CN1928128A - Ingot slow cool annealing process for low-carbon steel - Google Patents

Abstract

The present invention is low carbon steel ingot slowly cooling annealing process and belongs to the field of ferrous metallurgy technology. The low carbon steel ingot slowly cooling annealing process includes heating demolded steel ingot in a furnace to 800-900 deg.c, maintaining for some time, cooling in the furnace to 760+/-15 deg.c, maintaining for some time, cooling in the furnace to 650+/-15 deg.c, and discharging at the temperature not higher than 200 deg.c. The present invention has raised steel ingot demolding temperature, heating and temperature maintaining after demolding to eliminate stress caused by inside and outside temperature difference and stepped maintaining and cooling, and can reduce stress during steel ingot cooling and avoid cracking.

Description

Ingot slow cool annealing process for low-carbon steel

One, technical field

The present invention relates to a kind of ingot slow cool annealing process for low-carbon steel, belong to the ferrous metallurgy field.

Two, background technology

At present, the technology that stove is cold, the hole is cold or stove is cold again, the hole is cold behind insulation certain hour about 650 ℃ is all adopted in steel ingot annealing in the metallurgy industry, but aborning, during the smelting low carbon steel alloy, to after ingot slow cool or the annealing, crackle appears in large quantities of steel ingots traditionally, and the lighter needs the crack site excision is utilized, weight person directly causes steel ingot to be scrapped, and has a strong impact on ingot quality and lumber recovery.

The drawback of former technology is: after the steel ingot demoulding, after waiting to expect for some time, when temperature was 650 ± 10 ℃, all insulation, descent of temperature were come out of the stove.Any prevention crackle measure that it adopts, all consider from reducing steel ingot demoulding postcooling speed, because for low-carbon alloy steel, ferritic generation temperature will be far above medium carbon steel, and not before the demoulding, existing intensity, all relatively poor ferrite of plasticity go out along partial crystallization steel ingot as yet, this kind organized very easily and produce intergranular crack under the internal stress effect, after intergranular crack produced, no matter follow-up how slow cooling all can't avoid the generation of crackle.

Three, summary of the invention

The technical problem that the present invention solves is: eliminate the stress that hot stage produces, avoid ferritic intergranular crack, make a kind of ingot slow cool annealing process for low-carbon steel that does not occur crackle in the ingot slow cool process.

The technology of the present invention solution: comprise the steel ingot demoulding, insulation, descent of temperature, steel ingot demoulding fed to boiler, intensification are when temperature is brought up to 800 ℃-900 ℃, be incubated 3-10 hour, descent of temperature≤20 ℃/h when temperature is reduced to 760 ± 15 ℃, are incubated 3-10 hour; Descent of temperature≤20 ℃/h, when temperature is reduced to 650 ± 15 ℃, equal soaking time: 〉=1h/100mm, come out of the stove in descent of temperature≤20 ℃/h, tapping temperature≤200 ℃.

The present invention is owing to improved the steel ingot calcining temperature, before not separating out as yet, be about to the steel ingot demoulding along grained ferrite, earlier steel ingot is heated and isothermal after the demoulding, eliminate the stress that it is produced by internal-external temperature difference, progressively isothermal or cooling in annealing furnace subsequently until room temperature, thereby significantly reduced thermal stresses and structural stress in the steel ingot process of cooling, make it not produce big stress all the time, avoided the generation of crackle.

Four, description of drawings

Fig. 1 is the prior art processes graphic representation:

Fig. 2 is process curve figure of the present invention:

Five, embodiment

After the steel ingot demoulding of the present invention, go into stove as early as possible, heat up as early as possible, when temperature rises to 850 ± 15 ℃, insulation 30min/100mm, descent of temperature≤20 ℃/h, when temperature is reduced to 760 ± 15 ℃, insulation 30min/100mm, descent of temperature≤20 ℃/h, when temperature is reduced to 650 ± 15 ℃, equal soaking time: 〉=1h/100mm, descent of temperature≤20 ℃/h, come out of the stove tapping temperature≤200 ℃.

The north, Inner Mongol heavy industry group company adopts an above-mentioned technology annealed hundreds of steel ingot that crackle did not take place again.The grade of steel that relates to has: 21CrMo10,12Cr2MoG, 12Cr1MoVG, 17CrNiMo6,20CrMnMo, 20CrNiMo etc.

Claims (1)

1, ingot slow cool annealing process for low-carbon steel, comprise the steel ingot demoulding, insulation, descent of temperature, it is characterized in that: steel ingot demoulding fed to boiler, intensification, when temperature is brought up to 800 ℃-900 ℃, be incubated 3-10 hour, descent of temperature≤20 ℃/h when temperature is reduced to 760 ± 15 ℃, are incubated 3-10 hour; Descent of temperature≤20 ℃/h, when temperature is reduced to 650 ± 15 ℃, equal soaking time: 〉=1h/100mm, come out of the stove in descent of temperature≤20 ℃/h, tapping temperature≤200 ℃.

Images