Products for Casting Aluminum Alloys

Complete mold QA system controls quality in every stage from design review, material incoming inspection, machining, heat treatment, surface treatment, mold trial to final delivery. This article describes Xinfeng mould full-stage QA checkpoints and acceptance criteria.

Stage 1: Design review. 3D model check, gating/riser simulation review, cooling and vent layout review, FEM thermal stress analysis, tolerance stack-up check. Sign-off required before machining.

Stage 2: Raw material incoming inspection. H13 steel blank UT ultrasonic test, material certificate verification, hardness test and surface defect inspection. Reject non-conforming steel blanks.

Stage3: Machining process inspection. Rough machining allowance check, semi-finish CMM inspection, EDM electrode inspection, parting surface flatness and cavity dimension check.

Stage4: Heat treatment QA. Furnace temperature curve recording, hardness testing, distortion measurement, metallographic sampling for batch validation.

Stage5: Surface treatment QA. Nitriding layer thickness measurement, surface roughness test, nitriding layer adhesion test.

Stage6: Mold assembly inspection. Insert assembly clearance, ejector movement test, sealing surface flatness, cooling circuit hydraulic leak test.

Stage7: Mold trial QA. Dry mold test, first shot trial, parameter window test, continuous run test. Collect CMM, X-ray, mechanical and pressure tightness test data.

Stage8: Pre-delivery final inspection. Full mold appearance check, spare parts verification, document package audit, anti-rust treatment and packaging inspection.

Non-conformity handling: any non-conformity found at checkpoint must be isolated, root cause analyzed, corrected and re-inspected before entering next process.

QA document archive: all inspection reports, certificates, simulation files and mold drawings are stored for at least 10 years for traceability.

### FAQ

Q1: What is the first checkpoint in Xinfeng mould mold QA system?
A1: Design review including simulation, thermal stress analysis and tolerance stack-up check.
Q2: What test is required for incoming H13 mold steel blank?
A2: UT ultrasonic inspection, material certificate check and hardness test.
Q3: How long are mold QA documents retained?
A3: QA documents and mold drawings are archived and stored for at least 10 years.

Multi-cavity mold improves production efficiency and reduces unit mold investment. Unbalanced filling between cavities causes inconsistent casting quality, different shrinkage and dimensional deviation among cavities. This article introduces multi-cavity LPDC and gravity mold design rules and balance control.

Cavity layout principle: symmetric layout to balance melt flow path and thermal field. Asymmetric layout creates temperature difference between cavities and inconsistent solidification sequence.

Runner system design: equal runner length and cross-section for each cavity. Runner volume difference among cavities controlled below 7%.

Filling velocity deviation between different cavities ≤0.02 m/s. Unequal filling speed leads to oxide inclusion difference.

Thermal balance design: each cavity equipped with independent cooling loop for high requirement parts. For low demand parts, shared cooling circuit with symmetrical cooling channel layout.

Vent area of each cavity must be identical. Unequal vent area causes different gas trapping status between cavities.

Mold preheating: multi-cavity mold adopts multiple embedded heating rods to ensure cavity temperature difference ≤12℃ before casting.

Cavity number selection: for large automotive structural castings, 2-cavity is common; small parts can adopt up to 4 cavities. Too many cavities increase filling balance difficulty.

Defect sampling rule during mold trial: sample castings from every cavity separately for X-ray and dimensional inspection, not only from one cavity.

Ejection system: symmetric ejector layout for each cavity, same ejector pin quantity and diameter to avoid uneven deformation between parts.

Mold maintenance: inspect each cavity vent, soldering and wear separately; replace worn inserts individually rather than whole mold block.

### FAQ

Q1: What is the core requirement for multi-cavity mold runner system?
A1: Equal runner length and cross-section to guarantee balanced melt filling for every cavity.
Q2: What temperature difference limit between cavities for multi-cavity mold preheating?
A2: Temperature difference between different cavities controlled ≤12℃.
Q3: How to sample castings in multi-cavity mold trial?
A3: Sample castings from each cavity separately for X-ray and dimensional inspection.

