JPH0481296A - Method for drying coated electrode - Google Patents

Abstract

PURPOSE:To prevent the generation of a dent and drying crack in a flux film by imposing the coated electrode coated with the flux on an elastic member of a transporting conveyor, bringing the welding electrode into surface contact with the elastic member and drying the electrode. CONSTITUTION:Felt 1 is stuck as the elastic member to the transporting conveyor installed in a drying furnace and the welding electrode 2 coated with the flux is imposed on this felt 1 and is transported in the drying furnace to dry the flux. The surface contact region of the felt 1 and the welding electrode 2 is so determined as to have the length of >=1/8 the circumference of the welding electrode 2 in its circumferential direction. The tensile force generated by the shrinkage of the flux on drying is decreased and dispersed in this way and, therefore, the generation of the drying crack in the flux film is prevented and the load per unit area of the flux film is decreased, by which the generation of the dent is prevented.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is a coated arc welding rod in which a coated arc welding rod coated with flux is placed on a conveyor conveyor and is continuously conveyed in a drying oven to dry the flux. Concerning a method for drying welding rods.

[Prior Art] Usually, a coated arc welding rod is dried by being continuously conveyed by a conveyor into a drying oven having a zone maintained at a predetermined temperature after flux is applied around the core wire. .

FIG. 2 is a schematic side view showing a conventional method of drying a coated arc welding rod. The conveyor is composed of a magnetic chain 3. The exposed portion (grip) of the core wire of the covered arc welding rod 2 is attracted to the magnet portion of the magnetic chain 3 by magnetic force, and the covered arc welding rod 2 is suspended below the magnet chain 3. Then, the flux is dried by transporting the welding rod 2 in a drying oven (not shown) by moving the magnet chain 3.

FIG. 3 is a schematic perspective view showing another conventional drying method. The conveyor is composed of two chain conveyors 4 arranged parallel to each other and spaced apart from each other in the horizontal direction. The welding rods 2 are placed on the two chain conveyors 4 so as to be orthogonal to the moving direction of the chain conveyors 4, with appropriate distances between them. Then, the welding rod 2 is conveyed in a drying oven by the movement of the conveyor 4, and the flux is dried.

In addition, as shown in Fig. 4, two chain con hair 6
There is also a conveyor in which the welding rods 2 and the steel plates 5 are arranged in parallel, and a steel plate 5 is attached to each chain conveyor 6 so that the welding rod 2 and the steel plate 5 are in linear contact with each other. This increases the contact area with the welding rod 2 and reduces the load per unit area of the flux coating.

Note that the core of a coated arc welding rod is usually made of mild steel or stainless steel, and the weight ratio of the core and flux is 7:3.
[Problems to be Solved by the Invention] However, the above-described conventional method for drying a coated arc welding rod has the following drawbacks.

As shown in Fig. 2, when the welding rod 2 is transported by the magnetic chain 3, the welding rod 2 may come off from the magnetic chain 3 if the welding rod 2 has a large diameter and is heavy. .

In addition, as shown in FIG. 3, when the welding rods 2 are conveyed by two chain conveyors 4 arranged horizontally, each welding rod 2 is placed on the chain conveyor 4 at four points as shown in FIG. supported by contact.

However, the flux film immediately after applying flux to the core wire contains about 10% by weight of water and is extremely soft. Further, since the core wire of the welding rod 2 is usually made of mild steel or stainless steel, the welding rod 2 is relatively heavy. For this reason, when the core wire diameter of the welding rod 2 is approximately 5.0 mm or more, the load per unit area of the flux coating in the part that is in contact with the chain conveyor 4 will be large, and the flux coating in this part will be dented. Occur. This dent reduces the commercial value of the welding rod 2, and makes it easy for dry cracks to occur in the flux film starting from the dent.

Furthermore, as shown in FIG. 4, when the steel plate 5 is attached to the chain conveyor 6, the welding rod 2 is supported in linear contact with the conveyor 6, as shown in FIG. 6(a). . For this reason, although the generation of dents can be suppressed, the portions that are in linear contact are difficult to dry. In other words, the moisture distribution of the flux film is
), the moisture content is highest in the contact area B with the conveyor 6. In the regions on both sides of the contact portion B, the moisture content decreases rapidly as the flux film moves away from the contact portion B along the circumferential surface of the flux film. Therefore, the shrinkage force acting on the flux film during drying is non-uniform in the circumferential direction. Due to this non-uniform contraction force, as shown in FIG. 6(d), a tensile force acts on the area with a high moisture content, that is, the contact area B, from the nearby area, and the flux coating on the contact area B is destroyed and dry cracks occur.

The present invention has been made in view of such problems, and includes:
An object of the present invention is to provide a method for drying a coated arc welding rod that can prevent dents and dry cracks.

[Means for Solving the Problems] A method for drying a coated arc welding rod according to the present invention includes drying a coated arc welding rod by placing a coated arc welding rod coated with flux on a conveyor and drying it while being conveyed. In the method, the conveyor is provided with an elastic member at a portion that comes into contact with the welding rod, and the elastic member deforms due to the weight of the welding rod when the welding rod is placed thereon, and the welding rod is deformed by the weight of the welding rod. It is characterized by contact with the surface.

[Operations] In general, welding rods coated with flux expand during the initial stage of drying and then contract. At this time, if the entire welding rod is not dried uniformly, drying cracks are likely to occur in the flux film due to local differences in the degree of shrinkage. That is, when the welding rod is in contact with the chain conveyor at a point or a line, the contact portion is not exposed to hot air in the drying oven, so drying is slow and the shrinkage force is small. On the other hand, in the areas near both sides of this contact area, drying progresses quickly and the shrinkage force is large. Therefore, a tensile force is generated in the contact portion from both sides thereof in a direction along the large arc surface. This causes dry cracks in the flux film.

Therefore, in the present invention, an elastic member is provided in the portion of the conveyor that comes into contact with the welding rod, and when the welding rod is placed on this elastic member, the elastic member is caused by the weight of the welding rod. It is made to deform into a shape that follows the circumferential surface of the welding rod. This brings the welding rod into surface contact with the elastic member. In this case, as the flux film dries, tensile force is generated at two boundaries between the surface contact area with the conveyor and the non-contact area in the flux film, but the tensile force is dispersed between these two boundaries, and Since the degree of dryness changes slowly at this boundary, it is possible to prevent dryness cracks from occurring. Furthermore, since the load per unit area of the contact portion between the flux film and the conveyor is reduced, the occurrence of dents can also be prevented.

Note that the surface contact area between the elastic member and the welding rod is
It is preferable that the length in the circumferential direction of the welding rod is 1/8 or more of the circumference of the welding rod. If the length in the circumferential direction of the area of surface contact between the elastic member and the welding rod is less than 1/8 of the circumference of the welding rod, the tensile force will not be sufficiently distributed and dry cracking will occur in the flux film. Cheap. For this reason, when the welding rod is placed on the elastic member, it is preferable that the elastic member has such elasticity that the welding rod comes into contact with the welding rod over 1/8 or more of its circumferential length.

[Embodiments] Next, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1(a) is a perspective view showing an embodiment of the method of the present invention.

A felt 1 is placed as an elastic member on the conveyor installed in the drying oven where the coated arc welding rod 2 is placed.
is pasted. Therefore, the welding rod 2 coated with flux is placed on the felt 1 and conveyed through a drying oven, and the coated flux is dried. In this case, when the welding rod 2 is placed on the felt 1, the felt 1 is deformed by the weight of the welding rod 2, and in the circumferential direction of the welding rod 2, an area of 1/8 or more of the circumference is Contact with felt 1. That is, the welding rod 2 is conveyed through the drying oven while being in surface contact with the felt 1.

In this way, when the welding rod 2 is transported by the conveyor in the drying oven and the welding rod 2 is dried, the flux in the part that is in contact with the felt 1 is dried and the felt 1 is dried.
The flux in the areas that are not in contact with the surface is likely to dry out. In other words, the moisture distribution of the flux film is as shown in Figure 1(b), (
As shown in c), the moisture content is highest in the center C of the surface contact area between the felt 1 and the flux coating of the welding rod 2.

