CN109988972B - Round steel for low-carbon sulfur-containing air conditioning pipe and production process thereof - Google Patents
Round steel for low-carbon sulfur-containing air conditioning pipe and production process thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/0006—Adding metallic additives
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/0087—Treatment of slags covering the steel bath, e.g. for separating slag from the molten metal
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/06—Deoxidising, e.g. killing
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
- C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/20—Ferrous alloys, e.g. steel alloys containing chromium with copper
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- 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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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Abstract
The invention discloses a round steel for a low-carbon sulfur-containing air conditioning pipe and a production process thereof. The composition comprises the following components in percentage by weight: 0.12 to 0.20%, Si: 0.05-0.20%, Mn: 0.60-1.10%, Cr: 0.30 to 0.50%, Cu: 0.10-0.40%, P is less than or equal to 0.040%, S: 0.08-0.20%, less than or equal to 0.010% of [ Al ], and the balance of Fe and inevitable impurities. The preparation method comprises the steps of converter smelting, LF refining, bloom continuous casting and rolling. Through reasonable component design and process parameter control, the produced round steel for the low-carbon sulfur-containing air-conditioning pipe has good mechanical property and cutting property, stable sulfur absorption rate and good castability, does not need calcium treatment, can be continuously cast for 8-15 furnaces, and solves the technical problems of easy occurrence of nodulation, breakout, unstable sulfur yield and the like in casting of the low-carbon sulfur-containing round steel.
Description
Technical Field
The invention belongs to the field of metal material manufacturing, and particularly relates to a round steel for a low-carbon sulfur-containing air conditioning pipe and a production process thereof.
Background
Free-cutting steel is made by adding a certain amount of free-cutting elements, such as sulfur (S), phosphorus (P), lead (Pb), bismuth (Bi), tellurium (Te) and the like, into steel to improve the cutting performance of the steel, thereby achieving the purposes of reducing cutting resistance, improving cutting quality, improving the surface roughness of a cutting workpiece and prolonging the service life and production efficiency of a cutter. Therefore, the free-cutting steel is mainly used for manufacturing cutting products, such as axes of copying machines and printers, cold-pressed products, electronic products, precision parts, aviation products and the like. The sulfur-containing free-cutting steel is the most common free-cutting steel, accounts for about 70 percent and 90 percent of the total production of free-cutting steel in China, and is widely applied to the fields of automobiles, instruments, machine tools, hardware, standard parts and the like due to lower production cost, convenient raw material source and easy processing.
The low-carbon sulfur-containing round steel for the air-conditioning pipe is sulfur-containing free-cutting steel. Due to the special working environment, the low-carbon sulfur-containing air conditioner pipe requires good mechanical property, good cutting property, high surface finish and corrosion resistance, and at present, the conventional round steel for the low-carbon sulfur-containing air conditioner pipe often has the phenomena of difficult drilling in the machining process, rough surface of the prepared finished product, unsatisfactory mechanical property and the like, so that the service life of the air conditioner pipe is greatly reduced, and the complaint of customers is caused. Meanwhile, the round steel for the air conditioner pipe has the technical problems of poor continuous casting performance, easy occurrence of nodulation, bleed-out, unstable sulfur yield, poor surface quality of casting blanks and round steel, easy occurrence of head blooming during rolling, unstable quality and the like in the production process of the round steel.
How to optimize the chemical components, designing reasonable process parameters, and producing the finished product with the characteristics of good cutting performance, high surface smoothness, excellent mechanical performance, long service life and the like under the condition of low cost, wherein the finished product is a common problem encountered by related manufacturers of round steel for air-conditioning tubes.
With the rapid development of the machinery manufacturing industry and the improvement of the automation degree in the processing process in China in recent years, the requirement on the cutting performance of raw material materials is higher and higher, at present, the technical schemes related to low-carbon high-sulfur-phosphorus composite free-cutting steel in Chinese patent databases in China are more, but the technical schemes for researching the low-carbon sulfur-containing round steel are few.
Disclosure of Invention
Aiming at the technical problems, the invention provides the round steel for the low-carbon sulfur-containing air conditioner pipe and the production process thereof by designing reasonable chemical components and selecting reasonable process parameters, so that the round steel is low in cost, excellent in mechanical property, good in castability, stable in sulfur absorption rate, free of calcium treatment, capable of being continuously cast for 8-15 furnaces and free of bleed-out and head blooming; the round steel has good cutting performance in the processing process, and the air conditioner pipe manufactured by the round steel has high surface smoothness, excellent mechanical performance and long service life.
