JP2016132072A - Repairing method of cast steel member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To securely repair a crack generated on a cast steel member at a job site.SOLUTION: A method of repairing a cast steel member 10 by cutting a part including a crack 12 generated on a surface 11 of the cast steel member 10 and forming a groove part 17, and burying a repair member 30 in the formed groove part 17 includes: an expansion part forming process of arranging an expansion part 20 expanded laterally on at least a bottom part 21 of the groove part 17; and a repair member filling process of filling the groove part 17 having the expansion part with the repair member 30.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a technique for reliably repairing a crack generated in a cast steel member on site in a repair method for a cast steel member.

  Some cast steel members in power plant facilities, such as steam turbine casings and valves, are subjected to thermal stress when starting and stopping, and this causes cracks mainly. If a crack occurs, that part is ground and removed. When the wall thickness after removing the crack becomes thinner than the minimum required wall thickness, the member becomes unusable and must be replaced with a new one.

  As a method for repairing a crack in a butterfly valve in a cooling water pipe in a power plant, for example, in Patent Document 1, after washing with high-pressure water, a damaged portion is exposed, and a substantially U-shaped groove is formed with a grinder. Describes a method of applying an adhesive to the entire inner surface of the groove and then filling the entire groove with a natural vulcanized rubber repair material.

JP 2013-238302 A

  Patent Document 1 is to fill a crack removing portion with a rubber repair material, but from the viewpoint of maintaining its strength while maintaining the thickness of the cast steel member even after crack repair in an environment where high-temperature steam flows. It is considered preferable to build-up weld the crack removal part. However, many cast steel members in power plant facilities are large, and welding must be performed in the field. Since the temperature control is difficult in the field welding, the welded part is rapidly cooled after welding and cracking occurs. There is a possibility.

  This invention is made | formed in view of such a situation, The objective is to provide the repair method of the cast steel member for repairing the crack which generate | occur | produced in the cast steel member on-site reliably.

  In order to achieve the above-mentioned object, the present invention provides a method for repairing a cast steel member by cutting a portion including a crack generated on the surface of a cast steel member to form a groove and embedding a repair member in the formed groove. And the expansion part formation process which provides the expansion part which spreads laterally at least in the bottom part among the above-mentioned groove parts, and the repair member filling process which fills the above-mentioned repair member in the groove part which provided the above-mentioned expansion part Features.

  As in the present invention, at least the bottom portion of the groove portion is provided with an extended portion that expands laterally, and the repair member can be hardly separated from the groove portion by filling the groove portion with the repair member. Thereby, the crack which generate | occur | produced on the surface of the cast steel member can be repaired easily and reliably on-site. For example, even if the cast steel member to be repaired is a large member such as a turbine casing of a power plant, it can be reliably repaired on site without being moved to a repair factory or the like.

  Moreover, in this invention, you may make it the said repair member consist of a metallic raw material with a higher extensibility than the said cast steel member. Thereby, the thermal stress which a repair member applies to a repair site | part can be reduced, and durability of the repair site | part with respect to a thermal stress can be improved.

  Further, in the present invention, the repair member is provided with a recess, and in the repair member filling step, the repair member is inserted into the groove portion so that the recess is on the bottom surface side of the groove portion, and the inserted repair is performed. The repairing member may be filled in the groove portion by hitting a member and bringing the inner surface of the recess into contact with the bottom surface of the groove portion.

  As in the present invention, a repair member having a recess is inserted into the groove and struck to bring the inner surface of the recess into contact with the bottom surface of the groove, thereby filling the groove with the repair member. It can be filled without any gaps. Thereby, the thermal stress concerning a repair site | part can be relieve | moderated effectively with a repair member.

  Moreover, in this invention, you may make it form the inner surface of the opening of the said groove part so that it may become substantially perpendicular | vertical to the surface of the said cast steel member.

  By making the inner surface of the opening of the groove portion substantially perpendicular to the surface of the cast steel member, it is possible to prevent notching (chipping) when the repair member is inserted from the opening.

