Engineering Guide / Zinc Alloy Die Casting
Zinc Alloy Die Casting Technical Specification: GB/T 13821-2023 and GB/T 13818-2024
A practical technical specification for zinc alloy die casting parts, covering material composition, melting temperature, die casting process windows, internal inspection and application requirements.
Material Specification
Material control should focus on alloy grade, controlled elements, impurity limits and melting stability. Composition affects strength, fluidity, aging deformation, corrosion behavior and long-term reliability.
- Common alloy grades include ZA3, ZA8 and ZA12; ZA8 aluminum content is typically 7.5%-8.5%, while ZA12 is typically 10.5%-12.0%.
- Aluminum affects strength and fluidity; ZA3 may use 3.8%-4.3%, while ZA8 may use 7.5%-8.5%.
- Copper may be controlled around 0.7%-1.1%; excessive copper increases brittleness risk.
- Magnesium may be controlled around 0.035%-0.06% to reduce intergranular corrosion, but excessive magnesium can increase hot cracking risk.
- Lead should be controlled at <=0.003% and cadmium at <=0.001% to reduce aging deformation, cracking and compliance risks.
Melting Process Control
A stable melting window is a prerequisite for zinc alloy die casting quality. Excessive temperature can accelerate iron crucible corrosion, introduce iron into the alloy and create hard particles that increase mold wear and surface defects.
- Initial melting temperature can be controlled at 435-440 deg C.
- After complete melting, holding temperature can be reduced to 420-430 deg C to reduce aluminum and magnesium burning loss and zinc dross.
- When temperature exceeds 450 deg C, watch for iron contamination, hard particles and mold wear.
- Inert gas protection or vacuum melting is recommended to reduce hydrogen absorption and internal porosity.
Die Casting Process Window
The process window should cover injection pressure, filling time, mold temperature, release agent, vacuum assistance and feeding stability. Thin-wall, functional and cosmetic parts require stronger control of filling speed, residual gas and temperature fluctuation.
| Item | Recommended Window / Checkpoint |
|---|---|
| Injection pressure | 45-50 kg/cm² to ensure sufficient filling of complex cavities. |
| Filling time | <=0.01 s; thin-wall parts require shorter filling time to reduce cold shut risk. |
| Mold preheating | 150-200 deg C; cold mold injection can cause cold marks or poor filling. |
| Release agent ratio | Water-based release agent can be mixed with water at around 1:200 to reduce VOC emissions. |
| Vacuum die casting | High-precision parts should use vacuum-assisted die casting and keep residual cavity pressure <=30 kPa. |
| Temperature stability | Central melting furnace plus automatic feeding can help keep pouring temperature deviation within +/-5 deg C. |
Quality Inspection Specification
GB/T 13821-2023 differentiates inspection requirements by casting type. For structural, functional and safety-related parts, internal quality should not depend only on visual and dimensional sampling; X-ray, industrial CT or other non-destructive inspection methods should be considered.
| Category | Application | Required Inspection Items |
|---|---|---|
| Class 1 | Structural or functional parts, such as automotive seat belt buckles. | Chemical composition, mechanical properties, dimensional tolerance, surface quality and internal quality. |
| Class 2 | General parts, such as decorative components. | Chemical composition, mechanical properties, dimensional tolerance and surface quality. |
- Internal quality inspection may use industrial CT and digital X-ray imaging to evaluate porosity and shrinkage defects.
- Pin-hole grading may be judged by defect quantity within a 1 cm² area.
- ZA8 tensile strength may reference >=280 MPa, with elongation after fracture >=10%.
- Brinell hardness should follow typical values in the standard appendix; ZA8 may reference 80-100 HBW.
- Dimensional tolerance can follow GB/T 6414-2017, with critical mating surfaces managed at CT4 precision grade where required.
Application Requirements
- Automotive applications such as seat belt buckles and door lock housings should focus on salt spray testing, internal shrinkage and critical mating dimension stability.
- Automotive safety-related parts may reference GB/T 10125-2021 salt spray testing, with typical requirements reaching >=96 hours.
- Electronics applications such as 5G base station shielding covers should review electromagnetic shielding and high-thermal-conductivity zinc alloy requirements.
- High-thermal-conductivity zinc alloy can be evaluated for applications requiring thermal conductivity >=120 W/m·K.
Management Priorities After the Standard Upgrade
- Older, vague quality-assurance clauses are replaced by more specific inspection rules and nonconforming product handling processes.
- Chemical composition limits are broadly compatible with ASTM B86-19, supporting export and international project communication.
- Restrictions on harmful elements such as lead and cadmium are clearer, supporting RoHS and ELV compliance review.
- Manufacturers should update inspection equipment and optimize process windows according to typical parameters in the GB/T 13821-2023 appendix.
For new energy vehicles, 5G communication and automotive safety parts, vacuum die casting, industrial CT / X-ray inspection and a complete material-process-inspection loop are no longer optional extras. They are becoming quality-entry conditions.
