32 results about "Carbonitriding" patented technology

The invention relates to the technical field of metal stators, and provides a carbonitriding process of a metal stator for a screw drill, which comprises the following steps: preheating the metal stator, and then carrying out salt bath carbonitriding and salt bath oxidation treatment to obtain the metal stator for the screw drill; during salt bath carbonitriding, a carbonitriding agent comprises the following components in parts by weight: 24 parts of a composite carbon material, 10-15 parts of ammonium chloride, 4-8 parts of urea, 3-6 parts of yttrium oxide, 4-8 parts of potassium ferrocyanide and 10-15 parts of potassium chloride; raw materials of the composite carbon material comprise charcoal, carbon nanotubes and light calcium carbonate. According to the technical scheme, the problem that a metal stator is poor in wear resistance in the prior art is solved.

By carburizing nitriding treatment with steel, can provide high surface fatigue strength and high temperature tempering hardness is sufficient high carburizing nitriding treatment with steel and carburizing nitriding steel made of carburizing nitriding treatment, the carburizing nitriding treatment with steel contains C, Si, Mn, P, S, Cu, Ni, Cr, Mo, Al, N, the balance is made of Fe and inevitable impurities, by implementing carburizing nitriding, thereby obtaining carburizing nitriding steel, the carburizing nitriding steel satisfies surface C concentration (mass %) + 12 / 14 x surface N concentration (mass %) = 0.6-1.4, and satisfies 129.7805 x [Cr (mass %)]-76.9797 x [Cr (mass %)] 2 + 339.3375 x [surface N concentration (mass %)]-539.345 x [surface N concentration (mass %)] 2 + 181.4983 x [Cr (mass %)] x [surface N concentration (mass %)]+437.6799>560, and in the case of implementing tempering treatment at 500 DEG C after the carburizing nitriding, the hardness of the part of 0.05 mm depth from the surface is 560 HV or more.

The application discloses a valve box processing method, comprising the following steps: S1, rough machining of a pressure pump valve box forge blank; S2, normalizing treatment; S3, first tempering treatment; S4, carbonitriding treatment; S5, precooling quenching treatment; S6, second tempering treatment; and S7, packaging. The application simultaneously permeates carbon and nitrogen into the workpiece in the form of carbonitriding to form a carbonitriding layer, on the one hand, carbon atoms enter the metal surface and combine with metal atoms to form carbide, thereby improving the hardness and wear resistance of the workpiece surface, and wear and scratches on the metal surface can be effectively prevented; on the other hand, the permeation of nitrogen forms a dense nitride layer on the workpiece surface, improves the corrosion resistance, and enables the workpiece to be applicable to a harsh environment during oil exploitation; and on the third aspect, the residual compressive stress of the carbonitriding layer can improve the fatigue limit of the workpiece, thereby improving the fatigue strength of the workpiece and reducing brittleness.

This invention belongs to the field of bearing heat treatment technology, specifically relating to a heat treatment process for high-speed bearings. The heat treatment process for high-speed bearings is characterized by the following steps: (1) Heating stage: placing the high-carbon steel workpiece in a heat treatment furnace, heating, controlling the carbon potential in the furnace, and holding at that temperature; (2) Holding stage: continuing to hold at that temperature; (3) Carbon potential increase stage: maintaining the temperature and increasing the carbon potential in the furnace; (4) Carbonitriding stage: performing carbonitriding treatment; (5) Carbon potential reduction stage: reducing the carbon potential; (6) Diffusion stage: holding at that temperature; (7) Quenching stage: after diffusion, transferring the workpiece to a quenching medium for quenching treatment; (8) Tempering stage. This invention significantly improves the surface quality, dimensional stability, mechanical properties, and service reliability of bearing parts through segmented carbonitriding with controlled carbon potential, characteristic quenching media, and precise tempering control, significantly improving surface microstructure quality and enhancing wear resistance and fatigue resistance.

