CN116275039A - Method for reducing hardness of 420w material by sintering mode combined with heat treatment annealing - Google Patents
Method for reducing hardness of 420w material by sintering mode combined with heat treatment annealing Download PDFInfo
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- CN116275039A CN116275039A CN202310381480.XA CN202310381480A CN116275039A CN 116275039 A CN116275039 A CN 116275039A CN 202310381480 A CN202310381480 A CN 202310381480A CN 116275039 A CN116275039 A CN 116275039A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/10—Sintering only
- B22F3/1003—Use of special medium during sintering, e.g. sintering aid
- B22F3/1007—Atmosphere
- B22F3/101—Changing atmosphere
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/24—After-treatment of workpieces or articles
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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
- C21D1/26—Methods of annealing
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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
- C21D6/002—Heat treatment of ferrous alloys containing Cr
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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
- C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
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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
- C21D6/005—Heat treatment of ferrous alloys containing Mn
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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
- C21D6/008—Heat treatment of ferrous alloys containing Si
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/24—After-treatment of workpieces or articles
- B22F2003/248—Thermal after-treatment
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy
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Abstract
The invention discloses a method for reducing the hardness of a 420w material by combining sintering modes of heat treatment annealing, which comprises the steps of adjusting the rate of a cooling stage of a sintering process, namely firstly preserving heat in the cooling stage of 800 ℃, then keeping the cooling rate of 50 ℃/min to reduce the temperature from 800 ℃ to 500 ℃, and then cooling the material from 500 ℃ to normal temperature along with a furnace. The invention has reasonable design, combines the heat treatment annealing process and the sintering cooling stage of the 420W stainless steel material, can reduce the sintering hardness of the 420W stainless steel material only by adjusting the parameters of the sintering process cooling stage, is convenient for the subsequent working procedures of shaping, tapping, polishing and the like, does not need to additionally adopt the heat treatment special furnace annealing, reduces the heating and cooling time of the heat treatment special furnace, reduces the material transfer time, saves the labor cost, is equivalent to reducing the cost of the heat treatment, and ensures that the size and the hardness stability of the sintered product are suitable for mass production.
Description
Technical Field
The invention relates to the technical field of stainless steel material processing, in particular to a method for reducing hardness of a 420w material by combining sintering modes of heat treatment annealing.
Background
The MIM-420w stainless steel is 420 'cutting tool grade' martensitic steel, is the earliest stainless steel like Brinell high chromium steel, has certain wear resistance and corrosion resistance, has higher hardness, has lower price than the stainless steel, and is suitable for the working environment with hardness requirement on the stainless steel.
The Rockwell hardness of the 420W stainless steel material subjected to common sintering treatment is 34-40 HRC, and under the condition of high hardness, if a product with large sintering deformation is to be shaped and corrected, the loss of the shaping die is high, and the shaping effect cannot reach the ideal effect. Meanwhile, tapping cannot be completed under the condition of high hardness, and the tap is damaged to be not completed yet. When the hardness exceeds 30HRC, the polishing process is also greatly affected, and the polishing productivity and yield are greatly reduced. In combination with the above, for products with shaping, tapping and surface polishing, the hardness of the common sintered stainless steel 420w material is higher, so that the manufacturing of a hand plate sample is difficult, the hand plate sample is not suitable for mass production, the hardness needs to be reduced by increasing the annealing process, the hardness reaches the hardness range of about 120HV similar to 316L or about 280HV of 17-4ph, and then the working procedures such as shaping, tapping and polishing are performed.
According to the annealing process requirement of 420W, a heat treatment annealing mode of independent furnace opening can be used, the product needs to be heated to 800-850 ℃ from normal temperature, the temperature is kept for 1-2 hours, then the temperature is slowly reduced to 500 ℃ at 30 ℃/min, and then the product is cooled to normal temperature along with the furnace, the mode has the advantages that the hardness can be reduced to about 160-200 HV under the condition that vacuum pumping is not needed in the furnace, the shaping and polishing processes are more beneficial, but the process has the defects that after the sintering furnace is out of the furnace, the material needs to be reentered into the heat treatment special furnace for annealing, the transfer time of material entering and exiting the furnace is increased, the heating and cooling processes of the heat treatment special furnace are increased, the whole process time in the furnace needs to be 17-18 hours, and the appearance is in a brown state, and the original color can be recovered after quenching and tempering hardening through heat treatment.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, and provides a method for reducing the hardness of a 420w material by combining sintering modes of heat treatment annealing, which takes into account the hardness requirement after annealing, is convenient for subsequent shaping, tapping, polishing and other procedures, does not need to additionally adopt a heat treatment special furnace for annealing, reduces the heating and cooling time of the heat treatment special furnace, and reduces the material transfer time.
