Smelting method for weathering bridge steel

Abstract

The present invention discloses weather-resistant bridge steel and its smelting method, and relates to the technical field of steel production. Its chemical composition and mass% are as follows: C: 0.030%-0.080%, Si: 0.10%-0.40%, Mn: 1.50%-1.80%, P≦0.015%, S≦0.0010%, Nb: 0.030%-0.050%, V: 0.005%- 0.050%, Ti:0.006%~0.020%, Cr:0.20%~0.80%, Ni:0.05%~0.20%, Mo≦0.05%, Cu:0.05%~0.20%, B≦0.0005%, Al:0.005%~0.015%, Mg:0.0008%~0.0015%, N≦0.0050%, the rest are Fe and unavoidable impurities. Smelted by upper and lower combined blowing rotary furnace, processed by LF+RH refining, magnesium treatment effectively reduces inclusions, refines grain size, increases the formation rate of acicular ferrite, effectively improves welding performance, and improves the corrosion resistance of steel plate.

Description

[Technical field]

[0001] The present invention relates to the technical field of steel production, in particular to weathering bridge steel and a method for smelting the same. [Background technology]

[0002] With the development of macro-economy, China has vigorously promoted the construction of transportation infrastructure such as steel bridges, and the production volume of bridge structures has increased rapidly. The Beijing-Shanghai Expressway, the strait crossing and the river crossing bridges adopt steel structures, while the subway, the light rail project, the urban overpass, the viaduct, the environmental protection project and the urban public facilities are related to personal safety, so the requirements for the quality of the bridge structure steel products are becoming more and more stringent, and the molten steel purity and weldability of the bridge steel are the key to whether the products can meet the requirements of important national projects. Summary of the Invention [Means for solving the problem]

[0003] The present invention provides a weathering bridge steel for solving the above technical problems and overcoming the shortcomings of the prior art, and its chemical composition and mass% are as follows: C: 0.030%-0.080%, Si: 0.10%-0.40%, Mn: 1.50%-1.80%, P≦0.015%, S≦0.0010%, Nb: 0.030%-0.050%, V: 0.005 %~0.050%, Ti: 0.006%~0.020%, Cr: 0.20%~0.80%, Ni: 0.05%~0.20%, Mo≦0.05%, Cu: 0.05%~0.20%, B≦0.0005%, Al: 0.005%~0.015%, Mg: 0.0008%~0.0015%, N≦0.0050%, and the rest is Fe and unavoidable impurities.

[0004] Further technical solutions of the present invention are as follows:

[0005] The chemical composition and mass percentage of the weathering bridge steel are as follows: C: 0.030% to 0.050%, Si: 0.10% to 0.20%, Mn: 1.50% to 1.70%, P≦0.013%, S≦0.0010%, Nb: 0.030% to 0.040%, V: 0.005% to 0.030%, Ti: 0.00 6%~0.018%, Cr: 0.20%~0.50%, Ni: 0.05%~0.15%, Mo≦0.05%, Cu: 0.05%~0.15%, B≦0.0005%, Al: 0.005%~0.013%, Mg: 0.0008%~0.0013%, N≦0.0050%, and the remainder is Fe and unavoidable impurities.

[0006] The chemical composition and mass percentage of the weathering bridge steel are as follows: C: 0.050% to 0.070%, Si: 0.20% to 0.30%, Mn: 1.60% to 1.70%, P≦0.014%, S≦0.0010%, Nb: 0.035% to 0.045%, V: 0.020% to 0.040%, Ti: 0.00 9%~0.020%, Cr: 0.40%~0.60%, Ni: 0.10%~0.15%, Mo≦0.05%, Cu: 0.10%~0.15%, B≦0.0005%, Al: 0.008%~0.015%, Mg: 0.0010%~0.0015%, N≦0.0050%, and the remainder is Fe and unavoidable impurities.

[0007] The chemical composition and mass percentage of the weathering bridge steel are as follows: C: 0.060% to 0.080%, Si: 0.30% to 0.40%, Mn: 1.60% to 1.80%, P≦0.012%, S≦0.0010%, Nb: 0.040% to 0.050%, V: 0.030% to 0.050%, Ti: 0.01 0%~0.020%, Cr:0.60%~0.80%, Ni:0.15%~0.20%, Mo≦0.05%, Cu:0.15%~0.20%, B≦0.0005%, Al:0.010%~0.015%, Mg:0.0010%~0.0015%, N≦0.0050%, and the remainder is Fe and unavoidable impurities.

