High-strength weather-resistant hot continuous rolling checkered steel strip and production method thereof

Abstract

The invention provides a high-strength weather-resistant hot continuous rolling checkered steel strip and a production method thereof, and the steel strip with the thickness of 2.0-5.0 mm comprises the following chemical components in percentage by weight: 0.13-0.19% of C, 0.10-0.30% of Si, 0.40-0.50% of Mn, 0.030-0.050% of P, less than or equal to 0.025% of S, 0.40-0.50% of Cr, 0.25-0.40% of Cu, 0.03-0.15% of Ni, 0.01-0.03% of Als and the balance of iron and inevitable impurities. By adjusting the contents of the elements C and P, high strength and weather resistance are guaranteed, the content of the element Mn is finally controlled at a low level, the alloy cost is greatly reduced, and it is guaranteed that the strength of the steel strip can reach the level of Q355.

Description

Technical Field

[0001] The invention relates to the technical field of iron and steel metallurgy, and in particular to a high-strength weather-resistant hot-rolled patterned steel strip and a production method thereof. Background Art

[0002] Hot-rolled patterned steel has the advantages of being beautiful, non-slip, and saving steel. It is widely used in steel bridges, piers, steel structure factories, building decoration, machinery, ships, and car manufacturing.

[0003] At present, high-strength weather-resistant hot-rolled patterned steel products are popular in China, because the high-strength characteristics can make the product thinner and lighter, and the weather-resistant characteristics can make the product free of painting and extend the service life. The high-strength patterned plates produced in the prior art are usually low-carbon designs, lacking weather-resistant elements Cu, Ni, and Cr, making the products not weather-resistant, and the weather-resistant steel currently used usually contains more expensive alloy elements such as Cu, Ni, Cr, Nb, and Mo, thereby increasing the production and use costs. Summary of the invention

[0004] The problem to be solved by the present invention is how to produce a high-strength weather-resistant patterned steel strip at a low cost.

[0005] In order to solve the above problems, the present invention provides a high-strength weather-resistant hot-rolled patterned steel strip, wherein for a steel strip with a thickness of 2.0-5.0 mm, the weight percentage of the chemical composition thereof is: C: 0.13-0.19%, Si: 0.10-0.30%, Mn: 0.40-0.50%, P: 0.030-0.050%, S: ≤0.025%, Cr: 0.40-0.50%, Cu: 0.25-0.40%, Ni: 0.03-0.15%, Als: 0.01-0.03%, and the rest is iron and unavoidable impurities;

[0006] For the steel strip with a thickness of 5.01-15.0mm, the weight percentage of its chemical composition is: C: 0.13-0.19%, Si: 0.10-0.30%, Mn: 0.50-0.65, P: 0.045-0.065%, S: ≤0.025%, Cr: 0.40-0.50%, Cu: 0.25-0.40%, Ni: 0.03-0.15%, Als: 0.01-0.03%, and the rest is iron and unavoidable impurities.

[0007] The advantages of the high-strength weather-resistant hot-rolled patterned steel strip of the present invention over the prior art are:

[0008] The present invention not only takes into account the strength performance and weather resistance of the steel strip through the design of the P content, but also avoids the high P content, the P element is easy to be segregated at the grain boundary and the surface of the steel plate, resulting in grain boundary embrittlement, affecting the processing performance of the steel plate, and the P segregation on the surface of the steel plate is easy to increase the iron scale on the surface of the steel plate, which also affects the surface quality and appearance of the steel plate. The present invention also adopts a medium carbon content, and through the adjustment of the C and P element contents, while ensuring high strength and weather resistance, the content of the Mn element is finally controlled to a low level (below 0.65%), which is equivalent to the Mn content level of Q235 steel, far lower than the 0.9% Mn content in Q355 steel, greatly reducing the alloy cost, and also ensuring that the hot-rolled patterned steel strip has a high strength, reaching the strength level of Q355 steel. In addition, compared with the prior art that the full-thickness steel strip has only one chemical composition, the present invention provides two groups of chemical compositions of the full-thickness steel strip, the difference in strength between thick and thin specifications is small, and the alloy cost is reduced.

