JP3562054B2 - Repair welding method for existing welds - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a repair welding method for an existing weld, and more particularly to a technique suitable for repair welding of a build-up weld such as a container.
[0002]
[Prior art]
Large vessels such as reactor pressure vessels are described in, for example, JP-A-63-072831, JP-A-02-044960, JP-A-02-154145, JP-A-03-119755, and JP-A-06-033137. As described above, a structure in which a tubular body such as a housing for a control rod drive mechanism or a small-diameter pipe for transmitting signals of various sensors is attached to the lower mirror portion in a penetrating state by welding is adopted.
[0003]
In these welding techniques, build-up welding is performed around the upper edge of the pipe through-hole to form a stub tube (stub base) and the like in a standing state.
[0004]
On the other hand, when the build-up welded portion has a reduced thickness phenomenon caused by corrosion or the like, or when the above-described stub tube is removed, for example, by TIG welding, the existing build-up welded portion is removed. On top of that, it is necessary to perform repair overlay welding in which a new weld metal is superimposed.
[0005]
[Problems to be solved by the invention]
However, if the weld metal is overlaid on the existing overlay weld, the weld pool (melt pool) of the weld metal generated by the heating will be affected by uneven cooling due to the uneven shape of the base (existing overlay). In addition, by mixing impurities generated based on the aging of the weld overlay, the shape of the weld bead is distorted by meandering, and the quality of the weld bead is deteriorated.
[0006]
The present invention has been made in view of such circumstances, and achieves the following objects.
(1) Improve the quality of the formed weld.
{Circle around (2)} To suppress the occurrence of adverse effects due to the underlying metal and impurities.
(3) To increase the flexibility of the repair work of the weld overlay and the work of forming a new weld overlay and expand the applicable range.
(4) To improve the efficiency of overlay welding by automatic TIG welding.
[0007]
[Means for Solving the Problems]
While moving the welding arc, a molten pool in a molten state is formed by heating the base to be heated, and after the formation of the molten pool, the filler material is fed into the molten pool while moving the welding arc. A technique of forming a weld bead and repeating the above-described heating of the heated base and formation of the weld bead on the heated base near the end point of the formed weld bead is employed.
When the weld bead is extended linearly, the welding arc is moved from the end of the weld bead in the extending direction of the weld bead to form a continuous molten pool at the end of the weld bead, and the welding arc is turned back In the following, a technique for forming a weld bead while moving the welding arc in the forward direction again along the weld pool by holding the weld pool by moving the weld pool in the forward direction is adopted.
When the welding bead is extended, it is desirable to form the welding bead inside the turning point where the moving direction of the welding arc is changed from the forward direction to the reverse direction. In the case of forming the weld bead to be spread in a parallel state in the adjacent direction, the weld arc is moved in the opposite direction to form a molten pool by heating the base to be heated, and then forming the molten pool. After forming, the welding arc is moved in the direction of turning back to hold the weld pool, and in the middle, a filler material is fed into the weld pool to form a weld bead, and then in the direction adjacent to the formed weld bead. A technique is employed in which the welding arc is shifted, the welding arc is moved in the opposite direction, and a process of forming a weld pool and a process of forming a weld bead are repeated.
In the case of forming the weld bead to be spread in the adjacent direction, it is desirable to form the weld bead in a range narrower than the range in which the welding arc is turned back.
As a welding method, TIG, MIG, or a submerged welding technique is applied.
The present invention is applied to a case where a same type of weld metal and a different type of weld metal are welded on a substrate to be heated by overlay welding and clad welding, and where repair and new welding are performed.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a first embodiment of a repair welding method for an existing weld according to the present invention will be described with reference to FIGS. 1 to 3.
1 shows a welding sequence (welding work process) diagram when the repair welding work is performed while extending linearly, FIG. 2 shows a time chart of the example of FIG. 1, and FIG. 3 shows the state of implementation of the repair welding work. Is shown.
