JPH0669634B2 - Self-shielded arc welding flux-cored wire for thin plates - Google Patents

Description

TECHNICAL FIELD The present invention relates to a self-shielded arc welding flux-cored wire that can be welded without supplying shield glass or flux from the outside, and particularly to a low current region (20).
The present invention relates to a self-shielded arc welding flux-cored wire suitable for thin sheet welding, characterized by having a bead appearance (shape) with less spatter generation at 0 A or less).

(Prior art) In recent years, the demand for thin plates (thicknesses around 0.6 to 3.2 mm) has been rapidly increasing, starting with automobiles, housing, agricultural equipment, etc., and has reached about 40% of steel material demand. . In addition, for the purpose of improving product quality such as corrosion resistance and appearance, the adoption of surface-treated steel sheets centering on galvanized steel sheets is also in progress.

Currently, the welding materials used in this field are mainly wire diameters from 0.6 mmφ to 1.2 mm from the viewpoint of improving the efficiency of welding work.
It is a small diameter solid wire of mmφ, and the gas shield arc welding method using this is adopted.

However, gas shielded arc welding with such a solid wire has the following problems: (1) Spatters are often generated and the bead appearance (shape) is poor; (2) Defects (pits, blow holes) are generated in the surface-treated steel sheet. (3) It is easily affected by wind and it is difficult to work outdoors (especially on-site welding of construction, repair welding of agricultural machinery, etc.), (4) Using expensive shielding gas (Ar, CO ₂ ). In some cases, it is necessary to make efforts to remove spatter, repair defects, and prevent wind damage, which is a problem.

(Problems to be Solved by the Invention) As a measure for solving such a problem, Japanese Patent Application Laid-Open No. 61-1691
No. 96 is proposed. However, the self-shielded arc welding flux-cored wire according to this proposal has the above-mentioned problems.
Although (1) to (4) have been almost solved, there is a drawback that the applicable plate thickness is limited due to insufficient welding workability especially in the low current region (200 A or less), and it is still in practical use. Has not arrived. Welding thin plates with a plate thickness of 0.6 to 2.0 mmt,
That is, in welding in the low current region, (i) the amount of spatter generated is very large, and (ii) the bead appearance shape is poor.
It is pointed out that the work efficiency is lower than that of the solid wire in this range.

The present invention was made in order to solve the problem in the low current region (200 A or less) of the self-shielded arc welding flux-cored wire, in which the spatter generation amount is small in the low current region, and an excellent bead appearance ( It is an object of the present invention to provide a self-shielded arc welding flux-cored wire which has a shape and is particularly suitable for welding thin plates.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present inventor has investigated a spatter generation mechanism in a low current region, and variously relates to a bead appearance shape with respect to outer metal composition, flux rate, flux composition and the like. As a result of the study, it was found that it is effective to specify the variation in the (outer skin cross-sectional area) / (wire cross-sectional area) ratio in the wire longitudinal direction and the wire moisture content, Ca content, and metal fluoride content. It was

Therefore, based on this knowledge, the general requirements for the self-shielded arc welding flux-cored wire have been studied in more detail, and as a result, the present invention has been made.

That is, the present invention, the wire moisture content is 300 ~ 1000ppm,
Steel shell with the following components in the total weight ratio to the wire, metal fluoride (converted to fluorine): 0.1 to 1.0% Ca: 0.1 to 1.5% Al: 2.0 to 4.0% Mg: 0.3 to 1.5% Mn: 0.3 to 1.8% C: 0.2-0.5% flux containing 6% as an essential component
A gist of a self-shielded arc welding flux cored wire for thin plates, which is filled so as to have a weight of 20 and has a variation of (cover cross-sectional area) / (wire cross-sectional area) ratio in the wire longitudinal direction of 0.05 or less. To do.

The present invention will be described in more detail below.

As described above, the present inventor has conducted various basic experiments in order to solve the problems of the prior art.

Variation of wire moisture and (outer skin cross-sectional area) / (wire cross-sectional area) ratio in the longitudinal direction of the wire: First, self-shield arc welding flux spatter generation mechanism in low current range (200A or less) High arc rate As a result of various studies including camera observation, most of the spatter is caused by arc instability, and as shown below, the factor controlling the low spatter is that the wire has a (skin cross-sectional area) / (wire cross-sectional area) ratio. Longitudinal variation It was recognized that wire moisture is important.

