CN103451553A - Reinforced bar used in ultra-low temperature environments and preparation method thereof - Google Patents
Reinforced bar used in ultra-low temperature environments and preparation method thereof Download PDFInfo
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- CN103451553A CN103451553A CN2013103843419A CN201310384341A CN103451553A CN 103451553 A CN103451553 A CN 103451553A CN 2013103843419 A CN2013103843419 A CN 2013103843419A CN 201310384341 A CN201310384341 A CN 201310384341A CN 103451553 A CN103451553 A CN 103451553A
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Abstract
The invention relates to a reinforced bar used in ultra-low temperature environments. The reinforced bar comprises the following chemical components in percentage by mass: less than or equal to 0.20% of C, less than or equal to 0.8% of S, less than or equal to 1.6% of Mn, less than or equal to 0.025% of P, less than or equal to 0.025% of S, less than or equal to 0.04% of Al, less than or equal to 1.5% of Ni, less than or equal to 0.5% of Cr, less than or equal to 0.5% of Cu, less than or equal to 0.03% of Ti, less than or equal to 0.03% of V and the balance of Fe and inevitable impurities; and the carbon equivalent (Ceq) (%) is less than or equal to 0.65% and meanwhile is equal to C+Mn/6+Si/24+Ni/40+Cr/5+Mo/4+V/14. The invention also discloses a preparation method of the reinforced bar. The reinforced bar used in ultra-low temperature environments has excellent low-temperature property, relatively high strength, relatively good elongation percentage, good welding property and excellent combination property.
Description
Technical field
The present invention relates to field of metallurgy, particularly reinforcing bar and preparation method thereof for a kind of ultra-low temperature surroundings.
Background technology
Sweet natural gas and oil are more and more favored as a kind of clean energy, and have been given more and more concern as the most effective a kind of storage mode-deep cooling storage.LNG(Liquefied Natural Gas, i.e. natural gas liquids) construction of low temperature storage tank makes concrete structure may be applied to the ultra-low temperature surroundings of-165 ℃.
The yield strength of regular reinforcement under low temperature environment and ultimate strength all are significantly increased during with respect to normal temperature: under low temperature, the Young's modulus of reinforcing bar increases approximately 10%, and linear expansivity substantially remains unchanged in the temperature range of 70 ℃ to-165 ℃, is 10
-5/ ℃ left and right; Reinforcing bar toughness drop and fragility under cold condition strengthen, however the performance that under low temperature, reinforcing bar becomes fragile can be improved by adding alloying element nickel, vanadium or titanium, thereby make to keep the toughness of reinforcing bar under cold condition to become possibility.
Manufacture the ultra-low temperature surroundings reinforcing bar, except adding alloying element, need after roll forming to coordinate can reach required low-temperature performance with suitable thermal treatment process.The technical process of producing regular reinforcement is: blast-melted → converter (electric furnace) → refining → billet continuous casting → scale cutting → warehouse-in → heater for rolling steel → merchant bar mill → control cooling → cold bed → cutting to length → collection bundling → warehouse-in of weighing → list.Control cooling step wherein (rolling rear immediate quenching or Heat Treatment) is quenched to rebar surface and utilizes self-tempering and then complete thermal treatment by wearing water cooling.If control cooling technology of the prior art is the production with reinforcing bar for ultra-low temperature surroundings, the low temperature reinforcing bar of producing can't reach needed low-temperature performance, or unstable properties.
Summary of the invention
The object of the invention is to overcome the unsettled defect of reinforcement property for ultra-low temperature surroundings of the prior art, thereby reinforcing bar and preparation method thereof for ultra-low temperature surroundings of a kind of stable performance is provided.
To achieve these goals, the invention provides a kind of ultra-low temperature surroundings reinforcing bar, its chemical composition comprises according to mass percent: C≤0.20%, Si≤0.8%, Mn≤1.60%, P≤0.025%, S≤0.025%, Al≤0.04%, Ni≤1.5%, Cr≤0.5%, Cu≤0.5%, and Ti≤0.03%, V≤0.03%, all the other are Fe and inevitable impurity; And carbon equivalent Ceq(%)≤0.65 also meets: Ceq(%)=C+Mn/6+Si/24+Ni/40+Cr/5+Mo/4+V/14 simultaneously.
