JPS6039478B2 - coated arc welding rod - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a weld metal with a good COD value, and
This invention relates to a coated arc welding rod that improves welding efficiency.

COD (CrackOpenin) is used for brittle fracture of metal materials.
When welding low-temperature tanks, pipelines in cold regions, offshore structures, etc., the weld metal is required to have a COD value in addition to Charpy 1 grade impact rut resistance.

Conventionally known low-hydrogen welding rods are mainly designed to satisfy Charpy impact axial properties depending on the welded structure, but 0.5-3.5% Ni-based welding rods are used for low temperatures. However, the COD value of that weld metal at -50°C is 0.
It is about 0.01 to 0.2 skin, which is hard to say that it is a satisfactory value. However, in view of the actual situation, the present inventors have already proposed a coated arc welding rod for improving the COD value of weld metal in Japanese Patent Application Laid-open No. 114445/1982. As a result of various studies on coated arc welding rods that can ensure a more stable COD value, carbonates, metal oxides, Si, and Mn were used as coating materials for low-hydrogen welding rods.
In addition to Tj02, B203, Ti, rainbow, Mg, Zr,
Add an appropriate amount of one or more types of Ca, and further increase the nitrogen content by 10
By adding iron powder limited to 3 ppm or less, Ti oxide in the weld metal becomes the core of the microstructure, and further B
It has been found that due to the synergistic effect with the weld metal, the weld metal has a uniform microstructure and the COD value is significantly increased. That is, an object of the present invention is to provide a welding rod capable of obtaining a welded metal such as Charpy having good impact resistance and COD value, and the gist thereof is to reduce the nitrogen content to 103 ppm.
Iron powder limited to 13-40%, Ti021-10
%, the total of one or more of Ti, AI, Mg, Zr, and Ca is 0.2 to 8%, and the shelving oxide or shelving oxide compound is 0.2 to 2% in terms of B203. , the total amount of one or more types of carbonates is 20 to 55%, the total amount of one or more types of metal fluorides is 1 to 30%, Si is 1 to 5%, Mn is 1 to 8%, and the balance is slag other than the above. The present invention relates to a coated arc welding rod in which a carbon steel core wire is coated with a coating agent consisting of one or more of a generating agent, an arc stabilizer, an alloying agent, and a semi-occupying agent. A detailed explanation of the present invention will be given below.

First, the following experiment was conducted to investigate the influence of the nitrogen content in the iron powder blended into the coating material.

That is, low hydrogen-based coating CaC0340%, CaF2
With a basic composition of 15% Si, 42% Si, 7% Fe-Si, and 5% metal Mn, Ti02, metal Ti, and Na2
807, by mixing an appropriate amount of Fe-AI or AI-Mg,
Furthermore, the amount of iron powder with various nitrogen contents added was 5, 13.
Water glass was added to the coating agent containing 5 levels of 20, 30, and 40%, and 4.0 arms? Coated on carbon steel core wire, then 400
Test welding rods were prepared by firing at ℃. In addition, iron powder is 40
A prototype coating material containing more than 10% of the total amount of carbon dioxide was also produced, but since it was impossible to weld in all positions, no experiments were conducted on this.

The test was conducted on an aluminum killed steel plate with a thickness of 2 ribs at a bevel angle of 50o.
A root gap of 1 to 3 ribs was taken with the V groove, and using the above test welding sample, welding was carried out using a root pass of 130A in a vertical position, and then welding was performed at 150A and a welding heat input of 40KJ'c, and then British Standard Shigeru 5762-197
A COD test of weld metal was conducted at -50 qo based on No. 9. As a result of these tests, FIG. 1 shows the relationship between the amount of iron powder added with different nitrogen contents and the COD value.

The COD value is the lowest value of three test pieces in repeated tests. According to Figure 1, the COD of weld metal at -50C0
To obtain a value of 0.2 or more, the nitrogen content must be 103pp.
It became clear that it was necessary to add 13 to 40% of iron powder, which was limited to less than m.

Addition of such iron powder makes the transition state of port droplets during welding into a spray-like state, which reduces entrainment of nitrogen from the atmosphere, resulting in a stable COD value. Next, the types of coating materials for the welding sheath of the present invention and the reasons for limiting their range will be described.

First, it is optimal to add iron powder in an amount of 13 to 40%.

If the amount added is less than 13%, the transition state of the port droplets will not be spray-like, and nitrogen from the atmosphere will be excessively involved, resulting in a low COD value. If the amount added exceeds 40%, all-position welding will become impossible. If the iron powder has a nitrogen content of 103 ppm or less, the N content in the weld metal can be limited and a stable COD can be achieved.
value is obtained. Furthermore, by adding 13 to 40% iron powder to the coating material, it is possible to prevent magnetic blowing that occurs during DC welding, and it is also possible to form a stable uranami bead during single-sided welding, improving welding work efficiency. can be significantly improved. As Ti02, rutile, illuminite, titanium slag, etc. are used, and when used in combination with one or more of Ti, AI, Mg, Zr, and Ca, which are strong deoxidizers, they reduce Ti in the weld metal. It is added to stabilize the arc and adjust the viscosity of the slag, and T
If it is less than 1% in terms of i02, it has no effect, and if it exceeds 10%, the viscosity of the slag increases and welding work in vertical welding becomes difficult, so it must be added in a range of 1 to 10%. Since Ti, AI, Mg, Zr, and Ca are all strong acid agents, by adding them to the coating agent, Ti02 in the coating agent is reduced and an appropriate amount of T is added to the weld metal.
It is possible to increase the yield of i. Ti, Al, Mg, Zr
If the total amount of one or more types of Ca is less than 0.2%, the effect will not be achieved, and if it exceeds 8%, excessive deoxidation will occur, resulting in poor fluidity of the slag and deterioration of the bead shape.
The range shall be 8%. The side element oxide or the shelf element oxide compound is added to supply B to the weld metal and to improve the COD value in relation to Ti in the weld metal.

