Last updated: 25 September 2026.
Quick answer. Investment casting, also called lost-wax casting, is metal casting produced in a ceramic shell around an expendable pattern. ISO 16468 covers the technical requirements for steel, nickel and cobalt alloy investment castings; ASTM A957/A957M-21 covers common requirements; ISO 8062-3:2023 covers casting tolerances and machining allowances.
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Investment casting in China: how the lost-wax process works, which ISO and ASTM standards govern it, and what to specify on a drawing or RFQ.
Every standard reference on this page was retrieved on 25 September 2026 from the standards body's own page, and the retrieval date and status are stated next to each one.
The term has a formal definition in the ISO system rather than only a workshop meaning. In ISO 16468, the standard for investment castings of steel and related alloys, the entry reads: investment casting / lost wax casting — metal casting that is produced in a ceramic shell using an expendable pattern, with a note that the expendable pattern may consist of wax, plastics or other material and is removed before the mould is filled with liquid metal.
Two consequences follow from that definition, and both matter when you buy:
The Investment Casting Institute, the North American technical association for the sector (founded 1953, per its own site), publishes the process as a numbered walk-through. Its pages run in this order: creating a wax pattern, tree assembly, shell building, dewax, metal pouring, cut-off, shell knock-off, finished castings. Two of those steps are described on the Institute's pages in terms you can plan against:
| Step | What the Institute's own description says |
|---|---|
| Creating a wax pattern | Wax patterns are typically made by injecting wax into a metal tool or die. With the evolution of additive manufacturing, patterns can also be printed. Outside industrial production, one-off pieces are carved from wax blocks, and for multiple castings a silicone tool is usually made from the artist's sculpture and wax is injected or poured into the cavity. |
| Shell building | A ceramic shell is built around the wax tree and eventually becomes the mould that metal is poured into. The tree is dipped into a ceramic bath (slurry); fine sand or "stucco" is applied to the wet surface; the mould is allowed to dry; and the process is repeated until a layered ceramic mould capable of withstanding the casting process has been built. |
| Dewax, pouring, cut-off, knock-off | The Institute lists these as sequential stages of the same process. Its public pages carry a one-line heading for each; the operating parameters are foundry-specific and are not published. |
For a buyer, the shell-building step is the one that explains most quality arguments later: it is a repeated dip-and-dry cycle, so shell thickness, drying between coats and slurry control at the foundry decide whether a complex part fills cleanly. That is a process-control question, not a drawing question (see the process-control section below).
China has extensive foundry capacity, but the standards your drawing references will normally be international or American rather than Chinese, because that is what buyers and their end customers name. Three families recur in investment-casting enquiries.
| Standard | Status on the publisher's own page (retrieved 25 September 2026) | What it governs |
|---|---|---|
| ISO 16468:2025, Investment castings (steel, nickel alloys and cobalt alloys) | Listed in the ISO catalogue; catalogue entry dated 26 May 2025 | Technical requirements for investment castings of steel, nickel alloys and cobalt alloys |
| ISO 16468:2005 (previous edition, same title) | The ISO Online Browsing Platform page states: "This standard has been withdrawn" | The edition most older drawings still cite; prepared by ISO/TC 17, Steel, Subcommittee SC 11, Steel castings |
| ASTM A957/A957M-21, Standard Specification for Investment Castings, Steel and Alloy, Common Requirements, for General Industrial Use | Page states "Standard Active"; last updated 24 May 2021; developed by Subcommittee A01.18; Book of Standards Volume 01.02; ICS code 77.100 | Common requirements that are mandatory for castings produced by the investment casting process, applied on top of the individual material specification |
| 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 | Second edition; its foreword states it cancels and replaces ISO 8062-3:2007 and incorporates Technical Corrigendum 1:2009 | General dimensional and geometrical tolerances, plus machining allowance grades, for castings as delivered to the purchaser |
The edition question is not academic. A drawing that still cites ISO 16468:2005 is citing a withdrawn edition, while the ISO catalogue now lists a 2025 edition under the same number. The same applies to tolerances: ISO 8062-3 moved to a second edition in 2023, and the change list in its own foreword explains what moved (draft-angle definitions added, tolerance-grade tables renumbered, the wall-thickness grade concept clarified, and the rejection clause rewritten). Ask a supplier which edition it is quoting against, and put the answer in the purchase order.
