When a quotation comes back from a Vietnamese foundry, reading it the way you would read a machining or sheet-metal quotation usually leads to a misunderstanding. A casting is not priced as “this shape, at this price”. It is priced as how much metal is melted, what kind of mould is made, how much is machined away and how much is proved by testing.
This article is for designers and buyers about to send an iron-casting drawing to a Vietnamese foundry. It covers what to add to the drawing and the purchase order first, in the order the decisions actually fall: process, material grade, certificates and test bars, hidden defects, and how first-article approval ties down production.
💬 Not sure whether your part is a realistic casting job for a Vietnamese foundry? Send us an outline of the drawing and we will tell you what a foundry will ask first.
Why a casting price is not unit price times quantity
A casting’s cost starts from the metal actually melted and the moulding set-up, not from the finished weight, so it has to be read in layers.
Every casting needs a running system — the channels the metal flows through — and feeders that supply metal as the casting shrinks while it solidifies. The metal melted is therefore always more than the finished weight, by an amount that depends on the shape and on how the foundry designs the running system. A “finished weight times price per kilo” estimate is always off. Castings are also heavy, so sea freight and packing form a larger share of the landed cost than they do for plastic or electronic parts.
Ask every foundry to price the same five layers separately:
| Layer | What it covers | Why it differs between quotations |
|---|---|---|
| Metal and melting | Grade, metal actually poured, yield assumption | Running-system design differs by foundry |
| Pattern and moulding | Moulding method, pattern making and upkeep | Pattern cost may be separate, amortised or omitted |
| Finishing | Fettling, shot blasting, machining, painting | One quotation is as-cast, another fully machined |
| Inspection | Visual, dimensional, material tests, non-destructive testing | Testing scope is rarely the same unless specified |
| Packing and logistics | Crates, rust protection, port of loading, Incoterm | Heavy parts make this a significant line |
The port of loading depends on the foundry’s location: Hai Phong for most northern foundries, Cat Lai or Cai Mep–Thi Vai in the south. How the Incoterm then moves local charges onto one side or the other is covered in Vietnam local charges by Incoterm.
Patterns are a separate question of cost and ownership — who pays, and whether they come back if you move the work. See tooling and mould ownership in Vietnam.
Which process: sand, investment or lost foam?
The process follows from what you prioritise — shape freedom, dimensional accuracy or volume — and until it is fixed, foundries are quoting different products.
| Sand casting | Investment (lost-wax) casting | Lost-foam casting | |
|---|---|---|---|
| Suited shapes | Large, heavy-section, simple to moderate shapes | Small to medium complex shapes with fine detail | One-piece shapes that would otherwise need many cores |
| Accuracy and surface | Coarser; allow machining stock | Finer; can reduce machining | Between the two |
| Pattern needed | Wood, metal or resin patterns, depending on moulding method | Wax patterns from a die | Foam patterns |
| Volume fit | Small to large lots | Depends on shape; pattern die cost must be recovered | Leans towards volume |
High-pressure die casting is a different process, mainly for aluminium and zinc; see aluminium die casting from Vietnam. If you are still deciding between casting and machining from solid, compare with CNC machining in Vietnam.
Specify the grade with the standard number, not a symbol alone
Cast iron grades are named differently in every standards system, so a bare symbol leaves room for a similar but different material to be poured.
| Material | Japan | United States | Europe | International |
|---|---|---|---|---|
| Grey (flake graphite) iron | JIS G 5501 (FC grades) | ASTM A48 (Class grades) | EN 1561 (EN-GJL grades) | ISO 185 |
| Ductile (spheroidal graphite) iron | JIS G 5502 (FCD grades) | ASTM A536 (e.g. 60-40-18) | EN 1563 (EN-GJS grades) | ISO 1083 |
The numbers mean different things in each system. ASTM A536 grades combine tensile strength, yield strength and elongation in imperial units; EN-GJS grades combine tensile strength in megapascals and elongation. “Equivalent to FCD450” is not a safe instruction. Vietnamese foundries that work for Japanese customers often quote in JIS symbols by default; that may suit you, but agree it rather than discover it.
Write three things on the purchase order: the standard number, the grade, and how conformity is verified — which test, on which test piece. If the foundry proposes to work to another standard, have it name the standard and grade in writing before you accept.
Certificates: name the type, the tests and the test piece
Asking for “a mill certificate” is not enough; specify the certificate type, the tests it must report and how the test piece is taken.
