CN116275914A - Production method of fireproof steel bar mechanical connecting sleeve - Google Patents
Production method of fireproof steel bar mechanical connecting sleeve Download PDFInfo
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- CN116275914A CN116275914A CN202310347980.1A CN202310347980A CN116275914A CN 116275914 A CN116275914 A CN 116275914A CN 202310347980 A CN202310347980 A CN 202310347980A CN 116275914 A CN116275914 A CN 116275914A
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 83
- 239000010959 steel Substances 0.000 title claims abstract description 83
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 29
- 238000010791 quenching Methods 0.000 claims abstract description 38
- 230000000171 quenching effect Effects 0.000 claims abstract description 38
- 238000010079 rubber tapping Methods 0.000 claims abstract description 31
- 238000005496 tempering Methods 0.000 claims abstract description 21
- 238000001125 extrusion Methods 0.000 claims abstract description 15
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 12
- 229910052802 copper Inorganic materials 0.000 claims abstract description 9
- 229910052720 vanadium Inorganic materials 0.000 claims abstract description 8
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 7
- 239000012535 impurity Substances 0.000 claims abstract description 6
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 6
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 6
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 5
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 5
- 238000000034 method Methods 0.000 claims description 62
- 230000008569 process Effects 0.000 claims description 49
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 38
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 34
- 238000001816 cooling Methods 0.000 claims description 34
- 238000010438 heat treatment Methods 0.000 claims description 27
- 238000009749 continuous casting Methods 0.000 claims description 23
- 238000005096 rolling process Methods 0.000 claims description 23
- 239000002893 slag Substances 0.000 claims description 20
- 239000000126 substance Substances 0.000 claims description 19
- 229910052786 argon Inorganic materials 0.000 claims description 17
- 239000010949 copper Substances 0.000 claims description 17
- 238000006477 desulfuration reaction Methods 0.000 claims description 17
- 230000023556 desulfurization Effects 0.000 claims description 17
- 229910052742 iron Inorganic materials 0.000 claims description 17
- 238000007670 refining Methods 0.000 claims description 16
- 238000003723 Smelting Methods 0.000 claims description 14
- 239000000203 mixture Substances 0.000 claims description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 12
- 238000003756 stirring Methods 0.000 claims description 11
- 238000005275 alloying Methods 0.000 claims description 9
- 238000004321 preservation Methods 0.000 claims description 9
- 235000008733 Citrus aurantifolia Nutrition 0.000 claims description 6
- 229910000519 Ferrosilicon Inorganic materials 0.000 claims description 6
- 235000011941 Tilia x europaea Nutrition 0.000 claims description 6
- 238000009826 distribution Methods 0.000 claims description 6
- 239000004571 lime Substances 0.000 claims description 6
- 239000011572 manganese Substances 0.000 claims description 6
- 150000003839 salts Chemical class 0.000 claims description 6
- 238000007711 solidification Methods 0.000 claims description 6
- 230000008023 solidification Effects 0.000 claims description 6
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 4
- 238000005266 casting Methods 0.000 claims description 4
- 239000003795 chemical substances by application Substances 0.000 claims description 4
- 239000004973 liquid crystal related substance Substances 0.000 claims description 4
- 150000004767 nitrides Chemical class 0.000 claims description 4
- 229910000604 Ferrochrome Inorganic materials 0.000 claims description 3
- 229910000616 Ferromanganese Inorganic materials 0.000 claims description 3
- 229910000592 Ferroniobium Inorganic materials 0.000 claims description 3
- 229910001200 Ferrotitanium Inorganic materials 0.000 claims description 3
- 229910001199 N alloy Inorganic materials 0.000 claims description 3
- SKKMWRVAJNPLFY-UHFFFAOYSA-N azanylidynevanadium Chemical compound [V]#N SKKMWRVAJNPLFY-UHFFFAOYSA-N 0.000 claims description 3
- 229910021538 borax Inorganic materials 0.000 claims description 3
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 claims description 3
- 239000010436 fluorite Substances 0.000 claims description 3
- 230000006698 induction Effects 0.000 claims description 3
- DALUDRGQOYMVLD-UHFFFAOYSA-N iron manganese Chemical compound [Mn].[Fe] DALUDRGQOYMVLD-UHFFFAOYSA-N 0.000 claims description 3
- 239000007788 liquid Substances 0.000 claims description 3
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 claims description 3
- 230000001105 regulatory effect Effects 0.000 claims description 3
- 238000007789 sealing Methods 0.000 claims description 3
- 238000002791 soaking Methods 0.000 claims description 3
- 239000004328 sodium tetraborate Substances 0.000 claims description 3
- 235000010339 sodium tetraborate Nutrition 0.000 claims description 3
- 230000002787 reinforcement Effects 0.000 claims 1
- 229910000859 α-Fe Inorganic materials 0.000 description 27
- 229910001562 pearlite Inorganic materials 0.000 description 15
- 239000011150 reinforced concrete Substances 0.000 description 14
- 230000006872 improvement Effects 0.000 description 11
- 229910001563 bainite Inorganic materials 0.000 description 10
- 229910045601 alloy Inorganic materials 0.000 description 9
- 239000000956 alloy Substances 0.000 description 9
- 238000005728 strengthening Methods 0.000 description 9
- 239000002245 particle Substances 0.000 description 7
- 238000001556 precipitation Methods 0.000 description 7
- 230000001276 controlling effect Effects 0.000 description 6
- 238000013461 design Methods 0.000 description 6
- 230000009970 fire resistant effect Effects 0.000 description 5
- 238000012545 processing Methods 0.000 description 5
- 230000009466 transformation Effects 0.000 description 5
- 229910001566 austenite Inorganic materials 0.000 description 4
- 239000006104 solid solution Substances 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 3
- 238000001514 detection method Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000002349 favourable effect Effects 0.000 description 3
- 230000009471 action Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000001953 recrystallisation Methods 0.000 description 2