[0008] Another object of the present invention is to provide a method for smelting weathering bridge steel, S1. The molten iron is pretreated for desulfurization using the KR method, cinder scraped, and then blown in a rotary furnace. S2. Blowing by upper and lower combined blowing method, adding nickel, copper and molybdenum alloy together with scrap steel into the rotary furnace, discharging the steel from the rotary furnace and deoxidizing it by strong deoxidation mode, refining it in the rotary passage, so that the aluminum content satisfies 0.030%-0.050% and the sulfur content ≦0.010%; S3. After the molten steel reaches the LF furnace, adjust the steel ladle to blow in argon gas from the bottom, and set the argon gas flow rate to 300NL / min~380NL / min; turn on the power to raise the temperature; use lime and aluminum wire to slug; after white slag, sample and analyze; add lime and aluminum wire according to the sample to desulfurize; after desulfurization, perform alloying treatment; after alloying, perform molten steel oxygen fixing operation, and make the oxygen content ≦5ppm; after oxygen fixing, use magnesium aluminum composite alloy to perform precipitation and deoxidization; lift the molten steel to RH for vacuum treatment; S4. After the molten steel reaches RH, it is vacuum treated, and the vacuum holding time is 8min to 12min. After the vacuum treatment, it is lifted to continuous casting for casting; S5. The continuous casting adopts a purging upper nozzle to ensure smooth casting, adopts electromagnetic stirring and dynamic soft reduction, and cools the billet stack for 48 hours, after which the surface quality is inspected and treated to meet requirements.

[0009] In the smelting method for weathering bridge steel, in step S3, the magnesium content of the magnesium-aluminum alloy is 20% to 30%. Effect of the Invention

[0010] The present invention has the following beneficial effects:

[0011] (1) The present invention uses an upper and lower combined blowing rotary furnace for smelting and then LF+RH refining. The magnesium treatment effectively reduces the size of inclusions, solving the cleanliness problem of molten bridge steel. The magnesium element has high vapor pressure and low melting and boiling points at the molten steel smelting temperature, and its strong chemical activity is utilized to generate fine and diffused magnesium-based inclusions after magnesium treatment. The grain size of the product reaches 11 or above, and acicular ferrite is formed as the main structure, which can improve the toughness index of the steel plate and improve the welding performance of the product.

[0012] (2) In the present invention, the magnesium-treated molten steel is adopted, and the total oxygen content in the steel is effectively reduced.

[0013] (3) In the present invention, by using molten steel treated with magnesium, it is possible to remove long magnesium sulfide inclusions in steel and generate spherical magnesium sulfide inclusions, thereby improving the quality of molten steel.

[0014] (4) In the present invention, the molten steel treated with magnesium is used to generate finely diffused nano-level MgO·Al2O3 spinel, and the fine inclusions act as the nucleus for microstructural transformation during rolling, forming a large number of acicular ferrite, which can effectively improve the toughness and welding performance of the product. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] [Example 1] The weathering bridge steel provided in this embodiment has the following chemical composition and mass percentage: C: 0.033%, Si: 0.33%, Mn: 1.73%, P: 0.011%, S: 0.0010%, Nb: 0.0350%, V: 0.035%, Ti: 0.013%, Cr: 0.77%, Ni: 0.15%, Mo: 0.03%, Cu: 0.15%, B: 0.0003%, Al: 0.013%, Mg: 0.0011%, N: 0.0036%, and the remainder is Fe and unavoidable impurities.

[0016] The smelting method is S1. The molten iron is pretreated for desulfurization using the KR method, cinder scraped, and then blown in a rotary furnace. S2. Blowing by top and bottom combined blowing method, adding nickel, copper and molybdenum alloy together with scrap steel into the rotary furnace, discharging the steel from the rotary furnace and deoxidizing it by strong deoxidation mode, refining it in the rotary passage, so that the aluminum content meets 0.042% and the sulfur content meets ≦ 0.006%; S3. After the molten steel reaches the LF furnace, adjust the steel ladle to blow in argon gas from the bottom, set the argon gas flow rate to 360NL / min, turn on the power to raise the temperature, use lime and aluminum wire to slug, after white slug, sample and analyze, add lime and aluminum wire according to the sample to desulfurize, after desulfurization, perform alloying treatment, after alloying, perform molten steel oxygen fixing operation, set the oxygen content to 3ppm, after oxygen fixing, use magnesium aluminum composite alloy to perform precipitation and deoxidization, the magnesium content of magnesium aluminum alloy is 26%, and lift the molten steel to RH for vacuum treatment; S4. After the molten steel reaches RH, it is vacuum treated, and the vacuum holding time is 11 minutes. After the vacuum treatment, it is lifted to continuous casting for casting; S5. The continuous casting adopts a purging upper nozzle to ensure smooth casting, adopts electromagnetic stirring and dynamic soft reduction, and cools the billet stack for 48 hours, after which the surface quality is inspected and treated to meet requirements.

