SK104295A3 - Method and manufacture of a metal part coated with mineral materials, part obtained and use thereof - Google Patents

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

Technical field

The invention relates to the production of a metal component covered with mineral substances. Specifically, it is the production of a metal component covered with a mineral coating based on silica and sodium oxide.

BACKGROUND OF THE INVENTION

The production of glass-cast iron objects is already known (see, for example, FR-2 495 190).

The mineral coating provides effective protection for the metal component and, in direct contact with the liquid, provides good chemical inertness.

SUMMARY OF THE INVENTION

The object is to obtain a metal component whose coating, providing protection and chemical inertness, is adherent to the substrate and has low porosity due to porosity, thus forming a passive barrier between the fluid and the substrate.

In order to reduce the porosity and improve the adhesion of the mineral coating to the metal substrate and to ensure a very good impermeability of the coating to protect the surface against corrosion, several layers of said mineral coating are successfully applied, in particular to one part of the surface of the metal component. Depending on the individual layers, the minerals are present in different proportions.

The first coating layer must be sufficiently opaque to form an antioxidant film, and this layer must also be thin enough to allow degassing and settling of gas bubbles formed in the reaction between the first layer and the metal.

In addition, the first layer must consist of a substance having the desired fluidity. Thus, the mineral substance applied to form the first coating layer is enamel with the following:

CIM weight composition: sieve ₂ 50 up to 70% CaO + MgO 5 up to 20% ^B 3 ° 3 < 10% CoO < 2% ^Fe 2 ° 3 < 5% ^a1 2 ° 3 < 10% Na ₂ 0 + K ₂ 0 15 up to 25% ^F 2 < 2% NiO < 2% First layer The coating is applied Of a thickness of less than 200 pm. To form a coating at least partly at the time he has metal temperature higher than 700 ° C, the first layer is applied

acts by using a mineral substance in the form of a powder, in particular a dry powder.

During the formation of the first coating layer, the fluidity of the mineral must be adjusted to ensure the melting of the powder which is necessary to coat and adhere to the substrate and to limit chemical reactions between the substrate and the first mineral coating layer.

A reducing substrate, as with cast iron and the first oxidation coating layer, presents a risk of oxidative reduction reactions with gas evolution and the occurrence of unevenness.

Too fluid a composition may cause the coating to drain, with the following failures such as loss of covering effect and oxidation of the substrate.

Insufficiently fluid compositions do not allow good powder melting and result in adhesion failure and poor coverage and thus the risk of substrate oxidation.

The oxidation of the substrate is particularly pronounced during high temperature heat treatments.

The flowability of the composition depends on the silica content and the flux content.

To reduce the oxidation reduction reactions between the coating and the substrate, the mineral is reduced during its ϊ

S κ

β ι

processing.

To allow powder melting, good coating and good adhesion, the first coating layer is applied at a thickness of 100 µm.

To deposit the mineral on a warm object, the second layer of coating is carried out by applying the mineral in the form of a dry powder.

In order to deposit the mineral substance on the object at ambient temperature, the second layer of coating is carried out by applying a slurry of mineral substance.

The slurry is a very thin mixture of finely divided mineral and water with additives such as antioxidants and suspending agents.

In order to adsorb the first layer of coating, to dissolve the iron oxide crust formed on the surface of the metal substrate, since it is formed by iron, and to induce surface decomposition of the substrate, the second layer of mineral substance coating is formed by applying the mineral enamel weight composition:

sieve ₂ 40 to 60% CaO + MgO <5% ₂ ° <5% tío ₂ 5 to 15% NiO <2% ZnO <2% ^A1 ° 2 <10% Na 2 O 4 * K 2 O 15 to 20% ^B 3 ° 3 5 to 15% CoO <2% <2% To get good at:

For example, the absorbent, dissolution and surface decomposition as defined above, the second coating layer is applied at a thickness greater than 100 µm.

To prevent the second layer from becoming too porous, it is applied at a thickness of 200 µm.

In order to ensure a good seal of the coating and to obtain a regular thickness of the coating which limits porosity due to porosity and imparts a smooth surface to the coating, the rotating component is coated by applying three layers of mineral material, the third layer being applied in powder or slurry.

