CN111468891B - Production process of high-precision deep-hole valve element - Google Patents
Production process of high-precision deep-hole valve element Download PDFInfo
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- CN111468891B CN111468891B CN202010184212.5A CN202010184212A CN111468891B CN 111468891 B CN111468891 B CN 111468891B CN 202010184212 A CN202010184212 A CN 202010184212A CN 111468891 B CN111468891 B CN 111468891B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
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- B23P15/001—Making specific metal objects by operations not covered by a single other subclass or a group in this subclass valves or valve housings
Abstract
The invention discloses a production process of a high-precision deep-hole valve core, which comprises the following steps: the method comprises the following steps: rough turning and pretreatment; step two: gun drilling; step three: finish turning; step four: milling; step five: induction high-frequency heat treatment; step six: reaming; step seven: sulfurizing; step eight: and (5) final grinding. The valve core workpiece provided by the invention has the advantages that the heating depth reaches more than 3mm through high-frequency induction heat treatment, the surface quality is good, the brittleness is small, the quenching surface is not easy to oxidize and decarbonize, and the deformation is small, and meanwhile, the valve core prepared by combining pretreatment and sulfurization operation has good wear resistance and pressure resistance.
Description
Technical Field
The invention relates to the technical field of mechanical manufacturing, in particular to a production process of a high-precision deep-hole valve core.
Background
The valve core is the most critical part of a valve, and directly influences the quality and the service life of the valve. When the current engineering hydraulic equipment works, the flow of hydraulic oil needs to be controlled to ensure that the operation part of the equipment effectively and durably operates. The deep-hole valve core moves back and forth in the valve body at a high speed, and hydraulic oil is controlled to flow between two or more valve cavities through the axial hole and the radial hole, so that the axial performance and the radial performance of the valve core play a very important role in the operation of the whole device.
The traditional high-precision deep-hole valve core mainly has two surface treatment schemes: firstly, the chromium plating treatment is adopted, the processing cost of parts is high, and the axial size is unstable; and the other method adopts carburizing and quenching treatment, although the heat treatment cost is low, deep holes are difficult to process, so that the cost of the tool is high.
Induction heat treatment is a surface heat treatment process for locally heating a workpiece by using induced current, and is widely used for surface quenching of workpieces such as gears, shafts, crankshafts, cams, rollers and the like, in order to improve the wear resistance and fatigue fracture resistance of the workpieces. The main advantages of induction heating are: integral heating is not needed, the deformation of the workpiece is small, and the power consumption is low. ② no pollution. Thirdly, the heating speed is high, and the surface of the workpiece is oxidized and decarburized lightly. Fourthly, the surface hardening layer can be adjusted according to the requirement and is easy to control. The heating equipment can be arranged on a machining production line, so that the mechanization and automation are easy to realize, the management is convenient, the transportation can be reduced, the labor is saved, and the production efficiency is improved. The quenched layer has fine martensite structure and high hardness, strength and toughness. The surface layer of the workpiece after surface quenching has larger compression internal stress, and the workpiece has higher anti-fatigue breaking capacity.
Therefore, the induction heating technology can be optimized, the traditional valve core preparation technology is combined, and the high-precision deep-hole valve core with stable axial dimension and low processing cost is provided through special induction high-frequency treatment.
Disclosure of Invention
Technical problem to be solved
The invention provides the high-precision deep-hole valve core with stable axial dimension and low processing cost by optimizing the induction heating technology, combining with the traditional valve core preparation process and carrying out special induction high-frequency induction treatment.
