JP2519308B2 - Self shielded arc welding flux cored wire - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a self-shielded arc welding flux cored wire, and particularly to a self-shielded arc welding flux cored that can stably obtain a sound weld portion without welding defects. Regarding wires.

(Prior art and problems to be solved) Self-shielded arc welding is easy to handle because there is little risk of defects such as pits and blowholes caused by wind, and no external shielding gas is required. It has the characteristics suitable for outdoor welding and can be said to be a welding method suitable for construction sites.

However, although self-shielded arc welding has the above-mentioned advantages, it requires a high level of welding skill because the workability changes significantly depending on the welding conditions, and welding defects (slag inclusion, It can be said that it is extremely difficult to obtain a sound welded portion because there are many opportunities for fusion failure). Defects are likely to occur particularly in a horizontal posture commonly used on construction sites. For this reason, gas shielded arc welding is applied to welding at construction sites.

However, in gas shielded arc welding, it is necessary to take measures to prevent wind because it is easily affected by wind, and there is a drawback that the welding operation must be interrupted especially when the wind speed is strong.

Under these circumstances, the development of a self-shielded arc welding wire that can easily obtain a sound weld is desired, and various proposals have been made in the past. For example, Japanese Patent Publication No.
No. 479 and the like have been proposed, but they are not always sufficient for horizontal welding.

The present invention eliminates the disadvantages of the prior art, and the occurrence rate of welding defects is extremely small even in multilayer welding in a horizontal position,
It is an object of the present invention to provide a self-shielded arc welding flux-cored wire having excellent welding performance such as toughness and bending ductility.

(Means for Solving the Problem) In order to achieve the above-mentioned object, the present inventor first analyzed factors that cause a welding defect in a welded portion using a conventional self-shielded arc welding flux-cored wire, and found the following: It was found that welding defects are likely to occur due to such factors.

Since the bead is convex, a narrow groove is formed between the bead and slag inclusion or poor fusion occurs.

A cold wrap is formed because the bead is easy to sag.

Due to the poor bead alignment, irregularities may occur, causing poor fusion and slag inclusion.

Since the slag is seized on the bead, it is difficult to sufficiently remove the slag, and when welding is performed on the slag that has been seized, slag inclusion or cold wrap is likely to occur.

Since the arc is not stable, it is difficult to obtain a stable penetration or a stable molten state, which easily causes welding defects.

If the protruding length of the wire is short, or if the arc voltage is too high, pits are generated, and the pits are weak to condition fluctuations and the range of welding conditions is narrow.

Among these factors, it is considered that ~ is due to the physical properties of the slag, ~ is due to the stability of the flux rate, and ~ is due to the shielding properties.

Therefore, the present inventor has intensively studied based on the knowledge that a sound welded part can be obtained by creating a flux-cored wire having a stable flux rate while enhancing the shielding properties and giving appropriate properties to the slag. Was piled up.

As a result, it was found that it is possible to adjust the flux rate by adjusting metal fluoride, metal carbonate, Li, deoxidizer, iron powder, etc. as essential components as a flux to be filled in the steel sheath, and regulating the flux rate. The present invention has been made.

That is, the self-shielded arc welding flux-cored wire according to the present invention has, in the steel shell, metal fluoride: 18 to 30%, metal carbonate: 2 to 15%, Li: 0.1 to 4%, Al: 8 to 15%, Mg: 3 to 10%, Mn: 0.2 to 8%, iron powder: 30 to 60%, but the flux ratio of the flux containing metal fluoride / iron powder: 0.4 to 0.7 as an essential component It is characterized by being filled so as to be 17 to 23% by weight.

 The present invention will be described in more detail below.

(Operation) First, the reasons for limiting the components of the flux used in the self-shielded arc welding flux cored wire of the present invention will be described.

Metal Fluoride: Metal Fluoride is a shielding agent as well as a main slag forming agent, and is added in the range of 18 to 30%.

