JPS6268695A - High temperature calcined flux for submerged arc welding - Google Patents

Abstract

PURPOSE:To obtain good mechanical properties and to improve working environment and working efficiency by limiting the compsn. calcining temp. and bulk density of a high-temp. calcined flux. CONSTITUTION:The flux is calcined at >=750 deg.C and the compsn. of the flux is made to consist of 5-10W% either or both of CaO; MgO as basic oxide, 3-30W% metallic fluoride except alkali metal fluoride in terms of fluorine, 5-50W% SiO2 as acidic oxide or 25-60W% of both of said SiO2 and <=44W% Al2O3 which are used in the form of metallic powder. Si in the flux is made <=0.5W%. The bulk density is made 0.8-1.2g/cm<3>. The resultant flux is granular and does not generate dust, fumes, smell and exposing arcs and provides the good mechanical properties in welding of steel products for which low-temp. toughness is required.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a flux for submerged arc welding, and more particularly to a high temperature firing flux.

(Prior Art) In recent years, from the viewpoint of occupational health, there has been a demand for welding that does not generate exposed arc sources and generates less fumes, and submerged arc welding, which has fewer of these problems, has been reconsidered. In addition, from the viewpoint of materials, many steel structures are used in low-temperature regions, and materials with excellent low-temperature toughness are required. In submerged arc welding, the heap and toughness are mainly determined by the morphology and composition of the 7 lux.

The flux used in submerged arc welding is made up of two types: one is a molten type flux in which various raw materials are melted in an electric furnace, etc. so that the components within the flux particles are uniform, and the other is a molten type flux in which various raw material powders are combined with an alkali silicate, etc. It is roughly divided into granulated type 7 Lasox, in which the fired 7 Lasox particles are composed of aggregates of particles of each raw material. Furthermore, the latter is 40% depending on the firing temperature.
Low-temperature firing flux fired at 0 to 550°C, and 550°C
It is divided into 7 lacs fired at a high temperature of ~1000°C.

Furthermore, there have conventionally been two ways of thinking regarding the firing temperature of high-temperature firing flux. Namely, Special Public Interest Publication 31-715
Publication No. 7 states, ``Solvent raw material @ fine powder mixed with a binder such as silicic acid powder or potassium silicate, and individual solvent raw material powders of aggregates will not melt and react with each other, and the binder will not react with each other. Appropriate temperature sufficient to melt and harden (e.g. 649 ~
760°C) through a kiln. ” manufacturing method, and the other is “roasting at a temperature below the melting point of the alkali silicate as a binder (550 to 800°C)”
This is a manufacturing method described in Japanese Patent No. 7-3258.

Although the ideas of the two are different, the firing temperature in each example is almost the same. This may be because the melting point differs depending on the type of adhesive. However, in any case, the above-mentioned patent document does not disclose anything about the effects on the hygroscopicity or the amount of diffusible hydrogen of the flux.

On the other hand, since this high-temperature fired flux does not contain a gas generating agent like the molten flux, it generates significantly less fume than a low-temperature fired flux in which limestone or the like is completely added as a gas generating agent.

Furthermore, since the flux is in the form of granules, there is less dust generation, which is one of the disadvantages of the molten fine-grained 7-Lux. Furthermore, it has the advantage of superior occupational hygiene, such as not producing the irritating odor (thought to be caused by HF or 5iF3) that occurs when using acidic or neutral molten 7LAX. .

However, although this high-temperature fired flux is widely used in Europe and America, it is currently hardly used in Japan.

Therefore, the present inventors conducted a detailed investigation on high-temperature fired 7 lacs. The products with a high MgO content disclosed in JP-A-57-106496 and JP-B-32-409 are low-temperature fired, and although they have a lower moisture content when drying than wood, they do not cause pores or hydrogen cracking during welding. It was found that even a small amount of moisture absorption increases the amount of diffusible hydrogen that causes this. Furthermore, in the example of Japanese Patent Publication No. 44-13249, there is a flux with a low MgO content and a relatively small amount of diffusible hydrogen, but conventional high-temperature fired fluxes, such as this example, generally have a high Si content in the 7 lac flux. Toughness at low temperatures is not very good. Furthermore, it was found that there was a problem in that the workability of welding with alternating current was inferior to that of the fusion type 7LAX. In other words, these conventional high-temperature fired fluxes tend to absorb a lot of moisture because there are many humid periods in Japan, and
Since AC is mainly used as the power source for submerged arc welding, AC welding workability becomes a problem. Furthermore, it is thought that conventional high-temperature fired fluxes are not popular because their toughness is unsatisfactory. If high-temperature fired fluxes could reduce the amount of diffusible hydrogen and moisture absorption, improve toughness, and improve AC workability at the same time, it would be possible to create a high-performance flux that is favorable for occupational health. There was almost no consideration.

