High-performance small conduit hot-rolled steel strip for highway tunnel and preparation method of high-performance small conduit hot-rolled steel strip

Abstract

The invention relates to a high-performance small guide pipe hot rolled steel strip for a highway tunnel and a preparation method thereof, and belongs to the technical field of hot continuous rolling plate strip production. The high-performance small guide pipe hot rolled steel strip for the highway tunnel is prepared through the procedures of molten iron smelting, continuous casting, heating in a heating furnace, rough rolling, coiling in a hot coiling box, finish rolling, laminar cooling and coiling. The yield strength is larger than or equal to 450 MPa, the tensile strength is larger than or equal to 500 MPa, the percentage elongation after fracture is larger than or equal to 30%, and the impact energy at-20 DEG C is larger than or equal to 45 The problems that in the prior art, the thickness of a small guide pipe manufactured by drawing a seamless steel pipe is 4 mm or above, cost is high, the yield is low, impact resistance is poor, and the road tunnel development requirement cannot be met are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of high-performance small catheter hot-rolled steel strip for highway tunnel and its preparation method, belong to the technical field of hot strip production. BACKGROUND

[0002] In recent years, with the rapid development of China's economy and the gradual increase of high-grade highway construction investment, China's highway tunnel construction has made great achievements. Especially in mountainous areas of high-grade highways, most of them pass through high mountains and steep mountains in the form of tunnels. In tunnel construction, some tunnels often pass through shallow or soft loose strata, broken rock strata and other adverse geological sections, and the self-stability time of the surrounding rock of the tunnel roof is less than the time required to complete the support. In order to reduce the safety risk of tunnel construction and prevent personnel casualties, when building tunnels in broken rock mass, collapse body, sand / loess stratum, fracture and broken zone and other surrounding rocks, small catheter grouting and other advanced support methods are often used to pre-reinforce the strata in front of the working face of the tunnel, to ensure the stability of the working face and the surrounding rock of the tunnel roof, and to control the deformation of the surrounding rock, forming an advanced support system.

[0003] Small catheter for tunnel is a very important pre-supporting means in tunnel engineering. The small catheter is punched into the surrounding rock in front of the tunnel excavation contour line at a certain angle, and the tail end of the catheter is supported on the steel arch frame that has been erected, so that the catheter forms a umbrella-shaped or shed-shaped protective structure in front of the excavation. The bending and shearing capacity of composite beam structure is much larger than that of single catheter. It can effectively transfer the pressure of the surrounding rock above to the stable rock mass behind and the completed support structure, forming a continuous force-bearing system. After grouting, the catheter group and the surrounding reinforced rock mass form a "shell" or "arch" with certain thickness and strength, which cements the original loose and separated rock fragments and soil particles into a whole, forming a solid "rock mass", greatly improving the integrity, strength and self-stability of the surrounding rock.

[0004] The core requirements of small conduit steel are strength, toughness and processability (welding, drilling), the domestic patent CN118639105 A discloses a high-strength high-impact absorbing anchor rod steel and its preparation method, the present application provides a high-strength high-impact absorbing anchor rod steel and its preparation method and application, the chemical composition of the anchor rod steel and its mass percentage content are C: 0.30~0.52%, Si: 0.51~1.39%, Mn: 1.2~2.60%, Cr+Mo+V: 0.60~0.90%, S≤0.04%, P≤0.03%, the balance is iron and inevitable impurities, the preparation method comprises the following steps: smelting and casting into a billet, cutting the billet into segments, quenching, the quenching temperature should be not lower than 1100 DEG C, not higher than 1400 DEG C, the holding time is 10~25 seconds; then rapid water cooling and removing the oxide layer, the temperature is reduced to below 400 DEG C within 10 seconds; then tempering, the tempering heating temperature is 500~800 DEG C, the anchor rod steel is obtained, the anchor rod impact absorbing power produced by the method is more than 70J, the yield strength is more than 1000MPa, the elongation after fracture is more than 12%, and the maximum force total elongation Ag is more than 5%. The alloy element addition amount of the present application is relatively high, the process is long, the cost is high, and the production efficiency is low. Therefore, in order to reduce the cost, the most commonly used material in the prior art is a seamless steel pipe, which is produced by drawing, but the product is more than 4.0mm, and the cost is high, the yield is low, the impact resistance is poor, and the development demand of highway tunnel cannot be met. SUMMARY

[0005] The technical problem to be solved by the present application is that the small conduit made of the seamless steel pipe drawn in the prior art has a thickness of more than 4mm, and has high cost, low yield, poor impact resistance and cannot meet the development demand of highway tunnel.

