退火工艺对采暖系统用耐沟状腐蚀钢带性能的影响

通过对耐沟状腐蚀现象的研究,结合生产设备能力,设计了6种成分钢带和6种退火工艺。借助光学显微镜、扫描电镜、拉伸试验、中性盐雾试验等手段,研究了采暖系统用耐沟状腐蚀钢带生产过程中冷轧退火工艺对其性能的影响。结果发现:低于Ac₁温度(650、700 ℃)的退火不可能改变原来冷轧铁素体晶界的遗传结构,冷轧α相的再结晶长大不充分,碳化物的聚合和长大过程也不充分;当退火温度达到Ac₁左右(750 ℃),由于碳元素的固溶加剧,导致α相再结晶和析出物的聚合长大,得到极优的延展性,对深冲非常有利;退火温度位于Ac₁~Ac₃之间(850 ℃),发生α→γ相再结晶,可以取得最好的软化效果。对于含Ti的试验钢,随着退火温度的降低,其塑性应变比r值呈下降趋势。Cr的加入不利于耐沟状腐蚀性能,但是Al的加入有利于耐沟状腐蚀性能。采用两段式退火工艺进行工业化生产,可以得到外观和性能优良的采暖系统用耐沟状腐蚀产品。

Effect of annealing process on properties of grooving-corrosion resistant steel strip for heating system

Through the research on the phenomenon of the resistance to grooving corrosion, and combining with the production equipment capacity, six kinds of steel strip chemical compositions and six kinds of annealing processes were designed. The effect of cold rolling annealing process on the properties of grooving-corrosion resistant steel strips for heating system was studied by means of metallography, SEM, tensile test, and salt spray test. The results show that the annealing at temperature lower than Ac₁(650 and 700 ℃) can not change the genetic structure of the original grain boundary of cold-rolled ferrite, under such conditions the recrystallization of cold rolled α phase does not grow sufficiently, and the polymerization and growth of carbides are also insufficient. When the annealing temperature reaches about Ac₁(750 ℃), the solid solving of carbon increases, leading to recrystallization and growth of α phase as well as the polymerization of precipitates, resulting in excellent ductility, which is very beneficial for deep drawing. When the annealing temperature is between Ac₁-Ac₃(850 ℃), α→γ phase transformation and recrystallization occur, and the best softening effect can be obtained. While for the Ti-bearing tested steel, the plastic strain ratio r value tends to decrease with the decrease of annealing temperature. The addition of Al is conducive to increase the resistance to grooving corrosion, but the Cr addition has the opposite effect. Using two-stage annealing process for industrial production can get grooving-corrosion resistant products for heating systems with excellent appearance and properties.