KR20080080294A - An arrangement and a method for heating metal objects - Google Patents

Abstract

The invention relates to a an arrangement and a method for heating metal objects such as metal bars by convection. The metal objects are passed on a conveyor through a series of chambers where hot air is blown through the conveyor. The temperature is controlled by a sensor connected to a control devise such as a thyristor.

Description

Heating apparatus and method for metal bodies {AN ARRANGEMENT AND A METHOD FOR HEATING METAL OBJECTS}

The present invention relates generally to the field of heating metal objects, in particular elongated metal bars.

It is known to heat metal bodies before carrying out machining operations on the objects. As an example, US Pat. No. 4,343,209 describes a method of heating a bar by heating the coil with a heating coil in a localized area along the length of the bar. The bar is one component that is progressively advanced at certain intervals through shear coils with shear shears. After each progressive advancement of the bar, it is cut into one part from the end of the bar in the heating zone. The aforementioned method is said to allow cutting without substantial cracking or breaking.

It is an object of the present invention to provide an improved apparatus and method for heating a metal body to facilitate cutting of the metal body. Such improved apparatus and methods can be advantageously used for the purpose of heating the metal body to be subsequently cut into smaller parts.

The present invention relates to an apparatus for heating a metal body. The device of the present invention comprises an envelope that encloses an interior space. The sheath has an inlet opening and an outlet opening. Inside the outer shell the inner wall divides the inner space into a rear chamber, at least one intermediate chamber and a front chamber. The transmissive conveyor extends from the inlet opening of the skin through the rear chamber, the intermediate chamber and the front chamber to the outlet opening of the skin. In this way, objects loaded on the conveyor can be transported through the chamber. In at least one intermediate chamber, a fan is arranged to direct the gas flow towards the conveyor and the object placed on the conveyor. The heating element is also arranged in the intermediate chamber. The heating element can heat the gas flowing from the fan before the gas reaches the conveyor. The chamber has at least one outlet of at least one intermediate chamber in communication with the rear chamber, at least one outlet of the intermediate chamber in communication with the front chamber, and at least one outlet of the intermediate chamber is the outlets of the rear and front chambers. Are connected to each other so as to communicate with each other. In this way, the operation of the fan will create a rear circulation that passes gas twice through the conveyor and a forward circulation that passes gas twice through the conveyor.

In one embodiment, the temperature sensor is located inside the shell and is connected to a control device that controls the temperature of the heating element according to the nominal value and the value indicated by the temperature sensor. The temperature sensor can be placed in the front chamber between the conveyor and the exit of the front chamber.

In some embodiments, the apparatus of the present invention includes a plurality of heating elements arranged in a row and extending perpendicular to the direction of movement of the plurality of fans and conveyors. The heating device may be connected to a cutting device for cutting the metal body heated by the heating device.

The present invention also relates to a method of heating a metal body. The method includes passing a metal body on a transmissive conveyor through an interior space surrounded by an enclosure and divided by an interior wall to a rear chamber, at least one intermediate chamber and a front chamber. As the conveyor passes through at least one intermediate chamber, the air is heated and the heated air enters through the conveyor. The first portion of heated air passing through the conveyor in the at least one intermediate chamber is converted to back circulating air. The back circulating air passes through the conveyor in the back chamber and back to at least one intermediate chamber. The second portion of heated air passing through the at least one intermediate chamber is converted to forward circulating air. The front circulating air passes through the conveyor in the front chamber and back to at least one intermediate chamber.

In one embodiment of the invention, the temperature of the air is measured inside the shell and the heating of the air is controlled in accordance with the nominal and measured values. Suitable nominal values for this temperature may be 70 ° C. When the temperature is measured, this can be done in the front chamber at that location where the temperature of the air is measured after passing through the conveyor in the front chamber.

In an effective embodiment, the air is heated by a heater located inside at least one intermediate chamber and the temperature of the heater is maintained in the range of 200 to 300 ° C.

