A low-cost high-formability 650mpa-grade pickling high-strength steel and its manufacturing method and application

Abstract

The application provides a low-cost high-forming-property tensile strength 650MPa-grade pickling high-strength steel and a manufacturing method and application thereof, and the steel has the following weight percentage chemical components: C 0.035-0.065%, Si 0.250-0.650%, P 0.020-0.050%, Mn 1.350-1.800%, Als 0.025-0.060%, Ti 0.080-0.125%, B 0.0010-0.0025%, Ca 0.0010-0.0050%, S≤0.0050%, N≤0.0050%, O≤0.0050%, and the balance of Fe and inevitable impurities. Compared with the prior art, the application uses Si and P to compound strengthen ferrite, adopts a low-temperature coiling process, refines grains, and comprehensively improves the flanging and hole-expanding forming property of the pickling coil.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-strength steel for automobiles, and in particular relates to a low-cost, high-formability, 650MPa-level pickled high-strength steel, a manufacturing method thereof, and an application thereof. Background Art

[0002] As competition in the automotive manufacturing industry becomes increasingly fierce, automakers are tightening their control over the cost of steel raw materials. As a steel supplier, how to produce high-quality automotive steel materials at low cost that meet market demand is a key factor in improving competitiveness in the automotive steel market.

[0003] Poor formability is one of the most common technical issues facing automotive steel materials used by customers. This directly impacts the quality of stamping and determines customer satisfaction with steel suppliers. Therefore, low-cost, high-formability advanced high-strength steels are highly competitive in the market.

[0004] Chinese patent CN 112779401 A, published on May 11, 2021, discloses "a high-expansion hot-rolled pickled steel plate with a yield strength of 550 MPa". The chemical composition of the steel plate is as follows by weight: C 0.05~0.08%, Mn 1.0~1.2%, Si0~0.10%, P 0~0.020%, S 0~0.003%, Alt 0.02~0.05%, N 0~0.005%, Nb 0.01~0.02%, Ti 0.04~0.08%, and the balance is Fe and unavoidable impurities. The continuous casting billet is heated in a furnace at a temperature of 1230-1260°C, the rough rolling temperature is 1030-1050°C, the finishing rolling temperature is 850-880°C, and the laminar cooling adopts a segmented cooling method. It is first cooled to 700-750°C at a water cooling rate of 30-40°C / s, and then cooled to 600-640°C at a water cooling rate of 80-100°C / s (and coiled in this temperature range). The metallographic structure is polygonal ferrite + bainite + carbide particles, the ferrite grain size grade is 10-11, the bainite volume content is 2.0-5.0%, the inclusion rating is below D1.0, the yield strength is 550-620MPa, the tensile strength is 650-710MPa, the yield strength ratio is 0.8-0.9, and the elongation is A 80 ≥20%, hole expansion performance λ≥70%. This patented product contains Nb, resulting in high alloy cost. The hot rolling process uses a segmented cooling method for laminar cooling, which has poor process stability. Coiling is carried out in the temperature range of 600-640℃, resulting in a low volume content of bainite and poor flanging and hole expansion performance.

[0005] Chinese patent CN 113755745 A, published on December 7, 2021, discloses "a tensile strength of 650 MPa grade high-expansion hot-rolled pickled steel plate", the chemical composition of the steel plate is: C 0.05-0.08%, Mn 0.9-1.2%, Si 0.023-0.10%, P≤0.020%, S≤0.003%, Alt 0.02-0.05%, N 0.002-0.004%, Nb 0.01-0.02%, Ti 0.04-0.10%,

[0006] [C]-([Ti]-3.5[N]-1.5[S]+1.2[Nb])≥0.1, the balance is Fe and inevitable impurity elements. The continuous casting billet is heated at a temperature of 1230-1260℃ in a furnace, the holding time is 1.0-2.0 hours, the rough rolling temperature is 1030-1050℃, the finish rolling temperature is 850-880℃, the laminar flow cooling adopts a step cooling mode, first cooled to 790-820℃ at an air cooling speed of 5-10℃ / s, and then cooled to 400-500℃ at a water cooling speed of 80-100℃ / s (and coiled at this temperature range). The metallographic structure is polygonal ferrite+acicular ferrite+carbide particles, the ferrite grain size is grade 11-12, the inclusion rating is D1.0 or less, the yield strength is 580-640MPa, the tensile strength is 650-700MPa, the yield strength ratio is 0.90-0.95, the elongation A 80 ≥18%, the hole expansion performance λ is 80%-140%. The product of the invention patent contains Nb element, the alloy cost is relatively high; the hot rolling process adopts a step cooling mode, the air cooling time cannot be accurately controlled, the process stability is poor, and it is not easy to manufacture.