In order to achieve the above object, the present invention provides a method for reducing hardness of 420w material by sintering combined with heat treatment annealing, comprising the steps of:
step one: placing 420w stainless steel blanks to be sintered into a sintering furnace, heating the furnace temperature from normal temperature to 300 ℃, preserving heat for 25-35 minutes, setting the furnace pressure to 0Pa, and setting the flow of nitrogen to 30L/min;
step two: after the heat preservation at 300 ℃ is finished, continuously heating to 450 ℃, further preserving heat for 85-95 minutes, and setting the flow rate of the introduced nitrogen to be 40L/min;
step three: keeping the flow rate of nitrogen and the pressure in the furnace unchanged, continuously heating to 600 ℃, and preserving heat for 55-65 minutes;
step four: continuously keeping the flow of nitrogen and the pressure in the furnace unchanged, heating to 850 ℃, and preserving heat for 25-35 minutes in a vacuumizing state;
step five: heating to 1050 ℃ under the vacuum internal combustion state, and preserving heat for 55-65 minutes;
step six: setting the pressure in the furnace to 10Pa from 0Pa, continuously heating to 1200 ℃ under the condition that argon is introduced and the flow is 15L/min, and preserving heat for 15-25 minutes;
step seven: keeping the flow rate of argon and the pressure in the furnace unchanged, continuously heating to 1350 ℃, and preserving the temperature for 175-185 minutes;
step eight: maintaining the flow of argon and the pressure in the furnace unchanged, and cooling to 800 ℃;
step nine: changing into a vacuumizing and internal burning state, setting the pressure in the furnace to be 0Pa, setting the flow rate of argon to be 0L/min, and preserving heat for 55-65 minutes at 800 ℃;
step ten: changing the furnace into a forced cooling state under the conditions that the pressure in the furnace is 0Pa and the argon flow is 0L/min, and cooling to 500 ℃ at a cooling rate of 50 ℃/min;
step eleven: setting the pressure in the furnace to 86Pa, and under the condition that the flow of argon is 0L/min, cooling to normal temperature along with the furnace, and discharging to obtain a 420w stainless steel semi-finished product (namely a semi-finished product blank to be shaped).
Preferably, in the first step, the temperature in the furnace is heated from normal temperature to 300 ℃ for 55-65 minutes.
Preferably, in the second step, the temperature is raised to 450 ℃ for 55-65 minutes.
Preferably, in step three, the time to raise the temperature to 600 ℃ is 75-85 minutes.
Preferably, in step four, the time to raise the temperature to 850 ℃ is 45-55 minutes.
Preferably, in step five, the time to raise the temperature to 1050 ℃ is 55-65 minutes.
Preferably, in step six, the time to raise the temperature to 1200 ℃ is 60-70 minutes.
Preferably, in step seven, the time to raise the temperature to 1350 ℃ is 35-45 minutes.
Preferably, in step eight, the temperature is reduced to 800 ℃ for 85-95 minutes.
Preferably, in step ten, the temperature is reduced to 500 ℃ for 355-365 minutes.