- 238000000137 annealing Methods 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000011246 composite particle Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000003009 desulfurizing effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- ZFGFKQDDQUAJQP-UHFFFAOYSA-N iron niobium Chemical compound [Fe].[Fe].[Nb] ZFGFKQDDQUAJQP-UHFFFAOYSA-N 0.000 description 1
- 238000005272 metallurgy Methods 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 238000003908 quality control method Methods 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
- B23P15/00—Making specific metal objects by operations not covered by a single other subclass or a group in this subclass
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B19/00—Tube-rolling by rollers arranged outside the work and having their axes not perpendicular to the axis of the work
- B21B19/02—Tube-rolling by rollers arranged outside the work and having their axes not perpendicular to the axis of the work the axes of the rollers being arranged essentially diagonally to the axis of the work, e.g. "cross" tube-rolling ; Diescher mills, Stiefel disc piercers or Stiefel rotary piercers
- B21B19/04—Rolling basic material of solid, i.e. non-hollow, structure; Piercing, e.g. rotary piercing mills
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C19/00—Devices for straightening wire or like work combined with or specially adapted for use in connection with drawing or winding machines or apparatus
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C23/00—Extruding metal; Impact extrusion
- B21C23/21—Presses specially adapted for extruding metal
-
- 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
- C21D1/34—Methods of heating
- C21D1/42—Induction heating
-
- 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
- C21D1/62—Quenching devices
- C21D1/63—Quenching devices for bath quenching
-
- 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
- C21D11/00—Process control or regulation for heat treatments
-
- 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
- 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
-
- 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
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
-
- 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
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
-
- 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
-
- 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
- C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
-
- 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
-
- 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
- Y02P10/25—Process efficiency
Abstract
The invention discloses a production method of a fireproof steel bar mechanical connecting sleeve, which comprises the steps of wire rod drawing and straightening, extrusion molding, thread tapping, gradient quenching and low-temperature tempering to prepare the sleeve; in the wire rod, 0.35 to 0.42 percent of C, 0.12 to 0.25 percent of Si, 1.6 to 2.0 percent of Mn, 0.25 to 0.35 percent of Cr, 0.10 to 0.15 percent of Nb, 0.04 to 0.08 percent of V, 0.02 to 0.05 percent of Ti, 0.15 to 0.25 percent of Cu, 0.001 to 0.003 percent of B, less than or equal to 0.02 percent of P, less than or equal to 0.02 percent of S, 0.01 to 0.02 percent of N, and the balance of Fe and impurities; FRE= [ Nb ] +1.5[ Cr ] +0.8[ V ] +0.5[ Ti ] +0.1[ Cu ], FRE is 0.60-0.75%, and the obtained sleeve has excellent mechanical performance and fireproof performance.
Description
Technical Field
The invention belongs to the technical field of metallurgy, and relates to a production method of a mechanical connecting sleeve of a refractory steel bar.
Background
With the development of society and the progress of science and technology, reinforced concrete structure buildings gradually develop to large and high-rise directions, and the requirements on the fireproof performance of the reinforced concrete structure buildings are continuously improved based on the safety performance. A large number of hot-rolled steel bars are usually adopted in the reinforced concrete structure, and the GB/T37622-2019 hot-rolled refractory steel bars for reinforced concrete has stipulated the refractory properties of the hot-rolled steel bars in the reinforced concrete structure at present.
However, it is far from sufficient to use only hot-rolled steel bars with fire-resistant properties, and in the actual construction process, it is often necessary to mechanically connect the hot-rolled steel bars by using a steel bar mechanical connection sleeve, and when a fire occurs, the stability and the use safety of the reinforced concrete structure will be seriously affected once the sleeve fails. It is therefore desirable to produce a reinforced mechanical joint sleeve having fire resistance and excellent toughness.
Disclosure of Invention
The invention aims to provide a production method of a fireproof steel bar mechanical connecting sleeve.
In order to achieve one of the above objects, an embodiment of the present invention provides a method for producing a mechanical connection sleeve for refractory steel bars, in which a wire rod is manufactured into a sleeve through drawing straightening, extrusion forming, thread tapping, gradient quenching and low-temperature tempering processes; wherein, the liquid crystal display device comprises a liquid crystal display device,
the wire rod comprises the following chemical components in percentage by mass: 0.35 to 0.42 percent of C, 0.12 to 0.25 percent of Si, 1.6 to 2.0 percent of Mn, 0.25 to 0.35 percent of Cr, 0.10 to 0.15 percent of Nb, 0.04 to 0.08 percent of V, 0.02 to 0.05 percent of Ti, 0.15 to 0.25 percent of Cu, 0.001 to 0.003 percent of B, less than or equal to 0.02 percent of P, less than or equal to 0.02 percent of S, 0.01 to 0.02 percent of N, and the balance of Fe and unavoidable impurities; fire resistance index FRE= [ Nb ] +1.5[ Cr ] +0.8[ V ] +0.5[ Ti ] +0.1[ Cu ], FRE is 0.60-0.75%;
in the drawing and straightening process, the wire rod is drawn to a set size and then sent to a straightener for straightening, and then cut and finished according to the set sleeve length to obtain a sleeve blank;
in the extrusion forming process, perforating the sleeve blank subjected to drawing straightening, and performing equal 6-angle, equal 8-angle or equal 12-angle extrusion forming according to the diameter of the sleeve after perforating;
in the thread tapping procedure, an automatic tapping machine is utilized to perform thread tapping on the sleeve blank after extrusion molding, and the thread angle is 75 degrees.
