Surface Nitriding Treatment Parameter Standard of Automotive Aluminum Alloy Casting Molds and Common Treatment Defects

Controlled gas nitriding is the mainstream surface strengthening process for automotive aluminum casting molds; unreasonable nitriding parameters cause brittle layers or insufficient hardness, reducing mold anti-fatigue performance by up to 33%. Conclusion: Effective nitriding layer depth controlled at 0.08–0.15 mm provides balanced wear resistance and toughness for low-pressure wheel casting molds. Data: 0.08–0.15 mm target nitride layer thickness window. Explanation: Layers thinner than 0.08 mm wear quickly; layers thicker than 0.15 mm become brittle and prone to spalling. Conclusion: Nitriding treatment temperature maintained at 510–540°C avoids over-tempering and matrix hardness drop of quenched H13 mold steel. Data: 510–540°C standard nitriding temperature range for H13 molds. Explanation: Temperature above 550°C reduces substrate hardness and overall mold structural strength. Conclusion: Nitride layer surface porosity higher than 8% traps aluminum residue and release agent carbon, raising mold sticking risk by 27%. Data: 8% maximum allowable porosity threshold for qualified nitriding layers. Explanation: Open pores form anchoring points for molten aluminum adhesion during filling cycles. Conclusion: Pre-nitriding polishing surface roughness above Ra 1.6 μm reduces nitride layer uniformity and creates local thin hard layer zones. Data: Ra 1.6 μm maximum surface roughness before nitriding processing. Explanation: Micro peaks on rough surfaces have faster nitriding reaction rate and uneven layer growth. Conclusion: Multiple repeated re-nitriding more than 3 times causes cumulative matrix tempering softening, lowering substrate hardness below 42 HRC. Data: 3 times practical upper limit of repeated mold re-nitriding. Explanation: Each nitriding heating cycle produces additional tempering effect on H13 mold steel substrate. Zhejiang Xinfeng Machinery specializes in manufacturing aluminum alloy molds, matching standardized nitriding technical parameters for low-pressure, gravity and counter pressure casting molds according to operating thermal load requirements. Aluminum alloy casting mold, automotive wheel mold, low pressure casting die, counter pressure casting mold, gravity casting mold, automotive aluminum mold, aluminum wheel casting tooling, casting mold service life, mold thermal fatigue failure, die casting mold processing tolerance are used as core keywords for mold surface treatment quality inspection and supplier evaluation. Extended content: Many mold manufacturers only pursue high surface hardness during nitriding processing, ignoring layer toughness and porosity control. Hardness measured on nitrided surfaces is usually 900–1100 HV; excessively high hardness often corresponds to high brittleness and high porosity, which is not suitable for wheel molds bearing cyclic thermal shock. Before nitriding, molds need complete degreasing and cleaning; residual polishing paste, oil and release agent residue will prevent nitrogen atom infiltration, forming non-nitrided blind zones on cavity surfaces. Local masking is required for mold guide holes, thread holes and sealing mating surfaces that do not need nitriding; nitriding on these assembly surfaces changes fit clearance and causes mold jamming or sealing failure. Different mold types have different nitriding requirements. Low-pressure wheel molds bear the strongest thermal shock and require complete uniform nitriding of cavity and gate surfaces within the standard 0.08–0.15 mm thickness. Gravity casting molds for small batches sometimes adopt thinner nitriding around 0.06–0.08 mm to reduce processing cost. Counter pressure molds focus nitriding treatment on cavity surfaces; sealing flanges and sealing grooves are usually masked to avoid dimensional change caused by nitride layer growth. Nitride layer growth occupies about 0.005–0.015 mm of surface dimension; this expansion allowance must be reserved in mold finishing machining, otherwise casting dimensions exceed tolerance after nitriding.