JPH08267280A - Sio2-mno baked flux for submerged arc welding - Google Patents

Abstract

PURPOSE: To obtain a flux capable of preventing the inclusion of hydrogen into weld metal by compounding Mn3 O4 of a specific particle size as a granulatability improving agent into SiO2 -MnO flux raw material powder, granulating this raw material powder and baking the granules at a low temp. CONSTITUTION: The Mn3 O4 having a grain size of <=45μm is added and compounded at a ratio of 5 to 35wt.% as the granulatability improving agent into the SiO2 -MnO flux for submerged arc welding contg. Mn oxide at 3 to 30wt.% in terms of the content of Mn. After this flux raw material powder is granulated, the granules are baked at a low temp. of 500 to 700 deg.C. The flux grain size is preferably a grain size distribution contg. about >=50% particles of a grain size of about 300 to 1000μm. The flux components are preferably 40 to 60% SiO2 , 3 to 30% manganese oxide (in terms of content of Mn), 5 to 25% MgO, 2 to 15% Al2 O3 and 0.5 to 10% Si and Mn. Beautiful beam appearance is obtd. at a high yield if such flux is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a SiO ₂ -MnO-based firing type flux for submerged arc welding, and particularly to a high speed submerged fillet joint welding of a welded assembly type H type member used for a steel frame beam for construction. It is suitable for use in cases such as arc welding.

[0002]

2. Description of the Related Art Downward submerged arc welding is widely used for fillet welding of H-shaped steel of building steel because of its high efficiency and beautiful bead appearance. Also, as a flux, a molten flux is usually used. used. Above all,
The molten flux containing SiO ₂ and MnO as the main components is widely used because it has a beautiful bead appearance, has a high application speed limit, and is easy to handle. However, since this molten type flux needs to be melted in an electric furnace, it requires a large-scale facility, so that the production lot is large and the production cost is high.

In this respect, the so-called baking type flux which is produced by adding a binder such as water glass to the raw material powder and then granulating and firing is not only low in cost because it can be produced by relatively simple equipment, There is an advantage that the alloying element can be added to adjust the weld metal composition. However, SiO ₂
In the -MnO-based calcined flux, Mn oxide undergoes a reduction reaction with molten steel to generate CO gas, which causes a problem that the bead appearance is likely to deteriorate.

Various problems have been attempted in the past regarding the problem of such a burning type flux. For example, Japanese Patent Publication No. 32-409 and Japanese Patent Publication No. 44-13249 have been improved by adding a metal component. A measure is proposed. However, in these methods, since the hydrogen concentration in the weld metal is high due to the water glass contained as a binder, it is necessary to take measures against moisture absorption during use, so there is a problem that the application is limited. It was

For this reason, the firing type flux is usually
The amount of hydrogen in the weld metal is reduced by adding a carbonate such as CaCO ₃ to the raw material and reducing the hydrogen partial pressure by generating CO ₂ gas during welding. However, since the generation of gas from the flux deteriorates the high-speed weldability, such a hydrogen reduction method cannot be used when performing high-speed welding such that the welding speed exceeds 100 cm / min. In addition, as a measure for improving the hygroscopicity of the flux, there is a method of reducing the kind and amount of the binder.
No. 35, Japanese Examined Patent Publication No. 2-37833, etc., but the former cannot be applied to ordinary flux because it increases the cost of the binder, while the latter is granulated with a flux containing alumina as the main component. Since it is intended to improve the property, a flux containing no alumina as a main component is not effective.

[0006]

The present invention advantageously solves the above problems and effectively reduces the amount of binder added without generating gas from a flux such as carbonate. The purpose of this is to propose a SiO ₂ -MnO-based calcined flux that can effectively prevent hydrogen from being mixed into the weld metal, and can achieve a beautiful bead appearance with high efficiency in downward submerged arc welding. .

[0007]

Means for Solving the Problems The clarification process of the present invention will be described below. Now, as mentioned above, SiO ₂ -Mn
O 2 type flux has been conventionally known as a typical component system of flux for submerged arc welding, and the molten type is mainly used. When used as a baking type, there is an advantage that a deoxidizer can be added, but if the baking temperature is increased to reduce the binder, the deoxidizer is oxidized and consumed,
On the other hand, there is a problem that the amount of diffusible hydrogen increases when firing is performed at a temperature at which the deoxidizer is not consumed. Therefore, the firing type is hardly used at present.

