JPS58187299A - Production of fused flux for submerged arc welding - Google Patents

Abstract

PURPOSE:To prevent the welding defect occurring in hydrogen, by using manganese dioxide contg. a speific ratio of particles having specific grain sizes as an MnO raw material for a fused flux for submerged arc welding. CONSTITUTION:Manganese dioxide controlled in grain size in such a way that particles of <=350mu particle size are contained at >=65% by wt% is used as an MnO raw material for a fused flux for submerged arc welding. Since the manganese dioxide having such grain sizes permits easy removal of the moisture occluded therein, the effect of reducing the hydrogen in the flux is substantial and prevents the generation of any welding defect.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a melting mold for low hydrogen submerged arc welding which is effective in preventing welding defects caused by hydrogen.

Welding defects caused by hydrogen, such as cold cracks, pits, and blowholes, have become a serious problem in submerged arc welding. In order to prevent these defects, various efforts have been made to reduce the hydrogen content of the flux from the perspective of welding materials, but as a trade-off for the low hydrogen content, deterioration in toughness or welding workability was unavoidable. Therefore, at present, preventive measures are taken from the viewpoint of welding work, such as preheating of the welded part, post-heating of the welded part, and cleaning of the welded part. However, these increased man-hours lead to a decrease in construction efficiency, and there is a strong demand for the provision of low-hydrogen fluxes.

Therefore, the inventors of the present invention have conducted intensive studies on a method for lowering the hydrogen content without changing the composition of the molten type 7g.
It was discovered that hydrogen in flux is largely affected by occluded moisture in flux raw materials, and that this occluded moisture can be more easily removed by melting using fine powder raw materials, reducing hydrogen by 7 lux. . In particular, it has been found that manganese dioxide, which is commonly used as a raw material for the MnO component, has a higher amount of occluded water than other raw materials, and that the use of manganese dioxide has a more significant hydrogen reduction effect.

In other words, Table 1 shows the combination of silica sand, manganese dioxide, and magnesia clinker-1 fluorite with different particle sizes.
%910□, 40%Mn0, 10%Mg0.

Five types of molten fluxes having a composition of 40% CaF2 were manufactured, and the amount of diffusible hydrogen in the weld metal was determined by
The results are shown in the results measured using the test method shown in the table, and the effect of raw material particle size on hydrogen content is that for silica sand and magnesia clinker-1 fluorite, the hydrogen content is slightly lower with fine grain raw materials than with coarse grains. While there is a tendency, 2
In the case of manganese oxide, reducing the particle size significantly reduces the amount of hydrogen.

11 Figure 1 shows the same (46% 8102.40%Mn0
In the molten type FLA, which has a composition of 110% MgO14, CaF2, the particle content of 350μ or less in the particle structure of manganese dioxide used for its production and the second
This table shows the relationship between the amount of diffusible hydrogen according to the test method shown in the table, and the amount of hydrogen decreased as more small-diameter particles of manganese dioxide were contained.

In this way, we have obtained a completely new finding that it is possible to reduce the amount of diffusible hydrogen in the weld metal by making the particle size of manganese dioxide, in particular, finer among the raw materials for the molten 7LAX.

The present invention is based on the above knowledge, and its gist is that particles with a particle diameter of 350μ or less are
MmO
A method for producing a molten flux for submerged arc welding, which is characterized in that it is used as a raw material.

The present invention will be explained in detail below.

Hydrogen is thought to exist in the form of OH groups in the molten W7 lux, which is chemically absorbed when moisture comes into contact with the molten W7 lux.If other conditions are constant, 7) The amount of water in the raw materials used has been reduced.

This greatly affects the amount of hydrogen in the rice cake.

Moisture in raw materials is divided into adhering moisture and occluded moisture. Adhering moisture is physically adsorbed on the raw material surface and can be removed by drying at a relatively low temperature, so it easily evaporates during flux dissolution. It has little to do with the hydrogen that is removed and ultimately in the flux. On the other hand, occluded moisture exists inside the raw material in a form similar to chemical bonds, such as water of crystallization or OH groups, and is removed only when the temperature reaches a high temperature of about 50° C. or higher.

Table 3 shows the analysis results of the adhering moisture and occluded moisture of the main raw materials used in the production of melt-type rice cakes.
Adhering moisture was determined by gravimetrically determining the amount of moisture removed up to 110.degree. C., and occluded moisture was determined by the Karlfi-Schar method by determining the amount of moisture released between 110.degree. C. and 1000.degree.

As can be seen from this table, manganese dioxide has a higher moisture content than other raw materials, and is characterized by a large amount of occluded moisture that cannot be removed, especially at low temperatures.

