JP2007504364A - Stainless steel strip coated with aluminum - Google Patents

Abstract

  The present invention provides a coated stainless steel strip product (1) having a dense and uniformly distributed aluminum layer (2) on one or both sides of the steel strip. This layer consists essentially of pure aluminum, the thickness of this layer is a maximum of 15 μm, the tolerance of this layer is a maximum plus or minus 30% of the thickness of this layer, the Cr content of the base material of this steel strip Good that the coated stainless steel strip can be bent 180 degrees over a radius equal to the thickness (3) of this strip without any tendency to delamination etc. Adhesiveness. This Al coated strip product is suitable for applications in high humidity environments or in humid conditions, such as outdoor life applications, sports and marine life applications, family applications, and personal care applications.

Description

  The present invention relates to a method for producing stainless steel coated with aluminum in a continuous rolling-rolling process in which a thinly covered aluminum layer provides excellent adhesion. Specifically, the present invention relates to an aluminum coated stainless steel in which a thin layer of aluminum on the steel surface exhibits excellent adhesion and is suitable for cost-effective and productive manufacture of components for corrosion resistance applications. Related to steel.

  It is known that aluminum coatings can be used in corrosion resistant applications. However, it is difficult to find a method that can meet the requirements of quality and productivity in order to produce small sized components in a cost effective and productive manner. For productivity reasons, a continuous rolling-rolling coating process is essential, and for quality reasons, a thin layer with excellent adhesion is required.

  Good adhesion is required for the functional quality of the final product, but it is also required to enable cost-effective and productive manufacture of the components. That is, a coated strip material with poor adhesion results in, for example, a peeling problem, which results in low yielding and is a failure caused by its own peeling during the manufacturing process, especially if the manufacturing process is a continuous line Is brought about. Furthermore, frequent stoppages are required for quality inspection and cleaning of the production line by peeling. Overall, the poor adhesion of the coating results in unacceptably high manufacturing costs and low quality.

A known method for producing steel coated with aluminum in the rolling-rolling process is as follows.
-Coating the base steel material with aluminum foil (cladding)
This cladding process is the continuous production of strips by joining the metals "metallurgically" together. This is a relatively simple and easy technique that yields high yields at a low cost. However, this method has some major drawbacks. First, there is a problem that adhesion is inferior. Furthermore, with this cladding technique, it is technically difficult to achieve a uniform, thin and excellent coating.
The dipping method can be used to apply a low melting point metal to the substrate material by immersing it in a molten bath. One obvious disadvantage of this method is that aluminum has a relatively high melting point (658 ° C.). This is very complicated to control the process factors, and it is difficult to achieve a uniformly distributed and thinly coated coating layer with good adhesion.

  There are several deposition methods that can be used to deposit aluminum. The most common methods are processes such as batch processing, but there are also several continuous processes.

  An example rolling-to-rolling method using electron beam evaporation is described in International Patent WO 98/08986, which achieves an aluminum coating of the substrate material in the rolling-to-rolling process, thereby producing a ferritic stainless steel FeCrAl— A method of manufacturing a steel strip is disclosed. However, the method described in this patent specification is optimized for a product suitable for use in a high temperature corrosive environment, i.e. requires good high temperature strength and also good high temperature corrosion resistance, for example acid resistant It is a change. Within this specification, aluminum also serves as an oxide-forming element, which is beneficial for high temperature corrosion resistance. This improves that the substrate material is alloyed with the rare earth metal and that an aluminum coating is created on both sides of the strip. In addition, this patent specification proposes to homogenize the coating at a temperature between 950 and 1150 ° C. in order to have a uniformly distributed aluminum in the ferrite. Therefore, if anything, this is a FeCrAl-steel composition with alloying elements distributed uniformly including aluminum. Furthermore, this means that there is no requirement for an oxide-free interface and good adhesion of this layer. For example, there is no separate cleaning step prior to the PVD coating step, rather than the usual wet cleaning step with deionized water. Since the role of aluminum is to diffuse into the ferrite, there is no special uniformity requirement for this layer. This method cannot be used in the present invention as described in international patent WO 98/08986.

