Method for producing a housing central part of a high-pressure slide gate valve

Abstract

The invention relates to a method for producing a central housing part (1) of a high-pressure slide gate valve from high-temperature steel, in the case of which two die-forged central-housing-part half-shells (1a, 1b) with forged-on connectors (4a, 4b) are welded to one another, using electron-beam welding without any welding filler material, by a butt weld seam (2), which runs in a plane (3) which runs transversely to the connectors (4a, 4b) and subdivides the central housing part (1). In order to increase the creep resistance, and to reduce the weight, of such a central housing part, the production costs at the same time being advantageous, the invention proposes that the wall thicknesses of the central-housing-part half-shells (1a, 1b) should be designed overall on the basis of a weld strength factor (WSF=1), and that, once the weld seam (2) has been produced, the entire central housing part (1) should be subjected to a rigorous heat treatment involving heating to beyond the transformation temperature, quenching and tempering.

Claims

1. A method for producing a central housing part of a high-pressure slide gate valve from high-temperature steel, with first and second die-forged central-housing-part half-shells with forged-on connectors welded to one another, using electron-beam welding without any welding filler material, by a butt weld seam, which runs in a plane which runs transversely to the connectors and subdivides the central housing part, the method comprising: designing wall thicknesses of the first and second central-housing-part half-shells overall on a basis of a weld strength factor equal to one, and once the butt weld seam has been produced, subjecting the entire central housing part to a rigorous heat treatment involving heating to beyond the transformation temperature, quenching and tempering, wherein walls of the first and second central-housing-part half shells are designed to be as thin as possible, with account being taken of the static, thermal and dynamic loading.

2. The method as claimed in claim 1, further comprising forging during die forging the first and second central-housing-part half-shells, including the seat surfaces and the connectors of the first and second central-housing part half-shells, to form one piece.

3. The method as claimed in claim 1, further comprising forging during die forging first and second housing-neck half-shells onto the first and second central-housing-part half-shells to form one piece, and during electron-beam welding, welding the first and second central-housing-part half-shells with the first and second housing-neck half-shells forged on the first and second central-housing-part half-shells in one piece, to form a housing with a neck, wherein the butt weld seam runs in the same plane between the first and second central-housing-part half-shells and the first and second housing-neck half-shells.

4. The method as claimed in claim 3, wherein, during die forging, grooves for accommodating a supporting ring of a self-sealing housing-neck cover closure are made in the sides of the first and second housing-neck half-shells.

5. The method as claimed in claim 3, wherein, during die forging, guide elements for slide plates of the high-pressure slide gate valve are forged into inner sides of the first and second central-housing-part half-shells and/or of the first and second housing-neck half-shells.

6. A method for producing a central housing part of a high-pressure slide gate valve from high-temperature steel, the method comprising: (a) providing a first central-housing-part half-shell and a second central-housing-part half-shell, the first and second central-housing-part half shells having a respective wall thickness configured to obtain a weld strength factor equal to one, (b) die-forging a first connector to the first central-housing-part half-shell and a second connector to the second central-housing-part half shell to form die-forged first and second central-housing-part half shells, (c) welding the first and second die-forged central-housing-part half-shells to one another so that the central housing part is formed with a weld strength factor equal to one, the welding using electron-beam welding without any welding filler material and forming a butt weld seam, the butt weld seam running in a plane, the plane running transversely to the first and second connectors and subdividing the central housing part, and (d) after the welding, subjecting all of the central housing part to a heat treatment, the heat treatment comprising heating to beyond a transformation temperature, quenching, and tempering.

