CN102268506B - Method for preparing nodular cast iron - Google Patents

Method for preparing nodular cast iron Download PDF

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Publication number
CN102268506B
CN102268506B CN 201110188339 CN201110188339A CN102268506B CN 102268506 B CN102268506 B CN 102268506B CN 201110188339 CN201110188339 CN 201110188339 CN 201110188339 A CN201110188339 A CN 201110188339A CN 102268506 B CN102268506 B CN 102268506B
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cast iron
melting
nodular cast
spheroidal graphite
graphite cast
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CN102268506A (en
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张海鸥
胡双锋
王桂兰
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Huazhong University of Science and Technology
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Huazhong University of Science and Technology
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Abstract

The invention discloses a method for preparing nodular cast iron, which comprises the following steps: firstly determining chemical components and a mass ratio of each chemical component according the components and a mass ratio of each component of the nodular cast iron to be prepared so as to obtain raw materials, wherein the carbon element in the used raw materials is in a form of granular graphite, and the dimension grade equals the dimension grade of the graphite in the nodular cast iron to be prepared; then melting the raw materials in the presence of a protective medium or in vacuum environment, and cooling to obtain the nodular cast iron. The invention avoids the characteristics of excessive intermediate treatment processes and strict process parameter control in traditional preparation processes, overcomes the defects of low nodulizing grade and non-uniform spheroidal graphite distribution in melting processes of nodular cast iron, reaches nodularity of above 90%, and obtains a nodular cast iron material with uniform distribution.