The experimental conditions (test wire, welding conditions, measuring method of spatter amount) were as follows.

[Test wire]

 Wire diameter: 1.0mmφ Hoop used: Mild steel Cross-sectional shape: Fig. 4 (A) Flux: No. 1 compound in the examples described below Flux rate: 13% [Welding condition] Welding current: 80A, Polarity: DCEN Arc voltage: Voltage for arc length of about 1 mm Welding speed: 15 cm / min Distance between tip and base metal: 15 mm Base metal: SS41 (12 mmt) Welding method: Bead-on-flate method [Method for measuring spatter amount] Method.

FIG. 1 shows the relationship between the variation in the (outer skin cross-sectional area) / (wire cross-sectional area) ratio in the wire longitudinal direction (hereinafter referred to as ΔS) and the amount of spatter generation. Here, the (outer skin cross-sectional area) / (wire cross-sectional area) ratio is measured by obtaining the outer skin area and the wire area in the wire cross section by image processing (area analysis), calculating the ratio, and measuring the variation of this ratio. Is
N = 30 was measured at 10 cm intervals in the longitudinal direction of the wire, and the maximum and minimum values of the ratio were calculated. At that time, regarding the sampling of the wire cross section, in the case of spool winding, the sampling was performed from the center of one spool, and in the case of the packed wire, the sampling was performed from the center of the storage.

From FIG. 1, it is recognized that the reduction of ΔS is effective for reducing the spatter. If ΔS is large, the current density locally changes, so the arc length fluctuates and spatter occurs.
That is, when ΔS exceeds 0.05, the variation of the arc length becomes large and the spatter increases sharply. The conventional self-shielded arc welding flux-cored wire has a ΔS of 0.07-
It was 0.08.

From this, it was found that it is important to control ΔS to be 0.05 or less in order to reduce spatter.

The ΔS can be adjusted by adjusting the production technology such as molding and wire drawing speed, the die schedule, and the wire composition such as the flux particle size.

FIG. 2 shows the relationship between the wire moisture and the amount of spatter generated. The water content here is 75 in an oxygen atmosphere.
It is the value obtained by quantifying the water extracted from the wire at 0 ° C by the Karl Fischer method.

As shown in FIG. 2, it can be seen that increasing the water content of the wire is effective in reducing spatter. The amount is effective at 300 ppm or more. Moisture has the property of increasing the spraying power and concentration of the arc, and is particularly effective for the stability of the arc in the low current region.
However, since the porosity resistance deteriorates when it exceeds 1000 ppm,
It was found that the proper range of wire moisture should be in the range of 300-1000 ppm.

As described above, the present invention, compared to the prior art,
It is characterized by (1) stabilizing ΔS and (2) adjusting the wire moisture to a higher value, which can significantly reduce the spatter generation amount, especially in the low current region. .

Ca Content, Amount of Metal Fluoride: Next, the inventor of the present invention has the second problem of bead appearance shape (uneven slag encapsulation, deterioration of appearance due to slag seizure, convex bead). As a result of various studies on the outer metal composition, flux rate, flux composition, etc., by specifying the Ca content and the amount of metal fluoride, a good bead appearance shape can be obtained even in welding in the low current region (200 A or less). I found that I could get it.

The experimental conditions (test wire, welding conditions, bead shape evaluation method) were as follows.

[Test wire]

The same wire as the above basic experiment [Welding conditions] Welding current: 80 A, Polarity: DCEN Arc voltage: Voltage that makes the arc length about 1 mm Welding speed: 15 cm / min Tip-base metal distance: 15 mm Base metal: SS41 (1.2 Welding position: T-shaped horizontal fillet [Evaluation method of bead appearance shape] Same as in the example described later, depending on bead gloss, corrugation, equipodality, flank angle θ, etc. Evaluated comprehensively.

Metal fluoride is a shielding agent and has a major slag forming action, but if it is less than 0.1% in terms of fluorine, the shield will be insufficient, and defects such as pits and blow holes will occur, and the bead shape will also deteriorate. On the other hand, if it exceeds 1.0%, the melting point of the slag is too low, so that the bead shape is deteriorated and the fume is increased. Therefore, the amount of metal fluoride is regulated within the range of 0.1 to 1.0% in terms of fluorine.