[0009] The present invention also provides a method for producing a high-strength weather-resistant hot-rolled patterned steel strip, comprising:

[0010] Desulfurized molten iron, ordinary scrap steel and weathering scrap steel are smelted in a converter, alloys are added during the steelmaking process, the molten steel is refined in an argon station and then continuously cast to obtain slabs, the slabs are heated and hot rolled, and then laminar cooled and coiled to obtain high-strength weathering hot rolled patterned steel strips.

[0011] Preferably, double slag blocking is used during steel tapping, and alloy is added when 1 / 2-2 / 3 of the steel is tapped to ensure that the alloy is completely melted; the argon station fine-tunes the composition and temperature of the molten steel, with the total Ar blowing time being ≥15min, the soft blowing time being ≥5min, and the molten steel calming time being 10min-20min.

[0012] Preferably, during the slab heating treatment, for a steel strip with a thickness of 2.0-4.0 mm, the furnace temperature is 1220±30°C; for a steel strip with a thickness of 4.01-15.0 mm, the furnace temperature is 1210±30°C.

[0013] Preferably, the hot rolling adopts high temperature rapid rolling, and the final rolling temperature is 890±20°C.

[0014] Preferably, for a steel strip with a thickness of 2.0-4.0 mm, the reduction amount of the finishing roller is 0.8-1.2 mm, and for a steel strip with a thickness of 4.01-15.0 mm, the reduction amount of the finishing roller is 1.2-2.5 mm.

[0015] Preferably, the laminar cooling adopts a constant speed cooling mode, wherein, for the steel strip with a thickness of 2.0-4.0 mm, the laminar cooling rate is 35°C / s, and the coiling temperature is 610±20°C; for the steel strip with a thickness of 4.01-15.0 mm, the laminar cooling rate is 32°C / s, and the coiling temperature is 600±20°C.

[0016] Preferably, the method for producing the high-strength weather-resistant hot-rolled patterned steel strip further comprises rolling the upper and lower surface patterns according to demand.

[0017] The advantages of the production method of the high-strength weather-resistant hot-rolled patterned steel strip of the present invention over the prior art are:

[0018] The present invention adds alloy when 1 / 2-2 / 3 of the steel is tapped from the converter to ensure that the alloy is completely melted, and no LF furnace refining is used. At the same time, hot rolling adopts high-temperature rapid rolling and F7 (final roller of finishing rolling) high pressure to ensure good pattern shape and height, and adopts a lower coiling temperature to ensure that the phase transformation (austenite → ferrite + pearlite) is basically completed at the end of coiling. Laminar cooling adopts a constant cooling mode to improve the bending performance of the steel strip. The remaining advantages are the same as those of high-strength weather-resistant hot-rolled patterned steel strip compared to the prior art, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a bending test diagram of the pattern surface of the high-strength weather-resistant hot-rolled patterned steel strip in the embodiment of the present invention;

[0020] Figure 2 This is the metallographic structure diagram of the high-strength weather-resistant hot-rolled patterned steel strip produced in Example 1 of the present invention. DETAILED DESCRIPTION

[0021] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0022] The high-strength weather-resistant hot-rolled patterned steel strip of the embodiment of the present invention adjusts the chemical composition according to the different thickness of the steel strip. Specifically, for a steel strip with a thickness of 2.0-5.0 mm, the weight percentage of the chemical composition is: C: 0.13-0.19%, Si: 0.10-0.30%, Mn: 0.40-0.50, P: 0.030-0.050%, S: ≤0.025%, Cr: 0.40-0.50%, Cu: 0.25-0.40%, Ni: 0.03-0.15%, Als: 0.01-0.03%, and the rest is iron and unavoidable impurities;

[0023] For the steel strip with a thickness of 5.01-15.0mm, the weight percentage of its chemical composition is: C: 0.13-0.19%, Si: 0.10-0.30%, Mn: 0.50-0.65, P: 0.045-0.065%, S: ≤0.025%, Cr: 0.40-0.50%, Cu: 0.25-0.40%, Ni: 0.03-0.15%, Als: 0.01-0.03%, and the rest is iron and unavoidable impurities.