  Another example of an apparatus used in a continuous deposition process is described in US Pat. No. 4,655,168, which is accomplished by using a special control panel inside the vacuum chamber. . The example shown is for a mild steel Zn coating, but what has been shown is that aluminum can be coated according to the invention. However, this method is completely different from the present invention. For example, there is a roll along which the strip is guided and heated to above the melting point temperature to coat the substrate, which in the case of aluminum is above 658 ° C. This temperature is a temperature that negatively affects the structural stability of some stainless steels. An energy source for vapor deposition is not described, and ion etching is not discussed. Also, there are no specific requirements for good adhesion of oxide-free interfaces or layers. It is stated that this layer is uniformly distributed, but no details are given and the tolerance range is not specified. The method of controlling the deposited substrate is rather complicated. That is, the method as described in US Pat. No. 4,655,168 cannot be used in the present invention.

  Yet another example of an aluminum coating using vapor deposition is described in US Pat. No. 5,429,843, in which a substrate is attached to the surface of a steel material in a vacuum atmosphere. The steel material is kept at a temperature between 100-400 ° C. in order to form active spots on the surface in order to allow the necessary properties, eg good adhesion. Also, ion beam irradiation is used in this coating process, but is performed in the same chamber as the coating. This formed layer is for use as an adhesion layer in the subsequent plating process. In general, the invention describes two different coating combinations Al + Zn and Al + Ti. However, in both cases, it is shown that essentially aluminum coatings cannot be used in the subject specification. For Al + Zn, Al and Zn are co-deposited so that an Al / Zn coating with a Zn content of between 3 and 30% is produced as an optimal condition. For Al + Ti, a two-layer coating is used to achieve acceptable properties and to have the prerequisite that the layer adjacent to the steel is a Ti layer. When substantially aluminum is coated, problems with pinhole-initiated pitting corrosion occur in the film, ie, creating a galvanic cell that promotes corrosion of the steel sheet material. One major difference with the present invention is that the substrate material is flat and not stainless steel, and inhibitors such as Zn addition or Ti layers are used to avoid the occurrence of galvanic cells. In addition, this method differs from the continuous coating in the step between rolling and rolling of the stainless steel strip material of the present invention in that the process used in this method is batch coating of steel plates. This method as described in US Pat. No. 5,429,843 cannot therefore be used in the present invention.

  In view of the above, it is an object of the present invention to provide a new rolling-to-rolling process and to achieve a thin and continuous aluminum coating that provides excellent adhesion to the surface of stainless steel.

  A further object of the present invention is to enable cost-effective and productive production of components in the corrosion resistance application of coating materials.

  Yet another object of the present invention is to provide a coating with as uniform a thickness as possible.

  These objects and still other objects of the present invention have been achieved in a surprising way by providing a coated steel product according to the features as defined in claim 1. Furthermore, preferred embodiments of the invention are defined in the dependent claims.

  The present invention relates to a method for producing an aluminum-coated stainless steel in a continuous rolling-rolling process, which produces excellent adhesion to an aluminum layer covered thinly. Aluminum coated stainless steel strips require thin layers to have good adhesion, which is suitable for cost-effective and productive manufacture of components in corrosion resistant applications. In aluminum coated strip materials, the final product is suitable for use as a corrosion resistant composition in consumer related applications often used in high humidity environments or humid conditions. This aluminum-coated stainless steel composition can then protect other metal parts from corrosion by galvanocurrent, i.e. acts as a sacrificial anode.

  The aluminum layer is deposited by electron beam evaporation (EB) during the rolling-to-rolling process and is preferably a uniformly distributed layer having a thickness of 15 μm. The substrate material is stainless steel having a Cr content of about 10% (by weight) or more and a strip thickness typically less than 3 mm. As a first step, the rolling-to-rolling step can include an etching chamber to remove oxide layers other than those normally present in stainless steel.

Description of Coatings and Uses of the Invention The final product is related to consumers, from the shape of the strip material coated with aluminum, to outdoor life applications, sports and marine life applications, family applications, and personal care applications. It is appropriate to use it as a corrosion resistant composition for the application. In particular, they are all applications that are mostly used in high humidity environments or humid conditions. At the same time, these types of applications are expected to be attractive, with a glossy or “high-quality” appearance throughout their lifetime. Matte surfaces have spots or flat rust and are generally not suitable.

  In order to prevent corrosion of the final product, it is appropriate to have a composition made of stainless steel coated with at least one aluminum. This composition can then prevent other metal parts from being corroded by the galvano current, i.e. acts as a sacrificial anode. Although one or both sides can be coated with a coating, the advantage of using stainless steel as the substrate material is that the stainless steel itself has good basic corrosion resistance, so it is one in terms of corrosion resistance. A surface coating is sufficient. Also, if the substrate material is made of steel that is more noble than the part to prevent, the required aluminum content can be reduced to a minimum to prevent during the lifetime of the critical part. Therefore, this has a positive effect on cost.

