JPS62238093A - Core wire for coated electrode - Google Patents

Abstract

PURPOSE:To decrease the content of hydrogen in a deposited metal, the amt. of the fume to be generated in the stage of welding and the frequency of pits generation by inserting a flux-cored core wire formed by coiling a specifically composed filler with a carbon steel strip into a steel pipe and adjusting the filler to a specific filling factor. CONSTITUTION:The filler ontains, by weight %, 50-90% >=1 kinds among carbide, fluoride, oxide and composite of metals and 10-50% >=1 kinds of iron powder and metallic powder. The flux 1-cored core wire formed by coiling such filler with the carbon steel strip 2 is further inserted into the steel pipe 3 and the filling factor is adjusted to 2-30% relative to the sum of the steel strip weight and the pipe weight to form the core wire for a coated electrode. The content of the hydrogen in the deposited metal, the amt. of the fume to be generated in the stage of welding and the generation of pits in a paint coated steel pipe are decreased by using such core wire for a welding rod. The coated electrode having good workability is thus obtd.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention provides a coating that significantly reduces the amount of hydrogen in deposited metal, the amount of fume generated during welding, and the amount of bits generated by omitting the flux granulation step. This invention relates to a flux-cored core wire for arc welding rods.

[Conventional technology]

Covered arc welding rods using carbon steel core wires such as JIS G35235 revision-11 have been widely used in various welded structures such as shipbuilding, machine building, vehicles, architecture, IA beams, various pressure vessels, and offshore structures. .

However, recently, various coated arc welding rods using a filled core wire have been proposed which can further improve the productivity, welding workability, welding efficiency, etc. of the welding rod.

A filled core wire is a steel pipe filled with granular flux, and when used as a welding rod, a coating material is applied and dried by conventional means. In terms of manufacturing, the characteristics of the filled core wire are, for example, as disclosed in JP-A-59-107792, it is filled with substances such as metal powder, alloy, iron alloy powder, etc. that react with water glass, and the outer periphery of the core wire is filled with water glass, etc. By coating with a chemically stable substance with low reactivity,
It has been proposed to prevent scratches and cracks on the coated surface, and is characterized by improved productivity. In terms of welding performance, for example, Japanese Patent Application Laid-Open No. 196292/1983 discloses a core wire containing metal powder filled with metal powder with a controlled amount of oxygen and coated with a normal coating material, which can significantly improve the welding speed. This method has been proposed to improve welding work efficiency. In addition, according to Japanese Patent Publication No. 60-57434, a low-hydrogen coated arc welding rod is welded by using a flux-cored core filled with flux containing regulated metal carbonates, fluorides, oxides, iron powder, and metal powder. Suggest ways to improve work efficiency, etc.
It has achieved remarkable effects.

As mentioned above, while there are advantages to using filled core wires, there is a disadvantage in that the steel pipe is filled by vibrating in the manufacturing process of these filled core wires, and in order to uniformly fill flux with various densities, it is necessary to If the granules are not granulated to a particle size within the range, they will segregate, so the granulation process must be performed to make the particle size uniform before filling.Since a fixing agent containing crystal water is used during granulation, the amount of hydrogen in the weld metal must be reduced. It has been found that there are problems such as increased cracking resistance and poor cracking resistance when welded to painted steel sheets, such as poor pit resistance.

The present applicant has addressed these issues in Japanese Patent Application No. 59-18854.
The flux granulated according to specification No. 8 was heated at 400 to 800°C.
We proposed a bonding or sintering method. Although this method has been shown to be effective to some extent, when the carbonate minerals and metal powders added in large quantities to the flux are exposed to high temperatures of around 800°C, these fluxes may decompose or exhibit oxidation phenomena. In some cases, the intended effect could not be achieved.

[Problem that the invention seeks to solve]

The present invention carefully examines the filler in view of the above-mentioned circumstances, and fills it with flux without going through the granulation process, thereby ensuring the features obtained by using conventional filled core wire, and at the same time ensuring that the weld metal does not contain hydrogen. The object of the present invention is to provide a coated arc welding rod core wire that significantly reduces the amount of fume generated during welding and the frequency of bits generated on paint-coated steel plates.