[0024] The hot-rolled patterned steel strip of this embodiment has a carbon content of 0.13-0.19%. Since carbon is the most effective and economical element for improving steel strength, increasing the carbon content can improve the strength of steel. However, a higher carbon content will also affect the bending performance and aggravate the segregation of phosphorus. Therefore, under the premise of ensuring strength, the usual practice in this field is to reduce the carbon content as much as possible and control it within a smaller fluctuation range, that is, the so-called low-carbon design. Therefore, under normal circumstances, the C content will be controlled at a level below 0.10%, usually in the range of 0.04-0.07%. This embodiment adopts a medium carbon design, which increases the carbon content and is conducive to improving the strength of the steel strip. At the same time, the phosphorus content is controlled within the range of 0.030-0.050% and 0.045-0.065%. Phosphorus is an effective element for improving the corrosion resistance of the steel strip and can ensure the weather resistance of the steel strip. The design of the P content in this embodiment not only takes into account the strength performance and weather resistance of P, but also avoids the high P content. The P element is easily concentrated at the grain boundary and the surface of the steel plate, resulting in grain boundary embrittlement, affecting the processing performance of the steel plate, and the P concentration on the surface of the steel plate is easy to increase the iron oxide scale on the surface of the steel plate, which also affects the surface quality and appearance of the steel plate.

[0025] This embodiment adjusts the content of C and P elements, while ensuring high strength and weather resistance, and finally controls the content of Mn element to below 0.65%. Compared with the 0.9% Mn content in high-strength steel Q355, it is at a lower level, which greatly reduces the alloy cost. Since the Mn element has a certain influence on the toughness of steel, the reduction of the content will have a certain influence on the strength, but through the adjustment of the above chemical composition, the hot-rolled patterned steel strip of this embodiment finally has a higher strength, and the strength can reach the level of Q355. Generally speaking, the Mn content of Q355 is above 0.9%, and the alloy cost is usually high. In this embodiment, the Mn content is reduced to below 0.65% through the above ratio, and the Mn content is equivalent to the level of Q235, but this embodiment can achieve the strength of Q355 level.

[0026] The embodiment of the present invention also provides a method for producing the above-mentioned high-strength weather-resistant hot-rolled patterned steel strip, and the process flow is: molten iron desulfurization → converter smelting → argon station refining → continuous casting → slab heating → hot rolling → laminar cooling → coiling.

[0027] After desulfurization, the molten iron enters the converter. When the molten steel smelted in the converter is poured into the ladle, double slag is used, and alloy is added when the steel is 1 / 2-2 / 3 tapped to ensure that the alloy can be completely melted. Ordinary scrap steel refers to the steel waste (such as trimming, cutting, etc.) that does not become a product in the production process of a steel plant, as well as the steel materials in the equipment and components that are scrapped after use. In this embodiment, the desulfurized molten iron is smelted in a converter together with ordinary scrap steel and weathering scrap steel, so that the ordinary scrap steel is fully utilized, and the content of P, Cu, Ni, Cr, etc. in the molten steel is increased by adding weathering scrap steel (such as SPA-H, etc.), which can reduce the use of alloys. According to the market situation, copper-nickel alloy or copper plate + nickel plate is selected to adjust the copper-nickel content in the molten steel to reduce the alloy cost. Among them, SPA-H is a kind of weathering steel. The steel grade adopts Japanese steel grade SPA-H, and its chemical composition, mechanical properties, thickness, and width deviation requirements are implemented in accordance with Japanese standard JISG3125-2004 "High Weathering Rolled Steel".

[0028] After converter smelting, the molten steel is subjected to argon station refining to fine-tune the composition and temperature of the molten steel. During the argon station refining process, the total argon blowing time is ≥15min, the soft blowing time is ≥5min, and the molten steel calming time is 10-20min to ensure the purity of the molten steel.

