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A kind of ductile iron annealing process

A technology of nodular cast iron and annealing process, which is applied in the field of metallurgy, can solve problems such as carbides that cannot be eliminated, and achieve the effects of extremely low fracture rate of parts, consistent temperature, and elimination of heat treatment stress

Active Publication Date: 2019-03-22
GUANGDONG ZHONGTIAN CHUANGZHAN DUCTILE IRON CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

It has been proved by practice that the annealing process described in the literature for super large section ductile iron parts cannot eliminate the high number of carbides

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0061] Main wall thickness of ductile iron parts: 300-400mm, Cr: 0.20-0.275%, V: 0.010-0.0125%, carbide quantity: 3-10%:

[0062] From room temperature to 400°C at 50°C / h, keep warm for 2 hours, continue to heat at 50°C / h to 650°C, keep warm for 2.5 hours, continue to heat at 60°C / h to 960°C, keep warm for 6 hours; then 30°C / h h Cool down to 500°C with the furnace, keep warm for 4 hours; finally cool with the furnace to less than or equal to 50°C and take out of the furnace.

Embodiment 2

[0064] Main wall thickness of ductile iron parts: 300-400mm, Cr: 0.275-0.35%, V: 0.0125-0.015%, carbide quantity: 10-15%:

[0065] From room temperature to 400°C at 50°C / h, keep warm for 2 hours, continue to heat at 50°C / h to 650°C, keep warm for 2.5 hours, continue to heat at 60°C / h to 970°C, keep warm for 8 hours; then 30°C / h h Cool down to 500°C with the furnace, keep warm for 4 hours; finally cool with the furnace to less than or equal to 50°C and take out of the furnace.

Embodiment 3

[0067] Main wall thickness of ductile iron parts: 300-400mm, Cr: 0.275-0.35%, V: 0.0125-0.015%, carbide quantity: 10-15%:

[0068] From room temperature to 420°C at 30°C / h, keep warm for 2 hours, continue to heat at 30°C / h to 650°C, keep warm for 2.5 hours, continue to heat up at 60°C / h to 990°C, keep warm for 8.5 hours; then 30°C / h h Cool down to 500°C with the furnace, keep warm for 4 hours; finally cool with the furnace to less than or equal to 50°C and take out of the furnace.

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Abstract

The invention discloses a spheroidal graphite cast iron annealing process which comprises the following steps: A) heating a spheroidal graphite cast iron part to 380-420 DEG C in an annealing furnaceat a velocity of 25-55 DEG C / hour, and keeping the temperature for 1.5-2.5 hours; B) further heating to 630-680 DEG C at a velocity of 25-55 DEG C, and keeping the temperature for 2-3 hours; C) further heating to 960-990 DEG C at a velocity of 55-65 DEG C / hour, and keeping the temperature for 3.5-4.5 hours; and E) finally cooling the annealing furnace to be less than or equal to 50 DEG C, and discharging the spheroidal graphite cast iron part. The annealing process disclosed by the invention is developed for a spheroidal graphite cast iron part of which the wall thickness is greater than 300mm, and the spheroidal graphite cast iron part comprises 0.20-0.35% of Cr, 0.010-0.015% of V and 3-15% of carbide. The spheroidal graphite cast iron part applicable to the annealing process disclosed bythe invention can be a cylindrical solid part or a square solid part, the annealing process disclosed by the invention is excellent in carbide elimination effect, and after annealing is completed, the contents of carbide on the surface and the heart part of the part are both less than 0.5%.

Description

technical field [0001] The invention relates to the field of metallurgy, in particular to an annealing process for ductile iron. Background technique [0002] With the continuous development of ductile iron technology, nodular cast iron gradually replaces cast steel and becomes a new type of metal material, which has been widely used in construction machinery, basic parts of injection molding machines, basic parts of die-casting machines and wind power generation foundations or key parts parts etc. [0003] In the manufacturing process of ductile iron castings, especially when the wall thickness is greater than 300mm and super large section ductile iron castings, since the raw materials (such as ordinary pig iron, scrap steel, etc.) contain elements that strongly form carbides, such as chromium (Cr), vanadium (V), Carbide is easily formed during the solidification of molten iron. When the carbide exceeds 3%, it will seriously affect the mechanical properties of ductile iro...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C21D5/00C21D1/26C22C37/04C22C37/06
CPCC21D1/26C21D5/00C22C37/04C22C37/06
Inventor 柯志敏陈永成黄梓波
Owner GUANGDONG ZHONGTIAN CHUANGZHAN DUCTILE IRON CO LTD
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