If the content of shelf element oxide or shelf element oxide compound is less than 0.1% in terms of &03, B in the weld metal will be insufficient and there will be no effect on improving the COD value, and it will be 0.1 to 2. % range, the COD value can be improved, and if B is added in excess of 2%, B becomes excessive in the weld metal, lowering the COD value and making temperature cracking more likely to occur. Note that the shelf element oxides or shelf element oxide compounds mentioned here include shelf sand, anhydrous shelf sand, natural shelf sand, schistolith, kernite, and the like.
Carbonates are gas generating agents that shield the welding atmosphere from the atmosphere, but if the total content of one or more carbonates is less than 20%, shielding may be insufficient and blow holes etc. may easily occur in the weld metal.
Moreover, if it exceeds 55%, penetration becomes excessive and welding workability deteriorates, so a range of 20 to 55% is appropriate. The carbonates mentioned here include CaC03, MgC03, BbC03, MN.
Refers to metal carbonates such as C03, Na2C03, K2C03, Li2C03. Metal fluorides round the melting point of slag and improve its fluidity.

If it is less than 1%, biting properties will deteriorate, and if it exceeds 30%, the arc will become unstable, so a range of 1 to 30% is appropriate.

Note that the metal fluorides mentioned here include CaF2, MgF2,
NF2, Na3 mountain F6, LiF, NaF, K22rF6
refers to metal fluorides such as Si and Mn are added as deoxidizers or alloying agents, but if Sj is less than 1%, deoxidation is insufficient and blow holes are likely to occur in the weld metal.
If it is added in an amount exceeding 5%, Si in the weld metal becomes excessive, resulting in poor impact resistance and a high COD value cannot be obtained. If Mn is less than 1, the strength will be insufficient, and if it exceeds 8%, the strength will be too high and hot cracking will easily occur. In addition, the above Ti,
AI, Mg, Zr, Ca, Si and Mn are respectively elemental metals or Fe-Ti, Fe-AI, Fe-Si,
Iron alloys such as Fe-Mn, Si-AI, and AI-K are
It is also possible to add alloys such as i-Mn, Ca-Si, and Zr-Si.

In addition to the above components, Si
02, A! 203, slag forming agents such as Mg○, Ca○
, Li20, Na20, K20, KAISi308, N
A coating rate of 20-50% can be achieved by adding an appropriate amount of one or more types of arc stabilizers such as aAISj308 and binders such as water glass.
A carbon steel core wire (for example, JISC 35031 class No. 1) is coated with a conventional welding camellia coater and fired so that the resultant coating becomes as follows.
In addition, in the welded electrode of the present invention, in order to further improve the strength of the weld metal, a total of 13% or less of Ni, Cr, and Mo is added to the coating material.
It is also possible to add alloying agents such as.

The effects of the present invention will be illustrated in more detail with reference to Examples below.

Examples Examples of the welding rods of the present invention and comparative welding rods are shown in Table 1.

The welding method was the same as above, using a 2mm thick aluminum killed steel plate with a V-bevel with a joint angle of 50o on the root gap 1 to 3 sides, and welding using a root pass 13 ship in a vertical position, and then 15, welding was performed with a welding heat input of 40 KJ', and then -50q based on the spot 5762-1979.
0 also passed the COD test of weld metal.

As for the judgment criteria, a COD value at -5000 (hereinafter referred to as 6c) of 0.2 or more was considered good. Also, the impact value is -50
A score of 5k9f- or higher was considered good. In the welding blades AI to AI3 of the present invention, the nitrogen content in the iron powder is 97 ppm or less and 6 co. Impact value is 5kgf-m for 2 or more enemies.
The above is good.

Comparative welding BI~B4 has a nitrogen content of 115p in the iron powder.
pm and has good impact value and welding workability, but 6c is 0.15 or less, which is low. In B5, since the amount of iron powder added is small, the arc state does not become spray-like, the welding workability is poor, and the COD value is low. In B6, the amount of iron powder added is too large, and the molten metal tends to drip, making it impossible to weld in all positions. B7 is T
Due to lack of Tj02, which is a source of i, Ti in the coating material is further reduced.
Since no is added, the COD value and impact value are low.
B8 has too much Fe-Sj in the coating and lacks iron powder, so its COD value and impact value are low. As explained above, if welding is performed using the welding rod of the present invention, weld metal with good impact ballability and COD value at low temperatures can be obtained, and a good COD value can be obtained even with single-sided welding, so welding with molten acid is possible. Efficiency can be improved.

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[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the amount of iron powder added with different nitrogen contents and the COD value at -5000.

Claims (1)

[Claims] 1 Iron powder with nitrogen content limited to 103 ppm or less
3-40%, TiO_2 1-10%, Ti, Al, M
The total amount of one or more of g, Zr, and Ca is 0.2 to 8%, the boron oxide or boron oxide compound is 0.2 to 3% in terms of B_2O_3, and one or more of carbonates is total 20
~55%, the total of one or more metal fluorides from 1 to 30%,
A carbon steel core wire is coated with a coating agent consisting of 1 to 5% Si, 1 to 8% Mn, and the remainder consisting of one or more of slag forming agents, arc stabilizers, alloying agents, and binders other than those mentioned above. A coated arc welding rod.