However, this metal fluoride is preferably a fluoride containing 40% or more of SrF ₂ . As described above, the metal fluoride is the main slag agent, and the physical properties of the slag differ depending on the type, so the effect on the bead shape also differs. That is, as shown in FIG. 3, 40% or more of SrF ₂ is preferable to obtain a good bead shape. As the remaining metal fluoride, any metal fluoride such as CaF ₂ , BaF ₂ , LiF ₂ , NaF, and Na ₂ SiF ₆ may be used.

Next, with respect to Ca, Ca is generally used for the purpose of acting as a deoxidizing and denitrifying agent, but in the present invention, as in the case where CaO is added as a slag agent, Ca is used as a slag agent. It is added for the purpose of effect. However, if the amount of Ca is less than 0.1%, such an effect does not occur, and if it exceeds 1.5%, fume and spatter increase, which is not preferable.
As the Ca source, an intermetallic compound such as Ca-Al, Ca-Si, Ca-Mg, and Ca-Al-Mg is used, but it is preferable to use Ca-Al from the viewpoint of workability (particularly sputtering and fume). Incidentally, for reference, CaO is effective in making the slag encapsulating property uniform, improving the peeling property, and improving the bead appearance, particularly the bead gloss and the evenness of corrugations.

Based on the above basic experiment, the main configuration of the self-shielded arc welding flux-cored wire according to the present invention is (1) that the stability of ΔS is particularly improved as compared with the conventional technique,
(2) The amount of metal fluoride is set to a low level, (3) Ca source is added, etc., which causes spatter generation and bead appearance shape in the low current range (200 A or less). In addition to welding with a plate thickness of 2.3 mm or more, it is possible to weld a thin plate with a plate thickness of less than 2.3 mm.

In order to sufficiently achieve the object of the present invention, it is necessary to further satisfy the general requirements for the self-shielded arc welding flux-cored wire, and the flux component and the flux rate are regulated as described below.

Al: Al acts as a deoxidizing and denitrifying agent, but 2.0%
If it is less than the above, welding defects such as pits and blow holes occur. On the other hand, if it exceeds 4.0%, the amount of Al remaining in the deposited metal increases, and ductility is significantly impaired, which is not preferable.
Also, the amount of fumes increases. Therefore, Al is 2.0-4.0
The range is%.

As the Al source, in addition to Me-Al, Fe-Al, Al-Li, Al
-Mg and other alloys can be used.

Mg: Mg acts as a deoxidizer, and also has the effect of generating metal vapor during welding to shield the arc column and molten pool and stabilize the arc. However, if it is less than 0.3%, the effect is not sufficient and welding defects such as pits and blow holes occur.
Also, the arc tends to be unstable. On the other hand, if it exceeds 1.5%, the blowing force of the arc becomes too strong, and the fume increases. Therefore, Mg is in the range of 0.3 to 1.5%.

As the Mg source, in addition to Me-Mg, Al-Mg, Ni-Mg, Si
Alloys such as Mg can be used.

Mn: Mn acts as a deoxidizer and is for maintaining the strength in the weld metal, but if it is less than 0.3%, the strength will be insufficient,
If it exceeds 1.8%, the strength becomes excessive and the bending ductility is impaired, so the content is made 0.3 to 1.8%.

Note that Fe-Mn, Fe-Si-Mn, or the like can be used as the Mn source.

C: C is an element for strengthening the hardness of the weld metal and has the effect of increasing the spraying force of the arc, and it is necessary to add C in the range of 0.2 to 0.4%. If it is less than 0.2%, there is no effect, the arc blowing force is weak, and the arc tends to become unstable especially in the low current region. Further, if it exceeds 0.4%, the hardness becomes excessive and the impact performance deteriorates. Further, the arc blowing force becomes too strong and the fumes increase.

As the C source, graphite, an alloy containing C, or the like can be used.

Li, Sr composite oxide: Li, Sr composite oxide F It acts as a slag-forming agent, and is effective in improving the bead appearance (gloss) and slag releasability. % Or less can be added. If it exceeds 1.0%, fumes increase, which is not desirable. Incidentally, as these composite oxides, Li ₂ SiO
₃ , LiFeO ₂ , Li ₂ MnO ₃ , Li ₂ TiO ₃ , Li ₂ ZrO ₃ , SrFe ₂ O _{4 and the} like can be used.