The metal body is a long metal bar. The heating operation may advantageously be followed by a sequential operation such as cutting of the metal bar. The heating operation itself may be considered as part of the method of heating and cutting the metal bar.

1 is a schematic cross-sectional view of a heating device according to the invention,

FIG. 2 is a cross sectional view taken along line II-II of FIG. 1,

3 is a view showing a cutting device;

4 is a view for explaining the operation of the cutting device shown in FIG.

5 is a schematic cross-sectional view of a heating device according to another embodiment.

Referring to FIG. 1, it can be seen that the invention relates, in particular, to an apparatus 1 for heating the metal body 19 as a primary operation preceding a sequential cutting operation. In the embodiment shown in FIG. 1, a metal body 1 as long is placed in the reservoir 20. The metal body 19 is mounted on the conveyor 17 and is conveyed through the heating device 1. To dispense an object as long as it is from the reservoir 20, the reservoir 20 may be provided with one or several flexible elements 37 that hold the metal body in the reservoir 20. When the flexible element 37 is shortened, the bar 19 is lifted so that the bar 19 falls on the conveyor 17 by gravity. The flexible element 37 can be one or several belts 37 that can be shorter, for example, by winding the end of the belt 37 onto a reel (not shown). In the embodiment shown in FIG. 1, the conveyor 17 is provided with protrusions 18 which make the transfer to the conveyor more reliable and keep the bars 19 spaced apart from each other on the conveyor 17.

The heating device 1 comprises an envelope 2 which encloses an interior space 3. The sheath 2 has an inlet opening 4 and an outlet opening 5. Inside the shell 2, the interior walls 6, 7 divide the interior space 3 into a rear chamber 8, at least one intermediate chamber 9 and a front chamber 10. The conveyor 17 is air permeable and passes from the inlet opening 4 of the shell 2 to the outlet opening 5 of the shell 2 through the rear chamber 8, the intermediate chamber 9 and the front chamber 10. Extend. In this way, the object 19 loaded on the conveyor 17 can be transferred from the inlet opening 4 to the outlet opening 5 through the chambers 8, 9, 10. In the embodiment of FIG. 1, the conveyor extends out of the shell 2 on both sides of the shell 2. Next to the conveyor 17 is a cutting device 31 schematically shown in FIG. 1. After a metal body such as the long bar 19 is heated in the heating device 1, it is softened a lot and can be more easily cut into smaller parts by the cutting device 31.

Within at least one intermediate chamber 9, a fan 21 is arranged to direct the flow of air (or other possible gas) towards the conveyor 17 and the object 19 resting on the conveyor 17. The heating element 22 in the intermediate chamber 9 is arranged to heat the air flowing from the fan 21 before the air reaches the conveyor 17. In the embodiment shown in FIG. 1, the fan 21 is driven by a motor M which can be an electric motor M. The electric motor M is preferably located inside the intermediate chamber 9 together with the fan 21.

The chambers 8, 9, 10 are connected to each other such that at least one outlet 14 of the at least one intermediate chamber 9 is in communication with the rear chamber 8. At least one outlet 14 of the intermediate chamber 9 is in communication with the front chamber 10 and at least one inlet 13 of the intermediate chamber 9 is connected to the outlet of the rear chamber 8 and the front chamber 10. Communicating. In this way, the operation of the fan 21 will result in two back circulations of air through the conveyor and two forward circulations of air through the conveyor 17. As shown in FIG. 1, a separation wall 23 can be located at the outlet 14 of the intermediate chamber 9. The separating wall 23 serves to separate the air flow from the intermediate chamber 9 into the front circulation of the air and the rear circulation of the air.

In one embodiment, the temperature sensor 25 is located inside the shell 2 and controls the temperature of the heating element 22 according to the nominal value and the value indicated by the temperature sensor 25. ) The temperature sensor 25 is preferably arranged in the front chamber 10 between the conveyor 17 and the outlet 16 of the front chamber 10 but may be located elsewhere, for example in an intermediate chamber. The heating element 22 can be an electric coil, for example.