  The method described in the present invention is basically suitable for thin films of pure aluminum with a thickness of 15 μm or less, but is preferably made thinner. The aluminum layer is originally 0.1 to 15 μm, generally 0.1 to 12 μm, more generally 0.1 to 10 μm, preferably 0.1 to 7 μm or even 0.1 to 5 μm in total. If thicker layers are to be coated, the optimal cost for properties can be achieved by using up to 10 layers, each layer being 0.1-8 μm, suitably 0. It is between 1 and 6 μm, more suitably between 0.1 and 5 μm, preferably between 0.1 and 3 μm, more preferably between 0.1 and 2 μm.

  The tolerances achieved by EB technology are generally very good. That is, the allowable tolerance of each layer can be a maximum of plus / minus 30%, usually plus / minus 20%, preferably plus / minus 10% at a strip width of 400 μm or less. This means that very tight tolerances can be achieved, which is an advantage for accuracy in use and product quality.

  This thin layer should have good adhesion for its application and their use. In use, it is unacceptable for the aluminum to begin to exfoliate. Furthermore, the layer / layer according to the invention should be able to be used without any joining layer, i.e. it has to be attached directly on the substrate. This coating layer must have excellent adhesion on the substrate without any bonding layer or coating.

  An example of good adhesion is that a coated stainless steel strip according to the present invention can be bent 180 degrees over a radius equal to the thickness of the strip without showing any tendency to delamination (FIG. 1). And 2).

  The covering layer should be sufficiently resistant to withstand the wear and shear applied by the treated material, while not being too thick for the first economic reason. For corrosion resistance applications, the thickness ratio of this coating to the substrate material is 0.1% to 12%, typically 0.1% to 10%, usually 0.1% to 7.5%, most preferably Should be between 0.1% and 5%.

  Variations on the thinly covered aluminum layer coating described above can be a combination of a coating of aluminum with a coating of other metal elements such as Ti, Ni and / or Mo. By using a multilayer system of 10 layers or less, a coating consisting of a combination of several different metal coatings contains aluminum in at least one layer and allows for custom corrosion properties, and in a very harsh environment It is preferably used for applications intended to be used in

  The final product in the form of a coated strip material according to the present invention needs to be easily manufacturable into a suitable composition for application in a cost-effective and productive manufacturing process as described above, Productive manufacturing processes include forming processes such as deep drawing processes, punching processes, stamping processes, and the like (eg, FIGS. 1 and 2).

Description of the substrate material to be coated The material to be coated should have good basic corrosion resistance, preferably 12% or more, or at least 11% or at least 10 depending on the composition of the other alloying elements. % Chromium content. Suitable materials for use are alloys such as precipitation hardened stainless steels such as type AISI 400 series ferritic chromium steels, type AISI 300 series austenitic stainless steels, or alloys described in WO 93/07303. It is. For example, other stainless steel grades such as AISI 200 series can be used.

  This coating method can be attached to any kind of products, preferably in the form of strips or foils, such as strips, rods, wires, foils, fibers, etc. made from stainless steels of the type described above, which are excellent It has hot workability and can be cold worked to thin dimensions. This alloy can also be easily manufactured into a component in a productive manufacturing process including a forming process such as a deep drawing process, a punching process, and a stamping process.

  The thickness of the strip substrate material is between 0.015 and 3 mm, usually between 0.03 and 2.0 mm, preferably between 0.05 and 1.5 mm, more preferably between 0.05 and 1.0 mm.

  The thickness of the substrate material depends on if the coating is done before and after the expected cutting operation. In addition, the thicknesses described above are preferably selected to provide a thickness that is appropriate for manufacturing to the final thickness of the composition intended for use in corrosion resistance applications. In principle, the thickness of the substrate material is therefore between 1 and 1500 mm, suitably between 1 and 1000 mm, or preferably between 1 and 500 mm, or more preferably between 5 and 500 mm. The length of the substrate material is suitably between 10 and 20000 m, preferably between 100 and 20000 m.

For use in environments with high humidity or humid conditions, the substrate material is a suitable composition. This usually means ferritic stainless steel, or austenitic stainless steel, or duplex stainless steel, or hard chromium stainless steel,
Basically this composition is: 0.001-1% C, 10-26% Cr, 0.01-8% Mn, 0.01-2% Si, 0.001-25% Ni, 6% or less of Mo, 0.001 to 0.5% N, 1.5% or less of Al, 2% or less of Cu and essentially Fe, or precipitation hardening stainless steel: 0.001 to 0 .3% C, 10-16% Cr, 4-12% Ni, 0.1-1.5% Ti, 0.01-1.0% Al, 0.1-6% Mo 0.001-4% Cu, 0.001-0.3% N, 0.01-1.5% Mn, 0.01-1.5% Si, and essentially Fe is there.