Description

(1) Exemplary embodiments of the invention will be explained in more detail hereinbelow with reference to the drawing, in which:

(2) FIG. 1 shows a longitudinal section of a central housing part according to the invention;

(3) FIG. 2 shows a longitudinal section through the left-hand central-housing-part half-shell from FIG. 1;

(4) FIG. 3 shows a view of FIG. 2 as seen in the throughflow direction;

(5) FIG. 4 shows a perspective view of the central-housing-part half-shell according to FIGS. 2 and 3;

(6) FIG. 5 shows a plan view, as seen from above, of FIG. 2;

(7) FIG. 6 shows a longitudinal section of a housing with a housing neck produced by the method of the invention;

(8) FIG. 7 shows a longitudinal section through the left-hand housing half-shell with neck according to FIG. 6;

(9) FIG. 8 shows a view of FIG. 7 as seen in the throughflow direction;

(10) FIG. 9 shows a plan view, as seen from above, of FIG. 7;

(11) FIG. 10 shows a perspective view of the housing half-shell according to FIG. 7;

(12) FIG. 11 shows a longitudinal section of a housing with a neck in a modified embodiment produced by the method according to the invention; and

(13) FIG. 12 shows a view of FIG. 11 as seen in the throughflow direction.

(14) The drawing uses reference sign 1 to denote the high-temperature-steel central housing part of a high-pressure slide gate valve in its entirety. Said central housing part comprises two central-housing-part half-shells 1a and 1b, which are welded to one another along a butt weld seam 2, with weld-seam flanks 2a and 2b, by electron-beam welding without any welding filler material. The butt weld seam 2 runs in a plane 3 which runs transversely to the throughflow direction of the high-pressure slide gate valve and subdivides the central housing part 1 approximately in the center.

(15) The central-housing-part half-shells 1a and 1b are forged in the die by the method according to the invention. They are particularly well-suited for such working in the die because they are accessible over a large surface area from opposite sides.

(16) The walls of the central-housing-part half-shells 1a and 1b are designed to be as thin as possible, with account being taken of the static, thermal and thermodynamic loading, and, in particular in the region of the weld-seam flanks 2a and 2b have no material thickenings. The wall thicknesses are thus designed overall on the basis of a weld strength factor WSF=1.

(17) As can also be seen from the drawing, the two central-housing-part half-shells 1a and 1b are provided with forged-on, tubular connectors 4a and 4b and with seat surfaces 5 which are forged in one piece into their inner sides and enclose the connectors 4a and 4b.

(18) As can also be gathered from FIGS. 6 to 10 and FIGS. 11 and 12, it is also possible, in die forging, for the central-housing-part half-shells 1a and 1b to be provided with forged-on housing-neck half-shells 6a and 6b which, in a manner similar to the central-housing-part half-shells 1a and 1b, are connected, by electron-beam welding without any welding filter material, to form a housing neck 6 which extends the central housing part 1 upward. The butt weld seams connecting the housing-neck half-shells 6a and 6b run in the same plane here, as does the weld seam 2 which connects the central-housing-part half-shells 1a and 1b.

(19) As can also be seen from FIG. 11, grooves 7, which serve for supporting a cover closure (not illustrated) which seals the housing neck 6 in the upward direction, can be forged into the inner sides of said housing-neck half-shells 6a and 6b. It is likewise possible for the central-housing-part half-shells 1a and 1b and/or the housing-neck half-shells 6a and 6b to be provided with forged-in guide elements (not illustrated specifically) for the slide plates of the high-pressure slide gate valve.

(20) In order to prepare for the electron-beam welding operation, first of all the surfaces which are to be welded to one another are ground to a smooth state. During the following welding operation, the abutting flanks are fused to one another directly without any welding filler material. The heat which is necessary for this purpose is introduced into the gap between the smooth-ground flanks by means of an electron beam.

(21) The definitively welded housing is then subjected as a whole to a rigorous heat treatment involving heating beyond the transformation temperature, quenching and tempering. As the welded housing is quenched and tempered anew in its entirety, this process being executed in accordance with the customary quenching and tempering rules of the relevant high-temperature steel, it is also the case that, above and beyond the weld seams, an undisturbed quenched-and-tempered microstructure is achieved. As a result, the housing which is produced in this way has the properties of a seamless housing produced from the same material.