CN115537668B - Low-temperature steel bar and production method thereof - Google Patents
Low-temperature steel bar and production method thereof Download PDFInfo
- Publication number
- CN115537668B CN115537668B CN202211356682.0A CN202211356682A CN115537668B CN 115537668 B CN115537668 B CN 115537668B CN 202211356682 A CN202211356682 A CN 202211356682A CN 115537668 B CN115537668 B CN 115537668B
- Authority
- CN
- China
- Prior art keywords
- temperature
- equal
- low
- percent
- less
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 99
- 239000010959 steel Substances 0.000 title claims abstract description 99
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 25
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 18
- 239000000126 substance Substances 0.000 claims abstract description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 11
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 11
- 239000000956 alloy Substances 0.000 claims abstract description 11
- 239000012535 impurity Substances 0.000 claims abstract description 7
- 238000005096 rolling process Methods 0.000 claims description 91
- 238000000034 method Methods 0.000 claims description 79
- 230000008569 process Effects 0.000 claims description 61
- 238000001816 cooling Methods 0.000 claims description 37
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 31
- 238000009749 continuous casting Methods 0.000 claims description 25
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 24
- 238000010438 heat treatment Methods 0.000 claims description 24
- 238000007670 refining Methods 0.000 claims description 19
- 230000003014 reinforcing effect Effects 0.000 claims description 18
- 229910001563 bainite Inorganic materials 0.000 claims description 17
- 239000002893 slag Substances 0.000 claims description 16
- 239000000463 material Substances 0.000 claims description 13
- 230000000149 penetrating effect Effects 0.000 claims description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 13
- 229910052786 argon Inorganic materials 0.000 claims description 12
- 229910052742 iron Inorganic materials 0.000 claims description 11
- 229910001568 polygonal ferrite Inorganic materials 0.000 claims description 11
- 229910001562 pearlite Inorganic materials 0.000 claims description 7
- 238000003756 stirring Methods 0.000 claims description 7
- 238000003723 Smelting Methods 0.000 claims description 6
- 238000003825 pressing Methods 0.000 claims description 6
- 229910000859 α-Fe Inorganic materials 0.000 claims description 6
- 239000000443 aerosol Substances 0.000 claims description 5
- 230000035945 sensitivity Effects 0.000 claims description 5
- 230000015572 biosynthetic process Effects 0.000 claims description 4
- 230000002950 deficient Effects 0.000 claims description 4
- 238000006356 dehydrogenation reaction Methods 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 4
- 238000002791 soaking Methods 0.000 claims description 4
- 238000005266 casting Methods 0.000 claims description 3
- 238000007711 solidification Methods 0.000 claims description 3
- 230000008023 solidification Effects 0.000 claims description 3
- 238000009864 tensile test Methods 0.000 claims description 3
- 238000003466 welding Methods 0.000 abstract description 58
- 229910052757 nitrogen Inorganic materials 0.000 abstract description 13
- 229910052759 nickel Inorganic materials 0.000 abstract description 11
- 229910052710 silicon Inorganic materials 0.000 abstract description 9
- 229910052782 aluminium Inorganic materials 0.000 abstract description 8
- 229910052802 copper Inorganic materials 0.000 abstract description 8
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 29
- 239000010949 copper Substances 0.000 description 18
- 230000006698 induction Effects 0.000 description 13
- 229910001294 Reinforcing steel Inorganic materials 0.000 description 10
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 8
- 230000001276 controlling effect Effects 0.000 description 7
- 238000010079 rubber tapping Methods 0.000 description 7
- 238000012360 testing method Methods 0.000 description 7
- 229910052760 oxygen Inorganic materials 0.000 description 6
- 229910052698 phosphorus Inorganic materials 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- 238000005516 engineering process Methods 0.000 description 5
- 230000001965 increasing effect Effects 0.000 description 5
- 229910052717 sulfur Inorganic materials 0.000 description 5
- 239000012300 argon atmosphere Substances 0.000 description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 239000003345 natural gas Substances 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 239000006104 solid solution Substances 0.000 description 4
- 238000005728 strengthening Methods 0.000 description 4
- 230000007704 transition Effects 0.000 description 4
- 229910001566 austenite Inorganic materials 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
- 229910052739 hydrogen Inorganic materials 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 238000003860 storage Methods 0.000 description 3
- 230000009466 transformation Effects 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 2
- 238000005452 bending Methods 0.000 description 2
- 238000007664 blowing Methods 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000006731 degradation reaction Methods 0.000 description 2
- 238000006477 desulfuration reaction Methods 0.000 description 2
- 230000023556 desulfurization Effects 0.000 description 2
- 230000002542 deteriorative effect Effects 0.000 description 2
- 230000004927 fusion Effects 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 239000003949 liquefied natural gas Substances 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 238000005498 polishing Methods 0.000 description 2
- 230000035882 stress Effects 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 229910000616 Ferromanganese Inorganic materials 0.000 description 1
- 229910001200 Ferrotitanium Inorganic materials 0.000 description 1
- 229910052581 Si3N4 Inorganic materials 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- DALUDRGQOYMVLD-UHFFFAOYSA-N iron manganese Chemical compound [Mn].[Fe] DALUDRGQOYMVLD-UHFFFAOYSA-N 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 239000011819 refractory material Substances 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 238000005482 strain hardening Methods 0.000 description 1
- 238000010301 surface-oxidation reaction Methods 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/16—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling wire rods, bars, merchant bars, rounds wire or material of like small cross-section
- B21B1/18—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling wire rods, bars, merchant bars, rounds wire or material of like small cross-section in a continuous process
-
- 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
- C22C33/06—Making ferrous alloys by melting using master alloys
-
- 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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
-
- 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
- C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
-
- 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
- C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
-
- 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)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
The invention discloses a low-temperature steel bar and a production method thereof. The steel bar comprises the following chemical components in percentage by mass: 0.03 to 0.06 percent of C, 0.12 to 0.25 percent of Si, 1.65 to 1.85 percent of Mn, 0.92 to 1.25 percent of Ni, 0.25 to 0.48 percent of Cu, 0.045 to 0.06 percent of Al, 0.02 to 0.06 percent of Ti, 0.008 to 0.015 percent of N, and the balance of Fe and impurities; the ratio of [ Ni ] +0.5[ Cu ] +1.5[ Al ] +1.2[ Ti ] +5[N ] is 1.30-1.65%, and the carbon equivalent Ceq is less than or equal to 0.46%. The steel bar has low alloy cost and low production difficulty, and simultaneously has excellent normal temperature mechanical property, welding property, low temperature mechanical property and plastic toughness, and the welded joint also has excellent normal temperature property and low temperature property.
Description
Technical Field
The invention belongs to the technical field of steel materials, and particularly relates to a low-temperature steel bar and a production method thereof.
