High-toughness green surface cleaning steel plate for automobile frame and manufacturing method of high-toughness green surface cleaning steel plate

Abstract

The invention relates to the technical field of steel plates for automobile frames, in particular to a high-toughness green clean-surface steel plate for an automobile frame and a manufacturing method of the high-toughness green clean-surface steel plate. The tensile strength reaches 450 MPa grade or above, the surface cleanliness reaches 3.0 grade, and the steel is prepared from, by weight, 0.06%-0.08% of C, 0.05%-0.15% of Si, 0.95%-1.10% of Mn, 0.015%-0.045% of Als, 0.015%-0.030% of Nb, 0.010%-0.025% of Ti, smaller than or equal to 0.020% of P, smaller than or equal to 0.010% of S and the balance Fe and inevitable impurities. The structure of the finished steel plate is composed of ferrite and pearlite. On the basis of C-Mn series steel components, a low-silicon and low-carbon component system with Nb and Ti added compositely is adopted, hot rolling process control is matched, and wet-type sand blasting descaling treatment is conducted on the surface. The anti-rust oil can be applied to manufacturing of automobile frame parts, has an obvious weight reduction effect, has high surface quality, can be kept rustless for 180 days under the condition that anti-rust oil is not used, and has the advantages of zero pollution, low cost, greenness and cleanness.

Description

Technical Field

[0001] The invention relates to the technical field of steel plates for automobile beams, in particular to a high-toughness green clean-surface steel plate for automobile beams and a manufacturing method thereof. Background Art

[0002] In recent years, with the rapid development of the automobile industry, automobile manufacturers have more and more requirements on the surface quality of steel plates and environmental protection factors. Advanced manufacturing technology, reduced structural quality and green new processes have become the focus of attention of all parties. As an important component of the automobile, lightweight and environmentally friendly manufacturing processes have become new development trends.

[0003] However, in the current production of automobile beams, the first is to use the pickling process technology to remove the iron oxide scale on the surface of the steel plate before forming the beam parts, but the pickling process has defects such as large acid mist pollution, high cost of waste acid treatment, uneven descaling, and large substrate loss; the second is to use the method of adding Cr elements to obtain dense Fe3O4 iron scale on the surface of the steel plate, which can be directly used in the stamping and rolling process of the beam, but occasionally the iron oxide scale falls off and affects production and the cost is high. Therefore, high-surface quality steel plates with excellent processing performance, environmental protection, corrosion resistance, and low cost have become a new demand for industrial development.

[0004] The Chinese patent document with publication number CN103320683A discloses the "production process of thin-gauge high-elongation hot-rolled pickled 610L automobile beam steel strip". Although the thin-gauge high-elongation hot-rolled pickled 610L automobile beam steel produced can replace 510L automobile beam steel, while improving the strength of the frame and related parts, it reduces the thickness of the steel plate used and reduces the weight of the whole vehicle. However, after the heating, rolling and cooling processes, it must pass through a continuous pickling production line and undergo three-stage continuous hydrochloric acid pickling, which has the disadvantages of high acid cost, large acid mist pollution, and high waste acid treatment cost.

[0005] The Chinese patent document with publication number CN106119687B discloses "a high surface quality pickling-free hot-rolled steel strip and its manufacturing method". Although the oxide layer on its surface has higher adhesion and better formability than the iron oxide scale on the surface of black steel, it can effectively avoid the oxide layer from falling off during the stamping process and achieve a surface quality similar to that of pickled and cold-rolled plates. However, its surface roughness cannot be adjusted and its compatibility with subsequent processes is not high.

[0006] The Chinese patent document with publication number CN105369134A discloses "a 400MPa grade pickling-free automotive structural hot-rolled steel plate and its production method". The yield strength of the steel plate is higher than 255MPa, the tensile strength is higher than 400MPa, and the elongation is higher than 34%. The iron oxide scale produced on the surface of this hot-rolled steel product is in the form of Fe3O4+Fe, which has good plasticity and good adhesion. However, it cannot completely avoid peeling and cracking due to bending during the subsequent deep processing, and the surface roughness is uncontrollable; at the same time, the strength of the steel plate is low, and its role in lightweighting the automobile is limited. Summary of the invention

