The quality control of silicon brick involves many testing items to ensure its performance and stability in high temperature environment. The following are the main inspection items for quality control of silicon bricks:

I. Chemical composition analysis

SiO content: determined by X-ray fluorescence spectrometry (XRF) or chemical titration, the SiO content is usually not less than 93%.

Analysis of impurity elements: the content of impurities such as Al₂O₃, Fe₂O₃ and CaO should be mainly detected, and the total amount of impurities should be controlled within 3%-5%.

Free silica content: chemical dissolution method is used to detect it, so as to avoid the problem of volume stability caused by excessive free SiO₂.

II. Physical performance test

Bulk density and apparent porosity: According to GB/T 2997 standard, the apparent porosity is required to be ≤23% by water saturation method.

Compressive strength at room temperature: tested by universal testing machine, with standard value ≥30MPa.

Bending strength: testing the bending resistance at high temperature (1350℃) and normal temperature.

Determination of true density: analyze the compactness of microstructure by helium replacement method.

III. Thermal performance testing

Refractory test: according to GB/T 7322 standard, the softening temperature of silicon brick is determined, generally ≥1690℃.

Softening temperature under load: the initial deformation temperature is measured under the pressure of 0.2MPa.

Thermal expansion rate: the thermal expansion coefficient in the temperature range of 20-1000℃ is detected by a thermal expansion instrument.

Thermal shock stability: the thermal shock resistance was evaluated by 1100℃- water cooling cycle test.

IV. Slag resistance test

Static crucible method: after charging the specified slag, it is calcined in a high-temperature furnace to detect the penetration depth of the slag.

Rotary slag resistance method: dynamically test the erosion rate of slag on silicon brick.

Chemical erosion analysis: the microstructure changes of erosion interface were observed by electron microscope.

V. Appearance quality and size inspection

Surface crack detection: crack width ≤0.5mm and length ≤ 1/3 of side length.

Section spalling inspection: the depth shall not exceed 1/3 of the thickness.

Measurement of dimensional deviation: the allowable error of length is ±2mm and the thickness is ±1mm.

Torsion test: use the platform feeler gauge to test the flatness of the plane.

VI. Other testing items

Re-firing linear expansion rate: detect the linear expansion after high temperature firing.

Open porosity: detect the distribution of pores in the material.

Creep resistance: Assess the deformability at high temperature and pressure.

Through the above testing items, the quality and performance of silicon bricks can be comprehensively evaluated to ensure their reliability and safety in high-temperature industrial equipment.