EP0998589B1 - Method and device for producing "light steel" by continuous casting with gas inclusion - Google Patents

Abstract

The problem with continuous casting methods is the production in a single cast of structured material shapes presenting hollow cavities. To this end the invention provides for a continuous casting method comprising the following steps: a) the material is melted and a continuous strand formed from said material; b) the material strand is cooled or left to cool so that at least a part thereof has a temperature at which its structure is pasty; c) gas is introduced into that part of the material strand which has a pasty structure so as to form hollow cavities, the material strand being moved from the top towards the bottom; and d) the material is left to solidify. The invention also relates to a device for carrying out this method.

Description

The invention relates to a continuous casting process for Manufacture of material profiles that have cavities and a continuous casting device for performing such Procedure.

According to the prior art, various methods are available Manufacture of porous metal foam bodies, honeycomb structures Steel parts and process for the continuous casting of Metal strands based on the principle of communicating tubes, also with gas supply, from the following patent and published documents known:

The German patent application 38 14 030 A1 relates a foam steel as a structural dressing material. This will by sticking together of spherical or with Trough-provided sheet metal, which then has a honeycomb structure form, manufactured.

From German published patent application 44 16 371 A1 is a Process for producing long, porous metal foam bodies known on aluminum basis. Increase these metal foam bodies, inserted in aluminum hollow profiles, their section modulus against bending and twisting. The metal foam body are made of metal powder and blowing agent under heating this mixture to at least the melting temperature of the Foamed metal to a porous metal body.

The disadvantage of the prior art from DE 38 14 030 A1 and DE 44 16 371 A1 is that those described there Process from the production of components several prepared parts with pores Cavities allowed. A production of material profiles with voids from a single mold is not possible.

Methods are described in WO 86/06 431 and WO 88/04 586 described, although a good shape for cavities in Allow material profiles, but for a lightweight construction of load-bearing components are not particularly suitable. In the WO 88/04 586 discloses a method and apparatus for continuous Pouring metal strands from high-melting Metals with cross sections close to the final dimensions according to the principle of the communicating tubes.

From German Offenlegungsschrift 35 16 737 A1 are a Method and device for producing gas bubbles as cavities penetrated by metallic materials in Form of profiles known, which in relation to their own weight a higher section modulus at bending, buckling and have torsional stresses.

The method described there has the disadvantage that the introduced gas bubbles can not be positioned because them into an upward strand of material in the still liquid Condition and are therefore due to their First move the buoyancy in the melt until it melts stiffens. In addition, only one is relative in this method slight reduction in the specific gravity of the starting material possible.

US-A-3 941 182 discloses a method and an apparatus for covering steel wires with a metal foam compound described. The metal foam is used only for protection the wires from breaking. The production of material profiles cavities are not addressed there. The Gas is introduced to produce the metal foam via feed lines to which a stirrer for distributing the gas bubbles is connected downstream within the molten metal is arranged. An exact positioning of cavities in the metal foam is not possible due to the stirrer.

The invention has for its object a continuous casting process for the production of material profiles, especially steel profiles, which have cavities, and a continuous casting device to carry out such a procedure the material weight of the profiles by insertion of gas bubbles, which are preferred in their location and extent can be designed flexibly and form cavities becomes.

a) Schmelzen des Materials und Bilden eines Strangs aus dem Material;

b) Abkühlen oder Abkühlenlassen des Materialstrangs, so daß wenigstens ein Teil des Materialstrangs eine Temperatur aufweist, bei der eine teigige Struktur vorliegt;

c) Einleiten von Gas in den Materialstrangteil teigiger Struktur zur Ausbildung der Hohlräume, wobei der Materialstrang von oben nach unten geführt wird; und

d) Erstarrenlassen des Materials.

This object is achieved by a continuous casting process for producing material profiles which have cavities, with the steps:

a) melting the material and forming a strand of the material;

b) cooling or allowing the strand of material to cool so that at least part of the strand of material has a temperature at which a doughy structure is present;

c) introducing gas into the material strand part of the doughy structure to form the cavities, the material strand being guided from top to bottom; and

d) allowing the material to solidify.

