JP2667635B2 - Stainless steel flux cored wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stainless steel flux cored wire, and more particularly to a stainless steel flux cored wire developed for welding stainless steel for high temperature applications.

[0002]

2. Description of the Related Art Flux-cored wire for stainless steel is a welding material that has rapidly spread in recent years, and has excellent workability and good welding workability. It is a major factor in its spread. However, with the widespread use of wires, the use of flux-cored wires has caused unexpected problems in some industrial fields.

[0003] In other words, there is a field in which stainless steel is used as heat-resistant steel, or a thick stainless steel weld is subjected to solution treatment or hot bending. It is known that when a flux-cored wire for stainless steel is used for such a material in a high-temperature application field, a weld often cracks during high-temperature heating / cooling or hot bending. Also, in equipment that has been operating for a long time at high temperature, cracks often occur in the welded part using the flux cored wire, and the creep rupture life of the welded part is different from that of TIG welding or covered arc welding, which is the conventional construction method. In recent years, phenomena of remarkably lowering and lowering of the ductility at the time of creep rupture have been confirmed (see FIG. 1).

[0004] The present invention has been developed to solve the above-mentioned problems when the current flux-cored wire is used.
An object of the present invention is to provide a flux-cored wire for stainless steel, which has good properties as a welding material for high-temperature applications, has excellent welding workability, specifically, excellent slag removability and has a small amount of spatter.

[0005]

As a means for solving the above-mentioned problems, the present invention provides a flux-cored wire for stainless steel in which an outer shell made of stainless steel is filled with a flux. Oxygen content: 50 to 1000 ppm, Nb: 0.015% or less, V: 0.10% or less, Carbon: 0.015% or less, Nitrogen: 0.025% or less, and filling flux Inside, metal C as a carbon source and a nitrogen source
r, from metal Mn or various alloy raw materials or compounds with these elements, and / or at least one of carbon compound raw materials excluding graphite or carbonate, in a wire weight ratio, carbon: 0.020 to 0.10% Nitrogen: 0.008 to 0.08%, and the filler flux contains substantially no deoxidizer containing metal Si and / or a Si alloy. The filler flux contains slag as a slag component. at a weight _{ratio, TiO 2: 5.50~15.50%, SiO} 2: 0.20~1.50%, Al 2 O 3: 0.20~1.50%, metal fluoride: 0.25 At least one of Fe, Mn and Mg metal oxides:
02-1.00%, and Nb and V, which are mixed as unavoidable impurities from the filling flux, and these compounds, in Nb and V conversion amounts by wire weight ratio, Nb: 0.075 %, V: 0.10% or less, and the low melting point metals As, Sb, Pb, Bi and their oxides or compounds which are intentionally added or inevitably mixed in the filling flux. , Wire weight ratio, A
s, Sb, Pb, Bi conversion amount, As: 0.010% or less, S
b: 0.010% or less, Pb: 0.008% or less, Bi: 0.0.
The gist of the present invention is a flux-cored wire for stainless steel, which is regulated to 008% or less.

The present invention also relates to S, As, S in the wire.
b, Pb, Bi in wire weight ratio S: 0.003 ~
0.035%, 5 × (Bi + Pb) + 2 × (As + Sb): 0.065% or less,
It is characterized by having been regulated.

[0007]

The present invention will be described below in more detail.

In order to solve the above-mentioned problems, the present inventors have focused on the tensile properties of a flux-cored wire welded metal for stainless steel at a high temperature, particularly on ductility. We focused on both the outer shell component made of stainless steel, which is the raw material constituting the wire, and the raw material composition of the filled flux.

The present inventors believe that the above-mentioned problems occurring in the current stainless steel flux-cored wire are solely due to the lack of high-temperature ductility of the weld metal, and therefore, TIG, which is a weld metal by the conventional construction method, is used. A high-temperature tensile test at 500 to 800 ° C. was performed for each of the deposited metal and the coated arc deposited metal and the deposited metal with the current commercially available flux cored wire to compare ductility at break. One example of the test results is shown in FIG. As is clear from this, it was found that at a high temperature of 600 ° C. or higher, the fracture ductility of the flux-cored wire weld metal was clearly lowered at about 600 ° C., although there was no significant difference between them.