Background
Natural gas is used as a clean energy source, and the ratio of the natural gas in the currently used energy system is increasing. The natural gas is compressed and liquefied to greatly improve the storage and transportation capacity of the natural gas, but the temperature of the liquefied natural gas is reduced to-165 ℃, and the conventional steel-concrete structure storage tank is difficult to meet the service requirement. Aiming at the severe low-temperature environment, various low-temperature steel bars for the liquefied natural gas storage tanks have been developed at home and abroad successively.
The low-temperature steel bar needs to be welded in the actual construction process, so that the low-temperature steel bar needs to have excellent normal-temperature mechanical properties, excellent welding properties and low-temperature mechanical properties; moreover, the toughness directly affects the difficulty of low-temperature steel bars in production, such as low-temperature steel bars with poor toughness, and microcracks are easy to occur in rolling, so that the rolling difficulty is increased.
Disclosure of Invention
In order to solve the technical problems, the invention aims to provide a low-temperature steel bar and a production method thereof, which have excellent normal-temperature mechanical property, welding performance, low-temperature mechanical property and plasticity and toughness at the same time of low alloy cost.
In order to achieve the above object, an embodiment of the present invention provides a low-temperature steel bar, which comprises the following chemical components in percentage by mass: 0.03 to 0.06 percent of C, 0.12 to 0.25 percent of Si, 1.65 to 1.85 percent of Mn, 0.92 to 1.25 percent of Ni, 0.25 to 0.48 percent of Cu, 0.045 to 0.06 percent of Al, 0.02 to 0.06 percent of Ti, less than or equal to 0.010 percent of P, less than or equal to 0.012 percent of S, 0.008 to 0.015 percent of N, less than or equal to 20ppm of O, less than or equal to 2ppm of H, and the balance of Fe and unavoidable impurities; and, ni+0.5Cu+1.5Al+1.2Ti+ 5[N is 1.30-1.65%, the carbon equivalent Ceq= [ C ] + [ Mn ]/6+ ([ Cr ] + [ Mo ] + [ V ])/5+ ([ Ni ] + [ Cu ])/15 is less than or equal to 0.46%, wherein [ C ], [ Mn ], [ Cr ], [ Mo ], [ V ], [ Ni ], [ Cu ], [ Al ], [ Ti ], [ N ] respectively represent the mass percent of the corresponding elements in the low-temperature reinforcing steel bar.
Preferably, the chemical components of the low-temperature steel bar comprise the following components in percentage by mass: 0.03 to 0.06 percent of C, 0.12 to 0.18 percent of Si, 1.65 to 1.85 percent of Mn, 0.92 to 1.20 percent of Ni, 0.27 to 0.48 percent of Cu, 0.045 to 0.06 percent of Al, 0.03 to 0.06 percent of Ti, less than or equal to 0.010 percent of P, less than or equal to 0.012 percent of S, 0.012 to 0.015 percent of N, less than or equal to 20ppm of O, less than or equal to 2ppm of H, and the balance of Fe and unavoidable impurities; and [ Ni ] +0.5[ Cu ] +1.5[ Al ] +1.2[ Ti ] +5[N ] is 1.30-1.60%, and the carbon equivalent Ceq is not more than 0.46%.
Further, the structure of the low-temperature steel bar is polygonal ferrite, bainite and a very small amount of pearlite, wherein the bainite accounts for more than or equal to 75%, and the pearlite accounts for less than 1%.
Further, at normal temperature, the yield strength R of the reinforcing steel bar p0.2 450-485 MPa, tensile strength R m 650-685 MPa, elongation after break A of 23-26%, and total elongation with maximum force A gt 13-15% of the ratio of strong to strong m /R p0.2 1.35 to 1.50.
Further, after the low-temperature steel bar is welded as a base material, a breaking point in a room-temperature tensile test is formed at the base material of the steel bar, and a welded joint is 180 ° cold-bent at room temperature without cracks, d=4d dw Wherein D is the diameter of the center of curvature, D dw Is the diameter of the steel bar.
Further, after the low-temperature steel bar is used as a parent material for welding, the structure of the welded joint is polygonal ferrite, acicular ferrite and granular bainite, wherein the polygonal ferrite accounts for less than or equal to 8 percent, and the granular bainite accounts for more than or equal to 65 percent.
Further, the yield strength R of the steel bar of the low-temperature steel bar in a non-notch state under the low-temperature condition of-165 DEG C p0.2 Not less than 600MPa and tensile strength R m More than or equal to 720MPa and maximum force total elongation A gt More than or equal to 5.5 percent; yield strength R in notched form p0.2 More than or equal to 610MPa and tensile strength R m More than or equal to 700MPa and the maximum force total elongation A gt More than or equal to 3.5 percent; the notch sensitivity index is more than or equal to 1.18, and is the tensile strength R in a notched form m Yield strength R in the non-defective state p0.2 。
In order to achieve the above object, an embodiment of the present invention provides a method for producing a low-temperature steel bar, which includes a molten iron pretreatment process, a converter smelting process, an LF refining process, an RH refining process, a continuous casting process, and a controlled rolling and cooling process, which are sequentially performed;
in the LF refining procedure, the components of the slag former adopted in slag formation are as follows by mass percent: 45-55% of Ca, 30-40% of Al and the balance of O, and controlling the alkalinity of refining slag to be 0.8-1.2; and argon is blown into the bottom of the whole slag making process for soft stirring, the argon flow is 120-160L/min, and the soft stirring time is 7-10min;
in the RH refining process, deoxidization and dehydrogenation are firstly carried out, and then an alloy cored wire is fed by a wire feeder according to the wire feeding quantity of 0.25-0.45 kg and the wire feeding speed of 0.8-1.2 m/s per ton of molten steel, wherein the cored wire comprises the following components in percentage by mass: 50-55% of Al, 15-20% of Si, 5-10% of N and the balance of Fe;
in the continuous casting process, full-protection casting is carried out, dynamic light reduction is adopted in a solidification secondary cooling zone, the reduction is 2-4.5 mm, the reduction rate is 0.4-0.55 mm/min, and the continuous casting drawing speed is 0.18-0.25 m/min;
in the rolling and cooling control process, after leaving a continuous casting machine, a continuous casting billet directly enters a heating furnace for heating at the temperature of 550-600 ℃, and the soaking temperature is 1070-1120 ℃; then, sequentially carrying out a rough rolling stage, a medium rolling stage, a finish rolling first stage and a finish rolling second stage on the heated continuous casting billet on a continuous rolling mill, wherein the inlet temperature of each stage is 960-985 ℃, 930-955 ℃, 850-875 ℃ and 800-825 ℃ in sequence; finally, the steel bar rolled by the continuous rolling mill is air-cooled to room temperature by a cooling bed, and the temperature of the cooling bed is 500-550 ℃; before the upper cooling bed, the steel bars are cooled by a water penetrating device after leaving the continuous rolling mill.