[0007] Therefore, it has practical application significance to provide a low-cost, process-stable and controllable high-expansion performance pickled high-strength steel and a manufacturing method thereof. SUMMARY

[0008] The purpose of the present application is to provide a low-cost high-forming performance tensile strength of 650 MPa grade pickled high-strength steel and a manufacturing method thereof, using Si, P composite strengthened ferrite (using B element to inhibit the segregation of P element at grain boundary, so that the beneficial effect of P element on strengthening ferrite can be fully played), reducing the hardness difference between ferrite soft phase and bainite hard phase, and using low temperature coiling process, refining the grain, and comprehensively improving the flanging and hole expansion forming performance of the pickled finished coil. The laminar flow cooling of the hot rolling process adopts a continuous cooling mode, the process is simple and stable and controllable, and it is easy to manufacture. No Mo, Nb, V and other valuable alloy elements are used, the alloy cost is low, and the market competitiveness is strong.

[0009] The application of the low-cost high-forming performance tensile strength of 650 MPa grade pickled high-strength steel provided by the present application is used for automobile parts manufacturing.

[0010] The specific technical solutions of the present application are as follows:

[0011] A low-cost high-forming-property tensile strength 650MPa-grade pickling high-strength steel comprises the following weight percentage chemical components:

[0012] C 0.035-0.065%, Si 0.250-0.650%, P 0.020-0.050%, Mn 1.350-1.800%, Als 0.025-0.060%, Ti 0.080-0.125%, B 0.0010-0.0025%, Ca 0.0010-0.0050%, S≤0.0050%, N≤0.0050%, O≤0.0050%, and the balance of Fe and inevitable impurities.

[0013] Preferably, the low-cost high-forming-property tensile strength 650MPa-grade pickling high-strength steel comprises the following mass percentage chemical components:

[0014] C 0.035-0.060%, Si 0.250-0.550%, P 0.020-0.035%, Mn 1.500-1.650%, Als 0.035-0.050%, Ti 0.090-0.115%, B 0.0010-0.0021%, Ca 0.0011-0.0035%, S≤0.0035%, N≤0.0035%, O≤0.0025%, and the balance of Fe and inevitable impurities.

[0015] The chemical components of the low-cost high-forming-property tensile strength 650MPa-grade pickling high-strength steel satisfy 0.50≤Si+10×P≤1.00 and 0.25≤10×B / P≤0.95.

[0016] Preferably, the chemical components of the low-cost high-forming-property tensile strength 650MPa-grade pickling high-strength steel satisfy 0.55≤Si+10×P≤0.90 and 0.35≤10×B / P≤0.90.

[0017] In the above formula calculation, each element represents its content×100.

[0018] The thickness of the low-cost high-forming-property tensile strength 650MPa-grade pickling high-strength steel is

[0019] 1.50-5.50mm, and the width is 880-1800mm.

[0020] The metallographic structure of the low-cost high-forming-performance tensile strength 650MPa grade pickling high-strength steel contains 69.0-81.0% of ferrite and 19.0-31.0% of bainite in volume percentage, and the ferrite grain size is 12.5-15.0.

[0021] The low-cost high-forming-performance tensile strength 650MPa grade pickling high-strength steel has a yield strength of ≥510MPa, a tensile strength of ≥650MPa, and an elongation (A 50 ) of ≥21.0%, and a hole expansion ratio (HER) of ≥75.0%.

