DE2059896B2 - Process for the production of an enamel layer - Google Patents

Description

There have been such filler materials as

Feldspar and quartz, added to enamel coatings to prevent the

The invention relates to a method for forming an enamel layer to reduce it to a minimum. This formation of an enamel coating on a metallic additive has so far been limited to subgenic proportions provided with a large number of openings below 7 percent by weight, based on the content of enamel by immersing the substrate in an aqueous solution. The incorporation of refractory slurry, which contains 15 to 60 percent by weight of particles with a grain size of 37 to 44 μm suspended in an enamel, and finally an aqueous slurry of a vitreous ßende firing of the coating at temperatures enamel has not been proposed so far,
above 600 ° C. It is therefore an object of the invention to provide a

German Offenlegungsschrift 1 809 572 describes the application of hole-free enamel layers a process for the production of Isolations- th by aqueous slurries on one with to write layers for electronic microcircuits on a conductive base with 60 openings, which sharply demarcated edges and fen.

Have openings. The insulation material is in It is also an object of the invention, a

Screen printing method using a screen printing stencil Method for the formation of hole-free layers from the aluminum oxide support body for the glass-like enamel applied to an aperture provided. The insulation material consists of a substrate obtained using a low temperature deposition process containing refractory oxide particles.
Glazing agents with grain sizes smaller than 20 μm. It is a further object of the invention to provide a method

In the German Auslegeschrift 1032 638 a ren for the formation of electrically insulating enamel

Coating on a perforated substrate with electrooxide, calcium fluoride, nepheline, lithium titanate, aluphoretic To achieve coating process. minium oxide, etc. with a softening temperature

It is a further object of the invention to provide a use of the enamel above the softening temperature for novel apertured and with email, the implementation of the method, coated substrate for applying electronic 5 which receive relatively shear components at the firing temperature of the enamel. is unresponsive to the email. Such oxides as

According to the invention, these objects are achieved by, for example, potassium oxide and sodium oxide, which are achieved with a method of the type mentioned above, react to the vitreous enamel and the physidas is characterized in that the substrate is immersed in a slurry in see and electrical properties of the enamel, which additionally contains 10 io by making them more flowable and producing a low melting point of up to 40%, based on the weight of the enamel, materials with a particle size between 37 should be avoided. Refractory oxides should also contain 44 μm, which should avoid a softening temperature that has electrical properties that are higher than the firing temperature and that affect the enamel. In general, the refractory additives used for the process should not react with the enamel at the firing temperature, ^ie a softening temperature above

From the following description in connection with 1000 ° C and should have a specific context with the figures of exemplary electrical resistance, the at least guide forms a better understanding of the specific electrical resistance of the further objects and advantages of the invention. _ao is vitreous enamels used for the coating.

Fig. 1 is an enlarged isometric view prior to being fed to the slurry development of a substrate provided with holes, which preferably the refractory additives to grain sizes according to the inventive method with enamel of about 37 to 44 μΐη ground to a good Susoeschicht shall be; pension of the particles of the slurry and a

M g. Z is an enlarged isometric view of sufficient dispersion of the refractory additives over the treatment of a method of the invention to achieve the surface of the sheet metal 10. Same enamel coated substrate. early the particles should have a sufficient

u ! Per process with a coating knife to have to provide substrate in the vitreous enamel coating is m F i g. 1 and in order to generate a viscosity which, during the Brentaasse, generally consists of a metal sheet 10, which at one point inhibits the flow of the enamel, for example consists of enamelling iron, ie a.

Iron with a carbon content of less than wise a coefficient of thermal expansion between υ, /, 0, and has a large number of openings 12, see 9 X 10 "" and 11 X 10- «cm / cm ⁰ C, which completely through the sheet metal run through. that is, in an area where the thermal expansion coefficient of the sheet to be coated is less than about 0.88 mm and contains more than 100 mm, the sheet metal 10 has a thickness of 35 mm . The tension induced thermal stress is kept to a minimum, the diameter of the openings is approximately reduced, and it is ensured that at operating 1.3 and 6.3 mm, depending on whether the opening conditions in the cover, a pressure is generated for the mounting of components or for the 40, when the heat that is generated in the components on which the electrical lines are to pass through enamel-coated sheet metal is generated. The edges of the sheet metal lying underneath are preferably passed on. To those with a rounded radius that is about half the amount of inert refractory additives that make the desired "? WTr a " ^{S en} ! ^S P ^r ' ^cht ' to ^reduce _{the effects of calcium, fluoride} , nepheline, lithium titanate and mixtures of these, while the enamel has high thermal expansion properties.

