OA17671A - Painted steel plate provided with a zinc coating. - Google Patents
Painted steel plate provided with a zinc coating. Download PDFInfo
- Publication number
- OA17671A OA17671A OA1201600047 OA17671A OA 17671 A OA17671 A OA 17671A OA 1201600047 OA1201600047 OA 1201600047 OA 17671 A OA17671 A OA 17671A
- Authority
- OA
- OAPI
- Prior art keywords
- chamber
- layer
- steel sheet
- déposition
- coated
- Prior art date
Links
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 49
- 239000010959 steel Substances 0.000 title claims abstract description 49
- 239000011701 zinc Substances 0.000 title claims abstract description 22
- 238000000576 coating method Methods 0.000 title claims abstract description 20
- HCHKCACWOHOZIP-UHFFFAOYSA-N zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 title claims abstract description 20
- 229910052725 zinc Inorganic materials 0.000 title claims abstract description 20
- 239000011248 coating agent Substances 0.000 title claims abstract description 19
- 239000003973 paint Substances 0.000 claims abstract description 25
- 238000001962 electrophoresis Methods 0.000 claims abstract description 16
- 238000004519 manufacturing process Methods 0.000 claims abstract description 7
- 238000000034 method Methods 0.000 claims description 4
- 229910000922 High-strength low-alloy steel Inorganic materials 0.000 claims description 2
- 239000012535 impurity Substances 0.000 claims description 2
- 238000001771 vacuum deposition Methods 0.000 abstract 1
- 239000000758 substrate Substances 0.000 description 7
- NBIIXXVUZAFLBC-UHFFFAOYSA-K [O-]P([O-])([O-])=O Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 3
- 229910052804 chromium Inorganic materials 0.000 description 3
- 239000011651 chromium Substances 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 3
- 238000010422 painting Methods 0.000 description 3
- 239000010452 phosphate Substances 0.000 description 3
- 238000005452 bending Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000012467 final product Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000009434 installation Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 238000007493 shaping process Methods 0.000 description 2
- 230000001131 transforming Effects 0.000 description 2
- 210000003800 Pharynx Anatomy 0.000 description 1
- 241000282485 Vulpes vulpes Species 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- REDXJYDRNCIFBQ-UHFFFAOYSA-N aluminium(3+) Chemical class [Al+3] REDXJYDRNCIFBQ-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000005755 formation reaction Methods 0.000 description 1
- 238000005246 galvanizing Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- FAPWRFPIFSIZLT-UHFFFAOYSA-M sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Abstract
The invention relates to a steel plate provided with a coating comprising at least a layer of zinc and an upper layer of paint formed by cataphoresis, the zinc layer being formed by a vacuum deposition method using a sonic steam jet in a deposition chamber maintained at a pressure of between 6.10-2 mbar and 2.10-1 mbar. The invention also relates to the associated production method.
Description
Painted steel sheet provided with a zinc coating
This invention relates to a steel sheet provided with a coating comprising a layer of zinc covered by paint, which is intended in particular for the fabrication of automobile parts, although it is not limited to that application.
Galvanized coatings comprising essentially zinc are conventionally used for the effective protection they provide against corrosion, whether in the automotive sector or in the construction industry, for example.
In the following text, a zinc coating means a coating of pure zinc, potentially including the unavoidable impurities acquired during production and présent in trace quantities.
The sheets coated in this manner can then be eut and shaped, for example by stamping, bending or shaping, to form a part that can then be painted to form a paint film on top of the coating. This paint film is generally applied by cataphoresis.
The methods most frequently used to deposit a zinc coating on the surface of a steel sheet are galvanizing and electrogalvanizing. However, these conventional methods do not make it possible to coat grades of steel that contain high levels of oxidizabie éléments such as Si, Mn, Al, P, Cr or B, which has led to the development of new coating methods, and in particular vacuum déposition technologies such as jet vapor déposition (JVD).
Nevertheless, the surfaces of the sheets coated according to these vacuum déposition methods, following the step of painting by cataphoresis, exhibit surface defects that adversely affect the aesthetic appearance of the shaped parts.