[0009]
A rail 1 is laid in the vicinity of the heated base a, such as an existing overlay welding portion, and the bogie 2 is linearly driven by the rail 1, and a welding machine (TIG welding machine) 3 is mounted on the bogie 2. The position of the welding torch 6 is set by the left and right position adjusting means 4 and the vertical position adjusting means 5, and a welding arc b is generated between the tip of the welding torch 6 and the substrate a to be heated to form a molten pool c. The welding material supply means 7 mounted on the trolley 2 supplies the welding material 8 to the molten pool c to form a weld bead d. These welding operation steps are as described below. Is set.
[0010]
[Timing of first step t ₀ to t ₁ ]
It timing (time) t ₀ is not in forward travel and 2 in FIG. 1 as indicated by t _1, while moving the welding arc b which is generated by the welding torch 6, the heated base by heating a heated base a is melted to form a molten pool c in a molten state. The moving distance of the welding arc b at this time is set to a distance or a time range (for example, 5 seconds) indicated by a scale 5 in FIG.
In the process from timing t ₀ to t ₁ , as shown in FIG. 2, the welding current and the arc length are set to high values, the filler material 8 is set to a non-supply state (no wire feed), and The heating base a is heated and melted.
Note that, for the base to be heated a, for example, a low alloy steel or a nickel-based alloy is selected, and as the filler material 8, for example, a nickel-based alloy is selected.
[0011]
[Timing t ₁ to t _{2 of} first step]
When the welding arc b is moved by a considerable amount on the scale 5 in FIG. 1, the movement of the welding arc b is stopped and the welding current is set to a low value.
[0012]
[First Step Timing t ₂ to t ₃ ]
The welding arc b is moved (retracted) from the turning point Q in the turning direction, and the once formed molten pool c is heated to maintain the molten state.
The moving distance of the welding arc b at this time is set in the range of the distance or time indicated by the scale 3 in FIG.
At the timing t ₂ to t ₃ of the process, as shown in FIG. 2, both of the welding current and arc length is set to a low value, in the filler 8 is set to the non-supply state.
[0013]
First step timing _{t 3} to _{t 4]}
When the welding arc b is moved by a considerable amount on the scale 3 in FIG. 1, the movement of the welding arc b is stopped and the welding current is set to a high value.
[0014]
[It is no timing _{t 4} of the first step _{t 5]}
The welding arc b is moved in the forward direction (forward direction) again, and at that time, the filler material 8 is supplied by the operation of the filler material supply means 7 to form the weld bead d.
The moving distance of the welding arc b at this time is set in the range of the distance or time indicated by the scale 3 in FIG.
At the timing t ₄ to t ₅ step, as shown in FIG. 2, is set to a high value both the welding current and arc length.
[0015]
[Timing _{t 5} without the second step _{t 6]}
With the supply of the filler material 8 stopped, the welding arc b is continuously moved in the forward direction by three graduations in FIG. 1 while maintaining the high value, and the portion before the end point of the welding bead d is heated. Heat dissolution (base treatment) is performed.
[0016]
[Timing t ₆ to t _{7 of} second step]
The movement (advance) of the welding arc b is stopped, and the welding current is set to a low value.
[0017]
Second step timing _{t 7} to _{t 8]}
The welding arc “b” is moved by three graduations in the direction in which the welding arc “b” is folded, and the molten pool “c” in the molten state is held.
[0018]
[It is no timing _{t 8} of the second step _{t 9]}
After the movement of the three scales in FIG. 2, the movement of the welding arc b is stopped, and the welding current is set to a high value.
[0019]
[Timing of Second Step t ₉ to t ₁₀ ]
The welding arc b is moved in the forward direction (forward direction) again, and the welding bead d is formed by supplying the filler material 8.
At this time, the supply of the filler material 8 is set to two scales.
[0020]
Third step timing _{t 10} after the]
Hereinafter, based on the process of t ₅ to t _10, while repeating the backward and forward, repeating the surface treatment and auxiliary by formation of the molten pool c, and formation of the weld bead d, linearly extending weld bead d The process is repeated.
[0021]
4 and 5 show a second embodiment of the repair welding method for an existing weld according to the present invention, in which a welding sequence and welding are performed when the repair welding operation is performed while extending in a lateral direction in parallel. The bead formation is shown.
