JPH0457439B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a low hydrogen-based coated arc welding rod with improved resistance to shedding of the coating material. (Prior art) In general, the drop-off resistance of a low-hydrogen coated arc welding rod depends on the type of slip agent that improves the fluidity of the coating during coating, the particle size structure of the coating, the drying temperature, and the concentration of the adhesive. It is often affected by In order to improve the fluidity of the coating material during painting, non-low hydrogen coated arc welding rods containing a large amount of water of crystallization, such as mica, kaolin, talc, and bentonite, are used. This increases the amount of carbon dioxide and causes cold cracking.
There is a problem that it cannot be applied to low-hydrogen coated arc welding rods. Therefore, in order to improve the fluidity of the coating material in low-hydrogen coated arc welding rods, it is effective to add sodium alginate or CMC, which improves slipperiness and increases viscosity. It shows a tendency to carbonize at drying temperatures higher than 350°C to 450°C, which is the typical drying temperature for low-hydrogen coated arc welding rods. There is a problem that the degree of adhesion becomes weak and the resistance to falling off deteriorates. On the other hand, the deterioration of the bonding strength and degree of adhesion of the coating material itself can be improved by increasing the concentration of the fixing agent, but if the concentration of the fixing agent is increased too much, it will tend to dry when kneaded with the coating material, and the coating will deteriorate. There is a problem that the fluidity of the agent is deteriorated. In addition, as a method to strengthen the bonding force of the coating material itself, although it is not a fundamental improvement measure, it is possible to improve the particle size structure of the coating material.
Broadly leveling the range may be effective to some extent, but when considering the particle size of each raw material used and its blending amount in accordance with the characteristics of the welding rod, leveling the particle size composition is not realistic. becomes a rather difficult problem. As described above, in order to improve the falling-off resistance of a low-hydrogen coated arc welding rod, it is necessary to find a lubricant that contains almost no crystal water and does not deteriorate the falling-off resistance. Improving shedding resistance has been an important research topic in terms of preventing the occurrence of welding defects such as pits and blowholes caused by shedding of coating material and improving on-site welding work efficiency. In order to solve the above problems, as proposed in JP-A-54-102254, in the coating material particles, 13 to 22% of the particles are 10 to 20μ, 10% or less of the particles are 30 to 60μ, and 105 By containing 13 to 22% of ~149μ particles, it is possible to prevent dry cracking and improve resistance to falling off, reducing labor at the manufacturing site, as well as preventing defects such as pits and blowholes. A technique has been disclosed that allows for improved welding workability. However, according to the research results conducted by the present inventors, it is extremely difficult to fundamentally improve the drop-off resistance of low-hydrogen coated arc welding rods by simply leveling the particle size structure of the coating material. It has been recognized that it is difficult to use, but we have improved the drop-off resistance to the same level as non-low hydrogen coated arc welding rods.
This did not satisfy the inventors' goal of improving welding efficiency. (Problems to be Solved by the Invention) An object of the present invention is to provide a low-hydrogen coated arc welding rod with good resistance to shedding of the coating material. (Means for Solving the Problems) The present invention prevents the occurrence of welding defects such as pits and blowholes by using a low-hydrogen coated arc welding rod with excellent drop-off resistance of the welding rod coating material. At the same time, it aims to improve the efficiency of on-site welding work, and its main points are: ultrafine titanium oxide with a particle size of less than 1 μm at 95% by weight or more; 0.2 to 5% by weight; organic matter: 0.5% by weight. A low hydrogen-based coated arc welding rod is characterized in that a fixing agent is added to a coating material containing the following and applied to the outer periphery of a steel core wire. (Function) The present invention is characterized by focusing on the influence of organic matter on the deterioration of shedding resistance, which improves the fluidity of the coating material. In low-hydrogen coated arc welding rods that contain 0.2 to 5% by weight of titanium oxide in the coating material and have strict welding control, welding defects such as pits and blowholes may occur due to shedding of the coating material. In addition to preventing this, it also enables extremely efficient on-site welding work. The effects of each component and the reason for limiting the amount of each component in the present invention will be described below. [Ultrafine titanium oxide with a particle diameter of less than 1 μm at 95% by weight or more: 0.2 to 5% by weight] The ultrafine titanium oxide in the coating material is different from the commonly used coarse titanium oxide, and has a high bonding agent. It is dispersed uniformly during kneading, and at the same time, due to its characteristics, it has a large hiding power, so it has the property of completely covering and coating the surfaces of other particles. This means that
The ultrafine titanium oxide particles exist between other particles, expanding the spacing between other particles or entering the interparticle voids to form a close-packed layer.
Therefore, when kneaded with a fixing agent, the frictional energy possessed by other particles is released, and the fluidity of the coating material during coating is made extremely good. It has been found that the effect of improving fluidity is equal to or greater than that of the conventional method, and it has become possible to significantly reduce the amount of organic matter that degrades shedding resistance. On the other hand, as mentioned above, ultrafine titanium oxide has the effect of expanding the spacing between other particles or penetrating the interparticle spaces to form a close-packed layer.
In other words, it causes a swelling phenomenon and improves the fluidity of the coating material, but if it is added too much, water glass, which is an adhesive agent, will stand out on the coating surface after coating the welding rods, making it easier for the welding rods to adhere to each other. , which causes adhesive cracking of the coating during the drying process. Moreover, it is easy to get scratched during conveyor transportation, which causes a decrease in yield. In this way, the addition of ultrafine titanium oxide has contradictory effects in terms of improving the fluidity of the coating without deteriorating its shedding resistance and improving productivity after painting. The optimal range of ultrafine titanium oxide was investigated by making various test rods. [Dropout test method] Insert 12 welding rods (approximately 3 kg) of _6.0 × 700 ^L _nn into a container of 80 ^W _nn × 320 ^H _nn × 920 ^L _nn , and
After rotating at a speed of 30 rpm for 3 minutes and applying a shock,
The shedding rate of the coating material was investigated. Shedding rate = W ₁ - W ₂ / W ₁ × 100 (%) However, W ₁ : Weight of coating on the sample rod before test W ₂ : Weight of coating on sample rod after test The fluidity, adhesion cracks and scratches on the coating were investigated, and the results were evaluated as good (○ mark), slightly poor (△ mark), and poor (×
As a result of the comprehensive evaluation in three stages (marked), the results shown in Figure 1 were obtained. However, regarding the dropout rate, 3% or less was considered good. Table 1 shows the particle size distribution of the ultrafine titanium oxide used in this test. Table 2 shows the basic formulation of the test welding rods. FIG. 1 shows the investigation results of the relationship between the ultrafine titanium oxide content of each test welding rod in Table 2 and the evaluation of the test welding rod. In Figure 1, when the ultrafine titanium oxide in the coating material is less than 0.2%, all test welding rods have good drop-off resistance, but due to the poor fluidity of the coating material, eccentricity of the welding rod occurs frequently. The yield decreased. On the other hand, if it exceeds 5%, the fluidity of the coating material will be extremely good without deteriorating the drop-off resistance, but the coating surface will be easily scratched as the coating pressure decreases, and the welding rods will adhere to each other, causing problems when drying. It has been found that the upper limit should be 5% because adhesive cracking of the coating occurs. [Organic matter: 0.5% by weight or less] The amount of organic matter added as a lubricant in low-hydrogen coated arc welding rods varies slightly depending on the other raw materials blended, but it is generally added at least 1.5%. It is true. However, in the present invention,
By adding 0.2 to 5% by weight of the aforementioned ultrafine titanium oxide, the fluidity of the coating material will not deteriorate even if the amount of organic matter added is 0.5% or less, and the shedding resistance will be good. If this value is exceeded, the drop-off resistance will deteriorate rapidly. Therefore, the amount added should be 0.5% or less. Since the low-hydrogen coated arc welding rod of the present invention is constructed as described above, it has excellent resistance to shedding of the coating material, and welding defects such as pits and blowholes due to shedding of the coating material do not occur. A low-hydrogen-based coated arc welding rod was obtained that satisfies the demands of on-site welders who want to reduce the rework rate as much as possible and improve welding work efficiency. (Example) Next, the effects of the present invention will be illustrated in more detail through Examples. Test bars having the composition and structure shown in Table 3 were prepared. Using these, we evaluated the shedding resistance using the method shown below, and at the same time conducted a comprehensive evaluation of the presence or absence of adhesion cracks and scratches on the coating, as well as the fluidity of the coating material, and evaluated the results in three stages, as shown in Table 3. The following results were obtained. The evaluations in the table are as follows: ○ mark: good, △ mark: slightly poor, × mark: poor. [Dropout test method] Insert 12 welding rods (approximately 3 kg) of 6.0〓 _nn × 700 ^l _nn into a container of 80 ^W _nn × 320 ^H _nn × 920 ^L _nn , and
After rotating at a speed of 30 rpm for 3 minutes and applying a shock,
The shedding rate of the coating material was investigated. Dropping rate = W ₁ - W ₂ / W ₁ × 100 (%) However, W ₁ ; Covering weight of the sample rod before the test W ₂ ; Covering weight of the test rod after the test (dropping rate judgment criteria) ○ mark; Good (<3 %) △: Slightly poor (3-6%) ×: Poor (>6%)

