JPH03123856A - Life decision device for hydrogen-corroded member - Google Patents

Abstract

PURPOSE:To decide the life quantitatively by detecting the degrees of material deterioration of the surface layer part of the hydrogen-corroded structure member and in the member and calculating the mechanical deterioration of a structure member according to the detection results. CONSTITUTION:An image and a photograph of the metane bulb and cracking of the structure member which is corroded with hydrogen are obtained by an optical microscope and inputted to an image processing means 1 to remove noises and set a survey area. Then a grain boundary identifying and deciding means 2 converts the image into binary data, remove small particles, and performs edge detection and line thinning processing to extract the number of all grain boundaries and a metane bulb and cracking identifying and deciding means 3 carried out binary coding, the removal of small particles, contraction, diffusion, and line thinning to extract the metane bulbs and cracking. Then a metane bulb and cracking generation rate arithmetic unit 4 calculates a metane bulb and cracking generation rate and a mechanical deterioration degree arithmetic unit 5 calculates the degree of mechanical deterioration; and then a life arithmetic unit 6 calculates the life, and consequently the life can be decided quantitatively with high reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for determining the degree of mechanical deterioration and remaining life of a hydrogen-eroded member in a mechanical structure based on the degree of deterioration due to hydrogen attack.

[Conventional technology]

Conventionally, steel structural members in chemical plant equipment such as oil refining have suffered material deterioration over time due to hydrogen erosion due to long-term operation in high-temperature, high-pressure hydrogen atmospheres. Hydrogen that penetrates into steel in a high-pressure hydrogen atmosphere reacts with carbides to generate methane bubbles, increasing the internal pressure of the bubbles, causing cracks and deteriorating the mechanical properties of the material, as shown in the diagram in Figure 6. This is qualitatively determined by the Nelson curve shown, and is a problem in terms of the operating conditions of mechanical structures.

However, as methods for non-destructively detecting hydrogen corrosion occurring in structural members, the ultrasonic flaw detection method and the replica method are used as the most effective inspection methods. That is, in the ultrasonic flaw detection method, as shown in FIG. 7(A), a probe 9 is brought into contact with the outer surface of a portion to be inspected 8 of a structural member 7 through a solution such as glycerin, and an ultrasonic beam is applied. When an ultrasonic wave is incident on the material, this ultrasonic wave propagates at a sound speed specific to the material, and when it hits a crack or end face at an angle close to perpendicular, it is reflected, transmitted, or diffracted, and the echo 10.11 of the crack or end face is detected. The echo is converted into a voltage by the sensor 9 and further amplified, and the intensity and temporal changes of the echo are displayed on the cathode ray tube 13 of the ultrasonic flaw detector 12.

In the replica method, as shown in FIG. 7(B), first, the structural member 7 to be inspected 8 is buffed using a grinder, etc., and then etched with a corrosive solution to reveal the structure. let Next, using a thin film replica (material: near acetyl cellulose, thickness: 0.025 m), as shown in the same figure, after transferring the tissue surfaces such as methane bubbles 15 and cracks 16 onto the replica 14, vacuum Using a vapor deposition device, a thin vapor deposition layer 17 of Cr or the like is shadow-winged onto the transfer surface of the replica 14. The transfer surface of the replica 14 is then observed using an optical microscope and a scanning electron microscope (hereinafter referred to as SEM) to detect methane bubbles 15, cracks 16, and the like.

However, although ultrasonic flaw detection can detect large exfoliated cracks and clusters of extremely small cracks, it cannot detect methane bubbles and small cracks that occur in the early stages of hydrogen attack due to its detection sensitivity. However, the replica method can detect methane bubbles and minute cracks by observing the test area using a replica, but the determination of methane bubbles and cracks is based on the human judgment of the measurer. This method causes data to vary and is problematic in terms of reliability.Furthermore, although this method can detect the surface layer of a structural member, it cannot detect the internal direction at all.

Therefore, such a method is only a method for non-destructively detecting hydrogen erosion, and it is possible to accurately detect methane bubbles and minute cracks due to hydrogen erosion, and furthermore, based on the degree, mechanical It is impossible to quantitatively judge the degree of deterioration and remaining life of the product.

[Problem to be solved by the invention]

The present invention was proposed in view of these circumstances, and
A hydrogen-eroded structural member that can accurately detect the degree of material deterioration in the surface layer and inside of the structural member, and based on this, determine the mechanical deterioration degree and remaining life of the structural member quantitatively and with high reliability. The purpose of the present invention is to provide a remaining life determination device.

