CN111270141A - Corrosion-resistant steel bar for reinforced concrete and preparation method thereof - Google Patents
Corrosion-resistant steel bar for reinforced concrete and preparation method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
- C21D8/08—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires for concrete reinforcement
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/002—Bainite
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
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Abstract
The invention discloses a corrosion-resistant steel bar for reinforced concrete and a preparation method thereof, wherein the corrosion-resistant steel bar comprises the following chemical components in percentage by mass: c: 0.11 to 0.13%, Si: 0.50-0.60%, Mn: 1.20 to 1.30%, Nb: 0.015-0.030%, Cr: 0.65-0.75%, Ni: 0.40-0.65%, Cu: 0.40-0.50%, S: 0-0.008%, P: 0-0.015% and the balance of Fe and inevitable impurities; the preparation method of the corrosion-resistant steel bar solves the technical problems of refining and homogenization of the microstructure of the steel bar by reasonably setting the production parameters of rough rolling, intermediate rolling and finish rolling of a steel bar steel rolling production line and comprehensively utilizing a plurality of process measures, achieves the technical effects of refining and homogenization of the microstructure of the steel bar, has low cost, and can utilize various control mechanisms and meet the rolling control requirements of different specifications and components.
Description
Technical Field
The invention belongs to the technical field of metallurgy, and particularly relates to a corrosion-resistant steel bar for reinforced concrete and a preparation method thereof.
Background
Corrosion of steel reinforcement has long been a major cause of early deterioration of reinforced concrete structures. The natural pores of the reinforced concrete cause the corrosion of the steel bars, which leads to the cracking of the concrete and the peeling of the protective layer, and the reduction and even the loss of the bearing capacity of the building, thus causing catastrophic accidents. Research shows that the corrosion loss of the steel bars is 6 times of the comprehensive loss of natural disasters such as flood, fire, hurricane, earthquake and the like. With the increase of reinforced concrete buildings such as coastal ports and wharfs, cross-sea bridges and the like, more buildings face a severe challenge of chloride corrosion.
Measures for improving the durability of buildings can be summarized into two points: firstly, the penetration speed of chloride ions is prevented or slowed down; and secondly, the corrosion resistance of the steel bar matrix is improved. A large number of engineering practical experiences show that: the measures for blocking the penetration speed of chloride ions can only be taken as auxiliary measures, and the improvement of the structural durability is only essential when corrosion-resistant reinforcing steel bars are adopted.
The existing corrosion-resistant reinforcing steel bars mainly comprise stainless steel reinforcing steel bars, epoxy coating reinforcing steel bars, alloy coating reinforcing steel bars, FRP reinforcing steel bars and the like. The corrosion resistance of the stainless steel bars is excellent, but the high price thereof greatly increases the construction cost, and it is difficult to support the rapidly growing scale of coastal construction. Although the epoxy resin coating steel bars are widely used in developed countries such as the United states, Europe and the like, the tracking and inspection result shows that the epoxy resin coating steel bars are difficult to avoid local failure caused by collision in the process of carrying and installing. Meanwhile, the aging problem of the epoxy resin is difficult to avoid the failure beginning in 15 years, and the reinforcing steel bar still faces serious corrosion problems. The alloy plating layer is easy to dissolve and erode, the long service life of the concrete structure cannot be ensured, and the two coating reinforcing steel bars can cause the reduction of the bonding force between the reinforcing steel bars and the concrete. The FRP bar, i.e. a Fiber Reinforced Polymer (FRP), has the characteristics of high strength-to-mass ratio, good fatigue resistance, easy construction, corrosion resistance, etc. However, the high strength resistance of the FRP rib and the linear relationship between stress and strain lead to low ductility and brittle failure of the concrete structure, which limits the wide-range application of the FRP rib.
Disclosure of Invention
The invention provides the corrosion-resistant reinforcing steel bar for the reinforced concrete and the preparation method thereof, the obtained corrosion-resistant reinforcing steel bar meets the mechanical property requirement of 400MPa steel, the refinement and homogenization of the microstructure of the steel are achieved, various control mechanisms can be comprehensively utilized, the requirements of different specifications and component controlled rolling are met, the corrosion-resistant reinforcing steel bar can effectively prevent the engineering construction damage caused by the corrosion of reinforcing steel bar materials, the service life and the use safety of the construction are greatly improved,
in a first aspect, an embodiment of the present invention provides a corrosion-resistant steel bar for reinforced concrete and a preparation method thereof, where the corrosion-resistant steel bar for reinforced concrete specifically comprises the following chemical components by mass: c: 0.11 to 0.13%, Si: 0.50-0.60%, Mn: 1.20 to 1.30%, Nb: 0.015-0.030%, Cr: 0.65-0.75%, Ni: 0.40-0.65%, Cu: 0.40-0.50%, S: 0-0.008%, P: 0-0.015%, and the balance of Fe and inevitable impurities.