Compared with the prior art, the invention has the beneficial effects that:
the invention has reasonable design and simple method, combines the heat treatment annealing process and the sintering cooling stage of the 420W stainless steel material, can reduce the sintering hardness of the 420W stainless steel material only by adjusting the parameters of the sintering process cooling stage, is convenient for the subsequent working procedures of shaping, tapping, polishing and the like, does not need to additionally adopt the heat treatment special furnace annealing, reduces the heating and cooling time of the heat treatment special furnace, reduces the material transfer time (namely the time of a converting furnace), saves the labor cost, is equivalent to the reduction of the cost of the heat treatment, and ensures that the size and the hardness stability of the sintered product are suitable for mass production.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The embodiment of the invention provides a method for reducing the hardness of a 420w material by combining sintering modes of heat treatment annealing, which comprises the following steps:
step one: placing 420w stainless steel blanks to be sintered into a sintering furnace, heating the furnace temperature from normal temperature to 300 ℃ for 55-65 minutes, then preserving heat for 25-35 minutes, setting the furnace pressure to 0Pa, and setting the flow of nitrogen to 30L/min;
step two: continuously heating to 450 ℃ after finishing the heat preservation at 300 ℃ for 55-65 minutes, then preserving the heat for 85-95 minutes, and setting the flow of the introduced nitrogen to 40L/min;
step three: keeping the flow rate of nitrogen and the pressure in the furnace unchanged, continuously heating to 600 ℃, keeping the temperature for 75-85 minutes, and keeping the temperature for 55-65 minutes;
step four: continuously keeping the flow of nitrogen and the pressure in the furnace unchanged, heating to 850 ℃, using for 45-55 minutes, and preserving heat for 25-35 minutes in a vacuumizing state;
step five: heating to 1050 ℃ under vacuum internal combustion state for 55-65 minutes, and then preserving heat for 55-65 minutes;
step six: setting the pressure in the furnace to 10Pa from 0Pa, continuously heating to 1200 ℃ under the condition of introducing argon and the flow of 15L/min, keeping the temperature for 60-70 minutes, and keeping the temperature for 15-25 minutes;
step seven: keeping the flow rate of argon and the pressure in the furnace unchanged, continuously heating to 1350 ℃, keeping the temperature for 35-45 minutes, and keeping the temperature for 175-185 minutes;
step eight: keeping the flow rate of argon and the pressure in the furnace unchanged, and cooling to 800 ℃ for 85-95 minutes;
step nine: changing into a vacuumizing and internal burning state, setting the pressure in the furnace to be 0Pa, setting the flow rate of argon to be 0L/min, and preserving heat for 55-65 minutes at 800 ℃;
step ten: changing the furnace into a forced cooling state under the conditions that the pressure in the furnace is 0Pa and the argon flow is 0L/min, and cooling to 500 ℃ at the cooling rate of 50 ℃/min for 355-365 minutes;
step eleven: setting the pressure in the furnace to 86Pa, and under the condition that the flow of argon is 0L/min, cooling to normal temperature along with the furnace, and discharging to obtain a 420w stainless steel semi-finished product (namely a semi-finished product blank to be shaped).
Comparative example: the parameters of the individual sintering process (not counting the annealing process) of 420W are as follows:
on the premise of not carrying out an annealing process, the total duration of the sintering curve of the comparative example is about 22-24 hours, and the cooling time is prolonged when the sintering is carried out in a full furnace in relation to the quantity of sintered products.
This example (preferred example): the sintering process combined with the heat treatment annealing is as follows:
the total duration of the sintering curve of the embodiment is about 28-31 hours, and the cooling time is prolonged when the sintering is carried out in a full furnace in relation to the quantity of sintered products.
Comparison of total duration of the two processes described above: the sintering process of the comparative example takes 22 to 24 hours, the sintering process of the combined heat treatment annealing of the present example takes 28 to 31 hours, and although the sintering time is increased relative to the sintering time of the comparative example, the hardness of the product sintered by the comparative example is relatively high, the subsequent annealing by a special heat treatment furnace is required to reduce the hardness, the annealing process by the special heat treatment furnace is required to raise the temperature from normal temperature to a preset temperature, keep the temperature and then cool down, and the total time from furnace in and furnace out is 17 to 18 hours, and the total time of the materials in and furnace out is only 39 to 42 hours.
Through multiple verification and comparison, the sintering mode of the combined heat treatment annealing of the embodiment can reduce the cycle period of one-time furnace inlet and one-time furnace outlet relative to the comparative example, namely, the material transfer time length is reduced, the labor cost is also reduced, and meanwhile, the heating stage from normal temperature to preset temperature in the heat treatment furnace is reduced, namely, the heat treatment time length in the furnace is reduced. Considering the waiting time of material turnover, the time of the embodiment is reduced at least over 11-12 hours compared with the common sintering and heat treatment special furnace annealing mode.
After the sintering process of the combined heat treatment annealing of the embodiment, the hardness of the product can be in the range of 200-240 HV, the average hardness is about 220HV, the hardness is about 15% lower than that of the 17-4ph material after sintering, and the hardness is slightly higher than that of the single open furnace heat treatment, but the requirements of shaping, tapping and polishing processes in a large scale can be met, and the size and the hardness are uniform and the stability are relatively good.
In the embodiment, the sintering hardness of the 420w stainless steel material can be reduced only by adjusting the parameters of the cooling stage of the sintering process, namely the Vickers hardness of the sintered blank is reduced, the subsequent shaping, tapping, polishing and other procedures are facilitated, and after the shaping, tapping, polishing and other procedures are completed, the hardness of the 420w stainless steel material can be increased again through heat treatment quenching and tempering, so that the requirements of customers are met.
The present invention is not limited to the above embodiments, but is capable of other modifications, adaptations, alternatives, combinations and simplifications without departing from the spirit and principles of the invention.
Claims (7)
1. A method for reducing the hardness of a 420w material by sintering in combination with a heat treatment anneal, comprising the steps of:
step one: placing 420w stainless steel blanks to be sintered into a sintering furnace, heating the furnace temperature from normal temperature to 300 ℃, preserving heat for 25-35 minutes, setting the furnace pressure to 0Pa, and setting the flow of nitrogen to 30L/min;
step two: after the heat preservation at 300 ℃ is finished, continuously heating to 450 ℃, further preserving heat for 85-95 minutes, and setting the flow rate of the introduced nitrogen to be 40L/min;
step three: keeping the flow rate of nitrogen and the pressure in the furnace unchanged, continuously heating to 600 ℃, and preserving heat for 55-65 minutes;
step four: continuously keeping the flow of nitrogen and the pressure in the furnace unchanged, heating to 850 ℃, and preserving heat for 25-35 minutes in a vacuumizing state;
step five: heating to 1050 ℃ under the vacuum internal combustion state, and preserving heat for 55-65 minutes;
step six: setting the pressure in the furnace to 10Pa from 0Pa, continuously heating to 1200 ℃ under the condition that argon is introduced and the flow is 15L/min, and preserving heat for 15-25 minutes;
step seven: keeping the flow rate of argon and the pressure in the furnace unchanged, continuously heating to 1350 ℃, and preserving the temperature for 175-185 minutes;
step eight: maintaining the flow of argon and the pressure in the furnace unchanged, and cooling to 800 ℃;
step nine: changing into a vacuumizing and internal burning state, setting the pressure in the furnace to be 0Pa, setting the flow rate of argon to be 0L/min, and preserving heat for 55-65 minutes at 800 ℃;
step ten: changing the furnace into a forced cooling state under the conditions that the pressure in the furnace is 0Pa and the argon flow is 0L/min, and cooling to 500 ℃ at a cooling rate of 50 ℃/min;
step eleven: setting the pressure in the furnace to 86Pa, and under the condition that the flow of argon is 0L/min, cooling the furnace to normal temperature along with the furnace, and discharging the furnace to obtain the 420w stainless steel semi-finished product.
2. The method for reducing hardness by sintering combined with heat treatment annealing according to claim 1, wherein in step one, the time for heating the furnace temperature from normal temperature to 300 ℃ is 55 to 65 minutes;
in the second step, the temperature is raised to 450 ℃ for 55-65 minutes.
3. The method of reducing hardness by sintering combined with heat treatment annealing according to claim 1, wherein in step three, the time to raise the temperature to 600 ℃ is 75-85 minutes;
in the fourth step, the temperature is raised to 850 ℃ for 45-55 minutes.
4. The method of reducing hardness by sintering combined with heat treatment annealing according to claim 1, wherein in step five, the time to raise the temperature to 1050 ℃ is 55-65 minutes;
in the sixth step, the temperature is raised to 1200 ℃ for 60-70 minutes.
5. The method of reducing hardness by sintering combined with heat treatment annealing according to claim 1, wherein in step seven, the time to raise the temperature to 1350 ℃ is 35-45 minutes.
6. The method of claim 1, wherein in step eight, the temperature is reduced to 800 ℃ for 85-95 minutes.
7. The method of claim 1, wherein in step ten, the temperature is reduced to 500 ℃ for 355-365 minutes.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202310381480.XA CN116275039A (en) | 2023-04-11 | 2023-04-11 | Method for reducing hardness of 420w material by sintering mode combined with heat treatment annealing |
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| CN202310381480.XA CN116275039A (en) | 2023-04-11 | 2023-04-11 | Method for reducing hardness of 420w material by sintering mode combined with heat treatment annealing |
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