A wire rod for 1200mpa grade cableway rope and a method for manufacturing the same

Abstract

The application discloses a 1200MPa-grade wire rod for cableway ropes and a preparation method thereof. The wire rod 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% or less, S: 0.0030% to 0.012%, N: 0.0040% or less, 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 being iron and inevitable impurities. The wire rod has good tensile strength and meets the quality requirements of users for the super-high-strength wire rod for cableway ropes by designing the optimal component system and matching the production process with the components.

Description

Technical Field

[0001] This invention relates to the fields of materials and metallurgy, and more specifically, to a 1200MPa grade cableway wire rod and its preparation method. Background Technology

[0002] Cableway ropes are steel wire ropes with extremely high safety requirements. During service, cableway ropes must withstand repeated tension, impact, and friction. Therefore, to ensure the safety performance of cableway ropes, the wire rods need to have high deformation properties to meet the production and service performance requirements. Ultra-high strength cableway rope wire rods with a strength rating of 1200MPa are more prone to fatigue failure during service due to their high strength.

[0003] Chinese patent application CN202310976619.5 discloses a high-strength hot-dip galvanized steel wire rope coil and its production method. Its chemical composition (by 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%, with the balance being Fe and unavoidable impurities. This patent focuses on the high-strength hot-dip galvanized steel wire rope coil and does not describe a 1200MPa high-strength cableway rope coil or its production method.

[0004] Due to their high strength, 1200MPa ultra-high strength cable ropes are more prone to breakage under repeated tension, impact and friction during service. Therefore, there is an urgent need to provide a type of ultra-high strength cable rope rod that can meet the service performance requirements. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned defects in the prior art and provide a 1200MPa grade cableway wire rod and its preparation method to meet the user's performance requirements for cableway ropes during service.

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

[0007] A 1200MPa grade cableway rope bar comprises the following components by 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%, with the balance being iron and unavoidable impurities.

[0008] The present invention also discloses a method for preparing 1200MPa grade cableway wire rod 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 process, scrap steel and molten iron are used as furnace charge, with the proportion of scrap steel being 3% to 12%.

[0010] In the LF refining process, the molten steel after being tapped from the converter smelting furnace is fed into the LF furnace for refining treatment. The LF furnace refining temperature is 1470℃~1540℃ and the refining time is 40min~55min.

[0011] In the continuous casting process, the molten steel refined by the LF is continuously cast to obtain a continuously cast billet.

[0012] In the continuous casting billet heating and rolling process, the continuous casting billet that comes off the production line in the continuous casting process is sent to a heating furnace for heating, and the heated continuous casting billet is continuously rolled, with a final rolling temperature of 970℃~1000℃.

[0013] In the aforementioned wire rod rolling process, the continuously rolled steel billet is heated in a heating furnace, and then sequentially undergoes roughing rolling, intermediate rolling, pre-finishing rolling, finishing rolling, and wire drawing.

[0014] During the wire rod cooling process, the wire rod is cooled on an air-cooled roller conveyor after spinning to obtain the 1200MPa grade cableway wire rod.

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

[0016] This invention, through chemical composition design, optimization of component ratio, and adjustment of continuous casting billet heating, rolling, and cooling process parameters, enables the wire rod to have excellent comprehensive mechanical properties, with a tensile strength of 1170MPa~1250MPa, meeting the quality requirements of users for ultra-high strength cableway rope wire rods. Detailed Implementation

[0017] The present invention will be further described below with reference to specific embodiments, but this does not limit the present invention in any way.

[0018] I. Chemical composition and mechanical properties

[0019] This invention discloses a 1200MPa grade cable car wire rod, comprising the following components by 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%, with the balance being iron and unavoidable impurities.

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

[0021] Excessive carbon content in wire rod will cause the cableway ropes produced from the rods to exceed the required strength range; simultaneously, higher strength will increase the breakage rate of the wire rods during cableway rope manufacturing, leading to a higher scrap rate for users. Insufficient carbon content in the wire rods will not meet the user's strength requirements for the wire ropes. Therefore, in this invention, the carbon content is controlled between 0.89% and 0.95%.

[0022] Silicon increases the eutectoid transformation temperature of steel and increases the grain size of pearlite, which is detrimental to the complex deformation during wire rod processing. Silicon is the main deoxidizing element in high-carbon steel. Excessive silicon content leads to coarse silicates and impurities after deoxidation, while insufficient silicon content results in inadequate deoxidation, thus reducing the deformation capacity of the wire rod during cable rope wire processing. Therefore, the silicon content in this invention is controlled at 0.10%–0.20%.

[0023] Manganese helps ensure that the wire ropes processed from wire rod meet the user's tensile strength requirements; manganese is a carbide-forming element that enters the cementite and replaces some iron atoms. Manganese also refines the pearlite structure of the wire rod, improving its deformability during the processing of cableway wire. Therefore, the manganese content in this invention is controlled at 0.20%–0.35%.

[0024] Phosphorus reduces the deformation capacity of wire rods during cable rope processing, causing cracking and breakage of the steel wires. Therefore, the phosphorus content in this invention is controlled to be no higher than 0.014%.

[0025] MnS inclusions in steel exhibit good deformability, and an appropriate amount of sulfur in the steel can reduce the harmful effects of crystalline inclusions. However, high sulfur content reduces the cold working performance of wire rods. Therefore, in this invention, the sulfur content is controlled between 0.0030% and 0.012%.

[0026] The nitrogen content needs to be controlled to a low range to reduce the hardening effect during the cable rope processing and improve the deformation capacity of the steel wire. Therefore, in this invention, the nitrogen content 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 numerous, which easily leads to cracking and breakage during the cableway rope 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 cableways ropes. Therefore, in this 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, large Al2O3 inclusions will appear in the steel; 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 prone to occur between the inclusions and the matrix during processing, leading to cracking and breakage of the cableway rope during processing. Therefore, the acid-soluble aluminum content of this invention is controlled at 0.0005% to 0.0015%.

[0029] Niobium can refine the pearlitic structure of wire rod by inhibiting grain growth in the billet during heating, thereby improving the deformation capacity of the wire rod during cable rope processing. However, a higher niobium content leads to a higher niobium carbonitride content in the steel, resulting in severe work hardening of the wire rod during wire processing, which easily leads to cracking and breakage of the wire. Therefore, the niobium content in this invention is controlled at 0.0002% to 0.0010%.

[0030] Vanadium dissolves into steel to increase its strength. However, the vanadium content in the steel should not be too high to prevent the high strength of the wire rod from reducing its drawing performance. Vanadium can inhibit grain growth in the billet during heating, thereby refining the pearlite structure of the wire rod and improving its uniform deformation ability during cable rope processing. Therefore, the vanadium content in this invention is controlled between 0.0003% and 0.0010%.

[0031] To fully utilize the combined effects of niobium and vanadium, the Nb+V ratio needs to be controlled between 0.0010% and 0.0020%.

[0032] In one specific embodiment, the tensile strength of the 1100MPa grade cable rope wire rod of the present invention is 1170MPa to 1250MPa.

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

[0034] II. Production Process Technology

[0035] The present invention also discloses a method for preparing 1200MPa grade cableway wire rod 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] Furthermore, the specific steps include:

[0037] S1. In converter smelting, scrap steel mixed with molten iron is used as furnace charge, with the scrap steel ratio being 3% to 12%. Slag-blocking markers are used after the converter to prevent converter slag from being inherited into the LF furnace refining process.

[0038] In the S2 and LF refining processes, the molten steel after being tapped from the converter smelting furnace is fed into the LF furnace for refining. The refining temperature in the LF furnace is 1470℃~1540℃, and the refining time is 40min~55min.

[0039] In one specific embodiment, argon gas stirring is performed during refining at an intensity of 100 NL / min to 400 NL / min.

[0040] S3. In continuous casting, molten steel that has been refined by LF is continuously cast to obtain a continuously cast billet.

[0041] In one specific embodiment, the cross-sectional dimensions of the continuously cast billet are (300~340)mm×(400~420)mm.

[0042] S4. In the continuous casting billet heating and rolling process, the continuous casting billet that comes off the production line in the continuous casting process is sent to a heating furnace for heating, and the heated continuous casting billet is continuously rolled. The final rolling temperature is 970℃~1000℃.

[0043] In one specific embodiment, the continuously cast billet is hot-charged, and the total heating time of the continuously cast billet in the furnace is 3.5h to 4.8h; the temperature of the soaking zone is 1190℃ to 1220℃, and the holding time is 40min to 50min.

[0044] In one specific embodiment, the cross-sectional dimensions of the continuously rolled billet are (140~180)mm*(140~180)mm; the size of the inclusions in the core of the continuously rolled billet is ≤35μm, the size of the inclusions at the position 1 / 4 thickness away from the surface of the continuously rolled billet is ≤30μm, and the size of the inclusions on the surface of the continuously rolled billet is ≤25μm.

[0045] S5. In the wire rod rolling process, the continuously rolled steel billet is heated in a heating furnace, and then successively passes through rough rolling, intermediate rolling, pre-finishing rolling, finish rolling, and wire drawing.