As a further improvement of an embodiment of the invention, in the gradient quenching procedure, the sleeve after tapping the screw thread is subjected to induction heating, the heating temperature is 900-950 ℃, and the heating time is 3-5 min; then the mixture enters a first salt bath furnace for isothermal quenching, wherein the quenching temperature is 600-680 ℃ and the quenching time is 10-25 min; then transferring the mixture into a second salt bath furnace for isothermal quenching, wherein the quenching temperature is 400-460 ℃, and the quenching time is 8-15 min; then oil quenching is carried out, wherein the temperature of quenching oil is 30-50 ℃, and the cooling speed is 0.1-0.5 ℃/s.
As a further improvement of an embodiment of the invention, in the low-temperature tempering process, the sleeve after gradient quenching is sent into a muffle furnace for tempering, the tempering temperature is 200-250 ℃, the tempering time is 20-40 min, and the sleeve is left in the muffle furnace for cooling to room temperature after tempering, wherein the cooling speed is less than or equal to 1 ℃/s.
As a further improvement of an embodiment of the invention, the wire rod is prepared by sequentially performing molten iron pre-desulfurization, electric furnace smelting, LF refining, continuous casting, heating, controlled rolling and controlled cooling procedures.
As a further improvement of an embodiment of the invention, in the molten iron pre-desulfurization procedure, the KR method pre-desulfurization is carried out on the blast furnace molten iron, S in the molten iron at the desulfurization end point is less than or equal to 0.01%, and the skimming rate of desulfurization slag is more than or equal to 98%;
in the electric furnace smelting process, scrap steel and pre-desulfurized blast furnace molten iron are sequentially added into an electric furnace, wherein the scrap steel accounts for more than or equal to 75 percent, C in molten steel at the smelting end point of the electric furnace is less than or equal to 0.15 percent, P is less than or equal to 0.015 percent, the tapping temperature is 1595-1625 ℃, argon is blown into a ladle in the whole process of tapping, and the flow of argon blown into the ladle is 200-250L/min; and after tapping 1/5, sequentially adding ferrosilicon nitride, ferrosilicon manganese, ferromanganese, high-carbon ferrochromium, copper blocks and lime for deoxidization alloying.
As a further improvement of an embodiment of the invention, in the LF refining process, after molten steel obtained in the electric furnace smelting process is injected into an LF furnace, 2.4-3.8 kg of lime and 0.8-1.2 kg of fluorite are added into each ton of molten steel to turn yellow slag, and then the materials are electrified and heated and are stirred for 5-8 min, and the flow rate of argon blown from the bottom of a ladle during soft stirring is 150-200L/min; and after regulating the alkalinity of refining slag to 2.0-2.5, sequentially adding borax, vanadium-nitrogen alloy, ferrocolumbium and ferrotitanium for alloying, wherein the flow of argon blown into the ladle bottom during alloying is 250-300L/min, and the tapping temperature at the LF refining end point is 1550-1580 ℃.
As a further improvement of an embodiment of the invention, in the continuous casting process, the temperature of a tundish is 1525-1550 ℃, a large ladle long nozzle, a sealing gasket, a submerged nozzle and an alkaline tundish covering agent are adopted for full protection casting in the continuous casting process, argon is blown from the long nozzle in the whole process, the covering slag adopts low-carbon covering slag, and the slag thickness is 8-10 mm; the water distribution flow of a crystallizer for solidifying a cold area is 1800-2400L/min, and the temperature difference between a water outlet and a water inlet of the crystallizer is less than 10 ℃; electromagnetic stirring is adopted in the solidification secondary cooling zone, the electromagnetic stirring frequency is 3-5 Hz, the fluctuation of the liquid level is controlled within +/-2 mm, the water distribution flow of a crystallizer in the solidification secondary cooling zone is 500-800L/min, and the continuous casting drawing speed is 2.2-2.5 m/min.
As a further improvement of an embodiment of the invention, in the heating process, the heating temperature is 1150-1220 ℃, the total heating time is 60-90 min, and the soaking period time is more than or equal to 40min.
As a further improvement of an embodiment of the invention, in the rolling control process, the continuous casting billet after the heating process is rolled into a wire rod and is collected into a coil, the starting rolling temperature is more than or equal to 1080 ℃, the finish rolling inlet temperature is 980-1020 ℃, the finishing rolling speed is 12-15 m/s, the collecting temperature is more than or equal to 950 ℃, and all fans are turned off in the collecting process.
As a further improvement of an embodiment of the invention, in the cooling control procedure, the coil is sent into a heat preservation pit for stacking cooling, the heat preservation pit is covered with a heat preservation cover, the cooling speed is less than or equal to 0.7 ℃/s, and the coil is cooled to below 300 ℃ and then is taken out of the pit for air cooling.
Compared with the prior art, the invention has the beneficial effects that:
(1) In the design of chemical components, under the action of comprehensively considering the high-temperature strength and creep strength of different elements on steel, the addition or not and the content of each element are accurately selected and controlled, the content relation of each element is further coordinated through the control of the fire resistance index FRE, on one hand, the tissue control of the steel bar mechanical connecting sleeve is facilitated, the toughness and the fire resistance of the sleeve are improved, the use safety of the steel bar mechanical connecting sleeve in a reinforced concrete structure building is comprehensively improved, the steel bar mechanical connecting sleeve is suitable for important fire prevention engineering, on the other hand, the production cost is reduced, and the production flow is simplified.
(2) Based on the design of chemical components, the process design of the production process of the reinforced mechanical connecting sleeve is combined, so that the sleeve prepared by the production method has excellent mechanical properties and excellent fire resistance, and the use safety of the reinforced mechanical connecting sleeve in reinforced concrete structure buildings can be comprehensively improved, so that the reinforced mechanical connecting sleeve is suitable for important fireproof engineering.
