CA1039541A - Method for welding cast steel material containing vanadium - Google Patents
Method for welding cast steel material containing vanadiumInfo
- Publication number
- CA1039541A CA1039541A CA248,008A CA248008A CA1039541A CA 1039541 A CA1039541 A CA 1039541A CA 248008 A CA248008 A CA 248008A CA 1039541 A CA1039541 A CA 1039541A
- Authority
- CA
- Canada
- Prior art keywords
- welding
- cast steel
- vanadium
- steel material
- welded
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- Arc Welding In General (AREA)
Abstract
METHOD FOR WELDING CAST STEEL MATERIAL CONTAINING VANADIUM
Abstract of the Disclosure Cast steel materials containing a vanadium component are welded to each other through a first step of build-up welding a vanadium-free metallic material, having a high creep strength at elevated temperatures, individually to the necessary parts of the cast steel material at a place having good welding conditions, and a second step of coalescing the build-up welded parts to each other at a place having less fovourable welding conditions by welding therebetween a vanadium-free metallic material having a high creep strength at elevated temperatures. In this way, cracking of the vanadium-containing cast steel materials on welding can be avoided.
Abstract of the Disclosure Cast steel materials containing a vanadium component are welded to each other through a first step of build-up welding a vanadium-free metallic material, having a high creep strength at elevated temperatures, individually to the necessary parts of the cast steel material at a place having good welding conditions, and a second step of coalescing the build-up welded parts to each other at a place having less fovourable welding conditions by welding therebetween a vanadium-free metallic material having a high creep strength at elevated temperatures. In this way, cracking of the vanadium-containing cast steel materials on welding can be avoided.
Description
1~;39S4~
This invetltion relates to a method of welding cast -- steel materials containing a vanadium component, and more par-ticularly to a method of welding such cast steel materials while preventing the occurrence oE cracks in the region of the weld.
The recent development oE high temperature, high ; pressure steam turbines has required the rapid development of suitable high temperature and high pressure-withstanding cas~
steel products to be used therein, for example as turbine casings, valve cases for steam valves, etc. In order to improve the high temperature withstanding characteristics of such materials, an attempt has been made to increase the creep strength at elevated temperatures by using Cr-Mo-V cast steels which, as can be seen, contain a vanadium component.
Although Cr-Mo-V cast steel products have the necessary creep strength at elevated temperatures, they also have a con-siderably higher susceptibility to cracking than other cast steel products owing to the presence of the vanadium component.
Consequently, cracking is very liable to occur during welding.
That is to say, when welding Cr-Mo-V cast steel products, a secondary hardening occurs after a stress relief annealing step, owing to the influence of the welding heat, and cracking of the welded parts is disadvantageously liable to take place because of the influence of the thermal stress during the stress relief annealing step.
Therefore, when welding Cr-Mo-V cast steel products, a complicated welding technique has been required, such as the application of peening as a means for relieving the residual stress from the welded parts. For example, such welding has 30 been carried out by skilled welding engineers in well adjusted, -good welding atmospheres, such as in a welding shop. However, .: ~ :
ir~ - 1 , - :: -: -.
.. . .
: , : ., :
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when s~ch Cr-~o-V cast steel products are actually used in steam turbine casings, the welding of the products must be carried out outdoors at the erection site of a power plant, and thus it is almost impossible to maintain a good welding - atmosphere. Even if the welding is carried out when taking the best possible precautions it is very difficult to prevent the occurrence of cracks due to the inclusion of vanadium component.
One of the methods previously employed for overcoming this difficulty comprises preparing forged parts free from the vanadium component and having cross-sectional shapes identical to those of the parts to be welded and consisting of high tem-perature, high pressure materials having good high temperature- -~
withstanding characteristics. These forged parts are then individually welded to the necessary parts made of the Cr-Mo-V
cast steel products within a shop where it is possible to weld the parts under suitable conditions. The forged parts are then welded to each other at the erection site, thereby preventing the occurrence of cracks in the welded parts due to the presence of the vanadium component.
However, in this welding method, the forged parts to ` ~ `
be shop welded to the Cr-Mo-V cast steel products must be pre-pared separately, and furthermore it is necessary to make the cross-sectional shapes of the forged parts identical to those of the vanadium-containing parts. Thus, much additional labor is required.
An object of the present invention is to thus provide a method for welding cast steel materials containing a vanadium ;-~
component in a simple manner while preventing ~the occurrence of cracks in the welded parts.
