SU69664A1 - The method of accelerating the annealing of white iron - Google Patents

Description

In order to accelerate the annealing of white iron, it is proposed to heat the iron to 350-400 ° C, to withstand it for 4-8 hours. in order to increase the number of graphitization centers, and then to anneal in a known manner immediately after aging or after the iron is cooled.

During annealing in white iron, a number of processes take place, for example, the evolution of gases (hydrogen), the mechanical action of one component on another due to the difference in their expansion coefficients, the change in volume upon passing through the critical point of the magnetic transformation of cementite, which under certain conditions can have significant effect on the rate of graphitization in both the first and second annealing stages.

For the usual composition of ductile iron with a silicon content of at least 1.15-1.20%. Such a condition turned out to be a preliminary thermal treatment of white iron at temperatures of 350-400 ° for 4-8 hours. When this occurs, a significant increase in the centers of graphitization (15-20 times),

what allows to reduce the duration of the first stage of annealing by 1.5-2 times, the second stage - by 4-5 times, and the total cycle time (including pretreatment) - 1.3-1.8 times.

It has been established by experiments that the reduction & squeezing of the ductile iron annealing cycle can be carried out in three ways.

1. White castings, after their cleaning, are subjected to preliminary heat treatment at 350-400 ° G for 4 hours. in separate furnaces and after that - reduced annealing in chamber or tunnel furnaces.

2. After cleaning, white iron castings are loaded, as usual for annealing, into chamber or tunnel furnaces, heated to 350-400 ° C and kept at this temperature for 4-8 hours. (depending on the uniformity of temperature distribution in different zones of the furnace). Further annealing is carried out, as usual, on an abbreviated schedule.

3. White cast iron after

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NO 69664 - 2-

knocking them out of the flasks during the cool-down

waits kept at a temperature that accelerates the annealing of white

the Zoa-400 ° C tour, continuing with the distinction

4 hours, after which it is cooled to a previously normal normal temperature. Further up to 350-400 ° C, withstand

Shea annealing are reduced to -8 hour. in order to increase the number

graphics. With this method, the sokra centers of graphitization and anneal

The time spent on graphitization in a semi-well-known way is immediately mediated, but the method is not soaked up or after fuel consumption is required.