JP2000334596A - Manufacturing method of fired flux for submerged arc welding - Google Patents

Abstract

(57) [Summary] [Problem] High-temperature sintering for submerged arc welding not only having excellent pock mark resistance but also having good welding workability by effectively suppressing gas generation even during high-speed welding. Provide mold flux. SOLUTION: After sintering type flux raw material powder is granulated,
When producing a flux for submerged arc welding by firing at a temperature exceeding 750 ° C., the temperature is raised from 700 ° C. to (maximum temperature −50 ° C.) at a rate of 5 ° C./min or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a fired flux for submerged arc welding suitable for welding steel structures such as ships, marine structures, storage tanks, steel frames, bridges, etc. For high-speed submerged arc welding of fillet joints of weldable H-type members used for beams, etc., for submerged arc welding with excellent welding workability that can stably obtain defect-free welds The present invention relates to a method for producing a fired flux.

[0002]

2. Description of the Related Art Submerged arc welding (submerged arc welding)
Lux is usually silicon dioxide (SiO _Two).
Magnesium oxide (MgO), manganese oxide (Mn
O, Mn_Three0 _Four Etc.), calcium oxide (CaO), alumina (A
l_Two0_Three) And other oxides, fluorides, etc.
Manufactured. And this submerged arc welding
Flux can be produced by melting mold flux depending on the manufacturing method.
Flux, fired flux (including sintered flux)
And the same shall apply hereinafter) and mixed fluxes.

[0003] Among them, the calcination type flux generally includes a process of adding water glass (sodium silicate) or the like as a binder (binder) to a flux raw material powder such as an oxide or a fluoride, and kneading, granulating, drying and firing. It has been manufactured through. In rare cases, the binder may be omitted. Such a sintering type flux has an advantage that it can be manufactured with relatively simple equipment and thus is inexpensive, and that a welding metal component can be adjusted because a deoxidizing agent and an alloy element can be added.

[0004] However, this calcined flux is
The quality of the flux, and thus the properties of the weld, vary greatly depending on the raw material. For example, welding defects such as pits and pock marks occur at the welded portions. These welding defects are caused by moisture such as water of crystallization in the raw material or raw material oxides,
It is generated due to CO and CO ₂ gas generated during welding.

[0005] In order to solve the above problem, in a low-temperature firing type flux which is fired at a low temperature (700 ° C. or lower), improvement in welding defect resistance has been attempted by adding a carbonate or a deoxidizing agent to the flux. On the other hand, a high-temperature firing flux that fires at a high temperature (700 to 1200 ° C) can reduce the hydrogen content of the deposited metal without using a carbonate, and although it has excellent high-speed weldability, it can be used as a deoxidizing agent. Was very poor, and the pock mark resistance was poor. Moreover,
At present, little has been considered.

Examples of adding metal powder for the purpose of deoxidation include, for example, Japanese Patent Publication No. 32-409 and Japanese Patent Publication No. 44-13249.
In the publication, examples of Fe-Si and Si-Mn are described.
In high-temperature sintering fluxes, the deoxidizing agent is often degraded (oxidized or nitrided) during high-temperature sintering and the effect of the deoxidizing agent is reduced, so these two types of deoxidizing agents are used. Is the main. However, even when Fe-Si and Si-Mn are used as the deoxidizing agent, the deoxidizing agent is deteriorated due to high-temperature sintering conditions or the like. Problems such as not being able to obtain excellent welding workability remain.

In addition, Japanese Patent Application Laid-Open No. 62-68695 discloses a high-temperature sintering type flux containing 0.5 wt% or less of Si in the flux. However, this technology reduces the amount of Si in the flux to 0.5 wt% or less,
The effect of deterioration of the deoxidizer during high-temperature firing on welding workability is reduced, and a method of firing the deoxidizer and flux has not been studied.

[0008]

SUMMARY OF THE INVENTION The present invention has been developed in view of the above-mentioned situation, and uses Fe-Si as a deoxidizing agent. It is an object of the present invention to propose an advantageous method for producing a fired flux for submerged arc welding having a stable welded portion free from defects by controlling the rate of temperature rise in the above-mentioned method and having excellent welding workability.

[0009]

Means for Solving the Problems Now, the inventors have studied 750
In the production of firing flux for submerged arc welding, which is fired at a temperature of ℃ or more, as a result of earnestly examining a method for stably obtaining defect-free welds,
With the flux to which Fe-Si is added, it has been found that optimizing the firing conditions during production is effective for improving workability during welding and suppressing the occurrence of defects. The present invention is based on the above findings.

That is, the gist of the present invention is as follows. 1. After granulating the sintering type flux raw material powder and firing at a temperature exceeding 750 ° C to produce a flux for submerged arc welding, the temperature range of 700 ° C or more and (maximum temperature -50 ° C) or less is 5 ° C / min. A method for producing a fired flux for submerged arc welding, characterized in that the temperature is raised at the above-mentioned heating rate and then fired.

