CN1049379A - Life-prolongging measure at labour Germany EBV st 45.8/III seamless steel tube for boiler - Google Patents
Life-prolongging measure at labour Germany EBV st 45.8/III seamless steel tube for boiler Download PDFInfo
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Abstract
The present invention relates at labour Germany, power station EBV st 45.8/III seamless steel tube for boiler life-prolonging method.In the Germany EBV company when supply of material, do not carry out normalizing treatment and domestic boilermaker for st 45.8/III seamless steel tube for boiler and do not anneal after to this steel pipe clod wash, thereby make this tubing that demolition accident easily take place.Utilization the present invention is easy, do not need glass-tube, in this steel pipe of labour annealing thermal treatment, naturally cooling can be eliminated the embrittlement phenomenon, increases the service life, the present invention has tangible economic benefit and social benefit.
Description
The inventive method relates to the Heat Treatment Of Steel method, particularly the heat treating method of lengthening the life at labour West Germany EBV st 45.8/III seamless steel tube for boiler.
St 45.8/III seamless steel tube for boiler is the West Germany Eschwellet Bergwerks-Verein Metallurgical Factory product of (being called for short EBV), based on contract, ton surplus China reaches 1000 from 1979～nineteen eighty-three import total amount, in 11 power stations of China, use respectively, this batch import tubing has caused four power plant that explosion takes place, accidents such as leakage and crackle, the elbow of the water supply distribution piping of No. 5 stoves of in October, the 1988 Tangshan generating general factory accident that is in operation that an explosion occurred particularly, cause very big loss, therefore, the safety of 14 large-sized boilers of 11 power plant of China in the use serious threat of this batch import tubing.Owing to this situation do not occur in the past, therefore, do not find to align the life-prolongging measure report that seamless steel tube for boiler is under arms taked.
The object of the invention is: a kind of pipe cutting that do not need is provided, to the easy life-prolongging measure of taking at labour West Germany EBV st 45.8/III seamless steel tube for boiler, to remove since this import pipe workpiece quality and technological problems cause to the threat due to the power plant safety.
The present invention seeks to reach like this:, as check and monitoring means, eliminate steel elbow embrittlement phenomenon with annealing thermal treatment, thereby this batch seamless steel tube for boiler is increased the service life with hardness according to Metallkunde and metal strength principle.
The present invention is described in detail below in conjunction with accompanying drawing.
Wherein, accompanying drawing 1 is a room temperature strength change curve under the different states; Accompanying drawing 2 is the following 350 ℃ of Strength Changes curves of different states; Accompanying drawing 3 is change curves of unit elongation δ value under the different states; Accompanying drawing 4 is change curves of percentage reduction of area ψ value under the different states; Accompanying drawing 5 is horizontal, impact of collision change in toughness curves of room temperature under the different states; Accompanying drawing 6 is following 350 ℃ of horizontal, impact of collision change in toughness curves of different states; Accompanying drawing 7 is room temperature changes in hardness curves under the different states.Tubing after booster and the thermal treatment metallurgical analysis and electron microscope observation have all been carried out.