[0022] The manufacturing method of the low-cost high-forming-performance tensile strength 650MPa grade pickling high-strength steel comprises the following technological process: hot metal pretreatment, converter smelting, alloy fine adjustment station, LF furnace refining, continuous casting, hot rolling (→ finishing), pickling, oiling and precision packaging.

[0023] After the LF furnace refining is completed, calcium treatment is performed, the stopper argon blowing is promoted to promote the floating of inclusions, the dynamic soft reduction and electromagnetic stirring roller are used, and the superheat degree of the molten steel is controlled to be 10-25℃, so as to reduce the segregation and loose defects of the continuous casting billet.

[0024] The hot rolling is first heated, the continuous casting billet discharge temperature is 1215-1265℃, and the furnace time is 2.1-5.0h, and the mechanical properties and application performance (especially the yield strength) of the product are extremely sensitive to the discharge temperature, and the discharge temperature must not be too high or too low.

[0025] The hot rolling is rough rolling opening temperature 1150-1190℃, intermediate billet thickness 25-50mm, and finishing rolling opening temperature 1000-1100℃, and final rolling temperature 830-900℃.

[0026] The hot rolling is laminar cooling using cooling water or other cooling medium, and the strip steel temperature is cooled to 350-480℃ in a continuous cooling manner.

[0027] After the hot rolling, if the hot rolled coil plate shape is poor, finishing is needed to correct the plate shape, and the finishing elongation is 1.0-3.1%, and if the hot rolled coil plate shape is good, finishing is not needed.

[0028] The pickling is acid liquid temperature 80-95℃, flattening elongation 0.5-1.5%, and strip steel running speed 90-195m / min.

[0029] The oiling and fine packaging, the strip steel is dried at 100-180 DEG C, and then electrostatically oiled, the oiling amount is 0.50-1.50 g / m 2 The pickling finished product coil is obtained after fine packaging.

[0030] The application provides a low-cost high-forming-performance tensile strength 650MPa-grade pickling high-strength steel, which has simple manufacturing process, low alloy cost and excellent flanging and hole-expanding forming performance and is applied to automobile part manufacturing.

[0031] Compared with the prior art, the application adopts Si and P composite strengthening ferrite (B element is used to inhibit segregation of P element at grain boundaries, so that the beneficial effect of P element on strengthening ferrite can be fully exerted), reduces the hardness difference between ferrite soft phase and bainite hard phase, and adopts low-temperature coiling process to refine grains and comprehensively improve the flanging and hole-expanding forming performance of the pickling finished product coil. The laminar flow cooling in the hot rolling process adopts continuous cooling mode, and the process is simple, stable and controllable, and easy to manufacture. No valuable alloy elements such as Mo, Nb and V are used, the alloy cost is low, and the product has strong market competitiveness. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The scanning microstructure diagram of the low-cost high-forming-performance tensile strength 650MPa-grade pickling high-strength steel in Example 1. DETAILED DESCRIPTION

[0033] The application provides a low-cost high-forming-performance tensile strength 650MPa-grade pickling high-strength steel, which comprises the following weight percentage chemical components:

[0034] C 0.035-0.065%, Si 0.250-0.650%, P 0.020-0.050%, Mn 1.350-1.800%, Als 0.025-0.060%, Ti 0.080-0.125%, B 0.0010-0.0025%, Ca 0.0010-0.0050%, S≤0.0050%, N≤0.0050%, O≤0.0050%, and the balance is Fe and inevitable impurities.

[0035] Preferably, the low-cost high-forming-performance tensile strength 650MPa-grade pickling high-strength steel comprises the following weight percentage chemical components:

[0036] C 0.035-0.060%, Si 0.250-0.550%, P 0.020-0.035%, Mn 1.500-1.650%, Al 0.035-0.050%, Ti 0.090-0.115%, B 0.0010-0.0021%, Ca 0.0011-0.0035%, S≤0.0035%, N≤0.0035%, O≤0.0025%, the balance being Fe and inevitable impurities.

[0037] The chemical composition of the low-cost high-forming-property tensile strength 650MPa grade pickling high-strength steel satisfies 0.50≤Si+10×P≤1.00 and 0.25≤10×B / P≤0.95.

[0038] Preferably, the chemical composition of the low-cost high-forming-property tensile strength 650MPa grade pickling high-strength steel satisfies 0.55≤Si+10×P≤0.90 and 0.35≤10×B / P≤0.90.

[0039] In the above formula, each element represents its content × 100.

[0040] The low-cost high-forming-property tensile strength 650MPa grade pickling high-strength steel has a thickness of

[0041] 1.50-5.50mm and a width of 880-1800mm.

[0042] The low-cost high-forming-property tensile strength 650MPa grade pickling high-strength steel has a metallographic structure containing 69.0-81.0% by volume of ferrite and 19.0-31.0% by volume of granular bainite, and a ferrite grain size of 12.5-15.0.

[0043] The low-cost high-forming-property tensile strength 650MPa grade pickling high-strength steel has a yield strength of ≥510MPa, a tensile strength of ≥650MPa, and an elongation (A 50 ) of ≥21.0%, and a hole expansion ratio (HER) of ≥75.0%.

[0044] A manufacturing method of the low-cost high-forming-property tensile strength 650MPa grade pickling high-strength steel comprises the following process flow: hot metal pretreatment, converter smelting, alloy fine-tuning station, LF furnace refining, continuous casting, hot rolling (→ finishing), pickling, oiling and precision packaging.

[0045] The continuous casting is carried out after the LF furnace refining is completed, the calcium treatment is carried out, the argon blowing of the stopper promotes the floating of the inclusions, the dynamic soft reduction and the electromagnetic stirring roller are used, the overheating degree of the molten steel is controlled to be 10-25℃, the segregation and the loose defect of the continuous casting billet are reduced, the continuous casting billet is formed after the conventional smelting, the pulling speed of the continuous casting billet is controlled to be 0.80-1.90m / min, the thickness of the continuous casting billet is 210-250mm, and the center segregation quality of the continuous casting billet is stably controlled to be above C1.0.

[0046] The hot rolling is firstly carried out, the continuous casting billet is discharged at a temperature of 1215-1265℃, and the furnace time is 2.1-5.0h, the mechanical property and the application performance (especially the yield strength) of the product of the application are extremely sensitive to the discharging temperature, and the discharging temperature must not be too high or too low.

[0047] The hot rolling is carried out, the rough rolling opening rolling temperature is 1150-1190℃, the intermediate billet thickness is 25-50mm, the fine rolling opening rolling temperature is 1000-1100℃, and the final rolling temperature is 830-900℃.

[0048] The hot rolling is carried out, the laminar flow cooling is carried out by using the cooling water or other cooling medium, and the strip steel temperature is cooled to 350-480℃ in a continuous cooling mode.

[0049] After the hot rolling process, if the shape of the hot rolled plate is poor, the finishing is needed to correct the plate shape, and the finishing elongation is 1.0-3.1%, if the shape of the hot rolled plate is good, the finishing is not needed.

[0050] The pickling is carried out, the acid liquid temperature is 80-95℃, the flattening elongation is 0.5-1.5%, and the strip steel running speed is 90-195m / min.

[0051] The oiling and the precise packaging process are carried out, the strip steel is dried at a temperature of 100-180℃, and then the electrostatic oiling is carried out, the oiling amount is 0.50-1.50g / m 2 The pickling finished product coil is obtained after the precise packaging.

[0052] The design principle of the alloy elements and the content of the product of the application is as follows:

[0053] C: C element is the most effective and basic inexpensive solid solution strengthening element for the steel to obtain sufficient strength, but the C element content is too high, which reduces the flanging and hole expanding forming performance of the steel, therefore, the C element content is controlled to be 0.035-0.065% in the application.

[0054] Si: Si element purifies and strengthens ferrite, which can improve the strength and the flanging and hole expanding forming performance of the steel, and the price is low, but the Si element content is too high, which makes the surface quality of the steel worse, therefore, the Si element content is controlled to be 0.250-0.650% in the application.

[0055] P: P element is dissolved in ferrite, plays a role in strengthening ferrite, reduces the hardness difference between ferrite soft phase and bainite hard phase, improves the flanging and expanding forming performance of the steel, especially cooperates with B element, the beneficial effect of P element is more obvious, but if the content of P element is too high, the plasticity and toughness of the steel will be reduced, therefore, the content of P element is controlled at 0.020-0.050% in the application.

