CN113182439A - Hot stamping process for axle housing steel - Google Patents
Hot stamping process for axle housing steel Download PDFInfo
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- CN113182439A CN113182439A CN202110403072.0A CN202110403072A CN113182439A CN 113182439 A CN113182439 A CN 113182439A CN 202110403072 A CN202110403072 A CN 202110403072A CN 113182439 A CN113182439 A CN 113182439A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D37/00—Tools as parts of machines covered by this subclass
- B21D37/16—Heating or cooling
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
- B21D22/02—Stamping using rigid devices or tools
Abstract
The invention provides a hot stamping process for axle housing steel, belonging to the technical field of metal material pressure processing, and the hot stamping process comprises the following steps: heating the axle housing steel to 660-700 ℃, and keeping the temperature for less than or equal to 180 s; stamping the axle housing steel after heat preservation to obtain an axle housing; and cooling the axle housing at the speed of 5-8 ℃/s to obtain an axle housing finished product. The strength of the finished axle housing obtained by adopting the hot stamping process is improved by 80-130MPa compared with the yield strength of the traditional hot stamping process, and the reduction of the yield strength and the tensile strength after hot stamping is less than or equal to 45MPa, so that the problem of remarkable reduction of the strength of the finished hot stamping axle housing is solved.
Description
Technical Field
The invention belongs to the technical field of metal material pressure processing, and particularly relates to a hot stamping process for axle housing steel.
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. At present, according to the difference of production and manufacturing processes, axle housings can be divided into four types, namely cast axle housings, punching and welding axle housings, mechanical bulging axle housings and hydraulic bulging axle housings, wherein the punching and welding axle housings are widely applied to the fields of heavy trucks, medium trucks, light trucks, micro trucks, passenger cars, automobile cranes and the like, have the widest application range and are used for replacing cast axle housings with complicated manufacturing processes, low production efficiency, heavy weight and high cost.
The punching and welding axle housing is formed by punching and forming a steel plate, then is formed by welding and shaping, can be divided into a hot punching axle housing and a cold punching axle housing according to different punching temperatures, is generally limited by the tonnage of punching equipment for a medium-weight truck because the thickness of the axle housing is generally more than 14mm, and generally adopts a hot punching process, namely, the axle housing steel is heated before punching, and then is punched and formed under a high-temperature state so as to reduce the deformation resistance and realize the effect of easy punching. The traditional hot stamping process mainly adopts the processes of heating at 840-900 ℃, preserving heat for 5-8min, then performing high-temperature stamping forming, and finally air cooling to room temperature, and the biggest defect of the technology is that the strength of the steel plate after hot forming is obviously reduced, and the general strength is reduced to 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.
Disclosure of Invention
In order to solve the technical problem of strength reduction of the hot stamping axle housing, the invention provides a hot stamping process of axle housing steel, the yield strength of the axle housing finished product obtained by adopting the hot stamping process is improved by 80-130MPa compared with the yield strength of the traditional hot stamping process, and the reduction of the yield strength and the tensile strength after hot stamping is less than or equal to 45MPa, so that the problem of remarkable reduction of the strength of the hot stamping axle housing finished product is solved.
The invention is realized by the following technical scheme:
the embodiment of the invention provides a hot stamping process for axle housing steel, which comprises the following steps:
heating the axle housing steel to 660-700 ℃, and keeping the temperature for less than or equal to 180 s;
stamping the axle housing steel after heat preservation to obtain an axle housing;
and cooling the axle housing at the speed of 5-8 ℃/s to obtain an axle housing finished product.
Optionally, the axle housing steel is heated to 660-700 ℃, and the heat preservation time is less than or equal to 180s, and the method specifically comprises the following steps:
heating the axle housing steel to 660-700 ℃ at the speed of more than or equal to 400 ℃/s, and keeping the temperature for less than or equal to 180 s.
Optionally, the heat preservation time of the axle housing steel is 120-180 s.
Optionally, the axle housing steel after keeping warm is punched, obtains the axle housing, specifically includes:
and stamping the axle housing steel at the temperature of 650-700 ℃ to obtain the axle housing.
Optionally, cooling the axle housing at the speed of 5-8 ℃/s to obtain an axle housing finished product, specifically comprising the following steps of;
and controlling the temperature of the axle housing mold to be less than or equal to 200 ℃, independently placing the axle housing, and carrying out air cooling at the speed of 5-8 ℃/s to obtain an axle housing finished product.
