JPH0635078B2 - Bond flux for latent arc welding - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a bond flux for submerged arc welding, and is particularly suitable for corner joint welding of a steel box column, and it is a two-electrode large heat input single layer of extremely thick plate. The present invention relates to an economical bond flux for latent arc welding, which has excellent slag peeling resistance, hydrogen cracking resistance, and repeated use resistance in flat welding and multi-pass welding, and has low flux consumption.

(Prior art and problems to be solved) In recent years, along with the skyrocketing land prices and the increase in intelligent buildings with high-tech functions, the skyscrapers and large spaces have been developed and used in order to effectively utilize the ground space. Steel columns have a tendency to become thicker and thicker, and welding of super-thick plates of 50 to 100 mm is performed in various places.

As the welding method for steel, there are a covered arc welding method, a carbon dioxide gas arc welding method, a submerged arc welding method, and the like.However, in the welding of thick plates, high current welding is possible by using a large diameter wire, so a high welding speed The resulting latent arc welding method is generally widely used.

However, the following problems are presently present problems in the latent arc welding of the ultra-thick plate corner joint of the steel box column.

In multi-layer welding, the slag generated during welding gets stuck in the groove, so it takes a lot of time and effort to remove the slag.

Since the amount of diffusible hydrogen in the weld metal increases with an increase in welding heat input, especially in multi-pass welding of thick plates, strict control of preheating and interpass temperature is necessary to prevent hydrogen cracking (cold cracking). It is necessary and requires a lot of work.

Since it is a high heat input welding, in order to secure the shielding property from the atmosphere by the invisible arc, the flux dispersion height needs to be extremely higher than that of the ordinary subarc welding. Therefore, it takes time and effort to collect the flux, and a powerful flux collector is often used. As a result, the flux is easily pulverized into fine particles, which adversely affects the welding workability and the mechanical performance of the weld metal.

In the large heat input welding of thick plates, the amount of slag generated by welding will be enormous, and the cost and quantity required for its disposal will be enormous.

With respect to each of these problems, conventionally, improvement measures have been proposed, which are intended to improve the slag removability (Japanese Patent Laid-Open Nos. 2-41795 and 58-23593).
No.), which is intended to reduce hydrogen (Japanese Patent Laid-Open No. 60-19629).
No. 0, JP-A-62-203698), those intended to improve flux recovery (Japanese Patent Publication No. 2-39358 and Japanese Patent Publication No. 58-19491), those intended to reduce the amount of slag (Japanese Patent Publication No. 62-182277) and the like.

However, none of them can solve all the above problems in high heat input welding of 100 to 200 KJ / cm or more.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and to provide a welding material particularly suitable for large heat input latent arc welding of extremely thick plates.

(Means for Solving the Problems) The present inventor has made extensive studies as to the composition of the flux for box-type latent arc welding in order to solve the above problems, and as a result, the present invention has been made. is there.

That is, the present invention _{is, totalSiO 2: 10~20% Al 2} O 3: 10~20% totalTiO 2: 3~14% MgO: 10~20% CaCO 3: 5~15% totalMn: 0.5~8% Iron powder: 20-40% sol. SiO _2: 1.0~6.0% sol. Na ₂ O: 1.5 to 3.5%, and sol. Na ₂ O / totalNa ₂ O ratio: 0.60 to 0.98 (however, sol.Na ₂ O is _{sol.Na 2 O + sol.K 2 O +} so
l. Total amount of Li ₂ O, totalNa ₂ O is totalNa ₂ O + to
talK ₂ O + total Li ₂ O) MgO / SiO ₂ (total) ratio: 0.75 to 1.30 The bond flux for latent arc welding is characterized by the following.

The present invention will be described in more detail below.

(Function) The reasons for limiting the chemical components in the present invention are as follows.

totalSiO ₂ : 10 to 20% SiO ₂ is an acidic component and is an essential component because it adjusts the viscosity of the slag, but if it is less than 10%, the viscosity of the slag becomes insufficient and the bead width becomes unstable or uneven. Become. Furthermore, the amount of slag produced increases, which is not preferable. On the other hand, 20
If it exceeds%, the viscosity of the slag becomes excessive and the spread of the beads becomes poor. In addition, the peelability of the slag also deteriorates and the basicity decreases, so the toughness also tends to deteriorate.