(Another Means to Solve the Problems) The gist of the present invention is that 50 to 90% by weight of one or more of metal carbonates, fluorides, oxides, or composites, one or more of iron powder and metal powder. A flux-cored core wire containing 10 to 50% filler wrapped in carbon steel strip is further inserted into the steel pipe, and the filling rate is 2 to 30% with respect to the sum of the weight of the strip and the weight of the pipe. The coated arc welding rod core wire is characterized by:

When a flux-cored core wire containing a filler wrapped in carbon steel strip is used directly in a coated arc welding rod, it has an opening in the length direction, so the water glass used to fix the coating material can be inserted into the opening. It becomes extremely difficult to remove the moisture contained in the adhesive. The present invention has been made in order to eliminate this drawback, and is a welding rod that has a built-in flux by inserting the flux-cored core wire into a steel pipe and has no opening in the length direction. This is something that gives you a precaution.

Welding rods using the filled core wire obtained in this way have excellent arc conditions and melting properties when metal carbonates, fluorides, oxides, or composites, iron powder, and metal powder sealed as fillers are melted. Because slag is formed, the molten metal becomes finer, the droplet transfer becomes smoother, the arc becomes more stable, spatter is reduced, and welding workability and efficiency are significantly improved.

In addition, since the current density is high relative to the cross-sectional area, which is a characteristic of flux-cored core wires, a good arc atmosphere is formed when the enclosed filler melts, and H2,0□
, H1+02, which prevents the intrusion of NZ, provides an excellent weld metal with a sharply reduced amount of N2, and eliminates the occurrence of blowholes, bits, or insufficient fusion at the starting end of the weld bead and joint, and the X-ray performance is significantly improved. Furthermore, by mechanically entraining the flux evenly into the carbon steel strip, the filler to be encapsulated can omit the granulation process without using a fixing agent such as water glass. By inserting the filler into the weld metal, the filler does not absorb moisture from the outside, and the moisture content of the core wire is extremely low, resulting in an extremely low hydrogen content in the weld metal, improving cracking resistance and pit resistance. In addition, it has an extremely excellent feature that it contains less alkaline components such as Na2O and 0, and the amount of fume generated is low.

In other words, the coated arc welding rod using the core wire of the present invention not only has excellent welding workability and efficiency in welding in all positions or in downward and horizontal fillet positions, but also has a low hydrogen content in the deposited metal. It exhibits excellent effects such as significantly reducing the amount of fumes and pits generated during welding.

Note that the metal carbonate in the present invention is CaCO3゜Mg.
CO31CaC0z ・MgCO5+ MnCO3,B
aC01, Na2CO3°K2CO, etc., and metal fluoride is CaF2. ΔIF3°Bang, MgF
z, NaF*KF, Na5AJF, etc., and metal oxides are TiOz, 5iOz,
CaO, MnO, MgO.

FeO, Fe2O+, LizO+ BaO, Naz
O, KzO and their composites TiO2, FeO, ZrO
2.SiO2, 2CaO.MgO.2SiOz, etc., and the metal powder is Mn + Si ITI IN+ +
Cr + Mo + V + Fe-K + Fe-5
t, Fe-A l + Pe4t + A I -Tt
+＾l-Mg, Ca-5t, 51-Mn, etc. Note that % used herein below refers to % by weight.

The operation of the present invention will be explained in detail below.

[For production]

In the coated arc welding rod core wire of the present invention, first, the filler is made up of 50 to 90% of one or more of metal carbonates, fluorides, oxides, or composites in the coating material around the core wire. This is to replenish the gas generating agent, slag generating agent, and arc stabilizer that improve welding workability and protect the molten metal if only the welding agent is used alone. If it is less than 50%, the gas generating agent, slag generating agent and arc stabilizer will be insufficient, making it impossible to obtain a good bead and welding workability. When it exceeds 90%, slag becomes excessive and welding efficiency decreases.

The reason why one or more of iron powder and metal powder is set at 10 to 50% is that these are added to the center of the molten metal, which is sufficiently stirred by the welding arc force, to cause segregation, and also to prevent droplets from forming. The particles become finer and the bead appearance becomes better.If it is less than 10%,
The above effect is not significantly exhibited. If it exceeds 50%, the amount of generated slag and gas will be insufficient, making it impossible to obtain good welding workability and bead appearance.

The reason for setting the filling rate to 2 to 30% is that if it is less than 2%, slag generation and gas generating agent replenishment will be insufficient, and if it exceeds 30%, the amount of slag will be too large, making the arc unstable and causing arc breakage. becomes raw. The filling rate is the ratio of the weight of the filler to the weight of the carbon steel strip and steel vibrator (
It is expressed as filler weight/stripe weight and pipe weight x 100).

