EP4696803A1

EP4696803A1 - High-strength economical high-carbon steel wire rod and manufacturing method therefor

Info

Publication number: EP4696803A1
Application number: EP24788251.7A
Authority: EP
Inventors: Zan YAO; Ziquan YU; Xuan QU; Yanfeng QI; Feng Jin
Original assignee: Baoshan Iron and Steel Co Ltd
Current assignee: Baoshan Iron and Steel Co Ltd
Priority date: 2023-04-14
Filing date: 2024-04-15
Publication date: 2026-02-18
Also published as: AU2024249930A1; JP2026512853A; CN118792574A; WO2024213156A1; KR20250174046A

Abstract

Disclosed in the present invention is a high-strength economical high-carbon steel wire rod, comprising Fe and inevitable impurities, and further comprising the following chemical elements in percentage by mass: C: 0.84%-0.89%; Si: 0.60%-1.00%; Mn: 0.30%-0.80%; Cr: 0.25%-0.50%; V: 0.02%-0.06%; Al: 0.02%-0.05%; O: 0.0015%-0.0035%; and N: 0.004%-0.008%. Correspondingly, also disclosed in the present invention is a manufacturing method for the wire rod. According to the present invention, by means of a reasonable chemical component design, the processing requirements of 2000MPa high-strength high-torsion zinc-plated steel wires can be met at low processing cost.

Description

Technical Field

The present disclosure relates to a wire rod and a preparation method therefor, in particular to a wire rod for cables and a preparation method therefor.

Background Art

A wire rod is a raw material for production of a high-strength steel wire for a bridge cable and a steel strand. A large-size wire rod can be processed into a high-strength steel wire through processes such as drawing, galvanization, and stabilization. However, in order to accomplish the drawing process of a steel wire having a large area reduction rate, the wire rod first needs to have good drawability.
In addition, the improvement of the strength level of steel wires also requires the continuous improvement of the strength of wire rods. Alloy strengthening and structure refinement are the two most effective means to improve the strength of wire rods. For example, the Chinese patent document with the publication number of CN101565797A, published on October 28, 2009 , and titled "A High-Strength Galvanized Steel Wire and Application Thereof in Bridge Cable Manufacture", further enhances the strength of materials by increasing the content of Si element and using the compound addition of micro-alloy elements of V and Nb.
Another important mean to improve the strength of a wire rod is to provide a high-carbon wire rod with a highly sorbitized structure. For example, the Chinese patent document with the publication number of CN107299280, published on October 27, 2017 , and titled "A Heat-treated Wire Rod for 2000MPa Grade Cable Steel Wire" discloses a wire rod which still needs to undergo offline isothermal treatment to control the structure after hot rolling. The hot-rolled wire rod is unwound and then subjected to austenitizing heating, isothermal salt bath, cleaning and take up to obtain a heat-treated wire rod. The austenitizing heating temperature is 880-980°C, and the isothermal salt bath temperature is 520-600°C
However, when the strength of steel wire reaches above 1960MPa, the existing direct hot-rolled high-carbon wire rods cannot simultaneously meet the requirements of strength and high plastic toughness. The wire rods need to undergo offline isothermal treatment, or add a large amount of alloying elements, or two-step rolling production of large blooms, etc. The quality control is difficult and the production cost is high.
As such, it is desired to provide a high-carbon steel wire rod and a manufacturing method therefor, which can produce high strength and high plastic toughness wire rods at a relatively low cost.

Summary

One object of the present disclosure is to provide a high-strength economical high-carbon steel wire rod. By means of a reasonable chemical component designed, the processing requirements of 2000MPa high-strength high-torsion galvanized steel wires can be met at low processing cost.
In order to achieve the above object, the present disclosure provides a high-strength economical high-carbon steel wire rod, comprising Fe and unavoidable impurities, and further comprising the following chemical elements in mass percentages:

C: 0.84-0.89%;
Si: 0.60-1.00%;
Mn: 0.30-0.80%;
Cr: 0.25-0.50%;
V: 0.02-0.06%;
Al: 0.02-0.05%;
O: 0.0015-0.0035%; and
N: 0.004-0.008%.

