CN110317935B - Treatment process of ultrahigh-strength steel BR1500HS - Google Patents
Treatment process of ultrahigh-strength steel BR1500HS Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/56—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering characterised by the quenching agents
- C21D1/60—Aqueous agents
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/002—Heat treatment of ferrous alloys containing Cr
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
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- 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
- C21D2211/008—Martensite
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Abstract
The invention discloses a BR1500HS treatment process for ultrahigh-strength steel, which belongs to the technical field of ultrahigh-strength steel heat treatment, and is characterized in that the BR1500HS is placed in a heating container to be heated to 900-; placing the austenitized ultrahigh-strength steel on a die, performing hot stamping forming and quenching treatment, performing heating treatment after quenching to room temperature for the first time, performing secondary quenching to room temperature after heating, performing upper die forming after quenching is finished, and performing performance testing after cooling to room temperature; the carbon enriched in the martensite is distributed to the austenite which does not complete the martensite transformation through the secondary quenching, so that the austenite which does not complete the martensite forms stable martensite in the secondary quenching, and the hardness and the tensile strength of the material are improved.
Description
Technical Field
The invention belongs to the technical field of ultra-high strength steel heat treatment, and particularly relates to a BR1500HS treatment process for ultra-high strength steel.
Background
In the field of automobile manufacturing, the problem of environmental pollution caused by the automobile industry is always the focus of social wide attention, the weight of an automobile is reduced, the use of high-performance and light-weight materials is one of important ways for realizing energy conservation, emission reduction and environmental pollution reduction, and the automobile parts produced by using the thin high-strength steel plates can improve the collision-proof capability of an automobile body and reduce the weight of the automobile body; the BR1500HS steel is an ultrahigh strength steel, has higher strength and toughness, can bear higher stress, has higher corrosion resistance, and is widely applied to the field of automobile manufacturing.
Ultrahigh strength steel sheet BR1500HS intensity is higher, difficult taking shape in the course of working, the cutting degree of difficulty is big, cutter damage is serious in the cutting process, machining efficiency is low, when ultrahigh strength steel cold forming at normal atmospheric temperature, required pressure is big, the shaping piece appears the fracture easily and kick-backs comparatively seriously in the forming process, conventional cold stamping forming process can't take shape almost, and lead to local temperature to rise easily in the course of working, cause the steel sheet surface texture to change, thereby influence the performance of processing back steel sheet, consequently mainly carry out heat treatment to ultrahigh strength steel sheet BR1500HS at present, tensile strength is usually about 1400MPa-1500Mpa after the heat treatment.
The heat treatment is a metal heat processing technology for obtaining required performance by changing the chemical components and structures on the surface or in the material of a metal material in a solid state through heating, heat preservation and cooling, steel is heated to a temperature above a critical temperature, after heat preservation is carried out for a period of time, the steel is quickly placed into a quenching medium, and the steel is quickly cooled at a speed higher than the critical cooling speed.
The Chinese patent publication No. CN108504985A is entitled as a heat treatment method of a high-strength hot-forming torsion beam for an automobile, and the heat treatment method of the invention solves the problem of low fatigue strength of the high-strength hot-forming torsion beam caused by decarburization of the steel surface in the forming process through heat treatment modes of pretreatment temperature rise, carburization and quenching treatment, but has the disadvantages that an oil bath is adopted for quenching in the quenching stage, the process is complex, the temperature is difficult to control, the uniformity of a temperature field is not high, and the tensile strength after quenching is 1210 MPa.
Disclosure of Invention
In view of the above problems in the prior art, the present invention provides a BR1500HS processing technology for ultra-high strength steel, which uses secondary quenching to distribute the carbon enriched in martensite to the austenite without martensite transformation, so that the austenite without martensite forms stable martensite in the secondary quenching, and the tensile strength and hardness of the material are improved.
A BR1500HS treatment process for ultrahigh-strength steel comprises the following steps:
(1) austenitizing: placing the ultra-high strength steel BR1500HS in a heating container for heating, and preserving heat to austenitize the ultra-high strength steel BR1500 HS;
(2) quenching: placing the austenitized ultrahigh-strength steel on a die, performing hot stamping forming and quenching treatment, performing heating treatment after the ultrahigh-strength steel is quenched to room temperature for the first time, and performing secondary quenching to the room temperature after the ultrahigh-strength steel is heated;
(3) and (3) performance testing: and after quenching is finished, forming the upper die, cooling to room temperature, and carrying out performance test.
