Die Casting in China: Process, Aluminium Alloys and How to Specify Parts

Last updated: 20 September 2026.

Every standard number, alloy designation and tolerance scope below is dated and linked to the official or standards-body source in the list at the end of this page. Standards are revised on their own cycles — check the current edition before you release a drawing.

1. Where die casting sits in a custom-parts programme

Die casting is a shaping process, not a finishing process. Metal is melted and forced into a hardened steel die, so the geometry of the tool — not the skill of a machinist — decides the shape of every part that comes out. That single fact drives most of the commercial and engineering decisions around it.

The consequence for a buyer is that die casting has a genuine threshold: the tool is the main cost, and it is paid once, while the parts that come out of it are cheap and repeatable. Above that threshold, die casting is one of the most economical ways to make a complex metal part at volume. Below it, machining from bar or plate is usually the better answer, because there is no tool to amortise.

Two practical implications follow:

• Design for the die, not for the drawing. Everything that would be easy on a milling machine — a sharp internal corner, a sudden change in wall section, an undercut — is either difficult or impossible in a two-part die. The design decisions in section 5 are the ones that decide whether your part runs well.
• The tolerance conversation happens before the tool is cut. The die caster cannot tighten tolerances later without changing the tool. Fix the tolerance system on the drawing first, then quote.

NADCA, the North American Die Casting Association, publishes the industry's specification and design manuals for conventional high-pressure die castings; its Product Specification Standards manual covers tooling and process information, alloy properties, standard and precision tolerances, geometric dimensioning and tolerancing, design guidelines and quality assurance provisions. Its chapter structure — process and material selection, tooling, alloy data, coordinate dimensioning, miniature die casting, geometric dimensioning, additional design guidelines, quality assurance, commercial practices and casting examples — is a fair map of what a die casting programme actually involves.

China is a large die casting base for exactly the reason above: tool making and high-volume casting sit close together, and the process suits the volumes at which tooling amortises. That does not change the engineering. It changes the questions you should ask before you place the order.

This guide sits in the Manufacturing section, alongside sheet metal fabrication, CNC machining and material selection — the four routes most custom-parts enquiries end up choosing between.

2. Hot chamber and cold chamber: the alloy picks the machine

The single most useful process distinction in die casting is not "which machine is better" but "which machine can run your alloy".

ASTM B85/B85M, the standard specification for aluminium-alloy die castings, records this directly in its table notes: alloys 360.0, 380.0, 413.0, C443.0 and 518.0 are suitable for the production of die casting by either the hot-chamber or the cold-chamber process, while die castings of alloys A360.0, A380.0, 383.0, 384.0 and A413.0 may be made only in cold-chamber machines.

That is the practical rule. If your part is specified in one of the cold-chamber-only grades — which includes the widely used A380.0 family — then the machine type is not negotiable, and any supplier conversation about "switching to hot chamber to save cost" is a conversation about changing the alloy.

ASTM B85/B85M also records that, with respect to mechanical properties, alloys A380.0, 383.0 and 384.0 are substantially interchangeable. That note matters commercially: it means a substitution between those three grades is defensible on mechanical grounds, but it is still a change to the material you specified, and it should be documented rather than assumed.

3. Alloys: what the standards actually fix — and what they leave to you

Two families dominate the standardisation.

Aluminium. ASTM B85/B85M covers aluminium-alloy die castings designated in its Table 1, and it specifies what may go into the furnace: unless otherwise specified, only aluminium alloy conforming to the requirements of Specification B179, or producer's foundry scrap, shall be used in the remelting furnace from which molten metal is taken for pouring directly into castings, with small additions of modifiers and grain-refining elements or alloys permitted. Alloy and temper designations follow ANSI H35.1/H35.1(M), and the equivalent Unified Numbering System designations follow Practice E527. Where the standard's Table 1 and the Aluminium Association's registered composition limits — commonly called the Pink Sheets — disagree, the standard states that the registered limits control.

On the international side, ISO 3522 is the aluminium casting alloy standard: its title is Aluminium and aluminium alloys — Castings — Chemical composition and mechanical properties, which is the scope you are relying on when you write "chemical composition and mechanical properties to ISO 3522" on a drawing.

