SU1717283A1 - Process for recovering lump waste of tungsten-cobalt hard alloys - Google Patents

Abstract

The invention relates to the field of powder metallurgy, in particular, to methods for producing carbides and hard alloys based on them from secondary raw materials. The aim of the invention is to simplify the process and increase the operational durability of the regenerated hard alloys. The essence of the method is that the total amount of carbon in a carbon-containing controlled atmosphere during carbidization is determined by the ratio Ig, 084 Ig (Co) + + 2.12, where C is the amount of carbon, g per 1 kg of waste; Co is the amount of cobalt in the hard alloy, May.%. At the same time, carbidization is carried out in two stages: the first - at a temperature of 900-1000 ° C, specific atmospheric consumption of 2.2-2.6 m / h and a carbon content of 46.7-72.1 g per 1 kg of processed material ; the second, at a temperature of 800-900 ° C, specific atmospheric consumption of 1.6-1.8 m3 / h and a carbon content of 74.2-82.4 g per 1 kg of the processed material. 1 tab. cl

Description

The invention relates to powder metallurgy, in particular, to methods for producing carbides and hard alloys based on them from secondary raw materials, and can be used in the manufacture of cutting tools and rapidly wearing structural parts.

The purpose of the invention is to simplify the process of regeneration and increase the operational durability of the regenerated hard alloys.

In the method of regenerating lumpy waste of hard alloys, including oxidation, carbidization, grinding, pressing and sintering, carbidization is carried out in a carbon-containing atmosphere, the total amount of carbon in which is determined by the ratio

Ig C 0.084 Ig (Co) + 2.12, where C is the amount of carbon, g per 1 kg of waste;

Co is the amount of cobalt in the solid alloy, wt.%.

At the same time, carbidization is carried out in two stages: the first stage at a temperature of 900-1000 ° C, the specific consumption of controls (XI GO 00 C)

Atmospheric concentration 2.2-2.6 m / h and carbon content 46.7-72.1 g per 1 kg of the processed material, the second - at a temperature of 800-900 ° С, specific consumption of the controlled atmosphere 1.6-1.8 m / h and a carbon content of 74.2-82.4 g per 1 kg of the processed material.

The method is carried out as follows.

The piece waste of a certain type of hard metal (BK6, BK15, etc.) is oxidized in air or in an oxygen environment to produce a friable oxide product. Oxides are loaded into boats and subjected to carbidization in a carbon-containing gaseous medium (for example, containing methane CH4 in two stages). In this case, the first stage is carried out at a temperature of 900-1000 ° C in an atmosphere containing 46.7-72.1 g of carbon per 1 kg of the processed material and a specific gas consumption of 2.2-2.6 m3 / h-kg. The second stage is carried out at a temperature of 800-900 ° C in an atmosphere containing 74.2 ... 82.4 g of carbon per 1 kg of the processed material and the specific gas flow rate of 1.6-1.8 m / h-kg.

Carrying out carbidization in a gas atmosphere allows combining the reduction and carbidization operations, eliminating the operation of displacing the oxide product with soot. In addition, the gas-thermal carbidization process is low-temperature, high-speed, and allows automatic control of the composition of the gas and the product obtained. Due to these advantages, the regeneration process is greatly simplified.

Since the properties of hard alloys, obtained both from traditional raw materials and from waste, primarily depend on the phase composition of carbide mixtures determined by their carbon content, in order to achieve high operational durability (at least not lower than similar properties). for standard hard alloys) in the proposed method, the carbon content in the gas atmosphere is determined from the ratio that allows to take into account the change in the composition of the material being processed (hard alloy grade).

Ig C 0.084 Ig (Co) + 2.12, where C is the amount of carbon, g per 1 kg of waste;

Co is the amount of cobalt in the solid alloy, wt.%.

In order to evenly distribute carbon and obtain a predominantly two-phase product after carbidization, (1MS + Co) and, consequently, an increase in operational properties, the process is proposed to be carried out in two stages. First stage

carried out with a higher specific consumption of the atmosphere, contributing to the better washing of the particles of the material being processed with fresh gas and the rapid removal of reaction products. This takes into account the higher energy of formation of L / 2C compared to WC, which led to the choice of higher temperatures (900-1000 ° C) at this stage.

