JPS6216754B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a coated arc welding rod that produces sound weld metal with excellent X-ray performance. Conventionally, the welding current range recommended by welding rod manufacturers when welding using a coated arc welding rod is limited to a certain range, although it varies depending on the rod diameter. For example, when performing downward welding using a welding rod with a rod diameter of 4 mm and a rod length of 450 mm, the current range is approximately
It is 120 to 190Amp, and the rod diameter is larger,
For example, a rod with a rod diameter of 6 mm and a rod length of 450 mm generally has approximately 250 to 300 Amps. The main reason for limiting the current range in this way is that if a current below the lower limit is used, the arc will be weak.
Moreover, because of the instability, defects such as poor fusion and slag entrainment occur in the weld metal, and beads with good shapes cannot be obtained. On the other hand, if a current exceeding the upper limit is used, the arc becomes strong and unstable, making it susceptible to atmospheric influences, resulting in insufficient shielding, which causes blowholes in the weld metal and significantly deteriorates X-ray performance. be. For example, for a mild steel plate with a thickness of 12.7 mm, the rod diameter is 4
Using a conventional illuminite welding rod with a rod length of 450 mm, the groove shape and dimensions shown in Figure 1 and the
If the front side A and the back side B are welded according to the stacking procedure shown in Figures A and B, the result will be as shown in Table 1.

[Table] In Fig. 2, a indicates a steel plate, b indicates a welded metal, and the dashed line in Fig. 2 (b) indicates the dimensions of the hanging portion on the back. In other words, in the recommended welding current range of 120 to 190Amp, for 120Amp, 140Amp, 160Amp, and 190Amp,
The wire class is 1st class, which is good, but in order to improve work efficiency, the upper limit of the current range is 190Amp.
If the X-ray rating is increased further, the X-ray rating will deteriorate, especially when the operating current reaches 230Amp, which is about 20% higher than the upper limit.
The line grade will be grade 4. In view of the drawbacks of conventional welding rods, the present invention
In order to perform highly efficient welding, even if a high current is used that is 20 to 30% higher than the upper limit of what is said to be the appropriate current range, weld metal with extremely low blowholes and excellent X-ray performance can be obtained. To provide coated arc welding rods. That is, the present invention contains 0.0035% to 0.009% of O and 0.0035 to 0.009% of Al.
This is a coated arc welding rod characterized in that a normal coating material is coated around a carbon steel core wire containing 0.005 to 0.03% of N and N limited to 0.008% or less. Note that the carbon steel core wire in the present invention means that the chemical components other than the chemical components in the claims are compliant with JIS G3523. The reasons for limiting the core wire composition of the welding rod of the present invention will be described below. The present invention contains O from 0.0035% to 0.009% and Al from 0.005% to
By using a carbon steel core wire containing 0.03% N and limiting N to 0.008% or less, the aim is to obtain a sound weld metal with excellent X-ray performance, which is based on the following test results. be. That is, C0.05~0.07%, Si0.01~0.03%,
0, N, Al in carbon steel core wire containing Mn0.59~0.64%
Carbon steel core wire (diameter 4
mm, length 450mm), SiO ₂ 27.4%,
_TiO2 14.9%, _Al2O3 4.8 _% , _CaCO3 18.3%, starch
4.2%, cellulose 2.0%, Na ₂ O + K ₂ O 4.0%, iron oxide converted to FeO 4.1%, Mn oxide
We made a prototype welding rod coated with a coating consisting of 1.6% MnO, 10.6% Mn, 3.1% Fe, and 5% other components such as MgO and CaO, as shown in Figures 1 and 2. Downward welding was performed at 250 Amp according to the welding procedure shown in . The welded area was then X-rayed according to the JIS method, and the respective grades were determined. As shown in Figure 3, O was 0.0035% to 0.009%, Al was
It was found that the X-ray performance was significantly improved when N was contained at 0.005 to 0.03% and N was limited to 0.008% or less. That is, when O is less than 0.0035%, pitting is likely to occur, when it exceeds 0.009%, blowhole resistance is poor, when Al is less than 0.005%, blowhole resistance is poor, and when Al is more than 0.03%, pitting occurs. .
Further, when N exceeds 0.008%, blowhole resistance deteriorates and toughness deteriorates, and in both cases, X-ray performance was poor. For the above reasons, in the present invention, the contents of O, Al, and N in the core wire are determined as described above. In addition, so-called all-position welding rod coatings, fillet welding rod coatings, and low-hydrogen welding rod coatings are commonly used to investigate the relationship between the core wire composition and coating in more detail. When we examined the combinations with the above-mentioned core wire by changing the blending ratio of each, it was confirmed that the X-ray performance was extremely good in all cases within the coating composition range shown in Table 2.

