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METALLURGY

QUALITY STEELMAKING PROCESS.

Metallurgical facilities of NKMZ allow to ma­nufacture the press-forging ingots weighing between 1.6 and 170 t and castings weighing as much as 120 t.

Metallurgical facilities include the following equipment:

  1. 2 open-hearth furnaces with the capacity of 50 t each;
  2. 2 electric arc furnaces ÄÑÏ with the capacity of 12 t each;
  3. 1 electric arc furnace ÄÑÏ with the capacity of 5 t;
  4. after-furnace ladle steel treatment unit "Ladle- furnace";
  5. sector of steel vacuum treatment based on the steam-jet pump and 4 vacuum chambers.

 

Depending on the preset chemical compositi­on and the required properties of steel its casti­ng may be performed either in vacuum or in air, by means of bottom or top pouring.
Row sheet for producing the high-quality steel by melting it in the revamped open-hearth furnace No.3 with subsequent vacuum-degas­sing:

  • Open-hearth furnace No.3.
  • Pneumatic unit for lime feed.
  • Pneumatic unit for coke feed.
  • Wire feeder.
  • After-furnace ladle steel treatment unit.
  • Bin trestle.
  • Cover of vacuum chamber No.4 for oxygen lancing.
  • Steam-jet vacuum pump.

 

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AFTER-FURNACE LADLE STEEL TREATMENT UNIT "LADLE-FURNACE"

The "Ladle-furnace" unit in the open-hearth workshop is equipped with the slidegate ladles of three type sizes: 40, 60, 90 t that allows liquid steel between 20 and 88 t to be treated in the ladle and when using the "Ladle-furnace" unit (LFU) in the mixing mode to pour steel treated in it for pressing ingots weighing up to 170 t. In the course of the after-furnace Ladle steel ref­ining the: realloying, reheating, flux-cored wire treatment by means of the wire-feeders, argon blowing of metal are performed that provides a reduction of non-metallic inclusions and gases contents in metal. Open-hearth and arc-furnace steel is also treated in the Ladle-furnace unit (maximum volume of steel treated in the LFU is 170 t when using the mixing mode).
HB content in steel after ladle treatment is 25...30 ppm.
Sulphur content in metal after ladle treatment may be reduced down to 0.005%.
Temperature difference of steel across the ladle section is no more than 5°C.
Homogeneous chemical composition of metal along the ladle height is provided.

 

 
 

 

VACUUM-DEGASSING SECTION

Treatment of metal in vacuum chambers allows ingots weighing between 1.6 and 170 t to be cast in vacuum.
Vacuum chamber No.4 is fitted with argon, oxygen and nitro gen supplying system, wire feeders, sliding lid with the videosu- pervision system, water-cooling oxygen lance, sampling and temperature measuring unit, vacuum lockage bins. This equipment allows steel treating according to VD and VOD processes. By means of VOD technology high chromium steel with the carbon content of < 0.03% is obtained.
Working vacuum not more than 0.5 mm Hg in the course of vacuum degassing is provided by the vacuum steam-jet pump.
For vacuum degassing of steel the unified stock of the slide- gate ladles of the "Ladle-furnace" unit (capacity of 40, 60, 90 t) is used that makes it possible to effect vacuum degassing of steels for pressing ingots of different type sizes.
Quality level of steel meets the highest world standards.

Gases contents of metal after vacuum-degassing are as follows:

- oxygen (O2) - 25...35 ppm;
- hydrogen (H2) < =2 ppm;
- nitrogen (N2) - 70...90 ppm.

 
 

PRODUCTION OF ROLLING MILLS
COMPOSITE ROLLS
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Comparative diagram of durability of work rolls for 1700 mm Hot-roiling mill finishing stands, Mariupol Integrated Iron and Steel Works, Ukraine.
 
  
   

Rolls with high-speed steel operating layer

Rolls with high-chromium Iron operating layer

Rolls with Indefinitely chilled operating layer manufac­tured using conventional methods