EA028006B1 - A mixture for saturation of corrosion-resistant steel parts with carbon and chromium - Google Patents

Abstract

The invention is related to the field of metallurgy, in particular, to combined chemical and heat treatment, and can be used for production of diffusion-strengthened steel parts having higher durability in operation under wearing conditions. The objective of the invention is increasing the zone of carbide inclusions in the cemented layer and diffusion saturation of corrosion-resistant steels, which will extend service life of the parts. Said objective is attained by provision of mixture for saturation of corrosion-resistant steel parts with carbon and chromium containing chromium and Bondiuzhsky carburizer that further includes tin chloride and sodium hydrocarbonate with the following proportion of components, wt.%: chromium - 30-35; Bondiuzhsky carburizer - 50-55; tin chloride - 2-4; sodium hydrocarbonate - 10-15.

Description

The invention relates to the field of metallurgy, and in particular to chemical-thermal treatment (XTO), and can be used for the manufacture of diffusion-hardened steel parts having increased durability during operation in conditions of wear.

A known mixture for saturation of steel products [1], containing the following components, wt.%: Coke - 85, soda - 15.

With CTO in this composition, on corrosion-resistant steels, diffusion layers of uneven thickness are formed without a surface carbide zone, having a dark layer on the surface that is easily removed by scraping.

A known medium for the corbochromation of steel parts [2], adopted as a prototype, containing the following components, wt.%: Chromium - 50-65; Bondyuzhsky carburetor - 0.3-1.0; ammonium chloride - 15; aluminum oxide - the rest.

During diffusion saturation of corrosion-resistant steels, a uniform diffusion layer is formed from this mixture with a zone of carbide inclusions on the surface, which provides high wear resistance.

However, when using this mixture for hardening parts in which wear greater than 0.0.2 mm is allowed (thickness of the zone of carbide inclusions), the parts have a short service life.

The problem solved by the invention is to increase the thickness of the zone of carbide inclusions in the diffusion layer during saturation of corrosion-resistant steels, which will increase the life of the parts.

The problem is solved in that tin chloride and sodium bicarbonate are additionally introduced into the mixture containing chromium, the Bondyuzh carburetor in the following ratio of components, wt.%: Chromium - 30-35; Bondyuzhsky carburetor - 50-55; tin chloride - 2-4; sodium bicarbonate - 1015.

During diffusion saturation, the oxide film located on the surface of the steel prevents the diffusion of carbon atoms deep into the steel. The introduction of tin chloride in the mixture allows you to destroy the oxide film on the surface of the steel and create a liquid metal layer, which prevents the further formation of oxides. The plating mixture supplies additional chromium atoms to form a diffusion layer. Sodium bicarbonate reduces the oxidizing ability of the mixture.

Example. Samples of 06x1949t steel 10x10x40 in size were placed in the center of a steel crucible with a diameter of 50 mm and a height of 150 mm and filled with a mixture for diffusion saturation. A fusible shutter was created on top of the crucible based on sand and boric anhydride; the crucible was placed in a furnace heated to 1050 ° С and held for 6 h. After saturation, the samples were removed from the crucible and subjected to metallographic studies, the results of which are presented in the table.

No. experience The composition of the mixture, wt. % Zone Thickness carbide inclusions in diffusion layer, microns Bondyuzhsky carburizer Bicarbonate sodium Powder chromium Chloride tin one 55 10 33 2 80 2 fifty fifteen 31 4 70 3 54 thirteen thirty 3 80 4 fifty 12 35 3 90 5 61 nine 29th one 25 6 43 sixteen 36 5 thirty Prototype: Chrome 50 - 65%, Bondyuzhsky carburetor 7 0.3 - 1%, ammonium chloride 1-5% oxide twenty aluminum rest

The data in the table indicate that when using the claimed composition of the mixture (experiments 1-4) after diffusion saturation under conditions identical with the prototype, the thickness of the zone of carbide inclusions is 70-90 microns. When using the mixture adopted for the prototype (experiment 7), the thickness of the zone of carbide inclusions does not exceed 20 microns. When using mixtures, the ratio of components of which goes beyond the declared composition (experiments 5-6), the thickness of the zone of carbide inclusions decreases.

Sources of information taken into account when preparing the application:

1. Cementation of chrome stainless steel. HELL. Shipilov, V.G. Mikheev. MITOM No. 6, 1962, p. 55-56.

2. USSR Author's Certificate No. 956615, publ. 09/07/1982 Bull. No. 33, N.N. Mitrokhovich, B.N. Pankin, V.P. Fetisov. Carbochromizing medium for steel products.

Claims (1)

CLAIM The mixture for saturating steel parts from corrosion-resistant steels with carbon and chromium, containing chromium, Bonduge carburizer, characterized in that it additionally contains tin chloride and sodium bicarbonate in the following ratio of components, wt.%: Chromium - 30-35; Bonduge carburizer - 50-55; tin chloride - 2-4; sodium bicarbonate - 10-15.