JPH05318178A - Coated electrode - Google Patents

Abstract

PURPOSE:To lessen the generation of pits, blow holes, etc., in welding of galvanized steel plates, etc., by limiting the contents of TiO2, SiO2 and CaCO3 and the contents of Si, Al and Ti in a coating material and adding proper ratios of Mn, Nb and V to the coating material. CONSTITUTION:The compsn. of the coating material is constituted to contain 10 to 40wt.% TiO2, 10 to 25% SiO2, 6 to 18% CaCO3, 4 to 13% Fe-Mn, 10 to 40% iron powder and 0.1 to 2.5% one or two kinds of Nb and V. Further, an arc stabilizer, slag forming agent and binder other than the above-mentioned elements are incorporated into the coating material. In addition, >=1 kinds among the Si, Al and Ti are limited to <1.5% in total. The coated arc electrode is formed by coating a core wire consisting of a carbon steel with this coating material. This coated electrode less generates the pits and blow holes and has excellent welding workability in welding of the galvanized steel plates.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is excellent in that pits and blowholes are unlikely to occur even when welding a steel material which has been previously subjected to rustproof treatment such as zinc plating, which is likely to be defective in ordinary arc welding. The present invention relates to a covered arc welding rod having a different bead shape.

[0002]

2. Description of the Related Art In the present specification, a steel sheet whose surface is galvanized for the purpose of rust prevention is generically called a galvanized steel sheet. Conventionally, galvanized steel sheets have been mainly used for building materials, but since the introduction of continuous galvanizing equipment, the quality such as appearance and workability has improved dramatically,
It has come to be used in various fields such as electric equipment, automobiles, and civil engineering.

When welding a galvanized steel sheet, zinc having a boiling point (906 ° C.) lower than the melting point of iron from the surface of the steel material enters a droplet or a molten pool at the time of welding to vaporize the vapor and entrain the atmosphere. During the solidification process of the weld metal, it does not float up and remains as air bubbles, frequently causing pits and blow holes. Mechanical removal of zinc from the welding line in advance is effective as a means for reducing the damage of zinc, but it is time-consuming and inefficient.

In welding electric equipment and automobiles using a galvanized steel sheet, indoor robot welding is often used, gas shielded arc welding is frequently used, and a dedicated solid wire has been developed. 63-724
No. 98 discloses C, Si, P, S in a solid wire.
And a welding material containing Ti, Al, Ni, and Cu as appropriate is proposed. Furthermore, Japanese Patent Laid-Open No. 2-2
In Japanese Patent No. 63594, a gas shielded arc welding wire in which pits and blowholes are less likely to occur and high-speed welding is possible by limiting C, Si, Mn, and Al to specific ranges and limiting Cu, Nb, and V to specific ranges. Is disclosed.

On the other hand, since galvanized steel sheets are used for roofing materials in buildings and the like, and the welding process is carried out outdoors, the development of a covered arc welding rod that is not easily affected by wind is awaited. In Japanese Patent Laid-Open No. 51-37046,
As a coated arc welding rod for a galvanizing pot, a welding rod in which the deposited metals C, Si, Mn, P, and Mo, V are limited is proposed. This is a welding rod used when welding steel materials for galvanizing pots, which has excellent corrosion resistance at high temperatures. Not a welding rod to get.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a covered arc welding rod in which defects such as pits and blowholes are less likely to occur in welding galvanized steel sheets as described above. ..

[0007]

In order to meet the above-mentioned demand, the present invention has been obtained by variously examining coating material components, and the gist thereof is TiO ₂ ;
_{40wt%, SiO 2; 10~25wt%} , CaCO 3; 6
-18 wt%, Fe-Mn; 4-13 wt%, iron powder; 10
40 wt%, one or two of Nb and V; 0.1 to 2.5
wt%, other than the above, an arc stabilizer other than the above, a slag generator, a binder, and a carbon steel core containing a coating agent in which the total of one or more of Si, Al, and Ti is limited to less than 1.5 wt%. It is a coated arc welding rod characterized in that the wire is coated and coated.

[0008]

In the welding of galvanized steel sheets, the inventors of the present invention promote the entrainment of air due to bumping of zinc at the time of welding as well as the fact that zinc that has entered the molten metal is an iron. The molten metal is in a vapor state even during the solidification process because it is difficult to dissolve in the steel and has a low boiling point, and this remains as bubbles, and in the covered arc welding rod, the coating is deoxidized to obtain clean weld metal. In many cases, strong Si, Al, Ti, etc. are added, but if the deoxidizing action is excessively strengthened, molten zinc remains as bubbles without being oxidized, further promoting the formation of pits and blowholes. It was considered that there was a factor.

