Metal treatment – Process of modifying or maintaining internal physical... – Chemical-heat removing or burning of metal
Reexamination Certificate
2002-06-26
2004-11-30
Kastler, Scott (Department: 1742)
Metal treatment
Process of modifying or maintaining internal physical...
Chemical-heat removing or burning of metal
C266S067000
Reexamination Certificate
active
06824624
ABSTRACT:
The present invention relates to a method and to apparatus for oxygen cutting pieces of steel, such as slabs, sheets, billets, and blooms.
The technological background is illustrated by document EP-A-0 639 416 which describes a two-line oxygen cutting installation, in which each line has a moving carriage with an oxygen cutting torch of the pendular or swinging type.
Document EP-A-0 235 588 describes a similar installation using a main torch that performs pendular motion above the piece to be cut transversely, and an additional torch for trimming the cutting bead. Document DE-U-84 28 017 describes another installation for oxygen cutting, which installation uses nozzles placed beneath the slab so as to expel projections horizontally, and nozzles for projecting water, also disposed beneath the slab, for cooling an anti-erosion plate. Reference can also be made to document U.S. Pat. No. 2,820,420 which describes an oxygen cutting torch mounted so as to be cantilevered out on a carriage that can be moved horizontally, and to document WO-A-96/20818 which describes an overhead crane supporting a telescopically extensible vertical working arm.
It is known that the operation of oxygen cutting pieces of steel, and more specifically pieces such as slabs, sheets, billets, and blooms in steel works, generally generates residues of unburnt molten metal on the exit surface for the cutter jet, with a fraction thereof not being expelled into ambient air by the cutter jet but becoming stuck to and solidifying on the exit lips of the cut slot, with this taking place over the entire length of the slot, thereby forming respective cutting beads. These unwanted beads adhere strongly to the bodies of such cut pieces, and it is necessary to implement an additional operation for removing the beads which are of greater or lesser size depending on the grade of steel involved, the cutting speed, and the type and adjustment of oxygen cutting torch. In the past, cutting beads were generally removed either by manual trimming using a torch or a chisel, or else mechanically using an appropriate machine.
Proposals have subsequently been made to trim the cutting bead simultaneously with the bead being formed on the face of the piece in question, as described in document WO-A-99/16570. Nevertheless, that technique makes use of a horizontal cutter jet which means that it is unsuitable for cutting slabs or other products of great width. In addition, the flow of molten metal remains incomplete when using horizontal cutter jets, so detaching the particles that constitute the cutting bead requires a trimming jet that is very powerful in order to be capable of expelling the molten particles downwards. Finally, conventional techniques do not make it possible to avoid the presence of a large amount of smoke in the exit zone of the cutter jet, with such smoke emissions being generated by the post-combustion of unburnt molten metal residues that are ejected by the cutter jet and by the trimmer jet.
The above-mentioned drawbacks have been overcome to a large extent by an oxygen cutting method in which a cutter member is moved in such a manner that the cutter jet is directed towards a first face of the piece in order to attack said piece in a substantially vertical direction so as to form a slot, and synchronously therewith a trimmer member and a spray member are moved in such a manner that their respective jets are directed towards a second face of said piece, opposite from its first face, attacking said second face in an oblique direction at the cutter jet exit so as to trim the cutting bead being formed on said second face while simultaneously reducing smoke emission, said trimmer and spray members being carried by a blade-shaped support passing through the cut slot. Document WO-A-01/28727 in the name of the Applicant describes such an oxygen cutting method in detail together with associated apparatus for implementing the method. The use of a blade-shaped support passing directly through the cut slot is very attractive insofar as all of the active components of the apparatus for implementing the method can be located above the piece to be cut, leaving the space under said piece unoccupied. Nevertheless, it has been found that incidents can arise in operation, e.g. due to excessive cutting speed or to defects in the metal being cut such as inclusions or seams, which incidents can lead to showers of particles being generated in which the particles are constituted by a mixture of molten steel and slag and in which these particles strike the blade-shaped support inside the cut slot. When such incidents or defects occur during the cutting process, the showers of particles can generate obstructions and can even jam the blade-shaped support, preventing it from advancing normally and thus preventing the associated trimmer member from advancing. This makes the cutting and trimming operation insufficiently reliable and makes high cutting speeds completely unattainable.
In addition, when the pieces being cut are slabs coming directly from continuous casting in steel works, the temperatures involved are very high (about 1000° C.) such that the blade-shaped support supporting the trimmer member is heated very severely, and such heating can prevent the trimming process from being continued normally.
An object of the invention is to provide a method of oxygen cutting a piece of steel, and apparatus for implementing the method, capable of cutting a wide variety of pieces of steel in regular manner without leaving a cutting bead and without emitting smoke, and above all without running the risk of jamming the forward advance of the trimmer member whose support passes through the cut slot. It is also desirable for the technique to be capable of cutting pieces of steel that come directly from continuous casting.
According to the invention, this problem is solved by a method of oxygen cutting a piece of steel, in which a cutter member is moved in such a manner that the cutter jet is directed towards a first face of the piece in order to attack said face in a substantially vertical direction so as to form a slot, and synchronously therewith a trimmer member and a spray member are moved in such a manner that their respective jets are directed towards a second face of the piece, opposite from its first face, attacking said second face in an oblique direction at the cutter jet exit so as to trim the cutting bead being formed on said second face while simultaneously reducing smoke emission, said trimmer and spray members being carried by a blade-shaped support passing through the cut slot, said method being remarkable in that at least one pressurized fluid jet is projected directly into the cut slot and into the portion thereof which lies between the cutting front and the blade-shaped support, said jet forming a barrier protecting said blade-shaped support against particle projections during advance of the support along the cut slot.
The jet of pressurized fluid thus emitted directly into the cut slot provides a genuine protective barrier or curtain by creating a protected zone in the cut slot, and it does this over the entire thickness of the piece of steel being cut, expelling from the slot all unwanted particles created by the cutter jet. By eliminating any risk of the blade-shaped support being obstructed, it is possible to envisage very high advance speeds while cutting, speeds that are at least twice the advance speeds that can be obtained with traditional oxygen cutting techniques.
In a first implementation of the method of the invention, at least one fluid jet is projected obliquely towards the cutting front, and preferably towards the lower portion of said cutting front. It is then preferable for the selected fluid to be an oxygen cutting fluid, and in particular oxygen or a mixture of oxygen and a fuel gas. The fluid jet projected directly into the cut slot then also makes it possible perform additional cutting in the lower portion of the cutting front, and also makes it possible to deliver additional heat, which improves the performa
Prioretti Guy
Prioretti Jean-Michel
Prioretti Véronique
Prioretti-Hacking Françoise
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