CN113981320A - Axle housing steel for 510MPa grade cold stamping and preparation method thereof - Google Patents
Axle housing steel for 510MPa grade cold stamping and preparation method thereof Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 80
- 239000010959 steel Substances 0.000 title claims abstract description 80
- 238000002360 preparation method Methods 0.000 title claims abstract description 11
- 238000001816 cooling Methods 0.000 claims abstract description 29
- 238000005452 bending Methods 0.000 claims abstract description 12
- 238000005098 hot rolling Methods 0.000 claims abstract description 8
- 239000012535 impurity Substances 0.000 claims abstract description 7
- 238000012360 testing method Methods 0.000 claims abstract description 7
- 238000005096 rolling process Methods 0.000 claims description 68
- 238000000034 method Methods 0.000 claims description 28
- 238000010438 heat treatment Methods 0.000 claims description 21
- 238000003466 welding Methods 0.000 claims description 19
- 229910052799 carbon Inorganic materials 0.000 claims description 14
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 9
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- 238000003723 Smelting Methods 0.000 abstract description 6
- 239000000306 component Substances 0.000 description 19
- 230000000052 comparative effect Effects 0.000 description 18
- 238000004519 manufacturing process Methods 0.000 description 16
- 239000000047 product Substances 0.000 description 12
- 238000005728 strengthening Methods 0.000 description 12
- 229910001566 austenite Inorganic materials 0.000 description 9
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 9
- 230000008569 process Effects 0.000 description 9
- 238000012545 processing Methods 0.000 description 8
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- 229910045601 alloy Inorganic materials 0.000 description 7
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- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 6
- 229910052748 manganese Inorganic materials 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- 238000001556 precipitation Methods 0.000 description 5
- 238000004080 punching Methods 0.000 description 5
- 239000013078 crystal Substances 0.000 description 4
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- 229910052757 nitrogen Inorganic materials 0.000 description 4
- 229910052698 phosphorus Inorganic materials 0.000 description 4
- 238000001953 recrystallisation Methods 0.000 description 4
- 229910052710 silicon Inorganic materials 0.000 description 4
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
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- 239000000463 material Substances 0.000 description 3
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- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
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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
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- 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
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
-
- 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
-
- 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
-
- 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
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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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
-
- 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
-
- 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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- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
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- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Sheet Steel (AREA)
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Abstract
The invention discloses a 510 MPa-grade axle housing steel for cold stamping, which comprises the following components in percentage by weight: 0.05-0.10% of C, 0.05-0.20% of Si, 1.10-1.30% of Mn, less than or equal to 0.020% of P, less than or equal to 0.008% of S, 0.015-0.030% of Nb, 0.010-0.030% of Ti, less than or equal to 0.008% of N, 0.015-0.050% of Als, and the balance of Fe and inevitable impurities. The invention also discloses a preparation method of the axle housing steel for 510 MPa-level cold stamping, which comprises the steps of smelting the components of the axle housing steel for 510 MPa-level cold stamping into a plate blank, and then sequentially carrying out hot rolling, coiling and cooling to obtain a finished product. The structural uniformity of the axle housing steel for the 510MPa grade cold stamping prepared by the components and the preparation method is good in the thickness direction; the yield strength is more than or equal to 345MPa, the tensile strength is more than or equal to 510MPa, the elongation after fracture is more than or equal to 24 percent, and the 180-degree bending test D is a, so that the high strength, the excellent plasticity and the bending property are realized.
Description
Technical Field
The invention relates to the technical field of hot continuous rolling plate strip production, in particular to axle housing steel for 510 MPa-level cold stamping and a preparation method of the axle housing steel for 510 MPa-level cold stamping.
