Wire rod for 1100 MPa cableway rope and preparation method of wire rod

Abstract

The invention discloses a wire rod for a 1100 MPa cableway rope and a preparation method of the wire rod. The wire rod comprises the following components in percentage by mass: 0.79%-0.85% of C, 0.10%-0.20% of Si, 0.50%-0.60% of Mn, less than or equal to 0.015% of P, 0.0030%-0.010% of S, less than or equal to 0.0040% of N, 0.0010%-0.0020% of total oxygen, 0.0005%-0.0020% of Als, 0.0002%-0.0010% of Nb, 0.0003%-0.0010% of V, 0.0005%-0.0015% of (Nb + V) and the balance of iron and inevitable impurities. Through chemical component design, component proportion optimization and process parameter adjustment, the wire rod has good comprehensive mechanical properties, and meets the performance requirements of users for cableway ropes in the service process.

Description

Technical Field

[0001] The present invention relates to the technical field of materials and metallurgy, and more specifically, to a wire rod for a 1100MPa-level cableway rope and a preparation method thereof. Background Art

[0002] Ropeway rope is a kind of steel wire rope with extremely high safety performance requirements. Ropeway rope is subjected to repeated stretching, impact and friction during service. In order to ensure the safety performance of ropeway rope, wire rod needs to have high deformation performance to meet the production and service performance requirements of ropeway rope. 1100MPa strength grade wire rod for ropeway rope is a widely used wire rod for ropeway rope. The stability of the service performance of this kind of wire rod is of great significance to the safe operation of ropeway rope.

[0003] The Chinese invention patent with publication number CN102268596A discloses a high carbon steel wire rod for producing fine steel wire, the chemical composition weight percentage of the wire rod is: [C]: 0.6% to 0.88%, [Si]: 0.1% to 1.0%, [Mn]: 0.3% to 1.0%, [P] ≤ 0.015%, [S] ≤ 0.010%, [N] ≤ 0.004%, [O] ≤ 0.002%, [Al] ≤ 0.002%, [Ti] ≤ 0.002%, [Mg] ≤ 0.001%, other inevitable impurities are not higher than 0.1%, and the rest is iron. The patent focuses on the high carbon steel wire rod for producing fine steel wire, and does not introduce the wire rod for 1100MPa strength level cableway rope and its production method.

[0004] Since 1100MPa strength grade ultra-high strength ropeway ropes are widely used, there is an urgent need to develop a wire rod for ropeway ropes that can improve their ability to operate safely under repeated stretching, impact and friction, so as to meet the performance requirements of ropeway ropes. Summary of the invention

[0005] The object of the present invention is to overcome the above-mentioned defects in the prior art and provide a 1100MPa grade wire rod for ropeway and a preparation method thereof, so as to meet the performance requirements of users for ropeway in service.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A wire rod for a 1100MPa grade ropeway rope comprises the following components in percentage by mass: C: 0.79% to 0.85%, Si: 0.10% to 0.20%, Mn: 0.50% to 0.60%, P≤0.015%, S: 0.0030% to 0.010%, N≤0.0040%, total oxygen: 0.0010% to 0.0020%, Als: 0.0005% to 0.0020%, Nb: 0.0002% to 0.0010%, V: 0.0003% to 0.0010%, (Nb+V): 0.0005% to 0.0015%, and the balance is iron and unavoidable impurities.

[0008] The present invention also discloses a method for preparing the 1100MPa grade wire rod for ropeway ropes as described above, comprising the following steps: converter smelting, LF refining, continuous casting, continuous casting billet heating and continuous rolling, wire rod rolling, and wire rod cooling;

[0009] In the converter smelting, scrap steel and molten iron are used as furnace materials, and the scrap steel ratio is 5% to 10%; the oxygen activity of the molten steel after converter smelting is controlled at 60ppm to 120ppm;

[0010] In the LF refining, the molten steel discharged from the converter is put into the LF furnace for refining treatment. The refining temperature of the LF furnace is 1490° C. to 1540° C., and the refining time is 30 min to 50 min.

