Procedure of and device for thermally cutting workpieces.

The invention relates to a method and a device for thermal cutting of workpieces.

For thermal cutting of workpieces z. Z. are three methods used industrially primarily, namely oxyacetylene flame cutting, plasma cutting and laser cutting.

The autogenous flame cutting, which can be used without special measures only for steel, the heating is carried out mainly by a chemical reaction whose rate depends on the diffusion rate of the reactants. Of the reaction rate, in turn, depends on the cutting speed, which amounts for the material of structural steel in a large thickness range between 0.5 m / min to 1.5 m / min. The kerf here are different widths up to several millimeters.

In plasma cutting the power supply via an electric arc (plasma) with a high electric power to more than 100 kW. The heated material is removed by means of the plasma jet by momentum transfer from the kerf area. The cutting speeds for plasma cutting are higher than in flame cutting with small cutting blankets, but the kerf with 3 mm to 10 mm width are quite wide, which affects the accuracy of the cut.

During laser cutting, the energy is applied by a laser beam and removes the melted or vaporized material by means of a gas jet from the kerf. The laser cutting yields advantageous narrow kerf and thus a high accuracy at high cutting speed and a low thermal stress of being separated workpiece. For larger slice thicknesses, z. B. for steel above 10 mm, depending on the kerf width, it is no longer possible to work with the particular as performers from laser high cutting speed, because at the required high flow rate of the removal of the melt gas jet used by a few millimeters penetration depth in the kerf solves a supersonic flow of the cutting front, and thereby the effective gas velocity where it should be high, is correspondingly lower. During laser cutting, the cutting speed is therefore limited by in thicker workpieces that a high pulse can be transferred only inadequate with a gas jet. A medium having a higher density than the gas, eg. As a liquid, with a greater impulse could carry, can not use in laser cutting, since light having the wavelength of a C0₂Laser is absorbed in all the relevant liquid.

The invention has for its object to provide a method for thermal cutting of workpieces, which can be a high pulse place into a cutting gap. At the same time the heating power required to be applied. It should be even with large sectional thicknesses made with narrow kerf a high cutting speed and to be used device should be simple and manageable.

To achieve this object, a method is proposed with the invention are thermally separated with the workpieces, such as sheets of meltable or thermally decomposable material by means of a temperature above the melting or decomposition temperature of the product placed to be separated workpiece liquid jet.

The invention is based on the consideration that with liquids due to its high density, a greater momentum can be transported as with gases. If the liquid is heated so high that their temperature is above the melting or decomposition temperature of the material to be separated workpiece, can be by means of the liquid jet and the thermal energy in the cutting gap introduce, where the material to be separated workpiece thermally due to this power supply melts or decomposes and is discharged through the liquid jet from the cutting gap. Since the speed of sound in a fluid is very high, to the liquid jet can give a very high speed, without getting into the area of ​​the sound velocity and the associated risk of detachment of shock waves.

Depending on the temperature at which melting to be separated workpiece or thermally decomposes, different liquid jets can be used. If plastics are separated by the inventive method, it is sufficient to liquids with a high evaporation temperature z. B. oils to bring to the required temperature and thus to form a hot liquid jet for applying this material.

For thermal cutting of higher melting materials such as metals, in particular steel, the liquid jet may be made from a metal melt. Preferably, the molten metal may be overheated to a temperature above the melting temperature.

It must therefore be concluded that it is possible to use for the liquid jet from a different material to be cut material or the same material. Further, the liquid jet may be made of the material to be cut exothermically reacting material, thereby providing an additional supply of heat in the cutting gap.

On the other hand, it is also possible to use a reactant with the material to be cut in the sense of lowering the melting point material for the liquid jet. This is the case, for. Example, when the liquid jet consists of a molten metal which can form a eutectic with a lower melting point with the material to be cut.

The liquid jet may preferably a high speed, but below the speed of sound in the liquid, preferably / are sec granted a speed of 150 m, which can be at a beam diameter of 0.3 mm achieve high thermal power supply and a high pulse of the liquid jet.

When using a molten metal, the liquid jet can be generated, that a metal wire or metal rod sealed by drive means specific speed introduced into a mold, melted in the mold and the melt through a nozzle from the mold by means of acting as a piston, not yet melted wire or rod is expelled. The speed of the melt jet can thereby be increased in a simple manner with respect to the velocity of the introduced into the mold the metal wire or metal rod, in that the nozzle cross-section for the melt jet is made smaller than the cross section of the metal wire or the metal bar.

An apparatus for performing the method can sealed off from a mold made of refractory material having an inlet opening for the inlet opening guided, one by drive rollers advanceable metal wire or metal rod, a heating device in the area of ​​the mold for melting the wire or rod end in the mold and with its outlet formed on a molten metal beam. Preferably, the cross section of the nozzle can be less than the cross-section wire or rod. With such a device can be produced in a simple manner a continuous molten metal beam, since the introduced into the mold, metal wire or metal rod acts as a pressure piston, melts at its front end and this melt is expelled from the nozzle with high speed and high temperature.

The apparatus for performing the method can also be formed by a pressure-resistant container made of heat-resistant material with a pressure-tight sealable filling opening for liquid or metal pieces, a heater, a pressurized gas supply to the reservoir and an outlet for heated liquid or molten metal.

Finally, the apparatus for performing the method also consist of a container made of heat-resistant material with a filling opening for the liquid or pieces of metal, a heating device, a pump for heated liquid or molten metal and a downstream outlet nozzle may be made.

The heating device can operate with flames, high-energy light beams, electric arcs, direct or indirect electrical resistance heating or inductive heating to couple the heat energy into the material for the cutting beam. In addition, the beam can overheat due to electric current (resistance heating).

