Bridge cable wire rod and steel wire resistant to delayed fracture and manufacturing method of bridge cable wire rod and steel wire

Abstract

The invention discloses a delayed fracture resistant bridge cable wire rod, which contains Fe and inevitable impurities, and also contains the following chemical elements in percentage by mass: 0.90-1.20 wt.% of C; %, Si: 1.20 to 2.50 wt.%; %, 0.40 to 0.90 wt.% of Mn; %, 0.20 to 0.70 wt.% of Cr; wt.% of Al: 0.01 to 0.30 wt.%; at least one of Zn and Mg, Zn < = 0.30 wt.%, and Mg < = 0.30 wt.%; wherein each chemical element also meets the following condition: 0.42 < = [Al] + (1.3 * [Mg] + [Zn]) 1 / 2 < = 0.70, and [Mg], [Al] and [Zn] are respectively substituted into numerical values before the mass percentage of each chemical element. The invention further discloses a steel wire which is made of the wire rod. The invention further discloses a manufacturing method of the wire rod and the steel wire.

Description

Technical Field

[0001] This invention relates to a type of steel and its preparation method, and more particularly to a cable wire rod, steel wire and its preparation method. Background Technology

[0002] With the improvement of domestic manufacturing capabilities, technological research level and the ability to apply new technologies, the strength of bridge cable steel wires is gradually increasing, which puts forward increasingly higher requirements for steel materials.

[0003] For example, Chinese patent document CN110066963A, published on July 30, 2019, entitled "A 2000MPa Grade Galvanized Steel Wire for Bridge Cables and Its Manufacturing Method," discloses a 2000MPa grade galvanized steel wire for bridge cables and its manufacturing method. The chemical composition of the steel wire is: C = 0.88-0.94%, Si = 1.05-1.35%, Mn = 0.40-0.50%, Cr = 0.25-0.35%, Cu ≤ 0.07%, with the balance being Fe and unavoidable impurity elements, and also includes any one or more of B = 0.0005-0.0015%, Nb = 0.01-0.03%, and Mo = 0.01-0.03%. The produced galvanized steel wire can achieve a tensile strength of 2000MPa or higher and a torsion value of not less than 18 turns.

[0004] For example, Chinese patent document CN112458356A, published on March 9, 2021, entitled "A φ14mm wire rod for 1860MPa grade galvanized steel wire for bridge cables and its preparation method," discloses a φ14mm wire rod for 1860MPa grade galvanized steel wire for bridge cables and its preparation method. The chemical composition of the steel wire is: C = 0.84-0.88%, Si = 0.15-0.25%, Mn = 0. 0.65-0.80%, Cr=0.35-0.45%, P≤0.015%, S≤0.010%, Al≤0.005%. The finished steel wire after drawing and galvanizing has a strength higher than 1860MPa, a torsion value ≥17 times, and the core network cementite level of the wire rod can be guaranteed to be ≤1.0 grade, the decarburization depth can be guaranteed to be ≤0.7%D, the sorbitization rate can reach more than 95%, and the pearlite lamellar spacing can be guaranteed to be 100-150nm.

[0005] For example, Chinese patent document CN112501506A, published on March 16, 2021, entitled "A Steel Wire Rod for Bridge Cables and Its Manufacturing Method", discloses a steel wire rod for bridge cables and its manufacturing method. By scientifically and rationally combining the Cr, V, Al, and Si elements in the composition of the steel wire rod for bridge cables, and by adopting a reasonable manufacturing method, it reduces the number of processes, saves costs, and ensures the mechanical performance requirements of the wire rod.

[0006] However, ultra-high strength steel wire is highly susceptible to delayed fracture failure, posing a safety hazard to bridge engineering. None of the aforementioned patent documents address the problem of delayed fracture. Summary of the Invention

[0007] One of the objectives of this invention is to provide a bridge cable coil resistant to delayed fracture, which has excellent resistance to delayed fracture.

