Method of manufacture of cylindrical articles provided with wear-resistant coats

FIELD: foundry, centrifugal casting in particular; manufacture of multi-layer vessels, pipe lines, bottles, connecting parts and other articles.

SUBSTANCE: proposed method includes placing the thermit mixture in cavities of article, followed by rotation, initiating of exothermic reaction, melting of thermit mixture, cooling of external surface of article and crystallization of molten thermit mixture. Thermit mixture contains additionally fluid material. Cooling of external surface of article is continued till temperature of its internal surface gets equal to melting point of metal of article.

EFFECT: reduced thickness of coat; improved control of heat removal.

 

The invention relates to foundry, in particular to the technology of centrifugal casting products with wear-resistant internal coating, and can be used in the manufacture of multilayer vessels, pipelines, tanks, fittings and other products.

A known method of manufacturing a pipe with a wear resistant inner coating (A.S. USSR №1678513, 22 D 13/02, publ. 23.09.1991), in which the pipe is placed in the mold, into the gap between the pipe and the mold asleep fraction in the cavity fall asleep thermite (a mixture of aluminium powder and Al oxides iron Fe2About3)set the mold in a centrifuge, rotating the mold, initiate an exothermic reaction, receive the molten thermite mixture, after crystallization which is formed of the wear-resistant coating.

The number of termite required for welding, determine the ratio

Pt=(0,9-1,1)P3,

where Rt- mass termite, kg;

P3- blank weight, kg

The experiments revealed that the upper limit on the mass of thermite mixture is limited by the heat absorption pipe and drumming, and the lower conditions of the exothermic reaction and the formation of high quality coatings. To exclude local melting of steel billets should reduce the amount of heat (thermite mixture), but the lack of heat (thermite mix) covered the e get loose, fragmented, i.e. poor quality.

The disadvantage of this method is to use the excess mass of thermite mixture and therefore the necessity to use fractions to sink.

The closest technical solution adopted for the prototype, is a method of manufacturing a pipe with an inner wear-resistant coating (A.S. USSR №804191, 22 D 13/02, publ. 18.02.1981), in which the pipe is placed in the mold, the gap between the mold and the pipe poured metal fraction, and additionally it condense in the tube cavity fall asleep thermite mixture, carry out the exothermic reaction during the rotation of the die, cooled outer surface of the chill mould.

The disadvantage of this method is the complexity of implementation of heat from the pipe metal fraction and cooling the outer surface of the die. When possible meltdown (burnout) pipe is fusion pipe and fractions, which makes it difficult to eject from the die. Excess weight thermite mixture degrades the quality of the pipes and increases the cost of the wear-resistant coating.

The technical problem solved by the invention is to reduce the complexity and cost of manufacture of products, improving the regulation of the heat sink and reduce the thickness of the coating.

The problem is solved due to the fact that in the method of manufacturing a cylindrical products with internal is it a wear resistant coating involving thermite mixture in the cavity of the product, its rotation, the initiation of the exothermic reaction, the melting of thermite mixture, cooling the outer surface of the product and crystallization of molten thermite mixtures according to the invention in thermite mixture impose additional flowable material, and cooling the outer surface of the product is carried out when the inner surface of the melting temperature of the metal product.

Reducing the complexity and cost is achieved due to the fact that the cylindrical article with a wear resistant coating made without the die and the fraction.

Improving the quality of the coating is achieved by direct heat from the surface of the product by cooling, in particular, the air-water mixture, reducing the mass of thermite mixture, introducing into thermite mixture of fusible (flowable) material (ETM), for example, magnesium, liquid, glass and other

The melting temperature of the glass and its derivatives in two times lower than the melt temperature of thermite mixture, therefore, increased fluidity ITM improves the quality of the coating and reduces the thickness of the wear-resistant coating.

Direct cooling of the outer surface of the product when the inner surface of the melting temperature of the metal b is more intensively to conduct heat away from the surface of the product in a controlled manner, to adjust the speed of crystallization of molten thermite mixture.

Regulation of the heat in an exothermic reaction allows to reduce the weight of thermite mixture.

To retain heat in the melt in the composition of thermite mixture is injected flowable material, which shields the molten thermite mixture and provides a time interval for crystallization of the melt without crystallization cracks, pores, gas and nonmetallic inclusions.

To ensure the quality of performance of the coating must satisfy two conditions: to receive the molten thermite mixture and to carry out its crystallization (cooling to a certain temperature). For initiating an exothermic reaction, the more reducing agent (aluminum or magnesium) in thermite mixture, the more intense is an exothermic reaction. Therefore, to obtain molten thermite mixtures possible in a shorter period of time, you must increase the percentage of reducing agent in thermite mixture.

Since the mass of thermite mixture is reduced relative to the mass products, introduces a low-melting component, which shields the molten thermite mixture. The increase of the period of crystallization of thermite melt allows you to equalize the thickness of the coating along the entire length of the product and to ensure its quality crystallization.

It is known that the combustion front thermite mixture is distributed with a certain velocity along the length of the product, so you need to get thermite melt mixture throughout the length of the product (to ensure uniform thickness of the coating) and its simultaneous crystallization. Thus, the reduced weight of thermite mixture prevents the melt procurement, to improve the content of reducing agent, providing a more intense passage of the exothermic reaction. Reducing heat in the cavity of the products, low-melt flowable material provides uniform crystallization of the melt along the entire length of the product.

The amount of flowable material (ETM) is determined from the following conditions. The experiments revealed that the coating thickness after crystallization of thermite melt approximately 9.2 and 10 times the ratio of the mass of thermite mixture to the weight of the processed product. And for shielding the main thermite melt should have a layer of melt ITM thickness of about 0.1-2 mm

A method of manufacturing a cylindrical products with a wear resistant internal coating is as follows.

Thermite mixture proposed composition (for example, the restorer Al or Mg, Fe2About3, liquid glass) in a specific weight ratio is placed in the cavity of the products, in particular, in the bands of the b pipe, installing the pipe in the device for rotation around the longitudinal axis. Rotate the pipe to distribute thermite mixture on the inner surface of the rotating pipe, initiate an exothermic reaction, after melting of thermite mixture is cooled outer surface of the pipe, for example, air-to-water mixture, while achieving its inner surface melting. Control the temperature of the outer surface of the pipe is performed by the pyrometer. The intensity of the heat sink regulate the pressure and composition of the supplied cooling the mixture, and therefore excludes fusion (burnout) pipe.

To retain heat in the melt used fusible material, for example, liquid glass, which is in the process of crystallization prevents the heat from the melt in the cavity. After solidification of the melt cooling pipe and its rotation is stopped.

The use of the proposed method of manufacturing a cylindrical products can reduce the cost and the thickness of the coating due to the lighter weight of thermite mixture and increase the fluidity of the melt, to improve the properties of the coating by controlling the crystallization of thermite melt, to avoid melting of steel billets, to reduce the complexity and time of deposition of the coating.

Using the proposed method it is possible to make the Tr who would wear resistant coating for pipelines, conveying abrasive and corrosive environments, multi-layered vessels, cylinders, connectors and components.

A method of manufacturing a cylindrical products with internal wear-resistant coating comprising placing thermite mixture in the cavity of the product, its rotation, the initiation of the exothermic reaction, the melting of thermite mixture, cooling the outer surface of the product and crystallization of molten thermite mixture, characterized in that thermite mixture impose additional flowable material, and cooling the outer surface of the product is carried out when the inner surface of the melting temperature of the metal product.



 

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