Lm the sheet 10 by dipping it with a water additive. The selected refractory additive

H ^ n ¹ Ti ¹¹⁸ C ¹¹ A ^e ! ^Se u ^ 7l ^{Td the glass is prepared by conven- ting the} slurry of the vitreous enamel in tional sandblasting or pickling processes for concentrations between 10 and 35 «/ * based on the enamel coating, and then it is in 50 the weight of the enamel frite in the Slurry, an aqueous slurry of a vitreous added. The good electrical insulation enamels are immersed in the inert refractory additives of the silicon dioxide and the magnesium Γηϋ ff ⁿ ™ ^hen . 1 ° ^d ™ I ⁵ weight percent sawn oxide together with the high Wärmeausdchnungszogen on the weight of the enamel frit in the up coefficients of these materials cause SRTT ^{8 6} Pm ^{'to e} .. J ^NEN _J ^Resistance against ^{en da} * 55 These refractory oxides are preferred in the practical implementation of the enamel during the subsequent implementation of the process. In the general burning of the sheet provided with the coating, vv, rd mean a far superior coverage of the

Anfa + r ™ * f ^{memen contains that achieved in the edge} < ^{if the additives are about 2} 5 to 35

GeSht ^ pift ™ ^{ended up being less} than 60 weight percent of the weight of the enamel frit in which the weight percent is sodium oxide, potassium oxide or gel 60 slurry

! riin2S; "T - ^dn f ^hOhe ? ^s P ^ezi « ^{schen eIek} "If a refractory additive with a heat

üher ™ hilft h il ^{m the} enamel expansion coefficient applied by more than 2X10 "«

όΓΙ ^^ Ζαμ * * α α- cm / cm ° C below the coefficient of thermal expansion

rend dei ηϊ.ηηΐη Ϊ ^dd # «» «^ * epen, wHh- pensions of the underlying metal sheet" is, £ n HNR ^. "f" ⁵ £ ^e Y '^ ositat thereby erhö- 65 of the enamel slurry is added, should the SÄ'f ™ ES ^0formi ^ ^Adhasions .P ^ te for the refractory additive in concentrations of the highest

E 2 MaS IT w ^ee ^ r · ^n> frt ^particles - ^{15 0/0 of the} weight of the enamel frit be present, shaped material, such as silicon dioxide, magnesium- For example, this is quicker when using Al, ™ !.

5 6th

Nium oxide with a coefficient of thermal expansion xotropy in the slurry is added 6 parts by weight between 7 × 10 ° and 8 × 10 ° cm / cm ° C. as part of the clay. Preferably, the additive for an enamel coating on an iron sub-slurry for the purpose of increasing the rheological strat with a coefficient of thermal expansion between properties is small proportions of an electrolyte, including 11 X 10 ~ ^e and 13 X 10- ° cm / cm ⁰ C. Men- 5, for example, a mixture of V ₈ parts by weight of the additive which are above this value, sodium nitrite, V ₈ parts by weight of magnesium carbona, the enamel _{will flake off the substrate and Vi 0} parts by weight of sodium aluminate present during subsequent cyclical temperature changes Ge causes. Likewise, very low concentrations are important parts of an inert refractory additive, in the case of finely divided aluminum oxide, undesirable because of e.g. added. For the production of a rend of the subsequent firing, whereby the coating in the immersion process is changed the slurry melting point of the enamel. Concentrations of the refractory A.ddi-15 are generally brought to a specific gravity of around 1.6. The metal sheet 10 is then immersed once or tivs between 10 and 15%, based on the weight several times, in the slurry, of the enamel, preferably if the refractory additive has a coefficient of thermal expansion around the sheet completely with an enamel layer to a coefficient of thermal expansion that which has a thickness of about 0.3 mm. The coated sheet is then dried. The coefficient of expansion of the sheet metal is 20 and 3 V for ₂ minutes at a temperature of

The remaining component of the coating is about 830 ° C fired to turn the enamel layer into one The enamel slurry used in sheet metal has an all-hole-free coating with a thickness between approximately Generally, in terms of its composition, 0.15 and 0.18mm are conventional. During the burning and contains in principle an aqueous suspension of the process, the refractory particles remain stable and Enamel particles. In the case of such an enamel, the 25 provide points of adhesion for the porcelain enamel. Da-enamel particles between 15 and 60 percent by weight by reducing the effect of the surfaces Slurry depending on the tension, which tends to remove the enamel from the the desired viscosity and the intended use of pulling away the edges of the openings in the sheet metal 10, of the email. For example, a high viscosity, generally the finished formed Eroaild. H. a weight ratio of the enamel frit to the layer less than about 0.25 mm thick (the thicknesses weight of the water above 80 ° o, desirable for which are typically between about 0.15 and Coating in the immersion process. For an elec- 0.18 mm) and still gives a coverage of trophoretic deposition is a lower viscous a thickness of at least about 0.13 mm on the sity, i.e. a weight ratio of about 30 ° 0, the edges of the openings.