[0022]
As shown in FIG. 4, the welding arc is moved to the left by 5 scales to form a molten pool (underlay processing), and after the underlay processing is performed, the welding arc is formed by 5 scales. The process of moving to the right and repeating the process of supplying the filler material 8 and forming the weld bead between two and four graduations is repeated one reciprocation (one step), thereby obtaining the width W shown in FIG. Is formed, and the next weld bead d is formed at a position adjacent to one weld bead d.
The bead pitch at this time is set within the width W of the weld bead d, as shown in FIG.
Hereinafter, the repair welding work is advanced by forming the weld bead d in a parallel state (extending in the lateral direction).
[0023]
【The invention's effect】
According to the repair welding method for an existing welded portion according to the present invention, the following effects can be obtained.
(1) Since a weld pool is formed in advance and a welding material is supplied while holding the weld pool to form a weld bead, even if the base has an uneven shape, the weld pool is formed. In this case, the thickness of the molten metal hardly changes, and the variation in the thickness of the weld bead can be suppressed to improve the quality of the weld overlay.
(2) As described above, the phenomenon that the metal component or the impurity of the base material enters the molten layer of the filler material is less likely to occur, and the quality of the weld bead can be stabilized and the quality can be improved.
(3) By setting the range of the molten pool and the supply range of the filler material, it can be applied to the work of forming a new overlay weld in addition to the repair work of the overlay weld, The range of application can be expanded.
(4) By setting and managing the generation range of the welding arc and the supply range of the filler material, the efficiency of the overlay welding work and the repair work thereof can be improved by applying automatic TIG welding or the like.
(5) These settings can be easily performed, and the welding operation can be efficiently performed with high accuracy.
[Brief description of the drawings]
FIG. 1 is a welding sequence diagram showing a first embodiment of a repair welding method for an existing weld according to the present invention.
FIG. 2 is a time chart of the repair welding operation of FIG.
FIG. 3 is a model diagram showing an implementation state of the repair welding work in FIG. 1;
FIG. 4 is a welding sequence diagram showing a second embodiment of the repair welding method for an existing weld according to the present invention.
FIG. 5 is a model diagram showing a formation state of a weld bead of FIG. 4;
[Explanation of symbols]
a Base to be heated b Welding arc c Weld pool d Weld bead Q Turn point 1 Rail 2 Dolly 3 Welding machine (TIG welding machine)
4 Right and left position adjusting means 5 Up and down position adjusting means 6 Welding torch 7 Filler supply means 8 Filler

Claims (5)

A step of forming a molten pool (c) in a molten state by heating the substrate to be heated (a) while moving the welding arc (b); and forming the molten pool (c) by moving the welding arc after the formation of the molten pool. Forming a weld bead (d) by feeding a filler material (8) by welding to form a weld pool and a weld bead with respect to the heated substrate near the end point of the weld bead. A repair welding method for an existing weld, characterized by being repeated. A step of forming a molten pool (c) in a molten state by heating the substrate to be heated (a) while moving the welding arc (b); and forming the molten pool (c) by moving the welding arc after the formation of the molten pool. Forming a weld bead (d) by feeding the filler material (8) by welding, and moving a welding arc in an extending direction from an end point (P) of the weld bead to form a molten pool continuous to the end point of the weld bead. A step of forming a welding bead while moving the welding arc along the molten pool, and a step of holding the molten pool by moving the welding arc in a direction in which the welding arc is turned back. Repair welding method. In the case where the welding bead (d) is extended, the formation of the welding bead is performed inside a turning point (Q) for changing the moving direction of the welding arc (b) from the forward direction to the reverse direction. Item 4. The repair welding method for an existing weld according to Item 2. A welding method for forming a welding bead (d) in a state parallel to an adjacent direction, wherein a welding arc (b) is moved in a reverse direction to heat a base (a) to be heated and a molten pool (c) in a molten state. Forming a weld pool, moving the welding arc in the direction of folding back after the formation of the weld pool, and holding the weld pool, and feeding a filler material (8) to the weld pool on the way to form a weld bead. A method for repairing an existing welded portion, comprising repeating a step of forming a molten pool and a step of forming a weld bead in a state where a welding arc is shifted in a direction adjacent to a weld bead. 5. The repair welding method for an existing weld according to claim 4, wherein the formation of the weld bead (d) is performed in a range narrower than a range in which the welding arc (b) is turned back.

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