CN112080700B - High-sulfur low-aluminum free-cutting steel continuous casting slab and production method thereof - Google Patents
High-sulfur low-aluminum free-cutting steel continuous casting slab and production method thereof Download PDFInfo
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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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
Abstract
The invention discloses a high-sulfur low-aluminum free-cutting steel continuous casting slab and a production method thereof, wherein the steel comprises the chemical components of C, Si, Mn, P, S, Cr, Mo, Ti, Ca and Alt; the production method comprises the following steps: lime slag washing is not added during converter tapping, S content is stably controlled, only aluminum blocks are added for pre-deoxidation, and slag discharging amount is controlled; the LF furnace is used for producing low-alkalinity yellow rice slag, the alkalinity of top slag is controlled to be less than 2, and the stable and accurate control of S content is ensured, so that the active oxygen content is not more than 5 ppm; after the VD/RH vacuum treatment is carried out to break the air, adding a top slag modifier, deoxidizing the slag surface, controlling FeO + MnO in the slag to be less than or equal to 2%, and strictly controlling the flow of argon; the casting adopts a weak cooling low-drawing speed technology and uses the covering slag; by the smelting continuous casting process, the occurrence ratio of longitudinal cracks on the surface of the high-sulfur low-aluminum free-cutting steel plate blank is lower than 0.5%, and the scrap judgment ratio caused by the cracks on the surface of the rolled steel plate is reduced to be lower than 0.3%.
Description
Technical Field
The invention belongs to the technical field of medium-thickness steel plate blank manufacturing, and particularly relates to a high-sulfur low-aluminum free-cutting steel continuous casting plate blank and a production method thereof.
Background
The free-cutting steel is produced in China from the 50 th of the 20 th century, the annual yield is low at that time, and the yield is increased at present, but the demand of the free-cutting steel is rapidly increased along with the development of the machining industry towards the automation direction. At present, the production level, yield, quality and variety of free-cutting steel in China are greatly different from those of the advanced steel producing countries in the world, especially the cutting speed is difficult to improve, the surface roughness of parts cannot meet the requirement, the service life of cutters is low, and the like.
At present, most domestic steel mills adopt a die casting (electric furnace and ingot casting) method to produce free-cutting steel ingots (billets) or a spray forming method to produce free-cutting die steel, the die casting process has high energy consumption, low metal yield and great environmental pollution, is not suitable for the current social development direction of energy conservation, emission reduction and environmental protection, and the segregation of sulfur is a main reason for causing the non-uniform cutting performance of the free-cutting die steel, but can not occur when the free-cutting die steel is produced by adopting a continuous casting process. The continuous casting has a high solidification rate, so that the sulfide particles are smaller than the die cast sulfide particles.
However, if the high-sulfur low-aluminum steel is produced by adopting a continuous casting method, a series of influences can be generated on the smelting and continuous casting processes of molten steel, which are mainly shown in the following steps: 1) white slag and desulfurization are not produced in the LF refining process; 2) because alumina inclusions have great influence on the cutting performance of the high-sulfur low-aluminum steel, aluminum is used for weak deoxidation after alloying and sulfur supplement, and meanwhile, calcium treatment is also used for carrying out denaturation treatment on the inclusions; 3) the high oxygen content and the high sulfur content of the free-cutting steel greatly reduce the surface tension of molten steel, so that the steel slag is difficult to separate, the steel slag is difficult to be mixed and coiled, a large amount of surface slag inclusion or subcutaneous defects are formed, and steel leakage is caused in serious conditions, so that the continuous casting production is difficult to carry out; 4) after oxygen in molten steel enters the casting powder, the viscosity and the melting temperature of the casting powder are increased, and the melting speed is slowed down, so that liquid slag flows in unevenly, and the heat transfer of a primary solidified shell is uneven; 4) the high-sulfur low-aluminum steel has extremely strong crack sensitivity, and is easy to generate surface longitudinal cracks, so that casting blanks are scrapped or the surface quality of the rolled steel plate is poor and the steel plate is judged to be a waste defective product.
