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Manufacturing method of high-strength and high-ductility ductile cast iron, ductile cast iron manufactured according to manufacturing method, and application of ductile cast iron

A technology of nodular cast iron and a manufacturing method, which is applied to the manufacturing field of nodular cast iron, can solve problems such as insufficient tensile strength, failure to meet national standards, etc., and achieve the effects of improved safety, effective and feasible manufacturing process, and guaranteed performance.

Active Publication Date: 2015-12-23
FUJIWA MASCH IND KUNSHAN CO LTD +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

According to the method described in this invention application, the tensile strength of the ductile iron obtained is ≥540MPa, and the elongation is ≥13%. Although the elongation is very high, the tensile strength is not enough, which obviously does not reach the national standard of QT700-2

Method used

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  • Manufacturing method of high-strength and high-ductility ductile cast iron, ductile cast iron manufactured according to manufacturing method, and application of ductile cast iron
  • Manufacturing method of high-strength and high-ductility ductile cast iron, ductile cast iron manufactured according to manufacturing method, and application of ductile cast iron
  • Manufacturing method of high-strength and high-ductility ductile cast iron, ductile cast iron manufactured according to manufacturing method, and application of ductile cast iron

Examples

Experimental program
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Effect test

Embodiment 1

[0052] A manufacturing method of ductile iron with high strength and high ductility, comprising the following process steps:

[0053] (1) smelting step, wherein milling iron → scrap steel → pretreatment agent → returning charge are added in sequence for smelting;

[0054] (2) quenching and tempering step;

[0055] (3) pouring step, wherein in the pouring barrel, a quick-melting recarburizer is added;

[0056] (4) molten iron releasing step;

[0057] Wherein, the step (1) includes adding a pretreatment agent with a mass of 0.5% of the molten iron obtained in the step (1) into the melting furnace, and the step (3) includes adding the molten iron obtained in the step (3) to the pouring barrel. Mass 0.4% quick-melting recarburizer.

[0058] The components of the pretreatment agent include Si with a mass fraction of 65% and non-equilibrium graphite C with a mass fraction of 28%, the remaining components are Ca and Al, and the particle diameter of the added quick-melting carburiz...

Embodiment 2

[0060] A manufacturing method of ductile iron with high strength and high ductility, comprising the following process steps:

[0061] (1) smelting step, wherein milling iron → scrap steel → pretreatment agent → returning charge are added in sequence for smelting;

[0062] (2) quenching and tempering step;

[0063] (3) pouring step, wherein in the pouring barrel, a quick-melting recarburizer is added;

[0064] (4) molten iron releasing step;

[0065] Wherein, the step (1) includes adding a pretreatment agent with a mass of 0.5% of the molten iron obtained in the step (1) into the melting furnace, and the step (3) includes adding the molten iron obtained in the step (3) to the pouring barrel. Mass 0.7% quick-melting recarburizer.

[0066] The components of the pretreatment agent include Si with a mass fraction of 70% and non-equilibrium graphite C with a mass fraction of 25%, the remaining components are Ca and Al, and the particle diameter of the added quick-melting carburiz...

Embodiment 3

[0073] A manufacturing method of ductile iron with high strength and high ductility, comprising the following process steps:

[0074] (1) smelting step, wherein milling iron → scrap steel → pretreatment agent → returning charge are added in sequence for smelting;

[0075] (2) quenching and tempering step;

[0076] (3) pouring step, there is no accelerated melting recarburizer;

[0077] (4) molten iron releasing step;

[0078] Wherein, the step (1) includes adding a pretreatment agent of 0.5% by mass of the molten iron obtained in the step (1) into the melting furnace.

[0079] The components of the pretreatment agent include 64% Si and 33% non-equilibrium graphite C by mass fraction, and the remaining components are Ca and AL.

[0080] Product inspection 2

[0081] The ductile iron products obtained in Comparative Example and Example 3 will be used for metallographic inspection to observe the quantity and size of graphite therein. As shown in the attached drawings, the bl...

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Abstract

The invention provides a manufacturing method of high-strength and high-ductility ductile cast iron. The manufacturing method comprises the following steps: (1) a smelting step, wherein pig iron, scrap steel and foundry returns are added to be smelted; (2) a hardening and tempering step; (3) a teeming step; and (4) a molten iron discharging step. The manufacturing method is characterized in that a pretreating agent is also added in the smelting step (1) to be subjected to mixed smelting; and a fast-melt carburant is added in a teeming ladle in the pouring step (3). Preferably, the pretreating agent of which the mass is 0.5% of that of molten iron obtained in the smelting step (1) is added in a melting furnace, and the fast-melt carburant of which the mass is 0.4%-0.8% of that of the molten iron obtained in the pouring step (3) is added in the teeming ladle. The manufacturing process is effective and feasible, economic and practical, and has a good application prospect and a good market potential. The invention also provides the ductile cast iron manufactured according to the manufacturing method. The ductile cast iron is greater than or equal to 700 MPa in tensile strength, greater than or equal to 450 MPa in yield strength, and greater than or equal to 6% in elongation, and is applied to manufacturing of a wheel bracket.

Description

technical field [0001] The present invention relates to a method for manufacturing ductile iron, in particular to a method for manufacturing ductile iron with high strength and high ductility, its product and application. Background technique [0002] In my country's national standard for ductile iron, the existing product material grade QT700-2 is suitable for parts with high strength requirements, such as crankshafts, camshafts, partial grinders, milling machines, and lathes of diesel and gasoline engines. Spindles, ball mill gear shafts , small turbine main shaft, etc., and the required tensile strength is above 700MPa, the yield strength is above 420MPa, and the elongation is above 2%. In the actual production demand, an effective manufacturing process of ductile iron with high strength and high ductility is urgently needed. [0003] It can be seen from the table of grades of ductile iron well known to those skilled in the art that the higher the tensile strength and the...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C21C1/10C22C33/08B22D1/00
CPCY02P10/20
Inventor 邵冬青芦勇沈伟刘佳韩祥秀胡小路黄磊马荣峰
Owner FUJIWA MASCH IND KUNSHAN CO LTD
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