Optionally, the temperature of the stamping die is controlled to be less than or equal to 200 ℃, and the method specifically comprises the following steps:
and after the axle housing steel is completely punched, carrying out water mist cooling on an axle housing die, and controlling the temperature of the axle housing die to be less than or equal to 200 ℃.
Optionally, the raw material component system of the axle housing steel comprises a carbon-manganese system or a microalloying component system.
Optionally, the microstructure type of the axle housing steel in the initial state comprises ferrite and pearlite;
alternatively, the microstructure type of the axle housing steel in the initial state comprises ferrite and pearlite, and bainite or martensite.
Optionally, the type of the microstructure of the axle housing finished product comprises ferrite and pearlite;
or the microstructure type of the axle housing steel comprises ferrite and pearlite, and tempered bainite or tempered martensite;
the average grain size of the ferrite is less than or equal to 8.0 mu m, and the level of the banded structure is less than or equal to 2.0.
Optionally, the thickness of the axle housing steel is 6-18 mm.
One or more technical schemes in the invention at least have the following technical effects or advantages:
according to the hot stamping process of the axle housing steel, the stamping temperature is influenced by the heating temperature, the heating temperature of the axle housing steel is controlled to be 660-700 ℃, the heat preservation time is less than or equal to 180s, the axle housing steel is not influenced to be formed, the phenomenon that the tissue type and the precipitated second-phase particles are obviously changed after the axle housing steel is austenitized at a high temperature can be avoided, the generation of coarse austenite grains and coarsened precipitates is avoided, the strength of a final axle housing finished product is favorably improved, the axle housing is cooled at the speed of 5-8 ℃/s, the phenomenon that the phase change of metal and the precipitation of microalloy elements are uncontrollable due to too low cooling speed is avoided, the strength after hot forming is obviously reduced, the yield strength and the tensile strength of an axle housing finished product obtained by adopting the hot stamping process are both less than or equal to 45MPa after hot stamping, and the problem that the strength of the hot stamped axle housing finished product is obviously reduced is solved.
The foregoing description is only an overview of the technical solutions of the present invention, and the embodiments of the present invention are described below in order to make the technical means of the present invention more clearly understood and to make the above and other objects, features, and advantages of the present invention more clearly understandable.
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 the drawings without creative efforts.
Fig. 1 is a structure phase diagram of an axle housing finished product of an axle housing steel hot stamping process provided by embodiment 1 of the invention.
Fig. 2 is a structure phase diagram of an axle housing finished product of the axle housing steel hot stamping process provided by embodiment 4 of the invention.
Fig. 3 is a structure phase diagram of an axle housing finished product of the axle housing steel hot stamping process provided by embodiment 6 of the invention.
FIG. 4 is a structure phase diagram of a finished axle housing product of the hot stamping process of the conventional axle housing steel provided by comparative example 1 of the invention.
Detailed Description
The present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly apparent therefrom. It will be understood by those skilled in the art that these specific embodiments and examples are for the purpose of illustrating the invention and are not to be construed as limiting the 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 this invention belongs. 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 present invention are commercially available or can be prepared by existing methods.
It should be further 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.
It is noted that, in this document, relational terms such as "first" and "second," and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions.
In order to solve the technical problems, the embodiment of the invention provides the following general ideas:
the applicant finds that the biggest disadvantage of the traditional hot stamping process is that the strength of the steel plate after hot forming is obviously reduced, and the strength is generally reduced to more than 100MPa, because:
the traditional hot stamping process mainly adopts heating at 840-900 ℃, heat preservation is carried out for 5-8min, after high-temperature austenitization, the tissue type of raw materials and precipitated second-phase particles can be obviously changed, and meanwhile, the cooling speed of an air cooling mode after stamping is uncontrollable, so that metal phase transformation and microalloy element precipitation are uncontrollable in cooling, the strength after hot forming is obviously reduced, and the general strength is reduced to 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. Therefore, controlling the rate of strength reduction after thermoforming is critical to automotive manufacturing.
