JPH05228691A - Flux cored wire for self-shielded arc welding - Google Patents

Abstract

PURPOSE:To obtain a weld zone having a good bead shape and good mechanical properties by executing flat and three o'clock welding of a steel structure while using the flux-cored wire formed by filling a specific amt. of a flux having a specific compsn. into a sheath made of steel. CONSTITUTION:The compsn. of the flux consists of 25 to 40wt.% total of CaF2 and BaF2, and >=5.0 and <0.75 BaF2/CaF2, to 23% iron oxide (in terms of Fe2O3), and >=0.4 and <=2.0 iron oxide/Al, 9 to 20% one or 12 kinds of Al and Al alloy (in terms of Al), 4 to 13% one or >=2 kinds of Mg and Mg alloy (in terms of Mg), 0.4 to 12% carbonate of one or two kinds of Li and Ba, 0.5 to 8% Mn or Mn alloy (in terms of Mn), >=0.03 and <=1.7% total sum of C in the flux (including the value obtd. by converting the C of the carbonate to C), <=5% other components exclusive of the iron (including unavoidable impurities) and the balance iron. This flux is so filled in the sheath that the weight of the flux is 10 to 25% of the entire part.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention is mainly applied to joint welding of steel structures in downward and sideways postures, and is capable of stably obtaining a welded portion having good X-ray and bending performance, and a machine. The present invention relates to a flux-cored wire for self-shielding arc welding (hereinafter referred to as self-shielding wire) having good static performance.

[0002]

2. Description of the Related Art The self-shielding arc welding method using a self-shielding wire shields the arc being welded and the molten pool from the atmosphere, so that welding can be performed without supplying flux or gas from other sources. Therefore, the structure of the welding device and torch is simple and light, and it does not require flux supply, removal or gas supply, replacement of cylinders, and piping. In terms of actual work, there is an advantage in that it is less likely to be restricted by the attitude of the latent arc welding method from the surface of the atmosphere shield, and by the gas shield method, which is difficult to be restricted by the wind which is a problem in outdoor work. However, in reality, the arc voltage, that is, the change in the shield property due to the arc length and its variation, the construction conditions such as the wire protrusion length, the moisture absorption of the welding material wire, the rust, and the work piece groove. Since it is sensitive to water such as rust, dirt and adhesion of anticorrosion paint and has a narrow tolerance, special skill and control are required to obtain a weld without defects. The conventional self-shielding wire does not have a complete air shield, and a large amount of Al and Mg are added as denitrifying and deoxidizing agents to prevent the generation of pores in the weld metal due to nitrogen and oxygen in the air that entered during welding. To do. Therefore, a large amount of Al remains in the weld metal and the crystal grains become coarse, so that good bending performance and toughness cannot be obtained.

Further, in this system, the solidification of slag is slow and the viscosity thereof is low, so that it is extremely difficult to perform the welding in the upright position and the upright position. It is easy to drip and requires special skill.

In order to solve these drawbacks, for example, JP-A-54-155139, JP-A-56-74395,
JP-A-59-42198, JP-A-59-141397
Japanese Patent Application Laid-Open No. 62-238097 discloses a self-shielding wire in which the diameter of the wire is reduced and good use characteristics in all postures, porosity resistance, low temperature toughness and bending performance are improved. These wires use BaF ₂ instead of CaF ₂ as the metal fluoride, which is the main slag material, and raise the solidification point of the slag to improve all-position weldability,
Improves impact toughness.

However, it has been found that with these wires, it is generally difficult to remove the generated slag, it is time-consuming, and the final bead appearance is poor, so that it is still a problem as a general-purpose material. That is, in the case of CaF ₂ , the slag peeling and the bead appearance are good, but the posture weldability and impact toughness are poor. Ba
The F ₂ system is excellent in all-position weldability and impact toughness, but has problems such as slag peeling and poor bead appearance.

Further, in order to solve these problems, Ca
F _2, JP-A was used in combination with BaF ₂ 58-148
095, JP-A-63-63600, JP-A 1-21
No. 0195, JP-A-1-289596, etc. are known. However, these wires are also aimed at improving all-position weldability and impact toughness, and other welding methods, such as hand welding, gas shield, and latent arc welding, are commonly used and are limited to the downward and sideways positions. There are still problems with welding workability, weld integrity, and mechanical properties, and their applications are limited.

