CN115652046A - Heat treatment process for eliminating band-shaped structure in steel - Google Patents
Heat treatment process for eliminating band-shaped structure in steel Download PDFInfo
- Publication number
- CN115652046A CN115652046A CN202211419695.8A CN202211419695A CN115652046A CN 115652046 A CN115652046 A CN 115652046A CN 202211419695 A CN202211419695 A CN 202211419695A CN 115652046 A CN115652046 A CN 115652046A
- Authority
- CN
- China
- Prior art keywords
- temperature
- quenching
- steel
- time
- heat treatment
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Images
Landscapes
- Heat Treatment Of Strip Materials And Filament Materials (AREA)
Abstract
A heat treatment process for eliminating band-shaped structures in steel belongs to the technical field of metal heat treatment. The process comprises the following steps: solution quenching: heating the steel from room temperature to a certain temperature, keeping the temperature for a period of time, and then quickly cooling; the certain temperature is +100-150 ℃ of the redissolution temperature of the carbide at the banded structure, and the period of time is the time for completely redissolving the carbide at the solid solution temperature of the banded structure; and (3) circulating quenching: the first quenching temperature is 10-20 ℃ below the solid solution quenching temperature, and the core of the steel part is rapidly cooled after reaching the temperature; repeating the quenching process repeatedly to set cycle quenching times, wherein the quenching temperature is reduced by 10-20 ℃ compared with the last quenching temperature when the quenching times are increased; the circulating quenching times are 2-4 times; the tempering temperature and time are set according to the service performance index. The invention regulates and controls the structure of the banded structure based on the phase change principle, has low process temperature and short time, and greatly improves the impact property of the steel.
Description
Technical Field
The invention belongs to the technical field of metal heat treatment, and particularly relates to a heat treatment process for eliminating a band-shaped structure in steel.
Background
The cast ingot, after rolling or forging, has a band-like structure due to the dendritic segregation inherent in the cast ingot. In the case of medium and high alloy steel, the band-shaped structure is rich in a large amount of alloy elements, and a large amount of carbides are easily generated at the band-shaped structure after final heat treatment, as shown in fig. 1. In addition, the grain size is much larger at the banded structure than at the non-banded structure. The presence of the ribbon-like structure not only greatly reduces the impact properties of the steel, but also reduces the isotropy of the steel properties. The root of the failure is that the banded structure becomes a crack source for fracture under the action of impact load in the service process, so that the component fails in advance, as shown in figure 2. Therefore, the method has important significance for improving the quality of steel and realizing the long-life service of the component by eliminating the influence of the banded structure on the mechanical property of the steel.
As mentioned above, the ribbon is enriched with a large amount of alloying elements. In order to achieve a uniform diffusion with the matrix components, diffusion annealing is usually performed for a long time at a temperature slightly lower than the solidus line. This temperature is usually in the range 1100-1200 ℃. However, this method is high in temperature, long in time and high in cost.
Disclosure of Invention
The invention aims to solve the problem of a banded structure in high-alloy steel and provide a heat treatment process for eliminating the banded structure in the steel.
In order to realize the purpose, the technical scheme adopted by the invention is as follows:
a heat treatment process for eliminating a band-shaped structure in steel, as shown in fig. 7, the process specifically comprises:
the method comprises the following steps: solution quenching: heating the steel from room temperature to a certain temperature, keeping the temperature for a period of time, and then quickly cooling; the certain temperature is the redissolution temperature of the carbide at the banded structure plus 100-150 ℃, and the period of time is the time for the carbide at the banded structure to completely redissolve at the solid solution temperature;
and (3) performing microstructure characterization on the steel quenched at different temperatures by using a scanning electron microscope, wherein if no carbide is observed at the strip-shaped structure, the corresponding quenching temperature is the re-dissolution temperature of the carbide. After the solid solution temperature is determined, the solid solution quenching heat preservation time is determined according to experiments, a scanning electron microscope is utilized to perform microstructure characterization on the steel after quenching at the temperature and at different time, and the time when the carbide can not be observed is set as the heat preservation time. The purpose of solution quenching is mainly to dissolve the coarse carbides at the banded structure, so the re-dissolving temperature of the carbides at the banded structure can be determined according to thermodynamic calculation or experiments and is set to be +100-150 ℃.
