JPS598478B2 - Flux for wide strip electrode overlay welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a flux particularly suitable for welding a wide band electrode overlay.

In recent years, fluxes that tend to form an electroslag state as a welding phenomenon are being developed in order to obtain beautiful weld beads with shallow penetration in strip electrode overlay welding.

For example, there is Japanese Patent Publication No. 53-29657, but as a result of hastily obtaining an electroslag state in such a flux component system, there is a problem in that a large amount of fluoride fume, which is undesirable in terms of safety and health, is generated during welding.

In addition, JP-A-1988-54 has been developed to reduce the generation of fluoride fume.
This flux includes a range of components with low basicity, and as a result, the range of electrical conductivity of the molten slag is wide. For this reason, especially when horizontal electroslag welding is carried out using a wide strip electrode, the welding speed is generally slow and the heat input is large, resulting in a large weld pool and increased fluoride fume, while the slag-metal reaction With fluxes with low basicity, the oxidative consumption of alloying elements, especially Mn and Cr, in the electrode is large, resulting in an excessive yield of 51, and convection in the molten pool, which disturbs the bead shape and causes damage to the electrode. Disadvantages include the possibility of arcing at both ends, resulting in deeper penetration, or undercutting at the bead overlap, and the need to pay special attention to welding conditions and flux distribution methods during welding work. Ta. On the other hand, in view of the current situation, the present inventors have separately proposed a flux in Japanese Patent Application No. 54-4724.
Although we have shown an appropriate electrical conductivity range depending on the amount of calcium fluoride, the flux in this composition range is only effective in that horizontal electroslag welding is likely to occur and the generation of fluoride fumes is small. However, there was a problem in that the above-mentioned drawbacks still remained.

Therefore, as a result of various studies, the present inventors have found that it is necessary to limit the electrical conductivity range of the molten slag due to the chemical components of the flux and to increase the basicity of the flux compared to when using a normal strip electrode. revealed.

In other words, it was found that even with the same amount of calcium fluoride and utanium oxide added, as the calcium (4) oxide/silica (%) or basicity increases, the electrical conductivity of the molten slag increases. , the present inventors noted that the electrical conductivity of molten slag mainly depends on the amount of titanium oxide and calcium fluoride added in the flux, but also depends considerably on basicity depending on the composition, By limiting the range of electrical conductivity of molten slag by titanium oxide calcium monofluoride and by increasing its basicity, even if a wide band electrode is used, consumption of alloying elements in the electrode can be kept low. Moreover, it is insensitive to the effects of welding conditions and flux distribution methods, there is no bead disturbance due to convection in the molten pool, there is no arcing at both ends of the electrode, and there is no undercut at the overlapped part of the bead. In addition to easily obtaining a smooth and beautiful overlay weld metal with shallow penetration, by actively adding manganese oxide or chromium oxide, Mn, which is particularly susceptible to oxidation due to the reaction between slag and metal during horizontal electroslag welding, can be easily obtained. We have developed a flux for overlay welding of wide-width electrodes in which the alloying elements of Cr and Cr are not consumed by oxidation, thereby saving the alloying elements in the strip-shaped electrode.

That is, the present invention contains 60% or less titanium oxide, 10-25% calcium fluoride, 10-25% silica, and 8% calcium oxide.
~20% as the main component, {calcium fluoride (a) + titanium dioxide (%}) is 35 to 45%, and calcium oxide (4) / silica (a) is 0.6 to 2.0. The first invention is a flux in which one or both of magnesium oxide and barium oxide are added in an amount of 4% or less, and barium oxide and 4% or less in such a manner that the total is 4% or less. ≦15%, Cr2O3
The second invention is a flux for overlaying a wide band-shaped electrode, characterized in that the flux includes a total of 20% of either one or both of them in combination.

In addition, in the present invention, wide width means that in normal submerged arc welding, unless a special method (for example, applying a magnetic field) is used,
Those with a width that is said to be impossible to weld due to the influence of magnetic blowing, i.e. 100-2007! It is within the Lm range and is mainly used for high-efficiency overlay welding.

The present invention will be explained in detail below.

