TECHNICAL FIELD

The invention relates to a cooling control system for a coiling mandrel positioned downstream of a hot rolling mill which is cooled internally and/or externally.

The core of the concept is a coiling mandrel for metal products originating from a hot rolling mill plant comprising:

(a) an internal shaft with a plurality of sectors;

(b) an external drum which as a whole contains coaxially said internal shaft and which is circumferentially subdivided into a plurality of segments arranged in a direct or indirect coupling connection with said sectors, wherein the indirect coupling connection is realized by wedges coupled to anyone of said sectors and interposed between said segments and said sectors;

(c) an internal and/or external cooling system of the mandrel;

wherein said segments are movable in radial direction with respect to said internal shaft by an axial movement of the latter, as a consequence of the direct or indirect coupling connection between the segments of the drum and the sectors of the internal shaft, determining the following radial expansion or collapse of the drum.

BACKGROUND ART

The mandrels operating on the downcoilers are used for coiling the rolled strip in a hot rolling line, as described below with reference to Figure 3.

The traditional mandrels, described for example in document US 3 658 274, are made by means of a system of radially expandable segments thanks to wedges coupled to the action of a conical shaft moved axially with respect to the mandrel so as to increase or decrease the mutual distance between said segments and said shaft. For a more detailed disclosure of an example for such a mandrel according to the state of the art, refer to the description of Figures 1 and 2. Another example of a traditional mandrel is disclosed in document EP 0 870 555 Al. During this coiling step and the intermediate step of waiting for the next strip, the mandrel is cooled. This operation is carried out in the state of the art in two ways: externally by pouring water at room temperature directly on the body of the mandrel, and internally by means of suitable distribution channels with loss of the same. The cooling of the high temperature areas due to the presence of the coil (hot rolled coil, coiled at around 600-700°C) generates non- homogeneous thermal expansions. When a section of a component is repeatedly heated and cooled with respect to the rest of the particular, the region affected by such thermal variations expands when heated and contracts when cooled. This implies that the same region undergoes compressive forces which, due to the lowering of the resistance and of the elastic modulus, when the region is heated, can reach the yield stress and when it is cooled, exert tensile stresses. The recurrence of the above shows thermal shocks on the mandrel body and consequent continuous fatigue cycles. These phenomena lead to the formation of cracks on the outer mantle of the segments or morphological variations of the internal components which will tend to increase over time until the breakdown of components during use. Alternatively, they oblige the manufacturer to an early replacement of them, with all the related costs.

DISCLOSURE OF THE INVENTION

The object of the invention is to overcome the aforesaid drawbacks. The need is therefore felt to limit these important thermal variations to obtain a reduction in the probability of the onset of thermal fatigue inside the mandrel, while increasing at the same time the useful life of the components.

The problem is solved by adopting a system that permits to monitor the temperature of the important components of the mandrel, to control the cooling and thus to limit the phenomena of thermal fatigue.

The object is achieved through a cooling control system for a coiling mandrel for metal products, in particular strips, originating from hot rolling of the kind initially illustrated, which is characterized in that the mandrel is provided with

(d) a group of temperature measuring sensors and that the system further comprises a control unit suitable for:

receiving temperature data measured in the mandrel,

and provided with an algorithm which: compares said data with temperature nominal values,

increases, reduces or maintains constant the flow of the cooling liquid based on the difference determined between the measured value of the temperature and the target nominal value of the temperature.

With the aid of the control unit as defined above, the internal and/or external cooling of the mandrel according to the invention can be governed, which in this regard, by means of its sensors, provides the temperature values which are the basis for deciding whether the cooling should be increased, reduced or maintained.

Mandrels such as those illustrated with reference to the field of the art are known and present on the market for decades, as an example the documents US 3 658 274 and US 4 107 969 are reported. The person skilled in the art will easily identify within the functional principle of such mandrels the construction details, such as for example the realization of segments and sectors with complementary inclinations in the contact areas between them for their direct coupling or the realization of wedges and sectors with complementary inclinations in the contact areas between them in case of an indirect coupling, where the axial displacement of the sectors causes a displacement of the complementary element in a radial direction with respect to the axis of the shaft thanks to the sliding along an inclined plane. The direction of the movement determines the increase or decrease in the diameter of the drum.

Advantageously, the mandrel according to the invention further comprises:

(e) electronics to manage said sensors; and

(f) an electric power supply unit to feed the electronics and the temperature sensors. Preferably, the mandrel according to the invention further comprises:

(g) a telecommunicating system to permit the transmission of the measured temperature data to an external receiver.

The preferred variant of the invention is a combination of the points (a), (b), (c), (d) with the points (e), (f) and (g). Needless to say, the system offers, where necessary, the necessary connections between the individual elements inside the mandrel. This creates a completely independent and autonomous system that does not require cables to the outside.

