JPS5910874B2 - Non-melting flux for submerged arc welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a non-melting flux used in submerged arc welding performed in various welding positions, and in particular is used for horizontal submerged arc welding mainly in the manufacture of storage tanks, pressure vessels, etc. to achieve good welding. This relates to a welding flux that provides good workability and mechanical properties.

Due to its high efficiency, submerged arc welding is often used for horizontal joints in the construction of cylindrical tanks, spherical tanks, steelmaking machinery such as blast furnaces and hot blast furnaces, reaction vessels in the chemical industry, and nuclear reactor containment vessels. . Due to gravity in submerged arc welding in a horizontal position, the weld bead is thin on the top side and thick on the bottom side, and gas tends to collect on the top plate side, causing hook marks and undercuts, and overlap on the bottom plate side. , sauce 1
Zero thickness is likely to occur, and since the groove angle is smaller than in downward welding, slag separation is difficult, and internal defects such as slag entrainment, pits, and blowholes are likely to occur. Furthermore, in horizontal submerged arc welding, the oxygen content in the weld metal is higher than in downward arc welding, and especially when using a direct 15 current power source and performing multilayer welding with a small current, the oxygen content in the weld metal increases significantly. The toughness deteriorates. Furthermore, in AC welding, the nitrogen content increases, making it difficult to obtain good toughness. Therefore, in flags applied to horizontal submerged arc welding, all of the above-mentioned problems regarding welding workability and mechanical properties of weld metal must be solved.

The present invention provides a flux that satisfies the characteristics that these fluxes for horizontal submerged arc welding should have.It mainly contains TiO_213-30%, CaF
_210-50%, MgO_20-40%, A1203
12-30%, 5iO_22-[20-(%CaF_2
)÷3]%, contains 0.1 to 1.0% of B203,
or caco33011.5 as required
This is a non-melting flux for submerged arc welding, characterized in that it contains % or less.

The present invention will be explained in detail below.

First, the flux of the present invention has a T
1O235 is one of the main components, B2O3 is contained, Ti and B are transferred from the flux into the weld metal, the transfer of Ti is promoted by the Al2O3 component, and C
The aF2 component and MgO component reduce oxygen in the weld metal. In addition, slag separation within narrow horizontal grooves is ensured by the synergistic effect of the TiO2 component and Al2O3 component, and the MgO component increases the fire resistance of the flux to suppress bead sag, and the Al2O3 component and S
The iO2 component improves the bead shape and bead gloss.In particular, the SiO2 component has the effect of maintaining arc stability by adjusting the content according to the CaF2 content for low oxygen content. It is something that demonstrates the.

In addition to the above-mentioned effects, the CaF2 component also has the effect of preventing slag entrainment, and CacO3 is further added to stabilize the arc and prevent hydrogen absorption in the weld metal. As described above, the content of each constituent component of the flux of the present invention is determined so as to exhibit an effective synergistic effect on both the material quality of the weld metal and the welding workability in relation to each other. Next, the reason for limiting the content of each component will be explained in detail. TiO2 adds titanium to the weld metal through the welding arc to improve the toughness of the weld metal. It also improves the separation of the initial layer of slag, especially in narrow grooves such as horizontal welding, and improves the bead surface. It is an essential acidic component to improve smoothness and reduce hock marks.

However, if the upper limit of 30 (I) is exceeded, the titanium concentration in the weld metal becomes too high, and in multilayer weld metal, embrittlement occurs due to the precipitation of titanium compounds due to the reheating effect, and the viscosity of the flux decreases too much, causing weld bead formation. It becomes impossible to press the bead, and the bead surface becomes sticky. Also, TiO
If 2 is less than 13%, the bead shape and surface quality will deteriorate,
It is easy to get stuck on the bead surface, the slag removability inside the groove is significantly deteriorated, and the titanium concentration in the weld metal is insufficient.
Its toughness cannot be increased. Sources of TiO2 added to the flux of the present invention include, for example, rutile sand, titanium flour, anatase, and artificial rutile produced by removing iron from illuminite, which accounts for 13 to 30% in terms of TiO2. It is added. As the amount of CaF2 added increases, the oxygen content in the weld metal decreases, promoting the toughness improvement effect of titanium in the weld metal, significantly increasing the fluidity of flux, and reducing the molten slag of molten steel during welding. Separation can be promoted and slag entrainment can be reduced.

