Production method of toughness nodular cast iron

A technology of ductile iron and a production method, applied in the field of foundry processing, can solve the problems of low forming efficiency, high production cost, reducing the carbon and silicon equivalent of cast iron, etc., and achieves improved fatigue resistance and wear resistance, improved structural strength and toughness, The effect of reducing internal stress concentration

Inactive Publication Date: 2018-06-29

WUHU JINMAO FLUID TECH CO LTD

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AI-Extracted Technical Summary

Problems solved by technology

[0002] The furnace charge for the production of ductile iron is generally composed of newborn iron, returned ductile iron and ferroalloy. Scrap steel is rarely used in the furnace charge. In some factories, a small amount of scrap steel is added to the furnace charge to purify the molten iron and improve the purity of the molten iron. The mechanical properties of scrap steel in the charge are generally 0-10% by weight, which reduces the carbon content in molten iron, thereby reducing the carbon-silicon equivalent of cast iron, affecting the spheroidization rate and spheroidization grade of graphite, and resulting in The service performanc...

Abstract

The invention relates to a production method of toughness nodular cast iron, which includes four steps of: mixing and smelting raw materials, performing metamorphic modification, performing modification and tempering, and performing tempering thermal treatment. In the invention, on one hand, by means of rare earth, the nodular cast iron which has uniform and continuous distribution and high hardness and is not reduced in ductility, is produced, wherein the structural strength and toughness of the nodular cast iron work piece are greatly improved; on the other hand, through metamorphic treatment, anti-fatigue performance and wear resistance of the nodular cast iron work piece are comprehensively improved; besides, by means of the casting method, defects, such as internal stress concentration, cracks and sand holes, in the nodular cast iron work piece are reduced effectively, thus improving the quality and structural strength of the nodular cast iron work piece.

Application Domain

Process efficiency improvement

Technology Topic

DuctilityContinuous distributions +10

Image

Examples

Experimental program(2)

Example Embodiment

[0020] Example 1

[0021] like figure 1 Shown is a production method of toughness ductile iron, comprising the following steps:

[0022] The first step is to mix and smelt the raw materials. First, steel scrap, returned gray iron, ferrosilicon alloy, ferromanganese alloy and ferrotitanium alloy are added to the melting furnace in proportion, of which 15% is returned gray iron, 3% is ferrosilicon alloy, 5% is ferromanganese alloy, 4% ferro-titanium alloy, the rest is scrap steel, then the air in the melting furnace is discharged by argon gas and the air pressure in the melting furnace is kept constant at 3 standard atmospheric pressures, and then the melting furnace is heated to 1450°C until the raw materials in the melting furnace are all After the molten metal is stirred evenly in the molten state, the molten metal sample is taken from the furnace for composition gap analysis, and the content of the molten metal in the furnace is adjusted according to the composition analysis results. for 40 minutes;

[0023] The second step is to modify the quality. After the first step is completed, the molten metal in the furnace is stirred at a uniform speed in one direction. The stirring speed is 50 minutes/revolution, and after the speed is stable, the carburizer and the modifier are blown separately. into the melting furnace, and fully stir the carburant and modifier with the molten metal in the furnace, and then keep it for 15 minutes, wherein the carburizer accounts for 1.5% of the total amount of molten metal, and the modifier accounts for 2% of the total liquid, and both the carburizer and the modifier are solid powder particles with a particle diameter of ≤400nm;

[0024] The third step is modification and modulation. After the second step is completed, 1.5% of the rare earth raw material accounting for the total amount of molten metal in the furnace is added to the molten metal within 3 minutes and stirred evenly, and then added to the molten metal Nodulizer and stir evenly, then keep it warm for 5 minutes, then add nitrogen removal agent accounting for 7% of the total amount of molten metal and slag removing agent accounting for 15% of the total amount of molten metal to the total amount of molten metal in the furnace for quenching and tempering treatment , After finishing the conditioning treatment and after quenching and tempering treatment, pour the molten metal into the forming mold for cooling and forming. Before casting, first heat the forming mold to 800 ° C, and then keep it warm for 2.5 hours before casting operation;

[0025] The fourth step is modulation heat treatment. When the molten metal is poured into the forming mold and cooled to 850°C, the forming mold and the metal in the forming mold are heated to 960°C within 40 minutes by heating equipment and kept for 8 hours, and then 40 ℃/hour The speed is uniformly cooled to 250 ℃, and then the forming mold and the metal in the forming mold are heated to 750 ℃ within 70 minutes through the heating equipment again and kept for 10 hours, and then naturally cooled to room temperature to remove the mold to obtain the finished ductile iron Blank, among which the chemical element content in the finished ductile iron blank is: C: 3.5%, Si: 2.8%, Cu: 0.8%, Ni: 0.3%, W: 0.6%, Mn: 0.4%, Ti: 1.4%, V: 0.4%, Cr: 0.25%, Zr: 0.15%, Ce: 0.06%, Hf: 0.2%, Dy: 0.05%, Sm: 0.01%, Gd: 0.04%, Lu: 0.05%, S: <0.02%; : 0.15-0.4%; the balance is Fe.