Therefore, no report of producing high-sulfur low-aluminum free-cutting steel by slab continuous casting exists at home and abroad, the high-sulfur low-aluminum free-cutting steel plate is rolled after die casting, and the large demand of the machining industry on the free-cutting steel plate cannot be met.
Disclosure of Invention
In order to solve the technical problems, the invention aims to provide a high-sulfur low-aluminum free-cutting steel continuous casting slab and a production method thereof, which realize stable continuous casting of continuous casting through a reasonable smelting continuous casting process, solve the problem that a steel plate is easy to generate surface longitudinal cracks, improve the hit rate of products and ensure that the produced high-sulfur low-aluminum free-cutting steel continuous casting slab has higher quality.
In order to achieve the purpose, the invention adopts the technical scheme that:
a production method of a high-sulfur low-aluminum free-cutting steel continuous casting slab comprises the following steps:
(1) smelting in a converter: the converter tapping is not washed by lime slag, and is deoxidized by adding an aluminum block, the thickness of a slag layer of a steel ladle discharged from a station is less than or equal to 50mm, so that the purity of molten steel is improved;
(2) LF refining; adding lime, aluminum particles, refining slag and submerged arc slag after LF enters the station, electrifying to melt the slag and matching with gold; controlling the alkalinity of top slag to be less than 2, and producing low-alkalinity beige slag without producing white slag; adding ferrous sulfide, controlling the S content to be 0.055-0.060%, determining oxygen before leaving the station, wherein the active oxygen content is less than or equal to 5ppm, the Als content is 0.010-0.015%, and the T.Fe content in the steel slag is less than or equal to 2% when leaving the station;
(3) VD or RH vacuum treatment: adding a top slag modifier after the slag is broken, and controlling FeO and MnO in the target slag to be less than or equal to 2%; controlling the flow of argon gas to be not more than 200NL/min, and controlling the hydrogen content to be not more than 2ppm before the station is out; ferrous sulfide can be added according to the sampling result to control the S content control target of the station to be 0.053% -0.058%; feeding seamless calcium line, and soft blowing for more than or equal to 12min after treatment;
(4) continuous casting pouring: adding calcium silicate powder into the tundish before casting, filling argon into the tundish, and controlling the seedling emergence time to be 70-90 seconds during casting; the superheat degree of the molten steel is 20-30 ℃; and adopting a weak cooling low-drawing speed technology, simultaneously adding the casting powder, and carrying out protective casting in the whole casting process.
Further, in the step (1), the converter blowing is carried out with one gun reaching the bottom, the complementary blowing is forbidden, and the end point carbon content is controlled to be 0.12-0.20%.
Furthermore, in the step (2), the addition amounts of the lime, the aluminum particles, the refining slag and the submerged arc slag are respectively 1.0-1.5kg/t steel, 0.25-0.35kg/t steel, 1.5-2.0kg/t steel and 2.5-4.0kg/t submerged arc slag.
Further, the step (2) also comprises the steps of sampling and observing the color of the slag after electrifying and slagging is finished, and adding 0.5-1.5kg/t steel of a purifying agent and 0.10-0.25kg/t steel of aluminum particles when the color of the slag is glassy light black to produce low-alkalinity beige slag.
The components of the purifying agent are controlled as follows: CaO 23-28%, Al2O3 25-30％、SiO2 4.0-5.0％、MgO 2.0-3.0％、S≤0.080％、Al 15-20％。
Further, in the step (3), VD or RH vacuum processing time is more than or equal to 20min, ultimate vacuum holding time is more than or equal to 15min, and vacuum degree is less than or equal to 67 Pa; the addition amount of the top slag modifier is 0.75-1.00kg/t steel; the feeding amount of the seamless calcium wire is 0.75-1.00 m/t steel.
