JP2002137089A - Coated arc welding electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coated arc welding electrode whose coating flux exhibits excellent coating property, improved falling-off resistance, and improved product yield when producing the welding electrode, and which exhibits excellent welding workability. SOLUTION: The coating flux of the coated arc welding electrode contains, per the total mass of the coating flux, 0.1-1.0 mass% sodium alginate having a bulk density of 0.40-0.70 g/ml, and 0.1-1.0 mass% sepiolite having a bulk density of 0.20-0.50 g/ml. An average particle size of the sodium alginate is <=70 μm and that of the sepiolite is <=110 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating for improving the coatability of a coating agent in the production of a coated arc welding rod, improving the productivity, preventing a decrease in the yield of products, and improving the welding workability. Related to arc welding rod.

[0002]

2. Description of the Related Art Coated arc welding rods are roughly classified into non-low hydrogen welding rods and low hydrogen welding rods, and are used in a wide range of fields. Non-low hydrogen welding rods include illuminite type, lime titania type, high titanium oxide type, etc.
In particular, it is used for welding thin and middle sheets of mild steel. The low hydrogen welding rod is a welding material intended for mild steel to 950 N / mm class ² high-strength steel, and has a low diffusible hydrogen content in the weld metal, a high toughness of the weld metal, It has good cracking properties and is used for welding important structures such as bridges, buildings, shipbuilding, and pressure vessels.

[0003] It is known to improve the coating properties by adding sodium alginate or sepiolite to a coating agent for a coated arc welding rod, as disclosed in JP-A-10-11878.
No. 4, JP-A-9-234589 and JP-A-9-234589
Japanese Patent Application Publication No. 201695 is cited as an example. According to this, by adding sodium alginate to the coating agent, the slipperiness and elasticity of the coating agent are improved, and the occurrence of coating chipping immediately after coating is prevented, thereby improving productivity. In addition, the inclusion of sepiolite in the coating improves the shedding resistance of the coating, improves the sticking property, and forms a suitable coating chip at the tip of the welding rod when an arc is generated. To improve the performance. However, even with this conventional technique, it is difficult to satisfy the coating property of the coating agent in the manufacture of a coated arc welding rod, and the coating surface cracks during drying, falling off resistance, welding workability deterioration, product yield deterioration, etc. There is a problem.

[0004]

As described above, in the conventional coated arc welding rod, it is required to improve the coating property in the production of the coated arc welding rod, improve the productivity, improve the product yield, and improve the drying efficiency. To prevent cracking of the coating surface during welding, to prevent the coating from falling off due to impact or drop during transport, to improve the welding workability such as arc stability during welding and to reduce spatter, and to develop a coated arc welding rod that satisfies all of these requirements. It was extremely difficult to do. SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a coated arc welding rod which improves the product yield by further improving the coating property of the coating agent and has good welding workability.

[0005]

SUMMARY OF THE INVENTION In order to meet the above-mentioned demands, the present invention has studied various coating agents for coated arc welding rods. This improves welding and improves welding workability. The gist of the invention is to use sodium alginate as a coating agent and to use a material having a bulk specific gravity of 0.40 to 0.70 g / ml based on the total mass of the coating agent in a range of 0.1 to 1.0.
It is characterized by containing 0.1 to 1.0% by mass of sepiolite having a bulk specific gravity of 0.20 to 0.50 g / ml based on the total mass of the coating agent. The coated arc welding rod is also characterized in that the average particle size of sodium alginate is 70 μm or less and the average particle size of sepiolite is 110 μm or less.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have carried out various studies for improving the coating properties of a coating agent for a coated arc welding rod, improving the product yield, and improving the welding workability.
As a result, focusing on the fact that it is extremely effective to improve the coating properties of the coating agent on the steel core wire in the production of coated arc welding rods, we focused on using sodium alginate and sepiolite with limited bulk specific gravity in the coating agent. It has been found that a very large effect can be obtained by using such a material.