Assemble altogether more than 120 tons EBV st 45.8/III steel pipe on No. 5 stoves of Tangshan generating general factory, this stove has 44 elbows for water distribution pipe. This factory is as follows for chemical composition and the mechanical performance test result of water distribution pipe material EBV st 45.8/III steel:
The chemical composition of table 1. booster (%)
| C | Si | Mn | P | S | N | O | Al | |
| DIN 17175-59 | ≤0.22 | 0.10～0.35 | ≥0.45 | ≤0.05 | ≤0.050 | 0.010 | -- | -- |
| Booster | 0.155 | 0.30 | 0.78 | 0.0145 | 0.029 | 0.0104 | 0.010 | Trace |
The mechanical performance of table 2. booster elbow
| δs (MPa) | δb (MPa) | δ (％) | ψ (％) | AK (U-shaped) (J/cm2) | HB (MPa) | Flatten | |
| Room temperature | 543.2 | 644.8 | 19.0 | 52 | Horizontal 8.8-17.5 indulges 14.4-18.8 | 2185～ 2244 | Defective |
| 350℃ | 406.9 | 617.8 | 4.8 | 60.2 | Horizontal 86.7-96.7 indulges 104.1-122.7 | --- | --- |
| DIN 17175 -59 | ＞255 | 441-539 | ＞21 | -- | --- | -- | -- |
The main seam broken of the water supply distribution piping of No. 5 stoves of Tangshan generating general factory is at bend part, and its fracture is the fragility even fracture, and internal surface is pulled straight way, and outside surface has pipe and hairline etc., and defective is serious.Because workmanship is bad, cause that crackle takes place, impel crack propagation again when the start and stop stove, this is one of reason that causes explosion: the tubing metallurgical quality is poor, N, O constituent content exceed standard, it is extremely low to contain sour molten Al amount, and non-metallic inclusion exists in a large number, therefore, intensity and hardness height, impelling strength plasticity is very low, is embrittlement state (see Table 1 and table 2), and these all are the primary conditions that fragility fracture takes place; Requirement according to the GB2106-80 standard, adopt the summer than V-type sample series shock test method, recording brittle transition temperature (FATT) in the sampling of steel elbow position is 125 ℃, grain fineness number is inhomogeneous in the metallographic structure, reach 5～8 grades, therefore segregation and Widmannstatten structure, can cause the low-stress explosion in a organized way.
From above experimental result as can be known, the brittle transition temperature of booster bend part (FATT) is up to 125 ℃, and Widmannstatten structure exists, and impact value aK value descends significantly.(Metallkunde is write " Metallkunde " that group is compiled, the Shanghai People's Press, the 21st page from data, publish in March, 1977) introduce: " superheated soft steel is easy to generate Widmannstatten structure under higher cooling rate; its appearance be since finishing temperature more than Ar3 point, thereby cause due to the cooling rate quickening, and do not carry out normalizing treatment subsequently ", experiment also confirms, booster is heated to 900 ℃, normalizing one hour, its grain fineness number refinement, Widmannstatten structure is eliminated, and perlite recovers lamellar morphology.As seen, because brittle transition temperature height, Widmannstatten structure exists, ferrite in the microstructure becomes the parallel band tissue of telling somebody what one's real intentions are of stratiform with perlite along the machining deformation direction, they have all strengthened the embrittlement trend of tubing, and its plasticity and toughness are reduced greatly, and hardness is also inhomogeneous, therefore, can cause the low-stress explosion.By above analysis, the finishing temperature that can infer West Germany EBV st 45.8/III steel pipe is more than 950 ℃.As seen, reduce the brittle transition temperature of steel with the method that reduces finishing temperature from data (the 221st page, publish in March, 1989 for Zhou Huijiu, Huang Mingzhi chief editor's " Strength of Metallic Materials ", Science Press's publication) again.Therefore, the brittle transition temperature height of explosion elbow is exactly because the finishing temperature height does not carry out due to the normalizing again.
In addition, also have the strain aging embrittlement problem, EBV st 45.8/III steel belongs to soft steel, because its metallurgical historical cause contains N, O and measures height, it is extremely low to contain sour molten Al, assemble thereby be enough to make N, the C atom dislocation heap after distortion to be gone up, its dislocation locking power is strengthened, mobile dislocation significantly reduces.(Li Junlin etc. write " boiler steel and welding " Heilungkiang press as data, 156 pages, publish in November, 1988) point out: " the clod wash deformation extent increases; timeliness is obvious further; though timeliness no longer increases when greater than 10% deflection; can make the aK value be reduced to 10～15% of virgin state, steel is become fragile fully ".The used EBV st of Tangshan generating general factory 45.8/III steel pipe carries out clod wash processing by Harbin Boiler Plant, and its deflection reaches more than 14%, therefore, is enough to cause strain aging.Experiment showed, that it is significantly that there is strain aging in EBV st 45.8/III steel, because the existence of strain aging embrittlement, make that allowable crack size reduces in these steel, be easy to take place brittle fracture.