The present invention has been made in view of such a situation. That is, the welding posture is generally limited to the most frequently used downward and sideways postures, without requiring high skill,
It is possible to efficiently weld relatively thick joints that require multi-layer welding, and to provide good-shaped beads and sound welds.
Moreover, the purpose of the present invention is to provide a self-shielding wire having improved mechanical performance.

[0008]

In order to achieve the above-mentioned object, the present inventor has already based on the prior art and has already prepared BaF ₂ / CaF ₂ , Al / (CaF ₂ + BaF) in the CaF ₂ , BaF ₂ system.
₂ ) By controlling the sum of C / Al ratio, it is possible to provide a self-shielding wire with good arc stability, bead shape, weld soundness and bending performance in joining with a plate thickness of less than 25 mm. did it.

However, when it is attempted to apply it to the joining of thick plates having a thickness of 25 mm or more, it has been found that defects such as slag-in increase and there is a problem in bending performance and mechanical performance such as impact toughness. As a result of further research to solve these problems, the present invention has found that the above problems can be solved by positively adding oxygen to the wire, and based on this finding, conventional raw materials This can be achieved by finely adjusting the ratio of the constituent components within the range of and.

That is, in the self-shielding wire according to the present invention, CaF ₂ and BaF ₂ as metal fluorides are added to the inside of the steel shell in a total amount of 25 to 40% (weight% based on the total weight of flux, the same applies hereinafter), and BaF ₂ / CaF ₂ :
0.5 to less than 0.75, 3 to 23% of iron oxide, and an iron oxide / Al ratio of 0.4 to 2.0, 1 of Al, Al alloy.
9 to 20% in terms of Al, Mg, Mg
4 to 13%, L of one or more alloys in terms of Mg
i, Ba one or two carbonates 0.4 to 12%,
0.5 to 8.0% of Mn or Mn alloy in terms of Mn, and 0.03 to 1.7% or less of the total amount of C in the flux including the value obtained by converting C of carbonate into C are contained as essential components. , And the weight ratio between the following components is Al / (CaF ₂ + BaF
₂ ): 0.3 to 0.4, the sum of C / Al: 0.07 or more, and if necessary, one or more of Li, K, Na and rare earth element compounds may be Li, K, Na. And converted to rare earth elements 0.1 to 1.0%, Ni 3 to 7
%, Zr and / or Ti of 0.2 to 5
%, And the flux is filled so as to be 10 to 25%. The present invention will be described in more detail below.

[0011]

The reason why the self-shielding wire component of the present invention is limited to the above structure will be described below. CaF ₂ and BaF ₂ as metal fluorides are the main constituents of the slag together with Al and Mg described below, and have the effect of partially vaporizing the arc heat during welding and shielding the arc atmosphere and molten pool from the atmosphere. .. However, if it is less than 25%, the shielding effect is insufficient, the amount of slag is insufficient, and the ratio of Al and Mg oxides having a high freezing point increases, so the freezing point of the slag rises and the fluidity deteriorates, stabilizing the beads. Cannot be covered with a bead, and good bead appearance, shape and porosity resistance cannot be obtained. If it is added in excess of 40%, the amount of slag increases and the ratio of fluoride in the slag increases, and the slag precedes in the groove due to the lowering of the freezing point and the increase in fluidity, and the arc becomes unstable. Especially in the horizontal position, the slag hangs down and the workability of welding deteriorates.

Even if the amount added is within the above range, CaF ₂ and B
When the weight ratio BaF ₂ / CaF _{2 of} aF ₂ is less than 0.50, the arc is not stable and spreads at a low voltage. Especially in the horizontal orientation where the welding speed is fast, the molten pool is long, the solidification of the slag is delayed, and the bead becomes convex. Further, it was found that when the ratio is 0.75 or more, the arc spreads too much, the wetting of the base material becomes unstable, the penetration decreases, the slag peeling deteriorates, and fusion failure easily occurs. Therefore, the metal fluoride Ba
F ₂ and CaF ₂ are added together in the range of 25 to 40%, and in this range, the ratio BaF ₂ / CaF ₂ is 0.
It is necessary to control to 50 to less than 0.75.

