High strength steel strand and method of making same

Abstract

The application relates to the technical field of steel strands, and discloses a high-strength steel strand and a preparation method thereof, which is obtained by twisting a plurality of steel wires, and the steel wire is composed of the following components in percentage by weight: C 0.8%-0.9%, Si 0.3%-0.5%, Mn 0.4%-0.5%, Cr 0.1%-0.2%, P 0.01%-0.015%, S 0.005%-0.01%, Ni 0.2%-0.3%, Mo 0.01%-0.015%, Al 0.02%-0.03%, Ti 0.03%-0.045%, and the balance is iron and inevitable impurities; wherein the percentage by weight of Mo, Al and Ti satisfies the relationship formula: (Mo+Al) / Ti=0.875-1. The steel strand adopts the steel wire with a tensile strength greater than or equal to 2009 MPa, so that the steel strand obtained by twisting the plurality of steel wires has high mechanical strength.

Description

Technical Field

[0001] This invention relates to the field of steel strand technology, specifically to a high-strength steel strand and its preparation method. Background Technology

[0002] As a core load-bearing and reinforcing component in cable structures, steel strand is widely used in cable products across various fields such as power transmission and distribution, communications, transportation, and construction. Examples include overhead ground wires for power transmission lines, steel-cored aluminum stranded wire reinforcing cores, reinforcing components for optical fiber cables, load-bearing structures for signal and power cables in subways and railways, and tensile strength components for cables used in marine engineering. Its mechanical strength directly determines the operational safety and service life of the cable. With the continuous expansion of cable applications under extreme conditions, higher requirements are being placed on the mechanical strength of steel strand used in cables.

[0003] Therefore, it is proposed that a high-strength steel strand and its preparation method be developed. Summary of the Invention

[0004] This invention proposes a high-strength steel strand and its preparation method. The steel strand has high mechanical strength, which can improve the safety and service life of cable operation.

[0005] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a high-strength steel strand, which is obtained by stranding several steel wires, wherein the steel wires are composed of the following components by weight percentage: C 0.8%~0.9%, Si 0.3%~0.5%, Mn 0.4%~0.5%, Cr 0.1%~0.2%, P 0.01%~0.015%, S 0.005%~0.01%, Ni 0.2%~0.3%, Mo 0.01%~0.015%, Al 0.02%~0.03%, Ti 0.03%~0.045%, with the balance being iron and unavoidable impurities; wherein the weight percentages of Mo, Al, and Ti satisfy the relationship: (Mo+Al) / Ti=0.875~1.

[0006] In one embodiment, the method for preparing the steel wire includes the following steps: after batching according to the composition of the steel wire, the steel wire is subjected to smelting, continuous casting, hot rolling, pickling, phosphating, drawing, heat treatment, and lead quenching to obtain the steel wire.

[0007] In one embodiment, the drawing process employs eight passes, with each pass having a compression rate of 10% to 20%.

[0008] In one embodiment, the pulling rate is 5~8 m / min.

[0009] In one embodiment, after the first, second, third, and fourth drawing passes are performed sequentially, the drawing is then heat-treated at 350-400℃ for 10-15 minutes, followed by the fifth, sixth, seventh, and eighth drawing passes in sequence.

[0010] In one implementation, the compression ratios of the third, fourth, fifth, and sixth drawing passes are all higher than those of the first, second, seventh, and eighth drawing passes.

[0011] In one implementation, the compression ratios of the fifth and sixth drawing passes are greater than the compression ratios of the third and fourth drawing passes.

[0012] In one embodiment, the heat treatment process is as follows: first, heat treatment at 450~500℃ in a heating furnace for 1~2 hours, then heat treatment at 550~600℃ at a rate of 5~10℃ / min for 1~2 hours, and then heat treatment at 650~700℃ at a rate of 5~10℃ / min for 30~40 minutes.

[0013] In one embodiment, the lead quenching process is as follows: standing in a lead bath at 550~570℃ for 2~4 minutes.

[0014] Secondly, the present invention provides a method for preparing the above-mentioned high-strength steel strand, comprising the following steps: stranding several steel wires together to obtain high-strength steel strand.