The larger the amount added, the more the shielding effect increases, but the amount of spatter and fume becomes too large, and the welding workability is significantly impaired. And, if the amount exceeds 30%, the melting point of the slag is raised,
Beads tend to hang down when welding in a horizontal position, etc.
It also causes cold wrap. From the viewpoint of shielding properties and workability, the optimum content is 20 to 26%,
Below the upper limit is acceptable. On the other hand, the smaller the amount of metal fluoride, the better the workability tends to be. However, if it is too small, the shield becomes insufficient and defects such as pits and blow holes occur. Therefore, it is desirable to keep the lower limit to 18%.

Although various kinds of metal fluorides can be used, fluorite (CaF ₂ ) is most preferable from the viewpoint of slag removability and moisture absorption resistance. A part of this fluorite amount is LiF, K ₂ SiF ₆ , NaF,
If it is replaced with BaF ₂ etc., it has a favorable effect such as smooth droplet transfer and improved spraying etc., but if it is too large, it will impair the slag peeling property etc., and rather the spatter amount will increase, so the replacement amount is 10%. The following is recommended.

Metal carbonate: Metal carbonate has an effect of improving the slag peeling property and the slag viscosity. Therefore, a shiny bead surface is obtained and the bead sag is improved,
A uniform and smooth bead shape is obtained. Further, it also acts as a shielding agent. For this purpose, the metal carbonate is added in the range of 2 to 15%.

The larger the amount added, the better the slag peelability, bead shape, and shielding properties are improved, but if it exceeds 15%, the decomposition gas (CO ₂ ) generated during welding will cause remarkably large spatters. Sexually undesirable. The optimum amount is 4-7
%, But up to 15% is acceptable. On the other hand, the content is 2
%, The slag tends to seize and the viscosity of the slag decreases, so that a uniform and smooth bead shape cannot be obtained.

As the metal carbonate, CaCO ₃ is most suitable, but BaCO ₃ , SrCO ₃ , LiCO _{3 and the} like can be used in combination of one or more.

Li: Li has an effect of suppressing the generation of pits due to variations in arc voltage and protrusion length, so that Li is added in the range of 0.1 to 4%.

Figure 1 shows the results of a bead-on-plate welding method for a self-shielded arc welding flux-cored wire that does not contain Li. It shows the situation in which pits occur when the protruding length becomes shorter. .

From the results of FIG. 1, FIG. 2 shows the results of testing a self-shielded arc welding flux-cored wire containing Li as a protruding length (15 mm) in which pits are likely to occur. From the figure, it can be seen that Li is effective in suppressing pits and expanding the arc voltage range. However, if it is less than 0.1%, the effect is small, and if it exceeds 4%, the slag flows easily. Particularly in the horizontal welding, the bead sags and becomes convex, which is not preferable.

Note that Li itself is not suitable as a raw material because of its strong reaction with the atmosphere. Therefore, it is preferable to use a powder alloyed with another metal as the raw material of the Li source.
Is the best. In this case, the Li content of Al-Li is 1.5 to 6
% Is preferable. If it is more than 6%, the reaction with the atmosphere becomes intense and the explosiveness also increases, which is not preferable.

As the raw material of the Li source, in addition to Al-Li, lithium carbonate,
Lithium ferrite, lithium manganate, lithium zirconate, lithium silicate and the like can be used. It should be noted that lithium carbonate decomposes to generate CO ₂ and increases the generation of spatter, so it is preferable to suppress it to 10% or less. Al-
By appropriately using Li, lithium carbonate, or a compound other than lithium carbonate, pit resistance can be improved over a wide range of conditions without impairing workability.

Al: Al acts as a deoxidizer and fixes N that has penetrated into the deposited metal to prevent pits and blow holes, so it is added in the range of 8 to 15%. However, if it is less than 8%, pits and blow holes are generated and a sound welded portion cannot be obtained. If it exceeds 15%, Al remaining in the deposited metal
Is increased, so that the crystal grains become coarse and the ductility is remarkably impaired. As the Al raw material, it is desirable to use not only metallic aluminum but also alloys such as Fe-Al, Al-Mg, and Al-Li.

Mg: Mg becomes vapor and shields the welded part and also acts as a deoxidizer, so it is added in the range of 3 to 10%.
However, if it is less than 3%, it is difficult to suppress pits and blow holes. Further, excessive addition lowers the viscosity of the slag, promotes dripping of the bead, and significantly increases the amount of fume. Therefore, addition exceeding 10% is not preferable. As the Mg raw material, in addition to Mg powder, Al-Mg, Fe-Si-Mg, Ni-Mg
Etc. are most suitable.

