The main differences between JN-42 and JN-40 clay refractory bricks are as follows:

I. Chemical composition

JN-42: ALO content ≥42%, Fe₂O₃ content ≤2.3%.

JN-40: ALO content ≥40%, Fe₂O₃ content ≤2.3%.

JN-42 has higher Al₂O₃ content, which means that it has stronger fire resistance and corrosion resistance.

II. Physical properties

(1) Apparent porosity:

JN-42：≤21.8%。

JN-40：≤24%。

JN-42 has lower apparent porosity, which means that the brick has higher compactness and stronger corrosion resistance.

(2) room temperature compressive strength:

JN-42：≥44.3 MPa。

JN-40：≥42.9 MPa。

JN-42 has higher compressive strength at room temperature, indicating that it has stronger mechanical strength at room temperature.

(3) load softening temperature (0.2MPa):

JN-42：≥1410℃。

JN-40：≥1390℃。

JN-42 has a higher softening temperature under load, which indicates that it has better stability at high temperature.

III. Thermal performance

Thermal shock stability:

JN-42: ≥ 15 times (water cooling at 1100℃).

JN-40: Not explicitly listed, but usually lower than JN-42.

JN-42 has stronger thermal shock stability and is more suitable for use in the environment with frequent temperature changes.

IV. Application site

JN-42: Suitable for key parts such as coal inlet of coke oven.

JN-40: Suitable for the main parts of coke oven.

JN-42 is more suitable for parts with higher requirements for fire resistance because of its higher performance index.

V. Fire resistance

JN-42：≥1750℃。

JN-40：≥1740℃。

JN-42 has higher fire resistance and can withstand higher temperatures.

VI. Summary

JN-42 clay refractory brick is superior to JN-40 in chemical composition, physical properties and thermal properties, especially in Al₂O₃ content, apparent porosity, compressive strength at room temperature, softening temperature under load and thermal shock stability. Therefore, JN-42 is more suitable for key parts of coke ovens with higher requirements on fire resistance.