Description of the Coating Method Variants of the vapor deposition method for coating media coating and coating processes can be used as long as the vapor deposition method is provided with a continuous uniform and adherent layer. Typical methods include chemical vapor deposition (CVD), metal-organic chemical vapor deposition (MOCVD), physical vapor deposition (PVD), or laser deposition, such as resistance heating, electron beam, induction, sputtering and evaporation with arc resistance. For the purposes of the present invention, electron beam evaporation (EB) is essentially preferred for vapor deposition. Optionally, this EB evaporation method can be plasma activated to further ensure an excellent quality dense layer coating.

  For the present invention, it is necessary in advance that the coating method be integrated into the rolling-rolling strip production line. As a result, this aluminum layer is deposited by electron beam evaporation (EB) during the rolling-rolling process. If multiple layers are required, the formation of the multiple layers can be accomplished by assembling several EB deposition chambers in a row. The deposition of aluminum needs to be done under a reduced pressure atmosphere at a maximum pressure of 0.01 mbar without adding any reaction gas to ensure a pure aluminum film.

  The coating process according to the invention is carried out at a speed of at least 5 m / min, preferably at least 8 m / min, or more preferably at a speed of at least 10 m / min.

  Various types of cleaning processes are used to allow excellent adhesion. First of all, the surface of the substrate material should be cleaned in a suitable way to remove the oil residue, otherwise the residue will negatively affect the coating process and the adhesion and quality of the coating layer. Bring about the impact. Furthermore, a very thin starting oxide layer which is usually always present on the stainless steel surface must be removed. This can preferably be done by including a pretreatment of this surface before the aluminum deposition. Therefore, in this rolling-to-rolling production line, preferably the first manufacturing process is ion-assisted etching of the metal strip surface to achieve good adhesion of the first covering aluminum layer (FIG. 4). See). For example, it can be used to remove oxides as an alternative pickling in HF.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION Two examples of embodiments of the invention will now be described in further detail. One example is based on a type AISI 430 substrate material, and another example is based on a type AISI 301 substrate material.

The nominal chemical composition of the substrate material is as follows:
AISI 430: up to 0.12% C, up to 1% Si, up to 1% Mn, 16.0 to 18.0% Cr, and the balance substantially Fe.
AISI 301: up to 0.15% C, up to 1% Si, up to 1% Mn, 16.0 to 18.0% Cr, 6.0 to 8.0% Ni, and the balance substantially Fe.

  First, the substrate material is made of ordinary metallurgical steel made with the chemical composition as described above. These steels are then hot rolled to an intermediate size and then cooled to a final thickness of 0.3 mm and a width of up to 400 mm in several stages with several recrystallization stages between rolling stages. Rolled for a while. The surface of the substrate material is then cleaned by a normal method to remove oil residue due to rolling. After that, the coating process is performed on the continuous processing line where the coil unwinding device starts. The first stage of the rolling-to-rolling processing line can be an inlet vacuum tablet leading to a vacuum chamber or etching chamber, in which ion assist is used to remove a thin oxide layer on the surface of the stainless steel substrate material. Etching is performed. The strip is then placed in an electron beam evaporation chamber in which aluminum deposition is performed. Usually an aluminum layer of 0.1 to 15 μm is deposited and the preferred thickness depends on this application. In the two examples described here, a thickness of 2 μm was deposited in a single electron beam evaporation chamber.

  After this electron beam evaporation, the coated strip material passes through an exit vacuum chamber or exit vacuum lock before being wound on a coil winder. This coated strip material can be further processed if required here, for example by rolling or cutting, to achieve the final dimensions preferred for the production of the composition.

