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Low-yield ratio and high-strength stirrup provided with bainite structure and used for buildings and production process
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A low yield-strength ratio and production process technology is applied in the field of low yield-strength ratio bainite structure and high-strength construction stirrups to achieve the effects of improving seismic performance, short heat treatment time, and high finished product strength.
Active Publication Date: 2015-02-25
ANYANG LONGTENG SPECIAL STEEL MFG +3
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[0003]Although Japan is using stirrups with a strength above 1200MPa, the yield strength ratio of this strength steel bar is above 0.95, and the external force increases during an earthquake, which is prone to fracture and there is still no chance of escape
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example 1
[0027] A ferrite plus pearlite ф8 hot-rolled crescent-ribbed disc, the chemical composition is: C: 0.21%, Si: 0.55%, Mn: 1.15%, P: 0.020%, S: 0.015%, and the rest is Fe and impurities. The disc is set out, descaled, straightened, drawn, heated to 960°C, water-cooled to 350°C for 3 seconds, kept warm for 40 seconds, cooled to room temperature, sheared, and coiled to obtain a finished steel bar.
[0028] The yield strength of the steel bar is 956MPa, the tensile strength is 1180MPa, the yield strength ratio is 0.81, the elongation after breaking is A: 18%, the total elongation under the maximum force is Agt: 5.6%, and there is no crack at the bend after bending 180 degrees (the bending radius R is the nominal 3 times the diameter), to obtain a ferrite plus bainite structure (see Figure 1).
example 2
[0030] A ferrite plus pearlite ф5.5 hot-rolled smooth disc, the chemical composition is: C: 0.30%, Si: 0.68%, Mn: 1.23%, P: 0.020%, S: 0.018%, and the rest is Fe and Impurities. The disc is made into a spiral groove after setting-off-scale-drawing-straightening-drawing-heating to 1050°C--water cooling to 400°C for 3 seconds-heating for 40 seconds-cooling to room temperature-shearing-shrinking Roll to get finished steel bars.
[0031] The yield strength of the steel bar is 1116MPa, the tensile strength is 1313MPa, the yield strength ratio is 0.85, the elongation A after breaking is 16.5%, the total elongation Agt under the maximum force is 5.0%, and there is no crack at the bend after bending 180 degrees (the bending radius R is the nominal 3 times the diameter), a ferrite plus bainite structure is obtained (see Figure 2).
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Abstract
The invention discloses a low-yield ratio and high-strength stirrup which is provided with a bainite structure and is used for buildings and a production process. The stirrup can improve the earthquake resistant performance of the buildings obviously, so that the collapse time of the buildings can be delayed under the condition of high-intensity earthquake levels or the buildings are not collapsed to provide escape opportunity for life. According to the production process, a ferrite and a hot-rolled steel bar with a pearlitic structure are used as raw materials, and the stirrup comprises the following chemical ingredients in percentage by weight: 0.15 to 0.30 percent of C, less than or equal to 1.5 percent of Si, 0.5 to 1.5 percent of Mn, less than or equal to 0.025 percent of P, less than or equal to 0.025 percent of S and the balance of Fe and impurities, wherein one of V and B is added appropriately according to requirements. According to the process, the raw materials are subjected to isothermal treatment to prepare the finished product; and during isothermal treatment, the processed steel bar is heated to above 850 DEG C, and then is water-cooled to 350 to 400 DEG C to obtain dual-phase steel with the ferrite and the bainite structure, wherein the isothermal treatment is completed within one minute. The strength level of the stirrup serving as the finished product is 800 to 1,100 MPa, the yield ratio is about 0.8 to 0.85, A is more than or equal to 12 percent, Agt is more than or equal to 3.5 percent, cracks at the bending position after the stirrup is bent 180 degrees are avoided, and the diameter of the finished product is 5 to 12 millimeters.
Description
Technical field: [0001] The invention relates to a production process of stirrups for construction with low yield ratio bainite structure and high strength. Background technique: [0002] The amount of stirrups in the construction field accounts for a considerable proportion. my country's stirrups are currently using 235-400MPa hot-rolled steel bars. Although the yield ratio is 0.6-0.7, the strength level is low. During the earthquake, the stirrups are easily broken, and the concrete is broken, causing the column to collapse. No escape opportunities in the building. Due to the low strength level, the amount of stirrups used in construction is large, and even the concrete pouring is difficult due to the excessive use of stirrups, which brings troubles to construction. [0003] Although Japan is using more than 1200MPa strength stirrups, the strength steel bar yield-tensile ratio is more than 0.95, and the external force increases during an earthquake, which is prone to frac...
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