EP0910677A1

EP0910677A1 - Method and device for temper-hardening flat metal products

Info

Publication number: EP0910677A1
Application number: EP97929041A
Authority: EP
Inventors: Jacques Benoít Adrien Ghislain MICHOTTE
Original assignee: Fabrique de Fer de Charleroi; Ti Consult
Current assignee: T.I. CONSULT; USINOR INDUSTEEL (BELGIUM)
Priority date: 1996-07-11
Filing date: 1997-07-01
Publication date: 1999-04-28
Also published as: CA2259693A1; KR20000023677A; CN1230229A; WO1998002592A1; BE1010419A3; BR9710259A; AU3330597A; JP2001505250A; CN1074463C; US6153026A

Abstract

The invention discloses a method for temper-hardening flat metal products, comprising the following steps: introducing a flat product (31) coming out of the furnace into a temper-hardening bay, depositing this flat product (31) on supporting elements forming a lower substantially horizontal supporting table (5), causing a sudden cooling of the flat product (31) in the deposited position, by spraying a temper-hardening liquid simultaneously on the whole of its upper surface and on the whole of its lower surface, removing the flat product (31) from the temper-hardening bay, and further, before the sudden cooling, transferring staying elements forming together a substantially horizontal staying table (9) to a horizontal staying plane located at a predetermined distance above the upper surface of the flat product (31) and, during the sudden cooling, optionally staying the flat product on the upper staying table (9), within the limits imposed by the said horizontal plane. The invention also discloses a device for implementing this method.

Description

Method and device for quenching flat metal products

The present invention relates to a method for quenching flat metal products, comprising introducing a flat product leaving an oven into a quenching station, with an upper surface facing upwards and a lower surface facing downwards. , depositing this flat product on support elements together forming a substantially horizontal lower support table of the quenching station, abrupt cooling of the flat product in the deposition position, by spraying a quenching liquid simultaneously over its entire surface upper and all of its lower surface, and an evacuation of the cooled flat product from the quenching station, and to a quenching device for the implementation of such a process.

Quenching processes of this kind have been known for a long time, intended for quenching flat metallic products, such as sheets, strips and similar products. These are discontinuous processes in which an upper press table is lowered onto the flat product to be dipped and is either pressed or deposited on it. The devices implementing this type of process are called dipping presses. These methods make it possible to simultaneously spray the entire upper surface and the entire lower surface of the flat product leaving the oven with quenching liquid, for example water. However, they have the major drawback of forming claws on the surface of the hardened sheets. Indeed at the time of quenching, these undergo an abrupt withdrawal while they are sandwiched between the support elements in the form of fingers of the upper and lower tables. Another drawback lies in the fact that at the time of quenching, the front part of the sheet has a temperature difference with respect to its rear part which has just come out of the oven. The stresses due to quenching are therefore not uniform over the entire surface of the hardened sheets.

Continuous quenching processes are also known in which the sheets are quenched as they come out of the oven. Each sheet part is therefore always cooled under the same conditions. However, the same sheet has enormous temperature differences in this process between a part which has already been quenched and another which leaves the oven and is not yet quenched. These differences cause efforts and deformations in the sheets, to the point that this type of process is currently almost abandoned, in particular for large sheets (see on this subject the patents FR-1415912, US-A-3423254, US-A- 3420083, NL-135696, BE-A-758799, BE-A-789130 and US-A-4149703).

The object of the present invention is to develop a quenching process and device operating discontinuously and no longer having the major drawbacks described above. Their purpose is in particular to allow quenching or hyper quenching of thin flat products, for example stainless steel sheets with a thickness of 3 to 30 mm. or carbon steel sheets with a thickness of 3 to 10 mm, producing flat sheets and substantially without claws.

To solve this problem, a method as described at the outset has been provided, according to the invention, which comprises, before the sudden cooling, a transfer of retaining elements together forming a substantially horizontal upper retaining table up to a plane horizontal retention located at a predetermined distance above the upper surface of the flat product and, during the sudden cooling, possible retention of the flat product by the upper retention table, within the limits imposed by said horizontal retention plane. This process therefore no longer represents a quenching under compression and therefore it no longer has the disadvantages thereof. On the other hand, the advantages of spraying simultaneously and uniformly over the entire upper surface and the entire lower surface of the sheet to be cooled are maintained.

