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Heat treatment method of ausferrite nodular cast iron

A ductile iron and austenitic technology, applied in the field of warm quenching, can solve the problems of low production efficiency, low cooling capacity of castings and high cost, and achieve the effect of improving production efficiency and ensuring output

Active Publication Date: 2016-08-24
HEBEI UNIV OF TECH
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0004] The technical problem to be solved by the present invention is to provide a heat treatment method for ausferitic ductile iron, which is a method of austempering nodular cast iron in two stages, reducing the cost of austempering heat treatment for each batch. The weight of the casting, the cooling of the casting in the nitrate solution isothermal salt bath furnace is very fast, so the temperature fluctuation of the casting in the first stage of the isothermal process in the salt bath furnace is very small, which greatly improves the hardenability of the casting and overcomes the The isothermal quenching process of ductile iron in the prior art has the defects of low cooling capacity and unstable mechanical properties of castings, low production efficiency and high cost in the salt bath temperature fluctuation of nitrate solution isothermal salt bath furnace

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  • Heat treatment method of ausferrite nodular cast iron
  • Heat treatment method of ausferrite nodular cast iron

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0027] The first step, high temperature austenitization treatment:

[0028] First, place the carbide-containing ductile iron castings-semi-autogenous mill austeric ductile iron balls in batches into continuous high-temperature Carry out high-temperature austenitization in the furnace. The weight of each batch of semi-autogenous austenitic ductile iron grinding balls is 350 kg, and the austenitization temperature is 920±10°C. After holding for 100 minutes, transfer to the next step The first stage isothermal quenching heat treatment is carried out in the salt solution isothermal salt bath furnace;

[0029] The second step, the first stage of austempering heat treatment:

[0030] Place the austenitic nodular cast iron grinding balls of the semi-autogenous mill that have been treated in the first step of high-temperature austenitization in an isothermal salt-bath furnace with a weight of 9 tons and a temperature of 250±3°C. According to the wall thickness or modulus of the ausfer...

Embodiment 2

[0037] First, according to the total amount of ductile iron castings to be processed, the ductile iron castings are placed in batches in a continuous high-temperature furnace for high-temperature austenitization. The weight of each batch of ductile iron castings is 300 kg, and the austenitization The temperature is 900°C, after 60 minutes of heat preservation, it is transferred to the next step of isothermal salt bath furnace with nitrate solution for the first stage of isothermal quenching heat treatment;

[0038] The second step, the first stage of austempering heat treatment:

[0039] Place the ductile iron castings treated with high-temperature austenitization in the first step in an isothermal salt bath furnace with a weight of 8 tons and a temperature of 210°C. The isothermal time in the bath furnace is 10 minutes, that is to complete the first stage isothermal quenching heat treatment of ductile iron castings in the salt bath furnace;

[0040] The third step, the secon...

Embodiment 3

[0045] The first step, high temperature austenitization treatment:

[0046] First, put the ductile iron castings containing carbides in batches into a continuous high-temperature furnace for high-temperature austenitization according to the total amount of ductile iron castings to be processed. The weight of each batch of ductile iron castings containing carbides For 500 kg, the austenitizing temperature is 930°C, after 180 minutes of heat preservation, transfer to the next step of nitrate solution isothermal salt bath furnace for the first stage of isothermal quenching heat treatment;

[0047] The second step, the first stage of austempering heat treatment:

[0048] Place the carbide-containing ductile iron castings treated in the first step of high-temperature austenitization in an isothermal salt-bath furnace with a weight of 12 tons and a temperature of 300°C. Thickness or modulus size, the isothermal time in the salt bath furnace is determined to be 25 minutes, that is, ...

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Abstract

The invention provides a heat treatment method of ausferrite nodular cast iron, relating to isothermal quenching in heat treatment methods of ferrous metals. The method is used for carrying out isothermal quenching heat treatment on ausferrite nodular cast iron by two stages. The method comprises the following steps: I, carrying out high temperature austenitizing; II, carrying out first stage of isothermal quenching heat treatment in a salt bath furnace; III, carrying out second stage of isothermal quenching heat treatment in a continuous low temperature tempering furnace; and IV, carrying out cooling, water washing and drying treatment. The heat treatment method has the beneficial effects that the castings are cooled quickly in a nitrate solution isothermal salt pond as the weights of each batch of castings subjected to isothermal quenching heat treatment are reduced, so the temperature fluctuation of the castings in the salt bath isothermal process is small, thus greatly improving the through quenching capacities of the castings and overcoming the defects in the prior art that the salt bath temperature fluctuation of the nitrate solution isothermal salt bath furnace in the nodular cast iron isothermal quenching treatment process is big, thus causing low cooling capacities and unstable mechanical properties of the castings, lower production efficiency and higher cost.

Description

technical field [0001] The technical solution of the invention relates to austempering in a heat treatment method for ferrous metals, in particular to a heat treatment method for ausferic ductile iron. Background technique [0002] Nodular cast iron with austeric matrix has excellent comprehensive mechanical properties, high strength, good toughness and high wear resistance, and has been widely used in automobile, metallurgy, mining and construction machinery industries. Obtaining the matrix structure of ausferrite requires the austempering heat treatment of ductile iron obtained by traditional casting method. The conventional isothermal quenching treatment is to quickly immerse the high-temperature austenitized nodular cast iron into a nitrate solution of a certain temperature, and hold it for a certain period of time, that is, all the isothermal processes are carried out in the nitrate furnace, and then from the nitrate solution. Take out the salt bath furnace and cool to...

Claims

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Application Information

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IPC IPC(8): C21D1/20C21D5/00
CPCC21D1/20C21D5/00C21D2211/001
Inventor 刘金海杨为廷赵雪勃付彬国董天顺李国禄张建军
Owner HEBEI UNIV OF TECH
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