A low-cost production process for microalloyed construction steel

Abstract

The invention provides a low-cost production process for micro-alloyed steel for construction, which specifically includes the following steps: step 1: electric furnace steel tapping silicon, manganese alloying; step 2: LF furnace slag making, heating; step 3: vanadium-containing pig iron preheating and adding to ladle; step 4: adding vanadium-containing pig iron for vanadium alloying; step 5, LF refining furnace treatment, to obtain target vanadium-containing molten steel, and subsequent continuous casting; wherein the vanadium-containing pig iron includes by weight percentage: metallic iron 85-92%, V is 0.5-1.5, Si is 0.4-1.5%, Mn is 0.5-3%, carbon content is 3.5-4.5%, P content is 0.05-0.15%, S content is 0.01-0.03%, and the particle size of the vanadium-containing pig iron is 30-80mm. The technical problem that the temperature and molten steel quality are difficult to control when the molten steel adopts vanadium-containing pig iron raw material for micro-alloying is solved by optimizing the process and other measures, and the process cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of iron and steel metallurgy, and in particular to a low-cost production process of micro-alloyed steel for construction. Background Art

[0002] Rebar steel is the main product of steel mills, and its production cost directly affects the profitability of enterprises. Steel enterprises should further tap the potential for cost reduction, which is of great importance to steel enterprises themselves, downstream industries and even the entire economic growth. Reducing production costs does not mean reducing product quality. On the contrary, by improving production processes and improving efficiency, steel enterprises can improve product quality and win the trust of more customers. To this end, the project innovatively designs micro-alloying production processes to reduce the production costs of construction steel.

[0003] Alloy steel has become an indispensable steel frame material in my country's modern infrastructure. Alloy steel is mainly made by adding one or more alloys to ordinary carbon steel as raw material, and through different processing techniques, it is obtained as a special alloy steel with different physical and chemical properties such as high strength, high toughness, wear resistance, corrosion resistance, low temperature resistance, high temperature resistance, etc.

[0004] As one of the main alloying elements, vanadium has the effects of grain refinement and dispersion hardening in high-strength low-alloy steel, high-speed steel, etc. Even adding a small amount of vanadium can effectively improve the wear resistance, tensile strength and high-temperature strength of carbon steel.

[0005] The traditional process of adding vanadium to molten steel uses vanadium-nitrogen alloy or 50 / 80 ferrovanadium. The smelting of this type of alloy first uses vanadium slag to smelt ferrovanadium as an alloying raw material. The production process not only consumes a lot of energy and chemical raw materials, but also has high production costs and a long production cycle. Summary of the invention

[0006] The purpose of the present invention is to provide a low-cost production process for micro-alloyed construction steel, which solves the technical problem of difficult control of temperature and molten steel quality when molten steel is micro-alloyed with vanadium-containing pig iron raw materials by optimizing the process and other measures, thereby reducing the process cost.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0008] A low-cost production process for microalloyed construction steel comprises the following steps:

[0009] Step 1: Electric furnace steel is alloyed with silicon and manganese;

[0010] Step 2: LF furnace slag making and heating;

[0011] Step 3: Preheating the vanadium-containing pig iron and adding it into the ladle;

[0012] Step 4: adding vanadium-containing pig iron for vanadium alloying;

[0013] Step 5: LF refining furnace treatment to obtain the target vanadium-containing molten steel, followed by continuous casting;

[0014] The vanadium-containing pig iron comprises, by weight percentage: 85-92% metallic iron, 0.5-1.5% V, 0.4-1.5% Si, 0.5-3% Mn, 3.5-4.5% carbon, 0.05-0.15% P, 0.01-0.03% S, and the particle size of the vanadium-containing pig iron is 30-80 mm.

[0015] Furthermore, in step 1, after the molten steel is tapped from the electric furnace, silicon and manganese are added to the ladle for alloying treatment, and the silicon and manganese alloy elements are 90%, and the content meets the required range of steel grade composition control.