[Means to solve the problem]

To this end, the present invention provides a means for preprocessing an image of a hydrogen-eroded structural member, a means for comparing and determining grain boundaries from the preprocessed image signal with reference data input in advance, and a method for identifying and determining grain boundaries such as methane bubbles and cracks. means for comparing and determining the occurrence rate of methane bubbles and cracks by comparing them with pre-input reference data; a means for calculating the occurrence rate of methane bubbles and cracks by calculating the above two judgment data; The present invention is characterized by comprising means for calculating the degree of mechanical deterioration by comparing and calculating the degree of mechanical deterioration with reference data, and means for calculating the remaining life from the data on the degree of mechanical deterioration.

[Effect]

In the remaining life determination device for hydrogen-eroded parts of the present invention, SEM of methane bubbles and cracks in structural members subjected to hydrogen attack is used.
Input the image or photograph into an image processing means to remove noise,
The exploration area is set, and then the image is binarized, small particles are removed, edges are detected and thinned using a grain boundary identification/judgment method to extract the total number of grain boundaries, and methane bubbles and cracks are identified.・Methane bubbles and cracks are extracted by the judgment means by binarization, removal of small particles, contraction/diffusion, and thinning, and then the methane bubble and crack occurrence rate is calculated by the methane bubble and crack occurrence rate calculation unit. Further, after calculating the degree of mechanical deterioration using a mechanical deterioration degree calculating unit, the remaining life is calculated using a remaining life calculating unit.

〔Example〕

An embodiment of the apparatus for determining the remaining life of a hydrogen-eroded member according to the present invention will be explained with reference to the drawings. Fig. 1 is a block diagram illustrating the structure and operation of the apparatus, and Fig. 2 is an explanation of the relationship between the degree of material deterioration and the degree of mechanical deterioration. 3 is an explanatory diagram of the relationship between the degree of material deterioration and the remaining life, FIG. 4 is an explanatory diagram of the equation for estimating the remaining life, and FIG. 5 is an explanatory diagram of the relationship between temperature and the remaining life.

First, in FIG. 1, to explain the outline of the configuration of the apparatus of the present invention, 1 is an image processing means, 2 is a grain boundary identification/judgment means,
Reference numeral 3 denotes a means for identifying and determining methane bubbles and cracks, 4 a calculator for calculating the incidence of methane bubbles and cracks, 5 a calculator for calculating the degree of mechanical deterioration, and 6 a calculator for calculating the remaining life.

The operation of this device will be explained in detail below.

(1) Create a photograph or SEM image of the replica transfer surface taken by the image processing method Luprika method, and the photograph and image are A/
The D converter converts the image into a digital image, and the image processing means 1 performs preprocessing such as noise removal on the image. This preprocessing uses a filter that outputs a median (intermediate value) to remove noise without impairing important image information such as grain boundaries and methane bubbles. Also, set the exploration area for image processing here.

(2) Grain boundary identification/judgment means 2 The preprocessed image is image-processed in parallel by the grain boundary identification/judgment means 2 and the next methane bubble/cracks identification/judgment means 3. The grain boundary identification/determination means 2 performs arithmetic processing such as binarization, removal of small particles, edge detection, and line thinning in order to extract the total number of grain boundaries (one line in the X direction). Binarization is performed by creating a histogram of the density value distribution of an image using the P-tile method, and then binarizing the density values whose cumulative distribution of density values is a known value as a dark value. This binarization process extracts grain boundaries, methane bubbles, and cracks.

Next, methane bubbles are removed by a small particle removal process. To remove these small particles, image contraction processing is performed to remove methane bubbles, and only methane bubbles are removed. The grain boundaries are what restore the original shape. Finally, after extracting only grain boundaries by edge detection and thinning, the total number of grain boundaries is determined. Note that edge detection is performed using Laplacian filter processing (
Grain boundary edges are extracted using second-order differential processing).

Line thinning is for finding the center line of grain boundaries.

(3) Method for identifying and determining methane bubbles and cracks 3 On the other hand, methane bubbles and cracks are extracted from preprocessed images using processes such as binarization, removal of small particles, contraction, diffusion, and thinning. This is done by determining the number of grain boundaries where bubbles and cracks have occurred.

(4) Methane bubble and crack occurrence rate calculator 4 The methane bubble and crack occurrence rate calculator 4 calculates the methane bubble and crack occurrence rate from the following equation (1).

Here, P: grain boundary occurrence rate of methane bubbles and cracks M: grain count of methane bubbles and cracks N: total number of grain boundaries (5) Mechanical deterioration degree calculator 5 Mechanical deterioration degree is the mechanical deterioration degree The methane bubbles and the cracking occurrence rate determined in the previous section are inserted into the calculator 5, and the calculation is performed based on the calculation reference data determined in advance.