The main components of the top slag modifier are controlled as follows: CaO 20-25%, Al2O3 20-25％、SiO2 2.0-3.0％、MgO 2.0-3.0％、S≤0.050％、Al 38-42％。
Further, in the step (4), the thickness difference of the upper crystallizer copper plate is less than or equal to 1mm, the outer arc positive taper of the crystallizer and the taper of the narrow surface are 1.0%, the cooling water flow rate of the wide and narrow surfaces of the crystallizer is 3900-.
In the step (4), the adding amount of the calcium silicate powder is 0.10-0.20kg/t steel; the slab pulling speed is controlled to be 0.70-0.95m/min, the secondary cooling specific water quantity is 0.33-0.60L/kg, and the water inlet insertion depth is controlled to be 120-150 mm; the alkalinity R of the covering slag is 0.95 to 1.2, the melting point is 1110-1170 ℃, and the viscosity is 0.20 to 0.35 Pa.s; the technology of weak cooling and low drawing speed is adopted, and meanwhile, the covering slag is added, so that the stable control of the whole continuous casting process is realized, and the problem of longitudinal cracks of the high-sulfur low-aluminum free-cutting steel plate blank is thoroughly solved.
Further, in the step (4), acid-base covering agents are comprehensively used in the whole continuous casting process to be well protected for pouring, the surface of the tundish steel liquid is prevented from being exposed, the sliding plate is controlled to be opened slowly in the ladle changing process, and the molten steel is prevented from being coiled and mixed due to overlarge impact flow;
the main components of the alkaline covering agent are controlled as follows: CaO is more than or equal to 45.0 percent, and Al2O3≥35.0％、SiO2≤7.0％、TC≤1.0％、H2O is less than or equal to 0.80 percent, and the bulk density is less than or equal to 0.80 g/mL;
the main components of the acidic covering agent are controlled as follows: CaO 10.0-20.0%, Al2O3≤5.0％、SiO2≥60.0％、TC≤5.0％、H2O is less than or equal to 1.0 percent, and the bulk density is less than or equal to 0.50 g/mL.
The invention also provides a high-sulfur low-aluminum free-cutting steel continuous casting slab produced by the production method.
Further, the high-sulfur low-aluminum free-cutting steel comprises the following chemical components in percentage by weight: 0.38-0.48% of C, 0.30-0.45% of Si, 1.45-1.60% of Mn, less than or equal to 0.040% of P, 0.050-0.100% of S, 1.85-2.00% of Cr, 0.15-0.25% of Mo, 0.010-0.020% of Ti, 0.0012-0.0040% of Ca, less than or equal to 0.015% of Alt, and the balance of Fe and inevitable impurities.
The general idea of the invention is as follows: 1) lime slag washing is not added during converter tapping, S content is stabilized, aluminum blocks are added for deoxidation as early as possible, and meanwhile, sliding plate slag blocking equipment is adopted for slag blocking, so that the slag amount is effectively controlled, and the purity of molten steel is improved; 2) LF refining produces low-alkalinity yellow rice slag, white slag is not produced, the alkalinity of top slag is controlled to be less than 2, the stability of S content is ensured, desulfurization is not carried out in the refining process, the S content is controlled to be 0.055-0.060%, the crack sensitivity is reduced, the active oxygen content is ensured to be less than or equal to 5ppm, and the T.Fe content in the steel slag is less than or equal to 2% when the steel slag is out of the station; 3) VD/RH vacuum refining processing time is more than or equal to 20min, ultimate vacuum holding time is more than or equal to 15min, molten steel hydrogen content is effectively controlled, a top slag modifier is added after the vacuum breaking, the slag surface is deoxidized, FeO + MnO in the slag is controlled to be less than or equal to 2%, the continuous casting covering slag is prevented from being denatured, and the argon flow is strictly controlled; 4) the technology of weak cooling and low drawing speed is adopted during continuous casting, and the covering slag is used at the same time, so that the whole process is stably controlled, and the problem of longitudinal cracks of the high-sulfur low-aluminum free-cutting steel plate blank is thoroughly solved.
