DE102006032932A1 - Manufacturing seamless, bulbous pressure vessels in steel or other metals, produces blank body from massive wire, and expands it freely by application of heat and high internal pressure - Google Patents

Abstract

A blank body (3) of suitable shape is made by cold massive forming. Subsequently, the final shape (4) is reached by high internal pressure forming. The body (3) is made from massive wire, by cold massive forming. It includes only one opening for application of internal pressure. The blank is transformed to its final shape without using a surrounding mold, i.e. it is allowed to expand freely. The blank is inductively-heated before and/or during final forming under high internal pressure. It is heated by a defocused laser beam before and/or during the final forming. The blank is tapped with an internal or external thread, before final forming. To produce high internal pressure, the blank, which contains a substance, is sealed pressure-tight using a threaded stopper. During heating, the substance produces the high internal pressure.

Description

The invention relates to a method combination of two forming processes for producing bulbous hollow bodies (US Pat. 2 ) made of metal, preferably steel. In this case, in a first step by cold massive forming a hollow starting body ( 1 ), which is then brought by internal high pressure in the final shape. This combination of methods enables, for example, the production of seamless pressure vessels. The hydroforming can be carried out at room temperature with a liquid high pressure medium or at elevated temperature with a gaseous high pressure medium. The sealing in the hydroforming can be done conventionally in an hydroforming system or via a threaded connection, which is attached after the cold massive forming. The hydroforming can be done both in a molding tool and under free flow of material.

State of the art

bulbous hollow body made of metal, such as pressure vessels, have long been made both in several parts as well as in one piece.

The multi-part manufactured container are usually welded constructions with the associated problems of the weld. The welded body are usually tube sections and deep-drawn or pressed spherical caps.

one-piece seamlessly manufactured containers are made, for example, from pipes whose two ends z. B. by spin forming or swaging be reduced so far in the diameter that the desired container shape arises.

In general, the shape or size of the container thus produced is then no longer changed. From the registration DE 36 03 415 In the case of a welded, cylindrical container, the initially flat container bottoms are brought into a quasi-elliptical shape by applying an internal pressure to the outside. From the registration DE 698 26 234 For example, a method is known according to which a tubular starting body is shaped at elevated temperature by internal pressurization with gaseous medium to form a container.

task

Of the Invention is based on the object, a cost-effective alternative to those known in the art, integrally manufactured in one piece containers to find. Starting material for this is a wire, preferably made of steel, which is used as a wound coil of a multi-stage press for cold massive forming supplied becomes. This starting material is considerably cheaper than a pipe.

By suitable, customary forming process is on this multi-stage press a bottle-like body ( 1 ) 3 ), which serves as a starting body for the subsequent hydroforming. Depending on the desired container, this starting body may also have an opening on both sides ( 1 ).

The Forming achievable by cold massive forming alone is known in a measure limited, that the manufacturable hollow body often not those for pressure tanks can provide required volumes.

Of the -extruded Blank is therefore subsequently pressurized in a suitable system with internal high pressure and under Volume increase too a bulbous hollow body reshaped.

He follows hydroforming cold by means of a liquid high-pressure medium, so the blank must be previously annealed to the by the Cold forming achieved undoing solidification and the maximum Deformability of the to obtain metallic material.

The Hydroforming can also be carried out at elevated temperature. In In this case, the high-pressure medium is usually gaseous. By the softening of the metallic material decreases the necessary internal pressures as far that transmits the forming force from a gaseous medium can be.

One an important criterion in hydroforming is sealing the pressurized cavity. With a bottle-shaped starting body offers the opportunity an internal or external thread to install over that the high pressure line can be coupled. This thread can be at the same time for later Connection of the container serve to a pressure circuit.

One Such thread also offers the possibility of the output body by means to seal a locking screw. Is located in the starting body suitable medium (for example water), it is possible to when heating the pressure-tight outlet body through the internal pressure to generate the expansion of the trapped medium. This could on an elaborate Device for generation and transmission be waived the hydroforming.

The warming on forming temperature can, for. B. inductive or by means of a defocused Laser beam done. In this case, the starting body about its longitudinal axis to be turned around.

at The hydroforming can the desired final shape by a tool be set with the appropriate inner contour or it can a free formation are allowed, with appropriate shutdown criteria for the Hydroforming.

Claims (8)

Method for producing bulbous hollow bodies ( 2 ) 4 ) characterized in that from a geometrically suitable, produced by cold mass forming body ( 1 ) 3 ) the final shape is achieved by a subsequent hydroforming. Method according to claim 1, characterized in that the basic body ( 1 ) 3 ) is made by means of cold massive forming of solid wire. Method according to claim 1, characterized in that the basic body ( 1 ) 3 ) has only one opening for the pressurization. Method according to claim 1, characterized in that the main body ( 1 ) 3 ) by the hydroforming without enclosing tool free to the final shape ( 2 ) 4 ) converts. Method according to claim 1, characterized in that the basic body ( 1 ) 3 ) is inductively heated before and / or during the hydroforming. Method according to claim 1, characterized in that the basic body ( 1 ) 3 ) is heated before and / or during the hydroforming by means of a defocused laser beam. Method according to claim 1, characterized in that the basic body ( 1 ) 3 ) before hydroforming with an internal ( 5 ) or external thread ( 6 ) 3 ). A method according to claim 1, characterized in that the pressure in the hydroforming is generated in that the main body ( 1 ) 3 ) is pressure-tightly sealed with a threaded plug and contains a medium which generates the necessary internal pressure during heating of the blank.