Composition of charge and technology of induction surfacing of composite carbide steel based on powder high-speed steel 10p6m5 with hardener in form of added refractory carbides

Abstract

FIELD: powder metallurgy.SUBSTANCE: method for producing composite powder carbide steel based on high-speed steel, obtained by induction surfacing, as well as to a charge for producing composite powder carbide steel based on high-speed steel. Can be used for manufacturing products using additive technologies. By mixing powdered high-speed steel 10P6M5 and 5-15 wt.% tungsten carbide powder or a mixture of tungsten carbide powder and carbide powder, a charge for surfacing is obtained. Flux and binder are added to the resulting mixture and molding is carried out to obtain a pressed product. The resulting pressing is placed on a pre-prepared steel substrate and induction surfacing is carried out by heating with high-frequency currents. The charge for surfacing powder carbide steel based on powder high-speed steel contains, by wt.%: tungsten carbide or a mixture of tungsten carbide and titanium carbide 5-15, high-speed steel 10P6M5 - the rest.EFFECT: improvement of physical, mechanical and operational characteristics is ensured.8 cl, 3 dwg, 1 tbl, 4 ex

Description

[0001] The invention relates to powder metallurgy, primarily to composite powder carbide steel based on high-speed steel with added carbides, produced by induction surfacing on a substrate of structural carbon steel. It can be used in additive manufacturing technologies for the production of various products.

[0002] An invention based on powdered carbide steel for producing a sintered metalworking tool is known from patent RU 260363, C22C 38 / 28, C22C 29 / 02, C22C 33 / 02, published 11 / 10 / 2016 [1].

[0003] The invention relates to powder metallurgy and can be used to manufacture sintered metalworking tools. The tools are made of powdered carbide steel containing carbon, titanium, molybdenum, tungsten, vanadium, chromium, zinc stearate and iron in the following ratio of components, wt.%: carbon 0.3-0.5, titanium 1.0-2.0, molybdenum 3.0-5.0, tungsten 2.5-4.0, vanadium 3.0-4.0, chromium 8.0-10.0, zinc stearate 0.1-0.3, iron - the rest. Increased wear resistance of the tool is ensured.

[0004] A disadvantage of the known invention is the low carbon content in the proposed composition, which requires an additional high-temperature operation—carburization of the resulting compacts. The small amounts of tungsten and molybdenum, which are the main components of refractory carbides, prevent the production of a significant amount of the strengthening phase in the carbide steel.

[0005] A blank of a hard alloy plate made of powdered carbide steel and a method for its heat treatment are known from patent RU 2756600, C22C 33 / 02, C22C 38 / 04, C22C 38 / 14, B22F 3 / 12, published 04.10.2021 [2].

[0006] The invention relates to powder metallurgy, namely to the production of a blank from powdered carbide steel used in the tool production of carbide inserts, as well as in additive technologies. The blank is produced by grinding and mixing the initial components of the powder mixture, followed by pressing the blank containing, by weight: carbon 1.0-1.5, manganese 1.0-1.5, vanadium 1.0-2.0, titanium 20-30, iron - the rest, and stepwise sintering. Powders obtained by separate milling of the components with a dispersion of no more than 10 μm are used as the initial components of the powder mixture. Pressing of the blank is carried out by double-sided pressing at a pressure of 100-150 MPa. The pressed blank is placed in a vacuum heating furnace, where it undergoes two-stage sintering with simultaneous vacuumization of the furnace working space to a pressure of 10 -3Pa, with solid-phase sintering performed in the first stage at a temperature of 0.7-0.8 times the melting point of the base mixture (iron) at a heating rate of 70-90°C / hour for 60-90 minutes. In the second stage, liquid-phase sintering is performed at a temperature of 0.85-0.9 times the melting point of the refractory component of the mixture (titanium) at a heating rate of 100-120°C / hour for 30-60 minutes. The furnace is then turned off, and the workpiece is cooled along with the furnace. This results in a dense, uniform material structure, ensuring high physical, mechanical, and operational properties.

