JPS62144069A - Measurement of temperature received by metal material - Google Patents

Abstract

PURPOSE:To measure the temperature received by metal material accurately and handily, by previously depositing various metals differing in Cr content on a metal material to be used at a high temperature to measure width of the decarbonated layer or carburized layer on the weld interface. CONSTITUTION:In a metal material to be used at a high temperature, for example, boiler heat exchanger tube 2, deformed welded part 1 on which various type of metals are previously deposited differing in Cr content from a boiler heat exchanger tube 2 is formed on the surface or in a channel of the tube 2 and then, used for an actual machine. For inspection or the like, the tube 2 is taken out and the weld part 1 is ground and etched to measure the width of the decarbonated layer 5 of the weld part 1 poor in the Cr content and/or that of the carburized layer 4 of the tube 2 rich in the Cr content. From these widths, parameters of temperature history of the tube 2 can be estimated by a well known formula. As operation in the tube 2 can be estimated by determining the operation temperature.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for measuring the temperature experienced by Gold 1 and 4 materials, and is particularly a measuring method suitable for application to plants that are actually in operation. It is related to.

<Conventional technology and its problems> Materials for boilers and chemical plants are used at high temperatures, resulting in material deterioration. Specifically, ferritic materials undergo material changes such as decomposition of pearlite and bainite structures and agglomeration of carbides during operation, and their tensile strength and creep strength gradually decrease. In addition, in austenitic materials, carbide precipitation and agglomeration occur during operation.
Coarsening occurs, and a sigma phase, which is an intermetallic compound of iron and chromium, precipitates and acts like a creep void, promoting the creep phenomenon. Such material deterioration is controlled by operating temperature, operating time, and applied stress.

In actual plants, taking into account such material deterioration, the
It is designed with a life expectancy of more than 10,000 hours. However, in boiler heat exchanger tubes and the like designed to have a lifespan of 100,000 hours or more, accidents often occur in which the tubes blow out or bulge out over time. The cause of such accidents is often that the actual operating temperature is higher than the design temperature due to a decrease in the amount of water vapor, which is the internal fluid of the combustion gas.

FIG. 8 shows the relationship between creep strain and time of a steel material under constant stress, using temperature as a parameter. As shown in FIG. 8, the higher the temperature, the shorter the time until breakage. especially,
It is known that the rupture life is greatly affected by temperature at high temperatures such as the operating temperature of a boiler. Additionally, the stress acting on the boiler heat transfer tubes is due to internal pressure, which can be easily estimated by considering pressure calculations during design and differential pressures from measurements at key locations to the locations. From this, it is easy to estimate the stress acting on the heat exchanger tubes of an actual boiler during operation. Therefore, in order to investigate the degree of material deterioration of boiler heat exchanger tubes and predict blowout or bulge accidents of boiler heat exchanger tubes, it is necessary to accurately measure the operating temperature of the actual boiler.

As mentioned above, temperature is the most important factor governing material deterioration of heat exchanger tubes in actual boilers. However, at present, temperature measurements of heat transfer tubes of actual boilers during operation have not been carried out. One possible way to measure the temperature of heat transfer tubes is to weld a thermocouple to the heat transfer tubes of an actual boiler.
This method is difficult to implement because of problems such as the tangential wiring between the thermocouple and the amplifier being extremely long, making it impossible to perform accurate measurements, and the wiring being directly exposed to high-temperature combustion gas and being damaged. Furthermore, even if these problems are resolved,
In actual equipment, it is necessary to measure temperatures at a large number of points.
The installation of thermocouples and the maintenance of the measuring equipment requires extensive work and expense. Currently, in order to prevent boiler heat transfer tubes from blowing out or bulging, and to estimate their remaining life, boiler heat transfer tubes are handled over time and mechanical tests and metallographic observations are conducted. The estimation results vary widely.

As mentioned above, if the operating temperature of the boiler heat exchanger tubes could be accurately measured, such a labor-intensive and time-consuming work would be eliminated.

<Objective of the Invention> The object of the present invention is to accurately and accurately measure the temperature received by members such as boiler heat exchanger tubes, which have been difficult to measure in the past, and whose measuring points are exposed to combustion gas. The objective is to provide a method that can be used to measure

<Importance of Means> In short, the present invention involves welding dissimilar metals with different chromium contents to actual machine parts in advance, and reducing the size of the decarburized layer or carburized layer in the welded area caused by the carbon diffusion phenomenon determined by temperature and time. This is to measure the heated temperature of the actual machine parts.

<Example 1> Before describing specific examples of the present invention, first, the relationship between the decarburized layer and temperature of a dissimilar metal weld between an austenitic material and a ferritic material will be described.

First, 5 US 304,321,347 and 27 for carbon steel.
Welding of Or-IMo based welded bodies was performed by covered arc welding to create various welded parts of dissimilar materials.

