SU1077950A1 - Method for producing protective coating - Google Patents

Abstract

A METHOD FOR PREPARING A PROTECTIVE COATING, mainly on rolled products of copper and its alloys, including surface treatment in an aqueous solution of boric acid or its salt and drying, characterized in that, in order to improve the quality of the coating, reduce the consumption of chemicals, current density of 540 A / dm for 1-20 s. (/)

Description

The invention relates to non-ferrous metallurgy, in particular to methods for producing coatings used to protect non-ferrous metal rolling from oxidation during heat treatment in an oxidizing atmosphere, and can be used in continuous heat treatment lines. Borate coatings are known to protect copper alloys from oxidation during heat treatment, obtained from aqueous solutions of boric acid or its salts ft}. However, due to the presence on the surface of the copper and alloys based on it so-called carbon black deposits, which are formed during the thermal decomposition of the lubricant in the deformation zone during cold rolling, boric acid does not wet the surface. To ensure wetting of the surface, the rolling is subjected to ogistko in organic solvents, degreased in alkaline solutions or emulsifiers and additives to an aqueous solution of boric acid are used. The closest to the proposed technical essence and achievable results is a method of obtaining a borate coating for copper-based alloys, including the application to the surface of rolling by rolling or spraying a hot 2 to 27% aqueous solution of boric acid or borate containing a wetting agent lis-floor and zinc oxide, and drying to a hard coating {2}. A significant amount of impurities (0.45 g / m) remaining on the surface of the car during the application of boric acid or borate solution prevent the formation of a uniform continuous borate coating, which leads to oxidation of the alloys during heat treatment. In addition, the toxicity of the wetting agent (Lisapol), which requires special equipment to neutralize it, and the increased consumption of chemical reagents lead to an increase in the cost of the finished product. The aim of the invention is to increase the quality of the coating and reduce the consumption of chemical reagents. The goal is achieved by the fact that according to the method of obtaining a protective coating, preference is given to rolling copper and its alloys, including surface treatment in an aqueous solution of boric acid or its salt and drying, processing is electrolytically at a current density of 5-40 A / dm within 1-20s. Increasing the continuity and uniformity of the coating is achieved by improving the wettability of the rolled surface with borate solution. During the polarization of the processed strip with direct current to the hydrogen evolution potentials in a 2-27% solution of boric acid or in a 3.5-24% solution of N878407 at 30-80 ° C, as a result of the reactions occurring on its surface, removal of non-metallic films and wear particles of the rolls and strip. Improving the wettability is accompanied by a more uniform spreading of the borate solution over the surface of the car when it leaves the bath and the formation of a thinner and more solid coating after drying, which protects the car from oxidation during the heat treatment process. 25 samples are tested (by the known and proposed methods) of L-68, L-63, L-90 brass, MOI alloy and MO copper with dimensions of 50x150 mm and 0.1-0.2 mm thick, obtained by cold rolling. The amount of impurities in the form of residues of emulsion and wear products of rolling rolls and strip, determined by the gravimetric method by double treatment with trichlorostilen, is 0.9-2.2 g / m. In the initial state, the samples are not moistened with 2-27%, the solution of NZOZ and 3.5-24% solution of N823407 at 3080 ° С. The technological operations of testing the samples are given in Table. 1. Table 1

The composition of the solution,%

Callback

Emulsifier (OP-7 analog

lipasol)

Zinc oxide

N328407 Solution temperature, С

2-27

3.5-24 30-80

Indicators

Cathode or anodic cathode polarization by external current, A / dm Processing time, with Drying temperature, C Drying time, with heat treatment temperature in a muffle furnace, With heat treatment time, min. Rinse time with cold water, with Air drying time, with

The continuity of the coating oueHHsaHrr after heat treatment of the samples and removal of the protective coating by inspection under a microscope MBS-9 with increasing X50, the number of oxides by the gravimetric method. The adhesion of the borate coating is determined by a net incision method.

In tab. 2 shows examples of coating. GTable II 2

Copper, brand MO

40

Number of impurities after boronization, g / m (mass of rolling lubricant and wear products)

The mass of the film borate in terms of grit, g / cm

The number of samples on which full wettability was achieved after borization

Continued tab. -one

tnoco6

3 known T proposed

5-40

1st

105 20

450-650

650 0.5-5

15 20

Continued table. 2

10 10

10 15

Note: The coating is uniform, there are no oxides on the car.

35

In tab. 3 shows the results of the original coatings obtained by the known and proposed methods.

Table 3

0.45 ± 0.04 Not detected

0,001-0,002 0,0008-0,001

25

1 1 Number of samples with poor adhesion of borate coating

Number of samples with spots of oxides after boronation and heat treatment As can be seen from the above data, the proposed method of obtaining a protective coating on rolled metal from copper and its alloys provides high quality coatings that protect the car from oxidation during heat treatment. The absence of emulsifiers and additives in borate solution. and also decrease in thickness

23

Not

23 covers in comparison with the known method reduces the consumption of chemical reagents. The expected economic effect from the introduction of the method will be 48 thousand rubles. for one heat treatment line.

Claims (1)

METHOD FOR PRODUCING PROTECTIVE COATING, mainly on rolled products from copper and its alloys, including surface treatment in an aqueous solution of boric acid or its salt and drying, characterized in that, in order to increase the quality of the coating,> reduce the consumption of chemical reagents, the processing is carried out electrolytically at a current density of 540 A / dm ² for 1-20 s. > 1077950 2