Large deformation cold-rolled wire rod and its production method and profiled wire

Abstract

This invention relates to a large deformation cold-rolled wire rod, its production method, and shaped steel wire, belonging to the technical field of steelmaking. The wire rod has a carbon equivalent of 0.43~0.52%, and the contents of some elements are: C 0.30~0.35%, Mn 0.80~1.00%, B 0.0010~0.0025%, and Ti 0.01~0.05%. The production method involves feeding the rolled wire rod clockwise through a straightening roller conveyor into a heating furnace. After heating, the wire rod enters a salt bath. The salt bath temperature (°C) is set according to the wire rod diameter (mm) as follows: Salt bath temperature = 430 - [(wire rod diameter - 10) / 2] × 10. The shaped steel wire produced from the wire rod obtained by this invention through drawing and cold rolling exhibits high strength, high plasticity, and excellent uniformity throughout the rod.

Description

Technical Field

[0001] This invention relates to a large deformation cold-rolled wire rod, its production method, and special-shaped steel wire, belonging to the technical field of steelmaking. Background Technology

[0002] Wire rod (also known as wire) is produced by drawing, cold rolling and other processing methods into various types of steel wire with cross-sections such as round, rectangular and Z-shaped. It is then further processed to make the required steel wire ropes, springs, pipes and so on, which are widely used in the automotive, machinery and energy industries.

[0003] Marine hoses are primarily used to connect pipelines between offshore oil and gas fields and drilling platforms, enabling oil and gas transportation and other functions. They are an essential product for offshore oil and gas development. Marine hoses are made by twisting together multiple layers of metal structures and hot-melt polymer non-metallic materials. To prevent the hoses from being crushed by seawater pressure and broken by ocean currents, the metal structural layers must possess good strength and flexibility. Since the metal structural layers are woven from shaped steel wires, the strength and flexibility of the marine hose mainly depend on the strength and plasticity of these shaped steel wires, which typically have a C-shaped or Z-shaped cross-section.

[0004] Currently, the low-strength profiled steel wire used in China's flexible oil pipe industry has been domestically produced. The steel wire manufactured using the "wire rod-cold rolling-high temperature annealing-cold rolling-finished product" process has a tensile strength of 800-900 MPa, a yield strength of 720-870 MPa, and an elongation of 5-8%. High-strength profiled steel wire still relies on imports, with imported steel wire having a tensile strength ≥1100 MPa, a yield strength ≥990 MPa, and an elongation ≥5%.

[0005] Patent application CN 116695012 A discloses a 1000MPa grade high-carbon steel wire rod for the production of shaped steel wire and its production method. The chemical composition of the wire rod is: C 0.70~0.74%, Si 0.22~0.27%, Mn 0.45~0.52%, P ≤0.020%, S 0.0020~0.015%, N≤0.0050%, O 0.0025~0.0035%, Als 0.0015~0.0025%, Nb 0.0002~0.0010%, Co 0.0003~0.0010%. The production method includes steel smelting and continuous casting, heating and rolling of continuously cast billets, wire rod rolling, and wire rod cooling. Through chemical composition and process control, the tensile strength of the wire rod is 980~1060MPa, and the reduction of area is 30~36%. The main technical defects are: 1. The reduction of area of ​​the wire rod is only 30~36%, which cannot meet the production requirements of large deformation cold rolling. 2. The carbon content is high, i.e., C 0.70~0.74%, and the carbon equivalent reaches 0.77~0.82%, resulting in poor weldability of the wire rod.

[0006] Patent application CN 121472708 A discloses a wire rod for non-quenched and tempered fasteners, its production method, and the fastener itself. The wire rod's chemical composition is: C 0.18~0.24%, Si 0.15~0.25%, Mn 1.30~1.60%, P≤0.015%, S≤0.010%, Cr≤0.10%, Mo≤0.03%, B 0.0010~0.0025%, Ti 0.05~0.10%, Al 0.020~0.045%, N≤0.007%, with the remainder being Fe and unavoidable impurities. The production process employs converter smelting-LF refining-large billet continuous casting-billing-wire rolling-offline salt bath wire rod production. The wire rod has a tensile strength of 1050~1250 MPa and a reduction of area of ​​65~70%; the tensile strength fluctuation range within the same coil is ≤20 MPa. The wire rod obtained by this invention is intended for fasteners, not for use as profiled steel wire in marine hoses. Its chemical composition, performance, and process design are unsuitable for the requirements and applications of this invention. 1. Elongation is a crucial technical indicator for profiled steel wire; however, this invention only discloses a tensile strength of 1050-1250 MPa and a reduction of area of ​​65-70%, without specifying elongation requirements. 2. The high residual phosphorus content affects the cold-rolling deformation capability of the wire rod. 3. Inclusion control levels can affect the fatigue life of profiled steel wire. This invention only employs LF refining and does not disclose inclusion control requirements, failing to meet the technical requirements for the final application of the wire rod obtained by this invention. 4. This patent does not specify requirements for controlling banded structure. Banded structure gives the wire rod good cold-rolling deformation capability in the axial direction, but poor cold-rolling deformation capability in the radial direction. Banded structure can cause radial square cold-rolling cracking or internal cracking of the wire rod. Summary of the Invention

[0007] To address the aforementioned problems, this invention discloses a wire rod for large deformation cold rolling and a production method thereof, the specific technical solution of which is as follows: A type of cold-rolled wire rod with large deformation has the following chemical composition by mass percentage: C 0.30~0.35%, Si 0.15~0.25%, Mn 0.80~1.00%, P≤0.010%, S≤0.010%, Cr 0.15~0.25%, B 0.0010~0.0025%, Ti 0.01~0.05%, Al 0.020~0.035%, N≤0.0050%, with the remainder being Fe and unavoidable impurities; the carbon equivalent is 0.43~0.52%, and the carbon equivalent is calculated using the formula: C%+Mn% / 6.