  For example, the final product as described in two examples of 302 and 430 coated strip materials with a strip thickness of 0.3 mm and a thinly covered aluminum layer of 2 μm, the aluminum layer adheres very well. And therefore suitable for use in the production of cost-effective and productive components in corrosion-resistant applications. The good adhesion of this phase is further illustrated in FIGS. In order to produce a coated strip product according to the present invention, a substrate material 1 of a stainless steel strip coated with a thinly covered layer 2 has a top 5 shaped to have a radius at most equal to the thickness 3 of the strip. 4 is placed on top. A bending test is then carried out in a way that the strip is bent 180 degrees over a radius 5 equal to the thickness of the strip at the maximum, this bending being continued until the ends 6 of the strip meet each other. When the bending is completed in such a bending test, the specimen is inspected in particular for the quality of the layer 7 after bending, the quality of the substrate 8 after bending, and the adhesion between the layer and the substrate. Test specimens according to the examples described herein do not show any tendency, such as delamination. This is also shown in the diagram of FIG. 3, which is a photograph taken on a cross section of a test specimen tested in a bending test as described in FIGS. The cross section of the specimen in the photograph was taken at the middle part 9 where bending was most intense, ie, bending.

  The electron beam evaporation process between the above rolling and rolling is illustrated in FIG. The first part of such a production line is a coil unwinder 13 in a vacuum chamber 14, followed by a series of ion-assisted etching chambers 15 followed by a series of electron beam evaporation chambers (EB) 16. The number of EB evaporation chambers required can be varied from 1 to 10 chambers and, if necessary, a multilayer structure can be achieved. All of the EB evaporation chamber 16 is equipped with an EB gun 17 and a water-cooled copper crucible 18 for evaporation. After these chambers have advanced to the outlet vacuum chamber 19 and the coil winder 20 of the coated strip material, the coil winder is located in the vacuum chamber 19. The vacuum chambers 14 and 19 can also be replaced by an inlet vacuum lock system and an outlet vacuum lock system, respectively. In the latter case, the coil unwinding machine 13 and the coil winder 20 are arranged in an open atmosphere.

FIG. 1 shows an illustration of a test piece according to the present invention, in other words, a thin film with good adhesion before the adhesion test, bending over 180 degrees and covering a radius equal to the thickness of this strip. 1 shows a coated stainless steel strip having a dense and dense aluminum layer. FIG. 2 shows an illustration of a test piece according to the invention, in other words, having a thin and dense aluminum layer with good adhesion after bending in a bending test as shown in FIG. A coated stainless steel strip is shown. FIG. 3 shows a cross-sectional photograph of a 3 mm thick coated stainless steel strip with a thin 2 micron aluminum coating, the strip being bent in a test bending 180 degrees over a 0.3 mm radius, No tendency to peel at all. FIG. 4 shows a schematic diagram of a rolling-to-rolling production line according to the present invention.

Claims (9)

A coated stainless steel strip product with a dense and evenly distributed layer on one or both sides of the steel strip,
The layer consists essentially of pure aluminum and is directly attached to the steel strip;
The thickness of the layer is at most 15 μm;
The tolerance of the layer is a maximum plus or minus 30% of the thickness of the layer;
A coated stainless steel strip having a Cr content of at least 10% of the base material of the steel strip and the layer covering a radius at most equal to the thickness of the steel strip without exhibiting a tendency to delamination or the like; Coated stainless steel strip product characterized by good adhesion that it can be bent 180 degrees.   The coated stainless steel strip product of claim 1, wherein the strip substrate has a thickness between 0.015 mm and 3 mm.   Coated stainless steel strip product according to claim 1 or 2, characterized in that it is made from ferritic stainless steel, hardenable chrome steel, austenitic stainless steel, duplex stainless steel or precipitation hardened stainless steel.   Coated stainless steel strip product according to any one of claims 1 to 3, characterized in that the layer has a multilayer structure with a maximum of 10 layers.   Coated stainless steel strip product according to claim 4, characterized in that each individual layer has a thickness between 0.1 and 8 m.   Coated stainless steel according to claim 5, characterized in that it has a multilayer structure of individual layers of different metal coatings such as Al, Ni, Ti, Mo and at least one layer consists essentially of pure aluminum. Strip products.   Coated stainless steel strip product according to any one of claims 1 to 6, characterized in that it is suitable for use in corrosion resistant applications that act as a sacrificial anode.   Suitable for cost-effective and productive manufacture of corrosion-resistant compositions and in high humidity environments or in humid conditions, such as outdoor life applications, sports and maritime life applications, family applications, and personal care applications Coated stainless steel strip product according to any one of claims 1 to 7, characterized in that it is used.   Coated stainless steel strip product is produced in a continuous roll-to-roll process included in a strip production line using electron beam evaporation having a minimum strip speed of at least 5 meters / min and including an etching chamber in series. The method for producing a coated stainless steel strip product according to any one of claims 1 to 8.

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