JPS6032544B2 - Vertical downward overlay welding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas-shielded arc vertical downward overlay welding method for the surface of thin-walled pipes, and in particular, the present invention relates to a method for welding the surface of thin-walled pipes by vertical downward welding. The present invention relates to a vertical downward build-up welding method for repairing or increasing the thickness of thinned areas or areas that need to be prevented from thinning by build-up welding.

Conventionally, as a method for managing soda recovery boilers and on-site repair of superheater tubes that have experienced significant wall thinning due to smelt corrosion and high-temperature oxidation, ordinary manual welding using a coated arc welding rod (
Upward welding method) has been adopted, but because the wall thickness of the material to be welded is extremely thin (about 3 side T), there is a risk of burn-through of the pipe wall during welding, and it requires a high degree of skill. .

In addition, if the thickness loss is particularly significant, welding may not be possible and the pipe may have to be replaced.For this reason, conventional methods not only require a large number of man-hours for repair work, resulting in high costs, but also lead to poor quality. It was unstable. In order to avoid such drawbacks of the conventional methods, the present invention focuses on a vertical downward welding method that has low heat input and shallow penetration, and applies the vertical downward welding method to use a pongee wire. The aim is to establish an automatic gas-shielded arc welding method. That is, the present invention uses a welding wire with a diameter of 0.9 to 1.2 mm and a shielding gas of argon gas or a mixture of argon gas and carbon dioxide gas in overlay welding on the surface of thin-walled tubes arranged almost vertically. 9. Move the welding wire in the welding direction toward the surface to be welded.
The welding heat input obtained from the combination of conditions of 0 to 110 degrees, welding current 120 to 200 A, welding voltage 18 to 24 V, and welding speed 30 to 70 min/min is 3,000 to 5,000
The gist is a gas-shielded arc vertical downward overlay welding method for the surface of a thin-walled pipe, which is characterized by performing vertical downward welding within a range of 0 Joule/skin.

The present invention can be applied to build-up welding on the surface of thin-walled steel plates or thin-walled steel pipes arranged substantially vertically in boilers, chemical equipment, and the like.

Table L summarizes the range of appropriate welding conditions in the method of the present invention.

Table 1 The reasons for limiting the numerical values in Table 1 are as follows.

[1; The reason for setting the diameter of the welding wire to the 0.9 to 1.2 side is that if a wire of 0.9 or less diameter is used, the welding current cannot be large, so welding with a bead width of 4 mm is inefficient. Also, when using a wire with a length of 1.2 ribs or more, the arc will not stabilize unless the welding current is increased, and when the arc is stable, the lacquer metal burns through and it is difficult to obtain a good bead. It is.

{2) The reason why the inclination angle of the welding wire with respect to the surface to be welded is set to 90 to 11 degrees in the welding direction is because if it is less than 900, the direction of the arc will be in the welding direction, so the port metal will tend to lead and cause poor penetration. , burn-through also occurs and a good bead cannot be formed.On the other hand, if the temperature exceeds 110o, the melt is blown up by the arc force, spatter increases, the bead surface becomes rough, and a uniform reinforcement height cannot be obtained. It's for a reason.

{3} The welding current was set to 120 to 200 A under the conditions that vertical downward welding can be performed well within the range of the wire diameter, and below 120 A, the welding speed decreases and the cross-sectional dimension of the bead decreases. It is small and inefficient, and 20
This is because if it is 0 A or more, there is a risk that the amount of molten metal will become excessive and cause burn-through, or that the penetration will be too large and cause burn-through of the material to be welded. (4) Set the welding voltage to 18~
The reason why we chose 24V is that if it is 18V or less, the arc will be unstable and good welding results will not be obtained in the appropriate current range, and if it is more than 24V, the stable short-circuit transition phenomenon will be impaired and welding will be unstable. This is to become.

