Wire rod for 1200MPa-grade cableway rope and preparation method of wire rod

Abstract

The invention discloses a wire rod for a 1200 MPa cableway rope and a preparation method of the wire rod. The wire rod comprises the following components in percentage by mass: 0.89%-0.95% of C, 0.10%-0.20% of Si, 0.20%-0.35% of Mn, less than or equal to 0.014% of P, 0.0030%-0.012% of S, less than or equal to 0.0040% of N, 0.0010%-0.0025% of total oxygen, 0.0005%-0.0015% of Als, 0.0002%-0.0010% of Nb, 0.0003%-0.0010% of V, 0.0010%-0.0020% of (Nb + V) and the balance of iron and inevitable impurities. By designing an optimal component system and matching with a production process matched with the components, the prepared wire rod has good tensile strength, and the quality requirement of the wire rod for the ultrahigh-strength cableway rope of a user is met.

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 1200MPa-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 needs to withstand repeated stretching, impact and friction during service. Therefore, in order to ensure the safety performance of ropeway rope, wire rod needs to have higher deformation performance to meet the production and service performance requirements of ropeway rope. 1200MPa strength grade ultra-high strength ropeway wire rod is more prone to fatigue failure during service due to its high strength.

[0003] The Chinese patent application with application number CN202310976619.5 provides a wire rod for ultra-high strength hot-dip galvanized steel wire rope and its production method, and its chemical composition mass percentage is: C: 0.85-0.88%, Si: 0.18-0.25%, Mn: 0.50-0.55%, Cr: ≤0.05%, P≤0.012%, S≤0.008%, Ni≤0.05%, Cu≤0.05%, Mo≤0.03%, Al≤0.0020%, Ti≤0.0012%, O≤0.0030%, N≤0.0050%, and the balance is Fe and unavoidable impurities. The patent focuses on the wire rod for ultra-high strength hot-dip galvanized steel wire rope, and does not introduce the wire rod for 1200MPa ultra-high strength ropeway rope and its production method.

[0004] Due to its high strength, 1200MPa ultra-high strength ropeway rope is more prone to breakage under repeated stretching, impact and friction during service. Therefore, it is urgent to provide an ultra-high strength ropeway rope wire rod that can meet the service performance requirements. Summary of the invention

[0005] The object of the present invention is to overcome the above-mentioned defects in the prior art, provide a 1200MPa grade wire rod for ropeway and a preparation method thereof, and meet the performance requirements of users for ropeway ropes during service.

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

[0007] A wire rod for a 1200MPa grade ropeway rope comprises the following components in percentage by mass: C: 0.89% to 0.95%, Si: 0.10% to 0.20%, Mn: 0.20% to 0.35%, P≤0.014%, S: 0.0030% to 0.012%, N≤0.0040%, total oxygen: 0.0010% to 0.0025%, Als: 0.0005% to 0.0015%, Nb: 0.0002% to 0.0010%, V: 0.0003% to 0.0010%, (Nb+V): 0.0010% to 0.0020%, and the balance is iron and unavoidable impurities.

[0008] The present invention also discloses a method for preparing the 1200MPa 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 3% to 12%;

[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 1470° C. to 1540° C., and the refining time is 40 min to 55 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 970° C. to 1000° 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 1200 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 optimizes the ingredient ratio by designing the chemical composition, and adjusts the continuous casting billet heating and continuous rolling, rolling and cooling process parameters, so that the wire rod has good comprehensive mechanical properties and a tensile strength of 1170MPa to 1250MPa, meeting the quality requirements of users for wire rods for ultra-high strength cableway ropes. 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 1200MPa grade ropeway rope, comprising the following components in mass percentage: C: 0.89%-0.95%, Si: 0.10%-0.20%, Mn: 0.20%-0.35%, P≤0.014%, S: 0.0030%-0.012%, N≤0.0040%, total oxygen: 0.0010%-0.0025%, Als: 0.0005%-0.0015%, Nb: 0.0002%-0.0010%, V: 0.0003%-0.0010%, (Nb+V): 0.0010%-0.0020%, and the balance is iron and inevitable 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 0.89% to 0.95%.

[0022] Silicon increases the eutectoid transformation temperature of steel and increases the grain size of pearlite structure, which is not conducive to the complex deformation of wire rod processing. Silicon is the main deoxidizing element in high carbon steel. If the silicon content in 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 capacity of the wire rod in the process of processing ropeway rope steel wire. Therefore, the silicon content in the present invention is controlled at 0.10% to 0.20%.

[0023] Manganese helps to ensure that the steel wire rope processed from the wire rod meets the user's tensile strength requirements; manganese is a carbide-forming element, which enters the cementite to replace a part of the iron atoms. Manganese has the effect of refining the pearlite structure of the wire rod and improving the deformation ability of the wire rod in the process of processing the ropeway rope steel wire. Therefore, the manganese content in the present invention is controlled to be 0.20% to 0.35%.

[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 0.014%.

[0025] MnS inclusions in steel have good deformation ability, and an appropriate amount of sulfur in steel can reduce the harm of spar inclusions. However, a higher sulfur content reduces the cold working performance of the wire rod. Therefore, the sulfur content in the present invention is controlled at 0.0030% to 0.012%.

[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 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; 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. Therefore, in the present invention, the total oxygen content of the wire rod is controlled at 0.0010% to 0.0025%.

