US20070220906A1

US20070220906A1 - Method and Device for Rapid Cooling of Work Pieces

Info

Publication number: US20070220906A1
Application number: US11/688,767
Authority: US
Inventors: Anders Astroem; Ernst Wandke
Original assignee: Linde GmbH
Current assignee: Linde GmbH
Priority date: 2006-03-21
Filing date: 2007-03-20
Publication date: 2007-09-27
Also published as: ATE440970T1; BRPI0700848A; PL1837410T3; DE102006012985A1; ES2332811T3; EP1837410A1; EP1837410B1; DE502006004656D1; DK1837410T3

Abstract

A method for cooling a work piece in a cold chamber using a cooling medium that enters the cold chamber through a feed and is taken through one or more nozzles into a space to receive the work piece, is disclosed. A liquid gas or a liquid gas mixture is used as the cooling medium, whose heat of vaporization is used to cool the cold chamber and/or to cool the surface of the work piece. A device to carry out the method and use of the device for metallic work pieces, are also disclosed.

Description

This application claims the priority of German Patent Document No. 10 2006 012 985.7, filed Mar. 21, 2006, the disclosure of which is expressly incorporated by reference herein.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to a method for cooling a work piece, wherein the work piece is introduced into a cooling zone which adjoins a cold chamber and wherein a cooling medium is brought to the cold chamber by a supply and is taken by way of one or more nozzles from the cold chamber into the cooling zone.
The invention additionally relates to a device for cooling a work piece having a cold chamber with a supply for a cooling medium and one or more nozzles and having a cooling zone to receive the work piece.
A plurality of methods and devices for cooling is known. For example, a plurality of methods and devices for cooling and quenching work pieces has been used in the realm of heat treating for centuries. For example, quenching in fluids such as oils, water, emulsions or others, quenching in salts, or with the assistance of gases is common. Gases are conventionally used in manifold forms, for example at high pressure, which increases the ability of the gas to transfer heat energy. With the same object in view, in the prior art gases are brought into contact with the hot surface of the work piece to be cooled at a high relative velocity. In accordance with a relatively new method, known as gas quenching, gas at high pressure and at a high flow velocity is brought into contact with the hot surface of the work piece to be cooled.
A cooling method for pipes and other semi-finished products, e.g., rods, profiles, wire, and the like, is known as unpublished prior art in which the work pieces to be cooled are cooled as a bundle, or also individually, by way of a nozzle field conforming to their shape over which the gas is blown onto the work pieces, while the work pieces are moved through the nozzle field. The nozzle field can be enclosed to conform to their shape. The cooling result could be still better, however, particularly for work pieces with a high initial temperature of more than 550° C.
The object of the present invention is to make available an improved method and a device for carrying out this method for cooling work pieces.
The object proposed is achieved with respect to the method by introducing the work piece into a cooling zone which adjoins a cold chamber and where a cooling medium is supplied to the cold chamber and taken through one or more nozzles from the cold chamber into the cooling zone, where the cooling medium comprises a liquid gas or a liquid gas mixture whose heat of vaporization is used to cool the cold chamber and/or to cool the surface of the work piece.
In accordance with the invention, the gas introduced into the cooling zone through the nozzles—in a liquid or gaseous state—is used to cool the work piece by convection. On the other hand, the cooling medium also cools the cold chamber which adjoins the cooling zone. In this way, the heat transfer which predominates particularly at high temperatures is reinforced by radiation.
A liquid gas or a mixture of gases in liquid and gaseous form is preferably used as the cooling medium whose heat of vaporization is used to cool the cold chamber and/or to cool the surface of the work piece. The environment of the work piece is brought to a temperature which allows a particularly effective cooling of the work piece. Particularly for the event that the work piece has an initial temperature of more than 550° C., the prevalence of the heat dissipation through radiation which exists in this temperature range compared with heat dissipation through heat transfer or convection can be taken into account using the method in accordance with the invention.
The use of liquid gas or a mixture of gases in liquid and gaseous form has, in addition to the particularly advantageous low temperature which is thereby achieved, the advantages of a clean, environmentally friendly process in which post-cleaning of the work piece can be dispensed with, no process-related corrosion occurs, and the process sequence can be easily controlled because the cooling medium can be easily metered. Overall, a highly effective cooling process is available in a device which occupies very little space.
Preferably the liquid gas or the liquid gas mixture is vaporized completely or partially in the cold chamber, where the heat of vaporization is used completely or partially for cooling the cold chamber.
Alternatively, or in addition, the liquid gas or a mixture of gases in liquid or gaseous form is advantageously effective completely or partially directly on the surface of the work piece through vaporization, where the heat of vaporization is used completely or partially to cool the surface of the work piece.
In accordance with a particularly advantageous refinement of the invention, the work piece is moved through the cooling zone, where the cooling zone is matched to the shape of the work piece so that the cooling medium remains for sufficient time in the cooling zone so that the surface of the work piece can dissipate heat adequately to the cooling medium on the one hand, and on the other hand the now heated cooling medium leaves the cooling zone at high velocity.
The liquid gas or a mixture of gases in liquid and gaseous form is preferably introduced into the cooling zone at a high flow velocity.
Liquid nitrogen, liquid hydrogen, liquid helium, or liquid argon is used especially preferably as the liquid gas. In accordance with an advantageous embodiment, a mixture of two or more of the aforementioned liquid gases is used as a liquid gas mixture.
One or more additional components are added to the liquid gas or the liquid gas mixture to particular advantage. For example, carbon dioxide and/or methane is mixed with the liquid gas or liquid gas mixture.