  Moreover, in this invention, you may make it have a welding process which joins the said cast steel member and the said repair member by heating the boundary part of the said cast steel member and the said embedded repair member. By welding the cast steel member and the repair member in this manner, it is possible to prevent the vapor from entering the gap between the cast steel member and the repair member to generate and grow a crack.

  According to the present invention, a crack generated on the surface of a cast steel member can be reliably repaired on site.

It is a figure explaining the outer shell member of a steam turbine casing. It is a figure which shows an example of the crack which generate | occur | produces on the surface of an outer shell member. It is a flowchart explaining the procedure of the repair method of this embodiment. 2 is a plan view of a crack 12 as viewed from above a surface 11. FIG. FIG. 5 is a cross-sectional view of a groove section cut along a surface in a crack short direction perpendicular to the surface 11. FIG. 5 is a perspective view showing an example of a repair member that fills a groove 15. FIG. 3 is a cross-sectional view of a groove portion 17 cut along a surface in a crack short direction perpendicular to the surface 11. FIG. 3 is a cross-sectional view of a groove portion 17 cut along a surface in a crack short direction perpendicular to the surface 11. FIG. 3 is a cross-sectional view of a groove portion 17 in which a repair member 30 is embedded, cut along a surface in a crack short direction perpendicular to the surface 11. FIG. 5 is a cross-sectional view of a groove section cut along a surface in the crack longitudinal direction perpendicular to the surface 11. 3 is a perspective view of a repair member 60. FIG. 3 is a front view of a repair member 60. FIG. 3 is a side view of a repair member 60. FIG. FIG. 5 is a cross-sectional view of a groove portion 50 in which a repair member 60 is embedded, cut along a plane in the crack longitudinal direction perpendicular to the surface 11.

<Example 1>
The method for repairing a cast steel member according to the present embodiment can be applied to repair of a crack generated in a cast steel member due to thermal stress, and steam provided in a thermal power plant or a nuclear power plant as shown in FIG. It can be applied to the outer shell member 10 of the turbine casing.

  The outer shell member 10 of the steam turbine casing is made of, for example, CrMoV cast steel or the like, and is subjected to thermal stress as it starts and stops. As a result, the outer shell member 10 is subjected to creep damage, and a crack 12 is generated on the inner surface 11. For example, as shown in FIG. 2, the crack 12 is a crack that appears on the surface 11 and has a maximum depth H. In this embodiment, a case where the crack 12 is repaired will be described.

  FIG. 3 is a flowchart for explaining the procedure of the repair method of this embodiment. As shown in the figure, first, the direction and dimensions of the crack 12 are confirmed (S1, hereinafter referred to as crack confirmation step S1). Next, the surface 11 including the crack 12 is cut to form a groove (S2; hereinafter referred to as a groove forming step S2). Next, a repair member is embedded in the groove (S3, hereinafter referred to as a repair member embedding step S3). Then, the buried repair member and the outer shell member 10 are welded (S4, hereinafter referred to as welding step S4). Details of these steps will be described below.

  First, the crack confirmation process S1 will be described.

  FIG. 4 is a plan view of the crack 12 as viewed from above the surface 11 of the outer shell member 10. In order to determine the cutting range for the crack 12, first, the longitudinal direction of the crack 12 on the surface 11 (hereinafter referred to as the crack longitudinal direction) and the short direction of the crack 12 on the surface 11 that is perpendicular to the crack longitudinal direction ( (Hereinafter referred to as crack short direction). Then, the length of the crack 12 in the crack longitudinal direction and the length of the crack 12 in the crack short direction are measured with a caliper or the like. In the present embodiment, it is assumed that the length in the crack longitudinal direction is L and the length in the crack short direction is W, as shown in FIG. Normally, the length of the crack 12 in the crack longitudinal direction is about 5 mm to 100 mm, and the length in the crack short direction is about 0.1 mm to 10 mm.

