Preparation method of high-quality steel belt with 650MPa-grade tensile strength for heavy truck rims

Abstract

The invention discloses a preparation method of a high-quality steel belt for a heavy truck rim with the tensile strength of 650 MPa. The preparation method comprises the following steps: a steelmaking process; a hot rolling process; heating, wherein the soaking time is 25-45 min; the tapping temperature is 1190 DEG C to 1210 DEG C; rough rolling: rolling for 3 + 3 passes, wherein the reduction of the first pass is controlled to be 32-35mm; descaling is required to be carried out on odd-number passes; the thickness of the intermediate billet is controlled to be 45-50mm; 7 passes of rolling are adopted for finish rolling; the finish rolling development temperature is controlled to be 950-1050 DEG C, and the finish rolling temperature is 830-850 DEG C; cooling treatment is conducted through the laminar flow cooling technology, the laminar flow cooling speed is 25-40 DEG C / s, and the final cooling temperature is 435-465 DEG C. According to the product prepared by the process, the tensile property meets the standard requirement, and the strength fluctuation range is within 50MPa; and the processing cracking defect caused by welding is greatly reduced and is controlled within 0.3%.

Description

Technical Field

[0001] The present invention relates to the technical field of wheel steel production, and particularly to a preparation method for a high-quality steel strip for heavy-duty truck wheel rims with a tensile strength of 650 MPa grade. Background Art

[0002] Heavy-duty commercial vehicles play a key role in China's transportation system and have a significant impact on energy consumption and carbon emissions. To ensure China's energy security and reduce the weight of heavy-duty commercial vehicle bodies, thereby achieving energy consumption reduction and pollution reduction, has become the mainstream trend in the industry's development.

[0003] Among the many ways to reduce vehicle body weight, the weight reduction effect of wheel rotating parts is particularly prominent. Its energy consumption reduction and pollution reduction effect is 1.2 to 1.3 times that of vehicle-mounted non-rotating parts. Developing high-strength wheel steel has become an industry consensus, and high-strength wheel steel with a tensile strength of 650 MPa grade is the focus product currently being developed and promoted. The wheel forming process is complex and the service environment is harsh. When the strength of wheel steel is increased, a series of quality problems follow, such as an increased amplitude of mechanical property fluctuations, an increased deformation and cracking rate after flash welding, and a decrease in fatigue performance. How to solve the above-mentioned existing technical problems and achieve an overall improvement in product quality has become the key to determining whether the steel for wheel rims with a tensile strength of 650 MPa grade can be widely promoted and applied.

[0004] Chinese patent application with publication number CN109023087A discloses a wheel steel with a tensile strength of 650 MPa grade and good post-welding formability and its production method. The chemical composition of the wheel steel is: C: 0.06 - 0.08%, Si: 0.10 - 0.20%, Mn: 1.20 - 1.40%, P ≤ 0.0080%, S ≤ 0.002%, Als: 0.020 - 0.060%, Nb: 0.056 - 0.065%, and the balance is Fe and inevitable impurities. The main hot rolling process of the wheel steel is: the heating temperature is 1250 - 1270 °C, the finishing rolling temperature is 820 - 860 °C, and the coiling temperature is: 600 - 620 °C. Considering the comprehensive composition and hot rolling process, the structure of the wheel steel described in this patent is ferrite + pearlite + a small amount of bainite structure, which is the traditional lower-level wheel steel structure control concept. The presence of pearlite with higher hardness in high-strength wheel steel will reduce its fatigue performance. Many studies have shown that bainite structure is more effective than pearlite in inhibiting the propagation of fatigue cracks. This patent forms a 650 MPa grade wheel steel with ferrite + bainite structure control through differential design of composition and hot rolling process, and has better fatigue performance than it.

[0005] The Chinese patent application with the publication number CN110551942A discloses a 650 MPa grade hot-rolled dual-phase steel for automotive wheel rims and its preparation method. The chemical composition of the wheel steel is as follows: C: 0.06 - 0.10%, Si: ≤0.20%, Mn: 1.50 - 1.70%, P ≤ 0.015%, S ≤ 0.005%, Al: 0.3 - 0.5%, Cr: 0.15 - 0.35%, Nb: 0.03 - 0.05%, Ti: 0.010 - 0.030%, and the balance is Fe and inevitable impurities. The main hot-rolling process of the wheel steel is: the heating temperature is 1200 - 1260 °C, the finish rolling temperature is 840 - 880 °C, and the coiling temperature is: 460 - 550 °C. Compared with the disclosed preparation methods of 650 MPa grade wheel steels, the method described in this patent has a certain degree of advancement. However, due to the design defects in the tapping temperature and the contents of Ti and N elements, the welding deformation cracking rate of the product is relatively high (mentioned in the patent book as ≤1%), which affects the processing efficiency and cost of the wheel rim. The welding deformation cracking rate of the wheel rim is a technical problem in the industry, which is directly related to the promotion and application of the product. This patent precisely limits the contents of Ti and N elements in the steel, and uses the formation of TiN with a size of less than 20 mm in hot-rolled austenite to inhibit the grain coarsening in the heat-affected zone of welding, thereby improving the welding performance of the 650 MPa grade wheel steel and further enhancing the product quality.

[0006] The Chinese patent application with the publication number CN110551942A discloses a manufacturing method of a 650 MPa grade steel for commercial vehicle wheel rims. The chemical composition of the wheel steel is as follows: C: 0.08 - 0.15%, Si: 0.10 - 0.60%, Mn: 1.40 - 1.70%, P ≤ 0.020%, S ≤ 0.003%, Als: 0.10 - 0.60%, Cr: 0.10 - 0.50%, Nb: 0.050 - 0.080%, Ti: 0.005 - 0.030%, N: ≤0.0060, O ≤ 0.0030%, and the balance is Fe and inevitable impurities. The main hot-rolling process of the wheel steel is: the heating temperature is 1240 - 1270 °C, the finish rolling temperature is 830 - 850 °C, and the coiling temperature is: 530 - 560 °C. Element C will have many adverse effects in the steel. In the wheel steel described in this patent, the content of element C is controlled at 0.08 - 0.15%. On the one hand, it will increase the hardening tendency of the steel, form brittle martensite structure in the heat-affected zone of welding and reduce the welding performance. On the other hand, banded structure is likely to form in the steel, reducing the fatigue performance of the product. Based on theoretical analysis, the welding deformation cracking and fatigue performance of the 650 MPa grade steel for wheel rims described in this patent are relatively poor (specific indicators are not presented in the patent book). This patent adopts a low-C composition design, and the differential design of other composition elements and hot-rolling process makes the product have the characteristics of low welding deformation cracking rate and fatigue resistance compared with the product described in this patent. Summary of the Invention

[0007] Aiming at the problems of large fluctuations in the mechanical properties of products, high deformation and cracking rates after flash welding, and low fatigue limit strength in the existing technology, the purpose of the present invention is to provide a preparation method for steel strips used for heavy-duty truck wheel rims with a high-quality tensile strength of 650 MPa, solve the key performance defects of current products, promote the wide promotion and application of 650 MPa grade wheel steel in the industry with high-quality advantages, and contribute to the implementation of the national green development concept. The present invention adopts a composition system of "low C + Mn + Nb + Ti + Cr" and is combined with a rolling process of "low-temperature steel burning + rapid rolling + low-temperature coiling". By forming refined polygonal ferrite and granular bainite structures and ensuring that Ti elements in the steel are completely precipitated in the form of TiN in high-temperature austenite with a size less than 20 nm. The products prepared by this process not only meet the standard requirements in terms of tensile properties, but also the strength fluctuation range can be accurately controlled within 50 MPa; the processing cracking defects caused by welding are significantly reduced and controlled within 0.3%; the radial fatigue life of the wheels is significantly improved and exceeds 2 million times. In addition, the products have excellent surface quality and precise dimensional shapes, fully meeting the stringent processing and use requirements of customers, bringing new technological breakthroughs and product upgrades to the field of heavy-duty truck wheel rim manufacturing.

[0008] To solve the above technical problems, the present invention adopts the following technical solutions:

[0009] A preparation method for steel strips used for heavy-duty truck wheel rims with a high-quality tensile strength of 650 MPa according to the present invention includes:

[0010] Steelmaking process: KR desulfurization, converter smelting, LF refining, RH refining, continuous casting; where:

[0011] KR desulfurization: Remove impurities S in the hot metal through hot metal pretreatment, reduce the desulfurization pressure in the converter smelting and refining processes. When desulfurization ends, the sulfur content in the hot metal should be ≤0.002%, and the removal ratio of the slag on the surface of the hot metal ladle should be ≥95%;

[0012] Converter smelting: Pour the pre-desulfurized hot metal into the converter and perform a series of treatment operations such as decarburization, deoxidation, and desulfurization; during this process, accurately add appropriate amounts of low-carbon ferromanganese, ferrosilicon, and ferrochromium into the converter to carry out preliminary microalloying operations, so as to initially adjust the chemical composition of the molten steel; in the converter tapping process, strictly control the tapping temperature within the range of 1620°C to 1660°C, and the tapping time is controlled within 4 - 6 minutes; to prevent converter slag from flowing into the ladle, at the beginning and end of converter tapping, the slide gate slag blocking operation technology is adopted. With the precise control of the slide gate device, effectively prevent the slag from entering the ladle together with the molten steel, and ensure that the quality of the molten steel is not affected by the slag;

[0013] LF refining: The slag-making desulfurization operation is carried out in the LF furnace stage. By adding slag-making materials, the sulfur element in the molten steel reacts with the slag, thereby reducing the sulfur content in the molten steel. At the same time, ferroaluminum, ferrosilicon, low-carbon ferromanganese, and ferrocolumbium alloys are added to the molten steel for secondary microalloying.

[0014] RH refining: Remove gases and inclusions through RH treatment to further improve the purity of the molten steel. First, evacuate the vacuum to ≤2.6 mbar and maintain the vacuum time for 15 - 20 min. During the vacuum treatment, ferro-titanium alloy is added for tertiary microalloying, and the circulating pure degassing time is controlled within 7 - 10 min. After the RH vacuum treatment, calcium treatment is carried out. After calcium treatment, ensure the soft blowing time is 10 - 15 min, and stir the molten steel by bottom-blowing argon to promote the floating of inclusions.

[0015] Continuous casting: During the casting process of the casting machine, the ladle is protected by argon throughout the process. The slag detection equipment is turned on during the ladle casting process, and it is ensured that no ladle slag flows into the tundish when the ladle casting ends. The casting process of the casting machine adopts constant casting speed control, and the casting speed setting range is 1.1 m / min - 1.4 m / min according to different casting cross-sections. The superheat of the tundish casting is controlled within 20℃ - 35℃; the liquid level fluctuation of the mold is controlled within ±3 mm.

[0016] Hot rolling process: Heating, rough rolling, finish rolling, cooling, and coiling; among which:

[0017] Heating: Set the soaking time within 25 - 45 min; control the tapping temperature at 1190℃ - 1210℃.

[0018] Rough rolling: The rough rolling adopts a 3 + 3 pass mode of rolling. At the same time, the reduction of the first pass is controlled to be 32 - 35 mm; it is required that descaling is carried out for odd passes; the thickness control requirement of the intermediate billet is 45 - 50 mm.

[0019] Finish rolling: The finish rolling adopts 7 passes of rolling; the rolling temperature during finish rolling is controlled at 950 - 1050℃, and the final rolling temperature is controlled at 830 - 850℃.

[0020] Cooling: Cooling treatment is carried out using the laminar water cooling technology. The laminar cooling rate is controlled at 25 - 40℃ / s, and the final cooling temperature is 435℃ - 465℃.

[0021] Furthermore, the chemical composition of the converter end point in mass percentage is: C ≤ 0.06%, Si ≤ 0.15%, Mn 1.40 - 1.60%, P ≤ 0.015%, S ≤ 0.010%, Alt ≥ 0.040%, Cr 0.20 - 0.30%, and the rest is Fe and unavoidable impurities.

[0022] Furthermore, the chemical composition of the LF end point by mass percentage is: C 0.065 - 0.085%, Si 0.10 - 0.20%, Mn 1.55 - 1.65%, P ≤ 0.015%, S ≤ 0.005%, Alt 0.020 - 0.040%, Nb 0.05 - 0.06%, Cr 0.20 - 0.30%, and the balance is Fe and inevitable impurities.

