CN113528779B - Method for controlling strength reduction of axle housing steel after hot forming and axle housing steel prepared by method - Google Patents
Method for controlling strength reduction of axle housing steel after hot forming and axle housing steel prepared by method Download PDFInfo
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- CN113528779B CN113528779B CN202110693709.4A CN202110693709A CN113528779B CN 113528779 B CN113528779 B CN 113528779B CN 202110693709 A CN202110693709 A CN 202110693709A CN 113528779 B CN113528779 B CN 113528779B
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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
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60B—VEHICLE WHEELS; CASTORS; AXLES FOR WHEELS OR CASTORS; INCREASING WHEEL ADHESION
- B60B35/00—Axle units; Parts thereof ; Arrangements for lubrication of axles
- B60B35/12—Torque-transmitting axles
- B60B35/16—Axle housings
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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
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/0068—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for particular articles not mentioned below
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
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Abstract
The embodiment of the invention discloses a method for controlling strength reduction of axle housing steel after hot forming and the axle housing steel prepared by the method, wherein the method comprises the following steps: carrying out rough rolling, finish rolling, cooling after rolling and coiling on the casting blank in sequence to obtain a raw material of the axle housing; heating, hot stamping and water mist cooling the axle housing raw material, and then air cooling to room temperature to obtain a high-strength axle housing steel finished product, wherein the heating rate is more than or equal to 400 ℃/s, the heating temperature is 600-650 ℃, and the heating heat preservation time is less than or equal to 180s. According to the invention, the condition of hot stamping is controlled, so that the fine regulation and control of the axle housing structure and the precipitate are realized, the yield strength is improved by over 145MPa compared with that of the traditional hot forming process, the reduction of the yield strength and the tensile strength after warm forming is less than 25MPa, and the surface quality is excellent.
Description
Technical Field
The embodiment of the invention relates to the technical field of ferrous metallurgy, in particular to a method for controlling strength reduction of axle housing steel after hot forming.
Background
The drive axle is connected with the frame through the suspension assembly, and transmits various acting forces and moments between the frame and the wheels, so that the requirements on strength, rigidity and fatigue life are very high. The punching-welding axle housing is formed by punching and forming a steel plate, then welding and shaping, the thickness of the hot-punching axle housing is generally more than 14mm according to different punching temperatures and is limited by the tonnage of punching equipment, a hot-forming process is generally adopted, the traditional hot-forming process mainly adopts a process of heating at 840-900 ℃, preserving heat for 5-8min, then carrying out high-temperature punching and forming, and finally air-cooling to room temperature, and the biggest defect of the technology is that after high-temperature austenitization, the tissue type of raw materials and precipitated second-phase particles can obviously change, and the cooling speed of an air-cooling mode after punching is uncontrollable, so that metal phase transformation and microalloy element precipitation in cooling are uncontrollable, the strength after hot-forming is obviously reduced, and the general strength is reduced by more than 100 MPa. Due to the obvious reduction of the strength, the performance of the finished axle housing is obviously lower than the designed strength, so that the bearing capacity is insufficient, the safety is reduced, and the phenomenon of truck bridge breakage occurs in severe cases.
Aiming at the problem that the strength of the axle housing steel finished product is remarkably reduced, the research focus of domestic axle housing special steel mainly focuses on the aspect of product component design, general axle housing steel is based on medium carbon content, and the strength of the axle housing steel finished product is improved by adding microalloying elements to improve the precipitation strengthening proportion.
Therefore, how to develop a method for controlling strength reduction of the axle housing steel after hot forming becomes a technical problem to be solved urgently.
Disclosure of Invention
The embodiment of the invention aims to provide a method for controlling strength reduction of axle housing steel after hot forming, compared with the prior art that the strength reduction is more than or equal to 100MPa, the yield strength of an axle housing finished product is reduced by less than 25MPa, and therefore the problem that the strength of the axle housing steel finished product is obviously reduced is solved.
In order to achieve the above object, an embodiment of the present invention provides a method for controlling strength reduction of axle housing steel after hot forming, the method including:
carrying out rough rolling, finish rolling, cooling after rolling and coiling on the casting blank in sequence to obtain a raw material of the axle housing;
heating, hot stamping and water mist cooling the axle housing raw material, and then air cooling to room temperature to obtain a high-strength axle housing steel finished product, wherein the heating rate is more than or equal to 400 ℃/s, the heating temperature is 600-650 ℃, and the heating heat preservation time is less than or equal to 180s.