[0016] Among them, in step 2, auxiliary materials are added after the ladle LF refining furnace enters the station, and then the LF furnace starts to heat up and slag, the temperature of the molten steel is raised to above 1620°C and the composition of the molten steel is analyzed.

[0017] Among them, the auxiliary materials are lime and fluorite, with 5-10kg of lime and 0-2kg of fluorite added to every ton of steel.

[0018] Furthermore, the vanadium-containing pig iron is heated and prepared in an alloy baking silo, and the baking temperature is 700-900°C.

[0019] Preferably, after the LF furnace slag is oxidized and the temperature is raised, the baked vanadium-containing pig iron is added into the ladle, and the added amount is controlled at 10-30 kg / ton steel according to the requirements of the steel grade; and according to the content of alloy elements, the carbon, silicon and manganese contents are fine-tuned to meet the requirements of the steel grade, and the temperature of the molten steel is further adjusted to between 50-70°C above the liquidus temperature of the corresponding steel grade.

[0020] Furthermore, in step 5, argon is blown from the bottom during the entire LF refining process. The gas is nitrogen or argon, and the bottom blowing gas flow rate is 50-150m 3 / hour, the air blowing pipeline is connected to the air-permeable bricks at the bottom of the electric furnace through a pipe, and the number of bottom-blowing air-permeable bricks is 1-3 pieces.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] This patent proposes a low-cost production method for micro-alloyed construction steel. The molten steel from the electric furnace is micro-alloyed with vanadium using vanadium-containing pig iron in the LF refining furnace, which solves the high cost problem of using vanadium-nitrogen alloy or 50 vanadium iron to increase vanadium in reinforced steel. For large-scale applications, relevant process plans are proposed, and the technical problems of alloying temperature control and difficult control of molten steel quality are solved by optimizing the process and other measures. DETAILED DESCRIPTION

[0023] Embodiment 1

[0024] This embodiment discloses a low-cost production process for microalloyed construction steel, which specifically includes the following steps:

[0025] Step 1: Electric furnace steel is alloyed with silicon and manganese;

[0026] Step 2: LF furnace slag making and heating;

[0027] Step 3: Preheating the vanadium-containing pig iron and adding it into the ladle;

[0028] Step 4: adding vanadium-containing pig iron for vanadium alloying;

[0029] Step 5: LF refining furnace treatment to obtain the target vanadium-containing molten steel, followed by continuous casting;

[0030] The vanadium-containing pig iron comprises, by weight percentage: 85-92% metallic iron, 0.5-1.5% V, 0.4-1.5% Si, 0.5-3% Mn, 3.5-4.5% carbon, 0.05-0.15% P, 0.01-0.03% S, and the particle size of the vanadium-containing pig iron is 30-80 mm.

[0031] Furthermore, in step 1, after the molten steel is tapped from the electric furnace, silicon and manganese are added to the ladle for alloying treatment, and the silicon and manganese alloy elements are 90%, and the content meets the required range of steel grade composition control.

[0032] Preferably, in step 2, auxiliary materials are added to the ladle LF refining furnace after entering the station, and then the LF furnace starts to heat up and slag, the temperature of the molten steel is raised to above 1620° C. and the composition of the molten steel is analyzed.

[0033] Furthermore, the auxiliary materials are lime and fluorite, and 5-10kg of lime and 0-2kg of fluorite are added to each ton of steel. For steel grades with high sulfur content in molten steel, the amount of auxiliary materials added will be relatively large; for steel grades with low sulfur content in molten steel, the amount of auxiliary materials added will be relatively small.

[0034] Among them, the vanadium-containing pig iron is heated and prepared in the alloy baking silo, and the baking temperature is 700-900°C. To better utilize the heat energy, part of the scrap steel is preheated while the ladle is baked, and the time is generally 20-40 minutes.

[0035] Furthermore, after the LF furnace slag-forming and heating are completed, the baked vanadium-containing pig iron is added into the ladle, and the added amount is controlled at 10-30 kg / ton steel according to the requirements of the steel grade; and according to the content of alloy elements, the carbon, silicon and manganese contents are fine-tuned to meet the requirements of the steel grade, and the temperature of the molten steel is further adjusted to between 50-70°C above the liquidus temperature of the corresponding steel grade.

[0036] In step 5, argon is blown throughout the LF refining process. The gas is nitrogen or argon, and the bottom blowing gas flow rate is 50-150m 3 / hour, the air blowing pipeline is connected to the air-permeable bricks at the bottom of the electric furnace through a pipe, and the number of bottom-blowing air-permeable bricks is 1-3 pieces.

[0037] In order to facilitate those skilled in the art to further understand the present invention, the present invention is further described below in conjunction with specific implementation cases.

[0038] Case 1

[0039] After the steel is blown in an electric furnace to the final composition, the steel output is 140 tons. 500kg of ferrosilicon (FeSi75), 2600kg of silicon manganese (Mn68Si 18), and 350kg of high carbon ferromanganese (FeMn78c8.0) are added to the ladle. The ladle is hoisted to the LF furnace, and bottom blowing of argon is adopted throughout the process, with a bottom blowing pressure of 0.35MPa. 800kg of lime and 120kg of fluorite are added, and the temperature is raised to 1610℃, and slag removal is completed.

[0040] 20 tons of vanadium-containing pig iron containing 1% vanadium is added to the ladle. The composition of vanadium-containing pig iron is 91% of metallic iron, V is 1.0, Si is 1.0%, Mn is 1.5%, carbon content is 4.0%, P content is 0.1%, and S content is 0.02%. The particle size of vanadium-containing pig iron is 60mm, and the temperature of vanadium-containing pig iron is 750℃. The molten steel is further heated to 1560℃, and the sampling composition results are: C: 0.23%, Si: 0.40%, Mn: 1.36%, P: 0.03%, S: 0.018%, V: 0.020%. LF refining treatment is completed, and the subsequent process continuous casting is prepared.

[0041] Case 2

[0042] After the steel is blown in an electric furnace to the final composition, the steel output is 150 tons. 550kg of ferrosilicon (FeSi75), 2630kg of silicon manganese (Mn68Si 18), and 380kg of high carbon ferromanganese (FeMn78c8.0) are added to the ladle. The ladle is hoisted to the LF furnace, and bottom blowing of argon is adopted throughout the process. The bottom blowing pressure is 0.35MPa. 750kg of lime and 100kg of fluorite are added. The temperature is raised to 1600℃, and slag is finished. 15 tons of vanadium-containing pig iron containing 1.5% vanadium are added to the ladle. The composition of vanadium-containing pig iron is 89% metallic iron, 1.5% V, 1.5% Si, 2.5% Mn, 4.5% carbon, 0.11% P, and 0.025% S. The particle size of vanadium-containing pig iron is 50mm, the temperature of vanadium-containing pig iron is 800℃, the molten steel is further heated to 1570℃, and the sampling composition results are: C: 0.23%, Si: 0.44%, Mn: 1.38%, P: 0.025%, S: 0.015%, V: 0.022%. LF refining treatment is completed and the subsequent continuous casting process is prepared.

[0043] Case 3

[0044] After the steel is blown in an electric furnace to the final composition, the steel output is 145 tons. 530kg of ferrosilicon (FeSi75), 2620kg of silicon manganese (Mn68Si 18), and 400kg of high carbon ferromanganese (FeMn78c8.0) are added to the ladle. The ladle is hoisted to the LF furnace, and bottom blowing of argon is used throughout the process. The bottom blowing pressure is 0.35MPa. 700kg of lime and 50kg of fluorite are added. The temperature is raised to 1590℃, and slag is completed. 18 tons of vanadium-containing pig iron containing 0.7% vanadium are added to the ladle. The composition of vanadium-containing pig iron is 891% metallic iron, 0.7% V, 1.3% Si, 2.6% Mn, 4.0% carbon, 0.06% P, and 0.025% S. The particle size of vanadium-containing pig iron is 70mm, the temperature of vanadium-containing pig iron is 780℃, the molten steel is further heated to 1560℃, and the sampling composition results are: C: 0.22%, Si: 0.41%, Mn: 1.36%, P: 0.027%, S: 0.018%, V: 0.021%. LF refining treatment is completed and the subsequent continuous casting process is prepared.

