회사 소식 Germany | How Should Automotive Foundries Control MgFeSi Magnesium Content Variation to Meet Composition Needs?

Magnesium content variation in MgFeSi has two layers, and only one of them is visible on the certificate. Between lot variation sits inside the grade tolerance, which for FeSiMg6Re1 is 5.0 to 7.0 percent Mg, while within lot variation is the spread between bags of the same delivery. German automotive foundries that meet composition requirements reliably control both: they sample every lot, they track magnesium by statistical process control rather than by single readings, and they correct the treatment weight for analysed content instead of trusting the nominal grade figure.

Composition requirements for automotive ductile iron are not written around a single magnesium number. They are written around a residual magnesium window that has to hold across a production run, alongside silicon, carbon equivalent and trace elements. MgFeSi is the input that moves that window, and a grade tolerance of two percentage points is wide enough to consume most of the allowed variation if it is ignored.

Magnesium is the most volatile element in the alloy, so its final content is a result of the smelting and casting process rather than a fixed recipe.

The practical consequence is that a supplier can be fully inside its grade range and still deliver two lots that behave differently in a foundry, because the lots sit at opposite ends of the range.

The published grade table defines the window. Reading it as a treatment instruction rather than a purchase label changes how the alloy is dosed.

A lot at 5.0 percent magnesium and a lot at 7.0 percent magnesium differ by forty percent in contained magnesium. Dosing both with the same alloy weight is a decision to accept that spread in the residual magnesium of the iron.

Sampling discipline converts a certificate into usable data. Three habits do most of the work.

1. Take a composite sample per lot from at least three bags at different heights in the container

2. Prepare the sample by drilling or milling through the full section, discarding surface oxide

3. Analyse magnesium by a method agreed with the supplier, and retain the sample until the lot is consumed

4. Record MgO alongside magnesium, because oxidised magnesium is paid for and does not nodulize

5. Trend the lot means on a control chart with the grade range drawn on it

The fourth point is the one most often skipped. A lot can show a healthy total magnesium figure while a meaningful share of it sits as oxide, and that share leaves the treatment as slag rather than as nodulant.

Correction is arithmetic, and it should be done before the heat rather than after the casting.

A foundry that corrects only when a defect appears is using composition control as a repair function. A foundry that corrects per lot is using it as process control, and the difference shows in capability indices.

Not every element needs a chart. Four do, because they move casting results directly.

• Residual magnesium in treated iron, sampled at a fixed point in the pour sequence

• Silicon, since it sets carbon equivalent and carbide risk together with carbon

• Rare earth, where the grade carries it, because it changes graphite morphology in heavy sections

• Magnesium oxide in incoming alloy, as an early warning of storage and handling problems

Charts should carry the grade range as reference lines and the internal target as a separate, tighter band. When a lot mean drifts toward an edge of the grade range, the chart shows it before the castings do.

Composition variation leaves a signature, and reading it saves a chemistry round trip.

It is a process reality within the grade range. The supplier controls it to the published window, and the foundry controls its effect by sampling each lot and correcting the treatment weight.

For FeSiMg6Re1 the published range is 5.0 to 7.0 percent, and for FeSiMg7Re1 it is 6.0 to 8.0 percent. Higher grades reach 9.0 to 11.0 percent in FeSiMg10Re7.

Where the casting warrants it, a narrowed range can be agreed as a specification item, usually at a cost. Most foundries instead buy the standard range and manage variation through lot sampling and weight correction.

Not on the certificate, but it does in the ladle. Oxidised magnesium does not enter solution, so a lot with high MgO behaves like a lower magnesium alloy while testing to the nominal figure.

Every lot for automotive work, with a composite sample from several bags. Reducing frequency is only defensible after a long run of stable results from the same supplier and production line.

Yes, up to a point. Excess alloy also adds silicon and calcium, which changes carbon equivalent and inoculation balance, so weight correction is bounded by the composition of the iron rather than by magnesium alone.

XRF is fast and adequate for routine lot checks when prepared properly, while ICP methods give better accuracy for disputes. The important point is that the foundry and supplier use comparable methods so that figures can be discussed.

Audits look for evidence that variation is measured and acted upon, which means lot records, control charts, correction calculations and a traceable link from lot to heat to casting.

ZhenAn supplies MgFeSi in FeSiMg6Re1 through FeSiMg10Re7 with ISO 9001:2015 certification, 1 MT big bags holding 20 to 25 MT per 20 foot container, and delivery 7 to 10 working days after payment from a 2000 MT monthly capacity. Lot level certificates and retained samples support incoming inspection programmes.

Send your grade, magnesium tolerance requirement, monthly tonnage and discharge port to start an RFQ.

Composition ranges that support lot correction are published on the 38 percent silicon FeSiMg grade table page, and the FeSiMg6Re1 nodulizer page gives the 5.0 to 7.0 percent magnesium window in full. For heavy section work the rare earth FeSiMg nodulant lump page lists the higher rare earth options.