KR101168161B1 - Flux for one side submerged arc welding - Google Patents

Abstract

It is to provide flux for single-sided submerged arc welding that can secure sound surface and backside bead and stable welding metal impact strength, in weight%, SiO ₂ : 4 ~ 8%, Al ₂ O ₃ : 4 ~ 8 %, TiO ₂ : 5 ~ 10%, MgO: 20 ~ 30%, CaF ₂ : 4 ~ 9%, CaO: 5 ~ 10%, Ti: 0.4 ~ 1.2%, B: 0.003 ~ 0.006%, Iron: 25 ~ It contains 35%, the ratio of CaF ₂ / CaO is 1.0 to 1.4, with respect to the total weight of the flux, less than 5% of the flux with a particle size exceeding 850㎛ in flux, and more than 80% of the flux with 250 to 850㎛ A flux for single-sided submerged arc welding with a flux of less than 250 μm of 10% or less is provided.

Description

Flux for single sided submerged arc welding {FLUX FOR ONE SIDE SUBMERGED ARC WELDING}

The present invention relates to a flux for one side submerged arc welding, and more particularly, a single sided submerged to obtain a healthy surface bead and a backside bead, and to obtain a weld metal having excellent low temperature impact toughness. It relates to a flux for de-arc welding.

In general, submerged arc welding is carried out by surface welding, and then the base material is rotated to further weld the back surface. In one-sided submerged arc welding, there is no need to rotate the base material. It means a welding technique that can be formed at the same time.

Since the one-sided submerged arc welding has to be formed simultaneously from the surface side to the backside bead, there is a problem in that the penetration shape is deepened vertically, and in the case of high-speed welding, the molten pool is lengthened in the direction of the welding line. The cooling rate is also fast, so there is a problem that the solidification rate of the metal also increases. In particular, in the case of single-sided submerged welding, there is a problem that the width of the bead on the surface side is not widened, the shape is incomplete, and undercut is likely to occur.

As a technique for solving this problem, Japanese Patent Application Laid-open No. Hei 6-277878. The patent suggests that a good bead appearance can be secured by solving the problems associated with single-sided submerged welding by controlling the composition of the flux and the particle size of the flux. However, the method according to the patent has a limit in securing sound surface beads and back beads of the level required in the current welding site, in particular, there is a problem that the impact strength of the weld metal is not sufficiently secured.

In addition, Korean Patent Laid-Open Publication No. 2004-0061852 is a technique for solving the problem of lowering the impact strength. The patent relates to a technique for improving the impact toughness of a welded metal together with a healthy surface and backside beads by defining a composition ratio of CaF ₂ to CaO. However, although the patent has been recognized to some extent in the past, there was a shortcoming in securing a higher level of stable impact toughness, which is required by recent welding construction.

One aspect of the present invention defines the composition of the flux, the ratio of CaF _{2 to} CaO and the particle size distribution of the flux, as well as the addition of an appropriate amount of Ti and B to ensure sound surface and backside beads and stable weld metal impact strength. It is to provide a flux for single-sided submerged arc welding.

In the present invention, by weight%, SiO ₂ : 4-8%, Al ₂ O ₃ : 4-8%, TiO ₂ : 5-10%, MgO: 20-30%, CaF ₂ : 4-9%, CaO: 5 to 10%, Ti: 0.4 to 1.2%, B: 0.003 to 0.006%, iron: 25 to 35%, and the CaF ₂ / CaO ratio is 1.0 to 1.4,

Flux for single-sided submerged arc welding with less than 5% of flux whose particle size exceeds 850 µm, flux of 250 to 850 µm and flux of less than 80% and total flux of less than 250 µm To provide.

The present invention stipulates flux composition, particle size, and composition ratio of CaF2 to CaO, which not only secures healthy surface beads and backside beads, but also adds appropriate amounts of Ti and B components to provide stable weld metal impact strength. There is an effect that can provide a flux for one-sided submerged arc welding can be secured.

Hereinafter, the present invention will be described in detail.

The present inventors have studied to improve the impact strength of the weld metal during single-sided submerged arc welding and to secure good surface beads and backside beads, thereby controlling the composition and particle size of the flux and adding (CaF ₂ / CaO) The present invention has been realized by recognizing that it can be achieved by controlling the composition ratio of and adding Ti and B components in appropriate amounts.

