The Sugar Engineers

Use of 3CR12 in the Sugar Industry

3CR12 is a weldable, structural, corrosion resistant steel containing
a nominal 12% Chromium. 3CR12 was originally developed as an
alternative material of construction to materials such as mild steel,
galvanised and alurninised steel, where the mechanical properties and
corrosion resistance of these materials was unsuitable.

With an average life expectancy of 5 to 10 times that of mild steel
and at considerably less cost than higher grades of stainless steel,
3CR12 is recognised as an extremely effective alternative to coated mild
steel, resulting in minimum capital cost increases and significant
maintenance cost savings.

3CR12 has been in use in the sugar industry, locally and world-wide,
since 1980 and has become an accepted material in many applications
ranging from the cane yard to the final product.

3CR12 exhibits excellent properties in wet sliding abrasion
applications by resisting corrosive attack, therefore improving flow and
reliability. This allows widespread use of 3CR12 in cane sugar and beet
handling applications, where abrasion is aggravated by the moisture and
solids present in the cane and beet being processed.

The Benefits Of 3CR12 Corrosion Resistance

All metals react with oxygen and water in he air to form a surface
layer of oxide. That formed on carbon steel is soft, friable, hydrated
iron oxide rust. The process of rust degeneration is greatly accelerated
by surface abrasion or scouring.

3CR12 with a nominal 12% Chromium content, has an inert tough surface
layer of iron-chromium oxide. This passive layer is invisible to the
naked eye, allowing the natural brightness of the metal to be seen. If
scratched, the film has the ability to reform instantaneously, thus
maintaining protection.

Corrosion Abrasion

With mild steel, abrasion removes the corroded layer and exposes fresh reactive surfaces for further corrosion to take place.

3CR12’s excellent wet sliding abrasion properties are derived from
its superior corrosion resistance and slideability. Under dry
conditions, 3CR12 offers only marginal improvement over mild steel, but
under wet or damp conditions (eg. over 4% moisture), the corrosion
vector is underestimated. Dry conditions are seldom encountered in the
cane sugar and beet sugar industry.

When the cost per unit loss by corrosion abrasion is taken into
account, 3CR12 is superior to other grades tested. (See histogram
below).

Cane Sugar Processing

The sugar industry is characterised by high maintenance costs due to
the replacement and repair of equipment due to corrosion and corrosion
abrasion.

Sugar cane is not washed prior to cutting and crushing in the mills
and the presence of sand and stone contribute to the abrasive conditions
that already exist.

3CR12 with its excellent wet sliding properties improves the flow of
materials and has gained rapid acceptance in cane handling and bagasse
applications. It has also gained acceptance in most other areas within
the sugar mills due to its corrosion resistance and superior mechanical
properties.

Examples of the many applications where 3CR12 has been used in the processing of sugar cane are listed below

Maidstone Diffuser

Maidstone Sugar Mill have installed their second diffuser which was
comissioned in the 1995 season. The diffuser is 70 metres long, 10
metres wide and capable of processing 300 tonnes of sugar cane per hour
The roof, side wall internals, perforated floor sections and lifting
screws have been fabricated from 3CR12.

Felixton Ash Settler

3CR12 is proving its worth in corrosion abrasion applications as
liners on cane carriers and deck plates on intercarriers and ash
disposal carriers. The photograph on the left is of the Felixton sugar
mill ash seffler deck plates which were installed in 1992 and are still
in excellent condition. The carrier disposes wet ash originating from
bagasse burnt in the boilers.

Komati Mill

Transvaal Sugar’s (T.S.B.) new Komati mill in Komatipoort started
production in March 1994, processing 225 tonnes of cane per hour which
has doubled over the past five years.

3CR12 is being used in areas where corrosion and corrosion abrasion present high maintenance demands.

The Komati mill has installed 3CR12 in its conveyor systems, cane
carrying, diffuser feed slat and sample system conveyors. In the juice
extraction area where the acidic nature of the product can rapidly
degrade mild steels, 3CR12 has been used for the diffuser side walls,
roof and some juice piping. Chutes and intercarriers in this area have
also been fabricated in 3CR12.

Downstream production machinery fabricated using 3CR12 includes the
clarifier launders and root mud mixers, filter frame, agitator, trough
and hood filtration piping. The evaporator tubes and fourth effect
condenser, pan tubes and condensation pipes have also been fabricated
from 3CR12. Further into the mill, 3CR12 has also been used to build
the centrifugal monitor casings, sugar screw conveyors and sugar scales.

In total, over 450 tonnes of 3CR12 has been used in the Komati mill,
demonstrating the versatility of the 3CR12 applications throughout the
factory.

Technical Data

Chemical Compostion

C	Ni	Mn	Si	P	S	Cr	Ti
0.03%	1.5%	1.5%	1%	0.03%	0.03%	11% to 12%	0.6%

Mechanical Properties at Room Temperature

Ultimate Tensile Strength		460	MPa	min
Proof Strength (0.2% offset)		280	MPa	min
Elongation (in 50mm)	t < 4.5 mm	18	%	min
	t > 4.5 mm	20	%	min
Hardness	t < 12 mm	220	BHN	max
	t>12 mm	250	BHN	max
Charpy Impact (20\B0C)		35	J/cm3	min

Physical Properties

Density		7860	kg/m3
Modulus of Elasticity (tension)		200	GPa
Specific Heat Capacity		460	J/kgK
Thermal Conductivity	at 100\B0C	23	W/mK
	at 500\B0C	25	W/mK
Electrical Resistivity	at 25\B0C	660
Coefficient of thermal expansion	0-100\B0C	10.8	μ/m\B0C
	0-300\B0C	11.3	μ/m\B0C
	0-700\B0C	12.5	μ/m\B0C
Melting Range		1430-1510	\B0C
German Werkstoff Equivalent		1.4003
American Equivalent		ASTM A240 410S