JPH1010095A - Method of improving ultrasonic flaw detection inspectablity of welded metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the ultrasonic flaw detection inspectbility to a base material by roller-pressurizing a welded part every layer welding in the multilayer welding of a stainless steel, and heating and holding it at a specified temperature for a specified time after the welding of all the layers is terminated. SOLUTION: The groove 7 of a stainless steel pipe 6 is roller-pressurized with a welding metal 5 in the part about 20-30mm back of a fusing pool 1 every TIG welding of each layer by use of a welding wire 8 to impart a plastic distortion. The pressurization is performed by a hydraulic jack. The magnitude of pressurizing force may be set within a range of about 5t to about 30t in a thickness of 15mm. The roller pressurization may be carried out after the first layer to the final layer are continuously welded. After the welding of all the layers, a solution heat treatment of holding it at a temperature from 800 deg.C to 1250 deg.C for 1-30 minutes to recrystallize the fused metal is performed to refine the crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving ultrasonic flaw detection (UT performance) applied to a welded portion between a stainless steel plate and a steel pipe in a power plant or the like.

[0002]

2. Description of the Related Art Conventional stainless steel welding metals such as SUS304 and SUS316 have the problem that ultrasonic inspection (UT performance) is poor because columnar crystals are formed as shown in a micrograph of the metal structure in FIG. was there. Also, even when peening the weld metal for each layer weld during multi-layer welding, the plastic strain is small, so it disappears when the next layer is welded, and there is no change in the structure, eliminating columnar crystals. It was difficult.

[0003]

Generally, in a weld metal of stainless steel, columnar crystals grow upward from the bottom surface. The columnar crystal grows by epitaxy even if the welding is multi-layer welding. Therefore, there is a problem that ultrasonic waves are refracted by columnar crystals at the time of ultrasonic inspection, thereby causing noise and impairing transmittance. In addition, the columnar crystal is larger than the crystal of the base material, so that even if there is a welding defect or the like, the UT property is impaired due to the generation of noise or a decrease in transmittance due to the columnar crystal, and thus, it may not be detected.

[0004] In view of the above-mentioned state of the art, the present invention eliminates columnar crystals of a weld metal in stainless steel welding, and
An object of the present invention is to provide a method for refining a crystal and thereby improving the UT property as well as the base material.

[0005]

According to the present invention, there is provided (1) a multi-layer welding of stainless steel, in which a plastic strain is applied by applying a roller pressure to a welding portion for each layer welding, and 800 to 800 mm after completion of all-layer welding.
A method for improving the ultrasonic flaw detection of weld metal, which comprises subjecting to a solution treatment of heating to 1250 ° C. for 1 to 30 minutes to refine the crystal, and (2) all layers in stainless steel multi-layer welding Ultrasonic flaw detection of weld metal characterized by applying a plastic strain by applying a roller pressure to the weld after welding, further subjecting the weld to a solution treatment of heating at 800 to 1250 ° C. for 1 to 30 minutes to refine the crystal. It is an improvement method.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a construction procedure of the method of the present invention. 1A is a partially cutaway front view showing an embodiment of the present invention, FIG. 1B is a side view thereof, and FIG. 1C is an explanatory view showing an example of a construction method.

For example, a welding wire (SUS316) is formed in a groove 7 of a plate or a steel pipe 6 made of stainless steel (SUS316).
(L, Y316L) 8 is applied to each layer TIG welding, preferably by applying roller pressure to the weld metal 5 at a portion of about 20 to 30 mm behind the molten pool 1 to apply plastic strain. The roller 2 has a tip radius of about 20 to 25 mmR, and is pressurized by a hydraulic jack 3 or the like. The load cell 4 is inserted between the roller 2 and the hydraulic jack 3 to set a pressing force. The magnitude of the pressing force varies depending on the thickness of the plate or tube, but the thickness is 15 mm.
In the case of (1), the process may be performed in a range from about 5 tons that can apply plastic strain to a range where the next layer is not melted by welding, to about 30 tons that can apply plastic strain to the entire thickness of the welded portion. Also, behind the molten pool 1, about 20-30
The reason why the pressure is preferably applied in the area of mm is that the yield stress is smaller in the area where the weld metal is about 300 ° C. than about 20 to 30 mm behind the molten pool at about 300 ° C., so that plastic strain is easily applied.

FIG. 1 shows a method of applying roller pressure.
(C) As shown in the example, after the method of applying for each layer welding and successively successive welding from the first layer to the final layer,
There is a method of construction. There is no significant difference in the effect of either method, but when applying the roller pressure after welding all layers without applying the roller pressure for each layer, only one pressing operation is required, but a relatively large pressing force Is required, and the size of the apparatus becomes large. On the other hand, when the roller is pressed for each layer welding, the pressing force can be small, so that the apparatus can be downsized and the workability is good.