(II) technical scheme
In order to achieve the purpose, the invention provides the following technical scheme:
a preparation process of a high-precision deep-hole valve core comprises the following steps:
the method comprises the following steps: rough turning and pretreatment
Discharging machining allowance according to the excircle and the length of the valve core, and turning a valve core workpiece, wherein allowance is reserved on the excircle to obtain a valve core workpiece to be pretreated;
placing the valve core workpiece into a vacuum sintering furnace, heating to 680-750 ℃ under the protection of Ar gas, preserving heat for 0.5h, then annealing to 520-530 ℃, preserving heat for 2-3h, and then cooling to room temperature;
step two: gun drill
Firstly, clamping a workpiece by using a drill jig, positioning the workpiece by using a drill positioning seat, and drilling a working shoulder, a supporting shoulder and a groove;
step three: finish turning
And (4) turning each shoulder and each groove, and processing the rest until the requirement is met.
Step four: milling process
Milling 1 hole diameter at the right end of the workpiece
The axial bore of (a).
Step five: induction high frequency heat treatment
Putting the workpiece obtained in the step into a high-frequency induction heat treatment device for carrying out high-frequency induction heat treatment for one time, wherein the process parameters are as follows: frequency: 15KHZ, raising the temperature to 1000 ℃ and 1100 ℃ at the temperature raising speed of 1000 ℃/s, and preserving the temperature for 3 s; rapidly cooling to 220 ℃ and 240 ℃, and preserving heat for 1-2 h; cooling to-20-25 ℃, and keeping the temperature for 1-2 h;
step six: reaming
Reaming the axial hole by adopting a forming reamer, and after reaming, enabling the axial hole to reach the required size
Step seven: sulfurizing
Hydrogen sulfide is used as a sulfur permeation source, H2S-Ar-H2 is used as a sulfur permeation atmosphere, high-purity (99.999%) Ar and H2 (the proportion is 1: 1) are used as carrier gas, the using amount of H2S is 3 percent of the total gas amount, the flow rate of mixed gas is about 80-120L/H, the sulfur permeation temperature is 175-;
step eight: final grinding
And positioning the workpiece by using double ejector pins, and finely grinding the support shoulder, the working shoulder, the groove and the axial hole.
Through the technical scheme, the valve core workpiece provided by the invention has the advantages that through high-frequency induction heat treatment, the heating depth reaches more than 3mm, the surface quality is good, the brittleness is small, the quenching surface is not easy to oxidize and decarbonize, and the deformation is small, and meanwhile, the valve core prepared by combining pretreatment and sulfurization operation has good wear resistance and pressure resistance.
Preferably, in the pretreatment in the first step, the valve core workpiece is placed in a vacuum sintering furnace, the temperature is raised to 720 ℃ along with the heat preservation for 0.5h under the protection of Ar gas, then the annealing is carried out to 526 ℃ along with the heat preservation for 2.5h, and then the temperature is reduced to the room temperature.
Through the pretreatment scheme, the uncleaned grease on the valve core workpiece can be burnt, and carbon black is not easy to form; reacting oxygen with iron to produce Fe3O4The film improves the surface activity of the valve core workpiece, accelerates the speed of carbon atom adsorption on the surface of the steel part, and can improve the carburizing speed and uniformity; stress is eliminated, and deformation is reduced; therefore, the pretreatment can ensure that the valve core workpiece can obtain uniform structure and hardness after the pretreatment, and the preparation of metallographic structure is made for the second heat treatment.
The research finds that: in the case of a steel structure which is only carburized and not sulfurized, the surface layer is high-carbon martensite and carbide, and although hard particles and a matrix exist, under the action of continuous and high load, the surface of the material bears high friction force, the friction force causes extremely high stress to locally generate on the wear surface to cause plastic deformation, so that welding points are formed between the friction surface and a dual friction surface, the strength of the welding points is generally high, and in the subsequent sliding process, the welding points are damaged and then migrate to the dual surface to form adhesive substances, so that adhesive abrasion occurs, and the abrasion of the steel structure is high.