[0006] The technical solution adopted by the present application to solve the technical problem is: a high-performance small conduit hot-rolled steel strip for highway tunnel, according to the mass percentage of chemical composition: C 0.18~0.23%, Si 0.18~0.28%, Mn 0.40~0.50%, P≤0.020%, S≤0.010%, V 0.04~0.06%, N 0.01~0.02%, Als 0.010~0.050%, the balance is Fe and inevitable impurities.

[0007] Further, the yield strength is ≥450MPa, the tensile strength is ≥500MPa, the elongation after fracture is ≥30%, and the impact energy under the condition of-20 DEG C is ≥45J.

[0008] Further, the microstructure is acicular ferrite+pearlite, the volume fraction of acicular ferrite is 80%~90%, and the volume fraction of pearlite is 10%~20%.

[0009] A kind of highway tunnel high-performance small catheter hot-rolled steel strip preparation method, it include: hot metal smelting, continuous casting, heating furnace heating, rough rolling, hot coil box coiling, finish rolling, laminar cooling, coiling;And hot metal smelting includes hot metal desulfurization, converter, LF refining.

[0010] Further, hot metal smelting at least meets one of the following: According to the above chemical component smelting continuous casting into slab, and when S≤0.005% when hot metal enters converter; Converter needs to be washed before smelting, and ladle is argon-blowing throughout the process of tapping; LF refining process is argon-blowing throughout, and liquid steel cannot be exposed; Continuous casting process is protected casting throughout, low-alloy protective slag is used, and the thickness of casting blank is 200±10mm.

[0011] Further, the heating temperature of continuous casting blank is 1180℃-1220℃, and the heating time is 130-170min, wherein the soaking time is ≥30min.

[0012] Further, the continuous casting blank is rolled by 5 passes or 7 passes rough rolling, and is descaled throughout the odd pass, to obtain 38±2mm intermediate blank, which is then coiled by hot coil box for heat preservation.

[0013] Further, the thickness of intermediate blank after finish rolling by 7 passes is 3.0mm.

[0014] Further, the rough rolling temperature is 1050±30℃, and the reduction of the last three stands is ≥17%, ≥13% and ≥10% respectively, and the finish rolling temperature is 850℃-890℃.

[0015] Further, the laminar cooling adopts front cooling mode, and the cooling speed is 65±5℃ / s;The coiling temperature is 600±20℃, and the thickness of plate coil product is 3.0mm.

[0016] The beneficial effects of the present application are: in the range of low alloy steel Q355B standard requirements, the present application reduces the C content to improve the toughness of the material, adds a certain amount of vanadium nitride alloy, VC and VN can be formed by vanadium element and C and N in the steel, in the controlled rolling and controlled cooling process, disperses and precipitates on the ferrite matrix, plays the role of fine grain strengthening, can improve the strength and toughness of the material (especially low temperature impact toughness), the high performance small conduit product obtained by the present application has the characteristics of simple process flow, easy to control organization, high strength, good impact resistance, finished product thickness is 3.0mm or less, can realize the light weight of the product, etc. The high performance small conduit hot-rolled strip steel product for highway tunnel prepared by the composition and the preparation method of the present application has yield strength ≥450MPa, tensile strength ≥500MPa, elongation after fracture ≥30%, anchor rod impact absorbed energy under-20℃ condition ≥45J, meets the technical requirements of product use, is suitable for making highway tunnel support and slope guardrail, at the same time can be applied to railway, tunnel, bridge and mine field, has wide market application prospect. It is expected that 600 yuan can be created per ton of steel, and according to the annual output of 5000 tons, it is expected that 3 million yuan can be created. DETAILED DESCRIPTION

[0017] The present application is further illustrated by the following examples.