The utility model discloses a molded bottle punch capable of reducing the proportion of inner color points. The molded bottle punch comprises a connecting part, the punch part is arranged at the top of the connecting part, and the connecting part and the punch part are both made of tungsten carbide materials; the auxiliary mechanism is used for optimizing the punch part; the protection mechanism is arranged outside the connecting part and used for carrying out wear-resistant protection on the outside of the connecting part, and the connecting part comprises a first step located at the bottom of the punch part and a second step located at the bottom of the punch part; and the second step is fixedly connected to the bottom of the first step. The connecting part, the punch part, the carbonitriding layer, the carburizing layer, the hardening layer, the nano coating and the solid lubricating layer are matched with one another, the connecting part and the punch part are made of tungsten carbide materials, the nano coating improves the mold release performance of the punch part, the hardness and the high-temperature-resistant strength of the molded bottle punch are improved, and the service life of the molded bottle punch is prolonged. Therefore, the occurrence probability of inner color points is reduced.

The utility model relates to the field of carbonitriding treatment equipment, in particular to efficient carbonitriding equipment. The equipment comprises a heating furnace, a first gas inlet pipe, a second gas inlet pipe, a mixing pipe and a fan, one end of the first gas inlet pipe and one end of the second gas inlet pipe extend into the heating furnace, the mixing pipe is located in the heating furnace and provided with two communicating ports connected with the first gas inlet pipe and the second gas inlet pipe respectively, and the fan is used for driving gas in the heating furnace to flow. And two fans which are symmetrically arranged relative to the center of the heating furnace are arranged. In addition, the equipment further comprises a base plate and a frame body which are used for containing materials, and through grooves are formed in the base plate and the frame body to promote gas circulation. By optimizing the gas distribution and improving the mass transfer efficiency, the technical effect of remarkably improving the carbonitriding treatment speed and uniformity is achieved.

The invention relates to a fuel injector for an internal combustion engine, in particular for liquid alternative fuels. The injector comprises an injection nozzle, the end of which has a seat body with a sealing surface and at least one injection hole. The injection holes (5) are produced in a portion of a dome, downstream of a sealing surface. The seat body is made of martensitic stainless steel and has an anti-cavitation surface layer (6) covering at least the sealing surface, the inner surface of the dome and the injection holes. The anti-cavitation surface layer is obtained via low-temperature carbonitriding and extends over a maximum depth of 30 µm, and has a hardness of at least 1000 Hv, for a load of 0.1 kgF (0.98 N).

The invention discloses a double glow plasma low-temperature carbonitriding method for a titanium alloy screw, and relates to the technical field of metal material surface treatment.The key point of the technical scheme is that a safety protection method specifically comprises the following steps that S1, screw surface cleaning is conducted, specifically, oil stains, particle impurities and oxide layers on the surfaces of the titanium alloy screw and a graphite barrel are cleaned; the cleaned screws and graphite barrels are placed in a furnace; after the air in the furnace body is removed, argon and nitrogen are introduced into the furnace until the air pressure in the furnace reaches a set value, and H2 is added to adjust the atmosphere activity; s2, pre-bombardment treatment is conducted, specifically, voltage is applied to the screws and the graphite barrel, and adsorbed impurities and oxide skin on the surfaces are cleaned; and S3, composite layer diffusion is conducted, through the titanium alloy screw double glow plasma low-temperature carbonitriding method, a Ti (C, N) diffusion layer of 10 micrometers and a TiN hardened layer of 5 micrometers are formed on the surface of a titanium alloy screw base body, the total alloy layer thickness is 15 micrometers, and the performance of the titanium alloy screw is improved.

The present invention provides a rolling bearing component (outer ring or inner ring) and a rolling bearing using the same, which can dramatically improve the indentation resistance required for rolling bearings. [Solution] A rolling bearing raceway is made of alloy steel containing, by mass%, C: 0.40~0.95%, Si: 0.70~2.50%, Mn: 0.10~1.00%, Cr: 1.00~4.00%, W+2Mo: 0.40~3.00%, V: 0.05~0.80%, with the remainder being iron and unavoidable impurities. The raceway surface of the rolling bearing raceway has a carburized nitride layer with a thickness of 300 μm or more, and the amount of retained austenite on the raceway surface is in the range of 15 volume% to 30 volume%.

