JPS6366639B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of manufacturing a coated arc welding rod. Water glass is commonly used as a binder in the flux of coated arc welding rods (hereinafter referred to as welding rods). This is because water glass has a simple composition that does not conflict with the quality objectives of welding rods, and its physical properties are convenient for manufacturing welding rods. As is well known, the general process for manufacturing welding rods is to mix flux, add a predetermined amount of water glass to it, make a wet kneading material (coating) with appropriate plasticity and caking properties, and then mix this with an appropriate amount. A coating machine extrudes the coating material from the cylinder and at the same time coats it around a predetermined core wire, and then dries it in a dryer to form a welding rod. However, in recent years, as the quality required for welding rods has become more specialized or sophisticated, and as there has been a strong desire to improve productivity, various problems have arisen in terms of manufacturing. One of them is the problem of decreased productivity during the summer. Table 1 is D5026 (iron powder low hydrogen type) specified in JIS Z3212, 7mmφ×700mm
The defect rate and details of defects when manufacturing lengths are classified into summer and winter. As can be seen from this table, the defect rate increases in the summer, and many of the defects are related to defects in the appearance of the coating. This phenomenon often occurs with general low-hydrogen welding rods containing carbonates such as CaCO ₃ and MgCO ₃ . This is a problem that must be resolved immediately in order to stabilize quality and reduce costs.