The third layer is formed by applying enamel with the following composition by weight:

SiO ₂ 40 up to 60% CaO + MgO < 5% Li ₂ 0 < 5% tío ₂ 5 up to 15% NiO < 2% ZnO < 2% ^A1 ° 2 < 10% Na ₂ 0 + K ₂ 0 15 up to 20% ^B 3 ° 3 5 up to 15% CoO < 2% Sb ₂ O ₃ < 2%

This composition, which may be the same as or different from the second layer, makes it possible to cover the previous layers by forming a covering film.

In order to ensure the impermeability and overlap functions, the third layer is applied at a thickness of more than 100 μπι.

In order to achieve good melting due to deposition, the third layer is applied at a thickness of 200 µm.

The manufacture of tubular cast iron parts covered with glass is known (see, for example, FR-2 297 817, Demanderesse).

According to the invention, the production of the metal rotating component is carried out by a process comprising at least the following steps:

- treatment with magnesium

- vaccination

- a process for centrifuging said cast iron, during which a first coating layer as defined above is applied.

This process allows the coating to be deposited during the manufacture of the metal rotating member and the use of the thermal energy of the metal to melt the first layer.

The inclusion of the coating steps in the production of the rotary metal component makes it possible to reduce the number of manufacturing operations and thus make the manufacturing process less expensive.

The invention also relates to a hollow metal rotating component coated on the inner surface with mineral substances and which is produced by the method according to the invention described above.

This component allows the transport of aggressive fluids without altering their properties or damaging the hollow rotating component.

The invention also relates to the use of a component obtained by the described process for the transport of aggressive liquids.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is represented by one embodiment of a water pipe element or by the recovery of malleable cast iron as illustrated in the accompanying drawings.

Fig. 1 is a perspective view of a pipe element obtained by the method according to the invention, characterized by: pipe element (1), mineral coating (2), cast iron substrate (3), individual layers of coating (4, 5, 6), neck connection (7); Smooth tip (8).

Fig. 2 is a photomicrograph with a 100-fold increase in the enamel coating of the central zone of the cast iron substrate of the pipe element shown in FIG. First

DETAILED DESCRIPTION OF THE INVENTION

In this example of manufacturing the pipe element 1, with the inner coating 2, the liquid cast iron was treated with magnesium and then seeded. The casting of the cast iron is carried out by means of an inoculant by introducing ferrosilicon into the liquid melt in the form of powder or wire, in a manner known, for example, from FR-A-2 546 783 (Demanderesse).

The method comprises centrifuging the cast iron. During this centrifugation, a first layer 4 of coating 2 is applied at a thickness of 100 μπι, by applying a reduced enamel having the following composition:

Si0 ₂ to 100% CaO + MgO 10 % ^B 3 ° 3 5 % CoO 1 % ^Fe 2 ° 3 2 % ^A1 ° 2 5 % Na ₂ 0 + K ₂ O 22 % ^F 2 1 % NiO 1 % This enamel sa; used in the form of dry powder

After centrifugation, the pipe element 1 is graphitized. A second layer 5 of the coating 2 with a thickness of 200 gm is then formed, using powdered enamel having the following composition by weight:

Si0 ₂ up to 100% CaO + MgO 0.5 % Li ₂ 0 4% Ti0 ₂ 6.5 % NiO 0.5 % ZnO 0.5 % ^A1 ° 2 6% Na ₂ 0 + K ₂ 0 19% B ₃ ° 3 11% CoO 1.5 % Sb ₂ O ₃ 1% Second layer 5 of the coating

even at a temperature between 800 ° C and 700 ° C. Fermentation of the pipe element is then carried out at temperatures of up to 800 ° C, ensuring the second layer 5 of coating 2 is fired. Then, a third layer 6 of coating 2 is applied with a thickness of 200 gm using enamel in powder form with the same composition as above. This powder is applied to the pipe element even at a temperature of up to 800 ° C.

After application of the third layer 6, glazing is carried out

Ί f;

This third layer, i. firing for a maximum of 5 minutes at a temperature between 750 ° C and 700 ° C.

In a first variant, the cast iron obtained after centrifugation is a gray pearlitic spheroidal graphite cast iron. Thus, the process differs from the previously described process in that the graphite element is not graphitized. Under these conditions it is possible to apply a second layer 5 of the coating 2 during or after centrifugation, by applying enamel in the form of a dry powder.

