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EP-4741525-A1 - MEDIUM-CHROMIUM HEAT-RESISTANT FERRITIC STAINLESS STEEL, AND PREPARATION METHOD FOR MEDIUM-CHROMIUM HEAT-RESISTANT FERRITIC STAINLESS STEEL COLD PLATE AND USE THEREOF

EP4741525A1EP 4741525 A1EP4741525 A1EP 4741525A1EP-4741525-A1

Abstract

The present invention discloses a medium-chromium heat-resistant ferritic stainless steel and a cold-rolled sheet preparation method and use thereof. The chemical composition of the medium-chromium heat-resistant ferritic stainless steel is: C≤0.020%, N≤0.020%, Si: 0.30%-0.50%, Mn: 0.20%-0.50%, Cr: 17.0%-19.0%, Al: 2.0%-4.0%, Ni: 0.05%-0.30%, Mo: 0.10%-0.30%, Ti: 0.10%-0.30%, with the balance being Fe and unavoidable impurity elements, and 60≤( w Al + w Si )× w Cr ≤70, 1.0≤4 w Ni +8 w Mo - w Mn ≤2.0. The preparation method for the medium-chromium heat-resistant ferritic stainless steel cold-rolled sheet comprises steps of smelting, continuous casting, hot rolling, and cold rolling. The medium-chromium heat-resistant ferritic stainless steel cold-rolled sheet of the present invention combines excellent high-temperature oxidation resistance and electrical resistance properties with good processing performance and corrosion resistance, effectively expanding the application fields of medium-chromium heat-resistant ferritic stainless steel products.

Inventors

  • DUAN, Xiufeng
  • LIU, Chunlai
  • FU, Jinzhu
  • WEI, Hairui
  • WU, MIN
  • ZHANG, LITAO

Assignees

  • Shanxi Taigang Stainless Steel Co., Ltd.

Dates

Publication Date
20260513
Application Date
20250519

Claims (10)