First, the coating properties were evaluated by changing the contents of sodium alginate and sepiolite in the coating agent. Increasing the content of sodium alginate and sepiolite in the coating improved the product yield and improved the resistance of the coating to fall off.However, it was not possible to obtain satisfactory results in the appearance of the coating surface and welding workability. could not. Therefore, attention was paid to the bulk specific gravity, and as a result of investigation using sodium alginate and sepiolite having various bulk specific gravities, the coatability of the coating agent in the production of a coated arc welding rod was improved, and the appearance of the coated coating was improved. Further, it was confirmed that the arc stability in the welding operation was improved, and it was extremely effective. Furthermore, it has been found that welding workability is improved by limiting the average particle size of sodium alginate and sepiolite in the coating agent.

The reasons for limiting the contents of sodium alginate and sepiolite in the coating agent, the bulk specific gravity, and the particle size of the coated arc welding rod of the present invention will be described below.
The bulk specific gravity in the present invention is JIS K6720-2.
This is a value measured by the method specified in. The bulk specific gravity of sodium alginate added to the coating agent is 0.40 to 0.4.
The reason for limiting to 70 g / ml is to achieve good welding workability and uniform dispersibility of the coating agent to improve productivity. When the bulk specific gravity is less than 0.40 g / ml, the dispersibility in the coating agent is good, but the welding performance is deteriorated. This increases the proportion of the volume occupied by the sodium alginate, which makes the arc state unstable during welding, increases spatter and undercuts at the end of the bead, and deteriorates welding workability and bead appearance. On the other hand, bulk specific gravity is 0.70 g / m
If it exceeds 1, the dispersibility in the coating agent is inferior, the coating property of the coating agent is deteriorated, cracks are generated on the coating surface, and the arc force is weakened during welding.

Next, the reason why the total mass of sodium alginate added to the coating agent is limited to 0.1 to 1.0% by mass is to improve the coating property of the coating agent at the time of manufacturing the coated arc welding rod and to improve the coating efficiency of the coating agent. This is to improve the falling resistance and improve the product yield. If the addition amount is less than 0.1% by mass, no effect of improving the coating property is obtained at all, the adhesion of the coating agent is weak, and the falling-off resistance is deteriorated. On the other hand, when the addition amount is 1.0
Exceeding the mass% enhances the adhesiveness of the coating agent and enhances the paintability, but the arc force during welding becomes excessively strong, causing an increase in spatter and undercut at the bead end, resulting in poor welding workability and bead appearance. Will deteriorate.

The reason why the bulk specific gravity of sepiolite added to the coating agent is limited to 0.20 to 0.50 g / ml is that, similarly to sodium alginate, it has good welding workability and uniform dispersibility of the coating agent. This is to improve productivity. This sepiolite is a natural hydrous magnesium silicate, and its chemical structural formula is (OH ₂ ) ₄ (OH) ₄ Mg ₈ S
represented by _{i 12 O 30 · 6~8H 2 O} . The crystalline structure has a fibrous shape, and has good dispersibility in a fixing agent (water glass). When added to a coating agent, the fibers become complicatedly entangled or loosened when mixed with the fixing agent. Has the effect of increasing viscosity.

Further, in the drying step of manufacturing a coated arc welding rod, sepiolite has a property of solidifying itself,
It also has the property of solidifying other coating agents. Therefore,
Because of their good viscosity and consolidation properties, the fixability of the coating agent is excellent, which can contribute to preventing the coating agent from falling off and improving the coating property. The bulk specific gravity of this sepiolite is 0.20 g /
When the amount is less than ml, the dispersibility in the coating agent is good, but the welding performance is deteriorated. This is because the volume ratio of sepiolite occupies more than other coating agents, the arc state becomes unstable at the time of welding, spatter increases and undercut occurs at the bead end, and welding workability and bead appearance deteriorate. I will. On the other hand, when the bulk specific gravity exceeds 0.50 g / ml, the dispersibility in the coating agent is poor, and the coating property of the coating agent in the production of a coated arc welding rod is deteriorated, cracking of the coated surface occurs, and the arc force becomes weak during welding. Would.