Preferably, the fifth step includes a second high-frequency induction heat treatment, and the process parameters are as follows: frequency: 15KHZ, raising the temperature to 830 ℃ and 850 ℃ at the temperature-raising speed of 800 ℃/s, and keeping the temperature for 1.5 s; rapidly cooling to 170 ℃ and 180 ℃, and preserving heat for 2-3 h; cooling to-30-35 ℃, and keeping the temperature for 1-2 h;
according to the technical scheme, induction heating surface quenching is a quenching method which utilizes the principle of electromagnetic induction to generate induction current with high density on the surface layer of a workpiece, rapidly heats the workpiece to an austenite state, and then rapidly cools the workpiece to obtain a martensite structure. When an alternating current with a certain frequency passes through the induction coil, an alternating magnetic field with the same frequency as the current change is generated inside and outside the induction coil. The metal workpiece is placed in the induction coil, and under the action of the magnetic field, induced current with the same frequency and the opposite direction as the induction coil is generated in the workpiece. A closed loop, commonly referred to as eddy current, is formed along the surface of the workpiece due to the induced current. The eddy current converts electrical energy into heat energy, which rapidly heats the surface of the workpiece. Eddy currents are mainly distributed on the surface of the workpiece, and almost no current flows inside the workpiece, which is called a surface effect or skin effect. The induction heating utilizes the skin effect and relies on the current heat effect to rapidly heat the surface of a workpiece to the quenching temperature. The induction coil is made of copper tube and is internally filled with cooling water. When the surface of the workpiece is heated to a certain temperature in the induction coil, water is sprayed and cooled immediately, so that the surface layer obtains a martensite structure. The invention carries out high-frequency induction heat treatment for 2 times; the heating depth reaches more than 3mm, the induction heating surface quenching has the advantages of good surface quality, small brittleness, difficult oxidation and decarbonization of the quenching surface and small deformation.
Preferably, in the seventh step, after the sulfurization is finished, the temperature is rapidly reduced to-40 to-45 ℃, and the temperature is kept for 0.5 to 1 hour.
Through the technical scheme, for the steel structure which is only carburized and not sulfurized, the surface layer is high-carbon martensite and carbide, although hard particles and a matrix exist, under the action of continuous and high load, the surface of the material bears high friction force, the friction force causes the local high stress of the wear surface to generate plastic deformation, and as a result, welding points are formed between the friction surface and the dual friction surface, the strength of the welding points is higher than that of the steel structure in general, and in the subsequent sliding process, the welding points are damaged and then migrate to the dual surface to form adhesive substances, so that the adhesive wear is generated, and the wear of the steel structure is high; after the sulfurization is finished, the temperature is rapidly reduced, and the metallographic structure of the workpiece can be well solidified.
(III) advantageous effects
Compared with the prior art, the invention provides a production process of a high-precision deep-hole valve core, which has the following beneficial effects:
1. the thickness of a hardened layer of the processed valve core is 4.1mm, and the torsional fatigue strength (789-5MPa, surface hardness 71-76 HRC; the following relevant standards are better specified: according to the GB/T5772-2010 and ZBJ94007-1988 standards.
2. The processed valve core has good wear resistance and pressure resistance.
Drawings
FIG. 1 is a schematic structural view of the valve cartridge of the present invention;
in the figure: 1-supporting shoulder, 2-working shoulder, 3-groove and 4-axial hole.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in the valve core of fig. 1, 6 shoulders are arranged on the valve core, the leftmost shoulder and the rightmost shoulder are supporting shoulders 1 for connecting a coupler, and the rest 4 shoulders are working shoulders 2 which are marked as I, II, III and IV from left to right. The rectangular grooves 3 are uniformly processed in the circumferential direction on the two shoulders II and III respectively, the central angle corresponding to the rectangular grooves is 5.6 degrees, the dislocation angle between the two shoulders II and III and the rectangular grooves is 11.25 degrees, and the dislocation ensures that the grooves on the two shoulders and the corresponding valve sleeve windows are in dislocation communication when the valve core continuously rotates, namely when the grooves on the shoulders II and the windows on the valve sleeve are opened, the grooves on the shoulders III and the valve sleeve windows are closed, and vice versa. The hydraulic oil alternately enters and exits the flutter cylinder to form the reciprocating vibration of the elastic end cover. The axial hole 4 that the diameter is 1.5mm is seted up to the case right-hand member, this because in the assembling process of excitation valve, can form 1 narrow and small air cavity between case and the end cap, because the compressibility of gas for the installation accuracy of case is influenced in the existence of air cavity, and the axial hole can make air cavity and excitation valve T mouth link to each other, takes away the gas in the valve along with hydraulic circuit, thereby improves the installation accuracy of case, can set up a plurality of axial holes 4 according to actual need.
