Material and production of slag pots

Material

The slag pots are made out of vacuum degassed cast steel, processed to a fine grain size structure with improved properties both in toughness and in elongation.

The mechanical properties are checked at a room temperature in the delivery condition i.e. after completion of the quality heat treatment from cylindrical cast-on test blocks (Ø 60mm x 250mm) available on every slag pot: both sampling preparation and the testing comply with ASTM A 370-96.

Production Of Slag Pots

Moulding: Moulding is performed within a modular flask by using a sand preparation based on resin bonding.

Trunnions: Trunnions – when any – are preferably cast-in: basically they are manufactured from steel grade S355 J2G3 acc. to DIN EN 10250-2 and forged as per DIN 7527. Cast-on and hot-fitted trunnions can also be provided.

Melting: Melting is carried out in the oxygen steel plant (2 off 180 MT BOF converters); the ladle capacity allows a continuous bottom pouring process with fully monitored and controlled speed. The metal analysis is checked by using a computed linked spectrograph.

Heat treatment: Every pot undergoes a combined quality heat treatment (annealing) aiming both to grain refining and stress relieving i.e.:

Heating to a temperature above Ar3, austenitising at about 915℃ and controlled cooling in furnace,

Intermediate holding at 600℃ -630℃  and completion of cooling in furnace down to 300℃ .

Fettling And Dressing

The inner surface is processed fit-to-purpose, eliminating surface irregularities, which might cause some sticking of the slag. In addition, the castings are descaled by shot-blasting and the outside is additionally coated for transportation.