Further, the ultrahigh-strength steel BR1500HS comprises 0.21-0.25% of carbon, 0.27-0.30% of silicon, 1.33-1.42% of manganese, 0.12-0.15% of chromium, 0.039-0.041% of aluminum, 0.0023-0.0051% of boron, 0.047-0.051% of titanium, 0.0098-0.01% of phosphorus, 0.0011-0.0015% of sulfur and the balance of iron and trace impurities.
The BR1500HS ultrahigh-strength steel plate contains boron, the boron plays an important role in the hardenability of the steel plate in the quenching process, on one hand, the hardenability of the steel plate in the quenching process can be improved, so that the martensite transformation amount is increased in the cooling process, the strength of the steel plate is further improved, on the other hand, the boron is segregated at the boundary of austenite grains in the heat treatment process, the nucleation process of ferrite is delayed, and the formation of martensite is further promoted.
Further, the thickness of the ultra-high strength steel BR1500HS steel plate is 1-1.5 mm.
Further, in the step (1), the austenitizing heating vessel is an induction heating furnace, and the induction heating furnace is composed of a power supply, a cooling system, an induction heating system and a temperature detection control system.
Further, in the step (1), the heating temperature in the induction heating furnace is 900-.
Further, in the step (2), hot stamping forming is carried out on austenite on a die, after the austenite is quenched and cooled to room temperature for the first time, the temperature is raised to 400-450 ℃, the temperature raising rate is 110 ℃/h, the temperature is kept for 4-5min, and the austenite is quenched and cooled to room temperature again.
Further, the quenching in the step (2) is carried out by water cooling.
Further, the cooling rate in the step (2) is 45-50 ℃/s.
Further, in the step (2), the distance between the water channels of the mold in the water-cooling mold is 25mm, the diameter is 6-9mm, and the distance between the center of the cooling water channel and the mold surface is 15 mm.
Further, in the step (2), the pressure maintaining pressure is 10-15MPa in the hot stamping forming process.
Advantageous effects
(1) The invention adopts a secondary quenching process to distribute the enriched carbon in the martensite under the first quenching to the austenite without martensite transformation, thereby forming stable martensite by the austenite without martensite in the second quenching, improving the hardness and tensile strength of the material, wherein the tensile strength reaches over 1750Mpa, and the hardness is over 55 HRB.
(2) The induction heating furnace is used, the preheating time of the induction heating furnace is short, the temperature of the furnace chamber does not obviously fluctuate in the material taking and adding processes, and the material sheets can be conveniently and quickly fed and discharged.
(3) According to the invention, high-temperature punch forming is adopted, so that the ultrahigh-strength steel BR1500HS has better plasticity and better forming performance, and high-precision forming can be realized; the high-strength steel plate has good mechanical property and higher hardness and tensile strength.
(4) The quenching cooling mode is water cooling, in the water cooling process, the heat of the die taken away by the cooling channel in the same time is gradually increased, the temperature of the die is reduced, the water circulation performance in the cooling water channel is enhanced, the cooling effect is continuously enhanced, the uniformity of a temperature field is continuously enhanced, the martensite is transformed from mixed martensite with different sizes to mixed martensite with uniform crystal grains, and in the pressure water cooling stage, the martensite structure tends to be uniform and gradually refined, so that the effects of refining the crystal grains and improving the tensile strength are achieved.
Drawings
FIG. 1 is a flow chart of the treatment process of the ultra-high strength steel BR1500 HS.
Detailed Description
The technical solutions of the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings, and it is to be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments; all other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without any inventive step, are within the scope of the present invention.