As everyone knows, Low Carbon Steel Pipe is after the clod wash distortion, and inside produces a large amount of dislocations, and the distribution of these dislocations is disorderly interlacing, is in upper state; In addition, also being accompanied by a large amount of rooms interstitial atom exists.Because after the clod wash, make Low Carbon Steel Pipe produce work hardening, the distortional strain energy of metal inside has raise, thereby plays pendulum.According to the principle that free energy reduces, their states that will spontaneously tend to balance, and the carrying out of this process will could be realized by heating generally speaking.When being heated to certain temperature, obvious variation just takes place in microstructure, along being subjected to force direction extended ferrite to form new equi-axed crystal gradually, not only change has taken place in crystal grain, and the distortion of intracrystalline has also disappeared, high dislocation density after the distortion also reduces to the state before the distortion, numerical value when intensity and hardness also correspondingly return to virgin state, recrystallization annealing that Here it is is handled, and experiment shows, after the recrystallization annealing processing, intensity, the hardness of cold deformation of low-carbon steel pipe obviously descend; Plasticity, toughness improve greatly, and internal stress and work hardening phenomenon are eliminated.
When deformation extent is big, between various technical pure metals and its fusing point certain relation is arranged, the recrystallization temperature of technically pure iron is 650～700 ℃, and the recrystallization temperature of EBV st 45.8/III steel is 600～650 ℃, therefore, explosion bend pipe pipeline section has been carried out 600 ℃, 620 ℃, 640 ℃, 660 ℃ recrystallize annealing in one hour heat treatment test respectively, tabulated in table 3, various testing data change curves are shown in accompanying drawing 1～7.
From accompanying drawing 1 as seen, room temperature strength after handling through each recrystallization annealing annealing temperature (comprises yield strength δ s (with * table) and tensile strength δ b (with zero table), unit is (MPa), be equipped with rationally at 630～640 ℃ of following intensive propertieses, otherwise, explosion bend pipe (B) and not the intensity of explosion bend pipe (W) seem too high, embrittlement is easy to break; The variation trends of accompanying drawing 2 expression different states following 350 ℃ (operating temperatures) with * expression δ s, is represented δ b with △, and this accompanying drawing shows 620～640 ℃ of following performances fine, and the intensity of B and W is too high, and is easily crisp and break; The variation tendency of the unit elongation δ value under room temperature (showing it) and 350 ℃ under the accompanying drawing 3 expression different states (with * table) with △, this accompanying drawing shows that the unit elongation after 620～640 ℃ of annealing improves more than B and W, plasticity strengthens, accompanying drawing 4 shows the variation tendency of the percentage reduction of area ψ under room temperature under the different states (showing it with △) and 350 ℃ (with zero table), show that handling the back down at 620～640 ℃ improves a lot than B and W, plasticity increases a lot: the variation of laterally (with * table) of room temperature and vertical (with zero table) impelling strength aK value under the accompanying drawing 5 expression different states, aK is the impact value of U-shaped sample, and its unit is J/cm
2, after the result showed 620～640 ℃ of processing, notched bar impact strength improved greatly; The following 350 ℃ of horizontal impelling strength change curves of (with zero table) and vertical (with zero table) of accompanying drawing 6 expression different states, the result shows that notched bar impact strength improves greatly after 620～640 ℃ of processing; The changing conditions of room temperature hardness HB (MPa) value under the accompanying drawing 7 expression different states, hardness HB descends greatly after 620～640 ℃ of anneal, proves the embrittlement elimination.Above processing is all annealed down at 600,620,640,660 ℃ respectively and was carried out in 1 hour.
From table 3 and accompanying drawing 1-7 as seen, different annealing temperatures has tangible influence to the mechanical property of EBV st 45.8/III steel elbow, increase along with temperature, yield strength δ s and tensile strength δ b hardness HB descend, and unit elongation δ and percentage reduction of area ψ increase, and impact value aK value improves greatly, wherein best with 620～640 ℃ of annealed net effects, so for the big EBV st 45.8/III steel elbow of deflection at 620～640 ℃, preferably 1 hour naturally cooling of 640 ℃ of recrystallization annealing is advisable, but for this steel straight length of no cold additional deformation 620～640 ℃ of recrystallization annealing DeGrains then.Certainly, because former steel pipe can be implemented 900 ℃ of normalizing treatment to straight tube with the supply of material of finish to gauge state, in the intensity of 350 ℃ of lower straighttubes raising is arranged through this processing back, plasticity and plasticity also improve a lot.
