EP2451612B1 - Cutting by means of a jet of liquid cryogenic fluid with added abrasive particles - Google Patents

Description

The invention relates to a method and a device for cutting materials, such as metals, concrete, wood, plastics or any other type of material, by a jet of cryogenic fluid at very high pressure with added abrasive, in particular corundum.

The cutting of materials can be done with the disqueuse (concrete, stone, metals ..), with the saw (metals, wood, plastics ...), by laser beam (metals, plastics ...), with jet of plasma (metals), water jet Ultra High Pressure (UHP) with or without abrasives (all types of materials) ...

However, when there is no hot spot in contact with hard materials, during the cutting process, only UHP waterjet cutting with abrasive is used. In this case, according to a rather widespread cutting process, water at a pressure (UHP) of between 1000 and 4000 bar is brought to a stainless steel mixing chamber, into which a flow of compressed air conveying a garnet or olivine-type abrasive so as to form a mixture of water and ultrahigh-pressure abrasive. This water / abrasive mixture is then sent towards the material to be cut by a tungsten carbide focusing gun, such as that shown in FIG. Figure 1 .

So, the figure 1 schematizes a conventional tungsten carbide focusing gun structure used to send an abrasive material to a material to be cut. This focusing gun 5 comprises a first inlet or inlet 1 by which the barrel is fed with an abrasive / compressed air mixture, a second inlet or inlet 2 by which the barrel 5 is fed with UHP water, for example between 1000-4000 bars, a venturi type head 3, a mixing chamber 4 and an outlet for the mixture of pressurized water and abrasive.

However, in some cases, the use of water itself is problematic. Indeed, the use of water for certain contaminated part cutting applications, for example following contamination by chemical, nuclear or other radiation, carries risks of pollution and requires complex recovery systems and expensive.

An alternative solution to water cutting is proposed by the use of cryogenic jets, as taught by the document US Patent 7,310,955 for example. In this case, a cryogenic fluid, generally liquid nitrogen, is used at very high pressure to replace the water to achieve the desired cut.

However, this method is not used to cut some hard materials, such as metal, stone, concrete ..., especially when their thickness becomes too large, for example greater than about 10 mm.

In addition, it has been noted that the cryogenic fluid distribution barrel, or even the mixing chamber, of the cutting device can be very quickly eroded when the fluid is supplemented with abrasive particles, in particular when the particles have a high hardness.

It follows that the problem is to be able to use a process and a UHP cryogenic fluid jet cutting device to cut different types of materials, including hard materials, such as concrete, metals, stone, wood, plastics ...., and / or having thicknesses up to 10 cm, not having the aforementioned disadvantages. A device according to the preamble of claim 9 is disclosed in the document WO 99-51393 .

• le jet de coupe est formé par mélange d'au moins un premier composé sous forme liquide et à une température cryogénique inférieure à -100°C, et de particules abrasives solides formées d'au moins un matériau abrasif ayant un indice de dureté d'au moins 6 Mohs, les particules abrasives solides étant contenues dans un flux gazeux, et
• le jet de découpe est dirigé vers le matériau à couper au moyen d'un canon de focalisation alimenté en ledit mélange, la matière formant, totalement ou partiellement, le canon de focalisation ayant une dureté supérieure à la dureté des particules abrasives solides utilisées.

The solution of the invention is then a method of cutting a material, in which said material is cut by means of a cutting jet at a pressure of at least 100 bars, characterized in that

• the cutting jet is formed by mixing at least a first compound in liquid form and at a cryogenic temperature below -100 ° C, and solid abrasive particles formed of at least one abrasive material having a hardness index of at least 6 Mohs, the solid abrasive particles being contained in a gaseous flow, and
• the cutting jet is directed towards the material to be cut by means of a focusing gun supplied with said mixture, the material forming, totally or partially, the focusing gun having a hardness greater than the hardness of the solid abrasive particles used.

• le mélange entre le flux liquide et les particules abrasives solides véhiculées par le flux gazeux se fait dans une chambre de mélange.
• la pression du jet de coupe est comprise entre 500 et 4000 bars, entre 1000 et 3800 bars, de préférence de l'ordre de 3000 à 3500 bars.
• le composé sous forme liquide est à une température inférieure à -150°C, de préférence entre -160°C et -230°C.
• le composé sous forme liquide est de l'azote liquide.
• les particules abrasives solides comprennent au moins un matériau abrasif choisi dans le groupe formé par le corindon, le grenat, le carbure de tungstène, le carbure de silicium, l'olivine, l'alumine et le carbonate de calcium.
• les particules abrasives solides ont une granulométrie comprise entre 20 et 200 mesh, de préférence 60 et 100 mesh.
• les particules abrasives solides sont avantageusement des particules de corindon, grenat ou olivine, avantageusement du corindon.
• le matériau à découper est en métal, en béton, en céramique, en bois, en plastique, en tout autre polymère ou en matière organique dure.
• le matériau à découper a une épaisseur comprise entre 1 cm et 20 cm, typiquement entre 1 et 10 cm.
• la vitesse de coupe est comprise entre 0,01 et 4 m/min selon la nature du matériau à couper.
• le jet de coupe comprenant le composé sous forme liquide et les particules abrasives solides est obtenu par mélange dudit composé sous forme liquide avec un flux d'air comprenant les particules abrasives solides.
• le mélange entre le flux liquide et l'abrasif véhiculé par un flux gazeux, se fait dans une chambre de mélange formée, totalement ou partiellement, i.e. pièce massive ou revêtement surfacique interne, d'acier trempé, de carbure de tungstène, de carbure de silicium, de titane ou de bore, nitrure de bore, de préférence nitrure de bore cubique, ou de diamant, de préférence en un matériau ayant une dureté supérieure à la dureté des particules abrasives solides utilisées.
• le jet de découpe est dirigé vers le matériau à couper au moyen d'un canon de focalisation alimenté par le mélange obtenu dans ladite chambre de mélange.
• la matière formant, totalement ou partiellement, i.e. pièce massive ou revêtement surfacique interne, le canon de focalisation a une dureté supérieure à la dureté des particules abrasives solides utilisées lorsque lesdites particules sont du corindon.
• la matière formant, totalement ou partiellement, i.e. pièce massive ou revêtement surfacique interne, le canon de focalisation est du carbure de tungstène avec un taux de cobalt compris entre environ 0.1 et 10%, de préférence de l'ordre de 0.15% à 0.5%, par exemple de l'ordre 0.25%, du carbure de silicium, du carbure de titane, du carbure de bore, du nitrure de bore cubique ou du diamant.
• le mélange entre le flux liquide et l'abrasif véhiculé par un flux gazeux, se fait dans une chambre de mélange formée, totalement ou partiellement, d'acier trempé, de carbure de tungstène avec un taux de cobalt compris entre environ 0.1 et 10%, de carbure de silicium, de carbure de titane, de carbure de bore, de nitrure de bore cubique ou de diamant.
• la chambre de mélange ou le canon est formé, au moins partiellement, de carbure de tungstène avec un taux de cobalt compris entre environ 0.1 et 10%, et les grains de carbure de tungstène ont une taille inférieure à 1,5 µm, de préférence entre 0,1 et 0,6 µm.

Depending on the case, the cutting method of the invention may comprise one or more of the following characteristics:

• the mixture between the liquid stream and the solid abrasive particles carried by the gas flow is in a mixing chamber.
• the pressure of the cutting jet is between 500 and 4000 bar, between 1000 and 3800 bar, preferably of the order of 3000 to 3500 bar.
• the compound in liquid form is at a temperature below -150 ° C, preferably between -160 ° C and -230 ° C.
• the compound in liquid form is liquid nitrogen.
• the solid abrasive particles comprise at least one abrasive material selected from the group consisting of corundum, garnet, tungsten carbide, silicon carbide, olivine, alumina and calcium carbonate.
• the solid abrasive particles have a particle size of between 20 and 200 mesh, preferably 60 and 100 mesh.
• the solid abrasive particles are advantageously particles of corundum, garnet or olivine, advantageously corundum.
• the material to be cut is metal, concrete, ceramic, wood, plastic, any other polymer or hard organic material.
• the material to be cut has a thickness of between 1 cm and 20 cm, typically between 1 and 10 cm.
• the cutting speed is between 0.01 and 4 m / min depending on the nature of the material to be cut.
• the cutting jet comprising the compound in liquid form and the solid abrasive particles is obtained by mixing said compound in liquid form with a stream of air comprising the solid abrasive particles.
• the mixture between the liquid flow and the abrasive conveyed by a gaseous flow is made in a mixing chamber formed, totally or partially, the solid part or inner surface coating, hardened steel, tungsten carbide, carbide of silicon, titanium or boron, boron nitride, preferably cubic boron nitride, or diamond, preferably a material having a hardness greater than the hardness of the solid abrasive particles used.
• the cutting jet is directed to the material to be cut by means of a focusing gun fed by the mixture obtained in said mixing chamber.
• the material forming, totally or partially, the solid piece or internal surface coating, the focusing gun has a hardness greater than the hardness of the solid abrasive particles used when said particles are corundum.
• the material forming, totally or partially, the solid piece or internal surface coating, the focusing gun is tungsten carbide with a cobalt content of between about 0.1 and 10%, preferably of the order of 0.15% to 0.5% for example of the order 0.25%, silicon carbide, titanium carbide, boron carbide, cubic boron nitride or diamond.
• the mixture between the liquid flow and the abrasive conveyed by a gas flow, is in a mixing chamber formed, totally or partially, of hardened steel, tungsten carbide with a cobalt content between about 0.1 and 10% , silicon carbide, titanium carbide, boron carbide, cubic boron nitride or diamond.
• the mixing chamber or the barrel is formed, at least partially, of tungsten carbide with a cobalt content of between approximately 0.1 and 10%, and the tungsten carbide grains have a size of less than 1.5 μm, preferably between 0.1 and 0.6 μm.

The invention also relates to a cutting jet cutting device with a pressure of at least 100 bar comprising a source of cryogenic liquid under pressure fluidly to a mixing chamber for supplying said mixing chamber with cryogenic liquid under pressure, and a focusing gun fluidly connected to said mixing chamber, characterized in that it further comprises a source of abrasive particles having a hardness index at least 6 Mohs, feeding the mixing chamber so as to feed the focusing gun into a mixture of cryogenic liquid under pressure and said abrasive particles, which mixture is delivered by the focusing gun in the form of a jet of cutting, the focusing gun being formed, totally or partially tungsten carbide with a cobalt content between about 0.1 and 10%, silicon carbide, titanium carbide, boron carbide, cubic boron nitride or in diamond.

• la chambre de mélange est formée, totalement ou partiellement, d'acier trempé, de carbure de tungstène avec un taux de cobalt compris entre environ 0.1 et 10%, de carbure de silicium, de carbure de titane, de carbure de bore, de nitrure de bore cubique ou de diamant.
• le canon de focalisation ou la chambre de mélange est formé, totalement ou partiellement, de carbure de tungstène comprenant un taux de cobalt compris entre environ 0.1 et 10%, les grains de carbure de tungstène ayant une taille inférieure à 1,5 µm.

As the case may be, the device of the invention may comprise one or more of the following characteristics:

• the mixing chamber is formed, totally or partially, of hardened steel, tungsten carbide with a cobalt content between about 0.1 and 10%, silicon carbide, titanium carbide, boron carbide, nitride of cubic boron or diamond.
• the focusing gun or the mixing chamber is formed, totally or partially, of tungsten carbide comprising a cobalt content of between about 0.1 and 10%, the tungsten carbide grains having a size less than 1.5 microns.

The invention will now be better understood by the following explanations and the following embodiments.

The cutting method according to the invention consists in using a cutting jet formed, on the one hand, of a cryogenic fluid in liquid form, in particular liquid nitrogen, with UHP, that is to say typically more than 100 bar or more than 1000 bar, and secondly, abrasive particles formed of one or more materials having a hardness index of at least 6 Mohs, to cut a material.

The abrasive particles are supplied by a flow of gas, such as air, to the mixing chamber feeding the focusing gun for dispensing the jet of liquid / abrasive nitrogen mixture.

The abrasives used in combination with UHP liquid nitrogen are preferably corundum, garnet and olivine for the reasons explained below.

However, other abrasives, such as tungsten carbide, silicon carbide, alumina and calcium carbonate may also be used, depending on the application considered, including the nature, the thickness of the material to be cut, type of gun used, the nature of the material forming the mixing chamber.

The performance of an abrasive depends on its particle size, shape and hardness. The cutting tests were made with abrasives with a grain size of 80 mesh, ie 150 to 180 μm, and having the same grain shape (sharp angles at about 60 °).

It is therefore the hardness of the abrasives that determines their effectiveness here. The hardness indices of several materials are given in Table 1 below. <u> Table I </ u> Material Hardness index (Mohs) Diamond 10 Cubic boron nitride 9.8 Boron carbide (B4C) 9.5 Silicon carbide 9.3 alumina 9.2 Chromium 9 Corundum 9 Standard tungsten carbide (WC) 8.5 Stainless steel <8.5 Garnet 7.5 olivine 6.5

As seen in this Table I, according to the scale of hardness (Mohs), the corundum is more efficient than the garnet which is itself more efficient than the olivine since the corundum is, among other things, the hardest of these three compounds.

However, it has been found that, with corundum, the standard tungsten carbide (WC) focusing gun and, to a lesser extent, the hardened steel mixing chamber, undergo greater erosion than the garnet. In fact, these degradations are explained by the fact that the hardness of the corundum is greater than that of the hardened steel and that of the standard tungsten carbide.

Table II below illustrates the degradation of a focusing gun according to the material constituting said barrel, in tests operated with a mixture of liquid nitrogen and corundum. <u> Table II </ u> After 1 hour of test: Corundum + liquid nitrogen Focusing gun type Standard WC WC + abrasion resistant (Roctec® 500) WC + abrasion resistant (Ultramant 3000) alumina B4C (Tetrabor®) Mark / KMT Ceratizit Sceram ESK Results Inoperative after 2 min No loss of efficiency No loss of efficiency Inoperative after 15 minutes No loss of efficiency Inside diameter before use 1.02 mm 1.02 mm 1.02 mm 1.20 mm 1.20 mm Inside diameter after use Between 2 and 2.5 mm 1.04 mm 1.08 mm 3à4mm 1.20 mm Compatibility with corundum bad Very good Very good bad excellent

It can be seen that Roctec® 500 and Ultramant 3000 focusing guns are harder than standard tungsten carbide (WC) guns and are much more resistant to corundum erosion.

This is due to the proportion of cobalt present in the tungsten binder used to make guns. Indeed, the lower the amount of cobalt (Co) tungsten binder, the more tungsten is resistant to abrasion but also fragile to shocks.

However, since a focusing gun is not subjected to shock but simply to friction erosion, it is preferred to use tungsten focusing guns comprising less than 0.5% by weight of cobalt, preferably less than 0.30% by weight. example of the order of 0.25%, when corundum is chosen as abrasive material mixed with the flow of liquid nitrogen.

As already mentioned, the mixing chamber 4 is very eroded by the stream of abrasive particles.

Thus, Table III below shows the degradation of a hardened steel mixing chamber following the use of a mixture of liquid nitrogen and corundum for 8 hours, in particular of the part 11 of the mixing chamber. where the abrasive arrives, the part of the mixing chamber 12 where liquid nitrogen arrives and the part of the mixing chamber where the nitrogen / abrasive mixture comes out, as illustrated in FIG. Figure 2 . <u> Table III </ u> After 8 hours of testing: corundum + liquid nitrogen Focusing chamber hardened steel (cf. Figure 2 ) Internal diameter Mixing chamber before use Part 11 Part 12 Part 13 3 mm 2 mm 4.5 mm after use 3.1 mm 4.2 mm 6.5 mm

The results obtained show that, despite a significant erosion of its diameter, in particular parts 12 and 13 of the Figure 2 the mixing chamber 4 made of stainless steel remained effective for producing the corundum / liquid nitrogen mixture during the 8h of tests.

Nevertheless, to minimize the wear of the mixing chamber and the focusing gun, a focusing gun, or even a mixing chamber, which is formed (ie solid pieces or surface coatings) of a harder material, will be used. the abrasive particles used, in particular harder than the corundum, thus making it possible to overcome the problem of erosion caused by these abrasive particles, in particular corundum.