[0015] To improve the strength of the steel strand, this invention rationally selects the steel wire composition and limits the mass percentages of Mo, Al, and Ti to satisfy the relationship: (Mo+Al) / Ti=0.875~1, which has the following beneficial effects: Ti is a carbonitride forming element in steel wire composition. The carbonitrides formed have a reinforcing effect and can inhibit grain growth. However, Ti alone tends to form coarse titanium nitride. Al can preferentially combine with N to form aluminum nitride, reducing the formation of coarse titanium nitride and refining the grains. Mo can inhibit carbide precipitation and reduce brittleness. By limiting Mo, Al and Ti to satisfy the relationship (Mo+Al) / Ti=0.875~1, grain growth can be better inhibited, precipitation strengthening can be achieved, brittleness can be reduced, thereby improving the mechanical strength of steel wire and thus improving the overall mechanical strength of steel strand. Detailed Implementation

[0016] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0017] Existing steel strands suffer from insufficient mechanical strength, making them unsuitable for applications involving long spans and high loads. Consequently, they are prone to tensile deformation and strand breakage during use, seriously threatening the safe operation of cables. To address this issue, this invention provides a high-strength steel strand, which is formed by twisting several steel wires together. The mass percentage relationship of Mo, Al, and Ti in the steel wire composition is further defined to improve the tensile strength of the steel wires, thereby enhancing the overall tensile strength of the resulting steel strand.

[0018] Specifically, in order to better understand the technical solution of the present invention, it is described in the following parts.

[0019] Part One This invention provides a high-strength steel strand wire, which is obtained by stranding several steel wires. The steel wire is composed of the following components by weight percentage: C 0.8%~0.9%, Si 0.3%~0.5%, Mn 0.4%~0.5%, Cr 0.1%~0.2%, P 0.01%~0.015%, S 0.005%~0.01%, Ni 0.2%~0.3%, Mo 0.01%~0.015%, Al 0.02%~0.03%, Ti 0.03%~0.045%, with the balance being iron and unavoidable impurities; wherein the weight percentages of Mo, Al, and Ti satisfy the relationship: (Mo+Al) / Ti=0.875~1, preferably 0.95.

[0020] In this invention, the steel wire composition includes 0.8%~0.9% C, for example, 0.8%, 0.82%, 0.84%, 0.85%, 0.86%, 0.88%, or 0.90%, etc.; it forms the matrix of the high-strength steel wire; the carbon content ensures sufficient cementite lamellars, providing the upper limit of matrix strength. The steel wire composition includes 0.3%~0.5% Si, for example, 0.3%, 0.32%, 0.35%, 0.36%, 0.38%, 0.40%, 0.45%, 0.50%, etc.; it has the functions of solid solution strengthening, inhibiting cementite coarsening, deoxidation, reducing inclusions, and improving drawing toughness. The steel wire composition includes 0.4%~0.5% Mn, for example, it can be 0.4%, 0.42%, 0.44%, 0.45%, 0.46%, 0.48%, 0.50%, etc.; it has the functions of deoxidation and desulfurization, solid solution strengthening, and improving hardenability. The steel wire composition includes Cr 0.1%~0.2%, for example, 0.1%, 0.12%, 0.14%, 0.15%, 0.16%, 0.18%, 0.20%, etc.; P 0.01%~0.015%, for example, 0.01%, 0.011%, 0.012%, 0.013%, 0.014%, 0.015%, etc.; S 0.005%~0.01%, for example, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, etc.; Ni 0.2%~0.3%, for example, 0.2%, 0.22%, 0.24%, 0.25%, 0.26%, 0.28%, 0.30%, etc.; Mo The steel wire composition includes Al 0.01%~0.015%, for example, 0.01%, 0.011%, 0.012%, 0.013%, 0.014%, 0.015%, etc.; the steel wire composition includes Al 0.02%~0.03%, for example, 0.02%, 0.022%, 0.024%, 0.025%, 0.026%, 0.028%, 0.03%, etc.; the steel wire composition includes Ti 0.03%~0.045%, for example, 0.03%, 0.032%, 0.035%, 0.038%, 0.040%, 0.042%, 0.045%, etc.

[0021] In some embodiments of the present invention, the method for preparing steel wire includes the following steps: after batching according to the composition of steel wire, the steel wire is smelted, continuously cast, hot rolled, pickled, phosphated, drawn, heat treated, and lead quenched to obtain steel wire.

[0022] In some embodiments of the present invention, the drawing process employs eight passes, with each pass having a compression rate of 10% to 20%, for example, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc.

[0023] In some preferred embodiments of the present invention, the drawing process employs eight passes, with the compression rates as follows: 12.1% for the first pass, 13.5% for the second pass, 16.4% for the third pass, 17.5% for the fourth pass, 18.9% for the fifth pass, 19.5% for the sixth pass, 14.2% for the seventh pass, and 13.0% for the eighth pass. The drawing process parameters of the present invention employ a combination of gradual shaping with small deformation, progressively increasing pressure in the middle stage to peak deformation for grain refinement and fiberization, and final small deformation for sizing. This, along with mid-process stress-relief heat treatment, results in eight passes of non-uniform gradient compression rate drawing, which maximizes the tensile strength of the steel wire and consequently improves the tensile strength of the stranded steel wire.

