JPH04105786A - Coated electrode - Google Patents

Abstract

PURPOSE:To provide the coated electrode which can weld a narrow part and can form a good bead state of string beads by coating a base material at the thickness increasing gradually from both ends of the long side thereof so as to maximize the coating thickness at the center on the counter base material side long side having a rectangular core wire section. CONSTITUTION:The core material of the coated electrode having the rectangular shape of the core wire section is coated at the thickness increasing gradually from both ends so as to maximize the coating thickness at the center on the counter base material side long side thereof. The coated electrode is so formed that the ratio of the max. coating thickness thereof and the coating thickness on the base material contact side long side facing the above-mentioned long side is about 2 to 6, the ratio of the min. coating thickness and the coating thickness on the base material contact side is about <=3 and the ratio of the coating thickness on the side face and the coating thickness on the base material contact side is in an about <=3 range.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a coated arc welding rod used in a coated arc welding method.

[Prior art] Overlay welding is widely used in the field of welding technology to modify the surface of the base metal, and in this case, it is covered arc welding, gas-shielded arc welding, self-shielded arc welding, and submerged arc welding. Welding methods are generally used. Of these, the coated arc welding method has the advantage that welding can be easily performed manually and the equipment cost is lower than other welding methods, but as with the above welding methods, the stringer bead Since the shape is semicircular and a flat surface cannot be obtained, a flat bead surface is usually obtained by weaving the bead. However, this process requires considerable skill in shielded arc welding, and it is especially difficult to weld in narrow areas, and the work efficiency is low, so this welding method is mostly limited to high-mix, low-volume production. It is used as For the purpose of eliminating such drawbacks, for example, a coated welding rod (US Pat. No. 3,999,035) in which the cross-sectional shape of the core wire is rectangular is known. This is convenient when used in narrow areas, such as joining in a groove in the base material, and allows the formation of a flat bead with a stringer bead. When overlay welding is performed using the horizontal welding method or extremely low angle arc welding method, the melt extends long backward in the welding direction, and the arc extends long in the opposite direction to the welding direction, forming a bead. For this reason, the bead waves form an uneven surface that extends long toward the rear of the weld, pits and blowholes occur here and there, and the cross section of the bead becomes convex. Like this-
If a crack is formed, the desired alloy structure cannot be obtained, resulting in poor welding.

[Problems to be Solved by the Invention] Under these current circumstances, the present invention enables welding in narrow areas and at the same time forms a good bead condition in the stringer bead.

The equipment cost is aimed at providing a coated arc welding rod suitable for mass production and easy overlay welding.

[Means for solving the problem] In a coated arc welding rod with a rectangular core wire cross section, the coating thickness on the long side opposite to the base metal is made to be gradually thicker from both ends so that it reaches the maximum at the center. The ratio of the coating thickness to the long side of the base metal contacting side opposite to the long side is about 2 to 6, the ratio of the minimum coating thickness to the coating thickness of the base metal contacting side is about 3 or less, and the side surface is coated. It is characterized in that the ratio of the thickness to the coating thickness on the base metal abutting side is within a range of about 3 or less.

[Effect] Observing the arc phenomenon by high-speed photography and visual observation,
It can be seen that, in general, the poles of an arc do not remain fixed at one point but constantly move across the cross section of the core wire, and the time spent at the center of the rectangle is the longest and gradually becomes shorter towards both ends. The coated arc welding rod according to the present invention has a thickness that is gradually increased from both ends of the long side so that the coating thickness is maximum at the center of the long side of the rectangular core wire cross section on the side opposite to the base material, where the arc pole point is the longest. Since the coating is applied to the arc, the melting of the thick portion directly above the arc generation point is delayed as the arc generation point progresses, and an unmelted coating portion near the outer surface of the thick wall portion is formed in the shape of an eaves. This part exerts a shielding effect against the arc, and the directionality of the arc is strengthened and the arc blows in the direction directly below the core wire, forming an extremely short molten liquid at the rear of the weld.As a result, when using a known coated arc welding rod, Eliminates beat defects that may be seen when

[Example] FIG. 1 shows a partial perspective view of an embodiment of the invention.

1 is a core wire, 2 is a coating material, 2a, 2b, and 2c are one long side of the core wire l (base material contact g4), and coating portions formed on both sides thereof, respectively, to a thickness of -, 2d is the above-mentioned This covering part is thicker than each of the above-mentioned covering parts at both ends of the opposite long side (anti-base material contact l1l) and is formed in a shape that gradually becomes thicker toward the center. Second
The figure is a perspective view of a known coated arc welding rod having a core wire l with a rectangular cross section, and the coating material is coated in parallel to the entire circumferential surface of the core wire.

Hereinafter, the arc welding rod according to the present invention will be used for overlay welding on a flat plate of a mild steel base material using an alloy used for overlay welding, and the shape and dimensions that are expected to produce good welding will be discussed, as well as the present invention. It is revealed that the coated arc welding rod according to the present invention can eliminate the above-mentioned drawbacks of known coated arc welding rods.

Table 1 shows the chemical composition of the core wires used in the experiment, where C-1 is mild steel and C-2 is 5US309 stainless steel. Table 2 shows the shape and dimensions of the core wire used in the experiment, including the thickness of the core wire,
Indicates radius, radius/thickness, and cross-sectional area. Table 3 shows the composition of the coating material applied at high pressure around the core wire. F-1 is mild steel,
F-2 is a typical composition for obtaining a weld metal of low alloy steel, F-3 is a high alloy steel, and F-4 is a stainless steel. Table 4 shows the shape and dimensions of the welding rod covering portion according to the present invention.