In order to achieve the purpose, the round steel for the low-carbon sulfur-containing air-conditioning pipe comprises the following chemical components in percentage by weight: [C] the method comprises the following steps 0.12 to 0.20%, [ Si ]: 0.05-0.20%, [ Mn ]: 0.60 to 1.10%, [ Cr ]: 0.30-0.50%, [ Cu ]: 0.10-0.40%, [ P ] is less than or equal to 0.040%, [ S ]: 0.08-0.20%, less than or equal to 0.010% of [ Al ], and the balance of Fe and inevitable impurities.
Preferably, the chemical components are as follows by weight percent: [C] the method comprises the following steps 0.15-0.18%, [ Si ]: 0.12-0.18%, [ Mn ]: 0.90-1.10%, [ Cr ]: 0.30-0.40%, [ Cu ]: 0.10-0.30%, [ P ] is less than or equal to 0.030%, [ S ]: 0.10-0.15%, less than or equal to 0.005% of [ Al ], and the balance of Fe and inevitable impurities.
The invention has the following design reasons:
c is the most effective element for improving the strength in the steel, the solid solution strengthening effect is obvious, but the hardness of the steel is obviously improved and the toughness is sharply reduced due to the excessively high content, and the content is preferably 0.15-0.18% in the invention;
si can obviously improve the elastic limit, yield point and tensile strength of steel, but Si is a deoxidizing element, the sulfide form is deteriorated due to too high content of Si, the cutting performance is reduced, and the content of Si is preferably 0.12-0.18%;
the preferable range of Si in the invention is 0.12-0.18%, mainly because the manufactured steel has higher requirements on mechanical properties, and simultaneously, the manufactured steel also has good cutting performance and is provided with a proper process.
Mn can play a role in solid solution strengthening, but the brittleness of steel is increased when the content is too high, and the content is preferably 0.90-1.10% in the invention;
cr can improve the strength, wear resistance and corrosion resistance of steel, but the toughness of the steel can be reduced when the content of Cr is too high, and the Cr content is preferably 0.30-0.40% in the invention;
cu can improve the strength and the corrosion resistance of steel, but the defects of surface cracks and the like are easily caused by too high content, and the content is preferably 0.10-0.30 percent;
al is a strong deoxidizing element and can influence the form of sulfide in steel and the pouring process, and is preferably less than or equal to 0.005 percent in the invention;
p is a harmful element in steel, and is preferably less than or equal to 0.030 percent in the invention;
s is a free-cutting element, but the mechanical property of the steel is affected by the content of S is too high, preferably 0.10-0.15 percent in the invention,
the Mn/S is controlled to be more than or equal to 6, so that the condition that the sulfur-containing steel is easy to precipitate at the grain boundary and FeS with low melting point is easy to generate cracks due to grain boundary brittleness is avoided, and meanwhile, more MnS is easy to generate, and the steel is in a spindle shape and easy to cut and process.
The invention provides a production process of the round steel for the low-carbon sulfur-containing air-conditioning pipe, which comprises the steps of converter smelting, LF refining, bloom continuous casting and rolling, and specifically comprises the following operations:
(1) adding steelmaking raw materials into a converter for smelting, adopting whole-process bottom argon blowing stirring, controlling 0.05-0.12% of steel tapping [ C ], controlling the content of [ P ] to be less than or equal to 0.025% of steel tapping, sequentially adding a deoxidizer, an alloy and slag charge along with steel flow during 1/4 steel tapping, adopting a sliding plate slag blocking operation during the steel tapping process, strictly prohibiting slag tapping, and controlling the steel tapping time to be 3.5-5 min.
Preferably, the steelmaking raw materials adopted in the step (1) are scrap steel and molten iron, the scrap steel accounts for 10% -20% of the total weight of the steelmaking raw materials, the molten iron accounts for 80% -90% of the total weight of the steelmaking raw materials, the total loading amount of the steelmaking raw materials is 135-150 t/furnace, the converter smelting is carried out for 13-16 min, and the tapping temperature is 1600-1660 ℃;
preferably, the addition amount of the deoxidizer and the added agent in the step (1) is 0.4-0.7 kg/t of the aluminum block and 0.7-0.9 kg/t of the silicon carbide; the alloy in the step (1) is silicomanganese, silicon iron, low-carbon ferromanganese, low-carbon ferrochrome, copper and ferrosulfur, wherein the addition amount of the silicon manganese is 6.7-7.2 kg/t, the silicon iron is 0.4-0.8 kg/t, the low-carbon ferromanganese is 6.5-7.5 kg/t, the low-carbon ferrochrome is 5.6-6.2 kg/t, the copper is 1.0-2.5 kg/t and the ferrosulfur is 2.8-3.5 kg/t; the slag charge and the addition amount of the lime in the step (1) are 400 kg/furnace.
The slag is strictly forbidden in the tapping process, so that the oxidability of the refining slag can be effectively reduced, and the rapid component adjustment and the accurate oxygen content control are facilitated.
In order to control the form of the manganese sulfide inclusion, the manganese sulfide inclusion is made to grow large in particle size and small in length-width ratio (in a spindle shape) to ensure the cutting performance of steel, so that deoxidation is not sufficient, and certain balance between FeO and MnO and oxygen in the steel needs to be maintained; the addition of aluminum blocks and silicon carbide serving as deoxidizers in the tapping process is strictly controlled, the phenomenon that excessive deoxidation of molten steel is caused due to excessive addition, the MnS form in steel is influenced, and further the free-cutting performance of round steel is influenced is avoided, and the alloy oxidation is serious due to too little addition, the purity of the molten steel is influenced, and further the mechanical performance of the steel is influenced.
Adding ferrosilicon to raise the silicon content in the initial sample and controlling the addition of lime is favorable for stably controlling the sulfur content in the steel; the ferro-sulphur is added to the right place during tapping, the addition amount of refining is reduced, the form of sulfide in steel can be effectively controlled, and the free-cutting performance of the steel is improved.
(2) LF adopts silicon carbide 0.4-0.6 kg/t to perform steel slag interface deoxidation according to slag conditions, aluminum deoxidation is strictly forbidden, aluminum deoxidation is not easy to be added in a refining period in order to enable the steel to have a certain oxygen content and generate more spindle-shaped MnS due to strong deoxidation capability of aluminum, reasonable binary alkalinity of refining slag is controlled, the refining time is ensured to be 20-60 minutes, and alpha [ O ] is 10-30 ppm; adjusting components properly in the early stage of refining, strictly prohibiting sulfur adjustment of a sulfur supplementing line in the later stage of refining, switching to soft argon blowing operation after the temperature is adjusted properly, wherein the soft argon blowing time is 15-30 minutes, and ensuring proper ladle temperature after soft blowing;
further, the binary alkalinity in the step (2) is that R is 1.5-3.0; the temperature of the soft-blown ladle after hoisting in the step (2) is 1585-1605 ℃ of the casting furnace number and 1565-1585 ℃ of the continuous casting furnace number;
reasonably controlling the alkalinity of the refining slag, the addition amount of the deoxidizer and the refining time, and effectively controlling the a [ O ] in the molten steel]Improving the sulfide in steelThe form (2) improves the free-cutting property of the steel while ensuring the mechanical properties. The desulfurization rate of the slag with too high alkalinity is high, so that the yield of sulfur is reduced, and the components are difficult to adjust; too low basicity may cause Al in the steel2O3And silicate inclusions are not effectively removed, and are not favorable for easy cutting and mechanical properties, so that the refining slag is required to have appropriate basicity.
The sulfur adjustment of the sulfur line is strictly forbidden in the later stage of refining, so that a large amount of CaS impurities can be effectively prevented from being formed in the molten steel, the nodulation in the casting process is caused, and the formation of the long-strip-shaped sulfide which is not beneficial to the cutting performance in the steel is avoided.
(3) The continuous casting process adopts full-process protection casting, argon sealing protection of a large ladle long nozzle, an acid covering agent is used in a middle ladle, an integral stopper rod middle ladle is adopted in a continuous casting middle ladle, the diameter of the nozzle is more than or equal to 35mm, reasonable superheat degree and pulling speed control are adopted, the superheat degree is controlled to be 20-40 ℃, the pulling speed is controlled to be 0.90 +/-0.05 m/min, and quick change operation is not allowed;
the crystallizer adopts an electromagnetic stirring and sine vibration mode, and crystallizer covering slag is used, the primary cooling water flow is 1850 +/-100L/min, the water temperature difference is 6.5-8.5 ℃, and the secondary cooling adopts an ultra-weak cooling water distribution mode;
preferably, the using time of the tundish in the step (3) is less than or equal to 12 hours, the using time of the water gap is 5.0-7.0 hours, the electromagnetic stirring parameter of the crystallizer is 180A/3HZ, the non-sinusoidal vibration parameter is amplitude +/-2.5 mm, and the frequency is 130+40V opm; the crystallizer casting powder is special casting powder for sulfur-containing steel protected by Xibao, the alkalinity is 0.65-0.85, the melting point is 1220-1300 ℃, and the viscosity is 0.45-0.75 Pa.S/1300 ℃; measuring the thickness of the liquid slag layer once every 2 hours to ensure that the depth of the liquid slag layer is 5-10 mm, and further, in the ultra-weak cold water distribution mode in the step (3), the specific water amount is 0.20L/kg;
because the steel contains a certain amount of sulfur element, the crack sensitivity is strong, the oxygen content in the steel is high, and the defects of subcutaneous bubbles, scabs, surface cracks and the like are easy to generate; meanwhile, because the interface tension of the steel is small, the steel slag is difficult to separate, and the casting blank is easy to generate slag inclusion and slag adhesion, the lubricating capability of the steel can be improved by using the crystallizer covering slag with high melting point, low alkalinity and low viscosity, and the crystallizer covering slag not only influences the surface quality of the casting blank, but also is the key of smooth casting.
The continuous casting billet drawing stress can be reduced by adopting ultra-weak cold water distribution and reasonable superheat degree and drawing speed, the straightening temperature of the casting billet is ensured to be more than or equal to 960 ℃, and the defects of billet drawing, straightening, cracking and the like are prevented. In addition, the solidification speed of the molten steel is reduced, the growth of MnS inclusions is facilitated, the improvement of the cutting performance is facilitated, and the segregation of sulfides in the core of a casting blank can be reduced.
(4) The rolling procedure adopts the processes of high-temperature heating, low-temperature final rolling, water cooling after rolling, saw cutting and dephosphorization by adopting high-pressure water.
Preferably, the temperature of the first section of the furnace top of the heating furnace in the step (4) is 1050 +/-50 ℃, the temperature of the second section of the furnace top of the heating furnace is 1220 +/-20 ℃, the temperature of the soaking section is 1200-1250 ℃, the tapping rhythm is less than or equal to 40 counts/hour, the rolling temperature is 1150 +/-40 ℃, the temperature of the KOCKS rolling mill is 900 +/-40 ℃, the surface of the KOCKS rolling mill is likely to have prismatic platforms when the temperature is lower than the temperature, the cutting processing is affected, and the mechanical property is lower when the temperature is higher than the temperature, so that the. The temperature of the upper cooling bed is 710 +/-30 ℃; the sawing temperature is more than or equal to 150 ℃; the dephosphorization pressure of the high-pressure water is more than or equal to 18 MPa.
The steel has a certain sulfur content, so that the hot working performance of the steel is correspondingly deteriorated, and the phenomena of slipping, cracking, head blooming and steel holding are easily caused during rolling. And the brittleness sensitive temperature of the sulfide is 830-1050 ℃, in order to avoid the hot brittleness sensitive temperature area, high-temperature heating and heat preservation are adopted for enough time, the uniformity of the internal temperature of the steel billet is ensured, reasonable starting and finishing rolling temperature and tapping rhythm are formulated, and the hot brittleness phenomenon is prevented.
The temperature of the KOCKS rolling mill and the temperature of the upper cooling bed are reasonably controlled, water cooling is performed after rolling is enhanced, and the temperature of the upper cooling bed is reduced, so that pearlite transformation is promoted, the mechanical property of steel can be effectively improved, the surface quality is ensured, and the phenomena of edges and corners and multiple surfaces on the surface are avoided to influence subsequent turning. The temperature of the KOCKS-passing rolling mill is low, the phenomena of edges and corners and multiple faces occur in the surface quality, the subsequent turning is influenced, and the mechanical property is low due to the overhigh temperature of the KOCKS-passing rolling mill, so that the ideal requirement of a client can not be met.
The invention has the beneficial effects that:
according to the invention, a certain amount of Cr and Cu elements are added, the aluminum content and the Mn/S ratio are strictly controlled, and reasonable process parameters are matched and selected, so that the round steel for the low-carbon sulfur-containing air-conditioning pipe and the production process thereof are provided, the round steel is low in cost, excellent in mechanical property, good in castability, stable in sulfur absorption rate, free of calcium treatment, capable of being continuously cast for 8-15 furnaces, free of steel leakage and head blooming, good in cutting performance in the round steel processing process, and capable of completely meeting various technical requirements of the round steel for the air-conditioning pipe.
The invention can achieve better effect without calcium treatment, mainly the steel contains a certain oxygen content, the manganese sulfide can be attached to the oxide, and the cutting performance is improved, which is determined by the composition and the process condition of the steel. If calcium treatment is carried out, calcium sulfide inclusion can be formed in the casting process to cause nozzle nodulation, and normal production is influenced.
Compared with the prior art, the process has the characteristics of simple operation, high production efficiency, high surface smoothness of the air conditioner pipe prepared by the round steel, excellent mechanical property, long service life and the like, improves the market competitiveness of the product, and has remarkable economic benefit and social benefit.
Detailed Description
The production process is briefly described as follows:
120t converter smelting → LF refining → bloom continuous casting (220 x 260 mm)2) → rolling in a rolling mill.
Example 1
(1) The steelmaking raw materials adopted by the converter are scrap steel and molten iron, the scrap steel accounts for 14% of the total weight of the steelmaking raw materials, the molten iron accounts for 86% of the total weight of the steelmaking raw materials, and the total charging amount is 142 t/furnace;
(2) during the smelting process of the converter, bottom blowing argon stirring is adopted in the whole process, smelting is carried out for 15min, 0.08 percent of steel tapping [ C ] and 0.018 percent of steel tapping [ P ], the steel tapping temperature is 1635 ℃, 0.5kg/t of aluminum blocks, 0.8kg/t of silicon carbide, 6.9kg/t of silicon manganese, 0.6kg/t of silicon iron, 7.0kg/t of low-carbon ferromanganese, 5.8kg/t of low-carbon ferrochromium, 1.3kg/t of copper and 3.2kg/t of ferro-sulphur are sequentially added along with steel flow when steel is tapped 1/4; 400kg of lime, slag stopping operation is adopted in the tapping process, slag is strictly forbidden to be discharged, and the tapping time is 4.1 min;
(3) performing slag surface deoxidation on LF by using calcium carbide with the concentration of 0.5kg/t, adjusting timely according to the slag condition to ensure the fluidity of slag, ensuring the binary alkalinity of refined slag to be R1.9, strictly adding aluminum for deoxidation, refining for 35 minutes, ensuring the content of alpha [ O ] to be 20ppm, after the components and the temperature are adjusted properly, switching to soft argon blowing operation, wherein the soft argon blowing time is 20 minutes, and after soft blowing, the ladle temperature is raised, and the casting furnace is started for 1600 times;
(4) the continuous casting process adopts full-process protection casting, argon sealing protection is carried out on a large ladle and a long water gap, the middle ladle is covered by an acid covering agent and carbonized rice hulls in a double-layer mode, the continuous casting middle ladle adopts an integral stopper rod middle ladle, the using time of the middle ladle is 12 hours, the diameter of the water gap is 40mm, the using time of the water gap is 6 hours, the superheat degree is 38 ℃, and the drawing speed is 0.90 m/min; the crystallizer adopts electromagnetic stirring, the parameters are 180A/3HZ, the sine vibration mode is adopted, the amplitude is +/-2.5 mm, and the frequency is 130+40V opm; and special protecting slag for sulfur steel is used, the alkalinity is 0.71, the melting point is 1263 ℃, and the viscosity is 0.65Pa.S/1300 ℃; measuring the thickness of the liquid slag layer every 2 hours to ensure that the depth of the liquid slag layer is 5-10 mm; the flow of primary cooling water is 1850 +/-100L/min, the water temperature difference is 6.5-8.5 ℃, and the secondary cooling adopts an ultra-weak cooling water distribution mode, the specific water amount is 0.20L/kg, and quick change operation is not allowed;
(5) the rolling procedure adopts the processes of high-temperature heating, low-temperature final rolling, water cooling after rolling and saw cutting, and the phosphorus removal pressure of high-pressure water is 20 MPa. The furnace top temperature of the first section of the heating furnace is 1040 ℃, the furnace top temperature of the second section of the heating furnace is 1225 ℃, the furnace temperature of the soaking section is 1230 ℃, the tapping rhythm is 38/h, the rolling start temperature is 1152 ℃, the temperature of the KOCKS rolling mill is 902 ℃, the temperature of the upper cooling bed is 708 ℃, and the sawing temperature is more than or equal to 150 ℃.
Example 2
Compared with example 1, wherein
Tapping [ C ] in the step (2): 0.09 percent, tapping [ P ]0.020 percent,
after soft blowing, the temperature of the ladle is 1580 ℃ for continuous casting,
in the step (4), the superheat degree is 30 ℃,
the rest of the operation was the same as in example 1.
Example 3
Compared with example 1, wherein
The rolling temperature in the step (5) is 1148 ℃, the temperature of the rolling mill passing the KOCKS is 903 ℃, the temperature of the upper cooling bed is 707 ℃, and the rest of the operation is the same as that of the embodiment 2.
Comparative example 1
The "strictly adding aluminum deoxidation" in the step (3) of example 1 was modified to "adopting aluminum deoxidation", and the other conditions were the same as those in example 1. The finally prepared steel is detected, and the detected sulfide is in a strip shape, has poor cutting performance and is far inferior to the quality of the round steel prepared in the embodiment of the invention.
Comparative example 2
The "temperature of the mill passing KOCKS of 902 ℃ in the step (5) of example 1 was modified to" temperature of the mill passing KOCKS of 831 ℃ ", and the other conditions were the same as those in example 1. The steel finally prepared is detected, and the subsequent turning is influenced by the phenomena of edges and corners and multiple surfaces of the detected surface quality.
The chemical composition, continuous casting process, surface quality, cutting performance and mechanical properties of steels prepared in examples 1 to 3 are shown in tables 1 and 2
TABLE 1 Final chemical composition (wt/%) of steels prepared in examples 1-3
TABLE 2 continuous casting process, sulfur receiving rate, surface quality, cutting properties and mechanical properties
Claims (4)
1. A production process of round steel for a low-carbon sulfur-containing air conditioner pipe is characterized by comprising the following steps: the round steel comprises the following chemical components in percentage by weight: 0.15-0.18%, [ Si ]: 0.12-0.18%, [ Mn ]: 0.90-1.10%, [ Cr ]: 0.30-0.40%, [ Cu ]: 0.10-0.30%, [ P ] is less than or equal to 0.021%, [ S ]: 0.10-0.15%, less than or equal to 0.005% of [ Al ], and the balance of Fe and inevitable impurities;
the production process comprises the steps of converter smelting, LF refining, bloom continuous casting and rolling, and comprises the following specific operations:
(1) smelting in a converter
Adding steelmaking raw materials into a converter for smelting, adopting whole-process bottom argon blowing stirring, controlling 0.05-0.12% of steel tapping [ C ], controlling the content of [ P ] to be less than or equal to 0.025% of steel tapping, sequentially adding a deoxidizer, an alloy and slag charge along with steel flow during 1/4 steel tapping, adopting a sliding plate slag blocking operation during the steel tapping process, strictly prohibiting slag tapping, and controlling the steel tapping time to be 3.5-5 min;
(2) LF refining
LF adopts 0.4-0.6 kg/t of silicon carbide to perform steel slag interface deoxidation according to slag conditions, aluminum materials are strictly forbidden to be added for deoxidation, reasonable binary alkalinity is controlled, refining time is ensured to be 20-60 minutes, and alpha [ O ] is 10-30 ppm; adjusting components properly in the early stage of refining, strictly prohibiting sulfur adjustment of a sulfur supplementing line in the later stage of refining, switching to soft argon blowing operation after the temperature is adjusted properly, wherein the soft argon blowing time is 20-30 minutes, and ensuring proper ladle temperature after soft blowing;
the binary alkalinity in the step (2) is R = 1.5-1.9; the temperature of the soft-blown ladle after hoisting in the step (2) is 1585-1605 ℃ of the casting furnace number and 1565-1585 ℃ of the continuous casting furnace number;
(3) continuous bloom casting
The continuous casting process adopts full-process protection casting, argon sealing protection is carried out on a large ladle long nozzle, the middle ladle is covered by an acidic covering agent and carbonized rice hulls in a double-layer mode, the continuous casting middle ladle adopts an integral stopper rod middle ladle, the diameter of the nozzle is larger than or equal to 35mm, reasonable superheat degree and pull speed control are adopted, the superheat degree is controlled to be 20-40 ℃, the pull speed is controlled to be 0.90 +/-0.05 m/min, and quick change operation is not allowed;
the crystallizer adopts an electromagnetic stirring and sine vibration mode, and crystallizer covering slag is used, the primary cooling water flow is 1850 +/-100L/min, the water temperature difference is 6.5-8.5 ℃, and the secondary cooling adopts an ultra-weak cooling water distribution mode;
the using time of the tundish in the step (3) is less than or equal to 12 hours, and the using time of the water gap is 5.0-7.0 hours; the crystallizer casting powder is carbon steel casting powder special for sulfur-containing steel protected by west, the alkalinity is R = 0.65-0.85, the melting point is 1220-1300 ℃, and the viscosity is 0.45-0.75 Pa.s/1300 ℃; measuring the thickness of the liquid slag layer every 2 hours to ensure that the depth of the liquid slag layer is 5-10 mm;
(4) rolling of
The rolling procedure adopts the processes of high-temperature heating, low-temperature finish rolling, water cooling after rolling, saw cutting and descaling by high-pressure water;
the high-temperature heating in the step (4) is that the temperature of the first section of the furnace top of the heating furnace is 1050 +/-50 ℃, the temperature of the second section of the furnace top of the heating furnace is 1220 +/-20 ℃, the temperature of the soaking section is 1200-1250 ℃, the tapping rhythm is less than or equal to 40 counts/hour, the rolling temperature is 1150 +/-40 ℃, the temperature of the steel passing through a KOCKS rolling mill is 900 +/-40 ℃, and the temperature of the cooling bed is 700 +/-30 ℃; the sawing temperature is more than or equal to 150 ℃; the high-pressure water descaling pressure is more than or equal to 18 MPa.
2. The process for producing the round steel for the low-carbon sulfur-containing air-conditioning pipe as claimed in claim 1, wherein the process comprises the following steps: the steelmaking raw materials adopted in the step (1) are scrap steel and molten iron, the scrap steel accounts for 10% -20% of the total weight of the steelmaking raw materials, the molten iron accounts for 80% -90% of the total weight of the steelmaking raw materials, the total loading amount of the steelmaking raw materials is 135-150 t/furnace, converter smelting is carried out for 13-16 min, and the tapping temperature is 1600-1660 ℃.
3. The process for producing the round steel for the low-carbon sulfur-containing air-conditioning pipe as claimed in claim 1, wherein the process comprises the following steps: the addition amount of the deoxidizer in the step (1) is 0.4-0.7 kg/t of aluminum block and 0.7-0.9 kg/t of silicon carbide; the alloy in the step (1) is silicomanganese, silicon iron, low-carbon ferromanganese, low-carbon ferrochrome, copper and ferrosulfur, wherein the addition amount of the silicon manganese is 6.7-7.2 kg/t, the silicon iron is 0.4-0.8 kg/t, the low-carbon ferromanganese is 6.5-7.5 kg/t, the low-carbon ferrochrome is 5.6-6.2 kg/t, the copper is 1.0-2.5 kg/t and the ferrosulfur is 2.8-3.5 kg/t; the slag charge and the addition amount of the lime in the step (1) are 400 kg/furnace.
4. The process for producing the round steel for the low-carbon sulfur-containing air-conditioning pipe as claimed in claim 1, wherein the process comprises the following steps: in the ultra-weak cold water distribution mode in the step (3), the specific water amount is 0.20L/kg.
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| CN110722119B (en) * | 2019-10-25 | 2021-12-07 | 广东韶钢松山股份有限公司 | Continuous casting production process for preparing low-carbon high-sulfur high-oxygen free-cutting steel at high drawing speed |
| CN112626420A (en) * | 2020-12-24 | 2021-04-09 | 常州东方特钢有限公司 | Production method of steel for lightweight high-performance automobile structural pipe |
| CN112792307A (en) * | 2020-12-28 | 2021-05-14 | 江苏永钢集团有限公司 | Process method for improving surface quality of low-carbon tube blank steel |
| CN113814365A (en) * | 2021-08-24 | 2021-12-21 | 南京钢铁股份有限公司 | Casting process control method for directly turning non-quenched and tempered steel |
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