[0056] Mn: Mn element is a cheap solid solution strengthening element which can significantly improve the strength of the steel, but if the content of Mn element is too high, strip-shaped structure (reduces the uniformity of the structure) is easy to be formed, and the flanging and expanding forming performance of the steel is reduced, therefore, the content of Mn element is controlled at 1.350-1.800% in the application.

[0057] Als: Al element can effectively deoxidize, and reacts with N element to generate AlN (reduces the reaction between N element and Ti element, and increases the effective Ti content), AlN effectively prevents grain coarsening, and plays a role in refining grains to a certain extent; but if the content of Al element is too high, the smelting castability will be reduced, therefore, the content of Al element is controlled at 0.025-0.060% in the application.

[0058] Ti: Ti element is a strong carbonitride forming element, plays a role in precipitating strengthening and fine-grain strengthening, and comprehensively improves the strength and plasticity and toughness of the steel; refines and strengthens ferrite, reduces the hardness difference between ferrite soft phase and bainite hard phase, and improves the flanging and expanding forming performance of the steel; but if the content of Ti element is too high, the yield strength of the steel is significantly affected by the process stability of the tapping temperature, therefore, the content of Ti element is controlled at 0.080-0.125% in the application.

[0059] B: B element can eliminate the segregation of P element at the grain boundary, so that the beneficial effect of P element being dissolved in ferrite can be fully played, and the flanging and expanding forming performance of the steel is improved, but if the content of B element is too high, the strength (low-temperature coiling temperature range) of the steel will be obviously increased, therefore, the content of B element is controlled at 0.0010-0.0025% in the application.

[0060] Ca: Ca element plays a role in deoxidizing and desulfurizing, so that the beneficial effect of Si element being dissolved in ferrite can be fully played; refines, plasticizes and homogenizes non-metallic inclusions, and improves the flanging and expanding forming performance of the steel; but if the content of Ca element is too high, the purity of the molten steel will be reduced, therefore, the content of Ca element is controlled at 0.0010-0.0050% in the application.

[0061] S: S element is a harmful impurity element in the steel, which significantly reduces the flanging and expanding forming performance of the steel, therefore, the content of S element is strictly controlled below 0.0050% in the application.

[0062] N: N element can improve the strength and welding performance of the steel, but N element is not conducive to the control of inclusions, and reduces the effective Ti content, affects the mechanical property stability of the Ti micro-alloyed steel, therefore, the N element content is strictly controlled below 0.0050% in the application.

[0063] O: O element is a harmful impurity element in the steel, which is easy to form non-metallic inclusions and reduce the flanging and flaring forming performance of the steel, therefore, the O element content is strictly controlled below 0.0050% in the application.

[0064] The alloy system design of the product in the application needs to meet the following calculation formula: 0.50≤Si+10×P≤1.00, 0.25≤10×B / P≤0.95, and the role is: Si, P compound strengthening ferrite (eliminate P grain boundary segregation by B, so that the beneficial effect of P can be played), reduce the hardness difference between soft phase and hard phase. If the (Si+10×P) value is too low, the effect of strengthening ferrite is not obvious, if the (Si+10×P) value is too high, the surface quality of the pickling finished product coil cannot be guaranteed, and the harmful effect of P element is greater than the beneficial effect. If the (10×B / P) value is too low, P grain boundary segregation cannot be eliminated, and the harmful effect of P is greater than the beneficial effect, if the (10×B / P) value is too high, the yield strength of the steel will be significantly reduced.

[0065] Compared with the prior art, Si, P compound strengthening ferrite (B element is used to inhibit the segregation of P element at the grain boundary, so that the beneficial effect of P element strengthening ferrite can be fully played), the hardness difference between ferrite soft phase and bainite hard phase is reduced, and low temperature coiling process is adopted, the grain is refined, and the flanging and flaring forming performance of the pickling finished product coil is comprehensively improved. The laminar cooling of the hot rolling process adopts continuous cooling mode, the process is simple and stable and controllable, and easy to manufacture. No Mo, Nb, V and other valuable alloy elements are used, the alloy cost is low, and the product market competitiveness is strong.

[0066] The application will be further described below in combination with specific examples.

[0067] Examples 1-3

[0068] A low-cost high-forming-property tensile strength 650MPa-grade pickling high-strength steel, comprising the following weight percentage chemical components: as shown in Table 1, the balance of Table 1 is not shown Fe and unavoidable impurities.

[0069] Table 1 Chemical composition of steel of each example and comparative example

[0070]

[0071]

[0072] Table 1 (continued)

[0073] Serial number Si + 10 x P 10 x B / P Example 1 0.60 0.52 Example 2 0.65 0.50 Example 3 0.55 0.50 Comparative Example 1 0.18 0 Comparative Example 2 0.17 0 Comparative Example 3 1.15 0.20 Comparative Example 4 0.66 0.46 Comparative Example 5 0.56 0.35

[0074] Note: Comparative Example 1 is Chinese Patent Publication CN 112779401 A, and Comparative Example 2 is Chinese Patent Publication CN 113755745 A.

[0075] The manufacturing method of the low-cost high-forming-property tensile strength 650 MPa grade pickling high-strength steel of each of the above embodiments includes the following process flow: hot metal pretreatment, converter smelting, alloy fine adjustment station, LF furnace refining, continuous casting, hot rolling (→ finishing), pickling, oiling and precision packaging.

[0076] The specific manufacturing method is as follows:

[0077] (1) After hot metal pretreatment, converter smelting, alloy fine adjustment station, LF furnace refining, and continuous casting, a tensile strength 650 MPa grade pickling high-strength steel continuous casting billet with the chemical composition in Table 1 is prepared. After the LF furnace refining process, calcium treatment is performed, argon blowing through the stopper promotes the floating of inclusions, dynamic soft reduction and electromagnetic stirring rollers are used, and the superheat degree of the molten steel is controlled at 10-25℃, so as to reduce the segregation and porosity defects of the continuous casting billet. After conventional smelting, the continuous casting billet is formed, the casting speed of the continuous casting billet is controlled at 0.80-1.90 m / min, the thickness of the continuous casting billet is 210-250 mm, and the center segregation mass of the continuous casting billet is stably controlled at C1.0 or more.

[0078] (2) After the continuous casting billet is heated, rough rolled, finished rolled, and laminarly cooled, it is coiled to obtain a hot-rolled coil. The specific process parameters are as follows: first, heating, the continuous casting billet is discharged at a temperature of 1215-1265℃, and the furnace time is 2.1-5.0 h; rough rolling, the opening rolling temperature is 1150-1190℃, the intermediate billet thickness is 25-50 mm, the finishing rolling opening rolling temperature is 1000-1100℃, and the final rolling temperature is 830-890℃; laminar cooling, the strip steel temperature is cooled to the temperature range of 350-480℃ in a continuous cooling manner using cooling water or other cooling medium, and the hot-rolled coil is obtained by coiling; the key process parameters of the hot-rolling process of the steel of each embodiment are shown in Table 2.

[0079] Table 2 Key process parameters of the hot-rolling process of the steel of each embodiment

[0080]

[0081] (3) After the hot-rolled coil is finished, pickled, oiled, and precision packaged, a pickling finished coil is obtained. The specific process parameters are as follows: acid temperature 80-95℃, flattening elongation 0.5-1.5%, strip running speed 90-195 m / min; the strip is dried at a temperature of 100-180℃, then electrostatically oiled, the oiling amount is 0.50-1.50 g / m 2 , and the pickling finished coil is obtained after precision packaging.

[0082] The mechanical properties and application properties of the steel of the examples and the comparative examples are shown in Table 3.

[0083] Table 3 Mechanical properties and application properties of the steel of each example and the comparative example

[0084]

[0085] Note: The determination method of the mechanical properties (yield strength, tensile strength, elongation) is GB / T 228.1-2010, the test type number is P6, and the sample direction is transverse (90° direction). The determination method of the application property technical index of the flanging and hole expanding forming performance, i.e. the hole expansion rate (HER), strictly adopts GB / T 15825.4-2008.

