EP0896639B1 - Method and installation for metallizing cast-iron pipes - Google Patents

Abstract

The invention discloses an installation for metallizing a metal pipe obtained by vertical uphill continuous casting with vertical continuous displacement, characterized in that it comprises, along the path of the pipe, a metallizing station consisting of a passage for the pipe, a metallizing chamber (6), spray guns (11) mounted in the said chamber on an oscillating plate (10) encircling the said path, means (12) for supplying metallizing material to each gun and means for oscillating the support plate and for displacing the guns in the said chamber with an oscillating movement, the frequency and the angular amplitude of which ensure a uniformly thick coating.

Description

The present invention relates to a method of metallization of metallic supports and relates more particularly to the hot metallization of pipes in particular cast iron pipes which are obtained by casting continuous vertical.

• la galvanisation à chaud à façon;
• le revêtement de Zn ou de ZnAl en continu de tôles d'acier;
• les méthodes de projection thermique d'alliages de Zn ou de ZnAl;
• le zingage de tuyaux.

Among the known methods of hot metallization of pipes, we know:

• hot-dip galvanizing;
• continuous coating of Zn or ZnAl with steel sheets;
• thermal spraying methods of Zn or ZnAl alloys;
• galvanizing pipes.

Existing galvanizing solutions have the following disadvantages.

Hot dip galvanizing lines the pipe internally and externally and the pipe undergoes temperature rise, so the results other previous operations performed on the pipe to lower temperatures may be compromised.

Hot dip galvanizing by liquid parade poses the currently insoluble problem of waterproofing in the liquid bath between the vertical pipe and the metal liquid, as well as the problem of managing a bath healthy (without mattes) and of stable composition over time.

Cold metallization associated with annealing would ensure good dissemination if we respect draconian conditions of surface preparation of the tip and would likely require treatment thermal under inert atmosphere.

The cost of such a treatment cycle would be important and would therefore be of economic interest limit.

The pipe to be coated from continuous casting is not rough which makes it impossible to hang a cold coating without preparation of area.

To obtain a diffuse coating, a pipe free of oxide skin and working temperature must be high or the holding time of the hose must be long.

The invention aims to produce a coating uniform spread with good impact resistance.

The invention further aims to achieve a very adherent coating on the outside of a pipe whose position and diameter vary, continuously scrolling in vertical direction and cannot be rotated, everything avoiding subjecting the pipe to thermal quenching.

The invention further aims to achieve a coating ensuring self-healing of wounds.

The invention finally aims to achieve a coating which contributes to corrosion resistance in buried situation.

• à refroidir le tuyau dans une atmosphère inerte vis-à-vis de l'oxydation jusqu'à une température de 700 à 900°C; et
• à projeter sur le tuyau préalablement refroidi à la température précitée, un alliage de métallisation à base de zinc à l'aide d'un ensemble de pistolets de projection disposés de manière à entourer le trajet du tuyau à métalliser.

It therefore relates to a process for metallizing a metal pipe obtained by vertical casting and moved vertically continuously in an upward movement, characterized in that it consists:

• cooling the pipe in an inert atmosphere with respect to oxidation to a temperature of 700 to 900 ° C; and
• to spray onto the pipe previously cooled to the aforementioned temperature, a zinc-based metallization alloy using a set of spray guns arranged so as to surround the path of the pipe to be metallized.

According to a particular characteristic of the invention, the spray guns are made to oscillate around the pipe path with a frequency and a angular amplitude adapted to the speed of movement of the pipe in order to obtain a uniform coating in thickness.

The invention also relates to an installation of metallization of a metal pipe obtained by vertical upward and vertically displaced continuous casting continuously, characterized in that it comprises on the path of the pipe, a metallization station comprising a passage for the pipe, a metallization enclosure, projection guns mounted in said enclosure on an oscillating plate surrounding said path, means for supplying each pistol with metallization material and means for oscillating the support plate and to move the guns in said enclosure in an oscillating movement, the frequency and angular amplitude ensure the realization a uniform coating in thickness.

The invention further relates to a pipe metallic obtained by vertical casting, characterized in that it includes a metallization coating obtained by the process defined above.

