High-strength steel for seat slide rails and method for producing the same

Abstract

The application relates to the technical field of low-alloy high-strength steel for automobiles, and discloses a high-strength steel for seat slide rails, the chemical components and mass percentage of which satisfy the following conditions: Mn: 0.50-0.90%, Cr: 0.15-0.50%, and Nb+Ti: 0.085-0.110%. The application further discloses a production method of the high-strength steel for seat slide rails. The high-strength steel for seat slide rails and the production method thereof can realize one steel with multiple levels of 700MPa, 750MPa and 800MPa low-alloy high-strength steel, and have stable performance, good cold bending performance, high yield strength ratio and good welding performance, and can meet the extremely high requirements of seat slide rails on formability, shape fixability, assembly and weldability.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of low-alloy high-strength steel for automobiles, in particular to a high-strength steel for seat slide rails and a production method thereof. BACKGROUND

[0002] An automobile seat mainly comprises a backrest side plate, a seat pan edge plate, a seat pan, a slide rail and an angle adjuster, and the weight of the seat accounts for about 6% of the weight of the whole vehicle and the cost of the seat accounts for about 5% of the cost of the whole vehicle. With the gradual improvement of the technical maturity and the development of light weight, the light weight of the seat is increasingly favored by the industry. The seat slide rail is the most important functional and safety part in the seat framework of the automobile, and needs to meet the requirements of four key characteristics of safety, connection, support and adjustment, and is extremely high in forming performance, welding performance and assembly performance. High-strength low-alloy high-strength steel (HC700LA, HC750LA and HC800LA) is a typical material for the seat slide rail.

[0003] A Chinese patent (publication date: March 5, 2021, publication number: CN112442635A) discloses a high-performance 800MPa-grade or above low-alloy high-strength steel plate and a preparation method thereof. The scheme of 0.15~0.30% high-carbon composition + 1.20~2.00% medium-high manganese + 810~845℃ high-temperature annealing + 285~415℃ tempering is adopted to obtain a low-alloy high-strength steel with a yield strength of 800~950MPa, a tensile strength of 950~1100MPa, A80≥10.0% and a hole expansion rate of 25~40%, and the microstructure characteristics are ferrite + 7~15% pearlite. However, the application has the following defects: 1) the composition design of high-carbon + medium-high manganese is prone to composition segregation, and the strength fluctuation in the coil and between the coils is bound to be large, and the forming quality is unstable; 2) as can be seen from the 15 examples, the yield strength ratio of 0.82~0.92 is scattered, which inevitably leads to poor dimensional accuracy of the parts, and cannot fully meet the high requirements of the seat slide rail on the shape retention and assembly; 3) the composition design of high-carbon is not conducive to welding; 4) a very high annealing temperature is adopted, which increases the energy consumption.

[0004] CN116121655A discloses a yield strength of 700MPa hot base plated low alloy high strength steel and its production method. The process steps are smelting, continuous casting, hot rolling, pickling, hot dipping. By adopting the composition design of not adding niobium and 0.10%-0.50% high aluminum, and the process design of 1240-1270℃ heating temperature, 900-940℃ final rolling temperature, 620-700℃ coiling temperature, 610-720℃ low temperature annealing, 30-75s soaking time, the difference between horizontal and vertical yield strength of 700MPa low alloy high strength steel is controlled to be ≤25MPa and the hole expansion rate is ≥75%. However, the invention has the following defects: 1) high aluminum composition design is adopted, which increases the risk of cold bending cracking; 2) high aluminum composition design is adopted, the longitudinal yield strength ratio is greater than 0.83 and less than 0.94, which inevitably leads to poor part size precision, and cannot fully meet the high requirements of seat slide rail on shape and assembly; 3) only 700MPa low alloy high strength steel can be obtained under low temperature annealing.