The composition range of the flux of the present invention will be described in detail (hereinafter, by weight).

SiO ₂ : 4 ~ 8%

SiO ₂ is a vitrification component and is included in the flux of the present invention as a slag forming agent, and its addition amount is preferably 4 to 8%. When the SiO ₂ is less than 4%, the viscosity of the slag is lowered, so that the fluidity is increased, so that the uniformity of the welding bead is decreased. Since the content of oxygen in the metal increases the toughness, the SiO ₂ is preferably 4-8%.

Al ₂ O ₃ : 4 ~ 8%

Al ₂ O ₃ is a necessary component to maintain the weldability while improving the bead appearance by adjusting the slag viscosity and solidification temperature while increasing the softening temperature of the slag. However, if the added amount is less than 4%, the slag solidification temperature is lowered, resulting in poor slag peelability, fork marks on the surface of the weld bead, and the appearance of the weld bead is not good. This not only worsens, but also causes a decrease in toughness. Therefore, the content of Al ₂ O ₃ is preferably 4-8%.

TiO ₂ : 5 ~ 10%

TiO ₂ stabilizes slag peelability and arc generation, and serves to obtain a good weld bead appearance. If the content is less than 5%, the slag peelability is deteriorated, and if it exceeds 10%, the viscosity of the flux becomes high and the beads Not only the appearance is worsened, but also the flux consumption increases, so that the content is preferably 5 to 10%.

MgO: 20 ~ 30%

MgO is a useful component to secure the slag peelability by adjusting the melting point and viscosity of the slag. However, if the content is less than 20%, there is a problem in that the slag is fused to the weld bead surface deteriorated slag peelability, if the content exceeds 30%, the melting point of the slag is too high, the slag induction is worse, the weld bead of Since the width becomes narrow and the surface thereof becomes rough, the content thereof is preferably 20 to 30%.

CaF ₂ : 4-9%

CaF ₂ improves toughness by increasing the basicity of slag and reducing the amount of oxygen in the weld metal, thereby controlling the fluidity of slag and improving the shape of beads. However, if the content is less than 4%, the above effect is not sufficient, and if it is added in excess of 9%, the melting point of the slag is so high that the slag peeling property is deteriorated and there is a problem that damages the appearance of the beads, the content is 4-9%. Is preferably.

CaO: 5 ~ 10%

CaO has the effect of raising the melting point and improving the toughness of the weld metal. However, if the content is less than 5%, it is difficult to expect a sufficient addition effect, and if it exceeds 10%, the content is preferably 5 to 10% because it causes a decrease in slag peelability.

Ti: 0.4 ~ 1.2%

Ti acts as a deoxidizer and increases toughness by miniaturizing tissue. However, if the addition amount is less than 0.4%, it is difficult to expect the effect according to the addition. If the addition amount is more than 1.2%, since the slag fluidity is lowered and hot cracking due to peroxidation may be promoted, the content is 0.4 to 1.2. It is preferable to set it as%.

B: 0.003-0.006%

B is added together with Ti, and serves to increase toughness as well as refinement of the tissue. However, B is distributed in the grain boundary by boride (Boride) to form a separate inclusions can act as a crack source, so it is important to control the content, so in the present invention includes 0.003 ~ 0.006%. If the content of B is less than 0.003%, the toughening effect is not exerted. If the content of B is more than 0.006%, boride is formed into a continuous network to reduce impact strength due to hardening, deterioration of toughness, and melting. There is a problem that deterioration and hot cracking can occur.

Iron: 25 ~ 35%

If the content of iron is less than 25%, a sufficient amount of weld metal cannot be obtained. If the content of iron is more than 35%, solidification of the weld metal is accelerated, and iron is easily attached to the surface of the bead, and it is difficult to secure a predetermined bead width. The content is preferably 25 to 35%.

In addition to the above components, the flux of the present invention may further include 1-5% Na ₂ O. Na ₂ O is a component for agglomerating each raw material in powder form when producing flux, but does not significantly affect the flux properties of the present invention, but if the addition amount is less than 1%, it is difficult to prepare a flux having an appropriate particle size due to its low coking force. If it exceeds 5%, the caking force is too strong to prevent the flux particle size from being produced properly, so it is preferably 1 to 5%.

