Horizontal continuous casting refers to the type of continuous
steel casting in which the molten steel is poured horizontally
into a horizontally placed crystallizer, and the solidification
process of the billet and movement in the caster until it reaches
the horizontal state of the cooling bed. This method can simplify
the process, improve production efficiency, facilitate automation
and improve casting quality.
The crystallizer is a key component of the continuous casting
equipment and its quality is directly related to the continuous
casting technology's effectiveness and economic benefits.
Graphite material has the characteristics of high temperature
resistance, oxidation resistance, chemical resistance,
self-lubricating and excellent thermal conductivity, and is the
most ideal material for making crystallizers. It is generally
believed that graphite crystallizer (also known as continuous
casting graphite) has many advantages compared with metal molds,
such as not being eroded by molten metal, the friction
coefficient is low when the casting is moving, and it is easy to
process, and no cold septum is produced on the casting surface
(especially Continuous casting of large flat copper pieces), as
well as the continuous casting surface without processing.
Therefore, XRD graphite has given considerable attention to the
research and production of graphite materials for continuous
casting, continuously improving the structure of continuous
casting graphite and increasing its service life.
Horizontal continuous casting machine use multi-stages, ie copper
sleeves are used in the front section and graphite sleeves are
used in the rear section. The function of the graphite sleeve at
the back of the crystallizer is mainly to act as a lubricant
under high temperature, and it also has the function of secondary
cooling of ordinary casters. The billet first cools and
solidifies in the copper jacket, and after the initial solidified
shell is formed, it enters the graphite sleeves to cool more
slowly. Since the graphite has self-lubricating properties at
high temperatures, the length of the copper sleeve that is easily
bonded to the blank shell is very short, so that the casting
resistance of the entire crystallizer inner sleeve can be ensured
to be small. In order to reduce the effect of air gap on heat
transfer, the copper sleeve and the graphite sleeve have
corresponding taper. The heat flux density of the copper jacket
in the front section of the crystallizer is estimated to be 1.5
to 1.8 MW/m on average, which can reach **3.8 to 4.5 MW/m in the
vicinity of the separation ring, and only 0.5 MW/m in the
graphite sleeve. The graphite sleeve of the rear section of the
horizontal continuous casting mold is longer, and the billet is
thicker (****5mm) after the casting mold emerges from the
crystallizer, and it is no longer necessary to continue the spray
cooling. The slab thus obtained has a uniform cooling and good
quality.
The choice of graphite sleeve material must be suitable for the
characteristics of the copper alloy produced. The fitting
tolerances of graphite sleeve and water-cooled copper sleeve must
be appropriate, and the appearance roughness should be small. The
high density graphite materials such as XRD Graphites XRD*5 have
good strength, small coefficient of thermal expansion, high wear
resistance and good self-lubricity, and are ideal materials for
making crystallizer graphite sleeves. Graphite sleeve working
surface can also be processed by coating or electroplating, which
can not only improve the surface quality of the slab, but also
prolong the service life of the graphite sleeve.