The invention relates to a screw shank (1) for fixing pipes to a concrete surface, comprising a head (2) having a first thread (3) and a self-tapping cylindrical seat (4) having a second thread (5). According to the invention, the screw shank (1) has undergone a hardening treatment of the nitriding or carbonitriding type, and said cylindrical seat (4) has a nominal diameter of 5.5 mm. Figure for the abstract: Fig. 1

The application discloses a gear enhancement treatment device for gear pump machining and belongs to the technical field of gear enhancement treatment, which comprises a carbonitriding furnace for gear enhancement of an internal gear pump, an electromagnetic heater is arranged on the carbonitriding furnace, and a sealing driving assembly for controlling a feeding opening of the carbonitriding furnace is arranged on the carbonitriding furnace. The application drives the whole driving column to rotate by using the flow kinetic energy of process gas itself through the pneumatic control round table and the driving fan blade, and then drives the gear ring, the crescent piece supporting mechanism and the internal gear to move synchronously. The continuous rotation breaks the static treatment atmosphere boundary layer, ensures that all surfaces of the workpiece can fully and uniformly contact with the active atmosphere, greatly improves the uniformity of the penetration layer, and fundamentally guarantees the high consistency of the carbonitriding layer depth, the organizational structure and the mechanical properties of the three precisely matched parts, i.e. the gear ring, the crescent piece and the internal gear, by treating the three parts in the same furnace and the same process cycle.

The invention relates to a fuel injector for an internal combustion engine, particularly for liquid alternative fuels. The injector comprises an injection nozzle whose tip has a seat body with a sealing surface and at least one injection orifice. The injection orifices (5) are formed in a portion of a dome, downstream of a sealing surface. The seat body (6) is made of martensitic stainless steel and has an anti-cavitation surface coating (6) covering at least the sealing surface, the inner surface of the dome, and the injection orifices. The anti-cavitation surface coating is obtained by low-temperature carbonitriding and extends to a maximum depth of 30 µm, and has a hardness of at least 1000 Hv, for a load of 0.1 kgF (0.98 N). (Fig. 1)

The utility model discloses a secondary quenching system for reducing the thermal expansion amount of a 20Cr piston pin, which relates to the technical field of quenching and comprises a mounting base provided with a quenching mechanism convenient for secondary quenching of the piston pin. The quenching mechanism comprises a gantry support, a heat treatment furnace and a quenching pool, the heat treatment furnace is fixedly mounted at the upper end of the mounting base, and the quenching pool is fixedly mounted at the upper end of the mounting base. The secondary quenching process is adopted, the surface of the piston pin can obtain higher hardness and strength through secondary quenching, a hard carbonitriding compound layer is formed on the surface after carbonitriding, the martensite structure is further refined through secondary quenching, the bearing capacity of the material is enhanced, the swelling capacity of the material is reduced, and the service life of the material is prolonged. And in actual use, the influence of environment temperature is smaller, and the use is more stable.

The application discloses a kind of carbonitriding clamping piece heat treatment process method, specifically relates to heat treatment process technical field, its specific process method is in turn: cleaning, drying, carbonitriding, quenching, secondary cleaning, tempering and air cooling;The cleaning mode of air foaming flushing and high-pressure spray cleaning is used in the application, to ensure the thoroughness and uniformity of the clamping piece cleaning;Centrifugal circulating fan is used to control atmosphere circulation and heat transfer during carbonitriding process, to ensure the uniformity of penetration layer depth and the uniformity of furnace temperature, secondary cleaning process is used to remove the oil stains on the surface of the clamping piece caused by carbonitriding, to ensure the tempering quality;Mobile trolley automation control and linear turnover mode are used in the overall process flow, reducing the product loading and unloading frequency, improving the turnover efficiency;Controllable atmosphere sealed box type multi-purpose furnace is monitored by furnace body, to control the flow of propane, ammonia and other gas flow meters, so that the flow is within the set range, to control the carbon potential reasonably.

The invention discloses a carbonitriding method for an automobile rocker arm roller, and relates to the technical field of surface strengthening heat treatment of metal material parts, the carbonitriding method comprises the following steps: S1, pretreatment of a workpiece; step S2, coating a rare earth catalytic permeation agent; s3, dynamic carbonitriding is carried out; and S4, quenching and subzero treatment. The carbonitriding method for the automobile rocker arm roller is simple in process; the automobile rocker arm roller treated by the co-permeation method is high in hardness, long in fatigue life and good in wear resistance.

