WO2008041117A1

WO2008041117A1 - High speed quenching assembly for metal products

Info

Publication number: WO2008041117A1
Application number: PCT/IB2007/002972
Authority: WO
Inventors: Tullio Caselli; Alberto Pedrazzini
Original assignee: SHAP SOLAR HEAT AND POWER SpA
Current assignee: SHAP SOLAR HEAT AND POWER SpA
Priority date: 2006-10-06
Filing date: 2007-10-05
Publication date: 2008-04-10
Anticipated expiration: 2009-04-06
Also published as: ITRM20060535A1

Abstract

A high speed quenching assembly (1) for metal products, comprising: an absorption chiller (5), designed to be supplied by fumes coming from processing of the metal products themselves and to cool a cooling liquid; a heat exchanger (3), designed to cool a current of air by means of the cooling liquid; conduction means, designed to convey the cooling liquid from the absorption chiller (5) to the heat exchanger (3); a quenching chamber (2), designed to house the metal products to be quenched; and further conduction means, designed to convey the cooled air from the heat exchanger (3) to the quenching chamber (1).

Description

HIGH SPEED QUENCHING ASSEMBLY FOR METAL PRODUCTS

TECHNICAL FIELD

The present invention relates to a high speed quenching assembly for metal products.

In particular, the present invention regards high speed quenching of aluminium products , to which the ensuing description will make explicit reference, without this implying any loss in generality.

BACKGROUND ART

The quenching of aluminium for making a wide range of products in different sectors of industry, such as for example the aeronautics and automotive industries, is one of the most critical operations in the process of Tβ-type thermal treatment of aluminium. An adequate design and provision of the quenching step enables production of elements with minimal residual stresses and small deformations. Currently, quenching is carried out by means of immersion of the blocks in a liquid, typically water, or through blowing of a current of air (air quenching) at room temperature.

In particular, in the cycle of production of aluminium products, the quenching step is always preceded by a step of heating in a furnace, in which the blocks are brought to a high temperature (>500°C) , and by a subsequent step of thermal ageing, which operates at medium temperatures (25O⁰C) .

DISCLOSURE OF INVENTION

The aim of the present invention is to provide a high speed quenching assembly for metal products that will present higher efficiency and lower expenditure of energy as compared to techniques of the known art.

The subject of the present invention is a high speed quenching assembly for metal products , characterized in that it comprises: an absorption chiller device, designed to be supplied by fumes coming from processing of said metal products and to cool a cooling liquid; a heat exchanger, designed to cool a current of air by means of said cooling liquid; conduction means, designed to convey said cooling liquid from said absorption chiller to said heat exchanger; a quenching chamber, designed to house the metal products to be cooled; and further conduction means, designed to convey cooled air from said heat exchanger to said quenching chamber.

According to a preferred embodiment, the assembly forming the subject of the present invention comprises means for distribution of the cooled air into said quenching chamber. The distribution means comprise a fan and a plurality of nozzles facing directly inside said quenching chamber.

According to a further preferred embodiment, the assembly forming the subject of the present invention comprises a tank for the cooling liquid, designed to receive the cooling liquid coming from the absorption chiller and to supply the cooling liquid to the heat exchanger.

BRIEF DESCRIPTION OF THE DRAWINGS

The example described in what follows is provided merely by way of non-limiting illustration for a better understanding of the invention with the aid of the figures of the annexed plate of drawings, wherein:

Figure 1 is a schematic illustration of the assembly forming the subject of the present invention,- and

Figure 2 is a graph which represents the surface of the heat exchanger as a function of the temperature of the air at output from the quenching chamber . BEST MODE FOR CARRYING OUT THE INVENTION

In Figure 1 designated as a . whole by 1 is the quenching assembly forming the subject of the present invention. The assembly 1 comprises a quenching chamber 2, a cooled water/undercooled air heat exchanger 3 , a tank 4 of cooled water, an absorption chiller 5, which uses as heat supply the exhaust fumes coming from furnaces in which the blocks of aluminium are brought to a temperature higher than 500⁰C, and a fan 6.

The absorption chiller 5 supplies refrigerating energy using thermal energy instead of mechanical energy. In fact, instead of an electrical compressor, an absorber, a generator, a pump, and a restriction device are used. In the assembly 1, a double acting absorption chiller is employed, which uses the hot fumes coming from the thermal treatments of aluminium that precede the quenching step, and uses this energy for undercooling to 7⁰C the water, which is then stored in the tank 4.

Sizing of the chiller 5 is ^' determined as a function of the refrigerating energy to be supplied to the flow of water- processed. ^■ •

The heat exchanger 3 has the function of undercooling a current of dried external air having a flowrate that depends upon the quenching chamber 2. In particular, the flow of air entering the heat exchanger 3 is dehumidified by means of purposely provided dehumidification devices (known and not described in detail) , supplied by the heat of the fumes coming from processing and from the absorption chiller 5.