Advantageously, the above-mentioned retaining plane is situated at a distance of the order of 0.5 to 2.5 mm from the upper surface of the flat product to be soaked, preferably of the order of 0.8 to 1.2 mm. , in particular 1 mm.

According to one embodiment of the invention, the transfer comprises a permanent measurement of the position of the retaining table relative to a fixed reference and a stop of the transfer when the above-mentioned measurement reaches a predetermined value, in which the retaining table is located. at said predetermined distance. This embodiment advantageously makes it possible to quench sheets of different thicknesses, by varying said predetermined value correspondingly as a function of the thickness of the sheet to be quenched. According to an advantageous embodiment of the invention, the transfer comprises a permanent measurement of the position of the retaining table, in several places, relative to a fixed reference, an averaging of these measurements, a calculation of the difference between each of these measurements and this average, a differential control of the transfer to each aforesaid location in accordance with the corresponding calculated difference, and a stop of the transfer when the above-mentioned average reaches a predetermined value, in which the retaining table is located at said distance predetermined. It is thus possible to ensure a perfectly perfect horizontality of the upper table and a completely reliable retaining plane. According to an improved embodiment of the invention, the quenching liquid comes from sources of quenching liquid arranged above and below the flat product to be cooled and the method comprises a relative displacement between the sources of quenching liquid and the product. dish to cool. Thus, it becomes possible to eliminate the cooling heterogeneities from one point to the other of the sheet, resulting from the fact that the sources of quenching liquid and the sheet are fixed relative to each other. Advantageously, the sheet is subjected to a horizontal displacement, in particular according to a back-and-forth movement.

Other embodiments of the invention are indicated in claims 1 to 7 below. The invention also relates to a device for tempering flat metal products, comprising

means for introducing a flat product leaving an oven into the device, with an upper surface facing upwards and a lower surface facing downwards, - support elements, forming a lower support table, on which the introduced flat product is deposited in a substantially horizontal position, - means for abruptly cooling the flat product in the deposit position which subject it to a spraying of quenching liquid simultaneously over its entire upper surface and over its entire lower surface, and - means for discharging the cooled flat product from the quenching device.

According to the invention, this device comprises

- retaining elements, together forming a substantially horizontal upper retaining table, transfer means capable of transferring the retaining elements above the upper surface of the flat product, and control means of transfer means capable of controlling the transfer means and stopping them when the retaining elements are in a horizontal retaining plane situated at a predetermined distance above the upper surface of the flat product to be soaked. Other embodiments of the invention are indicated in claims 8 to 15 below. Other details and particularities of the invention will emerge from the description given below, by way of nonlimiting example and with reference to the appended drawings.

Figure 1 shows a schematic front view of a quenching device 1 according to the invention.

FIG. 2 represents a schematic plan view of the device according to FIG. 1. FIG. 3 represents a block diagram of the control of a device according to the invention.

FIG. 4 represents a detail of the upper table of the device according to FIG. 1. In the various drawings, the identical or analogous elements are designated by the same references.

As is apparent from the embodiment of the device illustrated in Figures 1 and 2, it comprises a series of gantries consisting of two columns 1 and 2 and two fixed crosspieces 3 and 4. The lower fixed crosspieces 4 support, via longitudinal members 6, a lower table 5, which in the illustrated case is fixed. This table 5 is formed of parallel beams 7, located at a distance from each other. These beams themselves support in a manner not shown known support elements, for example in the form of claws. These may for example have the shape of the retaining elements 8 shown in Figure 4, in the inverted position.

On the upper side, an upper table 9 similar to the lower table is fixed to mobile beams 10 by means of longitudinal members 11. The mobile beams 10 are provided with end shoes 12 and 13 capable of sliding on slides 14 and 15 arranged on columns 1 and 2. In the illustrated case, each of the mobile beams 10 is supported by two hydraulic cylinders 16 and 17.

Like the lower table 5, the upper table 9 is formed of parallel beams 18 located at a distance from each other. From these beams 18 are suspended, according to the invention, retaining elements which, in the present example, can be retaining claws 8 such as those shown in FIG. 4. The means for introducing the quenching sheet 31 are common in the art and are therefore not shown. Between the exit from the reheating oven and the entry into the quenching device, they are parallel rollers rotating on their axis, so as to drive the sheet horizontally, that is to say with an upper surface oriented upwards and a lower surface downwards (see for example in FR-1415912). Inside the quenching device, identical rollers are mounted on a frame which can, in known manner, be raised and lowered. During the entry of the sheet, the frame is raised and the rollers move the sheet. When the latter has completely entered the device, the chassis is lowered and the rollers are retracted between the beams 7 of the lower table. Such an arrangement is provided in known dipping presses, and in particular in those put on the market by the firm DREVER cy. It has therefore not been shown in detail in the drawings. Likewise, the means for discharging the cooled flat product from the quenching device are similar rollers, known to the specialist, and which are therefore neither shown nor described in more detail here.

