CN114941061A - Heat treatment method for steel forging of hot-working die with ultra-thick section - Google Patents
Heat treatment method for steel forging of hot-working die with ultra-thick section Download PDFInfo
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- CN114941061A CN114941061A CN202210527075.XA CN202210527075A CN114941061A CN 114941061 A CN114941061 A CN 114941061A CN 202210527075 A CN202210527075 A CN 202210527075A CN 114941061 A CN114941061 A CN 114941061A
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- 238000005242 forging Methods 0.000 title claims abstract description 120
- 238000010438 heat treatment Methods 0.000 title claims abstract description 61
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 39
- 239000010959 steel Substances 0.000 title claims abstract description 39
- 238000000034 method Methods 0.000 title claims abstract description 20
- 238000001816 cooling Methods 0.000 claims abstract description 55
- 238000000137 annealing Methods 0.000 claims abstract description 15
- 238000007664 blowing Methods 0.000 claims abstract description 8
- 238000007599 discharging Methods 0.000 claims description 10
- 239000002344 surface layer Substances 0.000 abstract description 6
- 238000009826 distribution Methods 0.000 abstract description 3
- 229910001563 bainite Inorganic materials 0.000 abstract description 2
- 230000015572 biosynthetic process Effects 0.000 abstract description 2
- 238000004321 preservation Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000005299 abrasion Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 239000010410 layer Substances 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000009827 uniform distribution Methods 0.000 description 1
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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
- C21D1/28—Normalising
-
- 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
- C21D1/32—Soft annealing, e.g. spheroidising
-
- 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
A heat treatment method for a steel forging of a hot working die with an extra-thick section comprises the steps of normalizing a forging blank by a heating furnace, cooling the forging blank by blowing strong air by an industrial fan, spheroidizing annealing the forging blank by the heating furnace, performing oil cooling on the forging blank, and finally performing air cooling to room temperature. The air cooling rate of the forced air cooling can reach 2-4 ℃/min and is far higher than the air cooling rate, and the oil cooling rate after spheroidizing annealing is also far higher than the air cooling rate, so that the cooling rate is greatly improved, the cooling time is reduced, the formation of an upper bainite structure can be effectively avoided, the coarsening of carbide is inhibited, the temperature gradient in the thickness direction of the forge piece can be obviously reduced by improving the normalizing treatment and the spheroidizing annealing cooling rate, the temperature difference between the forge piece core and the surface layer area is reduced, the tissue difference between the forge piece core and the surface layer area is reduced, and the microstructure distribution uniformity is improved.
Description
Technical Field
The invention relates to the field of hot-work die steel forgings, in particular to a heat treatment method of an extra-thick section hot-work die steel forging.
Background
The hot die steel forging plays an important role in the field of industrial manufacturing, and is a necessary equipment material for forming various products. The service environment of the hot die steel forging is harsh, and the hot die steel forging is required to bear the tests of high temperature, high pressure and abrasion for a long time. Therefore, the industrial field has high requirements on the macroscopic mechanical property and the microstructure characteristic of the hot die steel forging. In order to meet the industrial requirements, the hot die steel forging is subjected to a heat treatment process of normalizing and annealing after forging so as to improve the comprehensive mechanical properties of the material.
However, when the thickness dimension of the hot-work die steel forging is larger than 700mm (an extra-thick section), a large temperature gradient can occur in the thickness direction of the forging in the normalizing air cooling process, and the core temperature is 300-400 ℃ higher than the surface temperature, so that the microstructure type and the grain size of the core are greatly different from the surface region; similarly, in the annealing and air cooling process of the forging, the core temperature in the thickness direction is still higher than the surface temperature by 200-300 ℃, so that the center region and the surface region of the forging after annealing have great differences in carbide nodularity, precipitate morphology size, strength, plasticity and toughness, and the microstructure and mechanical property homogeneity of the super-thick section hot work die steel forging are poor, and the performance requirements of the hot work die steel forging are difficult to meet. Therefore, how to improve the uniform distribution of the microstructure and the mechanical property of the super-thick section forging by improving the heat treatment process is a technical problem to be solved urgently by hot work die steel production enterprises.
Disclosure of Invention
The invention provides a heat treatment method of an extra-thick section hot work die steel forging, aiming at solving the problem of poor homogeneity of microstructure and mechanical property of the extra-thick section hot work die steel forging after heat treatment.