Preferably, the temperature control is performed between the rough rolling stage and the intermediate rolling stage in an aerosol cooling mode, and the temperature control is performed between the intermediate rolling stage and the finish rolling first stage, and between the finish rolling first stage and the finish rolling second stage by using a water penetrating device.
Preferably, in the rolling and cooling control process, the maintaining time of the continuous casting billet in a heating furnace at 1100 ℃ is less than or equal to 5min.
Compared with the prior art, the invention has the beneficial effects that: by adjusting the respective contents of Ni, cu, al, ti and N and establishing the association relation [ Ni ] +0.5[ Cu ] +1.5[ Al ] +1.2[ Ti ] +5[N ] between Ni, cu, al, ti and N and defining the value of the relation, the contents of the corresponding elements are reversely restrained, so that the embodiment ensures excellent low-temperature performance of the low-temperature reinforcing steel bar without adding low-temperature performance element Cr and reducing low-temperature performance element Ni, and the problems of plastic degradation, inclusion increase and the like of the low-temperature reinforcing steel bar are not caused; compared with other existing low-temperature steel bars, the low-temperature steel bar has more excellent normal temperature performance, plasticity and toughness, welding performance and low-temperature performance, and is low in alloy cost and production difficulty.
Detailed Description
The technical scheme of the invention is further described below with reference to specific embodiments.
An embodiment of the invention provides a low-temperature steel bar, which comprises the following chemical components in percentage by mass: 0.03 to 0.06 percent of C, 0.12 to 0.25 percent of Si, 1.65 to 1.85 percent of Mn, 0.92 to 1.25 percent of Ni, 0.25 to 0.48 percent of Cu, 0.045 to 0.06 percent of Al, 0.02 to 0.06 percent of Ti, less than or equal to 0.010 percent of P, less than or equal to 0.012 percent of S, 0.008 to 0.015 percent of N, less than or equal to 20ppm of O, less than or equal to 2ppm of H, and the balance of Fe and unavoidable impurities; and, the carbon equivalent Ceq= [ C ] + [ Mn ]/6+ ([ Cr ] + [ Mo ] + [ V ])/5+ ([ Ni ] + [ Cu ])/15 is less than or equal to 0.46%, wherein, the mass percentages of the corresponding elements in the low-temperature reinforcing steel bars are respectively represented by [ C ], [ Mn ], [ Cr ], [ Mo ], [ V ], [ Ni ], [ Cu ], [ Al ], [ Ti ], [ N ] are defined as 1.30-1.65%.
Further preferably, the chemical components of the low-temperature steel bar comprise the following components in percentage by mass: 0.03 to 0.06 percent of C, 0.12 to 0.18 percent of Si, 1.65 to 1.85 percent of Mn, 0.92 to 1.20 percent of Ni, 0.27 to 0.48 percent of Cu, 0.045 to 0.06 percent of Al, 0.03 to 0.06 percent of Ti, less than or equal to 0.010 percent of P, less than or equal to 0.012 percent of S, 0.012 to 0.015 percent of N, less than or equal to 20ppm of O, less than or equal to 2ppm of H, and the balance of Fe and unavoidable impurities; and [ Ni ] +0.5[ Cu ] +1.5[ Al ] +1.2[ Ti ] +5[N ] is limited to 1.30-1.60%, and the carbon equivalent Ceq= [ C ] + [ Mn ]/6+ ([ Cr ] + [ Mo ] + [ V ])/[ Ni ] + [ Cu ]/15 is not more than 0.46%.
The preferred chemical composition of the low temperature rebar is described below.
C: c is an inexpensive and effective strength enhancing element. However, the cold brittleness and aging sensitivity of the steel can be improved due to the excessively high content of C, so that the ductile-brittle transition temperature is improved, and the low-temperature performance of the steel bar is reduced; meanwhile, too high C content increases the carbon equivalent, deteriorating the welding performance. In the present embodiment, the content of C is 0.03 to 0.06%.
Si: si has the effect of solid solution strengthening, increases the elastic limit and the yield limit, and improves the strength and the wear resistance of the steel. However, too high a Si content reduces the plasticity of the steel while affecting the low temperature toughness. In the present embodiment, si is 0.12 to 0.25%, and more preferably 0.12 to 0.18%.
Mn: mn is also an effective solid solution strengthening element, can strengthen the hardenability of steel, reduce the brittleness index of steel, and obviously improve the strength. Increasing the Mn/C ratio helps to reduce the ductile-brittle transition temperature and improve the low temperature performance. However, the addition of Mn increases the carbon equivalent and directly affects the weldability. In this embodiment, mn is 1.65 to 1.85%.
Ni: ni is an element for effectively improving the low-temperature toughness of steel, can expand the austenitic phase region of steel, strengthen stable austenite, reduce critical quenching speed, refine grains, obviously reduce the ductile-brittle transition temperature of steel and synchronously improve the toughness. In the present embodiment, ni is 0.92 to 1.25%, and more preferably 0.92 to 1.20%.
Cu: cu acts like Ni, and by forming a solid solution in steel, the stable austenite phase region is enlarged, hardenability is improved, and ductile-brittle transition temperature is lowered, so that it is possible to replace a part of Ni, but excessive addition is liable to segregate and affect plasticity. Cu also forms high melting point compounds with high Ni content, reducing the tendency to hot embrittlement. In this embodiment, cu is 0.25 to 0.48%, and more preferably 0.27 to 0.48%.
Al: al is an effective deoxidizing element to effectively reduce the oxygen content in steel. Meanwhile, al and proper amount of N are combined into AlN, so that the grain structure is refined, and the low-temperature toughness is improved. In the present embodiment, 0.045 to 0.06% of Al is contained.
Ti: ti is similar to Al, and can be combined with proper amount of N to separate out fine dispersed TiN and refine crystal grains so as to obtain better low-temperature strength and toughness, but excessive addition is easy to produce large-size inclusions. In the present embodiment, the Ti content is 0.02 to 0.06%, and more preferably 0.03 to 0.06%.
N: the proper amount of N can effectively exert the fine crystal strengthening effect of Al and Ti and improve the low-temperature performance. Excessive amounts can produce large-size brittle inclusions and deteriorate toughness. In this embodiment, N is 0.008 to 0.015%, and more preferably 0.012 to 0.015%.
P, S: s can form strip MnS inclusion with Mn to influence the plasticity and toughness of the steel plate; p tends to gather in the grain boundary, and the grain boundary strength is lowered, deteriorating the low-temperature toughness. In this embodiment, P is defined to be 0.010% or less, and S is defined to be 0.010% or less.