The purpose of this invention is therefore to eliminate the disadvantages of steels coated using methods of the prior art by making available a steel sheet coated with zinc by vacuum déposition and a layer of paint that has a good surface appearance.
For this purpose, a first object of the invention is a steel sheet as recited in Claim 1.
The sheet can also hâve the characteristics of Claims 2 to 5, considered indîvidually or in combination.
An additional object of the invention is a method as recited in Claim 6.
The method can also hâve the characteristics of Claims 7 to 8, considered individually or in combination.
Additional characteristics and advantages of the invention are described in greater detail below.
To illustrate the invention, tests hâve been conducted and will be described by way of non-restricting examples, in particular with reference to the accompanying figures, in which:
- Figure 1 illustrâtes a jet vapor déposition installation that can be used to carry out the method claimed by the invention
- Figure 2 is a photograph at an x4 enlargement of a sheet coated according to the prior art.
- Figure 3 is a photograph at an x4 enlargement of a sheet coated according to the invention.
The sheet coated according to the invention first comprises a steel substrate, preferably hot-rolled then cold-rolled so that it can be used for the fabrication of automobile body parts. The invention is not limited to this field, however, and can be used for any steel part regardless of its intended final use.
The steel substrate can in particular be one of the following grades of a VHS (Very High Strength steel, generally between 450 and 900 MPa) or UHS (Ultra High Strength, generally greater then 900 MPa) steel that contain high levels of oxidizable éléments:
- steels without interstitial éléments (IF, Interstitial Free), which can contain up to 0.1% by weight Ti;
- dual-phase steels such as DP 500 steels, up to DP 1200 steels, which can contain up to 3% by weight Mn in association with up to 1% by weight Si, Cr and/or Al,
- TRIP (TRansformation Induced Plasticity) steels such as TRIP 780 steel, which contains, for example, approximately 1.6% by weight Mn and 1.5% by weight Si;
- TRIP steels or dual phase steels containing phosphorus;
- TWIP (TWinning Induced Plasticity) steels with a high content of Mn (generally 17 25% by weight),
- low-density steels such as Fe-Al steels, which can contain up to 10% by weight Al, for example;
- stainless steels, which hâve a high concentration of chromium (generally 13-35% by weight), in association with other alloy éléments (Si, Mn, Al etc.).
The steel sheet can optionally be coated with one or more additional layers in addition to the zinc iayer in a manner appropriate to the desired properties of the final product. The zinc layer will preferably be the top iayer of the coating.
A method for the fabrication of the steel sheet according to the invention is illustrated more particularly in Figure 1, which shows an installation l that comprises a vacuum déposition chamber 2. This chamber comprises an entry lock and an exit lock (not shown), between which the steel sheet 3 to be coated circulâtes. The sheet 3 can be moved by any appropriate means, for example a rotating support roller on which the strip can be supported.
Situated facing the surface of the strip to be coated is an éjection chamber 7 equipped with a slot 8, the upper part of the slot 8 being situated at a distance d from the surface of the strip to be coated, of for example, between 20 and 60 mm. This chamber 7 is mounted on an évaporation crucible 4 that contains the liquid zinc 9 to be deposited on the surface of the steel strip 3. The évaporation crucible 4 is advantageously equipped with an induction-heating device 5 that makes possible the formation of the vapor. The vapor then escapes from the crucible via conduit 10 that conducts it to the éjection chamber 7 and the slot 8, which is preferably calibrated to form a jet directed toward the surface of the substrate to be coated. The presence of the slot 8 allows for the régulation of the mass flow of vapor, at a constant sonie speed along the slot (sonie throat) that has the advantage of achieving a uniform deposit. Reference to this technology is made below, using the acronym “JVD” (for Jet Vapor Déposition). Additional information on this technology is presented in patent EP07447056.
In another embodiment not illustrated, the crucible and the éjection chamber are one and the same part, comprising a slot directed toward the surface of the substrate to be coated. In this embodiment, the vapor created by heating the zinc rises directly toward the slot and forms a jet directed toward the surface of the substrate to be coated.
The pressure Pchambcr in the déposition chamber 2 is maintained at a pressure between 6· 102 mbar and 2· 10'1 mbar.