According to the present invention there is provided a method of welding a cast steel material containing a vanadium ,;'.1` ' ' `; , ' ' .
.: .: . ,.,... . :,. . : . ~ -1'3~5~
component, comprising a first step of build-up welding a first vanadium-Eree metallic material, having as high a creep strength ; at elevated temperatures as said cast steel material, to a part of said cast steel material, and a second step of coalescing the built-up weldecl part to a second vanadium-free metallic material by welding therebetween a third vanadium-free metallic material, having as high a creep strength at elevated temperatures as said cast steel material.
An advantage of the present invention, at least in its preferred forms, is that it can provide a method for welding cast steel materials containing a vanadium component to each other in a simple manner even under unfavourable welding con-ditions such as at an erection site of a power plant, while preventing the occurrence of cracks in the welded parts.
A preferred embodiment of the present invention will be described in detail in the following with reference to the ~`
accompanying drawings, in which: `
Figure 1 is a vertical cross-sectional view of one embodiment of the present invention showing a steam turbine casing consisting of a Cr-Mo-V cast steel material;
Figure 2 is a view along line II-II of Figure l; and Figure 3 is a partial cross-sectional view along line III-III of Figure 2.
Figures 1 to 3 show a steam turbine casing 10 made from a Cr-Mo-V cast steel material. The casing consists of a semi-cylindrical upper half casing 11 and a lower half casing 12, and has an upper half 13 of a steam chest and a lower half 14 of a steam chest, each of which is in the form of a steam chamber for guiding steam into the casing. Furthermore, the upper half casing 11 has a coupling flange 15 for connection to a crossover pipe for guiding steam to the low pressure side of ~; `
1~3~S~
tlle turblnc casin~, allcl tlle lower llalf casing 12 has a number of connection terminals, i.e. a maln steam inlet terminal 18, wh~ch is connected to a main steam inlet pipe 28 for guiding high temperature, high pressure steam from a boiler into the casing, a low temperature reheatlng pipe terminal 16, which is whicll is connected to a -Low temperature relleatlng p;pe 26 for guiding steam from the inside of the casing to a reheater, a high temperature reheating pipe terminal 17, which is connected to a high temperature reheating pipe 27 for guiding high temperature steam into the casing from a reheater, and a steam extraction pipe terminal 19, which is connected to a steam extraction pipe 29 for extracting steam from the casing. All of these pipe terminals are forged integrally with the casing.
Each of these pipe terminals 16, 17, 18 and 19 require not only high pressure and high temperature withstanding properties, but also high creep strength at elevated temperatures, because the pipe terminals come into contact with high temperature steam.
Consequently, Cr-Mo-V cast steel is used as the material of con-struction for these pipe terminals.
When a combined reheating valve, comprising a reheating stop valve and an interceptor, is used as a steam valve in a portion of the high temperature reheating pipe 27 near the casing - 10, that portion must also be in an integrated structure with the valve casing, and thus must also be made from a Cr-Mo-V cast steel material.
The low temperature reheating pipe 26 and the steam extraction pipe 29, are made from Cr-Mo cast steel containlng no vanadium component 5 because the temperature of the steam passing through these pipes is not very higll. Ultimately these steam pipes 26, 27, 28 and 29 are welded to the respective pipe terminals :~ ;. , .: , :
~:. :: - : ... ..
5~L
16, 17, 18 and 19 on the turbine casing 10. Since the casing material is Cr-Mo-V cast steel, direct welding will bring about cracking of the welded parts. Thus, as shown ln Figures
This invetltion relates to a method of welding cast -- steel materials containing a vanadium component, and more par-ticularly to a method of welding such cast steel materials while preventing the occurrence oE cracks in the region of the weld.
The recent development oE high temperature, high ; pressure steam turbines has required the rapid development of suitable high temperature and high pressure-withstanding cas~
steel products to be used therein, for example as turbine casings, valve cases for steam valves, etc. In order to improve the high temperature withstanding characteristics of such materials, an attempt has been made to increase the creep strength at elevated temperatures by using Cr-Mo-V cast steels which, as can be seen, contain a vanadium component.
Although Cr-Mo-V cast steel products have the necessary creep strength at elevated temperatures, they also have a con-siderably higher susceptibility to cracking than other cast steel products owing to the presence of the vanadium component.
Consequently, cracking is very liable to occur during welding.
That is to say, when welding Cr-Mo-V cast steel products, a secondary hardening occurs after a stress relief annealing step, owing to the influence of the welding heat, and cracking of the welded parts is disadvantageously liable to take place because of the influence of the thermal stress during the stress relief annealing step.
