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CN-117660844-B - Ultralow-temperature steel and steel rolling method and application thereof

CN117660844BCN 117660844 BCN117660844 BCN 117660844BCN-117660844-B

Abstract

The invention discloses ultralow-temperature steel, a steel rolling method and application thereof. The ultralow-temperature steel takes C, mn, mo, si as an alloy element, is an austenite structure with proper stacking fault energy, has the performance characteristics of high strength and high plasticity at-269 ℃, and can be used as a high-strength material of superconducting coil armor materials, liquid helium container materials and the like in an ultralow-temperature environment. Compared with the stainless steel material with the same use condition, the strength is higher, the Ni element is not added, and the economy of the material is improved.

Inventors

  • SUN CHAO
  • ZHOU YUWEI
  • SUN XUDONG
  • MA LIUJUN
  • LI SEN
  • LI WEI

Assignees

  • 南京钢铁股份有限公司

Dates

Publication Date
20260505
Application Date
20231229

Claims (9)

  1. 1. An ultralow-temperature steel is characterized by comprising, by mass, 0.75% -0.85% of C, 22% -26% of Mn, 0.5% -1.0% of Mo, 0.1% -0.4% of Si, and the balance of Fe and unavoidable impurity elements, wherein the austenitic fault energy of the ultralow-temperature steel at the temperature of-269 ℃ is 42 xC+3.1xMn-15 xC 2 -0.026×Mn 2 -0.063 xC xMn-58, the yield strength is not lower than 1500MPa, and the elongation after breaking is not lower than 30%; The steel rolling method of the ultralow-temperature steel comprises the following steps of: (1) Heating, namely heating blanks with the same components and 15 times of the thickness of the steel plate, wherein the heating temperature is 1100-1150 ℃, the total furnace time is 1.5-1.7 min/mm multiplied by the thickness of the blanks, and the thickness of the steel plate is 10-20 mm; (2) Descaling, namely removing iron scales of the heated blank, wherein the high-pressure water pressure is 22-24 MPa; (3) Rolling, namely rolling at an initial rolling temperature of 1005-1030 ℃ and a final rolling temperature of 800-830 ℃; (4) And (3) cooling, namely performing accelerated cooling on the rolled steel plate, wherein the water inlet temperature is 730-765 ℃, the water outlet temperature is 130-240 ℃, and the cooling rate is 27-48 ℃ per second.
  2. 2. The ultra-low temperature steel according to claim 1, wherein the thickness of the steel sheet is 10-20 mm, the structure is austenite, and the grain size is 4-5 grade.
  3. 3. The ultra-low temperature steel according to claim 1, wherein the austenitic stacking fault energy is 20-28 mj/m 2 .
  4. 4. The composition according to claim 1, wherein the composition comprises, by mass, 0.75% of C, 22% of Mn, 0.5% of Mo, 0.1% of Si, and the balance of Fe and unavoidable impurity elements.
  5. 5. The composition according to claim 1, wherein the composition comprises, by mass, 0.79% of C, 24% of Mn, 0.7% of Mo, 0.3% of Si, and the balance of Fe and unavoidable impurity elements.
  6. 6. The composition according to claim 1, wherein the composition comprises, by mass, 0.85% of C, 26% of Mn, 1.0% of Mo, 0.4% of Si, and the balance of Fe and unavoidable impurity elements.
  7. 7. A method of rolling ultra-low temperature steel according to claim 1, comprising the steps of: (1) Heating, namely heating blanks with the same components and 15 times of the thickness of the steel plate, wherein the heating temperature is 1100-1150 ℃, the total furnace time is 1.5-1.7 min/mm multiplied by the thickness of the blanks, and the thickness of the steel plate is 10-20 mm; (2) Descaling, namely removing iron scales of the heated blank, wherein the high-pressure water pressure is 22-24 MPa; (3) Rolling, namely rolling at an initial rolling temperature of 1005-1030 ℃ and a final rolling temperature of 800-830 ℃; (4) And (3) cooling, namely performing accelerated cooling on the rolled steel plate, wherein the water inlet temperature is 730-765 ℃, the water outlet temperature is 130-240 ℃, and the cooling rate is 27-48 ℃ per second.
  8. 8. The steel rolling method according to claim 7, wherein the blank has a preparation liquidus temperature of 1369 to 1391 ℃.
  9. 9. Use of the ultra-low temperature steel of claim 1 in the preparation of low temperature storage and transportation containers, pipelines, superconducting coil armor.