Further, the water mist cooling includes: cooling with water mist at the cooling speed of 8-15 ℃/s to the final cooling temperature of 300-400 ℃.
Furthermore, the temperature of the hot stamping is 580-640 ℃, and the speed of the hot stamping is 550-700 mm/s.
Furthermore, in the rough rolling, 3+3 passes are adopted for rolling, the rolling speed is controlled to be 2-5 m/s, the total deformation of the rough rolling is controlled to be 75-85%, and the inlet temperature of the rough rolling is controlled to be 1140-1170 ℃.
In the fine rolling, 3+3 passes are adopted for rolling, the rolling speed is controlled to be 8-12 mm/s, the total deformation amount of the fine rolling is controlled to be 85-95%, and the inlet temperature of the fine rolling is controlled to be 1030-1060 ℃.
Further, the coiling temperature is 580-620 ℃.
The embodiment of the invention also provides the axle housing steel prepared by the method.
Further, the metallographic structure of the axle housing steel comprises ferrite and pearlite, and the average grain size of the ferrite is less than or equal to 5.0 mu m.
Furthermore, the metallographic structure of the axle housing steel further comprises at least one of tempered bainite and tempered martensite, and nanoscale precipitates.
One or more technical solutions in the embodiments of the present invention at least have the following technical effects or advantages:
the embodiment of the invention provides a method for controlling strength reduction of axle housing steel after hot forming, which comprises the following steps: carrying out rough rolling, finish rolling, cooling after rolling and coiling on the casting blank in sequence to obtain a raw material of the axle housing; heating, hot stamping and water mist cooling the axle housing raw material, and then air cooling to room temperature to obtain a high-strength axle housing steel finished product, wherein the heating rate is more than or equal to 400 ℃/s, the heating temperature is 600-650 ℃, and the heating heat preservation time is less than or equal to 180s. The invention realizes the fine regulation and control of axle housing tissues and precipitates under the condition of hot stamping, and particularly, the axle housing raw materials are quickly heated to a ferrite and austenite two-phase region (the heating temperature is 600-650 ℃) by ultra-quick heating (the heating rate is more than or equal to 400 ℃/s), the thermal deformation resistance of the temperature region is small, the combination is short-time heat preservation (the heating time is less than or equal to 180 s), austenite grains are fine, and the coarsening of second-phase precipitates can be prevented for microalloyed steel; after hot stamping, the axle housing is rapidly cooled by water mist, ferrite nucleation dynamics is improved, and the structural ferrite grains grow up, so that uniform and fine ferrite grains can be obtained, and the occurrence of serious banded structures is avoided. The strength of the finished axle housing obtained by adopting the warm forming process is improved by over 145MPa compared with the yield strength of the traditional hot forming process, the reduction of both the yield strength and the tensile strength after warm forming is less than 25MPa, and the finished axle housing has excellent surface quality. Meanwhile, the heating temperature and the heat preservation time are reduced, so that the effects of saving energy, protecting environment and improving the production efficiency are realized.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a flow chart of a method for controlling strength drop after axle housing steel is hot formed according to an embodiment of the invention;
FIG. 2 is a structural metallographic diagram of an axle housing finished product of the warm forming process of the axle housing steel provided by the embodiment 1 of the invention;
FIG. 3 is a structural metallographic diagram of an axle housing finished product of the warm forming process of the axle housing steel provided by embodiment 3 of the invention;
fig. 4 is a structural fine topography of an axle housing finished product of the warm forming process of the axle housing steel provided by embodiment 3 of the invention.
Detailed Description
The embodiments of the present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the embodiments of the present invention will be more clearly apparent therefrom. It will be understood by those skilled in the art that the present embodiments and examples are illustrative of the present invention and are not to be construed as limiting the present invention.
Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of the invention belong. If there is a conflict, the present specification will control.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the examples of the present invention are commercially available or can be prepared by an existing method.