Further, the present disclosure also provides a high-strength economical high-carbon steel wire rod, comprising the following chemical elements in mass percentages:

C: 0.84-0.89%;
Si: 0.60-1.00%;
Mn: 0.30-0.80%;
Cr: 0.25-0.50%;
V: 0.02-0.06%;
Al: 0.02-0.05%;
O: 0.0015-0.0035%;
N: 0.004-0.008%; and
a balance of Fe and other unavoidable impurities.

The design principles of the various chemical elements in the high-strength economical high-carbon steel wire rod of the present disclosure will be described in detail as follows:

C: C element is an essential chemical component that ensures the high strength of the wire rod and galvanized steel wire. The content of C element determines the volume fraction of cementite in the sorbite structure in the high-carbon steel wire rod. Increasing the content of carbon in the wire rod is conducive to formation of more cementite lamellas. A refined sorbite lamellar structure possesses better deformation performance and work hardening performance, which is beneficial to increase of the strength of the steel wire in subsequent processing. Therefore, the content of C should be controlled at 0.84% or more in the present disclosure. However, as the content of carbon in the material increases, it's more difficult to control segregation during the smelting and continuous casting process, and especially, reticular cementite is formed and precipitates along grain boundaries, leading to sharply reduced plastic toughness of the material. And as the content of carbon increases, the spheroidization phenomenon of cementite is easy to occur in the cooling process after rolling. As such, the upper limit of the content of carbon is controlled to be 0.89 % in the present disclosure.
Si: Si element is often added to the steel as a deoxygenating agent during the smelting process, and Si solid-dissolved in the ferrite phase of the wire rod will significantly increase the strength of the material. In addition, during the cooling phase transformation process of the wire rod, Si element will further be enriched at the interface between the ferrite phase and the cementite phase. When the steel wire that has been drawn at a large area reduction rate is degreased in a lead bath and hot-dip galvanized, the enrichment of Si element at the phase interface will slow down decomposition of large deformed cementite lamellas, so that the loss of the strength of the steel wire can be reduced. As such, in order to ensure that the wire rod has high strength and the steel wire obtained after drawing has higher strength, the content of Si in the present disclosure is controlled to be higher than 0.6%. However, if the content of Si in the present disclosure is too high, the plasticity of the steel will be reduced significantly, so that the material will be embrittled, and splitting will occur during the torsion process. Hence, the content of Si element is controlled at 0.60-1.0% in the present disclosure.
Mn: Mn element is also often added as a deoxygenating agent during the steelmaking process. At the same time, Mn tends to combine with the harmful element S in the steel to form MnS, so that the harm of S can be reduced. Mn is also a commonly used strengthening element in the steel. It mainly effectuates solid solution strengthening, so that the resulting alloy cementite has higher strength. Hence, it is necessary to control the content of Mn in the steel to be higher than 0.30%. However, in the present disclosure, when the content of Mn is too high, the grains in the material are more prone to coarsening during the heating process, and it's more difficult to control the structure during controlled cooling, especially when the contents of C and Si in the material are both high. As such, the addition amount of Mn element is controlled to be less than 0.80% in the present disclosure.
Cr: the addition of Cr element helps to refine the lamellar structure of sorbite in the wire rod in the present disclosure, and at the same time increase the strength of cementite, thereby improving the strength and plasticity of the material. Hence, the content of Cr in the present disclosure is higher than 0.25%. On the other hand, in order to prevent occurrence of abnormal martensite structure and reduce the difficulty of structure control, and because the tendency of spheroidization of cementite is stronger as the content of Cr increases, the upper limit of the content of Cr in the present application is controlled to be 0.50%.
V, Al, O and N: V and Al elements are prone to combine with C and N to form nanoscale carbon-nitrogen precipitates, and Al also combines with O to form aluminum oxide, so that during the hot rolling process of the wire rod it is conducive to refining the austenite structure, increasing the grain boundary area, providing more nucleation points for the transformation of sorbite structure. This promotes the formation of a well-layered sorbite lamellar structure, reducing the proportion of degraded cementite in spherical shape and short-rod shape, thereby increasing the strength and torsional performance of the steel wire during the subsequent direct drawing process of the hot-rolled wire rod. As such, in order to play the role of Al element in refining grains in the present disclosure, the content of Al is controlled at 0.02-0.05%, and the content of O is controlled to be higher than 0.0015%. On the other hand, in order to prevent excessive generation of aluminum oxide and thus deterioration of performance, the content of O is controlled to be less than 0.0035% in the present disclosure. In addition, to ensure that the carbonitrides of V and Al are fully precipitated within the temperature of 800-900°C and to prevent excessive V from promoting the nucleation growth of large-grained spheroidized carbides, the addition amount of V is controlled at 0.02-0.06%, and the content of N element is controlled at 0.004-0.008%.

