Gray cast iron - properties, features and application

Gray cast iron - what are its properties, features and application?

Cast iron is the most numerous group of foundry iron alloys (Fe). These are, to be more precise, alloys of iron and carbon, in which the carbon content is above 2%, with a maximum content ranging from 3.8% to 6.7%. Today we will discuss another type of cast iron: a gray cast iron.

If you want to learn more about cast iron in general, its properties and applications, check out our article What are the differences between cast iron and cast steel?

In this article you will learn:

  • what gray cast iron is,
  • what are the chemical composition, grades and types of this alloy,
  • how this type of cast iron is made,
  • what are the mechanical properties of this alloy,
  • where is it used,
  • what are the advantages and disadvantages of this alloy.

Grey cast iron

Gray cast iron is an alloy of iron with lamellar graphite (EN-GJL). This alloy owes its name to the dark gray color occurring in the fracture, caused by the presence of graphite.

It is considered to be of higher quality than white cast iron, because it is more ductile, easier to machine, has good castability and has lower casting shrinkage (around 1.0%) than white cast iron. 

A particular advantage of it is its economic nature: namely the low cost of production. 

What is the chemical composition of gray cast iron?

Gray cast iron is an alloy in which carbon is present in the so-called free form. Graphite, metallic matrix and added elements containing phosphorus and sulfur are the main components of the structure of gray cast irons.

Gray cast iron grades

The properties of gray cast irons are distinguished not only by the structure of the metallic matrix, but also by the form of graphite itself. We wrote about it in the article Ductile iron - properties, features and application.

Depending on the amount of bound carbon in gray cast iron, we divide them into:

  • ferritic, in which almost all the carbon contained in the alloy is in the form of graphite,
  • pearlitic-ferritic - the structure of which consists of ferrite, pearlite and graphite precipitates, and the amount of bound carbon content is less than 0.77%,
  • pearlitic, the structure of which is formed by perlite with graphite secretions. Pearlite contains 0.77% C, so in pearlitic cast iron the amount of bound carbon is 0.77%. The rest of the carbon occurs there in a free state, i.e. in the form of graphite,
  • hyperperlite (variegated) in the structure, next to graphite and perlite, it also contains cement.

Types of gray cast iron

Within the group of this alloys, its different grades are distinguished, being classified on the basis of tensile strength and ability to elongate, for example:

  • EN-GJL-250 which is distinguished by low production cost and good casting properties. It also has e.g. good machinability and machinability as well as high vibration damping capacity.

Properties of gray cast iron

The basis for dividing cast irons into different classifications is their tensile strength. The compressive strength of this type of cast iron is about 4 times greater than the tensile strength, and the elongation does not exceed over 1%.

Good machinability and workability of this alloy allows it to be used for the production of castings with thin-walled contours, often distinguished by a complicated form.

Its greatest advantages are:

  • vibration absorption, 
  • good castability,
  • low casting shrinkage of 1.0%

However, it has lower resistance to corrosion and abrasion than, for example, ductile iron.

Gray cast iron - advantages and disadvantages

We have summarized the advantages and disadvantages of this alloy in the following table:

advantages disadvantages 
good machinability it is not very plastic, has low bending and tensile strength
helps dampen vibrations low strength
it increases sliding properties low resistance to abrasion and corrosion in chemical enviroment
improves fatigue strength worse mechanical properties than ductile iron
has good compressive strength
low production cost

Where is gray cast iron used - applications

It is used in various environments, which are amongst others:

  • for the production of castings that do not carry loads, such as grates, doors and stove plates, bathtubs, sinks or radiators,
  • automotive industry (cylinders, ingot molds, pistons and machine parts),
  • industrial elements,
  • garden furniture,
  • benches,
  • railway and automotive industry (machine bodies, brake drums).

Need help choosing casting materials? Write to us.

Do you want to order castings from professionals? Check our offer.

Masz pytania? 
Nasza oferta wydaje Ci się ciekawa i chcesz dowiedzieć się czegoś więcej? Zadzwoń lub jeśli wolisz napisz do nas w formularzu.

Chcesz wiedzieć więcej?

Zapisz się do naszego Newslettera, a raz w miesiącu otrzymasz od nas eksperckie treści, nowinki z branży odlewniczej i informacje o specjalnych ofertach.

Twoje dane są bezpieczne. Sprawdź jak przetwarzamy dane.

Zgoda 1 *
Zgoda 2 *
ENGIMETAL Sp. z o.o.
Odlewy z żeliwa szarego, żeliwa sferoidalnego, żeliwa stopowego, staliwa węglowego i stopowego, staliwa odpornego na korozję i ścieranie. Obróbka mechaniczna odlewów oraz metali z wykorzystaniem maszyn takich jak: tokarki, frezarki, wytaczarki, wiertarki i inne. Na życzenie klienta jesteśmy również w stanie pomalować odlewy natryskowo.
DANE KONTAKTOWE
NIP
682-17-97-221
REGON
521171681
KRS
0000956494
NUMER KONTA
02 1090 1665 0000 0001 4990 7276
ADRES
32-130 Koszyce, Książnice Małe
TELEFON
797 290 707
EMAIL
kontakt@odlewnictwo.pl
BIURO HANDLOWE
30-442 Kraków, ul. Zawiła 45
Prawa autorskie © 2022 Zakład odlewniczy Engimetal sp.z.o.o (dawniej Zakład odlewniczy Książnice Małe sp. z o.o.). Wszelkie prawa zastrzeżone. Odlewnia żeliwa Kraków | odlewnia staliwa Kraków

chevron-down