CN-121737581-B - In-situ autogenous Al2O3Reinforced composite low-density steel and heat deformation method thereof

Abstract

The invention discloses in-situ self-generated Al 2 O 3 reinforced composite low-density steel and a thermal deformation method thereof, wherein the in-situ self-generated Al 2 O 3 reinforced composite low-density steel comprises a steel matrix and Al 2 O 3 reinforced phases distributed in the steel matrix, the in-situ self-generated Al 2 O 3 reinforced composite low-density steel comprises, by mass, 2-5.5% of Al 2 O 3 , 9-11% of Al, 1.5-2.5% of Cu, 0.1-0.3% of C and the balance of Fe and unavoidable impurities, and the grain size of ferrite in the steel matrix is in a bimodal distribution structure, and the average grain size is 20-60 mu m. The invention can obtain the composite low-density steel with the synergistic enhancement of finer delta-ferrite matrix and fine Al 2 O 3 reinforcing phase particles, thereby remarkably improving the structure and comprehensive mechanical properties of the composite low-density steel.

Inventors

• CHU SHUANGJIE
• CHEN SAI
• MAO BO
• LIN CHUANHUA
• HU GUANGKUI
• HUANG CAIGEN
• Que Yuehai

Assignees

• 宝山钢铁股份有限公司
• 上海交通大学

Dates

Publication Date

20260512

Application Date

20260227

Claims (6)

1. 1. The in-situ self-generated Al 2 O 3 reinforced composite low-density steel comprises a steel matrix and Al 2 O 3 reinforced phases distributed in the steel matrix, and is characterized in that the in-situ self-generated Al 2 O 3 reinforced composite low-density steel comprises, by mass, 2-5.5% of Al 2 O 3 , 9-11% of Al, 1.5-2.5% of Cu, 0.1-0.3% of C, and the balance of Fe and unavoidable impurities; The grain size of ferrite in the steel matrix is in a bimodal distribution structure, and the average grain size is 20-60 mu m; The average size of the Al 2 O 3 reinforcing phase is 1.5-3 mu m, the Al 2 O 3 reinforcing phase is formed by in-situ reaction of oxygen element in metal oxide molten salt and aluminum element in high-aluminum steel melt in the smelting process, the Al 2 O 3 reinforcing phase is uniformly dispersed and distributed in a steel matrix, and the proportion of agglomerated particles of the Al 2 O 3 reinforcing phase is less than or equal to 3%; The tensile strength sigma b of the in-situ self-generated Al 2 O 3 reinforced composite low-density steel is 1000-1200 MPa, the yield strength sigma 0.2 is 800-900 MPa, and the after-fracture elongation delta is 15-25%.
2. 2. A heat deformation method of in-situ self-produced Al 2 O 3 reinforced composite low-density steel as claimed in claim 1, comprising the following steps: S1, homogenizing an in-situ self-generated Al 2 O 3 reinforced composite low-density steel ingot at the temperature of 1000-1150 ℃, and then transferring the homogenized steel ingot into normal-temperature circulating water for cooling; s2, heating the homogenized cast ingot to 900-1100 ℃ for high-temperature thermal deformation treatment, wherein the deformation mode adopts multidirectional forging, the single-pass deformation is 5-10%, and the accumulated deformation is controlled to be 50-70%; S3, carrying out solution treatment on the cast ingot subjected to the high-temperature heat deformation treatment, wherein the solution treatment temperature is 650-750 ℃, and then cooling to room temperature; and S4, heating the ingot subjected to solution treatment to 350-550 ℃ for medium-temperature heat deformation treatment, wherein the deformation mode adopts multidirectional forging, the single-pass deformation is 5-10%, the cumulative deformation is controlled to be 20-30%, and finally the in-situ self-produced Al 2 O 3 reinforced composite low-density steel with ferrite grain sizes in a bimodal distribution structure is formed.
3. 3. The method for heat deformation of in-situ self-produced Al 2 O 3 reinforced composite low-density steel according to claim 2, wherein in the step S1, the equipment used for homogenizing treatment is a muffle furnace, and the heat preservation time is 1-3 h.
4. 4. The method for heat deformation of in-situ self-produced Al 2 O 3 reinforced composite low-density steel according to claim 2, wherein in the step S2, the strain rate of the high-temperature heat deformation treatment is 0.1-10S -1 , and the temperature is kept at 900-1100 ℃ for 3-5 min after each reduction.
5. 5. The method for heat deformation of in-situ self-produced Al 2 O 3 -reinforced composite low-density steel according to claim 2, wherein in step S3, the equipment used for solution treatment is a vacuum heat treatment furnace, and the solution treatment time is 0.5-1 h.
6. 6. The method for heat deformation of in-situ self-produced Al 2 O 3 reinforced composite low-density steel according to claim 2, wherein in step S4, the strain rate of the medium-temperature heat deformation treatment is 0.1-10S -1 , and the temperature is kept at 350-550 ℃ for 3-5 min after each reduction.

Description

In-situ self-generated Al 2O3 reinforced composite low-density steel and thermal deformation method thereof Technical Field The invention relates to the technical field of steel-based composite materials, in particular to in-situ self-generated Al 2O3 reinforced composite low-density steel and a thermal deformation method thereof. Background Along with the increasing requirements of energy conservation, emission reduction and sustainable development in the global scope, the requirements of the fields of aerospace, transportation and the like on lightweight and high-performance structural materials are urgent. Iron and steel materials are dominant in structural applications due to their mature production process, low cost and excellent combination of properties. Therefore, development of lightweight steel materials with high specific strength (strength/density) is one of the hot spots of current materials science research. Currently, the most commonly used method for reducing the density of steel is to add a certain amount of Al to the steel, and the density of the steel can be reduced by 1.3% every time 1wt% of Al is added, however, the introduction of a large amount of Al also causes a series of problems. The high-aluminum low-density steel has the problems of low elastic modulus, coarse grains, pure delta-ferrite of matrix structure, insufficient strong plastic matching and the like while reducing the density. Al 2O3 particles which are dispersed and distributed are generated in the steel matrix by utilizing in-situ autogenous reaction, so that the elastic modulus and the strength of the material can be effectively improved. However, as the as-cast structure has defects and the delta-ferrite grains of the matrix are coarse, the plasticity of the material is poor, and the engineering application of the material is limited. Chinese patent publication No. CN119571201A discloses an in-situ self-generated Al 2O3 reinforced low-density steel-based composite material and a preparation method thereof, wherein the in-situ self-generated Al 2O3 reinforced low-density steel-based composite material comprises a steel matrix and Al 2O3 reinforced phases distributed in the steel matrix, the steel matrix is high-alumina steel, the Al 2O3 reinforced phases are generated by in-situ reaction of oxygen elements in metal oxide molten salt and aluminum elements in high-alumina steel melt in the smelting process, the volume percentage of the Al 2O3 reinforced phases in the steel matrix is 10-20%, the technology realizes the primary metallurgical combination of the reinforced phases and the matrix through in-situ reaction although the Al 2O3 reinforced phases are generated in the steel matrix, but the obtained as-cast composite material still has typical as-cast structure defects such as coarse dendrite structures, remarkable component segregation, holes, shrinkage cavities, microcracks and the like caused by rapid solidification, so that the Al 2O3 reinforced phases are unevenly distributed in the matrix, the local area reinforced phases are enriched, and the interface combination quality is unstable. In addition, the high-density residual stress and insufficiently digested dislocation structure formed in the as-cast solidification process often lead to lower overall mechanical properties of the material and larger fluctuation. As mentioned above, the technical route of generating the dispersed Al 2O3 particles in the steel matrix by in-situ autogenous reaction faces a key technological problem in the industrial application, namely how to optimize the coarse and brittle as-cast structure. Because the low density steel matrix is pure delta-ferrite, no transformation occurs during the cooling process, and the traditional steel fails by virtue of a mechanism of 'transformation induced crystallization' for refining grains. Thus, achieving significant refinement of matrix grains without phase changes has become a significant challenge. In the prior art, single thermal deformation (such as rolling and forging) or subsequent heat treatment is mostly relied on, however, the methods have the limitations that the single thermal deformation can break coarse grains, but the reinforcing phase grains are difficult to uniformly distribute, the energy storage in a deformed structure is higher, if proper heat treatment is not matched, the performance is unstable, and the single heat treatment has limited grain refinement effect on the phase-change-free material, so that the as-cast defect cannot be effectively improved. Therefore, the existing technology often fails to realize three aims of uniform dispersion distribution of particles, remarkable refinement of matrix grains and synergistic improvement of strong plasticity in a synergistic way. In conclusion, the development of a novel thermal deformation method capable of effectively coordinating Al 2O3 particle distribution, refining ferrite grains and finally realizing excellent comprehensiv