JP2003311468A - Flux cored wire for gas-shielded arc welding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flux cored wire for gas-shielded arc welding which can exhibit satisfactory wire feedability without causing the cut of lubrication even in a severe using environment where feed resistance is made high, e.g. by the curve of a liner. <P>SOLUTION: The flux cored wire for gas-shielded arc welding is obtained by packing an outer skin made of steel with flux. In the wire, Si and Mn are contained by 0.4 to 1.4 mass% in terms of Si+0.2Mn in the outer skin made of steel. The surface of the steel base is provided with cracks by grain boundary oxidation. Further, the coating weight of a feeding lubricant is 0.1 to 2.0 g per 10 kg of the wire. The charging ratio of the flux is 3 to 20 mass%. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flux-cored wire for gas shielded arc welding, which is excellent in wire feedability and is used for fully automatic and semi-automatic welding.

[0002]

2. Description of the Related Art A flux-cored wire for gas shielded arc welding has a stable arc due to the addition of a slag-forming agent and an arc stabilizer as compared with a solid wire, which enables welding with a small amount of spatter, and produces beads. The appearance is beautiful because it is completely covered by slag. Therefore, the flux-cored wire for gas shielded arc welding (hereinafter referred to as the flux-cored wire) is widely used for welding steel structures in various industrial fields such as shipbuilding and steel bridge fields.

The flux-cored wire is used for welding in a form wound on a spool or loaded in a pail pack. When using this flux-cored wire, pull out the wire from the spool or pail pack by the feeding roller of the feeder and push it into the liner enclosed in the subsequent conduit cable, then through this liner to the end of the conduit cable. The method of feeding to the feeding tip inside the attached welding torch is adopted. The flux-cored wire is subjected to arc welding by applying a voltage between the power feed tip and the material to be welded.

The liner used here is a flexible guide tube formed by spirally forming a steel wire, and its length is usually about 3 to 6 m, but 10 to 20 m in the case of wide area welding. It is a long type and is selected and used according to the distance to the welding point. According to this method, a conduit cable (liner) can be used even if the welding location is narrow or has a height difference, such as a shipbuilding site.
There is an advantage that welding can be performed relatively easily by following the above.

In order to carry out stable welding, it is necessary that the flux-cored wire is supplied to the welded portion at a predetermined constant speed, that is, the wire feedability is good. The wire is pushed into the liner by the feeding force of the feeding roller, while the liner inner surface receives a feeding resistance due to contact friction. At this time, when the liner is in a relatively gentle use environment in which the liner is in a straight line state, the feeding resistance is not so large and the wire feeding property does not occur. But on the other hand,
In a severe operating environment where there are many bending points, the bending radius (curvature radius) is small, or the liner is elongated, the feeding resistance increases and the balance with the feeding force is lost.
Wire feedability deteriorates.

The surface condition of the flux-cored wire has a great influence on the quality of the wire feeding property. That is, when the feed resistance increases, if the amount of lubricant on the wire surface is small, the feed rate becomes unstable, and the wire feedability deteriorates. Further, the wire is buckled in the liner, the wire surface is scraped by the feeding roller, and the shavings enter the liner and accumulate, so that the feeding resistance is further increased. . On the contrary, if the amount of lubricant on the wire surface is large, the amount of slip of the wire in the feeding roller portion increases, and the wire cannot maintain a predetermined feeding speed, resulting in poor wire feeding performance. As a result, problems such as destabilization of the welding arc, uneven bead shape, defective fusion, and undercut occur.

There are few welding sites where the conduit cable is used in a straight line state, and it is usual to weld the work while bending the conduit cable in a complicated and complicated place. There has been a strong demand for flux-cored wires with good feedability.