[0024] In some embodiments of the present invention, the drawing rate is 5~8 m / min, for example, it can be 5 m / min, 5.5 m / min, 6 m / min, 6.5 m / min, 7 m / min, 7.5 m / min, 8 m / min, etc.

[0025] In some embodiments of the present invention, after the first, second, third, and fourth drawing passes in the eight-pass drawing process, the drawing is heat-treated at 350-400°C for 10-15 minutes, followed by the fifth, sixth, seventh, and eighth drawing passes in sequence. The 350-400°C can be, for example, 350°C, 360°C, 370°C, 380°C, 390°C, 400°C, etc.; the 10-15 minutes can be, for example, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes, 15 minutes, etc.

[0026] In some embodiments of the present invention, the compression ratios of the third, fourth, fifth, and sixth drawing passes are all higher than those of the first, second, seventh, and eighth drawing passes.

[0027] In some embodiments of the present invention, the compression ratio of the fifth and sixth drawing passes is greater than that of the third and fourth drawing passes.

[0028] In some embodiments of the present invention, the heat treatment process is as follows: first, heat treatment at 450-500°C in a heating furnace for 1-2 hours; then, heat treatment at 550-600°C at a rate of 5-10°C / min for 1-2 hours; and finally, heat treatment at 650-700°C at a rate of 5-10°C / min for 30-40 minutes; wherein the 450-500°C heat treatment for 1-2 hours can be, for example, 450°C, 460°C, 470°C, 480°C, or 490°C. ℃, 500℃, 1~2h, for example, 1h, 1.2h, 1.4h, 1.5h, 1.6h, 1.8h, 2h, etc.; among which, 650~700℃ heat treatment for 30~40min, 650~700℃ for example, 650℃, 660℃, 670℃, 680℃, 690℃, 700℃, etc., 30~40min for example, 30min, 32min, 34min, 35min, 36min, 38min, 40min, etc. In the heat treatment process parameters of this invention, a low-temperature holding treatment of 450~500℃ is first adopted. On the one hand, this facilitates the preferential combination of Al and N to form AlN, avoiding the rapid formation of coarse titanium nitride at subsequent high temperatures. On the other hand, it can eliminate residual internal stress in the drawing process. Then, the medium-temperature range of 550~600℃ allows Mn, Cr, and Ni to fully dissolve and diffuse, resulting in a uniform microstructure. At the same time, Ti and Mo carbonitrides pin the grain boundaries, effectively inhibiting abnormal grain growth. Finally, the high-temperature range of 650~700℃ allows for sufficient precipitation strengthening. The short-time heat treatment avoids grain coarsening, and the limited heating rate further avoids the generation of thermal stress and compositional inhomogeneity, fully utilizing the strengthening effect of each component in the steel wire, further improving the mechanical strength of the steel wire, and thus improving the overall mechanical strength of the steel strand.

[0029] In some embodiments of the present invention, the lead quenching process is as follows: standing in a lead bath at 550~570℃ for 2~4 minutes; wherein 550~570℃ can be, for example, 550℃, 555℃, 560℃, 565℃, 570℃, etc., and 2~4 minutes can be, for example, 2 minutes, 2.5 minutes, 3 minutes, 3.5 minutes, 4 minutes, etc.

[0030] Part Two, The present invention also provides a method for preparing a high-strength steel strand, which includes the following steps: stranding several steel wires together to obtain a high-strength steel strand.

[0031] method The following methods are used to determine the performance defined in the examples and comparative examples.

[0032] Tensile strength shall be tested in accordance with the method in GB / T 228.1-2021 "Metallic materials, tensile testing - Part 1: Test at room temperature"; Example 1 A method for preparing high-strength steel strand includes the following steps: After the steel wire components are batched according to the mass percentages shown in Table 1, the process involves smelting, continuous casting, hot rolling, pickling, phosphating, drawing, heat treatment, and standing in a 550℃ lead bath for 4 minutes, followed by cooling to obtain steel wire. One steel wire is used as the core wire, and 16 steel wires are used as the edge wires for stranding to obtain steel strand. The drawing process parameters and heat treatment process parameters are shown in Tables 2 and 3.

[0033] Example 2 A method for preparing high-strength steel strand includes the following steps: After the steel wire components are prepared according to the mass percentages shown in Table 1, the process involves smelting, continuous casting, hot rolling, pickling, phosphating, drawing, heat treatment, and standing in a 570℃ lead bath for 2 minutes, followed by cooling to obtain steel wire. One steel wire is used as the core wire, and 16 steel wires are used as the edge wires to be stranded together to obtain steel strand. The drawing process parameters and heat treatment process parameters are shown in Tables 2 and 3.