Preferably, the microstructure of the high-strength steel bar includes pearlite, ferrite, bainite, and a precipitation structure.
Preferably, the strength grade of the high-strength steel bar is 400 MPa.
Preferably, the diameter of the corrosion-resistant reinforcing steel bar is 10-32 mm.
Preferably, the corrosion-resistant reinforcing steel bar has an elongation of not less than 16%.
Another aspect of the present invention provides a method for preparing a corrosion-resistant steel bar for reinforced concrete, the method being used for preparing the corrosion-resistant steel bar, and the method including:
step 1: smelting molten steel in a converter, then sending the molten steel into a refining furnace for refining and alloying, and adjusting the alloy element components and the content of the molten steel to obtain a steel billet;
step 2: sending the steel billet obtained in the step 1 into a continuous casting machine for continuous casting to obtain a continuous casting steel billet;
and step 3: inspecting the continuous casting billet, judging whether the continuous casting billet meets the preset billet condition, and if so, marking the continuous casting billet as a qualified product;
and 4, step 4: sending the qualified steel billets into a heating furnace for heating; the temperature range of the heating furnace in the heating process is 1150-1250 ℃, and the heating time is 1.5-2.5 hours;
and 5: presetting production parameters of a rough rolling unit, and roughly rolling the steel billet obtained in the step (4); the temperature range of the rough rolling process is 1000-1100 ℃;
step 6: presetting production parameters of a medium rolling mill set, and carrying out medium rolling on the billet obtained in the step 5; the temperature range of the middle rolling process is 1000-1100 ℃;
and 7: presetting production parameters of a finishing mill group, and finishing rolling the steel billet obtained in the step 6 to obtain a steel bar; the temperature range of the finish rolling process is 1050-1150 ℃;
and 8: and cooling the reinforcing steel bars on a cooling bed.
Preferably, in the step 5, during the initial rolling, the corrosion-resistant steel bar is rolled in an austenite recrystallization zone under control, wherein the rolling temperature is in the range of 1000-1050 ℃;
preferably, in the step 6, during the intermediate rolling, the corrosion-resistant steel bar is rolled in the austenite recrystallization zone under control, and the rolling temperature is in the range of 1000-1050 ℃.
Preferably, in the step 2, the superheat degree of the molten steel in the continuous casting process is 20-30 ℃.
Preferably, in the step 3, the preset billet condition is specifically: the defect grade of the continuous casting billet is less than 1 grade, and the defect type of the continuous casting billet comprises one or more of looseness, shrinkage cavity and segregation; and when the continuous casting billet does not meet the preset billet condition, finishing the inspection and marking as an unqualified product.
Preferably, in the step 5, after presetting the production parameters of the rough rolling mill group and performing rough rolling on the billet obtained in the step 4, the method further includes: the first crop, crop and break are carried out through the crank arm scissors.
Preferably, in the step 6, after presetting the production parameters of the intermediate mill group and performing intermediate rolling on the billet obtained in the step 5, the method further includes: controlling the temperature of the pre-cooling section to realize low-temperature finish rolling; and performing secondary crop, tail crop and fragmentation through the rotary scissors.
Preferably, in the step 8, the cooling the steel bar on the cooling bed includes: cutting the reinforcing steel bars by sections by adopting a multiple length shear; sending the sheared steel bars into a cooling bed for cooling;
the cooling bed is provided with a heat preservation cover for controlling the cooling speed, the temperature range in the cooling process is 280-1070 ℃, the cooling is slowly carried out in the heat preservation cover, and the cooling time range is 600-800 s.
Preferably, after the sheared reinforcing steel bars are sent to a cooling bed for natural cooling, the method further comprises the following steps: carrying out fixed-length shearing on the cooled steel bars by adopting cold shears; and removing the reinforcing steel bars which do not meet the size requirement to obtain the reinforcing steel bars meeting the requirement.