Step two: and (3) circulating quenching: the first quenching temperature is 10-20 ℃ below the solid solution quenching temperature, and the core of the steel part is rapidly cooled after reaching the temperature; repeating the quenching process repeatedly to set cycle quenching times, wherein the quenching temperature is reduced by 10-20 ℃ compared with the last quenching temperature when the quenching times are increased; the cycle quenching times is 2-4 times; the purpose of the circular quenching is to refine grains and provide more nucleation sites for carbide precipitation during tempering to refine carbides. The cooling is carried out at a high speed in order to avoid the growth of the crystal grains from the core to the temperature. In the case of ensuring hardenability, carbide is prevented from being precipitated during cooling.
Step three: the tempering temperature and time are set according to the service performance index.
Further, the steel is a medium high alloy steel. Low alloy steel with an alloying element content <5 wt.%, medium alloy steel 5-10 wt.%, high alloy steel >10 wt.%. The method is suitable for medium-alloyed steels and high-alloyed steels, since the content of alloying elements is too low and no coarse carbides are formed at the strip structure.
Further, in the first step, the rapid cooling is one of air cooling, oil cooling or water cooling.
Further, in the first step, the carbide re-dissolution temperature is obtained by the following method: and determining chemical components of the strip-shaped structure in the steel by using a spectrometer, calculating an equilibrium phase component-temperature diagram by using commercial thermodynamic calculation software Thermo-calc or Jmatpro and the like according to the chemical components, and obtaining the re-dissolution temperature of the carbide.
Further, in the third step, the tempering temperature and time are selected according to the service performance index setting, namely according to the required hardness and impact energy index.
1Cr11Ni2W2MoV steel is taken as an example. The service performance of the steel requires that the Brinell hardness after quenching and tempering is 269-321 HBW, the hardness after quenching is 441HBW, the hardness after tempering at 680 ℃ for 1h is 287HBW, the hardness after tempering for 2h is 273HBW, and the hardness after tempering for 4h is 259HBW. Therefore, the tempering temperature of 680 ℃ can be selected for a tempering time of 1h or 2h. The hardness after tempering for 1h at 700 ℃ is 276HBW, the hardness after tempering for 2h is 270HBW, and the hardness after tempering for 4h is 261HBW. Therefore, the tempering temperature can also be selected to be 700 ℃ and the tempering time can be 1h or 2h. For 1Cr11Ni2W2MoV steel, the tempering temperature is 660-710 ℃, and the tempering time is 1-4h.
Compared with the prior art, the invention has the beneficial effects that: the diffusion annealing process is based on the diffusion principle of alloy elements, and requires high temperature (1200 ℃) and long time (dozens of hours to dozens of hours) to make the whole components in the steel uniform. The invention regulates and controls the structure of the banded structure based on the phase change principle, has low process temperature and short time, and greatly improves the impact property of the steel.
Drawings
FIG. 1 is a scanning electron micrograph of a band-like structure in steel;
FIG. 2 is a scanning electron microscope image of impact fracture after heat treatment of steel containing a band-shaped structure;
FIG. 3 is a metallographic image of comparative example 1;
FIG. 4 is a metallographic picture according to example 1;
FIG. 5 is a scanning electron micrograph of a band-shaped structure of comparative example 1;
FIG. 6 is a scanning electron micrograph of a band-shaped structure according to example 1;
FIG. 7 is a graph of a 3-stage heat treatment process;
FIG. 8 is a metallographic image of comparative example 2;
FIG. 9 is a metallographic picture according to example 2;
FIG. 10 is a scanning electron micrograph of a banded structure of comparative example 2;
FIG. 11 is a scanning electron micrograph of a band-shaped tissue of example 2;
FIG. 12 is a schematic diagram of a temperature field and a curve of a temperature-raising process of a metal component.
Detailed Description
The technical solution of the present invention is further described below with reference to the drawings and the embodiments, but the present invention is not limited thereto, and modifications or equivalent substitutions may be made to the technical solution of the present invention without departing from the spirit of the technical solution of the present invention, and the technical solution of the present invention is covered by the protection scope of the present invention.
