AU678818B2

AU678818B2 - Manufacturing process for a metal substrate coated with mineral materials, coated substrate obtained and its use

Info

Publication number: AU678818B2
Application number: AU61113/94A
Authority: AU
Inventors: Stephane Ebalard; Pierre Genelot; Didier Perrin; Simone Rey
Original assignee: Pont a Mousson SA
Current assignee: Pont a Mousson SA
Priority date: 1993-02-26
Filing date: 1994-02-23
Publication date: 1997-06-12
Anticipated expiration: 2014-02-23
Also published as: BR9406163A; EG20502A; EP0686212A1; CA2157008A1; TR28278A; NO953355D0; HUT72451A; ES2147572T3; HRP940138A2; FR2701963B1; CZ284752B6; NO953355L; PL310406A1; AU6111394A; SK104295A3; CZ213495A3; DE69424933D1; HU9502510D0; TNSN94019A1; FR2701963A1

Abstract

Method of manufacture of a metal part (1) coated with several layers (4, 5, 6) of mineral materials, said method allowing some oxidation of the metal part's surface. The invention also concerns a hollow revolving part manufactured according to the above-mentioned method. The manufacture of the hollow revolving part comprises the following stages wherein a liquid casting is subjected to: a treatment using magnesium, an inoculation process and a centrifugal operation during which the first layer (4) of the coating (2) is applied to the metal part. The metal part of the invention is for use in the transport of aggressive fluids.

Description

OPI DATE 14/09/94 A0)JP DATE 17/11/94 PTN NUBE 611/F9419 111111 lll111 IU111 jl ii PCTLNUM E ID11/ 94 9 111111!i l ii II 11111 11111 f11111 111,11 1 11 In11!1 AU9461 113 DEMAI.

(PCI)

(51) Classification internationale des brevets 5: (11) Nurn~ro de publication internationale: WO 94/19511 C23D 5/00) Al (43) Date de publication internationale: icr Lieptembre 1994 (01.09.94) (21) Nun~ro de In demande internationale: PCT/FR94/00197 (81) Etats d~sign~s: AU, BG, BR, CA, CZ, HU, NO, PL, RO, Rlu, SI, US, VN, brevet europ~en (AT, BE, CH, DE, ES, (22) Date de depot international: 23 f~vrier 1994 (23.02.94) FR, GB, GR, 1M, IT, LU, MC, Nt, PT, SE).

Donn~es relatives i In priorit6: Publi~.e 93/02419 26 fivrier 1993 (26.02.93) FR Avec rapport de recherche inzernationale, (71) D~posant (pour tous les Etats d&signds sauf US): FONT-A- MOUSSON S.A. [FR/FR]; 91, avenue de la Liberation, F- 54000 Nancy (FR).

(72) Inveateurs; et 67881i8 1nventeursINpoants (US seulement): PERRIN, Didier [FR/FR]; 3, rue Jobb6-Duval, F-75015 Paris (FR).

EBALARD, Stdphane [FR/FR]; 2F, aII~e Rayniond-Cornon, F-35000 Rennes GENELOT, Pierre [FR/FR]; 27, rue G~n~ral-Houdemont, F-54700 Pont-A-Mousson REY, Simone 14, rue Traverse, F-93200 Saint-Denis

(FR).

(74) Mandataires: MUNIER, Laurent etc.; Pont-A-Mousson S.A., Service Proprdi Industrielle, Bolte postale 109, F-54704 Pont-A-Mousson C~lex (FR).