According to a particular characteristic, the projection pistols are three in number and are arranged on the plate at 120 ° from each other.

According to another particular characteristic, projection guns are flame guns or arc pistols.

According to yet another characteristic of the invention, the metallization material is an alloy wire Zn _x Al _1-x and the means for supplying the metallization material comprise for each gun a reserve of wire and a controlled unwinding device by the oscillation movement of the gun support plate.

• la Fig.1 est une vue schématique en coupe verticale d'une installation de métallisation suivant l'invention;
• la Fig.2 est une vue schématique en coupe suivant la ligne 2-2 de la figure 1;
• la Fig.3 est une vue schématique partielle de côté de l'installation de métallisation de la figure 1;
• la Fig.4 est une vue en coupe partielle d'un pistolet à flamme de l'installation; et
• la Fig.5 est une micrographie d'un revêtement obtenu par le procédé suivant l'invention.

The invention will be better understood on reading the description which follows, given solely by way of example and made with reference to the appended drawings, in which:

• Fig.1 is a schematic view in vertical section of a metallization installation according to the invention;
• Fig.2 is a schematic sectional view along line 2-2 of Figure 1;
• Fig.3 is a partial schematic side view of the metallization installation of Figure 1;
• Fig.4 is a partial sectional view of a flame gun of the installation; and
• Fig.5 is a micrograph of a coating obtained by the process according to the invention.

The metallization installation shown in Figure 1 comprises on the path of a pipe T obtained in an ascending vertical continuous casting installation not shown and above this installation, a chimney 1 for the passage of the pipe T during manufacture, into which is injected through a pipe 2, nitrogen to allow the pipe T to move between the outlet of the casting plant and the metallization plant in a protective atmosphere of the surface of the pipe T against oxidation.

The chimney 1 has a lower part 3 in which the pipe passes progressively during its upward movement from 1100 ° C to 1000 ° C and part upper 4 water-cooled located immediately below of the metallization zone and in which La pipe temperature goes from 1000 ° C to a temperature between 700 and 900 ° C.

A sliding mask 5 made of insulating material is placed in the chimney 1 at the level of the junction of the lower part 3 and the upper part 4 of it and its displacement in the part upper 4 cooled to control cooling of the pipe T by interposition between the pipe and the wall of said cooled part.

Above the chimney 1 is arranged a metallization enclosure 6 comprising an inclined bottom 7 down, from the center to the periphery, and provided with suction lines 8.

In its central part, the bottom 7 is connected to a fall protection cover 9 through which the pipe T coating pass with minimal play to prevent the projected metallization product which does not adhere to the pipe wall does not fall to the bottom of the installation.

The enclosure further comprises an oscillating plate 10 on which spray guns are mounted such as the flame metallization gun 11.

Each gun is supplied with metallization wire 12 in a manner which will be described with reference to Figures 2 to 4.

The pistols 11 are for example the number of three and are arranged on the plate 10 at 120 ° one others.

Each gun 11 projects a jet 13 of material metallization on the pipe T during its movement ascending.

Projection guns can also be bow pistols.

They can also consist of liquid metal spraying devices.

However, flame guns have the advantage of being a hot technology that does not not disturb the cooling kinetics of the product.

They ensure an excellent yield of the projection of the sprayed alloy droplets because the droplets are not expelled from the support as by example in the case of the use of arc pistols.

The flow of flame guns is finer than that of arc pistols.

They require a single wire of material metallization when two wires are needed for the guns arc.

The upper wall 14 of the enclosure 6 comprises also suction pipes 15.

The enclosure 6 is surmounted by a sheath 16 water cooled allowing metallized pipe to exit of the metallization installation at a temperature of 750 ° C and forming a heat shield which avoids heating excessively installation.

The installation shown in section in figure 2 comprises a platform (not shown) crossed by the pipe in formation, on which the enclosure is mounted metallization provided with the annular plate 10.

The plate 10 is rotated according to a oscillating movement by a suitable mechanism not shown.

As noted above, in this example, she carries three flame metallization guns 11.

