JP2013167297A - Method for manufacturing pressure vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to suppress the cost of manufacturing facilities low as well as sufficiently reducing and removing a residual stress even when a pressure vessel having a large-sized pressure chamber is manufactured, and further, to set the dimensions within the pressure vessel with high precision.SOLUTION: A method for manufacturing a pressure vessel includes: an intermediate product forming step P2 of forming an intermediate product in a shape corresponding to a final shape of the pressure vessel; a preliminary pressure applying step P3 of plastically deforming the intermediate product by applying a preliminary pressure larger than a withstanding pressure required as a pressure chamber in the pressure vessel in the final shape into the pressure chamber in the intermediate product; a finish machining step P4 of finishing the intermediate product after the preliminary pressure is applied thereto in the preliminary pressure applying step into the final shape by machining it; and a withstanding pressure test step P5 of performing a withstanding pressure test to apply a withstanding pressure into the pressure chamber of the pressure vessel in the final shape subjected to finish machining.

Description

  The present invention relates to a method for manufacturing a pressure vessel used for a compressor, a turbine, or the like.

  In general, it is known that residual stress is generated in a pressure vessel when plastic working, welding, or the like is performed in the manufacture of a pressure vessel used in a rotary machine such as a compressor or a turbine. If a pressure test is performed to confirm the pressure resistance required for a pressure vessel as a product with such residual stress remaining, the pressure vessel may be plastically deformed and permanent pressure may remain in the pressure vessel. The pressure vessel cannot meet the product requirements.

Therefore, conventionally, it has been considered to carry out an annealing process (SR process) in which the pressure vessel is heated to a predetermined temperature or higher to reduce or remove the residual stress after the above-described processes such as plastic working and welding. Usually, the annealing treatment is performed in a state where the pressure vessel is accommodated in a heat treatment furnace.
As an example of the annealing treatment, Patent Document 1 discloses that a high-frequency heating coil (heating / cooling coil) is used to uniformly remove the vicinity of the welded portion by high-frequency heating so as to reduce or remove residual stress in the vicinity of the welded portion of the pipe joint. It describes that a heating / cooling coil is used to cool a surface on which residual stress is to be reduced / removed after heating.

  Furthermore, conventionally, as a technique for removing the residual stress of the metal tube, the tube is filled with fluid and pressurized (Patent Document 2), or the liquid (water) filled in the tube is cooled and solidified to form a solid ( It is also considered that the metal tube is plastically deformed by utilizing the volume expansion at the time of (ice) (Patent Document 3). In the methods described in Patent Documents 2 and 3, the outer dimensions of the metal tube in the product state are set by inflating the metal tube while the metal tube is housed in a mold or a restraining jig. .

Japanese Patent Laid-Open No. 9-308985 Japanese Patent Laid-Open No. 61-227126 JP-A-2005-95948

However, as in the conventional case, in order to perform the annealing treatment, it is necessary to prepare a heat treatment furnace that can accommodate the pressure vessel. However, a pressure vessel used for a rotary machine such as a compressor or a turbine has a large size. In many cases, it is difficult to prepare a heat treatment furnace that can accommodate such a large pressure vessel. Even if a large heat treatment furnace can be prepared, there is a problem that the equipment cost required for manufacturing the pressure vessel is increased.
In addition, in order to reduce / remove residual stress of a large pressure vessel, it is difficult to prepare the heating / cooling coil described in Patent Document 1, as in the case of a heat treatment furnace. -Even if a cooling coil is prepared, there is a problem that the equipment cost required for manufacturing the pressure vessel is increased.

Furthermore, when annealing is performed using a heat treatment furnace, it is necessary to keep the temperature inside the heat treatment furnace uniform, but in a large heat treatment furnace, it is difficult to keep the temperature inside the furnace uniform. May not be sufficiently reduced / removed, and unintended plastic deformation may occur due to internal thermal stress generated in the pressure vessel during the annealing process.
Further, depending on the material of the pressure vessel, there is a possibility that the annealing resistance may cause a decrease in corrosion resistance. For example, when the pressure vessel is made of stainless steel, a phenomenon of sensitization in which chromium and carbon in the material are bonded is caused by the annealing treatment. As a result, the corrosion resistance of the pressure vessel is lowered, and further, stress corrosion cracking (SCC) ) May occur.

Further, even when the methods described in Patent Documents 2 and 3 are applied to reduce / remove the residual stress of the large pressure vessel, the large pressure vessel is accommodated as in the case of the heat treatment furnace described above. It is difficult to prepare large molds and restraining jigs, and even if large molds and restraining jigs can be prepared, the equipment cost required to manufacture pressure vessels will increase. There is.
Furthermore, when the methods described in Patent Documents 2 and 3 are applied to the production of a pressure vessel, the outer dimensions of the pressure vessel can be set by using a mold or a restraining jig, but the pressure vessel (pressure chamber) ) Cannot be set. In particular, when the application of the pressure vessel to be manufactured is a rotary machine such as a compressor or a turbine, an impeller, a blade, etc. must be arranged with high positional accuracy in the pressure vessel. Although high accuracy is required, the methods described in Patent Documents 2 and 3 cannot meet this requirement.

  The present invention has been made in view of the above-described circumstances, and even when manufacturing a large pressure vessel, the residual stress can be sufficiently reduced and removed, and the manufacturing equipment cost can be kept low. Furthermore, it aims at providing the manufacturing method of the pressure vessel which can also set the dimension in a pressure vessel with high precision.

  In order to solve this problem, the pressure vessel manufacturing method of the present invention is a pressure vessel manufacturing method having a pressure chamber to be pressurized, and forms an intermediate product having a shape corresponding to the final shape of the pressure vessel. An intermediate product forming step, and a pre-pressure operation step for plastically deforming the intermediate product by applying a pre-pressure greater than a pressure resistance required as a pressure chamber in the final-shaped pressure vessel in the pressure chamber of the intermediate product. Then, the intermediate product after the preliminary pressure is applied in the preliminary pressure application step is processed to finish the final shape, and the pressure resistance is set in the pressure chamber of the final shape pressure vessel. And a pressure resistance test process for performing a pressure resistance test to be applied.

And in the said manufacturing method, when welding etc. are implemented in the intermediate product formation process, residual stress will generate | occur | produce in the intermediate product after an intermediate product formation process like the conventional case.
Next, if the intermediate product is plastically deformed by applying preliminary pressure to the intermediate product in the preliminary pressure application process, the residual stress generated in the intermediate product temporarily increases, but by removing (unloading) this preliminary pressure. The shape of the intermediate product is elastically restored (elastic return).

