CN113430449B - Smelting and continuous casting production process of sulfur-containing free-cutting steel ASTM1141 - Google Patents
Smelting and continuous casting production process of sulfur-containing free-cutting steel ASTM1141 Download PDFInfo
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- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
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- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
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- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
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- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
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Abstract
The invention relates to a smelting and continuous casting production process of sulfur-containing free-cutting steel ASTM1141 capable of improving the yield of molten steel to a forge piece, which is characterized in that the smelting process control sulfur mode and the process route are optimized on the basis of the original die casting production process, and the process flow of electric furnace batching → electric furnace primary smelting → refining fine adjustment (containing adjusting sulfur) → VD degassing → continuous casting steel → hot delivery forging is adopted, so that the problem of long refining time of the steel is solved, the smelting efficiency is greatly improved, and meanwhile, a multi-furnace continuous casting round billet is adopted to replace die casting steel ingot forging, and the yield of the molten steel to the forge billet is improved to more than 85%.
Description
Technical Field
The invention belongs to the technical field of smelting of sulfur-containing free-cutting steel, and particularly relates to a smelting and continuous casting production process of sulfur-containing free-cutting steel ASTM1141, which can improve the yield of steel liquid to forgings.
Background
The ASTM1141 steel is a high-sulfur and medium-carbon alloy structural steel with good cutting performance, and is widely applied to the aspects of screw rods, screw rotors, polished rods, racks, spline shafts and the like due to the excellent cutting performance. At present, the steel grade is smelted mainly by adopting the process flow of electric arc furnace batching → electric arc furnace primary smelting → refining furnace fine adjustment (no sulfur) → VD degassing → returning to the refining furnace for sulfur adjustment → die casting → hot transfer forging, and the problems of long time for returning to the refining furnace for sulfur adjustment after VD, low yield of molten steel to a forge piece which is less than 75 percent, low qualified rate of low times and the like exist, meanwhile, cr of the steel grade is less than or equal to 0.20 percent, ni is less than or equal to 0.20 percent, mo is less than or equal to 0.08 percent and is strict, and Cr, ni and Mo are not easy to control because no molten iron exists for electric arc furnace smelting. Therefore, the problems that the tapping component of the electric arc furnace is controlled, the material is returned to the refining furnace after VD for rapid sulfur increase, and the continuous casting blank of the material is developed to improve the molten steel until the forging yield reaches more than 80 percent are urgently needed to be solved at present.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a production process for smelting and continuously casting the sulfur-containing free-cutting steel ASTM1141, which has high efficiency, low power, qualified inclusion and high utilization rate by optimizing the prior smelting and casting technology of the ASTM1141 steel.
The purpose of the invention is realized as follows:
a smelting and continuous casting production process of sulfur-containing free-cutting steel ASTM1141 adopts the process flow of electric arc furnace batching → electric arc furnace primary smelting → refining furnace fine adjustment and sulfur adjustment during refining furnace fine adjustment → VD degassing → continuous casting steel → hot delivery forging, and comprises the following specific steps:
step 1), electric arc furnace batching: the electric arc furnace comprises the following ingredients in percentage by weight: 10-40% of second-grade and above carbon steel scrap, 40-70% of carbon steel scrap and 10-20% of pig iron, wherein the carbon steel scrap, the carbon steel scrap and the pig iron are all low-chromium, low-molybdenum and low-nickel materials, namely the weight percentages are as follows: chromium is less than or equal to 0.30 percent, molybdenum is less than or equal to 0.07 percent and nickel is less than or equal to 0.19 percent, no bonding steel or other waste steel or steel scraps with unknown components can be added into the ingredients of the electric arc furnace, and the materials are loaded into the electric arc furnace through a material basket;
