Abstract: Protective cap for a plasma arc working torch, includes a cap body (7) having an opening (17) for the passage of plasma gas, the cap body (7) being made of at least one material of ceramic type. The ceramic is a silicon nitride or an aluminum silicate. Preferably, the ceramic cap body (7) is clad with boron nitride deposited on the external surface of the cap body, the thickness of the cladding of boron nitride being less than 3 mm. Torch provided with such a cap and its use in a steel plate plasma cutting operation.

Abstract: An installation and a method for oxygen arc cutting of a metal workpiece containing at least a ferrous material, in particular a structural steel workpiece, which consists in: pre-heating locally a priming zone of the metal workpiece to be cut by subjecting the priming zone to a plasma jet; then in producing a localized fusion and/or combustion of the ferrous material contained in the workpiece, using the plasma jet or a combination of the plasma jet and an oxidizing gas flow to obtain a perforation along the whole thickness of the metal workpiece; once the perforation has been obtained, in synchronously displacing, the plasma jet and the oxidizing gas flow along a cutting path to produce a predefined slit through the metal workpiece.

Abstract: Protective cap for a plasma arc working torch, includes a cap body (7) having an opening (17) for the passage of plasma gas, the cap body (7) being made of at least one material of ceramic type. The ceramic is a silicon nitride or an aluminum silicate. Preferably, the ceramic cap body (7) is clad with boron nitride deposited on the external surface of the cap body, the thickness of the cladding of boron nitride being less than 3 mm. Torch provided with such a cap and its use in a steel plate plasma cutting operation.

Abstract: Process and unit for the arc working, particularly plasma cutting, of a workpiece, in which a plasma torch is supplied with an electric current and with a gas mixture containing oxygen and nitrogen, and a plasma jet obtained by the ionization of the gas mixture by the electric current is delivered by means of the plasma torch. The concentration of nitrogen and oxygen in the gas mixture is less than 50%. The gas mixture is obtained by adding a defined amount of nitrogen or, depending on the case, oxygen immediately before the gas mixture is introduced into the torch. The amount of nitrogen or oxygen is defined according to the thickness of the workpiece, to the grade of the constituent material of the workpiece, to the desired work rate and/or to the intensity of the electric current.

Abstract: Process and unit for the arc working, particularly plasma cutting, of a workpiece, in which a plasma torch is supplied with an electric current and with a gas mixture containing hydrogen and nitrogen and/or argon, and a plasma jet obtained by the ionization of the gas mixture by the electric current is delivered by means of the plasma torch. The hydrogen concentration in the gas mixture containing hydrogen and nitrogen and/or argon is less than 50%. The gas mixture is obtained by adding a defined amount of hydrogen to nitrogen and/or argon, immediately before the gas mixture is introduced into said torch. The defined amount of hydrogen is defined according to the thickness of the workpiece, to the grade of the constituent material of the workpiece, to the desired work rate and/or to the intensity of the electric current.

Abstract: Process and unit for the arc working, particularly plasma cutting, of a workpiece, in which a plasma torch is supplied with an electric current and with a gas mixture containing oxygen and nitrogen, and a plasma jet obtained by the ionization of the gas mixture by the electric current is delivered by means of the plasma torch. The concentration of nitrogen and oxygen in the gas mixture is less than 50%. The gas mixture is obtained by adding a defined amount of nitrogen or, depending on the case, oxygen immediately before the gas mixture is introduced into the torch. The amount of nitrogen or oxygen is defined according to the thickness of the workpiece, to the grade of the constituent material of the workpiece, to the desired work rate and/or to the intensity of the electric current.

Abstract: Process and unit for the arc working, particularly plasma cutting, of a workpiece, in which a plasma torch is supplied with an electric current and with a gas mixture containing hydrogen and nitrogen and/or argon, and a plasma jet obtained by the ionization of the gas mixture by the electric current is delivered by means of the plasma torch. The hydrogen concentration in the gas mixture containing hydrogen and nitrogen and/or argon is less than 50%. The gas mixture is obtained by adding a defined amount of hydrogen to nitrogen and/or argon, immediately before the gas mixture is introduced into said torch. The defined amount of hydrogen is defined according to the thickness of the workpiece, to the grade of the constituent material of the workpiece, to the desired work rate and/or to the intensity of the electric current.