COATING FOR HEAVY CASTINGS, ESPECIALLY CAST IRON AND CAST STEEL I METHOD OF PRODUCING COATINGS FOR HEAVY CASTINGS, ESPECIALLY CAST IRON AND CAST STEEL

Description

[0001] The object of the invention is a coating for heavy castings, especially of cast iron and cast steel, and a method of manufacturing coatings for heavy castings, especially of cast iron and cast steel.

[0002] Casting coatings are generally divided into the following types: passive coatings, active coatings, reinforcing coatings and absorbing coatings. Alcohol-based casting coatings and aqueous coatings are known from common use due to the solvents used.

[0003] Patent application CN104550663A discloses an aqueous polyvinyl alcohol coating for use in protecting castings. The coating comprises a solution of polyvinyl alcohol, calcined magnesium oxide powder, activated magnesium powder, activated bentonite and an aqueous solution of carboxymethyl cellulose.

[0004] From patent application CN103878302A, a fast-drying water-based coating for use in foundry applications is known. The invention includes refractory materials such as zirconia powder, chromite powder or zirconia composite mineral silicate powder and a silicate binder of the fast-drying type.

[0005] Currently, the elimination of alcoholic coatings is being pursued, not least because of their flammability and negative environmental impact. However, in the case of water-based coatings, we observe problems with drying. The heat of vapourisation of water is 2441 kJ/kg. This is approximately three to four times higher than for alcohol. Also, volatility, as an important factor in the evaporation rate, is 10 times higher with alcohol than with water. The result is that water-based coatings dry out many times slower than alcohol-based coatings. It is therefore important to limit the amount of water in aqueous coatings as much as possible. The main difficulty in developing compositions for waterborne coatings - with low water content - is the inappropriate viscosity of the coating which prevents proper application of coatings to cores and moulds.

[0006] The essence of the solution according to the first invention is that the coating consists of zirconium meal (Zirconium silicate) in an amount of 50 to 75 per cent by weight, water in an amount of 18 to 25 per cent by weight, an aqueous solution of aluminium polyiforate in a concentration of 40 to 70 per cent in an amount of 2.5 to 7 per cent by weight and bentonite in an amount of 0.2 to 2.0 per cent.
Advantageously, the coating contains iron red in an amount of 1 to 3% by weight.
Advantageously, the coating contains graphite in an amount of 3 to 10 per cent by weight.
Advantageously, the coating for iron castings contains zirconium meal (Zirconium silicate) in an amount of 50 to 70 per cent by weight.
Advantageously, the coating for steel castings contains zirconium meal (Zirconium silicate) in an amount of 60 to 75 per cent by weight.
Advantageously, the bulk ingredients have a fineness of 160 to 220 mesh.
Advantageously, the density of the coating is between 1.9 and 2.29 g/cm³ .
Advantageously, the viscosity of the coating is between 30 and 60 s.

[0007] The essence of the solution according to the second invention is that bentonite in an amount of 0.2 to 2% by weight is added to water in an amount of 18 to 25% by weight and mixed for 10 to 30 minutes, after which an aqueous solution of aluminium polyiforate in a concentration of 40 to 70% in an amount of 2.5 to 7% by weight is added and further mixed for 10 minutes, followed by the addition of zirconium meal (Zirconium silicate) in an amount of 50 to 75% by weight. After the last ingredient is added, the whole is mixed until completely homogenised.
Advantageously, iron red is added to a mixture of water, bentonite and an aqueous solution of aluminium polyphosphate in an amount of 1 to 3% by weight and stirred for 10 to 15 minutes.
Advantageously, graphite is added to the mixture of all ingredients in an amount of 3 to 10 per cent by weight and mixed until completely homogenised.
Advantageously, zirconia meal (Zirconium silicate) in an amount of 50 to 70 per cent by weight is used to prepare the coating for iron castings.
Advantageously, zirconia meal (Zirconium silicate) in an amount of 60 to 75 per cent by weight is used to prepare the coating for steel castings.
Advantageously, the bulk ingredients have a fineness of 160 to 220 mesh.
Advantageously, the mixing speed is between 500 and 700 rpm.

[0008] The advantage of the solutions according to the inventions is the obtaining of an ecological coating, which does not emit gaseous substances harmful to the environment and which is not subject to thermodestruction at high temperatures. The addition of special thixotropic substances ensures adequate technological properties at low water content. The developed coating shows a drying time similar to that of alcohol coatings, without the need for a drying process in special chambers. The coating dries spontaneously in 4 to 10 hours depending on ambient temperature and humidity.

[0009] Solutions according to the inventions are illustrated by the following implementation examples.

Example I

[0010] The coating for cast iron consists of:

• water at 23% by weight,
• bentonite at a rate of 1%,
• an aqueous solution of 45% polyiforphate at 7% by weight,
• iron red at 3% by weight,
• zirconium meal at 62% by weight
• graphite at 4% by weight.

[0011] The fineness of all bulk ingredients ranges from 160 to 220 mesh.

Example II

[0012] The coating for cast iron consists of:

• water at 23% by weight,
• bentonite at 2% by weight,
• an aqueous solution of 60% polyiforphate at 3% by weight,
• zirconium meal at 67% by weight,
• graphite at 4% by weight,
• iron red at 1% by weight.