Magnesium. ASTM B94 covers magnesium-alloy die castings, with the current alloy compositions specified under the designations in its Table 1. Its notes are unusually explicit about the elements that matter in magnesium: in alloys AS41B, AM50A, AJ52A, AM60B, AJ62A and AZ91D, if either the minimum manganese limit or the maximum iron limit is not met, then the iron-to-manganese ratio shall not exceed 0.010, 0.015, 0.015, 0.021, 0.021 and 0.032 respectively. If other elements are suspected or indicated in routine analysis, the standard requires further analysis to establish that those elements are not in excess of 0.3 %. ASTM alloy designations follow Practice B951 and UNS designations follow Practice E527.

What the standards do not do. They fix composition and, through referenced test methods, the acceptance framework. They do not tell you which alloy suits your part. That is a service-environment and load question — the same logic that governs material selection generally, and it is worth settling before the die is designed, because the alloy constrains both the machine and the tool.

A note on zinc and other families. Zinc die casting alloys are widely used for small, thin-walled and decorative parts, and NADCA's manual includes zinc cross-reference specifications and composition data alongside aluminium and magnesium. If your part is zinc, the aluminium clauses above do not apply and the alloy data you need sits in the zinc section of the same NADCA manual.

4. Tolerances: what ISO 8062-3 gives you, and what it deliberately leaves out

The tolerance system for castings is ISO 8062-3. The current edition is ISO 8062-3:2023 (Edition 2, published 2023-02), and it replaced ISO 8062-3:2007, which ISO now lists as withdrawn.

What the 2023 edition specifies, in its own words: general dimensional and geometrical tolerances as well as machining allowance grades for castings that use plus-or-minus tolerances for indicated dimensions, as delivered to the purchaser according to ISO/TS 8062-2. It applies to the tolerancing of dimensions and geometry of castings in all cast metals and their alloys produced by various casting manufacturing processes, and it explicitly does not apply to 3D CAD models used without indicated dimensions.

The dimensional tolerances it covers are tolerances for linear dimensions. The geometrical tolerances it covers are tolerances for:

• straightness
• flatness
• roundness
• parallelism
• perpendicularity
• symmetry
• coaxiality

And the exclusions are as important as the inclusions. The standard does not cover other position tolerances, angular dimensional tolerances or cylindricity tolerances.

That gap is where most die casting disputes start. If your part has a hole pattern located by position tolerance, an angular feature held by an angular dimension, or a cylindrical bore held by cylindricity, the general casting tolerance standard is not the document that governs it — your drawing has to, either by an individual tolerance indication or by calling up the geometric dimensioning framework you actually want. NADCA's manual treats geometric dimensioning as its own section, which reflects the same reality from the supplier side.

Practical consequence: write the general tolerance callout and the individual indications. A drawing that says only "general tolerances to ISO 8062-3" is silent on exactly the features that are hardest to hold.

5. The design decisions that decide whether the part runs

These are qualitative on purpose. The specific values — minimum wall, draft per surface, fillet sizes, machining stock — sit in the standard and in NADCA's design sections, and they depend on the alloy, the wall section and the surface in question. Take them from the current edition you are working to rather than from a web page, including this one.

Four decisions cause most of the trouble:

1. Wall section uniformity. A casting cools at different rates in thick and thin sections, and that difference is what produces internal porosity and dimensional variation. Uniform walls, with gradual transitions where thickness must change, are the single biggest lever you have.
2. Draft. Every surface that must release from the die needs taper, otherwise the part fights the tool on ejection and the surface is torn. Draft is not a constant: it varies with the type of wall or surface and with the depth of the feature, so it has to be set feature by feature rather than as one blanket angle.
3. Fillets and radii. Sharp internal corners concentrate stress in the part and heat in the die. Rounding them is not cosmetic; it is what lets metal flow and the die survive. NADCA's design guidance treats radii and fillets as a design requirement rather than a finishing preference.
4. Machining stock, and how much of it you remove. If the part will be machined after casting, the allowance has to be both specified and limited. Removing a deep cut to reach final dimensions is how you open up porosity that would otherwise have stayed inside the casting — and on a pressure-tight part, that is the defect that shows up at leak test rather than at goods-in.