Example 1
A preparation process of a high-precision deep-hole valve core comprises the following steps:
the method comprises the following steps: rough turning and pretreatment
Discharging machining allowance according to the excircle and the length of the valve core, and turning a valve core workpiece, wherein allowance is reserved on the excircle to obtain a valve core workpiece to be pretreated; the composition of the spool is shown in the following table (not written Fe):
| composition (I) | C | Si | Mn | Cr | Ni | S | P |
| Content (%) | 0.42 | 0.17 | 0.5 | 0.25 | 0.25 | 0.025 | 0.025 |
Placing the valve core workpiece into a vacuum sintering furnace, heating to 680-fold and 720 ℃ under the protection of Ar gas, preserving heat for 0.5h, then annealing to 523 ℃ at 520-fold and preserving heat for 2h, and then cooling to room temperature;
step two: gun drill
Firstly, clamping a workpiece by using a drill jig, positioning the workpiece by using a drilling positioning seat, and drilling a working shoulder 1 and a supporting shoulder 2;
step three: finish turning
And (4) turning each shoulder and the groove 3, and processing the rest until the requirement is met.
Step four: milling process
Milling the aperture at the right end of the workpiece
And an axial hole 4.
Step five: induction high frequency heat treatment
Putting the workpiece obtained in the step into a high-frequency induction heat treatment device, and carrying out high-frequency induction heat treatment twice, wherein the technological parameters of the first high-frequency induction heat treatment are as follows: frequency: 15KHZ, raising the temperature to 1050 ℃ at the temperature raising speed of 1000 ℃/s, and keeping the temperature for 3 s; rapidly cooling to 230 ℃ and preserving heat for 1 h; cooling to-20 deg.C, and maintaining for 1 h; the technological parameters of the second high-frequency induction heat treatment are as follows: frequency: 15KHZ, raising the temperature to 830-835 ℃ at the temperature-raising speed of 800 ℃/s, and keeping the temperature for 1.5 s; rapidly cooling to 170-; cooling to-30-32 deg.C, and keeping the temperature for 1 h.
Step six: reaming
Reaming the axial hole 4 by using a forming reamer, and after reaming, enabling the axial hole 4 to reach the required size
Step seven: sulfurizing;
using hydrogen sulfide as a source of sulfur seepage and using H2S—Ar—H2As a sulfurizing atmosphere, Ar and H were present in high purity (99.999%)2(ratio 1: 1) as carrier gas, H2The dosage of S is 3 percent of the total gas quantity, the flow of the mixed gas is about 80-120L/h, the sulfurization temperature is 175-; after sulfurization is finished, quickly cooling to-40 ℃, and preserving heat for 0.5 h;
step eight: final grinding
And positioning the workpiece by using double ejector pins, and finely grinding the support shoulder 1, the working shoulder 2, the groove 3 and the axial hole 4.