The invention discloses a carbonitriding heat treatment process for a shallow infiltrated layer of a rolling body part, which adopts a carrier roller type mesh belt furnace continuous production line with a controllable atmosphere to carry out carbonitriding treatment on the part, and comprises the following steps in sequence: strong carbonitriding, quenching, cleaning, low-temperature tempering, and air cooling along with the furnace and basketing. A controllable atmosphere carrier roller type mesh belt furnace continuous production line is adopted for carrying out shallow permeation layer carbonitriding on rolling body parts, high hardness, wear resistance and fatigue resistance of the surfaces of products are achieved, surface carbide particles are dissolved, the content of surface retained austenite is made to be 20-30%, generation and expansion of cracks are effectively controlled, and the quality of the rolling body parts is improved. And particularly when foreign matters exist or lubrication is lacked, the method is helpful for starting point type abrasion of the surface, so that the service life of the product is prolonged.

The invention discloses a vacuum carbon-nitrogen pulse composite strengthening method for a high-hardness large-carburized layer on a surface layer of a bearing type workpiece, which comprises the following steps: firstly, preparing a thicker hardened layer as a bearing layer through vacuum variable pulse carburizing, and then, carrying out vacuum variable pulse carbon / nitrogen double carburizing to improve the hardness of the surface layer. Due to the fact that carbon and nitrogen atoms occupy octahedral gap positions of body-centered cubic lattices in steel, the carbon atoms entering firstly in the carburizing process can hinder diffusion of the nitrogen atoms entering in the double-carburizing process, and the situation that intergranular carbon and nitrogen compounds are separated out and the quality of a carburizing layer is reduced is easily caused. By changing parameters such as temperature, pulse frequency, pulse period and pressure in the vacuum carburizing and vacuum carbonitriding processes, the distribution gradient of carbon atoms in a carburizing layer is strictly controlled, nitrogen atoms enter the carburizing layer in the double-nitriding process, generation of poor carbonitrides and nitrides is avoided, and therefore the carbon-nitrogen alloy with the thickness larger than 3 mm, the surface hardness larger than 64 HRC (-795 HV) and the surface hardness larger than 60 HRC is successfully prepared. The carbon-nitrogen compound is superior to a second-level composite strengthening layer, and the technical limits of single carburizing and nitriding are broken through.

The invention provides a shaft part heat treatment process which comprises the following steps: S1, normalizing treatment: normalizing a shaft blank in a trolley furnace; s2, rough machining is conducted, specifically, rough machining is conducted on the workpiece subjected to normalizing treatment; s3, aging treatment is conducted, specifically, the workpiece subjected to rough machining is subjected to aging treatment in a tempering furnace; s4, carbonitriding and quenching treatment: performing stage preheating by adopting an atmosphere multi-purpose furnace, introducing methanol, propane and ammonia gas, and then performing strong carburizing, diffusion, secondary carburizing supplementation and quenching; s5, hot straightening treatment is conducted, specifically, the workpiece is bent and corrected after preheating; s6, semi-finish machining is conducted, specifically, semi-finish machining treatment is conducted on the workpiece subjected to hot straightening treatment; s7, qualitative treatment is conducted, specifically, the workpiece obtained after semi-finish machining is heated to 200 DEG C for qualitative treatment; and S8, finish machining is conducted, specifically, the outer circle and the spline of the workpiece subjected to qualitative treatment are machined to the design size. The hardness and hot straightening are improved, the workpiece quality is optimized, the process time is greatly shortened, and the production efficiency is improved.