Conventionally, in order to secure the wire feeding property, various lubrication treatments have been performed on the wire surface. For example, Japanese Examined Patent Publication No. 50-3256 discloses a wire having a dense and smooth surface coated with lubricating oil. However, if the wire surface is dense and smooth, it is difficult to apply a predetermined amount of lubricating oil evenly and stably, and in order to obtain a wire with good feedability, there is no choice but to apply a large amount of lubricating oil. Absent. However, for wires with a lot of lubricating oil on the surface, as described above, the wires tend to slip at the feed roller due to the increase in feed resistance, which makes it difficult to deal with bending of the conduit liner, etc. There is a drawback that the material quality of the weld metal deteriorates due to an increase in the amount of diffusible hydrogen.

On the other hand, as an example of using a solid lubricant, JP-A-50-146541 discloses that a main component is a mixture of molybdenum disulfide powder and graphite powder, or a mixture thereof and one or more flux components. A method for manufacturing a wire drawn by a wire drawing agent is disclosed. Further, in Japanese Patent Application Laid-Open No. 58-135795, either one of graphite and molybdenum disulfide is attached to the wire surface.
A wire is disclosed which comprises only a mixture of seeds or both and 10 to 60% by weight of glass powder, the amount of said lubricant being 5 x 10 ^{-2 to} 5 x 10 ^-2 % of the weight of the wire. There is.

However, with the above technique, it is difficult to control the amount of lubricant adhered, and there are problems that excessive lubricant adheres to some spots and that the lubricant adheres unevenly after wire drawing. Excessive lubricant buildup can cause blockages in the liner, making wire feeding difficult.
Further, if the lubricant is unevenly attached, it becomes difficult to perform stable feeding.

Therefore, a technique has been proposed in which the roughness of the surface of the wire is increased and the lubricating oil is retained in the recesses so that the lubricating oil can be applied stably and evenly in the longitudinal direction of the wire. For example, Japanese Patent Publication No. 1-15356 discloses that
A technique is disclosed in which the surface of the wire is covered with porous plating having a porosity (5 to 50%) and the plated layer contains a lubricating oil. Further, Japanese Patent Publication No. 58-56677 discloses a manufacturing technique for increasing the roughness of the wire surface by increasing the lubricating oil pressure and forcibly lubricating the wire, and drawing the wire with a hole die.

However, in Japanese Patent Publication No. 1-15356, it is difficult to control the plating, and the plating layer is made porous while the wire surface is flat, so that the roughness in the depth direction can be obtained. It's hard to be beaten. In addition, Japanese Patent Publication Sho 58-5
In the case of Japanese Patent No. 6677, although the flatness of the wire surface can be made small, it is still difficult to obtain the roughness in the depth direction. Therefore, the balance between the feeding force of the wire feeding roller and the frictional resistance in the liner is required. It is not possible to maintain a good wire feedability that is fixed.

[0013]

SUMMARY OF THE INVENTION Therefore, the present invention has a crack effective on the surface of the wire as a reservoir for the lubricant to be fed, and by stably depositing the lubricant to be fed, it is possible to feed it by bending the liner or the like. An object of the present invention is to provide a flux-cored wire for gas shielded arc welding, which can exhibit good wire feedability without causing lubrication even in a severe operating environment where resistance becomes high.

[0014]

SUMMARY OF THE INVENTION The gist of the present invention is a flux-cored wire for gas shielded arc welding in which a steel sheath is filled with flux.
It contains 0.4 to 1.4 mass% of n in Si + 0.2Mn, has cracks due to grain boundary oxidation on the surface of the steel base material, and has a feed lubricant adhesion amount of 0.1 to 2.0 g per 10 kg of wire. It is a feature. In addition, it is also characterized in that the flux filling rate is 3 to 20% by mass.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
In order for the flux-cored wire to have good feeding performance, the feeding lubricant (lubricating oil, solid lubricant) effective for the wire feeding property should be applied uniformly and stably in the longitudinal direction of the wire. is necessary. For that purpose, it is necessary to form a lubricating oil reservoir on the wire surface.

For this purpose, in the present invention, the surface of the steel base of the steel shell has cracks due to intergranular oxidation, and the feed lubricant is held uniformly and firmly. The method for producing a flux-cored wire having cracks due to grain boundary oxidation on the surface of the steel body of the steel shell of the present invention is as follows. First, the wire shell (2-4 mm in diameter) after filling the steel shell with flux is subjected to a batch furnace or Using a continuous annealing furnace, it is annealed at 600 to 900 ° C. for 3 to 480 minutes to oxidize the grain boundaries of the steel outer surface layer. After removing the scale on the wire surface by pickling, cracks are generated on the surface of the steel substrate from grain boundaries hardened by oxidation in the wire drawing step, and a feed lubricant is applied to the wire surface. As described above, in order to oxidize the grain boundaries in the furnace, the annealing atmosphere is preferably weakly oxidizing. Therefore, for example, N ₂
An atmosphere containing oxygen within a few percent is used. It is also possible to apply a potassium carbonate solution or the like to the wire and anneal it in N ₂ to make the surface of the wire weakly oxidizable by the generated CO ₂ .

In order to oxidize the grain boundaries in the surface layer of the steel skin in the above annealing step, Si, which is a component that promotes grain boundary oxidation, is used.
And Mn must be contained in appropriate amounts in the steel skin. The amount of Si and Mn in the steel shell is Si + 0.2Mn and is 0.4-
1.4% by mass. Si + 0.2Mn is 0.4 mass%
If it is less than the above range, the grain boundaries of the surface layer of the steel skin cannot be oxidized in the annealing step, and cracks due to grain boundary oxidation do not occur on the surface of the steel base of the steel skin. Therefore, since no cracks are formed on the wire surface as a lubricating pool, the feed lubricant cannot be applied uniformly and stably in the longitudinal direction of the wire, the friction resistance in the liner increases during wire feeding, and the feed roller The wire starts to slip at the section. On the contrary, when Si + 0.2Mn in the steel shell exceeds 1.4 mass%, cracks due to intergranular oxidation occur on the steel base surface of the steel shell,
The diameter of the wire drawing process reduces the hardness of the steel shell, causing wire breakage and degrading productivity. In addition, the weld metal components Si and Mn
Adjustment becomes difficult, the strength of the weld metal increases, and the toughness decreases.

In addition to Si and Mn, the steel shell has a C, N content within a range that does not deteriorate wire drawability and weld metal performance.
i, Cr, Mo, Ti, Al, etc. can be included.

In the present invention, the feed lubricant is attached to the surface of the flux-cored wire. The feed lubricant referred to in the present invention means a lubricating oil and a solid lubricant. These feed lubricants are uniformly and firmly retained by cracks due to grain boundary oxidation on the surface of the steel base material. The feed lubricant adheres to the surface of the wire to reduce the friction coefficient between the inner wall of the liner and the wire, and suppresses an increase in feed resistance, thereby ensuring good wire feedability of the flux-cored wire.

The amount of the lubricant fed is required to be 0.1 to 2.0 g (hereinafter referred to as g / 10 kgW) per 10 kg of wire. Adhesion amount of feed lubricant is 0.1g / 10kgW
If it is less than the above, the effect of suppressing the increase of the feeding resistance is not recognized, and the improvement of the wire feeding property cannot be expected. On the other hand, when it exceeds 2.0 g / 10 kgW, it excessively adheres to the surface of the wire, and the wire largely slips at the feeding roller portion, which makes stable feeding of the wire difficult. Further, the inside of the liner is polluted, and the feeding failure due to the clogging of the lubricant occurs. Further, in the case of lubricating oil, it is thermally decomposed during welding to generate a large amount of hydrogen, so that deterioration of the material of the weld metal due to an increase in the amount of diffusible hydrogen is likely to occur.

The lubricating oil may be animal or vegetable oil, mineral oil or synthetic oil. Palm oil as animal and vegetable oil,
Rapeseed oil, castor oil, pork oil, beef oil, fish oil and the like can be used, and as mineral oil, machine oil, turbine oil, spindle oil and the like can be used. As synthetic oils, hydrocarbon-based, ester-based,
Polyglycol type, polyphenol type, silicone type,
Fluorocarbon type etc. can be used. In order to further improve the lubricating performance in the lubricating oil, various fatty acids and other oiliness agents and phosphorus-based, chlorine-based, and sulfur-based extreme pressure additives may be added, and the oxidation of the lubricating oil is prevented. For this purpose, an additive (antioxidant) may be added. Here, the desirable amount of lubricating oil adhered is preferably 0.05 to 2.0 g / 10 kgW. It has the function of reducing the friction coefficient between the die and the wire during wire drawing as well as the feed lubricant.

The solid lubricant is a solid lubricant containing one or two kinds of MoS ₂ and WS ₂ , and other components include polytetrafluoroethylene (hereinafter referred to as PTFE), graphite, dry lubricant and the like. To be The amount of solid lubricant adhered to the wire 1 is
It is preferable to set it to 0.05 to 1.0 g / 10 kgW per 0 kg. In addition, the amount of the lubricant to be fed was analyzed by chemical analysis (toluene
It can be measured by the ether extraction method).

The flux-cored wire of the present invention comprises a slag forming agent, a deoxidizing agent, and a flux as a flux to be filled in the steel shell.
Use a flux containing an appropriate amount of alloying agent, iron powder and arc stabilizer. The filling rate of the flux with which the steel shell is filled is 3 to 20% by mass. If the flux filling rate is less than 3% by mass, it is difficult to fill the flux at the time of production and productivity is deteriorated. On the other hand, the flux filling rate is 20% by mass
If it exceeds, the outer skin thickness becomes thin in the wire drawing step, and cracks due to the grain boundary oxidation on the surface of the steel base material of the steel outer skin serve as a starting point to cause wire breakage and deteriorate productivity.

The flux-cored wire of the present invention may have a steel outer shell with or without a seam. However, it is necessary to anneal the flux-filled wire element wire in order to oxidize the grain boundaries of the steel element surface of the steel shell, and to remove the scale generated on the wire element wire surface by annealing.
At this time, since the scale generated on the surface of the wire strand is removed by pickling from the viewpoint of manufacturing cost, it is preferable to use a seamless flux-cored wire having no opening in the steel shell.

Further, the flux-cored wire of the present invention can be manufactured with or without plating treatment on the wire surface, and in any case, it has cracks due to grain boundary oxidation as a feed lubricant reservoir on the surface of the steel base material. Therefore, the wire feedability during welding is good.

[0026]

The present invention will be described in detail below with reference to examples. A steel shell having the components shown in Table 1 was filled with a flux containing a slag forming agent, a deoxidizing agent, iron powder and an arc stabilizer, rolled to a wire having a diameter of 3 mm, and potassium carbonate was applied to the steel shell in a nitrogen atmosphere at 650. JI with wire diameter 1.2 mm, annealed in a batch furnace at ~ 750 ° C for 60 to 240 minutes, pickled and drawn.
Various flux-cored wires corresponding to YFW-C50DR specified in SZ3313 were manufactured as prototypes. The feed lubricant shown in Table 1 was applied to the wire surface during and after wire drawing.

[0027]

[Table 1]

The wire feedability evaluation test was carried out using the apparatus shown in FIG. In FIG. 1, the spool-wound flux-cored wire 2 set in the feeder 1 is the feeding roller 3
And is fed to the welding torch 5 at the tip of the conduit cable 4 through the liner included in the conduit cable 4. Then, bead-on-plate welding was performed between the energizing tip and the steel plate 6. The conduit cable 4 has a length of 6 m, and is provided with a curved portion 7 in which two loops having a diameter of 75 mm are formed in order to give a feeding resistance to the wire.

The feeder 1 has a peripheral velocity Vr (=
A set wire speed detector (not shown) and a wire actual speed (Vw) detector 8 are provided. The slip ratio Sl of the feedability evaluation index is Sl = (Vr-Vw) / Vr × 100%
It is represented by. Further, the reaction force received from the liner by the wire at the time of feeding by the load cell 9 provided in the feeding roller portion was detected as the feeding resistance R. When the feeding resistance R is 6 kgf or less and the slip ratio Sl is 10% or less, it is determined that the feeding performance is good. The wire feedability test was conducted under the welding conditions shown in Table 2.
After welding for 0 minutes, the feed resistance R and the slip ratio Sl were measured to obtain an average value. The results are shown in Table 3.

[0030]

[Table 2]

[0031]

[Table 3]

In the table, wire symbols W1 to W6 represent the present invention,
Wire symbols W7 to W12 are comparative examples. The wire symbols W1 to W6 of the present invention are Si + 0.2Mn of the steel outer shell.
Since the amount is appropriate, the steel base surface has cracks due to grain boundary oxidation, and the feed lubricant adhesion amount and the flux filling rate are in the appropriate range. Therefore, there is no problem such as disconnection at the time of manufacture and the productivity is good, and in the wire feedability test, both the feed resistance R and the slip ratio Sl are low, and the wire feedability is excellent, which is a very satisfactory result. .

In the comparative example, the wire symbol W7 is S of the steel outer sheath.
Since the amount of i + 0.2Mn was low, the grain boundaries of the surface layer of the steel outer shell could not be oxidized in the annealing step, and cracks due to grain boundary oxidation did not occur on the surface of the steel base of the steel outer shell. Therefore, since a crack as a lubricating pool is not formed on the wire surface, the feed lubricant is non-uniformly attached, and the feed resistance R and the slip ratio Sl are increased in the wire feedability test.
The arc became unstable.

The wire symbol W8 is Si + 0.
Since 2Mn was high, cracks due to grain boundary oxidation occurred on the surface of the steel base material of the steel shell, but the steel shell became hard due to the diameter reduction in the wire drawing step, and wire breakage frequently occurred. Therefore, the wire feedability test was stopped.

In the wire symbol W9, since the amount of the fed lubricant adhered was small, the feeding resistance R became high and the arc became unstable. Since the wire symbol W10 has a large amount of the fed lubricant, the slip ratio Sl becomes large and the arc becomes unstable.

Since the wire symbol W11 has a low flux filling rate, the flux filling rate in the longitudinal direction of the wire is not uniform at the time of manufacture, and the amount of feed lubricant adhered is small.
In the wire feeding test, the feeding resistance R became high and the arc became unstable.

Since the wire symbol W12 has a high flux filling rate, the outer skin thickness was thinned in the wire drawing step, and the wire breakage was caused by the crack caused by the grain boundary oxidation of the steel base surface of the steel outer skin. Further, since the amount of the fed lubricant was large, the slip ratio Sl increased in the wire feedability test, and the arc became unstable.

[0038]

As described in detail above, according to the flux-cored wire for gas shielded arc welding of the present invention, lubrication will be lost even in a harsh operating environment in which the feed resistance becomes high due to the bending of the liner or the like. It is possible to provide a flux-cored wire for gas shielded arc welding, which can exhibit good wire feedability without causing the above phenomenon.

[Brief description of drawings]

FIG. 1 is a diagram showing a wire feedability test apparatus used in an example of the present invention.

[Explanation of symbols]

1 feeder 2 wires 3 feeding rollers 4 conduit cable 5 torch 6 steel plate 7 Conduit cable bend 8 wire speed detector 9 load cell

Claims (2)

[Claims] 1. A flux-cored wire for gas shield arc welding, comprising a steel outer shell filled with flux, wherein the steel outer shell contains Si and Mn of Si + 0.2Mn and 0.4
Flux of 0.1 to 2.0 g per 10 kg of wire and having cracks due to intergranular oxidation on the surface of the steel base, and flux of 0.1 to 2.0% by mass. Cored wire. 2. The flux-cored wire for gas shielded arc welding according to claim 1, wherein the flux filling rate is 3 to 20 mass%.