In-line loading furnace for wires and wire rods annealing in protected atmosphere

Abstract

A furnace for the annealing of steel products, such as wires and wire rods, in a protected atmosphere where the loading of the material to be treated takes place in-line. The furnace for the annealing of steel wires and wire rods, of the invention comprises a heat treatment chamber for said steel wires and wire rods in a controlled atmosphere of nitrogen or other inert gas, said heat treatment chamber being provided with a closable / openable access opening, the loading of said steel wires and wire rods into said heat treatment chamber taking place is an essentially horizontal movement.

Description

[0001] The present invention relates to the field of industrial furnaces. More particularly, the present invention relates to a furnace with in-line loading for annealing steel products, such as wires and wire rods, in a protected atmosphere.

[0002] As is well known, in the current state of the art, the heat treatment process of wires and wire rods is normally carried out by means of a battery of bell furnaces composed of a minimum of three furnace bases (necessary to receive the material to be treated), a minimum of two intermediate bell furnaces (necessary to guarantee the processing environment in an inert atmosphere), a minimum of one bell furnace (necessary to carry out the process of heating and holding the material to be treated during the processing phase), and a minimum of one cooling hood (necessary for the cooling processing step of the material to be treated).

[0003] The heat treatment process carried out with bell furnace batteries of the known type requires the execution of individual processes on different bases with different bells, according to a processing scheme that can be summarised as follows: a heating and holding phase: involves placing the material to be treated on a first base, followed by placing an intermediate bell on the first base, placing the bell furnace and heating and holding the material to be treated on the first base (sub-phases of material placement, inert atmosphere creation, heating and holding); a cooling phase: at the end of the heating and holding phase, the bell furnace is lifted and placed on the second base, followed by the lifting of the cooling hood from the third base and its placement on the first base to cool the material; final stages of the heat treatment process: lifting the cooling hood and moving it to the third base, lifting the first intermediate bell and placing it in the available surrounding space, lifting and removal of the treated material from the first base.

[0004] It is clear that the handling of suspended loads requires the use of equipment that enables such activities, such as hooks, overhead cranes, cranes and the like. These activities, moreover, can only be performed by specialised operators who must work on the processing site, i.e., cannot be carried out with remote operators.

[0005] Another considerable problem and disadvantage arises from the overall dimensions of the bells, which entail the need to have buildings where the heat treatment furnace line is placed with considerable heights and surfaces, or the need to carry out onerous foundation works to partially or totally encase the furnaces and their bases under the ground level, thus reducing the above-ground dimensions of the heat treatment furnace line.

[0006] It is therefore clear that, basically, the heat treatment process of wires and wire rods currently carried out in bell-type furnaces entails a considerable number of disadvantages in terms of the space and volume required, the lifting equipment required, the use of on-site personnel, the duration of heat treatments and the resulting energy expenditure, as well as safety, which have not yet been resolved to date.

[0007] In view of the above, the main purpose of the present invention is to provide a furnace for annealing steel products, such as wires and wire rods, in a protected atmosphere, which overcomes or mitigates the criticalities mentioned above.

[0008] More specifically, an aim of the present invention is to provide a furnace for annealing steel products, such as wires and wire rods, in a protected atmosphere that does not require dedicated areas with significant height.

[0009] Another purpose of the present invention is to provide a furnace for annealing steel products, such as wires and wire rods, in a protected atmosphere, in which suspended loads are not required to be handled.

[0010] As a further purpose, the present invention aims to provide a furnace for annealing steel products, such as wires and wire rods, in a protected atmosphere, having a compact design and easy installation in the field.

[0011] Yet another purpose of the present invention is to provide a furnace for annealing steel products, such as wires and wire rods, in a protected atmosphere, which can be easily produced on an industrial scale, at a cost competitive with state-of-the-art solutions.

[0012] To achieve these tasks and purposes, the present invention provides a furnace for the annealing of steel products, such as wires and wire rods, in a protected atmosphere, in which the loading of the material to be treated takes place in-line.

[0013] For the purposes of the present invention, the terms "loading of the material to be treated takes place in-line", is meant to designate a loading phase of the material to be treated with an essentially horizontal movement. The same applies to the unloading phase of the material to be treated which also takes place with an essentially horizontal movement.

[0014] The treatment furnace of the present invention comprises a treatment chamber for wire rods and wires of various types of alloy steels in a controlled atmosphere of nitrogen or other inert gas provided with a closable / openable access opening.

[0015] In the heat treatment furnace of the present invention, said treatment chamber is conveniently equipped with a heating system, an air / gas recirculation system and a cooling system.

[0016] The heat treatment furnace of the present invention further comprises a device for loading the material to be treated into said treatment chamber with a substantially horizontal movement through said access opening.