This process can be used to create voids in material profiles position as desired, because the gas bubbles will introduced into those material strand areas in which one pasty structure of the material is present. Under a batter Structure becomes a between liquid melt and solidification understood the lying state of the material in which there are still gas bubbles - possibly under high pressure - allow to be introduced into the material by means of nozzles or the like. There is therefore an inherent movement of the gas bubbles in the material strand - if at all - only possible to a very limited extent and should be completely omitted if a certain position and Structure of the cavities is sought.

In addition, by guiding the strand of material from above down, against the direction of buoyancy of the gas bubbles in the Material strand, reached that the gas bubbles the pasty Material strand area largely not in the direction of can leave the liquid area, but as intended form a cavity that is filled with the gas.

Metallic materials are preferably used as the material.

In step c), the gas is preferably at several points initiated within the strand of material on a Isothermal area. This way you can simultaneously several cavities created by the inclusion of gas bubbles become.

In step c), a noble gas, for example, is preferred as the gas Argon, used to avoid unwanted chemical reactions between the material and the gas a change in the material structure in the solidified state can take place.

In step c) the gas can be continuous or pulsed be fed. Thus, with continuous Movement of the strand of material along the mold both elongated, continuous cavities as well as in the longitudinal direction of the material strand arranged one behind the other Form cavities.

The structure of the cavities created can by at least an ultrasonic measuring device to be monitored in the area of running material strand is arranged.

The outer skin of the strand of material is preferably through Fibers reinforced.

In step c) the speed of the material strand is preferred greater than the rate of buoyancy from bubbles formed in the gas. In this case, the initiated Gas bubbles do not go up towards the liquid material area escape. Because of the doughy Structure of the material part in which the gas bubbles are introduced is, however, the rate of buoyancy in the normal case negligible small. Because of their dependence on in individual cases, however, it can contribute to the size of the cavities very large cavities of some importance.

• einem Vorratsbehälter für flüssiges Material, der eine verschließbare, bodenseitige Auslaßöffnung aufweist; und
• einer gekühlten Kokille zum Abkühlen von aus der Auslaßöffnung als Strang austretendem, flüssigem Material,

wobei

• die Kokille unterhalb der Auslaßöffnung und im wesentlichen senkrecht angeordnet ist;
• mindestens ein Gasrohr zum Einleiten von Gas vorgesehen ist, und
• das Gasrohr eine Austrittsöffnung hat, die, abhängig von dem verwendeten Material, im Inneren der Kokille in einem Bereich angeordnet ist, in dem der Materialstrang aufgrund der Abkühlung durch die Kokille eine teigige Struktur hat.

The invention also relates to a continuous casting device for producing material profiles which have cavities

• a storage container for liquid material, which has a closable, bottom-side outlet opening; and
• a cooled mold for cooling liquid material emerging from the outlet opening as a strand,

in which

• the mold is arranged below the outlet opening and essentially vertically;
• at least one gas pipe is provided for introducing gas, and
• the gas pipe has an outlet opening which, depending on the material used, is arranged inside the mold in an area in which the strand of material has a doughy structure due to the cooling by the mold.

This device ensures both guidance of the Strands of material from top to bottom as well as an introduction the gas bubbles in the area inside the mold, in the material with the appropriate pasty structure is present.

A control device, for example a controllable valve block, provided with which the gas inlet in the strand of material in their amount by that gas pressure used depends, and / or their shape, continuously or pulsed, can be controlled.

The supply of gas can be at the outlet end of the gas pipes Arranged nozzles are made, the openings of which depend on the desired cross-sectional shape for the cavities, for example a round, slit-shaped or rectangular cross-section can have.

At least one ultrasound measuring device for monitoring is preferred the structure of the voids of the running strand of material intended.

