DE1621401A1 - Method and device for applying hot melted mixtures to cast iron objects - Google Patents

Description

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Method and apparatus for applying hot melt mixtures to cast iron articles

The present invention relates to a method for applying hot melt coatings to cast iron objects, in particular a method for applying porcelain enamel coatings.

Porcelain enamel mixes are used for stoving or hot melting on metal surfaces by means of two conventional processes known as "wet processes" and known as the "dry process".

The wet process is used technically, for example, to produce porcelain enamel coatings on sheet steel.

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set, while the dry process is used to produce porcelain enamel coatings on heavy cast iron parts.

In the wet process, the powdered porcelain enamel mixture is suspended in water so that it hits the object can be applied by dipping or spraying. After dipping or spraying, the object is dried, thereby a dried porcelain enamel application is formed, which is then used to fuse and connect the Email is burned with the item.

In the dry process, the object is heated and dusted with powdered glass enamel. The one in the subject Existing heat initiates the melting of the enamel, which is followed by melting in an oven is completed. The dry process takes place after the wet process. For example, will When enamelling cast iron by the wet process, a base coat is applied, which is then fired in the furnace whereupon the object is taken out of the oven and while the enamel mixture is still melted with glass powder or dusted with a glass of sufficient strength by a skilled operator, the irregularities in the base coat

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of the surfaces, whereupon another Burning follows.

The use of the wet process for applying a top coat is due to the relatively thin layer of the Enamel coating that can be applied by this procedure, usually on relatively smooth surfaces limited. The suspension of the enamel mixture in the water necessarily requires a small particle size of the Enamels, which results in a relatively thin coating, so that in some cases the surface irregularities, as they exist on cast iron, cannot obscure. In addition, the watery is muddy The particles are so strongly dispersed that, on drying, the enamel application obtained shrinks to such an extent that a network-like crack formation occurs. When firing such an enamel application, a mottled surface is obtained, which shows a network of jumps. In some cases there are also difficulties with the wet process by the formation of bubbles, cracks and pinholes in the coating caused by entrained air during spraying too much water or too thick an application.

In other cases, the viscous sludge follows the irregularities, the holes and notches of the

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Object, so that the defects to be coated in the end product Surface can be reproduced and sometimes even emphasized * For these reasons, the wet process has limited scope and although it is not There has been a lack of attempts, e.g. for coating cast iron to devise a one-step wet coating process Such a process is of no technical interest found.

Also with the use of the dry process are many associated obvious disadvantages «The first stage of the dry process is the application of a Base coat to which the top coat is dusted connects. The metal must be kept at elevated temperatures while the powder is being atomized »In the case Cast iron often has to keep this at higher temperatures long enough to avoid unwanted structural changes and to cause metallic fatigue of the iron.

The bonding of the top layer with the base layer is weaker than the bonding of the base layer to the metal, so that easier peeling of the Emails can occur. Manufactured by the dry process Coatings cannot be baked satisfactorily, so that a.for this reason, after the article has cooled down

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only repaired minor errors using dental cement can be. Furthermore, the use of decorative materials, which are attached when reburning, not yet resolved satisfactorily.

Accordingly, it is an object of the present invention to provide a method for producing improved coatings on cast iron articles to accomplish. Another object of the invention is "a new method in a method of enamelling To create a dried enamel application and a device suitable for this purpose. It is another The aim of the invention is to provide a coating with improved bond strength compared to cast iron. It is a Another object of the invention to provide coatings with structural advantages and usabilities. ”It is a further object of the invention to provide coatings with enlarged To provide strength. It is another object of the invention to provide a finished article with a single To provide enamel application on cast iron, whereby the base coating can be dispensed with. It is a Another object of the invention is to provide covers which are suitable for decorative purposes. It's another goal of the invention to reduce the amount of work and costs involved in enamelling cast iron. It's another one

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The aim of the invention to provide a method available at which certain stages can be automated » Other objects of this invention will become apparent as the description proceeds clear.

With reference to the following drawings some advantageous embodiments of the present Invention to be explained »It means:

Fig. 1 is a flow diagram illustrating the process of the invention illustrates; ^ /

Fig. 2 is a schematic representation of the device for Applying powder.