[0008] To achieve the above objectives, the present invention provides a bridge cable coil resistant to delayed fracture, which contains Fe and unavoidable impurities, and further contains the following chemical elements in the following mass percentages:

[0009] C: 0.90–1.20 wt.%; Si: 1.20–2.50 wt.%; Mn: 0.40–0.90 wt.%; Cr: 0.20–0.70 wt.%; Al: 0.01–0.30 wt.%; at least one of Zn and Mg, Zn ≤ 0.30 wt.% and Mg ≤ 0.30 wt.%;

[0010] The chemical elements also satisfy the following condition: 0.42 ≤ [Al] + (1.3 × [Mg] + [Zn]). 1 / 2 ≤0.70, where [Mg], [Al], and [Zn] are respectively replaced with the values ​​before the mass percentage sign of each chemical element.

[0011] In the bridge cable wire rod described in this invention, the combined addition of Zn, Mg, and Al elements allows the wire rod to form an Al-Zn-Mg eutectic alloy structure between the steel substrate and the coating after drawing and galvanizing. This is achieved by controlling the ratio 0.42≤[Al]+(1.3*[Mg]+[Zn]). 1 / 2 A concentration of ≤0.70 can make the Al-Zn-Mg eutectic alloy structure more stable, thus giving it excellent resistance to delayed fracture.

[0012] Furthermore, in the bridge cable coil described in this invention, the mass percentage content of each chemical element is as follows:

[0013] C: 0.90–1.20 wt.%; Si: 1.20–2.50 wt.%; Mn: 0.40–0.90 wt.%; Cr: 0.20–0.70 wt.%; Al: 0.01–0.30 wt.%; at least one of Zn and Mg, Zn ≤ 0.30 wt.% and Mg ≤ 0.30 wt.%; balance Fe and unavoidable impurities.

[0014] The design principles of each chemical element in the bridge cable coil described in this invention are as follows:

[0015] C: In the bridge cable wire rod described in this invention, carbon (C) is an essential chemical component for ensuring the strength of the steel. Increasing the C content in the steel is beneficial for forming more cementite lamellars and refining the sorbite lamellar structure, thereby giving the steel better deformation and work hardening properties, which is beneficial for improving the strength of the steel wire during subsequent processing. When the mass percentage of C in the wire rod is too low, the strength of the material will not meet the requirements. When the mass percentage of C in the wire rod is too high, it will lead to increased component segregation during alloy solidification and deterioration of material toughness. Therefore, in the bridge cable wire rod described in this invention, the mass percentage of C is controlled between 0.90 and 1.20 wt.%.

[0016] Si: In the bridge cable wire rod described in this invention, Si is often added to steel as a deoxidizer during the smelting process. Simultaneously, Si dissolved in the ferrite phase significantly improves the strength of the steel. Furthermore, during the cooling phase transformation process, Si accumulates at the interface between the ferrite and cementite phases. After the steel wire is drawn with a large reduction in surface area, degreasing in a lead bath and hot-dip galvanizing, the accumulation of Si at the phase interface slows down the decomposition of the cementite lamellars under large deformation, thereby effectively reducing the strength loss of the steel. When the mass percentage of Si in the wire rod is too high, it will significantly reduce the plasticity of the steel, causing the material to become brittle. Therefore, in the bridge cable wire rod described in this invention, the mass percentage of Si is controlled between 1.20 and 2.50 wt.%.

[0017] Mn: In the bridge cable wire rod described in this invention, Mn is added to the steel as a deoxidizer during the steelmaking process. Simultaneously, Mn readily combines with sulfur (S), a harmful element in steel, to form MnS, thereby reducing its harmful effects. Furthermore, Mn is a commonly used strengthening element in steel, primarily playing a role in solid solution strengthening, resulting in alloy cementite with higher strength. However, the Mn content in the steel should not be too high. When the mass percentage of Mn in the wire rod is too high, it will increase the tendency for grain coarsening during heating, making it more difficult to control the cooling microstructure. Therefore, in the bridge cable wire rod described in this invention, the mass percentage of Mn is controlled between 0.40 and 0.90 wt.%.