After differing temps recrystallization annealing processing, metallographic structure also has corresponding variation, and along with annealing temperature increases, dislocation desity obviously descends on the ferrite.With the bend pipe of transmission electron microscope observing after thermal treatment under each annealing temperature, see that the dislocation born of the same parents of its different shape disappear to some extent.Opticmicroscope is observed metallographic structure down and is still added perlite for ferrite, and extended is organized and returned to former primary state behind the hardening deforming.After 900 ℃ of normalizing treatment, grain fineness number has very big refinement than former primary state tissue, has reverted to sheet than the block perlite of dispersive.Thus, as seen, be that to replace the judgement of last normalizing treatment be true for comparatively high temps with finish to gauge to former tubing.Tissue changes little after 600 ℃ of anneal; Perlite has nodularization slightly after 620 ℃ of processing, and major part still is a lamellar structure; After 640 ℃ of processing, the ferrite intracrystalline has the cementite of disperse, and perlite has the part nodularization, and dislocation born of the same parents eliminate, return to virgin state; After 660 ℃ of processing, the nodularization of perlite major part has chain-like carbonization body to separate out and assemble and grow up on the ferrite crystal boundary, the remarkable alligatoring of cementite particle, and number significantly reduces, and grain spacing increases, and dislocation born of the same parents eliminate.Therefore, from metallurgical analysis, the recrystallization annealing temperature also is advisable with 620～640 ℃, preferably 640 ℃.
After the thermal treatment of EBV st 45.8/III bend pipe through 1 hour naturally cooling of 640 ℃ of annealing, intensity and hardness decrease, plasticity and toughness improve greatly, but in order to verify its whether embrittlement after keeping for a long time under the operation conditions, the bend pipe of 640 ℃ of annealing after 1 hour kept 50 hours and 200 hours down at 350 ℃, and then the test mechanical performance, observing its variation, the result does not have any variation.Through 350 ℃ down long-term timeliness tests, every performance index reach more than the DIN 17175-59 standard-required, can not occur the embrittlement phenomenon again.
About the strain aging problem, obviously there is the strain aging phenomenon in EBV st 45.8/III steel pipe because its metallurgy is historical.In order to check of the influence of each recrystallization temperature to strain aging sensitivity coefficient, after utilizing straight length to carry out 10% and 15% cold deformation processing respectively, through two recrystallization annealing temperature (620 ℃, 640 ℃) and 900 ℃ of normalizing treatment 1 hour, then each group sample is carried out timeliness respectively under 250 ℃, 350 ℃ of room temperatures, it the results are shown in Table 4.As seen from Table 3, increase (10% to 15%) the strain aging sensitivity coefficient along with deflection increases; Along with aging temp rises (room temperature, 250 to 350 ℃), the strain aging sensitivity coefficient increases, and in the time of 250 ℃, the strain aging sensitivity coefficient reaches maximum, because this is the embrittlement district.Different annealing temperature is also very big to strain aging sensitivity coefficient influence, and along with annealing temperature rises, the strain aging sensitivity coefficient descends, and the strain aging phenomenon is eliminated gradually, and through after 640 ℃ or the 900 ℃ of thermal treatment, strain aging sensitivity drops to minimum value.Therefore, with 620～640 ℃, annealing thermal treatment also can be eliminated its strain aging embrittlement phenomenon.
In a word, show from above experiment, 620～640 ℃ at this batch EBV st 45.8/III seamless steel tube for boiler elbow, best 640 ℃, recrystallize thermal treatment is after 1 hour, naturally cooling, can reach standard-required, mechanical property can return to original level, and metallographic structure is stable, and this thermal treatment process can be used for the power station field conduct.Because of no cold deformation work hardening phenomenon, with the heat treated DeGrain of the present invention, therefore, the inventive method only is applicable to the bend part of EBV st 45.8/III seamless steel tube for boiler as for straight tube, and straight length does not need thermal treatment.