Most domestic axle housing manufacturers adopt Q345 and Q460 or girder steels 510L and 610L as raw materials, research focus of domestic axle housing special steel mainly focuses on the aspect of product component design, and general axle housing steel is based on medium carbon content, micro-alloying elements such as Nb, V and Ti are added independently or Nb + Ti, Nb + V, V + Ti or V + N are added in a composite mode, and the strength of the finished axle housing steel is improved in a mode of improving precipitation strengthening proportion. Few researchers have studied the impact of the hot stamping process of axle housing steel on strength. This leads to two negative effects: firstly, when adopting conventional product design, intensity behind the hot stamping can't satisfy the requirement, secondly improves the intensity behind the hot stamping through adding higher alloy content, causes a large amount of rises of cost, also causes certain influence to welding performance moreover.
Based on the problems of the existing axle housing steel, the invention provides a control method for solving the problem that the strength of the axle housing after hot stamping is obviously reduced only from the hot stamping process without considering the product design.
According to an exemplary embodiment of the present invention, there is provided a hot stamping process for axle housing steel, the hot stamping process including:
heating the axle housing steel to 660-700 ℃, wherein the heat preservation time is less than or equal to 180 s:
stamping the axle housing steel after heat preservation to obtain an axle housing;
and cooling the axle housing at the speed of 5-8 ℃/s to obtain an axle housing finished product.
In the hot stamping process, the heating temperature influences the stamping temperature, the heating temperature of the axle housing steel is controlled to be 660-700 ℃, the heat preservation time is less than or equal to 180s, the formation of the axle housing steel is not influenced, the tissue type and the precipitated second phase particles can be prevented from being obviously changed after the axle housing steel is austenitized at high temperature, the generation of coarse austenite grains and coarsened precipitates is avoided, the strength of the final axle housing finished product is favorably improved, the axle housing is cooled at the speed of 5-8 ℃/s, the uncontrollable precipitation of metal phase transformation and microalloy elements caused by too low cooling speed is avoided, the strength after hot forming is obviously reduced, the yield strength and the tensile strength of the axle housing finished product obtained by adopting the hot stamping process are both less than or equal to 45MPa after hot stamping, and the problem of obvious reduction of the strength of the hot stamped axle housing finished product is solved.
As an optional implementation mode, the axle housing steel is heated to 660-700 ℃, the heat preservation time is less than or equal to 180s, and the method specifically comprises the following steps:
heating the axle housing steel to 660-700 ℃ at the speed of more than or equal to 400 ℃/s, and keeping the temperature for less than or equal to 180 s.
In the embodiment of the invention, the axle housing steel temperature rise speed is more than or equal to 400 ℃/s, the aim is to rapidly heat the axle housing steel raw material to a ferrite and austenite two-phase region through ultra-rapid heating, the thermal deformation resistance of the temperature region is small, the austenite grains are fine in combination with short-time heat preservation, the micro-alloying steel can be prevented from coarsening a second-phase precipitate, the control of a final structure or the precipitate is facilitated, and the reduction of the axle housing strength and the fatigue life is avoided.
As an optional embodiment, the insulation time of the axle housing steel is 120-180 s.
In the embodiment of the invention, the heat preservation time is the same as the heating temperature, the size influence on original austenite grains and precipitates is obvious, so that the deformation resistance and the final structure are greatly influenced, the heating time is too long, the austenite grains are coarse, the refinement of the ferrite structure in the group is not facilitated, in addition, the high-temperature plasticity is gradually reduced along with the prolonging of the heat preservation time, and in order to ensure good high-temperature plasticity, the heat preservation time is controlled within 120-180 s from the comprehensive consideration of the structure control and the deformation resistance control. If the holding time is less than 120s, the precipitated second-phase precipitates do not have enough time to dissolve back to the matrix, secondary precipitation in the cooling process is influenced, and thus the contribution of precipitation strengthening to the strength of the steel is influenced, and the problem of high strength reduction rate is caused.
As an optional implementation manner, the axle housing steel after heat preservation is punched to obtain an axle housing, and the axle housing specifically includes:
and stamping the axle housing steel at the temperature of 650-700 ℃ to obtain the axle housing.
In the embodiment of the invention, the axle housing steel enters the stamping process after the heat preservation process, the temperature is slightly reduced to 650-700 ℃, the deformation resistance during stamping is mainly influenced by the hot stamping temperature and cannot be too low so as to avoid the deformation resistance being too high and causing damage to stamping equipment, the deformation resistance of the hot stamping is generally increased along with the reduction of the hot stamping temperature, and the stamping temperature is preferably controlled to be 650-700 ℃ in order to ensure the smooth operation of the stamping process.