Al ₂ O ₃ : 10 to 20% Al ₂ O ₃ is a neutral component and is an effective component for adjusting the viscosity and solidification temperature of slag without impairing the toughness of the weld metal. However, if it is less than 10%, the viscosity and solidification temperature of the slag become low, the bead width becomes non-uniform, and the bead shape becomes convex, which is not preferable. On the other hand, if it exceeds 20%, the solidification temperature of the slag becomes too high, so that the bead is not sufficiently spread or is easily meandered.

totalTiO _2: 3~14% TiO ₂ is a component effective as a melting point and viscosity modifiers of the slag. TiO ₂ also has the effect of adding [Ti] to the weld metal by a reduction reaction during welding and improving impact performance. Therefore, it is possible to add it from the TiO ₂ source such as rutile and rucoxin into the flux, but it is also possible to use it in combination with an alloying element such as Fe—Ti. In the present invention, including the case of adding Ti alloy such as Fe-Ti, in such a case in terms of TiO _2, was to be defined as the total amount of TiO ₂ ((total).

However, if the total amount of TiO ₂ is less than 3%, the amount of [Ti] in the weld metal is small, impact performance is deteriorated, and undercut is likely to occur, which is not preferable. On the other hand, if it exceeds 14%, the slag releasability deteriorates rapidly and the amount of slag produced also increases.

MgO: 10 to 20% MgO is a basic component and is an effective component for reducing [O] in the weld metal and ensuring toughness. It also has a function as a viscosity modifier. However, if it is less than 10%, the reduction hardening of [O] is small and the toughness deteriorates. Further, the bead is likely to meander, and undercut occurs.
On the other hand, if it exceeds 20%, seizure of slag is increased and a pock mark is likely to occur. Further, the amount of slag produced increases, which is not preferable.

CaCO ₃ : 5 to 15% CaCO ₃ is decomposed into CaO and CO ₂ during welding, and CO
₂ Gas shields the weld from the outside air,
It is an effective component for lowering the partial pressure of the impurity gas (H ₂ or N ₂ etc.) and preventing it from entering the weld metal. However, if it is less than 5%, the shielding effect by CO ₂ gas is insufficient, the amount of hydrogen and nitrogen in the weld metal increases, and cold cracking and toughness decrease easily. Especially one layer (One-Ru
n) During welding, the amount of hydrogen increases, so cracking is likely to occur. On the other hand, if it exceeds 15%, the amount of CO ₂ gas generated becomes excessive, the gas does not escape uniformly, and the blow-up phenomenon during welding becomes extremely large, and the bead appearance is likely to deteriorate. In particular, the slag removability in multi-pass welding deteriorates.

total Mn: 0.5 to 8% Mn is not only an effective component for adjusting the viscosity and solidification temperature of slag, but also adjusts the amount of Mn in the weld metal to ensure tensile performance and impact performance. It is an essential ingredient.
However, if it is less than 0.5%, undercut and slag seizure are likely to occur, which is not preferable. Also, when combined with an inexpensive low Mn wire, the amount of [Mn] in the weld metal is insufficient,
The tensile strength and toughness decrease. On the other hand, if it exceeds 8%, the bead tends to meander and the amount of flux consumed increases, which is not preferable.

The Mn component is added to the flux in the form of a compound such as metal Mn or Fe-Mn and an oxide such as MnO or MnO _{2. In} the present invention, the total amount of Mn is total M.
I decided to specify it by n. Therefore, the total Mn amount is set to the range of 0.5 to 8%.

Iron powder: 20-40% When iron powder is added to the flux, it shifts to the molten pool during welding and the consumption increases. This makes it possible to improve the welding efficiency and reduce the welding heat input. But 20
If it is less than%, this effect is small and the blow-up at the time of high heat input welding increases, which is not preferable. On the other hand, when it exceeds 40%, the spread of the beads becomes poor and slag entrainment easily occurs.

sol. SiO _2: 1.0~6.0% sol. SiO ₂ is regulated in order to improve the pulverization resistance and moisture absorption resistance of the flux (the amount of diffusible hydrogen in the weld metal increases as the amount of moisture absorption increases). Here, sol. SiO ₂ is water-soluble SiO ₂ .