2. In the above item 1, the flux component is
total SiO _2: 30~70wt%, manganese oxide (in amount of MnO terms): 5~40wt%, MgO: 3~30wt %, A1 2 0 3: 2~20
A method for producing a firing flux for submerged arc welding having a composition containing wt%.

3. As deoxidizer, Si content is 30 ~ 80wt%
And Fe-Si particles having a particle size distribution of 10% or less by weight when the particle size is more than 106 μm and 50% or less by weight when the particle size is less than 45 μm are blended in a ratio of 1 to 10% by weight. In the method for manufacturing a flux for submerged arc welding, which is performed by granulating the fired type flux raw material and firing at a temperature of 750 ° C or higher, the temperature range of 700 ° C or higher and (maximum temperature -50 ° C) At a heating rate of 5 ° C./min or more.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. First, the circumstances that led to the invention will be described based on experimental results. Raw materials adjusted to have the compounding ratios as shown in Table 1 were mixed with water glass as a binder in an amount of 12-200.
The mixture was granulated into a mesh and fired at 1100 ° C. for 5 minutes. At this time, the flux was fired using a stationary batch furnace, and the effect of the temperature rising rate during the flux firing was investigated. The heating rate was measured using a thermocouple at a temperature that was considered to be the average heating rate position in the flux-packed layer and that was 1/4 of the filling height from the surface of the central part of the flux-filled container. The average rate of temperature rise in the temperature range of 700 to 500 ° C. was determined.

These fluxes and 2 wt% Mn-based wire
(4.8mmφ), welding current: 750A, welding voltage: 35
V, welding speed: 40cm / min, under welding conditions, SS400 equivalent steel plate was subjected to single downward fillet welding and the bead appearance was investigated. The obtained results are shown in Table 2. As is clear from the table, it can be seen that the effect of the rate of temperature rise during flux firing on the appearance of the weld bead is extremely large.

[0015]

[Table 1]

[0016]

[Table 2]

The reason why the rate of temperature rise during flux firing is closely related to the appearance of the weld bead may be as follows. Usually, as the metal powder added to the high-temperature firing type flux for the purpose of deoxidation, Fe-Si and Si-
Mn is generally known, but also in the temperature range of 700 ° C. or higher, although the reaction rate is slow, the quality gradually changes (oxidizes) and the effect as a deoxidizing agent decreases. 700 ° C
When the temperature rise rate in the above temperature range is 5 ° C / min or more, the deoxidizer oxidation behavior changes which affects the oxidation rate of the deoxidizer near the maximum temperature. , And also slows down its oxidation),
It is considered that the oxidation loss of the deoxidizing agent is significantly reduced.

Hereinafter, the reason why the constituent elements in the present invention are limited to the above range will be described. In the present invention, in the heating process of the firing step, the temperature is 700 ° C. or more (the maximum temperature −
It is necessary to raise the temperature in the temperature range below 50 ° C) at a rate of 5 ° C / min or more. First, the lower limit of the temperature range in which the heating rate should be controlled was set at 700 ° C.
As described above, the alteration (oxidation) of the Fe-Si particles is concerned. On the other hand, since the heat transfer property of the flux powder is not so good, it is necessary to perform a soaking treatment for at least about 5 minutes in a soaking temperature range (a temperature range from a maximum temperature to a maximum temperature of −50 ° C.) in order to obtain a uniform material by the soaking. is necessary. Therefore, (maximum temperature −50 ° C.) was determined as the upper limit of the temperature range in the heating process up to the soaking temperature range. In addition, the reason why the heating rate in this temperature range is limited to 5 ° C./min or more is that when the heating rate is less than 5 ° C./min, the Fe—Si particles are altered (oxidized), and the deoxidizing effect during welding is reduced. This is because it becomes smaller.

Next, it is used as a deoxidizing agent when compounding the raw materials.
The conditions that Fe-Si should have will be described. Si content of Fe-Si: 30 to 80 wt% If the Si content exceeds 80 wt%, the absolute amount of Fe-Si to be added becomes small, making it difficult to distribute uniformly throughout the flux. And In addition, the Si content is 30
If it is less than wt%, it is necessary to add a large amount of Fe-Si, and the addition of a large amount increases the iron content in the flux, which deteriorates the surface properties of the weld bead.
% Or more.

Particle size composition of Fe—Si: The proportion of particles exceeding 106 μm is 10 wt% or less and the proportion of particles less than 45 μm is
50 wt% or less Of the Fe-Si particles, the ratio of particles exceeding 106 μm is 10 wt%
%, The deoxidizing effect and the deoxidizing efficiency decrease during repeated use, and a pock mark is likely to appear. Therefore, the content is limited to 10 wt% or less. On the other hand, when the proportion of particles having a particle size of less than 45 μm is 50 wt% or more, fine Fe—Si particles are oxidized and disappeared during high-temperature sintering.