Example 1
FIG. 1 is a flow chart of the treatment process of the ultra-high strength steel BR1500HS, and the treatment process of the ultra-high strength steel BR1500HS comprises the following steps:
(1) austenitizing: placing the ultrahigh-strength steel BR1500HS in an induction heating furnace for heating, wherein the induction heating furnace consists of a power supply, a cooling system, an induction heating system and a temperature detection control system, the heating temperature is 850 ℃, the heating rate is 130 ℃/h, the heating temperature is set by the temperature detection control system, the temperature is kept for 5min after the temperature reaches a preset temperature, and the steel plate is austenitized by heat preservation, and comprises the steel plate components of 0.21% of carbon element, 0.27% of silicon element, 1.33% of manganese element, 0.12% of chromium element, 0.039% of aluminum element, 0.0023% of boron element, 0.047% of titanium element, 0.0098% of phosphorus element, 0.0011% of sulfur element and the balance of iron and trace impurities, wherein the thickness of the steel plate is 1 mm;
(2) quenching: placing the ultra-high strength steel subjected to austenitization on a die, performing hot stamping forming and quenching treatment, wherein the pressure maintaining pressure is 10MPa, the quenching cooling mode is water cooling, the distance between die water channels in the water cooling die is 25mm, the diameter is 6mm, the distance between the center of the cooling water channel and the die surface is 15mm, the cooling rate is 45 ℃/s, performing hot stamping forming on austenite on the die, heating to 400 ℃ after the first quenching cooling to the room temperature, the heating rate is 110 ℃/h, keeping the temperature for 4min, and quenching again and cooling to the room temperature;
(3) and (3) performance testing: and after quenching is finished, forming the upper die, cooling to room temperature, and carrying out performance test.
The thermal simulator Gleeble1500 is used for researching the treatment process of the ultra-high strength steel BR1500 HS.
Considering the influence of the heating temperature in austenitizing on the properties of the BR1500HS ultra-high strength steel plate, the BR1500HS ultra-high strength steel plate properties of examples 1-5 are examined by changing the heating temperature in austenitizing and changing the heating temperature in austenitizing under the condition that other conditions are not changed, and are shown in Table 1.
Table 1:
| examples | Austenitizing Medium heating temperature (. degree. C.) | Tensile strength (Mpa) | Hardness (HRB) |
| 1 | 850 | 1553.8 | 42.5 |
| 2 | 900 | 1751.7 | 59.7 |
| 3 | 925 | 1778.6 | 61.2 |
| 4 | 950 | 1810.3 | 62.5 |
| 5 | 1000 | 1537.8 | 50.1 |
As can be seen from table 1, the tensile strength of the ultra-high strength steel BR1500HS shows a tendency of increasing and then decreasing with increasing temperature, mainly because when the temperature is lower, the austenitizing degree of the ultra-high strength steel BR1500HS is lower, the residual ferrite is lower, so that the tensile strength of the ultra-high strength steel BR1500HS is decreased, and when the temperature is higher, the austenitizing degree is increased, the martensite is uniformly distributed after quenching, so the tensile strength is higher, and when the temperature is continuously increased, the austenite grains are continuously increased, so that the width of martensite bundles is increased, and the tensile strength of the ultra-high strength steel is further decreased, so the heating temperature in austenite is 900-.
Examples 6 to 10
On the basis of example 1, wherein in the austenitizing stage: the heating temperature is 900 ℃, the temperature is kept for 5.5min after the temperature reaches the preset temperature, the steel plate comprises the components of 0.23 percent of carbon element, 0.28 percent of silicon element, 1.37 percent of manganese element, 0.14 percent of chromium element, 0.04 percent of aluminum element, 0.004 percent of boron element, 0.05 percent of titanium element, 0.0099 percent of phosphorus element, 0.0013 percent of sulfur element and the balance of iron and trace impurities, and the thickness of the steel plate is 1.25 mm; in the quenching stage: keeping the pressure at 5-20MPa, keeping the distance between water channels of the die in the water-cooled die at 25mm, keeping the diameter at 7mm, keeping the distance between the center of a cooling water channel and the die surface at 15mm, cooling at 47 ℃/s, performing hot stamping forming on austenite on the die, performing first quenching cooling to room temperature, heating to 425 ℃, keeping the temperature for 4.5min, and performing quenching cooling again to room temperature.