Iron oxide is generated during multi-layer welding by excessively or segregating at the time of welding and rapidly oxidizing and reducing or removing deoxidizing and denitrifying agents such as C, Al and Mg remaining in the weld metal. Reduces welding defects such as slag-in. It also has the effect of reducing the excessive amounts of C and Al in the weld metal and improving the mechanical properties of the weld metal such as tensile strength and impact toughness. Addition amount is 3% in terms of Fe ₂ O ₃
If it is less than 23%, the above effect is not obtained, and if it is added in excess of 23%, the slag easily flows, the bead encapsulation property deteriorates, the welding bead becomes convex, and blowholes frequently occur. Even within the above range, if the iron oxide / Al ratio is less than 0.4, the above effect does not occur, and if it exceeds 2.0, the residual Al amount is excessively reduced and defects such as pits and blow holes are formed in the weld metal. Occur. Therefore, iron oxide is ₃ to 23% in terms of Fe ₂ O _3.
And the ratio of Fe ₂ O ₃ converted iron oxide / Al is 0.4.
It is necessary to control to ~ 2.0. As the oxide, any compound that can oxidize C, Al, and Mg during welding, that is, a compound that serves as an oxygen source may be used, but in the present invention, it is limited to iron oxide that is reduced and has little influence on the weld metal performance. The iron oxide may be an oxide at each stage of iron and / or a complex oxide of an oxide at each stage of iron and another compound, and specifically, α-ferrite and γ-ferrite with stable oxygen grade. , Lithium ferrite, barium ferrite,
It is desirable to add in the form of strontium ferrite.

Al is added for the purpose of fixing nitrogen that has excessively penetrated into the weld metal, and as a deoxidizing agent for suppressing the generation of pores such as pits and blow holes. Further, it is a main component that constitutes the slag together with the metal fluoride described above and Mg described below, and has a great influence on the welding workability. 9
If it is less than 0.1%, denitrification and deoxidation are insufficient and pores are generated in the weld metal, resulting in poor X-ray performance. Further, if added in excess of 20%, Al in the weld metal becomes excessive, the crystal grains become coarse, and the impact toughness and bending performance deteriorate. This is C described later
It has a lot to do with the ratio to the sum of. As the Al raw material, metal Al and Fe-Al, Al-Mg, Zr-A are used.
It may be added in the form of an alloy such as l, Li-Al, Ca-Al, Ca-Al-Mg.

Mg is vaporized by arc heat during welding, shields the arc from the atmosphere, reduces the partial pressure of atmospheric components, and acts as a deoxidizer. Furthermore, when an appropriate amount is added, the transfer of droplets is stabilized, an appropriate arc strength is given, and penetration is increased. Further, it is one of the main slag constituents together with the metal fluoride and Al described above. In particular, if the Mg content is less than 4%, the droplet transfer becomes unstable. On the contrary, if it exceeds 13%, the encapsulation property of the slag is deteriorated. In addition, the amount of fumes and spatter increases and the deposition rate decreases. Further, slag is apt to be caught in the welded portion, and the elongation and bending performance of the tensile test piece are deteriorated. Therefore, it is necessary to add Mg in the range of 4 to 13%. Mg
Raw materials include metallic Mg and Al-Mg, Ni-Mg,
It can be added in the form of an alloy such as Li-Mg, Ca-Mg, Fe-Mg.

The carbonates of Li and Ba decompose during the welding to generate CO ₂ gas, which improves the air shielding property together with the metal fluoride and Mg, and the droplet transferability from the wire tip like the addition of Mg. , Give a suitable blend. The oxide after decomposition becomes slag. Among the alkali metals and alkaline earth metals, the carbonates of Li and Ba are selected and used. Li carbonate has a low water content and the highest CO ₂ content per mol. It gradually decomposes from the lowest temperature among alkali metals, releases carbon dioxide, and enhances the shielding effect. Further, the solidification temperature of the oxide produced by decomposition is close to that of weld metal. This is because it has effects such as keeping the arc length short and smoothing the transfer of droplets. Ba has a stable arc even at a low voltage. In particular, the decomposition temperature is close to the solidification temperature of iron, so that the shielding efficiency is good, and since the oxidation product to be slag has a high freezing point and a high specific gravity, it is well separated from molten iron, so it is added. Addition amount is 0.
If it is less than 4%, the above effect cannot be recognized. 12% again
If added in excess, the amount of gas generated becomes excessive and the arc becomes unstable, and the amount of spatter increases. Therefore, Li and / or Ba carbonate is added in the range of 0.4 to 12%. As raw materials, lithium carbonate and barium carbonate are added.