Background
With the development of the automobile industry in China, the demand of the automobile steel is gradually increased, and the performance requirements of the automobile steel are higher and higher. The axle housing is one of the main components of an automobile chassis system, and is used for supporting a vehicle frame, and meanwhile, a speed reducer, a differential mechanism, a transmission device for driving wheels and the like are arranged in the axle housing, so that the axle housing is required to have sufficient strength, good stamping forming performance, good welding performance and the like. The manufacturing process of the automobile axle housing is mostly adopted before the automobile axle housing is manufactured, but the manufacturing process of the cast axle housing is complex, the production efficiency is low, heavy and high in cost, and the manufacturing process of the axle housing which is formed by stamping the hot rolled steel plate into the half axle housing and then welding has the advantages of high production efficiency, light weight and low cost, so that the hot rolled steel plate stamping and welding axle housing becomes the development direction of the existing automobile axle housing manufacturing.
With the development of automobile axle housing manufacturing technology and the promotion of domestic truck load limiting mandatory measures, in order to meet the requirements of the automobile industry on energy conservation and weight reduction, the application of the hot rolled steel plate for the high-strength automobile axle housing becomes a great development trend of the axle housing steel, and the matching of the forming performance and the high strength of the axle housing steel is more and more important. The existing punching process for punching and welding the axle housing is divided into hot punching and cold punching. The hot stamping process is adopted, so that the energy consumption is increased, the production cost is higher, and the mechanical property of the steel plate is reduced after the hot stamping, so that the strength is possibly lower than a required value; and the cold stamping process has higher requirements on the cold forming performance of the steel plate.
The Chinese patent application with publication number CN110669989A discloses a high-elongation steel for an automobile axle housing for cold stamping and a production method thereof, wherein the steel for the automobile axle housing comprises the following components in percentage by weight: c: 0.14-0.17%, Si: 0.020-0.080%, Mn: 1.25-1.65%, Al: 0.010-0.065%, V: 0.025-0.065%, Cr: 0.15-0.25%, and limits P to be less than or equal to 0.020%, S to be less than or equal to 0.006%, and the balance of Fe and inevitable impurities. The steel has high elongation at the tensile strength of 470MPa, the elongation A is more than or equal to 40 percent, and the steel plate can be integrally formed by punching without welding, thereby saving the cost. However, the steel plate has high C content, reduced weldability, high alloy cost due to the addition of V element, and tensile strength only reaching 470MPa strength level.
The Chinese patent application with publication number CN110079740B discloses a high-toughness hot-rolled 530 MPa-grade automobile cold stamping axle housing steel plate and a manufacturing method thereof, wherein the steel plate comprises the following components in percentage by weight: c: 0.12-0.16%, Si: 0.20-0.30%, Mn: 1.30-1.45%, P is less than or equal to 0.015%, S is less than or equal to 0.008%, Als: 0.015 to 0.040%, Nb: 0.010-0.020%, Ti: 0.010-0.030%, and the balance of Fe and inevitable impurities. The steel plate has high C, Mn element addition amount, and reduces the weldability of the material.
The Chinese patent application with publication number CN112647016A discloses a steel plate for a 520 MPa-level bridge shell cover and a manufacturing method thereof, and the steel plate comprises the following chemical components in percentage by mass: c: 0.05 to 0.10%, Si: 0.05 to 0.50%, Mn: 1.0-1.5%, Al: 0.02-0.05%, P is less than or equal to 0.015%, S is less than or equal to 0.004%, Ti + Nb is less than or equal to 0.2%, Re: 0.002-0.004%, and the balance of Fe and inevitable impurities. The steel plate disclosed by the invention is added with Ti and Nb elements with higher contents and rare earth elements, so that the alloy components are complex and the production difficulty is high.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: provides the axle housing steel for 510MPa grade cold stamping with good forming performance and welding performance.
In order to solve the technical problems, the invention adopts the technical scheme that: the 510 MPa-grade axle housing steel for cold stamping comprises the following components in percentage by weight: 0.05-0.10% of C, 0.05-0.20% of Si, 1.10-1.30% of Mn, less than or equal to 0.020% of P, less than or equal to 0.008% of S, 0.015-0.030% of Nb, 0.010-0.030% of Ti, less than or equal to 0.008% of N, 0.015-0.050% of Als, and the balance of Fe and inevitable impurities.
