Introduction: A clear guide to how QT400-18, EN-GJS-400-18, Gr60-40-18, and FCE 400-18 name the same ductile iron family in BOF lip ring castings.
A BOF lip ring casting can arrive on a drawing with a Chinese grade, a European grade, a US grade, or a Japanese grade, and the first reaction is often that these must be four different materials. In practice, the four callouts belong to the same ductile iron family, written in different standard systems. The useful question is not which name sounds stronger. It is what each name promises about strength and elongation, how the prefixes differ, and why the drawing, furnace dimensions, and service conditions still decide the finished lip ring. This grade map helps a learner read those callouts without turning them into false equivalents.
How Ductile Iron Grade Names Are Built
Ductile iron grade names are compact labels. They usually combine a system prefix, a strength number, and an elongation number. The prefix tells you which national or regional standard family the writer is using. The first number points to a tensile strength target. The second number points to a ductility target, normally elongation in a tensile test. That is why QT400-18 and EN-GJS-400-18 look related even when the letters differ. They are shorthand for a set of minimum properties that a casting should meet after the agreed production route. General materials-processing teaching on solidification and foundry course material on mold systems both help explain why the same grade can be produced through different foundry routes while still aiming at the same property window. A simple classroom exercise makes the point. Place four grade callouts beside one BOF lip ring drawing: QT400-18 from a Chinese project sheet, EN-GJS-400-18 from a European sheet, Gr60-40-18 from a US sheet, and FCE 400-18 from a Japanese sheet. The geometry is the same, the furnace interface is the same, and the drawing title block is the same. Only the standard language changes. Students quickly see that a grade name is a material callout inside a larger document set. The exercise is classroom practice, not a production test. It teaches the reading habit that matters: find the standard behind the letters before comparing the numbers.
Mapping QT400-18, EN-GJS-400-18, Gr60-40-18, and FCE 400-18
The four names map onto one ductile iron family through both prefix conventions and property numbers. International grade comparison resources often arrange ductile iron grades this way, because the underlying idea is a nodular graphite cast iron with a specified strength and elongation target. The mapping is useful for reading drawings, comparing project specifications, and understanding why a buyer in one country may recognize a grade that a buyer in another country reads as unfamiliar. The drawing remains the controlling document for the finished part, because the lip ring's dimensions are custom to the furnace and the exact chemistry and testing are set by the drawing and order.
1. QT and EN-GJS Names Use Different Prefix Systems
QT400-18 uses the Chinese prefix QT, a shorthand for ductile iron, followed by 400 and 18. EN-GJS-400-18 uses the European designation GJS for spheroidal graphite cast iron, with EN marking the European standard family. The letters look different because the naming systems grew in different technical languages. The property message is close: a 400 MPa tensile strength class with 18% elongation. Gr60-40-18 comes from the US customary system. There, 60 means 60 ksi tensile strength, 40 means 40 ksi yield strength, and 18 means 18% elongation. FCE 400-18, the Japanese entry in the same four-grade list, keeps the 400 and 18 pattern. A learner who reads only the letters may see four unrelated grades; a learner who reads the prefix and unit system sees four routes into the same ductile iron neighborhood.
2. The Numbers Describe Strength and Elongation Rather Than a Single Recipe
The numbers are property targets, not a complete production recipe. A 400 MPa tensile target and an 18% elongation target tell a foundry what the material must achieve in the agreed test condition. The Gr60-40-18 label adds a yield target because the US grade convention includes both tensile and yield strength. These numbers are the property conversation; the exact carbon equivalent, nodularity, heat treatment, pouring temperature, and section size of a specific lip ring come from foundry practice and from the drawing and order. This is why two castings can carry related grade names and still differ in section thickness, machining allowance, inspection plan, and service history. The grade name sets the material target, and the manufacturing document set controls the actual part.
Why a Grade Name Alone Does Not Define the Finished Lip Ring
A BOF lip ring is a shape, an interface, and a service part, not just a material label. It sits in a converter mouth environment where thermal cycling, slag exposure, gas flow, and fit with the vessel all matter. The grade family gives the designer a ductile iron option with useful strength and elongation, which supports thermal-fatigue resistance and structural reliability when the casting is designed and made well. That is the material side of the decision. The finished lip ring is still defined by the drawing. Dimensions are custom to the furnace. Wall thickness, flange faces, machining allowances, tolerances, and inspection points belong to the drawing and order, not to the grade name. The same applies to exact chemistry and testing: they are agreed project details that sit alongside the grade callout. The Tianyu converter mouth casting reference lists QT400-18, EN-GJS-400-18, Gr60-40-18, and FCE 400-18 as grade options and treats the dimensions as custom to the furnace. Read in that light, the grade map is a translation tool. It helps a learner recognize the material family, compare standard languages, and then return to the drawing and service conditions for the real engineering decision.
Conclusion
The four names belong together as a reading exercise, while the drawing remains the controlling document for each casting. QT400-18 and EN-GJS-400-18 speak in metric property targets, Gr60-40-18 uses US customary units, and FCE 400-18 keeps the same 400/18 pattern in its own standard language. Once the property meaning is clear, the drawing regains its proper place: it sets the furnace-specific geometry, the agreed chemistry and testing, and the service conditions the lip ring must survive. A reader who can move between grade name, standard family, and drawing context has the useful skill. The grade name starts the conversation; the finished casting is defined by the full project document. For a concrete example of the listed grade options, the Tianyu converter mouth casting reference is a useful next stop.
FAQ
Q: What does QT400-18 mean in a BOF lip ring casting?
A: In a BOF lip ring casting, QT400-18 is the Chinese ductile iron grade callout: QT marks ductile iron, 400 is the minimum tensile strength in MPa, and 18 is the minimum elongation in percent. It tells the supplier which property class the drawing expects, while the drawing and order still set dimensions, exact chemistry, and testing.
Q: Are QT400-18, EN-GJS-400-18, and Gr60-40-18 equivalent grades?
A: They are equivalent in property intent, not identical in every acceptance detail. QT400-18 and EN-GJS-400-18 use metric targets of 400 MPa tensile and 18% elongation, while Gr60-40-18 uses US units of 60 ksi tensile, 40 ksi yield, and 18% elongation. A project can treat them as comparable ductile iron grades when the drawing and order name the governing standard and acceptance tests.
Q: Why can the same casting use different grade names in different countries?
A: The same casting can carry different grade names because countries and project owners use different standard systems. A Chinese drawing may call out QT400-18, a European drawing EN-GJS-400-18, a US drawing Gr60-40-18, and a Japanese drawing FCE 400-18. The names help suppliers and engineers map the material family; the drawing and order keep the final geometry, chemistry, and testing tied to one project.
Sources / References
Stress Corrosion Cracked Welds NiCrMo Steel | Total Materia
Materials Processing | Materials Science and Engineering | MIT OpenCourseWare
NPTEL: Advanced Foundry Technologies and Mold Systems
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