Preferably, after the steel bars which do not meet the size requirement are removed, the method further comprises the following steps: and counting and finishing the steel bars meeting the requirements, and after bundling and weighing, hoisting and warehousing.
One or more technical schemes in the invention have at least one or more of the following technical effects:
the reinforced concrete corrosion-resistant reinforcing steel bar provided by the invention has the advantages that the mass percentages of all components are reasonably regulated and controlled, and the strength of the reinforcing steel bar is improved in a microalloying mode, so that the microstructure of the corrosion-resistant reinforcing steel bar is refined and homogenized, the strength reaches 400MPa, the corrosion resistance is good, and the corrosion-resistant reinforcing steel bar can be widely applied to the design and use requirements of various structures (including primary and secondary anti-seismic structures).
The preparation method of the corrosion-resistant reinforcing steel bar for reinforced concrete reduces the production cost of the reinforcing steel bar, refines and homogenizes the microstructure of steel, and can comprehensively utilize various control mechanisms and meet the technical effects of different specifications and component controlled rolling requirements.
Detailed Description
The invention provides a corrosion-resistant steel bar for reinforced concrete and a preparation method thereof, and solves the technical problems of high production cost and poor corrosion resistance of the steel bar in the prior art.
The technical scheme in the embodiment of the invention has the following general idea:
the invention provides a corrosion-resistant steel bar for reinforced concrete, which comprises the following chemical components in percentage by mass: c: 0.11 to 0.13%, Si: 0.50-0.60%, Mn: 1.20 to 1.30%, Nb: 0.015-0.030%, Cr: 0.65-0.75%, Ni: 0.40-0.65%, Cu: 0.40-0.50%, S: 0-0.008%, P: 0-0.015%, and the balance of Fe and inevitable impurities.
Meanwhile, the embodiment of the invention also provides a preparation method of the corrosion-resistant steel bar, which mainly comprises the following steps: step 1: smelting molten steel in a converter, then sending the molten steel into a refining furnace for refining and alloying, and adjusting the alloy element components and the content of the molten steel to obtain a steel billet; step 2: sending the steel billet obtained in the step 1 into a continuous casting machine for continuous casting to obtain a continuous casting steel billet; and step 3: inspecting the continuous casting billet, judging whether the continuous casting billet meets the preset billet condition, and if so, marking the continuous casting billet as a qualified product; and 4, step 4: sending the qualified steel billets into a heating furnace for heating; and 5: presetting production parameters of a rough rolling unit, and roughly rolling the steel billet obtained in the step (4); step 6: presetting production parameters of a medium rolling mill set, and carrying out medium rolling on the billet obtained in the step 5; and 7: presetting production parameters of a finishing mill group, and finishing rolling the steel billet obtained in the step 6 to obtain a steel bar; and 8: and cooling the reinforcing steel bars on a cooling bed. By adopting the preparation method, the microstructure of the steel bar can be refined and homogenized, the production cost is reduced, and the technical effects of comprehensively utilizing various control mechanisms and meeting the rolling control requirements of different specifications and components can be realized.
Specifically, the corrosion-resistant steel bar for reinforced concrete provided by the invention mainly comprises the following chemical components: C. si, Mn, Nb, Ni, Cr, Cu, S and P, and the balance Fe and unavoidable impurities. The main effects of the added chemical components are as follows:
c: the content range of C of the corrosion-resistant steel bar is selected to be 0.11-0.13%, the carbon content is reduced as much as possible, the yield strength and the tensile strength meet the requirements, certain toughness is kept, good performance can be obtained, and the influence of excessively high carbon content on the corrosion resistance of the steel bar can be avoided.
Si: the silicon content of the corrosion-resistant steel bar is 0.50-0.60%, silicon is added as a reducing agent and a deoxidizing agent in the steelmaking process, so that the elastic limit, yield point and tensile strength of steel can be obviously improved, the corrosion resistance and oxidation resistance are improved, meanwhile, the bainite transformation is carried out at low temperature by solid solution strengthening, the bainite transformation C curve is shifted to the right, the stability of super-cooled austenite is improved, a super-cooled structure is formed, the content of proeutectoid ferrite is reduced, and the matrix strength of the corrosion-resistant steel bar is increased.
Mn: in the steelmaking process, Mn is a good deoxidizer and desulfurizer, and the content of Mn in the invention is set to be 1.20-1.30%. Therefore, the steel has enough toughness, higher strength and hardness, improved hardenability and hot workability.
