Mold Thermal Shock & Thermal Fatigue Analysis – Crack Initiation, Crack Propagation and Service Life Prediction

Thermal shock and thermal fatigue are primary root causes for mold surface cracking, Xinfeng Mold carries out thermal cycle simulation to predict fatigue life for aluminum casting molds. Alternating thermal stress arises from rapid heating by molten aluminum and fast cooling by cooling water; repeated stress cycles initiate surface heat checking cracks. Mold surface temperature swing amplitude exceeding 220°C greatly accelerates thermal fatigue crack formation; swing amplitude below 150°C extends service life significantly. H13 mold cavity can normally sustain 60,000–100,000 thermal cycles before visible heat checking cracks appear under standard operating conditions. Many premature mold cracking incidents are caused by violent temperature fluctuation; statistics show 50% of thermal fatigue cracks start at sharp cavity corners. Cavity sharp corners are modified to rounded radius ≥3 mm to reduce stress concentration and delay crack initiation. Nitriding and PVD coating improve surface thermal fatigue resistance, but coating will crack once substrate steel develops thermal fatigue cracks. Mold startup procedure requires gradual preheating; cold mold directly filled with high temperature molten aluminum creates severe thermal shock. Thermal fatigue simulation calculates stress distribution at hot spots, predicting crack-prone regions before mold machining. Local surface cracks less than 0.15 mm can be repaired by welding and polishing; deeper cracks require insert replacement. Mold temperature fluctuation monitoring during mass production helps track thermal fatigue accumulation and schedule preventive maintenance. Thermal fatigue life prediction is included in mold quotation for high-volume projects, supporting customer production planning. When mold stops production, controlled slow cooling is required; rapid air cooling increases thermal stress and shortens residual mold life. Weld repair zones have lower thermal fatigue resistance than original mold steel; repaired areas need more frequent inspection. Thermal fatigue analysis is combined with mold flow and cooling simulation to optimize cavity geometry and cooling layout simultaneously.

FAQ

Q1: What temperature swing threshold accelerates thermal fatigue crack formation? A1: Temperature swing amplitude exceeding 220°C sharply speeds up thermal fatigue cracking. Q2: What is the typical thermal cycle range for H13 cavity before heat checking cracks? A2: H13 cavity can withstand 60,000–100,000 thermal cycles before visible heat checking. Q3: What percentage of thermal fatigue cracks start at sharp cavity corners? A3: 50% thermal fatigue cracks initiate at sharp cavity corner stress concentration zones. Q4: What minimum radius is used for cavity corners to reduce thermal stress concentration? A4: Cavity transition corners adopt rounded radius ≥3 mm. Q5: What crack depth threshold determines whether cavity can be repaired by welding? A5: Cracks less than 0.15 mm can be repaired by welding and polishing. Q6: What operation causes severe thermal shock at mold startup? A6: Pouring molten aluminum into cold mold without gradual preheating causes heavy thermal shock.

Embedded Keywords: Thermal Shock, Thermal Fatigue, Heat Checking, Mold Surface Cracking, Thermal Stress, Stress Concentration, H13 Mold Steel, Mold Cycle Life, Crack Propagation, Mold Simulation