By the way, the hydrogen source is the binder as described above. Therefore, the inventors conducted a wide range of studies on the welding workability, the amount of diffusible hydrogen, and the granulating property of the SiO ₂ -MnO-based calcined flux, and the addition of finely powdered Mn oxide to the flux affects the amount of the binder. We investigated the impact. As a result, in the SiO ₂ -MnO based fired type flux, as Mn oxide, be added proper amounts of Mn oxide having a specific composition having a specific particle size distribution, it is possible to effectively reduce the required amount of binder It was found that a weld metal with a low amount of diffusible hydrogen can be obtained even by firing at a relatively low temperature with less consumption of the deoxidizing agent, and thus it can be handled in the same manner as a molten type. The present invention is based on the above findings.

That is, the present invention is 3 to 30 in terms of Mn amount.
for submerged arc welding containing wt% manganese oxide
A SiO ₂ —MnO-based flux, wherein the flux contains ₅ to 35 Mn ₃ O ₄ having a particle size of 45 μm or less as a granulation improver.
The flux raw material powder added and blended in the proportion of wt% was obtained by granulating and then low-temperature firing at 500 to 700 ° C.
SiO ₂ -MnO-based firing type flux for submerged arc welding.

In the present invention, it is preferable that the particle size of the flux is a particle size distribution containing particles having a particle size of 300 to 1000 μm in an amount of 50 wt% or more.

[0011] In this invention, the flux, the components, SiO _2: 40~60wt%, (in the amount of Mn equivalent) manganese oxide:
3 to 30 wt% MgO: 5 to 25 wt%, Al ₂ O ₃ : _{2 to} 15 wt% SiO ₂ -MnO based firing flux for submerged arc welding having a composition containing Si and / or Mn: 0.5 to 10 wt% is suitable. Is.

[0012]

The present invention will be described in detail below. In the present invention, with respect to the Mn oxide added to the flux, the composition and particle size of the Mn oxide are important, as well as the amount added, and it is customary to satisfy the following requirements.

Mn oxide: 3 to 30 wt% in terms of Mn amount As a flux for fillet welding, it is necessary that the bead end portion has good conformability even if the welding speed is high.
For this purpose, it is preferable to use a slag containing Mn oxide, but if the addition amount is less than 3 wt% in terms of Mn amount, the effect is not recognized, while if it exceeds 30 wt% The bead appearance deteriorates as a result of the intense CO reaction in the molten pool. Therefore, the amount of Mn oxide added should be 3 to 30 wt.
It was limited to the range of%.

Amount of Mn ₃ O ₄ having a particle size of 45 μm or less: 5 to 35 wt
% As described above, according to the research conducted by the inventors, SiO ₂ --MnO ₂
In the firing type flux, fine particles of Mn ₃ O ₄ are used as Mn oxide.
It was found that the use of a predetermined amount of the compound markedly improves the granulation property. Here, in order to obtain the above effect, it is necessary that the particle diameter first include particles having a particle diameter of 45 μm or less. , At least 5 wt% of the flux
Was found to be Mn ₃ O ₄ having a particle size of 45 μm or less. On the other hand, if it is contained in a large amount exceeding 35 wt%,
Since inconveniences such as a decrease in the flux fixing strength and a decrease in the flux product rate occur, such fine Mn ₃ O
The addition amount of ₄ was limited to the range of 5 to 35 wt%. Needless to say, the fine Mn ₃ O ₄ particles also have a role as Mn oxide in the flux.

[0015] In the present invention, the SiO ₂ -MnO based fired type flux, if satisfying the above requirements for the composition and particle size of the Mn oxide, it is possible to obtain the desired effect, SiO ₂ -MnO Flux Other representative compositions of are as follows. SiO _2: 40~60wt% First SiO ₂ is necessary to maintain good bead appearance as slag agents, especially when familiar bead ends as fast fillet welding important than 40 wt% Can not maintain a good bead appearance, and if it is contained in a large amount exceeding 60 wt%, the viscosity becomes too high and the bead appearance tends to be disturbed.
Moreover, since problems such as deterioration of slag removability occur, it is preferable to set the content to about 40 to 60 wt%.

