This paper investigated a novel technique that uses a slow-cooling heat treatment to reduce the strength of existing steels to produce a regional soft area for energy dissipation. This research investigated the performance and affecting mechanism of the slow-cooling heat-treatment on the mechanical properties of high strength steels. A total of 18 heat-treating cases were applied to Q420 and Q690 steels. The relation of critical strengths and ductility of the materials versus the heat-treating parameters, such as peak temperature, cooling rate, holding time and terminate temperature, were investigated and discussed. The strength reduction from the slow-cooling heat treatment process in high strength steels and normal strength steels was discussed. The results indicated that the slow-cooling heat treatment can effectively reduce the yield and ultimate strengths of high strength steels. The Q690 steel displayed a more prominent strength reduction than the Q420 steel, especially for the yield strength. The heat treatment also improved the material ductility, especially for the Q690 steels. The peak temperature and cooling rate were two determining factors for the strength reduction performance. A heat treatment process with a 900–1000 °C peak temperature and a 1–2 °C/min cooling rate was suggested for the strength reduction of Q420 steel.

本文研究了一种新技术，该技术使用慢冷热处理来降低现有钢的强度，从而产生区域性软区域以进行能量消散。本研究探讨了慢冷热处理对高强度钢力学性能的影响机理。Q420和Q690钢总共使用了18个热处理箱。研究并讨论了材料的临界强度和延展性与热处理参数（如峰值温度，冷却速率，保持时间和终止温度）的关系。讨论了高强度钢和普通强度钢在慢冷热处理过程中的强度降低。结果表明，慢冷热处理可有效降低高强度钢的屈服强度和极限强度。Q690钢比Q420钢表现出更显着的强度降低，特别是在屈服强度方面。热处理还改善了材料的延展性，特别是对于Q690钢。峰值温度和冷却速率是强度降低性能的两个决定因素。为降低Q420钢的强度，建议采用900-1000°C峰值温度和1–2°C / min的冷却速率的热处理工艺。峰值温度和冷却速率是强度降低性能的两个决定因素。为降低Q420钢的强度，建议采用900-1000°C峰值温度和1–2°C / min的冷却速率的热处理工艺。峰值温度和冷却速率是强度降低性能的两个决定因素。为降低Q420钢的强度，建议采用900-1000°C峰值温度和1–2°C / min的冷却速率的热处理工艺。