Next, these dissimilar metal welds were heated to various temperatures 2 as shown in Table 1.
Heat treatment was performed in an electric furnace for hours.

After heat treatment, the cross section of the welded part is polished and etched.
Tissue observation was performed. Figure 5 shows 5US304°347.3
21 shows a cross section of a welded part when weld build-up is performed on a 220r-IMo-based welded body. As shown in Table 1 of FIG. 5, 27Or-IM of weld boundary 3 after heat treatment.

There is a decarburized layer 5 on the steel 7 side, that is, on the material side with low chromium content.
However, a carburized layer 4 was observed on the austenitic stainless steel side, that is, on the material side with a high chromium content. This is because the carbon on the 2-Or-IMol5447 side diffused into the austenitic stainless steel 6 side. It was observed that in the decarburized layer 5, carbon movement decreased and the pearlite structure became a ferrite structure, and in the carburized layer 4, carbide was precipitated. Figure 6 shows carbon steel.
-2-0r-I series welding rod is used to build up the weld. As shown in Fig. 6, there is a decarburized layer 5 on the carbon steel 8 side of the weld boundary 3 after heat treatment, that is, on the material side with low chromium content, and a carburized layer 5 on the 21Cr-1Mo@7 side, that is, on the material side with high chromium content. Layer 4 was observed. As described above, when welds of dissimilar materials with different chromium contents are heat treated, carbon diffuses from the material with a low chromium content to the material with a high chromium content, and a decarburized layer is formed in the material with a low chromium content. A carburized layer forms in materials with high chromium content.

Austenitic stainless steel and 21Or-IM
In the case of the O steel combination, the weld boundary could be clearly identified and the width of the decarburized layer or carburized layer could be easily measured.

Next, the results of organizing the relationship between the width of the decarburized layer, the heat treatment temperature, and the heat treatment time will be explained. FIG. 7 shows the relationship between the width of the decarburized layer and the Larson-Miller parameter. However, the vertical axis is a logarithmic scale. Lar
The son-Miller parameter is a parameter that takes temperature and time into consideration, and is often used to organize material behavior at high temperatures, and is expressed by the following equation.

P2T (C!+log t) (1) Here, absolute temperature (K) I C is a material constant.

t is time (hour). As shown in Fig. 7, one hole in the decarburized layer does not depend on the material or temperature, and is
It is well organized with ller parameters.

Therefore, by using FIG. 7, the Larson-Miller parameter representing the temperature history can be estimated from the width of the decarburized layer. Furthermore, since the operating time of the actual machine is known, the operating humidity can be determined from equation (1).

Next, a case will be described in which the present invention is applied to a heat exchanger tube of an actual boiler. First, we selected a part of an actual boiler heat exchanger tube where the temperature is higher than other parts during operation and is likely to cause material deterioration, and using a welding rod with a different amount of chromium than the heat exchanger tube material, welded it as shown in Figure 1. Weld overlay in the axial direction to create a dissimilar metal weld. In this case, the strength of the heat exchanger tube may be slightly reduced due to weld build-up, so it is necessary to make the wall thickness of the heat exchanger tube thicker than a predetermined thickness. When it is necessary to measure the temperature of the heat exchanger tubes due to periodic boiler inspections, etc., cut out a part of the dissimilar metal weld, polish and etch the dissimilar metal weld, and measure the width of the decarburized layer using an optical microscope. . Next, Larson-Miller parameters are determined from the measured width of the decarburized layer according to FIG. The Larson-Miller parameter is a parameter determined from temperature and time, and since the operating time is known, the d-inversion temperature can be determined from equation (1).

The dissimilar metal welds previously made on the heat exchanger tube are not necessarily axial weld build-up as shown in FIG. 1, but may be circumferential build-up welds as shown in FIG. By performing overlay welding in the circumferential direction, it is possible to prevent cracks from occurring from the toe of overlay welding. In other words, the stress acting on the heat exchanger tube is due to internal pressure, and a large tensile stress is generated in the circumferential direction, but by performing circumferential overlay welding over the entire circumference of the heat exchanger tube, this tensile stress is removed at the weld toe. This is preferable because stress can be avoided. Second weld overlay
Even in the case of circumferential direction as shown in the figure, the temperature can be measured from the width of the decarburized layer by the same method as in the case of axial direction as shown in FIG.

In the method described above, it is necessary to cut out a dissimilar metal welded part made in advance and measure the width of the decarburized layer. Next, a method for non-destructively measuring the width of the decarburized layer without cutting out the welded portion of dissimilar materials will be described. First, in a heat exchanger tube of an actual boiler, a part where temperature measurement is required is selected, and an r114-shaped groove is processed so that the weld boundary 3 has a shape as shown in FIG. By making the welding part shape cedar as shown in FIG. 3, the boundary 3 of the dissimilar metal welded part created by weld overlay can be made perpendicular to the outer surface of the heat exchanger tube.

