Method for performing gas welding processing on metal

Abstract

According to the invention, a method for gas welding machining of metal is proposed, in which hydrogen as a fuel gas from a fuel gas source and oxygen as an oxidizing agent from an oxidizing agent source are combined on a machining tool, and a flame for machining a workpiece is generated in front of an inlet opening of a machining tool opening, the method is characterized in that a combustible, carbon-containing auxiliary gas is mixed into the fuel gas in the machining tool, and the auxiliary gas is combusted with oxygen in the form of a luminescent flame.

Description

[0001] The invention relates to a method for gas welding of metals, in which method hydrogen from a hydrogen source and oxygen from an oxygen source are combined on a processing tool and react with each other, wherein a flame for gas welding of a workpiece is generated in front of an access opening of the processing tool.

[0002] For gas-welding flame cutting and other gas-welding processes for metals, such as flame straightening, gouging or gas welding, hydrocarbon-based fuel gases such as propane, acetylene, propylene, ethylene, etc., as described in DE 2 823 305 A1, are now mainly used. Since carbon dioxide emissions are generated during the combustion of these gases, a CO2 tax will be imposed on these fuel gases and fuel gas mixtures in the near future by legal regulations that are currently being prepared. Regardless of the cost aspects, avoiding the generation of climate-damaging carbon dioxide and other emissions such as carbon monoxide or particulates (carbon) produced as reaction products of the combustion is of great significance for increasing work safety and environmental protection.

[0003] Instead of carbon-based fuel gases, hydrogen, which has also been known as a fuel gas in gas welding technology for more than 100 years, is provided as an alternative. However, the use of hydrogen as a fuel gas in gas welding technology is associated with the following disadvantages: hydrogen burns with oxygen in a blue transparent flame, which is almost invisible, especially in brighter surroundings. The resulting poor flame visibility makes it difficult or hinders the clear setting of the main flame cone and the operation while maintaining a defined distance between the flame cone and the surface of the workpiece to be processed. From this point of view, the setting of the optimal fuel gas-oxygen mixture can only be performed with difficulty or even cannot be achieved visually. Therefore, for manual work, it is only possible to use hydrogen as a fuel gas satisfactorily in special cases. In automated operation, it is possible to use suitable control technology with the help of flow meters or similar methods, but this requires additional equipment complexity, which in turn increases the susceptibility to errors.

[0004] EP 0 952 205 A1 discloses using a fuel gas mixture of hydrogen and acetylene in a ratio of 99:1 to 90:10 to achieve a better display of the hydrogen flame of a cutting torch. In this case, the gas mixture is provided in a container or produced in a mixing device arranged directly upstream of the cutting torch. However, the storage or transport of gas mixtures containing acetylene is not without problems, since acetylene has a tendency to spontaneously decompose explosively.

[0005] It is therefore an object of the present invention to provide a method for using hydrogen as fuel gas in gas welding technology which overcomes the above-mentioned disadvantages.

[0006] This object is achieved by a method according to patent claim 1. Advantageous embodiments of the invention are claimed in the dependent claims.

[0007] Therefore, according to the present invention, a method for gas welding of metal is proposed, in which method hydrogen from a hydrogen source and oxygen from an oxygen source are combined on a processing tool and react with each other, wherein a flame for gas welding of the workpiece is generated downstream of an access opening of the processing tool, the method being characterized in that, in a flow sense, an auxiliary gas from an auxiliary gas source, which burns with oxygen in a visible flame, is mixed into the hydrogen in the processing tool before the flame is generated.

[0008] According to the invention, only in the processing tool (for example a cutting torch) is an auxiliary gas mixed with the hydrogen used as the actual fuel gas for the gas welding process. Since the auxiliary gas is supplied very late, gases such as acetylene that have a tendency to spontaneously decompose can also be used as auxiliary gases that do not endanger the user. The auxiliary gas is also combustible and burns with oxygen in a flame that is easily noticeable in the visible spectrum. The combustion process triggered by the auxiliary gas mixed with hydrogen causes the flame generated as a whole to be easily noticeable. Parameters that are important for the gas welding process, such as the flame temperature, the ignition speed or the flame calorific value, are not affected by the auxiliary gas, or are only slightly or even positively affected. Therefore, the above-mentioned disadvantages of using pure hydrogen as fuel gas can be overcome.

[0009] In this context, “hydrogen” is understood to mean a gas having a hydrogen content of at least 99.5% by volume, preferably at least 99.99% by volume.

[0010] In this context, “oxygen” is understood to mean an oxygen-containing gas having an oxygen content of more than 90% by volume, preferably a gas having an oxygen content of more than 99% by volume, particularly preferably a gas having an oxygen content of more than 99.9% by volume.

[0011] As hydrogen and oxygen sources, sources customary for gas welding methods are used, which sources are in particular compressed gas cylinders, compressed gas cylinder bundles or tanks, respectively.

