FI84371B - FOERFARANDE FOER KARBONITRERING AV STAOLSTYCKEN VID LAOG TEMPERATUR. - Google Patents

Description

Method for performing carbon scrubbing of steel pieces at low temperature! 84371

TECHNICAL FIELD The present invention relates to the chemical heat treatment of metals and alloys, and more particularly to a method for performing carbon firing of steel pieces at a low temperature.

The method of the present invention can be applied to the manufacture of various tools and machining equipment from high speed steel and other high alloy steels and steel alloys.

Background of the invention

Low temperature carbon bedding is used to improve the wear resistance and prolong the service life of steel or steel alloy bodies that are characterized by redness at temperatures above the process temperature of 30-50 ° C.

A method is known in the art for low carbon carbon firing of high speed steel tools, the tools being charged to a shaft furnace preheated to 560 ° C, maintained at that temperature for 4-6 hours by simultaneously introducing gaseous carbon at a rate of 150 to 155 cm / h and then cooled.

The gaseous carbonaceous substance, which is in fact a mixture of triethanolamine and nitrogenous additives, develops an active gaseous medium which decomposes the surface layers of the tool with nitrogen and carbon.

2

A carbon-etched layer having a thickness of 100 to 130 μm is provided on the surface of a tool having a strength of 800 to 900 kp / mm, whereby the strength of the tool is increased to 2,940 or 1,180 kp / mm. The layer has a surface zone (10-35-30 μm thick) consisting of the brittle ε- and γ-phases of carbonitride and nitric acid. This reduces the bending strength of the tool by 6 ^ 25 to 35% and its impact toughness (or strength) factor by 1.5 to 2.5 times- (See AN Tarasov's article: "Due to gas charcoal 5 low temperature Improving the properties of high-speed cutting tools "in" Stanki i instrument "(machine tools and machining), No. 10, Moscow, 1979, pages 16-18 (in Russian).

The formation of brittle f- and γ-phases is due to the atmospheric oxygen present in the carbon-10 fluxing process, which has been introduced by loading the tools into the furnace and introducing gaseous carbon dioxide.

The process is characterized by an increased amount of diffusion layer formation and its overall depth, but the process does not prevent the formation of brittle ε and γ phases, which adversely affects both the strength of the tool and its wear resistance.

In order to reduce the detrimental effect of the brittle zones of the strength properties of the treated tool, the tool must be cut to a depth of 30 μm, which is a major obstacle to tool production.

Another method is known in the art (SU, A, 840 195) for performing low temperature carbon firing of steel pieces at which such pieces are treated in a furnace in a medium formed by gaseous decomposition products of an organic, nitrogenous reagent to continuously feed the reagent at a rate of 0. , 3-2 kg / h. The process is maintained between 480 and 660 ° C for 1-7 hours and then the pieces so treated are cooled. The organic reagent comprises 90 to 99.9% by weight of urea and 0.1 to 10% by weight of ammonium carbonate. An essential part of the process is the diffusion impregnation of the surface layers with nitrogen and carbon, resulting in the formation of nitrides and carbonitrides. However, the conditions under which the process is carried out are such that they do not impede the continuous entry of air into the furnace, whereby atmospheric oxygen degrades the quality of the surface-hardened layer due to the formation of a brittle carbonitride film having a thickness of 5 to 15 .mu.m. and a surface zone formed by v-phases. The presence of such zones adversely affects the strength, surface hardness and abrasion resistance of the treated parts. In this case, for example, a carbonitride layer with a thickness of about 40 μm and a strength of 900 to 1,100 kp / mm is provided for high-speed steel tools, the thickness of the ε- and γ-phase zone being 10 μm, resulting in a reduction in tool strength. - 25% and its premature wear and damage.

15 The practical implementation of the methods described above also involves special equipment for measuring, mixing and adding the organic reagent, as well as control and monitoring systems which make the process technology complex.

20 Summary of the Invention

It is a primary object of the invention to provide such a method for performing carbon scrubbing of steel pieces at a low temperature by selecting a suitable nitrogen-containing reagent and process conditions so as to provide increased wear resistance and operational strength of the treated pieces.

The above object is achieved by providing a method for low carbon charring steel steels by treating them in a medium formed by gaseous decomposition products of a nitrogenous organic reagent and then cooling them, wherein the process according to the invention is carried out in a closed state and polyamide is used as the organic nitrogenous reagent.

According to the method of the invention, a diffusion layer of metal carbonitrides and nitrides 4 84371, free of zones of the f- and y-phases, is provided on the steel bodies within 2-4 hours, said layer having a thickness of between 60 and 90 and a strength of between 2,100 - 1,250 kp / mm, after the original strength of the pieces 2 5 was 780 - 900 kp / mm. This makes it possible to increase the wear resistance of high-speed steel tools by 2-6 times and the wear resistance of high-alloy steel parts by 2-10 times.

The method does not involve any complex hardware, it is simple and reliable in the workplace.

In order to carry out the process under optimum conditions, it is preferred that the polyamide be added in an amount of 0.3 to 0.7% per kilogram of the pieces to be treated.

Best Mode for Carrying Out the Invention To carry out the method, the articles to be treated and the organic nitrogen-containing reagent in the form of granules are placed in an oven in a closed space. The retort is then gas-sealed and heated to 480-660 ° C and the pieces are heated isothermally at the above temperature for 2-4 hours, after which the pieces so treated are cooled. The enclosed space can be provided by any suitable device suitable for this purpose. Carrying out the process in a closed state makes it possible to prevent all contact of the objects to be treated with the surrounding atmosphere, in particular with atmospheric oxygen, during the entire carbon bed process, as well as to prevent the effect of oxygen on the thermochemical reactions.

When the retort of the furnace is heated, it gradually decomposes the polyamides according to the free-radical method, resulting in the formation of radicals which are characterized by a high reactivity. In this case, diffusion saturation of the surface layers of the bodies with nitrogen and carbon takes place, resulting in the formation of nit-35s and carbonitrides. Atmospheric oxygen enclosed in a gas-tight 5 84371 closed retort combines with the decomposition products of the polyamide, thus protecting against the formation of brittle carbonitride and nitride f- and y-phases. The amount of polyamide added to the reaction is selected to provide optimal process conditions that tend to produce a high quality diffusion layer. It is desirable to use polyamide in an amount of 0.3 to 0.7% per kilogram of pieces to be treated. The lower limit depends on the amount of carbonitride layers formed and their depth, while the upper limit is selected based on conditions that protect against the formation of resinous substances at those points.

The use of high molecular weight polyamides to perform carbon scrubbing of steel bodies at low temperature in a closed space makes it possible to obtain a good quality, wear-resistant carbonitride diffusion surface layer free of brittle ε and ν 'phases, which results in subsequent grinding or grinding treatments. The process proceeds at a high speed of 20 and the wear-resistant layer is characterized by high depth and hardness, which in practice do not adversely affect the strength of the treated parts, which is especially important for high-speed cutting tools. The increased durability of the pieces makes it possible to save on the use of tungsten alloy steels and in some cases it makes it possible to increase the cutting speed of the tools.

The following are some specific, e.g. intended embodiments of the proposed method.

30 Example 1

The stainless steel retort with a volume of -3 3 4 · 10 m is loaded with high-speed steel cutting tools (4 kg), high-alloy steel feed rollers (1 kg) and polyhexamethylene adipamide _2 35 (1.5 * 10 kg) and a retort placed in a shaft furnace. The retort of this residue is gas-sealed and heated to 570 ± 10 ° C, after which the isothermal process is allowed to proceed for three hours. The oven is then stopped and the pieces cooled. This is then prepared and subjected to microscopic structure analysis. The thickness of the diffusion layer is 70 μm for blade tools and 80 μm for rollers, while the strength is between 1,150 and 1,250 kp / mm for tools and 900 for 2 kp / mm for rollers. Zones of fragile E and phases 10 are not identified.

