Granite Component · Constant Temperature Heat Aging Standard Operating Procedure (Factory Practical Version, Follow Directly)
Core Purpose of Granite Heat Aging: Rapidly release internal crystalline stress and cutting/machining stress to avoid deformation, warping, and loss of precision during subsequent grinding or use. Replaces natural aging of 3–6 months, typically completed in 24–72 hours.
Below are the complete operation parameters, steps, temperature control, and precautions, which are industry-standard.
I. Equipment Preparation
Equipment: Industrial constant temperature oven / Hot air circulation aging chamber (Must have hot air circulation; no localized overheating)
Temperature Measurement: Built-in multi-point thermocouples for real-time monitoring of stone surface and internal temperatures
Fixturing: Components placed flat; bottom padded with solid wood or rubber blocks to keep components suspended and not touching the ground to avoid uneven heating
II. Component Pre-treatment (Before entering the oven)
Rough Machining Completed: All shaping, drilling, slotting, and embedded parts finished; only grinding allowance left
Cleaning: Dust and cutting slurry washed clean; surface dried
Placement:
Large components (bases) placed flat, single layer, no stacking
Irregular beams and columns placed vertically or horizontally padded to prevent bending from heat
Leave 5–10cm gaps between components for hot air circulation
III. Standard Heating — Soaking — Cooling Complete Process (Most Common Parameters)
- Heating Stage (Most critical; strictly prohibit rapid heating)
Heating Rate: 5–8°C per hour; must not exceed 10°C/h to prevent granite cracking
Gradually heat from room temperature to 55–60°C
Jinan Blue, Zhangqiu Black, and Indian stones all use 55–60°C; higher temperatures will cause internal cracks and discoloration. - Soaking Stage (Core of stress relief)
Soaking Temperature: 55°C ± 3°C
Soaking Time:
Small components (platforms, straight edges, square boxes): 24h
Medium machine bases, frames: 48h
Large / Ultra-precision semiconductor, CMM bases: 72h
Full hot air circulation throughout; temperature must be uniform with no localized high temperatures - Cooling Stage (Strictly prohibit opening door for rapid cooling)
Cooling Rate: 3–5°C per hour; slow natural cooling
Cool down to below 30°C before opening the oven to remove components
Prohibited to open door at high temperature, blow air, or pour water; this will cause instant stress rebound and cracking
IV. Post-Heat Aging Treatment
After removal, let stand in workshop at room temperature for over 24 hours to naturally return to temperature
Then proceed with semi-precision milling and precision grinding
After processing, stability is extremely strong; Class 0/00 precision remains unchanged for a long time
V. Industry Taboos & Pitfall Avoidance (Very Important)
Temperature must absolutely not exceed 70°C: Uneven thermal expansion of internal granite crystals will cause internal cracks and edge chipping later
Do not use rapid heating or rapid cooling; this is the cause of deformation in 90% of factory components
Must perform aging after rough machining; aging after precision machining or grinding will destroy precision
Components with metal embedded parts (stainless steel sleeves, screws) are unaffected by heat aging and can be placed in the furnace together
Jinan Blue has the best stability and most obvious heat aging effect; ordinary light-colored granites are not recommended for high-precision components