[0007] In order to overcome the shortcomings of the prior art, the present invention provides a high-toughness green clean surface steel plate for automobile beams and a manufacturing method thereof, which can be applied to the manufacture of automobile beam components, has obvious weight reduction effect, has high surface quality, can remain rust-free for 180 days without using anti-rust oil, and has the advantages of zero pollution, low cost, and green cleaning.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A high-toughness green clean surface steel plate for automobile beams, with a tensile strength of 450MPa or above and a surface cleanliness of 3.0, is composed of the following chemical components in percentage by weight:

[0010] C: 0.06%~0.08%, Si: 0.05%~0.15%, Mn: 0.95%~1.10%, Als: 0.015%~0.045%, Nb: 0.015%~0.030%, Ti: 0.010%~0.025%, P≤0.020%, S≤0.010%, and the balance is Fe and unavoidable impurities.

[0011] Furthermore, the yield strength of the steel plate is higher than 380 MPa, and the elongation A is ≥ 25%.

[0012] Furthermore, the roughness of the steel plate is less than 2.5 μm.

[0013] Furthermore, the final structure of the steel plate is ferrite and pearlite, with ferrite accounting for 95%.

[0014] A method for manufacturing a high-toughness green clean surface steel plate for an automobile beam, the manufacturing method specifically comprising the following steps:

[0015] 1) Heating process:

[0016] The continuous casting slab is heated to 1200-1250°C in a heating furnace and kept warm for 1-2 hours;

[0017] 2) Rolling process:

[0018] The starting temperature of finishing rolling is 1020~1080℃, and the final rolling temperature is 860~910℃;

[0019] 3) Cooling process:

[0020] After final rolling, the front-stage cooling method is adopted, and the coiling temperature is 580-620℃;

[0021] 4) Wet sandblasting descaling process:

[0022] The sandblasting descaling treatment temperature of steel coil is less than 60℃, the steel plate travel speed in the process section is 30-50m / min, the steel grit mesh number is 30-50, the steel grit hardness is HRC55-60, the sandblasting motor speed is 1800-2200rpm, and the medium is water-based rust inhibitor.

[0023] Furthermore, in the step 2), the thickness of the finished product is 2 to 12 mm.

[0024] Furthermore, in the step 4), straightening is performed after uncoiling.

[0025] Furthermore, in the step 4), the hardness of the steel sand is HRC57.

[0026] Furthermore, in the step 4), the speed of the sandblasting motor is 2000 rpm.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. Based on the C-Mn steel composition, the present invention adopts a low-silicon, low-carbon, composite Nb and Ti addition component system, cooperates with the hot rolling process control to utilize the solid solution strengthening and fine grain strengthening principles, and performs wet sandblasting descaling treatment on the surface to obtain a green clean surface steel plate for automobile structure with a tensile strength of 450MPa or above and an elongation A ≥ 25%.

[0029] 2. The conventional pickling process is a strong acid with high pollution. A large amount of pollution will be generated during the pickling process, posing a threat to the environment and the health of operators.

[0030] The present invention is a wet sandblasting descaling treatment process, which utilizes a physical method to remove iron scale. Compared with chemical pickling, no waste acid is discharged, and the process has the advantages of being clean and pollution-free.

[0031] 3. Compared with the pickling process, the process of removing iron oxide scale from the surface of the steel plate produced by the present invention can process steel plates with a thickness exceeding 6 mm, thereby expanding the product range.

[0032] 4. Compared with the pickling products, the products produced by the present invention can be adjusted according to the requirements of users by adjusting the steel sand particle size and adjusting the steel plates with different surface roughness, so as to better match the requirements of subsequent processing procedures for the surface quality of the steel plates.

[0033] 5. In the process of wet sandblasting descaling in the present invention, the medium is a water-based rust inhibitor, and the sandblasting liquid has an anti-corrosion function, which can ensure that the steel plate will not rust when stored for 180 days without oiling.

[0034] 6. The traditional pickling process requires the treatment of waste acid. The steel sand in the wet sandblasting descaling process of the present invention can be recycled. Compared with the traditional pickling process, the present invention reduces production costs and reduces the generation of process waste.