In order to reduce the effects of these zinc and nitrogen, the present inventors (a) fix harmful zinc or slag off as ZnO, (b) lower the viscosity of molten metal and molten slag. From the viewpoints that it is effective to release zinc vapor and nitrogen gas, and (c) fix solid-dissolved nitrogen in the molten metal, the inventors have made diligent studies on the composition of the coating agent to form the present invention. It has come.

That is, the present invention relates to (a) TiO in the coating material.
By limiting the amount of ₂ , SiO ₂ , and CaCO ₃ ,
To secure welding workability by forming a slag with an appropriate viscosity, (a) Limit the amount of Si, Al, and Ti to obtain an appropriate amount of Mn.
By optimizing the oxidizing power of the molten metal,
Promotes the oxidation of zinc, that is, suppresses the generation of zinc vapor, raises the temperature of molten metal due to the heat of oxidation reaction and lowers the viscosity of molten metal, and further enhances the stirring action of molten metal to release gas. The maximum effect is to suppress the occurrence of pits and blowholes by the combined action of reducing the effect of zinc and nitrogen by accelerating, and (c) adding Nb and V in appropriate amounts and fixing zinc and nitrogen. There are features.

The constituent features of the present invention will be described below. [TiO ₂ ] TiO ₂ is used as a slag generator, viscosity modifier and arc stabilizer. If the amount added is less than 10% (all% below represent wt%), the viscosity of the slag is too low, the slag has poor encapsulation, undercutting easily occurs, and the bead shape is also poor. If added over 40%, the viscosity of the slag becomes high, the bead shape is deteriorated, and the blowholes are increased.

[SiO ₂ ] SiO ₂ is used as a slag forming agent. If the addition amount is less than 10%, the sheath is shallow,
The arc becomes rough and spatter is generated more frequently. 25%
If added in excess, the melting point of the coating material becomes high, the coating cylinder becomes too long, an unstable arc state is formed, and the bead waveform becomes worse.

[CaCO ₃ ] CaCO ₃ is a gas generating agent,
Used as a slag generator. If the addition amount is less than 6%, the viscosity of the slag decreases, the bead shape deteriorates, and
The effect as a gas generating agent is insufficient and pits and blowholes are generated. If it exceeds 18%, the arc voltage decreases, the arc becomes unstable, short-circuiting easily occurs, and arc breakage occurs.

[Fe-Mn] Fe-Mn is effective as a deoxidizing agent and an alloying agent. If the addition amount is less than 4%, deoxidation becomes insufficient and a clean weld metal cannot be obtained. If it exceeds 13%, deoxidation becomes excessive, the influence of zinc vapor greatly acts, pits and blowholes are generated, the weld metal is hardened, and crack resistance is deteriorated.

[Iron Powder] Iron powder is added for the purpose of increasing the arc stabilizer and deposition amount. If the addition amount is less than 10%, the welding amount will be insufficient and undercutting will occur in fillet welding. 40
If it exceeds 0.1%, the covering cylinder becomes weak and a short circuit is likely to occur, the temperature of the weld metal is lowered, the gas is not sufficiently released, and pits and blowholes are generated.

[Nb, V] Nb and V have the effect of fixing zinc and nitrogen and suppressing the generation of pits and blowholes. Addition of 0.1% or more for both Nb and V is effective. Further, even if Nb and V are added in combination, it is similarly effective. However, if added over 2.5%, the weld metal is significantly hardened, the ductility is impaired, and the crack resistance is deteriorated. Similar effects can be obtained by adding these Nb and V as a simple metal powder, or as an iron alloy powder such as Fe-Nb or Fe-V or an alloy powder with another metal.

[Si, Al, Ti] Si, Al, and Ti are usually added as effective deoxidizing agents to obtain a clean weld metal, but as described above, in the welding of galvanized steel sheets, However, when deoxidation is strengthened, molten zinc is not oxidized and remains in the weld metal as bubbles and solidifies as it is to form pits and blowholes, so the total addition amount of these is less than 1.5%. Suppressed to. These elements also have similar effects in iron alloys and alloy powders with other metals, so Si, Al, and Ti in the metal powders are affected.
You need to limit the amount.