O, H: o is easy to generate large-size oxide inclusions to influence the plasticity and toughness and crack a welding area, and the O is limited to be less than or equal to 20ppm in the embodiment; h can generate hydrogen embrittlement, especially the higher the strength of steel, the lower the service temperature, the higher the hydrogen embrittlement sensitivity, and the H is less than or equal to 2ppm in the embodiment.
In summary, in terms of chemical components, on one hand, by adjusting the respective contents of Ni, cu, al, ti and N, and on the other hand, by establishing the association relation [ Ni ] +0.5[ cu ] +1.5[ al ] +1.2[ ti ] +5[N ] between Ni, cu, al, ti and N and defining the value of the relation, and restricting the content of the corresponding element in a reverse direction, the embodiment ensures excellent low-temperature performance of the low-temperature steel bar without adding Cr or lowering Ni, and does not cause problems such as plastic degradation, inclusion increase, etc. of the low-temperature steel bar; compared with other existing low-temperature steel bars, the low-temperature steel bar has more excellent normal temperature performance, plasticity and toughness, welding performance and low-temperature performance, and is low in alloy cost and production difficulty.
It should be noted that the association relationship [ Ni ] +0.5[ cu ] +1.5[ al ] +1.2[ ti ] +5[N ] between the element Ni, cu, al, ti and N has an important influence on the performance (particularly, low-temperature performance) of the low-temperature steel bar, which was first creatively obtained and proposed by the inventors, and is specifically defined herein as the low-temperature performance index LTE of the low-temperature steel bar, that is, lte= [ Ni ] +0.5[ cu ] +1.5[ al ] +1.2[ ti ] +5[N ]. Moreover, the present invention preferably defines 1.30% or less [ Ni ] +0.5[ Cu ] +1.5[ Al ] +1.2[ Ti ] +5[N ]. Ltoreq.1.65%, and further may preferably be 1.30% to 1.60%, based on which the obtained low-temperature reinforcing steel bar can have unexpected low-temperature properties, plasticity, weldability, and normal-temperature properties while having low alloy cost, and the welded joint obtained after welding also has excellent low-temperature properties, being able to satisfy the use requirements of the low-temperature reinforcing steel bar.
Specifically, the diameter of the low-temperature steel bar is 6-40 mm, and the structure of the low-temperature steel bar is polygonalFerrite, bainite and a very small amount of pearlite, wherein the bainite accounts for more than or equal to 75 percent, and the pearlite accounts for less than 1 percent; yield strength R of reinforcing steel bar at normal temperature p0.2 450-485 MPa, tensile strength R m 650-685 MPa, elongation after break A of 23-26%, and total elongation with maximum force A gt 13-15% of the ratio of strong to strong m /R p0.2 1.35 to 1.50; yield strength R in the non-notched form at-165℃low temperature p0.2 Not less than 600MPa and tensile strength R m More than or equal to 720MPa and maximum force total elongation A gt More than or equal to 5.5 percent; yield strength R in notched form p0.2 More than or equal to 610MPa and tensile strength R m More than or equal to 700MPa and the maximum force total elongation A gt More than or equal to 3.5 percent; the notch sensitivity index is more than or equal to 1.18, and is the tensile strength R in a notched form m Yield strength R in the non-defective state p0.2 。
In addition, when the low-temperature steel bar is used as a base material for welding, the obtained welded joint structure is excellent, and the welded joint structure is polygonal ferrite, acicular ferrite and granular bainite, wherein the polygonal ferrite accounts for less than or equal to 8 percent, and the granular bainite accounts for more than or equal to 65 percent; and, the obtained welded joint was cooled to room temperature and then subjected to performance test, a breaking point in room temperature elongation test was formed at the base material of the reinforcing steel bar, and the welded joint was 180 ° cold-bent at room temperature without cracks, d=4d dw Wherein D is the diameter of the center of curvature, D dw Is the diameter of the steel bar.
Furthermore, the preferred production method of the low-temperature steel bar is provided in the present embodiment, and it should be noted that the low-temperature steel bar may be prepared by other existing processes besides the production method, and the production method has advantages compared with the existing production process.
In this embodiment, the production method includes a molten iron pretreatment process, a converter smelting process, an LF refining process, an RH refining process, a continuous casting process, and a controlled rolling and cooling process, which are sequentially performed, and each process is described in detail below.
(1) Molten iron pretreatment process
The desulfurization pretreatment is carried out on the blast furnace molten iron, and the desulfurization slag skimming rate of the pretreated molten iron is more than or equal to 98 percent. Before pretreatment, the chemical components of the molten iron comprise the following components in percentage by mass: si is less than or equal to 0.10 percent, P is less than or equal to 0.12 percent. The temperature of the pretreated molten iron is more than or equal to 1385 ℃, and the S content in the molten iron is less than or equal to 0.005 percent by mass percent.
(2) Converter smelting process
The pretreated molten iron enters a converter to carry out oxygen blowing smelting, wherein the smelting end point C is less than or equal to 0.03%, P is less than or equal to 0.08% and Si is less than or equal to 0.05%. The tapping temperature of the converter is 1610-1625 ℃, and nitrogen or argon is purged to the ladle before tapping, so that oxygen uptake of molten steel is reduced. Ferromanganese, nickel plates and copper blocks are added when tapping is carried out 1/4, and ferrotitanium is added when tapping is carried out 1/2.
(3) LF refining procedure
After molten steel discharged from the converter enters an LF station, slag formation is carried out in a manner of adding 5.5-8.5 kg of alkaline slag former into each ton of molten steel. Wherein, the slag former comprises the following components in percentage by mass: 45% -55% of Ca, 30% -40% of Al and the balance of O. Controlling the alkalinity of refining slag to be 0.8-1.2, and the components mainly comprise CaO and Al 2 O 3 Thus, the slag pouring is facilitated, and the refractory material can be protected. And in the whole process of slag formation, argon is subjected to bottom blowing for soft stirring, the flow rate of the argon is 120-160L/min, and the soft stirring time is 7-10min, so that inclusions are floated to the greatest extent, and the cleanliness of molten steel is improved.
After soft stirring, electrifying and heating, sampling and detecting the added alloy, controlling LF refining tapping to 1565-1590 ℃, and controlling Si element in the obtained molten steel to be less than or equal to 0.08 percent by mass.
(4) RH refining step
And (5) enabling molten steel obtained through LF refining to enter an RH furnace for refining.
Specifically, argon circulation deoxidization and dehydrogenation are carried out firstly, the vacuum degree is controlled to be less than or equal to 1.5mbar, the static circulation time is controlled to be more than or equal to 15min, H is controlled to be less than or equal to 0.00016%, and O is controlled to be less than or equal to 0.0015%.