[0008] The method for producing the aforementioned large-deformation cold-rolled wire rods employs a production process of converter smelting - LF refining - RH vacuum treatment - large billet continuous casting - billet preparation - grinding - wire rod rolling - offline salt bath wire rod process, specifically as follows: Converter smelting: Converter tapping temperature 1580~1620℃, converter final slag basicity 4.0~4.5; LF refining process: White residue refining time is 10~15min; RH vacuum treatment: vacuum level of 1.0~1.8 mbar, holding time of 15~20 min; Large billet continuous casting: molten steel superheated to 20~30℃; Rolling: The large square billet is rolled into a (140~160) mm × (140~160) mm square billet, wherein the center segregation ratio of the square billet is ≤1.05; Grinding: After grinding, the surface roughness Ra of the billet is ≤60μm; Wire rod rolling: The diameter of the rolled wire rod is 10~16mm; Offline salt bath for wire rod: The rolled wire rod is laid out clockwise and enters the heating furnace through the straightening roller conveyor. After being heated, the wire rod enters the salt bath. The salt bath temperature (°C) is set with the following relationship to the wire rod diameter (mm): Salt bath temperature = 430 - [(wire rod diameter - 10) / 2] × 10.

[0009] Furthermore, in the converter smelting process: the amount of converter slag is 13±2 kg / ton, and the amount of steel retained after the converter tapping is 3~5 tons; The LF refining process is as follows: the amount of lime added is 2.0±0.5 kg / ton, the basicity of the refining slag is 3.5~4.0, and the bottom-blown argon flow rate is controlled at 200~400 NL / min; The RH vacuum treatment process involves argon gas soft stirring for 12-18 minutes and a soft stirring intensity of 40-80 NL / min.

[0010] Furthermore, in the large billet continuous casting process: the cross-sectional dimensions of the continuously cast billet are 300mm×390mm, the casting speed is 0.65±0.2m / min, the water content in the secondary cooling zone is 0.55±0.2L / kg, the reduction is 11.6~14.4mm, and the reduction of the 1~11# reduction rollers is 0mm, 0mm, 0mm, 0mm, 0.5±0.2mm, 0.5±0.2mm, 2.5±0.2mm, 3.0±0.2mm, 2.5±0.2mm, 2.5±0.2mm, 1.5±0.2mm.

[0011] Furthermore, in the billet-making process: the heating temperature of the large billet is 1220~1260℃, and the heating time is 240~300min.

[0012] Furthermore, the grinding process involves using a mechanical grinding machine to perform full grinding on the billet, with a single-sided grinding depth of 1.5±0.3mm; the grinding wheel roughness is 24 mesh, and the surface of the billet after grinding is free of cracks, pits, and surface defects, and free of grinding burrs.

[0013] Furthermore, in the wire rod rolling process: the billet heating temperature is 1080~1120℃, the initial rolling temperature is 970~1000℃, and the finishing mill inlet temperature is 890~920℃; the wire rod extrusion temperature is 880~900℃, the inlet section roller speed is 0.8~1.2m / s, all the insulation covers of the Stellmore cooling line are opened, all the fans are turned off, and the wire rod is collected into coils by the coiling drum, waiting for offline salt bath.

[0014] Furthermore, the offline salt bath process for the wire rod includes the following steps: heating temperature of 900±10℃, heating time of 8~10min, furnace carbon potential of 0.33±0.01%, wire rod feeding speed of 3.0~3.5m / min; salt bath temperature of 400~430℃, and salt bath time of 180~200 seconds.

[0015] The wire rod produced by the above method has a diameter of 10-16 mm and a strip structure grade of 0-0.5. The wire rod has a tensile strength of 850-950 MPa, a reduction of area of ​​70-75%, and an elongation of 20-25%. The number of Ca-Al-O composite inclusions in the wire rod is ≤5 per mm. 2 The number of Ca-Al-O composite inclusions with a size ≥5μm is ≤2 per mm. 2 .