MgO: 5 to 25 wt% MgO is a component useful for adjusting the melting point and viscosity of the slag and ensuring the slag removability, but if it is less than 5 wt%, a sufficient effect cannot be obtained, while 25 wt% %, The viscosity tends to be too low, and the melting point is too high, so that the bead appearance tends to be deteriorated. Therefore, it is preferable to set the content to about 5 to 25 wt%.

Al ₂ O ₃ : _{2 to} 15 wt% Al ₂ O ₃ is an important component for adjusting the viscosity and melting point of the slag, but if it is less than 2 wt%, these effects are poor, while if it exceeds 15 wt%. Since the melting point will rise excessively and the bead shape will be deteriorated, the content is preferably about 2 to 15 wt%.

Si and / or Mn: 1 to 10 wt% It is necessary to add a deoxidizing agent in addition to the slag constituent components. The deoxidizer is a component necessary to reduce oxygen in the weld metal, suppress CO reaction, and maintain a good bead appearance. Here, Si and Mn are suitable as the deoxidizing agent, but if the content is less than 1 wt%, the addition effect is poor, while if the content is more than 10 wt%, the welding arc tends to be narrowed Since there is a tendency for the appearance of the bead to deteriorate, it is preferable to set it to about 1 to 10 wt%.

Although a typical flux composition has been described above, other components commonly used in flux may be added. Such components include TiO ₂ , BaO, CaO, ZrO, B ₂ O ₃ , CO ₂ , Ti, Al, etc., TiO ₂ is 10 wt% or less, BaO, CaO, ZrO, CO ₂ is 5 wt% or less. , B ₂ O ₃ can be added in the range of 1 wt% or less. Here, TiO ₂ has the effect of transferring to the weld metal by a reduction reaction during welding and improving the toughness of the weld metal, but since it is expensive, it is added if necessary. BaO, CaO
ZrO and ZrO are effective components for adjusting the basicity and melting point of the slag, but addition in excess of 5 wt% impairs the bead appearance and slag removability. CO ₂ is a component effective in reducing the hydrogen partial pressure generated by the decomposition of carbonate during welding and reducing the amount of hydrogen in the weld metal, but if it exceeds 5 wt%, the appearance of the bead deteriorates due to the generation of gas. Becomes noticeable. B ₂ O ₃
Is an active ingredient that migrates into the weld metal by a reduction reaction during welding and contributes to the improvement of the toughness of the weld metal, but addition in excess of 1 wt% promotes solidification cracking of the weld metal and is not preferred. Ti and Al are useful as deoxidizers and contribute effectively to improving the toughness of the weld metal, but are expensive,
Add as needed.

Although the preferred composition of the flux has been described above, the size of the flux is also important in the present invention, and the particle size of the flux is 300 to 1000 μm.
It is desirable to have a particle size distribution containing 50 wt% or more of the above particles. That is, in the case of a calcination type flux containing Mn oxide, as described above, since the generation of CO gas is unavoidable, the particle size of the flux is important in terms of gas escape,
From this point of view, it is important to include relatively coarse particles of 300 to 1000 μm in an amount of 50 wt% or more. This is because if the amount of particles of such a suitable particle size is less than 50 wt%, the filling rate of the flux increases, gas permeability decreases, and the bead appearance deteriorates. If the amount is large, the gas permeability is poor, the bead width is narrow, and the appearance tends to deteriorate. On the other hand, if the number of particles coarser than 1000 μm is large, the corrugation becomes rough and avatars (pock marks) are also likely to appear. .

The flux raw material powder adjusted to the above-mentioned suitable composition and suitable particle size distribution is granulated and then fired to obtain a product flux. Here, the granulation method is not particularly limited, for example, by using a rolling method or an extrusion type granulator according to a conventional method, the removal of dust and the crushing and sizing of coarse particles are performed, and the particles are Diameter: 0.075 to 1.4 mm.

Regarding the firing temperature, as described above, in the present invention, the amount of the binder can be effectively reduced. Therefore, even after firing at a temperature of 700 ° C. or less, where the deoxidizer is less consumed, the diffusion after moisture absorption is reduced. It is possible to significantly reduce the mixing of the amount of hydrogen. However, if the baking temperature is lower than 500 ° C, the drying may be insufficient and the removal of water may be incomplete, so the baking temperature is limited to the range of 500 to 700 ° C. As the binder, water glass having a conventionally used molar ratio of 1 to 3 is sufficient. Regarding the amount of binder used, the conventional: raw material powder: 150 cc was required per 1 kg, but in the present invention, it is 90% of 2/3 or less.
It can be reduced to about cc.