[0011] In the continuous casting, the molten steel subjected to the LF refining treatment is continuously cast to obtain a continuously cast ingot;

[0012] During the continuous casting billet heating and continuous rolling, the continuous casting billet produced in the continuous casting process is sent into a heating furnace for heating, and the heated continuous casting billet is continuously rolled, and the final rolling temperature is 880° C. to 980° C.;

[0013] In the wire rod rolling, the steel billet after continuous rolling is heated in a heating furnace, and then subjected to rough rolling, intermediate rolling, pre-finishing rolling, finishing rolling, and wire laying in sequence;

[0014] During the cooling of the wire rod, the wire rod is cooled on an air-cooled roller after spinning to obtain the 1100 MPa grade wire rod for cableway ropes.

[0015] Implementing the embodiments of the present invention will have the following beneficial effects:

[0016] The present invention designs an optimal component system and uses smelting, continuous casting billet heating and continuous rolling, rolling, cooling and other production processes that match the alloy composition to produce a wire rod with good comprehensive mechanical properties and a tensile strength of 1050MPa to 1150MPa, which meets the user's performance requirements for the cableway rope in the service process. Compared with the current industrially produced wire rod for cableway ropes, the wire rod alloy cost is reduced, the product competitiveness is improved, and alloy resources are saved; the mechanical properties of the wire rod are improved, and its safe operation ability under repeated stretching, impact and friction is improved. At the same time, the preparation method of the present invention has the characteristics of low production cost and strong process applicability, can improve the comprehensive mechanical properties of the wire rod for cableway ropes, is conducive to its production and promotion and application, and has significant social benefits. DETAILED DESCRIPTION

[0017] The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited in any way.

[0018] 1. Chemical composition and mechanical properties

[0019] The invention discloses a wire rod for a 1100MPa-level cableway rope, comprising the following components in mass percentage: C: 0.79%-0.85%, Si: 0.10%-0.20%, Mn: 0.50%-0.60%, P≤0.015%, S: 0.0030%-0.010%, N≤0.0040%, total oxygen: 0.0010%-0.0020%, Als: 0.0005%-0.0020%, Nb: 0.0002%-0.0010%, V: 0.0003%-0.0010%, (Nb+V): 0.0005%-0.0015%, and the balance is iron and unavoidable impurities.

[0020] Specifically, the mechanism of action of each alloy component in the wire rod of the present invention is as follows:

[0021] Too high a carbon content in the wire rod will cause the ropeway rope made from the wire rod to exceed the strength requirement range; at the same time, a higher strength will increase the wire breakage rate of the wire rod in the process of preparing the ropeway rope, and increase the scrap rate of the user. Too low a carbon content in the wire rod cannot meet the user's requirements for the strength of the wire rope. Therefore, the carbon content in the present invention is controlled at 0.79% to 0.85%.

[0022] Silicon increases the eutectoid transformation temperature of steel and makes the pearlite structure of the wire rod coarse, which is not conducive to the complex deformation of the ropeway rope processing process. Silicon is the main deoxidizing element in high carbon steel. If the silicon content in the steel is too high, coarse silicates and impurities will appear after the molten steel is deoxidized. If the silicon content is low, the molten steel will be insufficiently deoxidized, thereby reducing the deformation ability of the wire rod in the ropeway rope process. Therefore, the silicon content in the present invention is controlled at 0.10% to 0.20%.

[0023] Manganese is an element that improves the strength of wire rods, which helps to ensure that the steel wire processed from wire rods meets the user's tensile strength requirements; manganese has the effect of reducing the eutectoid transformation temperature of steel, refining the pearlite structure of wire rods, and improving the deformation ability of wire rods in the process of processing cableway rope steel wires. Therefore, the manganese content in the present invention is controlled at 0.50% to 0.60%.