As shown in FIG. 2, an embodiment of the apparatus of the present invention may include a plurality of fans 21 and a plurality of heating elements 22 arranged in a line and extending perpendicular to the direction of movement of the conveyor 17. Can be. In an embodiment of the invention, the device may comprise twelve fans 21 and twelve heating elements 22. Each heating element 22 may be about 3500 watts in size in one embodiment. In the case of twelve heating elements the entire heating device may be 42 kilowatts in size.

The apparatus of the present invention operates as follows. The metal body 19 passes through the interior space 3 surrounded by the shell 2 on the permeable conveyor 17 and the chambers 8, 9, 10 of the interior space. In FIG. 1, the metal body 19 passes through the internal space 3 from the left to the right in the direction of the arrow A. As shown in FIG. Air is introduced by the fan 21 through the conveyor 17 toward the permeable conveyor 17 as the conveyor 17 passes through the intermediate chamber 10. Before the air reaches the conveyor 17, the air is heated by a heating element 22, which can be an electric heating element 22. When the heated air passes through the conveyor 17, the metal body 19 is heated by the air. The permeable conveyor 17 and the metal body 19 loaded on the conveyor serve as a throttle for pressurizing the air to increase the speed of the air as it passes through the conveyor 17. The increased velocity of air improves heat transfer to the metal body 19. In one embodiment, the air velocity may be about 8 to 10 m / s as hot air passes through the conveyor 17. Preferably, the throttle is nothing but one throttle marked on the conveyor 17. In other parts of the system, the air flow is significantly low, reducing frictional losses. Immediately downstream of the fan 21, the speed of air may be about 4 m / s in one embodiment of the present invention.

When hot air passes through the conveyor 17 to transfer some of the thermal energy to the metal body 19, the first portion of the heated air passes through the rear chamber 8 through the conveyor 17 of the rear chamber 8. It is switched to the rear air circulation RA which passes and returns back to the at least one intermediate chamber 9. The second portion of heated air passing through the conveyor 17 in the intermediate chamber 9 is the front passing through the front chamber 10 through the conveyor 17 as the conveyor 17 passes through the front chamber 10. Is switched to air circulation (FA). The air of the front air circulation FA is sent back to the intermediate chamber 9.

The motor M of the fan 21 is preferably located inside the shell 2 of the device. Positioning the motor M outside of the shell 2 results in a more complex design. If the motor M is an electric motor, it should be expected that the motor may fail or break if the ambient temperature is high. For the currently available electric motors that the inventors recognize, the ambient temperature should preferably not exceed 70 ° C. In a preferred embodiment of the invention, the temperature of the air is measured inside the shell 2 and the air heating is controlled in accordance with the nominal and measured values. In the embodiment shown in FIG. 1, the temperature sensor 25 has a front chamber adjacent to the conveyor 17 such that the temperature of air is measured at least once after passing through the conveyor 17 just before reaching the fan 21. 10). Although the temperature sensor 25 can be located anywhere else, this particular position is considered suitable because it does not change much from this point until the temperature of the air reaches the fan 21 again. Another suitable location for the sensor 25 may be the downstream side of the front air circulation FA, ie the side closer to the fan 21. Thus, the position of the sensor 25 may be anywhere in the front chamber 10 between the conveyor 17 and the outlet 16 of the front chamber. The sensor 25 may also be located in an intermediate chamber upstream of the fan 21 and the motor M. As shown in FIG. 1, the temperature sensor 25 may be connected by a cable 28 to a control device 26 such as, for example, a thyristor. In the embodiment shown in FIG. 1, the thyristor 26 can be connected by means of a cable 30 to an additional control device 27, for example a computer 27. Thyristor 26 may also be connected to heating element 22 by cable 29. The computer 27 provides the thyristor 27 with a nominal value for the temperature, while the actual value for the temperature is provided to the sensor 25 via the cable 28. The thyristor may control the output of the heating element 22 to increase or decrease the output. In order to protect the motor M of the fan 21, the temperature measured by the temperature sensor 25 should preferably not exceed 70 ° C. This means that the nominal value provided by the computer 27 is 70 ° C. Of course, in the range in which the motor M can function reliably at a temperature of 70 ° C. or more, the temperature measured by the temperature sensor 25 can be increased accordingly. In the embodiment shown in FIG. 1, cables or wires 28, 29, 30 connect thyristors 26 to heating elements, temperature sensors 25 and computers 27. However, the thyristor 26 may also be in wireless communication with these elements.