wishes. For application purposes with application 35 The method is particularly suitable for the cooker Emails using the immersion process result in the elec- tricity of coatings in the egg immersion process. That trolytic salt, for example sodium nitrite. Potash sheet can, however, also with an aqueous solution umcarbonate, sodium aluminate, magnesium carbonate, coated by enamel and inert particles, in Borax or mixtures of the foregoing, one of the methods for producing a coating slurry in amounts below 1%, based on 40 in the flow process. Although a Hcrsieidas Weight of the enamel particles added to give the coating by spraying not sufficient thixotropy to produce, which tends to adhere to the covering of the side walls of openings Sion of the enamel slurry on the sheet metal results in too small a diameter, for example for strengthen. Similarly, the openings are usually below diameter Slurry for dip coating a sus- 45 about 1.5 mm for metal sheets, such as those used as broadcasting havensers. For example, clay or bentonite are used in sis, spray \ can be experienced before Quantities between 4 and 7 "ο available in order to ensure the success of a coating Aiming of the desired thixotropic and the bus- the side walls of the openings by using. Pension use both the F.mail and the inert part of flow processes or immersion processes to assist in the slurry. Organ »- 50 in order to further disrupt the enamel layer Materials such as starch or rubber. ken.

such as rubber tragacan or rubber after burning with the slurry

Karaya can also be used to give the bin-coated metal sheet 10 a structure

dung and suspension of the solids in the list corresponding to FIG. 2. This is through a sheet of metal

support foaming. The proportion of suspen- 55 10 with a thickness of less than 0.88 mm has

However, the solvent can be significantly reduced, having at least 100 openings and one

when the slurry immediately in front of the enamel coating layer 14 with a thickness of less

Immersion of the sheet in violent motion offset ger than about 0.25 mm. The enamel coating

and the sheet metal from the bath to the combustion chamber generally consists of about 65 to 75%

60 molten enamel transported in a plane parallel to the running direction, in which 25 to 35 weight per-

is to prevent the run-off of the vitreous enamel of cent inert refractory oxide particles with a grain

to prevent the sheet metal. size of 37 to 44 μm are dispersed. That with

A slurry used for the manufacture of a glass-like enamel coated sheet shows a

of a coating on the sheet 10 by immersion dielectric breakdown voltage above

drive is suitable, an aqueous suspension can 65 2500 volts and is suitable for thick film and thin

of about 100 parts by weight of the ground enamel film application of electronic components. Example

contained in 90 parts by weight of water. To achieve this, a capacitor 15 can be deposited by deposition

increased suspension properties and a thi a palladium silver electrode 16 on the sheet metal plate

formed with the electrically grounded sheet emulsion, an acrylic acid compound in an An-10 represents the counter electrode. On the enamel over part of about 65 to 85%>, based on the weight train can in vacuum those with the reference numerals 17 of the selected anionic colloidal material, or 18 designated cermet resistors and copper be present. This is used to suppress a fer connecting lines are applied. Construction 5 foaming as a result of the generation of gases which is not for the deposition in a vacuum or rend the deposition and still allows the anim movies are suitable, for example a final burn without an excessive portion Voice capacitor 19 will be on the one with the excess of residue in the enamel. Small quantities toe provided sheet mechanically fastened, for example by other components, for example by hanweise with the help of bolts 20, the wetting agents available through io delsormally, the bath Openings are guided in the substrate. also, if desired, in amounts of less

The inert refractory additives can also advantageously be used as 0.5%, based on the weight of the water be joined during the production of a coating.

the sheet metal by electrophoretic processes. In a particularly preferred electrophoretic

