High-strength and low-yield ratio thin steel plate for concrete mixer truck and manufacturing method thereof

Abstract

The present invention relates to the technical field of hot-rolled high-strength steel production, specifically a high-strength and toughness, low-yield ratio thin steel plate for concrete mixer trucks and its manufacturing method. The steel plate comprises the following chemical components by weight: C: 0.10% to 0.15%, Si: 0.60% to 0.90%, Mn: 0.80% to 1.00%, P ≤ 0.015%, S ≤ 0.005%, Al: 0.25% to 0.29%, Cr: 0.40% to 0.60%, N ≤ 0.0040%, H ≤ 0.00020%, Nb: 0.008% to 0.030%, with the remainder being Fe and unavoidable impurities. Production costs are significantly reduced, and the product exhibits excellent performance, including high tensile strength, low yield ratio, good plasticity and toughness, high wear resistance, good fracture resistance, good formability, and low-temperature impact toughness. It can be a low-cost, comprehensive replacement for existing concrete mixer truck tank and blade manufacturing materials.

Description

Technical Field

[0001] The present invention relates to the technical field of hot-rolled high-strength steel production, in particular to a high-strength and toughness, low-yield ratio thin steel plate for a concrete mixer truck and a manufacturing method thereof. Background Art

[0002] Concrete mixer trucks are a type of engineering machinery used to transport bulk materials such as cement, sand, gravel, and lime paste. They offer advantages such as high mixing speed and excellent maneuverability. In the context of green manufacturing and low-carbon environmental protection, concrete mixer trucks are increasingly focusing on product structural upgrades aimed at high strength, reduced weight, and environmentally friendly longevity. Lightweight, safe, and reliable concrete mixer trucks are key development areas, placing high demands on steel materials, such as higher strength and greater wear resistance.

[0003] Currently, low-alloy materials such as Q345B and 520JJ are commonly used to manufacture the tanks and blades of concrete mixer trucks. These materials do not meet the requirements for lightweighting concrete mixer trucks. Although higher-strength materials such as 620JJ and 750JJ have been developed to upgrade product materials, the improvement in material strength is minimal, and the weight reduction effect is not significant. Traditional high-strength wear-resistant steel is mainly manufactured using the traditional offline quenching and low-temperature tempering process. Although this steel exhibits excellent strength and wear resistance, it lacks plasticity and formability, making it unsuitable for use in concrete mixers.

[0004] Chinese patent publication CN108411203A discloses "NM300 wear-resistant steel for high-silicon and high-aluminum concrete mixer trucks and its production method." While it has high tensile strength and surface Brinell hardness, a relatively low yield ratio, and superior wear resistance compared to conventional high-strength steel for concrete mixer trucks, its high Si and Al contents make it difficult to smelt and assure the quality of the ingots. Chinese publication CN108411203A discloses "NM300 wear-resistant steel with a strength of 1100 MPa and a low yield ratio for concrete mixer trucks and its preparation method." While it has high tensile strength and a relatively low yield ratio, its high Si and Al contents make it difficult to smelt and assure the quality of the ingots. Furthermore, it suffers from unstable cooling process control, large fluctuations in the proportions of various microstructures, and poor performance stability.

[0005] In summary, providing a steel plate with low cost, higher strength level, good processing performance and wear resistance to meet the requirements of concrete mixers for steel materials has become a technical problem to be solved in this field. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, the present invention provides a high-strength, low-yield ratio steel plate for concrete mixer trucks and its manufacturing method. This significantly reduces production costs while offering excellent product performance, including high tensile strength, low yield ratio, good plasticity and toughness, high wear resistance, good fracture resistance, good formability, and low-temperature impact toughness. This plate can be a low-cost, comprehensive replacement for existing concrete mixer truck tank and blade materials.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A hot-rolled thin steel plate for concrete mixer trucks with a Brinell hardness of 300 HBW, high strength, high toughness, and low yield ratio is composed of the following chemical components in percentage by weight: C: 0.10% to 0.15%, Si: 0.60% to 0.90%, Mn: 0.80% to 1.00%, P≤0.015%, S≤0.005%, Al: 0.25% to 0.29%, Cr: 0.40% to 0.60%, N≤0.0040%, H≤0.00020%, Nb: 0.008% to 0.030%, and the remainder being Fe and unavoidable impurities.

[0009] The present invention adopts an economical C-Mn composition design, adds appropriate amounts of Si and Al alloys, and supplements with a small amount of micro-alloying elements such as Cr and Nb. It does not need to add precious alloying elements such as Ni and Mo, and does not require offline quenching + tempering heat treatment, thereby greatly reducing production costs.

[0010] The hot-rolled thin steel plate of the present invention has a thickness of 6 mm or less, a tensile strength of 1000 MPa or more, a yield ratio of 0.70 or less, an elongation of 16% or more, a hardness of 300 ± 30 HBW, and an impact energy value of more than 35 J at -40°C. The product has excellent performance, including high tensile strength, low yield ratio, good plasticity and toughness, high wear resistance, good fracture resistance, formability, and low-temperature impact toughness.

[0011] A method for manufacturing a hot-rolled thin steel plate with a Brinell hardness of 300 HBW, high strength, high toughness, and low yield ratio for a concrete mixer truck, specifically comprising the following steps:

[0012] 1. Smelting and casting

[0013] Smelt and cast into billets according to the above ingredients.

[0014] 2. Slab reheating

[0015] The slab needs to be hot loaded into the heating furnace. Hot loading can prevent the slab from cracking after cooling to room temperature. The loading temperature is ≥500℃.

[0016] The heating temperature is 1240-1260℃, and the holding time is 150-200 minutes, including a soaking time of 30-50 minutes. During hot rolling of thin steel strips, the deformation resistance is relatively high, and the rolling mill load is relatively high. Therefore, the slabs must be evenly and thoroughly burned to ensure rolling stability.

[0017] 3. Controlled rolling

[0018] Rolling is divided into two stages: rough rolling and finishing rolling.

[0019] Large reduction rolling is adopted in the rough rolling stage. Depending on the thickness of the slab, rough rolling can be carried out in 4 to 7 passes, with a pass reduction rate of more than 22%, a thickness ratio of the intermediate slab to the finished product ≥5, and the end temperature of rough rolling is 1110 to 1150°C.

[0020] The thickness ratio of the intermediate billet to the finished product is ≥5 in order to ensure a larger compression ratio and obtain a fine grain size to improve the structure of the steel.

[0021] The insulation cover of the intermediate roller table between rough rolling and finishing rolling is put into use, and the hot coil box is put into use before finishing rolling.

[0022] The finishing rolling inlet temperature is 1060-1090°C, and the finishing rolling process consists of seven stands. The reduction rate of the first three passes is no less than 40%, and the reduction rate of the final pass is controlled to no more than 15%. The final rolling temperature is controlled at 930-950°C. The finishing rolling is carried out at a constant speed of 5-10m / s. This ensures a high reduction rate in the upstream stands, reducing the burden on the downstream stands and ensuring rolling stability in the downstream. The final stand has a low reduction rate, which better controls the plate shape.

[0023] 4. Controlled cooling

[0024] After rolling, the steel plate enters the cooling area and the cooling method is two-stage cooling. The front stage adopts ultra-fast cooling with a cooling rate of 40-70℃ / s and a cooling temperature of 620-670℃. Then it is air-cooled with an air cooling time of 9-14s. After air cooling, it is quickly cooled by laminar flow with a cooling rate of ≥20℃ / s. It is coiled after cooling to 210-290℃.

[0025] The goal is to ensure that part of the austenite is transformed into ferrite, and rapid cooling ensures that the ferrite grain structure is fine. The purpose is to ensure that the steel plate has good plasticity, thus giving it a certain degree of formability. After air cooling and rapid cooling, the remaining austenite is transformed into martensite, ensuring that the steel plate has high strength and hardness, thus giving the steel plate excellent wear resistance.

[0026] Finally, a ferrite + martensite structure + a small amount of retained austenite is obtained, wherein the ferrite structure is 25-35%, the retained austenite is within 5%, and the rest is martensite.

[0027] 5. Leveling, shearing and straightening

[0028] The rolled steel strip is leveled by a leveler with a leveling force controlled at 7000-10000KN. The leveler uses positive bending rollers with a bending roller force ≥ 5% of the leveling force.

[0029] After low temperature cooling, the steel strip has poor shape. After being leveled with high leveling force and appropriate bending force, the shape is greatly improved. After the steel strip is cut into steel plates, it is straightened by a straightening machine to eliminate residual stress and further improve the shape.

[0030] The flattened steel strip is cross-cut into steel plates of the size required by the user, and is straightened with a straightening machine to ensure that the unevenness of the steel plate meets 5mm / m.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The present invention adopts an economical C-Mn composition design, adds an appropriate amount of Si and Al alloys, supplemented by a small amount of micro-alloying elements such as Cr and Nb, does not require the addition of precious alloying elements such as Ni and Mo, and does not require offline quenching + tempering heat treatment, greatly reducing production costs.

[0033] The slab is hot-charged into the heating furnace by controlling the heating temperature and the holding time, controlling the reduction of the rolling mill, setting higher rough rolling end temperature, finishing rolling entrance temperature and final rolling temperature, and putting in an intermediate roller insulation cover and a hot coil box, thereby ensuring the temperature of the rolled piece and the stability of rolling.

[0034] The present invention adopts large reduction rolling in the rough rolling stage, controls the thickness ratio of the intermediate billet to the finished product, and other means to obtain fine grain size and thus improve the structure of the steel.

[0035] After rolling, the steel plate enters the cooling zone. The front section adopts ultra-dense rapid cooling with a cooling rate of 40-70℃ / s, a cooling temperature of 620-670℃, and an air cooling time of 9-14s. This is to quickly cool the strip steel to the ferrite transformation temperature range after rolling, ensuring that part of the austenite is transformed into ferrite. Rapid cooling is to ensure that the ferrite grain structure is small, its purpose is to ensure that the steel plate has good plasticity and thus has a certain degree of formability. After air cooling, rapid cooling is carried out with a cooling rate of ≥20℃ / s to 210-290℃. The remaining austenite is transformed into martensite, ensuring that the steel plate has high strength and hardness, thus giving the steel plate excellent wear resistance.

[0036] Adding an appropriate amount of Si and Al elements to the steel can reduce the austenite region and expand the ferrite phase transformation window, which is beneficial for obtaining a certain proportion of ferrite by controlling cooling. The steel plate of the present invention obtains about 25-35% ferrite, about 5% residual austenite, and the rest martensite by controlling the components such as Si and Al elements and staged cooling. The ferrite phase can effectively reduce the yield strength of the steel plate and improve the plasticity and cold formability of the steel plate, while the martensite phase can greatly increase the tensile strength of the steel plate and improve the wear resistance of the steel plate. The lower yield strength and high tensile strength make the steel have a lower yield strength ratio, thereby making the steel plate have higher fracture resistance. The high steel purity and uniform and fine structure ensure that the steel plate has higher low-temperature impact toughness.

[0037] 2. The composition design of the present invention cooperates with the comprehensive effects of controlled rolling and controlled cooling to ensure that the hot-rolled thin steel plate with a thickness of ≤6 mm has a tensile strength of more than 1000 MPa, a yield ratio of ≤0.70, an elongation of ≥16%, a hardness of 300±30 HBW, and an impact energy value of more than 35 J at -40°C.

[0038] 3. This invention controls strip shape by using a high reduction ratio in the upstream stand and a low reduction ratio in the downstream stand during finishing. High leveling force and appropriate bending roll force are used during flattening, significantly improving strip shape. After the strip is cut into plates, it is straightened in a leveler to eliminate residual stress and further improve the shape. The finished plate has an unevenness of 5 mm / m, ensuring excellent applicability.

[0039] In summary, the present invention's hot-rolled steel plate, with a Brinell hardness of 300 HBW, high strength and toughness, and low yield ratio, significantly reduces production costs while offering excellent product performance, including high tensile strength, low yield ratio, good plasticity and toughness, high wear resistance, good fracture resistance, good formability, and low-temperature impact toughness. This invention can be a comprehensive, low-cost alternative to existing concrete mixer truck tank and blade manufacturing materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is the metallographic organization diagram of the present invention. DETAILED DESCRIPTION

[0041] The present invention provides a high-strength and toughness, low-yield ratio thin steel plate for concrete mixer trucks and a method for manufacturing the same. Those skilled in the art can refer to the contents of this article and appropriately improve the process parameters to achieve the desired effect. It should be noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in the present invention. The methods and applications of the present invention have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0042] A hot-rolled thin steel plate for concrete mixer trucks with a Brinell hardness of 300 HBW, high strength, high toughness, and low yield ratio is composed of the following chemical components in percentage by weight: C: 0.10% to 0.15%, Si: 0.60% to 0.90%, Mn: 0.80% to 1.00%, P≤0.015%, S≤0.005%, Al: 0.25% to 0.29%, Cr: 0.40% to 0.60%, N≤0.0040%, H≤0.00020%, Nb: 0.008% to 0.030%, and the remainder being Fe and unavoidable impurities.

[0043] Reasons for designing the chemical composition of the present invention:

[0044] C: 0.10% to 0.15%. Carbon improves the hardenability of the steel plate and has a strong solid solution strengthening effect, significantly increasing the strength and hardness of high-wear-resistant martensitic wear-resistant steel plates. An appropriate amount of carbon combines with titanium to form TiC particles, which significantly improves wear resistance. If the carbon content is too high, the volume fraction of the TiC particles formed will be too high, reducing the elongation and impact energy performance of the high-wear-resistant martensitic wear-resistant steel plate and deteriorating its weldability.

[0045] Si: 0.60% to 0.90%. Si plays a role in solid solution strengthening in steel. Adding Si to metal materials can significantly improve the strength and hardness of the material. In addition, a higher Si content can expand the formation of ferrite phase.

[0046] Mn: 0.80% to 1.00%. Adding Mn to metal materials can expand the austenite region. In addition, this element can significantly improve the hardenability of steel, thereby obtaining more martensite at the same cooling rate. Increased Mn content can increase the high-temperature temper brittleness and heat sensitivity of the steel.

[0047] P ≤ 0.015%, S ≤ 0.005%. Sulfur combines with manganese and other elements in steel to form plastic inclusions called manganese sulfide, which is particularly detrimental to the steel's transverse plasticity and toughness. Therefore, the sulfur content should be kept as low as possible. Phosphorus is also a harmful element in steel, severely impairing the plasticity and toughness of the steel plate. For the purposes of the present invention, sulfur and phosphorus are unavoidable impurity elements and should be kept as low as possible.

[0048] Cr: 0.40% to 0.60%. It can reduce the austenite phase area. Due to the outstanding bonding ability of chromium atoms with carbon atoms, they can form different carbides with the carbon in the steel. At the same time, chromium can sometimes replace some iron atoms in the cementite, thereby forming cementite containing chromium atoms. Cr can also improve the hardenability of steel. This is because the amount of this element in cementite is greater than that in the solid solution. Therefore, when phase transformation occurs, Cr will inevitably diffuse from the cementite to the solid solution. However, due to the small intergranular gaps in austenite, diffusion is more difficult. During the diffusion process, Cr must combine with C atoms, which will slow down the diffusion rate of the C element and ultimately delay the decomposition time of austenite.

[0049] Al: 0.25% to 0.30%. Adding an appropriate amount of Al can accelerate the transformation kinetics of austenite to proeutectoid ferrite during the air cooling stage of the steel plate. On the other hand, the increase in Al content can increase the carbon content in the retained austenite, thereby improving the thermal stability of the retained austenite, and more retained austenite is retained during the cooling process.

[0050] Nb: 0.008% to 0.030%. A strong carbonitride-forming element, its role in steel is similar to that of Ti, primarily through the formation of small, stable MX-type precipitates, which inhibit grain growth at high temperatures and provide precipitation strengthening at low temperatures. The effects of Nb microalloying are particularly pronounced when combined with hot deformation techniques such as controlled rolling and controlled cooling.

[0051] A method for manufacturing a hot-rolled thin steel plate with a Brinell hardness of 300 HBW, high strength, high toughness, and low yield ratio for a concrete mixer truck, specifically comprising the following steps:

[0052] 1. Smelting and casting

[0053] Smelt and cast into billets according to the above ingredients.

[0054] 2. Slab reheating

[0055] The slab needs to be hot loaded into the heating furnace with a charging temperature of ≥500°C. The heating temperature is 1240-1260°C and the holding time is 150-200 minutes, including a soaking time of 30-50 minutes.

[0056] 3. Controlled rolling

[0057] Rolling is divided into two stages: roughing and finishing. Roughing employs high-reduction rolling. Depending on the slab thickness, roughing can be performed in 4 to 7 passes, with a reduction of at least 22% per pass. The intermediate slab to finished product thickness ratio should be ≥5, and the roughing end temperature is 1110-1150°C. An insulation cover is installed between the roughing and finishing stages, and a hot coil box is added before finishing. The finishing inlet temperature is 1060-1090°C. Finishing consists of seven continuous stands, with the first three passes achieving a reduction of no less than 40%, and the final pass achieving a reduction of no more than 15%. The final rolling temperature is controlled between 930-950°C. Finishing is performed at a constant speed within the range of 5-10 m / s.

[0058] 4. Controlled cooling

[0059] After rolling, the steel plate enters the cooling area and the cooling method is two-stage cooling. The front stage adopts ultra-fast cooling with a cooling rate of 40-70℃ / s and a cooling temperature of 620-670℃. Then it is air-cooled with an air cooling time of 9-14s. After air cooling, it is quickly cooled by laminar flow with a cooling rate of ≥20℃ / s. It is coiled after cooling to 210-290℃.

[0060] Finally, a ferrite + martensite structure + a small amount of retained austenite is obtained, wherein the ferrite structure is 15-30%, the retained austenite is within 5%, and the rest is martensite.

[0061] 5) Leveling, shearing and straightening

[0062] After rolling, the steel strip is leveled in a leveler with a leveling force controlled between 7,000 and 10,000 kN. The leveler uses positive bending rollers with a bending force ≥ 5% of the leveling force. The leveled steel strip is then cross-cut into steel plates of the desired size and straightened in a leveler to a flatness of 5 mm / m.

[0063] In the method for producing the steel plate of the present invention:

[0064] Slabs must be hot-charged into the furnace at a temperature ≥500°C to prevent cracking after cooling to room temperature. The heating temperature is 1240-1260°C, and the holding time is 150-200 minutes, including a soaking time of 30-50 minutes. This thin steel strip exhibits significant deformation resistance during hot rolling, placing high mill loads. Therefore, the slabs must be evenly and thoroughly fired to ensure rolling stability.

[0065] Rolling is divided into two stages: roughing and finishing. To achieve a fine, original austenite grain size, the roughing stage uses a high reduction ratio for the cast slab, with the reduction ratio controlled at above 22%. The thickness ratio of the intermediate slab to the finished product is ≥5, ensuring a high reduction ratio and fine grain size, thereby improving the steel structure. Finishing consists of seven stands, with the first three passes achieving a reduction ratio of no less than 40%. This ensures high reduction in the upstream stands, reduces the burden on downstream stands, and ensures rolling stability. The final pass of finishing is controlled to no more than 15%, ensuring a low reduction in the final stand for better control of plate shape.

[0066] Setting a higher rough rolling end temperature, finishing rolling entrance temperature, final rolling temperature and investing in intermediate roller insulation covers and hot coil boxes are to ensure the temperature of the rolled pieces and facilitate stable rolling.

[0067] The finishing rolling speed of each piece of steel must be kept constant to prevent excessive cooling rate fluctuations during the cooling process, ensuring a constant ferrite-martensite ratio throughout the rolled strip, and minimizing differences in mechanical properties. The rolling speed is controlled within the range of 5-10 m / s to ensure a reasonable rolling speed. If the rolling speed is too slow, the rolling temperature cannot be guaranteed, while if the rolling speed is too fast, rolling stability and cooling accuracy control will be affected.

[0068] After rolling, the steel plate enters the cooling zone. The front section adopts ultra-dense rapid cooling with a cooling rate of 40-70℃ / s, a cooling temperature of 620-670℃, and an air cooling time of 9-14s. This is to quickly cool the strip steel to the ferrite transformation temperature range after rolling, ensuring that part of the austenite is transformed into ferrite. Rapid cooling is to ensure that the ferrite grain structure is small, its purpose is to ensure that the steel plate has good plasticity and thus has a certain degree of formability. After air cooling, rapid cooling is carried out at a cooling rate of ≥20℃ / s to 210-290℃. The remaining austenite is transformed into martensite, ensuring that the steel plate has high strength and hardness, thus giving the steel plate excellent wear resistance.

[0069] After low-temperature cooling, the steel strip has poor flatness. However, after flattening with high leveling force and appropriate bending roller force, the flatness is significantly improved. After the steel strip is cut into steel plates, they are straightened in a leveler to eliminate residual stress and further improve the flatness. The finished steel plates have an unevenness of 5mm / m, ensuring excellent applicability.

[0070] The hot-rolled steel plate of the present invention has a thickness of ≤6mm, a tensile strength of more than 1000MPa, a yield ratio of ≤0.70, an elongation of ≥16%, a hardness of 300±30HBW, and an impact energy value of more than 35J at -40°C.

[0071] [Example]

[0072] The chemical composition (Wt%) of the embodiment of the present invention is shown in Table 1; the key process parameters of rolling of the embodiment of the present invention are shown in Table 2; the key process parameters of rolling and flattening of the embodiment of the present invention are shown in Table 3; the yield strength, tensile strength, yield strength ratio, hardness, impact energy, and flatness parameters of the present invention are shown in Table 4.

[0073] Table 1 Specific chemical composition of the examples

[0074]

[0075] Table 2 Key rolling process parameters

[0076]

[0077] Table 3 Key process parameters of rolling and tempering

[0078]

[0079] Table 4 Technical performance table

[0080]

[0081] like Figure 1 As shown, the structure of the thin steel plate is ferrite + martensite + a small amount of retained austenite, of which the ferrite structure is 20-35%, the retained austenite is within 5%, and the rest is martensite.

[0082] The present invention provides a hot-rolled thin steel plate for concrete mixer trucks with a Brinell hardness of 300 HBW, high strength, high toughness, and a low yield ratio, and a manufacturing method thereof. This significantly reduces production costs while offering excellent product performance, including high tensile strength, a low yield ratio, good plasticity and toughness, high wear resistance, good fracture resistance, good formability, and low-temperature impact toughness. This plate can be a low-cost, comprehensive replacement for existing materials used in the manufacturing of concrete mixer truck tanks and blades.

[0083] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for manufacturing a high-strength and low-yield ratio thin steel plate for a concrete mixer truck, characterized in that: The steel plate is composed of the following chemical components in percentage by weight: C: 0.10%~0.15%, Si: 0.60%~0.68%, Mn: 0.80%~0.98%, P≤0.015%, S≤0.005%, Al: 0.25%~0.29%, Cr: 0.40%~0.60%, N≤0.0040%, H≤0.00020%, Nb: 0.008%~0.030%, the rest is Fe and unavoidable impurities; The steel plate has a thickness of ≤6 mm, a tensile strength of 1000 MPa or more, a yield strength ratio of ≤0.70, an elongation of ≥16%, a hardness of 300±30 HBW, and an impact energy value of more than 35 J at -40°C; The steel plate structure is ferrite + martensite + a small amount of retained austenite, of which ferrite is 20-35%, retained austenite is within 5%, and the rest is martensite; The specific steps include: 1) Smelting and casting Smelting and casting into billets according to the above ingredients; 2) Slab reheating The slab is hot loaded into the heating furnace, and the charging temperature is ≥500℃; Heating temperature 1240~1260℃, holding time 150~200min, including soaking time 30~50min; 3) Controlled rolling Rolling is divided into two stages: rough rolling and finishing rolling; The rough rolling stage adopts large reduction rolling, the pass reduction rate is above 22%, the thickness ratio of the intermediate billet to the finished product is ≥5, and the rough rolling end temperature is 1110~1150℃; The finishing rolling inlet temperature is 1060~1090℃, and the finishing rolling is carried out in a multi-stand continuous rolling process. The reduction rate of the first three passes is not less than 40%, and the reduction rate of the last pass of the finishing rolling is controlled not to exceed 15%. The final rolling temperature is controlled at 930~950℃. The finishing rolling is carried out at a constant speed, and the rolling speed is controlled at 5~10m / s. 4) Controlled cooling The cooling method is two-stage cooling. The front stage adopts ultra-fast cooling with a cooling rate of 40~70℃ / s, cooling to a temperature of 620~670℃, and then air cooling with an air cooling time of 11~14s. After air cooling, laminar rapid cooling with a cooling rate of ≥20℃ / s is carried out, and coiling is carried out after cooling to 210~290℃. 5) Leveling, shearing and straightening The rolled steel strip is leveled by a leveler, the leveling force is controlled at 7000~10000KN, the bending roll force is ≥5% of the leveling force, and the steel plate unevenness is controlled below 5mm / m.

2. The method for manufacturing a high-strength and low-yield ratio thin steel plate for a concrete mixer truck according to claim 1, characterized in that: In the step 3), a heat-insulating cover is put into the intermediate roller table between rough rolling and finishing rolling, and a hot coil box is put into the hot coil box before finishing rolling.

3. The method for manufacturing a high-strength and low-yield ratio thin steel plate for a concrete mixer truck according to claim 1, characterized in that: In the step 5), the leveling machine adopts positive bending rollers.

4. The method for manufacturing a high-strength and low-yield ratio thin steel plate for a concrete mixer truck according to claim 1, characterized in that: In step 5), the flattened steel strip is cross-cut.

5. The method for manufacturing a high-strength and low-yield ratio thin steel plate for a concrete mixer truck according to claim 1, characterized in that: In step 5), straightening is performed using a straightening machine.

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