JPS591513B2 - Melting type flux for submerged arc welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a welding method that exhibits good welding workability and provides a welded metal with good impact toughness, particularly in fillet welding of 50 to 60 kg class high tensile strength steel. This article relates to a melt-type flux for submerged arc welding that has both workability and mechanical performance.

In submerged arc welding, fillet welding accounts for a high proportion of the many welding operations, and there is therefore a strong desire to improve efficiency.
Welding materials are required to have pit resistance that is unaffected by slight rust or primer, and a continuous bead appearance that blends smoothly with the base metal. These improvements in welding workability are achieved by using acidic fluxes such as SiO2-MnO, and such welding materials are widely used in construction where mechanical performance is not a big issue, such as with mild steel. There is.

However, such acidic fluxes cannot be used for high-strength steels that require high impact toughness because the amount of oxygen in the weld metal increases, and the amount of oxygen in the weld metal increases at the expense of work efficiency. A neutral flux was used, which resulted in a slightly lower temperature.

As described above, the welding workability and mechanical performance of flux for submerged arc welding have conventionally been generally viewed as contradictory.

Therefore, the inventors of the present invention have conducted extensive studies with the aim of developing a flux for submerged arc welding that is capable of welding 50 kg or 60 kg class high-strength steel and has good welding workability. The bulk density of the flux, MnO, MgO (■I
) The ratio of the components to SiO2 is determined within the optimum range, and the basicity of the flux is maintained in the acidic range.
The reduction in impact toughness caused by this can be prevented by making the weld metal crystal grains finer by adding TiO2, and the deterioration in slag removability due to the addition of TiO2 can be prevented by limiting the amount of coexistence of TiO2 and CaO. Depending on the method,
It has been found that there is a flux composition range with good welding workability and mechanical performance in a specific range.

That is, Fig. 1 shows that the analytical values are approximately 30% for MnO and about 30% for Ti.
O2 about 2%, T. The amounts of CaO and F are approximately constant at approximately 4% and 2%, respectively, and the amounts of SiO2 and MgO components are 42 to 58% each.
, bulk density 0.9-1, varied in the range of 6-15%
．． The results of an investigation on the influence of the MgQ/SlO2 ratio on the amount of diffusible hydrogen are shown for 10 types of prototype fluxes of 19/CTil.

Figure 1 is based on JISZ3ll3, welding conditions: 400
A300, 50 (1-J MoV1/MiTL wire: 3.2
mmφ, JISYSW-41. As is clear from this figure, the amount of diffusible hydrogen increases as the MgO/SlO2 ratio increases, particularly when it exceeds 0.30.

In addition, Figure 2 shows a JISZ33ll plate of 12mm thick 0SM-50B steel using the same flux as in Figure 1.
, 700A35V70 using YSW-41 equivalent wire
Downward fillet welding under welding conditions of cfL/Mm (welding length 1m)
) and the time required for slag removal and MgQ/SlO
This shows the relationship between the two ratios.

As is clear from this figure, most of the slags are naturally exfoliated, but when the MgO/SiO2 ratio is less than 0.16, the time required for exfoliation becomes longer and the slag releasability deteriorates. Figure 3 shows that the analysis value is Mg.
O about 10%, TiO2 about 2%, T. Prototype flux with a bulk density of 0.9 to 1.1 g/CTil, with approximately constant CaO of approximately 4% and F of approximately 2%, and varying the amounts of SlO2 and MnO components in the ranges of 41 to 58% and 24 to 4570, respectively. This figure shows the relationship between the incidence of hook marks and undercuts during horizontal fillet welding under welding conditions of 600A34V60CTIL/Burmese using wire equivalent to JISZ33ll and YSW-41, and the MnQ/SiO2 ratio.

As can be seen from this figure, as the MnQ/SiO2 ratio increases, there is a tendency for the number of hook marks to decrease and the number of undercuts to increase.
When the ratio was less than 0.55 and over 0.80, undercuts were extremely likely to occur. In addition, FIG. 4 shows Sl
In the blended raw material having a composition of O25l%, MnO38%, MgOll%, the analysis value is about 2% F, T. CaO
Using 15 kinds of prototype fluxes mixed and melted to have a range of 2% to 10% and 12% to 8% of TlO2, a plate of 12 mm (7) SM-50B steel was welded under the same conditions as in Fig. 2. The slag removability when performing downward fillet welding is T. CaO(!: is shown in relation to the TiO2 content. As can be seen from this figure, the slag removability tends to deteriorate as the T.CaO and TlO2 contents increase, but the sum of these T. CaO+TiO
There is no problem if 2 is within 9%. In this Figure 4, ◎ means that the slag will peel off naturally, O means that it will peel off with almost no resistance, △ means that it will peel off by hitting the slag lightly, and × means that it will peel off by hitting the slag quite hard. This indicates that the material will stick and peel off. Also, this 1
Among the five types of prototype fluxes, T. About 2% CaO is produced by T.I. using AlF3 as the F source without using fluorite (CaF2). This T. The CaO value is considered to be an impurity from other raw materials.