[0017] An embodiment of a heat treatment furnace according to the present invention is shown in the attached Figures, where: Figure 1 is perspective view of a heat treatment furnace according to the present invention; Figure 2 is a side view of a heat treatment furnace according to the present invention; Figure 3 is an example of a heat treatment cycle carried out in a heat treatment furnace according to the present invention.

[0018] Preferably, the heat treatment furnace of the present invention comprises a metal framework of profiled iron, tubular and electro-welded load-bearing sheets, reinforced where necessary. Inside the structure thus created, there is preferably an insulating coating.

[0019] In embodiments of the heat treatment furnace of the present invention, preferably, the thermal insulation of the walls may advantageously consist of ceramic fiber panels and / or mineral wool panels, with aluminum foil in between.

[0020] Preferably, the insulation of the heat treatment furnace of the present invention may be advantageously completed by internal panelling in order to prevent abrasion of the internal surface due to recirculation of hot fluids within the chamber.

[0021] Preferably, the vault of the heat treatment furnace of the present invention can be accessible by means of a ladder leading to a walkway that allows access at height on the sides of the heat treatment furnace.

[0022] In embodiments of the heat treatment furnace of the present invention, preferably, the lining of the oven floor may be shaped in relation to the profile of the paths of travel of the loading device and the supporting cabling of the charges / reels of material to be processed.

[0023] In preferred embodiments of the heat treatment furnace of the present invention, the access opening to the heat treatment chamber is openable / closable by means of, for example, a door that guarantees a perfect seal in a protective atmosphere.

[0024] More preferably, the access opening to the heat treatment chamber may be conveniently equipped with a double doors system. In particular, the double doors systems may comprise a first door that acts as a heat barrier and a second door that ensures the oven is hermetically sealed. For example, the tightness of the hermetically sealed door on the access opening can be ensured by an appropriate number of pneumatic cylinders, so as to ensure a perfect seal of the door itself.

[0025] In embodiments of the heat treatment furnace of the present invention, preferably, the heating system can advantageously comprise radiators (radiant tubes) heated, for example, by gas burners or electric heating elements. Preferably, the radiators / radiant tubes can be installed on both sides of the furnace and can be easily removed in the event of maintenance.

[0026] Preferably, the heat treatment furnace of the present invention can be conveniently divided into a number of independent control zones, each of which is equipped with an independent system for forced air recirculation.

[0027] Advantageously, a recirculation device, e.g. a fan, can be provided to carry out closed-loop cooling; the fan can be appropriately positioned so as to provide air suction from a pipe positioned, e.g., on the back wall of the furnace.

[0028] In preferred embodiments of the heat treatment furnace of the present invention, the fan can be controlled by appropriate means of control so as to adjust its flow rate to the actual requirements of the cooling cycle. Following the heat exchange in a suitable heat exchanger, the cooled gas can be sent back into the furnace through pipes appropriately fitted with shut-off valves, while a connecting pipe can be provided for the expulsion of the gas, so as to discharge the excess gas directly into the flue gas collector.

[0029] The heat treatment furnace of the present invention is designed to be able to work in a protective atmosphere and is therefore, as already mentioned, sealed. The flow of inert atmosphere can be interrupted when it is not necessary (e.g. when the door is open, the oven is switched off or when heat treatment in air is carried out).

[0030] In embodiments of the heat treatment furnace of the present invention, preferably, a minimum flow rate of inert gas can be provided in said treatment chamber throughout the heat treatment cycle in order to keep the furnace under pressure and eliminate any residual oxygen. Keeping the furnace under pressure also prevents oxygen from leaking into the furnace.

[0031] Preferably, the movement of the loading means may be of the electromechanical type. In particular, in embodiments of the present invention, the horizontal feed / retraction (loading / unloading) movement to / from the to the heat treatment chamber may advantageously be of the motorised wheel type, while any vertical movement may be of the traction type, e.g. by means of a worm screw jack on an inclined plane.

[0032] Advantageously, the heat treatment furnace of the present invention can be equipped with a control system with a dedicated programmable software, whose main functions can be summarised as follows: combustion system control: combustion safety management; sequence of furnace ignition cycles; management of heat treatment data; management and control of burner control units; alarm management; movement control; process data management; management of movement cycles; alarm management.

[0033] For example, in practical implementation of the heat treatment furnace of the present invention, the active temperature profile can be resident in a PLC as well as the temperature set-point as a function of time, the up or down ramps, or the holding temperature phases.

[0034] The various programs archive and data bases, on the other hand, may be resident in a PC, and the temperature program and heating / maintenance / cooling profiles chosen for a give heat treatment will be downloaded to the PLC from time to time.

