JPS5856679B2 - Melt flux for submerged arc welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a submerged arc welding melt flux that is used to obtain weld metal and has good welding workability.

As the tensile strength and thickness of structures increase, the submerged arc welding flux used therein is desired to have improved toughness, hydrogen cracking resistance, and welding workability.

Generally, melt flux is Si02-MnO
Many of them are based on CaO-MgO as their main components.

This type of flux has the following characteristics: (1) Fluxes that generally yield a weld metal with high toughness have a large amount of hydrogen.

(2) A flux with a low hydrogen content and good cracking resistance has low toughness.

(3) Fluxes with good welding workability such as bead shape and defect resistance have low toughness or have a high hydrogen content and poor cracking resistance.

It has the disadvantages of high toughness, low hydrogen, and good workability.
There was not enough flux to satisfy people.

Considerable knowledge has been obtained regarding the improvement of these individual performances, and improvements have been made one after another.For example, with regard to toughness 1qK, the basicity of the flux has been increased.

To lower the oxygen content in weld metal.

The content of oxides such as SiO2, MnO, etc., which allow oxygen to enter the weld metal from the melted flux during welding, is suppressed as much as possible, and instead, a large amount of substances with a high affinity for oxygen, such as A1203, CaF2, CaO, etc. are added.

It is possible to improve toughness by using a composition system that reduces the amount of oxygen that enters the weld metal.

On the other hand, it is known that most of the hydrogen in the weld metal that degrades the crack resistance ratio is hydrogen that enters from the flux, so hydrogen in the flux can be reduced.

Improves cracking resistance.

To this end, during production and melting of melt flux, hydrogen is reduced by adjusting the flux composition to a neutral to acidic range in order to reduce the dissolution of moisture in the atmosphere into the melt.

In addition, in order to maintain good welding workability, that is, arc stability, slag removability, bead appearance, and bead shape, the bulk density of the flux is reduced.

However, these improvements have to be carried out from a comprehensive viewpoint of toughness and hydrogen workability, and problems arise when focusing on individual performance improvements.

In other words, if 51022Mn0 is reduced and CaF2 and Al3O3 are increased to improve toughness, the basicity will increase and the amount of hydrogen will increase, and if the amount of flux sprayed during welding is even slightly large, the arc will become unstable. This makes the waveform of the weld bead extremely rough, which tends to result in an uneven bead appearance, resulting in extremely poor welding workability.

Regarding the amount of hydrogen, in order to reduce atmospheric moisture from dissolving into the molten material during melting, if the flux composition is made neutral to acidic, the amount of oxygen in the weld metal will increase, resulting in high toughness. do not have.

Furthermore, if you try to rapidly cool the molten material in water or the like to make the flux particles lighter and improve the welding work ratio.

In addition to the moisture that has entered the minute particles of flux particles,
Since the surface area is large, the amount of attached moisture increases and the hydrogen cracking resistance becomes significantly inferior.

For these reasons, it has been difficult to develop a melt flux that has good hydrogen cracking resistance, high toughness, and good welding workability.

However, the present inventors have conducted various research trials on medium MnO-based melt flux, and have found that it has good hydrogen cracking resistance.
As a result of studying the composition of melt flux, which has good welding workability to the extent that there is no need to limit the height of flux spraying and can obtain weld metal with high toughness, we have found the following findings. I got it.

First, in order to improve hydrogen cracking resistance, make the flux magnetically neutral to prevent moisture in the atmosphere from dissolving into the melt and increasing the amount of hydrogen when melting the blended raw materials. Therefore, the basicity (BI) needs to be in the range of 0.9 to 1.3.

In addition, the bulk density of the flux can be freely changed by cooling the molten material on a metal plate or rapidly cooling it in water and causing it to foam, but we investigated the effect of this bulk density on the amount of hydrogen. As a result, a light flux that is rapidly cooled and foamed in water has a significantly increased hydrogen content, which is not desirable.

However, the flux cooled on a metal plate has a low hydrogen content.

Those with a bulk density of 1.3 to 1.9 y7cmp show a low hydrogen content.

In addition, this bulk density was measured by the loose packing method, and specifically, it was measured according to the measurement of bulk specific gravity of "vinyl chloride resin test method" of JISK6721-1966.

In order to obtain the next highest toughness, it is effective to reduce the oxygen content in the weld metal, and for this purpose 5i02. It is necessary to reduce the MnO content, and it is necessary to reduce it to an extent that welding workability does not deteriorate.

S i 02 (%) + Mn0 (%) is 35 to 48
(%), a welding work ratio is good and the amount of oxygen in the weld metal is 500 ppm or less.

By the way, the amount of CaF2 becomes as large as 10 or more,
and its bulk density is 1.3 to 1. A problem with 'l/a- melt flux is that welding workability generally deteriorates in relation to the height of the flux during welding.