6. Porosity, pressure-tightness and what to specify

Porosity is not automatically a defect; it is a characteristic that has to be bounded against a use. A bracket with cosmetic porosity is fine. A housing that must hold gas is not.

For aluminium castings, ISO 10049 is the relevant reference: its title is Aluminium alloy castings — Visual method for assessing the porosity, and it addresses assessment of the machined surface. That is a useful limit to understand — a visual method applied to a machined face tells you about porosity exposed at that face, not about porosity anywhere in the section.

Two specification habits follow:

• State the acceptance criterion and the inspection method together. "No visible porosity" is not a criterion; it is an instruction that the supplier has to interpret, and interpretations differ. Name the method, the surface, and what counts as a reject.
• Say whether the part is pressure-tight. ASTM B85/B85M is explicit that the specification is for aluminium-alloy die castings used in general purpose applications, and that it may not address the mechanical properties, integrity testing and verification required for highly loaded or safety critical applications. If your part is in that second category, the general-purpose specification is the wrong document to be relying on by itself, and NADCA publishes a separate standard for high-integrity and structural die casting for exactly this case.

What happens to the surface after casting — coating, anodising, plating, passivation — is a separate specification exercise with its own standards; surface finishing for custom parts covers that side.

7. Tooling and die steel: the part of the programme you cannot fix later

The die is the capital item, and its life is set by the steel and its heat treatment as much as by the casting cycle.

NADCA publishes #207-2018, described as acceptance criteria for the procurement and heat treatment of high-quality die steel for extended die life. The association is explicit that these criteria are not intended for all die casting applications and apply where high-volume production and/or critical performance is required. That scoping is worth reading carefully: die steel acceptance criteria are a tool for programmes where die life is an economic variable, not a default requirement for every part.

NADCA also publishes die material specifications originating with individual vehicle manufacturers, which exist because tool life and heat treatment control are treated as procurement-critical in those supply chains. Where a programme has no such specification, the practical question is still the same: what die steel, heat-treated to what, and what evidence comes with it.

The 2024 edition of NADCA's Product Specification Standards added information on die technology and sizing, new information about loose inserts, considerations for datum locations, and P-20 as a possible option for miniature die casting die material — all of which are areas to cover in the tooling conversation rather than after the first shots.

8. What to put in the drawing and the enquiry

A die casting enquiry that produces comparable quotes names these items. Nothing here is a price or a commercial term; it is the technical package.

• Alloy, by standard designation, with the specification it is to meet — for aluminium, ASTM B85/B85M and, where chemistry and properties are being verified, ISO 3522; for magnesium, ASTM B94.
• The tolerance system, with the general callout named and individual indications on position, angular and cylindricity features that the general standard does not cover.
• Machining stock, and which faces carry it.
• Porosity and integrity requirements, with the method and the acceptance criterion, plus an explicit statement if the part must be pressure-tight.
• Surface finish expected as-cast and after any coating or treatment.
• Quantity and repeat demand, because that is what decides whether the tool is justified at all.
• The inspection document you expect with the parts, stated rather than assumed.

If the finished part also has to clear a market-access regime, ASTM vs CE vs UL sets out which framework applies where. The casting standard fixes the material and tolerance basis; it does not decide the market entry route.

9. When to ask the supplier, and what to ask

Bring the supplier in at the design stage, not at the quotation stage. Three questions get the most value:

Can this alloy run in this machine, and does that constrain my design? The hot-chamber and cold-chamber split in ASTM B85/B85M is the concrete version of this question, and it can rule out a machine before the tool is drawn.

Which edition of the tolerance standard are you working to, and how do you handle the features it excludes? ISO 8062-3 moved from the 2007 edition to the 2023 edition, and the standard's own scope statement lists the geometric tolerances it does not cover. A supplier who can answer this precisely is a supplier who reads drawings.

What specification is my part being made and inspected to? If the answer is the general-purpose aluminium die casting specification and your part is load-bearing or pressure-tight, that is a design conversation, not a paperwork one — and it is better had before the tool is cut.

When the specification is settled, send the drawing, the alloy and the tolerance callouts rather than a description. A die casting quotation is only comparable between suppliers when the technical package is the same.