Then, feeding an alloy cored wire with the diameter of 6-8mm by a wire feeder according to the wire feeding quantity of 0.25-0.45 kg and the wire feeding speed of 0.8-1.2 m/s per ton of molten steel, wherein the cored wire is prepared from aluminum particles and silicon nitride iron, and the components in percentage by mass are as follows: 50 to 55 percent of Al, 15 to 20 percent of Si, 5 to 10 percent of N and the balanceIs Fe. Thus, after RH deoxidization and dehydrogenation, al is added in a cored wire feeding mode and the content of Si and N is regulated and controlled, so that Al can be greatly reduced 2 O 3 -SiO 2 Is mixed, improves the yield of Al and precisely controls the content of N.
Finally, breaking vacuum and tapping, wherein the RH tapping temperature is 1555-1580 ℃.
(5) Continuous casting process
And (3) preparing the molten steel obtained by RH refining into a continuous casting blank with the cross section size of 150 multiplied by 150mm by adopting the continuous casting blank. The full protection casting is carried out in the continuous casting process, specifically, for example, a large ladle long nozzle, an argon seal, an alkaline tundish covering agent, a submerged nozzle, low-carbon covering slag and other protection modes are adopted. Dynamic light pressing is adopted in the solidification secondary cooling zone, the pressing amount is 2-4.5 mm, and the pressing rate is 0.4-0.55 mm/min. The continuous casting drawing speed is 0.18-0.25 m/min, so that the segregation of Cu, al and Ti elements at the center and 1/4 part can be prevented from forming microcracks, and further the cracking in the subsequent rolling control process is avoided.
(6) Controlled rolling and cooling process
Firstly, after leaving the continuous casting machine, the continuous casting billet directly enters a heating furnace for heating at the temperature of 550-600 ℃ (namely, when the continuous casting billet does not fall below 550 ℃). The soaking temperature is controlled to 1070-1120 ℃ in the heating process, the total heating time is 40-55 min, and the maintaining time above 1100 ℃ is less than or equal to 5min. On the one hand, the continuous casting blank with the temperature (for example, 550-600 ℃) enters the heating furnace, so that the continuous casting cracks of the cold blank can be reduced, the surface quality of the steel bar finished product is improved, and meanwhile, the operation rate is improved; in still another aspect, the total heating time is short and the soaking temperature is low, so that the copper-rich phase can be prevented from being partially melted in the steel billet, and cracking is further reduced.
Subsequently, the continuous casting slab enters a continuous rolling mill for controlled rolling after leaving the heating furnace. The control rolling process comprises a rough rolling stage, a medium rolling stage, a finish rolling first stage and a finish rolling second stage, wherein the initial rolling temperature of the control rolling process is 960-985 ℃ (namely, the inlet temperature of the rough rolling stage is 960-985 ℃), the inlet temperature of the medium rolling stage is 930-955 ℃, the inlet temperature of the finish rolling first stage is 850-875 ℃, and the inlet temperature of the finish rolling second stage is 800-825 ℃. In this way, the controlled rolling process of the embodiment adopts a gradient cooling rolling mode, so that rolling force can be improved, work hardening can be enhanced, and the controlled rolling process is in a non-recrystallization zone through a finish rolling process (comprising a finish rolling first stage and a finish rolling second stage), ferrite is fully refined, and meanwhile, the fine grain strengthening effect of AlN and TiN is fully exerted through a deformation induction effect.
Wherein preferably the rough rolling stage comprises 8 passes of rough rolling defined by a mill # 1 to 8, the intermediate rolling stage comprises 4 passes of intermediate rolling defined by a mill # 9 to 12, the finish rolling first stage comprises 2 passes of finish rolling defined by a mill # 13 to 14, and the finish rolling second stage comprises 4 passes of finish rolling defined by a mill # 15 to 18; of course, it will be appreciated that the number of lanes at each stage is not limited to this preferred design. In addition, the temperature control is performed between the rough rolling stage and the intermediate rolling stage by adopting an aerosol cooling mode, for example, an aerosol cooling device is arranged between an 8# rolling mill and a 9# rolling mill, and the temperature control is performed by using the aerosol cooling device before a rolled piece leaves the 8# rolling mill and enters the 9# rolling mill; moreover, temperature control is performed between the intermediate rolling stage and the finish rolling first stage, and between the finish rolling first stage and the finish rolling second stage by using water penetrating devices, for example, a first water penetrating device is arranged between a 12# rolling mill and a 13# rolling mill, temperature control is performed by using the first water penetrating device before a rolled piece leaves the 12# rolling mill and enters the 13# rolling mill, a second water penetrating device is arranged between the 14# rolling mill and the 15# rolling mill, and temperature control is performed by using the second water penetrating device before the rolled piece leaves the 14# rolling mill and enters the 15# rolling mill.
In one embodiment, the diameter of the steel bar rolled by the continuous rolling mill is 6-40 mm.
Finally, the steel bar rolled by the continuous rolling mill is cooled to room temperature by a cooling bed, and the temperature of the cooling bed is 500-550 ℃; before the upper cooling bed, the steel bars are cooled by a water penetrating device after leaving the continuous rolling mill. Specifically, for example, a third water penetrating device is arranged after a continuous rolling mill (such as an 18# rolling mill), the steel bar is rapidly cooled to 500-550 ℃ by using the third water penetrating device after leaving the continuous rolling mill (such as an 18# rolling mill), and then the steel bar is put on a cooling bed. Therefore, after finish rolling, strong penetrating water enables the steel bars to rapidly pass through the pearlite transformation area and enter the bainite transformation area, so that deformed austenite is fully transformed into bainite to obtain an ideal structure, and therefore the ideal steel bar structure can be obtained on the premise of low-carbon low-silicon components, and the strength of the obtained low-temperature steel bars is excellent.
Still further, an embodiment of the present invention also provides a flash butt welding method for the low-temperature steel bar. The flash butt welding method specifically comprises a pretreatment process, a clamping process, a preheating process, a welding process and a cooling process which are sequentially carried out. The respective steps are described in detail below.
(1) Pretreatment process
And polishing the surface of the end part to be welded of the low-temperature steel bar. Therefore, oxide skin and rust on the surface of the end to be welded are removed by polishing, so that oxygen exceeding caused by oxide is prevented, and the problem that the low-temperature performance is affected due to microcrack of the finally obtained welded joint is avoided.
Wherein the surface comprises an end face of the end to be welded and a circumferential surface with a certain length from the end face. Preferably, the certain length is controlled to be 25-40 mm, namely, the length of the polished end to be welded is 25-40 mm. It is further preferable that the certain length is not smaller than a length L of an end portion to be welded which is within a heating range of the induction coil, which will be described later, so that the area of the end portion to be welded which is within the heating range of the induction coil is polished in the pretreatment process.
(2) Clamping process
The polished end to be welded passes through an induction coil of a flash butt welding machine and is clamped on an electrode; it will be appreciated that the flash butt welder has electrodes arranged in pairs with two ends to be welded each clamped to one of a pair of electrodes.