Feed rollers are used to feed stainless steel wire in automatic welding machines. The service life of the roll is measured by the depth of the worn groove is 0.2 mm, at which value the wire slips over. Rolls treated according to the method of SU, A, 840 195 15 have a service life of 24 hours, while rolls treated according to the proposed method have a service life of 146 hours. Comparative durability tests of cutting tools on lathes have been performed by turning structural steel workpieces under the following 20 cutting conditions: cutting depth t = 2 mm; feed rate S = 0.25 mm / rev; cutting speed V 46 m / min and workpiece geometry as follows; f = 90 °, ^ = 10 °, v = 10 °, Q = = 10 °, r = 0.4 mm. According to SU, A, 840 195, 188 workpieces have been machined with machined tools, while 518 workpieces have been machined with tools treated according to the proposed method. The measure of tool durability is the uniformity of the dimensions of the machined workpieces.

Example 2 30 A stainless steel retort with a volume of -3 * 4 * 10 m is loaded with high speed steel milling cutters (3 kg), high alloy steel feed rollers (0.5 kg) and polyenantamide (1.4 * 10 m). kg), and the retort is placed in the shaft oven. The retort is then sealed and heated to 490 ± 10 ° C, 7 84371, after which the isothermal process is allowed to proceed for four hours. The oven is then stopped and the pieces cooled. The sweat is then prepared and subjected to microscopic structure analysis. 5 The thickness of the diffusion layer is 25 μm for milling cutters and 35 μm for rollers, the strengths being 1,150 to 1,200 2 2 kp / mm and 900 to 950 kp / mm, respectively. Zones of brittle ε and γ phases are not observed. Feed rollers are used to feed stainless steel wire in automatic hit-10 dryers. The service life of the roll is measured by the depth of the worn groove is 0.2 mm, at which value the wire slips over. The service life of the rolls treated according to the method of SU, A, 840 195 is 24 hours, while the service life of the rolls treated according to the proposed method is 48 hours. Comparative durability studies of milling machines have been performed by milling structural steel workpieces with end mills under the following cutting conditions: cutting depth t = 4 mm; feed rate S = 0.1 mm / tooth; cutting speed V = 64 m / min. The workpieces treated according to the method of SU, A, 840 195 have machined 86 workpieces, while the milling machines treated according to the proposed method have machined 212 workpieces. The measure of tool durability is the uniformity of the dimensions of the machined workpieces. Example 3 A 25 stainless steel retort with a volume of -3 * 4 * 10 m is charged with high speed steel drills (2 kg), high alloy steel flavors _2 (4 kg) and polycaprinoamide (3 · 10 kg) and the retort is placed in a shaft -uuniin. The retort is sealed and heated to 660 ± 10 ° C, after which the isothermal process is allowed to proceed for two hours. The oven is then stopped and the pieces cooled. The sweat is then prepared and subjected to microscopic structural analysis. The thickness of the diffusion layer is 50 μm for drills and 60 μm for punches, the strengths being 8,850 to 1,150 kp / nun and 850 to 900 2 kp / mm, respectively. Zones of brittle £ and γ 'phases are not observed.

Punches and bending punches treated according to the method of SU, A, 840 195 can produce 5 2,600 corner pieces, while punches treated according to the proposed method can produce 11,250 corner pieces. The 10 mm diameter drills treated in accordance with the present example and used to drill a 4 mm thick 10 stainless steel plate are three times more durable than the drills treated in SU, A, 840 195 according to the method.

Example 4

A stainless steel retort with a volume of -3 3 15 4 «10 m is loaded with high-speed steel cutters (0.5 kg), high-alloy steel Meisters (1.5 kg) and polyacrylamide (1.4 * 10 kg) and the re-cake is placed in the shaft oven. The retort is then gas-sealed and heated to 660 ± 10 ° C, after which the isothermal process is allowed to proceed for 2.5 hours. The oven is then stopped and the pieces cooled. The sweat is then prepared and subjected to microscopic structure analysis. The thickness of the diffusion layer is 40 μm for milling cutters and 50 μm for 25 punches, with strengths of 1,050-2 2,150 kp / mm and 850-900 kp / mm, respectively. No fragile 8- and Y-phase zones are observed. Comparative durability tests of 80 mm diameter end mills have been performed by milling 30 low alloy steel workpieces under the following cutting conditions: cutting depth t = 2 mm; feed rate S * 0.1 mm / tooth; cutting speed V = 56 m / min. 52 workpieces have been machined with the cutters treated by the method of SU, A, 840 195, while 118 workpieces have been machined with the milled cutters treated by the proposed method. The durability of tool 9 84371 is measured by the uniformity of the dimensions of the machined workpieces and the quality of the surface.