[0005] CN112680655A discloses a 700MPa low alloy high strength cold rolled steel sheet and its preparation method. The composition design of 0.06-0.10% low carbon, 0.02-0.05% medium niobium, 0.07-0.11% high titanium and the process design of 520-560℃ coiling temperature, 60-70% cold rolling reduction, 770-800℃ medium-high temperature annealing are adopted to obtain a yield strength of 700-850MPa, a tensile strength of ≥720MPa, A80 of ≥5%, and a yield strength of 700MPa cold rolled low alloy high strength steel with a yield strength ratio of >0.9. However, the invention has the following defects: 1) at 770-800℃ medium-high annealing temperature, the strength dispersion is large, the elongation after fracture is large, and there are many elongations after fracture A80<10.5%, which cannot fully meet the high requirements of seat slide rail on formability; 2) the actual effect of 0.90< yield strength ratio ≤0.94 cannot fully meet the high requirements of seat slide rail on shape and assembly; 3) no solution is provided for strength fluctuation within and between coils.

[0006] A kind of 500~800MPa grade low alloy high-strength steel and its production method are disclosed in Chinese patent (publication date: May 5, 2023, publication number: CN116065095A), the component design carbon is 0.07~0.09%, niobium is 0.025~0.035%, titanium is 0.055~0.070%, the soaking temperature of 820~835 ℃ is used to produce yield strength 500MPa grade, the soaking temperature of 800~820 ℃ is used to produce yield strength 600MPa grade, the soaking temperature of 760~780 ℃ is used to produce yield strength 800MPa grade. However, the invention has the following defects: 1) through the gradient design of soaking temperature, only yield strength 500MPa grade, yield strength 600MPa grade and yield strength 800MPa grade production can be realized, yield strength 700MPa grade and yield strength 750MPa grade cannot be covered; 2) the yield strength ratio of the produced 800MPa grade low alloy high-strength steel is <0.94, the shape and assembly of the part are not good; 3) there is no solution to the strength fluctuation within and between coils; 4) high annealing temperature increases energy consumption. SUMMARY

[0007] In order to overcome the above-mentioned defects, in view of the high requirements of automobile seat slide rail parts on formability, shape setting, assembly and weldability, the present application provides a high-strength seat slide rail steel and its production method, the strength fluctuation of the steel product is small, the cold bending performance is good, the springback is small, the surface quality is high, and the steel is easy to weld, which can meet the extremely high material requirements of seat slide rail.

[0008] To achieve the above-mentioned purpose, the high-strength seat slide rail steel designed by the present application meets the following conditions in terms of chemical composition and mass percentage: C: 0.055~0.075%, Si: 0.20~0.50%, Mn: 0.50~0.90%, Cr: 0.15~0.50%, Als: 0.010~0.065%, Nb: 0.020~0.040%, Ti: 0.055~0.085%, Nb+Ti: 0.085~0.110%, V≤0.015%, B≤0.0015%, P≤0.025%, S≤0.010%, N≤0.0065%, Ca≤0.0060%, the balance being Fe and unavoidable impurities.

[0009] The component design principle of the present application is as follows:

[0010] The essence of performance fluctuation of high-grade low-alloy high-strength steel is the coupling of composition segregation, non-uniform precipitation and non-uniform recrystallization. The combined control of 0.085%≤Nb+Ti≤0.110%, 0.50%≤Mn≤0.90%, 0.15%≤Cr≤0.50% researched by the application is the core measure to realize accurate and stable control of microstructure and performance. Compound addition of Nb and Ti can fully play the roles of fine-grain strengthening, precipitation strengthening and delayed recrystallization. If the content of Nb+Ti is too low, the effect of delayed recrystallization is not strong, not only sufficient fibrous ferrite cannot be stably obtained, but also the process sensitivity of recovery and recrystallization is high; if the content of Nb+Ti is too high, the effect of delayed recrystallization is too strong, the resistance of dislocation recovery is large, and the product plasticity is not good. The composition design of low manganese plus chromium can reduce composition segregation, improve the size uniformity and distribution uniformity of Nb-Ti precipitated phase, improve the recrystallization uniformity, reduce the resistance of recovery and recrystallization, adjust the microstructure and improve the product plasticity. If the content of manganese is high and the content of chromium is low, the above effects are weakened; if the content of manganese is low and the content of chromium is high, the risk of insufficient strength is increased. Si is a conventional solid solution strengthening element and ferrite forming element, and can improve the fluidity of molten steel. If the content of Si is low, the product plasticity is not high, the risk of corner crack of casting blank is increased, the hot charging rolling is not good and the energy consumption is increased. If the content of Si is high, the surface quality is reduced. C is the most economical and effective strengthening element. If the content of C is less than 0.055%, the strength is likely to be less than expected; if the content of C is greater than 0.075%, not only the welding is not good, but also the risks of corner crack of casting blank and composition segregation are increased.

[0011] Further, the yield strength covers 700MPa grade, 750MPa grade and 800MPa grade, the yield strength ratio is >0.94, the longitudinal sample is not cracked under 180° bending at bending diameter 0T, the transverse sample is not cracked under 130° bending at bending diameter 0T, and T is the thickness of the strip.

[0012] Further, the strength difference within the coil of the longitudinal sample is ≤50MPa, the strength difference between the coils is ≤80MPa, and the elongation A80 after fracture is ≥10.5%.

[0013] Further, when the yield strength is 700MPa grade, the yield strength of the longitudinal sample is 700~780MPa, the tensile strength is 740~820MPa, the elongation A80 after fracture is ≥11.5%, the yield strength ratio is >0.94, the strength difference within the coil is ≤50MPa, the strength difference between the coils is ≤80MPa, the longitudinal sample is not cracked under 180° bending at bending diameter 0T, and the transverse sample is not cracked under 130° bending at bending diameter 0T, and T is the thickness of the strip.

[0014] When the yield strength is 750 MPa, the yield strength of the longitudinal sample is 750-830 MPa, the tensile strength is 790-870 MPa, the elongation after fracture A80 is greater than or equal to 11.0%, the yield strength ratio is greater than 0.94, the strength difference in the coil is less than or equal to 50 MPa, the strength difference between the coils is less than or equal to 80 MPa, the longitudinal sample is not cracked under 180° bending with a bending diameter of 0T, the transverse sample is not cracked under 130° bending with a bending diameter of 0T, and T is the thickness of the strip steel;

[0015] When the yield strength is 800 MPa, the yield strength of the longitudinal sample is 800-880 MPa, the tensile strength is 830-910 MPa, the elongation after fracture A80 is greater than or equal to 10.5%, the yield strength ratio is greater than 0.94, the strength difference in the coil is less than or equal to 50 MPa, the strength difference between the coils is less than or equal to 80 MPa, the longitudinal sample is not cracked under 180° bending with a bending diameter of 0T, and the transverse sample is not cracked under 130° bending with a bending diameter of 0T.

[0016] Further, the thickness of the strip steel is 0.6-2.5 mm.

[0017] A production method of high-strength steel for seat slide rails, the production steps include smelting, continuous casting, hot rolling, acid rolling and continuous annealing, wherein:

[0018] When hot rolling, the discharge temperature is 1250±30℃, and the coiling temperature is 550±50℃. Due to the high content of Nb+Ti, carbonitride dissolves and grows during the heating of the casting blank. If the discharge temperature is less than 1220℃, the amount of carbonitride dissolution is small, the strengthening effect of niobium and titanium is weak, and if the discharge temperature is greater than 1280℃, the carbonitride in the precipitated state grows, and the austenite also grows further, which also affects the strength of the steel; when the coiling temperature is greater than 600℃, on the one hand, the proportion of ferrite in the hot coil increases, affecting the strength of the finished product, and on the other hand, the temperature difference in the coil during storage is large, the strength fluctuation in the coil is large, the strength fluctuation of the finished product is increased, and when the coiling temperature is less than 500℃, the laminar cooling strength is large, and the cooling uniformity is poor, which not only increases the strength fluctuation in the coil of the hot coil, but also deteriorates the shape of the hot coil, finally affecting the shape control of the finished product;

[0019] When acid rolling, the reduction is 45-70%. If the reduction is too low, the ferrite is not rolled enough, which reduces the strength, and if the reduction is too high, the rolling load is large, and the shape of the acid-rolled plate is not easy to control;

[0020] During continuous annealing, when producing yield strength 700MPa grade, the soaking temperature is 760±15℃, and the skin pass elongation is 0.30±0.20%; when producing yield strength 750MPa grade, the soaking temperature is 745±15℃, and the skin pass elongation is 0.20±0.15%; when producing yield strength 800MPa grade, the soaking temperature is 715±15℃, and the skin pass elongation is 0.20±0.15%; due to the high strength of the hard strip steel, if the skin pass elongation is too large, the skin pass rolling force is correspondingly increased, the shape control ability of the skin pass mill is deteriorated, and the wave-shaped defects are prone to occur; the high or low of the soaking temperature affects the degree of ferrite recovery and recrystallization; according to the strength grade, the soaking temperature is controlled in the form of grading, so that the yield strength 700-800MPa grade low alloy high strength steel can be realized.

[0021] Further, during continuous annealing, the strip steel speed in the furnace is 130±50m / min, the slow cooling temperature is 660±40℃, the fast cooling temperature is 410±30℃, and the overaging temperature is 380±30℃.

[0022] Further, during continuous casting, the mold arc precision is controlled within ±1.0mm, the target temperature of the surface of the straightening area of the casting blank is greater than or equal to 900℃, the composition design avoids the sub-peritectic high-risk area, and the reasonable matching of the continuous casting process can significantly improve the quality of the corner of the casting blank under the complex influence of thermal stress, phase transformation stress and mechanical stress.

[0023] Further, the finish rolling temperature is 900±30℃.

[0024] Further, during hot rolling, the casting blank loading temperature is greater than or equal to 400℃.

[0025] Compared with the prior art, the present application has the following advantages:

[0026] 1. Avoiding the sub-peritectic high-risk area (carbon equivalent 0.08-0.15%) from the source of composition design, significantly reducing the corner crack of the 700-800MPa grade low alloy high strength steel casting blank, and realizing batch-free corner cleaning hot rolling, so as to speed up the casting blank turnover efficiency, reduce the corner cleaning iron loss and reduce the heating furnace fuel consumption, which is beneficial to cost reduction and efficiency increase.

[0027] 2. Taking the organization and performance control as the breakthrough, the combination measures of 0.085%≤Nb+Ti≤0.110%, 0.50%≤Mn≤0.90% and 0.15%≤Cr≤0.50% are innovatively adopted, which not only can reduce the composition segregation, uneven precipitation and uneven recrystallization, but also can realize sufficient control of fibrous ferrite and promote recovery, so as to reduce the strength fluctuation, improve the comprehensive plasticity of the product and improve the finished plate shape quality, and solve the difficult problems of difficult control of the strength, difficult improvement of the plasticity and difficult control of the plate shape of the 700-800MPa grade low alloy high strength steel at a lower annealing temperature;

[0028] 3. By adopting the same component design and hot rolling process, and by grading control of annealing process, a steel with multiple levels of 700 MPa, 750 MPa and 800 MPa low alloy high strength steel is realized. The strength difference of longitudinal sample within a coil is ≤50 MPa, the strength difference between coils is ≤80 MPa, the yield strength ratio is >0.94, and the 180° bending without cracking under bending diameter 0T, the transverse sample bending diameter 0T under 130° bending without cracking, the elongation A80≥11.5% when the yield strength is 700 MPa, the elongation A80≥11.0% when the yield strength is 750 MPa, the elongation A80≥10.5% when the yield strength is 800 MPa, and the product performance is very excellent;

[0029] 4. The finished steel product has small strength fluctuation, high yield strength ratio, high dimensional accuracy of the parts, meets the requirements of seat slide rail steel on shape setting and assembly performance, has excellent elongation and cold bending performance, meets the requirements of seat slide rail steel on forming performance, the low-carbon component design is beneficial to welding, and meets the requirements of seat slide rail steel on welding performance. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The figure is the metallographic structure (ferrite+pearlite) of the hot coil of the high-strength seat slide rail steel embodiment 1-3 of the present application.

[0031] Figure 2 The figure is the metallographic structure (fibrous ferrite+carbide) of the finished product of the high-strength seat slide rail steel embodiment 1-3 of the present application.