The object proposed concerning the device is achieved by a device for cooling a work piece with a cold chamber having a supply for a cooling medium and one or more nozzles and having a cooling zone to receive the work piece, where the supply and the nozzle(s) are configured for the introduction of liquid gas or a liquid gas mixture.
The cold chamber is preferably provided as an apparatus for evaporating the liquid gas or the liquid gas mixture.
The cold chamber is especially preferably configured to match the shape of the work piece so that only a very small gap is provided between the nozzles for the cooling medium and the surface of the work piece. The cold chamber and the cooling zone advantageously adjoin each other so that on the one hand the cooling medium issuing through the nozzle from the cold chamber quickly comes into contact with the work piece to exchange heat, and on the other hand the radiant heat coming from the work piece is absorbed by the cold chamber. The cold chamber is preferably configured for this in such a way that it surrounds the work piece on several sides.
In accordance with a particularly advantageous refinement of the invention, the cold chamber is subdivided into two or more cold chamber sections which are spaced apart from each other by an interstice in the area of the nozzles.
Furthermore, the use of the previously described device for cooling metallic work pieces, in particular for cooling pipes or other half-finished goods such as rods, profiles, or wire is the subject of the present invention.
The invention offers a highly effective cooling or quenching method, in particular for hot metallic parts. At high temperatures, the transfer of heat takes place principally through radiation. In accordance with the invention, the cold chamber is kept at a low temperature by the liquid gas provided. Immediately adjacent the cold chamber is the cooling zone to receive the work piece. The temperature difference between the surface of the work piece and the cold chamber is maximized by the cooling of the cold chamber so that optimal cooling through radiation results. In addition, the cooling medium is taken through nozzle orifices in the cold chamber onto the surface of the work piece. This flow effects additional cooling through convection. Overall, the invention offers a particularly efficient exploitation of the different mechanisms of heat transfer.
The invention, as well as additional embodiments of the invention, are explained hereinafter with reference to the embodiments shown in the Figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic representation of a cold chamber in accordance with the invention with a work piece;
FIG. 2 shows a schematic representation of a cold chamber in accordance with the invention which is subdivided into three cold chamber sections; and
FIG. 3 show a schematic sectioned representation from FIG. 2 along line A-A.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a work piece 1, here a pipe 1, which is being moved through the cold chamber 3, by which the pipe is surrounded, in the direction indicated by the arrow 2. The cold chamber 3 and the cooling zone 10 advantageously adjoin each other. The cold chamber 3 is matched to the shape of the pipe 1. Liquid gas, here for example liquid nitrogen, is introduced continuously into the cold chamber 3 through the supply 4. According to requirements, the gas exits as liquid gas through the nozzle field formed by the nozzles 5 into the cooling zone 10, and, using the heat of vaporization, takes effect as a very cold cooling medium at high flow velocity on the surface of the work piece 1.
In another case, the cold chamber 3 works as an evaporator. The heat of vaporization is used in this case to cool and keep the cold chamber 3 cold.
In both variants, the cold chamber 3 has approximately the temperature of the liquid gas. This means that the temperature difference between work piece surface and cold chamber surface is permanently very high and the result is a corresponding cooling of the work piece 1 through the mechanism of radiation which is supported effectively by the transfer of heat as a result of the originally very cold stream of gas 6.
The effect of this method can be optimized so that the upper limit for the quantity of heat carried away is no longer determined by the volume of liquid gas supplied and its thermal properties but the heat conducting mechanism of the work piece 1 defines the upper limit.
For the embodiment shown in FIG. 1, the following values can be cited as examples: a steel pipe 1 with a diameter of 60 mm and a wall thickness of 3 mm is moved through the cold chamber 3 at a speed of 5 m/s. The initial temperature of the steel pipe is 1050° C. The final temperature after cooling is, as an example, 700° C. This final result is achieved by the use of liquid nitrogen as a cooling medium in an amount of 700 kg/h and a feed pressure of 3 bar. The nozzle field has 20 nozzles 5 with a diameter of 3 mm each. The total length of the cold chamber is 1200 mm.
FIG. 2 shows a further embodiment. Here the cold chamber 3 is divided into three cold chamber sections 8 between which gas in the form of a gas stream 6 exits through the interstice 7. The movement of the work piece again takes place in the direction indicated by the arrow 2. The work piece 1 in this example is a copper profile 1 having a greatest width of 35 mm which is leaving an extruding press at 100 mm/min and a temperature of 750° C. The final temperature after cooling is to be 200° C. The copper profile 1 is moved through the device shown in FIG. 2 and cooled with the aid of a liquid gas mixture fed in through the supply 4 and dispensed in the individual cold chamber sections 8 through the nozzles 5. Either liquid helium or, as a more economical variant, a mixture of 96% liquid nitrogen and 5% gaseous hydrogen is used. Gas consumption is 350 kg/h.
Because of the different temperature relationships, the heat transfer using the gas stream 6 plays a greater part in this example than in the example from FIG. 1. In order to optimize the flow relationships for the gas stream 6 and to ensure the exit of gas in spite of the very narrow gap 9, the cold chamber 3 here was divided into three cold chamber sections 8. The distances between the cold chamber sections 8 can be changed and optimized according to the concrete requirements of different applications.
FIG. 3 show a cross-sectional representation of FIG. 2 along line A-A. The shape of the cold chamber 3 which is matched to the work piece, or the section of the cold chamber 8 shown, can be seen particularly well here. As a result of this shape, the nozzles 5 are always advantageously positioned at a consistently short distance 9 from the surface of the work piece.
The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.