[0007] A disadvantage of the known invention is the use of a large percentage of titanium powder as a strengthening component in the carbide steel, which significantly increases the cost of the blank. Also, the high melting point of titanium (1670°C) complicates the manufacturing process for the blanks.

[0008] A composite material for wear-resistant electron beam surfacing is known from patent RU 2400339, B23K 35 / 32, published 09.27.2010 [3].

[0009] The invention relates to wear-resistant surfacing materials and can be used to manufacture new parts, as well as restore and extend the service life of worn parts operating under conditions of abrasive, impact-abrasive wear, and high contact endurance. The material is characterized by high wear resistance, contact endurance, low plastic deformation, and provides a uniform structure across the thickness of the hardened layer without a network of cracks. The high-speed steel-based material contains 15-25 wt.% tungsten carbide and 0.5-1 wt.% vanadium carbide.

[0010] A disadvantage of the known invention is the complexity of the technological process, caused by the use of the following parameters for electron beam surfacing: the need for vacuuming; limited shape and size of the parts being surfacing; high temperature difference in the surfacing zone, leading to cracking of the deposited layers and, as a consequence, the need for additional technological measures to prevent defects.

[0011] A method for producing surface-hardened powder carbide steel is known from patent RU 2354502, B22F 3 / 24, C22C 33 / 02, published 10.05.2009 [4].

[0012] The invention relates to powder metallurgy and can be used to manufacture low-carbon iron-based powder metalworking tools. A mixture of graphite, chromium, tungsten, molybdenum, vanadium, titanium, manganese, zinc stearate, and iron powders is prepared. The resulting mixture is pressed and sintered in a protective atmosphere at 1240-1250°C. After sintering, hot isostatic pressing or plastic deformation in a cold or heated state is carried out, followed by thermochemical treatment at 975-1000°C for 6-8 hours. Then, quenching is carried out in a salt bath at 950-1000°C and tempering at 180-220°C for 1 hour. The technical result is increased viscosity and wear resistance.

[0013] A disadvantage of the known invention is the use of a multi-component charge, which increases the cost of carbide steel. The complex technological process, consisting of numerous process steps, the use of protective atmospheres and specialized equipment, requires enhanced control and, as a result, leads to increased process costs.

[0014] The technical objective of the invention is to develop a charge composition and a technology for induction surfacing of composite carbide steel based on powder high-speed steel 10P6M5 with a hardener in the form of introduced refractory carbides with improved physical, mechanical and operational characteristics and a method for its manufacture.

[0015] The technical problem is solved by proposing a method for producing composite powder carbide steel. The method comprises preparing and mixing the powders of the deposited charge, adding flux and binder, compacting the compacts, drying the compacts, preparing the substrate, heating and cooling, characterized in that the heating occurs using high-purity currents. FK-235 is used as a flux, BF-6 glue is used as a binder, the compacts are additionally impregnated with an alcohol flux, and an alcohol solution of boric acid is used as an alcohol flux. The resulting deposit is subjected to accelerated cooling in water. Composite powder carbide steel based on high-speed steel 10P6M5, obtained by the proposed method with the introduced tungsten carbides WC, in the following ratio of components, wt.%:

[0016] metal carbide 5-20 high-speed steel 10P6M5 rest

[0017] WC, TiC or their combination is used as the metal carbide in the following ratio of components, wt.%

[0018] WC metal carbide 10 TiC metal carbide 5 high-speed steel 10P6M5 rest

[0019] The proposed invention is explained by the images shown in Figs. 1-3. Fig. 1 shows a diagram of an installation for induction surfacing with a sample. (1 - ferrite core, 2 - coil inductor, 3 - asbestos gasket, 4 - surfacing compaction made of powder composite carbide steel, 5 - steel substrate). Fig. 2 is a graph of the dependence of temperature on heating time. Fig. 3 shows the microstructure of the obtained powder composite carbide steel, strengthened with metal carbides.