[0009] After all layers are welded by a method in which rollers are pressed for each layer or a method in which rollers are pressed after all layers are welded,
The solution is held at a recrystallization temperature (a temperature from the lowest temperature at which recrystallization starts of 800 ° C. to a temperature at which coarse particles start to form at 1250 ° C.) for 1 to 30 minutes, and is subjected to a solution treatment for recrystallizing the weld metal to refine the crystal. . A holding time of 1 minute or more is effective, but if the time is too long, the particles are easily coarsened. The optimal holding time may be determined according to the thickness of the plate or tube.

[0010]

EXAMPLES The effects of the present invention will be specifically described below with reference to examples. (Examples and Comparative Examples) In accordance with the procedure of FIG.
6) The welding test was performed. Table 1 shows the welding conditions.

[0011]

[Table 1]

Micrographs of the metal structures of the weld metals of the samples subjected to the welding test under the conditions shown in Table 1 are shown in FIGS. 7, 8, 9 and 10, and the results of the hardness test are shown in FIGS.
As shown in FIG. Also, for comparison, peening treatment for each layer welding (apparatus: chipping hammer, number of peening:
A micrograph of the metal structure of the weld metal of a sample (sample according to the prior art) in which tipping hammer tip diameter: 1.5R) was performed at 1500 times / minute for 4 minutes and roller pressing and solution treatment were not performed, and The results of the hardness test are shown in FIGS. 11 and 2, respectively.

The following can be said from FIGS. (1) It can be seen that the columnar structure completely remains in the conventional peened sample of FIG. (2) FIGS. 7 and 8 show metallographic micrographs of the weld metal of the sample subjected to only the roller pressing (solution treatment 0 minutes) and the sample subjected to the solution treatment at 1100 ° C. for 10 minutes after the roller pressing. . It can be seen that the columnar crystals are slightly reduced in the sample subjected to the roller pressing only compared to the sample subjected to the conventional peening. Further, it can be seen that the columnar crystals disappeared by the roller pressing and the subsequent solution treatment, and the same fine structure as that of the base material was obtained.

(3) FIG. 2 shows the hardness distribution of a sample which has just been subjected to conventional peening.
Although it is 270 Hv, in the sample subjected to the roller pressing shown in FIG. Note that the greater the hardness, the greater the strain, and the easier it is to recrystallize by a subsequent heat treatment.

(4) FIGS. 4, 5 and 6 show hardness distributions of the samples which were subjected to a solution treatment at 1100 ° C. for 1 minute, 5 minutes and 10 minutes after the roller pressing, respectively. Can be at initial level, no problem. In other words, it is better to have a low hardness because the elongation and the like will be low if it is hard after heat treatment. Be improved.

(5) FIGS. 9 and 10 are micrographs of the metallographic structure of the weld metal of the sample which was subjected to a solution treatment at 1100 ° C. for 1 minute and 5 minutes after pressing the roller, respectively. It can be seen that a fine structure was obtained.

[0017]

According to the method of the present invention, the columnar crystal of the weld metal disappears, and it can be recrystallized to a fine structure equivalent to the base metal. Thereby, the UT property, which has been deteriorated in the conventional welded metal portion of the steel plate and the steel pipe, can be improved like a base material.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a construction procedure showing an embodiment of the present invention.

FIG. 2 is a diagram showing a hardness distribution of a conventional peening-only sample.

FIG. 3 is a diagram showing a hardness distribution of a sample which is subjected to a solution treatment 0 minutes after roller pressing.

FIG. 4 is a diagram showing a hardness distribution of a sample for one minute of solution treatment after roller pressing.

FIG. 5 is a diagram showing a hardness distribution of a sample for a solution treatment 5 minutes after roller pressing.

FIG. 6 is a diagram showing a hardness distribution of a sample for a solution treatment 10 minutes after roller pressing.

FIG. 7 is a diagram showing a micrograph of a metal structure of a sample of a solution treatment 0 minute after roller pressing.

FIG. 8 is a diagram showing a micrograph of a metal structure of a sample for a solution treatment 10 minutes after roller pressing.

FIG. 9 is a diagram showing a micrograph of a metal structure of a sample for one minute of solution treatment after roller pressing.

FIG. 10 is a diagram showing a micrograph of a metal structure of a sample of a solution treatment 5 minutes after roller pressing.

FIG. 11 is a diagram showing a micrograph of a metal structure of a conventional peening-only sample.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location C21D 8/00 9270-4K C21D 8/00 E (72) Inventor Noriyoshi Iriki Kobe City, Hyogo Prefecture 1-1-1 Wadazakicho, Hyogo-ku Mitsubishi Heavy Industries, Ltd. Kobe Shipyard

Claims (2)

[Claims] 1. When performing multi-layer welding of stainless steel, a solution treatment is performed in which a weld is roller-pressed for each layer welding to apply plastic strain, and after completion of all-layer welding, heating is performed at 800 to 1250 ° C. for 1 to 30 minutes. A method for improving the flaw detection of ultrasonic flaw detection of a weld metal, comprising: 2. When performing multi-layer welding of stainless steel, after welding all layers, the weld is roller-pressed to apply plastic strain, and further subjected to a solution treatment of heating to 800 to 1250 ° C. for 1 to 30 minutes. A method for improving ultrasonic flaw detection of weld metal, which is characterized by miniaturization.