Nb can refine grains, reduce the overheating sensitivity and the temper brittleness of steel and improve the strength, but the plasticity and the toughness are reduced. The content of Nb is 0.40-0.65%, and the main effect is that Nb is a strong carbon and strong nitrogen forming element, can generate stable and difficult-to-dissolve carbon and nitride in steel, is favorable for forming a fine casting structure, and can further strengthen precipitation, refine grains and improve the strength of the steel by controlling rolling.
Furthermore, the aim of improving the strength of the steel bar by adopting a micro-alloying route is fulfilled by the mutual combination effect of various elements.
Specifically, chromium can form a compact oxide film on the surface of steel, thereby improving the passivation capability of the steel and slowing down the growth speed of a rust layer. In the corrosion-resistant steel bar, the content of Cr is 0.65-0.75%. Preferably, the effect is particularly remarkable when chromium and copper are added simultaneously. The two are matched with each other to form a compact anti-corrosion layer, thereby reducing the corrosion-induced sensitivity of the matrix and better improving the corrosion resistance of the steel. Therefore, the Cu content in the corrosion-resistant steel bar is 0.40-0.50%. The nickel is a relatively stable element, and the addition of the nickel can change the self-corrosion potential of the steel to the positive direction, improve the repair capability of a passive film, reduce the corrosion sensitivity of the steel and further increase the stability of the steel. The mass percentage content range of the nickel in the invention is 0.40-0.65%. The atmospheric exposure test result shows that the nickel content in the range can obviously improve the atmospheric corrosion resistance of the seaside weathering steel. In addition, elements such as Nb and Cr can remarkably improve the hardenability of the steel bar, improve the stability of the super-cooled austenite, form bainite and increase the matrix strength.
Therefore, through the interaction among multiple elements such as Nb, Cr, Cu, Ni and the like, the microalloying of the steel bar structure can be realized, the microstructure of the obtained corrosion-resistant steel bar comprises pearlite, ferrite, bainite and a precipitation structure, the microstructure has good performance, and the strength of the corrosion-resistant steel bar is improved.
Meanwhile, Cr, Ni and Cu elements added into the corrosion-resistant reinforcing steel bar play a role in ensuring the corrosion resistance of the reinforcing steel bar besides playing a role in microalloying treatment.
The corrosion-resistant steel bar of the present invention is developed as a corrosion-resistant steel bar for reinforced concrete by adding elements such as Nb, Cr, Ni, Cu, etc. The strength grade of the corrosion-resistant steel bar is 400MPa, and the diameter of the corrosion-resistant steel bar is 10-32 mm. The microstructure comprises pearlite, ferrite, bainite and a precipitation structure, the performance of the microstructure is good, and the elongation of the high-strength steel bar is not less than 16%. Therefore, the corrosion-resistant steel bar of the present invention can be applied to a reinforcing bar structure having a high ductility requirement. When the requirements of the upper limit of the yield strength and the yield ratio of the steel bar required by the structural design are met, the design and use requirements of various structures (including primary and secondary anti-seismic structures) can be met.
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are a part of the embodiments of the present invention, but not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example one
The embodiment provides a corrosion-resistant steel bar for reinforced concrete, which comprises the following chemical components in percentage by mass: c: 0.12%, Si: 0.56%, Mn: 1.25%, Nb: 0.019%, Cr: 0.71%, Ni: 0.47%, Cu: 0.45%, S: 0.003%, P: 0.012%, and the balance Fe and inevitable impurities.
The microstructure of the corrosion-resistant steel bar in this embodiment includes pearlite, ferrite, bainite, and a precipitation structure.
In the embodiment, the strength grade of the corrosion-resistant steel bar is 400MPa, and the mechanical property is specifically tensile strength Rm: 772MPa, yield strength Rp0.2: 450MPa, elongation after break A5:19.5 percent, and the ratio of strength to yield: 1.72, maximum force total elongation Agt: 13 percent.
The diameter of the corrosion-resistant reinforcing steel bar is 32mm, the elongation is 19.5%, compared with the common reinforcing steel bar, the relative corrosion rate of the corrosion-resistant reinforcing steel bar is 48.5%, and the corrosion resistance is good.