Mn: Since Mn acts as a deoxidizing agent and gives a proper tensile strength to the deposited metal, it is added in the range of 0.2 to 8%. However, if it is less than 0.2%, the tensile strength will be insufficient, and if it exceeds 8%, the tensile strength will be excessive and bending and ductility will be significantly impaired, such being undesirable. In addition to Mn powder as the Mn raw material,
Alloys such as Fe-Mn and Fe-Si-Mn are suitable.

Iron powder: Iron powder stabilizes the flux rate because it increases the fluidity of the flux. It is considered that the function at the time of welding plays a role of heat conduction and promotes melting of metal fluoride. Therefore, iron powder stabilizes the arc and provides a stable molten state. However, when it is less than 30%, generation of flux columns is observed, which is not preferable for suppressing welding defects, and there is a problem of an increase in spatter. On the other hand, if it exceeds 60%, the amount of the bandit fluoride added is relatively decreased, which causes problems such as lowering of the shield, which is not preferable. The bulk specific gravity of the iron powder is desirably 2.5 to 3.7%, and there is no particular restriction on the components.

The present inventor investigated the welding phenomenon in relation to metal powder, which is the main slag forming agent for iron powder, and found that the ratio of (metal fluoride) / (iron powder) was closely related to the arc state. Was found to be extremely effective in the range of 0.4 to 0.7.

That is, as shown in FIG. 3, (metal fluoride) /
If the ratio of (iron powder) exceeds 0.7, the stability of the arc is impaired and the amount of spatter generated tends to increase. On the other hand, 0.
If it is less than 4, the formation of flux pillars is recognized and the defective shield occurs. The fact that this ratio is defined is also a feature of the present invention.

The desired welding performance can be obtained by filling a flux having the above composition into a steel outer shell at the following flux rate.

Flux rate: The flux rate in the wire composition should be kept in the range of 17-23%. If it is less than 17%, the required slag amount cannot be secured, so that the workability is deteriorated. On the other hand, if it exceeds 23%, wire breakage occurs during wire drawing, and efficient production cannot be performed.

In the present invention, a flux-cored wire can be manufactured by adding the following components as needed.

Ni: Ni improves toughness, so 0.2 per total wire weight
It can be added in the range of 3%. But 0.2%
If it is less than 3%, the effect cannot be obtained, and if it exceeds 3%, the tensile strength of the deposited metal becomes excessive and the toughness is impaired.

Moisture content of wire: Moisture content of wire is recommended in the range of 300-2000ppm.
If it is less than 300 ppm, there will be problems in terms of shielding properties, and if it exceeds 2000 ppm, there will be problems in terms of pit resistance and cracking. The water content of the wire is a value measured according to JIS K 0113 (1979).

The wire of the present invention is one in which a flux mixed with the above components is filled in a steel outer cover, but the chemical composition of the outer cover is not particularly limited, but Si: 1% or less, Total N: 100.
It is desirable that the composition be less than ppm. These components tend to affect the arc characteristics and increase the amount of spatters generated. In particular, N causes pits and blowholes. Therefore, it is desirable to regulate N as described above.

The method for manufacturing the self-shielded arc welding flux-cored wire of the present invention is not particularly different from the method for manufacturing a normal flux-cored wire, and can be manufactured in the same manner.

Also, the cross-sectional shape of the wire is not particularly limited, and the cross-sectional shape illustrated in FIG. 4 can be used. (B) is good in terms of workability.

The wire diameter may be any of 1.2 to 2.4 mmφ, but 1.6 mmφ and 2.0 mmφ are particularly preferable in terms of ease of use and performance.

The target steel types are mild steel, HT-50, and low temperature steel, but there are no particular restrictions.

 Positive polarity (DCEN) is desirable.

 Next, examples of the present invention will be described.

(Example) Based on the specifications shown in Table 1 and Table 2, wire diameter 2mmφ
A flux-cored wire was prepared. The wire cross-sectional shape is as shown in Fig. 4 (c), and the steel shell component is C: 0.07.
%, Mn: 0.3%, Si: 0.1%, Cr: 0.05%, TN: 70 ppm and the like.