Detailed Description
The technical scheme of the present invention will be further described with reference to the specific embodiments, but the scope of the claims is not limited to the description.
The invention provides a wire rod for a refractory steel bar mechanical connecting sleeve, which comprises the following chemical components in percentage by mass: 0.35 to 0.42 percent of C, 0.12 to 0.25 percent of Si, 1.6 to 2.0 percent of Mn, 0.25 to 0.35 percent of Cr, 0.10 to 0.15 percent of Nb, 0.04 to 0.08 percent of V, 0.02 to 0.05 percent of Ti, 0.15 to 0.25 percent of Cu, 0.001 to 0.003 percent of B, less than or equal to 0.02 percent of P, less than or equal to 0.02 percent of S, 0.01 to 0.02 percent of N, and the balance of Fe and unavoidable impurities; wherein the fire resistance index FRE= [ Nb ] +1.5[ Cr ] +0.8[ V ] +0.5[ Ti ] +0.1[ Cu ], FRE is 0.60-0.75%.
Wherein, [ Nb ] represents the mass percentage of Nb, [ Cr ] represents the mass percentage of Cr, [ V ] represents the mass percentage of V, [ Ti ] represents the mass percentage of Ti, and [ Cu ] represents the mass percentage of Cu.
The invention further provides a fire-resistant steel bar mechanical connecting sleeve, which is prepared by taking the wire rod for the fire-resistant steel bar mechanical connecting sleeve as a base material and has the same chemical composition as the wire rod for the fire-resistant steel bar mechanical connecting sleeve.
The function of each chemical component is described below:
c: as the most economical strengthening element in steel, the steel plays a solid solution strengthening role, is favorable for improving the connection strength of the steel bar mechanical connecting sleeve, and C can form fine carbide particles with Nb, V, ti, cr and the like, and strengthen ferrite by a precipitation strengthening mode so as to improve the fire resistance, but excessive C is unfavorable for the plasticity and toughness of the steel, and the content range of C is controlled to be 0.35-0.42 percent.
Si: the alloy has the advantages of solid solution strengthening effect in steel, improving hardenability, inhibiting C diffusion so as to delay phase change, being beneficial to improving the elastic limit and yield limit of the steel, improving the strength and wear resistance of the steel, being simultaneously used as deoxidizers in the steelmaking process, being unfavorable for the toughness of the steel due to excessive Si, reducing the creep strength of the steel and being unfavorable for the fire resistance, and controlling the content range of Si to be 0.12-0.25%.
Mn: the alloy is the most economical solid solution strengthening element except C, can stabilize austenite, enhance hardenability, improve strength and low-temperature toughness of steel, is favorable for reducing the brittle-ductile transition temperature of steel, can reduce diffusion of C, refines carbide particles, plays a role of strengthening ferrite, and is favorable for improving fire resistance, and the Mn content range is controlled to be 1.6-2.0%.
Cr: is an important refractory element, can obviously enhance the hardenability, one part is dissolved in ferrite in a solid solution way, and the other part is combined with C to form carbide particles, so that the ferrite is reinforced, and the high-temperature strength and creep strength of steel are effectively improved, and the Cr content range is controlled to be 0.25-0.35%.
Nb: the Nb-containing alloy is an important refined grain element and fire resistance improving element in steel, can delay the recrystallization of austenite, enlarge a recrystallization zone, delay ferrite transformation, reduce the transformation point of austenite-ferrite, promote the formation of granular bainite with better toughness, and has better fine grain strengthening and precipitation strengthening effects, but the Nb content is too high to easily cause continuous casting billet cracks, and the Nb content range is controlled to be 0.05-0.15%.
V: the V-containing alloy can be fully dissolved in the heating process of a continuous casting blank and is combined with C, N in the rolling deformation process to form a large number of fine-dispersion precipitated particles, and the precipitated particles can prevent the growth of crystal grains at high temperature, so that the high-temperature strength of steel is improved, and the V content range is controlled to be 0.04-0.08%.
Ti: the high-melting-point nitride particles are easy to form with N, on one hand, grains are refined, on the other hand, nucleation points are provided for precipitation of Nb and V, composite particles are promoted to be formed, the stability of the precipitation particles at high temperature is further improved, the high-temperature strength is improved, and the Ti content range is controlled to be 0.02-0.05%.
Cu: the copper-rich phase can be separated out in ferrite at high temperature, the strength and hardness are improved in a precipitation strengthening mode, the improvement of the fire resistance is facilitated, excessive Cu is easy to cause hot embrittlement of steel and is unfavorable for rolling, and the Cu content range is controlled to be 0.15-0.25%.
B: the high-strength ferrite phase transformation alloy is a strong carbide forming element, and a small amount of the high-strength ferrite phase transformation alloy can enhance the hardenability, delay ferrite phase transformation and promote the formation of high-strength phase bainite, and the content range of B is controlled to be 0.001-0.003%.
P, S: is an impurity element in steel, and P is easy to gather at a grain boundary, so that the grain boundary strength is reduced, and the low-temperature toughness of the steel is reduced; s is easy to form MnS inclusion, reduces the low-temperature toughness of steel, and is easy to be distributed in the rolling direction to cause anisotropy; in the invention, P is controlled to be less than or equal to 0.02 percent, and S is controlled to be less than or equal to 0.02 percent.
N: the precipitation effect of Ti and V can be obviously enhanced, the high-temperature strength enhancement is assisted, but excessively high N can be combined with part of alloy elements to form a large-size N-containing precipitation phase in steel so as to influence the toughness, and the content of N is controlled to be 0.01-0.02%.