The present invention is based on the above findings, and its gist is that SiO245-55%, Tl
Contains O2l~4%, F1~3%, 0.16% MgO
/SlO2ku0.30,0.55kuMn[SiO2ku0
．． 80,T. Ca0+TiO2 9%, bulk density 0.9
Basicity B of ~1,39/C77l and expressed by the following formula:
0.55 to 0.85.

The present invention will be explained in detail below.

First, since the present invention relates to a molten flux, all of the limiting values for the content of each component, component ratio, basicity, etc. are based on analytical values of the flux.

This means that the composition of the melted flux and the component content of the finished product flux after melting generally do not match, and the performance of the melted flux depends on the content of each component in the finished product flux.
Depending on the combination, the content of this component can only be known by analyzing the product flux. In addition, regarding the meaning of the analysis values of the components in molten flux, each component in molten flux, which has been melted and becomes glassy, has a crystal structure and molecular bonding state as it was blended as raw materials. Therefore, when analyzing the flux, all oxide-forming elements contained in the flux were identified as SiO2, MnO, MgO, CaO, and Ti, regardless of their form.
It will be quantified in the form of the most stable oxides such as O2 and Al2O3.

For example, Ca blended in the form of oxides and carbonates, Ca blended and added as a fluoride, or Ca mixed in from furnace materials are contained in the molten flux that is once melted and becomes glassy. Therefore, it is impossible to distinguish between them, and all are quantitatively analyzed in the form of CaO.

Therefore, such analytical values are expressed as T (total) to clarify that all Ca contained in the flux is expressed in the form of CaO. CaO
It is written as.

In this sense, the same applies not only to CaO but also to other oxides, and it can be said that T should be added to all oxides.

In particular, when MgF2, AlF3, etc. are used as the F source, T
．． MgO, T. Although it should be written as Al2O3, F
Since CaF2 (fluorite), which is inexpensive, is generally used as a source, only CaO is used. It has traditionally been written as CaO. The analytical values of oxides in molten fluxes have the characteristics described above, and the limiting values of oxide content, component ratio, basicity, etc. in the present invention are based on each element contained in such fluxes. All S
The values are based on quantitative analysis in the form of 1O2, MnO, MgO, CaO, and TiO2.

Furthermore, although there are many unknowns about the existence form of fluorides in molten flux, in molten flux the raw material fluoride is once melted and becomes a glass state, so CaF2, MgF2, AlF3, BaF2 It is thought that the crystal structure and molecular bonds have not changed to their original state.

Therefore, molten flux also has C in component analysis.
Since fluorides such as aF2 and MgF2 cannot be quantified in the form of fluorides, methods such as the fluoride chloride monosilver nitrate/kutankali titration volumetric method or the thermal decomposition method (see Journal of the Japan Institute of Metals, No. 6, 1970) are used. The F content in the flux is first quantified using a method, and then arithmetically converted into forms such as CaF2, MgF2, AlF3, etc., and is used as the fluoride content for convenience. It refers to the numerical value of the F content itself in flux, determined by the method described in .

Next, we will discuss the reasons for limiting each numerical value in the present invention.0 First, the reason why SiO2 is set to 45 to 55% in the present invention is as follows.
If SiO2 is less than 45% or more than 55%,
This is because the melting point and fluidity of slag are unsuitable for bead formation, and a good bead shape cannot be maintained, especially in horizontal fillet welding.

TiO2 is an effective component for refining the weld metal structure and improving toughness, but if it is less than 1%, the effect is insufficient, and if it exceeds 4%, there is no further improvement effect, and the slag removability is Only the negative effects of deterioration appear. F is an important component that prevents the occurrence of pits and blowholes due to its shielding effect, but if it exceeds 370, the arc becomes unstable.
A smooth bead cannot be obtained. Conversely, if it is less than 1%, the shielding becomes insufficient and pits and blowholes are likely to occur.

As for MgQ/SiO2, as mentioned above, when it exceeds 0.30, the amount of diffusible hydrogen increases and the occurrence of pits and blowholes increases. Moreover, if it is less than 0.16, slag removability deteriorates. As mentioned above, MnQ/SiO2 is 0.
If it is less than 55, deoxidation will be insufficient and more hook marks will occur, while if it exceeds 0.80, undercuts will be more likely to occur.

T. As mentioned above, when CaO+TiO2 exceeds 9%, the slag removability deteriorates.

When the bulk density exceeds 1.3 g/Crit, the arc becomes unstable and the bead waveform becomes rough.