Considering the influence of the holding pressure in the quenching stage on the performance of the ultra-high strength steel BR1500HS steel plate, the performance of the ultra-high strength steel BR1500HS steel plate is examined by changing the holding pressure in the quenching stage under the condition that other conditions are not changed, and examples 6-10 are shown in Table 2.
Table 2:
| examples | Pressure maintaining intensity (Mpa) in quenching stage | Tensile strength (Mpa) | Hardness (HRB) |
| 6 | 5 | 1111.9 | 45.2 |
| 7 | 10 | 1761.5 | 55.6 |
| 8 | 12.5 | 1725.2 | 61.9 |
| 9 | 15 | 1716.8 | 59.4 |
| 10 | 20 | 1520.1 | 40.2 |
As can be seen from table 2, with the increase of the pressure holding pressure, the tensile strength of the ultra-high strength steel BR1500HS shows a trend of increasing first and then decreasing, which is mainly because with the increase of the pressure holding pressure, the time taken for the ultra-high strength steel BR1500HS to cool to the quenching stage is gradually decreased, so as to increase the average cooling rate, the plastic deformation generated by the ultra-high strength steel BR1500HS cooling in the mold is larger, so as to increase the effective contact area with the mold, increase the heat transfer efficiency between the mold and the ultra-high strength steel BR1500HS, so as to increase the cooling rate in unit time, so as to increase the tensile strength of the steel plate, and with the continuous increase of the pressure holding pressure, the cooling plastic deformation of the ultra-high strength steel BR1500HS in the mold does not change greatly, so as to have no obvious change in the effective contact area with the mold, so as to have no obvious increase trend in the cooling rate in unit time, so as to have no obvious increase in, therefore, the pressure holding pressure is 10-15Mpa, and the performance of the super-strength steel BR1500HS steel plate is better.
Examples 11 to 15
On the basis of example 1, wherein in the austenitizing stage: the heating temperature is 950 ℃, the temperature is kept for 6min after the temperature reaches the preset temperature, the steel plate comprises the components of 0.25 percent of carbon element, 0.30 percent of silicon element, 1.42 percent of manganese element, 0.15 percent of chromium element, 0.041 percent of aluminum element, 0.0051 percent of boron element, 0.051 percent of titanium element, 0.01 percent of phosphorus element, 0.0015 percent of sulfur element and the balance of iron and trace impurities, and the thickness of the steel plate is 1.5 mm; in the quenching stage: keeping the pressure at 15MPa, keeping the distance between water channels of the die in the water-cooled die at 25mm, keeping the diameter at 9mm, keeping the distance between the center of a cooling water channel and the die surface at 15mm, cooling at the rate of 30-55 ℃/s, performing hot stamping forming on austenite on the die, performing primary quenching cooling to room temperature, heating to 450 ℃, keeping the temperature for 5min, and performing secondary quenching cooling to the room temperature.
Considering the influence of the cooling rate in the quenching stage on the properties of the ultra-high strength steel BR1500HS steel sheet, the properties of the ultra-high strength steel BR1500HS steel sheet were examined by changing the cooling rate in the quenching stage and changing the cooling rate in the quenching stage under the condition that other conditions are not changed, and examples 11 to 15 are shown in Table 3.
Table 3:
| examples | Rate of cooling in quenching stage (. degree. C/s) | Tensile strength (Mpa) | Hardness (HRB) |
| 11 | 30 | 1552.8 | 47.3 |
| 12 | 45 | 1791.2 | 60.1 |
| 13 | 47 | 1800.7 | 65.2 |
| 14 | 50 | 1811.4 | 67.8 |
| 15 | 55 | 1590.7 | 49.2 |
As can be seen from table 3, as the cooling rate increases, the hardness of the ultra-high strength steel BR1500HS tends to increase first and then decrease, which is mainly because, as the cooling rate increases, the more heat the water flow takes away from the inner wall of the cooling water channel, the more the temperature of the ultra-high strength steel BR1500HS in the mold is decreased, the average cooling rate is increased, the cooling effect is increased continuously, the martensite is distributed uniformly, and the tensile strength and hardness are increased; along with the increase of the cooling rate, the contact area between the inner wall of the cooling water channel and cooling water flow is continuously increased, the heat exchange rate is continuously increased, the demolding temperature of the super-strength steel BR1500HS is further reduced, along with the continuous increase of the cooling water flow speed, the effective contact area between the inner wall of the cooling water channel and the cooling water is not continuously increased, the demolding temperature and the average cooling speed change tend to be balanced, therefore, the cooling rate is 45-50 ℃/s, and the performance of the super-strength steel BR1500HS steel plate is better.