[0020] Disclosure of the essence of the invention

[0021] A method for producing composite powder carbide steel based on high-speed steel 10P6M5, strengthened with metal carbides by surfacing, by means of induction heating, and a composition of the composite powder carbide steel charge are proposed.

[0022] High-speed cutting powder steel 10P6M5 was chosen as the matrix component due to the following advantages: high hardness and wear resistance of finished products, economical alloying with expensive components.

[0023] Refractory tungsten and titanium carbides and their combinations were selected as the composite material's hardener. These carbides combine excellent physical and mechanical properties, making them suitable for use in the manufacture of metal-cutting tools and wear-resistant components, while remaining relatively inexpensive and, therefore, readily available in industry.

[0024] The amount of hardener added to the charge varies between 5 and 20% by weight. This is due to the need to ensure a combination of high hardness and wear resistance for parts operating under abrasive wear conditions with satisfactory toughness. According to the source (Artinger I. Tool steels and their heat treatment / / Moscow, 1982. - Pp. 203-223), powder high-speed steel has a specific structure, characterized by a relatively small amount of carbide phase in relation to the solid solution. This, combined with a small amount of dispersed introduced carbide phases, helps prevent the formation of large ledeburite inclusions in the structure of the weld deposits, which are typical for high-speed steel obtained by conventional casting.

[0025] Induction surfacing of carbide steel offers a number of significant advantages over other surfacing methods. For example, induction surfacing is relatively inexpensive and ensures low penetration of the substrate metal, preventing mixing of carbide steel and substrate components in the transition zone. This allows for high physical and mechanical properties of the deposited layer through the economical use of alloying components.

[0026] The proposed method for producing powder carbide steel with strengthening carbides consists of the following steps.

[0027] At the initial stage, the components of the powdered carbide steel are mixed with strengthening metal carbides in the required proportions. The base of the powdered carbide steel is 10P6M5 high-speed steel powder, to which strengthening metal carbides (WC, TiC, and their combinations) are added, in amounts ranging from 5 to 20% by weight.

[0028] FK-235 flux (TU 48-17228138) is added to the resulting powder mixture of 10P6M5 steel with metal carbides. Flux is added at a rate of 10-30% by weight of the charge. Reducing the flux percentage to less than 10% by weight is ineffective and leads to oxidation of the carbide steel powder components. Exceeding the flux amount of 30% by weight leads to excessive slag formation, thereby degrading the quality of the weld deposit. Excessive flux also increases the cost of the final product.

[0029] The mixing of the carbide steel powder and flux components was done manually. At the enterprise scale, powder mixing is performed dry using any known method; mechanical mixing, for example, using mixers, mills, etc., is also possible.

[0030] A binder is added to the resulting mixture of powdered steel, metal carbides, and flux to form weld pressings. Alcohol-based adhesive BF-6 (GOST 12172-2016) was chosen as the binder, as it produces no ash when exposed to high temperatures, which favorably affects the composition of the resulting material. The alcohol-based binder, at a rate of 15-20% of the pressing weight, is added to the resulting mixture of powdered steel carbide and flux and mixed until homogeneous.

[0031] The resulting mixture is divided into samples and formed into compacts using a manual mold at a pressure of 80 kPa. The compacted sample is air-dried at room temperature for at least 2 hours.

[0032] Individual compacts were additionally impregnated with an alcohol flux. A 5% solution of boric acid in ethyl alcohol was used as the flux. The dried carbide steel compacts were impregnated dropwise until they were visibly wet. This improves the compacts' strength before surfacing and reduces oxidation of the mixture components during surfacing. The impregnated specimen is air-dried at room temperature for at least 1 hour.

[0033] Before surfacing, the substrate must be prepared by blasting it with a coarse abrasive to remove surface contaminants and oxides. A layer of FK-235 powder flux is applied to ensure adhesion of the pressed part to the substrate during surfacing. The flux is necessary to protect the substrate-pressed contact area from oxidation during heating. At high temperatures, during the transition from solid to liquid, the flux additionally holds the welded part to the substrate, preventing its movement under the influence of the inductor's magnetic field. Grade 45 steel is used as the substrate material.