All sources retrieved and HTTP-tested on 2026-09-20. Every standard number, alloy designation and scope statement on this page has a row below.

Frequently asked questions

Sources

All sources retrieved 20 September 2026. This page is an independent reading of the sources listed; the official pages themselves are the specification.

Fact used on this page	Source
S1 — ISO 8062-3:2023 — Geometrical product specifications (GPS) — Dimensional and geometrical tolerances for moulded parts — Part 3: General dimensional and geometrical tolerances and machining allowances for castings using ± tolerances for indicated dimensions. Abstract: "This document specifies general dimensional and geometrical tolerances as well as machining allowance grades for castings using ± tolerances for indicated dimensions as delivered to the purchaser according to ISO/TS 8062-2. It is applicable for tolerancing of dimensions and geometry of castings in all cast metals and their alloys produced by various casting manufacturing processes. This document does not apply to 3D CAD models used without indicated dimensions." Coverage: dimensional tolerances are tolerances for linear dimensions; geometrical tolerances covered are straightness, flatness, roundness, parallelism, perpendicularity, symmetry and coaxiality; "This document does not cover other position tolerances, angular dimensional tolerances or cylindricity tolerances." Page data: Published, Edition 2, publication date 2023-02, stage 60.60 International Standard published (page also lists the RSS detail feed for the standard)	ISO https://www.iso.org/standard/77952.html
S2 — ISO 8062-3:2007 — same title, first edition. Abstract: "ISO 8062-3:2007 specifies general dimensional and geometrical tolerances, as well as machining allowance grades, for castings as delivered to the purchaser in accordance with ISO 8062-2. It is applicable for the tolerancing of dimensions and geometry, and required machining allowance of castings in all cast metals and their alloys produced by various casting manufacturing processes." Coverage: dimensional tolerances covered are tolerances for linear dimensions; geometrical tolerances covered are tolerances for straightness, flatness, roundness, parallelism, perpendicularity, symmetry and coaxiality. Status: Withdrawn, Edition 1, publication date 2007-06, stage 95.99 withdrawal of International Standard; "New version available: ISO 8062-3:2023"; number of pages 30; Technical Committee ISO/TC 213; ICS 17.040.10	ISO https://www.iso.org/standard/40495.html
S3 — ASTM B85/B85M — Standard Specification for Aluminum-Alloy Die Castings. Abstract: "This specification covers aluminum-alloy die castings of all compositions. Unless otherwise specified, only aluminum alloy conforming to the requirements of Specification B 179 or producer's foundry scrap shall be used in the remelting furnace from which molten metal is taken for pouring directly into castings. Additions of small amounts of modifiers and grain refining elements or alloys are permitted." Scope 1.1 covers aluminium-alloy die castings designated in Table 1; 1.2: "This specification is for aluminum-alloy die castings used in general purpose applications. It may not address the mechanical properties, integrity testing, and verification required for highly loaded or safety critical applications."; 1.3: alloy and temper designations per ANSI H35.1/H35.1(M); note (D): in case of discrepancy between Table 1 and the Aluminum Association "Pink Sheets", the registered composition limits control; note (G): "Alloys 360.0, 380.0, 413.0, C443.0 and 518.0 are suitable for the production of die casting by either the hot-chamber or the cold-chamber process. Die castings of alloys A360.0, A380.0, 383.0, 384.0, and A413.0 may be made only in cold-chamber machines."; note (H): "With respect to mechanical properties, alloys A380.0, 383.0 and 384.0 are substantially interchangeable."; note (J): cross reference to the Aluminium Association "Pink Sheets"; equivalent UNS designations per Practice E527; rounding per Practice E29 (cited page is b0085_b0085m-18)	ASTM International https://store.astm.org/b0085_b0085m-18.html
