JP3481146B2 - Flux-cored wire for stainless steel welding - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to welding of austenitic stainless steel and duplex stainless steel having a high nitrogen content and excellent in corrosion resistance and crevice corrosion resistance of a weld metal. The present invention relates to a flux-cored wire for stainless steel welding that is used, has no welding defects such as blowholes, and has excellent welding workability. [0002] SUS304N2, SUS304LN,
SUS316LN, SUS317LNSUS329J3
Austenitic stainless steel and duplex stainless steel having a high nitrogen content, such as L and SUS329J4L, are stainless steels having excellent corrosion resistance and strength properties. It is used as a corrosion-resistant material for chemical plant equipment, oil wells, gas wells and the like that require pitting corrosion resistance and crevice corrosion resistance, and because of its high strength, it is also used as a structural material for buildings and vehicles.
Materials used for these weldings are required to have the same weld metal performance as the base metal and good welding workability. Among the welding materials, flux-cored wires that can be welded with high efficiency have come to be used in many cases, and their demands are particularly high. However, when stainless steel with a high nitrogen content is welded using a conventional flux-cored wire for welding austenitic stainless steel, there is a problem that slag is scattered immediately after welding or a part of the slag is burned to a weld bead. . This not only significantly reduces the efficiency of welding work, but also has a problem in terms of safety because slag is scattered. [0003] There are flux cored wires described in JP-A-8-118071 and JP-A-9-239586 for welding high-nitrogen stainless steel to solve this problem. Welding workability such as bead shape, slag encapsulation and peelability, slag scattering resistance is not sufficient, and welding defects such as blowholes in the weld metal due to nitrogen have not been completely solved. Was. Therefore, there has been a strong demand for the development of a flux-cored wire for stainless steel welding that solves these problems. DISCLOSURE OF THE INVENTION [0004] The present invention provides a method for welding a stainless steel having a high nitrogen content, which has no welding defects, has an arc stability, a spatter generation amount, a bead shape, a slag encapsulating property, An object of the present invention is to provide a flux-cored wire for welding stainless steel having excellent welding workability such as peelability and slag scattering resistance. [0005] In order to solve the above-mentioned problems, the present inventors have focused on adjusting the N amount of the wire sheath, the slag agent component of the filling flux, and the slag agent amount. The composition of the slag agent component and the amount of the slag agent were variously examined. As a result, when welding stainless steel with a high nitrogen content, welding workability such as arc stability, spatter generation, bead shape, slag encapsulation and peeling properties, and slag scattering resistance is excellent. A flux-cored wire for welding stainless steel without welding defects such as blowholes in metal was found. That is, the gist of the present invention is to provide a flux cored wire for stainless steel welding in which a flux is filled in a stainless steel sheath, the N content of the wire sheath is 0.19% by weight or less, and the filling flux is TiO ₂ : 3.2 to 7.5% by weight based on the total weight of the wire, S
iO ₂ : 1.0 to 4.0%, Al ₂ O ₃ : 0.1 to 1.6
%, MgO: 0.15 to 1.0%, metal fluoride (F conversion value): 0.3 to 1.17%, K compound (K conversion value):
0.3 to 0.73%, N compound (N conversion value): 0.11
% Or less, and ZrO ₂ as an inevitable impurity: 0.
08% or less (including 0%), and the total of the slag agent components is 5.3 to 12.5% by weight, and furthermore, N contained in the wire sheath and N contained in the flux with respect to the total weight of the wire.
The total of the compounds (in terms of N) is 0.07 to 0.24% by weight.
A flux-cored wire for stainless steel welding, characterized in that: [0007] The reasons for limiting the components of the flux cored wire for stainless steel welding of the present invention will be described below. The TiO ₂ in the filling flux stabilizes the arc, forms a slag with good encapsulation and peeling properties, and further forms a slag with good scattering resistance. Is not exhibited, and if it exceeds 7.5%, the fluidity of the slag deteriorates, and the bead shape becomes poor. Also,
Not only spatter is likely to occur, but also slag entrainment defects are likely to occur. Rutile, titanium slag, illuminite, potassium titanate, sodium titanate and the like can be used as TiO ₂ . [0009] SiO ₂ is a component necessary for adjusting the fluidity of the slag, and is a component for improving the bead shape.