[0034] Welding of carbide steel pressings is performed using a high-frequency induction unit type UVG 2-25, with a GNOM-25M1 generator. An example of the induction welding process diagram is shown in Fig. 1.

[0035] The prepared substrate and carbide steel pressing 4 are placed under the inductor 2 and covered from above with a sheet of thin asbestos 3, which prevents the movement of the pressing, consisting of ferromagnetic powders, under the influence of the magnetic field of the inductor at the initial stage of surfacing.

[0036] From the moment inductor 2 is turned on, the surfacing process takes approximately 150 seconds. The temperature-heating time graph is shown in Fig. 2. Surfacing occurs at a frequency of 45-46 kHz and a power of up to 25 kW.

[0037] In the initial stage, at a temperature of 100-200°C, the binder burns out and the boric acid is activated. Boric acid melts during heating, further holding the charge together and preventing oxidation and the effects of the magnetic field on the ferromagnetic powders. During the intermediate heating stage, in the temperature range of 600-900°C, the FK-235 flux melts. This flux, like boric acid, prevents oxidation of the charge components within its temperature range and improves slag separation from the melt. When the charge reaches the Curie temperature, the ferromagnetic components of the charge become paramagnetic, allowing the removal of the asbestos lining and visual inspection of the deposition process. To ensure uniform melting across the entire sample surface, the substrate with the charge moves smoothly under the inductor using a special table with a screw transmission. After surfacing, some of the samples were subjected to air quenching during the cooling process, and some were subjected to quenching by immersion in water.

[0038] Some examples of implementation of the proposed method:

[0039] Example 1

[0040] The starting powders were mixed in a ratio of 90% 10P6M5 powder steel and 10% tungsten carbide (WC) (see table: weld composition No. 1). During the mixing process, 20% FK-235 flux was added, and the powders were pressed under a pressure of at least 80 kPa and dried. After the binder had dried, they were impregnated with an alcohol solution of boric acid.

[0041] Next, induction surfacing of the charge compact onto the substrate took place. The surfacing process was monitored visually and took an average of 150 seconds. The temperature versus heating time graph is shown in Fig. 2. After surfacing is complete, induction heating is stopped, and the sample is cooled in air.

[0042] The sample obtained in Example 1 has a hardness of 60 HRC.

[0043] Example 2

[0044] The starting powders were mixed in a ratio of 80% 10P6M5 powder steel and 20% tungsten carbide (WC) (see table: weld composition #2). During the mixing process, 25% FK-235 flux was added, and the mixture was pressed under a pressure of at least 80 kPa and dried. This example did not use the additional impregnation with an alcohol solution of boric acid described in Example 1.

[0045] Next, induction surfacing of the charge compact onto the substrate took place. The surfacing process was monitored visually and took an average of 150 seconds. The temperature versus heating time graph is shown in Fig. 2. After surfacing is complete, induction heating is stopped, and the sample is cooled in air.

[0046] The sample obtained in Example 2 has a hardness characteristic of 59 HRC.

[0047] Example 3

[0048] The starting powders were mixed in a ratio of 90% 10P6M5 powder steel and 10% tungsten carbide (WC) (see table: weld composition #3). During the mixing process, 30% FK-235 flux was added, and the powders were pressed under a pressure of at least 80 kPa and dried. After the binder had dried, they were impregnated with an alcohol solution of boric acid.

[0049] Next, induction surfacing of the charge compact onto the substrate took place. The surfacing process was monitored visually and took an average of 150 seconds. The temperature versus heating time graph is shown in Fig. 2. After surfacing was complete, induction heating was stopped, and the sample was rapidly cooled in water.

[0050] The sample obtained in Example 3 has a hardness of 54 HRC.