[0018] Cr: In the bridge cable wire rod described in this invention, the addition of Cr element is beneficial for refining the lamellar structure of the sorbite microstructure of the steel, while simultaneously improving the strength of cementite, thereby effectively improving the strength and plasticity of the material. To ensure that Cr element can effectively exert its benefits, the Cr element content in the steel needs to be higher than 0.20%. Correspondingly, to prevent the occurrence of abnormal martensitic microstructure and reduce the difficulty of microstructure control, the Cr element content in the steel needs to be controlled below 0.70%. Therefore, in the bridge cable wire rod described in this invention, the mass percentage content of Cr element is controlled between 0.20 and 0.70 wt.%.

[0019] Al: In the bridge cable wire rod described in this invention, Al is a deoxidizer, and its deoxidizing ability is much stronger than that of Si and Mn. Simultaneously, Al is an effective element for adjusting the grain size of steel; during solidification, a large amount of finely dispersed alumina promotes the formation of fine-grained steel. When the mass percentage content of Al in the wire rod is too high, the coarse alumina will severely reduce the drawing and fatigue properties of the wire rod and galvanized steel wire. Therefore, in the bridge cable wire rod described in this invention, the mass percentage content of Al is controlled between 0.01 and 0.30 wt.%.

[0020] Zn and Mg: In the bridge cable wire rod of this invention, the combined addition of Zn, Mg, and Al elements is beneficial for forming an Al-Zn-Mg eutectic alloy structure between the steel surface and the coating after drawing and galvanizing. By controlling the ratio of Zn and Mg alloy content, the Al-Zn-Mg eutectic alloy structure can be made more stable, improving the bonding force between the steel and the coating, thus exhibiting excellent resistance to delayed fracture. Therefore, in the bridge cable wire rod of this invention, the mass percentage of Zn is controlled to Zn ≤ 0.30 wt.%, and the mass percentage of Mg is controlled to Mg ≤ 0.30 wt.%.

[0021] Furthermore, in the unavoidable impurities of the bridge cable coils described in this invention: P ≤ 0.015 wt.%, S ≤ 0.015 wt.%.

[0022] It should be noted that in the above technical solution of the present invention, P element and S element are both impurity elements in the bridge cable coil of the present invention. When technical conditions permit, in order to obtain steel with better performance and higher quality, the content of impurity elements in steel should be reduced as much as possible.

[0023] P and S: In the bridge cable wire rod described in this invention, impurity elements P and S tend to segregate at grain boundaries, reducing the toughness of the steel and significantly affecting its cold working properties. Therefore, the content of P and S elements in the bridge cable wire rod described in this invention must be strictly controlled. The mass percentage of P element can be controlled to P ≤ 0.015 wt.%, and the mass percentage of S element can be controlled to S ≤ 0.015 wt.%.

[0024] Furthermore, in the bridge cable coils described in this invention, the performance requirements are: tensile strength ≥1380MPa and reduction of area ≥30%.

[0025] Another objective of this invention is to provide a steel wire that, after being drawn and galvanized, exhibits excellent resistance to delayed cracking and can be used in steel wire products for long-span suspension bridges and cable-stayed bridges.

[0026] To achieve the above objectives, the present invention provides a steel wire which is made from bridge cable coils as described above through at least drawing and galvanizing processes.

[0027] Furthermore, the steel wire of the present invention has a tensile strength ≥2160MPa, a breaking strength >1970MPa in an acidic solution environment, and a load strength loss rate ≤10% in an acidic solution environment.

[0028] Another objective of this invention is to provide a method for manufacturing bridge cable coils. This method, by controlling the online air-cooling process of the coils, can obtain bridge cable coils with good uniformity of structure, excellent strength and plasticity, and significant advantages in resistance to delayed fracture.

[0029] To achieve the above objectives, the present invention provides a method for manufacturing bridge cable coils, comprising the following steps:

[0030] Smelting and casting;

[0031] Rolled into wire rod;

[0032] Online air cooling of wire rod: control the spinning temperature at 900-920℃, the rapid air cooling time is 40-60s, and the temperature of the wire rod after cooling is 510-560℃, and then keep it warm.