“Mill certificate” is borrowed from steel mills. For castings, ask for an inspection certificate under EN 10204:2004, which applies to metallic products including castings:
| Type | Issued by | Content |
|---|---|---|
| 2.1 | Manufacturer | Declaration of compliance, no test results |
| 2.2 | Manufacturer | Test results, not necessarily from the delivered product |
| 3.1 | Inspection representative independent of manufacturing | Specific test results for the delivered lot |
| 3.2 | As 3.1, plus the purchaser’s or an official inspector’s countersignature | Specific results, witnessed and countersigned |
Then specify three more things:
- Which properties — chemical composition, mechanical properties (tensile, hardness), or both; for ductile iron, graphite nodularity where it matters.
- Which test piece — separately cast test bars or test pieces cast on to the casting. They do not give the same result for a heavy section, and the grade standards treat them differently.
- Which lot — per melt (ladle or furnace charge) or per shipment.
Which other documents to request from a parts supplier, and when, is covered in quality documents to request from a Vietnamese parts supplier.
💬 We can draft the grade, certificate and test-piece wording for your purchase order and carry it into Vietnamese for the foundry — see sourcing from Vietnam.
Casting defects that visual inspection does not catch
Gas porosity and shrinkage cavities form inside the casting, so a visual sample before shipment cannot find them; decide at which stage internal soundness is proved.
Typical casting defects are gas porosity, shrinkage cavities, misruns, sand inclusions and dimensional change from contraction. Internal shrinkage is hard to see from outside and is found with radiography, ultrasonic testing or by sectioning a first-article casting.
- At first article, section the casting or test it non-destructively, measure every dimension, and record the basis of approval in writing.
- Freeze what first article proved: the grade, the moulding method, the feeder positions and the machining datums become items that cannot change without your written approval.
- In production, agree the sampling plan and which lots are checked for internal defects.
Sampling plans for visible defects are covered in pre-shipment inspection and AQL, and what to look for on the foundry floor in what to check on a first visit to a Vietnamese factory.
What to add to the drawing and purchase order
A casting drawing missing these lines will draw scattered quotations from any foundry in any country.
- Material: standard number and grade; conditions for accepting another standard.
- Verification: composition or mechanical properties; separately cast or cast-on test pieces.
- Certificate: EN 10204 type, lot basis and when it is delivered.
- As-cast surface: acceptable surface condition on unmachined faces, with a reference sample.
- Machining stock and finish: how much stock on which faces, surface roughness on machined faces.
- Datums: whether machining locates from as-cast or machined faces.
- Draft: permitted draft angles, and faces where draft is not allowed.
- Weight tolerance: if the part is invoiced or accepted by weight.
- Paint and rust protection: surface preparation, coating, thickness, protection during transit.
- Marking and traceability: cast-in marks, lot numbers, the level of traceability.
- Acceptance: porosity limits, and whether weld repair is allowed.
The last line is the one most often missed. Write whether weld repair is permitted, and if it is, whether each repair must be declared and recorded. Without that, a repaired casting and a sound one arrive looking identical.
Customs classification also depends on the finished article: cast articles of iron or steel not covered elsewhere fall under heading 7325, but many castings are classified by their function as parts of a machine. Confirm the code before you rely on a preferential rate; origin documents by destination are covered in proof of origin by destination.
💬 Send us the drawing outline, even before the checklist is complete. For each project we find, vet and manage the foundry that fits the part, and arrange inspection and export documents. Get in touch.
Frequently asked questions
1. Will a foundry quote from the drawing alone?
It will produce a number, but not one you can compare. Add the grade and standard, the as-cast surface requirement, machining stock, inspection and certificate terms, and packing and Incoterm, and the quotations become comparable.
2. Is a JIS grade symbol enough?
Not on its own. Write the standard number with the grade and state which test decides conformity. If the foundry proposes an equivalent from another standard, agree it in writing.
3. Can a Vietnamese foundry issue material certificates?
Many can, but unless you specify the content and the test piece, the document you receive may not prove what you need. State the properties, the test-piece type and the lot basis on the order.
4. Can I buy castings machined complete?
Some foundries machine in-house; others send machining out. Where the work is split, agree in advance who fixes a defect found at machining — a pore exposed by a cutter is the classic case.
5. Will a foundry take a small order?
Minimum quantities vary widely by foundry and part. Melting is done in batches and moulding needs set-up, so very small lots tend to raise the unit price sharply; see negotiating minimum order quantities in Vietnam.
Sources: JIS G 5501, JIS G 5502, ASTM A48, ASTM A536, EN 1561, EN 1563, ISO 185, ISO 1083, EN 10204:2004; Harmonized System heading 7325. Checked on 17 October 2026.