Electrical signals of the ultrasound measuring device, the structure of the cavities can reproduce the control device are supplied so that, depending on the measurement results of the Ultrasonic measuring device, the desired structure of the cavities can be generated. For example, by increasing the Gas pressure in the cross section of the material strand larger voids or by extending the gas pulse width in the direction of the string more extensive cavities are formed.

The process and one adapted to the material to be processed Device can be used to manufacture profiles Light metal, non-ferrous metal or plastic are used, the method and apparatus according to the requirements of are designed for processing materials.

Fig. 1

eine Ansicht einer Ausführungsform einer Strangguß-Vorrichtung, teilweise im Schnitt;

Fig. 2A und 2B

eine Querschnitt- und eine Längsschnitt-Ansicht eines plattenförmigen Material-Profils;

Fig. 3A und 3B

eine Querschnitt- und eine Längsschnitt-Ansicht eines U-förmigen Material-Profils; und

Fig. 4A und 4B

eine Querschnitt- und eine Längsschnitt-Ansicht eines T-förmigen Material-Profils.

The invention is explained in more detail below on the basis of preferred embodiments with reference to the drawings. Show it:

Fig. 1

a view of an embodiment of a continuous casting device, partially in section;

2A and 2B

a cross-sectional and a longitudinal sectional view of a plate-shaped material profile;

3A and 3B

a cross-sectional and a longitudinal sectional view of a U-shaped material profile; and

4A and 4B

a cross-sectional and a longitudinal sectional view of a T-shaped material profile.

FIG. 1 shows an embodiment of a continuous casting device, which is partly shown in section. The Position of a feed line 1 from a transport container is marked with an arrow. A storage container 2 is for example filled with liquid steel, which by a Heater is kept at temperature. At the bottom of the Storage container 2 is a closable, as Funnel-shaped outlet opening that is regulated by a Valve 3 can be opened and closed, whereby level control by means of an ultrasonic sensor 17 is provided.

The reservoir 2 is of an electromagnetic type Agitator 4 surround so that the liquid steel degassed and can be homogenized. The melt is in an under the outlet opening of the storage container 2 arranged vertically Chilled mold 6, which is liquid-cooled. The mold 6 is in vertically arranged slide elements attached to the stage 5.

If steel is used as a material, it can melt for example, enter the mold area at around 1400 ° C and after cooling through the mold 6, a temperature of about 800 ° C, at which the melt becomes pasty becomes. Regardless of the temperatures mentioned, as explained later, but mainly on the Area of the melt at which this has a doughy structure shows.

In the melt tubes 7 are made of a high temperature resistant Material, such as ceramics, immersed in the a valve block 14 are connected. In addition to the gas supply 13 If necessary, a cooling device is provided. The gas is an inert gas, for example Argon, which has no connection with the steel. The Gas is pressure controlled and can so via the valve block 14 can be controlled so that each individual tube 7 is open in time and can be closed and if necessary different pressures can be set.

The gas pressure must be constantly controlled and regulated that no steel is pushed back into the gas pipes can. The gas is supplied through openings in the pipes 7 in an area where the melt is in batter is located, preferably along or near an area of the same Temperature, as shown in Figure 1 by an isotherm I. is.

The gas bubbles 8 that form can thus be positioned exactly and controllable in their extent, so that in the Material strand predeterminable cavities arise.

The mold 6 is designed and by means of a vertical guide 12 guided so that a vertical oscillation with a frequency of approx. 1 Hz is possible to prevent caking the melt on the mold wall and on the gas pipes 7 prevent and the introduced gas bubbles 8 better from each other to be able to separate.

A mounted, additional ultrasonic measuring device 15 enables an assessment of the bladder structure, with a water-cooled Graphite mass can serve as a transmission medium. Advantageous is about 2 measuring devices at an angle of 90 ° to each other to arrange a spatial assessment of the generated To be able to make bubble structure. The electrical Output signal of the ultrasonic measuring device 15 can be used for control of the valve block 14, for example the one set there Gas pressure and the gas pulse width used there, used to create the desired bubble and cavity structure to create.