[0016] A type of profiled steel wire produced from the aforementioned wire rod through drawing and cold rolling has a drawing area reduction rate of 14±1%, calculated as (cross-sectional area of ​​the wire rod before drawing - cross-sectional area of ​​the wire rod after drawing) / cross-sectional area of ​​the wire rod before drawing × 100%. After drawing, the wire rod has a tensile strength of 920~1030MPa, a reduction of area of ​​68~73%, and an elongation of 18~24%. The cold rolling deformation rate is 35±5%, and the cold rolling deformation rate = (cross-sectional area of ​​the wire rod before drawing - cross-sectional area of ​​the wire rod after drawing) / cross-sectional area of ​​the wire rod before drawing × 100%; The properties of the shaped steel wire are as follows: tensile strength of 1150~1250MPa, yield strength of 1035~1150MPa, elongation of 6~12%, yield strength ratio of 0.91~0.95, and the tensile strength fluctuation range of the shaped steel wire is ≤15MPa.

[0017] The beneficial effects of this invention are: This invention improves the weldability of steel by designing reasonable carbon and manganese content and controlling the carbon equivalent to 0.43~0.52%; it also improves the hardenability of steel by adding boron, and simultaneously enhances the strength and plasticity of the steel by matching reasonable wire rod rolling and offline salt bath processes. The special-shaped steel wire produced by drawing and cold rolling of the wire rod obtained by this invention has the characteristics of high strength, high plasticity and excellent uniformity of the whole rod, and can achieve import substitution. Attached Figure Description

[0018] Figure 1 The Z-shaped steel wire obtained in Embodiment 1 of the present invention is... Figure 2 The C-shaped steel wire obtained in Embodiment 3 of the present invention. Detailed Implementation

[0019] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0020] This invention provides a cold-rolled wire rod for large deformation. The chemical composition of this wire rod, by mass percentage, is: C 0.30~0.35%, Si 0.15~0.25%, Mn 0.80~1.00%, P≤0.010%, S≤0.010%, Cr 0.15~0.25%, B 0.0010~0.0025%, Ti 0.01~0.05%, Al 0.020~0.035%, N≤0.0050%, with the remainder being Fe and unavoidable impurities. This invention improves the weldability of the steel by designing reasonable carbon and manganese contents, controlling the carbon equivalent to 0.43~0.52%; the addition of boron improves the hardenability of the steel; and the combination of wire rod rolling and offline salt bath processes enhances the strength and plasticity of the steel.

[0021] Carbon (C) is the most basic and cheapest strengthening element in steel, but as the carbon content increases, the plasticity of wire rod decreases, reducing the cold heading performance and weldability of the steel. Therefore, the carbon content in this invention is controlled at 0.30~0.35%.

[0022] Silicon (Si) is a strengthening and deoxidizing element in steel, but excessive silicon can reduce the plasticity of wire rods. In this invention, the silicon content is controlled at 0.15~0.25%.

[0023] Manganese (Mn) is a strengthening element in steel, which can improve the strength and hardenability of steel. However, excessive manganese will reduce the plasticity and weldability of steel. In this invention, the manganese content is controlled at 0.80~1.00%.

[0024] Cr is a strengthening element in steel, which can improve the strength and hardenability of steel. However, excessive Cr will prolong the offline salt bath treatment time, which is not conducive to the efficiency of salt bath production. In this invention, the chromium content is controlled at 0.15~0.25%.

[0025] P and S are impurity elements in steel. Their segregation at grain boundaries causes grain boundary embrittlement, thereby reducing the strength and plasticity of the steel. This invention controls the phosphorus and sulfur content to below 0.010%.

[0026] Ti forms fine TiC and TiN in steel, preventing boron (B) from forming BN with nitrogen, thus allowing B to improve hardenability. Additionally, TiC and TiN refine grain size, increasing strength and plasticity. However, excessive Ti content can coarsen TiN and TiC, hindering fine-grain strengthening and continuous casting production. In this invention, the titanium content is controlled between 0.01% and 0.05%.

[0027] Boron (B) can improve the hardenability of steel, thereby increasing its strength. However, excessive addition of boron can cause the boron element to form a "boron phase" at the grain boundaries, reducing the steel's plasticity. In this invention, the boron content is controlled between 0.0010 and 0.0025%.

[0028] Al is a deoxidizing element in steel, effectively removing oxygen and improving its cleanliness. Additionally, Al reacts with nitrogen to form AlN, which helps refine the grain size. In this invention, the aluminum content is controlled between 0.020% and 0.035%.

[0029] Nitrogen (N) can reduce the plasticity of steel, affecting its cold heading properties. High nitrogen content can also coarsen AlN and TiN, hindering fine-grain strengthening. By employing converter smelting and RH vacuum treatment, the nitrogen content in this invention can be controlled below 0.0050%.

[0030] The following provides a production method for cold-rolled wire rod with large deformation: The production process adopts converter smelting - LF refining - RH vacuum treatment - large billet continuous casting - billet opening - grinding - wire rod rolling - wire rod offline salt bath.

[0031] Converter smelting process: Converter tapping temperature 1580~1620℃, converter final slag basicity 4.0~4.5, converter slag amount 13±2kg / ton, and converter tapping steel retention amount 3~5 tons.

[0032] LF refining process: lime addition is 2.0±0.5 kg / ton, refining slag basicity is 3.5~4.0, white slag refining time is 10~15 min, and bottom blowing argon flow rate is controlled at 200~400 NL / min.

[0033] RH vacuum treatment process: vacuum degree is 1.0~1.8mbar, holding time is 15~20min, argon soft stirring time is 12~18min, and soft stirring intensity is 40~80NL / min.