[Table] Iron oxides used as raw materials in Table 2 include illuminite, iron oxide in iron sand, hematite, mill scale, etc. Mn oxides include manganese dioxide, manganese slag, rhodonite, etc. , fluorides include fluorite,
Cryolite, magnesium fluoride, aluminum fluoride, etc. Alkalies such as K ₂ O, Na ₂ O, Li ₂ O, etc. Mn sources include metallic manganese, Si-Mn, Fe,
Organic substances such as Mn, starch, cellulose, dextrin, sodium alginate, etc., Si, metal Si,
It uses Fe-Si, etc. The present invention can be manufactured using a normal welding rod coating machine using the above-described core wire and coating material so as to have a coverage of 20 to 55%. Next, the effects of the present invention will be explained in more detail with reference to Examples. Examples Table 3 shows the chemical composition of the carbon steel core wires used in the welding rods of the present invention and comparative welding rods, and Table 4 shows the evaluation of welding workability and X-ray performance of the combinations of the core wires and coating materials. shows. Among the welding rods used, those for all-position welding rods and for low-hydrogen welding rods had a core wire diameter of 4 mm, a coating thickness of 1.7 mm,
The length is 450 mm, the welding current is 250 Amp, the groove shape and dimensions are shown in Figure 4, and the lamination procedure is shown in Figure 5.For fillet welding rods, the core wire diameter is 6 mm, and the coating thickness is 6 mm.
2.4mm, length 450mm, and the core wire diameter of only the first layer is 4mm.
At a welding current of 190Amp using a welding rod of
At 390Amp, the groove shape and dimensions shown in Figure 4 and Figure 6
Welding was performed according to the lamination procedure shown in the figure, and in both cases, the first layer was removed from the back side, and the welded area was X-rayed.
Judgment was made according to JISZ3104. As for the X-ray grade, since grades 1 and 2 are generally within an acceptable range, grades 1 and 2 were evaluated as good, and grades 3 and below were evaluated as poor.

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[Table] Welding rods of the present invention C-1 to C-5, D-1 to D-
No. 5 and E-1 to E-5 had good welding workability and good X-ray performance. The comparative welding rods all have good work performance, but F-1, G-1, and H-1 have N of carbon steel core wire.
X-ray performance deteriorated because the value was too high. F-2, G-2, H-2 have too high O in the core wire, F-3, G-3, H-3 have high Al in the core wire, so F-4, G-4, H -4 has low O content, and F-5, G-5, and H-5 have low O and Al content, so all welding rod systems had poor X-ray performance. As described above, according to the welding rod of the present invention, the blowhole resistance in the high current range, which was a drawback of conventional welding rods, is significantly improved, and in addition, it is possible to perform welding at high current, so that the work It improves efficiency and contributes greatly to industrial development.

[Brief explanation of the drawing]

Figure 1 shows the groove shape of the welding test plate, Figure 2
The figure shows the procedure for laminating weld metal. A is the front side, B is the back side. Figure 3 is O, N, Al
Diagram showing the relationship between quantity and X-ray grade of weld metal, No. 4
The figure shows the groove shape of the welding test plate used in the example, and FIGS. 5 and 6 are views showing the procedure for laminating weld metal in the example. a... Steel plate, b... Welded metal.

Claims (1)

[Claims] 1 A coated arc welding rod characterized in that a carbon steel core wire containing 0.0035 to 0.009% of 0, 0.005 to 0.03% of Al, and limited to 0.008% or less of N is coated with a normal coating agent. .