JPS6036876B2 - Flux for horizontal electroslag overlay welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flux for horizontal electroslag overlay welding using a stainless steel strip electrode.

In order to provide corrosion resistance to pressure vessels made of extremely thick steel plates used in chemical plants and the like, stainless steel overlay welding is applied to the inner surface of the vessel.

In this case, it is important for overlay welding to have high efficiency, shallow lacquer penetration, and a smooth overlay surface, and in Japan, band electrode overlay welding is exclusively used. In the strip electrode overlay welding method, the melting form of the electrode is divided into submerged arc type and electroslag type depending on the flux used.

Submerged arc type is 75 unless magnetic control is applied.
If the band-shaped electrode is wider than the side width, the depth of the undercut that occurs at the overlapping portion of the beads will be deep, making it difficult to put it to practical use. However, in the case of the electroslag type, by considering the flux, undercuts are unlikely to occur even if a strip electrode having a side width of 75 mm or more is used, and a smooth bead overlapping portion can be obtained. However, horizontal electroslag overlay welding is not possible with any kind of flux; unless the flux has appropriate physical properties, undercuts can occur when horizontal electroslag overlay welding is performed using a wide strip electrode with a width of about 10 mm. It is not possible to obtain a smooth bead without any defects. In other words, in horizontal electroslag overlay welding, the Joule heat of the current flowing in the molten slag a few millimeters between the base metal and the electrode is used to melt the strip electrode and overlay, and the flux is molten in an appropriate manner. It must have electrical conductivity. If the electrical conductivity is too low, an arc will occur, resulting in subsurge arc welding.If the electrical conductivity is too high, the flux will melt due to insufficient Joule heat generation, but even if the flux melts, the amount of melting at the electrode will be small, and the molten metal will not be able to connect to the base metal due to insufficient heat. The welding does not work well and a satisfactory bead cannot be obtained. Usually CaF
2 is often used in electroslag welding due to its high electrical conductivity, but flux containing more than 45% will emit a bad odor during welding, so adding a large amount will lead to a deterioration of the working environment.

Therefore, in order to keep the content of CaF2 low and ensure electrical conductivity, Ti02 can be added, but if the amount of Ti02 is increased beyond a certain limit, the melting point of the flux will increase and the electrical conductivity will be temperature dependent. As a result, the electrical conductivity is reduced and arcing occurs. In arc welding, when using a wide band-shaped electrode of about 10 strips, the toe of the bead is determined by the arc and cannot be completely filled with molten metal, resulting in an undercut. For this reason, it is important that the flux has an appropriate melting point. When CaF2 was removed and reduced, the CaF2 content at which the odor became less noticeable was found to be 35% or less. Therefore, the present inventors succeeded in finding and producing a flux that suppresses CaF2 to 35% or less and has an electrical conductivity equivalent to a flux that is 45% or more of CaF2. Another important property that the flux must have is good slag releasability.

The removability of slag not only affects welding efficiency, but also includes the risk of causing slag entrainment defects in subsequent peads stacked next to each other if slag removal is insufficient. Therefore, when developing flux, it is necessary to fully take into account the releasability of the slag. After considering the above matters, the present inventors have found that horizontal electroslag overlay welding using a wide stainless steel strip electrode has a beautiful bead appearance, no undercuts, well aligned bead toes, and good slag releasability. We have developed a flux that can produce good overlay metal with little penetration.

That is, in the present invention, CaF215-35%, Ti0215-35%
34%, Si0210~30%, Ca05~25%, M
g01-4%, and CaF2 equivalent k=CaF
2 (%) 10.7 Ca0 (%) 10.5 (Ti02 (%
The first invention is a horizontal electroslag welding flux in which k = 45 to 65 as Mg0 (%)),
Or further contains 10% of Z, and CaF
2 equivalent k=CaF2 (%) 10.7 Ca0 (%) 10.
2 (%) 10.5 (Ti02 (%) 10 Mg0 (%)
The second invention provides a flux for horizontal electroslag overlay welding in which k=45 to 65.