Content of Fe—Si in flux: 1
If the Fe-Si content is less than 1 wt% with respect to the entire flux, the desired deoxidizing effect cannot be obtained. On the other hand, even if it exceeds 10 wt%, the deoxidizing effect reaches saturation. The Fe-Si content was limited to the range of 1 to 10%.

In the present invention, when producing the flux for submerged arc welding, basically, the heating rate in the temperature range of 700 ° C. or more and (maximum temperature −50 ° C.) or less is 5 ° C./min.
By restricting as described above, and preferably, further, for Fe-Si particles added as a deoxidizing agent in the flux, the desired effects are obtained by restricting the components, the particle size composition and the amount of addition to the above ranges. However, for other typical compositions of calcined flux,
It is as follows.

Total SiO ₂ : 30 to 70 wt% SiO ₂ is added as a slag-making agent to keep the bead appearance good. However, if the total SiO ₂ content is less than 30 wt%, the effect of the addition is poor. In particular, in the case where penetration of the bead end is important such as high-speed fillet welding, a good bead shape cannot be maintained at less than 30 wt%. On the other hand, if it is contained in a large amount exceeding 70% by weight, the viscosity becomes too high, and the bead appearance tends to be disturbed, and the slag peeling property is deteriorated. Therefore, it is preferable that the total SiO ₂ amount be about 30 to 70 wt%.

Manganese oxide: 5 to 40% by weight (in terms of MnO content) As a fillet welding flux, it is necessary that the bead ends conform well even if the welding speed is increased. For that purpose, it is preferable to use a slag containing manganese oxide. However, if the added amount is less than 5 wt% in terms of the amount of MnO, the effect is not recognized, and if the added amount exceeds 40 wt%. As the CO reaction intensifies in the molten pool, the bead appearance deteriorates. Therefore, the amount of manganese oxide is preferably about 5 to 40 wt%.

MgO: 3 to 30 wt% MgO is a component useful for adjusting the melting point and viscosity of the slag and ensuring the slag removability. However, if the content is less than 3 wt%, a sufficient effect cannot be obtained.
%, The viscosity tends to be too low, and the melting point tends to be too high, and the bead appearance tends to deteriorate. Therefore, MgO is desirably about 3 to 30% by weight.

Al ₂ O ₃ : 2 to 20 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%, the effect of its addition is poor. If it exceeds, the melting point rises too much and the bead shape is deteriorated, so that the content is desirably about 2 to 20% by weight.

In addition, it is also preferable to contain CaO or CaF ₂ . CaO: 10 wt% or less CaO is a component that affects the fluidity of slag.
If it is contained in a large amount in excess of wt%, the fluidity is impaired and the bead shape is degraded, so CaO is preferably set to about 10 wt% or less.

CaF ₂ : 15 wt% or less CaF ₂ is a component that improves the fluidity of slag.
If it exceeds wt%, the slag will flow more easily, so CaF ₂
It is desirable to set it to about wt% or less. Note that a particularly preferable range is 5% by weight or less.

The typical flux composition has been described above. However, if necessary, TiO ₂ : 10 wt% or less,
BaO: 5 wt% or less, ZrO _2: 5wt% or less, B ₂ 0 _3: 4wt% or less, CaCO _3: may be added one or more selected from the following 5 wt%. TiO ₂ is reduced during welding and Ti
Has the effect of improving the toughness of the weld metal. However, if it exceeds 10% by weight, the toughness is rather deteriorated. BaO and ZrO ₂ are added to adjust the basicity and melting point of the slag. However, any addition exceeding 5 wt% deteriorates bead appearance and slag removability. B ₂ 0
_In No. ₃ , B is transferred into the weld metal due to a reduction reaction during welding, thereby contributing to improvement in toughness of the weld metal. However, 4
If it exceeds wt%, solidification cracking of the deposited metal is promoted. CaCO ₃
Decomposes during welding to generate CO ₂ and reduce the hydrogen partial pressure, which is effective in reducing the amount of hydrogen in the weld metal. However, if it exceeds 5% by weight, the bead appearance deteriorates.

