CS271762B1 - Grey cast iron - Google Patents

Abstract

The grey cast iron contains apart from the iron in % by weight 2.90 to 3.65 % of carbon, 1.5 to 2.6 % of silicon, 0.02 to 0.5 % of phosphorus, 0.002 to 0.2 % of sulphur, 0.05 to 0.2 of chromium, 0.2 to 0.9 % of manganese. The principle of the solution is the fact that it also contains 0.002 to 0.2 % of antimony, 0.10 to 2.5 % of copper, 0.002 to 0.30 % of tin and 0.001 to 1.85 % of aluminium.The grey cast iron with the eutecticity degree of 0.95 has a tensile resistance up to 298 MPa with a hardness of 221 HN and the grey cast iron with eutecticity degree of 0.92 has tensile resistance of up to 340 MPa and a hardness of 221 HB maintaining good workability and a high thermal stability.

Description

(57) _ET i comprises cast iron with weight% X 2.90 to 3.65 carbon, 1.5 to 2.6% silicon, 0.02 to 0.5% phosphorus, 0.002 to 0.2 X S 0.05 to 0.2% chromium, 0.2 to 0.9% manganese. It further comprises 0.002 to 0.2% antimony, 0.10 to 2.5% copper, 0.002 to 0.30% tin and 0.001 to 1.85% aluminum.

Gray cast iron with a degree of eutecticity

0.95 has a tensile strength of up to 298 MPa at a hardness of 221 HN and gray cast iron with a degree of eutecticity of 0.92 exhibits a tensile strength of up to 340 MPa and a hardness of 221 HB with good machinability and high thermal stability.

27 1 762 Italy (11) (13) B 1 (51) Int. Cl. ⁵ C 22 C 37/00

81

The invention relates to gray cast iron, in particular with flake graphite suitable for castings with high mechanical properties and good machinability, while maintaining good casting properties.

Castings with these properties are currently produced from low, medium and high alloy cast iron, mainly based on alloys such as nickel, chromium, vanadium, molybdenum. However, these castings do not meet most of the requirements for economical production with the necessary utility properties of the final product. These gray cast iron are susceptible to the formation of some defects such as turbidity, which adversely affects the increase in scrap casting and hidden defects.

In some cases it also happens that a given type of casting needs to be heat treated, thereby increasing the energy consumption of the production of these parts. Even though they have high temperature or wear resistance, the disadvantage is the very worse machinability. Otherwise, with good machinability, the castings in turn exhibit lower mechanical properties, in some cases not exceeding 200 MPa, of tensile strength.

These deficiencies are eliminated by gray cast iron with flake graphite having a composition in weight percent other than iron 2.90 to 3.65 X carbon, 1.50 to 2.60% silicon, 0.02 to 0.50% phosphorus, 0.002 to 0.20 % of sulfur, 0.05 to 0.20 SS of chromium, 0.20 to 0.90 X of manganese, characterized in that it contains 0.002 to 0.20 X of antimony, 0.10 to 2.50 X of copper by weight, 0.002 to 0.30 X of tin and 0.001 to 1.85 X of aluminum.

The gray cast iron according to the invention outperforms the properties of standard gray graphite cast iron. According to various requirements, gray cast iron according to the invention can be produced with a tensile strength in the range of 255 to 350 MPa, with a permanent hardness at heat stress of 190 to 260 HB and good machinability. Castings made of these gray cast iron also have high wear resistance and good casting properties, where even high strength castings can be cast as well as with lower strength and runability of these gray cast iron with a movement of over 650 mm according to Curry spiral. The advantage of these gray cast iron is also the fact that in the thin parts of the casting there is no free cementite.

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

Gray iron according to the invention contains, in addition to iron, 3.45 X carbon, 2.38 X silicon, 0.50 X manganese, 0.10 X phosphorus, 0.04 X sulfur, 0.05 X antimony, 0.10 X chromium, 0.32 X copper, 0.10 X tin, 0.006 X aluminum. Tensile strength of gray cast iron 298 MPa, hardness 221 HB with good machinability and heat resistance. The structure of the base metal is pearlitic without free cementite.

The flake graphite cast iron according to the invention contains, in addition to iron, 3.32% by weight of carbon, 2.21 X of silicon, 0.52 X of manganese, 0.10 X of phosphorus, 0.05 X of sulfur,

0.06 X of chromium, 0.90 X of copper, 0.18 X of tin, 0.005 X of aluminum and 0.002 X of antimony. The tensile strength of this gray cast iron was 316 MPa with a hardness of 215 HB, good machinability and casting properties, ie without internal defects, and good running-in. The microstructure is pearlitic without loose cementite even in thin parts of the casting.

The flake graphite cast iron according to the invention contains, in addition to iron, 3.40 X carbon, 1.87 X silicon, 0.50% manganese, 0.09 X phosphorus, 0.03 X sulfur,

0.09 X of chromium, 0.31 X of copper, 0.009 X of aluminum, 0.09 X of tin and 0.002 X of antimony. The tensile strength was 342 MPa hardness 221 HB with good machinability and heat resistance. The microstructure was pearlitic without free cementite in all parts of the casting.

Claims (1)

SUBJECT OF THE INVENTION Gray iron contains, in addition to iron, 2% to 3.65% by weight of carbon, 1.50 to 2.60% of silicon, 0.02 to 0.50% of phosphorus, 0.002 to 0.20% of sulfur, 0.05 to 0.20% chromium, 0.20-0.90% manganese, characterized in that it contains 0.002-0.20% antimony, 0.10-2.50% copper, 0.002-0.30% tin in weight percent and 0.001 to 1.85% of aluminum.