Because the standard's requirements "form an integral part of the material specification" and take precedence in case of conflict, it is worth knowing what it drags in. Its public scope states that it specifies technical requirements for castings of steel, nickel alloys and cobalt alloys produced by the investment-casting process, and that the metallurgical material requirements for individual grades sit in separate standards. Its normative reference list is effectively a checklist of the documents that will govern the order:
| Referenced document (as listed by ISO 16468) | Subject |
|---|---|
| ISO 4990 | Steel castings — general technical delivery requirements |
| ISO 4986 | Steel castings — magnetic particle inspection |
| ISO 4987 | Steel castings — penetrant inspection |
| ISO 4993 | Steel castings — radiographic inspection |
| ISO 10474 | Steel and steel products — inspection documents |
| ISO 11970 | Specification and approval of welding procedures for production welding of steel castings |
| ISO 13520 | Determination of ferrite content in austenitic stainless steel castings |
| ISO 6506-1, ISO 6507-1, ISO 6508-1 | Brinell, Vickers and Rockwell hardness test methods |
Its clause structure also shows where arguments start. Beyond scope and definitions, the standard is organised around materials and manufacture (melting, remelting), inspection and testing (general requirements, sampling), retests, cleaning and dressing, quality, production welds, and a long list of supplementary requirements that includes agreed manufacturing procedure, magnetic particle, radiographic, liquid penetrant and ultrasonic inspection, inspection of weld preparation, prior agreement on major finishing welds, low-temperature impact testing, hardness testing, a specified ferrite range in austenitic and austenitic-ferritic stainless steels, unspecified elements, test material removed from castings, tensile test coupons and specimen locations, weld maps, increased testing frequency for chemical analysis and tensile testing, inspection documents, marking and decarburization.
Read that as a menu rather than a default. Which of those supplementary items you invoke is a commercial decision that has to be written into the order.
The ASTM specification is the "common requirements" layer: it is mandatory for castings made by the investment process when the order names it, and it sits on top of a material specification. Its scope states that it covers a group of requirements mandatory for castings produced by the investment casting process to meet the metallurgical requirements of listed steel casting specifications — the list runs from general-application carbon steel castings (A27/A27M) through austenitic manganese (A128/A128M), high-strength structural (A148/A148M), heat-resistant iron-chromium and iron-chromium-nickel (A297/A297M), chromium-nickel-iron 25-12 class (A447/A447M), nickel and nickel alloy (A494/A494M), chromium-nickel (A560/A560M), investment carbon and low-alloy steel and cobalt alloy (A732/A732M), corrosion-resistant iron-chromium and iron-chromium-nickel (A743/A743M and A744/A744M), precipitation-hardening stainless (A747/A747M), duplex corrosion-resistant (A890/A890M), carbon and alloy steels with wrought-like chemical requirements (A915/A915M and A958/A958M) and nickel-aluminium ordered alloy (A1002).
Three scope points deserve to be quoted rather than paraphrased when you negotiate:
Tolerances are usually the first thing a Chinese foundry quotes back at you, because they drive whether a part can be cast to print or needs machining. ISO 8062-3:2023 is the document to name. Its scope states it specifies general dimensional and geometrical tolerances as well as machining allowance grades for castings using plus/minus tolerances for indicated dimensions as delivered to the purchaser, and that it applies to all cast metals and their alloys from various casting processes. It explicitly does not apply to 3D CAD models used without indicated dimensions, and it does not cover angular dimensional tolerances, cylindricity or position tolerances other than those listed.
| Clause area in ISO 8062-3:2023 | Why it appears on a purchase order |
|---|---|
| Tolerance grades: dimensional casting tolerance grades (DCTG) and geometrical casting tolerance grades (GCTG) | Lets the drawing state a general tolerance instead of a tolerance on every dimension |
| Surface mismatch (SMI) | Sets the acceptance basis for step or mismatch at joints |
| Wall thickness | A separate grade concept, following the change introduced in the 2023 edition |
| Required machining allowance (RMA) and RMA grades | Separates what is cast from what is machined |
| Indication on drawings: general DCTs, machining allowances, geometrical casting tolerances | Tells the foundry where to read the tolerance instruction |
| Rejection | Defines the basis on which a casting lot can be rejected |
The numeric tolerance tables inside the standard are the reason this page quotes no tolerance values at all: they are the standard's own content, and a casting tolerance copied from a secondary summary is exactly the kind of number that starts a dispute. Specify the grade and the standard, and let the tables in the current edition govern.
The following checklist is drawn from the structure of the four documents above rather than from foundry marketing material. Each line maps to a clause the foundry will recognise.