After clamping is finished, the gap d between the end faces of the two ends to be welded is controlled to be 2-5 mm, the length L of each end to be welded in the heating range of the induction coil is controlled to be 20-30 mm, and the distance between the two electrodes is larger than 2L+d, so that the electrodes can be prevented from being damaged by heating when the induction coil is used for heating in the subsequent working procedure.
Preferably, the distance between the two electrodes is controlled to be 50-80 mm.
(3) Preheating process
And preheating the end to be welded to 800-880 ℃ within 15-30 seconds by using an induction coil heating mode. That is, the induction coil of the flash butt welding machine is started to heat the end to be welded, so that the temperature of the end to be welded is quickly increased to 800-880 ℃ from normal temperature within 15-30 seconds, and then the induction coil is controlled to finish heating (namely, the preheating process is finished and the next welding process is started). Therefore, on one hand, the complete solid solution of the alloy element can be ensured, and on the other hand, the preheating time (such as 15-30 s) is shorter, so that the internal structure of the end to be welded is controllable, and the performance of the final welded joint is facilitated.
During the preheating, the argon atmosphere is maintained at the flow of 5-10 mL/s at the end to be welded, so that the probability of oxidization of the end to be welded after being heated is reduced, and the performance of the final welded joint is further ensured.
(4) Welding process
As described above, after the preheating is completed (i.e. the end to be welded reaches 800-880 ℃), the induction coil is controlled to finish heating, and the flash butt welding machine is started to enter the welding process. The welding process comprises a flashing stage and a pressure upsetting stage which are sequentially and continuously carried out.
Firstly, in the flashing stage, the flash butt welding machine is carried out according to preset flashing parameters, so that the end to be welded reaches a semi-molten state from 800-880 ℃. The flash parameters include flash heat of (0.2-0.5) kJ/mm 2 ×S dw +Q f Flash distance is (0.8-1.2) x d dw +d, flash time 8-15S, S in flash heat dw To be welded end section area, Q f D is floating heat dw Is the diameter of the steel bar.
Wherein, regarding Q f There are various options for the arrangement of (a). In a preferred embodiment, Q f Is associated with a carbon equivalent Ceq, in particular, for example, as previously mentioned, the carbon equivalent Ceq of the low-temperature rebar is less than or equal to 0.46%, then: q is equal to or less than 0.40% when Ceq f =1 to 5kJ; q is less than Ceq and less than or equal to 0.44 percent when 0.40 percent f =5 to 15kJ; q is less than or equal to 0.46% when Ceq is less than 0.44% f ＝15～40kJ, of course, Q f The arrangement of (c) is not limited to this preferred embodiment.
D is as previously described dw Is the diameter of the steel bar, for example, the diameter of the low-temperature steel bar is 6-40 mm.
Furthermore, the flash parameters are set as above, so that the end to be welded can reach a semi-molten state in a short time (for example, the flash time is 8-15 s), the requirement of subsequent fusion is met, and meanwhile, oxidation can be avoided, and the performance of the finally obtained welded joint is improved.
Next, in the pressure upsetting phase, the flash butt welder is operated according to preset pressure upsetting parameters so that the two ends to be welded are fused together, i.e. welded together. The pressure upsetting parameters comprise upsetting stress of 105-150 MPa and upsetting time of less than or equal to 0.8s.
In addition, in the whole welding process, argon atmosphere is maintained at the flow of 12-18 mL/s, so that the probability of oxidization of the end to be welded is reduced, and the performance of the final welded joint is further ensured.
(5) Cooling process
After the pressure upsetting is completed, the cooling process is started, and the whole cooling process is divided into three stages: the first stage, firstly, maintaining argon atmosphere at a flow rate of 45-60 mL/s (namely, increasing the flow rate of argon from 12-18 mL/s to 45-60 mL/s in the welding process), and controlling the obtained welding joint to be cooled to 600-650 ℃ at a cooling rate of 10-15 ℃/s, wherein the first stage is a rapid cooling stage, and the effects of reducing ferrite phase transformation and reducing surface oxidation can be realized; in the second stage, argon atmosphere is maintained at a flow of 5-10 mL/s (namely, the flow of argon is reduced from 45-60 mL/s to 5-10 mL/s in the first stage), the welding joint is controlled to maintain 530-560 ℃ and to maintain 300-480 s by using an induction coil in a heating mode during the second stage, namely, in the cooling process of the second stage, when the welding joint is cooled to 560 ℃, the welding joint is controlled to maintain 300-480 s in a temperature interval of 530-560 ℃ by using the induction coil, so that the welding joint is fully transformed to obtain ideal granular bainite structure, and the performance of the final welding joint is further ensured; and thirdly, when the temperature of the welded joint is reduced to below 530 ℃, controlling the welded joint to be cooled to the room temperature at a cooling rate of 0.2-0.5 ℃/s, and thus, fully releasing the internal stress of upsetting fusion through the heat preservation stage.
In the third stage of the process, there are various ways of controlling the temperature of the welded joint to be lowered slowly to room temperature, and in a preferred embodiment, the induction coil may be terminated to heat, argon gas may be stopped, and a heat-retaining cover may be added, so that the welded joint may be controlled to be lowered to room temperature at a cooling rate of 0.2 to 0.5 ℃/s. Of course, the specific implementation is not limited thereto.
Compared with the prior art, the traditional welding technology of the low-temperature steel bar is arc welding or gas shielded welding, and the flash butt welding technology is disclosed for the first time on the welding processing of the low-temperature steel bar due to the requirement of the low-temperature steel bar on the low-temperature performance of a welding joint, the flash butt welding technology can ensure the excellent low-temperature performance of the welding joint of the low-temperature steel bar, for example, the flash butt welding technology is adopted to weld by taking the low-temperature steel bar as a base material, the obtained welding joint has excellent structure of polygonal ferrite, needle-shaped ferrite and granular bainite, wherein the polygonal ferrite accounts for less than or equal to 8 percent, the granular bainite accounts for more than or equal to 65 percent, and further the excellent normal-temperature performance and the low-temperature performance are ensured, for example, the breaking point of two welded low-temperature steel bars in a room-temperature tensile test is formed at the base material of the steel bar, and D=4d when the welding joint is cold-bending performance at room temperature is 180 degrees dw Appearance is crack-free, wherein D is the core diameter; in still another aspect, the flash butt welding technique of the present invention may further have a greater advantage than arc welding or gas shielded welding, and in particular, the method may automatically and continuously operate through the whole process after the low temperature steel bar is clamped on the flash butt welding machine until the welding is completed and cooled to room temperature, without performing additional off-line heat treatment (i.e., without detaching the steel bar from the flash butt welding machine) before clamping or after the welding is completed as in the prior art, and may ensure excellent low temperature performance and normal temperature performance of the welded joint, with fewer overall process steps, short time, and high efficiency.