With reference to the flow diagram according to FIG. 1 are intended to highlight the main features of the present invention will. The objects to be coated are made of cast iron. These may already be in their final Molded form or as various individual cast parts, which are then to be joined together to form a unit and glued together. The applied according to the invention adhesive / coverings give the individual parts sufficient strength for bonding in many cases, so that the objects from different parts come together

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adds and. by coating according to the invention Process glued together and thereby become a unit can be joined together. ;

Before coating, the surfaces to be treated are pretreated, for example by sandblasting. Cracks and Unevenness can be removed with polishing pads, etc.

The surface to be coated is first covered with water wetted or moistened, for example by dipping or spraying. It is desirable that the ready-to-use water is free of such impurities, which could cause defects in the finished coating. It can also prove to be advantageous in some cases, add wetting agent to the water.

The objects are kept at such a temperature that the immediate evaporation of the water on the Surface is prevented. For this purpose it may be desirable be to cool the objects below the ambient temperature, for example before moistening, in some cases it may be desirable to place the items on one Temperature below the dew point of the air in which the objects are then treated during the atomization

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to cool down. The coating mass is applied to the moistened Surface in a sufficient to cover the desired area Strength dusted on. The atomization takes place in a Temperature below the melting point of the mixture instead, preferably at the usual room temperature "'The powder adheres to the moistened surface and creates an enamel coating the strength of the order plus moisture supplied will.

Sufficient moisture is added to the email application, that the cohesion of the particles is effected and that the Order is glued to the surface of the object. The moisture content is kept below that which would lead to the powder mixture becoming fluid. The moisture can be added to the powder when it is applied to the object.

A device for supplying the moisture with the powder is shown schematically in Fig. 2, in this Fig. 10 denotes a powder container which contains a suitable powder mixture to be melted on the cast iron articles. The powder is fed to the nozzle 12 through a hose 11 and is sprayed onto the objects from the former. A valve Ik can be provided in the line to control the flow of the powder to the nozzle.

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To reduce the clumping of the powder, as stated was, the hose or the line 11 with Teflon 15 or lined with another low friction material. . ....'_

The nozzle 12 wi £ d through the air line 20; moist air for example at a pressure of 0.14 kg / cm (2 psi). As already explained, it is desirable Provide moist air for coating the cast iron body. The chamber 21 serves to humidify the air. The chamber 21 is from the bomb 22 through the air line 26 compressed air and from the spray head 23 connected to the water line 24 Water jet supplied. The water in the chamber 21 is removed through the drain 27. The compressed air can the chamber 21, for example, with a pressure of 6.3 at pulls; leads and expanded upon entering the chamber 21,. fingering the pressure to suck in the powder.-In the chamber 21 is the. "compressed-.air · through from the Head 23 sprayed water and moistened by the elements 28 heated. The humidified air is passed through the separator 30, which removes the water droplets, guides and passes through the Lei tug 20 to the nozzle 12. J '. "- ..

The temperature of the object can be so high that a Evaporation of the moisture applied to it occurs before the dusting, so it is advantageous for this reason

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can be to keep the temperature of the object below the \ dew point of the air supplied from the nozzle 12. In most cases, therefore, the temperature of the object will be the ambient temperature or lower. The lower limit for the temperature of the object is of course the melting point of the water, 0 ⁰ C.

Although in some cases it is beneficial to moisten it the surface of the article and dusting with to do the powder in separate operations is it in other cases it is desirable to have the wetting done substantially simultaneously with the application of the dry powder. It can be seen that a device as shown in Fig. 2 is suitable for the object a sufficient Adding moisture to the surface at the same time. moisten during which the powder is fed. The present invention therefore envisions wetting the surface of the article and applying a moist Powder in one operation, just as with separate ones Imagine. ■

The present invention also contemplates the deposition of the Powder, an «electrostatic method, in which

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the nozzle and the article on an opposite electric Charge to be held. The invention also sees the formation of an electrolytic system in the enamel application to hold the powder in place.