Systematic mold failure analysis quickly identifies root causes, avoids repeated failure on subsequent molds and reduces production loss. This article sets up Xinfeng mould standardized failure analysis workflow, inspection methods and classification of failure modes.

Step 1: On-site data collection. Record failure cycle count, process parameters, mold temperature, defect location, alloy grade, maintenance history and photos/videos of damaged area.

Step 2: Macro inspection. Observe crack morphology, soldering distribution, surface peeling, deformation and leakage. Judge failure type: thermal fatigue, soldering, nitriding peeling, mechanical overload or corrosion.

Step 3: Non-destructive inspection: UT ultrasonic test, hardness test, surface roughness measurement and dimensional check.

Step 4: Sampling and metallographic analysis for critical cases. Observe microstructure, nitriding layer thickness, crack propagation path and inclusion distribution under microscope.

Step 5: Root cause classification: material defect, heat treatment abnormality, machining residual stress, improper surface treatment, design flaw or on-site process misoperation.

Step 6: Verification and countermeasure formulation. Use simulation or trial mold to validate improvement measures, update mold design specification and process SOP.

Step 7: Document archiving. Add failure case into Xinfeng mould database for future mold design reference.

Common failure mode statistical distribution: thermal fatigue cracks 34%, soldering 30%, nitriding peeling 18%, mechanical deformation 10%, cooling channel corrosion/leakage 8%.

Preventive knowledge transfer: feed failure analysis results back to design, machining, heat treatment and on-site production teams.

### FAQ

Q1: What is the first step of mold failure analysis?
A1: Collect on-site production data, process parameters and failure images.
Q2: What inspection is used to observe mold microstructure and nitriding layer?
A2: Metallographic microscope analysis on sampled mold specimen.
Q3: What accounts for the largest proportion of aluminum casting mold failure?
A3: Thermal fatigue cracks account for 34% of total mold failure cases.

Poor cooling water quality forms scale and corrosion inside cooling channels, gradually reducing cooling efficiency and causing mold temperature drift. Scale blockage accounts for 21% of thermal imbalance issues during mass casting. This article defines water quality index, water treatment and periodic cleaning plan.

Cooling water requirement: total hardness ≤8°dH, pH value 7.2–8.0, chloride ion less than 100 mg/L. Hard water easily precipitates calcium carbonate scale at high mold temperature.

Water filter installation: 50 μm filter before mold cooling inlet to remove suspended particles and rust.

Water temperature control: inlet water maintained at 32–42℃. Water temperature below 30℃ causes excessive thermal shock and accelerates mold thermal fatigue.

Scale formation mechanism: calcium and magnesium ions precipitate when heated on inner wall of cooling channels, forming insulating scale layer, thermal conductivity drops sharply.

Online inhibitor dosing: add low-phosphorus scale inhibitor to circulating water to suppress scale crystallization.

Cleaning cycle: chemical descaling every 6000 casting cycles. Circulate acid-based cleaning agent inside cooling circuit, then fully flush with clean water.

Pressure monitoring for cooling circuit: inlet and outlet pressure difference recorded daily. Pressure rise over 0.05 MPa indicates scale accumulation inside channels.

Corrosion protection: avoid excessive acid concentration during descaling, which will erode cooling channel inner wall and cause water leakage.

After chemical cleaning, hydraulic pressure test at 1.5 times working pressure to verify channel integrity.

### FAQ

Q1: What is the target pH range for mold cooling circulating water?
A1: Cooling water pH should be kept between 7.2 and 8.0.
Q2: How often to perform chemical descaling for mold cooling channels?
A2: Chemical descaling every 6000 casting cycles.
Q3: What is the sign of scale accumulation inside cooling circuit?
A3: Rise of inlet and outlet water pressure difference over 0.05 MPa.