(54) Title: N. (54) Titre: PROCEDE DE FABRICATION D'UNE PIECE METALUIQUE REVEI7UE DE MATERIAUX MINERAUX, PIECE OBTENUE ET' SON UTILISATION (57) Abstract Miethod of manufacture of a m~etal part coated with seversd layers 5, 6) of mineral materials, said method allowing some oxidation of the metal part's surface. The invention also concerns a hollow revolving part manufacturd according to the abovementioned methcod. The mnanufacture of the hollow revolving part comprises the following stages wherein a liquid casting is subjected to: a treatment using magnesium, an inoculation process and a centifugal op-A eration during which the first layer of the coating is applied to the metal part. The I W metal part of the invention is for 'nse in the transport of ag-~ gressive fluids. Aq' A P:\OPER\ADD\61113-94.056 19/3197 -1- IMATNUFACTURING PROCESS FOR A METAL SJUBSTRATE COATED WITH MINERAL MATERIALS, COATED SUBSTRATE OBTAINED AND ITS USE The present invention relates to the manufacture of a metal substrate covered at least in part with mineral materials. In particular, the invention relates to the manufacture of a metal substrate coated with a mineral coating based on silica and sodium oxide.

The manufacture of articles in cast iron coated in glass is known, for example from FR 2 495 190.

Mineral coating constitutes effective protection of a metal substrate and exhibits good chemical inertia with respect to a fluid contacting it.

The present invention advantageously provides a metal substrate having a coating which ensures a protective role adhered to the substrate, and which presents few open pores so as to form a passive barrier between a fluid and the substrate.

o In order to reduce the porosity and improve the adhesion of the mineral coating on the metal substrate and in order to ensure excellent closing of the coating so that it protects the substrate from corrosion, several layers of mineral coating are applied successively to at least a part of a surface of the metal substrate. The elements of the mineral material are present S* in differing proportions according to the layers.

20 According to the present invention, there is provided a process for the manufacture of a metal substrate covered at least in part with silica and sodium oxide based mineral materials, the process comprising successively applying to a surface of the metal substrate: a first layer of coating having a thickness of less than 200 [Im, and consisting of an enamel applied to the surface in the form of a powder, preferably a dry powder, having the following composition by weight: SiO 2 50 to CaO MgO 5 to

B

2 0 3 less than CoO less than 2% Fe 2 0 3 less than

I

P:\OPER\ADD\61 13-94.056- 19/3/97 -2- Al203 less than Na2O K 2 0 15 to

F

2 less than 2% NiO less than 2% wherein, prior to the application of the powder, the metal substrate is preheated to a temperature of more than 700 0 C; and a second layer and a third layer of coating each having a thickness of greater than 1 00pm and consisting of an enamel having the following composition by weight: SiO 2 40 to CaO MgO less than less than TiO 2 5 to NiO less than 2% 15 ZnO less than 2% A1 2 0 3 less than Na2O+ K 2 0 15 to

B

2 0 3 5 to CoO less than 2% 20 Sb 2 0 3 less than 2%; whelein the composition of th second layer is identical to or different from the composition of the third layer.

The invention also provides a coated metal substrate manufactured by a process as described in the immediately preceding paragraph, a tubular part, such as a piping element, comprising such a coated metal substrate and the use of such a tubular part for the transport of aggressive fluids.

The first coating layer advantageously sufficiently covers the substrate to form an antioxidant film. The layer is also preferably thin enough to allow degassing and decantation of the gas bubbles emanating from the reaction between the first layer and the metal.

a P:OMERAD\61 113-94.056 19/3/97 -3- During production of the first layer of coating, the fluidity of the mineral material advantageously ensures fusion of the powder required for blanketing the substrate and adhesion to the substrate, and for linliting the chemical reactions between the substrate and the first coating layer.

A reducing substrate, such as cast iron, and a first oxidising layer of coating present the risk of oxidation-reduction reaction with degassing and the appearance of blistering.

An overly fluid composition may cause the coating to run off, with the associated defects, loss of covering aspect and oxidation of the substrate.

An insufficiently fluid composition may not allow good fusion of the powder and consequently there may be an adhesion fault and poor covering, resulting in the risk of oxidation of the substrate.

Oxidation of the substrate is particularly marked during high-temperature thermal treatment.

The fluidity of the composition depends largely on the silica content and the flux powder a 15 content.

So as to limit the oxidation-reduction reactions between the coating and the substrate, the mineral material is preferably reduced during its application to said surface.

