High-strength high-ductility cold-rolled low-alloy steel strip

Abstract

The utility model relates to steel band structure technical field, concretely relates to high strength high elongation rate cold rolled low alloy steel band, including steel band and the steel band roller of setting in steel band inside, including the base material layer, transition layer and surface function layer that stack in turn in steel band, the base material layer is cold rolled low alloy steel sheet, and the thickness is 1.0~3.0mm, transition layer thickness is 5~15mu, surface function layer thickness is 10~25mu, the base material layer, transition layer and surface function layer are combined through rolling composite process, and the bonding strength is greater than or equal to 150MPa, adopt the five layer composite structure of base material layer, transition layer, surface function layer, through the synergistic effect of each layer material, realize the balanced promotion of strength and elongation, satisfy the use demand of high -end structural part, cooperate the good combination effect of transition layer, make steel band have excellent corrosion resistance, significantly promote its service life in humid, corrosive environment, expand the application range.

Description

Technical Field

[0001] This utility model relates to the field of steel strip structure technology, specifically to high-strength, high-elongation cold-rolled low-alloy steel strip. Background Technology

[0002] Cold-rolled low-alloy steel strip is widely used in automobile manufacturing, home appliance production, and machining due to its excellent formability, weldability, and cost-effectiveness. With the continuous development of industrial technology, the performance requirements of cold-rolled low-alloy steel strip in various application fields are becoming increasingly higher. It not only needs to have high strength to meet structural load-bearing requirements, but also needs good elongation to adapt to complex forming processes such as stamping and bending.

[0003] Existing cold-rolled low-alloy steel strips often face the challenge of balancing strength and elongation: increasing the alloy content to improve strength leads to decreased plasticity, reduced elongation, and poorer formability; conversely, pursuing higher elongation sacrifices strength, failing to meet the requirements of high-strength structural components. Furthermore, some high-strength cold-rolled low-alloy steel strips suffer from poor corrosion resistance and high production costs, limiting their application in more high-end fields. Utility Model Content

[0004] In view of the above-mentioned shortcomings of the existing technology, the present invention provides a high-strength, high-elongation cold-rolled low-alloy steel strip, which can effectively solve the problems in the existing technology.

[0005] This utility model provides a high-strength, high-elongation cold-rolled low-alloy steel strip, comprising a steel strip and a steel strip roll sleeved within the steel strip. The steel strip includes a substrate layer, a transition layer, and a surface functional layer stacked sequentially. The substrate layer is a cold-rolled low-alloy steel plate with a thickness of 1.0~3.0 mm; the transition layer has a thickness of 5~15 μm; and the surface functional layer has a thickness of 10~25 μm. The substrate layer, transition layer, and surface functional layer are bonded together by a rolling composite process, with a bonding strength ≥150 MPa.

[0006] Furthermore, the transition layer is a Ni-Cu alloy layer; the surface functional layer is a Cr-Ni stainless steel layer.

[0007] Further, the alloy composition of the substrate layer by mass percentage is: C: 0.05~0.15%, Si: 0.10~0.60%, Mn: 1.00~2.00%, P: ≤0.030%, S: ≤0.015%, Al: 0.010~0.070%, with the remainder being Fe and unavoidable impurities.

[0008] Furthermore, the cold-rolled low-alloy steel strip has a yield strength ≥450MPa, a tensile strength ≥550MPa, and an elongation after fracture ≥25%.

[0009] Furthermore, a transition layer and a surface functional layer are sequentially stacked on both the upper and lower surfaces of the substrate layer to form a symmetrical five-layer composite structure.

[0010] Furthermore, the bonding surfaces between the transition layer and the substrate layer, and between the transition layer and the surface functional layer, are all rough surfaces, with a surface roughness Ra of 0.8~3.2μm.

[0011] Compared with the prior art, the beneficial effects that this utility model can achieve are: by adopting a five-layer composite structure of substrate layer, transition layer and surface functional layer, the strength and elongation are balanced and improved through the synergistic effect of each layer of materials, and the final product has a yield strength ≥450MPa, tensile strength ≥550MPa and elongation after fracture ≥25%, which meets the use requirements of high-end structural components.