%, The fluidity of the slag is poor and the bead shape is poor, and if it exceeds 4.0%, the slag flows easily, and the slag removability and the bead shape are poor. Furthermore, the scattering resistance of the slag deteriorates. As SiO ₂ , besides silica sand and silica stone, potassium feldspar and the like can be used. [0010] Al ₂ O ₃ is a component that adjusts the fluidity of the slag to improve the bead shape. However, if it is less than 0.1%, the slag flows easily, so that the slag has poor encapsulation properties and the slag has a releasability. And the bead shape becomes poor. 1.
If it exceeds 6%, the viscosity of the slag decreases, the encapsulation of the slag is poor, and the bead shape is poor. As Al ₂ O ₃ ,
Alumina, potassium feldspar and the like can be used. MgO is a component necessary for adjusting the fluidity of the slag and the solidification temperature of the slag, and is a component for improving the bead shape. If the content of MgO is less than 0.15%, the fluidity of the slag is poor and the bead shape is poor. If it exceeds 1.0%, slag flows easily and the slag is not uniformly covered on the surface of the weld bead, so that the slag encapsulability and peelability are deteriorated, and the amount of spatter generated is increased, thereby deteriorating welding workability. Also,
Slag entrainment is likely to occur. The metal fluoride improves the pit resistance, adjusts the melting point of the slag, and improves the slag encapsulating property and the releasability. However, when the F value is less than 0.3%, pits are generated. The encapsulability and peelability of the slag deteriorate, and if it exceeds 1.17%, the melting point of the slag remarkably decreases, and the encapsulation of the slag deteriorates. Further, a large amount of fume is generated with the generation of fluorine gas. Metal fluorides are LiF, MgF ₂ , AlF ₂ ,
K ₂ Zr ₂ F ₆ or the like can be used, and the same effect can be obtained by using any metal fluoride. The K compound is added to stabilize the arc. In particular, in the present invention, the ratio of TiO ₂ is high,
It suppresses an increase in the amount of droplets and spatter generation. Further, it is a component that adjusts the fluidity of the slag to improve the bead shape. However, if it is less than 0.3% in terms of K, the arc becomes unstable and the amount of spatters increases, and
If it exceeds, the blowing force of the arc becomes too strong, and the amount of spatters increases, and the slag flows easily, the encapsulating property of the slag deteriorates, and the slag peeling property becomes poor. As the K compound, potassium oxide, zirconium fluoride, potassium fluorosilicate and the like can be used. N increases the strength and is a strong austenite-forming element, and is effective in obtaining high corrosion resistance in the form of coexistence with Cr, Ni and Mo. If the total of N contained in the wire sheath and the N compound contained in the flux (N conversion value) is less than 0.07% based on the total weight of the wire, the effect is not exhibited, and if it exceeds 0.24%, the strength and corrosion resistance are obtained. Is not only saturated, but also blow holes are generated. In this case, if the N compound (N-equivalent value) contained in the flux exceeds 0.11%, blowholes are generated in the weld metal, and the amount of spatters increases, thereby significantly deteriorating the welding workability. If the N content of the wire sheath exceeds 0.19%, the sheath becomes hard and the wire drawability is significantly deteriorated, and the number of annealings in the manufacturing process is increased, and the number of wire breaks is increased, and the productivity is significantly reduced. If the N content of the wire sheath is small, a large amount of the N compound must be added from the flux. However, if a large amount of the N compound is added from the flux, the amount of spatter is increased, and blow holes are generated in the weld metal. I do.
Further, the yield of N in the weld metal becomes unstable, and a stable weld metal may not be obtained. Therefore, it is desirable that the N content of the wire sheath be 0.02% or more. As the N compound in the flux, metal manganese nitride, ferromanganese nitride, chromium nitride, or the like can be used. ZrO ₂ forms a compound with N, and slag bites into the bead surface to significantly deteriorate the slag removability.