The present invention also provides a kind of method of using reinforcing bar for the preparation of described ultra-low temperature surroundings, comprising:
Step 1), according to chemical composition claimed in claim 1, adopt oxygen coverter or electric furnace to be smelted;
Step 2), through external refining;
Step 3), carry out billet continuous casting again;
Step 4), square billet is sent into to homogeneous heating in process furnace, controlling soaking temperature is 1100～1250 ℃;
Step 5), square billet are come out of the stove and are rolled by merchant bar mill, and start rolling temperature, between 980～1100 ℃, is chilled to 930～1020 ℃ a little less than inciting somebody to action after finish rolling;
Step 6), the reinforcing bar of roll forming is worn to water cooling or send the cold bed natural air cooling to room temperature;
Step 7), in step 6), through overcooled reinforcing bar, doing again off-line thermal treatment; Described off-line thermal treatment adopts the thermal treatment process of quenching+high tempering, and comprising: the reinforcing bar at first hot rolling obtained is quenched, and 900～960 ℃ of quenching temperatures carry out rapid water after being incubated 30～90 minutes cold; Carry out temper after quenching, the tempering Heating temperature is 560～630 ℃.
In technique scheme, in described step 7), by existing Wide and Thick Slab heat treatment furnace, realize off-line thermal treatment.
The invention has the advantages that:
The yield strength of low temperature reinforcing bar of the present invention is 520～560MPa, tensile strength is 600～650MPa, through reverse bending test, D=4d(d≤16mm), D=7d(d ﹥ 16mm), test its unit elongation with standard under normal temperature and be greater than 14%, ultimate load is acted on unnotched this reinforcing bar under-167 ℃, its uniform elongation is not less than 5% after tested.Therefore, this low temperature reinforcing bar has fabulous low-temperature performance, has higher intensity and unit elongation preferably simultaneously, and good welding property, and good over-all properties is arranged.
In addition, utilize existing Wide and Thick Slab equipment for Heating Processing to carry out batch thermal treatment to it, both saved facility investment, can enhance productivity again.
The accompanying drawing explanation
Fig. 1 is the thermal treatment process route map of low temperature reinforcing bar of the present invention.
Embodiment
Now the invention will be further described by reference to the accompanying drawings.
Ultra-low temperature surroundings of the present invention comprises according to mass percent by the chemical composition of reinforcing bar: C≤0.20%, Si≤0.8%, Mn≤1.60%, P≤0.025%, S≤0.025%, Al≤0.04%, Ni≤1.5%, Cr≤0.5%, Cu≤0.5%, and add a small amount of (below 0.03%) Ti, V, all the other are Fe and inevitable impurity; And carbon equivalent Ceq(%)≤0.65 also meets: Ceq(%)=C+Mn/6+Si/24+Ni/40+Cr/5+Mo/4+V/14 simultaneously.
Ultra-low temperature surroundings of the present invention is as follows with the effect of the main chemical compositions in reinforcing bar:
C(carbon) can improve intensity by the gap solid solution, but C is too much harmful to Low Temperature Impact Toughness of Heat-affected Zone, therefore, under the prerequisite of proof strength, C should be more low better.
Si(silicon) be deoxidant element in steel-making, extremely important to harmful element O content in reduction low temperature reinforcing bar.Si can improve intensity, and Si is except being present in by a certain percentage in steel to suppress, the Mn segregation, also can to suppress P at Grain Boundary Segregation with Mn simultaneously.
Mn(manganese) with low cost, be good reductor and sweetening agent, significantly improve hardening capacity.It is stable that Mn is conducive to rotary austenite, can improve intensity by precipitation strength simultaneously.
P(phosphorus) and S(sulphur) be all the harmful element in steel under normal conditions, can increase the fragility of steel.P can destroy welding property and the plasticity of steel; S is combined generation and is mingled with Mn, can also reduce the toughness of steel.Therefore should as much as possible reduce P, S content.