If an electric coil is used as the heating element, the temperature of the coil 22 is maintained in the range of 200 to 300 ° C such that the air reaching the conveyor in the intermediate chamber 9 also has a temperature in the range of 200 to 300 ° C. The life expectancy of the electric coil depends largely on the temperature at which the coil is heated. The life expectancy for such coils currently commercially available is almost infinite unless the temperature exceeds 300 ° C. Of course, the temperature of the air will be much lower after the air has passed through the conveyor 17 twice and a portion of the heat in the air has been transferred to the metal body 19. The metal body to be heated will normally be heated to a temperature above 300 ° C. which is detrimental to the metal itself. Instead, the use temperature is limited by the predetermined life expectancy of the motor M or the coil 22.

As described above, the cutting device 31 is connected after the heating device 1. With reference to FIG. 3, a description is given regarding possible designs for the cutting device. The cutting device may comprise a floating tool 32 and a movable tool 33. Channel 34 extends through floating tool 32 and movable tool 33. The punch 35 is arranged to collide with the movable tool 33. Attenuation element 36 may be included to receive the impact from the cutting operation and to return the movable tool 33 to its original position. To cut the metal bar 19, the bar is inserted inside the channel 34 so that the bar extends through the floating tool 32 to the movable tool 33. The punch 35 strikes the movable tool 33 as shown in FIG. 4 so that the bar 19 can be cut. Of course, a suitable cutting device 31 can take other forms. If the bar is heated before the cutting operation, cutting becomes easier and the actual cut surface can be much smoother.

In one embodiment, the heating apparatus and method can be used to heat stainless steel bars having a length of about 5.5 m and a diameter of 16 to 25 mm. In the case of currently available cutting devices, such bars can be continuously cut into 180 parts in a period of about 50 seconds. This means that new bars can be fed continuously and quickly.

The inventors have found that the use of heated air entails advantages over induction heating schemes. When objects such as long metal bars 19 are heated, it may be difficult to achieve uniform heating of the bars when using induction heating. For example, when inductively heating an elongated bar of stainless nickel steel, the surface of the bar can be heated to a harmful temperature while the inner portion of the bar is still cooled so that the bar can be cut as easily as possible. In addition, the inventors have found that it is more difficult to inductively heat an object with a glossy surface. Objects with a glossy surface may comprise stainless steel objects. Stainless steel bars have poor thermal conductivity that makes heating of such objects more difficult. The inventors have found that heating a metal object such as stainless steel by convection heating is more efficient than heating the metal object by induction heating. The practical way by convection heating is to pass the bar through the heated air flow. As noted above, embodiments of the present invention may include 12 heating coils and 12 fans, each heating coil having a 3.5 kW performance, such that the entire heating device has a 42 kW performance. To achieve a comparable heating effect on stainless steel bars by induction heating, a performance of about 100 kW is required. In addition, induction heating is harmful to the surface of stainless steel bars.

One practical problem with the heating process is that metal bodies heated by hot air can have very different starting temperatures. The bar to be cut can often be stored externally and cut directly in an external reservoir. Depending on the season and the climate, the temperature of the bar can be very variable from -30 ° C or below to +30 ° C or above. This means that the requirements for the heating operation can vary considerably. In addition, the size of the object, for example the diameter of the stainless steel bar, can also influence the amount of heating required. In order to control the temperature of the bar to be cut, it is preferred that the amount of heating can be controlled. Control equipment such as thyristors and the use of temperature sensors make it possible to control the heating temperature of the bars. This ensures that when the bar reaches the cutting device, the bar always has the same temperature. In addition, the motor M of the fan is protected from heat and it is easy to ensure the high life expectancy of the coil 22.

