CN104372235A - Nodular cast iron and manufacturing method thereof - Google Patents

Abstract

The invention discloses a nodular cast iron and manufacturing method thereof, relates to the technical field of cast iron, and in particular relates to a high-strength high-tenacity nodular cast iron. The manufacturing method comprises the following steps: reasonably selecting raw materials as follows: 3.3-3.8% of C, 2.3-2.7% of Si, not more than 0.40% of Mn, not more than 0.10% of P, not more than 0.035% of S, not more than 0.035-0.050% of Mg, not more than 0.02-0.04% of RE and the balance of molten iron, changing solidification mode of the nodular cast iron through composite late inoculation, and then obtaining high-strength or high tenacity nodular cast iron as cast condition without performing normalizing or annealing heat treatment, thus saving a mass of heat treatment cost. Parts which are of complex shapes, having multiple thermal centers and made of cast steel material can be replaced, the process yield is improved, the heat treatment is unnecessary, and the production cost is greatly lowered.

Description

A kind of spheroidal graphite cast iron and preparation method thereof

Technical field

the present invention relates to casting iron technology field, particularly relate to a kind of high-strong toughness nodular cast iron.

Background technology

Spheroidal graphite cast iron obtains globular graphite by nodularization and inoculation, and it improves the mechanical property of cast iron effectively, in particular improves plasticity and toughness, thus obtains the intensity also higher than carbon steel.Spheroidal graphite cast iron is 20th century a kind of meehanite cast iron materials of growing up of the fifties, and its over-all properties, close to steel, just based on the performance of its excellence, has been successfully used to cast some stressed complexity, and intensity, toughness, wear resistance require higher part.Spheroidal graphite cast iron developed rapidly for be only second to graphitic cast iron, application cast iron materials very widely.

As can be seen from the national standard of nodular cast iron: along with the rising of tensile strength, it is very fast that elongation declines, and when tensile strength is greater than more than 600MPa, need carries out normalizing thermal treatment and could to obtain and elongation is still very low.

Summary of the invention

Order of the present invention is to provide a kind of high-strong toughness nodular cast iron.

The technical solution used in the present invention is:

Carbon is graphite element, can affect basic content again simultaneously, choose C:3.3-3.8%;

Silicon is also graphite element, and its graphitizability is equivalent to 1/3 of carbon, chooses Si:2.3-2.7%;

Can there is segregation in manganese, wish that content is more low better, choose Mn≤0.40% in process of setting;

Phosphorus can produce segregation in process of setting, for the tough nodular cast iron of height, and P≤0.10%;

In order to ensure that nodularization is stablized, reduce slag inclusion, the defects such as subsurface porosity, S≤0.035%;

Ensureing the addition that should reduce rare earth and magnesium under the condition that nodularization is qualified as possible, control Mg≤0.035-0.050%, RE≤0.02-0.04%;

Surplus is molten iron.

Making step:

A, select 500kg middle frequency furnace to carry out melting, adopt pure soft steel and carry out carburetting by the carburelant that carbon content is greater than 99% and make base iron, turn off power supply when base iron rises to 1550 DEG C and leave standstill and carry out 3 slag making process;

B, use temperature measurer thermometric, base iron temperature controls evolution spheroidizing 1460 DEG C-1500 DEG C time, adds the FeSimg6RE2 that parts by weight are molten iron 0.7%, stirs 10-15 minute;

C, add the FeSimg6RE2 that parts by weight are molten iron 0.3%, stir 20-25 minute;

D, add that parts by weight are molten iron about 0.3% 75SIFE, parts by weight are molten iron about 0.1% 75SiBa, parts by weight are molten iron about 0.1% 75SiBa, stir 30-35 minute;

The present invention adopts Si-Ba-Ca alloy compound late inoculation technology to obtain as cast condition tensile strength To >=600MPa, the high-strong toughness nodular cast iron of elongation >=10%, tensile strength and yield strength ratio routine breed raising about 30%, elongation improves about 45%, hardness improves about 15%, make to be that magic ball becomes tiny with stream compound late inoculation, unit is whole and be evenly distributed, the effect of isolating of matrix is reduced greatly, the utilization ratio of matrix is promoted greatly, compound late inoculation changes the solidification mode of nodular cast iron, as cast condition the nodular cast iron of high strength or high tenacity can be obtained without the need to carrying out normalizing or annealing thermal treatment, save a large amount of thermal treatment expenses.Alternative complex-shaped, the part of the cast steel that thermal center is many, both improve product yield, again without the need to thermal treatment, greatly reduced production cost.

Embodiment

Choose: C:3.3-3.8%, Si:2.3-2.7%, Mn≤0.40%, P≤0.10%, S≤0.035%, Mg≤0.035-0.050%, RE≤0.02-0.04%, surplus are molten iron.

A, select 500kg middle frequency furnace to carry out melting, adopt pure soft steel and carry out carburetting by the carburelant that carbon content is greater than 99% and make base iron, turn off power supply when base iron rises to 1550 DEG C and leave standstill and carry out 3 slag making process;

B, use temperature measurer thermometric, base iron temperature controls evolution spheroidizing 1460 DEG C-1500 DEG C time, adds the FeSimg6RE2 that parts by weight are molten iron 0.7%, stirs 10-15 minute;

C, add the FeSimg6RE2 that parts by weight are molten iron 0.3%, stir 20-25 minute;

D, add that parts by weight are molten iron about 0.3% 75SIFE, parts by weight are molten iron about 0.1% 75SiBa, parts by weight are molten iron about 0.1% 75SiBa, stir 30-35 minute.

Claims (2)

1. a spheroidal graphite cast iron, is characterized in that, it contains with mass ratio:

C:3.3-3.8%, Si:2.3-2.7%, Mn≤0.40%, P≤0.10%, S≤0.035%, Mg≤0.035-0.050%, RE≤0.02-0.04%, surplus are molten iron.

2. a making method for spheroidal graphite cast iron, is characterized in that, making step is as follows:

A, select 500kg middle frequency furnace to carry out melting, adopt pure soft steel and carry out carburetting by the carburelant that carbon content is greater than 99% and make base iron, turn off power supply when base iron rises to 1550 DEG C and leave standstill and carry out 3 slag making process;

B, use temperature measurer thermometric, base iron temperature controls evolution spheroidizing 1460 DEG C-1500 DEG C time, adds the FeSimg6RE2 that parts by weight are molten iron 0.7%, stirs 10-15 minute;

C, add the FeSimg6RE2 that parts by weight are molten iron 0.3%, stir 20-25 minute;

D, add that parts by weight are molten iron about 0.3% 75SIFE, parts by weight are molten iron about 0.1% 75SiBa, parts by weight are molten iron about 0.1% 75SiBa, stir 30-35 minute.