CN116426865A - Carburizing heat treatment process for drill rod - Google Patents
Carburizing heat treatment process for drill rod Download PDFInfo
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- CN116426865A CN116426865A CN202211681245.6A CN202211681245A CN116426865A CN 116426865 A CN116426865 A CN 116426865A CN 202211681245 A CN202211681245 A CN 202211681245A CN 116426865 A CN116426865 A CN 116426865A
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- 238000000034 method Methods 0.000 title claims abstract description 85
- 238000005255 carburizing Methods 0.000 title claims abstract description 69
- 238000010438 heat treatment Methods 0.000 title claims abstract description 40
- 238000001816 cooling Methods 0.000 claims abstract description 86
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 60
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims abstract description 45
- 238000005496 tempering Methods 0.000 claims abstract description 35
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical group CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 claims abstract description 34
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 31
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 30
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 30
- 239000001294 propane Substances 0.000 claims abstract description 17
- 238000009792 diffusion process Methods 0.000 claims abstract description 10
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 8
- 239000012159 carrier gas Substances 0.000 claims abstract description 7
- 238000007599 discharging Methods 0.000 claims description 15
- 238000004321 preservation Methods 0.000 claims description 13
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 12
- 238000010791 quenching Methods 0.000 claims description 9
- 230000000171 quenching effect Effects 0.000 claims description 9
- 238000005261 decarburization Methods 0.000 claims description 7
- 229910000734 martensite Inorganic materials 0.000 claims description 7
- 229910052742 iron Inorganic materials 0.000 claims description 6
- 239000010410 layer Substances 0.000 description 7
- 229910001566 austenite Inorganic materials 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 4
- 239000002344 surface layer Substances 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 229910000851 Alloy steel Inorganic materials 0.000 description 1
- 208000034656 Contusions Diseases 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 208000034526 bruise Diseases 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000012797 qualification Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 239000011435 rock Substances 0.000 description 1
- 238000009991 scouring Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 230000006032 tissue transformation Effects 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 238000012795 verification Methods 0.000 description 1
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Classifications
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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
-
- 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
-
- 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
- C21D11/00—Process control or regulation for heat treatments
- C21D11/005—Process control or regulation for heat treatments for cooling
-
- 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
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/0075—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rods of limited length
-
- 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
- C23C8/80—After-treatment
-
- 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
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F17/00—Multi-step processes for surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by subclass C21D or C22F or class C25
-
- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/001—Austenite
-
- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Abstract
The invention discloses a drill rod carburizing heat treatment process, which comprises the process steps of carburizing treatment, air cooling, tempering and air cooling, wherein the carrier gas is methanol and nitrogen, and the carburizing agent of a carburizing furnace is propane; introducing safe nitrogen into the furnace below 780 ℃ and introducing propane above 820 ℃, wherein the flow rate of the process methanol is 3+/-0.1L/h, the flow rate of the process nitrogen is 3+/-0.1 cubic/h, and the flow rate of the safe nitrogen is 7+/-0.1 cubic/h; wherein, the carburization temperature is 920+/-5 ℃, the carbon potential is 0.74+/-0.04%, the whole carburization process has no strong carburization and diffusion, and the carburization time is stabilized by adopting the same carbon potential, thereby solving the problems of netlike and coarse carburized layers of products brought by the traditional process.
Description
Technical Field
The invention relates to the technical field of drill rod heat treatment, in particular to a carburizing heat treatment process for a drill rod.
Background
During the use of the drill tool, the drill tool often fails in a stress corrosion fatigue fracture mode due to severe abrasion of rock ore, high-pressure water flow or air flow, scouring corrosion of pit water and complex stress conditions. The screw in the drill rod, the application of the line drill rod is the most extensive, the research and production practice of the thread drill rod in several decades at home and abroad are integrated, and the best thread drill rod production process route is that alloy steel is carburized after being formed and processed.