In other words, when using a high CaF2 flux Vc, if too much flux is applied, the various gases generated from the molten metal and slag during welding will not be able to sufficiently escape to the outside, resulting in an unstable arc. An unstable arc occurs due to flux being blown up explosively and dissipating, resulting in extremely rough bead waveforms and uneven bead shapes, which impairs bead appearance and slag removability.

With this type of flux, it is necessary to place strict restrictions on the spray height during welding.

In particular, in order to use a relatively large amount of flux grains, which can produce a weld metal with low hydrogen and high toughness, and to obtain high toughness, CaF2
, and the addition of alkali oxides.
As a result, the melting point becomes low and the fluidity of the slag becomes excessive, which tends to occur.

It was also found that the density of the flux is a factor related to this problem, and that a flux with a high density cannot maintain a stable arc, and the appearance of the bead tends to deteriorate as soon as it is affected by the flux spray height. are doing.

In order to solve this problem, we investigated the effect of flux spraying height on bead appearance using a high CaF2 flux, using hydrogen and a range of components with good toughness.We found that CaO, MgO, Strong basic components such as BaO1 have a large atomic weight and high density, and alkali metal oxides have a large atomic weight of 20, and acidic components ZrO,...
It was confirmed that 5i02, which is the main component of flux, has a particularly bad effect when added in large amounts.
and the amount of MnO is S i 02 (%) + MnO (
%), it became clear that the range of articles 35 to 48 was the most preferable.

The present invention has been made based on the synthesis of the above findings.

That is, in the present invention, the main components are expressed in weight percent.

5iO225~38φ, Mn06~17%, Ca014
~27%, CaF212~20%, Al2035~
20 Mine, TiO21~5%, Na2O or Li2O
A submerged material obtained from a low-hydrogen, high-toughness weld metal characterized by comprising one or both of 0.3 to 2.0 liters of MgO6 or less, and satisfying the conditions of the following formulas (1) to (3). This is a melt flux for arc welding.

(1) 5i02 (%) + Mn0 (%) ~35~4
8 (%) (2) Basicity (BI) ~ 0.9 ~ 1.3 (3) Bulk density 1.3 ~ 1.9 V/am, "The reasons for the limitations for each component are described below. It is as follows.

First, SiO2 greatly affects the performance of the flux, and if it is less than 25%, the amount of hydrogen in the weld metal is large, resulting in poor cracking resistance and poor welding workability.

Moreover, if it exceeds 38 degrees, the oxygen content in the weld metal increases and the toughness decreases, which is not preferable.

Next, like 5i02, MnO has a strong influence on flux performance, and welding workability is affected when MnO is less than 6.

If it exceeds 17%, it is not preferable because the cracking resistance deteriorates, and if it exceeds 17%, the toughness decreases and is not preferable.

In addition, 5iO2 (%) + Mn0 (%) content is particularly important in order to maintain high toughness and good welding workability, and if 5iO2 (%') + Mn0 (%) is less than 35%, the hydrogen content As this increases, the melting point of the slag becomes too high and welding workability deteriorates.

Furthermore, when SiO□(4)+Mn0(2) exceeds 48, the amount of oxygen in the weld metal increases, making it impossible to obtain high toughness, and as described above, welding workability regarding the flux spray height deteriorates.

If CaO is less than 14%, welding workability deteriorates.

It is not desirable because the toughness is low, and if it exceeds 27%, the hydrogen content increases and the cracking resistance deteriorates, which is not desirable.

If CaF2 is less than 12%, the oxygen content in the weld metal will not be reduced and the hydrogen content will not be reduced either, which is not preferable.

Moreover, if it exceeds 20%, the arc becomes unstable and welding workability deteriorates.

5 or more Al2O3 is required to adjust the basicity, but if it exceeds 20, the amount of hydrogen will increase and the toughness will decrease.
This is not preferable because it also deteriorates the welding workability of the housing.

TiO2 is necessary to obtain high toughness, and if it is less than 1, it has no effect, and if it is more than 5, slag will seize and the toughness will decrease, which is not desirable.

One or both of Na2O and Li2O is necessary to obtain high toughness, but if it is less than 0.3%, it has no effect, and if it exceeds 2.0%, the amount of hydrogen increases, which is not desirable.

MgO is effective for achieving high toughness and making the bead surface beautiful, but if it exceeds 6%, the amount of hydrogen increases significantly, so it is necessary to limit it to less than 6%.

Furthermore, regarding the basicity of the flux (BI) is 0.9.
The value of ~1.3 is necessary to obtain a flux that provides high toughness and low hydrogen weld metal, and is 0.9
If it is less than this, the amount of oxygen in the weld metal increases and the toughness decreases, which is not preferable.