An example of calculation standard data is shown in Figure 2, which is the material:
This figure shows the relationship between the degree of material deterioration (methane bubble and crack occurrence rate) and the degree of mechanical deterioration (absorbed energy reduction rate) under the usage conditions of 1/2 Mo steel and hydrogen partial pressure: 150 kg/CrA. From the figure, it can be seen that there is a correlation between the degree of material deterioration and the rate of decrease in absorbed energy, as the degree of material deterioration increases in proportion to the increase in absorbed energy. Therefore, the degree of mechanical deterioration is It is obtained by inserting the value of the degree of material deterioration into this empirical formula.

(6) Remaining life calculator 6 The remaining life of a material due to hydrogen erosion in an environment with constant temperature and hydrogen partial pressure is calculated by the degree of material deterioration (
It is determined from a diagram of the rate of methane bubble and crack occurrence), the degree of deterioration of mechanical properties, the degree of material deterioration, and time.

In other words, the remaining life can be calculated by finding the relationship between the reciprocal of absolute temperature and usage time based on the graph of material deterioration degree and time shown in Figure 3, and then expressing the remaining life of the hydrogen-eroded material in terms of temperature and hydrogen partial pressure. , can be theoretically expressed by the following equation (2) shown in FIG.

Q ... (2) t = CP exp 荊; In addition, under the usage conditions of material: 1/ZMo steel and hydrogen partial pressure: 150 kg/crA, the remaining life of the material was taken as the absorbed energy reduction rate: 50%. case, 4
The usable limit time at 50°C and 500°C is determined from the experimental formula shown in Figure 3, and by expressing the linear relationship between temperature and remaining life as shown in Figure 5, material deterioration degree 2 mechanical properties can be calculated. The following equation (3) shown in FIG. 4 is obtained as a remaining life estimation equation that takes into account the degree of deterioration, temperature, and hydrogen partial pressure.

...(3) Furthermore, structural members used in high-temperature, high-pressure environments generate a hydrogen concentration gradient in the plate thickness direction that is determined by various factors such as temperature, hydrogen partial pressure, hydrogen diffusion rate, and plate thickness, as expressed by equation (3). There is a problem in applying it as is. Therefore, life evaluation in the plate thickness direction due to hydrogen erosion is performed by introducing the 5iverts equation and Fick's second law and converting the hydrogen concentration into hydrogen pressure. As a result, the life in the plate thickness direction... (4) Therefore, the remaining life calculator 6 can calculate the remaining life of the surface layer and inside of the material used quickly and with high precision using the method described above. can.

〔Effect of the invention〕

In short, according to the present invention, means for preprocessing an image of a hydrogen-eroded structural member, means for identifying and determining grain boundaries from the image signal after the preprocessing by comparing them with reference data input in advance;
Similarly, means for identifying and determining methane bubbles and cracks by comparing them with pre-input reference data, and means for calculating the occurrence rate of methane bubbles and cracks by calculating the above two judgment data,
By comprising means for calculating the degree of mechanical deterioration by comparing and calculating the data on the incidence rate with reference data of mechanical properties inputted in advance, and means for calculating the remaining life from the data on the degree of mechanical deterioration, A hydrogen-eroded structural member that can accurately detect the degree of material deterioration in the surface layer and inside of the structural member, and based on this, determine the mechanical deterioration degree and remaining life of the structural member quantitatively and with high reliability. The present invention is industrially extremely useful because it provides a remaining life determination device.

[Brief explanation of drawings]

Fig. 1 is a block diagram illustrating the structure and operation of an embodiment of the apparatus for determining the remaining life of a hydrogen-eroded member according to the present invention, Fig. 2 is an explanatory diagram of the relationship between the degree of material deterioration and the degree of mechanical deterioration, and Fig. 3 4 is an explanatory diagram of the relationship between the degree of material deterioration and the remaining life, FIG. 4 is an explanatory diagram of the equation for estimating the remaining life, and FIG. 5 is an explanatory diagram of the relationship between temperature and the remaining life. FIG. 6 is an explanatory diagram of a Nelson curve related to hydrogen erosion, and FIG. 7 is an explanatory diagram of a conventional hydrogen erosion detection method. 1... Image processing means, 2... Grain boundary identification/judgment means, 3... Methane bubble/cracking identification/judgment means, 4.
... Calculator for methane bubble and crack occurrence rate, 5... Calculator for mechanical deterioration degree, 6... Calculator for remaining life.

Claims (1)

[Claims] A means for preprocessing an image of a hydrogen-eroded structural member, a means for identifying and determining grain boundaries from the image signal after the above preprocessing by comparing them with reference data input in advance, and reference data in which methane bubbles and cracks are also input in advance. means for comparing and identifying and determining, means for computing the above two judgment data to determine the incidence of methane bubbles and cracks, and computing for comparing the above occurrence rate data with pre-input reference data of mechanical properties. A device for determining the remaining life of a hydrogen-eroded member, comprising: means for determining the degree of mechanical deterioration; and means for calculating the remaining life from the data on the degree of mechanical deterioration.