SU755891A1 - Boronizing composition - Google Patents

Description

The invention relates to the field of chemical heat treatment and can be used as a saturating medium for diffusion hardening of steel products in order to improve the wear resistance of the surface layers.

Known composition for borination,

containing the following Components, YU weight.%: > Boron carbide 58.0-64.0 Borax 10.0-13.0 Ammonium chloride 0.9-1.5 Sodium chloride 1.1-1.5 η 15 Iron powder Else [1].

This composition allows boration in an oxidizing environment without protective equipment.

The disadvantage of this composition 20 is the relatively low rate of formation of boride layers.

In addition, the presence of borax and sodium chloride in the coating increases its fluidity, and the presence of ammonium chloride as an activator in 25, due to the formation of a large amount of gaseous products, often leads to local burnout. thirty

Also known composition for boronation, containing the following components, wt.%:

Boron carbide 45-60

Boric anhydride 2-10

Sodium fluoride 5-10

Iron dross 25-40 [2],

Iron oxide (waste of forging production) and boric anhydride included in this composition require their preliminary grinding in vibratory or ball mills to a fraction size of 0.1-0.2 mm, which reduces the processability of the mixture and leads to its appreciation.

In addition, the disadvantage of this composition is that after the process of chemical-heat treatment on the hardened surface significant areas of sticking of the remnants of the mixture are formed. This is facilitated by the presence in the saturable mixture of such a low-melting component, as boric anhydride. Increased adhesion of particles leads to an increase in the complexity of cleaning the hardened surface.

The aim of the invention is to improve the manufacturability prepared3

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saturation of the mixture and the reduction of adhesion of the mixture on the hardened surface after the end of the process of chemical-thermal treatment.

The goal is achieved by the fact that the composition containing boron carbide and sodium fluoride is additionally injected with an abrasive-metal mixture (waste grinding and grinding production) in the following ratio of components, wt.%!

Carbide boron 45-60

Abrasive-metal mixture 35-52 Sodium fluoride 3-10.

A mixture of these components is applied as a plaster on the hardened surfaces, and in the future the process of chemical heat treatment can be combined with the heating process for heat treatment. Binder for coating is hydrolyzed ethyl silicate.

The proposed composition allows the process of thermal diffusion saturation in a conventional furnace oxidizing environment without protective equipment with long high-temperature exposure (1-20 h at 900-1100 ° C). The abrasive-metal mixture included in the proposed composition (waste of grinding and grinding production) has a fraction size less than 0.2 mm, which excludes its preliminary grinding before mixing.

According to chemical analysis data, an abrasive-metal mixture contains: a steel component of 3040%, an abrasive component of 50-70%, the presence of a mixture of 9-12% is established

.carbon.

³ It is known that carbon has non-stick properties, which largely eliminates the percentage of sticking on the steel surface. nosti. The diffusion layer at saturation of the proposed composition according to x-ray diffraction analysis consists of the phases ReB and Fe ₂ V.

Examples Thermal diffusion saturation was carried out from the proposed composition in plastering on samples of 5ХНМ and 45 steel with dimensions of 10x10x10 mm. Wash was prepared by mixing powder components (size ... 0.1-0.2 mm fraction) with hydrolyzed

20 ethylsilicate. Thick coating

4-5 mm was applied to the samples by dipping. After drying for 10–20 min at room temperature in air, the samples were placed in an electric furnace, heated to the temperature of the chemical heat treatment process, and kept for 4–8 h. The quenching was performed from the diffusion saturation temperature. With

g hardening coating was separated from the surface of the samples.

The results of the diffusion saturation of the samples of steel 45 and 5HNM are presented in table 1.

Table 1

No The composition of the coating, wt.% The duration of the process, h Layer thickness at a process temperature of 900 ° C, microns Carbide bora Sodium fluoride Abrasive metal mixture Steel 45 Steel 5ХНМ Ϊ 45 3 52 four 170 148 eight 224 209 2 52 b 42 four 179 160 eight 230 220 3 60 ten 40 four 182 169 · eight 240 220 four 60 five 35 four 180 165 eight 235 220

Components for saturation of the mixture were used in the following form: technical boron carbide GOST 3647-71 and 5744-74, sodium fluoride of the brand "Ch" GOST 4463-66; abrasive-metal mixture - powdered.

With saturation of the composition (60% 60

B4C, 30% iron oxide, 5% B ₂ 0 ₃ ,

5% of Mac), taken as a prototype, at 900 ° C in 4 hours a boride layer 160 μm thick was formed on 5HNM steel. The results of measuring the thickness of diffu 65

sultry layers after carrying out the processes of chemical-heat treatment indicate that the saturability of the proposed composition is not inferior to the saturating ability of the composition adopted for the prototype.

The results of the tests on the quantitative adhesion of the mixture on the hardened surface of steel 45 after the end of the process of chemical and thermal treatment are given in table. 2 (No. 1-4 - the proposed composition, No. 5 - the prototype).

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table 2 No Composition, wt.% The total area of the hardened surface exposed to sticking of particles,% one 45 В ₄ С + ИаР + 52 abrasive-metal mixture 12-15 2 52 В ₄ С + ИаР + 42 abrasive-metal mixture 10-15 3 60 В ₄ С + 5ИаР + 35 abrasive-metal mixture 8-10 four 60 В ₄ С + 1ОИаР + 40 abrasive-metal mixture 10-12 five 60 VDS + 5V2O3 + zo iron oxide 35-45 Preparation rich mixtures

five

ten

20

25

15

from the composition, taken as a prototype, includes the following operations: weighing, crushing iron oxide, sieving the mixture through a sieve with a cell, not more than 0.2 mm, mixing the composition. In the described composition, the technological operations of crushing the scale and sifting the mixture are excluded.

The use of the proposed composition for thermal diffusion saturation ·

In comparison with the known compositions, steel products provide the ability to carry out the process in a conventional furnace environment without using special protective equipment, improving the processability of preparing the saturating mixture, reducing the sticking of the mixture on the hardened surface after the end of the process of chemical heat treatment, combining diffusion hardening of large-sized products with their heating for hardening.

Claims (1)

Claim Composition for boronation, containing boron carbide and sodium fluoride, characterized in that, in order to improve the processability of preparation of the dry mixture and reduce sticking of the mixture on the hardened surface after the end of the process of chemical-heat treatment, it additionally contains abrasive-metal mixture in the following ratio of components .%: Boron carbide 45-60 Abrasive-metal mixture 35-52 Sodium fluoride 3-10.