In the present invention, in a strongly reducing atmosphere during welding, Mn in the wire is almost reduced regardless of the form such as metal or oxide and enters into the weld metal as an alloy component. Mn is added to give proper tensile strength. Mn in the filling flux
If the amount is less than 0.5% with respect to the total weight of the flux, the amount of Mn in the weld metal accumulated will be insufficient and the target tensile strength of the steel material will not be reached. On the other hand, if it is added in excess of 8%, the tensile strength of the beads that have been formed will become too high and the toughness will also decrease. Therefore, the amount of Mn in the flux is limited to the range of 0.5 to 8%. Mainly Mn and Fe-M as Mn raw materials
n, but added in the form of various alloys containing iron alloy such as Fe-Si-Mn, oxides such as some MnO, Li ₂ MnO
_It can also be added in the form of complex oxides such as ₂ and carbonates such as MnCO ₃ .

C is an element that affects the strength and impact toughness of the weld metal, but the total amount of C in the flux is 1.7.
If it exceeds%, the fume amount during welding increases, the arc becomes too strong, and the occurrence of undercut increases. In addition, the hardness and tensile strength of the weld metal become too high and the impact toughness decreases. On the contrary, if it is less than 0.03%, the arc force becomes weaker,
The transfer of droplets becomes unstable and sufficient penetration cannot be obtained. Moreover, the target tension cannot be obtained. As the C source, carbonate and Fe-Mn are mainly used, but when they are insufficient, they are added by C-containing compounds such as simple C and SiC.

If the flux filling rate is less than 10%, no matter how the flux components and ratios are adjusted, the required amount of slag cannot be secured and a sound welded portion cannot be obtained. 2 on the contrary
If it exceeds 5%, the cross-sectional area of the outer skin is reduced, and many wire breakages occur during wire drawing, resulting in extremely low productivity. Therefore, in the present invention, the flux rate is set to 10 to 25%.

The second invention is limited as follows. A
l / metal fluoride weight ratio, Al / (CaF ₂ + BaF
_The reason why ₂ ) is regulated to 0.3 to 0.4 is that, as a result of studying to further improve the workability of welding, it was found that the ratio of Al together with BaF ₂ / CaF ₂ has an effect. is there. That is, when Al / (CaF ₂ + BaF ₂ ) is less than 0.3, the droplet transfer during welding becomes rough and not smooth even if other components are adjusted, the solidification point of the slag is lowered, the fluidity is increased, and the bead matrix is increased. Wetting of the material is reduced. for that reason,
Welding workability deteriorates due to convex beads. vice versa,
This is because if it exceeds 0.4, the solidification point of the slag increases, and the fluidity deteriorates, the bead encapsulation of the slag deteriorates, the appearance deteriorates, and welding defects such as slag entrainment increase.

In the present invention, it is intended to easily join a relatively thick steel material having a plate thickness of about 10 mm to 25 mm or more, but in the case of three or more layers, Al in the wire is 1.7.
Even if it is in the range of up to 2.5%, it may break due to front bending. However, it was found that if the sum of C / Al: 0.07 or more, the weld metal structure becomes fine-grained, the elongation rate in the tensile test is good, and the result of the bending test is improved. This is the sum of C even if the amount of Al and C in the wire is within the above range.
If the Al content is less than 0.07, the crystals of the weld metal become coarse and the elongation sharply decreases, and the bending and impact toughness deteriorate.

Li, Na, K and a rare earth element compound are added as necessary to stabilize the arc and finely adjust the physical properties of the slag. 0.1% converted to each element
If less than 1.0%, the above effect is not observed, and if added in excess of 1.0%, the arc at low voltage becomes stable, but the arc is longer than necessary and spreads, so the weld pool droops greatly in welding in the horizontal position. It is easy, and the bead shape is deteriorated such that the upper side of the final pass is undercut. Therefore, Li, N
a, K and the rare earth element compound are added in the range of 0.1 to 1.0% in terms of Li, Na, K and the rare earth element. As the form of the raw material, except for lithium carbonate, oxides including complex oxides, fluorides including fluorine complex salts such as LiFeO ₂ , K ₂ O.SiO ₂ , LiF, NaF, L
iBaF ₃ , K ₂ SiF ₆ , Na ₂ SiF ₆ , K ₂ Zr
It can be added in the form of F ₆ , K ₂ TiF ₆ , RF ₃ or the like.