Further, the method comprises the following steps: the carbon equivalent CEV of the axle housing steel is less than or equal to 0.32 percent, and the welding crack sensitivity index Pcm is less than or equal to 0.17 percent.
Further, the method comprises the following steps: the yield strength of the axle housing steel is more than or equal to 345MPa, the tensile strength is more than or equal to 510MPa, the elongation after fracture is more than or equal to 24 percent, and the D & lta & gt bending test at 180 degrees is a.
Further, the method comprises the following steps: the thickness of the axle housing steel is 8.0-14.0 mm.
The invention also discloses a preparation method of the axle housing steel for 510 MPa-level cold stamping, which comprises the steps of smelting the components of the axle housing steel for 510 MPa-level cold stamping into a plate blank, and then sequentially carrying out hot rolling, coiling and cooling to obtain a finished product.
Further, the method comprises the following steps: the hot rolling step includes heating, rough rolling and finish rolling.
Further, the method comprises the following steps: in the heating step, the heating temperature is 1200-1240 ℃, and the heating time is 190-400 min.
Further, the method comprises the following steps: and in the rough rolling step, 6-pass rough rolling is carried out, the pass reduction is more than or equal to 19%, the odd-pass full-length dephosphorization is carried out, and the thickness of the intermediate billet is 55-57 mm.
Further, the method comprises the following steps: in the finish rolling step, 7 times of finish rolling are carried out, the reduction ratios of the three racks are respectively more than 17%, 13% and 10%, cooling water between the racks is used, the start rolling temperature of the finish rolling is less than or equal to 1050 ℃, and the finish rolling temperature is 830-870 ℃.
Further, the method comprises the following steps: the coiling temperature in the coiling step is 560-600 ℃; and the cooling step adopts a front-stage cooling mode to carry out laminar cooling.
The invention has the beneficial effects that: according to the invention, a certain amount of Nb and Ti elements are added to exert the effects of fine grain strengthening and precipitation strengthening, so that the product strength is ensured, and the good forming performance of the product is realized, the carbon equivalent and the welding crack sensitivity index are reduced by controlling the contents of C, Si and Mn elements, and simultaneously, the precipitate is formed in the welding process by adding the Ti element to inhibit the texture coarsening of the heat affected zone, so that the good welding performance of the product is realized, and the method is suitable for the cold stamping forming process of the automobile axle housing. The structural uniformity of the axle housing steel for the 510MPa grade cold stamping prepared by the components and the preparation method is good in the thickness direction; the yield strength is more than or equal to 345MPa, the tensile strength is more than or equal to 510MPa, the elongation after fracture is more than or equal to 24 percent, and the 180-degree bending test D is a, so that the high strength, the excellent plasticity and the bending property are realized.
Drawings
FIG. 1 is a metallographic structure diagram of axle housing steel for 510MPa grade cold stamping prepared by the invention.
Detailed Description
In order to facilitate understanding of the present invention, the present invention will be further described with reference to the following examples.
The invention discloses a 510 MPa-grade axle housing steel for cold stamping, which comprises the following components in percentage by weight: 0.05-0.10% of C, 0.05-0.20% of Si, 1.10-1.30% of Mn, less than or equal to 0.020% of P, less than or equal to 0.008% of S, 0.015-0.030% of Nb, 0.010-0.030% of Ti, less than or equal to 0.008% of N, 0.015-0.050% of Als, and the balance of Fe and inevitable impurities.