Optionally, an X-ray device can also be used, to get information about the bubble structure.

The gas bubbles 8 can be positioned according to the position of the gas pipes 7 and in their vertical and horizontal dimensions and Distribution on the cross section can be controlled. The latter can, for example, about the shape of the openings of the gas pipes 7 in connection with a corresponding gas pressure control be accomplished.

The falling and still externally cooled strand is below the mold 6 by a transport device 11 taken over, which regulated in their speed can be that an optimal process control is possible. Among other things, this means that e.g. the speed of the strand is greater than the speed of buoyancy introduced gas bubbles 8, if any Own movement possible in the doughy structure of the material is.

When the strand has reached the horizontal level, it can can be divided, and the separated sections can be used for Further processing can be performed. Below the facility is the drip pan 9 for any escaping liquid material.

The possible cross-sectional shapes of the material profiles produced range from plate-like structure, rectangular shape, U shape up to the double-T support structure, etc. In addition it is possible, preferably in the outer skin of the material profile to introduce a fiber reinforcement to the resistance moments against bending, kinking, twisting increase, the fibers from a fiber reinforcement device 16 in the form of roles, which accordingly over the Are distributed, uncoiled. A bias of the Fibers in certain areas, which are determined by the way they are used of the material profile appears appropriate, is also possible.

FIGS. 2A, 2B, 3A, 3B, 4A and 4B show the cross-sectional shapes, as described above, with the associated Longitudinal sections, however, the shape of the gas bubbles is variable.

The entire device is controlled by a process controller regulated that continuous production is possible.

Claims (12)

1. Continuous casting method for producing material profiles which have cavities, comprising the steps of:

   a) melting the material and forming a strand from the material;

   b) cooling or leaving to cool the material strand, so that at least part of the material strand is at a temperature at which there is a pasty structure;

   c) introducing gas into that part of the material strand which has a pasty structure so as to form cavities, the material strand being directed downwards from above; and

   d) leaving the material to solidify.
2. Method according to Claim 1, in which metallic materials are used as the material.
3. Method according to one of Claims 1 or 2, in which, in step c) , the gas is introduced at one or more points within the material strand.
4. Method according to Claim 3, in which, when the gas is introduced in step c) at a plurality of points within the material strand, these lie close to or on an isothermal surface.
5. Method according to one of Claims 1 to 4, in which, in step c) , an inert gas, for example argon, is used as the gas.
6. Method according to one of Claims 1 to 5, in which, in step c), the gas is supplied continuously or in a pulsed manner.
7. Method according to one of Claims 1 to 6, in which the structure of the cavities produced is monitored by at least one ultrasonic measuring device (15).
8. Method according to one of Claims 1 to 7, in which the outer skin of the material strand is reinforced by fibers (16).
9. Continuous casting apparatus for producing material profiles which have cavities, with

   a reservoir (2) for liquid material which has a closable outlet opening at the bottom; and

   a chilled mould (6) for cooling liquid material leaving the outlet opening as a strand,

   characterized in that

   the mould (6) is arranged beneath the outlet opening and essentially vertically;

   at least one gas tube (7) is provided for introducing gas, and

   the gas tube (7) has an outlet opening which, dependent on the material used, is arranged in the interior of the mould (6) in a region in which the material strand has a pasty structure on account of the cooling by the mould (6).
10. Apparatus according to Claim 9, characterized in that a control device (14) is provided, with which the introduction of gas into the material strand can be controlled in its amount and/or its form, continuously or in a pulsed manner.
11. Apparatus according to Claim 9 or 10, characterized in that at least one ultrasonic measuring device (15) is provided for monitoring the structure of the cavities of the material strand (10) running off.
12. Apparatus according to Claim 11, characterized in that signals of the ultrasonic measuring device (15) which reproduce the structure of the cavities are fed to the control device (14).

Images