Example two
The embodiment provides a preparation method of a corrosion-resistant steel bar for reinforced concrete, which is used for preparing the corrosion-resistant steel bar, and the method comprises the following steps:
step 1: and smelting the molten steel in a converter, then sending the molten steel into a refining furnace for refining and alloying, and adjusting the alloy element components and the content of the molten steel to obtain a billet.
According to different smelting purposes, the smelting furnace is classified into an argon blowing refining furnace, an LF refining furnace and the like, and the LF refining furnace is preferably used in the embodiment. In the preparation process of the reinforcing steel bar, the reinforcing steel bar is firstly smelted in a converter and then sent into an LF refining furnace for treatment. In the preparation process, corresponding raw materials containing corresponding alloy elements are added according to the component design requirements of the corrosion-resistant steel bar, and the content of elements such as C, Si, Mn, Nb, Cr, Ni, Cu and the like is adjusted, so that the corrosion-resistant steel bar can finally meet the requirements of the component composition and the mass percentage content of the corrosion-resistant steel bar.
Step 2: and (3) sending the steel billet obtained in the step (1) into a continuous casting machine for continuous casting to obtain a continuous casting steel billet. Further, in the step 2, the superheat degree of the molten steel in the continuous casting process is 20-30 ℃.
And after the molten steel is treated in the LF refining furnace, sending the obtained steel billet into a continuous casting machine for continuous casting to obtain a continuous casting steel billet, wherein the superheat degree of the molten steel is required to be 20-30 ℃ in the continuous casting process. If the degree of superheat is too high, the billet shell becomes thin, secondary oxidation of molten steel becomes easy, and inclusions increase. The billet is easy to have the defects of bulging, bleed-out, developed columnar crystals, center segregation, shrinkage cavity and the like.
And step 3: and inspecting the continuous casting billet, judging whether the continuous casting billet meets the preset billet condition, and if so, marking the continuous casting billet as a qualified billet.
Further, in the step 3, the preset billet conditions specifically include: the defect grade of the continuous casting billet is less than 1 grade. Wherein the defect type of the continuous casting billet comprises one or more of looseness, shrinkage cavity and segregation.
Further, when the continuous casting billet does not meet the preset billet condition, the inspection is finished and the continuous casting billet is marked as a unqualified billet.
Specifically, after the continuous casting billet is obtained, the quality of the continuous casting billet is further checked, and whether the obtained continuous casting billet meets the preset requirement is judged. Specifically, the method comprises the following steps: and comparing the continuous casting billet with preset parameters. The parameter in this embodiment may refer to a defect level, that is, the defect of the continuously cast steel billet is selected to be compared with a preset defect level, where the defect types of the continuously cast steel billet include porosity, shrinkage cavity and segregation, and the levels of the porosity, shrinkage cavity and segregation need to be less than 1 level. And when the defect grade of the continuous casting billet is less than 1 grade, marking the continuous casting billet at the moment as a qualified billet, and simultaneously, continuously sending the billet to the next flow for processing. And when the defect grade of the continuous casting billet is greater than 1 grade, marking the continuous casting billet at the moment as an unqualified billet, and simultaneously finishing the inspection process.
And 4, step 4: and (3) sending the qualified steel billets into a heating furnace for heating, wherein the temperature range of the heating furnace in the heating process is 1150-1250 ℃, and the heating time range is 1.5-2.5 hours.
In this embodiment, after the qualified steel billet is obtained through inspection, the qualified steel billet is continuously sent into the heating furnace for heating treatment, and at this time, the temperature range in the heating process needs to be guaranteed to be 1150-1250 ℃, and the heating time is preferably 2 hours in this embodiment, so as to sufficiently guarantee the uniformity of the temperature and components of the steel billet.
And 5: and (3) setting production parameters of a rough rolling unit according to actual field production conditions, and carrying out rough rolling on the steel billet obtained in the step (4), wherein the temperature range in the rough rolling process is 1000-1100 ℃.
Further, presetting the production parameters of the rough rolling mill set in the step 5, and after the rough rolling is performed on the billet obtained in the step 4, the method further comprises the following steps: the first crop, crop and break are carried out through the crank arm scissors.
Specifically, the production parameters of the roughing mill set are preset mainly according to actual field production conditions, in this embodiment, the rough rolling is performed on the billet, and the temperature range is controlled to be 1000-1100 ℃ in the rough rolling process. And after the rough rolling is finished, further performing head cutting, tail cutting and breaking by using a crank arm shear.