Accordingly, the present invention is one of the point to ensure that ZrO ₂ is not as much as possible is contained, ZrO ₂ content of 0%
And 0.08% or less. The filler flux adjusts the alloy composition depending on the steel plate to be welded. Ni, Cr, M as modifier
n, Mo, Si, Nb, Fe, Ti, Al, stainless steel powder or the like is used. Further, granulation may be performed using a fixing agent according to the raw material particle size, flux component, filling method, and the like. In this case, components resulting from the fixing agent, for example, in the case of water glass, SiO ₂ , Na ₂ O , slag agent amount in advance considering that K ₂ O or the like is increased 5.
It is necessary to mix the raw materials so as to be 0 to 12.5%. The slag agent component in the present invention means non-metal components such as oxides and fluorides, and P, S and the like as impurities, but also includes a regulator for adjusting alloy components. There is also. If the total amount of the slag is less than 5.3% based on the total weight of the wire, the amount of the slag is insufficient, the entire bead cannot be covered, the encapsulation of the slag is deteriorated, and the bead shape and the slag removability are deteriorated. become worse. Furthermore, the scattering resistance of the slag deteriorates. If it exceeds 12.5%, the amount of slag becomes excessive and the amount of spatter generated increases. Further, welding defects such as slag entrapment are likely to occur. The flux-cored wire of the present invention is shown in FIG.
A to d show a cross-sectional shape of the wire as shown in the example, and a sheath 1 made of an austenitic stainless steel pipe or a strip steel is covered with a filling flux 2 as shown in FIG. Seamless, or b-d
May have a seam 3 as shown in FIG. EXAMPLES Austenitic stainless steel pipes and strips having the components shown in Table 1 were used, and the fluxes shown in Tables 2, 3 and 4 were filled at 19 to 28% of the total weight of the wire. A flux-cored wire for welding stainless steel having a wire diameter of 1.2 mmφ was manufactured. After the pipe was drawn to a diameter at which the flux entered a predetermined filling rate, the flux was charged by vibration. In Tables 2, 3, and 4, the wire No. 1 to 19 are flux-cored wires of the present invention,
No. 20 to 39 are comparative examples. The welding test was conducted at a current of 200 A (DCEP),
The welding was performed under the conditions of a voltage of 31 V, a welding speed of 35 cm / min, and a shielding gas of 100% CO ₂ : 25 l / min. [0022] The test steel sheet was a wire no. 4, no. As for No. 5, SUS304N2 steel plate having the components shown in Table 1 and other wires were assembled in a T-shape using SUS329J3L steel plate, and one-pass horizontal fillet welding was performed on one side to confirm welding workability. Table 5 shows the results. The evaluation was evaluated as ○ when practically good, and × when practically problematic. Table 5 shows the results. The wire No. of the present invention example. 1 to 19
TiO ₂ , SiO ₂ , Al ₂ O ₃ , MgO, metal fluoride,
Since K and N etc. are contained in the flux in appropriate amounts and the total amount of slag agent in the flux is appropriate, welding workability is good, and welding defects such as blow holes and slag entrapment do not occur. It was a good result. In the comparative example, the wire No. In No. 20, since the amount of TiO ₂ was large, spatter frequently occurred, and welding workability was deteriorated.
