CN114525455A - Wire rod, preparation method thereof and prestressed concrete steel bar prepared from wire rod - Google Patents
Wire rod, preparation method thereof and prestressed concrete steel bar prepared from wire rod Download PDFInfo
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- CN114525455A CN114525455A CN202210168237.5A CN202210168237A CN114525455A CN 114525455 A CN114525455 A CN 114525455A CN 202210168237 A CN202210168237 A CN 202210168237A CN 114525455 A CN114525455 A CN 114525455A
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 70
- 239000010959 steel Substances 0.000 title claims abstract description 70
- 239000011513 prestressed concrete Substances 0.000 title claims abstract description 14
- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- 229910052742 iron Inorganic materials 0.000 claims abstract description 19
- 238000003756 stirring Methods 0.000 claims abstract description 15
- 238000005266 casting Methods 0.000 claims abstract description 9
- 239000012535 impurity Substances 0.000 claims abstract description 8
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 8
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 7
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 6
- 238000000034 method Methods 0.000 claims abstract description 6
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 5
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 5
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 4
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 36
- 238000007670 refining Methods 0.000 claims description 12
- 238000001816 cooling Methods 0.000 claims description 11
- 238000005096 rolling process Methods 0.000 claims description 11
- 238000009749 continuous casting Methods 0.000 claims description 10
- 238000004519 manufacturing process Methods 0.000 claims description 9
- 239000008186 active pharmaceutical agent Substances 0.000 claims description 7
- 238000005496 tempering Methods 0.000 claims description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- 238000003723 Smelting Methods 0.000 claims description 6
- 238000010438 heat treatment Methods 0.000 claims description 5
- 238000010791 quenching Methods 0.000 claims description 5
- 230000000171 quenching effect Effects 0.000 claims description 5
- 229910052786 argon Inorganic materials 0.000 claims description 3
- 238000007664 blowing Methods 0.000 claims description 3
- 230000003009 desulfurizing effect Effects 0.000 claims description 3
- 239000002994 raw material Substances 0.000 claims description 3
- 238000002791 soaking Methods 0.000 claims description 3
- 238000009987 spinning Methods 0.000 claims description 3
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 abstract description 20
- 230000003111 delayed effect Effects 0.000 abstract description 20
- 229910052739 hydrogen Inorganic materials 0.000 abstract description 20
- 239000001257 hydrogen Substances 0.000 abstract description 20
- 239000000126 substance Substances 0.000 abstract description 7
- 230000009286 beneficial effect Effects 0.000 abstract description 5
- 230000000052 comparative effect Effects 0.000 description 23
- 230000009931 harmful effect Effects 0.000 description 12
- 239000000047 product Substances 0.000 description 11
- 239000011572 manganese Substances 0.000 description 9
- 239000002244 precipitate Substances 0.000 description 8
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 7
- 239000000203 mixture Substances 0.000 description 7
- 239000004567 concrete Substances 0.000 description 5
- 230000007547 defect Effects 0.000 description 5
- SOIFLUNRINLCBN-UHFFFAOYSA-N ammonium thiocyanate Chemical compound [NH4+].[S-]C#N SOIFLUNRINLCBN-UHFFFAOYSA-N 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 4
- 230000009467 reduction Effects 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- 238000005728 strengthening Methods 0.000 description 4
- 238000004220 aggregation Methods 0.000 description 3
- 230000002776 aggregation Effects 0.000 description 3
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000006698 induction Effects 0.000 description 2
- 239000004615 ingredient Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 239000011593 sulfur Substances 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- 229910000859 α-Fe Inorganic materials 0.000 description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000004931 aggregating effect Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 230000001808 coupling effect Effects 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000009851 ferrous metallurgy Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
Classifications
-
- 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
-
- 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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
-
- 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
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/0075—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rods of limited length
-
- 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
-
- 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
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
-
- 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
-
- 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
- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
-
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
- Treatment Of Steel In Its Molten State (AREA)
Abstract
The invention discloses a wire rod, which comprises the following elements in percentage by mass: c: 0.28 to 0.33%, Si: 0.75 to 0.85%, Mn: 0.90-1.10%, Cr: 0.01 to 0.20%, Ti: 0.02-0.04%, N: 0.004-0.006 percent of Fe, less than or equal to 0.006 percent of S, less than or equal to 0.010 percent of P, less than or equal to 0.002 percent of O, and the balance of Fe and inevitable impurities. The invention also discloses a preparation method of the wire rod and a prestressed concrete steel bar prepared from the wire rod. The beneficial hydrogen traps are increased by improving the chemical components of the wire rod and controlling the mass ratio of Ti to N; adjusting casting process, limiting soft stirring time, pouring with low superheat degree, and controlling total amount and size of inclusions. The steel bar finally prepared by the method has high tensile strength and elongation after fracture, and has good delayed fracture resistance.