(Problems to be Solved by the Invention) The present invention aims to provide a flux that retains the advantages of conventional high-temperature fired fluxes, has a small amount of diffusible hydrogen, has good AC workability, and has high toughness. It is something.

(Means for solving all problems) The gist of the present invention is that 1::aO, Mg
5 to 10% for either or both of O, 3 to 30% for metal fluorides excluding alkali metal fluorides calculated as 1 fluorine, 5 to 2 i 5 to 50 t or this 5 I as acidic oxides.
25-60% for both O2 and At2o3 below 44%,
The flux for submerged arc welding is characterized in that, as a metal powder, St in 7 lux is 0.5% or less and a bulk density is 0.8 to 1.21Ax3.

The present invention will be explained in detail below.

First, in order to improve the increase in the amount of diffusible hydrogen due to moisture absorption in high-temperature fired flux, we investigated in detail the relationship between firing temperature and 7lux composition.

As a result of the study, we obtained the following new knowledge regarding hygroscopicity.

That is, 7 lacquer containing 3% CaO and 4% MgO as basic oxides and granulated with sodium silicate (water glass), and silicic acid containing 8% CaO and 20% MgO as basic oxides. Soda (Water) Flux granulated with lasing ■, flux M containing 16% CaCO2t'' as basic carbonate, 30% basic oxide MgOi, 4% CaO and granulated with sodium silicate (water glass) Each of the conventional low temperature firing flux ties f) was heated to 450 to 950℃.
The samples were fired at various temperatures within the range of 100%, and after cooling, they were exposed indoors for 24 hours, and the total amount of diffusible hydrogen was measured. The results are shown in Figure 1. Basic oxide CaOrMgO
For flux ■ with a low content, the amount of diffusible hydrogen decreases rapidly at temperatures above 700℃, and is extremely small. On the other hand, in flux (2) with a high content of CaO and MgO, the amount of diffusible hydrogen decreases little by little as the formation temperature increases, but it is very large and tends to cause pores and pockmarks. In addition, in the case of conventional low-temperature firing flux ■, the amount of diffusible hydrogen is 520℃
However, if it exceeds that point, CaCO3 will decompose, and the effect of reducing the H2 partial pressure in the arc cavity due to the CaCO3→CaO+CO2 reaction during welding will be lost, and at the same time, CaO and a large amount of MgO produced by the decomposition of CaCO3 will be extremely It was found that the amount of diffusible hydrogen increases rapidly because it is active and absorbs a large amount of moisture.

In addition, in Fig. 1, the amount of diffusible hydrogen is 8, +u/l
Pores, pockmarks, etc. were likely to occur in areas with 00 gdepo or more.

Next, we investigated the improvement of toughness by using a flux base containing less basic oxides CaO and MgO in order to reduce hygroscopicity and reduce the amount of diffusible hydrogen. As a result, metal fluorides other than alkali metal fluorides do not increase hygroscopicity;
It was found that it is an effective ingredient in reducing the amount of oxygen in the weld metal and improving its toughness.

By the way, in the past, DC power sources were mainly used in Europe and the United States, and with DC, the amount of oxygen in the weld metal is higher than with AC, or perhaps because alloying agents are added from 7 lux, even high temperature firing causes deterioration (oxidation and nitridation). F'5-3i and Si-
A fairly large amount of Mn is added as a deoxidizing or alloying agent. As a result of studying the metal powder used as the deoxidizing/alloying agent, we found that the 7LAX of the present invention can decompose and remove oxygen from diperoxide by specifying the firing temperature to 750°C or higher.
Furthermore, since fluoride is added according to the level of total required toughness (which has a correlation with the amount of oxygen), pockmarks and the like will be reduced if there are fewer metal powders; As shown in Figure 2, it was found that the toughness was significantly improved.

In addition, as a result of various studies to improve AC workability, we found that the bulk density of conventional high-temperature fired flux is 1.37? km3
However, by reducing the bulk density of the flux to 1.2 gAm3 or less by reducing the density of metal powder and changing the particle shape by improving the granulation method, the bead spreading, which was a problem in AC welding, could be avoided. It was found that the undercut performance was significantly improved.

The present invention was achieved by further investigating the three new findings regarding the above-mentioned high-temperature fired flux and the relationship between the flux and other components.

Next, the reasons for limiting the numerical values of the constituent elements of the present invention will be described.