Further, the arc stabilizer and the slag forming agent other than the above are MgO, Fe ₂ O ₃ , Al ₂ O ₃ or organic substances. The welding rod of the present invention has a coating rate of 20 to 4 around the carbon steel core wire by using the above-described compounded flux with a binder such as water glass typified by sodium silicate and potassium silicate.
The coating is applied by a normal extrusion welding rod coating machine so as to be 0%, and then dried at 120 to 230 ° C. to remove water, and thus manufactured.

The carbon steel core wire referred to in the present invention is not specified in terms of composition, but JIS G 35
It is preferable to use the coated arc welding rod core wire defined in No. 23.

[0020]

EXAMPLES Next, the effects of the present invention will be specifically shown by examples. Table 1 shows the chemical components of the core wire used in the examples, and Tables 2 and 3 (continued from Table 2) show the coating composition of the welding rod of the present invention and the welding rod used for comparison and various test results. ..
The welding rod symbols A-1 to A-8 are the welding rods of the present invention, and the welding rod symbols B-1 to B-10 are the welding rods used for comparison.

When manufacturing the welding rod, the diameter is 4.0 m.
A coating material was coated on a core wire having a length of m and a length of 400 mm by a conventional extrusion coating machine so that the coating rate was 29%, and dried. With this welding rod, hot-dip galvanized steel sheet SGH4
00, Z27 (thickness t = 4.3 mm, width w = 70 mm, length l = 500 mm) are overlapped as shown in FIG. 1, horizontal fillet welding is performed, and pits are generated in the fillet welded portion. Compare blowholes. At this time, welding workability was also determined. The welding conditions for this test are shown in Table 4.

After the completion of welding, the number of pits generated on the bead surface was visually measured. After that, the welding bead is JIS
A radiation transmission test was conducted in accordance with Z 3140 "Method of radiating transmission test of steel welded portion and grading method of transmission photograph" to observe blow hole generation state, and graded. In the surface inspection, no pits were found to be good, and in the radiation transmission test, grade 1 was good and grade 2 and below were bad.

Since the welding rods A-1 to A-8 of the present invention were properly deoxidized and Nb and V were added in appropriate amounts, no pits were generated and the results of the radiation transmission test were also JIS. According to the determination of Z 3140, all were first grade. It also had excellent workability in welding. On the other hand, the welding rod B-1 has a small amount of TiO ₂ and a large amount of iron powder.
Since the amount of iO ₂ is small, the welding rod B-3 has a small amount of CaCO ₃ , the welding rod B-6 has too much TiO ₂ , and the welding rod B-7 has too much SiO _{2 and} too little iron powder.
Since the welding rod B-8 contained too much CaCO ₃ , the welding workability was poor in all cases.

Since the welding rod B-1 contains too much iron powder, the welding rod B-2 contains a large amount of Si and Al.
No. ₃ has a small amount of CaCO ₃ , and Nb and V are not added. Therefore, the welding rod B-9 has too much Fe-Mn. Since the welding rod B-10 has a small amount of Nb, pits are generated on the bead surface. However, the result of the radiation transmission test was also poor.
Welding rod B-4 contains less Fe-Mn, so welding rod B-8
The result of the radiation transmission test was poor because the amount of Si and Ti was too large.

The welding rod B-5 had good welding workability and did not generate pits, but the weld metal was hardened due to too much Nb and V, and crack-like defects were observed in the radiation transmission test.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

[0029]

[Table 4]

[0030]

INDUSTRIAL APPLICABILITY As described above, the welding rod of the present invention is far less likely to cause pits and blowholes in the welding of galvanized steel sheets and is excellent in welding workability as compared with the conventional covered arc welding rod. ing. This will expand the fields of use of galvanized steel sheets in the future, and will greatly contribute to the development of various industries.

[Brief description of drawings]

FIG. 1 is a perspective view showing the shape of a test plate used in Examples.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Isao Nagano 20-1 Shintomi, Futtsu City, Chiba Shin Nippon Steel Co., Ltd.

Claims (1)

[Claims] 1. A _{TiO 2; 10~40wt%, SiO 2} ; 10~25wt%, CaCO 3; 6~18wt%, Fe-Mn; 4~13wt%, iron powder; 10~40wt%, Nb, V- 1 type or 2 types; 0.1 to 2.5 wt%, other than the above, an arc stabilizer, a slag generator, a binder, and a total of one or more of Si, Al, and Ti is 1.5 wt. A coated arc welding rod, characterized in that a carbon steel core wire is coated with a coating material limited to less than 10%.