Various reasons have been considered for the reason for the decrease in the high-temperature ductility at such a high temperature, and in the prior art, the ferrite reduction of the deposited metal (Delon
It is argued that reducing the FN value with gFN or the like to fall in the range of 2 to 6) or reducing the oxygen content of the deposited metal is effective. However, the present inventors have investigated the cause of the difference in ductility of these deposited metals, and as a result, it is presumed that the main cause is the presence of trace amounts of low-melting elements and their compounds contained in the deposited metal. Was. The low-melting elements referred to here are lead (Pb), bismuth (Bi), and antimony.
(Sb), arsenic (As) and the like.
The melting points of b, Bi and the like are extremely low at 270 ° C. and 327 ° C. when used alone, and it is considered that almost all of the deposited metal exists in the form of oxides and various compounds. The melting point of Bi ₂ O ₃ is 820 ° C., the melting point of Pb ₃ O ₄ is 830 ° C., the melting point of Na ₃ Sb is 865 ° C., and the melting point of K ₃ Sb is 812 ° C.

The present inventors have investigated the relationship between the content of these low-melting elements or their compounds in the deposited metal and the behavior of reducing the hot ductility of the deposited metal, and found that a clear relationship exists. Was found. That is, in order to prevent a decrease in the high-temperature ductility of the deposited metal, the content of these low-melting elements in the total weight of the wire is set to 0.010% or less for As :, 0.010% or less for Sb, and Pb: 0.008% or less, B
i: To be regulated to 0.008% or less. Preferably, 5 × (Bi + Pb) + 2 × (As + Sb): 0.065% or less,
It is.

Further, it is important that the high-temperature strength is large as a feature of the welding material for stainless steel which requires such high-temperature characteristics. Therefore, in order to sufficiently secure the strength of the deposited metal, carbon (C) and nitrogen (N) added to the wire are required.
It is well known that the amount of is very important. However, the present inventors have found that from the viewpoint of welding workability, it is important to minimize the elements such as C and N contained in the outer coating stainless steel used for the flux-cored wire.

That is, the inventors of the present invention have investigated the relationship between the carbon content in the outer coating stainless steel and the welding workability, and as a result, the smaller the carbon content in the outer coating, the lower the spatter generation amount. It has been found that even when the amount of carbon added to the filling flux increases, the amount of spatter generated is small when the carbon content in the outer skin is low.

Therefore, the smaller the amount of carbon in the outer shell is, the more preferable it is. However, in the present invention, the amount of carbon in the outer shell of stainless steel is 0 as a limit amount at which the effect of reducing spatter can be clearly recognized. 0.015% or less.

Regarding the nitrogen content in the outer coating stainless steel, the effect of reducing spatter by lowering the nitrogen content was confirmed as in the case of carbon. Therefore, the nitrogen content in the outer coating stainless steel was 0.025%. It was as follows.

However, as described above, in order to ensure the high-temperature strength of the deposited metal as a stainless steel flux cored wire for high-temperature applications, it is essential to add a certain amount of carbon source and / or nitrogen source to the wire. is there. In the present invention, in order to improve welding workability, C and N in the outer skin are
Since it is necessary to regulate the amount as described above, the present inventors have noted that the following C and N feed materials that can be added from the filling flux side while keeping in mind that welding workability is not impaired as much as possible. They were found, and the upper limit of the addition of these materials was examined from the viewpoint of welding workability (spatter generation amount).

As a result, in the wire of the present invention, metal Cr, as a carbon source and a nitrogen source,
From at least one kind of metal Mn or various alloy raw materials or compounds with these elements and / or a carbon compound raw material excluding graphite or carbonate, in a wire weight ratio, carbon: 0.020 to 0.10% nitrogen: 0.008 to 0.08%. The lower limit of each addition is the minimum amount necessary to secure strength. Here, as the carbon source and the nitrogen source, metal Cr, metal Mn, and alloy raw materials or compounds with these elements are cited because the ratio of the amount of C participating in the oxidation reaction during welding is reduced as much as possible, resulting in oxidation. This is because the aim was to minimize the generation of CO ₂ gas and the like. This is because the spatter generation increases as the amount of generated CO ₂ gas increases. For this reason, in the present invention, the amount of various carbonates mixed as impurities should be less than 0.1% of the total weight of the wire in terms of CO _2. Is desirable. In addition,
The reason why metals such as metal Cr and metal Mn are used as carbon sources is that they contain carbon and nitrogen as impurities. Examples of carbon compound raw materials other than carbonate include CF (carbon fluoride).

