CN111270194A - Heat treatment method for oil nozzle of marine diesel engine - Google Patents
Heat treatment method for oil nozzle of marine diesel engine Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/02—Pretreatment of the material to be coated
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/56—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering characterised by the quenching agents
- C21D1/613—Gases; Liquefied or solidified normally gaseous material
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/04—Hardening by cooling below 0 degrees Celsius
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
- C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
- C23C8/20—Carburising
- C23C8/22—Carburising of ferrous surfaces
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Abstract
The invention relates to a heat treatment method of a marine diesel engine oil nozzle, which is characterized by comprising the following steps of: firstly, cleaning a workpiece; the second step is that: calculating the flow of carburizing acetylene; the third step: pre-oxidizing; the fourth step: convection preheating; the fifth step: carrying out vacuum uniform heating; and a sixth step: carburizing; the seventh step: quenching; eighth step: performing cold treatment; the ninth step: tempering; the tenth step: and (5) aging. The invention can reduce the deformation of the oil nozzle, ensure the stable size, prolong the service life of the oil nozzle and ensure the working reliability of the diesel engine.
Description
Technical Field
The invention relates to chemical heat treatment of metal components, in particular to a heat treatment method of a marine diesel engine oil nozzle, and particularly relates to a heat treatment method of a marine oil nozzle made of 15NiMoSiCr10 steel.
Background
The fuel spray nozzle matching part is one of three large precision matching parts of a diesel engine, the performance of the fuel spray nozzle matching part determines the performance of the diesel engine, particularly, the fuel spray nozzle of the marine diesel engine has worse use working condition under the condition of burning heavy oil, and the fuel spray nozzle matching part puts forward higher requirements on the use performance of the fuel spray nozzle matching part.
The fuel spray nozzle is a key part of a diesel injector and is responsible for atomizing high-pressure fuel, and the atomized fuel is combusted in an engine cylinder so that a piston reciprocates. The performance of the fuel injection nozzle matching part plays a decisive role in the power of the engine. Poor heat treatment quality of the oil nozzle can cause frequent faults of the diesel engine, the service life of the oil nozzle is shortened, and the diesel engine is frequently disassembled and replaced, which is not allowed on commercial ships and warships and can cause great maintenance cost and potential safety hazards.
The scrapping or failure of the oil nozzle mainly occurs in two links, namely that the oil nozzle is unstable in size after being subjected to heat treatment processing, so that the oil nozzle is deformed, clamped and scrapped after being assembled, and the oil nozzle is scrapped due to the fact that a seat surface is collapsed, a ball head is broken, poor atomization is achieved and the like in the using process.
With the improvement of national energy-saving and emission-reduction targets and requirements, the emission requirements of the marine diesel engine are continuously improved, so that the jx continuously improves the quality and the performance of a diesel engine fuel injection system.
CN 109321837a discloses "a carburizing steel for an oil nozzle valve body and a preparation method thereof", which comprises the following main elements: carbon, manganese, copper, chromium, nickel, sulfur, aluminum, nitrogen, and niobium. The preparation method of the carburizing steel comprises the following steps: primary smelting; refining with a steel ladle; continuous casting; rolling a bar or a wire; drawing the bar or wire to a bright surface. The invention has the following beneficial effects: the steel for the oil nozzle valve body is annealed to obtain a spheroidized pearlite structure, hardness carbide particles are fine and uniform, the hardness is 185-210 HBW, cutting and tapping of the oil nozzle valve body are facilitated, and meanwhile, a prepared structure is provided for subsequent carburizing and quenching heat treatment.