  A rectangular cutting line 15 composed of a long side 13 (length L2) parallel to the crack longitudinal direction and a short side 14 (length W2) parallel to the crack short direction so as to surround the crack 12 as a whole. Set.

  Next, the groove part forming step S2 will be described.

  FIG. 5 is a cross-sectional view of the groove section cut along a plane in the crack short direction perpendicular to the surface 11. As shown in the figure, the formation of the groove portion 17 starts with the cutting line 15 as a base line. That is, the surface 11 of the outer shell member 10 is ground vertically downward along the cutting line 15 with a cutter or the like, and is ground until the grinding depth reaches H2 (at least the maximum depth H of the crack 12). Continue. Thereby, a rectangular parallelepiped space (hollow part 18) is formed in the outer shell member 10.

  In addition, the length of the short side (crack short direction) of the opening 19 which is the upper end of the cavity 18 is W2, and the length of the short side (crack longitudinal direction) of the opening 19 is L2 (not shown).

  Subsequently, an extended portion 20 is formed in the bottom portion of the cavity portion 18 so that the space expands laterally toward the bottom surface 21. The extended portion 20 extends in the crack short direction, and the length W3 in the crack short direction on the bottom surface 21 of the cavity 18 is longer than the length W2 of the short side of the opening 19. In addition, although the ratio of the height H21 from the opening 19 to the upper end of the expansion part 20 and the height H22 of the expansion part 20 is arbitrary, for example, both are assumed to be approximately the same. Further, as shown in FIG. 5, the corner portion 22 at the bottom edge of the extended portion 20 may be curved to make it easier to fill the repair member 30.

  As described above, by forming the extended portion 20 at the bottom of the groove portion 17, while forming the cavity portion 18 so that the inner surface of the opening 19 of the groove portion 17 is substantially perpendicular to the surface of the outer shell member 10, Chipping (chipping) at the time of inserting the repair member into the opening 19 can be prevented.

  FIG. 6 is a perspective view illustrating an example of the repair member 30 that fills the groove portion 17. As shown in the figure, the repair member 30 is a rectangular parallelepiped member and has a side corresponding to the dimension of the groove portion 17. Specifically, the repair member 30 includes a side 31 (length W2) corresponding to the short side of the opening 19, a side 32 (length L2) corresponding to the long side of the opening 19, and a depth H2 of the groove portion 17. It has a slightly longer side 33 (length H3). H3 is a length such that the volume of the repair member 30 is approximately the same as the space volume of the groove portion 17 (the reason will be described later).

  In addition, as shown in FIG. 6, the repair member 30 is formed with a recess 34. That is, a concave portion 34 extending in the longitudinal direction is provided in the center portion in the short direction of the bottom surface of the repair member 30.

  The repair member 30 is made of a metallic material having a higher spreadability than the outer shell member 10. For example, pure nickel, pure chromium, pure silver, silver-tin alloy and the like.

  Next, the repair member embedding process S3 will be described.

  7 and 8 are diagrams for explaining a method for inserting and embedding the repair member 30 into the groove portion 17.

  FIG. 7 is a cross-sectional view of the groove portion 17 cut along a surface in the crack short direction perpendicular to the surface 11 for explaining a method of inserting the repair member 30. As shown in the figure, the concave portion 34 of the repair member 30 is set downward, and the longitudinal direction of the bottom surface of the repair member 30 is the longitudinal direction of the opening 19, and the short direction of the bottom surface of the repair member 30 is the short side of the opening 19. After the orientation, the repair member 30 is inserted toward the bottom surface 21 of the groove portion 17.

  FIG. 8 is a cross-sectional view of the groove member 17 in which the repair member 30 is embedded, cut along a plane in the crack short direction perpendicular to the surface 11, illustrating a method for embedding the repair member 30. As shown in the figure, after the repair member 30 is inserted into the groove portion 17 until the concave portion 34 of the repair member 30 reaches the bottom surface 21 of the groove portion 17, the upper surface 41 of the repair member 30 is struck from above with a hammer or the like (reference numeral 40). ).