The whole carburization treatment of the drill rod is carried out by using a well type gas carburizing furnace, the control of the carbon content on the surface of the carburized layer is very important for the threaded drill rod, the carbon content on the surface of the carburized layer of the drill rod is too high, netlike carbide can appear, and the brittleness and notch sensitivity of the carburized layer are increased; coarse martensite and excessive retained austenite also appear after quenching, resulting in low surface hardness and reduced wear resistance of the drill rod. The traditional carburization adopts two-section carburization, namely strong carburization and diffusion, and the carburization process has the following defects due to the particularity of carburized steel for a drill rod: often causes quality defects such as coarse and network carbides.
Disclosure of Invention
The invention aims to solve the problems in the prior art, provides a carburizing heat treatment process for a drill rod, ensures that the carbon content of the surface layer of the produced drill rod is 0.74+/-0.04%, does not cause other quality problems, and reduces the deformation of heat treatment.
The technical scheme adopted by the invention for achieving the purpose is as follows: a carburizing heat treatment process for a drill rod comprises the steps of carburizing treatment, air cooling, tempering and air cooling, wherein,
step one, carburizing:
the carrier gas of the carburizing furnace is methanol and nitrogen, and the carburizing agent of the carburizing furnace is propane; introducing safe nitrogen into the furnace below 780 ℃ and introducing propane above 820 ℃, wherein the flow rate of the process methanol is 3+/-0.1L/h, the flow rate of the process nitrogen is 3+/-0.1 cubic/h, and the flow rate of the safe nitrogen is 7+/-0.1 cubic/h; wherein the carburization temperature is 920+/-5 ℃, the carbon potential is 0.74+/-0.04%, the whole carburization process has no strong carburization or diffusion, the carburization time is 12-20h according to the requirements of different drill rods by adopting the same carbon potential stable carburization mode, and the furnace pressure is 200-600Pa;
step two, air cooling:
the drill rod after carburization is placed in an air cooling tower to be cooled at 860 ℃, and the rotating speed of a fan is controlled in two stages: the first stage is 250-300r/min for 25-35min, the second stage is 400-500r/min for 75-90min;
step three, tempering:
tempering the drill rod after air cooling at 210+/-5 ℃ for 3-3.5 hours;
step four, air cooling:
and (3) air cooling the drill rod after tempering and discharging to room temperature.
As a further preferable scheme of the invention, the transferring process of the drill rod from the step to the step two is controlled within 3min, and the transferring process from the step to the step three is controlled within 2h.
As a further preferable scheme of the invention, in the first step, when the temperature in the furnace is raised, the furnace is empty for more than 6 hours of pre-carburization, and then the drill rod is placed in the furnace for carburization.
In the first step, one workpiece is placed on each furnace, the upper workpiece is hung at the position 20cm away from the hanging scaffold by the second ring of drill rods from the outer ring, and the lower workpiece is bundled at the lower end screw thread of the second ring of drill rods from the outer ring by the iron wires.
Wherein, the core hardness of the drill rod after heat treatment is not qualified or the surface hardness caused by non-decarburization is low, and the process is as follows: temperature: 860 ℃ for 1.5h, wherein the carbon potential is 0.8+/-0.04%, discharging, air cooling and carrying out the air cooling according to the second process.
Wherein, the martensite on the surface of the drill rod after heat treatment is unqualified, and the heat treatment is required according to the following process: the temperature is 240 ℃ for 3-3.5h, and the furnace is taken out and then cooled in air.
Wherein, the residual austenite on the surface of the drill rod after heat treatment is unqualified, and the heat treatment is required according to the following process: the temperature is 20 ℃ for 3-3.5h, and the air cooling is carried out after the furnace is taken out.
In the invention, the whole product transferred to the air cooling tower from the carburizing furnace falls into the air cooling tower, an air cooling program is started, the product after air cooling is directly loaded into the tempering furnace together with a tool, and the maximum interval time from the completion of air cooling to the loading of the tempering furnace is 2h. Air cooling after tempering, wherein the temperature is 0 ℃, and discharging can be performed after air cooling to the surface temperature of the product to the temperature which can be touched by hands. If the furnace product process has problems (including power failure, atmosphere hole blockage, long transfer time and the like), the furnace unloading or reworking is determined according to the detection result after the detection result is out.
Wherein, the heating process of the carburization treatment in the step one is as follows: the method comprises the steps of preheating at 860 ℃, loading a drill rod into a carburizing furnace with the temperature of 860 ℃ at room temperature, preserving heat at 860 ℃ for 10min, heating to 920 ℃, starting carbon potential control at 920 ℃, preserving heat at 920 ℃, cooling to 860 ℃ after finishing heat preservation for 35min, discharging, and air cooling.
Preferably, the temperature rise of 860-920 ℃ is performed by adopting a mode of raising the temperature by 0.5 ℃ per minute.
Preferably, the temperature of 920-860 ℃ is controlled to be reduced by 0.5 ℃ per minute.
The carburizing agent (enriched gas) of the carbon furnace of the present invention is propane.
The invention adopts a carburization process without strong carburization and diffusion, namely a single carbon potential carburization process, and the problems that a carburized layer of a product frequently appears in a net shape and is coarse caused by the traditional process are thoroughly solved.
Compared with the strong-diffusion carburizing process, the single-carbon potential carburizing process reduces the carburizing time by 0.1-1.5 hours, and saves the cost; the deformation of the drill rod is reduced by more than 30% by controlling the temperature rise and temperature reduction speeds.
The rotating speed of a fan in the air cooling tower is controlled in two stages, and the sectional air cooling (the first stage has low speed and the second stage has high speed) ensures the hardness of the surface and the core of the product and simultaneously further reduces the deformation of the drill rod.
Drawings
FIG. 1 is a graph showing the carburizing and air-cooling process of example 1.
Detailed Description
The invention will now be described in further detail with reference to the drawings and examples.
The embodiments of the invention have been presented for purposes of illustration and description, and are not intended to be exhaustive or limited to the invention in the form disclosed. The non-illustrated portions of the following examples of the present invention should be understood as techniques well known to those skilled in the art, such as carburizing furnaces, air cooling tower structures, and the like.
Example 1
A carburizing heat treatment process for a drill rod comprises the following steps of carburizing treatment, air cooling and tempering:
step one, carburizing:
the carrier gas of the carburizing furnace is methanol and nitrogen, and the carburizing agent of the carburizing furnace is propane; introducing safe nitrogen into the furnace below 780 ℃ and introducing propane above 820 ℃, wherein the flow rate of the process methanol is 3+/-0.1L/h, the flow rate of the process nitrogen is 3+/-0.1 cubic/h, and the flow rate of the safe nitrogen is 7+/-0.1 cubic/h; wherein the carburization temperature is 920+/-5 ℃, the carbon potential is 0.74+/-0.04%, the whole carburization process has no strong carburization or diffusion, the carburization time is 12-20h according to the requirements of different drill rods by adopting the same carbon potential stable carburization mode, and the furnace pressure is 200-600Pa; the temperature rising of the technology adopts a mode of preheating at 860 ℃, the room temperature of the product is filled into a well type carburizing furnace with the temperature of 860 ℃, and the temperature rising speed at the stage is not used as specific control.
Step two, air cooling:
the drill rod after carburization is placed in an air cooling tower to be cooled at 860 ℃, and the rotating speed of a fan is controlled in two stages: the first stage is 250-300r/min for 25-35min, the second stage is 400-500r/min for 75-90min;
step three, tempering:
tempering the drill rod after air cooling at 210+/-5 ℃ for 3-3.5h.