  1. A medium-chromium heat-resistant ferritic stainless steel, wherein the medium-chromium heat-resistant ferritic stainless steel comprises following chemical compositions by mass percentage: C≤0.020%, N≤0.020%, Si: 0.30%-0.50%, Mn: 0.20%-0.50%, Cr: 17.0%-19.0%, Al: 2.0%-4.0%, Ni: 0.05%-0.30%, Mo: 0.10%-0.30%, Ti: 0.10%-0.30%, with the balance being Fe and unavoidable impurity elements, contents of Al, Si and Cr elements satisfying 60≤( w Al + w Si )× w Cr ≤70, and contents of Mn, Ni, and Mo elements satisfying 1.0≤4 w Ni +8 w Mo - w Mn ≤2.0, where w Al , w Si , w Cr , w Mn , w Ni and w Mo represent mass percentage contents of the elements Al, Si, Cr, Mn, Ni and Mo respectively.
  2. The medium-chromium heat-resistant ferritic stainless steel according to claim 1, wherein the contents of C and N in the medium-chromium heat-resistant ferritic stainless steel are controlled to be C≤0.012% and N≤0.012%.
  3. The medium-chromium heat-resistant ferritic stainless steel according to claim 1, wherein total oxygen content in the medium-chromium heat-resistant ferritic stainless steel is T[O]≤10ppm.
  4. A preparation method for a medium-chromium heat-resistant ferritic stainless steel cold-rolled sheet, comprising the following steps: (1) smelting: using molten iron as a raw material, smelting is performed through processes of molten iron pretreatment, K-OBM-S, VOD and LF to achieve decarburization, reduction, and alloying, wherein chemical composition of the molten steel obtained is controlled by mass percentage as follows: C≤0.020%, N≤0.020%, Si: 0.30%-0.50%, Mn: 0.20%-0.50%, Cr: 17.0%-19.0%, Al: 2.0%-4.0%, Ni: 0.05%-0.30%, Mo: 0.10%-0.30%, Ti: 0.10%-0.30%, with the balance being Fe and unavoidable impurity elements, contents of Al, Si and Cr elements satisfying 60≤( w Al + w Si )× w Cr ≤70, and contents of Mn, Ni and Mo elements satisfying 1.0≤4 w Ni +8 w Mo - w Mn ≤2.0, where w Al , w Si , w Cr , w Mn , w Ni and w Mo represent mass percentage contents of the elements Al, Si, Cr, Mn, Ni and Mo respectively; (2) continuous casting: slab continuous casting is performed via a tundish, with electromagnetic stirring applied throughout the continuous casting, and an isometric crystal ratio of a casting blank is controlled to be >55%; (3) hot rolling: a heating temperature is controlled at 1150-1200°C, with 7 hot rolling passes, a final rolling temperature is controlled at ≤880°C, followed by layer cooling after hot rolling, and a coiling temperature is controlled at ≤500°C; and (4) cold rolling: first, hot coil annealing and pickling are performed, with a hot coil annealing temperature controlled at 940-1000°C, and a hot coil annealing time controlled at 1.4-1.8 min/mm; then multi-passes cold rolling is performed, with a total deformation rate of cold rolling controlled at 55%-85%, a cold coil annealing furnace temperature controlled at 880-940°C, and a cold coil annealing time controlled at 1.0-1.4 min/mm; and finally, a cold-rolled sheet surface is polished to produce the medium-chromium heat-resistant ferritic stainless steel cold-rolled sheet.
  5. The preparation method for a medium-chromium heat-resistant ferritic stainless steel cold-rolled sheet according to claim 4, wherein Cr alloying is performed in K-OBM-S, aluminum pellets are used for reduction in VOD followed by alloying of Al, Si, Mn, and Ti, and Ni and Mo alloying is performed in a LF furnace.
  6. The preparation method for a medium-chromium heat-resistant ferritic stainless steel cold-rolled sheet according to claim 4, wherein in the step of hot rolling, the final rolling temperature is controlled to ≤850°C, and the coiling temperature is controlled to ≤400°C.
  7. The preparation method for a medium-chromium heat-resistant ferritic stainless steel cold-rolled sheet according to claim 4, wherein in the step of cold rolling, the hot coil annealing temperature is controlled to 940-980°C, the total deformation rate of cold rolling is controlled to 60%-85%, the cold coil annealing furnace temperature is controlled to 880-920°C, and the surface of the cold-rolled sheet is polished with a 230# sandpaper.
  8. A medium-chromium heat-resistant ferritic stainless steel cold-rolled sheet prepared by the preparation method for a medium-chromium heat-resistant ferritic stainless steel cold-rolled sheet according to any one of claims 4 to 7, wherein the medium-chromium heat-resistant ferritic stainless steel cold-rolled sheet has a width of 1000-1300 mm and a thickness of 0.4-2.0 mm, and a surface type of the medium-chromium heat-resistant ferritic stainless steel cold-rolled sheet is a HL surface, with a roughness of < 0.40µm , and a total oxygen content of T[0] ≤ 10ppm.
  9. The medium-chromium heat-resistant ferritic stainless steel cold-rolled sheet according to claim 8, wherein the medium-chromium heat-resistant ferritic stainless steel cold-rolled sheet has a grain size of grade 7-8, a percentage elongation after fracture of 30%-33%, a plastic strain ratio r of 1.20-1.40, and a room-temperature resistivity of 1.15-1.20µΩ · cm; after continuous high-temperature oxidation in atmospheric conditions at 900 ° C for 200 h, the oxidation weight gain rate is 0.10-0.15mg/cm 2 ; in a salt spray test conducted in 35 ° C , 5% of NaCl spray, no rust spots are observed within 48h.
  10. Use of the medium-chromium heat-resistant ferritic stainless steel cold-rolled sheet according to claim 8 or 9 in household appliances, industrial combustion furnaces, automotive exhaust systems, and electric heating equipment of new energy vehicles, wherein the medium-chromium heat-resistant ferritic stainless steel cold-rolled sheet is used to manufacture high-temperature resistant components or electric heating elements in household appliances, industrial combustion furnaces, automotive exhaust systems, and new energy vehicles.