S4 — ASTM B94 — Standard Specification for Magnesium-Alloy Die Castings. Abstract: "This specification covers magnesium-alloy die castings. The magnesium alloys used for the manufacture of die castings shall conform to the chemical composition requirements of this specification. The producer or supplier is responsible for the performance of all inspection and test requirements when specified in the contract or purchase order… Die castings shall have uniform quality that is free from injurious discontinuities that will adversely affect their serviceability. All castings shall be properly marked for identification with the part number, name or brand of the producer, as agreed upon the contract." Scope 1.1: "This specification covers magnesium-alloy die castings. Current alloy compositions are specified under the designations shown in Table 1."; note (A): where other elements are suspected or indicated, further analysis shall be made to determine that these other elements are not in excess of 0.3 %; note (D): ASTM alloy designations established in accordance with Practice B951, UNS designations in accordance with Practice E527; note (E): in alloys AS41B, AM50A, AJ52A, AM60B, AJ62A and AZ91D, if either the minimum manganese limit or the maximum iron limit is not met, then the iron/manganese ratio shall not exceed 0.010, 0.015, 0.015, 0.021, 0.021 and 0.032, respectively; note (B): rounding per Practice E29 Section 3 (cited page is b0094-18)	ASTM International https://store.astm.org/b0094-18.html
S5 — ISO 3522:2006 — Aluminium and aluminium alloys — Castings — Chemical composition and mechanical properties (standard number and full title verified against the ISO official detail feed for the standard, which returns title "ISO 3522:2006 - Aluminium and aluminium alloys — Castings — Chemical composition and mechanical properties"; publication date recorded as 2007-10-23)	ISO https://www.iso.org/standard/33497.html
S6 — ISO 10049:1992 — Aluminium alloy castings — Visual method for assessing the porosity (standard number and full title verified against the ISO official detail feed for the standard, which returns title "ISO 10049:1992 - Aluminium alloy castings — Visual method for assessing the porosity")	ISO https://www.iso.org/standard/18014.html
S7 — NADCA published die casting standards (official association page). "NADCA is the trusted source for providing technical standards to the die casting industry and publishes Die Casting Pressure, SSM, Die Steel and Safety Standards." 2024 Product Specification Standards for Die Castings: "This manual covers specification, design and production guidance for both users and manufacturers of conventional high pressure die castings. The manual presents tooling and processes information, alloy properties, standard and precision tolerances, GD&T, design guidelines, quality assurance provisions and more. Revisions for this edition include: rewrite of the first chapter to focus on an overview of the die casting process; additional information about die technology and sizing; new information about loose inserts; considerations for datum locations; moved around the order of alloy families…; updated alloy reference tables; added P-20 as a possible option for miniature die casting die material…". Standards for High Integrity and Structural Die Casting Process (2024): same coverage statement for conventional high pressure die castings. 2019 Machine Safety Standard: "The NADCA B152.1-2019 Safety Requirements for the Design, Manufacture, Maintenance and Operation of Die Casting Machines… covers high pressure die casting machines and addresses ancillary equipment associated with die casting machine cells." Recommended Procedures for Die Steel: "This document covers the NADCA #207-2018 acceptance criteria for procurement and heat treatment of high quality die steel for extended die life. These criteria are not intended for all die casting applications. They apply where high volume production and/or critical performance is required."	North American Die Casting Association (NADCA) https://www.diecasting.org/Web/R_D/Standards/Web/R_D/Standards.aspx
S8 — NADCA Product Specifications Standards for Die Castings — contents and scope (official NADCA design site). "The NADCA Product Specifications Standards manual is available online for download. This manual covers specification, design and production guidance for both users and manufacturers of conventional high pressure die castings. The manual presents tooling and processes information, alloy properties, standard and precision tolerances, GD&T, design guidelines, quality assurance provisions and more." Revisions for the cited edition include "EN specifications and chemical compositions for aluminum alloys; expanded zinc cross reference specifications and chemical compositions; clarified parting line calculation terminology; additional miniature die casting die materials; information on small metal savers and bumping ejector pins". Table of contents: Section 1 Process & Material Selection for Recyclability; Section 2 Tooling for Die Casting; Section 3 Alloy Data; Section 4A Engineering & Design: Coordinate Dimensioning; Section 4B Engineering & Design: Miniature Die Casting; Section 5 Engineering & Design: Geometric Dimensioning; Section 6 Engineering & Design: Additional Guidelines; Section 7 Quality Assurance; Section 8 Commercial Practices; Section 9 Casting Examples; Section 10 Index & Glossary of Terms	NADCA (via diecastingdesign.org, NADCA's design publication site) https://www.diecastingdesign.org/product-specifications-standards-for-die-castings