Example 2
Discharging machining allowance according to the excircle and the length of the valve core, and turning a valve core workpiece, wherein allowance is reserved on the excircle to obtain a valve core workpiece to be pretreated; the composition of the spool is shown in the following table (not written Fe):
| composition (I) | C | Si | Mn | Cr | Ni | S | P |
| Content (%) | 0.50 | 0.37 | 0.8 | 0.15 | 0.15 | 0.015 | 0.015 |
Placing the valve core workpiece into a vacuum sintering furnace, heating to 730-plus-750 ℃ under the protection of Ar gas, preserving heat for 0.5h, then annealing to 525-plus-530 ℃, preserving heat for 3h, and then cooling to room temperature;
step two: gun drill
Firstly, clamping a workpiece by using a drill jig, positioning the workpiece by using a drilling positioning seat, and drilling a working shoulder 1 and a supporting shoulder 2;
step three: finish turning
And (4) turning each shoulder and the groove 3, and processing the rest until the requirement is met.
Step four: milling process
Milling the aperture at the right end of the workpiece
And an axial hole 4.
Step five: induction high frequency heat treatment
Putting the workpiece obtained in the step into a high-frequency induction heat treatment device, and carrying out high-frequency induction heat treatment twice, wherein the technological parameters of the first high-frequency induction heat treatment are as follows: frequency: 15KHZ, raising the temperature to 1060-1100 ℃ at the temperature-raising speed of 1000 ℃/s, and keeping the temperature for 3 s; rapidly cooling to 235 ℃ and 240 ℃, and preserving heat for 2 h; cooling to-23-25 ℃, and keeping the temperature for 2 h; the technological parameters of the second high-frequency induction heat treatment are as follows: frequency: 15KHZ, raising the temperature to 840 ℃ and 850 ℃ at the temperature raising speed of 800 ℃/s, and keeping the temperature for 1.5 s; rapidly cooling to 178-; cooling to-33-35 deg.C, and keeping the temperature for 2 h.
Step six: reaming
Reaming the axial hole 4 by using a forming reamer, wherein the axial hole 4 reaches the required size after reaming;
step seven: sulfurizing;
using hydrogen sulfide as a source of sulfur seepage and using H2S—Ar—H2As a sulfurizing atmosphere, Ar and H were present in high purity (99.999%)2(ratio 1: 1) as carrier gas, H2The dosage of S is 3 percent of the total gas quantity, the flow of the mixed gas is about 80-120L/h, the sulfurization temperature is 180 ℃, and the time is 30-35 min; after sulfurization is finished, quickly cooling to-45 ℃, and preserving heat for 1 h;
step eight: final grinding
And positioning the workpiece by using double ejector pins, and finely grinding the support shoulder 1, the working shoulder 2, the groove 3 and the axial hole 4.
Example 3
Discharging machining allowance according to the excircle and the length of the valve core, and turning a valve core workpiece, wherein allowance is reserved on the excircle to obtain a valve core workpiece to be pretreated; the composition of the spool is shown in the following table (not written Fe):
| composition (I) | C | Si | Mn | Cr | Ni | S | P |
| Content (%) | 0.45 | 0.25 | 0.65 | 0.20 | 0.20 | 0.020 | 0.020 |
Placing the valve core workpiece into a vacuum sintering furnace, heating to 720-plus-material 730 ℃ under the protection of Ar gas, preserving heat for 0.5h, then annealing to 523-plus-material 528 ℃, preserving heat for 2.5h, and then cooling to room temperature;
step two: gun drill
Firstly, clamping a workpiece by using a drill jig, positioning the workpiece by using a drilling positioning seat, and drilling a working shoulder 1 and a supporting shoulder 2;
step three: finish turning
And (4) turning each shoulder and each groove, and processing the rest until the requirement is met.
Step four: milling process
Milling the aperture at the right end of the workpiece
And an axial hole 4.
