains Ca and Comparative Example 30 contains Mg, the toughness is not good.

Further, Comparative Example 5 has C, and Comparative Example 10 has Mn.
However, Comparative Example 12 is Mo, Comparative Example 15 is Ni, Comparative Example 16 is Nb + Ta, Comparative Example 18 is V, Comparative Example 20 is Ti, Comparative Example 22 is Al, and Comparative Example 24 is N. Since it does not fall within the scope of the present invention, sufficient creep rupture life was not obtained.

From the above results, it is clear that the present invention is a welding material which has good welding workability and crack resistance and is capable of obtaining excellent mechanical performance.

[0039]

[Table 1]

[0040]

[Table 2]

[0041]

[Table 3]

[0042]

[Table 4]

[0043]

As described above, according to the invention of the present application, the high temperature strength characteristics mainly including creep rupture strength are extremely excellent, and good welding workability and crack resistance can be obtained.
Furthermore, excellent mechanical performance can be obtained. Therefore, by using the welding wire of the present invention, it becomes possible to apply the high chromium ferritic steel to various fields making the best use of its characteristics, and the present invention exhibits excellent effects.

Claims (1)

[Claims] 1. C: 0.01 to 0.19% by weight, S
i: 0.01 to 1.50 wt%, Mn: 0.01 to 2.00 wt%, Cr: 7.00 to 13.00 wt%, Mo: 0.01 to 1.60 wt%, 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 further, W: 0.10 to 3.00% by weight, Cu:
0.005 to 4.00 wt%, Co: 0.005 to 5.00 wt% and B: 0.0005 to 0.01 wt% at least one selected from the group consisting of,
The welding wire for high chromium ferritic steel, characterized in that the balance consists of iron and inevitable impurities.