Zr and Ti are added as deoxidizing and denitrifying agents, and have the effects of preventing pits and blow holes and reducing the consumption of Al. However, if it is less than 0.2%, there is no effect, and if it exceeds 5%, the peelability of the slag deteriorates, which is not preferable. Fe-Zr, Zr-Si, Z as a Zr source
It can be added in the form of alloy powder such as r-Si-Ca. Ti
The source can be added in the form of metallic Ti, Fe-Ti, or the like.

Fe is mainly added as iron powder in the flux for the purpose of adjusting the flux rate, the melting rate, and improving the flux molten state, and other Fe comes from the iron alloy. Other components such as P, S, Si, Cu, S
iO ₂ , FeO, MgO, CaO, ZrO ₂ , Cr, M
Inevitable impurities such as o and fine adjustment components are included up to 5%.

The outer skin used in the present invention is not particularly limited, but may be a product capable of producing a flux-cored wire by a usual method, that is, a commercially available strip steel or the like. Therefore, C, Si, Mn, P, S, Al, out of the normal range,
It is desirable to exclude the skins of components such as Cu, Cr, N and O. However, in order to control the amount of C in the weld metal, it is possible to use a low carbon crust of about C: 0.001 to 0.005%, if necessary. Further, the flux-cored wire of the present invention can be produced by a usual production method.

Further, the cross-sectional shape of the wire is not particularly restricted as shown in FIG. 1, but when the diameter is 2.4 mm or less, the wire shown in FIG.
A simple circle as shown in (b), (c), and (d), and a diameter greater than that, a cross-sectional shape such as (e) in which a skin is complicatedly folded is desirable. In addition, in this method, since welding is performed in a strongly reducing atmosphere, moisture reacts very actively and it is easy to generate pores in the weld. Therefore, it is desirable that the water content is as small as possible. However, since a small amount of water is usually contained in the inside and outside of the wire in the form of attached water, bound water, etc., the present invention pays attention to the water content and particle size of the raw material, and heat-treats as necessary to reduce the water content of the wire to 0. It is desirable to be 3% or less. The thickness of the steel sheet used is not limited, but the strength is limited to mild steel and 50 kg or less. The welding conditions are not particularly limited, but a wire (-) using a DC power source is desirable.

[0027]

EXAMPLES Examples of the present invention will be described below. With the flux composition shown in Table 1, a 2.0 mm diameter flux-cored wire was manufactured by a conventional method. The cross section of the wire is a simple circle as shown in Fig. 1 (a), and the skin is C corresponding to JIS SPCC:
0.06%, Si: 0.1%, Mn: 0.3%, Cr:
0.05%, Al: 0.002%, N: 0.005%,
O: 0.054% (wt%) and C: 0.002% corresponding to JIS SPUD, Si: 0.1%, Mn: 0.
26%, Cr: 0.05%, Al: 0.004%, N:
A 0.005% and O: 0.02% (wt%) polished steel strip was used. Next, using these wires, SM of 40mm thickness
Welding in a horizontal position with a 50B steel square groove (with back plate, gap 5 mm, groove angle 40 °), welding workability, X
The composition of the wire, bending, tension, impact test and weld metal was investigated. Welding conditions are DC electrode negative (DCEN), current: 280
A, voltage: 22-24V, wire protrusion length: 15
Was ~ 25 mm. The test results are shown in Table 2.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

[Table 3]

[0031]

[Table 4]

[0032]

[Table 5]

[0033]

[Table 6]

[0034]

[Table 7]

In the above table, No. Nos. 1 to 10 are examples of the present invention, and all of them have excellent workability in welding, no defects are observed in the welded portion, and excellent X-ray, tensile properties, impact toughness and bending performance are obtained.