[0029] After refining in the argon station, the molten steel is cast by the continuous casting machine to obtain slabs, which are then sent to the heating furnace for heating and then hot rolled after being taken out of the furnace. For steel strips with a thickness of 2.0-4.0 mm, the furnace temperature is 1220±30℃; for steel strips with a thickness of 4.01-15.0 mm, the furnace temperature is 1210±30℃.

[0030] Hot rolling adopts high temperature fast rolling process, the final rolling temperature is 890±20℃, and the F7 (finishing roller) is pressed down to ensure good pattern shape and height, and the upper and lower surface patterns are rolled according to the needs. Among them, for steel strips with a thickness of 2.0-4.0mm, the finishing roller pressure is 0.8-1.2mm, and for steel strips with a thickness of 4.01-15.0mm, the finishing roller pressure is 1.2-2.5mm.

[0031] In some of the implementation methods, in view of the pattern interference in measuring the thickness of the online thickness gauge, the hot rolling secondary model uses the rolling force and reduction rate simulation calculation to set the roll gap, and the first level uses absolute AGC and relative AGC control to ensure that the thickness accuracy of the patterned plate substrate is higher than the national standard PT.B.

[0032] The laminar cooling adopts a constant cooling mode to improve the bending performance of the steel strip. In some embodiments, for a steel strip with a thickness of 2.0-4.0 mm, the laminar cooling rate is 35°C / s, and for a steel strip with a thickness of 4.01-15.0 mm, the laminar cooling rate is 32°C / s.

[0033] The coiling temperature ensures that the phase transformation (austenite → ferrite + pearlite) is basically completed at the end of coiling, preventing the thin-gauge steel coil from flattening. Specifically, for steel strips with a thickness of 2.0-4.0mm, the coiling temperature is 610±20℃; for steel strips with a thickness of 4.01-15.0mm, the coiling temperature is 600±20℃.

[0034] The hot-rolled patterned steel strip produced above was subjected to tensile and pattern surface bending tests, and the results are shown in Table 1. Figure 1 These are the samples for the pattern surface bending test. The figure shows the bending effects of two pattern steel samples with different thicknesses.

[0035] Table 1:

[0036]

[0037] Compared with the prior art, which has a lower C content and stricter control of P and S contents, which increases the steelmaking cost, the hot-rolled patterned steel strip of this embodiment has a higher C content and lower alloy element cost; the P content control is relaxed, which reduces the steelmaking cost and increases the strength and weather resistance of the steel strip; the S content control is relaxed, which reduces the steelmaking cost. In addition, compared with the prior art, which has only one chemical composition for the full-thickness steel strip, this embodiment provides two groups of chemical compositions for the full-thickness steel strip, with a small difference in strength between thick and thin specifications, and a lower cost of strength elements for thin specifications.

[0038] Example 1

[0039] In this embodiment, in order to produce a steel strip with a specification of 2.5*1250mm (thickness is 2.5mm, width is 1250mm), the process steps are as follows:

[0040] After desulfurization, the molten iron enters the converter, double-stop slag is used for steelmaking, and alloy is added when 1 / 2-2 / 3 of the steel is tapped. After refining in the argon station, continuous casting is carried out. The continuously cast slab enters the heating furnace for heating. The furnace outlet temperature is 1210℃. After tapping, hot rolling is carried out. The final rolling temperature is 892℃, and the F7 reduction is 0.9mm. After rolling, laminar cooling is carried out with a cooling rate of 34.9℃ / s. The slab is coiled into a steel coil by a coiler with a coiling temperature of 607℃.

[0041] The metallographic structure diagram of the steel strip produced in this embodiment is as follows: Figure 2 As shown, the steel strip has uniform structure and grain size of 11 levels.

[0042] The above steel strip was subjected to tensile and bending tests, and the results are shown in Table 2:

[0043] Table 2:

[0044]

[0045] Example 2

[0046] In this embodiment, in order to produce a steel strip with a specification of 12.0*1500mm (thickness is 12.0mm, width is 1500mm), the process steps are as follows:

[0047] After desulfurization, the molten iron enters the converter, double-stop slag is used for steelmaking, and alloy is added when 1 / 2-2 / 3 of the steel is tapped. After refining in the argon station, continuous casting is carried out. The continuously cast slab enters the heating furnace for heating, and the furnace outlet temperature is 1198℃. After tapping, hot rolling is carried out, and the final rolling temperature is 885℃. The F7 reduction is 2.0mm. After rolling, laminar cooling is carried out, and the cooling rate is 32.2℃ / s. The slab is coiled into a steel coil by a coiler, and the coiling temperature is 592℃.

