JPH0129636B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of manufacturing a coated arc welding rod. As is well known, coated arc welding rods are made by adding water glass as a binder to a predetermined mixed flux, kneading it to give it appropriate plasticity and formability, and applying this kneading around the core wire using a coating machine. After the product is coated and painted, it is dried in a dryer, and the good and defective products are sorted and finished. The above-mentioned water glass is widely used as a binder because its composition and physical properties are convenient for manufacturing welding rods. In general, various compositions of welding rod coating materials have been proposed that are optimal depending on the type of steel to be welded, welding posture, welding workability, etc. For example, cellulose-based, lime-titania-based, low-hydrogen-based , iron powder oxide systems, etc. have been standardized. Many improvements have been made in the composition and proportion of these coatings.
In recent years, in order to improve the productivity of manufacturing welding rods, proposals have been made for the process of coating the core wire with a coating material, and the process of drying and burning the coating material after coating. However, when considering the productivity of each line of coated arc welding rods, we found that the production of cellulose-based welding rods and lime titanium-based welding rods for stainless steel has been prone to dry cracking of the coating material.
Productivity was significantly lower than that of general-purpose welding rods (illuminite type). This coating drying crack is caused by a complex interplay of various factors.
It can be roughly divided into three types. That is, vertical warping due to mechanical adhesion of the welding rod, horizontal warping and warping due to inappropriate kneading, painting, and drying conditions, and vertical warping and warping due to chemical reaction between flux and water glass. Regarding the present invention, horizontal warping and warping caused by kneading conditions are particularly problematic. Table 1 compares the trends in coating drying crack occurrence rates for general purpose rods (illuminite type), low hydrogen type welding rods, cellulose type welding rods, and lime titania type welding rods for stainless steel in summer and winter.

【table】

[Table] As can be seen from the table above, coating drying cracks are more likely to occur in cellulose-based and lime titania-based welding rods for stainless steel than in general-purpose rods, and they are more likely to occur in winter than in summer. it is obvious. As a result of various studies aimed at improving the productivity of such cellulose-based and lime titania-based products for stainless steel, the present inventors investigated the cause of coating drying cracks, found a countermeasure for the problem, and completed the present invention. . That is, in the coating drying method described above, the blended flux constituting the coating material and the water glass as a binder have poor wetting, and the water glass does not uniformly cover each particle of the flux. In other words, the permeability of water glass is poor. This tendency is particularly noticeable in the winter when the temperature is low, and can be said to be due to the characteristics of water glass. Figure 1 shows the results of investigating the incidence of welding rod coating drying when welding rods were produced by varying the water glass temperature and wet kneading time. It can be seen that if the length is short, cracks are likely to occur. In addition, Figure 2 shows the results of the inventors' measurements of the relationship between temperature and viscosity for JIS No. 1 sodium silicate (measured using a rotational viscometer type B), which shows that the viscosity becomes extremely high at low temperatures. I understand that. This is thought to be because the welding rod coating material cannot be sufficiently kneaded with the blended flux during the wet process, and as a result, the water glass does not penetrate sufficiently between the particles, resulting in coating drying cracks. In order to improve the permeability, a method of lengthening the kneading time has been considered, but in actual production there is a problem in that productivity decreases. In consideration of the above, the present invention has been devised to produce a coated arc welding rod that can prevent the coating from drying out and improve the productivity of cellulose-based or lime titanium-based coated arc welding rods for stainless steel. The purpose is to provide However, the feature of the present invention is that a coating agent prepared by adding water glass at 30 to 60°C as a binder to a cellulose-based or lime titania-based flux for stainless steel is applied to the core wire. be. The contents of the present invention will be explained in detail below. In the present invention, coating material raw materials adjusted to the composition and blending ratio necessary to obtain the desired coating are first dry mixed, and then added as an adhesive at 30 to 60°C.
Water glass preheated to a temperature of A coated arc welding rod is manufactured by uniformly coating the surrounding area and going through a drying process. Water glass has a simple composition of R ₂ O·nSiO ₂ ·mH ₂ O (R: alkali metal), and is an extremely complex hydrate with an OH structure. Therefore, when applying this to welding rods, once the type of alkali metal, molar 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 force, and chemical activity are complicated, and it is easily affected by temperature, and if this temperature is not appropriate, it will be wet-kneaded. The physical properties of the coating, such as plasticity and caking, become unstable, resulting in reduced productivity. Therefore, in the present invention, the permeability of water glass is mainly taken into consideration, and the temperature is defined in the range of 30 to 60°C. At temperatures below 30°C, it is difficult to obtain good water glass permeability and wettability with flux deteriorates, and at temperatures above 60°C, even if permeability is sufficient, the coating material may deteriorate due to evaporation after mixing with flux. A hardening phenomenon occurs, resulting in poor coating. Next, examples of the present invention will be shown together with comparative examples. Example When adding water glass (JIS No. 1 sodium silicate, 44 degrees Baume) to a cellulose-based and lime titania-based flux for stainless steel and kneading it for 10 minutes, the water glass was maintained at the temperature shown in Table 2. A coating material was prepared, applied to the core wire, and dried to produce a coated arc welding rod. Table 2 shows the results of testing the condition of these coated dry sheets. Nos. 2 to 5 are the invention, Nos. 1 and 6 are comparative examples, and the temperature of the water glass is
Within the range of 30 to 60°C, almost no coating drying cracks occurred and the coating work was good. On the other hand, in the comparative example, drying cracks occur or coating defects occur. Incidentally, the term "coating dryness" has the same meaning as that in Table 1.

[Table] As described above, according to the present invention, by maintaining the temperature of water glass within a predetermined range, coated arc welding rods of good quality can always be efficiently manufactured.
Its industrial effects are extremely large. In particular, the present invention is effective when applied to the production of coated arc welding rods of cellulose type and lime titania type for stainless steel.

[Brief explanation of drawings]

FIG. 1 is a chart showing the relationship between kneading conditions and coating drying crack occurrence rate. FIG. 2 is a chart showing the relationship between temperature and viscosity of water glass.

Claims (1)

[Claims] 1. A coating characterized by applying to the core wire a coating prepared by adding water glass at 30 to 60°C as a binder to a blended flux for cellulose-based or lime-titania-based welding rod coatings for stainless steel. A method of manufacturing arc welding rods.