The present invention is related to the turbine rotor formed by which the two different members are joined by welding in an axial direction of a turbine rotor.
Priority is claimed on Japanese Patent Application No. 2011-064657, filed on Mar. 23, 2011, the content of which is incorporated herein by reference.
In a turbine rotor which configures a turbine such as a steam turbine or the like, depending on the location along an axial direction of the turbine rotor, the temperature of the steam passing therethrough is different. Thus, a dissimilar-metal-welding rotor joined a plurality of different members together by contacting and welding each other in axial direction has conventionally used as the turbine rotor.
As the method to weld the two members in this dissimilar-metal-welding rotor, there is a method in which front surfaces of the two members contacting each other at the tips thereof are welded so as to not penetrate to the back surfaces thereof (for example, Patent Document 1). However, in the welding of one surface as above, there is a possibility that a crack develops from seams of the two members in the weld portion remaining on the back surface. Therefore, it is necessary to perform full penetration welding that the two contacting members are welded from the front surfaces to the back surfaces thereof so as to penetrate therethrough to avoid problems as such described above.
In TIG welding generally used for producing the dissimilar-metal-welding rotor, an oxidizing of the front surface of the member at the side close to a welding torch is prevented by the inert gas introduced from the welding torch. However, in a case of performing the full penetration welding, it is necessary to prevent the oxidizing of a penetration bead formed at the back side of the two members.
In the general full penetration welding not limited in the turbine rotor, the method conventionally used to prevent the oxidizing of the penetration bead includes introducing inert gas in the back side of the members or forming a space so as to enclose penetration bead at the back side of the members and filling inert gas inside the space (for example, Patent Document 2).
In a case of the turbine rotor, a cavity portion is formed at the back side of the welding portion inside the turbine rotor, and inert gas is filled inside the cavity portion in advance. For a method to introduce the inert gas inside the cavity portion, an inspecting hole formed so as to connect from the front surface of the members to the cavity portion is used. The inspection hole is used for inspecting the welding condition on the back side of the members by inserting the fiberscope or the like, therein during the welding operation or after completing the welding operation. In addition, inert gas is introduced inside the cavity portion through the inspecting hole.
Patent Document 1: Japanese Unexamined Patent Application, First Publication No.2010-31812
Patent Document 2: Japanese Unexamined Patent Application, First Publication No. H8-206830
In the conventional turbine rotor, there is a possibility that stress concentration occurs in a surrounding area of the inspection hole formed inside the turbine rotor, and thus, it is not preferable in terms of the strength design. Therefore, a turbine rotor and the method of producing the same in which inert gas is filled in the cavity portion without forming the inspection hole are necessary to be developed.
The invention is made in view of such circumstances, and the object of the present invention is to provide a method of filling inert gas inside the turbine rotor without quality loss of the turbine rotor after welding in the turbine rotor that the two different members are in contact with each other and welded at the tips of the two different members in the axial direction of the turbine rotor.
A turbine rotor related to the present invention provides with a first member, and a second member joined to the first member, wherein the first and the second members are extended in an axial direction of the turbine rotor, a groove portion for welding is formed at a border between the first and the second members and penetrates the bottom portion of the groove portion, and a gas-introducing hole for introducing inert gas inside the turbine rotor is covered by welding.
In the turbine rotor of the present invention, inert gas is introduced into the cavity inside the turbine rotor through the gas-introducing hole to prevent oxidizing of penetration bead occurring on the members when welding the first and second members. According to the present invention, after welding the first and second members, since weld metal is filled at the gas-introducing hole, stress concentration is less likely to occur in a surrounding area of the gas-introducing hole which was existed before welding. Therefore, it is possible to prevent a reduction in strength of the turbine rotor.
In the turbine rotor related to the present invention, the material of the first member is different with that of the second member, and the border between the first and the second members in the groove portion may be close to either one of the first and second members.
In the turbine rotor of the present invention, since the border between the first and second members in the groove portion is positioned so as to be close to at least one of the two members, the gas-introducing hole can be formed at a position away from the border of the bottom of the groove portion. As described above, it is possible to form the gas-introducing hole at the desirable position by forming the gas-introducing hole at the position away from the border without reducing a positional accuracy of the hole caused by slipping a drill, which drills a hole, at the border. In addition, it is possible to drill the gas-introducing hole exactly at a predetermined drilling position, since the positional accuracy of forming the hole becomes high. Thereby, the gas-introducing hole is reliably covered during welding of the first member and the second member.