If the basicity exceeds 1.3, more water will enter the molten material during welding and the hydrogen cracking resistance will deteriorate, so it must be within this range.

It was a residue.

The bulk density measured by the method described above is 1.3 to 1.9 V/
cmF' is necessary to obtain a flux of high toughness and low hydrogen weld metal, and 1.3S'/
If it is less than C-, the permeability of the flux becomes good, the shielding from the atmosphere becomes incomplete, the toughness decreases, and the amount of hydrogen increases, which is not preferable.

If it exceeds 1,9 Vcln, 3, the welding workability will deteriorate significantly, so it must be less than this.

However, in the flux of the present invention, the performance can be sufficiently satisfied with the above-mentioned additive components.
O, ZrO2, etc. can be added as necessary.

※※ First, if BaO has a relatively high basicity.

Although 10% CaoK can be used in the old days, if it exceeds 10%, the flux density becomes too high, a stable arc cannot be maintained, and welding workability deteriorates, so it is necessary to limit it to 10% or less.

Furthermore, it is possible to use ZrO in an amount of 5 or less to improve the slag removability of the high CaF2 flux and adjust the fluidity and melting point, but if it exceeds 5, it will have an extremely negative effect on welding workability. , the melting point becomes too high, the arc becomes unstable, and welding workability deteriorates, so 5%
The following must be limited to one.

Furthermore, in the flux of the present invention, the point of welding workability is
Although it is preferable that there be no 20% of the content, it is unavoidably mixed in by about 0.5% from other raw materials such as MnO.

However, if it is less than this level, it is permissible because there is no adverse effect on welding workability.

In addition, basicity (when BaO, ZrO2, K20 is included)
BI) is based on the following formula.

Furthermore, the flux of the present invention can be melted and produced by adding an appropriate amount of a reducing agent such as ordinary graphite.

The effects of the present invention will be described in detail below based on Examples.

Examples Inventive fluxes F1 to F6 and comparative flux Fγ
~ Using F14, in order to confirm the difference, (1) the amount of diffusible hydrogen in the weld metal, (2) as an investigation of welding workability, an investigation of the influence of flux spray height on the flat plate bead appearance and shape, (3) The mechanical properties and chemical composition of all weld metals were investigated.

Table 1 shows the chemical composition of the test steel plate, Table 2 shows the chemical composition of the test wire, and Table 3 shows the chemical composition and specifications of the test flux. F1 to F6 are the fluxes of the present invention, and F7 ~F
14 is the comparative flux.

All of these fluxes are made by mixing and melting various powdery or granular raw materials, and in F1 to F13, the melted material is poured onto a metal plate and left to cool.

In addition, F14 was rapidly cooled in water and 20x Dust
It is produced by sizing into mesh.

Table 4 describes the test method, but the amount of diffusible hydrogen was measured using Perfume S-2 shown in Table 1.
Processed into a test plate with a size of 130m x 40m, and
Welding condition 600A, 30V with wire W-2 shown in the table
, 26/'777/min.

Other conditions were performed according to the method of JIS Z3113,
Measure the amount of υ diffusible hydrogen using the glycerin method, and
This is the average value of the times.

In addition, welding workability using a flat plate was investigated regarding the influence of flux spraying height on bead appearance using 25 mm x 5
Wire W- from Table 2 on a plate with a size between 00mm x 200mm
2, the height of flux spraying was 50m door, welding conditions were 700A, 33mm, 30 cm in 1.
A pass bead was placed and the appearance of the bead was investigated to see if there were any pockmarks and if the bead shape was uneven.

Note that welding was performed without preheating.

Additionally, the mechanical properties and chemical composition of all weld metals are.

Using Perfume S-1 (equivalent to 80kg steel) shown in Table 1, two plates with the size of 2511tπ x 500mm x 200 plates were formed with a groove with a groove angle of 30°. The gas cutting root gap is 12.7 mm, and the same steel type (plate thickness 251 mm) is used.
1LN) with a width of 3Qmm and abutted it on the back side of the groove to wire W-1 (80kg wire) in Table 2.
Welding conditions were 550°C and preheating pass temperature was 150℃.
A, 15 passes of multilayer welding were performed at 31 V and 40/777 y/min.

Thereafter, a 2-myrt Notch Charpy impact test piece 3 and a No. A1 round bar tensile test piece 2 were taken from the bead 1 in the manner shown in FIG.

In addition, in the same figure, t = 2.5 mal. t'=9
．． It is 5 mm.

Also, what is the chemical composition of all weld metal? The test was conducted using test piece 2 after the tensile test.

The results of each of these tests are shown in Tables 5 and 6.
As is clear from Tables 5 and 6, the fluxes of the present invention (Fl to P6) all have a diffusible hydrogen amount of 1, QeC
/l OOf or less, good cracking resistance, the amount of oxygen in the weld metal is less than 500 ppm, and the impact value is 8 at -15℃.
A high value of kg to m or more can be obtained, and even if the flux spreading height is increased to 5Qmln, a beautiful bead appearance can be obtained and welding workability is good.

