Degradation and regeneration of quenched nitrate

doi:10.13251/j.issn.0254-6051.2020.04.048

Abstract

Abstract: The deterioration products of nitrate bath used for step quenching or austempering were comprehensively analyzed by means of SEM, EDS and chemical analysis.The results show that nitrate degradation is mainly caused by the reaction products of nitrate (Na₂CO₃, NaOH), oxidation products (FeO·Fe₂O₃·Fe₃O₄) of equipment (mainly salt bath, salt pump, pipeline and roller),fixtures,pans and workpieces and foreign substances (dust, carbon black) during the use of nitrate. Accordingly, the counter-measures to prevent deterioration of quenched nitrate are put forward, including choosing base salt with good quality or mixed salt with high thermal stability, keeping the temperature of the quenching salt bath uniform, controlling the temperature rise before and after quenching, trying to avoid “instantaneous” overheating and foreign impurities, and doing daily maintenance well. And the method of regeneration of quenched nitrate is also briefly introduced.

Key words: nitrate, deterioration, regeneration

CLC Number:

X758

Zhang Fuquan, Xiao Yunwei. Degradation and regeneration of quenched nitrate[J]. Heat Treatment of Metals, 2020, 45(4): 229-235.

References

[1]张峦, 顾敏, 王爱香, 等. 硝盐淬火介质的冷却特性[J]. 金属热处理, 2015, 40(6): 212-215.
Zhang Luan, Gu Min, Wang Aixiang, et al. Cooling characteristics of nitrate quenching medium[J]. Heat Treatment of Metals, 2015, 40(6): 212-215.
[2]殷汉奇, 许红军. 硝盐淬火技术[J]. 热处理, 2015, 30(3): 36-39.
Yin Hanqi, Xu Hongjun. Quenching in nitrate-nitrite salt[J]. Heat Treatment, 2015, 30(3): 36-39.
[3]赫佳, 尚玉俊, 赵清环, 等. 一种熔盐中无机盐成分的快速检测方法[J]. 河南职工医学学院学报, 2008, 20(6): 561-563.
Hao Jia, Shang Yujun, Zhao Qinghuan, et al. A rapid detection method for inorganic salts in molten salts[J]. Journal of Henan Medical College for Staff and Workers, 2008, 20(6): 561-563.
[4]路青梅. 载热熔盐中硝酸根分析方法[J]. 河北化工, 2007, 30(9): 65.
Lu Qingmei. Analysis method of nitrate in the molten salts[J]. Hebei Chemical Industry, 2007, 30(9): 65.
[5]龙兵, 魏小兰, 丁静, 等. 三元硝酸熔盐高温劣化的化学热力学计算[J]. 太阳能学报, 2011, 32(2): 253-255.
Long Bing, Wei Xiaolan, Ding Jing, et al. Chemical thermodynamics calculation of three elements nitrate degradation at high temperature[J]. Acta Energiae Solaris Sinica, 2011, 32(2): 253-255.
[6]王健, 刘金海, 赵雪勃, 等. 等温淬火硝盐“结垢”的形成机制及预防措施[J]. 材料热处理学报, 2013, 34(11): 39-41.
Wang Jian, Liu Jinhai, Zhao Xuebo, et al. Mechanism of nitrate formation and its prevention during austempering process[J]. Transactions of Materials and Heat Treatment, 2013, 34(11): 39-41.
[7]Foreman R W. 盐浴淬火的新发展[J]. 铸锻热-热处理实践, 1994(2): 8-9.
Foreman R W. New development of salt bath quenching[J]. Practice of Casting-forging Thermal Treatment, 1994(2): 8-9.
[8]吴玉庭, 王涛, 马重芳, 等. 二元混合硝酸盐的配制及性能[J]. 太阳能学报, 2012, 33(1): 149-152.
Wu Yuting, Wang Tao, Ma Zhongfang, et al. Preparation and experimental study of binary nitrate salts[J]. Acta Energiae Solaris Sinica, 2012, 33(1): 149-152.