Further, the present inventors examined the effects of Si, Ti, Al, Zr, which are usually added as a deoxidizing agent in the welding material, and their iron-based alloys and composite alloys on the welding workability. As a result, metal Si, Ca-Si, Fe-Si, Fe-Si
It has been clarified that the use of a Si alloy-based deoxidizing agent such as -Mn or Fe-Si-Mg lowers the slag removability during welding. Therefore, in the present invention, the metals Si and Si
It has been decided that the alloy-based deoxidizer is not substantially contained. In the present invention, as a level substantially not contained, in consideration of contamination as an impurity, the amount of metal Si in the filling flux may be 0.2% or less (filling flux weight%) as a guide. .

The slag forming agent in the flux filled in the wire of the present invention is TiO ₂ , SiO ₂ , Al ₂ O ₃ ,
Although it is mainly composed of metal fluoride, metal oxide and the like, it is necessary to limit the content (total weight ratio of wire) of these raw materials as follows.

TiO ₂ : TiO ₂ is a main raw material of the slag forming agent of the wire of the present invention, and is added in the range of 5.5 to 15.50% by weight based on the total weight of the wire. If it is less than 5.5%, the encapsulation of the weld bead is deteriorated and the arc stability becomes insufficient. On the other hand, if it exceeds 15.50%, the viscosity of the slag becomes too high, and welding defects such as slag winding and poor fusion are likely to occur.

SiO ₂ : SiO ₂ forms a slag forming agent together with TiO ₂ , and has an effect of particularly adjusting a bead shape at the time of welding and improving conformity with a base material. However, if the content of SiO ₂ is less than 0.20%, such an effect cannot be expected. On the contrary, if the content is too large, the viscosity of the molten slag decreases and the bead shape is rather deteriorated. At the same time, SiO ₂
The slag peelability at the time of welding also decreases with the increase in slag. Therefore, the amount of SiO ₂ is 0.20 to 1.50% in the total weight ratio of the wire.
And

[0022] _{Al 2 O 3: Al 2 O} 3 is also intended to form a slag-forming agent together with TiO _2, SiO _2, the effect of improving the affinity with the base material together adjust the bead shape during welding as well as SiO ₂ There is. Particularly, it is a raw material effective for appropriately adjusting the high-temperature viscosity of slag. If the slag is less than 0.20%, the viscosity of the slag is too low, and the bead tends to sag during vertical welding or the like. However, on the other hand, if the amount is too large, the slag viscosity becomes too high, so that welding defects such as slag winding are likely to occur, and the slag peeling property is also reduced. For this reason, Al ₂ O
The addition range of ₃ is 0.20 to 1.50% by weight of the wire.

Metal Fluoride: Various metal fluoride raw materials such as CaF ₂ , sodium fluoride, potassium silicofluoride and cryolite are generally well known for their action of adjusting the high temperature viscosity and basicity of slag during welding. Have been. However, the present inventors have found that the addition of these metal fluorides in the wire of the present invention improves slag peelability. The effect of improving the slag releasability is not clear when the wire weight ratio is less than 0.25%, and the slag releasability improves with an increase in metal fluoride, and the slag releasability is improved up to about 5.0%. It was confirmed that it would maintain. However, since the occurrence of spatter becomes remarkable with the increase of the metal fluoride, the upper limit of the addition of the metal fluoride is set to 1.35% in the present invention.