[0035] In summary, the steel plate of the present invention has excellent comprehensive performance, yield strength ≥380MPa, tensile strength ≥450MPa, elongation ≥25%, roughness less than 2.5μm, surface cleanliness reaching level 3.0, and good formability. It can be applied to the manufacture of automobile beam parts, with obvious weight reduction effect, and can remain rust-free for 180 days without using anti-rust oil. Moreover, the manufacturing method of the present invention has the advantages of zero pollution, low cost, and green cleaning. DETAILED DESCRIPTION

[0036] The present invention discloses a high-toughness green clean surface steel plate for automobile beams and a method for manufacturing the same. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve the same. It is particularly important to point out 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 method and application of the present invention have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the method and application described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0037] A high-toughness green clean surface steel plate for automobile beams, with a tensile strength of 450MPa or above, a surface cleanliness of level 3.0, a steel plate yield strength higher than 380MPa, an elongation A ≥ 25%, a steel plate roughness less than 2.5μm, and a final structure of the steel plate of ferrite and pearlite, with ferrite accounting for 95%.

[0038] The above-mentioned high-toughness green clean surface steel plate for automobile beams is composed of the following chemical components in percentage by weight:

[0039] C: 0.06%~0.08%, Si: 0.05%~0.15%, Mn: 0.95%~1.10%, Als: 0.015%~0.045%, Nb: 0.015%~0.030%, Ti: 0.010%~0.025%, P≤0.020%, S≤0.010%, and the balance is Fe and unavoidable impurities.

[0040] Based on the cost and comprehensive performance of the steel plate, the components and main functions of the steel plate in the present invention are:

[0041] C: It is a strong solid solution strengthening element, which can significantly improve the strength of steel. If the C content in steel is too low, the content of other elements that increase the strength of the steel plate will increase accordingly, which is not conducive to reducing the cost of the steel plate. If the C content is too high, the strength of the steel plate will increase, but the elongation will decrease, which is not conducive to the forming of the steel plate. Taking comprehensive considerations, the C content in steel is limited to between 0.06% and 0.08%.

[0042] Si: replaces solid solution alloy elements, promotes C enrichment in austenite and increases the stability of austenite. At the same time, it can play a deoxidation role and reduce impurities in steel. Too low Si content is not conducive to deoxidation and increasing the stability of austenite. Too high Si content will reduce the surface quality of the steel plate. Therefore, the present invention limits the content of Si element in steel to 0.05% to 0.15%.

[0043] Mn: Improves the hardenability of steel plates and helps obtain martensite structure under controlled cooling rate. Too low a content will not produce significant results, while too high a content will increase production costs. Therefore, its content is limited to 0.95% to 1.10%.

[0044] S, P: harmful elements, the lower the content, the better. Too low content will increase production cost. Under the premise of not affecting the performance of steel plate, the content is limited to p≤0.020%, S≤0.010%.

[0045] Nb: Niobium can refine ferrite grains. At the same time, niobium combines with carbon and nitrogen to form small carbonitrides, which can also delay recrystallization, prevent austenite grain growth, and have a significant precipitation strengthening effect. However, too high a niobium content will have an adverse effect on ferrite phase transformation, so the optimal range of niobium content in the present invention is Nb: 0.015% to 0.030%.

[0046] Ti: Titanium has the effects of precipitation strengthening, fine grain strengthening and inhibiting austenite recrystallization. Adding niobium and titanium elements in steel can effectively increase the precipitation of carbonitrides and significantly improve the strength and cold forming performance of the steel plate through precipitation strengthening. The optimal range of titanium content in the present invention is between 0.010% and 0.025%.

[0047] Als: Aluminum is a deoxidizing element in steel, which reduces oxide inclusions in steel, purifies steel, and is beneficial to improving the formability of steel plates. At the same time, aluminum can form AlN precipitation, which plays a certain role in grain refinement. The optimal range of aluminum is between 0.015 and 0.045%.

[0048] The present invention adopts the above chemical composition to produce a green and clean surface automobile structural steel plate through smelting, hot rolling and wet sandblasting descaling treatment processes. The specific manufacturing method includes the following steps:

[0049] (1) Heating process: The continuous casting slab is heated to 1200-1250°C in a heating furnace and kept warm for 1-2 hours to allow the alloy elements in the slab to be completely dissolved and the composition of the slab to be uniform.

[0050] (2) Rolling process: controlled rolling is adopted, the starting temperature of finishing rolling is 1020-1080℃, the final rolling temperature is 860-910℃, and the finished product thickness is 3-12mm.

[0051] (3) Cooling process: After final rolling, the front-end cooling method is adopted, and the coiling temperature is 580-620℃.