[0026] In this embodiment, the rare earth in the third step is a lanthanide element including elements such as Ce, H, Dy, Sm, Gd and Lu.

[0027] In the present embodiment, in the first step, after the iron alloy is added into the furnace, the air in the furnace is exhausted by inert gas, and the internal environment of the furnace is protected by inert gas from the first step to the end of the third step. middle.

[0028] In the present embodiment, the nitrogen removal agent is lithium carbonate.

[0029] In this embodiment, the slag remover is perlite with a particle size of 30-50 mesh.

Example Embodiment

[0030] Example 2

[0031] like figure 1 Shown is a production method of toughness ductile iron, comprising the following steps:

[0032] The first step is to mix and smelt the raw materials. First, steel scrap, returned gray iron, ferrosilicon alloy, ferromanganese alloy and ferrotitanium alloy are added to the melting furnace in proportion, of which 15% is returned gray iron, 9% is ferrosilicon alloy, 4% is ferromanganese alloy, Titanium-iron alloy 3.5%, the rest is scrap steel, then the air in the melting furnace is discharged by argon gas and the air pressure in the melting furnace is kept constant at 1.5 standard atmospheres, and then the melting furnace is heated to 1550 °C until the raw materials in the melting furnace are all After the molten metal is stirred evenly in the molten state, the molten metal sample is taken from the furnace for composition gap analysis, and the content of the molten metal in the furnace is adjusted according to the composition analysis results. 15 minutes;

[0033]The second step is to modify the quality. After the first step is completed, the molten metal in the furnace is stirred at a uniform speed in one direction. The stirring speed is 30 minutes/revolution, and after the speed is stable, the carburizer and modifier are blown separately. into the melting furnace, and fully stir the carburant and modifier with the molten metal in the furnace, and then keep it for 10 minutes, wherein the carburant accounts for 2% of the total amount of molten metal, and the modifier accounts for 2.5% of the total liquid, and both the carburizer and the modifier are solid powder particles with a particle diameter of ≤400nm;

[0034] The third step is modification and modulation. After the second step is completed, 1% of the rare earth raw material accounting for the total amount of molten metal in the furnace is added to the molten metal within 1.5 minutes and stirred evenly, and then added to the molten metal Nodulizer and stir evenly, then keep it warm for 3-10 minutes, then add nitrogen removal agent accounting for 8% of the total amount of molten metal and slag removing agent accounting for 25% of the total amount of molten metal to the total amount of molten metal in the furnace for adjustment Quality treatment, after the conditioning treatment is completed, the molten metal liquid is cast into the forming mold for cooling and forming. Before casting, the forming mold is first heated to 800 ° C, and then the casting operation can be carried out after 1.5 hours of heat preservation ;

[0035] The fourth step is modulation heat treatment. When the molten metal is poured into the forming mold and cooled to 840°C, the forming mold and the metal in the forming mold are heated to 950°C within 100 minutes through the heating equipment and kept for 10 hours, and then heated at 50°C ℃/hour The speed is uniformly cooled to 280 ℃, and then the forming mold and the metal in the forming mold are heated to 760 ℃ within 30 minutes through the heating equipment again and kept for 10 hours, and then naturally cooled to room temperature to remove the mold to obtain the finished ductile iron The content of chemical elements in the blank and finished ductile iron blank is: C: 3.5%, Si: 2.8%, Cu: 1%, Ni: 0.2%, W: 0.5%, Mn: 0.4%, Ti: 1.5%, V: 0.5 %, Cr: 0.2%, Zr 0.2%, Ce 0.1%, Hf: 0.2%, Dy: 0.05%, Sm: 0.05%, Gd: 0.03%, Lu: 0.05%, S: <0.02%; P: 0.15- 0.4%; the balance is Fe.

[0036] In this embodiment, the rare earth in the third step is a lanthanide element including elements such as Ce, H, Dy, Sm, Gd and Lu.

[0037] In the present embodiment, in the first step, after the iron alloy is added into the furnace, the air in the furnace is exhausted by inert gas, and the internal environment of the furnace is protected by inert gas from the first step to the end of the third step. middle.

[0038] In the present embodiment, the nitrogen removal agent is lithium carbonate.

[0039] In this embodiment, the slag remover is perlite with a particle size of 30-50 mesh.

[0040] Compared with the prior art, the present invention, on the one hand, uses rare earth elements to obtain a ductile iron material with uniform and continuous distribution, high hardness and no reduction in elongation, which greatly improves the structural strength and toughness of ductile iron workpieces; on the other hand, Through the metamorphic treatment, the anti-fatigue performance and wear resistance of the nodular cast iron workpiece are comprehensively improved. In addition, the ductile iron casting process of the present invention can also effectively reduce the defects such as internal stress concentration, cracks and trachoma of the nodular cast iron workpiece, Improve the structural strength of the product quality of ductile iron workpieces.

PUM

Property	Measurement	Unit
Particle diameter	<= 400.0	nm

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Classification and recommendation of technical efficacy words

high hardness

Production method of toughness nodular cast iron

AI-Extracted Technical Summary

Problems solved by technology

Abstract

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Examples

Example Embodiment

Example Embodiment

PUM

Description & Claims & Application Information

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