Description

A kind of method for preparing spheroidal graphite cast iron
Technical field
The present invention relates to the preparation method of spheroidal graphite cast iron, particularly adopt beam (such as laser beam, electron beam, plasma beam, welding machine arc) thermal source melting to prepare the method for spheroidal graphite cast iron.
Background technology
Spheroidal graphite cast iron has preferably mechanical property because its carbon is spherical in cast iron, thereby its application is very extensive.
Traditional spheroidal graphite cast iron smelting preparation process is as follows:
According to the chemical composition of spheroidal graphite cast iron with the shared mass ratio of each composition, select starting material.General starting material comprise the pig iron, steel scrap, coke, sweetening agent, nodulizing agent, carburelant, pretreating agent etc.
2. the melting of material, concrete melting technology process is as follows:
1) main raw material fusing obtains iron liquid, comprises the pig iron, useless soft steel material etc.
2) pre-treatment, specific practice are to utilize the method that adds pretreating agent in the stove to improve the metallurgical performance of iron liquid before the liquid that taps a blast furnace.For example add main take barium as the master, take lanthanum as auxiliary pretreating agent.
3) spheroidizing is adopted before coming out of the stove through pretreated iron liquid and (is poured method as in wrapping) someway and add nodulizing agent (such as magnesium ferro-silicon or rare elements nodulizing agent), and the graphite glomeration of crystallization is separated out.
4) inoculation after nodulizing agent adds, adds nucleating agent (such as gallium, aluminium, ferrosilicon nucleating agent) again and carries out inoculation.Prevent because of the adding of nodulizing agent so that the super cooling tendency of spheroidal graphite cast iron increases, thereby reduce separating out of carbide, promote to separate out a large amount of tiny and graphite pebbless of rounding.
5) demoulding of cast iron materials and aftertreatment.
Summary of the invention
The object of the present invention is to provide a kind of method for preparing spheroidal graphite cast iron, the method has been avoided the characteristics that intermediate treatment technique is many, process parameter control is strict in above-mentioned traditional preparation process, overcome in the spheroidal graphite cast iron fusion process nodulizing grade not high, the defective of spheroidal graphite skewness.
A kind of method for preparing spheroidal graphite cast iron provided by the invention the steps include:
The 1st step material choice:
According to the composition of spheroidal graphite cast iron to be prepared and the mass ratio of each constituent mass ratio-dependent chemical composition and each chemical composition, and the carbon in the employed raw material exists with the form of granular graphite, and its size grades equals the size grades of graphite in the spheroidal graphite cast iron to be prepared, obtains raw material;
The raw material melting of the 2nd step:
Under protective medium or vacuum environment, raw material is carried out melting, afterwards cooling obtains spheroidal graphite cast iron.
The present invention only need to be according to the selected suitable granular graphite of the size grades (GB9441-88) of graphite in the spheroidal graphite cast iron, remaining composition is by elemental composition in the spheroidal graphite cast iron and mass ratio requirement apolegamy, then according to the characteristics melting raw material of beam thermal source, can obtain the nodularization rate and reach more than 90%, the ductile cast iron material that is evenly distributed.Compared with prior art, present method has following features:
1, the size grades of granular graphite has determined the size grades of graphite in the spheroidal graphite cast iron to be prepared substantially in the starting material.
2, adopt in the beam thermal source melting preparation process, preparation process is once finished, there is not intermediate treatment technique, the series of process such as pre-treatment in traditional spheroidal graphite cast iron melting preparation process, spheroidizing and inoculation have been avoided, and the strict characteristics of process parameter control in the fusion process have been overcome, avoided simultaneously traditional spheroidal graphite cast iron melting preparation process Raw component to divide different time, the characteristics that the differing temps section adds.
3, starting material are selected according to the desired material composition of spheroidal graphite cast iron to be prepared, the melting preparation process is once finished, do not need pretreating agent, nodulizing agent and nucleating agent etc., the characteristics of the nodulizing agent of having avoided in the fusion process needing selection to adapt owing to the ductile cast iron material composition is different, nucleating agent, pretreating agent.
Description of drawings
Fig. 1 is the metallograph (x100) of ductile Ni-resist cast iron;
Fig. 2 is the metallograph (x100) of spheroidal graphite cast iron;
Fig. 3 is the metallograph (x100) of spheroidal graphite cast iron.
Embodiment
A kind of method for preparing spheroidal graphite cast iron provided by the present invention the steps include:
1) selection of raw material: 2 foundations are arranged, 1. according to the composition of spheroidal graphite cast iron to be prepared and the mass ratio of each constituent mass ratio-dependent chemical composition and each chemical composition; 2. the inventive method is applicable to prepare various spheroidal graphite cast iron, but require the carbon in the employed raw material to exist with the form of granular graphite, simultaneously, according to the size grades requirement of graphite in the spheroidal graphite cast iron to be prepared, then select the granular graphite of suitable size in the starting material.
Usually, material choice powder or particulate material, especially with laser beam, electron beam, plasma beam etc. during as thermal source, but with welding machine as thermal source, need and will make a material after the material choice.
2) melting of raw material: under protective medium (shielding gas, solder flux etc.) or vacuum environment, the raw material of selecting is carried out melting, afterwards cooling obtains spheroidal graphite cast iron.
Be exemplified below:
When I. selecting welding machine that thermal source is provided, as selecting submerged arc welding machine, then select the solder flux protection that adapts with welding wire; As when selecting the MIG/MAG welding machine, adopt argon shield, select parameter such as voltage, electric current, wire feed rate etc. to carry out melting according to the diameter of welding wire afterwards.
II. select laser beam that thermal source is provided, then select argon gas or nitrogen protection or adopt vacuum environment, then set power, the parameters such as scan mode and speed are carried out melting.
III. select electron beam that thermal source is provided, then select vacuum environment, set acceleration voltage, line, and initialization height and the correlation parameters such as surface sweeping mode, speed and frequency carry out melting.
IV. select plasma beam that thermal source is provided, need to select argon shield, according to the powdered material composition, select corresponding argon flow amount, electric current, voltage and water coolant arrange etc. and to carry out melting.
The inventive method does not have special requirement to the technological process of melting itself, can be according to the thermal source of selecting, adopt existing or other processing method is carried out melting to raw material.
Example 1: adopt the MIG welding machine to prepare the ductile Ni-resist cast iron that graphite pebbles is 6 grades (GB9441-88)
Each composition and the proportioning of pressing in the table 1 are made welding wire; Wherein carbon was selected 400 mesh sieve graphite; employing has the MIG welding machine of argon shield; welding wire is carried out melting; its processing parameter is: under the protective atmosphere of 12 liter/mins of clock argon gas; setting weldingvoltage is 30 volts, and electric current is 300 amperes, and wire feed rate is 35 m/hs; the melting diameter is 2.0 millimeters welding wires, cooling.
With the material after the cooling, metallographicobservation obtains photo as shown in Figure 1, and according to the nodularization classification (GB9941-88) of graphite, spheroidization of graphite grade and graphite stepped diameter are 6 grades among the present invention, and the mechanical property that test obtains is as shown in table 2.
Table 1 chemical composition
Table 2 mechanical property
Tensile strength/MPa Yield strength/MPa Elongation (%) Hardness (10/3000) HB
≥345 ≥207 12 ≤240
Example 2: it is 8 grades spheroidal graphite cast iron that the melting of using plasma arc thermal source prepares graphite pebbles
(1) raw-material selection: with 200 order iron powders and 4000 order Graphite Powder 99s in mass ratio example mix oven dry at 16: 4.
(2) utilize the melting of plasma transferred arc thermal source; setup parameter is as follows: under the argon gas atmosphere protection of 12 liter/mins of clocks; setting voltage is 32V; electric current is 350 amperes; adopt the powder feed rate of 5 gram/minute; the metallographic that cooling obtains after the melting of plasma arcs thermal source as shown in Figure 2, according to the nodularization classification (GB9941-88) of graphite, spheroidization of graphite grade and graphite stepped diameter are 8 grades among the present invention.
Example 3: adopting the melting of laser beam thermal source to prepare graphite pebbles is 8 grades spheroidal graphite cast iron
With 200 order iron powders and 4000 order Graphite Powder 99s in mass ratio example mix at 16: 4, oven dry is sent into Processing Room later, under the environment of vacuum, adopting sweep velocity is 2.5 mm/second, and laser power is 1 kilowatt, the melting raw material, obtain spheroidal graphite cast iron after the cooling, as shown in Figure 3.
The present invention not only is confined to above-mentioned embodiment; persons skilled in the art are according to content disclosed by the invention; can adopt other multiple embodiment to implement the present invention; therefore; every employing project organization of the present invention and thinking; do some simple designs that change or change, all fall into the scope of protection of the invention.