Furthermore, in the high-strength economic high-carbon steel wire rod according to the present disclosure, the mass percentages of the chemical elements of the steel wire rod also satisfy: (V+Al)/(C+100N) ≥1/35, wherein each chemical element is substituted with the numerical value before the percentage sign of its mass percentage content.
In order to further ensure that the carbonitrides of V and Al are fully precipitated at a temperature of 800-900°C, and at the same time to prevent excessive V from promoting the nucleation and growth of large spheroidized carbides in the present disclosure, the value of (V+Al)/(C+100N) is controlled to be ≥1/35. In some embodiments, the value of (V+Al)/(C+100N) is controlled to be ≥0.030. In some embodiments, the value of (V+Al)/(C+100N) is controlled at 0.030~0.065.
Further, among the other unavoidable impurities in the high-strength economic high-carbon steel wire rod according to the present disclosure, Ti≤0.003%, Ca≤0.001%, P≤0.010% and S≤0.010%.
P, S, Ti and Ca are the mainly unavoidable impurities in the present disclosure. If the contents of elements P and S in the steel are too high, the brittleness of the steel will be increased, especially when segregation occurs. Therefore, in some embodiments according to the present disclosure, the content of P is controlled to be less than 0.010%, and the content of S is controlled to be less than 0.010%.
If the content of Ti element is too high, a large amount of carbonitrides are formed in the steel, which is not conducive to the torsional performance and fatigue life of the steel wire. Therefore, in some embodiments according to the present disclosure, the content of Ti is controlled to be less than 0.003%.
Ca may help to lower the melting point of brittle inclusions in the wire rod and improve the torsional performance of the steel wire. However, if the content of Ca is too high, a large number of spherical inclusions will be formed, and it is not conducive to the formation of sorbite lamellar structure. Therefore, the content of Ca should be controlled to be less than 0.001%.
Further, in the high-strength economic high-carbon steel wire rod according to the present disclosure, the microstructure of the steel wire rod comprises sorbite pellets, and the size of the sorbite pellets is 2-30µm.
Further, in the high-strength economic high-carbon steel wire rod according to the present disclosure, the area ratio of spherical and short rod-shaped degraded cementite in the microstructure of the steel wire rod is less than or equal to 0.6%.
Further, in the high-strength economic high-carbon steel wire rod according to the present disclosure, the steel wire rod has a tensile strength of ≥ 1320 MPa, and an area reduction rate of ≥30%. In some embodiments, the steel wire rod has a tensile strength of ≥ 1350 MPa. In some embodiments, the steel wire rod has a tensile strength of 1320~1410 MPa. In some embodiments, the steel wire rod has a tensile strength area reduction rate of 30~40%.
Another object of the present disclosure is to provide a manufacturing method for the high-strength economic high-carbon steel wire rod. The present disclosure utilizes a relatively simple processing technique to produce a high-carbon steel wire rod that meets the processing requirements of 2000MPa high-strength high-torsion galvanized steel wires.
To achieve the above object, the present disclosure further provides a manufacturing method for the high-strength economic high-carbon steel wire rod, comprising the steps of:

(1) Smelting;
(2) Billet casting;
(3) Heating: heating to 950-1150°C with a holding time of 1.5-2.5h;
(4) Wire rod rolling: a rolling speed is controlled at 20-60m/s;
(5) Air cooling.