As an optional implementation mode, the axle housing is cooled at the speed of 5-8 ℃/s to obtain an axle housing finished product, and the method specifically comprises the following steps of;
and controlling the temperature of the axle housing mold to be less than or equal to 200 ℃, independently placing the axle housing, and carrying out air cooling at the speed of 5-8 ℃/s to obtain an axle housing finished product.
In the embodiment of the invention, the temperature of the axle housing die mainly influences the cooling speed of materials in the stamping process, the die temperature is high, the temperature difference between the axle housing and the die is small, and the axle housing cooling speed is slow, so that the obtained structure is coarse ferrite, and the banded structure is serious; the lower the temperature of the die is, the faster the heat exchange speed between the die and the axle housing is, and the faster the cooling speed of the axle housing steel is, so that the lower final cooling temperature is favorably controlled, the ferrite nucleation rate is increased, the growth of ferrite grains is inhibited, the strength of the hot-stamped axle housing is favorably ensured, and the temperature of the hot stamping die of the axle housing is set below 200 ℃ in comprehensive consideration.
As an optional implementation manner, the controlling the temperature of the stamping die to be less than or equal to 200 ℃ specifically includes:
and after the axle housing steel is completely punched, carrying out water mist cooling on an axle housing die, and controlling the temperature of the axle housing die to be less than or equal to 200 ℃.
In the embodiment of the invention, the axle housing mold is cooled by water mist, and the temperature of the axle housing mold can be controlled below 200 ℃ by other feasible cooling modes.
As an alternative embodiment, the raw material component system of the axle housing steel comprises a carbon-manganese system or a microalloying component system.
In the embodiment of the invention, the axle housing raw material component system is not limited, and can be a carbon-manganese system, a microalloying component system or other raw material systems which can be used as axle housing steel.
As an alternative embodiment, the microstructure type of the axle housing steel in the initial state comprises ferrite and pearlite;
alternatively, the microstructure type of the axle housing steel in the initial state comprises ferrite and pearlite, and bainite or martensite.
In the embodiment of the invention, the type of the microstructure of the axle housing used is not limited, and the microstructure can be ferrite + pearlite structure, and bainite or martensite structure can also exist.
As an alternative embodiment, the microstructure type of the axle housing finished product comprises ferrite and pearlite;
or the microstructure type of the axle housing steel comprises ferrite and pearlite, and tempered bainite or tempered martensite;
the average grain size of the ferrite is less than or equal to 8.0 mu m, and the level of the banded structure is less than or equal to 2.0.
In the embodiment of the invention, the microstructure type of the axle housing steel comprises ferrite and pearlite, and tempered bainite or tempered martensite; the average grain size of the ferrite is less than or equal to 8.0 mu m, the level of a banded structure is less than or equal to 2.0, the uniform and fine ferrite contributes to the strength and the shaping of the axle housing, and the coarse structure causes the reduction of the strength and the toughness; the existence of the banded structure destroys the continuity of the matrix, and leads to the reduction of ductility and toughness; in addition, severe ribbon-like structures have a severe influence on fatigue properties.
As an optional implementation mode, the thickness of the axle housing steel is 6-18 mm.
In the embodiment of the invention, the hot stamping process is suitable for the axle housing steel with the thickness of 6-18 mm.
In conclusion, the axle housing raw material is quickly heated to a ferrite-austenite two-phase region through ultra-quick heating, the thermal deformation resistance of the temperature region is small, the austenite grains are fine in combination with short-time heat preservation, and the coarsening of second-phase precipitates can be prevented for microalloyed steel; after stamping, carrying out water mist cooling on the die, ensuring that the die has lower temperature, rapidly cooling the axle housing, and improving ferrite nucleation dynamics, thereby obtaining fine ferrite tissues; the axle housing after the line is put in parallel independently and is cooled by a fan, so that the cooling speed of the axle housing is increased, the growth of ferrite grains is prevented, uniform and fine ferrite grains are obtained, and the formation of serious banded structures is avoided. The strength of the finished axle housing obtained by adopting the new hot stamping process is improved by 80-130MPa compared with the yield strength of the traditional hot stamping process, the reduction of the yield strength and the tensile strength after hot stamping is less than or equal to 45MPa, 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.