The above detailed description is merely illustrative of possible embodiments of the present invention, which should not be construed as limiting the scope of the invention, and all equivalent embodiments or modifications that do not depart from the spirit of the invention are intended to be included in the scope of the invention.
Several embodiments of the present invention are provided below to further illustrate the technical aspects of the present invention. Of course, these embodiments are only a preferred part, but not all, of the many variations encompassed by the present invention.
Examples A1 to G1 of the low-temperature reinforcing bars are shown here, and the low-temperature reinforcing bars are implemented according to the technical scheme of the previous embodiment of the present invention, for example, the chemical composition of the low-temperature reinforcing bars is designed according to an embodiment of the present invention, and the low-temperature reinforcing bars are produced by the production method of an embodiment of the present invention (of course, the production method of the low-temperature reinforcing bars is not limited to the present invention). Referring to tables 1 to 3 below, table 1 shows chemical compositions of the low temperature reinforcing bars of examples A1 to G1, table 2 shows specifications (i.e., diameters), microstructures, and normal temperature mechanical properties of the low temperature reinforcing bars of examples A1 to G1, and table 3 shows low temperature mechanical properties of the low temperature reinforcing bars of examples A1 to G1.
TABLE 1
TABLE 2
TABLE 3
As can be seen from the above examples, the low-temperature reinforcing steel bar of the present invention has excellent structure, low-temperature property and normal-temperature property, and in addition, has excellent ductility and toughness, and has low alloy cost, low production cost, high production efficiency and low difficulty.
Further, the welding tests performed using the low-temperature reinforcing bars of the foregoing examples A1 to G1 as the base materials, and the obtained test examples A2 to G2 and A3, A4 are shown in table 4, respectively, and specifically, the base materials used in the respective test examples (i.e., the examples in the index table 1), the welding technique used, the microstructure of the obtained welded joint, and the performance test results at room temperature are shown in table 4; in addition, table 5 also shows the low temperature mechanical properties of the welded joints obtained in test examples A2 to G2.
TABLE 4
TABLE 5
As can be seen from tables 4 and 5, test examples A2 to G2 were welded by the flash butt welding method provided by the present invention, while test examples A3 and A4 were welded by the existing known arc welding and gas shield welding, and the welded joint of the present invention satisfies the application requirements of the low temperature steel bar after welding, and the welding performance of the low temperature steel bar of the present invention is excellent; in addition, the flash butt welding method disclosed by the invention is used as a flash butt welding technology which is disclosed for the first time in the industry and is suitable for low-temperature steel bars, the obtained welded joint has an excellent microstructure, and the normal-temperature tensile property, the cold bending property and the low-temperature mechanical property are excellent, so that the application requirements of the low-temperature steel bars after welding are met, and in addition, the flash butt welding method has the advantages of full-process automatic continuous operation, less overall process steps, short time, high efficiency and the like.
Claims (8)
1. The production method of the low-temperature steel bar is characterized by comprising the following chemical components in percentage by mass: 0.03-0.06% of C, 0.12-0.25% of Si, 1.65-1.85% of Mn, 0.92-1.25% of Ni, 0.25-0.48% of Cu, 0.045-0.06% of Al, 0.02-0.06% of Ti, less than or equal to 0.010% of P, less than or equal to 0.012% of S, 0.008-0.015% of N, less than or equal to 20ppm of O, less than or equal to 2ppm of H, and the balance of Fe and unavoidable impurities; and, ni+0.5Cu+1.5Al+1.2Ti+ 5[N is 1.30-1.65%, the carbon equivalent Ceq= [ C ] + [ Mn ]/6+ ([ Cr ] + [ Mo ] + [ V ])/ 5+ ([ Ni ] + [ Cu ])/15 is less than or equal to 0.46%, wherein [ C ], [ Mn ], [ Cr ], [ Mo ], [ V ], [ Ni ], [ Cu ], [ Al ], [ Ti ], [ N ] respectively represent the mass percent of the corresponding elements in the low-temperature steel bar; the structure of the steel bar is polygonal ferrite, bainite and a very small amount of pearlite, wherein the bainite accounts for more than or equal to 75 percent, and the pearlite accounts for less than 1 percent;
the production method comprises a molten iron pretreatment process, a converter smelting process, an LF refining process, an RH refining process, a continuous casting process and a rolling and cooling control process which are sequentially carried out;
in the LF refining procedure, the components of the slag former adopted in slag formation are as follows by mass percent: 45% -55% of Ca, 30% -40% of Al and the balance of O, and controlling the alkalinity of refining slag to be 0.8% -1.2; argon is blown into the slag forming process at the bottom in the whole process to carry out soft stirring, the argon flow is 120-160L/min, and the soft stirring time is 7-10min;
in the RH refining process, deoxidization and dehydrogenation are firstly carried out, then an alloy cored wire is fed by a wire feeder according to the wire feeding quantity of 0.25-0.45 kg and the wire feeding speed of 0.8-1.2 m/s per ton of molten steel, and the cored wire comprises the following components in percentage by mass: 50-55% of Al, 15-20% of Si, 5-10% of N and the balance of Fe;
in the continuous casting process, full-protection casting is carried out, dynamic light pressing is adopted in a solidification secondary cooling zone, the pressing amount is 2-4.5 mm, the pressing rate is 0.4-0.55 mm/min, and the continuous casting drawing speed is 0.18-0.25 m/min;
in the rolling and cooling control process, after leaving a continuous casting machine, directly entering a heating furnace for heating at the temperature of 550-600 ℃, wherein the soaking temperature is 1070-1120 ℃; sequentially performing a rough rolling stage, a medium rolling stage, a finish rolling first stage and a finish rolling second stage on the heated continuous casting billet on a continuous rolling mill, wherein the inlet temperature of each stage is 960-985 ℃, 930-955 ℃, 850-875 ℃ and 800-825 ℃ in sequence; finally, cooling the steel bar rolled by the continuous rolling mill to room temperature by using a cooling bed, wherein the temperature of the cooling bed is 500-550 ℃; before the upper cooling bed, the steel bars are cooled by a water penetrating device after leaving the continuous rolling mill.
2. The method for producing a low-temperature reinforcing bar according to claim 1, wherein the chemical composition of the reinforcing bar comprises, in mass percent: 0.03-0.06% of C, 0.12-0.18% of Si, 1.65-1.85% of Mn, 0.92-1.20% of Ni, 0.27-0.48% of Cu, 0.045-0.06% of Al, 0.03-0.06% of Ti, less than or equal to 0.010% of P, less than or equal to 0.012% of S, 0.012-0.015% of N, less than or equal to 20ppm of O, less than or equal to 2ppm of H, and the balance of Fe and unavoidable impurities; and [ Ni ] +0.5[ Cu ] +1.5[ Al ] +1.2[ Ti ] +5[N ] is 1.30 to 1.60%, and the carbon equivalent Ceq is not more than 0.46%.