This number of three ensures the best compromise between the cost of installation and the regularity of the thickness of the coating. However, the number of pistols may be different from three.

The amplitude of angular displacement of the plate 10 and its frequency are a function of the angle of dispersion of the jets 13 of molten metal which are projected the pistols 11 as well as the speed of movement of the pipe T in order to allow the application of a layer of uniform thickness metallization.

To each metallization gun 11 which includes means for supplying oxygen and gas, by means of suitable hoses (not shown), is associated with a product supply device metallization in the form of wire 12.

Each device includes a reserve of wire 20 and a reel designated by the general reference 21, intended to bring the metallization wire 12 from the reserve of wire 20 to the associated gun 11 taking account of the movements oscillating to which the pistol 11 carried is subjected by the oscillating plate 10.

The wire 12 advantageously consists of a alloy containing 5 to 15% Al.

It is also possible to use a cored wire formed from a core of Zn surrounded by an Al sheath, in which case a Zn ₄₅ Al ₅₅ alloy can be obtained after melting. The cored wire can also be formed from an aluminum core and a Zn sheath.

We choose the best cored wire or the best alloy to achieve a metallization composition of Zn _x Al _{1-x type} desired.

In Figure 3, one of the projection guns 11 carried by the oscillating stage 10 of the installation as well as the wire reserve 20 and the unwinding device or reel 21 associated.

The metallization wire 12 is placed in the form coil in a drum 22, for example a drum of the type standard for petroleum products with a core central 23 on which the wire spool (not shown) is threaded inside the barrel.

Next to the barrel is arranged a frame 25 comprising a bracket 26 which supports a rectifier device of wire 27 with four rollers to which is associated a cone input 28 for wire 12 facing barrel 22.

At the outlet of the wire straightener 27, is disposed a set of wheels of which a first wheel 30 is carried by an oblique support 31 fixed at a point 32 of the upright vertical of the stem 26. A second wheel 34 is mounted oscillating around a point close to the fixing point 32 for fixing the first wheel 30 via a bracket or mobile support 35 to which is suspended a weight 36.

The weight 36 is fixed to a rod 37 articulated on the gallows 35.

A third wheel 38 for returning the wire to the plate, arranged above the oscillating plate 10 is fixed to the structure of the installation, not shown.

At the exit of the third wheel 38 is provided a second four-roller wire straightener 40.

The pistol 11 carries at its rear end opposite its projection nozzle 42, a fourth wheel 44 or wire inlet wheel into the gun, mounted on a swivel support for changing the tilt metallization wire 12 as a function of the oscillations of plate 10.

The metallization wire 12 is dislodged from the reserve coil contained in drum 22, goes through the entry collar 28, is straightened for the first time in the rectifier 27, passes on the first wheel 30, then under the second wheel 34, then again on the third wheel 38. It is kept in tension by the weight 36 acting on the oscillating bracket 35 for supporting the second wheel 34.

It is again rectified by the second rectifier of wire to four rolls 40 and it enters the flame gun 11 after passing on the fourth wheel 44.

The gun 11 includes a drive device wire in order to bring it into the melting zone.

This device known per se and not shown includes a servo motor with tachometer generator incorporated, a transmission assembly with reducers and wire drive wheels and a clamping device pneumatic wheels which, via a piston ensure the tightening of the wire between them.

As can be seen more clearly at the Figure 4, the flame gun 11 having a base 46 fixed to the plate 10, is provided at its opposite end to the metallization nozzle 42, a cradle 48 comprising bearings 49.50 on which is oscillatingly mounted a fork 51 for supporting the fourth intake wheel 44.

Bearings 49 and 50 are oriented radially relative to the oscillating stage 10.

A guide 52 of the metallization wire 12 at the entry of the wheel 44 is further carried by the fork 51.

The bearing 50 of the cradle 48 which is the most close to the melting zone of the gun 42 has a axial passage 56 crossed by the wire 12.

The pistol also has 58.60 tips intended to receive unrepresented supply hoses of the gas and oxygen gun.

The gas used can advantageously be propane, acetylene or natural gas.

The ZnAl alloy of the wire is therefore routed to the projection gun 11 fusion zone to be there melted into fine droplets and sprayed.