The reason for adopting the components and the component proportion of the axle housing steel for the 510MPa grade cold stamping is as follows:
c is an effective strengthening element in steel, can be dissolved in a matrix to play a role of solid solution strengthening, can be combined with Nb and Ti to form carbide precipitated particles to play a role of fine grain strengthening and precipitation strengthening, improves the carbon content, and is favorable for improving the strength, but too high carbon content can form more large and thick brittle carbide particles in the steel, is unfavorable for plasticity and toughness, can form a segregation zone in the center of the steel plate due to too high carbon content, is unfavorable for bending property formability, and increases welding carbon equivalent and welding crack sensitivity index due to too high carbon content, and is unfavorable for welding processing; therefore, the value range of C in the invention is set to be 0.05-0.10%.
Si has higher solid solubility in steel, is beneficial to thinning rust layer tissues, reduces the integral corrosion rate of the steel and improves the toughness, but the scale removal is difficult during rolling due to the over-high content, and the welding performance is reduced. Therefore, the value range of Si in the invention is set to be 0.05-0.20%.
Mn has a strong solid solution strengthening effect, can obviously reduce the phase transition temperature of steel, refines the microstructure of the steel, is an important strengthening and toughening element, but when the content of Mn is excessive, a casting blank crack is easy to generate in the continuous casting process, and simultaneously, the core component segregation of a steel plate can be caused, and the welding performance of the steel can be reduced; therefore, the value range of Mn in the invention is set to be 1.10-1.30%.
P and S elements can generate adverse effects on the structure performance of the steel plate, the plasticity and the low-temperature toughness of the steel can be obviously reduced when the content of P is too high, and sulfide inclusions can be formed by S to deteriorate the performance of the steel; therefore, the value ranges of P and S are set to be less than or equal to 0.020% and less than or equal to 0.008%.
Nb can pin austenite grain boundaries to prevent grain growth, and finally refine grains, so that the impact toughness is improved, but the yield strength is obviously improved due to fine grain strengthening, the yield ratio is increased, and the production cost is increased due to overhigh Nb content; therefore, the value range of Nb in the invention is set to be 0.015-0.030%.
Ti (C, N) precipitates formed by Ti and C, N can effectively refine austenite grains, inhibit coarsening of a coarse grain region in a welding process and simultaneously generate a precipitation strengthening effect, but micron-sized liquated TiN is easily formed due to excessively high Ti or N content and causes reduction of forming performance and fatigue performance, a volume fraction of the liquated TiN at 1500 ℃ can be obtained by a solid solubility product formula of the TiN in the liquid steel and an ideal chemical proportion of the TiN along with the change relation of the Ti content, so that the critical N content of the liquated TiN is 100ppm for the steel containing 0.030% of Ti, and the N content needs to be further reduced in order to further reduce the risk of producing the liquated TiN; therefore, the value ranges of Ti and N are set to be 0.010-0.030% of Ti and less than or equal to 0.008% of N.
Al is added into steel to play a role in deoxidation, and the steel quality can be improved, but the content of Al is too high, and nitrogen oxide is easy to precipitate at austenite grain boundaries to cause casting blank cracks to generate; therefore, the value range of Als is set to be 0.015-0.050%.
As can be seen from FIG. 1, the structural uniformity in the thickness direction of the metallographic structure of the axle housing steel for cold stamping of 510MPa grade disclosed in the invention is good. The thickness of the axle housing steel for the 510 MPa-level cold stamping prepared by adopting the components is 8.0-14.0 mm, the carbon equivalent CEV is less than or equal to 0.32%, the welding crack sensitivity index Pcm is less than or equal to 0.17%, the yield strength is greater than or equal to 345MPa, the tensile strength is greater than or equal to 510MPa, the elongation after fracture is greater than or equal to 24%, and the 180-degree bending test D is equal to a; high strength, excellent plasticity and bending performance are realized.
The invention also discloses a preparation method of the axle housing steel for 510MPa grade cold stamping, and when the axle housing steel for 510MPa grade cold stamping is prepared, the components of the axle housing steel for 510MPa grade cold stamping are smelted into a plate blank, and then the steps of hot rolling, coiling and cooling are sequentially carried out to obtain a finished product of the axle housing steel for 510MPa grade cold stamping.