[0023] Furthermore, the chemical composition of the RH end point by mass percentage is: C 0.065 - 0.085%, Si 0.10 - 0.20%, Mn 1.55 - 1.65%, P ≤ 0.015%, S ≤ 0.005%, Alt 0.020 - 0.040%, Nb 0.05 - 0.06%, Cr 0.20 - 0.30%, Ti 0.01 - 0.02%, N 0.0020 - 0.0060%, and the balance is Fe and inevitable impurities.

[0024] Furthermore, the chemical composition of the steel strip by mass percentage is: C 0.07%, Si 0.14%, Mn 1.56%, P 0.010%, S 0.002%, Alt 0.032%, Nb 0.056%, Cr 0.28%, Ti 0.016%, N 0.0039%, and the balance is Fe and inevitable impurities.

[0025] Furthermore, the chemical composition of the steel strip by mass percentage is: C 0.08%, Si 0.13%, Mn 1.53%, P 0.009%, S 0.002%, Alt 0.033%, Nb 0.054%, Cr 0.27%, Ti 0.013%, N 0.0040%, and the balance is Fe and inevitable impurities.

[0026] Furthermore, the chemical composition of the steel strip by mass percentage is: C 0.07%, Si 0.17%, Mn 1.63%, P 0.012%, S 0.001%, Alt 0.029%, Nb 0.058%, Cr 0.25%, Ti 0.018%, N 0.0032%, and the balance is Fe and inevitable impurities.

[0027] Furthermore, the chemical composition of the steel strip by mass percentage is: C 0.08%, Si 0.15%, Mn 1.50%, P 0.013%, S 0.004%, Alt 0.038%, Nb 0.053%, Cr 0.24%, Ti 0.015%, N 0.0050%, and the balance is Fe and inevitable impurities.

[0028] The reasons for the selection and range control of its main elements are as follows

[0029] C: Carbon is an inexpensive solid solution strengthening element. At the same time, it forms carbides with alloying elements such as Nb, V, and Ti to produce precipitation strengthening. However, if the content of C element in the steel is relatively high, it will reduce the welding performance and form carbide and pearlite segregation bands, damaging the cold forming performance and fatigue performance of the product. Considering that the product needs to have good welding performance, cold forming performance, and fatigue performance while meeting the strength requirements, the content of this invention is limited to 0.065 - 0.085%.

[0030] Si: Silicon plays a role in solid solution strengthening in steel. When the content of Si is relatively high, it can inhibit the precipitation of carbides and promote the formation of ferrite. For the properties of wheel steel, Si is a beneficial element. However, the content of Si element should not exceed 0.20%. Excessive Si element will cause red oxides on the surface of the strip steel, affecting the surface quality. Considering the comprehensive product performance and surface quality, the content of this invention is limited to 0.10 - 0.20%.

[0031] Mn: Manganese can be infinitely replaced and dissolved with iron and is a very good solid solution strengthening element. At the same time, Mn can increase the hardenability of the steel and contribute to the formation of bainite structure. However, if the Mn element is too high, it will reduce the welding performance and easily produce segregated pearlite bands, damaging the cold forming performance and fatigue performance. Based on giving full play to the strengthening effect of the Mn element and improving the hardenability of the steel, and controlling the adverse effects on the product performance within an acceptable range, the content of this invention is limited to 1.55 - 1.65%.

[0032] Nb: In the steel, the Nb element will react with non-metallic elements such as C and N during the hot rolling stage and the cooling and coiling stage to form fine and dispersed Nb(CN), which has the effects of grain refinement and precipitation strengthening. Moreover, the Nb(CN) precipitate has good stability, which is conducive to the stable control of product performance. Therefore, the Nb element is the most common micro-alloying element in steel. The main purpose of adding the Nb element in this patent is also to refine the grain size and improve the product strength. However, when the Nb element reaches a certain quantity and continues to increase the Nb content, its beneficial effects will no longer increase. The content of this invention is limited to 0.050 - 0.060%.

[0033] Ti: Titanium element has a strong precipitation strengthening effect and grain size refinement effect. The main purpose of adding Ti element to general steel is to improve the strength of the product. In this patent, adding Ti element is not for enhancing strength. On the contrary, its strengthening effect is to be avoided. Instead, by precipitating TiN with a size below 20 nm during the austenite stage of hot rolling, the cold forming performance, fatigue performance, especially the welding performance of the product is improved. This is the key technical point of this patent. TiN of this size has a strong inhibitory effect on the grain size in the welding heat affected zone and the austenite grain size during the production process. How to control the precipitation behavior of TiN and control the Ti content is the key. If the Ti element content is low, Ti element reacts with O, S, and N during the smelting process to form compounds, depleting the Ti element and making it impossible to precipitate TiN during the austenite rolling stage at high temperature. If the Ti element content is relatively high, the precipitation size of TiN in the high-temperature austenite is relatively large, and the above effects are weakened. In addition, TiC with precipitation strengthening effect will precipitate during the cooling and coiling process, affecting the performance stability of the product. Therefore, the content of this invention is limited to 0.01 - 0.02%.

[0034] Cr: The main function of adding chromium element is to improve the hardenability of steel and form bainite structure. The content of chromium is not less than 0.20%, otherwise it will affect the hardenability of steel; it should not be higher than 0.30% to ensure cost economy.

[0035] N: In order to precipitate TiN with a size below 20 nm during the austenite stage of hot rolling, the content of this invention is limited to 20 - 60 ppm.

[0036] P, S: Phosphorus and sulfur are inevitable harmful elements in steel. The lower, the better, but too low requirements will increase production costs. In this invention, P ≤ 0.015% and S ≤ 0.005%.

[0037] Compared with the prior art, the beneficial technical effects of this invention are as follows:

[0038] This invention provides a preparation method for hot-rolled steel strip for high-quality heavy-duty truck wheel rims with a tensile strength of 650 MPa grade (brand: BT650CL). The strength of the product is stably controlled within 50 MPa, the welding deformation cracking rate is controlled within 0.3%, and the radial fatigue life of the wheel exceeds 2 million times. Compared with the prior art, there is a significant improvement, which helps to further promote and apply the 650 MPa grade wheel steel in the industry and provides important material support for the lightweight development of heavy-duty trucks.

[0039] The successful development and application of BT650CL enrich the variety of Baotou Steel's wheel steel, and also means that Baotou Steel has entered the ranks of high-end wheel steel suppliers, which is of great significance for enhancing the market influence of Baotou Steel's wheel steel products. BT650CL belongs to high-value-added products, and the upgrade and adjustment of the product structure can create objective economic benefits for the enterprise. Description of the Drawings

[0040] The present invention will be further described below in conjunction with the accompanying drawings.

[0041] Figure 1 Microstructure of the example

[0042] Figure 2 Microstructure of Comparative Example 1

[0043] Figure 3 Microstructure of Comparative Example 2 Detailed implementation manners

[0044] In order to better understand the above technical solutions and their advantages, the following will further describe with specific examples and comparative examples.

[0045] The production processes and operations of 4 groups of examples and 2 groups of comparative examples are the same, but there are differences in the chemical compositions and the design of controlled rolling and controlled cooling process parameters. The chemical composition controls of 4 groups of examples and 2 groups of comparative examples are shown in Table 1. The controls of each parameter of heating-rolling-cooling for 4 groups of examples and 2 groups of comparative examples are shown in Table 2. The mechanical properties of 4 groups of examples and 2 groups of comparative examples are shown in Table 3.

[0046] Table 1 Chemical compositions of examples and comparative examples (wt%)

[0047]

[0048] As can be seen from Table 1, the chemical composition controls in Examples 1-4 meet the requirements; in Comparative Example 1, the Ti element and Cr element are not added compared with the examples, and the controls of other elements are similar; in Comparative Example 2, more Ti is added compared with the examples, and the controls of other elements are similar.

[0049] Table 2 Hot rolling processes of examples and comparative examples

[0050]

[0051]

[0052] As can be seen from Table 2, the controls of the key process parameters of heating, rolling and cooling in Examples 1-4 meet the requirements; in Comparative Example 1, the coiling temperature control is higher than that of the examples, and the other process controls are similar; in Comparative Example 2, the coiling temperature control is higher than that of the examples, and the other process controls are similar.

[0053] Table 3 Mechanical properties of examples and comparative examples

[0054]

[0055] As can be seen from Table 3, for the 650 MPa grade wheel steel provided by the present invention, the yield strength is controlled within 618 - 640 MPa, the tensile strength is controlled within 678 - 690 MPa, and the elongation is controlled at 21 - 24%. The tensile property indexes meet the requirements of the metallurgical standard (YB / T 4151) and are stably controlled. The welding deformation cracking rate of the product is controlled within 0.3%, and the radial fatigue of the processed wheel is more than 2 million times. The tensile properties of Comparative Example 1 and Comparative Example 2 also meet the requirements of the metallurgical standard (YB / T 4151), but the welding deformation defect rate and the wheel radial fatigue performance are lower than those of the examples.

[0056] As can be seen Figure 1 from the above, the microstructure of the example is polygonal ferrite + granular bainite, the microstructure of Comparative Example 1 is polygonal ferrite + pearlite, and that of Comparative Example 2 is polygonal ferrite + granular bainite.

[0057] Comprehensive chemical composition, controlled rolling and controlled cooling process, metallographic structure, welding cracking defects and bending fatigue performance prove that this patent uses a "low C + Mn + Nb + Ti + Cr" composition system, combined with a rolling process of "low-temperature slab reheating + rapid rolling + low-temperature coiling". By forming refined polygonal ferrite and granular bainite structures, and generating TiN precipitates with a size below 20 nm, the product is more excellent in terms of performance stability, welding performance and fatigue performance.

[0058] The above-described examples are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A preparation method for a steel strip used for a heavy-duty truck rim with a high-quality tensile strength of 650 MPa grade, characterized in that: Including: Steelmaking process: KR desulfurization, converter smelting, LF refining, RH refining, continuous casting; where: KR desulfurization: Remove the impurity S in the hot metal through hot metal pretreatment to reduce the desulfurization pressure in the converter smelting and refining processes. At the end of desulfurization, the sulfur content in the hot metal should be ≤0.002%, and the removal ratio of the slag on the surface of the hot metal ladle should be ≥95%; Converter smelting: Pour the pre-desulfurized hot metal into the converter and perform a series of treatment operations such as decarburization, deoxidation, and desulfurization; during this process, accurately add appropriate amounts of low-carbon ferromanganese, ferrosilicon, and ferrochromium into the converter to carry out preliminary microalloying operations, so as to initially adjust the chemical composition of the molten steel; in the tapping process of the converter, strictly control the tapping temperature within the range of 1620°C to 1660°C, and the tapping time is controlled at 4 - 6 minutes; to prevent the converter slag from flowing into the ladle, at the beginning and end of the converter tapping, the slide gate slag blocking operation technology is adopted. With the precise control of the slide gate device, effectively prevent the slag from entering the ladle together with the molten steel, ensuring that the quality of the molten steel is not affected by the slag; LF refining: Perform slag-making desulfurization operations in the LF furnace stage. By adding slag-making materials, promote the reaction between the sulfur element in the molten steel and the slag, thereby reducing the sulfur content in the molten steel; at the same time, add ferrotitanium, ferrosilicon, low-carbon ferromanganese, and ferroniobium alloys to the molten steel for secondary microalloying; RH refining: Remove gases and inclusions through RH treatment to further improve the purity of the molten steel; first, evacuate the vacuum to ≤2.6 mbar and maintain the vacuum time for 15 - 20 minutes; add ferrotitanium alloy for tertiary microalloying during the vacuum treatment, and control the cyclic pure degassing time at 7 - 10 minutes; after the RH vacuum treatment, perform calcium treatment, and ensure a soft blowing time of 10 - 15 minutes after calcium treatment. Stir the molten steel by bottom-blowing argon to promote the floating of inclusions; Continuous casting: The whole process of the tundish during the casting process of the caster is protected by argon. The slag detection equipment is turned on during the casting process of the tundish, and it is ensured that no tundish slag flows into the intermediate ladle at the end of the tundish casting; the casting process of the caster is controlled at a constant casting speed, and the casting speed setting range according to different casting cross-sections is 1.1 m / min to 1.4 m / min; the superheat of the intermediate ladle casting is controlled at 20°C to 35°C; the liquid level fluctuation of the mold is controlled within ±3 mm; Hot rolling process: Heating, rough rolling, finish rolling, cooling, and coiling; where: Heating: Set the soaking time at 25 - 45 minutes; control the furnace outlet temperature at 1190°C - 1210°C; Rough rolling: The rough rolling adopts a 3 + 3 pass mode of rolling. At the same time, the reduction in the first pass is controlled to be 32 - 35 mm; it is required that descaling is carried out in all odd passes; the thickness of the intermediate billet is controlled to be 45 - 50 mm; Finish rolling: The finish rolling adopts 7 passes of rolling; the temperature control during finish rolling is carried out at 950 - 1050°C, and the final rolling temperature is controlled at 830 - 850°C; Cooling: Adopt the laminar water cooling technology for cooling treatment. The laminar cooling rate is controlled at 25 - 40°C / s, and the final cooling temperature is 435°C - 465°C.

2. The preparation method of the steel strip for heavy-duty truck rims with a high-quality tensile strength of 650 MPa according to claim 1, characterized in that: The chemical composition by mass percentage at the BOF tapping is: C ≤ 0.06%, Si ≤ 0.15%, Mn 1.40 - 1.60%, P ≤ 0.015%, S ≤ 0.010%, Alt ≥ 0.040%, Cr 0.20 - 0.30%, and the balance is Fe and inevitable impurities.

3. The preparation method of the steel strip for heavy-duty truck rims with a high-quality tensile strength of 650 MPa according to claim 1, wherein: The chemical composition by mass percentage at the LF tapping is: C 0.065 - 0.085%, Si 0.10 - 0.20%, Mn 1.55 - 1.65%, P ≤ 0.015%, S ≤ 0.005%, Alt 0.020 - 0.040%, Nb 0.05 - 0.06%, Cr 0.20 - 0.30%, and the balance is Fe and inevitable impurities.

4. The preparation method of the steel strip for heavy-duty truck rims with a high-quality tensile strength of 650 MPa according to claim 1, characterized in that: The chemical composition by mass percentage at the RH tapping is: C 0.065 - 0.085%, Si 0.10 - 0.20%, Mn 1.55 - 1.65%, P ≤ 0.015%, S ≤ 0.005%, Alt 0.020 - 0.040%, Nb 0.05 - 0.06%, Cr 0.20 - 0.30%, Ti 0.01 - 0.02%, N 0.0020 - 0.0060%, and the balance is Fe and inevitable impurities.

5. The preparation method of the steel strip for heavy-duty truck rims with a high-quality tensile strength of 650 MPa according to claim 1, characterized in that: The chemical composition by mass percentage of the said steel strip is: C 0.07%, Si 0.14%, Mn 1.56%, P 0.010%, S 0.002%, Alt 0.032%, Nb 0.056%, Cr 0.28%, Ti 0.016%, N 0.0039%, and the balance is Fe and inevitable impurities.

6. The preparation method of the steel strip for heavy-duty truck rims with a high-quality tensile strength of 650 MPa grade according to claim 1, characterized in that: The chemical composition by mass percentage of the said steel strip is: C 0.08%, Si 0.13%, Mn 1.53%, P 0.009%, S 0.002%, Alt 0.033%, Nb 0.054%, Cr 0.27%, Ti 0.013%, N 0.0040%, and the balance is Fe and inevitable impurities.

7. The preparation method of the steel strip for heavy-duty truck rims with a high-quality tensile strength of 650 MPa as described in claim 1, characterized in that: The chemical composition by mass percentage of the said steel strip is: C 0.07%, Si 0.17%, Mn 1.63%, P 0.012%, S 0.001%, Alt 0.029%, Nb 0.058%, Cr 0.25%, Ti 0.018%, N 0.0032%, and the balance is Fe and inevitable impurities.

8. The preparation method of the steel strip for heavy-duty truck rims with a high-quality tensile strength of 650 MPa as claimed in claim 1, characterized in that, The chemical composition by mass percentage of the said steel strip is: C 0.08%, Si 0.15%, Mn 1.50%, P 0.013%, S 0.004%, Alt 0.038%, Nb 0.053%, Cr 0.24%, Ti 0.015%, N 0.0050%, and the balance is Fe and inevitable impurities.

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