To ensure the powder fuses for good blanketing and good adhesion, the first coating 20 layer is preferably made to a thickness of 100 im.

20 If the second coating layer of mineral material is to be applied to a hot metal substrate, the mineral material of that layer is preferably applied in the form of a powder, preferably a dry powder. If the mineral material is to be applied to the metal substrate at ambient temperature, the mineral material of the second coating layer is preferably in the form of a porcelain slip.

The porcelain slip is preferably a highly fluid mixture of finely comminuted mineral material and water with various additives, such as antioxidants and suspension agents.

The composition of the second coating layer advantageously enables absorption of the first coating layer, dissolution of any iron oxide skin which has formed at the surface of the metallic substrate when it is constituted by a ferrous metal, and a superficial attack on the substrate.

In order to obtain good adhesion of the coating by absorption, dissolution and superficial

-I

P:\OPERADD611 13-94.056- 19/3197 -4attack, the second coating layer is produced at a thickness greater than 100 Jam. Preferably, to ensure the second coating layer is not too porous, it is produced at a thickness of 200 jm.

The application of three layers of mineral material advantageously ensures closing of the coating and uniformity in the thickness of the coating, which restricts the open pores and imparts a smooth surface to the coating. The material forming the third layer may be applied as a powder or porcelain slip. Advantageously, the third layer results in a blanketing of the preceding layers by forming a covering film. To ensure the closing and blanketing functions, the third layer is produced at a thickness greater than 100 jim.

To ensure good fusion with the deposit, the third layer is preferably produced at a thickness of 200 jm.

Manufacture of tubular parts in cast iron coated in glass is already known, for example, from FR 2 297 817 in the name of the present applicant.

:..According to one embodiment, the manufacture of the metal substrate from a liquid cast iron comprises at least the following successive steps: 15 a magnesium treatment; an inoculation; a centrifuging operation of said cast iron, during which operation the first layer of coating is produced.

This process enables the coating to be deposited during manufacture of the metal 20 substrate and for advantage to be taken of the thermal energy of the metal to create fusion of the S.first layer.

Integrating the steps of deposit and coating with the steps of manufacture of the metal substrate or part may enable a reduction of the number of manufacturing operations and thus may render the manufacturing process less expensive.

The metal substrate may include a tubular metal part, such as a piping element, having the coating layers applied to an internal surface thereof. This part may be useful in transporting aggressive fluids without alteration to the characteristics of these fluids and/or without the part being damaged.

An embodiment of the present invention will now be described by way of example only with reference to the accompanying figures, in which: 1 1-9 PM\OPERMADD16L 113-94.056- 19/3197 Figure 1 shows in perspective view a piping element obtained according to the process of the invention; Figure 2 is a micrograph magnified 100 times of the enamel coating with the common zone of the cast iron substrate of the piping element illustrated in Figure 1.

In this manufacturing example of a piping element 1 exhibiting an internal coating 2, the liquid cast iron undergoes magnesium treatment followed by inoculation. The cast iron is inoculated by means of an inoculant such as iron silicide introduced into the liquid cast iron as a powder or wire, in a known manner, as in FR-A- 2 546 783 in the name of the present applicant.

The process comprises a centrifuge operation of the cast iron, during which first layer 4 of coating 2 is produced at a thickness of 100 Im by application of a reduced enamel of the following composition: Si02 balance S* CaO MgO 15 B 2 0 3 CoO 1% Fe 2

O

3 2% A1 2 0 3 Na 2 O K20 22% 20 F 2 1% S. NiO 1% This enamel is applied as a dry powder.

Following the centrifuge operation, piping element 1 is graphitised. Next, second layer 5 of coating 2 is produced at a thickness of 200 Am by application of the following composition by weight: SiO balance CaO MgO 4% TiO,

L

P:\OPER\ADD\61113.94.056- 19/3/97 -6- NiO ZnO A1 2 0 3 6% Na 2 O K 2 0 19%

B

2 0 3 11% CoO SbzO 3 1 Second layer 5 of coating 2 is applied to piping element 1 at a temperature of between 950° and 700°C. Next, ferritising of piping element 1 is carried out in a range of temperatures less than 800°C, ensuring baking of second layer 5 of coating 2. Then third layer 6 of coating 2 is produced at a thickness of 200 Am by application of enamel in the form of a powder having a composition identical to the composition of the enamel of second layer of coating 2 detailed hereinabove. This powder is deposited on piping element 1 at a temperature less than 800 0

C.