Firing temperature: If the firing temperature is less than 750°C, the hygroscopicity becomes extremely poor, and bits, pockmarks, cracks, etc. due to moisture are likely to occur. This is especially a problem in humid atmospheric conditions like Japan. In addition, MnO2'if is used as a raw material in the flux containing Mn oxide.
When all the ores contained in the weld metal are used, if the firing temperature is less than 750°C, the decomposition and removal of excess oxygen (MnO2→Mn2O3+ O) will be insufficient, the amount of oxygen in the weld metal will increase, and the toughness will deteriorate.

Note that when the firing temperature is approximately 550 to 700°C, the strength of the adhesive is low, and the flux is likely to be powdered.

Basic component: 1 of CaO, MgO or both
If it exceeds 0%, moisture absorption becomes large and pitting resistance and pockmark resistance and hydrogen cracking resistance deteriorate, which is a problem.

On the other hand, these basic oxides, like metal fluorides, function to suppress the increase in the amount of oxygen in the weld metal.

It also relates to slag physical properties such as slag viscosity and fluidity. Therefore, when either or both of CaO and MgO are not grooved in 5 grooves, the amount of oxygen in the weld metal increases and the toughness deteriorates. In addition, slag fluidity is poor and pock marks occur.
Bead uniformity deteriorates.

Metal fluoride: Metal fluoride is an important component that suppresses the increase in the amount of oxygen in the weld metal, adjusts the fluidity of the generated slag, and reduces the amount of diffusible hydrogen. However, when an alkali metal fluoride is added in an amount exceeding 1%, which is different from other metal fluorides, the hygroscopicity becomes significant and the amount of diffusible hydrogen increases, so from this point of view it is better not to add it. Therefore, if the value of the metal fluoride converted to fluorine, excluding the alkali metal fluoride, is less than 3%, these effects will be insufficient, the toughness will deteriorate, and pock marks will easily occur. On the other hand, if it exceeds 30%, the slag tends to flow, the arc becomes unstable, and the bead waveform becomes rough.

5jO7 is an essential component to maintain good welding workability! When l is less than 15%, the bead waveform is rough and smooth beads cannot be obtained. Also, 50%? If the slag is exceeded, the viscosity of the slag becomes too strong and pock marks and pits are likely to occur. In addition, the amount of oxygen in the weld metal increases and the toughness deteriorates.

When Al2O3 exceeds 44 inches, the slag has a high viscosity and melting point, which tends to cause pockmarks and pit-4 formation, and the bead width becomes small, making it easy to form convex beads. Also, like 5IO2, toughness deteriorates.

Furthermore, when 8102 + Al2O5 is less than 25%,
Since the slag has a low viscosity and a high melting point, the beads tend to become rough and good beads cannot be obtained. 5IO2+Al2O
If 3 exceeds 60%, the amount of oxygen in the weld metal increases and good toughness cannot be obtained. Furthermore, the viscosity of the slag is too high and pock marks are likely to occur.

As mentioned above, the Si content in the flux is 0.0% to ensure toughness.
It won't happen unless it's 5% or less.

The bulk density needs to be 1.2 E/CrIL3 or less to maintain good welding workability, especially AC welding workability.

However, if the ratio is less than 3 to 0.8, 7 lux will easily turn into powder during use, causing dust generation.

The effects of the present invention will be explained in more detail below with reference to Examples.

(Example 1) After firing, the raw material powder blended so as to have the final chemical composition shown in Table 1 was mixed with the adhesive shown in Table 2 and granulated.
A to 0 granular flux intermediate product pre-dried at
As shown in the table, all seven lasoxes were prepared by firing at various temperatures and compared with the flux of the present invention. Furthermore, Table 4 shows the component system, particle size, and bulk density of the conventional flux used for comparison. For comparison of hygroscopicity, the flux was re-dried at 350° C. for 2 hours, exposed to the atmosphere for 15 hours, and used in the following welding.

Next, the present invention fluxes AI and Bl shown in Table 3.

CI, Dl, El, Fl, comparative example flux A2
．． C2゜Horizontal fillet of a T-shaped member made by combining Kl, LL, Ml and the conventional flux FP shown in Table 4 with the WL wire shown in Table 6 and using the steel plate P1 shown in Table 5 under the welding conditions shown in Table 7 1. Performed welding. In addition, using the same 7 lux and wire, the mechanical properties of the deposited metal were investigated in accordance with the NK standard using steel plate P2 in Table 5 and welding condition (1) in Table 7. These results are also shown in Table 8.