【table】

[Table] The present invention aims to solve the above-mentioned conventional problems, and its gist is as follows:
When applying the coating material, which is made by adding and kneading water glass as a binder to the blended flux, to the core wire, 10
A coating characterized in that a coating material obtained by adding and kneading water glass pre-adjusted to a temperature of ~20°C to a blended flux is controlled at a temperature of 10 to 20°C throughout the coating process from the kneading process to the coating process. The gist of this is a method for manufacturing arc welding rods, which maintains the viscosity and caking properties of water glass well throughout the kneading and coating processes, suppresses the reaction between water glass and blended flux, and produces a wet mixture. The physical properties such as plasticity and caking properties of the coating material are made to be in a favorable state for the process of applying the coating material to the core wire, so that the defective rate can be reduced and welding rods of good quality can be obtained. , which attempts to stabilize it. For example, the temperature of the water glass can be set using a thin pipe 2 installed in the cooling water passage 1 in the apparatus shown in FIG.
This may be carried out by passing a water glass through it, or it may be carried out in a constant temperature room. Of course, it is necessary to set the temperature of the water glass to be added to the blended flux at 10 to 20°C, but also in the kneading process after adding water glass to the blended flux.
Furthermore, in the process of coating the core wire, the temperature of the kneaded material, that is, the coating material, should be set at 10 to 20°C.
If it is less than 20°C, the viscosity will be high and flow will be poor, resulting in poor work efficiency, and if it exceeds 20°C, the negative effects of the decrease in viscosity will be noticeable. The present invention will be explained in detail below. As mentioned above, the production of welding rods involves the process of adding water glass to the blended flux to form a wet kneading material (coating) with appropriate plasticity and caking properties.
From a production standpoint, the quality of the coating material greatly influences the quality of the welding rod produced through the subsequent coating and drying steps, that is, the defective rate. In other words, water glass is R ₂ O・nSiO ₂・mH ₂ O (R:
It has a simple composition (alkali metal) and is structurally an extremely complex hydrate with an OH group. Therefore, when applying this to welding rods, once the type of alkali metal, molar specific concentration, and addition rate to the blended flux are determined, the composition resulting from water glass as a coating agent is determined, and the compositional properties of the welding rod quality are determined. It can be stabilized on the surface. However, because water glass has a complex structure, its properties such as viscosity, cohesive strength, and chemical activity are complicated, and the plasticity of the wet-kneaded coating material is affected by temperature. and physical properties such as caking properties become unstable, resulting in a decrease in productivity. An experimental example of the change in viscosity of water glass due to temperature will be shown to support this. Experimental example 1 2.2 mol, 44 Baume degree soda water glass (JIS1
The viscosity of Na ₂ O: 12%, SiO ₂ : 26%) was measured using a B-type viscometer at different temperatures. At 10°C, the viscosity was approximately 100 cP (centipoise), but at 30°C, the viscosity was significantly reduced to 30 cP. decreased. In addition, the composition and particle structure of the blended flux are subject to restrictions from the viewpoint of weldability and workability during welding of the welding rod, and at the same time, consideration is given to productivity. In general, low-hydrogen fluxes include carbonates (CaCO ₃ , MgCO _{3 ,} etc.): 10-50%, fluorite (CaF ₂ ): 2-25%, and deoxidizers (Si, Mn, etc.): 5-50%.
It is a flux that essentially contains about 10% and about 0.5 to 1.5% of a coating agent or plasticizer (sodium alginate, CMC, etc.), and has a particle size of 5 μ to 1 mm. In the summer when the atmospheric temperature is high, the temperature of this low-hydrogen flux increases,
The following reaction occurs with water glass whose viscosity has decreased. Na ₂ O・2SiO ₂・nH ₂ O＋MgCO ₃ →Mg(OH) ₂ +Na ₂ CO ₃ +2SiO ₂ (n-1)
H ₂ O Na ₂ O・2SiO ₂・nH ₂ O＋MeSi →Na ₂ O・2SiO ₂ (n−2)H ₂ O＋SiO ₂ +
2H ₂ If such a reaction occurs, a part of the wet-kneaded coating material will harden and gas will be generated, resulting in poor plasticity or caking during coating, and the welding rod may become eccentric. The coating pressure, ie, the extrusion pressure of the coating material, may increase, and the surface of the welding rod immediately after coating may become soft and easily scratched. It is clear from the following experimental results that this reaction between water glass and flux occurs more easily at higher temperatures. Experimental example 2 2.2 mol, 44 Baume degree soda water glass (JIS1
No. Na ₂ O: 12%, SiO ₂ : 26%) and flux 1
Component Fe-Si (JIS G2304 No. 3, particle size 50 μ~
The reaction with 150μ) was investigated using the reaction test apparatus shown in Figure 2 at different temperatures. At this time, sample 3 (Fe
-Si) gas generation amount in 3 hours is 2 at 10℃
cc/g, 3c.c./g at 20℃, but 8 at 30℃
cc/g, it was confirmed that the reaction was significantly more likely to occur. In the figure, 4 is a water glass, 5 is a gas collection bottle, 6 is a container, and 7 is a constant temperature bath. Next, an example comparing an example of the present invention and a conventional example will be described. The water glass shown in Table 3 is added to the blended flux shown in Table 2 and mixed wet to form a coating material, 7
A welding rod was produced by coating a steel core wire with a length of mmφ x 700mm. At this time, as an example of the present invention, the water glass was heated to 15°C using a device for setting the temperature of the water glass as shown in Fig. 1.
As a conventional example, water glass was added to the flux at a temperature of 32°C in summer. In both the inventive example and the conventional example, welding rods were produced at a weight of 2000 kg each with an addition rate of water glass to the mixed flux of 20% and a wet mixing time of 8 minutes, and the appearance of the coating and the amount of eccentricity were examined and compared. The results are shown in Table 4. As can be seen from the results, the examples of the present invention have excellent paintability, good coating appearance, low defective rate, and improved production yield compared to the conventional examples.

【table】

【table】

【table】

【table】

[Table] *Measured using a green hardness meter.
In this way, according to the present invention, by controlling the temperature of the water glass to be added to the blended flux, the temperature of the coating material in the kneading process of the water glass and the blended flux, and the coating process within a predetermined range, even in summer, Furthermore, it becomes possible to always produce coated arc welding rods of good quality even in winter, which is of great industrial benefit.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a device for setting the temperature of water glass, and FIG. 2 is a diagram showing a reaction test device for water glass and flux components.

Claims (1)

[Claims] 1 Coating material obtained by adding and kneading water glass as a binder to a blended flux when applying it to the core wire, by adding and kneading water glass that has been adjusted to a temperature of 10 to 20°C in advance to a blended flux. of,
10 to 20 times throughout the coating process from the kneading process to the coating process.
A method for manufacturing a coated arc welding rod, characterized by controlling the temperature to ℃.