How do you use ASTM E505 to specify X-ray porosity limits on die castings?

What does the ASTM E505 reference set actually contain?

The set is a binder of original film radiographs. For each of the two alloy families, aluminum and magnesium, it pictures three kinds of internal defect, each shown at four steps of increasing severity, plus two ungraded images of foreign material.

The physical films are an adjunct you buy from ASTM, and ASTM states that the films are checked against a fixed prototype image, so a set produced in any year still represents the same acceptance levels (ASTM E505-22). The table below summarizes the layout described in the standard’s scope.

First, the set illustrates only a few wall thicknesses, so other sections are judged by equivalence. Per ASTM E505, the document may be applied to other materials, thicknesses or energy levels only where it has been found applicable and the purchaser and manufacturer agree. Second, zinc is not in the set at all. A Zamak 3 part can still carry an X-ray requirement, but the use of E505 plates for it is an agreement between the two parties, and the drawing or purchase order should say so explicitly.

Should the drawing cite E505, E2973, E155 or E2422?

Cite the document that matches both the casting process and the imaging method: E505 for film radiography of die castings, E2973 for digital radiography of die castings, and E155 or E2422 for other aluminum and magnesium castings.

E505 itself tells anyone imaging these castings digitally to use the digital reference images of E2973 instead of the film plates (ASTM E505-22, section 1.5). If your drawing cites E505 and the supplier’s lab shoots digitally, the two parties should agree which reference applies before the first parts are imaged.

Two details are worth noticing. The die-casting documents grade in four steps, while the documents for other castings grade in eight, so a severity number copied from a sand-casting drawing does not carry over to a die casting. And the thickness coverage differs. ASTM E2422 notes that the E505 radiographs are meant for die castings no thicker than 1 in (25 mm) (ASTM E2422), and E505 Note 2 points to E155 for reference radiographs of aluminum and magnesium castings up to 2 in (50 mm) thick (ASTM E505-22, Note 2). Our reading: a die-cast section thicker than 1 in is better matched against E155 than E505, and the drawing should say which set applies.

How many die castings should be X-rayed?

ASTM E505 does not set a sample size, so the frequency belongs in the purchase order or the quality plan. Common practice is heavier inspection at first article and after any process change, then a defined periodic sample in steady production.

Porosity is driven mainly by the process (gating, venting, shot parameters, die temperature, melt handling), so sampling is best tied to events as well as counts:

• First article. Radiograph enough castings from each cavity to see where porosity forms, and confirm it falls outside the critical zones. This is also when the X-ray views are agreed.
• Process changes. Re-examine after die repair or modification, a change of alloy source, a machine change or a significant parameter change.
• Steady production. A fixed number of castings per lot or per shift, per cavity, recorded with the lot number so a rejection can be traced.
• Escalation. A rule for what happens after a reject: tightened sampling, a hold on the lot, or full inspection until the cause is found.

For parts that are machined afterward, a sectioning or machined-surface check on a small sample often catches what matters more cheaply than radiographing every casting.

What does X-ray inspection add to the cost of a die-cast part?

The cost comes from four places: the inspection itself, the sampling rate, the strictness of the acceptance level, and the process development needed to meet it. The last two usually outweigh the first.

Inspection itself is a visible line item (fixturing, imaging, interpretation, records), whether done at the die caster or at an outside testing lab, and the sampling rate multiplies it. Full inspection is usually reserved for safety-critical parts or for periods when a process problem is being fixed.

The less visible cost is in the acceptance level. A strict level over a large zone can mean a die with more venting or vacuum assistance, slower cycles, tighter melt control and higher scrap, all of which show up in the piece price or the tooling quote rather than in an inspection line. Zoning is the main lever to control that: the stricter levels go only where the part seals or carries load. When porosity is a leak-path concern rather than a strength concern, it is also worth asking whether a leak test plus impregnation would meet the function at lower cost than a strict radiographic level.

When comparing suppliers, including die casters in Vietnam or elsewhere in Southeast Asia, ask each one to state who performs the examination, which reference document and imaging method they will use, who interprets the images and to which qualification scheme, and what records ship with each lot. Those answers are comparable; a bare “X-ray available” is not. The RFQ package guide lists what else to send, and the quality page explains what documentation we issue today.