In preferred embodiments of the invention, the temperature measuring sensors are located inside the mandrel in selected positions among the drum segments, the wedges if present, the sectors of the internal shaft, the free spaces inside the mandrel and the outer surface of the drum and/or combinations thereof. Advantageously, the solution according to the invention provides for dislocating the sensors in the critical areas of the machine in order to monitor its thermal state. A homogeneous distribution of the sensors inside the mandrel is preferable. Based on the data measured by them, it is possible to adjust the cooling, keeping the components at an even temperature, permitting a consequent homogeneous expansion.

Another important point is that, by guaranteeing an adequate temperature of the mechanical components and limiting their expansion, the tolerance plays in the desired neighbourhood are maintained. This prevents an early friction wear generated by excessive expansion between mechanically coupled components.

In a preferred variant of the invention, the temperature measuring sensors are located mainly in the free spaces inside the mandrel. In these positions, where the internal cooling is preferably made to circulate, the temperature changes are more immediate with respect to areas inside the constructive components of the mandrel which are more "isolated" from cooling.

Advantageously, the temperature measuring sensors are selected from junction thermocouples, infrared thermocouples, optic fibre temperature sensors and infrared sensors. The list is only exemplary and not conclusive.

Electronics and sensors can be powered by means of various suitable solutions, for example, in addition to simple batteries, on the basis of flywheels mass inserted on the rotational axis of the mandrel: the rotation of the shaft rotates the flywheel mass which allows, through an alternator, the generation of an electromotive force that powers the electronics of the sensors.

Further, forms of power supply can be provided through permanent magnets, Peltier elements. In a power supply device with permanent magnets, these generate an electromotive force with respect to the containment system of the mandrel. The Peltier elements generate an electromotive force proportional to the thermal delta between the surfaces of said elements: the external side is affected by the heat of the wrapped product, the internal side is cooled by the internal cooling.

Advantageously, the electronics that can be used in the mandrel is structured in such a way that it comprises

(e. l) an A/D converter to convert the data measured by the sensors from analog signals into digital signals; and (e.2) an antenna to send digital signals to an external reader,

wherein the electronics is preferably able to self-power thanks to the action of a flywheel mass located in this regard in the rotational axis of the mandrel (inertial electric generator) but can also benefit from a battery, for example a backup battery charged by the action of said inertial generator. A preferred electronics circuit for supplying the sensors is disclosed below with reference to Figure 10.

Advantageously, in the disclosed electronics, the sensors, such as for example thermocouples, detect an analog temperature signal which is converted to digital and sent directly to an external reader by means of the antenna, stored in a memory and sent outside in the form of data packages.

This external analysis unit analyses the data and uses them to feedback control the cooling of the mandrel, as described below.

A second aspect of the invention relates to a method for monitoring and adjusting the temperature of a coiling mandrel by means of cooling control which comprises the following steps:

(I) making available a cooling control system for a coiling mandrel according to the invention;

(II) coiling a product coming from a hot rolling mill around said mandrel and simultaneous internal cooling of the mandrel;

(III) measuring, by means of said temperature measuring sensors, preferably with a desired frequency, the temperature at various measurement points of the mandrel;

(IV) data processing and sending to a control unit;

(V) comparing the measured data with nominal data stored in the control unit; and (VI.1) increasing the flow of the cooling liquid where the measured value is greater than the nominal value,

(VI.2) reducing the flow of the cooling liquid where the measured value is lower than the nominal value,

(VI.3) maintaining the flow of the cooling liquid where the measured value is equal to the nominal value.

Once the completely coiled coil has been unloaded from the coiling mandrel, it is also possible to start an external cooling of the same, driven by the above-disclosed steps III to VI.3. Temperature measurement is performed, then it is processed by the electronics and sent to the processing and cooling management unit: if the measured temperature is equal to the desired threshold, the flow of the cooling liquid remains unchanged. On the other hand, if the temperature is higher than the threshold temperature, the cooling is increased; vice versa, if it is lower than the threshold, the cooling is decreased.

Through this active cooling management, the mandrel will undergo fewer thermal stresses.

It is also possible to use temperature sensors outside the mandrel, detecting the surface temperature of the same. This allows a further precision in determining the thermal stresses to which the mandrel is subjected.

The features described for one aspect of the invention may be transferred mutatis mutandis to other aspects of the invention.

The embodiments of the invention described reach the objects of the invention. In particular, they allow to limit the thermal variations inside the mandrel to obtain a probability reduction of the onset of thermal fatigue and provide a system with autonomous supply.