The high-sulfur low-aluminum free-cutting steel continuous casting slab produced by the method has high quality, the surface quality of the slab is normal, after the statistics of multiple batches of production, the occurrence ratio of longitudinal cracks on the surface of the high-sulfur low-aluminum free-cutting steel slab is lower than 0.5 percent, and the waste judgment ratio caused by the cracks on the surface of the rolled steel plate is reduced to be lower than 0.3 percent.
Drawings
FIG. 1 is a macro-morphology diagram of low-alkalinity beige slag in the smelting process LF refining in example 1;
FIG. 2 is a macro-topography of the surface of 2312 high-sulfur low-aluminum free-cutting steel slab of example 2;
FIG. 3 is a graph showing the change in thickness of a molten slag layer of mold flux in the continuous casting process in comparative example 1, wherein (a) the thickness of the molten slag layer at 10 minutes of casting, (b) the thickness of the molten slag layer at 45 minutes of casting;
FIG. 4 is a surface longitudinal crack profile of the 2312 free-cutting die steel slab in comparative example 2.
Detailed Description
The present invention will be described in detail with reference to examples.
The main components of the purifying agent used in each of the following examples were controlled as follows: CaO 23-28%, Al2O3 25-30％、SiO24.0-5.0 percent of MgO, 2.0-3.0 percent of S, less than or equal to 0.080 percent of Al and 15-20 percent of Al; the main components of the top slag modifier are controlled as follows: CaO 20-25%, Al2O3 20-25％、SiO22.0-3.0 percent, 2.0-3.0 percent of MgO, less than or equal to 0.050 percent of S and 38-42 percent of Al; the main components of the alkaline covering agent are controlled as follows: CaO is more than or equal to 45.0 percent, and Al2O3≥35.0％、SiO2≤7.0％、TC≤1.0％、H2O is less than or equal to 0.80 percent, and the bulk density is less than or equal to 0.80 g/mL; the main components of the acidic covering agent are controlled as follows: CaO 10.0-20.0%, Al2O3≤5.0％、SiO2≥60.0％、TC≤5.0％、H2O is less than or equal to 1.0 percent, and the bulk density is less than or equal to 0.50 g/mL.
Example 1
The steel is 2312 high-sulfur low-aluminum free-cutting steel, and the target components are as follows: 0.4% of C, 0.32% of Si, 1.48% of Mn, 0.013% of P, 0.055% of S, 1.87% of Cr, 0.181% of Mo, 0.012% of Ti, 0.0019% of Ca, 0.012% of Alt, and the balance of Fe and inevitable impurities. The production is carried out by adopting a 200-ton converter, and the thickness of a casting blank for rolling a base metal is 300 mm.
The smelting and continuous casting process of the embodiment is as follows:
1) smelting in a converter: the converter blowing is carried out from one gun to the bottom, the converter is not blown additionally, the carbon content at the end point is 0.12 percent, 105kg of aluminum blocks are added for pre-deoxidation during tapping, lime is not added, sliding plate slag blocking equipment is adopted for slag blocking during tapping, the slag tapping amount is effectively controlled, the purity of molten steel is improved, and the thickness of a measured slag layer in a ladle is 40mm after tapping;
2) LF refining: 280kg of lime, 60kg of aluminum particles, 356kg of refining slag and 680kg of submerged arc slag are added into a station, the electrified slagging is carried out for 14min, after the electrified slagging is finished, a sample is taken to observe the color of the slag, the color of the slag is glassy light black, 150kg of purifying agent and 32kg of aluminum particles are required to be added, and then low-alkalinity beige slag is formed, and the alkalinity is 1.8; 690kg of ferrous sulfide is added to control the S content to be 0.056%, the oxygen content of the molten steel before the steel is out of the station to be 4.3ppm, the Als content to be 0.014%, and the T.Fe content of the slag sample taken out of the station to be 1.82%.