As a result, in the case of the flux of the present invention, the amount of diffusible hydrogen is small in fillet welding, so no pits are formed, the bead appearance is good, there is no fume or odor, and the slab peelability is good, and the welding work Excellent quality. and,
The mechanical properties of the deposited metal are also good.

In the case of comparative example flux A2, the bulk density is 1.3p3
Since the diameter is too large, undercuts occur at convex peeds, causing problems. In C2, since the firing temperature was as low as 650° C., the amount of diffusible hydrogen was large, and pock marks and pits were generated. Since K1 has a large amount of CaO+MgO (11 chips), the amount of diffusible hydrogen is large, and pits are likely to occur.

Furthermore, since the amount of Si is as high as 0.7 inches, the toughness is poor. Ll has too much ht2o5 of 49 degrees and has a high melting point, so undercuts are likely to occur in convex beads. Since Ml has a large MgO content of 13% and the firing temperature is as low as 720° C., the amount of diffusible hydrogen is large and pits are likely to occur. Furthermore, since the number of 5102 is as large as 52, slag seizure occurs and the toughness is low. Conventional flux FP generates a pungent odor during welding, which obstructs work in the vicinity of the welding head.

The slag removability is also poor and requires strong hitting with a chisel.

In addition, pockmarks and pits occur, and the toughness is low, leaving room for improvement.

(Example 2) Invention fluxes Gl and H1 shown in Table 3, Comparative Example 7 flux G2. G3. Nl and conventional flux BF in Table 4 and wire W2f in Table 6! : Combination Welding of 3 squares on each side of steel plate P3 shown in Table 5 was performed under the welding conditions shown in Table 7. Table 9 shows the bead appearance, X-ray results, and mechanical property investigation results.

As a result, in the case of the fluxes Gl and I(l) of the present invention, the bead was in good condition with no defects on the surface or inside, and the mechanical performance was also very good.

Comparative example flux G2 had a low firing temperature of 600° C., so the amount of diffusible hydrogen was large, and pock marks, hydrogen cracks, and blowholes occurred. In G3, the bulk density was too small, 7 lux was powdered during welding, dust was easily generated during flux distribution, and the bead width was uneven, causing slag entrainment. N1 had a good bead appearance and no internal defects, but the Si content was 3%.
The impact value is low because there are many.

Since the conventional flux BF contains lime gold carbonate as a gas generating agent, fume is generated during welding, and when bathing in a gondola such as a tank, there is a problem in terms of occupational health unless a heap collector is used. In addition, it had high hygroscopicity and a large amount of diffusible hydrogen, causing pock marks and hydrogen cracks.

(Example 3) The flux 11 of the present invention shown in Table 3. Jl, comparative example flux J2,01 and conventional example flux FC in Table 4
A weld metal test was conducted using the wire W3i in Table 6 and the steel plate P4 in Table 5 under the conditions of ■ in Table 7 in accordance with the NK standard. The results are shown in Table 10.

Fluxes II and Jl of the present invention had good bead appearance, no internal defects, and good mechanical properties.

Comparative Example 7 Lux J2 had a low firing temperature of 680° C. and a large bulk density of 1.317 i/cm 3 , so pock marks and blowholes occurred. Same (01 has 3 fluorine
The arc was unstable due to the excessive number of 3 beads, and the 9 beads were convex and uneven, causing dis-slag entrainment.

Conventional flux FG has a particle size of 48 x D mesh
Because it is a fine grain, it is highly hygroscopic and may cause puncture marks. Furthermore, there is room for improvement as dust is generated during flux dispersion and collection.

(Effects of the Invention) As described above, the flux of the present invention is granular and difficult to powder, so it hardly generates dust, and since it does not contain a gas generating agent, it does not generate fumes or odors, and of course, it does not generate exposure arc light. Because there is no such thing, it is extremely difficult for occupational health reasons.
It provides good mechanical properties and is extremely effective in improving the working environment and work efficiency in welding steel materials that require low-temperature toughness.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the firing temperature and the amount of diffusible hydrogen for various fluxes, and FIG. 2 is a diagram showing the relationship between the amount of St in the flux and absorbed energy. Figure 1 Incineration i! (°c)

Claims (1)

[Claims] In the high-temperature fired flux fired at 750°C or higher, 5 to 10% (wt%, same hereinafter) of either or both of CaO and MgO as basic oxides and fluorine as metal fluorides other than alkali metal fluorides. 3 to 30%,
5 to 50% of SiO_2 as acidic oxide or this Si
Both O_2 and 44% or less Al_2O_3 from 25 to 6
0% Si in the flux as metal powder.
5% or less, and the bulk density is 0.8 to 1.2 g/cm^
3. A high-temperature firing flux for submerged arc welding.