This effect of CaF2 on flux has already been generally acknowledged, and efforts have been made to utilize this CaF2 since conventional fluxes mainly composed of SiO2 tend to have a particularly high oxygen content in the weld metal. However, if CaF2 exceeds 15%, the arc becomes unstable and cannot be used effectively, so the amount of CaF2 added has generally been limited to a low value. To solve this problem, the inventors
It was discovered that this problem can be solved by limiting the amount of iO2 added according to the amount of CaF2 added, and in order to effectively utilize the effect of CaF2 in the flux of the present invention, 5%
It was concluded that it was necessary to add the above. However, if it exceeds 50%, even if the amount of SiO2 added is limited, the arc will become unstable and arc breakage may occur.
It was found that the wire is more likely to be pushed in, creating a chance for slag entrainment, and furthermore, an excessive decrease in the viscosity of the flux lowers the bead control, resulting in sagging and overlapping. For these reasons, the appropriate range for the amount of CaF2 added is 10 to 50%.
It was determined that Sources of CaF2 used in the present invention include, for example, as-mined fluorite, purified fluorite, molten flux powder containing CaF2 as a main component, and the amount is added in an amount of 10 to 50% in terms of CaF2. It is something. MgO increases the basicity of the flux, suppresses the increase in oxygen content in the weld metal, increases the refractory properties of the flux, and in particular suppresses the sag of horizontal beads, so it is necessary to have an amount of 20% or more.
However, if it exceeds 4001), the arc becomes unstable, slag inclusion tends to occur, and the bead surface becomes less glossy. Examples of sources of MgO added to the flux of the present invention include silica bonded magnesia clinker,
Examples include iron-bonded magnesia clinker, electrofused magnesia, seawater magnesia, lightly calcined magnesia, and MgO-containing spinel, which are added in an amount of 20 to 40% in terms of MgO. By adding a large amount of Al2O3 together with TiO2, it exhibits an excellent synergistic effect, particularly improving the slag removability of the initial layer within the groove and reducing the addition of titanium from TiO2 to the weld metal. Effective for promotion.

That is, as mentioned above, TiO2 alone is effective in improving the slag removability of the initial layer within the groove, but Al2O
By coexisting with 3, its effect is further enhanced. Further, under the same amount of -TiO2, the amount of titanium reduced to the weld metal increases as the amount of Al2O3 increases. A in flux
12O3 is also reduced through welding, and a small amount of aluminum is added to the weld metal, and the presence of an appropriate amount of aluminum in the weld metal contributes to improving the toughness of titanium and boron. In addition, the addition of TiO2 reduces the viscosity of the slag and deteriorates the bead shape.
The addition of l2O3 controls the slag viscosity to a suitable value that provides good bead shape. Also, low Si
The coexistence of TlO2 and Al2O3 improves the reduction in gloss on the surface of Bi-1 bales, which is likely to occur due to O2 flux. In order to exhibit these effects, Al2O3 needs to be 1201) or more. However, if it exceeds 30%, the amount of titanium reduced from TiO2 to the weld metal becomes too large, causing embrittlement, and the aluminum concentration in the weld metal increases, causing embrittlement due to an increase in the amount of ferrite in the microstructure. Moreover, the viscosity increases too much, resulting in poor bead shape and furthermore, flux granulation properties deteriorate. Al2 to the flux of the present invention
Examples of sources of O3 to be added include industrial refined alumina, calcined bauxite, siyamoto, mullite clinker, andalusite, and high alumina cement, which are added in an amount of 12 to 30% in terms of Al2O3. In addition to adding MgO and Al2O3 individually, spinel (MgO・A
It can also be added as 12O3). SiO2 is an acidic component that is necessary for slag vitrification to control the viscosity of the flux and maintain a good gloss on the bead surface.Also, it is unavoidably mixed in from other flux raw materials, so it should be contained at least 2% or more. However, when transverse multi-layer welding is performed using flux containing a large amount of SiO2, particularly with DC reverse polarity, the oxygen content of the weld metal increases significantly and its toughness deteriorates. Furthermore, when coexisting with a large amount of CaF2, the size of the arc cavity fluctuates violently, the arc becomes unstable and the bead shape is significantly damaged, and this phenomenon is caused by the maximum SiO2
The amount added varies depending on the amount of CaF2. That is, C
When the aF2 addition amount is 50%, which is the upper limit, it is 3.3%, and the lower limit of CaF2 is 100! ) 16.7%
, and there is a linear relationship between them, so the relationship is (%
It was found that SiO2)≦[20-(%CaF2)÷3]. Therefore, the upper limit of the amount of SiO2 added is [20
−(%CaF2)÷3]%. In this way, SiO2
Even if the amount is limited to a low value, the flux of the present invention can provide good welding workability because it contains 13 to 30 fl of TlO2 as an acidic component. In addition, sources of SiO2 added to the flux of the present invention include silica sand, wollastonite, and potassium feldspar, and in terms of SiO2, 2 to [20-(
%CaF2)÷3]%. B2O3 can add boron to the weld metal depending on the amount added, and 0.1% or more is required in order to coexist with titanium to make the microstructure of the weld metal uniform and fine and to significantly improve toughness. However, if there is an excessive amount of boron in the weld metal, the effect of improving the toughness of the weld metal will decrease, and the possibility of hot cracking will increase, so the upper limit of the amount of B2O3 added is 1.0%.
And so. Sources of B2O3 added to the flux of the present invention include, for example, boric acid, borax, colemanite tourmaline, borosilicate glass, danburite, dojiite, suianite, etc.
It is added in an amount of 0.1 to 1.0% in terms of O3.
Adding CacO3 at 11.5% or less is effective for improving arc stability and reducing hydrogen absorption in the weld metal, but if CacO3 is added in excess of 11.5%, it reacts with TiO2, Perovskite (CaO-TiO2), which has a high melting point and tends to precipitate on the bead surface, is produced, impairing slag releasability, which is not preferable.