[0017] [Example 2] The weathering bridge steel provided in this embodiment differs from that in Example 1, and its chemical composition and mass % are as follows. C: 0.058%, Si: 0.16%, Mn: 1.66%, P: 0.012%, S: 0.0008%, Nb: 0.033%, V: 0.03%, Ti: 0.012%, Cr: 0.29%, Ni: 0.03%, Mo: 0.03%, Cu: 0.11%, B: 0.0002%, Al: 0.010%, Mg: 0.0013%, N: 0.0041%, and the remainder is Fe and unavoidable impurities.

[0018] The state of inclusions in the steel sheets obtained in Examples 1 and 2 is shown in the table below.

[0019] [Table 1]

[0020] In summary, the present invention is a new manufacturing method that uses a unique smelting production process based on product design, changes the traditional inclusion morphology, and focuses on magnesium deoxidation. It transforms the large and harmful inclusions to obtain fine diffused inclusions of 10 μm or less. Test results show that such fine diffused inclusions can be good nucleation points in the process of microstructural transformation, and the product is easy to form acicular ferrite, so that the grain size of the product can reach 11 grade or above, which enhances the toughness of the product, greatly improves the welding performance of the product, and ensures the use performance of bridge steel.

[0021] In addition to the above embodiments, the present invention may be implemented in other forms. Any technical solutions formed by equivalent replacement or equivalent modification shall fall within the scope of protection of the present invention.

[0022] (Additional Note) (Appendix 1) The chemical composition and mass% are as follows: C: 0.030%~0.080%, Si: 0.10%~0.40%, Mn: 1.50%~1.80%, P≦0.015%, S≦0.0010%, Nb: 0.030%~0.050%, V: 0.005%~0.050%, Ti: 0.006%~0.020%, Cr: 0 A weathering bridge steel characterized by the following composition: Cu: 0.05%~0.20%, Mo≦0.05%, Cu: 0.05%~0.20%, B≦0.0005%, Al: 0.005%~0.015%, Mg: 0.0008%~0.0015%, N≦0.0050%, and the remainder being Fe and unavoidable impurities.

[0023] (Appendix 2) The chemical composition and mass% are as follows: C: 0.030%~0.050%, Si: 0.10%~0.20%, Mn: 1.50%~1.70%, P≦0.013%, S≦0.0010%, Nb: 0.030%~0.040%, V: 0.005%~0.030%, Ti: 0.006%~0.018%, Cr: 0.20 2. Weathering bridge steel according to claim 1, characterized in that: Mo: 0.05% to 0.15%, Mo≦0.05%, Cu: 0.05% to 0.15%, B≦0.0005%, Al: 0.005% to 0.013%, Mg: 0.0008% to 0.0013%, N≦0.0050%, and the remainder being Fe and unavoidable impurities.

[0024] (Appendix 3) The chemical composition and mass% are as follows: C: 0.050%~0.070%, Si: 0.20%~0.30%, Mn: 1.60%~1.70%, P≦0.014%, S≦0.0010%, Nb: 0.035%~0.045%, V: 0.020%~0.040%, Ti: 0.009%~0.020%, Cr: 0.40 2. Weathering bridge steel according to claim 1, characterized in that: Mo: 0.10% to 0.15%, Mo≦0.05%, Cu: 0.10% to 0.15%, B≦0.0005%, Al: 0.008% to 0.015%, Mg: 0.0010% to 0.0015%, N≦0.0050%, and the remainder being Fe and unavoidable impurities.

[0025] (Appendix 4) The chemical composition and mass% are as follows: C: 0.060%~0.080%, Si: 0.30%~0.40%, Mn: 1.60%~1.80%, P≦0.012%, S≦0.0010%, Nb: 0.040%~0.050%, V: 0.030%~0.050%, Ti: 0.010%~0.020%, Cr: 0.60 2. Weathering bridge steel according to claim 1, characterized in that: Mo: 0.15% to 0.20%, Mo≦0.05%, Cu: 0.15% to 0.20%, B≦0.0005%, Al: 0.010% to 0.015%, Mg: 0.0010% to 0.0015%, N≦0.0050%, and the remainder being Fe and unavoidable impurities.

