CN114836696B - 390 MPa-level steel for automobile axle housing for hot stamping and production method thereof - Google Patents
390 MPa-level steel for automobile axle housing for hot stamping and production method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
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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
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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
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/80—Technologies aiming to reduce greenhouse gasses emissions common to all road transportation technologies
- Y02T10/86—Optimisation of rolling resistance, e.g. weight reduction
Abstract
The 390MPa grade automobile axle housing steel for hot stamping comprises, by weight, 0.075-0.155% of C, 0.05-0.20% of Si, 1.15-1.45% of Mn, 0.010-0.062% of Al, 0.004-0.035% of Ti, 0.045-0.105% of V, 0.08-0.11% of Mo, 0.0010-0.0030% of B, 0.010-0.018% of La+Ce, 0.0011-0.0030% of Ca, less than or equal to 0.010% of P, less than or equal to 0.005% of S, less than or equal to 0.003% of N, and the balance of Fe and impurities. Heat preservation is carried out at 700-740 ℃ for 40-60 s, the yield strength is more than or equal to 415MPa, the tensile strength is more than or equal to 510MPa after hot stamping, A 50 ≥36％。
Description
Technical Field
The invention relates to the field of metal materials, in particular to 390 MPa-level steel for an automobile axle housing for hot stamping and a production method thereof. The method is mainly suitable for manufacturing the steel for the automobile axle housing for hot stamping.
Background
The axle housing is one of the main components of the vehicle running system, it supports the weight of the frame and the rear part of the frame, and it protects the components of the transmission system. In the field of axle housing industry manufacturing, there are two distinct product manufacturing methods of impact welding axle housings and casting axle housings. With the development of axle housing manufacturing technology and the requirements of automobile weight reduction and energy saving, particularly for axle housings driven by trucks, hot continuous rolling steel plates with the thickness of 12-16 mm are used for manufacturing stamping axle housings, so that casting axle housings with complex manufacturing process, low production efficiency, heavy weight and high cost are replaced.
The Chinese patent application with publication No. CN 102383032B discloses a production method of steel for a 12-ton axle housing, which is a hot rolled steel plate produced by adding a certain amount of Nb by using a common C-Mn component system design. However, the elongation of the steel sheet is 35% at the highest, which does not meet the requirement for forming an automobile part with difficulty.
The Chinese patent application with publication number of CN 102383034B discloses a production method of steel for a 13-ton axle housing, which utilizes a common C-Mn component system to design and add a certain amount of niobium and titanium, and improves the strength of the produced hot rolled steel plate through solid solution strengthening of carbon and manganese elements and fine crystal strengthening of niobium and titanium elements. However, the elongation of the steel sheet is 31% at the highest, which does not meet the requirement for forming an automobile part with difficulty.
The Chinese patent application with publication number of CN 103805862B discloses a steel for axle housing and a preparation method thereof, wherein a common C-Mn component system is utilized to design and add a plurality of microalloy elements, and the produced hot rolled steel plate is required to be subjected to modulation heat treatment subsequently, so that the production cost is high. However, the elongation of the steel sheet is 31% at the highest, which does not meet the requirement for forming an automobile part with difficulty.
The Chinese patent application with publication number of CN 106480367A discloses a production method of high-strength cold-formed steel for automobile axle housing, which designs a hot-rolled steel plate produced by adding a certain amount of niobium, vanadium and titanium through solid solution strengthening of carbon and manganese elements and fine crystal strengthening of niobium, vanadium and titanium elements by utilizing a common C-Mn component system, but the elongation of the steel plate is 22.99% at most, and does not meet the requirement of difficult-to-form automobile parts.
Disclosure of Invention
The invention aims to provide 390 MPa-grade steel for an automobile axle housing for hot stamping and a production method thereof, wherein the yield strength of a steel plate is more than or equal to 390MPa, the tensile strength is more than or equal to 540MPa, and the transverse elongation A is higher than or equal to 50 More than or equal to 40 percent, and at 700-740 ℃, heat preservation is carried out for 40-60 s, air cooling is carried out to room temperature after hot stamping, the yield strength of the automobile axle housing is more than or equal to 415MPa, the tensile strength is more than or equal to 510MPa, and the transverse elongation A is higher than or equal to 50 More than or equal to 36 percent, and the transverse impact energy at minus 40 ℃ is more than or equal to 102J.
