高温后600MPa级高强钢筋力学性能试验

Mechanical properties of 600MPa high-strength bars after exposure to high temperatures

为了得到不同加热温度和冷却方式对600 MPa级高强钢筋力学性能的影响规律,首先进行27组600MPa级高强钢筋高温加热,并采用不同冷却方式进行降温处理,然后进行静力拉伸试验,对断口纵向组织进行了观察,分析不同加热温度和冷却方式对钢筋力学性能参数的影响规律,并与其他等级强度的钢筋进行了比较,最后根据试验数据拟合得到600MPa级高强钢筋经不同冷却方式后各力学性能参数随加热温度变化的表达公式。研究结果表明:当温度较低时冷却方式对钢筋组织基本没有影响,而加热温度较高时,不同冷却方式对其组织影响较大;当加热温度低于550℃时,钢筋力学性能基本没有变化,当加热温度为625℃时,屈服强度、极限强度和弹性模量参数有下降的趋势,而断后伸长率基本不变;当加热温度大于775℃时,不同冷却方式对其力学性能影响差别较大,特别是采用浸水冷却方式的试件,试件断口无颈缩现象,断面较整齐,应力-应变曲线无屈服台阶,屈服强度和极限强度增加较大,断后伸长率急速降低;在925℃时,断后伸长率只有1.7%,具有明显的脆性破坏特征,而采用另外2种冷却方式的试件断后伸长率约为30%,差别较大。

To examine the influence of different heating temperatures and cooling methods on the mechanical properties of 600 MPa high-strength bars,27 groups of 600 MPa high-strength bars were subjected to the following sequence of experimental treatments.The bars were heated to high temperatures and cooled by different cooling methods.Static tensile tests were performed on the bars,and the longitudinal tissue of the resulting fractures was observed.The results were compared with those from other grades of reinforcement.Based on the experimental data obtained,formulas for estimating the changes in mechanical properties with temperature underdifferent cooling modes were derived.The results show that the cooling mode has no effect on the basic tissue at low temperatures,but the influence of the different cooling methods on the tissue is greater at high temperatures.When the temperature is less than 550 ℃,the mechanical properties of the steel bars remain basically unchanged,and when the temperature is 625 ℃,three parameters(yield strength,limit strength,and elastic modulus)show declining trends,but the elongation rate is basically unchanged.When the temperature is greater than 775 ℃,the different cooling methods significantly affect the mechanical properties,especially when the cooling bar is immersed in water.In particular,the test specimen has no neck shrinkage,the section is relatively neat,and the stress-strain curve has no yield platform.The yield strength and limit strength increase,and the elongation decreases rapidly.When the temperature is925℃,the elongation is only 1.7%,and the damage indicates obvious brittleness.Although the elongation of the specimens exposed to the other two cooling methods is about 30%,the mechanical properties vary substantially.