The rest contains inevitable impurities.

In the flux component, the CaF ₂ / CaO ratio preferably satisfies 1.0 to 1.4. As described above, CaF ₂ controls the content of O ₂ in the weld metal, and controls the gas generation by lowering the viscosity and solidification temperature of the molten slag, so that defects such as pit and blow hole are eliminated. Ensure that no welds are available. However, CaF ₂ decomposes, as shown in Equation 1, and partly becomes CaO.

Equation 1) CaF ₂ + H ₂ O → CaO + HF

Therefore, there is a problem in that since the CaO of the slag is relatively high, decomposition suppression of CaF ₂ in the formula (1) relative to the CaF ₂ feet in sex is reduced can not be obtained with the good weld. Therefore, the present invention controls such that a CaF ₂ / CaO is 1.0 to 1.4. When the ratio is less than 1.0, since the addition amount of CaO is more than CaF ₂ , the forward reaction of Equation 1 is suppressed, so that the pit resistance is lowered and the impact strength of the weld metal is lowered. When the ratio exceeds 1.4, the appearance of beads may be worsened.

The flux of the present invention is less than 5% of the flux whose particle diameter exceeds 850 µm (ASTM 20mesh), and the flux of 250 to 850 µm (ASTM 60 to 20 mesh) is 80% or more and less than 250 µm, based on the total weight of the flux. It is preferred that the flux is 10% or less.

It is necessary to control the particle size distribution in order to obtain a healthy welding bead and high impact strength by using the flux of the composition described above. If there are too many fine flux particles, gas defects occur in the weld metal, and the bead width becomes narrow. On the contrary, if the coarse particles are excessive, the arc becomes unstable and the slag fluidity deteriorates, resulting in poor bead appearance. There is a problem that can not ensure uniform melt. Therefore, the flux of the present invention is less than 5% flux having a particle diameter of more than 850㎛ (ASTM 20mesh), less than 10% flux of less than 250㎛, the flux of 250 ~ 850㎛ (ASTM 60 ~ 20mesh) is 80% or more It is preferable.

Hereinafter, embodiments of the present invention will be described in detail. The following examples are only examples of the present invention, and the present invention is not limited by the examples.

(Example)

The single-sided submerged welding was performed under the welding conditions shown in Table 3 using the wires shown in Table 2 below in the weld base materials shown in Table 1 below. In Tables 1 and 2, the composition unit is weight percent, and the remainder in the weld base material and the wire is made of Fe and unavoidable impurities.

Kinds Thickness (mm) C Si Mn P S SM400 25 0.11 0.28 1.06 0.015 0.007

Wire diameter (mm) C Si Mn P S 4.8 0.12 0.05 1.89 0.016 0.011

Polarity and current
(A) Current (A) Voltage (V) Welding speed (cpm) Angle of improvement AC 1000 1000 36 18 40

At this time, the composition of the flux used for the submerged welding is shown in Table 4 below, and the composition ratio and particle size of each flux (CaF ₂ / CaO) are shown in Table 5.

After the one-sided submerged welding using the flux of Table 4, the weld bead appearance and the weld metal impact strength were evaluated, and the results are shown in Table 5 together.

division SiO ₂ CaO Al ₂ O ₃ MgO TiO ₂ CaF ₂ Ti B iron content Etc Inventory 1 5 6 4 25 8 7 1.0 0.004 27 impurities Inventive Example 2 5 5 8 22 6 5 0.6 0.004 26 impurities Inventory 3 6 6 6 28 6 7 1.1 0.005 28 impurities Honorable 4 8 7 4 26 7 8 0.8 0.005 33 impurities Inventory 5 4 8 7 23 9 9 1.1 0.003 31 impurities Inventory 6 7 7 6 27 8 9 1.0 0.006 34 impurities Honorable 7 6 7 8 28 7 8 1.2 0.006 34 impurities Inventive Example 8 5 8 4 21 5 9 0.5 0.003 26 impurities Proposition 9 4 5 5 25 7 7 0.7 0.005 30 impurities Inventory 10 7 7 5 30 9 8 1.1 0.006 30 impurities Comparative Example 1 5 6 11 24 4 8 0.4 0.003 35 impurities Comparative Example 2 6 5 6 28 6 8 0.5 0.004 31 impurities Comparative Example 3 7 6 2 33 7 7 0.8 0.004 29 impurities Comparative Example 4 8 6 5 28 12 3 1.4 0.004 30 impurities Comparative Example 5 4 9 9 27 10 5 1.1 0.005 33 impurities Comparative Example 6 7 6 8 29 7 7 0.2 0.002 26 impurities Comparative Example 7 8 11 7 18 8 10 0.8 0.004 37 impurities Comparative Example 8 5 7 7 25 8 8 0.9 0.008 30 impurities Comparative Example 9 10 7 6 27 6 8 1.1 0.004 32 impurities Comparative Example 10 3 6 8 28 6 9 1.0 0.005 31 impurities