The residual stress in the intermediate product after the preliminary pressure application process that has been elastically restored in this way can be set lower than the residual stress in the intermediate product before the preliminary pressure application process by appropriately setting the size of the preliminary pressure. Is possible.
In other words, in the pressure vessel manufacturing method, the magnitude of the preliminary pressure is determined so that the residual pressure in the intermediate product after unloading the preliminary pressure is higher than the residual stress in the intermediate product before the preliminary pressure application step. It will be set to be smaller.
By performing the preliminary pressure application process as described above, the residual stress of the intermediate product generated by welding or the like can be reduced / removed.

  In the pressure test process performed after the preliminary pressure application process, the pressure resistance applied to the pressure vessel is lower than the preliminary pressure, and the residual stress generated by welding or the like is reduced / removed in the preliminary pressure application process. Therefore, even if pressure resistance acts in the pressure chamber of the pressure vessel, the pressure vessel only elastically deforms and does not plastically deform. That is, by removing (unloading) the pressure resistance in the pressure test process, the shape and dimensions of the pressure vessel are returned to the state after the finishing process.

As described above, according to the above manufacturing method, in the preliminary pressure application step, since the preliminary pressure is applied in the intermediate pressure chamber, even if the pressure vessel to be manufactured is large, the residual stress of the intermediate product is reduced. It can be sufficiently reduced and eliminated.
Further, since the preliminary pressure operation step is a step in which pressure is applied to the pressure chamber in the same manner as the pressure test step that has been conventionally performed, it can be performed using the same equipment as the pressure test step. . Further, in these preliminary pressure application process and pressure test process, pressure is applied from the inside of the intermediate product or pressure vessel, so that no facility for accommodating the intermediate product or pressure vessel is required. Therefore, according to the said manufacturing method, even if it is a case where a large sized pressure vessel is manufactured, the installation expense required for manufacture of a pressure vessel can be restrained low.

  Further, according to the above manufacturing method, the finishing process is performed to finish the intermediate product into the final shape pressure vessel after the preliminary pressure application process and before the pressure test process. Since the container is not plastically deformed, it is possible to provide a pressure container having a highly accurate dimension as a product even when a large pressure container is manufactured. In particular, since the size of the pressure chamber can be set with high accuracy, the pressure vessel can be provided as a product used for a rotary machine such as a compressor or a turbine.

  Further, according to the above manufacturing method, since the conventional annealing treatment is not performed, it is possible to prevent unintended plastic deformation due to internal thermal stress, and further, the corrosion resistance of the pressure vessel is reduced regardless of the material of the pressure vessel. And stress corrosion cracking can be prevented.

  Then, in the intermediate product forming step in the pressure vessel manufacturing method, the intermediate product is plastically deformed by the preliminary pressure application step, and the pressure-receiving surface of the pressure chamber in the intermediate product is displaced, and the finishing process is performed. The pressure in the final shape pressure vessel so that the pressure surface of the pressure chamber in the intermediate product after the preliminary pressure application step can be finished to the pressure surface of the pressure chamber in the final shape pressure vessel in the process. It is preferable that a surplus wall is provided on the pressure-receiving surface of the chamber to form a pressure-receiving surface of the pressure chamber in the intermediate product.

That is, in the intermediate product forming step in the above manufacturing method, even if a preliminary pressure higher than the withstand pressure acts in the pressure chamber in the preliminary pressure application step, the intermediate product is covered within a range in which the intermediate product can be plastically deformed without being damaged. The thickness of the wall portion forming the pressure surface is set so as to be thicker than the thickness of the wall portion in the final-shaped pressure vessel.
According to the manufacturing method, within the above-described range, the thickness of the wall portion forming the pressure-sensitive surface in the intermediate product in the intermediate product forming step is set to be thicker than the thickness of the wall portion in the final-shaped pressure vessel. Thus, the intermediate product can be reliably plastically deformed in the preliminary pressure application step, and the finishing process can be performed on the intermediate product after the preliminary pressure application step.

  The pressure vessel manufacturing method further includes a design step of designing the intermediate product before the intermediate product forming step, and in the design step, the pressure resistance is set in a pressure chamber of the final shape pressure vessel. It is preferable to analyze the amount of displacement of the pressure surface generated by plastic deformation of the pressure vessel when it is applied, and set the thickness of the surplus wall to a value equal to or greater than the amount of displacement.

  By setting the thickness of the surplus wall in this way, the wall thickness of the intermediate product after the preliminary pressure application step becomes equal to or greater than the wall thickness of the final shape pressure vessel. Therefore, in the finishing process, it is possible to finish the final-shaped pressure vessel according to the dimensions of the pressure vessel that are reliably requested by cutting or the like. In other words, it is possible to reliably prevent the finishing process from being performed on the intermediate product after the preliminary pressure application process.

  Furthermore, in the design step in the method for manufacturing the pressure vessel, a first step of analyzing a displacement amount of the pressure surface for a plurality of portions of the pressure vessel having different shapes of the pressure surface, and a plurality of the pressure surfaces A second step of setting the largest value of the displacement amounts as the maximum displacement amount, a third step of setting a value larger than the maximum displacement amount as the thickness of the surplus to be given to the pressure surface in the pressure vessel, and When the preliminary pressure is applied to the pressure chamber of the intermediate product taking into account the thickness of the surplus, the amount of displacement of the pressure-receiving surface at the plurality of locations resulting from plastic deformation of the plurality of locations of the intermediate product is analyzed. After sequentially performing the fourth step, the first of the plurality of portions until the displacement amount of the plurality of portions analyzed in the fourth step is equal to or less than the thickness of the surplus corresponding to each of the plurality of portions. Four steps In the fourth step, an additional surplus is added and set to a new surplus thickness on the pressure-receiving surface of the intermediate product where the displacement analyzed in the step is larger than the surplus thickness. The thickness of the surplus when the amount of deformation of the plurality of parts is equal to or less than the thickness of the surplus corresponding to each of the plurality of parts in the fourth step is determined in the intermediate product forming step. It is even better if it is set as the thickness of the surplus that is imparted to the pressure chamber surface of the pressure chamber.

According to the above manufacturing method, even if the pressure chamber of the pressure vessel to be manufactured has a complicated shape, the thickness of the surplus is set for each part of the pressure vessel in the design process. It is possible to minimize the thickness of the surplus to be applied. In other words, the wall thickness of the intermediate product can be prevented from becoming unnecessarily thick.
In addition, by minimizing the thickness of the surplus, it is possible to reduce the amount of processing of the intermediate product pressure surface into the pressure vessel pressure surface in the finishing process, thereby reducing the number of steps in the process. .

  Further, in the design step in the method for manufacturing a pressure vessel, after analyzing the stress at the time of the test that occurs in the pressure vessel when the pressure resistance is applied in the pressure chamber of the pressure vessel of the final shape, The preliminary pressure may be set so that the stress generated when pressure is applied to the pressure chamber of the intermediate product taking into account the thickness of the meat is equal to or greater than the stress at the time of the test.

