JPS5913953B2 - coated arc welding rod - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coated arc welding rod with good blowhole resistance.

5. Coated arc welding rods are classified into several groups depending on the ingredients and composition of the coating composition.
Welding rods coated with a coating composition mainly composed of iO2 or SiO2 have better arc stability and a smoother bead shape than corresponding welding rods mainly composed of caco3. It has the advantage that it is easy to weld, and that the welding speed is fast and efficiency can be improved.

However, if a high welding current is used in butt welding, for example, there is a drawback that blowholes are likely to occur, and there is a problem in application to large plate thickness structures and large restraint structures. The present invention has been made in view of these circumstances, and aims to provide a coated arc welding rod that has improved blowhole resistance without adversely affecting welding workability and work environment integrity. ■0 It is something to do. And the coated arc welding rod provided here, in which the coating material is fixed to the steel core wire with a binder, includes TiO2: 2 to 55% as the coating material,
SiO2: 5-30%, carbonate: 0.5-27%, deoxidizer 2-18%, organic compound: 0.2-10%, FeO
and one or more types of iron oxides selected from the iron oxide group consisting of Fe2O3: 20% or less, and one or more types of alkali metal oxides selected from the alkali metal oxide group consisting of 20 and Na2O: 5% or less. At least 20% or more of the titania minerals containing TiO2 and suppressing the Cl content to 307 OPIXII or less and used as a TiO2 source are
1): 6 to 50 FeO+Fe2O3 (2) Cl content: 100 P- or less 35 The gist lies in the use of a titania mineral that satisfies the following two requirements.

The reason for such requirements and limitations will be explained below.

If the content of TiO2 is less than 2%, the fluidity of the slag will decrease and the bead appearance will be impaired.

On the other hand, if it exceeds 55 (fl), the slag releasability deteriorates,
Since work efficiency decreases, it is set at 2 to 55 (!). SiO
2 is required to be at least 5%; if it is less than 5%, the arc blowing will be weak and the compatibility with the base material will be poor.

On the other hand, if it exceeds 30(f), the arc voltage becomes high and undercuts are likely to be formed due to excessive penetration. Also, carbonates such as alkali metal carbonates or alkaline earth metal carbonates are used as gas generating agents, but if it is less than 0.5%, the arc spreads poorly and overlaps are likely to be formed, and if it exceeds 2701), slag is baked onto the bead surface and makes peeling difficult, so it is set in the range of 0.5 to 2701).
As a deoxidizing agent, metal MnsFe-MnlFe-Sil
Fe-Ti. ．． Fe-Al etc. are mixed, but if it is less than 20t), the strength will be insufficient, and 180! ), pits occur due to excessive deoxidation, so it is set at 2 to 18%.

It is also possible to incorporate wood flour, starch, cellulose, dextrin, pulp waste, etc. as organic matter, but if it is less than 0.2%, pitting may occur due to insufficient shielding.
If it exceeds l), spatter will increase rapidly, so 0.2 to 10%.
shall be.

Next is the iron oxide group consisting of FeO and Fe2O3,
There is no particular lower limit set for the amount of these used alone or in combination.

However, if it exceeds 20%, the viscosity of the slag decreases and the bead shape deteriorates, so the upper limit is set at 20%. '5/. N
Regarding the alkali metal oxide group consisting of a2O and K2O, one or more of these is used, but if it exceeds 5%, spatter will increase, so it should be kept at 10% or less. Next, there are titania minerals such as rutile, lyucotacine, and illuminite, each of which has a characteristic composition, but even if you look at them individually, they have different aspects depending on the place where they are mined. It shows. Therefore, titania-based, lime-titania-based, and illuminite-based coating materials were prepared using various titania minerals, and coated on mild steel core wires to produce coated arc welding rods. The chemical components and the like are shown in Table 1. Using the obtained welding rod, the groove shown in FIG. 1 (the unit in the figure is Mll, the weld line length is 300 m0) was welded.

The diameter of the welding rod used in this test was 5m7fLφ
The welding current is 240A.

When we compared the relationship between the number of blowholes in weld metal and titania mineral (sometimes abbreviated as titania ore), we obtained the results shown in Figure 2.

In other words, it is clear that the number of blowholes occurs rapidly when Ti/Fe is around 50, and it is important to reduce Ti/Fe to 50 or less in order to improve blowhole resistance. I learned that. However, if Ti/Fe is too small and becomes less than 6, spatter and undercuts occur frequently and workability is reduced, so Tl/Fe should be set at 6 as the lower limit. That is, among the titania minerals, only leucoccine satisfies the above conditions, and other minerals have problems in terms of blowhole resistance or workability because the Ti/Fe ratio is outside the range of 6 to 50. Next, we conducted research on the content of the titania mineral that satisfies the above conditions among the titania minerals added to the coating composition. That is, in order to see the relationship between the proportion of titania minerals that satisfy the Ti/Fe range of 6 to 50 in the total TiO2 source minerals and the number of blowholes, we selected Lieucoccin (Lb) shown in Table 1. Ryuukokushin (L
When the effect on the number of blowholes generated was investigated while varying the blending ratio (total amount of TiO2 source minerals) in b), crystals as shown in FIG. 3 were obtained. That is, Ti/F
As the blending ratio of titania minerals that satisfies e within a certain range decreases, the number of blowholes increases.
In particular, it seemed to increase rapidly from around 20%. Therefore, in the present invention, the ratio of titania minerals satisfying Tl/Fe to the total TiO2 source minerals is at least 2.
00! ). Furthermore, titania minerals are heavy minerals that are weathered and transported to the beach by rivers, which are then selected, concentrated and deposited by wave action, forming deposits in inland areas where the coastline or former coastline has risen. Therefore, its components contain Cl. Therefore, Cl2 gas generated by arc heat gets mixed into the welding fume and deteriorates the working environment, and welding workers who may inhale this gas directly may experience strong discomfort depending on the Cl content. . Therefore, Ti/Fe is in the range of 6 to 50 and C
A coated arc welding rod was prepared by individually blending four types of high titania minerals with different Cl contents, and the relationship between the Cl content in the high titania minerals and the discomfort of welding workers was investigated. Got the results. In preparing the welding rods, only the type of high titania mineral was changed, and the other coating material components were kept constant. From the results shown in Table 2, if the Cl content in the total coating material is 70PF1 or less, the welder can work without feeling discomfort. However, depending on the welding environment, such as outdoors, indoors, a narrow place such as inside a tank, or the capacity of ventilation equipment, welding conditions such as 50PF or less, 3
It becomes necessary to suppress the amount to 0PI1n or less, preferably 10P or less. Note that high titania minerals A or B cause discomfort to welders unless the amount added is small, but C,
In D, no discomfort was felt regardless of the amount added.

Of course, if A and B are mixed with a high titania mineral with a low Cl content, the overall Cl content will be reduced and it may become possible to use them, but in this case, two or more of the same type of raw materials may be stored. This is extremely uneconomical and impractical, as it requires storage, requires an extra storage silo or site, increases the number of weighing operations, and complicates the work. Based on this result, it was decided to further impose a requirement that the Cl content be 100PF1 or less for minerals satisfying Ti/Fe.

Although the essential requirements of the coating composition according to the present invention have been explained above, the blending range of other components in the soil composition will be explained below.

Iron powder is added to increase welding efficiency, but if it exceeds 60%, the insulation of the coating deteriorates and there is a safety problem, so 60% is the upper limit.

MgO is added to improve the bead shape and to improve the peeling of the slag, but if it exceeds 10 (fl), the slag coverage becomes uniform and the bead appearance deteriorates, so it is limited to 10% or less.

Next, examples and comparative examples of the present invention will be described.

The titania minerals used here are Ra,
La, Lb, Ld, and I, and the coating material compositions in the test welding rods are shown in Table 3 (1) to (). The welding rod was made by coating a mild steel core wire with a diameter of 5 mm and a length of 450 mm using a binder. Zhou: In these tables, "Others" include Al2O3, zrO2, caO, etc., and the evaluations also listed in Table 3 are: ◎: Very good, ○: Good, △: Poor, ×: Very It was based on the criterion that it was inferior.
In addition, water glass is used as the binder, and the coating material is 100%
18g was added per g.

For the evaluation of blowhole resistance, the groove shown in Figure 1 was welded, and for the evaluation of workability, a T-type joint (plate thickness 12m7) was used.
7! ) were welded, and the welding current was 240A in both cases.

In Table 3 (1), (S-1) to (S-6) are conventional welding rods, especially examples made only of minerals that do not satisfy the Ti/Fe condition of 6 to 50 (S-1, 2, 5), (S-1) has a large number of blowholes, and (S-1) has a large number of blowholes.
2 and 5) have poor workability.

In addition, (S-3, 4, 6) uses leucoccin, but since it accounts for less than 20% of the total amount of TiO2 source minerals, no blowhole reduction effect is exhibited. (A-1) ~
(A-10) and (B-1) to (B-6) are all examples of the present invention, but group A does not contain iron powder,
Group B contains iron powder.

However, in terms of blowball resistance and workability, they show equally good results. (M-1) ~ (M-9
) is the total T
This is an example in which the iO2 source mineral contains 20 (f:) or more, and there is almost no problem with blowhole resistance.
Since some of the other coating components do not satisfy the above-mentioned preferred ranges, there are problems with workability.

Since the coated arc welding rod of the present invention is constructed as described above, a remarkable improvement effect can be obtained particularly in blowhole resistance, and there is no particular adverse effect on workability or working environment. Therefore, it can be safely applied to structures with large plate thickness or structures with large constraints.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the material to be welded used for test welding, Figures 2 and 3
The figure is a graph showing the influence of composition on the number of blowholes.

Claims (1)

[Claims] 1. TiO_2:2-55%, S
iO_2: 5-30%, carbonate: 0.5-27%, deoxidizer: 2-18%, organic matter: 0.2-10%, one or more selected from the iron oxide group consisting of FeO and Fe_2O_3 iron oxide: 20% or less, one or more alkali metal oxides selected from the alkali metal oxide group consisting of K_2O and Na_2O: 5% or less, and suppresses the Cl content to 70 ppm or less, and TiO_2 At least 20% of the titania minerals used as sources are (T
iO_2)/(FeO+Fe_2O_3): 6~50C
A coated arc welding rod characterized in that it is made of titania mineral that satisfies the requirement that l content: 100 ppm or less.