[0034] Large billet continuous casting process: The cross-sectional dimensions of the continuously cast billet are 300mm×390mm, the superheat of the molten steel is 20~30℃, the casting speed is 0.65±0.2m / min, the water content in the secondary cooling zone is 0.55±0.2L / kg, the reduction is 11.6~14.4mm, and the reduction of the 1~11# pressing rolls is 0mm, 0mm, 0mm, 0mm, 0mm, 0.5±0.2mm, 0.5±0.2mm, 2.5±0.2mm, 3.0±0.2mm, 2.5±0.2mm, 2.5±0.2mm, 1.5±0.2mm.

[0035] Billet rolling process: The large billet is heated to 1220~1260℃ for 240~300min, and then rolled into a (140~160)mm×(140~160)mm billet with a center segregation ratio ≤1.05. A sample from the center of the billet is taken, and the carbon content in the sample is tested using a carbon-sulfur analyzer. The center segregation ratio is the ratio of the carbon content at the center of the billet to the carbon content of the continuously cast steel in the large billet.

[0036] Grinding process: The billet is fully ground using a mechanical grinding machine with a single-sided grinding depth of 1.5±0.3mm. The grinding wheel roughness is 24 mesh. The surface of the billet after grinding is free of surface defects such as cracks and pits, and there are no grinding burrs. The surface roughness Ra of the billet after grinding is ensured to be ≤60μm.

[0037] Wire rod rolling process: billet heating temperature is 1080~1120℃, initial rolling temperature is 970~1000℃, and finishing mill inlet temperature is 890~920℃; wire rod extrusion temperature is 880~900℃, and inlet section roller speed is 0.8~1.2m / s; the insulation covers of the Stellmore cooling line are all open, and all fans are all turned off. The wire rod is collected into coils by the coiling drum and awaits offline salt bath. The diameter of the rolled wire rod is 10~16mm.

[0038] Offline salt bath process for wire rod: The rolled wire rod is fed clockwise through a straightening roller conveyor into a heating furnace. The heating temperature is 900±10℃, the heating time is 8~10min, the carbon potential in the furnace is 0.33±0.01%, and the wire rod feeding speed is 3.0~3.5m / min. After heating, the wire rod enters a salt bath at a temperature of 400~430℃ for 180~200 seconds. The salt bath temperature setting is related to the wire rod diameter as follows: Salt bath temperature = 430 - [(wire rod diameter - 10) / 2] × 10.

[0039] After offline salt bath treatment, the wire rod exhibits a tensile strength of 850~950MPa, a reduction of area of ​​70~75%, and an elongation of 20~25%. The number of Ca-Al-O composite inclusions in the wire rod is ≤5 per mm. 2 The number of Ca-Al-O composite inclusions with a size ≥5μm is ≤2 per mm. 2 The diameter of the wire rod is 10~16mm, and the banded structure is grade 0~0.5.

[0040] The profiled steel wire produced from wire rod after offline salt bath drawing and cold rolling has a drawing area reduction rate of 14±1%, calculated as (cross-sectional area of ​​wire rod before drawing - cross-sectional area of ​​wire rod after drawing) / cross-sectional area of ​​wire rod before drawing × 100%. After drawing, the wire rod has a tensile strength of 920~1030MPa, a reduction of area of ​​68~73%, and an elongation of 18~24%. The cold rolling deformation rate is 35±5%, calculated as (cross-sectional area of ​​wire rod before drawing - cross-sectional area of ​​wire rod after drawing) / cross-sectional area of ​​wire rod before drawing × 100%.

[0041] The properties of the shaped steel wire are as follows: tensile strength of 1150~1250MPa, yield strength of 1035~1150MPa, elongation of 6~12%, yield strength ratio of 0.91~0.95, and tensile strength fluctuation range within the same coil ≤15MPa. The tensile strength of the weld of the shaped steel wire is ≥900MPa.

[0042] The present invention is further illustrated by the following embodiments: The present invention can be better understood from the following embodiments. However, those skilled in the art will readily understand that the specific material ratios, process conditions, and results described in the embodiments are for illustrative purposes only and should not, and will not, limit the present invention as described in detail in the claims.

[0043] Example 1

[0044] This embodiment provides a production method for large deformation cold-rolled wire rod, employing a production process of converter smelting - LF refining - RH vacuum treatment - large billet continuous casting - billet opening - grinding - wire rod rolling - offline salt bath process: Converter smelting process: Converter tapping temperature 1580℃, converter final slag basicity 4.5, converter slag quantity 15kg / ton, and converter tapping steel retention quantity 5 tons.

[0045] LF refining process: lime addition is 2.5 kg / ton, refining slag basicity is 4.0, white slag refining time is 15 min, and bottom blowing argon flow rate is controlled at 400 NL / min.

[0046] RH vacuum treatment process: vacuum degree is 1.0 mbar, holding time is 15 min, argon soft stirring time is 12 min, and soft stirring intensity is 80 NL / min.