Example 1:
1. the carbide re-dissolution temperature of the strip structure in the 1Cr11Ni2W2MoV steel is determined to be 950 ℃ through experiments. The 1Cr11Ni2MoV steel comprises the following components: c: 0.10-0.16 wt%, cr 10.5-12.0 wt%, ni 1.40-1.80 wt%, W: 1.50-2.00 wt%, mo 0.35-0.50 wt%, V:0.18 to 0.30 weight percent of silicon, less than or equal to 0.60 weight percent of silicon, less than or equal to 0.50 weight percent of manganese and less than or equal to 0.03 weight percent of phosphorus.
2. Solution quenching: heating 1Cr11Ni2W2MoV steel from room temperature to 1050 ℃, preserving heat for 30min, and then air cooling (or oil cooling) to room temperature after finishing the heat preservation.
3. Quenching for the first time: heating the 1Cr11Ni2W2MoV steel subjected to primary quenching from room temperature to 1030 ℃, and cooling the steel in air (or oil) to room temperature after the temperature of the center is raised.
4. And (3) quenching for the second time: heating the 1Cr11Ni2W2MoV steel after secondary quenching from room temperature to 1010 ℃, and air cooling (or oil cooling) the steel to room temperature after the center part is warmed.
5. Tempering: heating the 1Cr11Ni2W2MoV steel subjected to the three-time circular quenching from room temperature to 700 ℃, preserving the heat for 2 hours, discharging from the furnace and air cooling.
6. And characterizing the microstructure and mechanical property of the 1Cr11Ni2W2MoV steel after the circular quenching and tempering.
In this example, the explanation about the core to temperature is as follows:
the planar infinite flat plate shown in fig. 12 is taken as an example because the actual member is sized. It can be seen that there is a temperature difference between the surface and the core of the component during the temperature rise. The heating time of the metal is defined as temperature rise time, temperature equalization time and heat preservation time, wherein the temperature rise time is the time when the surface temperature of the component reaches the set temperature, the temperature equalization time is the time when the core temperature of the component reaches the set temperature minus the time when the surface temperature of the component reaches the set temperature, and the heat preservation time is the heat treatment process time.
(1) The length of the temperature rise time mainly depends on the heating mode. For example, electric furnaces (primarily by radiative heat transfer) can provide short warm-up times, while fuel furnaces (primarily by convective heat transfer) can provide long warm-up times.
(2) The length of the temperature equalizing time mainly depends on the charging amount and size of the workpiece and the material composition. The larger the component size is, the larger the charging amount is, and the longer the temperature equalizing time is. The temperature equalization time of the alloy steel is longer than that of the carbon steel. (the higher the content of alloy elements in the steel, the lower the thermal conductivity)
(3) The holding time is mainly determined by the heat treatment process requirements and the initial structure of the material. For the quenching process, the holding time of the pearlite structure should be longer than that of the ferrite structure. (the dynamic process of austenitizing steel consists of four steps of nucleation, growth, cementite dissolution and component homogenization)
Therefore, theoretically, for a certain component, the heating time should be determined by calculation in consideration of the heating mode, the component, the size, the charging amount, the process requirement and the initial structure of the component. However, for convenience in actual production, the following semi-empirical formula is generally adopted
τ＝α×KD
Wherein, tau is the heating time of the metal, min; the alpha-heating coefficient, min/mm, is usually selected within the range of 0.7-0.8; the correction coefficient of the K-reaction charging amount is usually selected within the range of 1.0-1.3; d-effective thickness of the workpiece, mm.
Therefore, the core-to-temperature means that the core of the steel part (with the size) reaches the set quenching temperature, and can be calculated by an empirical formula, or calculated by simulation, or measured in real time by inserting a thermocouple into the core of the simulated steel part.
Comparative example 1:
1. quenching: heating 1Cr11Ni2W2MoV steel from room temperature to 1010 ℃, preserving heat for 30min, and then air cooling (or oil cooling) to room temperature after heat preservation is finished.