Examples 16 to 20
On the basis of example 1, wherein in the austenitizing stage: the heating temperature is 925 ℃, the steel plate is insulated for 5.5min after the temperature reaches the preset temperature, the steel plate comprises 0.25 percent of carbon element, 0.30 percent of silicon element, 1.42 percent of manganese element, 0.15 percent of chromium element, 0.039 percent of aluminum element, 0.0051 percent of boron element, 0.047 percent of titanium element, 0.01 percent of phosphorus element, 0.0015 percent of sulfur element and the balance of iron and trace impurities, and the thickness of the steel plate is 1 mm; in the quenching stage: keeping the pressure at 15MPa, keeping the distance between water channels of the die in the water-cooled die at 25mm, keeping the diameter at 4-11mm, keeping the distance between the center of a cooling water channel and the die surface at 15mm, cooling at 45 ℃/s, performing hot stamping forming on austenite on the die, performing primary quenching cooling to room temperature, heating to 400 ℃, keeping the temperature for 4min, and performing quenching cooling again to room temperature.
Considering the influence of the water cooling die water channel diameter in the quenching stage on the performance of the ultra-high strength steel BR1500HS steel plate, the performance of the ultra-high strength steel BR1500HS steel plate is examined by changing the water cooling die water channel diameter in the quenching stage under the condition that other conditions are not changed, and examples 16-20 are shown in Table 4.
Table 4:
| examples | Water cooling mould water channel diameter (mm) in quenching stage | Tensile strength (Mpa) | Hardness (HRB) |
| 16 | 4 | 1537.4 | 57.5 |
| 17 | 6 | 1811.2 | 60.2 |
| 18 | 7 | 1852.7 | 67.8 |
| 19 | 9 | 1791.6 | 65.7 |
| 20 | 11 | 1537.9 | 55.6 |
As can be seen from Table 4, with the increase of the diameter of the water passage of the water-cooled mold in the quenching stage, the tensile strength of the super-strength steel BR1500HS after quenching shows the tendency of gradually increasing and then decreasing, the main reason is that along with the increase of the diameter of the cooling water channel, the heat quantity of the die taken away by the cooling channel in the same time is gradually increased, the temperature of the die is reduced, the water circulation performance in the cooling water channel is enhanced, the cooling effect is continuously enhanced, the uniformity of a temperature field is continuously enhanced, the tensile strength is enhanced after quenching, along with the continuous increase of the diameter of the cooling water channel, the water circulation performance in the cooling channel is weakened, the heat quantity of the mould taken away in the same time is reduced, the temperature drop rate of the mould is slowed down, the cooling effect is weakened, the uniformity of the temperature field is weakened, and further, the tensile strength after quenching is caused, so that the diameter of a water channel of the water cooling die is 6-9mm, and the performance of the BR1500HS ultrahigh-strength steel plate is excellent.
Examples 21 to 25
On the basis of example 1, wherein in the austenitizing stage: the heating temperature is 900 ℃, the temperature is kept for 6min after the temperature reaches the preset temperature, the steel plate comprises the components of 0.21 percent of carbon element, 0.27 percent of silicon element, 1.33 percent of manganese element, 0.12 percent of chromium element, 0.039 percent of aluminum element, 0.0023 percent of boron element, 0.047 percent of titanium element, 0.0098 percent of phosphorus element, 0.0011 percent of sulfur element and the balance of iron and trace impurities, and the thickness of the steel plate is 1.25 mm; in the quenching stage: the pressure maintaining pressure is 15MPa, the distance between the water channels of the die in the water-cooled die is 25mm, the diameter is 9mm, the distance between the center of the cooling water channel and the die surface is 15mm, the cooling rate is 50 ℃/s, the austenite is subjected to hot stamping forming on the die, after the austenite is quenched and cooled to the room temperature for the first time, the temperature is increased to 350-fold-500 ℃, the temperature is preserved for 4min, and the austenite is quenched and cooled to the room temperature again.