In addition, the reason why the flux-cored core wire containing flux was further inserted into the steel pipe will be explained in detail based on the following basic experiment.

First, as a comparative example, the carbon steel strip shown in Table 1 (thickness 0.
7 dragons, width 14 m) was wrapped with the filling flux shown in Table 2, then drawn until the outer diameter was 5 mm, the filling rate was 10%, and it was cut to a length of 450 fins.
The outer periphery of the core wire was coated with the coating flux shown in Table 3 in a conventional manner so as to have a coverage rate of 24% and fired at 400° C. to produce a welding rod. On the other hand, as an example of the present invention, the above-mentioned carbon steel strip was filled with the filling flux shown in Table 2, then drawn until the outer diameter became 4.5 n+, and then
The coated arc welding rod core wire of the present invention was prepared by inserting it into the steel vibrator shown above (outer diameter 12.5 mm, inner diameter 8 mm), and drawing the wire until the outer diameter was 5 mm with a filling rate of 10%. did. After cutting the core wire of the present invention to a length of 450 mm, it was coated with the same coating flux as in the comparative example and heated to 400°C.
A welding rod was created by firing it.

Furthermore, in order to clarify the effects of the present invention, the conventional solid core wire with an outer diameter of 5 fins and a length of 450 fins (
JIS G3523) was coated with the coating flux shown in Table 3 at a coverage rate of 30%, and fired to create a welding rod.

Table 4 Welding tests were conducted on each of the welding rods thus obtained, and the amount of diffusible hydrogen, amount of fume generation, and pit resistance were investigated. However, the welding conditions and test method were as follows.

[Amount of diffusible hydrogen]...JISZ3113 Welding current: A, C, 205A Welding method: Manual welding [Amount of fume generation]...JISZ3930 Welding position: Downward Welding current: A, C, 205A test plate: 5M41 (plate thickness 12.7mm, width 75mm,
Length: 450 mm) Welding rod holding angle: Approximately 75 degrees [Bit resistance]: Conforms to Steel Ship Regulations (Part M) 4.3 fillet weld joint test.

Welding current double, C, 205A Welding method: Hand welding Rod ratio: 1.2 Test plate: 5M50 (plate FJ 12, 7 yna, width 90 long, length 700 n+), wash primer on the surface, film thickness 30 ±5 μm coating As is clear from Table 4, coated arc welding rods that use a core wire that is just a filler wrapped around a carbon steel strip have openings in the length direction, so they do not stick. The agent enters through the opening, making it extremely difficult to remove water even though it is fired at 400°C, resulting in a large amount of fume generation and diffusible hydrogen, and poor pit resistance. On the other hand, welding rods that use a core wire in which a flux-cored core wire containing a filler is inserted into a steel pipe do not have an opening in the length direction, so they tend to stick as described above. The agent does not penetrate into the filler, the amount of diffusible hydrogen is small compared to conventional core wires, and the pit resistance is also good. Furthermore, since no adhesive is used as a filler, the amount of fume generated is extremely small, indicating that welding workability is also good.

Note that the steel pipe here is preferably a seamless pipe or a pipe with welded seams.

Mild steel is the most common material, but low-alloy steel, high-alloy steel, etc. can also be used depending on the purpose, and the cross-sectional structure is not particularly limited, but it is generally cylindrical. A coated arc welding rod core wire of the present invention is schematically illustrated in FIG. This is a cross section of a flux 1 wrapped in a carbon steel strip @ 2, further inserted into a steel pipe 3, and drawn to an arbitrary core wire diameter. Furthermore, the welding rod using the core wire of the present invention is MgC0,1-MgO type, CaC03-CaFz
It has been found that the same effects as the present invention can be obtained even when applied to not only the low hydrogen-based coated arc welding rods mainly composed of the above-mentioned hydrogen-based metals, but also the above-mentioned non-low hydrogen-based coated arc welding rods and other coated welding rods. confirmed.

The effects of the present invention will be described in more detail below based on Examples and examples of the present invention and comparative examples.

〔Example〕

Table 5 shows the filler and coating composition of the flux-cored core of the welding rod using the coated arc welding rod core of the present invention and the comparative welding rod. Table 6 shows the performance test results of welding rods using the coated arc welding rod core wire of the present invention and comparative welding rods.