This application discloses a multi-gradient microstructure heat treatment process for achieving wear resistance and toughness enhancement in bearings, belonging to the field of bearing manufacturing. The steps are as follows: 1) Carbonitriding is performed on the bearing workpiece to form a continuous and gentle C and N composition gradient from the surface to the core. After carbonitriding, the workpiece is air-cooled; 2) Then, under a nitrogen protective atmosphere, the workpiece is austenitized through a three-stage heating process using a stepped heating method; 3) A gradient multiphase microstructure of martensite and bainite is constructed through isothermal quenching; wherein, the isothermal quenching time is based on the carbonitriding time and is precisely controlled according to the target bainite content, ultimately obtaining a bainite content of 10-20% on the surface and ≥60% in the core; 4) Finally, the workpiece is subjected to low-temperature tempering treatment to obtain a wear-resistant and toughened bearing. This invention achieves precise control of the multi-gradient heterogeneous microstructure, achieving wear resistance and toughness enhancement through the construction of a microstructure ratio gradient, meeting the synergistic performance requirements of high wear resistance on the bearing surface and impact resistance in the core.

The invention belongs to the technical field of composite heat treatment technologies, and particularly relates to a composite heat treatment technology and equipment for improving the wear resistance of parts, which comprises the following steps: step 1, heating the parts in a heating device to 850 DEG C, keeping the temperature for a period of time, and then carrying out water quenching; 2, after water quenching, the part is put into a heating device to be heated to 500-600 DEG C for tempering treatment, and after heat preservation is conducted for a period of time, cooling is conducted; 3, the tempered part is soaked in a salt bath containing nitrogen for nitrogen treatment; 4, after nitriding treatment, the part is put into a heating device to be heated, and low-temperature tempering treatment is conducted; through double-layer strengthening of salt bath nitriding and carbonitriding, a high-hardness protective layer is formed on the surface layer of the part, the hardness of a nitriding layer reaches 800-1200 HV, a high-hardness carbonitriding compound such as Fe (C, N) is formed on a carbonitriding layer, the thickness of the nitriding layer (the nitriding layer ranges from 0.1 mm to 0.3 mm, and the nitriding layer ranges from 0.2 mm to 0.5 mm) is controllable, the wear resistance of the part can be improved by 30-50% compared with traditional single heat treatment, and the high-frequency wear scene such as a gear and a bearing can be adapted.

The invention discloses high-strength and high-toughness carburizing and nitriding bearing steel, a preparation method thereof and a bearing component, and the preparation method comprises the following steps: mixing high-carbon bearing steel powder with nitrogen-containing iron alloy powder, and compacting through hot isostatic pressing to prepare a bearing steel prefabricated part; endogenous outward diffusion treatment is applied to the prefabricated part, electromigration driving force and stress-induced diffusion force are cooperatively applied, and carbon and nitrogen atoms are outwards and directionally migrated to a surface layer from a steel core; maintaining the carbon-nitrogen potential of the external atmosphere in an extremely low potential well state, forming an element concentration difference, and dynamically controlling oxygen partial pressure to form a selectively permeable nano oxide protective layer; after migration of the carbon and nitrogen atoms is completed, quenching treatment is conducted on the prefabricated part, decoupling double-stage aging heat treatment is conducted, and bearing steel coated with a hardened layer is obtained; according to the method, carbon and nitrogen are driven to directionally migrate from the interior of the prefabricated part to the free surface without being limited by the geometrical shape of the part, so that the uniformity of the hardened layer on the surface of the bearing part with the complex geometrical shape is ensured.

A shaft member for manufacturing a bearing raceway member by performing carburization or carbonitriding, the bearing raceway member being provided with a power transmission section having teeth, the shaft member being configured from a cylindrical or cylindrical shaft member having a center shaft, the shaft part is provided with a first part on the first side in the axial direction and a second part on the second side in the axial direction of the first part, the first part and the second part are integrated, the first part is made of first steel, the second part is made of second steel, and the first steel and the second steel are made of steel. The first part is provided with a part serving as a raceway, the second part is provided with a part serving as a tooth, the alloy composition of the first steel material is different from the alloy composition of the second steel material, and the third part comprises a joint surface connected with the second part on the second side of the first part in the axial direction. The fourth part comprises a joint face connected with the first part on the first axial side in the second part, the fifth part is located on the first axial side of the third part in the first part, and the sixth part is located on the second axial side of the fourth part in the second part. The hardness of the third part is higher than that of the fifth part, the hardness of the fourth part is higher than that of the sixth part, and the part serving as the roller path is located on the fifth part and not located on the third part.

