BG3469U1 - Composition of powder medium for nitriding of steels - Google Patents

Abstract

The utility model relates to the composition of a powder medium for the chemical-thermal treatment of metals, in particular for the nitriding of steels in a solid medium, and finds application in metallurgy and mechanical engineering for the surface modification of components and products, including those operating in conditions of wear-and-tear and corrosion. The created powder medium for nitriding of steels includes nitrogen-containing agent and activator, as the nitrogen-containing agent is crushed nitrided metallic manganese with nitrogen content over 7% and size less than 0.4 mm, and the activator is ammonium chloride with size less than 0.2 mm, and the ratio of components in weight percent is nitrogen-containing agent - from 95 to 98, activator - from 2 to 5.

Description

Field of technology

The utility model relates to the composition of a powder medium for chemical-thermal treatment of metals, in particular for nitriding of non-alloy and alloy steels in a solid medium and is used in metallurgy and mechanical engineering for surface modification of parts and products, including those operating in conditions of wear and corrosion.

BACKGROUND OF THE INVENTION

Nitriding is part of the chemical-thermal treatment of metals and alloys and is a surface diffusion saturation. Nitrogen is the purpose of obtaining a nitrided layer, which increases the hardness, strength, wear resistance and corrosion resistance of the surface of the treated metal parts.

Nitriding of steels is performed in different nitrogen-containing media - gas, liquid, solid or plasma, in the temperature range 400-1000 ° C depending on the method and the environment.

The gaseous medium is most often used in the nitriding of steels. This is a medium of ammonia, which at process temperatures dissociates is the release of active nitrogen. The active nitrogen is adsorbed on the surface of the steel and diffuses to a depth, whereby a nitrided layer is obtained, certain characteristics depending on the process parameters. The main disadvantage of this environment is its high toxicity and the need for specialized equipment to regulate its parameters. This makes the process more expensive and increases the cost of machined parts.

Plasma nitriding is a high-tech process that takes place in vacuum furnaces in which a medium of nitrogen and hydrogen or ammonia is ionized in a glow discharge on the surface of the workpiece. Plasma nitriding requires complex and expensive equipment, which makes the process expensive and inefficient in small-scale production.

As a liquid medium for nitriding steels, a melt of salts containing cyanides and cyanates, which are highly toxic, is used.

As a solid medium for nitriding steels, compositions containing inorganic and organic nitrogen-containing compounds are used, which emit active nitrogen when heated to the temperatures of the process. Nitriding of steels in solid media is more technologically accessible and does not require specialized equipment, but the known solid nitriding media cannot provide uniform distribution of nitrogen in the medium and cannot maintain the required saturation capacity for a long period of time, which leads to unevenness of the nitrided layer, and hence to reduce the quality of the details.

U.S. Pat. No. 4,119,444 discloses a solid steel nitriding medium consisting of vermiculite, pre-soaked in an aqueous urea solution and then dried. When packing the parts in containers, part of the vermiculite breaks, and since the urea is only on the surface of the vermiculite, this leads to an uneven distribution of nitrogen in the enrichment medium. In addition, this solid steel nitriding medium depletes rapidly, making its use in nitriding processes inefficient for more than 8 hours.

CN 103045992 (A) discloses a solid nitriding composition for steels which includes in percentages by weight the following components: 35% urea, 5% ammonium bicarbonate, 10% charcoal over 0.15 μg and 50% graphite. Urea is the nitrogen-containing component, ammonium bicarbonate is the activator, charcoal is the oxygen-absorbing component, and graphite is the filler. Charcoal acts as an oxygen scavenger and, together with graphite, reduces the adhesion of the mixture to the surface of the parts. However, this medium cannot provide high saturation capacity for a long period of time, which makes it unsuitable for nitriding processes for a long time. At process temperatures, urea turns into a molten state, which makes it difficult to distribute it evenly in the environment and leads to uneven nitriding of the surface of the parts. The low relative weight of graphite and charcoal and the high relative share in the environment and their low relative weight lead to strong dust in the air in the workplace and create an unhealthy working environment.

5719 Descriptions to utility registration certificates № 03.1 / 16.03.2020

Technical essence of the utility model

The task of the utility model is to create a composition of solid medium for nitriding of steels, which provides long-term high saturation and even distribution of the nitriding agent, does not stick to details, is not highly toxic and its use does not lead to excessive dusting. of air in the workroom. Another task of the utility model is to create a nitriding environment that is low cost and its use does not require specialized equipment to reduce the cost of nitriding and the process is efficient and when processing single or small batches is a different size and configuration.

The problem is solved by creating a composition of powder medium for nitriding of steels, which contains in weight percent from 95 to 98% crushed nitrided metallic manganese with nitrogen content over 7% and size less than 0.4 mm and from 2 to 5% ammonium chloride (NH ₄ Cl) is less than 0.2 μg in size, which acts as an activator.

Advantages of the composition for powder medium for nitriding of steels according to the utility model are that it has a high saturation ability in nitriding processes is long duration, provides uniform distribution of the nitriding component in the medium, no warming and sticking of the powder medium on the surface of the treated details, it is not highly toxic and its use does not lead to excessive dust in the air in the workplace and does not create an unhealthy working environment, its use does not require complex and expensive equipment. Another advantage of the powder medium, according to the utility model, is the possibility of the nitrogen-containing component to be used repeatedly, since the spent medium is deazonized to a certain extent crushed metallic manganese, which can be subjected to subsequent nitriding and then reused in the composition. powdered medium for nitriding steels. This reduces the cost of nitriding steels, making this powder medium particularly suitable for small machine-building enterprises that produce single or small series and non-standard parts.

Examples of implementation of the utility model

The utility model is illustrated by several exemplary embodiments of compositions (in weight percentages): Composition 1% finely divided nitrated electrolytic manganese with a content of 7.65% nitrogen and a size less than 0.4 μm, and 2% ammonium chloride is a size less than 0.2 shsh.

Composition 2% finely divided nitrided electrolytic manganese with a content of 7.16% nitrogen and a size of less than 0.4 μm, and 5% ammonium chloride is a size of less than 0.2 μm.

The pre-ground components are mixed and homogenized, after which the medium is ready for use.

Using the utility model

The parts are placed in steel containers of suitable dimensions and are packed in advance with a well-homogenized powder medium, which envelops them tightly on all sides. The containers are then sealed and heated in an oven to a temperature in the range of 530 ° -700 ° C for 10 to 90 hours, depending on the desired characteristics of the nitrided layer. After completion of the process, the parts are removed from the containers, and the spent medium, which is deazonized to some extent crushed metallic manganese, can be subjected to subsequent nitriding, and then again used as a nitrogen component in the powder medium for nitriding steels, according to the useful model.

When nitriding steel parts 45 is a powdered nitriding medium according to composition 1 at a temperature of 580 ° C for 20 hours, a nitride layer is obtained at a depth of 3-4 ppm.

When nitriding steel parts S235 is a powdered nitriding medium according to composition 2 at a temperature of 700 ° C for 90 hours, a nitride layer is obtained with a depth of 8-10 μηι.

Claims (1)

5720 Descriptions to utility registration certificates № 03.1 / 16.03.2020 Claims Composition of a powder mixture for nitriding steels, comprising a nitrogen-containing agent and an activator, characterized in that the nitrogen-containing agent is crushed nitrided metallic manganese with a nitrogen content of more than 7% and a size of less than 0.4 mm, and the activator is ammonium chloride with a size of less than 0.2 mm, the ratio of components in weight percent is: nitrogen-containing agent - from 95 to 98, activator - from 2 to 5.