Al(aluminium) Main Function is deoxidation, but in steel, adds a small amount of aluminium crystal grain thinning can improve impelling strength simultaneously, but the aluminium too high levels can cause the oxide inclusion of Al to increase, and reduces the purity of steel.
Ni(nickel) be the austenite stable element, especially extremely important to stablizing rotary austenite, the rotary austenite of rich Ni is very stable under extremely low temperature, and in deformation process, rotary austenite is the soft phase in tissue, energy absorption portion strain energy; After distortion acquires a certain degree, can also be converted into martensitic phase by deformation induced phase transformation, be one of toughness reinforcing mechanism; Ni is conducive to improve hardening capacity and intensity simultaneously; Ni can also promote low temperature to hand over slippage, improves cold plasticity.But Ni is expensive, under the prerequisite that guarantees low-temperature flexibility, should save as far as possible.
Cr(chromium) Main Function is the hardening capacity that improves steel, the matrix of solution strengthening simultaneously, and thinning microstructure, also can improve the welding property of steel.
Cu(copper) can improve intensity and the toughness of steel, also can improve in steel austenitic stability and then improve hardening capacity, when copper content be less than 0.5% on weldability without impact.
The Ti(titanium), V(vanadium) can add in right amount.Titanium is strong reductor in steel, and it can make the dense internal organization of steel, and crystal grain thinning reduces aging sensitivity and cold shortness, improves welding property.Microalloy element vanadium Grain refinement is strong, and the vanadium of solid solution in austenite can improve hardening capacity, with the carbonitride form disperse educt, can stop weld grain thick, can improve the welding property of steel.
The raw material of being mentioned in take above, as basis, is below stated by the method for reinforcing bar preparing ultra-low temperature surroundings.
Step 1), will there is the blast-melted of aforementioned composition and smelt in oxygen coverter or electric furnace;
Step 2), through external refining;
Step 3), carry out billet continuous casting again;
Step 4), square billet is sent into to homogeneous heating in process furnace, controlling soaking temperature is 1100～1250 ℃;
Step 5), square billet are come out of the stove and are rolled by merchant bar mill, and start rolling temperature, between 980～1100 ℃, is chilled to 930～1020 ℃ a little less than inciting somebody to action after finish rolling;
Step 6), the reinforcing bar of roll forming is worn to water cooling or send the cold bed natural air cooling to room temperature;
Step 7), in step 6), through overcooled reinforcing bar, doing again off-line thermal treatment; Described off-line thermal treatment adopts the thermal treatment process of quenching+high tempering, and comprising: the reinforcing bar at first hot rolling obtained is quenched, and 900～960 ℃ of quenching temperatures carry out rapid water after being incubated 30～90 minutes cold; Carry out temper after quenching, the tempering Heating temperature is 560～630 ℃, obtains and take tempered sorbite as main tissue.Over-all properties through the heat treated reinforcing bar of off-line can be further enhanced, especially low-temperature performance.
Embodiment 1
φ 10mm low temperature reinforcing bar specific chemical composition is in Table 1:
Table 1 be φ 10mm low temperature reinforcing bar chemical composition (mass percent, %)
Carry out the oxygen coverter smelting by above chemical composition, then continuous casting becomes square billet after external refining.
Square billet is heat-treated (quenching+high tempering) after continuous rod mill roll forming.
Quenching system: be heated to 930 ℃, soaking time 30min, water-cooled; Tempering system: be heated to 580 ℃, soaking time 25min, air cooling.
The concrete mechanical property detected result of φ 10mm low temperature reinforcing bar is in Table 2:
Table 2 is φ 10mm low temperature steel bar mechanics performance
Embodiment 2
φ 30mm low temperature reinforcing bar specific chemical composition is in Table 3:
Table 3 be φ 30mm low temperature reinforcing bar chemical composition (mass percent, %)
Carry out the oxygen coverter smelting by above chemical composition, then continuous casting becomes square billet after external refining.
Square billet is heat-treated (quenching+high tempering) after continuous rod mill roll forming.
Quenching system: be heated to 950 ℃, soaking time 90min, water-cooled; Tempering system: be heated to 600 ℃, soaking time 75min, air cooling.