The specific design principle of partial hot stamping technological parameters is as follows:
heating rate: the heating rate has obvious influence on the coarsening behavior of original austenite grains and precipitates, when the heating rate is slow, 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.
Heating temperature: the heating temperature mainly affects two aspects, namely deformation resistance, austenite grains, precipitate re-dissolution amount, precipitate coarsening and the like, and the control is important. The deformation resistance generally decreases gradually along with the increase of the heating temperature, but when the heating temperature exceeds 700 ℃, the deformation resistance decreases slowly when the heating temperature is increased; considering that the tonnage of the axle housing hot stamping equipment is generally between 1000 and 2500 tons, when the heating temperature reaches more than 660 ℃, the thickness of the axle housing can realize stable stamping within 6-18mm, and the damage to a mold can not be caused. For high-temperature structure transformation, the original structure of the axle housing steel is transformed along with the axle housing raw material entering a ferrite and austenite two-phase region, the higher the heating temperature is, the faster the thermal diffusion speed is, the faster the structure transformation is, and the formed austenite grains are about coarse; on the other hand, for microalloying elements Nb and Ti, the carbonitride thereof has a high dissolution temperature, and is difficult to dissolve or has a small dissolution amount in the axle housing heating process, and the coarsening thereof is about serious at a higher temperature, which results in the existence of coarse precipitates in the final structure; both coarse austenite grains and coarse precipitates are not beneficial to improving the strength of the final axle housing. Therefore, the heating temperature is controlled at 650-700 ℃ in consideration of the equipment capacity and performance control.
Axle housing down-line cooling mode: the traditional hot stamping axle housing finished product is cooled by stacking, the cooling speed is slow, and thick tissues and precipitates are caused. The placing mode and the cooling mode of the finished axle housing during cooling after the axle housing is off line have great influence on the cooling rate, the grain size of the finished product is directly influenced, the cooling rate after the axle housing is off line is better, and in order to improve the cooling speed of the axle housing, a fan is adopted for air cooling. Therefore, the axle housing is put off line and then is put in a parallel and independent mode, and air cooling is adopted for accelerated cooling.
The hot stamping process of the axle housing steel of the present application will be described in detail with reference to examples, comparative examples and experimental data.
Examples
The hot stamping process of the axle housing steel comprises the following steps:
(1) heating axle housing steel with the thickness of 6-18mm to 660-700 ℃ at the speed of more than or equal to 400 ℃/s, and keeping the temperature for 120-180 s;
(2) stamping the axle housing steel at the temperature of 650-700 ℃ to obtain an axle housing;
(3) after the axle housing steel is punched, carrying out water mist cooling on an axle housing die, controlling the temperature of the axle housing die to be less than or equal to 200 ℃, independently placing the axle housing, and carrying out air cooling at the speed of 5-8 ℃/s to obtain an axle housing finished product.
Based on the hot stamping process, the invention discloses 6 typical examples and 2 comparative examples, wherein the axle housing steels adopted by the examples 1 to 3 and the comparative example 1 are the same, the thicknesses of the axle housing steels are 14m, and the axle housing steels adopted by the examples 4 to 6 and the comparative example 2 are the same, and the thicknesses of the axle housing steels are 16 mm. The main chemical components of the raw materials and the hot stamping process parameters adopted in the examples 1 to 6 and the comparative examples 1 and 2 are shown in the table 1, wherein the stamping temperature represents the temperature of the axle housing steel entering the stamping process.
TABLE 1 Main chemical composition of axle housing steel and Hot stamping Process parameters
Correlation test
And (3) carrying out mechanical property test on the raw material axle housing steel and the axle housing finished products of the examples 1-6 and the comparative examples 1 and 2.
The related test method comprises the following steps:
the yield strength test method comprises the following steps: according to GB/T228-.
The test method of the tensile strength comprises the following steps: tensile specimens were cut out in the transverse direction from the surfaces of hot-rolled steel sheets and square tubes according to GB/T228-.
The test results are shown in table 2, in table 2:
yield reduction: representing the yield strength difference of the axle housing steel and the axle housing finished product;
tensile reduction: and the tensile strength difference of the raw material axle housing steel and the axle housing finished product is shown.