The invention relates to the technical field of alloy heat treatment, in particular to a low-carbon alloy steel carbonitriding continuous furnace system and a heat treatment method. According to the specific technical scheme, the interior of a continuous furnace is sequentially divided into a pre-oxidation zone, a preheating zone, a strong carburizing zone, a diffusion zone, an intercooling zone, a secondary heating zone and a cooling zone, the tail end of the cooling zone is connected with double oil tanks for quenching, outlets of the double oil tanks are communicated with an oil blowing zone, and the oil blowing zone is communicated with an oil inlet. An outlet of the oil blowing area is sequentially communicated with the rear cleaning area, the tempering area and the air cooling area. The continuous furnace and intercooling process is adopted for carbonitriding, the production efficiency is effectively improved, the production cost is reduced, meanwhile, grain refinement can be conducted on workpieces with poor original structures, and quality improvement is achieved.

The application provides a forming manufacturing method of a gradient Mabe composite phase structure of an extreme working condition high-carbon steel bearing, and relates to the technical field of bearing manufacturing. The method comprises the following steps: determining a target carbonitriding temperature according to a first target carbon potential of a workpiece to be processed, determining a target carbonitriding time according to a target carbonitriding depth, and performing carbonitriding on the rolled workpiece to be processed according to the target carbonitriding temperature and the target carbonitriding time; determining a target austenitizing temperature according to a second target carbon potential of a carbonitriding furnace, and placing the workpiece to be processed after the carbonitriding treatment into a high-temperature box-type furnace to perform austenitizing on the workpiece to be processed after the carbonitriding treatment according to the target austenitizing temperature; determining a target isothermal quenching temperature according to the second target carbon potential in the carbonitriding furnace, and immersing the workpiece to be processed after the austenitizing into a low-temperature salt bath furnace to perform isothermal quenching according to the target isothermal quenching temperature. The application can improve the wear resistance, strength and toughness of the bearing.

The invention discloses a carbonitriding heat treatment process for a high-temperature-resistant bearing ring, which belongs to the technical field of heat treatment and comprises the following steps: preheating the bearing ring made of a high-carbon-chromium material for a short time at the temperature lower than the austenitizing critical temperature; the preheated bearing ring is subjected to sectional type co-permeation treatment in a carbon and nitrogen atmosphere at the temperature of 830-850 DEG C; the bearing ring subjected to co-permeation is subjected to quenching treatment; and the quenched bearing ring is sequentially subjected to isothermal subzero treatment, first-time low-temperature tempering and second-time low-temperature tempering. By means of the steps, the technical contradiction that in traditional carbonitriding, coarsening is achieved at the high temperature, and low temperature is insufficient is successfully solved, the hardness of the surface and the core of the bearing ring reaches 63 HRC or above, the effective carburizing layer depth is 0.40 mm or above, the grain size of the carburizing layer is finer, and compared with an existing carburizing technology, the fatigue life is prolonged; and a systematic solution is provided for reliable service of the high-end bearing under high-speed and high-temperature working conditions.

The invention belongs to the technical field of bearing heat treatment, and particularly relates to a heat treatment process for a high-speed bearing. The heat treatment process for the high-speed bearing is characterized by comprising the following steps: (1) heating stage: placing a high-carbon steel workpiece in a heat treatment furnace, heating, controlling carbon potential in the furnace, and preserving heat; (2) a heat preservation stage: continuously preserving heat; (3) a carbon potential increasing stage: keeping the temperature, and increasing the carbon potential in the furnace; (4) a carbonitriding stage: carrying out carbonitriding treatment; (5) a carbon potential reduction stage: reducing the carbon potential; (6) diffusion stage: heat preservation; (7) quenching stage: after the diffusion is finished, transferring the workpiece into a quenching medium for quenching treatment; and (8) tempering. Through segmented carbon potential control carbonitriding, characteristic quenching medium and precise tempering control, the surface quality, the dimensional stability, the mechanical property and the service reliability of the bearing part are remarkably improved, the surface structure quality is remarkably improved, and the wear resistance and the fatigue resistance are improved.