[0024] Phosphorus reduces the deformation capacity of the wire rod in the ropeway rope processing, causing the steel wire to crack and break, so the phosphorus content in the present invention is controlled to be no higher than 0.015%.

[0025] A higher sulfur content in the steel reduces the cold working performance of the wire rod. Since MnS inclusions have good deformation ability, a proper amount of sulfur in the steel can reduce the harm of spar inclusions, so the sulfur content in the present invention is controlled at 0.0030% to 0.010%.

[0026] The nitrogen content needs to be controlled to a lower range to reduce the hardening effect during the ropeway rope processing and improve the deformation capacity of the steel wire. Therefore, the nitrogen content in the present invention is controlled to be no higher than 0.0040%.

[0027] When the oxygen content is low, the inclusions in the wire rod have poor deformation ability, which is not conducive to the processing of the ropeway rope; when the oxygen content in the wire rod is high, the inclusions in the steel are large in size and large in number, which easily leads to cracking and breaking of the ropeway rope during processing. Therefore, the total oxygen content of the wire rod in the present invention is controlled at 0.0010% to 0.0020%.

[0028] When the acid-soluble aluminum content is high, larger Al2O3 inclusions will appear in the steel; when the acid-soluble aluminum content in the wire rod is too low, the inclusions in the steel have a high melting point, and cracks are likely to occur between the inclusions and the matrix during processing, resulting in cracking and breaking of the ropeway rope during processing. Therefore, the acid-soluble aluminum content of the present invention is controlled to be 0.0005% to 0.0020%.

[0029] Niobium can refine the pearlite structure of the wire rod by inhibiting the grain growth of the steel billet during the heating process, thereby improving the deformation capacity of the wire rod during the ropeway rope processing process. However, a higher niobium content leads to a higher niobium carbonitride content in the steel, and the wire rod is severely hardened during the steel wire processing process, which is easy to cause cracking and breaking of the steel wire. Therefore, the niobium content of the present invention is controlled at 0.0002% to 0.0010%.

[0030] The vanadium element is dissolved in the steel to improve the strength of the steel. However, the vanadium content in the steel should not be too high to prevent the higher wire rod strength from reducing the drawing performance of the wire rod. The vanadium element can inhibit the growth of the grains of the steel billet when the billet is heated, thereby refining the pearlite structure of the wire rod, which is beneficial to improving the uniform deformation ability of the wire rod during the ropeway rope processing process. Therefore, the vanadium content in the present invention is controlled at 0.0003% to 0.0010%.

[0031] The present invention further sets the total content of Nb and V to be controlled within the range of 0.0005% to 0.0015%, which is beneficial to ensuring the processing performance of the wire rod and preventing excessive carbide precipitation, which leads to too fast work hardening during the wire rod drawing process.

[0032] In a specific embodiment, the tensile strength of the 1100 MPa grade wire rod for cableway ropes of the present invention is 1050 MPa to 1150 MPa.

[0033] In a specific embodiment, the oxygen content at the interface between the matrix of the wire rod and the iron oxide scale is 3.0% to 6.5%, and the iron content is 76.5% to 80.5%.

[0034] 2. Production technology

[0035] The present invention also discloses a method for preparing a 1100MPa grade wire rod for a cableway rope as in any embodiment of the present invention, comprising the following steps: converter smelting, LF refining, continuous casting, continuous casting billet heating and continuous rolling, wire rod rolling, and wire rod cooling.

[0036] Further, the method specifically includes the following steps:

[0037] S1. In converter smelting, scrap steel and molten iron are used as furnace charge, and the scrap steel ratio is 5% to 10%; the oxygen activity of the molten steel after converter smelting is controlled at 60ppm to 120ppm.

[0038] In S2 and LF refining, the molten steel discharged from the converter is put into the LF furnace for refining. The refining temperature of the LF furnace is 1490°C to 1540°C, and the refining time is 30min to 50min.

[0039] In a specific embodiment, the size of the molten steel inclusions at the LF inlet position is ≤60 μm, the size of the molten steel inclusions at the LF outlet position is ≤50 μm, and the size of the molten steel inclusions at the tundish position is ≤40 μm.