Furthermore, the fluidity of the slag deteriorated, and the bead shape became poor. The wire No. with a small amount of TiO ₂ 21 is
The arc state became unstable, and the encapsulating property and peeling property of the slag deteriorated. In addition, the slag became less splash resistant. The wire No. having a large amount of SiO ₂ was used. In No. 22, the slag flowed easily, the encapsulation of the slag was deteriorated, the slag was seized, and the slag peeling property and the slag scattering resistance were deteriorated. Further, the bead shape was defective. The wire No. having a small amount of SiO ₂ . 23 is
The fluidity of the slag was poor, and the bead shape was poor. The wire No. having a large amount of Al ₂ O ₃ was used. In No. 24, the viscosity of the slag was reduced, the encapsulation was poor, and the bead shape was poor. The wire No. having a small amount of Al ₂ O ₃ was used. 25 is
The slag flowed easily, the encapsulation property was deteriorated, and the slag peelability was reduced. Further, the bead shape was defective. The wire No. having a large amount of ZrO ₂ was used. In No. 26, the slag bitten into the surface of the weld metal, and the slag peelability became poor. Further, immediately after welding, a part of the slag rebounded, and the slag scattering resistance was deteriorated. The wire No. having a large amount of MgO was used. In No. 27, the slag flowed easily, the slag was not uniformly covered on the surface of the weld bead, and the slag was poor in encapsulation property, and the peelability was reduced. Also, the amount of spatter generated was large, and welding workability was poor. The wire No. having a small amount of MgO was used. In No. 28, the fluidity of the slag was poor, the encapsulation property was deteriorated, and the bead shape was poor. When the wire No. has a large K content, In No. 29, the spraying of the arc was too strong and a lot of spatters were generated. Further, the slag flowed easily, the slag was poor in encapsulation, and the peelability was reduced. The wire No. having a small K amount. In No. 30, the arc became unstable and a lot of spatters were generated. The wire No. containing a large amount of metal fluoride was used. 31 is
The amount of generated fluorine gas was excessive, and the amount of generated spatter and welding fume was increased. Further, the melting point of the slag was lowered, and the encapsulation of the slag was deteriorated. The wire No. having less metal fluoride was used. 32
The slag was not uniformly encapsulated in the weld metal, and the slag removability was poor. Furthermore, pits were generated on the bead surface. The wire No. having a large amount of N in the flux was used. 33
In the test, a large amount of spatter was generated, and blow holes were generated in the weld metal. The wire No. having a large amount of N in the outer skin was used. In No. 34, the work hardening of the wire was large in the manufacturing process, the number of times of annealing of the wire increased, and the number of times of wire disconnection also increased, resulting in inferior productivity. The wire No. having a large total N of the wires. 37 is
Blow holes occurred in the weld metal. The wire No. having a small total N In No. 38, although the welding workability was good, a tensile strength equivalent to that of the base material was not obtained in a separately performed weld metal test. Wire N having a large total amount of all slag components
o. In No. 35, the amount of slag became excessive, slag was involved, and the amount of spatter generated increased. The wire N having a small total amount of the slag agent components
o. In No. 36, the amount of slag was insufficient, the entire bead could not be covered, the encapsulation of the slag was deteriorated, and the bead shape and the slag removability were poor. Furthermore, the scattering resistance of the slag deteriorated. [Table 1] [Table 2] [Table 3] [Table 4] [Table 5] As described above in detail, the flux-cored wire for stainless steel welding of the present invention can satisfy the mechanical performance in welding stainless steel having a high nitrogen content while satisfying the mechanical performance.
It is useful as a flux-cored wire for welding stainless steel having excellent welding workability such as arc state, spatter generation amount, slag encapsulation / peeling property, and slag scattering resistance.

[Brief description of the drawings] FIG. 1 is a cross-sectional view of a flux-cored wire. [Explanation of symbols] 1 skin 2 Filling flux 3 seams

Continuation of front page (72) Inventor Shinichi Kaneda 3-5-4 Tsukiji, Chuo-ku, Tokyo Nippon Steel Welding Industry Co., Ltd. Laboratory (56) References JP-A-8-1118071 (JP, A) JP-A-9 -122977 (JP, A) JP-A-9-122978 (JP, A) JP-A-9-239586 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 35/368 B23K 35/30

Claims (1)

(1) A flux-cored wire for stainless steel welding in which a flux is filled in a stainless steel sheath, wherein the N content of the wire sheath is 0.19% by weight or less, Filling flux is T by weight% based on the total weight of wire.
_{iO 2: 3.2~7.5%, SiO 2} : 1.0~4.0
_{%, Al 2 O 3: 0.1~1.6} %, MgO: 0.15~
1.0%, metal fluoride (F conversion value): 0.3 to 1.17
%, K compound (K conversion value): 0.3 to 0.73%, N compound (N conversion value): 0.11% or less, and ZrO ₂ as an unavoidable impurity: 0.08% or less (0 %, And the total amount of the slag agent components is 5.3 to 12.5% by weight, and the total of N contained in the wire sheath and N compounds contained in the flux (N-converted value) is based on the total weight of the wire. A flux-cored wire for welding stainless steel, wherein the flux is 0.07 to 0.24% by weight.