Provided is a rolling bearing that can be used in a low-temperature, lean-lubrication environment and can achieve exceptional durability by further improving wear resistance. A rolling bearing (1) comprises a bearing ring composed of an outer ring (10) and an inner ring (20), and a plurality of rolling elements (30) rollably held between the outer ring (10) and the inner ring (20), the rolling bearing (1) being used in a low-temperature, lean-lubrication environment. At least one of the outer ring (10), the inner ring (20), and the rolling elements (30) is formed using a steel material containing 0.1-0.7 mass% of C, 1.1-1.8 mass% of Cr, 0.7-1.3 mass% of Si, 0.3-1.1 mass% of Mn, and 0.6-1.3 mass% of Mo, and is subjected to a carbonitriding process and a quenching / tempering process in the stated order. The surface carbon concentration is 0.6-1.5 mass%, and the surface nitrogen concentration is 0.05-0.8 mass%.

The application provides a carbonitriding process for GCr15 parts, and steps are as follows: pre-oxidation, strong penetration, diffusion, quenching, hot cleaning, cold cleaning, cold treatment, tempering, taking out GCr15 parts, and air cooling after discharging. The application realizes continuous production by using a continuous mesh belt furnace production line with controllable atmosphere for carbonitriding, improves production efficiency, reduces labor intensity of workers, increases production capacity, reduces gap furnace opening and closing actions, reduces energy consumption, and saves at least 50% of cost compared with ordinary carbonitriding. In addition, carbon potential of each zone in the furnace can be controlled, so that quality stability is ensured. The surface hardness of the GCr15 parts obtained by the heat treatment process of the application can reach 62-65HRC, the core hardness is 61-64HRC, the carbide layer is less than 0.02mm, the carbonitriding layer is greater than 0.4mm, the surface carbon content is 1.15-1.5%, and the carbonitriding metallography can reach level 1.

This invention provides a surface treatment method for steel parts based on ultrasonic nano-strengthening, comprising the following steps: Step a: performing carbonitriding treatment on the steel parts; Step b: performing ultrasonic nano-strengthening treatment on the carbonitriding treated steel parts obtained in Step a; In Step a, the carbonitriding agent for carbonitriding treatment includes a boronizing agent and a carbonitriding agent, wherein the carbonitriding agent comprises the following components by mass percentage: 40-50% carbon black and 30-40% modified nitrogen-doped carbon material; The preparation method of the modified nitrogen-doped carbon material includes: adding sodium carboxymethyl cellulose to water, stirring to obtain sodium carboxymethyl cellulose hydrogel, adding NH4Cl to obtain NH4Cl / sodium carboxymethyl cellulose gel, drying, calcining, cooling to obtain nitrogen-doped carbon material, adding nitrogen-doped carbon material to a rare earth chloride aqueous solution, stirring, centrifuging, drying to obtain modified nitrogen-doped carbon material. This surface treatment method can significantly improve the fatigue resistance of steel parts.

The invention discloses a method for detecting composite carbonitriding inclusions in steel, which comprises the following steps: providing a to-be-detected sample; detecting the to-be-detected sample by using a scanning electron microscope and an energy spectrum analyzer to obtain data information of the to-be-detected sample; comparing and analyzing the data information of the to-be-tested sample with the inclusion standard database to obtain a measurement result of the composite carbonitriding inclusion in the steel. According to the embodiment of the invention, the sample preparation method and the parameters of the scanning electron microscope and the energy disperse spectroscopy are adjusted; the height difference between the highest point and the lowest point of a detection surface is controlled to be 0.5 mm-10 mm, the grating size of a scanning electron microscope is 10 [mu] m-25 [mu] m, the beam current of the scanning electron microscope is 2.5 nA-3nA, and the signal acquisition time of an energy spectrum analyzer on a single impurity is 80 ms-200 ms, so that the recognition rate of the small-particle-size composite carbonitriding inclusion with the particle diameter of 0.5 [mu] m-1. 0 [mu] m can be greatly improved, and the detection accuracy is improved. The influence of the impurities in the steel on the steel performance can be more accurately analyzed and researched.