Thus, the material of the focusing gun, or even of the mixing mixing chamber, may be tungsten carbide containing a low level of cobalt (<0.5%), silicon carbide, boron, titanium or other, cubic boron nitride, diamond or any material compatible and harder than corundum.

In all cases, in the context of the invention, it is essential that at least the focusing gun of the jet is made of a material resistant to erosion caused by the abrasive particles because it is the gun that undergoes the stronger erosion.

Although less efficient than garnet, olivine can also be used, as shown by additional tests performed under the same conditions as the previous tests.

In the end, these tests show that using adapted tools makes it possible to increase life expectancy despite the use of abrasives that are effective in cutting but very eroding for materials, such as corundum.

This is all the more important for applications where the number of preventive and / or corrective maintenance operations must be minimized, for example, in applications where human intervention is difficult, typically in radioactive environments.

Claims (11)

1. Method for cutting a material, wherein said material is cut by means of a cutting jet at a pressure of at least 100 bar, the cutting jet being:

   - formed by mixing at least a first compound in liquid form and at a cryogenic temperature of less than -100 °C, and solid abrasive particles formed from at least one abrasive material having a hardness index of at least 6 Mohs, the solid abrasive particles being contained in a gas stream, and said particles comprising at least one abrasive material chosen from the group formed by corundum, garnet, tungsten carbide, silicon carbide, titanium carbide, olivine, alumina and calcium carbonate; and

   - being directed towards the material to be cut by means of a focusing gun, the material forming, in full or in part, the focusing gun having a hardness greater than the hardness of the solid abrasive particles used, and said material being chosen from among tungsten carbide having a cobalt content of between around 0.1 and 10 %, silicon carbide, titanium carbide, boron carbide, cubic boron nitride and diamond.
2. Method according to claim 1, characterised in that the pressure of the cutting jet is between 500 and 4000 bar.
3. Method according to either claim 1 or claim 2, characterised in that the compound in liquid form is at a temperature of less than -150 °C.
4. Method according to any of the preceding claims, characterised in that the compound in liquid form is liquid nitrogen.
5. Method according to any of the preceding claims, characterised in that the material to be cut is made of metal, of ceramic material, of concrete, of wood, of plastics material or of polymer.
6. Method according to any of the preceding claims, characterised in that the gas stream comprising the solid abrasive particles is an air stream.
7. Method according to any of the preceding claims, characterised in that the mixing of the liquid stream and the solid abrasive particles transported by a gas stream takes place in a mixing chamber formed, in full or in part, of hardened steel, tungsten carbide having a cobalt content of between around 0.1 and 10 %, silicon carbide, titanium carbide, cubic boron carbide, boron nitride or diamond, preferably a mixing chamber formed of a material having a hardness greater than the hardness of the abrasive used.
8. Method according to any of the preceding claims, characterised in that the solid abrasive particles comprise at least one abrasive material chosen from the group formed by corundum, garnet and olivine, preferably corundum.
9. Device for cutting using a cutting jet at a pressure of at least 100 bar comprising a source of pressurised cryogenic liquid in fluid communication with a mixing chamber (4) for supplying pressurised cryogenic liquid to said mixing chamber (4), and a focusing gun (5) in fluid communication with said mixing chamber (4), characterised in that it further comprises a source of abrasive particles having a hardness index of at least 6 Mohs, supplying the mixing chamber (4) so as to supply the focusing gun (5) with a mixture formed of at least the pressurised cryogenic liquid and said abrasive particles, which mixture is emitted by the focusing gun (5) in the form of a cutting jet, the focusing gun (5) being formed, in full or in part, of tungsten carbide having a cobalt content of between around 0.1 and 10 %, silicon carbide, titanium carbide, boron carbide, cubic boron nitride or diamond.
10. Device according to claim 9, characterised in that the mixing chamber (4) is formed, in full or in part, of hardened steel, tungsten carbide having a cobalt content of between around 0.1 and 10 %, silicon carbide, titanium carbide, boron carbide, cubic boron nitride or diamond.
11. Device according to either claim 9 or claim 10, characterised in that the focusing gun (5) or the mixing chamber (4) is formed, in full or in part, of tungsten carbide comprising a cobalt content of between around 0.1 and 10 %, the tungsten carbide grains having a size of less than 1.5 µm.

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