The mechanical property of table 3. blasting cartridge elbow under the different heat treatment state
Annotate: 1) all properties data are mean value in the table;
| ????δs(MPa) | ??????δb(MPa) | ????δ(％) | ????ψ(％) | ??HB(MPa) | AK (laterally) | AK (vertically) | |||||||
| Room temperature | ?350℃ | Room temperature | ?350℃ | Room temperature | ?350℃ | Room temperature | ?350℃ | Room temperature | Room temperature | ?350℃ | Room temperature | ?350℃ | |
| Former primary state | ????565.7 | ??490.9 | ??659.8 | ??644.5 | ??19.0 | ??14.8 | ??50.1 | ??34.8 | ????2244.2 | ????12.5 | 92.9 | ??16.5 | ??110.3 |
| 600℃ | ????359.8 | ??330.0 | ??506.8 | ??537.1 | ??21.8 | ??22.4 | ??57.8 | ??49.2 | ????1734.6 | ????55.9 | 125.0 | ??103.5 | ??159.9 |
| 620℃ | ????368.4 | ??264.8 | ??505.1 | ??499.4 | ??23.8 | ??24.0 | ??59.2 | ??53.3 | ????1456.9 | ????118.5 | 129.3 | ??138.1 | ??173.8 |
| 640℃ | ????3320 | ??294.7 | ??477.4 | ??478.0 | ??27.8 | ??24.6 | ??64.6 | ??53.3 | ????1535.7 | ????135.8 | 155.7 | ??197.5 | ??198.2 |
| 660℃ | ????311.9 | ??258.3 | ??464.9 | ??483.1 | ??32.7 | ??26.0 | ??63.9 | ??52.1 | ????1558.2 | ????84.8 | 118.1 | ??174.6 | ??174.9 |
2) aK is the impact value of U-shaped notched specimen, and unit is J/cm
2
3) data of hardness HB are the data that are converted into MPa.
Strain aging sensitivity coefficient under the table 4. different treatment state
| Room-temperature aging | 250 ℃ of timeliness | 350 ℃ of timeliness | ||||
| ???10％ | ???15％ | ??????10％ | ????15％ | ????10％ | ????15％ | |
| The booster straight length | ?42.8％ | ?69.0％ | ????83.0％ | ??80.3％ | ??74.6％ | ??60.7％ |
| After 620 ℃ of annealing | ?24.0％ | ?30.5％ | ????41.3％ | ??56.5％ | ??27.1％ | ??48.1％ |
| After 640 ℃ of annealing | -12.0％ | -13.9％ | ????34.1％ | ??40.9％ | ??19.5％ | ??24.3％ |
| After 900 ℃ of normalizings | -32.2％ | ??7.8％ | ????14.2％ | ??37.4％ | ??-3.7％ | ??32.2％ |
The present invention be directed to the longevity measure of locating, a kind of easy, life-prolonging method of not needing pipe cutting that provides at labour power station West Germany EBV st 45.8/III seamless steel tube for boiler.This method is the hardness and the metallographic structure of spot inspection elbow, as finding that hardness exceeds standard or metallographic changes, promptly this bend part is carried out on-the-spot anneal, periodic monitoring changes in hardness after the thermal treatment.
The detailed step of the inventive method is as follows:
1) will check the position cleaning to polish earlier, utilization Richter scale portable hardometer spot inspection bend part hardness, as find more than its hardness HB140, promptly tackle it and carry out the recrystallization annealing processing;
2) in case of necessity, metallographic structure with multiple film metallographic method check bend part, as find that the cementite in the perlite becomes the segmentation shape by sheet, and nodularization taken place, on the ferrite crystal boundary precipitate is arranged, when very big and the precipitate that particle is very tiny of dispersity is arranged in the ferrite, tackle it and carry out recrystallization annealing and handle;
3) the recrystallization annealing processing is with far infrared rope formula well heater, 620～640 ℃ of annealing in 1 hour are carried out at the nonconforming scene, bend pipe position of this hardness and metallographic, the formula of will restricting far infrared heater is around in this position, rise with the lagging material bag again, remote measurement and Long-distance Control temperature, annealing back naturally cooling;
4) to the bend part after the thermal treatment with its changes in hardness of Richter scale portable hardometer periodic monitoring.
Life-prolongging measure of the present invention has many advantages, and effect is obvious, and the inventive method is easy, does not need blowing out and pipe cutting, can implement in the operational process of power station.Utilization the inventive method is found and is handled the underproof elbow of hardness, can make its hardness reduce HB30～50 units or more, and effect is fine.Measure hardness and far infrared rope formula heater heats with the portable sclerometer of Richter scale, operating procedure is simple, and detection means is convenient and accurate.Therefore, can create big wealth and eradicate hidden danger for country.