[0012] As auxiliary gas, preferably a carbon-containing gas such as acetylene, methylacetylene, butyne or butadiene is used, which is mixed with hydrogen in a volume flow ratio of 1% to 50%, preferably 2% to 10%, particularly preferably 2% to 3%. Alternatively, as auxiliary gas, phosphorus compounds, preferably gaseous phosphorus-hydrogen compounds such as PH3 or gaseous sulfur compounds such as hydrogen sulfide (H2S) can also be used. In this case, the volume or volume flow of the hydrogen mixed with auxiliary gas should not exceed 50 vpm, preferably between 10 vpm and 50 vpm; even with such low doping, it is always sufficient to produce an easily visible flame. It is also conceivable to use auxiliary gas in the form of a mixture of two or three of the above-mentioned gases. In addition, during the operation of the processing tool, the volume flow ratio of hydrogen and auxiliary gas should be able to be changed within the above-mentioned limits or should also be able to be changed as desired, for example in order to achieve a more obvious flame visibility required for a short time.

[0013] As auxiliary gas source, a container suitable for the corresponding auxiliary gas, such as a pressure container or a tank, is used; in the case of acetylene, for example, a bottle approved for storing acetylene or a bundle of approved acetylene cylinders is used.

[0014] According to the invention, as processing tools, tools common to gas welding processes are used, such as gas welding flame cutting machines, flame spraying devices, planing devices or gas welding welders. Therefore, the method according to the invention is particularly suitable for all gas welding processing methods mentioned at the beginning.

[0015] The supply of auxiliary gas to the hydrogen in the process tool is preferably carried out at a suitable mixing accessory, which is arranged upstream of the oxygen supply in the process tool. For example, a pressure nozzle is provided in the process tool, the mixing of auxiliary gas into the hydrogen is carried out at the pressure nozzle, and the pressure nozzle is arranged upstream of the combination of the hydrogen-auxiliary gas mixture with the supplied oxygen (viewed in the flow direction of the hydrogen). This can also be a pressure nozzle.

[0016] In an advantageous embodiment of the invention, the ratio of the volume flows of hydrogen and auxiliary gas (more precisely, of a hydrogen-auxiliary gas mixture) to oxygen is variably adjustable during the use of the processing tool, wherein the change in the volume flow ratio can be achieved by changing the volume flow of one component while keeping the volume flow of the other component constant, or by changing both volume flows while keeping the total volume flow essentially constant. For this purpose, the processing tool is preferably equipped with a mixing accessory that allows the volume flow to be adjusted accordingly. The volume flow is preferably adjusted manually; however, alternatively or supplementarily, an automatic controller can also be provided, which controls the volume flow ratio of the respective components according to a predefined program and / or as a function of measured parameters. For example, a certain flame brightness, a predefined value or curve of the mixing ratio, or a limit value of a substance in the exhaust gas are considered as control variables, which are compared continuously or at predefined time intervals with the measured values ​​of the corresponding variables. In the case of the above-mentioned pressure nozzles connected in series, control devices are provided, which are preferably adjustable independently of each other, and which enable manual or automatic adjustment of the volume flow ratio at the respective pressure nozzles.

[0017] The freely adjustable volume flow ratio enables the gas flow to be flexibly adapted to the flame type and / or the respective conditions under which the gas welding process is to be carried out. For example, depending on the gas welding method and / or the material to be processed, an oxidizing flame (i.e. a flame operated with an excess of oxygen), a reducing flame (a flame operated with an excess of hydrogen) or a neutral flame is used. In order to be able to assess the state of the mixture, the user must be able to identify the main flame cone, which is invisible or barely visible in the case of a pure hydrogen flame. Since the metering of the auxiliary gas is freely adjustable, the main flame cone can be clearly seen by the user even in the case of different flame types or other conditions (e.g. light conditions in the working area).

[0018] The method according to the invention is suitable for all known gas welding methods, for example for gas welding, flame cutting, flame straightening or gouging. In addition, all materials that can usually be processed using gas welding technology can also be processed, in particular unalloyed or low-alloy steels or aluminum. In particular, the method according to the invention is suitable for flame cutting of unalloyed or low-alloy steels, in particular unalloyed or low-alloy steels with a metal sheet thickness of more than 10 mm.

Claims

1. A method for gas welding of metals, in which method hydrogen from a hydrogen source and oxygen from an oxygen source are combined and reacted on a processing tool, wherein a flame for gas welding a workpiece is generated downstream of an inlet opening of the processing tool, It is characterized in that In terms of flow, before the flame is generated, an auxiliary gas from an auxiliary gas source is mixed with the hydrogen in the machining tool, which auxiliary gas burns with oxygen in a visible flame.

2. The method according to claim 1, characterized in that During use of the process tool, a ratio of the volume flow rates of hydrogen gas to auxiliary gas at the process tool is variably adjustable.

3. The method according to claim 1 or 2, characterized in that: The ratio of the volume flows of hydrogen and oxygen is adjustable.

4. The method according to any one of the preceding claims, characterized in that A carbon-containing gas such as acetylene, methylacetylene or butadiene is used as the auxiliary gas.

5. The method according to any one of the preceding claims, characterized in that A gas containing a phosphorus compound and / or a sulfur compound is used as the auxiliary gas.

6. The method according to claim 4, characterized in that The carbon-containing gas used as an auxiliary gas is mixed into the hydrogen gas in a content of 0.1 to 10 volume %, preferably between 2 and 5 volume %.

7. The method according to any one of the preceding claims, characterized in that The gas welding process on the workpiece includes welding, flame cutting, flame straightening or gouging.