That is, the flux and filling rate to be rolled into the carbon steel strip shown in Table 1 were determined and adjusted, and the outer diameter was formed to 4.5 mm, and the flux-cored core wire was inserted into the steel vibrator shown in Table 1. 5 Dragon

In some of the comparative examples, water glass was added as a fixing agent to the flux filled in the steel pipe shown in Table 1 at 1% by weight.
After adding 0 to 15%, kneading, granulating, and sizing the flux, set the bonding or sintering temperature and filling rate, and fill the flux-cored core wire, which is then molded into a size of 5 mm x 450 in the same manner as described above. Each of the processed core wires was coated with a coating agent using a known method at a coverage rate of 24%, and then subjected to preliminary drying and firing steps to produce a welding rod.

The amount of diffusible hydrogen, amount of fume generation, pit resistance, and welding workability were tested and determined in detail using the welding rods using the coated arc welding rod core wire of the present invention and the comparative welding rods. The criterion for determining whether the amount of diffusible hydrogen in the deposited metal was good or bad was the above-mentioned welding conditions, and if the amount of hydrogen was 4nl/100g or less, it was considered good.

The criteria for determining whether the amount of fume generation is good or bad is the welding conditions described above, and the amount of fume generation per unit time is 350 mg.
/mjn or less was judged to be good.

The criteria for determining whether the pit resistance was good or bad was determined to be good if the number of bits generated was 3 bits/m or less under the above-mentioned welding conditions.

For welding workability, tests are conducted on arc stability, concentration, sprayability, slag fluidity, peelability, bead appearance, bead shape, etc. If all of these test items are excellent, it is considered good. Cases that were inferior in any item were judged to be defective.

In Table 6, symbols A-1 to A-9 are for welding with a welding rod using the flux-cored core wire according to the present invention, and the amount of diffusible hydrogen, amount of fume generation, and bit resistance are significantly reduced. In addition, it is easy to weld in each welding position, and welding work can be performed efficiently and effectively.

Next, symbols B-1 to B-4 are comparative welding rods using a flux-cored core wire with a filler wrapped around a carbon steel strip and inserted into a steel pipe. amount of fluoride, oxide or composite, iron powder, metal powder;
Or the filling rate is outside the scope of the present invention. Symbols B-1 and B
-2: Metal carbonates, fluorides, oxides, or composites of these are added as gas generating agents, slag generating agents, arc stabilizers, deoxidizing agents, and mechanical performance modifiers because the amount of filling flux is unfavorable. , metal powder is insufficient or excessive, resulting in poor welding workability. Symbols B-3 and B-4 have unfavorable filling rates. Since the filling rate of symbol B-3 is too low, the amount of fume generation and welding workability are particularly poor. Symbol B-4 has too high a filling rate, resulting in poor forming processability of the filled core wire and poor welding workability.Furthermore, the filler flows out during welding, increasing the amount of diffusible hydrogen in the weld metal and generating fumes. The amount and pit resistance become unstable.

Furthermore, symbols B-5 to B-7 do not use carbon steel strips, but fillers are granulated and filled into steel pipes. Symbols B-5 and B-6 indicate that the drying temperature of the filling flux is 400
Although the temperature was set at ~500°C, the crystallization water was not completely removed and the welding workability was good, but the amount of diffusible hydrogen in the weld metal, the amount of fume generation, and the bit resistance were poor. Symbol B-7 was obtained by setting the drying temperature of the filling flux to 800° C., and although the amount of diffusible hydrogen and bit resistance were good, the amount of fume generation and welding workability were poor.

〔Effect of the invention〕

As explained above, if the welding rod core wire of the present invention is used,
The present invention contributes to industrial development by providing a coated arc welding rod that significantly reduces the amount of hydrogen in deposited metal, the amount of fumes generated during welding, and the occurrence of pits on paint-coated steel plates, and has good welding workability. It's big.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a coated arc welding rod core wire of the present invention. 1...Flux, 2...Carbon steel strip, 3...
wA pipe.

Claims (1)

[Claims] 50-90% by weight of one or more metal carbonates, fluorides, oxides, or composites, one or more iron powders and metal powders 10% by weight
A flux-cored core wire containing ~50% filler wrapped around carbon steel strip is further inserted into the steel pipe, and the filling rate is 2 to 30% relative to the sum of the weight of the strip and the weight of the pipe.
% coated arc welding rod safety wire.