CN113957359A - High-strength steel for automobile wheels and preparation method thereof - Google Patents
High-strength steel for automobile wheels and preparation 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
- B22D11/18—Controlling or regulating processes or operations for pouring
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/28—Manufacture of steel in the converter
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/064—Dephosphorising; Desulfurising
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/10—Handling in a vacuum
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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
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
Abstract
The invention discloses a high-strength steel for automobile wheels, which comprises the following components in percentage by weight: 0.05-0.10% of C, 0.10-0.20% of Si, 1.40-1.60% of Mn, less than or equal to 0.020% of P, less than or equal to 0.008% of S, 0.15-0.30% of Cr, 0.04-0.06% of Nb, 0.020-0.040% of Ti, 0.015-0.050% of Als, and the balance of Fe and inevitable impurities. The invention also discloses a preparation method of the high-strength steel for the automobile wheel, which comprises the following steps of: molten iron desulfurization → converter smelting → LF refining → RH → slab continuous casting → hot rolling → coiling → cooling. The yield strength of the steel for the automobile wheel prepared by the components and the preparation method is more than or equal to 500MPa, the tensile strength is more than or equal to 650MPa, the elongation after fracture is more than or equal to 18 percent, and high strength and excellent plasticity are realized.
Description
Technical Field
The invention relates to the technical field of hot continuous rolling strip production, in particular to high-strength steel for automobile wheels and a preparation method of the high-strength steel for the automobile wheels.
Background
With the attention of human beings on the environment and resources, light weight, energy conservation, environmental protection, safety and low cost become new targets of the automobile manufacturing industry. The energy-saving effect brought by the weight reduction of rotating parts such as automobile wheels is 1.2-1.3 times that of non-rotating parts, and meanwhile, the automobile wheels are important safety parts in an automobile running system and play roles in bearing, steering, driving, braking and the like, so that the mass of the automobile wheels is reduced as much as possible on the premise of ensuring the reliability and the safety in the technical development direction of the automobile wheels, and higher requirements are provided for the strength, the forming performance, the welding performance and the like of steel for the automobile wheels. Because a certain content of alloy elements are added into the high-strength wheel steel, a welded joint is easy to generate a softening region after welding, the softening region is easy to generate concentrated deformation in the subsequent deformation process, the defects of thinning, necking and even cracking are formed, and the quality of the steel wheel is seriously influenced.
Chinese patent application with publication number CN109628839A discloses wheel steel with excellent welding performance and a production method thereof, but the product has yield strength of 340-480 MPa, tensile strength of 470-630 MPa and lower strength.
The Chinese patent application with publication number CN111334715A discloses a wheel steel suitable for welding heat influence and a production method thereof, but the product is 380CL-540CL series wheel steel and has lower strength.
The Chinese patent application with publication number CN111500924A discloses a high-strength wheel steel and a production method thereof, which comprises the following components in percentage by weight: c: 0.05-0.12%, Si: 0.01 to 0.25%, Mn: 1.50-2.00%, P is less than or equal to 0.015%, S is less than or equal to 0.006%, Nb: 0.03-0.09%, Ti: 0.015-0.080%, Mo is less than or equal to 0.30%, Cu is less than or equal to 0.30%, Ni is less than or equal to 0.30%, Cr is less than or equal to 0.30%, and the balance of Fe and inevitable impurities. The wheel steel disclosed by the patent is complex in alloy composition, high in Mn content and a certain amount of Mo, Cu, Ni and Cr elements are added, so that the alloy cost is increased, the Carbon Equivalent (CEV) and the welding crack sensitivity index (Pcm) are obviously increased, and the welding performance of the product is reduced.
