JP5005494B2 - Bellows, universal bellows using the bellows, piping system for fast breeder reactor, and fast breeder reactor facility - Google Patents

Description

  The present invention relates to a bellows applied to equipment and piping through which a high-temperature fluid of 500 ° C. or higher flows, a universal bellows using the bellows, a fast breeder reactor piping system, and a fast breeder reactor facility, and in particular, high Cr. The present invention relates to a bellows made of ferritic heat resistant steel suitable for equipment and piping made of ferritic steel.

  In recent years, in addition to conventional austenitic stainless steel, high Cr ferritic steel excellent in high temperature strength is used for equipment and piping such as a fast breeder reactor facility through which a high-temperature fluid flows. Moreover, installation of bellows for absorbing thermal expansion is indispensable for equipment and piping through which this type of high-temperature fluid flows.

On the other hand, at present, stainless steel is widely used as bellows installed in equipment and piping through which high-temperature fluid flows, and many ferritic stainless steel plates for bellows base pipes have been proposed (Patent Document 1). , 2, 3). All of the bellows tube materials described in these patent documents are ferritic stainless steels, and none using ferritic steels or tempered martensitic steels. Thus, the bellows using the ferritic steel used at high temperature has no track record.
JP 2007-16311 A JP 2007-16306 A JP-A-11-159616

  From the viewpoint of ensuring the reliability and soundness of equipment and piping having a welded structure, it is preferable to use a bellows made of the same material as the piping. In other words, when stainless steel bellows is used for a pipe made of ferritic material, it has a dissimilar material weld between ferritic steel and austenitic steel, but this dissimilar material weld has a rapid strength when used at high temperatures. This is because there is a problem in long-term use in terms of reliability and soundness. Therefore, it is particularly desirable to apply a ferrite heat resistant steel bellows to ferritic heat resistant steel equipment and piping used at high temperatures.

  The present invention has been made in view of the actual situation of the prior art, and an object thereof is to provide a ferritic heat resistant steel bellows capable of forming a suitable welded structure with a ferritic heat resistant steel device and piping. And to provide a universal bellows, a fast breeder reactor piping system and a fast breeder reactor facility using the same.

  The present inventors investigated the properties and plastic workability of ferritic heat resistant steels and studied the plastic working method. As a result, the following forming method has been found and the present invention has been achieved.

  In the present invention, the bellows is made of a ferritic heat-resistant steel, and the bellows bellows portion includes a plurality of annealing heat treatments at temperatures lower than the tempering temperature of the ferritic heat-resistant steel used and molding within a uniform elongation range. It is characterized by being formed by repeating the process once.

  The ferritic heat resistant steel used for the bellows is, by weight, C 0.05 to 0.20%, Si 0.5% or less, Mn 0.05 to 1.5%, Ni 3.0% or less, Cr 8.5 to 13.0. %, Mo 0.05 to 3.0%, W 0 or 0.05 to 1.8%, V 0.05 to 0.30%, a total of one or two of Nb and Ta, 0.01 to 0.00. It is a heat resistant steel that is used in a temperature range mainly not exceeding 600 ° C., including 20% and N 0.01 to 0.1%.

  The reasons for limiting each element will be described below.

C is an indispensable element for ensuring hardenability and precipitating M ₂₃ C ₆ type carbides in the tempering process to increase the high temperature strength, and at least 0.05% is required. If it exceeds 20%, M ₂₃ C ₆ type carbide is excessively precipitated and the strength of the matrix is lowered to deteriorate the high temperature strength on the long time side, so it is limited to 0.05 to 0.20%. Desirably, it is 0.09 to 0.13%. More desirably, it is 0.10 to 0.12%.

  Si promotes the formation of Laves phase and reduces ductility due to grain boundary segregation and the like, so it is limited to 0.5% or less as a harmful element. Desirably, it is 0.25% or less, more desirably 0.15% or less. Si is added as a deoxidizing agent, but it is not added when vacuum deoxidizing, and the content at that time is about 0.01%. 0.01 to 0.1% is preferable.

Mn suppresses the formation of δ ferrite, promotes the precipitation of M ₂₃ C ₆ type carbide, and at least 0.05% is required as an element for improving hot workability, but if it exceeds 1.5% Since oxidation resistance is deteriorated, it is limited to 0.05 to 1.5%. Desirably, it is 0.2 to 1.0%, and more desirably 0.3 to 0.7%.

  Ni is an element that suppresses the formation of δ ferrite and imparts toughness, and is 3% or less. Ni is preferably 2 to 3% of high Ni up to 550 ° C, and 0.5 to 1.0% at higher temperatures. However, it is preferably at least 0.05%.

Cr is an indispensable element for imparting oxidation resistance to high-temperature Na and precipitating M ₂₃ C _6- type carbides to increase high-temperature strength. At least 8.5% is required, but 13% If it exceeds, δ ferrite is formed and the high temperature strength and toughness are lowered, so the content is limited to 8.5 to 13.0%. Desirably, it is 9.0 to 11.8%.

Mo has the effect of promoting the fine precipitation of M ₂₃ C ₆ type carbide and hindering the aggregation, and is therefore effective in suppressing the reaction in Na and maintaining the high temperature strength for a long time. 05% is necessary, but if it becomes 3.0% or more, δ ferrite is easily generated, so it is limited to 0.05 to 3.0%.

W has a stronger effect of suppressing the aggregation and coarsening of M ₂₃ C ₆ type carbides than Mo, strengthens the matrix in solid solution, and is effective for improving high temperature strength, and needs to be about 1.5%. If it is more than this, δ ferrite and Laves phase are likely to be generated. The use temperature is preferably up to 500 ° C., and W is preferably 0.05 to 1.5%, more preferably 0.1 to 0.7%.

V is effective for precipitating the carbonitride of V and increasing the high-temperature strength in Na as described above, and at least 0.05% is required. excessively _fixed, limited to 0.05 to 0.3% as it reduces the high temperature strength in the opposite by subtracting the amount of precipitated _M 23 _{C 6} type carbide. Desirably, it is 0.15 to 0.25%.

Nb generates NbC to help refine crystal grains, and partly dissolves during quenching to precipitate NbC during the tempering process, thereby increasing the high-temperature strength in Na. 0.01% is necessary, but if it exceeds 0.20%, carbon is excessively fixed in the same manner as V, the amount of precipitation of M ₂₃ C ₆ type carbide is reduced, and the high temperature strength is lowered. Limited to 0.20%. Desirably, it is 0.05 to 0.13%. More desirably, it is 0.05 to 0.11%.

  N precipitates V nitride, and also has the effect of increasing the high temperature strength by IS effect (interaction of interstitial solid solution element and substitutional solid solution element) jointly with Mo and W in a solid solution state. However, at least 0.01% is necessary, but if it exceeds 0.1%, the ductility is lowered, so it is limited to 0.01 to 0.1%. Desirably, it is 0.02 to 0.04%. More desirably, it is 0.02 to 0.03%.

  The ferritic steel in the present invention is a material that satisfies the above components and has a tempered martensite structure or a ferrite structure. In order to ensure this structure, it is known that the component forming the ferrite structure is evaluated by Cr equivalent equivalently converted to Cr amount, and the chromium equivalent obtained by the following formula is preferably 4 to 11.

Chromium equivalent = -40xC% -30xN% -2xMn% -4xNi% + Cr% + 6xSi%
+ 4xMo% + 11xV% + 5xNb% -2xCo%
Next, heat treatment and molding processing when manufacturing the bellows according to the present invention will be described.

  The bellows is manufactured by forming a cylindrical seamless tube using the above-mentioned heat-resistant steel, or a welded tube, using cold or hot. In order to maintain a uniform thickness by molding and produce a bellows without scratches, the workability of the material used, that is, plastic deformability is required. The above-mentioned plastic deformability at room temperature of the heat-resistant steel is related to the material thickness and has a formable characteristic, but is slightly inferior to austenitic stainless steel.

  The hardness, strength, and ductility of the heat-resistant steel can be controlled by heat treatment. Therefore, the bellows having a desired shape can be manufactured by repeatedly performing molding and heat treatment.

  In the heat treatment, first, annealing is performed at a temperature lower than the tempering temperature of the material within a uniform elongation range, and this is repeated until a predetermined shape is reached. The annealing temperature is desirably 680 ° C. to 730 ° C., and the heating time is preferably 1 hour / 1 inch thick.

In the molding process, the mold is placed outside the raw tube and pressed from the inside with hydraulic pressure. At this time, the pressing amount is preferably in the range of uniform elongation, and the uniform range by repetition (εn: n is the number of repetitions) is preferably ε1>ε2> ε3.
The thickness of the tube is characterized by 1.0 mm to 15.0 mm. In addition, assuming that the unit of the thickness of the pipe is mm and the unit of the outer diameter of the pipe is m, the ratio of the pipe thickness to the outer diameter (thickness / outer diameter) is 0.8 to 1. 5 or 10-30. 0.8 to 1.5 are bellows mainly applied to containers, and 10 to 20 are bellows mainly applied to piping.

  The bellows of the present invention is characterized in that the inner surface residual stress is removed by heat treatment after completion of molding, and further, a surface hardening treatment is performed on the outer surface or the inner surface after the heat treatment.

  The bellows of the present invention is intended to absorb deformation due to thermal changes. This thermal change is often repeatedly applied by starting and stopping high temperature equipment. Due to this repeated temperature change, the bellows may be damaged due to thermal fatigue. This thermal fatigue damage occurs not on the inside of the material but on the surface based on conventional knowledge. In order to prevent thermal fatigue damage occurring on the surface, the outer surface or the inner surface is subjected to a surface hardening treatment after the heat treatment. The reason why the heat treatment is performed before the surface hardening treatment is to remove the inner surface residual stress by the heat treatment and ensure the plastic deformability of the inner surface for absorbing the thermal deformation.

  When the bellows of the present invention is applied to a fast breeder reactor power plant, the target is a primary system having a primary main circulation pump, a primary system having an intermediate heat exchanger, a secondary main circulation pump, and a secondary system having a steam generator.

Each pipe is arranged in each of the primary system and the secondary system, and high-temperature molten Na is circulated through these pipes. The temperature of Na varies depending on plant equipment, and the maximum temperature is set to 500 ° C., 550 ° C., and 600 ° C., respectively. The bellows of the present invention is installed for the purpose of absorbing the thermal expansion of each device and piping in the primary system and the secondary system.

  The bellows used in this fast breeder reactor differs in shape depending on temperature, pressure, heat fluctuation amount, etc., but the connection of equipment or piping system is carried out by welding. In this case, it becomes easy to control the length and arrangement of the piping system by using a universal bellows, which is characterized by a short tube made of the same kind of heat-resistant steel as bellows and bellows. .

  According to the present invention, it is possible to eliminate the use of dissimilar joints from equipment and piping used at high temperatures, and it is possible to use equipment and piping using only joints of the same material, so high reliability for high temperature equipment and piping. Performance and long life, and weight reduction of equipment.

  Further, according to the present invention, when applied to a fast breeder reactor facility, leakage monitoring can be simplified by simplifying a method of laying a heat insulating material for the fast breeder reactor primary system piping, thereby improving the reliability and safety of the facility. can do.

Example 1
No. shown in Table 1. 1-No. An alloy having a composition of 5 was cast by vacuum induction melting to obtain a 10 kg ingot. The ingot was forged into a 30 mm square bar at 1150 ° C., and then heated at 1050 ° C. for 2 hours, quenched in oil, and tempered at 760 ° C. for 2 hours in this order to prepare a sample. Thereafter, a tensile test and a creep rupture test were performed on each sample.

Table 2 shows no. The test result of 1 is shown. The tensile strength at room temperature showed a high value of 1080 MPa or more, and was a high value of about 660 to 770 MPa even at 500 to 550 ° C., which is the operating temperature when applied to a fast breeder reactor. Furthermore, it can be seen that a high creep rupture life of 350 MPa or more at 500 ° C. and 200 MPa or more at 550 ° C. can be obtained even at a creep rupture strength of 100,000 hours. The elongation is 10 to 20% at any temperature, and the drawing ratio is 55 to 85%.

Table 3 shows no. 2 shows the test results. The tensile strength at room temperature showed a value of 700 MPa or more, and was a high value of 460 to 490 MPa even at 500 to 550 ° C., which is the operating temperature when applied to a fast breeder reactor. Further, the elongation is 20% or higher at any temperature, and the aperture is high at 75% or higher at any temperature.

Table 4 is No. The test result of 3 is shown. The tensile strength at room temperature showed a value of 900 MPa or more, and was a high value of about 580 to 660 MPa even at 500 to 600 ° C. at the operating temperature when applied to a fast breeder reactor. Further, the elongation rate is 17% or higher at any temperature, and the diaphragm shows a high value of 56% or higher at any temperature. In addition, No. No. 4 is No. for tensile strength and 100,000 hour creep strength. A value slightly higher than 3 is shown. It was equivalent to 3.

Table 5 shows no. The test result of 5 is shown. The tensile strength at room temperature showed a value of 820 MPa or more, and was a high value of about 550 to 600 MPa even at 500 to 600 ° C. at the use temperature when applied to a fast breeder reactor. Further, the elongation rate is 20% or higher at any temperature, and the diaphragm shows a high value of 70% or higher at any temperature.

(Example 2)
No. shown in Table 1. A seamless tube having a thickness of 10 mm was prepared using an alloy having the composition of 2, and a bellows was manufactured using the seamless tube as a bellows base tube.

  The bellows is manufactured by repeating annealing heat treatment and molding three times alternately, and finally the bellows bellows having a thickness (mm) / outer diameter (m) = 15, pitch = 60 mm, and mountain height = 100 mm. The bellows 4 having was obtained.

As shown in FIG. 1, in the molding process, a mold 2a having a small mountain height, a mold 2b having a medium height, and a mold 2c having a large mountain height are respectively used as a mold for the first molding, The mold 2a, 2b, 2c is used outside the seamless tube 1 or the intermediate product in each molding process, and is used as the mold for the molding process and the mold for the third molding process. The hydraulic pressure was applied from the inside of the seamless tube 1 or the intermediate product by pressing the seamless tube 1 or the intermediate product against the molds 2a, 2b, 2c. The amount of pressing at each time was within the range of uniform elongation. The annealing heat treatment was performed at 720 ° C. for 30 minutes.
The applied deformation (uniform elongation) (εn: n is the number of repetitions) is 15%, 10%, and 8% for ε1, ε2, and ε3, respectively.

(Example 3)
No. shown in Table 1. A test piece was prepared using an alloy having a composition of 2, and tests for surface treatment and fatigue strength were performed. The surface of the fatigue test piece was peened to give a hardened surface layer. The surface hardened layer has compressive residual stress due to the peening. Table 6 shows the fatigue test results. The fatigue strength of a test piece having a hardened layer with a compressive stress remaining on the surface is about 1.5 times that of a test piece that has been heat-treated without a hardened layer. After the bellows molding, a heat treatment for removing the residual stress generated at the time of molding is given, and then a bellows having excellent fatigue strength can be obtained by giving a compression hardened layer by peening.

Example 4
FIG. 2 is a system diagram of a fast breeder reactor power plant according to the present invention. This plant includes a primary system, a secondary main circulation pump 15, a steam generator 16, and a secondary system pipe 17 having a primary main circulation pump 11, a reactor 12, an intermediate heat exchanger 13, and a primary system pipe 14. The secondary system has a water-steam system centered on the steam turbine 18. High-temperature molten Na circulates in each pipe in the primary system and the secondary system. The temperature of Na varies depending on plant equipment, and the maximum temperature is set to 500 ° C., 550 ° C., and 600 ° C. depending on the operation temperature. In the present invention, the bellows 4 described above is used for each device and piping in the primary system and the secondary system.

  The structure of the primary system and the secondary system piping is shown in an enlarged view in FIG. The pipe is composed of an inner tube 19, an outer tube 20, an elbow 21, a bellows 4 having a bellows bellows portion produced as described above, a short tube 23, and the like. A combination of a plurality of bellows and a short pipe is called a universal bellows, and a combination of a universal bellows, a pipe and an elbow is called a fast breeder reactor piping system.

The equipment is a bellows in which the unit of the thickness of the tube is mm, the unit of the outer diameter of the tube is m, and the ratio of the thickness of the tube to the outer diameter (thickness / outer diameter) is 0.8 to 1.5, Moreover, 10-30 bellows are used for each piping. Table 7 shows the thickness and outer diameter of the bellows pipe used for the intermediate heat exchanger (equipment) and the primary system pipe (pipe) in the fast breeder reactor.

  According to the above embodiment, by using the bellows made of the same material as the structural member for the container / pipe structure in contact with Na, the occurrence of thermal strain due to the difference in thermal expansion is suppressed, and Na It is difficult for the constituent elements of the thermochemical material related to the movement to occur, and a long-life plant with little change in material properties can be obtained.

It is a figure which shows typically the manufacturing method of the bellows concerning this invention. It is a systematic diagram of a fast breeder reactor power plant according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bellows elementary pipe 2a, 2b, 2c Mold 3 Hydraulic device 4 Bellows 11 Primary main circulation pump 12 Reactor 13 Intermediate heat exchanger 14 Primary system piping 15 Secondary main circulation pump 16 Steam generator 17 Secondary system Piping 18 Steam turbine 19 Inner pipe 20 Outer pipe 21 Elbow 23 Short pipe

Claims (13)

