Magnesium treatment ladle: the foundry reaction vessel for ductile iron

01

Choose the treatment method and ladle type

In an ASK Chemicals answer in Foundry Management & Technology, a pour-over or sandwich treatment is described as giving 30–50% magnesium recovery, less efficient than a tundish treatment process at 50–70%, and the best treatment temperature is given as around 1,454–1,482 °C (2,650–2,700 °F), because magnesium is lost faster at higher temperatures. The same answer gives 0.035–0.045% magnesium in the casting for ductile iron and 0.015–0.023% for compacted graphite iron, and names 5–6% MgFeSi as the favoured treatment alloy. [1]

Researchers from AGH University in Kraków note that vertical treatment ladles are used on the assumption that the height of the metal column must be at least twice the ladle diameter (2:1). In their foundry trial a drum ladle of about 950 kg replaced the vertical treatment ladle, receiving two 9 mm cored wires and then serving for transport and pouring; sulphur fell by 0.004% during treatment and residual magnesium averaged 0.054%. [2]

Editorial note: a tundish cover only improves recovery if the alloy pocket, dam and filling hole are sized for your tap rate and metal mass; ask the supplier for the ladle drawing with pocket volume, cover hole diameter and the metal level at full charge.

Give the supplier the treatment method (sandwich, tundish cover, cored wire), metal mass per treatment, base iron sulphur, target residual magnesium, treatment temperature, alloy type and size, crane or forklift handling, tilt or bottom pour, refractory type and preheating, and any cover, lid or fume hood required.

02

Size the magnesium addition from sulphur and recovery

The AGH papers calculate magnesium recovery as ηMg = [(0.76·ΔS + Mgr)·m] / (magnesium added), where 0.76 is the Mg/S atomic-weight ratio, ΔS the drop in sulphur during treatment, Mgr the residual magnesium and m the metal mass. With cored wire in a drum ladle they report recovery rising from 42% to 55% as wire length and treatment temperature (from about 1,460 °C) were reduced for SiMo ductile iron, and from 66% to 70% for austenitic high-nickel ductile iron, with recovery about 6% lower when a ladle was treated below full capacity. [2] [3]

Editorial calculation: for 1,000 kg of iron losing 0.010% sulphur and needing 0.045% residual magnesium, the magnesium that must stay in or react with the iron is (0.76 × 0.010 + 0.045)% × 1,000 kg ≈ 0.53 kg. At 60% recovery (tundish range) that needs 0.53 / 0.60 ≈ 0.88 kg of magnesium, or about 16 kg of 5.5% MgFeSi; at 40% (sandwich range) about 1.32 kg of magnesium, or about 24 kg of alloy. [2] [1] The sulphur and residual values are assumptions for the example; use your own base iron analysis.

Editorial note: the higher the base sulphur, the more magnesium the ladle consumes before nodularising, so the vessel and its alloy pocket must hold the larger addition; desulphurising the base iron first reduces the alloy needed.

03

Pocket and cover drawing, refractory and capacity to request from a foundry ladle maker

The companies linked to this product make laboratory and pharmaceutical reaction vessels, not foundry ladles. Ask any foundry ladle supplier for the drawing with pocket and cover details, refractory specification, lifting and tilting arrangement, and the design capacity.

04

Shell and trunnions, refractory lining, alloy pocket and dam, tundish cover and wire ports

05

Metal capacity, treatment temperature, lining and metal-column height for a magnesium treatment ladle

Pressure, stirring and sealing fields do not apply to an open pocket-treatment ladle; capacity, lining and the height-to-diameter of the metal column do. [2]

06

Send the iron, treatment and handling together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Iron: [grade; mass per treatment; base sulphur; target residual Mg]
Treatment: [sandwich; tundish cover; cored wire]
Alloy: [type; Mg content; size]
Temperature: [treatment range]
Ladle: [capacity; metal height; pocket; cover]
Handling: [crane; forklift; tilt or bottom pour]
Refractory: [type; preheating]

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