First, the chemical composition range of flux will be described.

The present inventors have conducted various studies and found that titanium oxide and calcium fluoride are essential components for increasing the electrical conductivity of molten flux and maintaining the melting point of the flux at an appropriate temperature. Calcium fluoride is twice as effective as titanium oxide, and when a normal width strip electrode (generally 751 m or less) is used, {calcium fluoride (% + 1/2 titanium oxide)} is 40 times more effective than titanium oxide.
It was previously found that the electrical conductivity range of the molten slag becomes appropriate when the electrical conductivity is 50%. However, when using a strip electrode with a width of 100 u or more, the welding speed is generally slow and electroslag is likely to occur. The appropriate range of electrical conductivity of slag is low.

That is, {calcium fluoride (% + 1/2 titanium oxide (
%} is less than 35%, the electrical conductivity of the molten flux does not increase and the arc state of normal submerged arc welding occurs,
The penetration depth will not become shallow. (1 to 2 m0 Also, when {Calcium Fluoride Co., Ltd. + 1/2 Titanium Oxide (%)} exceeds 45%, the electrical conductivity of the molten flux increases too much, the calorific value is insufficient, and the part in the electroslag state This results in unstable welding in which there are parts where the electrode contacts the base metal and generates an arc, and a smooth and beautiful bead cannot be obtained. (Calcium fluoride (% + 1/2 titanium oxide (%)
Only when it is 5 to 45%, a stable electroslag state is obtained during horizontal electroslag welding using a wide band electrode, shallow penetration (0.5 mH or less), and a smooth and beautiful bead can be obtained. Even in this case, if more than 60% of titanium oxide is added, the melting temperature of the flux will rise and slag will be involved, making welding impossible.
Must be 60% or less.

Furthermore, when using calcium fluoride with a normal width electrode, if the addition amount is 35% or less, fluoride fumes are extremely unlikely to be generated. However, when welding is performed with a large heat input using a wide electrode, fluoride Since the amount of fume increases, it is necessary to keep it below 25%.

That is, if it is less than 25%, fluoride fume will hardly be generated. Furthermore, if less than 10% of calcium fluoride is added, the effect is low, and arcs occur particularly at both ends of the wide strip electrode, so the addition of calcium fluoride must be 10 to 25%. Silica is an essential component as a slag-forming agent and for imparting electrical resistance to the molten slag, that is, lowering the electrical conductivity and increasing the calorific value to maintain the electrode at a temperature at which it can be melted.

On the other hand, calcium oxide is used as a slag forming agent and is an essential component to increase the basicity of the flux (to prevent oxidative consumption of alloying elements in the electrode and to obtain clean weld metal). Co., Ltd./Silica (
% also affects the electrical conductivity of the molten slag, and as the basicity increases, the electrical conductivity increases. It becomes almost constant at .60,
Calcium oxide (A) / Silica (%) If the ratio is 0.60 or more, the consumption of alloying elements will be small and there will be no excessive Si yield. If the melting point of the flux becomes too high, slag entrainment may occur, or the flux at both ends of the electrode may not melt, and the width of the weld bead may become significantly narrower than the electrode width. There must be.
Also, if silica is less than 10%, its effect is not sufficient, and 2
Silica must be in the range of 10 to 25% since addition of more than 5% tends to result in deep penetration and excessive Si retention. On the other hand, if calcium oxide is less than 8%, its effect will not be sufficient, and if it is added in excess of 20%, it will cause slag entrainment or form a bead narrower than the width of the electrode, so the content must be between 8 and 20%. . On the other hand,
Furthermore, by adding magnesium oxide and barium oxide, the basicity of the flux increases, the weld metal becomes cleaner, the oxidation consumption of alloy components is further reduced, the melting temperature of the flux is appropriately lowered, and the molten flux is transferred to the base metal. This improves the elasticity of the electrode and suppresses arcing at both ends of the electrode.