Chinese patent application with publication number CN112626421A discloses 650MPa grade steel for automobile wheels and a preparation method thereof, wherein the steel comprises the following chemical components: c: 0.05-0.12%, Mn: 1.00-2.00%, Si: 0.05-0.30%, Nb: 0.04-0.07%, Ti: 0.02-0.05%, Als: 0.01-0.06%, P is less than or equal to 0.020%, S is less than or equal to 0.010%, and the balance is Fe. The patent mainly improves the welding performance of products by reducing the carbon content and adding Ti element, but the final structure is ultrafine ferrite and trace pearlite structure, the coarsening of crystal grains in a welding heat affected zone, particularly a coarse crystal zone in the welding process causes great difference between the strength of the welding heat affected zone and the strength of a base metal, thereby generating a softening zone, and the defects of thinning, necking and even cracking are easily formed in the forming process.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: provided is a high-strength steel for automobile wheels, which has excellent formability and weldability.
In order to solve the technical problems, the invention adopts the technical scheme that: the high-strength steel for the automobile wheel comprises the following components in percentage by weight: 0.05-0.10% of C, 0.10-0.20% of Si, 1.40-1.60% of Mn, less than or equal to 0.020% of P, less than or equal to 0.008% of S, 0.15-0.30% of Cr, 0.04-0.06% of Nb, 0.020-0.040% of Ti, 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 high-strength steel for automobile wheels is less than or equal to 0.43 percent, the weld crack sensitivity index Pcm is less than or equal to 0.20 percent, the yield strength is greater than or equal to 500MPa, the tensile strength is greater than or equal to 650MPa, and the elongation after fracture is greater than or equal to 18 percent.
Further, the method comprises the following steps: the thickness of the high-strength steel for automobile wheels is 2.0-8.0 mm.
The invention also discloses a preparation method of the high-strength steel for automobile wheels, which comprises the following steps of preparing raw materials according to the components of the high-strength steel for automobile wheels, and then: molten iron desulfurization → converter smelting → LF refining → RH → slab continuous casting → hot rolling → coiling → cooling.
Further, the method comprises the following steps: in the step of molten iron desulphurization, the S content in the desulphurized molten iron is controlled to be less than or equal to 0.005 percent.
Further, the method comprises the following steps: in the converter smelting step, ferro-aluminum is adopted for deoxidation, alloying is carried out according to Si, Mn, Cr and Nb components, slag blocking and tapping are carried out, the slag thickness is less than 80mm, 1000 +/-100 kg of active lime is added along with steel flow, 150 +/-15 kg of ladle top slag modifier is added on the slag surface for slag surface modification, and the converter tapping temperature is controlled to 1670 +/-20 ℃.
Further, the method comprises the following steps: in the LF refining step, white slag is manufactured for desulfurization, alloying is carried out to control all components within a required range of a finished product, and the LF outlet temperature is controlled to be 1605 +/-5 ℃; in the RH step, the vacuum degree is less than or equal to 300Pa, the treatment time is more than or equal to 10min, ferrotitanium is added for Ti alloying, 400mCa-Al wire is fed to modify inclusions, and the RH leaving temperature is controlled to be 1575 +/-5 ℃.
Further, the method comprises the following steps: in the slab continuous casting step, the continuous casting process is carried out under a light press of more than or equal to 3mm, peritectic steel covering slag is adopted, the superheat degree of a tundish is controlled at 15-30 ℃, the secondary cooling water adopts a weak cooling mode, and the casting process adopts a constant drawing speed of 1.0m/min for casting.
Further, the method comprises the following steps: the hot rolling step comprises heating, side pressing, rough rolling and finish rolling; in the heating step, the heating temperature is 1180-1220 ℃, and the heating time is 180-400 min; in the step of side pressure, the side pressure is less than or equal to 100 mm; in the rough rolling step, 6-pass rough rolling is carried out, the pass reduction is more than or equal to 18%, the odd-pass full-length dephosphorization is carried out, and the thickness of the intermediate billet is 42-44 mm; in the finish rolling step, 7 times of finish rolling are carried out, 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 580-620 ℃; 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, the Nb and Ti elements are added to exert the fine grain strengthening and precipitation effects, the high strength performance of the steel for the automobile wheel is realized, the good forming performance of the product is ensured, the carbon equivalent and the welding crack sensitivity index of the product are reduced by controlling the contents of the C, Si and Mn elements, the precipitation is formed in the welding process by adding the Ti element to inhibit the texture coarsening of a heat affected zone, the hardenability of a welding joint is improved by adding the Cr element, the softening trend of the welding heat affected zone is remarkably reduced, and the final product has good welding performance. The yield strength of the steel for the automobile wheel prepared by the components and the preparation method is more than or equal to 500MPa, the tensile strength is more than or equal to 650MPa, the elongation after fracture is more than or equal to 18 percent, and high strength and excellent plasticity are realized.
