JPS5994578A - Repairing method of vessel for high-temperature and high-pressure hydrogen - Google Patents

Abstract

PURPOSE:To repair easily and adequately the stripping crack generated in the boundary part between a base material, such as carbon steel, constituting a vessel an a corrosion-resistant build up material by heating the boundary part to a specific temp. by high-frequency induction heating after repairing when said crack arises. CONSTITUTION:A stripping crack part 5 and the periphery thereof are cut off and a build-up material 3 is welded freshly in said part when said crack 5 arises in the boundary part between a base material 2 which is a carbon steel or low alloy steel and a corrosion-resistant build-up material 3 which is an austenitic stainless steel or the like, in a high-temp. and high pressure vessel 1 for hydrogen. The boundary part 4 between the material 2 and the material 3 is heated to 700-1,100 deg.C over the entire region built-up welded in a stage for manufacturing the vessel and in repair welding, by a high-frequency induction heater 6 after the repair welding. The repair is thus accomplished with ease and the stripping crack after the repair is prevented. The high-frequency induction heating is performed directly without repair welding when the stripping crack is minor.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for repairing a high-temperature, high-pressure hydrogen container installed in an oil refinery, coal gasification device, or the like.

In petroleum refineries, coal gasification equipment, etc., hydrogen is generally reacted in a high-temperature, high-pressure water accumulation atmosphere. An example of a high-temperature, high-pressure hydrogen container used for this hydrogen decomposition and reaction is shown in FIG. These containers (
In 1), carbon steel or low alloy steel is used as the base material (2), and a build-up material with excellent corrosion resistance such as austenitic stainless steel or Inconel is used on the inner surface of the container to improve corrosion resistance. (3) is overlay welded.

In addition, during the manufacturing process of container (1), stress relief annealing treatment is performed during and after welding in order to prevent cracking of the welded part, remove residual stress during welding, and improve the quality of the welded part (JI
SZ3700) is currently used, and the container made through this manufacturing process has a structure that is prone to hydrogen embrittlement at the boundary between the base material (2) and the overlay material (3). When used for a long time in a high-temperature, high-pressure hydrogen atmosphere, hydrogen-induced peeling cracks may occur at the boundary (4) as shown in FIG. 2 during operation or after the operation is stopped. If this peeling crack is left untreated, it will gradually propagate, and it is thought that the parts that have not peeled off will also have hydrogen embrittlement. Therefore,
If peeling cracks are discovered, appropriate treatment must be taken immediately.

Conventionally, the repair process when peeling cracks occur involves removing the part where the peeling cracks have occurred, then overlaying again, and then performing an annealing treatment. For this reason, repair work must be large-scale and take a long time, and the cost of the work must be enormous. Furthermore, if it is used in a repaired state, there is a risk that peeling cracks will occur again as described above.

In view of the above-mentioned current situation, the present invention provides a repair method that is simple, appropriate, and prevents hydrogen embrittlement from occurring later. If peeling cracks are detected, immediately if the peeling cracks are small, or if the peeling cracks are large enough, remove the peeling cracks, and after repair welding, weld the entire overlay area. It is characterized by performing high-frequency induction heating such that the temperature at the boundary between the layers is 700 to 1100°C.

The present invention will be described in detail below with reference to the drawings.

The presence or absence of exfoliation cracks is detected periodically or at appropriate times by a necessary means such as ultrasonic flaw detection.

If a peeling crack (5) shown by the broken line occurs as shown in Figure 2 (if the peeling crack is large), remove the peeling crack and its surroundings as shown in Figure 3 (α) and create a new one. Weld the overlay material (3) to.

After repair welding, the high-frequency induction heating device (6) is used to heat the entire area overlaid during the container manufacturing process and repair welding, and at the boundary (4) between the base material (2) and the overlay material (3). ) to 700 to 1
Heat at a temperature of 100°C.

The heating temperature and temperature distribution at this time are shown in FIG.

As shown in Figure 5, if high frequency induction heating is performed, the base material (3
) can be heated to a predetermined temperature without having a large thermal effect on the area (4), making it easy to specify the heating range and to easily control the temperature.

By heating this boundary area, the carbon diffused in the boundary area during the annealing process in the container manufacturing process and the precipitated carbide are dispersed and dissolved in the base material and overlay metal, and the crystal grains are further refined. This prevents peeling cracks.

In addition, if the material becomes too hard due to this heat treatment,
Perform a short softening treatment for less than 2 hours at around 0°C. The reason why the softening treatment was made for a short time is to suppress the diffusion of carbon and the precipitation of carbides in the boundary portion (4) as much as possible.

The heating characteristics during the above-mentioned repair work are shown in a graph as shown in FIG. The softening process does not need to be performed if it is not necessary, so it is shown by a broken line.

Next, if the peeling cracks are minute, high-frequency induction heating is directly performed without repair welding. By improving the material quality at the boundary using high-frequency induction heating, peeling cracks will not spread and propagate.

The table below shows that after repairing according to the present invention, a high temperature and high pressure hydrogen test was carried out at 450°C, hydrogen partial pressure 150, φ2, and holding time for 48 hours, and after the test, the test was left at room temperature for more than 24 hours and the presence or absence of peeling cracks was examined. It is something that

Next, an example of the high frequency induction heating device used in the present invention will be described in the fourth example.
This will be explained with reference to the figure.

A truck (8) having wheels (7) is attached to a fixed frame (4) via springs (9) etc., and an inductor (C) connected to a high frequency power source (B) is provided on the truck (8). in,
By energizing the duct (6) and moving the fixed frame (G) appropriately, it is possible to heat the entire area of the built-up portion. At this time, the cart (8) is moved by the spring (9) into the container (
Since it is pressed against the inner surface of the inductor (6) and moves along the inner surface, the gap between the inductor (6) and the inner surface is constant, and heating is performed uniformly.

As described above, according to the present invention, when peeling cracks occur, repair can be performed extremely easily, and furthermore, peeling cracks after repair can be prevented.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing an example of a high-temperature, high-pressure hydrogen container;
The figure is a partial view of the container wall, FIG. 6 is a diagram explaining the present invention,
Fig. 4 is an explanatory diagram of the high frequency induction heating device used in the present invention, Fig. 5 is a temperature distribution diagram when heating the boundary portion, and Fig. 6 is a diagram showing the heating characteristics when the present invention is implemented. . (1) is the container, (2) is the base material, (3) is the overlay material, (4
) shows the boundary, (5) shows the peeling crack, and (6) shows the high-frequency induction heating device. Patent applicant Ishikawajima Harima Heavy Industries Co., Ltd. Figure 1 Figure 43

Claims (1)

[Claims] (1) Austenite'1・carbon steel or low alloy steel base material
In high-temperature, high-pressure hydrogen containers welded with corrosion-resistant overlay materials such as stainless steel, if peeling cracks occur at the boundary between the base material and the overlay material, high-frequency induction heating may be applied to the boundary area to 700°C.
A method for repairing a high-temperature, high-pressure hydrogen container, the method comprising the step of heat treatment at a temperature of 1,100°C.