The pipe element is further subjected to ferritization at temperatures up to 800 ° C and the firing of the second layer 5 of the coating 2 is carried out simultaneously with the ferritization of the pipe element 1.

In a second variant, the cast iron obtained after centrifugation is a gray pearlitic spheroidal graphite cast iron. The process differs from that of the first variant in that the graphite element of the pipe 1 is not graphitized and that the second layer 5 of the coating 2 of said element 1 is fired at a temperature between 800 ° C and 700 ° C after the second layer 5 of the coating 2.

In a third variant, the process differs from the previously described process in that the enamel is applied in the form of a slurry after the graphitization to form the second layer 5 of the coating 2 and in that the pipe element X has an ambient temperature.

In a fourth variant, the process differs from the first variant in that the enamel is applied in the form of a slurry after centrifugation and in that the pipe element has an ambient temperature.

In a fifth variant, the third enamel layer is applied in the form of a slurry, while the pipe element X has an ambient temperature.

The pipe element X obtainable by the method according to the invention, comprising the five variants described above, is a ductile cast iron tube 3 provided on the inner surface with an enamel coating 2 consisting of three layers 4, 5, 6. This tube has a smooth end at one end 8 and at the other end a throat connection 7 allowing the connection of the smooth end of another identical tube.

A micrograph of the enamel coating 2 of the central zone of a cast iron substrate (FIG. 2) represents the substrate, the phase interface between substrate X and coating 2, the second layer 5 of coating 2 and the third layer 6 of coating 2. The substrate 3 is ferritic spheroidal cast iron. Regarding the phase interface between the substrate and the coating, the oxide crust was dissolved. The first layer 4 of the coating 2 has been absorbed by the second layer 5 of the coating 2. The phase interface between the coating and the cast iron substrate is continuous (coherent) and has low porosity. Local surface decomposition of the substrate leads to the creation of anchoring points for coating 2.

The second layer 5 has limited porosity.

The third layer 6 of the coating 2 does not have a reduced cohesion (cohesion) with the second layer 5 of the coating 2. It is weakly porous, creating a smooth surface and very good sealing of the coating.

The method according to the invention also allows the coating of oxidized metal parts having an adherent oxide bark in a thickness of up to 20 µm.

By combining the steps of manufacturing the enamel coating 2 with the steps of manufacturing the tube 1, the invention enables the gain of productivity and thermal energy. The invention allows one or more specific enamel firing steps to be omitted.

The process variants according to which the enamel is applied in the form of a slurry allow to obtain great flexibility of production.

The tubes thus produced allow the formation of a sewer for the transport of aggressive liquids such as acidic solutions, solutions with a high dissolved CO2 content, abrasive liquids, industrial waste, waste water or sewage sludge.

PnO <r2fíf

Claims (21)

PATENT CLAIMS Method for producing a metal component coated with a silica-based and sodium oxide-based mineral composition, characterized in that a plurality of layers (4, 5, 6) of the mineral coating (5) are successively applied. 2) on at least one part of the surface of said component and the minerals are present in different proportions depending on the individual layers, the first layer (4) of the coating (2) being formed by with enamel having the following composition by weight: sieve ₂ CaO + MgO ^Β 2θ3 CoO Fe ₂ ° 3 ^A1 2 ° 3 Na ₂ 0 + K ₂ 0 ^F 2 NiO and is applied in 50 to 70% 5 to 20% <10% <2% <5% <10% 15 to 25% <2% <2% a thickness of not more than 200 is applied at a greater thickness pm and second than 100 pm. layer (5) coating (2) 2. Method production of metal part by Claim 1 v y z n a č u j by learning that creating first The layer (4) of the coating (2) is carried out by applying a mineral substance in the form of a powder, especially a dry powder. Method for producing a metal component according to claim 1 or 2, characterized in that the enamel is reduced during its processing. Method for producing a metal part according to claim 3, characterized in that the first layer (4) of the coating (2) is formed in a thickness of 100 µπι. Method for producing a metal part according to one of Claims 1 to 4, characterized in that the embodiment The second layer (5) of the coating (2) is carried out by applying a mineral substance in the form of a powder, in particular a dry powder. Method for producing a metal component according to one of Claims 1 to 4, characterized in that the second layer (5) of the coating (2) is produced by depositing a mineral. in the form of slurry. Method for producing a metal component according to one of claims 1 to 6, characterized in that the mineral substance applied to form the second layer (5) of the coating (2) is an enamel having the following composition by weight: SiO ₂ 40 to 60% CaO + MgO <5% Li ₂ 0 <5% tío ₂ 5 to 15% NiO <2% ZnO <2% ^A1 ° 2 <10% 15 to 20% ^b 2 ° 3 5 to 15% CoO <2% ^Θ 2θ3 <2% Method for producing a metal part according to one of the preceding claims, characterized in that the second layer (5) of the coating (2) is applied at a thickness of 200 µm. Method for producing a metal part according to one of the preceding claims, characterized in that a coating (2) is formed on the surface of the part by applying three layers (4, 5, 6) of mineral substances, the substance forming the third layer being applied in powder form. or slums Method for manufacturing a metal part according to claim 9, characterized in that the third layer (6) of the coating (2) is formed by applying enamel with the following weight: composition: sieve ₂ 40 to 60% CaO + MgO <5% Li ₂ 0 <5% tío ₂ 5 to 15% NiO <2% ZnO <2% ^a1 2 ° 3 <10% Νθ-2θ + 15 to 20% ^B 3 ° 3 5 to 15% CoO <2% Sb2O ^ <2% 11. Method production of metal part according to one of the metal 9 or 10, mark your accounts and with the third the coating (6) of the coating (2) is applied in Thickness greater than 100 gm. 12. Method production of metal part by previous- claim yznačuj úci with and by the third the layer (6) of the coating (2) is formed in thickness 200 μπι. 13. Method production of metal part according to claim 1, značuj úc i do that production of metal parts, starting with liquid cast iron, it comprises at least the following steps: - treatment with magnesium - vaccination - a process for centrifuging said cast iron, during which a first layer (4) of the coating (2) is applied by a process corresponding to one of claims 1 to 5. Method for producing a metal part according to claim 13, characterized in that the cast iron has a temperature between 950 ° C at the time when the second layer (5) of the coating (2) is applied by a process corresponding to one of claims 5, 7, 8 or 9. and 700 C. Method for producing a metal part according to claim 13, characterized in that the cast iron has an ambient temperature at the time when the second layer (5) of the coating (2) is applied by the process corresponding to claim 6. Method for producing a metal component according to one of claims 14 or 15, characterized in that after the first layer (4) of the coating (2) has been formed, a second layer (5) of the coating (2) is applied after centrifuging. Method for producing a metal component according to claim 14, characterized in that after the first layer (4) of the coating (2) has been formed, the second layer (5) of the coating (2) is applied during centrifugation. Method for producing a metal component according to one of claims 14 to 17, characterized in that after the second layer (5) of the coating (2) is formed, the heat treatment is carried out by ferritizing the component at temperatures not exceeding 800 ° C. a third layer (6) of the coating (2) by a process corresponding to one of claims 9 to 11. Method for producing a metal component according to one of Claims 14 to 16, characterized in that after the cast iron has been centrifuged and before the second layer (5) of the coating (2) has been formed, a heat treatment of the cast iron is carried out. Method for producing a metal part according to one of claims 14 to 17, characterized in that after the second layer (5) of the coating (2) has been formed, the part is fired at a temperature between 800 ° C and 700 ° C. Method for producing a metal component according to the preceding claim, characterized in that after firing. the third layer (6) of the coating (2) being applied by a process corresponding to one of claims 9 to 12. í .¾ Method for producing a metal component 21, characterized in that the layers (6) of the coating (2) in the form of a slurry and not a coating at a temperature of between 750 ° C and according to claim 18 or A hollow metal rotary member (1), coated on the inner surface with at least one mineral, characterized in that it is produced by a method corresponding to any one of claims 1 to 22. Use of a hollow metal rotating component (1) according to claim 23 for the transport of aggressive liquids, in particular acidic solutions, high dissolved CO _{2 solutions} , abrasive liquids, industrial wastes, waste water and sewage sludge.