JPS5922635B2 - Manufacturing method of molten flux for submerged arc welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a melt-type flux for submerged arc welding that provides a good welded area without pits or blowholes.

When an appropriate amount of CaF2 is contained in a molten flux containing SiO2, MnO, CaO, etc., the deoxidation and dehydrogenation of the molten metal is promoted, and the viscosity and solidification temperature of the molten slag are also lowered, thereby improving the pitting resistance of the welded part. It is known that the properties and prohol resistance are improved.

In other words, CaF2 reacts with moisture during the welding process as shown in formula [I], and part of it is converted to CaO and generates HF. This HF is immediately radiated out of the molten pool, so there are no pits caused by moisture. and blowholes are suppressed. CaF2
+H2O→CaO+2HFCI] However, if the amount of CaO in the flux is large, the reaction of formula [I] will be suppressed and the effect of improving pitting resistance and blowhole resistance will decrease.
It is preferable that the amount of aO is small.

Therefore, flux raw materials with a low amount of CaO must be carefully selected and used. On the other hand, this type of flux is manufactured by mixing and melting two or more types of raw material ores containing the above-mentioned components, but the reaction of formula [I] progresses considerably even in this melting process, and CaF2 is converted to CaO. . Therefore, in order to obtain a molten flux with a small amount of CaO, the reaction of CaF2 in the melting process must be suppressed as much as possible. It was completed as a result of intensive research to develop a technology that can reduce weight and increase the yield of CaF2, and its composition consists of SiO2, MnO
When producing a molten flux by mixing and melting raw materials containing CaF2, after melting the raw material containing at least Mn0, the raw material containing CaF2 is added and mixed and melted to obtain 5i0220-55% ( Weight %: Same below),
The gist is that the main components are 20-50% Mn and 21-10% CaF.

When the present inventors investigated the progress of the reaction of formula [I] and the dissolution conditions in the mixing and dissolving process, it was found that 'CaF2→CaO
It was found that the amount of conversion changes significantly.

It has also been found that in order to suppress the amount of CaO produced, it is necessary to reduce the amount of water in the raw material as much as possible and to shorten the dissolution time of the raw material containing CaF2. However, Ca
Since F2 has a lower melting point than SiO2 and Mn0, when these raw materials are mixed and melted from the beginning, CaF2
After that, SiO2 and Mn0 are dissolved. That is, since CaF2 exists in a molten state for the longest time in the dissolution treatment process, the reaction of formula [I] progresses during this time, and CaF2
The yield D decreases. Furthermore, among the raw materials, the MnO-containing raw material contains a large amount of water (crystal water and attached water), and accounts for most of the water content in the entire raw material. Therefore, first of all, SiO
If a CaF2-containing raw material is added and dissolved after melting a raw material containing 2 and MnO, the melting time of CaF2 will be shortened [
We thought that the reaction force of equation 1 would be suppressed, and proceeded with the experiment along that line. As a result, if the CaF2-containing raw material is added after the raw material containing at least MnO is dissolved, the time for dissolving the CaF2-containing raw material is shortened, and the C
It was found that the yield b of aF2 was improved and the generation of CaO could be suppressed. The molten flux thus obtained contains the required amount of CaF2 and has a small amount of CaO, and exhibits excellent pit resistance and blowhole resistance. Furthermore, since the yield of CaF2 is high, the amount of CaF2-containing raw materials, which are more expensive than other raw materials, can be reduced, resulting in a reduction in material costs. Moreover, in the conventional dissolution method, a large amount of CaO is generated during the dissolution stage as mentioned above, so the amount of CaO produced must be taken into account and a raw material with a small amount of CaO must be carefully selected. Since the amount of CaO produced at this stage is small, some CaO may be present in the raw material.
It is advantageous that even raw materials that were previously considered inappropriate can be used. The main component of the molten flux according to the present invention is SlO2:20~
55%, MnO: 20-50% and CaF2: l-10
%, but the reasons for determining these components and content rates are as follows.

[SiO2] If the SiO2 content is less than 20%, the melting point of the slag will be too high, and welding workability will be deteriorated. This is not preferable because it reduces the toughness.

[MnO] When the MnO content is less than 20%, it becomes difficult to provide appropriate slag fluidity and maintain good workability.
If it exceeds 50%, the viscosity of the slag becomes too high, uniform beads are not formed, and the amount of oxygen in the weld metal increases, resulting in a decrease in notch toughness, which is undesirable.

[CaF2] As mentioned above, it promotes deoxidation and dehydrogenation of the weld metal to improve the physical properties of the weld, and also lowers the viscosity and solidification temperature of molten slag to achieve sound welding without pits or blowholes. It is an essential component to enable these effects, and in order to ensure these effects, it must be contained at least 1% or more.

However, if it exceeds 10%, hook marks tend to occur on the bead surface and undercuts occur, which is not preferable. Various manganese ores, silica stones, fluorite, etc. are used as flux raw materials, but as long as the blending ratio of the above three components is consistent with the above-mentioned ratio, there is no problem even if other components such as At2O3 are mixed in. In order to more effectively exhibit the features of the invention, it is desirable that the CaO content be as small as possible.

