SU897892A1 - Medium for complex saturation of steel articles - Google Patents

Description

(54) ENVIRONMENT FOR COMPLEX SATURATION OF STEEL PRODUCTS

one

 The invention relates to the chemical-heat treatment of steels in powder media, in particular to the complex diffusion saturation of the surface with chromium, titanium, nitrogen and carbon, it can be used in the engineering, metallurgical and instrument-making industries.

Known medium for chromotitanation (titanochroming), containing, May. %

Titan-25

Chrome2 5

Aluminum oxide 48

Sodium fluoride 2 Saturation is carried out for 9 h at 110-0 ° C. The titanium-chromium layer on steel grade 45 has a thickness of up to 0.436 mm. The hardness of the outer zone is 2500-2200 kgf / mm according to Vickers. At a depth of 0.376 mm, the hardness of the layer decreases to 210 kgf / mm. The layer structure consists of titanium carbides and a solid solution of chromium in iron. High hardness slol provides satisfactory wear resistance 1.

However, the titanium-chromium layer under increased mechanical loads is forced through, since under the: carbide layer there is a decarbonized layer with a thickness of up to 0.24 mm, drastically reducing the performance properties of the products.

The closest to the invention is a medium for chromotitanation, containing powders of chromium and titanium in a ratio of 2: 1, alumina

10 and halogen .activator. The thickness of the chromotitanated layer on steel with a carbon content of 0.6% reaches

0.035 mm. Its hardness over the entire depth is 4000 kgf / mm in Vickers. Layer structure - monocarbide

15 titanium alloyed with chromium. The decarburized sublayer is missing. The diffusion layer has a high wear resistance 2.

20

However, low heat resistance and high brittleness of the layer limit the possibilities of using the medium.

The aim of the invention is to increase the WEAR RESISTANCE and heat resistance of the diffusion hub.

This goal is achieved by the fact that the medium for the chemical and thermal treatment of steel products containing chromium, titanium, halogen activator, alumina, contains a solvent 30

but blood salt, and as a halogen activator - ammonium chloride in the following ratio of components, May.%

Chrome 40-60

Titan14-20

Ammonium chloride 1-3 Yellowing salt for 1-3 Alumina Rest The medium for chemical heat treatment is prepared as follows: All powdered components of the medium are calcined (dried) for 2 hours: chromium at 800-1000 ° С, titanium at 150 ° С ammonium chloride at, yellow blood salt at 100 ° C, alumina at 800-1000 ° C. Then the components are thoroughly mixed and the medium used for its intended purpose.

For chemical heat treatment, stainless steel containers with a hermetic closure are used. Processed products of 4H5MFS steel are placed in a container with the proposed medium and the container is placed in an electric oven heated to. After 2 hours, the furnace temperature is raised to and the container is kept for 3.5 hours. After the end of the exposure, the container is cooled in air to room temperature, and then unpacked. Before each subsequent heat treatment, the medium is enriched with yellow blood salt in an amount of 0.2-0.8 wt.% And ammonium chloride 0.2-0.8 wt.%. The composition of the medium is presented in table. one.

The content of chromium and titanium in the medium is determined by the condition of simultaneous diffusion of chromium and titanium into steel, which is observed | only with the proposed content of the named components. The lower limit of the content of yellow blood salt is determined from the condition that the required amount of nitrogen and carbon is formed in order to pass diffusion into steel. Increasing the content of the yellow blood salt CBHLUB 3 wt. The content of ammonium chloride (1-3 wt.%) In the medium provides a sufficient activation of diffusion processes. The addition of alumina to the medium up to 100 wt.% Provides inconsequence average.

The results of the study of the diffusion layer after saturation with chromium, titanium, nitrogen, carbon are given

5 in the table. 2

Chemical-thermal treatment in the proposed medium leads to the formation of a diffusion layer with a thickness of up to 0.017 mm. . Hardness of a layer to 3260 kgf / mm according to Vickers. The wear resistance of the layer after chemical-heat treatment is 1.5-2 times higher than the wear resistance of the layer formed in a known medium. The treatment in the proposed medium ensures an increase in the heat resistance of the layer in comparison with the treatment in the known medium by a factor of 2.5-3.7. In addition, after treatment in a known medium, an underlayer with a low hardness (up to 380 kgf / mm in Vickers) is formed under the carbide layer, as a result of which the carbide layer is forced under increased mechanical loads. After processing in the proposed medium under the carbide layer, a reinforced sublayer with a hardness up to 940 kgf / mm according to Vickers is formed. Such a more even distribution of hardness ensures the greatest increase in operational performance.

0 durability of products.

Table 1

less than the proposed content

Offered

40 50 60 1 2 3

0.8

Rest

0.8

13

Rest

14 17 20

Rest

With the content of the components above, we offer the Continuation of the Table. one

table 2

Claims (1)

Claim A medium for complex saturation of steel products containing chromium, titanium, a halide activator and aluminum oxide, characterized in that, in order to increase the wear resistance and heat resistance of the diffusion layer, it additionally contains a yellow blood salt as a halide activator - ammonium chloride, wt.% Chrome 40-60 Titanium 14-20 Ammonium Chloride 1-3 Yellow Blood Salt 1-3 45 Alumina Else