Therefore, when welding Cr-Mo-V cast steel products, a complicated welding technique has been required, such as the application of peening as a means for relieving the residual stress from the welded parts. For example, such welding has 30 been carried out by skilled welding engineers in well adjusted, -good welding atmospheres, such as in a welding shop. However, .: ~ :
ir~ - 1 , - :: -: -.
.. . .
: , : ., :
~'~3~59~
when s~ch Cr-~o-V cast steel products are actually used in steam turbine casings, the welding of the products must be carried out outdoors at the erection site of a power plant, and thus it is almost impossible to maintain a good welding - atmosphere. Even if the welding is carried out when taking the best possible precautions it is very difficult to prevent the occurrence of cracks due to the inclusion of vanadium component.
One of the methods previously employed for overcoming this difficulty comprises preparing forged parts free from the vanadium component and having cross-sectional shapes identical to those of the parts to be welded and consisting of high tem-perature, high pressure materials having good high temperature- -~
withstanding characteristics. These forged parts are then individually welded to the necessary parts made of the Cr-Mo-V
cast steel products within a shop where it is possible to weld the parts under suitable conditions. The forged parts are then welded to each other at the erection site, thereby preventing the occurrence of cracks in the welded parts due to the presence of the vanadium component.
However, in this welding method, the forged parts to ` ~ `
be shop welded to the Cr-Mo-V cast steel products must be pre-pared separately, and furthermore it is necessary to make the cross-sectional shapes of the forged parts identical to those of the vanadium-containing parts. Thus, much additional labor is required.
An object of the present invention is to thus provide a method for welding cast steel materials containing a vanadium ;-~
component in a simple manner while preventing ~the occurrence of cracks in the welded parts.
According to the present invention there is provided a method of welding a cast steel material containing a vanadium ,;'.1` ' ' `; , ' ' .
.: .: . ,.,... . :,. . : . ~ -1'3~5~
component, comprising a first step of build-up welding a first vanadium-Eree metallic material, having as high a creep strength ; at elevated temperatures as said cast steel material, to a part of said cast steel material, and a second step of coalescing the built-up weldecl part to a second vanadium-free metallic material by welding therebetween a third vanadium-free metallic material, having as high a creep strength at elevated temperatures as said cast steel material.
An advantage of the present invention, at least in its preferred forms, is that it can provide a method for welding cast steel materials containing a vanadium component to each other in a simple manner even under unfavourable welding con-ditions such as at an erection site of a power plant, while preventing the occurrence of cracks in the welded parts.
A preferred embodiment of the present invention will be described in detail in the following with reference to the ~`
accompanying drawings, in which: `
Figure 1 is a vertical cross-sectional view of one embodiment of the present invention showing a steam turbine casing consisting of a Cr-Mo-V cast steel material;
Figure 2 is a view along line II-II of Figure l; and Figure 3 is a partial cross-sectional view along line III-III of Figure 2.
Figures 1 to 3 show a steam turbine casing 10 made from a Cr-Mo-V cast steel material. The casing consists of a semi-cylindrical upper half casing 11 and a lower half casing 12, and has an upper half 13 of a steam chest and a lower half 14 of a steam chest, each of which is in the form of a steam chamber for guiding steam into the casing. Furthermore, the upper half casing 11 has a coupling flange 15 for connection to a crossover pipe for guiding steam to the low pressure side of ~; `
1~3~S~
tlle turblnc casin~, allcl tlle lower llalf casing 12 has a number of connection terminals, i.e. a maln steam inlet terminal 18, wh~ch is connected to a main steam inlet pipe 28 for guiding high temperature, high pressure steam from a boiler into the casing, a low temperature reheatlng pipe terminal 16, which is whicll is connected to a -Low temperature relleatlng p;pe 26 for guiding steam from the inside of the casing to a reheater, a high temperature reheating pipe terminal 17, which is connected to a high temperature reheating pipe 27 for guiding high temperature steam into the casing from a reheater, and a steam extraction pipe terminal 19, which is connected to a steam extraction pipe 29 for extracting steam from the casing. All of these pipe terminals are forged integrally with the casing.
Each of these pipe terminals 16, 17, 18 and 19 require not only high pressure and high temperature withstanding properties, but also high creep strength at elevated temperatures, because the pipe terminals come into contact with high temperature steam.
Consequently, Cr-Mo-V cast steel is used as the material of con-struction for these pipe terminals.