Step five: induction high frequency heat treatment
Putting the workpiece obtained in the step into a high-frequency induction heat treatment device, and carrying out high-frequency induction heat treatment twice, wherein the technological parameters of the first high-frequency induction heat treatment are as follows: frequency: 15KHZ, raising the temperature to 1040-; rapidly cooling to 225-; cooling to-21 deg.C, and maintaining for 1.5 h; the technological parameters of the second high-frequency induction heat treatment are as follows: frequency: 15KHZ, raising the temperature to 834 and 840 ℃ at the temperature raising speed of 800 ℃/s, and keeping the temperature for 1.5 s; rapidly cooling to 173-175 ℃, and preserving the temperature for 2.5 h; cooling to-32 deg.C, and keeping the temperature for 1.5
Step six: reaming
Reaming the axial hole 4 by using a forming reamer, and after reaming, enabling the axial hole 4 to reach the required size
Step seven: sulfurizing;
using hydrogen sulfide as a source of sulfur seepage and using H2S—Ar—H2As a sulfurizing atmosphere, Ar and H were present in high purity (99.999%)2(ratio 1: 1) as carrier gas, H2The dosage of S is 3 percent of the total gas quantity, the flow of the mixed gas is about 80-120L/h, the sulfurization temperature is 177, and the time is 33 in; after sulfurization is finished, quickly cooling to-43 ℃, and preserving heat for 0.7;
step eight: final grinding
And positioning the workpiece by using double ejector pins, and finely grinding the support shoulder 1, the working shoulder 2, the groove 3 and the axial hole 4.
Comparative example 1
In the fifth step, only the first high-frequency induction heat treatment is carried out;
comparative example 2
In the fifth step, the two high-frequency induction heat treatments are changed into the conventional one-time carburization treatment.
Comparative example 3
Step seven was omitted and the remaining conditions were in accordance with example 3
TABLE 1
As can be seen from the above table, the valve cores processed in examples 1-3 have a hardened layer thickness of 4.1mm and a torsional fatigue strength (789-5MPa, surface hardness 71-76 HRC; the following relevant standards are better specified: according to the GB/T5772-2010 and ZBJ94007-1988 standards, the valve core is subjected to carburizing heat treatment, and the following technical requirements are met: the depth of the hardening layer is 0.6-0.9 mm; the surface hardness is 57-62 HRC; the metallographic structure of the infiltrated layer is as follows: the K grade is less than or equal to 4 grades, namely, the block-shaped and granular carbides are densely distributed and have a net-shaped trend; ② the M grade is less than or equal to 3 grade, namely acicular martensite plus a medium amount of residual austenite. The size of the surface abnormal structure is less than or equal to 0.02 mm.
Comparative example 1, valve element machined without the second high frequency induction heat treatment, hardened layer thickness 3.4mm, torsional fatigue strength 685 105MPa, surface hardness of 62HRC, the hardened layer thickness is lower, and torsional fatigue strength is little, and surface hardness all has the decline to a certain extent, has explained to carry out the second high frequency induction heat treatment, has thickened the hardened layer to a certain extent, has improved torsional fatigue strength and surface hardness.
Comparative example 2, the valve core processed by changing the two high-frequency induction heat treatments into the conventional one-time carburization treatment, the thickness of the hardened layer is 1.8mm, and the torsional fatigue strength 586 x 105MPa, surface hardness 53 HRC; it can be seen that the conventional carburizing treatment only meets the standard requirement of the superficial hardness of the hardened layer with a relatively small thickness.
Comparative example 3, valve core machined after the step seven was omitted, hardened layer thickness 4.1mm, torsional fatigue strength 823 x 105MPa, surface hardness 65 HRC; it can be seen that the hardened layer has a low thickness, low torsional fatigue strength and a certain reduction in surface hardness after the sulfurization treatment lacking step seven.
The valve core finished products processed in the example 3 and the comparative examples 1 to 3 are subjected to the following performance test.
disassembling a valve cover, an ejector rod and an original valve core of the pressure relief valve, installing a valve core to be tested in advance, and closing the valve; and starting the machine, recording the conditions of 5 times, 50 times and 80 times of the valve core working under different pressures of 300MPa and the like, and recording.
