SU1468965A1 - Method of thermomechanical treatment of steel articles - Google Patents

Abstract

The invention relates to metallurgy, in particular to the chemical and heat treatment of steels and alloys, and can be used in mechanical engineering, energy, etc. The purpose of the intensification of the process of chemical-heat treatment of steel products. The method of chemical-heat treatment of steel products involves applying an iron layer with a thickness of 30-40 µm, heating to saturation temperature and aging in a saturating medium for 30-60 minutes, with the deposition of an iron layer and aging in an end-to-end medium repeated several times, the thickness of each subsequent layer of iron is reduced by 1.5-2.0 times. The method makes it possible to reduce the time required by dp for obtaining a diffusion layer on the surface of an article by 1.4-1.7 times. 3 tab.

Description

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The invention relates to metallurgy, in particular to the chemical and heat treatment of steels and alloys, and can be used in mechanical engineering, energy, etc.

The purpose of the invention is to intensify the process of chemical-thermal processing of steel products.

The method of chemical-heat treatment of steel products involves applying an iron layer with a thickness of 30-40 µm, heating to the temperature of saturation and aging in a pinching medium for 30-60 minutes, moreover, the coating of the iron layer on the surface and the exposure are repeated several times in succession this thickness of each subsequent layer of iron is reduced by 1.5-2 times.

Periodic deposition of iron on the surface of the processed product

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allows to reduce the total duration of the process of chemical heat treatment.

The method is carried out as follows.

The workpiece is placed in a saturation device, heated to saturation temperature and kept in a saturating medium at this temperature for 30-60 minutes. At the end of the exposure, a layer of iron with a thickness of 30-40 MKMi is applied to the treated surface, after which the product is again subjected to saturation at elevated temperature. The aging in a saturating medium and the deposition of iron on the surface of the product are repeated sequentially and repeatedly, with the thickness of each successive deposited layer of iron being reduced by 1.5-2 times.

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When the metal products surface is pressed, an increase in the concentration of the saturating element in the surface layer leads to a decrease in the chemical potential gradient and, consequently, to a decrease in velocity. saturation. Applying a thin layer of iron to the surface of the processed product helps to restore the gradient of the chemical potential of the saturating element to the initial level, as well as the diffusion of the saturating element into the deposited layer from

From the data presented in Table I, it can be seen that the proposed method, compared with the known method, allows more than a factor of 1.4-1.7 times to reduce the time required to obtain the required composition on the surface of the product of the diffusion layer. As a result, the residence time of products at elevated temperatures is reduced.

 saturated layer Thus, reaching-} 5 that allows you to avoid

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maintaining the maximum saturation rate as well as increasing the concentration of the saturating element throughout the depth of the diffusion layer.

Experimentally set20

(see Table 1) that to obtain the required depth and composition of the diffusion layer, the initial thickness of the iron layers applied to the surface should be 30-40 µm.

Example. 4XZEF steel and cementation of STU were nitrided. Four groups of samples of 30–30–5.0 mm each were made of each steel. The samples to be processed were placed in a stainless steel tube in a tubular furnace heated in the case of nitriding to 580 and before cementation Ammonia and natural gas were used as the medium. After heating to the saturation temperature, the samples were kept in a saturating medium for 40 min during nitriding and 30 min during cementation. Then, using vacuum evaporation, iron was applied to the samples with a thickness of 30 and 40 μm, respectively, on steel 4ХЗВМФ and СтЮ. The saturation and application of the treated surface of iron in the case of nitriding was repeated twice, and during cementation, five times. Dp of samples of the first group, the thickness of each subsequent sprayed iron layer was reduced by 1.4, the second — 1.5, the third — 1.8, and the fourth — 2.5 times.

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40

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brittle phases.

Tables 2 and 3 present the physic mechanical characteristics of the diffusion layers: microhardness, wear resistance and corrosion resistance.

Wear resistance was determined at a load of 3.5 kg by sliding in the inlet of gray iron breaths. The area of the rubbing surfaces was about 8 cm. The wear was taken into account by the weight loss of the samples with an accuracy of 0.1 mg when the sample was made 10 revolutions

Corrosion 1 ion resistance was determined by measuring the scaling resistance of the alloy at 200 hours.

It can be seen that for machined steels after treatment according to the proposed method, the physicomechanical characteristics are somewhat higher. This improves their performance.

Claims (1)

Invention Formula The method of chemical-thermal treatment of steel products, including the deposition of an iron layer with a thickness of 30-40 microns, heating to a saturation temperature and aging in a saturating medium for 30-60 minutes, characterized in that, in order to intensify the process of chemical-thermal processing , the deposition of an iron layer and the aging in a saturating medium are repeated successively several times, while the thickness of each, subsequent iron layer is reduced 1.5-2.0 times For comparison, nitriding and cementation of the same samples was carried out by a known method. The results are presented in Table 1. From the data presented in Table I, it can be seen that the proposed method, compared with the known method, allows more than a factor of 1.4-1.7 times to reduce the time required to obtain the required composition on the surface of the product of the diffusion layer. As a result, the residence time of products at elevated temperatures is reduced. which avoids the formation of five 0 0 five 0 five 0 brittle phases. Tables 2 and 3 present the physic-mechanical characteristics of diffusion layers: microhardness, wear resistance and corrosion resistance. Wear resistance was determined under a load of 3.5 kg by sliding in gray cast iron inserts. The area of the rubbing surfaces was about 8 cm. The wear was taken into account by the loss of the weight of the samples with an accuracy of 0.1 mg when the sample made 10 turns. The corrosion resistance to the ion resistance was determined by measuring the scale resistance of the alloy at 200 hours. It can be seen that for processed steels after processing by the proposed method, the physicomechanical characteristics are somewhat higher. This improves their performance properties. Invention Formula The method of chemical heat treatment of steel products, including the deposition of an iron layer with a thickness of 30-40 microns, heating to saturation temperature and aging in a saturating medium for 30-60 minutes, characterized in that, in order to intensify the process of chemical heat treatment, the deposition of an iron layer and the aging in a saturating medium are repeated successively several times, and the thickness of each, subsequent iron layer is reduced 1.5-2.0 times. T a b l and c a table 2