To prevent the surface of the reacting particles from blocking with a thin layer of black carbon and transferring the reaction from the gas phase to the solid phase (which reduces the reaction rate), the first stage is proposed to be carried out in an atmosphere with a reduced carbon content of 46.7-74.2 g per 1 kg of the processed material.

The use of lower temperatures (800–9QO ° C) in the second stage and the use of atmospheres with an increased amount of carbon are caused by the need to obtain a monocarbide (WC) product with a low content of free carbon, which makes it possible to achieve in products made from such materials , high performance.

PRI me R 1. Used carbide cutting plates VK 6 are oxidized in air at 900 ° C for 5 hours. The obtained oxides are loaded into boats and subjected to gas-thermal carbidization in a two-zone continuous furnace with the following parameters:

The temperature of the first zone 950 ° C

Specific consumption

atmosphere2.4 m3 / h-kg

SS content

in the atmosphere 5%

Holding time2 h

The temperature of the second zone. 850 ° С

Specific consumption

atmosphere1,7m3 / h-kg

Chu content

in the atmosphere of 8%

Holding time1 h

The powders obtained after carbidization are subjected to short grinding (48 h) in a drum mill in an alcohol medium. The dried carbide mixtures are separated from the balls, mixed with a plasticizer, granulated and pressed rods to obtain standard samples 5 x 5 x 35 and cutting plates of the form 02271. The blanks are sintered in vacuum (mm Hg) at 1430 ° C for 1 h,

The table shows the parameters of gas-thermal carbidization, the composition and physicomechanical properties of the regenerated hard alloy, as well as the results of the operational tests of the cutting plates for longitudinal turning of cast iron, at a cutting speed of 120 m / min and cutting section 0.2 x 1.0 mm / about (wear criterion of 0.8 mm).

Example2. The same plates as in example 1 are regenerated by a known method after oxidation, the resulting powders are reduced in hydrogen, mixed with lamp black, homogenized in a drum mill for 5 hours and annealed in steps in the temperature range 200 - 850 ° C for 8 hours in dissociated ammonia.

After carbidization, similarly to the technology of Example 1, standard rods and cutting inserts are made.

Froze The used sprays of mazut nozzles made of VK-15 alloy are oxidized by analogy to Example 1 in air for 5 hours at 900 ° C. The resulting oxides are then subjected to gas-thermal carbidization with the following parameters.

From the powders obtained after carbidization, similarly to the technology described in Example 1, standard 5 x 5 x 35 grades and 15 x 20 x 4.5 samples are made to determine the relative wear resistance of Ј45 (relative to steel 45).

PRI me R 4. The same materials are processed by a known method.

EXAMPLE 5 Spherostamp matrices are made of alloy B K 20, removed from the cage and oxidized in air at 900 ° C for 12 hours. The resulting oxides are then subjected to gas-thermal carbidization.

From the powders obtained after carbidization according to the technology of Example 1, standard 5 × 5 x 35 grades and spherostamp matrixes are made. Thereafter, the dies are subjected to tests directly under operating conditions and the number of punching tools is determined before the dies are worn.

Thus, as can be seen from the tabular data, only with the proposed parameters of gas-thermal carbidization, the regenerated hard alloys achieve the required composition and standard properties.

Claims (1)

Invention Formula A method for regenerating lumpy waste of tungsten-cobalt hard alloys, including oxidation, carbidization, grinding, pressing, sintering, characterized in that, in order to simplify the process and increase the operational durability of the regenerated hard alloys, carbidization is carried out in a controlled carbon containing atmosphere in two stages , first, at a temperature of 900-1000 ° С, specific consumption of a controlled atmosphere of 2.2-2.6 m3 / h and a carbon content of 46.7-72.1 g per 1 kg of the processed material, then at a temperature of 800-900 ° C, the specific flow rate of the controlled atmosphere is 1.6-1.8 m / h and the carbon content is 74.2-82.4 g per 1 kg of the processed material, while the total amount of carbon in the controlled atmosphere is chosen from the ratio Ig С -0.084 lg (Co) + 2.12. where C is the amount of carbon, g per 1 kg of the material being processed; Co is the amount of cobalt in the solid alloy, wt.%.