[0047] Large billet continuous casting process: The cross-sectional dimensions of the continuously cast billet are 300mm×390mm, the superheat of the molten steel is 30℃, the casting speed is 0.63m / min, the water content in the secondary cooling zone is 0.53L / kg, the reduction is 14mm, and the reduction of the 1~11# pressing rollers is 0mm, 0mm, 0mm, 0mm, 0.5mm, 0.5mm, 2.7mm, 3.2mm, 2.7mm, 2.7mm, and 1.7mm respectively.

[0048] Billet rolling process: The large billet is heated to 1220℃ for 300 minutes and rolled into a 140mm×140mm billet with a center segregation ratio of 1.03.

[0049] Grinding process: The billet is fully ground using a mechanical grinding machine with a single-sided grinding depth of 1.8 mm. The grinding wheel roughness is 24 mesh. The surface of the billet after grinding is free of surface defects such as cracks and pits, and there are no grinding burrs. This ensures that the surface roughness Ra of the billet after grinding is 50 μm.

[0050] The wire rod rolling process is as follows: the billet heating temperature is 1120℃, the initial rolling temperature is 1000℃, and the finishing mill inlet temperature is 890℃; the wire rod extrusion temperature is 880℃, and the inlet section roller speed is 1.2m / s; all insulation covers of the Stellmore cooling line are opened, and all fans are turned off. The wire rod is collected into coils by the coiling drum and awaits offline salt bath treatment. The diameter of the rolled wire rod is 10mm.

[0051] Offline salt bath process for wire rod: The rolled wire rod is fed clockwise and enters the heating furnace through the straightening roller conveyor. The heating temperature is 890℃, the heating time is 8min, the carbon potential in the furnace is 0.33%, and the wire rod feeding speed is 3.0m / min. After heating, the wire rod enters the salt bath. The salt bath temperature is 430℃, and the salt bath time is 200 seconds.

[0052] Comparative Example 1 The production process is as follows: converter smelting - LF refining - RH vacuum treatment - large billet continuous casting - billet opening - full grinding - wire rod rolling - wire rod offline salt bath process. The 140mm×140mm square billet obtained after billet opening in Example 1 is fully ground by a mechanical grinding machine. The grinding depth on one side is 1.0mm. The grinding wheel roughness is 20 mesh. The surface roughness Ra of the square billet after grinding is 80μm.

[0053] The wire rod rolling process is as follows: the billet heating temperature is 1120℃, the initial rolling temperature is 1000℃, and the finishing mill inlet temperature is 890℃; the wire rod extrusion temperature is 880℃, and the inlet section roller speed is 1.2m / s; all insulation covers of the Stellmore cooling line are opened, and all fans are turned off. The wire rod is collected into coils by the coiling drum and awaits offline salt bath treatment. The diameter of the rolled wire rod is 10mm.

[0054] Offline salt bath process for wire rod: The rolled wire rod is fed clockwise and enters the heating furnace through the straightening roller conveyor. The heating temperature is 890℃, the heating time is 8min, the carbon potential in the furnace is 0.33%, and the wire rod feeding speed is 3.0m / min. After heating, the wire rod enters the salt bath. The salt bath temperature is 430℃, and the salt bath time is 200 seconds.

[0055] Example 2

[0056] This embodiment provides a production method for large deformation cold-rolled wire rod, employing a production process of converter smelting - LF refining - RH vacuum treatment - large billet continuous casting - billet opening - grinding - wire rod rolling - offline salt bath process: Converter smelting process: Converter tapping temperature 1620℃, converter final slag basicity 4.0, converter slag quantity 11kg / ton, and converter tapping steel retention quantity 3 tons.

[0057] LF refining process: lime addition is 2.5 kg / ton, refining slag basicity is 3.5, white slag refining time is 10 min, and bottom blowing argon flow rate is controlled at 200 NL / min.

[0058] RH vacuum treatment process: vacuum degree is 1.8 mbar, holding time is 20 min, argon soft stirring time is 18 min, and soft stirring intensity is 40 NL / min.

[0059] Large billet continuous casting process: The cross-sectional dimensions of the continuously cast billet are 300mm×390mm, the superheat of the molten steel is 20℃, the casting speed is 0.67m / min, the water content in the secondary cooling zone is 0.57L / kg, the reduction is 11.6mm, and the reduction of the 1~11# pressing rollers is 0mm, 0mm, 0mm, 0mm, 0mm, 0.3mm, 0.3mm, 2.3mm, 2.8mm, 2.3mm, 2.3mm, 2.3mm, and 1.3mm respectively.

[0060] Billet rolling process: The large billet is heated to 1260℃ for 240 minutes and rolled into a 160mm×160mm billet with a center segregation ratio of 1.04.

[0061] Grinding process: The billet is fully ground using a mechanical grinding machine with a single-sided grinding depth of 1.2 mm. The grinding wheel roughness is 24 mesh. The surface of the billet after grinding is free of surface defects such as cracks and pits, and there are no grinding burrs. This ensures that the surface roughness Ra of the billet after grinding is 40 μm.

[0062] The wire rod rolling process is as follows: the billet heating temperature is 1080℃, the initial rolling temperature is 970℃, and the finishing mill inlet temperature is 920℃; the wire rod extrusion temperature is 900℃, and the inlet section roller speed is 1.0m / s; all insulation covers of the Stellmore cooling line are opened, and all fans are turned off. The wire rod is collected into coils by the coiling drum and awaits offline salt bath treatment. The diameter of the rolled wire rod is 16mm.