Step one, the drill rod is placed into a furnace with the room temperature of 860 ℃ for 10 minutes at the temperature of 860 ℃ and then heated to 920+/-5 ℃, and the temperature of 860 ℃ -920+/-5 ℃ is raised by adopting a mode of raising the temperature of 0.5 ℃ per minute; and after the isothermal temperature reaches 920+/-5 ℃, starting carbon potential control, keeping the temperature, finishing the temperature reduction to 860 ℃, keeping the temperature, reducing the temperature to 0.5 ℃ per minute by adopting a controlled temperature reduction mode at 920+/-5 ℃ to 860+/-5 ℃, keeping the temperature for 35 minutes, and discharging the steel, and carrying out air cooling quenching.
The process curves of the first step and the second step are shown in figure 1, wherein the A stage is an empty furnace preheating stage to 860 ℃, the B stage is a 860 ℃ heat preservation stage, the C stage is a 860 ℃ - (920+/-5 ℃) heating stage, the D stage is a (920+/-5 ℃) heat preservation start carbon potential control stage, the E stage is a (920+/-5 ℃) cooling stage to 860 ℃, the F stage is a heat preservation stage which is reduced to (860+/-5 ℃) and the G stage is an air cooling quenching stage.
The above is a basic embodiment of the present invention, and further improvements, optimizations and limitations can be made on the above basis, so as to obtain the following embodiments:
example 2
A drill rod carburizing heat treatment process comprises the following process steps of carburizing treatment, air cooling, tempering and air cooling:
step one, carburizing:
the carrier gas of the carburizing furnace is methanol and nitrogen, and the carburizing agent of the carburizing furnace is propane.
The drill rod is put into a furnace with the room temperature of 860 ℃ for 10 minutes at 860 ℃ and then heated to 920 ℃, and the temperature of 860-920 ℃ is raised by adopting a mode of raising the temperature by 0.5 ℃ per minute; and after the isothermal temperature reaches 920 ℃, starting carbon potential control, completing heat preservation, cooling to 860 ℃, carrying out heat preservation, cooling to 0.5 ℃ per minute by adopting a control cooling mode at 920-860 ℃, cooling to 860 ℃, carrying out heat preservation for 35 minutes, and discharging, air cooling and quenching.
Wherein, safe nitrogen is introduced into the furnace below 780 ℃, propane is introduced above 820 ℃, the flow rate of the process methanol is 3+/-0.1L/h, the flow rate of the process nitrogen is 3+/-0.1 cubic/h, and the flow rate of the safe nitrogen is 7+/-0.1 cubic/h; wherein the carburization temperature is 920+/-5 ℃, the carbon potential is 0.74+/-0.04%, the whole carburization process has no strong carburization or diffusion, the same carbon potential is adopted to stabilize carburization, the carburization time is 12-20h according to the requirements of different drill rods, and the furnace pressure is 200-600Pa;
step two, air cooling:
the drill rod after carburization is placed in an air cooling tower to be cooled at 860 ℃, and the rotating speed of a fan is controlled in two stages: the first stage is 250r/min for 30min, and the second stage is 400r/min for 80min;
step three, tempering:
tempering the drill rod after air cooling at 210 ℃ for 3 hours;
step four, air cooling:
and (3) air cooling the drill rod after tempering and discharging to room temperature.
Example 3
A drill rod carburizing heat treatment process comprises the following process steps of carburizing treatment, air cooling, tempering and air cooling:
step one, carburizing:
the carrier gas of the carburizing furnace is methanol and nitrogen, and the carburizing agent of the carburizing furnace is propane.
The drill rod is put into a furnace with the temperature of 860 ℃ at room temperature, kept at 860 ℃ for 10 minutes and then heated to 925 ℃, and the temperature of 860-925 ℃ is raised by adopting a mode of raising the temperature by 0.5 ℃ per minute; and after the isothermal temperature reaches 925 ℃, starting carbon potential control, completing heat preservation, cooling to 865 ℃, carrying out heat preservation, cooling to 925-865 ℃ by adopting a controlled cooling mode for 0.5 ℃ per minute, cooling to 865 ℃ and carrying out heat preservation for 35 minutes, and then discharging and carrying out air cooling quenching.
Wherein, safe nitrogen is introduced into the furnace below 780 ℃, propane is introduced above 820 ℃, the flow rate of the process methanol is 3+/-0.1L/h, the flow rate of the process nitrogen is 3+/-0.1 cubic/h, and the flow rate of the safe nitrogen is 7+/-0.1 cubic/h; wherein the carburization temperature is 920+/-5 ℃, the carbon potential is 0.74+/-0.04%, the whole carburization process has no strong carburization or diffusion, the same carbon potential is adopted to stabilize carburization, the carburization time is 12-20h according to the requirements of different drill rods, and the furnace pressure is 200-600Pa;
step two, air cooling:
placing the drill rod subjected to carburization treatment in an air cooling tower for air cooling at 865 ℃, and controlling the rotating speed of a fan in two stages: the first stage is 300r/min for 28min, and the second stage is 500r/min for 75min;
step three, tempering:
tempering the drill rod after air cooling at 215 ℃ for 3.2 hours;
step four, air cooling:
and (3) air cooling the drill rod after tempering and discharging to room temperature.
Example 4
A drill rod carburizing heat treatment process comprises the following process steps of carburizing treatment, air cooling, tempering and air cooling:
step one, carburizing:
the carrier gas of the carburizing furnace is methanol and nitrogen, and the carburizing agent of the carburizing furnace is propane.
The drill rod is put into a furnace with the temperature of 860 ℃ at room temperature, kept at 860 ℃ for 10 minutes and then heated to 915 ℃, and the temperature of 860-915 ℃ is raised by adopting a mode of raising the temperature by 0.5 ℃ per minute; and after the isothermal temperature reaches 915 ℃, starting carbon potential control, completing heat preservation, cooling to 855 ℃, cooling to 0.5 ℃ per minute by adopting a controlled cooling mode at 915-855 ℃, cooling to 855 ℃, preserving heat for 40 minutes, and discharging, cooling and quenching.
Wherein, safe nitrogen is introduced into the furnace below 780 ℃, propane is introduced above 820 ℃, the flow rate of the process methanol is 3+/-0.1L/h, the flow rate of the process nitrogen is 3+/-0.1 cubic/h, and the flow rate of the safe nitrogen is 7+/-0.1 cubic/h; wherein the carburization temperature is 920+/-5 ℃, the carbon potential is 0.74+/-0.04%, the whole carburization process has no strong carburization or diffusion, the same carbon potential is adopted to stabilize carburization, the carburization time is 12-20h according to the requirements of different drill rods, and the furnace pressure is 200-600Pa;
step two, air cooling:
placing the drill rod subjected to carburization treatment in an air cooling tower for air cooling at 855 ℃, and controlling the rotating speed of a fan in two stages: the first stage is 200r/min for 35min, the second stage is 450r/min for 90min;
step three, tempering:
tempering the drill rod after air cooling at 205 ℃ for 3.5 hours;
step four, air cooling:
and (3) air cooling the drill rod after tempering and discharging to room temperature.
The drill rod treated by each embodiment meets the effective carbon layer depth of 0.8-1.2mm; the surface hardness after carburization and tempering is required to be 55-HRC as qualified; the core hardness requirement is 38-is qualified after carburization and tempering; the surface residual austenite is less than or equal to 20 percent, the surface martensite is less than or equal to 3 grades, and the coarse reticular carbide is less than or equal to 2 grades.
The depth of the carburized and hardened layer is lower than the technological requirement, and carburization should be supplemented. If the quality of the finished product cannot be ensured, the coarse carbide is not qualified and should be reworked and diffused. And evaluating 1-2 grade qualification of coarse carbide on the surface layer after carburization and tempering according to a carbide grade chart of a metallographic examination standard of a carburized gear of a QC262 automobile. And (4) evaluating 1-3 grades of qualified surface layer martensitic structure and residual austenite according to QC262 car carburized gear metallographic examination standard residual austenite and martensite grade diagram after carburization and tempering. No crack and serious bruise; the appearance is even and consistent dark blue gray, and no thicker oxide skin or obvious specks and oxidation color are allowed to appear.