[0046] In one specific embodiment, the wire rod is produced using square billets. The total furnace time for the billet is 150-170 minutes, the soaking temperature is 1100-1150°C, and the soaking time is 30-50 minutes. The billet heating process takes place in the austenitic high-temperature region, with a carbon content of 1.35%-1.6% at the austenite-cementite interface. High-temperature diffusion in the billet reduces the segregation of elements such as carbon and manganese. After heating, the billet undergoes roughing, intermediate rolling, pre-finishing, and finishing rolling before wire rod extrusion. The wire rod exiting the pre-finishing rolling mill is 980-1005°C; entering the finishing rolling mill is 890-930°C; entering the double-module rolling mill is 900-920°C; and the wire rod extrusion temperature is 910-930°C. The higher wire rod extrusion temperature increases the cooling rate of the wire rod on the air-cooled roller conveyor, laying the foundation for controlling the final microstructure of the wire rod. The wire rod is rolled to a diameter of 8mm to 12mm.

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

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

[0049] The following are specific embodiments.

[0050] Examples 1-6

[0051] The chemical composition, preparation process, and performance parameters of the wire rods in Examples 1-6 of this invention are shown in Table 1.

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

[0053]

[0054]

[0055] Based on the above results, it can be seen that the present invention has carried out a large number of systematic experimental studies on alloy element screening and proportioning, converter smelting, LF refining, continuous casting, continuous casting billet heating and continuous rolling, wire rod rolling, and wire rod cooling process design optimization. Finally, the composition system and manufacturing process that can meet the purpose of the present invention were determined, and a wire rod for cableway rope with a tensile strength of up to 1170MPa to 1250MPa was obtained.

[0056] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A type of 1200MPa grade cableway rope wire rod, characterized in that, Includes the following components by 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%, with the balance being iron and unavoidable impurities; Wire rod ferrite grain size ≤35μm; The size distribution of wire rod ferrite grains is as follows: grain size ≤5μm, accounting for 62% to 68% of the total; grain size ≤10μm, accounting for 78% to 84% of the total.

2. The 1200MPa grade cableway wire rod according to claim 1, characterized in that, The tensile strength of the wire rod is 1170MPa~1250MPa.

3. A method for preparing 1200MPa grade cableway rope wire rod as described in any one of claims 1-2, characterized in that, Includes the following steps: Converter smelting, LF refining, continuous casting, continuous casting billet heating and rolling, wire rod rolling, wire rod cooling; In the converter smelting process, scrap steel and molten iron are used as furnace charge, with the proportion of scrap steel being 3% to 12%. In the LF refining process, the molten steel after being tapped from the converter smelting furnace is fed into the LF furnace for refining treatment. The LF furnace refining temperature is 1470℃~1540℃ and the refining time is 40min~55min. In the continuous casting process, molten steel that has been refined by the LF is continuously cast to obtain a continuously cast billet. In the continuous casting billet heating and rolling process, the continuous casting billet that comes off the production line in the continuous casting process is sent to a heating furnace for heating, and the heated continuous casting billet is continuously rolled, with a final rolling temperature of 970℃~1000℃. In the aforementioned wire rod rolling process, the continuously rolled steel billet is heated in a heating furnace, and then sequentially undergoes roughing rolling, intermediate rolling, pre-finishing rolling, finishing rolling, and wire drawing. During the wire rod cooling process, the wire rod is cooled on an air-cooled roller conveyor after spinning to obtain the 1200MPa grade cableway wire rod.

4. The preparation method according to claim 3, characterized in that, During the LF refining process, argon gas is used for stirring, with an argon gas stirring intensity of 100NL / min to 400NL / min.

5. The preparation method according to claim 3, characterized in that, In the continuous casting billet heating and rolling process, the total furnace heating time for the continuous casting billet is 3.5h to 4.8h; the soaking temperature is 1190℃ to 1220℃, and the holding time is 40min to 50min.

6. The preparation method according to claim 5, characterized in that, During the heating and rolling of the continuously cast billet, the size of the inclusions in the core of the continuously rolled billet is ≤35μm, the size of the inclusions at the position 1 / 4 thickness away from the surface of the continuously rolled billet is ≤30μm, and the size of the inclusions on the surface of the continuously rolled billet is ≤25μm.

7. The preparation method according to claim 3, characterized in that, In the aforementioned wire rod rolling process, the total furnace time for the billet is 150-170 minutes, the soaking temperature is 1100-1150℃, and the holding time in the soaking section is 30-50 minutes. The billet heating process takes place in the austenitic high-temperature region, with a carbon content of 1.35%-1.6% at the austenitic-cementite interface. After heating, the billet undergoes roughing, intermediate rolling, pre-finishing, and finishing rolling before wire rod production. The wire rod exiting the pre-finishing rolling mill is 980-1005℃; entering the finishing rolling mill is 890-930℃; entering the double-module rolling mill is 900-920℃; and the wire rod production temperature is 910-930℃.

8. The preparation method according to claim 3, characterized in that, During the wire rod cooling process, the wire rod is cooled on an air-cooled roller conveyor after spinning, and the phase change temperature of the wire rod is controlled at 620℃~670℃, and the phase change time is 15s~25s.

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