| Item on the RFQ | Where it comes from |
|---|---|
| The material specification and grade for the casting | ISO 16468 scope: the metallurgical grade requirements sit in the material specification, which this standard supplements |
| Which standard and which edition the foundry will work to | ISO 16468:2005 is withdrawn and a 2025 edition exists; naming the edition avoids two parties quoting different texts |
| Whether any supplementary requirements are invoked individually in the order | ASTM A957/A957M-21 scope 1.2 |
| The tolerance indication: general DCTG and GCTG, wall-thickness grade, machining allowance grade | ISO 8062-3:2023 clauses 7 to 11 |
| The inspection documents required | ISO 10474, referenced by ISO 16468 |
| Non-destructive testing methods and coverage | Magnetic particle ISO 4986, penetrant ISO 4987, radiographic ISO 4993, referenced by ISO 16468 |
| Welding on castings, and the approval of welding procedures | ISO 11970, referenced by ISO 16468 |
| Ferrite content requirement for austenitic grades | ISO 13520, referenced by ISO 16468 |
| Hardness test method | ISO 6506-1, ISO 6507-1, ISO 6508-1, referenced by ISO 16468 |
| Marking and traceability of heat and lot | ISO 16468 clauses on quality, marking and inspection documents; ASTM A957/A957M-21 common requirements |
Standards define the acceptance basis; process control decides whether you keep hitting it. The Investment Casting Institute runs a self-and-third-party programme for exactly this, and the structure is worth knowing when a supplier claims "certified":
That gives you a precise question to ask instead of a general one: which level, on what date, verified by whom, and when does it expire. For the wider supplier-side picture, our guides on quality control for Chinese suppliers and how tolerances are specified and checked cover the commercial workflow around these standards, and if you are comparing processes rather than sending an order, die casting, CNC machining and materials and finishes are the adjacent pages.
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Investment casting uses an expendable pattern inside a ceramic shell, as defined in ISO 16468, so the tooling economics differ from a permanent die. Die casting relies on a steel die that is reused. Investment casting is usually chosen for complex geometry and for steel, nickel and cobalt alloys; check which edition of the relevant standard a supplier is quoting before comparing prices.
The ISO Online Browsing Platform page for ISO 16468:2005 states that the standard has been withdrawn, and the ISO catalogue lists a 2025 edition under the same number. If a drawing cites the 2005 edition, confirm with the foundry which edition will govern the order and record the answer on the purchase order.
ISO 8062-3:2023 specifies general dimensional and geometrical tolerances and machining allowance grades for castings using plus/minus tolerances for indicated dimensions, applicable to all cast metals and alloys. It sets out the dimensional and geometrical casting tolerance grades, wall thickness, surface mismatch and required machining allowance grades, and how they are indicated on a drawing.
No. ASTM A957/A957M-21 states that its supplementary requirements apply only when specified individually by the purchaser in the order. Its main requirements, however, are mandatory for castings produced by the investment casting process when the specification is named, and they form an integral part of the material specification.
Ask for the level, date, verifier and expiry of its process control certification. The Investment Casting Institute's programme has three levels — Bronze by self-survey meeting 40% of the criteria, Silver by independent survey meeting 60% and Gold by independent survey meeting 80% — with certification valid for two years.
All sources retrieved 25 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 — Existence, number and catalogue date of ISO 16468:2025, investment castings of steel, nickel alloys and cobalt alloys | ISO official catalogue feed for the standard, retrieved 25 September 2026 (catalogue date 26 May 2025) https://www.iso.org/contents/data/standard/08/49/84905.detail.rss |
| S2 — Withdrawn status of ISO 16468:2005; verbatim scope; definition of investment casting / lost wax casting and of primary heat and sub-heat; shell/ceramic mould entry; normative reference list (ISO 4986, 4987, 4990, 4993, 10474, 11970, 13520, 6506-1, 6507-1, 6508-1); clause structure including supplementary requirements; technical committee ISO/TC 17/SC 11 | ISO Online Browsing Platform, ISO 16468:2005 page, retrieved 25 September 2026 https://www.iso.org/obp/ui#iso:std:iso:16468:ed-1:en |
| S3 — Full title, second-edition status and replacement of ISO 8062-3:2007 plus Corrigendum 1:2009; verbatim scope; applicability to all cast metals and their alloys; exclusions for CAD models without indicated dimensions, angular, cylindricity and unlisted position tolerances; clause list (DCTG, GCTG, surface mismatch, wall thickness, RMA and RMAG, indication on drawings, rejection); preparation by ISO/TC 213 with CEN/TC 190 under the Vienna Agreement | ISO Online Browsing Platform, ISO 8062-3:2023 page, retrieved 25 September 2026 https://www.iso.org/obp/ui#iso:std:iso:8062:-3:ed-2:en |
| S4 — ASTM A957/A957M-21 title, active status, last-updated date 24 May 2021, subcommittee A01.18, volume 01.02 and ICS 77.100; abstract; scope 1.1 to 1.5 including the list of material specifications, the purchaser-specified supplementary requirements rule, the integral-part and precedence wording, chemical and mechanical verification, the ICI test bar for austenitic alloy castings, and the WTO TBT reference | ASTM official store product page, retrieved 25 September 2026 https://store.astm.org/a0957_a0957m-21.html |
| S5 — Institute identity and founding year 1953; the sequence of process stages and the descriptions of wax-pattern creation and shell building; the Process Control Standards Program levels, criteria thresholds, two-year validity and internal surveyor requirement | Investment Casting Institute official site, home page and process-control pages, retrieved 25 September 2026 https://www.investmentcasting.org/ |