Further, in step (1) according to the present disclosure, vacuum degassing is carried out for 15-26 minutes during the smelting process. Preferably, the content of O is controlled at 0.0015-0.0035%, and the content of N is controlled at 0.004-0.008% at the endpoint.
Further, in step (2) of the manufacturing method according to the present disclosure, the billet is casted by a billet continuous casting machine. Preferably, argon gas protection may be adopted during the casting process, and the billet obtained by casting may have a size of ≤ 260mm and a width-to-thickness ratio of ≤ 4: 3; further preferably, a step of grinding the billet is also included, and after grinding, a depth of surface defects of the billet is ≤ 0.5mm.
Further, in step (2) of the manufacturing method according to the present disclosure, the drawing speed, cooling and terminal soft reduction parameters are adjusted during the continuous casting process to control a carbon segregation index in the core of the billet to be less than 1.06.
Further, in step (4) of the manufacturing method according to the present disclosure, an inlet temperature of the finishing rolling mill is controlled at 930-990°C, an inlet temperature of the reducing and sizing mill is controlled at 930-990°C, and a laying temperature is controlled at 920-980°C; preferably, a size of the rolled steel wire rod is Φ 11-16mm.
Further, in step (5) of the manufacturing method according to the present disclosure, the air cooling process is carried out on a Stelmor line.
Air cooling may be implemented by using the conventional Stelmor fan in this art. In some embodiments, in step (5) of the manufacturing method according to the present disclosure, the air flow rates of the Stelmor line are adjusted in the following ranges: fans F1-F8 have an air flow rate of 80-100%, and fans F9-F14 have an air flow rate of 0-45%.
In the manufacturing method according to the present disclosure, after rolling the wire rod, the air flow rate of the Stelmor line fan is adjusted to control the structure transformation of the wire rod, and thus optimize the structure of the wire rod. After cooled by Stelmor line, a good lamellar sorbite lamellar structure of the wire rod is formed without abnormal martensite structure, and a size of sorbite pellets is 2-30µm, and a proportion of spherical and short rod-shaped degraded cementite in the wire rod is ≤0.6%, so that it is conducive to the subsequent wire drawing.
The present disclosure further provides a galvanized steel wire made by drawing, galvanizing and stabilizing the above high-strength economical high-carbon steel wire rod. The galvanized steel wire has a tensile strength of ≥2000MPa, and a torsion value of ≥11 times.
The galvanized steel wire may be obtained by the conventional processes of drawing, galvanizing, and stabilizing treatment. In some embodiments, the high-carbon wire rod undergoes drawing of 6-9 passes at a drawing speed of 1.0-4.0 m/s. In some embodiments, a temperature of galvanizing is 430-480 °C. In some embodiments, a temperature of stabilizing treatment is 300-400 °C, and a speed of stabilizing treatment is 150-200 m/min.
Preferably, the galvanized steel wire has a tensile strength of ≥2020MPa, and a torsion value of ≥15 times. In some embodiments, the galvanized steel wire has a tensile strength of 2000~2075MPa, and a torsion value of 11~30 times.
The high-strength economical high-carbon steel wire rod have the following advantages and beneficial effects:
The high-strength economical high-carbon steel wire rod described in the present disclosure has fewer types of alloying elements added with relatively low content during the composition design, thus having the advantage of low cost.
The manufacturing method of the high-strength economic high-carbon steel wire rod according to the present disclosure is simple in production, and it does not require isothermal treatment or other steps to obtain wire rods with good strength-plasticity matching ability, which can meet the processing requirements of drawing and galvanization of the high-strength steel wire.
The microstructure of the high-strength economic high-carbon steel wire rod according to the present disclosure is dominated by sorbite structure, and the size of the sorbite pellets is refined to 2-30µm. The area ratio of spherical and short rod-shaped degraded cementite in the wire rod is less than 0.6%, a carbon segregation index in the core is less than 1.06, and there is no abnormal structure in the structure.
The high-strength economic high-carbon steel wire rod according to the present disclosure may has a tensile strength of ≥1320MPa, and at the same time has good plasticity, and has an area reduction rate of ≥30%. Therefore, the wire rod may be directly drawn, galvanized and stabilized to produce a galvanized steel wire for bridge cables and high-strength steel strands with a strength of higher than 2000MPa and a torsion value of higher than 11 times. It has low processing costs, and can meet the usage requirements of long-span bridges and construction projects, reduce project investment and save costs.