In the turbine rotor related to the present invention, the material of the first member is different from that of the second member, and the border between the first and the second members is close to the member higher in hardness of either one of the first and second members.
According to this configuration, the drill is prevented from slipping toward the low-hardness member by bouncing off from the high-hardness member and it is possible to form a hole by penetrating only the low-hardness member.
In the turbine rotor related to the present invention, each of connecting surfaces of the first and the second members may be formed in a shape fitted into each other.
According to this configuration, the position of the two members in a state of fitting into each other at the connecting surface is fixed. Thereby, it is possible to drill the gas-introducing hole exactly at a predetermined drilling position, since it is possible to perform a drilling operation and a welding operation with a high accuracy. In addition, it is possible to cover the gas-introducing hole during the welding operation by melting the gas-introducing hole.
The production method of a turbine rotor related to the present invention in which the turbine rotor is welded a first member and a second member having different thermal conductivity with the first member, the method comprises the steps of: disposing one member at the upper side of the other member, the one member being one of the first and the second members and being higher in thermal conductivity than the other member, and the other member being the other of the first and the second members, with extending the first and the second members in an axial direction of the turbine rotor, forming a gas-introducing hole for introducing inert gas inside the turbine rotor at a bottom portion of a groove portion for welding formed at a border between the first and the second members, and welding the first and the second members in the groove portion.
According to the above production method, the heat of the welding operation from the lateral direction goes upward when the two members, which are the first member and the second member, are abutted and welded each other from up and down. Thereby, the member disposed on the upper side (upper member) is heated more strongly than the member disposed on the lower side (lower member). However, the thermal conductivity of the upper member is higher than the lower member, and thus, the upper member radiates more heat than the lower member. Therefore, a large temperature difference does not occur between the upper member and the lower member, and the entire gas-introducing hole can be covered in the welding operation.
According to the present invention, it is possible to fill inert gas inside the turbine rotor without quality loss of the turbine rotor after welding in the turbine rotor that the two different members are in contact with each other and welded in the axial direction of a turbine rotor.
Embodiments of the present invention will be explained below with reference to the figures. First, the structure of turbine rotor related to the first embodiment of the present invention will be explained.
As shown in
The high-hardness member 14 is relatively higher in hardness than that of the low-hardness member 15. As shown in
The low-hardness member 15 is relatively lower in hardness than that of the high-hardness member 14. As shown in
Here, as a combination of the high-hardness member 14 and the low-hardness member 15, for example, 9% chrome steel (a steel containing 9% chrome; same description method is applied hereafter) may be used as the high-hardness member 14, while 2.25% chrome steel or 3.5% nickel steel is used as the low-hardness member 15. In addition, 12% chrome steel may be used as the high-hardness member 14, while 2.25% chrome steel or 3.5% nickel steel is used as the low-hardness member 15. Moreover, a nickel-based superalloy may be used as the high-hardness member 14, while 2.25% chrome steel, 9% chrome steel or 12% chrome steel is used as the low-hardness member 15. Furthermore, stainless steel may be used as the high-hardness member 14, while 2.25% chrome steel, 9% chrome steel or 12% chrome steel is used as the low-hardness member 15. The combination of the high-hardness member 14 and the low-hardness member 15 is not limited as described above, and any combination can be adopted if the hardness of the members is different.
As shown in
A welding portion 12 connects the high-hardness member 14 and the low-hardness member 15. As shown in
A cavity portion 13 is a space for filling inert gas which prevents oxidizing of a penetration bead 19 at a welding operation. The cavity portion 13 is formed by combining a first concave portion 131 formed in the high-hardness member 14 and a second concave portion 132 formed in the low-hardness member 15, as shown in
Next, a production method of the turbine rotor 10 related to the first embodiment is explained. First, the worker makes a state in which the high-hardness member 14 and the low-hardness member 15 are in contact. That is, as shown in
Next, the worker forms a gas-introducing hole 18 on the bottom portion of the groove portion 16. That is, a drill D is set at the center position C toward the groove width direction of the groove portion 16, as shown in
Since the drill D passes the position avoided from the position of the border 17, the problem in which the gas-introducing hole 18 is formed at the position different from the original drilling position where should be drilled can be prevented in advance. Here,
In addition, such problems become obvious, especially in a case where the hardness of the two members joined together by welding is different. Because, when a tip of the drill D inserted into the groove portion 16 for opening the gas-introducing hole 18 reaches to the border 17 between the two members 14 and 15, a tip of the drill D bounces off the high-hardness member 14 and slips toward the low-hardness member 15 side.