Metal oxides of Fe, Mn, Mg: In the development of the wire of the present invention, the effects of various metal oxide raw materials on the welding workability were investigated, and it was found that TiO ₂ , FeO (Fe ₂ O ₃₎
), MnO, MgO, etc. improve slag peelability,
It has been found that SiO ₂ , CrO (Cr ₂ O ₃ ), NbO, V ₂ O _3, etc., reduce the amount, and Al ₂ O ₃ has an optimum addition range. Therefore, in the present invention, as described above, regarding TiO ₂ , SiO ₂ , and Al ₂ O ₃ , the optimum range thereof is determined in consideration of the overall welding workability, and FeO, MnO, MgO, etc. are positively set. At least one of the metal oxides of Fe, Mn and Mg is added. The lower limit of the addition amount is set to 0.02% at which the improvement effect by addition is observed. However, excessive addition of any of these oxides causes remarkable spattering. Therefore, the upper limit of the addition is 1.00%.

Nb, V: As described above, the presence of Nb oxide and V oxide in the wire has been found to deteriorate the peelability of the weld slag even if the amount thereof is very small. Conventionally, these oxides have been considered as inevitable impurities, but in the present invention, slag removability has been successfully improved by positively removing them.

However, such elements are often mixed in the outer stainless steel as impurities, and are oxidized during welding to be mixed into the slag, resulting in a decrease in slag removability. It was also confirmed. Therefore, in the present wire, the Nb content as impurities in the outer stainless steel is set to 0.015% or less, the V content is set to 0.10% or less, and further, these elements mixed from the filling flux are included. And a compound such as an oxide thereof is represented by N
b, V conversion value, wire weight ratio, Nb: 0.075%
Hereinafter, V: 0.10% or less.

S: S in a normal flux cored wire for stainless steel is unavoidably mixed in from both the outer shell and the filling flux, and the presence of S together with P increases the hot cracking susceptibility of the deposited metal. In the prior art, efforts have been made to reduce this as much as possible.
However, the present inventors have succeeded in lowering the viscosity of the molten metal by positively adding an appropriate amount of S to the wire, and thereby, the detachment of the molten metal at the tip of the wire during welding /
It has been found that the transition state can be greatly stabilized and spatter generation can be drastically reduced. Based on this finding, in the present invention, S can be positively added as needed. When added, the lower limit of S at which such an effect is recognized is 0.003% in terms of the total weight of the wire, and the upper limit of the addition is 0.1% in terms of the total weight of the wire in view of the deterioration behavior of the hot-metal cracking resistance of the deposited metal. 035%.

O: Oxygen contained in the skin is usually mostly present in the form of inclusions as oxides. It is clear that such an oxide acts as the starting point of the arc in the unmelted part of the wire during welding, and serves as a stable arc generation point at the wire tip, which in turn is effective in reducing the amount of spatter generation. Was. The effect of enhancing the arc stability is that the oxygen content in the outer skin is 50 ppm.
This is clear. However, if the amount of oxygen in the outer skin becomes excessive, oxides (inclusions) in the outer skin may cause disconnection during wire drawing, so the upper limit of the oxygen amount is 300 pp.
It became clear that it was desirable to keep it to m. However, such an oxide as an arc stabilizer only needs to be present on the surface as a welding wire, and therefore does not need to be present as an oxide contained in the outer sheath of the wire, and the surface after the wire is drawn. The purpose is achieved even by forcibly oxidizing. In consideration of the case where such a treatment is performed, a desirable level is 50 ppm to 1000 ppm as the total oxygen content in the wire sheath.
The reason why the upper limit is set to 1000 ppm is that when a treatment such as surface oxidation is performed, as a bad influence of the excessive oxidation treatment, a decrease in wire feedability due to oxidation of the wire surface occurs.

It is needless to say that, as long as the component composition of the stainless steel shell is such that the above-mentioned respective component amounts are regulated, the other components can be elements and contents contained in so-called stainless steel. Examples of stainless steel include JIS G 4304 “Hot rolled stainless steel sheet”, JIS G 4305 “Cold rolled stainless steel sheet”, and JIS G 4307 “Cold rolled stainless steel strip”.
And austenitic stainless steels having similar component compositions are also possible. Of course, if the stainless steel to be used in the present invention is for a high temperature, those of these component systems and compositions can be used. Further, the cross-sectional shape of the flux-cored wire, the wire diameter, etc. are also appropriately determined.