When a combined reheating valve, comprising a reheating stop valve and an interceptor, is used as a steam valve in a portion of the high temperature reheating pipe 27 near the casing - 10, that portion must also be in an integrated structure with the valve casing, and thus must also be made from a Cr-Mo-V cast steel material.
The low temperature reheating pipe 26 and the steam extraction pipe 29, are made from Cr-Mo cast steel containlng no vanadium component 5 because the temperature of the steam passing through these pipes is not very higll. Ultimately these steam pipes 26, 27, 28 and 29 are welded to the respective pipe terminals :~ ;. , .: , :
~:. :: - : ... ..
5~L
16, 17, 18 and 19 on the turbine casing 10. Since the casing material is Cr-Mo-V cast steel, direct welding will bring about cracking of the welded parts. Thus, as shown ln Figures
2 and 3, when the reheating pipe terminal 17 is to be welded to the reheating pipe 27, built-up welding parts 31 and 32 are respectively welded to welding-requiring part 17a of the high temperature reheating pipe terminal 17 and welding-requiring part 27a of the high temperature reheating pipe 27, both of which are made of Cr-Mo-V material, with a welding rod of Cr-Mo steel containing no vanadium component and having as high a creep strength at elevated temperatures as that of the casing 10 made of Cr-Mo-V material. This step is carried out in a welding shop in a good welding atmosphere. Then, the outer surfaces of the built-up welded parts 31 and 32 of Cr-Mo steel material are processed to provide welding surfaces 31a and 32a, respectively. Furthermore9 a peening treatment is applied to the built-up welded parts 31 and 32 to release the residual stress. Then, the turbine casing 10, steam pipe 27, etc. are transported to the erection site of a power plant, and a welding 20 part 33 is welded between the built-up welded part 31a of the casing side and the built-up welded part 32a of the high tem- ~ -perature reheating pipe 27 in the unfavourable welding conditions, using a welding rod of Cr-Mo steel having a high creep strength -~
at elevated temperatures, thereby coalescing the built-up welded parts 31 and 32 to each other. Then, a peening treatment is applied to the welded part 33 to release the residual stress, ` whereby the welding operation is completed.
By carrying out the welding operation in the above manner, the welding can be attained effectively with a good 30 operability without the occurrence of any cracks in the welded parts, even although Cr-Mo-V cast steel materials are welded in : .
.
~35~54~
un~avourable welding atmospheres.
The Eor~golng embodiment only illustrates the welding together of two Cr-Mo-V cast steel products, but when the lower half casing 12 of Cr-Mo-V cast steel material is to be welded to a pipe made of Cr-Mo cast steel material, for example, such as the low temperature reheating pipe 26 or the steam extraction pipe 29, the build-up welding technique using a welding rod of Cr-Mo steel material containing no vanadium component and having a high creep strength at elevated temperatures need only be applied to the welding-requiring part of the lower half casing 12 in the favourable welding atmosphere~ and then the built-up welded part of the casing may be welded and coalesced to the low temperature reheating pipe 26 or steam extraction pipe 29 with a welding rod of Cr-Mo steel material containing no vanadium and having a high creep strength at elevated temperatures under the unfavourable welding conditions at the erection site. That ~ ;
is, the parts containing no vanadium components are welded to each other in the unfavourable welding atmosphere, whereby the occurrence of cracks in the welded parts due to the inclusion of 2~ the vanadium component can be prevented.
These welding methods can thus facilitate the welding operation and prevent the occurrence of welding cracks when cast steel materials containing a vanadium component are welded together, or to a cast steel material containing no vanadium.
. ~
. . . . .~ ; , ~:
:^ - - ; :
at elevated temperatures, thereby coalescing the built-up welded parts 31 and 32 to each other. Then, a peening treatment is applied to the welded part 33 to release the residual stress, ` whereby the welding operation is completed.
By carrying out the welding operation in the above manner, the welding can be attained effectively with a good 30 operability without the occurrence of any cracks in the welded parts, even although Cr-Mo-V cast steel materials are welded in : .
.
~35~54~
un~avourable welding atmospheres.