CN 108385056A discloses a heat treatment method of an oil nozzle of an engine fuel system, which comprises the following steps:
(1) placing the oil nozzle in a vacuum quenching furnace, replacing the air in the furnace with nitrogen, then heating to 1000-1050 ℃ for quenching treatment, preserving heat for 1.2 hours, and then cooling the oil nozzle to below 60 ℃ with high-pressure nitrogen;
(2) maintaining the oil nozzle in a vacuum quenching furnace in nitrogen atmosphere, then heating to 550-600 ℃, preserving heat for 2-5 hours, cooling to below 60 ℃ by using high-pressure nitrogen, and immediately transferring the oil nozzle into a vacuum nitriding furnace;
(3) and raising the temperature in the vacuum nitriding furnace to 530-580 ℃, introducing nitrogen-containing treatment gas into the furnace to perform nitriding treatment on the oil nozzle, and finally cooling the oil nozzle to be below 100 ℃ under the protection of N2 gas for discharging. The heat treatment method ensures the nitriding hardness of the bottom of the blind hole and the depth of an effective nitriding layer, and is suitable for industrial application.
The above prior art is of course a useful attempt in the field of said technology.
Disclosure of Invention
The invention aims to provide a heat treatment method of a marine diesel engine oil nozzle, which can reduce the deformation of the oil nozzle, ensure the dimensional stability, prolong the service life of the oil nozzle and ensure the working reliability of a diesel engine.
The basic principle of the invention is as follows: the heat treatment method flow is optimized, and the performance potential of the steel is exerted to the maximum extent by utilizing the mechanisms of solid solution strengthening, phase change strengthening and dispersion strengthening of the material, so that the use performance of the marine diesel engine fuel spray nozzle is improved.
The invention relates to a heat treatment method of a marine diesel engine fuel spray nozzle, which is characterized by comprising the following steps of:
firstly, cleaning a workpiece; the large ends of a plurality of workpieces (oil nozzles) are vertically inserted into a clamp downwards, gaps of more than 10mm are kept among the workpieces, the workpieces are placed into a cleaning tank filled with a water-based alkaline cleaning agent together, and the workpieces are cleaned in a soaking and spraying mode; then, hanging a fixture with a plurality of workpieces from the cleaning tank, and drying the fixture by hot air;
the second step is that: calculating the flow of carburizing acetylene; accurately calculating the flow of carburizing acetylene before charging and carburizing the workpiece, and modifying and storing the flow of acetylene in the method program;
the third step: pre-oxidizing; placing the fixture which is blow-dried and clamped with a plurality of workpieces in an air tempering furnace, and carrying out pre-oxidation treatment in the air tempering furnace, wherein the heating temperature is 355 +/-10 ℃, and the pre-oxidation time is 55 min;
the fourth step: convection preheating; placing the clamp which is clamped with a plurality of workpieces after preoxidation treatment in a low-pressure carburizing furnace, heating to 800 ℃ at the heating rate of 3-5 ℃/min, and filling nitrogen in a convection preheating stage below 800 ℃, wherein the convection preheating is carried out for 60-90 min, and the convection pressure in the furnace is 1200-2000 mbar;
the fifth step: carrying out vacuum uniform heating; carrying out convection preheating in a low-pressure carburizing furnace, immediately heating up to 960 ℃ at a heating-up speed of 5 ℃/min, controlling the vacuum degree within the range of 5-10 pa, and carrying out vacuum soaking for 60 min;
and a sixth step: carburizing; continuously performing in a low-pressure carburizing furnace, controlling the carburizing pressure to be 10 +/-0.5 mar, controlling the carburizing temperature to be 960 +/-10 ℃, introducing the acetylene flow (accurately through a mass flow meter) calculated in the second step into the furnace for multiple times of strong permeation, and vacuumizing and diffusing after each time of strong permeation so as to realize multiple times of low-pressure pulse carburization;
the seventh step: quenching; transferring the clamp which clamps a plurality of workpieces after the low-pressure pulse carburization is finished into a gas quenching chamber, and carrying out high-pressure nitrogen quenching, wherein the purity of nitrogen is more than 99.995%, the quenching pressure is 10-15 bar, and the quenching time is 30-35 min, so that the workpieces are cooled to below 60 ℃;
eighth step: performing cold treatment; after quenching high-pressure nitrogen, clamping a plurality of workpieces, transferring the workpieces into a cryogenic box within half an hour, reducing the temperature to-115 to-120 ℃ at the cooling rate of 3-5 ℃/min, and keeping the temperature for 180 +/-5 min; cooling the core of the workpiece to a cryogenic treatment temperature;
the ninth step: tempering; after the cold treatment is finished, clamping a plurality of workpieces, transferring the clamps into a nitrogen protection furnace for heating and tempering within half an hour, raising the temperature to 250 +/-10 ℃ at the heating rate of 5-10 ℃ for min, and tempering for 300 +/-10 min;
the tenth step: aging; and (3) clamping a plurality of workpieces after tempering, moving out of the nitrogen protective furnace, air-cooling to room temperature, transferring into an air tempering furnace, heating for aging treatment, heating to 140 +/-10 ℃ at the heating rate of 5-10 ℃ min, aging for 17 +/-1 h, and then discharging from the furnace and air-cooling to room temperature.
Further, the workpiece is an oil nozzle made of 15NiMoSiCr10 steel and provided with a middle hole and a seat surface.
Further, the water-based alkaline cleaning agent is HJ-921A, tap water is added to prepare a solution with the concentration of 3-5% (weight percentage), and 3-5% (weight percentage) of an antirust agent is added; the cleaning temperature is 80-100 ℃, and the cleaning time is 60-70 min.
Further, the calculation formula of the carburizing acetylene flow is as follows: carburizing acetylene flow L/h is equal to the total area m of the assembly2×200L/m2+1200～1300L；
In the formula: total area m of the package2Area m of one-piece workpiece2X number of workpieces.
Further, the low-pressure pulse carburization is performed by 6 times of strong carburization and 6 times of diffusion alternately, and the ratio of 6 times of strong carburization time to 6 times of diffusion time is 0.1186.
The invention has the beneficial effects that: the invention makes each heat treatment index of the 15NiMoSiCr10 steel oil nozzle obviously superior to that of the oil nozzle made of 18CrNi8, 18Cr2Ni4WA and other materials, especially has excellent anti-tempering performance above 250 ℃, and can reach 718HV at above 310 DEG C1The service life of the product is very favorable, no abnormality is found after the product is used for more than 4000 hours on a machine, and the service performance is stable and reliable. Although the price of the material is higher than that of 18CrNi8, 18Cr2Ni4WA and other materials, the cost of the method is reduced by more than 40 percent, and the production efficiency is improved by 35 percentAbove, the comprehensive cost is equivalent to the cost of other steel parts, but the performance is more excellent, and the method has a remarkable market prospect. Compare traditional gas carburization, its production efficiency can promote more than 30%, and its heat treatment processing cost can practice thrift more than 40%, and the product is anti tempering nature higher, the hardness is higher to metallographic structure is good, and comprehensive performance is better, can adapt to more abominable service behavior.
Drawings
FIG. 1 is a schematic structural diagram of a fuel spray nozzle made of 15NiMoSiCr10 steel.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
Referring to fig. 1, a heat treatment method for a marine diesel engine fuel injector is characterized by comprising the following steps:
firstly, cleaning a workpiece; the large ends of a plurality of workpieces 10 (oil nozzles) are vertically inserted into a clamp downwards, gaps of more than 10mm are kept among the workpieces 10, the workpieces are placed into a cleaning tank containing a water-based alkaline cleaning agent together, and the workpieces are cleaned in a soaking and spraying mode; then, hanging a fixture with a plurality of workpieces from the cleaning tank, and drying the fixture by hot air;
the second step is that: calculating the flow of carburizing acetylene; accurately calculating the flow of carburizing acetylene before charging and carburizing the workpiece, and modifying and storing the flow of acetylene in the method program; the determination of the acetylene flow can influence the carbon potential in the furnace during carburizing and has important influence on the carburizing quality.