Step 6: presetting production parameters of a medium rolling mill set, and carrying out medium rolling on the steel billet obtained in the step 5, wherein the temperature range in the medium rolling process is 1000-1100 ℃.
Further, presetting the production parameters of the intermediate mill set in the step 6, and after the intermediate rolling of the steel billet obtained in the step 5, the method further comprises the following steps: controlling the temperature of the pre-cooling section to realize low-temperature finish rolling; and performing secondary crop, tail crop and fragmentation through the rotary scissors.
Specifically, in this embodiment, after the rough rolling is completed, the intermediate rolling unit is used to perform intermediate rolling, and the temperature range in the intermediate rolling process needs to be controlled to be 1000-1100 ℃, and after the intermediate rolling is completed, the low-temperature finish rolling is further performed in the pre-water cooling section, and then the rotary shears are used to perform head cutting, tail cutting and breaking. The production parameters of the medium rolling mill set can be set according to actual field production conditions without excessive limitation.
Preferably, in the step 5, the corrosion-resistant steel bar is rolled in the austenite recrystallization zone in a controlled manner, wherein the rolling temperature is in the range of 1000-1050 ℃.
Preferably, in the step 6, the corrosion-resistant steel bar is rolled in the austenite recrystallization zone in a controlled manner, wherein the rolling temperature is in the range of 1000-1050 ℃.
Specifically, in the step 5 and/or the step 6, it is preferable to control rolling in the austenite recrystallization region, specifically, rolling in a temperature range (1000 to 1050 ℃) of not less than the austenite recrystallization temperature, and recrystallization and deformation may be alternately performed to refine austenite grains.
And 7: and (4) presetting production parameters of a finishing mill group, and finishing the steel billet obtained in the step (6) to obtain the steel bar. Further, in the step 7, the temperature range in the finish rolling process is 1050 to 1150 ℃.
Specifically, in this embodiment, a 6-stand finishing mill group is preferably adopted as the preferable selection, and the preset production parameters of the finishing mill group are mainly set according to field production conditions, which is not limited too much here. And (3) carrying out finish rolling on the steel billet after the intermediate rolling, and simultaneously controlling the temperature range in the finish rolling process to be 1050-1150 ℃, thereby obtaining the steel bar.
And 8: and cooling the reinforcing steel bars on a cooling bed.
Further, in the step 8, the cooling the steel bar on the cooling bed includes: cutting the reinforcing steel bars by sections by adopting a multiple length shear; sending the sheared steel bars into a cooling bed for cooling; the cooling bed is provided with a heat preservation cover for controlling the cooling speed, the temperature range in the cooling process is 280-1070 ℃, and the cooling is slowly carried out in the heat preservation cover. The cooling time is 600-800 s, and 720s is preferable in this embodiment, so that the steel is slowly cooled to obtain pearlite, ferrite, bainite and a composite phase with a uniform structure.
Further, after the sheared reinforcing steel bars are sent into a cooling bed for natural cooling, the method further comprises the following steps: carrying out fixed-length shearing on the cooled steel bars by adopting cold shears; and removing the reinforcing steel bars which do not meet the size requirement to obtain the reinforcing steel bars meeting the requirement. The diameter size requirement of reinforcing bar is 10 ~ 32mm, and the length requirement is required according to actual production needs, does not do too much restriction. For example, 12000mm may be set in the present embodiment.
Further, the method also comprises the following steps: and counting and finishing the steel bars meeting the requirements, and after bundling and weighing, hoisting and warehousing.
Specifically, after finishing rolling is completed, controlled cooling is performed through a post-rolling water cooling section, specifically: firstly, multi-length shearing is adopted to carry out segmented shearing on the reinforcing steel bars, then the sheared reinforcing steel bars are sent into a cooling bed to be naturally cooled, then the cold shearing is adopted to carry out fixed-length shearing on the cooled reinforcing steel bars, whether the sheared reinforcing steel bars meet the size requirement is judged, when the size requirement is not met, the short-sized reinforcing steel bars are removed, then counting, finishing, bundling and weighing are carried out, and finally, lifting and warehousing are carried out.
By adopting the preparation method of the embodiment, the prepared corrosion-resistant steel bar comprises the following chemical components in percentage by mass: c: 0.11 to 0.13%, Si: 0.50-0.60%, Mn: 1.20 to 1.30%, Nb: 0.015-0.030%, Cr: 0.65-0.75%, Ni: 0.40-0.65%, Cu: 0.40-0.50%, S: 0-0.008%, P: 0-0.015%, and the balance of Fe and inevitable impurities.