In order to solve the technical problems, the embodiment of the invention provides the following general ideas:
according to an exemplary embodiment of the present invention, there is provided a method for controlling strength reduction of axle housing steel after hot forming, as shown in fig. 1, including:
s1, carrying out rough rolling, finish rolling, cooling after rolling and coiling on a casting blank in sequence to obtain an axle housing raw material;
s2, heating, hot stamping and water mist cooling the axle housing raw material, and then air cooling to room temperature to obtain a high-strength axle housing steel finished product, wherein the heating rate is more than or equal to 400 ℃/S, the heating temperature is 600-650 ℃, and the heating heat preservation time is less than or equal to 180S.
From the above, it can be seen that the general idea of the method for controlling strength reduction of axle housing steel after hot forming provided by the embodiment of the invention is as follows:
(1) The heating rate is more than or equal to 400 ℃/s: the heating rate has obvious influence on the coarsening behavior of original austenite grains and precipitates, if the heating rate is less than 400 ℃/s, the austenite grains grow for a sufficient time, the microalloying elements have a sufficient time to coarsen, the size of the formed austenite grains is large, and if the precipitates cannot be redissolved, the coarse grains can be formed, which is not beneficial to the control of final tissues or precipitates, thereby reducing the strength and the fatigue life; meanwhile, the production rhythm and efficiency are influenced when the heating rate is slow. Therefore, the heating rate is ensured to be more than 400 ℃/s by comprehensively considering the equipment capacity.
(2) The heating temperature is 600-650 ℃: the heating temperature mainly affects two aspects, namely deformation resistance on one hand, and texture change, precipitate re-dissolution and coarsening behavior in heating on the other hand, and the control of the temperature is very important. The deformation resistance generally decreases gradually along with the increase of the heating temperature, but when the heating temperature reaches about 600 ℃, the deformation resistance is obviously reduced, and the thickness of the punching plate below 18mm does not have any problem for the equipment with the raw material below 800MPa and the punching tonnage above 1000 tons; considering that the tonnage of the axle housing warm forming equipment is generally between 1000 and 2500 tons, when the heating temperature reaches over 600 ℃, the thickness of the axle housing can realize stable stamping within 6 to 18mm, and the damage to a mold can not be caused. For the high-temperature structure change, when the heating temperature is less than 650 ℃, the structure is in a ferrite high-temperature area, the structure is in a recovery state, only a dynamic process of precipitation or dissolution of carbide occurs, the original structure type is not changed, and therefore benefits are provided for final axle housing structure control, namely, the finished product structure can be controlled through original structure control, and the axle housing steel with different strength grades is developed. On the other hand, for microalloying elements Nb and Ti, the carbonitride of the elements has higher dissolution temperature, the dissolution is difficult to occur or the dissolution amount is smaller in the axle housing heating process, and the growth process of the microalloying carbonitride is slower due to the lower temperature, so that the serious coarsening of the carbonitride can be avoided, and the strength of a finished product is not influenced. If the heating temperature is less than 600 ℃, the adverse effect of damaging the grinding tool is possible, and if the heating temperature is more than 650 ℃, the adverse effect of causing great performance loss is possible, so the heating temperature is controlled to be 600-650 ℃ by comprehensively considering the equipment capacity and the performance control.
(3) The heat preservation time is less than or equal to 180s: the holding time is the same as the heating temperature, and the degree of tissue recovery and the size of precipitates are greatly influenced, so that the strength of the finished product is greatly influenced. If the heating time is longer than 180s, more carbides are precipitated in the structure, the growth is obvious, and the strength and the shaping of the finished product are both adversely affected, so the angle of controlling the strength of the finished product is comprehensively considered, and the heat preservation time is controlled within 180s.
(4) Cooling by water mist: after stamping, the axle housing is rapidly cooled by water mist, ferrite nucleation dynamics is improved, and ferrite grains are organized to grow up, so that uniform and fine ferrite grains can be obtained, and the occurrence of serious banded structures is avoided.
In conclusion, the embodiment of the invention realizes the fine regulation and control of axle housing tissues and precipitates by controlling the hot stamping conditions (the heating rate is more than or equal to 400 ℃/s, the heating temperature is 600-650 ℃, and the heating time is less than or equal to 180 s), the yield strength is improved by over 145MPa compared with the traditional hot forming process, the reduction of the yield strength and the tensile strength after warm forming is less than 25MPa, and the surface quality is excellent.
As a preferred embodiment, the water mist cooling includes: cooling with water mist at the cooling speed of 8-15 ℃/s to the final cooling temperature of 300-400 ℃.