Next, examples of the present invention will be described.

[0031]

EXAMPLES Various flux-cored wires (wire diameter: 1.2φ) having the component compositions shown in Tables 1, 2, 3, and 4 were prototyped, welding tests were conducted, and high-temperature characteristics, welding workability, etc. were examined. Was. 304L stainless steel (main component is
Cr: 19%, Ni: 10% included) was used.

The high temperature characteristics are based on a 304 series stainless steel (commonly referred to as 304H) for high temperature, a current of 200 A and a voltage of 30.
Carbon dioxide arc welding was performed under welding conditions according to V. JIS Z3323, a tensile test specimen was collected from the welded portion, and a high-temperature tensile test was performed. The cases where the high-temperature tensile ductility at 750 ° C. and the high-temperature rupture strength were respectively 27% and 210 N / mm ² or more were judged to be acceptable within the design range of the present invention.

The welding workability was evaluated at the time of welding in the above-mentioned high temperature characteristic test, and also by performing horizontal fillet welding using SUS304 steel having a thickness of 6 mm. Also,
As other characteristics, the hot cracking susceptibility was evaluated by the Fisco cracking test based on the occurrence of crater cracking. The wire drawability was evaluated under the wire drawing conditions used in the actual production line.

As shown in the test results in Tables 5 and 6, in each of the examples of the present invention, excellent high-temperature characteristics were obtained, the slag peeling property was excellent, and the amount of spatter generated was small. Is also good.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

[0038]

[Table 4]

[0039]

[Table 5]

[0040]

[Table 6]

[0041]

As described in detail above, according to the present invention,
We can provide flux-cored wire for stainless steel that has good high-temperature properties as a welding material for high-temperature applications, excellent welding workability, and particularly excellent slag removability and low spatter generation. The effect of contributing to further diffusion is remarkable.

[Brief description of the drawings]

FIG. 1 is a diagram showing high-temperature characteristics of a TIG weld metal and a conventional flux-cored wire weld metal.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shogo Natsume 100, No. 1 Urakawachi, Fujimae, Fujisawa, Kanagawa, Ltd. Fujisawa Works, Kobe Steel Works (56) References Japanese Patent Publication 7-83952 (JP, B2) )

Claims (2)

(57) [Claims] 1. A flux-cored wire for stainless steel in which an outer shell made of stainless steel is filled with a flux in terms of% by weight (the same applies hereinafter), wherein the oxygen content is 50 to 1000 ppm as a content in the total weight of the stainless steel outer shell. , Nb: 0.015% or less, V: 0.10% or less, Carbon: 0.015% or less, Nitrogen: 0.025% or less, and as a carbon source and a nitrogen source in the filling flux , Metal C
r, from metal Mn or various alloy raw materials or compounds with these elements, and / or at least one of carbon compound raw materials excluding graphite or carbonate, in a wire weight ratio, carbon: 0.020 to 0.10% Nitrogen: 0.008 to 0.08%, and the filler flux contains substantially no deoxidizer containing metal Si and / or a Si alloy. The filler flux contains slag as a slag component. at a weight _{ratio, TiO 2: 5.50~15.50%, SiO} 2: 0.20~1.50%, Al 2 O 3: 0.20~1.50%, metal fluoride: 0.25 At least one of Fe, Mn and Mg metal oxides:
Nb, V and these compounds, which are contained as unavoidable impurities from the filling flux, are contained in an amount of Nb: V in terms of wire weight ratio of Nb: 0.075. %, V: 0.10% or less, and the low melting point metals As, Sb, Pb, Bi and their oxides or compounds that are intentionally added to the filling flux or are unavoidably mixed. , Wire weight ratio, As,
Stainless steel characterized in that: As: Sb, Pb, Bi conversion amount: As: 0.010% or less, Sb: 0.010% or less, Pb: 0.008% or less, Bi: 0.008% or less. Flux-cored wire for steel. 2. S, As, Sb, Pb and Bi in the wire are
In terms of wire weight ratio, S: 0.003 to 0.035%, 5 × (Bi + Pb) + 2 × (As + Sb): 0.065% or less,
The flux-cored wire for stainless steel according to claim 1, wherein