No. 11 to 28 show the test results of the comparative example. No. Nos. 11 and 12 are cases where the metal fluoride is out of the range of the present invention, and when the addition amount is small, blow holes occur, and when the addition amount is large, slag entrainment occurs and bending performance cannot be obtained. No. Nos. 13 to 16 are cases where the BaF ₂ / CaF ₂ ratio is out of the range of the present invention, and the properties of the slag are not proper in all cases, and slag entrainment occurs and a good weld cannot be obtained. No. In No. 17, the amount of Al added was small and a pit was generated in the welded part, so the test was stopped. No. In No. 18, the amount of Al added was too large, and Al / (CaF ₂ + BaF ₂ ) was 0.4.
Since it is larger, the freezing point of the slag rises and the fluidity is lowered, so that the slag is entrained and good bending performance cannot be obtained.

No. Nos. 19 to 21 are inferior in bending performance when the amount of iron oxide is out of the range of the present invention, and particularly, the wire having the amount of iron oxide added less than the range of the present invention has low impact toughness. N
o. No. 22 contains no carbonate, and No. 22 No. 23 is a case where a carbonate is added outside the range of the present invention. When the amount is small, the shielding property is deteriorated and blowholes are generated, and when the amount is large, the arc becomes unstable and the slag physical properties are not appropriate and sound welding is performed. No part has been obtained.

No. In Nos. 24 and 25, Mn was added outside the range of the present invention. In both cases, good welding workability and X-ray performance were obtained, but good bending performance was not obtained. No. 26 is Li,
When Na, K and a rare earth element compound are added beyond the range of the present invention, the arc is stable, but the slag easily flows and the bead becomes convex, resulting in poor bending performance.

No. In No. 27, when the C / Al ratio is outside the range of the present invention, the weld metal structure becomes coarse, there is almost no elongation, and fracture occurs in the bending test. No. No. 28 is a case where Ti and Zr are added in excess of the range of the present invention, and the welding workability and mechanical properties are also good, but the slag removability deteriorates, slag in is likely to occur, and the bending performance is poor.

[0040]

As described above, a flux-cored wire for self-shielding arc welding, which can easily make a welded joint in a downward and horizontal posture by controlling the constitution and ratio within the range of the present invention, is provided. It was possible. With this wire, it is possible to expand the application in this field and contribute to the improvement of efficiency and cost reduction.

[Brief description of drawings]

1A to 1E show examples of wire cross-sections that can be taken in the present invention.

[Explanation of symbols]

 1 Steel skin 2 Filling flux

Claims (5)

[Claims] 1. A steel shell is filled with a flux, and the flux contains CaF ₂ and BaF ₂ as metal fluorides in a total amount of 25 to 40% (weight% based on the total weight of the flux, the same applies hereinafter) and BaF ₂ / CaF ₂ : 0.50 to less than 0.75, ₃ to 23% of iron oxide in terms of Fe ₂ O ₃ , and iron oxide / Al: 0.4 to 2.0 or less, Al, one type of Al alloy Or 9 or more in terms of Al for 2 or more
20%, 1 to 2 kinds of Mg, Mg alloy or 4 to 4 in terms of Mg
13%, one or two carbonates of Li and Ba 0.4 to 12
%, Mn or Mn alloy is 0.5 to 8% in terms of Mn, and the total amount of C in the flux including the value obtained by converting C of carbonate into C is 0.03 to 1.7% or less, balance iron and 5 % Or less of other components (including unavoidable impurities), and the flux is filled so as to be 10 to 25%. A flux-cored wire for self-shielding arc welding, comprising: 2. The following ratio of each component to the total weight of the wire is Al / (CaF ₂ + BaF ₂ ): 0.3 to 0.4, the sum of C / Al: 0.07 or more. The flux-cored wire for self-shielding arc welding according to claim 1. 3. One or more of Li, K, Na and rare earth element compounds are contained in an amount of 0.1 to 1.0% in terms of Li, K, Na and rare earth elements. The flux-cored wire for self-shielding arc welding according to claim 2. 4. The flux-cored wire for self-shielding arc welding according to claim 3, which contains 3 to 7% of Ni. 5. At least one of Zr and Ti is added to 0.
The flux-cored wire for self-shield arc welding according to claim 3 or 4, wherein the flux-cored wire contains 2 to 5%.