  By setting the preliminary pressure in this way, when performing the preliminary pressure operation step on the intermediate product taking into account the thickness of the surplus, the intermediate product is more reliably plastically deformed, and the pressure chamber in the intermediate product is The pressed surface can be displaced more reliably. In addition, it is possible to reliably prevent plastic deformation from occurring in the final-shaped pressure vessel due to the pressure resistance in the pressure resistance test process.

  Further, in the design step in the method for manufacturing the pressure vessel, the intermediate in which the thickness of the surplus is taken into account after analyzing the stress at the time of testing for a plurality of portions of the pressure vessel having different shapes of the pressure surface When the pressure is applied to the product pressure chamber, the stress generated in each part of the intermediate product is equal to or greater than the stress at the time of the test corresponding to each part. It is further preferable to set a preliminary pressure and set the highest value among the plurality of site-specific preliminary pressures as the preliminary pressure.

When the pressure surface of the pressure chamber of the pressure vessel to be manufactured has a complicated shape, the type of load stress (for example, tensile stress or bending stress) generated in a plurality of parts of the pressure vessel or intermediate product with different shape of the pressure surface, The size varies depending on the site. For example, the types and magnitudes of the stresses generated in the respective portions are different between a pressure vessel or intermediate product portion having a curved pressure surface and a pressure vessel or intermediate product portion having a flat pressure surface.
Therefore, if the preliminary pressure is set as in the above manufacturing method, even if the pressure chamber of the pressure vessel to be manufactured has a complicated shape, a plurality of intermediate products with different shapes of the pressure-receiving surfaces are used in the preliminary pressure operation step. Thus, it is possible to reliably plastically deform all the parts (the entire intermediate product), and it is possible to reliably displace the pressed surfaces of all the plurality of parts of the intermediate product. Therefore, even if the pressure chamber of the pressure vessel to be manufactured has a complicated shape, it is possible to reliably prevent plastic deformation from occurring in the final shape pressure vessel due to the pressure resistance in the pressure resistance test process.

According to the present invention, even when a large pressure vessel is manufactured, residual stress due to welding or the like can be sufficiently reduced and removed, and manufacturing equipment costs can be kept low.
In addition, since the size of the pressure chamber can be set with high accuracy, the pressure vessel can be provided as a product used for a rotary machine such as a compressor or a turbine.

It is a partially cutaway perspective view showing a centrifugal compressor provided with a pressure vessel manufactured with a manufacturing method concerning a first embodiment of the present invention. It is a schematic sectional drawing which shows the pressure vessel manufactured with the manufacturing method which concerns on 1st embodiment of this invention. It is an expanded sectional view which shows the principal part I in FIG. It is a flowchart of the manufacturing method which concerns on 1st embodiment of this invention. It is a stress strain diagram of an intermediate article and a pressure vessel corresponding to a manufacturing method concerning a first embodiment of the present invention. In the manufacturing method concerning a first embodiment of the present invention, it is a graph which shows the relation between the pressure which acts in the pressure room of an intermediate article or a pressure vessel, and the stress which arises in an intermediate article or a pressure vessel. It is a flowchart implemented in a design process among the manufacturing methods which concern on 2nd embodiment of this invention.

[First embodiment]
The first embodiment of the present invention will be described below with reference to FIGS. In addition, the manufacturing method which concerns on this embodiment is a method of manufacturing the pressure vessel 1 with which the centrifugal compressor 50 is provided, for example, as shown in FIG.
The centrifugal compressor 50 includes a cylindrical rotary shaft S that is rotated around an axis O, an impeller 52 that is fixed to the rotary shaft S and compresses a fluid using centrifugal force, and the rotary shaft S in the direction of the axis O. And a casing 53 that accommodates the impeller 52.
The impeller 52 is formed in a disk shape centered on the axis O, and a flow path for flowing a fluid from the radially inner peripheral side to the outer peripheral side is defined in the impeller 52. A plurality of impellers 52 are arranged at appropriate intervals in the direction of the axis O.

The casing 53 is formed in a substantially cylindrical shape and forms an outline of the centrifugal compressor 50, and is disposed in the pressure container 1, and has a flow path for flowing fluid from the upstream side to the downstream side together with the impeller 52. And a flow path defining member 54 for defining.
As shown in FIGS. 1 and 2, the pressure vessel 1 covers the peripheral wall portion 2 formed in a substantially cylindrical shape centering on the axis O and the openings at both ends of the peripheral wall portion in the axis O direction. And an annular plate-shaped end plate portion (end plate portion) 3 formed at both ends.

A bearing portion 55 that rotatably supports the rotation shaft S is attached to each end plate portion 3 with no gap with respect to the inner peripheral surface of the end plate portion 3. That is, the rotation shaft S disposed so as to penetrate the center of the pressure vessel 1 is supported by the pressure vessel 1 via the pair of bearing portions 55.
Moreover, in this pressure vessel 1, the suction pipe 4 for letting a fluid flow in from the outside, and the discharge pipe 5 for letting a fluid flow outside are connected to the surrounding wall part 2 by welding. Further, a discharge flow path 6 is formed in the peripheral wall portion 2 so as to extend around the axis O and guide the fluid from the downstream flow path of the flow path defining member 54 described later to the discharge pipe 5.

The flow path defining member 54 is formed in a substantially cylindrical shape so as to allow the rotation shaft S to be inserted in the direction of the axis O and to accommodate the impeller 52 fixed to the rotation shaft S.
The flow path defining member 54 includes an intermediate flow path 56 that guides the fluid that has flowed from the upstream impeller 52A to the radially outer peripheral side to the radially inner peripheral side and then guides the fluid to the downstream impeller 52B. A downstream flow path 57 that guides the fluid that has flowed from the side impeller 52 </ b> B to the radially outer peripheral side to the discharge flow path 6 of the pressure vessel 1 is formed. Further, since the flow path defining member 54 is arranged in the pressure vessel 1, the fluid is guided from the suction pipe 4 to the upstream impeller 52 </ b> A by the inner surface of the pressure vessel 1 and the flow path defining member 54. A suction channel 58 is defined.

  In such a centrifugal compressor 50, since the inside of the pressure vessel 1 (mainly the pressure chamber 7 defined by the peripheral wall portion 2 and the end plate portion 3) is pressurized, the fluid is out of the flow path or outside the pressure vessel 1. Therefore, the pressure vessel 1 is required to have high pressure resistance and dimensional accuracy. Examples of the size of the portion of the pressure vessel 1 that requires high dimensional accuracy include the inner diameter size of the peripheral wall portion 2 with respect to the flow path defining member 54 and the size of the end plate portion 3 with respect to the bearing portion 55.