[0063] Offline salt bath process for wire rod: The rolled wire rod is fed clockwise and enters the heating furnace through the straightening roller conveyor. The heating temperature is 910℃, the heating time is 10min, the carbon potential in the furnace is 0.32%, and the wire rod feeding speed is 3.5m / min. After heating, the wire rod enters the salt bath. The salt bath temperature is 400℃, and the salt bath time is 180 seconds.

[0064] Comparative Example 2 The production process of converter smelting - LF refining - RH vacuum treatment - large billet continuous casting - billet opening - full grinding - wire rod rolling - wire rod offline salt bath process uses the square billet obtained after grinding in Example 2.

[0065] The wire rod rolling process is as follows: the billet heating temperature is 1060℃, the initial rolling temperature is 950℃, and the finishing mill inlet temperature is 860℃; the wire rod extrusion temperature is 870℃, and the inlet section roller speed is 1.4m / s; all insulation covers of the Stellmore cooling line are opened, and all fans are turned off. The wire rod is collected into coils by the coiling drum and awaits offline salt bath treatment. The diameter of the rolled wire rod is 16mm.

[0066] Offline salt bath process for wire rod: The rolled wire rod is fed clockwise and enters the heating furnace through the straightening roller conveyor. The heating temperature is 910℃, the heating time is 10min, the carbon potential in the furnace is 0.32%, and the wire rod feeding speed is 3.5m / min. After heating, the wire rod enters the salt bath. The salt bath temperature is 400℃, and the salt bath time is 180 seconds.

[0067] Example 3

[0068] This embodiment provides a production method for large deformation cold-rolled wire rod, employing a production process of converter smelting - LF refining - RH vacuum treatment - large billet continuous casting - billet opening - grinding - wire rod rolling - offline salt bath process: Converter smelting process: Converter tapping temperature 1600℃, converter final slag basicity 4.2, converter slag quantity 13kg / ton, and converter tapping steel retention quantity 4 tons.

[0069] LF refining process: lime addition is 2.0 kg / ton, refining slag basicity is 3.8, white slag refining time is 13 min, and bottom blowing argon flow rate is controlled at 300 NL / min.

[0070] RH vacuum treatment process: vacuum degree is 1.3 mbar, holding time is 18 min, argon soft stirring time is 15 min, and soft stirring intensity is 60 NL / min.

[0071] Large billet continuous casting process: The cross-sectional dimensions of the continuously cast billet are 300mm×390mm, the superheat of the molten steel is 25℃, the casting speed is 0.65m / min, the water content in the secondary cooling zone is 0.55L / kg, the reduction is 14.4mm, and the reduction of the 1~11# pressing rollers is 0mm, 0mm, 0mm, 0mm, 0.7mm, 0.7mm, 2.7mm, 3.2mm, 2.7mm, 2.7mm, and 1.7mm respectively.

[0072] Billet rolling process: The large billet is heated to 1240℃ for 280 minutes and rolled into a 160mm×160mm billet with a center segregation ratio of 1.03.

[0073] Grinding process: The billet is fully ground using a mechanical grinding machine with a single-sided grinding depth of 1.5mm. The grinding wheel roughness is 24 mesh. The surface of the billet after grinding is free of surface defects such as cracks and pits, and there are no grinding burrs. This ensures that the surface roughness Ra of the billet after grinding is 30μm.

[0074] The wire rod rolling process is as follows: the billet heating temperature is 1100℃, the initial rolling temperature is 990℃, and the finishing mill inlet temperature is 900℃; the wire rod extrusion temperature is 890℃, and the inlet section roller speed is 0.8m / s; all insulation covers of the Stellmore cooling line are opened, and all fans are turned off. The wire rod is collected into coils by the coiling drum and awaits offline salt bath treatment. The diameter of the rolled wire rod is 12mm.

[0075] Offline salt bath process for wire rod: The rolled wire rod is fed clockwise and enters the heating furnace through the straightening roller conveyor. The heating temperature is 900℃, the heating time is 9min, the carbon potential in the furnace is 0.34%, and the wire rod feeding speed is 3.3m / min. After heating, the wire rod enters the salt bath. The salt bath temperature is 420℃, and the salt bath time is 190 seconds.

[0076] Comparative Example 3 The production process, which includes converter smelting, LF refining, RH vacuum treatment, large billet continuous casting, billet preparation, full grinding, wire rod rolling, and offline salt bath processing, uses the wire rod obtained from the wire rod rolling process described in Example 3. The rolled wire rod is fed clockwise through a straightening roller conveyor into a heating furnace at 880°C for 7 minutes, with a furnace carbon potential of 0.30% and a wire rod feeding speed of 4.0 m / min. After heating, the wire rod enters a salt bath at 440°C for 150 seconds.

