JPH04313490A - Composite flux for submerged arc welding - Google Patents

Abstract

PURPOSE:To calcine flux containing a large quantity of iron powder, etc., at the high temperature by arranging iron (an alloy) as a granulation core at the central part of each flux grain and arranging hardly oxidizable metal, etc., at the high temperature on an outer shell part. CONSTITUTION:This is powder and granular material flux obtained by mixing and granulating >=2 kinds of raw material powder made Of metal (an oxide, a fluoride and a carbonate compound). It is characterized that >= one kind of iron (alloy) are arranged as the granulation core at the central part of each flux grain and >= one kind of hardly oxidizable metal, etc., at the high temperature and metallic oxide (fluoride and carbonate compound) are arranged on the outer shell part thereof.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an iron powder-added flux that allows deposited metal to be obtained with high efficiency in high heat input submerged arc welding of steel. The present invention relates to a flux for submerged arc welding that has been made possible.

0002

[Prior art] Flux for submerged arc welding is
Depending on the manufacturing method, it is broadly divided into molten flux and bonded flux.

[0003] Molten flux is made by melting various mineral raw materials in advance in an electric furnace or the like to solidify it as a uniform glassy or crystalline double oxide compound, which is then crushed and adjusted in particle size. Widely used for welding. Molten flux is chemically composed of uniformly dissolved oxides and fluorides, and moisture such as adhering water from raw materials or water of crystallization does not remain in the flux, so it is easy to reduce the hydrogen content of weld metal. Because it has a double oxide composition, it generally has a low softening and melting temperature and cannot be used for high heat input welding.Furthermore, when using a metal as a deoxidizing agent or when using a gas generating agent, mechanical It is very difficult to uniformly add a large amount of iron powder to increase the welding rate, as in the case of bond flux, which will be described later.

On the other hand, bonded flux is made by solidifying various mineral raw materials and metal powders with a binder such as water glass and granulating them to an appropriate particle size.It generally has a higher melting point than molten flux, but it is used to improve the welding speed. Because it is easy to add iron powder, metal as a deoxidizing agent, limestone as a gas generating agent, etc., it is used for high heat input welding and welding of low alloy steel, where it is difficult to apply molten flux. Particularly recently, high-efficiency iron powder-added bond flux containing about 30 wt% of iron powder has been used in large quantities for extra-thick steel plates for welding box column corner joints in steel frame buildings. However, when applying bond flux to weld such extremely thick steel plates, it is necessary to be careful about weld cracking caused by moisture in the flux, and it is desirable to use ultra-low hydrogen flux to reduce welding construction management. has been done.

[0005] Bond flux is usually fired at a temperature of about 300 to 600°C for the purpose of removing moisture in the binder and mineral raw materials, and the higher the firing temperature, the easier the moisture in the flux is removed. However, with the conventional flux in which raw materials are granulated simultaneously and randomly, the iron content of the iron powder on the surface layer of the flux particles oxidizes when the flux is fired, and when fired at a high temperature of around 500°C, the flux Therefore, the firing temperature of the iron powder-added bond flux is limited to around 400° C., making it difficult to hydrogenate the flux to an extremely low level.

An example of the high-temperature oxidation reaction of iron is shown in equation (1) below.

[0007]

[Math. 1] 3Fe+2O2 →Fe3O4…(1
)

[0008] In order to suppress the oxidation reaction of iron powder, there are methods such as firing in a non-oxidizing atmosphere and forming an appropriate protective film on the surface of iron powder. Methods such as firing in a non-oxidizing atmosphere or forming a protective film such as plating or chemical conversion treatment on iron powder require complicated processes to manufacture flux, which in turn significantly increases the cost of welding. Therefore, there are no examples of it being put into practical use.

[0009] The present invention is characterized by the particle form of the flux, but since the particle form of conventional bonded flux involves mixing various raw material powders at the same time, the flux particles have a form in which the raw materials are randomly dispersed throughout the particles. It was common for iron powder to be exposed on the surface layer. As a technology that controlled the form of flux,
No. 2-4565 discloses a flux in which iron sand and manganese dioxide are coated around a pre-granulated slag agent of a specific composition, and JP-A-51-119640 discloses a flux in which an inorganic binder is attached to a molten flux with a specific component. , Japanese Unexamined Patent Publication No. 63-252693 discloses a flux that has a high softening and melting point of the surface layer and can be used for both high heat input and low heat input. There are no examples of controlling the form of flux by focusing on oxidation reactions. Furthermore, although the flux of the present invention is classified as a bonded flux in the conventional classification, it is distinguished from the conventional bonded flux as a composite flux because its characteristic is a composite particle form.