Next, the reason why the total mass of sepiolite added to the coating agent is limited to 0.1 to 1.0% by mass is that the coating property of the coating agent in the production of the coated arc welding rod is improved, and the coating agent is resistant to the coating. This is to improve the dropout property and improve the product yield. If the addition amount is less than 0.1% by mass, no effect of improving the coating property is obtained at all, the adhesion of the coating agent is weak, and the falling-off resistance is deteriorated. On the other hand, the addition amount is 1.0% by mass.
Exceeding the temperature increases the adhesion of the coating agent and improves the resistance to falling off.However, the coating agent becomes too dense, making it difficult to release moisture in the drying process of manufacturing a coated arc welding rod, and causing diffusible hydrogen in the weld metal. The amount increases, and the crack resistance of the weld metal deteriorates. Further, the arc force becomes excessively strong at the time of welding, which causes an increase in spatter and an undercut at a bead end, thereby deteriorating welding workability and bead appearance.

The reason for limiting the average particle size of sodium alginate to 70 μm or less and the average particle size of sepiolite to 110 μm or less is that welding workability, which was impossible only by limiting the bulk specific gravity and the added amount of sodium alginate and sepiolite, was impossible. This is to improve the coating quality of the coating agent in the production of a coated arc welding rod. If the average particle size of sodium alginate exceeds 70 μm, the arc state becomes unstable during welding and the amount of spatter increases. Further, the dispersibility in the coating agent is deteriorated, so that the adhesion is weakened and the falling-off resistance is reduced.

When the average particle size of sepiolite exceeds 110 μm, the arc state becomes unstable at the time of welding and the amount of spatter increases as in the case of sodium alginate. Further, the dispersibility in the coating agent is deteriorated, so that the adhesion is made non-uniform. In the drying step of manufacturing the coated arc welding rod, cracks and scratches are generated on the coated surface, and the falling resistance is reduced. The addition of sodium alginate and sepiolite of the present invention can also be applied to low-hydrogen-based, illuminite-based, lime titania-based, titanium oxide-based coated arc welding rods, and the like.

[0015]

The present invention will be described in more detail with reference to the following examples. Sodium alginate and sepiolite having various bulk specific gravities and particle sizes shown in Table 2 were kneaded with fixing agents in various amounts shown in Table 1 with varying amounts of addition.
A coated arc welding rod was trial-produced by coating and coating a 0 mm, 450 mm long JIS G3523 steel core wire. The content of these evaluations includes product yield,
Table 3 shows the results of evaluation of the coating appearance and welding workability.

The method of evaluating the yield rate of the product was evaluated as good when it was 98.0% or more, and poor when it was less than 98.0%. In addition, the method of determining the rate of loss of the coating agent was about 1.5 kg in order to quantify the value.
55mm x 300mm made of 6mm thick welding rod
The sample was put in a steel box of × 500 mm, and the box was rotated at a speed of 40 rotations per minute for 5 minutes about the longitudinal direction of the box as an axis, and the mass ratio of the dropped coating agent was measured. The drop rate is 1.5
% And less than 1.5%, it was evaluated as poor.

Next, a method for evaluating the appearance of the coating is evaluated as follows. If the coating surface is free from cracks, scratches or dents and all can be satisfied, it is considered to be good. did. For the evaluation method of the evaluation of the welding workability, the plate thickness was 16 mm, the width was 100 mm, and the length was 450 m.
m in a T-shape, and using an AC welding machine, a current of 160 A for horizontal fillet welding and a current of 130 for vertical welding.
Under the welding conditions of A, the arc state and the degree of spatter were examined. If all were satisfied, it was determined to be good.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

No. in the table. K1-No. K10 is an example of the present invention. K11-No. K30 is a comparative example.
No. 1 of the present invention example. K1-No. Since K10 has appropriate bulk specific gravity, added amount and average particle size of sodium alginate and sepiolite, it has excellent coating properties, falling resistance and product yield of the coating agent in the production of a coated arc welding rod, and has good welding workability. The results were extremely satisfactory. In the comparative examples, K11 and no. Since K12 has a low bulk specific gravity of sodium alginate, the dispersibility in the coating agent is too good to deteriorate the welding workability, the arc state becomes unstable at the time of welding, and the spatter increases.