According to the invention, by combining chemical component regulation and control, according to the difference of rolling speed and reduction of rough, medium and finishing mill sets, the temperature control of each stage is distributed by utilizing the mechanisms of microalloy fine grain strengthening, recrystallization rolling, non-recrystallization rolling and deformation induced ferrite, and the refining and homogenization of the microstructure of the steel are realized through the continuous temperature control and deformation rolling process.
Specifically, in the hot rolling process, according to the difference of deformation temperature, the main core process is divided into 2 stages, ① rolling parameters are preset in the rough rolling process and the middle rolling process, particularly the rolling temperature range is preset, rolling is preferably controlled in an austenite recrystallization region, namely rolling is carried out in the temperature range (1000-1050 ℃) above the austenite recrystallization temperature, recrystallization and deformation are carried out alternately to refine austenite grains, ② cooling bed is provided with a heat preservation cover to control the cooling speed, and the cooling is slowly carried out to obtain pearlite, ferrite, bainite and a precipitated structure composite phase with uniform structure.
Therefore, the preparation method of the corrosion-resistant steel bar in the embodiment modifies production equipment according to the technical requirement of full-flow continuous temperature control rolling, comprehensively utilizes the recrystallization, non-recrystallization and deformation induced ferrite mechanism and the process measures of controlled cooling after rolling and the like according to the actual production equipment parameters of the rough, medium and finish rolling mill sets of the steel bar rolling production line, achieves the purposes of controlling the growth of crystal grains and homogenizing the structure, and improves the corrosion resistance of the steel bar on the premise of ensuring the strength of the steel bar.
One or more technical solutions in the embodiments of the present invention at least have one or more of the following technical effects:
according to the corrosion-resistant steel bar for reinforced concrete and the preparation method thereof provided by the embodiment of the invention, the corrosion-resistant steel bar regulates and controls the mass percentages of all components through reasonable configuration, and simultaneously, the strength of the steel bar is improved in a micro-alloying manner, so that the microstructure of the corrosion-resistant steel bar comprises pearlite, ferrite, bainite and an aspiration structure; the steel has good microscopic performance, the strength reaches 400MPa, the corrosion resistance is good, and the steel can be widely applied to the design and use requirements of various structures (including primary and secondary anti-seismic structures).
The preparation method of the corrosion-resistant steel bar solves the technical problems of refining and homogenization of the microstructure of the steel bar by reasonably setting the production parameters of rough rolling, intermediate rolling and finish rolling of a steel bar steel rolling production line and comprehensively utilizing various technological measures, has low production cost, and can comprehensively utilize various control mechanisms and meet the technical effects of different specifications and component rolling control requirements.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various modifications and variations can be made in the embodiments of the present invention without departing from the spirit or scope of the embodiments of the invention. Thus, if such modifications and variations of the embodiments of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to encompass such modifications and variations.
Claims (15)
1. The corrosion-resistant steel bar for reinforced concrete is characterized by comprising the following chemical components in percentage by mass:
c: 0.11 to 0.13%, Si: 0.50-0.60%, Mn: 1.20 to 1.30%, Nb: 0.015-0.030%, Cr: 0.65-0.75%, Ni: 0.40-0.65%, Cu: 0.40-0.50%, S: 0-0.008%, P: 0-0.015%, and the balance of Fe and inevitable impurities.
2. The corrosion-resistant steel for reinforced concrete according to claim 1, wherein the microstructure of the corrosion-resistant steel includes pearlite, ferrite, bainite, and precipitation structure.
3. The corrosion-resistant steel for reinforced concrete according to claim 1, wherein the corrosion-resistant steel has a strength grade of 400 MPa.
4. The corrosion-resistant steel bar for reinforced concrete according to claim 1, wherein the corrosion-resistant steel bar has a diameter of 10 to 32 mm.
5. The corrosion-resistant reinforcing bar for reinforced concrete according to claim 1, wherein the corrosion-resistant reinforcing bar has an elongation of not less than 16%.