[0045] The present invention discloses a low-cost production process for microalloyed construction steel, which has the advantage of significantly reducing costs. The specific comparison is as follows:

[0046] Using this method, taking an electric furnace plant with an annual output of 3 million tons as an example, the price of the conventionally used 70 vanadium-nitrogen alloy is 140,000 yuan / ton, and the price of vanadium-containing pig iron is 3,800 yuan / ton.

[0047] (1) Calculation of vanadium addition cost for 70% vanadium nitrogen alloy;

[0048] The amount of metallic vanadium required for a ton of steel = 1000 × 0.02% = 0.2 kg;

[0049] The amount of vanadium-nitrogen alloy required per ton of steel = 0.2÷70% = 0.286kg;

[0050] The cost of adding vanadium with 70 vanadium-nitrogen alloy = 0.286÷1000×140000 = 40.04 yuan / ton of steel;

[0051] (2) Calculation of vanadium-added cost for 1% vanadium-containing pig iron;

[0052] The amount of metallic vanadium required for a ton of steel = 1000 × 0.02% = 0.2 kg;

[0053] The amount of vanadium-containing pig iron required for one ton of steel = 0.2÷1% = 20kg;

[0054] The cost of adding vanadium with 1% vanadium-containing pig iron = 20÷1000×3800-20÷1000×2.5%×6000-20÷1000×90%×2650=25.3 yuan / ton of steel;

[0055] Profit per ton of steel = 40.04-25.3 = 14.74 yuan;

[0056] Based on the above, the use of the results of the present invention is expected to create benefits of more than 14 yuan per ton of steel.

[0057] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A low-cost production process for microalloyed construction steel, characterized in that: The specific steps include: Step 1: Silicon and manganese alloying of steel from electric furnace. After the molten steel is tapped from the electric furnace, silicon and manganese are added to the ladle for alloying treatment. The silicon and manganese alloy elements are 90%; Step 2: LF furnace slag making and heating; After the ladle LF refining furnace enters the station, auxiliary materials are added, and then the LF furnace starts to heat up and slag making, the molten steel temperature is raised to above 1620℃ and the molten steel composition is analyzed; the auxiliary materials are lime and fluorite, and 5-10kg of lime and 0-2kg of fluorite are added to each ton of steel; Step 3: Preheating the vanadium-containing pig iron and adding it into the ladle; the vanadium-containing pig iron is heated and prepared in the alloy baking silo, and the baking temperature is 700-900℃; Step 4: adding vanadium-containing pig iron for vanadium alloying; Step 5: LF refining furnace treatment to obtain the target vanadium-containing molten steel, followed by continuous casting; LF refining process is bottom-blown with argon throughout the process, the gas is nitrogen or argon, the bottom-blowing gas flow rate is 50-150m³ / hour, the blowing pipeline is connected to the air-permeable bricks at the bottom of the electric furnace through a pipeline, and the number of bottom-blown air-permeable bricks is 1-3 pieces; The vanadium-containing pig iron comprises, by weight percentage: 85-92% metallic iron, 0.5-1.5% V, 0.4-1.5% Si, 0.5-3% Mn, 3.5-4.5% carbon, 0.05-0.15% P, 0.01-0.03% S, and the particle size of the vanadium-containing pig iron is 30-80 mm.

2. A low-cost production process for microalloyed construction steel according to claim 1, characterized in that: After the LF furnace slag is oxidized and the temperature is raised, the baked vanadium-containing pig iron is added into the ladle. The amount added is controlled at 10-30kg / ton steel according to the requirements of the steel grade. According to the content of alloy elements, the carbon, silicon and manganese contents are fine-tuned to meet the requirements of the steel grade. The temperature of the molten steel is further adjusted to between 50-70℃ above the liquidus temperature of the corresponding steel grade.