TABLE 2 mechanical property test results of axle housing steel and axle housing finished product as raw materials
In Table 2, the axle housing of examples 1-6 had a yield loss of 45MPa or less and a tensile loss of 43MPa or less. The yield drop of the axle housing of the comparative examples 1 and 2 is more than or equal to 301MPa, and the tensile drop is more than or equal to 128 MPa. Under the condition that the axle housing steel raw materials have the same components, the yield strength of the axle housing finished products of the examples 1 to 3 is increased by 92 to 111MPa and the tensile strength is increased by 86 to 105MPa compared with the yield strength of the comparative example 1. The yield strength of the axle housing finished products of the examples 4-6 is improved by 118-134MPa and the tensile strength is improved by 114-129 MPa compared with the yield strength of the comparative example 2.
As can be seen from Table 2, the yield strength and tensile strength of the finished axle housing manufactured by the hot stamping process of the axle housing steel are reduced by less than 45 MPa. Because the lower heating temperature is adopted, the electric energy is saved.
Detailed description of the drawings 1-4:
as shown in fig. 1, a metallographic structure of an axle housing finished product of an axle housing steel hot stamping process according to embodiment 1 of the present invention shows ferrite + pearlite as a microstructure, ferrite is polygonal or quasi-polygonal, ferrite proportion is that ferrite grains have an average size of 3.0 μm, and a banded structure is 1.5 grade.
As shown in fig. 2, a metallographic structure of a finished axle housing product of an axle housing steel hot stamping process according to embodiment 4 of the present invention shows a metallographic structure, in which a microstructure of ferrite + pearlite is provided, the ferrite is composed of polygonal, quasi-polygonal and acicular ferrite, ferrite grains have an average size of 4.4 μm, and a band-shaped structure is 2-grade.
As shown in fig. 3, a metallographic structure of an axle housing finished product of an axle housing steel hot stamping process according to embodiment 6 of the present invention shows ferrite + pearlite as a microstructure, the ferrite mainly comprises polygonal ferrite and quasi-polygonal ferrite, ferrite has a ferrite proportion, ferrite grains have an average size of 5.2 μm, and a band-shaped structure is 2 grades.
As shown in FIG. 4, the metallographic structure of the finished axle housing product of the axle housing of the hot stamping process of the axle housing steel according to comparative example 1 of the present invention is ferrite + pearlite, the ferrite is a quasi-polygonal ferrite composition, the ferrite proportion is that the average size of ferrite grains is 15.6 μm, and the banded structure is 3.0 grade. Since the structure of comparative example 1 was significantly coarsened, the strength was significantly reduced due to coarse grains.
One or more technical solutions in the embodiments of the present invention at least have the following technical effects or advantages:
(1) in the hot stamping process of the axle housing steel of the embodiment of the invention, the heating temperature influences the stamping temperature, the heating temperature of the axle housing steel is controlled to be 660-700 ℃, the heat preservation time is less than or equal to 180s, while not influencing the axle housing steel molding, the method can avoid the obvious change of the tissue type and the precipitated second phase particles after the axle housing steel is austenitized at high temperature, avoid the generation of coarse austenite grains and coarsened precipitates, the method is beneficial to improving the strength of the final axle housing finished product, the axle housing is cooled at the speed of 5-8 ℃/s, uncontrollable metal phase change and microalloy element precipitation caused by too low cooling speed are avoided, the strength of the hot formed axle housing is obviously reduced, and the yield strength and the tensile strength of the axle housing finished product obtained by the hot stamping process are reduced by less than or equal to 45MPa after hot stamping, so that the problem of the obvious reduction of the strength of the hot stamped axle housing finished product is solved.
(2) According to the hot stamping process of the axle housing steel provided by the embodiment of the invention, the axle housing steel temperature rise speed is more than or equal to 400 ℃/s, the purpose is to rapidly heat the axle housing steel raw material to a ferrite and austenite two-phase region through ultra-rapid heating, the thermal deformation resistance of the temperature region is small, the combination with short-time heat preservation is realized, austenite grains are fine, the coarsening of a second-phase precipitate can be prevented for microalloyed steel, the control of a final structure or precipitate is facilitated, and the reduction of the axle housing strength and the fatigue life are avoided.