Description

Ultralow-temperature steel and steel rolling method and application thereof Technical Field The invention relates to ultralow temperature steel and a steel rolling method and application thereof, in particular to ultralow temperature steel with ultralow temperature performance of-269 ℃ and a steel rolling method and application thereof. Background The storage and transportation container of ultralow temperature medium such as liquefied natural gas, liquid hydrogen, liquid helium and the like is conventionally manufactured by adopting steel with high nickel content, such as invar steel (36 percent Ni), 316 stainless steel (12 percent Ni), 9 percent Ni steel and the like. Superconducting coil armor, liquid helium container, or the like requires a high strength material that can be used in an ultra-low temperature environment at-269 ℃. Stainless steel, while plastic, has low strength, and usually requires strain strengthening to increase its strength. Moreover, the stainless steel is added with a large amount of Ni element, and the alloy cost is high. When the material is used as a structural material in an ultralow temperature environment of-269 ℃, the mechanical property of the material is highly required, and the corrosion resistance of the material is not required. Therefore, as an ultralow-temperature structural material, the alloy components are required to be redesigned, so that the mechanical property is improved, and the material cost is reduced, thereby being more beneficial to practical application. The manganese is used for replacing nickel, which is an important direction for optimally designing materials such as stainless steel, and components and processes are designed in a targeted manner according to performance requirements of different use environments. Disclosure of Invention The invention aims to provide ultralow-temperature steel with excellent ultralow-temperature performance, and a steel rolling method and application thereof. According to the technical scheme, the ultralow-temperature steel comprises, by mass, 0.75% -0.85% of C, 22% -26% of Mn, 0.5% -1.0% of Mo, 0.1% -0.4% of Si, the balance of Fe and unavoidable impurity elements, the thickness of the steel plate is 10-20 mm, the structure is austenite, and the grain size is 4-5 levels. Preferably, the austenitic stacking fault energy of the ultralow-temperature steel at the temperature of-269 ℃ is 42 xC+3.1 xMn-15 xC 2-0.026×Mn2 -0.063 xC xMn-58, the yield strength is not lower than 1500MPa, and the elongation after fracture is not lower than 30%. Further preferably, the austenitic stacking fault energy is 20-28 mJ/m 2. Preferably, the ultra-low temperature steel of the present invention contains 0.75% of C, 22% of Mn, 0.5% of Mo, 0.1% of Si, and the balance of Fe and unavoidable impurity elements by mass; Or 0.79% of C, 24% of Mn, 0.7% of Mo, 0.3% of Si, and the balance of Fe and unavoidable impurity elements; Or 0.85% of C, 26% of Mn, 1.0% of Mo, 0.4% of Si, and the balance of Fe and unavoidable impurity elements. The design principle of the chemical components of the ultralow-temperature steel is as follows: Martensitic steels, while very strong, have a relatively low plasticity. Moreover, martensitic steels undergo embrittlement at low temperatures and have reduced toughness, so that their use temperatures are generally not lower than-60 ℃. Even 9% Ni steel excellent in low-temperature properties is used at a temperature of not lower than-196 ℃. The austenitic steel has low temperature performance superior to martensitic steel, has the advantages of high plasticity, no magnetism and the like, and can reach ultralow temperature of-269 ℃ at the lowest use temperature, such as SUS316 austenitic stainless steel with the Ni content of about 12 percent. Austenitic stainless steel is expensive because of the addition of a large amount of Ni element. Mn can inhibit austenite from transforming into martensite, and can be used as a substitute element of Ni for improving the stability of austenite structure. The effect of Mn on the austenite stability is about half that of Ni, so that the mass percent of Mn in the ultralow-temperature steel of the invention is most preferably 22% -26%. C has a strong austenite stabilizing effect and is also an effective element for improving the stability of austenite. And C can hinder dislocation movement, improve intensity. From the viewpoint of austenite stabilization, the addition of C can increase the austenite stacking fault energy so that austenite produces twin crystals when strained rather than martensitic transformation. The strain induced twinning mechanism of austenite can significantly improve plasticity. The stacking fault energy of austenite is related to composition and temperature. The austenitic fault energy of the ultralow temperature steel of the invention is mainly determined by the mass percentage of C and Mn at the temperature of-269 ℃, and the specific expression is 42 XC+3.1 XMn-15