Which Chemical Composition Differences Matter Between LM6 and A413?
Silicon, iron, copper, magnesium, manganese, zinc, nickel and residual-element limits all matter when comparing LM6 with A413. Silicon explains their shared high-silicon casting character, but differences in iron, copper and impurity allowances can change corrosion, ductility, intermetallic formation, machining, finish and consistency. Buyers should compare every controlled element under the current standards, not only silicon.
The comparison needs three columns for each designation: the official permitted limit, the supplier's internal target and the actual melt result. A lot that sits within an overlapping window may support a substitution trial. A grade name or nominal chemistry cannot prove that future production will remain inside the approved envelope.
Compare Full Limits, Not Nominal Alloy Recipes
Obtain the exact BS 1490 LM6 and applicable A413/ASTM B85 documents invoked by the project. Record standard revision and product scope. Copy minimum values, ranges, individual maxima and any total-other-element rule into one controlled matrix. If the supplier cites a different national equivalent, add it as a separate column rather than replacing the original requirement.
Nominal recipes hide compliance width. Two suppliers may quote the same A413 label while targeting different positions inside the allowed window. One early sample can match an LM6-like chemistry, yet later lots may move toward a limit that the LM6 drawing owner would not accept. Define the approved envelope and change-notification threshold rather than approving a name alone.
The following numbers are a screening comparison, not a purchase specification. The LM6 column reflects a public composition table attributed to BS 1490-1988; the A413 column reflects the current composition summary on Neway's A413 material page. Before release, replace both columns with the exact controlled editions named by the drawing and purchase order. This source note matters because website summaries can differ from a licensed standard in revision, product scope, rounding or omitted elements.
Element, wt% | LM6 Screening Limit | A413 Screening Limit | Substitution Concern |
|---|---|---|---|
Si | 10.0-13.0 | 11.0-13.0 | The shared high-silicon range explains similarity but does not prove full overlap |
Fe | 0.60 max | 1.30 max | A wider proposed maximum can affect intermetallics, ductility and surface response |
Cu | 0.10 max | 1.00 max | The difference can matter where low-copper corrosion intent controls |
Mg | 0.10 max | 0.10 max | Matching maxima still need actual-lot confirmation |
Mn | 0.50 max | 0.35 max | Use the stricter project limit unless an approved deviation states otherwise |
Zn | 0.10 max | 0.50 max | The wider proposed maximum can change corrosion and repeat-lot headroom |
Ni | 0.10 max | 0.50 max | Certificate coverage must include the element when either standard controls it |
Sn | 0.05 max | 0.15 max | Residual limits should not be hidden inside an unspecified total |
Other elements, total | 0.15 max | 0.25 max | Confirm definitions, exclusions and individual maxima in the controlling standards |
The table shows why silicon alone is a poor equivalence test. Even if a measured melt lies inside both silicon windows, it can approach an A413 Fe, Cu or Zn limit that is outside the LM6 screening envelope. The approval matrix should therefore calculate headroom against both requirements for every reported element and flag any element missing from either website summary for direct standard review.
The EN AC-44300 material page may help orient a European comparison, but EN AC-44300 does not erase the need to review LM6 and A413 directly. Cross-standard families are evidence maps, not transitive equations.
Connect Each Element Group to the Part Risk
Element or Rule | Functional Concern | Evidence | Escalation Trigger |
|---|---|---|---|
Silicon range | Fluidity, solidification, machining response and microstructure | Official range plus measured melt result | Result outside approved overlap or unexplained process claim |
Iron maximum | Die interaction, intermetallics, ductility and surface response | Standard maxima, supplier target and lot margin | Alternative standard permits materially more than the drawing intent |
Copper maximum | Strength contribution versus corrosion sensitivity | Actual value and application corrosion review | Coastal, fluid or galvanic duty depends on low-copper control |
Magnesium | Mechanical response, oxidation and processing behavior | Specified limit and measured result | Uncontrolled addition or mixed heat-treatment assumptions |
Mn, Zn and Ni | Process, properties and environmental performance | Complete element report | Supplier omits elements controlled by the standard |
Pb, Sn and other residuals | Integrity, machining, corrosion or customer restrictions | Individual and total impurity evidence | Partial certificate cannot prove the approved total |
Chemistry-property statements should remain conditional. A higher or lower value does not create a guaranteed component result because morphology, cooling, porosity, section and casting process also matter. Use chemistry to control material identity and screen likely behavior; use representative parts to validate function.
Define how samples represent the melt. A pre-pour, in-process or separately cast spectrometer sample may be suitable under the supplier's control method, but its identity and timing must be clear. If several furnaces, ladles or remelt additions can feed one production lot, the trace plan should show which analysis covers which parts. Averaging unrelated results can hide an out-of-limit portion.
Measurement quality matters near a boundary. State the analytical method, calibration or reference practice where required, reporting resolution and rule for a result close to a limit. Do not round a marginal value in whichever direction makes the substitution pass. The buyer and supplier should agree whether a confirmation measurement, hold or investigation applies before production begins.
For a hypothetical coastal valve cover, copper and residual limits may deserve more attention than a non-exposed decorative housing. If a machined seal or threaded port is present, iron- and silicon-related microstructure can also affect tool wear and exposed surface appearance. The element matrix should therefore include a “why it matters to this drawing” column instead of a generic alloy lecture.
Review Melt Evidence and Remaining Headroom
Request a report traceable to the sample and production melt. It should identify instrument or method as required, date, heat/melt or lot number, alloy callout and all elements needed by the controlling specification. A measured result without part linkage is an interesting laboratory record, not production traceability.
Calculate headroom to each approved maximum or range boundary. A source consistently centered inside the approved overlap presents a different repeat-order risk from one operating near a critical limit. Define whether drift inside the supplier's original A413 standard but outside the buyer-approved LM6 substitution envelope requires notification.
The testing overview can support method discussions, but never cite a machine page as proof that a delivered lot was measured. Retain the lot report and its link to parts. If recycled return metal, master alloy additions or source changes are controlled by the purchase specification, include those records and limits explicitly.
Finish the review with a signed chemistry disposition. It should list compliant overlaps, differences accepted by engineering, differences requiring part tests and any limits that prohibit substitution. The aluminum die-casting alloy library is useful for research, but the controlled matrix and actual melt evidence decide the LM6/A413 approval.