[0018] The high-performance small-catheter hot-rolled steel strip for highway tunnels according to the present application has the following chemical composition in terms of mass percentage: C 0.18-0.23%, Si 0.18-0.28%, Mn 0.40-0.50%, P≤0.020%, S≤0.010%, V 0.04-0.06%, N 0.01-0.02%, Al 0.010-0.050%, and the balance of Fe and inevitable impurities. Those skilled in the art should understand that carbon is an effective strengthening element in steel, which can dissolve into the matrix to play a role in solid solution strengthening, and can form carbide precipitate particles by combining with titanium to play a role in fine-grain strengthening and precipitation strengthening, thus increasing the carbon content is beneficial to improving the strength. However, too high carbon content will form more coarse and brittle carbide particles in the steel, which is not conducive to plasticity and toughness, and will also form a segregation band in the center of the steel plate, which is not conducive to bending performance, forming performance, etc. Therefore, the value range of C in the present application is set to 0.18%-0.21%. Silicon can dissolve into ferrite and austenite to improve the hardness and strength of the steel, which is beneficial to refining the rust layer structure and reducing the overall corrosion rate of the steel, but too high content will reduce the plasticity and toughness of the steel, making it difficult to remove scale during rolling. Therefore, the value range of Si in the present application is set to 0.18%-0.28%. Manganese has a strong solid solution strengthening effect, can significantly reduce the phase transition temperature of the steel, and refine the microstructure of the steel, which is an important strengthening and toughening element, but too much Mn content can easily cause cracks in the continuous casting process, and may also cause composition segregation in the center of the steel plate. Therefore, the value range of Mn in the present application is set to 0.40%-0.50%. Too high phosphorus content will significantly reduce the plasticity and low-temperature toughness of the steel, therefore the value range of P in the present application is set to ≤0.020%. Sulfur will have an adverse effect on the microstructure and performance of the steel plate, and too high sulfur content will increase the thermal brittleness tendency of the steel, and sulfur will form sulfide inclusions to deteriorate the performance of the steel. Therefore, the value range of S in the present application is set to S≤0.010%. Vanadium can form VC and VN with C and N in the steel, and in the controlled rolling and controlled cooling process, it is dispersedly precipitated in the ferrite matrix to play a role in fine-grain strengthening, which can improve the strength and toughness (especially low-temperature impact toughness) of the material. Therefore, the value range of V in the present application is set to 0.04-0.06%, and the value range of N is set to 0.01-0.02%.

[0019] Preferably, the yield strength is ≥450 MPa, the tensile strength is ≥500 MPa, the elongation after fracture is ≥30%, and the impact energy under the condition of -20℃ is ≥45 J. Those skilled in the art should understand that the hot-rolled strip steel product prepared by controlling the proportion of chemical components and optimizing the preparation method has a yield strength of ≥450 MPa, a tensile strength of ≥500 MPa, an elongation after fracture of ≥30%, and an anchor rod impact absorption energy of ≥45 J under the condition of -20℃, which meets the technical requirements of product use and is suitable for making public tunnel support and slope guardrail.

[0020] Preferably, the microstructure is acicular ferrite + pearlite, the volume fraction of which is 80% to 90% acicular ferrite and 10% to 20% pearlite. Those skilled in the art should understand that in order to refine the grains in the steel strip, the microstructure of the hot-rolled plate coil is preferably acicular ferrite + pearlite, the volume fraction of which is 80% to 90% acicular ferrite and 10% to 20% pearlite.

[0021] A method for preparing a high-performance small-catheter hot-rolled steel strip for highway tunnels, comprising: hot metal smelting, continuous casting, heating furnace heating, rough rolling, hot coil box coiling, finish rolling, laminar cooling, and coiling; and the hot metal smelting comprises hot metal desulfurization, converter, and LF refining.

[0022] Preferably, the hot metal smelting at least meets one of the following: The continuous casting is performed according to the above chemical components, and S≤0.005% when the hot metal enters the converter; The converter needs to be washed before smelting, and the ladle is blown with argon throughout the process; The LF refining process is blown with argon throughout the process, and the steel liquid cannot be exposed; The continuous casting process is fully protected casting, low-alloy protective slag is used, and the thickness of the casting blank is 200±10 mm. Those skilled in the art should understand that the preparation method smelts and casts a slab according to the components, S≤0.005% when the hot metal enters the converter, the converter needs to be washed before smelting, and the ladle is blown with argon throughout the process to ensure low contents of nitrogen, oxygen, and hydrogen in the steel liquid and remove residual non-metallic inclusions in the steel liquid; the LF refining process must be blown with argon throughout the process, and the steel liquid cannot be exposed; the continuous casting process is fully protected casting, low-alloy protective slag is used, and the casting blank cannot be "open poured", so that a continuous casting blank with chemical components meeting the design requirements is obtained, and the thickness of the casting blank is preferably 200 mm.

[0023] Preferably, the heating temperature of the continuous casting blank is 1180°C to 1220°C, the heating time is 130 to 170 min, and the soaking time is ≥30 min.

[0024] Preferably, the continuous casting blank is rolled by 5 passes or 7 passes of rough rolling, the scales are removed throughout the odd passes, a 38±2 mm intermediate blank is obtained, and the intermediate blank is then coiled and kept warm by a hot coil box.

[0025] Preferably, the thickness of the intermediate blank after 7 passes of finish rolling is 3.0 mm.

[0026] Preferably, the finish rolling opening temperature is 1050±30°C, the reduction rates of the last three stands are ≥17%, ≥13%, and ≥10% respectively, and the finish rolling temperature is 850°C to 890°C.