Next, the worker introduces inert gas into the cavity portion 13. That is, the worker fills inert gas such as argon gas into the cavity portion 13 formed inside the rotor body 11 via a tube, or the like (not shown), inserted into the gas-introducing hole 18.
Next, the worker performs welding of the high-hardness member 14 and the low-hardness member 15. That is, as shown in
Next, the structure of turbine rotor 20 related to the second embodiment of the present invention will be explained. The turbine rotor 20 of the present embodiment is different with the turbine rotor 10 of the first embodiment only at the structure of the rotor body 21. The other structures and the production method are the same, therefore, the same reference numbers are used and the explanation thereof is omitted.
b) shows a modification of the second embodiment. In the present modification, a convex portion 24 is formed at one end portion of the high-hardness member 14, while a concave portion 25 having a shape fitted into the convex portion 24 of the high-hardness member 14 is formed at one end of the low-hardness member 15. The operation and effects thereof are the same as those of the fitting between the steps 22 and 23 shown in
b) shows another modification of the second embodiment. In the present modification, a concave portion 26 is formed at one end portion of the high-hardness member 14, while a convex portion 27 having a shape fitted into the concave portion 26 is formed at one end portion of the low-hardness member 15. The operation and effects thereof is the same as that of the fitting between the steps 22 and 23 shown in
Next, the structure of turbine rotor 30 related to the third embodiment of the present invention will be explained. The turbine rotor 30 of the present embodiment is different from the turbine rotor 10 of the first embodiment only at the structure and production method of the rotor body 31. The other structures and production method are the same as the first embodiment, therefore, the same reference numbers of the first embodiment are used and the explanation of them is omitted.
In the production method of the turbine rotor 30 configured as according to the above, as shown in
According to this production method, as shown in
The present embodiment is performed with the members in which the high-hardness member 14 is relatively high in thermal conductivity and the low-hardness member 15 is relatively low in thermal conductivity. On the contrary, the present embodiment can be performed with the members in which the high-hardness member 14 is relatively low in thermal conductivity and the low-hardness member 15 is relatively high in thermal conductivity. In this case, in producing the turbine rotor 30, the high-hardness member 14 low in thermal conductivity is disposed at the lower side, and the low-hardness member 15 high in the thermal conductivity is disposed at the upper side. Therefore, aforementioned effect of the present invention can be obtained.
In addition, in each of the embodiments explained above, two members, which are the different hardness members to each other and configure the rotor body 11, 12, and 31, are took as an example of the structure in which the drill D tends to slip. However, the present invention is not limited to the above structures, and it can be two different members equal in hardness.
In addition, the shapes of each of the members, the combination thereof and operation steps thereof, or the like, shown in aforementioned embodiments are one of the example, and the present invention can be change within a scope not departing from the gist of the present invention according to design requirements or the like.
1 steam turbine
2 casing
3 control valve
4 vane
5 blade
6 bearing
10 turbine rotor
11 rotor body
12 welding portion
13 cavity portion
14 high-hardness member
15 low-hardness member
16 groove portion
17 border
18 gas-introducing hole
19 uranami bead
20 turbine rotor
21 rotor body
22 step portion
23 step portion
24 convex portion
25 concave portion
26 concave portion
27 convex portion
30 turbine rotor
31 rotor body
131 first concave portion
132 second concave portion
141 first recessed portion
151 second recessed portion
C center position
D drill
L1 length (first recessed portion)
L2 length (second recessed portion)
S Steam
T welding torch
X a certain distance
Y1 Arrow
Y2 Arrow
Number | Date | Country | Kind |
---|---|---|---|
2011-064657 | Mar 2011 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/JP2012/057303 | 3/22/2012 | WO | 00 | 9/11/2013 |