THE POSSIBILITY OF LARGE RINGS FORGING OUTSIDE THE PRESS SVOČ FST 2013

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Clare Baker
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1 THE POSSIBILITY OF LARGE RINGS FORGING OUTSIDE THE PRESS SVOČ FST 2013 Karel Ráž, University of West Bohemia, Univerzitni 8, Pilsen Czech Republic ABSTRACT Currently, there is higher demand for large forged rings, especially for the nuclear industry. It is not possible to forge these rings in the normal press because these rings are often so large. Therefore the press must be equipped with special device for forging outside the press. This paper deals with possibilities of large rings forging outside the press. There is done evaluation in terms of technological and design. KEY WORDS Hydraulic press, forging, rolling, reactor vessel INTRODUCTION Demand for large rings is caused by the continuous development of nuclear power plants. For the construction of nuclear reactors and heat exchanger tanks are necessary large steel rings with diameter up to 10 meters. Height of the ring can be up to 6 meters. Production of rings with these dimensions allows you to modify current design of reactor vessel (Fig. 1). Design with less amount of rings is better, because there is not so many welding operations. Figure 1: Dimensions of reactor vessel These rings with large diameter can be also used in the petrochemical industry as well as for parts of extreme types of wind turbines. Production of rings with these dimensions is not possible in normal hydraulic forging press. Distance between columns of the press must be greater than diameter of the ring. There not such a big press in the world. It would be possible to design a hydraulic press with this enormous size, but it will be cost high amount of money.

Figure 2: Example of reactor vessels Another option, how to produce these rings, is their production in special equipment for rolling.

Special rolling equipment also means an additional investment in to production.

required sizes. Different way, how to produce these rings, is design of an additional device to the hydraulic press. This device could allow forge these rings outside the working are of the press.

2 Figure 2: Example of reactor vessels Another option, how to produce these rings, is their production in special equipment for rolling. This rolling device must also cooperate with hydraulic forging press. This press can have smaller parameters, because it will produce only stocks for ring rolling machine. Special rolling equipment also means an additional investment in to production. Therefore the potential extreme rings manufacturers are looking for new solutions to their production, which would not be so capital-intensive, but would ensure the production of rings in the required sizes. Different way, how to produce these rings, is design of an additional device to the hydraulic press. This device could allow forge these rings outside the working are of the press. This is also cheaper than new rolling device. DEVICE FOR RINGS FORIGING- VARIANT 1 The principle of the solution is in inserting of a special crossbar, which is adjustable supported on one side and on the other side is a tool. Force is transmitted between movable crossbeam of press and this crossbar. Among tool and lower crossbeam is formed ring, hanging on the mandrel. Special shims can be adjusted depending on the thickness of the forged ring. In this variant is not a limit of maximum diameter of the ring. In following figure is modeled only one half of hydraulic press (for easier calculations). Figure 3: Device for rings forging- variant 1 DEVICE FOR RINGS FORIGING- VARIANT 2 The functional principle of variant 2 is an additional hydraulic mechanism. Movable crossbeam pushes the plunger of additional mechanism. This causes increasing of a pressure and motion of the output member which is forming the ring. In this variant is not a limit of maximum diameter of the ring. In following figure is modeled only one half of hydraulic press (for easier calculations).

Forging mandrel has in the rolling equipment function of roll. The final shape of the ring will be created by rolling. This operation will be situated next to the hydraulic press.

3 Figure 4: Device for rings forging- variant 2 DEVICE FOR RINGS ROLLING This option is a combination of forging and rolling of rings. Ring is forged on the hydraulic press up to maximal dimensions which press allows. Then, together with the forging mandrel, is ring transferred to rolling equipment. Forging mandrel has in the rolling equipment function of roll. The final shape of the ring will be created by rolling. This operation will be situated next to the hydraulic press. Figure 5: Device for rings rolling EVALUATION OF ALL VARIANTS Technological evaluation was done using the Deform 3D program, which is used for forming processes simulations. Energy, which is necessary for creation of similar rings by both methods (forging by variants 1,2 or rolling by variant 3), is here compared. For comparison of the two methods is chosen production of a ring with initial wall thickness 475 mm and final wall thickness 430 mm. ENERGY REQUIRED FOR CREATION OF A RING ON A HYDRAULIC PRESS The solution has two steps. First step is pushing of a tool into the ring. Second steps simulate steps after first step. Forged ring is in step two rotated and pushed by tool again. The simulation model considered perfectly rigid tool and mandrel. Mandrel is not moving. With a pre-defined speed 2 mm / s, is vertically moving the tool. For simplification of the simulation is modeled only part of the ring. On following figure is shown the consumption of energy during forging of a ring. Considered are only first two strokes of a tool. Delay in increasing of energy means time gap for rotating of ring and lifting of a tool.