0010

[Problems to be Solved by the Invention] As mentioned above, with conventional iron powder-added bond fluxes, it is easy to add a large amount of iron powder to significantly improve the welding speed, but the Because the oxidation reaction of the iron powder changes the chemical composition of the flux, it cannot be fired at high temperatures, making it extremely difficult to convert the flux to an extremely low hydrogen content.

The object of the present invention is to enable high-temperature firing of a flux containing a large amount of iron powder, which was impossible with conventional bonded flux particles, and to produce a flux with extremely low hydrogen content and excellent welding workability. It is about providing.

0012

[Means for Solving the Problems] The present invention was obtained as a result of various studies on particle forms in flux and granulation methods. A powder flux obtained by mixing and granulating two or more types of raw material powder, in which one or more types of iron or iron alloy are arranged as granulation nuclei in the center of each flux particle, and the outer shell A composite flux for submerged arc welding, characterized in that one or more of a difficult-to-oxidize metal, a metal oxide, a metal fluoride, or a metal carbonate compound is arranged in the center of each flux particle. Composite flux particles in which one or more types of iron or iron alloys are arranged as granulation nuclei, and one or more types of difficult-to-oxidize metals, metal oxides, metal fluorides, and metal carbonate compounds are arranged in the outer shell. Furthermore, it is a composite flux for submerged arc welding characterized by combining two or more fluxes. In this case, the specific surface area is 5 x 10-3 m2 /g or more 1 x 10-1 m2 /g
It is preferable to use the following iron or iron alloy as the granulation core.

[0013]

[Operation] The operation of the present invention will be explained in detail below.

First of all, one or more types of iron or iron alloys are placed in the center of each particle as a granulation core, and the outer shell is made of a metal that is difficult to oxidize at high temperatures, a metal oxide, a metal fluoride, or a metal. This effect is achieved by arranging one or more types of carbonate compounds, that is, by making the flux into a composite type. However, arranging iron or iron alloy in the center of the flux particles is due to the fact that iron or iron alloy is placed in the center of the flux particles when the iron or iron alloy is fired. This is to prevent deterioration of flux performance due to oxidation.

[0015] Here, the metals that are difficult to oxidize at high temperatures are metals that are difficult to oxidize under firing conditions, such as aluminum, titanium,
These metals are metals or alloys such as ferrosilicon and ferrochrome, and even if these metals are present in small amounts in the flux surface layer, they do not cause an increase in iron oxide, which adversely affects the welding workability of the flux.

[0016] When flux is heated to a high temperature, a temperature gradient occurs in the flux particles toward the center, and dehydration progresses gradually from the surface, and firing ends when the center is sufficiently dehydrated. When iron powders are randomly arranged within particles as in conventional fluxes, the iron powders in the surface layer of the flux are particularly susceptible to oxidation. When welding is performed using flux in which the iron powder in the flux is oxidized, not only the effect of adding iron powder to the flux, that is, the effect of increasing the welding speed, is not obtained, but also the iron oxide component in the slag increases significantly. The melting point and viscosity of the slag decreases,
Causes deterioration of welding workability. When such degraded flux is applied to ultra-high heat input welding of extremely thick steel plates, the bead shape and slag removability are significantly deteriorated, and defects such as slag entrainment in the weld metal occur. Cause.

FIGS. 1(A) to 1(C) are schematic diagrams showing the form of the composite flux of the present invention, and FIG. 2 is a schematic diagram showing the form of a conventional bonded flux. When the flux is composited so that the grain nucleus 1 is placed in the center, hydrated minerals such as metal oxides, metal fluorides, metal carbonates, etc. in the outer part 2 are removed before the iron or iron alloy in the center is altered. Since it is possible to dehydrate the flux, it is possible to reduce the hydrogen content of the flux while maintaining good welding workability. In addition, if the iron or iron alloy that serves as the granulation core is a fine powder, it is difficult to form a composite into the form shown in Figure 1 (B) with one-time granulation. A similar effect can also be obtained by arranging pre-granulated particles of one or more metals and other materials as the granulation nuclei 1a.