step 2), melting the electric arc furnace ingredients in the step 1) by electric arc furnace power transmission, adding a carburant according to 5.0-15.0 kg/t in the power transmission process, adding lime according to 10.0-20.0 kg/t, carrying out early-stage slagging, starting oxygen blowing for decarbonization, dechromization and slag flowing for dephosphorization after the electric arc furnace ingredients are melted down, wherein the sampling components meet the requirement C according to the weight percentage: 0.05 to 0.27 percent of Cr is less than or equal to 0.12 percent, P is less than or equal to 0.008 percent, si is less than or equal to 0.15 percent, mn is less than or equal to 1.00 percent, ni is less than or equal to 0.20 percent, mo is less than or equal to 0.07 percent, V is less than or equal to 0.05 percent, cu is less than or equal to 0.20 percent, nb is less than or equal to 0.02 percent, as is less than or equal to 0.020 percent, sn is less than or equal to 0.018 percent, pb is less than or equal to 0.020 percent, sb is less than or equal to 0.020 percent, and Bi is less than or equal to 0.012 percent; when the temperature is controlled at 1630-1670 ℃, discharging the molten steel into a prepared clean steel ladle, and strictly prohibiting slag discharging in the tapping process; in the process of tapping 1/4-3/4, adding 2.0-4.0 kg/t of aluminum blocks, 2.0-5.0 kg/t of lime, 1.0-2.0 kg/t of ferrosilicon and 5.0-10.0 kg/t of ferromanganese into a ladle;
step 3), hanging and transferring the primary molten steel smelted in the step 2) to a refining furnace, connecting argon, feeding power after refining, adding 2.0-5.0 kg/t of lime to ensure that the slag covers the liquid level of the steel, simultaneously adding 1.0-3.0 kg/t of calcium carbide in at least two batches, adding 1.0-2.5 kg/t of ferrosilicon powder and 1.0-2.0 kg/t of coke powder in at least three batches for slag burning, sampling after the slag is white, and controlling C according to the sampling result in percentage by weight: 0.37 to 0.45%, si:0.15 to 0.35%, mn: 1.35-1.65%, P is less than or equal to 0.015% to adjust the alloy components, and then the target S is controlled according to the weight percentage: 0.12 percent of sulfur wire is fed into the molten steel, and the sampling analysis control component range is as follows: c:0.37 to 0.45%, si:0.15 to 0.35%, mn: 1.35-1.65%, P is less than or equal to 0.015%, S:0.10 to 0.12 percent, less than or equal to 0.20 percent of Cr, less than or equal to 0.20 percent of Ni, less than or equal to 0.08 percent of Mo, less than or equal to 0.20 percent of Cu, less than or equal to 0.05 percent of V, al:0.030 to 0.050 percent of Nb, less than or equal to 0.02 percent of Nb, controlling the temperature of the molten steel to 1650 to 1680 ℃, and carrying out degassing by ladle-to-VD;
step 4), transferring the molten steel refined by the refining furnace in the step 3) to a VD station, switching on argon, controlling the flow of the argon to be 20-100 NL/min, placing the ladle into the VD tank, opening a tank cover vehicle to move above the VD tank, opening a vacuum pump to degas after the cover falls, keeping the vacuum degree at 0.7mbar for more than or equal to 20min, fixing hydrogen on line after breaking the air, controlling H to be less than or equal to 1.2ppm, sampling and analyzing components, controlling S to be 0.10-0.12% according to the weight percentage of an incoming sample, feeding a sulfur line, feeding a calcium line, 0-0.5 m/t, weakly stirring for more than or equal to 12min, and switching to continuous casting steel at the temperature of 1550-1570 ℃;
and 5) hoisting and transferring the molten steel ladle in the step 4) to a ladle rotary table after the temperature of the continuous casting platform is measured, rotating to a rotary continuous casting station, pouring the ladle molten steel through a long nozzle, pouring the ladle molten steel into a tundish through the long nozzle, protecting and casting by adopting a long nozzle argon protection mode, a tundish argon filling mode, a covering agent covering mode and an integral submerged nozzle mode, reducing secondary oxidation of the molten steel, casting into a continuous casting blank, and marking hot-transfer forging after the blank is discharged.