  By repeatedly hitting the repair member 30, the repair member 30 is deformed, and the space 42 surrounded by the bottom surface 21 of the groove portion 17 and the recess portion 34 is gradually narrowed. As a result, the repair member 30 enters the space of the expansion portion 20, and the entire groove portion 17 is filled with the repair member 30.

  Further, as described above, the height H3 of the repair member 30 is designed so that the volume of the repair member 30 is the same as the space volume of the groove portion 17, so that the groove portion 17 is filled with the repair member 30. Then, the height of the top surface of the repair member 30 is lowered to the height of the surface 11. Thereby, the surface of the repair site | part of the outer shell member 10 can be smoothed. If the upper surface 41 of the repair member 30 protrudes from the surface 11 of the outer shell member 10 even when the repair member 30 is completely filled in the groove portion 17, the protruding portion may be cut.

  Finally, the welding process S4 will be described.

  FIG. 9 is a cross-sectional view illustrating the welding step S <b> 4, in which the groove portion 17 in which the repair member 30 is embedded is cut along a surface in the crack short direction perpendicular to the surface 11. As shown in the figure, the outer shell member 10 and the repair member 30 are heated by heating the boundary between the repair member 30 and the outer shell member 10 (the peripheral edge 43 of the upper surface 41 of the repair member 30) with a laser welding machine or the like. Join (weld). Thereby, it can prevent that a vapor | steam penetrate | invades in the clearance gap between the outer shell member 10 and the repair member 30, and a crack generate | occur | produces and grows.

  Instead of joining using a laser welding machine, the repair member 30 may be melted (for example, melted at 900 ° C. or lower) by TIG welding using a welding torch (TIG torch or the like) (for example, When the material of the repair member 30 is pure silver).

  Further, instead of directly welding the boundary portion between the outer shell member 10 and the repair member 30, a groove is provided to straddle the outer shell member 10 and the repair member 30, and a predetermined metal member is built up on the groove. You may make it weld (laser welding).

  As described above, according to the method for repairing a cast steel member of the present embodiment, at least the bottom portion of the groove portion 17 is provided with the extended portion 20 that extends laterally, and the repair member 30 is filled in such a groove portion 17. The repair member 30 can be made difficult to be detached from the dovetail groove 17. Thereby, the crack 12 which arose on the surface of the cast steel member can be repaired easily and reliably on site. For example, even if the cast steel member to be repaired such as the outer shell member 10 is a large member such as a turbine casing of a power plant, it can be reliably repaired on site without being moved to a repair factory or the like. it can.

  In addition, since the repair member 30 is made of a metallic material having higher extensibility than the cast steel member, the repair member 30 can reduce the thermal stress applied to the repair site and improve the durability of the repair site against the thermal stress. it can.

  Further, the repair member 30 having the concave portion 34 is inserted into the groove portion 17 and struck to bring the concave portion 34 into contact with the bottom surface 21 of the groove portion 17, thereby filling the groove portion 17 with the repair member 30. The groove portion 17 can be reliably filled without a gap. Thereby, the thermal stress concerning a repair site | part can be relieve | moderated effectively by the repair member 30. FIG. The repair member 30 may not necessarily be provided with the recess 34 as long as the repair member 30 can be filled in the groove portion 17 without any gap.

<Example 2>
In the first embodiment, the groove portion 17 has a shape that expands in the lateral direction of the crack, and the repair member 30 is embedded in the groove portion 17. However, the groove portion 17 that extends in the longitudinal direction of the crack may be formed. .

  FIG. 10 is a cross-sectional view of the groove section cut along a plane in the crack longitudinal direction perpendicular to the surface 11 according to the present embodiment. As shown in the figure, the extension 51 in the groove 50 is a space that expands toward the bottom in the longitudinal direction of the crack. That is, the length L3 in the crack longitudinal direction at the bottom surface 52 of the groove 50 is longer than the length L2 in the crack longitudinal direction of the groove 50 (L3> L2).