[0086] The above underlined part does not meet the requirements of the present application.

[0087] The test results show that the pickling high-strength steel with low cost and high forming performance manufactured by the present application has a metallographic structure containing 69.0-81.0% of ferrite and 19.0-31.0% of granular bainite by volume percentage, and the ferrite grain size is 12.5-15.0, and the flanging and hole expanding forming performance of the pickling finished product coil is excellent.

[0088] According to the comparative examples 3-5, it can be obtained that only the chemical composition of the steel and the hot rolling process are controlled according to the present application, the technical effects of the present application can be obtained, otherwise, only the chemical composition of the steel meets but does not meet the calculation formula of the present application, or the key process parameters of the hot rolling process are controlled outside the range of the present application, which will result in the performance reduction of the pickling finished product coil.

[0089] The above description of the reference examples of the low-cost high-forming-performance pickling high-strength steel with a tensile strength of 650 MPa and the manufacturing method thereof is illustrative rather than limiting, and a number of examples can be listed according to the limited range, therefore, any changes and modifications under the overall technical concept of the present application should be within the protection scope of the present application.

Claims

1. A low cost high formability tensile strength 650 MPa grade pickling high strength steel, characterized in that, The low-cost high-forming-property tensile strength 650MPa-grade pickling high-strength steel consists of the following weight percentage chemical components: C 0.035~0.060%, Si 0.250~0.550%, P 0.020~0.035%, Mn 1.500~1.650%, Als 0.035~0.050%, Ti 0.090~0.115%, B 0.0010~0.0021%, Ca 0.0011~0.0035%, S≤0.0035%, N≤0.0035%, O≤0.0025%, the balance being Fe and unavoidable impurities.

2. The low cost, high formability, 650 MPa grade pickling high strength steel of claim 1, wherein, The chemical components of the low-cost high-forming-property tensile strength 650MPa-grade pickling high-strength steel satisfy 0.50≤Si+10×P≤1.00, 0.25≤10×B / P≤0.95, wherein the weight percentage content of each element is multiplied by 100 when the above formula is calculated.

3. The low cost, high formability, 650 MPa grade pickling high strength steel of claim 1, wherein, The metallographic structure of the low-cost high-forming-property tensile strength 650MPa-grade pickling high-strength steel contains 69.0~81.0% of ferrite and 19.0~31.0% of bainite by volume percentage, and the ferrite grain size is 12.5~15.

0.

4. The low cost, high formability, 650 MPa grade pickling high strength steel of claim 1, wherein, The low-cost high-formability tensile strength 650 MPa grade pickling high-strength steel has a yield strength of ≥ 510 MPa, a tensile strength of ≥ 650 MPa, and an elongation A of ≥ 21.0% 50 ≥ 21.0%; The hole expansion ratio is ≥75.0%.

5. A method of manufacturing a low cost high formability tensile strength 650 MPa grade pickling high strength steel according to any one of claims 1 to 4, characterized in that, The manufacturing method comprises hot rolling, and the strip steel temperature is cooled to 350~480℃ in a continuous cooling manner by using cooling water for laminar cooling.

6. The production method according to claim 5, wherein The manufacturing method comprises hot rolling, and the hot rolling is performed by first heating, with the continuous casting blank discharge temperature being 1215~1265℃ and the furnace time being 2.1~5.0h.

7. The production method according to claim 6, wherein In the hot rolling, the rough rolling opening temperature is 1150~1190℃, the intermediate blank thickness is 25~50mm, the finish rolling opening temperature is 1000~1100℃, and the final rolling temperature is 830~900℃.

8. The production method according to claim 6, wherein The manufacturing method comprises pickling, and the pickling is performed by using acid liquid with a temperature of 80~95℃, with the flattening elongation being 0.5~1.5% and the strip steel running speed being 90~195m / min.

9. Use of the low cost high formability tensile strength 650 MPa grade pickling high strength steel according to any one of claims 1 to 4, characterized in that, The application is applied to the manufacturing of automobile parts.

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