Furthermore, as shown in the schematic diagram of FIG. 1(C),
By combining two or more composite flux particles, the particle shape of the flux becomes long and the particle size distribution of the flux can be easily controlled, so the particle shape and particle size can be adjusted to suit the groove shape and welding speed. It can also be used as a flux.

Finally, regarding the specific surface area of the iron or iron alloy powder that serves as the granulation core, when producing a composite flux for submerged arc welding for steel welding using iron or iron alloy powder as the granulation core, the aforementioned composite By applying iron or iron alloy powder with optimal physical properties from the viewpoint of granulation properties and surface oxidation properties, it becomes possible to easily supply a composite flux with stable quality.

[0020] In order to composite the flux without pre-granulation and obtain a composite flux with a normal particle size distribution, the diameter is 0.1 mm.
Iron or iron alloy powder with a particle size of
Since surface oxidation is rate-limited by the diffusion rate of oxygen, surface oxidation can be prevented if iron or iron alloy powder particles have a small specific surface area. The particle size of iron or iron alloy powder is generally inversely proportional to the specific surface area, but iron powder with the same average particle size can be reduced to iron ore or atomized, and depending on its manufacturing history, those with a significantly larger specific surface area may not be able to withstand high temperatures. surface oxidation becomes large, and pretreatment such as preliminary granulation is required to apply it to the composite flux of the present invention.

[0021] The limited range of specific surface area was obtained from the results of experiments on composite granulation properties and high-temperature oxidation resistance of flux using various iron or iron alloy powders. The specific surface area of iron or iron alloy powder that can exhibit the composite effect of the present invention without pretreatment such as preliminary granulation is 1 × 1.
It is 0-1 m2/g or less. On the other hand, the specific surface area is 5×1
If it is less than 0-3 m2/g, the composite flux becomes too coarse, making it difficult to uniformly melt the flux due to the welding arc heat, making the arc unstable, and conversely deteriorating welding workability.

Here, the firing temperature of the flux is determined by the composition of the flux, that is, the decomposition temperature of the raw materials, and is difficult to specify, but it should be as high as possible in order to reduce the amount of hydrogen in the flux. is desirable.

[0023]

EXAMPLES The effects of the present invention will be explained by examples. First, in order to clarify the effect of composite flux, three types of composite fluxes F1 to F3 shown in Table 1 and conventional fluxes S1 to S2 shown in Table 2 were manufactured and fired at high temperature. The amount of diffusible hydrogen and welding workability were compared.

[0024] Composite flux F1 in Table 1 was prepared by cutting a 1.65% Mn steel wire shown in symbol I4 in Table 3 into a cylindrical shape to have an average grain size of 0.53 mm as a granulation nucleus, and using water as a granulation nucleus. Using glass as a binder, a slag agent, a deoxidizing agent, etc. were coated to obtain a flux as shown in FIG. 1(a). Similarly, F2 is a composite flux in the form shown in Figure 1 (b), in which the granulation cores are iron powder and ferromanganese shown in Table 3I1, and calcium carbonate pre-granulated using water glass, and F3 is shown in Table 3I1. This is a composite flux in the form shown in FIG. 1(c) using the iron powder shown in 3I2 as a granulation core. Coating was performed by supplying the hard-to-oxidize metal and slag agent, which will become the outer core, to the granulation device together with water glass while operating the powder granulation device into which the material that will become the granulation core has been charged in advance. . All these composite fluxes are 550
It was fired under the conditions of 1 hour at ℃.

Comparative bond fluxes S1, S2, and S3 were produced by uniformly premixing iron powder with other materials and simultaneously granulating the whole with water glass. It has the form shown in . Furthermore, S3 has the exact same composition as S2, but the firing conditions are 400℃×
The duration is 1 hr.

The above fluxes F1, F2, F3, S1
, S2 and S3 were used to conduct a weld metal hydrogen test and a welding workability test by two-electrode, one-run, one-layer high heat input welding using a square joint. The amount of hydrogen in the weld metal was measured using a wire with a wire diameter of 4.0 mm shown in Table 4, and in accordance with JIS Z31.
18-1986. In the welding workability test, welding was performed under the welding conditions shown in Table 5 using wires with a wire diameter of 6.4 mm shown in Table 4. Table 6 shows the chemical composition of the test specimens used in the welding workability test, and FIG. 3 shows the groove shape and dimensions (unit: mm) of the test specimens used in the welding workability test.

