JPH0631481A - Flux for welding - Google Patents

Abstract

PURPOSE:To provide the flux for welding which decreases defects in spite of high-speed welding by controlling the amts. of the CaO and CaF2 to be added and suppressing the amts. of Al2O3 and MgO which are high in m.p. CONSTITUTION:This flux contains, by weight %, 25.5%<=SiO2<=35%, 3%<=Al2O3<=10%, 2%<=TiO2<=8%, 5%<=MgO<=13%, 2%<=MnO<=8%, 15%<=CaO<=35% and 20%<=CaF2<=45% and consists of the balance impurities, consists of 1.0<=CaF2<=45% and has <=1100 deg.C softening temp. The quantity of the oxygen in a weld metal is decreased simply by decreasing the amt. of the SiO2 in a flux and increasing basic components, such as CaO, MgO and CaF2. Slag inclusion in hardly generated if the flux softening temp. is <=1100 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding flux, and more particularly to a welding flux suitable for high speed submerged arc welding performed by multiple electrodes having three or more electrodes.

[0002]

2. Description of the Related Art Welding defects such as undercuts and slag inclusions are more likely to occur during high-speed welding than under low-speed welding. In order to prevent such defects, generally, the amount of SiO ₂ is large, so-called low basicity. Flux is used. However, since the activity of SiO ₂ becomes large in the low basic flux with few welding defects, this S
iO ₂ is reduced during welding, increasing the amount of oxygen in the weld metal. Therefore, there is a problem that a high toughness weld metal cannot be obtained.

In order to obtain a high toughness weld metal, a method is generally known in which the amount of SiO ₂ is reduced and the basicity of the flux is increased to reduce the amount of oxygen in the weld metal. For example, in Japanese Patent Laid-Open No. 54-4255,
A technique for reducing the amount of oxygen in the weld metal by substituting ZrO ₂ for a part of Al ₂ O _{3 in} the low SiO ₂ -high Al ₂ O ₃ based flux is disclosed.

Further, in Japanese Patent Application Laid-Open No. 58-55197, the partial pressure of F gas in the arc atmosphere is increased by a flux containing a large amount of CaF ₂ and oxygen in the weld metal when two-electrode welding is performed. A method of reducing the amount is disclosed.

[0005]

By the way, as described above, when a flux having a reduced amount of SiO ₂ and increased basicity is applied to high-speed welding, a convex beat having a narrow beat width is likely to be formed. Defects such as undercut and slag inclusion are likely to occur. Undercut can be prevented to some extent by widening the bead width by optimizing the welding conditions, but it is difficult to solve under welding conditions because slag entrainment has a strong relationship with the physical properties of the slag.

In view of the above circumstances, it is an object of the present invention to provide a welding flux for preventing the occurrence of welding defects, particularly when used for high speed welding, and for obtaining a weld metal excellent in impact resistance. And

[0007]

Means for Solving the Problems
As a result of various experiments and research to achieve it, CaO
And CaF₂ Control the amount of addition of
Has a high melting point₂ O ₃ Hold down MgO and MgO
Welding by setting the softening temperature of the steel to 1100 ° C or less
Reduces oxygen content in metal and prevents slag entrapment
To find out that flux can be obtained, and to form the present invention
I arrived.

Specifically, the welding flux of the present invention is 25.5 wt. % ≦ SiO ₂ ≦ 35 wt. %, 3 wt. % ≦ Al ₂ O ₃ ≦ 10 wt. %, 2 wt. % ≦ TiO ₂ ≦ 8 wt. %, 5 wt. % ≦ MgO ≦ 13 wt. %, 2 wt. % ≦ MnO ≦ 8 wt. %, 15 wt. % ≦ CaO ≦ 35 wt. %, 20 wt. % ≦ CaF ₂ ≦ 45 wt. %, With the balance being impurities, and 1.0 ≦ Ca
It is F ₂ / CaO and is characterized by having a softening temperature of 1100 ° C. or lower. Here, for the flux softening temperature, a button with a diameter of 10 mm and a height of 10 mm is made,
This was continuously heated in a furnace and defined as the temperature at which the height was 80% of the original height.

The welding flux of the present invention is suitable as a flux for high-speed submerged arc welding performed by a multi-electrode having three or more electrodes. In addition, for improving the beat shape, refining the weld metal, and stabilizing the arc, BaO, Na ₂
It is preferable to add the respective components of O, K ₂ O and B ₂ O _{3 in} the following proportions.

BaO ≦ 5 wt. % Na ₂ O + K ₂ O ≦ 2 wt. % B ₂ O ₃ ≦ 1 wt. % Next, an experiment which is the basis of the present invention will be described. The present inventors conducted various experiments in order to obtain a welding flux capable of simultaneously reducing the amount of oxygen in the weld metal and preventing slag inclusion.