The flux raw material powder and the Fe and Fe particles adjusted to the above-mentioned components and particle size composition so as to have the above-mentioned preferred composition are provided.
After adding and blending an appropriate amount of Si and kneading with a binder, granulating, and then firing under the firing conditions described above. The granulation method is not particularly limited, but it is preferable to use a rolling granulator or an extrusion granulator. After granulation, sizing processing such as dust removal and crushing of coarse particles is performed to obtain a particle size of 0.
It is preferred that the particles have a size between 075 and 2.5 mm. The sizing process may be performed after firing. In addition, as the binder (binder), an aqueous solution such as polyvinyl alcohol or water glass is preferable. Above all, it has been used
Molar ratio of SiO ₂ to Na ₂ O: 1 to 5 sodium silicate (water glass)
Is advantageously fitted. The amount of water glass used may be about 80 to 150 cc per 1 kg of the flux material. Regarding the firing temperature, if the firing temperature is lower than 750 ° C, the moisture brought in from the binder (binder) will not be sufficiently dried, causing an increase in the diffusible hydrogen in the deposited metal.
It is necessary to be higher than ° C. The firing is performed using a rotary kiln, a stationary batch furnace, a belt-type firing furnace, or the like.

[0031]

EXAMPLES Example 1 Raw materials blended so as to have the ratios shown in Table 1 were prepared.
Granulate to 12-200 mesh using water glass as binder, 10
It baked on conditions of 00 degreeC and 5 minutes. 106 μm for Fe-Si
Those having a particle size distribution of more than 10 wt% or less than m and 50 wt% or less for less than 45 μm and having an Si content of 18 to 76 wt% were used. In addition,
The flux is baked in a rotary kiln, 700
The average heating rate in the temperature range of 950950 ° C. was 12 ° C./min. The heating rate was measured using a thermocouple with a 10 mm square iron piece. Using these fluxes and 2wt% Mn-based wire (4.8mmφ), under the welding conditions of welding current: 850A, welding voltage: 40V, welding speed: 50cm / min, downward fillet welding was performed on a steel plate equivalent to SM400. The bead appearance was examined. Table 3 shows the obtained results.

[0032]

[Table 3]

As is clear from the table, when the flux (No. 2, 3) in which the rate of temperature rise during firing, and furthermore, the composition and amount of Fe—Si satisfy the appropriate range of the present invention, are used. Obtained a good bead appearance. On the other hand, when the Si content in Fe-Si is less than the appropriate range (N
In o.1), the number of occurrences of pock marks was much larger than that of conforming cases, and the bead surface properties were remarkably inferior.

Example 2 Raw materials prepared by using olivine sand having the composition shown in Table 4 so as to have the ratio shown in Table 5 were mixed with water glass as a granulating agent, and granulated to 12 to 200 mesh. After drying and firing, the particle size was adjusted to obtain a flux. The flux was fired in a belt-type firing furnace at 900 ° C. for 5 minutes. The rate of temperature rise during flux firing was changed by changing the amount charged into the furnace, the belt speed, and the set temperature in the furnace without changing the thickness of the flux-filled layer in the furnace. In addition, Fe-47wt% Si whose particle size distribution was adjusted was used as the fuero silicon. Using these fluxes and 2wt% Mn-based wire (4.8mmφ), welding current: 900A, welding voltage: 40V, welding speed: 60cm / min. , And the bead appearance was examined. Table 6 shows the obtained results.

[0035]

[Table 4]

[0036]

[Table 5]

[0037]

[Table 6]

As is clear from Table 6, when the flux manufactured under the conditions satisfying the requirements of the present invention is used,
A good bead appearance could be obtained.

[0039]

Thus, according to the present invention, even during high-speed welding, the generation of gas is effectively suppressed, and the submerged arc welding not only has excellent pock mark resistance but also has good welding workability. High-temperature sintering type flux can be stably obtained.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Nobuo Tezuka 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Chiba Works, Ltd. F term in Chiba Works (reference) 4E084 AA03 AA06 AA07 AA11 CA16 DA18

Claims (3)

[Claims] Claims 1. A granulated powder of a calcined flux raw material,
When producing flux for submerged arc welding by firing at a temperature exceeding 750 ° C, the temperature range of 700 ° C or higher and (maximum temperature −50 ° C) or lower is raised at a rate of 5 ° C / min or higher, and firing is performed. A method for producing a fired flux for submerged arc welding. 2. The method of claim 1, the flux component, total SiO _2: 30 to 70 wt%, manganese oxide (in amount of MnO terms): 5~40wt%, MgO: 3~30wt %, A1 2 0 3: A method for producing a firing flux for submerged arc welding having a composition containing 2 to 20 wt%. 3. A deoxidizing agent having a Si content of 30 to 80 wt% and a particle size of more than 106 μm in a weight ratio of 10% or less,
Particle size: Fe-Si particles having a particle size distribution of less than 45 μm with a weight ratio of 50% or less are blended at a ratio of 1 to 10% by weight. In the method for producing a flux for submerged arc welding, which is performed, at the time of firing, 700 ° C or more, (maximum temperature −50
A method for producing a fired flux for submerged arc welding, wherein the temperature is raised at a rate of 5 ° C./min or higher in a temperature range of not higher than 5 ° C.