[5} The welding speed was set to 30 to 70 k/min because
If the welding speed is less than 30 k/min, defects such as poor penetration or overlap are likely to occur due to the advance of the molten metal, and the relatively large heat input may cause burn-through of the welded material, whereas if it is more than 70 k/min, In addition, the arc becomes somewhat unstable, and the dimensions of the bead cross section (excess height and bead width)
This is because the number of passes becomes smaller and the number of passes required to cover the required overlaying area increases, resulting in inefficiency.

'61 Welding heat input was increased from 3,000 to 5,000 Jo
/Skin was set as 1 within the range of heat input calculated from the following formula, H = 6F nose.

ule/skin where day = heat input Joyama e/ka 1 = welding current (A) E = welding voltage (V) v = welding speed (skin/min) Within the range of the above-mentioned welding current, welding voltage, and welding speed The amount of heat input obtained from the combination of
/must be within the range of the fairy tale.

That is, even if all of the above three conditions are within the range shown in Table i above, if the heat input is not within this range, good and efficient results cannot be obtained. Specifically, when the heat input is less than 3,000 Joules, the general tendency is that the settling amount is small and inefficient, causing defects such as poor penetration due to insufficient heat input, and
If the welding temperature exceeds 1/2, the amount of heat input is too large, resulting in excessive melting and burn-through of the welded material, instability of the arc, and irregularity of the bead shape. Hereinafter, the method of the present invention will be specifically explained using the accompanying drawings, experimental examples, etc.

FIG. 1 conceptually explains the welding method according to the present invention, and is a perspective view partially showing the tip of the nozzle in cross section.

In FIG. 1, 1 is a welding nozzle, 2 is a contact tip, 3 is a welding wire, 4 is a shielding gas, 5 is a welding bead, 6 is a material to be welded, and arrow a is a welding direction. FIG. 2 is a system diagram showing an example of the configuration of a welding apparatus used in the method of the present invention.

In Fig. 2, 7 is a welding torch, 8 is a conduit cable, 9 is a wire feeding device, 10 is a welding power source, 11 is a shielding gas cylinder, 12 is a welding cart, 13 is a guide rail, 14 is a magnetic clamper, and 15 is a welder. It's a wire. Further, FIG. 3 shows a front view A and a plan view B of a situation in which the welding cart 12 and guide rail 13 in FIG. 2 are attached to a boiler furnace tube wall, which is a material to be welded.

In Fig. 3, 121 is a welding cart traveling motor, 122
123 is the welding torch's left and right adjustment handle; 124 is the torch holder; 125 is the welding torch's left and right adjustment handle;
126 is a pinion gear driven by the welding cart traveling motor 121, and the rack gear 13 attached to the back side of the guide rail 13.
1 and rotates to encourage the carriage 12 to travel. 133
A clamper arm is fixed to the bottom surface of the guide rail 13, and the magnetic clamper 14 is attached to both ends of the clamper arm.

The attraction surface of the magnetic clamper 14 is designed to follow the surface shape of the material to be welded (pipe surface) in order to double the attraction effect. In addition, the materials to be welded 60, 61, 62, 6
Reference numeral 3 denotes a plurality of boiler tubes (steel tubes) constituting the boiler furnace wall, which are arranged vertically and approximately parallel to each other, and the front surface thereof is the furnace surface and requires welding. Moreover, 1601 shows an overlay weld bead when the method of the present invention is applied. Next, using the welding equipment set up as shown in FIGS. 2 and 3, overlay welding was performed on the European steel pipe by the downward welding method using the welding materials shown in Table 2.

*Table 2 First, move the welding cart 12 to the top of the welding area that requires overlay, and place the welding torch 7 fixed on the torch holder 124 on the surface of the workpiece 6 at an angle as described below. The welding wires 15 were adjusted to a predetermined position for forming a bead by adjusting the left and right adjustment handles 122, and the protrusion length of the welding wire 15 was adjusted by operating the front and rear adjustment handles 123.

Thereafter, an arc was generated between the tip of the welding wire 15 fed by the welding wire feeding device 9 and the workpiece 6 to be welded, and welding was performed while the welding cart 12 was moved downward.
The melting conditions were varied as described below. One of the experimental results is shown in Table 3 as an example of the influence of the welding torch angle (or welding wire angle) on the surface of the workpiece.