Next, the manufacturing method of the pressure vessel 1 which concerns on this embodiment is demonstrated.
In the manufacturing method of the present embodiment, as shown in the flowchart of FIG. 4, the design process P1, the intermediate product forming process P2, the preliminary pressure application process P3, the finishing process P4, and the pressure resistance test process P5 are sequentially performed. It is to be implemented.
The intermediate product forming step P2 is a step of forming an intermediate product 1A (see FIGS. 2 and 3) having a shape corresponding to the final shape of the pressure vessel 1, and the design step P1 is based on the final shape of the pressure vessel 1. This is a process of designing the shape and dimensions of the product 1A. Details of the design process P1 will be described later.

The intermediate product forming process P2 includes a casting process P21, a rough machining process P22, and a welding process P23. For example, the casting process P21, the rough machining process P22, and the welding process P23 are performed in order. To implement.
The casting process P21 is a process in which the peripheral wall portion 2A and the end plate portion 3A (see FIGS. 2 and 3) in the intermediate product 1A are integrally formed, and the suction pipe and the discharge pipe in the intermediate product 1A are separately formed. Further, the rough machining step P22 is performed on the peripheral wall portion 2A, the end plate portion 3A, the suction pipe, and the discharge pipe formed in the casting step P21 so as to have the dimensions of the intermediate product 1A set in the design step P1. Each of these is a process of performing cutting or the like. Furthermore, the welding process P23 is a process of connecting the suction pipe and the discharge pipe after the casting process P21 to the peripheral wall portion 2A by welding.

In the intermediate product forming process P2, for example, after the welding process P23, a rough machining process P22 for cutting the peripheral wall portion 2A and the end plate portion 3A may be performed.
Moreover, when especially the surrounding wall part 2 is large sized among the pressure vessels 1 of the last shape, for example, in the casting process P21, a plurality of divided bodies obtained by appropriately dividing the surrounding wall part 2A and the end plate part 3A in the intermediate product 1A are provided. The peripheral wall portion 2A and the end plate portion 3A in the intermediate product 1A may be formed by forming each separately and connecting the plurality of divided bodies by welding in the welding process P23.

  In the intermediate product 1A obtained by the intermediate product forming step P2, residual stress is generated in a part or the whole of the intermediate product 1A mainly by the above-described welding or the like. In the intermediate product 1A in this state, the residual stress σa is generated at the plot point a in the stress strain diagram of FIG.

The preliminary pressure application process P3 is a process in which the preliminary product Pe is applied to the pressure chamber 7A (see FIG. 2) in the intermediate product 1A after the intermediate product formation process P2 to plastically deform the intermediate product 1A. The preliminary pressure Pe is a pressure larger than the pressure resistance Pt applied to the pressure chamber 7 in the pressure vessel 1 in the pressure test step P5 described later.
In the preliminary pressure application process P3, for example, water pressure is applied as the preliminary pressure Pe. In other words, a hydraulic jig (not shown) or the like is attached to the intermediate product 1A so as to block a portion of the intermediate product 1A that opens to the outside (for example, the opening portion of the end plate portion 3A, the suction pipe, and the discharge pipe). Then, the pressure chamber 7A of the intermediate product 1A is filled with water. Then, this water causes a preliminary pressure Pe (water pressure) to act in the pressure chamber 7A, and this preliminary pressure Pe is held for a predetermined time. By applying the preliminary pressure Pe in this way, the preliminary pressure Pe acts uniformly on the surface to be pressurized in the pressure chamber 7A. Thereafter, the pressure in the pressure chamber 7A is lowered from the preliminary pressure Pe, and water is discharged from the pressure chamber 7A.
2 and 3, for example, as shown in FIGS. 2 and 3, the above-mentioned pressure-sensitive surface is the peripheral wall portion 2A of the intermediate product 1A and the inner surface 8A of the end plate portion 3A, and will be referred to as “pressure-sensitive surface 8A” in the following description.

In the preliminary pressure operation step P3 performed in this way, the intermediate product 1A is plastically deformed in a state where the preliminary pressure Pe is acting in the pressure chamber 7A of the intermediate product 1A. The stress increases temporarily. That is, in the intermediate product 1A in the state so far, the residual stress σb is generated by moving from the plot point a to the plot point b in the stress strain diagram of FIG.
As shown in the stress-strain diagram of FIG. 5, the stress generated in the intermediate product 1A by applying the preliminary pressure Pe, that is, the residual stress σa before the preliminary pressure application process P3, and the preliminary pressure application process P3 the difference between the residual stresses .sigma.b the (σb-σa), defined as the pre-pressure acting upon stress sigma _Pe.

Then, when the preliminary pressure operation step P3 is terminated by removing (unloading) the preliminary pressure Pe, the shape of the intermediate product 1A is elastically restored (elastically restored). By the unloading of the preliminary pressure Pe, the residual stress of the intermediate product 1A is relieved and moved from the plot point b to the plot point c in the stress strain diagram of FIG.
Here, the magnitude of the residual stress δc after the preliminary pressure application step 3 indicated by the plot point c is determined by the magnitude of the preliminary pressure Pe, and the stress strain line rises to the right in the plastic deformation region of the stress strain diagram. In general, the residual stress σc decreases as the preliminary pressure Pe increases.

Therefore, the residual stress σc can be set lower than the residual stress σa as shown in FIG. 5 by appropriately setting the magnitude of the preliminary pressure Pe in the preliminary pressure application step P3.
In other words, the magnitude of the preliminary pressure Pe is set so that the residual stress σc in the intermediate product 1A after unloading the preliminary pressure Pe is smaller than the residual stress σa in the intermediate product 1A before the preliminary pressure application step P3. Is done.
Thereby, the residual stress σa generated by welding or the like can be reduced / removed.

  The finishing process P4 is a process in which the intermediate product 1A after the preliminary pressure application process P3 is processed to finish the pressure vessel 1 into a final shape. That is, in this step, the final shape of the pressure vessel 1 is obtained by performing cutting or grinding on the intermediate product 1A.

  The pressure test step P5 that is finally performed is a step in which the pressure resistance Pt required as the pressure chamber 7 in the pressure vessel 1 is applied to the pressure chamber 7 of the final-shaped pressure vessel 1 that has been finished. That is, the pressure resistance Pt can act in the pressure chamber 7 of the pressure vessel 1 in a state where the pressure vessel 1 is actually used as a product (specifically, a state where the pressure vessel 1 is incorporated in the centrifugal compressor 50). The pressure is higher than the maximum pressure, and is set in advance in consideration of safety.

