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CN-122013047-A - Low-cost titanium-containing 440 MPa-level high-strength IF steel and production method thereof

CN122013047ACN 122013047 ACN122013047 ACN 122013047ACN-122013047-A

Abstract

The invention discloses a low-cost high-strength IF steel with the titanium content of 440MPa and a production method thereof, comprising 0.0005-0.0035% of C, 0.52-0.58% of Si, 0.60-0.85% of Mn, 0.085-0.098% of P, less than or equal to 0.010% of S, 0.035-0.050% of acid-soluble aluminum, 0.040-0.065% of Ti, 0.0006-0.0010% of B, less than or equal to 0.0040% of N, and the mass ratio of Ti to N is less than or equal to 14 and less than or equal to 25, thereby ensuring that free nitrogen in the steel is completely fixed, inhibiting coarse TiN from being precipitated and being beneficial to improving the plasticity and the formability of materials. The combination of optimized hot rolling, annealing and leveling processes has excellent comprehensive mechanical properties of 260-330MPa yield strength, 440-510MPa tensile strength, elongation of more than or equal to 33%, r 90 value of more than or equal to 1.75 and n 90 value of more than or equal to 0.19.

Inventors

  • WEN YULONG
  • LIU DINGWEN
  • YANG SHIQING

Assignees

  • 马鞍山钢铁有限公司

Dates

Publication Date
20260512
Application Date
20260318

Claims (10)

  1. 1. A low-cost high-strength IF steel with 440MPa level containing titanium is characterized by comprising the following chemical components in percentage by weight: 0.0005 to 0.0035 percent of C, 0.52 to 0.58 percent of Si, 0.60 to 0.85 percent of Mn, 0.085 to 0.098 percent of P, less than or equal to 0.010 percent of S, 0.035 to 0.050 percent of acid-soluble aluminum, 0.040 to 0.065 percent of Ti, 0.0006 to 0.0010 percent of B, less than or equal to 0.0040 percent of N, the mass ratio of Ti to N being less than or equal to 14 and less than or equal to 25 percent of Ti/N, and the balance being Fe and unavoidable impurities.
  2. 2. The low-cost high-strength IF steel with the titanium content of 440MPa grade according to claim 1, wherein the high-strength IF steel has a thickness of 0.8-1.5mm, a width of 900-2000mm, a yield strength of 260-330MPa, a tensile strength of 440-510MPa, an elongation of not less than 33%, a r 90 value of not less than 1.75, a n 90 value of not less than 0.19, a metallographic structure of ferrite, and an average grain size of 8.0-10.0.
  3. 3. A method for producing a high strength IF steel according to claim 1, comprising the steps of: Steelmaking and continuous casting, namely molten iron pretreatment, converter smelting, alloy fine adjustment, RH refining and continuous casting; hot rolling, namely heating a slab obtained by continuous casting to 1210-1250 ℃, preserving heat, dephosphorizing, rough rolling and finish rolling, controlling the finish rolling temperature to 900-925 ℃, and cooling the strip steel to 640-710 ℃ by adopting laminar cooling for coiling; Cold rolling, namely pickling the hot rolled coil, and then cold rolling to obtain a chilled coil; Continuous annealing, wherein the annealing temperature of a soaking section is 790-815 ℃, the annealing temperature of a slow cooling section is 660-700 ℃, the flash cooling section is 390-410 ℃, the overaging section is 340-380 ℃ and the final cooling temperature is 130-170 ℃; Leveling.
  4. 4. A method for producing high-strength IF steel according to claim 3, wherein the flattening process comprises flattening with a work roll having a roll diameter of 590-650mm, the work roll having a surface roughness of 3.0 μm or less and a flattening elongation of 0.7-1.2%.
  5. 5. The method for producing high-strength IF steel according to claim 3, wherein the flattening process comprises adjusting the rolling force in the flattening according to the thickness t of the strip steel before entering the flattening machine and the width b of the strip steel before entering the flattening machine so that the rolling force F/b in the unit width direction satisfies the following relationship: F/b is 0.25-0.60t/mm when t <1.0 mm; F/b is 0.14-0.48t/mm when t is less than or equal to 1.0mm and less than 2.0 mm; When t is more than or equal to 2.0mm and less than or equal to 2.5mm, F/b is 0.13-0.20t/mm; Wherein F is the flattening actual rolling force, and the units of t and b are both mm.
  6. 6. The method of producing high strength IF steel according to claim 3 wherein the heat-retaining time for heating the slab to 1210-1250 ℃ is 60-180min.
  7. 7. A method of producing high strength IF steel according to claim 3 wherein the total reduction of the cold rolling is 60% to 82%.
  8. 8. The method for producing high-strength IF steel according to claim 3, wherein the chilled rolls are cleaned and degreased before the continuous annealing to ensure that the reflectivity of the surface of the cleaned strip steel is not less than 90%.
  9. 9. A method of producing high strength IF steel according to claim 3 wherein the chilled rolls have a thickness of 0.6-2.5mm.
  10. 10. The method for producing high-strength IF steel according to claim 3, wherein the soaking period is 60-180s.