[0048] The above steel strips were subjected to tensile and bending tests, and the results are shown in Table 3:

[0049] Table 3:

[0050]

[0051] Although the disclosure is disclosed as above, the protection scope of the disclosure is not limited thereto. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the disclosure, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A high-strength weather-resistant hot-rolled patterned steel strip, characterized in that: For a steel strip with a thickness of 2.0-5.0 mm, the weight percentage of the chemical composition is: C: 0.13-0.19%, Si: 0.10-0.30%, Mn: 0.40-0.50, P: 0.030-0.050%, S: ≤0.025%, Cr: 0.40-0.50%, Cu: 0.25-0.40%, Ni: 0.03-0.15%, Als: 0.01-0.03%, and the rest is iron and unavoidable impurities; For the steel strip with a thickness of 5.01-15.0mm, the weight percentage of its chemical composition is: C: 0.13-0.19%, Si: 0.10-0.30%, Mn: 0.50-0.65, P: 0.045-0.065%, S: ≤0.025%, Cr: 0.40-0.50%, Cu: 0.25-0.40%, Ni: 0.03-0.15%, Als: 0.01-0.03%, and the rest is iron and unavoidable impurities.

2. A method for producing high-strength weather-resistant hot-rolled patterned steel strip, characterized in that: Used to produce the high-strength weather-resistant hot-rolled patterned steel strip as claimed in claim 1, comprising: Desulfurized molten iron, ordinary scrap steel and weathering scrap steel are smelted in a converter, alloys are added during the steelmaking process, the molten steel is refined in an argon station and then continuously cast to obtain slabs, the slabs are heated and hot rolled, and then laminar cooled and coiled to obtain high-strength weathering hot rolled patterned steel strips.

3. The method for producing high-strength weather-resistant hot-rolled patterned steel strip according to claim 2, characterized in that: Double slag blocking is used when tapping steel, and alloy is added when 1 / 2-2 / 3 of the steel is tapped to ensure that the alloy is completely melted; the argon station fine-tunes the composition and temperature of the molten steel, the total Ar blowing time is ≥15min, the soft blowing time is ≥5min, and the molten steel calming time is 10-20min.

4. The method for producing high-strength weather-resistant hot-rolled patterned steel strip according to claim 2, characterized in that: During the slab heating treatment, for the steel strip with a thickness of 2.0-4.0 mm, the furnace temperature is 1220±30°C; for the steel strip with a thickness of 4.01-15.0 mm, the furnace temperature is 1210±30°C.

5. The method for producing high-strength weather-resistant hot-rolled patterned steel strip according to claim 2, characterized in that: The hot rolling adopts high temperature rapid rolling, and the final rolling temperature is 890±20°C.

6. The method for producing high-strength weather-resistant hot-rolled patterned steel strip according to claim 2, characterized in that: For steel strips with a thickness of 2.0-4.0 mm, the reduction of the final roller of the finishing mill is 0.8-1.2 mm. For steel strips with a thickness of 4.01-15.0 mm, the reduction of the final roller of the finishing mill is 1.2-2.5 mm.

7. The method for producing high-strength weather-resistant hot-rolled patterned steel strip according to claim 2, characterized in that: The laminar cooling adopts a constant speed cooling mode, wherein, for the steel strip with a thickness of 2.0-4.0 mm, the laminar cooling speed is 35°C / s, and the coiling temperature is 610±20°C; for the steel strip with a thickness of 4.01-15.0 mm, the laminar cooling speed is 32°C / s, and the coiling temperature is 600±20°C.

8. The method for producing high-strength weather-resistant hot-rolled patterned steel strip according to claim 2, characterized in that: Also includes: The upper and lower surface patterns are rolled according to requirements.

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