As a result of this experiment, (1) regardless of the basicity of the flux, the problem of slag inclusion is small in low-speed welding, and (2) in the case of multi-electrode high-speed welding, the base metal naked at the bottom of the molten pool It has been found that when slag adheres to the surface (see FIG. 1, which will be described later), the molten steel has a unidirectional flow, so that this slag does not easily float, and that the tendency is particularly remarkable as the basicity of the flux increases.

First, the reason for the above (1) will be described with reference to FIG. FIG. 1 is a cross-sectional view showing a state in which slag is attached to the bare base metal surface of the bottom of the molten pool. As shown in FIG. 1, the base metal bare surface 1 at the bottom of the molten pool that is a part of the weld metal 10
Even if the slag 14 adheres to the molten steel 2, if the welding speed is slow, the flow of molten steel in the molten pool does not become a unidirectional flow toward the rear of the molten pool, but a reverse flow occurs, so that the molten steel in the molten pool The slag floats due to the stirring effect of. As a result, slag entrainment is small in low-speed welding regardless of the basicity of the flux.

On the other hand, in the case of multi-electrode high-speed welding, once using FIG.
When the slag adheres as shown in Fig. 4, the flow of molten steel in the molten pool is a unidirectional flow, so as described above, the slag is difficult to float, and in particular, the tendency becomes remarkable as the basicity becomes higher. . The main welding defect prevented by the welding flux of the present invention is slag (slag entrainment) of the type that adheres to the bottom of the molten pool in a dish shape as shown in FIG. Therefore, the welding flux of the present invention is
It is suitable as a flux for high-speed welding that is more than electrode welding.

By the way, in order to reduce the amount of oxygen in the weld metal, it is effective to make the flux highly basic as in the conventional knowledge. In this experiment, SiO ₂ is reduced to reduce CaO,
It has been found that the amount of oxygen in the weld metal can be greatly reduced by increasing the amount of basic components such as MgO and CaF ₂ . However, it has also been clarified that the number of slag inclusions during high-speed welding increases with an increase in the amount of highly basic components, and that a large number of man-hours are required to repair the slag.

Therefore, as a result of detailed examination of the relationship between the slag inclusion and the flux physical properties, it was found that there is an extremely strong correlation between the slag inclusion number and the flux softening temperature. FIG. 2 is a graph showing the relationship between various trial-produced high basic flux softening temperatures and slag entrainment during three-electrode high-speed welding. As shown in FIG. 2, when the flux softening temperature is 1100 ° C. or lower, slag entrapment is extremely unlikely to occur.

[0016]

Next, the reasons for limiting the component composition range and the flux softening temperature in the present invention will be described. SiO ₂ : SiO ₂ is a component that greatly affects the high-speed weldability of the flux, particularly the undercut and the toughness of the weld metal. If it is less than 25.5%, undercut is likely to occur during high-speed welding. On the other hand, if it exceeds 35%, the oxygen content of the weld metal increases and the toughness deteriorates.

Al ₂ O ₃ : Al ₂ O ₃ is an important component for forming glass, and if it is less than 3%, an undercut is likely to occur during high speed welding. On the other hand, if added in excess of 10%, the flux softening temperature rises and slag entrainment easily occurs. TiO ₂ : TiO ₂ is partially reduced in the arc,
Increases toughness by refining the weld metal. However, if it is less than 2%, its effect is small, and if it exceeds 8%, the slag removability deteriorates.

CaO: CaO is a component which is extremely effective in increasing the basicity of flux and reducing the amount of oxygen in the weld metal. However, if it is less than 15%, a significant reduction in the amount of oxygen in the weld metal cannot be expected, while if it exceeds 35%, the softening temperature of the flux increases significantly and the amount of hydrogen in the weld metal also increases. Similar to CaO, MgO: MgO has an effect of reducing the amount of oxygen in the weld metal, but if it is less than 5%, the effect is small.
If it exceeds 3%, the flux softening temperature rises.
Must be ~ 13%.

MnO: MnO is effective in improving beet shape and slag fluidity, but if it is less than 2%, the effect cannot be expected, and if it exceeds 8%, the appearance of beet is deteriorated. CaF ₂ : CaF ₂ is an important component for improving the fluidity of the slag and lowering the flux softening temperature because it has a low melting point as a simple substance. In the case of highly basic flux, it is necessary to add 20% or more in order to significantly reduce the flux softening temperature. On the other hand, if it exceeds 45%, an irritating odor due to F gas is generated and the arc becomes unstable.