Claims

1. A method for cooling a work piece, wherein the work piece is brought into a cooling zone which adjoins a cold chamber, and wherein a cooling medium is supplied to the cold chamber and taken through a nozzle from the cold chamber into the cooling zone, wherein the cooling medium comprises a liquid gas or a liquid gas mixture whose heat of vaporization is used to cool the cold chamber and/or to cool a surface of the work piece.

2. The method according to claim 1, wherein the liquid gas or the liquid gas mixture is vaporized completely or partially in the cold chamber where the heat of vaporization is used completely or partially to cool the cold chamber.

3. The method according to claim 1, wherein the liquid gas or the liquid gas mixture is vaporized completely or partially in the cooling zone, where the heat of vaporization is used completely or partially to cool the surface of the work piece.

4. The method according to claim 1, wherein the work piece is moved through the cooling zone during the cooling.

5. The method according to claim 1, wherein the cooling zone is matched to a shape of the work piece such that the cooling medium covers only a very short distance between the nozzle through which the cooling medium is introduced and the surface of the work piece.

6. The method according to claim 1, wherein the liquid gas or liquid gas mixture is brought into the cooling zone at a high flow velocity.

7. The method according to claim 1, wherein liquid nitrogen, liquid hydrogen, liquid helium, or liquid argon is used as the liquid gas.

8. The method according to claim 1, wherein a mixture of two or more of liquid nitrogen, liquid hydrogen, liquid helium, or liquid argon is used as the liquid gas mixture.

9. The method according to claim 1, wherein one or more additional components are added to the liquid gas or the liquid gas mixture.

10. The method according to claim 9, wherein carbon dioxide and/or methane is mixed into the liquid gas or liquid gas mixture.

11. A device for cooling a work piece having a cold chamber with a supply for a cooling medium and a nozzle, and having a cooling zone to receive the work piece, wherein the supply and the nozzle are suitably configured for an introduction of liquid gas or a liquid gas mixture.

12. The device according to claim 11, wherein the cold chamber vaporizes the liquid gas or the liquid gas mixture.

13. The device according to claim 11, wherein the cold chamber is configured to match a shape of the work piece such that only a very small gap is provided between the nozzle for the cooling medium and a surface of the work piece.

14. The device according to claim 11, wherein the cold chamber is subdivided into two or more cold chamber sections which are spaced apart from each other by an interstice in a nozzle area.

15. A use of the device according to claim 11 for cooling a metallic work piece, in particular for cooling pipes or other semi-finished products such as rods, profiles or wire.

16. A method for cooling a work piece, comprising the steps of:

supplying a cooling medium to a cold chamber;

cooling the cold chamber by the cooling medium;

supplying at least a portion of the cooling medium from the cold chamber through a nozzle to a cooling zone, wherein the cooling zone is disposed within the cold chamber and wherein the work piece is received within the cooling zone;

cooling the work piece by the cold chamber by absorbing radiant heat from the work piece; and

cooling the work piece by the cooling zone by flowing the at least the portion of the cooling medium supplied to the cooling zone from the nozzle over a surface of the work piece.

17. The method according to claim 16, wherein the cooling medium is a liquid gas or a liquid gas mixture.

18. An apparatus for cooling a work piece, comprising:

a cold chamber; and

a cooling zone disposed within the cold chamber, wherein the work piece is receivable within the cooling zone;

wherein a cooling medium is supplied to the cold chamber and wherein at least a portion of the cooling medium supplied to the cold chamber is supplied from the cold chamber to the cooling zone through a nozzle.

19. The apparatus according to claim 18, wherein the cold chamber includes a first chamber section and a second chamber section, and wherein the cooling medium in the cooling zone exits the cooling zone through a gap defined by the first chamber section and the second chamber section.

20. The apparatus according to claim 18, wherein the cooling medium is a liquid gas or a liquid gas mixture.