Axle housing end-of-line cooling rate and final cooling temperature: the finished product of the traditional hot forming axle housing rear axle housing is cooled in a stacking mode, and if the cooling speed is less than 8 ℃/s, coarse structures and precipitates are easily caused; after the axle housing finished product is off line, the mechanical property of the axle housing finished product is obviously influenced by the cooling speed and the final cooling temperature during cooling, the structure can be refined by increasing the cooling speed, but the cooling speed and the final cooling temperature must be controlled, the phenomenon that the fatigue life of the axle housing finished product is influenced because large residual stress is easy to occur if the cooling speed is more than 15 ℃/s and/or the final cooling temperature is less than 300 ℃ is avoided; if the final cooling temperature is higher than 400 ℃, the adverse effect of large performance reduction rate is caused; therefore, comprehensively considering, after stamping, the axle housing is cooled by water mist at the cooling speed of 8-15 ℃/s and the final cooling temperature of 300-400 ℃, and finally, the axle housing is cooled to the room temperature by air.
As an alternative embodiment, the temperature of the hot stamping is 580-640 ℃, and the speed of the hot stamping is 550-700 mm/s. The stamping speed is limited to 550-700 mm/s during stamping, the stamping temperature is 580-640 ℃, the surface quality of the stamped rear axle housing can be effectively ensured, and the problem of stamping wrinkles or stamping cracks is avoided;
the stamping temperature is 580-640 ℃: the warm forming temperature mainly influences the deformation resistance during stamping, and if the stamping temperature is lower than 580 ℃, the deformation resistance is easily overlarge, and the stamping equipment is damaged; if the stamping temperature is higher than 640 ℃, the adverse effect of large performance reduction rate is caused, the warm forming deformation resistance is generally increased along with the reduction of the warm forming temperature, and the stamping temperature is controlled to be 580-640 ℃ more appropriately in order to ensure the smooth operation of the stamping process.
The stamping speed is 550-700 mm/s: the stamping speed mainly influences the surface quality of the axle housing, if the stamping speed is higher than 700mm/s, the surface of the axle housing is easy to wrinkle, and if the stamping speed is lower than 550mm/s, the thinning amount of the axle housing is large, and the problem of cracking is easy to occur; the punching speed is controlled within the range of 550-700 mm/s by comprehensively considering the surface quality of the axle housing and the capacity of forming equipment.
As an alternative embodiment, the temperature of the heating before rolling is 1200-1230 ℃, and the time of the heating before rolling is 175-215 mim. If the heating temperature is too high, the original structure is easy to be coarse; if the heating temperature is too low, the rolling stability is poor, and the production cannot be easily discharged;
in an optional embodiment, in the rough rolling, 3+3 passes are adopted for rolling, the rolling speed is controlled to be 2-5 m/s, the total deformation of the rough rolling is controlled to be 75-85%, and the inlet temperature of the rough rolling is controlled to be 1140-1170 ℃. The rough rolling inlet temperature is too high, so that the original structure is easily thick; if the rough rolling inlet temperature is too low, partial recrystallization is easily caused;
in an optional embodiment, in the fine rolling, 6 passes are adopted for rolling, the rolling speed is controlled to be 8-12 mm/s, the total deformation of the finish rolling is controlled to be 85-95%, and the inlet temperature of the finish rolling is controlled to be 1030-1060 ℃. The inlet temperature of finish rolling is too low, so that poor rolling stability is easily caused; if the inlet temperature of finish rolling is too high, partial recrystallization is easily caused;
as an alternative embodiment, the coiling temperature is 580 to 620 ℃. If the coiling temperature is higher than 620 ℃, the mechanical property is easily reduced; if the coiling temperature is lower than 560 ℃, the hot coiling performance control is not facilitated;
according to another exemplary embodiment of the invention, the axle housing steel prepared by the method is provided. In the embodiment of the invention, the component system and the microstructure type of the axle housing raw material are not limited, and the axle housing raw material can be a carbon-manganese system, a micro-alloying component system, a ferrite + pearlite structure, or a bainite or martensite structure.