After third layer 6 is deposited, it is glazed, that is, it is baked for a period of less than five minutes at a temperature between 7500 and 700 0

C.

In a first variant, the cast iron obtained after centrifuging is a perlitic grey cast iron of spheroidal graphite. The process then differs from that previously described in that piping 20 element 1 is not graphitised.

S. Under these conditions, second layer 5 of coating 2 can be produced either during or after the centrifuging operation by deposit of the enamel as a dry powder.

The piping element subsequently undergoes ferritising treatment in a range of temperatures less than 800°C, and baking of second layer 5 of coating 2 takes place at the same time as ferritisation of piping element 1.

In a second variant, the cast iron obtained after centrifuging is a perlitic grey cast iron of spheroidal graphite. The process then differs from that of the first variant in that piping element 1 is not graphitised and in that second layer 5 of coating 2 is baked at a temperature between 8000 and 700°C of said element 1 after depositing of second layer 5 of coating 2.

In a third variant, the process differs from that described initially in that the enamel P:\OPERAD\6I 113-94,056 1913197 -7is deposited in the form of a porcelain slip to produce second layer 5 of coating 2, following graphitising and while piping element 1 is at ambient temperature.

In a fourth variant, the process differs from the first variant in that the enamel is deposited in the form of a porcelain slip after centrifuging and while piping element 1 is at ambient temperature.

In a fifth variant, the third layer of enamel is depos ;d in the form of a porcelain slip while piping element 1 is at ambient temperature.

A piping element 1 comprises a p,,e of ductile cast iron 3 exhibiting on the internal part of its surface a coating 2 of enamel constituted by three layers 4, 5, 6. This pipe has at one end a flat section 8 and at its other end a flanged recess 7 capable of taking up the flat section of an identical pipe.

Micrography of enamel coating 2 on a common zone of the cast iron substrate (Figure 2) shows the substrate, the interface between substrate 3 and coating 2, second layer 5 of coating 2 and third layer 6 of coating 2. Substrate 3 is a ferritic cast iron of spheroidal cast 15 iron. At the level of the interface between the substrate and the coating, the skin of oxides has been dissolved. First layer 4 of coating 2 has been absorbed by second layer 5 of coating 2. The interface between the coating and cast iron substrate 3 is coherent and presents little porosity. The localised superficial attack on the substrate leads to formation of anchor points for coating 2.

20 Second layer 5 presents limited porosity.

Third layer 6 of coating 2 does not present cohesion with second layer 5 of coating 2. It exhibits very low porosity, forms a smooth surface and produces good closure of the coating.

The process according to the present invention advantageously enables coating of the metal parts even oxidised which present an adhesive oxide skin of a thickness less than ym.

Owing to the integration of the manufacturing of enamel coating 2 with the manufacturing operations of piping 1, the present invention offers a gain in productivity and thermal energy. One or more specific steps in the baking of the enamel can be deleted in the present invention.

-I

PMOPR\ADD\61I 13.94.056- 19/3/97 -8- The variants of the process in which the enamel is applied as a porcelain slip permit considerable production flexibility.