Considering the influence of temperature rise on the performance of the ultra-high strength steel BR1500HS steel plate after the first quenching cooling to room temperature after the quenching stage, the performance of the ultra-high strength steel BR1500HS steel plate was examined by changing the temperature rise after the first quenching cooling to room temperature after the quenching stage and changing the temperature rise after the first quenching cooling to room temperature after the quenching stage without changing other conditions, and examples 21 to 25 are shown in Table 5.
Table 5:
| examples | After the quenching stage, the temperature is raised (DEG C) after the first quenching cooling to room temperature | Tensile strength (Mpa) | Hardness (HRB) |
| 21 | 350 | 1531.0 | 49.2 |
| 22 | 400 | 1699.1 | 62.7 |
| 23 | 425 | 1752.3 | 68.2 |
| 24 | 450 | 1762.4 | 65.5 |
| 25 | 500 | 1511.8 | 51.0 |
As can be seen from Table 5, as the temperature rises after the first quenching is cooled to room temperature after the quenching stage, the tensile strength of the super-strength steel BR1500HS after quenching shows a tendency of gradually increasing first and then decreasing, the process of transforming austenite structure into martensite structure is mainly carried out after quenching, the austenite of the first quenching is not completely transformed into martensite after the first quenching, a part of austenite is reserved for carbon distribution treatment, carbon in the carbon-rich martensite is diffused to the residual austenite which is not transformed, so that the austenite is rich in carbon, and the stability at normal temperature is obtained, in the second quenching, the phase transformation does not occur in the first quenching process to participate in the transformation of austenite into martensite, the tensile strength is enhanced, therefore, after the quenching stage, the temperature is raised to 400-450 ℃ after the first quenching is cooled to the room temperature, and the performance of the ultra-high strength steel BR1500HS steel plate is better.
Comparative example 1
On the basis of the embodiment 3, the austenitizing stage is the same as the embodiment 3, the quenching stage is carried out in an air cooling mode, and the specific implementation mode of the quenching stage is as follows: carrying out hot stamping forming on austenite on a die, keeping the pressure at 10MPa, quenching for the first time, cooling the austenite in the die to room temperature in air, heating to 400 ℃, preserving heat for 4min, and cooling the die to room temperature in air again.
The tensile strength of the comparative example 1 is 1321.7Mpa, the hardness is 49.1HRB, and it can be seen from the examples and the comparative example 1 that the tensile strength is higher by adopting the water cooling mode of the mold, mainly because, under the water cooling condition and the pressure maintaining condition, the martensite is transformed from the mixed martensite with different sizes to the mixed martensite with uniform crystal grains, and as the pressure maintaining pressure is increased, the martensite structure tends to be uniform and gradually refined, so as to achieve the effect of refining the crystal grains and improving the tensile strength, in the air cooling environment, the temperature distribution is easy to be non-uniform, the temperature difference exists, the thermal stress is generated by influencing the different expansion and contraction degrees among different parts, in the air cooling environment, the cooling effect of different cooling parts is easy to be different, so that the temperature difference is formed among the parts, the temperature distribution is non-uniform, the thermal stress is increased, and the super strength steel BR1500HS is seriously deformed, thereby lowering the tensile strength.
Comparative example 2
On the basis of the embodiment 3, the austenitizing stage is the same as the embodiment 1, the quenching stage is carried out in a way of primary quenching and cooling, and the specific implementation mode of the quenching stage is as follows: placing the ultra-high strength steel subjected to austenitization on a die, performing hot stamping forming and quenching treatment, wherein the quenching cooling mode is water cooling, the pressure maintaining pressure is 10-15MPa, the distance between die water channels in the water cooling die is 25mm, the diameter is 6-9mm, the distance between the center of the cooling water channel and the die surface is 15mm, the cooling rate is 45-50 ℃/s, performing hot stamping forming on austenite on the die, and performing primary quenching cooling to room temperature.