Specifically, in the step of hot rolling the slab, the hot rolling step includes heating, rough rolling and finish rolling.
More specifically, in the heating step, the slab is heated to homogenize the cast structure and component segregation and to dissolve the alloy elements, but the problems of burning loss, overheating, overburning and the like can occur when the heating temperature is too high and the heating time is too long. Therefore, in the heating step, the heating temperature is set to be 1200-1240 ℃ and the heating time is set to be 190-400 min.
Further specifically, in the rough rolling step, the rough rolling needs to reach enough deformation to ensure austenite recrystallization, refine austenite grains and prevent mixed crystal tissues, and the rough rolling descaling can fully remove iron scales and avoid the surface quality problem caused by pressing of the iron scales; if the intermediate slab thickness is too large, the rough rolling deformation amount may be insufficient and the finish rolling load increases, and if the intermediate slab thickness is too small, the finish rolling deformation amount may be insufficient. Therefore, in the invention, the rough rolling is performed for 6 times in the rough rolling step, the reduction of the rough rolling pass is more than or equal to 19%, the odd pass full-length scale removal is performed, and the thickness of the intermediate billet is 55-57 mm.
In the finish rolling step, the three stands are basically rolled in an austenite non-recrystallization region after finish rolling, the austenite crystal grains which are rolled in the recrystallization region and refined to a certain degree can be flattened and elongated by adopting a large deformation rate, the grain boundary area of the austenite in unit volume is increased, and meanwhile, a large amount of deformation zones and high-density dislocation can be generated in the crystal, so that the ferrite nucleation rate is improved, and a fine grain structure is obtained after phase transformation; if the initial rolling temperature of finish rolling is too high, the deformation of the non-recrystallization region of austenite in the finish rolling process is insufficient, and the structure refinement is not facilitated; the cooling water between the racks is opened, so that the cooling speed of the strip steel in the finish rolling process can be increased, the rolling speed is increased on the basis of ensuring the finish rolling temperature, the difference between the finish cooling temperature and the coiling temperature of the laminar cooling section is reduced, and the product performance is ensured; if the finish rolling temperature is too low, the difference between the finish rolling temperature and the initial rolling temperature is too large, so that the cooling speed in the finish rolling process is too high, the risk of rolling of a plurality of racks in a two-phase region after finish rolling exists, and the comprehensive performance of a product is poor; if the finishing temperature is too high, the deformation of the unrecrystallized area is insufficient, which is not beneficial to the refining of the final structure. Therefore, in the invention, 7 times of finish rolling is set in the finish rolling step, the reduction rates of three racks after finish rolling are respectively more than 17%, 13% and 10%, cooling water between the racks with the rolling temperature not higher than 1050 ℃ and the finishing temperature of 830-870 ℃ is used.
Specifically, in the coiling step, if the coiling temperature is too low, abnormal structures are generated due to too high cooling speed in the subsequent cooling process; if the coiling temperature is too high, the crystal grains become coarse, resulting in deterioration of the overall properties of the finished product. Therefore, the coiling temperature is set to be 560-600 ℃.
Particularly, in the cooling step, the laminar cooling section adopts front-section cooling, so that the final structure refinement can be realized by a larger supercooling degree, and the fine and dispersed second phase precipitation, fine grain strengthening enhancement and precipitation strengthening effects can be simultaneously facilitated. Therefore, the laminar cooling is performed in the cooling step in the front-end cooling mode in the present invention.
Examples
For further understanding of the present invention, two groups of examples using the composition and preparation method of the axle housing steel for cold stamping of 510MPa class according to the present invention and two groups of comparative examples are provided for comparative illustration, and the specific chemical compositions of the two groups of examples and the two groups of comparative examples are shown in Table 1.