[0012] In this device, the surface functional layer is made of Cr-Ni stainless steel, which, together with the good bonding effect of the transition layer, gives the steel strip excellent corrosion resistance. The salt spray test corrosion resistance time is ≥480h, which significantly improves its service life in humid and corrosive environments and expands its application range. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of the structure of this utility model; Figure 2 This is an exploded view of the structure of this utility model; Figure 3 This is a disassembled diagram of the steel strip structure in this utility model.

[0015] The labels in the diagram represent: 1. Steel strip; 11. Surface functional layer; 12. Transition layer; 13. Substrate layer; 2. Steel strip roller. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without creative effort are within the scope of protection of this utility model.

[0017] The present invention will be further described below with reference to the embodiments.

[0018] Example: High-strength, high-elongation cold-rolled low-alloy steel strip, see attached diagram. Figure 1 - Appendix Figure 3 It includes a steel strip 1 and a steel strip roller 2 sleeved inside the steel strip 1. The steel strip 1 includes a substrate layer 13, a transition layer 12 and a surface functional layer 11 stacked in sequence. The base layer 13 is a cold-rolled low-alloy steel sheet with a thickness of 1.0~3.0mm. Conventional cold-rolled low-alloy steel is selected as the base material to ensure the basic strength and elongation of the steel strip. Its composition design takes into account the basic mechanical properties, without the need to add expensive alloying elements, thus controlling production costs.

[0019] The transition layer 12 has a thickness of 5~15μm; the surface functional layer 11 has a thickness of 10~25μm; a Ni-Cu alloy layer is adopted, which utilizes the good ductility of Ni and the transition bonding characteristics of Cu to solve the interface bonding problem between the substrate layer and the surface functional layer, avoids the loose bonding caused by the difference in lattice matching degree of the two materials, and improves the stability of the overall structure.

[0020] The substrate layer 13, transition layer 12 and surface functional layer 11 are combined by a rolling composite process, with a bonding strength ≥150MPa; Cr-Ni stainless steel layer is selected, and the corrosion resistance is improved by the characteristic of Cr element to form a dense oxide film, while Ni element further enhances the plasticity and toughness of the surface layer, so that the steel strip surface has excellent corrosion resistance and formability.

[0021] The transition layer 12 is a Ni-Cu alloy layer; the surface functional layer 11 is a Cr-Ni stainless steel layer; the alloy composition of the substrate layer 13 by mass percentage is: C: 0.05~0.15%, Si: 0.10~0.60%, Mn: 1.00~2.00%, P: ≤0.030%, S: ≤0.015%, Al: 0.010~0.070%, with the remainder being Fe and unavoidable impurities.

[0022] The cold-rolled low-alloy steel strip has a yield strength ≥450MPa, a tensile strength ≥550MPa, and an elongation after fracture ≥25%. Through rolling composite, a tight bond of five layers is achieved with a bond strength ≥150MPa, ensuring that no interlayer delamination occurs during subsequent stamping, bending and other forming processes. At the same time, the rolling process can further refine the grains of the substrate layer and improve the overall strength.

[0023] The upper and lower surfaces of the substrate layer 13 are sequentially stacked with a transition layer 12 and a surface functional layer 11, forming a symmetrical five-layer composite structure. The bonding surfaces between the transition layer 12 and the substrate layer 13, and between the transition layer 12 and the surface functional layer 11, are rough surfaces with a surface roughness Ra of 0.8~3.2μm. The combination of rolling composite and annealing processes ensures that the five-layer structure is tightly bonded with a bonding strength ≥150MPa, avoids interlayer delamination during forming and processing, eliminates rolling stress, improves the uniformity of material structure, and enhances comprehensive mechanical properties.