The heat exchanger 3 is activated each hour only in the minutes in which the process of high speed quenching with undercooled water at 7⁰C coming from the tank 4 is required. The choice of the type and sizing of the heat exchanger 3 is made according to the flowrates and conditions of the two fluids, air and water, at input and at output in the operating conditions as represented in the graph of Figure 2.

The tank 4 for the undercooled water has the task of accumulating the volume of water necessary for heat exchange with the air in the minutes during which the quenching step is active. Its sizing is a function of the minimum volume of water .

Finally, the fan 6 has the purpose of blowing the cooling air into the quenching chamber 2 in order to optimize the power, expressed in kcal/h m^{2 0}C₇ for removal of the heat from the blocks of aluminium. For this purpose, the fan 6 is purposely designed for the specific pieces that are to be treated. Sizing of the fan is then carried out according to the required -flowrate of air, with a pressure gradient necessary to bestow upon the air the right kinetic energy downstream of nozzles that directly face the inside of the quenching chamber 2.

In use, the large amount of thermal energy contained in the fumes at output from the heating furnaces is reused for the production of cold useful for the entire process through the insertion of an absorption chiller 5. In detail, the process is a continuous process in which the absorption chiller 5 operates continuously and sends cold water to the tank 4.

The assembly 1 comprises a system for recirculation of cooling water from the absorption chiller 5 to the heat exchanger 3 .

When the high speed quenching step is required, typically a few minutes every hour, the cold water is sent to the air/water heat exchanger 3 where the external air is undercooled so as to be sent into the quenching chamber 2. After the blocks of aluminium have been in the solution furnace, they are sent into the quenching chamber 2, where within a few minutes their temperature is decreased through an appropriate -exchange with the flow of undercooled air at 10⁰C. The thermal power subtracted from the blocks and the necessary- flow of air are calculated as a function of the size of the blocks and the fluid-dynamic path designed for the chamber.

In particular, the assembly 1 is designed for supplying the correct amount of undercooled air such as to carry out cooling of the blocks of aluminium from 550 ⁰C to 100 ⁰C with a cooling rate of 70°C/min. The assembly can be sized as a function of the mass of aluminium to be cooled and the amount of air to be blown.

In other words, the assembly according to the present invention envisages continuous production of cooled water with the absorption chiller 5 and subsequent storage thereof in a tank 4. When the process of quenching of the blocks of aluminium in the quenching chamber 2 by the current of air is required, the heat exchanger 3 is activated, where the thermal exchange between the water stored in the tank 4 and the air coming from the environment and previously dried occurs . The distribution of the air in the quenching chamber 2 is carried out by a purposely provided fan 6 and by a plurality of nozzles that face the inside of the quenching chamber 2.

As may appear evident from the description provided above, the main advantages afforded by the assembly of the present invention derive from the use of air undercooled at a high rate produced by action of an absorption chiller, which carries out recovery of heat from the fumes deriving from the thermal treatments that precede the quenching step.

Claims

1. A high speed, quenching assembly (1) for metal products, characterized in that it comprises: an absorption chiller (5), designed to be supplied by fumes coming from processing of said metal products and to cool a cooling liquid; a heat exchanger (3), designed to cool a current of air by means of the cooling liquid; conduction means, designed to convey the cooling liquid from said absorption chiller (5) to said heat exchanger (3); a quenching chamber (2), designed to house the metal products to be cooled; and further conduction means (6) , designed to convey the cooled air from the heat exchanger (3) to the quenching chamber (2 ) .

2. The quenching assembly according to Claim 1, characterized in that it comprises an assembly for distribution of the cooled air into said quenching chamber (2); said distribution assembly comprising a fan (6) and a plurality of nozzles facing directly inside said quenching chamber (2) .

3. The quenching assembly according to Claim 2, characterized in that it comprises a tank (4) for the cooling liquid, designed to receive the cooling liquid coming from the absorption chiller (5) and to supply the cooling liquid to the heat exchanger (3) .

4. The quenching assembly according to Claim 3, characterized in that it comprises means for recirculation of the cooling liquid from the absorption chiller (5) to the heat exchanger (3) .

5. The quenching assembly according to any one of the preceding claims, characterized in that the cooling liquid is water.

6. The quenching assembly according to any one of the preceding claims, characterized in that it comprises means for dehumidification of the flow of air entering the heat exchanger (3); said dehumidification means being supplied by the heat of the fumes coming from processing and from said absorption chiller (5).

7. The quenching assembly according to any one of the preceding claims, characterized in that said products are made of aluminium.