In addition, the improvement difference of each element in the chemical composition of the wire rod for the refractory steel bar mechanical connecting sleeve on the refractory performance is comprehensively considered, and the refractory performance of the wire rod and the sleeve prepared by further processing the wire rod can be ensured by controlling the refractory index FRE to be 0.60-0.75%, so that the wire rod has enough high-temperature strength and creep strength, the low cost can be ensured, and the production difficulty and the quality control difficulty of continuous casting billets are reduced.
In the design of the chemical components, under the action of comprehensively considering the high-temperature strength and creep strength of different elements on steel, the invention not only precisely selects and controls the addition or non-addition and content of each element, but also coordinates the content relation of each element through controlling the fire resistance index FRE, thereby being beneficial to the tissue control of the wire rod for the steel bar mechanical connecting sleeve and the sleeve prepared by further processing the wire rod and the sleeve, improving the toughness and fire resistance of the wire rod and the sleeve, comprehensively improving the use safety of the steel bar mechanical connecting sleeve in reinforced concrete structure buildings, leading the steel bar mechanical connecting sleeve to be suitable for key fire-proof engineering, and also being capable of reducing the production cost and simplifying the production flow.
Specifically, in the aspect of microstructure, the structure of the wire rod with the diameter of 16-40 mm is a ferrite and pearlite two-phase structure, wherein the proportion of ferrite is more than or equal to 30%, and the grain size is more than or equal to 9.5 mu m; the sleeve has three-phase ferrite, pearlite and bainite structure, with ferrite proportion not higher than 10%, pearlite proportion not lower than 70% and grain size of 7.5-9.2 microns.
In terms of mechanical properties, the hardness of the wire rod is less than or equal to 200HV, the yield strength at room temperature is less than or equal to 500MPa, the tensile strength is less than or equal to 650MPa, and the elongation after breaking is more than or equal to 20%; the yield strength at 600 ℃ is more than or equal to 320MPa, the tensile strength is more than or equal to 400MPa, and the elongation after breaking is more than or equal to 25%; the hardness of the sleeve is more than or equal to 285HV, the yield strength at room temperature is more than or equal to 750MPa, the tensile strength is more than or equal to 920MPa, and the elongation after breaking is more than or equal to 16%; the yield strength at 600 ℃ is more than or equal to 480MPa, the tensile strength is more than or equal to 650MPa, and the elongation after breaking is more than or equal to 22%.
The invention further provides a preferable production method of the wire rod for the mechanical connecting sleeve of the refractory steel bar, which comprises the steps of molten iron pre-desulfurization, electric furnace smelting, LF refining, continuous casting, heating, controlled rolling and controlled cooling, which are sequentially carried out, so that the wire rod for the mechanical connecting sleeve of the refractory steel bar is prepared.
The wire rod comprises the following chemical components in percentage by mass: 0.35 to 0.42 percent of C, 0.12 to 0.25 percent of Si, 1.6 to 2.0 percent of Mn, 0.25 to 0.35 percent of Cr, 0.10 to 0.15 percent of Nb, 0.04 to 0.08 percent of V, 0.02 to 0.05 percent of Ti, 0.15 to 0.25 percent of Cu, 0.001 to 0.003 percent of B, less than or equal to 0.02 percent of P, less than or equal to 0.02 percent of S, 0.01 to 0.02 percent of N, and the balance of Fe and unavoidable impurities; wherein the fire resistance index
FRE= [ Nb ] +1.5[ Cr ] +0.8[ V ] +0.5[ Ti ] +0.1[ Cu ], FRE is 0.60-0.75%.
The production method is described in detail in the following production sequence.
(1) Molten iron pre-desulfurization process
The blast furnace molten iron is sent into a ladle, a desulfurizing agent is added into the ladle to perform KR method pre-desulfurization, S in the molten iron at the desulfurization end point is less than or equal to 0.01%, and the slag removal rate of desulfurization slag is more than or equal to 98%.
(2) Electric furnace smelting process
Sequentially adding scrap steel and pre-desulfurized blast furnace molten iron into an electric furnace, wherein the scrap steel accounts for more than or equal to 75 percent, C in the molten steel at the smelting end point of the electric furnace is less than or equal to 0.15 percent, P is less than or equal to 0.015 percent, the tapping temperature is 1595-1625 ℃, argon is blown from the bottom of the whole ladle in the tapping process, and the flow rate of the argon blown from the bottom of the ladle is 200-250L/min; and after tapping 1/5, sequentially adding ferrosilicon nitride, ferrosilicon manganese, ferromanganese, high-carbon ferrochromium, copper blocks and lime for deoxidization alloying so as to reduce oxidation burning loss and improve the service efficiency of the alloy.
(3) LF refining procedure
Injecting molten steel obtained in the electric furnace smelting process into an LF furnace, adding 2.4-3.8 kg lime and 0.8-1.2 kg fluorite into each ton of molten steel to turn yellow slag, electrifying, heating and soft stirring for 5-8 min, wherein the flow rate of argon blown into a ladle during soft stirring is 150-200L/min, and the total consumption of argon is 10-20L/t; after regulating the alkalinity of refining slag to 2.0-2.5, sequentially adding borax, vanadium-nitrogen alloy, ferroniobium and ferrotitanium for alloying so as to regulate chemical components; the flow of argon blown from the bottom of the steel ladle is 250-300L/min, and the total argon consumption is 30-55L/t during alloying; and then sampling and finely adjusting the chemical components of the molten steel, and tapping, wherein the tapping temperature at the LF refining end point is 1550-1580 ℃.
The chemical composition of the final molten steel of the LF refining process determines the chemical composition of the finally obtained mechanical connection sleeve for the refractory steel, i.e. the chemical composition of the final molten steel corresponds to the chemical composition of the finally obtained mechanical connection sleeve for the refractory steel.
(4) Continuous casting process
Continuously casting molten steel obtained in the RH refining process into a continuous casting blank, wherein the temperature of a tundish is 1525-1550 ℃, a large ladle long nozzle, a sealing gasket, a submerged nozzle and an alkaline tundish covering agent are adopted for full-protection casting in the continuous casting process, argon is blown into the long nozzle in the whole process, low-carbon covering slag is adopted for covering slag, and the slag thickness is 8-10 mm; the water distribution flow of a crystallizer for solidifying a cold area is 1800-2400L/min, and the temperature difference between a water outlet and a water inlet of the crystallizer is less than 10 ℃; electromagnetic stirring is adopted in the solidification secondary cooling zone, the electromagnetic stirring frequency is 3-5 Hz, the fluctuation of the liquid level is controlled within +/-2 mm, the water distribution flow of a crystallizer in the solidification secondary cooling zone is 500-800L/min, and the continuous casting drawing speed is 2.2-2.5 m/min.
Wherein, the continuous casting blank is a small square blank with the cross section dimension of 150mm multiplied by 150 mm.
(5) Heating process
And (3) placing the continuously cast blank into a heating furnace for heating after surface inspection, wherein the heating temperature is 1150-1220 ℃, the total heating time is 60-90 min, and the soaking period time is more than or equal to 40min so as to ensure that the added alloy elements are effectively dissolved in solid.
(6) Controlling the rolling process
Rolling the heated continuous casting blank into a wire rod, and collecting the wire rod into a coil, wherein the initial rolling temperature is more than or equal to 1080 ℃, the finish rolling inlet temperature is 980-1020 ℃, the finish rolling speed is 12-15 m/s, the collecting temperature is more than or equal to 950 ℃, and all fans are closed in the collecting process, so that the gradient cooling rolling of the wire rod is realized.
Preferably, after leaving the heating furnace, the continuous casting billet is rolled by a continuous wire rolling mill into a wire rod with a diameter of 16-40 mm.
(7) Controlling the cooling process
And (3) sending the coil into a heat preservation pit for stacking cooling, covering the heat preservation pit with a heat preservation cover, cooling to below 300 ℃ at a cooling rate of less than or equal to 0.7 ℃/s, and taking out of the pit for air cooling.
Thus, by controlling the chemical composition design and the whole production process, the microstructure of the prepared wire rod is a ferrite and pearlite two-phase structure, wherein the proportion of ferrite is more than or equal to 30%, the grain size is more than or equal to 9.5 mu m, and the hardness is less than or equal to 200HV; the yield strength at room temperature is less than or equal to 500MPa, the tensile strength is less than or equal to 650MPa, and the elongation after break is more than or equal to 20%, so that the processing difficulty in the process of preparing the sleeve by subsequent drawing can be reduced, the shaping processing can be performed without annealing, and the strength requirement in the process of preparing the sleeve by subsequent drawing can be met; the yield strength at 600 ℃ is more than or equal to 320MPa, the tensile strength is more than or equal to 400MPa, the elongation after breaking is more than or equal to 25%, the steel bar mechanical connecting sleeve has certain strength, good plasticity and excellent fire resistance, and lays a foundation for the comprehensive performance of the finished product of the fire-resistant steel bar mechanical connecting sleeve prepared by further processing.
Further, the wire rod for the refractory steel bar mechanical connecting sleeve is further processed through the following procedures, so that the refractory steel bar mechanical connecting sleeve can be prepared.
(8) Drawing and straightening process
And drawing the wire rod subjected to controlled cooling to a set size, then sending the wire rod to a straightener for straightening, and then cutting and finishing according to the set sleeve length to obtain a sleeve blank.
(9) Extrusion molding process
And (3) perforating the sleeve blank subjected to drawing straightening, and performing equal 6-angle, equal 8-angle or equal 12-angle extrusion molding according to the diameter of the sleeve after perforation.
(10) Thread tapping process
And (3) carrying out thread tapping on the sleeve blank after extrusion molding by using an automatic tapping machine, wherein the thread angle is 75 degrees, and obtaining the sleeve.
(11) Gradient quenching process
Induction heating is carried out on the sleeve after thread tapping, the heating temperature is 900-950 ℃, and the heating time is 3-5 min, so that the sleeve is completely austenitized; then entering a first salt bath furnace for isothermal quenching, wherein the quenching temperature is 600-680 ℃ and the quenching time is 10-25 min, so that austenite rapidly passes through a ferrite phase region to be transformed into pearlite; then transferring the mixture into a second salt bath furnace for isothermal quenching, wherein the quenching temperature is 400-460 ℃, and the quenching time is 8-15 min, so that the residual austenite is fully converted into bainite; then carrying out oil quenching, wherein the temperature of quenching oil is 30-50 ℃, and the cooling speed is 0.1-0.5 ℃/s so as to refine grains and improve the strength of the sleeve; by carrying out multi-temperature gradient continuous quenching on the wire rod, the sleeve can obtain a three-phase structure of pearlite, bainite and a small amount of ferrite, so that the sleeve can meet the strength and plasticity required by service at normal temperature, can ensure that the sleeve has small strength loss when the sleeve is in service at a high temperature of 600 ℃, has excellent fire resistance, can improve the automation degree, avoids waiting time between quenching with different temperature gradients, and further improves the production efficiency.
(12) Low temperature tempering process
And (3) sending the sleeve subjected to gradient quenching into a muffle furnace for tempering, wherein the tempering temperature is 200-250 ℃, the tempering time is 20-40 min, and the sleeve is left in the muffle furnace to be cooled to room temperature after tempering is finished, and the cooling speed is less than or equal to 1 ℃/s so as to eliminate the internal stress of the sleeve.
Thus, the production method of the embodiment is based on the design of the chemical components, and the microstructure of the finally prepared sleeve is a three-phase structure of ferrite, pearlite and bainite through the regulation and control of a series of technological means of molten iron pre-desulfurization, electric furnace smelting, LF refining, continuous casting, heating, controlled rolling, controlled cooling, drawing straightening, extrusion molding, thread tapping, gradient quenching and low-temperature tempering, wherein the proportion of ferrite is not more than 10%, the proportion of pearlite is not less than 70%, the grain size is 7.5-9.2 mu m, the hardness is not less than 285HV, the yield strength at room temperature is not less than 750MPa, the tensile strength is not less than 920MPa, and the elongation after fracture is not less than 16%; the yield strength at 600 ℃ is more than or equal to 480MPa, the tensile strength is more than or equal to 650MPa, the elongation after break is more than or equal to 22%, and the sleeve has excellent mechanical properties and plastic toughness at room temperature or 600 ℃, so that the sleeve can be ensured to have excellent mechanical properties and fire resistance when being applied to reinforced concrete structures.
The following describes the embodiments of the present invention further by way of 6 examples. Of course, these 6 examples are only some, but not all of the many variations encompassed by this embodiment. Other examples based on the foregoing embodiment do not depart from the gist of the present invention.
First, examples 1 to 6 each provide a wire rod for a mechanical connection sleeve for a refractory steel bar, and a mechanical connection sleeve for a refractory steel bar prepared from the wire rod further subjected to drawing straightening, extrusion molding, thread tapping, gradient quenching and low-temperature tempering processes, the chemical compositions of the wire rod and the sleeve being shown in table 1.
TABLE 1
The production method of the wire rod of each embodiment adopts a process route comprising molten iron pre-desulfurization, electric furnace smelting, LF refining, continuous casting, heating, controlled rolling and controlled cooling which are sequentially carried out, and the sleeve of each embodiment is prepared by further carrying out drawing straightening, extrusion molding, thread tapping, gradient quenching and low-temperature tempering on the wire rod of each embodiment. The specific operation of each process is described above, and will not be repeated here.
The wire rods and sleeves of examples 1 to 6 were sampled according to the same test method, and subjected to metallographic structure detection and mechanical property detection, the diameters of the wire rods of examples 1 to 6 are shown in table 2, and the detection results are as follows:
(1) In terms of structure, the wire rods of examples 1 to 6 were each a ferrite and pearlite two-phase structure, wherein the percentages of bainite and pearlite are shown in Table 2, respectively, and the grain sizes of the wire rods of examples 1 to 6 were each 9.5 μm or more; the structures of the sleeves of examples 1 to 6 were all three-phase structures of ferrite, pearlite and bainite, wherein the percentages of ferrite, pearlite and bainite are shown in table 3, respectively, and the grain sizes of the sleeves of examples 1 to 6 were all in the range of 7.5 to 9.2 μm;
(2) The hardness, yield strength, tensile strength and elongation after break at room temperature of the wire rods of examples 1 to 6 are shown in Table 2, respectively, in terms of mechanical properties; the hardness, yield strength, tensile strength and elongation after break at room temperature of the sleeves of examples 1 to 6 are shown in Table 3, respectively;
TABLE 2
As can be seen from Table 2, the wire rods of examples 1 to 6 produced according to the present embodiment have excellent comprehensive properties, and the structure thereof is a two-phase structure of ferrite and pearlite, wherein the proportion of ferrite is not less than 30%; the hardness is less than or equal to 200HV, the yield strength at room temperature is less than or equal to 500MPa, the tensile strength is less than or equal to 650MPa, and the elongation after breaking is more than or equal to 20%; the yield strength at 600 ℃ is more than or equal to 320MPa, the tensile strength is more than or equal to 400MPa, and the elongation after breaking is more than or equal to 25%.
TABLE 3
As can be seen from Table 3, the sleeves of examples 1 to 6 produced and prepared according to the present embodiment have excellent comprehensive properties, and the structures thereof are all three-phase structures of pearlite+bainite+a small amount of ferrite, wherein the proportion of ferrite is not more than 10%, and the proportion of pearlite is not less than 70%; the hardness is more than or equal to 285HV, the yield strength at room temperature is more than or equal to 750MPa, the tensile strength is more than or equal to 920MPa, and the elongation after breaking is more than or equal to 16%; the yield strength at 600 ℃ is more than or equal to 480MPa, the tensile strength is more than or equal to 650MPa, the elongation after break is more than or equal to 22%, the reinforced concrete structure has excellent mechanical properties at room temperature and 600 ℃ and excellent fire resistance, and the use safety of the reinforced concrete structure building of the reinforced concrete structure can be comprehensively improved, so that the reinforced concrete structure building is suitable for key fireproof engineering.
It should be understood that although the present disclosure describes embodiments, not every embodiment is provided with a separate embodiment, and that this description is for clarity only, and that the skilled artisan should recognize that the embodiments may be combined as appropriate to form other embodiments that will be understood by those skilled in the art.
Claims (10)
1. A production method of a fireproof steel bar mechanical connecting sleeve is characterized in that a wire rod is manufactured into the sleeve through the working procedures of drawing straightening, extrusion forming, thread tapping, gradient quenching and low-temperature tempering; wherein, the liquid crystal display device comprises a liquid crystal display device,
the wire rod comprises the following chemical components in percentage by mass: 0.35 to 0.42 percent of C, 0.12 to 0.25 percent of Si, 1.6 to 2.0 percent of Mn, 0.25 to 0.35 percent of Cr, 0.10 to 0.15 percent of Nb, 0.04 to 0.08 percent of V, 0.02 to 0.05 percent of Ti, 0.15 to 0.25 percent of Cu, 0.001 to 0.003 percent of B, less than or equal to 0.02 percent of P, less than or equal to 0.02 percent of S, 0.01 to 0.02 percent of N, and the balance of Fe and unavoidable impurities; fire resistance index FRE= [ Nb ] +1.5[ Cr ] +0.8[ V ] +0.5[ Ti ] +0.1[ Cu ], FRE is 0.60-0.75%;
in the drawing and straightening process, the wire rod is drawn to a set size and then sent to a straightener for straightening, and then cut and finished according to the set sleeve length to obtain a sleeve blank;
in the extrusion forming process, perforating the sleeve blank subjected to drawing straightening, and performing equal 6-angle, equal 8-angle or equal 12-angle extrusion forming according to the diameter of the sleeve after perforating;
in the thread tapping procedure, an automatic tapping machine is utilized to perform thread tapping on the sleeve blank after extrusion molding, and the thread angle is 75 degrees.
2. The method for producing a refractory steel mechanical connecting sleeve according to claim 1, wherein in the gradient quenching process, the sleeve after tapping is induction heated at 900-950 ℃ for 3-5 min; then the mixture enters a first salt bath furnace for isothermal quenching, wherein the quenching temperature is 600-680 ℃ and the quenching time is 10-25 min; then transferring the mixture into a second salt bath furnace for isothermal quenching, wherein the quenching temperature is 400-460 ℃, and the quenching time is 8-15 min; then oil quenching is carried out, wherein the temperature of quenching oil is 30-50 ℃, and the cooling speed is 0.1-0.5 ℃/s.
3. The method for producing the mechanical connecting sleeve for refractory steel bars according to claim 1, wherein in the low-temperature tempering process, the sleeve subjected to gradient quenching is sent into a muffle furnace for tempering, the tempering temperature is 200-250 ℃, the tempering time is 20-40 min, and the sleeve is left in the muffle furnace for cooling to room temperature after tempering, and the cooling speed is less than or equal to 1 ℃/s.
4. The method for producing a mechanical connecting sleeve for refractory steel according to claim 1, wherein the wire rod is prepared by sequentially performing molten iron pre-desulfurization, electric furnace smelting, LF refining, continuous casting, heating, controlled rolling and controlled cooling processes.
5. The method for producing a mechanical connecting sleeve for refractory steel according to claim 4, wherein in the pre-desulfurization process of molten iron, the pre-desulfurization is performed on the molten iron of the blast furnace by a KR method, S in the molten iron at the desulfurization end point is less than or equal to 0.01%, and the slag removal rate of desulfurization slag is more than or equal to 98%;
in the electric furnace smelting process, scrap steel and pre-desulfurized blast furnace molten iron are sequentially added into an electric furnace, wherein the scrap steel accounts for more than or equal to 75 percent, C in molten steel at the smelting end point of the electric furnace is less than or equal to 0.15 percent, P is less than or equal to 0.015 percent, the tapping temperature is 1595-1625 ℃, argon is blown into a ladle in the whole process of tapping, and the flow of argon blown into the ladle is 200-250L/min; and after tapping 1/5, sequentially adding ferrosilicon nitride, ferrosilicon manganese, ferromanganese, high-carbon ferrochromium, copper blocks and lime for deoxidization alloying.
6. The method for producing a mechanical connecting sleeve for refractory steel according to claim 4, wherein in the LF refining step, after molten steel obtained in the electric furnace smelting step is poured into an LF furnace, 2.4 to 3.8kg lime and 0.8 to 1.2kg fluorite are added per ton of molten steel to turn yellow slag, and then the steel is electrified and heated and stirred for a soft stirring time of 5 to 8 minutes, and the flow rate of argon blown from the bottom of a ladle during the soft stirring time is 150 to 200L/min; and after regulating the alkalinity of refining slag to 2.0-2.5, sequentially adding borax, vanadium-nitrogen alloy, ferrocolumbium and ferrotitanium for alloying, wherein the flow of argon blown into the ladle bottom during alloying is 250-300L/min, and the tapping temperature at the LF refining end point is 1550-1580 ℃.
7. The method for producing the mechanical connecting sleeve for refractory steel bars according to claim 4, wherein in the continuous casting process, the temperature of a tundish is 1525-1550 ℃, a large ladle long nozzle, a sealing gasket, a submerged nozzle and an alkaline tundish covering agent are adopted for full protection casting in the continuous casting process, argon is blown in the long nozzle in the whole process, low-carbon covering slag is adopted for covering slag, and the slag thickness is 8-10 mm; the water distribution flow of a crystallizer for solidifying a cold area is 1800-2400L/min, and the temperature difference between a water outlet and a water inlet of the crystallizer is less than 10 ℃; electromagnetic stirring is adopted in the solidification secondary cooling zone, the electromagnetic stirring frequency is 3-5 Hz, the fluctuation of the liquid level is controlled within +/-2 mm, the water distribution flow of a crystallizer in the solidification secondary cooling zone is 500-800L/min, and the continuous casting drawing speed is 2.2-2.5 m/min.
8. The method for producing a mechanical connecting sleeve for refractory reinforcement according to claim 4, wherein in the heating step, the heating temperature is 1150-1220 ℃, the total heating time is 60-90 min, and the soaking period time is not less than 40min.
9. The method according to claim 4, wherein in the controlled rolling step, the continuous casting billet after the heating step is rolled into a coil and collected into a coil, the initial rolling temperature is not less than 1080 ℃, the finish rolling inlet temperature is 980-1020 ℃, the finish rolling speed is 12-15 m/s, the collecting temperature is not less than 950 ℃, and all fans are turned off during the collecting process.
10. The method for producing a mechanical connecting sleeve for refractory steel according to claim 4, wherein in the cooling control step, the coil is fed into a heat preservation pit for stacking cooling, the heat preservation pit is covered with a heat preservation cover, the cooling speed is less than or equal to 0.7 ℃/s, and the coil is cooled to below 300 ℃ and then discharged from the pit for air cooling.
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