Abstract: A method for forming a hollow cylinder, in a single step, into a quartz glass tube with a large outer diameter and high dimensional stability is provided. To produce the tube, the cylinder, while rotating, is softened in portions in a heating zone which is moved at a relative feed rate Va and the softened portion is radially expanded by a centrifugal force and/or internal overpressure applied in the hollow cylinder bore so as to form a deformation zone. The radial expansion of the softened portion is carried out at a location-dependent radial expansion rate Vr, the profile of which along the deformation zone has a maximum value Vr,max which is smaller than 20 cm/min. The temperature in a rear heating portion of the heating zone, assigned to the end of the deformation zone, is lower than in a front heating portion assigned to the beginning of the deformation zone.

Abstract: A method for producing a component includes joining individual wall parts, especially for producing a melting crucible for use at a high operating temperature in a crucible-pulling method for quartz glass, wherein at least two wall parts of a refractory metal or of a base alloy of a refractory metal are provided, butt-joined to form a joint and joined together by sintering at a temperature above 1500° C. to form the component. A sealant is inserted into the joint to provide a component of improved tightness and to ensure improved sintering of the individual parts of the component. A component produced according to the method, particularly a melting crucible, particularly in a crucible pulling method for quartz glass, has the joint between the butt-joined walls closed in a gas-tight manner by a sealant.

Abstract: A method for forming a hollow cylinder, in a single step, into a quartz glass tube with a large outer diameter and high dimensional stability is provided. To produce the tube, the cylinder, while rotating, is softened in portions in a heating zone which is moved at a relative feed rate Va and the softened portion is radially expanded by a centrifugal force and/or internal overpressure applied in the hollow cylinder bore so as to form a deformation zone. The radial expansion of the softened portion is carried out at a location-dependent radial expansion rate Vr, the profile of which along the deformation zone has a maximum value Vr,max which is smaller than 20 cm/min. The temperature in a rear heating portion of the heating zone, assigned to the end of the deformation zone, is lower than in a front heating portion assigned to the beginning of the deformation zone.

Abstract: A method for forming a hollow cylinder, in a single step or in as small a number of steps as possible, into a quartz glass tube with a large outer diameter and high dimensional stability is provided. The cylinder, while rotating about a rotation axis, is softened in portions in a heating zone which is moved at a relative feed rate Va, and the softened portion is radially expanded by a centrifugal force and/or an internal overpressure applied in the hollow cylinder bore so as to form a deformation zone. The tube is continuously shaped with an outer diameter D2 which is greater than that of the hollow cylinder D1. The radial expansion of the softened portion is carried out at a location-dependent radial expansion rate Vr, the profile of which along the deformation zone has a maximum value Vr,max which is smaller than two times the feed rate Va.

Abstract: A method for forming a hollow cylinder, in a single step or in as small a number of steps as possible, into a quartz glass tube with a large outer diameter and high dimensional stability is provided. The cylinder, while rotating about a rotation axis, is softened in portions in a heating zone which is moved at a relative feed rate Va, and the softened portion is radially expanded by a centrifugal force and/or an internal overpressure applied in the hollow cylinder bore so as to form a deformation zone. The tube is continuously shaped with an outer diameter D2 which is greater than that of the hollow cylinder D1. The radial expansion of the softened portion is carried out at a location-dependent radial expansion rate Vr, the profile of which along the deformation zone has a maximum value Vr,max which is smaller than two times the feed rate Va.

Abstract: The present invention refers to a method for producing a component by joining individual wall parts—especially for producing a melting crucible for use at a high operating temperature in a crucible pulling method for quartz glass, in that at least two wall parts of a refractory metal or of a base alloy of a refractory metal are provided, butt-joined to form a joint and joined together by sintering at a temperature above 1500° C. to form the component. To provide a component of improved tightness and to ensure improved sintering of the individual parts of the component, a sealant is inserted into the joint. Furthermore, the present invention refers to a component produced according to the method, particularly a melting crucible, particularly in a crucible pulling method for quartz glass, in which the joint between the butt-joined walls is closed in a gas-tight manner by a sealant.