3. The method for producing a low-temperature reinforcing bar according to claim 1, wherein the yield strength R of the reinforcing bar is at normal temperature p0.2 450-4815 MPa, tensile strength R m 650-685 MPa, elongation after break A of 23-26%, and total elongation under maximum force A gt 13-15% of the ratio of strong to strong m /R p0.2 1.35 to 1.50.
4. The method of manufacturing a low temperature reinforcing bar according to claim 1, wherein after the reinforcing bar is welded as a base material, a breaking point in a room temperature tensile test is formed at the base material of the reinforcing bar, and a welded joint is 180 ° cold-bent at room temperature without cracks, d=4d dw Wherein D is the diameter of the center of curvature, D dw Is the diameter of the steel bar.
5. The method according to claim 1, wherein the welded joint has a structure of polygonal ferrite, acicular ferrite, and granular bainite, wherein the polygonal ferrite is 8% or less and the granular bainite is 65% or more, after the steel is welded as a base material.
6. The method for producing a low-temperature reinforcing bar according to claim 1, wherein the reinforcing bar has a yield strength R in a non-defective state at a low temperature of-165 °c p0.2 Not less than 600MPa and tensile strength R m More than or equal to 720MPa and maximum force totalElongation A gt More than or equal to 5.5 percent; yield strength R in notched form p0.2 More than or equal to 610MPa and tensile strength R m More than or equal to 700MPa and the maximum force total elongation A gt More than or equal to 3.5 percent; the notch sensitivity index is more than or equal to 1.18, and is the tensile strength R in a notched form m Yield strength R in the non-defective state p0.2 。
7. The method according to claim 1, wherein the temperature is controlled by aerosol cooling between the rough rolling stage and the intermediate rolling stage, and the temperature is controlled by a water penetrating device between the intermediate rolling stage and the finish rolling first stage, and between the finish rolling first stage and the finish rolling second stage.
8. The method according to claim 1, wherein the continuous casting is maintained in the heating furnace at 1100 ℃ or higher for 5min or less in the controlled rolling and cooling process.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211356682.0A CN115537668B (en) | 2022-11-01 | 2022-11-01 | Low-temperature steel bar and production method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211356682.0A CN115537668B (en) | 2022-11-01 | 2022-11-01 | Low-temperature steel bar and production method thereof |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN115537668A CN115537668A (en) | 2022-12-30 |
| CN115537668B true CN115537668B (en) | 2023-07-04 |
Family
ID=84719855
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202211356682.0A Active CN115537668B (en) | 2022-11-01 | 2022-11-01 | Low-temperature steel bar and production method thereof |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN115537668B (en) |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5292784B2 (en) * | 2006-11-30 | 2013-09-18 | 新日鐵住金株式会社 | Welded steel pipe for high-strength line pipe excellent in low temperature toughness and method for producing the same |
| CN102534376B (en) * | 2012-02-29 | 2014-01-29 | 江苏省沙钢钢铁研究院有限公司 | Steel plate with excellent low-temperature toughness in large heat input welding heat affected zone and production method thereof |
| CN102766748B (en) * | 2012-08-10 | 2013-07-24 | 江苏省沙钢钢铁研究院有限公司 | Production method of low-temperature steel plate capable of being welded at high heat input |
| CN103422033B (en) * | 2013-07-26 | 2016-01-27 | 南京钢铁股份有限公司 | A kind of low temperature Deformed Steel Bars and production technique thereof |
| CN114231834B (en) * | 2021-10-15 | 2022-12-16 | 首钢集团有限公司 | High-strength and good low-temperature toughness ultra-thick structural steel and production method thereof |
-
2022
- 2022-11-01 CN CN202211356682.0A patent/CN115537668B/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| CN115537668A (en) | 2022-12-30 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN110541117B (en) | 620 MPa-grade high-performance bridge steel welded at low preheating temperature and preparation method thereof | |
| CN111441000A (en) | 690 MPa-yield-strength low-yield-ratio high-strength steel plate and manufacturing method thereof | |
| CN102021497A (en) | X80 pipeline steel hot-rolled plate coil and manufacturing method thereof | |
| KR20230076811A (en) | Steel plate for polar marine process and manufacturing method thereof | |
| WO2022183522A1 (en) | Hot rolled seamless steel tube and deformation and phase transformation integrated control method for structure thereof | |
| CN114134406B (en) | Spherical tank steel plate with thickness of 20-50mm and excellent low-temperature toughness of core and manufacturing method thereof | |
| CN115418559B (en) | High-strength and high-toughness hot rolled H-shaped steel for building and preparation method thereof | |
| CN115927952B (en) | 690 MPa-grade hydrogen-induced delayed fracture resistant low-weld crack sensitivity quenched and tempered steel and manufacturing method thereof | |
| CN114134407A (en) | Easy-to-weld steel plate with excellent low-temperature toughness at core for volute and manufacturing method thereof | |
| CN114107811A (en) | 700 MPa-grade high heat input resistant welding steel and manufacturing method thereof | |
| CN112030071A (en) | 510 MPa-grade high-toughness automobile girder steel and preparation method thereof | |
| CN107974643B (en) | -70 ℃ normalized high-strength low-yield-ratio pressure vessel steel and manufacturing method thereof | |
| CN114107812A (en) | High-fracture-toughness 420 MPa-grade heat-treated steel plate for marine platform and preparation method thereof | |
| CN113957359A (en) | High-strength steel for automobile wheels and preparation method thereof | |
| CN112899558B (en) | 550 MPa-grade weather-resistant steel plate with excellent weldability and manufacturing method thereof | |
| CN113025885A (en) | Low-yield-ratio high-strength pipeline steel plate with good HIC (hydrogen induced cracking) resistance and manufacturing method thereof | |
| CN112626423A (en) | Production process for improving welding performance of rare earth high-strength steel | |
| CN102108467A (en) | High-heat-input-welded steel plate for low-temperature structure and manufacturing method thereof | |
| CN115537668B (en) | Low-temperature steel bar and production method thereof | |
| CN115502531B (en) | Flash butt welding method for low-temperature steel bars | |
| JPH0757886B2 (en) | Process for producing Cu-added steel with excellent weld heat-affected zone toughness | |
| CN112176147B (en) | Manufacturing method of normalized thick steel plate suitable for large-wire welding | |
| CN110814568B (en) | High-toughness medium manganese steel gas shielded welding wire | |
| CN110747390B (en) | High-strength corrosion-resistant steel for ships and preparation method thereof | |
| CN116497281B (en) | Hot rolled H-shaped steel for assembled building structure and preparation method thereof |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |