JP3532750B2 - Low hydrogen coated arc welding rod - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a low hydrogen coated arc welding rod used for important structures such as shipbuilding, construction, bridges, pressure vessels and the like. ~ 720N /
mm ² class high-strength steel, low hydrogen coated arc welding rod (hereinafter referred to as "high-strength") that excels in re-arcing after arc interruption and ensures deep penetration even when the no-load voltage on the secondary side of the welding machine is low. , Low hydrogen-based rods). 2. Description of the Related Art Low hydrogen rods have good fracture resistance and toughness, so they are used for steels for large structures, low temperature steels or heat resistant steels. It is also used for tack welding before main welding. Intermittent tack welding is important for building a welded structure, but it is often required to accurately weld to a predetermined position, and if the tack weld is removed, it is extremely dangerous In order to do so, it is necessary to use low hydrogen rods with sufficient penetration. In order to facilitate the tack welding, it is necessary that the re-arc property after the interruption of the arc is good, and various proposals have been made as low hydrogen rods dedicated to tacking for the purpose of improvement. For example, Japanese Patent Publication No. 58-047956 discloses a coating in which fine iron powder is contained in a coating agent to impart conductivity between the distal end portion of the core wire and the distal end portion of the protective tube, thereby improving re-arc characteristics. An arc welding rod is disclosed. However,
With this coated arc welding rod, if the no-load voltage on the secondary side of the welding machine drops due to the operation of large-scale equipment, or if the no-load voltage on the secondary side of the welding machine itself is low, it will be re-started due to insufficient starting voltage. Arcing becomes difficult. In addition, since the arc voltage is reduced by containing iron powder, there is a problem that sufficient penetration cannot be obtained due to insufficient arc force. [0004] Japanese Patent Application Laid-Open No. 9-70690 discloses that
In addition to limiting the content and particle size of the iron powder in the coating agent, by limiting the carbon and oxygen of the iron powder, a coated arc welding rod that ensures good re-arcability even with a welding machine with a low no-load voltage is disclosed. Have been. However, the coated arc welding rod also mainly contains iron powder, the arc force is weakened, and insufficient penetration occurs depending on welding conditions. On the other hand, as a means for deepening the penetration of a low hydrogen rod, as disclosed in Japanese Patent Application Laid-Open No. Hei 7-241696, carbonated lime containing a clay mineral is used for the purpose of strengthening the arc force. To ensure deep penetration.
However, if this means is applied to a low-hydrogen rod dedicated to tacking containing iron powder for the purpose of improving the re-arc property, there is a problem that the arc becomes unstable and scattering of spatters increases. [0006] As described above, the conventional low hydrogen rod does not satisfy any other welding performance, and there is no improvement that can ensure excellent re-arcability and deep penetration. It was actual. The present invention provides a low-hydrogen system that has excellent re-arc properties while satisfying various welding performances even when the no-load voltage on the secondary side of the welding machine is low, and has a deep penetration so as to form a strong tack. The purpose is to provide a stick. The inventors of the present invention have studied various coating components to solve the above-mentioned problems. As a result, the present inventors have found that they have excellent re-arc properties and have a deep penetration. I found a low hydrogen rod to get. That is, the gist of the present invention is that metal carbonate is 20 to 50% by weight (hereinafter referred to as%), metal fluoride is 0.5 to 3.5%, cellulose is 1.1 to 3.5%, iron powder comprises from 22 to 55%, by weight of the cellulose with respect to iron powder 0.04 to 0.10 der
Others include deoxidizers, arc stabilizers, slag forming agents and solids.
A low-hydrogen coated arc welding rod characterized by being coated on a steel core wire using an adhesive and a coating material that is an unavoidable impurity . In order to improve the re-arc property, the protection cylinder formed during welding is basically made to contain iron powder in order to increase the conductivity. In addition to this means, attention was paid to an organic substance which produces carbide having good conductivity in the protective cylinder, and it was found that this had a very great effect on the improvement of the re-arc property. It has also been found that the application of an organic substance generates CO or CO ₂ gas having a high ionization voltage in an arc column, so that the arc force is increased and deep penetration into a workpiece can be ensured. Furthermore, when the organic substance in the coating agent is used in combination with iron powder, the weight ratio of the organic substance to the iron powder greatly affects the penetration depth and the workability of welding, so it was important to determine the appropriate weight ratio. First, the types of organic substances for obtaining excellent re-arc properties were selected by the following investigation. That is, Table 1
In the iron powder-containing low hydrogen-based coating agent shown in (1), the organic substances such as cellulose, corn starch, wheat starch, and dextrin were changed to 0.3 to 5.0%, and the diameter was changed to 3.
JIS G3523 SWY11 of 0mm, length 400mm
Was coated and dried at a maximum temperature of 350 ° C. to produce a welding rod, and the re-arc property was examined using an AC welding machine having a no-load voltage of 60 V on the secondary side. [Table 1] The inspection method is as follows. A JIS G3106 SM490B steel plate having a thickness of 9 mm, a width of 100 mm, and a length of 300 mm is assembled in a T-shape, and a horizontal fillet bead is placed at a current of 200 A until the molten bar length becomes 200 mm. The body and the remaining welding rod were cooled to room temperature. Thereafter, the protection cylinder of the welding rod was lightly brought into contact with the fillet portion of the test piece, and immediately the one in which an arc was generated was determined to be a pass, and the result was repeatedly expressed as a total of 10 passes. The results obtained from this experiment are shown in FIG. These organic substances have higher heat resistance in the coating agent during welding than the simple substance and play the role of an insulator. However, in the protective cylinder exposed to a high temperature (600 to 800 ° C.) or in the vicinity thereof, it burns. As a result, a carbide having good conductivity was produced, which was effective for improving the re-arc property. In particular, cellulose exhibited the most excellent re-arc property. The major reason is that cellulose is fibrous unlike other organic substances, and the cellulose in the protective cylinder exhibits fibrous carbides, which are connected in a complicated manner. Since the conductivity between the tips is improved, extremely excellent re-arc properties can be obtained. Further, cellulose has a high carbonization temperature as a simple substance (cellulose: 310 to 350 ° C., other organic substances:
230-270 ° C.), in the protective case, the ash content of the insulator, which is the thermal final substance of the carbide, is also one of the factors that can improve the re-arc property. Next, with respect to cellulose and iron powder which have a great effect on improvement of re-arc properties, it was investigated how the content and the weight ratio of cellulose to iron powder affect re-arc properties and welding performance. . The procedure is as follows:
Cellulose was added to the coating agent in Table 1 in an amount of 0.3 to 5.0.
%, The iron powder was changed from 10 to 65%, and the weight ratio of cellulose to the iron powder became 0.01 to 0.32. The welding rod having a diameter of 4.0 mm and a length of 400 mm was prepared as described above. Were prototyped, and various welding performances were investigated using an AC welding machine having a no-load voltage of 60 V on the secondary side. First, in the re-arc test, a test was conducted based on the above-mentioned test pieces, welding conditions, and judgments. ×
Marked. In the penetration depth survey, the thickness was 20 mm and the width was 10 mm.
JIS G3106, SM490 with 0 mm and 300 mm length
B steel plate in downward position, current 200A, welding speed 18cm /
Perform straight rod movement at min, weld to obtain a bead length of 220 mm, 20 mm from the bead start part,
Macro sections were taken at positions of 60 mm, 100 mm, 140 mm, and 180 mm so that the penetration depth 2 shown in FIG. 2 could be measured. The values are average values obtained from the five cross sections, and the penetration depth was determined to be good when the penetration depth was 2.0 mm or more, slightly poor when 1.0 mm or more and less than 2.0 mm, and poor when less than 1.0 mm. In the investigation of the welding workability, it was found that
mm, width 100mm, length 450mm steel plate is assembled into T type, horizontal fillet and upright down posture using current 200A,
The arc state, the slag state, the degree of spatter, the sticking resistance and the appearance of the beads were examined. The judgment was a comprehensive judgment of each posture, and was determined to be good, slightly inferior, or inferior. FIG. 3 shows the results obtained from the above test. The re-arc properties are improved as the contents of iron powder and cellulose are increased. However, when the content of cellulose is less than 1.1%, the effect is not seen. , The burning resistance of the stick deteriorated. If the content of iron powder is less than 22%, the re-arc property is poor, and if it exceeds 55%, the melting rate becomes slow, so that the bar burning resistance is deteriorated. If the content of cellulose is small, the penetration depth becomes extremely shallow. If the weight ratio of cellulose to iron powder is less than 0.04, the arc force is weak and the penetration is shallow, and if it exceeds 0.10, the arc is excessively strong and unstable, and the scattering of spatter is increased. From the above, it is understood that, in order to obtain a good re-arcing property and a deep penetration even when the no-load voltage on the secondary side of the welding machine is low while maintaining good other performances, it is necessary to use cellulose in order to obtain a deep penetration. It was found that the weight ratio of cellulose to iron powder should be 0.04 to 0.10. Hereinafter, the action of each coating component in the present invention and the reason for limiting the component range will be described. [Metal carbonate: 20 to 50%] Metal carbonates are lime carbonate, magnesium carbonate, barium carbonate, and the like. Decomposes to generate CO ₂ gas, so that the weld metal and molten slag are shielded from the atmosphere, preventing the entry of nitrogen and oxygen and reducing the partial pressure of water vapor. The purpose is to adjust the fluidity and viscosity of the slag. If the content is less than 20%, the amount of diffusible hydrogen increases and the slag removability deteriorates. On the other hand, if it exceeds 50%, the arc force becomes excessively strong, the stability of the arc becomes poor, and the spatter increases. [Metal fluoride: 0.5 to 3.5%] Metal fluoride is fluorite, cryolite, sodium fluoride, or the like, which lowers the melting point of slag and produces slag with good fluidity. To be included. If it is less than 0.5%, appropriate fluidity cannot be obtained, resulting in poor bead appearance. If it exceeds 3.5%, slag encapsulation becomes poor, so that the bead appearance deteriorates, and it becomes difficult to perform downward welding. Arc stability deteriorates. [Cellulose: 1.1-3.5%] Cellulose is the most important part in the present invention. In the protective tube, it becomes a fibrous carbonized material and the conductive property between the tip of the core wire and the protective tube. When used together with iron powder, excellent re-arc properties can be obtained even when the no-load voltage on the secondary side of the welding machine is low. Further, since the arc force is increased in order to increase the arc voltage, deep penetration is obtained and it is extremely effective to secure a strong temporary welded portion. If it is less than 1.1%, no effect is obtained in improving the re-arc property, and sufficient penetration cannot be obtained.
If it exceeds 3.5%, the welding rod burns during welding, and the function of the low hydrogen rod cannot be exhibited. [Iron powder: 22 to 55%] Iron powder is a basic component of the present invention, and is an essential component for improving the re-arc property because it improves the conductivity of the protective tube. Further, since the amount of slag is reduced, the downward welding can be facilitated. If it is less than 22%, the effect of improving the re-arc property is not exhibited, and if it exceeds 55%, the arc power is weak and the melting rate is slow, so that the Joule heat increases and the bar burning resistance deteriorates. [Weight ratio of cellulose to iron powder: 0.1.
04-0.10] The weight ratio of cellulose to iron powder is
It is extremely important to obtain deep penetration and good welding performance while securing excellent re-arc properties in the present invention. If the ratio is less than 0.04, the arc voltage is reduced and the arc force is weakened, so that sufficient penetration cannot be obtained. If the ratio is more than 0.10, the arc force is excessively increased and spatters are scattered. Furthermore, in tack welding of downward or horizontal fillets, since the slag has a convex bead due to the deterioration of the encapsulation property, the bead shape of the main welding also deteriorates. In the present invention, it is preferable that a deoxidizing agent other than the above-mentioned coating agent, an arc stabilizer, a slag forming agent, and a fixing agent are contained in the following ranges. Examples of the deoxidizing agent include ferrosilicon, metal manganese, and ferro-titanium, which can provide a defect-free and healthy weld metal and ensure good toughness and strength. One or two of these can be used in combination, and the appropriate content thereof is 6.5 to 17.5.
%. The arc stabilizer includes rutile, wollastonite, etc., which can be used alone or in combination of two.
The proper content is preferably 0.5 to 4.5%. The slag forming agent includes silica sand, feldspar, magnesium oxide, and the like, and can be used in one kind or in combination of two or more kinds, and the appropriate range of the content is preferably 0.2 to 2.5%. The fixing agent of potassium silicate and sodium silicate is used alone or in a total of two solid masses of 3.5 to 8.5 in the coating agent.
% Is preferably used. In the steel core wire used in the present invention, the steel core wire contains 0.01 to 0.08% of C, 0.05% or less of Si, 0.2 to 1.0% of Mn, P is 0.03% or less, S
Is preferably contained in a range of 0.03% or less. EXAMPLE A coating composition having the composition shown in Table 2 was applied to a coating having a diameter of 4.0 mm.
After coating and coating a 400 mm long JIS G3523 SWY11 steel core wire, it was dried at a maximum temperature of 350 ° C.
Various kinds of welding rods were prototyped. Using an AC welding machine with a no-load voltage of 60 V on the secondary side of the welding machine, the re-arc property, penetration depth, and welding workability were examined by the above-described specimen, welding conditions, and judgment, respectively. In the evaluation of the welding workability and the overall evaluation, "good" was indicated by "O", "poor" was indicated by "", and "poor" was indicated by "x". Table 2 shows the results of these investigations and the overall judgment. [Table 2] In Table 2, welding rods No. 1 to No. 14 are examples of the present invention, and welding rods No. 15 to No. 28 are comparative examples.
The welding rods No. 1 to No. 14, which are examples of the present invention, have individual components satisfying the requirements of the present invention, and having a low no-load voltage on the secondary side of the welding machine while satisfying various welding performances. However, excellent re-arc properties were obtained, and good penetration was also ensured. The welding rods No. 15, No. 23, N
No. 26 is an example in which the content of cellulose in the coating agent was small, and therefore, sufficient carbide could not be formed in the protective cylinder, and the re-arc property was poor. In addition, No. 23 contained a large amount of iron powder and did not use cellulose, so that the arc force was weak, the welding workability was deteriorated, and the penetration was shallow. No.26
Because of the large amount of metal carbonate and metal fluoride, the arc became unstable and welding workability deteriorated, and the penetration ratio became shallow because the weight ratio of cellulose to iron powder was small. The welding rods No. 18 and No. 24 were excellent in re-arc properties due to the large amount of cellulose, but were poor in stick burning resistance. Further, in No. 24, the weight ratio of cellulose to iron powder was large, so that the amount of spatter was large, and since the amount of metal carbonate was small, slag peeling was also deteriorated, resulting in poor welding workability. The welding rods No. 20 and No. 28 have low re-arc properties due to the low content of iron powder, and No. 20 has a high arc force because the weight ratio of cellulose to iron powder is large, resulting in a bead appearance. Deteriorated, and spatters were scattered much and the amount of metal carbonate was large, so that the arc became unstable and welding workability was deteriorated. The welding rod No. 21 has a good re-arcing property and a sufficient penetration because the content of cellulose and the weight ratio of cellulose to iron powder are appropriate. Bar burnability was inferior, and welding workability was slightly inferior. The welding rods No. 22 and No. 25 are examples in which the weight ratio of cellulose to iron powder is not appropriate. No.22
Since the ratio was large, the amount of spatter was large and the welding workability was slightly deteriorated. Conversely, in No. 25, the ratio was small, so that the penetration depth was shallow. The welding rods No. 16, No. 17, No. 19 and No. 27 have excellent re-arc properties because the content of cellulose and iron powder and the weight ratio of cellulose to iron powder are moderate. Although deep penetration was obtained, welding workability was deteriorated because the content of metal carbonate or metal fluoride was not proper. In No. 16, the slag encapsulating property was deteriorated due to too much metal fluoride and the bead appearance was deteriorated. In No. 17, the slag peeling property was deteriorated because the metal carbonate was small. In addition, No. 19 was poor in fluidity of the slag and poor in bead appearance due to low content of metal fluoride, and No. 27 was unstable in arc due to high content of metal carbonate. As described above, the low-hydrogen rod of the present invention satisfies good welding performances and has excellent re-workability even in a welding machine with a low no-load voltage on the secondary side. Arc properties are obtained,
In addition, since a weld metal having a deep penetration can be secured, the work efficiency of tack welding can be remarkably improved, and the safety of the welded structure during construction can be greatly contributed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing the effect of the type of organic substance in a coating agent on re-arc properties. FIG. 2 is a diagram showing a penetration depth of a weld metal. FIG. 3 shows the content of cellulose and iron powder in the coating agent, and
It is a figure which shows the influence which the weight ratio of the cellulose with respect to iron powder has on re-arc property and various welding performances. [Explanation of symbols] 1: weld metal 2: penetration depth 3: test steel plate

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B23K 35/36-35/368

Claims (1)

(57) [Claim 1] 20 to 50% by weight of a metal carbonate, 0.5 to 3.5% by weight of a metal fluoride, and 1.1 to 1% of a cellulose.
3.5% by weight, containing 22 to 55% by weight of iron powder, and the weight ratio of cellulose to iron powder is 0.04 to 0.10 .
Yes, others are deoxidizers, arc stabilizers, slag generators and
A low hydrogen coated arc welding rod which is applied to a steel core wire using a fixing agent and a coating agent which is an unavoidable impurity .