In order to achieve the above purpose, the invention is realized by adopting the following technical scheme:
390MPa grade automobile axle housing steel for hot stamping comprises the following chemical components in percentage by weight: 0.075 to 0.155 percent of C, 0.05 to 0.20 percent of Si, 1.15 to 1.45 percent of Mn, 0.010 to 0.062 percent of Al, 0.004 to 0.035 percent of Ti, 0.045 to 0.105 percent of V, 0.08 to 0.11 percent of Mo, 0.0010 to 0.0030 percent of B, 0.010 to 0.018 percent of rare earth element La+Ce, 0.0011 to 0.0030 percent of Ca, less than or equal to 0.010 percent of P, less than or equal to 0.005 percent of S, less than or equal to 0.003 percent of N, and the balance of Fe and unavoidable impurities.
The 390 MPa-level steel for the automobile axle housing for hot stamping has the main functions that:
c: carbon is the most important solid solution strengthening element in steel, and is the guarantee of steel strength. Considering that the follow-up hot stamping forming is needed, the strength after hot stamping is ensured, the carbon content is too low, and the strength after hot stamping of the steel plate cannot reach the expected target. Meanwhile, the improvement of the carbon element is beneficial to the increase of the hardenability of steel, and the optimal range of the carbon in the invention is 0.075-0.155%.
Si: silicon is a solid solution strengthening element, and can improve the strength of the steel sheet by solid solution strengthening. Meanwhile, the method has the effect of improving the hardenability of the steel plate, however, the excessive silicon in the steel can influence the hot rolling surface quality, and a large amount of oxide scales appear. The silicon content in the invention is 0.05-0.20%.
Mn: manganese can form a substitutional solid solution in steel, plays a strong solid solution strengthening role, enables yield strength and tensile strength to be linearly increased, hardly reduces plasticity and toughness of the steel while increasing the strength of the steel within a certain range, and can improve hardenability of the steel at the same time, but the manganese content is too high, so that carbon equivalent of the steel can be increased, and structural uniformity of the steel plate can be deteriorated in smelting and hot rolling processes, and serious strip-shaped structural defects in the structure are easy to occur. Thus, the manganese content is selected to be 1.15-1.45%.
P: phosphorus can raise the formation temperature of the alpha phase and expand the temperature range of the alpha phase. However, too much phosphorus content deteriorates workability of the steel sheet, and the upper limit thereof is limited to 0.010% in order to obtain a high elongation.
S: sulfur forms sulfide inclusions such as MnS and becomes a starting point of cracks to deteriorate workability, so that the smaller the content, the better the content, and the upper limit is 0.005%.
Al: al is a common deoxidizer in steel, plays a role in deoxidizing and fixing nitrogen in the smelting process, and can effectively improve the oxidation resistance of the steel plate, but excessive aluminum can cause a large amount of aluminum inclusions, and a small amount of Al is added into the steel to form AlN precipitation, so that a certain effect of refining grains is achieved, and therefore, the Al content is limited to be 0.010-0.062%.
Ti: titanium can effectively delay the recrystallization of deformed austenite, prevent the growth of austenite grains, improve the austenite recrystallization temperature, refine grains, improve the strength and toughness of steel, and is a strong carbon and nitride forming element, and can combine with carbon and nitrogen to form stable and fine carbon and nitride to play a remarkable role in precipitation strengthening, so that the optimal range of the Ti content in the invention is between 0.004 and 0.035 percent.
V: vanadium has obvious precipitation strengthening and fine-grain strengthening effects, the effect of the vanadium is mainly realized by forming precipitates with carbon and nitrogen, especially VN precipitation with nitrogen can greatly improve the strength of the steel plate, inhibit BN precipitation and avoid strength reduction caused by B precipitation. In addition, V can be added in combination with H to improve the delayed fracture resistance of the steel plate, and the V addition amount is 0.045-0.105%.
Mo: molybdenum is carbide forming element, can improve the strength and toughness of the steel plate, and Mo can obviously improve the austenite stability and increase the hardenability of the steel, so that the Mo content of the invention is selected to be 0.08-0.11%.
B: the boron element can obviously improve the hardenability of the steel, when the B content is higher than 0.0050%, the excessive B and N in the steel form B compounds, and the performance of the steel plate is reduced, so that the boron content range of the invention is 0.0010-0.0030%.
RE: the rare earth has strong deoxidizing and desulfurizing capacity, and the formed spherical sulfide or oxysulfide replaces strip manganese sulfide inclusions, so that the plasticity and the anisotropism of the steel plate can be improved, the fatigue performance of the steel plate can be improved, the welding performance of the steel plate is improved, the rare earth has strong affinity with other impurity elements in the steel, the content of elements such as sulfur, oxygen, phosphorus, hydrogen and the like in the steel can be reduced, and the harmful effect of the rare earth is eliminated. Therefore, the rare earth (La+Ce) content is limited to 0.010-0.018 percent.
Ca: calcium can change the form of steel sulfide (MnS), prevent the formation of strip-shaped MnS inclusions, and improve the plasticity, toughness and fatigue performance of the steel plate. Therefore, the Ca content is controlled to be 0.0011-0.0030 percent.
N: for B-containing steels, the lower the N content, the better, but too low results in difficult production and increased cost, so the N content in the invention is less than or equal to 0.003%.
The volume percentage of the structure ferrite in the steel is 35-45%, and the volume percentage of the pearlite is 55-65%.
The yield strength of the steel plate is more than or equal to 390MPa, the tensile strength is more than or equal to 540MPa, and the transverse elongation A is higher than or equal to 50 ≥40％。
The convexity control precision of the steel plate is +/-45 mu m, the flatness is controlled within 20I, and the thickness control precision is +/-45 mu m.
The thickness of the finished steel plate is 12-18 mm.
A390 MPa grade automobile axle housing for hot stamping is produced from steel, which is insulated for 40-60 s at 700-740 ℃, air cooled to room temperature after hot stamping, the yield strength of the automobile axle housing is more than or equal to 415MPa, the tensile strength is more than or equal to 510MPa, and the transverse elongation A is higher than or equal to 50 More than or equal to 36 percent, and the transverse impact energy at minus 40 ℃ is more than or equal to 102J.
A production method of 390MPa grade steel for automobile axle housing for hot stamping specifically comprises the following steps:
1) The smelting process comprises the following steps: adopting an RH+LF process, strictly controlling the H, O content, wherein H is less than or equal to 0.0002 percent, O is less than or equal to 0.0015 percent, performing calcium treatment in a refining process, and ensuring that w (Ca)/w (Al) =0.09-0.14, and putting an electromagnetic stirring and soft reduction technology in the continuous casting process, wherein the casting blank pulling speed is less than or equal to 1.1m/min; and (5) stacking and slow cooling after the casting blank is taken off line.
2) The heating process comprises the following steps: directly hot-feeding a continuous casting slab with the thickness of (160-240) mm and the width of (1510-1910) mm into a step heating furnace for heating, wherein the hot-feeding temperature is more than 700 ℃, the preheating section carries out high-temperature rapid preheating at the furnace gas temperature of 750-950 ℃, the preheating time is 20-35 min, the temperature of the heating section 1 and the heating section 2 are respectively controlled at 1000-1200 ℃, the temperature of 1230-1260 ℃, the total time of the heating section 1 and the heating section 2 is 20-25 min, the temperature of the soaking section 1240-1260 ℃, and the soaking time is 110-165 min; the pressure of the hearth is always controlled in a micro positive pressure state in a dynamic state, and the positive pressure value is controlled to be 4-16 Pa; reducing oxidation burning loss. The proper heating temperature and proper heat preservation time lead the alloy elements in the slab to be completely solid-solved, the slab components to be uniform, and the functions of controlling the original austenite grain size, saving energy and the like are achieved.