  In this pressure resistance test process P5, the water pressure is made to act as the pressure resistance Pt, as in the case of the preliminary pressure application process P3. That is, the pressure chamber 7 of the pressure vessel 1 is filled with water after a hydraulic jig or the like is attached to the pressure vessel 1 so as to block the portion of the pressure vessel 1 that opens to the outside. Then, with this water, a pressure resistance Pt (water pressure) is applied to the pressure chamber 7, and the pressure resistance Pt is maintained for a predetermined time. By applying the pressure resistance Pt in this way, the pressure resistance Pt acts uniformly on the surface to be pressurized of the pressure chamber 7. Thereafter, the pressure acting on the pressure chamber 7 is lowered from the pressure resistance Pt, and water is discharged from the pressure chamber 7. The above-mentioned pressure-receiving surface is, for example, as shown in FIGS. 2 and 3, the peripheral wall portion 2 of the pressure vessel 1 and the inner surface 8 of the end plate portion 3, and will be referred to as “pressure-receiving surface 8” in the following description.

In the pressure test step P5 performed in this way, it is necessary to set the pressure resistance Pt as follows.
As shown in the stress-strain diagram of FIG. 5, the stress generated in the pressure vessel 1 by applying the pressure resistance Pt, that is, the increase in the stress due to the pressure resistance Pt from the residual stress σc after the preliminary pressure application step P3. _Is defined as a stress at test σ _Pt .
According to the stress strain diagram of FIG. 5, the pressure resistance Pt applied to the pressure vessel 1 in the pressure test step P5 is the residual stress σb at the preliminary pressure application step P3 and the residual pressure after the preliminary pressure application step P3. The relationship between the stress σc and the test stress σ _Pt is
σb ≧ σc + σ _Pt ,
It is necessary to set within the range that satisfies As described above, since the preliminary pressure Pe is set to a value higher than the withstand pressure Pt, the residual stress σc after the preliminary pressure application process P3 is made smaller than the residual stress σa before the preliminary pressure application process P3. Generally, this relationship is satisfied if the preliminary pressure Pe is set appropriately.

By setting the pressure resistance Pt in this way, in the pressure resistance test process P5, even if the pressure resistance Pt acts in the pressure chamber 7 of the pressure vessel 1, the pressure vessel 1 is only elastically deformed and is plastic. Does not deform. That is, in the pressure vessel 1 in a state where the pressure resistance Pt is applied in the pressure chamber 7, the pressure vessel 1 only moves from the plot point c to the plot point d in the stress strain diagram of FIG. The residual stress σb during the preliminary pressure application process P3 is not exceeded.
Then, when the pressure resistance test process P5 is terminated (unloading) except for the pressure resistance Pt, the pressure container 1 is elastically restored, so that the shape and dimensions of the pressure container 1 return to the state after the finishing process P4. (Returns to plot point c in the stress-strain diagram of FIG. 5).

By the way, in the manufacturing method of the present embodiment, the preliminary pressure Pe is applied to the pressure chamber 7A in the intermediate product 1A in the preliminary pressure application step P3 to plastically deform the intermediate product 1A. It will be displaced to the outside of the product 1A. Therefore, in the intermediate product forming process P2 described above, as shown in FIGS. 2 and 3, the surplus surface 9 of the pressure chamber 7 in the final-shaped pressure vessel 1 is provided with a surplus wall 9, so that the pressure chamber 7A in the intermediate product 1A A pressure-receiving surface 8A is formed.
Here, the thickness Δt (remaining thickness Δt) of the surplus material 9 is set so that the intermediate product 1A is plastically deformed and the pressure-receiving surface 8A is displaced at least in the preliminary pressure application process P3, and the finishing process P4. Thus, the pressure-receiving surface 8A of the pressure chamber 7A in the intermediate product 1A after the preliminary pressure application step P3 may be set to such an extent that the pressure-receiving surface 8 of the pressure chamber 7 in the final-shaped pressure vessel 1 can be finished. In other words, in the intermediate product forming step P2, the intermediate product 1A can be plastically deformed without being damaged even if the preliminary pressure Pe higher than the pressure resistance Pt acts on the pressure chamber 7A in the preliminary pressure application step P3. The wall thickness ta of the product 1A may be set so as to be thicker by the surplus thickness Δt than the wall thickness tc of the final-shaped pressure vessel 1. The wall portion in the pressure vessel 1 (intermediate product 1A) mainly indicates the peripheral wall portion 2 (2A) and the end plate portion 3 (3A). In the following description, “wall portions 2 and 3”. Or it may be described as “wall portions 2A, 3A”.

The surplus thickness Δt in the present embodiment is set in the design process P1 that is performed before the intermediate product forming process P2.
That is, in the design process P1, the amount of displacement of the pressure-receiving surface 8 generated by plastic deformation of the pressure vessel 1 when the pressure resistance Pt is applied to the pressure chamber 7 of the pressure vessel 1 is analyzed by FEM analysis. The thickness Δt is set to a value equal to or greater than this displacement amount.
Here, when the shape of the pressurized surface 8 is different among a plurality of parts (for example, the peripheral wall portion 2 and the end plate portion 3) of the pressure vessel 1 as in the pressure vessel 1 of the present embodiment, the analysis is performed by the FEM analysis. Since the displacement amount of the pressure-receiving surface 8 is different depending on a plurality of parts, in the design process P1 of the present embodiment, after setting the largest value among the displacement amounts of the plurality of pressure-receiving surfaces 8 as the maximum displacement amount, The surplus thickness Δt is set to a value greater than the maximum displacement. The specific surplus thickness Δt is preferably set to be not less than 2 times and not more than 3 times the maximum displacement amount in consideration of safety.

Further, in the design process P1, after setting the surplus thickness Δt, the preliminary pressure Pe to be applied in the pressure chamber 7A of the intermediate product 1A is set in the preliminary pressure application process P3.
Specifically, in the design process P1, after analyzing the stress σ _Pt at the time of the test that occurs in the pressure vessel 1 when the pressure resistance Pt is applied to the pressure chamber 7 of the pressure vessel 1 by FEM analysis, as preliminary pressure acting upon stress sigma _Pe generated when the pressure is applied to the pressure chamber 7A of the intermediate article 1A obtained by adding the excess material thickness Δt is tested at stress sigma _Pt or sets the preliminary pressure Pe .

A specific method for setting the preliminary pressure Pe will be described with reference to FIG. In the graph of FIG. 6, the horizontal axis is the pressure P applied to the pressure chambers 7 and 7A in the pressure vessel 1 or the intermediate product 1A taking into account the surplus thickness Δt, and the vertical axis is the pressure P. This is a stress σ generated in the pressure vessel 1 or the intermediate product 1A by acting in the chambers 7 and 7A.
As apparent from the graph of FIG. 6, the relationship between the pressure P and the stress σ is a simple proportional relationship in which the increase amount of the stress σ (the increase rate of the stress σ) is constant with respect to the increase amount of the pressure P. Further, the rate of increase of the stress σ decreases as the wall thickness tc (ta) of the walls 2 and 3 (2A and 3A) in the pressure vessel 1 (or the intermediate product 1A) increases. That is, the increase rate of the stress σ in the intermediate product 1A is smaller than the increase rate of the stress σ in the pressure vessel 1. The stress σ acting on the pressure-receiving surfaces 8 and 8A of the pressure vessel 1 or the intermediate product 1A can be uniquely determined by the pressure P acting on the pressure-receiving surfaces 8 and 8A and the wall thicknesses tc and ta. .