Detailed Description

The high-strength economic high-carbon steel wire rod and the preparation method therefor will be further explained and illustrated with reference to the specific examples. Nonetheless, the explanation and illustration are not intended to unduly limit the technical solution of the disclosure.

Examples 1-10 and Comparative Examples 1-3

The high-strength economic high-carbon steel wire rods of Examples 1-10 were all made using the following steps:

(1) After smelting in an electric furnace or a converter, refining was performed outside the furnace. An LF furnace plus a VD or RH degassing treatment process was used for the refining outside the furnace. The composition and amount of synthetic slag added during the smelting process were adjusted. The content of elements P and S was controlled to be less than 0.010% and less than 0.010%, respectively. The vacuum degassing time was controlled at 15-26min. The content of O was controlled at 0.0015-0.0035%, and the content of N was controlled at 0.004-0.008% at the endpoint.
(2) A billet continuous casting machine was used to cast a billet. During the casting process, argon gas protection was adopted. The billet had a size of ≤ 260mm and a width-to-thickness ratio of ≤ 4: 3. The drawing speed, cooling and terminal soft reduction parameters were adjusted in the continuous casting to control the carbon segregation index in the core of the billet to be less than 1.06. The chemical compositions of the obtained billets were shown in Table 1. The billets were undergone by eddy current flaw detection, magnetic powder flaw detection, grinding wheel polishing, supplemental magnetic particle flaw detection and polishing, to remove surface cracks, pits and other defects of the cast billet. The depth of the defects was ≤0.5mm.
(3) The billet was heated to 950-1150°C, and a hold time was 1.5-2.5h.
(4) Wire rod rolling: a rolling speed was controlled at 20-60m/s; an inlet temperature of the finishing rolling mill was controlled at 930-990 °C; an inlet temperature of the reducing and sizing mill was controlled at 930-990 °C; and a laying temperature was controlled at 920-980 °C. A size of the rolled steel wire rod was Φ 11-16mm.
(5) Stelmor fan cooling: fans F1-F8 had an air flow rate of 80-100%, and fans F9-F14 had an air flow rate of 0-45%.

The comparative wire rods of Comparative Examples 1-3 were all made using the above steps, but there are chemical compositions and specific process parameters in each of steps that fail to meet the design requirements according to the present disclosure.

Table 1 lists the mass percentages of the chemical elements in the high-strength economic high-carbon steel wire rods of Examples 1-10 and in the comparative steel wire rods of Comparative Examples 1-3.

Table 1. (wt%, the balance is Fe and other unavoidable impurities except for P, S, Ti, and Ca)

No.	C	Si	Mn	Cr	V	Al	O	N	Ti	Ca	P	S	(V+Al) /(C+100N)
Ex. 1	0.84	0.9	0.5	0.3	0.03	0.025	0.002	0.008	0.0005	0.0002	0.008	0.005	0.034
Ex.2	0.87	0.85	0.3	0.35	0.06	0.025	0.003	0.0045	0.003	0.0009	0.002	0.006	0.064
Ex.3	0.86	0.65	0.6	0.45	0.04	0.03	0.0035	0.0049	0.0025	0.0007	0.003	0.009	0.052
Ex.4	0.88	0.95	0.8	0.3	0.05	0.045	0.0019	0.008	0.0015	0.0009	0.009	0.002	0.057
Ex.5	0.87	1	0.55	0.35	0.035	0.02	0.0035	0.004	0.0008	0.001	0.002	0.001	0.043
Ex.6	0.84	0.88	0.69	0.25	0.03	0.045	0.0026	0.0063	0.0009	0.0002	0.01	0.008	0.051
Ex.7	0.89	0.98	0.8	0.5	0.02	0.02	0.0032	0.004	0.0021	0.0001	0.003	0.01	0.031
Ex.8	0.86	0.8	0.75	0.45	0.02	0.05	0.0015	0.0045	0.0025	0.0004	0.001	0.0085	0.053
Ex.9	0.89	1	0.35	0.5	0.04	0.028	0.0028	0.0056	0.0018	0.001	0.008	0.006	0.047
Ex.10	0.87	0.6	0.55	0.3	0.05	0.046	0.0029	0.0065	0.0023	0.0008	0.003	0.001	0.063
Comp. Ex.1	0.87	*0.2*	*0.9*	*0.55*	*0.01*	0.025	0.0015	0.005	0.002	0.0009	0.002	0.005	*0.026*
Comp. Ex.2	*0.92*	1.2	0.5	0.3	0.06	*0.002*	*0.0008*	*0.009*	0.01	*0.002*	*0.015*	0.001	0.034
Comp. Ex.3	*0.82*	0.7	0.6	*0.6*	0	0.025	*0.0045*	*0.003*	0.003	0.0007	0.009	*0.012*	*0.022*