The energy for melting of the material needed for the cutting beam can be saved when the container with liquid metal filled directly from a smelting process and the liquid metal is superheated in the container only. In this way, can process particularly when the inventive method for cutting slabs or plates produced in the continuous casting is used in a metallurgical plant.

The invention is illustrated below with reference to several illustrated in the drawing embodiments of the closer. In the drawings:<ul><li>Fig. 1 is a schematic representation of an apparatus for performing the method according to the invention according to a first embodiment,</li><li>Fig. 2 is a schematic representation of an apparatus for performing the method according to the invention according to a second embodiment, and</li><li>Fig. 3 is a schematic representation of an apparatus for performing the method according to the invention according to a third embodiment.</li></ul>

In a container 1 made of refractory material is a liquid, in particular a molten metal 3. This liquid can fill in the liquid state into the container 1, when it is z. B. is an oil which can be used for thermal cutting of plastics should. It is also possible to fill liquid metal directly into the container. 1 Finally, solid metal pieces may be filled in the container 1 in order then to be melted by a heating apparatus 2, and heated above the melting temperature. The heating device 2 is shown schematically as the container 1 surrounding the device. It may be from oil to electric resistance heating to Erwär men. Likewise, the use of an induction coil for inductive heating of metal in the container 1 is possible. Furthermore, the material can be in the container 1 apply to reflow building under container 1 metal and heating above the melting temperature directly with flames, high-energy light beams or electric arcs. Finally, a direct or indirect electric resistance heating is possible.

From the container 1 enters the heated liquid, in particular molten metal via a pump 4 to a nozzle 5 which is located above a workpiece to be separated. 6 By means of a nozzle 5 from the exiting heated liquid beam 7, in particular of a molten metal beam, the material of the workpiece 6 is melted or thermally decomposed and discharged by means of the pulse in the liquid jet 7 from the thus formed kerf eighth From the kerf 8 thus exits a beam 9, which consists of a mixture of the material of the liquid jet and the molten or thermally-decomposed material. The liquid jet 7 is moved relative to the workpiece. 6

A melt stream of steel from 0.3 mm diameter and a jet velocity of 150 m / sec resulting in overheating of 200 C above the melting temperature a thermal output of about 125 kW with what a power flux density of about 1.8 ^*10^8th W / cm² equivalent. The latent heat capacity in the melt, which is directly thereof to melt the part to cut material, such. As steel, available is 12 kW. From this performance with the correspondingly high power flux density, a high proportion of heat can be used for cutting. Furthermore, the cutting beam pulse is very high at the given jet velocity, while the beam speed is below the speed of sound of the melt. A coupling of the pulse in the cutting gap for transporting the molten material is therefore easily possible, even if the kerf is very narrow in accordance with the beam diameter. The cutting speed can be very high and results from the pulse and current account.

Besides those already mentioned for the liquid jet materials, such as oil and metal at these other conspecific or alien materials for different materials can be used that can be selected so that chemical reactions to release exothermic energy or to lower the melting temperature or to prevent the emergence of a cutting beard or take place for easy removal of the cutting beard.

The inventive method can be thermally unstable materials such as plastics or composites separate when the temperature of the liquid jet is above the melting or decomposition temperature of the respective material.

Since it is difficult to use pumps for high temperatures, the energy for accelerating the liquid jet can carry 3 acts upon pressurized gas via the melt. For this purpose, the device according to FIG. 2 to a pressure-resistant container 10 with a pressurized gas supply eleventh A nozzle 12 is directly connected to the lower region of the pressure-resistant container 10th The present in the vessel 10 heated liquid or melt 3 can be driven out by about the supply of compressed gas 11 supplied pressurized gas at high velocity from the nozzle 12 and cuts the workpiece 6 in the manner described above.

While the devices shown in FIG. 1 and 2 are operated intermittently in the first place, since the container 1, 10 have only a limited capacity, can be 3 to perform a continuous cutting process with the apparatus of FIG.. The apparatus of FIG. 3 consists of a mold 13, which is designed tubular and into which a metal wire or metal rod 15 is inserted by means of drive rollers 17. In the example shown, the mold 13 has an inner diameter, which is the outer diameter of the metal wire or metal rod 15 is substantially the same, but may also be designed as a container, the mold is in transported when the metal wire or metal rod 15 is sealed by a corresponding insertion opening. To the mold 13, a heating device 14 is arranged, which melts the metal wire or metal rod 15 at its front end, and heated above the melting temperature, so that there is 13 molten metal 16 in the area in front of a discharge nozzle 18 in the mold. This molten metal 16 is driven by means of the piston acting as a metal wire or metal rod 15, which is driven by the drive rollers 17 constantly driven into the mold 13, from the nozzle 18 at high speed. The exit velocity is proportional to the ratio of the cross section of the metal wire or metal rod 15 to the cross section of the nozzle 18. This means that it is possible to easily achieve a high exit velocity. If the wire diameter z. B. 3 mm and the nozzle diameter is 0.3 mm, resulting in a discharge velocity of the melt 16 from the nozzle 18, which is 100 times the rate of feed of the metal wire or metal bar 15. If one wants to achieve an exit velocity of 150 m / sec, a feed speed of the metal wire or the metal bar 15 of only 1.5 m / sec is sufficient. is furthermore advantageous that the sealing of the metal wire or metal rod 15 in the mold 13 without special measures results, since the melt 16 a possibly present gap between the metal wire or metal rod 15 and the mold 13 fills and solidifies to the entrance opening, without characterized that a significant hindrance to the entry movement of the metal wire or metal rod 15 enters into the mold 13, when selecting a suitable material for the mold 13 and, if necessary, to ensure suitable lubrication.