Table 3 In Table 3, the welding wire angles are obtained by changing the angle Q between the surface of the workpiece 6 and the welding wire 15 shown in FIG. 4 (in FIG. 4, the arrow a is (indicates welding direction)
The cross-sectional shape of the bead was observed from the cross-sectional shape of the bead 601 in FIG. 4, and was as shown in FIGS. 5A to 5E.

As is clear from Table 3, the range of 95 to 1050 is the best, the ranges of 90 to 950 and 105 to 1100 are good, the ranges of 90 o or less and 1100 or less are poor, and 90 to 11
It can be seen that 0o is a weldable range.

Another of the above experimental results is shown in FIG. 6 as the relationship between welding current and welding speed.

In FIG. 6, the range b is the appropriate range. The dimensions of the weld bead obtained from this appropriate range are as follows: the symbol W in the cross-sectional view of the weld bead shown in FIG.
3-2. It was a revenge. An example of the laminated form of beads when forming a built-up layer by the method of the present invention is shown in Fig. 8A,
B. Show this.

FIGS. 8A, B, and C show build-up layers, or bead 6, in a range of about 45° to the left and right, centering on the front surface of the tubular material 6 to be welded.
01 was formed. Fig. 8A shows a continuous method in which the layers are stacked one pass at a time from one side to the other, Fig. 8B shows a distribution method in which the layers are stacked one pass at a time from the center of the tube 6 to the left and right, and Fig. 8C shows a distribution method in which the layers are stacked one pass at a time from the center of the tube 6. This is a method of stacking layers one pass at a time toward the center (front). In addition, PEED 601
The code below indicates the welding order. The welding method of the present invention described above is a method of forming a pead at high speed by a vertical downward movement method in which a shielding gas such as argon gas or argon gas rich is combined with a peg wire, and has the following effects.

[11] The vertical downward welding process has a high welding speed and low heat input, making it efficient and maintaining high quality even on thin materials.

[2] The welding operation is simple and does not require any skill, and stable welding can be performed even under adverse conditions such as on-site.

Glue Welding equipment can be made lighter and smaller, making it convenient for work inside cramped structures.

{4} Due to low heat input, welding deformation is small.

[Brief explanation of drawings]

Figure 1 is a conceptual diagram of the welding method of the present invention, Figure 2 is a system diagram showing an example of the configuration of a welding device used in the welding method of the present invention, and Figure 3A.
, B are views showing how the welding cart 12 and guide rail 13 of FIG. 2 are attached to the workpiece, and FIG. 3A is a front view.
Fig. 3B is a plan view, Fig. 4 is a diagram for explaining the inclination angle of the welding wire, and Figs. 5A to 5E show bead cross-sectional shapes according to the inclination angle of the welding wire obtained in experimental examples of the present invention. Figure 6 is a chart showing the relationship between welding current and welding speed obtained in the experimental example of the present invention, and Figure 7 is a diagram showing the relationship between welding current and welding speed obtained in the experimental example of the present invention. FIGS. 8A to 8C are diagrams showing an example of the stacked form of beads in the welding method of the present invention. 2 spears, 1 spear, 3 spears, 5 spears, 7 spears, 6 spears, 8 spears

Claims (1)

[Claims] 1 In overlay welding on the surface of thin-walled tubes arranged almost vertically, a welding wire with a diameter of 0.9 to 1.2 mm and a shielding gas of argon gas or a mixture of argon gas and carbon dioxide gas are used to cover the welding wire. Tilt the welding surface 90 to 110 degrees in the welding direction, welding current 120 to 200 A, welding voltage 18 to 24 V, welding speed 30 to 70 cm/min.
The welding heat input obtained from the combination of conditions is 3.000 to 5.
．． A gas-shielded arc vertical downward overlay welding method for the surface of a thin-walled pipe, characterized in that vertical downward welding is performed in the range of 000 Joule/cm.