Description
Technical Field
The invention relates to the field of ferrous metallurgy, in particular to a wire rod, a preparation method thereof and a prestressed concrete steel bar prepared from the wire rod.
Background
The prestressed concrete pipe pile is an important building base material and plays a supporting role for the whole building. In the last thirty years, along with the rapid development of national economy, the application of the concrete pipe pile is greatly increased. The prestressed steel bars are the core framework of the concrete pipe pile, and determine the performance of the concrete pipe pile to a great extent.
Delayed fracture is a core problem that hinders the application of concrete pipe piles. During the manufacturing and using processes of the concrete pipe pile, water is contacted, the water gradually permeates to the surface of steel, a part of hydrogen atoms are formed through a series of electrochemical actions, the hydrogen atoms are diffused into steel and gradually gathered around the hydrogen traps, some large defects in the steel belong to harmful hydrogen traps, the hydrogen atoms gradually weaken the bonding force of the defects and a matrix after being gathered on the surface of the large defects, and catastrophic sudden fracture occurs under the stress lower than the yield strength of the steel after a period of time accumulation under the coupling action of prestress and the environment.
Delayed fracture generally occurs in high-strength steel of 1000MPa or more, and the higher the strength, the greater the tendency to be. The tensile strength of the prestressed steel bar is generally above 1400MPa, the prestressed steel bar belongs to a quenching and tempering structure, delayed fracture is easy to occur, and hidden danger is caused to buildings. In order to solve the problem of delayed fracture, the invention adopts measures of introducing a beneficial hydrogen trap, reducing harmful defects and the like, and obtains remarkable effect.
Chinese patent document CN110747404A discloses a 1570 MPa-level delayed fracture resistant steel bar and a manufacturing method thereof, wherein the steel bar is mainly used for a high-strength delayed fracture resistant PC steel bar and can meet the requirement of delayed fracture resistance under the strength level of 1570MPa by improving the content of Si element, reasonably adding metal element Ti and adjusting the hot rolling and cooling control and steel bar production processes; although the Ti element is added to form an effective hydrogen trap and inhibit the delayed fracture tendency of the steel rod, the mass fraction of the Ti element is 0.05-0.08% or 0.06-0.08%, and the content is slightly higher, so that the coarsening effect of the precipitate can not be achieved, large-grain TiN inclusion can be formed, the wire rod drawing is not facilitated, and the method is not economical. Chinese patent document CN102703804A discloses a method for producing a wire rod for a high-strength prestressed steel rod, which comprises blast furnace smelting, converter smelting, LF ladle refining, and billet rolling, wherein silicon and manganese are used as main strengthening elements, and the emphasis is to improve the strength of the wire rod, and there is no content related to improving the delayed fracture performance of the steel rod. Chinese patent document CN110527917A discloses a 30MnSiBCa hot-rolled wire rod for PC steel rods and a preparation method thereof, wherein B and Ca elements are added into the 30MnSiBCa hot-rolled wire rod, and the proportion of B to Cr, Mn and Si and the content of Ca and B are controlled to improve the hardenability and the delayed fracture resistance of the wire rod.
Disclosure of Invention
Therefore, the technical problem to be solved by the invention is the defect of poor delayed fracture resistance of the existing prestressed steel bar, so that the wire rod, the preparation method thereof and the prestressed concrete steel bar prepared by the wire rod are provided.
Therefore, the invention adopts the following technical scheme:
the invention provides a wire rod, which comprises the following elements in percentage by mass:
c: 0.28 to 0.33%, Si: 0.75 to 0.85%, Mn: 0.90-1.10%, Cr: 0.01 to 0.20%, Ti: 0.02-0.04%, N: 0.004-0.006 percent of Fe, less than or equal to 0.006 percent of S, less than or equal to 0.010 percent of P, less than or equal to 0.002 percent of O, and the balance of Fe and inevitable impurities.
Further, the mass ratio of Ti to N is 5-7.
Furthermore, the grades of A, B, C, D, DS inclusions in the nonmetallic inclusions of the wire rod are all less than or equal to 1.0 grade; the sum of the grades A + B + C + D + DS of the five types of impurities is less than or equal to 3.0 grade, and the length-width product of the largest impurity is less than or equal to 1000 mu m2The density of inclusions with the equivalent diameter of more than 10 mu m is less than or equal to 10/cm2。
The invention also provides a preparation method of the wire rod, which comprises the following steps:
s1: pre-desulfurizing the raw material molten iron to ensure that the sulfur content is less than 50 ppm;
s2: smelting the desulfurized molten iron in a converter;
s3: refining the molten iron smelted by the converter;
s4: continuously casting molten steel square billets obtained after refining;
s5: carrying out high speed wire rolling on the obtained casting blank;
s6: and (4) carrying out stelmor controlled cooling on the obtained crude wire rod to obtain a wire rod finished product.
Further, in step S3, the molten iron is subjected to soft stirring after refining, the pressure of the soft stirring bottom blowing argon is 0.5-0.6MPa, and the time is 30-35min, so as to ensure that the inclusions float up sufficiently.
In step S4, pouring with a tundish is adopted for induction heating to ensure low superheat degree pouring, so that the temperature of molten steel is kept above liquidus temperature (varied according to different components, about 1495 ℃) by 15-25 ℃, and the aggregation and the enlargement of inclusions are prevented; adopts a submerged nozzle to carry out full-protection pouring, and the continuous casting is 140 multiplied by 140mm2Controlling the drawing speed of the small square billet to be 2.6 +/-0.1 m/min during continuous casting; meanwhile, crystallizer electromagnetic stirring and tail end electromagnetic stirring are adopted.
Step S5, before rolling, heating the casting blank, wherein the soaking temperature is 1160 +/-10 ℃, the initial rolling temperature is 1030 +/-10 ℃, and the spinning temperature is 870 +/-10 ℃;
in step S6, the entrance speed of the cooling control roller way is 0.43-0.48m/S, the cooling control environment is room temperature, all fans are closed, the diameter of the finally obtained wire rod is 8-14mm, the tensile strength Rm is more than or equal to 700MPa, and the reduction of area Z is more than or equal to 50%.
The invention also provides a prestressed concrete steel bar which is prepared from the wire rod.
The preparation method of the prestressed concrete steel bar comprises the steps of drawing and quenching a wire rod, and then tempering to obtain the prestressed concrete steel bar.
Further, specifically, the wire rod is drawn into a steel rod with the diameter of 7-13mm and then quenched, wherein the quenching temperature is 900-; then carrying out tempering treatment at the temperature of 440-460 ℃ for 1-3s, wherein the microstructure of the finally obtained product is tempered troostite.
The technical scheme of the invention has the following advantages:
(1) the invention defines the elemental composition in a wire rod, wherein:
c is the most basic strengthening element in steel, the strength of the wire rod is increased by about 10MPa when the content of C is increased by 0.01 percent, but excessive C can reduce the plasticity of the wire rod and deteriorate the processing and welding performance. Therefore, the range of C content in the present invention is strictly limited to 0.28 to 0.33%.