The tensile strength of comparative example 2 was 1397.6Mpa, and the hardness was 43.9HRB, and it can be seen from examples 3 and 2 that the tensile strength of the steel sheet in the secondary quenching mode was higher than that in the primary quenching mode in the quenching stage, mainly because some of the austenite that did not undergo phase transformation after the primary quenching cooling was not completely transformed into martensite, so that the stability at normal temperature was weakened, and thus the tensile strength was lowered.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.
Claims (9)
1. A BR1500HS treatment process for ultrahigh-strength steel is characterized by comprising the following steps:
(1) austenitizing: placing the ultra-high strength steel BR1500HS in a heating container for heating, and preserving heat to austenitize the ultra-high strength steel BR1500 HS;
(2) quenching: placing the austenitized ultrahigh-strength steel on a die, performing hot stamping forming and quenching treatment, performing heating treatment after the ultrahigh-strength steel is quenched to room temperature for the first time, and performing secondary quenching to the room temperature after the ultrahigh-strength steel is heated;
(3) and (3) performance testing: after quenching is finished, forming an upper die, cooling to room temperature, and carrying out performance test;
and (3) in the step (2), the distance between the mold water channels in the water-cooling mold is 25mm, the diameter is 6-9mm, and the distance between the center of the cooling water channel and the mold surface is 15 mm.
2. The BR1500HS process of claim 1, wherein the BR1500HS process comprises the steps of 0.21-0.25% carbon, 0.27-0.30% silicon, 1.33-1.42% manganese, 0.12-0.15% chromium, 0.039-0.041% aluminum, 0.0023-0.0051% boron, 0.047-0.051% titanium, 0.0098-0.01% phosphorus, 0.0011-0.0015% sulfur, and the balance of iron and trace impurities.
3. The processing technology of ultra-high strength steel BR1500HS, according to claim 1, wherein the thickness of said ultra-high strength steel BR1500HS steel plate is 1-1.5 mm.
4. The processing technology of ultra-high strength steel BR1500HS of claim 1, wherein in step (1), said austenitizing heating vessel is an induction heating furnace, said induction heating furnace is composed of a power supply, a cooling system, an induction heating system and a temperature detection control system.
5. The BR1500HS processing technology of ultra-high strength steel of claim 4, wherein in step (1), the heating temperature in the induction heating furnace is 900-950 ℃, the heating rate is 130 ℃/h, the heating temperature is set by a temperature detection control system, and the temperature is maintained for 5-6min after the temperature reaches a predetermined temperature.
6. The BR1500HS process of claim 1, wherein in step (2), austenite is hot stamped and formed on a die, and after first quenching and cooling to room temperature, the temperature is raised to 400-450 ℃ at a rate of 110 ℃/h, and the temperature is maintained for 4-5min, and then quenching and cooling are carried out again to room temperature.
7. The processing technology of ultra-high strength steel BR1500HS, according to claim 1, wherein the cooling mode of quenching in step (2) is water cooling.
8. The treatment process of ultra-high strength steel BR1500HS, according to claim 1, wherein the cooling rate in step (2) is 45-50 ℃/s.
9. The processing technology of ultra-high strength steel BR1500HS of claim 1, wherein said step (2) is performed in a hot stamping forming process under a dwell pressure of 10-15 MPa.
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| CN103045950A (en) * | 2012-12-28 | 2013-04-17 | 中北大学 | Low-alloy, high-strength and high-toughness composite phase steel and heat treatment method thereof |
| CN108504985A (en) * | 2018-04-21 | 2018-09-07 | 永康市求精热处理厂 | A kind of heat treatment method of automobile high-strength hot forming torsion beam |
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| CN102390335A (en) * | 2011-09-30 | 2012-03-28 | 力帆实业(集团)股份有限公司 | Front bumper anti-collision beam and processing method thereof |
| CN103045950A (en) * | 2012-12-28 | 2013-04-17 | 中北大学 | Low-alloy, high-strength and high-toughness composite phase steel and heat treatment method thereof |
| CN108504985A (en) * | 2018-04-21 | 2018-09-07 | 永康市求精热处理厂 | A kind of heat treatment method of automobile high-strength hot forming torsion beam |
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