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CN-121992300-A - Al-containing austenitic heat-resistant steel material

CN121992300ACN 121992300 ACN121992300 ACN 121992300ACN-121992300-A

Abstract

The invention relates to the technical field of metal structures, in particular to an Al-containing austenitic heat-resistant steel material, which comprises the following components in percentage by mass: 0.20 to 0.25 percent of C, 0.5 to 2.0 percent of Si, 1.0 percent of Mn, 18 to 20 percent of Cr, 5.5 to 6.5 percent of Ni, 0.2 to 0.5 percent of Mo, 1.0 to 2.0 percent of Al, 1.0 to 2.0 percent of N, less than or equal to 0.1 percent of Ce, and the balance of Fe and unavoidable impurities; smelting the material by adopting an intermediate frequency induction furnace, smelting the material at 1580-1620 ℃, refining the material by argon, and centrifugally casting and forming the material at 800 r/min; the microstructure consists of a fine-grain austenite matrix, the grain size is 3-4 grades, and NiAl phases distributed in a dispersed manner are contained in the fine-grain austenite matrix The phase forms a two-phase reinforced structure, and ensures the stability of the structure and creep resistance at high temperature.

Inventors

  • HOU XIANLIANG
  • LIU GUFENG
  • LI KEJIA
  • ZHANG FEIYU
  • WANG JING

Assignees

  • 哈密市盛镁镁业有限公司

Dates

Publication Date
20260508
Application Date
20260130

Claims (8)

  1. 1. The Al-containing austenitic heat-resistant steel material is characterized by comprising, by mass, 0.20-0.25% of C, 0.5-1.8% of Si, 0.5-0.9% of Mn, 18-20% of Cr, 5.5-6.5% of Ni, 0.2-0.5% of Mo, 1.0-2.0% of Al, and the balance of Fe and unavoidable impurities.
  2. 2. The Al-containing austenitic heat-resistant steel material according to claim 1, wherein the chemical components further comprise N and Ce rare earth, wherein the weight percentage of the N and the Ce rare earth is 1% -2% and the weight percentage of the Ce is less than or equal to 0.1%.
  3. 3. The Al-containing austenitic heat-resistant steel material according to claim 2, wherein the steel has room temperature mechanical properties of 600-730 MPa of tensile strength, 370-400 MPa of yield strength and 13-25% of elongation after breaking, and has a tensile strength of not less than 520MPa, a yield strength of not less than 350MPa and an elongation after breaking of 30% or more after 1280 ℃ x 100h of heat exposure.
  4. 4. The Al-containing austenitic heat-resistant steel material according to claim 1, wherein the material is subjected to primary homogenization heat treatment after casting, is heated to 1100-1150 ℃, is kept for 2-3 hours, and is air-cooled.
  5. 5. An Al-containing austenitic heat-resistant steel material according to claim 1, characterized in that: Aluminum element mainly forms an aluminum oxide film which is denser than chromium on the surface of the heat-resistant steel, refines the grain size of austenite in the heat-resistant steel, and precipitates needle-like NiAl phase on an austenite matrix of the heat-resistant steel in a working range of 200-450 ℃; Meanwhile, mo is precipitated at 200-450 ℃ in an austenite grain boundary And (3) strengthening phase.
  6. 6. The Al-containing austenitic heat-resistant steel of claim 1, wherein the heat-resistant steel casting has a density of 7.80-7.85 g/cm3, a microhardness of 230-260HV0.5, a surface oxide layer thickness of 8.5 μm or less after an oxidation test at 1250 ℃ for 5580 hours, and an oxidation rate of mm/h。
  7. 7. The Al-containing austenitic heat-resistant steel material according to claim 1, wherein nitrogen is added to the steel material by adding a nitrogen-containing iron alloy, and the nitrogen content is controlled to be 1.2-1.6%.
  8. 8. The Al-containing austenitic heat-resistant steel material according to claim 1 to 7, wherein the production process of the steel material comprises the steps of: preparing raw materials, namely selecting nickel plates, metal chromium, industrial pure aluminum and ferromolybdenum alloy with purity not lower than 99.7% as main materials, wherein the proportioning and weighing precision is not lower than +/-0.1%; Smelting and refining, namely smelting by adopting an intermediate frequency induction furnace, wherein the smelting atmosphere is under the protection of argon, and the alkalinity of slag is controlled to be 1.1-1.3; Pouring and cooling, namely immediately centrifugally pouring molten steel after refining, wherein the pouring temperature is 1570 ℃ plus or minus 10 ℃, naturally cooling to 200 ℃ after pouring, and then air cooling; step four, surface cleaning and defect repairing, namely, sand blasting the casting to Sa2.5 grade, wherein the difference of the surface hardness is less than or equal to 10HV; and fifthly, performance inspection, namely sequentially carrying out a high-temperature tensile test and an oxidation rate test.