6. A method for preparing a corrosion-resistant steel bar for reinforced concrete, which is used for preparing the corrosion-resistant steel bar as claimed in any one of claims 1 to 5, and which comprises the following steps:
step 1: smelting molten steel in a converter, then sending the molten steel into a refining furnace for refining and alloying, and adjusting the alloy element components and the content of the molten steel to obtain a steel billet;
step 2: sending the steel billet obtained in the step 1 into a continuous casting machine for continuous casting to obtain a continuous casting steel billet;
and step 3: inspecting the continuous casting billet, judging whether the continuous casting billet meets the preset billet condition, and if so, marking the continuous casting billet as a qualified billet;
and 4, step 4: sending the qualified steel billets into a heating furnace for heating, wherein the temperature range of the heating furnace in the heating process is 1150-1250 ℃, and the heating time is 1.5-2.5 hours;
and 5: presetting production parameters of a rough rolling unit, and roughly rolling the steel billet obtained in the step 4, wherein the temperature range in the rough rolling process is 1000-1100 ℃;
step 6: presetting production parameters of a medium rolling mill set, and carrying out medium rolling on the steel billet obtained in the step 5, wherein the temperature range in the medium rolling process is 1000-1100 ℃;
and 7: presetting production parameters of a finishing mill group, and finishing rolling the steel billet obtained in the step 6 to obtain a steel bar, wherein the temperature range of the finishing rolling process is 1050-1150 ℃;
and 8: and cooling the reinforcing steel bars on a cooling bed.
7. The method of manufacturing a corrosion-resistant reinforcing bar for reinforced concrete according to claim 6, wherein:
in the step 5, during initial rolling, the corrosion-resistant steel bar is rolled in an austenite recrystallization zone under control, wherein the rolling temperature range is 1000-1050 ℃.
8. The method of manufacturing a corrosion-resistant reinforcing bar for reinforced concrete according to claim 6, wherein: in the step 6, during medium rolling, the corrosion-resistant steel bar is rolled in an austenite recrystallization zone under control, wherein the rolling temperature is 1000-1050 ℃.
9. The method of manufacturing a corrosion-resistant reinforcing bar for reinforced concrete according to claim 6, wherein the degree of superheat of molten steel in the continuous casting process is 20 to 30 ℃ in the step 2.
10. The method of claim 6, wherein in the step 3, the predetermined billet conditions are as follows:
the defect grade of the continuous casting billet is less than 1 grade, and the defect type of the continuous casting billet comprises one or more of looseness, shrinkage cavity and segregation;
and when the continuous casting billet does not meet the preset billet condition, finishing the inspection and marking as an unqualified billet.
11. The method of manufacturing a corrosion-resistant reinforcing bar for reinforced concrete according to claim 6, wherein in the step 5, after the pre-setting of the production parameters of the roughing mill set and the rough rolling of the slab obtained in the step 4, further comprising:
the first crop, crop and break are carried out through the crank arm scissors.
12. The method of manufacturing a corrosion-resistant reinforcing bar for reinforced concrete according to claim 6, wherein in the step 6, after presetting production parameters of a medium rolling mill set and performing medium rolling on the billet obtained in the step 5, the method further comprises:
controlling the temperature of the pre-water cooling section to realize finish rolling;
and performing secondary crop, tail crop and fragmentation through the rotary scissors.
13. The method of manufacturing corrosion resistant reinforcing bars for reinforced concrete according to claim 6, wherein said cooling of said reinforcing bars on a cooling bed in said step 8 comprises:
cutting the reinforcing steel bars by sections by adopting a multiple length shear;
sending the sheared steel bars into a cooling bed for cooling;
the cooling bed is provided with a heat preservation cover for controlling the cooling speed, the temperature range in the cooling process is 280-1070 ℃, the cooling is slowly carried out in the heat preservation cover, and the cooling time range is 600-800 s.
14. The method of manufacturing corrosion resistant reinforcing bars for reinforced concrete according to claim 13, wherein after said feeding the sheared reinforcing bars into a cooling bed for cooling, further comprising:
carrying out fixed-length shearing on the cooled steel bars by adopting cold shears;
and removing the reinforcing steel bars which do not meet the size requirement to obtain the reinforcing steel bars meeting the requirement.
15. The method of manufacturing corrosion resistant steel reinforcement for reinforced concrete according to claim 14, wherein after removing the steel reinforcement that does not satisfy the dimensional requirement, the method further comprises:
and counting and finishing the steel bars meeting the requirements, and after bundling and weighing, hoisting and warehousing.
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