[0033] Furthermore, in the online air-cooling step of the bridge cable coil manufacturing method of the present invention, the coil enters the insulation cover for insulation for ≥30s, and the temperature of the coil exiting the insulation cover is 460~500℃.

[0034] Another objective of this invention is to provide a method for manufacturing steel wire. This method, which involves drawing, galvanizing, and stabilizing wire rods into steel wire, can be effectively applied to steel wire products for long-span suspension bridges and cable-stayed bridges, and has significant practical implications.

[0035] To achieve the above objectives, the present invention provides a method for manufacturing steel wire, comprising the steps of:

[0036] Smelting and casting;

[0037] Rolled into wire rod;

[0038] Online air cooling of wire rod: control the spinning temperature at 900-920℃, the rapid air cooling time is 40-60s, the temperature of the wire rod after cooling is 510-560℃, and then keep it at that temperature;

[0039] Pull;

[0040] Galvanized.

[0041] Furthermore, in the online air-cooling step of the wire rod manufacturing method of the present invention, the wire rod enters the heat insulation cover for heat preservation for ≥30s, and the temperature of the wire rod exiting the heat insulation cover is 460~500℃.

[0042] Furthermore, in the drawing step of the steel wire manufacturing method of the present invention, the total drawing compression is controlled to be ≤80% and the single-pass compression is controlled to be ≤20%.

[0043] Furthermore, in the galvanizing step of the steel wire manufacturing method of the present invention, the galvanizing temperature is controlled to be 430-470°C, and / or the galvanizing time is 40-90 seconds.

[0044] The bridge cable coils, steel wires, and manufacturing method resistant to delayed fracture described in this invention have the following advantages and beneficial effects compared to the prior art:

[0045] The bridge cable wire rod resistant to delayed fracture described in this invention has the advantages of good uniformity of structure and excellent strength and plasticity through reasonable design of chemical element composition and optimization of online air cooling process.

[0046] In some embodiments, the bridge cable coils resistant to delayed fracture described in this invention have a tensile strength ≥1380MPa and a reduction of area ≥30%.

[0047] The bridge cable steel wire with delayed fracture resistance described in this invention has significant advantages in terms of delayed fracture resistance after being drawn, galvanized, and stabilized. It can be effectively applied to steel wire products for long-span suspension bridges and cable-stayed bridges.

[0048] In some embodiments, the bridge cable steel wire resistant to delayed fracture of the present invention has a tensile strength ≥2160MPa, a breaking strength >1970MPa in an acidic solution environment, and a load strength loss rate ≤10% in an acidic solution environment. Detailed Implementation

[0049] The following will further explain and illustrate the bridge cable coils, steel wires and their manufacturing method that are resistant to delayed fracture according to the present invention with reference to specific embodiments. However, this explanation and illustration do not constitute an undue limitation on the technical solution of the present invention.

[0050] Examples 1-10

[0051] The bridge cable coils described in Embodiments 1-10 of this invention are all manufactured using the following steps:

[0052] (1) Smelting and casting: Smelting can be carried out in an electric furnace or converter, followed by ladle refining. It should be noted that during ladle refining, an LF furnace with VD or RH degassing treatment process can be used, controlling the vacuum degassing time to be >20 min and the calming time to be >20 min. Casting can use the end-of-solidation light reduction technique, and the carbon segregation in the billet core can be controlled by adjusting the superheat of the tundish, the billet casting speed, cooling, and reduction amount.

[0053] (2) Rolled into wire rod;

[0054] (3) Online air cooling of wire rod: control the spinning temperature to 900-920℃, the rapid air cooling time to 40-60s, and the temperature of the wire rod after cooling to 510-560℃; then keep it warm. In some embodiments, it enters the heat preservation hood for heat preservation, the heat preservation time is ≥30s, and the temperature of the wire rod exiting the heat preservation hood is 460-500℃.