[0024] Example 2: Substrate layer: 2.0 mm thick, alloy composition by mass percentage: C: 0.08%, Si: 0.35%, Mn: 1.50%, P: 0.012%, S: 0.004%, Al: 0.040%, the remainder being Fe and unavoidable impurities; Transition layer: a Ni-Cu alloy layer with a thickness of 10 μm; Surface functional layer: Cr-Ni stainless steel layer with a thickness of 20μm; Preparation process Substrate preparation: The substrate is prepared according to the above-mentioned composition, smelted in a converter, and then refined in an RH ladle, and continuously cast into a slab with a thickness of 200mm. The slab is heated to 1200℃ and held for 1.5 hours before hot rolling, with a final rolling temperature of 880℃. Hot-rolled steel strip with a thickness of 4.0 mm is obtained by rapidly cooling it to room temperature. The substrate layer is then cold-rolled with a reduction rate of 50% to obtain a thickness of 2.0 mm.

[0025] Interface preprocessing Prepare 10 μm thick Ni-Cu alloy strips and 20 μm thick Cr-Ni stainless steel strips. The composite interfaces of the substrate layer, Ni-Cu alloy strip, and Cr-Ni stainless steel strip were polished separately. Degrease with a degreasing agent, then remove the oxide scale by acid washing, rinse with water and dry.

[0026] Rolled composite The substrate layer, Ni-Cu alloy strip, and Cr-Ni stainless steel strip are stacked neatly in sequence and then fed into the rolling mill for hot rolling composite. Rolling temperature 900℃, rolling reduction rate 40%.

[0027] Cold rolling finishing The composite steel strip is then cold-rolled and finished with a cold rolling reduction of 15% to obtain a composite steel strip with dimensional accuracy. Annealing The cold-rolled and finished steel strip is continuously annealed at 750℃ for 3 minutes. Then cool to room temperature at a rate of 10°C / min to obtain the final product. Performance test results Yield strength: 480 MPa; Tensile strength: 580 MPa; Elongation after fracture: 28%; Interlayer bond strength: 180 MPa; Salt spray test corrosion resistance time: 520h.

[0028] Cross-sectional structural observation The five-layer structure is tightly integrated with no obvious interface gaps; Each layer has a uniform thickness.

[0029] The surface functional layer is made of Cr-Ni stainless steel, which, together with the good bonding effect of the transition layer, gives the steel strip excellent corrosion resistance. The salt spray test corrosion resistance time is ≥480h, which significantly improves its service life in humid and corrosive environments and expands its application range. The substrate layer is made of conventional cold-rolled low-alloy steel, which does not require the addition of precious alloying elements. The transition layer and surface functional layer are made of thin strip composite, resulting in lower overall production costs. Moreover, the preparation process is mature and controllable, making it suitable for large-scale industrial production.

[0030] The above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the technical solutions of the embodiments of this utility model.

Claims

1. A high-strength, high-elongation cold-rolled low-alloy steel strip, characterized in that, The system includes a steel strip (1) and a steel strip roller (2) fitted inside the steel strip (1). The steel strip (1) includes a substrate layer (13), a transition layer (12), and a surface functional layer (11) stacked in sequence. The substrate layer (13) is a cold-rolled low-alloy steel plate with a thickness of 1.0~3.0 mm. The transition layer (12) has a thickness of 5~15 μm. The surface functional layer (11) has a thickness of 10~25 μm. The substrate layer (13), the transition layer (12), and the surface functional layer (11) are combined by a rolling composite process, and the bonding strength is ≥150 MPa.

2. The high-strength, high-elongation cold-rolled low-alloy steel strip according to claim 1, characterized in that, The transition layer (12) is a Ni-Cu alloy layer; the surface functional layer (11) is a Cr-Ni stainless steel layer.

3. The high-strength, high-elongation cold-rolled low-alloy steel strip according to claim 1, characterized in that, The cold-rolled low-alloy steel strip has a yield strength ≥450MPa, a tensile strength ≥550MPa, and an elongation after fracture ≥25%.

4. The high-strength, high-elongation cold-rolled low-alloy steel strip according to claim 3, characterized in that, The substrate layer (13) has a transition layer (12) and a surface functional layer (11) stacked sequentially on both the upper and lower surfaces to form a symmetrical five-layer composite structure.

5. The high-strength, high-elongation cold-rolled low-alloy steel strip according to claim 1, characterized in that, The bonding surfaces of the transition layer (12) and the substrate layer (13) and the bonding surfaces of the transition layer (12) and the surface functional layer (11) are all rough surfaces, with a surface roughness Ra of 0.8~3.2μm.

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