Therefore, the test stress σ _Pt generated in the pressure vessel 1 when the pressure resistance Pt is applied acts on the pressure vessel 1 in a preset thickness ta of the walls 2 and 3 of the pressure vessel 1 and the pressure test step P5. The calculation is performed in consideration of the withstand pressure Pt.
Specifically, the preliminary pressure _{Pe at} which the _prestressing stress σ _Pe is equal to or greater than the test stress σ _Pt is the pressure P applied to the intermediate product 1A, which is the wall thickness tc, as shown in FIG. In the proportional relationship with the stress σ generated in the intermediate product 1A (straight line 1 in FIG. 6), a pressure Pe0 or more that is equal to or greater than the test stress σ _Pt (within the hatching region indicated by σ _Pe in FIG. 6) become.

  In the pressure vessel 1 of the present embodiment, as described above, the shape of the pressure-receiving surface 8 and the wall thicknesses tc of the wall portions 2 and 3 are formed in a plurality of portions (the peripheral wall portion 2 and the end plate portion 3) of the pressure vessel 1. Therefore, the type (for example, tensile stress and bending stress) and the magnitude of the load stress generated in the pressure vessel 1 or the intermediate product 1A differ depending on the part. For example, the type and magnitude of the generated stress are different between the peripheral wall portion 2 of the pressure vessel 1 having the curved pressure surface 8 and the end plate portion 3 of the pressure vessel 1 having the flat pressure surface 8.

For this reason, when the preliminary pressure Pe described above is set in the design process P1 of the present embodiment, the above-described test stress σ _Pt is analyzed for a plurality of parts of the pressure vessel 1 by FEM analysis, and then the intermediate product Corresponding to each of a plurality of parts so that the aforementioned stress σ _Pe at the time of the pre-pressing action generated at each part of 1A is _{equal to} or greater than the stress at test σ _Pt of each part of the pressure vessel 1 corresponding to each part of the intermediate 1A Set the preliminary pressure for each part. And the highest value among these several site | part preliminary pressures is set as the preliminary pressure Pe used in the preliminary pressure action process P3.
Further, when the preliminary pressure Pe is set as described above, the test stress σ _Pt and the preliminary pressure acting stress σ _Pe in the same part of the pressure vessel 1 and the intermediate product 1A are a plurality of types of load stress (for example, tensile stress). , Bending stress, etc.), and the largest one is selected and set.

Hereinafter, a specific setting example of the preliminary pressure Pe for the pressure vessel 1 of the present embodiment will be shown.
For example, the pressure resistance Pt that acts on the pressure vessel 1, the wall thickness tc of the peripheral wall portion 2 of the pressure vessel 1, and the wall thickness ta of the peripheral wall portion 2A of the intermediate product 1A, respectively,
Pt = 6 (MPa), tc = 90 (mm), ta = 95 (mm),
Is set, the site-specific preliminary pressure Pe1 that acts on the peripheral wall portion 2A of the intermediate product 1A is
Pe1 ≧ 6 × (95/90) ² = 6.3 (MPa),
Is calculated.
And, for example, the site-specific preliminary pressure Pe2 that acts on the end plate portion 3 of the intermediate product 1A is
Pe2 ≧ 6.8 (MPa),
Is calculated, the preliminary pressure Pe used in the preliminary pressure operation step P3 is
Pe ≧ 6.8 (MPa),
Is set.
Since the numerical value of 6.8 (MPa) is the lower limit value of the preliminary pressure Pe, the safety factor of the pressure vessel 1 after manufacture and the pressure acting on each part of the intermediate product 1A in the preliminary pressure operation step P3 Considering variation and the like, the preliminary pressure Pe may be set to 7.0 (MPa), for example.

As described above, according to the method for manufacturing the pressure vessel 1 according to the present embodiment, in the preliminary pressure application step P3, the preliminary pressure Pe acts uniformly on the pressure-receiving surface 8A of the entire pressure chamber 7A in the intermediate product 1A. Therefore, even if the pressure vessel 1 to be manufactured is large, the residual stress of the intermediate product 1A can be sufficiently reduced and removed.
Further, since the preliminary pressure application process P3 is a process of applying pressure to the pressure chamber 7A in the same manner as the pressure resistance test process P5, it can be performed using the same equipment as the pressure resistance test process P5. Further, in the preliminary pressure application process P3 and the pressure resistance test process P5, pressure is applied from the inside of the intermediate product 1A and the pressure vessel 1, so that no facility for accommodating the intermediate product 1A and the pressure vessel 1 is required. Therefore, even when the large pressure vessel 1 is manufactured, the equipment cost required for manufacturing the pressure vessel 1 can be kept low.

Further, in the above manufacturing method, the finishing process P4 is performed between the preliminary pressure application process P3 and before the pressure test process P5 to finish the intermediate product 1A into the final shape pressure vessel 1, but the pressure test is performed. In the process P5, since the pressure vessel 1 is not plastically deformed, even when the large pressure vessel 1 is manufactured, the pressure vessel 1 having a highly accurate dimension can be provided as a product. In particular, since the dimensions of the pressure chamber 7 can be set with high accuracy, it can be provided as a product used for the centrifugal compressor 50.
In addition, since the conventional annealing process is not performed in the above manufacturing method, unintentional plastic deformation due to internal thermal stress can be prevented, and the corrosion resistance of the pressure vessel 1 is reduced regardless of the material of the pressure vessel 1. And stress corrosion cracking can be prevented.

  And in the said manufacturing method, the surplus thickness 9 is given to the to-be-pressured surface 8A in the intermediate product 1A in the intermediate product forming step P2, and the wall thicknesses 2A and 3A of the intermediate product 1A are set in the pressure vessel 1 of the final shape. By setting the wall portions 2 and 3 to be thicker than the wall thickness tc, the intermediate product 1A can be reliably plastically deformed in the preliminary pressure application step P3, and the intermediate product 1A after the preliminary pressure application step P3. The finishing process P4 can be performed on the surface.

  Furthermore, in the design process P1, the surplus thickness Δt is equal to or greater than the displacement amount of the pressure-receiving surface 8 generated by plastic deformation of the pressure vessel 1 when the pressure resistance Pt is applied to the pressure chamber 7 of the pressure vessel 1. Since the value is set, the thickness ta of the wall portions 2 and 3 in the intermediate product 1A after the preliminary pressure application step P3 is equal to or greater than the wall thickness tc of the wall portion in the final-shaped pressure vessel 1. Therefore, in the finishing process P4, the final-shaped pressure vessel 1 can be finished according to the dimensions of the pressure vessel 1 that are reliably requested by cutting or the like. In other words, it is possible to reliably prevent the finishing process P4 from being performed on the intermediate product 1A after the preliminary pressure application process P3.