[0040] S3. During continuous casting, the molten steel subjected to LF refining treatment is continuously cast to obtain a continuously cast ingot.

[0041] In a specific embodiment, the cross-sectional size of the continuous casting billet is (250-300) mm×(350-400) mm.

[0042] S4. During the continuous casting billet heating and continuous rolling, the continuous casting billet off the line in the continuous casting process is sent to a heating furnace for heating, and the heated continuous casting billet is continuously rolled, and the final rolling temperature of the continuous rolling is 880°C to 980°C.

[0043] In a specific embodiment, during the continuous casting billet heating and continuous rolling, the total heating time of the continuous casting billet in the furnace is 3.8h to 4.7h; the temperature of the soaking section is 1170℃ to 1220℃, and the insulation time is 30min to 50min; the cross-sectional size of the continuously rolled billet is (140~180)mm×(140~180)mm.

[0044] S5. During the wire rod rolling, the steel billet after continuous rolling is heated in a heating furnace, and then sequentially subjected to rough rolling, intermediate rolling, pre-finishing rolling, finishing rolling, and wire drawing.

[0045] In a specific embodiment, during the wire rod rolling, the wire rod is produced by a square billet, the total furnace time of the billet is 150min to 170min, the temperature of the soaking section is 1100℃ to 1150℃, and the insulation time of the billet soaking section is 30min to 50min; the heating process of the billet is in the austenite high temperature zone, and the carbon content at the interface of austenite and cementite is 1.25% to 1.5%; the high temperature diffusion of the billet reduces the segregation of elements such as carbon and manganese. After the billet is heated, it is subjected to rough rolling, intermediate rolling, pre-finishing rolling and finishing rolling, and then the wire rod spinning operation is carried out; the pre-finishing rolling temperature of the wire rod is 980℃ to 1000℃; the finishing rolling temperature is 890℃ to 930℃; the temperature of the double module is 910℃ to 940℃; the wire rod spinning temperature is 900℃ to 930℃. The higher spinning temperature of the wire rod increases the cooling rate of the wire rod on the air-cooled roller, laying the foundation for controlling the final organization of the wire rod. The wire rod rolling specifications are 8mm~11mm.

[0046] S6. During the cooling of the wire rod, the wire rod is cooled on an air-cooled roller after spinning to obtain a 1100MPa grade wire rod for cableway ropes.

[0047] In a specific embodiment, during the cooling of the wire rod, the wire rod is cooled on an air-cooled roller after spinning, and the phase transformation temperature of the wire rod is controlled to be 600°C to 650°C. When the phase transformation time of the wire rod on the air-cooled line is 5s to 8s, the pearlite content of the wire rod is ≥40%; when the phase transformation time is 15s to 18s, the pearlite content is 85% to 95%. After the final cooling, the cord steel wire rod is mainly composed of sorbite structure, which is convenient for users to draw steel wires.

[0048] The following are specific embodiments

[0049] Examples 1-6

[0050] The chemical composition, preparation process and performance parameters of the wire rods of Examples 1-6 of the present invention are shown in Table 1.

[0051] Table 1 Chemical composition, preparation process and performance parameters of wire rods of Examples 1-6

[0052]

[0053]

[0054] According to the above results, the present invention has carried out a large number of systematic experimental studies from the aspects of alloy element screening and proportioning, converter smelting, LF refining, continuous casting, continuous casting billet heating and continuous rolling, wire rod rolling, wire rod cooling process design optimization, etc., and finally determined the component system and its manufacturing process that can meet the purpose of the present invention, and finally obtained a wire rod for cableway ropes with a tensile strength of up to 1050MPa ~ 1150MPa.