In other words, the width of the decarburized layer 5 must be measured in the direction perpendicular to the boundary 3 of the dissimilar metal weld, and the weld shape must be measured in the third direction.
The shape shown in the figure allows measurement from the surface of the heat exchanger tube. Next, overlay welding is performed using a heat exchanger tube material and a welding material with a different chromium content. In addition, to prevent stress concentration at the upper end of the weld, use a grinder to smooth the flashing part. Through the above steps, a dissimilar metal weld is formed in the actual boiler heat exchanger tube, and the temperature can be measured.

Next, a method of measuring the temperature experienced by the base metal using this dissimilar metal weld will be explained. First, the oxidized school on the surface of the dissimilar metal welded part of the boiler heat exchanger tube that has been made in advance is removed using a grinder, and then it is finished by puff polishing to a mirror surface and etched. Next, the decarburized layer 5 is removed from the outer surface of the heat exchanger tube using a mobile optical microscope or the IT replica method.
Measure the width of. As mentioned above, by making the weld shape as shown in Figure 3, the boundary 3 of the dissimilar metal weld created by weld overlay is perpendicular to the heat exchanger tube surface, and the decarburized layer 5 can be accurately formed from the heat exchanger tube surface. Width can be measured. The method for estimating the temperature history from the width of the decarburized layer is the same as in the previous case. Further, the shape of the dissimilar metal welded portion shown in FIG. 3 is effective in reducing stress concentration at the end of the weld 1F and preventing cracking.

<Example 2> The welded portion of dissimilar materials does not necessarily have to be in the axial direction as shown in FIG. 3, and it goes without saying that the welding shape in the circumferential direction as shown in FIG. 4 will have the same effect.

Moreover, in addition to the main purpose of aging deterioration, it is also effective for estimating the temperature distribution of pickles in large Ti such as boiler headers. In other words, since steam is supplied to the header via leg tubes (connecting pipes with a smaller diameter than the header), if a dissimilar metal weld is installed near the weld between each leg tube and header, The average temperature distribution in the longitudinal direction of the header becomes clear.

In the method for estimating humidity according to the present invention, it is of course possible to measure the temperature not only from the width of the decarburized layer (but also from the width of the carburized layer).

<Effects of the Invention> By carrying out the present invention, in order to prevent blowout or bulging accidents of heat exchanger tubes in actual boilers, it is possible to solve a series of problems that have been difficult to implement in the past, although they are necessary. It has become possible to measure the humidity during the boiling process with positive rjt (+) and easily.In addition, the temperature measuring method according to the present invention can be applied not only to boilers but also to high-temperature equipment in ponds. can.

4.+7tiqi- Explanation of the Drawings Figure 1 is a side view of a dissimilar metal weld formed in the longitudinal direction of a pipe according to the present invention, and Figure 2 is a side view of a dissimilar metal weld formed in the circumferential direction. What I did / Front view, Figure 3 (Also, A- in Figure 1)
A sectional view and Fig. 4 correspond to the longitudinal section G in Fig. 2, and the grooves are provided to form a dissimilar metal weld. Fig. 5 is a dissimilar metal weld with austenitic stainless steel S4 as the base material. Fig. 6 is a cross-sectional view of a dissimilar metal weld with carbon steel as the base material, Fig. 7 is a diagram showing the relationship between the width of the decarburized layer and the temperature received, and Fig. 8 is a diagram showing the relationship between creep strain and It is a drawing showing a time relationship.

1...Dissimilar metal welding part 2... Heat exchanger tube 3...Welding boundary 4...-Carburized layer 5... Decarburized layer No.1 C Figure 2 IW shoulder marriage Figure 3 Figure 4 Parrot 5 Figure 6

Claims (1)

[Claims] 1. A dissimilar metal weld is created by welding dissimilar metals with different chromium contents to a metal material to be used at high temperatures in advance, and desorption at the weld boundary of the dissimilar weld is performed. The method is characterized in that the width of the coal layer and/or carburized layer is measured, and the temperature at which the metal material is heated is measured using a previously prepared relationship diagram between the width of the decarburized layer or the carburized layer and the temperature. A method of measuring the temperature experienced by metallic materials. 2. The temperature to which the metal material according to claim 1 is subjected, characterized in that the dissimilar metal weld is created by welding an austenitic material to the ferritic material and a ferritic material to the austenitic material. How to measure. 3. A method for measuring the temperature experienced by a metal material according to claim 2, which comprises forming a dissimilar metal weld in the circumferential direction of the outer surface of the tube. 4. A method for measuring the temperature experienced by a metal material according to claim 2, characterized in that a dissimilar metal weld is formed in the longitudinal direction of the outer surface of the tube. 5. Any one of claims 1 to 4, characterized in that a groove is dug in the surface of a metal material, and a material different from the base material is welded to the groove to form a dissimilar metal weld. A method for measuring the temperature experienced by a metal material as described in .