Then, using this flux-cored wire, semi-automatic welding of a 25 mmt V-shaped groove (gap 6 mm, groove angle 35 °) was performed in a horizontal position, and the performance and workability of the welded portion were investigated.
The welding conditions are DCEN, 300A-24 to 26V. The evaluation of workability was observed when the test plate was prepared.

Table 3 shows the test results and is considered as follows.

No. 1 to No. 10 are examples of the present invention, and all of them have excellent workability (bead shape, slag peeling property, arc stability, spatter, pit) and welding performance (strength, bending ductility, toughness, Welding defects are also excellent, and good results are obtained.

No. 11 to No. 12 are comparative examples in which the compounding ratio of the metal carbonate is not appropriate, and if too much, arc instability, large amount of spatter, and poor welding performance. If it is too small, the Vito shape and slag removability are poor, and the welding performance is also poor.

Nos. 13 to 14 are comparative examples in which the compounding amount of the metal fluoride is not appropriate. If the amount is too large, the spatter is large and the welding workability is poor. If the amount is too small, welding defects increase.

Nos. 15 to 16 are comparative examples in which the amount of Li is not appropriate. If the amount is too small, there are many pits and the welding performance is not good.
If it is too large, the beat shape is poor and the welding performance is poor.

Nos. 17 to 18 are comparative examples in which the ratio of (metal fluoride) / (iron powder) is not appropriate. If this ratio is too high, the amount of spatter is large, and if it is too small, the welding performance is poor.

No. 19 ~ No. 20 is a comparative example in which the mixing ratio of Mg and Al is not appropriate, No. 21 ~ No. 22 is a comparative example in which the mixing amount of Mn and Ni is too large, No. 23 ~ No. No. 24 is a comparative example in which the compounding ratio of iron powder is not appropriate, and no good result was obtained in any of the comparative examples.

Further, No. 25 is a comparative example in which the flux rate is not suitable, and good results were not obtained.

(Effects of the Invention) As described in detail above, according to the self-shielding arc welding flux-cored wire of the present invention, a sound weld can be easily obtained, and particularly in the conventional self-shielding arc welding, the welding performance ( It is possible to significantly improve the soundness of the lateral welded portion where defects (bending performance, etc.) are not sufficiently ensured.

[Brief description of drawings]

FIG. 1 is a diagram showing a pit generation situation due to a change in protrusion length in a conventional flux-cored wire (without Li addition), and FIG. 2 is a Li content, the number of pits, and pits in the flux-cored wire of the present invention. FIG. 4 is a diagram showing the relationship of the upper limit voltage at which no generation of hydrogen, FIG. 3 is a diagram showing the relationship between the ratio of (metal fluoride) / (iron powder) and the amount of N in the sputter and deposited metal, FIG. )-(D) is a figure which shows an example of the cross-sectional shape of a flux cored wire. 1 ... Skin metal, 2 ... Flux.

Continuation of the front page (56) Reference JP-A-58-148095 (JP, A) JP-A-61-286090 (JP, A) JP-B 52-26498 (JP, B2) JP-B 52-26221 (JP , B2)

Claims (4)

(57) [Claims] 1. A positive self-shielding arc welding flux cored wire for multi-layer welding in a horizontal position, wherein a weight% (hereinafter the same) metal fluoride: 18 to 30%, metal carbonate: 2-15%, Li: 0.1-4%, Al: 8-15%, Mg: 3-10%, Mn: 0.2-8%, Iron powder: 30-60%, provided that metal fluoride / iron powder: Flux rate of 17 to 23% by weight of flux containing 0.4 to 0.7 as an essential component
A self-shielded arc welding flux-cored wire that is filled so that 2. The flux-cored self-shielded arc welding wire according to claim 1, comprising 0.2 to 3% of Ni based on the total weight of the wire. 3. The self-shielded arc welding flux-cored wire according to claim 1, wherein the water content of the wire is 300 to 2000 ppm. 4. An Al--Li alloy as a Li source (Li content: 1.5 to 6.
5%) Self-shielded arc welding flux cored wire according to claim 1, wherein powder is used.