Patent Application
20210260637
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:
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.
The mandrels operating on the downcoilers are used for coiling the rolled strip in a hot rolling line, as described below with reference to
The traditional mandrels, described for example in document U.S. Pat. No. 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
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.
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:
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 U.S. Pat. Nos. 3,658,274 and 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:
Preferably, the mandrel according to the invention further comprises:
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
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
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:
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.
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.
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.
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.
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 T1, 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,
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102018000006760 | Jun 2018 | IT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2019/055432 | 6/27/2019 | WO | 00 |
