Metal working – Method of mechanical manufacture – Assembling or joining
Reexamination Certificate
1999-09-07
2001-03-20
Rosenbaum, I Cuda (Department: 3726)
Metal working
Method of mechanical manufacture
Assembling or joining
C148S528000
Reexamination Certificate
active
06202281
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method for producing a multilayer thin-walled bellows, operating under the conditions of high temperature, high pressure and corrosive media.
BACKGROUND OF THE INVENTION
Multilayer thin-walled metal bellows are widely used in different engineering fields, in aircraft industry, engine manufacturing, and oil industry, for example, for securing a movable joint for the pipelines required for compensating their displacement as a result of external actions, in particular.
Different methods for producing the multilayer thin-walled bellows are known. Fabrication of multilayer bellows of separate thin plates by a welding is described in the U.S. Pat. No. 2,797,112 the U.S. Cl. 72-59, 1959. However, the known method is rather laborious and requires additional testing for securing the reliable operation of these bellows.
A method for producing thin-walled bellows is presented in the U.S. Pat. No. 3,782,156 the U.S. Cl. 72-59, 1974. This method consists of preliminary formation of turns on the external and internal surfaces of round billets, treatment of their internal surface by a roller, compaction with the formation of corrugations and heat treatment for the metal stress-relief. But the known technology requires special complicated equipment and much time for producing a bellows.
The USSR Inventor's Certificate No. 1076166 Int. Cl. B 21 D 15/00, 1984 proposes to make bellows by a mechanohydraulic skelping with the formation of ring corrugations on a round billet at subsequent subrecrystallization annealing at a temperature of 680±10° C. This method allowed a reduction of labor input during the fabrication and a raise in the operational reliability of the bellows.
The USSR Inventor's Certificate No. 1292870 Int. Cl. B 21 D 15/00, 1987 describes a method for producing a multilayer thin-walled bellows of stainless steel, including skelping round billets, several runs of each round billet drawing up to a given size, packing the drawn round billets into a multilayer bank, corrugating the bank with the bellows formation as a result and its heat treatment. According to the known method, the round billets are deformed by drawing through the matrix using the punches, their diameter changes, then the billets are inserted one into another, forming the bank, and corrugated with subsequent operations of surface deformation and heat procession—subrecrystallization annealing.
The operation of drawing each round billet before their packing allowed to increase a product quality due to the strength growth at repeated loading.
However, when alloys undergoing structural variations at heating, age-hardenable nickel-based alloys for example, are used as materials for round billets, such deformations as cracks on the billet walls are possible during their drawing and corrugating due to the low ductility of these alloys. Besides, because of the high tendency to oxidation being characteristic to alloys, there is a possibility for having such defects as cracks and faulty fusions in the bellows made of them at their welding with fittings. This fact limits the use of such bellows under the conditions of high temperature, high pressure and corrosive media during a long time period.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a method for producing a multilayer thin-walled bellows of the age-hardenable alloys on the nickel base, capable of operating under extreme conditions, gas oxidizing medium at high temperature and pressure for example, for a long period of time.
Prevention of crack formation in the walls of round billets and bellows is the technical result of this invention.
This object is achieved by a method for producing a multilayer thin-walled bellows, comprising skelping round billets, several runs of each round billet drawing up to a given size, packing the drawn round billets into a multilayer bank, corrugating the bank with the multilayer bellows formation as a result and heat treating the multilayer bellows. According to the invention each round billet is skelped of an age-hardenable nickel alloy containing a strengthening phase, after drawing each billet is heated up to the temperature of 1000-1130° C., held in a shielding medium at the above temperature until the strengthening phase is completely dissolved in the alloy, and cooled down to a temperature of the phase transition termination in the alloy, after that the above operations of drawing, heating, holding and cooling are repeated until the given size of each round billet is reached and are exercised the packing drawn round billets into the multilayer bank, welding the multilayer bank from two sides over its end faces and corrugating the bank for forming the multilayer bellows, the heat treatment of the bellows is made by its heating up to the temperature of 1000-1130° C., holding in the shielding medium at this temperature until the strengthening phase is completely dissolved in the alloy and subsequent cooling down to the temperature of the phase transition termination in the alloy.
A rarefied air medium under the pressure of 1×10
−4
-1×10
−3
mm of the mercury column may be used as the shielding medium.
The cooling of round billet and bellows may be made in an inert gas flow.
Argon may be used as the inert gas.
Niobium, titanium, tungsten and molybdenum may be used as the strengthening phase.
A layer of nickel of 5-15 &mgr;m in thickness may be applied onto peripheral parts of external and internal surfaces of each drawn round billet before the corrugation of the multilayer bank of the round billets.
The round billets of age-hardenable nickel alloy are subjected to the multiple drawing, the billets being heat treated after each drawing operation in the shielding medium at a temperature of the strengthening phase complete dissolving in the alloy with subsequent cooling securing a single-phase structure formation in it. The nickel layer is applied to the peripheral parts of the external and internal surfaces of the round billets, the billet is corrugated after that for forming the bellows that is heat treated according to a procedure of heat treating the billets after each drawing operation. The said operations are typical for producing single-layer thin-walled bellows also.
In this case, the cracking of the round billet walls during each operation on drawing and of the bellows walls at its corrugation is prevented due to the alloy ductility increase, and its oxidizing during the bellows welding to the fittings is prevented also due to the presence of a protective coating on its walls resulting in the growth of the unit strength during the operation.
REFERENCES:
patent: 2797112 (1957-06-01), Ziebold
patent: 3782156 (1974-01-01), Panfill
patent: 4041969 (1977-08-01), Acomb et al.
patent: 4046596 (1977-09-01), Metcalfe et al.
patent: 4116723 (1978-09-01), Gell et al.
patent: 4740866 (1988-04-01), Kajiwara et al.
patent: 4796632 (1989-01-01), Yonezawa et al.
patent: 5244515 (1993-09-01), Miglin
patent: 5250172 (1993-10-01), Vargas-Gutierrez et al.
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patent: 5413752 (1995-05-01), Kissinger et al.
patent: 5665180 (1997-09-01), Seetharaman et al.
patent: 5951792 (1999-09-01), Balbach et al.
patent: 6036791 (2000-03-01), Mitsuhashi et al.
patent: 6054096 (2000-04-01), Duhl et al.
patent: 1076166 (1984-02-01), None
patent: 1292870 (1987-02-01), None
V.D. Korsakov, “Reference Book of Foreman at Die Making”, Leningrad, 1972, p. 122.
Chvanov Vladimir Konstantinovich
Derkach Gennady Grigorievich
Movchan Jury Vasilievich
Polushin Valentin Georgievich
Semenov Viktor Nikonorovich
Birch & Stewart Kolasch & Birch, LLP
Cuda Rosenbaum I
Jimenez Marc
Otkrytoe Aktsionernoe Obschestvo "Nauchno-Proizvodstvennoe Obied
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