Said objects and advantages will be further highlighted during the description of preferred embodiment examples of the invention, given by way of example and not of limitation. Variants of the invention are the object of the dependent claims. The disclosure of the preferred exemplary embodiments of the coiling mandrel, of the cooling control system of a coiling mandrel for products coming from hot rolling and of the relative method according to the invention is given by way of non-limiting example with reference to the attached drawings.

DESCRIPTION OF PREFERRED EMBODIMENTS

Figure 1 shows a longitudinal section of a coiling mandrel according to the state of the art.

Figure 2 shows a cross-section along the line II-II of Figure 1 of the coiling mandrel according to the state of the art.

Figure 3 shows the insertion of a coiling mandrel in a hot rolling line.

Figure 4 shows a longitudinal section of a coiling mandrel according to the invention. Figure 5 shows in a sketched form a coiling mandrel according to the invention with a first exemplary embodiment of the configuration of the sensors inside the mandrel. Figure 6 shows in a sketched form a coiling mandrel according to the invention with a second exemplary embodiment of the configuration of the sensors inside the mandrel.

Figure 7 shows a coiling mandrel according to the invention with a first exemplary embodiment of the power supply of the electronics.

Figure 8 shows a coiling mandrel according to the invention with a second exemplary embodiment of the power supply of the electronics.

Figure 9 shows a coiling mandrel according to the invention with a third exemplary embodiment of the power supply of the electronics.

Figure 10 shows in a block diagram an exemplary embodiment for the electronics installed in a mandrel according to the invention.

Figure 11 shows a feedback scheme of an exemplary embodiment of a method for governing the internal and external cooling of a coiling mandrel according to the invention.

Figure 1 shows a longitudinal section of a coiling mandrel according to the state of the art. The traditional mandrels 2 (see for example US 3,658,274) are made by means of a system of radially expandable segments 4 thanks to wedges 6 coupled to the action of a conical shaft 8 moved axially along the arrow a with respect to the mandrel so as to increase or decrease the mutual distance between the segments and the shaft. The mandrel 2 is supported by means of bearings 10 supported by a frame 12. Figure 1 shows the sliding ratio created between the shaft and wedges/segments (arrow a).

Figure 2 shows in a cross-section along the line II- II of Figure 1 a coiling mandrel to the state of the art, which allows to understand how the mandrel 2 can expand or collapse according to the different steps of the coiling process. The area A shows the fully expanded segment 4, the area B shows an intermediate expansion of the segment 4, while the area C shows the segment 4 in the completely collapsed version. The shaping 14 represents the end of stroke for the expansion of the segments 4.

The coiling starts with the partially collapsed mandrel 2, therefore with a diameter close to the minimum and a reduced rotation speed. A strip (not shown) is driven by suitable known deflectors (not shown) around the mandrel 2 until the formation of at least one complete turn around it, so that the head of the strip is stuck and held by the following strip. Once this has occurred, the coiling speed is increased and the mandrel 2 begins the step of progressive expansion of its diameter: in this way the internal friction between the strip and the mandrel 2 gradually increases in order to avoid slippage between the coiled layers and thus increase the quality of the coiling. The coiling step lasts about 3 minutes with the strip temperature at 600- 700°C.

Figure 3 shows an example of a coiling mandrel in a hot rolling line. The mandrels 2 which operate on the downcoilers are used for coiling the rolled strip 16 in a hot rolling line.

A series of mill stands 18 provide a progressive thinning of the thickness of the strip 16, which then passes on a roller path 20 and is cooled by jets of water 22 at a temperature suitable for coiling (about 600-700°C).

The product is then sent through conveyor systems and bridles 24, suitable for keeping the strip 16 in traction, to the coiling area in a coiling mandrel 2, wherein the latter begins to coil the rolled product 16 on itself until it reaches the limit weight at which a known shear (not shown) intervenes separating the coil formed from the rest of the strip 16 upstream for its evacuation from the line.

Figure 4 shows a longitudinal section of a coiling mandrel 102 according to the invention. The mandrel 102 is provided with a shaft 108 with various conical sectors 109, interfacing with wedges 106, so as to permit the mutual approach/departure between the different segments 104 of the mandrel 102. The structure of the mandrel essentially corresponds to that of the mandrel disclosed in US 3.658.274. Further constructional details or possible variants of the mandrel are widely known and therefore do not require a more detailed disclosure. The inventive concept of thermal control of the mandrel is applicable to the most varied embodiments of mandrels of the type defined in the first claim.

The black points distributed both in the structure of the mandrel 102, and in the free spaces created between the different components, symbolize the measurement points of the temperature sensors (130 the sensors in the segments, 132 the sensors in the wedges, 134 the sensors in the conical sectors of the shaft and 136 the sensors in the free spaces) which are installed to measure the thermal gradient of the area. The electronics 142 deals with the power supply of the sensors 130, 132, 134, 136 and of the data accumulation which are sent through the antenna 140 to an external processing unit (not shown) which compares them with threshold or nominal values so as to actively drive the cooling. In a preferred variant, the electronics 142 is housed in the area supporting the rotation of the mandrel on the operator side.