[0077] Comparative Example 4 The production process, consisting of converter smelting, LF refining, RH vacuum treatment, large billet continuous casting, billet preparation, full grinding, wire rod rolling, and offline salt bath, utilizes the wire rod obtained from the wire rod rolling process described in Example 3. The rolled wire rod is fed clockwise through a straightening roller conveyor into a heating furnace at 950°C for 12 minutes, with a furnace carbon potential of 0.36% and a wire rod feeding speed of 2.5 m / min. After heating, the wire rod enters a salt bath at 380°C for 220 seconds.

[0078] Comparative Example 5 The wire rod obtained in Example 2 of patent CN 121472708 A is used as Comparative Example 5. The chemical composition of the wire rods obtained in Examples 1-3 and Comparative Examples 1-5 is shown in Table 1.

[0079] Table 1

[0080] Table 2

[0081] As shown in Tables 1 and 2, the P content in Comparative Example 5 was 0.011%, while the present invention, by designing converter smelting parameters such as converter tapping temperature, converter slag amount, and converter final rolling basicity, can control the P content below 0.010%. Compared with Comparative Example 5, the present invention adds an RH vacuum treatment process and sets RH vacuum treatment parameters, which can control the N content below 0.0042% and the number of Ca-Al-O composite inclusions is 3.8~4.4 per mm. -2 The number of Ca-Al-O composite inclusions with a size ≥5μm is 1.2~1.6 per mm. -2The nitrogen content and Ca-Al-O composite inclusion control levels of this invention are significantly higher than those of Comparative Example 5. Through the design of large billet continuous casting parameters and billet opening process, the segregation ratio of the billet obtained in this invention is 1.03~1.04, resulting in a banded structure rating of 0. In contrast, the banded structure rating of the wire rod obtained in Comparative Example 5 is higher, which is detrimental to cold rolling deformation. The mechanical properties of the wire rods obtained in Examples 1-3 are: tensile strength of 852~948 MPa, reduction of area of ​​70~75%, and elongation of 20~24%. Due to the unreasonable design of the wire rod rolling parameters in Comparative Example 2, the tensile strength of the wire rod is too low, failing to meet the requirements of this invention. Due to the unreasonable design of the offline salt bath parameters in Comparative Examples 3 and 4, the tensile strength, reduction of area, and elongation do not meet the requirements of this invention.

[0082] The wire rods obtained from Examples 1, 3, 1, 4, and 5 were drawn, and their mechanical properties were measured, as shown in Table 3. After drawing, the wire rods from Examples 1 and 3 had a tensile strength of 925–1042 MPa, a reduction of area of ​​68–73%, and an elongation of 18–22%. The wire rods from Comparative Examples 4 and 5 had a tensile strength of 1134–1300 MPa, a reduction of area of ​​66–67%, and an elongation of 12–15%. Because the wire rods from Comparative Examples 4 and 5 had excessively high tensile strength and poor plasticity, their reduction of area and elongation after drawing did not meet the requirements of this invention.

[0083] Table 3

[0084] The wire rods obtained in Examples 1, 3, 1, 4, and 5 were drawn and cold-rolled to produce shaped steel wires. The properties of the shaped steel wires were measured, as shown in Table 3. After drawing, the wire rods obtained in Examples 1 and 3 had a tensile strength of 1152~1250 MPa, a yield strength of 1048~1150 MPa, an elongation of 6~12%, and a yield-to-tensile ratio of 0.91~0.92. The wire rods obtained in Comparative Example 1, when drawn and cold-rolled to produce shaped steel wires, met the requirements of this invention. However, the shallow grinding depth of the billet during wire rod production and the poor surface roughness of the billet after grinding resulted in surface defects in the wire rods. These surface defects led to cracking during cold rolling, which does not meet the requirements for the production and use of shaped steel wires. Comparative Example 4, due to an unreasonable offline salt bath process design, resulted in wire rods with high strength but poor plasticity. The tensile strength and yield strength of the wire rods used in the drawn and cold-rolled shaped steel wire production were too high, and the elongation was too low, which does not meet the requirements of this invention. Comparative Example 5 exhibited significant segregation in the billet, resulting in severe banded structure and excessively high strength in the resulting wire rod. This led to poor plasticity and cold-rolling cracking during the cold rolling process. Furthermore, the tensile strength and yield strength of the shaped steel wire were excessively high, while the elongation was too low, failing to meet the requirements of this invention. As shown in Table 4, the shaped steel wire produced from the wire rod obtained by this invention through drawing and cold rolling is significantly superior to imported shaped steel wire, enabling import substitution.

[0085] Table 4

[0086] Those skilled in the art will understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0087] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A type of cold-rolled wire rod with large deformation, characterized in that, The chemical composition, by mass percentage, includes: C 0.30~0.35%, Si 0.15~0.25%, Mn 0.80~1.00%, P≤0.010%, S≤0.010%, Cr 0.15~0.25%, B 0.0010~0.0025%, Ti 0.01~0.05%, Al 0.020~0.035%, N≤0.0050%, with the remainder being Fe and unavoidable impurities; the carbon equivalent is 0.43~0.52%, calculated using the formula: C%+Mn% / 6.