[0023]

【Example】

Example 1 SiO ₂ : 28 wt%, Na ₂ O: 13 was added to the flux raw materials shown in Table 1.
Add 90 to 90 cc of water glass consisting of wt% and K ₂ O: 4 wt% per 1 kg of raw material, stir and mix for 5 minutes, granulate, and then calcinate at 600 ° C to prepare calcined flux. did. Particle size is 45μ with water glass content as a parameter
FIG. 1 shows the result of investigation on the relationship between the content of Mn ₃ O ₄ of m or less and the granulation property. The granulation property was evaluated by sieving the flux through a 12-mesh (9.4 mm) upper and a 200-mesh (75 μm) lower sieve, and the passed powder was regarded as dust, and the ratio remained on the lower sieve was evaluated.

[0024]

[Table 1]

As is clear from the figure, the particle size is 45 μm.
When the content of Mn ₃ O ₄ below is 5 wt% or more of the flux, the granulation property is remarkably improved. For example, Mn ₃ O ₄
When the compounding amount of is 5 wt%, water glass compounding amount: 80 cc /
Granularity equal to or more than the content of water glass when not contained in kg: 150 cc / kg.

Example 2 The above-mentioned water glass was added to the flux raw materials shown in Table 2 in an appropriate amount, stirred and mixed for 5 minutes, granulated, and then calcined at 600 ° C. to calcinate the component composition shown in Table 3. A mold flux was produced. Using the obtained flux and 2% Mn-based wire (4.0φ), under the welding conditions shown in Table 4, downward welding of fillet was performed on a steel plate equivalent to SM400, and the amount of diffusible hydrogen in the weld metal and the bead The appearance was investigated. The results obtained are
It shows in Table 5. The amount of diffusible hydrogen in the weld metal is JIS Z.
Measured according to 3118.

[0027]

[Table 2]

[0028]

[Table 3]

[0029]

[Table 4]

[0030]

[Table 5]

As is clear from Table 5, when Nos. 1 to 7 obtained according to the present invention were used as the flux, not only the diffusible hydrogen amount could be suppressed low, but also good. It was possible to obtain a nice bead appearance. On the other hand, the fluxes of Nos. 8 to 9 do not contain fine-grained Mn ₃ O _4, so a large amount of binder was required for granulation, resulting in a large amount of diffusible hydrogen and the flux after moisture absorption. Then a pit occurred. Further, NO.10 does not contain a deoxidizer, and No.11 to 14 have flux compositions outside the proper range of the present invention. Therefore, No.15 has a particle size composition outside the proper range. Therefore, the bead appearance was poor in all cases.

[0032]

As described above, according to the present invention, since the amount of the binder can be reduced and the granulation can be performed, the flux having the excellent moisture absorption resistance can be obtained even when the deoxidizing agent is consumed at a relatively low temperature. When it is applied to submerged arc welding, not only can the amount of diffusible hydrogen in the weld metal be reduced, but also an excellent bead appearance can be obtained.

[Brief description of drawings]

[Fig. 1] The particle size is 45 with the blending amount of water glass as a parameter.
₃ is a graph showing the relationship between the content of Mn ₃ O ₄ of μm or less and the granulation property.

Claims (3)

[Claims] 1. A SiO ₂ —MnO-based flux for submerged arc welding containing 3 to 30 wt% of manganese oxide in terms of Mn amount, wherein the flux has a particle size of 45 μm or less as a granulating property improving agent. SiO ₂ -MnO-based firing for submerged arc welding, which was obtained by granulating flux raw material powder with Mn ₃ O ₄ added in a proportion of ₅ to 35 wt% and then performing low-temperature firing at 500 to 700 ° C. Type flux. 2. The flux particle size according to claim 1, wherein
Particle size: SiO ₂ -MnO-based firing type flux for submerged arc welding with a particle size distribution containing particles of 300 to 1000 μm in an amount of 50 wt% or more. 3. The flux component according to claim 1, wherein the flux component is SiO ₂ : 40 to 60 wt%, and the manganese oxide (in terms of Mn amount):
3 to 30 wt% MgO: 5 to 25 wt%, Al ₂ O ₃ : _{2 to} 15 wt% Si 2 and / or Mn: 0.5 to 10 wt% SiO ₂ —MnO based firing type flux for submerged arc welding.