In addition, in this specification, % means weight %. below,
The present invention will be explained in detail. First, the chemical composition range of flux will be described.

CaF2 has high electrical conductivity and a suitable melting point (1
418:0), making it an essential component for electroslag welding. Especially CaF2 in flux
When the electrical conductivity exceeds 45%, the welding shifts from supmerged arc to horizontal electroslag welding, and although it has appropriate electrical conductivity for overlay welding, the generation of fluoride gas creates a bad odor and worsens the working environment. I will let you do it. Therefore, Ca
By keeping the upper limit of F2 at 35% and adding Ca○, Ti02, Mg0, etc. to ensure electrical conductivity comparable to CaF2 of 45% or more, it is possible to prevent the foul odor of fluoride gas generated during welding. can. However, CaF2 is 15
Attempts have been made to ensure electrical conductivity with other components below %, but it has been found to be difficult due to the increase in the flux welding point. Therefore, CaF2 was limited to a range of 15 to 35%. Ti02 can be combined with CaF2 to keep the flux at the proper electrical conductivity.

However, if it exceeds 34%, the flux melting point will increase,
Not only does this result in a lower electrical conductivity in the temperature range required for welding, but it also worsens slag removability. Further, Tj02 is a component that improves the bead appearance and slag removability, but if it is less than 15%, the effects of other components, including the improvement of electrical conductivity, will be too great and the effect will not be recognized. Therefore, Ti02 was limited to a range of 15 to 34%. Si
02 is when Ti02 is added to CaF2,
The melting point increases, which may actually reduce the electrical conductivity, but since Si02 acts to suppress the increase in the melting point due to the addition of Tj02, it can indirectly contribute to the electrical conductivity.

However, Si02 itself is a component that lowers electrical conductivity, and if the amount added is too large, it approaches the melting point of Si02 itself, increasing the flux melting point and adjusting the fluidity of slag, which is a good property of Si02. The function of obtaining a beautiful pead appearance is lost. Sj02 added to CaF2 is Ti
In combination with 02, it can be useful for horizontal electroslag welding. Its effect appears when the concentration exceeds 10%, and when it exceeds 30%, it not only lowers the electrical conductivity and increases the flux melting point, adversely affecting the bead appearance, but also impairs the slag removability. This causes harm such as lowering the basicity and increasing the Si content in the weld metal. Therefore, Sj02 is 10-30%
limited to the range of Ca0 becomes calcium ions in the molten slag and functions to increase electrical conductivity. In addition, adding an appropriate amount can maintain the flux melting point at an appropriate temperature, but adding more than the limit will cause a sudden rise in the melting point, resulting in a decrease in electrical conductivity in the temperature range necessary for welding. will come. Further, Ca0 has the function of improving the appearance of the pead, increasing the basicity, and suppressing an increase in the Si content in the weld metal. Increase these electrical conductivity,
The effect of improving the bead appearance is ineffective if it is less than 5%, and if it exceeds 35%, the bead appearance deteriorates due to the violent reaction of the molten slag pool due to the rapid increase in the flux melting point. Therefore, Ca0 was limited to a range of 5 to 35%. Like Ca○, Mg0 is a component that increases electrical conductivity.

Also, when added in small amounts, it works to lower the melting point of the flux, but when the amount added is increased, the melting point of the flux itself is very high, so the melting point of the flux increases rapidly, and the electric current in the temperature range required for welding is increased. This causes a decrease in conductivity. Mg0 also plays an important role in adjusting the toe of the peed. Also, like Ca○, it has the function of increasing basicity and suppressing the increase in Si in the weld metal. However, at 1% or more, these effects are absent, and at more than 4%, the flux tends to increase the melting point and the slag removability is impaired. Therefore, it was limited to M or a range of 1 to 4%. In addition, in the present invention, k as CaF2 equivalent:
CaF2 (%) 10.7 Ca○ (%) 10.5 (Ti0
2 (%) 10 Mg0 (%)), k is in the range of 45 to 65.