The pipe T to be metallized is at the right temperature working, about 800 ° C and free of oxides due to the nitrogen atmosphere surrounding it in the metallization zone, it receives jets 13 emitted by the pistols 11, a mist of droplets of ZnAl who come to stick there.

The translational movement of the hose combined with an alternative movement of rotation of the pistols 11 ensures good regularity of thickness of the coating 62 obtained.

The alloy remains liquid on the pipe but does not not flow by capillary action and also due very fast surface oxidation and solidification surface coating as well got.

During the entire cooling phase which follows the metallization phase and which lasts approximately 15 mm, the alloy reacts with the melting of the material which constitutes the pipe, to form intermetallics of the Fe _x , Al ( _1-x ) type charged with small proportion of interstitial Zn.

The result is a pipe coated with a exterior coating carried out continuously and perfectly adherent.

The suction system associated with the enclosure and connected in particular to the suction ducts 8 provided in the bottom 7 and 15 provided in the upper wall 14 thereof allows the recovery of alloy droplets which have not reached the pipe.

An example is given below. number of numerical indications relating to the parameters of operation and nature of the metallization alloy used.

The feed speed of the wire 12 is 3 m / min, its diameter is 4 mm, and its linear mass is 70 g / m.

The production yield is around 50%.

As indicated above, the wire is produced either from a Zn ₈₅ Al ₁₅ alloy or in the form of a cored wire with a Zn core allowing a Zn ₄₅ Al ₅₅ alloy to be obtained.

The angle of rotation of the spray guns 11 is 95 °.

The projection cycle step is 70 mm.

The tests carried out made it possible to obtain a coating of 100 g / m ² to 500 g / m ² with an alloy of Zn ₈₅ Al ₁₅ .

As shown in Figure 5, the micrograph of a cut of the coating obtained shows clearly the obtaining a broadcast interface.

We can see in this figure that between the cast iron wall 65 and the coating layer of ZnAl 66, a diffused intermetallic interface has formed 67.

The impact tests carried out on the coated pipe allowed to go up to 150 J, that is to say up to the deformation of the pipe without damaging the coating.

Corrosion characteristics of the coating obtained are of the same level as those that we could obtain by hot dip galvanizing on the same support and with the same alloy.

During its coating, the pipe does not undergo no quenching effect.

The metallization process according to the invention has the advantages over the state of the art following.

It allows control of the thickness of the coating metallization by adjusting the advance speed metallization alloy wires.

It allows to obtain a coating online in continued.

It provides a diffuse coating and anti corrosion.

It allows an easy installation of a sealer in due to the roughness imparted to the initially smooth pipe by the metallization coating.

Finally, it allows the use of cored wire as well than other alloys.

Claims (21)

1. A process for metallizing a metal pipe obtained by vertical casting and continuously moved vertically with an ascending movement, characterised in that it consists in:

   cooling the pipe down to a temperature of 700 to 900°C in an atmosphere inert with regard to oxidisation; and