TABLE 1 chemical composition/% of examples and comparative examples
| C | Si | Mn | P | S | Cr | Nb | V | Ti | N | Als | |
| Example 1 | 0.06 | 0.06 | 1.13 | 0.016 | 0.002 | // | 0.019 | // | 0.015 | 0.004 | 0.035 |
| Example 2 | 0.08 | 0.10 | 1.20 | 0.013 | 0.003 | // | 0.021 | // | 0.012 | 0.005 | 0.033 |
| Comparative example 1 | 0.17 | 0.02 | 1.40 | 0.020 | 0.006 | 0.15 | // | 0.056 | // | // | 0.065 |
| Comparative example 2 | 0.13 | 0.25 | 1.42 | 0.015 | 0.006 | // | 0.015 | // | 0.028 | // | 0.028 |
The specific processing technology of the embodiment 1 comprises the following steps: processing the plate blank obtained by smelting according to the chemical components in the table 1, wherein the heating temperature is 1220 ℃, and the heating time is 230 min; then, 6-pass rough rolling is carried out, the pass reduction is more than or equal to 19 percent, odd-pass full-length scale removal is carried out, and the thickness of the intermediate blank is 56 mm; performing finish rolling for 7 times, wherein the reduction ratios of the three last frames are respectively 18%, 13% and 10%, 3 frames of inter-frame cooling water are used, the start rolling temperature of the finish rolling is 1030-1040 ℃, the finish rolling temperature is 840-870 ℃, and the coiling temperature is 580-600 ℃; and carrying out laminar cooling after rolling, and adopting a front-section cooling mode.
The specific processing technology of the embodiment 2 is as follows: processing the plate blank obtained by smelting according to the chemical components in the table 1, wherein the heating temperature is 1230 ℃, and the heating time is 200 min; then, 6-pass rough rolling is carried out, the pass reduction is more than or equal to 19 percent, odd-pass full-length scale removal is carried out, and the thickness of the intermediate blank is 56 mm; performing finish rolling for 7 times, wherein the reduction ratios of the three last frames are respectively 17%, 14% and 10%, 3 frames of inter-frame cooling water are used, the start rolling temperature of the finish rolling is 1030-1050 ℃, the finish rolling temperature is 830-860 ℃, and the coiling temperature is 560-590 ℃; and carrying out laminar cooling after rolling, and adopting a front-section cooling mode.
The specific processing technique of comparative example 1 is: processing the plate blank obtained by smelting according to the chemical components in the table 1, wherein the heating temperature is 1210 ℃, and the thickness of the intermediate blank is 50 mm; and then carrying out 7-pass finish rolling, wherein the reduction rates of the three last stands are respectively 15%, 18% and 11%, the finish rolling temperature is 840 ℃, the coiling temperature is 612 ℃, and after rolling, laminar cooling is carried out, and a front-section cooling mode is adopted.
The specific processing technique of comparative example 2 is: the plate blank obtained by smelting is processed according to the chemical components in the table 1, the heating temperature is 1170 ℃, the thickness of the intermediate blank is 60mm, the precision rolling initial rolling temperature is 959 ℃, the final rolling temperature is 805 ℃, proper amount of water is poured after rolling in an ACC semi-automatic mode for cooling, and the temperature of red return is controlled to 672 ℃.
The finished products prepared by the two groups of examples and the two groups of comparative examples are subjected to performance tests, and the specific mechanical property and bending property test results are shown in table 2.
TABLE 2 results of performance test of examples and comparative examples
| Thickness/mm | Yield strength/MPa | Tensile strength/MPa | Elongation after break/% | 180 degree bend test | |
| Example 1 | 10.0 | 415 | 532 | 29.0 | D ═ a is qualified |
| Example 2 | 14.0 | 405 | 528 | 29.5 | D ═ a is qualified |
| Comparative example 1 | 8.0 | 368 | 479 | 44.5 | D is 2a qualified |
| Comparative example 2 | 16.0 | 375 | 552 | 27.0 | // |
Note 1: in Table 2, D is the bending indenter diameter and a is the specimen thickness.