In addition, the raw materials mentioned above contain trace amounts of phosphorus and sulfur, which impair the toughness and cracking resistance of the weld metal, so raw materials with low phosphorus and sulfur content are selected or It is desirable to perform dephosphorization and desulfurization treatment during the dissolution stage. Note that dephosphorization can be easily carried out by melting in a reducing atmosphere using a carbon-lined melting furnace. Further, desulfurization can be easily carried out by oxidizing with nascent oxygen (2Mn02→2Mn0+02) generated in the melting process using a resistor in which oxygen is bubbled in the melting process or a raw material containing MnO2. The present invention is roughly configured as described above, and by selecting the timing of addition of the CaF2-containing raw material, CaF2→Ca
Prevents O conversion, increases CaF2 yield, and C
It has become possible to produce a melt-type flux for submerged arc welding that suppresses the formation of aO and has excellent pit resistance and blowhole resistance at a relatively low cost.

In carrying out the present invention, MnO-containing ore, SiO2-containing ore and C
A predetermined amount of aF2-containing ore is weighed and prepared, and the timing of adding CaF2-containing ore is delayed in the mixing and dissolving process, but the first step is
If a predetermined amount of raw material is weighed and charged into a raw material container as shown in FIG. That is, the first
．． The raw material container 1 shown in FIG. 2 is divided by a partition wall 2. An opening/closing damper 3 is provided at the bottom of the partition wall 2.
Then, a raw material 4 containing MnO and SiO2 is charged into one chamber, and a raw material 5 containing CaF2 is charged into the other chamber.
During the melting process, open the discharge port 6 and first discharge SiO2.
・MnO-containing raw materials are put into a melting furnace and mixed and melted.
Next, at the end of the melting process, the fixing lock of the opening/closing damper 3 is removed, and the CaF2-containing raw material is introduced and mixed and melted. Use of such raw material containers allows standardization of melting operations, and is also advantageous when commercially available as a raw material for flux melting. Next, experimental examples will be given to clarify the effects of the present invention.

EXPERIMENTAL EXAMPLE Flux raw materials having the composition shown in Table 1 were mixed and melted under the conditions shown below to produce a molten flux for submerged arc welding.

In Table 1, manganese ores C and D are carefully selected high-grade raw material ores with low amounts of CaO and phosphorus, and manganese ores A and B are low-grade raw material ores that can be obtained relatively cheaply. be.

Manganese ore A is an ore with a very small amount of CaO (the amount of iron phosphorus is high and its usage is limited).
(f), SiO2 and MnO were used in appropriate amounts at 46% and 42%, respectively, and mixed and melted using a carbon-lined melting furnace.

However, the melting conditions were 1700℃ x 60 minutes, and in the case of the comparative example, all the raw materials were mixed and dissolved at the same time, and in the case of the example, the other raw materials were added from the beginning, leaving the fluorite, and only the fluorite was dissolved in the other raw materials. After completion, it was added and mixed and dissolved. The raw material blending ratio is the second
Table 3 shows the component composition of the obtained flux.
The above results can be considered as follows.

(1) Example 1 and Comparative Example 1 are both examples in which a large amount of low-grade raw materials were used together. However, in Example 1, the CaF2 yield is high and the amount of CaO is suppressed to a low level. On the other hand, in Comparative Example 1, a large amount of CaF2 was converted to CaO and C
The content of aF2 is decreasing and the amount of CaO is increasing.

(2) Example 2 and Comparative Example 2 are both experimental examples in which the raw materials were carefully selected and the amount of low-grade raw materials used was suppressed, and Comparative Example 2 also obtained somewhat satisfactory values in terms of ingredients.

However, in Example 2, the amount of CaO was suppressed to about half that of Comparative Example 2, and it was found that the flux was extremely excellent as a flux for submerged arc welding. (3) That is, in the conventional method (comparative example), if the raw materials are carefully selected, a good flux can be obtained, but a large amount of high-grade manganese ore and CaF2-containing ore must be used, which increases the raw material price. On the other hand, with the method of the present invention (example), even if the amount of low-grade manganese ore used is increased and the amount of CaF2-containing ore used is suppressed, a flux with performance comparable to that of the conventional method can be obtained.
If the raw materials used are carefully selected, it is possible to obtain an extremely excellent flux for submerged arc welding at the same cost as conventional products.

BRIEF DESCRIPTION OF PAGE 1 FIGS. 1 and 2 are explanatory diagrams showing a raw material reactor suitable for carrying out the present invention.

1... Raw material container, 2... Partition wall, 3.
...Open/close 6...Discharge port.

Claims (1)

[Claims] 1 In producing a molten flux by mixing and melting raw materials containing SiO_2, MnO, and CaF_2, after melting the raw material containing at least MnO, the raw material containing CaF_2 is added and melted to obtain SiO_220 to 55% by weight. %, MnO20-50% by weight and CaF_21-1
A method for producing a melt-type flux for submerged arc welding, characterized in that the flux contains 0% by weight as a main component.