PL212743B1 - Cast iron with flake graphite - Google Patents

Description

The subject of the invention is cast iron with flake graphite, especially for castings with various wall thicknesses.

Known from the literature and subject to ASTM A 48, GOST 1412, BS 1452 and EN 1561 standards, cast iron with flake graphite has the following chemical composition: 2.5 - 3.7% C, 1.2 - 2.6% Si, 0.5 - 1.1% Mn, max. 0.3% P, max. 0.15% S, the rest Fe, is characterized in that the mechanical properties in castings decrease with an increase in the value of the eutectic carbon equivalent and with an increase in the thickness of the casting walls. It is related to the increase in the amount of separated graphite and the enlargement of its size. Moreover, the cooling rate decreasing with the increase of wall thickness causes the increase of ferrite fraction in the metal matrix of cast iron, lowering the hardness. For example, cast iron with flake graphite with a CE carbon equivalent of 3.6 to 3.8%, with a 30 mm diameter ingot having a strength of 300 MPa and a hardness of 230 HB, with a 120 mm diameter ingot having a strength below 220 MPa and a hardness about 190 HB. On the other hand, cast iron with a carbon equivalent value ranging from 4.2 to 4.4%, showing a strength of 150 MPa in an ingot with a diameter of 30 mm and a hardness of 160 HB, in an ingot with a diameter of 120 mm, it has a strength of about 120 MPa and a hardness of 125 HB.

The cast iron with flake graphite according to the invention contains 2.5 e 4.5% C by weight, 1.5 e 5.0% Si, max. 1.0% Mn, max. 1.5% P, max. 0.40% S and the total content of% Cu +% Ni +% Cr +% V +% Mo +% Sn <2.0%, the rest is Fe, with the CE value <4.3%, S content> 0, 13% X (% CE - 2), and for CE> 4.3%, the content of S = 0.3 e 0.4%, where CE =% C + 0.31% Si + 0.33% P.

Cast iron with flake graphite, according to the invention, is characterized by the fact that its mechanical properties hardly change with the change of the cooling rate, which makes it possible to use this cast iron to make a casting with various wall thicknesses. This advantageous property of cast iron has been achieved by adjusting the sulfur content to the value of the eutectic carbon equivalent, which means that the size of the graphite flakes does not increase with a decrease in the cooling rate, and the cast iron matrix structure remains pearlitic.

Examples of the composition of cast iron with flake graphite according to the invention.

P r z k ł a d I

Cast iron with flake graphite with a composition of 3.30% C, 2.20% Si, 0.22% Mn, 0.03% P, 0.29% S, the rest Fe, with a CE value = 3.99%, after casting for sand molds has the following mechanical properties:

- in the ingot φ 30 mm: R _m = 313 MPa, hardness = 235 HB,

- in ingot φ 120 mm: R _m = 303 MPa, hardness = 230 HB.

P r z k ł a d No.

Cast iron with flake graphite with the composition of 3.64% C, 2.30% Si, 0.12% Mn, 0.04% P, 0.37% S, the rest Fe, with the CE value = 4.37%, after casting has the following mechanical properties:

- in ingot φ 30 mm: Rm = 262 MPa, hardness = 229 HB,

- in the ingot φ 40 mm: Rm = 251 MPa, hardness = 223 HB.

Cast iron with flake graphite, according to the invention, is used for making castings with walls of different thickness.

Claims (1)

Cast iron with flake graphite containing C, Si, Mn, P, S and Fe, characterized in that it contains 2.5 e 4.5% by weight of C, 1.5 e 5.0% Si, max 1.0% Mn, max. 1.5% P, max. 0.40% S and the total content% Cu +% Ni +% Cr +% V +% Mo +% S n <2.0%, the rest is Fe, with the CE value <4.3%, S content> 0 , 13 x (% CE - 2), and for CE> 4.3%, the S content is 0.3 e 0.4%, where CE =% C + 0.31% Si + 0.33% P.