Note: In the above formula: (V+Al)/(C+100N), for each chemical element in the formula is substituted with the numerical value before the percentage sign of its mass percentage content.

Table 2 lists the specific process parameters in the above steps for the wire rods of Examples 1-10 and the comparative wire rods of Comparative Examples 1-3.

Table 2

No.	Size of billet obtained by casting (mm)	Heating temperature (°C)	Holding Time (h)	Rolling speed (m/s)	Inlet temperature of finishing rolling mill (°C)	Inlet temperature of reducing and sizing mill (°C)	Laying temperature (°C)	Air flow rate of fans F1-F8 (%)	Air flow rate of fans F9-F14 (%)	Wire rod size (mm)
Ex.1	150×150	950	1.5	20	930	950	920	95	0	11
Ex.2	150×150	950	1.5	20	930	950	920	95	0	12
Ex.3	160×160	980	2.5	20	930	950	920	100	20	13
Ex.4	160×160	980	2.5	45	960	930	980	100	20	13
Ex.5	160×160	980	2.5	45	960	930	980	100	20	12.5
Ex.6	220×220	1050	2	35	990	970	960	80	45	16
Ex.7	200×150	1050	2	35	990	970	960	80	45	14
Ex.8	240×200	1150	2	35	990	970	960	80	45	16
Ex.9	240×200	1150	2	60	970	990	950	95	10	15
Ex.10	240×200	1150	2	60	970	990	950	95	10	12
Comp. Ex.1	160×160	1100	2	70	980	900	900	75	10	12
Comp. Ex.2	240×160	1060	3	50	950	930	920	80	0	14
Comp. Ex.3	270×160	*1200*	*3.5*	35	900	930	920	100	25	16

The wire rods of Examples 1-10 and the comparative wire rods of Comparative Example 1-3 obtained were sampled respectively, and the microstructure of the sample of each example was observed and analyzed. The observation and analysis results are listed in Table 3. The samples were detected by scanning electron microscopy, and the area proportions of the obtained structure images were statistically analyzed according to their types.

Table 3 lists the microstructure characteristics of the wire rods of Examples 1-11 and the comparative wire rods of Comparative Examples 1-3.

Table 3

No.	Size of sorbite pellets (µm)	Area ratio of spherical and short rod-shaped degraded cementite (%)
Ex.1	30	0.45
Ex.2	25	0.30
Ex.3	9	0.1
Ex.4	2	0.6
Ex.5	15	0.25
Ex.6	19	0.05
Ex.7	23	0.03
Ex.8	16	0.55
Ex.9	30	0.12
Ex.10	28	0.06
Comp. Ex.1	35	*0.85*
Comp. Ex.2	28	*1.05*
Comp. Ex.3	45	*0.9*

As shown by Table 3, the size range (average size) of the sorbite pellets of the wire rods of Examples 1-10 are 2-30µm. However, the size of the sorbite pellets of Comparative Examples is larger than that of the present disclosure. In addition, the area ratios of spherical and short rod-shaped degraded cementite in the microstructure of the wire rod of Examples 1-10 according to the present disclosure are all less than or equal to 0.6%, but those of Comparative Examples are all larger than 0.6%.
To verify the mechanical performances for the wire rods of each Examples and Comparative Examples, the wire rods of Examples 1-10 and the comparative wire rods of Comparative Examples 1-3 obtained by the above process steps were re-sampled by the inventor, and their mechanical performances were tested according to GB/T 228.1 Metallic materials-Tensile testing-Part 1: Method of Test at Room Temperature. And the mechanical performance test results are listed in Table 4.

Table 4 lists the performance test results for the wire rods of Examples 1-10 and the comparative wire rods of Comparative Examples 1-3.