Description

Low-cost titanium-containing 440 MPa-level high-strength IF steel and production method thereof Technical Field The invention relates to the technical field of steel materials and preparation thereof, in particular to low-cost 440 MPa-level high-strength IF steel containing titanium and a production method thereof. Background With the development of the automobile industry towards light weight, energy saving and environmental protection, the high-strength IF steel has high strength, excellent deep drawing forming performance and good corrosion resistance, and becomes a key material for manufacturing automobile body structural members and covering parts. The 440MPa grade is a typical strength grade in high-strength IF steel, and has wide application prospect. At present, the conventional 440 MPa-level high-strength IF steel in the market mainly adopts a component system of niobium (Nb) and titanium (Ti) composite microalloying. Niobium is used as a precious microalloy element, and can effectively improve the strength of steel and refine grains, but the high price of the niobium obviously increases the alloy cost, reduces the market competitiveness of products and restricts the large-scale application of the niobium. Chinese patent (publication No. CN 105861929A) discloses 440MPa grade cold-rolled high-strength IF steel and a production method thereof. The chemical components and weight percentage are 0.0015-0.0035wt% of C, 0.40-0.50wt% of Si, 0.75-0.95wt% of Mn, 0.08-0.10wt% of P, 0.02-0.03wt% of Nb, 0.018-0.035wt% of Ti, r value of 1.8-2.0 and elongation of 33.0-41.0%. Chinese patent (publication No. CN 117431459A) discloses 440 MPa-level P-containing hot-dip galvanized iron alloy high-strength IF steel, which contains Nb and Ti composite components and has higher P content (0.085-0.100 wt%) and B element (0.0010-0.00015 wt%). In order to obtain good comprehensive mechanical properties, the two patents adopt a Nb+Ti composite system component system, and the Nb is a relatively rare and expensive alloy element, so that the price is far higher than that of Ti, and the Nb+Ti composite system has high production cost and poor economical efficiency in industrial mass production. Therefore, the high-strength IF steel and the preparation method thereof are developed, which can greatly reduce the alloy cost and have stable and controllable process on the premise of ensuring the strength level of 440MPa and excellent forming performance, and have important economic value and practical significance. The present invention aims to provide a low cost solution with a single titanium microalloyed core. Disclosure of Invention The invention aims to solve the technical problem that the production cost is high due to the adoption of Nb-Ti composite alloying in the existing 440 MPa-level high-strength IF steel, and provides the titanium-containing 440 MPa-level high-strength IF steel with low cost, high performance and stable production process and a production method. In order to achieve the above purpose, the present invention adopts the following technical scheme: The low-cost 440 MPa-level high-strength IF steel comprises the following chemical components in percentage by weight: 0.0005 to 0.0035 percent of C, 0.52 to 0.58 percent of Si, 0.60 to 0.85 percent of Mn, 0.085 to 0.098 percent of P, less than or equal to 0.010 percent of S, 0.035 to 0.050 percent of Als (acid-soluble aluminum), 0.040 to 0.065 percent of Ti, 0.0006 to 0.0010 percent of B, less than or equal to 0.0040 percent of N, the mass ratio of Ti to N being less than or equal to 14 and less than or equal to 25 percent of Ti/N, and the balance being Fe and unavoidable impurities. Further, the yield strength of the high-strength IF steel is 260-330MPa, the tensile strength is 440-510MPa, the elongation is more than or equal to 33%, the r90 value is more than or equal to 1.75, the n90 value is more than or equal to 0.19, the metallographic structure is ferrite, and the average grain size level is 8.0-10.0. Ti is used for replacing Nb and Ti, so that one key element is reduced, the chemical composition control and the steelmaking operation are simplified, and meanwhile, certain surface defects (such as iron scales and the like) possibly caused are avoided. Through strict ULC and ULN control, C, N interstitial atoms in steel are completely fixed into carbon nitrogen compounds, and the interstitial atoms exist in the steel, so that the steel has excellent formability and non-timeliness, and meanwhile, the contents of substitutional solid solution strengthening atoms P, mn and Si are properly increased to ensure the strength. A certain amount of B is added in the reactor, reducing the grain boundary segregation of the P element to cause the strip steel to become brittle. In addition, the method ensures that enough Ti content provides precipitation strengthening and grain refinement, simultaneously excessive Ti inhibits the growth of TiN, precisely controls the Ti/