Table 7 shows the results of measuring the amount of hydrogen in the weld metal and the results of the welding workability test. As shown in T1 to T3, the composite flux does not show any deterioration in welding workability unlike the conventional fluxes T4 and T5 which were fired at high temperature. Furthermore, welding workability is maintained at a low temperature (
Flux T6 fired at 400°C has a higher amount of hydrogen in the weld metal than other fluxes fired at 550°C.

The flux of the present invention is shown in FIGS. 1(a), (b),
The effect can be fully demonstrated by compounding into the forms shown in (c), but by limiting the specific surface area of the iron or iron alloy that becomes the granulation nucleus, pretreatment such as preliminary granulation is not performed. It can be easily combined in the form shown in Figure 1 (A) or Figure 1 (C).

Composite fluxes having the compositions shown in Table 8 were prepared using iron or iron alloy powders having various specific surface areas shown in Table 3, and the welding workability was compared. Table 9 shows the results. The composite flux shown in Table 8 has the form shown in FIG. 1(A) or FIG. 1(C), and the manufacturing conditions are the same as those in Table 1F1 or F3, respectively. Here, in the case of flux F8 that uses iron powder with a specific surface area exceeding 1 x 10-1 m2 /g, the iron powder is fine and easily oxidized at high temperatures, so the flux cannot be used in a manufacturing method that does not use pre-granulation. It is not possible to form the shape as shown in FIG. 1(A), and the flux deteriorates when fired at 550° C., resulting in poor welding workability. On the other hand, the specific surface area is 5
In the case of flux F7 using iron alloy powder of less than ×10 −3 m 2 /g, the flux particles become too coarse as a whole, causing deterioration in welding workability. Specific surface area is 5 x 10-3
Good welding workability can be obtained only with fluxes F4 to F6 falling within the range of ~1×10 −1 m 2 /g.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

[0033]

[Table 4]

[0034]

[Table 5]

[0035]

[Table 6]

[0036]

[Table 7]

[0037]

[Table 8]

[0038]

[Table 9]

[0039]

[Effects of the Invention] As described above, by using the composite flux of the present invention, it is possible to achieve extremely low hydrogenation of the flux and at the same time to obtain good welding workability in metal powder addition excessive heat input welding where weld metal can be obtained with high efficiency. becomes possible.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram for explaining the form of the flux of the present invention.

FIG. 2 is a schematic diagram illustrating the form of conventional bond flux.

FIG. 3 is a front view illustrating the groove shape of a test specimen used in an example of the present invention.

[Explanation of symbols]

1, 1a, 1b, 1c, 1d, 1e, 1f...granulation nucleus 2,
2a, 2b, 2c, 2d, 2e, 2f...Outer shell part 3...Particles of conventional flux

Claims (3)

[Claims] Claim 1: A powder flux obtained by mixing and granulating two or more types of raw material powders consisting of metals, metal oxides, metal fluorides, and metal carbonate compounds, the powder flux being obtained by mixing and granulating two or more types of raw material powders consisting of metals, metal oxides, metal fluorides, and metal carbonate compounds, wherein One or more types of iron or iron alloys are arranged as granulation nuclei, and one or more types of difficult-to-oxidize metals, metal oxides, metal fluorides, and metal carbonate compounds are arranged in the outer shell. Composite flux for submerged arc welding. 2. Powder flux obtained by mixing and granulating two or more types of raw material powders consisting of metals, metal oxides, metal fluorides, and metal carbonate compounds, the powder flux being obtained by mixing and granulating two or more kinds of raw material powders consisting of metals, metal oxides, metal fluorides, and metal carbonate compounds, wherein Composite flux particles in which one or more types of iron or iron alloys are arranged as granulation cores, and one or more types of difficult-to-oxidize metals, metal oxides, metal fluorides, and metal carbonate compounds are arranged in the outer shell. Furthermore, a composite flux for submerged arc welding is characterized by combining two or more fluxes. 3. Submerged arc welding according to claim 1 or 2, characterized in that iron or iron alloy having a specific surface area of 5×10 −3 m 2 /g or more and 1×10 −1 m 2 /g or less is used as a granulation nucleus. composite flux.