[0026] (Appendix 5) A method for smelting weathering bridge steel according to any one of appendixes 1 to 4, S1. The molten iron is pretreated for desulfurization using the KR method, cinder scraped, and then blown in a rotary furnace. S2. Blowing by upper and lower combined blowing method, adding nickel, copper and molybdenum alloy together with scrap steel into the rotary furnace, discharging the steel from the rotary furnace and deoxidizing it by strong deoxidation mode, refining it in the rotary passage, so that the aluminum content satisfies 0.030%-0.050% and the sulfur content ≦0.010%; S3. After the molten steel reaches the LF furnace, adjust the steel ladle to blow in argon gas from the bottom, and set the argon gas flow rate to 300NL / min~380NL / min; turn on the power to raise the temperature; use lime and aluminum wire to slug; after white slag, sample and analyze; add lime and aluminum wire according to the sample to desulfurize; after desulfurization, perform alloying treatment; after alloying, perform molten steel oxygen fixing operation, and make the oxygen content ≦5ppm; after oxygen fixing, use magnesium aluminum composite alloy to perform precipitation and deoxidization; lift the molten steel to RH for vacuum treatment; S4. After the molten steel reaches RH, it is vacuum treated, and the vacuum holding time is 8min to 12min. After the vacuum treatment, it is lifted to continuous casting for casting; S5. A method for producing weathering bridge steel, comprising the steps of: adopting a purging upper nozzle in continuous casting to ensure smooth casting; adopting electromagnetic stirring and dynamic soft reduction; and cooling the billet stack for 48 hours, and then inspecting and treating the surface quality to meet requirements.

[0027] (Appendix 6) 6. The method for smelting a weathering steel for bridge construction according to claim 5, wherein in step S3, the magnesium content of the magnesium-aluminum alloy is 20% to 30%.

Claims

1. C: 0.030 mass% to 0.080 mass%, Si: 0.10 mass% to 0.40 mass%, Mn: 1.50 mass% to 1.80 mass%, P≦0.015 mass%, S≦0.0010 mass% %, Nb: 0.030 mass% to 0.050 mass%, V: 0.005 mass% to 0.050 mass%, Ti: 0.006 mass% to 0.020 mass%, Cr: 0.20 mass% to 0.80 mass% %, Ni: 0.05 mass% to 0.20 mass%, Mo≦0.05 mass%, Cu: 0.05 mass% to 0.20 mass%, B≦0.0005 mass%, Al: 0.005 mass% to 0.015 mass%, Mg: 0.0008 mass% to 0.0015 mass%, N≦0.0050 mass%, and the remainder being Fe and unavoidable impurities, S1. The molten iron is pretreated by the KR method for desulfurization, slag is removed, and then the iron is blown in a converter; S2. Blowing by top and bottom combined blowing method, adding nickel, copper, and molybdenum alloy together with scrap steel to the converter, discharging the steel from the converter and deoxidizing it by strong deoxidation mode, and refining it in the converter so that the aluminum content satisfies 0.030% to 0.050% and the sulfur content ≦ 0.010%; S3. After the molten steel reaches the LF furnace, adjust the steel ladle to blow in argon gas from the bottom, set the argon gas flow rate to 300NL / min-380NL / min, turn on the power to raise the temperature, use lime and aluminum wire to generate slag, whiten the slag, sample and analyze, add lime and aluminum wire according to the sample to desulfurize, after desulfurization, perform alloying treatment, after alloying, perform molten steel oxygen fixing operation, oxygen content ≦ 5ppm, after oxygen fixing, use magnesium aluminum composite alloy to precipitate and deoxidize, lift the molten steel to RH and perform vacuum treatment; S4. After the molten steel reaches the RH, it is vacuum treated, the vacuum holding time is 8 min to 12 min, and after the vacuum treatment, it is lifted to a continuous casting for casting; S5. The method for producing weathering bridge steel includes the steps of: using a nozzle with ventilation in the continuous casting to ensure smooth casting; using electromagnetic stirring and dynamic soft reduction; and cooling the billet stack for 48 hours, and then inspecting the surface quality and treating it to meet the requirements.

2. 2. The method for smelting weathering bridge steel according to claim 1, wherein in step S3, the magnesium content of the magnesium-aluminum composite alloy is 20% to 30%.