Rare Earth Elements: Rare earth elements (Ce, La, Sm, Y, Pr, Nd, etc.) reduce the viscosity of molten metal and slag, and are effective in improving the porosity resistance of surface-treated steel sheets such as galvanized steel sheets. If necessary, it can be added within the range of 0.2% or less. 0.2%
If it exceeds, the bead shape is deteriorated, which is not preferable.

Others: As the skin metal (band steel hoop) used in the present invention, cold-rolled steel or hot-rolled steel having good deep drawability is used from the viewpoint of formability, but is not particularly limited. . However, it is advantageous to use a method in which the amount of C is as small as possible.
Further, since Mn, Si, etc. in the metal act as a deoxidizing agent and have an effect of suppressing the generation amounts of CO and CO ₂ during the transfer of droplets, it is advantageous to contain them to some extent. However, if the content of these elements is too high, the workability will decrease.
The amount should be 2.0% or less, and the amount of Si should be 1.0% or less.

Further, the present invention can be a wire having any cross-sectional shape. For example, although four types of cross-sectional shapes of the wire are illustrated in FIGS. 4A to 4D, any of these shapes may be used.

And the wire diameter is 0.9mmφ, 1.0mmφ,
1.2mmφ, 1.4mmφ, 1.6mmφ, 2.0mmφ, 2.4mmφ, 3.2mm
It can be arbitrarily selected from φ and the like.

Further, the present invention is applicable to various steel types, mainly mild steel,
Although it is a high-strength steel, it can be expanded to low-alloy steel and high-alloy steel depending on the application.

Next, examples of the present invention will be described.

(Example) A flux-cored wire having the conditions shown in Table 1 was prepared by an ordinary method. Wire diameter is 1.2mmφ, wire cross section is 4th
The one shown in FIG. Also, mild steel is used as the outer metal of the wire, and its content components are C: 0.04%, Mn: 0.35
%, Si: 0.01%, P: 0.014%, S: 0.01%.

Then, using these flux-cored wires, a welding test was conducted under the following welding conditions.

Welding conditions Welding current: 120 A, Polarity: DCEN Arc voltage: Arc length approx. 1 mm Welding speed: 25 cm / min Chip-base metal distance: 15 mm Base metal: SS41 (12 mmt) Welding method: Downward bead-on-plate method Welding Table 2 shows the test results (spatter generation amount, bead shape, porosity resistance, welding workability, feedability, etc.).

For the measurement of the amount of spatter generated, welding is performed by the downward bead-on-plate method, and the device shown in FIG. 5 (3 is a spatter collecting plate, 4 is a wire feeding device, 5 is a torch, 6 is a base metal, 7 Indicates a trolley). That is, the amount of spatter generated was obtained by collecting spatter scattered around the arc point using the collecting plate shown in FIG. 5 and measuring the weight. The measurement time was 1 minute, and the value per unit time (g / min) was calculated.

As a method for evaluating the bead appearance shape, T-type horizontal fillet welding is performed to obtain the bead gloss, the uniform waviness, the isosceles property,
It was evaluated comprehensively by the flank angle θ.

Specifically, the gloss and corrugation of the beads were sensory evaluated.
Isopodity and flank angle θ were taken by macro sampling of the cross section (n =
3), the welded portion was enlarged and measured with a camera. That is, as shown in FIG. 6, the isosceles property is passed when the difference between the upper leg (a) and the lower leg (b) is less than 1 mm, and the flank angle θ is shown in FIG. 7 (10 is weld metal, (11 is the bond part, 12 is the heat-affected zone), the flank angle θ of the horizontal fillet weld toe is measured, and the flank angle becomes larger as the bead shape becomes worse (convex bead). Therefore, the case where θ was less than 55 ° was regarded as acceptable. Then, only when all of the bead gloss, the evenness of the corrugations, the isoscelesity, and the flank angle θ were satisfied, the comprehensive evaluation was ◯ (good).

The porosity resistance was evaluated by the X-ray transmission result of the downward bead-on welded portion.

From Table 2, the following is considered.

No. 1 to No. 6 are examples of the present invention, in which the generation of spatter is extremely small in the low current region and the bead shape is excellent. Of course, defects such as pits and blow holes do not occur, and welding workability and feedability are good.

No. 7 to No. 8 are comparative examples in which the amount of wire moisture is out of the range of the present invention.If the amount of wire moisture is too small, spatter increases, and if it is too large, welding defects such as pits and blow holes occur. Poor porosity resistance.