Description

TECHNICAL FIELD The present invention belongs to the field of stainless steel production technology, specifically relates to a medium-chromium heat-resistant ferritic stainless steel with combined properties of oxidation resistance, high resistivity, high workability and high corrosion resistance, as well as its cold-rolled sheet, preparation method and use of the cold-rolled sheet. BACKGROUND Cr content in medium-chromium ferritic stainless steel ranges between16~19%. This type of stainless steel has gained widespread application due to its excellent corrosion resistance, workability and cost-effectiveness. The most prototypical medium-chromium ferritic stainless steel is 430 stainless steel. By further reducing C and N element content and adding stabilizing elements such as Nb and Ti , ultra-pure ferritic stainless steels like 439 and 441 have been developed. To further enhance corrosion resistance, elements like Mo or Cu have been added, resulting in varieties such as 436, 444, and SUS430J1L. For heat-resistant ferritic stainless steel, the surface layer needs to form oxide films of Cr2 O3, Al2O3, or SiO2, in which the oxide film of Al2O3 is the most dense. Increasing Al and Si content, on one hand, raises the material's resistivity, but on the other hand, reduces its workability. Additionally, Al element can also weaken the material's corrosion resistance. Therefore, there is a need to design a new composition system and preparation process for medium-chromium heat-resistant ferritic stainless steel that can form a dense Al2O3 oxide film on the surface to improve high-temperature oxidation resistance while ensuring the material's resistivity and workability, along with maintaining certain corrosion resistance properties. SUMMARY To address the above technical issues, the present invention provides a medium-chromium heat-resistant ferritic stainless steel and its cold-rolled sheet, as well as preparation method and use of the cold-rolled sheet. The chemical composition of the medium-chromium heat-resistant ferritic stainless steel provided by the present invention is, by mass percentage, as follows: C≤0.020%, N≤0.020%, Si: 0.30%-0.50%, Mn: 0.20%-0.50%, Cr: 17.0%-19.0%, Al: 2.0%-4.0%, Ni: 0.05%-0.30%, Mo: 0.10%-0.30%, Ti: 0.10%-0.30%, with the balance being Fe and unavoidable impurity elements, contents of Al, Si and Cr elements satisfying 60≤(wAl+wSi)×wCr≤70, and contents of Mn, Ni, and Mo elements satisfying 1.0≤4wNi+8wMo-wMn≤2.0, where wAl, wSi, wCr, wMn, wNi and wMo represent mass percentage contents of the elements Al, Si, Cr, Mn, Ni and Mo, respectively. Preferably, the contents of C and N in the medium-chromium heat-resistant ferritic stainless steel are controlled to be C≤0.012% and N≤0.012%. Further, a total oxygen content in the medium-chromium heat-resistant ferritic stainless steel is T[O]≤10ppm. A preparation method for a medium-chromium heat-resistant ferritic stainless steel cold-rolled sheet provided by the present invention comprises the following steps: (1) smelting: using molten iron as a raw material, smelting is performed through processes of molten iron pretreatment, K-OBM-S, VOD, and LF to achieve decarburization, reduction, and alloying, wherein a chemical composition of the molten steel obtained is controlled by mass percentage as follows: C≤0.020%, N≤0.020%, Si: 0.30%-0.50%, Mn: 0.20%-0.50%, Cr: 17.0%-19.0%, Al: 2.0%-4.0%, Ni: 0.05%-0.30%, Mo: 0.10%-0.30%, Ti: 0.10%-0.30%, with the balance being Fe and unavoidable impurity elements, contents of Al, Si and Cr elements satisfying 60≤(wAl+wSi)×wCr≤70, and contents of Mn, Ni and Mo elements satisfying 1.0≤4wNi+8wMo-wMn≤2.0, where wAl, wSi, wCr, wMn, wNi and wMo represent mass percentage contents of the elements Al, Si, Cr, Mn, Ni and Mo, respectively;(2) continuous casting: slab continuous casting is performed via a tundish, with electromagnetic stirring applied throughout the continuous casting, and an isometric crystal ratio of a casting blank is controlled to be >55%;(3) hot rolling: a heating temperature is controlled at 1150-1200°C, with 7 hot rolling passes, a final rolling temperature is controlled at ≤880°C, followed by layer cooling after hot rolling, and a coiling temperature is controlled at ≤500°C; and(4) cold rolling: first, hot coil annealing and pickling are performed, with a hot coil annealing temperature controlled at 940-1000°C, and a hot coil annealing time controlled at 1.4-1.8 min/mm; then multi-pass cold rolling is performed, with a total deformation rate controlled at 55%-85%, a cold coil annealing furnace temperature controlled at 880-940°C, and a cold coil annealing time controlled at 1.0-1.4 min/mm; and finally, a cold-rolled sheet surface is polished to produce the medium-chromium heat-resistant ferritic stainless steel cold-rolled sheet. Further, Cr alloying is performed in K-OBM-S, aluminum pellets are used for reduction in VOD followed by alloying of Al, Si, Mn, and Ti, and Ni and Mo alloying is performe