Si is a ferrite strengthening element and can increase the strength of ferrite by solid solution strengthening, and Si is also an important deoxidizer and contributes to reduction of the oxygen content in steel and inclusion reduction. Meanwhile, Si can improve the thermal stability of the structure, weaken the strength reduction degree caused by the rise of the tempering temperature, improve the controllability of the performance of the steel bar and is beneficial to improving the delayed fracture resistance of the steel bar. But too much Si reduces the wire rod plasticity. The Si content range in the invention is selected to be 0.75-0.85%.
Mn is mainly used for increasing the strength of steel and simultaneously improving hardenability, and can change sulfide components and reduce the harmful effect of S, but excessive Mn can reduce the plasticity and weldability of wire rods and increase the delayed fracture sensitivity of steel. In the invention, the content of Mn is controlled to be 0.90-1.10%.
Cr can further improve the hardenability and the finished product strength and the tempering resistance of the steel bar. But excessive Cr also reduces the plasticity and weldability of the wire rod. The product performance and cost factors are comprehensively considered, and the Cr content is controlled to be 0.01-0.20%.
Ti is an important microalloy element, forms fine Ti (C, N) precipitates in steel, becomes a beneficial hydrogen trap in the steel, prevents hydrogen atoms from aggregating to a harmful hydrogen trap, and improves the delayed fracture resistance of the steel bar. However, too high Ti coarsens precipitates, which is disadvantageous in the smooth continuous casting. In the invention, the Ti content is controlled to be 0.02-0.04%.
N is a gas element in steel, and mainly combines with Ti to form fine precipitates, and the formation of the fine precipitates is not facilitated when the content of N is too high or too low, wherein the content of N is controlled to be 0.004-0.006%.
S and Mn are combined to form MnS large inclusions which are often the starting points of hydrogen induced cracks and can increase the delayed fracture sensitivity of the steel bar; p is a harmful element in steel, is easy to segregate, is enriched at a crystal boundary to cause embrittlement of steel, reduces plasticity and deteriorates welding performance; o is a major source of inclusions in steel and is one of the main causes of the formation of harmful hydrogen traps. Therefore, the content of S, P, O must be strictly controlled so that S is less than or equal to 0.006 percent, P is less than or equal to 0.010 percent and O is less than or equal to 0.002 percent.
(2) The present invention further defines the mass ratio of Ti to N to be 5 to 7, which can secure Ti (C, N) precipitates having a large number and a small size. The Ti (C, N) fine precipitates can pin the grain boundary, prevent austenite grains from growing, increase the area of the grain boundary and hinder the diffusion of hydrogen atoms in steel, and meanwhile, the Ti (C, N) precipitates can become beneficial hydrogen traps in the steel, capture and absorb hydrogen to prevent the hydrogen from diffusing, hinder the hydrogen atoms from gathering to harmful hydrogen traps, reduce the concentration of the hydrogen at the harmful hydrogen traps and achieve the purpose of improving the delayed fracture resistance of the steel rod.
(3) The present invention defines the size of the non-metallic inclusions in the wire rod. Non-metallic inclusions, particularly large inclusions, are important sources of harmful hydrogen traps, hydrogen atoms are highly enriched in local regions of the harmful hydrogen traps, and after the hydrogen concentration of the enriched regions reaches a critical value, the bonding force of the inclusions and steel bases is destroyed, cracks are formed and expanded, and the inclusions are broken under the stress lower than the yield strength of steel. The invention limits the rating of A, B, C, D, DS types of inclusions to be less than or equal to 1.0 grade, the sum of the ratings of five types of inclusions, namely A + B + C + D + DS, is less than or equal to 3.0 grades, and the length-width product of the largest inclusion is less than or equal to 1000 mu m2The density of inclusions with the equivalent diameter of more than 10 mu m is less than or equal to 10/cm2The number of harmful hydrogen traps can be effectively reduced, and the delayed fracture resistance of the steel bar is improved.
(4) The invention optimizes the preparation method of the wire rod, the production flow of the wire rod sequentially passes through the technical processes of 'molten iron pre-desulfurization → converter smelting → refining → square billet continuous casting → high-speed wire rolling → stelmor controlled cooling', and the like, particularly the soft stirring time after refining is controlled within 30-35min, so that the inclusions are ensured to float sufficiently, the continuous casting superheat degree is controlled within 15-25 ℃ (the liquidus temperature is about 1495 ℃), the aggregation and the enlargement of the inclusions are prevented, the sizes of the inclusions are controlled, the number of harmful hydrogen traps is reduced, and the delayed fracture resistance of the steel rod is improved.
(5) The steel bar prepared by the wire rod provided by the invention has good delayed fracture resistance on the basis that the tensile strength Rm-b is more than or equal to 1500MPa and the elongation A after fracture is more than or equal to 10%.
Detailed Description
The following examples are provided to further understand the present invention, not to limit the scope of the present invention, but to provide the best mode, not to limit the content and the protection scope of the present invention, and any product similar or similar to the present invention, which is obtained by combining the present invention with other prior art features, falls within the protection scope of the present invention.
The examples do not show the specific experimental steps or conditions, and can be performed according to the conventional experimental steps described in the literature in the field. The reagents or instruments used are not indicated by manufacturers, and are all conventional reagent products which can be obtained commercially.
Examples
The embodiment provides a preparation method of a wire rod, which comprises the following specific steps:
(1) pre-desulfurizing the raw material molten iron to ensure that the sulfur content is less than 50 PPM;
(2) smelting the desulfurized molten iron in a converter;
(3) refining the molten iron after the converter, and carrying out soft stirring on the molten iron after the refining, wherein the pressure of argon blowing at the bottom of the soft stirring is 0.5MPa, and the time is 30min, so that impurities are ensured to float sufficiently;
(4) continuously casting the refined molten iron square billet, and adopting tundish induction heating to ensure low superheat degree pouring, so that the temperature of the molten iron square billet is 20 ℃ above the solidification point of the molten iron, and the aggregation and enlargement of inclusions are prevented; adopts a submerged nozzle to carry out full-protection pouring, and the continuous casting is 140 multiplied by 140mm2Controlling the drawing speed to be 2.6m/min during continuous casting of the small square billet; meanwhile, crystallizer electromagnetic stirring and tail end electromagnetic stirring are adopted.
(5) And (3) carrying out high-speed wire rolling on the obtained casting blank, heating the casting blank before rolling, wherein the soaking temperature is 1160 ℃, the initial rolling temperature is 103 ℃, and the spinning temperature is 870 ℃.
(6) And (3) carrying out stelmor controlled cooling on the obtained coarse wire rod, wherein the inlet speed of a controlled cooling roller way is 0.45m/s, the controlled cooling environment is room temperature, all fans are closed, and the diameter of the finally obtained wire rod is 10 mm.
The chemical composition of the wire rod obtained in the examples is shown in table 1:
TABLE 1 wire rod chemical composition
| Ingredient/wt% | C | Si | Mn | P | S | Cr | Ti | O | N | Ti/N |
| Example 1 | 0.31 | 0.82 | 0.95 | 0.0090 | 0.0045 | 0.06 | 0.028 | 0.0018 | 0.0045 | 6.22 |
| Example 2 | 0.30 | 0.79 | 0.98 | 0.0079 | 0.0050 | 0.07 | 0.031 | 0.0010 | 0.0048 | 6.46 |
| Example 3 | 0.29 | 0.80 | 1.01 | 0.0082 | 0.0042 | 0.07 | 0.032 | 0.0014 | 0.0052 | 6.15 |
| Example 4 | 0.32 | 0.80 | 0.99 | 0.0084 | 0.0047 | 0.05 | 0.030 | 0.0008 | 0.0048 | 6.25 |
Comparative example 1
This comparative example is different from the examples in that the final chemical composition of the wire rod was changed so that Ti/N was 2.74.
Comparative example 2
This comparative example is different from the examples in that the final chemical composition of the wire rod was changed so that Ti/N was 8.63.
Comparative example 3
This comparative example is different from the examples in that the soft stirring time in refining was changed to 10 min.
Comparative example 4
Compared with the embodiment, the difference of the comparative example is that the superheat degree during continuous casting is changed, and the temperature of molten steel is 30 ℃ above the liquidus.
The chemical compositions of the wire rods obtained in comparative examples 1 to 4 are shown in table 2:
TABLE 2 wire rod chemical composition
| Ingredient/wt% | C | Si | Mn | P | S | Cr | Ti | O | N | Ti/N |
| Comparative example 1 | 0.30 | 0.81 | 0.95 | 0.0093 | 0.0056 | 0.06 | 0.017 | 0.0017 | 0.0062 | 2.74 |
| Comparative example 2 | 0.29 | 0.78 | 0.99 | 0.0084 | 0.0045 | 0.07 | 0.044 | 0.0015 | 0.0051 | 8.63 |
| Comparative example 3 | 0.30 | 0.80 | 0.98 | 0.0095 | 0.0051 | 0.05 | 0.030 | 0.0016 | 0.0045 | 6.67 |
| Comparative example 4 | 0.31 | 0.79 | 0.97 | 0.0089 | 0.0046 | 0.07 | 0.030 | 0.0018 | 0.0044 | 6.82 |
Test example 1
The inclusions in the wire rods obtained in the examples and the comparative examples are detected, the detection standard is GB/T10561-2005, and the detection results are shown in the following table 3:
TABLE 3 wire rod inclusions
As can be seen from the above table, in the embodiment of the invention, the grades of the A, B, C, D, DS types of inclusions are all less than or equal to 1.0 grade, the sum of the grades of the five types of inclusions A + B + C + D + DS is less than or equal to 3.0 grade, and the length-width product of the largest inclusion is less than or equal to 1000 mu m2The density of inclusions with the equivalent diameter of more than 10 mu m is less than or equal to 10/cm2. Comparative examples 1 and 2 are similar to the present application in inclusion status, while comparative examples 3 and 4 are clearly unsatisfactory in inclusion status because the conditions defined in the present application are not satisfied in soft stirring time and degree of superheat, respectively.
Test example 2
The steel wire rods for prestressed concrete prepared from the wire rods obtained in the examples and the comparative example 1 are specifically prepared by the following steps:
and drawing the wire rod into a steel rod with the diameter of 8mm, quenching at 920 ℃ for 1s, and then tempering at 450 ℃ for 1s to finally obtain the prestressed concrete steel rod.
The properties of the wire rod and the steel bar prepared by the wire rod are detected according to GB/T21839-2019, and the results are shown in the following table 4:
TABLE 4 Main Properties of wire rod and Steel bar
Obviously, as can be seen from the above table, the critical stress values of the steel bar in the embodiment of the invention when the steel bar is constantly loaded in the ammonium thiocyanate solution for 5 hours are all more than or equal to 0.80Rm-b, and the requirement that the prestressed product is loaded with tensile stress of 0.80Rm-b and does not break when the prestressed product lasts for 5 hours in the ammonium thiocyanate solution is met; the steel bars in the comparative examples are different from the steel bars in the comparative examples 1 and 2, the Ti/N ratio of which does not meet the requirements of the application, or the steel bars in the comparative examples 3 and 4, the soft stirring time of which is too short, and the comparative examples 4, the critical stress value of which is less than 0.80Rm-b when the steel bars are constantly loaded in an ammonium thiocyanate solution for 5 hours, show that the tensile stress loaded on the steel bars in the comparative examples 0.80Rm-b lasts for less than 5 hours in the ammonium thiocyanate solution, and the stress corrosion resistance of each pair of the comparative examples is poor.
The above examples are merely illustrative for clarity and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. This need not be, nor should it be exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.
Claims (10)
1. A wire rod is characterized by comprising the following elements in percentage by mass:
c: 0.28 to 0.33%, Si: 0.75 to 0.85%, Mn: 0.90-1.10%, Cr: 0.01 to 0.20%, Ti: 0.02-0.04%, N: 0.004-0.006 percent of Fe, less than or equal to 0.006 percent of S, less than or equal to 0.010 percent of P, less than or equal to 0.002 percent of O, and the balance of Fe and inevitable impurities.
2. A wire rod according to claim 1, wherein the mass ratio of Ti and N is 5 to 7.
3. A wire rod according to claim 1 or 2, wherein among the non-metallic inclusions of the wire rod, the A, B, C, D, DS-type inclusions are rated no more than 1.0; the sum of the grades A + B + C + D + DS of the five types of impurities is less than or equal to 3.0 grade, and the length-width product of the largest impurity is less than or equal to 1000 mu m2The density of inclusions with the equivalent diameter of more than 10 mu m is less than or equal to 10/cm2。
4. A method for preparing a wire rod according to any one of claims 1 to 3, comprising the steps of:
s1: pre-desulfurizing raw material molten iron;
s2: smelting the desulfurized molten iron in a converter;
s3: refining the molten iron smelted by the converter;
s4: continuously casting molten steel square billets obtained after refining;
s5: carrying out high speed wire rolling on the obtained casting blank;
s6: and (4) carrying out stelmor controlled cooling on the obtained crude wire rod to obtain a wire rod finished product.
5. The manufacturing method according to claim 4, wherein in step S3, the molten iron is subjected to soft stirring after refining, and the pressure of the soft stirring argon blowing at the bottom is 0.5-0.6MPa for 30-35 min.
6. The production method according to claim 5, wherein in step S4, the continuous casting is conducted with a low superheat degree of 140X 140mm2Controlling the drawing speed of the small square billet to be 2.6 +/-0.1 m/min during continuous casting.
7. The preparation method according to claim 6, wherein the step S5 further comprises heating the cast slab before rolling, wherein the soaking temperature is 1160 +/-10 ℃, the rolling temperature is 1030 +/-10 ℃, and the spinning temperature is 870 +/-10 ℃;
in step S6, the entrance speed of the controlled cooling roller path is 0.43-0.48m/S, the controlled cooling environment is room temperature, all fans are closed, and the diameter of the finally obtained wire rod is 8-14 mm.
8. A prestressed concrete steel bar produced from the wire rod according to any one of claims 1 to 3 or the wire rod produced by the production method according to any one of claims 4 to 7.
9. The method for manufacturing a prestressed concrete steel bar according to claim 8, wherein the prestressed concrete steel bar is manufactured by drawing, quenching, and tempering a wire rod.
10. The preparation method as claimed in claim 9, wherein the steel rod with the diameter of 7-13mm is drawn and quenched at 900-950 ℃ for 1-3s, and then is tempered at 440-460 ℃ for 1-3 s.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH07268547A (en) * | 1994-03-30 | 1995-10-17 | Nippon Steel Corp | High strength pc steel bar and its production |
| JP2000026919A (en) * | 1998-07-10 | 2000-01-25 | Kawasaki Steel Corp | Production of pc steel rod |
| CN107955914A (en) * | 2017-11-30 | 2018-04-24 | 攀钢集团攀枝花钢铁研究院有限公司 | Steel wire rod and its LF stove production methods are built containing Ti, Cr microalloy |
| CN111378901A (en) * | 2020-05-15 | 2020-07-07 | 武钢集团昆明钢铁股份有限公司 | Special base metal wire rod for 1420 MPa-level PC steel rod and preparation method thereof |
-
2022
- 2022-02-23 CN CN202210168237.5A patent/CN114525455B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH07268547A (en) * | 1994-03-30 | 1995-10-17 | Nippon Steel Corp | High strength pc steel bar and its production |
| JP2000026919A (en) * | 1998-07-10 | 2000-01-25 | Kawasaki Steel Corp | Production of pc steel rod |
| CN107955914A (en) * | 2017-11-30 | 2018-04-24 | 攀钢集团攀枝花钢铁研究院有限公司 | Steel wire rod and its LF stove production methods are built containing Ti, Cr microalloy |
| CN111378901A (en) * | 2020-05-15 | 2020-07-07 | 武钢集团昆明钢铁股份有限公司 | Special base metal wire rod for 1420 MPa-level PC steel rod and preparation method thereof |
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