[0028] When the acid-soluble aluminum content is high, larger Al particles will appear in the steel. 2 O 3 Inclusions: When the acid-soluble aluminum content in the wire rod is too low, the melting point of the inclusions in the steel is high, 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 0.0015%.

[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] In order to give full play to the comprehensive effect of niobium and vanadium elements, it is necessary to control Nb+V to 0.0010% to 0.0020%.

[0032] In a specific embodiment, the tensile strength of the 1100 MPa grade wire rod for cableway ropes of the present invention is 1170 MPa to 1250 MPa.

[0033] In a specific embodiment, the grain size of the wire rod ferrite of the present invention is ≤35μm; wherein, the size distribution of the wire rod ferrite grains is: particle size ≤5μm, accounting for 62% to 68% by number; particle size ≤10μm, accounting for 78% to 84% by number.

[0034] 2. Production technology

[0035] The present invention also discloses a method for preparing a 1200MPa 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 3% to 12%. Slag stopper is used after the converter to prevent converter slag from being inherited into the LF furnace refining process.

[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 1470℃~1540℃, and the refining time is 40min~55min.

[0039] In a specific embodiment, argon stirring is performed during refining, and the argon stirring intensity is 100 NL / min to 400 NL / min.

[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 (300-340) mm×(400-420) 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 970°C to 1000°C.

[0043] In a specific embodiment, the continuous casting billet is hot charged, and the total heating time of the continuous casting billet in the furnace is 3.5h to 4.8h; the temperature of the soaking section is 1190°C to 1220°C, and the holding time is 40min to 50min.

[0044] In a specific embodiment, the cross-sectional size of the continuous rolled billet is (140-180) mm*(140-180) mm; the inclusion size in the core of the continuous rolled billet is ≤35 μm, the inclusion size at a distance of 1 / 4 of the thickness from the surface of the continuous rolled billet is ≤30 μm, and the inclusion size on the surface of the continuous rolled billet is ≤25 μm.

[0045] 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.

[0046] In a specific embodiment, the wire rod is produced by billet, the total furnace time of the billet is 150min-170min, the temperature of the soaking section is 1100℃-1150℃, and the insulation time of the billet soaking section is 30min-50min; the billet heating process is in the austenite high temperature zone, and the carbon content at the interface of austenite and cementite is 1.35%-1.6%. 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℃-1005℃; the finishing rolling temperature is 890℃-930℃; the temperature of the double module is 900℃-920℃; the wire rod spinning temperature is 910℃-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 structure of the wire rod. The wire rod rolling specifications are 8mm~12mm.

[0047] S6. During the cooling of the wire rod, the wire rod is cooled on an air-cooled roller after spinning to obtain a 1200MPa grade wire rod for cableway ropes.

[0048] In a specific embodiment, after spinning, the wire rod is cooled on an air-cooled roller, and the phase change temperature of the wire rod is controlled to be 620° C. to 670° C., and the phase change time is 15s to 25s.

[0049] The following are specific embodiments

[0050] Examples 1-6

[0051] 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.

[0052] Table 1 Chemical composition, preparation process and performance parameters of wire rods of Examples 1-6

[0053]

[0054]

[0055] 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 1170MPa ~ 1250MPa.

[0056] 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 1200MPa grade wire rod for ropeway, characterized in that: The following components are included in mass percentage: C: 0.89% ~ 0.95%, Si: 0.10% ~ 0.20%, Mn: 0.20% ~ 0.35%, P ≤ 0.014%, S: 0.0030% ~ 0.012%, N ≤ 0.0040%, total oxygen: 0.0010% ~ 0.0025%, Als: 0.0005% ~ 0.0015%, Nb: 0.0002% ~ 0.0010%, V: 0.0003% ~ 0.0010%, and (Nb + V): 0.0010% ~ 0.0020%, and the balance is iron and unavoidable impurities.

2. The 1200MPa grade wire rod for ropeway according to claim 1, characterized in that: The tensile strength of the wire rod is 1170MPa-1250MPa.

3. The 1200MPa grade wire rod for ropeway according to claim 1, characterized in that: Wire rod ferrite grain size ≤35μm; The size distribution of the wire rod ferrite grains is as follows: the particle size is ≤5μm, accounting for 62% to 68% of the number; the particle size is ≤10μm, accounting for 78% to 84% of the number.

4. A method for preparing a 1200MPa 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 3% to 12%; 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 1470° C. to 1540° C., and the refining time is 40 min to 55 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 970° C. to 1000° 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 1200 MPa grade wire rod for cableway ropes.

5. The preparation method according to claim 4, characterized in that: In the LF refining, argon stirring is performed during the refining, and the argon stirring intensity is 100NL / min to 400NL / min.

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 3.5 hours to 4.8 hours; the temperature of the soaking section is 1190° C. to 1220° C., and the insulation time is 40 minutes to 50 minutes.

7. The preparation method according to claim 6, characterized in that: During the heating and continuous rolling of the continuous casting billet, the size of inclusions in the core of the continuous rolling billet is ≤35 μm, the size of inclusions at a position 1 / 4 of the thickness from the surface of the continuous rolling billet is ≤30 μm, and the size of inclusions at the surface of the continuous rolling billet is ≤25 μm.

8. 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 1.35%-1.6%; 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-1005°C; the finishing rolling temperature is 890°C-930°C; the double module temperature is 900°C-920°C; and the wire rod spinning temperature is 910°C-930°C.

9. 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 620° C. to 670° C., and the phase change time is 15s to 25s.

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