In the step 5), the ladle molten steel is injected into a tundish through a long water gap, argon is adopted between the long water gap and a lower water gap for protection, the tundish uses an argon blowing stopper rod, the tundish adopts 0.5-2.5 kg/t of alkaline covering agent and 0.2-0.8 kg/t of carbonized rice husk for covering, and is used for reducing the heat radiation loss of the molten steel and protecting the molten steel from secondary oxidation, and the superheat degree of the molten steel in the tundish is controlled between 15-40 ℃ in the continuous casting process; pouring molten steel in the tundish into the crystallizer through an integral submerged nozzle, wherein the insertion depth of the integral submerged nozzle is 100-150 mm, medium-carbon continuous casting mold powder is adopted, the molten steel in the crystallizer is electromagnetically stirred through an external crystallizer electromagnetic stirrer, the stirring parameters of the crystallizer are 345-355A, the frequency is 1.3-1.7 HZ, and the molten steel in the crystallizer is electromagnetically stirred through cold water cooling to form isometric crystals; the blank drawing machine draws blanks at a blank drawing speed of 0.18-0.22 m/min, and the blank drawing machine adopts three-roller clamping to eliminate clamping stress; the traveling direction of the casting blank is vertical to the steel pouring platform, and bending and straightening are not needed in the traveling process; the second cooling area adopts three-stage spraying to cool the round billet, and the specific water amount is controlled to be 0.11-0.16L/kg; electromagnetic stirring the molten steel by an external cast electromagnetic stirrer at the upper part of the solidification tail end of the liquid core at the lower part of the secondary cooling chamber to reduce segregation at the 1/2 radius of the round billet; cutting the casting blank into a fixed-length casting blank in the vertical direction by a flame cutting machine with the synchronous blank drawing speed, tilting the fixed-length casting blank onto a horizontal roller way by a tilting roller way, and lifting the fixed-length casting blank onto a knockout roller way by a steel hooking machine for knockout; cleaning the end face after knockout, marking, and hot-conveying forging.
In the step 2), the requirement that Cr is less than or equal to 0.20 percent is met by controlling the Cr discharged from the electric furnace to be less than or equal to 0.12 percent and selecting and using a clean ladle.
In the step 3) and the step 4), harmful substances such as oxygen and impurities in the steel are reduced through slag burning and deoxidation reduction at the early stage of refining, and the target S is controlled by controlling the amount of slag and the weight percentage after reduction: 0.12 percent of sulfur wire is fed into the molten steel, and the sulfur wire meets the following requirements: and (3) degassing by rotating VD at the ratio of 0.10-0.12%, wherein the degassing is performed after VD according to the weight percentage of S: controlling the content of S in the finished product to be 0.10-0.12%.
The invention has the following positive effects:
(1) The creative design optimization of the process flow of electric furnace batching → electric arc furnace primary smelting → refining furnace refining → VD degassing → returning to the refining furnace to adjust sulfur content → die casting steel casting is as follows: the process flow of electric arc furnace batching → electric arc furnace primary smelting → refining furnace fine adjustment of components (including sulfur adjustment) → VD vacuum degassing, fine adjustment of sulfur → continuous casting steel casting → hot transfer forging makes multi-furnace continuous production more than 4 furnaces possible;
(2) Controlling the amount of refining slag, feeding a sulfur line after white and full deoxidation of the refining slag, adjusting sulfur to enter the line while ensuring good deoxidation effect, and adjusting the refining slag to ensure the sulfur content control stability in the VD process;
(3) Fine-adjusting sulfur according to the sulfur content after VD to ensure timely steel feeding, and ensuring the connection stability between continuous casting furnaces, wherein the S component is qualified after continuous casting;
(4) The yield of molten steel is improved from 75% to more than 85% through continuous casting production, and inclusions are controlled stably;
(5) The continuous casting production reduces the operations of die casting swing die, building a base plate, demoulding and the like and die casting tool investment, and greatly reduces the labor intensity of staff and the tool cost.