The pressure Pchambcr in the déposition chamber 2 and the pressure PCjCC1 in the éjection chamber 7 are optionally maintained so that the ratio Pchambcr to Pejrel is between 2· 103 and 5.5· 10, which allows for the improvement ofthe temporary protection of thesecoatings.
A layer of oil is optionally applied to the surface of the sheet thus coated to provide temporary protection when the sheet is stored in a wet and/or saline environment before delivery or the transformation into the final product.
The sheet 1, which may or may not hâve been subjected to a skin-pass step, can then be eut and shaped, for example by stamping, bending or shaping, to form a part that can then be painted to form a paint film on the coating.
For automotive applications, after a phosphate treatment, each pîece is quenched in a cataphoresis bath and a layer of primer paint, a layer of base paint and optionally a finish vamish coat are applied in succession.
Before applying the cataphoresis layer to the part, the part is first de-greased then phosphatized to ensure the adhérence of the cataphoresis layer.
The cataphoresis layer provides additional protection for the part against corrosion. The layer of primer paint, generally applied with a paint gun, préparés the final appearance of the part and protects it against grit and against UV radiation. The base paint layer gives the part its color and its final appearance. The vamish layer gives the surface of the part good mechanical strength, résistance to aggressive chemical agents and a good surface appearance.
Generally, the weight of the phosphate layer is between 1.5 and 5 g/m2.
The paint films used to protect and guarantee an optimal surface appearance of the parts comprise, for example, a cataphoresis layer with a thickness of 15 to 25 pm, a layer of primer paint with a thickness of 35 to 45 pm and a layer of base paint with thickness of 40 to 50 pm.
In cases where the paint films also comprise a layer of vamish, the thicknesses of the different layers of paint are generally as follows:
- cataphoresis layer: between 15 and 25 pm, preferably less than 20 pm,
- layer of primer paint: less than 45 pm,
- layer of base paint: less than 20 pm, and
- layer of vamish: less than 55 pm.
The paint films can also not comprise a cataphoresis layer and comprise only one layer of primer paint and one layer of base paint, and optionally a layer of vamish.
Preferably, the total thickness of the paint films will be less than 120 pm, or even less than 100 pm.
Sometimes on the surface of the sheet following the application of the cataphoresis layer, crater-type defects are observed which, on steel sheets, are privileged sites for the origin of corrosion and significantly dégradé the appearance of the surface of the sheet. These craters are in the form of truncated conical holes that emerge in the surface of the cataphoresis layer and can possibly extend through the coating to reach the surface of the steel substrate; they generally hâve a diameter between 100 and 500 grn at the base and between 5 and 20 μιη at the summit.
The invention will now be explained below on the basis of tests performed by way of non-restricting examples.
Tests
Acceptance criteria
To evaluate the sensitivity of the product to the risk of the appearance of crater-type defects, there is a criterion relative to the number of defects présent on a coated steel sheet 10 cm x 15 cm, after this sheet has been subjected to polishing.
For the coated steel sheet to be accepted, it must hâve fewer than four defects per 10 x 15 cm2 plate, which is équivalent to less than 2.7 defects per square decimeter.
Tests sériés of cold-rolled IF steel sheets, type DC06, of the type marketed by ArcelorMittal, having a zinc coating 7.5 pm thick were built.
For both specimens, the coating was applied by JVD déposition at a different pressure in the déposition chamber, with a distance d between the upper part of the slot of the extraction [sic; éjection] chamber and the surface of the identical strip to be coated equal to approximately 35 mm.
| Specimen | Type of coating |
| 1 | JVD - pressure <10'2 mbar in the déposition chamber |
| 2* | JVD - pressure 1.1 · 10'1 mbar in the déposition chamber |
* According to the invention
The specimens were then coated with Quaker Ferrocoat oil N 6130 at 1.2 g/m2 ± 0.3 g/m2, and then subjected to the phosphate and then cataphoresis steps. An image capture and processing device such as the commercially available TalySurf CL1 2000 then made it possible to calculate the number of crater-type defects as defîned above présent on the surface of the coated strip. These craters are in the form of truncated conical holes that emerge in the surface of the cataphoresis Iayer and can possibly extend through the coating to reach the surface of the steel substrate.
| Specimen | Number of defects |
| 1 | »> 2.7 dm2 [sic; 2.7/dm2] (up to I600/dm2) |
| 2* | < 2.7/dm2 |
Specimen No. 2 according to the invention therefore satisfies the acceptance criterion, in contrast to specimen No. 1.
Figure 2 is an x4 enlarged photograph of a steel sheet of the prior art to which a coat of paint has been applied using a cataphoresis process. This sheet of cold-rolled IF steel sheet of DC06 was coated with 7.5 pm of Zn using a JVD process in which the pressure in the déposition chamber was maintained at a pressure of less than 10'2 mbar, the distance d being equal to 35 mm. The sheet coated in this manner was coated with a layer of Quaker Ferrocoat oil N 6130 at 1.2 g/m2 ± 0.3g/m2 to provide a temporary protection of the surface, and was then subjected to a cataphoresis-painting step. Crater-type defects 11 as defined above were observed on the surface of this sheet. These defects significantly dégradé the appearance of the surface of the sheet.
Figure 3 is an x4 enlarged photograph of a steel sheet according to the invention. This sheet of cold-rolled IF steel sheet of DC06 was coated with 7.5 pm of Zn, using a JVD process, whereby the pressure in the déposition chamber was maintained at a pressure of 1.1· 101 mbar, the distance d being equal to 35 mm. The sheet coated in this manner was coated with a layer of Quaker Ferrocoat oil N 6130 at 1.2 g/m2 ± 0.3g/m2 to provide a temporary protection of the surface, and was then subjected to a cataphoresis-painting step. The absence of crater-type defects on the surface of this steel sheet is apparent. The shades of gray that appear in the figure are related to the roughness of the surface of the steel sheet and are not related to defects in the sense described above.
The same results can be observed with the use of a Fuchs Anticorite oil RP 4107s at 1.2 g/m2 instead of the Quaker Ferrocoat.The inventors hâve also noted that the change in pressure inside the déposition chamber does not affect the rate of déposition of the coating on the surface of the steel sheet.
Claims (8)
1) Steel sheet provided with a coating comprising at least one layer of pure zinc, potentially including the unavoidable impurities acquired during production and présent in trace quantifies, and a top layer of paint applied by cataphoresis, wherein the zinc layer is the top layer of the coating before the application of the paint layer and the zinc layer being deposited by a sonie jet vapor déposition process in a déposition chamber maintained at a pressure Pchambcr between 6-10'2 mbarand 2· 10-1 mbar.
2) Steel sheet according to Claim 1 obtained by a method wherein the ratio between the pressure insîde the déposition chamber Pchambcr and the pressure insîde the zinc éjection chamber Pcjœt is between 2· 10’3 and 5.5· 10.
3) Steel sheet according to Claim 1 or 2 obtained by a method wherein the distance d between the upper portion of the slot 8 of the éjection chamber 7 and the steel sheet to be coated is between 20 and 60 mm.
4) Steel sheet according to anyone of daims 1 to 3 wherein the surface of this sheet has no more than 2.7 crater-type defects per square decimeter.
5) Steel sheet according to anyone of the above daims wherein the coated steel is a Very High Strength steel.
6) Method for the fabrication of a coated and painted sheet, comprising the coating of said sheet by a sonie vapor jet of zinc insîde a déposition chamber maintained at a pressure Pchambcr between 6· 10'2 mbar and 2· 10’’ mbar.
7) Method according to Claim 6, wherein the ratio between the pressure Pchambcr inside the déposition chamber and the pressure Ρη·«ι inside the éjection chamber is between
2-10'3 and 5.5-10'2.
8) Method according to Claim 6, wherein the distance d between the upper portion of the slot 8 of the éjection chamber 7 and the steel sheet to be coated is between 20 and 60 mm.
Publications (1)
| Publication Number | Publication Date |
|---|---|
| OA17671A true OA17671A (en) | 2017-06-28 |
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