[0032] Figure 3 The figure is the 180° bending appearance of the longitudinal sample of the high-strength seat slide rail steel embodiment 1-3 of the present application under bending diameter 0T. DETAILED DESCRIPTION

[0033] The technical solutions of the present application will be described clearly and completely below in combination with specific embodiments. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0034] A high-strength steel for seat slide rail, chemical composition and mass percentage: C: 0.055~0.075%, Si: 0.20~0.50%, Mn: 0.50~0.90%, Cr: 0.15~0.50%, Als: 0.010~0.065%, Nb: 0.020~0.040%, Ti: 0.055~0.085%, V≤0.015%, B≤0.0015%, Nb+Ti: 0.085~0.110%, P≤0.025%, S≤0.010%, N≤0.0065%, Ca≤0.0060%, the balance being Fe and unavoidable impurities.

[0035] The production method of the high-strength steel for seat slide rail, the production steps include smelting, continuous casting, hot rolling, acid rolling and continuous annealing, wherein:

[0036] During smelting, converter smelting is adopted, decarburization, dephosphorization and molten iron temperature control are carried out, deoxidation and alloying are carried out during converter tapping, alloy composition is further adjusted at the alloy fine adjustment station, deoxidation, desulfurization, alloy fine adjustment, temperature homogenization and inclusion removal are carried out in the LF refining furnace, calcium feeding treatment is carried out before the LF outlet station;

[0037] During continuous casting, the mold arc precision control is ±1.0mm, the target temperature of the surface of the straightening area billet is ≥900℃, the billet drawing speed is 1.1~1.6m / min, the liquid level fluctuation is controlled in ±5mm, protective casting is adopted, and the billet thickness is 220~240mm;

[0038] During hot rolling, hot charging rolling is adopted, the billet charging temperature is ≥400℃, the tapping temperature is 1250±30℃, the final rolling temperature is 900±30℃, and the coiling temperature is 550±50℃;

[0039] During acid rolling, the acid rolling reduction rate is 45~70%, and the hard rolling thickness is 0.6~2.5mm;

[0040] During continuous annealing, when producing a yield strength of 700MPa, the soaking temperature is 760±15℃, and the flatness elongation is 0.30±0.20%; when producing a yield strength of 750MPa, the soaking temperature is 745±15℃, and the flatness elongation is 0.20±0.15%; when producing a yield strength of 800MPa, the soaking temperature is 715±15℃, and the flatness elongation is 0.20±0.15%.

[0041] The following are specific examples, wherein the chemical compositions of Example 1-1, Example 1-2 and Example 1-3 are the same, and the same processes are used for smelting, continuous casting, hot rolling and pickling in production. The chemical compositions of Example 2-1, Example 2-2 and Example 2-3 are the same, and the same processes are used for smelting, continuous casting, hot rolling and pickling in production. The chemical compositions of Example 3-1, Example 3-2 and Example 3-3 are the same, and the same processes are used for smelting, continuous casting and hot rolling in production, but the reduction rates for pickling are different.

[0042] Table 1 Major components of each example, the balance being Fe and impurities

[0043]

[0044] Table 2 Main processes of continuous casting, hot rolling and pickling

[0045]

[0046] Table 3 Main processes of continuous annealing

[0047]

[0048] The seat slide rail steels of Example 1-1, Example 1-2, Example 1-3, Example 2-1, Example 2-2, Example 2-3, Example 3-1, Example 3-2 and Example 3-3 are respectively prepared according to the above processes. The surface quality and performance test results of each example are shown in Table 4:

[0049] Table 4 Surface quality and performance results of each example

[0050]

[0051] As can be seen from Table 4, the high-strength seat slide rail steels of 700-800 MPa grade in the 9 examples have excellent mechanical properties, and the performance meets:

[0052] When the yield strength is 700 MPa grade, the yield strength of the longitudinal sample is 700-780 MPa, the tensile strength is 740-820 MPa, the elongation A80 is ≥11.5%, the yield strength ratio is >0.94, the within-coil strength difference is ≤50 MPa, the between-coil strength difference is ≤80 MPa, the longitudinal sample does not crack under 180° bending at a bending diameter of 0T, the transverse sample does not crack under 130° bending at a bending diameter of 0T, and T is the thickness of the steel strip.