The abrupt cooling means of the flat product to be quenched are, in the case illustrated in FIG. 4, perforated pipes 19 supplied with quenching liquid under pressure, in particular water. Such pipes, known to the specialist, are arranged above and below the sheet to be cooled so as to be able to spray the upper surface and the lower surface thereof as uniformly as possible. The means of supplying these pipes have not been shown because they are widely known to the specialist. The quenching device according to the invention comprises means for transferring the upper table 9, which, in the illustrated case, are hydraulic cylinders 16 and 17. It should be noted that a table, as illustrated, commonly weighs a fifty tonnes. As it mainly consists of longitudinal and transverse beams, it does not have a very high rigidity. Consequently, it is necessary to control the jacks precisely in order to bring the ends of the fingers 20 of the retaining claws 8 in a horizontal plane situated at a predetermined distance from the sheet to be quenched.

The jack 17 in FIG. 1 is a so-called "master" jack which is provided with an integrated or external position encoder which makes it possible to continuously measure the position of the table at this location relative to a fixed reference. In FIG. 3, one can see such a position encoder consisting of a measurement scale 21 mounted on the fixed cross-member 3 and of a measurement reader 22 mounted on the lower table 9, at the foot of the master cylinder 17.

The jack 16 in FIG. 1 is controlled simultaneously with the jack 17, but it is a slave to the movement, that is to say to the flow of medium under pressure introduced. In Figure 2, we can see in this embodiment four master cylinders 17 arranged alternately left and right of the quenching device so as to ensure the accuracy of the upper table over its entire length. As illustrated in FIG. 3, the quenching device comprises a hydraulic group 23 intended for supplying the cylinders with pressurized medium. This group also controls the support frame for the sheet transport rollers and allows it to be raised and lowered. The hydraulic unit 23 comprises for example proportional valves, stop valves and flow dividers. These valves and these dividers are in number corresponding to the number of gantries of the device. The flow dividers distribute the flows of pressurized medium between left and right cylinders of the same gantry. The proportional valve makes it possible to adjust the flow rate sent to these cylinders, as a function of the position indicated by the position encoder which accompanies the master cylinder 17.

The stop valves allow the upper table to be stopped when it has reached the desired position.

This hydraulic group 23 is controlled by control means. These control means comprise the position encoder 21, 22 which permanently transmits its measurements to a comparator 24. This comparator receives from a programmable controller 25 a predetermined set value and compares it with the measurements received from the position encoder. The difference calculated by the comparator 24 is transmitted to a position regulator 29, which may consist of regulation cards, with a card per gantry comprising a master cylinder 17. Depending on the signals received, as described in more detail in thereafter, the cards control the proportional valves and the shut-off valves of the hydraulic unit 23. The programmable controller receives information and instructions from a computer supervision system 26, itself connected to a computer management system. factory 27. The operation of the quenching device according to the invention will now be described.

Flat products to be dipped, in particular sheets, are routinely taken out of a reheating furnace on a train of rollers and immediately introduced onto rollers supported on the chassis of a quenching device. When the sheet is fully inserted therein, the frame is lowered and the rollers are retracted between the beams 7 of the lower table of the quenching device. The sheet is thus deposited on support elements which in the present case may for example be known support claws, provided with fingers oriented upwards.

During the introduction and the deposition of the sheet, the pistons of the jacks 16 and 17 are in the retracted position and the upper table 9 is in the high position.

It is then lowered in a controlled manner until the retaining elements 8 in the form for example of retaining claws provided with fingers 20 pointing downwards are in a horizontal retaining plane located at a very small predetermined distance from the above the upper surface of the sheet (see Figures 1 and 3).