However, the other 7 luxes (F7 to F14) have a low amount of diffusible hydrogen and good cracking resistance, but the welding workability is poor, or the impact value is low and the impact value is high. does not satisfy the three requirements of hydrogen, toughness, and workability due to poor welding workability.

They are due to the following reasons.

First, since F7 has a high content of S i 02 (%) + MnO (%) of 51.6%, the amount of oxygen in the weld metal increases.

The impact value is low, and welding workability is also poor.

F8 contains more than 0.8 of 20 components and has poor welding workability.

Since F9 contains 6.3% of ZrO2 component,
Like the F8, there are problems with welding work.

FIO has a content of 5iO2 (%) +Mn0 (%) of 3
Although the amount of diffusible hydrogen increased slightly since it was as low as 3.2%, there was a problem with welding workability.

Since Fil has a high basicity of 1.42, the amount of diffusible hydrogen is as large as 2.4 CC/100 P, which poses a problem in crack resistance.

This is because F12 has a high Na2O content of 2.4%.

Although the amount of diffusible hydrogen increased slightly, welding workability was poor.

Since F13 has a low basicity (BI) of 0.85, the amount of oxygen in the weld metal increases and the impact value is low.

F14 is a flux produced by rapidly cooling the melt in water to reduce the bulk density.

The amount of diffusible hydrogen is 2.8cc/100? This caused a problem with cracking resistance.

Example 2 An example of using the flux obtained in Example 1 will be described.

The test method is shown at the end of Table 4.

S-3 (equivalent to SB-49) in Table 1, which is commonly used
Using 100771fflt, 100mmX10.
Cut into two pieces of 00 mm x 250 m 7 W, and butt weld with a groove shape as shown in Figure 2 aK, 6
A heat treatment of 13 hr at 20° C. was performed and tensile, impact, side bending and analytical tests were performed.

In addition. In Fig. 2a, t=100mm, 7=l (:
) mm, θ==14°, and R=127×711.

For the wire, use W-3 (for 50-60HT) in Table 2,
The flux is F2. Fl- and F6. F8 was used as a comparison flux, and the preheating and pass temperature were both 150°C, 65 OA, 34 V, 30
57 passes of multilayer welding were performed using clnAnin.

In addition, after welding on the B and P sides, the F and P sides were welded by carrying out Uratsuji sling using an arc cara zinc.

Further, the flux is sprinkled at a height of about 40 degrees.

Thereafter, SR was performed at 620° C. for 13 hours, and tensile test pieces 2 and impact test pieces 3 were taken from the weld bead 1 in the manner shown in Figure 2.

In addition, in the same figure, between t=100 and t'=1/4
t (25mm), t"=a/4t (75mm
).

In addition, the side bending test was performed at the full thickness (100πmt) with <b return 2
In this study, the chemical components were analyzed as in Test Piece 2 after the tensile test.

Table 7 shows the mechanical properties, and Table 8 shows the chemical composition of the weld metal.

As is clear from Table 7, the present invention flux F2,
F4 and F6 showed good ductility, but the comparative flux F8 had some slag entrainment defects in the side bending test, and even in the tensile test specimens taken from 3/4t, there were problems with poor elongation and narrowing. Ta.

This seems to be due to defects caused by poor bead shape (poor workability) during welding near the bottom of the groove.

Note that no particular difference is observed from the analysis results of the weld metals in Table 8.

As detailed above, the flux of the present invention has such good welding workability that there is no need to limit the spraying height.
It is possible to obtain a weld metal with good hydrogen cracking resistance and high toughness, such as HT-80 steel, which requires hydrogen cracking resistance and high toughness.

Its industrial value is extremely high in that it can efficiently carry out submerged arc welding of multilayer welding of extremely thick steel plates, which requires high toughness and good welding workability.

[Brief explanation of the drawing]

1 and 2a and 2b are diagrams showing the implementation procedure of the performance test in the embodiment of the present invention. 1...Bead, 2...Tensile test piece, 3
...impact test piece.

Claims (1)

[Claims] 1 The main components are 5i0225 to 38φ in weight%,
Mn06-17%, Ca114-27%. CaF212-20%, Al2035-20%, Ti0
21 to 5%, one or both of Na2O or Li2O, 0.3 to 2.0%, Mg0 or less to 6%. A melt flux for submerged arc welding that provides a low-hydrogen, high-toughness weld metal, which satisfies the following conditions (1) to (3). (1) S t02 (%) +Mn0 (%) =
35-48 (%) (2) Basicity (Bi) ~0.9-1
．． 3 (3) Is the bulk density 1.3 to 1.9? /am3