[0055] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A 1100MPa grade wire rod for ropeway, characterized in that: The following components are included in mass percentage: C: 0.79% ~ 0.85%, Si: 0.10% ~ 0.20%, Mn: 0.50% ~ 0.60%, P ≤ 0.015%, S: 0.0030% ~ 0.010%, N ≤ 0.0040%, total oxygen: 0.0010% ~ 0.0020%, Als: 0.0005% ~ 0.0020%, Nb: 0.0002% ~ 0.0010%, V: 0.0003% ~ 0.0010%, and (Nb + V): 0.0005% ~ 0.0015%, and the balance is iron and unavoidable impurities.

2. The 1100MPa grade wire rod for ropeway according to claim 1, characterized in that: The tensile strength of the wire rod is 1050MPa to 1150MPa.

3. The 1100MPa grade wire rod for ropeway according to claim 1, characterized in that: The oxygen content at the interface between the matrix and the iron oxide scale of the wire rod is 3.0% to 6.5%, and the iron content is 76.5% to 80.5%.

4. A method for preparing a 1100MPa grade wire rod for a ropeway rope according to any one of claims 1 to 3, characterized in that: The following steps are involved: Converter smelting, LF refining, continuous casting, continuous casting billet heating and rolling, wire rod rolling, wire rod cooling; In the converter smelting, scrap steel and molten iron are used as furnace materials, and the scrap steel ratio is 5% to 10%; the oxygen activity of the molten steel after converter smelting is controlled at 60ppm to 120ppm; In the LF refining, the molten steel discharged from the converter is put into the LF furnace for refining treatment. The refining temperature of the LF furnace is 1490° C. to 1540° C., and the refining time is 30 min to 50 min. In the continuous casting, the molten steel subjected to the LF refining treatment is continuously cast to obtain a continuously cast ingot; During the continuous casting billet heating and continuous rolling, the continuous casting billet produced in the continuous casting process is sent into a heating furnace for heating, and the heated continuous casting billet is continuously rolled, and the final rolling temperature is 880° C. to 980° C.; In the wire rod rolling, the steel billet after continuous rolling is heated in a heating furnace, and then subjected to rough rolling, intermediate rolling, pre-finishing rolling, finishing rolling, and wire laying in sequence; During the cooling of the wire rod, the wire rod is cooled on an air-cooled roller after spinning to obtain the 1100 MPa grade wire rod for cableway ropes.

5. The preparation method according to claim 4, characterized in that: In the LF refining, the size of the molten steel inclusions at the LF inlet position is ≤60 μm, the size of the molten steel inclusions at the LF outlet position is ≤50 μm, and the size of the molten steel inclusions at the tundish position is ≤40 μm.

6. The preparation method according to claim 4, characterized in that: During the continuous casting billet heating and continuous rolling, the total heating time of the continuous casting billet in the furnace is 3.8 hours to 4.7 hours; the temperature of the soaking section is 1170° C. to 1220° C., and the holding time is 30 minutes to 50 minutes.

7. The preparation method according to claim 4, characterized in that: During the wire rod rolling, the total furnace time of the steel billet is 150min-170min, the temperature of the soaking section is 1100°C-1150°C, and the insulation time of the steel billet soaking section is 30min-50min; the steel billet heating process is in the austenite high temperature zone, and the carbon content at the interface of austenite and cementite is 1.25%-1.5%; after the steel billet is heated, it is subjected to rough rolling, intermediate rolling, pre-finishing rolling and finishing rolling, and then the wire rod spinning operation is carried out; the pre-finishing rolling temperature of the steel rod is 980°C-1000°C; the finishing rolling temperature is 890°C-930°C; the double module temperature is 910°C-940°C; and the wire rod spinning temperature is 900°C-930°C.

8. The preparation method according to claim 4, characterized in that: During the cooling of the wire rod, the wire rod is cooled on an air-cooled roller after spinning, and the phase change temperature of the wire rod is controlled to be 600°C to 650°C. When the phase change time of the wire rod on the air-cooled line is 5s to 8s, the pearlite content of the wire rod is ≥40%; when the phase change time is 15s to 18s, the pearlite content is 85% to 95%.

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