The technical scheme adopted by the invention for solving the technical problems is as follows: a heat treatment method of a hot work die steel forging with an ultra-thick section is used for carrying out heat treatment on a hot work die steel forging blank with the section thickness of more than 700mm, and comprises the following steps:
normalizing the forging blank by a heating furnace at a normalizing temperature Ac3+ (10-50 ℃), and keeping the temperature for 10-12 h and then discharging the forging blank out of the furnace;
secondly, cooling the forging blank by blowing strong wind through an industrial fan, wherein the wind cooling rate is controlled to be 2-4 ℃/min;
when the section thickness of the forging blank is 700-850 mm, the forging blank is cooled to 400-450 ℃ by air, and then the forging blank is placed into a heating furnace;
when the section thickness of the forging blank is larger than 850mm, air-cooling the forging blank to 500 +/-30 ℃, then putting the forging blank into a heating furnace, and continuously cooling the forging blank to 400-450 ℃ in the heating furnace;
and step three, spheroidizing annealing the forging blank by a heating furnace, heating the forging blank to 600-650 ℃, preserving heat for 8-10 h, then continuously heating the forging blank to Ac1+ (10-30 ℃), preserving heat for 25-27 h, discharging the forging blank out of the furnace, cooling oil to 350-400 ℃, and then cooling air to room temperature to complete the heat treatment of the hot-work die steel forging.
Preferably, the air volume of the industrial fan used in the step two is not less than 12000m 3 The rotation speed is not lower than 1400r/min, the voltage is 380V, and the power is 0.2 KW.
According to the technical scheme, the invention has the beneficial effects that:
the process improves the normalizing treatment and spheroidizing annealing cooling process of the hot-work die steel forging with the extra-thick section, a pure natural air cooling mode is not adopted any more, an industrial fan is adopted for cooling by blowing strong air after the normalizing treatment, and the air cooling rate of the cooling by blowing strong air can reach 2-4 ℃/min and is far higher than the cooling rate of air cooling, so that the cooling rate of the hot-work die steel forging with the extra-thick section is greatly improved, and the cooling time is reduced; the cooling speed of oil cooling after spheroidizing annealing is also far higher than that of air cooling, so that the cooling rate is greatly improved, the cooling time is shortened, the formation of an upper bainite structure can be effectively avoided, and simultaneously the coarsening of carbide is inhibited. Therefore, the cooling speed of normalizing treatment and spheroidizing annealing is increased, the temperature gradient in the thickness direction of the forging can be obviously reduced, and the temperature difference between the center of the forging and the surface layer area is reduced, so that the tissue difference between the center of the forging and the surface layer area is reduced, and the uniformity of microstructure distribution is improved.
Drawings
FIG. 1 is a shape and size diagram of a hot-work die steel forging of the first embodiment;
FIG. 2 is a schematic view of a heat treatment process flow according to the first embodiment;
FIG. 3 is a shape and size diagram of the hot work die steel forging of the second embodiment;
FIG. 4 is a schematic view of a heat treatment process flow of the second embodiment.
Detailed Description
A heat treatment method of a hot-work die steel forging with an ultra-thick section is used for carrying out heat treatment on a hot-work die steel forging blank with the section thickness of more than 700mm and comprises the following steps.
Normalizing the forging blank by a heating furnace at a normalizing temperature Ac3+ (10-50 ℃), and discharging after heat preservation for 10-12 h.
Secondly, strong air blowing cooling is carried out on the forging blank through an industrial fan, and the air volume of the industrial fan is not less than 12000m 3 The rotation speed is not lower than 1400r/min, the voltage is 380V, the power is 0.2KW, and the air cooling rate is controlled to be 2-4 ℃/min.
When the section thickness of the forging blank is 700-850 mm, the forging blank is air-cooled to 400-450 ℃, and then the forging blank is placed into a heating furnace.
And when the section thickness of the forging blank is larger than 850mm, air-cooling the forging blank to 500 +/-30 ℃, then putting the forging blank into a heating furnace, and continuously cooling the forging blank to 400-450 ℃ in the heating furnace.
And step three, spheroidizing annealing the forging blank by a heating furnace, heating the forging blank to 600-650 ℃, preserving heat for 8-10 h, then continuously heating the forging blank to Ac1+ (10-30 ℃), preserving heat for 25-27 h, discharging the forging blank out of the furnace, cooling oil to 350-400 ℃, and then cooling air to room temperature to complete the heat treatment of the hot-work die steel forging.
The first embodiment is as follows: the hot work die steel forging blank which is made of 55NiCrMoV7 and has the size specification of 4500mm multiplied by 2500mm multiplied by 900mm is subjected to heat treatment, the shape and the size of the forging blank are shown in figure 1, the thickness of the forging blank is 900mm, the forging blank belongs to an extra-thick section hot work die steel forging, and the heat treatment process flow is shown in figure 2.
Step 1, normalizing the forging blank by a heating furnace at a normalizing temperature Ac3+ (10-50 ℃), and discharging the forging blank after heat preservation for 10-12 h.
Step 2, performing strong air blowing cooling on the forging blank through an industrial fan, wherein the air volume of the industrial fan is not less than 12000m 3 The rotating speed is not lower than 1400r/min, the voltage is 380V, the power is 0.2KW, the air cooling speed is controlled to be 2-4 ℃/min, the forging blank is cooled to 400-450 ℃, and then the forging blank is placed into a heating furnace.
And 3, spheroidizing annealing the forging blank by using a heating furnace, heating the forging blank to 600-650 ℃, preserving heat for 8-10 h, then continuously heating the forging blank to Ac1+ (10-30 ℃), preserving heat for 25-27 h, discharging the forging blank out of the furnace, cooling oil to 350-400 ℃, and then cooling air to room temperature to complete the heat treatment of the hot-work die steel forging.
Example two: the hot work die steel forging blank which is made of 55NiCrMoV7 and has the size specification of 4500mm multiplied by 2650mm multiplied by 800mm is subjected to heat treatment, the shape and the size of the forging blank are shown in figure 3, the thickness of the forging blank is 800mm, the forging blank belongs to an extra-thick section hot work die steel forging, and the heat treatment process flow is shown in figure 4.
Step 1, normalizing the forging blank by a heating furnace at a normalizing temperature Ac3+ (10-50 ℃), and discharging the forging blank after heat preservation for 10-12 h.
Step 2, performing strong air blowing cooling on the forging blank through an industrial fan, wherein the air volume of the industrial fan is not less than 12000m 3 The rotating speed is not lower than 1400r/min, the voltage is 380V, the power is 0.2KW, the air cooling speed is controlled to be 2-4 ℃/min, the forging blank is cooled to 500 +/-30 ℃, and then the forging blank is placed into a heating furnace, and the forging blank is continuously cooled to 400-450 ℃ in the heating furnace.
And 3, spheroidizing annealing the forging blank by using a heating furnace, heating the forging blank to 600-650 ℃, preserving heat for 8-10 h, then continuously heating the forging blank to Ac1+ (10-30 ℃), preserving heat for 25-27 h, discharging, cooling oil to 350-400 ℃, and then cooling air to room temperature to complete the heat treatment of the hot-work die steel forging.
And (4) machining the forging blank, and removing the surface oxide layer and the surface stress concentration cracking part to obtain the hot-work die steel forging with the standard size. The hot-work die steel forgings in the first embodiment and the second embodiment are respectively taken at different positions in the thickness direction, microstructure metallographic observation and mechanical property comparison are carried out, the grain sizes and microstructure types of the forgings at different positions tend to be consistent, mechanical property indexes are respectively shown in tables 1 and 2, and the mechanical properties at different positions in the thickness direction are almost not different.
TABLE 1 mechanical properties of different thickness positions of a forged piece
TABLE 2 mechanical properties of the second forging at different thickness positions
Therefore, the cooling speed of normalizing treatment and spheroidizing annealing is increased, the temperature gradient in the thickness direction of the forging can be obviously reduced, and the temperature difference between the center of the forging and the surface layer area is reduced, so that the tissue difference between the center of the forging and the surface layer area is reduced, the uniformity of microstructure distribution is improved, and the comprehensive mechanical property of the hot-work die steel forging with the ultra-thick section is finally improved.
Claims (2)
1. A heat treatment method of a hot work die steel forging with an ultra-thick section is used for carrying out heat treatment on a hot work die steel forging blank with the section thickness of more than 700mm, and is characterized by comprising the following steps:
normalizing the forging blank by a heating furnace at a normalizing temperature Ac3+ (10-50 ℃), keeping the temperature for 10-12 h, and discharging;
secondly, cooling the forging blank by blowing strong wind through an industrial fan, wherein the wind cooling rate is controlled to be 2-4 ℃/min;
when the section thickness of the forging blank is 700-850 mm, the forging blank is air-cooled to 400-450 ℃, and then the forging blank is placed into a heating furnace;
when the section thickness of the forging blank is larger than 850mm, air-cooling the forging blank to 500 +/-30 ℃, then putting the forging blank into a heating furnace, and continuously cooling the forging blank to 400-450 ℃ in the heating furnace;
and step three, spheroidizing annealing the forging blank by a heating furnace, heating the forging blank to 600-650 ℃, preserving heat for 8-10 h, then continuously heating the forging blank to Ac1+ (10-30 ℃), preserving heat for 25-27 h, discharging the forging blank out of the furnace, cooling oil to 350-400 ℃, and then cooling air to room temperature to complete the heat treatment of the hot-work die steel forging.
2. The heat treatment method for the hot work die steel forging with the extra thick section as claimed in claim 1, wherein the heat treatment method comprises the following steps: the air volume of the industrial fan used in the second step is not less than 12000m 3 The rotation speed is not lower than 1400r/min, the voltage is 380V, and the power is 0.2 KW.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210527075.XA CN114941061B (en) | 2022-05-16 | Heat treatment method for super-thick section hot work die steel forging |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210527075.XA CN114941061B (en) | 2022-05-16 | Heat treatment method for super-thick section hot work die steel forging |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN114941061A true CN114941061A (en) | 2022-08-26 |
| CN114941061B CN114941061B (en) | 2024-04-19 |
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