division CaF ₂ / CaO Flux granularity Bead Appearance Impact strength
(at -20 ℃) Over 850㎛ 850 ~ 250㎛ Less than 250㎛ surface Back side Inventory 1 1.16 3 88 9 ○ ○ ○ Inventive Example 2 1.00 5 90 5 ○ ○ ○ Inventory 3 1.16 2 96 4 ○ ○ ○ Honorable 4 1.14 4 89 7 ○ ○ ○ Inventory 5 1.12 5 84 9 ○ ○ ○ Inventory 6 1.28 3 91 6 ○ ○ ○ Honorable 7 1.14 4 88 8 ○ ○ ○ Inventive Example 8 1.12 One 96 5 ○ ○ ○ Proposition 9 1.40 4 90 6 ○ △ ○ Inventory 10 1.14 5 88 7 ○ ○ ○ Comparative Example 1 1.33 4 88 8 △ △ △ Comparative Example 2 1.60 3 88 9 X X ○ Comparative Example 3 1.16 7 86 7 X △ △ Comparative Example 4 0.50 4 88 8 X △ X Comparative Example 5 0.55 3 92 5 △ X X Comparative Example 6 1.16 5 88 7 ○ △ X Comparative Example 7 0.91 2 92 6 X △ X Comparative Example 8 1.14 4 83 13 X △ X Comparative Example 9 1.14 8 86 6 △ X X Comparative Example 10 1.50 5 91 4 X △ △

In Table 5, the appearance of the bead through the sensory evaluation of the operator, ○ is good, △ is normal, X is shown as bad, the impact strength at -20 ℃ of each weld metal obtained after welding is measured and the value is The case exceeding 80J was evaluated as excellent ((circle)), 40-80J was normal (△), and less than 40J was bad (X).

As shown in Table 5, in addition to the composition and particle size distribution of the present invention, in the case of Inventive Examples 1 to 10 satisfying the (CaF ₂ / CaO) composition ratio, a good bead appearance was obtained, and the impact strength of the weld metal was also obtained. All were better than 80J.

However, in the case of Comparative Example 1 in which the Al ₂ O ₃ and TiO ₂ contents were out of the range of the present invention, the bead appearance and impact strength were insufficient, and (CaF ₂ / CaO) composition ratios of the Comparative Examples 2 and 5 were out of the present invention range. In the case of bead appearance and impact strength was reduced.

In addition, in the case of Comparative Examples 3, 8, and 9 whose partial composition range and particle size distribution of the flux were outside the scope of the present invention, the bead appearance and impact strength evaluation results were not good overall. In addition, in the case of Comparative Examples 4, 7 and 10 in which some of the composition and the ratio of (CaF ₂ / CaO) were outside the scope of the present invention, it was confirmed that the appearance of beads and the impact strength were reduced, and the Ti and B contents were in the present invention range. In Comparative Example 6 deviated from the impact strength was lowered.

Claims (2)

By weight%, SiO ₂ : 4-8%, Al ₂ O ₃ : 4-8%, TiO ₂ : 5-10%, MgO: 20-30%, CaF ₂ : 4-9%, CaO: 5-10 %, Ti: 0.4-1.2%, B: 0.003-0.006%, iron: 25-35%, the ratio of CaF ₂ / CaO is 1.0-1.4,
Flux for single-sided submerged arc welding with less than 5% of flux whose particle size exceeds 850 µm, flux of 250 to 850 µm and flux of less than 80% and total flux of less than 250 µm .
The method according to claim 1,
The flux is a flux for one-sided submerged arc welding further comprises Na ₂ O: 1-5%.