2. Tempering: heating the quenched 1Cr11Ni2W2MoV steel from room temperature to 700 ℃, preserving heat for 2 hours, discharging and air cooling.
3. And characterizing the microstructure and mechanical property of the 1Cr11Ni2W2MoV steel after quenching and tempering.
Tissue comparison:
as can be seen from FIGS. 3 and 4, the 1Cr11Ni2W2MoV steel had a grain size of 21 μm after quench tempering, and the grain size of a portion after cycle quench tempering was refined to 3 μm. As can be seen from FIGS. 5 and 6, coarse carbides still exist in the band structure after the 1Cr11Ni2W2MoV steel is quenched and tempered. After the circular quenching and tempering, because crystal grains are refined and crystal boundaries are increased, carbides are refined at the same time.
And (3) mechanical property comparison:
the cycle quenching tempering process greatly improves the impact work KU 2 And lifting from 74J to 154J of the original quenching and tempering process.
Example 2:
1. the carbide re-dissolution temperature of the strip structure in the 1Cr11Ni2W2MoV steel is determined to be 950 ℃ through experiments.
2. Solution quenching: heating 1Cr11Ni2W2MoV steel from room temperature to 1050 ℃, preserving heat for 30min, and air cooling (or oil cooling) to room temperature after finishing the heat preservation.
3. Quenching for the first time: heating the 1Cr11Ni2W2MoV steel subjected to primary quenching from room temperature to 1030 ℃, and cooling the steel to room temperature after the center of the steel is warmed.
4. And (3) quenching for the second time: heating the 1Cr11Ni2W2MoV steel after secondary quenching from room temperature to 1020 ℃, and air cooling (or oil cooling) the steel to room temperature after the center part is warmed.
5. Quenching for the third time: heating the 1Cr11Ni2W2MoV steel after secondary quenching from room temperature to 1010 ℃, and air cooling (or oil cooling) the steel to room temperature after the center part is warmed.
6. Tempering: heating the 1Cr11Ni2W2MoV steel subjected to four-cycle quenching from room temperature to 680 ℃, preserving heat for 2 hours, discharging from the furnace and air cooling.
7. And (3) representing the microstructure and the mechanical property of the 1Cr11Ni2W2MoV steel after the cyclic quenching and tempering.
Comparative example 2:
1. quenching: heating 1Cr11Ni2W2MoV steel from room temperature to 1010 ℃, preserving heat for 30min, and then air cooling (or oil cooling) to room temperature after heat preservation is finished.
2. Tempering: heating the quenched 1Cr11Ni2W2MoV steel from room temperature to 680 ℃, preserving heat for 2 hours, discharging from the furnace and air cooling.
3. And (3) characterizing the microstructure and mechanical property of the 1Cr11Ni2W2MoV steel after quenching and tempering.
Tissue comparison:
as can be seen from FIGS. 8 and 9, the 1Cr11Ni2W2MoV steel had a grain size of 25 μm after quench tempering, and the grain size of a portion after cycle quench tempering was refined to 4 μm. As can be seen from FIGS. 10 and 11, coarse carbides still exist in the band structure after the 1Cr11Ni2W2MoV steel is quenched and tempered. After the circular quenching and tempering, because crystal grains are refined and crystal boundaries are increased, carbides are refined at the same time.
And (3) mechanical property comparison:
the cycle quenching tempering process greatly improves the impact work KU 2 And lifting to 122J from 72J of the original quenching and tempering process.
Claims (5)
1. A heat treatment process for eliminating band-like structure in steel, as shown in fig. 7, characterized in that: the process specifically comprises the following steps:
the method comprises the following steps: solution quenching: heating the steel from room temperature to a certain temperature, keeping the temperature for a period of time, and then quickly cooling; the certain temperature is the redissolution temperature of the carbide at the banded structure plus 100-150 ℃, and the period of time is the time for the carbide at the banded structure to completely redissolve at the solid solution temperature;
step two: and (3) circulating quenching: the first quenching temperature is 10-20 ℃ below the solid solution quenching temperature, and the core of the steel part is rapidly cooled after reaching the temperature; repeating the quenching process repeatedly to set cycle quenching times, wherein the quenching temperature is reduced by 10-20 ℃ compared with the last quenching temperature when the quenching times are increased; the circulating quenching times are 2-4 times;
step three: the tempering temperature and time are set according to the service performance index.