[0027] Preferably, the laminar cooling adopts a front-stage cooling mode, the cooling speed is 65±5°C / s, the coiling temperature is 600±20°C, and the thickness of the plate coil product is 3.0 mm. The obtained finished hot-rolled steel strip can be made into a hollow anchor rod by welding.

[0028] The present method provides three groups of key process parameter embodiments 1, 2 and 3 of the chemical composition of the high-performance small-catheter hot-rolled steel strip for highway tunnels and the preparation method thereof according to the present application and two groups of comparative examples 1 and 2, and the chemical composition thereof is shown in Table 1, and the balance is Fe and unavoidable impurities.

[0029] Table 1 The control parameters involved in the steps of casting blank heating, rough rolling, finish rolling, laminar cooling and coiling, and the indicators such as mechanical properties, process properties and microstructure types are shown in Table 2.

[0030] Table 2 As can be seen from the comparison of comparative examples 1 and 2 and embodiments 1, 2 and 3, embodiments 1, 2 and 3 all add a certain amount of vanadium nitride alloy, and VC and VN can be formed by the vanadium element and C and N in the steel, which is dispersedly precipitated in the ferrite matrix in the controlled rolling and controlled cooling process, plays a role of fine-grain strengthening, and can improve the strength and toughness (especially low-temperature impact toughness) of the material. The V and N contents in comparative examples 1 and 2 are relatively high and relatively low, respectively, which directly affects the bending test and impact energy parameters of the finished product, and causes the technical requirements of the anchor rod for highway tunnels to be unable to be met.

Claims

1. A high performance small duct hot rolled steel strip for highway tunnels, characterized by: Chemical composition: C 0.18-0.23%, Si 0.18-0.28%, Mn 0.40-0.50%, P≤0.020%, S≤0.010%, V 0.04-0.06%, N 0.01-0.02%, Al 0.010-0.050%, the rest being Fe and inevitable impurities.

2. A high performance small duct hot rolled steel strip for highway tunnels according to claim 1, characterized by: Yield strength≥450MPa, tensile strength≥500MPa, elongation after fracture≥30%, impact energy under-20℃≥45J.

3. A high performance small duct hot rolled steel strip for highway tunnels according to claim 1, characterized by: Microstructure: acicular ferrite + pearlite, volume fraction: acicular ferrite 80-90%, pearlite 10-20%.

4. A method for producing a high-performance small duct hot-rolled steel strip for highway tunnels, characterized by The method comprises the following steps: hot metal smelting, continuous casting, heating furnace heating, rough rolling, hot coil box coiling, finish rolling, laminar cooling, coiling; and the hot metal smelting comprises hot metal desulfurization, converter, LF refining.

5. A method of manufacturing a high-performance small duct hot-rolled steel strip for road tunnels according to claim 4, characterized in that: The hot metal smelting at least meets the following one: The hot metal is smelted into a slab according to the above chemical composition, and S≤0.005% when the hot metal enters the converter; The converter needs to be washed before smelting, and the ladle is blown with argon throughout the process; The LF refining process is blown with argon throughout the process, and the molten steel cannot be exposed; The continuous casting process is fully protected casting, low alloy protective slag is used, and the thickness of the casting blank is 200±10mm.

6. A method of manufacturing a high performance small duct hot rolled steel strip for highway tunnels according to claim 4, characterized in that: The heating temperature of the continuous casting blank is 1180-1220℃, the heating time is 130-170min, and the soaking time is≥30min.

7. A method of manufacturing a high performance small duct hot rolled steel strip for highway tunnels according to claim 4, characterized in that: The continuous casting blank is rolled by 5 passes or 7 passes of rough rolling, the whole process is descaled, a 38±2mm intermediate blank is obtained, and then it is coiled and kept warm by a hot coil box.

8. A method of manufacturing a high-performance small duct hot-rolled steel strip for road tunnels according to claim 7, characterized in that: The thickness of the intermediate blank after 7 passes of finish rolling is 3.0mm.

9. A method of manufacturing a high performance small duct hot rolled steel strip for highway tunnels according to claim 4, characterized in that: The opening rolling temperature of finish rolling is 1050±30℃, the reduction rates of the last three racks are≥17%, ≥13% and ≥10% respectively, and the final rolling temperature is 850-890℃.

10. A method of manufacturing a high performance small duct hot rolled steel strip for highway tunnels as claimed in claim 4, wherein: The laminar cooling adopts a front cooling mode, the cooling speed is 65±5℃ / s, the coiling temperature is 600±20℃, and the thickness of the finished plate coil is 3.0mm.

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