The third step: pre-oxidizing; placing the fixture which is blow-dried and clamped with a plurality of workpieces in an air tempering furnace, and carrying out pre-oxidation treatment in the air tempering furnace, wherein the heating temperature is (355 +/-10) DEG C, and the pre-oxidation time is 55 min;
the fourth step: convection preheating; placing the clamp which is clamped with a plurality of workpieces after preoxidation treatment in a low-pressure carburizing furnace, heating to 800 ℃ at a heating speed of 3-5 ℃/min, and filling nitrogen in a convection preheating stage below 800 ℃, wherein the convection preheating is carried out for 60-90 min, and the convection pressure in the furnace is 1200-2000 mbar;
the fifth step: carrying out vacuum uniform heating; carrying out convection preheating in a low-pressure carburizing furnace, immediately heating up to 960 ℃ at a heating-up speed of 5 ℃/min, controlling the vacuum degree within the range of 5-10 pa, and carrying out vacuum soaking for 60 min;
and a sixth step: carburizing; continuously performing in a low-pressure carburizing furnace, controlling the carburizing pressure to be 10 +/-0.5 mar, controlling the carburizing temperature to be 960 +/-10 ℃, introducing the acetylene flow (accurately through a mass flow meter) calculated in the second step into the furnace for multiple times of strong permeation, and vacuumizing and diffusing after each time of strong permeation so as to realize multiple times of low-pressure pulse carburization; the reasonable ratio of the strong cementation time to the diffusion time is selected, so that the carbon concentration gradient of a carburized layer can be better controlled, the carbide form can be better controlled, a smooth hardness gradient and a good metallographic structure can be obtained after quenching, and the service life of a product can be prolonged.
The seventh step: quenching; transferring the clamp which clamps a plurality of workpieces after the low-pressure pulse carburization is finished into a gas quenching chamber, and carrying out high-pressure nitrogen quenching, wherein the purity of nitrogen is more than 99.995%, the quenching pressure is 10-15 bar, and the quenching time is 30-35 min, so that the workpieces are cooled to below 60 ℃; high-pressure quenching is carried out by adopting high-purity nitrogen, the quenching requirement of high alloy steel can be met, the method is an environment-friendly and green heat treatment mode, cleaning is not needed after quenching, and the production efficiency is high.
Eighth step: performing cold treatment; after quenching high-pressure nitrogen, clamping a plurality of workpieces, transferring the workpieces into a cryogenic box within half an hour, reducing the temperature to-115 to-120 ℃ at the cooling rate of 3-5 ℃/min, and keeping the temperature for 180 +/-5 min; cooling the core of the workpiece to a cryogenic treatment temperature; the cold treatment is the continuation of quenching, can further promote the transformation of retained austenite to martensite, reduce the content of retained austenite, improve the dimensional stability and the hardness of work piece, still can precipitate the carbide of dispersion distribution, carry out dispersion strengthening to the work piece. The arrangement of the cold treatment immediately after quenching can enhance the effect of transformation of the retained austenite, but prevent cracking of the workpiece.
The ninth step: tempering; after the cold treatment is finished, clamping a plurality of workpieces by using a clamp, transferring into a nitrogen protection furnace for heating and tempering within half an hour, raising the temperature to (250 +/-10) DEG C at the heating rate of 5-10 ℃/min, and tempering for (300 +/-10) min; the determination of the tempering temperature and the tempering time plays an important role in the performance stability of the workpiece in the using process, and the structure stress and the thermal stress of the workpiece after heat treatment can be reduced.
The tenth step: aging; and (3) clamping a plurality of workpieces after tempering, moving out of the nitrogen protective furnace, air-cooling to room temperature, transferring into an air tempering furnace, heating for aging treatment, heating to 140 +/-10 ℃ at a heating rate of 5-10 ℃/min, aging for (17 soil) h, and then discharging from the furnace, and air-cooling to room temperature. The aging can further reduce the residual stress of the workpiece, stabilize the structure of the workpiece and improve the dimensional stability of the workpiece.
The workpiece 10 is a fuel injector made of 15nimo sicr10 steel and has a central bore 11 and a seating surface 12.
The water-based alkaline cleaning agent is HJ-921A, tap water is added to prepare a solution with the concentration of 3-5% (weight percentage), and 3-5% (weight percentage) of an antirust agent is added; the cleaning temperature is 80-100 ℃, and the cleaning time is 60-70 min. So as to remove oil stains and rust on the surface of the workpiece. The concentration of the water-based alkaline cleaning agent in the cleaning tank is checked once a day, a record is made, and the water-based alkaline cleaning agent is replaced in the whole tank every 100 times.
The calculation formula of the carburizing acetylene flow is as follows: carburizing acetylene flow (L/h) is equal to the total area (m) of the assembly2)×200(L/m2)+(1200～1300)L；
In the formula: total area of the package (m)2) Area (m) of a single workpiece2) X the number of workpieces;
the area of a single workpiece (oil nozzle) is 0.012 (m) by measurement and calculation2) (ii) a The number of carburized workpieces in each furnace is specifically 100; the carburized acetylene flow rate (L/h) is 0.012 (m)2)×100×200(L/m2) +1300(L) ═ 1540 (L/h). It should be noted that for a 500 kg charging amount of equipment, the maximum acetylene flow rate is not more than 6000L/furnace, and the minimum acetylene flow rate cannot be less than (1200-1300) L/h.
The low-pressure pulse carburization is carried out by 6 times of strong permeation and 6 times of diffusion alternately, and the distribution of 6 times of strong permeation time and 6 times of diffusion time is shown in a table 1;
TABLE 1 respective Strong penetration and diffusion time distribution
Unit(s)
The ratio of 6 times of strong penetration time to 6 times of diffusion time was 0.1186.
And the quality of the workpiece can be detected after aging. And (3) detecting the hardness, carbide level and residual austenite content of the excircle and the seat surface 12 of the workpiece 10 extracted 1 in each furnace, and simultaneously, detecting the deformation from the seat surface 12 to the large end surface size and the aperture of the middle hole 11 of 5-10% of the workpieces 10 extracted in each furnace.
The hardness of the outer circle was measured by a rockwell hardness tester, the hardness of the seat surface was measured by a microhardness tester, the grain size and carbide level were measured by an optical microscope, the retained austenite was quantitatively measured by XRD (X-ray diffractometer), and the elongation of the seat surface was measured by a depth gauge.
The surface hardness of the 15NiMoSiCr10 steel oil nozzle treated by the method can reach 720-730HV1The depth CHD of the hardened layer is 0.75-0.80 mm (at 550HV 1), the grain size can reach more than 5 grade, the carbide grade 1, the residual austenite is controlled below 10%, the size shrinkage of the seat surface 12 is 0.25-0.30 mm, the size shrinkage of the mesopore 11 is 0.12-0.15 mm, and no crack is generated.
Claims (5)
1. A heat treatment method for a marine diesel engine fuel spray nozzle is characterized by comprising the following steps:
firstly, cleaning a workpiece; vertically inserting the large ends of a plurality of workpieces 10 downwards into a clamp, keeping a gap of more than 10mm between the workpieces 10, putting the workpieces into a cleaning tank containing a water-based alkaline cleaning agent together, and cleaning the workpieces in a soaking and spraying mode; then, hanging a fixture with a plurality of workpieces from the cleaning tank, and drying the fixture by hot air;
the second step is that: calculating the flow of carburizing acetylene; accurately calculating the flow of carburizing acetylene before charging and carburizing the workpiece, and modifying and storing the flow of acetylene in the method program;
the third step: pre-oxidizing; placing the fixture which is blow-dried and clamped with a plurality of workpieces in an air tempering furnace, and carrying out pre-oxidation treatment in the air tempering furnace, wherein the heating temperature is 355 +/-10 ℃, and the pre-oxidation time is 55 min;
the fourth step: convection preheating; placing the clamp which is clamped with a plurality of workpieces after preoxidation treatment in a low-pressure carburizing furnace, heating to 800 ℃ at a heating speed of 3-5 ℃/min, and filling nitrogen in a convection preheating stage below 800 ℃, wherein the convection preheating is carried out for 60-90 min, and the convection pressure in the furnace is 1200-2000 mbar;
the fifth step: carrying out vacuum uniform heating; carrying out convection preheating in a low-pressure carburizing furnace, immediately heating up to 960 ℃ at a heating-up speed of 5 ℃/min, controlling the vacuum degree within the range of 5-10 pa, and carrying out vacuum soaking for 60 min;
and a sixth step: carburizing; continuously performing in a low-pressure carburizing furnace, controlling the carburizing pressure at 10 +/-0.5 mar and the carburizing temperature at 960 +/-10 ℃, introducing the acetylene flow calculated in the second step into the furnace for performing multiple times of strong permeation, and vacuumizing for diffusion after each time of strong permeation so as to realize multiple times of low-pressure pulse carburization;
the seventh step: quenching; transferring the clamp which clamps a plurality of workpieces after the low-pressure pulse carburization is finished into a gas quenching chamber, and carrying out high-pressure nitrogen quenching, wherein the purity of nitrogen is more than 99.995%, the quenching pressure is 10-15 bar, and the quenching time is 30-35 min, so that the workpieces are cooled to below 60 ℃;
eighth step: performing cold treatment; after quenching high-pressure nitrogen, clamping a plurality of workpieces, transferring the workpieces into a cryogenic box within half an hour, reducing the temperature to-115 to-120 ℃ at the cooling rate of 3-5 ℃/min, and keeping the temperature for 180 +/-5 min; cooling the core of the workpiece to a cryogenic treatment temperature;
the ninth step: tempering; after the cold treatment is finished, clamping a plurality of workpieces, transferring the clamps into a nitrogen protection furnace for heating and tempering within half an hour, raising the temperature to 250 +/-10 ℃ at the heating rate of 5-10 ℃/min, and tempering for 300 +/-10 min;
the tenth step: aging; and (3) clamping a plurality of workpieces after tempering, moving out of the nitrogen protective furnace, air-cooling to room temperature, transferring into an air tempering furnace, heating for aging treatment, heating to 140 +/-10 ℃ at the heating rate of 5-10 ℃/min, aging for 17 +/-1 h, and then discharging from the furnace, and air-cooling to room temperature.
2. The heat treatment method for the fuel injection nozzle of the marine diesel engine according to claim 1, characterized in that: the workpiece 10 is a fuel injector made of 15NiMoSiCr10 steel and has a central bore 11 and a seating surface 12.
3. The heat treatment method for the fuel injection nozzle of the marine diesel engine according to claim 1, characterized in that: the grade of the alkaline water-based cleaning agent is HJ-921A, tap water is added to prepare a solution with the weight concentration of 3-5%, and an antirust agent with the weight of 3-5% is added; the cleaning temperature is 80-100 ℃, and the cleaning time is 60-70 min.
4. The heat treatment method for the fuel injection nozzle of the marine diesel engine according to claim 1, characterized in that: the calculation formula of the carburizing acetylene flow is as follows: the carburized acetylene flow rate is L/h = square meter × 200L/1200-1300L;
in the formula: the total area of the workpiece is square meter, namely the area of a single workpiece is square meter multiplied by the number of workpieces.
5. The heat treatment method for the fuel injection nozzle of the marine diesel engine according to claim 1, characterized in that: the low-pressure pulse carburization is carried out by 6 times of strong carburization and 6 times of diffusion alternately, and the ratio of 6 times of strong carburization time to 6 times of diffusion time is 0.1186.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111270194B (en) | 2022-05-20 |
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