By way of example, these sensors 130, 132, 134, 136 can be junction thermocouples, infrared thermocouples, optic fibre temperature sensors, infrared sensors.

Figure 5 shows in a sketched form a coiling mandrel 202 according to the invention with a first exemplary embodiment of the configuration of the sensors 234, 236 inside the mandrel 202, and precisely in the conical sectors of the shaft and in the free spaces. The wiring 250 connects the sensors 234, 236, the electronics 242 and the antenna 240.

Figure 6 shows in a sketched form a coiling mandrel 302 with shaft 308 and wedges 306 according to the invention with a second exemplary embodiment of the configuration of the sensors inside the mandrel. Here it is possible to note sensors 332 inside the wedges 306 and sensors 336 in the free spaces. A wiring 350 connects the sensors 332, 336, the electronics 342 and the antenna 340.

Figure 7 shows a coiling mandrel 402 with sensors 43N (N stands for 0, 2, 4, 6 to indicate that the position of the sensor does not matter here, but that the types of power supply represented apply to all imaginable positions of the sensors) with a first exemplary embodiment of the power supply of the electronics which is represented here by permanent magnets 460. In addition, it is possible to note wiring 450, electronics 442 and antenna 440.

Figure 8 shows a coiling mandrel 502 according to the invention with sensors 53N (N stands for 0, 2, 4, 6 to indicate that the position of the sensor does not matter here, but that the types of power supply represented apply to all imaginable positions of the sensors) with a second exemplary embodiment of the power supply of the electronics which is represented here by a plurality of Peltier elements 570. In addition, it is possible to note wiring 550, electronics 542 and antenna 540. The wiring 550 also connects the Peltier elements 570 to the electronics 542. Figure 9 shows a coiling mandrel 602 according to the invention with sensors 63N (N stands for 0, 2, 4, 6 to indicate that the position of the sensor does not matter here, but that the types of power supply represented apply to all imaginable positions of the sensors) with a third exemplary embodiment of the power supply of the electronics which is represented here by a contactless device 680 comprising power supply with current and the signal transmission. The wiring is referred with 650. Figure 10 shows in a block diagram an exemplary embodiment for the electronics installed in a mandrel according to the invention for the power supply of the sensors.

The sensors (e.g. thermocouples) detect an analog signal which is converted into digital and stored in a memory and sent in the form of data packages to an external reader by means of the antenna. The sensors 3N of temperature Tl, T2, T3, T4, T5 send analog signals to the A/D converter 19 which converts them into digital signals which through a temperature recording and analysis electronics 17 and a receiver/transmitter module 15 are processed and sent to an external control unit (not represented) through the antenna 40. These disclosed elements constitute an analysis and communication module, which is powered by an electric power supply module composed of a battery 13, a battery charging module 11 and an energy converter 7 powered by an inertial generator 5 with connections and operations well known in the art. These electronic components can be powered in different ways. For example, it is possible to arrange a battery, vice versa the preferred solution is the ability of the system to self -power without the aid of external power supply sources but through the action of a flywheel mass inserted in the rotational axis of the mandrel and which behaves as an alternator and called an inertial electric generator.

Depending on the operating conditions, a second solution provides for the use of a backup battery which is charged by the energy made available by this inertial generator.

Finally, Figure 11 shows a feedback scheme of an exemplary embodiment of a method for governing the internal and external cooling of a coiling mandrel according to the invention. At the beginning 21 there is a heat source with a certain temperature which is measured 23 by a sensor. The measured temperature Tmeas is compared 25 with a target temperature nominal value Tn corresponding to a temperature at which the surface should remain. If the values coincide 29, the cooling system receives the message 31 to keep the cooling flow constant. If the values do not correspond 27, 33 there can be two situations wherein Tmeas ¹ Tn, and precisely the case 37 wherein Tmeas < T _n and the case 35 wherein Tmeas > T _n . In the first case 37, the cooling system receives the command to reduce the cooling flow 41, in the second case 35, it receives the command to increase the cooling flow. Subsequently 43 the process continues with a new temperature measurement 23, a following comparison of the temperature with respect to the target one and a subsequent cooling control. In the executive step, it will be possible to make non-disclosed further modifications or executive variants to the coiling mandrel for products originating from hot rolling, to the cooling control system of the coiling mandrel and to the procedure for controlling and adjusting the temperature of the coiling mandrel by controlling its cooling, object of the invention. If such modifications or such variants should fall within the scope of the following claims, they should all be considered protected by the present patent.