[0013] The density of the resulting coating is 2.1 g/cm³ , with a viscosity of 25.

[0014] The fineness of all bulk ingredients ranges from 160 to 220 mesh.

Example III

[0015] The coating for cast steel consists of:

• water at 20%,
• 3% bentonite
• an aqueous solution of 70 % aluminium polyiforate at 4 % by weight,
• iron red at 2% by weight,
• zirconium meal at 71% by weight.

[0016] The fineness of all bulk ingredients ranges from 160 d0 220 mesh.

[0017] The density of the coating is 2.2 g/cm³ and the viscosity is 50 .

Example IV

[0018] The coating for cast steel consists of:

• water at 22%,
• 0.7% bentonite
• an aqueous solution of 55% aluminium polyiforate at 6% by weight,
• zirconium meal at 71.3% by weight.

[0019] The degree of fineness of all bulk ingredients ranges from 160 to 220 mesh.

[0020] The density of the coating is 2.3 g/cm³ , and the viscosity is 27.

Example V

[0021] The coating for the iron casting was obtained as follows:

• to water at 23% by weight, bentonite at 1% by weight was added and stirred for 20 min,
• An aqueous solution of 55% aluminium polyiforate at 7% by weight was then added and further stirred for 10 minutes,
• Iron red was then added at 3% by weight and stirred for 10 minutes,
• followed by the addition of zirconia meal at 62% by weight and stirring for 10 minutes,
• Finally, graphite was added at 4% by weight and the whole mixed until completely homogenised.

[0022] The ingredients were mixed at 600 rpm.

Example VI

[0023] The coating for the cast steel was obtained as follows:

• to water at 22% by weight, bentonite at 0.7% by weight was added and stirred for 15 min,
• An aqueous solution of 55% aluminium polyphosphate at 6% by weight was then added and further stirred for 10 minutes,
• Finally, zirconia meal was added at 71.3 per cent by weight and the whole mixed until completely homogenised.

[0024] The ingredients were mixed at 600 rpm.

Example VII

[0025] The coating for the cast steel was obtained as follows:

• to water at 20% by weight, bentonite at 3% by weight was added and stirred for 15 min,
• An aqueous solution of 70% aluminium polyiforate at 4% by weight was then added and further stirred for 10 minutes,
• followed by the addition of iron red at 2 wt% and stirring for 15 minutes,
• Finally, zirconia meal was added at 71% by weight and the whole was mixed until completely homogenised.

Claims

1. Heavy casting coating based on zirconium meal (Zirconium silicate), characterised in that it consists of zirconium meal in an amount of 50 to 75 per cent by weight, water in an amount of 18 to 25 per cent by weight, an aqueous solution of aluminium polyiforphate in a concentration of 40 to 70 per cent in an amount of 2.5 to 7 per cent by weight and bentonite in an amount of 0.2 to 2.0 per cent.

2. Coating according to claim. 1, characterised in that it contains iron red in an amount of 1 to 3% by weight.

3. Coating according to claim. 1, characterised in that it contains graphite in an amount of 3 to 10% by weight.

4. Coating according to claim. 1, characterised in that, for use on iron castings, it contains zirconium meal in an amount of 50 to 70% by weight.

5. Coating according to claim 1, characterised in that, for use on steel castings, it contains zirconium meal in an amount of 60 to 75% by weight.

6. Coating according to claim. 1, characterised in that the bulk components have a fineness of 160 to 220 mesh.

7. Coating according to any of the claims. 1 to 6, characterised in that the density of the coating is 1.9 to 2.29 g/cm³.

8. Coating according to any of the claims. 1 to 6, characterised in that the viscosity of the coating is 30 to 60 s.

9. Method for the manufacture of a coating for heavy castings, in particular of cast iron and cast steel, as follows: to water in an amount of 18 to 25% by weight, bentonite in an amount of 0.2 to 2% by weight is added, followed by mixing for 10 to 30 min, after which an aqueous solution of aluminium polyiforate of 40 to 70% by weight in an amount of 2.5 to 7% by weight is added and further stirred for 10 minutes, followed by the addition of zirconium meal in an amount of 50 to 75% by weight and, after the last component is added, the whole is stirred until completely homogenised.

10. Method according to claim. 9, namely that iron red in an amount of 1 to 3% by weight is added to a mixture of water, bentonite and an aqueous solution of aluminium polyphosphate and stirred for 10 to 15 minutes.

11. Method according to claim. 9, characterised by the fact that graphite in an amount of 3 to 10% by weight is added to the mixture of all components and mixed until completely homogenised.

12. Method according to claim. 9, characterised by the fact that zirconium meal in an amount of 50 to 70% by weight is used to prepare the coating for iron castings.

13. Method according to claim. 9, characterised by the fact that zirconium meal in an amount of 60 to 75% by weight is used to prepare the coating for steel castings.

14. Method according to claim. 9, characterised in that the bulk ingredients have a fineness of 160 to 220 mesh.

15. Method according to claim. 9, characterised in that the stirring speed is between 500 and 700 rpm.