[0053] When the yield strength is 750 MPa, the yield strength of the longitudinal sample is 750-830 MPa, the tensile strength is 790-870 MPa, the elongation after fracture A80 is ≥11.0%, the yield strength ratio is >0.94, the strength difference within the coil is ≤50 MPa, the strength difference between the coils is ≤80 MPa, the longitudinal sample is not cracked under 180° bending at a bending diameter of 0T, the transverse sample is not cracked under 130° bending at a bending diameter of 0T, and T is the thickness of the strip steel.

[0054] When the yield strength is 800 MPa, the yield strength of the longitudinal sample is 800-880 MPa, the tensile strength is 830-910 MPa, the elongation after fracture A80 is ≥10.5%, the yield strength ratio is >0.94, the strength difference within the coil is ≤50 MPa, the strength difference between the coils is ≤80 MPa, the longitudinal sample is not cracked under 180° bending at a bending diameter of 0T, the transverse sample is not cracked under 130° bending at a bending diameter of 0T, and T is the thickness of the strip steel.

[0055] In the above embodiments, when the yield strength is 700 MPa, the metallographic structure is ferrite+pearlite+carbide; when the yield strength is 750 MPa, the metallographic structure is mainly ferrite+carbide, and a small amount of pearlite is allowed; and when the yield strength is 800 MPa, the metallographic structure is ferrite+carbide. Due to high strength, the ferrite morphology is mainly fibrous, supplemented by polygonal. Specifically, as shown in FIG. 1, it is the metallographic structure of the hot coil of Examples 1-3 (ferrite+pearlite); as shown in FIG. 2, it is the metallographic structure of the finished product of Examples 1-3 (fibrous ferrite+carbide), and as shown in FIG. 3, it is the 180° bending morphology of the longitudinal sample of Examples 1-3 at a bending diameter of 0T. Figure 1 Figure 2 Figure 3

[0056] In addition, in the above embodiments, the unevenness of the high-strength seat slide rail steel is <2.0 mm.

[0057] ​​​The high-strength seat slide rail steel and a production method thereof avoid a subperitectic high-risk zone from a source of component design, significantly reduce corner cracks of a casting blank of a 700-800 MPa grade low-alloy high-strength steel, and can realize batch-free corner cleaning hot rolling, thereby accelerating the casting blank turnover efficiency, reducing the corner cleaning iron loss, and reducing the heating furnace fuel consumption, which is beneficial to cost reduction and efficiency increase; the component design reduces the difficulty of structure control from the source, solves the difficult problems of the 700-800 MPa grade low-alloy high-strength steel, such as difficult control of strength, difficult improvement of plasticity, and large unevenness at a lower annealing temperature; the same component design and hot rolling process are adopted, and through grading control of the annealing process, one steel realizes multiple levels of the 700-800 MPa grade low-alloy high-strength steel; the strength difference of the longitudinal sample of the finished steel product is less than or equal to 50 MPa, the inter-roll strength difference is less than or equal to 80 MPa, the yield strength ratio is greater than 0.94, and the 180° bending under a bending diameter of 0T does not crack, the transverse sample does not crack under a bending diameter of 0T, the performance is very excellent; the strength of the finished steel product fluctuates less, the yield strength ratio is very high, the unevenness is small, the size precision of the parts made is high, the requirements of the seat slide rail steel on the setting property and the assembly performance are met, the elongation after fracture is excellent, the cold bending performance is excellent, the requirements of the seat slide rail steel on the forming property are met, the low-carbon component design is beneficial to welding, and the requirements of the seat slide rail steel on the welding performance are met.

[0058] Meanwhile, it should be noted that the description of the above technical solutions is exemplary, and the specification can be embodied in different forms, and should not be interpreted as being limited to the technical solutions set forth herein. On the contrary, providing these descriptions will make the present disclosure thorough and complete, and will fully convey the scope disclosed by the specification to those skilled in the art. In addition, the technical solutions of the present application are limited by the scope of the claims. The features of various embodiments of the present application can be partially or entirely combined with each other or spliced, and can be performed in various different configurations as can be fully understood by those skilled in the art. The embodiments of the present application can be executed independently of each other, or can be executed together in a mutually dependent relationship.

[0059] For those skilled in the art to which the present application belongs, without departing from the concept of the present application, a number of simple deductions or substitutions can be made, and the above structures should be regarded as belonging to the protection scope of the present application.

Claims

1. A high-strength steel for seat slide rails, characterized by: The chemical composition and mass percentage meet the following conditions: C: 0.055-0.075%, Si: 0.20-0.50%, Mn: 0.50-0.90%, Cr: 0.15-0.50%, Als: 0.010-0.065%, Nb: 0.020-0.040%, Ti: 0.055-0.085%, V≤0.015%, B≤0.0015%, Nb+Ti: 0.085-0.110%, P≤0.025%, S≤0.010%, N≤0.0065%, Ca≤0.0060%, and the balance of Fe and impurities; The yield strength covers 700MPa grade, 750MPa grade and 800MPa grade, the yield strength ratio is >0.94, the longitudinal sample is not cracked at 180° bending under bending diameter 0T, the transverse sample is not cracked at 130° bending under bending diameter 0T, T is the thickness of the strip, the difference of the strength in the coil of the longitudinal sample is ≤50MPa, the difference of the strength between the coils is ≤80MPa, and the elongation A80 after fracture is ≥10.5%.

2. The high-strength steel for seat slide rails according to claim 1, characterized by: When the yield strength is 700MPa grade, the yield strength of the longitudinal sample is 700-780MPa, the tensile strength is 740-820MPa, the elongation A80 after fracture is ≥11.5%, the yield strength ratio is >0.94, the difference of the strength in the coil is ≤50MPa, the difference of the strength between the coils is ≤80MPa, the longitudinal sample is not cracked at 180° bending under bending diameter 0T, and the transverse sample is not cracked at 130° bending under bending diameter 0T, T is the thickness of the strip; When the yield strength is 750MPa grade, the yield strength of the longitudinal sample is 750-830MPa, the tensile strength is 790-870MPa, the elongation A80 after fracture is ≥11.0%, the yield strength ratio is >0.94, the difference of the strength in the coil is ≤50MPa, the difference of the strength between the coils is ≤80MPa, the longitudinal sample is not cracked at 180° bending under bending diameter 0T, and the transverse sample is not cracked at 130° bending under bending diameter 0T, T is the thickness of the strip; When the yield strength is 800MPa grade, the yield strength of the longitudinal sample is 800-880MPa, the tensile strength is 830-910MPa, the elongation A80 after fracture is ≥10.5%, the yield strength ratio is >0.94, the difference of the strength in the coil is ≤50MPa, the difference of the strength between the coils is ≤80MPa, the longitudinal sample is not cracked at 180° bending under bending diameter 0T, and the transverse sample is not cracked at 130° bending under bending diameter 0T, T is the thickness of the strip.

3. The high strength steel for seat tracks according to claim 1, wherein: The thickness of the strip is 0.6-2.5mm.

4. The method of producing a high-strength steel for a seat track according to claim 1, characterized by: The production steps include smelting, continuous casting, hot rolling, acid rolling and continuous annealing, wherein: When hot rolling, the tapping temperature is 1250±30℃, and the coiling temperature is 550±50℃; When acid rolling, the reduction is 45-70%; When continuous annealing, when producing the yield strength of 700MPa grade, the soaking temperature is 760±15℃, and the flattening elongation is 0.30±0.20%; when producing the yield strength of 750MPa grade, the soaking temperature is 745±15℃, and the flattening elongation is 0.20±0.15%; when producing the yield strength of 800MPa grade, the soaking temperature is 715±15℃, and the flattening elongation is 0.20±0.15%.

5. The method of producing a high-strength steel for seat slide rails according to claim 4, characterized by: During continuous annealing, the strip speed in the furnace is 130±50 m / min, the slow cooling temperature is 660±40℃, the fast cooling temperature is 410±30℃, and the overaging temperature is 380±30℃.

6. The method of producing a high-strength steel for a seat track according to claim 4, characterized by: During continuous casting, the precision control of the arc of the crystallizer is ±1.0 mm, and the target temperature of the surface of the straightening area of the cast slab is ≥900℃.

7. The method of producing a high-strength steel for seat slide rails according to claim 4, characterized by: During hot rolling, the final rolling temperature is 900±30℃.

8. The method of producing a high-strength steel for a seat track according to claim 4, characterized by: During hot rolling, the cast slab loading temperature is ≥400℃.

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