[0055] The steel wires of Embodiments 1-10 of the present invention are further manufactured using the following steps based on the bridge cable coils obtained in each embodiment:

[0056] (4) Drawing: During the drawing process, the total compression amount can be controlled to be ≤80%, and the compression amount per pass can be ≤20%;

[0057] (5) Galvanizing: During the galvanizing process, the galvanizing temperature can be controlled between 430 and 470°C, and the galvanizing time can be controlled between 40 and 90 seconds.

[0058] Table 1 lists the mass percentage of each chemical element in the bridge cable coils of Examples 1-10 of the present invention.

[0059] Table 1. (wt%, balance Fe and other unavoidable impurities besides P and S)

[0060]

[0061]

[0062] Note: DF=[Al]+(1.3×[Mg]+[Zn]) 1 / 2 Where [Mg], [Al], and [Zn] are respectively replaced with the values ​​before the mass percentage sign of the corresponding chemical element.

[0063] Table 2 lists the specific process parameters of the bridge cable coils of Embodiments 1-10 of the present invention in the above process steps.

[0064] Table 2.

[0065]

[0066] Table 3 lists the specific process parameters of the steel wires in Examples 1-10 of the present invention in the above process steps.

[0067] Table 3.

[0068]

[0069]

[0070] Samples were taken from the bridge cable coils of Examples 1-10 obtained through steps 1-3 above, and the mechanical properties of the coil samples from each example were tested. The results of the mechanical property tests are listed in Table 4. The relevant mechanical property testing methods are described below:

[0071] Mechanical property testing: GB / T 228.1—2010 "Metallic materials, tensile testing - Part 1: Test method at room temperature" is used to test the mechanical properties of wire rod.

[0072] Table 4 lists the performance test results of the bridge cable coils in Examples 1-10 of the present invention.

[0073] Table 4.

[0074] serial number Tensile strength (MPa) Reduction of area (%) Example 1 1395 31 Example 2 1423 34 Example 3 1380 38 Example 4 1411 40 Example 5 1453 35 Example 6 1387 32 Example 7 1398 31 Example 8 1423 30 Example 9 1453 31 Example 10 1398 35

[0075] As can be seen from Table 4 above, the tensile strength of the bridge cable coils in Embodiments 1-10 of the present invention is greater than or equal to 1380 MPa and the section reduction rate is greater than or equal to 30%, thus exhibiting excellent mechanical properties.

[0076] Furthermore, samples were taken from the steel wires of Examples 1-10 of the present invention obtained through steps 1-5 above, and relevant performance tests were performed on the steel wires of each example. The results of the performance tests are listed in Table 5. The relevant performance testing methods are as follows:

[0077] Mechanical property testing: The mechanical properties of the steel wire were tested in accordance with GB / T 228.1—2010 "Metallic materials, tensile testing - Part 1: Test method at room temperature".

[0078] Delayed fracture resistance test: The steel wire was immersed in an HCl solution with pH=5 and subjected to a strain rate of 10. -6 Perform a tensile test and calculate the breaking strength of the steel wire. The formula for calculating the strength loss rate is: (Temperature loss rate of steel wire in HCl solution environment / Tensile strength of steel wire at room temperature) * 100%.

[0079] Table 5 lists the performance test results of the steel wires in Examples 1-10 of the present invention.

[0080] Table 5.

[0081] serial number Tensile strength (MPa) Fracture strength in HCl solution environment (MPa) Load strength loss rate (%) Example 1 2184 2024 7.3 Example 2 2193 2006 8.5 Example 3 2203 1997 9.4 Example 4 2160 1985 8.1 Example 5 2178 1979 9.1 Example 6 2192 1997 8.9 Example 7 2214 1993 10.0 Example 8 2163 1979 8.5 Example 9 2196 1983 9.7 Example 10 2175 1987 8.6

[0082] As can be seen from Table 5 above, the steel wires of Examples 1-10 of the present invention have significant advantages in corrosion resistance. Their tensile strength is greater than or equal to 2160 MPa, their breaking strength in acidic solution environment is greater than 1970 MPa, and their load strength loss rate in acidic solution environment is less than or equal to 10%, thus exhibiting excellent resistance to delayed fracture.

