# Stress Corrosion Cracking Analysis of a Hot Blast Stove Shell with an Internal Combustion Chamber
## 4 Conclusions  
In this study, the stress corrosion cracking behaviour of the internal combustion hot blast stove was analysed. The SCC SMM was modified to transform from a theoretical prediction of the stress corrosion crack in industrial problems. The weight calculated based on the water and acid condensation rates was applied to the crack propagation rate equation to consider the effect of the corrosion. By applying the fluid temperature and mapping to the shell temperature, the low-temperature corrosion (LTC) characteristics of condensed acid and the stress corrosion cracking in the metallic shell of the hot blast stoves while under operation could be predicted as distributions and values. The conclusions based on the analysis results can be summarised as follows:  
* Without considering the weight factor, the crack propagation velocity was the largest at the conical region of the upper combustion chamber. The causes of the high crack propagation velocity are higher maximum principal stress and temperature distributions on the region.
* The deposition rates of the water, sulfuric, and nitric acids were found to condense more at the lower part of the HBS. However, at the conical region between the checker and combustion chambers, the deposition rates were higher than in the other part of the conical region.
* The weight factor on the crack propagation rate made it possible to consider the effect of the acid condensation rates on the crack propagation rates. The crack propagation rates in the regions with high temperatures became lower since there was no sufficient condensed acid to be expected.
* The increase in the blast temperature had a low effect on the shell temperature. With the increase of 90 K on the blast temperature, the shell temperature only increased by 5.2 K maximum.
* The blast temperature had less effect on the maximum principal stress generated during the operation. However, when the blast temperature was increased by 90 K, the maximum crack propagation rate was increased from \(7.61\times 10^{-7}\) m/cycle to \(8.88\times 10^{-7}\) m/cycle, which means that there was a 16.7% increase since the stress corrosion cracking is affected by the shell temperature.  
Since the conical region showed higher crack propagation rates, monitoring the conical region can be important from the safety management perspective. Especially as the weld lines usually have residual stresses, the weld lines near the conical region should be the region of interest for managing the internal-combustion HBS. Suggestions for future work include applying the refined AHP method and the phenomenological relationship of the SCC process to evolution, including the application of damage models to access the damage evolution. In addition, the influence of the residual stresses from the weld lines on the SCC is also another candidate for future work.  
Conceptualisation, N.K.; methodology, D.P. and F.G.; software, D.P. and F.G.; validation, D.P. and F.G.; formal analysis, D.P. and F.G.; investigation, D.P. and F.G.; resources, N.K.; data curation, D.P. and F.G.; writing--original draft preparation, D.P. and F.G.; writing--review and editing, N.K.; visualisation, D.P. and F.G.; supervision, N.K.; project administration, N.K.; funding acquisition, N.K. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The data presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy.  
The authors declare no conflict of interest.  
The following abbreviations are used in this manuscript:  
\begin{tabular}{l l} ADP & acid dew point \\ CFD & computational fluid dynamics \\ CPR & crack propagation rate \\ FEA & finite element analysis \\ HBS & hot blast stove \\ LTC & low-temperature corrosion \\ SCC & stress corrosion cracking \\ SMM & surface mobility mechanism \\ \end{tabular}