[0051] Example 4

[0052] The starting powders were mixed in a ratio of 95% 10P6M5 steel powder and 5% titanium carbide (TiC) (see table: weld composition #4). During the mixing process, 28% FK-235 flux was added, and the mixture was pressed under a pressure of at least 80 kPa and dried. This example did not use additional impregnation with an alcohol solution of boric acid, as described in Examples 1 and 3.

[0053] Next, induction welding of the charge compact onto the substrate took place. The welding process is monitored visually and takes an average of 200 seconds. After welding is complete, induction heating is stopped, and the sample is cooled in air.

[0054] The sample obtained in Example 4 has a hardness characteristic of 59HRC.

[0055] Table. Composition and properties of composite powder carbide steel surfacings with added refractory carbides

[0056] No. of surfacing composition Composition of the charge for surfacing, % Hardness, HRC 1 10P6M5+10% WC 60 2 10P6M5+20% WC 59 3 10P6M5+10% WC (water quenching) 54 4 10P6M5+5% TiC 59 5 10P6M5+10% TiC 55 6 10P6M5+5% WC 61 7 10P6M5+10% WC+5% TiC 58 8 10P6M5 61 9 10P6M5 (water quenching) 62

[0057] The resulting samples were further heat treated. Studies showed that the sample obtained with weld deposition #1 had the best properties (see table). After heat treatment, namely, three temperings at 560°C and a hold time of 40 minutes, the resulting material exhibited high hardness—an increase of 2 HRC units.

[0058] At the same time, the sample obtained in surfacing No. 3 (see table) showed that after heat treatment (three-fold tempering) there was an increase in hardness by 10 HRC units.

[0059] A study of the microstructure and properties (hardness) of the resulting composite powder carbide steel with added refractory carbides showed that the addition of metal carbides contributes to increased wear resistance and hardness due to the network of MS and M6S type carbides at grain boundaries. Fig. 3 shows a typical microstructure of the resulting carbide steel. The presence of hard eutectic carbides at the grain boundaries of the solid solution and added carbides containing V, Cr, and Mo in the framework structure suggests that the resulting material structure has increased wear resistance, as it helps protect the austenite grains from abrasion during operation.

Claims

1. A method for surfacing powder carbide steel based on powder high-speed steel, which includes obtaining a surfacing charge by mixing high-speed steel and metal carbide powders and surfacing, characterized in that the surfacing charge is obtained by mixing 10P6M5 high-speed steel powder and 5-15 wt. % tungsten carbide powder or a mixture of tungsten carbide powder and titanium carbide powder, a flux and a binder are introduced into the resulting charge, then molding is carried out to obtain a compact, drying is carried out, the resulting compact is placed on a pre-prepared steel substrate and induction surfacing is carried out by heating with high-frequency currents.

2. The method according to paragraph 1, characterized in that FK-235 is used as a flux.

3. The method according to paragraph 1, characterized in that BF-6 glue is used as a binder.

4. The method according to paragraph 1, characterized in that the pressings are additionally impregnated with an alcohol flux.

5. The method according to paragraph 4, characterized in that an alcohol solution of boric acid is used as an alcohol flux.

6. The method according to paragraph 1, characterized in that the resulting weld is subjected to accelerated cooling in water.

7. A charge for surfacing powder carbide steel based on powder high-speed steel, containing powders of high-speed steel and metal carbide, characterized in that it contains powder high-speed steel 10P6M5 as the high-speed steel, and tungsten carbide or a mixture of tungsten carbide and titanium carbide as the metal carbide in the following ratio of components, wt. %: tungsten carbide or a mixture of tungsten carbide and titanium carbide 5-15 high-speed steel 10P6M5 rest 8. A charge for surfacing powder carbide steel according to paragraph 7, characterized in that a mixture of tungsten carbide WC and titanium carbide TiC is used as the metal carbide in the following ratio of components, wt. %: tungsten carbide WC 10 titanium carbide TiC 5 high-speed steel 10P6M5 rest

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