Detailed Description
The invention discloses a smelting and continuous casting production process of sulfur-containing free-cutting steel, wherein the sulfur-containing free-cutting steel is ASTM1141, and the smelting process flow is electric arc furnace batching → electric arc furnace primary smelting → refining furnace fine adjustment of components (including sulfur adjustment) → VD degassing, fine adjustment of sulfur → continuous casting steel casting → hot transfer forging. Meanwhile, in order to ensure the requirements of inclusion, performance, low power and continuous production of continuous casting, the smelting and continuous casting process comprises the following steps:
step 1), electric arc furnace batching: the electric arc furnace comprises the following ingredients in percentage by weight: 10-40% of second-grade and above carbon steel scrap, 40-70% of carbon steel scrap and 10-20% of pig iron, wherein the carbon steel scrap, the carbon steel scrap and the pig iron are all low-chromium, low-molybdenum and low-nickel materials, namely the weight percentages are as follows: chromium is less than or equal to 0.30 percent, molybdenum is less than or equal to 0.07 percent and nickel is less than or equal to 0.19 percent, alloy structural steel and other scrap steel or steel scraps with unknown components cannot be added in the ingredients of the electric arc furnace, and the materials are loaded into the electric arc furnace through a material basket;
step 2), melting the electric arc furnace ingredients in the step 1) by electric arc furnace power transmission, adding a carburant according to 5.0-15.0 kg/t in the power transmission process, wherein the carbon content of the carburant is more than or equal to 80%, adding lime according to 10.0-20.0 kg/t, carrying out early-stage slagging, starting oxygen blowing for decarbonization, dechroming and slag flowing for dephosphorization after the electric arc furnace ingredients are melted down, wherein the sampling components meet the requirement C according to the weight percentage: 0.05 to 0.27 percent of Cr, less than or equal to 0.12 percent of Cr, less than or equal to 0.008 percent of P, less than or equal to 0.15 percent of Si, less than or equal to 1.00 percent of Mn, less than or equal to 0.20 percent of Ni, less than or equal to 0.07 percent of Mo, less than or equal to 0.05 percent of V, less than or equal to 0.20 percent of Cu, less than or equal to 0.02 percent of Nb, less than or equal to 0.020 percent of As, less than or equal to 0.018 percent of Sn, less than or equal to 0.020 percent of Pb, less than or equal to 0.020 percent of Sb, and less than or equal to 0.012 percent of Bi; when the temperature is controlled at 1630-1670 ℃, discharging the molten steel into a prepared clean steel ladle, and strictly forbidding slag discharging in the tapping process; in the process of tapping 1/4-3/4, adding 2.0-4.0 kg/t of aluminum blocks, 2.0-5.0 kg/t of lime, 1.0-2.0 kg/t of ferrosilicon and 5.0-10.0 kg/t of ferromanganese into a ladle;
step 3), hoisting the primary molten steel smelted in the step 2) to a refining furnace, switching on argon, controlling the flow of the argon according to 20-100 NL/min, surging the slag surface within the range of 300-500 mm during stirring, properly not exposing the molten steel, feeding power after refining, adding 2.0-5.0 kg/t of lime to ensure that the slag covers the liquid level of the molten steel, simultaneously adding 1.0-3.0 kg/t of calcium carbide in at least two batches, adding 1.0-2.5 kg/t of ferrosilicon powder and 1.0-2.0 kg/t of coke powder in at least three batches for slag burning, sampling after white slag, and controlling C according to the sampling result in percentage by weight: 0.37 to 0.45%, si:0.15 to 0.35%, mn: 1.35-1.65%, P is less than or equal to 0.015% to adjust the alloy components, and then the target S is controlled according to the weight percentage: 0.12 percent of sulfur wires are fed into the molten steel, the sampling analysis control component range is as follows: c:0.37 to 0.45%, si:0.15 to 0.35%, mn: 1.35-1.65%, P is less than or equal to 0.015%, S:0.10 to 0.12 percent, less than or equal to 0.20 percent of Cr, less than or equal to 0.20 percent of Ni, less than or equal to 0.08 percent of Mo, less than or equal to 0.20 percent of Cu, less than or equal to 0.05 percent of V, al:0.030 to 0.050 percent of Nb, less than or equal to 0.02 percent of Nb, controlling the temperature of the molten steel to 1650 to 1680 ℃, and carrying out degassing by ladle-to-VD;
step 4), transferring the molten steel refined by the refining furnace in the step 3) to a VD station, switching on argon, controlling the flow of the argon to be 20-100 NL/min, placing the ladle into the VD tank, opening a tank cover vehicle to move above the VD tank, opening a vacuum pump to degas after the cover falls, keeping the vacuum degree at 0.7mbar for more than or equal to 20min, fixing hydrogen on line after breaking the air, controlling H to be less than or equal to 1.2ppm, sampling and analyzing components, controlling S to be 0.10-0.12% according to the weight percentage of an incoming sample, feeding a sulfur line, feeding a calcium line, 0-0.5 m/t, weakly stirring for more than or equal to 12min, and switching to continuous casting steel at the temperature of 1550-1570 ℃;
step 5) hoisting and transferring the molten steel ladle obtained in the step 4) to a continuous casting platform, measuring the temperature, then feeding the molten steel to a ladle revolving platform, rotating to a continuous casting station, sleeving a long water gap to cast the ladle molten steel, injecting the ladle molten steel into a tundish through the long water gap, protecting the upper water gap and a ladle lower water gap by argon gas, using an argon blowing stopper rod for the tundish, using 0.5-2.5 kg/t of alkaline covering agent and 0.2-0.8 kg/t of carbonized rice husk for reducing the heat radiation loss of the molten steel and protecting the molten steel from secondary oxidation, and controlling the superheat degree of the molten steel in the tundish at 15-40 ℃ in the continuous casting process; molten steel in the tundish is injected into the crystallizer through an integral submerged nozzle, the insertion depth of the integral submerged nozzle is 100-150 mm, medium carbon continuous casting mold powder is adopted, the using amount of the medium carbon continuous casting mold powder is 0.5-1.0 kg/t, the molten steel in the crystallizer is electromagnetically stirred through an external crystallizer electromagnetic stirrer, the stirring parameter current is 345-355A, the frequency is 1.3-1.7 HZ, the casting flow electromagnetic stirring parameters are 27-33A and 7.8-8.2 HZ, and the molten steel in the crystallizer is electromagnetically stirred through cold water cooling to form isometric crystals; the blank drawing machine draws blanks at a blank drawing speed of 0.18-0.22 m/min, and the blank drawing machine adopts three-roller clamping to eliminate clamping stress; the traveling direction of the casting blank is vertical to the steel pouring platform, and bending and straightening are not needed in the traveling process; the second cooling area adopts three-stage spraying to cool the round billet, and the specific water amount is controlled to be 0.11-0.16L/kg; electromagnetic stirring is carried out on the molten steel through an external cast electromagnetic stirrer on the upper part of the solidification tail end of the liquid phase cavity at the lower part of the secondary cooling chamber, and segregation at the 1/2 radius part of the round billet is reduced; cutting the casting blank into a fixed-length casting blank in the vertical direction by a flame cutting machine with the synchronous blank drawing speed, tilting the fixed-length casting blank onto a horizontal roller way by a tilting roller way, and lifting the fixed-length casting blank onto a knockout roller way by a steel hooking machine for knockout; cleaning the end face after blank ejection, marking, and forging by hot delivery forging.
The chemical compositions of the examples are shown in Table 1, and the macroscopic conditions are shown in Table 2.
TABLE 1 examples chemical composition after oven (%)
| Examples | C | Si | Mn | P | S | Cr | Ni | Mo | V | Cu | Al |
| 1 | 0.4 | 0.25 | 1.55 | 0.010 | 0.1 | 0.15 | 0.09 | 0.05 | 0.005 | 0.07 | 0.02 |
| 2 | 0.4 | 0.23 | 1.56 | 0.009 | 0.1 | 0.14 | 0.10 | 0.05 | 0.005 | 0.07 | 0.013 |
| 3 | 0.41 | 0.27 | 1.58 | 0.013 | 0.11 | 0.16 | 0.16 | 0.06 | 0.005 | 0.06 | 0.008 |
| 4 | 0.40 | 0.24 | 1.58 | 0.008 | 0.11 | 0.17 | 0.13 | 0.05 | 0.005 | 0.06 | 0.01 |
Table 2 example low power test (%)
Claims (3)
1. A smelting and continuous casting production process of sulfur-containing free-cutting steel ASTM1141 is characterized in that: the method adopts the process flows of electric arc furnace batching → electric arc furnace primary smelting → refining furnace fine adjustment and sulfur adjustment during refining furnace fine adjustment → VD degassing → continuous casting steel casting → hot transfer forging, and comprises the following specific steps:
step 1), electric arc furnace batching: the electric arc furnace comprises the following ingredients in percentage by weight: 10-40% of second-grade and above carbon steel scrap, 40-70% of carbon steel scrap and 10-20% of pig iron, wherein the carbon steel scrap, the carbon steel scrap and the pig iron are all low-chromium, low-molybdenum and low-nickel materials, namely the weight percentages are as follows: chromium is less than or equal to 0.30 percent, molybdenum is less than or equal to 0.07 percent and nickel is less than or equal to 0.19 percent, no bonding steel or other waste steel or steel scraps with unknown components can be added into the ingredients of the electric arc furnace, and the materials are loaded into the electric arc furnace through a material basket;
step 2), melting the electric arc furnace ingredients in the step 1) by electric arc furnace power transmission, adding a carburant according to 5.0-15.0 kg/t in the power transmission process, adding lime according to 10.0-20.0 kg/t, carrying out early-stage slagging, starting oxygen blowing for decarbonization, dechromization and slag flowing for dephosphorization after the electric arc furnace ingredients are melted down, wherein the sampling components meet the requirement C according to the weight percentage: 0.05 to 0.27 percent of Cr is less than or equal to 0.12 percent, P is less than or equal to 0.008 percent, si is less than or equal to 0.15 percent, mn is less than or equal to 1.00 percent, ni is less than or equal to 0.20 percent, mo is less than or equal to 0.07 percent, V is less than or equal to 0.05 percent, cu is less than or equal to 0.20 percent, nb is less than or equal to 0.02 percent, as is less than or equal to 0.020 percent, sn is less than or equal to 0.018 percent, pb is less than or equal to 0.020 percent, sb is less than or equal to 0.020 percent, and Bi is less than or equal to 0.012 percent; when the temperature is controlled at 1630-1670 ℃, discharging the molten steel into a prepared clean steel ladle, and strictly forbidding slag discharging in the tapping process; in the process of tapping 1/4-3/4, adding 2.0-4.0 kg/t of aluminum blocks, 2.0-5.0 kg/t of lime, 1.0-2.0 kg/t of ferrosilicon and 5.0-10.0 kg/t of ferromanganese into a ladle; in the step 2), the requirement that Cr is less than or equal to 0.20 percent is met by controlling the electric furnace tapping Cr to be less than or equal to 0.12 percent and selecting and using a clean ladle;
step 3), hoisting the primary molten steel smelted in the step 2) to a refining furnace, connecting argon, feeding power after refining, adding 2.0-5.0 kg/t of lime to ensure that slag covers the liquid level of the steel, simultaneously adding 1.0-3.0 kg/t of calcium carbide in at least two batches, adding 1.0-2.5 kg/t of ferrosilicon powder and 1.0-2.0 kg/t of coke powder in at least three batches for slag burning, sampling after slag is white, and controlling C according to the sampling result in percentage by weight: 0.37 to 0.45%, si:0.15 to 0.35%, mn: 1.35-1.65%, P is less than or equal to 0.015% to adjust the alloy components, and then the target S is controlled according to the weight percentage: 0.12 percent of sulfur wire is fed into the molten steel, and the sampling analysis control component range is as follows: c:0.37 to 0.45%, si:0.15 to 0.35%, mn: 1.35-1.65%, P is less than or equal to 0.015%, S:0.10 to 0.12 percent, less than or equal to 0.20 percent of Cr, less than or equal to 0.20 percent of Ni, less than or equal to 0.08 percent of Mo, less than or equal to 0.20 percent of Cu, less than or equal to 0.05 percent of V, al:0.030 to 0.050 percent of Nb, less than or equal to 0.02 percent of Nb, controlling the temperature of the molten steel to 1650 to 1680 ℃, and carrying out degassing by ladle-to-VD;
step 4), transferring the molten steel refined by the refining furnace in the step 3) to a VD station, switching on argon, controlling the flow of the argon to be 20-100 NL/min, placing the ladle into the VD tank, opening a tank cover vehicle to move above the VD tank, opening a vacuum pump to degas after the cover falls, keeping the vacuum degree at 0.7mbar for more than or equal to 20min, fixing hydrogen on line after breaking the air, controlling H to be less than or equal to 1.2ppm, sampling and analyzing components, controlling S to be 0.10-0.12% according to the weight percentage of an incoming sample, feeding a sulfur line, feeding a calcium line, 0-0.5 m/t, weakly stirring for more than or equal to 12min, and switching to continuous casting steel at the temperature of 1550-1570 ℃;
and step 5), hoisting and transferring the molten steel ladle obtained in the step 4) to a continuous casting platform, measuring the temperature, then feeding the molten steel ladle to a ladle revolving platform, rotating to a continuous casting station, sleeving a long nozzle, pouring the ladle molten steel into a tundish through the long nozzle, protecting and casting by adopting the long nozzle argon protection, the tundish inner argon filling, the covering agent covering and the integral submerged nozzle, reducing the secondary oxidation of the molten steel, casting into a continuous casting blank, and performing mark hot-delivery forging after the blank is discharged.
2. The smelting and continuous casting process of sulfur-containing free-cutting steel ASTM1141 as claimed in claim 1, wherein: in the step 5), the ladle molten steel is injected into a tundish through a long water gap, argon is adopted between the long water gap and a lower water gap for protection, the tundish uses an argon blowing stopper rod, the tundish adopts 0.5-2.5 kg/t of alkaline covering agent and 0.2-0.8 kg/t of carbonized rice husk for covering, and is used for reducing the heat radiation loss of the molten steel and protecting the molten steel from secondary oxidation, and the superheat degree of the molten steel in the tundish is controlled between 15 ℃ and 40 ℃ in the continuous casting process; pouring molten steel in the tundish into the crystallizer through an integral submerged nozzle, wherein the insertion depth of the integral submerged nozzle is 100-150 mm, medium-carbon continuous casting mold powder is adopted, the molten steel in the crystallizer is electromagnetically stirred through an external crystallizer electromagnetic stirrer, the stirring parameters of the crystallizer are 345-355A, the frequency is 1.3-1.7 HZ, and the molten steel in the crystallizer is electromagnetically stirred through cold water cooling to form isometric crystals; the blank drawing machine draws blanks at a blank drawing speed of 0.18-0.22 m/min, and the blank drawing machine adopts three-roller clamping to eliminate clamping stress; the traveling direction of the casting blank is vertical to the steel pouring platform, and bending and straightening are not needed in the traveling process; the second cooling area adopts three-stage spraying to cool the round billet, and the specific water amount is controlled to be 0.11-0.16L/kg; electromagnetic stirring is carried out on the molten steel through an external cast electromagnetic stirrer on the upper part of the solidification tail end of the liquid phase cavity at the lower part of the secondary cooling chamber, and segregation at the 1/2 radius part of the round billet is reduced; cutting the casting blank into a fixed-length casting blank in the vertical direction by a flame cutting machine with the synchronous blank drawing speed, tilting the fixed-length casting blank onto a horizontal roller way by a tilting roller way, and lifting the fixed-length casting blank onto a knockout roller way by a steel hooking machine for knockout; cleaning the end face after blank ejection, marking, and forging by hot delivery forging.
3. The process of claim 1, wherein the steel is produced by ASTM1141 smelting and continuous casting, and the process comprises the following steps: in the step 3) and the step 4), harmful substances such as oxygen, inclusion and the like in steel are reduced through slag burning and deoxidation reduction at the early stage of refining, and the target S is controlled by controlling the amount of slag and the weight percentage after reduction: 0.12 percent of sulfur wires are fed into the molten steel to meet the condition that S: and (3) degassing by rotating VD at the ratio of 0.10-0.12%, wherein the degassing is performed after VD according to the weight percentage of S: controlling the content of S in the finished product to be 0.10-0.12%.
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| WO2020078007A1 (en) * | 2018-10-17 | 2020-04-23 | 南京钢铁股份有限公司 | High-strength high-toughness non-quenched and tempered round steel and preparation method |
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| WO2020078007A1 (en) * | 2018-10-17 | 2020-04-23 | 南京钢铁股份有限公司 | High-strength high-toughness non-quenched and tempered round steel and preparation method |
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