Abstract: In a known method for drawing a tubular quartz glass strand, SiO2-containing starting material is fed to a melting crucible, softened therein into a viscous quartz glass mass (27), and said mass is pulled vertically downward as a cylindrical quartz glass strand (5; 33) through a die (4; 34) provided in the bottom region of the melting crucible (1), said die having a gap-shaped outlet (25; 36), which is defined by a bottom opening and a die inside part, and thereafter the quartz glass cylinder is cut to length.

Abstract: The invention relates to a known method for drawing a quartz glass cylinder from a melt crucible comprising an inner crucible chamber extending in the direction of a center crucible axis and bounded by a side wall and a floor, wherein SiO2 granulate is fed into the melt crucible and therein softened into a quartz glass mass, and said mass is drawn vertically downward as a cylindrical quartz glass strand by means of a first draw-off device through a first draw nozzle provided in the floor of the melt crucible, and the quartz glass cylinder is cut off therefrom.

Abstract: In a known melting crucible for use in a crucible drawing method, it is provided that the interior face of the crucible wall facing a crucible interior space is covered at least partially with a protective layer made of a noble metal. The known melting crucible does have good corrosion resistance with respect to the quartz glass melt, but the material costs are high because of the expensive coating metals. In order to provide a melting crucible for use in a crucible drawing method for quartz glass that exhibits good corrosion resistance at low material costs, it is proposed that the protective layer (2) be composed of a gas-tight, oxidic material that is not subject to a phase transition in the temperature range of 20° C. to 1800° C., and that the crucible interior space (17) have a gas space (17) above the quartz glass mass (27) to be held, and that the protective layer (2) be provided exclusively on the surface of the melting crucible interior face adjacent to the gas space (17).

Abstract: In a known method for coating a crucible for use at a high working temperature in a crucible drawing method for quartz glass, a base body wall of tungsten has applied thereto a protective layer containing a coating metal consisting of the group selected from iridium, rhenium, osmium and ruthenium. Starting therefrom, to provide a method for producing such a component exhibiting high corrosion resistance to the quartz glass melt at low material costs, it is suggested according to the invention that the protective layer should be produced from a layer material which contains tungsten and the coating metal, and in which the amount of the coating metal should be dimensioned such that it exceeds the limit amount of a coating metal-rich phase boundary of a solid mixture phase of tungsten and the coating metal, with the solid mixture phase being thermodynamically stable at the working temperature, by not more than 25 at. % (based on the total amount of tungsten and the coating metal in the layer material).

Abstract: In a known method for drawing a tubular quartz glass strand, SiO2-containing starting material is fed to a melting crucible, softened therein into a viscous quartz glass mass (27), and said mass is pulled vertically downward as a cylindrical quartz glass strand (5; 33) through a die (4; 34) provided in the bottom region of the melting crucible (1), said die having a gap-shaped outlet (25; 36), which is defined by a bottom opening and a die inside part, and thereafter the quartz glass cylinder is cut to length.

Abstract: In a known method for drawing a tubular quartz glass strand, a crucible is fed with SiO2-containing start material, the start material is softened in the crucible and, as a softened quartz glass mass, is drawn vertically downwards as a tubular quartz glass strand along a drawing axis through an annular gap between an outer member and an inner member, which is arranged in a through hole of the outer member, of a drawing nozzle provided in the bottom area of the crucible.

Abstract: In a known method for coating a crucible for use at a high working temperature in a crucible drawing method for quartz glass, a base body wall of tungsten has applied thereto a protective layer containing a coating metal consisting of the group selected from iridium, rhenium, osmium and ruthenium. Starting therefrom, to provide a method for producing such a component exhibiting high corrosion resistance to the quartz glass melt at low material costs, it is suggested according to the invention that the protective layer should be produced from a layer material which contains tungsten and the coating metal, and in which the amount of the coating metal should be dimensioned such that it exceeds the limit amount of a coating metal-rich phase boundary of a solid mixture phase of tungsten and the coating metal, with the solid mixture phase being thermodynamically stable at the working temperature, by not more than 25 at. % (based on the total amount of tungsten and the coating metal in the layer material).