It was also found that the addition of CaO reduces the amount of oxygen in the weld metal, while the increase in the softening temperature of the flux due to the addition of CaO can be canceled by the addition of CaF ₂ . That is, Ca
It has been found that F ₂ has an extremely effective function for lowering the flux softening temperature. Therefore, in order to reduce the amount of oxygen in the weld metal, prevent the flux softening temperature from rising, and prevent slag entrainment, the simultaneous addition amount of CaO and CaF ₂ is limited, and the flux softening temperature is also regulated. . Therefore, 35 wt. % ≦ CaO + CaF ₂ 1.0 ≦ CaF ₂ / CaO.

Further, BaO, B ₂ O ₃ , Na ₂ O and K ₂
When each component of O is added, it is effective in improving the beat shape, refining the weld metal, and stability of the arc as described above, but when BaO is added in excess of 5%, the beat shape is As it deteriorates, the flux softening temperature rises. Further, B ₂ O ₃ has a function of refining the weld metal structure and improving toughness by simultaneous addition with TiO ₂ , but if it is added in an amount exceeding 1%, too much B is added and the weld metal hardens and cracks. It will be easier. Also, Na ₂ O and K ₂ O
Is a component effective in arc stability, but if the total amount of these added exceeds 2%, the amount of hydrogen in the weld metal increases. Therefore, BaO, B ₂ O ₃ , Na ₂ O, K ₂
The amount of each component of O added is limited.

According to the welding flux of the present invention, it is possible to prevent the flux softening temperature from significantly increasing, so that slag entrainment is prevented and the amount of oxygen in the weld metal is reduced. This welding flux is particularly effective when performing high-speed welding using the three-electrode method or more.

[0023]

EXAMPLES Next, examples of the present invention will be described together with comparative examples. Tables 1 and 2 show the chemical composition and specifications of the flux of this example and the comparative example, Table 3 shows the chemical composition of the test steel sheet and test wire, and Table 4 shows the welding conditions (four-electrode method). FIG. 3 is a cross-sectional view showing the groove used in the test of this example.

Under the conditions shown in the above tables, welding was performed in one pass in the groove shown in FIG. 3, and after the X-ray transmission inspection, a 2 mm V-notch Charpy impact test piece was sampled from a position of 2 mm on the surface, and at -20 ° C. An impact test was conducted, and (1) the chemical composition and toughness of the weld metal with one layer of V-groove (2) welding defects (slag inclusion, undercut) were investigated.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

[0028]

[Table 4]

Tables 5 and 6 collectively show the results obtained by examining the chemical composition of the weld metal, the impact test, and the number of slag inclusions.

[0030]

[Table 5]

[0031]

[Table 6]

When each flux of this embodiment is used,
Compared with the case of using the flux of the comparative example, the amount of oxygen in the weld metal was small, and the absorbed energy at -20 ° C was also large, and slag entrainment did not occur even when high-speed welding with four electrodes was performed. On the other hand, when the flux of the comparative example is used, the effect of reducing the amount of oxygen is recognized to some extent, and although the absorbed energy is relatively good, the flux softening temperature exceeds 1100 ° C., so the slag winding is performed in four-electrode high speed welding. Congestion occurred.

[0033]

As described above, the welding flux of the present invention has a flux softening temperature of 1100 ° C. or lower,
By controlling the addition amounts of CaO and CaF ₂ and suppressing the addition amounts of Al ₂ O ₃ and MgO having a high melting point as a simple substance, it is possible to reduce the amount of oxygen in the weld metal and prevent the inclusion of slag. it can.

In particular, when the welding flux of the present invention is used for multi-electrode high-speed welding with three or more electrodes, a low-oxygen and high-toughness weld metal can be obtained without causing slag inclusion defects. It has great industrial value because it can satisfy both difficult toughness and excellent high-speed welding workability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a state in which slag is attached to a bare base metal surface of a bottom of a molten pool.

FIG. 2 is a graph showing the relationship between the softening temperature of a prototype highly basic flux and slag inclusion during high-speed welding with three electrodes.

FIG. 3 is a cross-sectional view showing a groove used in an example.

[Explanation of symbols]

 10 Weld Metal 12 Base Metal Bare Surface 14 Slag

Claims (1)

[Claims] 1. A 25.5 wt. % ≦ SiO ₂ ≦ 35w
t. %, 3 wt. % ≦ Al ₂ O ₃ ≦ 10 wt. %, 2 wt. % ≦ TiO ₂ ≦ 8 wt. %, 5 wt. % ≦ MgO ≦ 13 wt. %, 2 wt. % ≦ MnO ≦ 8 wt. %, 15 wt. % ≦ CaO ≦ 35 wt. %, 20 wt. % ≦ CaF ₂ ≦ 45 wt. %, With the balance being impurities, and 1.0 ≦ Ca
F ₂ / CaO, a softening temperature of 1100 ° C. or less, a welding flux.