Dividing the heating device into three separation chambers 8, 9, 10 provides a great advantage for the following reasons. Directly downstream of the fan 21 is an overpressure during operation of the fan. However, the throttle formed by the conveyor 17 in combination with the suction effect that the fan 21 produces in the rear chamber 8 and the front chamber 10 will have the effect of keeping the rear chamber and the front chamber under reduced pressure. will be. This reacts to ambient leakage of the heated air. Thus, this has the advantage of reducing the amount of energy required to operate such a process.

In order to heat stainless steel bars having a diameter of 16 to 25 mm, it may be suitable to keep the bars spaced from each other on the conveyor by about 50 mm. This spacing is determined by the distance between the protrusions 18 of the conveyor 17. In one embodiment of the invention, the distance from the inlet opening 4 to the outlet opening 5 can be about 700 to 1000 mm, which allows about 14 to 20 bars to be placed inside the heating device 1 at the same time. .

It should be understood that the aforementioned temperature control system can also be used for heating devices that are not divided into three chambers. In addition, it is to be understood that the idea of using three split chambers can be used regardless of whether the temperature is measured or not. However, temperature control is preferably combined with the principle of using three split chambers.

Perhaps in the present invention there may be two or more intermediate chambers, each of which has a separate set of fans 21 and heating elements 22.

Another embodiment will be described later with reference to FIG. 5. In FIG. 5, the rear chamber 8 according to the embodiment of FIG. 1 has been completely removed and the inlet opening 4 is directly connected inside the chamber 9 in which the fan 21 and the heating element 22 are located. have. In this embodiment, there is no intermediate chamber but only inlet chamber 9 and outlet chamber 10.

As another way of describing this embodiment there is a first chamber 9 and a second chamber 10, with the fan 21 and the heating element 22 being located in the first chamber 9.

Except that the rear chamber 8 is removed, the embodiment of FIG. 5 is substantially the same as the embodiment of FIG. Since the heater 22 and the fan 21 are located in the first chamber 9 bordering the outside of the shell 2, the heat loss through the inlet opening 4 is greater than in the embodiment according to FIG. 1. It is expected. Thus, it is judged by the inventors that the embodiment of FIG. 5 will have an advantage over the embodiment of FIG. 1. However, the leakage of hot air into the ambient atmosphere is still reduced to some extent because there is still a depressurization in the second chamber 10 which reacts to the leakage of hot air through the outlet opening 5.

As such, the invention provides that hot air is heated in one chamber 9 and introduced by a fan or fans 21 through a permeable conveyor 17 and at least a portion of the air flow is at least one additional chamber 8. More specifically, the apparatus and method of the present invention, which is converted to 10, and looped back to the chamber 9 where air is primarily heated, can be described more generally. Indeed, the present invention may also include an embodiment having two chambers in which heating is performed in the second chamber 10, although such an embodiment has reduced advantages over the embodiments of FIGS. 1 and 5. Judged by

Although the invention has been described in terms of apparatus and methods, it is to be understood that these categories may also reflect different aspects of the invention. Thus, the method of the present invention may include certain steps that may be the result of the natural operation of the device of the present invention, and whether such steps are explicitly mentioned or not.

Claims (11)

As a heating device for the metal body 19, An outer shell 2 enclosing the inner space 3 and having an inlet opening 4 and an outlet opening 5; Internal walls 6 and 7 for dividing the internal space 3 into a rear chamber 8, at least one intermediate chamber 9 and a front chamber 10 inside the shell 2; The rear chamber 8, the intermediate chamber 9 and from the inlet opening 4 of the shell 2 so that the object 19 loaded on the conveyor 17 is transported through the chambers 8, 9, 10. A permeable conveyor 17 extending through the front chamber 10 to the outlet opening 5 of the shell 2, A fan 21 arranged in the at least one intermediate chamber 9 to direct gas flow towards the conveyor 17 and the object 19 placed on the conveyor 17, and A heating element 22 arranged in the at least one intermediate chamber 9 to heat the gas flowing from the fan 21 before the gas reaches the conveyor 17, The chambers 8, 9, 10 have at least one outlet 14 of the at least one intermediate chamber 9 in communication with the rear chamber 8, 10 and at least one of the intermediate chambers 9. An outlet 14 communicates with the front chamber 10, and at least one inlet 13 of the intermediate chamber 9 communicates with outlets 12, 16 of the rear and front chambers 8, 10. Connected to each other in such a way that the operation of the fan 21 generates two rear gas circulations through the conveyor 17 and two forward gas circulations through the conveyor 17, The heating apparatus of the metal body 19. The method of claim 1, A temperature sensor 25 is located inside the shell 2, and the temperature sensor controls a temperature of the heating element 22 according to a nominal value and a value displayed by the temperature sensor 25. Connected to 26, The heating apparatus of the metal body 19. The method of claim 2, The temperature sensor 25 lies in the front chamber 10 between the conveyor 17 and the outlet 16 of the front chamber 10, The heating apparatus of the metal body 19. The method of claim 1, The apparatus comprises a plurality of fans 21 and a plurality of heating elements 22 arranged in a line perpendicular to the direction of movement of the conveyor 17, The heating apparatus of the metal body 19. As a heating method of the metal body 19, A permeable conveyor through an interior space 3 surrounded by a sheath 2 and divided by an interior wall 6, 7 into a rear chamber 8, at least one intermediate chamber 9 and a front chamber 10. Passing the metal body (19) over (17), Heating air and introducing heated air through the conveyor 17 when the conveyor 17 passes through at least one intermediate chamber 10; The first portion of the heated air passing through the conveyor 17 in the at least one intermediate chamber 10 passes through the conveyor 17 in the rear chamber 8 and the at least one intermediate chamber 9 Switching to back air circulation returning to, and Forward air passing through the conveyor 17 in the front chamber 10 and returning a second portion of the heated air that has passed through the at least one intermediate chamber 9 to the at least one intermediate chamber 9. Converting to circulation, The heating method of the metal body 19. The method of claim 5, wherein The temperature of the air is measured inside the sheath 2 and the heating of the air is controlled according to the nominal value and the measured value, The heating method of the metal body 19. The method of claim 6, The temperature is measured in the front chamber 10 at that location where the temperature of the air is measured after air passes through the conveyor 17 in the front chamber 10, The heating method of the metal body 19. The method of claim 5, wherein The air is heated by a heater 22 located inside the at least one intermediate chamber and the temperature of the heater 22 is maintained in the range of 200 to 300 ℃, The heating method of the metal body 19. The method of claim 6, The nominal value is 70 ℃, The heating method of the metal body 19. The method of claim 5, wherein The metal body 19 is a long metal bar 19, The heating method of the metal body 19. As a heating device for the metal body 19, An outer shell 2 enclosing the inner space 3 and having an inlet opening 4 and an outlet opening 5; At least one inner wall 6, 7 dividing the inner space 3 into separation chambers 8, 9, 10 inside the shell 2, and The sheath through the separation chamber 8, 9, 10 from the inlet opening 4 of the sheath so that the object 19 loaded on the conveyor 17 is transported through the separation chamber 8, 9, 10. A permeable conveyor 17 extending to the outlet opening 5 of the (2), At least one fan 21 arranged in the at least one intermediate chamber 9 to direct gas flow towards the conveyor 17 and the object 19 placed on the conveyor 17, and At least one heating element 22 arranged to heat the gas flowing from the at least one fan 21 before gas reaches the conveyor 17, The chambers 8, 9, 10 are heated in one chamber 9 and air introduced by the at least one fan 21 through the conveyor 17 is at least one additional chamber 8, 10. Are connected to each other so as to loop back to the chamber 9 which converts to and heats air primarily, wherein the additional chambers 8, 10 are inlet openings 4 or outlet openings for the conveyor 17. Which is a chamber (8, 10) having (5), The heating apparatus of the metal body 19.

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