Description

Al-containing austenitic heat-resistant steel material Technical Field The invention relates to the technical field of metal structures, in particular to an Al-containing austenitic heat-resistant steel material. Background The prior Cr-Ni austenitic heat-resistant steel is widely applied to a ferrosilicon magnesium-smelting reduction tank, but has a plurality of technical limitations in the high-temperature service process, and the traditional materials such as ZG3Cr24Ni7NRE, ZG35Cr25Ni20Si2 and the like are easy to generate needle-shaped martensitic transformation in a welding end socket area due to high carbon content (0.3% -0.4%), so that cracks are generated, and the welding joint strength and the tank yield are seriously reduced. In addition, the low-nickel steel has the advantages that austenite grains grow up rapidly and carbide is continuous under 1250 ℃ long-term use, so that the creep sliding of grain boundaries is obvious, and the tank body is easy to discard due to the fact that the tank body is changed from round shape into oval shape. Its oxidation resistance is mainly dependent onThe film is easy to be destroyed under the atmosphere containing sulfur and reducing, and the oxidation rate is up to more than 0.003 mm/h. Meanwhile, although the high nickel steel has excellent performance, the high cost and the shortage of resources limit the large-scale application, so the demand for an Al-containing austenitic heat-resistant steel material is growing. Most of the current markets exist, and thus, an Al-containing austenitic heat-resistant steel material is proposed in view of the above-mentioned problems. Disclosure of Invention The invention aims to provide an Al-containing austenitic heat-resistant steel material for solving the problems in the prior art. In order to achieve the above purpose, the present invention provides the following technical solutions: The Al-containing austenitic heat-resistant steel material comprises, by mass, 0.20-0.25% of C, 0.5-1.8% of Si, 0.5-0.9% of Mn, 18-20% of Cr, 5.5-6.5% of Ni, 0.2-0.5% of Mo, 1.0-2.0% of Al, and the balance of Fe and unavoidable impurities. The heat-resistant steel has a metallographic structure which is stable austenite after heat preservation for 100 hours at 1280 ℃, the grain size is 3.0-4.0 grade, the average grain diameter is not more than 80 mu m, and the material can be used without secondary solution heat treatment after smelting and centrifugal casting. Preferably, the chemical components of the alloy also comprise N and Ce rare earth, wherein the mass percent of the N and Ce rare earth is 1-2% and the content of Ce is less than or equal to 0.1%. Preferably, the steel has room temperature mechanical properties of 600-730 MPa of tensile strength, 370-400 MPa of yield strength and 13-25% of elongation after breaking, and has tensile strength of not less than 520MPa, yield strength of not less than 350MPa and elongation after breaking maintained above 30% after 1280 ℃ and 100h of heat exposure. Preferably, the material is subjected to one-time homogenization heat treatment after casting, and is heated to 1100-1150 ℃ and air-cooled after heat preservation for 2-3 hours, wherein the heat treatment ensures that elements in the alloy are uniformly distributed, the segregation degree is reduced, carbides are dispersed and distributed, and grain boundary carbide continuity is avoided; after the heat treatment, the grain diameter of carbide in the microstructure of the material is not more than 0.2 mu m, and the volume fraction of carbide is 2.5-3.0%. Preferably, the aluminum element is mainly in a solid solution form in an austenite matrix to partially form a NiAl strengthening phase, wherein the NiAl strengthening phase has a size of 0.05-0.2 mu m and is dispersed in the austenite matrix, and the distribution density is per square millimeterParticles, so that second phase precipitation strengthening is formed in a temperature range of 200-450 ℃; Meanwhile, mo is in a high temperature range The precipitate is formed and distributed along the grain boundary, and the average thickness of the grain boundary strengthening phase is 0.05-0.08 mu m. Preferably, the density of the heat-resistant steel casting is 7.80-7.85 g/cm < 3 >, the microhardness is 230-260HV0.5, and after oxidation experiment is carried out for 5580 hours under the condition of 1250 ℃, the thickness of the surface oxide layer is less than or equal to 8.5 mu m, and the oxidation rate ismm/h。 Preferably, the nitrogen in the steel is added by adding a nitrogen-containing iron alloy, the nitrogen content is controlled to be 1.2-1.6%, the austenite structure is stabilized, and the nitrogen is formed in the matrixAnd (3) a type compound for enhancing the solid solution strengthening effect. Preferably, the rare earth element Ce is as followsOr CeFe alloy form, the addition amount is 0.05-0.08%, and Ce is formed by preferentially reacting with oxygen and sulfur in the smelting proce