3) VD vacuum refining: vacuum treating for 22min, ultimate vacuum degree of 20Pa, ultimate vacuum maintaining time of 17min, breaking, adding top slag modifier 180kg, deoxidizing slag surface, and controlling argon flow to 185Nm3And h, 1.87 percent of FeO + MnO in the outbound slag, 1.3ppm of hydrogen in the molten steel, 0.055 percent of S content, 195 meters of seamless calcium line after the treatment is finished, and the soft blowing time is 15 min.
4) Continuous casting pouring: the thickness difference of the upper line crystallizer copper plate is 0.8mm, the outer arc taper of the crystallizer is 0.4%, the taper of the narrow surface is 1.0%, the cooling water flow of the wide and narrow surfaces of the crystallizer is 4221L/min and 509L/min respectively, the water inlet temperature of the crystallizer is 35 ℃, 30kg of calcium silicon powder is added into the tundish before casting, the seedling emergence time during casting is 79 seconds, the tundish is filled with argon, the method is characterized in that oxidation of molten steel is prevented, the superheat degree of the molten steel is 26 ℃, the plate blank drawing speed is controlled to be 0.75m/min, the secondary cooling specific water amount is 0.33L/kg, the insertion depth of a water gap is 125mm, casting powder with alkalinity R of 1.02, melting point of 1135 ℃ and viscosity of 0.27Pa.S is adopted, protective casting is carried out in the whole casting process, acid-base covering agents are comprehensively used, 90kg of alkaline covering agents are added firstly, 60kg of acid covering agents are added, the whole casting process is smooth, the surface quality of the plate blank is normal, and no crack occurs.
Example 2
The steel is 2312 high-sulfur low-aluminum free-cutting steel, and the target components are as follows: 0.41 percent of C, 0.32 percent of Si, 1.53 percent of Mn, less than or equal to 0.014 percent of P, 0.055 percent of S, 1.88 percent of Cr, 0.178 percent of Mo, 0.016 percent of Ti, 0.0021 percent of Ca, 0.013 percent of Alt, and the balance of Fe and inevitable impurities. The converter is used for producing the steel plate, and the thickness of a casting blank for rolling a base metal is 250 mm.
The smelting and continuous casting process of the embodiment is as follows:
1) smelting in a converter: the converter is not blown again, the carbon content at the end point is 0.11 percent, 70kg of aluminum blocks are added for pre-deoxidation during tapping, lime is not added, a sliding plate slag stopping device is adopted for slag stopping during tapping, the slag quantity is effectively controlled, the purity of molten steel is improved, and the thickness of a measured slag layer in a steel ladle is 43mm after tapping;
2) LF refining: 135kg of lime, 28kg of aluminum particles, 190kg of refining slag and 380kg of submerged arc slag are added when the steel is in a station, the electrified slagging is carried out for 11min, after the electrified slagging is finished, a sample is taken to observe the color of the slag, the color of the slag is glassy light black, 90kg of a purifying agent and 21kg of aluminum particles are required to be added, so that low-alkalinity beige slag is formed, the alkalinity is 1.8, 350kg of ferrous sulfide is added to control the S content to be 0.056%, the oxygen content of molten steel before the steel is taken out of the station to be 4.3ppm, the Als content to be 0.014%, and the T.Fe content of a slag sample taken when the steel is taken out of the station to be 1.82%.
3) RH vacuum refining: vacuum treating for 21min, ultimate vacuum degree of 13Pa, ultimate vacuum maintaining time of 16min, breaking, adding top slag modifier 90kg, deoxidizing slag surface, and controlling argon flow to 180Nm3The FeO and MnO content in the slag discharged from the station is 1.90 percent, the hydrogen content in the molten steel is 1.4ppm, the S content is controlled to be 0.056 percent, and the slag is added after the treatment is finishedThe seamless calcium line is 95 meters, and the soft blowing time is 16 min.
4) Continuous casting pouring: the thickness difference of the upper line crystallizer copper plate is 0.9mm, the outer arc taper of the crystallizer is 0.3%, the taper of the narrow surface is 1.0%, the cooling water flow of the wide and narrow surfaces of the crystallizer is 4050L/min and 470L/min respectively, the water inlet temperature of the crystallizer is 36 ℃, 30kg of calcium silicon powder is added into the tundish before casting, the seedling emergence time during casting is 75 seconds, the tundish is filled with argon, the method is characterized in that oxidation of molten steel is prevented, the superheat degree of the molten steel is 28 ℃, the plate blank drawing speed is controlled to be 0.90m/min, the secondary cooling specific water amount is 0.52L/kg, the insertion depth of a water gap is 125mm, casting powder with alkalinity R of 1.03, melting point of 1138 ℃ and viscosity of 0.29Pa.S is adopted, protective casting is carried out in the whole casting process, acid-base covering agents are comprehensively used, 90kg of alkaline covering agents are added firstly, 60kg of acid covering agents are added, the whole casting process is smooth, the surface quality of the plate blank is normal, and no crack occurs.
Comparative example 1
The other same example 1 only changes the VD process compared with the example 1, namely the refining slag is modified without adding a top slag modifier after the VD is broken, the slag surface is not deoxidized, and the flow of argon is not controlled. The method has the advantages that the fluctuation of the S content of the molten steel is large, the precise control cannot be realized, in the continuous casting process, the thickness of the liquid slag layer of the continuous casting mold flux begins to be thinned after 40 minutes of casting along with the lapse of the casting time, and is finally thinned to 4mm, as shown in figure 3, the molten slag is denatured mainly because the oxygen on the slag surface in a ladle permeates into the molten steel in the final stage of casting, the melting point and the viscosity of the mold flux are improved, so that the melting speed is slowed down, generally, the thickness of the liquid slag layer of the continuous casting mold flux is ensured to be 8-12mm, otherwise, the phenomenon of steel leakage is easily caused because the lubrication of the mold flux is insufficient, and therefore, in order to prevent the occurrence of the steel leakage accident, the continuous casting is stopped when the casting time reaches 50 minutes, and the subsequent molten steel is completely returned to the furnace.
Comparative example 2
The other embodiment 2 is the same as the embodiment 2 except that the converter pre-deoxidation and the non-yellow-brown slag production are changed compared with the embodiment 2, namely, no aluminum block is added during the converter tapping, the pre-deoxidation operation is not carried out, lime, refining slag and submerged arc slag are added after LF enters a station, no aluminum particles and a purifying agent are added, after electrified slagging is finished, ferrous sulfide is added, the S content is 0.055%, the oxygen content of molten steel detected before the molten steel is taken out of the station is 14.6ppm, the Als content is 0.005%, the color of a slag sample taken during the station leaving is black, and the T.Fe content in the slag is 3.56%. During continuous casting, the whole process is relatively stable, but a large number of longitudinal cracks appear on the surface of the slab after the slab is cast by the method, as shown in figure 4.
The above detailed description of a high sulfur low aluminum free-cutting steel continuous casting slab and the method for producing the same with reference to the embodiments is illustrative and not restrictive, and several embodiments can be cited within the limits thereof, so that changes and modifications that do not depart from the general concept of the present invention shall fall within the scope of the present invention.
Claims (5)
1. A production method of a high-sulfur low-aluminum free-cutting steel continuous casting slab is characterized by comprising the following steps:
(1) smelting in a converter: the converter tapping is not washed by lime slag, and is deoxidized by adding an aluminum block, and the thickness of the slag layer of the steel ladle discharged from the station is less than or equal to 50 mm;
(2) LF refining; adding lime, aluminum particles, refining slag and submerged arc slag after LF enters the station, electrifying to melt the slag and matching with gold; controlling the alkalinity of top slag to be less than 2, and manufacturing low-alkalinity yellow rice slag; adding ferrous sulfide, controlling the S content to be 0.055-0.060%, determining oxygen before leaving the station, wherein the active oxygen content is less than or equal to 5ppm, the Als content is 0.010-0.015%, and the T.Fe content in the steel slag is less than or equal to 2% when leaving the station;
(3) VD or RH vacuum treatment: adding a top slag modifier after the slag is broken, and controlling FeO and MnO in the target slag to be less than or equal to 2%; controlling the flow of argon gas to be not more than 200NL/min, and controlling the hydrogen content to be not more than 2ppm before the station is out; the control target of the outbound S content is 0.053% -0.058%; feeding seamless calcium line, and soft blowing for more than or equal to 12min after treatment;
(4) continuous casting pouring: adding calcium silicate powder into the tundish before casting, filling argon into the tundish, and controlling the seedling emergence time to be 70-90 seconds during casting; the superheat degree of the molten steel is 20-30 ℃; adopting a weak cooling low-drawing speed technology, simultaneously adding the casting powder, and carrying out protective casting in the whole casting process;
the step (2) also comprises electrifying to melt slagSampling and observing the color of the slag after the operation is finished, and adding 0.5-1.5kg/t steel of a purifying agent and 0.10-0.25kg/t steel of aluminum particles when the color of the slag is glassy light black to produce low-alkalinity beige slag; the purifying agent mainly comprises the following components: CaO 23-28%, Al2O3 25-30%、SiO2 4.0-5.0%、MgO 2.0-3.0%、S≤0.080%、Al 15-20%；
In the step (3), VD or RH vacuum processing time is more than or equal to 20min, ultimate vacuum holding time is more than or equal to 15min, and vacuum degree is less than or equal to 67 Pa; the addition amount of the top slag modifier is 0.75-1.00kg/t steel; the feeding amount of the seamless calcium line is 0.75-1.00 m/t steel;
in the step (4), the adding amount of the calcium silicate powder is 0.10-0.20kg/t steel; the slab pulling speed is controlled to be 0.70-0.95m/min, the secondary cooling specific water quantity is 0.33-0.60L/kg, and the water inlet insertion depth is controlled to be 120-150 mm; the alkalinity R of the covering slag is 0.95 to 1.2, the melting point is 1110-1170 ℃, and the viscosity is 0.20 to 0.35 Pa.s;
the high-sulfur low-aluminum free-cutting steel comprises the following chemical components in percentage by weight: 0.38-0.48% of C, 0.30-0.45% of Si, 1.45-1.60% of Mn, less than or equal to 0.040% of P, 0.050-0.100% of S, 1.85-2.00% of Cr, 0.15-0.25% of Mo, 0.010-0.020% of Ti, 0.0012-0.0040% of Ca, less than or equal to 0.015% of Alt, and the balance of Fe and inevitable impurities.
2. The production method according to claim 1, wherein in the step (1), converter blowing is performed with a gun at the bottom, additional blowing is prohibited, and the end point carbon content is controlled to be 0.12-0.20%.
3. The production method according to claim 1, wherein in the step (2), the lime, the aluminum particles, the refining slag and the submerged arc slag are added in an amount of 1.0 to 1.5kg/t steel, 0.25 to 0.35kg/t steel, 1.5 to 2.0kg/t steel and 2.5 to 4.0kg/t submerged arc slag, respectively.
4. The production method according to claim 1, wherein in the step (4), acid-base covering agent is comprehensively used for protection pouring in the whole continuous casting process, and the main components of the alkaline covering agent are controlled as follows: CaO is more than or equal to 45.0 percent, and Al2O3≥35.0%、SiO2≤7.0%、TC≤1.0%、H2O is less than or equal to 0.80 percent, and the bulk density is less than or equal to 0.80 g/mL; the main components of the acidic covering agent are controlled as follows: CaO 10.0-20.0%, Al2O3≤5.0%、SiO2≥60.0%、TC≤5.0%、H2O is less than or equal to 1.0 percent, and the bulk density is less than or equal to 0.50 g/mL.
5. A high-sulfur low-aluminum free-cutting steel continuous casting slab produced by the production method as set forth in any one of claims 1 to 4.
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| CN114959432A (en) * | 2022-06-21 | 2022-08-30 | 湖南华菱湘潭钢铁有限公司 | Production method of high-Ti wear-resistant steel |
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Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1664122A (en) * | 2005-03-04 | 2005-09-07 | 宝钢集团上海五钢有限公司 | Method for producing low-carbon high-sulfur (sulfur-phosphorous) easy-to-cut structural steel continuous casting billet |
| CN101580912A (en) * | 2009-06-19 | 2009-11-18 | 武汉钢铁(集团)公司 | Low carbon high sulfur free-cutting steel production process |
| CN102925806A (en) * | 2012-12-01 | 2013-02-13 | 新余钢铁集团有限公司 | Y55 mark free-cutting steel plate and manufacture method thereof |
| CN105121685A (en) * | 2013-04-10 | 2015-12-02 | 新日铁住金株式会社 | Case-hardening steel material and case-hardening steel member |
| CN105567899A (en) * | 2016-01-11 | 2016-05-11 | 中天钢铁集团有限公司 | Smelting method for improving cutting performance of round steel for machinery |
| CN106148844A (en) * | 2016-08-12 | 2016-11-23 | 常州东大中天钢铁研究院有限公司 | A kind of preparation method of sulfur-bearing ultralow titanium high standard bearing steel |
| CN107299271A (en) * | 2017-06-19 | 2017-10-27 | 南京钢铁股份有限公司 | A kind of smelting process of low carbon high sulfur free-cutting steel |
| JP2019127638A (en) * | 2018-01-26 | 2019-08-01 | 日本製鉄株式会社 | Mooring chain steel and mooring chain |
| CN111235341A (en) * | 2020-03-23 | 2020-06-05 | 江苏利淮钢铁有限公司 | Production method of high-cleanliness sulfur-containing and aluminum-containing steel |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01319651A (en) * | 1988-06-20 | 1989-12-25 | Daido Steel Co Ltd | Free cutting steel having excellent warm workability |
| JP3196579B2 (en) * | 1995-07-11 | 2001-08-06 | 住友金属工業株式会社 | Free-cutting non-heat treated steel with excellent strength and toughness |
-
2020
- 2020-09-14 CN CN202010958724.2A patent/CN112080700B/en active Active
Patent Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1664122A (en) * | 2005-03-04 | 2005-09-07 | 宝钢集团上海五钢有限公司 | Method for producing low-carbon high-sulfur (sulfur-phosphorous) easy-to-cut structural steel continuous casting billet |
| CN101580912A (en) * | 2009-06-19 | 2009-11-18 | 武汉钢铁(集团)公司 | Low carbon high sulfur free-cutting steel production process |
| CN102925806A (en) * | 2012-12-01 | 2013-02-13 | 新余钢铁集团有限公司 | Y55 mark free-cutting steel plate and manufacture method thereof |
| CN105121685A (en) * | 2013-04-10 | 2015-12-02 | 新日铁住金株式会社 | Case-hardening steel material and case-hardening steel member |
| CN105567899A (en) * | 2016-01-11 | 2016-05-11 | 中天钢铁集团有限公司 | Smelting method for improving cutting performance of round steel for machinery |
| CN106148844A (en) * | 2016-08-12 | 2016-11-23 | 常州东大中天钢铁研究院有限公司 | A kind of preparation method of sulfur-bearing ultralow titanium high standard bearing steel |
| CN107299271A (en) * | 2017-06-19 | 2017-10-27 | 南京钢铁股份有限公司 | A kind of smelting process of low carbon high sulfur free-cutting steel |
| JP2019127638A (en) * | 2018-01-26 | 2019-08-01 | 日本製鉄株式会社 | Mooring chain steel and mooring chain |
| CN111235341A (en) * | 2020-03-23 | 2020-06-05 | 江苏利淮钢铁有限公司 | Production method of high-cleanliness sulfur-containing and aluminum-containing steel |
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