The pipes obtained can be used for manufacture of conduits for the transport of ggressive fluids, such as acid solutions, solutions with a high content of dissolved C0 2 abrasive fluids, industrial waste, waste water or purification muds.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

*4* a o

Claims

1. A process for the manufacture of a metal substrate covered at least in part with silica and sodium oxide based mineral materials, said process comprising successively applying to a surface of said metal substrate: a first layer of coating having a thickness of less than 200 pm, and consisting of an enamel appi-:;. to said surface in the form of a powder, preferably a dry powder, having the following composition by weight: SiO 2 50 to CaO MgO 5 to B 2 0 3 less than CoO less than 2% Fe 2 O 3 less than A1 2 0 3 less than Na20 K 2 0 15 to F 2 less than 2% NiO less than 2% "wherein, prior to the application of the powder, said metal substrate is preheated to a temperature of more than 700°C; and S* a second layer and a third layer of coating each having a thickness of greater than 100pm and consisting of an enamel having the following composition by weight: 0 SiO2 40 to CaO MgO less than LiO2 less than TiO 2 5 to NiO less than 2% ZnO less than 2% A1 2 0 3 less than Na 2 O K 2 0 15 to P:\OPER\ADD\61113-94.056 19/3/97 B 2 0 3 5 to CoO less than 2% Sb 2 03 less than 2%; wherein the composition of said second layer is identical to or different from the composition of said third layer.

2. A process according to claim 1, wherein the enamel which constitutes the first layer of coating is reduced during its application to said surface.

3. A process according to claim 1 or claim 2, wherein the first layer of coating is produced with a thickness of 100pm.

4. A process according to any one of claims 1 to 3, wherein the second layer is applied in the form of a powder, preferably a dry powder.

5. A process according to claim 4, wherein the metal substrate is at a temperature of between 950 C and 700°C when the second layer of coating is applied.

6. A process according to any one of claims 1 to 3, wherein the second layer is applied in the form of a porcelain slip.

S7. A process according to claim 6, wherein the metal substrate is at ambient temperature when the second layer of coating is applied.

8. A process according to any one of the preceding claims, wherein the second layer of coating is produced with a thickness of 200 m.

9. A process according to any one of the preceding claims, wherein the third layer is applied in the form of a powder or a porcelain slip.

I I'\OI'I0 \ADD\6i 1394.056- 191397 -11- A process according to any one of the preceding claims, wherein the third layer of coating is produced with a thickness of 200 um.

11. A process according to any one of the preceding claims, wherein the manufacture of the metal substrate from a liquid cast iron comprises at least the following successive steps: a magnesium treatment, an inoculation, a centrifuging operation of said cast iron, during which operation the first layer of coating is produced.

12. A process according to claim 11, wherein the second layer of coating is applied to the substrate after said centrifuging operation. 9

13. A process according to claim 11 when appended to claim 5, wherein the second layer of coating is produced during the centrifuging operation.

14. A process according to any one of the preceding claims, wherein after production of the second layer of coating, a thermal ferritising treatment of the substrate is carried out within a I range of temperatures of less than 800 0 C, said thermal ferritising treatment being followed by .oo the production of the third layer of coating.

15. A process according to claim 12, wherein after the centrifuging operation of the cast iron and before the application of the second layer of coating, a thermal treatment of graphitization of the cast iron is carried out.

16. A process according to claim 12 or claim 13, wherein after the production of the second layer of coating a baking operation of the substrate is carried out at a temperature of between 00oC and 700 0 C. PMOPR\ADM611 1394.056- 91397 -12-

17. A process according to claim 16, wherein the third layer of coating is applied to said substrate after said baking operation.

18. A process according to claim 14 or claim 17, wherein the third layer of coating is deposited in the form of a porcelain slip, and thereafter a glaze baking of the coating is carried out at a temperature of between 750 C and 700°C.

19. A process for the manufacture of a metal substrate substantially as hereinbefore described with reference to the drawings.

A coated metal substrate manufactured by a process according to any one of claims 1 to 19.

21. A tubular metal part comprising a coated metal substrate according to claim 20, and having said first, second and third layers of coating applied to an internal surface thereof.

22. Use of a tubular metal part according to claim 21 for the transport of aggressive fluids, preferably acid solutions, solutions with a high content of dissolved CO 2 abrasive fluids, industrial discharge, waste water or purification mud. C O DATED this 18th day of March, 1997 Pont-Mousson S.A. by Davies Collison Cave Patent Attorneys for the Applicant(s)