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| Technologies
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The mill consists of
two main shops: Hot Extrusion Shop (HES) to produce
hot-finished tubes and Cold Rolling Shop (CRS)
to produce cold-finished tubes.
All the industrial processes are regulated by
Production Technical Procedures and process steps
as well as tooling standards tables. Production
procedures foresee the hold points and quality
control methods of technological process, as well
as the quality controls of the production.
Production of stainless tubes by hot-extrusion
HES produces tubes with diameter from 57 to 168.3
mm and wall thickness’ from 4 to 20 mm. Two extrusion
lines make up the shop production capacity. One
of them is laid off at present. The second line
including the vertical press of 1000 and the horizontal
press with a power of 3 150 tons are operating
in four-team continuous shifts.
HES produces finished hot-formed tubes, as well
as hollows for further redrawing. The round billet
before being put into production is weighed and
undergos incoming control: surface quality and
chemical composition of the billets is checked
for conformity with Technical Documents. The Production
Control Department based on the results issues
the Conformity Report and after this the round
billet is put into production.
Round billet is cut to lengths. To provide best
geometry of tubes, billets are drilled with through
holes, inlet cone and beveled on one end. Then
the round billet is heated up to reach necessary
temperature in the induction-arc furnaces. The
vertical press perform expansion of the hole by
inserting a conic piercing plug into the drilled
hole. In this way the semi-finished hollow is
obtained.
The hollow is re-heated again in induction-arc
furnace and transported to the horizontal extrusion
press. Before each operation of expansion and
pressing, inner and external surfaces of round
billet are coated with glass lubricant. The tube-extrusion
is performed in one cycle at steady speed. After
extrusion, the tubes are cooled in water or air
according to the steel grade.
After cooling, the tubes go to the chemical treatment
line: pickling in alkaline and acid baths removes
glass lubricant from the tube surfaces. Then the
tubes are straightened, cut at the ends and inspected.
Production Control Department carries out preliminary
visual inspection. The final check of tube quality
is carried out at the equipment for non-destructive
testing Eddy Current and Ultrasonic Test Units.
Finished tubes are packed into hexagonal bundles,
wrapped up into the polyethylene film and tied
up with plastic or metallic strips. The quality
engineers examine the bundle and issue the certificate
of conformity, then Hollows are transferred to
C.R.S for further processing.
Production of stainless tubes by cold-rolling
The C.R.S produces tubes with diameter from 4
to 114.3 mm, and wall thickness from 0.2 to12
mm. The manufacturing facilities of the shop include
21 cold-rolling mills (CR), 15 rolling roller
mills (CRR) and 4 drawing benches.
After rolling the tubes undergo chemical treatment
to remove lubricant layer, heat-treatment and
pickling. To produce tubes with wall thickness
lighter than 1 mm, tubes are worked at "roller
mills" after cold-rolling mills.
The "roller mills" allow production
of light-wall tubing with improved surface quality
and more stringent dimensional requirements. After
rolling at "roller mills" the tubes
are heat treated and checked by Production Control
Department.
To produce tubes of small diameter from 14 to
4 mm, drawing benches are used. The process lies
in tube drawing through the die of smaller diameter.
The tubes are processed, subjected to visual inspection
and final quality control by Eddy Current and
Ultrasonic Test (UT) devices.
The process is completed by finishing procedures
that are packing and marking. Marking takes place
by special ink-jet printer, plotting the data
of manufacturing mill, (steel quality, standard,
size and type of test the tube was subjected to)
along the entire tube length.
Finished tubes are packed depending on their destination,
surface quality and territory climate they will
be delivered to. As a rule the tubes are packed
into polyethylene film and tied up with plastic
or metallic strips. The tubes with high surface
quality are wrapped in paper, and the light-wall
tubing is put into wooden boxes.
Technology of Bright annealing
At the end of 2004 Tiancheng commissioned the
bright annealing furnace by Company “Tiancheng”.
The bright annealing furnace permits to carry
out the heat treatment without scale formation
and excludes the pickling procedure necessary
for its removing. The principle of operation of
the furnace is based on annealing in the protective
extra-pure hydrogen atmosphere with purity of
99.999 percent. The furnace is used to produce
high-quality tubes for Nuclear Power Stations
and high-pressure boilers to ISO 2037, JIS G 3459,
GOST 19277-73, ASTM A213, A269, as well as other
International Standards and Customers’ specifications.
Tube surface quality
Surface quality characterizes the marketing appearance
of the tube and reflects the level of technologies
used at the Mills. The work on surface quality
improvement begins from quality control of round
billet with the view of preventing any damage
of tube in course of multiple process operations.
The tube surface quality depends on several factors:
emulsions and oils used when rolling, the ways
of their removing, serviceability of tools and
equipment, quality of water used for tube flushing
at the last stage of re-rolling, the quality of
table and rack surfaces for operations of check,
drying, tube packing and other.
Additional processing of surfaces permits to remove
the surface defects and diminish the level of
roughness of any tube.
Tiancheng produces the tubes with following aspects:
- electropolished;
- polished
- bright annealed;
- annealed and pickled.
Besides hot-finished tubes with improved surface
quality acc. to TU 14-3-197-89 are machined inside
and outside along the full body of tubes.
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