Table 4

No.	Tensile strength (MPa)	Area reduction rate (%)
Ex.1	1390	35
Ex.2	1360	32
Ex.3	1401	30
Ex.4	1320	32
Ex.5	1365	34
Ex.6	1378	33
Ex.7	1339	39
Ex.8	1392	33
Ex.9	1370	37
Ex.10	1350	40
Comp. Ex.1	1350	29
Comp. Ex.2	1395	27
Comp. Ex.3	*1180*	35

As it can be seen from Table 4, the wire rods of Examples 1-10 have a tensile strength of ≥1320MPa, and an area reduction rate of ≥30%. However, the tensile strength for the wire rods of Comparative Examples 1-2 meet the requirements of the present disclosure, but the area reduction rate of Comparative Examples 1-2 is <30%. The area reduction rate of Comparative Example 3 meets the requirements of the present disclosure, but its tensile strength is less than that of the present disclosure. This indicates that it is impossible to achieve a balance between strength and plasticity for Comparative Examples 1-3.

To prove that high-strength galvanized steel wire can be obtained by using the wire rod according to the present disclosure, the wire rods of Examples 1-10 and the comparative wire rods of Comparative Examples 1-3 were subjected to 6-9 passes of drawing, steel wire galvanization and stabilization (Table 5) to obtain galvanized steel wires. The steel wires obtained from Examples 1-10 and Comparative Examples 1-3 were tested for various performances. The performance test results obtained are listed in Table 6.

Table 5

No.	Passes of drawing	Speed of drawing m/s	Temperature of galvanization °C	Temperature of stabilization °C	Speed of stabilization m/min
Ex.1	6	2.0	430	350	150
Ex.2	6	1.5	470	300	160
Ex.3	7	1.5	460	355	200
Ex.4	7	1.0	460	355	180
Ex.5	7	2.8	470	360	180
Ex.6	8	3.0	480	380	190
Ex.7	8	3.5	470	400	150
Ex.8	8	4.0	440	380	160
Ex.9	9	2.0	469	320	180
Ex.10	9	3.3	445	370	200
Comp. Ex.1	6	1.0	430	320	150
Comp. Ex.2	7	2.0	450	350	180
Comp. Ex.3	9	4.0	470	380	190

The relevant performance testing methods are as follows:
Tensile test: the tensile strength of the steel wires in Examples 1-10 and the comparative steel wires in Comparative Examples 1-3 was tested using GB/T 228.1 Metallic materials-Tensile testing-Part 1: Method of Test at Room Temperature.
Torsion Test: the torsion values measured on a 100D gauge sample of the steel wire in Examples 1-10 and the comparative steel wires in Comparative Examples 1-3 were tested by using GB/T 239.1 Metallic materials-Wire-Part 1: Simple Torsion Test.

Table 6 lists the performance test results of the steel wires of Examples 1-10 and the comparative steel wires of Comparative Examples 1-3.

Table 6

No.	Tensile strength (MPa)	Torsion value (times)
Ex.1	2030	18
Ex.2	2073	15
Ex.3	2025	20
Ex.4	2043	22
Ex.5	2018	11
Ex.6	2048	29
Ex.7	2029	27
Ex.8	2062	25
Ex.9	2045	19
Ex.10	2036	23
Comp. Ex.1	2025	6
Comp. Ex.2	2093	7
Comp. Ex.3	*1870*	10

As it can be seen from Table 6, the tensile strength of the steel wires in Examples 1-10 obtained by drawing, galvanizing and stabilizing the above wire rods is further improved. The steel wires of Examples 1-10 have a tensile strength is ≥ 2000MPa, and a torsion value is ≥8 times. They can effectively meet the production requirements of long-span and long-life bridge cables.
In addition, the ways in which the various technical features of the present disclosure are combined are not limited to the ways recited in the claims of the present disclosure or the ways described in the specific examples. All the technical features recited in the present disclosure may be combined or integrated freely in any manner, unless contradictions are resulted.
It should also be noted that the Examples set forth above are only specific examples according to the present disclosure. Obviously, the present disclosure is not limited to the above Examples. Similar variations or modifications made thereto can be directly derived or easily contemplated from the present disclosure by those skilled in the art. They all fall in the protection scope of the present disclosure.