In other words, when the CaF2 equivalent k is 45 or more, the electrical conductivity of molten slag is such that horizontal electroslag welding can be easily performed, and when k exceeds 65, the electrical conductivity is too high and Joule heat is insufficient, reducing the melting rate of the electrode. Only the flux will melt, and in extreme cases, the heat capacity of the molten metal will be insufficient, resulting in metal that will not settle on the base material. Therefore, k must be between 45 and 65. In this case, the coefficient of Ca○ is 0.7, and the coefficients of Ti02 and Mg○ are each 0.5 because of the CaF of each component.
The contribution factor of electrical conductivity for 2 is 0.7 times and 0.3, respectively.
This is because an experiment revealed that moss is 0.9 blue. Furthermore, we found that adding Zr02 as an additional component to flux produced a bead with a particularly shiny bead appearance and a well-finished overlay.

Zr02 is also a component that contributes to electrical conductivity. The range in which bead gloss can be obtained is 10% or less, and if it exceeds 10%, slag removability will be impaired. Therefore, ZrQ is 1
It was limited to 0% or less. In addition, in this case, k = CaF2 (%) +0.7Ca0 as CaF2 equivalent including 2 of Z
(%) 10. When 2 (%) 10.5 (Ti02 (%) 10 Mg0 (%)), k is in the range of 45 to 65. In this case, the coefficients of Ca○, Ti02 and Mg○ are the same as above, and the coefficient of Zr02 is 0.6 or the contribution rate of electrical conductivity to CaF2 is 0.6. This is because experiments have shown that it is a mochi sound. The flux of the present invention may be a melt flux obtained by melting a mixture of the above-mentioned various raw materials in a melting furnace, or a bond flux obtained by mixing the mixture with a binder such as water glass, granulating it, and firing it at 300 to 500°C.

However, melt flux from which gas components have been removed is more practical for horizontal electroslag welding. The effects of the present invention will be illustrated in more detail below with reference to Examples.

The steel plates shown in Table 1 were used as base materials in the examples.

Table 2 shows stainless steel strip electrodes. Table 3 shows all the fluxes used. For comparison, fluxes outside the scope of the present invention were also investigated. The flux used was melt flux melted in a melting furnace. The welding conditions are shown in Table 4, and the results of the welding performed in this manner are shown in Table 5. Chemical analysis was performed on samples taken from about 2 sides from the bead surface. As is clear from the welding results in Table 5, the flux shown as a comparative example had poor slag releasability, poor bead shape, etc., and also caused slag entrainment, and did not exhibit good workability. In comparison to these, all examples using the flux of the present invention exhibited good workability, with smooth and beautiful-looking beads being obtained. As explained in detail above, the flux of the present invention exhibits good welding workability for stainless steel strip electrodes, and provides excellent weld metal.

Table 1 *Table 2 for plate thickness 50, 〇. 4 x 100 pine spots k = CaF2o + 0.7 Cao + 0.5 (TiQ + Mg0 or if ZrQ is included)
Mg0 side) 4th Momogan

Claims (1)

[Claims] 1% by weight: CaF_215-35%, TiO_2
15-34%, SiO_210-30%, CaO5-2
5%, MgO 1-4%, and CaF_2 equivalent k
=CaF_2(%)+0.7CaO(%)+0.5(T
k = 45 to 65 as iO_2 (%) + MgO (%))
A flux for horizontal electroslag overlay welding, which is characterized by: 2 CaF_215-35%, TiO_2 as weight%
15-34%, SiO_210-30%, CaO5-2
5%, MgO1-4%, ZrO_2≦10%,
And CaF_2 equivalent k = CaF_2 (%) + 0.7C
aO (%) + 0.6 ZrO_2 (%) + 0.5 (TiO
A flux for horizontal electroslag overlay welding, characterized in that k=45 to 65 (_2 (%) + MgO (%)).