Made of ferritic heat resistant steel, the bellows bellows part is formed by repeating annealing heat treatment at a temperature lower than the tempering temperature of the ferritic heat resistant steel used and molding within the range of uniform elongation multiple times , When the annealing heat treatment at a temperature lower than the tempering temperature of the ferritic heat resistant steel to be used and molding within the range of uniform elongation are repeated a plurality of times, the range of uniform elongation by repetition increases the number of repetitions. Bellows characterized by being made small . The ferritic heat resistant steel is, by weight, C 0.05 to 0.20%, Si 0.5% or less, Mn 0.05 to 1.5%, Ni 3.0% or less, Cr 8.5 to 13.0%, Mo 0.05-3.0%, W 0.05-1.8%, V 0.05-0.30%, total of one or two of Nb and Ta 0.01-0.20% and N0.01 bellows according to claim 1, characterized in that it comprises a 0.1%. The ferritic heat resistant steel is, by weight, C 0.05 to 0.20%, Si 0.5% or less, Mn 0.05 to 1.5%, Ni 3.0% or less, Cr 8.5 to 13.0%, Mo 0.05 to 3.0% , V 0.05 to 0.30%, including one or two of Nb and Ta in total 0.01 to 0.20% and N 0.01 to 0.1% The bellows according to claim 1 . The bellows according to any one of claims 1 to 3 , wherein the bellows bellows part is molded by using a bellows element pipe made of a ferritic heat-resistant steel seamless pipe . The bellows according to any one of claims 1 to 3 , wherein the bellows bellows portion is molded by using a bellows base tube made of a welded tube made of ferritic heat resistant steel. The bellows according to any one of claims 4 and 5 , wherein the bellows tube has a tube thickness of 1.0 mm to 15.0 mm . The bellows base pipe is claims 5 to 6 The ratio of the thickness to the outer diameter of the tube (thickness (mm) / outer diameter (m)) is characterized in that 0.8 to 1.5 The bellows of any one of these. The said bellows raw tube has a ratio (thickness (mm) / outer diameter (m)) of the thickness of a pipe and an outer diameter of 10-30 , Any one of Claim 4 thru | or 6 characterized by the above-mentioned. Bellows as described in. The bellows according to any one of claims 1 to 8 , wherein the bellows portion has an inner surface residual stress removed by heat treatment . The bellows according to any one of claims 1 to 9, wherein the bellows portion is subjected to a surface hardening treatment on at least one of an outer surface and an inner surface thereof. . Made of ferritic heat-resistant steel, the bellows bellows is formed by repeating annealing heat treatment at a temperature lower than the tempering temperature of the ferritic heat-resistant steel used and molding within a uniform elongation multiple times. It consists of a combination of a bellows and a short tube made of the same or different type of ferritic heat resistant steel as the ferritic heat resistant steel constituting the bellows, and the bellows is a temperature lower than the tempering temperature of the ferritic heat resistant steel used. A universal bellows characterized in that, when the annealing heat treatment and molding within the range of uniform elongation are repeated a plurality of times, the range of uniform elongation by repetition becomes smaller as the number of repetitions increases. Made of ferritic heat-resistant steel, the bellows bellows is formed by repeating annealing heat treatment at a temperature lower than the tempering temperature of the ferritic heat-resistant steel used and molding within a uniform elongation multiple times. A universal bellows composed of a combination of a bellows and a short tube made of the same or different type of ferritic heat resistant steel as the bellows, and the same type as the ferritic heat resistant steel constituting the bellows and the short tube Or a seamless tube made of different types of ferritic heat-resistant steel, and the bellows are annealed at a temperature lower than the tempering temperature of the ferritic heat-resistant steel used and molded within a uniform elongation range. When repeating multiple times, the range of uniform elongation due to repetition is reduced as the number of repetitions increases. Fast breeder reactor piping system which is characterized the door. Made of ferritic heat-resistant steel, the bellows bellows is formed by repeating annealing heat treatment at a temperature lower than the tempering temperature of the ferritic heat-resistant steel used and molding within a uniform elongation multiple times. A universal bellows composed of a combination of a bellows and a short tube made of the same or different type of ferritic heat resistant steel as the bellows, and the same type as the ferritic heat resistant steel constituting the bellows and the short tube Alternatively, each device is connected by a fast breeder reactor piping system having a seamless pipe made of different types of ferritic heat resistant steel, and the bellows is lower than the tempering temperature of the ferritic heat resistant steel used. When repeating annealing heat treatment at temperature and molding within the range of uniform elongation multiple times, uniform elongation by repetition Enclose a fast breeder reactor facilities, characterized in that the number of repetitions was smaller increases.

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