  FIGS. 11-13 is a figure which shows an example of the repair member 60 which concerns on a present Example. 11 is a perspective view of the repair member 60, FIG. 12 is a front view of the repair member 60, and FIG. 13 is a side view of the repair member 60. As shown in these drawings, the repair member 60 is a substantially rectangular parallelepiped member similar to that of the first embodiment, but has a recess 64 having a shape different from that of the first embodiment. That is, the concave portion 64 is provided with the center of the bottom surface of the repair member 60 as the deepest portion.

  In the case of embedding the repair member 60, the operation is as follows.

  FIG. 14 is a cross-sectional view illustrating a method of embedding the repair member 60 in the groove 50, in which the groove 50 in which the repair member 30 is embedded is cut along a plane in the crack longitudinal direction perpendicular to the surface 11. As shown in the figure, the repair member 60 is inserted into the groove portion 50 until the concave portion 64 of the repair member 60 reaches the bottom surface 52 of the groove portion 50, and the repair member 60 is beaten from above with a hammer or the like.

  Similar to the first embodiment, by repeatedly tapping, the space 76 formed by the concave portion 64 and the bottom surface 52 of the groove portion 50 gradually narrows, and the repair member 60 moves in the short width direction and the long length direction of the crack of the groove portion 50. As a result, the entire dovetail groove 50 is filled with the repair member 60.

  As described above, in this embodiment, since the extended portion 51 is provided not only in the crack short direction but also in the crack longitudinal direction, the repair member 60 can be reliably fixed to the groove portion 50.

  The above description of the embodiments is intended to facilitate understanding of the present invention and is not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes equivalents thereof.

  For example, when the repair member is struck and the groove portion can be filled without a gap, the welding process of S4 can be omitted.

  In this embodiment, the extended portion 20 is formed only at the bottom of the groove portion 17. However, the extended portion 20 may be provided at least at the bottom portion of the groove portion 17. For example, the groove portion 17 as a whole extends from the opening to the bottom portion. You may make it become the dovetail shape (reverse C shape) which is expanding to the side, so that it goes.

DESCRIPTION OF SYMBOLS 10 Outer shell member, 11 Surface, 12 Crack, 13 Long side, 14 Short side, 15 Cutting line, 17 Groove part, 18 Cavity part, 19 Opening, 20 Expansion part, 21 Bottom face, 22 Corner part, 30 Repair member, 31 side , 32 sides, 33 sides, 34 recess, 41 top surface, 42 space, 43 peripheral edge, 50 groove portion, 51 expansion portion, 52 bottom surface, 53 opening, 60 repair member, 64 recess, 75 top surface, 76 space

Claims (5)

A method of repairing the cast steel member by cutting a portion including a crack generated on the surface of the cast steel member to form a groove, and embedding a repair member in the formed groove,
An extension portion forming step of providing an extension portion extending laterally at least at the bottom of the groove portion;
A repair member filling step of filling the repair member into the groove portion provided with the extension portion;
A method of repairing a cast steel member, characterized by comprising:   The method for repairing a cast steel member according to claim 1, wherein the repair member is made of a metallic material having a higher extensibility than the cast steel member. A recess is provided in the repair member,
In the repair member filling step, the repair member is inserted into the groove portion so that the concave portion is on the bottom surface side of the groove portion, and the inserted repair member is tapped to make the inner surface of the concave portion the bottom surface of the groove portion. The repair method for a cast steel member according to claim 1, wherein the groove is filled with the repair member by bringing the repair member into contact with each other.   The method for repairing a cast steel member according to any one of claims 1 to 3, wherein an inner side surface of the opening of the groove is formed to be substantially perpendicular to a surface of the cast steel member.   5. The method according to claim 1, further comprising a welding step of joining the cast steel member and the repair member by heating a boundary portion between the cast steel member and the embedded repair member. Repair method for cast steel members.

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