[0034] Example 3 Except for the mass percentages of each component of the steel wire as shown in Table 1, everything else is the same as in Example 1.

[0035] Example 4 Except for the mass percentages of each component of the steel wire as shown in Table 1, everything else is the same as in Example 2.

[0036] Example 5 Except for the mass percentages of each component of the steel wire as shown in Table 1, everything else is the same as in Example 2.

[0037] Examples 6-8 Except for the different drawing process parameters in Table 2, everything else is the same as in Example 1.

[0038] Examples 9-12 Except for the heat treatment process parameters in Table 3, everything else is the same as in Example 1.

[0039] Comparative Example 1 Except for the mass percentages of each component of the steel wire as shown in Table 1, everything else is the same as in Example 2.

[0040] Comparative Example 2 Except for the mass percentages of each component of the steel wire as shown in Table 1, everything else is the same as in Example 2.

[0041] Table 1. Weight percentage of each component in steel wire

[0042] Table 2 Drawing process parameters

[0043] Table 3 Heat treatment process parameters

[0044] Table 4. Tensile strength test results of steel wires in Examples 1-5 and Comparative Examples 1-2

[0045] Table 5. Results of tensile strength tests on steel wires in Examples 6-12

[0046] Compared with Examples 2, 4 and 5, Comparative Examples 1 and 2 changed the weight ratio of Mo, Al and Ti in the steel wire. As a result, the tensile strength of the steel wire in Comparative Examples 1 and 2 was lower than that in Examples 2 and 4 and 5. This shows that the limitation of the steel wire composition in the present invention can improve the tensile strength of the steel wire, and thus improve the overall tensile strength of the steel strand.

[0047] Compared with Example 1, Examples 6-8 changed the drawing process parameters, and the tensile strength of the steel wire in Example 1 was higher than that in Examples 6-8. Compared with Example 1, Examples 9-12 changed the heat treatment process parameters, and the tensile strength of the steel wire in Examples 1, 9, and 10 was higher than that in Examples 11-12. This shows that under the drawing process parameters and heat treatment process parameters further defined in this invention, the tensile strength of the steel wire can be further improved, thereby improving the overall tensile strength of the steel strand.

[0048] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-strength steel strand, characterized in that, It is obtained by stranding several steel wires, wherein the steel wires are composed of the following components by weight percentage: C 0.8%~0.9%, Si 0.3%~0.5%, Mn 0.4%~0.5%, Cr 0.1%~0.2%, P 0.01%~0.015%, S 0.005%~0.01%, Ni 0.2%~0.3%, Mo 0.01%~0.015%, Al 0.02%~0.03%, Ti 0.03%~0.045%, with the balance being iron and unavoidable impurities; wherein the weight percentages of Mo, Al, and Ti satisfy the relationship: (Mo+Al) / Ti=0.875~1.

2. The high-strength steel strand according to claim 1, characterized in that, The method for preparing the steel wire includes the following steps: after the steel wire is prepared according to its composition, it is smelted, continuously cast, hot rolled, pickled, phosphated, drawn, heat treated, and lead quenched to obtain the steel wire.

3. The high-strength steel strand according to claim 2, characterized in that, The drawing process employs eight passes, with each pass having a compression rate of 10% to 20%.

4. The high-strength steel strand according to claim 3, characterized in that, The drawing rate is 5~8 m / min.

5. A high-strength steel strand according to claim 3, characterized in that, The eight drawing passes consist of the first, second, third, and fourth drawing passes, followed by heat treatment at 350-400℃ for 10-15 minutes, and then the fifth, sixth, seventh, and eighth drawing passes.

6. A high-strength steel strand according to claim 5, characterized in that, The compression rates of the third, fourth, fifth, and sixth drawing passes are all higher than those of the first, second, seventh, and eighth drawing passes.

7. A high-strength steel strand according to claim 6, characterized in that, The compression ratios of the fifth and sixth drawing passes are greater than those of the third and fourth drawing passes.

8. A high-strength steel strand according to claim 2, characterized in that, The heat treatment process is as follows: first, heat treatment at 450~500℃ for 1~2 hours in a heating furnace, then heat treatment at 550~600℃ for 1~2 hours at a rate of 5~10℃ / min, and then heat treatment at 650~700℃ for 30~40 minutes at a rate of 5~10℃ / min.

9. A high-strength steel strand according to claim 2, characterized in that, The lead quenching process is as follows: stand in a lead bath at 550~570℃ for 2~4 minutes.

10. A method for preparing a high-strength steel strand, used to prepare the high-strength steel strand according to any one of claims 1 to 9, characterized in that, Includes the following steps: High-strength steel strands are obtained by twisting several steel wires together.

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