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Automatic molding machine manufacturers to explain how to improve the quality of investment casting ductile iron pieces?

Source: Time:2016-10-31 11:38:58 views:

Ductile iron pieces because of its good performance, by mechanical equipment, aerospace and many other areas sought after. But the use of investment casting production of ductile iron pieces, the production process is complex, the operation has a considerable difficulty, higher scrap rate. But the face of a wide range of market demand, many casting technical staff are trying to find effective ways to strive for more advanced technology and technology to enhance the investment casting ductile iron pieces of the quality and yield. Automatic level molding machine manufacturers from the investment casting production of ductile iron pieces of the characteristics of the corresponding measures and production processes and other aspects of how to improve the investment casting ductile iron pieces of quality?


1. Investment casting ductile iron production characteristics:

 (1) the requirements of the original iron liquid: C high, Si, Mn, P, S low;

 (2) less hot metal, spheroidization difficult, faster temperature drop;

 (3) poor ventilation (whole silica sol shell), exhaust difficult;

 (4) cast small, high quality requirements.

    2. In view of the above characteristics and existing problems, take appropriate measures:

 (1) the choice of raw and auxiliary materials:

A, the procurement of a class of low silicon, phosphorus, sulfur nodular cast iron with pig iron For example:
Q10-1, Q12-1, Q14-1;

B, due to the use of IF furnace smelting, but also the production of ferrite ductile iron, so the company selected FeSiMg8RE3 as a nodularizing agent, because the ball treatment of molten iron less, so the particle size of 8-10mm;

C, inoculant selection BaSiFe particle size of 0.5-3.0mm;

D, slag agent selection of small particle size of molten iron slag agent.

 (2) to improve the temperature of molten iron ballification, increase the amount of ball agent; to ensure the quality of the ball. Through long-term practice, iron liquid ballification treatment temperature of 1500 ℃ -1600 ℃, due to the high temperature of the ball, magnesium steam loss serious, magnesium absorption rate of less than 40%, so the amount of rare earth magnesium ferrosilicon addition is also increased. We tried to join the amount of 1.6%, 1.8%, 2.0% of the three programs, the residual magnesium content of the test results and metallographic analysis, the final choice of the amount of 1.8-2% of the most stable.

 (3) due to the high requirements of casting, scrap rate has been higher; and scrap rate mainly for slag and stomata.

      According to the analysis of the rejection rate of scrap rate, I have adopted the same pouring system design as the cast steel and added the exhaust system and the measures to increase the group tree, so that the process yield and process yield gradually increase.


      3. Brief description of the production process:

  Due to limited space, in this focus on smelting, casting process (to produce ferrite QT400-15 example).

(1) the choice of chemical composition:

 C3 0.5-3.9%, Si2.4-2.9%, Mn <0.5%, P≤0.08%, S≤0.02%, Mg0.04-0.06%, RE0.02-0.04%

(2) charge preparation:

  Scrap (05F or pure steel) 5%, QT400-15 (that is, with the same grade) back to the material 25%;

  Q12-1 (or Q10-1, Q14-1) 70% of pig iron.

  Plus 1.8-2% of the nodularizer, plus 1.5-2% inoculation agent and 0.1% of artificial cryolite powder.

 (3) Spheroidizing process:

  When the charge is fully melted, the temperature is overheated (about 1550 ℃), after standing and slagging; in the roasted ladle (dam type ladle, inner diameter and inner ratio is 1: 2), first in the side into the 1.8 % Of the nodularizer, then add 1.2% inoculant, the back cover on the dyed iron scrap (the same grade), tamping; the top of the ball pressure plate (principle or use: to extend the ball reaction time, increase the number of graphite balls and Improve the ballification level). Put the cryolite powder on the other side of the ladle (about 0.05-0.1%).

  When the furnace temperature reaches the required temperature, pour about 2/3 of the molten iron for spheroidizing. Spheroidization reaction time: about 30-50 seconds or so, the end of the ball fast, immediately into the remaining molten iron, while adding the remaining side of the inoculant. After pouring immediately after the addition of slag and take samples (triangular specimen to see the microstructure, to determine the degree of spheroidization; cold samples used for component analysis), then cover the cover agent, ash ash casting.


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