[0052] The steel plate is rolled flat before wet sandblasting descaling.

[0053] (4) Wet sandblasting descaling process: The sandblasting descaling temperature of the steel coil is less than 60°C, and the coil is straightened after unwinding. The steel plate travel speed in the process section is 30-50 m / min, the steel grit number is 30-50, the hardness is HRC57, and the sandblasting motor speed is 1800-2200 rpm.

[0054] [Example]

[0055] The chemical composition (wt%) of the steel plate of the embodiment of the present invention is shown in Table 1; the main production process parameters of the steel plate of the corresponding embodiment are shown in Table 2; and the mechanical properties of the steel plate of the corresponding embodiment are shown in Table 3.

[0056] Table 1 Chemical composition of the present invention (wt, %)

[0057] C Si Mn P S Als Nb Ti N Example 1 0.080 0.14 1.10 0.013 0.002 0.036 0.023 0.022 0.002 Example 2 0.060 0.05 1.02 0.018 0.003 0.044 0.030 0.015 0.003 Example 3 0.075 0.15 0.95 0.011 0.005 0.038 0.016 0.020 0.004 Example 4 0.061 0.07 0.97 0.010 0.001 0.027 0.022 0.023 0.001 Example 5 0.073 0.08 1.06 0.012 0.009 0.015 0.019 0.019 0.003

[0058] Table 2 Production process of the embodiment of the present invention

[0059]

[0060] Table 3 Organization and mechanical properties parameters of the embodiments of the present invention

[0061]

[0062]

[0063] As shown in Table 3, the steel plate of the present invention has excellent comprehensive performance, yield strength ≥380MPa, tensile strength ≥450MPa, elongation ≥25%, roughness less than 2.5μm, surface cleanliness reaching level 3.0, and good formability. It can be applied to the manufacture of automobile beam parts, with obvious weight reduction effect, and has the characteristics of high surface quality, zero pollution, low cost, and green cleaning.

[0064] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. High toughness green clean surface steel plate for automobile beam, characterized by: The steel plate has a tensile strength of 450 MPa or above, a surface cleanliness of 3.0, and is composed of the following chemical components in percentage by weight: C: 0.06%~0.08%, Si: 0.05%~0.15%, Mn: 0.95%~1.10%, Als: 0.015%~0.045%, Nb: 0.015%~0.030%, Ti: 0.010%~0.025%, P≤0.020%, S≤0.010%, and the balance is Fe and unavoidable impurities.

2. The high-toughness green clean surface steel plate for automobile beams according to claim 1, characterized in that: The steel plate has a yield strength higher than 380 MPa and an elongation A≥25%.

3. The high-toughness green clean surface steel plate for automobile beams according to claim 1, characterized in that: The steel plate has a roughness less than 2.5 μm.

4. The high-toughness green clean surface steel plate for automobile beams according to claim 1, characterized in that: The final structure of the steel plate is ferrite and pearlite, with ferrite accounting for 95%.

5. A method for manufacturing a high-toughness green clean surface steel plate for automobile beams as claimed in any one of claims 1 to 4, characterized in that: The manufacturing method specifically comprises the following steps: 1) Heating process: The continuous casting slab is heated to 1200-1250°C in a heating furnace and kept warm for 1-2 hours; 2) Rolling process: The starting temperature of finishing rolling is 1020~1080℃, and the final rolling temperature is 860~910℃; 3) Cooling process: After final rolling, the front-stage cooling method is adopted, and the coiling temperature is 580-620℃; 4) Wet sandblasting descaling process: The sandblasting descaling treatment temperature of steel coil is less than 60℃, the steel plate travel speed in the process section is 30-50m / min, the steel grit mesh number is 30-50, the steel grit hardness is HRC55-60, the sandblasting motor speed is 1800-2200rpm, and the medium is water-based rust inhibitor.

6. The method for manufacturing a high-toughness green clean surface steel plate for automobile beams according to claim 5, characterized in that: In the step 2), the thickness of the finished product is 2 to 12 mm.

7. The method for manufacturing a high-toughness green clean surface steel plate for automobile beams according to claim 5, characterized in that: In the step 4), straightening is performed after uncoiling.

8. The method for manufacturing a high-toughness green clean surface steel plate for automobile beams according to claim 5, characterized in that: In the step 4), the hardness of the steel sand is HRC57.

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