  Further, according to the manufacturing method of the present embodiment, the residual stress σc in the intermediate product 1A after unloading the preliminary pressure Pe is made smaller than the residual stress σa in the intermediate product 1A before the preliminary pressure application step P3. By setting the preliminary pressure Pe, it is possible to reliably prevent the pressure vessel 1 having the final shape from being plastically deformed in the pressure resistance test step P5 after the preliminary pressure operation step P3. Further, by setting the preliminary pressure Pe in this way, when the preliminary pressure operation step P3 is performed, the intermediate product 1A is more reliably plastically deformed, and the pressure-receiving surface 8A of the pressure chamber 7A in the intermediate product 1A is more reliably determined. It can also be displaced.

In particular, in the manufacturing method of the present embodiment, the _prestressing stress σ _Pe generated in each part of the intermediate product 1A is _{equal to} or greater than the stress σ _Pt during testing of each part of the pressure vessel 1 corresponding to each part of the intermediate product 1A. Thus, since the preliminary pressure for each part in each part is set and the highest value among the preliminary pressures for each part is set as the preliminary pressure Pe, the pressure chamber 7A as in the pressure vessel 1 of the present embodiment. Even when the preliminary pressure application step P3 is performed, all of the plurality of portions of the intermediate product 1A (the entire intermediate product 1A) can be reliably plastically deformed, and the plurality of intermediate products 1A It is possible to reliably displace the pressure-receiving surface 8A of all the parts. Therefore, even if the pressure chamber 7 of the pressure vessel 1 to be manufactured has a complicated shape, it is possible to reliably prevent the final shape of the pressure vessel 1 from being plastically deformed by the pressure resistance Pt in the pressure resistance test process P5.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG. The manufacturing method according to this embodiment includes the same steps as those in the first embodiment shown in FIG. 4 and differs only in the setting method of the surplus thickness Δt in the design step P1.
As shown in the flowchart of FIG. 7, in the design process P <b> 1 of the manufacturing method according to the present embodiment, first, with respect to a plurality of parts of the pressure vessel 1, the pressure resistance Pt is set in the pressure chamber 7 of the pressure vessel 1 by FEM analysis. When the pressure vessel 1 is made to act, the displacement amount of the pressure surface 8 caused by plastic deformation is analyzed (first step S1), and then the largest value among the displacement amounts of the plurality of pressure surfaces 8 is set as the maximum displacement amount. Set (second step S2). Then, a value equal to or greater than the maximum displacement amount is set as the surplus thickness Δt1 to be given to the pressure-receiving surface 8 of the pressure vessel 1 (third step S3). These first to third steps S1 to S3 are the same as in the first embodiment.

Thereafter, in the design process P1 of the present embodiment, when the preliminary pressure Pe is applied to the pressure chamber 7A of the intermediate product 1A in consideration of the surplus thickness Δt1, the plurality of parts of the intermediate product 1A are obtained by FEM analysis again. The amount of displacement of the pressure-receiving surface 8A at a plurality of sites caused by plastic deformation is analyzed (fourth step S4).
And the displacement amount of the to-be-pressed surface 8A of the some site | part analyzed in the 4th step is compared with the surplus thickness Δt1 of each corresponding site | part (5th step S5).

In this fifth step S5, when it is determined that there is a part (insufficient part) in which the displacement amount of the pressure-receiving surface 8A is larger than the surplus thickness Δt1 in the plurality of parts, The additional surplus Δt2 is added to the pressure-receiving surface 8A, the new surplus thickness Δt1 is set (sixth step S6), and the fourth step is performed again.
The additional surplus Δt2 added to the deficient site pressure surface 8A in the sixth step S6 includes the displacement amount of the deficient site pressure surface 8A analyzed in the fourth step, and the surplus thickness Δt1 before addition. It is set to be equal to or greater than the difference. That is, when the surplus thickness Δt1 before addition is “oldΔt1”, the new surplus thickness Δt1 is “newΔt1”, and the displacement amount of the pressed surface of the insufficient portion is “displacement amount”, “newΔt1”
newΔt1 = oldΔt1 + Δt2 ≧ displacement amount.

If it is determined in the fifth step S5 that the deformation amount of the plurality of parts is equal to or less than the surplus thickness Δt1 corresponding to each of the plurality of parts, the surplus thickness Δt1 is determined as the intermediate product forming step. It is set as the surplus thickness Δt given to the pressurized surface 8 of the pressure chamber 7 of the pressure vessel 1 at P2 (seventh step S7).
Thus, the design of the surplus thickness in the design process P1 of the present embodiment is completed.

As explained above, according to the manufacturing method of the pressure vessel 1 which concerns on 2nd embodiment, there exists an effect similar to 1st embodiment.
Moreover, in the manufacturing method of this embodiment, even if the pressure chamber 7 has a complicated shape like the pressure vessel 1 of this embodiment, the surplus thickness Δt is set for each part of the pressure vessel 1 in the design process P1. Therefore, it is possible to minimize the surplus thickness Δt applied in the intermediate product forming process P2. In other words, the wall thickness 2a, 3A of the intermediate product 1A can be prevented from becoming unnecessarily thick.
Furthermore, by suppressing the surplus thickness Δt to a minimum, the amount of processing the pressure-receiving surface 8A of the intermediate product 1A into the pressure-receiving surface 8 of the pressure vessel 1 in the finishing process P4 is reduced, and man-hours in the process are reduced. It becomes possible.

In order to minimize the surplus thickness Δt applied in the intermediate product formation process P2, for example, the additional surplus thickness Δt2 is determined by the amount of displacement of the pressure-receiving surface 8A of the insufficient portion analyzed in the fourth step, To be equivalent to the difference from the extra thickness Δt1 before addition, ie,
newΔt1 = oldΔt1 + Δt2 = displacement amount,
It is more preferable to set so that.

Although the details of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.
For example, the determination in the fifth step S5 in the second embodiment is not limited to being applied to the entire pressure vessel 1 (all portions of the pressure vessel 1), and at least high dimensional accuracy is required among the pressure vessels 1. It may be applied only to a part (high demand part).
In this case, it is not necessary to perform the determination in the fifth step S5 for the portion of the pressure vessel 1 that does not require high dimensional accuracy (low requirement portion). For example, the reference is looser than the fifth step S5. You may implement the step determined by.