The microstructure of the axle housing steel finished product obtained by the embodiment of the invention is 80-90% of ferrite and 10-20% of pearlite in volume fraction; or ferrite and pearlite and one or more of tempered bainite and martensite; the average grain size of the ferrite is less than or equal to 5.0 mu m; for microalloying component systems, there are also nanoscale precipitates. A small amount of banded structures exist in the axle housing steel finished product, and the grade of the banded structures is less than or equal to 1.5.
The thickness of the axle housing steel finished product obtained by the embodiment of the invention is 6-18 mm, the yield strength of the obtained axle housing finished product is improved by over 145MPa compared with that of the traditional hot forming process, and the reduction of both the yield strength and the tensile strength after warm forming is less than 25MPa. The axle housing steel finished product obtained by the embodiment of the invention has the specific yield strength range of 486-604 MPa and the tensile strength range of 630-725 MPa.
The method for controlling strength drop after hot forming of the axle housing steel according to the present application will be described in detail with reference to examples, comparative examples and experimental data.
S1, heating a casting blank before rolling, rough rolling, finish rolling, cooling after rolling and coiling in sequence to obtain a raw material of an axle housing;
s2, carrying out hot stamping and water mist cooling on the axle housing raw material, and carrying out air cooling to room temperature to obtain a high-strength axle housing steel finished product, wherein the hot stamping condition comprises: the heating rate is more than or equal to 400 ℃/s, the heating temperature is 600-650 ℃, the heating time is less than or equal to 180s, the stamping temperature is 580-640 ℃, and the stamping speed is 550-700 mm/s.
The components of the different groups are shown in table 1, and the process parameters in the comparative examples are different, specifically shown in table 2. The conditions not listed in the table can be applied by methods common in the art;
TABLE 1 chemical composition
| Group of | C | Si | Mn | Nb | V |
| Example 1 | 0.19 | 0.30 | 1.6 | 0 | 0 |
| Example 2 | 0.19 | 0.30 | 1.6 | 0 | 0 |
| Example 3 | 0.20 | 0.20 | 1.5 | 0.04 | 0.05 |
| Example 4 | 0.20 | 0.20 | 1.5 | 0.04 | 0.05 |
| Comparative example 1 | 0.19 | 0.30 | 1.6 | 0 | 0 |
| Comparative example 2 | 0.19 | 0.30 | 1.6 | 0 | 0 |
| Comparative example 3 | 0.19 | 0.30 | 1.6 | 0 | 0 |
| Comparative example 4 | 0.19 | 0.30 | 1.6 | 0 | 0 |
| Comparative example 5 | 0.19 | 0.30 | 1.6 | 0 | 0 |
TABLE 2 Process parameters
After the axle housing finished product is fully cooled to the room temperature, samples are taken from the parallel position for tensile test, the mechanical property is tested, and the mechanical property test result is shown in table 3.
TABLE 3
From the data in table 3, it can be seen that:
in the comparative example 1, the heating rate is 350 ℃/s and is less than or equal to the range of 400 ℃/s in the embodiment of the invention, other process parameters are the same as those in the embodiment 1, and the strength reduction rate is increased;
in the comparative example 2, the heating temperature is 500 ℃ which is less than the range of 600-650 ℃ in the embodiment of the invention, other process parameters are the same as those in the embodiment 1, and the defect of damaging the grinding tool exists;
in the comparative example 3, the heating temperature is 700 ℃, which is larger than the range of 600-650 ℃ of the embodiment of the invention, other process parameters are the same as those of the embodiment 1, and the strength reduction rate is increased;
in the comparative example 4, the heating holding time is 190s, which is more than or equal to the range of 180s in the embodiment of the invention, and other process parameters are the same as those in the embodiment 1, so that the strength loss rate is increased;
in comparative example 5, the cooling rate was 25 ℃/s (which is greater than the range of 8-15 ℃/s in the inventive example), the final cooling temperature was 250 ℃ (which is less than the range of 300-400 ℃) in the inventive example, although the strength loss is small, the water mist cooling rate could not be achieved, and the water spray amount needs to be increased, which results in an increase in cost;
in the embodiments 1-4, the yield strength and the tensile strength of the finished axle housing are reduced by less than 25MPa, the strength is higher than that of the traditional hot stamping process by more than 145MPa, and the axle housing has excellent surface quality. Because the lower heating temperature is adopted, the electric energy is saved.
