SU1742356A1 - Chemical treatment of metal articles - Google Patents

Abstract

Use: for chemical polishing of titanium products. Essence: the method involves etching and polishing products in a solution of acids — with intermediate and final washings in water, the process is carried out in a chamber equipped with a system for catching toxic emissions, the products are placed in a container with water, the chamber is sealed and blown with water pressure 1.1-1.3 atm, and before washing the product is blown with water vapor. 2 of FIG.

Description

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The invention relates to the technology of chemical processing of products from non-ferrous metals and can be used in mechanical engineering.

Advantageously, this invention is intended for chemical polishing of titanium products.

The known method of chemical polishing of titanium products, including preliminary etching in a solution of sulfuric, nitric, hydrofluoric and hydrochloric acids, with washing in water and polishing in an aqueous solution of nitric, sulfuric and hydrofluoric acids, heated to a temperature of 80-90 ° C, followed by washing in water in acid-resistant baths (see, for example, S. Grikhiles, Electrochemical and Chemical Polishing - L .: Mashinostroenie, 1987, pp. 149).

The disadvantages of this method are the release of a large number of harmful emissions.

The presence of harmful emissions is due to the fact that in the process of preliminary etching and polishing toxic oxides and vapors of acids are released. Carrying out the polishing process at elevated temperatures increases the volume of evaporating vapor, the catch of which is difficult and requires bulky and expensive equipment.

The closest in technical essence and the achieved result to the invention is a method of chemical polishing of titanium products, including preliminary etching in an aqueous solution of hydrofluoric, nitric and hydrochloric acid moistening with water, and polishing in a solution of hydrofluoric and nitric acid, followed by washing in water in acid-resistant baths located in a chamber communicated with a system for catching toxic emissions (see the Standard Technological Regulations VI N K W SL

ON

the mechanical process of mechanical and chemical polishing of titanium tubes).

The disadvantages of this method are the presence of toxic emissions.

The presence of toxic emissions due to the rapid release of harmful oxides and vapors, due to the exothermicity of the reaction. A more complete catch of vapor generated requires expensive equipment, which results in toxic emissions in existing systems,

The aim of the invention is to reduce the toxicity of emissions.

This goal is achieved by the fact that in a known method involving etching and polishing acid solutions with intermediate and final washings in water, the process is carried out in a chamber equipped with a system for catching toxic emissions, according to the invention, the product is placed in a container with water. pressurized and blown off with steam at a pressure of 1.1-1.3 atm, and before washing the product is blown off with steam.

This allows you to completely prevent harmful emissions into the environment. Pre-purging of the sealed gas meters and blowing the products after etching and polishing with water vapor allow the removal of inert gases from the system, which worsen the conditions of condensation of the toxic vapors formed intensively during the reactions. As a result, the toxic emissions that are generated have a nearly 100% concentration and are easily absorbed by water.

FIG. 1 is a schematic diagram of an installation for implementing the proposed method; FIG. 2 is a sectional view of a work lamer.

The installation includes a working chamber 1, i of which is a rotary table 2 with etching baths 3, polishing 4 and water baths 5, 6. The working chamber 1 is equipped with a lifting device 7 for hanging and vertically moving the basket 8 with articles, a water supply pipe a pair of 9 with a valve, a vacuum tube with a meter 10 and communicated through a chimney 11 with a condenser. The condenser is a two-stage system comprising a reflux condenser 12 and a mixing condenser 13. The reflux condenser 12 consists of an ejector 14 that communicates through the valve 15 with the system, extract the condensate cooling system 15 and the barometric pipe 17 connected to the condenser mix 13. Condenser

mixing 13 consists of a tank 18 equipped with a level gauge 19, a drain pipe 20, a pipe exhaust sampling 21 and a spray system including

a perforated disk 22 and a fluoroplastic filter 23. The condensate cooling system consists of a cooler 16 and a centrifugal pump 24 communicating with the tank 18 of the mixing condenser 13.

0 The method is carried out as follows.

The basket 8 with titanium products is suspended on the lifting device 7 and immersed in a bath 5 with water. Preliminary

5, placing the products in a water bath allows them to cool and prevent them from heating during the steam flushing process, which reduces the absolute amount of emissions due to the decrease in the temperature of the etching and polishing processes. The working chamber 1 is sealed. The tank 18 is filled (by opening the valve 15) with water from the mixing condenser 13. The centrifugal pump 24 is turned on and the cooled pipe 17 is irrigated

5 fluid. Chamber 1 is flushed through steam pipe 9 with saturated steam at a pressure of 1.1-1.3 atm, thereby injecting inert gases from the system. When purging with steam pressure of more than 1.3 atm,

Due to the high temperature, the intensity of vaporization of the mixture of acids increases, and at a pressure of less than 1.1 atm, the process of removing inert gas from the chamber is delayed. The basket 8 is removed from 5 baths from the bath 5 with water and the turntable 2 is moved to the bath 3 with the pickling solution. The basket 8 is lowered into the bath 3. After the etching process, the basket 8 is removed from the bath 3 and

0 rinsed with steam. The basket 8 is immersed in a bath 6 with water. Then, by dipping the products in the bath 4, polishing is performed. Steam basket blowing 8 heats the products and evaporates with

5 their surface residues of acids. The vapors released in the polishing and etching processes are discharged through the chimney 11 due to the pressure difference in the working chamber 1 and the barometric pipe 17 to the first stage of condensation — the irrigation condenser 12, which is carried along by the water jet. The non-condensed vapors are discharged into the mixing condenser 13, which is the second condensation stage. Steam flow

5, the passage through the perforated disk 22, the layer of fluoroplastic filter 23 is divided into separate bubbles that are mixed with water. The condensate cooled in the refrigerator 16. is injected with a centrifugal pump 24 into the ejector 14.

The replaceable capsule of the adsorbent at the sampling port 21 controls the amount of emissions to the environment. With an increase in the content of emissions, the height of the liquid column in the mixing condenser 13 is increased.

Products that have been washed in bath 5 are finally blown off with steam and thereby dried, while the working chamber 1 is cleaned of acid residues.

The advantage of the proposed method is illustrated by the following example of its implementation. Titanium tubes made of VT1-0 grade OST 190050- 72 with a diameter of 10 mm, a length of 100 mm and a wall thickness of 1 mm were used as polished products.

1. The composition of the etching, g / l:

HF - 96.7: NMOZ - 234; HCI - 779; water.

2. Composition for polishing, g / l: HF-322.35; HM03-981.5.

3. The temperature of the etching and polishing compositions is 20 ° C.

4. The temperature of the water for washing and cooling is 15 ° C.

5. Water vapor pressure is 1.1 1.3 atm.

6 Initial roughness Ra, micron - 0.82-0.91.

7. The final roughness Ra, microns - 0.13-0.2.

The research results of the proposed method allow to conclude that with the proposed method, compared with the known prototype method, toxic emissions into the environment are prevented.

Claims (1)

Invention Formula A method of chemical processing of metal products, including etching and polishing in solution of acids with intermediate and final washing in water, the process being carried out in a chamber equipped with a toxic emission catch system, characterized in that, in order to reduce the degree of toxic emissions, in a container with water, the chamber is sealed and blown with water vapor, at a pressure of 1.1-1.3 atm, and before rinsing the product is blown with water vapor.  EP7 FIG. 2