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工程指南 / 锌合金压铸
锌合金压铸技术规范：GB/T 13821-2023 与 GB/T 13818-2024
围绕锌合金压铸件的材料成分、熔炼温度、压铸工艺窗口、内部质量检测和行业应用要求，整理成适合采购、工程和质量团队检索的技术规范文档。
材料规范
锌合金压铸件的材料控制应围绕合金牌号、主控元素、杂质限量和熔炼稳定性展开。材料成分不仅影响强度和流动性，也直接影响铸件时效变形、腐蚀风险和长期可靠性。
- 常见牌号包括 ZA3、ZA8、ZA12 等；ZA8 的铝含量通常为 7.5%~8.5%，ZA12 的铝含量通常为 10.5%~12.0%。
- 铝 Al 影响强度和流动性；ZA3 可参考 3.8%~4.3%，ZA8 可参考 7.5%~8.5%。
- 铜 Cu 可参考 0.7%~1.1%，过高会增加脆性风险。
- 镁 Mg 可参考 0.035%~0.06%，有助于抑制晶间腐蚀，但超量可能引发热裂。
- 铅 Pb 应控制在 ≤0.003%，镉 Cd 应控制在 ≤0.001%，避免自然时效变形、破裂和环保合规风险。
熔炼工艺控制
熔炼窗口的稳定性是锌合金压铸质量的前置条件。温度过高会加速铁坩埚腐蚀，使铁元素进入合金并形成硬质颗粒，进而加剧模具磨损和表面缺陷。
- 初始熔化温度建议控制在 435℃~440℃。
- 完全熔化后可降至 420℃~430℃保温，减少铝、镁元素烧损和锌渣增加。
- 温度超过 450℃ 时应警惕铁元素污染、硬质颗粒和模具磨损风险。
- 建议采用惰性气体保护或真空熔炼，降低氢气吸入和内部气孔缺陷。
压铸工艺窗口
压铸过程需要从压射、充模、模温、脱模剂、真空辅助和送料稳定性几个维度建立参数窗口。薄壁件、结构功能件和高外观件应优先控制充模速度、残余气体和温度波动。
| 项目 | 建议窗口 / 要点 |
|---|---|
| 压射比压 | 45~50 kg/cm²，用于保证金属液充分填充复杂型腔。 |
| 充模时间 | ≤0.01 秒；薄壁件需更短，以降低冷隔风险。 |
| 模具预热温度 | 150℃~200℃；冷模压射容易导致表面冷纹或填充不良。 |
| 脱模剂配比 | 水性脱模剂与水比例可参考 1:200，以替代传统油性产品并降低 VOCs 排放。 |
| 真空压铸 | 高精度件建议采用真空辅助压铸，将型腔残余气压控制在 ≤30 kPa。 |
| 温度稳定性 | 建议采用中央熔炼炉 + 自动送料系统，控制浇注温度偏差 ≤±5℃。 |
质量检测规范
GB/T 13821-2023 将压铸件检验要求做了差异化管理。对于结构件、功能件和安全相关零件，内部质量检测不应只依赖外观和尺寸抽检，应加入 X 射线、工业 CT 或其他无损检测方法。
| 类别 | 适用场景 | 必检项目 |
|---|---|---|
| 1 类 | 结构 / 功能性零件，例如汽车安全带扣件。 | 化学成分、力学性能、尺寸公差、表面质量、内部质量。 |
| 2 类 | 普通零部件，例如装饰件。 | 化学成分、力学性能、尺寸公差、表面质量。 |
- 内部质量检测可采用工业 CT 和 X 射线数字成像技术，明确气孔、缩松等缺陷判定标准。
- 针孔度评级可按 1 cm² 区域内缺陷数量进行判定。
- ZA8 抗拉强度可参考 ≥280 MPa，断后伸长率可参考 ≥10%。
- 布氏硬度应符合标准附录中的典型范围，例如 ZA8 可参考 80~100 HBW。
- 尺寸公差依据 GB/T 6414-2017 执行，关键配合面可按 CT4 精密级管理。
重点应用要求
- 汽车领域：安全带扣件、门锁壳体等零件应关注盐雾试验、内部缩松和关键配合尺寸稳定性。
- 汽车安全相关零件可参考 GB/T 10125-2021 做盐雾试验，典型要求可达到 ≥96 小时。
- 电子领域：5G 基站屏蔽罩等应用需关注电磁屏蔽效能和高导热锌合金材料。
- 高导热锌合金可用于导热系数 ≥120 W/m·K 的应用场景评估。
标准升级带来的管理重点
- 旧版较模糊的质量保证条款被更具体的检验规则和不合格品处置流程取代。
- 化学成分限值与 ASTM B86-19 基本兼容，有助于出口和国际项目沟通。
- 铅、镉等有害元素限制更明确，需要兼顾 RoHS 和 ELV 等环保合规要求。
- 企业应更新检测设备，并依据 GB/T 13821-2023 附录中的典型参数优化工艺窗口。
对于新能源汽车、5G 通信和汽车安全件等高端项目，真空压铸工艺、工业 CT / X 射线检测和完整的材料-工艺-检测闭环，已经从“加分项”变成质量准入条件。
需要锌合金压铸项目评估或质量资料支持？
发送图纸、材料牌号、关键尺寸、年用量和检测要求，XSD 可协助评估 DFM 风险、压铸工艺窗口和质量文件准备。