However, if it is less than 1.0%, it is not preferable because the flux is pulverized and refined when the flux is recovered by an extremely efficient recovery machine. When the flux is pulverized, the most problematic factors are that outgassing becomes poor, abnormal blow-up occurs, and pock marks are likely to occur. On the other hand, if it exceeds 6.0%, the moisture absorption resistance of the flux deteriorates, and hydrogen cracking easily occurs particularly in multi-layer welding of thick plates, which is not preferable.

sol. Na ₂ O: 1.5~3.5% sol. Na ₂ O is an essential component for ensuring arc stability. The thicker the plate and the larger the heat input welding, the more difficult the welding becomes and the narrower the range of appropriate welding conditions. In particular, control of the arc voltage is very important. However, if it is less than 1.5%, the deflection of the voltmeter needle will be very large, so when setting to a predetermined voltage value, individual differences will occur depending on the welding operator, resulting in defects such as undercut and insufficient penetration. Very often connected. Further, since the arc voltage is unstable, there is a problem that it becomes difficult to obtain a uniform welding result as the welding length becomes longer. On the other hand, if it exceeds 3.5%, the moisture absorption resistance of the flux deteriorates, which is not preferable.

In addition, sol. Na ₂ O is sol. Na ₂ O + sol. K ₂ O + so
l. The total amount of Li ₂ O, sol. Na ₂ O, sol. K
₂ O, sol. Li ₂ O is water-soluble Na ₂ O and K, respectively.
₂ O and Li ₂ O.

sol. Na ₂ O / totalNa ₂ O ratio: .60 to .98 sol. Na ₂ O / totalNa ₂ O ratio is regulated to improve耐粉resistance and moisture absorption resistance of the flux. But,
If it is less than 0.60%, the product yield at the time of production is lowered and the arc stability is also inferior, which is not preferable. On the other hand, 0.98
If it exceeds, the resistance to pulverization of the iron powder bond flux containing 20 to 40% of iron powder deteriorates, and the flux is likely to become fine during repeated use. Further, the moisture absorption resistance of the flux is deteriorated, and hydrogen cracking is likely to occur, which is not preferable.

Here, totalNa ₂ O is totalNa ₂ O + totalK ₂ O + to
It is the total amount of talLi ₂ O.

MgO / SiO ₂ ratio: 0.75 to 1.30 The MgO / SiO ₂ ratio needs to be regulated in order to secure welding workability. However, if it is less than 0.75, the slag removability in the groove deteriorates. On the other hand, if it exceeds 1.30, the flux consumption amount (slag generation amount) increases, and slag baking occurs, which is not preferable. Also, the bead shape is convex, and the bead does not spread.

As other components, for example, it is well known that appropriate amounts of [Ti] and [B] are added to the weld metal in order to improve the toughness at the time of large heat input latent arc welding, but also in the present invention. Similarly, the addition amount of [B] is 0.
An amount of 0015 to 0.0050% can be added. In this case, it can be added from the flux or from the wire or both.

The flux of the present invention is of bond type,
Since the bond flux is manufactured in the process of granulating the raw material using a fixing agent such as water glass and then firing it, it is possible to add a metal carbonate such as CaCO ₃ as compared with the melt type flux. This is because it has advantages such as low hydrogenation, high deposition rate by adding iron powder, and easy adjustment of basicity of slag, solidification temperature, and viscosity required for high heat input welding. .

Next, examples of the present invention will be described.

(Example) Test wire equivalent to JIS Z 3351 YS-S6 and having chemical components shown in Table 1 (wire diameter: leading electrode is 6.4 mm)
φ, and the trailing electrode was 6.4 mmφ), and a test arc of chemical composition shown in Table 2 was used to perform a latent arc welding test under the following conditions. The sol.SiO ₂ amount and sol.Na ₂ O amount and the sol.Na ₂ O / totalNa ₂ O ratio in the test flux are
It was controlled mainly by combining the chemical composition of water glass and the drying conditions of flux.

[Other welding conditions]

-Number of electrodes: 2-electrode welding-Power supply polarity: AC-AC-Test steel plate and welding conditions: SM50B steel with dimensions of 50 mmt x 1000 mml is used and 3
Performs one-layer welding (one-run welding) by latent arc welding with a 5 ° Y-shaped groove (root surface 2 mm). Welding heat input is 41
It is 0 KJ / cm.

Using SM50B steel with dimensions of 100 mmt x 1000 mml,
With a 50Y ° groove (root surface 2mm), 7 by latent arc welding
Multi-layer welding with 16 passes is performed. The welding heat input is 180 KJ / cm on average for 16 passes.

Tables 3 and 4 show the test results (slag removability, hydrogen cracking resistance, flux recoverability, slag generation amount, welding workability and bead appearance, and weld metal impact characteristics).