The supervision computer system 26 is informed of the sheets which will be hardened by encoding the identification of these on a terminal not shown which is, at 28, connected to the system 26. The system 26 then interrogates the management computer system 27 to find out the characteristics of this product, in particular the thickness of the sheet to be quenched. On the basis of this information, the system 26 transmits the thickness and the optimal clearance (distance 30 between the sheet and the retaining elements 8 in the low position of the table 9) to the controller 25 which manages all the sequences of the process. quenching. These sequences are in particular those relating to the raising and lowering of the chassis carrying rollers, the movement of entry and exit of the sheet in and out of the device and the movement of the upper table. For the last cited movement, the automaton 25 transmits to the comparator 24 a predetermined position reference value, in which the retaining elements 8 are at said predetermined optimum distance 30. Comparator 24 compares this value with the average of the measurements which the position encoders attached to the master cylinders 17 continuously transmit to it. It also compares each measurement received from the position encoders with this average and thus determines different deviations. The deviations are then transmitted to the regulator 29 which correspondingly controls the valves of the hydraulic unit 23. As, for each master cylinder 17, a regulation card is allocated, it is possible to adjust the movement of the upper table 9 towards the position low in different ways depending on the place and so as to obtain a perfectly flat and horizontal position of the table 9 at the low point. In this position, the comparator 24 compares the above average of the measurements with the set value, finds that there is no longer a deviation and transmits a stop signal to the regulator.

Preferably the distance 30 will be of the order of mm or less. In this way, the retaining elements 8 do not touch the upper surface of the sheet. We then proceed to quenching or hyper-quenching the sheet. The automaton 25 controls the supply of quenching liquid under pressure to the pipes 19 which spread this as uniformly as possible on the upper surface and the lower surface of the sheet.

During this sudden cooling, the sheet can therefore carry out its removal without being sandwiched between an upper table and a lower table. The problems of the resulting tensions in the sheet and the appearance of claws on the surface disappear to a great extent. If, during this withdrawal, a sheet were to deform slightly, the distance 30 is calculated to retain the product within the limits of the horizontal retaining plane formed by the fingers 20 of the retaining elements 8, limits which are acceptable in the art. This avoids the cooling heterogeneities which, without this retention plane, would result from the formation of channels for the quenching liquid, generated by the deformation of the sheets. After quenching, the roller carriage is reassembled and the sheet comes out of the quenching device.

Sheets are thus obtained which have undergone practically no tension during cooling.

Contrary to what was the general opinion according to the prior art, the sheets treated according to the invention do not undergo leveling during cooling and the sheets are on the contrary "released" to avoid the formation of internal stresses during quenching . As the quenching is, according to the invention, carried out as homogeneously as possible, there is almost no stress in the sheet, and this without pressing, and there are no more claws, in any case on the upper surface of the sheets. The claws that are occasionally obtained on the underside are reduced to a minimum since, especially in the case of thin sheets, the contact pressure between the support elements and the sheet is very low and corresponds to the sole weight of the sheet. It should be understood that the present invention is in no way limited to the embodiment described above and that many modifications can be made thereto without departing from the scope of the appended claims. One can for example imagine that the support elements of the lower table and the retaining elements of the upper table are not claws, but rather rollers, for example like those described in the continuous quenching devices (see in particular US-A -3423254), these rollers being able to be stopped once the sheet entirely in the quenching device. Advantageously, these rollers can be ribs or grooves, possibly in a spiral fashion (see for example US-A-3420083 and US-A-4149703).

One can also imagine that, once the sheet completely entered the quenching device, these rollers continue to be driven in rotation, for example in a reciprocating movement. This makes it possible to cause an oscillating movement of the sheet with respect to the pipes 19 and therefore a better distribution of the quenching liquid on the surfaces of the sheet during the process, and this without contact of the sheet with the upper table. It is also possible to cause a displacement of the spraying system with respect to the sheet metal, for example by mounting spraying ramps on a mobile chassis provided with an oscillating movement controlled by a connecting rod / crank device. A rotation of the spray bars on their axis could also be planned.

One could also provide retaining and support elements in the form of rollers or balls. The front face of the fingers of the retaining elements and of the claw-shaped support elements could also be grooved, or chamfered or have a hemispherical shape.

Claims

1. A method of quenching flat metal products, comprising introducing a flat product out of an oven into a quenching station, with an upper surface facing upwards and a lower surface facing downwards, depositing this flat product on support elements together forming a substantially horizontal lower support table of the quenching station, sudden cooling of the flat product in the deposit position, by spraying a quenching liquid simultaneously over its entire upper surface and its entire surface lower, and an evacuation of the cooled flat product from the quenching station, characterized in that the process comprises, before the sudden cooling, a transfer of retaining elements together forming an upper retaining table substantially horizontal to a horizontal plane retainer located at a predetermined distance above the upper surface of the flat product and, during cooling sudden slippage, possible retention of the flat product by the upper retaining table, within the limits imposed by said horizontal retaining plane.