No. K13 and no. Since K14 has low bulk specific gravity of sodium alginate, dispersibility in the coating agent is inferior, coating property of the coating agent in the production of the coated arc welding rod is deteriorated, cracking of the coated surface is generated, and the arc force is weakened during welding. . No. K15 and no. Since K16 has a large average particle size of sodium alginate, the arc state became unstable during welding and the amount of spatter increased. Further, the dispersibility in the coating material was deteriorated, so that the adhesion was weakened and the falling-off resistance was lowered. No. K17 and No. In K18, since the amount of sodium alginate added to the coating agent was small, no effect of improving the coatability was obtained at all, the fixation of the coating agent was weakened, and the falling-off resistance was deteriorated.

No. K19 and no. In K20, since the amount of sodium alginate added to the coating agent was large, the adhesion of the coating agent was enhanced and the coating property was excellent, but the arc force was excessively increased during welding and spatter increased.
No. K21 and no. Since K22 has a low bulk specific gravity of sepiolite, its dispersibility in a coating agent is too good to deteriorate welding workability, and the arc state becomes unstable at the time of welding, increasing spatter. No. K23 and no. K2
In No. 4, the bulk specific gravity of sepiolite was high, so that the dispersibility in the coating agent was poor, the coating property of the coating agent in the production of a coated arc welding rod was deteriorated, and the generation of cracks on the coating surface and the weakening of the arc force during welding.

No. K25 and no. In K26, since the average particle size of sepiolite was large, the arc state became unstable during welding, and the amount of spatter increased. In addition, the dispersibility in the coating agent was deteriorated and the fixation became non-uniform, and the coating surface was cracked or scratched in the drying step of manufacturing the coated arc welding rod, and the falling-off resistance was reduced. No. K27 and no. K2
In No. 8, since the amount of sepiolite added to the coating agent was small, no effect of improving the coatability was obtained at all, the fixation of the coating agent was weakened, and the falling-off resistance was deteriorated.

No. K29 and no. In K30, since the amount of sepiolite added to the coating agent was large, the arc force was excessively increased during welding, and spatter increased. Also,
Although the adhesion of the coating agent is enhanced and the falling resistance is improved, the coating agent becomes too dense, and it becomes difficult to release water in the drying process of manufacturing the coated arc welding rod. The amount of diffusible hydrogen was large, and the crack resistance of the weld metal was deteriorated.

[0026]

As described in detail above, the coated arc welding rod according to the present invention can be used in a coating agent by limiting the bulk specific gravity of sodium alginate and sepiolite in the coating agent, the amount added, and the particle size. Excellent coating properties of the coating agent in arc welding rod production, improvement of dropout resistance, improvement of product yield,
A covered arc welding rod having good welding workability can be provided. Thereby, a covered arc welding rod with high welding work efficiency can be provided.

Claims (2)

[Claims] 1. A coated arc welding rod having a bulk specific gravity of 0.4 per unit mass of sodium alginate as a coating agent.
0.1 to 1.0% by mass of 0 to 0.70 g / ml
Sepiolite has a bulk specific gravity of 0.20 per total mass of the coating agent.
A covered arc welding rod characterized by containing 0.1 to 1.0% by mass of 0.5 to 0.50 g / ml. 2. The average particle size of sodium alginate is 70 μm.
The coated arc welding rod according to claim 1, wherein the average particle diameter of sepiolite is 110 µm or less.