Punches and bending punches treated by the method of SU, A, 840 195 can produce 1,580 workpieces, while corresponding punches treated by the proposed method can produce 3,280 workpieces.

Example 5

The stainless steel retort with a volume of -3 3 10 4 * 10 m is loaded with high-speed steel blade tools (2 kg), high-alloy steel feed rollers (0.5 kg) and polypyrrolidone (1.8 * 10 ^ kg) and the retort is placed in a shaft furnace. The retort is then gas-sealed and heated to 540 ± 10 ° C, after which the isothermal process is allowed to proceed for 3.5 hours. The oven is then stopped and the pieces cooled. It is then prepared and subjected to microscopic structure analysis. The thickness of the diffusion layer is 80 for tools and 85 for rolls, with strengths of 1,150 to 1,250 2 2 kp / mm and 900 to 950 kp / mm, respectively. Zones of brittle ε and γ phases are not observed.

Feed rollers are used to feed stainless steel wire in automatic welding machines. The service life of the roll 25 is measured by the depth of the worn groove of 0.2 mm, at which value the wire slips over. The rolls treated by the method of SU, A, 840 195 have a service life of 24 hours, while the rolls treated according to the present example have a service life of 158 hours. Comparative durability tests of cutting tools 30 have been performed on automatic lathes by turning structural steel workpieces under the following cutting conditions: cutting depth t = 3 mm; feed rate S = 0.18 mm / rev; cutting speed V = 58 meters / min and workpiece geometry as follows -f = 45 °, = 35 45 °, ύ = 10 °, Q = = 10 °, r = 0.1 mm. Tools machined by the method of SU, A, 10 84371 840 195 have machined 130 workpieces, while tools treated by the proposed method have machined 620 workpieces. The measure of the workpiece's durability is the uniformity of the dimensions of the machined workpieces.

Example 6

A shaft furnace equipped for carrying out the process according to SU, A, 840 195 is loaded with cutting tools for automatic lathes, milling cutters with a diameter of 18 mm and 24 mm, high-speed steel drills with a diameter of 10 mm, punches and bending punches, as well as high-alloy steel feed rollers for automatic welding machines. The total weight of the loaded pieces is 20 kg. The carbon-15 cheating process is carried out at 570 ± 10 ° C by continuously blowing a mixture of 97% urea and 5% ammonium carbonate for six hours at a rate of 2 kg / h, after which the pieces are cooled.

The sweat is then prepared and subjected to 20 microscopic structure analysis. The thickness of the diffusion layer is 40 μm for cutting tools made of high-speed steel and 50 μm for rollers and dies, the strengths 2 2 being 1,000 to 1,100 kp / mm and 850 to 890 kp / mm, respectively.

The sizes of the fragile £ and> J phase zones are 25 10 to 15 pm.

Applicability in industry

The method of the present invention can be used to make a variety of tools and machining tools from high speed steels and other high alloy steels and steel alloys.

Claims (2)

11 84371 1. A process for carrying out low temperature carbon fumigation of steel pieces by treating them in a medium formed by gaseous decomposition products of an organic nitrogen-containing reagent and then cooling said pieces, characterized in that the process is carried out in a closed state and the organic nitrogen-containing reagent used is polyamide. Method according to Claim 1, characterized in that the polyamide is fed in an amount of 0.3 to 0.7% per piece to be treated. 12 84371 1. The use of carbonylation at a temperature such as the temperature of the genome in the form of a gaseous form of a non-organic product which is an organic, highly reactive reactor and is determined by the use of these stems, in turn, the organic, highly reactive reactive polyamide. 10 2. A preferred composition according to claim 1, wherein the polyamide is incorporated, wherein the polyamide is present in an amount of 0.3-0.7% per kg of rubber.