On the other hand, if it is less than 0.9, the amount of hydrogen in the flux will increase, making pits, blowholes, and hook marks more likely to occur.
The term "bulk density" as used herein refers to a density measured by a loose packing method, and is measured in accordance with the method specified in "Vinyl chloride resin test method 1" of JIS K672l-1966. If the basicity B exceeds 0.85, the arc becomes unstable and the waveform of the bead becomes rough, making it impossible to obtain a uniform and well-fitting bead.

On the other hand, if it is less than 0.55, the amount of oxygen in the weld metal will be excessive, resulting in not only a decrease in impact toughness but also a decrease in C1 to the weld metal.
Alternatively, the yield of alloy components such as Sl and Mn decreases, which causes a problem of insufficient tensile strength, especially in multilayer welding of high-strength steel. This basicity calculation formula B is a simplified version of the Mori method BL (see Journal of the Japan Institute of Metals, No. 6, 1960), and the Mori method BL, which is expressed as a summation, is expressed as a fraction. Furthermore, by dividing each coefficient of BL by its molecular weight, the amount of each component can be directly calculated in weight percent without converting it into a mole fraction.

However, the coefficient of the Al2O3FeO component is relatively small, and in the flux of the present invention, the content is small and has almost no effect, so it was omitted from the calculation formula. As for other components, first of all, regarding MnO, MnQ/Si
Although the reason for limiting the O2 ratio has been stated, the MnO component is 40
% or less is desirable.

This is because when MnO exceeds 40%, fire resistance deteriorates and welding workability in a large current range tends to deteriorate. As for MgO, the reason for limiting the MgQ/SiO2 ratio was mentioned above, and it is desirable that the MgO component be 15% or less.

This is because when MgO exceeds 15%, the viscosity of the slag begins to increase and the bead shape tends to deteriorate.
Al2O3, FeO, K2O, Na2O, etc. are components mixed as impurities in the raw materials used, but if these components are 6% or less, 2% or less, 1% or less, and 1% or less, the characteristics of the flux of the present invention will not be affected. There is no effect.

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

After melting the mixed raw materials F-1 to F-6 blended as shown in Table 1 in an electric furnace in a reducing atmosphere, cooling with water and solidifying,
The particles were sized to a particle size of 12×48 mesh.

These fluxes were combined with the comparative fluxes and the wire steel plates shown in Table 2, and the welding conditions shown in Table 3 were used to perform horizontal fillet welding, impact testing of Y-groove double-sided single-layer butt weld metal, and glycerin replacement. Law (JISZ3l
A diffusible hydrogen test was carried out according to 13 standard).

The analytical values of the component contents of these fluxes were as shown in Table 4.

These results are shown in Table 5. Among the comparative fluxes, those with good mechanical performance had poor welding workability, and those with good welding workability had poor mechanical performance or had a high amount of diffusible hydrogen. On the other hand, the flux of the present invention had just the right performance and was good in all of them.

In addition, the impact test piece in Y-groove double-sided butt welding was F.
Samples were taken mainly at a position 7u below the surface of the P side plate.

In Table 4, good slag peeling and bead shape are indicated by ◎, almost good by 01, slightly poor by △, and poor by ×.

Regarding defects such as hook marks, pits, and undercuts, those that do not occur are ◎, and those that slightly occur are ○.
Those that occur somewhat frequently are indicated by △, and those that occur frequently are indicated by ×. As described above, the present invention provides a flux that is compatible with welding workability and mechanical performance, and has an extremely wide range of applications.

[Brief explanation of drawings]

Figures 1 and 2 show MgQ in the flux system of the present invention.
Figure 3 shows the relationship between the MnO/SiO2 ratio, the amount of diffusible hydrogen, and the slag removal time, and Figure 4 shows the relationship between the MnO/SiO2 ratio, the number of hook marks, and the undercut length. T. in flux. CaO and Ti
Figure 5 is a diagram showing the relationship between O2 content and slag removability, and Figure 5 is a diagram showing (a) horizontal fillet welding procedure and (b) groove shape of Y groove double-sided single-layer butt welding, respectively, in the example. be.

Claims (1)

[Claims] 1% by weight SiO_245-55%, TiO
Contains _21-4%, F1-3%, 0.16≦MgO
/SiO_2≦0.30, 0.55≦MnO/SiO_
2≦0.80, T, CaO+TiO_2≦9%, bulk density 0.9 to 1.3 g/cm^3, and basicity B expressed by the following formula is 0.55 to 0.85. Melting type flux for submerged arc welding. B=0.108T. CaO+0.068MnO+0.1
0MgO/0.105SiO_2+0.062TiO_
2