In both cases, X is 1.5mm and Z is changed to F.
FS-4 to FS-8 are obtained by changing the maximum coating thickness Y from S-1 to FS-3, and F are obtained by changing the cross-sectional width W.
S-9 to FS-1].

Table 5 shows the specifications of welding rods formed according to the specifications shown in Tables 1 to 4. Examples are shown in E-] to E-13. Table 6 uses E-] to E-13 in Table 5 to show the welding conditions, bead formation, and predetermined conditions when welding on a flat plate of mild steel base material by horizontal welding method and ultra-low angle welding method. Compare with the organization and provide an overall judgment of quality. From the results of this experiment, the thickness of the rectangular core wire is 2.0-4.5 mm, the width is 10-35 mm,
For welding rods with a coating thickness of 1.5 mm on the side that contacts the base metal, the maximum coating thickness on the side opposite to the base metal (Y) Maximum coating thickness on the side opposite to the base metal (Z) Side coating It can be seen that good results are obtained when the thickness is W3.

Figure 3 shows a longitudinal section of a beat seen when overlay welding is performed on the base metal using a known coated arc welding rod using horizontal arc welding or extremely low angle arc welding, and Figure 4 shows Figure 3A. -A
The cross-sectional view shows the state with the slap removed, and Figure 5 shows the top view of Figure 4, which shows an engraving of the previous specification (no changes to the contents) Table 4 Chemical composition of the core wire Second table Shape of the core wire Reprint of the dimensional specification (no changes to the contents) Table 5 This is a sketch of the results obtained under the experimental conditions described in the specifications of the welding rod. In the figure, 1 is a core wire, 2 is a coating material, 3 is a base material, 4 is an arc, 5 is a slap, 6 is a molten pool, 7 is a bead, 7t is a beat surface, 8 is a beat wave, 9 is a pit, and 10 is a It represents a blowhole, and the arrow is in the welding direction. As seen in these figures, the molten pool 6 extends long backward in the welding direction, and the arc 4 blows in the opposite direction to the welding direction to form a bead 7.
The bead waves 8 extend long in the welding direction, resulting in unevenness on the bead surface, forming pits 9 and blowholes lO here and there, and the bead surface 7t bulges upward in a semicircular shape. Fig. 6 is a longitudinal section of a beat seen when overlay welding is performed on a flat plate of base metal 3 using the welding rod according to the present invention, and Fig. 7 is a sectional view taken along line B-B in Fig. 6 with the slap removed. FIG. 8 shows a top view of FIG. 6, that is, a top view of the bead.

Comparing these figures with Figs. 4 and 5, we can see that when the coated arc welding rod of the present invention is used, the arc 4 has strong directionality, blows directly below the core, and leaves a very short molten liquid behind the welding. form 6. As a result, a good bead wave is obtained, and a flat beat with almost no pits or pinholes is obtained.

Note that the required width of overlay welding may not be sufficient with a single bead, but in this case, an additional bead is formed along the previously formed bead, but as shown in Fig. 9(a), it is often A gap is created between these two beads, and rework is required. When the welding rod E-6 is brought into contact with the side of the bead 7 formed under the conditions of No. 6 E-6 and an arc is generated, the bead 7 formed earlier and the back It was confirmed that no gap was formed between the bead 7 and the bead 7 formed in the above.

Also, in the case of a core wire with an axisymmetric trapezoidal cross section where the difference between the long side and the short side of the two parallel sides is small, when the difference between the long side and the short side is small,
When the shape of the coating was made as in the present invention, good heat was obtained as in the case where the cross section was rectangular, so such a case is also included in the present invention.

[Effects of the Invention] Technically, the present invention allows forming a flat bead surface with a stringer bead and welding in narrow areas, and is particularly suitable for overlay welding, and is economically advantageous. It has excellent effects not seen with known welding rods, such as low equipment costs.

[Brief explanation of the drawing]

Fig. 1 is an embodiment of the present invention, Fig. 2 is a known coated arc welding rod, Fig. 3 is a longitudinal section of a beat seen when using a known coated arc welding rod, and Fig. 4 is Fig. 3 5 is a top view of FIG. 4, FIG. 6 is a vertical cross-section of the same point as seen when using the coated arc welding rod according to the present invention, and FIG. The figure shows a cross section taken along the line B-B in Fig. 6 with the slap removed, Fig. 8 shows a top view of Fig. 7, and Fig. 9 shows a state in which two beads are connected in parallel. 1 is a core wire with a rectangular cross section, 2 is a coating material, and 2a. 2b, 2c, 2d...One long side of the core wire, both sides of the long side on the base metal abutting side, covering portion on the side opposite to the base material, 3...Base material, Fig. 6, Fig. 7, Fig. 8

Claims (1)

[Claims] "1" In a coated arc welding rod with a rectangular core wire cross section,
The coating thickness on the long side of the side opposite to the base metal is gradually thickened from both ends so that it reaches the maximum at the center, and the maximum coating thickness is equal to the coating thickness of the long side of the base metal contact side opposite to the long side. The ratio is approximately 2 to 6, the ratio of the minimum coating thickness to the coating thickness on the side that contacts the base material is approximately 3 or less, and the ratio of the coating thickness on the side surface to the coating thickness on the side that contacts the base material is approximately 3 or less. A coated arc welding rod featuring: