Annealing-free ultrahigh-strength steel and production process thereof

Abstract

The invention discloses annealing-free ultrahigh-strength steel and a production process thereof, and relates to the technical field of steel production, and the annealing-free ultrahigh-strength steel comprises the following chemical components in percentage by mass: less than or equal to 0.1% of C, 0.50-1.50% of Si, 2.00-4.00% of Mn, 0.5-2.5% of Cr, 1.5-3.5% of Ni and the balance of Fe and inevitable impurities. The ultra-low C component design is adopted, the C content is smaller than or equal to 0.1%, the hot rolling state martensite structure transformation tendency is reduced, according to the ultra-high-strength steel produced through the production technology, the hot rolling state tensile strength is 1150-1250 MPa, the percentage reduction of area is larger than or equal to 70%, the metallographic structure is bainite + ferrite, a user can achieve annealing-free drawing machining, and the expected effect is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of steel production, and particularly to an annealing-free ultra-high strength steel and its production process. Background Art

[0002] The annealing-free drawing technology is a new technology developed on the basis of the traditional drawing process, and has the significant advantages of energy conservation, environmental protection, improving production efficiency and reducing costs. Ultra-high strength steels face challenges such as low reduction of area, poor plasticity, severe work hardening and process stability. Drawing and processing in the hot-rolled state are prone to drawing fracture, and the traditional production process requires annealing and softening treatment before drawing and processing. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide an annealing-free ultra-high strength steel and its production process.

[0004] In order to solve the above technical problems, the technical solution of the present invention is as follows: An annealing-free ultra-high strength steel, the chemical components and mass percentages thereof are: C: ≤0.1%, Si: 0.50% - 1.50%, Mn: 2.00% - 4.00%, Cr: 0.5 - 2.5%, Ni: 1.5 - 3.5%, and the balance is Fe and inevitable impurities.

[0005] As a preferred scheme of the annealing-free ultra-high strength steel of the present invention, wherein: the tensile strength of the annealing-free ultra-high strength steel is 1150 - 1250 MPa, the reduction of area ≥70%, and the metallographic structure is bainite + ferrite.

[0006] The present invention also provides a production process of an annealing-free ultra-high strength steel, including: Spinning at a preset temperature; After spinning, it enters the Stelmor air-cooling line for controlled cooling.

[0007] As a preferred scheme of the production process of the annealing-free ultra-high strength steel of the present invention, wherein: the preset temperature for spinning is 800 - 930 °C.

[0008] As a preferred scheme of the production process of the annealing-free ultra-high strength steel of the present invention, wherein: the controlled cooling after spinning includes: Using 5 - 10 fans to cool the wire rod.

[0009] As a preferred scheme of the production process of the annealing-free ultra-high strength steel of the present invention, wherein: the cooling rate of the wire rod is 10 - 20 °C / s.

[0010] As a preferred embodiment of the production process of the non-annealed ultra-high strength steel of the present invention, wherein: the controlled cooling after wire laying into the Stelmor air cooling line further includes: Set the air cooling roller table to a roller table speed increase of 110%-120%.

[0011] The beneficial effects of the present invention are: The present invention adopts an ultra-low C composition design, with a C content ≤ 0.1%, reducing the transformation tendency of martensite structure in the hot-rolled state. Moreover, for the ultra-high strength steel produced by the production process of the present invention, the hot-rolled state meets a tensile strength of 1150-1250 MPa, a reduction of area ≥ 70%, and the metallographic structure is bainite + ferrite. Users can achieve non-annealed drawing processing to achieve the expected effect. Specific embodiments

[0012] To make the content of the present invention more clearly understood, the following further detailed description of the present invention is made according to specific embodiments.

[0013] The present application provides a non-annealed ultra-high strength steel, and its chemical components and mass percentages are: C: ≤ 0.1%, Si: 0.50% - 1.50%, Mn: 2.00% - 4.00%, Cr: 0.5 - 2.5%, Ni: 1.5 - 3.5%, and the balance is Fe and a small amount of inevitable impurities.

[0014] Among them, an ultra-low C composition design is adopted, with a C content ≤ 0.1%, reducing the transformation tendency of martensite structure in the hot-rolled state.

[0015] The present application also provides a production process of a non-annealed ultra-high strength steel, and this production process specifically includes the following steps: Step S101: Carry out wire laying at a preset temperature.

[0016] Specifically, carry out wire laying operation at a preset temperature of 800 - 930 °C.

[0017] Step S102: After wire laying, enter the Stelmor air cooling line for controlled cooling.

[0018] Specifically, after wire laying, enter the Stelmor air cooling line for controlled cooling. Use 5 - 10 fans to cool air at a cooling rate of 10 - 20 °C / s, so that the supercooled austenite is fully transformed into bainite + ferrite structure to obtain ideal comprehensive mechanical properties. At the same time, set the air cooling roller table to a roller table speed increase of 110% - 120% to reduce the temperature difference between the lapping point and the middle point and improve the overall uniformity of the wire rod.

[0019] The ultra-high strength steel produced by using the above production process, in the hot-rolled state, meets a tensile strength of 1150 - 1250 MPa, a reduction of area ≥ 70%, and the metallographic structure is bainite + ferrite. Users can achieve non-annealed drawing processing to achieve the expected effect.

[0020] The following is a further illustration through specific embodiments.

[0021] For a certain enterprise's ultra-high-strength steel wire rod, the Φ8mm wire rod is obtained through production rolling. The specific requirements are as follows: The composition design includes the following components by weight percentage: C: 0.9%, Si: 1.1%, Mn: 2.8%, Cr: 0.9%, Ni: 3.0%, and the balance is Fe and a small amount of inevitable impurities. The addition of Mn, Si, Cr, and Ni components improves the strength and toughness of the steel. Among them, an ultra-low C composition design is adopted, with a C content of 0.9%, reducing the transformation tendency of martensite structure in the hot-rolled state.

[0022] Spinning is carried out at a temperature of 850°C. After spinning, it enters the Stelmor air-cooling line for controlled cooling. 8 fans are used for air-cooling at a cooling rate of 12°C / s, enabling the supercooled austenite to be fully transformed into bainite + ferrite structure, obtaining ideal comprehensive mechanical properties. The air-cooling roller table is set with a 115% roller speed increase to reduce the temperature difference between the lapping point and the middle point and improve the overall uniformity of the wire rod.

[0023] For the high-strength steel wire rod produced by the above process, the mechanical properties and metallographic structure detection results in the hot-rolled state are shown in Table 1:

[0024] Table 1 As can be seen from Table 1, for the Φ8mm ultra-high-strength steel wire rod, the tensile strength in the hot-rolled state is 1155 - 1160 MPa, the elongation after fracture is ≥70%, the metallographic structure is bainite + ferrite, and all the finished product detections after production meet the technical requirements. The user can achieve annealing-free drawing processing, and the comprehensive performance is excellent.

[0025] In addition to the above embodiments, the present invention can also have other implementation manners; all technical solutions formed by equivalent replacement or equivalent transformation fall within the protection scope required by the present invention.

Claims

1. An annealing-free ultra-high strength steel, characterized in that: Its chemical composition and mass percentage are: C: ≤0.1%, Si: 0.50%~1.50%, Mn: 2.00%~4.00%, Cr: 0.5-2.5%, Ni: 1.5-3.5%, and the balance is Fe and unavoidable impurities.

2. The annealing-free ultra-high strength steel according to claim 1, characterized in that: The tensile strength of the annealing-free ultra-high strength steel is 1150-1250 MPa, the cross-sectional shrinkage is ≥70%, and the metallographic structure is bainite+ferrite.

3. A production process for annealing-free ultra-high strength steel according to claim 1 or 2, characterized in that: include: The silk is spun using a preset temperature; After spinning, the silk enters the Stelmore air-cooled line for controlled cooling.

4. The production process of annealing-free ultra-high strength steel according to claim 3, characterized in that: The preset temperature for spinning is 800-930°C.

5. The production process of annealing-free ultra-high strength steel according to claim 3, characterized in that: The controlled cooling of the silk after spinning into the Stelmore air cooling line includes: 5 to 10 fans are used to cool the wire.

6. The production process of annealing-free ultra-high strength steel according to claim 5, characterized in that: The cooling rate of the wire is 10-20℃ / s.

7. The production process of annealing-free ultra-high strength steel according to claim 5, characterized in that: The step of entering the Stelmore air-cooling line for controlled cooling after spinning also includes: Set the air-cooled roller to 110%-120% roller speed increase.

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