3) A) rolling process: the rough rolling adopts a rolling process of 3+3 modes, (R1 adopts 3-pass rolling and R2 adopts 3-pass rolling) and adopts 6-pass rolling and 4-pass descaling processes, the first frame of R1 rough rolling mill adopts 1-pass descaling and 3-pass descaling, the upper and lower 2 rows of water spray headers of a descaling box are simultaneously opened, the high-pressure water outlet pressure is 18-25 MPa, the second frame of R2 rough rolling mill adopts 4-6-pass descaling, the upper and lower 2 rows of water spray headers of the descaling box are simultaneously opened, the high-pressure water outlet pressure is 20-32 MPa, the rough rolling outlet temperature is 1080-1130 ℃, the thickness of an intermediate billet is 50-65 mm, the width is 1510-1910 mm, the intermediate billet is kept warm by adopting a heat preservation cover before entering a hot rolling mill group, the temperature drop of the intermediate billet on a delay roller table and the head-tail and plate width directions are reduced, the finish rolling is N-frame continuous rolling, N is less than or equal to 8, the front high-pressure water descaling inlet temperature is not higher than 1060 ℃, the finish rolling temperature is 800-920 ℃, the finish rolling mill is controlled to be 20-7 mm by adopting high tension rolling, and the tension between a finishing mill F (N-4) and finishing mill F (N-3) is controlled to be 20-7 mm/7 mm 2 The tension between the frames of the finishing mill F (N-3) and the finishing mill F (N-2) is controlled to be 8-22N/mm 2 Tension control between frames of finishing mill F (n-2) and finishing mill F (n-1)Is made to be 6-20N/mm 2 Tension between frames of finishing mill F (N-1) and finishing mill F (N) is controlled to be 6-20N/mm 2 Meanwhile, the F (n-1) and F (n) frames adopt high water pressure of 20-32 MPa for descaling, and cooling water among other frames is completely started;
4) The cooling process comprises the following steps: after finishing rolling, adopting front-stage rapid continuous laminar cooling with cooling rate more than or equal to 65 ℃/s; the continuous laminar cooling process ensures that a large amount of ferrite is rapidly precipitated, and ensures the content of ferrite while inhibiting the growth of the crystal grains, thereby refining the crystal grains of the ferrite.
5) Coiling temperature: the coiling temperature is 600-650 ℃. The steel plate has insufficient strength due to the excessively high coiling temperature, the elongation is reduced due to the excessively low coiling temperature, and the sufficient precipitation of second phase particles after the coiling of the steel plate can be ensured in a temperature range, and meanwhile, the plasticity is good.
Compared with the prior art, the invention has the beneficial effects that:
1) The addition of Ti can effectively delay the recrystallization of deformed austenite, prevent the austenite grain growth, improve the austenite recrystallization temperature, refine grains, improve the strength and toughness of steel, and the Ti is a strong carbon and nitride forming element, can combine with carbon and nitrogen to form stable and fine carbon and nitride, and plays a remarkable role in precipitation strengthening;
2) The V added vanadium has obvious functions of precipitation strengthening and fine grain strengthening, especially VN precipitation formed by nitrogen can greatly improve the strength of the steel plate, inhibit BN precipitation and avoid strength reduction caused by B precipitation. Besides, the addition of V can be combined with H, so that the delayed fracture resistance of the steel plate is improved;
3) The strength and toughness of the steel plate can be improved by adding Mo, the austenite stability can be obviously improved by Mo, and the hardenability of the steel is improved;
4) The rare earth has strong deoxidizing and desulfurizing capabilities, the formed spherical sulfide or oxysulfide replaces strip manganese sulfide inclusions, the plasticity and the anisotropism of the steel plate can be improved, the fatigue performance of the steel plate can be improved by the rare earth, and the welding performance of the steel plate is improved;
5) The addition of Ca can change the form of steel sulfide, and improve the plasticity, toughness and fatigue performance of the steel plate;
6) After rolling, adopting a front-section rapid continuous cooling process, avoiding the generation of strip-shaped tissues in the steel plate;
7) The invention has excellent mechanical properties, the yield strength is more than or equal to 390MPa, the tensile strength is more than or equal to 540MPa, the transverse elongation A50 is more than or equal to 40 percent, the heat preservation is carried out for 40s-60s at 700 ℃ to 740 ℃, the air cooling is carried out to room temperature after hot stamping, the yield strength of an automobile axle housing is more than or equal to 415MPa, the tensile strength is more than or equal to 510MPa, the transverse elongation A50 is more than or equal to 36 percent, and the transverse impact energy at minus 40 ℃ is more than or equal to 102J.
Detailed Description
The present invention will be described in more detail by way of examples, which are merely illustrative of the best modes of carrying out the invention, and do not limit the scope of the invention in any way.
The heating, rolling and heat treatment process of the invention comprises the following steps:
directly hot-feeding a continuous casting slab with the thickness of (160-240) mm and the width of (1510-1910) mm into a step heating furnace for heating, wherein the hot-feeding temperature is higher than 700 ℃, the preheating section carries out high-temperature rapid preheating at the furnace gas temperature of 750-950 ℃, the preheating time is 20-35 min, the temperature of the heating section 1 and the heating section 2 are respectively controlled at 1000-1200 ℃, 1230-1260 ℃, the total time of the heating section 1 and the heating section 2 is 20-25 min, the temperature of the soaking time is 110-165 min, the rough rolling adopts a rolling process in a 3+3 mode, (R1 adopts 3-pass rolling and R2 adopts 3-pass rolling) 6-pass rolling and a 4-pass descaling process, the first R1 roughing mill carries out 1 and 3-pass descaling, the upper row and the lower row of water spraying headers of the descaling box are simultaneously opened, the high-pressure water outlet pressure is 18-25 MPa, the second frame R2 roughing mill is used for 4-6 times descaling, the upper row and the lower row of water spraying headers of the descaling box are simultaneously opened, the high-pressure water outlet pressure is 20-32 MPa, the roughing outlet temperature is 1080-1130 ℃, the thickness of an intermediate billet is 50-65 mm, the width is 1510-1910 mm, the heat preservation cover is adopted before the intermediate billet enters a hot rolling finishing mill group, the temperature drop of the intermediate billet on a delay roller way and the temperature difference in the head-tail and plate width directions are lightened, the finish rolling is n frames (n is not more than 5 and not more than 8) for continuous rolling, the high-pressure water descaling is carried out before the finish rolling, the finish rolling inlet temperature is not higher than 1060 ℃, and the finish rolling temperature is 800-920 ℃,the finish rolling adopts high tension rolling, and ensures that the tension between the frames of the finishing mill F (N-4) and the finishing mill F (N-3) is controlled to be 7-20N/mm 2 The tension between the frames of the finishing mill F (N-3) and the finishing mill F (N-2) is controlled to be 8-22N/mm 2 The tension between the frames of the finishing mill F (N-2) and the finishing mill F (N-1) is controlled to be 6-20N/mm 2 Tension between frames of finishing mill F (N-1) and finishing mill F (N) is controlled to be 6-20N/mm 2 Meanwhile, the F (n-1) and F (n) frames adopt high water pressure of 20-32 MPa for descaling, and cooling water among other frames is completely started; the convexity control precision of the steel plate is +/-45 mu m, the flatness is controlled within 20I, the thickness control precision is +/-45 mu m, the thickness of a finished product is 12-18 mm, the front stage rapid continuous laminar cooling is adopted after finishing rolling, the cooling rate is more than or equal to 65 ℃/s, and the coiling temperature is 600-650 ℃.
The specific components of 6 examples of the invention are shown in Table 1, the temperature schedule is shown in Table 2, the finish rolling tension control parameters are shown in Table 3, the properties of the steel plate are shown in Table 4, the volume percentage of the structure is shown in Table 5, and the properties after hot stamping are shown in Table 6.