Note that these evaluation methods are as follows.

Slag releasability Since slag releasability is a particular problem in the first layer of multi-layer welding, it was evaluated by multi-layer welding of 100 mmt test steel sheets. The criteria are as follows.

◯: Slag is peeled off without using a chipper.

X: Slag is difficult to peel off even if a chipper is used.

Hydrogen cracking resistance It was evaluated by multi-pass welding of a test steel plate having 100 mmt. That is, multi-layer welding was carried out while controlling the preheating temperature: room temperature and the temperature between passes: 75 ° C., and after leaving for 48 hours or more, cracks were investigated by an ultrasonic flaw detection test. The flux used was one that was re-dried at 250 ° C. for 1 hour before starting the welding of the first layer. However, after that, it was left as it was in the atmosphere. The evaluation criteria are as follows.

◯: No cracks, ×: Cracks Flux recovery was evaluated by 1-layer welding of 50 mmt sample steel sheet. That is, new flux was repeatedly collected 10 times by a collecting machine, and then welding was performed to examine workability. The evaluation criteria are as follows.

◯: Similar to new flux, no significant change in workability was observed.

X: Abnormal blow-up, occurrence of pock mark, and deterioration of bead appearance.

Evaluation was carried out by single-layer welding of a test steel sheet having a slag generation amount of 50 mmt. That is, the flux consumption amount per 1 m of welding length and the wire consumption amount were measured, and the flux consumption rate (flux consumption amount / wire consumption amount) was calculated.
High flux consumption is economically problematic and was evaluated using this method. The evaluation criteria are as follows.

○: Flux consumption rate ... Less than 1.15 △: Flux consumption rate ... 1.15 to 1.40 ×: Flux consumption rate ... 1.40 Welding workability and bead appearance inspection Each of both test steel sheets of 50 mmt and 100 mmt In welding, it was judged by visual inspection.

◯: good, ×: poor Impact performance of weld metal Evaluated by single-layer welding of a test steel sheet of 50 mmt. That is, a JIS Z 311A4 test piece was sampled from the surface of the base material 10 mm, and the test was carried out at 0 ° C. to obtain the average value of three pieces.

Further, sol.SiO _2, sol.Na ₂ O Quantification was carried out following the instructions at 1-3.

(Procedure 1) Flux is sufficiently crushed by a vibration mill, and about 0.2 g of the flux is sampled and put into a quartz Erlenmeyer flask together with 100 ml of distilled water to extract soluble components.

(Procedure 2) Soluble components were extracted under boiling for 4 hours.

(Procedure 3) After allowing the extract to stand overnight, the supernatant was sampled, and alkali metal ions such as Li, Na, and K were quantified by an atomic absorption method, and the amount of Si was quantified by an absorptiometry method.

As is clear from Tables 3 and 4, it is obvious that the examples of the present invention have excellent welding workability in single-layer welding and multi-layer welding of extremely thick plates, as well as slag removability and hydrogen resistance. It has excellent cracking resistance, repeated use resistance, etc., and consumes less flux.

(Effects of the Invention) As described in detail above, according to the present invention, particularly in the arc welding of the plate thickness, excellent workability, slag peeling resistance, hydrogen cracking resistance, repeated use resistance and the like are excellent. Demonstrate the performance,
In addition, it consumes less slag and is economical. Suitable for two-electrode large heat input single-layer welding and multi-layer welding of extremely thick plates such as corner joint welding of steel box columns.

Claims (2)

[Claims] 1. A weight% (hereinafter, the _{same), totalSiO 2: 10~20% A} 2 O 3: 10~20% totalTiO 2: 3~14% MgO: 10~20% CaCO 3: 5~15% total Mn: 0.5-8% Iron powder: 20-40% sol. SiO _2: 1.0~6.0% sol. Na ₂ O: 1.5 to 3.5%, and sol. Na ₂ O / totalNa ₂ O ratio: 0.60 to 0.98 (however, sol.Na ₂ O is _{sol.Na 2 O + sol.K 2 O +} so
l. Total amount of Li ₂ O, totalNa ₂ O is totalNa ₂ O + to
talK ₂ O + total Li ₂ O) MgO / SiO ₂ (total) ratio: 0.75 to 1.30, which is a bond flux for latent arc welding. 2. The bond flux for latent arc welding according to claim 1, which is for welding two-layer one-layer or multi-layer welding.