The Eor~golng embodiment only illustrates the welding together of two Cr-Mo-V cast steel products, but when the lower half casing 12 of Cr-Mo-V cast steel material is to be welded to a pipe made of Cr-Mo cast steel material, for example, such as the low temperature reheating pipe 26 or the steam extraction pipe 29, the build-up welding technique using a welding rod of Cr-Mo steel material containing no vanadium component and having a high creep strength at elevated temperatures need only be applied to the welding-requiring part of the lower half casing 12 in the favourable welding atmosphere~ and then the built-up welded part of the casing may be welded and coalesced to the low temperature reheating pipe 26 or steam extraction pipe 29 with a welding rod of Cr-Mo steel material containing no vanadium and having a high creep strength at elevated temperatures under the unfavourable welding conditions at the erection site. That ~ ;
is, the parts containing no vanadium components are welded to each other in the unfavourable welding atmosphere, whereby the occurrence of cracks in the welded parts due to the inclusion of 2~ the vanadium component can be prevented.
These welding methods can thus facilitate the welding operation and prevent the occurrence of welding cracks when cast steel materials containing a vanadium component are welded together, or to a cast steel material containing no vanadium.
. ~
. . . . .~ ; , ~:
:^ - - ; :
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of welding a cast steel material containing a vanadium component, comprising a first step of build-up welding a first vanadium-free metallic material, having as high a creep strength at elevated temperatures as said cast steel material, to a part of said cast steel material, and a second step of coalescing the built-up welded part to a second vanadium-free metallic material by welding therebetween a third vanadium-free metallic material, having as high a creep strength at elevated temperatures as said cast steel material.
2. A method according to claim 1 wherein said second vanadium-free metallic material is build-up welded to a cast steel material containing a vanadium component.
3. A method of welding together cast steel materials containing a vanadium component, which comprises a first step of separately build-up welding a first vanadium-free metallic material, having as high a creep strength at elevated tempera-tures as that of said cast steel materials, to respective parts of each of said cast steel materials, in good welding conditions, and a second step of coalescing the built-up welded parts to each other in less favourable welding conditions by welding a second vanadium-free metallic material between said built-up welded parts.
4. A method according to claim 3, wherein the second metallic material has as high a creep strength at elevated temperatures as said cast steel materials.
5. A method of welding a cast steel material containing a vanadium component to a vanadium-free cast steel material, com-prising a first step of build-up welding a vanadium-free metallic material, having as high a creep strength at elevated temperatures as that of the vanadium-containing cast steel material, to a part of said vanadium-containing cast steel material indoors in favourable welding conditions, and a second step of coalescing the built-up welded part to said vanadium-free cast steel material outdoors in less favourable welding conditions by welding therebetween a vanadium-free metallic material, having as high a creep strength at elevated temperatures as that of the vanadium-containing cast steel material.
6. A method of welding a turbine casing made of Cr-Mo-V
cast steel material to a pipe made of the same Cr-Mo-V cast steel material, which comprises a first step of separately build-up welding a Cr-Mo steel material, having as high a creep strength at elevated temperatures as that of the turbine casing, to respective parts of said casing and said pipe indoors in good welding conditions, and a second step of coalescing the built-up welded parts to each other by welding therebetween a Cr-Mo steel material, having as high a creep strength at elevated temperatures as said casing and pipe, outdoors in less favourable welding conditions.
cast steel material to a pipe made of the same Cr-Mo-V cast steel material, which comprises a first step of separately build-up welding a Cr-Mo steel material, having as high a creep strength at elevated temperatures as that of the turbine casing, to respective parts of said casing and said pipe indoors in good welding conditions, and a second step of coalescing the built-up welded parts to each other by welding therebetween a Cr-Mo steel material, having as high a creep strength at elevated temperatures as said casing and pipe, outdoors in less favourable welding conditions.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3433675A JPS51109241A (en) | 1975-03-24 | 1975-03-24 | GANBANAJIUMUCHUKOHINNO YOSETSUHOHO |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1039541A true CA1039541A (en) | 1978-10-03 |
Family
ID=12411289
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA248,008A Expired CA1039541A (en) | 1975-03-24 | 1976-03-16 | Method for welding cast steel material containing vanadium |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS51109241A (en) |
| AR (1) | AR215432A1 (en) |
| CA (1) | CA1039541A (en) |
-
1975
- 1975-03-24 JP JP3433675A patent/JPS51109241A/en active Pending
-
1976
- 1976-03-16 CA CA248,008A patent/CA1039541A/en not_active Expired
- 1976-03-22 AR AR26264576A patent/AR215432A1/en active
Also Published As
| Publication number | Publication date |
|---|---|
| JPS51109241A (en) | 1976-09-28 |
| AR215432A1 (en) | 1979-10-15 |
| AU1222476A (en) | 1977-09-29 |
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