According to the performance test results of the two groups of examples and the two groups of comparative examples obtained in the table 2, the yield strength and the tensile strength of the comparative example 1 are reduced compared with those of the two groups of examples, and the comparative example 1 has high content of C, reduced weldability of the material, and high alloy cost due to the addition of V element; comparative example 2 has strength and plasticity basically equivalent to those of two groups of examples, but in comparative example 2, the addition amount of C, Mn element is high, and the weldability of the material is reduced; the alloy costs for both sets of examples are lower than those for the comparative examples.
In conclusion, the axle housing steel for 510MPa grade cold stamping and the preparation method thereof disclosed by the invention realize high strength, good plasticity and bending property, excellent forming property and welding property of the product through reasonable alloy components and production process design, the production method of the product is simple, the alloy cost is low, the comprehensive performance is excellent, and the axle housing steel is suitable for a cold stamping forming process of an automobile axle housing and has good application prospect.
Claims (10)
1.510MPa level axle housing steel for cold stamping, its characterized in that: the axle housing steel comprises the following components in percentage by weight: 0.05-0.10% of C, 0.05-0.20% of Si, 1.10-1.30% of Mn, less than or equal to 0.020% of P, less than or equal to 0.008% of S, 0.015-0.030% of Nb, 0.010-0.030% of Ti, less than or equal to 0.008% of N, 0.015-0.050% of Als, and the balance of Fe and inevitable impurities.
2. The axle housing steel for 510MPa grade cold stamping of claim 1, wherein: the carbon equivalent CEV of the axle housing steel is less than or equal to 0.32 percent, and the welding crack sensitivity index Pcm is less than or equal to 0.17 percent.
3. The axle housing steel for 510MPa grade cold stamping of claim 1, wherein: the yield strength of the axle housing steel is more than or equal to 345MPa, the tensile strength is more than or equal to 510MPa, the elongation after fracture is more than or equal to 24 percent, and the D & lta & gt bending test at 180 degrees is a.
4. The axle housing steel for 510MPa grade cold stamping of claim 1, wherein: the thickness of the axle housing steel is 8.0-14.0 mm.
The preparation method of the 5.510 MPa-level axle housing steel for cold stamping is characterized by comprising the following steps: the axle housing steel for cold stamping under 510MPa according to any one of claims 1 to 4 is smelted into a plate blank, and then the steps of hot rolling, coiling and cooling are sequentially carried out to obtain a finished product.
6. The method for preparing the axle housing steel for the 510MPa grade cold stamping as claimed in claim 5, is characterized in that: the hot rolling step includes heating, rough rolling and finish rolling.
7. The method for preparing the axle housing steel for the 510MPa grade cold stamping of claim 6, wherein the method comprises the following steps: in the heating step, the heating temperature is 1200-1240 ℃, and the heating time is 190-400 min.
8. The method for preparing the axle housing steel for the 510MPa grade cold stamping of claim 6, wherein the method comprises the following steps: and in the rough rolling step, 6-pass rough rolling is carried out, the pass reduction is more than or equal to 19%, the odd-pass full-length dephosphorization is carried out, and the thickness of the intermediate billet is 55-57 mm.
9. The method for preparing the axle housing steel for the 510MPa grade cold stamping of claim 6, wherein the method comprises the following steps: in the finish rolling step, 7 times of finish rolling are carried out, the reduction ratios of the three racks are respectively more than 17%, 13% and 10%, cooling water between the racks is used, the start rolling temperature of the finish rolling is less than or equal to 1050 ℃, and the finish rolling temperature is 830-870 ℃.
10. The method for preparing the axle housing steel for the 510MPa grade cold stamping as claimed in claim 5, is characterized in that: the coiling temperature in the coiling step is 560-600 ℃; and the cooling step adopts a front-stage cooling mode to carry out laminar cooling.
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