CN1575888A

CN1575888A - Treatment method for improving iron casting frozen tissue

Info

Publication number: CN1575888A
Application number: CN 03128849
Authority: CN
Inventors: 翟启杰; 范金辉; 陈宇; 富知愚; 华勤; 李仁兴; 侯旭; 李祖齐
Original assignee: University of Shanghai for Science and Technology
Current assignee: Shanghai University; University of Shanghai for Science and Technology
Priority date: 2003-05-27
Filing date: 2003-05-27
Publication date: 2005-02-09

Abstract

The cast iron solidifying structure improving method features that to grey cast iron with carbon equivalent of 2.5-5.0 %, pulse current is led in before and during cast iron solidification while the cast iron temperature is 1000 deg.c to 1500 deg.c. The pulse current parameters includes pulse frequency of 0.1-10000 Hz, pulse voltage of 50-5000 V, and pulse current peak value of 400-100,000 A. The current may be led into the crucible or ladle or in the cast mold.

Description

A kind of processing method of improving cast iron solidified structure

Technical field

The present invention relates to a kind of processing method of improving cast iron solidified structure, belong to field of metal material heat processing technology.

Background technology

Cast iron solidified structure form for a change, obtain the graphite of even refinement, prevent that simultaneously spoken parts in traditional operas from appearring in cast iron, the major measure of taking in foundry goods or strand production process both at home and abroad has three kinds at present: the one, and chemical method promptly adds chemical substances such as ferrosilicon, rare earth or magnesium, to reach the purpose of inoculation, spheroidising or wriggling processing in cast iron solidified forward direction iron liquid, make cast iron avoid occurring spoken parts in traditional operas, indigenous graphite is evenly tiny, perhaps changes graphite form, makes graphite be spherical or vermiform.These materials are by changing the thermodynamics and kinetics condition of growth of graphite when cast iron solidified, thereby reach the purpose that changes its form.The outstanding problem of this method is to add chemical substance can form flue gas and high light in the interpolation process, and environment is caused very big pollution.In addition, add material and also can itself pollute, influenced the reuse of material, thereby increased the carrying capacity of environment of material iron liquid.Another kind is the thermal conduction study method, comprises improving cooling velocity and control pouring temperature.The raising of cooling velocity makes liquid metals obtain big degree of supercooling, nucleation rate increases, and makes austenite dendrites and eutectic cell refinement, but for thick big strand of section and foundry goods, often be difficult to improve its inner cooling velocity, particularly cooling also can produce defectives such as internal stress, spoken parts in traditional operas fast.The control pouring temperature often is subjected to the restriction of working condition, though and this method the refinement of solidified structure is had certain effect, the effect aspect change solidified structure form is but very limited.The third method is a dynamic method, refers to adopt means such as mechanical agitation and electromagnetic agitation, impels that dendrite fractures, fragmentation, and crystal grain quantity is increased, and size reduces.This method also is a kind of processing method of environment-friendly type, and is significantly not enough but this method exists.At first, compare with common clotting method, this method does not make the nucleation rate of nucleus take place significantly to change, so refining effect is not clearly.Secondly, strong agitation is stirred molten metal up and down, so also is easy to be involved in air and other some oxide inclusions, and molten metal is just inevitably polluted.Have again, stir the restriction be subjected to its stirring intensity, neither be too desirable to the effect of the homogenising of temperature field and composition.Particularly continuous casting facts have proved, strong stirring can make strand cause banded segregation.

Summary of the invention

The purpose of this invention is to provide a kind of environment-friendly type and improve the processing method of cast iron solidified structure, just make ironcasting in process of setting, change the processing method of graphite form.

A kind of processing method of improving cast iron solidified structure of the present invention, it is characterized in that: for the casting pig of carbon equivalent at 2.5-5.0%, before cast iron solidified or in the process of setting, feed pulse current, it is 1200-1500 ℃ that cast iron begins treatment temperature, when temperature was reduced to 1000 ℃, cast iron solidified finishing stopped energising and handles; The parameter of its pulse current is: pulse frequency 0.1-10000Hz, pulse voltage U are 50-5000V, and pulse current peak I is 400-100000A; Energising can be carried out in crucible or casting ladle, also can carry out in the casting mold after cast.

The most significant advantage of the inventive method and effect are: it is a kind of environment-friendly type processing method of green non-pollution for (1).(2) technological operation is simple and convenient, be not subjected to the influence of foundry goods and strand size and shape, (3) the pulse current processing cost is cheap, energy savings, (4) ironcasting after the inventive method is handled, obvious refinement of its solidified structure and homogenising, thus the serviceability of ironcasting improved, have positive effect.

The specific embodiment

Embodiment one: smelting iron liquid is carried out sand casting, pour into the cylindrical iron staff of φ 50 * 200mm.The pulse current processing is carried out to it in the cast back in iron liquid process of setting, solidify until iron liquid to finish.

The composition of cast iron and content (percentage by weight) are: C 4.10%, and Si 1.92%, and Mn 0.22%, P0.058%, and S 0.023%, and Fe surplus, the temperature that iron liquid begins to handle are 1250 ℃, when temperature is reduced to 1000 ℃, stop energising and handle; Its technological parameter is as follows: pulse frequency 0.8Hz, and output voltage U is 2000V, current strength I is 30000A.

Embodiment two: process of the test and embodiment one are identical, and the chemical composition of cast iron is also identical with content (percentage by weight).But adopted different technological parameters, its technological parameter is: pulse frequency 1000Hz, and output voltage U is 50V, current strength I is 800A.

Embodiment three: process of the test and embodiment one are identical, the composition of cast iron and content (percentage by weight) are: C 3.58%, Si1.60%, Mn 0.18%, and P 0.045%, and S 0.020%, the Fe surplus, the temperature that iron liquid begins to handle is 1250 ℃, when temperature is reduced to 1000 ℃, stops energising and handles; Its technological parameter is as follows: pulse frequency 0.1Hz, and output voltage U is 5000V, current strength I is 100000A.

Embodiment four: process of the test and embodiment one are identical, and the chemical composition of cast iron is identical with embodiment three with content (percentage by weight).The temperature that iron liquid begins to handle is 1250 ℃, when temperature is reduced to 1000 ℃, stops energising and handles; Its technological parameter is as follows: pulse frequency 10000Hz, and output voltage U is 60V, current strength I is 400A.

More than four embodiment, foundry goods after promptly handling through pulse current, through its solidified structure of crystalline phase microscopic examination, the graphite that can see in the cast iron has become tiny bulk, sheet even point-like by original thick bulk, perhaps the wedge angle rust present approximate vermiform or spherical, and Graphite Distribution is more even, in addition, the mechanical strength of foundry goods has had tangible improvement.

Claims

1. processing method of improving cast iron solidified structure, it is characterized in that: for the casting pig of carbon equivalent at 2.5-5.0%, before cast iron solidified or in the process of setting, feed pulse current, it is 1250 ℃ that cast iron begins treatment temperature, when temperature was reduced to 1000 ℃, cast iron solidified finishing stopped energising and handles; The parameter of its pulsed magnetic field is: pulse frequency 0.1.-10000Hz, pulse voltage U are 50-5000V, and pulse current peak I is 400-100000A; Energising can be carried out in crucible or casting ladle, also can carry out in the casting mold after cast.