  Specifically, the amount of displacement of the pressure-requiring surface 8A of the low requirement portion analyzed in the fourth step is obtained by adding a virtual predetermined thickness to the surplus thickness Δt1 of the low requirement portion (virtual surplus thickness) In comparison with the second embodiment, the sixth step and the fourth step similar to those of the second embodiment are performed until the displacement amount of the pressure-receiving surface 8A of the low-requirement region is equal to or less than the virtual surplus thickness, When the displacement amount of the pressure surface 8A becomes equal to or less than the virtual surplus thickness, the surplus thickness Δt1 of the low requirement part is applied to the pressure-receiving surface 8 of the pressure chamber 7 of the pressure vessel 1 in the intermediate product forming process P2. It may be set as Δt.

  In addition, the steps and order performed in the intermediate product forming step P2 of the above embodiment are not limited to those of the above embodiment, and may be appropriately changed depending on the application, shape, and the like of the pressure vessel 1. Accordingly, the intermediate product forming process P2 may include, for example, at least one or two of the casting process P21, the rough machining process P22, and the welding process P23, or the casting process P21 and the rough machining process P22. The order of the welding process P23 may be changed as appropriate.

  Furthermore, the manufacturing method of the present invention is not limited to being applied to the pressure vessel 1 used in the centrifugal compressor 50 as in the above embodiment, but is applied to the pressure vessel 1 having at least the pressure chamber 7 to be pressurized. For example, the present invention can be applied to a pressure vessel used for another rotating machine (for example, a turbine) different from the centrifugal compressor 50.

For example, when the pressure vessel has a simple shape such as a hollow sphere, or when a portion of the pressure vessel that requires high dimensional accuracy is a simple shape, the design process P1 includes the maximum It is not necessary to set the surplus thickness Δt based on the amount of displacement or to set the preliminary pressure Pe based on the preliminary pressure for each region.
Further, the manufacturing method of the present invention may not include the design process P1 as in the above-described embodiment, for example, at least the intermediate product forming process P2, the preliminary pressure application process P3, the finishing process P4, and the pressure resistance test process. What is necessary is just to provide P5.

DESCRIPTION OF SYMBOLS 1 ... Pressure vessel, 2 ... Peripheral wall part (wall part), 3 ... End plate part (wall part), 7 ... Pressure chamber, 8 ... Pressurized surface (inner surface), Pt ... Pressure resistance, 1A ... Intermediate product, 2A ... Peripheral wall Part (wall part), 3A ... end plate part (wall part), 7A ... pressure chamber, 8A ... pressure surface (inner surface), 9 ... surplus, Δt, Δt1 ... surplus thickness, Pe ... pre-pressure

Claims (7)

A method of manufacturing a pressure vessel having a pressure chamber to be pressurized,
An intermediate product forming step for forming an intermediate product having a shape corresponding to the final shape of the pressure vessel;
A pre-pressure operation step of plastically deforming the intermediate product by applying a pre-pressure greater than a pressure resistance required as a pressure chamber in the final-shaped pressure vessel in the pressure chamber of the intermediate product;
A finishing process for processing the intermediate product after the preliminary pressure is applied in the preliminary pressure application process and finishing the final product,
A pressure vessel manufacturing method comprising: a pressure test step for performing a pressure test for applying the pressure resistance in a pressure chamber of a final-shaped pressure vessel that has been finished.   The size of the preliminary pressure is set so that the residual pressure in the intermediate product after unloading the preliminary pressure is smaller than the residual stress in the intermediate product before the preliminary pressure application step. The manufacturing method of the pressure vessel of Claim 1. In the intermediate product forming step,
The intermediate product is plastically deformed by the preliminary pressure operation step, and the pressure-receiving surface of the pressure chamber in the intermediate product is displaced.
And,
In the finishing step, the pressure surface of the pressure chamber in the intermediate product after the preliminary pressure application step can be finished to the pressure surface of the pressure chamber in the final shape pressure vessel.
The pressure vessel manufacturing method according to claim 1 or 2, wherein a surplus wall is provided to a pressure-receiving surface of the pressure chamber in the final-shaped pressure vessel to form a pressure-receiving surface of the pressure chamber in the intermediate product. Method. Before the intermediate product forming step, comprising a design process for designing the intermediate product,
In the design process, when the pressure resistance is applied to the pressure chamber of the final-shaped pressure vessel, the amount of displacement of the pressure surface caused by plastic deformation of the pressure vessel is analyzed, and the thickness of the surplus wall is calculated. The method for manufacturing a pressure vessel according to claim 3, wherein the value is set to a value equal to or greater than a displacement amount. In the design process,
A first step of analyzing a displacement amount of the pressure surface for a plurality of portions of the pressure vessel having different shapes of the pressure surface;
A second step of setting the largest value among the displacement amounts of the plurality of pressure-receiving surfaces as the maximum displacement amount;
A third step of setting a value larger than the maximum displacement amount as a thickness of the surplus wall to be given to the pressure surface in the pressure vessel;
When the preliminary pressure is applied to the pressure chamber of the intermediate product taking into account the thickness of the surplus, the amount of displacement of the pressure-receiving surface at the plurality of locations caused by plastic deformation of the plurality of locations of the intermediate product is analyzed. After performing the fourth step in order,
The amount of displacement analyzed in the fourth step among the plurality of portions is the amount of displacement analyzed in the fourth step until the displacement amount of the plurality of portions analyzed in the fourth step is equal to or less than the thickness of the surplus corresponding to each of the plurality of portions. After adding an additional surplus to the pressure-receiving surface of the intermediate product that is larger than the surplus thickness and setting a new surplus thickness, the fourth step is performed again,
The thickness of the surplus when the amount of deformation of the plurality of parts in the fourth step is equal to or less than the thickness of the surplus corresponding to each of the plurality of parts, and the pressure chamber in the pressure vessel in the intermediate product forming step The method of manufacturing a pressure vessel according to claim 4, wherein the thickness is set as a thickness of surplus material to be provided to the pressure-receiving surface. In the design process,
After analyzing the stress at the time of testing generated in the pressure vessel when the pressure resistance is applied in the pressure chamber of the pressure vessel of the final shape,
5. The preliminary pressure is set such that a stress generated when pressure is applied to the pressure chamber of the intermediate product in consideration of the thickness of the surplus is equal to or greater than the stress at the time of the test. Or the manufacturing method of the pressure vessel of Claim 5. In the design process,
After analyzing the test stress for a plurality of parts of the pressure vessel having different shapes of the pressure-receiving surface,
Each stress generated in each part of the intermediate product when the pressure is applied in the pressure chamber of the intermediate product taking into account the thickness of the surplus is equal to or greater than the stress at the time of the test corresponding to each part, Set a plurality of site-specific preliminary pressures respectively corresponding to a plurality of sites,
The method for manufacturing a pressure vessel according to claim 6, wherein the highest value among the plurality of site-specific preliminary pressures is set as the preliminary pressure.

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