Claims

A high-strength economical high-carbon steel wire rod, comprising Fe and unavoidable impurities, wherein the steel wire rod further comprises the following chemical elements in mass percentages:
C: 0.84-0.89%;

Si: 0.60-1.00%;

Mn: 0.30-0.80%;

Cr: 0.25-0.50%;

V: 0.02-0.06%;

Al: 0.02-0.05%;

O: 0.0015-0.0035%; and

N: 0.004-0.008%.
The high-strength economical high-carbon steel wire rod according to claim 1, wherein the mass percentages of each chemical elements of the steel wire rod are:
C: 0.84-0.89%;

Si: 0.60-1.00%;

Mn: 0.30-0.80%;

Cr: 0.25-0.50%;

V: 0.02-0.06%;

Al: 0.02-0.05%;

O: 0.0015-0.0035%;

N: 0.004-0.008%; and

a balance of Fe and other unavoidable impurities.
The high-strength economical high-carbon steel wire rod according to claim 1 or 2, wherein the mass percentage of the chemical elements of the steel wire rod further satisfy:(V+Al)/(C+100N)≥1/35, wherein each chemical element is substituted with the numerical value before the percent sign of its mass percentage content.
The high-strength economical high-carbon steel wire rod according to claim 1 or 2, wherein among the other unavoidable impurities: Ti≤0.003%, Ca≤0.001%, P≤0.010%, and S≤0.010%.
The high-strength economical high-carbon steel wire rod according to claim 1 or 2, wherein a microstructure of the steel wire rod comprises sorbite pellets, and a size range of the sorbite pellets is 2-30µm.
The high-strength economical high-carbon steel wire rod according to claim 1 or 2, wherein an area ratio of spherical and short rod-shaped degraded cementite in a microstructure of the steel wire rod is ≤0.6%.
The high-strength economical high-carbon steel wire rod according to claim 1 or 2, wherein the steel wire rod has a tensile strength of ≥1320MPa, and an area reduction rate of ≥30%.
A manufacturing method for the high-strength economical high-carbon steel wire rod according to any one of claims 1-7, comprising the following steps:
(1) Smelting;

(2) Billet casting;

(3) Heating: heating to 950-1150°C with a holding time of 1.5-2.5h;

(4) Wire rod rolling: a rolling speed is controlled at 20-60m/s;

(5) Air cooling.
The manufacturing method according to claim 8, wherein in step (1), vacuum degassing is carried out for 15-26 minutes during the smelting process; preferably, the content of O is controlled at 0.0015-0.0035%, and the content of N is controlled at 0.004-0.008% at the endpoint.
The manufacturing method according to claim 8, wherein in step (2), a billet is casted by a billet continuous casting machine; preferably, argon gas protection is adopted during the casting process, and the billet obtained by casting has a side length of ≤ 260mm and a width-to-thickness ratio of ≤ 1.06; further preferably, a step of grinding the billet is also included, and after grinding, a depth of surface defects of the billet is ≤ 0.5mm.
The manufacturing method according to claim 10, wherein a carbon segregation index in the core of the billet is less than 1.06.
The manufacturing method according to claim 8, wherein in step (4), an inlet temperature of a finishing rolling mill is controlled at 930-990 °C, an inlet temperature of a reducing and sizing mill is controlled at 930-990 °C, and a laying temperature is controlled at 920-980 °C; preferably, a size of the rolled steel wire rod is Φ 11-16mm.
The manufacturing method according to claim 8, wherein in step (5), the air cooling process is carried out on a Stelmor line.
The manufacturing method according to claim 13, wherein, in step (5), air flow rates of F1-F8 fans on the Stelmor line are controlled at 80-100%, air flow rates of F9-F14 fans on the Stelmor line are controlled at 0-45%.
A galvanized steel wire made by drawing, galvanizing and stabilizing the high-strength economical high-carbon steel wire rod according to any one of claims 1-7, wherein the galvanized steel wire has a tensile strength of ≥2000MPa, and a torsion value of ≥11 times; preferably, the galvanized steel wire has a tensile strength of ≥2020MPa, and a torsion value of ≥15 times.