Figure 6: Consumption of energy on hydraulic press during first two steps In this simulation is not considered energy, which is necessary to additional support operations, such as manipulation with

4 Figure 6: Consumption of energy on hydraulic press during first two steps In this simulation is not considered energy, which is necessary to additional support operations, such as manipulation with the ring in the working space and lifting of a movable crossbeam. The total energy is calculated as the sum of the energy required for the first stroke and energy for following strokes. Energy of following strokes is determined from energy for second stroke and total number of strokes. E T = E STEP 1 +X.E STEP X (1) E STEP 1 = Nmm= 20 MJ E STEP X = Nmm= 14 MJ X= number of partial rotations Partial rotation after each stroke is 5. Figure 7: Partial rotation in simulation model X= 360 / 5= 72 partial rotations E T = E STEP 1 +X.E STEP X = *14= 1028 MJ ENERGY REQUIRED FOR CREATION OF A RING BY ROLLING Here is solved amount of energy, which is necessary to create a rolled ring. The boundary conditions are defined as two working rolls which are absolutely rigid. The outer roll has a diameter 1000mm, the inner roll has a diameter 1500mm. Movement is defined as constant and it is 15mm per one rotation of the ring.

5 The diagram of the total energy for creation of a ring by rolling (final stroke of the moving roll is 45 mm): Figure 8: Consumption of energy during ring rolling CONCLUSION In this article was done simple overview of large rings production possibilities. This production is in now often discussed. Mostly are these rings used in areas of the nuclear industry, especially in reactor vessels. Here are considered several options of large rings production. Chosen are only these, which are suitable for real production. Research Centre of Forming Machines at the University of West Bohemia in Pilsen deals with this problem. In this time are done some basic calculation and design works. The technological comparison clearly shows advantages of rolling in this case. The main danger here is the possibility of ring deformation during forging because of rings will be thin. This problem can be solved by forming rings in vertical position or adding supporting rollers. ACKNOWLEDGMENTS This article was done with cooperation with research group CVTS and factory TS Plzen, a.s.. Special thanks to University of West Bohemia for providing software support. I would like also to thank all project participants and other employees of CVTS for valuable advice.

6 REFERENCES A Book Publication: [1] KOVÁČ, A., JENKUT, M. Tvárniace stroje. Bratislava: ALFA vydavateľstvo technickej a ekonomickej literarúry, ISBN [2] RUDOLF B.; KOPECKÝ, M. Tvářecí stroje Základy výpočtů a konstrukce. Praha: SNTL, ISBN A Chapter in the Magazine or in the Collective Publication: [3] ČERMÁK, J., JÍLEK, J.: Volné kovárny opět začínají s jadernou energetikou. Kovárenství. prosinec 2009 A Research Report: [4] ČECHURA, M.; STANĚK, J.; CÍREK, M.; HLAVÁČ, J.; KUBEC, V.; CHVAL, Z. Závěrečná zpráva o činnosti za rok 2008, Plzeň : ZČU, s [5] ČECHURA, M.; STANĚK, J.; CÍREK, M.; HLAVÁČ, J.; KUBEC, V.; CHVAL, Z. Závěrečná zpráva o činnosti za rok 2009, Plzeň : ZČU, s [6] ČECHURA, M.; KUBEC, V.; RÁŽ, K. Analýza současného stavu v oblasti velkých hydraulických lisů (nad 50 MN), Plzeň : ZČU, s [7] ČECHURA, M.; STANĚK, J.; CÍREK, M.; HLAVÁČ, J.; KUBEC, V.; CHVAL, Z. Závěrečná zpráva o činnosti za rok 2009, Plzeň : ZČU, s [8] Company literature of TS Plzeň a.s The article has been supported by the form of professional advice within framework of the Project No. CZ.1.07/2.3.00/ Popularization of research and development in mechanical engineering and its results (Popular) and co-financed by European Social Fund and a state budget of the Czech Republic..

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