2. The heat treatment process for eliminating the band-shaped structure in the steel according to claim 1, characterized in that: the steel is medium and high alloy steel.
3. The heat treatment process for eliminating the band-like structure in steel according to claim 1, characterized in that: in the first step, the rapid cooling is one of air cooling, oil cooling or water cooling.
4. The heat treatment process for eliminating the band-like structure in steel according to claim 1, characterized in that: in the first step, the carbide redissolution temperature is obtained by the following method: and determining chemical components of the strip-shaped structure in the steel by using a spectrometer, calculating an equilibrium phase component-temperature diagram by using commercial thermodynamic calculation software Thermo-calc or Jmatpro and the like according to the chemical components, and obtaining the re-dissolution temperature of the carbide.
5. The heat treatment process for eliminating the band-shaped structure in the steel according to claim 1, characterized in that: in the third step, the tempering temperature and the tempering time are selected according to the service performance index setting, namely the required hardness and impact energy index.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211419695.8A CN115652046A (en) | 2022-11-14 | 2022-11-14 | Heat treatment process for eliminating band-shaped structure in steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211419695.8A CN115652046A (en) | 2022-11-14 | 2022-11-14 | Heat treatment process for eliminating band-shaped structure in steel |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN115652046A true CN115652046A (en) | 2023-01-31 |
Family
ID=85020389
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202211419695.8A Pending CN115652046A (en) | 2022-11-14 | 2022-11-14 | Heat treatment process for eliminating band-shaped structure in steel |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN115652046A (en) |
-
2022
- 2022-11-14 CN CN202211419695.8A patent/CN115652046A/en active Pending
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP4018905B2 (en) | Hot rolled wire rod and bar for machine structure and manufacturing method thereof | |
| JP5440203B2 (en) | Manufacturing method of high carbon hot rolled steel sheet | |
| CN103255340B (en) | A kind of automobile high-strong toughness thermoforming steel plate and preparation method thereof | |
| CN105063291A (en) | Thermal processing method improving impact resistance of 13Cr9Mo2Co1NiVNbNB forged piece | |
| JP5105235B2 (en) | Mold quenching method | |
| EP2006398A1 (en) | Process for producing steel material | |
| CN109852777B (en) | H13 die steel and heat treatment process thereof | |
| KR100654695B1 (en) | Method for heat treatment of cam and the parts for a large ship | |
| JPH0156124B2 (en) | ||
| CN107794348A (en) | A kind of Technology for Heating Processing of raising Cr12MoV steel combination properties | |
| JP4061003B2 (en) | Cold forging bar wire with excellent induction hardenability and cold forgeability | |
| JPH039168B2 (en) | ||
| KR101628175B1 (en) | Heat treatment process of boron alloy steel for track link of construction vehicles | |
| CN103614521B (en) | Medium carbon steel material large diesel engine output shaft tempering process | |
| CN115652046A (en) | Heat treatment process for eliminating band-shaped structure in steel | |
| JP2018165408A (en) | Production method of steel material excellent in cold workability or machinability | |
| KR101721591B1 (en) | Method for manufacturing low-carbon alloy steel for cold forging | |
| WO2021125793A1 (en) | Wire rod for high strength cold head quality steel with excellent resistance to hydrogen embrittlement, and manufacturing method thereof | |
| CN103484606A (en) | Heat treatment method for improving low-temperature toughness of WC6-1.7357 material | |
| JP7229827B2 (en) | Manufacturing method of high carbon steel sheet | |
| CN108342658B (en) | Steel for shafts and gears and heat treatment method thereof | |
| JPH0217608B2 (en) | ||
| KR100633522B1 (en) | Method for heat treatment of cam for a large ship | |
| JP3046183B2 (en) | Manufacturing method of low hardness and high toughness seamless steel pipe with excellent SSC resistance | |
| JP2006213990A (en) | Manufacturing method of hot working die |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |