{"id":7576,"date":"2026-10-16T07:52:12","date_gmt":"2026-10-16T07:52:12","guid":{"rendered":"https:\/\/www.lyafs.com\/?page_id=7576"},"modified":"2026-10-16T09:41:54","modified_gmt":"2026-10-16T09:41:54","slug":"ductile-iron-casting","status":"publish","type":"page","link":"https:\/\/www.lyafs.com\/id\/services\/ductile-iron-casting\/","title":{"rendered":"Ductile Iron Casting"},"content":{"rendered":"
\nDuctile iron casting service\n<\/span>

\nDuctile iron castings, QT400 to QT700, sand cast without a pattern\n<\/h1>

\nWe print the sand mould and the sand cores from your CAD file, so a single ductile iron casting is economic. No pattern, no pattern cost, no pattern lead time. Pour weight to 2 t, envelope to 3 m.\n<\/p>

\nSend your drawing for a quote\n<\/a>\nSee the grades we pour\n<\/a><\/div><\/div>
\"Engine<\/div><\/div><\/section>
\n2 t<\/b>Largest single iron pour, one casting<\/span>\n<\/div>
\n3 m<\/b>Maximum casting envelope<\/span>\n<\/div>
\nQT400\u2013QT700<\/b>Ductile grades we pour<\/span>\n<\/div>
\n1,000 t<\/b>Iron casting capacity a year<\/span>\n<\/div><\/div><\/section>
\n01\n<\/span>

\nWhat ductile iron casting is, and when we quote it\n<\/h2><\/div>

\nDuctile iron is cast iron whose graphite grows as nodules instead of flakes. That single change is why it behaves like a metal rather than a brittle one: tensile strength from 400 MPa to 700 MPa with real elongation, on a foundry process that is still sand casting. We pour it in sand moulds that we print from your CAD file, which removes the pattern from the critical path.\n<\/p>

\nSend us a drawing and a quantity. If the part is ferrous, thicker-walled, and the annual volume does not justify a pattern or a die, ductile iron in a printed sand mould is usually the cheapest sound route. If you need thin walls under about 4 mm, or volumes in the tens of thousands, we will tell you that a different process wins and point you at it.\n<\/p>

\nThis page is about the casting service<\/strong>. If what you need is the printed sand mould itself, or ductile iron is the wrong alloy for your duty, the links at the bottom of the page take you to the right service.\n<\/p><\/div><\/div><\/section>

\n02\n<\/span>

\nWhy ductile iron, and not grey iron or cast steel\n<\/h2><\/div>

\nThree ferrous options land on the same foundry floor. Picking between them is a design decision, not a price decision, so it is worth being precise about what separates them.\n<\/p>

\nAgainst grey iron.<\/strong> Grey iron is cheaper and damps vibration better, and for a rigid machine base it is still the right answer. What it does not have is elongation. Its flake graphite acts as an internal crack, so it fails without warning; ductile iron's nodules blunt the crack tip and give you 2% to 18% elongation before fracture, plus roughly double the tensile strength. Anything that sees impact, fatigue or a pressure boundary should not be grey iron.\n<\/p>

\nAgainst cast steel.<\/strong> Steel is stronger and weldable. But steel shrinks far more on solidifying and has no graphite expansion to offset it, so it needs much heavier feeders and a bigger yield loss \u2014 and it pours about 100\u00a0\u00b0C hotter, which is harder on the mould. Ductile iron's graphite expansion during solidification partly feeds the shrinkage, so the rigging is lighter, the yield is better, and it machines considerably more freely. For a thick-walled housing or a pump body, ductile iron usually lands cheaper than the steel equivalent.\n<\/p>

\nAgainst a printed sand mould in another alloy.<\/strong> The mould-making side is identical across all of them \u2014 the same printed sand, the same no-pattern economics. So choose the alloy on the duty, not on the supply route.\n<\/p>

\nFerrous casting routes compared. Use this to shortlist; your drawing's material callout governs the final choice.\n<\/caption>
\nProperty\n<\/th>\nDuctile iron\n<\/th>\nGrey iron\n<\/th>\nCast steel\n<\/th><\/tr><\/thead>
\nGraphite form\n<\/th>\nNodules (spheroidal)\n<\/td>\nFlakes\n<\/td>\nTidak ada\n<\/td><\/tr>
\nTensile strength\n<\/th>\n400\u2013700 MPa\n<\/td>\n150\u2013350 MPa\n<\/td>\n450\u2013650 MPa\n<\/td><\/tr>
\nElongation\n<\/th>\n2\u201318%\n<\/td>\nUnder 1%\n<\/td>\n12\u201325%\n<\/td><\/tr>
\nShrinkage on solidifying\n<\/th>\nPartly offset by graphite expansion\n<\/td>\nPartly offset\n<\/td>\nFull, heavy feeders needed\n<\/td><\/tr>
\nMachinability\n<\/th>\nFree-cutting\n<\/td>\nExcellent\n<\/td>\nHarder on tooling\n<\/td><\/tr>
\nVibration damping\n<\/th>\nGood\n<\/td>\nBest\n<\/td>\nPoor\n<\/td><\/tr>
\nWeldability\n<\/th>\nLimited, needs procedure\n<\/td>\nPoor\n<\/td>\nGood\n<\/td><\/tr>
\nPick it when\n<\/th>\nImpact, fatigue or pressure duty on a thick-walled part\n<\/td>\nRigidity and damping, no tensile duty\n<\/td>\nHighest strength or a welded assembly\n<\/td><\/tr><\/tbody><\/table><\/div><\/div><\/section>
\n03\n<\/span>

\nThe ductile grades we pour\n<\/h2><\/div>

\nWe pour QT400, QT450, QT500 and up to QT700, plus grey iron HT250 for the parts that do not need ductility. QT grades are Chinese national standard (GB\/T 1348) designations, and the number carries the specification: the first figure is minimum tensile strength in MPa, the second is minimum elongation. So QT400-18 guarantees 400 MPa and 18% elongation.\n<\/p>

\nMost overseas drawings call the same material by its ASTM A536 designation. The table below is the cross-reference our application engineers use when they read your drawing.\n<\/p>

\nDuctile iron grades. Tensile and elongation figures are the grade definitions in GB\/T 1348. ASTM A536 is an approximate cross-reference for enquiry only.\n<\/caption>
\nGrade\n<\/th>\nTensile, min\n<\/th>\nElongation, min\n<\/th>\nMatrix\n<\/th>\nNearest ASTM A536\n<\/th>\nTypical duty\n<\/th><\/tr><\/thead>
\nQT400-18\n<\/th>\n400 MPa\n<\/td>\n18%\n<\/td>\nFerritic\n<\/td>\n60-40-18\n<\/td>\nLow-temperature impact, pressure-retaining bodies, wind hubs\n<\/td><\/tr>
\nQT450-10\n<\/th>\n450 MPa\n<\/td>\n10%\n<\/td>\nFerritic\u2013pearlitic\n<\/td>\n65-45-12\n<\/td>\nGeneral engineering housings, pump and valve bodies\n<\/td><\/tr>
\nQT500-7\n<\/th>\n500 MPa\n<\/td>\n7%\n<\/td>\nPearlitic\n<\/td>\n70-50-05\n<\/td>\nGears, brackets, transmission parts\n<\/td><\/tr>
\nQT600-3\n<\/th>\n600 MPa\n<\/td>\n3%\n<\/td>\nPearlitic\n<\/td>\n80-55-06\n<\/td>\nHigher-load gears and crankshaft-class parts\n<\/td><\/tr>
\nQT700-2\n<\/th>\n700 MPa\n<\/td>\n2%\n<\/td>\nPearlitic, heat treated\n<\/td>\n100-70-03\n<\/td>\nMaximum strength where ductility is secondary\n<\/td><\/tr>
\nADI\n<\/th>\nTo grade\n<\/td>\nTo grade\n<\/td>\nAustempered\n<\/td>\nA897\n<\/td>\nWear plus toughness: gears, camshafts, wear plates\n<\/td><\/tr>
\nHT250\n<\/th>\n250 MPa\n<\/td>\nNot specified\n<\/td>\nGrey iron\n<\/td>\nClass 35 \/ GJL-250\n<\/td>\nMachine bases, covers, non-pressure housings\n<\/td><\/tr><\/tbody><\/table><\/div>

\nThe elongation figure is what separates these grades in service, not the tensile figure. A drawing that specifies QT500-7 because it looks stronger can be the wrong call on a part that sees thermal cycling or impact \u2014 QT400-18 is the tougher material despite the lower number. Send us the duty and we will say which grade we would pour.\n<\/p><\/div><\/div><\/section>

\n04\n<\/span>

\nHow the mould is made: printed sand, no pattern\n<\/h2><\/div>

\nA conventional ductile iron job starts with a pattern. Someone cuts a wooden or metal copy of your part, and that pattern is what sets your lead time and your minimum order quantity. It is also the reason a single casting is normally uneconomic.\n<\/p>

\nWe delete that step. Your CAD model is printed directly as a sand mould and as sand cores on a binder-jetting sand printer, using furan resin at 1.5\u20132.5% by weight. The mould arrives at the pouring floor in days rather than weeks, and the mould-making cycle drops by about 70% against the traditional route. Because no pattern exists, there is nothing to amortise: one casting costs what one casting costs.\n<\/p>

  1. \"3D\n01 \u00b7 Print\n<\/span>

    \nMould and cores printed from CAD\n<\/h3>

    \nThe outer mould and every internal core are printed in one setup. No pattern, no core box, no draft angle to design around.\n<\/p><\/li>

  2. \"Complex\n02 \u00b7 Assemble\n<\/span>

    \nCores set as one assembly\n<\/h3>

    \nPrinted cores are glued into the mould as a single assembly, so internal passages and water jackets have no joint line and no core print to leak past.\n<\/p><\/li>

  3. \"3D\n03 \u00b7 Pour and finish\n<\/span>

    \nPoured, knocked out, machined\n<\/h3>

    \nIron is poured into the mould under gravity, then the casting is knocked out, shot blasted, heat treated and machined to the faces that need it.\n<\/p><\/li><\/ol><\/div><\/section>

    \n05\n<\/span>

    \nWhat we can cast: size, weight, tolerance\n<\/h2><\/div>

    \nThese are the real limits of the iron line, not a marketing range. If your part sits outside them, say so in your enquiry and we will tell you straight away rather than after a week of quoting.\n<\/p>

    \nDuctile and grey iron casting limits.\n<\/caption>
    \nParameter\n<\/th>\nCapability\n<\/th>\nNote\n<\/th><\/tr><\/thead>
    \nLargest single pour\n<\/th>\n2 t\n<\/td>\nOne casting, iron\n<\/td><\/tr>
    \nMaximum envelope\n<\/th>\n3 m\n<\/td>\nLargest dimension of the finished casting\n<\/td><\/tr>
    \nAnnual iron capacity\n<\/th>\n1,000 t\n<\/td>\nAcross the iron casting line\n<\/td><\/tr>
    \nAs-cast tolerance\n<\/th>\nCT8\u2013CT12\n<\/td>\nSand casting, ISO 8062\n<\/td><\/tr>
    \nAs-cast surface\n<\/th>\nRa 12.5\u201325 \u00b5m\n<\/td>\nPrinted mould surface, before machining\n<\/td><\/tr>
    \nMinimum practical wall\n<\/th>\nAbout 4 mm\n<\/td>\nThinner walls need a machined or die-cast route\n<\/td><\/tr>
    \nMinimum order quantity\n<\/th>\n1 piece\n<\/td>\nNo pattern cost to amortise\n<\/td><\/tr><\/tbody><\/table><\/div>

    \nMachining, heat treatment, surface treatment and inspection all run in the same chain, so you receive a finished part rather than a raw casting. That includes CNC machining from 3-axis to 5-axis, and nine inspection methods with CMM and 3D scanning.\n<\/p><\/div><\/section>

    \n06\n<\/span>

    \nThe iron foundry behind every ductile iron casting\n<\/h2><\/div>

    \nDuctile iron is poured on our own iron and steel line, not bought in and resold. Composition, heat treatment and inspection all stay inside the same iron foundry, and the records ship with the casting.\n<\/p>