In each embodiment, the transferring process of the drill rod from the step to the step two is controlled within 3min, and the transferring process from the step to the step three is controlled within 2h. In the first step, when the temperature in the furnace rises, the furnace is empty for pre-carburizing for more than 6 hours, and then the drill rod is placed in the furnace for carburizing. In the first step, each furnace is provided with a workpiece up and down, the upper workpiece is hung at the position 20cm away from the hanging scaffold by the second ring of drill rods from the outer ring by using an iron wire, and the lower workpiece is bundled at the thread at the lower end of the second ring of drill rod body from the outer ring by using the iron wire.
The tempering needs to be kept for a period of time, so that the core and surface temperatures of the drill rod are uniform, the full progress of tissue transformation is ensured, and the quenching stress is fully eliminated. If the tempering time is too short, insufficient tempering can be caused, and cracks can appear on the drill shank during grinding; however, too long tempering time can increase production cost and reduce equipment utilization rate. Taking the above aspects into consideration, taking out of the furnace for air cooling to room temperature after heat preservation for 3-3.5 hours.
Wherein, the surface hardness of the drill rod after heat treatment is low, and whether the drill rod is caused by decarburization is firstly eliminated. If the decarburization is caused, the hardness is re-increased after the decarburization layer is removed. Secondly, if the hardness is low and is caused by non-decarburization, re-annealing and quenching are needed; the surface/core hardness is low due to disqualification or non-decarburization, and the process is as follows: temperature: 860 ℃ for 1.5h, wherein the carbon potential is 0.8+/-0.04%, discharging, air cooling and carrying out the air cooling according to the second process.
Wherein, the martensite on the surface of the drill rod after heat treatment is unqualified, and the heat treatment is required according to the following process: the temperature is 240 ℃ for 3-3.5h, and the furnace is taken out and then cooled in air.
Wherein, the residual austenite on the surface of the drill rod after heat treatment is unqualified, and the heat treatment is required according to the following process: the temperature is 20 ℃ for 3-3.5h, and the air cooling is carried out after the furnace is taken out.
For each furnace, three samples are respectively placed up, down during process test or process verification, the upper sample is hung at the position, which is 20cm away from the hanging scaffold, of the first, second and innermost ring drill rods from the outer ring, the lower sample is bundled at the threads of the lower ends of the first, second and innermost ring drill rods from the outer ring (a screw cap is screwed at the threads of the bundle of samples for convenience), and the middle sample is bundled on the first, second and innermost ring drill rods from the outer ring.
And (5) after the carburization is discharged from the furnace, loading the carburized product into the next furnace. And introducing safe nitrogen into the furnace below 780 ℃ with the flow of +/-0.1 cubic meter/h. The flow rate of nitrogen is +/-0.1 cubic meter/h, and the flow rate of methanol is +/-0.1 liter/h. And (3) introducing propane at the temperature of above 820 ℃ and automatically controlling on-off of a propane instrument. The furnace pressure is controlled between 200 Pa and 600Pa.
Cheng Shiyang 2-3 process sample ports are placed when a process test or a new product is developed, and the process sample is placed when the temperature of the product to be tested reaches 920 ℃, wherein the placing depth of the process sample is based on the contact tool. The time taken out of the first process sample is 45-60% of the total time of the predicted carburization.
During normal production, each furnace is provided with a sample up and down, an upper sample is hung at a position about 20cm away from the hanging scaffold by using an iron wire, and a lower sample is bundled at a thread at the lower end of the rod body of the second ring of the drill rod by using the iron wire (a screw cap is screwed at the thread for conveniently bundling the samples).