H13 heat treatment is the core process to achieve target hardness, toughness and thermal fatigue resistance. Improper heat treatment causes inconsistent hardness, distortion and early mold failure. This article describes H13 standard heat treatment curve and quality inspection standards.

Preheating: two-stage preheating at 650℃ and 850℃ to reduce thermal gradient inside mold blank, avoid quenching distortion for large mold blocks.

Quenching: austenitizing at 1020–1040℃, hold time 20–30 min per 100 mm thickness. Gas quenching to 150–200℃, cooling rate controlled to prevent thermal stress cracking.

Double tempering: first temper at 560–580℃, hold 2 hours; second temper at 570–590℃. Final hardness target HRC44–49. Single temper cannot fully relieve quenching stress.

Cryogenic treatment after quenching: cool down to -180 ~ -190℃, hold for 2–4 hours. Convert retained austenite into martensite, reduce residual stress and stabilize mold dimension.

Hardness inspection: 5–8 measuring points distributed on cavity surface, hardness deviation within ±1.5 HRC.

Distortion inspection after heat treatment: mold block deformation ≤0.04 mm per 500 mm length. Excessive distortion requires correction and re-machining.

Heat treatment defects: overheating leads to grain coarsening and low toughness; insufficient austenitizing results in low hardness and poor wear resistance.

Weld repaired local region needs local stress relief tempering at 550℃, to match substrate hardness.

Heat treatment batch traceability: record furnace temperature curve, hardness log and distortion measurement report for every mold block.

### FAQ

Q1: What is the austenitizing temperature range for H13 quenching?
A1: H13 quenching austenitizing temperature is 1020–1040℃.
Q2: Why adopt double tempering for H13 mold steel?
A2: Double temper fully relieves quenching residual stress and stabilizes final hardness.
Q3: What is the function of cryogenic treatment after quenching?
A3: Transform retained austenite, reduce residual stress and improve dimensional stability.

Precision CNC machining determines cavity dimensional accuracy, assembly clearance and final casting quality. Poor machining control leads to core offset, uneven wall thickness and assembly interference. This article introduces Xinfeng mould CNC machining sequence, tolerance allocation and inspection standards.

Cavity rough machining: leave 0.4–0.6 mm finishing allowance, control machining vibration to avoid residual stress. Roughing tool path keeps 0.25–0.35 mm depth per cut.

Semi-finish machining: leave 0.12–0.20 mm allowance for final polishing. Check cavity deformation after semi-finishing, especially for large mold inserts over 400 mm.

Finish machining: cavity profile tolerance ±0.03 mm; core pin position tolerance ±0.025 mm. Machining temperature controlled at 22±2℃ to reduce thermal expansion error.

Draft angle machining tolerance: ±0.1°, directly affects ejection drag marks.

Fillet machining: continuous milling for large fillet R≥3.0; small fillet manually polished after CNC. Fillet radius tolerance ±0.05 mm.

Parting surface flatness within 0.02 mm per 500 mm length, to guarantee parting line clearance ≤0.03 mm and prevent flash.

H13 material machining after roughing: stress relief tempering before finish machining to release cutting residual stress, avoiding cavity deformation after final machining.

CMM inspection after finish machining: full 3D scanning of cavity, core pins, cooling holes and vent slots, generate dimensional deviation report.

Electrode design for EDM: used for deep narrow rib cavities where milling tool cannot reach. EDM surface must be polished to Ra0.8 before nitriding.

Machining marking: each insert engraved with part number, serial number and heat treatment batch for full traceability.

### FAQ

Q1: What finishing allowance is reserved after mold semi-finish machining?
A1: 0.12–0.20 mm finishing allowance left before polishing.
Q2: What is flatness requirement of mold parting surface?
A2: Parting surface flatness controlled within 0.02 mm per 500 mm length.
Q3: Why stress relief tempering after H13 rough machining?
A3: Release cutting residual stress and prevent cavity deformation after finish machining.