JP2549313B2 - Manufacturing method of flux-cored wire for welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention processes a steel pipe or hoop material into a U-shaped cross section, fills it with welding flux, and has a circular cross section and a small diameter. The present invention relates to a method for manufacturing a flux-cored wire for welding, which is manufactured by stretching the wire into a wire.

[Conventional technology]

The flux to be filled in the flux-cored wire for welding has a method of blending several to ten or more kinds of raw materials, a method of filling the flux as it is mixed, and a method of filling the mixed flux by drying after granulating, When filling the inside of the pipe, it is general to use a flux that has been granulated.

The raw material of the filling flux is metal oxides, metal powders, and the like, which are metered and mixed according to a predetermined mixing ratio. In the case of granulating, generally, as a sticking agent, an aqueous solution of sodium silicate or potassium silicate is added alone or mixed, and the mixture is uniformly mixed with the sticking agent in a wet mixer, and then, for example, by a plate type granulator. It is granulated, dried and classified to obtain a product having a predetermined degree of distribution. For the conventional granulation flux, the raw material with a particle size of 44 μm or more is mainly used, and the adhesion strength of the granulated product is mainly adjusted by the type and concentration of the adhesive and the addition amount. The agent also has a great influence on the granulation property, and is also positioned as a part of the components of the produced flux. Therefore, the concentration and the amount of the fixing agent are naturally limited in the range of use, and the concentration may be too low and granulation may not be possible if the addition amount is less than a certain value.

The filling of the flux into the pipe is performed by a method in which a bobbin formed by winding the pipe in a coil shape is vibrated to supply the flux from the end of the pipe to continuously convey and fill the flux. in this case,
The particle size of the flux to be filled has a great influence on the filling rate, filling speed, and drawability. If the particle size is less than 1 mm, coarser particles are easier to fill and the filling speed is faster, but fluxes with a particle size of less than 500 μm are generally used for reasons such as filling rate adjustment and breakage during drawing (hereinafter wire drawing). It Even so, breakage often occurs during the process of drawing a tube after flux filling to finish a product with an outer diameter of 0.1 to 2.0 mmφ.

One of the major causes of this fracture is due to the filling flux. For example, even if the grain size is 500 μm, if this is a single hard grain such as silica stone, the steel of the outer skin is stretched due to ductility during wire drawing. However, since the silica stone in the pipe is hard and not ductile, it does not deform and only the outer skin of that portion is thinly stretched, and finally it breaks beyond the breaking strength of steel (hereinafter referred to as disconnection). Therefore, the raw material particles are 297 μm in advance.
The following crushed products are used. Moreover, even if the particles of each raw material are fine, even if the fixing force is given too much in the granulation step, for example, the particles of the granulation flux are 400 μm.
In the pipe, it is not crushed during wire drawing, and only the steel outer shell (hereinafter referred to as wire) of that portion is thinly stretched, which causes a wire breakage or a so-called constriction phenomenon in which the wire surface becomes uneven. If a wire becomes constricted,
During welding, it hinders the feedability of the wire and causes a trouble in welding.

From such a situation, the adhesion strength of the particles of the granulation flux is measured by a so-called pulverization strength test, and in the case of the flux for latent arc welding, so as not to be broken during repeated use,
Rather, it is required to increase the fixing strength. Since the production of the filling flux is also granulated by such a production method, the fixing strength of the flux particles tends to be excessively higher than necessary, and after filling the pipe, it passes through the die in the wire drawing process. The deformation resistance is larger than the outer skin against the compressive force at that time, the outer skin is stretched preferentially, and the yield stress of the outer skin is often exceeded without breakage of the flux particles, resulting in disconnection.

[Means for solving the problem]

The present invention provides a method for manufacturing a flux-cored wire for welding, which eliminates such a major cause of the wire disconnection phenomenon.
297 μm or less, add a fixing agent to this, granulate and dry, classify into a flux with a particle size of 500 μm, and flux with a pulverizing strength C value of 12 to 20 into a steel sheath. A method of manufacturing a flux-cored wire for welding, which fills and draws a wire, and further, TiO ₂ , SiO ₂ of a filling flux raw material,
One or two or more kinds of Al ₂ O ₃ having a particle size of 10 μm or less is characterized by adding 3 to 15% of the whole raw material.