However, if magnesium oxide and barium oxide are added alone or in combination in an amount exceeding 4%, arcing is likely to occur at both ends of the electrode, causing undercuts, so the amount must be 4% or less. In addition, since no arc occurs in the electroslag state and the weld metal does not come into contact with the atmosphere, most of the reaction is due to the slag-metal reaction. Therefore, if one or both of manganese oxide and chromium oxide are added in combination, oxidation can be prevented. It is possible to prevent the oxidation reaction of Mn or Cr, which are easy alloy components, and improve the yield of Mn and Cr in the electrode. However, if manganese oxide exceeds 15% or chromium oxide exceeds 15%,
If the amount exceeds 20% when both are combined, it changes the properties of the flux and destabilizes the electroslag state.
% or less, chromium oxide 15% or less, and if both are added in combination, 20% or less. The flux used in the present invention is produced by melting and cooling the raw materials and then pulverizing them into granules, or by dry mixing the raw materials, then adding a suitable binder and wet mixing.
Similar effects can be achieved by sintering or drying. In this case, it is also possible to add alloy powder to the flux. The flux of the present invention has such a structure, and has less fluoride fume, which is more harmful than stiffness, and has shallow penetration, which results in extremely low dilution of the weld metal by the base metal, thereby suppressing the carbon content and improving corrosion resistance. Furthermore, the flux of the present invention can be used to reduce the alloy composition of the electrode material, and has superior effects in terms of productivity and economy.
Since the welding phenomenon is in a stable electroslag state over the entire width of the electrode, it not only has the advantage of shallower penetration, but is also less susceptible to magnetic blowing and the electrode melts almost uniformly in the width direction. This also enables stable welding.

In addition, the fact that no arc is generated at both ends of the electrode means that when beads are overlapped, the weld metal blends well at the overlapped portions, resulting in beautiful weld metal. Furthermore, since the weld metal does not come into contact with a gaseous atmosphere, the amount of oxygen and inclusions in the weld metal can be kept low, and good corrosion resistance, particularly pitting corrosion resistance, can be obtained. EXAMPLE Welding was carried out by combining the base material shown in Table 1, the strip electrode shown in Table 2, and the flux shown in Table 3.

Incidentally, the flux was used by blending the raw materials, dissolving and pulverizing the mixture, then drying and pulverizing. The welding conditions are as follows. Table 4 shows the results of welding performed in this manner.

Chemical analysis is approximately 21 from the bead surface! The dilution rate of the weld metal by the base metal was calculated from the area ratio of the base metal penetration part to the entire weld metal based on the macrostructure of the cross section of the test piece. be. As is clear from the results in Table 4, the flux of the present invention has low generation of harmful fluoride fumes and has good welding workability.
No welding defects occur, the bead overlap area in particular is smooth and beautiful, the penetration of the weld metal is shallow, and the alloy components in the weld metal, especially the content of Si, Mn, and Cr, are appropriate. However, with the flux of the comparative example, fluoride fumes were generated, the penetration became deeper due to transition to an arc state, the amount of Si increased significantly, and undercuts occurred in the repeat overlapped parts where Mn and Cr were worn out. Welding workability deteriorated due to slag formation, slag entrainment, slag burning, etc., and in severe cases, welding became impossible.

Claims (1)

[Claims] 1. Titanium oxide 60% or less, calcium fluoride 10-25%
%, silica 10-25%, calcium oxide 8-20% as main components, {calcium fluoride (%) + 1/2 titanium oxide (%)} 35-45%, calcium oxide (%)
/ silica (%) is 0.6 to 2.0, and further comprises one or both of magnesium oxide and barium oxide at 4% or less for a total of 4% or less Flux for electrode overlay welding. 2 Titanium oxide 60% or less, calcium fluoride 10-25
%, silica 10-25%, calcium oxide 8-20% as main components, magnesium oxide 4% or less and barium oxide 4% or less, one or both of which are combined and the total is 4% or less, and { Calcium fluoride (%) +1
/Titanium dioxide (%)} is 35 to 45%, and
Calcium oxide (%)/silica (%) is 0.6 to 2.0
A flux for welding a wide band-shaped electrode overlay, characterized in that the total amount of manganese oxide or chromium oxide is 15% or less, chromium oxide is 15% or less, or a combination of both is 20% or less.