(3) According to the hot stamping process of the axle housing steel, the heat preservation time is the same as the heating temperature, the size influence on original austenite grains and precipitates is obvious, so that the deformation resistance and the final structure are greatly influenced, the heating time is too long, the austenite grains are large and are not beneficial to the refinement of the ferrite structure in the assembly, in addition, the high-temperature plasticity is gradually reduced along with the extension of the heat preservation time, and in order to ensure good high-temperature plasticity, the heat preservation time is controlled within 120-180 s from the perspective of the structure control and the deformation resistance control. If the holding time is less than 120s, the precipitated second-phase precipitates do not have enough time to dissolve back to the matrix, secondary precipitation in the cooling process is influenced, and thus the contribution of precipitation strengthening to the strength of the steel is influenced, and the problem of high strength reduction rate is caused.
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 invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (10)
1. The hot stamping process of the axle housing steel is characterized by comprising the following steps of:
heating the axle housing steel to 660-700 ℃, and keeping the temperature for less than or equal to 180 s;
stamping the axle housing steel after heat preservation to obtain an axle housing;
and cooling the axle housing at the speed of 5-8 ℃/s to obtain an axle housing finished product.
2. The hot stamping process for the axle housing steel as claimed in claim 1, wherein the axle housing steel is heated to 660-700 ℃ for less than or equal to 180s, and specifically comprises the following steps:
heating the axle housing steel to 660-700 ℃ at the speed of more than or equal to 400 ℃/s, and keeping the temperature for less than or equal to 180 s.
3. The hot stamping process for the axle housing steel as claimed in claim 1 or 2, wherein the heat preservation time of the axle housing steel is 120-180 s.
4. The hot stamping process for the axle housing steel as claimed in claim 1, wherein the axle housing steel after heat preservation is stamped to obtain an axle housing, and the process specifically comprises:
and stamping the axle housing steel at the temperature of 650-700 ℃ to obtain the axle housing.
5. The hot stamping process for the axle housing steel as claimed in claim 1, wherein the axle housing is cooled at a speed of 5-8 ℃/s to obtain an axle housing finished product, and specifically comprises the following steps;
and controlling the temperature of the axle housing mold to be less than or equal to 200 ℃, independently placing the axle housing, and carrying out air cooling at the speed of 5-8 ℃/s to obtain an axle housing finished product.
6. The hot stamping process for the axle housing steel as claimed in claim 5, wherein the temperature of the stamping die is controlled to be not more than 200 ℃, and the process specifically comprises the following steps:
and after the axle housing steel is completely punched, carrying out water mist cooling on an axle housing die, and controlling the temperature of the axle housing die to be less than or equal to 200 ℃.
7. The hot stamping process for the axle housing steel as claimed in claim 1, wherein the raw material composition system of the axle housing steel comprises a carbon manganese system or a microalloyed composition system.
8. The hot stamping process for the axle housing steel as claimed in claim 1, wherein the microstructure type of the axle housing steel in the initial state comprises ferrite and pearlite:
alternatively, the microstructure type of the axle housing steel in the initial state comprises ferrite and pearlite, and bainite or martensite.
9. The hot stamping process for axle housing steel according to claim 1, wherein the microstructure type of the axle housing finished product comprises ferrite and pearlite;
or the microstructure type of the axle housing steel comprises ferrite and pearlite, and tempered bainite or tempered martensite;
the average grain size of the ferrite is less than or equal to 8.0 mu m, and the level of the banded structure is less than or equal to 2.0.
10. The hot stamping process for the axle housing steel as claimed in claim 1, wherein the thickness of the axle housing steel is 6-18 mm.
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|---|---|---|---|---|
| US4756466A (en) * | 1986-03-27 | 1988-07-12 | Rockwell International Corporation | Method of manufacturing a drive axle housing |
| 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 |
| CN111672955A (en) * | 2020-06-09 | 2020-09-18 | 首钢集团有限公司 | Hot stamping process for improving strength of hot stamping axle housing steel finished product |
| CN112011746A (en) * | 2019-05-28 | 2020-12-01 | 宝山钢铁股份有限公司 | Steel material with yield strength of 600MPa grade after hot stamping and manufacturing method thereof |
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2021
- 2021-04-14 CN CN202110403072.0A patent/CN113182439A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4756466A (en) * | 1986-03-27 | 1988-07-12 | Rockwell International Corporation | Method of manufacturing a drive axle housing |
| 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 |
| CN112011746A (en) * | 2019-05-28 | 2020-12-01 | 宝山钢铁股份有限公司 | Steel material with yield strength of 600MPa grade after hot stamping and manufacturing method thereof |
| CN111672955A (en) * | 2020-06-09 | 2020-09-18 | 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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