   discharging a zinc-based metallizing alloy onto the pipe which has already been cooled down to the above-mentioned temperature, with the aid of a set of discharge guns arranged in a manner as to surround the path of the pipe to be metallized.
2. A process according to Claim 1, characterised in that the zinc-based alloy is Zn_xAl_1-x.
3. A process according to one of Claims 1 and 2, characterised in that the metallizing alloy is in the form of a wire.
4. A process according to one of Claims 2 and 3, characterised in that the said wire is a wire of an alloy containing between 5 and 15% of Al.
5. A process according to one of Claims 2 and 3, characterised in that the said wire is a wire of Zn₈₅Al₁₅.
6. A process according to one of Claims 2 and 3. characterised in that the said wire is a core wire made up of a core of Zn surrounded by a sheath of Al, enabling an alloy Zn₄₅Al₅₅ to be obtained after fusion.
7. A process according to one of Claims 2 and 3, characterised in that the said wire is a core wire made up of a core of Al surrounded by a sheath of Zn.
8. An installation for metallizing a metal pipe obtained by uphill vertical continuous casting and continuously moved vertically, characterised in that along the path of the pipe it has a metallizing station comprising a passage for the pipe, a metallizing chamber (6), discharge guns (11) mounted in the said chamber on an oscillating plate (10) surrounding the said path, means (20, 21) for supplying each gun with metallizing material (12) and means to cause the supporting plate to oscillate and to move the guns in the said chamber with an oscillating movement whose frequency and angular amplitude guarantee that a coating of uniform thickness is produced.
9. An installation according to Claim 8, characterised in that the passage for the pipe (T) to be coated has a lower part (3), a water-cooled upper part (4), a sliding screen (5) to control cooling of the pipe (T) being arranged where the lower (3) and upper (4) parts meet, the metallizing chamber (6) being arranged above the said upper part (4) and being surmounted by a water-cooled sleeve (16).
10. An installation according to one of Claims 8 and 9, characterised in that the discharge guns (11) are three in number and arc arranged on the plate at 120° relative to one another.
11. An installation according to one of Claims 8 to 10, characterised in that the discharge guns (11) are flame guns or arc guns.
12. An installation according to one of Claims 8 to 11, characterised in that the metallizing material (12) is a wire of alloy ZnAl and the means for supplying metallizing material comprise, for each gun. a reserve of wire (20) and an unwinder (21) which is controlled by the oscillation of the plate (10) for supporting the guns provided with means for feeding the wire.
13. An installation according to one of Claims 8 to 12, characterised in that the metallizing chamber (6) has a bottom (7) which is inclined downwards, from the centre towards the periphery, and which is provided with suction conduits (8), the said bottom (7) being joined in its centre to a remainders-proof hood (9) through which the pipe (T) to be coated passes with minimum clearance in order to prevent the discharged metallizing product which has not adhered to the wall of the pipe from falling towards the bottom of the installation.
14. An installation according to one of Claims 8 to 13, characterised in that the means for supplying each gun (11) with metallizing product (12) comprise a wire reserve (20) and a device for unwinding the said wire from the reserve and conveying it towards the corresponding gun (11).
15. An installation according to Claim 14, characterised in that the wire reserve associated with each gun (11) comprises a drum (22) which is for receiving a coil of metallizing wire and which is provided with a core (23) on which the coil of wire is placed.
16. An installation according to one of Claims 14 and 15, characterised in that the device for unwinding the metallizing wire comprises a set of wheels (30, 34, 38) for conveying the wire (12) from the reserve (20) to above the oscillating plate (10), and a wheel (44) for intake of the wire - coming from the set of wheels (30, 34, 38) - into the corresponding gun (11), the said intake wheel being mounted so as to oscillate on the gun in a radial direction of the said plate (10), its position following the oscillations of the said plate (10).
17. An installation according to Claim 16, characterised in that the set of wheels (30. 34, 38) comprises a first wheel (30) which supports the wire (12) and which is borne by a fixed support (31), a second wheel (34) which proceeds on the wire (12) and which is borne by an oscillating support (35) with which tension means (36, 37) for the wire (12) arc associated, and a third wheel (38) for returning the wire (12) towards the wheel (44) for intake of the wire (12) into the gun (11).
18. An installation according to Claim 17, characterised in that furthermore the unwinding device has an entry cone (28) for the wire (12) and a first wire-straightening device (27) which are located between the drum (22) and the first wheel (30), and has a second wire-straightening device (40) located upon leaving the third wheel (38).
19. An installation according to one of Claims 17 and 18, characterised in that the tension means for the wire (12) comprise a weight (37) suspended from the oscillating support (35) of the second wheel (34).
20. An installation according to one of Claims 16 to 19, characterised in that the wheel (44) for intake of the wire (12) into the gun (11) is mounted so as to oscillate in a cradle (48) of the latter by means of a fork (51) and bearings (49, 50) arranged radially with respect to the oscillating plate (10). the bearing (50) located closest to the fusion zone of the gun (11) having a passage (56) through which the wire (12) passes.
21. A metal pipe obtained by uphill vertical continuous casting, characterised in that it has a metal coating which has been obtained by the process according to any one of Claims 1 to 7.

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