【table】

【table】

[Table] In Table 3, (A-1) to (A-7) show comparative examples, and (B-1) to (B-4) show examples of the present invention. Since (A-1) did not contain ultrafine titanium oxide, the fluidity of the coating material was poor, and the welding rod was eccentric due to frequent occurrences, resulting in a defect. In (A-2), the shedding resistance deteriorated due to the excessive amount of organic matter. (A-3) had an excessive amount of ultrafine titanium oxide, so cracks in the adhesion of the coating occurred, and there were many scratches and it was extremely poor. (A-4) had an excessive amount of ultrafine titanium oxide and organic matter, so it had poor resistance to falling off, and the coating had many adhesive cracks and scratches, making it extremely poor. (A-5) was defective because ultrafine titanium oxide was not added, so the fluidity of the coating material was poor, and the welding rod was eccentric frequently. (A-6) was unsatisfactory due to poor shedding resistance due to excessive organic matter. Since the content of (A-7) was 95% by weight or less of titanium oxide having a particle size of less than 1 μm, the fluidity of the coating material was poor and the coating material was poor. (Effects of the Invention) As explained above, by using the low hydrogen-based coated arc welding rod of the present invention, welding defects such as pits and blowholes caused by shedding of the coating material do not occur, so it is possible to This will significantly improve the efficiency of on-site welding work related to bridges.
The contribution to industry is extremely large.

[Brief explanation of the drawing]

Figure 1 is a graph showing the optimal blending amount of ultrafine titanium oxide that provides good fluidity of the coating material without deteriorating the shedding resistance, and does not cause adhesive cracking or poor appearance of the coating. .

Claims (1)

[Claims] 1. A fixing agent is added to a coating material containing 0.2 to 5% by weight of ultrafine titanium oxide with 95% by weight or more of particles with a particle size of less than 1 μm and 0.5% by weight or less of organic matter, and the adhesive is applied to the outer periphery of the steel core wire. Characteristic low hydrogen coated arc welding rod.