2. A method for producing the large deformation cold-rolled wire rod as described in claim 1, characterized in that, The production process adopts a converter smelting-LF refining-RH vacuum treatment-large billet continuous casting-billing-grinding-wire rolling-wire offline salt bath process, specifically as follows: Converter smelting: Converter tapping temperature 1580~1620℃, converter final slag basicity 4.0~4.5; LF refining process: White residue refining time is 10~15min; RH vacuum treatment: vacuum level of 1.0~1.8 mbar, holding time of 15~20 min; Large billet continuous casting: molten steel superheated to 20~30℃; Rolling: The large square billet is rolled into a (140~160) mm × (140~160) mm square billet, wherein the center segregation ratio of the square billet is ≤1.05; Grinding: After grinding, the surface roughness Ra of the billet is ≤60μm; Wire rod rolling: The diameter of the rolled wire rod is 10~16mm; Offline salt bath for wire rod: The rolled wire rod is laid out clockwise and enters the heating furnace through the straightening roller conveyor. After being heated, the wire rod enters the salt bath. The salt bath temperature (°C) is set with the following relationship to the wire rod diameter (mm): Salt bath temperature = 430 - [(wire rod diameter - 10) / 2] × 10.

3. The method for producing large deformation cold-rolled wire rod according to claim 2, characterized in that, The converter smelting process: In the converter smelting process, the amount of converter slag is 13±2 kg / ton, and the amount of steel left after the converter tapping is 3~5 tons; The LF refining process is as follows: the amount of lime added is 2.0±0.5 kg / ton, the basicity of the refining slag is 3.5~4.0, and the bottom-blown argon flow rate is controlled at 200~400 NL / min; The RH vacuum treatment process involves argon gas soft stirring for 12-18 minutes and a soft stirring intensity of 40-80 NL / min.

4. The method for producing large deformation cold-rolled wire rod according to claim 2, characterized in that, The large billet continuous casting process has the following characteristics: the cross-sectional dimensions of the continuously cast billet are 300mm×390mm, the casting speed is 0.65±0.2m / min, the water content in the secondary cooling zone is 0.55±0.2L / kg, the reduction is 11.6~14.4mm, and the reduction of the 1~11# pressing rollers is 0mm, 0mm, 0mm, 0mm, 0.5±0.2mm, 0.5±0.2mm, 2.5±0.2mm, 3.0±0.2mm, 2.5±0.2mm, 2.5±0.2mm, 1.5±0.2mm.

5. The method for producing large deformation cold-rolled wire rod according to claim 2, characterized in that, The billet opening process involves heating the large billet at a temperature of 1220~1260℃ for 240~300 minutes.

6. The method for producing large deformation cold-rolled wire rod according to claim 2, characterized in that, The grinding process involves using a mechanical grinding machine to fully grind the billet, with a single-sided grinding depth of 1.5±0.3mm. The grinding wheel roughness is 24 mesh, and the surface of the ground billet is free of cracks, pits, and grinding burrs.

7. The method for producing large deformation cold-rolled wire rod according to claim 2, characterized in that, The wire rod rolling process is as follows: the billet heating temperature is 1080~1120℃, the initial rolling temperature is 970~1000℃, and the finishing mill inlet temperature is 890~920℃; the wire rod extrusion temperature is 880~900℃, the inlet section roller speed is 0.8~1.2m / s, all the insulation covers of the Stellmore cooling line are opened, all the fans are turned off, and the wire rod is collected into coils by the coiling drum and awaits offline salt bath.

8. The method for producing large deformation cold-rolled wire rod according to claim 2, characterized in that, The offline salt bath process for the wire rod is as follows: the heating temperature is 900±10℃, the heating time is 8~10min, the carbon potential in the furnace is 0.33±0.01%, and the wire rod feeding speed is 3.0~3.5m / min; the salt bath temperature is 400~430℃, and the salt bath time is 180~200 seconds.

9. Wire rod produced by the method according to any one of claims 2 to 8, characterized in that, The diameter of the wire rod is 10~16mm, and the banded structure is grade 0~0.5; The wire rod has a tensile strength of 850~950MPa, a reduction of area of ​​70~75%, and an elongation of 20~25%. The number of Ca-Al-O composite inclusions in the wire rod is ≤5 per mm. 2 The number of Ca-Al-O composite inclusions with a size ≥5μm is ≤2 per mm. 2 .

10. A profiled steel wire produced from the wire rod of claim 9 by drawing and cold rolling, characterized in that, The reduction in area after drawing is 14±1%, and the reduction in area after drawing is calculated as (cross-sectional area of ​​the wire rod before drawing - cross-sectional area of ​​the wire rod after drawing) / cross-sectional area of ​​the wire rod before drawing × 100%. After drawing, the tensile strength of the wire rod is 920~1030MPa, the reduction in area is 68~73%, and the elongation is 18~24%. The cold rolling deformation rate is 35±5%, and the cold rolling deformation rate = (cross-sectional area of ​​the wire rod before drawing - cross-sectional area of ​​the wire rod after drawing) / cross-sectional area of ​​the wire rod before drawing × 100%; The properties of the shaped steel wire are as follows: tensile strength of 1150~1250MPa, yield strength of 1035~1150MPa, elongation of 6~12%, yield strength ratio of 0.91~0.95, and the tensile strength fluctuation range of the shaped steel wire is ≤15MPa.

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