极薄高强钢板高效气淬技术

High-efficiency air-jet quenching technology of ultra-thin high-strength steel sheets

极薄高强钢板在高温下空冷迅速降温且不可控、淬火应力大易瓢曲,是制约高品质生产与性能提升的关键因素。将高压气淬技术引入极薄高强钢板淬火领域,通过气冷温降分析、力学性能及显微组织检测,探究了气冷工艺对极薄高强钢板淬火组织性能的影响。结果表明,气冷淬火工艺可减小钢板厚度和长度方向上的热梯度,降低淬火过程的热应力与组织应力,在板形调控方面具有优势。当钢板转移时间过长时,开冷温度将低至Ar3点以下,发生上贝氏体和下贝氏体相变,导致钢板强度和硬度显著下降。在加热温度970℃、保温时间5 min、淬火开冷温度840℃的条件下,获得了抗拉强度1 226 MPa、布氏硬度385 HB、钢板整板淬火不平度不大于3 mm/m的2 mm淬火态NM400极薄高强钢板,为新型极薄规格板材高平直度淬火工艺的开发奠定基础。

The rapid and uncontrollable air cooling of ultra-thin high-strength steel sheet at high temperature and the large quenching stress are the key factors restricting high-quality production and performance improvement. The high-pressure air-jet quenching technology had been introduced in the field of ultra-thin high-strength steel sheet quenching. Through the analysis of temperature drop of air-jet cooling, mechanical properties and microstructure detection, the influence of air-jet quenching technology on the quenching structure and properties of ultra-thin high-strength steel sheet was explored. The results show that the air-jet quenching process reduces the thermal gradient in the thickness and length direction of the steel sheet, reduces the thermal stress and structural stress during the quenching process, and has advantages in shape control. When the transfer time of the steel sheet is too long, the cooling temperature will be lower than Ar3, and the transformation of upper bainite and lower bainite will occur, resulting in a significant decrease in the strength and hardness of the steel sheet. Under the conditions of heating temperature of 970 ℃, holding time of 5 min, and quenching temperature of 840 ℃, a 2 mm quenched NM400 ultra-thin high-strength steel sheet with tensile strength of 1 226 MPa, Brinell hardness of 385 HB, and the whole sheet′s quenching unevenness of not larger than 3 mm/m was obtained, laying the foundation for the development of new ultra-thin sheet′s high flatness quenching process.