2. Method according to claim 1, characterized in that the above-mentioned retaining plane is located at a distance of the order of 0.5 to 2.5 mm from the upper surface of the flat product to be quenched, preferably from range from 0.8 to 1.2 mm, in particular 1 mm.

3. Method according to either of Claims 1 and 2, characterized in that the transfer comprises a permanent measurement of the position of the retaining table relative to a fixed reference and stopping the transfer when the aforementioned measurement reaches a predetermined value, in which the retaining table is located at said predetermined distance. 4. Method according to claim 3, characterized in that the transfer comprises a permanent measurement of the position of the retaining table, in several places, relative to a fixed reference, an average of these measurements, a calculation of the difference between each of these measurements and the average, a differential control of the transfer in each aforesaid location, in accordance with the corresponding calculated difference, and a stop of the transfer when the above-mentioned average reaches a predetermined value, in which the retaining table is located at said predetermined distance.

5. Method according to any one of claims 1 to 4, characterized in that the quenching liquid comes from sources of quenching liquid arranged above and below the flat product to be cooled and in that the method comprises a displacement relative between the sources of quenching liquid and the flat product to be cooled.

6. Method according to any one of claims 1 to 5, characterized in that, during the sudden cooling, the flat product is stationary.

7. Method according to any one of claims 1 to 5, characterized in that, during the sudden cooling, the flat product is subjected to a horizontal displacement, in particular according to a back-and-forth movement.

8. Device for tempering flat metal products (31), comprising

means for introducing a flat product leaving an oven into the device, with a surface upper facing upwards and a lower surface facing downwards,

- support elements, forming a lower support table (5), on which the introduced flat product is deposited in a substantially horizontal position,

abrupt cooling means (19) for the flat product in the deposit position which subjects it to a spraying of quenching liquid simultaneously over its entire upper surface and over its entire lower surface, and

- means for discharging the cooled flat product from the quenching device, characterized in that it comprises - retaining elements (8), together forming a substantially horizontal upper retaining table (9),

- transfer means (10, 12, 15, 16, 17) capable of transferring the retaining elements above the upper surface of the flat product, and

- control means (21-29) transfer means capable of controlling the transfer means and of stopping them when the retaining elements (8) are in a horizontal retaining plane situated at a predetermined distance (30 ) above the upper surface of the flat product to be soaked.

9. Device according to claim 8, characterized in that the control means comprise at least one position measuring element (22) which permanently measures the position of the retaining table (9) relative to a fixed reference (21 ), a comparator (24) which determines a presence or absence of deviation between said measurement and a predetermined value, in which the retaining elements (8) are at said predetermined distance (30) from the product dish to be quenched, and a position regulator (29) acting on the transfer means (10, 12, 15, 16, 17) according to the determined gap.

10. Device according to claim 9, characterized in that the control means comprise several position measuring elements (22) which each permanently measure the position of a particular place of the retaining table relative to a fixed reference ( 21), in that the comparator further compares the difference between each measurement and their average, and in that the position regulator (29) acts differently on each or some of the transfer means as a function of the difference determined in each of these particular places, and stops the transfer means when the comparator determines that there is no difference between said average and the predetermined value. he. Device according to any one of Claims 8 to 10, characterized in that the transfer means comprise hydraulic cylinders (16, 17) connected between a fixed frame (1, 2, 3) of the device and the upper retaining table ( 9) and supplied by a hydraulic group (23) as a function of signals received from the control means.

12. Device according to any one of claims 8 to 11, characterized in that the retaining elements (8) and the support elements are identical elements arranged symmetrically with respect to a horizontal plane.

13. Device according to any one of claims 8 to 12, characterized in that the support elements and / or the retaining elements (8) are claws, jaws, rollers, preferably grooved or ribbed, or similar means which, when in contact with the flat member to soak, only cover a very partial area of it.

14. Device according to any one of claims 8 to 13, characterized in that the support elements are rollers which drive the flat element in a back-and-forth movement during the abreoidal stiffening.

15. Device according to any one of claims 8 to 14, characterized in that the sudden cooling means comprise spray pipes (19) provided with an oscillating movement, and possibly driven in rotation on their axis.