Revealing microstructural and mechanical characteristics of cold-drawn pearlitic steel wires undergoing simulated galvanization treatment
Revealing microstructural and mechanical characteristics of cold-drawn pearlitic steel wires undergoing simulated galvanization treatment
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DOI：
10.1016/j.msea.2012.03.075
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发表时间：
2012-06
期刊：
影响因子：
6.4
通讯作者：
F. Fang;Xianjun Hu;Shao-hui Chen;Zonghan Xie;Jianqing Jiang
中科院分区：
文献类型：
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作者：
F. Fang;Xianjun Hu;Shao-hui Chen;Zonghan Xie;Jianqing Jiang
冷拔珠光体钢丝在镀锌处理过程中，经常会出现片状珠光体团球化现象，导致力学性能下降。因此，研究镀锌工艺对冷拔钢丝组织和力学性能的影响具有重要意义。本文通过对直径为13 mm ~ 6.9mm的珠光体钢棒进行冷拉，制备了冷拔钢丝。在450°C下的热退火用于模拟钢丝的镀锌处理。测定了退火处理前后钢棒和钢丝的抗拉强度、延伸率和扭转圈数。用扫描电镜（SEM）和透射电镜（TEM）观察了复合材料的微观结构。此外，还用差示扫描量热法（DSC）对石墨球化温度进行了探讨。实验结果表明，退火时间<5 min时，钢丝的抗拉强度从1780 MPa上升到1940 MPa，然后下降。退火时间> 10 min时，拉伸强度基本不变。退火时间<2.5min时，延伸率下降，随后略有恢复。退火时间> 5 min时，该值趋于恒定。钢丝的抗拉强度和伸长率均受应变时效硬化和静态回复过程的影响。当退火时间小于2.5min时，扭转圈数变化不大，随后迅速减小。当保持时间大于10 min时，其值趋于恒定。当退火时间大于2.5min时，片层状珠光体开始球化，球化开始于珠光体晶界，并向内移动。在380°C ~ 480°C之间有一个宽的放热峰，这主要是由于片层状石墨球化所致，是导致冷拔钢丝扭转性能下降的主要原因。
Spheroidization of lamellar cementite often occurs in cold-drawn pearlitic steel wires during galvanizing treatment, leading to the degradation of mechanical properties. Therefore, it is important to understand effects of galvanization process on microstructure and mechanical properties of cold-drawn wires. In this paper, cold-drawn steel wires were fabricated by cold drawing pearlitic steel rods from 13mm to 6.9mm in diameter. Thermal annealing at 450°C was used to simulate galvanizing treatment of steel wires. Tensile strength, elongation and torsion laps of steel rods and wires with, and without, annealing treatment were determined. Microstructure was observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition, differential scanning calorimetry (DSC) was used to probe the spheroidization temperature of cementite. Experimental results showed that tensile strength of wires increased from 1780MPa to 1940MPa for annealing <5min, and then decreased. Tensile strength became constant for annealing >10min. Elongation of wires decreased for annealing <2.5min, and then recovered slightly. It approached a constant value for annealing >5min. Tensile strength and elongation of wires were both influenced by the strain age hardening and static recovery processes. Notably, torsion laps of wires hardly changed when annealing time was less than 2.5min, and then decreased rapidly. Its value became constant when the hold time is greater than 10min. Lamellar cementite began to spheroidize at annealing >2.5min, starting at the boundary of pearlitic grains, and moving inward. A broad exothermic peak was found at temperatures between 380°C and 480°C, resulting primarily from the spheroidization of lamellar cementite, which is responsible for the degradation of torsion property of cold-drawn wires.