SU1715884A1 - Mixture for borating of steel products - Google Patents

Abstract

The invention relates to chemical heat treatment, in particular, to the process of thermal diffusion boronation in daubings, and can be used in various industries, in particular in railway transport, in hardening locomotive parts, whose assemblies operate under difficult conditions of increased abrasive-impact wear. The goal is to increase wear resistance by forming a single-phase boride layer with reduced brittleness and processability by eliminating the weldability of the coating. The composition contains 48-54% by weight of boron carbide, 8-10% by weight of sodium fluoride, 18-25% by weight of a PG-C27 grade filler powder and the rest is an abrasive-metal mixture. Wear resistance is increased by 2.5 times and the weldability of the coating to the surface of the parts is eliminated. 2 tab.

Description

The invention relates to chemical heat treatment, in particular, to a process of thermal diffusion boronation in coatings and can be used in various industries, in particular, in railway transport for hardening parts of locomotives, whose assemblies work under difficult conditions of increased abrasive impact wear and tear.

In the process of boring steel products, coatings are used that allow saturation in furnaces with an oxidizing atmosphere without the use of sealing containers.

Known coating for surface saturation with boron, containing boron carbide and sodium fluoride. The disadvantages of this coating are the instability of the boring results and the increased brittleness of the boride layer.

The closest to the invention is a coating (prototype) for boronization.

steel products containing boron carbide, sodium fluoride and an abrasive-metallic mixture.

The composition of the prototype coating is as follows. wt.%:

Carbide boron45-60

Sodium fluoride 3-10

Abrasive-metal mixture The remaining disadvantage of the known plastering is the brittleness of the boride layer and, as a result, the narrowing of the field of application of the coating, as well as the weldability of the mixture to the saturable surface.

The purpose of the invention is to increase the wear resistance of products by forming a single-phase boride layer with reduced brittleness, as well as processability by eliminating the weldability of the coating.

The goal is achieved by those. that a coating for boring steel products containing boron carbide, fluoride

with

with

01 00 00

four

sodium and abrasive-metal mixture, additionally contains powder surfacing PG-C27, in the following ratio, wt.%;

Boron carbide 48-54

Sodium fluoride8-10

Powder of surfacing PG-S2718-25 Abrasive-metal blendEverything The presence of boron carbide and sodium fluoride in the mixture in the indicated proportions makes it possible to obtain a stable process of saturation of steel products without reducing the brittleness of the boride layer.

A decrease in the boron carbide content below 48% leads to a decrease in the saturability, and an increase in its content of more than 54% leads to an increase in the weldability of the coating to the product.

With the introduction of sodium fluoride into the boron composition less than 8%, the saturation rate decreases, more than 10%, the oxidation of the tooling increases.

The surfacing granulated powder of the brand PG-S27 of the type PN-U40x28N2C2BM, which is part of, consists mainly of iron and also contains. %: chromium 25-28, manganese 0 | 8-1,5, silicon 1-2. Nickel 1.5-2, molybdenum 0.08, tungsten 0.2-0.4, carbon 3.3-4.5, which contributes to the formation of a single-phase boride layer having a lower brittleness compared to two-phase, resulting in increased wear resistance in conditions of abrasive impact wear, it also acts as an anti-stick protection, completely eliminating welding of the coating to a saturable surface, thereby improving the processability of the process.

A decrease in the content of PG-C27 powder below 18% leads to the formation of two-phase boride layers, an increase above 25% leads to an increase in weldability. . The addition of the composition of the abrasive-metal mixture increases the stabilization process. According to chemical analysis data, the abrasive-metal mixture (waste grinding and grinding production) contains 30-40% of iron oxides and other metals, 50-70% of abrasive particles and 8-12% carbon. In the process of saturation, the iron oxides interact with the liberated boron fluoride and form iron borides, which play the role of a frame material in the coating, preventing it from spreading over the treated surface.

For experimental verification of this composition, 5 mixtures were prepared (see Table 1).

Water was used as a binder. Mixtures were obtained by simply mixing the components to form a pasty mass-mix, which in a layer of 4-5 thick

mm applied to the surface of the samples of steel grade Art. 3. Samples were dried at 120 ° С for 40 min, and then kept in an electric furnace with an oxidizing atmosphere for 2.5 hours at 940 ° С with cooling with a furnace to 800 ° С, then in air.

The method is carried out as follows.

Sheet steel grade Art. 3 with a thickness of 7–10 mm cut the lugs of box and frame electric locomotives VL 8. The working surfaces of the parts were boronized at 930–950 ° C for 2.5 h without subsequent heat treatment. Lining after inspection and verification were installed on

0 electric locomotive under repair.

Operational tests on an experimental electric locomotive showed that with a run of 65,000 km, the total clearance between two

5 rubbing pads mounted on the frame and axle box increased by 0.2 mm, i.e. each part had a wear / equal to 0.1 mm, and parts treated with a known composition and mounted on the same locomotive.

0 had a wear of 0.25 mm.

The results of studies of samples and steel products subjected to borination, are presented in Table. 2

From the data it follows that

5, the proposed composition eliminates the weldability of the mixture to the saturable surface and the boride layer is 1.6-1.8 times less brittle.

The use of the proposed composition makes it possible to increase by 2.5 times the wear resistance of the axle and frame linings of the VL8 series locomotive installed in the axle box, which is not structurally protected from sand, dust and working under conditions of friction with shock loads.

The use of the invention improves the quality of the saturable surface by producing a single-phase boron layer, improves the properties of the boride coating by reducing the fragility of the layer and expands the possibility of using products boron in industry and rail transport due to

5 technology improvements.

Claims (1)

A composition for boring steel products containing boron carbide, sodium fluoride and an abrasive-metal mixture, characterized in that improving the wear resistance of products by forming a single-phase boride layer with reduced brittleness and processability by eliminating the weldability of the coating, the composition additionally contains welding powder PG-C27 with the following content of components, wt.%: Boron carbide Sodium fluoride Powder napladoch PG-S27 Abrasive-metal blend Table 1 table 2