Suitable for use in the process of the invention Mixtures include those previously considered as top coats. Examples are more typical Mixtures are given below:

Example 1: White coating 28.70 borax 24.80 .Silicon oxide
- - - 20.30 Cryolite / 2.30 Sodium nitrate 4.10 Anhydrous soda 2.30 Fluorspar 11.30 Black lead 6.30 Antimony oxide Acid-proof white coating Example 2:: 8.70 Kalifidspat 11.60 borax 25.80 S 11icium oxide ■ 5.10 Sodium nitrate '- 14.30 Anhydrous soda

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Sodium antimonate x 10.10

Sodium fluorosilicate 1.70

• Black lead -. . 7.80

Zinc oxide 5.10

Chalk white 3.00

Titanium oxide 6.80

The particle size of the mixture is not critical. In some cases it has been found to be expedient, in order to prevent air being entrained, to use larger particles than have hitherto been used in the wet process. Typical particle sizes are between? 6 μ and 251 μ (200 mesh - 60 mesh) _{or similar}

The enamel application can be baked before firing to remove liquids such as water. Carbon dioxide, organic substances and the like. by heating to sufficiently high temperatures and for a sufficiently long time. For example, · the order before burning about 5 minutes at temperatures between about room temperature to _e cao. 5 ^ 0 ⁰ C, be heated. The article is fired at temperatures high enough to melt the coating. The method according to the invention permits the use of lower firing temperatures with the associated advantages. The temperatures can be between about 5 ^ 0 C and 81 6 ° C, usually between

C and 788 ⁰ C, the burning time being approx. 10 minutes: The burning temperature is preferably kept below that at which the formation; brown spots caused by the reaction of iron with the enamel mass takes place :. The temperature and the duration are also kept so low "/ that there is no significant increase in the iron ο / /; /:

After burning, the item is usually burned off / cools. On the other hand, the method according to the invention allows certain effects before cooling. obtain,. For example, can on the melted; Mixture decals or artistic material to be superimposed. Decals ^ which for branding on chines. Porcelain are made ι are satisfactoryο After applying the decorative material, the object is fired again, namely usually at the firing temperatures given above and then let cool down.ν: - ■■ '"■ ■ -" ■■ / ■ /., "":

It is possible to form hiss in the email order. to be read for ornamentation in the finished article to create special effects. The formation of a cracked Order can be done by the fact that before burning the Moisture content of the order is increased * For example, by the fact that the / moisture content of the nozzle 12 supplied air increased. ; /:,

The cooling process is usually carried out so slowly that that cracking in the order is avoided.

The above described method is associated with many unusual advantages in coating Gußeisengegenständen "It can not only the basic layer are dispensed with, and carried out the coating in a single step, but the final coating is also to Oer surface of the cast iron klebkräftiger than the _o received so far - '^ -.,

In addition, the order is denser, which facilitates melting and flow and the cracking of the order reduced when drying »The lower firing temperatures reduce the blistering caused by the formation of brown spots Defects »The object can be fired again, which enables special effects to be achieved.

The apparatus described herein is more convenient to use than the hand strainer, which has to be refilled. the inventive device ensures the continuous Supply of the powder.

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Claims (1)

I b I \ k U i Pat e η t a ns ρ r ti c h e . Process for the production of hot melted coatings on cast iron objects, thereby geke η η ζ calibrated η et _t that a) the surface of a cast iron object on the to coating surface is wetted, b) that a powdery mixture, MtL before hot-meltable components, is applied to the wetted surface to form an enamel _{application, -:} C-) that the body containing the contract burned and d) allowing the object to cool. 2. The method according to claim 1, characterized z e i ch η e t that a porcelain enamel mixture as a powdery mixture is applied " 3. The method according to claim 1, characterized in that g e k en'η - ζ e i c h η e t that the powder mixture at least 2 @ wt .- ^ Contains silicon oxide. . "■" - ". ^ _{0 The} method according to claim 1, characterized geke ή η ζ ei without t that the powder mixture is sprayed onto the surface to be coated with air _e - 16 - . ■ "■" ..! 62UOT • V: - i6.- 5s method according to claim 1, characterized geke η η - ζ ed ö h η et that the powder mixture is sprayed onto the surface with an air stream which • has sufficient moisture that the particles of the pre-mix stick together after application * Se method flat claim i, characterized geke η η ζ e ic h in 6 t that the enamel application is dried before firing to volatilize undesirable substances at temperatures below | ^ Ö ^Ö G,. ^ 7. The method according to claim 1, characterized in that the object is fired at temperatures from Q to about 816 ° G. 8. The method according to claim 1, characterized in that the object is fired ^{at temperatures of approx * 732 0} G to approx * 788 ^{0 G.} 9 -. A method according to claim 1, characterized in that the article is dried for some time at a temperature which is sufficiently high to volatilize certain of the undesired components and which is below 5 ^ 0 ⁰ C and that this article is at temperatures from approx. 732 ⁰ Obis approx. 788 ⁰ C is burned « 10 9 819 / 019S - 17 BAD ORiGiNAt. 10, - A method according to claim 1, characterized characterizing g_ & ^{-: i} ν is characterized in that cooling vor'dem be applied to denüberzug decoration materials, and the counter-stand. Is re-fired ""V; ■ 11. Method of making cast iron is tight objects with thermally fused coatings thereon, dadureh g e k e. η η ze i c h'n et that, ■ -_. a) on the surface of a cast iron object that is too bad a thin film of water is produced, b) that thereupon a powder-ier tiiermiseh to be melted Mixture applied and that c) said object is fired at elevated temperatures which are so high that said Mixture melts. - /. ; ; 12. The method according to claim 11, characterized geke rx ^ n-- ζ e worth doing that on the said melted mixture Decorative materials are applied and that the said item is again febrannl;. 13. The method according to claim 11, characterized in that g e k e η ii - ζ e 1 c h η e t that as a carrier for applying the teased Powder aiffed the mentioned object to be seen moist air is used. 1621AOI 14. A method for the production of cast iron articles with hot melted coatings, thereby geke η η ζ e ■ ich net that a powder anail mixture containing hot meltable components is applied to a moistened cast iron surface that is to be coated so that the cast iron surface draws sufficient moisture -. "," Is used to form an order of the enamel mixture mentioned and that the order mentioned at temperatures of approx. 5 ^ 0 ⁰ G to approx. 8l6 ° C is burned for a time sufficient to hot melt the mixture mentioned. 15ο Method according to claim Ik ₁ characterized geke η η ζ ei / oh net that the application mixture is a porcelain. Email mix is. 16. The method according to claim Ik , characterized geke η η - ζ e i c h η et that said powder mixture on the surface to be coated is sprayed with air. 17. The method according to claim Ik, characterized ge ke η η ze I η et that said powder mixture is applied to the surface with an air stream which has sufficient moisture that the particles of said powder mixture stick together after application » - 19 1 0 9 8 Ί 9 / Π 1 9 B ^BAD ORIGJNAL Ib ^ 1401 18 * A process according to claim 14, characterized ge Ken ri "ν draw t that the order before the · ^ burning feel temperatures below 5 ^ O ⁰ G sufficient leit V & rilÜGhtigung undesirable substances is getrockhet. ' 19 ο The method according to claim 14, characterized in that, prior to cooling, decorative materials are applied to the above-mentioned overlay and. the item rises. is launched. _; - - 20. Device for applying voii powder mixtures to a surface to form an egg-flow carrier ^ ge k e Vl ii ζ eic h η et through a nozzle-shaped Einrichtühg (12) for supplying a powder with air to the upper surface-i means (14 ^ 15) for Feeding the powder mixture to the nozzle mentioned, means (03 ₁ 3 ^) for feeding the air to the nozzle mentioned above pressure and means (21) for increasing the moisture content of the air supplied to the nozzle mentioned. 21 * Device according to claim 20, ge ke * η ϊί ζ ei ch η et by means (28) for heating the "deiv nozzle trains- * led 22. The device according to claim 20, k en h ζ eich net "by further means for increasing the humidity of the air supplied to the nozzle _e · to Empty e