The concrete mechanical property detected result of φ 30mm low temperature reinforcing bar is in Table 4:
Table 4 is φ 30mm low temperature steel bar mechanics performance
It should be noted last that, above embodiment is only unrestricted in order to technical scheme of the present invention to be described.Although with reference to embodiment, the present invention is had been described in detail, those of ordinary skill in the art is to be understood that, technical scheme of the present invention is modified or is equal to replacement, do not break away from the spirit and scope of technical solution of the present invention, it all should be encompassed in the middle of claim scope of the present invention.
Claims (3)
1. a ultra-low temperature surroundings reinforcing bar, is characterized in that, its chemical composition comprises according to mass percent: C≤0.20%, Si≤0.8%, Mn≤1.60%, P≤0.025%, S≤0.025%, Al≤0.04%, Ni≤1.5%, Cr≤0.5%, Cu≤0.5%, and Ti≤0.03%, V≤0.03%, all the other are Fe and inevitable impurity; And carbon equivalent Ceq(%)≤0.65 also meets: Ceq(%)=C+Mn/6+Si/24+Ni/40+Cr/5+Mo/4+V/14 simultaneously.
2. use the method for reinforcing bar for the preparation of the described ultra-low temperature surroundings of claim 1, comprising:
Step 1), according to chemical composition claimed in claim 1, adopt oxygen coverter or electric furnace to be smelted;
Step 2), through external refining;
Step 3), carry out billet continuous casting again;
Step 4), square billet is sent into to homogeneous heating in process furnace, controlling soaking temperature is 1100～1250 ℃;
Step 5), square billet are come out of the stove and are rolled by merchant bar mill, and start rolling temperature, between 980～1100 ℃, is chilled to 930～1020 ℃ a little less than inciting somebody to action after finish rolling;
Step 6), the reinforcing bar of roll forming is worn to water cooling or send the cold bed natural air cooling to room temperature;
Step 7), in step 6), through overcooled reinforcing bar, doing again off-line thermal treatment; Described off-line thermal treatment adopts the thermal treatment process of quenching+high tempering, and comprising: the reinforcing bar at first hot rolling obtained is quenched, and 900～960 ℃ of quenching temperatures carry out rapid water after being incubated 30～90 minutes cold; Carry out temper after quenching, the tempering Heating temperature is 560～630 ℃.
3. method according to claim 2, is characterized in that, in described step 7), by existing Wide and Thick Slab heat treatment furnace, realizes off-line thermal treatment.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103741078A (en) * | 2013-12-31 | 2014-04-23 | 江苏永钢集团有限公司 | Remained heat treatment steel bar production process |
| CN108531816A (en) * | 2018-05-24 | 2018-09-14 | 南京钢铁股份有限公司 | A kind of 500MPa grades of steel for engineering machinery and its manufacturing method |
| CN110669995A (en) * | 2019-11-08 | 2020-01-10 | 广东韶钢松山股份有限公司 | Hot-rolled ultralow-temperature steel bar and preparation method thereof |
| CN114318175A (en) * | 2021-12-15 | 2022-04-12 | 石横特钢集团有限公司 | HRB500DW ribbed steel bar and production process thereof |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103741078A (en) * | 2013-12-31 | 2014-04-23 | 江苏永钢集团有限公司 | Remained heat treatment steel bar production process |
| CN108531816A (en) * | 2018-05-24 | 2018-09-14 | 南京钢铁股份有限公司 | A kind of 500MPa grades of steel for engineering machinery and its manufacturing method |
| CN110669995A (en) * | 2019-11-08 | 2020-01-10 | 广东韶钢松山股份有限公司 | Hot-rolled ultralow-temperature steel bar and preparation method thereof |
| CN110669995B (en) * | 2019-11-08 | 2021-11-16 | 广东韶钢松山股份有限公司 | Hot-rolled ultralow-temperature steel bar and preparation method thereof |
| CN114318175A (en) * | 2021-12-15 | 2022-04-12 | 石横特钢集团有限公司 | HRB500DW ribbed steel bar and production process thereof |
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