The test results of test 1 and test 2 are shown in table 2:
TABLE 2
As can be seen from the above table, the valve core manufactured in example 3 has no crack in the magnetic flaw detection test; in the life test, 5, 50 and 80 times of tests are carried out, and no damage is caused;
comparative example 1, valve core machined without the second high frequency induction heat treatment, was crack free in the magnetic flaw detection test; in the life test, 5 times of tests are carried out without damage; 50 times, the surface is slightly damaged; the surface damage and cracks are obvious after 80 times of tests;
comparative example 2, the two high-frequency induction heat treatments were changed to conventional one-time carburization treatment, and the valve core was formed, and in the magnetic flaw detection test, there were several wire cracks; in the service life test, 5 times of tests are carried out, and the surface damage and the cracks are obvious;
comparative example 3, after step seven was omitted, the valve core was formed without cracks in the magnetic flaw detection test; in the life test, 5 and 50 were carried out, and no damage was observed, and 80 times of tests were carried out, with slight surface damage.
Therefore, by combining the results of example 3 and comparative examples 1 to 3, it can be found that the valve core has excellent performance in the magnetic flaw detection test and the life test after the high-frequency induction heat treatment is performed once or 2 times, and further, the high-frequency induction heat treatment is further explained, so that the surface uniformity of the workpiece is good, and the workpiece has good pressure resistance.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (1)
1. A preparation process of a high-precision deep-hole valve core is characterized by comprising the following steps:
the method comprises the following steps: rough turning and pretreatment
Discharging machining allowance according to the excircle and the length of the valve core, and turning a valve core workpiece, wherein allowance is reserved on the excircle to obtain a valve core workpiece to be pretreated;
placing the valve core workpiece into a vacuum sintering furnace, heating to 700-plus-one 720 ℃ under the protection of Ar gas, preserving heat for 0.5h, then annealing to 523-plus-one 526 ℃, preserving heat for 2.5h, and then cooling to room temperature;
step two: gun drill
Firstly, clamping a workpiece by using a drill jig, positioning the workpiece by using a drill positioning seat, and drilling a working shoulder, a supporting shoulder and a groove;
step three: finish turning
Turning each shoulder and each groove, and processing the rest to the requirements;
step four: milling process
Milling an axial hole with the diameter phi of 1.5mm at the right end of the workpiece;
step five: induction high frequency heat treatment
Putting the workpiece obtained in the step four into a high-frequency induction heat treatment device for carrying out high-frequency induction heat treatment for one time, wherein the process parameters are as follows: frequency: 15KHZ, raising the temperature to 1000 ℃ and 1100 ℃ at the temperature raising speed of 1000 ℃/s, and preserving the temperature for 3 s; rapidly cooling to 220 ℃ and 240 ℃, and preserving heat for 1-2 h; cooling to-20-25 ℃, and keeping the temperature for 1-2 h;
step six: reaming
Reaming the axial hole by adopting a forming reamer, and after reaming, enabling the axial hole to reach the required size
Step seven: sulfurizing
Using hydrogen sulfide as a source of sulfur seepage and using H2S—Ar—H2As a sulfurizing atmosphere, highAr and H with purity of 99.999%2As carrier gas, H2The dosage of S is 3 percent of the total gas quantity, the flow of the mixed gas is 80-120L/h, the sulfurization temperature is 175-;
step eight: final grinding
Positioning a valve core workpiece by using double centre pins, and finely grinding a support shoulder, a working shoulder, a groove and an axial hole;
in the seventh step, after the sulfurization is finished, the temperature is rapidly reduced to-40 to-45 ℃, and the temperature is kept for 0.5 to 1 hour;
the fifth step comprises a second high-frequency induction heat treatment, and the technological parameters are as follows: frequency: 15KHZ, raising the temperature to 830 ℃ and 850 ℃ at the temperature-raising speed of 800 ℃/s, and keeping the temperature for 1.5 s; rapidly cooling to 170 ℃ and 180 ℃, and preserving heat for 2-3 h; cooling to-30-35 ℃, and keeping the temperature for 1-2 h;
in the seventh step, Ar and H2The ratio was 1: 1.
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