The inventors of the present invention focused on the method of controlling the pulverization strength, developed a method of using a filling flux manufactured so that the strength of the flux particles is equal to or less than the deformation resistance strength of the outer cover, and the welding flux using this is used. The manufacturing method of the cored wire was completed.

[Action]

In the method of manufacturing the filling flux of the flux-cored wire for welding, by adjusting the degree of raw material and the type and concentration of the adhesive at the granulation stage of the flux, the pulverization strength of the flux particles after granulation and drying The effect of the present invention was demonstrated by filling the tube with a granulating flux adjusted so that the C value was in the range of 12 to 20 according to the method for measuring the pulverization strength, and manufacturing the tube.

That is, the degree of fabrication of the single raw material is 297 μm (48 mesh)
Using the following raw materials, the powdering strength was adjusted so that the granulation flux could be easily granulated to 297 μm or less by the pressing force during wire drawing, and the flux was classified to 500 μm (32 mesh) or less. Is prepared and filled in a tube. The reason why the flux particle size is 500 μm or less is that the inner diameter is 8
This is to reduce the variation in the filling rate in the tube after filling when it is filled into a tube of mmφ or less. The granulation rate of the single raw material is 297 μm or less when granulating as a flux. This is to reduce the variation in the composition of one particle and keep the composition within a certain range due to the difference in flux particle size.

On the other hand, it is well known that the concentration and addition amount of the fixing agent have a great influence on the pulverizing strength of the flux after granulation and drying. Furthermore, the range of addition of the fixing agent capable of granulating is naturally determined. That is, if the amount of addition is too large, the flux after wet mixing becomes sticky and cannot be granulated, and if it is too small, it cannot be granulated in a loose state. For this reason, the concentration of the fixing agent is greatly related to the factor that changes the fixing force that affects the pulverization strength of the flux. That is, in the case of the conventional raw material having a combination of particle sizes, when the concentration of the fixing agent (water glass) becomes thinner than a certain value, the granulating action disappears and the fixing force also disappears. As a method of suppressing such a phenomenon and significantly lowering the concentration of the adhesive as compared with the conventional method and maintaining the granulation action, a part of the raw material has a particle size of 10 μm.
By substituting ultrafine particles of m or less, the cohesive force is utilized, granulation is possible even with a thin fixing agent, the fixing force of the flux particles after drying is reduced, and the pulverizing strength is weakened. It can be adjusted.

That is, the particle size is 10μ in a part of the raw material powder for flux.
Granulated flux by the combination of adding one or two or more of TiO ₂ , SiO ₂ , and Al ₂ O ₃ of m or less to ₃ to 15% of the whole raw material and decreasing the concentration of the adhesive. The powdering strength of can be adjusted in a direction that makes it weaker than the conventional one,
The influence of the content of raw materials of m or less on the pulverization strength tends to change less as the content increases, while the cost of powder raw materials of 10 μm or less is high, so the economical efficiency of industrial products Considering this, it is essential to set the addition rate so that the effect can be maximized. From such a judgment, the particle size
The range of the content rate of the powder raw material of 10 μm or less was set to 3 to 15%.

The method for measuring the pulverizing strength C value of the particles of the filling flux in the present invention is as follows.

50g of flux with the composition ratio (% by weight) of particles smaller than 210μm is A, along with 9 iron balls of 8mm in diameter
Put it in a cylindrical container of 40 mm and length of 300 mm, center at a point 150 mm in the axial direction from the center of both ends of the container, pass through that point, and rotate at 30 rpm around a line orthogonal to the cylindrical axis. After rotating for 60 minutes, the constituent ratio (% by weight) B of particles smaller than 210 μm is measured, and the value C obtained by the following equation is taken as the pulverization strength of the particles.

C = B-A is an index indicating that the larger the C value, the weaker the fixing strength of the flux particles.

It has a C value of less than 12 produced by the usual method 20
Flux of mesh (approx. 800μm) or less, outer diameter 10mm
A low-carbon steel pipe with a wall thickness of 1mm and a wall thickness of 1mm filled at a filling rate of 15% was contracted to an outer diameter of 3.2mm by a rolling wire drawing machine, but the outer surface had a smooth outer circumference as usual. By cutting the pipe in the vertical direction, removing the flux, and observing the inner surface, it was found that the portion where the 20-mesh flux was in contact had a flux digging into the surface and was in an uneven state. I did.

As described above, when the flux fixing strength is high, the pressing force by the wire drawing machine preferentially acts on the pipe inside the process of drawing the pipe, and the flux is not crushed. Therefore, in order for the tube and the flux to be smoothly deformed and reduced in diameter in the wire drawing step, it is necessary to control and weaken the flux fixing strength to a C value of 12 or more. On the other hand, when the C value exceeds 20, it is easily pulverized, the handleability up to the filling step is poor, the filling speed is lowered, and the productivity is deteriorated.

Usually, the flux is filled at room temperature and may be annealed at 600 ° C or higher in the welding wire manufacturing process. However, if the C value is less than 12 before the annealing process, the inside of the pipe as described above When the wire is drawn to 3.2 mmφ or less due to the occurrence of surface irregularities in (3), the irregularities cause frequent disconnection. According to the present invention, this disconnection is filled with the filling flux in the pipe, and then in the wire drawing step,
When a compressive force is applied from the outer skin side of the pipe, the outer skin and the granulation flux filled therein are simultaneously deformed, the outer skin is stretched, and the flux is finely divided by pulverization and the inside of the pipe is It flows in the wire-drawing direction, and the cross-sectional layer of the filled flux is reduced in the same manner as the outer skin, and the outer skin is drawn without breaking.

〔Example〕

 An example will be described below.

Table 1 is an example of the compounding components of the flux to be filled in the flux-cored wire for welding.

Of these components, some of the TiO ₂ , SiO ₂ , and Al ₂ O ₃ components have a particle size of 10 μm or less (hereinafter referred to as “fine particle raw material”).
Tables 2 to 4 show examples of trial-produced flux when replaced with.

As the fixing agent, 3 mol of sodium silicate and a stock solution of 3 mol of potassium silicate similarly diluted and mixed with water were used. The granulation was carried out by a mixing granulator of a type having a vertical rotation axis in the center of the cylindrical tank and horizontal blades. In addition, the hot air temperature
After drying with a fluidized bed dryer set at 350 ° C, the water content after drying was less than 0.3%.

Granulation may be performed by a dish type granulator after the wet mixing, and the granulating action may be further imparted. As shown in Fig. 3, a granulation flux having a particle size distribution that can be sufficiently applied could be obtained.

As shown in Tables 3 and 4 and FIGS. 4 and 5,
The content of the raw material of 10 μm or less in the flux raw material and the concentration of the fixing agent are greatly related to the fixing strength of the flux particles after granulation. In this case, if the fixing strength is high, it can be considered that the pulverizing strength of the flux particles is high.
That is, the concentration of the fixing agent was kept constant and 10
When the content of the raw material of less than μm is increased, the pulverization strength is increased (the C value is decreased), and when the content of 10 μm or less in the flux raw material is kept constant and the concentration of the fixing agent is decreased,
The pulverization strength tends to decrease (C value increases).

Also, the fixing strength of the fixing agent becomes smaller as the concentration of the flux particles after granulation and drying decreases, but by adjusting the addition amount (the addition amount increases little by little when the concentration decreases) Was possible. However, in the case of 3 mol of potassium silicate and sodium silicate, the limit of dilution with water is the concentration of the fixing agent that can maintain the fixing force such that the flux particles after drying are not powdered during handling such as transportation and movement. It was about 10 times.

The particle size distribution of the flux produced by granulating, drying and classifying and the particle size distribution after measuring the pulverizing strength are shown in FIGS. 1 to 3. The solid line shows the particle size distribution before the powder strength test and the dotted line shows the particle size distribution after the powder strength test.

In addition, the results of Tables 3 and 4 and FIGS. 1 to 3 are summarized by the number of wire breakages when manufactured using a flux having a pulverizing strength C value and a particle size of 500 μm or less. It is shown in FIGS. 4 and 5. As shown in these figures, it can be seen that the wires having a crushing strength C value of 12 to 20 are excellent in the number of breaks per ton or less. The number of disconnections shown in Fig. 2 is from a low carbon steel pipe (C0.05%) with an outer diameter of 10 mmφ and a wall thickness of 1 mm filled with flux at a filling rate of 15%,
The number of wire breakages per ton when finishing wire drawing to 1.2 mmφ using the material of the intermediate process that was drawn to an outer diameter of 2.6 mmφ by a wire drawing machine is summarized in tons. And the number of wire breaks. Before finishing wire drawing
Use the one annealed at 700 ℃ for 2 hours. The wire drawing condition is 1mm from the initial die 2.6mmφ using the die wire drawing machine.
Using two dies, with liquid lubricant, final speed 1000m
/ Wire was drawn in minutes. As is clear from this figure, it is understood that the number of wire breaks is reduced by lowering the powdering strength of the flux particles by the powdering strength control of the present invention. With the conventional filling flux, the number of disconnection is 5 times /
It is not uncommon to generate tons. For this reason, the work efficiency in the wire drawing work may be reduced, and the wire may be broken in the winding work process on the spool.

The present invention is extremely effective as a method for reducing such disconnection troubles, and although there are some differences depending on the flux component system and the steel type of the pipe used, the flux must be C ≧ 12. As shown in FIG. 6, it has been proved that the wire breakage trouble can be reduced to 1 time / ton or less by filling the particles with weaker pulverization strength. The numbers marked with a circle in FIGS. 4 and 5 represent the numbers shown in the change content column of each table. In addition, pulverizing the flux particles before handling will cause another trouble, but work such as transferring the granulated / dried / classified flux to a segregation prevention container or passing it through a flux filling machine In C, it was confirmed that C ≦ 20 had no problem.

〔The invention's effect〕

Thus, the particle size of the flux raw material powder according to the present invention, the particle size of the granulated product and the pulverization strength are controlled,
After filling in the pipe, the manufacturing method of wire drawing is to eliminate the constriction phenomenon of the sheath due to hard particles of flux in the middle of the wire drawing process, remove the cause of disconnection, and effectively produce the flux-filled wire for welding. Applicable.

Furthermore, by using the technology for controlling the pulverization strength of the flux particles and using a tube with an inner diameter of 8 mmφ or more to adjust the filling rate, the particle size of the flux to be filled will be roughly 800 μm or less, making it easy to produce flux. In addition, the filling speed into the pipe can be increased.

Further, if the finely divided material such as sulfur is filled as it is, it takes a long time to fill it or the filling tends to vary.
As an application of the present invention, a part of ultrafine atomized sulfur is used and granulated with a low-concentration fixing agent such that water or components do not affect, for example, a low-concentration aqueous solution of dextrin.
It can also be applied to the production of injection wires by filling with dried and classified sulfur particles, and it is also possible to exert the effect of making the filling rate uniform and improving the productivity.

[Brief description of drawings]

1 to 3 are several examples of the particle size distribution of the granulating flux used in the examples, the solid line is a graph showing the particle size before the powdering test, and the dotted line is a graph showing the particle size after the powdering test. FIG. 5 and FIG. 5 are graphs showing the granulation strength of the flux particles of the example displayed by the granulation strength C value, and FIG. 6 is the powder strength C and the wire drawing from the outer diameter of 2.6 mmφ to 1.2 mmφ. It is a graph showing the relationship with the number of wire breakage per ton when processed.

Claims (2)

(57) [Claims] 1. A method for producing a flux-cored wire for welding in which a steel sheath is filled with flux and drawn, wherein the particle diameter of the raw material powder for filling flux is 297 μm or less, and a sticking agent is added to Granulate and dry, classify into a flux with a particle size of 500 μm or less, and pulverize strength C of the flux
A method for producing a flux-cored wire for welding, which comprises filling a steel sheath with a flux having a value of 12 to 20 and drawing it. 2. One or more of TiO ₂ , SiO ₂ , and Al ₂ O ₃ having a particle size of 10 μm or less is 3 to 15% of the whole raw material.
The method for producing a flux-cored wire for welding according to claim 1, wherein the flux-cored wire is added.