High-hardness gray cast iron and smelting method thereof

Abstract

The invention provides high-hardness gray cast iron and a smelting method thereof, and belongs to the field of smelting of molten metal for casting. The quality defect of a thick-wall gray cast iron piece caused by insufficient hardness of a gray cast iron piece is overcome. The gray cast iron is prepared from the chemical components in percentage by mass: 3.0-3.3% of carbon, 1.8-2.1% of silicon,0.7-1.0% of manganese, equal to or less than 0.05% of phosphorus, 0.08-0.12% of sulphur, 0.6-0.9% of copper, 0.5-0.7% of molybdenum, 1.4-1.6% of chrome, and the balance of iron, and of course, a traceamount of other impurities in the gray cast iron is not excluded; and the gray cast iron is smelted through the raw materials in percentage by mass: 3-3.5% of pig iron, 60-64% of steel scrap, 28-32%of organic iron, and 1.5-1.7% of silicon iron. By changing the proportion of the raw materials for smelting of the gray cast iron and adding alloys and through inoculation after smelting, the chemicalcomponents of the gray cast iron are reasonably controlled, thus the produced gray cast iron reaches the surface hardness being not lower than 240 HB, A-type graphite accounts for 99% or above, and no supercooled graphite is generated.

Description

technical field [0001] The invention relates to the technical field of casting, in particular to gray cast iron and its smelting method. Background technique [0002] Gray cast iron can be regarded as a matrix of carbon steel plus flake graphite. The mechanical properties of gray cast iron are related to the structure of the matrix and the morphology of graphite. The flake graphite in gray cast iron severely splits the matrix, and it is easy to cause stress concentration at the sharp corners of graphite, so that the tensile strength, plasticity and toughness of gray cast iron are far lower than steel, but the compressive strength is equivalent to steel, and it is also commonly used in cast iron. The cast iron with the worst mechanical properties in the parts. For gray iron parts with a wall thickness greater than 60mm, gray cast iron needs to have a certain hardness, which requires improvement of the standard gray cast iron material. Contents of the invention [0003] I...

AI Technical Summary

Problems solved by technology

The flake graphite in gray cast iron severely splits the matrix, and it is easy to cause stress concentration at the sharp corners of graphite, so that the tensile strength, plasticity and toughness of gray cast iron are far lower than steel, but the compressive strength is equivalent to steel, and it is also commonly used in cast iron. Cast iron with the worst mechanical properties in parts

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