TABLE 1 chemical composition (wt.%)
TABLE 2 Hot Rolling temperature System according to the examples of the invention
TABLE 3 finish rolling tension control parameters (n is 5) according to the example of the invention
TABLE 4 mechanical Property parameters of the examples of the invention
TABLE 5 volume percent of tissue in examples of the invention
| Numbering device | Ferrite body | Pearlite |
| Example 1 | 35％ | 65％ |
| Example 2 | 38％ | 62％ |
| Example 3 | 40％ | 60％ |
| Example 4 | 41％ | 59％ |
| Example 5 | 44％ | 56％ |
| Example 6 | 45％ | 55％ |
TABLE 6 performance of automotive axle housing after hot stamping in examples of the invention
Claims (4)
1. The 390 MPa-level steel for the automobile axle housing for hot stamping is characterized by comprising the following chemical components in percentage by weight: 0.075 to 0.105 percent of C, 0.05 to 0.124 percent of Si, 1.15 to 1.45 percent of Mn, 0.025 to 0.062 percent of Al, 0.004 to 0.035 percent of Ti, 0.045 to 0.105 percent of V, 0.08 to 0.11 percent of Mo, 0.0010 to 0.0030 percent of B, 0.010 to 0.018 percent of rare earth element La+Ce, 0.0011 to 0.0030 percent of Ca, less than or equal to 0.010 percent of P, less than or equal to 0.005 percent of S, less than or equal to 0.003 percent of N, and the balance of Fe and unavoidable impurities;
35-45% of ferrite volume percentage and 55-65% of pearlite volume percentage of steel plate structure;
the yield strength of the steel plate is more than or equal to 390MPa, the tensile strength is more than or equal to 540MPa, and the transverse elongation A is higher than or equal to 50 ≥40%；
The steel plate is insulated for 40s to 60s at the temperature of 700 ℃ to 740 ℃, air-cooled to room temperature after hot stamping, the yield strength of the produced automobile axle housing is more than or equal to 415MPa, the tensile strength is more than or equal to 510MPa, and the transverse elongation A is higher than or equal to 50 More than or equal to 36 percent, and the transverse impact energy at minus 40 ℃ is more than or equal to 102J;
the production method of 390MPa grade steel for automobile axle housing for hot stamping comprises the following steps:
1) The smelting process comprises the following steps: adopting an RH+LF process, controlling the content of H, O, controlling H to be less than or equal to 0.0002 percent, O to be less than or equal to 0.0015 percent, and performing calcium treatment in a refining process to ensure that w (Ca)/w (Al) =0.09-0.14, and the casting blank pulling speed to be less than or equal to 1.1m/min;
2) The heating process comprises the following steps: heating the continuous casting slab in a step heating furnace at the temperature of more than 700 ℃, the temperature of a preheating section of 750-950 ℃ and the preheating time of 20-35 min, controlling the temperature of a heating section 1 and a heating section 2 at 1000-1200 ℃ and 1230-1260 ℃ respectively, heating the total time of the heating section 1 and the heating section 2 for 20-25 min, and the temperature of a soaking section of 1240-1260 ℃ and the soaking time of 110-165 min;
3) A) rolling process: the intermediate billet is subjected to heat preservation by adopting a heat preservation cover before entering a hot rolling finishing mill group, and the finishing rolling is continuous rolling with n frames, 5N is more than or equal to 8, descaling is performed before finish rolling, the finish rolling inlet temperature is not higher than 1060 ℃, the finish rolling temperature is 800-920 ℃, and the tension between the frames of the finishing mill F (N-4) and the finishing mill F (N-3) is controlled to be 7-20N/mm 2 The tension between the frames of the finishing mill F (N-3) and the finishing mill F (N-2) is controlled to be 8-22N/mm 2 The tension between the frames of the finishing mill F (N-2) and the finishing mill F (N-1) is controlled to be 6-20N/mm 2 Tension between frames of finishing mill F (N-1) and finishing mill F (N) is controlled to be 6-20N/mm 2 Meanwhile, the F (n-1) and F (n) frames adopt high water pressure of 20-32 MPa for descaling;
4) The cooling process comprises the following steps: after finishing rolling, adopting front-stage rapid continuous laminar cooling with cooling rate more than or equal to 65 ℃/s;
5) Coiling temperature: the coiling temperature is 600-650 ℃.
2. The 390 MPa-grade automotive axle housing steel for hot stamping as claimed in claim 1, wherein the convexity control accuracy of the steel sheet is ±45 μm, the flatness is controlled within 20I, and the thickness control accuracy is ±45 μm.
3. The 390 MPa-grade steel for automobile axle housing for hot stamping as claimed in claim 1, wherein the thickness of the finished steel sheet is 12-18 mm.
4. The 390MPa grade automotive axle housing steel for hot stamping according to claim 1, wherein the rough rolling adopts a rolling process of 3+3 modes, the total 6-pass rolling and 4-pass descaling processes are performed by a first R1 roughing mill for 1 and 3-pass descaling, the high-pressure water outlet pressure is 18-25 MPa, the second R2 roughing mill for 4 and 6-pass descaling, the high-pressure water outlet pressure is 20-32 MPa, and the rough rolling outlet temperature is 1080-1130 ℃.
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