No. 9 is a comparative example in which the variation ΔS of the (outer skin cross-sectional area) / (wire cross-sectional area) ratio in the wire longitudinal direction is too large, and the arc fluctuates, so that the spatter increases.

No. 10 to No. 11 are comparative examples in which the flux filling rate is out of the range of the present invention. If the flux filling rate is too small, the arc stability is poor and the spatter is slightly increased. If it is too large, the wire becomes soft and feeding problems (breakage, etc.) occur.

No. 12 to No. 13 are comparative examples in which the amount of metal fluoride is out of the range of the present invention. If it is too small, the shield becomes insufficient and welding defects (pits, blow holes) occur. If the amount is too large, the bead shape deteriorates, resulting in convex beads.

Nos. 14 to 15 are comparative examples in which the amount of Al in the flux is out of the range of the present invention, and if it is too small, pits and blow holes are generated. If it is too large, the ductility and toughness deteriorate and the fume also increases.

No. 16 to No. 17 are comparative examples in which the amount of Mg in the flux is out of the range of the present invention, and when it is too small, deoxidation becomes insufficient and pits and blowholes occur. Furthermore, the arc is also somewhat unstable. On the other hand, if too much, fumes increase.

No. 18 to No. 19 are comparative examples in which the amount of Mn in the flux is out of the range of the present invention. If it is too small, the strength becomes insufficient, and if it is too large, the bending ductility deteriorates.

No. 20 to No. 21 are comparative examples in which the amount of Ca is out of the range of the present invention, and if the amount is too small, the slag has poor releasability, the bead gloss and the uniformity of the corrugation deteriorate, and if the amount is too large, fume, Spatter increases.

No. 22 to No. 23 are comparative examples in which the amount of C in the flux is out of the range of the present invention. If it is too small, the arc becomes unstable, and if it is too large, fumes increase and toughness deteriorates.

(Effects of the Invention) As described in detail above, according to the present invention, in short, it is possible to obtain a stable ratio of the variation ΔS in the wire longitudinal direction of the (outer skin cross-sectional area) / (wire cross-sectional area) ratio and to increase the wire moisture content. Adjusting to the eyes, setting the amount of metal fluoride to a low level, Ca
By including a source, it is possible to significantly improve the generation of spatter and the bead appearance shape in the low current range (200 A or less), which is a problem of conventional self-shielded arc welding flux-cored wire. This greatly contributes to expanding the applications of arc welding flux-cored wires.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the variation ΔS in the wire longitudinal direction of the (outer skin cross-sectional area) / (wire cross-sectional area) ratio and the amount of spatter generation, and FIG. 2 is a diagram showing the relationship between the wire moisture and the amount of spatter generation. FIG. 3 is a diagram showing the relationship between the amount of metal fluoride and the proportion of SrF ₂ and the bead shape. FIGS. 4 (A) to 4 (D) are schematic cross-sectional views showing an example of the wire cross-sectional shape, and FIG. It is a figure which shows a collecting device, (a) is a side view, (b) is a top view, FIG. 6 is a figure explaining the upper leg and lower leg of a bead, FIG. 7 shows the flank angle in a heed shape evaluation method. It is a figure explaining. 1 ... Skin metal, 2 ... Flux, 3 ... Sputter collection plate,
4 ... Wire feeding device, 5 ... Torch, 6 ... Base material, 7 ... Truck, 8 ... Truck driving device, 9 ... Weld metal, 10 ... Bond part,
11 ... Heat affected zone.

Claims (2)

[Claims] 1. A wire moisture content of 300 to 1000 ppm, and a flux containing 6 to 20 weight of flux containing the following components as essential components in the total weight ratio of the wire to the steel shell, and ( A self-shielded arc welding flux-cored wire for thin plates, which has a variation in the longitudinal direction of the wire of the ratio of the cross-sectional area of the sheath / the cross-sectional area of the wire of 0.05 or less. Metal fluoride (calculated as fluorine): 0.1 to 1.0% Ca: 0.1 to 1.5% Al: 2.0 to 4.0% Mg: 0.3 to 1.5% Mn: 0.3 to 1.8% C: 0.2 to 0.5% 2. In the flux, Ca-as a Ca source
The self-shielding arc welding flux-cored wire for thin plates according to claim 1, wherein Al is used.