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Mono-Block Large-Sized Plates

#3081.2


Development of New Methods of Manufacturing Unique Mono-Block Large-Sized Plates

Tech Area / Field

  • FIR-ENG/Reactor Engineering and NPP/Fission Reactors
  • MAN-MPS/Manufacturing, Planning, Processing and Control/Manufacturing Technology

Status
8 Project completed

Registration date
18.09.2006

Completion date
29.12.2010

Senior Project Manager
Latynin K V

Leading Institute
NPO Lutch, Russia, Moscow reg., Podolsk

Supporting institutes

  • NIKIMT (Institute of Assembly Technology), Russia, Moscow\nMISIS (Steel and Alloys), Russia, Moscow

Collaborators

  • FQZ-EKO Stahl, Germany, Eisenhuttenstadt\nGesellschaft für Metallurgische Technilogie- und Softwareentwicklung mbH, Germany, Berlin\nTU Bergakademie Freiberg / Institut für Metallformung, Germany, Freiburg

Project summary

Introduction and Overview

Purpose of the project #3081 is the development of method of manufacturing mono-block large-sized plates with the sizes 5500 x 5500 x 265 mm and more. Thus high quality of metal, uniformity of structure and properties of metal, accuracy of the geometrical sizes will be achieved. Uniqueness of the method: The offered way was not applied in world (global) practice earlier. This way will allow increasing quality of metal due to removal of defects of an axial zone of an ingot. This way raises reliability of the important parts as allows avoiding threefold (cross) welded seams.

Application areas: machine building for power, transport, chemical and mechanical engineering.

The basic tendency of development of modern machine building is increasing specific capacity of stationary and mobile power installations, units of the chemical industry and other unique equipment. This tendency leads to requirement in large billets such as thick large-sized plates. For example, manufacture of the bottoms of modern power nuclear installations demands manufacturing of plates by thickness 265-400 mm with size from 5500x5500 mm up to 8500x8500 mm.

Nowadays manufacture of large-sized plates is carried out by various methods of metal forming and welding. Basically, mono-block plates are manufacturing by rolling or forging. However the existing rolling equipment and technology cannot provide obtaining thick plates in width of 5000 mm and more. The maximal width of a plate during forging process by powerful hydraulic forging presses is limited by the sizes of a press table and size of distance between press columns, i.e. size less than 5000 mm. It is necessary to say that defective metal of an axial zone of an ingot remains in a body in the case of using existing technologies. This defective metal decreases quality of final products.

Manufacturing of large-sized plates by electroslag welding of two or more forged or rolled billet-plates is difficult process with small output, instability of technology and poor quality of the welded plate. The subsequent manufacturing of products from these plates (for example, the bottoms) and welding to installation case (installation block) leads to formation of crossed welded seams, which considerably reduce reliability of work of these products.

The purpose of the project is development of a method of manufacturing mono-block large-sized plates with the sizes 5500 x 5500 x 265 mm and more. Thus high quality of metal, uniformity of structure and properties of metal, accuracy of the geometrical sizes will be achieved.

Uniqueness of the method: The offered way was not applied in world (global) practice earlier. This way will allow increasing quality of metal due to removal of defects of an axial zone of an ingot. This way raises reliability of the important parts as allows avoiding threefold (cross) welded seams.

Materials: The method is possible for applying to various metals and alloys. In this project, research will be carried out with steel “15Kh2NMFA –Russian classification” which is applied to manufacturing the important details of cases of nuclear reactors. Interesting application of the given way for manufacturing plates from hardly-deformed metals (such as refractory) is represented.

The description of the method: The method includes the following basic technological operations:


1. Manufacturing of tube

1.1.Melting of an ingot of the special form;
1.2.Heating; producing cylindrical billet of needed sizes from ingot by deformation in radial direction;
1.3.Heating and upsetting;
1.4.Cooling of pressed billet for obtaining needed distribution of temperature along billet section
1.5.Subsequent insertion (piercing) by inserter with axial hole (hollow punch) with moving away defected axial zone for obtaining a tube;
1.6.Heating of the tube; deformation in radial direction for increasing inner diameter;
1.7.Heating of the tube, deformation for decreasing of wall thickness in several stages;
1.8.Thermal treatment of the tube;
1.9.Mechanical treatment

2. Cutting of the tube wall in parallel of axis (producing reach-through slit).
3. Heating and unwrapping of the tube from cylindrical shape to a plate with hydraulic stamp press by specially developed technological tool.
4. Metal plate hot flattening
5. Heat treatment of the plate; the control of the geometrical parameters and structures of metal; a cutting of billet of the required sizes.
6. Punching (stamping) of required products (for example, the bottoms of power installations).
7. Quality control.

The first stage (manufacturing of large-sized tube) demands research and development of new methods of their manufacturing, because it is impossible to receive a thick-walled tube of big diameter by existing methods of manufacture of tubes on working tube-rolling equipment.

The subsequent stages allow obtaining a large-sized plate with application existing forging and stamping hydraulic presses. The basic problem of manufacturing of such large-sized plates consists in absence powerful forging presses with the big distances between columns. The offered technological scheme allows solving this problem. For realization of an offered way it is not required development of the additional special equipment. All operations are possible for carrying out on existing hydraulic presses. Final deformation processing of products (unwrapping of the tube from cylindrical shape to a plate) will be carried out with hydraulic stamp press. There are hydraulic stamp presses with the big distances between columns in the metallurgical plants.

For realization of this technological scheme, it is necessary to fulfillment: the big volume of researches on calculations of temperature and deformation modes of processing; researches of metal structure; researches on prevention of occurrence of superficial defects etc. All these researches will be carried out within the framework of performance of the project.

Target properties: The following parameters are exposed to the control: mechanical properties at the room and increased temperatures, structure of metal, impurity (quality of inclusions) and geometrical parameters. In the project it is supposed to obtain the following parameters:

In a plate, impurity of metal by oxides, sulphidic and silicate inclusions will not exceed “point 1” in accordance with GOST 1778.

Metal of a plate will have fine-grained structure, practical absence of anisotropy of mechanical properties. Mechanical properties will be not less than following level:

At 20 °C:

  • Ultimate strength 610 MPa,
  • Conventional yield strength 490 MPa,
  • Tensile strain: more than 15 %.
  • Reduction of area 55 %.
  • Impact toughness 90 J/cm-2

At 350 °C:
  • Ultimate strength 535 MPa
  • Conventional yield strength 440 MPa
  • Tensile strain: more than 14 %
  • Reduction of area 50 %
  • Impact toughness 49 J/cm-2

Good flatness of the plate after unwrapping is provided by reduction (spellerizing) of metal between heads of hydraulic press. Thus it is possible to achieve a various level of flatness. A usual level of flatness, which provides realization of the following operations, is 5 % from thickness of a plate.

The offered way allows achieving uniform distribution of mechanical properties and structures of metal both on thickness of a plate, and on the area. Divergence (deviations) from average value do not exceed 7-10 %. It is provided (and explained) by absence of defected metal from an axial zone of an ingot.

The method allows to achieve a low level of poly-thickness, because forging allows to achieve a required level of wall thickness accuracy.

From the economic point of view the offered way will allow to lower labour-intensiveness (laboriousness) of manufacturing of large-sized plates in 2-3 times, the charge of metal on 10-15 % in comparison with “rolled-welded” variant of plates manufacturing


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