Claims (1)

1. a method for preparing spheroidal graphite cast iron the steps include:
The 1st step material choice:
According to the composition of spheroidal graphite cast iron to be prepared and the mass ratio of each constituent mass ratio-dependent chemical composition and each chemical composition, and the carbon in the employed raw material exists with the form of granular graphite, and its size grades equals the size grades of graphite in the spheroidal graphite cast iron to be prepared, obtains raw material;
The raw material melting of the 2nd step:
Under protective medium or vacuum environment, adopt the beam thermal source to carry out melting to raw material, afterwards cooling obtains spheroidal graphite cast iron, and the melting preparation process is once finished, and does not have intermediate treatment technique, does not need pretreating agent, nodulizing agent and nucleating agent.
CN 201110188339 2011-07-06 2011-07-06 Method for preparing nodular cast iron Active CN102268506B (en)

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Families Citing this family (5)

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Publication number Priority date Publication date Assignee Title
CN103820704B (en) * 2012-11-19 2016-08-17 天津新伟祥工业有限公司 Form in High Nickel Austenite Nodular Cast Iron material of vehicle turbine housing and preparation method thereof
CN104451020A (en) * 2013-09-12 2015-03-25 杨长国 Technology for producing spheroidal graphite cast iron
CN106021860A (en) * 2016-05-09 2016-10-12 哈尔滨理工大学 A nodular cast iron base iron metallurgical state comprehensive evaluation method
CN108213428A (en) * 2018-01-11 2018-06-29 昆明理工大学 A kind of method that 3D printing prepares vermicular graphite iron material
CN108642368B (en) * 2018-04-27 2020-06-19 武汉理工大学 As-cast high-toughness synthetic nodular cast iron QT800-5 and preparation method thereof

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CN1792513A (en) * 2005-12-28 2006-06-28 华中科技大学 Method for mouldless directly mfg. of parts and mould
CN101177769A (en) * 2007-10-30 2008-05-14 华中科技大学 Plasma spraying direct rapid manufacturing method for mushy material
CN101255524A (en) * 2007-12-22 2008-09-03 繁昌县金贸铸造有限责任公司 Method for producing nodular graphite cast iron
CN101362272A (en) * 2008-09-17 2009-02-11 华中科技大学 No-mold fusion stacking manufacture method of parts or mold
CN101671754A (en) * 2009-10-09 2010-03-17 青特集团有限公司 Method for smelting ductile cast iron

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