[0035] In various embodiments of the heat treatment furnace of the present invention, in addition to the PLC, the automation can be conveniently completed by the use of a man / machine interface PC of the SCADA type.

[0036] In practice, the heat treatment to be carried out in the heat treatment furnace of the present invention generally consists of several stages: Heating; Maintaining; Cooling.

[0037] An example of a of a heat treatment cycle carried out in a heat treatment furnace according to the present invention is represented in the attached Figure 3.

[0038] A defined and pre-determined number of customer-agreed programs can be made available to the customer, and the programs can be fully set by the operator via a supervisor. For instance, each program shall be able to handle 10 steps, with each step that can be either of the heating, maintenance or cooling type.

[0039] The furnace for annealing steel products, such as wires and wire rods, in a protected atmosphere, according to the present invention, is relatively simple and economical to manufacture industrially using established manufacturing techniques. It can therefore be realised at competitive costs with conventional switching apparatus.

[0040] The furnace for annealing steel products, such as wires and wire rods, in a protected atmosphere, according to the present invention, thus comprises a heat treatment chamber with substantially horizontal access, which makes it possible to reduce the overall dimensions and costs of construction. It is therefore characterised by a very compact structure which is particularly simple and economical to construct at an industrial level and which does not require lifting and moving in height of the articles to be treated, thus eliminating the problems typical of bell-type furnaces of the known art.

Claims

1. A furnace for the annealing of steel products, such as wires and wire rods, in a protected atmosphere characterized in that the loading of the material to be treated takes place in-line.

2. The furnace for the annealing of steel wires and wire rods, according to claim 1, characterized in that it comprises a heat treatment chamber for said steel wires and wire rods in a controlled atmosphere of nitrogen or other inert gas, said heat treatment chamber being provided with a closable / openable access opening, the loading of said steel wires and wire rods into said heat treatment chamber taking place is an essentially horizontal movement.

3. The furnace for the annealing of steel wires and wire rods, according to claim 1 or 2, wherein said heat treatment chamber is equipped with a heating system, an air / gas recirculation system and a cooling system.

4. The furnace for the annealing of steel wires and wire rods, according to claim 2 or 3, further comprising a device for loading the material to be treated into said heat treatment chamber with a substantially horizontal movement through said access opening.

5. The furnace for the annealing of steel wires and wire rods, according to one or more of the previous claims, further comprising a structure with a metal framework of profiled iron, tubular and electro-welded load-bearing sheets, reinforced where necessary, a thermal insulating coating being provided inside said structure.

6. The furnace for the annealing of steel wires and wire rods, according to claim 5, wherein said thermal insulating coating comprises ceramic fiber panels and / or mineral wool panels, with aluminum foil in-between.

7. The furnace for the annealing of steel wires and wire rods, according to one or more of the previous claims, wherein said heat treatment chamber is provided with abrasion-resistant panels positioned on its internal surface.

8. The furnace for the annealing of steel wires and wire rods, according to one or more of the previous claims, wherein said heat treatment chamber is provided with a double doors system comprising a first door that acts as a heat barrier and a second door that ensures hermetically sealing of said heat treatment chamber.

9. The furnace for the annealing of steel wires and wire rods, according to one or more of the previous claims, wherein said heat treatment chamber is provided with a heating system which comprises radiators (radiant tubes) heated by gas burners or electric heating elements, said radiators / radiant tubes being preferably installed on both sides of said heat treatment chamber.

10. The furnace for the annealing of steel wires and wire rods, according to one or more of the previous claims, wherein said heat treatment chamber is divided into a number of independent control zones, each of which is equipped with an independent system for forced air recirculation.

11. The furnace for the annealing of steel wires and wire rods, according to one or more of the previous claims, wherein said heat treatment chamber is provided with a recirculation device, preferably a fan, to carry out closed-loop cooling of said heat treatment chamber.

12. The furnace for the annealing of steel wires and wire rods, according to one or more of the previous claims, wherein a minimum flow rate of inert gas is provided in said heat treatment chamber.

13. The furnace for the annealing of steel wires and wire rods, according to one or more of the previous claims, further equipped with a control system with a dedicated programmable software, adapted to carry out the following main functions: - combustion system control: - combustion safety management; - sequence of furnace ignition cycles; - management of heat treatment data; - management and control of burner control units; - alarm management; - movement control; - process data management; - management of movement cycles; - alarm management.

14. The furnace for the annealing of steel wires and wire rods, according to one or more of the previous claims, wherein the heat treatment to be carried out in said heat treatment chamber comprises the following stages: - Heating; - Maintaining; - Cooling.

15. The furnace for the annealing of steel wires and wire rods, according to one or more of the previous claims, wherein a defined and pre-determined number of customer-agreed programs is made available to the customer.

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