In other words, if the manganese dioxide contained in the blended raw materials is fine particles, it will quickly lose moisture during the period when it is exposed to high temperatures until it is put into the furnace, comes into contact with the molten flux, and is melted. is removed and is not absorbed into the molten flux. On the other hand, when the inorganic dioxide gun is coarse particles, the moisture removed is limited to the surface layer of the particles, leaving moisture inside. Moisture is melted because it is melted.

It is thought that it is absorbed into the dispersion as OH groups.

Furthermore, it is thought that the amount of adhering moisture increases due to grain refinement, but
Since this is easily evaporated and removed in the initial stage of dissolution as described above, it is hardly affected by the amount of hydrogen in the flux.

In addition, it is considered that other raw materials had a small amount of occluded water to begin with, so even if they were apparently made into upper-shaft granules, no significant effect was observed.

Table 3 This is the reason why, in the present invention, the raw material to be refined is limited to only ion dioxide. In addition, regarding the particle size structure, the reason why the content of particles with a particle size of 350μ or less was set to 65q6 or more by weight is because if it is less than 65%, the particle size structure will become coarse and the hydrogen reduction effect in the flux will be insufficient. If this content is high, the grain size structure will be closer to the fine grain side, and the root water volume lowering effect will be greater. However, in actual operation, it is desirable to keep the content of particles of 63 tones or less (250 tones) low, as this causes problems such as the generation of powder II and a decrease in yield.

Incidentally, the particle size of 350 μm corresponds to 42 Messier.

Also, the 31st! In addition to the raw materials listed above, rutile, magnesite, silica, fluorite, cryolite, etc. are also used as raw materials for the molten type 7LAX for submerged arc welding, but all of these raw materials are It has the same amount of absorbed moisture as other raw materials except manganese oxide.

Examples of the present invention will be described below.

Manganese dioxide having the particle size structure of the five types shown in Table 4 is M! 10 As a raw material, a molten flux having the composition shown in No. 5 was manufactured, and the amount of diffusible hydrogen in the weld metal was determined by
It was measured by the method specified in JIS z3116 shown in 9.

In addition, in Table 4, the raw ores of M1, M2, M3, M4, and M5 are all the same, and among these, M3, M4, and M5 have particles of 350μ or less, respectively.
90. This is the particle size structure of the present invention adjusted to 100 weight 11 times.

Table 4 Table 5 The method shown in Table 1 and 2, that is, JIS Z31
The water content amount #j of the Kusumano arc weld specified in 16
In accordance with the established method, welding current 500A, arter torque 33V
, welding speed of 30 m, and welding speed of 41 nm under welding conditions using the glycerin substitution method). According to those results, 7% of any composition,
(Even in the case of wood grains, the finer the particle size composition of manganese dioxide), the lower the diffusible hydrogen i1 becomes, and compared to the conventional use of dispersed manganese that contains many aggregated particles, the hydrogen content is about 1/2 to 115 It is clear that the present invention has a comfortable effect on wear.

Table 6 As stated above, according to the present invention, a low hydrogen melting flux can be obtained without changing the conventional flux composition and without deteriorating the rounding resistance and welding workability. The number of man-hours required for construction to prevent welding defects caused by free hydrogen hydroxides is greatly reduced, and its industrial value is enormous.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the relationship between the content of particles of 350 tones or less in the particle structure of manganese dioxide and the rate of diffusible water. Patent applicant: Shin Nippon Seimei Co., Ltd. Figure zS 5θ 7J 10
028 Ihimanganon hand construction person 1; Particles below 35 yen (quantity 2) Procedural amendment (voluntary) June 1981 170 Special 11'1 Office Commissioner Kazuo Wakasugi 1, of the case Large and Small Patent Application No. 069529 of 1982 2 Title of Invention Melting My Flux Gourd Making Method for Submerged Arc Welding 3, hl
Relationship with the case of the person who engages in +E Patent applicant: Otemachi 2-chome, Chiyo 11-ku, Tokyo [No. 16-3 (665) Shin [1] Takeshi 1, representative of Nippon Steel Co., Ltd., Toyo 4, agent 〒100 Tokyo 2-114-1-6, Marunouchi 2-chome, 111-ku, Chiyo, Miyako, Detailed explanation of the invention in the specification subject to amendment 7 Contents of amendment-51'

Claims (1)

[Claims] Melting type 7 for submerged arc welding, characterized in that the particle size is adjusted to contain 65% or more by weight of particles with a particle size of 350μ or less, and manganese 92 oxide is used as the MnO raw material,
How to make sou.