Claims (10)
1. A carburizing heat treatment process for a drill rod is characterized by comprising the process steps of carburizing treatment, air cooling, tempering and air cooling, wherein,
step one, carburizing:
the carrier gas of the carburizing furnace is methanol and nitrogen, and the carburizing agent of the carburizing furnace is propane; introducing safe nitrogen into the furnace below 780 ℃ and introducing propane above 820 ℃, wherein the flow rate of the process methanol is 3+/-0.1L/h, the flow rate of the process nitrogen is 3+/-0.1 cubic/h, and the flow rate of the safe nitrogen is 7+/-0.1 cubic/h; wherein the carburization temperature is 920+/-5 ℃, the carbon potential is 0.74+/-0.04%, the whole carburization process has no strong carburization or diffusion, the carburization time is 12-20h according to the requirements of different drill rods by adopting the same carbon potential stable carburization mode, and the furnace pressure is 200-600Pa;
step two, air cooling:
the drill rod after carburization is placed in an air cooling tower to be cooled at 860 ℃, and the rotating speed of a fan is controlled in two stages: the first stage is 250-300r/min for 25-35min, the second stage is 400-500r/min for 75-90min;
step three, tempering:
tempering the drill rod after air cooling at 210+/-5 ℃ for 3-3.5 hours;
step four, air cooling:
and (3) air cooling the drill rod after tempering and discharging to room temperature.
2. The drill rod carburizing heat treatment process according to claim 1, wherein the drill rod is transferred from the step to the step two, the process is controlled within 3min, and the process is controlled within 2h from the step to the step three.
3. The drill rod carburizing heat treatment process according to claim 1, wherein in the first step, when the temperature in the carburizing furnace rises, the drill rod is placed in the furnace for carburizing after the empty furnace is pre-carburized for more than 6 hours.
4. The carburizing heat treatment process of the drill rod according to claim 1, wherein in the first step, one workpiece is placed on each furnace, the upper workpiece is hung at the position 20cm away from the hanging scaffold by the second ring of drill rods from the outer ring, and the lower workpiece is bundled at the thread at the lower end of the rod body of the second ring of drill rods from the outer ring by the iron wires.
5. The carburizing and heat treating process of drill rod according to claim 1, wherein the heat treated drill rod has low surface hardness caused by unqualified core hardness or non-decarburization, and needs re-furnace return air cooling quenching, and the process comprises the following steps: temperature: 860 ℃ for 1.5h, wherein the carbon potential is 0.8+/-0.04%, discharging, air cooling and carrying out the air cooling according to the second process.
6. The drill rod carburizing heat treatment process according to claim 1, wherein the drill rod after heat treatment has unqualified surface martensite, and the heat treatment is carried out according to the following process: the temperature is 240 ℃ for 3-3.5h, and the furnace is taken out and then cooled in air.
7. The carburizing heat treatment process of the drill rod according to claim 1, wherein the heat treatment process is characterized in that the heat treatment process is carried out according to the following steps: the temperature is 20 ℃ for 3-3.5h, and the air cooling is carried out after the furnace is taken out.
8. The carburizing heat treatment process for the drill rod according to claim 1, wherein the heating process for the step one carburizing treatment is as follows: the method comprises the steps of preheating at 860 ℃, loading a drill rod into a carburizing furnace with the temperature of 860 ℃ at room temperature, preserving heat at 860 ℃ for 10min, heating to 920 ℃, starting carbon potential control at 920 ℃, preserving heat at 920 ℃, cooling to 860 ℃ after finishing heat preservation for 35min, discharging, and air cooling.
9. The drill rod carburizing heat treatment process according to claim 8, wherein the temperature rise of 860 ℃ to 920 ℃ is performed by adopting a mode of raising the temperature by 0.5 ℃ per minute.
10. The drill rod carburizing heat treatment process according to claim 8, wherein the temperature of 920 ℃ to 860 ℃ is controlled to be reduced by 0.5 ℃ per minute.
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