Then, from this center C to the surface contact area and the felt 1
The moisture content gradually decreases toward the boundaries B and D between the areas that are not in contact with the felt 1, and the area A that is not in contact with the felt 1.
, E the water content decreases further. At this time, as shown in FIG. 1(d), a tensile force is applied along the circumferential direction to the boundaries B and D of the surface contact area, respectively, due to the contraction force acting on the flux film. In this case, in this example, this tensile force is dispersed to the boundaries B and D of the surface contact area, and the fluctuation of the contractile force at these boundaries B and D is small, so the tensile force is small and the flux coating is cracking is suppressed.

Next, the results of actually drying a welding rod using the method of this example will be explained in comparison with a comparative example.

As Example 1, a welding rod was conveyed in a drying oven by a conveyor provided with felt at the contact portion with the welding rod. On the other hand, as Comparative Examples 1, 2, and 3, a conveyor in which the welding rod is conveyed by a chain conveyor, a conveyor in which a steel plate is attached to the chain conveyor, and a conveyor in which the contact part with the welding rod is formed of a hard belt. were prepared, and the welding rods were transported into a drying oven by these conveyors. In this case, Example 1 and Comparative Example 2,
The contact ratios between the conveyor and the welding rod in No. 3 are 1/8, 1/12 and 1/9 of the circumference of the welding rod in the circumferential direction, respectively. Further, in Comparative Example 1, the contact was substantially a point contact.

After drying, these Examples and Comparative Examples were examined for occurrence of dents and dry cracks. The results are summarized in Table 1 below.

However, regarding dents and dry cracks, cases where no dents and dry cracks occurred are indicated by ◯, cases where they have occurred are indicated by ×, and cases where they have occurred but the degree is slight are indicated by △.

As is clear from Table 1, in Example 1,
A high quality welding rod could be manufactured without any dents or dry cracks. On the other hand, in Comparative Example 1, in which the welding rod was conveyed by a chain conveyor, dents occurred, and Comparative Examples 2 and 3 had a low contact ratio between the welding rod and the conveyor belt.
In this case, drying cracks occurred in the flux film.

[Effects of the Invention] As explained above, according to the method of the present invention, the conveyor is provided with an elastic member in the portion that contacts the covered arc welding rod, and the conveyor and the covered arc welding rod are in surface contact with each other. Since the welding rod is transported in a drying oven, the flux contracts as it dries and generates tensile force, but this tensile force is small and dispersed at the two boundaries in the circumferential direction of the welding rod in the surface contact area. Therefore, it is possible to prevent dry cracking of the flux film from occurring. Furthermore, the load per unit area of the flux film at the contact portion between the conveyor and the welding rod is reduced, and the occurrence of dents can be prevented. Thereby, the present invention has the effect of being able to continuously manufacture high-quality coated arc welding rods.

[Brief explanation of the drawing]

FIG. 1(a) is a perspective view showing an embodiment method of the present invention;
Figure (b) is a side view of the same, Figure 1 (C) is a graph showing the moisture distribution of the flux film, and Figure 1 (
d) is a schematic side view showing how the tensile force is generated, FIG. 2 is a side view showing the drying method of a conventional coated arc welding rod, and FIGS. 3 and 4 are other conventional coated arc welding rods. FIG. 5 is a front view showing the conventional method shown in FIG. 3, FIG. 6(a) is a perspective view showing the conventional method shown in FIG. 4, and FIG. 6(b) is a perspective view showing the method of drying the welding rod. Similarly, its side view, Figure 6 (
C) is a graph showing the moisture distribution of the flux film, and FIG. 6(d) is a schematic side view showing the state of generation of tensile force. 1; Felt, 2; Welding rod, 3; Magnetic chain,
4, 6; Chain conveyor, 5: Steel plate ￥φ + Susho (b) (C) (Q) Fig. 6 (1) (d) Fig. 6 (2)

Claims (2)

[Claims] (1) In a method for drying a coated arc welding rod, in which a coated arc welding rod coated with flux is placed on a conveyor and dried while being conveyed, the conveyor has an elastic member in a portion in contact with the welding rod. a method for drying a covered arc welding rod, wherein the elastic member is deformed by the weight of the welding rod when the welding rod is placed on the welding rod, and comes into surface contact with the welding rod. (2) The surface contact area between the elastic member and the welding rod is
2. The method for drying a coated arc welding rod according to claim 1, wherein the welding rod has a length in the circumferential direction that is ⅛ or more of the circumference of the welding rod.