JPH0688120A - Method for regenerating structure by beam-heating - Google Patents

Abstract

PURPOSE:To prolong the life of parts used for long term at high temp. in power plant such as boiler, turbine. CONSTITUTION:By using a YAG laser beam generator 21, the focused laser beam 24, through a reflecting mirror 22 and a focusing lens 23, irradiates a welding heat affecting part 27 where is most easily creep-damaged in the welded metal 26 of boiler piping 25 of the specimen, while weaving. Mechanical opening crack of creep crack 28, etc., is remelted and repair-welded and, at the same time, after reheating the deteriorated structure part developing the creep void 29 at the solution treatment temp. or high (>=900 deg.C), rapid cooling is executed to eliminate the creep void 29, and the structure is regenerated. Further, after executing a series of the treatments, the laser beam is made out of focus so that the highest temp. becomes about 700 deg.C, and reheating is executed while weaving and slowly cooled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for regenerating tissue by beam heating, and particularly to extend the life of parts such as boilers and turbines used for a long time at high temperatures in power plants.

[0002]

2. Description of the Related Art An example of creep damage of a welded portion of a boiler pipe in a conventional technique will be described with reference to FIG.

As shown in the figure, for example, in a boiler pipe 10 of a power plant or the like, a straight pipe 10b and a straight pipe 10c are connected via a curved pipe 10a, and these are joined by metal welding 11 at their respective connecting portions. Has been done.

For this reason, when it is used at a high temperature for a long period of time in a power plant or the like, as shown in FIG. 2 (B) (FIG. 2 (A)
As shown in the enlarged view of the middle X part), in the coarse grain region of the welding heat-affected zone 12 which is being heated by the welding in the vicinity of the metal weld 11, especially when exposed to the high temperature steam 13 or the like, the structure becomes larger than that of other portions. Deterioration occurs, creep damage occurs, and creep voids 14 occur at grain boundaries.

If the creep voids 14 are continuous, in some cases, an inferior defective portion 15 may occur, which is a problem.

Therefore, conventionally, a method of removing the defective portion 15 before the creep void 14 is generated, replacing it with a new member, and welding again is used.

[0007]

Problems such as the above-mentioned creep damage, which causes structural deterioration, and mechanical opening, require replacement and replacement of a new member, which is a problem. is there.

It is an object of the present invention to provide a beam-heated tissue regeneration method capable of extending the life of a member used at high temperature for a long time and contributing to reduction of labor and cost by replacing a new member. .

[0009]

A beam-heated tissue regeneration method according to the present invention which achieves the above object, is a method for regenerating a member having creep damage and causing structural deterioration or mechanical opening deterioration, or a machine by fatigue damage. Regeneration of mechanical defects or regeneration removal of systematic creep voids while performing remelting treatment or heat treatment up to the solution temperature range with a laser beam or electron beam when regenerating a member that has suffered mechanical opening It is characterized by performing.

The contents of the present invention will be described below.

Here, the laser beam or electron beam for regenerating tissue in the present invention means carbon dioxide gas laser, Nd: YA.
A laser beam used for laser processing such as a G laser, an excimer laser, a free electron laser, or the like, which exhibits a thermal effect induced by laser light.

As a suitable laser beam for the tissue regenerating method by the laser beam in the present invention, the YAG laser can be mentioned as an example among the above-mentioned laser beams. An example of chemical treatment and reheating treatment while weaving will be described. Since the proper processing temperature range varies depending on the material, a 2Cr low alloy steel will be described as an example here. "Table 1" below
Shows the applicable temperature range and heating time of these treatment methods.

[0013]

[Table 1] * 1: Numerical value determined by solution temperature of material (example using 2Cr-based low alloy steel). * 2: This value is also determined by the SR treatment temperature of the material as in * 1 (example using 2Cr-based low alloy steel).

With reference to the above processing conditions, for example, tissue regeneration of a deteriorated member is performed on site. Specifically, using a YAG laser device at the site, the laser beam is irradiated from the YAG laser oscillator through the optical fiber to the deteriorated welding heat-affected zone coarse-grained region and heated to a temperature above the solution temperature, and then stress relief is performed. The material is also annealed and reheated immediately below the annealing temperature to be cooled.
As a result, it is possible to reproduce the same quality as the received base metal.

Further, a mechanically damaged portion caused by creep damage or the like can be remelted by a laser beam to repair and weld a microscopic defective portion and regenerate to an initial state.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic view showing a regenerated state of a tissue regeneration method by laser beam heating according to this embodiment.

In this embodiment, as shown in FIG.
Using the AG laser oscillator 21, the laser beam 24 focused through the reflecting mirror 22 and the focusing lens 23 is applied to the heat-affected zone 27 of the specimen, which is most susceptible to creep damage, of the weld metal 26 of the boiler pipe 25 while weaving it. Then
Mechanical opening cracks such as creep cracks 28 are remelted and repair welded.

At the same time, the deteriorated structure portion having the creep voids 29 is reheated to a solution temperature (900 ° C. or higher) or more and then rapidly cooled to eliminate the creep voids 29 to regenerate the structure.

Further, after the above-mentioned series of treatments, the laser beam 24 is obscured so that the maximum heating temperature is around 700 ° C. and reheating is performed while weaving.
Cool off.

In order to carry out this cooling treatment, the welding portion is immediately covered completely with a heat insulating material, and the cooling rate is controlled so as to be close to the furnace cooling treatment.

The above processing is efficient because not only repair and regeneration in the factory but also on-site construction processing is possible.

[0023]

As described above together with the embodiments, the present invention has the following effects. (1) By using a repair welding method in which only the part that has been conventionally switched and welded to a new pipe is structurally damaged and deteriorated by laser heating, or the mechanical opening crack part is remelted.
It is possible to extend the service life of the piping and other members in use, and reduce running costs and total costs. (2) If the damaged part is found, it can be easily constructed,
It can contribute to shortening the construction period.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a tissue regeneration state by laser beam heating according to the present embodiment.

FIG. 2 is a schematic diagram of an example of creep damage of a conventional boiler pipe.

[Explanation of symbols]

 10 Boiler Pipe 11 Metal Welding 12 Weld Heat Affected Zone 13 High Temperature Steam 14 Creep Void 15 Crack Defect 21 YAG Laser Oscillator 22 Reflection Mirror 23 Focusing Lens 24 Laser Light 25 Boiler Piping 26 Weld Metal 27 Weld Heat Affected Zone 28 Creep Crack 29 Creep void

Claims (1)

[Claims] 1. A laser beam or an electron beam is used for regenerating a member having creep damage and causing structural deterioration or mechanical opening deterioration, or for regenerating a member having mechanical opening deterioration due to fatigue damage. A method for regenerating a tissue by beam heating, which comprises performing remelting treatment or heat treatment up to a solution treatment temperature range to regenerate a mechanical defect portion or regenerate and remove a systematic creep void.