Drawings
FIG. 1 is a metallographic structure diagram of steel for high-strength automobile wheels prepared by the present 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 high-strength steel for automobile wheels, which comprises the following components in percentage by weight: 0.05-0.10% of C, 0.10-0.20% of Si, 1.40-1.60% of Mn, less than or equal to 0.020% of P, less than or equal to 0.008% of S, 0.15-0.30% of Cr, 0.04-0.06% of Nb, 0.020-0.040% of Ti, 0.015-0.050% of Als, and the balance of Fe and inevitable impurities.
The reason why the steel for high-strength automobile wheels of the present invention employs the above components and component ratios 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 0.10-0.20%.
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 1.40-1.60%.
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%.
Cr can increase the hardenability of steel, thereby improving the hardness of the steel, and simultaneously can increase the stability of undercooled austenite, so that the austenite is subjected to phase change at a lower temperature and a larger undercooling degree, thereby refining the structure, but the production cost is improved due to overhigh Cr content; therefore, the value range of Cr in the invention is set to be 0.15-0.30%.
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 0.04-0.06%.
Ti (C, N) precipitates formed by Ti and C, N can effectively refine austenite grains, inhibit the coarsening of the structure of a coarse grain region in the welding process and simultaneously generate a precipitation strengthening effect, but micron-sized TiN is easily formed due to excessively high Ti content, so that the forming performance and the fatigue performance are reduced; therefore, the value range of Ti in the invention is set to be 0.020-0.040 percent of Ti.
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 is clear from FIG. 1, the steel for high-strength automobile wheels disclosed in the present invention has a good uniformity of the microstructure in the thickness direction. The low-alloy-cost high-strength steel for automobile wheels, which is prepared by adopting the components, has the thickness of 2.0-8.0 mm, the carbon equivalent CEV (carbon equivalent) of less than or equal to 0.43%, the welding crack sensitivity index Pcm of less than or equal to 0.20%, the yield strength of more than or equal to 500MPa, the tensile strength of more than or equal to 650MPa and the elongation after fracture of more than or equal to 18%; high strength and excellent welding performance are realized.
The invention also discloses a preparation method of the high-strength steel for automobile wheels, which comprises the following steps of preparing raw materials according to the components of the high-strength steel for automobile wheels when preparing the high-strength steel for automobile wheels: molten iron desulfurization → converter smelting → LF refining → RH → slab continuous casting → hot rolling → coiling → cooling.
Specifically, in the molten iron desulphurization step, the molten iron obtained by blast furnace smelting is pre-desulfurized, and the S content in the desulfurized molten iron is controlled to be less than or equal to 0.005 percent.
Specifically, in the converter smelting step, the desulfurized molten iron is subjected to converter smelting, aluminum iron is adopted for deoxidation, the adding amount of the aluminum iron is equal to the oxygen activity of tapping multiplied by 1+100 (+ -50 kg), alloying is carried out according to Si, Mn, Cr and Nb components, slag is retained and tapped, the slag thickness is less than 80mm, 1000 +/-100 kg of active lime is added along with the steel flow, 150 +/-15 kg of ladle top slag modifier is added on the slag surface for slag surface modification, and the converter tapping temperature is 1670 +/-20 ℃.
Specifically, in the LF refining step, the LF refining process is adopted, white slag is manufactured for desulfurization, and all components are controlled within the required range of a finished product by alloying, wherein the LF outbound temperature is 1605 +/-5 ℃.
Specifically, in the RH step, the treatment time with the vacuum degree less than or equal to 300Pa is not less than 10min, ferrotitanium is added for Ti alloying, 400mCa-Al wire is fed to modify inclusions, and the RH outbound temperature is 1575 +/-5 ℃.
Specifically, in the slab continuous casting step, the continuous casting process is carried out under a light pressure of more than or equal to 3mm to reduce center segregation, peritectic steel casting powder is adopted, the superheat degree of a tundish is controlled at 15-30 ℃, a weak cooling mode is adopted for secondary cooling water, and the casting process adopts a constant drawing speed of 1.0m/min for casting as much as possible.
In the step of hot rolling the slab, the hot rolling step includes heating, side pressing, rough rolling and finish rolling.
More specifically, in the heating step, the slab is heated in a regenerative heating furnace, the slab is heated to homogenize the cast structure and component segregation, and alloy elements are dissolved in the solid solution, 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 1210-1250 ℃, and the heating time is set to be 190-400 min.
In the step of side pressing, a fixed width press is adopted to perform side pressing on the steel billet, the side pressing on the steel billet is carried out by adopting the fixed width press so as to realize the requirement of a user on the width of a steel strip, but the steel billet can form a bone-like shape due to overlarge side pressing amount, the edge part is thickened excessively, the pressing amount of the middle part of the plate blank is insufficient during subsequent rough rolling, the austenite in the thickness direction is not completely recrystallized, and a mixed crystal structure is generated; therefore, the side pressure of the fixed width press is set to be less than or equal to 100mm in the side pressure step.
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 18%, the odd pass full-length scale removal is performed, and the thickness of the intermediate billet is 42-44 mm.
In the finish rolling step, if the start 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 is not refined; 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 are set in the finish rolling step, the start rolling temperature of the finish rolling is less than or equal to 1050 ℃, and the finish rolling temperature is 830-870 ℃.
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 580-620 ℃.
Specifically, in the cooling step, a front-section cooling mode is adopted to realize larger supercooling degree so as to refine the final structure, and simultaneously, the fine and dispersed second phase is precipitated, and the fine grain strengthening and precipitation strengthening effects are enhanced. Therefore, the laminar cooling is carried out by adopting a front-stage cooling mode in the invention.
Examples
To further understand the present invention, two examples using the steel for high-strength automobile wheels according to the present invention and the method of preparing the same and a comparative example are provided for comparative explanation
In the smelting process of example 1, firstly, pre-desulfurization is performed on molten iron, and the content of S is controlled to be 0.003%; adding aluminum iron to deoxidize in a converter smelting process, alloying Si, Mn, Cr and Nb, stopping slag, tapping, adding 1000kg of active lime along with steel flow, adding 150kg of ladle top slag modifier to a slag surface, and tapping at 1675 ℃ in the converter; an LF procedure, namely, white slag is manufactured for desulfurization, and alloying is carried out to control all components within the required range of a finished product, wherein the LF outlet temperature is 1602 ℃; RH process, wherein the processing time of the vacuum degree is less than or equal to 300Pa is 15min, ferrotitanium is added for Ti alloying, 400mCa-Al wire is fed to modify inclusions, and the RH leaving temperature is 1573 ℃; in the continuous casting process, soft reduction of 3mm is adopted, peritectic steel casting powder is adopted, the superheat degree of a tundish is controlled at 25 ℃, the secondary cooling water adopts a weak cooling mode, and the casting speed is 0.9-1.0 m/min.
In the smelting process of example 2, firstly, pre-desulfurization is performed on molten iron, and the content of S is controlled to be 0.003%; adding aluminum iron to deoxidize in a converter smelting process, alloying Si, Mn, Cr and Nb, stopping slag, tapping, adding 1000kg of active lime along with steel flow, adding 150kg of ladle top slag modifier to a slag surface, and tapping at 1673 ℃ in the converter; an LF procedure, namely, white slag is manufactured for desulfurization, and alloying is carried out to control all components within the required range of a finished product, wherein the LF outlet temperature is 1605 ℃; RH process, wherein the processing time of the vacuum degree is less than or equal to 300Pa is 15min, ferrotitanium is added for Ti alloying, 400mCa-Al wire is fed to modify inclusions, and the RH leaving temperature is 1578 ℃; in the continuous casting process, soft reduction of 3mm is adopted, peritectic steel casting powder is adopted, the superheat degree of a tundish is controlled at 20 ℃, the secondary cooling water adopts a weak cooling mode, and the casting speed is 0.9-1.0 m/min.
In the smelting procedure of comparative example 1, firstly, pre-desulfurization is carried out on molten iron, and the content of S is controlled to be 0.003%; adding aluminum iron to deoxidize in a converter smelting process, alloying Si and Mn, stopping slag and tapping, adding 1000kg of active lime along with steel flow, adding 150kg of ladle top slag modifier on a slag surface, and tapping at 1680 ℃ in the converter; an LF procedure, namely, white slag is manufactured and desulfurized, Nb and Ti are alloyed according to the component requirements of a finished product, and the LF exit temperature is 1572 ℃; and in the casting process, peritectic steel casting powder is adopted under the condition of light pressure of 3mm, the superheat degree of a tundish is controlled at 30 ℃, the secondary cooling water adopts a weak cooling mode, and the casting speed is 1.0-1.1/min.
The steel billets of two groups of examples and a group of comparative examples are obtained by the smelting method, and the specific components of the steel billets are shown in table 1, wherein the comparative examples are low in Mn content, high in Mb content and free of Cr element.
TABLE 1 chemical composition/% of examples and comparative examples
| C | Si | Mn | P | S | Cr | Nb | Ti | Als | |
| Example 1 | 0.07 | 0.11 | 1.52 | 0.013 | 0.004 | 0.20 | 0.048 | 0.032 | 0.028 |
| Example 2 | 0.06 | 0.09 | 1.52 | 0.011 | 0.002 | 0.19 | 0.044 | 0.030 | 0.035 |
| Comparative example 1 | 0.07 | 0.13 | 1.25 | 0.009 | 0.003 | // | 0.053 | 0.029 | 0.026 |
In the embodiment 1, the plate blank obtained by smelting is continuously processed, and the specific processing technology comprises the following steps: heating at 1230 deg.C for 220 min; the side pressure of the fixed width press is 90mm, the reduction of the rough rolling pass is more than or equal to 18 percent, the odd pass full-length scale removal is carried out, and the thickness of the intermediate blank is 43 mm; the initial rolling temperature of finish rolling is 1030-1050 ℃, the finishing rolling temperature is 840-860 ℃, and the coiling temperature is 580-610 ℃; and carrying out laminar cooling after rolling, and adopting a front-section cooling mode.
In the embodiment 2, the plate blank obtained by smelting is continuously processed, and the specific processing technology comprises the following steps: heating at 1220 deg.C for 210 min; the side pressure of the fixed width press is 90mm, the reduction of the rough rolling pass is more than or equal to 18 percent, the odd pass full-length scale removal is carried out, and the thickness of the intermediate blank is 42 mm; the initial rolling temperature of finish rolling is 1030-1050 ℃, the finishing rolling temperature is 850-870 ℃, and the coiling temperature is 590-620 ℃; and carrying out laminar cooling after rolling, and adopting a front-section cooling mode.
In comparative example 1, the plate blank obtained by smelting is continuously processed, and the specific processing technology comprises the following steps: heating at 1220 deg.C for 210 min; the side pressure of the fixed width press is 130mm, the reduction of the rough rolling pass is more than or equal to 18 percent, the full-length scale removal of the odd pass is carried out, and the thickness of the intermediate blank is 42 mm; the initial rolling temperature of finish rolling is 1030-1050 ℃, the finishing rolling temperature is 860-880 ℃, and the coiling temperature is 600-630 ℃; and carrying out laminar cooling after rolling, and adopting a front-section cooling mode.
The finished products prepared by two groups of examples and one group 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/% | Weld softening cracking rate/%) | |
| Example 1 | 3.0 | 622 | 688 | 23.5 | 0.84 |
| Example 2 | 4.5 | 609 | 678 | 20.0 | 0.95 |
| Comparative example 1 | 4.5 | 600 | 666 | 24.0 | 5.64 |
According to the performance test results of two groups of examples and one group of comparative examples obtained in the table 2, the high-strength steel for automobile wheels and the preparation method thereof disclosed by the invention have the advantages that through reasonable alloy components and production process design, the softening tendency of welding heat influence is obviously reduced while the high strength, excellent forming performance and excellent welding performance of the product are realized, the production method of the product is simple, the comprehensive performance is excellent, and the application prospect is good.