Sources of CacO3 include dense limestone, crystalline limestone, marble, etc., which is equivalent to 11.5 CacO3.
(:Ff) The following are added.

In addition, manganese oxides such as manganese silicate, manganese dioxide, manganese slag, and manganese carbonate can be added to increase the manganese concentration in the weld metal and improve toughness, but these tend to cause hook marks. , increases the oxygen content in the weld metal and impairs slag releasability, so the amount added is 5 (fl) in terms of MnO.
The following are desirable. In addition, Mg, Al, Si fluorides,
There is no problem in adding small amounts of Zr, K, Na, and Ll oxides, fluorides, iron powder, and alloy powder for arc stabilization and the like. In addition, as an alloying agent and deoxidizing agent as necessary,
Metals or alloys of Si, Mn, Ni, MO, Cr, or iron alloys thereof can be added. When producing the flux of the present invention, if the entire flux is melted in advance, the support of the bead becomes weak and the arc becomes unstable, especially in horizontal welding, and furthermore, the amount of diffusible hydrogen in the weld zone increases, which is undesirable. Therefore, the method for producing the flux of the present invention is limited to a non-melting method. That is, there is either a method in which raw material powder is granulated using a binder and fired, or a method in which the entire material is sintered at a high temperature and then pulverized and sized. It goes without saying that the flux of the present invention is not limited to horizontal welding, but can also be applied to downward welding and complete penetration horizontal fillet welding, which have fewer restrictions. The effects of the present invention will be explained in more detail below using Examples. Example 1 A bevel of the shape shown in Fig. 1 was prepared on a 30 mm thick low-temperature killed aluminum steel whose chemical composition and mechanical properties are shown in Table 1.
It has a diameter of 3.2ILI with the chemical composition shown in Table 2.
Using IL wire, current 450A with DC reverse polarity power supply
(first layer only 350A), voltage 28V) speed 40CIn/
Min) Torch angle: 300) Overhang length: 25''l Horizontal multi-layer welding was performed on each side with 3 passes under welding conditions where the inter-pass temperature was 150°C or less.

The chemical composition of the flux used at that time is shown in Table 3.

Table 4 shows the blending ratios of the raw materials constituting these fluxes in percentages. Fluxes F-1 to F-8 are subject to the present invention, and F-9 and F-10
is the flux of the comparative example.

Table 5 shows the welding workability results and the oxygen content and mechanical properties of the weld metals obtained with these fluxes. As seen in the table, welding workability and mechanical properties of weld metal using fluxes F-1 to F-8 are both excellent, but
F-9 had a large amount of CaF2 and SiO2, so the arc voltage fluctuated violently, arc breakage and wire thrusting occurred frequently, and it was not suitable for practical use. With F-10 flux, the arc was stable, but since it did not contain B2O3, the resulting weld metal had poor toughness, and in addition, the slag was so stuck that the slag could not be peeled off at all. Example 2 Using HT6O steel whose chemical composition and mechanical properties are shown in Table 6, welding wire, and a submerged arc welding machine for AC small-diameter wire, current 350A1 voltage 28-29,
Four passes of multilayer welding were performed on each side at a welding speed of 50 CTIL/Min.

The fluxes used were F-3, F-4, F-6, and F-9.
It was hot. The results are shown in Table 7. F-3, F-
4. With F-6 flux, there are no defects such as slag entrainment, pits, and hook marks, and a sound horizontally welded joint with good mechanical properties is obtained, whereas F-6
With a flux of -9, the arc was still unstable and the joint had many defects. Example 3 A groove of the shape shown in Fig. 2 was prepared on a SM5O steel plate with a thickness of 20 m10), and a welding wire with a diameter of 4.8 mm having the composition shown in Table 2 and F-5 of the fluxes shown in Table 3 were prepared. AC welding current 650A, welding voltage 31V, welding speed 5
Downward multilayer welding was performed at 0 cm/min with 3 passes on each side.

As a result, if F-5 flux, which is the object of the present invention, is used, the welding workability is excellent, and the impact value of the weld metal is
-45% was 10.2 kg-m. Example 4 A steel plate with a composition shown in Table 1 was prepared with a groove shown in FIG.
Complete penetration horizontal fillet multi-layer welding was performed using fluxes F-3, F-4, and F-10 in the table using an AC small-diameter wire submerged arc welding machine.

Claims (1)

[Claims] 1 Main components: TiO_213-30%, CaF_2
10-50%, MgO_20-40%, Al_2O_3
12-30%, SiO_22-[20-(%CaF_2
) ÷ 3]%, a non-melting flux for submerged arc welding characterized by containing 30.1 to 1.0% of B_2O_3. 2 Main components: TiO_213-30%, CaF_2
10-50%, MgO_20-40%, Al_2O_3
12-30%, SiO_22-[20-(%CaF_2
)÷3]%, B_2O_30.1-1.0% and Ca
A non-melting flux for submerged arc welding characterized by containing 11.5% or less of CO_3.