Description of the drawings 2-4:
FIGS. 2-3 are metallographic diagrams of structures of axle housing finished products of examples 1 and 3, respectively, and it can be seen that the structures retain the structural morphology in a hot rolling state, the structures are composed of mixed structures of ferrite and pearlite, and the structures of example 3 added with micro-alloying elements are finer;
fig. 4 is a fine morphology diagram of the structure of the axle housing finished product in embodiment 3 of the present invention, which shows that after the warm forming process is adopted, the morphology of the structure retains the morphology characteristics of lath bainite in the original hot rolled structure, and the strength after warm forming is ensured.
Finally, it should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the embodiments of the invention.
It will be apparent to those skilled in the art that various modifications and variations can be made in the embodiments of the present invention without departing from the spirit or scope of the embodiments of the invention. Thus, if such modifications and variations of the embodiments of the present invention fall within the scope of the claims of the embodiments of the present invention and their equivalents, the embodiments of the present invention are also intended to encompass such modifications and variations.
Claims (6)
1. A method of controlling strength degradation after hot forming of axle housing steel, comprising:
carrying out rough rolling, finish rolling, cooling after rolling and coiling on the casting blank in sequence to obtain a raw material of the axle housing;
will axle housing raw materials heats, hot stamping and water smoke cooling, and back air cooling to room temperature obtains the axle housing steel finished product of high strength, axle housing steel finished product yield strength descends and < 25MPa, wherein, the rate of heating > 400 ℃/s, the temperature of heating is 600 ~ 650 ℃, the heat preservation time of heating is less than or equal to 180s, the temperature of hot stamping is 580 ~ 640 ℃, the speed of hot stamping is 550 ~ 700mm/s, the water smoke cooling includes: cooling with water mist at the cooling speed of 8-15 ℃/s until the final cooling temperature is 300-400 ℃,
in the rough rolling, 3+3 passes are adopted for rolling, the rolling speed is controlled to be 1-8 m/s, the total deformation of the rough rolling is controlled to be 65-85%, and the inlet temperature of the rough rolling is controlled to be 1100-1190 ℃;
in the finish rolling, 3+3 passes are adopted for rolling, the rolling speed is controlled to be 5-12 mm/s, the total deformation of the finish rolling is controlled to be 75-95%, the inlet temperature of the finish rolling is controlled to be 1000-1100 ℃, and the finish rolling temperature is 800-850 ℃.
2. A method of controlling the drop in strength after hot forming of axle housing steel as claimed in claim 1 wherein said post-rolling cooling comprises cooling to 580-620 ℃ at a rate of 2-5 ℃/s.
3. A method for controlling the drop in strength after hot forming of axle housing steel as claimed in claim 1 in which the temperature of the coils is 580-620 ℃.
4. An axle housing steel prepared by the method of any one of claims 1 to 3.
5. The axle housing steel of claim 4, wherein the metallographic structure of the axle housing steel comprises ferrite and pearlite, and the ferrite has an average grain size of 5.0 μm or less.
6. The axle housing steel of claim 5, wherein the thickness of the axle housing steel is 6-18 mm.
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|---|---|---|---|---|
| KR100815747B1 (en) * | 2001-12-22 | 2008-03-20 | 주식회사 포스코 | A method for manufacturing a high strength TMCP steel plate for hot forming |
| CN101289700A (en) * | 2008-06-17 | 2008-10-22 | 钢铁研究总院 | Method for preparing thermal and warm punching parts of high strength martensitic matrix |
| CN103805862B (en) * | 2014-02-19 | 2016-02-03 | 山东交通职业学院 | Axle shell steel and preparation method thereof |
| CN111074148B (en) * | 2018-10-19 | 2022-03-18 | 宝山钢铁股份有限公司 | 800 MPa-level hot stamping axle housing steel and manufacturing method thereof |
| CN111647805B (en) * | 2020-05-12 | 2021-12-21 | 首钢集团有限公司 | Axle housing steel with yield strength of 600MPa after hot forming, preparation method thereof and axle housing |
| CN111534758B (en) * | 2020-06-09 | 2021-10-26 | 首钢集团有限公司 | Axle housing steel for controlling strength reduction after hot forming, preparation method thereof and axle housing |
| CN111672955B (en) * | 2020-06-09 | 2022-05-17 | 首钢集团有限公司 | Hot stamping process for improving strength of hot stamping axle housing steel finished product |
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2021
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