CN114990435A - Low-cost high-strength welded pipe steel produced by CSP process and manufacturing method thereof - Google Patents
Low-cost high-strength welded pipe steel produced by CSP process and manufacturing method thereof Download PDFInfo
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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
- C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/46—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting
- B21B1/463—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting in a continuous process, i.e. the cast not being cut before rolling
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
- B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/001—Continuous casting of metals, i.e. casting in indefinite lengths of specific alloys
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/10—Supplying or treating molten metal
- B22D11/11—Treating the molten metal
- B22D11/111—Treating the molten metal by using protecting powders
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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
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
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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
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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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
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
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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
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
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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
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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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
- C22C38/02—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
- C22C—ALLOYS
- 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
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/003—Cementite
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- 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 low-cost high-strength steel for welded pipes produced by a CSP process and a manufacturing method thereof, wherein the steel for welded pipes comprises the following chemical components in percentage by weight: c is less than or equal to 0.003 percent, Mn: 0.35-0.45%, Si: 0.06-0.1%, P: 0.03-0.04%, S is less than or equal to 0.012%, Ti: 0.03-0.050%, Als: 0.02-0.045%, N is less than or equal to 0.0025%, B: 0.0002 to 0.0010 percent, and the balance of Fe and other inevitable impurities. The manufacturing method adopts CSP short flow as follows: blast furnace iron making → molten iron pretreatment → converter smelting → RH treatment → corrugated plate blank continuous casting → soaking furnace → descaling → rough rolling → finish rolling → laminar cooling → coiling → finishing → inspection → packaging. The metallographic structure of the steel for the welded pipe produced by the invention is as follows: the yield strength of the steel plate is 180-.
Description
Technical Field
The invention relates to the technical field of metal material manufacturing, in particular to low-cost high-strength welded pipe steel produced by a CSP (cast-in-place steel plate) process and a manufacturing method thereof.
Background
The steel for the welded pipe is applied to the product fields of condenser pipes, heat exchange pipes, automobile braking systems, fuel oil delivery pipes, electric box compressor vaporizers and the like in the household appliance industry, has high strength, high ductility and good forming performance, and simultaneously meets the welding, drawing and galvanizing processes of the welded pipe. With the rising segment of market application amount, market competition is more and more intense, and who can produce and manufacture with lower cost can win larger market share.
Through searching domestic and foreign literature resources, 11 documents related to the research project are searched. The invention patent with the application number of CN201210270618.0 discloses a production method of a steel strip for a copper-plated precision welded pipe, which comprises the following steps: performing KR desulfurization treatment, converter dephosphorization-less slag decarburization process and RH deep decarburization treatment on molten iron, and then continuously casting to obtain a plate blank; after the plate blank is heated, a hot rolled plate is obtained through rough rolling and finish rolling, and the hot rolled plate is coiled into a hot rolled coil after being cooled; the hot rolled coil is coiled into a finished product after cold rolling, annealing and leveling.
The invention with the application number of CN201110233531.1 discloses a cold-rolled strip steel for a double-layer roll-welded pipe and a manufacturing method thereof, and mainly solves the technical problems that the existing steel for the double-layer roll-welded pipe is generally subjected to cover annealing, and the product yield and the performance uniformity are poor. The cold-rolled strip steel for the double-layer coil-welded pipe comprises the following chemical components in percentage by weight: c: 0.015-0.054%, Si is less than or equal to 0.034%, Mn: 0.15-0.25%, P is less than or equal to 0.020%, S is less than or equal to 0.020%, Alt: 0.015 to 0.050% and the balance of Fe and inevitable impurity elements.
The invention patent with the application number of CN201710108129.8 discloses a high-strength precision welded pipe steel and a manufacturing method thereof, wherein the steel comprises the following chemical elements in percentage by mass: c: 0.001 to 0.005%, Mn: 0.4-1.2%, P: 0.025-0.05%, Al: 0.025 to 0.06%, Nb: 0.005-0.02%, Ti: 0.01-0.08%, and the balance of Fe and other inevitable impurities.
The invention adopts the ultra-low carbon and low carbon steel containing Ti or Nb, which has better stamping forming performance and welding performance, but adopts the traditional process, has relatively higher cost and can not better control the cost.
In conclusion, many people researching at home and abroad for manufacturing welded pipe original plates propose different schemes, but the steel for welded pipes produced by adopting the CSP process at low cost and the manufacturing method thereof are not reported.
Disclosure of Invention
The invention aims to overcome the defects of the background technology and provide the low-cost high-strength welded pipe steel produced by the CSP process and the manufacturing method thereof, so that the welded pipe steel is stably produced by the CSP short-flow process with lower cost, the cost is reduced by 10-20% compared with the traditional process, and the proper mechanical property is ensured.
In order to achieve the purpose, on one hand, the low-cost high-strength steel for the welded pipe produced by the CSP process provided by the invention comprises the following chemical components in percentage by weight: c is less than or equal to 0.003 percent, Mn: 0.35-0.45%, Si: 0.06-0.1%, P: 0.03-0.04%, S is less than or equal to 0.012%, Ti: 0.03-0.050%, Als: 0.02-0.045%, N is less than or equal to 0.0025%, B: 0.0002 to 0.0010 percent, and the balance of Fe and other inevitable impurities.
Preferably, the yield strength of the steel for the welding pipe is 180-240MPa, the tensile strength is 340-400MPa, and the elongation is more than or equal to 40 percent.
On the other hand, the invention provides a method for manufacturing the low-cost high-strength welded pipe steel produced by the CSP process in the scheme, which is characterized in that the CSP short flow is adopted as follows: blast furnace iron making → molten iron pretreatment → converter smelting → RH treatment → corrugated plate blank continuous casting → soaking furnace → descaling → rough rolling → finish rolling → laminar cooling → coiling → finishing → inspection → packaging.
Preferably, in the continuous casting process of the corrugated plate blank, the whole-process protective casting is adopted, the long water gap during the replacement of the large ladle is protected by an asbestos bowl for casting, and the water gap of the tundish is introduced with argon for protective casting.
Further preferably, the tundish adopts a dry tundish and an alkaline tundish covering agent.
Preferably, the furnace inlet temperature of the soaking furnace is controlled to be 800-950 ℃, the furnace time is more than 15min, the temperature difference between the soaking furnace and the plate after the soaking furnace is taken out is less than 20 ℃, and the furnace outlet temperature is controlled to be 1230 +/-20 ℃.
Further preferably, the finishing temperature is controlled at 820 +/-20 ℃.
Still more preferably, the coiling temperature is controlled to 620. + -. 20 ℃.
The functions of each element and the main process in the invention are as follows:
c: carbon is the most effective solid solution strengthening element, the raw steel gradually hardens with the increase of the content of C, and the cold processing performance (stamping, drawing), the welding performance and the aging resistance of the raw steel also deteriorate, so that the weight percentage content of C needs to be controlled within 0.003% to ensure the welding performance and the forming performance.
Si: the higher the Si content in the steel sheet, the higher the SiO2 content of Si generated by oxidation. The higher the SiO2 content of the surface of the raw steel, the poorer the adhesion of the coating. Therefore, the Si content is controlled to 0.06-0.1% by weight.
Mn: manganese strengthens ferrite, increases hardness of the steel sheet by solid solution, and the higher the content of Mn in the steel sheet, the higher the strength. In addition, the addition of manganese to steel prevents embrittlement of steel due to sulfur during hot working, but as the content of Mn in steel sheet is higher, workability is gradually decreased. Therefore, the weight percentage of Mn in the invention is controlled to be 0.35-0.45%.
P: p element steel contains elements for improving tensile strength, and phosphorus is easy to segregate, so that the content needs to be controlled to be 0.03-0.04%.
S: s is a harmful impurity element in steel, and the smaller the content of S, the better the corrosion resistance of steel. Therefore, the weight percentage of S is controlled to be less than 0.012 percent.
And (3) Als: al added to steel forms acid-soluble aluminum (Als) and acid-insoluble aluminum, and Als includes solid-solution aluminum and AlN, and dispersed AlN particles prevent austenite grains from growing and refine the grains, thereby contributing to improvement in the workability of steel sheets. However, for aluminum killed steel, the quantity of Al2O3 inclusions in the steel is increased along with the increase of Als, the sizes of the inclusions are also increased, and the formability of the steel plate is deteriorated, but the weight percentage of Als is guaranteed to be more than or equal to 0.01% in order to guarantee the complete deoxidation of molten steel and the surface quality of continuous casting billets. Therefore, the invention controls the Als content within 0.02-0.045%.
Ti: titanium is a typical microalloying element. The Ti has the function of refining grains, and improves the toughness of the steel while improving the strength of the steel. At high temperature, Ti and N or O generate TiN or Ti2O3 micro-particles, and austenite grains are refined and used as nucleation cores of the pre-eutectoid alpha-Fe. In addition, Ti combines with N or C to generate a stable compound TiC or Ti (CN), so that solute components are withdrawn from the solid solution, thereby effectively inhibiting the generation of 'Coriolis gas clusters' and effectively preventing the generation of wrinkles during the processing of the electric steel plate. If the Ti content is too high, large titanium nitride particles are formed, so that the steel becomes brittle, the stamping processability of the electro-galvanized sheet is deteriorated, and the production cost is increased; if the Ti content is too small, it is difficult to completely fix C, N element in the steel, and the effect of preventing the working wrinkles is not obtained. In cold-rolled ultra-low carbon steel, the addition amount of Ti is generally considered to be not less than 0.02%, and the Ti content in the steel is determined to be 0.03-0.05% by combining the factors.
B: boron can improve the hot ductility of steel and the cold processing deformation performance, and B is added into the Nb and Ti composite ultra-low carbon steel, so that the weld hardness of a welding tank can be improved, and the welding cracking defect of a steel plate during welding can be improved. In addition, B can strengthen grain boundaries and prevent secondary processing brittleness of the ultra-low carbon steel. If the B content is too high, large boron nitride particles are formed, so that the steel becomes brittle, the stamping processability and the welding performance of the electric steel plate are deteriorated, and the production cost is increased; if the B content is too small, the cold workability and weldability cannot be improved. And (4) determining that the content of B in the steel is 0.0002-0.0010% by combining the factors.
N: like carbon, nitrogen is a solid solution element. The increase of the content of N in steel leads to the deterioration of the stamping processability, and the solid solution of N is a main cause of aging of the finished steel plate, particularly the influence of nitrogen on the strain aging effect after flattening is large, so that N is required to be as low as possible. For the steel plate of the invention, the N content in the steel should be controlled below 0.0025%.
The invention contains the chemical components, and the balance of Fe and inevitable impurities.
The invention relates to a continuous casting and rolling process for a welded pipe by using steel as a thin slab, which comprises the following steps: in the continuous casting process, the whole process is adopted for protection casting, the long water gap during ladle replacement is adopted for protection casting by an asbestos bowl, and the water gap of the tundish is introduced with argon for protection casting. The tundish adopts a dry tundish material and an alkaline tundish covering agent. The advantages of the method are that the air can be better isolated, the influence of increasing C and N on the molten steel components can be prevented, and compared with an acid covering agent, the covering agent in alkalinity has the advantages of heat insulation and heat preservation, secondary oxidation prevention of the molten steel, effective absorption of non-metal impurities in the molten steel, corrosion prevention of an alkaline tundish lining material and the like.
The furnace inlet temperature of the soaking furnace is controlled to be 800-950 ℃, the furnace time is more than 15min, the temperature difference between the same plate and the soaking furnace is less than 20 ℃ after the soaking furnace is taken out, and the furnace outlet temperature is controlled to be 1230 +/-20 ℃. Before rolling, an online furnace roller cleaning program is put into use, and the furnace atmosphere is adjusted according to the condition of iron scale. And descaling by a high-pressure water descaler. The steel billet can be fully austenitized by adopting high heating temperature to achieve the purpose of uniform tissue, meanwhile, compounds in the steel can be fully dissolved, and are precipitated in the cooling process to play a role in refining crystal grains, the effect is brought by controlling hot rolling temperature, the rolling temperature control involved in the text is main control process parameters, rough rolling is carried out firstly, then finish rolling is carried out, and the steel billet can be fully austenitized and two-phase region rolling is avoided only by controlling tapping temperature and finishing rolling temperature (the finishing rolling temperature is controlled at 820 +/-20 ℃, the tapping temperature is controlled at 1230 +/-20 ℃), so that the uniform tissue is ensured, and the size of the crystal grains and the precipitated phases are fully precipitated by controlling coiling temperature. The coiling temperature is controlled at 620 +/-20 ℃, so that the precipitated phase can be fully precipitated, the grain refinement is facilitated, and the cold processing performance is improved.
Compared with the prior art, the invention has the following advantages:
1) the steel for the welded pipe is designed by adopting the Ti-added ultra-low carbon steel, so that the smelting control is convenient, and the production is stable.
2) The invention adopts the CSP thin slab continuous casting and rolling process, and the method has short production process, high unit operation speed and high production efficiency.
3) The metallographic structure of the steel for the welded pipe produced by the invention is as follows: the yield strength of the steel plate in production is 180-240MPa, the tensile strength is 340-400MPa, and the elongation is more than or equal to 40 percent.
Detailed Description
The following describes the embodiments of the present invention in detail with reference to the embodiments, but they are not intended to limit the present invention and are only examples. While the advantages of the invention will be apparent and readily appreciated by the description.
Example 1: the chemical components of the corresponding examples are shown in the table 1 according to the weight percentage, and the balance is Fe and other inevitable impurities; feeding the casting blank with the thickness of 70mm into a roller hearth soaking pit furnace, discharging at 1215 ℃, roughly rolling the casting blank by a high-pressure water descaler and a vertical rolling mill, finishing by a 7-stand continuous rolling mill, and rolling to obtain a 1.0mm thin plate, wherein the final rolling temperature is 815 ℃, and the coiling temperature is 615 ℃. The steel for welded pipes of example 1 was produced.
Example 2: the chemical components of the corresponding examples are shown in the table 1 according to the weight percentage, and the balance is Fe and other inevitable impurities; sending the casting blank with the thickness of 70mm into a roller hearth soaking pit furnace, discharging at 1230 ℃, passing through a high-pressure water descaler, roughly rolling by a vertical rolling mill, finely rolling by a 7-stand continuous rolling mill to obtain a 1.2mm thin plate, wherein the final rolling temperature is 815 ℃, and the coiling temperature is 620 ℃. The steel for welded pipes of example 2 was produced.
Example 3: the chemical components of the corresponding examples are shown in the table 1 according to the weight percentage, and the balance is Fe and other inevitable impurities; feeding the casting blank with the thickness of 70mm into a roller hearth soaking pit furnace, discharging at the temperature of 1235 ℃, roughly rolling the casting blank by a high-pressure water descaler and a vertical rolling mill, finishing by a 7-stand continuous rolling mill, rolling the casting blank to a 1.5mm thin plate, wherein the final rolling temperature is 825 ℃, and the coiling temperature is 625 ℃. The steel for welded pipes of example 3 was produced.
Example 4: the chemical components of the corresponding examples are shown in the table 1 according to the weight percentage, and the balance is Fe and other inevitable impurities; sending the casting blank with the thickness of 70mm into a roller hearth soaking pit furnace, discharging at 1230 ℃, roughly rolling the casting blank by a high-pressure water descaler and a vertical rolling mill, finishing by a 7-stand continuous rolling mill, and rolling to obtain a 1.8mm thin plate, wherein the final rolling temperature is 825 ℃ and the coiling temperature is 615 ℃. The steel for welded pipes of example 4 was produced.
Example 5: the chemical components of the corresponding examples are shown in the table 1 according to the weight percentage, and the balance is Fe and other inevitable impurities; feeding the casting blank with the thickness of 70mm into a roller hearth soaking pit furnace, discharging at the temperature of 1237 ℃, roughly rolling the casting blank by a high-pressure water descaler and a vertical rolling mill, finishing by a 7-stand continuous rolling mill, rolling the casting blank to a 1.2mm thin plate, wherein the final rolling temperature is 825 ℃ and the coiling temperature is 610 ℃. The steel for welded pipes of example 5 was produced.
Example 6: the chemical components of the corresponding examples are shown in the table 1 according to the weight percentage, and the balance is Fe and other inevitable impurities; feeding the casting blank with the thickness of 70mm into a roller hearth soaking pit furnace, discharging at the temperature of 1236 ℃, roughly rolling the casting blank by a high-pressure water descaler and a vertical rolling mill, finishing by a 7-stand continuous rolling mill, rolling the casting blank to a 1.2mm thin plate, wherein the final rolling temperature is 825 ℃ and the coiling temperature is 610 ℃. The steel for welded pipes of example 6 was produced.
Comparative example 1: the chemical components of the corresponding examples are shown in the table 1 according to the weight percentage, and the balance is Fe and other inevitable impurities; feeding the casting blank with the thickness of 70mm into a roller hearth soaking pit furnace, discharging at the temperature of 1235 ℃, roughly rolling the casting blank by a high-pressure water descaler and a vertical rolling mill, finishing by a 7-stand continuous rolling mill, rolling the casting blank to a 1.0mm thin plate, wherein the final rolling temperature is 825 ℃ and the coiling temperature is 618 ℃. The steel for welded pipes of comparative example 1 was prepared.
Comparative example 2: the chemical components of the corresponding examples are shown in the table 1 according to the weight percentage, and the balance is Fe and other inevitable impurities; sending the casting blank with the thickness of 70mm into a roller hearth soaking pit furnace, discharging at 1230 ℃, passing through a high-pressure water descaler, roughly rolling by a vertical rolling mill, finely rolling by a 7-stand continuous rolling mill to obtain a 1.2mm thin plate, wherein the final rolling temperature is 825 ℃, and the coiling temperature is 626 ℃. The steel for welded pipes of comparative example 2 was prepared.
Comparative example 3: the chemical components of the corresponding examples are shown in the table 1 according to the weight percentage, and the balance is Fe and other inevitable impurities; feeding the casting blank with the thickness of 70mm into a roller hearth soaking pit furnace, discharging at the temperature of 1231 ℃, roughly rolling the casting blank by a high-pressure water descaler and a vertical rolling mill, finishing by a 7-stand continuous rolling mill, rolling the casting blank to a 1.5mm thin plate, wherein the final rolling temperature is 825 ℃, and the coiling temperature is 625 ℃. The steel for welded pipes of comparative example 3 was prepared.
Table 1 examples chemical composition (w%)
The steel for welded pipes prepared in the examples 1 to 6 and the comparative examples 1 to 3 is detected, and the performance data of the steel product for welded pipes are obtained, and are shown in table 2.
TABLE 2 test results of the properties of the finished products
As can be seen from Table 2, the steel for welded pipes produced by the present invention has excellent mechanical properties, and meets the performance requirements of the steel for welded pipes in the current market.
While the invention has been described with reference to specific embodiments, it should be understood that various changes and modifications within the spirit and scope of the invention as disclosed herein may be suggested to one skilled in the art and that these changes and modifications are within the scope of the invention and are not in the spirit and purview of the appended claims.
Claims (7)
1. The low-cost high-strength steel for the welded pipe produced by the CSP process is characterized by comprising the following chemical components in percentage by weight: c is less than or equal to 0.003 percent, Mn: 0.35-0.45%, Si: 0.06-0.1%, P: 0.03-0.04%, S is less than or equal to 0.012%, Ti: 0.03-0.050%, Als: 0.02-0.045%, N is less than or equal to 0.0025%, B: 0.0002 to 0.0010 percent, and the balance of Fe and other inevitable impurities.
2. The steel for the low-cost high-strength welding pipe produced by the CSP process as claimed in claim 1, wherein the steel for the welding pipe has a yield strength of 180-240MPa, a tensile strength of 340-400MPa and an elongation of 40% or more.
3. A method for manufacturing a low-cost high-strength steel for welded pipes produced by the CSP process according to claim 1 or 2, characterized by adopting a CSP short process comprising: blast furnace iron making → molten iron pretreatment → converter smelting → RH treatment → corrugated plate blank continuous casting → soaking furnace → descaling → rough rolling → finish rolling → laminar cooling → coiling → finishing → inspection → packaging.
4. The method for manufacturing the steel for the low-cost high-strength welded pipe produced by the CSP process according to the claim 3, wherein the full-flow protective casting is adopted in the corrugated plate blank continuous casting process, the asbestos bowl protective casting is adopted for a long water gap during ladle replacement, and argon is introduced for a tundish water gap for protective casting.
5. The method for manufacturing a steel for a low-cost high-strength welded pipe according to the CSP process as claimed in claim 4, wherein the tundish is a dry tundish and an alkaline tundish covering agent.
6. The method for manufacturing the steel for the low-cost high-strength welding pipe produced by the CSP process as claimed in claim 3, wherein the charging temperature of the soaking pit is controlled to be 800-950 ℃, the time of the soaking pit is more than 15min, the temperature difference of the same plate after the soaking pit is taken out of the furnace is less than 20 ℃, and the temperature of the soaking pit after the soaking pit is taken out of the furnace is controlled to be 1230 +/-20 ℃.
7. The manufacturing method of steel for a low-cost high-strength welded pipe produced by the CSP process according to claim 3 or 6, characterized by: the finishing temperature is controlled at 820 +/-20 ℃.
The method for manufacturing a steel for a low-cost high-strength welded pipe produced by the CSP process according to claim 7, characterized by: the coiling temperature is controlled at 620 +/-20 ℃.
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