Embodiment 1
West Germany's boiler steel bend pipe of No. 5 stoves of Tangshan Dou He power plant, 620～640 ℃ of annealing of process technology of the present invention naturally cooling after 1 hour makes this elbow hardness be reduced to HB140 from HB229; Metallographic structure becomes regular uniform tissue form from original non-rule.
No. 5 stove 670T/H of Qinling Powder Plant West Germany seamless steel tube for boiler elbow, with 640 ℃ of anneal of the inventive method 1 hour, naturally cooling, make tubing bend part hardness be reduced to HB156 from HB209, eliminated the embrittlement phenomenon, multiple film metallographic examination, originally the extended metallographic structure becomes the regular uniform formation form of rule after thermal treatment.
Embodiment 3
Jingmen heat power plant uses processing method of the present invention West Germany's seamless steel tube for boiler elbow was carried out 635～640 ℃ of anneal 1 hour, and naturally cooling makes tubing hardness reduce HB30～50 units, and effect is fine.The even rule that becomes is organized in the metallurgical phase complex film check.
Claims (3)
1, the life-prolongging measure with West Germany EBV st 45.8/III seamless steel tube for boiler in the labour power station is characterized in that:
1) the seamless steel tube for boiler bend part is detected hardness with Richter scale portable hardometer scene;
2) it carries out the recrystallization annealing processing as finding said position hardness to surpass 140 replies of HB;
3) said recrystallization annealing processing is with far infrared rope formula well heater the defective bend part of hardness to be carried out 620～640 ℃ of 1 hour anneal, naturally cooling subsequently;
4) to the Richter scale portable hardometer periodic monitoring changes in hardness of the bend part after the thermal treatment.
2, according to the said life-prolongging measure of claim 1, it is characterized in that: in case of necessity, the bend part behind Hardness Surveillance is checked metallographic structure with multiple film metallographic method.
3, according to the said life-prolongging measure of claim 1, it is characterized in that: said recrystallization annealing treatment temp is 640 ℃.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 90107754 CN1020117C (en) | 1990-09-19 | 1990-09-19 | Long-life measure of an active EBV st 45.8/III furnace steel pipe of GFR |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 90107754 CN1020117C (en) | 1990-09-19 | 1990-09-19 | Long-life measure of an active EBV st 45.8/III furnace steel pipe of GFR |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1049379A true CN1049379A (en) | 1991-02-20 |
| CN1020117C CN1020117C (en) | 1993-03-17 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 90107754 Expired - Fee Related CN1020117C (en) | 1990-09-19 | 1990-09-19 | Long-life measure of an active EBV st 45.8/III furnace steel pipe of GFR |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102492821A (en) * | 2011-12-30 | 2012-06-13 | 上海锅炉厂有限公司 | Heat treatment process for fine grain austenitic steel pipe bend |
| CN102059474B (en) * | 2008-05-27 | 2013-11-13 | 重庆理工大学 | Environmentally friendly lead-containing solder capable of suppressing lead from volatilizing at high temperature |
| CN104946932A (en) * | 2014-03-25 | 2015-09-30 | 新日铁住金株式会社 | Method for manufacturing austenite series heat-resistant alloy pipe and austenite series heat-resistant alloy pipe manufactured by the method |
-
1990
- 1990-09-19 CN CN 90107754 patent/CN1020117C/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102059474B (en) * | 2008-05-27 | 2013-11-13 | 重庆理工大学 | Environmentally friendly lead-containing solder capable of suppressing lead from volatilizing at high temperature |
| CN102492821A (en) * | 2011-12-30 | 2012-06-13 | 上海锅炉厂有限公司 | Heat treatment process for fine grain austenitic steel pipe bend |
| CN104946932A (en) * | 2014-03-25 | 2015-09-30 | 新日铁住金株式会社 | Method for manufacturing austenite series heat-resistant alloy pipe and austenite series heat-resistant alloy pipe manufactured by the method |
Also Published As
| Publication number | Publication date |
|---|---|
| CN1020117C (en) | 1993-03-17 |
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