Claims (10)
1. The high-strength steel for automobile wheels is characterized in that: comprises the following components in percentage by weight: 0.05-0.10% of C, 0.10-0.20% of Si, 1.40-1.60% of Mn, less than or equal to 0.020% of P, less than or equal to 0.008% of S, 0.15-0.30% of Cr, 0.04-0.06% of Nb, 0.020-0.040% of Ti, 0.015-0.050% of Als, and the balance of Fe and inevitable impurities.
2. The steel for high-strength automobile wheels according to claim 1, wherein: the carbon equivalent CEV of the high-strength steel for automobile wheels is less than or equal to 0.43 percent, the weld crack sensitivity index Pcm is less than or equal to 0.20 percent, the yield strength is greater than or equal to 500MPa, the tensile strength is greater than or equal to 650MPa, and the elongation after fracture is greater than or equal to 18 percent.
3. The steel for high-strength automobile wheels according to claim 1, wherein: the thickness of the high-strength steel for automobile wheels is 2.0-8.0 mm.
4. The preparation method of the high-strength steel for the automobile wheels is characterized by comprising the following steps: the preparation of the steel for high strength automobile wheels according to the composition of the steel for high strength for automobile wheels as set forth in any one of claims 1 to 3 is carried out by the steps of: molten iron desulfurization → converter smelting → LF refining → RH → slab continuous casting → hot rolling → coiling → cooling.
5. The method for producing a steel for high-strength automobile wheels according to claim 4, characterized in that: in the step of molten iron desulphurization, the S content in the desulphurized molten iron is controlled to be less than or equal to 0.005 percent.
6. The method for producing a steel for high-strength automobile wheels according to claim 4, characterized in that: in the converter smelting step, ferro-aluminum is adopted for deoxidation, alloying is carried out according to Si, Mn, Cr and Nb components, slag blocking and tapping are carried out, the slag thickness is less than 80mm, 1000 +/-100 kg of active lime is added along with steel flow, 150 +/-15 kg of ladle top slag modifier is added on the slag surface for slag surface modification, and the converter tapping temperature is controlled to 1670 +/-20 ℃.
7. The method for producing a steel for high-strength automobile wheels according to claim 4, characterized in that: in the LF refining step, white slag is manufactured for desulfurization, alloying is carried out to control all components within a required range of a finished product, and the LF outlet temperature is controlled to be 1605 +/-5 ℃; in the RH step, the vacuum degree is less than or equal to 300Pa, the treatment time is more than or equal to 10min, ferrotitanium is added for Ti alloying, 400mCa-Al wire is fed to modify inclusions, and the RH leaving temperature is controlled to be 1575 +/-5 ℃.
8. The method for producing a steel for high-strength automobile wheels according to claim 4, characterized in that: in the slab continuous casting step, the continuous casting process is carried out under a light press of more than or equal to 3mm, peritectic steel covering slag is adopted, the superheat degree of a tundish is controlled at 15-30 ℃, the secondary cooling water adopts a weak cooling mode, and the casting process adopts a constant drawing speed of 1.0m/min for casting.
9. The method for producing a steel for high-strength automobile wheels according to claim 4, characterized in that: the hot rolling step comprises heating, side pressing, rough rolling and finish rolling; in the heating step, the heating temperature is 1180-1220 ℃, and the heating time is 180-400 min; in the step of side pressure, the side pressure is less than or equal to 100 mm; in the rough rolling step, 6-pass rough rolling is carried out, the pass reduction is more than or equal to 18%, the odd-pass full-length dephosphorization is carried out, and the thickness of the intermediate billet is 42-44 mm; in the finish rolling step, 7 times of finish rolling are carried out, 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 producing a steel for high-strength automobile wheels according to claim 4, wherein: the coiling temperature in the coiling step is 580-620 ℃; and the cooling step adopts a front-stage cooling mode to carry out laminar cooling.
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