Case Study - Blast furnace main troughs


Aggressive oxidation leads to high porosity & low resistance. Root cause analysis of higher frequent repairs & lower yield.

Our Solution CASTFRAX® S25-NG

Different from the standard material and owing to the innovative concepts used in its formulation design, our outstanding CASTFRAX® S25-NG presents extremely high performance when exposed to air even after 11 hours at 1,000°C, which is the most critical temperature for Al2O3-SiC-Carbon castables. As a low oxidation rate leads to small variances on the castable porosity, those results indicate that the material’s corrosion resistance would clearly be increased during use.

Oxidation comparaison

We developed an optimal material mix with very low oxidation rate. Cross-sections of S25-S and S25-NG samples after oxiding test at 1,000°C for 6 hours and 11 hours.


S25-C Standard

S25-NG = New generation

Oxidizer layer (Relative index)

6 hours 100%
castfrax s25-s
castfrax S25-NG
11 hours 100%
castfrax S25-S
castfrax S25-NG


Results CASTFRAX® S25-NG

  Region Al2O3 SiC + C SlO2
castfrax S25-NG compare
CASTFRAX S25-S 1 62.2 11.7 22.4
2 65.4 11.9 17.6
3 59.6 13.7 16.2
CASTFRAX S25-NG 1 68.3 19.4 9.6
2 68.3 22.0 7.0
3 64.7 27.0 4.9

Chemical analyses of different regions in the post-mortem. Samples of standard material and CASTFRAX® S25-NG (Results expressed in wt.%).

Post-mortem samples of standard material CASTFRAX® S25-NG after 250 days of operation.

Post-mortem samples of both materials (highlighting the regions where chemical analyses were performed) show that it is clear that the reason for trough campaign instability at blast furnaces with two holes was directly related to the poor oxidation resistance of S25-S.

New material CASTFRAX® S25-NG shows improved performance - lower decomposition of refractory material.
Due to the constant thermal cycling and the direct exposure of the refractory lining to oxidizing environments during the main trough operation, the standard Al2O3-SiC-SiO2-C castable can be easily damaged and the trough campaign consequently reduced. When events like this happen, emergency repairs must be executed, resulting in increased refractory unit consumption and an unplanned shutdown of unit operation.

Our solution has provided better yield of iron produced for every kg of refractory used.

castfrax S25-NG campaign
castfrax S25-NG campaign

Value Proposition

Higher yield between repairs
Lower consumption of refractory material
Longer trough campaigns
Higher no. of campaigns

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