That means, it will see on the surface xs bath will be an aqueous enamel bath with 30 Gedes provided with a multitude of openings weight percent enamel with a particle size of sheet metal electrophoretically a mixture of an enamel about 37 to 44 μm with 100 parts by weight of water frit and an inert additive is applied, and a small amount of ammonium alginate and then during the firing process of the enamel of an acrylic acid emulsion, for example 0.1 part, the inert additives as points of adhesion for the »o based on the weight of the water, to prevent Enamel is used to reduce the surface tension mixed in foaming at the anode. To reduce the burned enamel. The electro-anionic wetting agent is suitably added to the bath Dhoretic bath 22 for the deposition of the enamel over- in very small proportions, ie ¹ Iw zues consists mainly of an aqueous sus- part by weight together with 30 parts by weight of silicon-Dension of between 15 and 60 percent by weight of 25 µm dioxide , which was ground to a grain size between about 37 enamel frit for the electrophoretic and 44 μπι. After the pickling of the sheet metal with openings provided with a bath with relatively low viscosity, the sheet metal is then suspended in an electrophoresis bath containing 15 to 40 percent by weight of enamel in inactive cathodes. The bath also contains, when immersed and in the bath, a potential of about that of an anionic colloidal material, for example 30-30VoIt from a voltage source, preferably ammonium alginate, in amounts to generate a current flow of about 2.5 A on the sheet metal below 3 ⁰ Zo based on the weight of the water. The electrophoresis is continued in the bath until this material is deposited on the sheet at the same time as a coating of a thickness from the enamel on the sheet 10 and thereby separates about 0.3 to 0.38 mm. Then the bath is removed from the metal sheet in order to undergo electrolysis, the sheet metal is pressed dry and nevertheless the further deposition and 3 " ₂ minutes in an oven with tempering of the enamel on the sheet metal are allowed. door of 830 ° C, in order to keep the enamel in a shielding of the coated electrode, further to the like enamel layer on the with openings and to suppress an excessive build-up of sheet metal with a thickness between about 0.15 and enamel on the edges of the substrate, 40 0.18 mm convert. Because of the presence & ^ is a commercially available emulsion of a Sihziumdioxidteilchen in the enamel is applied to the rhs Acrvlsäureverbindurr the bath in amounts of GR substrate passes through openings 12 a Bedek- ^ "ic n ^ t. ht7oeen added to the weight of the kung of the edges with a thickness of more than about enamelfrL in general the 0.13 mm should be achieved.

1 sheet of drawings

4021

Claims (5)

1 2 wear-resistant enamel coating described, the claims of which: Resistance to abrasion is improved by adding powdery hard substances. Included 1. Method for forming an enamel over- is used as the hard substance noble corundum niit a preferably on a metallic, with a large number of grain size of about 60 to 65 um, of openings provided substrate by thawing in an aqueous slurry, the fire resistance of an enamel can be improved, mung, which 15 to 60 percent by weight of one that consists essentially of granite and z. B. contains an AI-Emails suspended, and then consists of potassium silicate. For this purpose, titanium oxide is added to this preferably after firing at temperatures of 2 to 5%,
above 600 ° C, characterized in that the substrate is immersed in a slurry of a metallic, with a large number of openings, the additional 10 to 40%>, related to the end product on the weight of the enamel, a material requirements that cannot be met by these known methods with a particle size between 37 and 15. 44 μηι contains, which has a softening temperature If the substrate has many openings, which is above the firing temperature, and, for example, has every substrate for a broadcasting device at the firing temperature with the enamel usually more than 100 openings reacted. of the most varied of dimensions, then tends to 2. Method of forming an enamel over- 20 probably the surface tension in the liquid lift according to claim 1, characterized in sludging as well as during firing in the that the substrate is softened in a slurry enamel layer to cover the is immersed, which is used as an additional material to reduce silicon edges on the openings. Through this Umdioxid, Magnesiumoxid, Calciumfluorid, Alu- is the use of the enamel coated Mix minium oxide, nepheline, lithium titanate or Ge 25 substrate as an electrically isolated end level of these materials in amounts between 25. The coating of an apertured and 35%, based on the weight of the enamel, of the substrate produced by spraying a contained, slightly lower surface tension in the liquid 3. Process for making an enamel excess slurry due to evaporation of the Zugs according to claim 1 and 2, characterized by 30 water during the spraying. The surface marks that a layer of the fired enamel becomes tension in the enamel during firing with a layer thickness of less than 0.25 mm, however, by applying the glass-like enamel will be produced. not significantly influenced by spraying. 4. Method of making an enamel over- In addition, generally prohibits the fact Zugs according to claim 1, characterized in that one is not able to by spraying the that the substrate is compressed into a slurry sidewalls of small diameter openings is that as an additional material aluminum, for example less than about 1.5 mm, hinreiminiumoxid in amounts between 10 and 15%, to be coated accordingly, the separate application of based on the weight of the enamel. Spray process for coating substrates 5. Method of making a multi-hole emah over 40. Even by electrophoresis traction layer according to claim 1, characterized by the characteristic coating process achievable by far overdrawn, that as a substrate an electrically insulated covering of the substrate is not sufficient, Sheet metal with a multitude of openings around the incomplete covering of the edges of and a thickness of less than 0.88 mm in the openings to prevent emerging from the surface slurry is dived. 45 tension during the firing of the enamel.