[0083] Furthermore, the combination of the technical features in this case is not limited to the combination methods described in the claims of this case or the combination methods described in the specific embodiments. All technical features described in this case can be freely combined or combined in any way, unless they contradict each other.

[0084] It should also be noted that the embodiments listed above are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made thereto are those that can be directly derived or easily conceived by those skilled in the art from the content disclosed in the present invention, and should all fall within the protection scope of the present invention.

Claims

1. A bridge cable coil resistant to delayed fracture, containing Fe and unavoidable impurities, characterized in that, It also contains the following chemical elements in the following percentages by mass: C: 0.90~1.20wt.%; Si: 1.20~2.50wt.%; Mn: 0.40~0.90wt.%; Cr:

0. 20–0.70 wt.%; Al: 0.01–0.30 wt.%; at least one of Zn and Mg, Zn ≤ 0.30 wt.%, Mg≤0.30wt.%; The chemical elements also satisfy the following condition: 0.42 ≤ [Al] + (1.3 × [Mg] + [Zn]). 1 / 2 ≤0.70, where [Mg], [Al], and [Zn] are respectively replaced with the values ​​before the mass percentage sign of each chemical element.

2. The bridge cable coil as described in claim 1, characterized in that, Its mass percentage content of each chemical element is as follows: C: 0.90~1.20wt.%; Si: 1.20~2.50wt.%; Mn: 0.40~0.90wt.%; Cr: 0.20–0.70 wt.%; Al: 0.01–0.30 wt.%; at least one of Zn and Mg, Zn ≤ 0.30 wt.% and Mg ≤ 0.30 wt.%; balance Fe and unavoidable impurities.

3. The bridge cable coil as described in claim 1 or 2, characterized in that, In unavoidable impurities: P ≤ 0.015 wt.%, S ≤ 0.015 wt.%.

4. The bridge cable coil as described in claim 1 or 2, characterized in that, Its performance meets the following requirements: tensile strength ≥1380MPa, reduction of area ≥30%.

5. A steel wire, characterized in that, It is made from bridge cable coils as described in any one of claims 1-4, through at least drawing and galvanizing processes.

6. The steel wire as described in claim 5, characterized in that, Its tensile strength at room temperature is ≥2160MPa, its fracture strength in acidic solution environment is >1970MPa, and its load strength loss rate in acidic solution environment is ≤10%.

7. The method for manufacturing bridge cable coils as described in any one of claims 1-4, characterized in that, It includes the following steps: Smelting and casting; Rolled into wire rod; Online air cooling of wire rod: control the spinning temperature at 900-920℃, the rapid air cooling time is 40-60s, and the temperature of the wire rod after cooling is 510-560℃, and then keep it warm.

8. The method for manufacturing bridge cable coils as described in claim 7, characterized in that, In the online air-cooling process of wire rod, the wire rod enters the insulation cover for insulation for ≥30 seconds, and the temperature exiting the insulation cover is 460~500℃.

9. The method for manufacturing steel wire according to any one of claims 5-6, characterized in that, Including the following steps: Smelting and casting; Rolled into wire rod; Online air cooling of wire rod: control the spinning temperature at 900-920℃, the rapid air cooling time is 40-60s, the temperature of the wire rod after cooling is 510-560℃, and then keep it at the temperature; Pull; Galvanized.

10. The method for manufacturing steel wire as described in claim 9, characterized in that, In the online air-cooling process of wire rod, the wire rod enters the insulation cover for insulation for ≥30 seconds, and the temperature exiting the insulation cover is 460~500℃.

11. The method for manufacturing steel wire as described in claim 9, characterized in that, During the drawing process, the total compression amount should be controlled to be ≤80%, and the compression amount per pass should be ≤20%.

12. The method for manufacturing steel wire as described in claim 9, characterized in that, In the galvanizing process, the galvanizing temperature is controlled at 430–470°C, and / or the galvanizing time is 40–90 seconds.

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